To elucidate the possible catalytic action of iron-based direct coal liquefaction (DCL) catalysts, we model various surfaces of FeS and Fe-(1-x)S-y, clusters with a molecular orbital approach. We have studied the adsorption of toluene and l-methylnaphthalene at various Sites on FeS and related defect clusters and have calculated bond-breaking energies of the aromatic-aliphatic linkage. A preliminary explanation of the catalytic activity of FeS is the donation of electrons to the iron surface by the adsorbate, followed by a subsequent decrease in the bond-breaking energies as compared to the nonchemisorbed species.