Side-arm Donor Research Articles

Dichlorovanadium(IV) diamine-bis(phenolate) complexes for ethylene (co)polymerization and 1-olefin isospecific polymerization

Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)2}Cl2] (1) and [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)}Cl2] (2), were synthesised and characterized by FTIR and 1HNMR spectroscopy. Upon activation with Al(iBu)3/Ph3CB(C6F5)4, these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm ∼ 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhibited very high activity (up to 3.3 · 107 g/(molV h)) in ethylene polymerization and produced copolymers with the highest comonomer content (up to 9.1 mol%), moderate molecular weight and narrow chemical composition distribution (CCD). Both vanadium complexes, when combined with trityl borate activator, led to ethylene copolymers with lower 1-octene content and broad CCD. In addition, the copolymers were characterized by very high molecular weight (∼1 · 106 g/mol) and narrow dispersity (Mw/Mn = 1.4–2.0).

Dioxidomolybdenum(VI) and –tungsten(VI) complexes with tetradentate amino bisphenolates as catalysts for epoxidation

Sixteen molybdenum and tungsten complexes with tripodal or linear tetradentate amino bisphenol ligands were studied as catalysts for the epoxidation of cis-cyclooctene, 1-octene, styrene, limonene and α-terpineol. These complexes can be divided into different categories upon key features, i.e. central metal (Mo versus W), side-arm donor (O versus N), hybridization of the N-donor (pyridine versus amine), ligand geometry (tripodal versus linear diamine) and sterical hindrance (Me versus tert-Bu substituents in the phenol part). All complexes can catalyse selectively the epoxidation of cis-cyclooctene by tert-butylhydroperoxide whereas the activities and selectivities towards other olefins (1-octene, styrene, limonene and α-terpineol) show large differences. When H2O2 was used as an oxidant in the epoxidation of cis-cyclooctene, only two of eight Mo complexes and four of eight W complexes showed any activity. This study revealed no clear correlations between the Mo and W catalyst structures and their activities.

Cover Picture: Intramolecularly-stabilized Group 14 Alkoxides - Promising Precursors for the Synthesis of Group 14-Chalcogenides by Hot-Injection Method (Z. Anorg. Allg. Chem. 11/2017)

The cover picture shows the wet chemical synthesis of phase-pure group 14/16 semiconducting materials (ME) by scrambling reactions of bistrialkylsilylchalcogenides E(SiR3)2 with germanium, tin and lead alkoxide complexes M(OC2H4NR2)2 containing a hemilabile side-arm donor function. The reactions proceed at moderate reaction temperatures in the absence of any capping agent with elimination of the corresponding silylether. Details are discussed in the article by Monika Rusek et al. on page on page 676 ff.

Polypropylene and poly(ethylene-co -1-octene) effective synthesis with diamine-bis(phenolate) complexes: Effect of complex structure on catalyst activity and product microstructure

A series of group 4 metal complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor: (μ-O)[Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)2ZrCl]2 (1a), R2N(CH2)2N(CH2-2-O-3-R1-5-R2-C6H2)2TiCl2 (R = Me, R1, R2 = tBu (2a), R = iPr, R1, R2 = tBu (2b), R = iPr, R1 = tBu, R2 = OMe (2c)), and Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)TiCl2 (2d) are used in ethylene and propylene homopolymerization, and ethylene/1-octene copolymerization. All complexes, upon their activation with Al(iBu)3/Ph3CB(C6F5)4, exhibit reasonable catalytic activity for ethylene homo- and copolymerization giving linear polyethylene with high to ultra-high molecular weight (600·× 103–3600·× 103 g/mol). The activity of 1a/Al(iBu)3/Ph3CB(C6F5)4 shows a positive comonomer effect, leading to over 400% increase of the polymer yield, while the addition of 1-octene causes a slight reduction of the activity of the complexes 2a-2d. The complexes with the NMe2 donor group (2a, 2d, 1a) display a high ability to incorporate a comonomer (up to 9–22 mol%), and the use of a bulkier donor group, N(iPr)2 (2b, 2c), results in a lower 1-octene incorporation. All the produced copolymers reveal a broad chemical composition distribution. In addition, the investigated complexes polymerized propylene with the moderate (1a, 2a) to low (2b-2d) activity, giving polymers with different microstructures, from purely atactic to isotactically enriched (mmmm = 28%). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

Novel diamine-bis(phenolate) Ti(IV) complexes – tuning the complex structure to control catalytic properties in α-olefin polymerization

Four monomeric titanium(IV) dichloride complexes of amine-bis(phenolate) ligands having an extra donor arm (2a–2d) and one oxo-bridged complex 3 were successfully synthesized in the reaction of TiCl4 with a sodium salt of the appropriate ligand, and they were characterized by 1H NMR spectroscopy. The ligands had either a dimethylamino side‐arm donor and t-Bu substituents on both (1a) and one (1d) phenolate rings or a diisopropylamino side-arm donor and t-Bu (1b) and t-Bu along with OMe (1c) phenolate substituents. All complexes upon activation with [Ph3CB(C6F5)4] and MAO were used to catalyze polymerization of 1-octene (in liquid monomer) into poly(1-octene). Their activities as well as product microstructures were found to be highly dependent on the structure of the diamine-bis(phenolate) ligand. The catalytic activities of the complexes towards 1-olefin polymerization decreased in the following order: 2a>>2b>2c>2d. The polymers produced were atactic or isotactic with the [mmmm] pentad content varied from about 4 up to 90%. The highest isotacticity was exhibited by poly(1-octene) synthesized by 2d. The catalytic activities increased and polymer molecular weight decreased with the increasing reaction temperature. Moreover, catalyst 2a/Al(iBu)3Ph3CB(C6F5)4 was used in the bulk polymerization of other α-olefin and it was found that the monomer conversion decrease in the order: 1-octene>1-decene>1-dodecene>1-hexene>>4-methyl-1-pentene.

Rhodium catalyzed hydroamination of C2H4 with NH3 with pincer derived PE(CH2CH2X)P ligands – Fighting the energy span

Density functional theory (DFT) calculations were carried out on a variety of rhodium complexes with a variety of pincer derived PE(CH2CH2X)P ligands (E = B, C, N; X = O, NH, CH2, PH, SiH2) to answer the question if computationally a catalyst for the as yet unresolved hydroamination of ethylene with ammonia can be designed. The influence of the different side arm donor groups X was studied with the central pincer backbone element E being carbon. Additionally to rhodium as the metal center cobalt and iridium were studied. Furthermore, the influence of solvation for four solvents (toluene, dichloromethane, tetrahydrofuran, acetonitrile) was investigated on an optimized system. While the majority of the study focuses on neutral catalysts the influence of the complex charge was also studied briefly. Anionic complexes generated by exchanging the backbone carbon E from C to B were studied as well as cationic complexes which were generated by replacing C with N. The variation of the calculated energy spans is large with many systems yielding spans of ca. 40 kcal/mol or above. The lowest energy span (ΔG = 28.7 kcal/mol) was identified for a neutral rhodium catalyst with E = C and X = NH in dichloromethane or tetrahydrofuran solution yielding a predicted TOF of 90 h−1 at 130 °C. Outer sphere mechanisms were studied briefly and cannot compete energetically with inner sphere mechanisms.

Metal complexes of an amine bisphenol with a thiophene side-arm

Dioxomolybdenum(VI) and oxotungsten(VI) complexes with a new amine bisphenol ligand (H2L) are reported. The ligand which carries a neutral nitrogen atom, two phenolic oxygen atoms and a thiophene side-arm was synthesized by a simple one-pot Mannich reaction. Further reaction with [MoO2(acac)2] yielded a monomeric molybdenum complex [MoO2(L)(MeOH)] (2a) or a dimeric complex [Mo2O2(μ-O)2(L)2] (2b), depending on the reaction conditions. The reaction with a tungsten trisglycolate [W(eg)3] led to the formation of a monomeric compound [WO(eg)(L)] (3). In these complexes, the potentially tetradentate amine bisphenolate dianion coordinates as a tridentate O,N,O donor while the sulfur side-arm donor remains intact. The solid-state structure of 2a was investigated by X-ray crystallography.

Group IV Complexes of a Tetradentate Amine Mono(phenolate) Ligand: a Second Side-Arm Donor Stabilizes Cationic Species

An amine mono(phenolate) ligand bearing two side-arm donors led to octahedral trialkoxo and trialkyl group IV metal complexes, in which one of the donors was unbound, and to exceptionally stable cationic complexes in which the two side-arm donors were tightly bound.

Dioxomolybdenum(VI) and -tungsten(VI) complexes with tetradentate aminobis(phenol)s

Aminobis(phenol) ligands (H 2L n ) carrying either a dimethylamino, a pyridyl or a methoxy sidearm donor were used in the preparation of new tungsten and molybdenum complexes. Treatment of [W(eg) 3] (eg = 1,2-ethanediolate dianion) with H 2L n under hydrolytic conditions in a CHCl 3–MeOH mixture gave the cis-dioxotungsten(VI) complexes [WO 2(L n )] in good yields. The corresponding molybdenum complexes [MoO 2(L n )] were prepared from [MoO 2(acac) 2] and respective ligands. The solid-state structures of two molybdenum and one tungsten compounds were determined by single crystal X-ray diffraction, which revealed that the dianionic aminobis(phenolate) backbones of the ligands have coordinated to the metal centre as [O,N,O] donors, whereas the last coordination sphere has been occupied by a N or O donor atom of the ligand sidearm. All synthesized new complexes can catalyse the oxotransfer reaction between benzoin and dmso at 120 °C.

