Salicylaldiminato Ligands Research Articles

Highly efficient oxidation of alcohols catalyzed by Ru(II) carbonyl complexes bearing salicylaldiminato ligands

Reaction of Ru3(CO)12 with 2.0 equiv of RN = CH(3,5-tBu2C6H2OH) (R = C6H5, L1; R = 4-MeC6H4, L2; R = 4-OMeC6H4, L3; R = 4-ClC6H4, L4; R = 4-BrC6H4, L5; R = 4-CF3C6H4, L6) in refluxing xylene afforded the corresponding bis-chelate Ru(II) complexes 1a–1f [RN = CH(3,5-tBu2C6H2O)]2Ru(CO)2 and one of the imine bonds reduced complexes {[RN = CH(3,5-tBu2C6H2O)]-[RNH-CH2(3,5-tBu2C6H2O)]}Ru(CO)22a–2f. All the ruthenium complexes were fully characterized by NMR, IR and elemental analysis. In addition, the structures of complexes 1a–1f, 2b, 2d and 2f were further confirmed by single-crystal X-ray diffraction. When activated with N-methylmorpholine-N-oxide (NMO), these Ru complexes displayed high catalytic activities toward oxidation of both 1° and 2° alcohols. For most cases, the reaction can complete within 1 h in refluxing CH3CN.

Syntheses and crystal structures of ruthenium complexes with bidentate salicylaldiminato and dithiophosphato ligands

Abstract Treatment of the bidentate Schiff base 2-[(2,6-diisopropyl-phenylimino)-methyl]-phenol (HL1) with one equivalent of (Et4N)[RuCl4(MeCN)2] in the presence of triethylamine afforded (Et4N)[RuCl3(κ 2-N,O-L1)(MeCN)] (1), which reacted with two equivalents of K[S2P(O i Pr)2] to produce a neutral ruthenium(III) complex [Ru(κ 2-N,O-L1){η 2-S2P(O i Pr)2}2] (2) bearing both salicylaldiminato and dithiophosphato ligands. Reactions of the bidentate Schiff bases 2-[(3-chloro-phenylimino)-methyl]-phenol (HL2) and 2-[(2,4,6-trimethyl-phenylimino)-methyl]-phenol (HL3) with one equivalent of [Ru(CO)2Cl2] in the presence of triethylamine led to formation of the corresponding anionic ruthenium(II) carbonyl complexes (Et3NH)[RuCl2(κ 2-N,O-L2)(CO)2] (3) and (Et3NH)[RuCl2(κ 2-N,O-L3)(CO)2] (4). The molecular structures of complexes 2–4 have been determined by single-crystal X-ray diffraction.

Synthesis, characterization and crystal structures of ruthenium complexes with bidentate chiral salicylaldiminato ligands

Abstract Condensations of salicylaldehyde and 4-chlorosalicylaldehyde with (R)-α-methylbenzylamine in refluxing ethanol afforded the chiral Schiff base ligands (R)-N-(1-phenylethyl)salicylidene (HL1∗) and (R)-N-(1-phenylethyl)(4-chlorosalicylidene) (HL2∗), respectively. Similarly, reaction of 3,5-di-tert-butylsalicylaldehyde and (S)-2-amino-3-methylbutan-1-ol gave the chiral Schiff base ligand (S)-N-(1-hydroxymethylisobutyl)(3,5-di-tert-butylsalicylidene) (HL3∗). Treatment of (Et4N)[RuCl4(MeCN)2] and [RuCl3(NO)(PPh3)2] with HL1∗ in the presence of triethylamine afforded an anionic ruthenium(III) complex (R,R)-(Et4N)[Ru(κ2-N,O-L1∗)2Cl2] (1) and a neutral ruthenium(II) nitrosyl complex (R)-[Ru(κ2-N,O-L1∗)(NO)Cl2(PPh3)] (2), respectively. Interaction of [RuCl2(PPh3)3] and 2 equiv. HL2∗ led to isolation of a ruthenium(III) complex (R,R)-[Ru(κ2-N,O-L2∗)2Cl(PPh3)] (3). Reaction of [Ru(NO)Cl3·xH2O] and HL3∗ gave an anionic ruthenium(II) nitrosyl complex (S)-(Et3NH)[Ru(κ2-N,O-L3∗)(NO)Cl3] (4). The molecular structures of ligands HL1∗, HL2∗ and ruthenium complexes 1–4 have been determined by single-crystal X-ray crystallography.

