Cationic ruthenium complex of the formula [RuCl(2,6-diacetylpyridine)(PPh3)2]BArF and its catalytic activity in the formation of enol esters

A new ruthenium 2,6-diacetylpyridine complex was synthesized and applied in the atom-economic synthesis of enol esters through Markovnikov-directed addition of carboxylic acids to terminal alkynes. The ruthenium complex [RuCl(dap)(PPh₃)₂]⁺BArF^? was synthesized from [RuCl₂(PPh₃)₂] and the corresponding ligand 2,6-diacetylpyridine (dap). The complex was characterized structurally. The new ruthenium complex was utilized under ambient conditions as a catalyst in the Markovnikov addition of carboxylic acids to terminal alkynes to afford the corresponding enol esters in 93% to 52% isolated yields (85?°C, 16?h reaction time, 1?mol% catalyst loading).     

New indenyl phosphinooxazoline complexes of iron and their catalytic activity in the Mukaiyama aldol reaction

New phosphinooxazoline (PHOX) η⁵-indenyl complexes of iron were synthesized and applied as catalysts in the Mukaiyama aldol reaction. Reaction of three different PHOX ligands with [Fe(η⁵-Ind)I(CO)₂] afforded the iodide salts of three complexes of the general formula [Fe(η⁵-Ind)(CO)(PHOX)]⁺ in 73-81% isolated yields. The molecular structure of one of the new complexes was determined, revealing a pseudo octahedral coordination geometry about the iron center. The iron complexes are catalytically active in the Mukaiyama aldol reaction between aldehydes and 1-(tert-butyldimethylsilyloxy)-1-methoxyethene to give the corresponding aldol adducts (3 mol % catalyst, 15 min, room temperature, 48-83% isolated yields). A previously synthesized iron complex of the general formula [Fe(η⁵-Cp)(CO)(PHOX)]⁺ was found to be catalytically active in the title reaction as well, but needed three hours at room temperature to convert the starting materials to the products.     

Preparation and structural characterization of [RuCl2(CO)2{Te(CH2SiMe3)2}2] and [RuCl2(CO){Te(CH2SiMe3)2}3]

The objective of the present work was to synthesize mononuclear ruthenium complex [RuCl₂(CO)₂{Te(CH₂SiMe₃)₂}₂] (1) by the reaction of Te(CH₂SiMe₃)₂ and [RuCl₂(CO)₃]₂. However, the stoichiometric reaction affords a mixture of 1 and [RuCl₂(CO){Te(CH₂SiMe₃)₂}₃] (2). The X-ray structures show the formation of the cis(Cl), cis(C), trans(Te) isomer of 1 and the cis(Cl), mer(Te) isomer of 2. The ¹²⁵Te NMR spectra of the complexes are reported. The complex distribution depends on the initial molar ratio of the reactants. With an excess of [RuCl₂(CO)₃]₂ only 1 is formed. In addition to the stoichiometric reaction, a mixture of 1 and 2 is observed even when using an excess of Te(CH₂SiMe₃)₂. Complex 1 is, however, always the main product. In these cases the ¹²⁵Te NMR spectra of the reaction solution also indicates the presence of unreacted ligand.     

Synthesis of new C1-symmetric bis(oxazoline) ligands with a chelating sidearm for stereoselective Mukaiyama aldol condensations

Novel C₁-symmetric bis(oxazoline) ligands with a secondary binding sidearm were prepared in enantiomerically pure form in good yields, in only four steps starting from commercially available reagents. These new chiral ligands were tested in the enantioselective Mukaiyama aldol condensation between the trimethylsilyl keteneacetal of methyl isobutyrate and a non-chelating substrate such as benzaldehyde to afford the product in up to 55% ee.     

Hydrolytic cleavage of Schiff bases by [RuCl2(DMSO)4]

New hexa-coordinated Ru(II) complexes of the type [RuCl₂(DMSO)₂(diamine)] (diamine = o-phenylenediamine and ethylenediamine) have been prepared by reacting cis-[RuCl₂(DMSO)₄] with Schiff bases (H₂sal-en, 1; H₂nap-en, 2; H₂sal-o-pdn, 3; H₂nap-o-pdn, 4) in a 1:1 ratio. The ligands, which were expected to act as tetradentate (N₂O₂) chelates under the normal reaction conditions, were found to undergo hydrolytic cleavage to form the diamine and the corresponding aldehyde. All the complexes have been characterized by analytical and spectroscopic (IR, electronic and¹H NMR) data. Single-crystal X-ray analysis of the complex [RuCl₂(DMSO)₂(o-pndn)] revealed that the coordination environment around the ruthenium metal consists of a N₂S₂Cl₂ octahedron.     

