Abstract

A series of new cobalt(ii) and nickel(ii) tris(3,5-diphenylpyrazolyl)borate (Tp^Ph2) dithiocarbamate complexes [Tp^Ph2M(dtc)] (M = Co, dtc = S<inf>2</inf>CNEt<inf>2</inf>1, S<inf>2</inf>CNBz<inf>2</inf>2 and S <inf>2</inf>CN(CH<inf>2</inf>)<inf>4</inf>3; M = Ni, dtc = S <inf>2</inf>CNEt<inf>2</inf>4, S<inf>2</inf>CNBz<inf>2</inf>5 and S <inf>2</inf>CN(CH<inf>2</inf>)<inf>4</inf>6) have been prepared by the reaction of [Tp^Ph2MBr] with Nadtc in CH<inf>2</inf>Cl<inf>2</inf>. IR spectroscopy indicates that the Tp^Ph2 ligand is κ³ coordinated while the dithiocarbamate ligand is κ² coordinated. ¹H NMR and UV-Vis spectroscopy are consistent with high spin, five-coordinate metal centres. X-ray crystallographic studies of 1, 3 and 6 confirm the κ³ coordination of the Tp^Ph2 ligand and reveal an intermediate five-coordinate geometry with an asymmetrically coordinated dithiocarbamate ligand. Electrochemical studies of 1-6 reveal a metal centred reversible one-electron oxidation to M(iii). Attempted oxidation of [Tp^Ph2Co(dtc)] with [FeCpCp^COMe]BF<inf>4</inf> yields [Co(dtc)<inf>3</inf>], Hpz^Ph2 and a further product which may be [Tp^Ph2CoBp^Ph2]. DFT calculations indicate that the low redox potentials in these complexes result from a strongly antibonding M-S σ* HOMO. © 2011 The Royal Society of Chemistry.