Aryl Ether Cleavage by Group 9 and 10 Transition Metals: Stoichiometric Studies of Selectivity and Mechanism

Abstract

The reactivity of terphenyl diphosphines bearing aryl–methyl ether or aryl–aryl ether moieties with M0 (M = Ni, Pd, Pt), M′I (M′ = Co, Rh, Ir), or MII centers was investigated to gain mechanistic insight into intramolecular aryl–ether bond cleavage in structurally related metal complexes. RhI converts the aryl–methyl ether moiety to an aryl C–H bond. This is similar to reactivity previously observed at Ni0 that involves C–O oxidative addition, β-H elimination liberating CH2O, reductive elimination of an aryl C–H bond, and decarbonylation of CH2O. IrI leads to unselective aryl and alkyl C–O bond activation. In the presence of excess CO, RhI and IrI display a shift in selectivity and reactivity and cleave the alkyl C–O bond. CoI does not perform C–O cleavage. Alkyl C–O bond activation was observed with MII–halide complexes with loss of MeCl via a Lewis acid–base mechanism. Pd0 and Pt0 cleave selectively the O–Me bond via oxidative addition. With a diaryl ether moiety, Pd0 and Pt0 are found to be capable of ...