The reactions of 2-benzoylpyridine with [RuHCl(CO)(PPh3)3] and [(C6H6)RuCl2]2

The reactions of [RuHCl(CO)(PPh₃)₃] and [(C₆H₆)RuCl₂]₂ with 2-benzoylpyridine have been examined, and two novel ruthenium(II) complexes – [RuCl(CO)(PPh₃)₂(C₅H₄NCOO)] and [RuCl₂(C₁₂H₉NO)₂] – have been obtained. The compounds have been studied by IR and UV–Vis spectroscopy, and X-ray crystallography. The molecular orbital diagrams of the complexes have been calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the compounds have been calculated with the time-dependent DFT method, and the UV–Vis spectra of the compounds have been discussed on this basis.     

Transmetallation reactions of [Sn(R)2(Ph2PC6H4-2-S)2] with metal complexes of the Group 10: Stereoselective synthesis of cis-[M(Ph2PC6H4-2-S)2] (M=Ni, Pd, Pt)

The complexes cis-[M(Ph₂PC₆H₄-2-S)₂] M=Ni, Pd, Pt were stereoselectively synthesized by transmetallation reactions of [M(Cl)₂(NCC₆H₅)₂] M=Pd, Pt or NiCl₂·6H₂O with [Sn(R)₂(Ph₂PC₆H₄-2-S)₂] R=Ph, ⁿBu or ^tBu. The conformation of the Pd and Pt derivatives being unequivocally confirmed by single crystal X-ray diffraction studies showing both metal centers to be into a slightly distorted square planar environment, the main distortion being due to the steric hindrance caused by the aromatic rings in the phosphine moiety.     

Selective formation of trans and cis(CH3CN) isomers of [Ru(bpy)(CO)2(CH3CN)2] (bpy=2,2-bipyridine) from [Ru(CO)2(CH3CN)3]2(PF6)2 using an electrochemical oxidation step

The selective in situ synthesis of trans and cis(CH₃CN)-[Ru(bpy)(CO)₂ (CH₃CN)₂]²⁺ isomers from the same [Ru(CO)₂ (CH₃CN)₃]₂²⁺ dimer precursor but using either an electrochemical-chemical or chemical-electrochemical process is described.     

Tandem transmetallation and oxidative addition reactions of [Sn(R)2(Ph2PC6H4-2-S)2] with transition metal complexes of the Group 9

The reactions of [Sn(Ph)₂(Ph₂PC₆H₄-2-S)₂] with trans -[M(Cl)(CO)(PPh₃)₂] M=Ir, Rh afford the complexes [Rh(Ph₂PC₆H₄-2-S)₂(SnClPh₂)] (1) and [Ir(CO)(Ph₂PC₆H₄-2-S)₂(SnClPh₂)] (2) as final products of two processes, a transmetallation reaction and an oxidative addition process. The crystal structures of both complexes have been determined, showing the rhodium compound to be into a slightly distorted square base pyramidal geometry, while that of the iridium derivative can be described as a distorted octahedron.     

Reaction of [(C6H6)RuCl2]2 with 7,8-benzoquinoline and 8-hydroxyquinoline

The reaction of [(C₆H₆)RuCl₂]₂ with 7,8-benzoquinoline and 8-hydroxyquinoline in methanol were performed. The obtained complexes have been studied by IR, UV–VIS, ¹H and ¹³C NMR spectroscopy and X-ray crystallography. In the reaction with 8-hydroxyquinoline the arene ruthenium(II) complex oxidized to Ru(III). The electronic spectra of the obtained compounds have been calculated using the TDDFT method. Magnetic properties of [Ru(C₉H₆NO)₃] · CH₃OH complex suggest the antiferromagnetic coupling of the ruthenium centers in the crystal lattice. EPR spectrum of [Ru(C₉H₆NO)₃] · CH₃OH compound indicates single isotropic line only characteristic for Ru³⁺ with spin equal to 1/2.     

