Synthesis of ruthenium carbonyl cluster complexes containing bis(2′-pyridylethynyl)benzene derivatives: Construction of an extended Zero-valent ruthenium chain

Abstract

The reactions of Ru3(CO)12 in a refluxing acetonitrile-toluene solution with a half equivalent of the ligand 1,3-bis(pyridin-2-ylethynyl)benzene afforded Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,3-C6H3)(2-PyCC)]Ru4(CO)12 (compound 1) and Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,3-C6H2)(2-PyCCH)]Ru3(CO)8 (compound 2). Separately, Ru3(CO)12 was treated with a half equivalent of 1,4-bis(pyridin-2-ylethynyl)benzene in a refluxing acetonitrile-toluene solution to generate Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,4-C6H3)(2-PyCC)]Ru4(CO)12 (compound 3) and Ru3(CO)8Ru(CO)2[μ-(2-PyCCH)(1,4-C6H2)(2-PyCCH)]Ru3(CO)8 (compound 4). Compounds 1–4 were characterized by FT-IR, NMR, ESI-HRMS and single-crystal X-ray diffraction. The structure of compound 2 was found to contain two triruthenium triangular frameworks, and compound 1 was found to be an intermediate of compound 2. Compounds 1 and 3 were shown to consist of triruthenium and tetraruthenium frameworks. Both compounds 1 and 3 exhibited two types of fluxional behavior in solution due to degenerate rearrangement of the acetylide ligand and restricted rotation. This assumption was confirmed by the variable-temperature 1H NMR, COSY and NOESY spectra. Noticeably, compound 4 possessed a quasilinear pentaruthenium structure, and compound 3 was shown to be an intermediate to compound 4.