Cycloaddition of Phosphaalkynes to High-Oxidation-State Metal Alkylidenes: Synthesis and Characterization of a Unique Phosphametallacyclobutene via an Alkoxide Ligand Shift

The phosphametallacycle 3, [ArN][RO]MoC(t-Bu)P(OR)C(H)(t-Bu) (Ar = 2,6-(i-Pr)2-C6H3, R = CMe(CF3)2), is formed from the cycloaddition of tert-butylphosphaacetylene to the high-oxidation-state molybdenum alkylidene [ArN][RO]2MoC(H)(t-Bu), accompanied by an alkoxide metal-to-ligand shift. The 1-phospha-3-molybdacyclobut-2-ene has been characterized by multinuclear NMR spectroscopy and its molecular structure determined by X-ray crystallographic analysis.