Polyhedron Vol. 12, No. 1, PP. 69-75, 1993 Printed in Great Britain

0277-5387/93 $6.00 + 40 0 1993 Pergallon Press Ltd

A NEW INORGANIC METALLOCYCLE CONTAINING TIN, SULPHUR, PHOSPHORUS AND NITROGEN. CRYSTAL AND

MOLECULAR STRUCTURE OF SPIROBICYCLIC Me,Sh(SPPh,NPPh,S),

IONEL HAIDUC* and CRISTIAN SILVESTRU

Chemistry Department, Babes-Bolyai University, RO-3400 Cluj-Napoca, Romania

and

HERBERT W. ROESKY, HANS-GEORG SCHMIDT and MATHIAS NOLTEMEYER

Institut fiir Anorganische Chemie der Universitat Giittingen, Tammannstr. 4, D-3400 Gottingen, F.R.G.

(Received 31 July 1992 ; accepted 27 August 1992)

Abstract-A new inorganic heterocycle is obtained by reacting potassium tetraphenyldithio- imidodiphosphinate with trimethyltin and dimethyltin chlorides, in benzene. X-ray diffrac- tion analysis reveals a spirocyclic structure with the dimethyltin moiety as the coordination centre with non-planar six-membered SnS2P2N rings. The coordination at tin is nearly perfectly octahedral, with equal Sn-S [273.3(2) and 273.7(2) pm] and P-S bonds [200.9(3) and 201.9(3) pm]. The S-Sn-S and H,C-Sn-CH, units are co-linear.

The most common inorganic heterocycles’T2 are non-metal rings. Although metal-containing inor- ganic heterocycles have been known for some time this area has started flourishing in the last 10 years, mainly by incorporation of metal heteroatoms into cyclothiazene3 and cyclophosphazene4 rings. Such rings are attractive as precursors for new types of inorganic polymers. ’ A particular class of carbon- free metallocycles includes inorganic chelate rings6 and this type of compound may add a new dimen- sion to both coordination chemistry and inorganic ring chemistry.

In addition to phosphazene metallocycles (1),7 chelate rings (2), in which an azadiphosphinate group is attached to a metal through oxygen or sulphur, have been reported.6 The known com-

1 2

* Author to whom correspondence should be addressed.

pounds of type 2, with E = sulphur, are chelate rings with M = Mn11,8 Fe”,9 CO~I,~C,%~C NiII,% 10 P&l,% ptII,9a znII,9a &I, EC, I I cu11,9c, 12 AgI, 13

Au’, 13, I4 BiIII I S or TeII. I6 The only derivatives with an organometallic coordination centre reported so far are a dimeric phenyltellurium(II) compound, [phTe(SPPh2NPh2PS)]2, ’ 7 and monomeric diorgano- gold(II1) derivatives, R2Au(SPR2NR2PS). 14*‘*

Several years ago one of us reported an organotin derivative, Me2Sn(SPPh2NPh2PS)2, which was not investigated in detail. l9 We now report some spectroscopic properties and a full crystal structure determination of this compound. This was promp- ted by the renewed interest in this type of chelate ring (e.g. 2, E = 0, M = Al, Ga, In, Sn, MO, V)20 and by the possible comparison with organotin dithiophosphates and dithiophosphinates, much investigated in recent years.21,22 Thus, nearly all diorganotin dithiophosphates and phosphinates whose structures were determined by single-crystal X-ray diffraction show that the ligand is aniso- bidentate, coordinated to the metal in an unsym- metrical fashion (3) and exhibits an intermediate geometry between tetrahedral and octahedral, with

69

70 I. HAIDUC et al.

short and long Sn-S bonds.2’a,d*e The only excep- tion known so far in or anotin compounds is diphenyltin bis(diisoprop, ldithiophosphate) ! (4)

IR

3i

4

(R = Ph, R’ = OP+),23 metrical structure with identical Sn-S bonds. metrical structure 4 rather than the rule makes difficult (isobidentate) of coor for transition metal dithi

In agreement wi derivative of the dithioi either an unsymmetrica cture 5 or a sym- metrical structure 6 coul e expected (M = Sn).

5 6

The single-crystal X-ray showed that the symmetri present in the dimethy

The potassium salt diphosphinic was prep Bu’OKz4 The IR spec and of the tin compou pellets on a Nicolet 310 The ’ ““Sn Miissbauer was recorded at liquid n

e recorded as KBr FT-IR spectrometer. rum of compound 8

en temperature, using

Preparation of Me,Sn[(SP h2)2N12

A solution of .44 g, 2 mmol) in anhy- drous benzene was add to a suspension of (SPPh2)2NK (1.95 g, 4 01) in the same solvent

and the reaction mixture was refluxed for 90 min. The remaining white solid was then filtered off and extracted several times in a Soxhlet apparatus, using acetonitrile as a solvent. Small white-pink crystals of the title compound deposited from the clear acetonitrile solution upon standing for 24 h. Yield : 1.23 g (61%). Found : P, 11 .O. Calc for C50H46N2P4 S4Sn : P, 11.8%.

