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International audience; The synthesis and characterization of novel chelate nitrogen ligands with phasmidic tails (pyridine-triazole ligand 1b; 2,2'bipyrimidine ligands 2b and 3b) is reported, as well as their titanium (IV) coordination complexes. The analogous ligands 1a, 2a and 3a with methoxy substituents instead of the tails were also synthesized, together with titanium complexes that could be crystallographically characterized. A good agreement is noticed between analytical data of the complexes in solution (NMR) and in the solid state (X-ray diffraction). The complexes are overall stable on phases like alumina or silica, so that they could be characterized by TLC and sometimes chromatographied. Supramolecular architectures were generated from an equimolar solution of titanium (IV) isopropoxide, ligand 1a and a polyphenol ligand 5-H4, leading to a double-stranded helicate characterized by MS, NMR and crystallography, which was then converted into a trinuclear complex as shown by MS and NMR DOSY data. The liquid-crystalline behaviour of the ligands 1b, 2b and 3b incorporating the long alkyl tails, and of the complexes derived from these ligands, has been investigated.

International audience; A multicomponent self-assembly reaction involving a bis-biphenolato ligand (LH 4), a 2,2′-bipyrimidine chelate substituted by two (anthryl)vinyl moieties (bAnt) and Ti(OiPr) 4 was investigated. An assembly {[Ti 3 (L) 3 (bAnt) 3 ]}, composed of three homochiral TiO 4 N 2 nodes, was characterized as being the ther-modynamically-end product. The crystal structure of this circular helicate highlighted an absence of symmetry for this compact compound. DOSY 1 H NMR indicated that the nuclearity Self-assembly processes driven by transition metals are highly powerful methods to access complex architectures. [1] These self-assembled architectures, which are impossible to obtain through conventional step-by-step synthetic strategies, result from the mutual programmed recognition between metal ions and organic ligands. An impressive number of rationally designed helicates, [2] cages, [3] squares, [4] spheres, [5] grids, [6] top-ological non-trivial molecules [7] and other architectures [8] have been reported so far. Whereas the main interest in self-assembly is focused on the thermodynamically-end products, the characterization and the isolation of intermediate architectures generated during the self-assembly is rather scarce. [9] This is mainly linked to the low energy barriers existing between transient compounds. However, it is an important issue since the full identification of intermediates could provide fundamental information to apprehend some mechanistic aspects of a self-assem-[a] Dr. 3527 observed in the solid state for [Ti 3 (L) 3 (bAnt) 3 ] was maintained in solution. An intermediate formulated as [Ti 4 (L) 4 (bAnt) 4 ] was isolated. The structural analysis revealed that [Ti 4 (L) 4 (bAnt) 4 ] was a symmetrical circular hollow helicate composed of four homochiral metallovertices. This study, supported by DFT calculation , brought some evidences on the sequences and the reasons leading to the symmetry decrease for this self-assembly process. bly reaction. Therefore, the isolation and characterization of one or several intermediates produced in the course of a self-assembly process is a challenging and major task. [10] Over the latest decade, our group has developed a tita-nium(IV)-based coordination chemistry involving a bis-biphe-nolato ligand named as LH 4 as shown in Figure 1, leading to neutral self-assembled helical structures. [11,12] By following a multicomponent self-assembly approach with the 2,2′-bipyrimi-dine (bpym) chelate, a circular trinuclear bowl-shaped helicate constructed around octahedral TiO 4 N 2 motifs, [Ti 3 (L) 3 (bpym) 3 ], was generated. [13] This study also highlighted the formation of a tetranuclear intermediate {[Ti 4 (L) 4 (bpym) 4 ]} detected only by mass-spectrometry and 1 H NMR. Figure 1. Structure of LH 4 and bAnt.

