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Vibrational spectra and structure of triphenyltin halides
Spectrochimica Acta. Vol. 49A. No. II. Printed in Great Britain
pp. 1683-1684.
1993
0584-a.539193 $6.00+0.00 @ 1993 Pergam~n Resr Ltd
SHORT NOTE
Vibrational spectra and structure of triphenyltin halides (Received 30 October 1992; in final form 14 December 1992; accepted 18 December 1992) Abstract-The solid state IR and Raman spectra of SnPhsBr do not show any band at 338 cm-‘, and there is not C,, point group inversion between v, SnCs and v, SnCs for SnPhJ (X = Cl, Br). The presence or absence of a band around 338 cm-’ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh, groups.
DISCUSSION note, a polymeric structure with bridging X atoms has been assigned to SnPhrX (X=F, I) [l]. While SnPh$ is indeed such a polymer, as confirmed by a recent X-ray structure determination [2], there is conclusive evidence that SnPhJ has a tetrahedral monomeric structure. In particular, the Mdssbauer parameters isomer shift (1s) and quadrupole splitting (QS) can yield structural information as p values (QSlZs) higher than 2.1 are often associated with higher-thanfour coordination at tin [3]. The Miissbauer parameters of SnPhjF (IS= 1.30, QS=3.62 mm/s; p=2.78) [4], SnPhFl (fS=1.35, Qs=2.53mm/s; p-1.87) [4], SnPh3Br (IS= 1.40, Q,S=2.48mm/s; p= 1.77) [5] and SnPhrI (IS= 1.41, Qs=23Omm/s; p= 1.63) [5], are consistent with a polymeric pentacoordinate structure for SnPhJ: and monomeric structures for SnPh& (X = Cl, Br, I). These structures have been confumed crystallographically for SnPh,F [2], SnPhsCl [6] and SnPhrBr [7], and there is little doubt that the structure of SnPhJ consists of isolated tetrahedral molecules. DIOP and coworkers have claimed a C,, point group inversion (v, SnCr at a higher frequency than v, SnC3) for SnPh&l [S] and SnPhJ3r [l]. They have further proposed that v, SnCS appears at cu 338 cm-’ in the IR spectrum of triphenyltin compounds when the SnC, group belongs to the C,, point group, and that the absence of that band implies that the SnCr group is planar. This criterion has led to the (wrong) proposal of a trigonal bipyramidal environment for the tin atom in SnPhJ [l]. Nevertheless, no band at 338 cm-’ has been reported in the IR spectrum of SnPh$ in CC& solution [9], though it is reasonable to assume that (whatever the solid state structure is) SnPhJ should be monomeric (C,, point group) in solution in non-coordinating solvents. Indeed, the 1J(L19Sn-*3C)coupling constant (570.9 Hz) in the “C NMR spectrum of SnPh31 in CDCl, [lo] can be used to estimate a C-Sn-C angle of cu 111” [ll]. The idea that V~SnC3 appears at 338 cm-’ when the SnC3 group belongs to the C3. point group [l] comes from a reassignment of the IR spectrum of SnPhFI, with v, SnC3 assigned at 338 cm-’ and v SnCl at 276 cm-’ [S]. Nevertheless, the band at 276 cm-’ is depolarized in the Raman spectra of CS2 solutions and must be assigned to v, SnC3, while a polarized band at 339 cm-’ should be assigned to v SnCl [12]. Therefore, the reported medium band at 338 cm-’ in the IR spectrum of SnPh& [l] should be re-examined. For that reason, I have prepared SnPh&lr and studied its solid state IR (4OOO-24Ocm-‘, Nujol mull) and Raman (350-145 cm-‘) spectra (Fig. 1). The IR spectrum shows v SnBr at 253 cm-’ and v, SnC, split at 270 and 276 cm-‘, but no significant band at 338 cm-’ is observed. In addition, the Raman spectrum does not show a band around 338 cm-‘, but v, SnC3 at 273 cm-’ and v SnBr at 251 cm-‘. v, SnC3 is more difficult to assign, but it probably appears at 222cm-’ as a shoulder to the phenyl u vibration which is centred at 209cm-i (very strong) with a shoulder at 215 cm-‘. v, SnC3 has been assigned at 232 cm-’ in the IR spectrum of SnPh& [13]. Therefore, v. SnC, does not appear at 338 cm-‘, and there is not C,, point group inversion between vas SnC3 and v, SnC3 for SnPh& (X=Cl, Br). In conclusion, the presence or absence of a band around 338 cm-’ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh, groups. Bearing in mind that v, SnC3 is not very sensitive to the environment of the Sn atom, and that v, SnC3 is very close to phenyl u frequencies, they are usually of little use for structural assignments. IN A RECENT
Acknowledgement-Financial support from the Spanish Direcci6n General de Investigaci6n Cientffica y Tecnica (Project PS90-0023) is gratefully acknowledged. 1683
1684
Short Note
,.
