Abstract The synthesis of tris(ortho‐carboranyl)borane (BoCb3), a single site neutral Lewis superacid, in one pot from commercially available materials is achieved. The high fluoride ion affinity (FIA) confirms its classification as a Lewis superacid and the Gutmann‐Beckett method as well as adducts with Lewis bases indicate stronger Lewis acidity over the widely used fluorinated aryl boranes. The electron withdrawing effect ofortho‐carborane and lack of pi‐delocalization of the LUMO rationalize the unusually high Lewis acidity. Catalytic studies indicate that BoCb3is a superior catalyst for promoting C−F bond functionalization reactions than tris(pentafluorophenyl)borane [B(C6F5)3].
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Tuning the formal potential of ferrocyanide over a 2.1 V range
We report the synthesis and characterization of homoleptic borane adducts of hexacyanoferrate( ii ). Borane coordination blueshifts d–d transitions and CN IR and Raman frequencies. Control over redox properties is established with respect to borane Lewis acidity, reflected in peak anodic potential shifts per borane of +250 mV for BPh 3 and +350 mV for B(C 6 F 5 ) 3 . Electron transfer from [Fe(CN-B(C 6 F 5 ) 3 ) 6 ] 4− to photogenerated [Ru(2,2′-bipyridine) 3 ] 3+ is very rapid, consistent with voltammetry data. Coordination by Lewis acids provides an avenue for selective modification of the electronic structures and electrochemical properties of cyanometalates.
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- PAR ID:
- 10087337
- Date Published:
- Journal Name:
- Chemical Science
- ISSN:
- 2041-6520
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The synthesis and catalytic reactivity of a class of water-tolerant cationic phosphorus-based Lewis acids is reported. Corrole-based phosphorus( v ) cations of the type [ArP(cor)][B(C 6 F 5 ) 4 ] (Ar = C 6 H 5 , 3,5-(CF 3 ) 2 C 6 H 3 ; cor = 5,10,15-(C 6 H 5 ) 3 corrolato 3− , 5,10,15-(C 6 F 5 ) 3 corrolato 3− ) were synthesized and characterized by NMR and X-ray diffraction. The visible electronic absorption spectra of these cationic phosphacorroles depend strongly on the coordination environment at phosphorus, and their Lewis acidities are quantified by spectrophotometric titrations. DFT analyses establish that the character of the P-acceptor orbital comprises P–N antibonding interactions in the basal plane of the phosphacorrole. Consequently, the cationic phosphacorroles display unprecedented stability to water and alcohols while remaining highly active and robust Lewis acid catalysts for carbonyl hydrosilylation, C sp3 –H bond functionalization, and carbohydrate deoxygenation reactions.more » « less
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