Bidentate N,O-prolinate ruthenium benzylidene catalyst highly active in RCM of disubstituted dienes

The synthesis of a bidentate N,O-prolinate ruthenium benzylidene from commercially available starting materials and its activity in ring-closing metathesis of functionalized disubstituted dienes at 30 degrees C is disclosed.     

Silica-immobilized binuclear chromium-molybdenum complexes

ESR and UV spectra of a binuclear complex [n-(C₄H₉)₄N]₃ CrMoOCl₉ in solution and supported on SiO₂ have been studied. Upon fixing this complex followed by oxidation-reduction treatment, a highly disperse state is observed, as evidenced by the ESR spectra of the Cr³⁺ ions.

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[H–(C₄H₉)₄N]₃CrMoOCl₉ SiO₂. - , Cr³⁺.

     

Pyridine as trigger for chloride isomerisation in chelated ruthenium benzylidene complexes: implications for olefin metathesis

The cationic pyridine adduct of a ruthenium complex bearing a chelating benzylidene and an N-heterocyclic carbene was identified as an intermediate during the activation of cis dichloro species and a novel triggering concept for olefin metathesis catalysts based on cationic species was disclosed.     

Strong agostic-type interactions in ruthenium benzylidene complexes containing 7-azaindole based scorpionate ligands

The complexes [Ru(Tai)Cl{=C(H)Ph}(PCy(3))] (4) and [Ru((Ph)Bai)Cl{=C(H)Ph}(PCy(3))] (5) [where Tai = HB(7-azaindolyl)(3) and (Ph)Bai = Ph(H)B(7-azaindolyl)(2)] have been prepared and structurally characterised. The borohydride unit is located in the coordination site trans to the chloride ligand in both complexes. The degree of interaction between the borohydride group and the metal centre was found to be significantly large in both cases. Thermolysis reactions involving complex 4 led to a dehydrogenation reaction forming [Ru(Tai)Cl{PCy(2)(η(2)-C(6)H(9))}] (6) where the benzylidene group acts as a hydrogen acceptor.     

Bimetallic nickel and palladium complexes for catalytic applications

South Africa is a mineral-rich country and one area in which minerals can be very important is catalysis. Over an extended period of time, homogeneous catalysis has grown to become very useful, particularly in the chemical and pharmaceutical industries. The organometallic compounds required in the catalysis industry have advanced from metallocenes to an alternative in the form of a-diimines. Most a-diimines are prepared from iminopyridyl moieties and are most active with nickel and palladium transition metals. This review providesa history of homogeneous catalysis and a discussion on iminopyridines, with the main focus on the nickel and palladium complexes formed from them. There follows a discussion of the bimetallic nickel and palladium complexes in various catalytic applications such as Suzuki and Heck coupling, with the main focus on ethylene polymerisation. The limitations are addressed and possible solutions presented to overcome those challenges. Several reviews in the related topics are to be found in the literature but not the a-diimine with iminopyridines and bimetallic nickel and palladium metals.     

Synthesis,characterization, and catalytic properties of some new ruthenium(II)/(III) complexes containing N,N-donor ligands

This article describes the preparation and characterization of cis-[Ru(bipy)₂L](ClO₄)₂ and trans-[RuCl₂L₂]?·?Cl (bipy?=?2,2′-bipyridyl and L?=?ortho-phenylenediamine (o-phd), 2-aminopyridine (2-apy) and 2-aminobenzonitrile (2-abn), and examines the catalytic oxidations of benzyl alcohol, benzohydrol and pipronyl alcohol by cis-[Ru(bipy)₂ (o-phd)](ClO₄)₂ and trans-[RuCl₂(o-phd)₂]?·?Cl complexes at room temperature and in the presence of N-methyl morpholine-N-oxide (NMO) as co-oxidant.     

Synthesis and catalytic activity of histidine-based NHC ruthenium complexes

Main-chain C,N-protected histidine has been successfully alkylated at both side-chain nitrogens. The corresponding histidinium salt was metallated with ruthenium(II) by a transmetalation procedure, thus providing histidine-derived NHC ruthenium complexes. These bio-inspired complexes show appreciable activity in the catalytic transfer hydrogenation of ketones.     

Synthesis,characterization, catalytic and antimicrobial studies of ruthenium(III) complexes

Ru(III) complexes of the type [RuXB(L)2] have been prepared by the reaction of 3,4-dihydropyrimidin-2(1H)-ones/thiones (HL¹–HL⁴) with the precursors of the type [RuX₃B₃] where X=Cl or Br; B=PPh₃ or AsPh₃ and L is the deprotonated ligand. The synthesized complexes were characterized by physico-chemical methods, electrochemical and magnetic moment data. The catalytic efficiency of the complexes were examined in the oxidation of alcohols and antimicrobial studies were also carried out.      

