Mono-, di-, and tri-ruthenium complexes with the ligand 2,2′-dipyridylamide (dpa): insights into the formation of extended metal atom chains

Reactions between Hdpa (2,2′-dipyridylamine) and either RuCl3 · xH2O and Ru2(OAc)4Cl produce mono-, di-, and tri-ruthenium complexes under various conditions. The ligand Hdpa and RuCl3 · xH2O react in boiling DMF to form the ionic species [Ru(Hdpa)2Cl2]Cl (1). Reaction of Ru2(OAc)4Cl with molten Hdpa leads to scission of the Ru–Ru bond and formation of the vertex-sharing bioctahedral complex Ru2(dpa)3(OAc)0.64Cl1.36 (2). A mixture of both of these species results from the reaction of Ru2(OAc)4Cl with Hdpa and LiCl in refluxing o-dichlorobenzene/EtOH mixtures. This mixture of compounds reacts further with KOBut and n-butanol in refluxing naphthalene to give low yields of the extended metal atom chain (EMAC) complex Ru3(dpa)4Cl2 (I).