Date of Award
1986
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
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.
Recommended Citation
Laws, William John, "An Investigation Of Dinuclear Alkylidene-bridged Carbonyl Complexes" (1986). Digitized Theses. 1506.
https://ir.lib.uwo.ca/digitizedtheses/1506