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 . xH(2)O and Ru-2(OAc)(4)Cl produce mono-, di-, and tri-ruthenium complexes under various conditions. The ligand Hdpa and RuCl3 . xH(2)O react in boiling DMF to form the ionic species [Ru(Hdpa)(2)Cl-2]Cl (1). Reaction of Ru-2(OAc)(4)Cl With molten Hdpa leads to scission of the Ru-Ru bond and formation of the vertex-sharing bioctahedral complex Ru-2(dpa)(3)(OAc)(0.64)Cl-1.36 (2). A mixture of both of these species results from the reaction of Ru-2(OAc)(4)Cl with Hdpa and LiCl in refluxing o-dichlorobenzene/EtOH mixtures. This mixture of compounds reacts further with KoBu' and n-butanol in refluxing naphthalene to give low yields of the extended metal atom chain (EMAC) complex Ru-3(dpa)(4)Cl-2 (I). (C) 2004 Elsevier B.V. All rights reserved.