Novel and efficient approach to (Z)-4-trifluoroethylidene-1,3-dioxolane derivatives via (trifluoromethyl)ethynylation of ketones and aldehydes

Perfluoroalkylated 4-trifluoroethylidene-1,3-dioxolanes 2a-p were prepared in quantitative yields from the reaction of new stable (trifluoromethyl)ethynylation reagent 1a with TBAF at −15 °C for 10 min, followed by treatment with phenyl perfluoroalkylated ketones at room temperature. The use of aldehydes under the same reaction condition afforded 1,3-dioxolanes 2q-r in good yields. The reaction of 1a with TBAF, followed by treatment with aldehydes or ketones at −15 °C for 10 min and then with trifluoroacetophenone at room temperature provided 1,3-dioxolane derivatives 2s-t in good yields. Tetrabutylammonium trifluoropropynylide [II] was treated with benzaldehyde derivatives at −15 °C for 10 min, followed by treatment with trifluoroacetophenone, to give the corresponding 1,3-dioxolanes 2u-z and 1,3-dioxines 3u-z with different reaction condition.     

Synthesis, crystal structure and biological activities of four novel tetranuclear di-organotin(IV) carboxylates

Four complexes: [Bu₂(L₁)SnOSn(L₁)Bu₂]₂ (1), [Bu₂(L₂)SnOSn(L₂)Bu₂]₂ (2), [Bu₂(L₃)SnOSn(L₃)Bu₂]₂ (3), and [Bu₂(L₄)SnOSn(L₄)Bu₂]₂ (4), (HL₁ = 2-(4-methylbenzoyl)benzoic acid, HL₂ = 2-(2,4-diethylbenzoyl)benzoic acid, HL₃ = 2-(4-chlorobenzoyl)benzoic acid, HL₄ = 2-(4-isopropylbenzoyl)benzoic acid) have been prepared and structurally characterized by means of elemental analysis and vibrational, ¹H NMR and FT-IR spectroscopies. The crystal structures of all complexes have been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement. Each structure is centro-symmetric and features a central rhombus Sn₂O₂ unit with two additional tin atoms linked at the O atoms. Complex 1 exhibited good antibacterial and antitumor activities and have a potential to be used as drugs.     

The preparation of [closo-1-CB9H8-1-COOH-10-(4-C3H7C5H9S)] as intermediate to polar liquid crystals

The preparation of iodo acid [closo-1-CB₉H₈-1-COOH-10-I]⁻ (1) is optimized and scaled from 1 to 40 g of B₁₀H₁₄. The improved preparation of the [arachno-6-CB₉H₁₃-6-COOH]⁻ (5) uses four times smaller volume and can be run conveniently in up to 40 g scale in a 3-L vessel. The optimized oxidation of 5 to [closo-2-CB₉H₉-2-COOH]⁻ (4) requires less oxidant, 12 times smaller volume, and significantly shorter reaction time. The overall yields of the iodo acid 1 as the [NMe₄]⁺ salt are typically 8-10% (10-12 g) for 40 g of B₁₀H₁₄. The iodo acid 1 was transformed to amino acid 8, then to dinitrogen acid 10, and finally to sulfonium acid 2[3] in overall yield of about 13%. The search for a more efficient phosphine ligand for the Pd-catalyzed amination process was not fruitful. Three routes to the sulfonium acid 2[n] were investigated, and the best yield of about 47% was obtained for Cs₂CO₃-assisted cycloalkylation. Liquid crystalline ester of acid 2[3] and 4-butoxyphenol was prepared and investigated.     

