The reaction between Re-2(C6H5NCOCH3)(4)Cl-2 and water in air yields a blue compound [Re-4(C6H5NCOCH3)(6)(Cl)(mu-O)(mu-OH)(MeOH)(3)][ReO4](2). It crystallizes in a triclinic cell with a = 12.356(3) Angstrom, b = 14.820(6) Angstrom, c = 20.064(6) Angstrom, alpha = 103.38(3)degrees, beta = 91.61(2)degrees, gamma = 110.37(2)degrees, V = 3327(2) Angstrom(3), and Z = 2. The X-ray crystallography revealed an unprecedented tetranuclear structure together with two perrhenate ions. The tetranuclear dication is formed by two quadruply bonded dirhenium units linked through an oxygen ligand and a hydroxy ligand. One unit uses two rhenium atoms and the other unit uses only one rhenium atom to form a Re-Re-O-Re-OH five-membered ring. The formula of this compound was further confirmed by mass spectral analysis.