Reaction Of ZrCl4 Research Articles

Pore Surface Engineering with Controlled Loadings of Functional Groups via Click Chemistry in Highly Stable Metal–Organic Frameworks

Reactions of ZrCl(4) and single or mixed linear dicarboxylic acids bearing methyl or azide groups lead to highly stable isoreticular metal-organic frameworks (MOFs) with content-tunable, accessible, reactive azide groups inside the large pores. These Zr-based MOFs offer an ideal platform for pore surface engineering by anchoring various functional groups with controlled loadings onto the pore walls via the click reaction, endowing the MOFs with tailor-made interfaces. Significantly, the framework and crystallinity of the functionalized MOFs are well-retained, and the engineered pore surfaces have been demonstrated to be readily accessible, thus providing more opportunities for powerful and broad applications of MOFs.

Inside Cover: A Series of Isoreticular, Highly Stable, Porous Zirconium Oxide Based Metal–Organic Frameworks (Angew. Chem. Int. Ed. 37/2012)

Waterproof MOFs are prepared from the reaction of ZrCl4 with the corresponding dicarboxylic acid. In their Communication on page 9267 ff., C. Serre and co-workers show that the members of this new series of isoreticular metal–organic frameworks (MOFs) are hydrophobic, and have a one-dimensional pore system and Lewis acidity. They also have a higher hydrothermal and mechanical stability than their UiO MOF polymorph counterparts.

Highly Active Ethylene Polymerization and Regioselective 1-Hexene Oligomerization Using Zirconium and Titanium Catalysts with Tridentate [ONO] Ligands

A series of tridentate dianionic ligands [4-(t)Bu-6-R-2-(3-R'-5-(t)Bu-2-OC(6)H(2))N=CH C(6)H(2)O](2-) (L) [R = R' = (t)Bu (L1); R = CMe(2)Ph, R' = (t)Bu (L2); R = adamantyl, R' = (t)Bu (L3); R = R' = CMe(2)Ph (L4); R = SiMe(2)(t)Bu, R' = CMe(2)Ph (L5)] were synthesized. Reactions of TiCl(4) with 1 equiv of ligands L1-L5 in toluene afford five-coordinate titanium complexes with general formula LTiCl(2) [L = L1 (1); L2 (2); L3 (3); L4 (4); L5 (5)]. The addition of tetrahydrofuran (THF) to titanium complex 5 readily gives THF-solvated six-coordinate complex 6, which also was obtained by reaction of TiCl(4) with 1 equiv of ligand L5 in THF. Reactions of ZrCl(4) with 1 or 2 equiv of ligands L1-L5 afford six-coordinate zirconium mono(ligand) complexes LZrCl(2)(THF) [L = L2 (7); L4 (8); L5 (9)], and bis(ligand) complexes L(2)Zr [L = L1 (10); L4 (11)]. The molecular structures of complexes 2, 8, and 11 were established by single-crystal X-ray diffraction studies. Upon activation with methylaluminoxane, complexes 1-9 are active for ethylene polymerization. The activities and half-lifes of the catalyst systems based on zirconium complexes are more than 10(6) g of polyethylene (mol Zr)(-1) h(-1) and 6 h, respectively. Complex 9 is more active and long-lived, with a turnover frequency (TOF) of 2.6 × 10(5) (mol C(2)H(4)) (mol Zr)(-1) h(-1), a half-life of >16 h, and a total turnover number (TON) of more than 10(6) (mol C(2)H(4)) (mol Zr)(-1) at 20 °C and 0.5 MPa pressure. Even at 80 °C, complex 9/MAO catalyst system has a long lifetime (t(1/2) > 2 h), as well as high activity that is comparable with that at 20 °C. When activated with methylaluminoxane (MAO), complex 9 also show moderate catalytic activity and more than 99% 2,1-regioselectivity for 1-hexene oligomerization.

