Alkylation-Induced O-Atom Rearrangement in Nickel S-Oxygenates

Reactions of organic halides MeI and Br(CH₂)₃Br with square planar nickel complexes of tetradentate N₂SS‘ or N₂S‘₂ ligands (S‘ = RS(O)) have been explored for their potential to direct alkylation of metallosulfoxide sulfur and yield metal-bound organic sulfoxides. In fact, as established by spectroscopic and electrochemical signatures, isolated products were characterized as the result of O-atom rearrangements or transfers leading primarily to metallosulfones (Ni−SO₂R) and metallothiolates (Ni−SR) (which were subsequently alkylated to nickel-bound thioethers). Proposed intermediates in the reactions of the monosulfoxide, Ni-4*, N-(2-mercapto-2-(methylpropyl))-N‘-(2-sulfenato-2-(methylpropyl))-1,5-diazacyclooctanenickel(II) and the bis-sulfoxide, Ni-5*, N,N‘-bis(2-sulfenato-2-(methylpropyl))-1,5-diazacyclooctanenickel(II), with 1,3-dibromopropane include S-bound R‘S−OR moieties resulting from ring closure of the pendant alkyl bromide on the nucleophilic sulfoxide oxygen. X-ray crystal structures of N-(sulfinato-2-(methylpropyl))-N‘-(2-thia-2-(methylpropyl))-1,5-diazacyclooctanenickel(II) iodide and a bimetallic composed of two units of N-(2-mercapto-2-(methylpropyl))-N‘-(2-sulfinato-2-(methylpropyl))-1,5-diazacyclooctanenickel(II) linked by (CH₂CH₂CH₂) are reported.