Reactivity of the 16e(p-cymene)Ru half-sandwich complex containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand towards diynes

Abstract

The reactions of the 16e half-sandwich complex (p-cymene)Ru(S₂C₂B₁₀H₁₀) (Ru16e) with 1,4-diethynylbenzene (L1), 3′,6-diethynyl-1,1′-binaphthyl-2,7′-diyl diacetate (L2), 2-bromo-5-ethynylthiophene (L3) and 2,5-diethynylthiophene (L4) lead to 18e mononuclear complexes (p-cymene)Ru(S₂C₂B₁₀H₉)(H₂CCPhCCH) (1), (p-cymene)Ru(S₂C₂B₁₀H₉)[H₂CC(C₂₄H₁₆O₄)CCH] (2), (p-cymene)Ru(S₂C₂B₁₀H₉) [H₂CC(C₄H₂S)Br] (3) and (p-cymene)Ru(S₂C₂B₁₀H₉) [H₂CC(C₄H₂S)CCH] (4), respectively. In all of them, metal-induced B–H activation has occurred, which leads to a stable Ru–B bond, and the structures take a cisoid arrangement. Only in the case of L4, the binuclear complexes [(p-cymene)Ru(S₂C₂B₁₀H₉)]₂[H₂CC(C₄H₂S)CCH₂] (5a and 5b) are observed, which are conformational isomers generated by the differing orientations of the p-cymene unit. 4 can be readily converted to the complex (p-cymene)Ru(S₂C₂B₁₀H₉)[H₂CC(C₄H₂S)COCH₃] (6) in the presence of silica and H₂O. All of these products 1–6 were characterized by NMR, IR, elemental analysis and mass spectrometry. The structures of 1, 3, and 5a were also determined by single-crystal X-ray diffraction analysis.