International audience; A coordination chemistry involving trans-TiO4N2 motifs is described, where the oxygen ligands are 2,2′-biphenolato derivatives (L1 or L2) and the nitrogen ligands are pyridine (Pyr), 2,3-dihydro-7-azaindole (DHA) or 2-(methylamino)pyridine (MePyr). Monomeric complexes and double-stranded helicates incorporating this set of ligands are characterized. The monomeric species are obtained from the precursor [Ti(L1)2(HOiPr)2] whereas the helical dinuclear architectures are synthesized following a multicomponent self-assembly approach starting from L2H4, Ti(OiPr)4 and two equivalents of the nitrogen ligand. It is proposed that the trans isomerism in TiO4N2 observed in these structures results from the destabilisation of the cis isomer by the trans influence of the Ti–N bonds. The crystal structures and infra-red analysis demonstrate hydrogen bonding interactions occurring between the NH group of DHA or MePyr and the oxygens belonging to the titanium coordination sphere. The strength of these interactions is estimated using the PACHA (Partial Atomic Charges Analysis) software.

International audience; This article describes the formation of neutral TiO 4 N 2-based coordination entities where the titanium centers are coordinated by oxygenated ligands incorporating one or two biphenolato units, i.e. L 1 and L 2 respectively. In these systems, the sixfold coordination spheres of each metallic center are completed by the enantiopure bi-dentate diphenylethene-1,2-diamine compound, abbreviated as dpeda. A solvent dependent diastereomeric ratio is evaluated by 1 H NMR for the monomeric [Ti(L 1) 2 ((1R,2R)-dpeda)] or [Ti(L 1) 2 ((1S,2S)-dpeda)] (abbreviated as [R-Ti] or [S-Ti] respectively) complexes. The highest diastereomeric ratio for [Ti(L 1) 2 (dpeda)] is obtained in chloroform (2 : 1). Energy calculation and circular dichroism spectra simulation, obtained by DFT, permit to assign the configuration of the stereoisomer formed in excess. The (1R,2R)-(+)-dpeda privileges the Δ form and (1S,2S)-(-)-dpeda the Λ form of the [Ti(L 1) 2 (dpeda)] stereoisomers. The helicates formulated as [Ti 2 (L 2) 2 ((1S,2S)-dpeda) 2 ] and [Ti 2 (L 2) 2 (1R,2R)-dpeda) 2 ] (abbreviated as [S-Ti2] or [R-Ti2] respectively) are obtained by following a multi-component self-assembly approach. In this case, the diastereomeric ratios evaluated by 1 H NMR are much lower compared to those determined for the monomeric species, and a privileged P and M configuration for the [Ti 2 (L 2) 2 (1R,2R)-dpeda) 2 ] helicate and the [Ti 2 (L 2) 2 ((1S,2S)-dpeda) 2 ] helicate respectively is assigned through theoretical calculations. Overall, this article describes a strategy to favour handedness in a helicate system where the chiral control is originated from a ligand that is not inscribed within the helical framework of the architecture.

International audience; In this work, we report the formation of a coloured inorganic–organic hybrid material generated from the [Ti10O12(cat)8(py)8] (catecholato (cat), pyridine (py)) oxo-cluster and poly(4-vinylpyridine). The titanium oxo-cluster is linked to the organic polymer through Ti–N coordination bonds. Vibrational spectroscopies (FT-IR and Raman scattering) and thermogravimetric analysis highlight the quantitative incorporation of the cluster in the polymeric matrix with no degradation of the inorganic core of the starting complex, and also highlight the good homogeneity of the resulting materials. Solid-state NMR measurements (13C CP-MAS) also reveal that the hybrid material results only from the substitution of the labile pyridine ligands within [Ti10O12(cat)8(py)8] by the pyridines of the P4VP polymer. Next, the functionalization of SiO2 surfaces with monolayer or multilayer films composed of alternate layers of the oxo-cluster and of the polymer is detailed. The thickness of these films, as evaluated by ellipsometry, ranges from a few nanometers to tens of nanometers for the monolayer films and the multilayer films, respectively

