bis-NHC Ligand Research Articles

Catalytic Benefits of an Ethynylphenyl-Based PdII Bis(NHC) over a Phenyl-Based PdII Bis(NHC): Insights into the Structural Aspects and Donor Strength Probing.

The amount of cooperation between the metal centers by tailored ligand design is vital to achieve the multimetallic catalytic benefits. Herein, a bimetallic PdII NHC/pyridine complex is synthesized utilizing a novel extended C2-symmetric bis-NHC ligand featuring 1,4-disubstituted ethynylbenzene as a central ligand platform. The complex was further employed for the preparation of a dinuclear complex possessing a combination of NHC and PPh3 ligands. Dinuclear complexes have also been synthesized using a 1,4-di(NHC)-substituted parent benzene ring platform with no acetylene linker units. The donor strengths of both bis-NHC ligands were compared with the help of 13C and 31P chemical shift values as probes. All of the bimetallic complexes were tested as precatalysts in the intermolecular α-arylation of 1-methyl-2-oxindole and Sonogashira coupling reactions. The dinuclear PdII complexes with the ethynylbenzene-bridged bis-NHC ligand showed impressive catalytic outcomes that outweigh the catalytic outcomes obtained with dinuclear bis-NHC complexes possessing no such acetylene linkers. The corresponding mononuclear PdII complexes were synthesized for comparison purposes utilizing both types of central ligand platforms. The dinuclear complexes appeared more active than the corresponding mononuclear complexes in catalysis. Furthermore, higher cooperative index values were obtained in catalysis using the dinuclear PdII complexes with an acetylene-bridged bis-NHC ligand compared to those with no such acetylene linkers.

Restriction of reaction sites on metal-sulfide cores induced by steric repulsion of bis-N-heterocyclic carbene ligands in trinuclear complexes bearing triply bridging sulfide ligands.

Mixed-ligand and mixed-metal trinuclear complexes bearing two {Pt-bisNHC-C1} moieties, [{Pt(bisNHC-C1)}2(ML)(μ3-S)2] n+ (ML = Pt(bisNHC-C2), n = 2; ML = Pt(bisNHC-C3), n = 2; ML = Rh(cod), n = 1; ML = RhCp*, n = 2), where bisNHC-C1, bisNHC-C2 and bisNHC-C3 represent methylene-, ethylene- and propylene-bridged bis-NHC ligands, respectively, were synthesised and structurally characterised. Reactions of these complexes with a half eq. of Ag(i) ions were examined using 1H and 195Pt NMR spectroscopy. The results exhibit that the trinuclear complexes react with Ag(i) ions accompanied by the formation of Ag-Pt bonds with the {Pt-bisNHC-C1} moieties in the first step affording corresponding heptanuclear complexes except for the RhCp* complex. The RhCp* complex gave a tetranuclear complex bearing the trinuclear unit with an Ag(i) ion. Further addition of Ag(i) ions for the other complexes resulted in disassembling of the heptanuclear clusters affording tetranuclear complexes confirmed by the observation of exchange of the Ag(i) ions in 195Pt NMR measurements, which exhibited signals with no coupling to Ag nuclei.

Synthesis of heteroleptic bis-phosphine bis-NHC iron (0) complexes: a strategy to enhance small molecule activation.

We report the synthesis of heteroleptic iron complexes supported by both a bis-phosphine ligand (depe) and a bis-NHC ligand. The mixed ligand sets provide access to iron (0) adducts of N2 and CO that are highly activated, in comparison to homoleptic (i.e. Fe(depe)2L) variants. Computational and experimental studies revealed the mixed ligand set distorts the geometric and electronic structure to yield an unusually basic iron. Although protonation occurred at Fe, silylation of the Fe(0)N2 complex afforded a highly activated silyldiazenido [FeNNSiMe3]+ complex.

