Synthesis,structural characterization,and olefin polymerization behavior of vanadium(III) complexes bearing bidentate phenoxy‐phosphine ligands

Vanadium(III) complexes bearing phenoxy‐phosphine ligands ( 2a–g ) (2‐R₁‐4‐R₂‐6‐PPh₂‐C₆H₂O)VCl₂(THF)₂ ( 2a : R₁ = R₂ = H; 2b : R₁ = F, R₂ = H; 2c : R₁ = Ph, R₂ = H; 2d : R₁ = tBu, R₂ = H; 2e : R₁ = R₂ = Me; 2f : R₁ = R₂ = tBu; 2g : R₁ = R₂ = CMe₂Ph) were prepared from VCl₃(THF)₃ by treating with 1.0 equiv of the ligand in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA). The reaction of VCl₃(THF)₃ with 2.0 equiv of the ligand in THF in the presence of excess TEA afforded vanadium(III) complexes bearing two phenoxy‐phosphine ligands ( 3c–f ). These complexes were characterized by FTIR and mass spectrum as well as elemental analyses. Structures of 2f and 3c were further confirmed by X‐ray crystallographic analyses. Complexes 2a–g and 3c–f were employed as the catalysts for ethylene polymerization under various reaction conditions. On activation with Et₂AlCl, these complexes exhibited high catalytic activities (up to 41.3 kg PE/mmol_V·h·bar) even at high temperature (70°C), and produced high molecular weight polymer with unimodal molecular weight distributions, indicating the polymerization took place in a single‐site nature. Complexes 3c–f displayed better thermal stability than the corresponding complexes 2a–g under similar conditions. In addition, copolymerizations of ethylene and 1‐hexene with precatalysts 2a–g were also explored in the presence of Et₂AlCl. Catalytic activity, comonomer incorporation, and properties of the resultant polymers can be controlled over a wide range by tuning catalyst structures and reaction parameters.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Substituted cyclopentadienylchromium(III) complexes containing neutral donor ligands. Synthesis, crystal structures and reactivity in ethylene polymerization

Lithium derivatives of substituted cyclopentadiene ligands reacted with CrCl₃(THF)₃ in THF solution to afford homodinuclear complexes of the type [{(η⁵-RCp)CrCl(μ-Cl) }₂] [R=SiMe₃ (1), CH₂C(Me)CH₂ (2)]. Complex 1 reacts with pyrazole (C₃H₄N₂) to yield the mononuclear half-sandwich complex [(η⁵-Me₃SiCp)CrCl₂(pyrazole)] (3). The similar complex [Cp*CrCl₂(pyrazole)] (4) was synthesised by reaction of [{Cp*CrCl(μ-Cl)}₂] with pyrazole. Complex 2 reacts with bidentate ligands to give binuclear complexes of the type [{(η⁵-CH₂C(Me)CH₂Cp)CrCl₂ }₂(μ-L-L)] [L-L=Ph₂PCH₂CH₂PPh₂ (5), trans-Ph₂P(O)CHCHP(O)Ph₂ (6)]. All complexes were structurally characterised by X-ray diffraction. After reaction with methylaluminoxane these complexes are active in the polymerization of ethylene. At 25 °C and 4 bar of ethylene, complex 3 yields polyethylene with a bimodal molecular weight distribution centred at 155,000 and 2000 g/mol. Complex 4 shows similar activity, yielding only the low molecular weight fraction. On the other hand, the binuclear complexes 5 and 6 under the same conditions were three times more active than mononuclear complexes. The melting point of the polymers indicates the formation of linear polyethylene.     

Synthesis of anionic methylpalladium complexes with phosphine-sulfonate ligands and their activities for olefin polymerization

Reaction of diarylphosphinobenzene-2-sulfonic acids with tertially amines, followed by addition of [PdMeCl(cod)], provided anionic methylpalladium(II) complexes with bidentate phosphine-sulfonate ligands, which show high activity for copolymerization of ethylene with methyl acrylate.     

