Zirconium Amides Research Articles

NNC-Scorpionate Zirconium-Based Bicomponent Systems for the Efficient CO2 Fixation into a Variety of Cyclic Carbonates.

Two new derivatives of the bis(3,5-dimethylpyrazol-1-yl)methane modified by introduction of organosilyl groups on the central carbon atom, one of which bearing a chiral fragment, have been easily prepared. We verified the potential utility of these compounds through the reaction with [Zr(NMe2)4] for the preparation of novel zirconium complexes in which an ancillary bis(pyrazol-1-yl)methanide acts as a robust monoanionic tridentate scorpionate in a κ3-NNC chelating mode, forming strained four-membered heterometallacycles. These κ3-NNC-scorpionate zirconium amides were investigated as catalysts in combination with tetra-n-butylammonium bromide as cocatalyst for CO2 fixation into five-membered cyclic carbonate products. The study has led to the development of an efficient zirconium-based bicomponent system for the selective cycloaddition reaction of CO2 with epoxides. Kinetics investigations confirmed apparent first-order dependence on the catalyst and cocatalyst concentrations. In addition, this system displays very broad substrate scope, including mono- and disubstituted substrates, as well as the challenging biorenewable terpene derived limonene oxide, under mild and solvent-free conditions.

Crystal structure of tris-(di-methyl-amido-κN)-bis-(di-methyl-amine-κN)-zirconium(IV) iodide.

Zirconium amides have become increasingly popular and useful due to their widespread use as precursors to other zirconium complexes and their use in the production of solid oxide fuel cells (SOFCs). Herein we report the mol-ecular structure of tris-(di-methyl-amido)-bis-(di-methyl-amine)-zirconium(IV) iodide, [Zr(C2H6N)3(C2H7N)2]I. The bond lengths and bond angles are consistent with a slightly distorted trigonal-bipyramidal coordination geometry around the metal atom. N⋯I contacts of 3.6153 (15) and 3.5922 (14) Å are consistent with the presence of N-H⋯I inter-actions. These N-H⋯I inter-actions link the complex cations and iodide anions into extended chains that propagate parallel to the a axis.

Homoleptic zirconium amidates: single source precursors for the aerosol-assisted chemical vapour deposition of ZrO2

We report the development of a true single source precursor for the growth of zirconia thin films by aerosol-assisted chemical vapour deposition using an original family of zirconium(iv) amidate derivatives.

Preparation of all N-coordinated zirconium amide amidinates and studies of their reactions with dioxygen and water

Zr(NR2)2[MeC(NiPr)2]2 (R=Me, 1; Et, 2) have been prepared through aminolysis and their reactions with O2 and water have been studied. Two major products from the reactions are the oxo dimer {(μ-O)Zr[MeC(NiPr)2]2}2 (3) and its insoluble polymer {(μ-O)Zr[MeC(NiPr)2]2}n (4). Over time the dimer 3 polymerizes to 4. Zr peroxo trimer {(μ-η2:η2-O2)Zr[MeC(NiPr)2]2}3 (5) was also observed from the reaction of 1 with O2 and its crystal structure is reported. DFT calculations show that the reaction of 1 with O2 follows a radical process, yielding the peroxo trimer 5. Mass spectrometric studies of the reactions of water in air with 1 and 2 show the formation of the oxo monomer (O=)Zr[MeC(NiPr)2]2 (6), oxo dimer {(μ-O)Zr[MeC(NiPr)2]2}2 (3), and the dihydroxy monomer (HO)2Zr[MeC(NiPr)2]2 (7). In addition, the cations {Zr(NR2)[MeC(NiPr)2]2}+ (R=Me, Et) were observed. 2 revealed an interesting dynamic NMR behavior. Variable-temperature (VT) NMR spectroscopy has been used to study the Bailar twist process in 2, giving activation parameters ΔH‡=10.9(1.1)kcalmol−1, ΔS‡=−11(4)eu and ΔG‡303 K=14(2)kcalmol−1.

Reactions of zirconium amide amidinates with dioxygen. Observation of an unusual peroxo intermediate in the formation of oxo compounds.

