10 P hosp h azenes

BY R. KEAT

1 Introduction The most significant feature during the past year has been the continued growth of publications dealing with potential applications of cyclic and polymeric phosphazenes. Apart from this, there does not appear to have been any parti- cularly noteworthy chemical advance. Cyclophosphazenes form the subject of one comprehensive review,l and other more specialized reviews are noted in their respective sect ions.

2 Synthesis of Acyclic Phosphazenes From h i d e s and Phosphorus(m) Compounds.-The elimination of nitrogen by the reaction of phosphorus(rrr) compounds with azides remains one of the most convenient methods of synthesizing monophosphazenes. Recent examples include the syntheses of (1)-(4).

R,PNPr'CH,CO,Et + PhN, R,P(=NPh)NPriCFI,CO,Et + N, (ref. 2) ( 1 ) R = EtO or Et,N

(EtO),P(O)NMePR'R* + PhN, (T:tO),P(0)NMeP(=NPh)R'R2 + N, (ref. 3) ( 2 ) R' = R2 = OEt;

R' = OEt, R2 = NMe,; R' = R' = NMe,

+ Ph,P=C(PMe,)bPh, C1- + PhN, + Ph,P=C[ PMe,(=NPh)]PPh, C1-+ N, (ref. 4)

(3)

X X

P$P + N /'="\CN, --+ N CN=PPh3 + N, Nc-/ - N// X X

(4) X = OMe or NMe,

(ref. 5 )

1 S. S. Krishnamurthy, A. C. Sau, & M. Woods, Adu. Inorg. Chem. Radiochem., 1978,21,41. 2 L. I. Nesterova, L. F. Kashukhin, M. P. Ponomarchuk, and Yu. G. Gololobov, J. Gen.

8 T. I. Klepa, L. F. Kashukhin, M. P. Ponomarchuk, and Yu. G. Gololobov, J. Gen. Chem.

4 T. A. Mastryukova, I. M. Aladzheva, I. V. Leont'eva, V. A. Svoren', P. V. Petrovskii, and

6 K. Fujinuma, Y. Hashida, and K. Matsui, Bull. Chem. SOC. Jpn., 1978,51, 2394.

Chem. USSR (Engl. Transl.), 1978, 48, 966.

USSR (Engl. Transl.), 1978, 48, 970.

M. I. Kabachnik, J . Gen. Chem. USSR (Engl. Transl.), 1977, 47, 2239.

219

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220 Organophosphorus Chemistry

The kinetics of formation of (1) and (2) were measured and it was found that the reactions were slower with dialkylamino-phosphorus(rI1) substituents than with alkoxy-phosphorus(u1) substituents. The phosphazene ( 5 ) represents a convenient intermediate for the one-flask synthesis of phosphoranes (6) because of its ready reactions with diols.6 In connection with azide reactions, it may be noted that a series of phosphorus(m) azides, PX3-n(N3)n (X = C1 or Br ; n = 1-3), have recently been obtained’ from the reactions of PX3 with sodium azide in aceto- nitrile; P(N3)3 evolves nitrogen in solution at just above room temperature, but the product has yet to be identified.

( 6 ) X = (CH,),- 5 , q, or aryl

From Amines and Phosphorus Halides.-The reaction of the hydrazone (7) with phosphorus trichloride had previously been shown to give a diazaphosphole hydrochloride, which on reaction with triethylamine gave (8). An isomer of (8), the phosph(rrr)azene (9), has now been separated and its crystal structure estab-

/Me M e N H N=C,

M e

+ PCl.. - HCl

( b ) + Et,N, - Et3NHCI

M e

Me$> + N\p

lished.$ An analogous reaction was carried out with cyclopentanone methyl- hydrazone. Phosphazene synthesis using phosphorus(v) halides and amines is, of course, more commonplace, and several new methods have appeared. Thus the syntheses of (10) and (1 1)l0 constitute variations of the Kirsanov reaction, whilst the N-cyanoethylene-derivative (12) has been obtainedll by a variety of reactions. The synthesis of phosphazenyl-phosphonium salts such as [(H,N),P=

C,I;,NIIK + PCI, - C,F5N=PCI, -t RCI + 11C1

(R = H , COCI,, or COCF,) (10)

6 J. I. G. Cadogan, N. J. Stewart, and N. J. Tweddle, J. Chem. SOC., Chem. Commun., 1979,

7 K. B. Dillon, A. W. G. Platt, and T. C. Waddington, Inorg. Nucl. Chem. Lett., 1978, 14,

8 J. H. Weinmaier, J. Luber, A. Schmidpeter, and S . Pohl, Angew. Chem., Int. Ed. Engl.,

* T. D. Petrova, V. E. Platonov, T. I. Savchenko, and L. M. Marshalkina, Izu. Akud. Nuuk

10 V. P. Kukhar’, E. V. Grishkun, and V. P. Rudavskii, J . Gen. Chem. USSR (Engl. Transl.),

11 V. P. Kukhar’, and N. G. Pavlenko. J. Gen. Chem. USSR (Engl. Transl.), 1978,48, 71 1.

191.

511.

1979, 18, 412.

SSSR, Ser. Khim., 1978, 2635 (Chem. Abs., 1979, 90, 71 849).

1978,48, 1159.

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Phosphazenes 221

PCI, + .RNH, -+

(11) R = S0,Ar or COCCI,

\ NaC(CN), + PBr,

NP(NH,),]+ Cl- is included in a review12 of tetra-aminophosphonium salts and, in related work, phosphazenes (13) were obtained1, by heating the products of chlorination of amino-phosphines. The formation of (1 3) probably proceeds by

+ heat c 1, (K,N)Q --+ (R,N),PCI C1- KN=PCI(NK:),

( 1 3 ) R =’ d k y l , but not Me

nucleophilic attack of the chloride ion on the carbon atom bonded to nitrogen in the R2N group, a view which is supported by observations on the thermal decomposition of (PhEtN),PCl X- (X= Br or I), in which EtX is eliminated and PhN=P(NEtPh),CI is formed,

The reactions of lithiated silylamides with phosphorus halides have been further investigated. The phosphazene (14), formed by the cleavageof Si-N bonds,

L

~ u ‘ hIe2Si LiCl

)NLi + PCl, Hu‘Me2SiN=PCl,

appears to be only marginally more stable than Cl,P=NSiMe,, in that it eliminates Me,ButSiCl on standing at ambient temperatures. l4 The possibility of migration of a silyl group in the products (15) and (16) of the reaction of phosphoryl

halides with LiN(SiMe,) has been considered, and stereochemical arguments and 13C n.m.r. data have been interpreted in terms of the phosphazene-structure (16) for a wide range of X and Y substituents [X = Y = F; X = Y = C1; X = Y = Ph l6

1 2

13

14 15

A. Schmidpeter, Actes Congr. Int. Composes Phosphores, ls t , 1977, 277 (Chem. Abs., 1978, 89, 122 279). A. P. Marchenko, V. A. Kovenya, and A. M. Pinchuk, J. Gen. Chem. USSR (Engl. Transl.) 1978, 48, 501. R. H. Nielson and W. A. Kusterbeck, J. Organomet. Chem., 1979, 166, 309. R. H. Neilson, R. D. Jacobs, R. W. Scheirman, and J. C. Wilburn, Inorg. Chem., 1978,17, 1880.

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222 Organophosphorus Chemistry

and X = Ph, Y = C1; X = NMe,, Y = C1; X = NMe,, Y = Ph (difficult to purify)ls]; (Me,Si),NP(=NSiMe,)(OSiMeJCl was also obtained from the reaction with phosphoryl chloride. l6 Other Methods.-The reversible formation of phosph(w)azenes (1 8) in aromatic solvents at elevated temperatures (up to 140 "C) from the cyclotetraphosphazanes (17; R= Prn, Pri, Bus, or CH,Ph) has been rep0rted.l' Evidence for compounds (18) comes from 31P n.m.r. data, where low-field signals (& 225-236) appeared,

which may be compared with (17) (dp 81-89), and from reactions with boron trifluoride which are believed to give the isomeric adducts (19) and (20). Further details l8 of the use of a 'three-phase test' for the detection of phosphazene (meta- phosphoramidate) intermediates such as (21) have been reported (cf. Volume 7).

A simple exchange reaction can be used to obtain the phosphazene (23) from the analogous arsazene (22).lB It is known that the reaction of bis(trimethylsily1)-

(19) $. B F3

(20)

ButN=AsCI, + YCl, Bu'N=PCI, + AsCI,

(22) (23)

aminophosphonium iodides with n-butyl-lithium results in the formation of phosphazenes such as (24; R1 = R2 = Me); the scope of this type of reaction has now been further explored20 and the compounds (24)--(26) have been obtained. Reactions with mono(sily1)aminophosphonium salts are dependent on the substituents in the silyl group and on the solvent.

