Differentiation of planar chiral enantiomers of 〚Cp*M(2-alkyl-Phenoxo)〛 〚BF4〛 {M = Rh,Ir} by the trisphat anion

Precursor oxo-dienyl rhodium and iridium complexes 〚(η⁵-Cp*)M(η⁵-2-alkyl-oxodienyl)〛 〚BF₄〛 (2a–c) were prepared according to literature procedure. Addition of 〚n-Bu₄N〛 〚Δ-trisphat〛 (6) to a CD₂Cl₂ solution of these chiral derivatives has led to the NMR differentiation of the enantiomers. These results pave the way towards the preparation of enantiomerically pure o-quinone methide complexes.     

Classical and non-classical iron hydrides: synthesis,NMR characterisation,theoretical investigation and X-ray crystal structure of the iron(IV) dihydride 〚Cp*Fe(dppe)(H)2〛+BF4–

Protonation of Cp*Fe(dppe)H (1; Cp* = η⁵-C₅Me₅, dppe = Ph₂PCH₂CH₂PPh₂) by HBF₄Et₂O at –80 °C in diethylether affords the dihydrogen complex 〚Cp*Fe(dppe)(η²-H₂)〛⁺BF₄^– (2⁺BF₄^–) in 90% yield. Its PF₆^– salt analogue (2⁺PF₆^–) is obtained in 94% yield by reaction between the 16-electron derivative 〚Cp*Fe(dppe)〛⁺PF₆^– (3⁺PF₆^–) with H₂ gas at –80 °C. The presence of a bound dihydrogen ligand in 2⁺ is indicated by a short T₁ minimum values consistent with a H–H distances of 0.98(1) Å. For the partially deuterated derivative 2⁺–d₁, the observed J_HD value of 27.0 Hz confirms the presence of the coordinated dihydrogen ligand, which displays an H–H separation of 0.97(1) Å, in complete agreement with the distance calculated using the T₁ static rotation model. Variable temperature NMR study shows the gradual, complete and irreversible transformation of the dihydrogen complex into its classical dihydride isomer trans-〚Cp*Fe(dppe)(H)₂〛⁺ (4⁺). Thermal solid state reaction (–20 °C, 48 h) of 2⁺BF₄^– gives quantitatively 4⁺BF₄^–, whereas 4⁺PF₆^– is obtained by simple contact of H₂ with a solution of 3⁺PF₆^– in THF at room temperature. The crystal structure of 4⁺BF₄^– has been determined and shows a transoid arrangement of hydride ligands, consistent with the formulation of 4⁺ as an iron(IV) dihydride. DFT calculations on both dihydride and dihydrogen isomers of 〚Cp*Fe(dppe)H₂〛⁺ indicate that 4⁺ is more stable than 2⁺ by 0.19 eV, while this energy difference is reversed in the case of 〚CpFe(dpe)H₂〛⁺ (dpe = H₂PCH₂CH₂PH₂). The preference for the dihydride form in the case of 〚Cp*Fe(dppe)H₂〛⁺ and of the dihydrogen one in the case of 〚CpFe(dpe)H₂〛⁺ is due to the larger π-donor and σ-acceptor abilities of the 〚Cp*Fe(dppe)〛⁺ fragment, as compared to the 〚CpFe(dpe)〛⁺ unit.     

Synthesis and structure of dimeric Rh-bis(tertiary phosphine) complexes,exceptionally useful synthetic precursors

Removal of the MeOH and hydrogen from the known cis,trans,cis-Rh^III-dihydrido complexes 〚Rh(H)₂(PR₃)₂(MeOH)₂〛PF₆ (R = Ph, p-tolyl) results in formation of the dimeric species 〚Rh₂(PR₃)₄〛〚PF₆〛₂; X-ray analysis shows the complexes to be 〚(Ph₃P)Rh(μ-PhPPh₂)〛₂〚PF₆〛₂ (and the p-tolyl analogue) containing bridged η⁶-arene moieties, while ¹H and ¹³C NMR data in CD₂Cl₂ provide evidence for η⁴-coordination of the arene within the dimer. In more strongly coordinating solvents, formation of cis-〚Rh(PR₃)₂(solvent)₂〛PF₆ is observed, while formation of 〚(PR₃)₂Rh(η⁶-toluene)〛PF₆ is evident in toluene solution, and this exists in equilibrium with the bis(solvent) species in the presence, for example, of acetone or MeOH. At ambient conditions, none of the arene-containing complexes effected catalytic H₂-hydrogenation of toluene.     