Reaction of d(0) Zr(NMe2)2[MeC(N(i)Pr)2]2 (1) with O2 at -30 °C gives three Zr containing products: a peroxo trimer {(μ-η(2):η(2)-O2)Zr[MeC(N(i)Pr)2]2}3 (2), an oxo dimer {(μ-O)Zr[MeC(N(i)Pr)2]2}2 (3), and an oxo polymer {(μ-O)Zr[MeC(N(i)Pr)2]2}n (4). is a rarely observed peroxo complex from the reaction of a d(0) complex with O2.

Amidate ligand design effects in zirconium-catalyzed enantioselective hydroamination of aminoalkenes

In situ generated axially chiral zirconium biphenyl amidate complexes are efficient precatalysts for the enantioselective intramolecular hydroamination of aminoalkenes, generating α-substituted pyrrolidines and piperidine with up to 74% ee. Five new chelating amide proligands and three new zirconium amidate complexes have been prepared and fully characterized in this investigation of ligand structure/catalyst function. Solid-state molecular structures of the complexes suggest that the observed moderate and highly variable enantioselectivities are a consequence of the multiple isomers accessible to this family of complexes, including a κ 2-( O, O)-bonding motif. Thermal stability studies of the complexes further revealed the tendency of these complexes to undergo diastereoselective dimerization to afford homochiral dimers. These dimeric precatalysts are less efficient when used for the cyclization of aminoalkenes in comparison to their monomeric precursors. These results illustrate the variable coordination modes accessible to amidate ligands and suggest steric factors that must be considered in advanced ligand design.

Synthesis, structure, and catalytic activity of group 4 complexes with new chiral biaryl-based NO 2 ligands

A new series of chiral bis-ligated group 4 complexes have been prepared from the reaction between M(NMe 2) 4 (M = Ti, Zr) and C 1-symmetric biaryl-based NO 2 ligands, ( R)-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl ( 1H), ( R)-2-(mesitoylamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl ( 2H), ( S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl ( 3H), ( R)-2-(3,5-di- tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-1,1′-binaphthyl ( 4H), ( R)-2-(3- tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl ( 5H), which are derived from ( R)-2-amino-2′-methoxy-1,1′-binaphthyl, ( R)-2-amino-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl or ( S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-amino-2′-methoxy-1,1′-binaphthyl. Treatment of M(NMe 2) 4 with 2 equiv. of mesitoylamides 1H, 2H or 3H gives, after recrystallization from a toluene or n-hexane solution, the bis-ligated chiral titanium amides ( 1) 2Ti(NMe 2) 2 ( 6), ( 2) 2Ti(NMe 2) 2 ( 8), ( 3) 2Ti(NMe 2) 2 ( 10), and zirconium amides ( 1) 2Zr(NMe 2) 2 ( 7), ( 2) 2Zr(NMe 2) 2 ( 9), ( 3) 2Zr(NMe 2) 2 ( 11), respectively, in good yields. Under similar reaction conditions, treatment of M(NMe 2) 4 with 2 equiv. of Schiff base ligands 4H or 5H gives, after recrystallization from a toluene solution, the chiral bis-ligated titanium complex {( R)-2-[3,5-(Me 3C) 2-2-O-C 6H 2CH(NMe 2)N]-2′-(MeO)-1,1′-C 20H 12} 2Ti ( 12) and zirconium complex {( R)-2-[3-Me 3C-2-O-C 6H 3CH(NMe 2)N]-2′-(MeO)-1,1′-(6-Me-C 6H 3) 2}( 5)ZrNMe 2 ( 13), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 1H, 6, 8, 9, 12 and 13 have further been confirmed by X-ray diffraction analyses. The titanium and zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to excellent yields with good ee values.