400
350
300
250
200
150
cm-1 Fig. 1. IR and Raman spectra of SnPhxBr.
Departamento de Quimica Universidad Autbnoma de Madrid 28049-Madrid Spain
DAVIDTIJDELA
REFERENCES [l] [2] [3] [4] [5] [6] [7] [8] [9] [lo] [ll] [12] [13]
A. S. Sall, 0. Sarr and L. Diop, Spectrochim. Acra 48A, 613 (1992). D. Tudela, E. Guti&rez-Puebla and A. Monge, J. Chem. Sot. Dalton Trans., 1069 (1992). R. H. He&r, H. A. Stiickler and W. T. Reichle, J. Chem. Phys. 42, 2447 (1%5). K. C. Molloy and K. Quill, J. Chem. Sot. Dalton Trtm.s., 1417 (1985). L. May, G. Eng. S. P. Coddington and L. L. Stockton, Hype&e Interact. 42,909 (1988). J. S. Tse, F. L. Lee and E. J. Gabe, Acta Cryst. C42, 1876 (1986). H. Preut and F. Huber, Actu Cryst. B35, 744 (1979). A. S. Sal1 and L. Diop, Spectrochim. Acta 46A, 793 (1990). R. C. Poller, Spectrochim. Acta 22,935 (1966). I. Wharf, Inorg. Chim. Acra 159,41 (1989). J. Hole&k, K. Handlff, M. Nddvornik and A. LyEka, Z. Chem. 30,265 (1990). D. Tudela and J. M. Calleja, Spectrochim. Acta, 49, 1023 (1993). J. R. May, W. R. McWhinnie and R. C. Poller, Spectrochim. Acra 27A. %9 (1971).
pp. 1683-1684.
1993
0584-a.539193 $6.00+0.00 @ 1993 Pergam~n Resr Ltd
SHORT NOTE
Vibrational spectra and structure of triphenyltin halides (Received 30 October 1992; in final form 14 December 1992; accepted 18 December 1992) Abstract-The solid state IR and Raman spectra of SnPhsBr do not show any band at 338 cm-‘, and there is not C,, point group inversion between v, SnCs and v, SnCs for SnPhJ (X = Cl, Br). The presence or absence of a band around 338 cm-’ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh, groups.
DISCUSSION note, a polymeric structure with bridging X atoms has been assigned to SnPhrX (X=F, I) [l]. While SnPh$ is indeed such a polymer, as confirmed by a recent X-ray structure determination [2], there is conclusive evidence that SnPhJ has a tetrahedral monomeric structure. In particular, the Mdssbauer parameters isomer shift (1s) and quadrupole splitting (QS) can yield structural information as p values (QSlZs) higher than 2.1 are often associated with higher-thanfour coordination at tin [3]. The Miissbauer parameters of SnPhjF (IS= 1.30, QS=3.62 mm/s; p=2.78) [4], SnPhFl (fS=1.35, Qs=2.53mm/s; p-1.87) [4], SnPh3Br (IS= 1.40, Q,S=2.48mm/s; p= 1.77) [5] and SnPhrI (IS= 1.41, Qs=23Omm/s; p= 1.63) [5], are consistent with a polymeric pentacoordinate structure for SnPhJ: and monomeric structures for SnPh& (X = Cl, Br, I). These structures have been confumed crystallographically for SnPh,F [2], SnPhsCl [6] and SnPhrBr [7], and there is little doubt that the structure of SnPhJ consists of isolated tetrahedral molecules. DIOP and coworkers have claimed a C,, point group inversion (v, SnCr at a higher frequency than v, SnC3) for SnPh&l [S] and SnPhJ3r [l]. They have further proposed that v, SnCS appears at cu 338 cm-’ in the IR spectrum of triphenyltin compounds when the SnC, group belongs to the C,, point group, and that the absence of that band implies that the SnCr group is planar. This criterion has led to the (wrong) proposal of a trigonal bipyramidal environment for the tin atom in SnPhJ [l]. Nevertheless, no band at 338 cm-’ has been reported in the IR spectrum of SnPh$ in CC& solution [9], though it is reasonable to assume that (whatever the solid state structure is) SnPhJ should be monomeric (C,, point group) in solution in non-coordinating solvents. Indeed, the 1J(L19Sn-*3C)coupling constant (570.9 Hz) in the “C NMR spectrum of SnPh31 in CDCl, [lo] can be used to estimate a C-Sn-C angle of cu 111” [ll]. The idea that V~SnC3 appears at 338 cm-’ when the SnC3 group belongs to the C3. point group [l] comes from a reassignment of the IR spectrum of SnPhFI, with v, SnC3 assigned at 338 cm-’ and v SnCl at 276 cm-’ [S]. Nevertheless, the band at 276 cm-’ is depolarized in the Raman spectra of CS2 solutions and must be assigned to v, SnC3, while a polarized band at 339 cm-’ should be assigned to v SnCl [12]. Therefore, the reported medium band at 338 cm-’ in the IR spectrum of SnPh& [l] should be re-examined. For that reason, I have prepared SnPh&lr and studied its solid state IR (4OOO-24Ocm-‘, Nujol mull) and Raman (350-145 cm-‘) spectra (Fig. 1). The IR spectrum shows v SnBr at 253 cm-’ and v, SnC, split at 270 and 276 cm-‘, but no significant band at 338 cm-’ is observed. In addition, the Raman spectrum does not show a band around 338 cm-‘, but v, SnC3 at 273 cm-’ and v SnBr at 251 cm-‘. v, SnC3 is more difficult to assign, but it probably appears at 222cm-’ as a shoulder to the phenyl u vibration which is centred at 209cm-i (very strong) with a shoulder at 215 cm-‘. v, SnC3 has been assigned at 232 cm-’ in the IR spectrum of SnPh& [13]. Therefore, v. SnC, does not appear at 338 cm-‘, and there is not C,, point group inversion between vas SnC3 and v, SnC3 for SnPh& (X=Cl, Br). In conclusion, the presence or absence of a band around 338 cm-’ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh, groups. Bearing in mind that v, SnC3 is not very sensitive to the environment of the Sn atom, and that v, SnC3 is very close to phenyl u frequencies, they are usually of little use for structural assignments. IN A RECENT
Acknowledgement-Financial support from the Spanish Direcci6n General de Investigaci6n Cientffica y Tecnica (Project PS90-0023) is gratefully acknowledged. 1683
1684
Short Note
,.
400
350
300
250
200
150
cm-1 Fig. 1. IR and Raman spectra of SnPhxBr.
Departamento de Quimica Universidad Autbnoma de Madrid 28049-Madrid Spain
DAVIDTIJDELA
REFERENCES [l] [2] [3] [4] [5] [6] [7] [8] [9] [lo] [ll] [12] [13]
A. S. Sall, 0. Sarr and L. Diop, Spectrochim. Acra 48A, 613 (1992). D. Tudela, E. Guti&rez-Puebla and A. Monge, J. Chem. Sot. Dalton Trans., 1069 (1992). R. H. He&r, H. A. Stiickler and W. T. Reichle, J. Chem. Phys. 42, 2447 (1%5). K. C. Molloy and K. Quill, J. Chem. Sot. Dalton Trtm.s., 1417 (1985). L. May, G. Eng. S. P. Coddington and L. L. Stockton, Hype&e Interact. 42,909 (1988). J. S. Tse, F. L. Lee and E. J. Gabe, Acta Cryst. C42, 1876 (1986). H. Preut and F. Huber, Actu Cryst. B35, 744 (1979). A. S. Sal1 and L. Diop, Spectrochim. Acta 46A, 793 (1990). R. C. Poller, Spectrochim. Acta 22,935 (1966). I. Wharf, Inorg. Chim. Acra 159,41 (1989). J. Hole&k, K. Handlff, M. Nddvornik and A. LyEka, Z. Chem. 30,265 (1990). D. Tudela and J. M. Calleja, Spectrochim. Acta, 49, 1023 (1993). J. R. May, W. R. McWhinnie and R. C. Poller, Spectrochim. Acra 27A. %9 (1971).