EARLY TRANSITION-METAL CHEMISTRY OF BENZYL AND RELATED LIGANDS
Abstract
Use of the benzylating agent Mg(CH(,2)Ph)(,2) has led to the isolation of the molybdenum-benzyl species Mo(,2)(CH(,2)Ph)(,6) and Mo(,2)(CH(,2)Ph)(,2)(O(,2)CCH(,3))(,2)(PMe(,3))(,2). Solid state structural analyses of both compounds has shown purely (sigma)-bound benzyl ligands. The picolyl ligand 2-(6-methylpyridyl)methyl (CH(,2)-py-6Me) has been shown to react with a variety of early metals. Picolyl complexes of Zr, Hf and Th containing the bulky ancillary ligands Cp and OAr (Cp = (eta)('5)-C(,5)H(,5);OAr = 2,6-di-tert-butylphenoxide) have been isolated. Solid state structural studies have shown that the ligand can be either C,N bound or purely C bound. Reaction of Cp(,2)M(CH(,2)-py-6Me)(,2) (M = Zr,Hf) with one or two equivalents of CNxy (CNxy = 2,6-dimethylphenyl isocyanide) has shown insertion of isocyanide followed by H-atom migration, yielding an vinylamide ligand. First order kinetics have been observed for this process at room temperature. Solid state structural studies have confirmed the nature of this newly formed ligand. Tungsten (VI) tris-catecholate complexes were prepared and their electrochemistry investigated. For less sterically demanding catechols (4-methyl- and 4-tert-butylcatechol) the species appeared dimeric in solution. Upon reduction, isomerization occurred leading to formation of anionic monomers which redimerized upon reverse oxidation. The electrochemistry of the more bulky 3,5-di-tert-butylcatechol was consistent with a monomeric species in solution, comparable to the homoleptic W(OAr')(,6) (OAr' = 4-methylphenoxide).
Degree
Ph.D.
Subject Area
Chemistry
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