Synthesis of tetracarboxylatediruthenium(II) compounds: reduction and disproportionation reactions of diruthenium(II,III) units. Crystal structure of Ru 2(μ-O 2CCOPh) 4(thf) 2

Abstract

The treatment of Ru 2Cl(μ-O 2CR) 4 with zinc amalgam in thf, under a nitrogen atmosphere, leads to the isolation of diruthenium(II) compounds of the type Ru 2(μ-O 2CR) 4 (R = Me ( 1), Ph ( 2), C 6H 4- o-Cl ( 3), C 6H 4- p-CMe 3 ( 4), CHMe 2 ( 5), CMe 3 ( 6), CHEt 2 ( 7)). These unsolvated diruthenium complexes are soluble in coordinating solvents giving bis(adducts) of the type Ru 2(μ-O 2CR) 4(S) 2 (S = solvent molecule: MeOH, thf). The substitution of the axial solvent molecules by OPPh 3 affords new compounds of the type Ru 2(μ-O 2CR) 4(OPPh 3) 2 (R = Me ( 8), Ph ( 9), C 6H 4- o-Cl ( 10), C 6H 4- p-CMe 3 ( 11), CHMe 2 ( 12), CMe 3 ( 13), CHEt 2 ( 14)). From the reaction of Ru 2Cl)μ-O 2CMe) 4 with phenylglyoxylic acid the diruthenium(II) compound Ru 2(μ-O 2CCOPh) 4(thf) 2 ( 15) has been isolated in the absence of any additional reducing agent. The crystal structure of 15 has been determined by X-ray crystallography. The structure of this complex shows a diruthenium(II) unit bridged by four phenylglyoxylate ligands with the axial positions occupied by thf molecules, the RuRu distance being 2.2736(8) Å.