Nuclear magnetic resonance study of crystalline bis(cyclooctatetraene)iron

Abstract

Crystalline bis(cyclooctatetraene)iron has been studied by investigation of n.m.r. line-width and second moment variations with temperature. The experimental second moment has been compared with that calculated for the rigid lattice. It was found that, while below –185°C the rate of the motions presumably present in the crystal is not great enough to affect the second moment, above this temperature the molecules start to move at an increasing rate. At room temperature the only possible type of motion of the molecules is completely activated and consists of oscillations of the cyclooctatetrane rings. The n.m.r. data allow us to conclude that the structural disorder observed at room temperature with X-rays is of a dynamic type.