Solid-state cis–trans isomerization reaction of (η5-MeC5H4)W(CO)2P(OiPr)3I

cis-(η5-MeC5H4)W(CO)2P(OiPr)3I (1) was converted to the trans isomer 2 in the solid state (90–110 °C). The reaction was monitored by heating 1 in NMR tubes for periods of time (2–60 min), cooling the tubes to room temperature and determining the conversion by solution 31P and 1H NMR spectroscopy. The data were consistent with a first-order reaction and yielded an activation energy of 59 ± 3 kJ mol−1. Comparative kinetic data were obtained from an in situ analysis of a powder-XRD study of 1. The powder-XRD study was conducted at 80–100 °C (10–60 min), yielding an activation energy of 52 ± 2 kJ mol−1 (first-order reaction). The reaction could not be monitored by single crystal X-ray diffraction as the crystal disintegrated over time on heating. This disintegration process was monitored by optical microscopy and revealed that while the bulk crystal morphology was retained the crystal surface roughened with time. The compounds 1 and 2 were also structurally characterised by X-ray crystallographic techniques.