The first publication of the structure of wheel shaped cluster anion, first determined for the nitrosyl derivative by Achim Müller et al.  was announced in New Scientist as "Big Wheel rolls back the molecular frontier". Further work by the same group then refined the initial findings and determined the structure of the wheel produced in molybdate solutions as [MoOH(HO)]. The  Mo-type cluster was then shown to be the basic structural type of molybdenum blue compounds obtained under slightly different conditions.
The structure of the big wheel is constructed from  units containing 11 Mo atoms ({Mo}-type units), 14 of which are linked together to form the {Mo}-type cluster that has an external diameter of 3.4 nm. (12 {Mo}-type units are also involved in the construction of higher symmetrical spherical systems called Keplerates) These units consist of a central MoO bipyramid sharing edges with 5 MoO octahedra (an illustration of this is on page 155 of the review ). With 5 more linking MoO octahedra the repeating {Mo}-type unit is built up.