A new family of uranium(IV) imido complexes of the form Tp*U(NR) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate; R = benzyl (Bn), para-tolyl (p-Tol), 2,6-diethylphenyl (detp), and 2,6-diisopropylphenyl (dipp)) have been generated by bibenzyl extrusion from Tp*UBn. Tp*U(NBn), Tp*U(Np-Tol), and Tp*U(Ndetp), along with previously reported Tp*U(NPh) and Tp*U(NAd) (Ad = 1-adamantyl), readily undergo [2π+2π] cycloaddition with isocyanates and isothiocyanates to generate κ-ureato and κ-thioureato derivatives, respectively. These new uranium(IV) complexes were characterized via multinuclear NMR, vibrational and electronic absorption spectroscopies, and, where possible, X-ray crystallography. The steric demands of the ligands were quantitatively assessed using computational modeling, and it was shown that cycloaddition only occurs for imido species where ligands occupy 90% or less of the coordination sphere.

A family of dinuclear bis(Tp*) (Tp* = hydrotris(3,5dimethylpyrazolyl)borate) uranium compounds with conjugated organic linkers was synthesized to explore possible electronic communication between uranium ions. Trivalent diuranium phenyl alkynyl compounds, Tp* 2 UCC(1,3-C 6 H 4 )CCUTp* 2 (2-meta) or Tp* 2 UCC(1,4-C 6 H 4 )-CCUTp* 2 (2-para), and tetravalent diuranium phenylimido compounds, Tp* 2 U(N-1,3-C 6 H 4 −N)UTp* 2 (3-meta) and Tp* 2 U(N-1,4-C 6 H 4 − N)UTp* 2 (3-para), were generated from trivalent Tp* 2 UCH 2 Ph. All compounds were fully characterized both spectroscopically and structurally. The electronic structures of all derivatives were interrogated using magnetic measurements, electrochemistry, and were the subject of computational analyses. All of these data combined established that little electronic communication exists between the uranium centers in these trivalent and tetravalent diuranium molecules.

Treating a family of uranium benzyl compounds, Tp*2U­(CH2Ph) (1-Bn), Tp*2U­(CH2-para- i PrPh) (1- i Pr), Tp*2­U­(CH2-para- t BuPh) (1- t Bu), or Tp*2­U­(CH2-meta-OMePh) (1-OMe), which are supported by two hydro­tris­(3,5-di­methyl­pyra­zolyl)­borate (Tp*) ligands, with a single equivalent of triphenylphosphine oxide (OPPh3) causes a unique carbon–carbon coupling to occur. The products of this reaction, Tp*2U­[OP­(C6H5)2­(C6H5­CH2­C6H5)] (2-Ph), Tp*2U­[OP­(C6H5)2­(C6H5­CH2-p-iPr­C6H4)] (2- i Pr), Tp*2U­[OP­(C6H5)2­(C6H5­CH2-p-tBu­C6H4)] (2- t Bu), and Tp*2U­[OP­(C6H5)2­(C6H5­CH2-m-OCH3­C6H4)] (2-OMe), are characterized by coupling between the benzyl substituent and the para-carbon of one of the phenyl groups of OPPh3. To probe the scope of this unusual reactivity, 1-Bn was treated with different tris­(aryl)­phos­phine oxides, including tris­(p-tolyl)­phos­phine oxide, which yields Tp*2U­[OP­(p-tolyl)2­(C6H4­(CH3)­CH2­C6H5)] (3-tolyl). All compounds were characterized by multinuclear NMR, vibrational, and electronic absorption spectroscopies. When possible, X-ray diffraction was used to confirm molecular structures.

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A series of reduced PDI neodymium complexes by the PDI ligand acting as an electron sink.