Trimethyl-silyl, -germyl and -stannyl complexes of platinum

Abstract

Two series of compounds (chelate)PtCl(MMe3)(I) and (chelate)Pt(MMe3)2(II)[chelate =(Ph2PCH2)2; M = Si, Ge, or Sn] have been isolated. For M = Si or Ge both are obtained by the reaction of (chelate)PtCl2 with (Me3M)2Hg. Trimethylstannyl–platinum compounds have been isolated (a) by exchange reactions e.g. Pt–MMe3+ Me3SnH → Pt–SnMe3+ Me3MH (M = Si, Ge) and (b) from the oxidative addition of Me3SnH to (chelate)2Pt. Trimethylstannane adds reversibly to (I) and (II) when M = Sn yielding the octahedral complexes (chelate)Pt(H)(Cl)(SnMe3)2 and (chelate)Pt(H)(SnMe3)3 respectively. Stepwise hydrogen chloride cleavage of Pt–MMe3 groups has been investigated: the products from (chelate)Pt(MMe3)2 are (chelate)PtCl(MMe3) and (chelate)PtCl2. Hydrogenolysis of Pt–MMe3 bonds proceeds readily when M = Si or Ge (1 atmos. H2 and 25°). For the reaction (chelate)Pt(SiMe3)2+ H2→(chelate)PtH(SiMe3) the rate constant at 25° is ca. 5·0 × 10–2 l mol–1 s–1, the reaction being first-order with respect to H2 and (II). At 70° and 1 atoms. H2 the second Me3Si–Pt bond is hydrogenated to Me3SiH and a platinum cluster compound, formulated as (chelate)3Pt4. Equilibrium constants have been derived for the hydrogenolysis of trans-(Et3P)2PtCl(SiMe3). Exchange reactions of the types: Pt–SiMe3+ Me3GeH → Pt–GeMe3+ Me3SiH and Pt–GeMe3+ Me3SnH → Pt–SnMe3+ Me3GeH have been investigated; the position of equilibrium favours R3M–Pt products in the order, Sn Ge > Si. Cleavage of Pt–M bonds by 1,2-dibromoethane is considered to involve an octahedral intermediate. 1H n.m.r., i.r. and mass spectra of the various compounds and reactions are discussed.