CN and NO Bond Cleavages of Acetonitrile and Nitrosyl Ligands at a Dimolybdenum Center to Render Ethylidyne and Acetamidinate Ligands

Extended reduction of [Mo2Cp2(mu-Cl)(mu-(PBu2)-Bu-t)(NO)(2)] (1) with Na(Hg) in acetonitrile (MeCN) at room temperature resulted in an unprecedented full cleavage of the C N bond of a coordinated MeCN molecule to yield the vinylidene derivative Na[Mo2Cp2(mu-(PBu2)-Bu-t)(mu-CCH2)(NO)(2)], which upon protonation with (NH4)PF6 gave the ethylidyne complex [Mo2Cp2(mu-(PBu2)-Bu-t)(mu-CMe)(NO)(2)] [Mo1-Mo2 = 2.9218(2) angstrom] in a selective and reversible way. Controlled reduction of 1 at 273 K yielded instead, after protonation, the 30-electron acetamidinate complex [Mo2Cp2(mu-(PBu2)-Bu-t)(mu-kappa N:kappa N '-HNCMeNH)(mu-NO)]PF6 [Mo1-Mo2 = 2.603(2) angstrom], in a process thought to stem from the paramagnetic MeCN-bridged intermediate [Mo2Cp2(mu-(PBu2)-Bu-t)(mu-NCMe)(NO)(2)], followed by a complex sequence of elementary steps including cleavage of the N O bond of a nitrosyl ligand.