16 J. Butvinik and R. H. Nielson, Znorg. Nucl. Chem. Lett., 1978, 14, 497. 17 G. Malavaud, M. T. Boisdon, Y. Charbonnel, and J. Barrans, TetrahedronLett., 1979,447. 18 J. Rebek, F. Gaviiia, and C. Navarro, J. Am. Chem. Soc., 1978, 100, 81 13. 1 0 A. M. Pinchuk, V. A. Kranovskii, 2. I. Kuplennik and L. P. Filonenko, J. Gen. Chem.

20 T r Wilhutn and R. H. Neilson, Znorg. Chem. 1979, 18, 347. USSR (Engl. Transl.), 1977, 47, 49.

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Phosphazenes 223 + Bu"Li

(Me,Si),NPMeR'R2 I- - Me,SiN=P(CH,SiMe,)R'R*

(24) R' = R2 = Me or Ph; R' = Me, R2 = Ph

* R'Me,SiN=P(CH,SiMe,R2)Me, 13uf Me,Si(Me,Si)NiMe, 1- Bu"Li

(26) R' = Me, R2 = But; R1 = But, R2 = Me

The product of the reaction of triphenylphosphine and tetracyanoethylene, once thought to be a phospholidine, has now been shown 2 1 p 2 2 to be the phos- phazene (27). In one caSe21 this was confirmed by X-ray crystallography (see Section 8). The zwitterionic product of the reaction of triphenylphosphine with azidocarboxylic acid esters reacts with amines to give phosphazenes (28) in widely variable yields. 23

Ph3b-N- NC0,Me MeO,CNHNHCO,Me +

Ph,P=NR MeO,CN=NCO,Me + Ph,P -C- I

C02Me

(28) R = EtCO,,PhCO,, S0,tol - p , PhCO, etc.

3 Properties of Acyclic Phosphazenes Ha1ogenoderivatives.-Addition of hydrogen halides across the phosphazene bond usually results in the formation of aminophosphonium salts, but it was recently showna4 that hydrogen fluoride can give aminophosphorane (29). Work

21 P. J. Butterfield, J. C. Tebby, and T. J. King, J . Chem. SOC., Perkin Trans. 1, 1978, 1237. 22 H. Fritz and C. D. Weiss, J. Org. Chem., 1978, 43, 4900. 23 H.-J. Niclas and D. Martin, Tetrahedron Lett., 1978, 4031 24 E. S. KOZ~OV, L. G. Dubenko, and M. I. Povolotskii, J . Gen. Clzem. USSR (Engl. Transl.),

1978,48, 1734.

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224 Organophosphorus Chemistry

on the aminolysis of chlorophosphazene (30) shows that thephosphazerzyl-chlorine atoms are most reactive to methylamine and t-butylamine, leading to (31) and (32), although the site of displacement of a second chlorine atom is dependent on the amine as shown by the formation of (33) and (34) in Scheme l.25 The possi- bility that (32) might be present as its tautomer, C12P(0)NHP(=NBut)C12, could

Reagents: i, NHzMe; ii, NHzBut.

Schema 1

not be dismissed. In another study,26 it was shown that C-Cl, rather than P-Cl, bonds in (35) are more reactive towards hydrazine dihydrochloride, leading to the diphosphazene (36). Chlorination of (36) results in the re-formation of (35; R= CCl,) and the chlorine atoms in (36) are readily replaced by anilino-groups.

(35) (36) R = CCl,, CH,CCJ, or C€.,

The dioxaphosphole-derivative (37) is converted into the phosphorane (38) on reaction with pyrocatechol;27 no evidence was obtained for a product in which the chlorine atom was simply replaced by the -oC6H,0H-o group. Recently, 35Cl n.q.r. data have been reported for phosphazenes of the type R1R2R3P= NC(Cl)=CCl, (R1, R2, R3 include C1, Et, and Ph)28 and for Cl,P=NR (R= alkyl

25 G. Bulloch a R. Keat, Inorg. Chim. A d a , 1979, 33, 245. 26 T. N. Kasheva and V. P. Kukhar', J. Gen. Chem. USSR (Engl. Transl.), 1977, 47, 2470. 27 V. P. Kukhar', E. V. Grishkun, and V. P. Rudavskii, J . Gen. Chem. USSR (Engl. Transl.),

28 E. A. Romanenko, M. I. Povolotskii, N. G. Pavlenko, and Yu. P. Egorov, Teor. Eksp. 1978,48, 1308.

Khim., 1978,14, 834 (Chem. Abs., 1979,90, 103 215).

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Phosphazenes 225

or flu~roalkyl).~~ The 31P n.m.r. data for the latter group of compounds were also discussed. 29 The anti-tumour properties of chlorophosphazenes C13P=NR (R = halogenoalkyl) have been Amino-, Alkoxy-, Alkyl-, and Aryl-derivatives.-The reactions of phosph(nx)azenes continue to provide interesting new compounds. Thus (39) undergoes oxidative addition with hexafluoroacetone and with perfluorobiacetyl to give (40) and (41) respectively (Scheme 2).31 Compounds of the type (40), containing three-membered rings, were previously unknown. The ring compound (42) was isolated in connec- tion with work directed at the trapping of Me,Si=NR1 interrnediate~.~~

NR II

RN-PNR,

(42) R' = 2,4,6-C6H,Me,

Reagents: i, (CF3)2CO; ii, CF3C(O)C(O)CF3; iii, FMezSiNRILi.

Scheme 2

Phosph(n1)azene (43) gives a typical trans-square-pIanar complex (44) with Zeise's Salt.33 Addition of water and methanol across the phosphazene linkage in (44) gives [Cl,Pt{P(OR2)(NHR1),),] and [C1,Pt(P(OMe)(NHR1)(NR1R2))21 res- pectively, the latter as a mixture of diastereoisomers. The addition of (39) to a phosph(v)azene (45) is reversible, although this is not the case with (47), which is the addition product of (45) and (46). N.m.r. evidence for the fluxional behaviour indicated was obtained for (47). 34 Phosphazenes analogous to (45) also undergo

R1R2N c1 \ I //""I

R'R'NP-NR' + K[ PtCl,(C,H,)] -+ (4 3)

(44) R1 = But, R2 = SiMe,

29 E. S . Kozlov, S. N. Gaidamaka, M. 1. Povolotskii, I. A. Kyuntsel', V. A. Mokeeva, and

30 A. 1. Kutovoi, T. A. Syadro, V. S. Petrenko, G. F. Solodushchenko, and V. G. Telyuk,

31 G.-V. Roschenthaler, K. Sauerbrey, and R. Schmutzler, Cltem. Ber., 1978, 111, 3105. 32 U. Klingebiel, Chem. Ber., 1978, 111, 2735. 33 0. J. Scherer, K. Kuhn, and H. Jungmann, 2. Naturforsch., Teil B, 1978, 33, 1321. 34 A. Schmidpeter and T. von Criegern, Z. Naturforsch., Ted B, 1978, 33, 1330.

G. B. Soifer, J. Gen. Chem. USSR (Engl. Transl.), 1978, 48, 1155.

Mikrobiol. Zh. (Kiev), 1978, 40, 633.

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226 Organophosphorus Chemistry

RN-PNR, Me,/ I

Ph2 + R2NP=NR ,P-N

CO,Me (39) R = SiMe, C0,Me

(45) NR II RN NR y---

RN-PNR, Me,( 1

T \ N R , P-N Me

(45) + R,NP(=NR), -+ 'i-N (46) R = SiMe, M e ' u P h, e'QP h

MeO,C C0,Me C0,Me

addition reactions with isothiocyanates to give (48), (49), and (50) as shown in Scheme 3, the proportions being dependent on the R group [Ph or Me,P(S)] and

SCN'

Z = R'C=CR'CPh2, \vhere R' = C0,Me

X,P=N is a phosphazene

Lj

R \ 2 N-C I t

HNR s-c. I I

X,P-N

(49)

Reagents: i, RNCS. Scheme 3

on the Diphenylketen and (45) and its PP-diphenyl analogue give un- stable adducts (51 ; X= Me) and (51 ; X= Ph) by addition of the carbonyl group across the phosphazenyl bond.%

X\I I ,P-N

C0,Me (51)

35 A. Schmidpeter and T. von Criegern, Angew. Chem., Int. Ed. Engl., 1978,17,443. 36 A. Schmidpeter and T. von Criegern, Chem. Ber., 1978,111, 3747.

