Taming a monomeric [Cu(η⁶-C₆H₆)]⁺ complex with silylene

Abstract

Realization of a hitherto elusive unsupported η6 binding mode of benzene to a copper(i) cation employing silylene as a ligand. The back-donation from Cu to Si(ii) diminishes the repulsion between d-electrons and the benzene ring and enforces the η6 binding mode.

Tris(pentafluoroethyl)difluorophosphorane: A Versatile Fluoride Acceptor for Transition Metal Chemistry

“…The Cu−C distance to the ipso carbon atom C2 (2.156(4) Å) is significantly shorter than the distances to the carbon atoms in ortho positions C3 and C4 (2.312(5) and 2.355(5) Å, respectively). Similar η 3 coordination was observed by Khan and co‐workers, who realized halide abstraction from [(Dipp 2 Im)CuBr] with Ag[SbF 6 ] in the presence of hexamethylbenzene to give [(Dipp 2 Im)Cu(C 6 Me 6 )][SbF 6 ] [59] . The distances between the copper atom and both the carbenic carbon atom and the ipso / ortho carbon atoms of hexamethylbenzene in this complex are very similar to those found in 4 [59] .…”

“…Similar η 3 coordination was observed by Khan and co‐workers, who realized halide abstraction from [(Dipp 2 Im)CuBr] with Ag[SbF 6 ] in the presence of hexamethylbenzene to give [(Dipp 2 Im)Cu(C 6 Me 6 )][SbF 6 ] [59] . The distances between the copper atom and both the carbenic carbon atom and the ipso / ortho carbon atoms of hexamethylbenzene in this complex are very similar to those found in 4 [59] . Additionally, there is a “cuprophilic” interaction [60] with a Cu ⋅⋅⋅ Cu distance of 2.8014(13) Å, which is slightly longer than those in similar NHC‐stabilized dinuclear dicationic complexes [{( R NHCP t Bu )Cu} 2 ] 2+ 2 [PF 6 ] − ( R NHCP t Bu =3‐alkyl/aryl‐1‐bis(di‐ tert ‐butylphosphino)‐imidazolin‐2‐ylidene; R=Me, Mes) and [{( R NHC(CH 2 )P t Bu )Cu} 2 ] 2+ 2 [PF 6 ] − ( R NHC(CH 2 )P t Bu =3‐alkyl/aryl‐1‐(di‐ tert ‐butylphosphinomethyl)‐imidazolin‐2‐ylidene; R=Me, Mes) reported by Hofmann et al.…”

“…[59] The distances between the copper atom and both the carbenic carbon atom and the ipso/ortho carbon atoms of hexamethylbenzene in this complex are very similart ot hose found in 4. [59] Additionally, there is a" cuprophilic" interaction [60] with aC u •••Cu distance of 2.8014(13) ,w hichi ss lightly longer than those in similar NHC-stabilized dinuclear dicationic complexes [{( R NHCP tBu )Cu} 2 ] 2 + 2[PF 6 ] À ( R NHCP tBu = 3-alkyl/aryl-1-bis(di-tertbutylphosphino)-imidazolin-2-ylidene;R = Me, Mes) and [{( R NHC(CH 2 )P tBu )Cu} 2 ] 2 + 2[PF 6 ] À ( R NHC(CH 2 )P tBu = 3-alkyl/aryl-1-(di-tert-butylphosphinomethyl)-imidazolin-2-ylidene;R = Me, Mes) reported by Hofmann et al (2.575-2.744 ). [61] The bis-NHC complex [(Dipp 2 Im) 2 Cu]FAP (5a)w as formedi n small amounts during the reaction of [(Dipp 2 Im)CuF] (3)w ith (C 2 F 5 ) 3 PF 2 ,a si se vident from the 1 HNMR spectrum.T his complex was subsequently prepared from [{(Dipp 2 Im)Cu} 2 ] 2 + 2 FAP À (4)a nd the free carbene( Scheme 5).…”

“…The cationic hexamethylbenzene Cu I complex of [(Dipp 2 Im)Cu(C 6 Me 6 )][SbF 6 ] [59] is accessible as [(Dipp 2 Im)Cu(C 6 Me 6 )] FAP ( 5 f ) as the sole product starting from the fluoride complex [(Dipp 2 Im)CuF] ( 3 ), (C 2 F 5 ) 3 PF 2 , and C 6 Me 6 . Complex 5 f was also prepared by addition of C 6 Me 6 to a solution of 4 in CD 2 Cl 2 .…”

Heterobimetallic Coinage Metal‐Ruthenium Complexes Supported by Anionic N‐Heterocyclic Carbenes

“…[29] Likewise, the copper(I) complexes [(IDipp) Cu(arene)][SbF 6 ] (arene = η 2 -benzene, η 3 -C 6 Me 5 , η 3 -toluene, η 3m-xylene) were isolated by reaction of [(IDipp)CuBr] with AgSbF 6 in CH 2 Cl 2 /arene solution and feature η 2 -or η 3 -coordination modes in the solid state. [30] Similar metal-arene interactions were also observed for coinage metal complexes of Nheterocyclic silylene ligands. [31] Originally, we envisaged that the silver(I) and copper(I) toluene complexes 5 might be ideally suited for WCA-NHC transfer to transition metals, with the ultimate goal to prepare ruthenium(II) WCA-NHC complexes for application in olefin metathesis.…”