Online determination of natural gas propertiesCaractérisation des propriétés du gaz naturel

Methane number and Lower Heating Value (LHV) of natural gas are determined by the online measurement of thermal conductivity at two different temperatures. Natural gas is first considered as a ternary mixture of the most important components. A pseudo-ternary composition can then be calculated, using the thermal conductivity formula for mixtures derived from kinetic theory. A non-linear system is solved numerically using the Newton–Raphson method. A sensor based on thermal conductivity measurement has been developed and tested successfully for many natural gas compositions. To cite this article: C. Rahmouni et al., C. R. Mecanique 331 (2003).     

Syntheses of a 2,6-bis-(methylphospholyl)pyridine ligand and its cationic Pd(II) and Ni(II) complexes - application in the palladium-catalyzed synthesis of arylboronic esters

2,6-Bis(2,5-diphenylphospholyl-1-methyl)pyridine (2) was prepared from the reaction of 2,5-diphenylphospholide anion with 2,6-bis(chloromethyl)pyridine. The X-ray crystal structure of 2 was recorded. Reaction of 2 with [Pd(COD)Cl₂] in the presence of AgBF₄ yields the cationic complex [Pd(2)Cl][BF₄] (3). The analogous Ni complex [Ni(2)Br][BF₄] (4) was prepared in a similar way by reacting ligand 2 with [NiBr₂(DME)] in the presence of AgBF₄ and its formulation was confirmed by an X-ray crystal structure study. Complex 3 efficiently catalyzes the coupling between pinacolborane and iodo and bromoarenes with good TON (up to 1 × 10⁵ with iodo derivatives and 8.9 × 10³ with bromo derivatives).     

Clique inference process for solving Max-CSP

Few works on problems CSP, Max-CSP and weighted CSP was carried out in the field of Combinatorial Optimization, whereas this field contains many algorithmic tools which can be used for the resolution of these problems.In this paper, we introduce the binary clique concept: clique which expresses incompatibilities between values of two CSP variables. We propose a linear formulation for any binary clique and we present several ways to exploit it in order to compute lower bounds or to solve Max-CSP. We also show that the binary clique concept can be exploited in the weighted CSP framework.The obtained theoretical and experimental results are very interesting and they open new prospects to exploit the Combinatorial Optimization algorithmic tools for the resolution of CSP, Max-CSP and weighted CSP.     

Combining Metaheuristics and Exact Methods for Solving Exactly Multi-objective Problems on the Grid

This paper presents a parallel hybrid exact multi-objective approach which combines two metaheuristics – a genetic algorithm (GA) and a memetic algorithm (MA), with an exact method – a branch and bound (B&B) algorithm. Such approach profits from both the exploration power of the GA, the intensification capability of the MA and the ability of the B&B to provide optimal solutions with proof of optimality. To fully exploit the resources of a computational grid, the hybrid method is parallelized according to three well-known parallel models – the island model for the GA, the multi-start model for the MA and the parallel tree exploration model for the B&B. The obtained method has been experimented and validated on a bi-objective flow-shop scheduling problem. The approach allowed to solve exactly for the first time an instance of the problem – 50 jobs on 5 machines. More than 400 processors belonging to 4 different administrative domains have contributed to the resolution process during more than 6 days.      

A sigma 4, lambda 5-phosphinine palladium complex: a new type of phosphorus ligand and catalyst. Application to the Pd-catalyzed formation of arylboronic esters

A palladium(II) complex of a S-P-S pincer ligand featuring a metallated ylidic P-atom efficiently catalyzes the coupling between pinacolborane and various iodoaryls to yield the corresponding arylboronic esters (TON between 5100 and 76,500).     

Phosphinines and Diphosphaferrocenes: Recent Advances

Recent developments in the chemistry of phosphinines and phosphaferrocenes are reviewed. Phosphinine-based macrocycles such as silacalix-[4]-phosphinines efficiently stabilize gold(0). 2,2'Biphosphinines which behave as powerful chelates show a greater ability than their nitrogen counterparts for the stabilization of highly reduced and electron-excessive transition metal centers. On the other hand, diphosphaferrocenes coordinate various metal centers via a side-on bonding mode. Palladium(0) complexes of octa-alkyl diphosphaferrocenes behave as efficient catalysts both in the Suzuki cross-coupling reaction and in the synthesis of arylboronic esters.     

