Reductions of a Rhenium(III) Terminal Oxo Complex by Isocyanides and Carbon Monoxide

Abstract

We report on the reductive reactivity of the d4 rhenium(III) oxo olefin complex ORe(η2-DHF)(BDI) (DHF = dihydrofulvalene, BDI = N,N′-bis(2,6-diisopropylphenyl)-2,4-dimethyl-β-diketiminate) with isocyanides, R–NC (R = tBu, 2,6-xylyl), as well as carbon monoxide (CO). These reactions all proceed by an oxygen atom transfer (OAT) to generate rhenium(I) BDI complexes containing 4 equiv of the respective π-acidic reagent. In the case of isocyanides, the products (R–NC)4Re(BDI) (1, R = tBu; 2, R = 2,6-xylyl) were isolated and characterized. While these tetrakis(isocyanide) complexes are stable at room temperature, the tetracarbonyl complex (CO)4Re(BDI) quickly degraded upon formation, leading to demetalation of the BDI ligand. However, inclusion of a strong σ-donor in the reaction of ORe(η2-DHF)(BDI) with CO afforded the tricarbonyl complex fac-(CO)3Re(DMAP)(BDI) (3). In addition to 3, the oxidation product (O)2Re(DMAP)(BDI) (4) was also consistently isolated from this reaction in low yield. We hypothesize compl...