Isolation and Characterization of the Molybdenum Alkylidyne Complex [(F3C)Me2CO]2Mo(C-t-Bu)[N(Ar)PC(H)(CMe2Ph)] and Its Conversion to a Phosphamolybdacyclobutene

Novel molybdenum alkylidyne [(F3C)Me2CO]2Mo(C-t-Bu)[N(Ar)PC(H)(CMe2Ph)] (Ar = 2,6-(i-Pr)2C6H3; 3b) is formed in the reaction of tert-butylphosphaalkyne 2 with molybdenum alkylidene 1b. Alkylidyne 3b, which contains a formal (phosphaalkenyl)amido ligand, rearranges quantitatively at elevated temperature to form the alkoxide-shifted phosphamolybdacyclobutene 4b. Complexes 3b and 4b have been fully characterized by spectroscopic and X-ray crystallographic analysis; cleavage of the P⋮C-t-Bu triple bond in complex 3b is confirmed.