Cyclometalation of (2R,5R)-2,5-diphenylpyrrolidine (1) with [(η5-Cp*)MCl2]2 using NaOAc in CH2Cl2 at room temperature, followed by cationization with KPF6 in CH3CN, cleanly yielded the cationic cyclometalated amines 2a,b (a, M = Ir; b, M = Rh). This constituted an improvement with regard to another cyclometalation pathway, which had led to unwanted oxidation of the ligand to an imine. Compounds 2a,b were characterized by elemental analysis and X-ray diffraction of single crystals; the latter gave evidence of an R configuration of the metal center, and a λ envelope conformation of the five-membered metallacycle. Successful application of the NaOAc/CH2Cl2 methodology to the cycloiridation and cyclorhodation of the imidazolines 3–5 led to the neutral half-sandwich chloro complexes 6–8, which were completely characterized, with yields ranging from 44% to 82%. In these complexes, the labile NH proton was localized in a γ position with regard to the metal. From the enantiopure chiral ligands 4 and 5, both diast...

The reaction of (2R,5R)-2,5-diphenylpyrrolidine (L1) with [(η5-C5Me5)MCl2]2 (M = Rh, Ir) in acetonitrile in the presence of KPF6 and NaOH at room temperature led to mixtures of two products, [(η5-C...

Various cycloruthenated complexes were used as homogeneous catalysts for the atom-transfer radical addition of polyhalogenated compounds to several olefinic substrates. Yields obtained through conventional or microwave heating could reach high values (up to 98% with CBrCl 3 and 88% with CCl 4 ).

The mechanism of asymmetric hydrogen transfer catalyzed by a ruthenacycle has been studied. Ruthenium-hydride intermediates have been characterized by 1H NMR and IR. These hydride complexes appeared as a diastereomeric mixture (de = 64%) responsible for the enantiomeric excess of the hydrogen transfer reaction (ee = 60%). Kinetic measurements have been performed as a function of substrate concentration and temperature. Michaelis−Menten kinetics were observed indicating substrate−catalyst complex formation (thermodynamic data for the complexation reaction: ΔG0 = −13 kJ mol−1 at 273 K, ΔH0 = −58 kJ mol−1, ΔS0 = −170 J K−1 mol−1). The complexation process is accomplished prior to an intracomplex chemical reaction. As the substrate is still bound to the catalyst, pericyclic hydrogen transfer is deduced with an activation energy Ea = 83 kJ mol−1. On the basis of these data, a mechanism is proposed for the overall hydrogen transfer reaction.

The cyclometalation of chiral secondary amines through ortho-metalation of an aryl group occurred readily with [(η6-benzene)RuCl2]2 in acetonitrile. Reasonable to good yields of the expected cationic products of the form [(η6-benzene)Ru(N−C)(NCMe)](PF6), in which N−C represents the cyclometalated ligands, were obtained with bis-(R)-phenylethylamine, bis-(R)-1-naphthylethylamine, and (2R,5R)-2,5-diphenylpyrrolidine. Variable proportions of the expected four diastereoisomers were found according to NMR studies. The stereochemistry of complexes was investigated by 2D NMR in solution and by X-ray diffraction of single crystals. The (S) configuration at the metal was generally associated with a δ conformation of the metallacycle, and conversely, the (R) configuration with the λ conformation.

The cyclometalation of chiral and achiral primary amines occurred readily with Ru(II), Rh(III), and Ir(III) derivatives. Thus, the metalation of (R)-1-phenylethylamine by [(η6-benzene)RuCl2]2, [(η5-Cp*)RhCl2]2, and [(η5-Cp*)IrCl2]2 was studied. Good yields of the expected cationic products in which the phenyl group was ortho-metalated were obtained for the rhodium and the ruthenium derivatives, whereas a mixture of products was formed in the case of the iridium complex. Benzylamine, (R)-1-phenylpropylamine, (R)-1-(1-naphthyl)ethylamine, and (R)-1-aminotetraline afforded also the cycloruthenation products whose general formula is [(η6-benzene)Ru(N−C)(NCMe)]PF6 where N−C represents the ortho-metalated ligands. Substitution of the acetonitrile ligand by PMe2Ph occurred readily on the ruthenium complexes, affording stable compounds that were characterized by X-ray diffraction studies on single crystals, thus ascertaining the existence of the cycloruthenated five-membered rings. Accurate analyses of the struct...

