Harnessing low-valent metal centers through non-bonding orbital interactions

The synthesis, characterization, and computational analysis of a series of low-valent, In(I) complexes bearing the bis(imino)pyridine scaffold, {Ar'N=CPh}(2)(NC(5)H(3)), is reported. A stepwise steric reduction of the aryl groups on the imine substituents around the coordination site, (Ar' = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3), 2,6-(CH(3)CH(2))(2)C(6)H(3)) is explored through the spectroscopic and crystallographic examination of complexes [{Ar'N=CPh}(2)(NC(5)H(3))]In(+)(OTf)(-) (1-3). Compounds 1-3 displayed long In-N and In-OTf distances indicating only weak or no coordination. Application of the ligand with Ar' = 2,6-(CH(3))(2)C(6)H(3) led to an In(III) bis(imino)pyridine complex, [{2,6-Me(2)C(6)H(3)N=CPh}(2)(NC(5)H(3))]In(OTf)(2)Cl 4 with coordinated ligand, chloride, and triflate groups. Computational analysis of the interactions between the In cation and the ligands (orbital populations, bond order, and energy decomposition analysis) point to only minimal covalent interactions of the In(I) cation with the ligands. Although it features three N donor centers, the bis(imino)pyridine ligand provides little ligand-to-metal donation. A thorough electronic structure analysis revealed a correlation of compound stability with the reduced contribution of the In(I) 5s lone electron pair to the highest occupied molecular orbital (HOMO) of the cation. This effect, originating from non-bonding orbital interactions between the metal and the ligand, is more prominent in sterically crowded environments. The discovery of this correlation may help in designing new low-valent complexes.     

Racemic iron(III) and cobalt(III) complexes containing a new pentadentate "helmet" phthalocyaninato ligand

Solvothermal reactions of iron(II) acetate tetrahydrate and cobalt(II) acetate tetrahydrate with 1,2-dicyanobenzene in methanol solution result in the formation of racemic six-coordinate iron(III) and cobalt(III) complexes, respectively, with a new bicyclic pentadentate 14,28-[1,3-diiminoisoindolinato]phthalocyaninato ligand.     

Aerobic intramolecular oxidative amination of alkenes catalyzed by NHC-coordinated palladium complexes

[reaction: see text] Palladium(II) complexes bearing a single N-heterocyclic carbene ligand serve as effective catalysts for the aerobic oxidative cyclization of alkenes with pendant sulfonamides. The use of carboxylic acid cocatalysts (AcOH and PhCO(2)H) often leads to significant improvements in catalyst stability and product yield and enables catalytic turnover to be achieved with air, rather than pure oxygen gas, as the source of O(2).     

The rate of convergence of the Walk on Spheres Algorithm

In this paper we examine the rate of convergence of one of the standard algorithms for emulating exit probabilities of Brownian motion, the Walk on Spheres (WoS) algorithm. We obtain a complete characterization of the rate of convergence of WoS in terms of the local geometry of a domain.     

Synthesis of electron-poor 4-halo-2-azabuta-1,3-dienes by Rh(II)-catalyzed diazo ester-azirine coupling. 2-Azabuta-1,3-diene-2,3-dihydroazete valence isomerism

The Rh₂(OAc)₄-catalyzed reaction of alkyl 2-acyl-2-diazoacetates and dimethyl diazomalonate with methyl 2-bromo- and 2-chloro-3-phenyl-2H-azirine-2-carboxylates gives rise to electron-poor 4-halo-substituted (3E)-2-azabuta-1,3-dienes. Their formation proceeds with complete stereoselectivity via ring-opening of the intermediate azirinium ylide. 2-Azabuta-1,3-dienes with electron-withdrawing substituents at the 1,1,4-positions are stable compounds at room temperature, but are in equilibrium with cyclic valence isomers, 2,3-dihydroazetes, at elevated temperatures.     

Action of Weyl group on zero-weight space

For any simple complex Lie group, we classify irreducible finite-dimensional representations ρ for which the longest element $w_0$ of the Weyl group acts non-trivially on the zero-weight space. Among irreducible representations that have zero among their weights, $w_0$ acts by ±Id if and only if the highest weight of ρ is a multiple of a fundamental weight, with a coefficient less than a bound that depends on the group and on the fundamental weight.     

Mean field theory of melting

A simply microscopic theory of melting is presented and applied to derive Lindemans law for alkali metals and to estimate the melting density and temperature of a Coulomb solid.     

Two polymorphs of chlorido(cyclohexyldiphenylphosphine)gold(I)

The title compound, [AuCl(C₁₈H₂₁P)], a monomeric two‐coordinate gold(I) complex, has been characterized at 100 K as two distinct monoclinic polymorphs, one from a single crystal, (Is), and one from a pseudo‐merohedrally twinned crystal, (It). The molecular structures in the two monoclinic [P2₁/n for (Is) and P2₁/c for (It)] polymorphs are similar; however, the packing arrangements in the two lattices differ considerably. The structure of (It) is pseudo‐merohedrally twinned by a twofold rotation about the a* axis.