Structural and electrochemical investigations of the high fluoride affinity of sterically hindered 1,8-bis(boryl)naphthalenes

The reaction of 10-bromo-9-oxa-10-boraanthracene with the tetrakis(tetrahydrofuran)lithium salt of dimesityl-1,8-naphthalenediylborate in diethyl ether affords 1-(dimesitylboryl)-8-(10'-bora-9'-oxaanthryl)naphthalene (2). This diborane reacts with [Me3SiF2][S(NMe2)3)] to afford the anionic complex [2-mu2-F]-, which has been isolated as a [S(NMe2)3]+ salt. The cyclic voltammograms of diborane 2 as well as 1-(dimesitylboryl)-8-(10'-bora-9'-thiaanthryl)naphthalene (1) exhibit two reversible reductions at E(1/2) = -2.200 and -2.566 V (vs FcH/FcH+) for 1 and E(1/2) = -2.248 and -2.620 V (vs FcH/FcH+) for 2 corresponding to the sequential reduction of the two boron centers. These two waves simultaneously disappear upon fluoride addition, thus indicating the formation of fluoride chelate complexes [1-mu2-F]- and [2-mu2-F]-. To identify the origin of the high fluoride affinity displayed by these diboranes, the structures of 2 and [2-mu2-F]- have been studied experimentally and computationally. The crystallographic studies show that the structure of 2 is distorted, thus indicating the presence of important steric repulsions between the neighboring boryl moieties. By contrast, the structure of the anionic complex [2-mu2-F]- is much more sterically relaxed than that of 2, as indicated by a reduction of the B-B distance from 3.279(4) A in 2 to 2.922(7) A in [2-mu2-F]-. The structural results suggest that the high fluoride affinity displayed by 2 results, at least in part, from the relief of steric repulsions induced by fluoride binding. Finally, the nature of the bonding as well as the strength of the interactions involved in the B-F-B bridge of [2-mu2-F]- has been studied using density functional theory calculations and Atoms-In-Molecules analyses. These calculations indicate that the enthalpic gain associated with the formation of two B-F bonds in [2-mu2-F]- only amounts to a fraction of the energy of a terminal B-F bond. These calculations also suggest that the relief of steric repulsions induced by fluoride binding in 2 may contribute to the high fluoride affinity of these types of molecules.     

Reactivity of a 1,3,2‐diazaphosphinine toward propargyl‐phosphine derivatives and activated alkenes

2,5‐Diphenylphosphole and diphenylphosphino derivatives 2, 3 of 1‐phenylpropargyl were prepared by reacting the corresponding diphenylphosphinolithium and 2,5‐diphospholyl lithium salts with (3‐bromo‐prop‐1‐ynyl)‐benzene in THF at low temperature. Sulfurization of these propargyl derivatives was then carried out with elemental sulfur in toluene at 90°C to yield the corresponding phosphole 8 and phosphino 9 derivatives. Reaction of 3,5‐di‐tert‐butyl‐1,3,2‐diazaphosphinine 1 with the free phosphole derivative led to a mixture of diazaphosphinines 4 and 5 that were converted to the corresponding phosphinines 6 and 7 upon treatment with trimethylsilylacetylene in excess. Reaction of 1 with 1‐phenylpropargyl derivatives of diphenylphosphine 8 and phosphole 9 afforded 7,8‐dihydro‐1‐phospha‐2,6‐diazabarrelenes 10 and 11 having an exocyclic double bond. Formation of these compounds results from a (1,3)‐shift of a hydrogen atom from the methylene carbon atom to the bridge of the barrelene moiety. Depending on the nature of the phosphine group, the sulfur atom can also be displaced to the P atom of the barrelene moiety. The X‐ray structure of the phosphole derivative 10 was recorded. Three 6,7‐dihydro‐1‐phospha‐2,6‐diazabarrelenes bearing two ( 16 ) or one ester ( 17a,b ), or one cyano group ( 18a,b ) on the bridge were also synthesized through the reaction of 1 with ethyl acrylate, dimethyl fumarate, and acrylonitrile. The X‐ray structure of the cyano derivative 18a is also presented. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:326–333, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10152