Cu-Catalyzed P-C bond formation/cleavage: straightforward synthesis/ring-expansion of strained cyclic phosphoniums.

Upon reaction with copper(i), peri-halo naphthyl phosphines readily form peri-bridged naphthyl phosphonium salts. The reaction works with alkyl, aryl and amino substituents at phosphorus, with iodine, bromine and chlorine as a halogen. It proceeds under mild conditions and is quantitative, despite the strain associated with the resulting 4-membered ring structure and the naphthalene framework.

Simplified and versatile access to low valent Ni complexes by metal-free reduction of Ni precursors.

The reduction of [Ni(DME)Cl2] with 2 equiv. of bis(trimethylsilyl)-1,4-tetramethyldihydropyrazine in the presence of a ligand L and an excess of olefin cleanly leads to [Ni(L)(alkene)2] complexes. When reduction is performed in the presence of 1,5-cyclooctadiene (COD), [Ni(COD)2] is obtained.

Formation of a peri-Bridged Phosphonio-Naphthalene by Cu-Mediated Phosphine-Aryl Coupling.

The peri-iodo naphthyl phosphine 1 reacts with CuI to give the peri-bridged phosphonio-naphthalene 2, which has been fully characterized (multi-nuclear NMR, MS, XRD). The outcome of the reaction differs markedly from that observed with gold. A two-step pathway involving P-assisted C-I oxidative addition to copper, followed by P-C reductive elimination is shown to be energetically feasible by DFT calculations.

Outer-Sphere Reactivity Shift of Secondary Phosphine Oxide-Based Nickel Complexes: From Ethylene Hydrophosphinylation to Oligomerization.

A new dimension for secondary phosphine oxide (SPOs) ligands is described in this article. Demonstrated on original π-allylic nickel structures, these self-assembled complexes trigger catalytic hydrophosphinylation reactions. Addition of a Lewis acid B(C F ) switches the reactivity towards migratory insertion and thus ethylene oligomerization through an unprecedented outer-sphere interaction with the coordinated SPO ligand.

A Straightforward Access to Stable, 16 Valence-electron Phosphine-Stabilized Fe Olefin Complexes and their Reactivity.

The use of the dialkene divinyltetramethyldisiloxane (dvtms) allows easy access to the reactive 16 valence-electron complexes [Fe(L-L)(dvtms)], (L-L) = dppe (1,2-bis(diphenylphosphino)ethane), (), dppp (1,2-bis(diisopropylphosphino)propane), (), pyNMeP(Pr) (N-(diisopropylphosphino)-N-methylpyridin-2-amine), (), dipe (1,2-bis(diisopropylphosphino)ethane), (), and [Fe(L)(dvtms)], L = PMe, (), by a mild reductive route using AlEt(OEt) as reducing agent. In contrast, by the same methodology, the 18 valence-electron complexes [Fe(L-L)(ethylene)], (L-L) = dppm (1,2-bis(diphenylphosphino)methane), , (L-L) = dppa (1,2-bis(diphenylphosphino)amine) or (L-L)=dppe, , were obtained, which do not contain dvtms. In addition, a combined DFT and solid-state paramagnetic NMR methodology is introduced for the structure determination of .

Alternative aluminum-based cocatalysts for the iron-catalyzed oligomerization of ethylene.

Multinuclear aluminum cocatalysts have been obtained by the reaction of various phenols, alcohols or diols with trimethylaluminum and were used in situ or as isolated, well-defined species, for the activation of an iron(ii) or an iron(iii) pre-catalyst for the oligomerization of ethylene. The best cocatalyst candidate involves 2,2'-biphenol () in a /AlMe3 ratio of 2/3.

Synthesis and characterization of palladium(II) and nickel(II) alcoholate-functionalized NHC complexes and of mixed nickel(II)-lithium(I) complexes.

