Synthesis and catalytic activity of some cationic complexes of rhodium(I) with norbornadiene and group Vb ligands

Summary The syntheses of [Rh(NBD)L₂ ]ClO₄ complexes (L=nitrogen donor ligand), obtained from [Rh(NBD)₂]ClO₄, and their reactions with triphenylphosphine and carbon monoxide are described.The catalytic activity of some of these and related complexes is considered.     

Synthesis, structures and anti-malaria activity of some gold(I) phosphine complexes containing seleno- and thiosemicarbazonato ligands

A series of both mono- and dinuclear gold(I) phosphine complexes containing monoanionic seleno- and thiosemicarbazones as ligands were prepared and fully characterized by spectroscopic methods and, in some cases, by single crystal X-ray diffraction. The in vitro anti-malaria activity of some of these compounds was investigated in chloroquine sensitive strains of Plasmodium falciparum. The IC(50) results show that the sulfur containing compounds exhibit activity similar to that of chloroquine, whilst the selenium derivatives display only moderate anti-malaria activity.     

Preparation and catalytic activity of cationic rhodium(I) and iridium(I) complexes with phosphine sulphide ligands

The preparation and properties of cationic rhodium and iridium complexes of types [M(diolefin)L₂](ClO₄) and [M(diolefin)L(PPh₃)](ClO₄) [M = Rh, diolefin = 1,5-cyclooctadiene (COD) or 2,5-norbornadiene; M = Ir, diolefin = COD; L = phosphine sulphide] are described. The complexes have been characterized by IR, ¹H NMR and ³¹P NMR spectroscopy. The use of [M(diolefin)L₂](ClO₄) as catalyst precursors in homogeneous hydrogenation of olefins has been studied.     

Synthesis, characterization and catalytic activity of three palladium(II) complexes containing Schiff base ligands

Three new Pd(II) complexes of Schiff base ligands, namely, [Pd₄(L¹)₄] (1), [Pd₂(L²)₂Cl₂] (2) and [Pd(L³)₂Cl₂] (3) [HL ¹ ?=?N-(benzylidene)-2-aminophenol; L ² ?=?N-(2,4-dichlorobenzylidene)-2,6-diethylbenzenamine, L ³ ?=?4-(2,4-dichlorobenzylide-neamino)phenol] have been synthesized using solvothermal methods and characterized by elemental analysis, spectroscopy and single crystal X-ray diffraction. The crystal structures of the free ligands were also determined. The ??-oxygen-bridged tetranuclear cyclometallated Pd(II) complex (1) contains four nearly planar units, in which Pd^II is four-coordinate. Complex 2 is a ??-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas complex 3 is mononuclear. The Heck reactions of bromobenzene with acrylic acid catalyzed by complexes 1?C3 have also been studied.     

Dinickel(II) complexes: preparation and catalytic activity

Ligands (L(a-c)) based on 2,7-bis(3,5-di-R-pyrazol-1-yl)-1,8-naphthyridine (a, R = H; b, R = CH(3); c, R = Ph) were prepared for the construction of a series of dinickel complexes. Treatment of L(x) with NiCl(2) in an anhydrous methanol/THF solution resulted in the formation of dinuclear complexes [(L(x))(μ-Cl)(2)Ni(2)Cl(2)(CH(3)OH)(2)] (3, x = a; 4, x = b; 5, x = c). These new complexes were characterized by elemental analysis, IR and UV-Vis spectroscopic techniques. The structures of complexes 3 and 4 were further confirmed by X-ray diffraction studies. Interestingly, crystals of 4 were obtained as a co-crystallization of 4 and the methanol substituted species [{(L(b))(μ-Cl)(2)Ni(2)Cl(CH(3)OH)(3)}Cl] (4'). These dinickel complexes have been tested in the catalytic homo-coupling of terminal alkynes with the use O(2) as the oxidant, showing excellent activities. A clear improvement on the catalytic activity of these complexes is observed as compared to the mono-nuclear species.     

Anionic and neutral rhodium(I) complexes containing trichlorostannato ligands

The complexes Et₄N[Rh(SnCl₃)₂(diolefin)(PR₃)] (diolefin = COD or NBD) have been isolated and their reactions studied. Reaction with arylic tertiary phosphines led to SnCl₃⁻ displacement and isolation of neutral pentacoordinated Rh(SnCl₃)(diolefin)(PR₃)₂ complexes. Reaction with carbon monoxide involved diolefin displacement when the diolefin was COD, thus giving Et₄N[Rh(SnCl₃)₂(CO)₂(PR₃)] compounds, but SnCl₃⁻ displacement when it was NBD, thus yielding Rh(SnCl₃)(CO)(NBD)(PR₃) complexes. The complexes [Rh(diolefin)Cl]₂ were found to react with triarylphosphines in the presence of SnCl₂ and with CO bubbling through the solution to give Rh(SnCl₃)(CO)(NBD)(PR₃) when the diolefin was NBD but Rh(Cl)(CO)(PR₃)₂ when the diolefin was COD.     

