Synthesis and structural characterization of a homoleptic rhodium carbonyl cluster dianion and monoanion (see abstract): An unprecedented example of carbonyl substitution by alkylamines in a homoleptic metal carbonyl cluster anion

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 [Rh5(CO)15]-. Two derivatives, the bis-monosubstituted ([Rh5(CO)14]-(H2N (CH2)4NH2)- [Rh5(CO)14])2- dianion (1) and the disubstituted chelated [Rh5(CO)13 (H2N(CH2)2NH2)]- 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. 13C NMR spectra of 2 revealed localized fluxionality of the CO ligands over the temperature range 298-183 K.