‘A rendezvous with an old flame’: revisiting olefin hydrogenation with new rhodium and iridium catalysts

A novel tridentate hemilabile ligand 2 containing phosphine, imine and pyridyl donor groups has been prepared in analogy with the synthesis of the known related ligand 1. The reaction of 1 or 2 with 〚Rh(COE)₂Cl〛₂ resulted in the formation of the neutral complexes 〚Rh(L)Cl〛. By a method using 〚M(diene)Cl〛₂ as starting material, cationic complexes of the type 〚M(diene)(L)〛X were also obtained (M = Rh, diene = NBD, L = 1, 2; M = Ir, diene = COD, L = 1; X = BF₄, OTf). A comparative study of the catalytic activity of the new complexes towards the hydrogenation of various olefins has been reported. In particular, the catalysts of the type 〚Rh(L)Cl〛 are remarkably active when prepared in situ, especially for the reduction of hindered olefins.     

Assembly and encapsulation of coordination tectons driven by hydrogen-bondingand space-filling

The synthesis and characterisation of 〚Fe(L^I)₃〛₂〚Fe(H₂O)₆〛(ClO₄)₆ (2), L^I = 1,10-phenanthroline-5,6-dione, is described. The crystal structure 2 is an unprecedented example of two-dimensional non-covalent array made up of 〚Fe(L^I)₃〛²⁺ species assembled by 〚Fe(H₂O)₆〛²⁺ cations encapsulated in pseudo-hexagonal cages. These cages are sustained by 12 hydrogen bonds established between the coordinated water molecules and the dione groups of six alternating Δ, Λ chiral 〚Fe(L^I)₃〛²⁺ moieties.     

Synthèse des 2-hydroxy-7-〚benzimidazol-2-yl〛-méthyl-5-méthylpyrazolo〚1,5-a〛pyrimidines à partir de la 4-hydroxy-6-méthylpyran-2-one

Condensation of 3-amino-5-hydroxypyrazole 1 with triacetic acid lactone 2 in refluxed alcohols afforded 2-hydroxy-5,7-dimethylpyrazolo〚1,5-a〛pyrimidine 3 beside to 7-alkoxycarbonylmethyl-2-hydroxy-5- methylpyrazolo〚1,5-a〛pyrimidine 4. Action of hydrazine on compounds 4 yielded 7-hydrazinocarbonylmethyl-2-hydroxy-5-methylpyrazolo〚1,5-a〛pyrimidine 5. Condensation of o-phenylenediamines 6 with hydrazide 5 to melting reactants afforded 2-hydroxy-7-〚benzimidazol-2-yl〛methyl-5-methylpyrazolo〚1,5-a〛pyrimidines 7. Structures of the obtained products have been assigned by means of spectroscopic measurements.     

Dédoublement et détermination des excès énantiomériques des complexes de ruthéniumII hexacoordinés 〚Ru(bpy)2ppy〛+ et 〚Ru(bpy)2Quo〛+ (bpy = bipyridine,ppy = phénylpyridine,Quo = 8-quinolate) utilisés comme templates dans la construction de réseaux anioniques tridimensionnels

The bimetallic networks coordinated with oxalate bridges {〚M^IIM^III(C₂O₄)₃〛^–C⁺〛}_n form an important family of molecular magnets. The role of the cation C⁺ is fundamental for the nature of the obtained network (bi- or tridimensional). Thus, tridimensional polymers can be obtained in optically active forms using monocationic resolved templates such as 〚Ru(bpy)₂ppy〛⁺ 1 and 〚Ru(bpy)₂Quo〛⁺ 2. These cations were synthesized and resolved. A ¹H NMR technique based on the formation of diastereomeric salts obtained with optically active anion 〚ΔTrisphat〛^– {Trisphat = tris(tetrachlorobenzenediolato)phosphate(V)} was used to measure the enantiomeric excesses. To cite this article: M. Brissard et al., C. R. Chimie 5 (2002) 53–58     

How well do we understand self-assembly algorithms? From prototype grid to polymers

Algorithms used for the assembly of metallosupramolecular constructs are simple and based upon well-established principles of coordination chemistry. The multinucleating ligand 3,6-bis(2-pyridyl)pyridazine forms a 〚2 × 2〛 grid with copper(I); the related ligand 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (dptz) is expected to behave in a similar manner with silver(I). However, instead of the expected grid, 〚Ag(dptz)₂〛⁺ solution species are formed. In the solid state, dinuclear 〚Ag₂(dptz)₂〛²⁺ and polymeric 〚{Ag(dptz-N,N’)(μ-dptz)}_n〛ⁿ⁺ complexes have been structurally characterised.     

