Unsymmetrical RPNPR′ pincer ligands and their group 10 complexes

Abstract

Two new unsymmetrical (R)PNP(R')-type pincer ligands based on a bis(tolyl)amine framework have been synthesized and characterized by a variety of techniques, including X-ray crystallography. These ligands have been coordinated to Ni, Pd, and Pt precursors to provide a number of well-characterized group 10 halides. Conversion of these metal halides to metal hydrides was accomplished using borohydride reagents, or by direct interaction of the ligand with the zerovalent metal precursor. The insertion of oxygen into these hydrides in an attempt to prepare metal hydroperoxides has been examined; however, we were unable to obtain stable and isolable hydroperoxide species.

Ligand survey results in identification of PNP pincer complexes of iridium as long-lived and chemoselective catalysts for dehydrogenative borylation of terminal alkynes

“…Nonetheless, we were encouraged by the results because the PNP framework offers facile opportunities for optimization of the ligand via substituent variation. We selected previously reported PNP ligands 15-H , 50 16-H , 60 and 17-H 50 , 61 for further testing in DHBTA. The syntheses of the corresponding Ir-COE complexes are depicted in Scheme 4 .…”

Reactions of Pd and Pt Complexes with Molecular Oxygen

“…Kemp, Goldberg, et al also reported that Pd hydrides supported by unsymmetrical Ph 2 PNP R 2 ligands (33 a/b,(2-Ph 2 P(4-methyl-phenyl))(2-R 2 P(4-methylphenyl))amido, Figure 4) can undergo O 2 insertion to form PdÀOOH and PdÀOH moieties. [65] Studies of O 2 insertion into Pd II ÀH bonds in non-pincerligated systems by Stahl et al revealed a different mechanism. [66][67][68][69] In this case, initial reductive elimination of HX from the Pd II hydride complex to generate a Pd 0 species (Scheme 8) is followed by reaction of the Pd 0 with O 2 to form an h 2 -peroxo complex (as described above).…”

“…Unsymmetrical PNP ligands that support PdÀH complexes demonstrating O 2 reactivity. [65] Scheme 8. Formal oxygen insertion into a PdÀH bond by a mechanism involving reductive elimination.…”

“…Kemp, Goldberg, et al. also reported that Pd hydrides supported by unsymmetrical PNP ligands ( 33 a/b ,(2‐Ph 2 P(4‐methyl‐phenyl))(2‐R 2 P(4‐methylphenyl))amido, Figure 4) can undergo O 2 insertion to form PdOOH and PdOH moieties 65…”

Cobalt(ii) and copper(ii) supramolecular networks with a 1-iminoisoindoline asymmetric pincer

“…4 The majority of these compounds have been obtained in direct one-pot reactions in solution; and a few other approaches, such as post-synthetic modication and mechanochemistry, have been recently reported. 11,12 Among N,N,N type pincer ligands, those with symmetric 1,3-bis-(arylimino)isoindoline are investigated in catalytical processes due to simplicity of synthesis, ease of deprotonation, robustness, preferential meridional coordination to metal center and stabilization of its certain valence. 10 Another advantage of the pincer ligands is nowadays their asymmetric structure, hemilability and chirality which are the features required for asymmetric catalysis.…”