Alkylation-induced O-atom rearrangement in nickel S-oxygenates
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abstract
Reactions of organic halides Mel and Br(CH2)aBr with square planar nickel complexes of tetradentate N2SS or N2S2 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))-l,5-diaza-cyclooctanenickel(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.
