Ni(ii) and Co(ii) bis(acetylacetonato) complexes for alkene/vinylsilane silylation and silicone crosslinking

Abstract

Commercially available Ni(ii) and Co(ii) complexes - M(acac)2(acac = acetylacetonate) and M(tmhd)2(tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato) - exhibit catalytic activity for alkene/vinylsilane dehydrogenative silylation (DS) and hydrosilylation (HS) with tertiary silanes without the use of any external reducing agents. Using the model compounds divinyltetramethylsiloxanea.k.advtms and vinylpentamethyldisiloxanea.k.avpmds, different selectivities (HS,DS, undesired non-C-Si bond-forming reactions…) are observed whether nickel or cobalt catalysts are employed, withNibeingDS-selective and Co yieldingbothHSandDSproducts. All four complexes are efficient at thermally inducing silicone-oil crosslinking under a non-inert atmosphere, and promote metal-dependent selectivity that is slightly different from model reactions, which HR-MAS NMR spectroscopy unveils. Additional observations as well as NMR studies of [Ni(tmhd)2+ reagent] mixtures provide some insights into the possible activation pathways.