The development of catalytic systems is a central area of research in carbon dioxide (CO₂) and epoxy copolymerization. A novel trinuclear cyclohexane-bridged tetradentate Schiff base chromium complex 1 was synthesized as a catalyst for the ring-opening copolymerization (ROCOP) of CO₂ and cyclohexene oxide (CHO), resulting in the formation of poly (cyclohexene carbonate) (PCHC). The impact of polymerization temperature, CO₂ pressure, reaction time, and catalyst loading on complex 1's polymerization activity was systematically investigated. It was observed that, with the addition of the co-catalyst PPNN₃ (PPN = bis(triphenylphosphine)iminium), complex 1 exhibited enhanced catalytic activity for the ROCOP of CO₂ and CHO under mild conditions. In contrast, the mononuclear tetradentate Schiff base chromium complex 2 system showed low activity under the same conditions. Compared to complex 2, complex 1 achieved a higher CHO conversion rate (70%) and 85% PCHC selectivity, with a turnover frequency (TOF) of 419 h⁻¹, which is 5.3 times greater than that of complex 2. Additionally, the polymer produced by complex 1 had a molecular weight of 13 790 g mol⁻¹, which is higher than that produced by complex 2 (8800 g mol⁻¹) and the commercial Salen CrCl catalyst (9610 g mol⁻¹). By varying the amounts of complex 1 and CHO, PCHC with different molecular weights (6000 g mol⁻¹ to 14 000 g mol⁻¹) and low dispersity can be easily obtained. Notably, the activation energy barrier for polycarbonate formation in the complex 1 system was 21.63 kJ mol⁻¹, compared to 32.88 kJ mol⁻¹ in the complex 2 system.

中文翻译：

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二氧化碳和环己烯氧化物通过三核环己烷桥式四齿希夫碱铬络合物催化共聚


催化系统的开发是二氧化碳 （CO₂） 和环氧树脂共聚研究的中心领域。合成了一种新型三核环己烷桥四齿希夫基铬络合物 1 作为 CO₂ 和环己烯氧化物 （CHO） 开环共聚 （ROCOP） 的催化剂，从而形成聚（环己烯碳酸酯）（PCHC）。系统研究了聚合温度、CO₂ 压力、反应时间和催化剂负载对复合物 1 聚合活性的影响。据观察，在添加助催化剂 PPNN₃ （PPN = bis（三苯基膦）亚胺）后，复合物 1 在温和条件下对 CO₂ 和 CHO 的 ROCOP 表现出增强的催化活性。相比之下，单核四齿希夫基铬复合物 2 系统在相同条件下表现出低活性。与复合物 2 相比，复合物 1 实现了更高的 CHO 转化率 （70%） 和 85% 的 PCHC 选择性，周转频率 （TOF） 为 419 ^h-1，是复合物 2 的 5.3 倍。此外，复合物 1 生产的聚合物分子量为 13 790 g ^mol-1，高于复合物 2 （8800 g ^mol-1） 和商用 Salen CrCl 催化剂 （9610 g ^mol-1）。通过改变复合物 1 和 CHO 的量，可以很容易地获得具有不同分子量（6000 g ^mol-1 至 14 000 g ^mol-1）和低分散度的 PCHC。 值得注意的是，在复合物 1 系统中形成聚碳酸酯的活化能势垒为 21.63 kJ ^mol-1，而复合物 2 系统中为 32.88 kJ ^mol-1。