Three Fluorinated Trityl Alcohols and their Lithium Salts – Synthesis, Molecular Structures, and Acidity

Abstract

The fluorinated trityl alcohols (C 6 F 5 ) 3 COH, (C 6 H 2 F 3 ) 3 COH and (C 6 (CF 3 ) 2 H 3 ) 3 COH were prepared in good to excellent yields by one-step procedures. These alcohols and their lithium salts were fully characterized by NMR and IR spectroscopy, mass spectrometry and XRD analysis. The molecular [a]

Strengths of Acids in Acetonitrile

“…The origin of the compounds published by us earlier, as well as the pK a measurement methods, can be found from the following references: [5,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The most comprehensive method description is given in ref [5].…”

Metal Complexes of the Perfluorinated Trityl Alkoxide [(C6F5)3CO]−

“…In total, each magnesium atom is coordinated by three oxygen and three fluorine atoms (Mg⋅⋅⋅F distances between 2.166(2) and 2.742(2) Å). Dimers with [M 2 O 2 ] squares were also found for the Et 2 O and THF adducts of [(C 6 F 5 ) 3 COLi ⋅ 2Solv] 2 : Therein, bridging alcoholates are revealed and the lithium atoms are additionally coordinated by the neutral solvent donors in the terminal positions [7] …”

“…A tetrameric cube‐like structure similar to [Na(OC(C 6 F 5 ) 3 )] 4 was reported for the adduct free [Li(OC(CF 3 ) 3 )] 4 after crystallization from the weak donor solvent 1,2‐difluorobenzene [13] . Recently we described the crystal structures of the lithium salts of (C 6 F 5 ) 3 COH and two related polyfluorinated trityl alcohols (C 6 H 2 F 3 ) 3 COH and (C 6 (CF 3 ) 2 H 3 ) 3 COH in the presence of donor molecules: [((C 6 F 5 ) 3 CO)Li(THF)] 2 , [((C 6 F 5 ) 3 CO)Li(Et 2 O)] 2 , [((C 6 F 3 H 2 ) 3 CO) 2 Li 2 (THF) 3 ] and [((C 6 (CF 3 ) 2 H 3 ) 3 CO)Li(MeCN) 2 ] 2 form dimers with a [M 2 D 2 ] (D=O or N) square as a common structural motif [7] …”

“…A new synthetic procedure from C 6 F 5 MgBr and decafluorobenzophenone was reported by Delany et al [6] . and we also published a synthesis protocol to obtain (C 6 F 5 ) 3 COH in high yields [7] . The perfluorinated trityl alcohol stands out due to the high steric demand of the C(C 6 F 5 ) 3 backbone and the fifteen fluorine atoms attached to the aryl substituents provide an increased acidity compared to non‐fluorinated alcohols.…”

“…Next to the oxygen donor, the ligand's fluorine atoms can serve as extra donor sites for the formation of metal fluorine contacts as interesting coordination modes [8] . However, rapid decomposition in polar solvents has been found for deprotonated (C 6 F 5 ) 3 COH: A solution of its lithium salt in THF or MeCN rapidly turns yellow, probably as a consequence of a nucleophilic attack at the para ‐position of the C 6 F 5 substituents [7] . This lability could also occur for other coordination compounds of the ligand (C 6 F 5 ) 3 COH preventing broad characterization in solution.…”