2′-Iodo-2,2′′,3,3′′,4,4′′,5,5′′,6,6′′-deca­methyl-1,1′:3′,1′′-terphenyl chloro­form monosolvate

The title compound, C28H33I·CHCl3, forms dimers through C—I⋯π inter­actions. The crystal structure is consolidated by the presence of C—H⋯π inter­actions between the chloro­form solvent and the main mol­ecule

(2,4,6-Trimethyl­phen­yl)boronic acid–triphenyl­phosphine oxide (1/1)

In the crystal structure of the title compound, C9H13BO2·C18H15OP, there are O—H⋯O hydrogen bonds between the O atom of triphenyl­phosphine oxide and one hy­droxy group of the boronic acid. Boronic acid mol­ecules form inversion-related hydrogen-bonded dimers in an R 2 2(8) motif. The structure is consolidated by inter­molecular C—H⋯O bonds and C—H⋯π inter­actions

Stable divalent germanium, tin and lead amino(ether)-phenolate monomeric complexes: structural features, inclusion heterobimetallic complexes, and ROP catalysis

International audienceStable germanium(ii) and lead(ii) amido complexes {LO(i)}M(N(SiMe3)2) (M = Ge(II), Pb(II)) bearing amino(ether)phenolate ligands are readily available using the proteo-ligands {LO(i)}H of general formula 2-CH2NR2-4,6-tBu2-C6H2OH (i = 1, NR2 = N((CH2)2OCH3)2; i = 2, NR2 = NEt2; i = 3, NR2 = aza-15-crown-5) and M(N(SiMe3)2)2 precursors. The molecular structures of these germylenes and plumbylenes, as well as those of {LO(3)}GeCl, {LO(3)}SnCl and of the congeneric {LO(4)}Sn(II)(N(SiMe3)2) where NR2 = aza-12-crown-4, have been determined crystallographically. All complexes are monomeric, with 3-coordinate metal centres. The phenolate systematically acts as a N^Ophenolate bidentate ligand, with no interactions between the metal and the Oside-arm atoms in these cases (for {LO(1)}(-), {LO(3)}(-) and {LO(4)}(-)) where they could potentially arise. For each family, the lone pair of electrons essentially features ns(2) character, and there is little, if any, hybridization of the valence orbitals. Heterobimetallic complexes {LO(3)}M(N(SiMe3)2)*LiOTf, where the Li(+) cation sits inside the tethered crown-ether, were prepared by reaction of {LO(3)}M(N(SiMe3)2) and LiOTf (M = Ge(II), Sn(II)). The inclusion of Li(+) (featuring a close contact with the triflate anion) in the macrocycle bears no influence on the coordination sphere of the divalent tetrel element. In association with iPrOH, the amido germylenes, stannylenes and plumbylenes catalyse the controlled polymerisation of l- and racemic lactide. The activity increases linearly according to Ge(II) ≪ Sn(II) ≪ Pb(II). The simple germylenes generate very sluggish catalysts, but the activity is significantly boosted if the heterobimetallic complex {LO(3)}Ge(N(SiMe3)2)*LiOTf is used instead. On the other hand, with 10-25 equiv. of iPrOH, the plumbylenes afford highly active binary catalysts, converting 1000 or 5000 equiv. of monomer at 60 °C within 3 or 45 min, respectively, in a controlled fashion

