Structural reorganizations accompanying the nickel(II)–nickel(I) redox change in nickel complexes with the tripodal ligand MeC(CH2PPh2)3(triphos, L). X-Ray crystal structure of [NiL(I)]2[As6I8]

Abstract

The stereodynamic aspects of the nickel(II)–nickel(I) conversion in complexes of the tridentate phosphine MeC(CH₂PPh₂)₃, (triphos, L) have been analysed. The structural reorganization, which accompanies the redox change, is pointed out. The substantial electrochemical reversibility observed for the nickel(II)–nickel(I) reduction, being indicative of minor molecular rearrangement, is consistent with the simple elongation of the Ni–I bond distance in the nickel(I) with respect to the nickel(II) derivative [2.546(2)vs. 2.414(4)Å]. The nickel(II) complexes [NiL(X)]Y (X = Cl, Br, or I, Y = ClO₄) and [NiL(I)]₂[As₆I₈] have been synthetized and characterized. A complete X-ray analysis has been carried out for [NiL(I)]₂[As₆I₈]. a= 22.500(8), b= 19.092(5), c= 24.912(12)Å, β= 109.29(4)°, space group C2/c, Z= 4. The X-ray results showed two very interesting features: the isolation of a tetrahedral nickel(II) complex with the unprecedented P₃X donor atom set and the formation of the new polyanionic cluster species [As₆I₈]^2–. An angular overlap model analysis was performed to rationalize the electronic spectra of the [NiL(X)]⁺ complexes (X = Cl, Br, or I).