Biomimetic Molybdenum Chemistry Spanning all Four Molybdopterin Enzyme Families: From Stoichiometric Oxygen Atom Transfer to Catalytic C─H Oxidation
Prajal Chhetri, Ananthu V. Modappilappally, Xin Zheng, Neal P. MankadABSTRACT
Molybdopterin enzymes catalyze a diverse array of redox transformations, ranging from oxyanion reduction to C─H hydroxylation, through Mo VI /Mo IV cycling at active sites with conserved dithiolene‐coordinated structures. Synthetic models of these active sites have struggled to replicate this versatility in part due to comproportionation to inactive Mo V dimers, and catalytic turnover remains scarce. Here we report that a [N 2 S 2 ] 2− ‐supported Mo IV ═O complex abstracts oxygen atoms from substrates representative of three molybdopterin enzyme families: Me 2 SO, Me 3 NO, ClO 4 − , NO 3 − , and SeO 4 2− (DMSO reductases); methionine sulfoxide (sulfite oxidases); and benzamidoxime and N ‐hydroxyphthalimide (mARCs). In the cases of ClO 4 − and NO 3 − , oxygen atom transfer (OAT) requires Lewis acid activation by B(C 6 F 5 ) 3 . The corresponding Mo VI (O) 2 redox partner oxidizes formate via hydride abstraction, akin to formate dehydrogenases. The same complex has previously been shown to promote C─H hydroxylation of substrates inspired by the XO family, thus demonstrating reactivity that spans all four molybdopterin families. Coupling OAT and hydride transfer half‐reactions enables catalytic turnover, as demonstrated here for both benzimidazoline C─H hydroxylation and formate decarboxylation using DMSO as terminal oxidant, thus demonstrating the first examples of catalytic C─H oxidation by a molybdopterin‐inspired synthetic platform.