Nickel thioether chemistry: syntheses of nickel(II) complexes of tetra- and penta-thia macrocyclic ligands. The single-crystal structures of [Ni([16]aneS4)(OH2)2][BF4]2 and [Ni([15]aneS5)][PF6]2([16]aneS4=1,5,9,13-tetrathiacyclohexadecane, [15]aneS5=1,4,7,10,13-pentathiacyclopentadecane)

Abstract

Treatment of [Ni(OH₂)₆][BF₄]₂ with 1 molar equivalent of [12]aneS₄([12]aneS₄= 1,4,7,10-tetrathiacyclododecane) or [16]aneS₄([16]aneS₄= 1,5,9,13-tetrathiacyclohexadecane) in MeNO₂ in the presence of acetic anhydride for 30 min affords blue solutions from which the complexes [Ni([12]aneS₄)(OH₂)₂]²⁺ and [Ni([16]aneS₄)(OH₂)₂]²⁺ can be isolated. The complex [Ni([16]aneS₄)(OH₂)₂][BF₄]₂ crystallises in the triclinic space group P, with the octahedral nickel atom lying on a crystallographic centre of symmetry, the aqua ligands mutually trans, Ni–S 2.4290(10), 2.4231(10), Ni–O 2.083(3)Å, and the macrocycle co-ordinated in the equatorial plane. Treatment of [Ni(OH₂)₆][BF₄]₂ or [Ni(OH₂)₆][PF₆]₂ with [15]aneS₅ in MeNO₂ in the presence of acetic anhydride affords purple solutions of the complex [Ni([15]aneS₅)]²⁺. A single-crystal structure determination on [Ni([15]aneS₅)][PF₆]₂, which crystallises in the monoclinic space group P2₁, shows the cation to adopt a square-pyramidal geometry, Ni–S_apical 2.413(5), Ni–S_basal 2.146(7), 2.169(6), 2.177(6), 2.198(6)Å. The complex cation [Ni([15]aneS₅)]²⁺ forms six-co-ordinate adducts with MeCN, pyridine and chloride.