The Transfer Hydrogenation of Cinnamaldehyde Using Homogeneous Cobalt(II) and Nickel(II) (E)-1-(Pyridin-2-yl)-N-(3-(triethoxysilyl)propyl)methanimine and the Complexes Anchored on Fe3O4 Support as Pre-Catalysts: An Experimental and In Silico Approach.

The imino pyridine Schiff base cobalt(II) and nickel(II) complexes (C1 and C2) and their functionalised γ-Fe3O4 counterparts (Fe3O4@C1 and Fe3O4@C2) were synthesised and characterised using IR, elemental analysis, and ESI-MS for C1 and C2, and single crystal X-ray diffraction for C1, while the functionalised materials Fe3O4@C1 and Fe3O4@C2 were characterized using IR, XRD, SEM, TEM, EDS, ICP-OES, XPS and TGA. Complexes C1, C2 and the functionalised materials Fe3O4@C1 and Fe3O4@C2 were tested as catalysts for the selective transfer hydrogenation of cinnamaldehyde and all four pre-catalysts showed excellent catalytic activity. Complexes C1 and C2 acted as homogeneous catalysts with high selectivity towards the formation of hydrocinnamaldehyde (88.7% and 92.6%, respectively) while Fe3O4@C1 and Fe3O4@C2 acted as heterogeneous catalysts with high selectivity towards cinnamyl alcohol (89.7% and 87.7%, respectively). Through in silico studies of the adsorption energies, we were able to account for the different products formed using the homogeneous and the heterogeneous catalysts which we attribute to the preferred interaction of the C=C moiety in the substrate with the Ni centre in C2 (-0.79 eV) rather than the C=O (-0.58 eV).

Desulfurization of Morupule Coal with Subcritical Aqueous Ethanol Extraction.

Coal combustion greatly contributes to global emissions of toxic gases into the atmosphere, with sulfur emissions as one of the prominent pollutants in addition to carbon dioxide. Nevertheless, Botswana utilizes Morupule's sub-bituminous coal with average sulfur and ash contents, as determined in this study being 1.9 and 24.4 % by weight with an average calorific value of 22 MJ Kg-1 to generate electricity. We report an optimized extraction method for reducing total sulfur in Morupule coal from 1.9±0.2 to 0.43±0.02 wt.% at optimum conditions of ethanol/water (90/10, v/v %) at 129 °C (105 bars) in 10 minutes. A Box-Behnken experimental design was employed to select the optimal conditions of temperature (100-180 °C), water proportion in ethanol (10-90, v/v %) and extraction time (10-30 minutes), thus reducing the total sulfur under these mild conditions compared to conventional extraction. The optimized conditions were however not efficient in removing ash.

Glyco disulfide capped gold nanoparticle synthesis: cytotoxicity studies and effects on lung cancer A549 cells.

Background: Glyco disulfide gold nanoparticles (GDAuNPs) were prepared by three methods: direct, photochemical irradiation and ligand substitution. Glyco disulfide acted as reducing and capping agents of gold ions, to produce AuNPs GD1-GD16. Results: Shorter chains of glyco disulfides (n = 1 and 2) offered monodispersed and stable GDAuNPs in physiological pH, while longer chains (n = 3) furnished unstable nanoparticles. ζ-potential study of direct method GDAuNPs revealed surface charge dependency on the alkyl unit length. Transmission electron microscope imaging indicated that sizes/shapes of the ligand exchange AuNPs remained post-exchange step. The mechanism of GDAuNP formation was forecast as the Ostwald ripening effect at low pH of ligand (5.1-8.9) and reinforcement of static stabilization at high pH (12.4-13.0). Conclusion: GDAuNPs recorded moderately anticancer activity against the A549 cancer cell line, with IC50 between 14.95 and 64.95 µg/ml.

The anti-tumor effects of imidazolium salts on oral squamous cell carcinoma.

