The preparation and properties of a new cyano complex containing the Ru-3(mu(3)-O) core, [Ru-3(mu(3)-O)(mu-CH3COO)(6)(py)(2)(CN)] (1; py = pyridine), are reported. Complex 1 in CH2Cl2 showed intense absorption bands at 244, 334, and 662 nm, corresponding to a pi-pi* transition of the ligand, cluster-to-ligand charge transfer, and intracluster transitions, respectively. The cyclic voltammogram of 1 in 0.1 M (n-Bu)(4)NPF6-CH2Cl2 showed redox waves for the processes Ru-3(II,II,III)/Ru-3(II,III,III), Ru-3(II,II,III)/Ru-3(III,III,III), and Ru-3(III,III,III)/Ru-3(III,III,IV) at E-1/2 = -1.49, -0.26, and +1.03 V vs Ag/AgCl, respectively. The first two redox potentials are more negative by ca. 0.2 V in comparison with the corresponding potentials of [Ru-3(mu(3)-O)(mu-CH3COO)(6)(py)(3)](+). This is in sharp contrast to the positive shifts of the corresponding waves of [Ru-3(II,III,III)(mu-CH3COO)(6)(py)(2)(CO)]. Density,/ functional theory (DFT) calculations of [Ru-3(II,III,III)(mu(3)-O)(mu-CH3COO)(6)(py)(3)], [Ru-3(II,III,III) (mu(3)-O)(mu-CH3COO)(6)(py)(2)(CN)](-), and [Ru-3(II,III,III),(mu(3)-O)(mu-CH3COO)(6)(py)(2)(CO)] showed that the positive charge of the ruthenium is delocalized over the triruthenium cores of the first two and is localized as Ru-II(CO){Ru-III(py)}(2) in the CO the difference in the it interactions of the two ligands with the triruthenium cores. complex. The calculations explain