Synthesis and Reactivity of Me4PCP and Me4POCOP Iridium Complexes

Abstract

This thesis describes new syntheses of Me4PCP and Me4POCOP pincer ligands (R4PCP = 1,3-bis(dialkylphosphinomethyl)-benzene; R4POCOP = 1,3-bis(dialkylphosphinito)-benzene), and the coordination chemistry of the corresponding iridium complexes. Bis(dimethyl)phosphine ligands have been difficult to synthesize because their precursors are expensive or dangerous to obtain. As such, they have not been as extensively studied as the larger R4PCP (R = tBu, iPr) derivatives. Chapter 2 shows that aminophosphines, which can be safely synthesized on large scales, are excellent precursors to bis(dimethyl)phosphine ligands: Me4PCP, Me4POCOP, and DMPE. Iridium complexes of Me4PCP and Me4POCOP show similar and novel reactivity compared to that of larger analogs (R = tBu, iPr). Chapter 3 illustrates the steric environment of (Me4PCP)Ir(CO) through structure and reactivity comparisons. Chapter 4 describes the facile nature of H2 addition to (Me4PCP)Ir(CO) and subsequent isomerization. The nature of this reaction allowed us to investigate the isomerization mechanism and revealed that the isomerization likely proceeds through a CO insertion pathway. Chapter 4 also reports the surprising reactivity of DCM and silver acetate with (Me4PCP)Ir(CO), which likely is facilitated by the ligand’s reduced steric profile.