198766-06-2Relevant academic research and scientific papers
Internally phosphine-stabilized zirconocene cations employing substituted ((diarylphosphino)methyl)cyclopentadienyl ligand systems
Bosch, Boris E.,Erker, Gerhard,Fr?hlich, Roland,Meyer, Oliver
, p. 5449 - 5456 (2008/10/08)
The dimethylzirconocene complex [(Cp-CMe2-PAr2)2ZrMe2], 2a (Ar = p-tolyl), was treated with 1 molar equiv of B(C6F5)3 to yield the salt [(Cp-CMe2-PAr2)2ZrMe+MeB(C 6F5)3-], 3a. The X-ray crystal structure analysis of 3a shows that both -PAr2 units are intramolecularly coordinated to zirconium in a close to C2-symmetric arrangement with the [Zr]-CH3 group placed in the central position in the bent metallocene σ-ligand plane. Treatment of 2a with 2 equiv of B(C6F5)3 generates the highly reactive dication system [(Cp-CMe2-PAr2)2Zr2+] (4 with two MeB(C6F5)3- anions). The highly electrophilic cation 4 abstracts chloride from, e.g., dichloromethane solvent to yield [(Cp-CMe2-PAr2)2Zr-Cl+] (5, with MeB(C6F5)3- anion). The same cation (5′, with ClB(C6F5)3- anion) was obtained from the reaction Of[(Cp-CMe2-PAr2)2ZrCl2] (1Ia) with B(C6F5)3. The C2-symmetric, internally -PAr2-stabilized dication adds acetonitrile or 2,6-dimethylphenyl isocyanide to give the respective C2-symmetric donorligand adducts in which the -PAr2 coordination to zirconium is retained. The complexes 3a (ΔG?enant (300 K) = 14.0 ± 0.5 kcal/mol) and 5 (ΔG?enant (360 K) = 17.5 ± 0.5 kcal/mol) show dynamic NMR spectra due to an intramolecular enantiomerization process proceeding with a rate-determining cleavage of the Zr-P linkages. Complex 5 was also characterized by an X-ray crystal structure analysis.
