Synthesis, reactivity, and X-ray crystal structure of the cationic cluster complex [Os4H3(CO)12(NCMe)2][BF4]

Abstract

The anion [Os₄H₃(CO)₁₂]^– reacts with NOX (X = BF₄ or PF₆) in McCN to give the salt [Os₄H₃(CO)₁₂(NCMe)₂]X in moderate yield. The fluoroborate salt crystallises in space group P2₁/c with a= 17.555(7), b= 9.252(4), c= 17.767(8)Å, β= 108.93(3)°, and Z= 4. The structure was solved by a combination of direct methods and Fourier-difference techniques, and refined to a converged R= 0.049 for 3 454 diffractometer data. The four Os atoms in the cation adopt a ‘butterfly’ arrangement with 4.338(2)Å between the two ‘wingtip’ Os atoms. Each of these two metal atoms is co-ordinated to three carbonyl ligands and an axial acetonitrile ligand oriented away from the centre of the cluster. Each of the two ‘hinge’ Os atoms has three terminal carbonyl groups associated with it. The [Os₄H₃(CO)₁₂(NCMe)₂]⁺ cation reacts with X^–(X = CI or I) to give the neutral complex [Os₄H₃(CO)₁₂X], and with NO₂^– to give the cluster anion [Os₄H(CO)₁₂(NCMe)₂]^–. Protonation of this anion regenerates the title cation. The anion reacts with Au(PPh₃)CI to produce the neutral mixed-metal cluster [Os₄H(CO)₁₂(NCMe)₂{Au(PPh₃)}], a derivative of the unobserved neutral molecule [Os₄H₂(CO)₁₂(NCMe)₂].