The synthesis of a variety of 2-coordinate aminophosphorus cationic compounds has been previously achieved by several experimental techniques. In this work, the preparation of analogous oxygen substituted species was investigated and the ('31)P NMR data presented. The reaction of the potent metal nucleophile, Fe((eta)('5)-Cp)(CO)(,2)('-), with a wide variety of compounds of the type Cl-P(ER)(,2) (E = O, S, NR) produced a number of interesting complexes including the cis and trans-Fe((eta)('5)-Cp)(CO)(P(ER)(,2))(,2) complexes. ('1)H, ('13)C, and ('31)P NMR spectral data for these compounds are presented. Linear correlations between ('31)P NMR and infrared (nu)(,CO) parameters were observed for the first time and are rationalized in terms of the expected bonding within the complex;An X-ray crystallographic study of the cis and trans isomers of Fe((eta)('5)-Cp)(CO)((mu)-P(OCH(,2)C(Me)(,2)CH(,2)O))(,2)(' )was completed and confirmed the predicted structures. Several interesting structural features are presented and discussed in terms of bonding considerations;From the reaction of the Fe((eta)('5)-Cp)(CO)(,2)('-) anion with ClP(OC(Me)(,2)C(Me)(,2)O),(' )the unique (eta)('4)-cyclopentadiene complex, Fe((eta)('4)-C(,5)H(,6))(CO)(L)(OC)(,3)Fe, was obtained in addition to the cis and trans isomers mentioned above. An X-ray crystallographic investigation of this complex was undertaken and is reported here. The structure confirmed the predicted composition, based upon spectral data, and showed a number of very interesting features including very short P-Fe and very long Fe-Fe and P-P bond distances and large Fe-P-Fe and flap angles. These are rationalized in terms of isovalent hybridization and molecular orbital theories;Synthetic procedures for the preparation, isolation, and purification of chiral trivalent phosphites with the primary chiral site at phosphorus were developed. Three methods for the optical resolution of these complexes were investigated. The first successful separation into enantiomers of a trivalent phosphite was achieved using diastereomeric platinum(II) complexes. These complexes were separated chromatographically followed by the destruction of the complex with cyanide. The free, resolved enantiomers were obtained in purified form by chromatography.