[(NHC)Cu^I–ER₃] Complexes (ER₃ = SiMe₂Ph, SiPh₃, SnMe₃): From Linear, Mononuclear Complexes to Polynuclear Complexes with Ultrashort Cu^I···Cu^I Distances

Abstract

A series of complexes of the type [(NHC)Cu-ER3] (NHC = IDipp, IMes, ItBu, Me2IMe, and ER3 = SiMe2Ph, SiPh3, SnMe3) and [(NHC)Cu-R'] (NHC = IDipp, Me2IMe and R' = Ph, C≡CPh) was synthesized in good yields by the reaction of the corresponding [(NHC)Cu-OtBu] complex with the respective silylborane pinB-ER3 (pin = OCMe2CMe2O; ER3 = SiMe2Ph, SiPh3), the stannylborane ((C2H4)(iPrN)2)B-SnMe3, or a boronic acid ester pinB-R' (R' = Ph, C≡CPh). Solid structures of all complexes were systematically studied by X-ray diffraction analysis. The solid state structures of the complexes [(NHC)Cu-ER3] show a dependence of the structural motif from the steric properties of the NHC ligand. The sterically demanding NHC ligands (IDipp, IMes, ItBu) lead to monomeric, linear complexes [(NHC)Cu-ER3], while with the less demanding Me2IMe ligand, polynuclear, μ-ER3-bridged complexes with ultrashort Cu···Cu distances are observed. For the related complexes [(NHC)Cu-R'] no analogous complexes with bridging anionic ligands are realized. Instead, irrespective of the NHC ligand, linear coordinated copper complexes of different types are formed. (29)Si heteronuclear solution NMR spectroscopic data on [(NHC)Cu(I)-SiR3] exhibit distinctly different chemical shifts for the (in the solid state) monomeric and dimeric complexes suggesting different structure types also in solution. This agrees well with the observation of a trinuclear complex [(Me2IMe)Cu-SnMe3]3 both in the solid state and in solution. Initial catalytic studies suggest that [(NHC)Cu-OtBu] complexes (NHC = ItBu, Me2IMe) are, in addition to the established [(IDipp)Cu-OtBu] complex, efficient precatalysts for the silylation of aldehydes and α,β-unsaturated ketones with pinB-SiMe2Ph.

Linear Copper Complex Arrays as Versatile Molecular Strings: Syntheses, Structures, Luminescence, and Magnetism

“…The 2e‐3c bond results in very short Cu⋅⋅⋅Cu distances [2.3749(8) and 2.4192(8) Å] and a bent geometry of the Cu I 3 chain [Cu out ⋅⋅⋅Cu in ⋅⋅⋅Cu out′ : 130.54(3)°]. The unusual cuprocuprate 16 was obtained from the complex [( Me 2 IMe )Cu(C≡CPh)] upon recrystallization . The monovalent complex cation contains an ideally linear chain of three Cu I centers (Cu out ⋅⋅⋅Cu in ⋅⋅⋅Cu out′ : 180.0°) and intrachain Cu I ⋅⋅⋅Cu I separations [2.6011(4) Å] that are clearly below the sum of two copper van der Waals radii …”

“…More recently,t he trinuclearo rganocopper aggregate 15 has been obtainedf rom 1,2,3,4-tetra(n-propyl)-1,4-dilithio-1,3butadien, CuCl, and LiI in 63 %y ield. [29] [30] The monovalentc omplex cation contains an ideally linear chain of three Cu I centers (Cu out ···Cu in ···Cu out' :1 80.08)a nd intra-chain Cu I ···Cu I separations [2.6011(4) ]t hat are clearly below the sum of two copper van der Waals radii. [10]…”

[(PPh3)4Pt2S2(SnCl)]+: A Pt‐Sn‐S Cluster with a Ternary Trigonal Bipyramidal Cluster Core

“…Further trigonal bipyramidal metal clusters containing Sn have been known for several elemental combinations, preferably with Fe, Cu, or the group 10 metals Ni, Pd, and Pt. Examples – besides the Pt/Sn/S clusters referred to above – are {Fe 3 (CO) 9 [μ 3 ‐SnRe(CO) 5 ] 2 }, [Ni 3 (μ‐dppm) 3 (μ 3 ‐Cl)(μ 3 ‐SnCl) 3 ], or [(Me 2 IMe)Cu‐SnMe 3 ] 3 . A series of highly related clusters based on the elemental combination Pd/Sn/Se was recently published, which also exhibited trigonal bipyramidal cluster cores, but in which the two types of metal atoms are combined in another way .…”

Dinuclear N-heterocyclic carbene copper(I) complexes

“…More recently, the Corrigan group used an S-Hg-S bridge to connect two copper-NHC fragments (Scheme 15) [ 27.9; %V Bur = percentage of a sphere, centered on the metal, which is occupied by the ligand], dinuclear complexes containing a chalcogenide bridge were obtained, namely [Cu(μ-SSiMe 3 )( i Pr 2 -bimy)] 2 (38) ] core, with Cu-S-Cu and Cu-Se-Cu angles of 119° and 138.04(4)° respectively. The copper centers in both species exhibit a distorted trigonal planar geometry, each coordinating a C NHC and two μ-ESiMe 3 groups.…”

“…When compared with a mononuclear analogue [Cu{Si(SiMe 3 ) 3 }(IMe)], possessing a larger silicon group, the C NHC -Cu distance is longer for 33, as well as the Cu-Si distances, due to the different coordination mode of the copper. Later on, Kleeberg and co-workers used Me 2 IMe as NHC to synthesize the silyl bridged species [Cu(μ-SiPh 3 )(Me 2 IMe)] 2 (34) and [Cu(μ-SiMe 2 Ph)(Me 2 IMe)] 2 (35) from the corresponding tert-butoxide complexes and pinB-SiR 3 (Scheme 13)[38]. In these complexes the copper is tri-coordinated with one NHC ligand and two bridging silyl ligands, giving an almost planar [Cu 2 Si 2 ] core similar to the one observed in 33.Scheme 13.…”