Conformational studies of dithiastannolanes by dynamic nuclear magnetic resonance spectroscopy

Abstract

The barriers to conformational interconversion of the five-membered rings of the title compounds of general type SnRR′(SCH₂CHR″S)(R, R′= Me or Ph; R″= H or Me) have been measured for the first time by low-temperature n.m.r. studies. Room-temperature measurements indicate that the chelate rings exist as half-chair conformations with the –CH₂CHR″– moiety in a fully staggered configuration, as in the solid state. These findings are at variance with a previous n.m.r. study of this type of system. The ΔG‡ values for the interconversion of the two half-chair conformations lie in the range 30–32 kJ mol^–1 and are essentially independent of the substituents on the Sn^IV atom and on the five-membered ring.