Nickel(II)-SNS Thiolate Complexes: Reactivity and Solution Dynamics.

Nickel coordination chemistry with a biomimetic thiolate-imine-thioether SNS ligand is accompanied by diverse reactivity and multidentate ligand dynamics. Reaction of Ni(acac) with 2 equiv of 2-(methylthio)-phenyl-benzothiazolidine (MPB) affords the bis(arylimino-phenylene-thiolate) complex Ni(κ-SNS) (; acac = acetylacetonate). Thermolysis of in refluxing toluene is accompanied by imine C-C bond formation, yielding [Ni(NS)] () with a redox-active ligand. Protonation of with NHTf at a low temperature released 1 equiv of MPB, yielding crystals of the dimeric dication {[Ni(μ-κ-SNS)]}(NTf) (; Tf = SOCF) in high yield. In contrast, the same reaction at room temperature gave also paramagnetic complexes {Ni[μ-Ni(κ-SNS)]}(NTf) () and {Ni[μ-Ni(κ-SNS)]}(NTf) () that feature coordination of two or three pseudo-octahedral, paramagnetic Ni(κ-SNS) units to a central Ni(II) dication via thiolate bridges. Remarkably, dissolution of in a variety of solvents, including weakly coordinating CHCl, rapidly generates a mixture of and Ni(NTf). Treatment of this mixture with Lewis bases L gave high yields of dimers {[Ni(μ-κ-SNS)L]}(NTf) for L = CNXylyl () and {Ni(μ-κ-SNS)}(NTf) (; dmpm = bis(dimethylphosphino)methane) or monomers Ni(κ-SNS)L for L = PMe () and P(OMe) (). Addition of 2 equiv of the strong donor -heterocyclic carbene ligand, IPr, to , however, led to thioether demethylation, affording neutral dithiolate complex Ni(κ-SNS)(IPr) (). Reaction products were characterized by NMR and mass spectrometry and complexes -, , , , and by single-crystal X-ray diffraction.