Diverse Structure−Activity Trends in Amine Bis(phenolate) Titanium Polymerization Catalysts

The activity of amine bis(phenolate) Ti dibenzyl complexes in 1-hexene polymerization catalysis as a function of the phenolate substituents was investigated. Two series of Ti complexes carrying either a dimethylamino or a methoxy sidearm donor were prepared and characterized. In each series, the substituents on the phenolate rings were either alkyl groups of varying bulk or electron-withdrawing chloro groups. When activated with a suitable Lewis acid, all precatalysts have shown reactivity toward 1-hexene. Different structure-activity trends were observed in the two series: The activity of the catalysts of the “OMe” series was low to moderate and was almost independent of the phenolate substituents. In contrast, the activity of the “NMe2” catalysts had a strong dependence on both the steric and electronic character of the phenolate substituents, ranging from mild to highly active. The difference in polymerization activity trends between the two series may be traced back to their different tendency toward misinsertions. A “NMe2”-Ti complex having Cl groups in the ortho, para positions of the phenolate rings led to the most active catalyst and to a remarkably high-Mw polymer (>4 000 000) obtained withi n1ho fpolymerization at RT. The characterization of this ultrahigh-Mw atactic poly(1-hexene) by means of oscillatory rheometry and stress relaxation experiments indicated typical elastomeric behavior at RT.

Tribenzyl Tantalum(V) Complexes of Amine Bis(phenolate) Ligands: Investigation of α-Abstraction vs Ligand Backbone β-Abstraction Paths

The synthesis, structure, and reactivity of tribenzyl Ta(V) complexes of amine bis(phenolate) ligands were investigated as a function of the ligands' structure: i.e., the steric bulk of the phenolate substituents and the presence of a “side arm” donor. The tribenzyl complexes were prepared by toluene-elimination reactions of Ta(CH2Ph)5 with the ligand precursors. They were found to be of octahedral mer geometry, with the side-arm donor (if present) unbound. These complexes underwent two well-defined toluene elimination reactions determined by the structural features of the ligands. An α-abstraction reaction, leading to alkyl−alkylidene complexes, occurred only if the phenolate ortho substituents were small (H, Cl) and a side-arm donor was present. Bulkier phenolate substituents (Me) or the lack of a side-arm donor led to a β-abstraction process from the ligand backbone, forming a dibenzyl complex with a metallaazacyclopropane ring. The side-arm donor, if present, was found to bind to the metal in both pat...

From THF to Furan: Activity Tuning and Mechanistic Insight via Sidearm Donor Replacement in Group IV Amine Bis(phenolate) Polymerization Catalysts

Weakening the sidearm donor of amine bis(phenolate) titanium and zirconium polymerization catalysts causes a 10-fold enhancement in activity of the former and no difference in activity of the latter, while increasing the termination to propagation ratios in both.

Group IV complexes of an amine bis(phenolate) ligand featuring a THF sidearm donor: from highly active to living polymerization catalysts of 1-hexene

A new amine bis(phenolate) ligand bearing a THF donor on a sidearm and several dialkyl complexes of the group IV triad are introduced. The crystal structures of a zirconium dibenzyl complex and a titanium dibenzyl complex were solved, and revealed a strong binding of the oxygen donor of the THF group to the metal center. Upon activation with tris(pentafluorophenyl)borane the zirconium and the hafnium dibenzyl complexes lead to highly active 1-hexene polymerization catalysts. In comparison, titanium complexes (a dibenzyl complex and a dimethyl complex) lead to slower but living polymerization of 1-hexene at room temperature. Polymerization of neat 1-hexene under high dilution conditions was found to be living for an exceptionally long time of 6 days, leading to poly(1-hexene) of M w=816 000 and PDI=1.09. A block copolymerization of 1-hexene and 1-octene at room temperature could be obtained using the titanium catalysts.