Synthesis and catalytic activity of rhenium carbonyl complexes containing alkyl-substituted tetramethylcyclopentadienyl ligands

A series of six alkyl-substituted tetramethylcyclopentadienyl mononuclear metal carbonyl complexes [(η ⁵-C₅Me₄R)Re(CO)₃] [R = allyl (1), i-Pr (2), n-butyl (3), t-butyl (4), benzyl (5), CH(CH₂)₄ (6)] have been synthesized by treating the corresponding ligands (C₅Me₄R) [R = allyl, i-Pr, n-butyl, t-butyl, benzyl, CH(CH₂)₄] with Re₂(CO)₁₀ in refluxing xylene. The six new complexes were characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. The crystal structures of all six complexes were determined by X-ray crystal diffraction analysis, showing that they have similar molecular structures, being mononuclear carbonyl complexes. In each of these complexes, the Re atom is η ⁵ -coordinated to the cyclopentadienyl ring. Complexes 1–5 have significant catalytic activity in Friedel–Crafts reactions of aromatic compounds with alkylation reagents. Compared with traditional catalysts, these mononuclear rhenium carbonyl complexes have obvious advantages such as lower amounts of catalyst, mild reaction conditions and environmentally friendly chemistry.     

Synthesis and catalytic activity of some cationic rhodium(I) complexes with substituted quinolines

Summary The synthesis and properties of cationic complexes of the type [Rh(NBD)L₂]ClO₄, [Rh(NBD)L(PPh₃)]ClO₄ and [Rh(CO)L(PPh₃)₂]ClO₄ (L = substituted quinolines) are described. The diolefin complexes catalyse hydrogen transfer from isopropanol to some unsaturated substrates.     

New copper(I) isocyanide complexes containing other donor ligands

The preparation and physical properties of some new copper (I) isocyanide complexes containing other neutral donor ligands such as Ph₃P, pyridine(Py), 1,10- phenanthroline (Phen), bipyridine (Bipy), or 1,2-bis(diphhenylphosphino)ethane (Dipphos) are described. Possible structures for these new complexes, in the solid state and in solution, are discussed.     

Synthesis and catalytic activity of some π-allylic bis(trifluorophosphine)(triphenylphosphine)cobalt(I) complexes

The syntheses of Co(π-all)(PF₃)₂(PPh₃) complexes (π-all = π-allyl, anti-1-Me-π-allyl, syn-1-Me-π-allyl, 1,1-dimethyl-π-allyl, anti-1,2-diMe-π-allyl, syn,syn-1,3-diMe-π-allyl, 2Et-π-allyl, π-cyclooctenyl, h³-π-cycloheptadienyl) are described. ¹H and ¹⁹F NMR data are presented and discussed in relation to the structures of the complexes. The compound Co(π-C₅H₉)(PF₃)(PPh₃)₂ is also reported. Several of the π-allylic complexes are found to be active catalysts for the isomerisation of 1-octene to 2-octene under a hydrogen atmosphere.     

Synthesis,crystal structure and catalytic activity of ruthenium(II) carbonyl complexes containing ONO and ONS donor ligands

Diamagnetic ruthenium(II) complexes of the type [Ru(L)(CO)(B)(EPh₃)] [where E = As, B = AsPh₃; E = P, B = PPh₃, py (or) pip and L = dibasic tridentate ligands dehydroacetic acid semicarbazone (abbreviated as dhasc) or dehydroacetic acid phenyl thiosemicarbazone (abbreviated as dhaptsc)] were synthesized from the reaction of [RuHCl(CO)(B)(EPh₃)₂] (where E = As, B = AsPh₃; E = P, B = PPh₃, py (or) pip) with different tridentate chelating ligands derived from dehydroacetic acid with semicarbazide or phenylthiosemicarbazide. All the complexes have been characterized by elemental analysis, FT-IR, UV–Vis and ¹H NMR spectral methods. The coordination mode of the ligands and the geometry of the complexes were confirmed by single crystal X-ray crystallography of one of the complexes [Ru(dhaptsc)(CO)(PPh₃)₂] (5). All the complexes are redox active and are monitored by cyclic voltammetric technique. Further, the catalytic efficiency of one of the ruthenium complexes (5) was determined in the case of oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine-N-oxide.     

Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thiazoleacetic acid (HL²), and 2-mercaptobenzothiazole (HL³) have been investigated. Neutral complexes [RuCl(CO)(PPh₃)₂(HL¹)] (1), [RuCl(CO)(PPh₃)₂(HL²)] (2), [RuCl(CO)(PPh₃)₂(HL³)] (3), [Ru(PPh₃)₂(HL¹)₂] (4), [RuCl(PPh₃)₃(HL²)] (5), and [RuCl(PPh₃)₃(HL³)] (6) imparting κ²-S,N-bonded ligands have been isolated from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh₂Py) to give neutral κ¹-P bonded complexes [RuCl(CO)(κ¹-P-PPh₂Py)₂(HL¹)] (7), and [Ru(κ¹-P-PPh₂Py)₂(HL¹)₂] (8). Complexes 1-8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption) and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallographically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL¹-HL³) to ruthenium as κ²-N,S-thiolates and presence of rare intermolecular S-S weak bonding interaction in complex 1.     