Spectral,catalytic, and antifungal studies of ruthenium(II) chalcone complexes

Reactions of [RuHCl(CO)(B)(EPh₃)₂] (B = EPh₃ or Py; E = P or As) and chalcones in benzene with equal molar ratio led to the formation of new complexes of the type [RuCl(CO)(EPh₃)(B)(L^1?4)] (B = PPh₃, AsPh₃ or Py; E = P or As; L = chalcone). The new complexes have been characterized by analytical and spectroscopic (IR-, electronic, ¹H-, ³¹P-, and ¹³C-NMR) data. Based on these data, an octahedral structure has been assigned for all the complexes. The chalcones are monobasic bidentate (O,O) donors and coordinate to ruthenium via phenolic and carbonyl oxygen. The new complexes exhibit efficient catalytic activity for the transfer hydrogenation of carbonyl compounds. Antifungal properties of the ligands and their complexes have been examined and compared with standard Bavistin.     

Preparation, characterization, and catalytic properties of ruthenium nitrosyl complexes with polypyrazolylmethane ligands

Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl₃] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm^∗)Ru(NO)Cl₃] [Bpm^∗ = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl₂][PF₆] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm^∗)Ru(NO)Cl₂][PF₆] [Tpm^∗ = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm^∗)Ru(NO)Cl₃] (2) and [(Tpm^∗)Ru(NO)Cl₂][PF₆] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.     

Synthesis,characterization and catalytic studies of ruthenium(II) chalconate complexes

Stable ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh₃)(B)(L)] (E = P or As; B = PPh₃, AsPh₃ or Py; L = 2′‐hydroxychalcones) were synthesized from the reaction of [RuHCl(CO)(EPh₃)₂(B)] (E = P or As; B = PPh₃, AsPh₃ or Py) with 2′‐hydroxychalcones in benzene under reflux. The new complexes were characterized by analytical and spectroscopic (IR, electronic ¹H, ³¹P and ¹³C NMR) data. They were assigned an octahedral structure. The complexes exhibited catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide (NMO) as co‐oxidant and were also found to be efficient transfer hydrogenation catalysts. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,spectral, and catalytic studies of ruthenium(II) unsymmetrical Schiff-base complexes

Unsymmetrically-substituted ruthenium(II) Schiff-base complexes, [Ru(CO)(B)(L ^x )] [B = PPh₃, AsPh₃ or Py; L ^x = dianion of tetradentate unsymmetrical Schiff-base ligand; x = 4–7, L⁴ = salen-o-hyac, L⁵ = valen-o-hyac, L⁶ = salphen-o-hyac, L⁷ = valen-2-hacn], were prepared and characterized by analytical, IR, electronic, and ¹H NMR spectral studies. The new complexes were tested for their catalytic activity towards the oxidation of benzylalcohol to benzaldehyde.     

Palladium and half sandwich ruthenium(II) complexes of selenated and tellurated benzotriazoles: Synthesis, structural aspects and catalytic applications

1-(Phenylselenomethyl)-1H-benzotriazole (L¹) and 1-(4-methoxyphenyltelluromethyl)-1H-benzotriazole (L²) have been synthesized by reacting 1-(chloromethyl)-1H-benzotriazole with in situ generated nucleophiles PhSe⁻ and ArTe⁻, respectively. The complexes of L¹ and L² with Pd(II) and Ru(II)(η⁶-p-cymene) have been synthesized. Proton, carbon-13, Se-77 and/or Te-125 NMR spectra authenticate both the ligands and their complexes. The single crystal structures of L¹, L² and [RuCl(η⁶-p-cymene)(L)][PF₆] (L = L¹: 3, L = L²: 4) have been solved. The Ru-Se and Ru-Te bond lengths have been found 2.4801(11) and 2.6183(10) Å, respectively. The palladium complexes, [PdCl₂(L)] (L = L¹: 1, L = L²: 2) have been explored for Heck and Suzuki-Miyaura C-C coupling reactions. The TON values are upto 95,000. The Ru-complexes have been found promising for catalytic oxidation of alcohols (TON ∼ 7.8-9.4 × 10⁴). The complexes of telluroether ligands are as efficient catalysts as those of selenoether ones and in fact better for catalytic oxidation.     

