On the basis of the 18-electron rule, we theoretically designed a series of sandwich complexes [M3L2(CO)(3)](q) (M = Ni, Pd, Pt; L = C7H7, P-5, P-6, As-5, As-6; q = 2+, 0, or 2-) by means of density functional theory computations. These sandwich structures are of high stability, revealed by their strong donating and back-donating metal ligand interactions, considerable aromatic characters as well as sizable energy gaps. All these proposed sandwich structures might serve as promising building blocks for new nanomaterials.