Synthesis, structure, and catalytic activity of group 4 complexes with new chiral binaphthyldiamine-based ligands

Abstract Five group 4 metal complexes (1)2Zr(NMe2)2 (5), (2)2Ti(NMe2)2 (6), (2)2Zr(NMe2)2 (7), (3)2Zr (8) and (4)2Ti(NMe2)2 (9) have been readily prepared from the reaction between M(NMe2)4 (M = Ti, Zr) and chiral binaphthyldiamine-based ligands, (R)-2,2′-bis(diphenylthiophosphoramino)-1,1′-binaphthyl (1H2), (R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis(diphenylthiophosphoramino)-1,1′-binaphthyl (2H2), (R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis(methanesulphonylamino)-1,1′-binaphthyl (3H2), and C1-symmetric ligand, (R)-2-(mesitylenesulphonylamino)-2′-(dimethylamino)-1,1′-binaphthyl (4H). All the complexes have been characterized by various spectroscopic techniques, elemental analyses and X-ray diffraction analyses. The zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good yields with moderate ee (enantiomeric excess) values.

Rhodium‐Catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes

Rhodium‐Catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes

Rhodium‐Catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes

Rhodium‐Catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes

Synthesis and characterization of group 4 metal amides with new C2-symmetric binaphthyldiamine-based ligands and their use as catalysts for asymmetric hydroamination/cyclization

A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe(2))(4) (M = Ti, Zr) and chiral ligands, (R)-2,2'-bis(p-toluenesulfonylamino)-1,1'-binaphthyl (1H(2)), (R)-2,2'-bis(diphenylphosphinoylamino)-1,1'-binaphthyl (2H(2)), (R)-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (3H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(pyrrol-2-ylmethyleneamino)-1,1'-binaphthyl (4H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (5H(2)), and (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitylenesulfonylamino)-1,1'-binaphthyl (6H(2)), which are derived from (R)-2,2'-diamino-1,1'-binaphthyl. Reaction of M(NMe(2))(4) with 1 equiv of arylsulfonylamides 1H(2) and 6H(2), diphenylphosphoramide 2H(2), mesitoylamides 3H(2) and 5H(2), or Schiff base ligand 4H(2) at room temperature gives, after recrystallization from a benzene, toluene or n-hexane solution, the chiral titanium amides (1)Ti(NMe(2))(2).3C(6)H(6) (7.3C(6)H(6)), (4)Ti(NMe(2))(2) (11), (5)Ti(NMe(2))(2) (13) and (6)Ti(NMe(2))(2) (15), and zirconium amides (1)Zr(NMe(2))(2) (8), (2)Zr(NMe(2))(2) (9), (3)Zr(NMe(2))(2) (10), (4)Zr(NMe(2))(2) (12), (5)Zr(NMe(2))(2) (14) and (6)Zr(NMe(2))(2).C(7)H(8) (16.C(7)H(8)) respectively, in good yields. These amides are stable below 90 degrees C in toluene solution, but they degrade via ligand redistribution at a higher temperature. For example, treatment of (1)Zr(NMe(2))(2) (8) or (5)Zr(NMe(2))(2) (14) in refluxing toluene for three days leads to the isolation of the complexes (1)(2)Zr.C(7)H(8) (17.C(7)H(8)) and (5)(2)Zr.3C(7)H(8) (18.3C(7)H(8)) respectively, in moderate yields. These new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 7-9, 11-13, and 15-18 have further been confirmed by X-ray diffraction analyses. The titanium amide 13 and all the zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to excellent yields with moderate to excellent ee values (up to 93%). Theoretical studies reveal the interaction between the carbon chain of the substrate and the sterically demanding ligand groups plays a key role in the stereodirection of the enantioselection during the Zr=N bond approaches to the C=C bond.

Synthesis, structure, and catalytic activity of titanium(IV) and zirconium(IV) amides with chiral biphenyldiamine-based ligands

