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International audience; A series of reactions have been performed by mixing 2-diphenylphosphino-6-methyl-pyridine (dpPyMe) and [Cu(CH3CN)4]BF4 in different molar ratios. Starting from equimolar quantities of dpPyMe and Cu+, a dinuclear Cu(I) complex with two P,N binucleating bridging ligands has been obtained. This compound is stable in the solid state, however ligand exchange reactions leading to a mixture of species have been evidenced in solution. By increasing the amount of dpPyMe, the reaction of dpPyMe and [Cu(CH3CN)4]BF4 afforded the dinuclear Cu(I) complex [Cu2(μ-dpPyMe)3(CH3CN)](BF4)2 in which the three bridging dpPyMe ligands are in a head-to-head arrangement. This compound is remarkably stable in solution. It has been also shown that the axial CH3CN ligand of [Cu2(μ-dpPyMe)3(CH3CN)](BF4)2 can be suitably exchanged with other nitrile ligands [benzonitrile, 4-(dimethylamino)-benzonitrile, 4-nitrobenzonitrile and bromoacetonitrile] but also with triphenylphosphine oxide. The electrochemical and photophysical properties of the resulting complexes have been systematically investigated. The [Cu2(μ-dpPyMe)3(L)](BF4)2 derivatives are weak emitters in solution but remarkable emission quantum yields (6 to 46%) have been found in rigid matrices at room temperature. One complex was utilized as active material for preliminary tests in LEC devices.

Hemichelation is emerging as a new mode of coordination where non-covalent interactions crucially contribute to the cohesion of electron-unsaturated organometallic complexes. This study discloses an unprecedented demonstration of this concept to a Group 9 metal, that is, Rh(I). The syntheses of new 14-electron Rh(I) complexes were achieved by choosing the anti-[(η(6):η(6)-fluorenyl){Cr(CO)3}2] anion as the ambiphilic hemichelating ligand, which was treated with [{Rh(nbd)Cl}2] (nbd=norbornadiene) and [{Rh(CO)2Cl}2]. The new T-shaped Rh(I) hemichelates were characterized by analytical and structural methods. Investigations using the methods of the DFT and electron-density topology analysis (NCI region analysis, QTAIM theory) confirmed the closed-shell, non-covalent and attractive characters of the interaction between the Rh(I) center and the proximal Cr(CO)3 moiety. This study shows that, by appropriate tuning of the electronic properties of the ambiphilic ligand, truly coordination-unsaturated Rh(I) complexes can be synthesized in a manageable form.

International audience; : A rational method of synthesis of stable neutral T-shaped 14 electron Pd and Pt complexes is proposed. It takes advantage of the ambiphilic character of the tricarbonyl(η(6)-indenyl)chromium anion, of which the main property is to behave as a hemichelating ligand, that is a nonconventional heteroditopic ligand capable of chelating a metal center by way of covalent and noncovalent bonding, thus preserving its unsaturated valence shell. The reaction of the in situ formed tricarbonyl(η(6)-2-methylindenyl)chromium anion with a series of Pd and Pt metallacycles afforded new air-stable and persistent synfacial heterobimetallic complexes in which the metallacycle binds the indenyl fragment via its metal in an η(1) fashion, leaving the fourth coordination site at the chelated metal virtually vacant. The structures of eight of these novel complexes are disclosed, and their bonding features are investigated by an array of theoretical methods based on the density functional theory (NBO, EDA, ETS-NOCV, AIM, NCI region analysis). Theory shows that the formation of these unusual structures of bimetallic synfacial η(1)-indenyl-Pd/Pt complexes is driven thermodynamically by attractive Coulombic occlusion of the fourth vacant coordination site at Pd/Pt centers by the Cr(CO)3 moiety.

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...

This research was supported by the University of Strasbourg, the Centre Nationale de la Recherche Scientifique (CNRS), the Spanish project CTQ2012-35692, the FEDER founds and the Swiss National Science Foundation (grant number 200020-140298). I. N. thanks the Agence National de la Recherche (ANR) and S. G. the Swiss National Science Foundation for postdoctoral fellowships.

