67108-80-9Relevant articles and documents
Reactions of (η5-C5Me5)ZrF3, (η5-C5Me4Et)ZrF3, (η5-C5Me5)2ZrF2, (η5-C5Me5)HfF3
Herzog, Axel,Roesky, Herbert W.,J?ger, Felix,Steiner, Alexander,Noltemeyer, Mathias
, p. 909 - 917 (1996)
The reaction of Cp*ZrF3 (1) (Cp* = η5-CsMes) and AlMe3 resulted in the formation of cis-{[Cp*ZrMe(μ2-F)][(μ2-F) 2AlMe2]}2 (6) and [(Cp*Zr)3Al6Me8(μ3-CH 2)2(μ4-CH)4(μ3-CH)] (7), respectively. Analogously, (η5-C5Me4Et)ZrF3 (3) reacts with AlMes in a molar ratio of 1:5 with methane elimination to give the Zr3Al6C7 cluster of composition {[(η5-C5Me4Et)Zr]3Al 6Me8-(μ3-CH2) 2(μ4-CH)4(μ3-CH)} (8), which has been characterized by elemental analysis and 1H NMR and mass spectrometry. Reaction of 2 equiv of AlMe3 with Cp*2ZrF2 (2) leads quantitatively to Cp*2ZrMe2 (12). Reaction of Cp*HfF3 (4) with AlMe3 in an equimolar ratio gives {[Cp*HfMe (μ2-F)][(μ2-F)2AlMe2]} 2 (9) stereospecifically as its cis isomer in high yield. 9 crystallizes in the space group P21/c with four molecules in the elemental cell (Z = 16). From the reaction of 1 equiv of Cp*HfF3 (4) with 3 equiv of AlMe3, Cp*HfMe3 (10) can be obtained in a yield of 85%. As a byproduct of this reaction the Hf3Al6C7 cluster [(Cp*Hf)3-Al6Me8(μ3-CH 2)2(μ4-CH)4(μ3-CH)] (11) can be isolated in a yield of 5%. The characterization of 11 by single-crystal X-ray diffraction and 1H, 13C NMR and mass spectroscopic data will be discussed. Cp*TaF4 (5) reacts with a 5-fold excess of AlMe3, leading quantitatively to Cp*TaMe4 (13) without further decomposition via C-H activation processes.
Nucleophilicity of Alkyl Zirconocene and Titanocene Precatalysts, and Kinetics of Activation by Carbenium Ions and by B(C6F5)3
Berionni, Guillaume,Kurouchi, Hiroaki,Eisenburger, Lucien,Mayr, Herbert
supporting information, p. 11196 - 11200 (2016/08/03)
Kinetics of activation of methyl and benzyl metallocene precatalysts by benzhydrylium ions, tritylium ions, and triarylborane B(C6F5)3were measured spectrophotometrically. The rate constants correlate linearly with the electrophilicity parameter E of the benzhydrylium and tritylium ions employed, allowing us to determine the σ-nucleophilicities of the metal–carbon bond of several zirconocenes and titanocenes. Bridging, substitution, metal, and ligand effects on the rates of metal–alkyl bond cleavage (M=Zr, Ti) were studied and structure–reactivity correlations were used to predict the kinetics of generation of metallocenium ions pairs, which are active catalysts in polymerization reactions and are highly electrophilic Lewis acids in frustrated Lewis pair catalysis.
Zirconium-91 chemical shifts and line widths as indicators of coordination geometry distortions in zirconocene complexes
Bühl, Michael,Hopp, Gudrun,Von Philipsborn, Wolfgang,Beck, Stefan,Prosenc, Marc-Heinrich,Rief, Ursula,Brintzinger, Hans-Herbert
, p. 778 - 785 (2008/10/08)
91Zr NMR chemical shifts and line widths (Δυ1/2) are reported for a number of ring-bridged and ring-substituted zirconocene dichloride, dibromide, and dimethyl complexes. Ab initio computations at the SCF level employing basis sets of moderate size suggest that the magnitude of the electric field gradient (EFG) at the Zr atom dominates Δυ1/2 when the substituents X at Zr are varied (X = Br, Cl, Me). Substituents at the cyclopentadiene (Cp) rings affect the computed EFGs much less; in these cases, the line widths Δυ1/2 are governed by the molecular correlation times τc, which were obtained for several zirconocene dichlorides from T1(13C) measurements. Experimental trends in δ(91Zr) of zirconocenes are well reproduced computationally with the IGLO (individual gauge for localized orbitals) or GIAO (gauge including atomic orbitals) SCF methods employing large basis sets. Model calculations suggest that δ(91Zr), as well as the EFG, are quite sensitive to the inclination and twist angles of the Cp rings and, to a lesser extent, to the CpZrCp′ angle. A substantial deshielding, δ(91Zr) ca. 700 ppm, is predicted for (C5H5)2ZrMe+, presumably the active olefin-polymerizing catalyst.
