Date of Award
Doctor of Philosophy (PhD)
George G. Stanley
The purpose of this project was to build upon previous results obtained with the ligand Et$\sb2$PCH$\sb2$CH$\sb2$P(Ph)CH$\sb2$P(Ph)CH$\sb2$CH$\sb2$PEt$ \sb2$, (hereafter referred to as et,ph-P4). The ligand was designed to both bridge and chelate two metal centers to hold them in close proximity so that cooperativity between the two metals is possible in homogeneous catalysis. This project concentrated on the synthesis of new bimetallic complexes using this ligand and the investigation of their catalytic potential. A highly regioselective bimetallic hydroformylation catalyst racemic- (Rh$\sb2$(nbd)$\sb2$(et,ph-P4)) 2BF$\sb4$ was previously synthesized in our laboratories. Structure reactivity studies were undertaken to prove our theory that the high linear to branched regioselectivity of this catalyst is due to cooperativity between the two metals. A study of the addition of non-coordinating nitrogen bases was performed to see if the undesirable side reactions of alkene isomerization and hydrogenation could be minimized. A new synthetic route to the catalyst racemic- (Rh$\sb2$(nbd)$\sb2$(et,ph-P4)) 2BF$\sb4$ was found to increase the yield of isolated catalyst from 40% to 70%. Three other bimetallic complexes were synthesized: PdCl$\sb2$(et,ph-P4), racemic- (Ir$\sb2$(cod)$\sb2$(et,ph-P4) 2BF$\sb4$, and racemic- (Ru$\sb2$Cl$\sb4$(cod)$\sb2$(et,ph-P4)). All three were tested for catalytic activity. The racemic form of the ligand et,ph-P4 was separated into the (R,R) and (S,S) enantiomers with a semi-prep Chiralcel OD chiral HPLC column. Those ligands were used to make chiral bimetallic hydroformylation catalysts. The chiral catalysts were used to hydroformylate vinyl acetate to 2-acetoxypropanal. Enantioselectivities of $\sim$85% were obtained. The % ee was determined by GC using a Chiraldex $\beta$-TA GC column.
Broussard, Melanie Eilleen, "Bimetallic Hydroformylation Catalysis." (1993). LSU Historical Dissertations and Theses. 5616.