Subvalent Group 4B metal alkyls and amides. Part III Mössbauer spectroscopy studies of bis[bis(trimethylsilyl)methyl]tin(II) and its derivatives

Abstract

Mössbauer spectra of SnR₂[R = CH(SiMe₃)₂] and of 16 of its derivatives have been recorded. The latter fall into two classes: (i) the dialkylstannylene complexes such as [Cr(CO)₅(SnR₂)] in which bivalent Sn is three-co-ordinate: and (ii) dialkylstannylene insertion products into C–X, M–H, M–Cl, M–Me, or M–M bonds (M = a transition metal, X = halogen) such as [Fe(η-C₅H₅)(CO)₂(SnR₂Cl)], in which quadrivalent tin is four-co-ordinate. The compound SnR₂ and class (i) complexes are characterised by isomer shifts of 2.15 ± 0.1 mm s^–1 relative to BaSnO₃ and large quadrupole splittings [2.31 (for SnR₂) or 4.25 ± 0.2 mm s^–1 for class (i)]. Class (ii) complexes show lower isomer shifts (1.49 ± 0.25 mm s^–1) and quadrupole splittings (<2.37 mm s^–1). Magnetic Mössbauer measurements on SnR₂ and [Cr(CO)₅(SnR₂)] show that for both complexes the sign of the quadrupole coupling constant eQV_zz, is negative and hence V_zz the principal component of the field gradient tensor, is positive.