Nickel Alkyl Complexes for Polymerization Catalysis via Oxidative Addition-Decarbonylation of Phosphinephenol Esters

Phosphinephenol esters react with Ni⁰ to afford otherwise difficult to access Ni^II-alkyl complexes. The reaction proceeds efficiently and cleanly by coordination of phosphine to the Ni⁰, which directs an intramolecular oxidative addition into the C(acyl)-O bond followed by rapid carbon monoxide elimination. The potential of this mild preparative pathway was demonstrated by the synthesis of a higher Ni^II-n-alkyl complex, and of a five-membered chelate that is the key intermediate in the nonalternating copolymerization of ethylene and carbon monoxide, as well as its ¹³C-labeled analog. Further, the title reaction can regenerate active polymerization catalyst after CO-induced deactivation under pressure reactor conditions, highlighting its broader utility. This shows the directed oxidative addition-decarbonylation of phenolesters provides a broad platform to access catalytically relevant Ni alkyl complexes.