Zirconium complexes containing a diarylamido diphosphine ligand: Structural preferences controlled by ligand electronics and sterics

This work describes the preparation of [PNP]ZrX 3 ([PNP] − = [N( o-C 6H 4P i Pr 2) 2] −; X = Cl, Me, CH 2SiMe 3) whose structural preference is found to be a function of the electronic and steric nature of the monodentate ligand X −. The reaction of ZrCl 4(THF) 2 with [PNP]Li in toluene at room temperature generates [PNP]ZrCl 3 as a red solid in 60% yield. Alkylation of [PNP]ZrCl 3 with three equivalents of Grignard reagents in diethyl ether at −35 °C produces cleanly [PNP]ZrR 3 (R = Me, CH 2SiMe 3) as yellow crystalline materials. An X-ray diffraction study of [PNP]ZrCl 3 showed it to be a chloride-bridged binuclear species {[PNP]ZrCl 2(μ−Cl)} 2 in which both zirconium atoms are 7-coordinate whereas that of [PNP]ZrMe 3 revealed a mononuclear, 6-coordinate core structure. Interestingly, with the incorporation of more sterically demanding alkyls, [PNP]Zr(CH 2SiMe 3) 3 is a 5-coordinate compound wherein the amido phosphine ligand is κ 2-N,P bound to zirconium. The solution structures of these molecules were also assessed by variable-temperature NMR spectroscopy.

Mixed-sandwich complexes of zirconium(III) and hafnium(III): Potential analogues of [U(η-C 8H 6{Si iPr 3-1,4} 2)(η-Cp ∗)] for cyclooligomerisation of CO

Reaction of ZrCl 4 or HfCl 4 with 2 equivalents of K 2(COT{Si i Pr 3-1,4} 2), followed by in situ treatment of the resultant sandwich complexes M(COT{Si i Pr 3-1,4} 2) with a further equivalent of MCl 4 affords the mono-COT chloro-bridged dimers [M(η-COT{Si i Pr 3-1,4} 2)(μ-Cl)Cl] 2, M = Zr ( 1); M = Hf ( 4). Further reaction of the latter with 2 equivalents of KCp ∗ yields the crystallographically characterised M(IV) mixed-sandwich complexes [M(η-COT{Si i Pr 3-1,4} 2)(η-Cp ∗)Cl], M = Zr ( 2); M = Hf ( 5). Reduction of 2 with KC 8 in toluene affords the monomeric Zr(III) mixed-sandwich complex [Zr(η-COT{Si i Pr 3-1,4} 2)(η-Cp ∗)], whereas the analogous reaction with 5 results in coupling of the COT rings to give dimeric [Hf(η-Cp ∗)] 2(μ-η 7,η 7-(C 8H 6{Si i Pr 3-3,6} 2C 8H 6{Si i Pr 3-3,6} 2)); both 2 and 5 have been structurally characterised.

C- ansa-zirconocene complexes with O/S donor ligands: Novel homoleptic six coordinate 4-mercaptophenolate complex of Zr(IV)

New C- ansa-zirconocene complexes containing methoxythiophenolate and mercaptophenolate ligands have been synthesized and characterized. The reaction of (HSC 6H 4- n-OMe) ( n = 2, 3 or 4) with [Zr{( t-Bu)HC(η 5-C 5Me 4)(η 5-C 5H 4)}Me 2] ( 1) led to the formation of monosubstituted complexes [Zr{( t-Bu)HC(η 5-C 5Me 4)(η 5-C 5H 4)}Me(κ,S-SC 6H 4- n-OMe)] ( n = 2 ( 2); n = 3 ( 3)) and the disubstituted complex [Zr{( t-Bu)HC(η 5-C 5Me 4)(η 5-C 5H 4)}(κ,S-SC 6H 4-4-OMe) 2] ( 4). The complexes [Zr{(R)HC(η 5-C 5Me 4)(η 5-C 5H 4)}(κ,O-OC 6H 4-4-SH) 2] (R = t-Bu ( 6); R = CH 2CH CH 2 ( 7)) and [Zr(η 5-C 5H 4) 2(OC 6H 4- n-SH) 2] ( n = 3 ( 9); n = 4 ( 10)) have been synthesized using the corresponding dimethyl zirconocene and mercaptophenol. However, the reaction of [Zr{( t-Bu)HC(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] ( 11) with 4-mercaptophenol in the presence of NEt 3 led to the formation of the first example of a homoleptic six-coordinate mercaptophenolate complex of zirconium, namely [HNEt 3] 2[Zr(κ,O-OC 6H 4-4-SH) 6] ( 12). Complex 12 can be obtained in higher yield by the reaction of ZrCl 4 with six equivalents of 4-mercaptophenol and NEt 3. The reaction of 12 with [Zr(η 5-C 5H 4) 2Cl 2] gave the unexpected disubstituted complex [Zr(η 5-C 5H 4) 2(OC 6H 4-4-SH) 2] ( 10). The molecular structures of 4 and 12 have been determined by single-crystal X-ray diffraction studies.

