Subvalent Group 4B metal alkyls and amides. Part II. The chemistry and properties of bis[bis(trimethylsilyl)methyl]tin(II) and its lead analogue

Abstract

Bis[bis(trimethylsiiyl)methyl]tin, SnR₂, has an extensive chemistry, behaving as (i) a Lewis base, (ii) a Lewis acid, or (iii) undergoing oxidative addition (insertion reactions). The following complexes have been isolated, many as well characterised crystals. For class (i), these include (M = Cr or Mo)[M(CO)₅(SnR₂)], trans-[M(CO)₄-(SnR₂)₂], [Fe₂(η-C₅H₅)₂(CO)₃(SnR₂)], [RhCl(PPh₃)₂(SnR₂)], and [PtCl(PEt₃)(SnR₂)(SnR₂Cl)]: for class (ii), the readily thermally-dissociable 1 : 1 adducts with pyridine, 4-methylpyridine, or piperidine, and for class (iii), SnR₂(A)B (AB = HCl,HF, MeI, RCl, Cl₂, Br, O₂, CH₂:CMeCMe:CH₂, [Mo(η-C₅H₅)(CO)₃X](X = H or Me), [Fe(η-C₅H₅)(CO)₂X](X = Cl or Me), [{Fe(CO)₄}₂]. and [PtCl₂(PEt₃)(SnR₂)]). An interesting feature is the appearance in the ¹H n.m.r. spectra of doublets characteristic of diastereotopicallv distinct SiMe₃ groups in compounds of the form SnR₂(A)B (A ≠ B). The complex [Mo(CO)₅(PbR₂)] has also been obtained.