Efficient and stereoselective synthesis of monomeric and bimetallic pincer complexes containing Pd-bonded stereogenic carbons

Abstract

Optically-pure aliphatic N–C(sp3)–E Pd pincer complexes with C-stereogenic centers were synthesized via stepwise (1) enantioselective catalytic hydrophosphination, (2) P(iii) → P(v) oxidation and (3) diastereoselective C(sp3)–H activation.

Divergent Reactivity of Phosphapalladacycles toward E–H (E = N, P, As) Bonds

“…Chemical shifts are reported in ppm and referenced to an internal SiMe 4 standard (0 ppm) for 1 H NMR, chloroform-d (77.23 ppm) for 13 C NMR, and external 85% H 3 PO 4 for 31 P{ 1 H} NMR. The complexes 1b, 22 1c, 22 2b, 23 3b, 23 5 21 and 6 21 were prepared according to literature methods. All other reactants and reagents were used as supplied.…”

“…20 These structurally rigid chelate complexes were resistant to decomplexation by phosphines even under catalytic conditions. 21 However, HAsPh 2 rapidly afforded preligands 5′ and 6′ after 30 min at room temperature (Scheme 8). No undesirable/uncontrolled fragmentation to the ligand backbone was observed for this quantitative transformation.…”

Design, synthesis and applications of chiral functionalized phosphapalladacycles

“…[112][113][114] The chiral tridentate phosphine cyclometal pincer 53, 54, and 57 were synthesized through sequential bihydrophosphination and metalation. [113][114][115][116][117] The yields of the bihydrophosphination were almost full conversion > 99%, and the dr for most of the ligands were better than 95:5. After the P-H addition completed, the cyclometallation was conducted via treatment the free ligands with appropriate metal source directly.…”

“…After the sulfurization or oxidation of the air-sensitive free phosphine ligand, the metalation formed the complex 56, because the two five-membered ring was much more preferred. 113 In the case of the compounds 59 and 60, it is difficult to get the PCP pincer even if there were two phosphine atoms. Because of the position of the two P-atoms, it is impossible to form the pincer complexes bearing five-membered ring.…”

“…Because of the position of the two P-atoms, it is impossible to form the pincer complexes bearing five-membered ring. 113 In this case, the PCN pincer complexes were formed after the coordination of nitrogen atom in the pyridyl group to the metal.…”