Cyclic Voltammetric Studies of Arylisocyanidecobalt(I) Complexes with Tertiary Phosphine Ligands

摘要

50 Arylisocyanide-Co(I) complexes with tertiary phosphine ligands,both monosubstituted [Co(CNR)_4PR'_3]X and disubstituted [Co(CNR)3(PR'3)2]X,X = ClO4,BF4,have been investigated by cyclic voltammetry in acetonitrile solution.Behaviour ranges from reversible to irreversible.Several distinct trends emerge.The E_(ox) values systematically increase as substituents in the arylisocyanide ligand progress from electron-donating to electron-withdrawing.Sometimes this trend is reversed,possibly attributable to steric hindrance.The E_(ox) values also systematically increase as the tertiary phosphine ligand becomes weaker sigma-donating/stronger pi*-accepting due to substituents.Trialkylphosphines show weaker 7t-acidity than triarylphosphines,except with electron-withdrawing substituents,like P(CH2Ph)3 and P(CH2CH2CN)3.Cobalt(I) complexes of 4:1 arylisocyanide: tertiary phosphine ligand composition tend to have substantially higher E_(ox) values than 3:2 complexes with identical arylisocyanide and tertiary phosphine ligands.