Mechanism of an oxygen atom transfer reaction involving an oxo-bridged Mo(V) complex

• Published in: Inorganica Chimica Acta 1995-09, Vol.237 (1), p.117-122
• Main Authors: Baird, D.M., Aburri, C., Barron, L.S., Rodriguez, S.A.
• Format: Article
• Language: English
• Subjects: Kinetics and mechanism; Molybdenum complexes; Oxo-bridged complexes; Oxygen atom transfer
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/0020-1693(95)04664-U

The kinetics of the oxygen atom transfer reaction Mo 2O 3I 2(dtc) 2 (THF) 2 (1) + pyridine- N-oxide= 2MoO 2I(dtc) + pyridine was investigated in methylene chloride solution using a variety of substituted pyridine- N-oxides. This is the first kinetics study of the reaction of an oxobridged Mo(V) complex participating in an oxo-transfer reaction. Reactions were studied using pseudo-first-order conditions of excess N-oxide. These reactions were characterized by saturation kinetics in which 1 reversibly forms a Mo 2O 3 4+- N-oxide precursor complex that generates products via irreversible breaking of an MoO b bond to give two equivalents of MoO 2 2+ complex and the appropriate pyridine derivative. A considerable group effect was observed (two orders of magnitude) when substituents on the pyridine- N-oxides were varied, with electron releasing substituents slowing the rate of reaction. This observation is used to support a proposed mechanism by which the rate of MoO b bond breaking in the precursor complex is determined by the NO bond strength of the substrate N-oxide.