In summary, we introduce a new Ni(0) catalyst ( ) complexed with IMes and two stabilizing di-(otolyl) fumarate ligands, and we demonstrate it to be a competent catalyst in the reductive coupling of aldehydes and alkynes using silanes as the terminal reductant. The catalyst is easily prepared and handled, while undergoing rapid catalyst activation under mild reaction conditions. Computational study of a panel of catalysts that range in stability and catalyst activity illustrated that simple dissociation of fumarate ligand was unlikely to serve as the catalyst activation step, as the thermodynamics of ligand exchange are uncorrelated with catalyst activity. Instead, consumption of the fumarate through a cascade cycloaddition process involving the reaction components was identified as a likely pathway for catalyst activation.