Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The objective of this research was to synthesize binuclear (mu)-alkylidene complexes of manganese or cobalt, to study their chemical properties, and to assess their potential as model intermediates in the Fischer-Tropsch synthesis.;Excess diazoalkane addition to Mn(,2)(CO)(,4)((mu)-CO)((mu)-dppm)(,2) ; dppm = Ph(,2)PCH(,2)PPh(,2), produces 1:1 adducts of formula Mn(,2)(CO)(,4) (mu)-C(O)CHRN(,2) ((mu)-dppm)(,2) (R = H,Me,CO(,2)Et) containing a novel metallacycle derived from coupling of the diazoalkane molecule with a carbonyl ligand. The structure was established by an X-ray analysis of Mn(,2)(CO)(,4) (mu)-C(O)CH(,2)N(,2) ((mu)-dppm)(,2) . Photolysis or thermolysis of each adduct regenerates Mn(,2)(CO)(,4)((mu)-CO)((mu)-dppm)(,2) .;A series of ((mu)-alkylidene)dicobalt complexes was prepared via CO displacement from Co(,2)(CO)(,4)((mu)-CO)(,2)((mu)-dppm) at 25(DEGREES)C by excess diazoalkane addition. Low temperature NMR studies revealed a facile, concerted interconversion from bridging to terminal sites for the bridging units in Co(,2)(CO)(,4)((mu)-CO)((mu)-CH(,2))((mu)-dppm) and Co(,2)(CO)(,4)((mu)-CH(,2))(,2)((mu)-dppm) only.;Carbon-carbon coupling reactions occur at 25(DEGREES)C in reactions of Co(,2)(CO)(,4)((mu)-CH(,2))(,2)((mu)-dppm) with RCCR to give C(,2)H(,4) and Co(,2)(CO)(,4)((mu)-RCCR)((mu)-dppm) (R = CF(,3),Ph), with C(,2)H(,4) to give C(,3)H(,6), and, at 80(DEGREES)C, with H(,2) to yield C(,2)H(,6). Deuterium-labelling studies reveal that the easy methylene coupling reactions to give C(,2)H(,4) from Co(,2)(CO)(,4)((mu)-CH(,2))(,2)((mu)-dppm) involve a complex, intermolecular coupling process associated with a large isotope effect. Addition of CO, SO(,2) or CF(,3)CCCF(,3) to each ((mu)-alkylidene)dicobalt complex induces coupling of the respective alkylidene unit with a carbonyl ligand and subsequent ketene elimination.;Differences in structure and stability noted from the identical diazoalkane additions to the analogous complex Co(,2)(CO)(,4)((mu)-CO)(,2)((mu)-dmpm) ; dmpm = Me(,2)PCH(,2)PMe(,2), were attributed to the higher basicity and smaller steric effects introduced by dmpm versus dppm.;Reaction of the dianionic complexes Co(,2)(CO)(,6)((mu)-L) ('2)(L = dppm,dmpm) with CH(,2)I(,2) or (alpha),(omega)-diiodoalkanes did not produce the expected dicobaltacycles. The resultant halogen abstraction in each case is suspected to arise from an electron transfer process.



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