Alkane coordination, carbon monoxide/carbon dioxide activation, and nitrogen atom transfer chemistry employing low- and high-valent complexes of uranium

The hexadentate tris-aryloxide triazacyclononane ligand, (t-Bu ArOH)3tacn, and its sterically more demanding adamantyl derivative have provided access to relatively stable but highly reactive, electron-rich coordination compounds of uranium, namely [(( RArO)3tacn)U] (1, R = t-Bu (1a), Ad (1b)). In this thesis, three fundamentally important reactions are presented that result in alkane coordination, CO/CO2 activation, and nitrogen atom-transfer chemistry.; Reaction of various tris-aryloxide functionalized triazacyclononane ligands, (RArOH)3tacn, with [U(N(SiMe3)) 3] yields [((RArO)3tacn)U] (R = tBu (1a), R = Ad (1b)). Simple re-crystallization of 1a from pentane solutions containing cycloalkanes affords coordination of the cycloalkane molecule in an eta2-H,C fashion to the electron-rich U center. The molecular structures of a variety of these complexes were studied by X-ray diffraction. These species represent unique examples of metal-coordination of saturated hydrocarbons.; Coordinatively unsaturated, 1a reacts with carbon dioxide by reducing the CO2, resulting in evolution of CO and formation of a U(IV-O-U(IV) complex. Complex 1a also binds and activates CO to yield a mu-CO bridged diuranium species [{lcub}((t-BuArO) 3tacn)U{rcub}2(mu-CO)] (2). The molecular structure of 2 reveals an iso-carbonyl bonding motif, which is unique in actinide chemistry. The sterically more encumbering derivative 1b prevents dimerization and thus, reacts with CO2 to form the mononuclear U-CO2 complex, namely [((AdArO)3tacn)U(CO 2)] (3). Complex 3 represents a charge-separated U(IV)-CO2•- species with a never before seen CO2 co-ordination mode, an unprecedented linear, oxygen bound eta 1-OCO fashion.; Complex 1b reacts with TMS azide to yield two different uranium complexes: [((AdArO)3tacn)U(N3)] (4) and [((AdArO)3tacn)U(NSiMe 3)] (5). The high-valent uranium(V) imido complex 5 reacts with pi-acids, such as carbon monoxide and methyl isocyanide, to form the uranium(IV) [((AdArO)3tacn)U(NCO)] ( 6) and [((AdArO)3tacn)U(NCNMe)] (7 ). Furthermore, the isocyanate and carbodiimide ligand in 6 and 7 react with CH3I and CH2Cl2 to release the functionalized organic isocyanate and carbodiimide with formation of the corresponding uranium(IV) halide complexes [((AdArO) 3tacn)U(X)], which can be regenerated to the uranium(III) starting complex 1b via sodium/amalgam reduction. This series of reactions represents a synthetic cycle, in which the imido nitrogen atom is transferred from the uranium complex and incorporated into an organic substrate via C≡O and R'N≡C/U≡NR multiple-bond metathesis.