Structural and chemical relationships in metal phosphine complexes relevant to homogeneous catalysis

The aim of this research work was to improve the fundamental understanding of the role selected tertiary bicyclic and conventional phosphine ligands play in modified cobalt-catalyzed hydroformylation. Selected bicyclic ligands were synthesized by radical addition of 1-alkenes to the 2° phosphines shown in Figure 1 (see in full text PDF). The following ligands were synthesized in this way: Phoban-Q (Q = CH2CH3 (C2), (CH2)4CH3 (Cs), (CH2)3N(CH3)2 (C3NMe2), Lim-Cs, VCH-Cs and PA-Cs. Phoban-Cy was made from the reaction between a diene and a 1° phosphine, H2PCy, with a radical initiator at 100°C. the second set ranging from PnBu3 to the Lim family with hydrogenation ranging from 9 - 15% respectively. Crystal structures of the cobalt dimers of the following ligands; Phoban[3.3.1]-C21 Phoban[3.3.1]-C5, Phoban[3.3.1]-C3NMe2, Phoban[3.3.1]-Cy, PA-C5, PCy3, and PCp3 were obtained and characterised by X-ray crystallography. A series of [Rh(acac)(CO)(P-Ph)] complexes where P-Ph = Phoban[3.3.1]-Ph, Phoban[4.2.1]-Ph, a mixture of 4R, 8S- and 4S, 8S-Lim-Ph, a mixture of VCH[3.3.1]-Ph and VCH[3.2.2]-Ph and PA-Ph were successfully synthesized and characterised by NMR and IR spectrophotometers. The crystal structures of [Rh(acac)(CO)(4R, BS-Lim-Ph)] and [Rh(acac)(CO)(PA-Ph)] were obtained and characterised by X-ray crystallography. The oxidative addition and CO-insertion reactions of the rhodium complexes of these ligands were carried out and the results indicate that the Lim-Ph systems were the most active among the bicyclic ligands included in the study. The general reactivity trend for the oxidative addition was found to be: 4S, 8S-Lim-Ph > 4R, 8S-Lim-Ph > VCH-Ph > Phoban[3.3.1]-Ph > Phoban[4.2.1]Ph> PPh3 - PCy3 >PA-Ph. The overall reactivity trend for the CO-insertion reaction was determined as 4S, 8S-Lim-Ph > 4R, 8S-Lim-Ph > Phoban[4.2.1]-Ph > VCH-Ph > Phoban[3.3.1]-Ph > PA-Ph.