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.