François Mercier

Spatial patterns of two rodent-dispersed rain forest trees Carapa procera (Meliaceae) and Vouacapoua americana (Caesalpiniaceae) at Paracou, French Guiana

The spatial distribution of two rain forest tree species, Carapa procera (Meliaceae) and Vouacapoua americana (Caesalpiniaceae) was analysed within and between plots of different sizes (6.25 and 25 ha) at Paracou, French Guiana. The L(d) function was used to characterize spatial patterns, and the Lij(d) intertype to study independancy between young and adult trees. Although both species are known to be dispersed by caviomorph rodents within short distances (c. 10-20 m and up to 50 m) of parent tree crowns, the analysis of tree positions led to different spatial patterns between species depending on soil drainage characteristics. Over- all, while V. americana showed a strongly aggregated spatial distribution, C. procera had a weaker propensity to depart from complete spatial randomness (CSR). A complex distribution, sometimes clustered in areas with hydromorphic soils (swamps and around streams) and sometimes very near CSR outside these areas characterized the C. procera population. When C. procera tree aggregation occurred, there was a slight attraction between juveniles and adults. The aggregation of V. americana trees was evidenced at different levels depending on the scale of investi- gation. Within small plots (6.25 ha), a first level of aggregation with short distance radii of c. 10-25 m giving small clusters, and a second level which is composed of small clusters aggregated at c. 40-50 m distance radius, were observed. A third level of aggregation was suggested by analysing the tree population at the larger scale (25 ha) whose boundaries outside the plot were not delimited. Aggregation of V. americana trees at all levels was enhanced by a strong attraction between

Nouvelles voies d'acces aux phospha-7-norbornenes trivalents

New λ3-7-phosphanorbornenes are prepared either through the nickelocene reduction-complexation of the corresponding P-sulfides (syn structure) or through the direct [14 + 2] cycloaddition of tervalent phospholes with N-phenylmaleimide (anti structure).

Synthesis and some reactions of a 2,2′-biphospholyl

Abstract 1,1′-Diphenyl-3,3′,4,4′-tetramethyl-2,2′,5,5′-tetrahydro-2,2′-biphosphole obtained by reductive dimerization of the appropriate phosphole has been converted into the corresponding 2,2′-biphosphole by P -bromination followed by dehydrobromination of the resulting P,P′ -tetrabromo compound with α-picoline. This 2,2′-biphosphole gives two isomeric P -sulfides upon reaction with sulfur, and a Mo(CO) 4 chelate upon reaction with Mo(CO) 6 . Cleavage of the two P -phenyl bonds by lithium in THF yields the corresponding biphospholyl anion, which is converted into a mixture of two isomeric bis(η 5 ,η 5 -2,2′-diphosphafulvalene)diirons by treatment with FeCl 2 . The reaction of Mn 2 (CO) 10 in boiling xylene affords a mixture of three complexes, including a (η 5 ,η 5 -2,2′-diphosphafulvalene)hexacarbonyldimanganese produced by thermal cleavage of the two PPh bonds. Under CO pressure there is a [1,5] P → C shift of the two phenyl groups, leading to formation of (η 5 ,η 5 -3,3′-diphenyl-2,2′-diphosphafulvalene)hexacarbonyldimanganese.

A new type of water-soluble phosphine for biphasic catalysis

Abstract The reaction of the [4 + 2] dimer of 3,4-dimethyl-2H-phosphole with maleic anhydride in boiling THF gives the 2H-phosphole-maleic anhydride [4 + 2] endocyclo-adduct in 60% yield. Upon treatment with sodium hydroxide, this cyclo-adduct is transformed into the sodium salt of 3,4-dimethyl- 1-phospha-2-norbornene-5,6-dicarboxylic acid which is very soluble in water (⪖ 300 g/1) and is not extracted from water by organic solvents such as toluene and dichloromethane.

