ANGEWANDTE CHEMIE V O L U M E 4 - N U M B E R 12

D E C E M B E R 1 9 6 5

PAGES 1 0 0 7 - 1 102

New Products of Reaction of Organometallic Compounds with Sulfur, Selenium, Tellurium, and Phosphorus

BY DR. HERBERT SCHUMANN AND PROF. DR. MAX. SCHMIDT

INSTITUT FUR ANORGANISCHE CHEMIE DER UNIVERSITAT W R Z B U R G (GERMANY)

Bond fission of molecular sulfur, selenium, and tellurium by lithiotriphenylmetal compounds (of Ge, Sn, Pb) is summarized. The products are suitable as starting materials for synthesis of new “ether analogues”. Transphenylation with tetraphenylstannane is interpreted as a high-temperature variant of the usual fission of chalcogen molecules by nucleophilic reagents. In principle, transphenylation can be applied also to other elements, as is illustrated for phosphorus. In the syntheses achieved, many of the tin-phosphorus compounds arising as intermediates can be isolated.

I. Introduction

The strikingly easy fission, by nucleophilic reagents, of sulfur-sulfur bonds in compounds (“modifications”) of sulfur with itself and in sulfane chains has been ascribed by us to a marked tendency of the sulfur atom to expand its octet, thereby forming multiple bonds be- tween sulfur atoms. The stability and behavior of such sulfur-sulfur bonds, and the appearance of favored electrophilic centers in sulfur chains, are readily inter- preted in terms of this assumption of a delocalized electron system 111. This hypothesis provides a simple explanation of the formation of fission products of sulfur (S), by nucleophilic reagents such as SO3H-, SH-, SR-, CN-, RC-C-, NO;, HASO:-, NR;, etc. Such fission reactions of S-S bonds have not only analytical but also considerable preparative importance; they can be rationally extended to the sulfur homologues selenium and tellurium. Among the particularly good “thiophilic” reagents are carbanions such as occur in organolithium and Gri- gnard compounds. Molecular sulfur reacts spontane- ously with these carbanions, yielding mercaptides or thiophenoxides. We asked ourselves whether analogous reactions could be carried out with compounds that are formally derived from organometallic compounds in that the metalated carbon atom is replaced by germani- um, tin, or lead. The expected covalent chaicogen com- pounds should be very reactive and should open a

[I] M . Schmidt, Osterr. Chemiker-Ztg. 64, 236 (1963). .

simple preparative route to the little investigated field of organometallic derivatives (with germanium, tin, or lead) of chalcogens.

II. Chalcogen Fission by Lithiotriphenyl-germane, -stannane, and -plumbane

The formation of formal analogues of triphenylmethyl- lithium by replacement of the tertiary carbon atom by Ge, Sn, or Pb is illustrated by the well-known lithio- triphenylstannane [2-19J. This is best prepared by treat-

[2] C. A . Kraus and W . V . Session, J. Amer. chem. Soc. 47, 2361 (1925). [3] R. F. Chambers and P. C . Scherrer, J . Amer. chem. SOC. 48, 1054 (1926). [4] C. A. Kraus and S. L. Forster, J. Amer. chem. Soc. 49, 457 (1927). [5] C. A. Krausand W . H . Kahler, J . Amer. chem. Soc. 55, 3531 (1933). [6] H. Gilman and R. V. Joung, J. org. Chemistry I, 315 (1963). [7] G. Wittig, R . Mangold, and G. Felletschin, Liebigs Ann. Chem. 560, 116 (1940). [8] G. Wittig and F. J. Meyer, Liebigs Ann. Chem. 571, 167 (1951). [9] H. Gilman and S. D. Rosenberg, J. Amer. chem. Soc. 74, 531 (1952). [lo] H, Gilman, L. Summes, and R. W . Leeper, J. org. Chemistry 17, 630 (1952). [ l l ] H. Gilman and E. Bindschadler, J. org. Chemistry 18, 1675 (1953). 1121 H. Gilman and C. A. Gerow, J. Amer. chern. Soc. 77, 5509, 5740 (1955).

