Synthesis, Characterization, and Electronic Structures of a Series of Two-Dimensional Trimetallic Cluster Complexes, Ru₃(CO)₉(μ-SnPh₂)₃[Pt(PBu^t₃)]_x, x = 0−3

The triruthenium-tritin cluster complex, Ru₃(CO)₉(μ-SnPh₂)₃, 13 was obtained from the reaction of Ru₃(CO)₁₂ with Ph₃SnH. Compound 13 reacts with Pt(PBu^t₃)₂ to yield three new Pt(PBu^t₃) adducts of 13 Ru₃(CO)₉(μ-SnPh₂)₃[Pt(PBu^t₃)]_x, 14−16 x = 1 − 3 formed by the addition of Pt(PBu^t₃) groups to the Ru−Sn bonds. The new complexes form a novel series of trimetallic complexes having planar arrangements of the metal atoms. The UV−vis absorptions of the four complexes shift progressively to longer wavelengths as the number of platinum atoms is added to the cluster. The electronic structures of these complexes have been investigated in the ground and excited states by density functional theory and time-dependent density functional theory, and this has provided a detailed understanding of the metal−metal bonding and electronic transitions that are responsible for their UV−vis absorption properties. The predicted absorption maximum for the model structures for 13, 14, 15, and 16 at 465, 508, 556, and 585 nm differ only 4−18 nm from the experimental values of 474, 490, 552, and 576 nm. The shift of principal UV−vis absorption can be explained by a lowering of the HOMO−LUMO energy gap due to interactions of the platinum atoms with the HOMO and LUMO of the Ru₃Sn₃ core.