Cobalt-carbon bond disruption enthalpies: the first reliable measurement of a Co-methyl BDE via solution thermochemical methods

The determination of the strength of the metal-carbon /sigma/ bonds has become very important because such bonds have been implicated as or demonstrated to be integral components of many homogeneous catalytic cycles. The use of iodinolytic isoperibol solution calorimetry for the measurement of the absolute value of the bond disruption energies, D(Co-R), for pyCo(CH)/sub 2/R where py=pyridine, DH = the monoanion of dimethylglyoxime, and R = I, CH/sub 3/, CH/sub 2/C/sub 6/H/sub 5/, or CH(CH/sub 3/)/sub 2/ is reported herein. The assumption is made that the pyCo(DH)/sub 2/ moiety remains basically unchanged so that the enthalpy of iodinolysis for the reaction can be expressed as the difference in bond disruption enthalpies for bonds being made or broken in the iodinolysis reaction. It is felt that values of D(Co-R) determined in nonpolar solvents should be a tolerably good approximation for gas-phase data.