POTENTIAL INTERMEDIATES IN CARBON-DIOXIDE REDUCTION PROCESSES - SYNTHESIS AND STRUCTURE OF (MU-FORMATO)DECACARBONYLTRIRUTHENIUM AND (MU-ACETATO)DECACARBONYLTRIRUTHENIUM ANIONS
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The cluster anions [HCO2Ru3(CO)10] and [CH3CO2Ru3(CO)10] have been prepared in high yields by the reaction of Ru3(CO)12 with PPN(O2CH) and PPN(O2CCH3), respectively, in refluxing THF. The formate derivative was characterized structurally and stereodynamically by X-ray crystallography and 13C NMR. The salt [N(PPh3)2][HCO2Ru3(CO)10] crystallizes in the triclinic space group PI with the cell dimensions a = 12.346 (1) ,b= 18.878 (2) , c = 10.843 (2) , = 100.80 (1), = 94.77 (1), = 108.48 (1), V = 2326.6 3, and Z = 2. With use of 3550 reflections having I > 3s(I) the structure was refined to discrepancy indices of R1 = 0.036 and R2 = 0.042 and a goodness-of-fit index of 1.07. The three ruthenium atoms define an isosceles triangle with the formate ligand bridging diaxially the shortest edge. The triruthenium core is symmetrically bridged with three CO ligands. A variable-temperature 13C NMR study of [PPN] [HC-O2Ru3(CO)10] reveals the anion to be fluxional in the solution. The spectra are indicative of several dynamic processes occurring over the range -100 to +40 C. Decarboxylation of HCO2Ru3(CO)10 in the presence of CO was observed at elevated temperatures to provide HRu3(CO)11; the reverse reaction takes place slowly at 60 psi and more readily at 400 psi of CO2 pressure. 1983, American Chemical Society. All rights reserved.