Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands

The syntheses of the two dicarbonyl complexes [Ru(bdmpza)Cl(CO)(2)] (3) and [Ru(2,2-bdmpzp)Cl(CO)(2)] (4), bearing a bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) or a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionato (2,2-bdmpzp) scorpionate ligand, are described. Both complexes are obtained by reacting the polymer [RuCl2(CO)(2)](n) with either K[bdmpza] or K[2,2-bdmpzp]. Reaction of the acid Hbdmpza with [Ru-3(CO)(12)] results in the formation of two structural isomers of a hydrido complex, [Ru(bdmpza)H(CO)(2)] (5a,b). Under aerobic conditions conversion of [Ru(bdmpza)H(CO)(2)] (5a,b) to form the Ru(I) dimer [Ru(bdmpza)-(CO)(mu-CO)](2) (6) seems to be hindered in comparison to the case for the eta(5)-C5H5 (Cp) analogues. Dimer 6 is obtained via a reaction of Hbdmpza with catena-[Ru(OAc)(CO)(2)](n) instead. The molecular structures of 3, 4, and 6 have been obtained by single-crystal X-ray structure determinations. The precatalytic properties of the two dicarbonyl complexes 3 and 4 toward the catalytic oxidation of cyclohexene with different oxidizing agents are discussed as well.