Chimie organométallique des complexes alcalinoterreux à base de ligands fluorés

L'addition catalysée des amines ou phosphines sur des substrats insaturés (alcènes, alcynes ou allènes) constitue une méthode efficace pour la production d’amines et phosphines à hautes valeurs ajoutées. Pour ces réactions, les complexes hétéroleptiques des métaux alcalino-terreux ont émergé comme des précatalyseurs effi caces. Cette thèse décrit la synthèse de complexes des alcalino-terreux supportés par des ligands aminoalcoolates fluorés de type [{RO}AeN(SiMe2H)2] ({RO} = aminoalcoolate fluoré; Ae = Ca, Sr). Des études par diffraction de rayons X montrent que ces complexes utilisent des interactions Ae···F–C and β-Si–H···Ae pour être cinétiquement inertes. Étonnamment, la somme de ces interactions non-covalentes dites secondaires est prédominante par rapport à la coordination d'éthers sur le centre métallique. En outre, les ligands aminoalcoolates fluorés ont été utilisés pour préparer de rares exemples de complexes Ae hétéroleptiques impliquant la coordination intramoléculaire de donneurs d'électrons π (i.e. alcènes et alcynes). Ainsi, pour la première fois, des complexes Ae stabilisés par des combinaisons d’interactions Ae···Cπ, Ae···F−C et β-Si−H···Ae ont été synthétisés. La nature de ces interactions a été sondée par des moyens spectroscopiques, cristallographiques et calculatoires (DFT). En revanche, nos efforts pour obtenir des complexes Ca–aryles ont conduit à la formation de complexes trinucléaires originaux présentant des interactions secondaires β-Si-H···Ca extrêmement fortes. Certains de ces complexes de calcium ont ensuite été testés en catalyse d’hydrophosphination du styrène avec la diphénylphosphine. Ils ont démontré des activités remarquables (TOF ≈ 50 h−1) en conditions douces, ainsi qu’une régiosélectivité de 100% vers la formation du produit d'addition anti-Markovnikov. En collaboration avec le Pr. M. Etienne et le Dr C. Dinoi du Laboratoire de Chimie de Coordination (Toulouse), un précatalyseur hétéroleptique de calcium supporté par un ligand tris(indazolyl)borate fluoré a été utilisé pour l’hydroamination intramoléculaire du 2,2-diméthylpent-4-en-1-amine, et a fait preuve d’une activité catalytique parmi les plus élevées à ce jour.The catalysed additions of amines or phosphines across unsaturated substrates (alkenes, alkynes or allenes) constitute atom-efficient routes for the production of valuable fine chemicals such as amines and phosphines. For these reactions, heteroleptic alkaline-earth complexes have emerged as promising precatalysts. This PhD thesis describes the synthesis and characterisation of a series of alkaline-earth complexes of type [{RO}AeN(SiMe2H)2] supported by fluorinated aminoalkoxides ({RO} = fluorinated aminoalkoxide; Ae = Ca, Sr ). X-ray diffraction studies show that these complexes heavily involve Ae···F–C and β-Si–H···Ae secondary interactions to achieve kinetic stabilisation. Remarkably, these so-called secondary, non-covalent interactions can be more beneficial towards the stabilisation of the metallic species than the coordination of ethers onto the metal centre. Furthermore, fluorinated aminoalkoxo ligands were used to prepare rare examples of Ae heteroleptic complexes featuring intramolecular coordination from π donors (i.e. alkenes and alkynes). For the first time, Ae complexes stabilised by a combination of Ae···Cπ, Ae···F–C and β-Si–H···Ae interactions were described. The structural and electronic features of these unique complexes were probed by crystallographic, spectroscopic and computational (DFT) methods. The utilisation of aryl-containing ligands resulted in the formation of trinuclear complexes featuring a unique pattern of strong β-Si–H···Ca agostic interactions. Some of these calcium heteroleptic complexes were tested in the hydrophosphination of styrene and HPPh2. They displayed high activities (TOF ≈ 50 h–1) under mild conditions with 100% regioselectivity towards the anti-Markovnikov addition product. In a collaboration with Prof. M. Etienne and Dr. C. Dinoi from the Laboratoire de Chimie de Coordination (Toulouse), a heteroleptic calcium complex supported by a fluorinated tris(indazolyl)borate was used in the intramolecular hydroamination of 2,2-dimethylpent-4-en-1-amine, and it displayed excellent performances

