Verknüpfung von Cyanamiden mit einem Carbinliganden – Bildung von η2-(C,N)-Imidazolium- und Ansa-Carben-Komplexen†

Abstract

Coupling of Cyanamides with a Carbyne Ligand – Formation of η2-(C,N)-Imidazolium Complexes and Ansa-Carbene Complexes†Dicarbonyl(cyclopentadienyl)(phenylcarbyne)manganese complexes [Cp(CO)2Mn≡CPh]+X- (1-X) (X = BF4, BCl4) react with dimethyl- (2a), diethyl- (2b), and diisopropylcyanamide (2c) in five-fold excess by a head-to-tail cyclization of two cyanamides with the carbyne ligand to give η2-(C,N)-imidazolium complexes (3a–c–X). As byproducts ansa-amino(alkylide-neamino)carbene complexes (4a–c) are formed in which a N=C(Ph) group bridges the carbene carbon and the Cp ring. With increasing excess of the cyanamide the product ratio 3-X: 4 increases. Among the products of the reaction of 1-X with the cyanamides N≡CNR2 [NR2 = N(iBu)2, N(Bzl)2, N(Me)Ph] no imidazolium complexes 3-X are detected, only ansa-carbene complexes 4 are isolated. PMe3/H2O or pyridine/H2O displaces the heterocyclic ligand from 3a-BF4. The structure of 3a-BF4 is established by an X-ray analysis.