Complexes with the general formula of [Ru2(RCOO)4X], where R=H, X=Cl, or Br; R=Me, X=Cl, Br, I, SCN, NO3, or MeCOO; R=ph, X=Cl, or Br, were prepared. The magnetic properties, conductivities, polarographic behavior, and infrared spectra of these complexes were investigated. All the complexes show magnetic moments of 2.84–2.96 B.M., and their susceptibilities, at from about 300 to 100°K, can be fitted to the Curie-Weiss law with negative values of the Weiss constant (θ=−30–−60°K). These complexes seem to be isostructural. Monochloroacetato-, and trichloroacetatoruthenium complexes ([Ru2(CH2ClCOO)4Cl]·2H2O and [Ru(OH)(CCl3COO)2(H2O)]) were also prepared.

The crystal structure of Ru2(OCOCH3)4Cl has been determined from visually estimated Cu Kα data. The crystal is composed of the dinuclear, carboxylato-bridged species Ru2(OCOCH3)4+ and the bridging chloride anions. The molecular structure is almost identical with that of the analogous butyrato complex, but the chloridebridged chains run parallel with the c axis only.

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X-Ray structural determination of Ru2(HCOO)4Br showed that the unit cell contains two crystallo-graphically independent formato bridged dinuclear units, Ru2(HCOO)4+, each of which is centrosymmetric. Two adjacent units are bridged by bromide ion to make infinity zigzag chains.

Several ruthenium acetato complexes have been prepared by various methods.,-3) Recently, T. A.Stephenson and G. Wilkinson prepared crystalline complexes with the formula Ru2(OCOR)4Cl, (R= Me, Et, n-Pr) ; those complexes contain two ruthenium atoms of the formal oxidation state of II and 111.3) These complexes have high magnetic moments over the temperature range of 300-100°K and appear to be the first spin-free complexes of ruthenium.We have prepared independently the formato and acetato complexes of ruthenium, Ru2(HOCO)4-Cl and Ru2(CH3OCO)4X (X=C1, Br, I),4) by the reaction in a sealed tube of ruthenium (III and IV) chloride with formic and acetic acid solutions respectively.The formato complex prepared is a black-brown crystal and is not dissolved in any common organic solvents except the alcohols. The infrared spectra of this complex are similar to those of hydrous Cu(II) formate.s) However, the absorptions of the carboxyl-stretching vibrations of the ruthenium formato complex shift to a lower wave number region compared with those of Cu(II) formate.in an acetato complex where acetate functions as a bidentate-bridging group may be expected not to be greatly different from that in a free acetate 150 cm-1) suggests that the complex has four bidentate formates. No absorptions due to the OH or the OH2 group were found in the infrared spectra. The magnetic moment of this complex is 2.92 B.M. per ruthenium atom. This value is similar to those for Ru2(CH3OC0)4X4) and Ru2-(OCOR)4C13) at room temperature and is higher than the magnetic moments of ruthenium d5 spinpaired complexes.7) These findings, along with the molecular weight, suggest a dimer structure, Ru2(HOCO)4C1, for the formato complex prepared; the complex is considered to be of a type similar to the acetato complex previously reported.3)Experimental. Ruthenium trichloride trihydrate (300 mg) was dissolved in 3 M formic acid (5 ml) and was gently heated for about 60 min in a sealed tube. The solution thus obtained was transferred to a porcelain dish and concentrated on a water bath to produce crystals. The crude product was dissolved in a 3 M formic acid solution; this solution was evaporated at room temperature for several days to obtain the crystalline product. The crystals were washed with water and ethanol in turn, and dried in vacuo.