Pyridine Adducts Research Articles

N-Aromatic Complexation in Tetraphenyl Porphyrin Iron (III)-Pyridine: Evidence of Spin-Flip via Gas-Phase Electronic Spectroscopy.

There is growing interest in the electronic properties of metalloporphyrins especially in relation to their interactions with other molecular species in their local environment. Here, UV-VIS laser photodissociation spectroscopy in vacuo has been applied to an iron-centred metalloporphyrin (FeTPP+) and its N-aromatic adduct with pyridine (py) to determine the electronic effect of complexation. Both the metalloporphyrin (FeTPP+) and pyridine adduct (FeTPP+⋅py) absorb strongly across the spectral region studied (652-302 nm: 1.91-4.10 eV). Notably, a large blue shift was observed for the dominant Soret band (41 nm) upon complexation (0.47 ± 0.02 eV), indicative of strong pyridine binding. Significant differences in the profiles (i.e. number and position of bands) of the electronic spectra are evident comparing FeTPP+ and FeTPP+⋅py. Time-dependent density functional theory calculations were used to assign the spectra, revealing that the FeIII spin-state flips from S = 3/2 to S = 5/2 upon complexation with pyridine. For FeTPP+, all bright spectral transitions are found to be π-π* in character, with electron density variously distributed across the porphyrin and/or its phenyl substituents. Similar electronic excitations are observed for FeTPP+⋅py, with an additional bright transition which involves charge transfer from the porphyrin to the pyridine moiety.

Tetra-Amido Macrocyclic Ligand (TAML) at Silicon(IV): A Structurally Constrained, Water-Soluble Silicon Lewis Superacid.

Tetracoordinate silicon species are typically tetrahedral, weak Lewis acids, and often sensitive to moisture. In this study, we present a tetra-amido macrocyclic ligand (TAML)-substituted Si(IV), isolated as its bis(pyridine) adduct. Due to structural constraint toward anti van't-Hof/Le Bel geometry, this compound exhibits Lewis superacidity and effectively catalyzes the hydroboration of pyridine. Kinetic and computational analyses of the catalytic cycle reveal that TAML-Si(IV) acts as a hydride transfer agent, and the hydrido silicate key intermediate is isolated. Notably, the Lewis acid is highly soluble (5 g/L) and long-term stable in water. Unlike previously described silicon-H2O adducts, the bound water becomes substantially acidified, reaching the Bro̷nsted superacidity range. A comparison of water affinity versus pKa lowering confirms our previous theory of the strength and the effect of Lewis acids. Overall, the compound's unlimited water compatibility and its mechanistically understood catalytic efficiency mark significant progress in applying structural constraint strategies for p-block element-based catalysis, while the acidification touches critical aspects of zeolite and silica surface chemistry.

Neutral Adducts of Molybdenum Hexafluoride: Structure and Bonding in MoF6(NC5H5) and MoF6(NC5H5)2.

The first Lewis acid base adducts of MoF6 and an organic base have been synthesized, i. e., MoF6(NC5H5) and MoF6(NC5H5)2. These adducts are structurally characterized with X-ray crystallography, showing that both adducts adopt capped trigonal prismatic structures. The MoF6(NC5H5) and MoF6(NC5H5)2 adducts are fluxional on the NMR time scale at room temperature. Two different fluorine environments could be resolved by 19F NMR spectroscopy at -80 °C for the 1 : 2 adduct, MoF6(NC5H5)2, whereas MoF6(NC5H5) remains fluxional at that temperature. Density functional theory (DFT) calculations aide the assignment of the infrared and Raman spectra. Natural Bond Order and Molecular Electrostatic Potential analyses elucidate the structures and properties of the MoF6 pyridine adducts. Regions of significantly higher molecular electrostatic potential, i. e., σ-holes, in trigonal prismatic compared to octahedral MoF6 rationalize the capped trigonal prismatic geometry of the adducts. Whereas MoF6(NC5H5) is stable at room temperature under exclusion of moisture, MoF6(NC5H5)2 decomposes at 60 °C in pyridine solvent, and the solid slowly decomposes at room temperature after 24 h.

Controlling carbodiimide-driven reaction networks through the reversible formation of pyridine adducts.

