Molecular helicity in inorganic complexes; bi- and tri-nuclear complexes of 2,2′:6′,2″:6″,2″′:6″′,2″″:6″″,2″″′-sexipyridine and the crystal and molecular structure of bis(µ-2,2′:6′,2″:6″,2″′:6″′,2″″:6″″,2″″′-sexipyridine-κ3N,N′,N″:κ3N″′,N″″,N″″′) dicadmium hexafluorophosphate–acetonitrile (1/4)

Abstract

The potentially sexidentate ligand 2,2′:6′,2″:6″,2‴:6‴,2â�—:6â�—,2â�—′-sexipyridine (L) has been prepared and shown to demonstrate considerable structural versatility in forming double helical binuclear complex cations of the type [M₂L₂]⁴⁺(M = Mn^II, Fe^II, Cu^II or Cd^II) or [M₃L₂]³⁺(M = Cu^I and Ag^I). A binuclear palladium(II) complex with a metal : ligand stoichiometry of 2 : 1 has also been characterised. The electrochemical properties of these complexes are reported, together with redoxinitiated interconversions of [Cu₃L₂]ⁿ⁺ and [Cu₂L₂]ⁿ⁺ species. The crystal and molecular structure of the double helical complex [Cd₂L₂][PF₆]₄·4MeCN [space group C2/c, a= 20.466(8), b= 18.872(6), c= 20.617(5)Å, β= 111.98(2)°, R= 0.0599, R′= 0.0634] is reported; the two metal centres are separated by 4.173(4)Å and coplanar pyridyl rings of the two independent ligands within the cation show short π-stacking interactions.