THE REVERSIBLE INSERTION REACTION OF CARBON-DIOXIDE WITH THE W(CO)(5)OH- ANION - ISOLATION AND CHARACTERIZATION OF THE RESULTING BICARBONATE COMPLEX [PPN][W(CO)(5)O2COH]

[Et(4)N][W(CO)(5)OH] (1) and [PPN][W(CO)(5)O2COH] (2) have been synthe sized and characterized by H-1 and C-13 NMR and IR spectroscopies and the X-ray crystal structure of 2 has been determined. Complex 2 crysta llizes in the triclinic space group P (1) over bar with unit cell para meters a = 12.208(2) Angstrom, b = 13.497(2) Angstrom, 13.681(2) Angst rom, alpha = 101.06(2)degrees, beta = 114.76(1)degrees, gamma = 98.45( 2)degrees, V = 1942.6(5) Angstrom(3), and Z = 2. The structure of the anion of complex 2 consists of a central W(0) bound to five carbonyl l igands, and the coordination around the metal is completed by a monode ntate bound bicarbonate ligand located 2.19(1) Angstrom away from the metal center. In the solid state, two anions are hydrogen bonded to on e another via the bicarbonate ligands in the unit cell. Complex 1 inse rts CO2, COS, or CS2 to rapidly afford the corresponding bicarbonate o r thiocarbonate complexes. The lower limit for the rate constant for t he carboxylation of complex 1 has been determined to be 4.2 x 10(-4) M (-1) s(-1) at -70.2 degrees C, and the lower limit for the rate consta nt for the decarboxylation of complex 2 has been found to be 2.5 x 10( -3) s(-1) at 20.0 degrees C. In addition, the rate constant for the de carbonylation of 2 was determined to be 7.60 x 10(-3) s(-1) at 36.0 de grees C, a value which is somewhat faster than anticipated on the basi s of analogous data for a large variety of W(CO)(5)O(2)CR(-) derivativ es. This is attributed to a diminution of the electron-withdrawing abi lity of the OH substituent in O2COH as a result of hydrogen bonding to solvent. Nevertheless, it is clear that the rate of decarboxylation o f the anion from complex 2 is faster than the rate of CO dissociation. Concomitantly, carboxylation of complex 1 is faster than CO dissociat ion, since the W(CO)(5)OH- is inert toward (CO)-C-13 exchange on the t ime scale of carboxylation at -70.2 degrees C.