Synthesis,structure and olefin polymerization catalysis of nickel(II) complexes bearing N,O-chelate ligands

Four β-ketoimine ligands (two series) were prepared through traditional condensation reactions of β-diketones with 2,6-substituted anilines. Reaction took place only at the cyclohexanone carbonyl rather than at the acetyl or benzoyl carbonyl, even if more than two equivalents of the amines were added. Consequently, four new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes, Ni[2–CH₃C(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (1); Ar?=?2, 6-Me₂C₆H₃, (2) and Ni[2–PhC(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (3); Ar?=?2, 6-Me₂C₆H₃, (4) were obtained and characterized. The solid-state structures of complex 1, 2 and 3 have been determined by single-crystal X-ray diffraction. Additionally, these complexes can be applied as highly active catalyst precursors for vinyl polymerization of norbornene (NBE) after activation with methylaluminoxane (MAO).     

Synthesis of (1-adamantylimido)vanadium(V) complexes containing aryloxo, ketimide ligands: effect of ligand substituents in olefin insertion/metathesis polymerization

A series of (1-adamantylimido)vanadium(V) complexes containing anionic donor ligands of the type, V(NAd)Cl2(L) [Ad = 1-adamantyl; L = O-2,6-Me2C6H3 (2), O-2,6-(i)Pr2C6H3 (3), NC(t)Bu2 (5), NC((t)Bu)CH2SiMe3 (6), NC((t)Bu)Ph (7), NCPh2 (8)], have been prepared from V(NAd)Cl 3, which was in turn prepared from VOCl3 by treatment with 1-adamantylisocyanate in octane, by treatment with the corresponding lithium salts (lithium phenoxides, lithium ketimides) in Et2O. These complexes (2, 3, 5-8) were identified by NMR spectroscopy and elemental analysis, and the structures for 2 and 5 were determined by X-ray crystallography. The reaction of V(NAd)Cl3 with 2,6-dimethylphenol in n-hexane afforded the tris(aryloxo) analogue V(NAd)(O-2,6-Me2C6H3)3 (4), the structure of which was determined by X-ray crystallography. 8 gradually decomposed in toluene to give a dimeric species, [N(Ad)H3](+)[V2(mu2-Cl)3Cl2(NAd)2(NCPh2)2](-) (10), but 8 was stabilized as a PMe 3 coordinated species, V(NAd)Cl2(NCPh2)(PMe3)2 (9): the structures for 9 and 10 were determined by X-ray crystallography. These complexes were evaluated as catalyst precursors for ethylene polymerization in the presence of MAO. The ketimide analogues, especially 5, exhibited moderate catalytic activity, and the activity with a series of V(NAd)Cl2(L)-MAO catalyst systems increased in the order: L = NC(t)Bu2 (5, 516 kg-PE/mol x V x h) > NC((t)Bu)Ph (7, 300) > NCPh2 (8, 105) > NC((t)Bu)CH2SiMe3 (6, 70.8). These complexes (2, 3, 5, 6) were found to be effective as catalyst precursors for the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) in the presence of MeMgBr and PMe3.     

Synthesis,spectroscopic and structural characterisation of vanadium(IV) and oxovanadium(IV) complexes with arsenic donor ligands

The reaction of o-C₆H₄(AsMe₂)₂ with VCl₄ in anhydrous CCl₄ produces orange eight-coordinate [VCl₄{o-C₆H₄(AsMe₂)₂}₂], whilst in CH₂Cl₂ the product is the brown, six-coordinate [VCl₄{o-C₆H₄(AsMe₂)₂}]. In dilute CH₂Cl₂ solution slow decomposition occurs to form the V^III complex [V₂Cl₆{o-C₆H₄(AsMe₂)₂}₂]. Six-coordination is also found in [VCl₄{MeC(CH₂AsMe₂)₃}] and [VCl₄{Et₃As)₂]. Hydrolysis of these complexes occurs readily to form vanadyl (VO²⁺) species, pure samples of which are obtained by reaction of [VOCl₂(thf)₂(H₂O)] with the arsines to form green [VOCl₂{o-C₆H₄(AsMe₂)₂}], [VOCl₂{MeC(CH₂AsMe₂)₃}(H₂O)] and [VOCl₂(Et₃As)₂]. Green [VOCl₂(o-C₆H₄(PMe₂)₂}] is formed from [VOCl₂(thf)₂(H₂O)] and the ligand. The [VOCl₂{o-C₆H₄(PMe₂)₂}] decomposes in thf solution open to air to form the diphosphine dioxide complex [VO{o-C₆H₄(P(O)Me₂)₂}₂(H₂O)]Cl₂, but in contrast, the products formed from similar treatment of [VCl₄{o-C₆H₄(AsMe₂)₂}_x] or [VOCl₂{o-C₆H₄(AsMe₂)₂}] contain the novel arsenic(V) cation [o-C₆H₄(AsMe₂Cl)(μ-O)(AsMe₂)]⁺. X-ray crystal structures are reported for [V₂Cl₆{o-C₆H₄(AsMe₂)₂}₂], [VO(H₂O){o-C₆H₄(P(O)Me₂)₂}₂]Cl₂, [o-C₆H₄(AsMe₂Cl)(μ-O)(AsMe₂)]Cl·[VO(H₂O)₃Cl₂] and powder neutron diffraction data for [VCl₄{o-C₆H₄(AsMe₂)₂}₂].     

