New trinuclear rhodium(III) complexes, [Rh3(//3-0)(/i-CH3C00)6(L)3]+ (L = imidazole (Him), 1-methylimidazole (Meim), and 4-methylpyridine (Mepy)) have been prepared. The Him, Meim, and Mepy complexes show reversible one-electron oxidation waves at E1/2 = +1.12, +1.12, and +1.28 V vs Ag/AgCl, respectively, in acetonitrile. Electronic absorption spectra of the one electron oxidized species of these complexes and [Rh3(M3-0)(M-CH3C 0 0 )6(py)3]+ (py = pyridine) (E 1 /2 = +1.32 V ) were obtained by spectroelectrochemical techniques. While the Rh3(III,III,III) states show no strong visible absorption, the Rh3(III,III,IV ) species give a band at ca. 700 nm (e = 3390-5540 mol dm" 3 cm" 1). [Ir3(«3-0)(//-CH3C00)6(py)3]+ with no strong absorption in the visible region, shows two reversible one-electron oxidation waves at +0.68 and +1.86 V in acetonitrile. The electronic absorption spectrum of the one-electron oxidized species (Ir3(III,III,IV )) also shows some absorption bands (688 nm ( e, 5119), 1093 (2325) and 1400 (ca. 1800)). It is suggested that the oxidation removes an electron from the fully occupied anti-bonding orbital based on metal-d7r-/^3-0-pjr interactions, the absorption bands of the (III,III,IV ) species being assigned to transitions to the a«r/-bonding orbital.esting because of their characteristic strong visible absorption and reversible multi-step redox behav iour [2][3][4][5][6][7][8][9][10][11][12][13][14]. It has been suggested that such char acteristic properties are associated with strong intermetallic interactions through the central oxide bridge. The Ru(d^r)-^3 -0 (p jr) interaction is sig nificantly stronger than that of analogous tri nuclear complexes o f first row transition elements. The djr-pjr molecular orbitals shown in Fig. 1 have been proposed for the trinuclear ruthenium complexes [3,15,16], In the study of mixed ruthenium-rhodium complexes, it was suggested that a similar molecular orbital scheme should be appli cable to trirhodium and mixed ruthenium-rhodium complexes [7]. Electronic states o f the oxocentered triiridium (III) complexes [17,18] should also be considered in terms of the djr-pjr molec ular orbital scheme. Thus the oxo-centered tri metal complexes of heavy transition elements could be significantly different from those of first row transition elements with respect to the extent of metal-oxygen-metal interactions. The trinuclear