Formation of a cyclooctatetraenylsamarium(III) inverse sandwich that ring-opens tetrahydrofuran.

Reductive trapping of the cyclooctatetraenyl dianion (COT 2- ) by treatment of [Sm(DippForm) 2 (thf) 2 ] (DippFormH = N , N '-bis(2,6-diisopropylphenyl)formamidine; thf = tetrahydrofuran) with 1,3,5,7-cyclooctatetraene (C 8 H 8 ) in toluene yields an inverse sandwich dinuclear complex [Sm 2 (DippForm) 4 (COT)] (1), but [Sm(DippForm)(COT)(thf) 2 ] (2) and [Sm(DippForm) 2 (O-C 4 H 8 -DippForm)(thf)] (3) in thf, and 1 yields 2 and 3 on treatment with thf.