The new cyanurates Sr-3(O3C3N3)(2) (SCY) and Eu-3(O3C3N3)(2) (ECY) were prepared via exothermic solid state metathesis reactions from MCl2 (M = Sr, Eu) and K(OCN) in silica tubes at 525 degrees C. Both structures were characterized by means of powder and single crystal X-ray diffraction, and their structures are shown to crystallize with the noncentrosymmetric space group R3c (No. 161). Infrared spectra and nonlinear optical properties (NLO) of SCY and ECY are reported in comparison to those of CCY and beta-BaB2O4 (beta-BBO).