Novel Heterobimetallic Compounds with Metal−Metal Bonds: The Use of Quinolyl-Substituted Metallocenes as Tridentate Ligands^†

1,1‘-Bis(quinolyl)ferrocene (1) and 1,1‘-bis(quinolyl)ruthenocene (2) were prepared by palladium-catalyzed cross-coupling of zincated metallocenes ((C5H4ZnCl)2M; M = Fe, Ru) with 8-bromoquinoline. Both complexes can serve as tridentate ligands toward d10 metal ions. Their reactions with anhydrous zinc chloride or with tetrakis(acetonitrile)copper(I) tetrafluoroborate lead to the bimetallic complexes 3−6, in which the zinc or copper ion is coordinated in a tridentate manner by the metallocene derivative 1 or 2, respectively. Two different coordination modes of the ligands 1 and 2 were observed, both with a metal−metal bond as proved by X-ray analysis. The bond distances Fe−Zn in 3 and Ru−Zn in 4 are practically identical (2.56 Å); the Ru−Cu bond in 6 is somewhat longer (2.63 Å). Whereas the zinc adducts 3 and 4 contain the metallocene ligand in a Cs-symmetric arrangement with a 4-fold-coordinated Zn atom, the Ru−Cu compound 6 has a C2 symmetry with a 3-fold-coordinated Cu atom. The heterobimetallic compounds 3 and 4 are the first structurally characterized ferrocene and ruthenocene derivatives containing a metal to zinc bond. The complexes 5 and 6 are, to the best of our knowledge, the first examples of adducts of ferrocene and ruthenocene derivatives with copper.