The crystal and molecular structure of (pentahaptofluorenyl)(trihaptofluorenyl)dichlorozirconium(IV)

Kowala, C.; Wunderlich, J. A.

doi:10.1107/s0567740876004007

Cited by 38 publications

(21 citation statements)

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“…4.3 it is clear that the whole notion of a "perfect" molecular symmetry, bilateral or otherwise, in the solution phase should be handled with caution and not t taken very literally. We saw that even with initially "perfect" bilateral symmetric metallocene molecules like 1 (2) and 6 (7), the perfect symmetry may be lost, at least in part, in solution and during different stages of the polymerization due to incessant η 5 , η 3 , and possibly η 1 reversible hapticity change or occasional ring slippage [149][150][151][152][153][154][155][156][157][158][159][160]161, and references therein; 162,163]. Thus, the question to be answered is whether or not the bilateral symmetry embodies the necessary and/or sufficient condition(s) for syndiotactic specificity of a catalyst system.…”

Section: Metallocene Molecular Symmetry and The Catalyst's Syndiotactmentioning

confidence: 99%

“…2.3 it was shown by the example of complexes 1 (2) and 6 (7), that the phenomenon of hapticity change or bond order variation between the transition metal and the aromatic ligands can change the kinetic pathways of the polymerization process and its outcome dramatically. The haptotropic behavior of metallocenes is a known phenomenon in transition organometallic chemistry and homogeneous catalysis [149][150][151][152][153][154][155][156].…”

Section: Stereorigidity Of Bridged Metallocenes and Stereoselectivitymentioning

confidence: 99%

“…In this context, it is important to be aware of at least two dynamic phenomena regarding the fluxional behavior of metallocene molecules in solution, namely, the phenomena of haptotropy [149][150][151][152][153][154][155][156] and ring slippage. The haptotropy and ring slippage [157][158][159][160]161, and references therein] [162,163], depicted schematically in Fig.…”

Section: Stereorigidity Of Bridged Metallocenes and Stereoselectivitymentioning

confidence: 99%

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Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Razavi¹

2013

Advances in Polymer Science

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This chapter covers the discovery that enabled, for the first time, the manufacturing of high molecular weight, highly stereoregular syndiotactic polypropylene polymers with narrow molecular weight distribution via the new class of metallocene molecules with bridged cyclopentadienyl-fluorenyl ligands. First, the salient crystal structural features of the neutral metallocene molecules and the crystal structure of the corresponding mono-alkyl-zirconocenium cation is introduced. Then, by employing the structural and geometrical data, a realistic working model for the active site precursor is developed and presented. The stereochemistry of the catalytic propylene poly-insertion reaction and the formation of syndiotactic polypropylene according to the enantiomorphic site control mechanism at the enantiotopic cationic active sites, formed after the activation of the prochiral metallocene dichloride with methylaluminoxane, MAO, is reviewed and further delineated. In the following sections, the impact of the introduction of substituents with proper size and composition at some selected positions of the ligand is discussed and the methods for increasing the molecular weight and stereoregularity of syndiotactic polypropylene polymers are elaborated. With the aid of computational calculations on real and hypothetical catalyst systems with substitutionally altered ligand structures, it is shown that the degree of enantioselectivity of syndiospecific catalyst systems can be determined and/or predicted for these systems quantitatively and with high precision. The calculations confirm that the introduction of substituent(s) reinforcing the preferential conformational orientation of the polymer chain enhances the overall enantioselectivity of the active site, and to certain extends stereoselectivity in general, by affecting the site epimerization processes. The computational calculations reveal that to account correctly for the frequency of the site epimerization-dependent m-type stereo-errors it is essential to include the counter-ion, as an integrated part of the A. Razavi (*) 35 Domaine de la Brisee, 7034 Obourg, Belgium e-mail: abbasrazavi@skynet.be catalyst system, into the calculations. The relevance of the symmetry and stereorigidity of the metallocene structure for the syndiospecificity of the final catalyst is debated by presenting a few "non-conforming" catalyst examples.Finally, the challenges involved in the manufacture of syndiotactic polypropylene in commercial scale continuous production processes are highlighted as well as the polymer's unique structural, physical, mechanical and rheological properties.