Cobalt complexes of terpyridine ligands: Crystal structure and nuclease activity

Cobalt(II) (1) and cobalt(III) (2) complexes of tridentate ligand, imidazole terpyridine (Itpy), have been synthesized and characterized by both spectroscopic and electrochemical techniques. Single crystal X-ray diffraction studies of complexes 1 and 2 shows that the complexes belong to monoclinic crystal system, with the two Itpy ligands coordinated to the central metal ion. The binding behavior of both the cobalt complexes to calf thymus DNA has been investigated by UV–Vis, fluorescence spectroscopy, viscosity and electrochemical measurements. The results suggest that complexes 1 and 2 bind to DNA through intercalation. The intrinsic DNA binding constant values obtained from absorption spectral titration studies were found to be (5.07 ± 0.12) × 10³ M⁻¹ and (7.46 ± 0.16) × 10³ M⁻¹, respectively, for complexes 1 and 2. Gel electrophoresis studies with the cobalt complexes show that while complex 1 cleaves DNA in the presence of hydrogen peroxide, complex 2 cleaves DNA in the presence of ascorbic acid and hydrogen peroxide.     

Self-assembly of di- and triorganotin(IV) complexes: Syntheses, characterization and crystal structures of 1D polymeric chain containing O,O-diethyl or O,O-diisopropyl phosphoric acid ligands

A series of organotin(IV) complexes with O,O-diethyl phosphoric acid (L¹H) and O,O-diisopropyl phosphoric acid (L²H) of the types: [R₃Sn · L]_n (L = L¹, R = Ph 1, R = PhCH₂2, R = Me 3, R = Bu 4; L = L², R = Ph 9, R = PhCH₂10, R = Me 11, R = Bu 12), [R₂Cl Sn · L]_n (L = L¹, R = Me 5, R = Ph 6, R = PhCH₂7, R = Bu 8; L = L², R = Me 13, R = Ph 14, R = PhCH₂15, R = Bu 16), have been synthesized. All complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy analysis. Among them, complexes 1, 2, 3, 5, 8, 9 and 11 have been characterized by X-ray crystallography diffraction analysis. In the crystalline state, the complexes adopt infinite 1D infinite chain structures which are generated by the bidentate bridging phosphonate ligands and the five-coordinated tin centers.     

Synthesis, structural characterization, and initial electroluminescent properties of bis-cycloiridiated complexes of 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine

A series of bis-cyclometalated Ir(III) complexes (8-10, 12, 15, 17, 19, 21, 23, 25, 28, 29 and 33) bearing two chromophoric N^∧C cyclometalated ligands derived from 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1) and a third nonchromophoric ligand has been synthesized. A palladium-catalyzed cross-coupling reaction between 2-chloro-4-methylpyridine (2) and 3,5-bis(trifluoromethyl)phenylboronic acid (3) was used to prepare 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1). Cyclometalation of (1) by IrCl₃ was carried out in (MeO)₃PO, with the formation of chloro-bridged dimer [N^∧C]₂Ir(μ-Cl)₂Ir[C^∧N]₂ (8). Reaction of (8) with lithium 2,4-pentanedionate, lithium 2,2,6,6-tetramethyl-heptane-3,5-dionate (13), dipivaloyltrimethylsilylphosphine (14), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadione (16), 1,1,1,3,3,3-hexafluoro-2-pyridin-2-yl-propan-2-ol (18), 1,1,1,3,3,3-hexafluoro-2-pyrazol-1-ylmethyl-propan-2-ol (20), 2-diphenylphosphanylethanol (22), and 1-diphenylphosphanylpropan-2-ol (24), afforded octahedral iridium complexes 9, 12, 15, 17, 19, 21, 23 and 25, respectively. Complex 10, which contains three different ligands (L₁ = N^∧C of 1; L₂ = N^∧C of 4,4′-dimethyl-[2,2′]bipyridinyl 4; L₃ = O^∧O of 2,4-pentanedione), and complex 11, which contains no cyclometalated ligands (L₁ = 4; L₂ = L₃ = Cl; L₄ = O^∧O of 2,4-pentanedione) were also isolated as minor products in a one-pot reaction between a 94:5 mixture of 1 and 4, IrCl₃ and lithium 2,4-pentanedionate. Reaction of 8 with diphenylphosphanylmethanol (27) in 1,2-dichloroethane unexpectedly led to complexes 28 and 29. The reactions of 8 with benzoylformic acid resulted in the formation of hydroxyl-bridged dimer [N^∧C]₂Ir(μ-OH)₂Ir[C^∧N]₂ (33). According to X-ray analyses, Ir-to-Ir distances in the crystal cell increase from 6.86 Å for 10 to 13.31 Å for 33. The angle theta, which represents the twisting of two cyclometalated C-Ir-N planes relative to each other, varies from 97.5° for 21 to 90.76 for complex 28. OLED devices were fabricated from several Ir complexes and preliminary results are discussed.     

