Seeking Heteroatom-Rich Compounds: Synthetic and Mechanistic Studies into Iron Catalyzed Dehydrocoupling of Silanes

A detailed synthetic
investigation into the dehydrocoupling of
silanes with amines, phosphines, and alcohols using an iron precatalyst
(1) is presented. We have furnished over 30 examples
of aminosilane synthesis along with kinetic studies using MeBnNH and
MePhSiH2 as coupling partners. The kinetic studies suggest
a reversible reaction with silane which generates aminosilane and
an Fe-hydride dimer that undergoes rate-limiting protonolysis with
amine with N–H bond cleavage in the transition state, consistent
with a primary KIE of 2.42(3). The presence of dimers as on-cycle
intermediates was analyzed in depth. Beyond this we have explored
the substrate scope of phosphinosilane formation which shows a preferential
heterodehydrocoupling to give the phosphinosilane with primary and
secondary silanes. Silylethers can also be prepared and alcohols that
contain alkene functionality do not show any tendency to reduce the
double bond.