Lanthanide organometallics divalent compounds

Organometallic compounds of lanthanide metals other than Sm, Eu, and Yb are very rare until now. But the development of this chemistry became possible after the synthesis of divalent precursors of Tm, Dy, and Nd in the late 1990s, namely of their diiodides (see Scandium, Yttrium the Lanthanides Inorganic Coordination Chemistry) and by using hgands such as phospholyl or arsolyl, which stabilize divalent lanthanide ions. 

Divalent lanthanide compounds are generally non-volatile this observation is consistent with a polymeric constitution. However, some organometallic compounds have been sublimed. Yb(Me3SiC5H4)2 sublimes at 300°C/10 Torr (Lappert et al., 1980) and YbCp2 sublimes at 360°C/10 Torr with considerable decomposition (Calderazzo et al., 1966). 

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