Incorporation of alkyne and vinylidene ligands into tetrazolate groups at a sulfur-rich dimolybdenum site using sodium azide

Treatment of either the μ-alkyne complex [Mo2Cp2(μ-SMe)3(μ-PhCCH)](BF4) (1) or the μ-vinylidene derivatives [Mo2Cp2(μ-SMe)3(μ-η1:η2-(CCHR)](BF4) (2) (R=Ph, Tol, nPr, C(CH3)CH2) with NaN3 in ethanol at room temperature readily afforded μ-tetrazolate carbene complexes [Mo2Cp2(μ-SMe)3){μ-η1(C):η1(N)-N4CCR)}] (R=Ph (4a), Tol (4b), nPr (4c), C(CH3)CH2 (4d)). A mechanism which accounts for the formation of 4 by intramolecular 1,3-dipolar cycloaddition of metal-coordinated azide ligands to metal-coordinated nitriles is discussed. The structure of complex 4a has been determined by single X-ray diffraction analysis.