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Phosphazenes 227

The phosphazene (52) is a useful substrate for the synthesis of a wide range of heterocycles (Scheme 4), and it reacts with methanol to give (R1R2N)(R1HN)- (MeO)PS.37 The reaction of (52) with trimethylphosphine gives R1R2NP=NR1 and Me3PS, but more complex products (53)--(55) are obtained with trimethyl ph~sphite.~'

R'

iif R' R'

/N\pfSnC'l S N O NP/ \s/ - i R'R'N-P 2

\N/ 'SMe K'

Rl / \N/ c1 R'

(52) R" = But Rz = SiMe,

R' s N NP' 'Ma / \N/ c1

R'

Reagents: i, SOCla; ii , GeC14; iii, SnC14; iv, MC13 (M = P or As). Scheme 4

R'

(54)

R1R2NPRS + (MeO),P - (MeO),P=NR'+ + (5 3) S NR'

/ \pH \NR'

(52) R' = But, R1R2NP R2 = SiMe, 'S' 'N R' R2

( 5 5 )

37 0. J. Scherer, N.-T. Kulbach, and W. Glassel, 2. Naturforsch., Ted B, 1978, 33, 652.

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228 Organophosphorus Chemistry

Desilylation of the phosphazene (56) can be conveniently carried out, using methanol and sulphuric acid (as a cataly~t).~8~~9 The product, (57), is stable to water and can be protonated by hydrogen halides, to give But3PNH2X- (X = hal), or quaternized by methyl iodide, leaving a mixture of But3PNH2 I- and But3PNHMe I-, the latter in larger yield.38 Thermolysis of (57) gives good yields of tri-t-butylphosphine, and N-lithiation provides a useful substrate for reactions with various halides of the elements of Group IV.38 Desilylation of N-trimethyl- silyl-phosphazenes (58) has also been achieved40 by heating with phosphites, which leads to the phosphazenes (59).

+

+

+

H P , But,P=NSiMe, + MeOH - Bd,P=NH + MeOSiMe,

(56) ( 5 7)

25 -1 00 "c R',P=NSiMe, + P(OR2), R',P=NP(OR2), + Me,SiOR2

( 5 9 ) R' = Me, NMe,, or Ph R2 = CH,CF, or Ph

The formation of olefins by the reactions of phosphazenes, for example (60), with potassamide has been olefins are only obtained in reasonable yield when the alkyl substituents on phosphorus include t-butyl or isopropyl

But3P=NH + KNH, __f But2PNHK + H,C=CMe, + NH,

(60)

groups. The isocyanate (61), obtained42 by the reaction of an amide with phos- gene, was further characterized by the products of reactions with alcohols and amines, i.e. (62). On the other hand, N-carboxyl phosphazenes (63) can be used 43

Ph,P=NSO,NHCONHPrn + COCl, --+ Ph,P=NSO,NCO + Pr"NC0 + HCI

(61)

1.. Ph,P=NSO,NHCOR

(62) R = Oalk, NH,, NHC,H,,, or NEt,

R*3P=NC0,R2 heat_ RZNCO + (R2NCO), + R1,PO

(63) R' = Bu, OEt, OPh, or Ph R2 = various alkyl groups

38 W. Wolfsberger, Z . Naturforsch., Teil B, 1978, 33, 1452. 39 H. Schmidbaur and G. Blaschke, 2. Naturfursch., Teil 8, 1978, 33, 1556. 4O E.-P. Flindt, 2. Anorg. Alfg. Chem., 1978, 447, 97. 41 B. Ross and K.-P. Reetz, Chern. Ber., 1979, 112, 1756. 42 D. E. Arrington, J. Chem. Res., 1978, ( S ) 320; ( M ) 4331. 43 H. J. Niclas and D. Martin, Tetrahedron, 1978, 34, 703.

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Phosphazenes 229

to obtain isocyanates by a route which does not involve the use of phosgene. [4 + 21-Cycloaddition reactions with phosphazenes are rarely reported, but recent examples 44 were provided by the synthesis of the triazine (64) and related hetero- cycles. The base properties of the phosphazene (65) have been utilized45 in its use as an initiator for formation of the carbene (66).

“AN Ph$=NR + RN=C-NR --+ I 1

(64) R = aryl

ArCHClX + Ph,P=NH - (ArCX] + Ph,iNH, Cl- ArXC-CXAr

(65 ) (66) Ar = stilbene derivative X = CN or CC1,

Few publications have been forthcoming on the imide-amide (phosphazene- phosphazane) rearrangement, but the topic has been reviewed,46 and it has been found 47 that the rearrangement of (67) is catalysed by alkyl halides, zinc halides, iodine, and MeCOBr. The ionic intermediate (68) has been proposed for reactions with alkyl halides, giving rearrangement products (69). The unusual dimethyl-

EtO OEt

/ ?. (EtO),P=NPh + RX _.) ‘PL X- _t (EtO),P(O)NPhR + EtX

EtO’ \“Ph (69) R = alkyl X = ha1 R

(6 8)

phosphinoamino-phosphazenes (70) have been synthesized 48 and oxidation reactions carried out; attack occurs at the tervalent phosphorus atom, leading to (71). Attempts to form a diphosphazene by reaction with trimethylsilyl azide, however, resulted in the formation of (72) and elimination of the polymer

RMeP(=NMe)NLiMe + Me,PCl _+ RMeP(=NMe)NMePMe, + LiCl (70) R = Me or But

/ \ ; . - N,. + - Me,SiN, IMe,PNI,

RMeP(=NMe)NMeSiMe, RMeP(=NMe)NMeP(X)Me, (72) R = But (71) X = S or Se

44 J. Bodeker, P. Kochritz, and K. Couralt, 2. Chem., 1979, 19, 59. 45 V. A. Zasorina, A. Shtepanek, and A. V. Kirsanov, J. Gen. Chem. USSR (Engl. Trartsl.)

1978,48, 1953. V. A. Gilyarov, Rum. Chem. Rev. (Engl. TransE.), 1978, 47, 870.

47 B. C. Challis, J. A. Challis, and J. N. Iley, J. Chem. Soc., Perkin Trans. 2, 1978, 813. 48 0. J. Scherer, G. Schnabl, and Th. Lenhard, 2. Anorg. Allg. Chem., 1979, 449. 167.

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230 Organophosphorus Chemistry

[Me ,PN 1, . The p hosphazene-cont aining nie t a1 carbonyl [Ph3PNPPh,] +

[Mn(CO),]- is a convenient alternative to Na[Mn(CO),] for the synthesis49 of alkyl, germyl, and stannyl derivatives of [Mn(CO),]-. The formation and properties of radicals derived from phosphazenes of the type (R10),P=NR2 have been studied 50 by e.s.r. spectroscopy. Thus the phosphoranyl radical (EtO),PN- (CH,Ph)SiMe, undergoes B-scission to form (EtO),P=NSiMe, and a benzyl radical. Radical addition to (EtO),P=NMe did not give phosphoranyl radicals (EtO),PNMeR. In the same study, (EtO),P(O)NMeP(OEt), was obtained by the reaction of (EtO),PCI with (EtO),P=NMe, and abstraction of hydrogen from (RO)3P=NCHR2 gives radical imine ions (RO),P=NcR,, and not imino- phosphoranyl radicals (RO)3PN=CR2.

The acyclic phosphazenes have been subjected to numerous spectroscopic studies. The lH, 14N, and 16N n.m.r. spectra of a series of diazaphospholes (73/74; R=H, MeCO, Ph, or CH,CH,CN) indicateK1 that (73) is the predominant

R N-N

R N-N

H (73)

H

(74)

tautomer. The temperature dependence of the 31P n.m.r. chemical shifts of a series of phosphazenes (R10)3P~=N-P~(0)(oR2)2, where R1 and R2 are various alkyl groups, is greater for PA than for PB.~, Mass spectroscopic studies have also been reported for Me,P=NH, Me,P=NMe,53~ 54 and aryl-substituted phos- p h a z e n e ~ . ~ ~ The dipole moments of a series of phosphoranes, including that of Ph,P=NN=CH2, have been measured,S6 and the electronic spectra of the acetylenic derivatives (PhC-C)R1R2P=NX, where R1 and R2 are Ph or PhC=C and X is H, NO2, or N=NC,H,NO,, have been relateds7 to the sum of the u-coefficients for different groups.

4 Synthesis of Cyclic Phosphazenes The synthesis of new cyclic phosph(1n)azenes (9)8 and (18)67 has already been noted in Section 2. Only one development of the PCI, + NH3 reaction for chloro- cyclophosphazenes has been proposed,68 and this indicates that yields of the 49 D. N. Duffy and B. K. Nicholson, J. Organomet. Chem., 1979, 164,227. 60 R. S. Hay, B. P. Roberts, K. Singh, and J. P. T. Wilkinson, J. Chem. Soc., Perkin Trans. 2,

1979,756. 51 V. V. Negrebetskii, L. Ya. Bogel'fer, A. V. Vasil'ev, R. G. Bobkova, N. P. Ignatova, N. I.

Shvetsov-Shilovskii, and N. N . Melnikov, J. Struct. Chem. (Engl. Transl.), 1978, 19, 462. 52 L. Riesel, J. Steinbach, and B. Thomas, 2. Anorg. Allg. Chem., 1979, 451, 5 . 521 0. R. Hartmann, K. P. Wanczek, and H. Hartmann, Dyn. Mass Spectrom., 1978, 5, 146

64 0. R. Hartmann, K. P. Wanczek, and H. Hartmann, Led. Notes Chem., 1978, I, 283 (Chem.