We have synthesized and fully characterized three chiral ligands with a rigid xanthene backbone having phosphorus and/or nitrogen donor atoms, viz. the diimine 5 and the iminophosphines 15a and 15b . When the imine functions were derived from (1 R )-camphor (compounds 5 and 15a ), their configuration was ( E ), whereas a dynamic mixture of ( Z ) and ( E ) isomers was observed in solution for the (1 S )-fenchone derivative 15b . Attempts to coordinate palladium (II) with these ligands have led to untractable mixtures. By contrast, we isolated in good yields the well-defined silver (I) complexes 18–20 , in which the ligands were bidentate, and the rhodium (III) complex 21 in which ligand 15a was tridentate. Complexes 18 , 19 and 21 were characterized by X-ray crystallography. A fluxionality of the silver complexes owed to conformational (flip-flop) equilibrium was revealed by VT-NMR analysis. The rhodium complex was not fluxional. In the silver complexes, the camphimine was in the ( E ) configuration as in the free ligand, whereas it had isomerized to ( Z ) in the rhodium complex. Pd-, Ag- or Rh-catalyzed reactions implemented with our ligands have in general led to good conversions but modest enantioselectivities (0–36%).

Cycloruthenated complexes obtained by direct C-H activation of enantiopure aromatic primary and secondary amines are efficient catalysts in asymmetric hydride transfer reaction. Reduction of acetophenone has been achieved rapidly with enantiomeric excesses (ee's) ranging from 38 to 89 %. The importance of Ru-C bond in the catalytic efficiency is highlighted.

[reaction: see text] Ruthenacycles obtained by cyclometalation of enantiopure aromatic primary or secondary amines with [(eta6-benzene)RuCl2]2 or with [(eta6-p-cymene)RuCl2]2 are efficient catalysts for asymmetric transfer hydrogenation (TOF up to 190 h(-1) at room temperature). Enantioselectivities in the transfer hydrogenation of acetophenone ranged from 38% to 89%. It is possible to prepare the catalysts in situ, which allows the use of high throughput experimentation.

The chiral diphospholane ligands Duphos (1) and Duxantphos (2), which can be differentiated by their bite angle, were applied to palladium-catalysed asymmetric reactions, essentially allylic alkylations with symmetrically (3a−d) or unsymmetrically (5a,b) substituted allylic acetates as substrates. The most interesting results were found with the first series of substrates in which 2 was more reactive and/or selective than 1. The model complexes of the catalytic intermediates [Pd{(S,S)-1}(η3-cyclohexenyl)](BF4) (10) and exo-[Pd{(R,R)-2}(η3-cyclohexenyl)](SbF6) (11) could be characterised by X-ray crystallography. 1H and 31P NMR spectroscopic analyses of [Pd{(R,R)-2}(η3-diphenylallyl)](SbF6) (12) and [Pd{(R,R)-2}(η3-allyl)](SbF6) (13) revealed the presence of exchanging isomers in solution. Structural data provided by these techniques combined with the preferential rotation model led to a satisfactory interpretation of the catalytic allylic alkylation results. It appears that the bite angle plays a crucial role in the positioning of the proximal methyl groups, which determines the distribution of allyl isomeric intermediates and the balance between clockwise and anticlockwise rotations in the enantioselective step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The new pyridinediphosphinite ligand PONOP (1) was synthesized in one step from 2,6-pyridinedimethanol and diphenylchlorophosphane. Reaction of 1 with PtCl(2)(PhCN)(2) led to the neutral homobimetallic complex [Pt(2)Cl(4)(PONOP)(2)] (2), where the benzonitriles have been substituted by the phosphorus atoms of 1. The X-ray structure of 2 revealed a metallamacrocycle where the pyridines remained free. Addition of 2 equiv of [Cu(MeCN)(4)](BF(4)) to 2 led to CuCl and to the binuclear dicationic complex [Pt(2)Cl(2)(PONOP)(2)](BF(4))(2) (3), where chloro ligands have been substituted by pyridine groups. Conversely, reaction of 3 with chloride anions gave back complex 2. Solid-state (X-ray) and solution (NMR) studies indicated that after the transformation of 2 into 3, the platinum centers were brought much closer and the pyridinediphosphinite ligand was stiffened. The methylene NMR protons of 3 were strongly deshielded, and the corresponding proton-phosphorus coupling constants followed a Karplus-type relationship.

