Synthesis of Non-classical Divalent Lanthanide Complexes

The first non-classical divalent lanthanide iodide Tml2(DME)3 (DME = dimethoxyethane), which is prepared by the reaction of thulium metal with iodine under argon (Equation 8.33), was reported in 1997 [101]. Subsequently, Dyl2(DME)3 andNdl2(THF)5 have been synthesized by an analogous manner. The success of the synthesis of non-classical divalent lanthanide iodides opens up a new area in divalent lanthanide chemistry [102, 103]. 

Tml2(DME)3, Dyl2 (DME)3, and Ndl2(THF)5 have similar structures to those of the classical divalent lanthanide iodides. However, metathesis reaction with these iodides usually affords not a divalent complex but a trivalent lanthanide complex instead, because of their strong reductive ability [102], To date, only one structurally characterized divalent organothulium complex has been synthesized by metathesis reaction (Equation 8.34) [104]. 

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