Olefin complexes bond dissociation energy

M—H bond dissociation energies, 1, 287 photochemistry, 1, 251 single crystal neutron diffraction, 1, 578 stability toward disproportionation, 1, 301 Metal—hydrogen bonds bond dissociation energy in 1,2-dichloroethane, 1, 289 stable metal hydrides in acetonitrile, 1, 287 thermochemical cycle, 1, 286 in THF and dichloromethane, 1, 289 olefin insertion thermodynamics, 1, 629 in Zr(IV) bis-Cp complexes, 4, 878 Metal—hydrogen hydricity data, 1, 292... 

Metal—Ligand Bond Dissociation Energies in CpMn(CO)2L and Cr(CO)g(olefin) Complexes... 

In complex 33a, the Cr-Cr bond is strongly polarized, and the larger charge density focuses on Cr (q(C ) = —0.31e vs. q(C ) = —0.18e). The longer Co-CO bond length is calculated for CO at trans-positioned with respect to R. Therefore, it is reasonable to expect this CO ligand to dissociate more easily, as supported by the calculated bond dissociation energy of 101.3 kJ/mol. The olefin then occupies the vacant coordination site, which leads to the observed a-methylcyclopentenone. 

Table 10 Calculated and Experimental Bond Lengths (A) of Metal-Olefin Complexes and Calculated L2M—C2H4 Dissociation Energies Dq (kcal/mol) ... 

As a result, activation enthalpies of many dissociative substitution reactions of 18-electron complexes are relatively high and close to the M-L BDE. The weak M-CO bond energy of Ni(CO) (25 2 kcal /mol) allows this complex to react rapidly at room temperature, but the higher M-L bond energies of the olefin in CpRhCethylene) and CO in Cr(CO)g (31 kcal/ mol and 37 2 kcal/mol, respectively) cause the reactions of these complexes to require temperatures of > 100 °C and 80-140 °C, respectively, to occur at reasonable rates. 

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