An Unusually Static, Sterically Hindered Silver Bis(N-heterocyclic carbene) Complex and Its Use in Transmetalation

Abstract

A dimeric silver complex of the bulky bis(Nheterocyclic carbene) ligand 1,1′-dimesityl-3,3′-methylenediimidazol-2,2′-diylidene exhibits a surprisingly static structure in solution, due to a favorable chelate ring conformation, yet serves as a convenient transmetalation reagent for the formation of a new κ 2 -bis(NHC) rhodium(I) complex. The latter complex demonstrates a strong influence of N-substituent steric bulk on the bis(NHC) binding mode.

Synthesis of palladium(0) and -(ii) complexes with chelating bis(N-heterocyclic carbene) ligands and their application in semihydrogenation

“…52 The silver(I) complexes were also prepared by following reported procedures; in MeOH for R = Me, Benz, nBu 29 or dichloromethane for R = Mes. 28 The NMR spectra were recorded on Varian Mercury 300 MHz, Bruker DRX 300 and Bruker AMX 400 MHz spectrometers. Data for NMR are reported as follows: chemical shift in parts per million (δ, ppm) relative to TMS, determined by reference to residual 1 H and 13 C solvent resonances, where applicable multiplicity (s = singlet, d = doublet, t = triplet, q = quartet and m = multiplet), the number of hydrogens and coupling constant (Hz).…”

“…12,27 The silver(I) complexes, 2, were obtained by reacting the corresponding bisimidazolium dibromide salts (1a-e) with Ag 2 O at room temperature in dichloromethane (R = Mes) or methanol (R = Me, Benz, nBu) (Scheme 2) according to literature procedures. 28,29 Complete conversion can be monitored by the disappearance of the imidazolium-H peak around 9-10 ppm in the 1 H NMR spectrum and the appearance of a 13 C-Ag(I) resonance around 180 ppm in 13 C NMR. The silver complex from the mesityl bisimidazolium salt forms oligo-and polymeric structures as was shown by Wanniarachchi et al, 28 while other substituents lead to dimeric complexes.…”

“…28,29 Complete conversion can be monitored by the disappearance of the imidazolium-H peak around 9-10 ppm in the 1 H NMR spectrum and the appearance of a 13 C-Ag(I) resonance around 180 ppm in 13 C NMR. The silver complex from the mesityl bisimidazolium salt forms oligo-and polymeric structures as was shown by Wanniarachchi et al, 28 while other substituents lead to dimeric complexes. 30 The reaction mixtures containing the silver(I) bis-carbene complexes were filtered over Celite, concentrated and used in the subsequent reaction without further purification.…”

New homoleptic carbene transfer ligands and related coinage metal complexes

“…These compounds show potentially facially opposed coordination abilities (Janus-type) thus forming homo-binuclear complexes. In this paper, we have developed a new synthetic pathway to the syn- The transmetallation from a silver(I) NHC complex prepared by treatment of the azolium salt with Ag 2 O is an useful coordination method in the preparation of chelating N-heterocyclic carbene complexes [28]; in most cases this procedure can be carried out under aerobic conditions, and the process has been successful with a variety of metals such as Au, Cu, Ni, Pd, Pt, Rh, Ir and Ru [29][30][31].…”

Crystal structure of bis-(1-(2-(diethylamino)ethyl)-3-methylimidazolin-2- ylidene) di-silver(I) bis-(triflimide), Ag2[C10H19N3]2[C2F6NO4S2]2, C24H38Ag2F12N8O8S4

“…The triflimide was selected as aw eakly coordinating anion in order to lend lipophilic properties to the resulting salt. Nonetheless, the triflimide ions accept several weak hydrogen bonds from the [12,13], but here the distance betweenthe silver atoms(Ag×××Ag 4.478 Å) is safely beyond the range of any interaction. Symmetry codes: i:1+x, y, -1+z; ii:1-x,-y,-z; iii:x,y,-1+z; iv:1-x, 1-y,-z.…”