Properties of isocyanide ligands in metal complexes. Characterisation and voltammetric properties of bis(tertiary phosphine)tris(iso-nitrile)cobalt(I) complexes

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Abstract
The cobalt complexes [Co(PPh3)2(CNR)3][PF6](R = Me, Pri, But, p-MeC6H4, or p-ClC6H4), [Co(PMePh2)2-(CNR)3][PF6], [Co(Ph2PCH2CH2PPh2)(CNR)3][PF6](R =p-Me6CH4 or p-ClC6H4) and [Co(Ph2PCH2CH2PPh2)(CNBut)4][PF6]3, have been prepared and characterised. The half-wave potential for the general reaction [Co(PR′3)2(CNR)3]+⇌[Co(PR′3)2(CNR)3]2++ e– depended on the nature of R and R′. Chemical oxidation of the appropriate cobalt(I) complex afforded [Co(PPh3)2(CNBut)3][PF6]2. Assuming that the σ-donor characteristics of RNC remain constant, it is shown that as a π-acceptor ButNC is better than MeNC, and that aryl iso-cyanides are better than their alkyl analogues.