A spirocyclic tetraoxyphosphorane with an apically located chlorine in a trigonal bipyramid and its hydrolysis product

Abstract

The spirocyclic (chloro)tetraoxyphosphorane CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(Cl)(1,2-O₂C₆Cl₄) (2) and its hydrolysis product CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)(OC₆Cl₄-2-OH) (3) have been synthesized and characterized by X-ray crystallography and solution state NMR. Unlike the previously reported spirocyclic chlorophosphoranes where chlorine occupies an equatorial position of a trigonal bipyramid (TBP), in 2 it is apical. The hydrolysis product 3 is a hydrogen bonded dimer. Compound CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(Cl)[1,2-O₂-3,5-(t-Bu)₂C₆H₂] (4) was also synthesized in a manner analogous to that of 2. Attempts to isolate structurally characterizable pentacoordinate compounds by reacting CH₂(6-t-Bu-4-Me-C₆H₂O)₂PX [X=Cl (1), 2,6-Cl₂C₆H₃O (5), cycl-C₆H₁₁NH (6)] with N-chlorodiisopropylamine were not successful, although in some cases a pentacoordinate species was detected; the corresponding oxidized products CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)X [X=Cl (7), 2,6-Cl₂C₆H₃O (8), cycl-C₆H₁₁NH (9)] were isolated by this route. Variable temperature (¹H, ³¹P) NMR spectra of 2 have been recorded; at low temperatures, two ³¹P NMR signals of unequal intensity are seen in the pentacoordinate region. A probable intramolecular process involving equatorial-equatorial↔apical<->equatorial (for the eight-membered ring) has been invoked to explain the spectral features.