Pseudohalide supported mononuclear trans-Ni II complexes of cationic and neutral dinitrogen heterocycles

Abstract

Two mixed ligand complexes trans-[Ni(NCS) 4(PpzH) 2] ( 1) and trans-[Ni(NCO) 2(Imd) 4] ( 2) (where Ppz = piperazine; Imd = imidazole) were synthesized from one-pot reactions, and their crystal and molecular structures were determined. The reaction of NiCl 2·4H 2O with piperazine and KSCN in a 1:2:4 mole ratio in aqueous MeOH at room temperature under stirring condition affords 1. Whereas the reaction of NiCl 2·6H 2O with imidazole and NaOCN in a 1:4:2 mole ratio in aqueous MeOH at room temperature under stirring condition yields 2 quantitatively. The nickel ions are hexacoordinated by six nitrogen donor atoms of two different origin, thiocyanate and piperazinium ions in case of 1 and cyanate ion and neutral imidazole in case of 2, to form tetragonally elongated and quite regular octahedral arrangements. In 1, the average Ni–N ppz distance is 2.198 Å is longer than the average Ni–N thc distance at 2.070 Å, whereas, in case of 2, the average Ni–N imd distance at 2.112 Å and is close to the average Ni–N cyt distance at 2.107 Å. The reactions in other varying stoichiometries failed to provide the hitherto unknown complexes [Ni(NCS) 2(Ppz) 4] and [Ni(NCO) 4(ImdH) 2] confirming the ease of protonation on non-bonding of piperazine is more compared to that of imidazole.