Main‐Chain Organometallic Microporous Polymers Bearing Triphenylene–Tris(N‐Heterocyclic Carbene)–Gold Species: Catalytic Properties

Abstract

Two triphenylene‐based tris(N‐heterocyclic carbene)–gold–acetylide main‐chain organometallic microporous polymers (MOMPs) were obtained and fully characterized. Both materials show spherical shapes, and their size is highly dependent on the type of acetylene used in the synthetic protocol. The new solids were tested in the catalytic reduction of nitroarenes with NaBH4 and in the three‐component Strecker reaction for the synthesis of α‐aminonitriles, and showed high activity in both processes. Whereas the activity of the solids in the reduction of nitroarenes may be attributed to the formation of Au nanoparticles due to the use of NaBH4 as reducing agent, the activity in the Strecker reaction may originate from the Lewis acidic activation of the ketone or imine on coordination to Au.

A D3h-symmetry hexaazatriphenylene-tris-N-heterocyclic carbene ligand and its coordination to iridium and gold: preliminary catalytic studies

“…6a The same tris-NHC ligand was also used as scaffold for the preparation of main-chain organometallic polymers, therefore also showing potential to afford three-dimensional structures. 7 Prompted by these precedents, we became interested in merging the properties associated with planar and rigid tris-NHC ligands with the presence of a HAT core. We thought that the introduction of HAT into a tris-NHC core should provide interesting properties, given the electrondeficient character of this molecule compared to the electronrich triphenylene (Chart 1).…”

Single‐Step Synthesis of Organometallic Molecular Squares from NR,NR′,NR′′,NR′′′‐Substituted Benzobiscarbenes

“…Recently,N -heterocyclic carbenes (NHCs) [7] have emergeda sanew class of ligands for the preparationo fm etallosupramolecular structures such as dinuclearm olecular rectangles, [8] molecular cylinders, [9] and organometallic polymers. [10]…”

“…Recently,N -heterocyclic carbenes (NHCs) [7] have emergeda sanew class of ligands for the preparationo fm etallosupramolecular structures such as dinuclearm olecular rectangles, [8] molecular cylinders, [9] and organometallic polymers. [10] Amongt he coordination-driven supramolecular architectures, molecular squares are the moste xtensively studied derivatives startingw ith the pioneering work by Fujitae tal. on the synthesis of molecular squares by the self-assembly of end-capped Pd II complexes and 4,4'-bipyridine building blocks.…”

Metal compounds with rigid polyaromatic ligands. Catalytic consequences

“…12,85 Most of the efforts for tuning the electronic properties of NHC ligands are based on changing the substituents on the N, C4 and C5 atoms, as well as in the nature C4-C5 bridge (I, Chart 1.3). 76,81,[86][87][88][89] A very interesting example of the modification of the electron donating properties of a NHC ligand was described by…”

“…44,45,[85][86][87][88][89] Junto con estos bis(carbenos) lineales, una serie de tris(carbenos) con un core de naturaleza rígida y con simetría D 3h , han sido descritos recientemente (Esquema 7.16). 45,88,98,99 El primer tris(NHC) de este tipo fue descrito por Bielawski en 2010 y es un derivado de tripticeno (5), más recientemente nuestro grupo describió dos tris(NHC); uno basado en trifenileno (6) y el otro tribenzotriquinaceno (7). Basados en lo anteriormente dicho, y en la experiencia del grupo de investigación en desarrollar nuevos ligandos NHC politópicos con sistemas poliaromáticos, decidimos preparar dos nuevos ligandos NHC (Esquema 7.17); uno tipo Janus (H) y uno con forma de "estrella" (I), ambos incorporan sistemas poliaromáticos más extendidos que los anteriormente descritos.…”