s-trans-Diene Complexes of a First-Row Transition Metal. Half-Sandwich s-trans-η4-1,3-Diene Nitrosyl Complexes of Chromium

The first s-trans-1,3-diene complexes of a first-row transition metal have been prepared and characterized both in solution and in the solid state. The unexpected s-trans configuration was obtained from photolytic decarbonylation of Cp‘Cr(NO)(CO)2 (Cp‘ = η5-C5H5 and η5-C5Me5) in the presence of conjugated dienes. Related η2-olefin and η2-2-alkyne complexes have also been prepared.