THERMAL-DECOMPOSITION OF PLATINUM(IV)-SILICON, PLATINUM(IV)-GERMANIUM, AND PLATINUM(IV)-TIN COMPLEXES

The thermal decomposition of a number of complexes of the type [PtMe2( Me3E)X(diimine)] (E = Si, Ge, Sn; X = Cl, Br, I) has been studied. The thermal stability of complexes, as determined by thermogravimetric an alysis (TGA), varies depending on the diimine ligand in the order 2,2' -bipyridyl (bpy) > 4,4'-di-tert-butyl-2,2'-bipyridyl (bpy-(t)bu(2)) > N-(2-(dimethylamino)ethyl)pyridine-2-aldimine (paen-me(2))> (2-imino-n -propyl)pyridine (py-n-pr). Stability also varies according to the tre nds E = Sn approximate to Ge > Si and X = I > Br > Cl. The products of thermal decomposition have also been determined by H-1 NMR and three distinct modes of decomposition are evident: reductive elimination of Me3EX, reductive elimination of Me4E, and alpha-elimination of Me2E. T he competition between reductive elimination of Me3EX and Me4E depends primarily on the halide, X: with the ratio Me3EX:Me4E highest for X = Cl and lowest for X = I. The competition between reductive eliminatio n and alpha-elimination depends primarily on E, with the tendency to a lpha-elimination of Me2E increasing as E = Si < Ge < Sn. Differential scanning calorimetry (DSC) has been used to estimate D(Pt-Si)for the c omplex [PtIMe2(Me3Si)(bpy)] as 233 +/- 14 kJ mol(-1).