Tris(trimethylsilyl)methyl-lead oxinates: their solvolysis, redistribution, and reductive elimination reactions

Abstract

The complex PbMe₂[C(SiMe₃)₃](ox)(where ox = the anion of 8-hydroxyquinoline) is stable to boiling ethanol over short periods, but on prolonged heating undergoes redistribution and reductive elimination reactions yielding Pb(ox)₂, PbMe₃(ox), PbMe₃[C(SiMe₃)₃], and 8-methoxyquinoline. By contrast, when PbCl₂Me[C(SiMe₃)₃] is treated with 8-hydroxyquinoline at pH ca. 10 in methanol, ethanol, or aqueous dioxan the bis(trimethylsilyl)methyl complex PbMe[CH(SiMe₃)₂](ox)₂(1) is formed together with SiMe₃(OR)(R = H, Me, or Et) rather than the expected tris(trimethylsilyl)methyl complex. Refluxing (1) in ethanol or aqueous dioxan results in further nucleophilic displacement of SiMe₃ groups yielding, successively, PbMe(CH₂SiMe₃)(ox)₂(2) and PbMe₂(ox)₂(3). These cleavage reactions occur in competition with disproportionation and reductive elimination processes, the final products derived from (3) being Pb(ox)₂, PbMe₄, PbMe₃(ox), and 8-methoxyquinoline. The corresponding 8-hydroxy-2-methylquinolinate complexes are also examined.