The Suzuki coupling of aryl chlorides in TBAB-water mixtures

Palladium acetate in a mixture of TBAB and water can be used as an effective catalyst for the Suzuki coupling of deactivated aryl chloride substrates.     

Carbene‐Catalyzed Desymmetrization and Direct Construction of Arenes with All‐Carbon Quaternary Chiral Center

Multisubstituted arenes such as indanes with attached all‐carbon quaternary centers are unique scaffolds in synthetic functional molecules and sophisticated natural products. A key challenge in preparing such molecules lies in the enantioselective installation of the quaternary carbon centers. Conventional methods in this direction include asymmetric substitution reactions and substrate‐controlled cyclization reactions. These reactions lead to poor stereoselectivities and/or require long and tedious synthetic steps. Disclosed here is a one‐step organic catalytic strategy for enantioselective access to this class of molecules. The reaction involves an N‐heterocyclic carbene catalyzed process for direct benzene construction, indane formation, remote‐carbon desymmetrization, and excellent chirality control. This approach will enable the concise synthesis of arene‐containing molecules, including those with complex structures and challenging chiral centers.     

3,6-dioxypyridazine bridged tungsten-tungsten quadruple bonds. Comparisons of electron delocalisation with oxalate bridged compounds

The preparation and characterisation of the tungsten-tungsten quadruply bonded, 3,6-dioxypyridazine bridged complex [((t)BuCO(2))(3)W(2)](2)([micro sign]-H(2)C(4)N(2)O(2)) and its single electron oxidised radical cation are reported and, when compared with related bridged dimolybdenum complexes, reveal a different mechanism of electronic coupling from that seen in related oxalate bridged systems.     

Studies on pyridazine azide cyclisation reactions

Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.     

Synthesis of pyridone and pyridine rings by [4+2] hetero-cyclocondensation

Substituted pyridones and pyridines have been synthesised efficiently by employing iminium salt as a key precursor. These compounds were prepared using tandem [4+2] cycloaddition/deamination between azabutadiene and dienophiles.     

Group 14 Metal Terminal Phosphides: Correlating Structure with |J(MP)|

A series of heavier group 14 element, terminal phosphide complexes, M(BDI)(PR(2)) (M = Ge, Sn, Pb; BDI = CH{(CH(3))CN-2,6-iPr(2)C(6)H(3)}(2); R = Ph, Cy, SiMe(3)) have been synthesized. Two different conformations (endo and exo) are observed in the solid-state; the complexes with an endo conformation have a planar coordination geometry at phosphorus (M = Ge, Sn; R = SiMe(3)) whereas the complexes possessing an exo conformation have a pyramidal geometry at phosphorus. Solution-state NMR studies reveal through-space scalar coupling between the tin and the isopropyl groups on the N-aryl moiety of the BDI ligand, with endo and exo exhibiting different J(SnC) values. The magnitudes of the tin-phosphorus and lead-phosphorus coupling constants, |J(SnP)| and |J(PbP)|, differ significantly depending upon the hybridization of the phosphorus atom. For Sn(BDI)(P{SiMe(3)}(2)), |J(SnP)| is the largest reported in the literature, surpassing values attributed to compounds with tin-phosphorus multiple-bonds. Low temperature NMR studies of Pb(BDI)(P{SiMe(3)}(2)) show two species with vastly different |J(PbP)| values, interpreted as belonging to the endo and exo conformations, with sp(2)- and sp(3)-hybridized phosphorus, respectively.     

Tuning azolium azolate ionic liquids to promote surface interactions with titanium nanoparticles leading to increased passivation and colloidal stability

The passivation and stability of suspensions of titanium nanoparticles in azolium azolate ionic liquids can be tuned by introducing metal specific binding sites in the azolate anion.     

Theoretical reference values for the AE6 and BH6 test sets from explicitly correlated coupled-cluster theory

We propose a new computational protocol to obtain highly accurate theoretical reference data. This protocol employs the explicitly correlated coupled-cluster method with iterative single and double excitations as well as perturbative triple excitations, CCSD(T)(F12), using quadruple-z\zeta basis sets. Higher excitations are accounted for by conventional CCSDT(Q) calculations using double-z\zeta basis sets, while core/core-valence correlation effects are estimated by conventional CCSD(T) calculations using quadruple-z\zeta basis sets. Finally, scalar-relativistic effects are accounted for by conventional CCSD(T) calculations using triple-z\zeta basis sets. In the present article, this protocol is applied to the popular test sets AE6 and BH6. An error analysis shows that the new reference values obtained by our computational protocol have an uncertainty of less than 1 kcal/mol (chemical accuracy). Furthermore, concerning the atomization energies, a cancellation of the basis set incompleteness error in the CCSD(T)(F12) perturbative triples contribution with the corresponding error in the contribution from higher excitations is observed. This error cancellation is diminished by the CCSD(T*)(F12) method. Thus, we recommend the use of the CCSD(T*)(F12) method only for small- and medium-sized basis sets, while the CCSD(T)(F12) approach is preferred for high-accuracy calculations in large basis sets.     

A New Silicate Clathrate Hydrate: An X-Ray Diffraction and Nuclear Magnetic Resonance Study of a System with Octameric Silicate Anions and Trivalent Cations

The first crystal structure is reported for a silicate clathrate hydrate involving a triply charged cation [C₁₈H₃₀N₃]³⁺ and an octameric cubic silicate cage. The structure is essentially a host/guest system, with the silicate cages linked into a framework by hydrogen bonding to water molecules. The space group is P with Z = 2, and the asymmetric unit includes a complete cation and half the anion, plus 21 water molecules (4 of which are in disordered positions). Solid-state (CPMAS) ²⁹Si and ¹³CNMR spectra are consistent with the diffraction-determined structure and indicate substantial distortion of the anion from cubic symmetry. Solution-state spectra of precursor solutions and of melted material are also presented and discussed.     

Polychloride monoanions from [Cl3]- to [Cl9]- : a Raman spectroscopic and quantum chemical investigation

Polychloride monoanions stabilized by quaternary ammonium salts are investigated using Raman spectroscopy and state-of-the-art quantum-chemical calculations. A regular V-shaped pentachloride is characterized for the [N(Me)(4)][Cl(5)] salt, whereas a hockey-stick-like structure is tentatively assigned for [N(Et)(4)][Cl(2)???Cl(3)(-)]. Increasing the size of the cation to the quaternary ammonium salts [NPr(4)](+) and [NBu(4)](+) leads to the formation of the [Cl(3)](-) anion. The latter is found to be a pale yellow liquid at about 40 °C, whereas all the other compounds exist as powders. Further to these observations, the novel [Cl(9)](-) anion is characterized by low-temperature Raman spectroscopy in conjunction with quantum-chemical calculations.