Eric Manoury

Olefin Epoxidation by H2O2/MeCN Catalysed by Cyclopentadienyloxidotungsten(VI) and Molybdenum(VI) Complexes: Experiments and Computations

Compounds [Cp*(2)M(2)O(5)] (M = Mo, 1; W, 2) are efficient pre-catalysts for cyclooctene (COE) epoxidation by aqueous H(2)O(2) in acetonitrile/toluene. The reaction is quantitative, selective and takes place approximately 50 times faster for the W system (k(obs) = 4.32(9)x10(-4) s(-1) at 55 degrees C and 3x10(-3) M concentration for the dinuclear complex, vs. 1.06(7)x10(-5) s(-1) for the Mo system). The rate law is first order in catalyst and COE substrate (k = 0.138(7) M(-1) s(-1) for the W system at 55 degrees C), whereas increasing the concentration of H(2)O(2) slows down the reaction because of an inhibiting effect of the greater amount of water. The activation parameters for the more active W systems (DeltaH(double dagger) = 10.2(6) kcal mol(-1); DeltaS(double dagger) = -32(2) cal mol(-1) K(-1)) were obtained from an Eyring study in the 25-55 degrees C temperature range. The H(2)O(2)urea adduct was less efficient as an oxidant than the aqueous H(2)O(2) solution. Replacement of toluene with diethyl ether did not significantly affect the catalyst efficiency, whereas replacement with THF slowed down the process. The epoxidation of ethylene as a model olefin, catalysed by the [Cp*MO(2)Cl] systems (M = W, Mo) in the presence of H(2)O(2) as oxidant and acetonitrile as solvent, has been investigated by DFT calculations with the use of the conductor-like polarisable continuum model (CPCM). For both metal systems, the rate-limiting step is the transfer of the hydroperoxido O(alpha) atom to the olefin, in accordance with the first-order dependence on the substrate and the zero-order dependence on H(2)O(2) found experimentally in the catalytic data. The activation barrier corresponding to the rate-limiting step is 4 kcal lower for the W complex than for the corresponding Mo analogue (32.3 vs. 28.3 kcal mol(-1)). This result reproduces well the higher catalytic activity of the W species. The different catalytic behaviour between the two systems is rationalised by a natural bond orbital (NBO) study and natural population analyses (NPA). Compared to Mo, the W(VI) centre withdraws more electron density from the sigma bonding [O-O] orbital and favours, as a consequence, the nucleophilic attack of the external olefin on the sigma*[O-O] orbital.

Core–Shell Nanoreactors for Efficient Aqueous Biphasic Catalysis

Water-borne phosphine-functionalized core-cross-linked micelles (CCM) consisting of a hydrophobic core and a hydrophilic shell were obtained as stable latexes by reversible addition-fragmentation chain transfer (RAFT) in water in a one-pot, three-step process. Initial homogeneous aqueous-phase copolymerization of methacrylic acid (MAA) and poly(ethylene oxide) methyl ether methacrylate (PEOMA) is followed by copolymerization of styrene (S) and 4-diphenylphosphinostyrene (DPPS), yielding P(MAA-co-PEOMA)-b-P(S-co-DPPS) amphiphilic block copolymer micelles (M) by polymerization-induced self-assembly (PISA), and final micellar cross-linking with a mixture of S and diethylene glycol dimethacrylate. The CCM were characterized by dynamic light scattering and NMR spectroscopy to evaluate size, dispersity, stability, and the swelling ability of various organic substrates. Coordination of [Rh(acac)(CO)2 ] (acac=acetylacetonate) to the core-confined phosphine groups was rapid and quantitative. The CCM and M latexes were then used, in combination with [Rh(acac)(CO)2 ], to catalyze the aqueous biphasic hydroformylation of 1-octene, in which they showed high activity, recyclability, protection of the activated Rh center by the polymer scaffold, and low Rh leaching. The CCM latex gave slightly lower catalytic activity but significantly less Rh leaching than the M latex. A control experiment conducted in the presence of the sulfoxantphos ligand pointed to the action of the CCM as catalytic nanoreactors with substrate and product transport into and out of the polymer core, rather than as a surfactant in interfacial catalysis.

Palladium( ii ) complexes with planar chiral ferrocenyl phosphane–(benz)imidazol-2-ylidene ligands

We describe here the first examples of planar chiral ferrocenyl phosphane–benzimidazol-2-ylidene ligands and their coordination chemistry with palladium(II). All ligand precursors, namely enantiopure ferrocenyl phosphane–(benz)imidazolium salts, and all enantiopure palladium complexes have been fully characterised by 1H, 31P and 13C NMR, mass spectrometry and X-ray diffraction methods for seven examples. The potential of these very bulky bidentate ligands in catalysis was evaluated and compared to their imidazol-2-ylidene analogues. The influence of sterics was shown to be non-negligible as the bulkiest ligand gave the lowest activities in the asymmetric Suzuki–Miyaura reaction.