Ruthenium-tin complexes from the reaction of HSnPh3 with Ru3(CO)10(NCMe)2 and their reactions with bis(tri-t-butylphosphine)platinum

The compounds Ru₃(CO)₉(SnPh₃)₂(NCMe)(μ-H)₂ (1), Ru₃(CO)₁₀(SnPh₃)₂(μ-H)₂ (2), Ru(CO)₄(SnPh₃)₂ (3) and Ru(CO)₄(SnPh₃)(H) (4) were obtained from the reaction of Ru₃(CO)₁₀(NCMe)₂ with HSnPh₃ in hexane solvent. Compounds 1, 3 and the new compound Ru₃(CO)₇(SnPh₃)₃(NCMe)₂(μ-H)₃ (5) were obtained from reaction of Ru₃(CO)₁₀(NCMe)₂ with HSnPh₃ in a CH₂Cl₂ and MeCN solvent mixture. Compound 2 and the new compound Ru₃(CO)₉(SnPh₃)₃(μ-H)₃ (6) were obtained from reactions of 1 and 5 with CO, respectively. Compounds 2 and 6 eliminated benzene when heated to yield Ru₃(CO)₁₀(μ-SnPh₂)₂ (7) and Ru₃(CO)₉(μ-SnPh₂)₃ (8) which contain bridging SnPh₂ ligands. Compound 7 was found to react with to yield the adduct, (9) in 59% yield by the addition of groups to two of the Ru-Sn bonds to the bridging SnPh₂ ligands. Fenske-Hall molecular orbital calculations were performed to provide an understanding of the metal-metal bonding in the clusters of 7 and 9. Compounds 1, 2, 5, 6, 7 and 9 were characterized structurally by single crystal X-ray diffraction analysis.     

Reaction of [CpRu(CH3CN)3]PF6 with bidentate ligands: structural characterization of [{CpRu(CH3CN)2}2(μ-η-dppe)](PF6)2 [dppe=1,2-bis(diphenylphosphino)ethane]

The reaction of [CpRu(CH₃CN)₃]PF₆ with the bidentate ligands L-L=1,2-bis(diphenylphosphino)ethane, dppe, and (1-diphenylarsino-2-diphenylphosphino)ethane, dpadppe, affords mononuclear or dinuclear complexes of formula [CpRu(η²-L-L)(CH₃CN)]PF₆, [{CpRu(CH₃CN)₂}₂(μ-η^1:1-L-L)](PF₆)₂ and [{CpRu(CH₃CN)}₂(μ-η^1:1-L-L)₂](PF₆)₂ (L-L=dppe, dpadppe). All of the compounds are characterized by microanalysis and NMR [¹H and ³¹P{¹H}] spectroscopy. The crystal structure of [{CpRu(CH₃CN)₂}₂(μ-η^1:1-dppe)](PF₆)₂ has been determined by X-ray diffraction analysis. The complex exhibits a dppe ligand bridging two CpRu(CH₃CN)₂ fragments.     

1-Heptyne semihydrogenation catalysed by [PdCl2(NH2(CH2)5CH3)2]

The [PdCl₂(NH₂(CH₂)₅CH₃)₂] complex was tested as catalyst for 1-heptyne semihydrogenation under mild conditions of temperature and pressure in homogeneous and heterogeneous systems. Species were characterized by XPS and FTIR techniques. This revised version was published online in June 2006 with corrections to the Cover Date.     

NMR approach for the identification of dinuclear and mononuclear complexes: The first detection of [Pd(SPh)2(PPh3)2] and [Pd2(SPh)4(PPh3)2] - The intermediate complexes in the catalytic carbon-sulfur bond formation reaction

In the present study we have analyzed the nature of palladium complexes in the catalytic system for selective carbon-sulfur bond formation via the addition of S-S and S-H bonds to alkynes. For the first time the mononuclear and dinuclear palladium complexes were clearly detected by DOSY NMR under the catalytic conditions. It was demonstrated that the concentration of these palladium complexes strongly depends on the amount of phosphine ligand available under reaction conditions.     

Catalytic hydrogenation of 1-hexene with RuCl2(TPPMS)3(DMSO), Part I: Aqueous biphasic system

RuCl₂(TPPMS)₃(DMSO) (complex I) shows good catalytic 1-hexene hydrogenation activity in toluene/water biphasic medium under moderate conditions, reaching 90% conversion in 5 hours, with good hydrogenation selectivity and low isomerization products. The effect of various parameters (temperature, H₂ pressure, reaction time, substrate/catalyst ratio, added electrolytes and other additives) on the hydrogenation reaction were studied. Complex (I) shows good stability in the reaction medium and can be reused several times. This revised version was published online in August 2006 with corrections to the Cover Date.     

