scholarly journals Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl] (Ar=2,6-Me2C6H3)

Polyhedron ◽  
2005 ◽  
Vol 24 (11) ◽  
pp. 1274-1279 ◽  
Author(s):  
Rocío Arteaga-Müller ◽  
Javier Sánchez-Nieves ◽  
Pascual Royo ◽  
Marta E.G. Mosquera
Keyword(s):  
X Ray ◽  
Cyclopentadienyl Ligands ◽  
Constrained Geometry ◽  
Niobium Complexes

The synthesis and polymerization behaviour of silicon-bridged [1]- and [2]ferrocenophanes with sterically demanding trimethylsilyl substituents attached to the cyclopentadienyl rings

1995 ◽  
Vol 73 (11) ◽  
pp. 2069-2078 ◽  
Author(s):  
Timothy J. Peckham ◽  
Daniel A. Foucher ◽  
Alan J. Lough ◽  
Ian Manners
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Monoclinic Space Group ◽  
Organometallic Polymers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cyclopentadienyl Ligands ◽  
Sterically Demanding ◽  
High Molecular Weight Poly

The silicon-bridged [1]ferrocenophane Fe(η-C5H3SiMe3)2(SiMe2) (5) was synthesized via the reaction of Li2[Fe(η-C5H3SiMe3)2]•tmeda (tmeda = tetramethylethylenediamine) with Me2SiCl2 in hexanes. The disilane-bridged [2]ferrocenophane Fe(η-C5H3SiMe3)2(Si2Me4) (7) was prepared using a similar route from the disilane ClMe2SiSiMe2Cl. Despite the presence of sterically demanding SiMe3 substituents on the cyclopentadienyl rings, compound 5 was found to undergo thermal ring-opening polymerization at 170 °C to produce very soluble, high molecular weight poly(ferrocenylsilane) 6 with Mw = 1.4 × 105, Mn = 8.4 × 104. However, the [2]ferrocenophane 7 was found to be resistant to thermal ring-opening polymerization even at 350 °C and decomposed above 380 °C. A single-crystal X-ray diffraction study of 7 revealed that the steric interactions between the bulky SiMe3 groups are relieved by a significant twisting of the disilane bridge with respect to the plane defined by the centroids of the cyclopentadienyl ligands and the metal atom. The angle between the planes of the cyclopentadienyl rings in 7 was found to be 5.4(6)°, slightly greater than that in the non-silylated analogue Fe(η-C5H4)2(Si2Me4) (4a) (4.19(2)°), and dramatically less than the corresponding tilt angle of the strained, polymerizable, silicon-bridged [1]ferrocenophane Fe(η-C5H4)2(SiMe2) (1) (20.8(5)°). The length of the Si—Si bond in 7 (2.342(3) Å) was found to be close to the sum of the covalent radii (2.34 Å). Crystals of 7 are monoclinic, space group C2/c, with a = 23.689(3) Å, b = 11.174(1) Å, c = 31.027(3) Å, β = 109.16(1)°, V = 7758(2) Å3, and Z = 12. Keywords: ring-opening polymerization, ferrocenophane, organometallic polymers.

Synthesis of Rhodium Complexes with Novel Perfluoroalkyl Substituted Cyclopentadienyl Ligands

2001 ◽  
Vol 66 (2) ◽  
pp. 382-396 ◽  
Author(s):  
Jan Čermák ◽  
Kateřina Auerová ◽  
Huong Thi Thu Nguyen ◽  
Vratislav Blechta ◽  
Pavel Vojtíšek ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Chemical Shifts ◽  
Rhodium Complexes ◽  
Carbonyl Complexes ◽  
X Ray Diffraction ◽  
Metal Catalysis ◽  
Chloro Complexes ◽  
X Ray ◽  
Cyclopentadienyl Ligands ◽  
C Nmr

