INTERCONVERSIONS BETWEEN RU3-BOUND AZOALKANE AND DIALKYHYDRAZIN-DERIVED BUILDING UNITS

Reactions involving hydrogen transfer have been investigated starting from the azoalkane-bridged clusters Ru3(CO)9-(RCH2N=NCH2R) (1 a, R = H; 1 b, R = Me). In boiling toluene they are isomerized to the hydrazonide-bridged clusters HRu3(CO)9(RCH2N-N=CHR) (2a, R = H; 2b, R = Me). Pd/C-catalyzed hydrogenation converts both compound types into the hydrazide-bridged clusters HRU3(CO)9(RCH2N-NHCH2R) (3a, R = H; 3b, R = Me). Hydride attachment to 1 and 2 and deprotonation of 3 yield a common anionic intermediate 4 which is converted into 3 upon protonation. While deuteration experiments and NMR spectra indicate that the anionic intermediate equilibrates between the N-H and Ru-H isomers, aurations of deprotonated clusters with Ph3PAuCl yield the Ru-Au-connected clusters Ph3PAuRu3(CO)9(EtN-N=CHMe) (5) and Ph3PAuRU3(CO)9(MeN-NHMe) (6). The reversible cluster expansion of 2b with Fe(CO)3 fragments which results in the formation of FeRu3(CO)12(mu4-eta2-N2Et2) (7) involves a reversible reconversion of the hydrazonide ligand to the azoalkane ligand.