Nickel (II) complexes bearing 2-ethylcarboxylate-6-iminopyridyl ligands: synthesis, structures and their catalytic behavior for ethylene oligomerization and polymerization

A series of nickel (II) complexes (L)NiCl₂ (7-9) and (L)NiBr₂ (10-12) were prepared by the reactions of the corresponding 2-carboxylate-6-iminopyridine ligands 1-6 with NiCl₂ · 6H₂O or (DME)NiBr₂ (DME = 1,2-dimethoxyethane), respectively. All the complexes were characterized by IR spectroscopy and elemental analysis. Solid-state structures of 7, 8, 10, 11 and 12 were determined by X-ray diffraction. In the cases of 7, 8 and 10, the ligands chelate with the nickel centers in tridentate fashion in which the carbonyl oxygen atoms coordinate with the metal centers, while the carbonyl oxygen atoms are free from coordinating with the nickel centers in 11 and 12. Upon activation with methylaluminoxane (MAO), these complexes are active for ethylene oligomerization (up to 7.97 × 10⁵ g mol⁻¹ (Ni) h⁻¹ for 11 with 2 equivalents of PPh₃ as auxiliary ligand) and/or polymerization (1.37 × 10⁴ g mol⁻¹ (Ni) h⁻¹ for 9). The ethylene oligomerization activities of 7-12 were significantly improved in the presence of PPh₃ as auxiliary ligands. The effects of the coordination environment and reaction conditions on the ethylene catalytic behaviors have been discussed.     

Synthesis, characterization and fluorimetric studies of novel photoactive poly(amide-imide) from anthracene 9-carboxaldehyde and 4,4′-diaminodiphenyl ether by microwave irradiation

Trimellitic anhydride acid chloride (2) was obtained by the reaction of trimellitic anhydride (1) and excess amount of thionyl chloride. The acid chloride was reacted with 4,4′-diaminodiphenyl ether (3), and produced the monomer 4. Anthracene-9-carboxaldehyde (5) was reacted with sulfuryl chloride to produce anthracene-9-carboxylic acid chloride (6) in a quantitative yield. Through the reaction of 6 and 2,4,6-triamino-1,3,5-triazine (7), the monomer 8 was produced in high yield. Two monomers were characterized by ¹H NMR and FT-IR spectroscopy, and then were used in the polymerization reaction. A new facile and rapid polycondensation reaction of the two monomers was performed by using a domestic microwave oven. The polymerization reaction proceeded rapidly, compared with the conventional solution polycondensation and was completed within 10 min, producing a photoactive poly(amide-imide) in a quantitative yield. The resulting polymer was characterized by IR, ¹H NMR and TGA techniques. Thermogravimetric analysis indicated that polymer 9 was thermally stable in nitrogen atmosphere. In addition the initial decomposition temperature, 5% and 10% weight loss (T5, T10) were 284, 356 and 408 °C. The residual weight percent at 700 °C was 51.5%, which shows it is moderately thermally stable. Fluorescence properties of polymer 9 were investigated in several solvents. The ideal concentration of each case was determined by fluorescence self quenching phenomena. Also the self quenching mechanism was studied according to the specific behavior of the polymer in different solvents.     