Angew. Chem. internat. Edit. Yol. 4 (1965) 1 No. 12 1007

iiig chlorotripheiiylstannane with an excess of lithium in tetrahydrofuran 11% 191; the primary product, formed according to Eq. (a), is hexaphenyldistannane, which is then more slowly cleaved according to Eq. (b).

Germanium [201 and lead compounds [211 can be similarly obtained. These reactive "metal organyls" R3MLi have not yet been isolated in pure free form. However, their solutions in tetrahydrofuran can be readily obtained on removal of lithium chloride and the excess of lithium under dry nitrogen. Even under mild conditions the compounds R3MLi (M = Ge, Sn, or Pb) react exactly like carbanions with sulfur, selenium, and tellurium in tetrahydrofuran, moisture being excluded. This reac- tion [see Scheme (c)] can be illustrated for tin/sulfur. The bonding in the s!3 ring is symbolized as in structures ( la ) and (Ib). One of the electronically equivaIent but

still electrophilic sulfur atoms in the s8 ring is attacked by, c'.g., the nucleophilic SnR3e anion (R = C&), whereby ring cleavage leads to the octasulfane deriva- tive (2). This unsyinmetrical anion (2) is then degraded

etc .

R3Sn'S'S@ -+ R3SnS@ + R,SnS@

t + %nR3

Sa + 8 LiSnR3 + 8 Li-S-SnI13

1131 H . Gilman, D. J . Peterson, and D. Wittenberg, Chem. and Ind. 1479 (1958). [I41 H. Gilmnn and D. Wittenberg, J. org. Chemistry 23, 1063 (1 958). [I51 H . Gilmnit and G. D. Lichtenwalter, J. Amer. chem. SOC. 80, 608 (1958). [I61 C. Tamborski, F. E. Ford, and W. L. Lehn, J. org. Chemistry 27, 619 (1962). 1171 H . Gilinan, 0. L. Morrs, and S. J. Sim, J. org. Chemistry 27, 4232 (1962). [ 181 H. Schuniann, K . F. Thorn, and M . Schmidt, Angew. Chem. 75, 138 (19631; Angew. Chem. internat. Edit. 2, 99 (1963). 1191 H. Schumann, K . F. Thoin, and M . Schmidt, J. organornet. Chemistry I , 167 (1963). [20] M. C. Henry and W . E. Davirlson, J. org. Chemistry 27, 2252 (1962). [21] M. C. Henry and A. W. Krebs, J. org. Chemistry 28, 225 (1963).

stepwise by an SN2 mechanism: the ion SnR30, acting as nucleophile, attacks the electrophilic center, namely the terminal S atom with its formal octet [the negative charge is equally distributed ocer the R3Sn-(S),- chain], and ejects the weaker nucleophilic group R3SnS,-1 e. In each cleavage step, down to x = I , a new (terminal) electrophilic center is created. The &st step - ring-opening - is rate-determining since it involves a formal electron decet; the further steps involve formal octets. Selenium and tellurium react in principle like sulfur. Thus, solutions of R3MXLi (R = C6H5; M = Ge, Sn, or Pb; X = S, Se, or Te) [19~21-241 in tetrahydrofuran can be obtained fairly easily. As expected, compounds R3MXLi are sensitive to solvolysis, oxidation, and elevated temperature (condensation: 2R3MSLi + R3M-S-MR3 + Li2S) and thus can be isolated only with difficulty, if at all. Up to the present, only triphenyltin-lithium sulfide has been actually isolated c19l; it forms colorless crystals and is dimeric in benzene, probably forming a four- membered ring (3). Isolation is not necessary if the compounds R3MXLi are to be used for syntheses that can be carried out in tetrahydrofuran (see Section i l l ) .

I Li

It has not yet been possible to synthesize trimethyl- germanyl-lithium chalcogenides corresponding to t -

butyl mercaptides by the above procedure because the lithiotrimethylgermane, (CH&GeLi, needed as starting material is not yet available. Ruidiscli 1251 prepared ti-i- methylgermanyl-lithium chalcogenides in a different way: dichlorodimethylgermane and triethy Iammonium sulfide in benzene solution afford the cyclic, trimeric di- methylgermanium sulfide; the corresponding selen- ide, [(CH3)2GeSe]3 (4), is formed from sodium selenide 1261. These cyclic inorganic compounds are smoothly and quantitatively cleaved by methyl-lithium, yielding the desired "mercaptides" according to reac- tion (d).

