Synthesis, characterization, and reactivity of titanium(IV) complexes supported by proximally bridged p-tert-butylcalix[4]arene ligands

Ozerov, Oleg V.; Rath, Nigam P.; Ladipo, Folami T.

doi:10.1016/s0022-328x(99)00279-x

Cited by 32 publications

(41 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The NMR data for 3-5 demonstrate that they possess C s symmetry and adopt 1,2-alternate conformation in solution. 1 H and 13 C NMR resonances for the endo-SiR group (located inside the calixarene cavity) of 1,2-alternate R 2 Si-bridged calix [4]arene compounds are always strongly shielded compared to signals for the exo-SiR group (located outside the calixarene cavity) [12,13], due probably to ring current effect [14]. For example, 1 H NMR resonances for the endo-SiCH 2 CH 3 group of (DESC)H 2 (3) show as a triplet at d 0.65 (SiCH 2 CH 3 ) and a quartet at d )0.63 (SiCH 2 CH 3 ) while the exo-SiCH 2 CH 3 group is observed as a multiplet at d 0.86-0.96.…”

Section: Resultsmentioning

confidence: 98%

“…We presume that titananorbornadiene and paramagnetic calixarene-containing species are produced via competing pathways since black solutions result immediately upon addition of THF to a suspension of L 2 TiCl 2 (9-12), Mg* and Me 3 SiCBCH in toluene or C 6 D 6 . In contrast, very sluggish reaction of (DMSMC)TiCl 2 (11) or (DPSC)TiCl 2 (12) with Mg* and Me 3 SiCBCH (10 equiv) occurred in toluene (in the absence of THF). The orange suspensions did not change color for 1.5 h and 1 H NMR revealed plenty of unreacted titanium dichloride.…”

Section: Synthesis and Reactivity Of Titanium Complexesmentioning

confidence: 99%

“…Terminal alkynes are cyclotrimerized with high regioselectivity ( Table 4, entries 1 and 2) while steric properties of the substituent groups of internal alkynes greatly influence both efficacy and regioselectivity of the reaction. Thus, an ethyl or phenyl unit is about the limit of a substituent that may be placed inside the calixarene cavity and still observe catalytic cyclotrimerization under our conditions (Table 4, entries [3][4][5][6][7][8][9][10][11][12][13][14][15]. In the case of unsymmetrically substituted internal alkynes, preference for 1,2,4-substitution decreased as the size difference of the substituent groups decreased (Table 4, entries 2, 4, and 6).…”

Section: Synthesis and Reactivity Of Titanium Complexesmentioning

confidence: 99%

“…Group 4 metal complexes containing non-cyclopentadienyl ligand arrays, such as aryloxides [2], chelating diamides [3], porphyrins [4], amine-bis(phenolate)s [5], bis(salicylaldiminate)s [6], carboranes [7], amidinates [8], boratabenzenes [9], Schiff bases [10], and calixarenes [11,12], have increasingly been investigated. While precise control of chemical reactivity is difficult, the expectation is that compounds with comparable or superior reactivity to group 4 metal metallocenes can be developed since steric and electronic properties of ancillary ligands profoundly influence the reactivity of transition metals.…”

Section: Introductionmentioning

confidence: 99%

“…We have been exploring the chemistry of titanium complexes supported by dianionic, proximally bridged p-t-butylcalix [4]arene ligands [12]. Previously, we reported the synthesis of conformationally stable Ti(IV) Journal of Organometallic Chemistry 689 (2004) 502-514 www.elsevier.com/locate/jorganchem q Supplementary data associated with this article can be found, in the online version, at doi:10.1016 /j.jorganchem.2003.10.039. dichlorides that contain calixarene-derived bis(aryloxide) ligands in 1,2-alternate conformation, (DMSC)-TiCl 2 (1a) [12b] and (t-BuPC)TiCl 2 (1b) [12a] (Fig.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation

Ladipo

Sarveswaran

Kingston

et al. 2004

Journal of Organometallic Chemistry

Self Cite

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 98%

Section: Synthesis and Reactivity Of Titanium Complexesmentioning

confidence: 99%

Section: Synthesis and Reactivity Of Titanium Complexesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation

Ladipo

Sarveswaran

Kingston

et al. 2004

Journal of Organometallic Chemistry

Self Cite

View full text Add to dashboard Cite

Oxo‐ and Imidovanadium Complexes Incorporating Methylene‐ and Dimethyleneoxa‐Bridged Calix[3]‐ and ‐[4]arenes: Synthesis, Structures and Ethylene Polymerisation Catalysis

