Die Oxidation von Triisopropylphosphan mit Iod: Zur Rolle von trockenem und feuchtem Lösungsmittel

Oxidation of Triisopropylphosphane with Iodine: The Role of Dry or Moist Solvent i‐Pr₃P ( 1 ) and iodine give i‐Pr₃PI₂ ( 2 ). In crystals obtained from CH₂Cl₂ solution, ion pairs i‐Pr₃PI⁺I^–] of 2 exhibiting I…I interactions are linked by CH₂Cl₂ molecules. With a second equivalent of iodine, i‐Pr₃PI⁺ I₃^– ( 3 ) is formed; the reaction of 2 with AgSbF₆ provides i‐Pr₃PI⁺SbF₆^– ( 6 ). The presence of moisture and air leads to the formation of i‐Pr₃POH⁺ salts. Solid i‐Pr₃POH⁺I^– ( 4 ) exhibits P–O–H…I cation‐anion contacts, solid (i‐Pr₃PO)₂H⁺I₃^– ( 5 ) contains a centrosymmetric P=O…H…O=P‐bridged cation. Distinguishing i‐Pr₃PI⁺ salts 2 , 3 from hydrolysis products 4 , 5 by ³¹P‐NMR in reaction mixtures is not trivial, because both kinds of cations exihibit similar ³¹P‐NMR shifts and both participate in interactions with their anions, and in equilibria with uncharged donors: rapid I⁺ transfer reactions and I…I soft‐soft interactions involving 1 , and rapid H⁺ transfer reactions and hydrogen bonds involving i‐Pr₃P=O ( 7 ).