Synthèse de nouvelles 7 (5)-〚benzimidazol-2-yl〛méthyl-2 (7)-méthyl-1,2,4-triazolo〚1,5-a〛(〚4,3-a〛)pyrimidines

Condensation of 4-hydroxy-6-methyl pyran-2-one 2 with 3-amino-1,2,4-triazole 1 in refluxing alcohol afforded 5-alkoxycarbonylmethyl-7-methyl-1,2,4-triazolo〚1,5-a〛pyrimidines and their isomers 5-alkoxycarbonylmethyl-7-methyl-1,2,4-triazolo〚4,3,-a〛pyrimidines 4. Reaction of hydrazine hydrate with compounds 4 and 5 yielded the corresponding hydrazid acids 6 and 7. Condensation of o-phenylenediamines 8 with esters 3(4) in refluxing xylol or with hydrazid acid 6(7) by melting reagents afforded 7(5)-〚benzimidazol-2-yl〛methyl-5(7)methyl-1,2,4-triazolo〚1,5-a〛(〚4,3-a〛)pyrimidines 9(10). The structures of the annealed compounds have been elucidated by their ¹H, ¹³C NMR and Mass Spectroscopy data.     

Synthesis of tridentate 2,6-bis(imino)pyridyl aminechlorohydro ruthenium(II) complexes: The convenient use of amine hydrochlorides to generate metal-hydride

The reaction of low-valent ruthenium complexes with 2,6-bis(imino)pyridine ligand, [η²-N₃]Ru(η⁶-Ar) (1) or {[N₃]Ru}₂(μ-N₂) (2) with amine hydrochlorides generates six-coordinate chlorohydro ruthenium (II) complexes with amine ligands, [N₃]Ru(H)(Cl)(amine) (4). Either complex 1 or 2 activates amine hydrochlorides 3, and the amines coordinate to the ruthenium center to give complex 4. This is a convenient and useful synthetic approach to form ruthenium complexes with amine and hydride ligands using amine hydrochloride.     

Group 4 metallocene complexes with pendant nitrile groups

The preparation of a new functionalized cyclopentadienyl ligand bearing a nitrile pendant substituent, (C₅H₄CMe₂CH₂CN)^? is reported. The corresponding lithium salt of this ligand (1) was prepared by the reaction of in situ lithiated acetonitrile with 6,6-dimethylfulvene. The ligand was subsequently utilized for the synthesis of group 4 metal complexes [(η⁵–C₅H₄CMe₂CH₂CN)₂MCl₂] (M = Ti, 2; M = Zr, 3; M = Hf, 4), [(η⁵–C₅H₅) (η⁵–C₅H₄CMe₂CH₂CN)MCl₂] (M = Ti, 7; M = Zr, 8), and [(η⁵-C₅Me₅) (η⁵ C₅H₄CMe₂CH₂CN)₂ZrCl₂] (9). Alternative route to 2 comprised the preparation of half-sandwich complex [(η⁵–C₅H₄CMe₂CH₂CN)TiCl₃] (6). The prepared compounds were characterized by common spectroscopic methods and the solid state structures of complexes 2, 3, 4, 7, and 9 were determined by the single-crystal X-ray diffraction analysis. In addition, compound 7 was converted to the corresponding dimethyl derivative [(η⁵–C₅H₅) (η⁵–C₅H₄CMe₂CH₂CN)TiMe₂] (10) and also treated with the chloride anion abstractor Li[B(C₆F₅)₄] to generate the cationic complex with the coordinated nitrile group, as suggested by the NMR spectroscopy. A formation of yet another cationic complex was observed upon treating compound 10 with (Ph₃C)[B(C₆F₅)₄].     