Abstract A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe2)4 (M = Ti, Zr) and C2-symmetric ligands, (R)-2,2′-bis(pyridin-2-ylmethylamino)-6,6′-dimethyl-1,1′-biphenyl (2H2), (R)-2,2′-bis(pyrrol-2-ylmethyleneamino)-6,6′-dimethyl-1,1′-biphenyl (3H2), (R)-2,2′-bis(diphenylphosphinoylamino)-6,6′-dimethyl-1,1′-biphenyl (4H2), (R)-2,2′-bis(methanesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (5H2), (R)-2,2′-bis(p-toluenesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (6H2), and C1-symmetric ligands, (R)-2-(diphenylthiophosphoramino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (7H) and (R)-2-(pyridin-2-ylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (8H), which are derived from (R)-2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl. Treatment of M(NMe2)4 with 1 equiv. of N4-ligand, 2H2 or 3H2 gives, after recrystallization from an n-hexane solution, the chiral zirconium amides (2)Zr(NMe2)2 (9), (3)Zr(NMe2)2 (11), and titanium amide (3)Ti(NMe2)2 (10), respectively, in good yields. Reaction of Zr(NMe2)4 with 1 equiv of diphenylphosphoramide 4H2 affords the chiral zirconium amide (4)Zr(NMe2)2 (12) in 85% yield. Under similar reaction conditions, treatment of Ti(NMe2)4 with 1 equiv. of sulphonylamide ligand, 5H2 or 6H2 gives, after recrystallization from a toluene solution, the chiral titanium amides (5)Ti(NMe2)2·0.5C7H8 (13·0.5C7H8) and (6)Ti(NMe2)2 (15), respectively, in good yields, while reaction of Zr(NMe2)4 with 1 equiv. of 5H2 or 6H2 gives the bis-ligated complexes, (5)2Zr (14) and (6)2Zr (16). Treatment of M(NMe2)4 with 2 equiv. of diphenylthiophosphoramide ligand 7H or N3-ligand 8H gives, after recrystallization from a benzene solution, the bis-ligated chiral zirconium amides (7)2Zr(NMe2)2 (17) and (8)2Zr(NMe2)2 (19), and bis-ligated chiral titanium amide (8)2Ti(NMe2)2 (18), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 10, 12, 13, and 17–19 have further been confirmed by X-ray diffraction analyses. The zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good to excellent yields with moderate ee values, while the titanium amides are not.

Bis(cyclopentadienyl) zirconium(IV) amides as possible precursors for low pressure CVD and plasma-enhanced ALD

Low pressure chemical vapour deposition (LPCVD) of [ZrCp 2(NMe 2) 2] ( 1), [ZrCp 2(η 2-MeNCH 2CH 2NMe)] ( 2), [ZrCp′ 2(NMe 2) 2] ( 3) and [ZrCp′ 2(NEt 2) 2] ( 4) (Cp = η 5-cyclopentadienyl, Cp′ = η 5-monomethylcyclopentadienyl), onto glass substrates at 600 °C, afforded highly reflective and adhesive films of zirconium carbide and amorphous carbon. Powder XRD indicated that the films were largely amorphous, although small, broad peaks accounting for ZrC and ZrO 2 were present, suggesting that the remaining carbon was due to amorphous deposits from the cyclopentadienyl ligands. SEM images showed an island-growth mechanism with distinct crevices between the concentric nodules. Plasma-enhanced atomic layer deposition (PEALD) of compounds 1 and 2 showed that the precursors were not sufficiently stable or volatile to give a good rate of film growth.

Synthesis and Structural Characterization of Group 4 Metal Complexes Bearing Pentavalent Phosphorus-Bridged Ligands [(C13H8)(iPr2N)P(−O)(C2B10H10)]2− and [(C13H9)(iPr2N)P(═O)(C2B9H10)]2−

Treatment of (C13H9)(iPr2N)PCl with Li2C2B10H10 gave, after neutralization with Me3NHCl, a trivalent phosphorus-bridged compound, (C13H9)(iPr2N)P(C2B10H11). It was easily converted to a pentavalent phosphorus-bridged ligand, (C13H9)(iPr2N)P(═O)(C2B10H11) (4), by reacting with excess hydrogen peroxide in toluene. An equimolar reaction of 4 with Zr(NMe2)4 in toluene at room temperature afforded a zirconium amide incorporating a fluorenylide unit, [σ:σ-(C13H8)(iPr2N)P(-O)(C2B10H10)]Zr(NMe2)2(THF) (5). Complex 5 was converted to the zirconacarborane [η1:η5-(C13H9)(iPr2N)P(═O)(C2B9H10)]Zr(NMe2)2 (6) in refluxing toluene in the presence of Me2NH. Its titanium analogue, [η1:η5-(C13H9)(iPr2N)P(═O)(C2B9H10)]Ti(NMe2)2 (7), was directly prepared from the reaction of 4 with Ti(NMe2)4 in refluxing toluene. Complex 7 reacted with KH in C6D6 to generate the deprotonated product {[η1:η5-(C13H8)(iPr2N)P(═O)(C2B9H10)]Ti(NMe2)2}{(η6-C6D6)2K} (8). These new complexes were fully characterized by various spectroscopic techniqu...

