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Exploration of 2-aminophenol and 1,2-phenylenediamine ligands in hypervalent phosphorus(V) chemistry

University of British Columbia

Phosphoranes P(OC₆H₄NR)₂(OC₆H₄NHR) [R = Me (2.2a), Ph (2.2b), C6F5 (2.2c)] were synthesized by treating PCl5 with the respective 2–aminophenol derivative (2.1a–c, 3.1 equiv). In one instance, an intermediate species, P(OC₆H₄NR)₂Cl [R = Me (2.3a)], was isolated and structurally characterized. Deprotonation of the amine moieties (–NHR) in phosphoranes 2.2a and 2.2b with a strong alkali–metal base (e.g. n–BuLi) in the presence of a strong–donor solvent (e.g. THF) afforded salts composed of the hexacoordinate P(V)–anions [P(OC₆H₄NR)₃]– (R = Me, [2.4a]– ; Ph, [2.4b]–). Employing precursor 2.2a, the salt Li(THF)₃fac–[2.4a] was isolated. The X–ray crystal of each enantiomer was determined and, to our knowledge, represents the first structurally characterized example of a salt containing a hexacoordinate P(V)N₃O₃ anion featuring P(V)–N bonds. Efforts have also been made to synthesize analogous hypervalent P(V)–derivatives with 1,2–phenylenediamine ligands. Following the synthetic methodology to prepare phosphoranes 2.2a, 2.2b and 2.2c, preliminary investigations with three symmetrical 1,2–phenylenediamine derivatives (3.1a–c) were conducted. No evidence for the formation of five– or six–coordinate product was observed. Instead, an interesting phosphonium cation featuring a four–coordinate phosphorus(V) moiety was isolated as a chloride salt, P(OC₆H₄NR)₂Cl [R = Me (3.2b)], which was characterized spectroscopically.

Text

2019-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/65662

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/