We report in this communication the preparation of the BrMPPA ligand, a new tris(2-pyridylmethyl)amine-type tripod in which di-α-substitution by an amido group and a bromine atom, respectively, provide functionality and sterically induced ligand flexibility. The coordination versatility of this tripod is evidenced by the complete characterization of two dichlorido and di-triflato FeII complexes in the solid state and in solution. The new tripod can potentially act as a κ5 ligand with coordination of the carbonyl group of the amide function. This is true when there is little steric hindrance at the coordination site. With bulky chlorido ligands, however, decoordination occurs, and the tripod becomes a κ4 chelate. In this case, a state-dependent coordination mode is reported: A dangling pyridyl group is observed in solution, whereas the carbonyl group is noncoordinated in the solid state, the three pyridine groups remaining bound.

The trans-configurated square-planar palladium complex trans-[{(Ph2PC6H4CONH)2C6H4}PdCl2] (1), which catalyzes the Suzuki cross coupling of 4-bromotoluene with phenylboronic acid, was found to react with potassium carbonate in toluene at 90 °C (Suzuki conditions) to give cis-[{(Ph2PC6H4CON)2C6H4}Pd] (2). The single-crystal X-ray structure analysis of 2 reveals the square-planar palladium center to be in a cis configuration. The trans–cis configuration change at palladium is possible because of the elimination of two HCl equivalents in the conversion of 1 into 2. Both complexes 1 and 2 show approximately the same catalytic performance for Suzuki reactions, suggesting 2 to be the catalytically active species.

The reaction of 1,4-dimethyl-1,4,7-triazacyclononane (L-Me2) with MnCl2 • 4H2O in acetonitrile gives, in the presence of sodium formate, hydrogen peroxide, triethylamine and KPF6, the dinuclear Mn(III)–Mn(IV) complex cation [(L-Me2)2Mn2 (O) 2 (OOCH)]2+ (1) which crystallises as the hexafluorophosphate salt.The analogous reaction with sodium benzoate, however, yields the dinuclear Mn(III)–Mn(III) complex cation [(L-Me2)2Mn2 (O)(OOCC6H5)2]2+ (2), isolated also as the hexafluorophosphate salt.In the case of sodium acetate, both cations, the Mn(III)–Mn(IV) complex [(L-Me2)2Mn2 (O) 2 (OOCCH3)]2+ (3) and the known Mn(III)–Mn(III) complex [(L-Me2)2Mn2 (O)(OOCCH3)2]2+ (4) are available, depending upon the molar ratio.The single-crystal X-ray structure analyses show for the green crystals of [1][PF6]1.5 [Cl]0.5 • 1.5 H2O and [3][PF6]2 • (CH3)2CO, a Mn–Mn distance of 2.620(2) and 2.628(4) Å, respectively, while for the red-violet crystal of [4][PF6]2, a Mn–Mn distance of 3.1416(8) Å is observed.All four compounds show catalytic activity for the oxidation of isopropanol with hydrogen peroxide in water and in acetonitrile to give acetone in the presence of oxalic or ascorbic acid as co-catalysts.

To bring evidence for or against the hypothesis of catalytic hydrogenation by intact trinuclear arene ruthenium clusters containing an oxo cap, cationic Ru3O clusters with three different arene ligands (intrinsically chiral tetrahedra) have been synthesized as racemic mixtures. By introduction of a chiral auxiliary substituent at one of the three different arene ligands, the separation of the two diastereomers was possible. The chiral Ru3O framework was evidenced by X-ray crystallography, by circular dichroism in the UV and IR regions, and by chiral shift reagents in the NMR spectra. The catalytic hydrogenation of the prochiral substrate methyl 2-acetamidoacrylate using a chiral Ru3O cluster showed no asymmetric induction, suggesting that the catalytically active species is not the intact Ru3O cluster.

The new aryl phosphinites PPh 2 OR (R = 2,4,6-Me 3 C 6 H 2 , 1 ; R = 2,6-Ph 2 C 6 H 3 , 2 ) have been prepared from chlorodiphenylphosphine and the corresponding phenols. In these ligands, the ortho -positions of the aromatic phosphite function are blocked by methyl and phenyl substituents, which allows coordination to metal centres without ortho -metallation. Thus, reaction with [PdCl 2 (cod)] leads to the complexes trans -[PdCl 2 (PPh 2 OR) 2 ] (R = 2,4,6-Me 3 C 6 H 2 , 3 ; R = 2,6-Ph 2 C 6 H 3 , 4 ), while the reaction with [Rh 2 (CO) 4 Cl 2 ] gives trans -[Rh(CO)Cl(PPh 2 OR) 2 ] (R = 2,4,6-Me 3 C 6 H 2 , 5 ; R = 2,6-Ph 2 C 6 H 3 , 6 ). The single-crystal X-ray structure analyses of 3 and 5 confirm the trans -coordination of the new ligands in these square-planar complexes.

