Synthesis of (Phosphino)silyl-Ligated Nickel Complexes for the Catalytic Hydroboration of Alkenes

Abstract

Bis(phosphino)silyl (PSiP) pincer ligands have been studied extensively. While there are several examples of late transition metal complexes, in recent years there has been a shift to study these ligands on first-row transition metals (i.e., Fe, Co, Ni). These complexes have shown to be active in catalytic hydrofunctionalization; however, the turn-over for larger substrates has proved challenging. Therefore, the question of reducing the size of the phosphino(silyl) ancillary ligand is investigated in this document. While varying the substitution at phosphorus is common, access to smaller substituents is not straightforward. A different approach is to eliminate a phosphine donor. A new bidentate PSi ligand has been synthesized and studied with respect to Ni complexes. In this regard, studying the catalytic hydroboration with a substrate scope involving terminal, di-, and tri-substituted alkenes and three Ni(II) precatalysts has been explored, where selectivity for chain-walking of internal alkenes to the terminal position was observed.