Titanium complexes containing bulky eta(2)-1,2,4-triazolato

The unusual eta(2)-coordination of a 1,2,4-triazolato ligand to a transition metal is described. The synthesized compounds [Ti(eta(2)-tz)(4)] (1), [(C5Me4CH2Ph)Ti(eta(2)-tz)Cl-2] (2), [Cp Ti(eta2-tz)-Cl-2] (3) and [Cp Ti(eta(2)-tz)(3)] (4) (tzH = 3,5-diisopropyl-1,2,4-triazole) were characterized by H-1 and C-13 NMR spectroscopy and, in the case of 1 and 2, by X-ray crystallography. Both structures confirm the eta(2)-coordination of the ligand. In compound 1 all four ligands coordinate in an T, 2 fashion leading to a metal center surrounded by eight nitrogen atoms. The core of the fragment formed by the central atom and the triazolato planes exhibits a distorted D-2d symmetry. A variable temperature NMR spectroscopy experiment performed on 1 confirms the occurrence of two different isopropyl groups at low temperature. The structure of compound 2 shows the geometry of the molecule in a distorted C, symmetry, with the mirror plane perpendicular to the cyclopentadienyl and triazolato rings. The tz ligand is oriented in a transoid position relative to the benzyl substituent of the C5Me4CH2Ph group.