Synthesis, Structure, and Catalytic Activity of TiIV and ZrIV Complexes Derived from (R)‐2,2′‐Diamino‐1,1′‐binaphthyl‐Based N4‐Donor Ligands

AbstractReaction of (R)‐bis(pyrrol‐2‐ylmethyleneamino)‐1,1′‐binaphthyl (1H2) or (R)‐N,N′‐bis(pyridin‐2‐ylmethyl)‐1,1′‐binaphthyl‐2,2′‐diamine (2H2) with Zr(NMe2)4 (1 equiv.) gives chiral zirconium amides 1‐Zr(NMe2)2·C7H8 (4·C7H8) or 2‐Zr(NMe2)2 (6) in good yields, respectively. Under similar conditions, 1H2 reacts with Ti(NMe2)4 (1 equiv.) to give chiral titanium amide 1‐Ti(NMe2)2·C6H6 (3·C6H6), whereas treatment of 2H2 with Ti(NMe2)4 (1 equiv.) leads to the isolation of bis(ligated) product (2)2‐Ti·C7H8 (5·C7H8) in 74 % yield. All complexes were characterized by various spectroscopic techniques, elemental analysis, and X‐ray diffraction analysis. Zirconium amides 4 and 6 are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, and cyclic amines were obtained in good‐to‐excellent yields with moderate ee values (up to 59 %); titanium amides 2 and 5 were not active under the reaction conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Lanthanide and group 4 metal complexes with new chiral biaryl-based NNO-donor ligands

A new series of lanthanide and group 4 metal complexes have been prepared from the reactions between Ln[N(SiMe(3))(2)](3) or M(NMe(2))(4) and chiral ligands, (R)-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-1,1'-binaphthyl (H), (S)-5,5',6,6',7,7',8,8'-octahydro-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-1,1'-binaphthyl (H) and (R)-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-6,6'-dimethyl-1,1'-biphenyl (H). The steric effect of the ligand coupled with the size effect of the ions plays an important role in the formation of the lanthanide complexes. For example, treatment of H with 1 equiv of Ln[N(SiMe(3))(2)](3) (Ln = Y, Yb) in toluene gives the tris-ligated complexes, ()(3)Y.C(7)H(8) (.C(7)H(8)) and ()(3)Yb.2C(7)H(8) (.2C(7)H(8)) in good yields; reaction of H with 1 equiv of Sm[N(SiMe(3))(2)](3) also gives the tris-ligated product ()(3)Sm (), while treatment of H with 1 equiv of Ln[N(SiMe(3))(2)](3) (Ln = Y, Yb) leads to the isolation of the bis-ligated organolanthanide amides ()(2)LnN(SiMe(3))(2).2C(6)H(6) (Ln = Y (.2C(6)H(6)), Yb (.2C(6)H(6))) in good yields. Reaction of H, H or H with 1 equiv of M(NMe(2))(4) gives, after recrystallization from a toluene or benzene solution, the chiral bis-ligated titanium amides ()(2)Ti(NMe(2))(2).0.75C(7)H(8) (.0.75C(7)H(8)), ()(2)Ti(NMe(2))(2) (), ()(2)Ti(NMe(2))(2).C(6)H(6) (.C(6)H(6)), and zirconium amides ()(2)Zr(NMe(2))(2).C(7)H(8) (.C(7)H(8)), ()(2)Zr(NMe(2))(2) (), ()(2)Zr(NMe(2))(2).C(6)H(6) (.C(6)H(6)), in good yields, respectively. Treatment of Zr(NMe(2))(4) with 1 equiv of (R)-2-(pyrrol-2-ylmethylamino)-2'-methoxy-1,1'-binaphthyl (H(2)), which was prepared from the reduction of H with an excess of NaBH(4) in a solvent mixture of MeOH and toluene (1 : 1) at 50 degrees C, gives the trinuclear complex [(R)-2-O-C(20)H(12)-2'-(NCH(2)C(4)H(3))](2)Zr(3)(NMe(2))(6).2C(7)H(8) (.2C(7)H(8)) in 65% yield. Organolanthanide amides and zirconium amides are active catalysts for asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to good yields with moderate ee values, while the titanium amides are not. During the course of the catalytic reaction, is decomposed leading to the isolation of ()(3)Y.C(7)H(8) (.C(7)H(8)) in 35% yield from a toluene solution. The organolanthanide amides are also active catalysts for ring-opening polymerization of rac-lactide, giving isotactic-rich polylactides. All compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds H, H, , and have further been confirmed by X-ray diffraction analyses.

