Polymeric and monomeric barocene:: Synthesis and structure of Ba(C5H5)2•DMSO and Ba(C5H5)2(18-crown-6) (DMSO = dimethylsulfoxide)

Dicyclopentadienylbarium, Ba(C5H5)(2), crystallizes from dimethyl sulfoxide in a polymeric form with four C5H5- groups surrounding tetrahedrally the central Ba2+ ion; the reaction of Ba(C5H5)(2) with 18-crown-6 affords monomeric Ba(C5H5)(2)(18-crown-6) with two axial C5H5- rings and an equatorial 18-crown-6 ligand at the central Ba2+ ion. In this study, we present the solid-state structure of the heaviest alkaline earth metallocene, Ba(C5H5)(2) (containing dimethyl sulfoxide not coordinated to barium), and the reaction of Ba(C5H5)(2) with the polydentate ligand 18-crown-6.