Nickel thioether chemistry: syntheses and crystal structures of [Ni2L2(µ-Cl)2][BF4]2(l = 1,4,7,10-tetrathiacyclododecane, 1,4,8,11-tetrathiacyclotetradecane or 1,5,9,13-tetrathiacyclohexadecane)

Abstract

Reaction of NiCl₂ with 1 molar equivalent of the macrocycles (L) 1,4,7,10-tetrathiacyclododecane ([12]aneS₄), 1,4,8,11-tetrathiacyclotetradecane ([14]aneS₄) or 1,5,9,13-tetrathiacyclohexadecane ([16]aneS₄) and NaBF₄ in MeNO₂ for 30 min afforded green or blue solutions, from which the complexes [Ni₂L₂Cl₂][BF₄]₂ can be isolated. The complex [Ni₂([12]aneS₄)₂Cl₂][BF₄]₂·2MeNO₂ crystallises in the monoclinic space group C2/m with a= 11.0651(20), b= 13.4977(24), c= 12.7222(21)Å, β= 104.824(21)° and Z= 2. The complex [Ni₂([14]aneS₄)₂Cl₂][BF₄]₂·6MeNO₂ crystallises in the triclinic space group P with a= 10.6341(18), b= 11.6481(22), C= 12.2457(25)Å, α= 88.547(7), β= 67.288(12), γ= 68.647(6)° and Z= 1. The complex [Ni₂([16]aneS₄)₂Cl₂][BF₄]₂·2MeNO₂ crystallises in the monoclinic space group Ccwith a = 16.024(4), b= 1 3.6862(17), c= 1 9.7329(24)Å, β= 92.042(19)° and Z= 4. Single-crystal structure determinations on each of these products showed the presence of dichloro-bridged dimeric cations exhibiting edge-sharing bioctahedral structures, with the macrocyclic ligands co-ordinated in a cis fashion about the Ni. The Ni–S bond lengths and internal crystallographic symmetry vary significantly between the structures, the shortest distances being observed for [Ni₂([14]aneS₄)₂Cl₂]²⁺[Ni–S 2.3694(22), 2.3765(21), 2.3756(21), 2.3798(21)Å, Ni–Cl 2.4416(20), 2.4252(20)Å]; for [Ni₂([12]aneS₄)₂Cl₂]²⁺, Ni–S 2.412(3), 2.4144(25), 2.373(3), Ni–Cl 2.411(3), 2.382(3)Å and for [Ni₂([16]aneS₄)₂Cl₂]²⁺, Ni–S 2.4098(22)–2.4421 (22), Ni–Cl 2.3860(21 )–2.4205(20)Å. These variations are related to the differing hole sizes of the three tetrathia macrocyles. The Ni ⋯ Ni distances are similar in all three structures, 3.5534(12)–3.5692(12)Å. The complexes [Ni₂L₂Cl₂][BF₄]₂ exhibit only irreversible electrochemical oxidation and reduction processes according to cyclic voltammetry in MeCN–0.1 mol dm^–3 NBuⁿ₄PF₆ at 293 K. Reaction of NiCl₂ with 1,4,7-trithiacyclononane ([9]aneS₃) and NaBF₄ affords the triply bridged dimeric complex [Ni₂([9]aneS₃)₂Cl₃]BF₄.