Coupling of Alkynyl Ligands at a Quadruply Bonded Molybdenum Dimer

The complex [Mo 2 (C≡CSiMe 3 ) 3 (μ,η 2:η 2 -HC≡CSiMe 3 ){μ,η 1 -C C(SiMe 3 )-η 2 -C⋮CSiMe 3 }(μ-dmpm) 2 ][Li(dme)] ([ 1 ][Li(dme)]; dmpm = 1,2-bis(dimethylphosphino)methane, dme = 1,2-dimethoxyethane) was prepared in 32% yield from the reaction between Mo 2 Cl 4 (dmpm) 2, LiCCSiMe 3, and HCCSiMe 3 in dme. A single-crystal X-ray diffraction study of [ 1 ][Li(dme) 0.5 (OEt 2 ) 0.5 ] revealed that 1 contains an alkynylvinylidene ligand derived from the head-to-tail coupling of two alkynyl ligands.