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

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journal contribution
posted on 03.10.1998 by John A. Bellefeuille, Craig A. Grapperhaus, Rizalia M. Buonomo, Joseph H. Reibenspies, Marcetta Y. Darensbourg
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.