Synthesis and X-ray structure of novel 2- and 3-heteroatom-substituted ansa-zirconocene complexes

New ansa -zirconocene complexes with amino and alkoxy substituents attached to the η 5 -bonded indenyl fragment have been synthesized. Crystallographic analysis showed that heteroatom substituents, especially those in the 3-position on the indenyl ligand, have a substantial effect on the structure of metallocenes leading to an increase in the gap aperture in those complexes. New ansa -zirconocene complexes with amino ( 8 – 11 ) and alkoxy ( 12 ) substituents attached to the η 5 -bonded indenyl fragment have been synthesized by the reaction of ZrCl 4 with the appropriate dilithium salt in toluene. In addition to HRMS, NMR spectroscopy, and elemental analysis, all new metallocenes have been characterized by single crystal X-ray analysis. Crystallographic analysis showed that heteroatom substituents, especially those in the 3-position on the indenyl ligand, have a substantial effect on the structure of metallocenes leading to an increase in the gap aperture in those complexes. Slippage of the indenyl fragments toward η 3 -bonding was found to correlate with the electron donating ability of the substituent in the 3-position, being larger for amino than alkoxy substituents. Based upon the amount of slippage, 3-amino-substituted indenyl complexes bear strong resemblance to a fluorenyl complexes.

Synthesis, Structures and Reactivity of Group 4 Hydrazido Complexes Supported by Calix[4]arene Ligands

Reaction of TiCl(2)(Me(2)Calix) with 2 equiv of LiNHNRR' afforded the corresponding terminal hydrazido(2-) complexes Ti(NNRR')(Me(2)Calix) (R = Ph, R' = Ph (1) or Me; R = R' = Me (3)) which were all structurally characterized. The X-ray structure of Ph(2)NNH(2) is reported for comparison. Compound 1 was also prepared from Na(2)[Me(2)Calix] and Ti(NNPh(2))Cl(2)(py)(3). Reaction of ZrCl(2)(Me(2)Calix) with 2 equiv of LiNHNR(2) afforded only the bis(hydrazido(1-)) complexes Zr(NHNR(2))(2)(Me(2)Calix) (R = Ph or Me). Treatment of Ti(NNMe(2))(Me(2)Calix) (3) with MeI gave the zwitterionic hydrazidium species Ti(NNMe(3))(MeCalix) (6) via a net isomerization reaction which was found to be catalytic in MeI. The corresponding reaction of 3 with CD(3)I gave Ti(NNMe(2)CD(3))(MeCalix) (6-d(3)) with concomitant elimination of MeI. Reaction of 3 with 1 equiv of MeOTf gave [Ti(NNMe(3))(Me(2)Calix)][OTf] (7-OTf) which in turn reacted with (n)Bu(4)NI to form 6 and MeI. Addition of PhCHO to 3 gave the mu-oxo dimer [Ti(mu-O)(Me(2)Calix)](2) and benzaldehyde-dimethylhydrazone. Reaction of either 3 or 6 with (t)BuNCO gave the zwitterionic species Ti{(t)BuNC(NNMe(3))O}(MeCalix) (10) which has been crystallographically characterized. Compound 10 is the formal product of insertion of an isocyanate into the Ti=N(alpha) bond of a titanium hydrazide or hydrazidium species (Me(2)Calix or MeCalix = dianion or trianion of the di- or monomethyl ether of p-tert-butyl calix[4]arene, respectively).

