Synthesis and cyclic voltammetry of trinuclear sulphido clusters of nickel(II), palladium(II) and platinum(II) and selenido clusters of nickel(II) with 1,2-bis(diphenylphosphino)ethane, and crystal structures of sulphido and selenido clusters of nickel(II)

Abstract

The reaction between M²⁺(M = Ni, Pd or Pt), 1,2-bis(diphenylphosphino)ethane (dppe), and NaSH or NaSeH in acetonitrile affords the trinuclear clusters [Ni₃S₂(dppe)₃][BPh₄]₂·MeCN 1[Ni₃Se₂(dppe)₃][BPh₄]₂2, [Pd₃S₂(dppe)₃][PF₆]₂3, and [Pt₃S₂(dppe)₃][PF₆]₂·MeCN 4. The X-ray structures of [Ni₃S₂(dppe)₃][PF₆]₂·MeCN and 2 were determined and cyclic voltammograms of 1–4 recorded. The structures of [Ni₃S₂(dppe)₃]²⁺ and [Ni₃Se₂(dppe)₃]²⁺ comprise three square-planar NiE₂P₂(E = S or Se) co-ordination planes sharing two µ₃-E ligands. The Ni–E, Ni ⋯ Ni, and E ⋯ E lengths for [Ni₃S₂(dppe)₃]²⁺ are 2.192, 2.827 and 2.924(6)Å, while for 2 they are 2.311, 3.004 and 3.051(4)Å, indicating a smaller central Ni₃S₂ core for [Ni₃S₂(dppe)₃]²⁺ than the Ni₃Se₂ core of 2. Cyclic voltammograms of complexes 1 and 2 in dimethylformamide (dmf) at 293 K give two reduction peaks with associated oxidation peaks. Moreover, a broad oxidation peak appears at –0.87 V for 1. Two couples at –1.64 and –2.04 for 1 and at –1.59 and –1.87 V for 2 are reversible in acetonitrile solution at 255 K. The cyclic voltammogram of 3 in dmf gives only one reduction peak at a scan rate of 50 mV s^–1 at 293 K, but at 255 K a reversible couple is exhibited at –1.96 V. A reduction peak at –2.10 V with an associated smaller oxidation peak at –2.07 V is observed for 4 in dmf at a scan rate of 50 mV s^–1 at 293 K.