High temperature microcalorimetric studies of the thermal decomposition and halogenation of nonacarbonylcobaltmanganese, nonacarbonylcobaltrhenium and decacarbonylmanganeserhenium

Microcalorimetric measurements at elevated temperatures of the enthalpies of sublimation, bromination and iodination of CoMn(CO)(9), CoRe(CO)(9) and MnRe(CO)(10) have been made to obtain the standard enthalpies of formation Delta(f)H(0) (c) and Delta(f)H(0) (g) (in that order) as follows (values in kJ mol(-1)): CoMn(CO)(9) -(1460 +/- 36), -(1388 +/- 42); CoRe(CO)(9) -(1452 +/- 36), -(1369 +/- 42); MnRe(CO)(10) -(1630 +/- 24), -(1544 +/- 28). The values of Delta(f)H(m)(0) (g) are used to derive the enthalpy contributions of the metal-metal bonds in these molecules D(Co-Mn) = (114 +/- 23), D(Co-Re) = (122 +/- 25) and D(Mn-Re) = (145 +/- 29) kJ mol(-1). In each case, the value of D(M-M') is less than the mean of the corresponding homometallic bond enthalpy contributions.