Copolymerisation of Propylene Oxide and Carbon Dioxide by Dinuclear Cobalt Porphyrins

Abstract

Two dinuclear cobalt porphyrins comprising different structural tethering motifs at the porphyrin periphery were synthesised, along with a representative mononuclear cobalt porphyrin, and their catalytic activities tested towards carbon dioxide–propylene oxide copolymerisation in the presence of bis(triphenylphosphoranyl)ammonium chloride cocatalyst. The catalytic activities of the mononuclear and the bis‐para‐tethered dinuclear cobalt porphyrin with selective formation of poly(propylene carbonate) are largely comparable, showing no benefit of dinuclearity in contrast to the case of cobalt salen complexes and suggesting that polymer growth proceeds exclusively from one metal centre. The alternative bis‐ortho‐tethered porphyrin demonstrated considerably reduced activity, with dominant formation of cyclic propylene carbonate, as a result of hindered substrate approach at the metal centre. Time‐resolved UV/Vis spectroscopic studies suggested a general intolerance of the cobalt(III) porphyrin catalysts towards the copolymerisation conditions in the absence of carbon dioxide pressure, leading to catalytically inactive cobalt(II) species. In the presence of carbon dioxide, the bis‐ortho‐tethered catalyst showed the fastest deactivation, which is related to an unfavourable steric arrangement of the linker fragment, as was also confirmed by NMR spectroscopic measurements.

The Antioxidant Properties of Asymmetrically Substituted Tetra(meso-aryl)porphyrins with One Phenolic Substituent: The Contribution of Phenol and Porphyrin Fragments to Antioxidant Activity

“…В спектрах ЯМР 1 Н порфиринов 7 и 8 присутствуют сигналы порфи-ринового фрагмента (H β -пиррольных и внутрицикличе-ских NH-протонов) и ароматических заместителей, при-чем соотношение интегральных интенсивностей сиг-налов протонов порфиринового фрагмента и сигналов протонов фенольного фрагмента соответствует одному фенольному фрагменту в молекуле. Строение описанных ранее порфиринов 1-6 подтверждено сопоставлением их спектральных (UV-Vis, ЯМР, масс) характеристик с данными известными из литературы: [23][24][25][26][27] порфирины 1-6 соответствуют заявленной структуре. Спектральные характеристики неописанных ранее порфиринов 7 и 8 аналогичны известным порфиринам 1-6.…”

Dinuclear Metal Complex-Mediated Formation of CO2-Based Polycarbonates

“…As discussed earlier, in many cases, the rationale for these studies is that two metal centres held in close proximity to one another have shown better activity than monometallic counterparts [33,63,77,79,84,85,[141][142][143].…”

“…Moreover, the utilisation of a cocatalyst was found to be essential. One explanation for the poor performance of the bimetallic catalyst is that catalyst deactivation, by reduction of cobalt(III) to cobalt(II), appears faster in the case 18 [143,159]. …”

Porphyrins as nanoreactors in the carbon dioxide capture and conversion: a review

“…98 9Cobalt bis-porphyrins along with a mono-nuclear cobalt porphyrin have been synthesized and used10 as catalysts for carbon dioxide-propylene oxide copolymerization, showing that the copolymerization 11 was effective in the presence of bis(triphenylphosphoranyl) ammonium chloride cocatalyst 141. 98 9Cobalt bis-porphyrins along with a mono-nuclear cobalt porphyrin have been synthesized and used10 as catalysts for carbon dioxide-propylene oxide copolymerization, showing that the copolymerization 11 was effective in the presence of bis(triphenylphosphoranyl) ammonium chloride cocatalyst 141.…”