H3C;Ce/Se\GeLH3 H:C I I 'cH3 + 3 LiCH3 - 3 Li-Se-Ge(CHs),

Se, ,Se

H3CNGe\CH3 (4 )

(CH3)3GeSLi[251 (decornp. M 85 "C) and (CH&GeSeLi 1271

(decomp. M 65OC) can be obtained as colorless solids. (C6H&SnC12 reacts with lithium, in principle like

(22) H. Schumann, K . F. Thorn, and M . Schmidt, J. organomet. Chemistry 4, 22 (1965). (231 H. Schumann, K. F. Thorn, and M . Schmidt, J. organomet. Chemistry 2, 361 (1964). [241 H. Schuinann, K . F. Thoni, and M Schniidt, J. organomet. Chemistry 4, 28 (1965). [25] I . Ruidisch and M . Schmidt, Chem. Ber. 96, 1424 (1963). [26] M . Schmidt and H. Ruf, J. inorg. nuclear Chem. 25, 557 (1963). [27] I. Ruidisch and M. Schmidt, J. organomet. Chemistry 1, 160 (1963).

-

1008 Angew. Chem. internnt. Edit. 1 VoG. 4 (1965) No. 12

(C6H5)3SnCIr yielding (C6H&SnLi2 (not isolated), which with sulfur affords the unusually sensitive and reactive (C6H&Sn(SLi)2 [2*'.

Compound

Table 1. "Ether analogues" prepared by double decompositiou according to reaction (e).

1 M.p. ["C] I Ref

Compound

120(decomp.) 145 117

136(decomp.) 150

1 29

M.p. [ "Cl

138 137 I29 144 138 I40

I221 I221 [221 1231

1241 [231

-22 -27 - 8 -12 -19 - 6

68/12 63/10 90/12 94/12 79/12 7211

Sn-S-Sn

376 st

330 m

Pb-S-Pb Ge-S-Sn Ge-S-Pb Sn-S-Pb I I I

336 st

404 m 400 m 355 m 365 m

317 m 305 m

278 m

III. Condensation of Chalcogen Cleavage Products with Organylmetal Halides

As expected, the organylmetal chalcogenides described above (which, however, were not all isolated in sub- stance) are very reactive. Their interesting properties can be illustrated by their behavior with triorganyl- metal chlorides of the germanium, tin, and lead series. In solution they react readily, forming symmetrical and unsymmetrical formal analogues of thio-, seleno-, and telluro-ethers according to reaction (e).

Compound I M.p. ["Cl 1 Ref.

151 145 119 148 I38 101

RSMX-Li + Cl-M'R, + LiCl+ R3M-X-M'R3 (el

R = CsHS or CH3; M, M' = Ge, Sn, or Pb; X = S, Se, or Te

This reaction opens a simple preparative route to a class of compounds of which only a few representatives have been synthesized, by a considerably more circui- tous method. No covalent germanium-, tin-, or lead- tellurium compound has been described previously. Table 1 summarizes the compounds obtained by reaction (e). Other reactive halogen compounds behave analogously, as shown by the synthesis of SS-diphenyltin bis(thio- benzoate) (S) [2*1.

Compound I M.P. I "Cl/ B.P. I "Clmm] 1 Ref.

solvents such as benzene, dioxane, tetrahydrofuran, and chloroform. Particularly noteworthy is their thermal stability and, in many cases, their resistance to solvolysis. Final statements cannot yet be made about the bonding in molecules of the type R3M-X-MR3. Help should come from X-ray determination, now in progress, of the valence angles at the chalcogen atom, about which information will also be provided by further evaluation of the infrared spec- traC341 - these are almost identical in the NaCl region. Skeletal vibrations of the sulfur compounds occur between 250 and 4OOcm-1 (CsBr region); their assignment is given in Table 2. Corresponding bands are to be expected at still longer wavelengths for the Se and Te compounds. The stability of Si-0-Si bonds, which is so important in inorganic Nature, is ascribed to a noteworthy con- tribution by (p-d), bonding between oxygen and

The hexaphenyl compounds listed in Table 1 all crystallize readily; the sulfur compounds are colorless, the selenium compounds have a yellow tinge, and the tellurium compounds are yellow. They are readily soluble in anhydrous organic

Table 2. Wave-numbers [cm-11 of M-S vibrations of hexaphenyl sulfides [*I. (For clarity the phenyl and phenyl-metal vibrations are not included; s t = strong, rn = medium).