Mixtures of isomers of (perfluoroalkyl)tetramethylcyclopenta-1,3-dienes (CH3)4C5H(CF2)nCF3 (n = 3, 5, 7, 9) were synthesized as precursors of new cyclopentadienyl ligands for organotransition metal catalysis in fluorous biphase media and characterized by combination of GC-MS and 13C NMR spectroscopy. Rhodium(III) chloro complexes [Rh{(CH3)4C5(CF2)nCF3}Cl2]2 and rhodium(I) carbonyl complexes [Rh{(CH3)4C5(CF2)nCF3}(CO)2] were prepared from the cyclopentadienes and molecular structure of [Rh{(CH3)4C5(CF2)5CF3}Cl2]2 was determined by X-ray diffraction. The ligands are electronically close to the unsubstituted cyclopentadienyl as shown by values of carbonyl stretching frequencies in the carbonyl complexes. Neither carbonyl frequencies nor NMR chemical shifts of the complexes are substantially affected by the length of the perfluoroalkyl chain.

scholarly journals Polymerization of Propene with Modified Constrained Geometry Complexes. Double-Bond Isomerization in Pendant Alkenyl Groups Attached to Cyclopentadienyl Ligands

2003 ◽  
Vol 68 (6) ◽  
pp. 1119-1130 ◽  
Author(s):  
Oetze K. B. Staal ◽  
Dirk J. Beetstra ◽  
Andries P. Jekel ◽  
Bart Hessen ◽  
Jan H. Teuben ◽  
...  
Keyword(s):  
Double Bond ◽  
Spectroscopic Data ◽  
Catalyst Activity ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molecular Weights ◽  
Constrained Geometry ◽  
Internal Position ◽  
Moderate Effect ◽  
C Nmr

Polymerization of propene with dimethylsilylene-bridged (amidocyclopentadienyl)dichlorotitanium(IV) complexes [TiCl2{η5-1-(t-BuSiMe2N-κN)-2,3,4-Me3-5-R-C5}], where R = Me (1), H (2), Ph (3), 4-fluorophenyl (4), but-2-en-2-yl (5), and butyl (6), combined with excess methylaluminoxane revealed a moderate effect of the substituent R on the catalyst activity and the molecular weight of polypropene. The asymmetric substitution in the position adjacent to the bridging carbon atom resulted in polymer yields decreasing in the order 1 > 6 > 3 ≈ 5 > 4 > 2 while polymers with the molecular weights (Mw) close to 2.5 × 105 for 1, 3, and 4, 1.5 × 105 for 5 and 6, and 7.5 × 104 for 2 were obtained. The 13C NMR analysis of the polymers has shown that atactic polypropene is slightly enriched with syndiotactic triads for all the catalysts. Investigation of the crystal structure of 5 by X-ray crystallography revealed that the double bond in but-3-en-2-yl had shifted to an internal position to give the isomeric, but-2-en-2-yl-substituted complex. Likewise, the spectroscopic data for complex 7 prepared from the ligand containing but-3-en-1-yl substituent, indicate the absence of terminal double bond.

Preparation and Crystal Structures of Low-Valent Zirconocene Complexes Containing Tetramethyl(phenyl)cyclopentadienyl Ligands

2007 ◽  
Vol 72 (5-6) ◽  
pp. 679-696 ◽  
Author(s):  
Michal Horáček ◽  
Jiří Pinkas ◽  
Jiří Kubišta ◽  
Ivana Císařová ◽  
Róbert Gyepes ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Spectroscopic Methods ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Cyclopentadienyl Ligands ◽  
Low Valent

Zirconocene complex [ZrCl2(η5-C5Me4Ph)2] (1) prepared by metathesis of the appropriate lithium cyclopentadienide and ZrCl4 was reduced with magnesium in tetrahydrofuran in the presence of excess bis(trimethylsilyl)acetylene, yielding the low-valent complex [Zr(η5-C5Me4Ph)2- (η2-Me3SiC≡CSiMe3)] (2). However, in addition to 2, the reduction afforded an unexpected Zr(II) complex [Zr(η5-C5Me4Ph)2(s-trans-η4-buta-1,3-diene)] (3). Compounds 1-3 were characterized by spectroscopic methods and by X-ray single-crystal diffraction.

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