A Three-Coordinate and Quadruply Bonded Mo−Mo Complex

Reaction of MoCl3(THF)3 with [Me2Si{NLi(Dipp)}2]2 (Dipp = 2,6-i-PrC6H3) afforded a triply bonded dimolybdenum complex 1,2-Mo2Cl2[Me2Si(NDipp)2]2 1, spanned by two Me2Si[N(Dipp)]2 ligands, thus resulting in a syn conformation. The air- and moisture-sensitive compound 1 was characterized by NMR spectroscopic, elemental, and single-crystal X-ray crystallographic analysis. Reduction of 1 by Na/Hg yielded the quadruply bonded dimeric complex Mo2[Me2Si(NDipp)2]2 2, which was also characterized by the aforementioned analytical methods. The Mo−Mo bond was determined to be 2.1784(12) Å, which is considered a long quadruple bond. In addition, density functional theory (DFT) computations on compound 2 provided insight into the intriguing Mo−Mo quadruple bond.