The coordination-driven self-assembly of two metal-carbonyl-cluster-coordinated dipyridyl donors, (4-C5H4N)(2)C equivalent to CCo2(CO)(6) (1) and (4- C5H4N)(2)C equivalent to CMo2Cp2(CO)(4) (2), with a linear diplatinum (11) acceptor ligand was investigated. The structures of the resulting self-assembled polygons were found to be controlled by the steric bulk of the metal-carbonyl cluster adduct. The use of a sterically less imposing ligand 1 resulted in a pentagon-hexagon mixture, which was characterized by electrospray ionization time-of-flight mass spectroscopy. The exclusive formation of a [5 + 5] pentagon was achieved by the self-assembly of the bulkier molybdenum donor ligand 2 with a linear organoplatinum(II) acceptor ligand. Molecular force field modeling was used to study the structural details of the pentagonal and hexagonal architectures. The first Fe-3-Co-6-Pt-6 trimetal [3 + 3] hexagon was also synthesized via the combination of 1 with a 120 degrees ferrocenyldiplatinum(II) acceptor.