Trivalent uranium complexes

The heteroscorpionate pyrazolylborate derivative K[H2B(pzf Bu,Me)(pzMe2)] upon reaction with UI3(thf)4, afforded a series of seven-coordinated trivalent complexes of formula U /t, -BpzM " Me (Hpzf"Bu Me)I(p-I)]2 (55). The absence of empty coordination sites provide these complexes with a remarkable stability. Along the same line, the reaction of bis(2-mercapto-2-methylimidazolyl)borates [H(R)B(tim)2 R = H, Ph] with UI3(thf)4 in the presence of Tl(BPh4) in THF gave another rare case of a cationic trivalent uranium complex U[H(R)B-(tim)2]2 (thf)3 (BPh4) (56). 

U(Tp )2CH2Ph] and the high thermodynamic stabihty of the +4 oxidation state.The trivalent uranium complex [U(Tp )2(CH2Ph)] has been investigated by DFT as catalyst to promote the fimctionahzation ofC02 and CS2-It has been found that the interaction between CO2 and CS2 is not with central uranium atom, but due to the steric hindrance the first step is the cleavage of the U—C benzyl bond to form a C—C covalent bond. " ... 

Ding W, Fang W, Chai Z, Wang D. Trivalent uranium complex as a catalyst to promote the functionalization of carbon dioxide and carbon disulfide a computational mechanistic study. J Chem Theory Comput. 2012 8 3605-3617. 

The trivalent uranium complex UCp3 (Cp = j/ -CsHs) can be prepared via the following routes [22-24] ... 

Coordination Chemistry. The coordination chemistry of trivalent uranium is certainly characterized by the large atomic dimensions as appearing in series of compounds featuring C-, N-, S-, and O-donor based ligand complexes. 

The presence of two rather than three Cp rings around the trivalent uranium centers seems to provide an optimum stability to the complex. The synthesis of the Cp UI2(thf)3 and Cp 2UI(thf) was achieved in high yield upon treatment of UI3(thf)4 with the appropriate amount of Cp K (Scheme 17). Further functionalization of Cp UI2(thf)3 was obtained via a metathetic reaction with silazanate. The crystal structure of the resulting Cp U[N(SiMe3)2]2 showed the presence of agostic interactions between the U center and the methyl groups of the silazanate moiety (47). 

This is a convenient, facile, and high-yield preparative route for quantitative preparation of the complexes above no special equipment is required. UI3(THF)4 crystallizes in a P2x/c space group. It is mononuclear with pentagonal-pyramidal coordination geometry around the central uranium atom. This compound is stable until 75°C, then THF molecules are removed by steps, forming UI3 at 162°C. Lewis base adducts of uranium tri-iodide, such as UI3(THF)4 above, are synthetically useful precursors for trivalent uranium chemistry (see Sec. 5.3.2) [360]. 

Trivalent homoleptic complexes An[N(SiMe3)2]3 have been generated for uranium, neptunium, and plutonium " by metathesis reactions (see Equations (1) and (2)). The molecular structure of U[N(SiMe3)2]3 has been determined ... 

---