We investigate theoretically the electronic structure of I.CO 2 and I.OCS van der Waals complexes including spin-orbit interaction. For the T-shaped geometry of I.CO 2 , we calculate the potentials using a fully polyatomic treatment and compare the results to the widely used pseudo-diatomic approximation. The latter becomes increasingly invalid at I-CO 2 distances shorter than 4 Å. We calculate the potentials of linear I.SCO and I.OCS, and analyze the zero-order electronic structure of nonlinear I.OCS. We also discuss the validity of treating the spin-orbit interaction in I.CO 2 and I.OCS as an atomic property of iodine and find this approximation justified at characteristic van der Waals distances.