Reactions of [η:σ-Me2C(C5H4)(C2B10H10)]Ru(COD) with Lewis bases: Synthesis, structure, and electrochemistry of ruthenium amine, nitrile, carbene, phosphite and phosphine complexes

Treatment of [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(COD) (1) with phosphites, phosphines, amines or N-heterocyclic carbene in THF afforded the COD displacement complexes [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[P(OEt)₃]₂ (2), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[PPh₂(OEt)]₂ (3), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[NH₂CH₂CH₂Prⁱ]₂ (4), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)₂ (5), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru (η²-NH₂CH₂CH₂NH₂) (6), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[η²-NH(CH₃)CH₂CH₂NH(CH₃)] (7) or [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[NHC]₂ (8, NHC = 1,3,4,5-tetramethylimidazol-2-yilidene), respectively. Ruthenium-amine complexes were much more labile than 1. Upon exposure to moisture, 5 was converted into [{η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)}Ru(μ-H₂O)]₂ (9). Reactions of 5 with PR₃ (R = PPh₃, Cy), TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) and CH₃CN afforded the corresponding amine replacement products[η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)(PPh₃) (10), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)(PCy₃) (11), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(TMEDA) (12) and [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NCCH₃)₂ (13). These results indicated that the steric factor dominated these substitution reactions. The electrochemical studies showed that the electron richness of the Ru atom decreased in the order L₂Ru(NHC)₂ > L₂Ru(amine)₂ > L₂Ru(NCMe)₂ > L₂Ru(P)₂. All of these complexes were fully characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 2, 3, 5-10, 12 and 13 were further confirmed by single-crystal X-ray analyses.     

硅氮化合物的结构与水解稳定性的关系

采用硅氮化合物本体与水蒸汽直接作用的方法,研究了一系列硅氮化合物的结构与水解稳定性之间的关系.结果表明,空间位阻越大则硅氮化合物水解稳定性越好,环张力对硅氮烷的水解稳定性有一定的影响,但空间位阻的作用更为显著.带有苯基的环二硅氮烷、六苯基环三硅氮烷和含硅氮键的高分子聚合物具有较大的空间位阻,因此水解稳定性非常好.     

The effect of the finite size of ions and Debye layer overspill on the screened Coulomb interactions between charged flat plates

Screened repulsion between uniformly charged plates with an intervening electrolyte is analyzed for strongly overlapped electrical double layers (EDL), accounting for the steric effect of ions and their expulsion from EDL edges into the surrounding solution. As a generalization of a study by Philipse et al. which does not account for these effects, an analytical expression is derived for the repulsion pressure in the limit of infinitely long plates with a zero-field assumption, which agrees closely with the corresponding numerical solution at low inter-plate separations. Our results show an augmented repulsive pressure for finite-sized ions at strong EDL overlaps. For plates with a finite lateral size, we demonstrate a further extended domain of low inter-plate gaps where the repulsion pressure increases with ion size due to a strong interplay between the steric interaction of ions and the EDL overspill phenomenon, considered earlier in a study by Ghosal & Sherwood limited to the linear Debye-Hückel regime (which cannot account for the steric effect of ions). This investigation on a simple model should enhance our understanding of the interaction between charged particles in electrophoresis, nanoscale self-assembly, active particles, and various other electrokinetic systems.     

A general approach to the design of high-performance near-infrared (NIR) D-π-A type fluorescent dyes

A four-step method is presented as a general guideline for design of high performance NIR absorbing/emitting dyes.     

Investigation of adsorbed polymer layers by flocculation of oppositely charged sols III. Effect of molecular mass of polymers

The stabilizing effect of water-soluble neutral polymers with different chemical structure and relative molecular mass on AgI sol has been studied. It was shown that the stabilizing effect of the polymers used is independent of the relative molecular mass of the polymer when equal amounts of the adsorbed polymers are compared with each other as stabilizers. The high stabilizing effect of polymers with high relative molecular mass is presumably due to the larger adsorbed amount.Among polyvinyl alcohol, polyvinyl pyrrolidone and methylcellulose, polyvinyl pyrrolidone exhibits the smallest stabilizing layer thickness at equal adsorbed amounts. According to our earlier results this is due to the fact that the polyvinyl pyrrolidone shows the strongest affinity for AgI surfaces, forming short loops or tails.     

