Mixed Co-Rh Nitrido-Encapsulated Carbonyl Clusters : Synthesis, Solid-State Structure, and Electrochemical/EPR Characterization of the Anions [Co10Rh(N)2(CO)21]3-, [Co10Rh2(N)2(CO)24]2-, and [Co11Rh(N)2(CO)24]2-

The nitrido-encapsulated heterometallic cluster anions [Co 10Rh(N)2(CO)21]3- (1), [Co 10Rh2(N)2(CO)24]2- (2), and [Co11Rh(N)2(CO)24]2- (3) have been obtained by tailored redox-condensation reactions. These three anions are rare high-nuclearity mixed-metal clusters containing two interstitial nitrogen atoms. Their structures have been determined by single-crystal X-ray diffraction on their [NR4]+ salts (R = Me for 1 and 3, R = Et for 2), and their electrochemical and ESR properties have been studied in detail. It is noteworthy that 1 has an unprecedented stereochemistry that does not exhibit a close geometrical resemblance with the isoelectronic homometallic anion [Co 11N2(CO)11(μ2-CO) 10]3-, and 2, despite its even number of electrons, is a paramagnetic species.