Syntheses, structures and properties of tri-n-butylphosphine cobalt complexes containing o-benzenedithiolate ligands in unusual co-ordination modes

Abstract

The complex [Co₃(bdt)₃(PBuⁿ₃)₃]1(H₂bdt = benzene-1,2-dithiol) was obtained by the reaction of CoCl₂, Na₂bdt and PBuⁿ₃ in 1:1:2 molar ratio in methanol. It crystallizes in triclinic space group P with a= 13.694(4), b= 18.460(4), c= 13.656(4)Å, α= 100.69(2), β= 108.68(2), γ= 85.06(2)°, Z= 2, from 6366 reflections with I > 3σ(I), final R(R′)= 0.059 (0.066). The Co₃ atoms form an isosceles triangle with rather short Co-Co bonds. The bdt ligands either bridge between two Co atoms or strongly chelate terminally to one Co atom and simultaneously bridge weakly to the others. Restricted air oxidation of 1 results in the isolation of [PHBuⁿ₃][Co(bdt)₂(PBuⁿ₃)]2, which crystallizes in triclinic space group P with a= 10.800(3), b= 13.533(4), c= 15.342(2)Å, α= 96.37(2), β= 108.57(2), γ= 97.02(2)°, Z= 2, from 3801 reflections with I > 3σ(I), R(R′)= 0.086 (0.088). The Co atom is in a square-pyramidal co-ordination environment with P in the axial position. The PBuⁿ₃ group dissociates easily in dimethyl sulphoxide yielding paramagnetic [Co(bdt)₂]^–3 with square-planar cobalt co-ordination. Proton NMR data are discussed and cyclic voltammetry data reported.