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The Bis(pentafluoroethyl)phosphinous Acid (C 2 F 5 ) 2 POH
Author(s) -
Hoge Berthold,
Bader Julia,
Beckers Helmut,
Kim Yong Seol,
Eujen Reint,
Willner Helge,
Ignatiev Nikolai
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801837
Subject(s) - chemistry , yield (engineering) , tautomer , density functional theory , medicinal chemistry , quantum chemical , gas phase , oxide , chloride , nuclear magnetic resonance spectroscopy , computational chemistry , stereochemistry , organic chemistry , molecule , materials science , metallurgy
Phosphinous acid or phosphane oxide? Both tautomers of (C 2 F 5 ) 2 POH (see picture) are found in the neat liquid, whereas only phosphinous acid is present in the gas phase or in solution. The synthesis starting from (C 2 F 5 ) 3 PF 2 , the thermodynamics of the tautomerization, and the detection and thermodynamics of the cis ‐/ trans ‐POH rotamers of the acid are described.The industrial product (C 2 F 5 ) 3 PF 2 is transformed into the phosphinic acid chloride (C 2 F 5 ) 2 P(O)Cl, which reacts with an excess of Bu 3 SnH in a clean, multistep reaction to give the stannyl derivative (C 2 F 5 ) 2 POSnBu 3 . Subsequent treatment with gaseous HBr leads to the formation of (C 2 F 5 ) 2 POH, which is isolated in 70 % yield. Besides (CF 3 ) 2 POH, bis(pentafluoroethyl)phosphinous acid, (C 2 F 5 ) 2 POH, represents the second known example of a phosphinous acid that is predicted by using density functional theory calculations at the B3PW91/6–311G(3d,p) level to be more stable than the phosphane oxide tautomer, the energy difference being 11.7 kJ mol −1 . Only the phosphinous acid isomer is detectable in the gas phase and in solution. However, investigations of the neat liquid reveal a temperature‐dependent tautomeric equilibrium with the phosphane oxide isomer (C 2 F 5 ) 2 P(O)H, which is characterized by vibrational and multinuclear NMR spectroscopic methods in combination with quantum‐chemical calculations.