Complexes containing a Ru₂ⁿ⁺ core (n = 4, 5 or 6) have been of great interest because of their variety of electronic configurations and magnetic properties. Herein, we report a novel homovalent Ru₂⁶⁺-based complex, (H₂pip)₂[Ru₂(hedp)₂Cl₂]·6H₂O (pip = piperazine) (1), isolated by the direct reaction of the mixed-valent Ru₂⁵⁺-based anion Ru₂(hedp)₂³⁻ [hedp = 1-hydroxyethylidenediphosphonate, CH₃C(OH)(PO₃)₂] with oxidant peracetic acid under room temperature conditions. Magnetic measurements unambiguously confirm that this complex contains four unpaired electrons with a spin ground state of S = 2.