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3,3′,5,5′-Tetrasubstituted-2,2′-biphenolate complexes of titanium(IV) with bis(diketonate) (Bob), bis(hydroxamate) (Hox) and mixed diketonate–hydroxamate (Hob) ligands have been prepared from the corresponding diisopropoxide complexes. Four of the twelve compounds have been characterized crystallographically, and in the solid state all show the (Δ,R)/(Λ,S) relative stereochemistry at titanium and the biaryloxide, respectively, as previously observed in (acac)2Ti(1,1′-bi-2-naphtholate) complexes. In solution the compounds epimerize by atropisomerization of the biphenolate moiety with ΔG‡ ≈ 14 kcal mol−1. The bis(diketonate) complexes show high diastereoselectivity except for the most electron-poor tetranitrobiphenolate. In contrast, the bis(hydroxamate) shows low to moderate selectivity which correlates with the steric but not electronic properties of the biphenolates (Br < CH3 < NO2 < tBu). The mixed diketonate–hydroxamate complexes show intermediate behaviour. These observations are rationalized on the basis of MO arguments regarding ligand-metal π bonding. Symmetrical chelates such as diketonates foster mixing of two dπ orbitals and create a dissymmetric electronic environment. This mixing does not take place with unsymmetrical ligands such as hydroxamates, which therefore do not create an environment where electronic effects contribute significantly to binding stereoselectivity.

Ionic liquids (ILs) are attractive alternatives to water, high temperature molten salts or conventional organic solvents for electrodeposition of technologically important metals. Designing ILs containing functional groups specifically targeted to interact with or even chelate metals, such as carboxylate, may increase the metal solubility and affect thermodynamic and electrochemical properties. This paper reports the synthesis and characterization of three ionic liquids comprised of one or two tetra-alkyl phosphonium cations paired with a hydrogen oxalate or oxalate anion, with the general formula [(PRRRR′)x][C2O4H2−x], R = 4,6 and R′ = 4, 14. These compounds were characterized by 1H, 13C, 31P NMR, and Raman spectroscopy. Electrochemical windows, electrical conductivities, densities and viscosities were also determined experimentally. Thermal gravimetric analysis (TGA) revealed decomposition temperatures above 200 °C and differential scanning calorimetry (DSC) analysis revealed that the two [(P66614)x][C2O4H2−x] salts have similar glass transition temperatures while [(P4444)2][C2O4] has a melting point above room temperature. Raman and powder X-ray diffraction spectroscopy confirm that Nd2O3 dissolves and complexes with [P66614][C2O4].

The carboxyl-functionalized phosphonium ionic liquid (IL), [HCTMP][Tf(2)N], enabled the directed nucleation of monomeric or dimeric uranyl(vi) compounds. This new IL is the first carboxyl-functionalized IL which is liquid at room temperature and exhibits a wider electrochemical window and lower melting point than its ammonium analogue.

A diarylamino-substituted N-methyl tetrahydrosalen (salan) ligand, (An2N)LH(2), is prepared in four steps and overall 53% yield from 5-bromosalicylaldehyde, with the key step a palladium-catalysed Hartwig-Buchwald amination of the tert-butyldimethylsilyl-protected 5-bromo-N-methylsalan ligand. Reaction of (An2N)LH(2) or its bromo analogue with Ti(O(i)Pr)(4) or TiF(4) results in metalation of the ligand. The isopropoxide groups are readily exchanged with α- or β-hydroxyacids to form chelated complexes. X-ray crystallography and NMR spectroscopy indicate that the salan ligands are quite flexible, with (An2N)LTiF(2), for example, showing four stereoisomers in its (19)F NMR spectrum. The major stereoisomer of (salan)Ti(X)(Y) depends principally on the trans influence of the X and Y groups. Complexes of (An2N)L show two reversible, closely spaced redox couples at approximately + 0.1 V vs. ferrocene/ferrocenium, and a second set of two closely spaced redox couples at ~ + 0.8 V vs. Fc/Fc(+).