BACKGROUND: Imidazolium salts (IS), ionic derivatives of neutral imidazoles, have properties that can be adjusted by structural modifications to their cations and anions, which makes this particular class of compounds a promising option for developing biologically active compounds. The anti-tumor effects of the IS 1-n-butyl-3-methylimidazolium chloride (C4 MImCl), 1-n-decyl-3-methylimidazolium chloride (C10 MImCl), 1-n-hexadecyl-3-methylimidazolium chloride (C16 MImCl), 1-n-hexadecyl-2,3-dimethylimidazolium chloride (C16 M2 ImCl), 1-n-octadecyl-3-methylimidazolium chloride (C18 MImCl), 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16 MImMeS), and 1-n-hexadecyl-2,3- dimethylimidazolium methanesulfonate (C16 M2 ImMeS) on oral squamous cell carcinoma (OSCC) have been studied here. METHODS: Oral squamous cell carcinoma cells (CAL27) were incubated with increasing IS doses and then submitted to proliferation (2D), cell death (2D) and spheroid assay (3D). RESULTS: The IS anti-tumor effect was dependent on both its N-alkyl chain length and anion, whereby C16 MImCl proved to be more effective in combination for inhibiting cell proliferation and cell-cell adhesion, outperforming the methylated C16 M2 ImCl derivative and, most importantly, the gold standard-cisplatin. In addition, C16 MImCl had little effect on keratinocytes and more pronounced effects on more aggressive tumor cells. It also exhibited similar effects on inducing cell death when compared to Cisplatin. This compound spread to a greater area of the tumor sphere and produced an enhanced number of apoptotic and necrotic cells in the tumor cell line, demonstrating only a small rise in the healthy cells. CONCLUSION: These data indicate that the effect of C16 MlmCl on OSCC is promising, as it is selective for cancer cells.

Ring opening polymerization of d,l-lactide and ε-caprolactone catalysed by (pyrazol-1-yl)copper(ii) carboxylate complexes.

1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L) reacts with [Cu(OAc)2] and C6H5COOH, 4-OH-C6H4COOH, 2-Cl-C6H4COOH and (3,5-NO2)2-C6H3COOH to afford the copper complexes [Cu2(C6H5COO)4(L)2] (1), [Cu2(4-OH-C6H4COO)4(L)2] (2), [Cu2(2-Cl-C6H4COO)4(L)2] n (3) and [Cu{(3,5-NO2)2-C6H3COO}2L] n (4) which are characterised by IR, mass spectrometry, elemental analyses, and X-ray crystallography. The structural data revealed two geometries that are adopted by the complexes: (i) paddle wheel in 1, 2·7H2O, 3 and (ii) regular chains in 3 and 4. Magnetic studies show strong antiferromagnetic couplings in the paddle wheel complexes and a weak antiferromagnetic coupling in the monometallic chain one. Catalysis studies performed with these complexes (1-4) showed that they initiate ring opening polymerization (ROP) of ε-caprolactone (ε-CL) under solvent-free conditions and d,l-lactide in toluene at elevated temperatures. Polycaprolactone (PCL) and poly(d,l-lactide) (PLA) obtained from the polymerization reactions are of low molecular weights (858 for PCL and 602 Da for PLA for initiator 1) and polydispersity indices (typically 2.16 for PCL and 1.64 for PLA with 1 as the initiator). End group analysis of the polymers, determined by MALDI-ToF MS, indicates that the polymers have benzoate, hydroxyl, methoxy and cyclic end groups.

Chiral-at-Metal: Iridium(III) Tetrazole Complexes With Proton-Responsive P-OH Groups for CO2 Hydrogenation.

