Investigation of P-H, O-H, and Si-H Oxidative Addition Involving Group 9 Metal PSiP Complexes

Abstract

Group 9 transition metal pincer complexes have shown remarkable reactivity with respect to E-H (E = main group element) bond activation chemistry. In this context, this research focuses on developing new Ir and Rh complexes supported by bis(phosphino)silyl ligands of the type[K3-(2-Cy2PC6H4)2SiMe]- (Cy-PSiP). A prominent feature of this ligand is the presence of a highly trans-labilizing and electron donating silyl group located at the central anionic position. These properties may allow for the stabilization of reactive, coordinatively unsaturated compounds. This document details the synthesis of neutral and cationic (Cy-PSiP)M (M = Ir, Rh) complexes, and their application towards E-H bond oxidative addition (E = P, O, and Si) reactions. With the goal of observing E-H bond oxidative addition mediated by the (Cy-PSiP)M system, considerable progress has been made in isolating unusual monomeric phosphido-hydride, alkoxy-hydride, and silyl-hydride species. In particular, several examples of successful Ir-mediated P-H, O-H and Si-H bond oxidative addition were demonstrated. Furthermore, phosphido-hydride species showed interesting reactivity in subsequent E-H bond activation featuring alkynes, hydrosilanes, and H2. Migratory insertions of CO2 and isocyanates involving alkoxy-hydride complexes were also observed. Efforts were undertaken to generate silylene species (Cy-PSiP)Ir(H)(=SiR2) from complexes of the type (Cy-PSiP)Ir(H)(SiRR’) (R = H, Cl; R’ = Ph, Mes). While such silylene species remain elusive, a better understanding of the behaviour of Ir-silyl complexes was garnered. Lastly, syntheses of cationic MIII complexes of the type [(Cy-PSiP)MR]+X- (M = Ir, Rh, R = H, Me; X = OTf, BF4, B(C6F5)4) were explored. Challenges were encountered, associated with either the reactivity or the stability of the synthesized complexes. The inclusion of a neutral L donor resulting in complexes of the type [(Cy-PSiP)MRL]+X- (L = PMe3) afforded increased stability, allowing for the isolation of Ir-methyl cations.