- Complexes useful as active components in supported epoxidation catalysts
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Method of preparing epoxidation catalysts are disclosed, including methods comprising reacting an inorganic siliceous solid with a metal complex of the formulas: wherein the variables are defined herein.
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Page/Page column 25
(2017/04/07)
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- Synthesis, structure, coordination expansion and theoretical modelling of dichlorobis(phenoxo) titanium(IV) complexes
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Thermalisation of TiCl4 and two equivalents of a phenol in toluene is found to be the best preparative method for quantitative yields of a variety of dichlorobis(phenoxo) complexes. [TiCl2(OC 6H4CMe3-4)2] (1) is monomeric in benzene, a phenoxo-bridged dimer in the solid state and undergoes coordination expansion with 4,4′-dimethyl-2,2′-bipyridine (dmbipy) to give [TiCl2(OC6H4CMe3-4) 2(dmbipy)] (2). Also monomeric are [TiCl2(OC 6H2Me3-2,4,6)2] (3) and [TiCl 2(OC6H3iPr2-2,6)2] (5) which expand their coordination with dmbipy to give [TiCl2(OC 6H2Me3-2,4,6)2(dmbipy)] (4) and [TiCl2(OC6H3iPr2-2,6) 2(dmbipy)] (6). In contrast [TiCl2(OC6H 2{CMe3}2-2,6-Me-4)2] (7) is only partially formed by the thermolysis reaction and does not coordinatively expand with dmbipy. [TiCl2(OC6H3Me2-2,4) 2] (8) is monomeric in benzene and reacts to form [TiCl 2(OC6H3Me2-2,4)2(dmbipy)] (9). [TiCl2(OC6H3{CMe3} 2-2,4)2] (10) forms along with the tri-phenoxo complex [TiCl{OC6H3(CMe3)2-2,4} 3]. [TiCl2(OC6H3CMe 3-2-Me-6)2] (11) is monomeric in benzene and forms [TiCl2(OC6H3CMe3-2-Me-6) 2(dmbipy)] (12). 2-Phenylphenol and 1-napthol form [TiCl 2(OC6H4Ph-2)2] (13) and [TiCl 2(OC10H9)2] (14) which are monomeric in benzene. DFT calculations give structural parameters for monomeric [TiCl2(OC6H5)2] (15) in good agreement with the X-ray data for [TiCl2(OC6H 3Me2-2,6)2]. Each oxygen of the phenoxo ligand in 15 acts essentially as a 2π donor to titanium and there is substantial pπ(O)-pπ*(C=C) backbonding with the phenyl ring, which is absent in [TiCl2(OCH3)2] (16). The global minimum for the dimer [(TiCl2{OC6H 5}{μ-OC6H5})2] is in almost perfect agreement with the crystal structure obtained for [(TiCl 2{OC6H5}{μ-OC6H 5})2] or [(TiCl2{OC6H 4CMe3-4}{μ-OC6H4CMe 3-4})2] (1). The dimerisation energy for 15 is -26.2 kJ·mol-1.
- Nielson, Alastair J.,Shen, Chaohong,Schwerdtfeger, Peter,Waters, Joyce M.
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p. 1343 - 1352
(2007/10/03)
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- Titanium aryloxide catalyzed cross-coupling and oligomerization reactions involving 1,3-cyclohexadiene, 1,3-cyclooctadiene, and α-olefins
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The dimerization/oligomerization and cross coupling of 1,3-cyclohexadiene (1,3-CHD) with α-olefins can be achieved using a variety of titanium aryloxide catalysts. The titanabicyclic compound [Ti(OC6H3Ph4-2,3,5,6)2{CH 2(C6H10)CH2}] initiates the rapid, non-Diels-Alder catalytic dimerization of 1,3-CHD to produce exclusively threo-5-(3-cyclohexenyl)-1,3-cyclohexadiene. Following dimerization of the majority of 1,3-cyclohexadiene into 8, the titanium catalyst then isomerizes (1,5-shift) 8 into 1-(3-cyclohexenyl)-1,3-cyclohexadiene 9 and eventually into a 70/30 mixture (GC analysis) of 9 and 2-(3-cyclohexenyl)-1,3-cyclohexadiene 10. Further cross coupling of dimers 8-10 with themselves and 1,3-CHD leads to trimers (C18 species) and tetramers (C24). This reaction can also be catalyzed by the dichlorides [Ti(OAr)2Cl2] (OAr = 2,6-diphenyl-, 2,3,5,6-tetraphenyl-, 2,6-diphenyl-3,5-dimethyl-, and 2,6-di-isopropyl-phenoxide) and [Cp-(OAr)TiCl2] (OAr = 2,6-diphenyl-3,5-dimethyl-phenoxide) activated with 2 equiv of n-butyllithium (BunLi). In the case of the catalyst system [Ti(OAr)4] or [Ti(OAr)2Cl2] (OAr = 2,6-dimethylphenoxide), activation with 2 equiv of BunLi leads to isomeric mixtures of trimers and tetramers of 1,3-CHD with detectable amounts of pentamers following dimerization. The dimerization product is argued to originate via initial coupling of 1,3-CHD at the Ti metal center to produce 9-titana-octahydrofluorenes. A 1,3-metal shift followed by β-hydrogen abstraction/elimination accounts for the observed regio- and stereochemistry. When the α-olefin Me3SiCH= CH2 is added to 1,3-CHD, these titanium systems generate the cross-coupled product 5-(β-trimethylsilylethyl)-cyclohexa-1,3-diene followed by the formation of trans-5,6-bis(β-trimethylsilylethyl)-cyclohexa-1,3-diene. A mechanism involving initial coupling of the 1,3-CHD and Me3SiCH=CH2 at titanium prior to a 1,3-metal shift and β-hydrogen abstraction/elimination from the initial cyclohexadiene ring is invoked. In contrast cross-coupling of cycloocta-1,3-diene (1,3-COT) with α-olefins RCH=CH2 (R = Ph, Bun, SiMe3) leads to trans-3-(β-alkylvinyl)-cyclooctenes. In this case the reaction is proposed to proceed via similar titanacycles with β-hydrogen abstraction taking place from the alkyl tether instead of the cyclooctene ring.
- Waratuke, Steven A.,Thorn, Matthew G.,Fanwick, Phillip E.,Rothwell, Arlene P.,Rothwell, Ian P.
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p. 9111 - 9119
(2007/10/03)
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- Synthesis and reactions of an (aryloxy)titanium(IV) hydride
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Attempts to prepare (ArO)2Ti(BH4)2, 6 (Ar = 2,6-diisopropylphenyl), from (ArO)2TiCl2, 4, and LiBH4 failed due to its decomposition by ligand exchange and reduction into (ArO)3Ti-
- N?th, Heinrich,Schmidt, Martin
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p. 4601 - 4610
(2008/10/09)
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- Synthesis and characterization of alkoxo- and chloro-aryloxo derivatives of titanium and zirconium
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The reactions of MX4 (M=Ti, Zr; X=Cl, OPr-i) with a number of sterically demanding phenols, have resulted in the synthesis of novel alkoxo- and chloro-aryloxides of the type MX4-n(OAr)n (where X=Cl, OPr-i; OAr=OC6H2Me3-2, 4, 6(OAr1), OC6H3Pr2-i-2, 6-(OAr2), OC6H2Bu2-t-2, 6-Me-4(OAr3); n=1, 2, 3 or 4).These complexes have been characterized on the basis of IR and NMR spectral studies.
- Shah, A.,Singh, A.,Mehrotra, R. C.
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p. 632 - 635
(2007/10/02)
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