198765-93-4Relevant academic research and scientific papers
The synthesis of substituted bis [(diarylphosphinomethyl)cyclopentadienyl] zirconocene dichloride complexes for the preparation of heterodimetallic complexes containing early/late transition metal combinations
Bosch, Boris,Erker, Gerhard,Fr?hlich, Roland
, p. 446 - 458 (2008/10/08)
Fulvenes (1a-e) derived from condensation of cyclopentadiene with acetone or a variety of aldehydes were treated with LiPAr2 (Ar=phenyl, p-tolyl) to yield the respective substituted (diarylphosphinomethyl)cyclopentadienides (2, 3). Subsequent reaction with ZrCl4 (THF)2 gave the respective bis [(diarylphosphinomethyl)cyclopentadienyl] zirconium dichlorides (Ar=phenyl (4), p-tolyl (5)). The complex rac-[C5H4-CH(CH3)-PPh2] 2ZrCl2 (rac-4b) was characterized by X-ray diffraction. The reaction of complexes 4a and 5a [(Cp-CMe2-PAr2)2ZrCl2] with PdCl2(NCPh)2 or PtCl2(NCPh)2 leads to the formation of the trans-(metallocene-chelate-phosphane)metal complexes 6-9 (e.g. trans-Cl2Pd(Ph2P-CMe2-Cp)2ZrCl 2]. Chloride abstraction from the reaction product of [Cp-CH(CMe3)PPh2]2ZrCl2 with PdCl2(NCPh)2 eventually gave the cationic complex [meso,trans-(Cp-CH(CMe3)PPh2) 2(Cl)Zr(μ-Cl)Pd(Cl)]+ (10) that was also characterized by X-ray diffraction. It features a dimetallabicyclic framework with two Cp-CHR-PPh2 ligands and a chloride bridging between the early and the late transition metal center.
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.