Syntheses, characterization, and crystal structures of ruthenium(II)/(III) complexes with tridentate salicylaldiminato ligands

Treatment of [Ru(PPh3)3Cl2] with one equivalent of tridentate Schiff base 2-[(2-dimethylamino-ethylimino)-methyl]-phenol (HL) in the presence of triethylamine afforded a ruthenium(III) complex [RuCl3(κ2-N,N-NH2CH2CH2NMe2)(PPh3)] as a result of decomposition of HL. Interaction of HL and one equivalent of [RuHCl(CO)(PPh3)3], [Ru(CO)2Cl2] or [Ru(tht)4Cl2] (tht = tetrahydrothiophene) under different conditions led to isolation of the corresponding ruthenium(II) complexes [RuCl(κ3-N,N,O-L)(CO)(PPh3)] (2), [RuCl(κ3-N,N,O-L)(CO)2] (3), and a ruthenium(III) complex [RuCl2(κ3-N,N,O-L)(tht)] (4), respectively. Molecular structures of 1·CH2Cl2, 2·CH2Cl2, 3 and 4 have been determined by single-crystal X-ray diffraction.

Photoluminescence properties of tetrahedral zinc(ii) complexes supported by calix[4]arene-based salicylaldiminato ligands.

The synthesis and photophysical properties of four new hybrid salicylaldiminato-calix[4]arene ligands and their corresponding zinc(ii) complexes are described. The Schiff bases were obtained from condensation reactions between cone-25,27-di(aminoethoxy)-26,28-dihydroxy-calix[4]arene and salicylaldehyde (H2L1) or o-vanillin (H2L2) and 1,3-alt-25,27-di(aminoethoxy)-26,28-di(n-propyloxy)-calix[4]arene and 3,5-di-tert-butyl-salicylaldehyde (H2L3) or o-vanillin (H2L4). Complexation reactions were investigated by ESI-MS, IR, NMR, UV-vis absorption and steady-state and time resolved fluorescence spectroscopy, and X-ray crystallography. All ligands support 1 : 1 complexes (ZnL1-ZnL4), with equilibrium constants derived from absorption spectrophotometry in the range log K11 = 5.5-8.2 (MeCN or MeOH/CH2Cl2, I = 0.01 M). The zinc complexes show blue fluorescence, both in solution as well as in the solid state, with λem, Φf, and τ ranging from 472-504 nm, 0.11-0.60, and 2-9 ns, respectively. The nature of the substituents on the salicylaldiminato fragments was found to be the main parameter that influences the photophysical properties of the zinc complexes. Insights into the electronic nature of the UV-vis transitions were obtained with time dependent density functional theory (TD-DFT) calculations.

Syntheses, structures, and solid-state phosphorescence characteristics of trans-bis(salicylaldiminato)Pt(II) complexes bearing perpendicular N-aryl functionalities

The syntheses, structures, and solid-state emission characteristics of trans-bis(salicylaldiminato)Pt(II) complexes bearing N-aromatic functionalities are described herein. A series of Pt complexes bearing various N-phenyl (1) and N-(1-naphthyl) (2) groups on the salicylaldiminato ligands were prepared by reacting PtCl2(CH3CN)2 with the corresponding N-salicylidene aromatic amines, and the trans-coordination and crystal packing of these complexes were unequivocally established based on X-ray diffraction (XRD). Complexes with 2,6-dimethylphenyl (1c), 2,6-diisopropylphenyl (1d), 1-naphthyl (2a), and 1-(2-methylnaphthyl) (2b) groups on the N atoms exhibited intense phosphorescent emission at ambient temperature in the crystalline state, while those with phenyl (1a), 2,6-dibromophenyl (1b), and 2,6-bis(N,N-dimethylamino)phenyl (1e) functionalities were either less emissive or non-emissive under the same conditions. XRD analyses identified significant intramolecular interactions between Pt and H atoms of the N-aryl functionalities in the emissive crystals of 1c, 1d, and 2a. These interactions were evidently an important factor associated with intense emission at ambient temperature.

