Construction of CN−-bridged molecular squares employing penta-, hexa- and octa-coordinated metal ions

Three new cyanido-bridged discrete bimetallic assemblies based on [W(CN)6(bpy)]2− building block have been synthesised and structurally characterised. Neutral molecular square {[Ni(bpy)2]2[W(CN)6(bpy)]2}·nH2O (1) (bpy = 2,2′-bipyridine) has been constructed from [NiII(bpy)2(H2O)2]2+ complex. Since the attempt to obtain analogous structure with Cu(II) ion was unsuccessful, we introduced tetradentate blocking ligand tren (tren = tris(2-aminoethyl)amine) on Cu, which resulted in dinuclear molecule {[Cu(tren)][W(CN)6(bpy)]} (2). In order to create square cluster with Cu(II) ions we employed tridentate ligand di-(2-picolyl)amine (dpa), which yielded the desired structure of {[Cu(dpa)]2[W(CN)6(bpy)]2} (3). Compounds (1) and (3), the first molecular squares based on [W(CN)6(bpy)]2− building block, are paramagnetic and follow the Curie law.

Hexa-coordinated Ni(II) and penta-coordinated Cu(II) were used in the design of the first molecular squares based on capped W(IV) cyanido complex [WIV(CN)6(bpy)]2−. The molecular systems reported reveal π–π stacking interactions as well as channel structure.Figure optionsDownload as PowerPoint slideHighlights
► Capped cyanido complex of W(IV) was used to construct discrete bimetallic assemblies.
► Structures were engineered by the use of hexa- and penta-coordinated 3d metal ions.
► Two molecular squares Ni2W2 and Cu2W2 and a dinuclear molecule CuW were obtained.