65 S. Yolles, M. F. Sartori, and J. H. Woodland, J. Chem. Eng. Data, 1978, 23, 260. 66 H. Lumbruso, J. Cure, and H. J. Bestmann, J. Organomet. Chem., 1978, 161, 347. 57 I. N. Zhmurova and V. G. Yurchenko, J. Gen. Chem. USSR (Engl. Transl.), 1978, 48, 71. 58 H. Kodama, T. Kodama, M. Senoura, and H. Tamura, Japan. P. 77 35 356 (Chem. Abs.,

(Chem. Abs., 1978, 89, 196 402).

Abs., 1978, 89, 107 139).

1978 88. 193 922L

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Phosphazenes 23 1 cyclic products (NPCI& can be improved if, initially, the solvent contains small quantities of these cyclic materials (2 5 %).

Several new cyclic compounds containing phosphorus, nitrogen, and other elements have been prepared. Examples in which carbon can be incorporated in the ring are provided by (75),6s (76),$O and (77).61 The thermal degradation of the

N R’C -//N\cR2 RICH ‘CR2

I1 + pc15 - I 11 + HC1 N N

I NH, NH

R’, R2 include CF3, CCI,, and Ph

NP/ C’2

(75) H

ClR

(76) R = Me,Et,Ph,orCCl,

(77) R = (CF,),CIJ3 or fluoro-ether groups

latter compounds and related six-membered rings containing one phosphorus atom has been discussed.s2 Boron and sulphur have also been incorporated in phosphazene ring systems (78)s3 and (79)64 respectively, and the sulphur- chlorine bond is more labile than the phosphorus-chlorine bonds, as shown by the

N Ph,P,dy>PPh,

MeN,- ,NMe R

Ph,(MeHN)P=NkNHMe)Ph, CI- + BC1, - I i :I + HCI

59 P. P. Kornuta and N. V. KoIotilo, J . Gen. Chem. USSR (Engl. Transi.), 1978, 48, 1081. eo P. P. Kornuta, L. S. Kuz’menko, M. V. Voek, E. A. Romanenko, S. V. Iksanova, and L. N.

Markovskii, J. Gem Chem. USSR (Engl. Transl.), 1977, 47, 2305. R. H. Kratzer, K. J. L. Paciorek, J. Kaufman, T. I. Ito, and J. H. Nakahara, J. Fluorine Chem., 1979, 13, 189.

62 R. H. Kratzer, K. J. L. Paciorek, J. Kaufman, T. I. Ito, and J. H. Nakahara, J. Ffuorinc Chem., 1979,13, 199.

63 H. Binder and J. Palmtag, 2. Naturforsch., Teil B, 1979, 34, 179. 64 S . Pohl, 0. Peterson, and H. W. Roesky, Chem. Ber., 1979, 112, 1545.

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232 Organophosphorus Chemistry

(Me,Si)N=S=N(SiMe,) + PCl, 2 (79)

reaction of (79) with antimony pentachloride to give (80). The formation of (82) may proceed via the tautomers (81), but neither of these was isolated.66

Me,P(O) -NHP(O)(OEt),

/ _3 0

\ Me,P(OH)-NP(O)(OEt), E ~ ~ T , ~ ‘ N & ~ e2

n

(Et O),P( O)NII,

Me,P(O)CI

Further examples of the synthesis of cyclophosphazenes in which a transition metal forms part of the ring system, e.g. (83)se and (84),67 have appeared; the latter compound is formed by insertion of the benzonitrile ligand into the P-N bond. The vibrational spectra of a series of metal complexes obtained using [Ph,P(S)],NH as a ligand have been reported.67a Some contain the anionic species [Ph,P(S)],N-, whose chelate complexes can be considered to contain the ring system (85).

Me CI N

H2C/ \N/ Me,P(=NMe)NMeLi + K [ PtCI,(C,H,)] - \-rtJ \PMe, + LK‘1 + KCl

11 Me

(83) (other canonical forms are H2C

possible)

Me M e Me,Y-N N-.PMe,

PhC--N N-CPh Me Me

Me,P(=NMe)NMeLi + cis-[CI,Pt(NCPh),] __f N< ‘Pt/ ‘hN + LiCl 1. .... . / \ ___ . :*Y

(84) (cis- and rraris-isomers)

Ph P=S

N i . \ y

65 H. Richter and E. Fluck, 2. Anorg. Allg. Chem., 1978, 443, 5 . 66 0. J. Scherer and A. Nahrstedt, Angew. Chem., In t . Ed. Engl., 1979, 18, 234. 67 0. J. Scherer and A. Nahrstedt, J. Organomet. Chem., 1979, 166, Cl. g7@ G. P. McQuillan and I. A. Oxton, Inorg. Chim. Acta, 1978, 29, 69.

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Phosphazenes 233

This topic forms the subject matter of a review,s* and aspects of the aminolysis of chloro-cyclophosphazenes,eg as well as the chemistry of compounds containing NPCI, and NSOCl Halogeno4erivatives.-It has been found that oligomeric chloro-cyclophospha- zenes (NPCI,)n (n= 3-7) can be converted into a mixture of oligomers with increased proportions of compounds with n= 3 or 4 on heating at 300 "C, under reduced pressure.71 The chlorine atoms in the chlorofluorophosphazenes (86) are preferentially replaced by azide and by cyanide to give (87); the azides were further characterized by their reactions with phosphines to give [87; X=N, Z= N=PR, (R= OMe or NMe,)] and [87; X=NPF2N, Z=N=PR3 (R=OMe or Ph)].72* 7s

5 Properties of Cyclic Phosphazenes

have been discussed.

(86) X = N o r NPF,N (87 ) X = N or NPF2N Z = N , o r C N

The first example of a hydridophosphazene (88), formed as the result of a reaction between an organometallic reagent and a pre-formed phosphazene, has been The alcohol is the source of the phosphorus-bound hydrogen in (88). In another reaction, the organometallic reagent Na[Fe(CO),Cp] and N3P3Fs produced a compound (89) containing a P-Fe--Fe three-membered ring.76

- Me I I

I I 1 IBU:PCUI), N,P,Cl, + MeMgCl . =-

P h i cl*P,,N,PcI,

(88)

68 R. A. Shaw and M. Woods, Actes Congr. Int. Composes Phosphores, Ist, 1977,249 (Chem. Abs., 1978, 89, 52 540).

69 S. S. Krishnamurthy, A. R. Vasudeva Murthy, R. A. Shaw, and M. Woods, J. Indian Znst. Sci., Sect. B, 1979, 61, 57.

70 J. C. van de Grampel, Actes Congr. Int. Composes Phosphores, Ist, 1977, 269 (Chem. Abs., 1978, 89, 52 541).

7 1 V. V. Kireev, V. V. Korshak, W. Sulkowski, I. P. Mulyashova, I. I. Zhuravleva, T. P. Sadkova, and G. M. Maiorova, Dokl. Akad. Nauk SSSR, 1978, 239, 853 (Chem. Abr., 1978, 89, 59 495).

72 H. W. Roesky and M. Banek, Chem.-Ztg., 1978,102, 155. 73 H. W. Roesky and M. Banek, 2. Naturforsch., Teil B, 1979, 34, 752. 74 P. J. Harris and H. R. Allcock, J. Am. Chem. SOC., 1978, 100, 6512. 75 P. P. Greigger and H. R. Allcock, J. Am. Chem. SOC.. 1979. 101. 2492.

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234 Organophosphorus Chemistry 0 II

(89)

The crystal structure of (89) has been determined (see Section 8). The phosphazene (90; X= C1) has been fluorinated by SbF, to give (90; X= F), but a reaction of (90; X= Cl) with methylammonium fluoride and water resulted in ring cleavage, leaving FS(O)(=NH)N=C(CF,)NHP(O)F,, along with other The isothiocyanato-derivatives (92; Y = F or Ph) and (93; Y = F or Ph) have been identified from reactions of the analogous tetrachloride (91) with KSCN, although only the fluorine-containing derivatives could be isolated.77 The trans isomer of (94) was obtained in an analogous manner. The reactions of compound

(95) with a variety of reagents (Scheme 5 ) clearly demonstratedS a greater degree of reactivity at the boron atom than at the phosphorus atoms. Complete replace- ment of all the chlorine atoms in (95) could, however, be achieved by reaction with excess dimethylamine. An unusual spin coupling of the type %J(PNl1B) (= 13.75 Hz) was detected in the ,lP-{lH} and l1B-(lH} n.m.r. spectra of (95).

