This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO(2)(2+). Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO(2)(AO)(x)(OH(2))(y)](2-x) (x = 1-3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η(2) binding with the N-O bond. The theoretical results establish the η(2) motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO(2)(2+) complexes with acetamidoxime and benzamidoxime anions.

A series of titanium complexes containing a terminal neopentylidene functionality have been prepared by a one electron oxidatively induced α-hydrogen abstraction from the corresponding bis-neopentyl precursor (Nacnac)Ti(CH2 tBu)2 (Nacnac- = [Ar]NC(CH3)CHC(CH3)N[Ar], Ar = 2,6-(CHMe2)2C6H3), among them (Nacnac)TiCHtBu(OTf) and (Nacnac)TiCHtBu(I). It was determined that bulky alkyl groups bound to titanium as well as a bulky coordinating anion from the oxidant are needed to promote α-hydrogen abstraction. Complex (Nacnac)TiCHtBu(OTf) serves as a template for other four-coordinate titanium neopentylidene complexes such as (Nacnac)TiCHtBu(X) (X- = Cl, Br, and BH4). Complexes (Nacnac)TiCHtBu(X) undergo cross-metathesis reactivity with the imine functionality of the Nacnac- ligand forming the imido complexes (HtBuCC(Me)CHC(Me)N[Ar])TiNAr(X) (X- = OTf, Cl, Br, I, BH4). In addition, C−H activation of two tertiary carbons also takes place to afford the titanacycles Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(CMe2)(CHMe2)C6H3](X) (X- = OTf, Cl, Br and η2-BH4). Kinetic studies in C6D6 reveal the formation of (HtBuCC(Me)CHC(Me)N[Ar])TiNAr(I) from (Nacnac)TiCHtBu(I) to be independent of solvent (C6D6, Et2O−d10, THF-d8) and the reaction to be first order in titanium (k = 8.06 × 10-4 s-1 at 57 °C, with activation parameters ΔH ⧧ = 21.3(2) kcal/mol, ΔS ⧧ = −8(3) cal/mol K). Compound (Nacnac)TiCHtBu(OTf) reacts with various substrates to afford products in which the alkylidene functionality has been significantly transformed. When the alkylidene derivatives (NacnactBu)TiCHtBu(X) (X- = OTf, I; NacnactBu - = [Ar]NC(tBu)CHC(tBu)N[Ar]) were prepared, the intramolecular cross-metathesis transformation observed with (Nacnac)TiCHtBu(X) was inhibited completely.

We present an extensive study of a novel class of de novo designed tetrahedral M(4)L(6) (M = Ni, Zn) cage receptors, wherein internal decoration of the cage cavities with urea anion-binding groups, via functionalization of the organic components L, led to selective encapsulation of tetrahedral oxoanions EO(4)(n-) (E = S, Se, Cr, Mo, W, n = 2; E = P, n = 3) from aqueous solutions, based on shape, size, and charge recognition. External functionalization with tBu groups led to enhanced solubility of the cages in aqueous methanol solutions, thereby allowing for their thorough characterization by multinuclear ((1)H, (13)C, (77)Se) and diffusion NMR spectroscopies. Additional experimental characterization by electrospray ionization mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray diffraction, as well as theoretical calculations, led to a detailed understanding of the cage structures, self-assembly, and anion encapsulation. We found that the cage self-assembly is templated by EO(4)(n-) oxoanions (n ≥ 2), and upon removal of the templating anion the tetrahedral M(4)L(6) cages rearrange into different coordination assemblies. The exchange selectivity among EO(4)(n-) oxoanions has been investigated with (77)Se NMR spectroscopy using (77)SeO(4)(2-) as an anionic probe, which found the following selectivity trend: PO(4)(3-) ≫ CrO(4)(2-) > SO(4)(2-) > SeO(4)(2-) > MoO(4)(2-) > WO(4)(2-). In addition to the complementarity and flexibility of the cage receptor, a combination of factors have been found to contribute to the observed anion selectivity, including the anions' charge, size, hydration, basicity, and hydrogen-bond acceptor abilities.

Density functional theory computational methods were used to calculate the entropies of various molecules; computed entropies correlated closely with measured values. For organic systems, an average of 8.4 kcal/mol for the reaction entropy (one particle to two at 298.15 K) was observed; this value is largely determined by translational entropy gain. The average reaction entropy is slightly lower for reactions that produce two linear molecules and up to 4 kcal/mol higher when no linear molecules are produced, due to differences in rotational entropy of the reactants and products. Translational and rotational entropy are generally independent of molecular identity except for increases in mass and generation of additional moments of inertia; vibrational entropy, which is more dependent on the molecule itself, is a small contributor to the nearly constant entropy of reaction. A variety of inorganic and non-hydrocarbon main group reaction entropies were also calculated; there is an increased contribution of vibrational entropy in inorganic molecules with "softer" vibrations. The trends discussed in this paper can serve as a basis for understanding the contributions of different sources of entropy to the overall reaction TΔS° for students and practicing chemists; the method employed (i.e., using a commercial program to "discover" trends in a thermodynamic property) can serve as an example of discovery-based learning in the curriculum.

The ligand (tBu2PCH2SiMe2)2N1- (PNP) in [PNP]RuCl leads to an intermediate spin ground state, S = 1, which has been characterized by NMR and X-ray diffraction as having a planar structure. This spin state is attributed in part to N --> Ru pi donation. DFT calculations confirm that the singlet state lies higher in energy and is nonplanar. The molecule is converted to a diamagnetic product by addition of 2 mol of PhCN. The half-filled orbitals of the S = 1 state are suggested to be the reason agostic interactions do not compensate for the 14-valence electron count.