Titanium and zirconium complexes supported by dipyrrolide ligands.

The reactions between meso-disubstituted dipyrromethanes and titanium and zirconium amides and alkyls have generated the first examples of dipyrrolide complexes of Group 4 metals.

Zirconium Amide, Halide, and Alkyl Complexes Supported by Tripodal Amido Ligands Derived fromcis,cis-1,3,5-Triaminocyclohexane

Zirconium complexes containing the chelating triamido ligands [cis,cis-1,3,5-(C6F5N)3C6H9]3- and {cis,cis-1,3,5-[3,5-(CF3)2C6H3N]3C6H9}3- are reported. The dimethylamido complexes [cis,cis-1,3,5-(C...

Synthesis and structures of dinuclear low-coordinate lithium and zirconium(iv) complexes derived from the diamido ligands 1,3-(CH2N̄C6H3R12)2C6H4(R1= Me or Pri)

Treatment of 1,3-bis(bromomethyl)benzene with two equivalents of the appropriate compound Li[N(H)C6H3R12-2,6] yielded the diamines 1,3-[CH2N(H)C6H3R12-2,6]2C6H41 [R1 = Me, abbreviated as H2(D)] or 2 [R = Pri, abbreviated as H2(D′)]. The crystalline complex [Li2(D′)]23 was obtained from 2 and 2 LiBun; the analogue from 1 and 2 LiBun was an incompletely characterised oil. The binuclear, crystalline zirconium(IV) amides [{Zr(NMe2)3}2(μ-D′)] 4, its D analogue 5 and [{Zr(NMe2)2}2(μ-D)2] 6 were prepared from [{Zr(NMe2)3(μ-NMe2)}2] and H2(D′) [or 2 H2(D′)], H2(D) and 2 H2(D), respectively. The single crystal X-ray molecular structures of complexes 3 and 4 have been elucidated. That of 3 comprises a sixteen-membered, twisted macrocyclic LiNC5NLiNC5N core with each of the two-coordinate lithium atoms part of the LiNLiN rhombus. The four-coordinate zirconium atoms in 4 are in an only slightly distorted tetrahedral environment, with the two Zr(NMe2)3 units arranged trans to one another across the central aromatic ring. None of 4–6, with MAO, showed catalytic activity for ethylene polymerisation under ambient conditions.

Immobilization of zirconium amide on a Cp-modified silica surface and its use as a catalyst for ethylene polymerization

Abstract Heterogeneous ethylene polymerization catalysts were prepared by supporting tetrakis(dimethylamino)zirconium on chemically modified silica surface. The silica was modified with a silane coupling agent, Cp(CH 2 ) 3 Si(OEt) 3 , using ALCVD-technique. On the resulting cyclopentadienyl surface zirconium amide, Zr(NMe 2 ) 4 , was immobilized with and without using methyllithium. Depending on the use of methyllithium the immobilization resulted in either mono- or bis-cyclopentadienyl zirconium complexes, which were characterized using chemical analysis, FT-IR, 13 C- and 29 Si-NMR results. Moreover, a homogeneous model compound, (Me 3 SiCp) 2 Zr(NMe 2 ) 2 , was synthesized with a reaction between Zr(NMe 2 ) 4 and Me 3 SiCp. The preliminary results of ethylene polymerization with these supported and unsupported organometallic complexes are presented.