Carbodiimides and pyridines form reversible adducts that slowly deliver carbodiimide "fuels" to out-of-equilibrium reaction networks, slowing activation kinetics and elongating transient state lifetimes. More-nucleophilic pyridines give more adduct under typical conditions. This approach can be used to extend the lifetimes of transient polymer hydrogels.

From the Glovebox to the Benchtop: Air-Stable High Performance Molybdenum Alkylidyne Catalysts for Alkyne Metathesis.

Molybdenum alkylidynes endowed with tripodal silanolate ligands belong to the most active and selective catalysts for alkyne metathesis known to date. This paper describes a new generation that is distinguished by an unprecedented level of stability and practicality without sacrificing the chemical virtues of their predecessors. Specifically, pyridine adducts of type 16 are easy to make on gram scale, can be routinely weighed and handled in air, and stay intact for many months outside the glovebox. When dissolved in toluene, however, spontaneous dissociation of the stabilizing pyridine ligand releases an active species of excellent performance and functional group tolerance. Specifically, a host of polar and apolar groups, various protic sites, and numerous basic functionalities proved compatible. The catalysts are characterized by crystallographic and spectroscopic means, including 95Mo NMR; their activity and stability are benchmarked in detail, and the enabling properties are illustrated by advanced applications to natural product synthesis. For the favorable overall application profile and ease of handling, complexes of this new series are expected to replace earlier catalyst generations and help encourage a more regular use of alkyne metathesis in general.

Direct Spectroscopic Identification of BN-Arynes and Subtle Steric Effects on Nitrogen Fixation.

1,2-Azaborinines are the BN analogues of arynes through exchange of the formal CC triple bond by an isoelectronic BN bond. The BN-arynes are an underexplored class of reactive intermediates. Dibenzo[c,e][1,2]azaborinine (10,9-BN-phenanthryne) 1 was inferred as reactive intermediate by trapping reactions. Here it is shown that 1 can be generated in the gas phase by thermolysis from the pyridine adduct of 9-azido-9-borafluorene by cleavage of the dative bond with pyridine and dinitrogen extrusion. The ionization potential of 1 is 8.2 eV with ionization resulting from the π HOMO. Under cryogenic matrix isolation conditions, 9-azido-9-borafluorene photolysis results in isomerization to the dinitrogen adduct of 1 without involvement of a triplet borylnitrene intermediate. Photochemical nitrogen extrusion from 1 ⋅ N2 is not possible and nitrogen fixation is irreversible under cryogenic conditions. In contrast, 2,4,7,9-tetra-tert-butyldibenzo[c,e][1,2]azaborinine can be photogenerated from the corresponding azidoborole precursor under cryogenic matrix isolation conditions, and nitrogen fixation is precluded due to steric hindrance. The BN stretching vibration at about 1750 cm-1 is much weaker than in typical linear diaryl iminoboranes.

Fluorination of vanadates with organic fluorinating agents

The organic fluorinating agents [bis(2-methoxyethyl)amino]sulfur trifluoride (Deoxo-fluor®), diethylaminosulfur trifluoride (DAST), and N-fluorobenzenesulfonimide (NFSI) were used to inspect the efficiency of fluorination of monovanadate, HxVO4(3−x)− (V1), and decavanadate, HxV10O28(6−x)− (V10), in solution by 51V NMR spectroscopy. It was observed that either VOF4− or VO2F2− can be generated in acetonitrile solutions at room temperature after one hour selectively for HxVO4(3−x)−, while HxV10O28(6−x)− is more sensitive towards reduction and only NFSI can be used to generate VOF4−. The differences in reactivity can be attributed to the electrophilicity of fluorine in Deoxo-fluor® and DAST, and its nucleophilicity in NFSI. Tetrabutylammonium fluoride, triethylamine trifluoride, and hydrogen fluoride–pyridine adduct were also used under the same conditions for comparison of the efficiency and selectivity of fluorination. It was observed that only HF.pyridine provided a complete transformation of V1 and V10 into VOF4−. The pilot experiments introduced in this work are the first example of fluorination of polyoxometalates with organic fluorination agents and other less commonly used fluorides with organic cations and show their great potential in the synthesis of polyoxometalates with fluorido ligand.