The monocationic chloro complexes containing chelating 1,10-phenanthroline (phen) ligands [(arene)Ru(N∩N)Cl] + (1: arene = C6H6, N∩N = phen; 2: arene = C6H6, N∩N = 5-NO2-phen; 3: arene = p-MeC6H4Pri, N∩N = phen; 4: arene = p-MeC6H4Pri, N∩N = 5-NO2-phen; 5: arene = C6Me6, N∩N = phen; 6: arene = C6Me6, N∩N = 5-NO2-phen; 7: arene = C6Me6, N∩N = 5-NH2-phen) have been prepared and characterised as the chloride salts. Hydrolysis of these chloro complexes in aqueous solution gave, upon precipitation of silver chloride, the corresponding dicationic aqua complexes [(arene)Ru(N∩N)(OH2)]2+ (8: arene = C6H6, N∩N = phen; 9: arene = C6H6, N∩N = 5-NO2-phen; 10: arene = p-MeC6H4Pri, N∩N = phen; 11: arene = p-MeC6H4Pri, N∩N = 5-NO2-phen; 12: arene = C6Me6, N∩N = phen; 13: arene = C6Me6, N∩N = 5-NO2-phen; 14: arene = C6Me6, N∩N = 5-NH2-phen), which have been isolated and characterised as the tetrafluoroborate salts. The catalytic potential of the aqua complexes 8–14 for transfer hydrogenation reactions in aqueous solution has been studied: complexes 12 and 14 catalyse the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide with turnover numbers around 200 (80 °C, 7 h). In the case of 12, it was possible to observe the postulated hydrido complex [(C6Me6)Ru(phen)H]+ (15) in the reaction with sodium borohydride; 15 has been characterised as the tetrafluoroborate salt, the isolated product [15]BF4, however, being impure. The molecular structures of [(C6Me6)Ru(phen)Cl]+ (1) and [(C6Me6)Ru(phen)(OH2)]2+ (12) have been determined by single-crystal X-ray structure analysis of [1]Cl and [12](BF4)2.

The unsaturated trihydrido complex [(C6Me6)2Ru2(μ2-H)3]+ reacts with diaryl- or dialkylphosphines PR2H to give the dinuclear cations [(C6Me6)2Ru2(μ2-PR2)(μ2-H)2]+ (R= Ph, 1; R = t-Bu, 2). Surprisingly, complexes of the type [(C6Me6)2Ru2(μ2-PR2)(μ2-H)2]+ with R = Ph (1), n-Bu (3), n-Oct (4) are also accessible in high yield from the reaction of [(C6Me6)2Ru2(μ2-H)3]+ with the corresponding triaryl- or trialkylphosphine PPh3, P(n-Bu)3, or P(n-Oct)3 by carbon−phosphorus bond cleavage. A possible intermediate of the reaction with PPh3, [(C6Me6)2Ru2(μ2-PPh2)(μ2-H)(μ2-Ph)]+ (5), could be isolated from the reaction mixture as the tetrafluoroborate salt, the single-crystal X-ray structure analysis of which reveals a bridging phenyl ligand coordinated in an η1-μ2 fashion to the diruthenium backbone. With the mixed phosphine PMe2Ph, [(C6Me6)2Ru2(μ2-H)3]+ reacts to give [(C6Me6)2Ru2(μ2-PMe2)(μ2-H)2]+ (6) and the corresponding intermediate [(C6Me6)2Ru2(μ2-PMe2)(μ2-H)(μ2-Ph)]+ (7). All dinuclear cations are isolated as...

