Multiple and Highly Selective Alkyne-Isonitrile C-C and C-N Couplings at Group 4 Metallocenes

摘要

Reactions of the group 4 metallocene alkyne complexes [Cp'M-2(eta(2)-Me3SiC2SiMe3)] [Cp'(2)=rac-(ebthi)=rac-1,2-ethylene-1,1'-bis(eta(5)-tetrahydroindenyl): M=Ti, Zr, Hf; Cp'(2)=Cp*(2) (Cp*=eta(5)-pentamethylcyclopentadienyl): M=Zr] with 2,6-dimethylphenyl isocyanide (2-xylyl isonitrile, XyNC) were investigated. Depending on the metal, the Cp' ligand, and/or the stoichiometry, as well as the reaction temperature and time, different products were obtained. The products included simple end-on coordination compounds of XyNC in addition to those of the coupling of Me3SiC2SiMe3 with two, three, or four isonitriles to form enimine complexes, aza-metallacycloallenes, and fused heterocyclic systems, respectively. One example of the latter tricyclic compounds was subject to demetalation by using HCl. Molecular structures of the heterometallacycles were determined by X-ray crystallography. The interconversion of the products was investigated by H-1 NMR spectroscopy.