Facile C–S, S–H, and S–S bond cleavage using a nickel(0) NHC complex

Abstract

[Ni₂(iPr₂Im)₄(COD)] 1 (iPr₂Im = 1,3-di(isopropyl)-imidazol-2-ylidene) reacts at room temperature with the thioethers methyl para-tolyl sulfide, ethyl phenyl sulfide, benzothiophene and dibenzothiophene to afford the C–S bond cleavage products [Ni(iPr₂Im)₂(4-CH₃-C₆H₄)(SMe)] 2, [Ni(iPr₂Im)₂(C₆H₅)(SEt)] 3, [Ni(iPr₂Im)₂(1,8-benzothiophenylato)] 4 and [Ni(iPr₂Im)₂(C,S-dibenzothiophenylato)] 5. In contrast to the reaction of thioethers or sulfoxides (reported earlier), no C–S bond cleavage was observed for the reaction of 1 with the sulfones bezothiophene-1,1-dioxide and methyl phenyl sulfone. In those cases the stable compounds [Ni(iPr₂Im)₂(η²-2,3-benzothiophene-1,1-dioxide)] 6 and [Ni(iPr₂Im)₂(η²-MeSO₂C₆H₅)] 7 with a η²-coordinated sulfone ligand have been isolated. Compound 6 has been structurally characterized. S–H bond cleavage was observed using 2-methyl-2-propanthiol to afford [Ni(iPr₂Im)₂(H)(StBu)] 8. The reaction of 1 with disulfides led to the dithiolato complexes [Ni(iPr₂Im)₂(SR)₂] (R = tBu 9, Me 10, Ph 11) by S–S bond scission.