Estimating the effective steric impact of PtBu2Me, PiPr3, and PCy3

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)2L2

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

Agenda & Meeting Minutes

Meeting regarding University Senate, Bowling Green Community College, Center for Gifted Studies, graduate assistants, sponsored research, graduation rates, summer school, productivity levels and administrator evaluations

PARAMAGNETIC MONOCYCLOPENTADIENYL HYDROCARBYL AND BOROHYDRIDE COMPOUNDS OF VANADIUM(II) AND VANADIUM(III) - SYNTHESIS, STRUCTURE, AND REACTIVITY

Paramagnetic high-spin d2 and d3 monocyclopentadienyl vanadium hydrocarbyl complexes CpVIII2(PMe3)2 (R = Me, Ph) and CpVIIR(dmpe) (R = Me, Pr, Ph) have been prepared from their corresponding halide precursors. From CpV(Me)Cl(PMe3)2, prepared by ligand exchange, the mixed hydrocarbyl complex CpV(η3-C3H5)Me(PMe3) could be obtained. The V(II) borohydride complex CpV(η2-BH4)dmpe is shown by EPR and solution magnetic measurements to have a low-spin (S = ½) d3 configuration. X-ray structures of CpVMe(dmpe) (P212121, a = 12.526 (3) Å, b = 9.285 (2) Å, and c = 12.772 (3) Å at -158 °C, Z = 4) and CpV(BH4)dmpe (P21/m, a = 8.198 (2) Å, b = 13.435 (3) Å, c = 13.987 (4) Å, and β = 102.09 (1)° at -160 °C, Z = 4) have been determined. Several structural and electronic features are correlated to EHMO calculations. Both V(II) and V(III) alkyl compounds have been reacted with molecular hydrogen. Although catalytic activity in hydrogenation and isomerization of olefins has been observed, no stable V(III) hydrido species could be obtained, reductive elimination processes probably precluding their isolation. Reaction of CpVMe2(PMe3)2 with H2 generates active CpV fragments that can bind ligands like benzene and 2,3-dimethyl-1,3-butadiene