ONXO]-Type Amine Bis(phenolate) Zirconium and Hafnium Complexes as Extremely Active 1-Hexene Polymerization Catalysts

Several [ONXO]-type zirconium and hafnium dibenzyl complexes of amine bis(phenolate) ligands, where X is a heteroatom donor located on a pendant arm, were synthesized directly from the ligand precursors and the corresponding tetrabenzylmetal complexes in quantitative yields (X = N, O, S). All complexes exhibited remarkable activities in the polymerization of 1-hexene, yielding high-molecular-weight polymers, the highest activity being unprecedented under the conditions employed. An unexpected metal-dependent activity pattern was demonstrated. The high activity of the complexes is derived from the binding of the side-arm donor to the metal and is affected by its nature. The activity order of the zirconium complexes as a function of the side-arm donor was found to be OMe > NMe2 > SMe (5:2:1). The X-ray structures of all zirconium complexes were solved and revealed very similar binding of the [ONO] ligand cores to the metal. The distances between the side-arm donor atoms and the zirconium are relatively long (Zr−O, 2.45 Å; Zr−N, 2.59 Å; Zr−S, 2.86 Å). The X-ray structures of all hafnium complexes were solved as well and found to be closely related to those of the zirconium analogues (Hf−O, 2.45 Å; Hf−N, 2.56 Å; Hf−S, 2.84 Å). However, the activity order was found to be different in the hafnium series, namely SMe > OMe > NMe2 (3.5:1.5:0.2), the [ONSO]-type complex exhibiting the highest activity ever reported for a hafnium complex under the conditions employed. Various NMR experiments supported the notion that the side-arm donor remains attached to the metal in the reactive compounds, which exist as well-separated ion pairs.

Intermolecular axial solvation of bound cations by sidearm donor groups in lariat ethers: formation of a supramolecular network

Previously studied disubstituted 4,13-diaza-18-crown-6 derivatives, R<N18N>R, in which the substituents were cyanomethyl or propargyl did not show intramolecular, lariat-type cation solvation. The ring-bound cation in the propargyl derivative is solvated by the six macroring heteroatoms and apically by a bifurcated interaction of the type F⋯K +⋯F. In contrast, when the sidearm is cyanoethyl, an extended intermolecular network forms when the bound cation is either Na + or K +.

Molecular design of calixarenes. Part 3. Complexation thermodynamics of light lanthanoid nitrates with a novel p-tert-butylcalix[4]arene Schiff base in acetonitrile: an enhanced Eu3+ selectivity by side-arm ligation

A novel double-armed calix[4]arene derivative, 5,11,17,23-tetra-tert-butyl-25,27-bis{2-[N-(2-hydroxy-3-methoxybenzylidene)amino]ethoxy}-26,28-dihydroxycalix[4]arene (3), has been synthesized by the reaction of 1,3-alternately lower-rim-modified bis(2-aminoethoxy)-substituted calix[4]arene (2) with o-vanillin in 90% yield. Calorimetric titrations have been performed in anhydrous acetonitrile at 25 °C to give the complex stability constant (KS) and thermodynamic quantities for the complexation of light lanthanoid(III) nitrates (La–Gd) with 3. Using the present and reported data, the complexation behavior of the structurally related cyanomethyl analogue (1), aminoethyl analogue 2, and 3 is discussed comparatively from a thermodynamic point of view. Possessing donating vanillin side-arms and structural flexibility, 3 gave the highest KS for Eu3+ among the light lanthanoid series. Having the same calix[4]arene skeleton in common, these hosts afforded distinctly different cation selectivity profiles. Thus, fairly low and invariant KS values over the entire light lanthanoid series were obtained with the cyano analogue 1, while the incorporation of amino side-arms in 2 greatly enhanced the KS for La3+ and less extensively for Ce3+ but no change was observed thereafter, giving a sharply declining pattern from La3+ to Pr3+ followed by a sudden leveling-off. In contrast, the vanillino analogue 3 showed a global enhancement of KS for all light lanthanoids, displaying a unique selectivity profile with a broad peak at Nd3+ and a sharp spike at Eu3+. These results are accounted for in terms of the three-dimensional induced fit to lanthanoid ions by the lower-rim and side-arm donor atoms, which play a decisive role upon recognition of trivalent lanthanoid ions by the calix[4]arenes with flexible donating side-arms. Thermodynamically, the complexation is absolutely driven by the favorable enthalpy changes, but the cation selectivity is mainly determined by the less negative entropy changes.

