Effect of 2‐Bromopyridine Ancillary Ligand in the Catalysis of Pd(II)‐NNN Pincer Complexes towards Suzuki‐Miyaura Cross‐Coupling Reaction

Abstract

Pd(II)‐NNN pincer complexes containing sterically hindered 2‐bromopyridine (sp2 hybridized N donor) as ancillary ligand have been synthesized in order to compare their catalytic efficiency with the reported analogous complexes containing acetonitrile (sp hybridized N donor) ancillary ligand. The complexes have been characterized by analytical and spectroscopic techniques. Single crystal XRD reveals distorted square planar structure of complex 1. These complexes have been investigated as catalysts for the Suzuki‐Miyaura cross‐coupling (SMC) reaction. The scope is extended using various substituted aromatic/aliphatic halides. The activity of the Pd(II)‐NNN pincer complexes bearing bulky 2‐bromopyridine ancillary ligand is not higher compared to that of the complexes with acetonitrile ancillary ligand, which shows superiority of acetonitrile ancillary ligand.

Palladium nanoparticles-anchored dual-responsive SBA-15-PNIPAM/PMAA nanoreactor: a novel heterogeneous catalyst for a green Suzuki–Miyaura cross-coupling reaction

“…41 In the experiments conducted to understand the steric effect exerted by different electronwithdrawing groups, p-bromobenzaldehyde was consumed exceptionally well and gave excellent conversion compared to mbromo and o-bromobenzaldehyde (Table 2, entries 7-9). 42 To study the mechanistic pathway, the combined effect of SBA-15, PdNPs, and the stimuli-responsive polymers is Scheme 3 The proposed mechanism for the SMC reaction. explained by a plausible route, demonstrated in Scheme 3, based on the above results and from the literature reports.…”

Pd(II)‐NNN Pincer Complexes for Catalyzing Transfer Hydrogenation of Ketones

“…The other bond lengths and angles were within the reported ranges (Table 1). [6,7,19] Scheme 1. Synthesis of the NNN pincer ligand (L1) and its Pd(II) complex (1).…”

“…The need for catalysis has been neverending, and many metals have stood out in this area, particularly the precious metals like Ru, Rh, Pd, etc. [2][3][4][5][6][7] Interestingly, Pd has progressively evolved as a popular metal catalyst for hydrogenation. Pd-catalyzed hydrogenation reaction is one of the most noteworthy methodologies in organic synthesis; Pd/C being the extensively used catalyst in pharmaceutical industries.…”

“…[16][17][18] Further, complexes with CH 3 CN ancillary ligand have already been known as superior catalysts in many reactions. [6,7,[19][20][21][22] These facts encouraged us to give special attention towards Pd pincer complexes bearing acetonitrile ancillary ligand for catalytic applications. In the present report, we discuss the results of our investigations on the use of Pd(II)-NNN pincer complexes as catalysts for TH of ketones.…”

“…Throughout the literature, metal catalysts have had a significant impact from both academic and industrial viewpoints. The need for catalysis has been never‐ending, and many metals have stood out in this area, particularly the precious metals like Ru, Rh, Pd, etc [2–7] …”