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Research has been conducted on the complexes containing functionalized cycloheptatrienyl ligands. The syntheses of the molybdenum complexes which contain linked cycloheptatrienyl-phenolate ligands capable to bind to the metal center are reported.

We investigate a number of complex patterns driven by the electroconvection instability in a planarly aligned layer of a nematic liquid crystal. They are traced back to various secondary instabilities of the ideal roll patterns bifurcating at onset of convection, whereby the basic nematohydrodynamic equations are solved by common Galerkin expansion methods. Alternatively these equations are systematically approximated by a set of coupled amplitude equations. They describe slow modulations of the convection roll amplitudes, which are coupled to a flow field component with finite vorticity perpendicular to the layer and to a quasihomogeneous in-plane rotation of the director. It is demonstrated that the Galerkin stability diagram of the convection rolls is well reproduced by the corresponding one based on the amplitude equations. The main purpose of the paper is, however, to demonstrate that their direct numerical simulations match surprisingly well new experiments, which serves as a convincing test of our theoretical approach. [ABSTRACT FROM AUTHOR]

Measurements of fluctuations and convection patterns in horizontal layers of fluid heated from below and near the onset of Rayleigh-Bénard convection (RBC) are reported under conditions where the fluid properties vary strongly over the temperature range ΔT =Tb - Tt (Tb and Tt are the temperatures at the bottom and top of the sample, respectively). To facilitate a comparison with the data, the theory of Busse (J. Fluid Mech., vol. 30, 1967, p. 625) of these so called non-Oberbeck-Boussinesq (NOB) effects, which applies to the case of relatively weak (and linear) temperature dependences, was extended to arbitrary variations with temperature. It is conceptually useful to divide the variations with temperature of the fluid properties into two disjunct parts. One part is chosen so that it preserves the reflection symmetry of the system about the horizontal midplane, while the remainder breaks that symmetry. The latter, exclusively considered by Busse, leads (in contrast to the formation of the typical convection rolls in RBC) to hexagons immediately above the transition to convection at the critical temperature difference ΔTc. The symmetric part, on the other hand, does not prevent the bifurcation to rolls, but may become very important for the determination of ΔTc. In the experiment the fluid was sulfur hexafluoride at temperatures above but close to the gas-liquid critical point, where all fluid properties vary strongly with temperature. All measurements were done along isobars by varying ΔT . Patterns were observed above onset (ΔT ≳ ΔTc), while for the conduction state at ΔT <ΔTc there were only fluctuations induced by Brownian motion. When the mean temperature Tm =(Tb + Tt )/2 was such that the density ρ at Tm was equal to the critical density ρ*, the mirror symmetry about the horizontal midplane of the sample was essentially preserved. In that case, as expected, we found a direct transition to rolls and the critical temperature difference ΔTc was considerably shifted compared to the critical value ΔTc, OB in the absence of NOB effects. When, on the other hand, Tm was not located on the critical isochore, the NOB effects broke the reflection symmetry and led to a hysteretic transition from fluctuations to hexagonal patterns. In this latter case the hexagonal pattern, the observed hysteresis at onset and the transition from hexagons to rolls at larger ΔT were consistent with the 'classical' predictions by Busse. [ABSTRACT FROM AUTHOR]

The synthesis of the tetrahydroborate complex [(2-iPr2PC6H4-η7-C7H6)Mo(η2-BH4)(P–Mo)] 3 containing the linked cycloheptatrienyl-phosphane ligand [2-(diisopropylphosphanyl)phenyl]cycloheptatrienyl is described, which provides the possibility to generate the 14-electron complex [(2-iPr2PC6H4-η7-C7H6)Mo(P–Mo)]+ (4) on treatment with dimethylanilinium salts such as [HNMe2Ph][BPh4]. Generation of (4)BPh4 in the presence of 2,6-dimethylphenyl isocyanide, 2,5-norbornadiene or phenylacetylene affords the diisocyanide complex (5a)BPh4, the diolefin complex (5b)BPh4 and the alkyne complex (6)BPh4, respectively. The latter complex can be used for the catalytic oligomerization of phenylacetylene affording predominantly the cyclotrimers 1,3,5- and 1,2,4-triphenylbenzene. [Copyright &y& Elsevier]