Pressure-Induced Reduction of Dicyanamide by Samarium(II) in a Coordination Polymer

High Resolution Image Download MS PowerPoint Slide A samarium(II) coordination polymer, [Sm(2.2.2-cryptand)(dca)]I (dca − = dicyanamide), has been prepared from the reaction of SmI 2 with tetrabutylammonium dicyanamide and 2.2.2-cryptand. The structure consists of [Sm(2.2.2-cryptand)] 2+ cations bridged by dicyanamide to form corrugated 1D chains. Single crystals of this compound have been studied spectroscopically using UV–vis–NIR and Raman spectroscopy as a function of pressure to reveal a pressure-induced two-electron reduction of dicyanamide by Sm 2+ to cyanide and cyanamide and Sm 3+ between 5 and 8 GPa. High-pressure single-crystal diffraction studies reveal a phase change at 2.6 ± 0.1 GPa, where a polymorph exhibiting a smaller Sm 2+ ···N≡C bond angle and shorter Sm 2+ ···C distance was observed. These observations provide mechanistic insight into the reduction of dicyanamide into cyanide and cyanamide by pressurized samarium(II).