The long-standing controversy concerning the bonding in N,P,CI, continues. Thus the results of a photoelectron spectroscopic study and X,-scattered wave calculations 78 provide no evidence for the three-centre localized bonding scheme so frequently invoked by other workers. Phosphorus-31 n.m.r. spectroscopy is recommended 7@ for the identification of cyclic homologues (NPCl& (n = 3-7), and a related series of compounds (n = 3-1 1) are useful as reference standards

'6 W. Heider and 0. Glemser, Chem. Ber., 1978, 111, 745. 77 E. Klei and J. C. van de Grampel, Recl. Trav. Chim. Pays Bas, 1978, 97, 307. 70 L. Noodleman, N. P. C. Westwood, and K. A. R. Mitchell, Chem. Phys. Lett., 1978, 58,

70 W. Sulkowski, V. V. Kireev, and V. V. Korshak, Deposited Document, 1976, VLNITI 987 252.

(Chem. A h . , 1978, 89, 110 445).

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Phosphazenes cvw

\B/ / \

c1 Cl'

235

Reagents: i, BC13; ii, Pc15; iii, SbFs; iv, NH4NCS; v, NaBH4; vi, Naz [SCHaCH2S].

Scheme 5

for negative-ion mass spectroscopyso because they give intense [MI*- and [ M - C1]- peaks (M=parent mass). The 36C1 n.q.r. spectra of the chlorophosphazenes N3P3C16, N3P3C16NHPri, N3P3CI6NC5H1,,, and cis- and ~~YI~s-N~P~C~,(NM~,) , have been carefully scrutinized.e1 Pressure and/or temperature effects on these spectra enable information to be obtained about molecular conformers and the identification of geometrical isomers. Recently, '@Br and slBr n.q.r. data have also been reportede2 for (NPBr,)% (n = 3 and 4). A colorimetric method for the detec- tion of trace quantities of N,P3CI, has been developed, using a diphenylcarbazone complex.83 Amino-derivatives-The steric requirements of amines, and their influence on the rate of aminolysis of NsP3C16 to give monoamino-derivatives (96), have been inve~tigated.~~ A reduction in the rate of the reactions (which all obey a second- order rate law) observed when

N,P,C1, + NHR'R*

increasingly bulky amines are used can largely be

THF - N,P,CI,NR'R* + R1R2NH,CI

(96) R', R2 = H , Et; H, Bun; H , Pri; H , But; Et, Et; Bun, Bun; or C J , ,

8o Y. Hirata, K. Matsumoto, and T. Takeuchi, Org. Mass Spectrom., 1978, 13, 11 1. s1 A. Connelly, W. H. Dalgleish, P. Harkins, R. Keat, A. L. Porte, I. Raitt, and R. A. Shaw,

8 2 K. R. Sridharan, J. Ramakrishna, S. S. Krishnamurthy, and M. N . Sudheendra Rao,

S3 T. M. Kochetkova, Zacod. Lab., 1978,44,28 (Clzern. Abs., 1978,89, 52 751).

J. Magn. Reson., 1978, 30, 439.

Curr. Sci., 1978,47, 938 (Chem. Abs., 1979, 90, 94 904).

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236 Organophosphorus Chemistry

attributed to increases in the enthalpy of activation. The isomeric composition of the isopropylamino-derivatives N3P3C14(NHPri)a has been re-inve~tigated.~~ Although t.1.c. indicates that one isomer is obtained, g.1.c. has enabled the three possible isomers to be separated and identified by n.m.r. spectroscopy. It is generally difficult to identify unambiguously the geometrical isomers of the type (97;X=C1) and (98;X= Cl), where R1andR2arealkyl, but arecent approach86,87 to this problem is to fluorinate these compounds with KS02F, which gives (97; X= F) and (98; X= F) respectively, without isomerization. The two fluorides

N \\ ,N ,p,\

x ‘x (97)

are then easily distinguished by 19F n.m.r. spectroscopy, having two and one chemically shifted l9F signals respectively. The sulphur(I1) amide (99; R = Me) has been prepared,88 but no reaction occurs when R is Et, Prn, or Bun.

N,P,Cl,NHR + ClSCCl, + Et,N -+ N,P,Cl,NRSCCI, + Et,NHCt

(99)

Replacement of chlorine atoms in N4P4C18 has been subjected to detailed e~amination,8~ and a series of derivatives N4P4C18-n(NMePh)n [n = 1,2 (two isomers), 3,4 (five isomers), and 61 have been isolated, the mode of replacement being predominantly non-geminal. The preparation of methoxy-derivatives N4P4(OMe)8-n(NMePh)n (n = 2,4, and 6) and the extensive use of lH n.m.r. spectroscopy enabled structural assignments to be made. N4P4C18 reacts with methylamine in chloroform solution to give N,P4(NHMe), and (100) (together with its hydrochl~ride).~~ The structure of (100) was established by n.m.r.

MeHN NHMe

s4 J. M. E. Goldschmidt and E. Licht, J. Chem. SOC., Dalton Trans., 1979, 1012. 85 D. J. Lingley, R. A. Shaw, M. Woods, and S. S . Krishnamurthy, Phosphorus Sulfur, 1978,4,

86 Z . Biran and J. M. E. Goldschmidt, Synth. React. Znorg. Metal-Urg. Chem., 1978, 8, 323. 87 Z. Biran and J. M. E. Goldschmidt, J. Chem. SOC., Dalton Trans., 1979, 1017.

89 S. S. Krishnamurthy, M. N. Sudheendra Rao, R. A. Shaw, A. R. Vasudeva Murthy, and M.

379.

B. Thomas and H. Scheler, 2. Chem., 1978, 18, 342.

Woods. Inorx. Chem. 1978 17 1527

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Phosphazenes 237

spectroscopy and by X-ray crystallography (see Section 8). As reported last year, complexes formed by N4P4(NHMe), and platinum halides have anti-cancer properties; a patent application relating to this work has now appeared.g1

There have been several reports of aminolysis studies on (101) and related compounds, and elegant examples of the use of n.m.r. spectroscopy for structural assignments have been demonstrated. Reactions with dimethylamineQ2 and piperidineQ3 initially occur at one of the sulphur atoms, and amino-derivatives for all degrees of chlorine-atom substitution have been isolated, including several isomeric products. By contrast, reactions with n-butylamine initially occur at the phosphorus atom, and an increasing degree of reactivity at sulphur relative to phosphorus is shown on passing from n- to s- to t-b~tylamine.~~ Reactions of the fluorides (102) and (103) with the heterocyclic amines piperidine, pyrrolidine, and morpholine invariably occur at the phosphorus atoms, and in no case was displacement of fluorine ~ b s e r v e d . ~ ~ The monophosphazene Ph,P=NH is not particularly reactive towards (101), (102), or (103) and related compounds, reaction always occurring at the phosphorus atoms to introduce one phosphazenyl grouping (104) per molecule.96 The aziridinyl derivatives (105) have been obtainedg7 by the reaction of the analogous phosphorus chlorides with aziridine and tri- ethylamine. Reactions with aziridine also occurred at -CCl= centres, although it was not clear to what extent this happened.

c1 N=PPh,

‘P’ + Ph,P=NH __f ‘P’ + Ph,PNH,Cl

‘a ‘Cl

90 S. S. Krishnamurthy, K. Ramachandran, and M. Woods, J. Chern. Res., 1979, (S ) 92;

91 H. R. Allcock, R. W. Allen, and J. P. O’Brien, Ger. Offen. 2 71 1 456 (Chem. A h . , 1979,90,

92 B. de Ruiter and J. C. van de Grampel, Inorg. Chim. Acta, 1978, 31, 195. 98 H. H. Baalmann, R. Keizer, J. C. van de Grampel, and C. Kruk, 2. Naturforsch., Teil B,

94 J. B. van den Berg, E. Klei, B. de Ruiter, J. C. van de Grampel, and C. Kruk, Red . Trav.

9s H. H. Baalmann and J. C. van de Grampel, 2. Naturforsch., Teil B, 1978, 33, 964. 96 A. P. Jekel and J. C. van de Grampel, Z. Naturforsch., Teil B, 1979, 34, 569. 97 L. D. Protenko, V. I. Shevchenko, P. P. Kornuta, and I. S. Trokhimenko, J. Gen. Chem.

( M ) 1267.

23 245).

1978, 33, 959.

Chim. Pays-Bas, 1976,95,206.

USSR (Engl. Transl.), 1977,47, 2008.

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238

R'

Organophosphorus Chemistry

(105) a; R' = C1, R' = Me, R3 = Et b; R' = NC,H,, R2 = H, R3 = C1 c; R' = NC2H,, Rz = R3 = C1 d; R' = NC,H,, R2 = Me, R3 = C1

Alkoxy-, Aryloxy, and Thioalkoxy-derivatives.-The synthesis of the (fluoro- alkoxy-phosphazenes N,P,CI,-, [OCH,(CF,),H], (n = 1-6) g* and of related compounds with mixed fluoroalkoxy-substituents, N3P3(ORp)n(OR),-n [n = 3 or 4; RF= CH2(CF2), or ,H; R= Prn, Bun, or 2-EtC6H12],99 from chlorocyclophos- phazenes and the corresponding sodium alkoxides has been reported. Members of the former series ( n = 2 4 ) were shown to have non-geminal structures. Compounds of a similar type, N3P, [OCH,(CF2)nH], (n = 0, 2, 4, and 6), are use ful as references for electron-impact and field-desorption mass spectroscopy.loO In an n.m.r. studylol of the products of rearrangement of N,P,(OMe), and N,P,(OMe),, i.e. the cyclophosphazanes (106) and (107), respectively, it was shown that (106) has two chemically shifted 31P signals, compatible with crystal-structure data.

