Syntheses, Structures, and Electrochemistry of the Defective ccp [Pt33(CO)38]2– and the bcc [Pt40(CO)40]6– Molecular Nanoclusters

The molecular [Pt33(CO)38]2– nanocluster was obtained from the thermal decomposition of Na2[Pt15(CO)30] in methanol. The reaction of [Pt19(CO)22]4– with acids (1–2 equiv) affords the unstable [Pt19(CO)22]3– trianion, which evolves with time leading eventually to the [Pt40(CO)40]6– hexa-anion. The total structures of both nanoclusters were determined via single-crystal X-ray diffraction. [Pt33(CO)38]2– displays a defective ccp Pt33 core and shows that localized deformations occur in correspondence of atomic defects to “repair” them. In contrast, [Pt40(CO)40]6– shows a bcc Pt40 core and represents the largest Pt cluster with a body-centered structure. The rich electrochemistry of the two high-nuclearity platinum carbonyl clusters was studied by cyclic voltammetry and electrochemical in situ Fourier transform infrared spectroscopy. The redox changes of [Pt33(CO)38]2– show features of chemical reversibility and electrochemical quasi-reversibility, and the vibrational spectra in the CO stretching region of the nine redox forms of the cluster [Pt33(CO)38]n (n = 0 to −4, −6 to −9) are reported. Almost all the redox processes exhibited by [Pt40(CO)40]6– are chemically and electrochemically reversible, and the eight oxidation states of [Pt40(CO)40] from −4 to −11 were spectroscopically characterized. The effect of the more regular bcc Pt-carbonyl cluster structure of [Pt40(CO)40]6– with respect to that of the defective ccp Pt33 core on the redox behavior is discussed.