A Study of Unsaturated Pyrazolate-Bridged Diruthenium Carbonyl Complexes

• Published in: Organometallics 2002-10, Vol.21 (22), p.4735-4742
• Main Authors: Song, Yi-Hwa, Chi, Yun, Chen, Yao-Lun, Liu, Chao-Shiuan, Ching, Wei-Li, Carty, Arthur J, Peng, Shie-Ming, Lee, Gene-Hsiang
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om020445r

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.