Binuclear Titanium Catalysts Based on Methylene-Bridged Tridentate Salicylaldiminato Ligands for Ethylene Homo- and Copolymerization

A series of methylene-bridged salicylaldiminato tridentate [ONS] ligands bearing different alkylthio sidearms and the corresponding binuclear titanium complexes (Ti 2 a , Ti 2 b , Ti 2 c ) were synthesized and characterized by elemental analysis, ESI-MS, FT IR, 1H and 13C NMR. To the best of our knowledge, these were the first non-metallocene tridentate binuclear Ti complexes reported. When activated by modified methylaluminoxane (MMAO), these binuclear Ti complexes displayed extremely high activities in the range of 106 g mol−1 h−1 atm−1 for ethylene polymerization and ethylene/α-olefins copolymerization at atmospheric pressure, producing high molecular weight polymers with narrow polydispersity. Both the catalytic behavior and the spectroscopic characterization indicated that the catalysts assumed symmetric structure and contained single-site active species. Most importantly, the catalytic activities towards ethylene (co)polymerization as well as comonomer incorporation ratios were much higher than that of the corresponding mononuclear complexes. Meanwhile, the properties of polymers and the comonomer incorporation ratios can be effectively tuned by the reaction conditions and the alkylthio side group on ligands. Complex Ti 2 c bearing the long octylthio sidearm showed significantly higher activity for ethylene polymerization than the methylthio functionalized Ti 2 a , presumably due to the increased solubility of the catalyst in the reaction medium. While for copolymerization, complex Ti 2 a demonstrated the highest catalytic activity and comonomer incorporation ratio, due the small steric hindrance of the methylthio side group.

Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have been shown to be efficient and versatile catalysts for the ROP of various cyclic esters. These species have the potential to function as active catalysts in the ROP because of their less coordinatively saturated nature with respect to analogous SALEN-type complexes. They have been used as efficient catalysts in the ROP of commercially available cyclic esters, such as ε-caprolactone, l-lactide, rac-lactide, and glycolide. Moreover, they resulted in efficient catalysts for the ROP of cyclic esters with large ring-size and for the ROP of functionalized lactide. Furthermore, they have been used in the co- and ter-polymerization of various cyclic esters affording well controlled polymerization and a plethora of microstructural architectures, ranging from random to block to multiblock.

A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

New titanium (IV), zirconium (IV) and hafnium (IV) alkoxide complexes supported by the tridentate [O,N,N] salicylaldiminato ligands were synthesized in high yields and characterized by conventional spectroscopic techniques and single crystal X-ray analysis. The structural composition for some of these complexes was as a result of in situ intramolecular Meerwein–Ponndorf–Verley (MPV) type reduction of the imine moiety from the ligand, resulting in the formation of unexpected amido compounds. Theoretical calculations were performed at the DFT level to calculate the energy barrier for this reduction and rationalize the reactivity pattern. These complexes were found to be active towards the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA), l-lactide (l-LA) and ε-caprolactone (CL), resulting in polymers with good number average molecular weight (Mn) and controlled molecular weight distributions (MWDs). The poly(lactic acid) (PLA) resulting from rac-LA were predominately heterotactic. Interestingly, these compounds were found to catalyze the ROP of epoxides such as rac-cyclohexene oxide (rac-CHO), rac-styrene oxide (rac-SO) and rac-propylene oxide (rac-PO) under solvent free condition. The kinetic and mechanistic studies associated with the polymerization have been included. In addition, these compounds were found to be useful as precatalysts for the polymerization of ethylene.

Ethylene/1-hexene copolymerization by salicylaldiminato vanadium(III) complexes activated with diethylaluminum chloride

Mono salicylaldiminato vanadium(III) complexes (1a-1f) [RN = CH(ArO)]VCl2(THF)2 (Ar = C6H4 (1a–1e), R = Ph, 1a; R = p-CF3Ph, 1b; R = 2,6-Me2Ph, 1c; R = 2,6-iPr2Ph, 1d; R = cyclohexyl, 1e; Ar = C6H2 tBu2(2,4), R = 2,6-iPr2Ph, 1f) and bis(salicylaldiminato) vanadium(III) complexes (2a–2f) [RN = CH(ArO)]2VCl(THF) x (Ar = C6H4 (2a–2e), x = 1 (2a–2e), R = Ph, 2a; R = p-CF3Ph, 2b; R = 2,6-Me2Ph, 2c; R = 2,6-iPr2Ph, 2d; R = cyclohexyl, 2e; Ar = C6H2 tBu2(2,4), R = 2,6-iPr2Ph, x = 0, 2f) have been evaluated as the active catalysts for ethylene/1-hexene copolymerization in the presence of Et2AlCl. The ligand substitution pattern and the catalyst structure model significantly influenced the polymerization behaviors such as the catalytic activity, the molecular weight and molecular weight distribution of the copolymers etc. The highest catalytic activity of 8.82 kg PE/(mmolV-h) was observed for vanadium catalyst 2d with two 2,6-diisopropylphenyl substituted salicylaldiminato ligands. The copolymer with the highest molecular weight was obtained by using mono salicylaldiminato vanadium catalyst 1f having ligands with tert-butyl at the ortho and para of the aryloxy moiety.

