M−O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)‐Oxyl and Cobalt(III)‐Oxo Complexes

Abstract

Terminal oxocomplexes of late transition metals are frequently proposed reactive intermediates.H owever,t hey are scarcely knownbeyond Group 8. Using mass spectrometry,we prepared and characterized two such complexes: 2+ (2). Infrared photodissociation spectroscopyr evealed that the Co À Ob ond in 1 is rather strong, in accordance with its lacko fc hemical reactivity.O nt he contrary, 2 has av ery weak CoÀOb ond characterized by as tretching frequency of 659 cm À1 .A ccordingly, 2 can abstract hydrogen atoms from non-activated secondary alkanes.P reviously,t his reactivity has only been observed in the gas phase for small, coordinatively unsaturated metal complexes.M ultireference ab-initio calculations suggest that 2,formally acobalt(IV)-oxo complex, is best described as cobalt(III)-oxyl. Our results provide important data on changes to metal-oxo bonding behind the oxow all and show that cobalt-oxo complexes are promising targets for developing highly active C À Ho xidation catalysts.