Teaching the Cummins Complex Heterodimerization: Formation of Unorthodox Heteroleptic X3MoMoY3 Dimers with Ultralong Metal-Metal Triple Bonds

Attempts to stabilize mononuclear trigonal-planar Mo(+3) complexes by (tripodal) silanolates or alkoxides, which had recently been shown to synergize exceedingly well with high valent molybdenum or tungsten alkylidynes, afforded unsymmetrical dimolybdenum complexes of the general type [X3MoMoY3]; not only is this ligand pattern unprece-dented, but these dimers incorporate the intact Cummins complex [(tBu)(Ar)N]3Mo (Ar = 3,5-dimethylphenyl), which is famous for not engaging in metal-metal triple bonding otherwise. The remarkable ease of heterodimerization likely reflects a pronounced kinetic selectivity. The new complexes were characterized by crystallographic and spectroscopic means; they show highly deshielded 95Mo NMR signals and comprise unusually long yet robust MoMo bonds