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 phosphorane s 1 and 5 were effected by oxidation reactions using potassium permaganate, while the phosphine oxide 2 was obtained by oxidation with hydrogen peroxi de. The readily available phosphines 3 and 4 were included in the study. Th e structures revealed that P-O coordination occurred for 1-3 in the presenc e of extensive hydrogen bonding and led to trigonal bipyramidal geometries. A similar structure was observed for 4 in the absence of hydrogen bonding. P-31 chemical shifts indicate retention of the basic coordination geometri es in solution. Consideration of the chirality of the phosphoranes I 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 energ ies of two competing bonding types indicated a range for P-O coordination a bove and below the hydrogen bond energy. The results suggest that phosphory l transfer enzyme mechanisms should benefit by taking into account donor in teractions to phosphorus by residues at active sites-in addition to the inc lusion of hydrogen bonding interactions.