Recently a series of divalent complexes of the type [Ln(NR2)3]− (R = SiMe3; Ln = Gd, Tb, Ho, Er) have been isolated which overturns the belief that (NR2)1- ligands are too electron-donating to support the +2 oxidation state for these metals. Previously, amide complexes of divalent lanthanides had been limited to Eu, Yb, Sm, and Tm, which form traditional 4fn+1 +2 ions. We have found that the ability to isolate amide complexes of these other metals can depend heavily on the nature of the counter-cation. Some metals form isolable complexes using a [K(2.2.2-cryptand)]1+ counter-cation, while the smaller metals Ho and Er require Rb. In other cases, 18-crown-6 is an ideal chelate with potassium as a reductant. Reactivity of the isolated divalent lanthanide complexes {K(chelate)}{Ln[N(SiMe3)2]3} with dinitrogen generates end-on bound dinitrogen complexes, {K(chelate)}2{[(R2N)3Ln]2[µ-η1:η1-N2]}, which differ from the side-on bound [(R2N)2Ln]2[µ-η2:η2-N2] complexes previously isolated from LnA3/K/N2 reactions. Reactivity of [K(18-crown-6)2][Ln(NR2)3] with CO results in the isolation of the ynediolate complex, {[K(18-crown-6)]2(18-crown- 6)}{[(R2N)3Ln]2(μ-OC≡CO)}, while reactivity with CO2 has shown evidence for a CO2 coordination polymer product in addition to a CO2 coupled oxalate product.

Reactivity of the isolated divalent lanthanide complexes {Ln[N(SiMe3)2]3}1− with small molecules: CO, CO2, N2

255th National Meeting (2018)

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