Zirconium Hydrazinediido Complexes Derived from Cyclic Hydrazines and Their Role in the Catalytic Synthesis of 1,7-Annulated Indoles

Reaction of cyclic 1,1′-disubstituted hydrazines with the bis­(dimethylamido)zirconium complex [Zr­{(NXyl)2Npy} (NMe2)2] (1) in the presence of dmap yielded the hexacoordinate zirconium hydrazinediido complexes [Zr­{(NXyl)2Npy}­(NNC9H10)­(dmap)2] (2) and [Zr­{(NXyl)2Npy}­(NNC12H8)­(dmap)2] (3). Hydrazinediides are thought to be key intermediates in the zirconium-catalyzed reaction of cyclic 1,1′-disubstituted hydrazines and disubstituted alkynes to yield 1,7-annulated indoles. Their basic structural motif is found in 5-HT3 receptor antagonists such as Cilansetron.