Synthesis and photophysical properties of dinuclear N-heterocyclic carbene (NHC) copper(I) complexes and their application to photoluminescent light-emitting diodes and anti-counterfeiting

Here, a series of dinuclear N-heterocyclic carbene (NHC) copper(I) complexes having 3,3′-(1,4-phenylenebis(methylene))bis(1-(pyridin-2-yl)-1H-imidazolylidene as bis-NHC ligand and bis[(2-diphenylphosphino)phenyl]ether (POP) as auxiliary ligand have been successfully prepared, and their photophysical properites were investigaged experimentally and theocitcally. The resulting complexes all exhibited intense green to yellow emission that originated from the thermally activated delayed fluorescence (TADF) with a high photoluminescence quantum yield of up to 0.67 and longer excited-state lifetimes on the microsecond time scale in the solid state. Green and yellow light-emitting diode (LED) devices based on Cu(I) complexes have successfully achieved good color rendering indices. Moreover, the anti-counterfeiting patterns and QR codes made of Cu(I) complexes have been applied to clothing, banknotes, books and glass plates with excellent anti-counterfeiting effects.

Selective Oxidation of Glycerol via Acceptorless Dehydrogenation Driven by Ir(I)-NHC Catalysts.

Iridium(I) compounds featuring bridge-functionalized bis-NHC ligands (NHC = N-heterocyclic carbene), [Ir(cod)(bis-NHC)] and [Ir(CO)2(bis-NHC)], have been prepared from the appropriate carboxylate- or hydroxy-functionalized bis-imidazolium salts. The related complexes [Ir(cod)(NHC)2]+ and [IrCl(cod)(NHC)(cod)] have been synthesized from a 3-hydroxypropyl functionalized imidazolium salt. These complexes have been shown to be robust catalysts in the oxidative dehydrogenation of glycerol to lactate (LA) with dihydrogen release. High activity and selectivity to LA were achieved in an open system under low catalyst loadings using KOH as a base. The hydroxy-functionalized bis-NHC catalysts are much more active than both the carboxylate-functionalized ones and the unbridged bis-NHC iridium(I) catalyst with hydroxyalkyl-functionalized NHC ligands. In general, carbonyl complexes are more active than the related 1,5-cyclooctadiene ones. The catalyst [Ir(CO)2{(MeImCH2)2CHOH}]Br exhibits the highest productivity affording TONs to LA up to 15,000 at very low catalyst loadings.

Self‐Assembly of a Bis‐NHC Ligand and Coinage Metal Ions: Unprecedented Metal‐Driven Chemistry between the Tri‐ and Tetranuclear Species

The discrete multinuclear AgI -NHC complexes [Agn (1)n )](X)n ; (n=3 or 4, X=BF4 , PF6 ), synthesized from a bis-NHC ligand 1 and AgI ions via multiligand self-assembly, were observed to be in equilibrium between two forms (tri- and tetranuclear) in solution on the NMR timescale, which is unprecedented in CNHC -donor based chemistry. The existence of both the species was confirmed by various studies such as NMR (1 H, VT, 2D-DOSY) and ESI-MS analysis along with concentration studies. Importantly, replacing AgI with other coinage metals (AuI and CuI ) was found to alter the phenomenon entirely: a slow exchange from the tetra- to trinuclear species was noticed for the AuI complexes (4 a, b), whereas no such process was detected in case of the CuI complexes (5 a, b).

Analysis of complexation between new bidentate bis-NHC ligand and some metal cations at different temperature

In this research, the determination and complexation process between 3,3'-(2,2'-(4-methyl-phenylenesulfonamido)bis(ethane-2,1-diyl))bis(1-benzyl-3H-benzo[d]imidazol-1-ium)dibromide with Ni2+, Zn2+, Pd2+, Ag+, and Hg2+ cations in the binary mixture of methanol (MeOH) and water (H2O) at different temperatures (15, 25, 35 and 45ºC) were studied using a conductometric method. The results show that the stoichiometry of the complexes in all binary mixed solvents for Ni2+, Zn2+, and Pd2+ were 1:1 (M:L), while in other cases 1:2 (M:L) and 2:1(M:L). The stability constants (log ) of complex formation have been determined by fitting molar conductivity curves using a computer program (GENPLOT). The obtained data shows that in the pure methanol solvent system, the stability order is Ni2+< Pd2+<Zn2+<Hg2+<Ag+ and the complexation process seems more stable in pure methanol in most cases. The thermodynamic parameters were determined conductometrically. The complexes in all cases were found to be enthalpy destabilized but entropy stabilized. The experimental data was tested by using an artificial neural network (ANN) program and was in good agreement with the estimated data.

