Complete defluorination of 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene by titanium tetrakis(dimethylamide) - Selective formation of a cyclic hexanuclear titanium fluoroamide and 6,6-dimethylaminotetramethylfulvene

1,2,3,4-Tetramethyl-5-(trifluoromethyl)cyclopentadiene (Cp*(CF3)-H,1) react s with [Ti(NMe2)(4)] (2) under mild conditions to give [Ti(mu -NMe2)(NMe2)( NMe2)(mu -F)(F)](6) (3) in nearly quantitative yield. The molecular structu re of 3 consists of a ring of six [TiF2(NMe2)(2)] edge-bridged octahedra. T itanium complexes containing the Cp*(CF3) ligand, which was the primary int ention of these investigations, were not observed. C5Me4=C(NMe2)(2) (4) was isolated as a by-product. The complete defluorination of an aliphatic CF3 group occurs during the reaction. The reaction mechanism involves the prima ry formation of a difluorofulvene intermediate C5Me4=CF2 (5), which was mon itored by NMR studies. Density functional theory calculations predict a hig hly charged C6 atom (+ 0.87) in 5, which is discussed as the driving force of the reaction.