M e 0 0

(106) (107)

The phenoxyphosphazenes N,P,CI,(OPh), and the monosodium derivatives of diols, NaOROH [R = (CH,), (n = 2, 3,4, or 6), CH,O(CH,),, or CH,CHMe], givelo, products of the type N,P,(OPh),(OROH), except when R is (CH,)* (n= 2 or 3), when the products are believed to contain the Z=PO(CH,)~O ring system. The structurally related compounds N,P,(OPh),-n(OArOH)n (n = 2 or 3 ; Ar = residue of dihydric phenols) lo3 and N,P,(OPh)n(glycidyloxy)6-n lo* have 96

9s

100

101

102

109

104

V. G. Derendyaeva, Yu. V. Kolodyazhnyi, S. G. Federov, S. K. Alieva, S. F. Zapuskalova, G. S. Gol'din, and 0. A. Osipov, J. Gen. Chem. USSR (Engl. Transl.), 1977, 47, 2286. S. G. Federov, G. S. Gol'din, S. F. Zapuskalova, N. G. Petrova, and A. N. Naumov, J. Gen. Chem. USSR (Engl. Transl.), 1978, 48, 483. K. L. Olson, K. L. Rinehart, and 5. C. Cook, Biomed. Mass Spectrom., 1977,4,284 (Chem. Abs., 1978, 89, 41 626). K. S. Dhathrathreyan, S. S. Krishnamurthy, A. R. Vasudeva Murthy, R. A. Shaw, and M. Woods, Inorg. Nucl. Chem. Lett., 1979, 15, 109. K. Brandt, V. V. Kireev, and V. V. Korshak, J. Gen. Chem. USSR (Engl. Transl.), 1978, 48, 623. L. A. Alekseenko, V. V. Kireev, and D. F. Kutepov, J. Gen. Chem. USSR (Engl. Transl.), 1978,48, 1153. L. A. Alekseenko, V. V. Kireev, and D. F. Kutepov, Plust. Mussy, 1978, 13 (Chem. Abs., 1979, 90, 104 709).

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Phosphazenes 239 also been reported; the latter can improve the thermal stability of epoxy-resins. The synthesis of aryloxycyclophosphazenes has also been described in patent applications. l o s s lo8

A series of thioethoxy-derivatives N3P3C1,-,(SEt), (n = 1-6) and NdP4C18-n- (SEt)n (n = 1-8) have been synthesized,lo7 and n.m.r. studies indicate that, as expected, replacement of a chlorine atom occurs geminally. Descriptions of applications of 16N n.m.r. spectroscopy in phosphazene chemistry are beginning to appear,108s109 and some of the above thioethoxy-derivatives, as well as the thiophenoxy-derivatives N3P3C&3Phn (n= 2, 4, and 6), have been studied by this technique. It is noteworthy that the coupling constant lJ(PN) generally decreases as the coupling constant aJ(PNP) increases. lo8

Alkyl- and &]-derivatives.-Alkenyl-phosphazenes (1 08), (1 09), and (1 10) have been obtainedllO from the reactions of organolithium reagents with fluoro- phosphazenes (see Scheme 6). Geminal N3P,F4(Ph)CH2CH=CH2 was also prepared, by an analogous method. Compound (108) undergoes the expected addition reactions across the olefinic bond with bromine and with hydrogen, and (110) forms copolymers with styrenes when dibenzoyl peroxide is used as a catalyst.lll, lZ

Reagents: i, LiCHzCH=CHz; ii, LiC(==CHa)Mc.

Scheme 6

Interesting new phosphino-phosphazenes (1 12) and (1 13) have been prepared1l8 from (1 11) and their reactions with sulphur studied. In these reactions, compound (113) is oxidized at the tervalent phosphorus atom, but (1 12) gives (1 14). Further examples of phosphino-phosphazenes are provided by compounds (1 15) and (1 16). Friedel-Crafts reactions of a series of amino-cyclophosphazenes N3PsCls-n- (NR1R2)n (R1, Ra include H, alkyl, and benzyl) with benzene give phenyl- substituted products and/or hydrocarbons. 114 Phenylation occurs most readily at =PCl(NRfR2) and=PClPh centres. The same type of reaction has been studiedlf6

105 R. L. Dieck and E. J. Quinn, Ger. Offen. 2 758 748 (Chem. Abs., 1978, 89, 180 852). l06 T. Skwarski and B. Laszkeiwicz, Pol. P. 92 874 (Chem. Abs., 1978, 89,43 521). 107 B. Thomas and G. Grossmann, 2. Anorg. Allg. Chem., 1979, 448, 100. 108 B. Thomas and G. Grossmann, 2. Anorg. AIIg. Chem., 1979, 448, 107. 109 B. Thomas, G. Seifert, G. Grossmann, and D. Scheller, Z. Phys. Chem. (Leipzig), 1979,

110 J. G. DuPont and C. W. Allen, Inorg. Chem., 1978, 17, 3093. 111 J. G . DuPont and C. W. Allen, Macromolecules, 1979, 12, 169. 112 C. W. Allen and J. G. DuPont, Ind. Eng. Chem. Prod. Res. Dev., 1979, 18, 80 (Chem. Abs.,

119 A. Schmidpeter and J. Hoegel, Chem. Ber., 1978, 111, 3867. 114 S. K. Das, Masood-U1-Hasan, R. A. Shaw, B. C. Smith, and M. Woods, 2. Naturforsch.,

115 J. B. van den Berg and J. C. van de Grampel, Z. Narurforsch., Teil B, 1979.34. 27.

260,225.

1979, 90, 104 389).

Teil B, 1979, 34, 58.

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240 Organophosphorus Chemistry

/A \/ Mk \a

+ /iH / R'R2PPR'R2

Me' 'PR'E \ 1: /4 \PH + R'R'PC1 'P'

M k 'H

(111) (1 12) \pH

// = -Ph,P=N---PPh,=N- (113)

Me/ \PR'R2 R', R2 = Me, Me; Me, Ph; Phi Ph; or OCH,CH,O

with (117). Compound (118) is obtained in three isomeric forms when the mole ratio of (117) to AlCl, is 1 :2, but with excess of AICls two isomers of (119) are formed, which can also be obtained from (120), benzene, and excess AICl,.

6 Polymeric Phosphazenes This topic has been reviewed several times,lls-lzo but unfortunately these reviews

116 H. Struszczyk, Polimery (Warsaw), 1978, 23, 77 (Chem. A h . , 1979, 90, 7178). 117 H. Saito, Kagaku (Kyoto), 1978, 33, 250 (Chem. Abs., 1978, 88, 191 509). 118 I. Cho and K. D. Ahn, Pollino, 1978, 2, 105 (Chern. Abs., 1979,90,24 024). 119 M. Chirca and C. Gheorghiu, Reu. Chirn. (Bucharest), 1978, 29, 1015 (Chern. Abs., 1979,

l a 0 R. E. Singler and G. L. Hagnauer, Organomet. Polym. (Symg.), 1977, 257 (Chem. Abs., 90, 13 822).

1079 QO i in7mi

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Phosphazenes 241

C1 NHHu” \ /

/

(120) (pyr = pyrrolidino)

are not readily available. Other reviews havecovered biomedical applications 121, l 2 B

and mesomorphic structures. 123, 124

The polymerization of cyclic chlorophosphazenes is catalysed by metal salts of transition elements,126 by sulphur,la6 and by alkylaluminium *las

in the latter case with little or no gel formation. Improvements in the synthesis of (NPCl& (n= 3-10) can be obtained by careful addition of phosphorus penta- chloride to reaction mixtures that contain ammonium chloride.129

Polymers of the type (NPF2)n are useful substrates for the preparation of substituted polymers (NPX,)% (X = OCH,CF,, aryloxy, or amino),13o although aminolysis also results in P-N chain cleavage and the formation of polymers of the type WF(NHR)ln. Generally, P-N chain cleavage is reduced relative to that occurring in the analogous chlorides (NPC12)n, and the latter amino- derivative provides a route to polymers, for example, [NP(NHBun)(OCH2CF,)ln. Amino-substituted phosphazene polymers such as [NP(NHMe),ln can act as carrier ligands for FeIII- and FeII-protoporphyrin IX.131 Numerous improve- ments in the synthesis of fluoroalkoxy-phosphazene polymers have been

1 2 1 H. R. Allcock, Organomet. Chem. (Symp.), 1977,283 (Chem. Abs., 1978,89, 12 006). 128 C. W. R. Wade, S. Gourlay, R. Rice, A. Hegyeli, R. E. Singler, and J. White, Organomet.

