Remarkable Stability of Metallocenes with Superbulky Ligands: Spontaneous Reduction of Sm^III to Sm^II

Abstract

Unexpected attraction between extremely bulky cyclopentadienyl ligands of opposite chirality has been observed in perarylated metallocenes [(Ar5C5)2M]. The exceptional stability of such sterically congested metallocenes (see structure) is explained by a merry-go-round CH⋅⋅⋅C(π) hydrogen-bond network. This stabilizing force even enables spontaneous reduction of a SmIII precursor to a SmII metallocene.