Electronic Structure, Spectroscopy, and Redox Properties of Highly Soluble (μ-oxo)Bis[Tetra(tert-butyl)(phthalocyaninato)Iron(III)] Complex and Its Pyridine Adduct Under Anaerobic Conditions in Non-Coordinating Solvents

The solid-state Mössbauer spectra of a highly soluble (μ-oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] complex 1 ((PctBuFe)2O) consist of two doublets that represent bent geometry μ-oxo(1) (1a, ΔEQ = 0.43 mm/s, T = 10K) and linear geometry μ-oxo(2) (1b) isomers (ΔEQ = 1.40 mm/s, T = 10K) with the ratio between two isomers depending on the purification method. Both isomers were found to be diamagnetic and transform entirely in 1a isomer in solution. The room- and low-temperature MCD spectra of 1a show one Faraday A- and one B-terms between 670 and 720 nm, which correlate with the 690 nm band and 709 nm shoulder observed in the UV-Vis spectrum of this compound. UV-Vis and MCD spectra of 1a are independent of the temperature. Both 1a and 1b are diamagnetic between room temperature and 4 K. Electrochemical experiments show up to three oxidation and up to four reduction processes in 1a. Its oxidation under spectroelectrochemical or chemical (in the absence of oxygen-containing oxidants) oxidation conditions in non-coordinating solvents results in the formation of a broad NIR band around 1195 nm (first oxidation) and 1264 nm (second oxidation). The MCD spectra of the redox-active species show a Faraday B-term signal with negative amplitude in this region and are very different from those in monomeric PctBu(1-)FeIIIX2 complexes 5X (X = Cl- or CF3CO2 -). Pyridine adduct of 1a ((PyPctBuFe)2O; 2Py) is paramagnetic (μB = 2.19, g = 2.11, and J = -6.1cm-1) and has a major peak at 627 nm in UV-Vis spectrum, which is associated with MCD pseudo A-term. Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) calculations, along with Kasha’s and Spano’s exciton coupling theories, were used to explain unusually red-shifted intense transitions in 1a as well as H-aggregate like spectra of the pyridine adduct 2Py.

Diiminium Nucleophile Adducts Are Stable and Convenient Strong Lewis Acids.

Strong Lewis acids are essential tools for manifold chemical procedures, but their scalable deployment is limited by their costs and safety concerns. We report a scalable, convenient, and inexpensive synthesis of stable diiminium-based reagents with a Lewis acidic carbon centre. Coordination with pyridine donors stabilises these centres; the 2,2'-bipyridine adduct shows a chelation effect at carbon. Due to high fluoride, hydride, and oxide affinities, the diiminium pyridine adducts are promising soft and hard Lewis acids. They effectively produce acylpyridinium salts from carboxylates that can acylate amines to give amides and imides even from electronically intractable coupling partners.

Tributyl(1-((dimethylamino)(dimethyliminio)methyl)-1,4-dihydropyridin-4-yl)phosphonium Ditrifluoromethanesulfonate

Site-selective functionalization of pyridines is a crucial tool for the synthesis of diverse pharmaceuticals and materials. We introduced diiminium pyridine adducts as highly convenient and potent Lewis acids. We report that tributylphosphine selectively adds to the 4-position of pyridine in tetramethyldiiminium pyridine ditrifluoromethanesulfonate, resulting in the formation of the title compound. This finding represents an advancement towards the utilization of diiminium units as organic reagents or catalysts for pyridine functionalization. We also employ computational models to determine fluoride and hydride ion affinities, Fukui function f+(r), molecular electrostatic potential, and pKa values, providing valuable insights for future investigations in this area.

The Cyanido-Sulfate Anion [SO3 CN

The reaction of the pyridine adduct of SO3 and tetra-n-butyl-ammonium cyanide, [N(n Bu)4 ][CN] at room temperature leads to the unprecedented cyanido-sulfate anion [SO3 CN]- stabilized in the salt [N(n Bu)4 ][SO3 CN]. The anion is a pseudo-halogen congener of the well-known fluoro- and chloro-sulfates. The new anion has been studied by vibrational spectroscopy and theoretical calculations.