1-23 N. S . Schneider, C. R. Desper, and J. J. Beres, ‘Liquid Crystals and Ordered Polymers’,

1-24 N. S. Schneider, C. R. Desper, and R. E. Singler, Organomet. Polym. (Symp.), 1977, 271

125 M. S. Pritchard, A. S. Hilton, M. L. Stayer, and T. A. Antkowiak, Ger. Offen. 2 816 277

1-26 Firestone Tire and Rubber Co., Belg. P. 866 783 (Chem. As., 1979, 90, 88 058). 197 D. L. Snyder, M. L. Stayer, and J. W. Kang, U.S. P. 4 123 503 (Chem. Abs., 1979,90,

1-28 Firestone Tire and Rubber Co., Fr. Demande 2 372 117 (Chem. A h . , 1979, 90,

129 J. Kuncicky, M. Nemec, and J. Vlk, Czech. P. 173 940 (Chem. Abs., 1979, 90,

130 H. R. Allcock, D. B. Patterson, and T. L. Evans, Macromolecules, 1979, 12, 172. 1 9 1 H. R. Allcock, P. P. Greigger, J. E. Gardner, and J. L. Schmutz, J . Am. Chem. SOC., 1979,

Chem. (Symp.), 1977,289 (Chem. Abs., 1978,89, 30 731).

ed. A. Blumstein, Academic Press, New York, 1978, p. 299.

(Chem. A h . , 1978,89, 6794).

(Chem. Abs., 1979,90, 39 442).

72 660).

88 076).

124 057).

101, 606.

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242 Organophosphorus Chemistry

~ u g g e s t e d , ~ ~ ~ - ~ ~ ~ and the stabilization of these polymers towards thermal degradation can be achieved by addition of zinc and magnesium complexes.137-13Q The polymers [NP(0R),ln (R=Et, CH2CF3, or Ph) and the oligomers (NPR,), (R=OEt, OCH2CF3, OPh, or NMe,) are moderately resistant to the effects of U.V. radiation.140 Sodium methoxide can act as a catalyst for the ring-opening polymerization of cyclic pho~phazenes,~~~ and the properties of the elastomers obtained by heating N,P3C16 with siloxanes have been investigated.14e

The synthesis of aryloxyphosphazene polymers is still of considerable i n t e r e ~ t , l ~ ~ - l ~ ~ and new advances include the preparation of structurally regulated species [NP(OPh)(OC6H,C1-p)]n which have properties superior to those of the analogous random polymers, 146 and azonaphthol-derived polymers which form coloured films and 148 The recovery of solvents used in the synthesis of phosphazene polymers has been described. 149

Fluoroalkoxy-polymers have an increasingly wide range of applications, including fuel hoses, 150 coatings for particles used in an electrophotographic process,151 as flotation agents, lS3 and as a sealant for alkaline batteries.16s-168

132 J. W. Fieldhouse, D. F. Graves, W. M. Cole, M. L. Stayer, and S. L. Fenske, U.S. P. 4 129 529 (Chem. Abs., 1979,90, 122 483).

133 J. W. Fieldhouse, D. F. Graves, W. M. Cole, M. L. Stayer, and S. L. Fenske, U.S. P. 4 128 710 (Chem. Abs., 1979,90, 88 059).

184 S. V. Vinogradova, D. R. Tur, V. V. Korshak, L. M. Gil'man, and N. N. Kararova, Vysokomol. Soedin., Ser. A, 1978,20, 1491 (Chem. Abs., 1978,89, 198 199).

135 M. A. Andreeva, E. G. Bulycheva, E. A. Lyubovskaya, G. L. Slominskii, V. V. Korshak, and S . V. Vinogradova, Vysokomol. Soedin., Ser. A, 1979,21, 48 (Chem. Abs., 1979, 90, 169 033).

136 V. N. Sharov, G. A. Ivanova, V. V. Korol'ko, V. P. Mileshkevich, A. L. Klebanskii, V. V. Pchelintsev, E. A. Siderovich, and S . K. Kurlyand, Dokl. Akad. Nauk SSSR, 1978, 239, 1113.

137 D. F. Lohr, R. W. Koch, and D. N. Schultz, U.S. P. 4 139 523 (Chem. Abs., 1979,90, 170 001).

138 D. F. Lohr, Ger. Offen. 2 811 525 (Chem. Abs. 1979, 80,24 538). 139 G. S. Kyker and J. K. Valaitis, Adu. Chem. Ser., 1978, 169, 293 (Chem. Abs., 1979, 90,

140 J. P. O'Brien, W. T. Ferrar, and H. R. Allcock, Macromolecules, 1979, 12, 108. 141 R. L. Dieck and A. B. Magnusson, Ger. Offen. 2 745 885 (Chem. Abs., 1978,89,25 099). 142 S. Yajima, J. Hayashi, and H. Kobayashi, Japan. Kokai Tokkyo Koho 78 81 600 (Chem.

1-43 R. L. Dieck, T. B. Garrett, and A. B. Magnusson, Ger. Offen. 2 754 245 (Chem. Abs.,

144 L. Goldfarb, N. D. Hann, and R. L. Dieck, J. Polym. Sci., Polym. Chem. Ed., 1978, 16,

145 V. V. Kireev, L. A. Alekseenko, D. F. Kutepov, and V. V. Korshak, Vysokomol. Soedin.,

1413 R. L. Dieck and E. J. Quinn, U.S. P. 4 108 805 (Chem. Abs., 1979,90, 72 830). 147 H. R. Allcock, S. D. Wright, and K. M . Kosydar, Macromolecules, 1978, 11, 357. 148 H. R. Allcock, S. D. Wright, and K. M. Kosydar, Ger. Offen. 2 821 013 (Chem. Abs., 1979,

149 C. R. Bergeron, U.S. P. 4 141 937 (Chem. Abs., 1979, 90, 139 619). 150 T. A. Antkowiak, U.S. NTIS A.D. Rep. 1977, A,D.-A047960, Gou. Rep. Announce Index

151 P. Datta, U.S. P. 4 097 617 (Chem. Abs., 1978, 89, 207 285). 152 B. N. Laskorin, A. V. Lomonov, S. N. Shcherbakova, B. N. Syromyatnikov, and R. S.

153 M. Yoshida and T. Kudo, Japan. Kokai Tokkyo Koho 78 107 623 (Chem. Abs., 1979,90,

154 M. Yoshida, H. Ohbayashi, and T. Kudo, Japan. Kokai Tokkyo Koho 78 122 727 (Chem.

56 031).

Abs., 1978, 89, 164 746).

1978, 89, 110 838).

1505.

Ser. A , 1979, 21, 108 (Chem. Abs., 1979, 90, 152 886).

90, 72 677).

(U.S.), 1978, 78, 145 (Chem. Abs., 1978, 88, 171 465).

Ryzhkova, USSR P. 626 652 (Chem. Abs., 1978, 89,218 361).

31 119).

A h . , 1979, 90, 63 567).

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Phosphazenes 243

Other polymers have been obtained from poly(phenylquinoxa1ine) and N,P,(NCS)6169 and from the hydrolysis of alkoxy-derivatives of (NPCI,)n,170 the latter being useful as a cation-exchange material.

7 Phosphazenes as Fire Retardants The fire-retardant properties of phosphazenes have been discussed in recent reviews. 171-176 Alkoxy- and aryl-phosphazenes form the subject of many patents relating to fire r e ~ i s f a n c e , ~ ~ ~ - ~ ~ ~ and of specific applications relating to synthetic fibres,180-185 natural fibres,186~187 and foaming agents.lssF 180 The amino-

