SYNTHESIS AND STRUCTURE OF INVERSE CYCLOOCTATETRAENYL SANDWICH COMPLEXES OF EUROPIUM(II) - [(C(5)ME(5))(THF)(2)EU](2)(MU-C8H8) AND [(THF)(3)K(MU-C8H8)]EU-2

The reaction of K2C8H8 with EuCl3, followed by reaction with KC(5)Me(5) forms the Eu-II inverse sandwich complex [(C(5)Me(5))(THF)(2)Eu](2)[mu-(eta(8):eta(8)-C8H8)] (1). A second type of Eu-II cyclooctatetraenyl species {(THF)(3)K[mu-(eta(8):eta(8)-C8H8)]}Eu-2 (2), is generated when K2C8H8 reacts with Eu-3(OCMe(3))(7)Cl-2(THF)(2). Both 1 and 2 are symmetrically bridged complexes of the cyclooctatetraenyl dianion which contain formally 10-coordinate europium(II) metal centres.