Abstract
Nickelacyclobutanes are mostly invoked as reactive intermediates in the reaction of nickel carbenes and olefins to yield cyclopropanes. Nevertheless, early work suggested that other decomposition routes such as β‐hydride elimination and even metathesis could be accessible. Herein, we report the isolation and characterization of a stable pentacoordinated nickelacyclobutane incorporated in a pincer complex. The coordination of different coligands to the nickelacyclobutane determines its selective decomposition along cyclopropanation, metathesis or apparent β‐hydride elimination pathways. DFT calculations shed light on the mechanism of these different pathways.
Highlights
Nickelacyclobutanes are mostly invoked as reactive intermediates in the reaction of nickel carbenes and olefins to yield cyclopropanes
Mechanistic studies using nitrogen ylides as the carbene source have shown that olefin coordination prior to carbene formation enhances nickelacyclobutane formation over unproductive decomposition of the nickel carbene intermediate.[9,10]. Direct observations of such [2+2] cycloadditions are limited to reactions of nickel fluorocarbenes with fluorinated olefins
Further indication for the feasibility of Ni-based olefin metathesis comes from early work by Miyashita and Grubbs, in which they identified carbene-derived products from the thermal decomposition of phosphine-supported nickelacyclobutanes.[11,13,14]
Summary
Nickelacyclobutanes are mostly invoked as reactive intermediates in the reaction of nickel carbenes and olefins to yield cyclopropanes. The resulting crystal structure confirms the h1(N) binding mode of the diazo ligand and the tridentate P-h2(C,C)-P pincer coordination (see SI, section 4).
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