Synthesis and Characterization of Enantiopure Chiral Bis NHC-Stabilized Edge-Shared Au10 Nanocluster with Unique Prolate Shape

Herein we report the first chiral Au10 nanoclusters stabilized by chiral bis N-heterocyclic carbene (bisNHC) ligands. ESI-MS and single-crystal X-ray crystallography confirmed the molecular formula to be [Au10(bisNHC)4Br2](O2CCF3)2. The chiral Au10 nanocluster adopts a linear edge-shared tetrahedral geometry with a prolate shape. DFT calculations provide insight into the electronic structure, optical absorption, and circular dichroism (CD) characteristics of this unique Au10 nanocluster. CD spectra demonstrate chirality transfer from the chiral bisNHC ligand to the inner Au10 nanocluster core. Examination of ESI-MS and UV-vis spectra show that cluster [Au9(bisNHC)4Br]Br2 is formed initially and then transformed into the Au10 nanocluster in solution.

Towards new coordination modes of 1,2,3-triazolylidene: controlled by the nature of the 1st metalation in a heteroditopic bis-NHC ligand.

An unusual effect of the nature of the first metal coordination of a heteroditopic N-heterocyclic carbene ligand (L2) towards the coordination behavior of 1,2,3-tzNHC is explored. The first metal coordination at the ImNHC site (complexes 3 and 4) was noted to substantially influence the electronics of the 1,2,3-triazolium moiety leading to an unprecedented chemistry of this MIC donor. Along this line, the RhIII/IrIII-orthometalation in complexes 4 makes the triazolium C4-H more downfield shifted than C5-H, whereas a reverse trend, although to a lesser extent, is observed in the case of the non-chelated PdII-coordination. This difference in behavior assisted us to achieve the selective activation of triazole C4/C5 positions, not observed before, as supported by the isolation of the homo- and hetero-bimetallic complexes, 5, 6 and 7-9via C5- and C4-metalation, respectively. Furthermore, the %V bur calculations eliminate any considerable steric influence and the DFT studies strongly support the selectivity observed during bimetalation.

Highly Efficient Phosphorescent Blue-Emitting [3+2+1] Coordinated Iridium (III) Complex for OLED Application.

Cyclometalated iridium (III) complexes are indispensable in the field of phosphorescent organic light-emitting diodes (PhOLEDs), while the improvement of blue iridium (III) complexes is as yet limited and challenging. More diversified blue emitters are needed to break through the bottleneck of the industry. Hence, a novel [3+2+1] coordinated iridium (III) complex (noted as Ir-dfpMepy-CN) bearing tridentate bis-N-heterocyclic carbene (NHC) chelate (2,6-bisimidazolylidene benzene), bidentate chelates 2-(2,4-difluorophenyl)-4-methylpyridine (dfpMepy), and monodentate ligand (-CN) has been designed and synthesized. The tridentate bis-NHC ligand enhances molecular stability by forming strong bonds with the center iridium atom. The electron-withdrawing groups in the bidentate ligand (dfpMepy) and monodentate ligand (-CN) ameliorate the stability of the HOMO levels. Ir-dfpMepy-CN shows photoluminescence peaks of 440 and 466 nm with a high quantum efficiency of 84 ± 5%. Additionally, the HATCN (10 nm)/TAPC (40 nm)/TcTa (10 nm)/10 wt% Ir-dfpMepy-CN in DPEPO (10 nm)/TmPyPB (40 nm)/Liq (2.5 nm)/Al (100 nm) OLED device employing the complex shows a CIE coordinate of (0.16, 0.17), reaching a deeper blue emission. The high quantum efficiency is attributed to rapid singlet to triplet charge transfer transition of 0.9–1.2 ps. The successful synthesis of Ir-dfpMepy-CN has opened a new window to develop advanced blue emitters and dopant alternatives for future efficient blue PhOLEDs.

Electronic and steric impact of bis-NHC ligands on reactions of Pt3S2 cores in trinuclear complexes bearing bis-NHC ligands with various lengths of alkylene bridges.

Alkylene-bridged bis-N-heterocyclic carbene ligands working as strong σ-donors enhance the reactivity of the Pt3S2 core in a triplatinum complex. Although an Ag(I) ion possibly reacts with the Pt-Pt bond, one of the sulfide ligands coordinates to an Ag(I) ion due to the steric hindrance of the ligands.

