Liquid coordination complexes of Lewis acidic metal chlorides: Lewis acidity and insights into speciation

James Hogg, Lucy Brown, Karolina Matuszek, Piotr Latos, Anna Chrobok, Malgorzata Swadzba-Kwasny

Research output: Contribution to journalArticle

10 Citations (Scopus)
130 Downloads (Pure)

Abstract

Coordination complexes of Lewis acidic metal chlorides AlCl3, GaCl3, InCl3, SbCl3, SnCl4, SnCl2, ZnCl2 and TiCl4 with trioctylphosphine (P888) and trioctylphosphine oxide (P888O) 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 P888O–InCl3, with Lewis acidity enhanced compared to chloroindate ionic liquids, and P888O–TiCl4, with hydrolytic stability enhanced with respect to neat TiCl4.
Original languageEnglish
Pages (from-to)2071-2085
JournalDalton Transactions
Volume99
Early online date21 Jul 2017
DOIs
Publication statusEarly online date - 21 Jul 2017

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  • Student Theses

    Ionic Liquids for Main Group Catalysis

    Author: Brown, L., Jul 2020

    Supervisor: Holbrey, J. (Supervisor) & Swadzba-Kwasny, M. (Supervisor)

    Student thesis: Doctoral ThesisDoctor of Philosophy

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