[Hg5O2(OH)4][(UO2)2(AsO4)2]: A complex mercury(II) uranyl arsenate

Under mild hydrothermal conditions UO₂(NO₃)₂·6H₂O, Hg₂(NO₃)₂·2H₂O, and Na₂HAsO₄·7H₂O react to form [Hg₅O₂(OH)₄][(UO₂)₂(AsO₄)₂] (HgUAs-1). Single crystal X-ray diffraction experiments reveal that HgUAs-1 possesses a pseudo-layered structure consisting of two types of layers: and . The layers are complex, and contain three crystallographically unique Hg centers. The coordination environments and bond-valence sum calculations indicate that the Hg centers are divalent. The layers belong to the Johannite topological family. The and layers are linked to each other through μ₂-O bridges that include Hg?O=U=O interactions.     

‘Fluorous nanoflow’ system for the Mukaiyama aldol reaction catalyzed by the lowest concentration of the lanthanide complex with bis(perfluorooctanesulfonyl)amide ponytail

‘Fluorous nanoflow’ system is extremely effective for the lanthanide bis(perfluorooctanesulfonyl)amide-catalyzed Mukaiyama aldol reaction with dramatic increase in the reaction rate by the continuously controlled nano feeder. Thus, the acceleration of the aldol reaction was achieved even in the lowest concentration (<0.0001 M) of the lanthanide fluorous catalyst and, hence, the reaction completed within seconds as a bi-phase contact time in the micro cell.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

Synthetic, spectral and catalytic activity studies of ruthenium bipyridine and terpyridine complexes: Implications in the mechanism of the ruthenium(pyridine-2,6-bisoxazoline)(pyridine-2,6-dicarboxylate)-catalyzed asymmetric epoxidation of olefins utilizing H2O2

Various Ru(L₁)(L₂) (1) complexes (L₁ = 2,2′-bipyridines, 2,2′:6′,2″-terpyridines, 6-(4S)-4-phenyl-4,5-dihydro-oxazol-2-yl-2,2′-bipyridinyl or 2,2′-bipyridinyl-6-carboxylate; L₂ = pyridine-2,6-dicarboxylate, pyridine-2-carboxylate or 2,2′-bipyridinyl-6-carboxylate) have been synthesized (or in situ generated) and tested on epoxidation of olefins utilizing 30% aqueous H₂O₂. The complexes containing pyridine-2,6-dicarboxylate show extraordinarily high catalytic activity. Based on the stereoselective performance of chiral ruthenium complexes containing non-racemic 2,2′-bipyridines including 6-[(4S)-4-phenyl-4,5-dihydro-oxazol-2-yl]-[2,2′]bipyridinyl new insights on the reaction intermediates and reaction pathway of the ruthenium-catalyzed enantioselective epoxidation are proposed. In addition, a simplified protocol for epoxidation of olefins using urea hydrogen peroxide complex as oxidizing agent has been developed.     

Rearrangement of phosphinohydrazide ligand -NPh-N(PPh2)2 in transition metal coordination sphere: Synthesis and characterization of nickel and cobalt spirocyclic complexes M(NPh-PPh2N-PPh2)2 and their properties

The reaction of diphosphinohydrazine PhNH-N(PPh₂)₂ (1) with cobalt(II) silylamide, Co[N(SiMe₃)₂]₂, proceeds via formation of unstable phosphinohydrazide complex Co[NPh-N(PPh₂)₂]₂ followed by rearrangement to a new chelating compound Co(NPh-PPh₂N-PPh₂)₂ (2). Disproportionation of nickel(I) silylamide, (Ph₃P)₂Ni-N(SiMe₃)₂, in the presence of 1, yields Ni(0) and Ni(II) phosphinoamide complexes: Ni[(Ph₂P)₂N-NPhH]₂ (3), Ni(NPh-PPh₂N-PPh₂)₂ (4). X-ray analysis reveals tetrahedral environment of the cobalt atom in 2 and square-planar environment of the nickel atom in cis-4. In contrast to the crystalline patterns, the solutions of 2 in THF or toluene have EPR signal which is typical to square-planar low-spin d⁷ cobalt complex. The reactions of 2 with dioxygen, elemental sulfur and diphenyldiazomethane led to the spirocyclic insertion products Co(NPh-PPh₂N-PPh₂X)₂ (X = O, S, NNCPh₂) while the absorption of carbon monoxide is reversible.