Facile Synthesis and Structural Characterization of [Cp₂Ti^IV(NCX)₂][AsF₆]₂ Complexes:  Adducts of Cp₂Ti(AsF₆)₂ with Halogen Cyanides (X = Cl, Br, I)

Abstract

A series of adducts between the highly reactive dicationic Cp 2 Ti IV 2+ center and the weak Lewis base halogen cyanides (ClCN, BrCN, ICN) have been prepared in a facile synthesis and in quantitative yields from the reaction of Cp 2 Ti(AsF 6 ) 2 with ClCN, BrCN, or ICN in liquid SO 2 . The extremely air-sensitive Cp 2 Ti(NCX) 2 (AsF 6 ) 2 (X ) Cl (1), Br (2), I (3)) complexes were characterized using IR and 1 H, 14 N, 19 F, and 75 As NMR spectroscopy, as well as X-ray diffraction. The structures of 1-3 were determined using X-ray diffraction techniques. The synthetic route employed should generally be applicable for the synthesis of a range of new cationic Cp 2 Ti IV L 2 2+ (L ) neutral ligand) species using anhydrous conditions and demonstrates the usefulness of liquid SO 2 as a solvent for such systems. Compounds 1-3 are the first structurally characterized Cp 2 Ti IV L 2 (EF 6 ) 2 (L ) neutral ligand; E ) As, Sb) complexes with the weakly coordinating AsF 6 -anion and are also the first adducts between cationic Cp 2 M x+ (M ) transition metal) centers and the halogen cyanides, which are weak Lewis bases in comparison with other nitriles such as CH 3 CN.