http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
chemistry of zero-valent group 6 carbonyl aryl- and alkoxide complexes
investigations into the insertion of CO₂ into transition metal-oxygen bonds
Mononuclear pentacarbonyl aryl- and alkoxide anionic derivatives, W(CO)5OR- (R = Ph, 2,6-Ph2-C6H3, CH2CF3 and(η^6-C6H4)Cr(CO)3) were synthesized by two routes. The aryloxide and alkoxide complexes were made by the addition of photolytically produced W(CO)5THF to a flask containing [Et4N][OR] and by the deprotonation of the corresponding alcohol by W(CO)5Me- anion. In the absence of a carbon monoxide atmosphere the mononuclear species readily lose a CO ligand and form aggregates of 1-4 nuclearity. A thorough investigation into the mechanism of this assembly reaction is reported. Two different dimers with bridging alkoxide or aryloxide ligands, [PPN]2[W2(CO)8(OCH2CF3)2] and [Et4N]3[W2(CO)6(OPh)3], which are proposed as intermediates, were isolated and characterized. Molecular modeling software was utilized to construct a tetranuclear derivative from [PPN]2[W2(CO)8(OCH2CF3)2] similar to the structurally characterized [W(CO)3OH]4^-4 tetramer. The role the lone pairs of the aryloxide and alkoxide ligands play in the carbonyl dissociation reaction was also examined. The tungsten pentacarbonyl derivatives which are more acidic were less prone to CO loss. In addition, it is reported how the two oxy ligands in the doubly bridged dimer [PPN]2[W2(CO)8(OCH2CF3)2] assist in the dissociation of the third carbonyl. The structural and electronic analog [Et4N]2[W(CO)4O2C6H4] was synthesized. The lability of the axial CO was studied. Under reduced pressure the tetracarbonyl complex spontaneously lost a carbonyl and made a formally unsaturated tricarbonyl species, [Et4N]2[W(CO)3O2C6H4]. Steric influences on the insertion of CO2 into metal oxygen bonds is examined. The compounds [Et4N][W(CO)5O-2,6-Ph2-C6H3] and [Et4N][W(CO)4(PPh2Me)OPh] have been synthesized and their reactivities towards CO2 studied...