A systematic study of the effect of chloride ions on the NMR characteristics of several cationic diphosphine η3-allyl palladium complexes has revealed in some instances a deshielding of the protons. Chloride ions also enhance the reactivity of the complexes. Thus 〚(Me-Duphos)(1,3-diphenylallyl)palladium〛chloride leads mostly to 〚(Me-Duphos)dichloropalladium〛 and to chalcone at room temperature, whereas at low temperature a pair of cationic and anionic allyl palladium complexes is obtained.

Pd(DBA)2 reacts with the azide C6F5N3 in the presence of terpy* to form the tetrazenido palladium(II) complex [(η2-terpy*)Pd{η2-N4(C6F5)2}] 1, whereas with TsN3 the amido complex [(η3-terpy*)Pd(NHTs)]+ is obtained. Another synthetic route involving abstraction of chloride ions from [(L)PdCl]Cl and transmetallation with KNHTs yields the complexes [(η3-L)Pd(NHTs)](BF4) (4: L = terpy*; 5: L = triphos). Compounds 1, 4 and 5 have been characterized in the solid state by single-crystal X-ray analysis as mononuclear, square-planar complexes. 1H and 19F NMR spectroscopy reveal that 1 is a fluxional molecule. Rotation of both C6F5 rings is hindered, with energy barriers of 53.9 kJ·mol−1 (293 K) and 60.7 kJ·mol−1 (325 K). Additionally, the lateral pyridines and the C6F5 rings exchange through an oscillatory process where one terminal pyridine enters the coordination sphere while the other leaves it. The corresponding energy barrier (74.9 kJ·mol−1 at 298 K) has been determined from selective inversion NMR experiments.

The potentially tridentate ligands 2,2′:6′,2"-terpyridine (terpy) and 2,6-bis(diphenylphosphanylmethyl)pyridine (PNP) have been used to prepare novel palladium−allyl complexes of general formula [(terpy)Pd(CH2CHCRR′)](BF4) [R = R′ = H (1); R = H, R′ = Me (2); R = R′ = Me (3)] and [(PNP)Pd(CH2CHCRR′)](BF4) [R = R′ = H (4); R = H, R′ = Me (5); R = R′ = Me (6)], which were characterized by elemental analysis, IR spectroscopy, and 13C, 31P and variable-temperature 1H NMR spectroscopy. The low-temperature 1H NMR spectra show that the configuration of the complexes in solution depends strongly on the nature of the ligand. The terpy complexes 1−3 are η3-allyl species, where terpy is dihapto and one pyridine ring remains uncoordinated, whereas the PNP complexes 4−6 occur as η1-allyl compounds with a trihapto PNP ligand. All complexes are fluxional through η3-η1 exchange processes. Energy barriers of 47.5−48.6 kJ·mol−1 (243−262 K) are reported for the interconversion of terminal allylic protons (complexes 2−4). ΔG‡ is higher (71.1 kJ·mol−1 at 350 K) for the interconversion of the methyl groups in complex 6. A lower-barrier oscillatory mechanism involving terpy (ΔG‡ = 43.9 kJ·mol−1 at 231 K) is also involved in complex 1. The X-ray structures of complexes [(η3-terpy)Pd(η1-C5H9)](BF4) (3a) and [(η3-PNP)Pd(η1-C4H7)](BF4) (5a) are reported; the structure of 3a corresponds to a species that is not observed in solution.

