Metallosupramolecular complexes containing ferrocenyl groups as redox spectators; synthesis and co-ordination behaviour of the helicand 4′,4‴-bis(ferrocenyl)2,2′ : 6′,2″ : 6″,2‴ : 6‴,2â�—-quinquepyridine

Abstract

The compound 4′,4‴-bis(ferrocenyl)-2,2′ : 6′,2″ : 6″,2‴ : 6‴ : 2â�—-quinquepyridine (L) has been prepared in two steps from ferrocenecarbaldehyde and 2,6-diacetylpyridine and its co-ordination behaviour investigated. Reaction with cobalt(II) and iron(II) salts gives the seven-co-ordinate complexes [ML(H₂O)₂][PF₆]₂(M = Co or Fe). The presence of ferrocenyl groups in the ligand appears not to present a steric barrier to the formation of helicates, and the double-helical complexes [Ni₂L₂(H₂O)₂][PF₆]₄, and [Cu₂L₂][PF₆]₃ can be obtained by reaction with nickel(II) and copper(II) salts respectively. The compound L reacts with [RuCl₃L′](L′= 2,2′ : 6′,2″-terpyridine or its 4′-dimethylamino, -methylsulfonyl or -ferrocenyl derivatives) to give the heteroleptic ruthenium(II) complexes [RuL(L′)][PF₆]₂. In these complexes L is acting as a tridentate hypodentate ligand leaving a non-co-ordinated didentate 2,2′-bipyridyl moiety. The latter may act as a didentate domain for an additional ruthenium centre, and the tetranuclear complexes [L′RuLRuCl(L′)][PF₆]₃ with two ruthenium(II) centres in two different, N₆ and N₅Cl, donor environments have been prepared.