Preparation of Me3Sn(SPPh2)2N

A solution of Me,SnCI (0.80 g, 4 mmol) in anhy- drous benzene was added to a stirred suspension of (SPPh2)2NK (1.95 g, 4 mmol) in the same solvent. The mixture was refluxed for 3-4 h and then the resultant KC1 was filtered off. The hot, clear solu- tion was allowed to reach room temperature slowly and colourless crystals deposited. Yield: 1.40 g (66%).

Crystallographic data for compound 8

C50H46N2P4S4Sn, M = 1045.7, monoclinic, space group P2Jn; a = 11.099(l), b = 15.551(3), c = 14.442(2) A, B = 103.30(l)” ; V = 2425.9(6) A3, Z = 2, dwlc = 1.43 g cm- 3, absorption coefficient 0.858 mm-‘, F(OOO) = 1068. A colourless crystal of the dimensions 0.3 x 0.4 x 0.5 mm was measured at room temperature on a STOE WED2 (rev. 6.2) four-circle goniometer with graphite mono- chromatized MO-& radiation in the profile optimiz- ing mode. Within 20 < 45”, 2259 symmetry-inde- pendent reflections were collected of which 1678 with F > 30(F) were used in the least-squares cal- culations (SHELX-76). The structure was solved by the heavy-atom method implemented in SHELX- 86. All non-hydrogen atoms were refined aniso- tropically and hydrogen atoms positioned geo- metrically. The final R values are r = 0.043 and Rw = 0.041 with weights w- ’ = a2(F)+0.0004 F2. The residual electron density was in the range -0.3 to 0.5 e A-‘. Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Informations mbH, W-7514 Eggenstein-Leopoldstr. 2 (FRG), on quot- ing the deposit number CSD 56534, the names of the authors and the journal citation.

RESULTS AND DISCUSSION

The potassium salt of the tetraphenyldithioimido- diphosphinato ligand reacted with trimethyltin chloride, in benzene, to give a crystalline product ; m.p. 135°C.

Metallocycle containing Sn, S, P and N

Table 1. IR data for methyltin derivatives and related compounds (in cm- ‘)

Compound

(SPPh&NH

(SPPh,),N-K+

MeGW(SPPh~Wl~

Me,Sn(SPPhJ,N

v(PN) v(P=S) v(P=S) v(PNP) v(SnC,) Ref.

928~s 652s - 5039 - 25 922~s

1199vs - 598s 511s - 25 576s

1217~s - 591m 520m 535m -O 570s 510m

1250vs - 560s 5oOm 546m -_’ 507w

‘This work.

71

Me,SnCl+K[(SPPh,),Nj-

Me$n(SPPh2)zN+KCl I

Similarly prepared, the dimethyltin derivative was a colourless, crystalline compound ; m.p. 265- 266°C (from acetonitrile).

Me&&Y, -t-2K[(SPPh&N’J-

Me,Sn[(SPPh,),Nj, +2KCl 8

The IR spectra of the two organotin compounds differ significantly from that of the neutral free ligand. The latter was shown by X-ray diffraction to have the structure of a bis(thiodiphenyl- phosphinyl)amine (9), Ph2P(S)NHP(S)Ph2.25 The important bands in the IR spectra of the organotin derivatives are compared with those of the neutral ligand 9 and the potassium salt containing the anion 10 in Table 1.9c*24 It is quite obvious that in the

organotin compounds both the v(PS) and v(PNP) frequencies are different, due to the delocalization of the negative charge over the whole SPNPS frag ment in the anion and changes in the P-S and P-N bond orders, as shown in structures 9 and 10.

The 1250 and 1217 cm-’ bands in Me,Sn[(SPPh2), WI2 and Me3Sn(SPPh2),N, respectively, were assigned to P=N=P asymmetrical stretching by comparison with a similar band in cyclophospha- xenes, (Ph2PN)3,d4,26 which exhibit v,(PNP) in the range 1220-I 190 cm-‘. The strong bands at 652 and 645 cm-‘, characteristic of the P=S double bond in the free ligand 9 and its N-

methyl derivative,24 are replaced by a strong band at 570 and 560 cm- 1 in the tin compounds, assigned to PfiS stretching. This suggests the coordination of all sulphur atoms to tin.