A rise in atmospheric CO2 levels, following years of burning fossil fuels, has brought about increase in global temperatures and climate change due to the greenhouse effect. As such, recent efforts in addressing this problem have been directed to the use of CO2 as a non-expensive and non-toxic single carbon, C1, source for making chemical products. Herein, we report on the use of tetrazolyl complexes as catalyst precursors for hydrogenation of CO2. Specifically, tetrazolyl compounds bearing P-S bonds have been synthesized with the view of using these as P∧N bidentate tetrazolyl ligands (1-3) that can coordinate to iridium(III), thereby forming heteroatomic five-member complexes. Interestingly, reacting the P,N'-bidentate tetrazolyl ligands with [Ir(C5 Me 5)Cl 2]2 led to serendipitous isolation of chiral-at-metal iridium(III) half-sandwich complexes (7-9) instead. Complexes 7-9 were obtained via prior formation of non-chiral iridium(III) half-sandwich complexes (4-6). The complexes undergo prior P-S bond heterolysis of the precursor ligands, which then ultimately results in new half-sandwich iridium(III) complexes featuring monodentate phosphine co-ligands with proton-responsive P-OH groups. Conditions necessary to significantly affect the rate of P-S bond heterolysis in the precursor ligand and the subsequent coordination to iridium have been reported. The complexes served as catalyst precursors and exhibited activity in CO2 and bicarbonate hydrogenation in excellent catalytic activity, at low catalyst loadings (1 µmol or 0.07 mol% with respect to base), producing concentrated formate solutions (ca 180 mM) exclusively. Catalyst precursors with proton-responsive P-OH groups were found to influence catalytic activity when present as racemates, while ease of dissociation of the ligand from the iridium center was observed to influence activity in spite of the presence of electron-donating ligands. A test for homogeneity indicated that hydrogenation of CO2 proceeded by homogeneous means. Subsequently, the mechanism of the reaction by the iridium(III) catalyst precursors was studied using 1H NMR techniques. This revealed that a chiral-at-metal iridium hydride species generated in situ served as the active catalyst.

Synthesis and anti-cancer activity of bis-amino-phosphine ligand and its ruthenium(II) complexes.

The development of both chemotherapeutic drug resistance as well as adverse side effects suggest that the current chemotherapeutic drugs remain ineffective in treating the various types of cancers. The development of new metallodrugs presenting anti-cancer activity is therefore needed. Ruthenium complexes have gained a great deal of interest due to their promising anti-tumour properties and reduced toxicity in vivo. This study highlighted the effective induction of cell death in a malignant melanoma cell by two novel bis-amino-phosphine ruthenium(II) complexes referred to as GA105 and GA113. The IC50 concentrations were determined for both the complexes, the ligand and cisplatin, for comparison. Both complexes GA105 and GA113 displayed a high anti-cancer selectivity profile as they exhibited low IC50 values of 6.72 µM and 8.76 µM respectively, with low toxicity towards a non-malignant human cell line. The IC50 values obtained for both complexes were lower than that of cisplatin. The new complexes were more effective compared to the free ligand, GA103 (IC50 = >20 µM). Morphological studies on treated cells induced apoptotic features, which with further studies could indicate an intrinsic cell death pathway. Additionally, flow cytometric analysis revealed that the mode of cell death of complex GA113 was apoptosis. The outcomes herein give further insight into the potential use of selected Ru(II) complexes as alternative chemotherapeutic drugs in the future.

Cyclometalation of lanthanum(iii) based MOF for catalytic hydrogenation of carbon dioxide to formate.

The hydrogenation of carbon dioxide (CO2) to formic acid is of great importance due to its useful properties in the chemical industry. In this work, we have prepared a novel metal-organic framework (MOF), JMS-1, using bipyridyl dicarboxylate linkers, with molecular formula [La2(bpdc)3(DMF)3] n . Network analysis of JMS-1 revealed a new 7-connected topology (zaz). The MOF backbone of the activated phase (JMS-1a) was functionalized by cyclometalation using [RuCl2(p-cymene)]2 to produce Ru(ii)@JMS-1a. Both JMS-1a and Ru(ii)@JMS-1a were able to convert CO2 in the presence of hydrogen to formate. Ru(ii)@JMS-1a displayed outstanding conversion evidenced by a yield of 98% of formate under optimized conditions of total pressure 50 bar (CO2/H2 = 1 : 4, temperature 110 °C, time 24 h, 5 mmol KOH, 8 mL ethanol). This work is significant in providing new strategies of incorporating active catalytic centres in MOFs for efficient and selective conversion of CO2 to formate.

Development and characterization of functionalized glyco thiolate capped gold nanoparticles for biological applications.

