Role of Wingtip Substituents on Benzene-Platform-Based Tetrapodal Ligands toward the Formation of a Self-Assembled Silver Carbene Cage

N-Heterocyclic carbenes and their precursors in functionalised porous materials

Though N-heterocyclic carbenes (NHCs) have emerged as diverse and powerful discrete functional molecules in pharmaceutics, nanotechnology, and catalysis over decades, the heterogenization of NHCs and their precursors for broader applications in porous materials, like metal-organic frameworks (MOFs), porous coordination polymers (PCPs), covalent-organic frameworks (COFs), porous organic polymers (POPs), and porous organometallic cages (POMCs) was not extensively studied until the last ten years. By de novo or post-synthetic modification (PSM) methods, myriads of NHCs and their precursors containing building blocks were designed and integrated into MOFs, PCPs, COFs, POPs and POMCs to form various structures and porosities. Functionalisation with NHCs and their precursors significantly expands the scope of the potential applications of porous materials by tuning the pore surface chemical/physical properties, providing active sites for binding guest molecules and substrates and realizing recyclability. In this review, we summarise and discuss the recent progress on the synthetic methods, structural features, and promising applications of NHCs and their precursors in functionalised porous materials. At the end, a brief perspective on the encouraging future prospects and challenges in this contemporary field is presented. This review will serve as a guide for researchers to design and synthesize more novel porous materials functionalised with NHCs and their precursors.

Self-Assembly of Benzimidazole-Derived Tris-NHC Ligands and AgI -Ions to Hexanuclear Organometallic Cages and Their Unusual Transmetalation Chemistry

Multi-ligand self-assembly to attain the Ag^I -N-heterocyclic carbene (NHC)-built hexanuclear organometallic cages of composition [Ag₆ (3 a,b)₄ ](PF₆ )₆ from the reaction of benzimidazole-derived tris(azolium) salts [H₃ -3 a,b](PF₆ )₃ with Ag₂ O was achieved. The molecular structures of the cages were established by X-ray diffraction studies along with NMR and MS analyses. The existence of a single assembly in solution was supported by diffusion-ordered spectroscopy (DOSY) ¹ H NMR spectra. Further, transmetalation reactions of these self-assembled complexes, [Ag₆ (3 a,b)₄ ](PF₆ )₆ , with Cu^I /Au^I -ions provided various coinage metal-NHC complexes having diverse molecular compositions, which included the first example of a hexanuclear Cu^I -dodecacarbene complex, [Cu₆ (3 b)₄ ](PF₆ )₆ .

Diverse Architectures and Luminescence Properties of Group 11 Complexes Containing Pyrimidine-Based Phosphine, N-((Diphenylphosphine)methyl)pyrimidin-2-amine

In this article, the synthesis, structural studies, and luminescence properties of Cu^I, Ag^I, and Au^I complexes of pyrimidine-based phosphine [C₄H₃N₂-2-NH(CH₂PPh₂)] (1) are described. The reactions of 1 with CuX led to the isolation of one-dimensional (1D) chain, tetranuclear ladder, or cyclic derivatives. The structural features of these complexes are greatly influenced by the metal-to-ligand ratio, reaction conditions, and CuX (X = Cl, Br or I) employed. In the case of CuCl and CuBr, one-dimensional coordination polymers [{CuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (2) and [{CuBr}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (3) were obtained, whereas CuI afforded tetracopper complex [{CuI}₄{C₄H₃N₂-2-NH(CH₂PPh₂)}₂(NCCH₃)₂] (4) having Cu₄ ladder structure supported by P∩N-bridging coordination of 1. The reaction of 1 with AgOTf yielded unprecedented one-dimensional chain structure [{AgOTf}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (5), whereas the reaction with AgBF₄ produced a 12-membered dinuclear complex, [{Ag}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂[BF₄]₂ (6), with each silver atom having a linear geometry. Gold complex [{AuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂ (7) was synthesized by reacting 1 with [AuCl(SMe₂)]. Compounds 2-4 were also prepared using a pestle and mortar by grinding method in almost quantitative yield. Complex 4 with a Cu···Cu distance of 2.828(5) Å shows high luminescence due to the nonbonded metal···metal interactions.

Synthesis and structural characterization of metal complexes with macrocyclic tetracarbene ligands

Fourteen Ag(i), Au(i), Ni(ii), Pd(ii) and Pt(ii) complexes were prepared with macrocyclic tetradentate N-heterocyclic carbene (NHC) ligands.

Structural diversities in Ag(i) complexes of xylyl platform based isomeric bis-NHC ligands: effects of pyridine wingtip substituents

In an infinite ID polymeric structure, Ag(i) atoms are arranged linearly in a xylyl platform based tetra-dentate bis-NHC ligand.

Structures of NHC Hg(ii) and Ag(i) complexes and selective recognition of nitrate anion

Eight N-heterocyclic carbene Hg(ii) and Ag(i) complexes were prepared, and the selective recognition of nitrate anion was studied.

Structural diversity of late transition metal complexes with flexible tetra-NHC ligands

Silver complexes with flexible tetra-NHC ligands were used as transmetalation agent to access a series of d-block metal complexes.

Breuil PA, Olivier-Bourbigou H, Braunstein P. Synthesis and characterization of oxygen-functionalised-NHC silver(i) complexes and NHC transmetallation to nickel(ii)

New silver(i) complexes bearing alcohol- or ether-functionalized NHCs were synthesized and characterized by X-ray diffraction. Their NHC transmetallation ability was assessed and gave rise to a Ni(ii) bis(NHC) complex in the case of the ether-functionalisation.