Syntheses, spectroscopic characteristics and thermolytic rearrangements of bis-[(trimethylgermyl) methyl]platinum(II) and bis-[(trimethylstannyl) methyl]platinum(II) complexes

Article abstract of DOI:10.1016/0022-328X(95)05908-8

The preparations and spectroscopic characteristics are reported of a series of (trimethylgermyl)methyl- and (trimethylstannyl)methyl- platinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH₂GeMe₃)₂L₂ (L = PPh₃ or PPh₂Me; L₂ = dppe or cod) and cis-Pt(CH₂SnMe₃)₂L₂ (L = PPh₃; L₂ = cod). Thermolysis of toluene solutions of cis-Pt(CH₂GeMe₃)₂(PPh₃)₂ leads to cis-Pt(Me)(CH₂GeMe₂CH₂GeMe₃)(PPh₃)₂ via β-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (ΔH_{298 K}? = 126 ± 3 kJ mol^-1, ΔS? = + 17 ± 7 J mol^-1 K^-1 and hence ΔG_{298 K}? = 121 ± 5 kJ mol^-1) suggest that this system is more migration labile than its silicon analogue, primarily as a result of a lower activation enthalpy. While cis-Pt(CH₂GeMe₃)₂(PPh₂Me)₂ reacts similarly but less readily, Pt(CH₂GeMe₃)₂(dppe)₂ is inert at operable temperatures. Thermolysis of Pt(CH₂GeMe₃)₂(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH₂SnMe₃)₂(PPh₃)₂, 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed.