Synthesis of a Crystalline Molecular Complex of Y2+, [(18-crown-6)K][(C5H4SiMe3)3Y]

The La2+ complex [K(18-crown-6)(OEt2)]-[Cp '' La-3] (1) [Cp '' = C5H3(SiMe3)(2)-1,3], can be synthesized under N-2, but in the presence of KC5Me5, 1 reduces N-2 to the (N=N)(2-) product [(C5Me5)(2)(THF)La](2)(mu-eta(2):- eta(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 Y2+ complex could be isolated using this logic, Cp'Y-3 (2) (Cp' = C5H4SiMe3) was synthesized from YCl3 and KCp' and reduced with KC8 in the presence of 18-crown-6 in Et2O at -45 degrees C under argon. EPR evidence was consistent with Y2+ and crystallization provided the first structurally characterizable molecular Y2+ complex, dark-maroon-purple [(18-crown-6)K] [Cp'Y-3] (3).