Reactivity of a Seven‐Membered Zirconacyclocumulene towards CN Multiple Bonds – Formation of Metallaheterocycles by Insertion of C≡N and C=N Groups

Abstract

AbstractThe reactions of the seven‐membered zirconacyclocumulene [Cp2Zr{η4‐Me3SiC4(SiMe3)–C(C2SiMe3)=CSiMe3}] (1) with nitriles (RC≡N, R = Me, Ph) started with an insertion of a cyanide group into the metal–butadiyne bond followed by an alkyne–nitrile coupling and formation of 1‐zircona‐2‐azacyclopenta‐2,4‐dienes. The reaction product for R = Me is stabilized by dimerization to give a compound containing a four‐membered –N–Zr–N–Zr– ring and two identical five‐membered 1‐metalla‐2‐aza‐cyclopentadiene rings. In case of R = Ph, a metallacycle could not be isolated, and a pyrimidine was formed. The catalytic potential of this reaction was investigated. For PhN=C(H)Ph, again after insertion and coupling, a corresponding 1‐zircona‐2‐azacyclopenta‐4‐ene was established. The reaction of this compound with carbon dioxide led to ring expansion and formation of a seven‐membered product, which released CO2 at higher temperature and to give back the reactant. The above‐mentioned products were characterized by NMR spectroscopy and single‐crystal X‐ray structure analysis.