Results from liquid X-ray scattering show that both [Ni(6)(CO)(12)](2)(-) and [Pt(6)(CO)(12)](2)(-) adopt an overall staggered ditriangular structure of D(3) symmetry in solution. Theoretical calculations show that the energy barrier of rotation is quite small, in particular for the platinum cluster. The possibilities to stabilize monotriangular carbonyl clusters of Ni and Pt in solution were also investigated. Only monotriangular [Pt(3)(CO)(6)](2)(-) can be stabilized as verified by NMR and IR spectroscopy as well as X-ray scattering. The structure is analogous to that found in the individual triangular units of [Pt(6)(CO)(12)](2)(-), and there is no unambiguous evidence for the need of additional apical CO's to stabilize [Pt(3)(CO)(6)](2)(-) in solution. Attempts to isolate the corresponding [Ni(3)(CO)(6)](2)(-) cluster instead produced the very stable [Ni(5)(CO)(12)](2)(-). Mixed solutions of the ditriangular clusters give rise to heteroclusters, whose chemistry is dominated by the facile disproportionation of the Ni(6) clusters.