Glyco-gold nanoparticles (AuNPs) in aqueous dispersions were prepared by two approaches, namely direct reduction and ligand substitution methods. In the direct method, potassium salts of glyco thiols, with the general formula (C6H11O6)NH(CH2) n CH2SK (where L1, n = 1; L2, n = 2; L3, n = 3, L4, n = 4; L5, n = 5), were used as reducing and capping agents to give the glyco thiolate capped gold nanoparticles (AuNPs G1-G5); meanwhile in the ligand exchange experiments, L1-L5 and their acetylated forms (L6-L8) replaced citrate ions in citrate-capped gold nanoparticles to give additional AuNPs G6-G11. UV-visible spectroscopy, surface charge (ζ-potential,) measurements and transmission electron microscopy (TEM) were used for physical and chemical characterization of all the resultant AuNPs. The ζ-potential studies of AuNPs prepared through the direct method revealed that the surface charge is dependent on the length of the alkyl unit of (C6H11O6)NH(CH2) n CH2S- ligands. TEM images of the acetylated and non-acetylated glyco thiolate capped gold nanoparticles (AuNPs G6-G11) prepared via the ligand exchange method indicate that the size and shape of the gold nanoparticles remained the same as those of the citrate-capped gold nanoparticles used to prepare them. Selected AuNPs were tested on peripheral blood mononuclear cells (PBMCs) and the A549 cancer cell line to investigate their respective toxicity and cytotoxicity profiles. All AuNPs showed indiscriminate activity against both PBMCs and A4549 cells, although the gold nanoparticles having an acetylated glyco moiety with an amino propyl thiol linker as the ligand (G10) prepared via the citrate exchange method had better selectivity (PBMCs >59 mg mL-1 and for A549 ∼7 µg mL-1).

A Novel Series of N-aryltriazole and N-acridinyltriazole Hybrids as Potential Anticancer Agents.

BACKGROUND: Triazoles are a class of aza-heterocycles with broad spectrum of biological importance. The synthetic tunability of the triazole moiety allows for the development of new pharmacophores with applications as drugs to contend with the burden of cancer. OBJECTIVE: In this study, we aimed to develop a series of N-aryltriazole and N-acridinyltriazole molecular hybrids and evaluate their potential as anticancer agents. METHODS: The triazole derivatives (1-10) were synthesized via a tandem nucleophilic substitution of aryl chlorides with sodium azide followed by 1,3-dipolar cycloaddition of the resulting organic azides with terminal/internal alkynes. From terminal alkynes, the well established copper(I) catalyzed azide-alkynes 1,3- dipolar cycloaddition, a premier example of click chemistry, was employed to access the 1,4-regioisomers of N-benzyl-1H-1,2,3-triazoles and N-acridynyl-1H-1,2,3-triazoles. All the compounds thus synthesized were characterized by 1D and 2D NMR spectroscopy and high resolution mass spectrometry. RESULTS: Thermally controlled 1,3-dipolar cycloaddition was used to deliver N-aryl-1H-1,2,3-triazoles with 1,4,5-substitution on the triazole framework. The unprecedented high regioselectivity promoted by the sterically-strained silylated 1,4,5-trisubstituted moiety 4a offers a useful synthetic precursor with the silyl group being a synthetic handle for further structural elaboration to the desired 1,(4),5-di(tri)substituted 1,2,3- triazoles. Notably, anticancer evaluation revealed good cytotoxic activities of the novel acridinyltriazole hybrids (6-10) at micromolar concentrations in the range of 12.5 µM-100 µM against cervical cancer HeLa, kidney cancer HEK293, lung cancer A549 and leukemic MT4 cancer cell lines (p < 0.05). CONCLUSION: A series of novel triazole-based acridine hybrids have been developed as potential leads for the development of multifaceted anticancer agents.

Synthesis, characterization and evaluation of bulky bis(pyrazolyl)palladium complexes in Suzuki-Miyaura cross-coupling reactions.