Synthesis and Structural Characterization of Bis(salicylaldiminato)magnesium Complexes of Varying Aggregation and Coordination State

AbstractA series of salicylaldiminato ligands [C6H5N=CHC6H4OH (1L), 2,6‐iPrC6H3N=CHC6H4OH (2L), and 2,6‐iPrC6H3N=CH‐3,5‐tBu2C6H2OH (3L)] were treated with Bu2Mg in the presence of the appropriate solvent system to yield the crystalline compounds [(1L6Mg3)·thf] (1), [(2L2Mg·thf)] (2), and [3L2Mg] (3). The products were characterized by 1H and 13C NMR spectroscopy and single‐crystal X‐ray diffraction. X‐ray crystallographic analysis revealed that 1 adopts a unique trimeric aggregation state consisting of six‐coordinate magnesium centers. Substitution of the ligand backbone resulted in the formation of the monomeric species 2 and 3. X‐ray crystallographic analyses revealed 2 as a five‐coordinate, distorted square‐pyramidal magnesium complex and 3 as a four‐coordinate, distorted tetrahedral species. Inspection of the metrical parameters in 1–3 indicates a decrease in the Mg–O and Mg–N bond lengths and an increase in the N–Mg–O bite angle with a decreasing coordination number at magnesium.

Synthesis, structures and ethylene polymerization behavior of half-metallocene chromium(iii) catalysts bearing salicylaldiminato ligands

A series of half-metallocene chromium(III) complexes bearing a salicylaldiminato ligand, Cp′[2-R1-4-R2-6-(CH = NR3)C6H2O]CrCl [Cp′ = Cp (1, 5), Cp* (2, 3, 4, 6, 7, 8); R1 = Ph (1, 2, 3, 5, 6, 8), iPr (4), tBu (7); R2 = H (1, 2, 3), Br (4), NO2 (5, 6, 7, 8); R3 = iPr (1, 2, 5, 6, 7), tBu (3, 4, 8)], were synthesized. The structures of complexes 1, 3–5, 7–8 were determined by single crystal X-ray diffraction analysis. The X-ray crystallographic analysis indicates that these complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry. Upon activation with a small amount of AlEt3, complexes 1–8 exhibit good to high catalytic activity for ethylene polymerization and produce ultra-high molecular weight polyethylene (PE) under mild conditions. The productivity of these complexes is relatively low when activated with AlMe3 and AliBu3. Both the productivity of these catalyst systems and the molecular weight of the produced PE can be tuned in a broad range by changing the ligands and the AlR3 co-catalyst.

Ethylene polymerization and ethylene/hexene copolymerization with vanadium(III) catalysts bearing heteroatom‐containing salicylaldiminato ligands

AbstractA series of novel vanadium(III) complexes bearing heteroatom‐containing group‐substituted salicylaldiminato ligands [RNCH(ArO)]VCl2(THF)2 (Ar = C6H4, R = C3H2NS, 2a; C7H4NS, 2c; C7H5N2, 2d; Ar = C6H2tBu2 (2,4), R = C3H2NS, 2b) have been synthesized and characterized. Structure of complex 2c was further confirmed by X‐ray crystallographic analysis. The complexes were investigated as the catalysts for ethylene polymerization in the presence of Et2AlCl. Complexes 2a–d exhibited high catalytic activities (up to 22.8 kg polyethylene/mmolV h bar), and affording polymer with unimodal molecular weight distributions at 25–70 °C in the first 5‐min polymerization, whereas produced bimodal molecular weight distribution polymers at 70 °C when polymerization time prolonged to 30 min. The catalyst structure plays an important role in controlling the molecular weight and molecular weight distribution of the resultant polymers produced in 30 min polymerization. In addition, ethylene/hexene copolymerizations with catalysts 2a–d were also explored in the presence of Et2AlCl, which leads to the high molecular weight and unimodal distributions copolymers with high comonomer incorporation. Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled over a wide range by the variation of catalyst structure and the reaction parameters, such as comonomer feed concentration, polymerization time, and polymerization reaction temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3573–3582, 2009

