Butenyl‐Substituted Alkaline‐Earth Metallocenes: A First Step towards Olefin Complexes of the Alkaline‐Earth Metals

Sandwich any one? The bis(butenyltetramethylcyclopentadienyl) complexes of calcium (2), strontium and barium exhibit an interaction of the alkaline-earth metals with olefin double bonds. Whereas the magnesium derivative (1) crystallizes as a sandwich complex with coplanar cyclopentadienyl ligands and free butenyl side chains, these coordinate to the metal in the analogous but open sandwich complexes of the larger metals calcium, strontium, and barium.