Preparation of benzyne complexes of group 10 metals by intramolecular suzuki coupling of ortho-metalated phenylboronic esters: molecular structure of the first benzyne-palladium(0) complex

A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr[o-C(6)H(4)B(pin)]L(2)] (M = Ni, L(2) = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L(2) = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KO(t)Bu to form the corresponding benzyne complexes [M(eta(2)-C(6)H(4))L(2)] (M = Ni, L(2) = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L(2) = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KO(t)Bu, but in this case disproportionation of the initially formed eta(2)-C(6)H(4) complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(mu(2)-C(6)H(4))Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C(6)H(4)C(6)H(4))(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.     

An examination of the validity of nonequilibrium molecular-dynamics simulation algorithms for arbitrary steady-state flows

Nonlinear-response theory of nonequilibrium molecular-dynamics simulation algorithms is considered under the imposition of an arbitrary steady-state flow field. It is demonstrated that the SLLOD and DOLLS algorithms cannot be used for general flows, although the SLLOD algorithm is rigorous for planar Couette flow. Following the same procedure used to establish SLLOD as the valid algorithm for planar Couette flow [D. J. Evans and E. P. Morriss, Phys. Rev. A 30, 1528 (1984)], it is demonstrated that the p-SLLOD algorithm is valid for arbitrary flows and produces the correct nonlinear response of the viscous pressure tensor.     

The α‐ and β‐epoxides of 3β‐acet­oxy‐5α‐lanost‐9(11)‐en‐7‐one

The structures of 3β‐acet­oxy‐9α,11α‐ep­oxy‐5α‐lanost‐9(11)‐en‐7‐one and 3β‐acet­oxy‐9β,11β‐ep­oxy‐5α‐lanost‐9(11)‐en‐7‐one, C₃₂H₅₂O₄, differ in their respective substituted cyclo­hexa­none rings but adopt similar conformations in the other three rings. In both of the crystal structures, weak inter­molecular C—H⋯O inter­actions are present.     

New nickel(II), copper(II), platinum(II) and palladium(II) complexes of a multidentate sulfur–nitrogen chelating agent

A new, potentially polydentate sulfur–nitrogen chelating agent, 2,6–bis(N-methyl-S-methyldithiocarbazato)pyridine (L) has been synthesized and characterized. With nickel(II) salts, the ligand yields complexes of empirical formula NiLX2·nH2O (X=Cl−, NCS− or NO3−; n=0 or 1) in which it behaves as a quadridentate NSSN chelating agent, coordinating to the nickel(II) ion via the two amino nitrogen atoms and the two sulfur atoms. Magnetic and spectral evidence support a distorted octahedral structure for these complexes. The ligand reacts with copper(II), platinum(II) and palladium(II) salts to yield homo-binuclear complexes of general formula [M2LX4]·nSol (M=CuII, PtII or PdII; X=Cl− or Br−; n=0.5, 1 or 2; Sol=H2O, MeOH or MeCOMe), in which each of the metal ions is in a square-planar environment. These complexes have been characterized by a variety of physicochemical techniques. This revised version was published online in June 2006 with corrections to the Cover Date.     

Liquid chromatography-mass spectrometry coupling and its application in pharmaceutical research

The advantages and technical problems related to the on-line connection of liquid chromatography and mass spectrometry are described, with special emphasis on applications in pharmaceutical chemistry. The most important characteristics of various interfaces, such as direct liquid introduction, Magic, continuous flow fast atom bombardment and thermospray, are discussed. Special applications to the study of thermally very labile compounds are considered.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

Flow-injection liposome immunoanalysis (FILIA) for alachlor

An automated Flow-Injection Liposome ImmunoAnalysis (FILIA) system has been modified from a previous design, using a specific environmental contaminant, the herbicide alachlor, as a model analyte. Signal amplification by means of fluorescent marker-loaded, analyte-tagged liposomes provides high sensitivity. The computer controlled system is composed of commercially available components, with the exception of the column packing material, which has to be prepared for each specific analyte to be determined. The use of such components means that the system is easily modified. The relationships between antibody concentration and assay speed and sensitivity are explored, and the possibilities of using the system for determination of multiple analytes is discussed.     

A study of the Li1+xTi2−xO4 spinel system by diffuse-reflectance spectroscopy

The room-temperature diffuse-reflectance spectra of compositions within the Li_1+xTi_2?xO₄ spinel system ($\text{0 ≤ x ≤}\text{1}\text{3}$) show three absorption bands in the range 4000 to 48,000 cm^?1. Two high-energy absorption bands correspond to charge-transfer transitions from the oxygen-2p valence band to the titanium t_2g and σ1 conduction bands, where the σ1 band of e_g character has hybridized titanium-3d and titanium-4s parentage. The absorption band arising from promotion of electrons to the empty σ1 band does not alter with composition whereas the absorption band arising from promotion of electrons to the partially filled t_2g band narrows as the concentration of conduction electrons in the t_2g band decreases. These two high-energy absorption bands fall entirely within the ultraviolet spectral region, and the absorption edge in $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4\text{(x =}\text{1}\text{3}\text{)}$ occurs at 24,300 cm^?1 (3.02 eV). A low-energy absorption band is observed in compositions with $\text{x <}\text{1}\text{3}$ and in samples of $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4$ reduced in hydrogen at elevated temperatures. This band straddles the boundary between the visible and infrared spectral regions and shifts toward lower energy as the concentration of conduction electrons in the t_2g band decreases. The possible origins of the band are discussed; the argument is in favor of a d-d interband transition from states in the partially filled t_2g band to states in the empty σ1 band.     

N-acyl (substituted) phenylglycine derivatives

Amidoalkylation of three benzoheterocycles, benzimidazole-2-one, 1,3-dihydrobenzo[c]-thiophene 2,2-dioxide and 1,3-dihydro-2,1,3-benzothiadiazole using N-acylhippuric acids was successful. The corresponding phenylglycine analogs were prepared by removal of the N-acyl protecting group.