The substitution of one or two carbonyls by many different primary and secondary alkylamines and -diamines has been established for the first time in a homoleptic carbonyl cluster anion, the trigonal bipyramidal [Rh-5(CO)(15)](-). Two derivatives, the bis-monosubstituted {[Rh-5(CO)(14)]-(H2N(CH2)(4)NH2)-[Rh-5(CO)(14)]}(2-) dianion (1) and the disubstituted chelated [Rh-5(CO)(13)(H2N(CH2)(2)NH2)](-) monoanion (2), have been structurally characterized, both in the solid state (as [PPh4](+) salts) and in solution, revealing that the sites of the substitution are the cluster apexes, C-13 NMR spectra of 2 revealed localized fluxionality of the CO ligands over the temperature range 298-183 K.