The 535 cm-’ band in the diorganotin com- pound, assigned to SnC2, indicates a linear ar- rangement of the two methyl groups in the central SnMe, moiety. For the trimethyltin(IV) derivative IR data suggest a non-planar orientation of the Sri--- bonds. Since both sulphur atoms seem to be coordinated, its possible solid-state molecular structures could be either monomeric (11) [as pro- posed for Me3SnS2P(OR)2, R = Et, Pr’, on the basis of Mijssbauer data2“J or dimeric (12) with bridging ligands (similar to Ph2SbS2PPhz2’). The coordination geometry of the tin atom would be distorted trigonal bipyramidal in 11, and octahedral in 12.

R S--P %

YSn/ ‘$ I

R’ \s_-pl/

w

11

The Miissbauer spectrum of the dimethyltin com- pound (IS = 1.63 mm s- ’ and QS = 3.98 mm s- ‘) is in agreement with the presence of tin(W) with a tram configuration of the Me-Sn-Me central unit. On the other hand, both the quadrupole split- ting and the QS/IS ratio (p = 2.44) are consistent with six-coordinate octahedral geometry around tin.28

These data were insufficient to distinguish between the chelate ring structure 5 and metallo- cycle structure 6 of the tin compounds. The X-ray

72 I. HAIDUC et al.

Fig. 1.

molecular structure dete rmi nation of the trimethyl- tin compound 7 was possible because -of disorder, but we were su ssful with the dimethyl- tin derivative 8.

Crystal and molecular struo we of Me2WWPhMl~ @I ;

The structure of corn crete Me,Sn[(SPPh structure in the

8 is built up of dis- lecules. Its molecular the atom numbering Selected bond lengths

The most unexpected e of this structure is its high symmetry be its crystallographic centrosymmetry. Both imidodiphosphinato ligands act as isobident metrical metallocycle, lie at equal distances respectively] from the tin om, which are inter- mediate between the ester e bonds (P-)S-Sn (average 248.5 pm) and ondary bonds (P=) S * * * Sn (average 321.5 (OEt)&.*‘” As a result, cycles, SnS2P2N, are fo atom. Moreover, opposite phur atoms belonging to different ligand are co-linear [i.e. S( I)-Sn-S( 1A) an -S(2A) angles are 180.0(l)“]. This leads to a anar SnS4 system in which the angle between same ligand is greater [ than that arising between ing to different ligand mo

co-linear opposite sulphur atoms was present in the tellurium(I1) derivative of the same ligand, i.e. TeKSPPh&Nlz,‘6 but here the Te-S bonds are unequivalent [267.5(2) and 269.9(3) pm] and the intraligand S( l)-Sn-S(2) bond angle [86.05(g)“] is lower than the interligand S(2)-Sn-S(2A) angle [93.95(8)“] (14).

In the central dimethyltin unit the tin-carbon bonds are equal [211.1(8) pm] and co-linear [C( I)-Sn-C( 1 A) 180.0(l)“]. The axis described by the SnC2 moiety is almost perpendicular to the SnS4 plane, as suggested by the C-Sn-S angles (range 86.3-93.7”). As a result the tin atom is placed in the centre of a slightly distorted octahedron.

A comparison with other octahedral compounds containing dithiophosphorus ligands will be useful. Thus, the bismuth(II1) complex of tetraphenyldithio- imidodiphosphinic acid, Bi[(SPPh2)$&, contains two sets of short and long Bi-S bonds (average values of 276 and 289 pm, respectively), indicating a structure analogous to 5 (M = Bi). The angles between opposite sulphur atoms are lower than 180” (range 166.3-174.4”). The distorted octa- hedral geometry around the metal atom was dis- cussed as a result of two concurrent factors, i.e. the electrostatic repulsions between bonded pairs

Metallocycle containing Sn, S, P and N

Table 2. Selected bond lengths (pm) and angles (“) for compound 8

73

Sn-C( 1) 211.1(8) Sn-S(2) 273.7(2) Sn-S( 1 a) 273.3(2) S(ljP(1) 200.9(3) P(l)--c(ll) 181.5(9) N(1 jP(2) 158.2(6) P(2)-C(31) 181.7(8)

C( 1 jSn-S( 1) S(ljSn-S(2) S(l)-Sn-C(la) C(l)-Sn-S(la) S(2jSn-S( 1 a) C( l jSn-S(2a) S(2jSn-S(2a) S( 1 ajSn-S(2a) S(ljP(ljN(1) N(ljP(l)-C(ll) N(ljP(l)--C(21) P(l)-N(ljP(2) ~(ljP(2)--~(31) N( l)-P(2jC(41) C(31)-P(2 jC(41) P(ljC(ll)-C(12) P(ljC(2ljC(22) P(2jC(31jC(32) P(2)-C(41)<(42)

86.3(2) 97.8(l) 93.7(2) 93.7(2) 82.2( 1) 90.1(2)

180.0(l) 97.8(l)

