Cyclization of Bisphosphines to Phosphacycles via the Cleavage of Two Carbon–Phosphorus Bonds by Nickel Catalysis

The nickel-catalyzed cyclization of bisphosphine derivatives to form various phosphacycles is reported. The reaction proceeds via the cleavage of two carbon–phosphorus bonds of the bisphosphine. Unlike the previously reported palladium catalysts, the use of nickel as a catalyst allows for the cyclization that requires C­(alkyl)–P bond cleavage. A phospha-nickelacycle intermediate was successfully isolated and characterized by X-ray crystallography.