Role of MCD and Mössbauer Spectroscopy in the Explanation of the Properties of a Highly Soluble (μ-Oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] Complex, Its Pyridine Adduct, and Redox Forms Oxidized under Anaerobic Conditions in Non-Coordinating Solvents.

Solid-state Mössbauer spectra of a highly soluble (μ-oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] complex 1 ((PctBuFe)2O) consist of two doublets that represent bent geometry in μ-oxo(1) (1a, ΔEQ = 0.43 mm/s, T = 10 K) and linear geometry in μ-oxo(2) (1b, ΔEQ = 1.40 mm/s, T = 10 K) isomers with the ratio between two isomers depending on the purification method. Both isomers were found to be diamagnetic and transform entirely to the 1a isomer in solution. The room- and low-temperature magnetic circular dichroism (MCD) spectra of 1a μ-oxo(1) show one Faraday A- and one B-term between 670 and 720 nm, which correlate with the 690 nm band and 709 nm shoulder observed in the UV-vis spectrum of this compound. UV-vis and MCD spectra of 1a are almost independent of the temperature. Both 1a and 1b are diamagnetic between room temperature and 4 K. Electrochemical experiments show up to three oxidations and up to four reduction processes in 1a. Its oxidation under spectroelectrochemical or chemical (in the absence of oxygen-containing oxidants) conditions in non-coordinating solvents results in the formation of broad NIR bands around 1195 nm (first oxidation) and 1264 nm (second oxidation). The MCD spectra of the redox-active species show a Faraday B-term signal with negative amplitude in this region and are very different from those in the monomeric PctBu(1-)FeIIIX2 complexes 5X (X = Cl- or CF3CO2-). The pyridine adduct of 1a ((PyPctBuFe)2O; 2Py) is paramagnetic (μB = 2.19, g = 2.11, and J = -6.1 cm-1) and has a major peak at 627 nm of its UV-vis spectrum, which is associated with a MCD pseudo A-term. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, along with the exciton coupling theory, were used to explain the unusually red-shifted intense transitions in 1a as well as the H-aggregate-like spectra of the pyridine adduct 2Py.

Effect of ligand steric bulk on coordination geometry of pyridine adducts of cadmium(II) carbamodithioates

Pyridine adducts of four different carbodithiolate cadmium compounds [Cd (2–mpipdtc)2(py)] (5); [Cd (4–mpipdtc)2(py)2] (6); [Cd(thqdtc)2(py)] (7) and [Cd(padtc)2(py)2] (8) have been successfully prepared and analysed by using Infrared and nuclear magnetic resonance spectroscopies and single crystal X–ray structural analysis. The N 13CS2 carbon signal for 5 and 6 noticed at 202.7 and 202.9 ppm due to an upfield shift of about 5 ppm matched with that found in 7 (208.2 ppm) and 8 (208.5 ppm). The observed shielding in 5 and 6 expresses the more electron density movement from 2–mpipdtc and 4–mpipdtc to cadmium and closer approach of the 2–mpipdtc & 4–mpipdtc and cadmium. Single crystal X–ray structural analysis showed that the structural patterns of [Cd (2–mpipdtc)2(py)], [Cd (4–mpipdtc)2(py)2], [Cd(thqdtc)2(py)] and [Cd(padtc)2(py)2] compounds are mononuclear distorted trigonal bipyramidal, mononuclear distorted octahedral, dimeric distorted octahedral and mononuclear highly distorted octahedral i.e. trigonal prismatic geometry, respectively. The variation in structure is due to the steric influence of organic substituents of corresponding ligands as well as the size of metal. This point is also supported by bond valence sum analysis.

Pyridine Adducts of Tricyano‐ and Dicyanoboranes

AbstractCyanoborane adducts of the Lewis acids B(CN)3, BF(CN)2, and BH(CN)2 with pyridine and 4‐cyanopyridine have been obtained in high yields. The syntheses were accomplished by oxidation of the readily available potassium salts of the cyano(hydrido)borate anions [BH(CN)3]− (MHB), [BFH(CN)2]− (FHB), and [BH2(CN)2]− (DHB) with bromine in the presence of the respective pyridine derivative C5H5N or 4‐CN‐C5H4N as starting material. All six cyanoborane adducts have been characterized by NMR and vibrational spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction. The reduction of the cyanoborane adducts has been investigated by cyclic voltammetry and the Lewis acidity of the different cyanoboranes has been assessed using the Gutmann‐Beckett method. Selected experimental data and trends are compared to theoretical ones, for example fluoride ion affinities (FIAs).