Insights into the Suzuki‐Miyaura Reaction Catalyzed by Novel Pd−Carbene Complexes. Are Palladium−Tetra‐ carbene Entities the Key Active Species?

AbstractThe assumption that the real active species involved in the Suzuki‐Miyaura reaction are homogeneous, heterogeneous or both is often proposed. However a lack in the characterization of true catalytic entities and their monitoring makes assumptions somewhat elusive. Here, three families of palladium(II) complexes bearing bisNHC, bispyridyl and bisphosphine ligands were synthesized in order to get new insights into the formation of active species in the Suzuki‐Miyaura reaction. Their comparative catalytic study reveals that the nature of the ligands as well as their spacer lengths are pivotal parameters governing the performance. All complexes evolve to Pd NPs under reaction conditions, and an orthogonal behavior is observed for two bisNHC complexes that form homoleptic tetracarbene species. Notably, these species are presumably involved in a new catalytic modus operandi. This ligand‐controlled reactivity and the formation of tetracarbene species open new routes towards the design of novel cross‐coupling catalysts via the mastering of highly‐active catalytic species.

Palladium coordinated in N-heterocyclic carbene-functionalized porous organic polymer for efficient oxidative carbonylation of glycerol

Palladium coordinated in N-heterocyclic carbene-functionalized porous organic polymer (Pd@PQP-NHC) was successfully prepared via a facile copolymerization and successive immobilization method. The obtained Pd@PQP-NHC that featured relatively large surface area, hierarchical pore structure, and strong electron interaction between Pd species and bis-NHC ligand, displayed very high catalytic activity for the oxidative carbonylation of glycerol. A 0.025 mol% of Pd loading was sufficient for 96% conversion of glycerol with a high turnover frequency (TOF) of 1901 h−1. Moreover, the catalyst could be reused at least nine consecutive recycles without obvious loss of its initial activity.

Molecular water oxidation catalysis by zwitterionic carboxylate bridge-functionalized bis-NHC iridium complexes

Carboxylate functionalized bis-NHC ligands allow for the stabilization of high-valent iridium intermediate species involved in homogeneous water oxidation catalysis.

IrIII/AuI and RhIII/AuI Heterobimetallic Complexes as Catalysts for the Coupling of Nitrobenzene and Benzylic Alcohol

Two simple bisimidazolium salts derived from m- or p-bisimidazolebenzenes have been used as ligand precursors for the preparation of a series of heterobimetallic RhIII/AuI and IrIII/AuI complexes. All complexes have been fully characterized, and the molecular structures of selected derivatives have been determined by X-ray diffraction studies. These analyses showed that, regardless of the ligand used, the direct coordination environment of the metals is composed of identical donors (MIII: CNHC, Cbenzene, η5-Cp*, and I–; AuI: CNHC and I–) and is rather similar in the heterobimetallic complexes. The catalytic activity of the heterobimetallic complexes in the coupling of nitrobenzene with benzylic alcohol has been investigated. In all cases, the performance observed for the heterobimetallic complexes was superior to that shown by mixtures of homometallic MIII/AuI complexes, suggesting a cooperative effect between the two metal centers. In addition and in spite of the similarity of the donor groups of the two bis-NHC ligands used, the slightly different relative orientation of the two metals in the heterobimetallic complexes also plays a role in the catalytic conversion observed.

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity.

