Influence of carboxylic acids on the reactions with chlorotetraacetatodiruthenium(II,III): X-ray crystal structure of [Ru 2(μ-O 2CC 4H 3S) 4(OPPh 3) 2]BF 4·2H 2O

Abstract

The reaction of Ru 2Cl(μ-O 2CCH 3) 4 with indole-2-carboxylic, N-methyl-pyrrole-2-carboxylic, furane-2-carboxylic, thiophene-2-carboxylic and benzofurane-2-carboxylic acids, which contain nitrogen, oxygen or sulphur atoms in the α position with respect to the carboxylate group, leads to compounds of the type Ru 2Cl(μ-O 2CR) 4. In these compounds O,O-coordination of the carboxylate ligands has been found. The analogous reaction with quinoline-2-carboxylic acid (Hquin) gives a disproportionation process with formation of Ru(quin) 3 and Ru 2(quin) 4; in this case, N,O-coordination of the ligand has been observed. The indole-2-carboxylato derivative has a non-polymeric structure, whereas with the other ligands polymeric structures with chlorine atoms bridging Ru 2 5+ units are formed. Treatment of Ru 2Cl(μ-O 2CR) 4 in thf or acetone with AgBF 4 gave [Ru 2(μ-O 2CR) 4L 2]BF 4 (L = thf, acetone; R = N-methyl-2-pyrrolyl, 2-furyl, 2-thienyl) or [Ru 2(μ-O 2CR) 4]BF 4 (R = 2-benzofuryl). The axial positions of these compounds can be occupied by OPPh 3 to give the corresponding [Ru 2(μ-O 2CR) 4(OPPh 3) 2]BF 4 The compounds have been characterized by analytical, spectroscopic and magnetic data. The structure of [Ru 2(μ-O 2CC 4H 3S) 4(OPPh 3) 2BF 4·2H 2O has been determined by X-ray crystallography. The dinuclear cation has two ruthenium atoms linked by four bridging thiophene-2-carboxylate ligands and two OPPh 3 ligands coordinated to axial positions, with an Ru—Ru distance of 2.2747(11) Å.