Effects of electron-donating ability of binding sites on coordination number: the interactions of a cyclic Schiff base with copper ions.

The stepwise addition of Cu2+ ions to the nonplanar cyclic Schiff base 5,9,14,18-tetramethyl-1,4,10,13-tetraazacyclooctadeca-5,8,14,17-tetraene-7,16-dione (H4daaden, C18H28N4O2), yields a one-end-open dinuclear copper chelate. The pyridine adduct of the dinuclear copper chelate, namely, [μ-6,11-dimethyl-7,10-diazahexadeca-5,11-diene-2,4,13,15-tetraolato(4-)](pyridine)dicopper(II), [Cu2(C16H20N2O4)(C5H5N)], was characterized by single-crystal X-ray crystallography. The two CuII atoms of the copper chelate display different coordination modes, i.e. inner-N2O2 and outer-O2O2. The Cu atom which is bonded in the outer-O2O2 mode is axially bonded to a pyridine molecule, which suggests that the electron-donating ability of the O2O2 site to the Cu atom is poor. As a result, the O2O2-bonded Cu atom has a coordination number of five, showing square-bipyramidal geometry around the Cu atom. The N2O2-coordinated site provides sufficient electron density to the other Cu atom to be stabilized with a coordination number of four, showing square-planar geometry around the Cu atom. The electron-donating ability of the ligand coordination sites plays a key role in determining the coordination number of the Cu atoms of the dicopper chelate.

Metal complexes of ‘Heena’ (2-hydroxy-1,4-naphthoquinone): Synthesis, Characterization and anticancer activity

The Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of Henna; 2-hydroxy-1,4-naphthoquinone (Lw) are synthesized at 0 °C (Mn2+; 1, Co2+; 2, Ni2+; 3, Cu2+; 4 and Zn2+; 5), 26 °C (Mn2+; 1A, Co2+; 2A, Ni2+; 3A, Cu2+; 4A and Zn2+; 5A) and characterized. The compositions of all complexes are of the type [M(Lw)2(H2O)2]. The geometry of the complexes synthesized at 26 °C is trans, whereas cis for complex 4 at 0 °C. The pyridine adduct (4Apy) of copper complexes 4A and methanol (4MeOH) adduct of complex 4 is characterized by single crystal X-ray diffraction studies. The molecular interactions are revealed from the X-ray structures of 2A, 5A, 4Apy, and 4MeOH. Anticancer activity of all complexes was evaluated against two cancer cell lines, MCF-7 (breast cancer cell line) and A-549 (lung cancer cell line). The complexes synthesized at 0 °C show enhanced activity against the A549 cell line. Cell cycle analysis, effect on mitochondrial potential, estimation of Reactive Oxygen Species (ROS), effect on peripheral blood mononuclear cells (PBMCs), Tunnel assay, etc., experiments were performed on complex 1A.

Versatile Reactivity of Half-Sandwich Rhodium(III) Iminophosphonamide Complexes.