Zirconium complexes with versatile β-diketiminate ligands: Synthesis, structure, and ethylene polymerization

A series of zirconium complexes ( 2c, 2d, 2f, 2g, 2h, 2i) containing symmetrical or unsymmetrical β-diketiminate ligands were synthesized by the reaction of ZrCl 4 · 2THF with lithium salt of the corresponding ligand in 1:2 molar ratio. X-ray crystal structures reveal that complexes 2d and 2g adopt distorted octahedral geometry around the zirconium center. These complexes showed moderate activities for ethylene polymerization, when methylaluminoxane (MAO) was used as cocatalyst. The steric and electronic effects of the substituents at the phenyl rings had considerable influence on the catalytic activities of the metal complex, as well as the molecular weights and molecular weight distributions (MWD) of produced polymers. Introduction of electron-withdrawing CF 3 group to phenyls in the ligand led to a significant increase of catalytic activities, and complex 2f ( p-CF 3) exhibited the highest catalytic activity of 7.45 × 10 5 g PE/mol-Zr · h among the investigated complexes. Complexes 2a– d could produce ultra-high molecular weight polyethylenes (UHMWPE) that were hardly dissolvable in decahydronaphthalene or 1,2-dichlorobenzene under the molecular weight measurement conditions. Nevertheless, polyethylenes with broad MWD could be afforded by complexes 2g– i, which was probably due to the introduction of bulky unsymmetrical ligands leading to the formation of multi active species under polymerization conditions. High-temperature 13C NMR data indicate the linear structure of obtained polyethylenes.

Heterocycle‐Substituted Indenes as Precursors for Supported Zirconocene Catalysts

AbstractThe indene ligands {1‐C9H7R} [R = C2H4(C4H7O2) (1), C2H4(C3H5O2) (2), CH2(C5H9O) (3)] were prepared by alkylation of indene and used to prepare the SiMe2‐bridged indenylcyclopentadiene ligands {Me2Si(3‐C9H6R)(C5Me4H)}[R = C2H4(C4H7O2) (4), CH2(C5H9O) (5)]. Bis(indenyl)‐and ansa‐indenylcyclopentadienyl zirconocenes [Zr{1‐η5‐C9H6R}2Cl2] {R = C2H4(C4H7O2) (6), C2H4(C3H5O2) (7), CH2(C5H9O) (8)} and [Zr{Me2Si(3‐η5‐C9H5R)(η5‐C5Me4)}Cl2] {R = C2H4(C4H7O2) (9), CH2(C5H9O) (10)} were prepared by the reaction of ZrCl4 with the appropriate mono‐ or dilithium salts of 1–5. The molecular structure of [Zr{Me2Si(3‐η5‐C9H5C2H4(C4H7O2))(η5‐C5Me4)}Cl2] (9) was determined by single‐crystal X‐ray diffraction studies. Indenylzirconium complexes 6–10 were immobilized on thf‐modified MgCl2, and these supported systems were used to polymerize ethylene in the presence of methylaluminoxane. The catalytic activity of these complexes in both homogeneous and supported polymerization reactions is discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis, characterization and catalytic behaviour of ansa-zirconocene complexes containing tetraphenylcyclopentadienyl rings: X-ray crystal structures of [Zr{Me 2Si(η 5-C 5Ph 4)(η 5-C 5H 3R)}Cl 2] (R = H, Bu t)

The ansa-bis(cyclopentadiene) compounds, Me 2Si(C 5HPh 4)(C 5H 4R) (R = H ( 2); Bu t ( 3)), have been prepared by the reaction of C 5HPh 4(SiMe 2Cl) ( 1) with Na(C 5H 5) or Li(C 5H 4Bu t ), respectively, and transformed to the di-lithium derivatives, Li 2{Me 2Si(C 5Ph 4)(C 5H 3R)} (R = H ( 4); Bu t ( 5)), by the action of n-butyllithium. The ansa-zirconocene complexes, [Zr{Me 2Si(η 5-C 5Ph 4)(η 5-C 5H 3R)}Cl 2] (R = H ( 6); Bu t ( 7)), were synthesized from the reaction of ZrCl 4 with 4 or 5, respectively. Compounds 6 and 7 have been tested in the polymerization of ethylene and compared with their methyl-substituted analogues, [Zr{Me 2Si(η 5-C 5Me 4)(η 5-C 5H 3R)}Cl 2] (R = H ( 8); Bu t ( 9)). Whilst 8 and 9 are catalytically active, the tetraphenyl-substituted complexes 6 and 7 proved to be inactive in the polymerization of ethylene. This phenomenon has been explained by DFT calculations based on the reaction intermediates in the polymerization processes involving 6 and 7, which showed that the extraction of a methyl group from the zirconocene complex to form the cationic active specie is endothermic and therefore unfavourable.

