Synthesis of a crystalline molecular complex of Y2+, [(18-crown-6)K][(C5H4SiMe3)3Y].

The La(2+) complex [K(18-crown-6)(OEt(2))][Cp″(3)La] (1) [Cp″ = C(5)H(3)(SiMe(3))(2)-1,3], can be synthesized under N(2), but in the presence of KC(5)Me(5), 1 reduces N(2) to the (N═N)(2-) product [(C(5)Me(5))(2)(THF)La](2)(μ-η(2):η(2)-N(2)). This suggests a dichotomy in terms of ligands that optimize isolation of reduced dinitrogen complexes versus isolation of divalent complexes of the rare earths. To determine whether the first crystalline molecular Y(2+) complex could be isolated using this logic, Cp'(3)Y (2) (Cp' = C(5)H(4)SiMe(3)) was synthesized from YCl(3) and KCp' and reduced with KC(8) in the presence of 18-crown-6 in Et(2)O at -45 °C under argon. EPR evidence was consistent with Y(2+) and crystallization provided the first structurally characterizable molecular Y(2+) complex, dark-maroon-purple [(18-crown-6)K][Cp'(3)Y] (3).