Cadmium iodide complexes with formamide (FA) and benzamide (BA) have
the same composition (1 : 4), but differ in structure.
The crystals of [Cd(BA)4I2] are tetragonal, space group I 4 , a = b = 14.328(4)
Å, c = 14.338(3) Å, V = 2943(2) Å3, Z = 4. The crystals of [Cd(FA)4I2] are
orthorhombic, space group Fdd2, a = 12.889(5) Å, b = 26.361(9) Å, c = 8.270(3)
Å, α = β = γ = 90°, V = 2809.87 Å3, Z = 8. The refinement converged to R = 0.046
and 0.0235, respectively.
Both complexes have molecular structures. The cadmium atoms in the
complexes are involved in the octahedral coordination with four oxygen atoms
of the amide molecules and two iodine atoms.
In the benzamide complex, the oxygen atoms occupy the equatorial
positions of the octahedron, and the iodine atoms are arranged in the axial
positions. The Cd–O and Cd–I distances vary in the 2.415–2.432 and 2.800–
2.843 Å ranges, respectively. The structure of the complex is stabilized by

four intramolecular hydrogen bonds involving carbonyl oxygen atoms and NH2
groups. All intermolecular contacts are of the van der Waals type.
In the formamide complex, the equatorial plane of the octahedron is built of
two iodine atoms and two oxygen atoms, and the axial positions are occupied by
two oxygen atoms. The Cd–O and Cd–I distances are 2.359–2.362 and 2.829
Å, respectively. No itramolecular hydrogen bonds are found. Every formamide
ligand is involved in H-bonding with one ligand of the adjacent complex.
Coordination of the ligands through the carbonyl oxygen atoms in both
complexes is supported by the IR spectroscopic data. The bands of the stretching
modes of carbonyl groups shift towards lower frequencies as compared to their
positions in the spectra of free ligands.