Rare earth alkyl and hydride complexes bearing silylene-linked cyclopentadienyl-phosphido ligands. Synthesis, structures, and catalysis in olefin hydrosilylation and ethylene polymerization

A series of silylene-linked cyclopentadienyl-phosphido rare earth alkyl and hydride complexes of type Me₂Si(C₅Me₄)(PR′)LnR (Ln=Y, Yb, Lu; R′=Ph, Cy, C₆H₂^tBu₃-2,4,6; R=CH₂SiMe₃, H) have been synthesized and structurally characterized, and their activity in ethylene polymerization and olefin hydrosilylation has been studied. These complexes represent the first examples of rare earth alkyl and hydride complexes bearing cyclopentadienyl-phosphido ligands, which are in sharp contrast both structurally and chemically with the analogous cyclopentadienyl-amido and metallocene complexes.     

Synthesis and reactions of rhodium compounds containing tellurium donor ligands

This paper describes the synthesis and characterization of a series of rhodium(I) and rhodium(III) complexes containing tellurium-rhodium bonds resulting from the coordination of diorgano telluride or organotelluro ligands. Oxidative addition, metathesis and substitution reactions of these compounds have been examined, and the resulting products are compared with those from the known reactions of rhodium(I) and rhodium(III) compounds containing phosphine ligands.     

Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl ligands: synthesis, characterization and olefin polymerization studies

The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{η⁵-(1-Ph-3-Me-C₅H₃)}₂Cl₂] and [Zr(η⁵-C₅H₅){η⁵-(1-Ph-3-Me-C₅H₃)}Cl₂] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C₅H₃) to ZrCl₄(THF)₂ and [Zr(η⁵-C₅H₅)Cl₃ · DME] (DME = dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li₂[(Me-Ph-C₅H₂SiMe₂)₂O] to MCl₄ gave the ansa-metallocenes [M{η⁵-(Me-Ph-C₅H₂SiMe₂)₂O}Cl₂] (M = Zr, Hf) for which the meso- and rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{η⁵-(2-Me-4-Ph-C₅H₂SiMe₂)₂O}Cl₂] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts for ethene and propene polymerization was evaluated.     

Synthesis, characterization, reactivity, and catalytic potential of model vanadium(IV, V) complexes with benzimidazole-derived ONN donor ligands

Reaction between [VO(acac)(2)] and the ONN donor Schiff base Hsal-ambmz (I) (Hsal-ambmz = Schiff base obtained by the condensation of salicylaldehyde and 2-aminomethylbenzimidazole) resulted in the formation of the complexes [V(IV)O(acac)(sal-ambmz)] (1), [V(V)O(2)(acac-ambmz)] (2) (Hacac-ambmz = Schiff base derived from acetylacetone and 2-aminomethylbenzimidazole), and the known complex [V(IV)O(sal-phen)] (3) (H(2)sal-phen = Schiff base derived from salicylaldehyde and o-phenylenediamine). Similarly, [V(IV)O(acac)(sal-aebmz)] (7) has been isolated from the reaction with Hsal-aebmz (II) (Hsal-aebmz derived from salicylaldehyde and 2-aminoethylbenzimidazole). Aerial oxidation of the methanolic solutions/suspensions of 1 and 7 yielded the dioxovanadium(V) complexes [V(V)O(2)(sal-ambmz)] (4) and [V(V)O(2)(sal-aebmz)] (8), respectively. Reaction of VOSO(4) with II gave [{V(IV)O(sal-aebmz)}(2)SO(4)] (9) and [V(IV)O(sal-aebmz)(2)] (10), along with 3 and 8. Under similar reaction conditions, I gave only [{V(IV)O(sal-ambmz)}(2)SO(4)] (5) and 3 as major products. Treatment of 1 and 7 with benzohydroxamic acid (Hbha) yielded the mixed-chelate complexes [V(V)O(bha)(sal-ambmz)] (6) and [V(V)O(bha)(sal-aebmz)] (11). The crystal and molecular structures of 2, 3.1/2DMF, 7.1/4H(2)O, 8, 9.2H(2)O, 10, and 11 have been determined, confirming the ONN binding mode of the ligands. In complex 10, one of the ligands is coordinated through the azomethine nitrogen and phenolate oxygen only, leaving the benzimidazole group free. In the dinuclear complex 9, bridging functions are the phenolate oxygens from both of the ligands and two oxygens of the sulfato group. The unstable oxoperoxovanadium(V) complex [V(V)O(O(2))(sal-aebmz)] (12) has been prepared by treatment of 7 with aqueous H(2)O(2). Acidification of methanolic solutions of 7 and 10 lead to (reversible) protonation of the bemzimidazole, while 8 was converted to an oxo-hydroxo species. Complexes 2, 4, and 8 catalyze the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide and methyl phenyl sulfone, a reaction mimicking the sulfideperoxidase activity of vanadate-dependent haloperoxidases. These complexes are also catalytically active in the oxidation of styrene to styrene oxide, benzaldehyde, benzoic acid, and 1-phenylethane-1,2-diol.     