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Section: Metallocene Molecular Symmetry and The Catalyst's Syndiotactmentioning

confidence: 99%

Section: Stereorigidity Of Bridged Metallocenes and Stereoselectivitymentioning

confidence: 99%

Section: Stereorigidity Of Bridged Metallocenes and Stereoselectivitymentioning

confidence: 99%

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Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Razavi¹

2013

Advances in Polymer Science

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“…Compared the alters in geometry on the ring slip of Cp or indenyl ligands, the more rigid fluorenyl ligand is not appreciably bowed in η 3 complexes, such as η 5 ‐fluorenyl)(η 3 ‐fluorenyl)ZrCl 2. 8 …”

Section: Introductionmentioning

confidence: 99%

Quantum‐chemical calculations on the slippage of cyclopentadienyl and indenyl ligands in the (η³‐dienyl)Ir(PX₃)₃; (X = H, F, Cl, Me) complexes

Ghiasi

Sofiyani

Emami

2020

J Chinese Chemical Soc

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The structure, electronic properties, and the slippage of cyclopentadienyl (Cp) and indenyl (In) ligands in the (η 3 -dienyl)Ir(PX 3 ) 3 ; (X = H, F, Cl, Me) complexes were illustrated using the hybrid density functional MPW1PW91 theory. The characteristics of chemical bond among the [Ir(PX 3 ) 3 ] + and monoanionic dienyl ligands (Cp and In) fragments was surveyed by the energy decomposition analysis (EDA). Charge decomposition analysis (CDA) and extended charge decomposition analysis (ECDA) were utilized to investigate the electron transfer among the fragments in the studying complexes. The correlations among the computed parameters and Tolman cone angles (θ), Tolman's Electronic Parameter (TEP), as well as the Crabtree's DFT Electronic Parameter (CEP) of the phosphine ligands were explained. K E Y W O R D S charge decomposition analysis (CDA), Crabtree's DFT electronic parameter (CEP), energy decomposition analysis (EDA), extended charge decomposition analysis (ECDA), substituent effect, Tolman cone angles (θ), Tolman's electronic parameter (TEP)

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“…(4) (Kowala & Wunderlich, 1976) and (r/5-C13H9)Cr(CO)2(NO) (5) (Atwood, Shakir, Malito, Herberhold, Kremnitz, Bernhagen & Alt, 1979). Compound (1) crystallizes with no important intermolecular contacts.…”

mentioning

confidence: 99%

Synthesis and structure of 3-fluorenyl-3-cobalta-1,2-dicarba-closo-nonaborane(11), 3-(η5-C13H9)-3,1,2-closo-CoC2B9H11

Lewis

Welch

1992

Acta Crystallogr C

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The crystal and molecular structure of (pentahaptofluorenyl)(trihaptofluorenyl)dichlorozirconium(IV)

Cited by 38 publications

References 6 publications

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Quantum‐chemical calculations on the slippage of cyclopentadienyl and indenyl ligands in the (η³‐dienyl)Ir(PX₃)₃; (X = H, F, Cl, Me) complexes

Synthesis and structure of 3-fluorenyl-3-cobalta-1,2-dicarba-closo-nonaborane(11), 3-(η5-C13H9)-3,1,2-closo-CoC2B9H11

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The crystal and molecular structure of (pentahaptofluorenyl)(trihaptofluorenyl)dichlorozirconium(IV)

Cited by 38 publications

References 6 publications

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Quantum‐chemical calculations on the slippage of cyclopentadienyl and indenyl ligands in the (η3‐dienyl)Ir(PX3)3; (X = H, F, Cl, Me) complexes

Synthesis and structure of 3-fluorenyl-3-cobalta-1,2-dicarba-closo-nonaborane(11), 3-(η5-C13H9)-3,1,2-closo-CoC2B9H11

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Quantum‐chemical calculations on the slippage of cyclopentadienyl and indenyl ligands in the (η³‐dienyl)Ir(PX₃)₃; (X = H, F, Cl, Me) complexes