Estimating the Effective Steric Impact of PtBu2Me, PiPr3, and PCy3
摘要:
Enthalpies of reaction of Ru(CO)(2)L(2) (L = (PPr3)-Pr-i, P(t)Bu(2)Me, and PCy(3)) with MeNC, PhC=CPh (both addition reactions) and PhCC-H (C-H oxidative addition) in toluene ape exothermic in the range 10-25 kcal/mol and are interpreted in terms of P(t)Bu(2)Me being more bulky than (PPr3)-Pr-i or PCy(3). Enthalpy comparisons show that the larger cone angle of PCy(3) than of (PPr3)-Pr-i can be overcome by the greater donor power of PCy(3); the origin of the greater donor power of PCy(3) is discussed.
Estimating the Effective Steric Impact of PtBu2Me, PiPr3, and PCy3
摘要:
Enthalpies of reaction of Ru(CO)(2)L(2) (L = (PPr3)-Pr-i, P(t)Bu(2)Me, and PCy(3)) with MeNC, PhC=CPh (both addition reactions) and PhCC-H (C-H oxidative addition) in toluene ape exothermic in the range 10-25 kcal/mol and are interpreted in terms of P(t)Bu(2)Me being more bulky than (PPr3)-Pr-i or PCy(3). Enthalpy comparisons show that the larger cone angle of PCy(3) than of (PPr3)-Pr-i can be overcome by the greater donor power of PCy(3); the origin of the greater donor power of PCy(3) is discussed.
Ligand (L) Influence on CO Binding Enthalpies to Ru(CO)<sub>2</sub>L<sub>2</sub>
作者:Chunbang Li、Montserrat Oliván、Steven P. Nolan、Kenneth G. Caulton
DOI:10.1021/om970220u
日期:1997.9.1
Reaction enthalpies for the addition of CO to Ru(CO)(2)L-2 (L = (PBu2Me)-Bu-t, (PPr3)-Pr-i, and PCy3) in toluene are -26.2(3), -31.4(2), and -28.9(4) kcal/mol, respectively. These are larger than the enthalpies of reaction with MeNC, PhC=CPh, and PhCC-H. (PBu2Me)-Bu-t consistently gives the least amount of enthalpy released, but only when CO (and MeNC) is the reagent does (PPr3)-Pr-i yield a more exothermic enthalpy of reaction than. PCy3. The generally subtle influences on Delta H by (PPr3)-Pr-i and PCy3 are rationalized in terms of the contradictory steric and electronic effects as isopropyl is replaced by cyclohexyl.