Atomically Precise Platinum Carbonyl Nanoclusters: Synthesis, Total Structure, and Electrochemical Investigation of [Pt 27 (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 HBF 4 · Et 2 O 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.