Intramolecular Arene C–H to C–P Functionalization Mediated by Nickel(II) and Palladium(II)

Abstract

A trisphosphine ligand with a triarylbenzene backbone was employed to support mono-nickel(II) and palladium(II) complexes. Two phosphine arms coordinated to the metal center, while the third phosphine was found to form a C-P bond with dearomatization of the central arene. Deprotonation effected the rearomatization of the central ring and metal reduction from M(II) to M(0). The overall conversion corresponds to a functionalization of an unactivated arene C-H bond to a C-P bond. This transformation represents a rare type of mechanism of C-H functionalization, facilitated by the interactions of the group 10 metal with the arene π-system. This conversion is reminiscent of and expands the scope of recently reported intramolecular rearrangements of biaryl phosphine ligands common in group 10 catalysis.

Metal-ligand cooperation between palladium and a diphosphine ligand with an olefinic backbone

“…38 Examples of ligands containing two phosphines and a  system donor in the same ligand framework were reported. 39,40 Agapie and coworkers described a tris(phosphine) triphenyl benzene ligand that supports a palladium(0) metal center.…”

“…Contrasting compound 2, a smaller P-Pd-P angle is observed (128.78°) due to the increased flexibility of their ligand side arms. 39 In addition, it was reported that 3,5-bis(2phosphinophenyl)-pyridine exhibits less flexibility than the tris(phosphine) triphenyl benzene. 39 The coordination sphere of palladium(0) when supported by 3,5-bis(2-phosphinophenyl)pyridine consists of the two phosphine donors and an η 1 -N interaction to the central pyridine ring.…”

“…39 In addition, it was reported that 3,5-bis(2phosphinophenyl)-pyridine exhibits less flexibility than the tris(phosphine) triphenyl benzene. 39 The coordination sphere of palladium(0) when supported by 3,5-bis(2-phosphinophenyl)pyridine consists of the two phosphine donors and an η 1 -N interaction to the central pyridine ring. Similarly to 2, the P-Pd-P angle is much wider (155.65°) than 120° however, the overall geometry is best described as T shaped in that situation.…”

In situ XAS study of the local structure and oxidation state evolution of palladium in a reduced graphene oxide supported Pd(ii) carbene complex during an undirected C–H acetoxylation reaction

“…11 One possibility is that Pd atoms are pi-bound to a CC double bond and 2.18 Å is a reasonable bond length in such configuration. [31][32][33] Scheme 1 describes the immobilization process based on our understanding.…”

Facile P−C/C−H Bond‐Cleavage Reactivity of Nickel Bis(diphosphine) Complexes

“…[12] In contrast, a-CÀH bond activation of ligands in Ni complexes has not been reported so far,t houghafew examples of a-CÀHd eprotonation by base in Ni complexes have been observed. [13,14] The green color observedi nt he reactiono f1 with dmpbz suggested that an unstable intermediate rapidly converted into 3a,p ossibly influenced by the steric repulsion between tert-butyl groups on P 2 N 2 and methyl groupso nd mpbz in the square-pyramidal coordination geometry of 2a' (structure showni nS cheme 4).…”