1282-31-1Relevant academic research and scientific papers
Stereochemical course of π-face coordination to isodicyclopentadiene during formation of mixed titanocene and zirconocene dichloride complexes
Paquette, Leo A.,Moriarty, Kevin J.,Meunier, Philippe,Gautheron, Bernard,Sornay, Carole,Rogers, Robin D.,Rheingold, Arnold L.
, p. 2159 - 2167 (2008/10/08)
Reaction of the isodicyclopentadienide anion with RCpTiCl3 (R = H, CH3, t-Bu) and Cp″TiCl3 in tetrahydrofuran solution at -78°C is shown to proceed stereoselectively with formation of endo titanocene dichloride complexes. When the same reactions are performed at 20°C up to the reflux temperature of the solvent, the stereoisomeric exo complexes are cleanly formed instead. Control experiments have not led to the interconversion of these isomer pairs. Comparable reaction of isodiCpLi with CpZrCl3 and Cp″ZrCl3 in boiling tetrahydrofuran also delivered only exo complexes. The structural parameters of several products, as defined by X-ray crystallographic analysis, are discussed. The endo complexes appear to be more sterically constrained than the exo isomers. Their formation at low temperatures is thought to be kinetically controlled and to stem from electronic features imparted to the Cp anion portion of the isodicyclopentadienyl ligand by its fused norbornyl framework.
Stereocontrolled bifacial complexation of the isodicyclopentadienyl ligand to cyclopentadienyltitanium dichloride fragments
Paquette, Leo A.,Moriarty, Kevin J.,Meunier, Philippe,Gautheron, Bernard,Crocq, Véronique
, p. 1873 - 1875 (2008/10/08)
Reaction of the isodicyclopentadienide anion with (RCp)TiCl3 (R = H, CH3) and Cp″TiCl3 is shown to proceed under conditions presumed to be kinetically controlled with complete bifacial stereoselectivity depending upon temperature. While endo complexation materializes at -78°C, exo coordination operates exclusively at room temperature and above, as ascertained by X-ray analysis. The isomeric complexes can also be easily distinguished spectroscopically.
Effects of methyl substituents at the cyclopentadienyl ligand on the properties of C2H5TiCl3 and C5H5TiAl2CL8-x(C2H5)x (x = 0-4) complexes
Mach, Karel,Varga, Vojtech,Antropiusova, Helena,Polacek, Jindrich
, p. 205 - 216 (2007/10/02)
The methyl substituents in the series of pTiCl3 compounds (p = Cp, MeCp, Me3Cp, Me4Cp, Me5Cp and EtMe4Cp) shift the position of their CT absorption band from λ = 384 nm to max. 438 nm and decrease the rate of reduction of pTiCl3 by ethylaluminium
Polynuclear oxo-bridged cyclopentadienyl transition-metal complexes. Formation and structural characterization of the titanoxane tetramer, [(η5-C5H4CH3)TiCl(μ-O)] 4
Petersen, Jeffrey L.
, p. 181 - 185 (2008/10/08)
The crystal structure of cyclo-tetrakis(μ-oxo-chloro(methylcyclopentadienyl)titanium(IV)), [(η5-C5H4CH3)TiCl(μ-O)] 4, has been determined by X-ray diffraction methods. The compound consists of four (η5-C5H4CH3)TiCl moieties linked together by four oxo groups to produce a molecular core of D2d symmetry, which contains an eight-membered ring of alternating Ti and O atoms. The tetramer's molecular geometry is constrained by a crystallographic twofold rotation axis which passes through two opposite O atoms. The relatively short Ti-O bonds of 1.8 A? (average) support the presence of partial double-bond character arising from the donation of electron density from filled pπ oxygen orbitals to unfilled metal orbitals on the electron-deficient d0 Ti atoms. The Ti4 arrangement possesses a butterfly structure with the dihedral angle between any two Ti3 planes which share a diagonal edge being 154.0°. The methyl substituents of the cyclopentadienyl rings introduce additional inter-ring repulsions, which produce an 8° increase in this dihedral angle and a larger variation in the independent Ti-O-Ti bond angles in comparison to [(η5-C5H5)TiCl(μ-O)]4. The tetramer is prepared by the hydrolysis of (η5-C5H4CH3)TiCl3. The compound crystallizes in a monoclinic space group, C2/c, with refined lattice parameters a = 18.344 (4) A?, b = 10.195 (2) A?, c = 17.178 (3) A?, β = 114.68 (1)°, V = 2918.7 (9) A?3, and Z = 4. Block-diagonal least-squares refinement of 1700 diffractometry data with |Fo| > σ(|Fo|) led to final discrepancy indices of R(Fo) = 0.036 and Rw(Fo) = 0.046 with σ1 = 1.66. A qualitative scheme for the tetramer's formation is discussed.
