Abstract The preparations are reported of the complexes Mg(biuret) 2X 2 (X = Cl or Br), Mg[(biuret) 2(H 2O) 2]X 2 (X = C1 or Br), Ca(biuret) 2Cl 2, Ca(biuret) 4Br 2· 2H 2O, Ca(biuret) 4X 2 (X = Cl or Br) and Sr(biuret) 4- Br 2. The infrared spectra, between 4000-400 cm−1, are recorded to distinguish the mode of coordination of biuret in these complexes. ESR spectra at both X- and Q-band are reported for manganese(II) ions doped in the lattices of these complexes, and the zero-field splitting parameters D and λ(= E/D) are deduced. The D values observed for Mg[(biuret) 2(H 2O) 2]X 2 (X = Cl or Br) are consistent with the coordination of water molecules instead of halides. ESR spectra of the complexes, Mg(biuret) 2X 2 X = Cl or Br) closely resemble those of analogous zinc complexes, which contain chelating biuret molecules. The IR spectrum shows monodentate coordination of biuret molecules in Ca(biuret) 2Cl 2 and the ESR spectrum is consistent with a trans-CaO 4Cl 2 chromophore, suggesting that the biuret is acting as a monodentate bridging ligand. For Ca(biuret) 4X 2 and Sr(biuret) 4Br 2 chelating ligands are present and the D values are very low, suggesting little distortion from cubic symmetry.