Structural distortions in homoleptic (RE)(4)A (E = O, S, Se; A = C, Si, Ge, Sn): implications for the CVD of tin sulfides

The structures of Sn(SBut)(4) and Sn(SCy)(4) have been determined and adopt S-4 and D-2 conformations respectively; the anion [(PhS)Sn-3](-), as its Ph4P+ salt, has a structure approaching C-s symmetry. In all three compounds, there are large variations in the (sic)S-Sn-S within the same molecule, which have been rationalised in terms of the C-S-Sn-S-C conformations. For Sn(SR)(4), the (sic)S-Sn-S increases as the conformations change from trans, trans to trans, gauche and gauche, gauche, as the number of eclipsed lone pairs decreases and this rationale is shown to be applicable to a variety of A(ER)(4) (A = C, Si, Ge, Sn; E = O, S, Se) and related [Mo(SR)(4), Ga(SR)(4)(-)] systems. AM1 calculations have been used to model the S-Sn-S magnitudes and also provide insights into the decomposition mechanisms of these and related species which are relevant to chemical vapour deposition processes.