The cyclopalladation reaction of 2-phenylaniline revisited

2-Phenylaniline reacted with Pd(OAc)₂ in toluene at room temperature for 24 h in a one-to-one molar ratio and with the system PdCl₂, NaCl and NaOAc in a 1 (2-phenylaniline):1 (PdCl₂):2 (NaCl):1 (NaOAc) molar ratio in methanol at room temperature for one week to give the dinuclear cyclopalladated compounds (μ-X)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ [1a (X = OAc) and 1b (X = Cl)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)₂ in one-to-one molar ratio in acid acetic at 60 °C for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ (1c) in moderate yield. A parallel treatment, but using monodeuterated acetic acid (DOAc) as solvent in the cyclopalladation reaction, allowed isolation of a mixture of compounds 1c, 1c_d1 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄](μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃] and 1c_d2 (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃}]₂ in moderate yield and with a deuterium content of ca. 60%. 1a and 1b reacted with pyridine and PPh₃ affording the mononuclear cyclopalladated compounds [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(X)(L)] [2a (X = OAc, L = py), 2b (X = Cl, L = py), 3a (X = OAc, L = PPh₃) and 3b (X = Cl, L = PPh₃)] in a yield from moderate to high. Furthermore, 1a reacted with Na(acac) · H₂O to give the mononuclear cyclopalladated compound 4 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(acac)] in moderate yield. ¹H NMR studies in CDCl₃ solution of 2a, 2b, 3a, 3b and 4 showed that 2a and 3a presented an intramolecular hydrogen bond between the acetato ligand and the amino group, and were involved in a dynamic equilibrium with water present in the CDCl₃ solvent; and that the enantiomeric molecules of 2b and 4 were in a fast exchange at room temperature, while they were in a slow exchange for 2a, 3a and 3b. The X-ray crystal structures of 3b and 4 were determined. 3b crystallized in the triclinic space group with a = 9.9170(10), b = 10.4750(10), c = 12.0890(10) Å, α = 98.610(10)°, β = 94.034(10)° and γ = 99.000(10)° and 4 in the monoclinic space group P2₁/a with a = 11.5900(10), b = 11.2730(10), c = 12.2150(10) Å, α = 90°, β = 107.6560(10)° and γ = 90°.     

Ethylene polymerization catalyzed by Pd-based β-ketoiminato complexes/MAO systems

The substituted β-ketoiminato palladium(II) complexes, Pd[CH₃C(O)CHC(NAr)CH₃](Pph₃)(Me) (1 Ar = α-napthyl, 2 Ar = fluorenyl), can be prepared from the reaction of (COD)PdMeCl and Pph₃ with the appropriate ligand. After activation of 1 and 2 with methylaluminoxane (MAO), the resulting palladium(II) complexes are used as catalysts for ethylene polymerization, yielding linear polyethylene. The effects of temperature, co-catalyst to catalyst molar ratio and polymerization time on catalyst activities are reported. The catalyst activity decreases above −20 °C due to catalyst deactivation and optimum co-catalyst to catalyst ratio is 300:1.     

Platinum-catalyzed double silylations of alkynes with bis(dichlorosilyl)methanes

Bis(dichlorosilyl)methanes 1 undergo the two kind reactions of a double hydrosilylation and a dehydrogenative double silylation with alkynes 2 such as acetylene and activated phenyl-substituted acetylenes in the presence of Speier’s catalyst to give 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes 4 as cyclic products, respectively, depending upon the molecular structures of both bis(dichlorosilyl)methanes (1) and alkynes (2). Simple bis(dichlorosilyl)methane (1a) reacted with alkynes [R¹-CC-R²: R¹ = H, R² = H (2a), Ph (2b); R¹ = R² = Ph (2c)] at 80 °C to afford 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 as the double hydrosilylation products in fair to good yields (33-84%). Among these reactions, the reaction with 2c gave a trans-4,5-diphenyl-1,1,3,3-tetrachloro-1,3-disilacyclopentane 3ac in the highest yield (84%). When a variety of bis(dichlorosilyl)(silyl)methanes [(Me_nCl_3 − nSi)CH(SiHCl₂)₂: n = 0 (1b), 1 (1c), 2 (1d), 3 (1e)] were applied in the reaction with alkyne (2c) under the same reaction conditions. The double hydrosilylation products, 2-silyl-1,1,3,3-tetrachloro-1,3-disilacyclopentanes (3), were obtained in fair to excellent yields (38-98%). The yields of compound 3 deceased as follows: n = 1 > 2 > 3 > 0. The reaction of alkynes (2a-c) with 1c under the same conditions gave one of two type products of 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes (4): simple alkyne 2a and terminal 2b gave the latter products 4ca and 4cb in 91% and 57% yields, respectively, while internal alkyne 2c afforded the former cyclic products 3cc with trans form between two phenyl groups at the 3- and 4-carbon atoms in 98% yield, respectively. Among platinum compounds such as Speier’s catalyst, PtCl₂(PEt₃)₂, Pt(PPh₃)₂(C₂H₄), Pt(PPh₃)₄, Pt[ViMeSiO]₄, and Pt/C, Speier’s catalyst was the best catalyst for such silylation reactions.     

