An end-on-coordinated As4 tetrahedron.

One time only: The reaction of [Cp*Ru(dppe)Cl] with the potent As4 transfer reagent [Ag(η(2)-As4)2](+)[pftb](-) leads to [Cp*Ru(dppe)(η(1)-As4)](+)[pftb](-) with an unprecedented end-on-coordinated As4 tetrahedron. Reaction with a second cationic ruthenium complex fragment does not lead to a second end-on coordination but to the cleavage of one basal As-As bond. This behavior, which differs from its phosphorus analogues, is rationalized by DFT calculations.