Flash Communication: Reactivity of Bis(phosphine) Ligands with Dicobalt Octacarbonyl

High Resolution Image Download MS PowerPoint Slide A series of bis(phosphine) cobalt carbonyl complexes were prepared and investigated in situ using cyclic voltammetry, 1 H, 31 P, and 59 Co NMR spectroscopy (including DOSY), and IR spectroscopy. X-ray diffraction analysis on isolated single crystals confirmed that complex speciation was highly dependent on the nature of the bis(phosphine) and ligand-to-metal stoichiometry. Reactions of [Co 2 (CO) 8 ] with 1,2-bis(dicyclohexylphosphino)ethane (DCyPE) and 1,2-bis(diphenylphosphino)benzene (DPPBz) led to disproportionation of the precursor, affording cationic κ 2 -Co(I) bis(phosphine) complexes with Co(−I) tetracarbonyl cobaltate counteranions. In contrast, ferrocenyl bis(phosphine) ligands 1,1′-bis(diphenylphosphino)ferrocene (DPPF), 1,1′-bis(di-isopropylphosphino)ferrocene (D i PrPF), and 1,1′-bis(dicyclohexylphosphino)ferrocene (DCyPF), displayed different reactivity. D i PrPF and DCyPF appeared to form polymeric species at 1:1 ligand-to-metal ratios but favored the formation of discrete neutral dinuclear complexes of the type [(μ 2 -L)Co 2 (CO) 6 ] when 0.5 equiv of ligand was employed. Reaction of [Co 2 (CO) 8 ] with DPPF yielded a significantly larger molecular assembly. Single-crystal X-ray diffraction revealed an unprecedented metallocyclic structure comprising six cobalt tricarbonyl centers interconnected by four bridging DPPF ligands.