Coordination of Carbonyl and Carboxyl Oxygen Atoms with Phosphorus in the Presence of Hydrogen Bonding. P−O Donor Action

A series of phosphorus compounds 1−5 containing carbonyl or carboxyl groups was obtained and subjected to
X-ray analysis. Syntheses of the phosphoranes 1 and 5 were effected by oxidation reactions using potassium
permaganate, while the phosphine oxide 2 was obtained by oxidation with hydrogen peroxide. The readily available
phosphines 3 and 4 were included in the study. The structures revealed that P−O coordination occurred for 1−3
in the presence of extensive hydrogen bonding and led to trigonal bipyramidal geometries. A similar structure
was observed for 4 in the absence of hydrogen bonding. 31P chemical shifts indicate retention of the basic
coordination geometries in solution. Consideration of the chirality of the phosphoranes 1 and 5 leads to a pair of
mirror images that are possible in solution but exist in preferred isomeric forms in the crystalline state. Evaluation
of the energies of two competing bonding types indicated a range for P−O coordination above and below the
hydrogen bond energy. The results suggest that phosphoryl transfer enzyme mechanisms should benefit by taking
into account donor interactions to phosphorus by residues at active sites in addition to the inclusion of hydrogen
bonding interactions.