Preparation of a series of NiL(η2-C60) complexes (L = 1,2-bis(diphenylphosphino)ethane, and 1,1′-bis(diphenylphosphino)ferrocene) by zinc dust reduction

Abstract

A simple method for preparation of nickel-fullerene coordination complexes has been developed. NiLCl2(Br2) and C60 mixtures are reduced by zinc dust upon heating in o-dichlorobenzene. Diffusion of hexane into the reaction mixture results in formation of crystals of NiL(η2-C60)⋅solvent (L = 1,2-bis(diphenylphosphino)ethane (dppe, 1), 1,3-bis(diphenylphosphino)propane (dppp, 2) and 1,1′-bis(diphenylphosphino)ferrocene (dppf, 3)). Nickel coordinates to the 6–6 bonds of C60 by η2- type and has distorted square-planar geometry. The average Ni–C(C60) bond lengths are 1.936(6)–1.977(3) Å. We found that increase in the P(L)–Ni–P(L) angle and the dihedral angle between the PNiP and CNiC planes results in elongation of the Ni–C(C60) and Ni–P(L) bonds by 0.04–0.06 Å. Complexes 1–3 contain zero-valent nickel since fullerenes are neutral according to the IR- and visible-NIR spectra. Some of the IR-active bands of C60 are split into three bands in spectra of 1–3 due to C60 symmetry lowering, and the F1u(4) C60 mode is shifted to lower wave numbers due to the π-back donation. The formation of 1–3 is accompanied by appearance of new bands in the visible range at 435–447 and 661–680 nm.