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 synthesized 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 crystallizes in the triclinic space group P (1) over bar with unit cell parameters a = 12.208(2) Angstrom, b = 13.497(2) Angstrom, 13.681(2) Angstrom, 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 ligands, and the coordination around the metal is completed by a monodentate bound bicarbonate ligand located 2.19(1) Angstrom away from the metal center. In the solid state, two anions are hydrogen bonded to one another via the bicarbonate ligands in the unit cell. Complex 1 inserts CO2, COS, or CS2 to rapidly afford the corresponding bicarbonate or thiocarbonate complexes. The lower limit for the rate constant for the 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 constant 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 decarbonylation of 2 was determined to be 7.60 x 10(-3) s(-1) at 36.0 degrees C, a value which is somewhat faster than anticipated on the basis of analogous data for a large variety of W(CO)(5)O(2)CR(-) derivatives. This is attributed to a diminution of the electron-withdrawing ability of the OH substituent in O2COH as a result of hydrogen bonding to solvent. Nevertheless, it is clear that the rate of decarboxylation of the anion from complex 2 is faster than the rate of CO dissociation. Concomitantly, carboxylation of complex 1 is faster than CO dissociation, since the W(CO)(5)OH- is inert toward (CO)-C-13 exchange on the time scale of carboxylation at -70.2 degrees C.