Catalytic applications of Cu-containing MOFs based on N-heterocyclic ligand in the oxidative coupling of 2,6-dimethylphenol

Two Cu^II complexes bearing a N-heterocyclic ligand, namely [Cu(SO₄)(pbbm)]_n (1) and {[Cu(Ac)₂(pbbm)] · CH₃OH}_n (2) (pbbm = 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole) have been synthesized with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that new polymeric complex 1 features 1-D double-chain framework. The catalytic studies on 1 and 2 indicate that they are efficient homogeneous catalysts for the oxidative coupling of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) and diphenoquinone (DPQ) with H₂O₂ as oxidant and NaOMe as co-catalyst at room temperature. Optimal reaction conditions are obtained by examining the effects of solvent, the reaction time, temperature as well as the amounts of co-catalyst, catalyst and oxidant. Under the optimal conditions, the selectivity to PPE is almost up to 90% for both complexes, and the conversion of DMP is 85% for 1 and 90% for 2, comparable to those observed for highly active catalyst systems in the literature. Further comparison of their catalytic performances with those of the corresponding copper salt together with organic ligand, copper salt alone and free ligand reveals that the coordination of ligand to Cu^II ion plays a key role in generating the superior reactivities of complexes.     

Cation-anion interactions involving hydrogen bonds: Syntheses and crystal structures study of hexafluorotitanate(IV) salts with pyridine and methyl substituted pyridines

Fluorotitanates (LH)₂[TiF₆]·nH₂O (1: R = pyridine, n = 1, 2: R = 2-picoline, n = 2, 3: R = 2,6-lutidine, n = 0, 4: R = 2,4,6-collidine, n = 0) and (LH)[TiF₅(H₂O)] (3a: L = 2,6-lutidine) have been synthesized by the reaction of pyridine or corresponding methyl substituted pyridines and titanium dioxide dissolved in hydrofluoric acid. The crystal structures of ionic compounds 1, 2, 3, 3a and 4 have been determined by single-crystal X-ray diffraction analysis. The hydrogen bonding led to the formation of discrete (LH)₂[TiF₆] units (4), chains (1-3), and layers (3a). The additional π-π interactions present in 1, 2, and 4 results in chain structures of 1 and 4 and in a layer structure of 2. The [TiF₆]²⁻ and [TiF₅(H₂O)]⁻ anions were observed by ¹⁹F NMR spectroscopy in aqueous solutions of 1, 2, 3, 3a and 4.     

Aqueous syntheses of [(Cp-R)M(CO)3] type complexes (Cp = cyclopentadienyl, M = Mn, Tc, Re) with bioactive functionalities

