Exploiting a dimeric silver transmetallating reagent to synthesize macrocyclic tetracarbene complexes

Abstract

A dimeric macrocyclic tetra-N-heterocyclic carbene (NHC) silver complex was synthesized and shown to successfully extend transmetallation of polydentate NHCs beyond bidentate NHCs. The silver complex was utilized in the preparation of a variety of monomeric tetra-NHC complexes ranging from early first row to late third row transition metals in moderate to high yield for a total of nine examples of transmetallation. Among these complexes are rare examples of silver transmetallation with first row transition metals: chromium, iron, and cobalt. Additionally, the first examples of tetracarbenes on chromium and gold are reported. All compounds were characterized by single crystal X-ray diffraction, ESI-MS, and spectroscopic techniques.

N-heterocyclic carbene complexes of Group 6 metals

“…This preparation shows the successful extension of transmetallation of polydentate NHCs beyond bidentate NHCs. It is an octahedral complex with Cr-C carbene bond lengths in the region of 2.09 and 2.14 Å[178], which are comparable to those in Cr dicarbene complexes. 12 Cr(II) tetra-NHC complex[178].4.1.2.2.3 Cr-NHC complexes containing hybrid NHC ligandIn 2006, Danopoulos et al reported the synthesis of 'pincer' dicarbene complexes Cr-78a and Cr-78b (Figure 4.13), which contain [C-N-C] type ligands.…”

“…11 Cr(II)(III) complexes with di-NHC ligands[176].The first tetracarbene Cr complex Cr-77[178] (Figure 4.12) was reported by Jenkins et al in 2012. It was prepared from a transmetallation method with a dinuclear silver complex with macrocyclic tetra-NHC.…”

Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis

“…The first approach utilizes the transmetallation route (Scheme 13) for preparing the (665), [201] (666−667), [202] (675), [203] (676), [161] (677−678), [204] (679), [203] (682), [205] (683), [206] (684−685), [207] (686−687), [208] (689), [209] (690), [210] (691), [211] (692−695), [203] (697−702), [203] (703−706), [212] (707), [213] (708) [214] and (709−710) [215] complexes from the respective Ag(I)−NHC complexes by the treatment with various Ni(II) precursors namely, NiCl 2 (PPh 3 ) 2 , (DME)NiX 2 (X = Cl, Br) and…”

“…(200),[91] (201),[92] (202),[93] (203),[91] (204−206),[92] (207) [94] and(208−209) [95] were synthesized by this method from the reaction of nickelocene derivatives and the azolium salts (Scheme 14 andFigure 16).…”

Solid-state structure, solution-state behaviour and catalytic activity of electronically divergent C,N-chelating palladium–N-heterocyclic carbene complexes

“…[4][5][6][7][8][9][10] Palladium represents one of the most versatile transition metals utilised for catalysing a multitude of transformations, being applied in the synthesis of polymers, 11 nanocomplexes, 12 liquid crystals 13 and, most commonly, natural products. [14][15][16] Numerous Pd-NHC complexes have been reported, including homoleptic Pd 0 bis-carbene, 17,18 chelating/macrocyclic Pd II carbene 19,20 and mixed carbenephosphine Pd complexes. 21,22 Well-defined Pd-NHCs bearing ancillary nitrogen donor ligands have demonstrated significant activities in both carbon-carbon and carbon-heteroatom crosscoupling reactions.…”