The reaction of the tridentate rigid ligand PNP (2,6-bis(diphenylphosphinomethyl)pyridine) with RUCl2(PPh3)3 led to the formation of two new ruthenium(II) complexes, RuCl2(PNP)(PPh3) (1) and [RuCl(MeCN)(PNP)(PPh3)]Cl (2), which were analytically and spectroscopically characterized. The X-ray diffraction study of 1 shows that the PNP ligand coordinates Ru in a meridional mode, and reveals some steric congestion within the complex.

International audience; The binuclear η6-benzene cycloruthenated complex 2, which bears an unsupported bridging hydride ligand, was synthesized by treating the monomeric cationic cycloruthenated (R)-(+)-1-(1-naphthyl)ethylamine 1 with potassium hydroxide under biphasic conditions and then with an alcoholic solvent. Alternatively, compound 2 was prepared from an equimolar amount of compound 1 and the homologous monomeric hydrido complex 3. The crystal structure of 2 revealed π- stacking interactions between the naphthyl groups of each cyclometalated amine; the hydride ligand is bent, with a Ru−H−Ru angle of 145.3(10)°. Compound 2 is fluxional as shown by variable-temperature NMR analysis. DFT analysis of homochiral 2 and of its hypothetical heterochiral counterpart 2* revealed that dispersion-based π−π interactions between the cyclometalated ring are not the only interactions that must be taken into account to rationalize the conformational preference for 2. Indeed, the overall dispersion-based interactions between all the ligands of the connected metallacycles provide an additional 5 to 6 kcal/mol of stabilization energy for 2 regardless whether the π-stacking interactions between the naphthyl rings exist or not.

International audience; A library of organometallic compounds derived from primary and secondary amines cyclometalated by ruthenium(II), rhodium(III) and iridi- um(III) was tested in the asymmetric transfer hydrogenation of a number of ketones and imines. All compounds displayed high catalytic activity for the reduction of ketones under mild conditions. The most enantioselective catalysts were based on secondary amines containing two asymmetric carbon atoms bound to the nitrogen atom. For the reduction of aryl alkyl ketones [Ar(C[DOUBLE BOND]O)R where R=CH3 or CH2R′] the cyclometalated ruthenium and rhodium derivatives of the (2R,5R)-2,5-diphenylpyrrolidine ligand displayed the best results with respect to activity and selectivity (ees up to 97%). However, for the reduction of aryl tert-alkyl ketones [Ar(C[DOUBLE BOND]O)R′′ in which R′′ is a tertiary alkyl group] the best catalyst was a ruthenium compound derived from bis[(R)-1-phenylethyl]amine, allowing the reduction of isobutyrophenone and cyclohexyl phenyl ketone which were both reduced with high enantioselectivities (ees up to 98%). This shows that the cyclometalated compounds have a high substrate specificity. In addition, acyclic and cyclic imines were reduced with good selectivities by both rhodium(III) and iridium(III) metalacycles built up with (2R,5R)-2,5-diphenylpyrrolidine.

