ANIONIC GROUP-6 METAL-CARBONYL OXALATE COMPLEXES - X-RAY STRUCTURES OF [ET4N]2[W(CO)4C2O4] AND [PPN]2[W2(CO)8C2O4]BULLET-1/2(CH3CH2)2O

The reaction of the oxalate anion, C2O42-, with W(CO)5(solvent) results in rapid formation of W(CO)4(eta-2-C2O4)2- (1). On the basis of kinetic parameters previously determined for a series of W(CO)5O2CR- derivatives, complexes containing a carboxylate ligand with a good electron-releasing group, R, are subject to facile displacement of a cis CO. Indeed, in the case of the predicted initial product, W(CO)5(eta-1-C2O4)2-, this displacement is anticipated to occur readily, as was observed, with t1/2 = 23 s. Complex 1 reacts with a second molecule Of W(CO)5(solvent) to form the stable dimer W2(CO)8(eta-2-C2O4)2- (2). Additionally, the dimeric species can be formed directly from W(CO)5(solvent) + 1/2C2O42-. This reaction initially gives W2(CO)10(eta-1-C2O4)2-, from which 2 can be produced by removal of two labile CO molecules. The X-ray structures of [Et4N]2[1] and [PPN]2[2].1/2(CH3CH2)2O are reported. The complex [Et4N]2[1] crystallizes in the monoclinic space group P2(1)/n with a = 8.581 (5) angstrom, b = 24.773 (9) angstrom, C= 13.151(5) angstrom, beta = 108.56 (3)-degrees, V = 2650(2) angstrom3, and Z = 4. Refinement converged at R = 5.51% and R(w) = 4.70% for those 2890 reflections with F > 4.0-sigma(F) at T = 193 K. The complex [PPN]2[2].1/2(CH3CH2)2O crystallizes in the monoclinic space group P2(1)/c with a = 14.745 (7) angstrom, b = 12.916 (4) angstrom, c = 20.415 (9) angstrom, beta = 95.60 (4)-degrees, V = 3869 (3) angstrom3, and Z = 2. Refinement converged at R = 6.47% and R(w) = 6.08% for those 4695 reflections with F > 4.0-sigma(F) at T = 193 K.