Atomically Precise Platinum Carbonyl Nanoclusters: Synthesis, Total Structure, and Electrochemical Investigation of [Pt27(CO)31]4- Displaying a Defective Structure

The molecular Pt nanocluster [Pt-27(CO)(31)](4-) (1(4-)) was obtained by thermal decomposition of [Pt-15(CO)(30)](2-) in tetrahydrofuran under a H-2 atmosphere. The reaction of 1(4-) with increasing amounts of HBF4 center dot Et2O afforded the previously reported [Pt-26(CO)(32)](2-) (3(2-)) and [Pt-26(CO)(32)](-) (3(-)). The new nanocluster 1(4-) was characterized by IR and UV-visible spectroscopy, single-crystal X-ray diffraction, direct-current superconducting quantum interference device magnetometry, cyclic voltammetry, IR spectroelectrochemistry (IR SEC), and electrochemical impedance spectroscopy. The cluster displays a cubic-close-packed Pt-27 framework generated by the overlapping of four ABCA layers, composed of 3, 7, 11, and 6 atoms, respectively, that encapsulates a fully interstitial Pt-4 tetrahedron. One Pt atom is missing within layer 3, and this defect (vacancy) generates local deformations within layers 2 and 3. These local deformations tend to repair the defect (missing atom) and increase the number of Pt-Pt bonding contacts, minimizing the total energy. The cluster 1(4-) is perfectly diamagnetic and displays a rich electrochemical behavior. Indeed, six different oxidation states have been characterized by IR SEC, unraveling the series of 1(n-) (n = 3-8) isostructural nanoclusters. Computational studies have been carried out to further support the interpretation of the experimental data.