Ge-S-Ge Assignment

vas (Ge-S-Ge) vas (Sn-S-Sn) Y ~ S (Pb-S-Pb)

v(Ge-S) v(Sn-S) v(Pb-S)

vs(Ge-S-Ge) vs(Sn-S-Sn) vs(Pb-S-Pb)

417 st

385 m

['I Perkin-Elmer Model 221, CsBr optics, in Nujol suspension.

[28] H. Schumann, K . F. Thom, and M . Schmidt, J. organomet. Chemistry 2, 97 (1964). [29] R. K. Ingham, S. D. Rosenberg, and H. Gilman, Chem. 1331 H. Schumann and M . Schmidt, unpublished work. Reviews 60, 459 (1960). 1301 G . Griittner, Chem. Ber. 51, 1303 (1918).

L311 M . Schmidt and H. 1321 M. Schmidt and H. RuA Chem. Ber. 96, 784 (1963).

[34] H. Schumann and M. Schmidt, J. organornet. Chemistry 3, 485 (1965).

Chem. 73, 64 (1961).

Angew. Chem. internat. Edit. Vol. 4 (1965) I No. 12 1009

silicon. If the bridging oxygen atom of disiloxanes is replaced by the larger sulfur atom the stability de- creases drastically: Si-S bonds are extremely suscepti- ble to hydrolysis. However, study of the new chalcogen derivatives R3M-X-MR3 of Table 1 shows that the stability increases on simultaneous increase in the size of the bridgehead atom M and the bridging atom X: the grouping Ge-S-Ge is more stable than Ge-0-Ge, although Ge-Se-Ge is, on the contrary, very sensitive to hydrolysis. Again, Sn-Se-Sn compounds do not react with water and can even be recrystallized from alcohol. Thus the relations between Sn-Te-Sn and Sn-Se-Sn groupings are similar to those between Si-S-Si and Si-0-Si groupings. In consequence the Pb-Te-Pb grouping is again very stable; the hexa- phenyl derivative is not attacked even by boiling water.

Analogous observations were made for unsymmetrical “ethers.” For example, Ge-Se-Pb and Sn-Te-Pb linkages resist hydrolysis, whereas compounds with Ge-Se-Ge and Sn-Te-Sn groups can be handled only in an anhydrous atmosphere. The hexamethyl com- pounds have similar properties.

Ascribing these findings to the (p-d), constituents of the M-X-M linkages for the heavier elements (given suitable size relations in M:X), although seeming at first sight a plausible interpretation, is certainly too primitive because d- the very small energy contribution from overlap of of orbitals of the heavier atoms.

b+ 6- R3Sn-R + @ S - ( S ) - S O --p R&hS-(S),-S-R .. .. x ..

( 9) R-iSnR3 j

R,Sn-Si-(S),fS-R + (x+2) R3Sn-S-R

x R-iSnR3 ( 6 ) R = C&fs

chain - occurs analogously to Scheme (c). The triphenyl- tin thiophenoxide (6) 1361 to be expected from reac- tions (g) is unstable at 200 “C and can therefore not be isolated. The degradation thus proceeds further in accordance with Scheme (h).

RS-Sn-R fi,+ b- + @:S-SX-So e RS-Sn-S-S,-S-R F R R

(h) 51 R-jSnRzSRi

R j x R-$nRzSR RS-Sn-S-(S),j-SR - (x+2) RzSn(SR)2

( 71 R = CsHs

Diphenyltin dithiophenoxide (7), which has been prepared by a different route [361, decomposes ap- preciably below the reaction temperature, eliminating diphenyl sulfide to give diphenyltin sulfide (formally analogous to the silico-ketones = silicones) which is not stable as monomer and yields the trimer (7).