Pyrazole-containing compounds have been used in recent times as ligands to stabilize metal complexes used as pre-catalysts in cross-coupling reactions. With various substituents at various positions in the pyrazole ring, the overall electrophilic and steric properties of the metal complexes can be fine-tuned. Herein, we report the synthesis of bulky pyrazole-based ligands by condensation of methyl 4-(bromomethyl)benzoate or benzyl bromide with various substituted pyrazole compounds. These ligands were utilised in the synthesis of bis(pyrazolyl)palladium(ii) complexes. The complexes' catalytic activity in Suzuki-Miyaura cross-coupling reactions was evaluated. Phenyl bearing pre-catalyst 7, at a catalyst loading of 0.33 mol%, successfully converted 98% of bromobenzene and phenylboronic acid to biphenyl in 4 h at 140 °C, while the tertiary butyl bearing pre-catalyst 8 converted up to 81% of the same substrates to biphenyl. An increase in conversion was seen for all pre-catalysts when an electron-withdrawing substituent was present on the aryl halide substrate, and the opposite was observed when the electron-withdrawing group was present on the phenyl boronic acid.

Effects of electrochemical properties of ferrocenylpyrazolylnickel(ii) and palladium(ii) compounds on their catalytic activities in ethylene oligomerisation reactions.

Palladium complexes of ferrocenylpyrazolylpyridine and ferrocenylpyrazolylamine were synthesised and screened as pre-catalysts (1-4) for olefin polymerisation. The pre-catalysts 1-4 on activation with EtAlCl2 in the presence of ethylene with chlorobenzene or hexane as solvent were highly active with 1 being the most active, with an activity of 360 kg mol Pd-1 h-1. The major product from the reaction was 1-butene and high carbon content oligomers. The molecular weight (m/z) of the high carbon content oligomers is as high as 623.0. When toluene is used as solvent, the products obtained were ethyltoluene and butyltoluene and 1-butene. The electronic properties of the ligands (L1-L7) and complexes (1-10) were determined by cyclic voltammetry (CV) and molecular modelling. The CV results show that the ferrocenyl is easily oxidized upon the introduction of pyrazolyl derivatives, the process is quasi-reversible. However, complexation of the ligands with palladium or nickel results in difficulty in oxidizing the ferrocenyl moiety. This is an indication of the electrophilic nature of both the palladium and nickel centres. The mechanism of the oxidation was observed to be diffusion-controlled and is independent of scan rate. Molecular modelling experiments show that nickel and palladium complexes have lower HOMO-LUMO gaps and high global descriptors, an indication of a highly electrophilic metal centre. A plot of the electrophilicity indices of the pre-catalysts against yield of the oligomers show a linear correlation, an indication that the electrophilicity of the metal centre plays an important role in the activity of these pre-catalysts.

Novel pyrazolylphosphite- and pyrazolylphosphinite-ruthenium(ii) complexes as catalysts for hydrogenation of acetophenone.

The new compounds and potential ligands 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyldiphenlyphosphinite (L1), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyldiethylphosphite (L2), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl-diethylphosphite (L3) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiethylphosphite (L4) were prepared from the reaction of (3,5-(disubstituted)pyrazol-1H-yl)ethanol and the appropriate phosphine chloride. The phosphinite (L1) and phosphites (L2-L4) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L5) were reacted with [Ru(p-cymene)Cl2]2 to afford the ruthenium(ii) complexes [Ru(p-cymene)Cl2(L1)] (1), [Ru(p-cymene)Cl2(L2)] (2), [Ru(p-cymene)Cl2(L3)] (3), [Ru(p-cymene)Cl2(L4)] (4), and [Ru(p-cymene)Cl2(L5)] (5). All ruthenium complexes were characterized by a combination of NMR spectroscopy, elemental analysis and, in selected cases, by single crystal X-ray crystallography. Complexes 1-5 and [Ru(p-cymene)Cl2(L6)] (6) (prepared from 2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L6)) were investigated as catalysts for both transfer and molecular hydrogenation of acetophenone to 1-phenylethanol. At 80 °C the percent conversion of acetophenone in transfer hydrogenation was moderate to high over 10 h (42-87%); for molecular hydrogenation acetophenone, conversions were as high as 98% in 6 h.