Mononuclear ruthenium complexes containing chiral aminooxazolines: Syntheses, X-ray studies and catalytic activity

The synthesis and characterisation of three novel mononuclear ruthenium(II) complexes containing one of the following chiral auxiliary ligands: 2-amino-(4R)-phenyl-2-oxazoline (amphox), indanyl-2-amino-(4R,5S)-2-oxazoline (aminox) or indanyl-(2′-anilinyl)-(4R,5S)-2-oxazoline (aninox) is described using [Ru₂Cl₄(η⁶-p-cym)₂] (p-cym = 1-isopropyl-4-methylbenzene) as the Ru starting material. The new complexes have been identified as the neutral derivatives [RuCl₂(η⁶-p-cym)(amphox-κ¹N_ox)] (1), [RuCl₂(η⁶-p-cym)(aminox-κ¹N_ox)] (2) and the salt [RuCl(η⁶-p-cym)(aninox-κ²N,N′)]Cl (3). These materials have been fully characterised (elemental analysis, NMR, IR, conductance, MS, etc.) and, in the case of 2 and 3, structurally elucidated in the solid-state using single crystal X-ray diffraction methods. All three complexes show good catalytic activity (max. conversion >99%, TOF = 424 h⁻¹) but only modest enantio-selectivity (max. ee = 40%) for the transfer hydrogenation reaction of acetophenone with isopropyl alcohol. The complexes were also tested in an asymmetric Diels-Alder reaction involving cyclopentadiene and acrolein (max. conversion >99%, TOF = 42 h⁻¹). In this case, the diastereo-selectivity was good to moderate (max. de = 84%), but the ee values were poor (max. ee = 12%).     

Synthesis,characterization and catalytic studies of ruthenium(II) Schiff base complexes

Complexes of the type [Ru(CO)(EPh₃)(B)(L)] (E = P or As; B = PPh₃, AsPh₃, py or pip; L = dianion of the Schiff bases derived from the condensation of salicyloyl hydrazide with acetone, ethyl methyl ketone and salicylaldehyde have been synthesised by the reaction of equimolar amounts of [RuHCl(CO)(EPh₃)₂(B)] and Schiff bases in benzene. The resulting complexes have been characterized by analytical and spectral (i.r., electronic, n.m.r.) data. The arrangements of Ph₃P groups around the Ru metal was determined from ³¹P-n.m.r. spectra. An octahedral structure has been assigned to all the new complexes. All the complexes exhibit catalytic activity for the oxidation of benzyl alcohol and cyclohexanol in the presence of N-methylmorpholine-N-oxide as co-oxidant.     

Ruthenium titanocene and ruthenium titanium half-sandwich bimetallic complexes in catalytic cyclopropanation

The reaction of the phosphine functionalised titanium half-sandwich complexes 7, 9 and 10 with the binuclear complex [(p-cymene)RuCl₂]₂ allowed the access to three new early-late bimetallic complexes (p-cymene)[(μ-η⁵:η¹-C₅H₄(CH₂)_nPR₂)TiX₃]RuCl₂ (11-13). The structure of 11 (n = 0, X = Cl) has been confirmed by X-ray diffraction. The ruthenium titanium half-sandwich bimetallic complexes so formed and the ruthenium titanocene analogues 4-6 catalyse the addition of ethyl diazoacetate to styrene with high selectivity toward cyclopropanation versus metathesis contrary to the monometallic complexes (p-cymene)RuCl₂PR₃.     

Structures, preparation and catalytic activity of ruthenium cyclopentadienyl complexes based on pyridyl-phosphine ligand

Ruthenium complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) and [(η⁵-C₅H₅)Ru(κ²-P-N-PPh₂Py)(PPh₃)]⁺ (1a) containing diphenyl-2-pyridylphosphine (PPh₂Py) are reported. Coordinated PPh₂Py in the complex [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) exhibits monodentate behavior. In presence of NH₄PF₆ in methanol at room temperature it afforded chelated complex [(η⁵-C₅H₅)Ru(κ²-P,N-PPh₂Py)(PPh₃)]⁺ (1a). Further, 1 reacted with various species viz., CH₃CN, NaCN, NH₄SCN and NaN₃ to afford cationic and neutral complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L]⁺ and [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L] [L = CH₃CN (1b); CN⁻ (1c); N₃⁻ (1d) and SCN⁻ (1e)] and it’s reaction with N,N-donor chelating ligands dimethylglyoxime (H₂dmg) and 1,2-phenylenediamine (pda) gave cationic complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(κ²-N-N)]PF₆ [κ²-N-N = dmg (1f) and pda (1g)]. The complexes 1-1g have been characterized by physicochemical techniques and crystal structures of 1, 1a, 1c, 1e and 1f have been determined by single crystal X-ray analyses. Catalytic potential of the complex 1 has been evaluated in water under aerobic conditions. It was observed that the complex 1 selectively catalyzes reduction of aldehyde into alcohol.     

Synthesis and catalytic properties of novel ruthenium N-heterocyclic-carbene complexes

The reaction of [RuCl₂(p-cymene)]₂ with 1,3-dialkylimidazolinium salts 1a–f in the presence of a small excess of cesium carbonate yields chelated η⁶-arene, η¹-carbene ruthenium complexes 2a–f. All synthesised compounds were characterized by elemental analysis, NMR spectroscopy. The catalytic activity of RuCl₂(η⁶-arene, η¹-imidazolinylidene) complexes 2a–f was evaluated in the direct arylation of 2-phenylpyridine with chlorobenzene derivatives.