Thermodynamic and Kinetic Studies of the Complexes W(CO)3(PCy3)2(L) (L = H2, N2, NCCH3, Pyridine, P(OMe)3, CO) Article

Gonzalez, AA, Zhang, K, Nolan, SP et al. (1988). Thermodynamic and Kinetic Studies of the Complexes W(CO)3(PCy3)2(L) (L = H2, N2, NCCH3, Pyridine, P(OMe)3, CO) . ORGANOMETALLICS, 7(12), 2429-2435. 10.1021/om00102a001

cited authors

  • Gonzalez, AA; Zhang, K; Nolan, SP; de la Vega, RL; Mukerjee, SL; Hoff, CD; Kubas, GJ

authors

abstract

  • The complexes W(CO)3(PCy3)2(L) have been studied by solution calorimetry. The enthalpies of binding (kcal/mol) of ligands to W(PCy3)2(CO)3 in toluene solution are as follows: H2, -9.9, N2, -13.5; NCCH3, -15.1; pyridine, -18.9; P(OMe)3, -26.5; CO, -30.4. Similar values are obtained in tetrahydrofuran solution. These data imply bond strengths much lower than expected from gas-phase studies. The origin of this discrepancy is attributed to the presence of the W•••H-C “agostic” interaction. This is estimated to be on the order of 10 ± 6 kcal/mol. In order to investigate the role of the “agostic” interaction in the energetics of this complex, the kinetics of reaction of W(CO)3[P(C6H11)3]2(py) and W(CO)3[P(C6D11)3]2(py) with P(OMe)3 in toluene were studied. A kinetic isotope effect, kH/kD = 1.20 ± 0.05, was observed, and verifies the importance of the “agostic” bond in ligand substitution for this complex. A mechanism is proposed that involves concerted replacement of coordinated pyridine by the three-center W•••H-C bond. © 1988, American Chemical Society. All rights reserved.

publication date

  • January 1, 1988

published in

Digital Object Identifier (DOI)

start page

  • 2429

end page

  • 2435

volume

  • 7

issue

  • 12