Two Ni(II) molecular metallacycles of [Ni4(bpz*tz•)4(N3)4] (1) and [Ni3(bpzPhtz•)3(pzPh(Cl)tz•)3]•1.3CH3OH•9.3H2O (2) (bpz*tz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine; bpzPhtz = 3,6-bis(3-phenyl-pyrazolyl)-1,2,4,5-tetrazine; pzPh(Cl)tz = 3-bis(3-phenyl-pyrazolyl)-6-Cl-1,2,4,5-tetrazine) were reported. The single-crystal X-ray diffraction study reveals that 1 displays...