Reversible Substrate Activation and Catalysis at an Intact Metal–Metal Bond Using a Redox-Active Supporting Ligand

An
electron rich Ni­(I)–Ni­(I) bond supported by a doubly
reduced naphthyridine–diimine (NDI) ligand reacts rapidly and
reversibly with Ph2SiH2 and Et2SiH2 to form stable adducts. The solid-state structures of these
complexes reveal binding modes in which the silanes symmetrically
span the Ni–Ni bond and exhibit highly distorted H–Si–H
angles and elongated Si–H bonds. This process is facilitated
by the release of electron density stored in the π-system of
the NDI ligand. Based on this dinuclear mode of activation, [NDI]­Ni2 complexes are shown to catalyze the high-yielding hydrosilylation
of alkenes, dienes, alkynes, aldehydes, ketones, enones, and amides.
In comparative studies of alkyne hydrosilylations, the [NDI]­Ni2 catalyst is found to be significantly more active than its
mononuclear counterparts for aryl-substituted substrates.