Facile one-step synthesis of the cobalt(III) and nickel(III) tertiary arsine complexes [MI3(AsMe3)2](M = Co or Ni) directly from the powdered elemental metals

Abstract

Diiodotrimethylarsine, Me₃AsI₂, was treated with cobalt or nickel metal powder to give the metal(III) complex, [MI₃(AsMe₃)₂]. In the case of cobalt, a metal(II) complex, [AsMe₃I][CoI₃(AsMe₃)], was also produced, whereas for the nickel reaction only the nickel(III) complex, [NiI₃(AsMe₃)₂], was formed in quantitative yield. The only other product from the reactions was diiodine, which was detected spectrophotometrically. Both complexes have been crystallographically characterised and found to be isostructural, consisting of a metal(III) atom with three equatorial iodide ligands capped by two trimethylarsine ligands. These complexes are unique examples of X-ray structural characterisation of compounds of this stoichiometry. Conventional wisdom would not have expected the ‘soft’ ligands I^– and AsMe₃ to bind to the relatively hard metal(III) centre.