Activity of phosphino palladium(II) and platinum(II) complexes against HIV-1 and Mycobacterium tuberculosis.

Treatment of human immunodeficiency virus (HIV) is currently complicated by increased prevalence of co-infection with Mycobacterium tuberculosis. The development of drug candidates that offer the simultaneous management of HIV and tuberculosis (TB) would be of great benefit in the holistic treatment of HIV/AIDS, especially in sub-Saharan Africa which has the highest global prevalence of HIV-TB coinfection. Bis(diphenylphosphino)-2-pyridylpalladium(II) chloride (1), bis(diphenylphosphino)-2-pyridylplatinum(II) chloride (2), bis(diphenylphosphino)-2-ethylpyridylpalladium(II) chloride (3) and bis(diphenylphosphino)-2-ethylpyridylplatinum(II) (4) were investigated for the inhibition of HIV-1 through interactions with the viral protease. The complexes were subsequently assessed for biological potency against Mycobacterium tuberculosis H37Rv by determining the minimal inhibitory concentration (MIC) using broth microdilution. Complex (3) showed the most significant and competitive inhibition of HIV-1 protease (p = 0.014 at 100 µM). Further studies on its in vitro effects on whole virus showed reduced viral infectivity by over 80 % at 63 µM (p < 0.05). In addition, the complex inhibited the growth of Mycobacterium tuberculosis at an MIC of 5 µM and was non-toxic to host cells at all active concentrations (assessed by tetrazolium dye and real time cell electronic sensing). In vitro evidence is provided here for the possibility of utilizing a single metal-based compound for the treatment of HIV/AIDS and TB.

Gold(I) complex of 1,1'-bis(diphenylphosphino) ferrocene-quinoline conjugate: a virostatic agent against HIV-1.

HIV infection is known for replicating in proliferating CD(+) T-cells. Treatment of these cells with cytostatic (anti-proliferation) compounds such as hydroxyurea interferes with the cells's ability support HIV replication. Combinations of such cytostatic compounds with proven anti-retroviral drugs (like ddI) are known as virostatic, and have been shown to aid in the control of the infection. The use of two different drugs in virostatic combinations however, carries the risk of adverse effects including drug-drug interactions, which could lead to augmented toxicities and reduced efficacy. Here, a novel digold(I) complex of ferrocene-quinoline (3) was investigated for cytostatic behaviour as well as anti-viral activity which if demonstrated would eliminate concerns of drug-drug interactions. The complex was synthesized and characterized by NMR, FT-IR and mass spectroscopy and the molecular structure was confirmed by X-ray crystallography. Bio-screening involved viability dyes, real time electronic sensing and whole virus assays. The complex showed significant (p = 0.0092) inhibition of virus infectivity (83 %) at 10 ug/mL. This same concentration caused cytostatic behaviour in TZM-bl cells with significant (p < 0.01) S and G2/M phase cell cycle arrest. These data supports 3 as a virostatic agent, possessing both anti-viral and cytostatic characteristics. In the absence of 3, TZM-bl cells were infected by a pseudovirus and this was demonstrated through luminescence in a luciferase assay. Pre-incubation of the virus with 3 decreased luminescence, indicating the anti-viral activity of 3. Complex 3 also showed cytostatic behavior with increased S-phase and G2/M phase cell cycle arrest.

Synthetic Approach to Biotinylated Glyco-Functionalized Quantum Dots: A New Fluorescent Probes for Biomedical Applications.

Technological advances that allow deeper penetration in live tissues, such as the development of confocal and the generation of ever-new fluorophores that facilitate bright labeling of cells and tissue components have made imaging of vertebrate model organisms efficient and highly informative. Recently, high luminescence, single-excitation narrow emission, low photo bleaching properties, and low toxicity of high-quality water-soluble QDs have attracted attention for in vivo labeling/imaging of cells. Herein we describe a synthetic approach to biotinylated glycopolymer functionalized quantum dots, with special emphasis on the development of high-quality water-soluble and bioactive QDs with low toxicity for fluorescent probes in biomedical applications.