A series of water-soluble zwitterionic complexes featuring a carboxylate bridge-functionalized bis-N-heterocyclic carbene ligand of formula [Cp*MIIICl{(MeIm)2CHCOO}] and [MI(diene){(MeIm)2CHCOO}] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; M = Rh, Ir; MeIm = 3-methylimidazol-2-yliden-1-yl; diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd)) were prepared from the salt [(MeImH)2CHCOO]Br and suitable metal precursor. The solid-state structure of both types of complexes shows a boat-shaped six-membered metallacycle derived of the κ2C,C' coordination mode of the bis-NHC ligand. The uncoordinated carboxylate fragment is found at the bowsprit position in the Cp*MIII complexes, whereas in the MI(diene) complexes it is at the flagpole position of the metallacycle. The complexes [RhI(diene){(MeIm)2CHCOO}] (diene = cod, nbd) exist as two conformational isomers in dichloromethane, bowsprit and flagpole, that interconvert through the boat-to-boat inversion of the metallacycle. An inversion barrier of ∼17 kcal·mol-1 was determined by two-dimensional exchange spectroscopy NMR measurements for [RhI(cod){(MeIm)2CHCOO}]. Reaction of zwitterionic Cp*MIII complexes with methyl triflate or tetrafluoroboric acid affords the cationic complexes [Cp*MIIICl{(MeIm)2CHCOOMe}]+ or [Cp*MIIICl{(MeIm)2CHCOOH}]+ (M = Rh, Ir) featuring carboxy and methoxycarbonyl functionalized methylene-bridged bis-NHC ligands, respectively. Similarly, complexes [MI(diene){(MeIm)2CHCOOMe}]+ (M = Rh, Ir) were prepared by alkylation of the corresponding zwitterionic MI(diene) complexes with methyl triflate. In contrast, reaction of [IrI(cod){(MeIm)2CHCOO}] with HBF4·Et2O (Et = ethyl), CH3OTf, CH3I, or I2 gives cationic iridium(III) octahedral complexes [IrIIIX(cod){(MeIm)2CHCOO}]+ (X = H, Me, or I) featuring a tripodal coordination mode of the carboxylate bridge-functionalized bis-NHC ligand. The switch from κ2C,C' to κ3C,C',O coordination of the bis-NHC ligand accompanying the oxidative addition prevents the coordination of the anions eventually formed in the process that remain as counterions.

2,6-Lutidine-linked bis-saturated NHC pincer ligands, silver complexes and transmetallation

Pincer ligands have proven to be valuable tools in the formation of robust transition metal complexes. To date, pincer ligands have featured an extremely diverse array of structural motifs, backbones and donor units. Carbene ligands have been easily integrated into a variety of pincer ligand structures and yet there are very few examples in which saturated NHC donor moieties are featured. Saturated NHCs are known to have unique donor and acceptor properties compared to their unsaturated analogs and therefore their implementation into pincer structures should lead to new electronic properties of the coordinated metal. To expand the use of saturated NHCs in pincer ligand chemistry, a bis-NHC pincer ligand, featuring a 2,6-lutidine linker, has been synthesized. The proligand can be directly metalated using silver oxide and the silver salt has been used in transmetallation chemistry to generate Ni(II) pincer complexes. This ligand is an excellent addition to known pincer ligands and will have applications in catalysis and other areas.

Synthesis and Characterization of Heteroleptic Ni(II) Bipyridine Complexes Bearing Bis(N-heterocyclic carbene) Ligands

The synthesis and characterization of four new Ni(II) bis(NHC) bipy complexes (bipy = 4, 4′-bipyridine, NHC = N-heterocyclic carbene) are reported. These represent the first examples of the NiII(NHC2) L2 class of compounds, where L is a two-electron-donor ligand. The introduction of a double propyl bridged bis-NHC ligand (CProp2C) imparts reversibility to the electrochemistry of these complexes. The electrochemical response includes two reductions, the first believed to be bipy ligand based, bipy0/–, and the second metal based. The unusual ligand arrangements in these complexes result in electronic structures in which both the HOMOs and LUMOs are ligand-based, as determined by DFT analysis of all four compounds.

Axially chiral benzimidazolium based silver(I) and gold(I) bis-NHC complexes of R-BINOL scaffold: synthesis, characterization and DFT studies

The axially chiral ligand of R-BINOL scaffold was synthesized by a series of manipulations which involved different chemical reactions to obtain the desired sliver(I) and gold(I) $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {M}\}\hbox {Cl}$$ ( $$\hbox {L} = 3{,}3'\hbox {-dimethyl-2}{,}2'\hbox {-dimethoxy-1,1}'\hbox {-binaphthyl}, \hbox {L}' = i\hbox {-propyl-benzo}[\hbox {d}]\hbox {imidazole})$$ (M =Ag and Au) complexes. Enantiopure R-BINOL was employed as a basic unit to synthesize a benzimidazole based bis-NHC ligand 1g which was obtained through the formation of different intermediate 1(a-f) compounds. The newly synthesized bis-NHC ligand precursor (1g) and its corresponding $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {Ag}\}\hbox {Cl}$$ (1h) and $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {Au}\}\hbox {Cl}$$ (1i) complexes were characterized by different spectroscopic techniques. The geometries of the optimized structure of the complexes 1h and 1i were computed at the B3LYP/SDD, 6-31G(d) level. Low temperature fluorescence spectroscopic studies did not show any evidence for the weak metal-metal interaction in these complexes. SYNOPSIS Synthesis, characterization of $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {M}\}\hbox {Cl}$$ (M = Ag and Au) (1h) and (1i) type sliver(I) and gold(I) complexes are reported. Molecular structures of these benzimidazole based, axially chiral complexes of R-BINOL scaffolds were determined by the computational studies. The results of spectroscopic and analytical data as well as the computational study show that the ligand (1g) prefers to form mononuclear bis-NHC silver(I) and gold(I) complexes in the given conditions.

