ISSN:
0044-2313
Keywords:
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Structure and Dynamics of a Nine-membered Metallacyclic Zirconoxycarbentungsten Complex Obtained by Coupling of Cp2Zr(butadiene), W(CO)6, and Me3C—CNReaction of the (butadiene)metallocene complexes (RCp)2Zr(η4-C4H6) 1 [s-cis-/s-trans-mixtures; R = H (a), CH3 (b)] with hexacarbonyltungsten followed by treatment with pivalonitrile produced the nine-membered metallacyclic zirconoxycarbene complexes 3 (a: R = H; b: R = CH3), exhibiting an endocyclic trans-C—C double bond [X-ray crystal structure analysis of 3b: space group P21/n, a = 8.417(1), b = 21.563(2), c = 15.494(1), β = 94.17(1)°, Z = 4, R = 0.045, RW = 0.043]. From the dynamic 1H NMR spectra an activation barrier of ΔGent≠ = 16.4 ± 0.5 kcal/mol is estimated for the enantiomerization process of the chiral metallacycle 3b at the coalescence temperature of the Cp-methylgroup resonances (297 K).
Notes:
Reaktion der (Butadien)metallocenkomplexe (RCp)2Zr(η4-C4H6) 1 [s-cis-/s-trans-Gemische; R = H (a), CH3 (b)] mit Hexacarbonylwolfram und anschließend mit Pivalonitril liefert die neungliedrigen metallacyclischen Zirconoxycarbenkomplexe 3 (a: R = H; b: R = CH3) mit trans-konfigurierter C—C-Doppelbindung im Ring [Röntgenstrukturanalyse von 3b: Raumgruppe P21/n, a = 8,417(1), b = 21,563(2), c = 15,494(1), β = 94,17(1)°, Z = 4, R = 0,045, RW = 0,043]. Aus den dynamischen 1H-NMR-Spektren wird eine Aktivierungsbarriere der Enantiomerisierung des chiralen Metallacyclus 3b von ΔGent≠ = 16,4 ± 0,5 kcal/mol bei der Koaleszenztemperatur der Cp-Methylgruppensignale (297 K) abgeschätzt.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19905810103
