Synthesis, Structure, and Spectroscopic Characterization of [H8−nRh22(CO)35]n−(n= 4, 5) and [H2Rh13(CO)24{Cu(MeCN)}2]−Clusters: Assessment of CV and DPV As Techniques to Circumstantiate the Presence of Elusive Hydride Atoms

The previously ill-characterized [HxRh22(CO)35]4−/5− carbonyl cluster has been obtained as a byproduct of the synthesis of [H3Rh13(CO)24]2− and effectively separated by metathesis of their sodium salts with [NEt4]Cl. Although the yields are modest and never exceed 10−15% (based on Rh), this procedure affords spectroscopically pure [H3Rh22(CO)35]5− anion. Formation of the latter in mixture with other Rh clusters was also observed by electrospray ionization-mass spectrometry (ESI-MS) in the oxidation of [H2Rh13(CO)24]3− with Cu2+ salts. The recovery of further amounts of [H3Rh22(CO)35]5− was hampered by too similar solubility of the salts composing the mixture. Conversely, the reaction in CH3CN of [H2Rh13(CO)24]3− with [Cu(MeCN)4]+[BF4]− leads to the [H2Rh13(CO)24{Cu(MeCN)}2]− bimetallic cluster. The X-ray crystal structures of [H4Rh22(CO)35]4−, [H3Rh22(CO)35]5−, and [H2Rh13(CO)24{Cu(MeCN)}2]− are reported. From a formal point of view, the metal frame of the former two species can be derived by interpenetra...