Synthesis, Structural Characterization, and Olefin Polymerization Behavior of Vanadium(III) Complexes Bearing Tridentate Schiff Base Ligands

Vanadium(III) complexes bearing tridentate salicylaldiminato ligands (2a−f) [OC6H4CH═NL]VCl2(THF) (L = CH2CH2OMe, 2a; CH2CH2NMe2, 2b; CH2C5H4N, 2c; 8-C9H6N (quinoline), 2d; 2-MeSC6H4, 2e; 2-Ph2PC6H4, 2f) and tridentate β-enaminoketonato ligands [OC6H8CH═N-2-Ph2PC6H4]VCl2(THF) (2g) and [O(Ph)C═CHCH═N-2-Ph2PC6H4]VCl2(THF) (2h) were prepared from VCl3(THF)3 by treating with 1.0 equiv of the deprotonated ligands in tetrahydrofuran (THF). These complexes were characterized by FTIR and mass spectrometry as well as elemental analysis. Structures of complexes 2e, 2f, and 2h were further confirmed by X-ray crystallographic analysis. These complexes were investigated as catalysts for olefin polymerization in the presence of organoaluminum compounds. On activation with Et2AlCl, complexes 2a−h exhibited high catalytic activities toward ethylene polymerization (up to 20.64 kg PE/mmolV·h·bar) even at high temperature, suggesting these catalysts possess high thermal stability. Moreover, high molecular weight polymers with unimodal molecular weight distribution can be obtained, indicating the single site behavior of these catalysts. The copolymerizations of ethylene and norbornene or 1-hexene with catalysts 2a−h were also explored in the presence of Et2AlCl, which led to high molecular weight poly(ethylene-co-1-hexene)s (Mw up to 138 000) and poly(ethylene-co-norbornene)s (Mw up to 164 000). Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled in a wide range by the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and polymerization reaction temperature.

Synthesis, Structural Characterization, and Ethylene Polymerization Behavior of the Vanadium(III) Complexes Bearing Salicylaldiminato Ligands

Vanadium(III) complexes bearing salicylaldiminato ligands (2a−k) [RN═CH(ArO)]VCl2(THF)2 (Ar = C6H4, R = Ph, 2a; p-CF3Ph, 2b; p-CH3Ph, 2c; 2,6-Me2Ph, 2d; 2,6-iPr2Ph, 2e; cyclohexyl, 2f; Ar = C6H3tBu(2), R = Ph, 2g; 2,6-iPr2Ph, 2h; Ar = C6H2tBu2(2,4), R = Ph, 2i; 2,6-iPr2Ph, 2j; Ar = C6H2Br2, R = Ph, 2k) were prepared from VCl3(THF)3 by treating with 1.0 equiv of (RN═CH)ArOH in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA). The reaction of VCl3(THF)3 with 2.0 equiv of (RN═CH)ArOH in THF in the presence of excess TEA afforded vanadium(III) complexes bearing two salicylaldiminato ligands (3a−k), [RN═CH(ArO)]2VCl(THF)x (Ar = C6H4, x = 1, R = Ph, 3a; p-CF3Ph, 3b; p-CH3Ph, 3c; 2,6-Me2Ph, 3d; 2,6-iPr2Ph, 3e; cyclohexyl, 3f; Ar = C6H3tBu(2), x = 1, R = Ph, 3g; x = 0, 2,6-iPr2Ph, 3h; Ar = C6H2tBu2(2,4), x = 1, R = Ph, 3i; 2,6-iPr2Ph, x = 0, 3j; Ar = C6H2Br2, x = 1, R = Ph, 3k). These complexes were characterized by FTIR and mass spectra as well as elemental analysis. Structures of complexes 2a...

Synthesis of Cobalt(III), Iron(III), and Chromium(III) Complexes with Salicylaldiminato Ligands: Evaluation of the Complexes as Catalysts for Oxidation of L-Cysteine

A series of new cobalt(III)-, iron(III)-, and chromium(III)-based complexes of the general formula [M(N∩O)2Cl] (N∩O: N-salicylidene(X)amine and sodium N-(4-sulfonatosalicylidene(X)amine)) (X = cyclohexyl and 1-naphthyl) was prepared and characterized. Some of the isolated complexes have been evaluated as catalysts for the oxidation of L-cysteine. Preliminary results show that the rate of oxidation of L-cysteine is influenced by the nature of the metal center, the geometry of the complex, the auxiliary substituents, and the backbone of the ligand.

