The correlations between the structural and electronic properties of the clusters [M3X3](3-) and sandwich complexes [M-3(C7H7)(2)X-3](-) (where M = Ni, Pd, Pt; X = F, Cl) were studied with density functional theory (B3PW91). All of the sandwich complexes are donating and back-donating metal-ligand bonding structures. The influence of the ligand, significant variations in the M-C, M-X, M-M, C-C bond lengths and binding energies were examined to obtain qualitative and quantitative pictures of the intramolecular C7R7+-M3X33- interactions. Our theoretical investigations show that the binding energies of the sandwich complexes gradually reduce from Ni to Pt, as well as from F to Cl. Meanwhile, the geometric and electronic structures and the relative stabilities have a strong relation to each other. (C) 2014 Published by Elsevier B.V.