  Diethyl sulfoxide (DESO) is far less known than its shorter-alkyl-chain
homolog, dimethyl sulfoxide. Although the field of senior dialkyl sulfoxides
does not currently exhibit an explosive growth, new fundamental and applied
research works routinely appear from a few research groups in the world.
Recently, the tetraethylammonium diethylsulfoxidopentachloroplatinate complex
compound was synthesized containing the DESO molecule as a neutral ligand. In
the present paper, we use a systematic computational method to rationalize the
mentioned synthetic achievement in coordination chemistry. We show that only up
to two DESO molecules may exist in the platinum (IV) complex ion, whereas all
higher contents of DESO are thermodynamically unstable and the sterical factor
plays an important role in their instabilities. Structural analysis of the
tetraethylammonium diethylsulfoxidopentachloroplatinate ion pair reveals its
rather strong cation-anion coordination and for the first time explains an
experimentally derived high melting point. The reported results are expected to
inspire experimental efforts to extend the universe of senior sulfoxides as
neutral organic ligands in d-metal complexes.