Trihydridoruthenium(IV) complexes: preparation and photo-induced H/D exchange reaction

The trihydrides (η⁵-C₅Me₅RuH₃(PR₃ = PMe₃, FEt₃, Pipr₃, PCy₃, PPh₂Me, and PPh₃) (2) are formed in the reaction of paramagnetic (η⁵C₅Me₅)RuCl₂(PR₃) (1) with NaBH₄ in ethanol. The reaction of 1 with NaBH₄, in THF yields intermediary tetrahydroborate complexes (η⁵-C₅Me₅)Ru(PR₃)(BH₄) (3), which are converted to the trihydrides 2 by treatment with ethanol. Irradiation of 2c and 2f in C₆D₆ solution with UV light causes H/D exchange reaction among the solvent, hydride ligands, and the coordinated phosphine.     

Efficient alkylation of ketones with primary alcohols catalyzed by ruthenium(II)/P,N ligand complexes

An efficient catalytic system containing [RuCl₂(η⁶-p-cymene)]₂ and one P,N ligand, N-diphenylphosphino-2-aminopyridine (L1) was loaded in catalyzing the alkylation of ketones with primary alcohols for a diverse array of substrates. Other five P,N ligands based on pyridin-2-amine and pyrimidin-2-amine were also examined in this reaction to explore the influence of steric hindrance and electronic effects. Monitoring by ¹H NMR and ESI-MS reveals a stable cationic L1-coordinated ruthenium hydride intermediate, identified as [Ru(η⁶-p-cymene)(κ²-L1)H]⁺. Organic intermediates consistent with a three-step dehydrogenation, alkylation and hydrogenation pathway were also observed. The final step in this reaction, the ruthenium-catalysed transfer hydrogenation reduction of α,β-unsaturated ketone with benzyl alcohol was performed separately.     

Transfer hydrogenation of ketones catalysed by half‐sandwich (η6‐p‐cymene) ruthenium(II) complexes incorporating benzoylhydrazone ligands

Neutral half‐sandwich η⁶‐p ‐cymene ruthenium(II) complexes of general formula [Ru(η⁶‐p ‐cymene)Cl(L)] (HL = monobasic O, N bidendate benzoylhydrazone ligand) have been synthesized from the reaction of [Ru(η⁶‐p ‐cymene)(μ‐Cl)Cl]₂ with acetophenone benzoylhydrazone ligands. All the complexes have been characterized using analytical and spectroscopic (Fourier transform infrared, UV–visible, ¹H NMR, ¹³C NMR) techniques. The molecular structures of three of the complexes have been determined using single‐crystal X‐ray diffraction, indicating a pseudo‐octahedral geometry around the ruthenium(II) ion. All the ruthenium(II) arene complexes were explored as catalysts for transfer hydrogenation of a wide range of aromatic, cyclic and aliphatic ketones with 2‐propanol using 0.1 mol% catalyst loading, and conversions of up to 100% were obtained. Further, the influence of other variables on the transfer hydrogenation reaction, such as base, temperature, catalyst loading and substrate scope, was also investigated.     

Catalytic hydrogenation reactions by a monobenzene complex of ruthenium, [Ru(η6-C6H6)(CH3CN)3](BF4)2, in biphasic medium

The water soluble monobenzene complex of ruthenium, [Ru(η⁶-C₆H₆)(CH₃CN)₃](BF₄)₂ (1) is an effective catalyst or catalyst precursor for the hydrogenation of olefinic functions in benzene/H₂O biphasic medium. The catalyst can be recycled by simple decantation. Complex 1 is capable of catalyzing H/D exchange reaction between H₂ and D₂O. A two-loop reaction mechanism for the catalytic hydrogenation reactions with 1 is postulated. In this mechanism, water acts as the base to assist the heterolytic hydrogen cleavage in one of the loops, but is not an active participant in the other.     

