Homoleptische 1,4-Diazadienverbindungen elektronenarmer Übergangsmetalle. Synthese, Eigenschaften und Strukturen von (DAD)2Ti und (DAD)3Ti [1] / Homoleptic 1,4-Diazadiene Compounds of Early Transition Metals. Syntheses, Properties and Structures of (DAD)2

Syntheses and structures of homoleptic 1,4-diaza-1,3-diene (DAD) complexes of titanium are described. The spiranoid DAD complexes of formula (DAD)2Ti 3a-c are formed by reaction of TiCl4·2THF with the disodium salts Na2DAD 2a-c or by reduction of TiCl4·2TH F with magnesium in presence of two equivalents of DAD 1a-c . The endiaide complexes 3a-c are thermally stable, very sensitive to oxygen and water, and soluble in all com monorganic solvents. An X-ray crystal structure determination of 3 c reveals the titanium atom to be in a strongly distorted tetrahedral environment. The two five-membered metallacyclic rings are folded along the N,N′ axis. Temperature-dependent 1H NMR spectra of 3a-c indicate a rapid intramolecular inversion of this non-planar ring system in solution even at room temperature. Reduction of TiCl4·2THF with magnesium in presence of excess DAD 1d-f leads to the formation of the blue-violet complexes (DAD)3Ti 4d-f. At low temperatures three sterically crowded DAD ligands cause a rigid conformation as demonstrated by their unique lowtemperature 1H NMR spectra.