I. New Routes to the Synthesis of Chelating Phosphines for Use in Hydroformylation Catalysis. II. Organometallic Complexes of Convex Hydrocarbons.
Date of Award
Doctor of Philosophy (PhD)
George G. Stanley
The focus of the research done to date has been directed at the modification of the ligand system, et-ph-P4, (Et2P(CH2)2P(Ph)CH 2P(Ph)(CH2)2PEt2) primarily to replace the phenyl groups on the internal phosphorus atoms with various alkyl groups. This would effectively tailor the electron density donated to the rhodium centers and control access to the metal's olefin binding site during hydroformylation catalysis. By changing the organic substituents on the phosphorus atoms, the donor/acceptor properties of the ligand can also be adjusted to optimize binding to the metal. In order to customize our ligand to meet this requirement many routes towards the alkylation of phosphines were explored before a breakthrough allowed us to obtain almost quantitative alkyl substitutions. We have developed a zinc modified route which provides an effective one pot synthesis for the aryl or alkyl halo- or dihalophosphines. With this procedure the halo- and dihalophosphines can be synthesized quantitatively and with stoichiometric control. The organozinc route is not limited to alkyl or aryl groups with large steric bulk as noted in the literature synthesis of halo and dihalophosphines using other organometallic reagents. We have also directed our efforts towards the synthesis of halogenated bisphosphines. Our efforts have resulted in reproducible success in the synthesis of bis(dichlorophosphino)methane starting with aluminum foil and dichloromethane. However, the isolation of the desired bisphosphine is complicated, tedious, and gives low yields. Attempts at improving the isolatable yields by using POCl3 by itself and in conjunction with other reagents to complex aluminum trichloride have had little or no success. The best result obtained involves the use of Na3PO4 as a complexing agent for AlCl3. The use of the polynuclear aromatic hydrocarbons with convex surfaces as ligands for transition metal complexes has not been accomplished yet. Our organometallic efforts are directed at exploring the coordination chemistry of these aromatics with a variety of mono- and polymetallic transition metal centers. Although a number of metals belonging to the early, middle and late transition series did show modest to excellent coordination with corannulene, the complex itself was never isolated.
Misquitta, Barry J., "I. New Routes to the Synthesis of Chelating Phosphines for Use in Hydroformylation Catalysis. II. Organometallic Complexes of Convex Hydrocarbons." (2000). LSU Historical Dissertations and Theses. 7213.