Thiocyanate functionalised ionic liquids: synthesis, characterisation and reactivity

The reaction of chloromethyl thiocyanate with 1-methylimidazole affords the imidazolium salt, 1-thiocyanomethyl-3-methylimidazolium chloride, [C1SCNmim]Cl (1a). Exchange of the chloride anion in 1a by [PF6]-, [BF4]-, [Tf2N]- or [AuCl4]- affords salts 1b, 1c, 1d and 1e, respectively. Salts [C1SCNmim][BF4] (1c) and [C1SCNmim][Tf2N] (1d) melt below 100 °C and can therefore be classified as ionic liquids. The reaction of 1a with PdCl2 affords [C1SCNmim]2[PdCl4] (2a), whereas 1c reacts with PdCl2 to form the complex [PdCl2{C1SCNmim}2][BF4]2 (2c). In the presence of HNO3 both 1a and 1c react with PdCl2 with the loss of HCN to form a sulfide-bridged palladium dimer [PdCl2{C1Smim}]2 (3). The structures of 1a, 1e, 2a and 3 have been determined in the solid state by single-crystal X-ray diffraction.