This work focuses on the interaction between the uranyl(VI) ([UO 2]2+) and uranyl(V) ([UO2]+) ions with soft (nitrogen, carbon, sulfur) donor ligands. We attempted to ligate various neutral nitrogen donor ligands to the [UO2(Ar 2nacnac)]+/0 fragments. Ar2nacnac (Ar 2nacnac = {(2,6-iPr2C 6H3)2NC(Me)}2CH--) is a very sterrically demanding ligand, and stabilizes uranyl(V). Using this framework we were able to ligate two nitrogen ligands (py and 1-methylimidazole (MeIm)) to the [UO2(Ar2nacnac)]+ fragment to produce UO2(Ar2nacnac)(OTf)py (2.1) and [UO2(Ar2nacnac)(MeIm)2][OTf] (2.2). We then compared the binding affinity of these ligands to that of the Ph2MePO ligand and found the Ph2MePO ligand to have a higher affinity for the uranyl(VI) fragment than either py or MeIm. Using 2.1 as a starting material, we were able to produce the uranyl(V) complex UO2(Ar2nacnac)(py)2 (3.1). 3.1 has proven to be an excellent starting material for the formation of other UO2(Ar2nacnac) complexes containing the other N-donor ligands: 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), N,N-tetramethylethylenediamine (TMEDA), and MeIm to make the corresponding UO2(Ar2nacnac)( N-donor)x (x=1,2) complexes. We then determined the binding affinity series for the UO2(Ar2nacnac) fragment as phen > MeIm > TMEDA > bipy > py.

Using the [UO2(Ar2nacnac)]+ scaffold, we have produced several uranyl organometallic complexes using MeIm based aryl ligands. The most stable of these complexes is [Li(MeIm)][UO(mu-O)(Ar 2nacnac)(mu:&eegr;-MeIm)2] (4.5). We have probed the reactivity of 4.5 and have performed the metathesis reaction between 4.5 and MCl2 (M = Fe, Co) to produce the bimetallic complexes [MCl(MeIm)][UO2(Ar2nacnac)(mu- N-MeIm)2] (M = Fe, 4.7; M = Co, 4.8 ).

The binding affinity between three thione ligands (2-mercaptomethylimidazolyl-pyridine (mpyMe), bis(mercaptomethylimidazolyl)methane (BmmMe ), and ortho-bis(mercaptomethylimidazolyl) xylene (O-BmxMe)) and the uranyl(VI) ion was explored. Using UO 2{N(TMS)2}2(THF)2 as a starting material we have been able to produce three UO2{N(TMS)2} 2(thione) complexes (5.1 -- 5.3), and have determined the binding affinity of these ligands against each other, as well as THF and DME.

Lastly, we probed the reactivity between (py-2-CH2)NHC(Me)CHC(Me) O (Mepyacnac) and the uranyl(VI) and U(IV) ions. We have been able to produce two uranyl(VI)mono(Mepyacnac) complexes (UO2(Mepyacnac)Cl(THF) (6.1) and UO2(Mepyacnac)(OTf)(THF) (6.2)), one uranyl(VI)bis(Mepyacnac) complex (UO2( Mepyacnac)2, 6.3), and two U(IV)bis(Mepyacnac) complexes (UCl2(Mepyacnac)2 (6.4 ) and U(N3)2(Mepyacnac)2 ( 6.5)). The initial studies on the reactivity these complexes were explored.