The synthesis of Pd(II) and Ni(II) alcohol-functionalized N-heterocyclic carbene (NHC) complexes was explored to examine the possible influence of the functional arm attached to the NHC backbone on their structure and reactivity and, in the case of a Ni(II) complex, on its catalytic properties in ethylene oligomerization. Starting from the alcohol-functionalized imidazolium salt [ImDiPP(C2OH)]Cl (2), the new functionalized NHC palladium(II) complex [PdCl(acac){ImDiPP(C2OH)-CNHC}] (3) was synthesized and fully characterized. Two byproducts, [PdCl{μ-ImDiPP(C2O)-CNHC,O}]2 (4) and trans-[PdCl2{ImDiPP(C2OH)-CNHC}2] (5), formed during the synthesis of 3, were also fully characterized.

Cycloalkyl-based unsymmetrical unsaturated (U₂)-NHC ligands: flexibility and dissymmetry in ruthenium-catalysed olefin metathesis.

Air-stable Ru-indenylidene and Hoveyda-type complexes bearing new unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands combining a mesityl unit and a flexible cycloalkyl moiety as N-substituents were synthesised. Structural features, chemical stabilities and catalytic profiles in olefin metathesis of this new library of cycloalkyl-based U2-NHC Ru complexes were studied and compared with their unsymmetrical saturated NHC-Ru homologues as well as a set of commercially available Ru-catalysts bearing either symmetrical SIMes or IMes NHC ligands.

Synthesis and characterization of oxygen-functionalised-NHC silver(I) complexes and NHC transmetallation to nickel(II).

The new alcohol- and ether-functionalised-NHC silver(I) complexes bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OH)}2]Cl (4), bis(1-(2-hydroxyethyl)-3-mesityl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMes(C2OH)}2]Cl (5), bis(1-(2-hydroxyethyl)-3-methyl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMe(C2OH)}2]Cl (6), bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) tetrafluoroborate, [Ag{ImDiPP(C2OH)}2]BF4 (9), and bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OMe)}2]Cl (13), were synthesized and fully characterized by NMR spectroscopy and single crystal X-ray diffraction. For some complexes, an uncommon heteronuclear coupling (4)J((107/109)Ag-H) was unveiled. Their ability to transfer the NHC ligand to Ni(II) was assessed in the presence of different nickel(II) sources; the bis-NHC Ni(II) complex bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)nickel(II) chloride, [NiCl2{ImDiPP(C2OMe)}2] (15), was obtained from 13 and shown by X-ray diffraction study to have a trans-arrangement of the two NHC ligands.

Ethylene oligomerization using iron complexes: beyond the discovery of bis(imino)pyridine ligands.

Since the discovery that bis(imino)pyridine ligands are able to confer high activities in ethylene oligomerization and polymerization to their iron complexes, considerable attention has been focused on catalyst design for these reactions and this research constitutes an ever-growing area in molecular catalysis. The tuning of the ligand structures and properties, and thus of catalysts, generally represents the basis for subsequent work contributing to process development and industrialization. Significant effort is therefore devoted to generate structural diversity in order to access the required catalyst stability and selectivity.

Unprecedented cubane-type silver cluster with a novel phosphinite functionalized N-heterocyclic carbene ligand.

A novel heterodifunctional phosphinite imidazolium salt was synthesized and reacted with Ag(I) to afford an unusual tetrasilver cubane-type cluster with two P-NHC ligands bridging between the Ag(I) centres of opposite Ag(2)I(2) faces.

A new stable C(NHC)--CH--C(NHC)N-heterocyclic dicarbene ligand: its mono- and dinuclear Ir(I) and Ir(I)-Rh(I) complexes.

The ligand [(1,3-phenylene)bis(methylene)]bis(1-ethyl-imidazol-2-ylidene) ( 2) (abbreviated as EtCNHC--CH--CNHC with CH = central aromatic ring, -- = CH2 spacer) has been synthesised, and isolated, by deprotonation of [(1,3-phenylene)bis(methylene)]bis(1-ethyl-imidazolium) dichloride, Et(CHimid.--CH--CHimid.)Cl2 ( 1) with LiN(SiMe3)2.