The cyclopalladation of the 4-aryl-2,1,3-benzothiadiazoles 1a-c with palladium acetate in acetic acid afforded the novel dimeric complexes 2a-c in good yields. These were then converted into the monomeric pyridine-, chloro-coordinated cyclometallated complexes 3a-c through reaction with lithium chloride in acetone and then pyridine in dichloromethane. All complexes were fully characterized by means of NMR, IR and elemental analysis. The X-ray structure of complex 2c revealed that it presents transoid geometry, whereas the X-ray structure of 3c shows that the pyridine ligand and the thiazole ring are mutually trans. Photophysical properties were investigated by means of UV-Vis absorption and fluorescence emission in solution. Solid-state diffuse reflectance UV-Vis spectra (DRUV) were also applied in order to better characterize the complexes photophysics in the solid state. All complexes present intense absorption at around 300 nm (λ(1)) via(1)LC transitions located in BTD ligands, and additional low energy absorption bands, higher than 450 nm (λ(2)) of (1)MLCT character. The complexes are fluorescent in solution at room temperature, where two emission bands could be observed, a high energy band (excitation @ λ(1)) ascribed to the ligand emission and an additional red shifted low intense band (excitation @ λ(2)) due to the complex emission.

The synthesis of one diimine and two iminophosphine chiral ligands bearing a xanthene backbone in, respectively, four and five steps is described. The diimine is characterised by X-ray crystallography. A preliminary test in palladium-catalysed asymmetric allylic alkylation is reported.

Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates. 1: R=Me, X=S; 2: R=H, X=C(CH3 )2 .

The syntheses of cycloruthenated compounds by several methods, and especially by the C–H activation pathway, have been reviewed. Many ruthenium-containing starting materials lead to these interesting organometallic compounds, which have found various applications in different fields of chemistry. Their reactivity highlights both thevariety of reactions that were found to occur at the Ru–C bonds as well as the inertness of the organometallic moiety when these species are exposed to strongly oxidizing molecules or to reactive halogenation reagents. Their use as catalyst precursors showed them to be particularly efficient for hydrogenation reactions, either by H2 or by hydride transfer. Physicochemical characteristics of cycloruthenated complexes include: (i) a cathodic shift of the electrochemical potentials corresponding to various redox couples, (ii) a bathochromic shift of UV/Vis absorption bands, (iii) valuable luminescence properties. Dinuclear cycloruthenated complexes display specific properties connected to interactions between the metals, such as strong electronic coupling, evidenced by intervalence bands of mixed-valence species, or efficient energy transfer.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The syntheses of cycloruthenated compounds by several methods, and especially by the C–H activation pathway, have been reviewed. Many ruthenium-containing starting materials lead to these interesting organometallic compounds, which have found various applications in different fields of chemistry. Their reactivity highlights both thevariety of reactions that were found to occur at the Ru–C bonds as well as the inertness of the organometallic moiety when these species are exposed to strongly oxidizing molecules or to reactive halogenation reagents. Their use as catalyst precursors showed them to be particularly efficient for hydrogenation reactions, either by H2 or by hydride transfer. Physicochemical characteristics of cycloruthenated complexes include: (i) a cathodic shift of the electrochemical potentials corresponding to various redox couples, (ii) a bathochromic shift of UV/Vis absorption bands, (iii) valuable luminescence properties. Dinuclear cycloruthenated complexes display specific properties connected to interactions between the metals, such as strong electronic coupling, evidenced by intervalence bands of mixed-valence species, or efficient energy transfer.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The title compound, [Ru(3)(C(12)H(12)N)(3)(CO(3))(C(6)H(6))(3)]PF(6)·CH(2)Cl(2), was obtained unintentionally as the product of an attempted deprotonation of the monomeric parent ruthenium complex [Ru(C(12)H(12)N)(C(6)H(6))(C(2)H(3)N)]PF(6). The carbonate ligand bridges three half-sandwich cyclo-ruthenated fragments, each of them exhibiting a pseudo-tetra-hedral geometry. The configuration of the Ru atoms is S. The naphthyl groups of the enanti-opure cyclo-ruthenated benzylic amine ligands point in the same direction, adopting a propeller shape.

Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates. 1: R=Me, X=S; 2: R=H, X=C(CH3 )2 .

