SYNTHESES, SPECTROSCOPIC CHARACTERISTICS AND THERMOLYTIC REARRANGEMENTS OF BIS-[(TRIMETHYLGERMYL)METHYL]PLATINUM(II) AND BIS-[(TRIMETHYLSTANNYL)METHYL]PLATINUM(II) COMPLEXES

摘要

The preparations and spectroscopic characteristics are reported of a series of (trimethylgemyl)methyl- and (trimethylstannyl)methyl platinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH(2)GeMe(3))(2)L(2) (L = PPh(3) or PPh(2)Me; L(2) = dppe or cod) and cis-Pt(CH(2)SnMe(3))(2)L(2) (L=PPh(3); L(2)=cod). Thermolysis of toluene solutions of leads to cis-Pt(Me)(CH(2)GeMe(2)CH(2)GeMe(3))(PPh(3))(2) via beta-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (Delta H-298K(double dagger)=126 +/- 3 kJ mol(-1), Delta S-double dagger=+17 +/- 7 J mol(-1) K-1 and hence Delta G(298K)=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(CH(2)GeMe(3))(2)(PPh(2)Me)(2) reacts similarly but less readily, Pt(CH(2)GeMe(3))(2)(dppe)(2) is inert at operable temperatures. Thermolysis of Pt(CH(2)GeMe(3))(2)(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH(2)SnMe(3))(2)(PPh(3))(2), 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed. [References: 27]