Synthesis,structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph₂PNR]₂MCl₂ (3: R = ^tBu, M = Ti; 4: R = ^tBu, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction of MCl₄ (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [Ph₂PN^tBu]₂TiCl₂ (3) was determined by X‐ray crystallography. The phosphinoamides functioned as η²‐coordination ligands in the solid state and the Ti? N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i‐Bu₃Al/Ph₃BC(C₆F₅)₄, catalytic activity of up to 59.5 kg PE/mol cat h bar was observed. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis, structure, and olefin polymerization with nickel(II) N-heterocyclic carbene enolates

Two novel N-heterocylic carbene enolate nickel complexes have been prepared and shown to be active for ethylene and propylene polymerization to yield linear polymers.     

Synthesis,structures and properties of two donor–acceptor acridone-based compounds

Two donor–acceptor acridone-based compounds, namely, 2-{10-[4-(diphenylamino)phenyl]acridin-9-ylidene}malononitrile ( TPA-AD-DCN ), C₃₄H₂₂N₄, and 2-{10-[4-(9H-carbazol-9-yl)phenyl]acridin-9-ylidene}malononitrile ( CzPh-AD-DCN ), C₃₄H₂₀N₄, have been synthesized in high yield and their structures determined. TPA-AD-DCN and CzPh-AD-DCN crystallized in the centrosymmetric space groups P and P2₁/c, respectively. Both molecules adopt a `butterfly-like' configuration of the common part of the structure and differences occur within the substituents on the acridine N atom. A Hirshfeld surface analysis showed that the H…H and C…H/H…C contacts constitute a high percentage of the intermolecular interactions. The optical and electrochemical properties, as well as theoretical calculations, of TPA-AD-DCN and CzPh-AD-DCN support the structural characterization of these materials. As crystallization-induced emission materials, TPA-AD-DCN and CzPh-AD-DCN are anticipated to be of potential use in the construction of promising optoelectronic materials.     

Synthesis, characterization and olefin polymerization of the nickel catalysts supported by [N,S] ligands

The novel nickel (II) complexes (2a, 2b) bearing 1-pyridyl-(3-substituedimidazole-2-thione) ligands were synthesized by the reaction of the corresponding ligands with NiBr₂(DME). 2a and 2b have been characterized by IR, NMR and elemental analysis. The nickel complexes show high catalytic activities for norbornene polymerization in the presence of MAO (methylaluminoxane), although low activities for ethylene polymerization.     

Synthesis and characterization of coordination compounds of organotin(IV) with nitrogen and sulfur donor ligands

The reactions of dimethyltin dichloride with nitrogen and sulfur donor ligands derived by condensation of S‐benzyldithiocarbazate with indol‐3‐carboxylaldehyde, thiophene‐2‐aldehyde and furfuraldehyde have been investigated in 1:1 and 1:2 molar ratios in anhydrous alcohol. These ligands act as mononegatively charged bidentate species and coordinate to the central tin(IV) atom through the thiosulfur by proton exchange with the azomethine nitrogen. The newly synthesized complexes have been characterized by elemental analysis, conductance measurements and molecular weight determinations. The mode of bonding and the geometry of the complexes have been suggested on the basis of infrared, electronic and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, and probable structures have been assigned to these complexes. A few representative ligands and their tin(IV) complexes have also been screened for their antifungal and antibacterial activities and found to be quite active in this respect. Copyright © 2001 John Wiley & Sons, Ltd.     

