THE PREPARATION AND VARIABLE-TEMPERATURE H-1-NMR CHARACTERIZATION OF 1-(TRI-N-BUTYLSTANNYL)INDENE, 1-(BU3SN)C9H7

The synthesis of 1-(tri-n-butylstannyl)indene, 1, was carried out by t he reacting lithium indenide with tributylstannyl chloride. The-pale y ellow product was collected by distillation in 65% yield, and the proc edure is scalable to large quantities. Examination of the room-tempera ture H-1 NMR spectrum of 1 revealed a fluxional process in which the t ributylstannyl group was rapidly interchanging between the 1 and 3 pos itions on indene. A variable-temperature H-1 NMR study was performed o n 1 from -60 degrees C to +40 degrees C and the free energy of activat ion for the 1,3-interchange was calculated as 15.4 kcal mol(-1) at 60 degrees C, using the Eyring equation. This result is compared to previ ous studies of the 1,3 migrations of trimethylsilyl and trimethylstann yl groups on indene. (C) 1997 Elsevier Science Ltd.