Synthesis and characterization of novel neutral nickel complexes bearing fluorinated salicylaldiminato ligands and their catalytic behavior for vinylic polymerization of norbornene

AbstractA series of salicylaldimine‐based neutral Ni(II) complexes (3a–j) [ArN = CH(C6H4O)]Ni(PPh3)Ph [3a, Ar = C6H5; 3b, Ar = C6H4F(o); 3c, Ar = C6H4F(m); 3d, Ar = C6H4F(p); 3e, Ar = C6H3F2(2,4); 3f, Ar = C6H3F2(2,5); 3g, Ar = C6H3F2(2,6); 3h, Ar = C6H3F2(3,5); 3i, Ar = C6H2F3(3,4,5); 3j, Ar = C6F5] have been synthesized in good yield, and the structures of complexes 3a and 3i have been confirmed by X‐ray crystallographic analysis. Using modified methylaluminoxane as a cocatalyst, these neutral Ni(II) complexes exhibited high catalytic activities for the vinylic polymerization of norbornene. It was observed that the strong electron‐withdrawing effect of the fluorinated salicylaldiminato ligand was able to significantly increase the catalyst activity for vinylic polymerization of norbornenes. In addition, catalyst activity, polymer yield and polymer molecular weight can also be controlled over a wide range by the variation of reaction parameters such as Al:Ni ratio, norbornene:catalyst ratio, monomer concentration, polymerization temperature and time. Copyright © 2008 John Wiley & Sons, Ltd.

Alkylphenyl-Substituted Bis(salicylaldiminato) Titanium Catalysts in Ethene Polymerization

Titanium complexes bearing anionic [N,O-] bidentate salicylaldiminato ligands were synthesized with excellent yields via one- or two-step processes. The common feature of these catalyst precursors is the presence of aliphatic substituents (adamantyl, benzyl, (CH2)2Ph, (CH2)3Ph, and i-Pr) at the aldimino moieties. X-ray structure analysis of the benzyl-substituted complex revealed a distorted octahedral geometry, wherein nitrogen and chlorine atoms form the basal plane while the oxygen atoms of the phenoxy moieties complete the coordination sphere of the Ti center by occupying the axial positions. However, according to dynamic 1H NMR measurements, these complexes can possess different structural isomers in solution, even at room temperature. After MAO activation, the catalysts displayed a range of catalytic activities [3−1700 kgPE/(molTi·h·bar)]. The complex with ethylphenyl substituents was the most active in the series. In general, the (CH2)2Ph- and (CH2)3Ph-substituted catalysts produce PE with unimodal...

Synthesis and structures of bimetallic and polymeric zinc coordination compounds supported by salicylaldiminato and anilido–aldimine ligands

A series of bimetallic zinc complexes bearing salicylaldiminato (1b-3b) or anilido-aldimine (4c-5c) ligand frameworks, in which the metal centres are separated by aliphatic spacer groups containing 3-6 methylene units, were targeted. X-Ray analysis of salicylaldiminato derivative 2b, with a 4 carbon spacer group, revealed a coordination polymer in the solid state where each zinc centre is ligated by two salicylaldiminato ligands. Contrastingly, the structure of the anilido-aldimine complex 4c, with a 3 carbon methylene spacer group, was found to be a discrete bimetallic complex. These differences are attributed to the differing steric protection at the anilido vs phenoxy donors, the latter more readily facilitating bridges between metal centres.

Binuclear neutral nickel complexes bearing bis(bidentate) salicylaldiminato ligands: Synthesis, structure and ethylene polymerization behavior

Reaction of sodium salts of the bridging [O,N,N,O]-type bisalylaldimine ligands [O,N,N,O = [3-phenyl-2-OH-(CH N)] 2-L (L = CH 2CH 2CH 2 3a, 1,4-C 6H 4 3b)] with trans-bis(triphenylphosphane)phenylnickel (II) chloride result in neutral bis(bidentate) binuclear nickel (II) complexes 4a and 4b. The structure of 4b has been confirmed by X-ray crystallography. 4a shows moderate activity for polymerization of ethylene in the presence of methylaluminoxane (MAO). Catalytic activities, molecular weights and molecular weight distribution of polyethylene have been investigated under the various reaction conditions.