Hexachloroplutonate

The hexachloroplutonate ion,, is an ion containing plutonium and chlorine. It forms several salts, which are called hexachloroplutonates.

Structure and bonding

The ion features a slightly distorted octahedral molecular geometry, with three distinct Pu-Cl bonds. The Pu-Cl bond lengths vary between 2.574 and 2.598 Å, and the Cl-Pu-Cl bond angles range between 88.54° and 91.46°.
The Pu-Cl bonds in are primarily ionic; however, they feature small but important amounts of covalent bonding. The chloride ligands bond using their s and p electrons, while plutonium bonds using its s, d, and f electrons. The Pu-Cl bond order is less than 1, and the shape of the Pu-Cl bond slightly deviates from cylindrical, possibly indicating a small amount of pi bonding. The 5f electrons in the have a large nephelauxetic effect.

It is the dominant species of plutonium in 11 M hydrochloric acid solution.

The ion forms several salts. Dicaesium hexachloroplutonate is a pale yellow solid which is precipitated from concentrated HCl solution by the addition of caesium chloride. can be used to prepare other plutonium compounds, such as the cyclopentadienide complex, and it has been proposed for use in the purification of plutonium metal. It has been used as a reference for plutonium, and due to its stability, it has been proposed for use as a primary standard for plutonium. Potassium and rubidium hexachloroplutonates, and, are also known. They are prepared by heating mixtures of plutonium chloride and the respective alkali metal chlorides under high chlorine pressures.
is also known to form salts with quaternary ammonium cations, including tetramethylammonium, tetraethylammonium, and tetrabutylammonium. The tetramethylammonium and tetraethylammonium salts, and, form orange-yellow crystals. was used in the first synthesis of plutonocene. The tetrabutylammonium salt,, is prepared by the addition of tetrabutylammonium chloride to plutonium in HCl aqueous solution. It is soluble in several organic solvents.
is also known to form salts with pyridinium, pyridinium dervatives, and tetraphenylphosphonium.