The palladium allyl complexes [(2,2‘:6‘,2‘‘-terpyridine)Pd(C3H5)]X (1, X- = BF4-; 2, X- = ClO4-) were synthesized and characterized. The molecular structures of the η3- and η1-allyl isomeric forms of 2, where the terpyridine ligand coordinates the palladium atom either in a bidentate or in a tridentate fashion, were determined by X-ray crystallography, whereas a variable-temperature 1H NMR analysis of 1 shows that the complex is fluxional.

The new pyridinediphosphinite ligand PONOP (1) was synthesized in one step from 2,6-pyridinedimethanol and diphenylchlorophosphane. Reaction of 1 with PtCl(2)(PhCN)(2) led to the neutral homobimetallic complex [Pt(2)Cl(4)(PONOP)(2)] (2), where the benzonitriles have been substituted by the phosphorus atoms of 1. The X-ray structure of 2 revealed a metallamacrocycle where the pyridines remained free. Addition of 2 equiv of [Cu(MeCN)(4)](BF(4)) to 2 led to CuCl and to the binuclear dicationic complex [Pt(2)Cl(2)(PONOP)(2)](BF(4))(2) (3), where chloro ligands have been substituted by pyridine groups. Conversely, reaction of 3 with chloride anions gave back complex 2. Solid-state (X-ray) and solution (NMR) studies indicated that after the transformation of 2 into 3, the platinum centers were brought much closer and the pyridinediphosphinite ligand was stiffened. The methylene NMR protons of 3 were strongly deshielded, and the corresponding proton-phosphorus coupling constants followed a Karplus-type relationship.

The title compound, [Ru3(C12H12N)3(CO3)(C6H6)3]PF6·CH2Cl2, was obtained unintentionally as the product of an attempted deprotonation of the monomeric parent ruthenium complex [Ru(C12H12N)(C6H6)(C2H3N)]PF6. The carbonate ligand bridges three half-sandwich cyclo­ruthenated fragments, each of them exhibiting a pseudo-tetra­hedral geometry. The configuration of the Ru atoms is S. The naphthyl groups of the enanti­opure cyclo­ruthenated benzylic amine ligands point in the same direction, adopting a propeller shape.

Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates. 1: R=Me, X=S; 2: R=H, X=C(CH

The cover picture shows the low-temperature 31P NMR signals and simplified 3D representations of exo and endo isomers of an (η3-1,3-diphenylallyl)palladium(II) complex in which the metal center is coordinated by a chiral xanthene-derived diphospholane ligand. Such complexes are intermediates in palladium-catalyzed allylic substitution, and their structures determined by 2D NMR spectroscopy allow for the interpretation of the enantioselectivities of the catalytic process in terms of preferential rotation of the allyl group. Key methyl groups of the chiral ligand that govern this rotation are represented by yellow spheres in the background. Details on these complexes and others and on asymmetric catalysis can be found in the article by J. A. Osborn, L. Barloy et al. on p. 3987 ff. The authors are indebted to Bernard Lafleuriel (CURRI-Visu) for his help concerning the artwork of the cover picture.

A supported Mn–porphyrin catalyst has been prepared by immobilisation of the tetracationic Mn [meso-tetra (4-N-methylpyridiniumyl)porphyrin]Cl4+ on montmorillonite, and is found to be efficient for alkene epoxidation and alkane hydroxylation by PhlO, with a higher ability to oxidize alkanes, and in particular short linear alkanes, than corresponding homogeneous or silica-supported Mn–porphyrin catalysts.

A supported Mn–porphyrin catalyst was prepared by strong adsorption of the tetracationic Mn[meso-tetra(4-N-methylpyridiniumyl) porphyrin](Cl)4+4Cl– on silica, and was found very efficient for cyclo-octene epoxidation (95% yield, 13 turnovers per min) and for alkane hydroxylation, with alcohol yields and alcohol: ketone ratios remarkably higher than those obtained with corresponding soluble Mn–porphyrins.