Preparation of Polymer Supported Phosphine Ligands by Metal Catalyzed Living Radical Copolymerization and Their Application to Hydroformylation Catalysis

A series of well‐defined polystyrene‐supported tertiary phosphine ligands were prepared by copper‐catalyzed atom transfer radical polymerization (ATRP), involving direct copolymerization of styrene and 4‐diphenylphosphinostyrene (or 4‐styryldiphenylphosphine, SDPP). Copolymerization of the two monomers at different molar ratios showed a decreasing level of control as the SDPP molar fraction (fSDPP) increased. A satisfactory level of control was achieved for fSDPP≤0.25 such that there was a constant concentration of growing “living chains”, and linear Mn growth with conversion and low dispersity. Copper‐free polymers with different chain lengths were prepared and tested as polymeric ligands in the rhodium‐catalyzed hydroformylation of 1‐octene. The polymeric ligands yielded higher linear/branched selectivity and lower activity relative to PPh3 at the same P/Rh ratio. The selectivity increased slightly as a function of the polymer chain length.

Phosphine-Containing Planar Chiral Ferrocenes: Synthesis, Coordination Chemistry and Applications to Asymmetric Catalysis

Chiral ferrocenyl phosphino ligands are certainly one of the most developed and successful classes of chiral ligands used in asymmetric catalysis. The literature describing their synthetic and coordination chemistry, as well as their metal-mediated applications in the field of catalysis, is extremely rich and varied. Moreover, they represent a rare example in which enantioselective chemical catalysts were used in industrial processes. The present chapter provides an account of the planar-chiral ferrocene ligands developed in the Authors’ laboratory, including their coordination chemistry with various metals as well as their use in different asymmetric catalytic reactions (allylic substitution, Suzuki coupling, methoxycarbonylation of alkenes, hydrogenation of ketones).

Coordination Chemistry Inside Polymeric Nanoreactors: Interparticle Metal Exchange and Ionic Compound Vectorization in Phosphine-Functionalized Amphiphilic Polymer Latexes.

Stable latexes of hierarchically organized core-cross-linked polymer micelles that are functionalized at the core with triphenylphosphine (TPP@CCM) have been investigated by NMR spectroscopic analysis at both natural (ca.u2005pHu20055) and strongly basic (pHu200513.6) pHu2005values after core swelling with toluene. The core-shell interface structuring forces part of the hydrophilic poly(ethylene oxide) (PEO) chains to reside inside the hydrophobic core at both pHu2005values. Loading the particle cores with [Rh(acac)(CO)2 ] (acac=acetylacetonate) at various Rh/P ratios yielded polymer-supported [Rh(acac)(CO)(TPP)] (TPP=triphenylphosphine). The particle-to-particle rhodium migration is very fast at natural pH, but slows down dramatically at high pH, whereas the size distribution of the nanoreactors remains unchanged. The slow migration at pHu200513.6 leads to the generation of polymer-anchored [Rh(OH)(CO)(TPP)2 ], which is also generated immediately upon the addition of NaOH to the particles with a [Rh(acac)(CO)] loading of 50u2009%. Similarly, treatment of the same particles with NaCl yielded polymer-anchored [RhCl(CO)(TPP)2 ]. Interparticle coupling occurs during these rapid processes. These experiments prove that the major contribution to metal migration is direct core-core contact. The slow migration at the high pHu2005value, however, must result from a pathway that does not involve core-core contact. The facile penetration of the polymer cores by NaOH and NaCl results from the presence of shell-linked poly(ethylene oxide) methyl ether functions both outside and inside the polymer core-shell interface.

Speciation of [Cp*2M2O5] in Polar and Donor Solvents

The speciation of compounds [Cp*2 M2 O5 ] (M=Mo, W; Cp*=pentamethylcyclopentadienyl) in different protic and aprotic polar solvents (methanol, dimethyl sulfoxide, acetone, acetonitrile), in the presence of variable amounts of water or acid/base, has been investigated by (1) Hu2005NMR spectrometry and electrical conductivity. Specific hypotheses suggested by the experimental results have been further probed by DFT calculations. The solvent (S)-assisted ionic dissociation to generate [Cp*MO2 (S)](+) and [Cp*MO3 ](-) takes place extensively for both metals only in water/methanol mixtures. Equilibrium amounts of the neutral hydroxido species [Cp*MO2 (OH)] are generated in the presence of water, with the relative amount increasing in the order MeCN≈acetone<MeOH<DMSO. Addition of a base (Et3 N) converts [Cp*2 M2 O5 ] into [Et3 NH](+) [Cp*MO3 ](-) , for which the presence of a Nuf8ffH⋅⋅⋅Ouf8feM interaction is revealed by (1) Hu2005NMR spectroscopy in comparison with the sodium salts, Na(+) [Cp*MO3 ](-) . These are fully dissociated in DMSO and MeOH, but display a slow equilibrium between free ions and the ion pair in MeCN and acetone. Only one resonance is observed for mixtures of [Cp*MO3 ](-) and [Cp*MO2 (OH)] because of a rapid self-exchange. In the presence of extensive ionic dissociation, only one resonance is observed for mixtures of the cationic [Cp*MO2 (S)](+) product and the residual undissociated [Cp*2 M2 O5 ] because of a rapid associative exchange via the trinuclear [Cp*3 M3 O7 ](+) intermediate. In neat methanol, complex [Cp*2 W2 O5 ] reacts to yield extensive amounts of a new species, formulated as the mononuclear methoxido complex [Cp*WO2 (OMe)] on the basis of the DFT study. An equivalent product is not observed for the Mo system. The addition of increasing amounts of water results in the rapid decrease of this product in favor of [Cp*2 W2 O5 ] and [Cp*WO2 (OH)].

