Air-stable μ-oxo-bridged binuclear titanium(IV) salophen perfluorooctanesulfonate as a highly efficient and recyclable catalyst for the synthesis of bis(indolyl) methane derivatives

An air-stable μ -oxo-bridged binuclear Lewis acid of titanium(IV) salophen perfluorooctanesulfonate [{Ti(salophen)H 2 O} 2 O][OSO 2 C 8 F 17 ] 2 ( 1 ) was successfully synthesized by the reaction of Ti IV (salophen)Cl 2 with AgOSO 2 C 8 F 17 and characterized by different techniques such as IR, NMR and HRMS . TG-DSC analysis showed that this complex was thermally stable at 220 °C. Meanwhile, it exhibited good solubility in polar organic solvents and good ionic dissociation in CH 3 CN solution. Fluorescence spectra and Hammett indicator results indicated that the complex had relatively strong acidity. And it showed high catalytic efficiency for the synthesis of bis(indolyl) methane derivatives through Friedel-crafts reaction of aldehyde/ketone with indoles . Moreover, it can be reused five times with minimal changes in catalytic efficiency.