A new compound in the BEDT-TTF family [BEDT-TTF = bis-(ethyl-enedi-thio)-tetra-thia-fulvalene] with a tetra-thio-cyanato-cuprate(II) anion, (BEDT-TTF)4[Cu(NCS)4].

A new phase combining BEDT-TTF and [Cu(NCS)4]2- as the counter-anion, namely bis-[bis(ethyl-enedi-thio)-tetra-thia-fulvalenium] tetra-thio-cyanato-cuprate(II) bis-[bis(ethyl-ene-di-thio)-tetra-thia-fulvalene], (C10H8S8)2[Cu(NCS)4]·2C10H8S8 or (BEDT-TTF)4[Cu(NCS)4] was obtained during a galvanostatic electrocrystallization process. As previously observed with BEDT-TTF-based compounds with oxalatometallate anions, the BEDT-TTF mol-ecules in (BEDT-TTF)4[Cu(NCS)4] exhibit the so-called pseudo-κ arrangement, with two BEDT-TTF mol-ecules being positively charged and two electronically neutral. The bond lengths and angles in the two unique BEDT-TTF mol-ecules differ slightly. The crystal structure consists of layers of BEDT-TTF mol-ecules extending parallel to (001). The width of this layer corresponds to the length of the a axis [16.9036 (17) Å]. The BEDT-TTF layers are separated by layers of centrosymmetric square-planar [Cu(NCS)4]2- dianions.