Nitrile Addition to (η4-Butadiene)zirconocene: The Formation of Organometallic and Metal-Free Hexatrienediamine Derivatives

✍ Scribed by Erker, Gerhard ;Pfaff, Ronald ;Krüger, Carl ;Nolte, Matthias ;Goddard, Richard

• Publisher: Wiley (John Wiley & Sons)
• Year: 1992
• Tongue: English
• Weight: 590 KB
• Volume: 125
• Category: Article
• ISSN: 0009-2940
• DOI: 10.1002/cber.19921250724

✦ Synopsis

Butadiene dianion equivalent, 1,Caddition / Metallocene template, bent / Enamine, primary, stable / Metallacycles, nine-membered, chiral / Zirconocene (q4-Butadiene)zirconocene adds one equivalent of benzonitrile to form the five-membered azazirconacyclopentene derivative 9, which contains an NH group in the ring and a vinyl substituent at the u-carbon center. The reaction of ? with an additional equivalent of benzonitrile furnishes the chiral ninemembered metallacycle [Cp2ZkN(H)C(Ph) = CHCH = CH-CH,C(Ph) = fi] (12) which may be isomerized to the thermodynamically favored tautomer [Cp,ZkN = C(Ph)CH2CH = CH-CH2C(Ph)=$J] (13). The Gibbs activation energy of the enantiomerization of the trans-cycloallcene-like 13 is AG*(323 K) = 15.5 k 0.3 kcal mol-'. The analogous conformational equilibration of 12 has a lower activation barrier of AG* (236 K) = 12.1 f 0.3 kcal mol-l; complex 13 is characterized by X-ray diffraction. Hydrolysis of 13 yields the conjugated 1,6-diamino-1,6-diphenylhexatriene 16 which is characterized by X-ray diffraction.