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 F_1u(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.

Keywords:

• Fullerenes
• Nickel
• Coordination complexes
• Crystal growth
• Solid-state structures
• IR and UV–vis spectroscopy

Notes

This work was supported by RFBR-JSPS (Japan – Russia Research Cooperative Program) [grant number 12-03-92107].