Amido/Amine Triazacyclononane-Based Zirconium Complexes: Syntheses, Reactivity, and Structures

The reactions of [Zr(NMe2)4]2 with triamido-triazacyclonane ligand precursors, {NH(Ph)SiMe2}3tacn (H3N3[9]N3) and {NH(C6H4F)SiMe2}3tacn (H3N3-F[9]N3), led to the formation of complexes [Zr(NMe2)2{N(Ph)SiMe2}2{NH(Ph) SiMe2}tacn], 1, and [Zr(NMe2)2{N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2} tacn], 2, where the zirconium is coordinated to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [{N(Ph')SiMe2}2{NH(Ph')SiMe2}tacn]2-, that formed from deprotonation of two amine pendent arms of the ligands' precursors. The third pendent arm of H3N3[9]N3 and H3N3-F[9]N3 remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the synthesis of [Zr(NMe2){N(Ph)SiMe2}2tacn], 3, that results from the cleavage of the N-Si bond of the original neutral pendent arm. Complexes [ZrCl{N(Ph')SiMe2}2tacn] (Ph' = C6H5, 4, and C6H4F, 5) have been obtained by reactions of ZrCl4 with {MN(Ph')SiMe2}3tacn.2THF (M = Li, Na). Reactions of 4 and 5 with LiC triple bond CPh led to the syntheses of [Zr(CCPh){N(Ph')SiMe2}2tacn] (Ph' = C6H5, 6, and C6H4F, 7). The solid-state structure of 3 shows a chiral metal center.

Activation process of 3-alkyl-substituted ansa-bis(indenyl) zirconocenes by MAO

The ansa-indene compound {1-Me 2Si(3-C 9H 6Et) 2} ( 1) was prepared by alkylation of the unsubstituted ansa-indene. This compound was converted, by reaction with nBuLi, to the dilithium compound [Li 2{1-Me 2Si(3-C 9H 5Et) 2}] ( 2). ansa-Zirconocene [Zr{1-Me 2Si(3-η 5-C 9H 5Et) 2}Cl 2] ( 3) was prepared by the reaction of ZrCl 4 with 2 in ether/toluene at −78 °C. The molecular structure of meso- 3 was determined by single crystal X-ray diffraction studies. The ansa-zirconocene 3 exhibits a greater activity in ethylene polymerization than reference complexes such as [Zr{1-Me 2Si(η 5-C 9H 6) 2}Cl 2] and [Zr{1-C 2H 4(η 5-C 9H 5) 2}Cl 2] and, in addition, it maintained a reasonable level of activity after 12 h of contact with MAO solution. Furthermore, the different elementary steps in the activation process of ethylene polymerization for substituted complexes [Zr{1-Me 2Si(3-η 5-C 9H 5R) 2}Cl 2] (R = Et 3, Me 4, nPr 5 and nBu 6) by commercial methylaluminoxane (MAO) have been studied by UV–vis spectroscopy. Addition of MAO in large excess ([Al]/[Zr] = 2000) at −78 °C yields a previously unreported intermediate in the activation process of metallocenes; this intermediate has an absorption band centered at λ = 639 nm. We report here the influence of the type of catalyst, ring substitution, type of cocatalyst and addition of THF on the activation process of these metallocenes.

Zirconium complexes of the tridentate bis(aryloxide)- N-heterocyclic-carbene ligand: Chloride and alkyl functionalized derivatives

The disodium salt of a bis(aryloxide)- N-heterocyclic-carbene dianionic ligand, Na 2[L], was prepared by reaction of 1,3-bis(4,6-di- tert-butyl-2-hydroxybenzyl)imidazolium bromide [H 3L]Br with 3 equiv. of NaN(SiMe 3) 2. Reaction of ZrCl 4(thf) 2 with 1 equiv. of Na 2[L] gave a mixture of [L]ZrCl 2(thf) ( 1) and [L] 2Zr ( 2). When the amount of Na 2[L] was increased to 2 equiv., the bis(bis(aryloxide)- N-heterocyclic-carbene) complex 2 was obtained in good yield. The dichloro complex 1 is a precursor to organometallic derivatives, and treatment with PhCH 2MgCl or Me 3SiCH 2Li yielded [L]ZrR 2 [R = CH 2Ph ( 3), CH 2SiMe 3 ( 4)]. The disodium salt of the ligand Na 2[L] is unstable and undergoes 1,2-benzyl migration, whereas zirconium complexes of the [L] 2− ligand are found to be thermally stable in solid and solution. The X-ray crystal structures of 1, 2, and 3 are described.

