Triple-decker complexes with a bridging diborolyl ligand: synthesis and structures

Triple-decker complexes with a bridging diborolyl ligand CpCo(μ-1,3-C₃B₂Me₅)-M(C₅R₅) (M = Fe, R = H (2a), Me (2b); M = Ni, R = H (3)) were synthesized in high yields by electrophilic stacking of the sandwich anion [CpCo(1,3-C₃B₂Me₅)]⁻ with the labile complexes [CpFe(SMe₂)₃]⁺, [Cp*Fe(MeCN)₃]⁺, and [CpNi(SMe₂)₂]⁺, respectively. The structures of complexes 2a, 2b, and 3 were determined by X-ray diffraction. The influence of additional unpaired electrons on the structural changes due to the transition from the 30-electron FeCo triple-decker complexes to the 32-electron NiCo complex was investigated.