Novel 18e̅ and 16e̅ pentamethylcyclopentadienyl rhodium(III) complexes [(η5-C5Me5)RhX(NPN)] (1a,b, X = Cl; 2a-c, X = PF6, BAr4F) with chelating zwitterionic iminophosphonamide (NPN) ligands (Ph2P(NR)(NR'); a, R = R' = p-Tol; b, R = p-Tol, R' = Me; c, R = R' = Me) were synthesized and characterized by single-crystal X-ray diffraction. In the 16e̅ complexes 2, the rhodium (Rh) atom is efficiently stabilized by π-donation of unshared N electrons, thus hampering coordination of the external ligands and rendering the 18e̅ complexes labile. Due to low coordination enthalpy, the cationic 18e̅ monocarbonyl and pyridine adducts 2a·L are stable only at low temperatures. At room temperature, 2·CO adducts readily give stable carbonyl-carbamoyl complexes [(η5-C5Me5)Rh(CO){(CO(NR')Ph2P(NR)}]+ (4) formed as a result of CO insertion into the Rh-N bond, thus showing high nucleophilicity of the N atoms in 18e̅ complexes. High basicity of the Na+NPN- precursors caused side deprotonation of the η5-C5Me5 ligand during the synthesis of 1 that yields unstable fulvene Rh(I) complexes [(η4-C5Me4CH2)Rh{Ph2P(NR)(NR')2}] (3a,b). Complex 3a undergoes a facile reaction with isoprene to yield an unusual [(η5:η1-C5Me4(CH2)C(Me)═CHCH2)Rh(NPN)] complex─the first example of intermolecular 1,4-metallacycloaddition of diene to the Rh-fulvene complex.

Electrochemical intercalation of alkali metal – Lewis bases adducts into layered structure of iron chalcogenides

The electrochemical intercalation of alkali metal – pyridine adducts into iron selenide matrix (FeSe0.98) was performed using galvanostatic conditions in two- and three-electrode setup. The system was examined using electrochemical impedance spectroscopy and analyzed with four-elements equivalent circuit, in which solution and charge transfer resistance, double layer capacitance, and Warburg impedance (diffusion) were identified. Charge transfer resistance was found to rise with increasing reaction time. X-ray powder diffraction analysis revealed elongation of the c axis as a result of intercalation and structural transition from primitive to body-centered unit cell in Na-intercalated system. Scanning electron microscopy with X-ray microanalysis, differential scanning calorimetry, and atomic emission spectroscopy confirmed introduction of guest species. Magnetic susceptibility measurements proved paramagnetic character of studied samples, with occurrence of transition to the superconducting state at around 9 ​K, similarly to the value observed in pure FeSe0.98.

Bimolecular Coupling in Olefin Metathesis: Correlating Structure and Decomposition for Leading and Emerging Ruthenium-Carbene Catalysts.

Bimolecular catalyst decomposition is a fundamental, long-standing challenge in olefin metathesis. Emerging ruthenium–cyclic(alkyl)(amino)carbene (CAAC) catalysts, which enable breakthrough advances in productivity and general robustness, are now known to be extraordinarily susceptible to this pathway. The details of the process, however, have hitherto been obscure. The present study provides the first detailed mechanistic insights into the steric and electronic factors that govern bimolecular decomposition. Described is a combined experimental and theoretical study that probes decomposition of the key active species, RuCl2(L)(py)(=CH2) 1 (in which L is the N-heterocyclic carbene (NHC) H2IMes, or a CAAC ligand: the latter vary in the NAr group (NMes, N-2,6-Et2C6H3, or N-2-Me,6-iPrC6H3) and the substituents on the quaternary site flanking the carbene carbon (i.e., CMe2 or CMePh)). The transiently stabilized pyridine adducts 1 were isolated by cryogenic synthesis of the metallacyclobutanes, addition of pyridine, and precipitation. All are shown to decompose via second-order kinetics at −10 °C. The most vulnerable CAAC species, however, decompose more than 1000-fold faster than the H2IMes analogue. Computational studies reveal that the key factor underlying accelerated decomposition of the CAAC derivatives is their stronger trans influence, which weakens the Ru−py bond and increases the transient concentration of the 14-electron methylidene species, RuCl2(L)(=CH2) 2. Fast catalyst initiation, a major design goal in olefin metathesis, thus has the negative consequence of accelerating decomposition. Inhibiting bimolecular decomposition offers major opportunities to transform catalyst productivity and utility, and to realize the outstanding promise of olefin metathesis.

1,3‐Bis(tricyanoborane)imidazoline‐2‐ylidenate Anion—A Ditopic Dianionic N‐Heterocyclic Carbene Ligand

The 1,3‐bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)3−pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H5O2 + salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N‐heterocyclic carbene (NHC), 1,3‐bis(tricyanoborane)imidazoline‐2‐ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)4] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ‐donor and π‐acceptor ability, make NHC 3 a unique and promising ligand and building block.