Novel unsymmetrical PCP′ pincer ligands and their palladium(II) complexes

Missing link: PCP pincer ligands containing P–N bonds and their Pd complexes

“…A more recent modification is the bis(phosphinite) PCP ligands (B) in which the phosphine donor arms are connected to the central aromatic ring via O links [3b,3c,4a]. A mixed PCP ligand with one CH 2 and one O link has also been synthesized [7]. Conspicuously missing from this array are PCP ligands in which the phosphine donor arms are connected to the central aromatic ring via NH or NR linkers.…”

Synthesis of a new class of unsymmetrical PCP′ pincer ligands and their palladium (II) complexes: X-ray structure determination of PdCl{C6H3-2-CH2PPh2-6-CH2PBut2}

“…As expected, compound 10 exhibits the same behavior in the 31 P{ 1 H} NMR spectra as that observed for ligand 7, presenting two different singlets, one at À9.46 ppm due to the PPh 2 substituent and the other displaced to lower field due to the presence of the PPr i 2 moiety at 10.68 ppm. Table 2 Selected bond distances (Å ) and angles (°) for PdCl{C 6 H 3 -2-CH 2 PPh 2 -6-CH 2 PBu t 2 } (11) Bond lengths (Å ) Angles (°)…”

“…The resulting reaction mixture was set to reflux for 5 h. The solution was filtered over a short pad of silica gel and the solvent evaporated under vacuum. Recrystalization of the crude product from CH 2 Cl 2 /hexane resulted in the quantitative formation of a colorless microcrystalline solid (1.11 g, 1.93 mmol, 70% (11) Crystalline yellow prisms of 11 grown by slow diffusion from a CH 3 Cl/MeOH solvent system; were glued to a glass fiber. The X-ray intensity data was measured at 293 K on a Bruker SMART APEX CCD-based X-ray diffractometer system equipped with a Mo-target X-ray tube (k = 0.71073 Å ).…”

“…PCP pincer ligands with anthryl backbones, as seen in Scheme 1b, and their metal complexes were recently prepared in an effort to generate pincer complexes of even greater thermal stability [3]. In order to elucidate structure-activity relationships, we have synthesized the first examples PCP pincer ligands of the following types: symmetrical bis-phosphinito (Scheme 2a) [6,7]; unsymmetrical bis-phosphinito (Scheme 2b) [10]; and hybrid phosphinito-phosphino (Scheme 2c and d) [11]. We have explored the reactivity of the palladium and 0022-328X/$ -see front matter Ó 2004 Elsevier B.V. All rights reserved.…”

Molecular‐Weight‐Enlarged Multiple‐Pincer Ligands: Synthesis and Application in Palladium‐Catalyzed Allylic Substitution Reactions

“…[30,31] In this respect, PCP-allyl complexes are usually synthesized by refluxing the corresponding metal precursor with a ligand in, for example, toluene or acetonitrile. [13,32,33] Catalytic Investigations: Batch Reactions PCP complexes have shown good to excellent activities in the palladium-catalyzed Heck and Suzuki couplings, [34,35] hydroamination, [36] ruthenium-catalyzed transfer hydrogenation, [37] and iridium-catalyzed dehydrogenation. [38] We were interested in the application of the supported phosphine ligands 13-15 in the palladium-catalyzed allylic alkylation [39] and in the allylic amination reaction.…”