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172 173 174 175

176

177

178 179 180 181 182

M. Yoshida, H. Ohbayashi, and T. Kudo, Japan. Kokai Tokkyo Koho 78 122 728 (Chem. Abs., 1979, 90, 78 437). T. Yasui and H. Hisamatsu, Japan. Kokai Tokkyo Koho 78 128 700 (Chem. Abs., 1979, 90,88 928). K. Yokohama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 131 441 (Chem. Abs., 1979,90,90 109). M. Yoshida, H. Ohbayashi, and T. Kudo, Japan. Kokai Tokkyo Koho 78 139 143 (Chem. Abs., 1979, 90, 124 662). M. Yoshida, H. Ohbayashi, and T. Kudo, Japan. Kokai Tokkyo Koho 78 145 029 (Chem. Abs., 1979, 90, 129 491). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 139 142 (Chem. Abs., 1979,90, 129 492). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 139 141 (Chem. Abs., 1979,90, 129 493). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 139 140 (Chem. Abs., 1979, 90, 129 494). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 139 139 (Chem. Abs., 1979,90, 129 495). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 78 139 138 (Chem. Abs., 1979,90, 129 496). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 79 01 830 (Chem. Abs., 1979, 90, 159 098). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 79 01 831 (Chem. Abs., 1979, 90, 159 101). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 79 01 839 (Chem. Abs., 1979, 90, 159 102). K. Yokoyama, A. Kawakami, N. Kotani, M. Yoshida, T. Kudo, and H. Ohbayashi, Japan. Kokai Tokkyo Koho 79 01 838 (Chem. Abs., 1979, 90, 159 103). Yu. S. Kochergin, A. P. Travnikova, A. A. Askadskii, E. S. Krongauz, G. L. Slominskii, and V. V. Korshak, Vysokomol. Soedin., Ser. A , 1978, 20, 839 (Chem. Abs., 1978, 88, 191 907). B. N. Laskorin, A. V. Lomonosov, and E. V. Kremneva, USSR P. 626 099 (Chem. Abs., 1978, 89, 216 301). C. Gheorghiu and M. Chirca, Rev. Chim. (Bucharest), 1978,29,210 (Chern. Abs., 1978,89, 75 671). H. Struszczyk, Polimery (Warsaw), 1978, 23, 41 (Chem. Abs., 1978 89 25 479). J. A. Beckman Rev. Gen. Caoutch. Plast., 1976, 53, 95 (Chem. Abs., 1978, 89, 25 777). N. Tanaka, Kagaku Kojo, 1977,21, 89 (Chem. Abs., 1978,89, 147 412). D. Popescu and A. Zaharia, Ind. Usoara: Text. Tricotaje Confectu Text., l978,29,226(Chem. Abs., 1979, 90, 73 148). M. Kajiwara, Sen'i Kako, 1977, 29, 495; 1978, 30, 61, 115, 285 (Chem. Abs., 1978, 89, 25 849, 25 701, 60 281, 147 986). R. L. Dieck, E. J. Quinn, and A. B. Magnusson, Ger. Offen. 2 758 747 (Chem. Abs., 1978, 89, 181 071). D. F. Lawson and T. C. Cheng, Fire Res., 1978, 1, 223 (Chem. Abs., 1979, 90, 72 617). A. E. Oberster and D. F. Lawson, U.S. P. 4 064 095 (Chem. Abs., 1978,89,45 161). A. Wilson, J. Coated Fabr., 1978, 233 (Chem. Abs., 1978, 88, 192 582). D. R. Brackenridge, U.S. P. 4 079 035 (Chem. Abs., 1978, 89, 44 646). R. J. Guschl, U.S. P. 4 117 041 (Chem. Abs., 1979, 90, 7517).

references 18 3-1 89 overleaf

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244 Organophosphorus Chemistry

derivatives [NP(NH,),],-, form fire-resistant foaming agents on condensation with formaldehyde,leO and N3P3(NHNH& imparts flame resistance to cellulose xanthate. lgl The condensation products of biphenyls with N3P,Cl, are fire- resistant polymers.1g2

8 Molecular Structures of Phosphazenes that have been determined by Diffraction Methods

Compound Comm en is*

Me,P=N SiMe,

CN

[ Ph,P=N-===PPh,]+ [ H Os,(CO),S] -

183

184

185

186

187 188

189

190

191

P=N 1.654(3) A LPNN 110.2(2)”

Ref:

8

Elect ro n-diffract ion study’. 193 P=N 1.542(5) A;LPNSi 144.6(1.1)” Angle at N is consistent with CND0/2 calculations.

P=N 1.6 1 S(2) A LPNC 130.0 (1 )”

P=N 1.580(20), 1.557(17) LPNP 144.7(13)”

LPNP 142.9(4)”

* All structurcs wcrc obtained by X-ray diCt‘raction unless otherwise stated.

21

194

195

Sandoz-Erfindungen Verwaltungsgesellschaft m.b.H., Austrian P. 343 78 1 (Chem. Abs., 1978, 89, 112 247). T. Skwarski, B. Laszkiewicz, J. Dutkiewicz, and 2. Wojtaszek, Pol. P. 93 515 (Chem. A h . , 1979, 90, 105 550). Z. Bielawski, J. Dutkiewicz, Z. Lewandowski, B. Laszkiewicz, T. Skwarski, and H. Strussczyk, Pol. P. 92 909 (Chem. Abs., 1979, 90, 122 995). J. W. Hudson, J. T.-F. Kao, and C. W. Lanier, Br. P. 1 497264 (Chem. Abs., 1978, 89, 181 191). M. Reidel and R. Wolf, Swiss P. 608 026 (Chem. Abs., 1979,90,73 549). A. H. Gerber and T. C. Paterson, Goo. Rep. Announce Index (U.S.), 1978,78,212 (Chem. Abs., 1979, 90, 7370). K. Brandt, V. V. Kireev, and V. V. Korshak, Vysokomol. Soedin., Ser. B, 1978, 20, 213 (Chem. Abs., 1978, 89, 110 907). E. Kobayashi and T. Kanayama, Japan. Kokai Tokkyo Koho 78 291 (Chem. Abs., 1978, 89,130 400). S. A. Kocharov, M. A. Tyuganova, and Z. A. Rogovin, Khirn. Volokna, 1978,46 (Chem. Abs.. 1978. 89, 91 062).

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Phosphazenes

Compound

[ Ph,P=N=-PPh,] +

[ IosKo), 5 1 -

245

Comments* Rex

P=N 1.570(18), 1.568(16) A 196 LPNP 142.3(13)"

N,P3C1,N=PPh,

N,P,CI,( N Me,), ( 2- tu t l~z . s~ -~ i s -6 - t ra i~s -8 )

Conformation of -N=PPh, is such that eyo P=N is perpendicular to P-CI. Preliminary report in Vol. 9

197

PA-N 1.63 A; remaining P-N 1.54-1.57 A

75

P-N (endo) 1.528-1.580 A 198 mean P-N (exo) 1.625 A

P-N(ettdo) 1.575(5), l.S74(6)t% 199,200 P--N(exo) 1.679(6), 1 :656(7) A Saddle-shaped ring

(N H Me) P

/ N // Me \ Second crystal structure of this type. 20 1

P-N(endo) 1.581-1.615 A; P-N(bridge) 1.723(6), 1.709(6) A

MeHNP-N-PNHMe //

'N \p/N (NHMe),

* All structures were obtained by X-ray diffraction unless otherwise stated.

192

193 194

195

196

197

198 199 200 201

E. I. du Pont de Nemours and Co., Japan. Kokai Tokkyo Koho 77 153 987 (Chem. Abs., 1978, 89, 76 312). E. E. Astrup, A. M. Bouzga, and K. A. Ostaja-Starzewski, J. Mol. Struct., 1979, 51, 51. B. F. G. Johnson, J. Lewis, D. Pippard, and P. R. Raithby, Acta Crystallogr., Sect. B, 1978,34, 3767. D. W. Hart, R. G. Teller, C.-Y. Wei, R. Bau, G. Longoni, S. Campanella, P. Chini, and T. F. Koetzie, Angew. Chem., Int. Ed. Engl., 1979, M-80. A. V. Rivera, G. M. Sheldrick, and M. B. Hursthouse, Acta Crystallogr., Sect. B, 1978, 34, 3376. Y. Sudhakara Babu, H. Manohar, and T. S. Cameron, Acta Crystallogr., Sect. B, 1979, 35, 1410. M. J. Begley and D. €3. Sowerby, J. Chem. Sot., Dalton Trans., 1978, 1094. J. -0 . Bovin, J. Galy, J.-F. Labarre, and F. Sournies, J. MoZ. Struct., 1978, 49, 421. J . - 0 . Bovin, J.-F. Labarre, and J. Galy, Acta Crystallogr., Sect. B, 1979, 35, 1182. T. S. Cameron, R. E. Cordes, and F . A. Jackman, Acta Crystallogr., Sect, B, 1979, 35, 980.

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246 Compourzd

Organophosphorus Chemistry Comments* Ref.

Two crystal structures, with X = H 202 and COPh; ring has tub conformation in both cases. X = H , mean P-N(endo) 1.609(9) A; P-N(exo) 1.679(2) A X = COPh, mean P-N(endo) 1.595(4) A; P-N(exo) 1.655(2) A

Structures of two out of three 20 3 monoclinic modifications obtained at 110 K . (a ) boat-shaped ring

( b ) irregularly shaped ring mean P-N 1.549(5) A

mean P-N 1.546(5)R

* All structures were obtained by X-ray diffraction unless otherwise stated.

SO* H. P. Calhoun, R. T. Oakley, N. L. Paddock, S. J. Rettig, and J. Trotter, Can. J . Chcm.,

103 J. G. Hartsuiker and A. J. Wagner, J. Chem. SOC., Dalton Trans., 1978, 1425. 1978,56, 2833.

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