The chemistry of fumarate and maleate inhibitors with platinum hydrosilylation catalysts

Article abstract of DOI:10.1016/0022-328X(96)06247-X

Pt(M^viM^vi)_x (M^viM^vi = 1,3-divinyltetramethyl disiloxane), 1, was reacted with dimethyl fumarate to give 2. Compound 2 was investigated by ¹H and ¹³C NMR spectroscopy which showed it to be a mono-nuclear platinum compound containing one dimethyl fumarate and one chelating M^viM^vi ligand. The reaction of 1 with dimethyl maleate gave 3 which was analogous¹³C NMR spectroscopy and extended X-ray absorption fine structure spectroscopy (EXAFS). The EXAFS analysis showed the presence of Pt-C bonds in structure to the fumarate product as shown by ¹H and ¹³C NMR spectroscopy and extended X-ray absorption fine structure to the EXAFS analysis showed the presence of Pt-C bonds and a through space close contact between Pt and the O from the carbonyl. The NMR assignments were confirmed by comparing the NMR spectra of 2 and 3 with that of (PPh₃)Pt(M^viM^vi), 4. Reaction of 2 or 3 with an excess of an Si-H-containing compound (either MD^HD^HM (MD^HD^HM = 1,3-bis(trimethylsiloxy)-1,3-dimethylsiloxane) or Et₃SiH) gave 5 in all cases. Compound 5 contains an alkyl succinate ligand. Hydrogenation of the fumarate ligand (of 2) or of the maleate ligand (of 3) occurs by reaction with Si-H; 5 appears to be an intermediate in the hydrogenation process. The reaction between 4, dimethylmaleate, and MD^HD^HM also gives dimethyl succinate. Differential scanning calorimetry was used to compare the effectiveness of the inhibitors in a curable formulation composed of vinyl-stopped-polydimethyl siloxane polydimethylsiloxanemethylhydrogen-copolymer, a platinum catalyst and either a maleate or fumarate inhibitor.