In order to study the reactivity pattern of Mo-O t bonds associated with anionic sulfur ligands, precursor complexes MoO 2 L‚D (H 2 L ) S-methyl 3-(2-hydroxyphenyl)methylenedithiocarbazate; D ) CH 3 OH (1), H 2 O (2)) were synthesized. Complex 2 crystallizes in the orthorhombic space group P2 1 2 1 2 1 , with a ) 6.079(1) Å, b ) 11.638-(2) Å, c ) 17.325(2) Å, V ) 1225.7(4) Å 3 , and Z ) 4. In its reaction with PhNHOH, 1 forms a seven-coordinate oxaziridine compound [MoO(η 2 -ONPh)L‚CH 3 OH] (3) by oxo-rearrangement (elimination-substitution) without a change in the molybdenum oxidation state. The crystal data for 3 are a ) 9.573(3) Å, b ) 9.859(2) Å, c ) 10.604(3) Å, R ) 95.90(2)°, β ) 95.81(2)°, γ ) 112.12(2)°, V ) 911.5(4) Å 3 , Z ) 2, and triclinic space group P1 h. In contrast to that of the precursor compound 1 (Mo-O t ) 1.700(4) Å), the terminal Mo-O t distance in 3 (1.668(2) Å) is typical of Mo-O bonds of order 3, which drives the formation of an apparently unstable threemembered metallacycle Via spectator oxo stabilization (Rappe ´, A. K.; Goddard, W. A., III. J. Am. Chem. Soc. 1982, 104, 448). With thioglycolic acid, 1 undergoes an oxo-transfer reaction through a coupled electronproton transfer mechanism involving two steps, each having first-order dependence on H 2 tga concentration. The system offers an interesting reactivity model for the oxo-transfer pathway of oxidoreductase Mo enzymes.+IV Via a short-lived mononuclear EPR-active Mo(V) (S ) 1 / 2 ) intermediate during the turnover. 5a,8,9 This information has prompted several recent reports on oxomolybdenum complexes of biomimetic ligands. 7d,10-25 Numerous reactions that replicate the primary oxygen atom transfer † Indian Association for the Cultivation of Science.