Molecular mechanics methods have been employed to compute energy-minimized structures of a series of CpRh-(CO)(PX3) complexes, where PX3 is CO, trialkylphosphine, trialkyl phosphite, mixed alkyl/arylphosphine, or mixed alkyl/aryl phosphite. The energy-minimized structures are applied to compute the ligand repulsive energy, E′R. Values of E′R are compared with relative values of ER (Brown, T. L. Inorg. Chem. 1992, 31, 1286) in Cr(CO)5 in which the geometric character of the metal center is substantially different from CpRh(CO). The values of E′R in CpRh(CO) and ER in Cr(CO)5 correlate reasonably well (rcorr = 0.93). The slope of the linear regression of E′R vs ER is 1.4. The magnitude of the slope indicates that the CpRh(CO) metal center is less crowded than the Cr(CO)5 metal center with respect to the ligands PX3. The correlation of E′R with cone angle is also fairly good (rcorr = 0.82). The trend in molecular mechanics energy changes of CpRh(CO) with ligand cone angle follows the same general pattern observed in Cr(CO)5. The structure of CpRh(CO)(PPh3) has been determined by X-ray diffraction measurement at 0 °C with Ew = 0.033. The crystals belong to the triclinic space group P1̄, with a = 10.024(2) Å, b = 10.589(2) Å, c = 11.282(2) Å, α = 72.06(1)°, β = 81.42(1)°, γ = 62.57(1)°, Z = 2, and V = 1011.2(3) Å3.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry