| The kinetics and mechanisms of the thermal substitution, halogenation, and oxidation reactions of the dimetal dacacarbonyls were investigated. The reaction between Mn(,2)(CO)(,10) and Re(,2)(CO)(,10) to produce MnRe(CO)(,10) does not occur at 130(DEGREES)C; however, triphenylphosphine readily substitutes CO under these conditions. Crossover experiments show that the low temperature substitution reactions of Re(,2)(CO)(,10) and MnRe(CO)(,10) proceeded by CO dissociation, and that cleavage of the metal-metal bond is, at best, a secondary pathway. In an attempt to study CO scrambling phenomena, (OC)(,5)MnRe(('13)CO)(,5) was prepared. Intramolecular CO scrambling occurs at 65(DEGREES)C in toluene presumably through a doubly CO bridged intermediate.;In CH(,3)CN M(,2)(CO)(,10) is oxidized by various oxidants to yield two equivalents of M(CO)(,5)(NCCH(,3)) ('+). For NOBF(,4) and Cu(O(,3)SCF(,3)) the rate-determining step was transfer of an electron from the metal-metal bond to oxidant to yield M(,2)(CO)(,10) ('+). This complex either dissociates into M(CO)(,5)(NCCH(,3)) ('+) and M(CO)(,5) or forms the products directly. The rate of oxidation increases proportionally with E(, 1/2), the oxidation potential, of the oxidants.;The complexes M(CO)(,5)(O(,3)SCF(,3)) (M = Mn, Re) are prepared by the reaction between M(CO)(,5)Br and AgCF(,3)SO(,3) in CH(,2)Cl(,2) solvent. The stoichiometry of the trifluoromethanesulfonate substitution reactions was studied for the ligands THF, acetone, ether, CH(,3)CN, and Pn-Bu(,3). For weak nucleophiles only the manganese complex reacts to form Mn(CO)(,5)L CF(,3)SO(,3) and Mn(CO)(,3)L(,3) CF(,3)SO(,3) . For Mn(CO)(,5)(O(,3)SCF(,3)) and THF the rate law was shown to obey first order kinetics. A two term rate law was found for Mn(CO)(,5)(O(,3)SCF(,3)) and CH(,3)CN. Improved syntheses of the pentacarbonyl rhenium halides are reported.;The reactions between halogens (X(,2) = Cl(,2), BR(,2), I(,2), and ICl) and M(,2)(CO)(,10) (M(,2) = Mn(,2), MnRe, Re(,2)) in CH(,3)CN solvent yield equal amounts of M(CO)(,5)X and M(CO)(,5)(NCCH(,3)) ('+). For X(,2) = I(,2) the rate low was shown to obey second order kinetics k M(,2)(CO)(,10) I(,2) . The relative rates of halogenation follow the order Re(,2)(CO)(,10) > MnRe(CO)(,10) > Mn(,2)(CO)(,10). The rate of iodination varies by more than a million-fold depending on the solvent. The evidence suggests that halogen attacks the metal-metal bond via one end of the dihalogen molecule and that heterolytic cleavage of the halogen-halogen bond takes place to yield free halide ion, and a halogenium bridged metal dimer. |