118.5(2) 106.4(4) 109.5(4) 136.0(4) 104.5(4) 112.3(3) 104.0(4) 120.9(7) 121.7(6) 120.4(7) 119.4(6)

and the lone pair of the bismuth atom, and the bulky nature of the ligand, respectively. ’ 5b

The coordination around tin in compound 8 is similar to that found in PhzSn[SzP(OPri)&, with a unique octahedral structure, containing linear Ph-Sn-Ph groups and symmetrically coor- dinated (isobidentate) dithiophosphato ligands with all four Sn-S bonds identical (average 268.4 pm). 23 In unsymmetrically coordinated (aniso- bidentate) diethyldithiophosphate, Ph2Sn[S2P (O%12,2’a and dimethyltin(IV) bis(dialkyldi- thiophosphinates), Me2Sn(S2PMe2)22’d and Me,Sn (S2PW2,21e there are two sets of long and short Sn-S distances (Table 3). The lengths of the P-S bonds also differ in these compounds.

Concerning the tetraphenyldithioimidodiphos- phinato ligand, since it is coordinated to tin through both its sulphur atoms, a twist about the P-N bond from the tram configuration of the sulphur atoms in the free ligand” to the cis orien- tation is required.

Although there are some small differences between the P-S and P-N bond lengths re- spectively reported in the structure of the free

Sn-S( 1) Sn-C(la) Sn-S(2a) P(l)-N(1) P(l)-C(21) P(2)-S(2) P(2)--c(41)

273.3(2) 211.1(g) 273.7(2) 158.2(7) 180.9(8) 201.9(3) 179.7(9)

C( l jSn-S(2) C(l jSn-C(la) SQjSn-C( la) S(ljSn-S(la) C(la)-Sn-S(la) S( 1)-Sn-S(2a) C( lajSn-S(2a) Sn-S(1 jP(l) S(ljP(l)--c(ll) S(ljP(l)--c(21) C(ll)-P(ljC(21) N(ljP(2)-S(2) S(2)-P(2 jC(31) S(2jP(2)-C(41) Sn-S(2jP(2) P(l)--c(l ljW6) P(l)--c(2ljC(26) P(2)-C(31jC(36) P(2jC(41)-C(46)

89.9(2) 180.0(l) 90.1(2)

180.0(l) 86.3(2) 82.2( 1) 89.9(2)

106.1(l) 111.1(3) 106.8(3) 103.5(3) 118.8(3) 106.2(2) 109.6(2) 106.0( 1) 120.9(7) 120.2(6) 120.5(6) 123.0(6)

ligand described by different authors,25 these bonds are of the same magnitude as the P=S double bond in P,$,,, (196 pm)29 and P-N single bonds in [ClP(S)NMe12 (167 pm)3o or (H,N),P(S)-NMe- P(S)(NH,)NHMe (173 pm). 3 ’ The isobiden- tate coordinated ligand in the tin compound 8 has equal phosphorus-sulphur and phosphorus-nitro- gen bond lengths, respectively. However, the for- mer are significantly longer and the latter shorter than in the free ligand, thus suggesting a con- siderable amount of double bond character result- ing from the delocalization of the Iz-electrons on the SnS2P2N metallocycle. Moreover, the lengths of the tin-sulphur and phosphorus-sulphur bonds in compound 8 are comparable to those observed in the highly symmetrical molecule of Ph2Sn ]S2P(OPri)212,23 which also involves an extensive electron delocalization on the SnS,P ring.

Both S-P-N and P-N-P angles in the dimethyltin(IV) complex are slightly larger than in the free ligand,25 to permit the symmetrical coor- dination of the ligand to the metal atom. The elec- trons of the phosphorus atoms are essentially sp3 hybridized, resulting in a distorted tetrahedral

74 I. HAIDUC et al.

Table 3. Comparison of M-S and P-S bond lengths for Me,Sn[(SPPh,)& and related compounds (in pm)

Bond lengths Structure (average)

Compound type M-S P-S Ref. I

6 273.5 201.4 This work 9 - 194.3 24a

- 191.6 24c 4 268.4 200.2 23 3 248.6 203.5 21a

321.5 193 3 248.2 204.7 21d

333.4 196.9 3 247.6 205.4 21e

333.6 196.1

BWlo/Ph&N13 5

Te[(S p PPh,) *Nl z 5

275.7 202.1 15b 289 200.6 267.5 202.2 16 269.9 202.3

geometry, with X-P- (X, Y = C and/or S atoms) angles close to the tetrahedral value (109”28’). 1

to E. Merck

otin halides used as starting aterials in this work. We

versiteit, Brussels, for provi ng the “‘%n Miissbauer

schaft is highly acknowledged

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Metallocycle containing Sn, S, P and N 75

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