Bonding and Oxidation State of a Transition Metal Atom Encapsulated in an Isolated Octahedral Cluster Cation of Main Group Elements: Synthesis, Crystal Structure, and Electronic Structure of Pt₂In₁₄Ga₃O₈F₁₅ Containing Highly Positive 18-Electr

Colorless transparent single crystals and white polycrystalline powder samples of Pt2In14Ga3O8F15 were obtained by heating a mixture of stoichiometric amounts of Pt, In, InF3, and Ga2O3, in a Pt crucible under Ar at 600 °C. The new oxyfluoride crystallizes in a new structure type in the trigonal space group R3̄m (No. 166) with a = 709.0(6) pm, c = 4556.4(3) pm, and Z = 6 with characteristic building units of PtIn6 octahedra (Pt−In = 255−257 pm), GaF6 octahedra (Ga−F = 189 pm), and GaO4 tetrahedra (Ga−O = 186−187 pm). This oxyfluoride consists of a highly positive 18-electron complex [PtIn6]10+ as well as low-valent In+ ions. Electronic band structure calculations for Pt2In14Ga3O8F15 and molecular orbital (MO) calculations for [PtIn6]10+ were carried out to analyze the electronic structure of [PtIn6]10+ and estimate the oxidation state of Pt. Our analysis indicates that the oxidation state of the Pt atom in [PtIn6]10+ is negative rather than positive. For other octahedral cluster cations of main group elements stuffed with a transition metal atom (e.g., [RuSn6]14+ and “[IrBi6]11+”) as well, we showed that the oxidation state of the transition metal atom is most probably negative by studying their electronic structures.