Abstract Crystals of the title compound,(C16H36N) 4 [(p-NC-C6H4As) 4MoI2 046] or (C16H36N) 4 [{As (C7 H4N)} 4MoI2-046], were synthesized by the reaction of p-cyano- phenylarsonic acid and sodium molybdate at low pH. With nitrile groups pointed in tetrahedral directions, these new organically modified polyoxometalate clusters are potential building blocks in coordination networks.