IV. Phenylation of Chalcogens by Tetraphenylstannane

Bond fission of molecular sulfur by nucleophilic reagents occurs under quite mild conditions [I]. Relations are apparently quite different if tetraphenylstannane is treated with sulfur. Sn(C6H5)4 is one of the most stable organometallic compounds; it can, for example, be heated for several h m r s at about 500 “C (b.p. 425 “C/ 760 mm) without decomposing. Nevertheless it reacts with sulfur at as low a temperature as 200 “C. As early as 1929 Bost and Borgstrom 1351 observed that diphenyl sulfide is thus formed, but, remarkably, they did not study the fate of the tin in this reaction. We have found1361 that the reaction takes place in a sealed tube at about 200°C, according to the overall equation (f). At this temperature, SnR4 is polarized by

3 Sn(CsH5h + 6 s + 3 s(csH5h + [(CsH~)zSnSl3 (f)

the “polar solvent” sulfur [*I in such a way (R3Sn-R) that a phenyl anion is foreshadowed and then, as a nucleophilic reagent, degrades the sulfur chain as shown in reactions (g). The degradation there outlined - with- out statement of the electron distribution in the sulfur

s+ s-

[35] R. W. Bost and P. Borgstrom, J. Amer. chem. SOC. 512, 192 (1929). [36] M. Schmidt, H. J . Devsin, and H. Schrimonn, Chem. Ber. 95, 1428 (1962). [“I Above the %iscosity maximum at co. 160 “C a sulfur melt has clearly a polarizing action, owing to the presence of some @ s -( S)x- s :e.

Good yields can be obtained of the products of sulfur- degradation, during which process the degrading agent is first formed from a reaction partner that has a polarizing action at high temperatures. Tin-sulfur six- membered rings are very stable; they are not attacked by boiling water. These compounds crystallize readily and are soluble in many organic solvents. If Sn(CsH5)4 is treated with a sufficient excess of sulfur, further phenyl anions are removed and high-polymeric prod- ucts are formed in which rings (8) are linked by sulfur bridges [37]. A temperature in excess of 220 “C leads - in principle by the same mechanism - to complete de- phenylation of the tin compound, with formation of di- phenyl sulfide and alloy-like “tin sulfides” which are also obtainable from the cyclic compounds (8) and the higher-polymeric subsequent products :

(RZSnS)3+ 3x S --f 3SnSx+ 3 R2S

(8)

Tetrabutylstannane - and the alkyl derivatives in general - react with sulfur even at lower temperatures. At as low as approximately 150 “C, reaction (k) occurs (for reaction of organyltin chlorides with sulfur see 9.

3 (C4HghSn + 6 S --f KC4H9hSnS13 + 3 (C4H9hS (k)

[37] M. Schmidt and H. Schumann, Chem. Ber. 96, 462 (1963). 1381 H. Schumann and M. Schmidt, Chem. Ber. 96, 3017 (1963).

1010 Angew. Chem. internat. Edit. [ Vol. 4 (I965) / No. I 2

Because of the lesser polarity of their "metal"-carbon bond, tetraphenyl derivatives of the lighter analogues of tip react only at higher temperatures [*I; the inter- mediates are no longer stable. Ge(C&)4 affords GeS, and diphenyl sulfide above 270 "C [39], and Si(C&)4 af- fords SiS, above 380 "C 1391. The higher reactivity of the n-butyl conipounds, on the other hand, still permits isolation of trimeric, cyclic dibutylgermanium sulfide [analogous to (811 and (C4H&Si-S-Si(C4H9)3, in addition to (n-C4Hg)zS, these products being formed by transalkylation 1391.

Selenium is also phenylated by tetraphenyltin at about 200 "C. Triphenyltin selenophenoxide (9) [**I is isolated in good yield as intermediate 1401. Above 240 "C

diphenylselenium (and some RzSe2) are formed along- side tin selenides, and above 270 "C also selenanthrene [cf. formula (IZ)]. Sn(C4H9)4, however, reacts at 200 "C with selenium (401 according to Equation (I), analogously

to sulfur. The corresponding phenyl derivative was obtained on treatment of R3Sn-SeLi with R2SnC12 1231, in accordance with reaction (m).

