Formyl C-H activation in N,N-Dimethylformamide by a dirhenium carbonyl complex

Abstract

The reaction of Re2(CO)8[μ-η2-C(H)=C(H)Bun](μ-H), 1 with N,N-dimethylformamide (DMF) at 70 C for 6 h has yielded three new compounds: Re2(CO)8(μ-η2-O=CNMe2)(μ-H), 2, (16% yield), Re2(CO)7(NHMe2)(μ-η2-O=CNMe2)(μ-H), 3, (30% yield), Re2(CO)9(NHMe2), 4 (14% yield). Compounds 2 and 3 contain a C,O-η2-bridging formamido (O=CNMe2) ligand and a bridging hydrido ligand that were formed by the elimination of hexene from 1 and the oxidative addition of the formyl C-H bond of the DMF to the dirhenium group of 1. Compound 3 also contains an NHMe2 ligand that was apparently formed by the decarbonylation of DMF and the transfer of the formyl hydrogen atom to the NMe2 group. Compound 4 contains a similarly formed NHMe2 ligand. Compound 2 was also obtained by the reaction of 3 with CO and compound 3 was obtained by the reaction of 2 with DMF. Compound 4 was obtained independently in a high yield by the reaction of Re2(CO)9(NCMe) with NHMe2. Compounds 2, 3 and 4 were characterized structurally by single-crystal X-ray diffraction analyses.