Hemilability of phosphine-thioether ligands coordinated to trinuclear Mo3S4 clusters and its effect on hydrogenation catalysis

Ligand-exchange reactions of [Mo3S4(tu)8(H2O)]Cl4·4H2O (tu = thiourea) with (PhCH2CH2)2PCH2CH2SR ligands, where R = Ph (PS1), pentyl (PS2) or Pr (PS3), afford new complexes isolated as [Mo3S4Cl3(PS1)3]PF6 ([1]PF6), [Mo3S4Cl3(PS2)3]PF6 ([2]PF6) and [Mo3S4Cl3(PS3)3]PF6 ([3]PF6) salts in 30–50% yields as the major reaction products. The crystal structures of [1]PF6 and [2]PF6 were determined by X-ray diffraction (XRD) analysis. Each of the three phosphine-thioether ligands is coordinated in a bidentate chelating mode to a different molybdenum atom of the Mo3S4 trinuclear cluster; herein, all the phosphorus atoms of the phosphino-thioether ligand are located trans to the capping sulfur (μ3-S). A second product that forms in the reaction of [Mo3S4(tu)8(H2O)]Cl4·4H2O with PS1 corresponds to the neutral [Mo3S4Cl4(PS1)2(PS1*)] complex. Its XRD analysis reveals both bidentate (PS1) and monodentate (PS1*) coordinating modes of the same ligand. In the latter mode the phosphine-thioether is coordinated to a Mo atom only via the P atom. All compounds were characterized using 1H and 31P{1H} NMR spectroscopy, electrospray-ionization (ESI) mass spectrometry and cyclic voltammetry (CV). Reactions of [1]PF6, [2]PF6 and [3]PF6 with an excess of Bu4NCl in CD2Cl2 were followed by 31P{1H} NMR spectroscopy. The spectra indicate equilibrium between cationic [Mo3S4Cl3(PSn)3]+ and neutral [Mo3S4Cl4(PSn)2(PSn*)] (n = 1, 2) species. The equilibrium constants were determined as 2.5 ± 0.2 × 103 M−1, 43 ± 2 M−1 and 30 ± 2 M−1 (at 25 °C) for [1]PF6, [2]PF6 and [3]PF6, respectively, indicating quantitative differences in the hemilabile behaviors of the phosphino-thioether ligands, depending on the substituent at the sulfur. Clusters [1]PF6, [2]PF6 and [3]PF6 were tested as catalysts in the reduction of nitrobenzene to aniline with Ph2SiH2 under mild conditions. Significant differences in the catalytic activities were observed, which can be attributed to different hemilabile behaviors of the PS1 and PS2/PS3 ligands.

Core-Cross-Linked Micelles and Amphiphilic Nanogels as Unimolecular Nanoreactors for Micellar-Type, Metal-Based Aqueous Biphasic Catalysis

Biphasic homogeneous protocols are attractive for catalyzed transformations in industry, especially when conducted with water as the catalyst phase as exemplified by the large-scale Rhone-Poulenc/Ruhrchemie hydroformylation process, but can only be applied when the substrate is sufficiently soluble in the aqueous phase to sustain sufficiently fast mass transport . Different solutions to reduce mass transport limitations include the use of additives to increase the substrate solubility in water or increase the water/organic interface, anchoring the catalyst onto a lower critical solution temperature (LCST) polymer to implement thermomorphic behavior, and anchoring the catalyst to the hydrophobic part of surfactants or amphiphilic block copolymers that self-assemble in the form of micelles in water. The use of catalytic micelles appears as the most attractive approach but is limited by the potential formation of stable emulsions and by loss of free macromolecules during separation. These limitations are removed by cross-linking the macromolecules into a unimolecular nanoreactor. This chapter covers the emerging area of unimolecular catalytic nanoreactors, focusing on transition metal-based catalytic applications. It will also present the synthesis of new types of catalytic unimolecular nanoreactors developed in our laboratories, conceived to function on the basis of the micellar catalysis principle. These nanoreactors consist of either core-cross-linked micelle (CCM) or amphiphilic functionalized nanogels (NG). The proof of principle of their catalytic performance in the aqueous biphasic hydroformylation of 1-octene will also be presented. The catalyst confinement objective which is highlighted in this chapter is process optimization in terms of the catalyst phase recovery and recycling.

Crystal structure of (±)-1-({[4-(all-yloxy)phen-yl]sulfan-yl}meth-yl)-2-(di-phenyl-thio-phosphor-yl)ferrocene.

The title compound is a ferrocene derivative substituted in 1,2 positions by a diphenylthiophosphoroyl and a {[4-(allyloxy)phenyl]sulfanyl}methyl chain.