We describe reactions of [^99mTc(H₂O)₃(CO)₃)]⁺ (1) with Diels-Alder products of cyclopentadiene such as “Thiele’s acid” (HCp-COOH)₂ (2) and derivatives thereof in which the corresponding [(Cp-COOH)^99mTc(CO)₃)] (3) complex did form in water. We propose a metal mediated Diels-Alder reaction mechanism. To show that this reaction was not limited to carboxylate groups, we synthesized conjugates of 2 (HCp-CONHR)₂ (4a-c) (4a, R = benzyl amine; 4b, R = N_α-Boc-l-2,3-diaminopropionic acid and 4c, R = glycine). The corresponding ^99mTc complexes [(4a)^99mTc(CO)₃)] 6a, [(4b)^99mTc(CO)₃)] 6b and [(4c)^99mTc(CO)₃)] 6c have been prepared along the same route as for Thiele’s acid in aqueous media demonstrating the general applicability of this synthetic strategy. The authenticity of the ^99mTc complexes on the no carrier added level have been confirmed by chromatographic comparison with the structurally characterized manganese or rhenium complexes.Studies of the reaction of 1 with Thiele’s acid bound to a solid phase resin demonstrated the formation of [(Cp-COOH)^99mTc(CO)₃)] 3 in a heterogeneous reaction. This is the first evidence for the formation of no carrier added ^99mTc radiopharmaceuticals containing cyclopentadienyl ligands via solid phase syntheses. Macroscopically, the manganese analogue 5a and the rhenium complexes 5b-c have been prepared and characterized by IR, NMR, ESI-MS and X-ray crystallography for 5a (monoclinic, P2₁/c, a = 9.8696(2) Å, b = 25.8533(4) Å, c = 11.8414(2) Å, β = 98.7322(17)°) in order to unambiguously assign the authenticity of the corresponding ^99mTc complexes.     

2-Oxazoline/benzoxazole-1,10-phenanthrolinylmetal (iron, cobalt or nickel) dichloride: Synthesis, characterization and their catalytic reactivity for the ethylene oligomerization

Series of 2-benzoxazole-1,10-phenanthrolines (L1-L4) and 2-oxazoline-1,10-phenanthrolines (L5-L8) were synthesized and used as tridentate N^N^N ligands in coordinating with metal (nickel, cobalt or iron) chlorides. Their metal complexes, nickel(II) (Ni1-Ni8), cobalt(II) (Co1-Co8) and iron(II) (Fe1-Fe8), were characterized by elemental and IR spectroscopic analyses. The molecular structures of the ligand L2 and the complexes Ni3, Co1, Co3 and Fe2 have been determined by the single-crystal crystallography. The nickel complex Ni3 and iron complex Fe2 display an octahedral geometry, whereas cobalt complex Co1 is with a distorted bipyramidal geometry and Co3 as square pyramidal geometry. At 10 atm ethylene, all the complexes showed good activities in ethylene dimerization upon activation with appropriate aluminum cocatalysts; the nickel complexes gave the activity up to 3.11 × 10⁶ g mol⁻¹(Ni) h⁻¹ upon activation with diethylaluminum chloride (Et₂AlCl), meanwhile the cobalt and iron complexes showed activities up to 1.51 × 10⁶ g mol⁻¹(Co) h⁻¹ and 1.89 × 10⁶ g mol⁻¹(Fe) h⁻¹, individually, upon activation with modified methylaluminoxane (MMAO).     

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.     

Design and synthesis of (E)-4-((3-ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid

(E)-4-((3-Ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid, 6, was synthesized in 87% starting from β-cyclocitral. The target compound 6 was synthesized starting from 1 via a Grignard reaction to form alcohol 2. Compound 2 was converted to Wittig salt 3 by treatment with aldehyde 4 in butyllithium and hexane at −78 °C to form ester 5. Ester 5 was saponified and, following acidification, acid 6 was isolated as white solid yield 87%.     

Synthesis, characterisation and catalytic activities of manganese(III) complexes of pyridoxal-based ONNO donor tetradenatate ligands

