Jacques Andrieu

Synthesis of New Cationic Donor-Stabilized Phosphenium Adducts and Their Unexpected P-Substituent Exchange Reactions

The reaction between two 1,3-dialkylimidazolium-2-carboxylates 1a and 1b and two different dichlorophosphines (RPCl(2), with R = Ph and NEt(2)) led to new donor-stabilized phosphenium adducts. When the reaction was performed with the 1,3-dimethylimidazolium-2-carboxylate 1a and PhPCl(2) in a 2:1 ratio, the phosphine 4a, bearing two imidazolium moieties, was obtained and led to 5a, after an anion exchange reaction with KPF(6), the latter being fully characterized by an X-ray structure analysis. In similar conditions, the bis-imidazolium phosphine or phosphene-di-ium, 4b, which is analogous to 4a, has been obtained by the addition of PhPCl(2) to the 1-dodecyl-3-methylimidazolium-2-carboxylate 1b. However, by the use of dichloro(diethylamino)phosphine, (Et(2)N)PCl(2), instead of PhPCl(2), the reaction with 1a did not afford the biscationic phosphorus product 6a, an analogue to 4a, but, instead, the water-soluble mixed mono-imidazolium chlorophosphine 7a. Subsequently, additional kinetic experiments have been investigated to rationalize the different reactivities observed with imidazolium-2-carboxylates and the phosphorus halide derivatives. We, thus, found that the bis-imidazolium phosphine 4b was very rapidly formed in the above-mentioned reaction and was slowly converted, thereafter, back to the mixed mono-imidazolium chlorophosphine 8b in the presence of the residual starting dichlorophosphine. Additionally, the addition of PhPCl(2) to the phosphene-di-ium 4b represents, to our knowledge, the first example of a P-substituent exchange reaction involving a P-C bond formation in imidazolium phosphines. On the other hand, the air stability and the solubility of these new cationic functional phosphines in different media render such ligands very appealing in coordination chemistry for catalysis in mono- or biphasic media.

Electrosynthesis of Imidazolium Carboxylates

Synthesis of imidazolium carboxylate compounds was efficiently achieved by electrochemical reduction of imidazolium precursors under very mild conditions.

Reversible P–C bond formation for saturated α-aminophosphine ligands in solution: stabilization by coordination to Cu(I)

The saturated α-aminophosphine ligands containing a secondary amine function Ph2PCH(R′)NHR″ establish a solution equilibrium with Ph2PH and R′CH2NR″ and are stabilized by electron-withdrawing substituents R′ and R″ and by coordination of the phosphorous donor to Cu(I).

Chiral α‐P,N Ligands From a Diastereoselective Ph2PH Addition to (η6‐Benzaldimine)tricarbonylchromium Complexes

Chiral α-aminophosphane (α-P–C–N) ligands have been prepared by reversible addition of Ph2PH to tricarbonylchromium benzaldimine complexes (CO)3Cr[η6-o-C6H4(Y)(CHNR)] (with Y, R = CH3, CH3 or CH2COOCH3; CH3O, CH3 or p-CH3OC6H4; Cl, C6H5), with complete diastereoselectivity. These complexes are stabilized in solution by electron-withdrawing group(s) on the imine.

Protonation and oxidation chemistry of a pentaethylcyclopentadienyl-containing molybdenum(IV) trihydride complex

Abstract Compound CpEtMoCl4 (CpEt=η5-C5Et5) (1) can be transformed into CpEtMoH3(dppe) (2) and CpEtMoD3(dppe) (2-d3) [dppe=1,2-(diphenylphosphino)ethane] by reaction with LiAlX4 (X=H and D, respectively). The protonation and oxidation studies of these two compounds, in comparison with previously reported studies on (C5Me5) analogs, show important differences that may be attributed to a kinetic stabilization of the products, which is steric in nature. Protonation of 2 with HBF4 in acetonitrile affords [CpEtMoH4(dppe)]+ (3), which only slowly decomposes to [CpEtMoH2(MeCN)(dppe)]+ (4). Further protonation of the latter affords the monohydride species [Cp*MoH(dppe)(MeCN)2]2+ in three different forms, 5–7. Direct protonation of 2 with 2 equiv. of HBF4 shows the formation of all of the above compounds, plus a new compound, [CpEtMoH3(dppe)(MeCN)]2+ (8), to which a classical structure is assigned. The protonation of 2-d3 indicates reversibility for the proton transfer processes. The oxidation of 2 in MeCN affords [2] +, which decomposes slowly in MeCN to afford a mixture of 4 and 5 as major products. No compound 8, on the other hand, is obtained by oxidation of 2, neither with 1 nor with 2 equiv. of oxidizing agent. Mechanistic schemes that rationalize all these observations are proposed.

