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Duncan F Wass - One of the best experts on this subject based on the ideXlab platform.
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Cationic Group 4 metallocene o phosphanylaryl oxido complexes synthetic routes to transition metal frustrated lewis pairs
European Journal of Inorganic Chemistry, 2012Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
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Cationic Group 4 Metallocene–(o‐Phosphanylaryl)oxido Complexes: Synthetic Routes to Transition‐Metal Frustrated Lewis Pairs
European Journal of Inorganic Chemistry, 2011Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
Andy M Chapman - One of the best experts on this subject based on the ideXlab platform.
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Cationic Group 4 metallocene o phosphanylaryl oxido complexes synthetic routes to transition metal frustrated lewis pairs
European Journal of Inorganic Chemistry, 2012Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
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Cationic Group 4 Metallocene–(o‐Phosphanylaryl)oxido Complexes: Synthetic Routes to Transition‐Metal Frustrated Lewis Pairs
European Journal of Inorganic Chemistry, 2011Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
Manfred Bochmann - One of the best experts on this subject based on the ideXlab platform.
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Cationic Group 4 metallocene complexes and their role in polymerisation catalysis the chemistry of well defined ziegler catalysts
Journal of The Chemical Society-dalton Transactions, 1996Co-Authors: Manfred BochmannAbstract:Cationic alkyl complexes of Group 4 metallocenes of the type [MCp2R]+(M = Ti, Zr or Hf, Cp = C5H5) have been recognised as the catalytically active species in metallocene-based olefin polymerisation catalysts. These highly electrophilic 14-electron species possess a very complex chemistry in which the formation of temporarily dormant stabilised adducts plays a dominant role. Cationic metal alkyls of this kind are found to be extremely active polymerisation catalysts, with high stereoselectivities and the potential to produce numerous previously inaccessible polymeric materials. A detailed understanding of the chemistry of these species promises to lead to a new generation of well defined polymerisation catalysts. Metallocene-based catalysts already play an increasing role in major industrial polymerisation processes.
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Cationic Group iv metal alkyl complexes and their role as olefin polymerization catalysts the formation of ethyl bridged dinuclear and heterodinuclear zirconium and hafnium complexes
Journal of Organometallic Chemistry, 1995Co-Authors: Manfred Bochmann, Simon J LancasterAbstract:Abstract Bis(cyclopentadienyl)hafnium diethyl (1) reacts with [CPh3][B(C6F5)4] in dichloromethane at −60 °C with hydride rather than alkyl transfer to give triphenylmethane and the ethyl-bridged dinuclear complex [(Cp2HfEt)2(μ-Et)][B(C6F5)4] (2). The complex is less stable than analogous methyl complexes but is stabilized by the presence of excess Cp2HfEt2. The reaction between Cp2HfEt2, [CPh3][B(C6F5)4], and AlEt3 under analogous conditions leads to [Cp2Hf(μ-Et)2AlEt2][B(C6F5)4] (3). The reaction between Cp2 HfMe2 and AlEt3 leads to alkyl ligand exchange to give, successively, Cp2Hf(Me)(Et) and Cp2 HfEt2. Similar fast ligand exchange reactions, take place between Cp′2ZrMe2 and AlEt3 and can be used for generating the thermally labile complex Cp′2ZrEt2 as a precursor for Cationic polymerization catalysts [Cp′2 = Cp2, rac-Me2Si(Ind)2]. Polymerization activities of rac-[Me2Si(Ind)2Zr(μ-R)2AlR2][B(C6F5)4] increase in the order R = Me
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Electron-deficient Group IV metal alkyl cations, and the synthesis of Zr(CH2Ph)3(η6-C6H5)BPh3: a fluxional arene π-complex of a d0 metal
Journal of The Chemical Society Chemical Communications, 1990Co-Authors: Manfred Bochmann, Gerhard Karger, Andrew J. JaggarAbstract:Mild protolysis of titanium and zirconium alkyls provides a general route to solvent or anion stabilised 6- and 10-electron Cationic Group IV alkyl complexes, including the first halide-free arene complex of a d0 metal.
Mairi F Haddow - One of the best experts on this subject based on the ideXlab platform.
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Cationic Group 4 metallocene o phosphanylaryl oxido complexes synthetic routes to transition metal frustrated lewis pairs
European Journal of Inorganic Chemistry, 2012Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
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Cationic Group 4 Metallocene–(o‐Phosphanylaryl)oxido Complexes: Synthetic Routes to Transition‐Metal Frustrated Lewis Pairs
European Journal of Inorganic Chemistry, 2011Co-Authors: Andy M Chapman, Mairi F Haddow, Duncan F WassAbstract:Synthetic routes to Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o-OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl Group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired Cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such Cationic Group 4 metallocene–(o-phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
Giuliano Giambastiani - One of the best experts on this subject based on the ideXlab platform.
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Cationic Group iv pincer type complexes for polymerization and hydroamination catalysis
Dalton Transactions, 2013Co-Authors: Lapo Luconi, Jerzy Klosin, Austin J Smith, Stephane Germain, Emmanuelle Schulz, Jerome Hannedouche, Giuliano GiambastianiAbstract:Neutral ZrIV and HfIV dimethyl complexes stabilized by unsymmetrical dianionic {N,C,N′} pincer ligands have been prepared from their corresponding bis-amido complexes upon treatment with AlMe3. Their structure consists of a central σ-bonded aryl donor Group (C) capable of forming robust M–C bonds with the metal center, enforced by the synergic effect of both the coordination of peripheral donor Groups (N) and the chelating rigid structure of the {N,C,N} ligand framework. Such a combination translates into systems having a unique balance between stability and reactivity. These ZrIV and HfIV dimethyl complexes were converted in situ into Cationic species [MIV{N−,C−,N}Me][B(C6F5)4] which are active catalysts for the room temperature (r.t.) intramolecular hydroamination/cyclization of primary and secondary aminoalkenes as well as for the high temperature ethylene–1-octene copolymerizations.
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intramolecular hydroamination reactions catalyzed by neutral and Cationic Group iv pyridylamido complexes
Chemcatchem, 2013Co-Authors: Lapo Luconi, Stephane Germain, Emmanuelle Schulz, Jerome Hannedouche, Andrea Rossin, Giulia Tuci, Giuliano GiambastianiAbstract:ZrIV and HfIV benzyl (neutral or Cationic) and amido catalysts stabilized by pyridylamido ligands are found to be good candidates for the intramolecular hydroamination/cyclization of primary and secondary aminoalkenes. In particular, Cationic monobenzyl derivatives have shown remarkable catalytic activity for the production of five and six-membered N-containing heterocycles from secondary amino alkenes. In addition, ZrIV and HfIV amido derivatives that are produced by a temperature-controlled prototropic rearrangement have provided evidence of the central role played by the metal coordination sphere in promoting such catalytic transformations efficiently.