Enthalpies of Reaction of [(<i>p</i>-cymene)OsCl<sub>2</sub>]<sub>2</sub> with Monodentate Tertiary Phosphine Ligands. Importance of Steric and Electronic Ligand Factors in an Osmium(II) System
作者:Jinkun Huang、Scafford Serron、Steven P. Nolan
DOI:10.1021/om980345e
日期:1998.8.1
The enthalpies of reaction of [OsCl2(p-cymene)](2) (1) (p-cymene = eta(6)-CH3C6H4CH(CH3)(2)) with a series of monodentate phosphines (PR3), leading to the formation of OsCl2(p-cymene)(PR3) complexes, have been measured by anaerobic calorimetry in CH2Cl2 at 30 degrees C. These reactions are rapid and quantitative. The overall relative order of stability established is as follows: PPh(NC4H4)(2) < P(NC4H4)(3) < P(p-CF3C6H4)(3) < PPh2(NC4H4) < PPh3 < P(p-ClC6H4)(3) < P(p-CH3C6H4)(3) < P(p-FC6H4)(3) < PCy3 < PBz(3) < (PPr3)-Pr-i < P(p-CH3OC6H4)(3) < P(NC4H8)(3) < PPh2Me < PPhMe2 < PEt3 < PMe3. A quantitative analysis of ligand effects for the present data helps clarify the exact steric versus electronic ligand contributions to the enthalpy of reaction in this system. Both steric and electronic factors appear to play an important role in dictating the magnitude of the enthalpy of reaction. The data are compared to the previously studied RuCl2(p-cymene)(PR3) system.