Highly Active Multidentate Alkyne Metathesis Catalysts: Ligand‐Activity Relationship and Their Applications in Efficient Synthesis of Porphyrin‐Based Aryleneethynylene Polymers

Abstract

A series of tris(arylmethyl)ammoniumcoordinated molybdenum(VI) propylidyne catalysts was synthesized. Such N-quarternized multidentate catalysts showed high robustness, strong resistance to small alkyne polymerization and significantly enhanced catalytic activity compared to their corresponding tris(arylmethyl)amine-based analogues. The high activity of these new catalysts also enabled the efficient synthesis of ethynylene-bridged porphyrin-based arylene ethynylene polymers via alkyne metathesis, which represents a highly efficient, defect-free, viable approach for the synthesis of this class of intriguing polymers.

Synthesis of a conjugated porous Co(ii) porphyrinylene–ethynylene framework through alkyne metathesis and its catalytic activity study

“…[46][47][48] was used as the catalyst in the alkyne metathesis polymerization of M1. The monomer 5,10,15,20-tetrakis(4 0 -propynylphenyl)porphyrin Co(II) 1 (M1) was synthesized in one step from the commercially available 5,10,15,20-tetrakis(4 0 -bromophenyl)porphyrin Co(II) through the Negishi cross-coupling reaction (Scheme 1).…”

High Oxidation State Molybdenum N‐Heterocyclic Carbene Alkylidyne Complexes: Synthesis, Mechanistic Studies, and Reactivity

“…Current state‐of‐the‐art catalysts containing fluorinated alkoxides, silanolates, amides, iminato ligands or multidentate ligands were developed by the groups of Schrock, Fürstner, Tamm, Zhang, Fischer, Veige, Moore and Nuckolls (e.g., compounds I – III , Figure ). These catalysts found widespread application in advanced organic synthesis, polymer chemistry and materials science . Advanced applications require tailor‐made catalysts to improve stability, handling and/or reactivity.…”

Highly Active Multidentate Ligand‐Based Alkyne Metathesis Catalysts

“…Recently, our group has developed a series of molybdenum(VI) alkylidyne catalysts consisting of multidentate phenolic ligands, which can shut down the undesired polymerization of small alkyne byproduct . The key feature of our design is the trigonal pyramid geometry of the multidentate ligands.…”

“…The proposed structures of active species are shown in Figure ( 3 a , 3 b ). We found the coordination of central nitrogen to molybdenum(VI) significantly decreases the catalytic activity of such complex as a result of lower Lewis acidity of the molybdenum center . To prevent such coordination, we developed analogous ligands with non‐coordinating silicon at the center ( 4 a – c ) .…”

“…Recently,o ur group hasd eveloped as eries of molybdenum-(VI) alkylidyne catalysts consisting of multidentate phenolic ligands,w hich can shut down the undesired polymerization of small alkyne byproduct. [42][43][44] The key feature of our design is the trigonal pyramid geometry of the multidentate ligands. The single crystal X-ray structure of ap henoxide-bridged molydenumd imer obtained from the mixture of Mo VI propylidyne precursor 1 and tris(2-hydroxybenzyl)amine 2a shows that all three phenolic oxygens and the central nitrogen of ligand 2a bind with the molybdenumc enter.…”