A new complex bis(hexafluoroacetylacetonato)tetrazinecopper(II), Cu(hfac) 2 (tetz) (1), has been prepared by reaction of Cu(hfac) 2 Á xH 2 O and 1,2,4,5-tetrazine in CH 2 Cl 2 . Orange crystals suitable for X-ray diffraction analysis of 1 were obtained by slow evaporation at room temperature. Complex 1 crystallizes in the triclinic space group P 1, with a ¼ 11.4825 (7), b ¼ 13.4950(8), c ¼ 13.8328(8) Å , ¼ 104.990(1), ¼ 111.888(1), ¼ 94.245(1) , V ¼ 1886.23(19) Å 3 , R 1 ¼ 0.0507 based on 6814 independent reflections. The complex is unstable at room temperature and decomposes with loss of the tetz ligand. Differential scanning calorimetry (DSC) and magnetic properties are reported.