Grømer Bendik, Saito Susumu
Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Chikusa, Nagoya 464-8602, Japan.
Inorg Chem. 2023 Aug 28;62(34):14116-14123. doi: 10.1021/acs.inorgchem.3c02412. Epub 2023 Aug 17.
Despite receiving significant attention, well-defined homogeneous complexes for hydrogenation of carbon dioxide (CO) to methanol (MeOH) are scarce and suffer issues of low catalyst turnover numbers (TONs) at high catalyst concentrations and deactivation in the presence of CO and at elevated temperatures. Herein, we disclose a system deploying sterically demanded (PNNP)Ir complexes for a sustained activity for hydrogenation of CO to MeOH at temperatures ∼200 °C in an alcohol solvent. Through reaction optimization, we achieved a TON of ∼9000 for MeOH formation, which exceeds most active homogeneous systems reported to date, and robustness on par with or exceeding most reactive systems utilizing amine additives was demonstrated. The key to achieving sustained catalyst turnover for the system was utilizing a catalytic amount of an alkali base additive, which serves the dual purpose of facilitating more efficient outer-sphere reduction of CO and HCOEt and enhancing the selectivity of MeOH over in situ formed CO.
尽管受到了广泛关注，但用于将二氧化碳（CO）氢化为甲醇（MeOH）的结构明确的均相配合物却很稀少，并且存在在高催化剂浓度下催化剂周转数（TONs）较低以及在CO存在和高温下失活的问题。在此，我们公开了一种使用空间位阻较大的（PNNP）Ir配合物的体系，该体系在醇类溶剂中于约200°C的温度下对CO氢化为MeOH具有持续活性。通过反应优化，我们实现了甲醇生成的TON约为9000，这超过了迄今为止报道的大多数活性均相体系，并且证明了其与使用胺添加剂的大多数活性体系相当或更高的稳定性。该体系实现持续催化剂周转的关键是使用催化量的碱添加剂，其具有促进CO和HCOEt更有效的外层还原以及提高甲醇相对于原位形成的CO的选择性这两个双重目的。
