Synthesis and Structural Characterization of the {[Rh5(CO)14]−(H2N(CH2)4NH2)−[Rh5(CO)14])}2- and [Rh5(CO)13(H2N(CH2)2NH2)]- Anions (as [PPh4]+ Salts): 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 [Rh 5 (CO) 1 5 ]. Two derivatives, the bis-monosubstituted {‖[Rh 5 (CO) 1 4 ]-(H 2 N(CH 2 ) 4 NH 2 )-[Rh 5 (CO) 1 4 ]} 2 dianion (1) and the disubstituted chelated [Rh 5 (CO) 1 3 (H 2 N(CH 2 ) 2 NH 2 )] monoanion (2), have been structurally characterized, both in the solid state (as [PPh 4 ] + salts) and in solution, revealing that the sites of the substitution are the cluster apexes. 1 3 C NMR spectra of 2 revealed localized fluxionality of the CO ligands over the temperature range 298-183 K.