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 [Ru3(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)­(μ-CO)]2 (6) seems to be hindered in comparison to the
case for the η5-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.