Heptamolybdate: a highly active sulfide oxygenation catalyst

摘要

The sulfide oxygenation activities of both heptamolybdate ([Mo _(7) O _(24) ] ~(6?) , [ 1 ] ~(6?) ) and its peroxo adduct [Mo _(7) O _(22) (O _(2) ) _(2) ] ~(6?) ([ 2 ] ~(6?) ) were examined in this contribution. [Mo _(7) O _(22) (O _(2) ) _(2) ] ~(6?) was prepared in a yield of 65% from (NH _(4) ) _(6) [Mo _(7) O _(24) ] ( 1a ) upon treatment of 10 equiv. of H _(2) O _(2) and structurally identified through single crystal X-ray diffraction study. ( n Bu _(4) N) _(6) [Mo _(7) O _(22) (O _(2) ) _(2) ] ( 2b ) is an efficient catalyst for the sequential oxygenation of methyl phenyl sulfide (MPS) by H _(2) O _(2) to the corresponding sulfoxide and subsequently sulfone with a 100% utility of H _(2) O _(2) . Surprisingly, ( n Bu _(4) N) _(6) [Mo _(7) O _(24) ] ( 1b ) is a significantly faster catalyst than 2b for MPS oxygenation under identical conditions. The pseudo-first order k _(cat) constants from initial rate kinetics are 54 M ~(?1) s ~(?1) and 19 M ~(?1) s ~(?1) for 1b and 2b , respectively. Electrospray ionization mass spectrometry (ESI-MS) investigation of 1b under the catalytic reaction conditions revealed that [Mo _(2) O _(11) ] ~(2?) is likely the main active species in sulfide oxygenation by H _(2) O _(2) .