Nitrile‐Rich Borate Anions – Application in Ionic Liquids

Heavy Neutral and Anionic Pnictogen Thiocyanates

When [PPN]SCN (1; PPN = [Ph₃P-N-PPh₃]) is treated with Me₃Si-SCN in methanol, [PPN][H(NCS)₂] (2), a hydrogen diisothiocyanate salt bearing the [H(NCS)₂]^- anion, was generated, isolated, and fully characterized. Pure heavy E(NCS)₃ [E = Sb (3), Bi (4)] species were obtained from the reaction of EF₃ and an excess of Me₃Si-SCN, while the tetrahydrofuran (THF) solvates E(NCS)₃·THF were isolated when the product was recrystallized from THF. When 2 equiv of 1 was combined with Me₃Si-SCN and SbF₃, [PPN]₂[Sb(NCS)₅] (5) could be isolated. When 1 was added to BiF₃, [PPN]₂[Bi(NCS)₃(SCN)₂·THF] (6·THF), containing three SCN^- ions coordinating via the N atom and two coordinating via the S atom, was isolated after recrystallization from THF. The structures of 1, 2, 3·THF, 4·THF, 5, and 6·THF were determined. 3·THF displayed a typical [3 + 3] coordination mode with a trigonal-pyramidal environment in the first coordination sphere of the Sb³⁺ ion, and the dianion of 5, [Sb(NCS)₅]^2-, featured a classical square-pyramidal molecular geometry around the Sb³⁺ ion with one additional Menshutkin-type interaction to one aryl ring of the [PPN]⁺ cation. 4·THF exhibited a distorted pentagonal-bipyramidal structure within a two-dimensional network, while in 6·THF, an octahedrally surrounded Bi³⁺ ion was observed.