Towards Nickel-Catalysed Olefin Metathesis: A Computational Study of Nickelacyclobutane Fragmentation Reactions

A detailed picture of the reactivity of metallacyclobutanes is key to the understanding and development of new reactions relying on these reactive intermediates, including olefin metathesis and cyclopropanation. More than 40 years ago, Miyashita and Grubbs reported experimental studies on the thermal decomposition pathways of a phosphine-supported nickelacyclobutane (NiCB) suggesting that nickel may be amenable to both cyclopropanation and olefin metathesis. Here we report a computational investigation of this system that shows that cyclopropane reductive elimination is the primary decomposition pathway for monometallic NiCBs, independently of the number of coordinated phosphine ligands. Further calculations suggest that bimetallic species may be responsible for the olefinic products of apparent [2+2] cycloreversion.