Facile CH Bond Formation by Reductive Elimination at a Dinuclear Metal Site

Abstract

The electronically unsaturated dirhenium complex [Re2(CO)8(µ-AuPPh3)(µ-Ph)] (1) was obtained from the reaction of [Re2(CO)8{µ-η(2)-C(H)=C(H)nBu}(µ-H)] with [Au(PPh3)Ph]. The bridging {AuPPh3} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re2(CO)8(µ-H)(µ-Ph)] (2) by reaction of 1 with HSnPh3. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 °C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses.

Binuclear Aromatic C−H Bond Activation at a Dirhenium Site

“…[1][2][3][4] Examples involving activation of aromatic C À Hb onds by polynuclear metal complexes are rare. [6] We have now found that 1 is equally capable of performing facile activation of aromatic CÀHbonds and can be used as ar eagent for the formation of new dirhenium complexes containing bridging aryl and bridging hydrido ligands.T he reaction of 1 with N,N-diethylaniline yielded benzene and the new dirhenium complex [Re 2 (CO) 8 (m-H)(m-h 1 -C 6 H 4 NEt 2 )] (2)i n6 1% yield after 5.5 hours at 50 8 8C[Equation (2)]. [6] We have now found that 1 is equally capable of performing facile activation of aromatic CÀHbonds and can be used as ar eagent for the formation of new dirhenium complexes containing bridging aryl and bridging hydrido ligands.T he reaction of 1 with N,N-diethylaniline yielded benzene and the new dirhenium complex [Re 2 (CO) 8 (m-H)(m-h 1 -C 6 H 4 NEt 2 )] (2)i n6 1% yield after 5.5 hours at 50 8 8C[Equation (2)].…”

“…Not surprisingly,t he initial stages of the process resemble that of the NCMe-induced elimination of benzene [6] from 1.I nb oth cases,t he transformation is initiated by approach of an uncoordinated solvent molecule to 1 in the region proximate to its bridging hydride ligand (Scheme 1). Not surprisingly,t he initial stages of the process resemble that of the NCMe-induced elimination of benzene [6] from 1.I nb oth cases,t he transformation is initiated by approach of an uncoordinated solvent molecule to 1 in the region proximate to its bridging hydride ligand (Scheme 1).…”

Multiple C−H Bond Activations in Corannulene by a Dirhenium Complex

“…Corannulene was prepared by a previously reported method . Re 2 (CO) 8 (μ‐C 6 H 5 )(μ‐H), 1 was prepared according to previously reported procedure . Product separations were performed by TLC in air on Analtech 0.25 or 0.5 mm silica gel 60 Å F 254 glass plates.…”

“…[5] The oxidative addition of aromatic CH bondst om etal complexes has attracted great interesti nr ecent years. [6] It was recently shown that the dirhenium complex Re 2 (CO) 8 (m-C 6 H 5 )(m-H), 1 whichc ontains ab ridging h 1 -phenyl ligand and ab ridging hydridol igand across its unsaturated ReÀRe bond [7] will eliminate benzene under very mild conditions and then react with other arenes by binuclear oxidative addition of CÀH bonds to yield new dirhenium complexes containing bridging aryl ligands, see Scheme 1. [8] In 2016, the mechanism for the binuclear oxidativea ddition for the activation of an aromatic CH bond of benzene to the dirhenium octacarbonyl group of 1 was established by ad ensity functional theory analysis.…”

“…[10] Re 2 (CO) 8 (m-C 6 H 5 )(m-H), 1 was prepared according to previously reported procedure. [7] Product separations were performed by TLC in air on Analtech 0.25 or 0.5 mm silica gel 60 F 254 glass plates. Reaction of Re 2 (CO) 8 (m-C 6 H 5 )(m-H), 1w ith corannulene in a1 :2 ratio A2 5.0 mg (0.037 mmol) amount of 1 and 8.0 mg (0.072 mmol) of corannulene, C 20 H 10 ,w ere dissolved in 1.6 mL CD 2 Cl 2 and placed in a5mm NMR tube.…”