Developing The Methods For Preparation Of Phosphinines And Their Derivatives

This dissertation which is divided into five chapters mainly expounds the research on developing the methods for preparation of phosphinines and their derivatives.In chapter one, it demonstrates the electronic properties and structural characteristics of phosphinines, and also summarizes the synthetic methods, coordination chemistry and applications of phosphinines and their derivatives.In chapter two, it describes a new versatile route for the conversion of phospholes into phosphinines. Phosphinines have long been regarded as "chemical curiosities". As a result of their aromaticity, phosphinines play a central role in phosphorus heterocyclic chemistry. Furthermore, since the demonstration of their extraordinary efficiency as ligands in the rhodium-catalyzed hydroformylation of olefins, the need for new versatile synthetic methods that allow the tuning of their electronic and steric properties becomes even more evident. So, we developed an efficient route to convert phospholes into phosphinines, which involved a key step of concerted extrusion of formaldehyde. This opens up the possibility to use the broad and versatile phosphole chemistry as a starting point for an equally broad variety of phosphinines.In chapter three, it illustrates the potential of the structural core of2-iodo-l-phosphanorbornadiene derivative which is a novel universal precursor to synthesize functionalized phosphinines. Although some different methods have been developed to build the structure of phosphinine in the past several decades, the direct functionalization of preformed phosphinine rings is still a synthetic challenge of phosphorus heterocyclic chemistry. In order to enrich its creativity of the new access to phosphinines from phospholes, we devised a novel approach to a-functionalized phosphinines, which is especially of high efficency for the introduction of donor-substituents. The key intermediate2-iodo-l-phosphanorbornadiene derivative was chosen not only the core of the target compound, but also the suitable linker for introducing and constructing new molecular fragment by Pd(0)-catalyzed Stille cross-coupling reaction. Using this new method, a variety of functionalized substituent ranging from aryl, alkynyl to heteroaryl can be successfully introduced to the a-position of the phosphinine structure, and it is noteworthy that the first phosphininyl-triazol mixed ligand was also successfully synthesized by this way. Additionally, via the exchange of tributyltin substituent with chloride, the heterogeneous reaction of2-tributyltin-l-phosphanorbornadiene derivative with CuCl2promoted by Pd(OAc)2provided an interesting access to a-chloro phosphinine whose P-Mo(CO)5complex was unambiguously confirmed by X-ray crystal structure analysis.In chapter four, three new representative phosphorus ligands based on the phosphinine skeleton were designed and synthesized. Phosphinines play a key role in the development of modern ligand system for a range of homogenous catalytic reactions. While their potential as ligands in homogeneous catalysis still remains largely unexplored. So, there are continuous requirements for the design and synthesis of new phospha-containing ligands based on the phosphinine skeleton. As it is known that the chelate effect is an essential feature especially for the stabilization of metal complexes in higher oxidation states, preventing otherwise fast ligand dissociation from the metal center. The combination of "soft" and "hard" donor-sites within the same molecule (hybrid ligand) leads to electronically different binding sites in the corresponding metal complexes, which can influence significantly their reactivities and selectivities in catalytic reactions. From the above considerations, three new P, P and P, N ligands based on the phosphinine backbone were designed and synthesized. These are (1) bis[2-(2-phosphininyl)phenyl] ether;(2) P, P bidentate ligand of2-(2-diphenylphosphino)phenylphosphinine;(3) P, N bidentate chiral ligand based on phosphinine backbone containing chiral oxazoline moiety. And preliminary coordination properties of these species with metal center were investigated also.In chapter five, a phospha-Wittig route to5-phosphaphenanthrene was introduced.5-Phosphaphenanthrenes which represent one of the most significant phosphinine derivatives are still a very poorly studied class of compounds in spite of their interesting structure. We investigated a new approach to5-phosphaphenanthrene based on the phospha-Wittig reaction. The reaction of tributylphosphane with a7-(2’-formyl-2-biphenylyl)phosphanorbornadiene P-W(CO)5complex leads to the5-phosphaphenanthrene P-W(CO)5complex via an intramolecular phospha-Wittig condensation. This complex is stable enough for detection by31P NMR spectroscopy but cannot be isolated due to its high reactivity. It is trapped by addition of MeOH or cycloaddition with2,3-dimethylbutadiene or a nitrileimine. The adducts were characterized by X-ray crystal structure analysis. In doing so, we highlight the phosphaalkene character of these species.