Thorium-ligand bond disruption enthalpies (D) have been determined in the series Cp prime //2ThR//2(Cp prime equals eta **5 minus (CH//3)//5C//5) for a range of R groups including R equals alkyl, aryl, metallacycle, hydride, and dialkylamide. Enthalpy data were obtained in an anaerobic batch-titration isoperibol reaction calorimeter from heats of solution in toluene followed by heats of alcoholysis with tert-butyl alcohol. Calculated Th-hydrocarbyl bond disruption enthalpies fall in the range 60-90 kcal/mol, with C//6H//5 greater than CH//3 approximately equals CH//2Si(CH//3)//3 greater than CH//2CH//3 greater than equivalent to CH//2C//6H//5 approximately equals n-C//4H//9 approximately equals CH//2C(CH//3)//3. Th-C bonds appear to be strengthened by ThOR coligands and possibly weakened by Th-Cl coligands. The strain energies in thoracyclobutanes Cp prime //2Th(CH//2)//2C(CH//3)//2 and Cp prime //2Th(CH//2)//2Si(CH//3)//2 are estimated to be ca. 16 and 8 kcal/mol, respectively. A Th-H bond is ca. 20 kcal/mol stronger than a Th-alkyl bond, while a Th-NR//2 bond is ca. 18 kcal/mol stronger.
|Number of pages||9|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - Jan 1 1983|
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