The Brønsted acidity of the perfluorinated trialkoxysilanol {(F 3 C) 3 CO} 3 SiOH is more than 13 orders of magnitude higher than that of orthosilicic acid, Si(OH) 4 , and even more for most previously known silanols. It is easily deprotonated by simple amines and pyridines to give the conjugate silanolates [OSi{OC(CF 3 ) 3 } 3 ] À , which possess extremely short SiÀ O bonds, comparable to those of silanones.
The perfluorinated alkoxy silanes {(F3C)3CO}3SiH (1) and {(F5C6)3CO}2Si(Cl)H (2) were prepared and fully characterized. Despite the high calculated Brønsted acidities, all attempts to deprotonate 1 and 2 to give the...
Unlike previously known alkoxysilanetriols, polyfluorinated examples of the formula Ar3COSi(OH)3 are resisted towards self-condensation, which is attributed to the stabilizing effect of the polyfluorinated alkoxy groups (Ar = C6F5, 3,5-(CF3)2C6H3).
Herein we investigate sodium, magnesium, zinc, titanium, silver and thallium complexes based on the perfluorinated trityl alcohol (C6F5)3COH (1) with respect to their structural motifs. The coordination compounds were prepared by alkane or salt elimination reactions in non‐polar solvents. XRD analysis revealed a monomeric structure for Ti[OC(C6F5)3]2[OCH(CH3)2]2 (2), dimers for [Mg(OC(C6F5)3)2]2 (3), [Zn(OC(C6F5)3)Et]2 (4) and [Tl(OC(C6F5)3)]2 (5) as well as tetrameric structural motifs for the homoleptic sodium and silver compounds with the general formula [M(OC(C6F5)3)]4: A distorted [NaO]4 cube is observed for [Na(OC(C6F5)3)]4 (6) whereas [Ag(OC(C6F5)3)]4 (7) exhibits a planar [AgO]4 square. Metal fluorine contacts play an important role in all molecular structures presented herein.
The reaction of sodium salts of perfluorinated tertiary alcohols R3COH with SiCl4 provided the di‐substituted dichlorosilanes (R3CO)2SiCl2 (1 a, R=CF3; 1 b, R=C6F5), the hydrolysis of which produced the corresponding silanediols (R3CO)2Si(OH)2 (2 a, R=CF3; 2 b, R=C6F5). Unlike most other dialkoxysilanediols known in the literature, 2 a and 2 b are stable towards self‐condensation at ambient conditions. In a similar way, the related disiloxanes [(R3CO)2SiCl]2O (3 a, R=CF3) and [(R3CO)2Si(OH)]2O (4 a, R=CF3) were prepared.
Compared to all previously known silanols, perfluorinated tris(tert‐butoxy)silanol has dramatically increased Brønsted acidity. It can be easily deprotonated by amines and pyridines, as indicated by the purple “dissolving proton”. The town musicians and the key are symbols of Bremen, the German city where the research was conducted. More information can be found in the Communication by S. Ketkov, S. Grabowsky, E. Hupf, J. Beckmann et al. (DOI: 10.1002/chem.202103177).
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