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 nanocluster was obtained from the thermal decomposition of Na2[Pt15(CO)30] in methanol. The reaction of Pt19(CO)22 with acids (1-2 equiv) affords the unstable Pt19(CO)22 trianion, which evolves with time leading eventually to the Pt40(CO)40 hexa-anion. The total structures of both nanoclusters were determined via single-crystal X-ray diffraction. Pt33(CO)38 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 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 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 = 0 to -4, -6 to -9) are reported. Almost all the redox processes exhibited by Pt40(CO)40 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 with respect to that of the defective ccp Pt33 core on the redox behavior is discussed.