Reaction of Mn^II(CH₃COO)₂ with dibasic tetradentate ligands, N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-en, I), N,N′-propylenebis(pyridoxylideneiminato) (H₂pydx-1,3-pn, II) and 1-methyl-N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-1,2-pn, III) followed by aerial oxidation in the presence of LiCl gives complexes [Mn^III(pydx-en)Cl(H₂O)] (1) [Mn^III(pydx-1,3-pn)Cl(CH₃OH)] (2) and [Mn^III(pydx-1,2-pn)Cl(H₂O)] (3), respectively. Crystal and molecular structures of [Mn(pydx-en)Cl(H₂O)] (1) and [Mn(pydx-1,3-pn)Cl(CH₃OH)] (2) confirm their octahedral geometry and the coordination of ligands through ONNO(2-) form. Reaction of manganese(II)-exchanged zeolite-Y with these ligands in refluxing methanol followed by aerial oxidation in the presence of NaCl leads to the formation of the corresponding zeolite-Y encapsulated complexes, abbreviated herein as [Mn^III(pydx-en)]-Y (4), [Mn^III(pydx-1,3-pn)]-Y (5) and [Mn^III(pydx-1,2-pn)]-Y (6). These encapsulated complexes are used as catalysts for the oxidation, by H₂O₂, of methyl phenyl sulfide, styrene and benzoin efficiently. Oxidation of methyl phenyl sulfide under the optimized reaction conditions gave ca. 86% conversion with two major products methyl phenyl sulfoxide and methyl phenyl sulfone in the ca. 70% and 30% selectivity, respectively. Oxidation of styrene catalyzed by these complexes gave at least five products namely styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde with a maximum of 76.9% conversion of styrene by 4, 76.3% by 5 and 76.0% by 6 under optimized conditions. The selectivity of the obtained products followed the order: benzaldehyde > benzoic acid > styrene oxide > phenylacetaldehyde > 1-phenylethane-1,2-diol. Similarly, ca. 93% conversion of benzoin was obtained by these catalysts, where the selectivity of the products followed the order benzil > benzoic acid > benzaldehyde-dimethylacetal. Tests for the recyclability and heterogeneity of the reactions have also been carried. Neat complexes are equally active. However, the recycle ability of encapsulated complexes makes them better over neat ones.     

Two-carbon homologation of ketones via sily ketene acetals: Synthesis of α,β-unsaturated acids and α-trimethylsilyl δ-ketoacids

The reaction of C,O,O-tris(trimethylsilyl)ketene acetal 1 with saturated, cyclic and aromatic ketones 2 proceeds smoothly in the presence of titanium chloride to give (E)-α,β-unsaturated carboxylic acids 3 with fairly good stereoselectivity. With α,β-unsaturated ketones 4, α-trimethylsilyl δ-ketoacids 5 (syn + anti) are obtained according to Michael-type 1,4 addition. These diastereoisomers are separated and the configurations of 5a are achieved by X-ray molecular analysis.     

Self-assembly syntheses and crystal structures of triorganotin(IV) pyridinecarboxylate: 1D polymers and a 42-membered macrocycle

A series of new triorganotin(IV) pyridinecarboxylates with 6-hydroxynicotinic acid (6-OH-3-nicH), 5-hydroxynicotinic acid (5-OH-3-nicH) and 2-hydroxyisonicotinic acid (2-OH-4-isonicH) of the types: [R₃Sn (6-OH-3-nic)·L]_n (I) (R = Ph, L = Ph·EtOH, 1; R = Bn, L = H₂O·EtOH, 2; R = Me, L = 0, 3; R = n-Bu, L = 0, 4), [R₃Sn (5-OH-3-nic)]_n (II) (R = Ph, 5; R = Bn, 6; R = Me, 7; R = n-Bu, 8), [R₃Sn (2-OH-4-isonic·L)]_n (III) (R = Bn, 9, L = MeOH; R = Me, L = 0, 10; R = Ph, 11, L = 0.5EtOH) have been synthesized. All the complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy analyses. Among them, except for complexes 5 and 6, all complexes were also characterized by X-ray crystallography diffraction analysis. Crystal structures show that complexes 1-10 adopt 1D infinite chain structures which are generated by the bidentate O, O or N, O and the five-coordinated tin centers. Significant O-H?O, and N-H?O intermolecular hydrogen bonds stabilize these structures. Complex 11 is a 42-membered macrocycle containing six tin atoms, and forms a 2D network by intermolecular N-H?O hydrogen.