Abstract Theophylline (L) adducts with Co(II) and Ni(II) chlorides, bromides and iodides and Fe(III) chloride and bromide were prepared by boiling under reflux 2:1 molar mixtures of L and hydrated metal salt in triethyl orthoformate-ethyl acetate. The new solid complexes obtained are adducts of the types CoL2X2 (X = Cl, Br, I), NiL2X2.H2O (X = Cl, Br), NiL2I2.2H2O, and FeL2X3.H2O (X = Cl, Br). On the basis of spectral, magnetic and conductance characterization, these complexes were formulated as being neutral monomeric with terminal N7-bound unidentate L, halo and, wherever applicable, aqua ligands. The Co(II)complexes are distorted tetrahedral species, the Ni(II) chloride and bromide adducts are pentacoordinated and the Ni(II) iodide and the Fe(III) complexes hexacoordinated.