Supramolecular architectures of dimethyltin(IV) isothiocyanate compounds containing diimine ligands: Structural phase transition and thermal properties

Abstract

Three diorganotin (IV) compounds with the general formula [SnMe2(NCS)2(NN)] have been synthesized and characterized using elemental analysis, IR, 1H, 13C, 119Sn , HH COSY, HSQC, and DEPT-135° NMR spectroscopy, and X-ray crystal structure determination. The complexes [SnMe2(NCS)2(Me2bpy)] (1), [SnMe2(NCS)2(phendione)] (2), and [SnMe2(NCS)2(4,4′-bpy)] (3) were synthesized by the reaction of SnMe2(NCS)2 with corresponding diimine ligands of 5,5ꞌ-dimethyl-2,2ꞌ-bipyridine (Me2bpy), 1,10-phenanthroline-5,6‑dione (phendione), and 4,4′-bipyridine (4,4′-bpy), respectively. NMR data reveals that 1–3 persists as the hexa-coordinated dimethyltin(IV) complexes in solution. The X-ray single crystal investigation of [SnMe2(NCS)2(Me2bpy)] (1) exhibits structural phase transition during the cooling from RT (295 K) to LT (100 K). This transition is associated with a doubling of the asymmetric unit in the low-temperature phase (1-LT) relative to the room-temperature phase (1-RT), which results in the change of the space group (P21/m in RT and P21/c in LT). The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping and visualization of the small differences in the intermolecular interactions between both crystallographic phases. Our results show that the reaction of SnMe2(NCS)2 with 4,4′-bipyridine is not dependent upon the mole ratio and reaction time and the resulting tin(IV) cations adopt the octahedral geometry which is linked by 4,4′-bipyridine into the coordination polymer while the pairs of μ-1,3-bridging thiocyanate anions further interconnected the tin atoms to form a 2D supramolecular chains. Thermal properties of the complexes reveal that they are thermally stable up to 173 °C for 1, 183 °C for 2, and 178 °C for 3.