| Abstract |
cis- and trans-Isomers of the platinum(II) nitrile complexes [PtCl2(NCR)(2)] (R = NMe2, N(C5H10), Ph, CH2Ph) were examined as catalysts for hydrosilylation cross-linking of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) producing high quality silicone rubbers. Among the tested platinum species the cis-complexes are much more active catalysts than their trans-congeners and for all studied platinum complexes cis-[PtCl2(NCCH2Ph)(2)] exhibits the best catalytic activity (room temperature, c = 1.0 x 10(-4) mol/L, (pot-life) 60 min, (curing) 6 h). Although cis-[PtCl2(NCCH2Ph)(2)] is less active than the widely used Karstedt s catalyst, its application for the cross-linking can be performed not only at room temperature (c = 1.0 x 10(-4) mol/L), but also, more efficiently, at 80 degrees C (c = 1.0 x 10(-4)-1.0 x 10(-5) mol/L) and it prevents adherence of the formed silicone rubbers to equipment. The usage of the cis- and trans-[PtCl2(NCR)(2)] complexes as the hydrosilylation catalysts do not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl terminated polysiloxanes are shelf-stable in air. Tested catalysts do not form colloid platinum particles after the cross-linking. |