P k

2 R3Sn-SeLi + RzSnClz - R3Sn-Se-Sn-Se-SnR3

(m) + '13 (RzSnSe)s + R3Sn-Se-SnR3 R = c6H5

Reaction between tellurium and tetraphenyltin sets in, slowly, only above 240 "C; after several days it leads to good yields of diphenyltellurium and tin tellurides C411.

If the temperature is raised above 310 OC, there is fornied the previously undescribed and remarkably air-sensitive telluranthrene (ZI) (m.p. 188-190 "C), as well as benzene.

[*I Pb(CdH& probably reacts by a free-radical mechanism [391. [39] M . Schmidt and H. Schurnann, Z. anorg. ally. Chem. 325, 130 (1963). [**I Existence of the sulfur analogue (C6H5)3Sn-SC6H5 has been only inferred. [401 M . Schmidt and H. Schumann, Chem. Ber. 96, 780 (1963). [411 M. Schmidt and H. Schuinnnir, Z. Naturforsch. 19b, 74 (1964).

V. Phenylation of Phosphorus by Tetraphenylstannane

The hypothesis developed "1 for element-element bond- ing in sulfur chemistry is valid equally for other elements from the second Period onwards, and for those of the third and fifth main Group. Compounds of these elements with themselves act electrophilically, as do the chalcogens (cf. the reaction of P4 with Grignard reagents discovered independently by Rauhut and SernselL421 and by ~81331). Thus phosphorus should, like sulfur, react with tetraphenylstannane at high temperatures. The tervalency of phosphorus, of course, complicates matters and makes a direct Comparison more difficult. In prac- tice, elementary phosphorus reacts with tetraphenyl- stannane in a sealed tube above about 235 "C. At higher temperatures the end products are tin phosphide and triphenylphosphine, according to reaction (n) [43,441.

(The triphenyl derivatives of As and Sb are also readily available by this process 1441.) If the temperature is kept between 235 and 250°C and the ratio P:Sn(C6H5)4 is varied, an intermediate product of the degradation of phosphorus by carbanions can be isolated: (12) (m.p. = 110 "C, yellow, spontaneously inflammable in air), (13) (yellow oil, extremely sensitive to oxidation), (14) (m.p. 66 "C, colorless).

Covalent tin-phosphorus compounds which, with two exceptions [45,4*1, were previously unknown, generally are extremely sensitive to oxidation, which greatly increases the difficulty of isolating them from the complex reaction mixture. The products of oxidation of the tin phosphines occurring in these mixtures can, however, be obtained, cleaved with caustic soda into characteristic fragments, and thus analysed [*I. Table 3 shows the oxidized decomposition products obtained.

[*I Tin was determined [49] by X-ray emission analysis, along- side photometrically determined phosphorus. [42] H. Rauhut and P. Semsel, J. org. Chemistry 28, 473 (1963). [43] H. Schumann, H. KOpL and M. Schmidt, Angew. Chem. 75, 672 (1963); Angew. Chem. internat. Edit. 2, 546 (1963). 1441 H. Schumann, H. KOpA and M . Schmidt, 2. anorg. allg. Chern. 331,200 (1964). [45] H. Schurnann, Ff. KOpL and M . Schmidt, Chem. Ber. 97, 1458 (1 964). [46] H. Schuniann, H . Kopf, and M . Schmidt, Z. Naturforsch. 196, 168 (1964). [47] A . B. Bucker, F. 8. Balashown, and I . S. Soborovskii, Dokl. Akad. Nauk SSSR 4, 843 (1960). [48] W. Kirchen and H. Buchwnld, Chem. Ber. 92, 227 (1959).

- ..-

Angew. Chem. internat. Edit. 1 Vol. 4 (1965) No. 1-3 101 1

Table 3. Oxidation products isolated as secondary products from the reaction of Sn(C6Hs)r with Px between 235 and 260% (R = GHs).