A zirconium dichloro complex supported by an ancillary stereorigid tetradentate bis(phenoxo-imino) Schiff-base-donor ligand: Evidence for a conformational equilibrium between two solution stereoisomers

Reaction of the dilithium salt of the Schiff-base N, N′- o-phenylene-bis(3,5-di- tert-butyl-salicylidene-imine) ( t Bu 4salophenH 2) with 1 equiv. of ZrCl 4(THF) 2 in toluene at −78 °C affords the dichloro complex ZrCl 2[C 6H 4-1,2-{N CH-(3,5- t Bu 2C 6H 2-2-O)} 2], isolated as a mixture of the C 2 v -( 3a) and C 2-( 3b) symmetry isomers. Thermodynamic and kinetic parameters for the equilibrium between 3a and 3b have been determined and studied by 1H NMR spectroscopy. Reactions of ZrCl 2[C 6H 4-1,2-{N CH-(3,5- t Bu 2C 6H 2-2-O)} 2] with alkylating reagents gave an intractable, unidentified mixture of products from which the NMR spectra in C 6D 6 solution are unusable.

Synthesis and Structure of Asymmetric Zirconium‐Substituted Silicotungstates, [Zr6O2(OH)4(H2O)3 (β‐SiW10O37)3]14‐ and [Zr4O2(OH)2(H2O)4 (β‐SiW10O37)2]10‐.

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Transition metal cyclopentadienyl complexes bearing perfluoro-4-tolyl substituents

Depending on the ratio of starting materials and the reaction conditions, perfluorotoluene (C 6F 5CF 3) reacts with sodium cyclopentadienide (NaCp; Cp = C 5H 5) and excess sodium hydride to afford, after acidic aqueous workup, moderate to high yields of mono-, bis-, tris-, and tetrakis(perfluoro-4-tolyl)cyclopentadiene ( 1, 2, 3, and 4, respectively). Treatment of 1 with excess NaH in THF afforded sodium (perfluoro-4-tolyl)cyclopentadienide ( 5) in 90% yield. Reaction of FeBr 2 with 2 equiv. of 5 afforded a 68% yield of (η 5-C 5H 4C 7F 7) 2Fe ( 6). Reaction of ZrCl 4(THF) 2 with 2 equiv. of 5 afforded a 58% yield of (η 5-C 7F 7C 5H 4) 2ZrCl 2 ( 7). Reaction of Mn(CO) 5Br with 5 afforded a 74% yield of (η 5-C 7F 7C 5H 4)Mn(CO) 3 ( 8). Treatment of 3b with NaH and then with Mn(CO) 5Br in DME afforded a 26% yield of [η 5-1,2,4-(C 7F 7) 3C 5H 2]Mn(CO) 3 ( 9). Treatment of 3b with NaH and then with FeBr 2 in DME afforded a trace yield of [η 5-1,2,4-(C 7F 7) 3C 5H 2] 2Fe ( 10), which was not fully characterized. Dienes 2a, 3a, and 3b and metal complexes 7, 8, and 9 were structurally characterized by single-crystal X-ray diffraction. Infrared spectroscopic analysis of the substituted CpMn(CO) 3 complexes showed a linear increase of 5 cm −1 in the A-symmteric stretching frequency for each C 7F 7 substituent, compared to the analogous value of 4 cm −1 reported earlier for each pentafluorophenyl (C 6F 5) substituent. Solution voltammetric analysis of the substituted ferrocene 6 revealed a shift in the E 1/2 of 465 mV relative to ferrocene, compared to the analogous value of about 340 mV for 1,1′-bis(pentafluorophenyl)ferrocene.

Synthesis and Structure of Asymmetric Zirconium-Substituted Silicotungstates, [Zr6O2(OH)4(H2O)3(β-SiW10O37)3]14- and [Zr4O2(OH)2(H2O)4(β-SiW10O37)2]10-

The reaction of ZrCl4 with [gamma-SiW10O36]8- in a potassium acetate buffer results in two different products depending on the reactant ratios. The trimeric species [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- (1) consists of three beta23-SiW10O37 units linked by an unprecedented Zr6O2(OH)4(H2O)3 cluster with C1 point group symmetry. The dimeric species [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10- (2) consists of beta22- and beta12-SiW10O37 units sandwiching a Zr4O2(OH)2(H2O)4 cluster, which also has C1 symmetry. Polyanion 1 contains more zirconium centers than any other polyoxometalate known to date.