The reaction of 2,3,4,7-tetrahydro-1H-inden-2-ol with ruthenium chloride hydrate in refluxing ethanol yields the chloro-bridged dinuclear complex [RuCl2(indanol)]2 (1). The mononuclear complex [Ru(indanol)(H2O)3]2+ (2), formed in situ from 1 in aqueous solution, reacts with the dinuclear complex [H3Ru2(C6Me6)2]+ to give a trinuclear arene-ruthenium cluster as a mixture of two isomers, the cations [H3Ru3(endo-indanol)(C6Me6)2(O)]+ (3a) and [H3Ru3(exo-indanol)(C6Me6)2(O)]+ (3b), in a 1:1 ratio. The hydroxy function of the indanol ligand is oriented towards the μ3-oxo cap of 3a, whereas the OH group is bent away from the metal skeleton of 3b. These two isomers, which can easily be separated by silica-gel chromatography, were isolated and characterised as their tetrafluoroborate salts. The single-crystal X-ray structure analysis of [3a][BF4] shows a strong intramolecular hydrogen bond between the μ3-oxo ligand and the hydroxyl function, which even persists in acetone solution, as demonstrated by NMR spectroscopy. On the other hand, the hydroxy function of 3b was found to be free in the solid state as well as in solution, as shown by an X-ray crystal structure analysis and by NMR spectroscopy. The catalytic activities of the water-soluble trinuclear cations 3a and 3b for the hydrogenation of benzene to give cyclohexane under biphasic conditions are considerably different, the exo isomer 3b being more active than the endo isomer 3a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Robust and air-stable homoleptic group 4 complexes of the type M(L)2 [1-3; M = Ti, Zr, Hf; L = dianionic bis(aryloxide) N-heterocyclic carbene (NHC) ligand] were readily synthesized from the NHC proligand 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)imidazolinium chloride (H3L,Cl) and appropriate group 4 precursors. As deduced from cyclic voltammetry studies, the homoleptic bis-adduct zirconium and hafnium complexes 2 and 3 can also be oxidized, with up to four one-electron-oxidation signals for the zirconium derivative 2 (three reversible signals). Electron paramagnetic resonance data for the one-electron oxidation of complexes 1-3 agree with the formation of ligand-centered species. Compounds 2 and 3 are luminescent upon excitation in the absorption band at 362 nm with emissions at 485 and 534 nm with good quantum yields (ϕ = 0.08 and 0.12) for 2 and 3, respectively. In contrast, the titanium complex 1 does not exhibit luminescent properties upon excitation in the absorption band at 310 and 395 nm. Complexes 2 and 3 constitute the first examples of emissive nonmetallocene group 4 metal complexes.

The new triple-bridged dinuclear cation [(η6-C6Me6)2Ru2(μ2-p-S-C6H4-OH)(μ2-PPh2)(μ2-H)]+, isolated and characterized as the tetrafluoroborate salt, was prepared by reacting the precursor [(η6-C6Me6)2Ru2(μ2-H)2(μ2-PPh2)](BF4) and p-hydroxythiophenol in refluxing ethanol. The single-crystal X-ray structure analysis of [(η6-C12H18)2Ru2(μ2-S-C6H4-OH)(μ2-H){μ2-P(C6H5)2}](BF4) shows the formation of the meso form; despite the two stereogenic centres the complex is not chiral.

An Eglinton-Galbraith diethyne cyclization preferentially yielded a structurally unusual macrocycle, comprising a strained conjugated oligo[2]cruciform wire, forced into a 2.2 nm bow-shape by a terpyridine rein or tether, and stabilized towards light and heat by four insulating triisopropylsilylacetylene (TIPSA) substituents. Spectroscopic ion-binding studies revealed the macrocycle to exhibit a particularly high UV/Vis selectivity for Pd(II) in dilute solution, and one of its precursors to afford a variety of luminescence quenching and color responses to particular metals, suggestive of promising ion-sensor applications. Under more concentrated conditions, the new macrocycle is able to bind specific metals (e.g., Au(I)) within its cavity despite the steric constraints. Intriguingly, variable-temperature (VT) UV/Vis/(1)H NMR investigations showed the TIPSA substituents to undergo restricted intramolecular motions along with reversible changes in the spectroscopic bandgap of the compound with temperature. In line with the theoretical calculations, the VT UV/Vis observations are consistent with a thermal modulation of the electronic conjugation through the strained oligo[2]cruciform bridge, which is coupled with redistributions within a mixture of conformational isomers of the macrocycle with differing relative twisting between the TIPSA-substituted phenyl rings. Overall, the generation of a para-oligo[2]cruciform, bent and flexed over nanoscopic dimensions through conformational tethering within the macrocyclic ring is noteworthy, and suggests a general approach to nanosized, curved, and strained, yet heat- and light-stable, para-phenyleneethynylene oligomers with unique physicochemical properties and challenging theoretical possibilities.

We report in this communication the facile synthesis of the new tris(thiazolylmethyl)amine TTA ligand and the full characterization in solution and in the solid state of two ferrous complexes, [(TTA)FeCl2] and [(TTA)Fe(OTf)2]. TTA, the first example of a simple tris(thiazolemethyl)amine chelate – the second one only within this class of tripods – exerts a weak ligand field and the tertiary amine is weakly bound to the metal centre.