Synthesis and Interconversions of Several Tri- and Tetranuclear Ruthenium Isocyanato Carbonyl Clusters. Crystal and Molecular Structure of H₃Ru₄(NCO)(CO)₁₂

The reaction of Ru₃(CO)₁₂ with PPN(N₃) was found to lead through several intermediates to PPN[Ru₄(NCO)(CO)₁₃]. The structure of this product is proposed to be analogous to [Ru₄Cl(CO)₁₃]- with the μ-NCO replacing the chloride. Spectroscopic characterization of the intermediates suggests that their formulations are [Ru₃(NCO)(CO)₁₁]- and [Ru₃-(NCO)(CO)₁₀]-. Protonation of the initial reaction solution containing these trimers allows the isolation of HRu₃(NCO)(CO)₁₀ in low yield. The tetranuclear cluster reacts with CO at room temperature to give [Ru₃(NCO)(CO)₁₁]-, and it reacts with H₂ under the same conditions to give [H₂Ru₄(NCO)(CO)₁₂]-. This anion reacts with CF₃SO₃H to give H₃Ru₄(NCO)(CO)₁₂, which was characterized by a single-crystal X-ray crystallographic study [P2₁/n space group; a = 9.836 (2), b = 22.063 (5), c = 10.056 (2) Å; β = 97.93 (1)°; V= 2161 (1) ų; Z = 4; final R = 0.024; final R_w = 0.028]. The structure contains a butterfly arrangement of ruthenium tricarbonyl groups with the isocyanate bridging the open edge. The hydrogen atoms were located and refined.