PHOSPHINOCYCLOPENTADIENYL ZIRCONIUM COMPLEXES IN SELECTIVE C-C BOND FORMATION

提出了对配合物（eta5-）的制备和反应研究

It is proposed to prepare and study the reactions of the complexes (eta5- C5H5)(eta5-C5H4P(C6H5)2)ZrXY (X,Y alkyl, halide, alkoxide ligands) as mononuclear complexes with small, unsaturated molecules and then allow these complexes to undergo nucleophilic attack by selected substrates. We expect that these complexes will lead to new methods for the synthesis of ketones, aldehydes, alcohols and amines by appropriate control of the auxiliary ligand X on the Zr atom. The alkyl complexes are quite susceptible to insertion of unsaturated polar molecules such as CO and isonitriles into the Zr-C bond. In previous work, we have observed that the mononuclear complex (eta5-C5H4P(C6H5)2)2Zr(CH3)Cl reacts with CO to form an insertion product which readily undergoes nucleophilic attack intramolecularly by the phosphorus ligand and also by external nucleophiles. The CO bond order is reduced to a single bond by this process and a distorted tetrahedral geometry is found around the C atom which is bound to Zr, O, C and P. The less symmetrical complexes, (eta5- C5H5)(eta5-C5H4P(C6H5)2)ZrXY, will not be able to undergo the intramolecular path and exposes only one face of the tetrahedral geometry (that "trans" to the phosphorus atom) to nucleophilic attach from an external nucleophile. Thus, stereospecificity is possible in the formation of new bonds with the inserted CO; use of a chiral auxiliary group, X, may lead to enantioselectivity in the formation of the product of nucleophilic attack. Other possible products include aldehydes and ketones obtained under non-oxidative conditions and imines (from insertion reactions of isonitriles). The methods developed around this reagent may find use in the preparation of natural products and precursors for therapeutic agents. This project will train students in the physical skills required in synthetic chemistry; the ability to manipulate compounds under inert atmospheres, spectroscopic methods of analyses are among the training they will receive. Intellectually, they will be required to contribute materially to their particular project, from experimental design (design of equipment to selection of appropriate direction of new experiments), to presentation of their results in written and spoken reports (both among their student peers and a professional meetings). These efforts will help them develop both the technical skills and self confidence to succeed in their professions in the health sciences.