Synthesis, Interconversion, and Structural Characterization of the Closo and Nido Clusters [(p-Cymene)₃M₃S₂]²⁺and [(p-Cymene)₃M₃S₂]⁰(M = Ru, Os)

The first (arene)metal sulfido clusters are described. Salts of the dicationic clusters of the general formula [(p-cymene)₃M₃S₂]²⁺ were prepared from the reaction of [(p-cymene)MCl₂]₂ (M = Ru, [1]²⁺; M = Os, [2]²⁺) with (Me₃Si)₂S, methanolic NaSH, or aqueous Na₂S as sulfide sources. [1](PF₆)₂ cyrstallizes in the triclinic space group P1 with a = 10.495 (3) Å, b = 11.064 (3) Å, c = 18.230 (6) Å, α = 100.62 (2)°, β = 90.93 (3)°, γ = 115.40 (2)°, Z = 2, and d_calcd = 1.883 g cm^-3. The dication [1]²⁺ exists as a closo trigonal-bipyramidal cluster with Ru-Ru distances of 2.763 (3)-2.796 (1) Å and an average Ru-S distance of 2.338 (2) Å. Cyclic voltammetric studies show that [1]²⁺ undergoes two one-electron reductions separated by only 0.137 V vs Ag/AgCl, and [2]²⁺ undergoes a simultaneous two-electron reduction at -0.761 V vs Ag/AgCl. Cobaltocene reduction of [1](PF₆)₂ gives dark blue [1]⁰. This neutral Ru₃S₂ cluster crystallizes in the triclinic space group P1 with a = 9.958 (3) Å, b = 10.270 (3) Å, c = 15.338 (5) Å, α = 78.26 (2)°, β = 85.92 (3)°, γ = 78.53 (2)°, Z = 2, and d_calcd = 1.700 g cm^-3. [1]⁰ adopts a nido framework with two bonding Ru-Ru distances of 2.733 (1) and 2.712 (1) Å and a nonbonding Ru-Ru distance of 3.612 (1) Å. The average Ru-S distances are elongated with respect to the closo cluster. The cymene ligands are bound in an η⁶-fashion and are closer to the metal centers by an average of 0.015 (6) Å. The reduced cluster is highly reactive, and it is oxidized by H⁺ to regenerate the dicationic closo cluster.