Synthetic Approach to Glycopolymer Base Nanoparticle Gold(I) Conjugate: A New Generation of Therapeutic Agents.

Advances in nanotechnology have led to the fabrication of nano-constructs of organic or inorganic origins with well-defined structures, surface properties, and can be made to respond to physical or chemical stimuli. These nano-constructs can provide a shift in the way diagnostic and therapeutic drugs are delivered to achieve target specificity and increased retention of therapeutic doses for considerable improvement in the overall treatment of the tumors. In this case we describe here a synthetic approach to glycopolymer base nanoparticle gold(I) conjugate for cancer therapy.

Effect of chalcogens on CO insertion into the palladium-methyl bond of [(N

Neutral chloromethylpalladium(II) complexes, [Pd(Cl)(CH3)(L)] (1a-5a) with ligands κ(2)-N^S-2-((3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl)-6-(phenylthiomethyl)pyridine (L1), κ(2)-N^S-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenylthiomethyl)pyridine (L2), κ(2)-N^Se-2-((3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl)-6-(phenylselanylmethyl)pyridine (L3), κ(2)-N^Se-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenylselanylmethyl)pyridine (L4), and κ(2)-N^N-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenoxymethyl)pyridine (L5) have been synthesised and characterised by various spectroscopic techniques. Ligands L1-L4 exhibit Npy^S/Se bidentate coordination whereas L5 shows an Npy^Npz bidentate coordination mode in their corresponding neutral palladium complexes. Abstraction of chloride in neutral palladium complexes with NaBAr4 (BAr4 = tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate) resulted in the formation of the cationic palladium complexes 1b-5b, in which L1-L4 adopt a tridentate Npz^Npy^X (X = S or Se) coordination mode in their respective cationic palladium complexes (1b-4b) whilst L5 in complex 5b adopts a Npy^Npz bidentate coordination mode and the palladium centre is stabilized by the weakly coordinating acetonitrile. Compounds 1b-5b readily undergo CO insertion into the Pd-CH3 bond to form Pd-acyl that determines their ability to catalyse CO/ethylene copolymerisation to polyketones.

(Phenoxyimidazolyl-salicylaldimine)iron complexes: synthesis, properties and iron catalysed ethylene reactions.

The reaction of 2-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), 2,4-di-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L2) or 4-tert-butyl-2-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L3) with iron(ii) precursors produced either iron(ii) or iron(iii) complexes, depending on the nature of the anions in the iron(ii) precursor and the ligand. When the anion is chloride and the ligand L1, the product is [(L1)2Fe][FeCl4] (1), but when the anion is triflate (OTf(-)) and the ligand is L2, the product is [(L2)2Fe][OTf]2 (2). With iron(ii) halides and tert-butyl groups on the phenoxy ligands L2 and L3, the iron(iii) complexes [(L2)FeX2] {where X = Cl (3), Br (4) and I = (5)} and [(L3)FeCl2] (6) were formed. Complexes 1-6 were characterised by a combination of elemental analyses, IR spectroscopy and mass spectrometry; and in selected cases (3 and 4) by single crystal X-ray crystallography. The crystal structures of 3 and 4 indicated that the iron(ii) precursors oxidised to iron(iii) in forming complexes 3-6; an observation that was corroborated by the magnetic properties and the (57)Fe Mössbauer spectra of 3 and 4. The iron(iii) complexes 3-6 were used as pre-catalysts for the oligomerisation and polymerisation of ethylene. Products of these ethylene reactions depended on the solvent used. In toluene ethylene oligomerised mainly to 1-butene and was followed by the 1-butene alkylating the solvent to form butyl-toluenes via a Friedel-Crafts alkylation reaction. In chlorobenzene, ethylene oligomerised mainly to a mixture of C4-C12 alkenes. Interestingly small amounts of butyl-chlorobenzenes and hexyl-chlorobenzenes were also formed via a Friedel-Crafts alkylation with butenes and hexenes from the oligomerisation of ethylene.