Low-dimensional compounds containing cyanido groups. XXII. Crystal structure, spectroscopic, thermal and magnetic properties of four Cu(II) tetracyanidoplatinates with atypical chain-like structures

Abstract

From the systems Cu(II)–L–[Pt(CN)4]2− (L=aliphatic tridentate N-donor ligands: aepn (3-(2-aminoethylamine)-propylamine), bapa (bis(3-aminopropyl)amine) and dien (bis(2-aminoethyl)amine)) four tetracyanidoplatinate complexes, [Cu(aepn)(NH3)Pt(CN)4]n·nH2O (1), [Cu(aepn)Pt(CN)4]n (2) and [Cu(bapa)Pt(CN)4]n (3) and [Cu(dien)Pt(CN)4]n (4), were isolated. The prepared compounds are formed by zigzag chains, which consist of [Cu(aepn)(NH3)]2+ (for 1) or [Cu(L)]2+ (for 2–4) moieties bridged by [Pt(CN)4]2− units. The different arrangement of two bridging cyanido groups on the copper (trans-coordination in 1 and cis-coordination in 2–4) and platinum atoms (trans-coordination in 4 and cis-coordination in 1–3) results in three different and atypical types of chains. The Cu(II) atoms in 2–4 are pentacoordinated by one L molecule and two bridging cyanido ligands in a form of a deformed square pyramid, while the Cu(II) atom in 1 is hexacoordinated in the form of strongly elongated octahedron. Higher number of ν(CN) absorption bands observed in IR spectra of 1–4 agrees with a higher number of crystallographically different cyanido groups of both, bridging and terminal, types. Thermal decompositions of the prepared complexes are few-step processes which comprise liberation of water and ammonia molecules (only for 1), decay of triamine molecules L and finally a pyrolysis of cyanido groups. The magnetic properties of 1–4 have been investigated in the temperature range 2–300K and prepared complexes exhibit the antiferromagnetic exchange. The different magnetic behavior is ascribed to the different coordination (cis vs. trans) of bridging cyanido groups on the Pt(II) atoms.