Benzyl Complexes of Lanthanide(II) and Lanthanide(III) Metals: Trends and Comparisons

A variety of benzyllanthanide complexes have been prepared by the metathesis reaction of benzylpotassium precursors with lanthanide halides. Syntheses and crystal structures for the following complexes are described: [2-Me2N-a-Me3Si-benzyl]2Eu(II)·(THF)2(1-Eu), (2-Me2Nbenzyl) 3Ln(III) (2-Ln with Ln = Nd, Sm, Dy, Ho, Yb), (4-R-C6H4CH2)3Ln·(THF)3(3-Y: Ln = Y, R = H; 3-La: Ln = La, R = tBu). Complexes of types 1 and 2 are thermally robust on account of a stabilization by a benzylic Me3Si substituent and/or intramolecular coordination of the Me2N substituent. Comparison of the crystal structures of these new series of lanthanide complexes shows several similarities and trends. In addition, comparisons with alkali metal and alkaline earth metal benzyl complexes are made.