Versatile coordination behaviour of Ph2AsCH2AsPh2 with Ru(II)

Treatment of ‘RuCl3 · 3H2O’ with Ph2AsCH2AsPh2 (dpam) in hot EtOH gives either trans-[RuCl2(dpam-As,As′)(dpam-As)2] (1), or cis-[RuCl2(dpam-As,As′)2] (2), depending on the mole ratio. On exposure to light, solutions of 2 isomerise to trans-[RuCl2(dpam-As,As′)2] (3). Treatment of [RuCl2(PPh3)3] with two equivalents of dpam in CH2Cl2 gave a mixture of two products, from which trans-[RuCl2(PPh3) (dpam-As,As′)(dpam-As)] (4) was isolated by recrystallisation. The crystal structures of 1–4 are reported. Complexes 1–3 in CH2Cl2 undergo electrochemical oxidation to Ru(III), and the Ru(III) form of 2 undergoes isomerisation on the voltammetric timescale to the Ru(III) form of 3.