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Electrochemical studies of group V metal carbonyl compounds

Thesis/Dissertation ·
OSTI ID:7178053
Two thin-layer infrared spectroelectrochemical cells are described. Another cell used to perform rapid bulk electrolysis to generate transient and unstable complexes is described. The electrochemistry and infrared spectroelectrochemistry of parent and substituted Group V carbonyls have been investigated. The second order disproportionation reaction of V(CO)[sub 6] in CH[sub 3]CN was studied using infrared spectroelectrochemistry. The electrochemical oxidation of [NEt[sub 4]][Nb(CO)[sub 6]] and [NEt[sub 4]][Ta(CO)[sub 6]] exhibited a two-electron irreversible wave in the potential region of [minus]50 to +200 mV versus Ag/AgCl. Infrared spectroelectrochemical data indicated coordination of the weakly coordinating anions of the supporting electrolyte to the Group V meter center. Elemental analysis, infrared data and low temperature [sup 19]F NMR experiments indicated the presence of coordinated BF[sup [minus]][sub 4] and PF[sup [minus]][sub 6] anions. Based on the characterization data, the proposed structure of these complexes is [M[sub 2](CO)[sub 8]((u-F)EF[sub n])[sub 3]][sup [minus]], where E = B, n = 3, E = P, n = 5. Infrared spectroelectrochemical data obtained during the oxidation of Ta(CO)[sup [minus]][sub 6] in the presence of less coordinating anions, such as SbF[sup [minus]][sub 6] and TFPB[sup [minus]] (tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), in CH[sub 2]Cl[sub 2] suggested the formation of a seven-coordinate species, Ta(CO)[sub 6]X, where X = Cl[sup [minus]], SbF[sup [minus]][sub 6] or TFPB[sup [minus]]. Low temperature studies were also performed in attempts to detect Ta(CO)[sub 6]. The highly substituted XM(CO)[sub 2](dppe)[sub 2] compounds, where M = Nb, Ta; X = I, Br, Cl, H; and dppe = 1,2-bis(diphenylphosphino)ethane, exhibited a one-electron reversible oxidation in CH[sub 2]Cl[sub 2] that generated the 17-electron species, XM(CO)[sub 2](dppe)[sup +][sub 2].
Research Organization:
Minnesota Univ., Minneapolis, MN (United States)
OSTI ID:
7178053
Country of Publication:
United States
Language:
English