Metallosupramolecular Architectures Obtained from Poly-N-heterocyclic Carbene Ligands.

Over the past two decades, self-assembly of supramolecular architectures has become a field of intensive research due to the wide range of applications for the resulting assemblies in various fields such as molecular encapsulation, supramolecular catalysis, drug delivery, metallopharmaceuticals, chemical and photochemical sensing, and light-emitting materials. For these purposes, a large number of coordination-driven metallacycles and metallacages featuring different sizes and shapes have been prepared and investigated. Almost all of these are Werner-type coordination compounds where metal centers are coordinated by nitrogen and/or oxygen donors of polydentate ligands. With the evolving interest in the coordination chemistry of N-heterocyclic carbenes (NHCs), discrete supramolecular complexes held together by M-CNHC bonds have recently become of interest. The construction of such metallosupramolecular assemblies requires the synthesis of suitable poly-NHC ligands where the NHC donors form labile bonds with metal centers thus enabling the formation of the thermodynamically most stable reaction product. In organometallic chemistry, these conditions are uniquely met by the combination of poly-NHCs and silver(I) ions where the resulting assemblies also offer the possibility to generate new structures by transmetalation of the poly-NHC ligands to additional metal centers forming more stable CNHC-M bonds. Stable metallosupramolecular assemblies obtained from poly-NHC ligands feature special properties such as good solubility in many less polar organic solvents and the presence of the often catalyticlly active {M(NHC)n} moiety as building block. In this Account, we review recent developments in organometallic supramolecular architectures derived from poly-NHC ligands. We describe dinuclear (M = AgI, AuI, CuI) tetracarbene complexes obtained from bis-NHC ligands with an internal olefin or two external coumarin pendants and their postsynthetic modification via a photochemically induced single or double [2 + 2] cycloaddition to form dinuclear tetracarbene complexes featuring cyclobutane units. Even three-dimensional cage-like structures can be prepared by this postsynthetic strategy. Cylinder-like trinuclear, tetranuclear, and hexanuclear (M = AgI, AuI, CuI, HgII, PdII) complexes have been obtained from benzene-bridged tris-, tetrakis-, or hexakis-NHC ligands. These complexes resemble polynuclear assemblies obtained from related polydentate Werner-type ligands. Contrary to the Werner-type complexes, cylinder-like assemblies with three, four, or six silver(I) ions sandwiched in between two tris-, tetrakis-, or hexakis-NHC ligands undergo a facile transmetalation reaction to give the complexes featuring more stable M-CNHC bonds, normally with retention of the metallosupramolecular structure. This unique behavior of NHC-Ag+ complexes allows the prepration of assemblies containing various metals from the poly-NHC silver(I) assemblies. Narcissistic self-sorting phenomena have also been observed for mixtures of selected poly-NHC ligands and silver(I) ions. Even a very early type of metallosupramolecular assembly, the tetranuclear molecular square, can be prepared from four bridging dicarbene ligands and four transition metal ions either by a stepwise assembly or by a single-step protocol. At this point, it appears that procedures for the synthesis of metallosupramolecular assemblies using polydentate Werner-type ligands and metal ions can be transferred to organometallic chemistry by using suitable poly-NHC ligands. The resulting structures feature stable M-CNHC bonds (with the exception of the labile CNHC-Ag+ bond) when compared to M-N/M-O bonds in classical Werner-type complexes. The generally good solubility of the compounds and the presence of the often catalytically active {M(NHC)n} moiety make organometallic supramolecular complexes a promising new class of molecular hosts for catalytic transformations and encapsulation of selected substrates.