Preparation and reactivity of half-sandwich hydrazine complexes of ruthenium and osmium

Hydrazine complexes [MCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ (1–6) [M = Ru, Os; R = H, Me, Ph; L = P(OEt)₃, PPh(OEt)₂, PPh₂OEt] were prepared by allowing dichloro complexes MCl₂(η⁶-p-cymene)L to react with hydrazines RNHNH₂ in the presence of NaBPh₄. Treatment of ruthenium complexes [RuCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ with Pb(OAc)₄ led to acetate complex [Ru(κ²–O₂CCH₃)(η⁶-p-cymene)L]BPh₄ (7). Instead, the reaction of osmium derivatives [OsCl(η⁶-p-cymene)(CH₃NHNH₂)L]BPh₄ with Pb(OAc)₄ afforded the methyldiazenido complex [Os(CH₃N₂)(η⁶-p-cymene)L}]BPh₄ (8). Treatment with HCl of this diazenido complex 8 led to the methyldiazene cation [OsCl(CH₃NNH)(η⁶-p-cymene)L}]⁺ (9⁺). The complexes were characterised spectroscopically and by X-ray crystal structure determination of [OsCl(η⁶-p-cymene)(PhNHNH₂){PPh(OEt)₂}]BPh₄ (6b) and [Ru(κ²–O₂CCH₃)(η⁶-p-cymene){PPh(OEt)₂}]BPh₄ (7b).     

Coordination de la phosphine organo-fer [CpFeIIC6Me5CH2PPh2]+ au RhI et proprietes spectroscopiques,electrochimiques et catalytiques des complexes heterobinucleaires FeII-RhI

The reactions between the phosphine-organoiron [CpFe^II-η⁶-C₆Me₅CH₂PPh₂]⁺ PF₆^? (1) and [RhCl(η⁴-diolefin)(μ-Cl)]₂ in CH₂Cl₂ at reflux give the new heterobinuclear air-stable crystalline complexes [CpFe^II-η⁶-C₆Me₅CH₂)P(Ph)₂Rh(η⁴-diene)Cl]PF₆,(D'*-diene=cyclooctadiene (COD): 65%, 2; trimethylfluorobenzobicyclo[2.2.2]octadiene (Me₃TFB): 48%, 3). Complexes 2 and 3 have been studied by ¹H, ¹³C and ³¹P NMR spectroscopy and they are carbonylated (CO, 1 atm). Cyclic voltammetry experiments with addition of MeOH show electron transfer Fe^IRh^I → Fe^IIRh⁰, the presence of a catalytic wave Fe^I/Fe^II and the possible formation of Rh hydrides. Under normal conditions 2 is a catalyst for hydrogenation of cyclohexene, but it is less efficient than the known mononuclear Rh¹ analogues.     

Hydrogenation of single and multiple N-N or N-O bonds by Ru(II) catalysts in homogeneous phase

The ruthenium(II) complexes RuH₂(CO)₂(PⁿBu₃)₂, RuH₂(CO)₂(PPh₃)₂, and RuH₂(PPh₃)₄ are catalytically active in the hydrogenation of organic substrates containing a NN, N(O)N or NO₂ group. The reduction of the first two groups leads to hydrazine as intermediate and amine as the final product, while reducing a NO₂ group the corresponding amine is selectively formed. A complete conversion was reached, depending on temperature, catalyst and substrate concentration. The catalysts are also active in the hydrogenolysis of an N-N group giving the corresponding amine with a 97.3% conversion using RuH₂(PPh₃)₄ as catalyst. A first-order reaction rate with respect to substrate, catalyst or hydrogen pressure was detected in all cases. Finally, the activation parameters and the kinetic constants of these reactions were calculated. In the hydrogenation of azobenzene, the rate determining step involves an associative or a dissociative step depending on the catalyst employed while in the hydrogenation of all other substrates an associative rate determining step is always involved. A catalytic cycle is suggested for the hydrogenation of azobenzene, taking into account the intermediate complexes identified in the reaction medium.     

Synthèse et propriétés biologiques des pyrazolo〚4,3-c〛triazolo〚4,3-a〛〚1,5〛benzodiazépines

The addition of carbon disulfide to 3(5)-N-〚methyl (ethyl)-2-aminophenyl amino-5(3)-phenylpyrazole 3 (4) afforded 10-methyl (ethyl)-3-phenylpyrazolo〚4,3-c〛 〚1,5〛 benzodiazepine-4-thione 7 (8). These compounds reacted with alkyl halides and acetylhydrazide or benzoylhydrazide, to afford new heterocyclic systems: pyrazolo 〚4,3-c〛 triazolo〚4,3-a〛-1,5-benzodiazepines 15–18. Biological properties of compounds 8, 9, 16 and 17 have been evaluated.