Potassium octachlorodimolybdate

Potassium octachlorodimolybdate(4−)

Identifiers
CAS Number	25448-39-9 N
Properties
Chemical formula	K4Cl8Mo2
Molar mass	631.9 g/mol
Appearance	red crystals
Density	2.54 g/cm3
Solubility in water	soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Potassium octachlorodimolybdate (systematically named potassium bis(tetrachloridomolybdate)(Mo–Mo)(4−)) is an inorganic compound with the chemical formula K
4Mo
2Cl
8 (also written as K
4[Cl
4MoMoCl
4]). It is known as a red-coloured, microcrystalline solid. The anion is of historic interest as one of the earliest illustrations of a quadruple bonding. The salt is usually obtained as the pink-coloured dihydrate.

The compound is prepared in two steps from molybdenum hexacarbonyl:

The reaction of the acetate with HCl was first described as providing trimolybdenum compounds, but subsequent crystallographic analysis confirmed that the product contains the Mo₂Cl4–
8 ion with D_4h symmetry. The Mo–Mo distance is 2.14 Å.