Recent advances of achiral and chiral diene ligands in transition-metal catalyses

A series of achiral and chiral diene and the related ligands in transition-metal complexes is evaluated by percent buried volume (%V_bur) based on their molecular structures by X-ray analysis. Steric bulk of cyclic diene ligands in [Ru(acac)₂L] and [RhClL]₂ are sorted in the order of %V_bur. Recent developments on transition-metal catalyses using these ligands such as (i) conjugate arylations, alkenylation, and alkynylation, (ii) imine-arylations and alkenylations, (iii) kinetic resolutions, (iv) allylation, (v) cyclizations, (vi) defluorinations, (vii) CH bond activations, and (viii) cross-dimerizations are reviewed.     

QSAR based modeling on a series of α-hydroxy amides as a novel class of bradykinin B1 selective antagonists

G-protein coupled receptors like Bradykinin (BK) B₁ represent a potential treatment route for chronic pain and inflammation. Quantitative structure activity relationship has been performed on a series of α-hydroxy amides as a novel class of bradykinin B₁ selective antagonists, using different physicochemical parameters along with appropriate indicator variables. It has been found that physicochemical parameters such as connectivity indices ³χ, ⁴χ and ⁵χ, molecular weight, molar refractivity, density along with indicator variables are significantly correlated with activity. In this paper best results were obtained by using multiple regression analysis. Different models were generated with high values of R² and low values of PRESS/SSY ratio. The significant equations were statistically tested by using leave one out (LOO) technique and cross validation methods.     

Analysis of the supramolecular structures of Sb(III) and Sb(V) catecholate complexes from the viewpoint of ligand solid angles

The ligand solid angle approach has been successfully applied to the analysis of the catecholate complexes of Sb(III) and Sb(V). The Sb(III) complexes possess an electron lone pair that influences their molecular structure but does not behave as a classic “ligand” when intermolecular interactions are concerned. The Sb(III) complexes in solid state form numerous intermolecular interactions that effectively increase metal shielding, and herein we analyze the effects of the lone pair of electrons on the complex coordination geometry. In the five-coordinate R₃CatSb(V) complexes (Cat = catecholate ligand, R = Ph, Me, Cl) the metal is shielded by 87(3)% and multiple intermolecular contacts are observed. The central metal in the six-coordinate antimony(V) complexes R₃CatSb(V) · L is shielded to the extent of 89(2)% and no strong attractive intermolecular interactions are detected in solid state. Thus, the metal shielding in excess of 85% is required to prevent complex dimerization or additional ligation of the central atom by a nucleophile.     

Exploration of conjugate addition routes to advanced tricyclic components of mangicol A

Two synthetic approaches to the cytotoxic marine natural product known as mangicol A are described. The starting material common to both pathways is the cyclopentenonecarboxylate 11. The first tactic involves the 1,4-addition to 11 of the cuprate derivable from iodide 10, while the second proceeds via base-promoted conjugate addition of the regiospecifically generated enolate anion of 41. The first strategy proceeds by a series of efficient steps to tricyclic aldol 21 and subsequently to β-diketone 7. The latter proved to be totally unresponsive to schemes aimed at introduction of a butenyl group. The second approach involves earlier introduction of this substituent as realized in stereocontrolled fashion via transition state 42. While further passage to 44 proved uneventful, this advanced intermediate and analogs thereof proved remarkably recalcitrant to cyclization in the precedented fashion. In no instance was generation of a suitable product realized. These studies serve to underscore the extent to which steric considerations can complicate matters and the extent to which they must be skirted. Finally, a direct enantioselective route to the side chain aldehyde 2 is detailed.     

Extending bond orbital-connection matrix method to the QSPR study of alkylbenzenes: Some thermochemical properties

The properties of alkylbenzenes were estimated, using the contributions of the σ bonds, the conjugated π bond and the steric effect in alkylbenzene molecule. And a novel bond orbital-connection matrix, conjugated π bond orbital-connection matrix in aromatic molecules, was proposed. The eigenvalues of the conjugated π bond orbital-connection matrix can well express the contribution of the conjugated π bond to the properties of aromatic molecules. Using this eigenvalue together with the parameters proposed in our early works, the bond orbital-connection matrix method was extended successfully to the QSPR studies of alkylbenzenes and a general model was obtained to evaluate the thermochemical properties of alkylbenzenes, that is,

p_{(alkylbenzene)}=aN_C–C+b∑X_1CC+cN_C–H+d∑X_1CH+eS_Z/E+k∑X_1π,