Palladium complexes of multidentate pyrazolylmethyl pyridine ligands: Synthesis,structures and phenylacetylene polymerization

The compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (_MeNˆNˆN) (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (_tBuNˆNˆN) (L2), react with either [Pd(NCMe)₂Cl₂] or [Pd(COD)ClMe] to form the mononuclear palladium complexes [Pd(_MeNˆNˆN)Cl₂] (1), [Pd(_MeNˆNˆN)ClMe] (2), [Pd(_tBuNˆNˆN)Cl₂] (3) and [Pd(_tBuNˆNˆN)ClMe] (4). Reactions of 1, 2 and 4 with the halide abstractor, NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of stable tridentate cationic species [Pd(_MeNˆNˆN)Cl]⁺(5), [Pd(_MeNˆNˆN)Me]⁺ (6) and [Pd(_tBuNˆNˆN)Cl]⁺ (7) respectively. The analogous carbonyl linker cationic species [Pd{(3,5-Me₂pz-CO)₂-py}Cl]⁺ (9) and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl]⁺ (10), prepared by halide abstraction of the neutral complexes [Pd{(3,5-Me₂pz-CO)₂-py}Cl₂] and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl₂] by NaBAr₄, were however less stable with t_1/2 of 14 and 2 days respectively. Attempts to crystallize 1 and 3 from the mother liquor resulted in the isolation of the salts [Pd(_MeNˆNˆN)Cl]₂[Pd₂Cl₆] (11) and [Pd(_tBuNˆNˆN)Cl]₂[Pd₂Cl₆] (12). Although when complexes 1–4 were reacted with modified methylaluminoxane (MMAO) or NaBAr₄, no active catalysts for ethylene oligomerization or polymerization were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerized and polymerized phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene.     

Synthesis,structural characterization,and ethylene polymerization behavior of (arylimido)vanadium(V) complexes bearing tridentate Schiff base ligands

A series of novel (arylimido)vanadium(V) complexes bearing tridentate salicylaldiminato chelating ligands, V(N‐2,6‐Me₂C₆H₃)Cl₂[(O‐2‐^tBu‐4‐R‐C₆H₃)CH?ND] (R = H, D = 2‐CH₃O? C₆H₄ ( 2a ); 2‐CH₃S? C₆H₄ ( 2b ); 2‐Ph₂P? C₆H₄ ( 2c ); 8‐C₉H₆N (quinoline) ( 2d ); CH₂C₅H₄N ( 2e ); R = ^tBu, D = 2‐Ph₂P? C₆H₄ ( 2f )), were prepared from V(NAr)Cl₃ by reacting with 1.0 equiv of the ligands in the presence of triethylamine in tetrahydrofuran. These complexes were characterized by ¹H, ¹³C, ³¹P, and ⁵¹V NMR spectra and elemental analysis. The structures of 2c and 2f were further confirmed by X‐ray crystallographic analysis. These (arylimido)vanadium(V) complexes are effective catalyst precursors for ethylene polymerization in the presence of Et₂AlCl as a cocatalyst and ethyl trichloroacetate as a reactivating agent. Complex 2c with a ? PPh₂ group in the sidearm was found to exhibit an exceptional activity up to 133800 kg polyethylene/mol_V h for ethylene polymerization at 75 °C, which is one of the highest activities displayed by homogeneous vanadium(V) catalysts at high temperature. Moreover, high molecular weight polymers with unimodal molecular weight distribution can be obtained, indicating the single site behavior of these catalysts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2633‐2642     

Synthesis and structures of (R)-cyclopentadienyl-binaphthoxy titanium(IV) complexes and catalytic properties for olefin polymerization

