Chromium complexes supported by bidentate thioether-imine [N,S] ligands: synthesis and ethylene oligomerization studies

Chromium complexes bearing thioether-imine ligands were synthesized and their catalytic behavior in ethylene oligomerization has been investigated, evaluating the effect of the ligand and the experimental parameters on the activity, selectivity, and product distribution.

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ-butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO:κO′)di-μ-hydroxido-bis[(butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO)(butyl 2,6-di-tert-butyl-4-methylphenyl phosphato-κO)chromium](Cr—Cr) heptane disolvate or {Cr2(μ2-OH)2[μ2-PO2(OBu)(O-2,6- t Bu2-4-MeC6H2)-κO:κO′]2[PO2(OBu)(O-2,6- t Bu2-4-MeC6H2)-κO]2[HOPO(OBu)(O-2,6- t Bu2-4-MeC6H2)-κO]2}·2C7H16, [Cr2(C19H32O4P)4(C19H33O4P)2(OH)2]·2C7H16, denoted (1)·2(heptane), [μ-bis(2,6-diisopropylphenyl) phosphato-1κO:2κO′]bis[bis(2,6-diisopropylphenyl) phosphato]-1κO,2κO-chlorido-2κCl-triethanol-1κ2 O,2κO-di-μ-ethanolato-1κ2 O:2κ2 O-dichromium(Cr—Cr) ethanol monosolvate or {Cr2(μ2-OEt)2[μ2-PO2(O-2,6-iPr2-C6H3)2-κO:κO′][PO2(O-2,6-iPr2-C6H3)2-κO]2Cl(EtOH)3}·EtOH, [Cr2(C2H5O)2(C24H34O4P)3Cl(C2H6O)3]·C2H6O, denoted (2)·EtOH, and di-μ-ethanolato-1κ2 O:2κ2 O-bis{[bis(2,6-diisopropylphenyl) hydrogen phosphato-κO][bis(2,6-diisopropylphenyl) phosphato-κO]chlorido(ethanol-κO)chromium}(Cr—Cr) benzene disolvate or {Cr2(μ2-OEt)2[PO2(O-2,6-iPr2-C6H3)2-κO]2[HOPO(O-2,6-iPr2-C6H3)2-κO]2Cl2(EtOH)2}·2C6H6, [Cr2(C2H5O)2(C24H34O4P)2(C24H35O4P)2Cl2(C2H6O)2]·2C6H6, denoted (3)·2C6H6. Complexes (1)–(3) have been synthesized by an exchange reaction between the in-situ-generated corresponding lithium or potassium disubstituted phosphates with CrCl3(H2O)6 in ethanol. The subsequent crystallization of (1) from heptane, (2) from ethanol and (3) from an ethanol/benzene mixture allowed us to obtain crystals of (1)·2(heptane), (2)·EtOH and (3)·2C6H6, whose structures have the monoclinic P21, orthorhombic P212121 and triclinic P\overline 1 space groups, respectively. All three complexes have binuclear cores with a single Cr—Cr bond, i.e. Cr2O6P2 in (1), Cr2PO4 in (2) and Cr2O2 in (3), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ2-OH in (1) or μ2-OEt in (2) and (3). The organophosphate ligands demonstrate terminal κO coordination modes in (1)–(3) and bridging μ2-κO:κO′ coordination modes in (1) and (2). All the complexes exhibit hydrogen bonding: two intramolecular Ophos...H—Ophos interactions in (1) and (3) form two {H[PO2(OR)2]2} associates; two intramolecular Cl...H—OEt hydrogen bonds additionally stabilize the Cr2O2 core in (3); two intramolecular Ophos...H—OEt interactions and two O...H—O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in (2)·EtOH. The presence of both basic ligands (OH− or OEt−) and acidic [H(phosphate)2]− associates at the same metal centres in (1) and (3) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short-chain branching. The formation of a small amount of α-olefins has been detected in this reaction.

Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new highly active and selective catalyst

The new 2-pyridinecarboxylate (2-pic) complex of chromium(III) has been designed and synthesized as a new highly active and selective oligomerization catalyst. The crystal structure of the new compound has been determined by X-ray diffraction. The composition and purity of [Cr(2-pic)₂(OH₂)₂]NO₃ have been confirmed by several spectroscopic methods and the elemental analysis. Furthermore, the new complex has been investigated towards its catalytic activity for the oligomerization of 2-chloro-2-propen-1-ol under the atmospheric pressure and at room temperature. It has turned out that the novel catalyst exhibits a very high catalytic activity. Consequently, [Cr(2-pic)₂(OH₂)₂]NO₃ belongs to a new generation of non-metallocene catalysts.

Synthesis and structural characterization of zirconium complexes supported by tridentate pyrrolide-imino ligands with pendant N-, O- and S-donor groups and their application in ethylene polymerization

Zirconium complexes supported by pyrrolide-imino ligands been synthesized and their catalytic behavior in ethylene polymerization has been investigated.

Transition metal complexes bearing tridentate ligands for precise olefin polymerization

This review covers key developments in the design of post-metallocene transition metal complexes (precatalysts) bearing tridentate chelating ligands and their application in olefin polymerization.

Ni(ii) complexes bearing pyrrolide-imine ligands with pendant N-, O- and S-donor groups: synthesis, structural characterization and use in ethylene oligomerization

Nickel complexes bearing pyrrolide-imine ligands with pendant N-, O- and S-donor groups have been synthesized and their catalytic behavior in ethylene oligomerization has been investigated.