Sodium cation complexation in a macrocycle containing thymines as sidearm donor groups

Previous studies of macrocycles having alkyl sidearms terminated in adenine or thymine have been focused on intermolecular association. Electrospray mass spectrometric analyses suggested that sodium complexation could be a major alternative process in the presence of the appropriate cation. Sodium cation complexation by N,N′-bis(3-(1-thyminyl)propyl)-4,13-diaza-18-crown-6 has been confirmed by X-ray crystallographic analysis. A sodium cation is bound in the center of the macroring. The four ether oxygens and two thyminyl carbonyl donors have the shortest contacts with the two, macroring nitrogen atoms being somewhat more remote. Neither the iodide counterion nor an acetone of solvation appears to interact with the sodium cation. Crystal Data: Triclinic, \(P_{\bar 1} \) , a = 11.9371(12), b = 12.1588(13), c = 13.7885(14) A, α = 78.083(2)°, β = 83.213(2)°, γ = 78.997(2)°, and Dcalc = 1.392 g cm−3, Z = 2.

New Molecular Receptors with Cyclophosphazene Subunits: Synthesis, Reactivity, and Structure-Property Relationships

A series of hydrophopic ( 2 and 3) and new hydrophilic ( 4– 7) molecular receptors of the PNP-lariat ether with tetra-substituted cyclotriphosphazene subunits have been prepared by the complete nucleophilic substitution of chlorine atoms in the reactive PNP-crown precursor 1 with the respective sodium cation-paired oxyanions (phenoxy → 2, β-naphthoxy → 3, and methoxytrioxyethylenoxy → 4) and aliphatic amines (n-propylamine → 5 aziridine → 6, and pyrrolidine → 7). Their structures were established by MS and 31P NMR spectroscopy and their metal ion complexing properties tested by a TLC method. Comparison of the complexation behaviour for ligands 1– 7 shows that the affinity for particular cations is strongly substituent-dependent and, in general, is significantly enhanced by cooperation of the side arm donor atoms (O or N) with the parent PNP-crown structure in the binding process. The remarkable affinity of some ligands for selected cations, in particular lithium, cesium, and silver ions, is interpreted in terms of structure-property relationships.

The remarkable indifference of alkali metal cation binding constants to sidearm thioether and sulfoxide donors in azalariat ethers

The first example of a lariat ether containing a sulfur sidearm donor is reported here along with a comparison of cation binding strengths to Na+ and K+. The binding strength differs remarkably little from analogs completely lacking a sidearm donor group and similar results are observed for the novel sulfoxide analog.

Copper(I) Schiff-base complexes: reversible carbon monoxide binding, reactions with dioxygen, and the structure of a dinuclear complex containing co-ordinated and unco-ordinated alkene groups

Copper(I) complexes of a series of acyclic Schiff-base ligands (L1–L5) derived from the condensation of 2,6-diacetylpyridine with 2 mol of 4-aminobut-1-ene (L1), allylamine (L2), 1-aminobutane (L3), 1 -aminopropane (L4), and 2-(ethylthio)ethylamine (L5), have been prepared. Crystals of the dinuclear complex[Cu2L12][BPh4]2 are orthorhombic with a= 17.74(1), b= 17.78(1), c= 21.90(1)Å, Z= 4, and space group Pb21a(no. 29). In the dimeric cation each CuI atom is bonded to the pyridine nitrogen and one imino nitrogen of one ligand molecule and to one imino nitrogen and one alkene group of the second ligand molecule in a distorted tetrahedral geometry. The second alkene group of each ligand remains unco-ordinated. In order to accommodate to this unusual co-ordination mode one imino group is severely twisted (by 83, 86° in the two ligand molecules) out of the plane of the pyridine ring, leading to two distinct ν(CN) vibrations in the i.r. spectrum. On the basis of i.r. and other properties, it is proposed that the complexes of L2–L5, as well as [Cu2L12][BPh4]2 in MeCN solution, have mononuclear structures in which the trimethine pyridyldi-imine group retains its customary planarity and acts as a tridentate ligand. For [CuL3][ClO4] and [CuL4][ClO4] having no side-arm donor groups, and for [CuL2][ClO4]·H2O having propene side chains, a T-shaped three-co-ordinated structure is suggested. For [CuL5][ClO4], as well as for [Cu2L12][BPh4]2 and [CuL2][ClO4]·H2O in solution, spectroscopic evidence indicates at least partial side-arm donor group co-ordination leading to four-co-ordinate species. All the complexes bind CO reversibly in MeCN solution to an extent dependent on the competition exercised by the pendant side-arm donor groups, where present. The complexes also bind O2 in solution in a 0.25:1 O2: Cu stoicheiometry at rates which parallel the CO affinities. The O2 binding is partially reversible in some cases as evidenced by electronic spectral and O2-uptake measurements on successive oxygenation/deoxygenation treatments. Among the ultimate products of the accompanying irreversible oxidation are the bis(ligand) CuII complexes [CuL2]2+.