Two new chiral pre-ligands, (R)-3,3'-bis(tetramethylcyclopentadienyl)-2,2'-bismethoxy-1,1'-bisnaphthalene (1) and (R)-3-tetramethylcyclopentadienyl-2,2'-bismethoxy-1,1'-bisnaphthalene (2), were synthesized by reaction of (R)-3,3'-dilithium-2,2'-bismethoxy-1,1'-bisnaphthalene with 2,3,4,5-tetramethyl-2-cyclopentenone at room temperature. Treatment of the pre-ligands 1 and 2 with butyllithium and Me(3)SiCl first, and subsequently with TiCl(4) (2 and 1 equiv for 1 and 2, respectively) afforded a binuclear complex (R)-3,3'-bis[(tetramethylcyclopentadienyl)trichlorotitanium]-2,2'-bismethoxy-1,1'-bisnaphthalene (3) and a mononuclear complex (R)-3-(tetramethylcyclopentadienyl)trichlorotitanium-2,2'-bismethoxy-1,1'-bisnaphthalene (4) in moderate yields. Complexes 3 and 4 were further converted into constrained geometry complexes (R)-1,1'-bis{2,2'-naphthoxy-3,3'-bis[(tetramethylcyclopentadienyl)dibromotitanium]} (5) and (R)-1-(2-naphthoxy)-1'-(2'-naphthol)-3-(tetramethylcyclopentadienyl)dibromotitanium (6) by treatment with BBr(3). The pre-ligands 1 and 2 were characterized by (1)H and (13)C NMR and high resolution mass spectroscopy (HRMS), and the new titanium complexes 3-6 were characterized by (1)H and (13)C NMR and elemental analyses. Molecular structures of 4, 5, and 6 were determined by single-crystal X-ray diffraction analysis. Complexes 4, 5, and 6 all have a pseudo-octahedral coordination environment and adopt a three-legged piano stool geometry around the titanium atom in their solid state structures. When activated with Al(i)Bu(3) and Ph(3)CB(C(6)F(5))(4), the chiral complexes 5 and 6 show moderate catalytic activities for propylene, 1-hexene, and 5-ethylidene-2-norbornene (ENB) polymerization and ethylene/1-hexene copolymerization. The polymers produced by the chiral 5/(i)Bu(3)Al/Ph(3)CB(C(6)F(5))(4) catalyst system from the 1-hexene, and ENB polymerization and ethylene/1-hexene copolymerization with high comonomer contents exhibit optical activity.     

Titanium(IV) complexes with monocyclopentadienyl and phenoxy-alkoxo ligands: Synthesis,structures and catalytic properties for ethylene polymerization

Three monochlorotitanium complexes Cp′Ti(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)Cl [Cp′ = η⁵-C₅H₅ (2), η⁵-C₅(CH₃)₅ (3), η⁵-C₅H₂Ph₂CH₃ (4)] have been synthesized in high yields (>90%) by the reaction of corresponding Cp′TiCl₃ with the dilithium salt of ligand 2,4-^tBu₂-6-(CPh₂OH)C₆H₂OH (1). When activated by [Ph₃C]⁺[B(C₆F₅)₄]⁻ and AlⁱBu₃, complexes 2–4 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points. Addition of excess water to complex 2 gave the oxo-bridged complex [Ti(η⁵-C₅H₅)(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)]₂O (5). Complexes 4 and 5 were characterized by single crystal X-ray diffraction.     

Group 4 complexes bearing bis(salphen) ligands: Synthesis,characterization, and polymerization studies

Six different complexes containing bis(salphen) [salphen = N,N'‐phenylenebis(salicylideneimine)] ligands were synthesized and characterized by various spectroscopic techniques and elemental analysis. In the presence of benzyl alcohol as an initiator, all the complexes catalyze the ring‐opening polymerization of lactide and ε‐caprolactone, generating high molecular weight (M_n) polymers in a controlled fashion. The linear relationship between the % conversion and M_n proved the control over the polymerization process. The presence of OBn group as an end group was confirmed by MALDI‐TOF and ¹H NMR spectral analysis of low M_n oligomers. The polymerization followed first‐order kinetics as revealed by kinetic experiments. All the complexes were good precatalysts for the polymerization of ethylene. The effect of temperature and time on the yield and activity toward the polymerization of ethylene were widely investigated. In addition, in the presence of tetrabutylammonium bromide as cocatalyst, the formation of degradable polycarbonate with moderate M_n value and narrow molecular weight distributions was observed by the copolymerization of cyclohexene oxide with CO₂. The effect of initiator structure, temperature, CO₂ pressure, catalyst/cocatalyst loading on the activity, and selectivity toward copolymerization were systematically examined. The thermal properties of the copolymer synthesized were explored using differential scanning calorimetric and thermogravimetric analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 809–824