Synthesis, Characterization, and Catalytic Properties of ansa‐Zirconocenes [Zr{1‐Me2Si(3‐η5‐C9H5R)2}Cl2] (R = Me, nPr, nBu, and Bz)

AbstractThe ansa‐indene ligands {1‐Me2Si(3‐C9H6R)2} [R = Me (1), nPr (2), nBu (3), and Bz (4)] were prepared by alkylation of the unsubstituted ansa‐indene. These ligands were converted, by reaction with nBuLi, to the di‐lithium compounds [Li2{1‐Me2Si(3‐C9H5R)2}] [R = Me (5), nPr (6), nBu (7), and Bz (8)]. ansa‐Zirconocenes, [Zr{1‐Me2Si(3‐η5‐C9H5R)2}Cl2] [R = Me (9), nPr (10), nBu (11), and Bz (12)], have been prepared by the reaction of ZrCl4 with 5–8 in diethyl ether/toluene at–78 °C. The molecular structure of meso‐[Zr{1‐Me2Si[3‐η5‐C9H5(CH3)]2}Cl2] (9) and rac‐[Zr{1‐Me2Si[3‐η5‐C9H5(CH2CH2CH3)]2}Cl2] (10) have been determined by single‐crystal X‐ray diffraction studies. Ethylene polymerization catalysis has been studied for complexes 9–12 as a mixture of meso and rac isomers in the presence of methylaluminoxane (MAO) as cocatalyst. Complexes 9–12 exhibit high activities and give rise to polyethylene with low molecular weights without the introduction of molecular hydrogen. In addition, active species from these complexes were found to be very stable in comparison with unsubstituted analogues.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Sterically Protected Titanium (Aminoethyl)dicarbollides: Synthesis of Novel Constrained-Geometry Complexes Showing an Unusual Cage B,N-Cyclization

The syntheses of group 4 metal complexes containing the ((dibenzylamino)ethyl)dicarbollide ligand DcabHC(2)N (nido-7-HNBz2(CH2)2-8-R-7,8-C2B9H10; 2) are reported. Various new types of constrained-geometry complexes [{(η5-RC2B9H9)(CH2)2(η1-NBz2)}MCl2] (M = Ti (3), Zr (4); R = H (a), Me (b)) were prepared by the reaction of the potassium salt of 2 with titanium or zirconium tetrachloride. The reaction of 2 with Ti(NMe2)4 in toluene affords [{(η5-RC2B9H9)(CH2)2(η1-NBz2)}Ti(NMe2)2] (5), which readily reacts with Me3SiCl to yield the corresponding chloride complex 3. The structure of the constrained-geometry complex [{(η5-C2B9H10)(CH2)2(η1-NBz2)}Ti(NMe2)2] (5a) was established by X-ray diffraction, which showed an η5:η1 bonding mode derived from the dicarbollylamino ligand fuctional group. In contrast, the reaction of 2 with Zr(NMe2)4 produced the untethered half-metallocene complexes [{(η5-RC2B9H9)(CH2)2(NBz2)}Zr(NMe2)2(NHMe2)] (6). The identity of 6 was confirmed by single-crystal X-ray diffraction. Due to coordination of free dimethylamine to the zirconium metal center, the sterically hindered dibenzylamine sidearm leaves the coordination sphere to form the corresponding untethered complexes. Furthermore, the titanium(IV) CGC complexes 3 exhibited unusual B,N-cyclization when reacted with O2, leading to the production of novel exocyclic dicarbollides (7). The crystallographic data were consistent with the formation of an unusual five-membered exocyclic ring, presumably due to steric interactions between the dibenzyl units and the dicarbollyl group. Finally, the sterically less bulky zirconium(IV) ((benzylamino)ethyl)dicarbollyl complex [{(η5-CH3C2B9H9)(CH2)(η1-NBz)}ZrCl2(THF)] (10b), in which the pendant amine is coordinated to the metal center, was prepared by the reaction of ZrCl4 with the potassium salt of [nido-7-NH2Bz+(CH2)-8-H-7,8-C2B9H10-] (9b) in toluene.