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A Study of Unsaturated Pyrazolate-Bridged Diruthenium Carbonyl Complexes

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journal contribution
posted on 2002-10-01, 00:00 authored by Yi-Hwa Song, Yun Chi, Yao-Lun Chen, Chao-Shiuan Liu, Wei-Li Ching, Arthur J. Carty, Shie-Ming Peng, Gene-Hsiang Lee
The reaction of Ru3(CO)12 with approximately 3 equiv of 3,5-di-tert-butylpyrazole, (dbpz)H, in hexane at 170 °C in a stainless steel autoclave afforded the unsaturated, pyrazolate-bridged diruthenium complex [Ru2(CO)5(dbpz)2] (2). The spectroscopic and structural analysis indicated that this compound contains a vacant coordination site at one axial position trans to the Ru−Ru linkage. This compound reacted with CO at room temperature to give the saturated complex [Ru2(CO)6(dbpz)2] (1b); its structure is analogous to that of the previously determined complexes [Ru2(CO)6(pz)2], pz = pyrazolate and 3,5-dimethyl pyrazolate, except that the equatorial CO ligands show a skew arrangement, an indication of steric constraints within the coordination sphere. Treatment of 2 with benzyl isocyanide or with pyridine in toluene leads to the formation of substitution products [Ru2(CO)4(L)(dbpz)2], L = CNCH2Ph and pyridine, in which the incoming donor ligand occupies an equatorial position at the saturated Ru center. The structural significance of this pyrazolate-bridged diruthenium complex 2 is discussed.