Towards Weakly Coordinating Anions with the Extremely Electron Withdrawing Perfluoropyridinoxy Ligand –OC5F4N. Issue 1 (21st November 2018)

• Record Type: Journal Article
• Authors: Riddlestone, Ian M.; Keller, Sarah; Kirschenmann, Florian; Schorpp, Marcel; Krossing, Ingo
• Is Part Of: European journal of inorganic chemistry. Issue 1(2019)
• Page Start: 59
• Page End: 67
• Publication Date: 2018-11-21
• Subjects: Weakly coordinating anions -- Lewis acids -- Aluminum -- Anions -- Borates; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201801136
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The extreme electron withdrawing properties of the perfluoropyridinoxy ligand –OC5 F4 N were used for the preparation of new (weakly) coordinating borate and aluminate anions of the type [E(OC5 F4 N)4 ] – (E = B or Al). These new anions are based on the potent parent Lewis acids E(OC5 F4 N)3, which possess exceptionally high calculated fluoride ion affinities (FIAs) of 500 and 587 kJ mol –1 for E = B and Al respectively. For aluminum, this extreme Lewis acidity dominates the chemistry and from mixtures of the neutral polymeric Lewis acid [Al(OC5 F4 N)3 ] n, the five‐ and six‐coordinate complexes Al(OC5 F4 N)3 (OEt2 )2 (1 ) and [Al(OC5 F4 N)2 (µ‐OC5 F4 N) (NCMe)2 ]2 (2 ) were crystallized upon addition of ether or MeCN. The aluminate salts M[Al(OC5 F4 N)4 ] (M = Li or K) were prepared from the reaction between the alcohol 4‐HO–C5 F4 N and either LiAlH4 or K[AlEt4 ] respectively. The aluminate anion [Al(OC5 F4 N)4 ] – remains Lewis acidic coordinating small donor molecules forming [Al(OC5 F4 N)4 (L)] – (L = THF or NMe3 ) and even supports formation and structural characterisation of the aluminum dianion containing salt [Na(OEt2 )2 ][Na][Al(OC5 F4 N)5 ] (8 ). The from NaBH4 and 4‐HO–C5 F4 N accessible borate salt Na[B(OC5 F4 N)4 ] shows increased kinetic stability in comparison to the aluminum analogue. Abstract : Very electron withdrawing …! Perfluoropyridinoxy ligands (–OC5 F4 N) possess extreme electron withdrawing properties that have been used to prepare (weakly) coordinating anions based on the Lewis superacids E(OC5 F4 N)3 (E = B or Al). The –OC5 F4 N ligand supports formation of neutral 5‐ and six‐coordinate aluminum species, a Lewis acidic aluminate anion, and even an aluminum dianion!