Synthesis, crystal structures and properties of quasi-one-dimensional platinum compounds

Quasi-one-dimensional complexes of the type [Pt(NH2R)4][Pt(mnt)2], where mnt designates maleodinitriledithiolate and R an ethyl (Et) or octyl (Oc) group, were synthesized and characterized. Single-crystal X-ray diffraction revealed that both compounds crystallized in the triclinic space group P1̄. The platinum atoms were arranged in linear arrays in both compounds; while the PtPt distances were equal in [Pt(NH2Et)4][Pt(mnt)2] (3.96 Å), surprisingly, two different intermetallic spacings (3.86 and 4.01 Å) were observed in [Pt(NH2Oc)4][Pt(mnt)2]. The PtPt distances in the [Pt(NH2R)4][Pt(mnt)2] compounds are large compared to those in the typical Magnus-salt-type complexes (3.15–3.62 Å). An uncommon, reversible solid-state phase transition was detected for [Pt(NH2Oc)4][Pt(mnt)2] at 70 °C, which might be related to a change in the packing of the octyl chains. The platinum stacks decayed when in solution, yielding predominantly ion pairs. The UV–Vis absorption spectra of such solutions were dominated by characteristics associated with [Pt(mnt)2]2− units, and UV emission maxima were found at 345 and 363 nm upon excitation with light of wavelengths between 250 and 340 nm.