Molecular and silica-supported metal complexes as new catalysts for hydrosilylation

Abstract

Two disiloxanes with pyridyl or isocyanide functional groups, as well as silica materials carrying pyridyl or thiol functionalities were used as ligands for Pt(IV) and Fe(III) ions. The molecular and silica-supported metal complexes were tested in a model hydrosilylation reaction between 1,3-divinyl tetramethyldisiloxane and 1,1,3,3-tetramethyldisiloxane, conducted in (pseudo)-heterogeneous conditions. The new hydrosilylation catalysts afforded 75-100 % conversion and 87-93 % selectivity, based on NMR data, while some of them presented recyclability; they were also successful in silicones crosslinking at room temperature. In particular, the iron-isocyanide disiloxane complex is proposed as a promising, cheap, unsophisticated and stable catalyst, capable to act in heterogeneous conditions, without the need of dry solvent or inert atmosphere. Silica-supported Pt or Pt/Pd catalysts, obtained with commercial or recovered noble metals precursors, presented high conversion and increased regioselectivity in the hydrosilylation reaction, being reusable, and are efficient in other hydrosilylation reactions, useful in organic and silicon chemistry.