Direct synthesis of a new class of N,N,N ligands based on 1,2-dihydro-1,10-phenanthroline backbone and their coordination to Pd complexes.

Reactions of acetylpyridine derivatives with 8-aminoquinolines provide a general and simple access to an unexpected class of versatile N,N,N ligands, which offer interesting perspectives in coordination chemistry.

Rhodium nanocatalysts stabilized by various bipyridine ligands in nonaqueous ionic liquids: influence of the bipyridine coordination modes in arene catalytic hydrogenation.

Rhodium nanoparticles stabilized by 2,2'-, 3,3'-, 4,4'-bipyridine ligands were prepared in various ionic liquids according to a chemical reduction approach. Zerovalent nanospecies in the size range of 2.0-2.

An unprecedented, figure-of-eight, dinuclear iridium(I) dicarbene and new iridium(III) 'pincer' complexes.

An unusual dinuclear Ir(I) complex bridged by two N-heterocyclic biscarbene ligands, forming a 20-membered, figure-of-eight dimetallacycle, and new CNHCCCNHC pincer complexes of Ir(III) have been obtained directly from the bis(imidazolium) precursors and [Ir(micro-Cl)(cod)]2.

Ethenolysis of methyl oleate in room-temperature ionic liquids.

Unsaturated vegetable oils are an attractive renewable feedstock, and the selective cleavage of unsaturated fatty esters is an important transformation in this respect. The efficient and selective cross-metathesis of methyl oleate with ethylene was achieved under mild conditions with ruthenium-alkylidene catalysts in toluene and room-temperature ionic liquids (RTILs) to give two important chemical intermediates, 1-decene and methyl 9-decenoate, without double-bond migration. As recovery of the catalyst is an important target with respect to industrial applications, catalyst recycling studies were also carried out in RTILs with the first-generation Hoveyda catalyst.

A selective synthesis of hydroxyborate anions as novel anchors for zirconocene catalysts.

A new family of hydroxytris(pentafluorophenyl)borate anions [B(C6F5)3OH](-) associated with organic and aprotic cations c+ (imidazolium, pyrrolidinium and phosphonium) has been prepared by a general one-pot synthesis that implies the chloride borate analogues [B(C6F5)3Cl](-)[c]+. The [c]+[B(C6F5)3OH](-) salts have been isolated and fully characterized. The borate anion [B(C6F5)3OH](-) has been shown to protonate the Zr-Me bond in the Cp2ZrMe2 complex forming CH4 and the first published example of anionic [Cp2Zr(Me)OB(C6F5)3](-) species.

Unexpected reduction pathway of a Co(2+) salt to [HCo(CO)(4)] via [Co(2)(CO)(8)] in an ionic liquid.

In the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquid ([BMI][NTf(2)]), [Co(NTf(2))(2)] is reduced under 5.5 MPa of H(2)-CO to [Co(2)(CO)(8)] prior to [HCo(CO)(4)], provided a pyridine ligand is present in the medium.

Capillary electrophoresis monitoring of halide impurities in ionic liquids.

Quantification of impurities in ionic liquids is a crucial task in assessing the reliability of physical constants and solvent properties: taking into account the particularities of the ionic matrix, a simple routine method using capillary electrophoresis (CE) is developed to determine the halide content at the ppm level in water-immiscible ionic liquids.

Determination of an acidic scale in room temperature ionic liquids.

The acidity scale of different Brønsted acids in ionic liquids such as [BMIM][NTf2], [BMIM][BF4], and [BMMIM][BF4] has been investigated by determination of Hammett functions, using a spectrophotometric indicator method. This scale should permit one to correlate the acidity strength of ionic liquid systems with their ability to achieve acid-catalyzed reactions.

Alkene metathesis catalysis in ionic liquids with ruthenium allenylidene salts.

Ring closing metathesis of dienes in 1-butyl-3-methylimidazolium salts in the presence of ruthenium allenylidene salts as catalyst is described.