Hogg James M, Brown Lucy C, Matuszek Karolina, Latos Piotr, Chrobok Anna, Swadźba-Kwaśny Małgorzata
School of Chemistry and Chemical Engineering, Queen's University of Belfast, Belfast, BT9 5AG, UK.
Dalton Trans. 2017 Sep 12;46(35):11561-11574. doi: 10.1039/c7dt02408h.
Coordination complexes of Lewis acidic metal chlorides AlCl, GaCl, InCl, SbCl, SnCl, SnCl, ZnCl and TiCl with trioctylphosphine (P) and trioctylphosphine oxide (PO) were synthesised. All compounds formed liquid coordination complexes (LCCs) at ambient temperature, although decomposition via a redox mechanism was detected in some cases. The Lewis acidity of the metal chlorides (measured in 1,2-dichloroethane solutions) and the LCCs (measured neat) was quantified by using the Gutmann acceptor number (AN) approach. In general, LCCs were equally or more Lewis acidic than the corresponding metal chlorides. The AN values were compared with the catalytic activity of selected LCCs in a model Diels-Alder reaction. Insight into speciation of LCCs was gained using multinuclear NMR spectroscopy, revealing that most LCCs comprised charge-neutral complexes rather than ionic ones. The relationship between the speciation, Lewis acidity (AN scale) and catalytic activity is discussed in detail. This approach reveals several new, promising catalytic systems, such as PO-InCl, with Lewis acidity enhanced compared to chloroindate ionic liquids, and PO-TiCl, with hydrolytic stability enhanced with respect to neat TiCl.
合成了路易斯酸性金属氯化物AlCl、GaCl、InCl、SbCl、SnCl、SnCl、ZnCl和TiCl与三辛基膦（P）和三辛基氧化膦（PO）的配位络合物。所有化合物在环境温度下均形成液体配位络合物（LCCs），不过在某些情况下检测到通过氧化还原机制发生了分解。通过使用古特曼受体数（AN）方法对金属氯化物（在1,2 - 二氯乙烷溶液中测量）和LCCs（纯态测量）的路易斯酸度进行了量化。一般来说，LCCs的路易斯酸性与相应的金属氯化物相同或更强。将AN值与选定LCCs在模型狄尔斯 - 阿尔德反应中的催化活性进行了比较。使用多核NMR光谱深入了解了LCCs的物种形成，结果表明大多数LCCs由电荷中性络合物而非离子络合物组成。详细讨论了物种形成、路易斯酸度（AN标度）和催化活性之间的关系。这种方法揭示了几种新的、有前景的催化体系，例如PO - InCl，其路易斯酸性比氯铟酸盐离子液体增强，以及PO - TiCl，其水解稳定性相对于纯TiCl有所提高。
