Two uranium(III) anilido complexes were synthesized, Tp* 2 U(NH-C 6 H 4 -p-terpyridine) (2-terpy) and Tp* 2 U(NH-C 6 H 4 -p-CH 3 ) (2-ptol), where Tp* = hydrotris(3,5-dimethylpyrazolyl)borate, by protonation of Tp* 2 UBn (1-Bn; Bn = benzyl) with 4-[2,6-di(pyridin-2-yl)pyridin-4-yl]benzenamine or p-toluidine, respectively. Conversion to the respective uranium(IV) imido species was possible by oxidation and deprotonation, forming Tp* 2 U(N-C 6 H 4 -p-terpyridine) (3-terpy) and Tp* 2 U(N-C 6 H 4 -p-CH 3 ) (3-ptol). These compounds were characterized by multinuclear NMR spectroscopy, IR spectroscopy, electronic absorption spectroscopy, and X-ray crystallography.

A family of low-valent uranium(III) anilido complexes supported by the bulky hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand was synthesized by combining Tp* 2 UBn (Bn = benzyl) (1-Bn) with anilines of varying steric bulk and electronic profiles, including 4fluoroaniline, 3,5-difluoroaniline, 3,5-bis(trifluoromethyl)aniline, 3,5dimethylaniline, 2,4,6-trimethylaniline, and 2,4,6-tri-t Bu-aniline. The corresponding uranium(III) anilido species, Tp*, and Tp* 2 UNH-(2,4,6-tri-t Bu-phenyl) (2-Mes*), were isolated, and reactivity was explored. Conversion to their respective uranium(IV) imido species (3-pF, 3-bisF, 3-bisCF 3 , 3-bisCH 3 , 3-Mes, and 3-Mes*) was achieved by hydrogen atom transfer using either Gomberg's dimer or the 2,4,6-tri-t Bu-phenoxy radical (•OMes*) which eliminates the need to use potentially explosive organic azides, a reagent that has been commonly used for the synthesis of uranium(IV) imido complexes. For comparison of yields and purity of all methods, the uranium imido complexes were also prepared using the corresponding organic azides. Where applicable, compounds were characterized by multinuclear NMR spectroscopy ( 1 H, 11 B, 19 F), infrared spectroscopy, electronic absorption spectroscopy, and single crystal X-ray crystallography.

In an effort to generate single-source precursors for the production of metal-siloxide (MSiO ) materials, the tris(trimethylsilyl)silanol (H-SST or H-OSi(SiMe) (1) ligand was reacted with a series of group 4 and 5 metal alkoxides. The group 4 products were crystallographically characterized as [Ti(SST)(OR)] (OR = OPr (2), OBu (3), ONep (4)); [Ti(SST)(OBu )] (5); [Zr(SST)(OBu )(py)] (6); [Zr(SST)(OR)] (OR = OBu (7), ONep, (8)); [Hf(SST)(OBu )] (9); and [Hf(SST)(ONep)(py) ] ( n = 1 (10), n = 2 (10a)) where OPr = OCH(CH), OBu = OC(CH), OBu = O(CH)CH, ONep = OCHC(CH), py = pyridine. The crystal structures revealed varied SST substitutions for: monomeric Ti species that adopted a tetrahedral ( T-4) geometry; monomeric Zr compounds with coordination that varied from T-4 to trigonal bipyramidal ( TBPY-5); and monomeric Hf complexes isolated in a TBPY-5 geometry. For the group 5 species, the following derivatives were structurally identified as [V(SST)(py)] (11), [Nb(SST)(OEt)] (12), [Nb(O)(SST)(py)] (13), 2[H][(Nb(μ-O)(SST))(μ-O)] (14), [NbO(OEt)(SST)·1/5NaO] (15), [Ta(SST)(μ-OEt)(OEt)] (16), and [Ta(SST)(OEt)] (17) where OEt = OCHCH. The group 5 monomeric complexes were solved in a TBPY-5 arrangement, whereas the Ta of the dinculear 16 was solved in an octahedral coordination environment. Thermal analyses of these precursors revealed a stepwise loss of ligand, which indicated their potential utility for generating the MSiO materials. The complexes were thermally processed (350-1100 °C, 4 h, ambient atmosphere), but instead of the desired MSiO, transmission electron microscopy analyses revealed that fractions of the group 4 and group 5 precursors had formed unusual metal oxide silica architectures.

A family of magnesium and calcium salen-derivatives was synthesized and characterized for use as subterranean fluid flow monitors. For the Mg complexes, di- n-butyl magnesium ([Mg(Bu )]) was reacted with N, N'-ethylene bis(salicylideneimine) (H-salen), N, N'-bis(salicylidene)-1,2-phenylenediamine (H-saloPh), N, N'-bis(3,5-di- t-butylsalicylidene)-ethylenediamine (H-salo-Bu ), or N, N'-bis(3,5-di- t-butylsalicylidene)-1,2-phenylenediamine (H-saloPh-Bu ), and the products were identified by single-crystal X-ray diffraction as [(κ-(O,N,N'),μ-(O')saloPh)(μ-(O),(κ-(N,N'),μ-(O')saloPh)(μ-(O),κ-(N,N',O')saloPh')Mg]·2tol (1·2tol; saloPh' = an alkyl-modified saloPh derivative generated in situ), [(κ-(O,N,N',O')saloPh)Mg(py)]·py (2·py), [(κ-(O,N,N',O')salo-Bu )Mg(py)] (3), [(κ-(O,N,N',O')saloPh-Bu )Mg(py)]·tol (4·tol), and [(κ-(O,N,N'),μ-(O')saloPh-Bu )Mg] (5), where tol = toluene; py = pyridine. For the Ca species, a calcium amide was independently reacted with H-salo-Bu and H-saloPh-Bu to generate the crystallographcially characterized compounds: [(κ-(O,N,N',O')salo-Bu )Ca(py)] (6), [(κ-(O,N,N',O')saloPh-Bu )Ca(py)]·py (7·py). The bulk powders of these compounds were further characterized by a number of analytical tools, where 2-7 were found to be distinguishable by Fourier transform infrared and resonance Raman spectroscopies. Structural properties obtained from quantum calculations of gas-phase analogues are in good agreement with the single-crystal results. The potential utility of these compounds as taggants for monitoring subterranean fluid flows was demonstrated through a series of experiments to evaluate their stability to high temperature and pressure, interaction with mineral surfaces, and elution behavior from a loaded proppant pack.

Two Np(III) halides, NpI3(THF)4 and NpBr3(THF)4, have been prepared and isolated in high yields as described in this work. Starting with neptunia (NpO2), NpCl4(DME)2 was first generated in an updated, higher yielding synthesis than what was previously reported by using HCl/HF. This material was then reduced with KC8, followed by subsequent ligand exchange, to generate NpBr3(THF)4 and NpI3‐(THF)4. Full characterization by single‐crystal X‐ray crystallography, 1H NMR spectroscopy and electronic absorption spectroscopy confirmed the molecular formulas and oxidation states. These trivalent materials are straightforward to synthesize and can be used as starting materials for non‐aqueous Np(III) chemistry, obviating the need for rare and restricted Np metal and elemental halogens.