SYNTHESIS AND REACTIVITY OF ARYL- AND ALKYL-PALLADIUM(II) COMPLEXES WITH FUNCTIONAL PHOSPHINES AND PHOSPHINOENOLATE LIGANDS : FIRST ANALOGUES OF MODEL NICKEL CATALYSTS

Phenyl- and methyl-palladium(II) complexes analogous to model nickel(II) catalysts were prepared from readily available precursors. The methods used allow different ligands to be introduced in the co-ordination sphere. For example, the chelating phosphinoenolate ligand in [[graphic omitted])NPh2}L2][L2= Ph2PCH2C(O)NPh2] was displaced by 1 equivalent of Ph2PCH2C(O)Ph (L1) to give [[graphic omitted])Ph}L2] whereas the terminal functional phosphine was displaced by P(C6H11)3 to give [[graphic omitted])NPh2}{P(C6H11)3}]. Owing to favourable ligand-redistribution reactions, treatment of a mixture of complexes trans-[PdMe(Cl)L22], trans-[PdMe(Cl)L12] and trans-[PdMe(Cl)L1(L2)](which cannot be isolated pure) with an excess of NaOMe in toluene selectively afforded the phosphinoenolate complex [[graphic omitted])Ph}L2]. The enolate moiety of [[graphic omitted])NPh2}L2] and of [[graphic omitted])NPh2}L2] reacted with R′NCO (R′= Ph or p-tolyl) with formation of a carbon–carbon bond in a Michael-type addition and the products were shown to exist in the form of two isomers a and b, characterised by a N–H ⋯ O or a N–H ⋯ N hydrogen bond within the ligand system. Insertion of CO into the Pd–Me bond of [[graphic omitted])NPh2}L2] or [[graphic omitted])NHPh]C(O)NPh2}L2] yielded the corresponding acyl complexes. Although [[graphic omitted])Ph}(PPh3)] inserted ethylene into its Pd–Me bond, as evidenced by quantitative formation of propylene, the palladium hydride that must be generated by the β-elimination reaction decomposes before further ethylene insertion can occur.

Linear Triphosphines as Ligands for Metal Complexes Immobilization in Ionic Liquids: Palladium-Catalyzed Methoxylation of Alkynes

Several novel palladium triphosphine complexes have been synthesized and tested as recyclable catalysts for the methoxylation of alkynes into acetals in ionic liquids. A complete conversion of phenylacetylene was achieved with only 0.2% of (Pd(Triphos)NCMe)((PF6)2) in a methanol/(BMIM)(BF4) mixture. We discovered that the addition of an ionic liquid to methanol allowed not only to increase the activity of the palladium catalyst but also to provide a recyclable catalyst which can be reused several times with a weaker drop of activity. To complete these catalytic studies, we describe the synthesis of the first poor -electron-donating/strong -electron-acceptor linear Triphosphine which, after palladium coordination, led to a better selectivity compared to its Triphos analogue. The performances of recovered ionic liquid re- action mixtures show for the first time that P-tridentate ligands efficiently immobilize palladium catalysts and lead to se- lective catalytic systems benign for environment.

Bio-based 1,3-diisobutyl imidazolium hydrogen oxalate [iBu2IM](HC2O4) as CO2 shuttle

This manuscript describes the using of biosourced L-valine, oxalic acid and glyoxal to produce a biobased imidazolium hydrogen oxalate [iBu2IM](HC2O4) which is converted to its related hydrogen carbonate salt by a simple electrolysis without using strong base. The addition of weak protic acids to the latter compound leads to a rapid and quantitative CO2 release with formation of the starting hydrogen oxalate salt or a new halide free bio-based ionic liquid [iBu2IM](AcO) which is able to adsorb reversibly the CO2 at room temperature. The protonation reactions, combined with electrolysis, could then be a promising alternative solution for storage and transport of CO2. They are indeed fast and use a thermally and air stable material produced from sustainable resources which are easily recycled by a low energy consuming process using non-expensive and corrosion-resistant equipment.

Cationic palladium complexes with ketophosphine and phosphino enolate ligands and their reactivity towards CC coupling reactions. Crystal structures of [PdMe{Ph2PCH2C(O)Ph}(PCy 3 )](PF 6 ) and [Pd{Ph2PCH⋯C(⋯Ō)Ph}(SMe 2 ) 2 ](PF 6 )

Abstract Two types of monocationic Pd(II) complexes are reported, which contain either the functional P,O phosphine ligands Ph2PCH2C(O)Ph or Ph2PCH2C(O)NPh2 or an anionic chelating phosphino enolate. The first set of complexes includes [ PdMe{Ph 2 PCH 2 C(O )Ph}(PPh3)](PF6) (1), [ PdMe{Ph 2 PCH 2 C(O )Ph}(PCy3)](PF6) (2), [ PdMe{Ph 2 PCH 2 C(O )NPh2}(PPh3)](PF6) (3), and the second [ Pd{Ph 2 PCH ⋯ C( ⋯ Ō)Ph}(SMe2)2](PF6) (5), which was obtained by an interesting ligand redistribution reaction between cis-[ Pd{Ph 2 PCH ⋯ C( ⋯ Ō)Ph}2] and [Pd(SMe2)4](PF6)2. Compounds 1 and 5 display catalytic activity for ethylene dimerization. A preliminary study on ethylene/CO copolymerization with complexes 1–3 identified compound 1 as a catalyst precursor. This led to the in situ preparation of an active species for ethylene/CO copolymerization, starting from a Pd(0) precursor and appropriate ligands. The structures of complexes 2 and 5 have been determined by X-ray diffraction.