Thermodynamic Studies of HRh(depx)2 and [(H)2Rh(depx)2](CF3SO3): Relationships between Five-Coordinate Monohydrides and Six-Coordinate Dihydrides
Citations Over TimeTop 16% of 2004 papers
Abstract
Four new rhodium complexes, [Rh(depx)2](CF3SO3), [(H)2Rh(depx)2](CF3SO3), [HRh(depx)2(CH3CN)](CF3SO3)2, and HRh(depx)2 (where depx = α,α‘-bis(diethylphosphino)xylene), have been synthesized and characterized. The pKa values of [(H)2Rh(depx)2]+ (30.6 ± 0.3) and [HRh(depx)2(CH3CN)]2+ (11.5 ± 0.4) in acetonitrile were determined by equilibrium reactions with appropriate bases. The hydride donor ability of [(H)2Rh(depx)2]+ (71.6 ± 1.0 kcal/mol) was determined by the heterolytic cleavage of hydrogen by [HRh(depx)2(CH3CN)]2+ to form [(H)2Rh(depx)2]+ in the presence of thioacetamide or benzamide. These equilibrium measurements, the half-wave potentials for the Rh(+1/0) and Rh(0/−1) couples of [Rh(depx)2]+, and the reversible one-electron oxidation of HRh(depx)2 (all measured at 22 ± 1.5 °C) were used to establish nine heterolytic and homolytic bond-dissociation free energies in acetonitrile. From these relationships, and those established previously for analogous cobalt and platinum complexes, we conclude that the homolytic bond-dissociation free energies of six-coordinate dihydride species are approximately 2 kcal/mol less than those of the corresponding five-coordinate monohydride species derived by deprotonation. Similarly, the pKa values of six-coordinate dihydride complexes are approximately 2 units lower than the corresponding five-coordinate species formally derived by homolytic bond cleavage.
Related Papers
- → Kinetico-Mechanistic Studies on a Reactive Organocopper(II) Complex: Cu–C Bond Homolysis versus Heterolysis(2023)9 cited
- → Hydroperoxysterols as a probe for the mechanism of cytochrome P-450scc-mediated hydroxylation. Homolytic versus heterolytic oxygen-oxygen bond scission.(1986)29 cited
- Determination of N—NO Bond Dissociation Energies of N-Nitrosoindoles and Their Radical Anions in Acetonitrile(2007)
- → Nonreductive homolytic scission of endoperoxide bond for activation of artemisinin: A parallel mechanism to Heterolytic cleavage(2022)2 cited
- → Pressure effects as mechanistic probes for homolytic thermal cobaltcarbon bond cleavage of cobalamins(1992)9 cited