I Structural units of

original I stannvlohosohine tin phosphonate I Fragments

I 9 b

R2Sn-0-PR

I

I fl P

RSn-0 -P-0 - I 1

9 1 Q c,

R2P-O-Sn-O-P-O- I

I

R2P-O-$n-O-PR B P " P

R$n-TR

I ! RSn-P-

I

I 1 R2P-Sn-P-

I

I R2P-Sn-PR

k l R

I t

I (RP-Sn)2-PR

P (RP-Sn)S-P

I 1

VI. Syntheses of Covalent Tin-Phosphorus Compounds

The above "direct synthesis" having shown that a variety of previously unknown tin-phosphorus corn- pounds can exist, we wished to prepare such compounds systematically. Only phenyl groups were used to render the tin and phosphorus inert. Two series of compounds appeared suitable as models. The first is derived from triphenylphosphine by replacement of one, two, or all three phenyl groups by triphenyltin. The second is derived in the reverse direction from tetraphenyl- stannane, by replacement of one, two, three, or four phenyl groups by diphenylphosphino groups. The first series of compounds is formed in tetrahydro- furan in good yield on reaction of lithiotriphenylstan- nane with appropriate phosphorus chlorides according to reaction (0) 1501. The colorless crystalline products (15) dissolve readily in anhydrous organic solvents.

n (C&s)3SnLi f (C6Hs)3-nPCIn +

[(CaHs)3sn]nP(CsHs)s-n + n Licl (0)

(15)

However, the products (15) arise only if the phosphorus chloride is present in excess until the end of the reaction. Otherwise, the primary reaction products are cleaved by the strongly nucleophilic triphenyltin anion. In this way,

[491 C. Mahr, H. Klamberg, and G. Storck, unpublished work. [ S O ] H. Schumann, H. KOpA and M. Schmidt, Chem. Ber. 97, 3295 (1964).

although the reaction mechanism is not yet finally clari- fied, the cyclic compounds (16) (m.p. 60 "C) 149,501 and ( 1 7) (m.p. 101 "C) [501 are obtained in satisfactory yields alongside hexaphenyldistannane, triphenylphosphine, and lithium chloride.

The second series of compounds (I8) 1511 is formed in good yield by reaction (p). (Use of alkali-metal diphenyl- phosphides in place of the free phosphine leads to com-

(C6H5)4-nSnCI, + n HP(C6Hs)z + n (CzHs)3N

+ (CsHs)4-nsn[P(CsHs)2In + n (GHs),N-HCl (P) (18)

plications [521.) The compounds (18), like the tin phos- phines described above, crystallize readily and are sol- uble in organic solvents. Table 4 presents the organyl- stannylphosphines prepared by reactions (0) and (p) or, in the meanwhile, by other authors analogously L531 or from stannylamines [541.

Table 4. Monomeric organylstannylphosphines.

M.p. [ "C]

96 130 114' 102 80

117 107 150 20 1

B.p. ["Clmml

14210.7 16810.7 10010.2 7010.2

17710.6 126/0.3 19210.6

Ref.

153, 541 148, 53, 541 1531 I531 [531 1531 151, 531 [SO, 51, 531

(511 151, 531

1511 [Sol [501

~ 5 1 1

1511

This process is suitable also for the preparation of analogous germanium and lead compounds, e.g., (CzHs)3Ge-P(C6H5)2

108 "c) [331, [(C&&Ge]3P (mp. 192 "C) 1331, and ( C & ~ ) J P ~ - P ( C ~ H ~ ) ~ (decornp. 100 "C) [561.

Covalent tin-phosphorus compounds are sensitive to oxygen (they do not react with oxygen-free water). The degree of this sensitivity depends considerably on the nature of the "shielding" organic radicals. Thus alkyl derivatives are, in general, less stable than the phenyl analogues. Tetrakis(dipheny1phosphino)stannane on

[51] H. Schumann, H. KOpL and M. Schmidt, J. organomet. Chemistry 2, 159 (t964). [52] H. KOpf, Dissertation, Universitat Marburg, 1963. [53] .I. G. M. Campell, G. JV. A . Fowles, andL. A . Nixon, J. chem. SOC. (London) 1964,1389. [S4] K. Jones and M . F. Lappert, Proc. chem. SOC. (London) 1964, 22. [55 ] F. Glockling and K. A. Hooton, Proc. chem. SOC. (London) 1963, 146. [56] H. Schumann, P. Schwabe, and M . Schmidt, J. organomet. Chemistry I, 366 (1963/64).

(b.p. 146 ' C / w 3 mm)cssI, (C6H5)3Ge-P(C6H5)2 (m.P.

_ - _

1012 Angew. Chem. internat. Edit. 1 Vol. 4 (1965) / No. I 2

the one hand and tris(triphenylstanny1)phosphine on the other react only slowly with air. The cyclic com- pounds are considerably more sensitive to oxygen. Un- symmetrical stannylphosphines can, however, be handled only in an oxygen-free atmosphere [*I. The oxidation occurs, in principle, according to reaction (9). either

>Sn-P< + o2 + 3Sn-0-P, 9, (4)

simply in air or, always quantitatively, with hydrogen peroxide in alcohol [50,511.

Infrared spectra1331 show that, with an excess of oxygen, one 0 atom first adds to the lone electron pair of phosphorus. Suppositions that this is the only and final reaction step 1571 are contradicted by the experimental facts. It seems that the structure (19a) rearranges to (I9b) in a reversal of the Arbusov rearrangement. Then a further oxygen atom adds to the phosphorus according to reaction (r), giving ( 1 9 ~ ) . The oxidation products of monomeric organylstannylphosphines are listed in Table 5.

Table 5. Oxydation products of organylstannylphosphines.

Organyltin phosphinate M.p. I "Cl

> 360 247 226 215

> 360 > 250

372 > 230 > 250

216 174

> 290 150

Ref.

[*] This has not always been taken into account, e.g., when considering the infrared frequency data for ( C ~ H ~ ) ~ S ~ - P ( C ~ H ~ ) Z and (C2H5)3Sn-P(C6H& 1531. The bands found at 1130 and 750 cm-1, and at 1145 and 760 cm-1, respectively, are certainly P=O and Sn-0 valence vibrations, respectively. [57] H. Schindlbauer and D . Hammer, Mh. Chem. 94,644 (1963). [58] J. Lorberth and M . R . Kula, Chem. Ber. 97, 3444 (1964). 1591 H. Schumann and M . Schmidt, Angew. Chem. 76,344 (1964); Angew. Chem. internat. Edit. 3, 316 (1964). [60] J . G . M . Campell, G . W. A . Fowles, and L. A . Nixon, J. chem. SOC. (London) 1964, 3026. 1611 H . Schumann and M . Schmidt, Chem. Ber., in press.

The new phosphinic esters can be cleaved, like the parent stannylphosphines, by hot sodium hydroxide solution to characteristic, readily detected fragments [50,511.

Questions about the nature of the (certainly covalent) bonding between the metal and phosphorus cannot yet be answered. Physical studies (infrared, Raman, crystal structure) should provide relevant information. Any considerable contribution from (p-d), bonding, as required between Sn and PI531 and indeed between Sn and NI58l (2p and 5d orbitals), seems to us to be ex- cluded by our results and by infrared and N.M.R. investigations. The same applies to the arsenic, anti- mony, and bismuth compounds r59.601 listed in Table 6,

Table 6. Organylstannyl-, organogerrnanyl-, and organylplumbyl- arsines, -stibines, and bismuthines.

Compound M.p. ["Cl

119 80 (decornp.) 85 (decornp.) 70

115 216 114 118 (decomp.)

215 138 (decomp.)

B.P. [ W m m l

136/0.05 143/0.15 161 /0.2 164/0.09

146/0.18 170/0.13 i m/o. I 5

not discussed in this paper. The investigations to date show clearly, at any rate, that tin, germanium, and lead can, just like carbon, form stable electron-pair links with elements of the main Groups.

We are grateful to Dr. H. Kopf for collaboration and sug- gestions in the study of the sensitive Sn-P compounds, also to Dr. K. F. Thom for work on the tin chalcogenides. We thank Dr. H . Dersin and Miss T. Ostermann for ex-

perimental help and the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaji for financial support.

Received: February 8th, 1965 [A 4671256 I€] German version: Angew. Chem. 77, 1049 (1965)

Angew. Chem. internat. Edit. Vol. 4 (1965) 1 No. 12 1013