 The ( C5H5 ) − ion in samarium <unk> can be replaced by the <unk> ( <unk> ) − or cyclooctatetraenide ( C8H8 ) 2 − ring , resulting in Sm ( <unk> ) 3 or <unk> ( η8 @-@ C8H8 ) 2 . The latter compound has a similar structure to that of uranocene . There is also a cyclopentadienide of divalent samarium , Sm ( C5H5 ) 2 – a solid that sublimates at about 85 ° C. Contrary to ferrocene , the C5H5 rings in Sm ( C5H5 ) 2 are not parallel but are tilted by 40 ° . 
