Spin trapping in the interaction between acetylenic hydrocarbons and group VIB metal carbonyls

1-Heptyne and 2-heptyne were reacted with Mo(CO)₆ (M=Cr, Mo, W) under different conditions. All samples exhibit ESR signals only in the presence of spin traps. Both carbon-centered and metal-centered radicals have been observed. The radical intermediates were identified by isotropic g-values and splitting constants for nitrone spin adducts obtained from the reaction systems under various conditions.