Reaction des phospholes avec les metaux carbonyles sous pression d'oxyde de carbone. Obtention de complexes derives des phospholes-2H

Abstract Above 150°C, 1-phenyl-3,4-dimethylphosphole ( 1 ) is in equilibrium, through phenyl and hydrogen [1,5] shifts, with 5-phenyl-3,4-dimethyl-2 H -phosphole ( 3 ). If the reaction of 1 with metal carbonyls is run under a CO pressure high enough to prevent the formation of phosphorus—metal bonds below 150°C, the metal carbonyls do not react with 1 but preferentially with 3 . Around 150°C, complexes derived from [4 + 2] Diels-Alder dimers of 3 are obtained in the presence of W(CO) 6 and Cr(CO) 6 and these complexes are described. Around 160°C, phosphido-bridged complexes are formed with 2-phenyl-3,4-dimethylphospholyl acting as the P-donor and Mo(CO) 6 and W(CO) 6 and the products are described. Above 170°C still another type of phosphido-bridged complexes is obtained with 2-phenyl-3,4-di-methyl-4,5-dihydrophospholyl acting as the P-donor and Cr(CO) 6 which is also described. The results are used for devising an optimized synthesis of 2-phenyl-3,4-dimethyl-1-phosphaferrocene from 1 and [CpFe(CO) 2 ] 2 at 160°C under CO pressure. 2-Phenyl-1-phosphaferrocene is similarly prepared from 1-phenylphosphole.

Asymmetric Isomerisation of a Cyclic Diene: a Comparative Study of BINAP and BIPNOR–Rhodium(I) Catalysts

Abstract The asymmetric isomerisation of 5,7-dibenzyloxy-6-(trialkylsilyloxy)cyclohepta-1,3-diene 1 to the corresponding 1,6-dibenzyloxy-7-(trialkylsilyloxy)cyclohepta-1,3-diene 2 can be accomplished at 90°C in a 75/25 mixture of toluene and DME in the presence of a [Rh(BIPNOR)(cod)] + catalyst with 92% ee. A much lower ee is observed with BINAP. In both cases, the observed ees increase with temperature. A mechanism involving an η 5 -pentadienyl–rhodium complex is proposed.

FROM 2H-PHOSPHOLES TO BIPNOR, A NEW EFFICIENT BIPHOSPHINE FOR ASYMMETRIC CATALYSIS

Abstract For many years now, we have studied the 1H-/2H-phosphole equilibrium and its synthetic applications. On reaction with alkynes, 2H-phospholes yield the corresponding 1-phosphanorbornadienes. As ligands of rhodium(I), these phosphines show some potential in catalytic hydrogenation and hydroformylation of alkenes. Starting from 3,3′,4,4′-tetramethyl-1,1′-biphospholyl and tolan, we have similarly obtained the corresponding 2,2′-bis-(1-phosphanorbornadienyl) (BIPNOR) with two chiral, non-racemisable, phosphorus atoms at the bridgeheads. The pure enantiomers of BIPNOR appear to be efficient ligands in asymmetric hydrogenation of CC and CO double bonds.

Reactions of (phosphine)pentacarbonyltungsten. Synthesis of primary and secondary phosphines in the coordination sphere of tungsten

Abstract A new preparation of W(CO) 5 (PH 3 ) ( 1 ) in fair yield on a multigram scale has been devised. 1 is metalated by one equivalent of n-BuLi to give W(CO) 5 (PH 2 Li) ( 2 ), which reacts with various electrophiles: with alkyl halides W(CO) 5 (PH 2 R) complexes are obtained, but with other electrophiles the species W(CO) 5 (PHR 2 ) is also obtained along with 1 . Disubstituted complexes can also be obtained when 1 is treated with an excess of n-BuLi followed by an excess of an electrophile. The results are rationalized by postulating that polysubstituted compounds are obtained by stepwise deprotonation of less-substituted complexes rather than via polylithiated complexes such as W(CO) 5 (RPLi 2 ) or W(CO) 5 (PL 3 ). A one-pot preparation of W(CO) 5 [P(SiMe 3 ) 3 ] in good yield from 1 was also achieved. The intermediate W(CO) 5 [LiP(SiMe 3 ) 2 ] was also made from 1 , and its reaction with BrCH 2 Cl followed by hydrolysis gave (CO) 5 W(PH 2 CH 2 PH 2 )W(CO) 5 .

Stabilisation of novel phosphine ligands by P-complexation with tungsten pentacarbonyl

Abstract The novel phosphines PH 2 Cl, PHCl 2 :, PH 2 F, PHFCl, PH(NEt 2 )F and PH(OH) 2 have been stabilised by ligation to [W(CO) 5 ]. The analogous PF 2 H, complex is also described. 31 P, 19 F, and 1 H NMR parameters for these and related compounds are presented and discussed.

Thermal isomerization of a secondary vinylphosphine into a phosphaalkene

Abstract When heated at 100°C, (mesityl)(propen-2-yl)phosphine rearranges via a radical mechanism to give (mesityl)(isopropylidene)phosphine.