Redshaw

Rowan

Warford

et al. 2007

Chemistry A European J

133

View full text Add to dashboard Cite

Reaction of [V(X)(OR)3] (X=O, Np-tolyl; R=Et, nPr or tBu) with p-tert-butylhexahomotrioxacalix[3]areneH3, LH3, affords the air-stable complexes [{V(X)L}n] (X=O, n=1 (1); X=Np-tolyl, n=2 (2)). Alternatively, 1 is readily available either from interaction of [V(mes)3THF] with LH3, and subsequent oxidation with O2 or upon reaction of LLi3 with [VOCl3]. Reaction of [V(Np-tolyl)(OtBu)3] with 1,3-dimethylether-p-tert-butylcalix[4]areneH2, Cax(OMe)2(OH)2, afforded [{VO(OtBu)}2(mu-O)Cax(OMe)2(O)2].2 MeCN (42 MeCN), in which two vanadium atoms are bound to just one calix[4]arene ligand; the n-propoxide analogue of 4, namely [{VO(OnPr)}2(mu-O)Cax(OMe)2(O)2].1.5 MeCN (51.5 MeCN), has also been isolated from a similar reaction using [V(O)(OnPr)3]. Reaction of [VOCl3], LiOtBu, (Me3Si)2O and Cax(OMe)2(OH)2 gave [{VO(OtBu)Cax(OMe)2(O)2}2Li4O2].8 MeCN (68 MeCN), in which an Li4O4 cube (two of the oxygen atoms are derived from the calixarene ligands) is sandwiched between two Cax(OMe)2(O)2. The reaction between [V(Np-tolyl)(OtBu)3] and Cax(OMe)2(OH)2, afforded [V(Np-tolyl)(OtBu)2Cax(OMe)2(O)(OH)]5 MeCN (75 MeCN), in which two tert-butoxide groups remain bound to the tetrahedral vanadium atom, which itself is bound to the calix[4]arene through only one phenolic oxygen atom. Reaction of p-tert-butylcalix[4]areneH4, Cax(OH)4 and [V(Np-tolyl)(OnPr)3] led to loss of the imido group and formation of the dimeric complex [{VCax(O)4(NCMe)}2].6 MeCN (86 MeCN). Monomeric vanadyl oxo- and imidocalix[4]arene complexes [V(X)Cax(O)3(OMe)(NCMe)] (X=O (11), Np-tolyl (12)) were obtained by the reaction of the methylether-p-tert-butylcalix[4]areneH3, Cax(OMe)(OH)3, and [V(X)(OR)3] (R=Et or nPr). Vanadyl calix[4]arene fragments can be linked by the reaction of 2,6-bis(bromomethyl)pyridine with Cax(OH)4 and subsequent treatment with [VOCl3] to afford the complex [{VOCax(O)4}2(mu-2,6-(CH2)2C5H3N)].4 MeCN (134 MeCN). The compounds 1-13 have been structurally characterised by single-crystal X-ray diffraction. Upon activation with methylaluminoxane, these complexes displayed poor activities, however, the use of dimethylaluminium chloride and the reactivator ethyltrichloroacetate generates highly active, thermally stable catalysts for the conversion of ethylene to, at 25 degrees C, ultra-high-molecular-weight (>5, 500,000), linear polyethylene, whilst at higher temperature (80 degrees C), the molecular weight of the polyethylene drops to about 450,000. Using 1 and 2 at 25 degrees C for ethylene/propylene co-polymerisation (50:50 feed) leads to ultra-high-molecular-weight (>2,900,000) polymer with about 14.5 mol% propylene incorporation. The catalytic systems employing the methyleneoxa-bridged complexes 1 and 2 are an order of magnitude more active than the bimetallic complexes 5 and 13, which, in turn, are an order of magnitude more active than pro-catalysts 8, 11 and 12. These differences in activity are discussed in terms of the structures of each class of complex.

show abstract

Niobium‐ and Tantalum‐Based Ethylene Polymerisation Catalysts Bearing Methylene‐ or Dimethyleneoxa‐Bridged Calixarene Ligands

Redshaw

Rowan

Homden

et al. 2007

Chemistry A European J

View full text Add to dashboard Cite

Treatment of p-tert-butylcalix[6]areneH(6) (H(6)tBu-L) or p-tert-butylcalix[8]areneH(8) (H(8)tBu-L(1)) with [MCl(5)] (M=Nb, Ta) in refluxing toluene or dichloromethane affords, after work-up, the complexes [{M(NCMe)Cl(2)}(2)(tBu-L)] (M=Nb (1), Ta (2)) and [(MCl(2))(2)(tBu-L(1)H(2))] (M=Nb (4), Ta (5)), respectively. Complex 1, as well as [{Nb(2)(mu-O)(2)(mu-Cl)(tBu-LH)}(2)] (3), is also available from [NbOCl(3)] and H(6)tBu-L. Reaction of [MOCl(3)] (M=Nb, Ta) with Li(3)(tBu-L(2)) in diethyl ether, where H(3)tBu-L(2) is p-tert-butylhexahomotrioxacalix[3]areneH(3), affords, after work-up, the trimeric complexes [{M(tBu-L(2))(mu-O)}(3)] (M=Nb (6), Ta (7)). The behaviour of 1 to 7 (not 3), as well as the known complexes [{(MCl)p-tert-butylcalix[4]arene}(2)] (M=Nb (8), Ta (9)) and [(MCl(2))p-tert-butylcalix[4]arene(OMe)] (M=Nb (10), Ta (11)), as pro-catalysts for the polymerisation of ethylene has been investigated. In the presence of dimethyl (or diethyl)aluminium chloride, methylaluminoxane or trimethylaluminium, these niobium and tantalum procatalysts are all active (<35 g mmol(-1) h(-1) bar(-1)), for the polymerisation of ethylene affording high-molecular-weight linear polyethylene. The dimethyleneoxa-bridged systems (derived from 6 and 7) are more active (84 and 46 g mmol(-1) h(-1) bar(-1), respectively) than the methylene-bridged systems. The molecular structures of 1-6 and 10 (acetonitrile solvate) are reported.

show abstract

Synthesis, characterization, and reactivity of titanium(IV) complexes supported by proximally bridged p-tert-butylcalix[4]arene ligands

Cited by 32 publications

References 47 publications

Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation

Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation

Oxo‐ and Imidovanadium Complexes Incorporating Methylene‐ and Dimethyleneoxa‐Bridged Calix[3]‐ and ‐[4]arenes: Synthesis, Structures and Ethylene Polymerisation Catalysis

Niobium‐ and Tantalum‐Based Ethylene Polymerisation Catalysts Bearing Methylene‐ or Dimethyleneoxa‐Bridged Calixarene Ligands

Contact Info

Product

Resources

About