A GREEN APPROACH FOR THE SELECTIVE REDUCTION OF AROMATIC CARBONYL COMPOUNDS USING RANEY Ni-Al ALLOY

Given the significant environmental risk associated with the use of organic solvents and catalysts in the classic reduction reaction catalysts, we are interested in adapting the reaction medium and in developing an eco-friendly methodology for the synthesis of corresponding alcohols in reasonably yields. In this study, the reduction of some aromatic carbonyl compounds with Ni-Al alloy in aqueous alkaline medium was carried out in two versions: with 20 wt% aq NaOH and with 1 wt% aq NaOH without organic solvent. The structures of the reaction products are rigorously proven by gas chromatography-mass spectrometry (GC-MS). There was observed an increase of the reduction reaction rate when we used 1 wt% aq NaOH without addition of organic solvent. For a good part of the studied substrates high conversion and selectivity were achieved by employing mild reaction conditions, minimal environmental pollution and simple work up procedure, foreshadowing yields above 90 % and representing candidates for convenient preparative applications

Tethered cationic alkaline earth – olefin complexes

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π Ligands in Alkaline Earth Complexes

International audiencePi ligands such as olefins and alkynes bind intramolecularly to the metal atom in d0 complexes of the large alkaline earths (Ae) calcium and strontium supported by fluoroalkoxo ligands with dangling unsaturated C=C or C≡C bonds, and having the amide N(SiMe2H)2– as the co-ligand. These O-bridged dinuclear complexes are further stabilized by secondary C-F→Ae and beta-Si-H∙∙∙Ae interactions. In a set of structurally related Ca-olefin complexes, the strength of these interactions gradually increases as the coordination of the olefin onto Ca2+ becomes weaker (from eta-2-coordinated to eta-1 to fully dissociated) upon increasing steric congestion, thus ensuring that overwhelming electronic depletion does not occur at calcium. NMR data imply that the olefins are metal-bound in [D8]toluene solutions. The Ae···C(pi), C-F→Ae and beta-Si-H∙∙∙Ae non-covalent interactions are also strong in the parent Ae-alkyne complexes, the first examples of non-acetylide Ae-alkynes compounds. Calcium-arene complexes could not be made, as the aromatic tether did not bind to the metal atom. Instead, a trinuclear complex with non-interacting C6H5 groups was obtained. It exhibits exceptionally strong C-F→Ca and beta-Si-H∙∙∙Ca interactions. NMR data indicate that the congeneric calcium-allene complex can be made, but it spontaneously isomerizes towards the more stable Ca-alkyne via an unusual 1,3-hydride shift intramolecular process

K⁺···Cπ and K⁺···F Non-Covalent Interactions in π-Functionalized Potassium Fluoroalkoxides

Secondary interactions stabilize coordinatively demanding complexes of s-block metals. The structures of potassium fluoroalkoxides that, in addition to intra- and intermolecular K⁺···F contacts, also exhibit K⁺···Cπ interactions with tethered π ligands, are reported. A potassium–arene, a rare potassium–alkyne, and a potassium–olefin complex have been prepared by deprotonation of functionalized α,α-bis(trifluoromethyl)alcohols with KN(SiMe₂R)₂. They all feature a cuboid K₄O₄ core with µ³-bridging O atoms, and multiple stabilizing K⁺···F contacts in the range 2.71–3.33 Å. The potassium–arene complex shows η², η³, and η⁶ K⁺···Cπ(arene) interactions in the range 3.35–3.47 Å. The potassium–alkyne and potassium–olefin compounds are stabilized by η² interactions with the unsaturated carbon–carbon bond, in the range 3.17–3.49 Å and 3.15–3.19 Å, respectively. Comparison with the parent complex devoid of a flanking π ligand illustrates the role of K⁺···Cπ interactions.Science, Faculty ofNon UBCChemistry, Department ofReviewedFacult

Alkaline Earth-Olefin Complexes with Secondary Interactions

International audienceStrontium and calcium (= Ae) olefin complexes stabilised by secondary Ae∙∙∙F-C and beta-agostic Ae∙∙∙H-Si interactions are presented. Olefin coordination onto the alkaline earths is plain in the solid-state, and it is thermodynamically favoured over the coordination of THF. The existence of the Ae∙∙∙olefin interactions is corroborated by solution NMR data and DFT computations. The coordination mode of the olefin varies with steric effects, and if enforced, olefin dissociation can be compensated by the other non-covalent interactions, as supported by DFT computation