Structural and catalytic aspects of copper(II) complexes containing 2,6-bis(imino)pyridyl ligands

The synthesis, structure, and ligand substitution mechanism of a new five-coordinate trigonal-bipyramidal copper(II) complex, [Cu^II(py ^tBuMe₂N₃)Cl₂] (1), with a sterically constrained py ^tBuMe₂N₃ chelate ligand, py ^tBuMe₂N₃?=?2,6-bis-(ketimino)pyridyl, are reported. The kinetics and mechanism of chloride substitution by thiourea, as a function of nucleophile concentration, temperature, and pressure, were studied in detail and compared with an earlier study reported for the analogous complex [Cu^II(py ^tBuN₃)Cl₂] (2) [py ^tBuN₃?=?2,6-bis-(aldimino)pyridyl]. Catalysis of the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone by 1 and 2 was studied. Correlations between the reactivity, chloride substitution behavior, and reduction potentials of both complexes were made. These show that the rate of oxidation is independent of the rate of chloride substitution, indicating that the substitution of chloride by catechol as substrate occurs in a fast step. Spectral data show a non-linear relationship between the ability of the complexes to oxidize 3,5-DTBC and the Lewis acidity of their copper(II) centers. Electrochemical data demonstrate that the most effective complex 1 has a E ⁰ value that approaches the E ⁰ value of the natural tyrosinase enzyme.     

Synthesis,reactions and catalytic activity of some mixed trifluorophosphine(triphenylphosphine)hydrido complexes of cobalt(I)

The complexes CoH(PF₃)_4?n (PPh₃)_n (n = 1–3) have been prepared by low from the reaction between CoH(PF₃)(PPh₃)₃ and butadiene. The hydrido complexes are active catalysts for the isomerisation of 1-octene to 2-octene under hydrogen or nitrogen.     

Synthesis, characterization and antitumor activity study of some cyclometalated organoplatinum(II) complexes containing aromatic N-donor ligands

A general approach has been designed to synthesize some mononuclear and binuclear cyclometalated platinum(II) complexes, containing aromatic N-donor ligands with the presence of one Cl⁻trans to carbon. In this way, cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, C^N = N(1),C(2′)-chelated, deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was used as a precursor to react with imidazole derivatives (1-methylimidazole, 2a, imidazole, 2b,), monodentate pyridine derivatives (4-methylpyridine, 2c, pyridine, 2d,) and bidentate pyridine derivative (4,4′-bipyridine, 3 and 4,). Synthesized complexes were fully characterized by using multinuclear NMR spectroscopy (¹H, ¹³C{¹H} and ¹⁹⁵Pt), correlation NMR spectroscopy (¹H-¹H COSY, ¹³C{¹H}-¹H Heteronuclear Multiple Quantum Correlation, HMQC, Heteronuclear Multiple Bond Correlation, HMBC, ¹⁵N-¹H HETCOR), elemental analysis, X-ray crystallography and ESI-Mass spectrometry. Antitumor effects of mononuclear cyclometalated platinum(II) complexes 2a, 2c, 2d and 3 were determined on Jurkat, K562, and Raji cell lines and results showed reasonable cytotoxicities.     

Photophysical properties of copper(I) and zinc(II) complexes containing phosphinoquinoline ligands

Several copper(I) and zinc(II) complexes with 8-(diphenylphosphino)quinoline (PPh₂qn) or 8-diphenylphosphinoquinaldine (PPh₂qna) have been prepared. These ligands contain both imine and phosphine moieties, which can act as coordinating groups. X-ray analysis of the Cu(I) complexes reveals that [Cu(PPh₂qn)₂]PF₆ (Cu-1) and [Cu(PPh₂qn)₂]PF₆ (Cu-2), coordinated by two PPh₂qn and PPh₂qna ligands respectively, are obtained. In the Zn(II) complexes, a structural study shows that [ZnCl₂(PPh₂qn)] (Zn-1), [ZnBr₂(PPh₂qn)] (Zn-2) and [ZnI₂(PPh₂qn)] (Zn-3) are coordinated by one PPh₂qn ligand and two of the corresponding halogeno ligands (Cl⁻, Br⁻ and I⁻). In the solid state Cu-1 and Cu-2 show luminescence which is assigned to a ³MLCT transition involving π∗ of the quinoline group, as shown in the [Cu(dmp)(diphosphine)]⁺ complexes; due to the reduced bulkiness of the coordination sphere around the copper atom, no emission is observed in solution. Zn-1 shows a similar emission band to that of free PPh₂qn at both room temperature and 77 K. It suggests the emission bands should be assigned to a ligand-centered (LC) transition. In the solid state, it is found that the emissive energy of the complexes shift to lower energy and the energy depends on the halogeno ligands in the zinc complexes.