Phosphoranes Containing P-H Bonds

Abstract

In an attempt to prepare o-dialkylphosphino-substituted benzoic acids we have discovered a unique cyclization process which affords phosphoranes containing P-H bonds. In this reaction the expected P(III) compound is not produced, but rather a phosphorane is formed by the internal oxidative addition of the carboxylic group to the substituted phosphine. Multi-nuclear NMR can yield a great deal of information about the exact structures of these compounds in solution. Characterization of the solid phase by DSC shows that the cyclic species formed can ring-open to yield the corresponding 8-P-3 phosphines. The P-H bond in these cyclic 10-P-5 complexes can be deprotonated using base to produce the o-dialkylphosphino-substituted benzoates rather than phosphoranides. These anions can chelate to metal ions, particularly nickel, to form highly active catalysts for the oligomerization of olefins. Use of these compounds as ligands to produce highly linear a-olefins will be discussed.

Key Words:

• phosphorane
• oligomerization
• apical P-H bond
• catalysis
• nickel chelate