Benzoatokomplexe des Rutheniums, 1. Mitt. Synthese, Eigenschaften und Kristallstruktur von Ru2(C6H5COO)4(C6H5COOH)2 und Ru2(C6H5COO)5·C6H5COOH / Benzoato Complexes of Ruthenium , Part 1 Synthesis, Properties and Crystal Structure of Ru2(C6H5COO)4(C6H5COOH)2 and Ru2(C6H5COO)5·C6H5COOH

Abstract

Ru2(C6H5COO)4(C6H5COOH)2 (1) is formed as main product besides small amounts of Ru2(C6H5COO)5·C6H5COOH (2) by the reaction of Ruthenium (III) acetylacetonate in molten benzoic acid. 1 forms monoclinic black crystals with the space group P21/n and the lattice constants a = 1091.0, b = 1164.1, c = 1526.8 pm, β = 90.53°, Z = 2.2 is obtained as triclinic red needles with the space group P1̄ and the lattice constants a - 1178.4, b = 1605.3, c = 1043.9 pm, a = 99.07°, β = 95.45°, y - 83.22°, Z = 2. Both com pounds exhibit carboxylate bridged dimers [Ru2(C6H5COO)4]n+ (n=0, 1). In case of the isolated Ru(II) dimer 1 two benzoic acid m olecules occupy axial positions and form hydrogen bridges to carboxylate O-atoms. 1 is paramagnetic with two unpaired electrons per dimeric unit corresponding to an electron configuration σ2π4δ2π*3δ* and a bond order of 2 (Ru-Ru = 226.3 pm ). It decomposes at 230 °C to Ru2(C6H5COO)4 and at 350 °C to Ru metal. 2 is polymeric. A benzoate anion functions as bridging ligand between [Ru2(C6H5COO)4]+ dimers. The benzoic acid molecule is weakly associated to the polymer by an H-bridge. A Ru-Ru bond order of 2.5 and a Ru-Ru distance of 227.7 pm are observed.