¹H NMR Direct Observation of Enantiomeric Exchange in Palladium(II) and Platinum(II) Complexes ContainingN,N‘ Bidentate Aryl-pyridin-2-ylmethyl-amine Ligands

Abstract

The complexes [MCl(2)(kappa2-N approximately N')] (N approximately N' = 2-C(5)H(4)N-CH2-NHAr; Ar = 4-MeC(6)H(4), a; 2,6-Me(2)C(6)H(3), b; 4-MeOC(6)H(4), c; 4-CF(3)C(6)H(4), d; M = Pd, 1a-d; Pt, 2a-d) have been prepared and fully stereochemically characterized both in the solid state and in solution. Their behavior in DMSO-d6 solution is dependent on the substituents of the aryl group and on the metal. Complexes of palladium with substituents at the para position (1a, 1c, 1d) display a dynamic 1H NMR pattern when the solutions are heated. An enantiomeric exchange Slambda/Rdelta is suggested to explain such behavior. On the basis of the calculated negative DeltaS values, an associative mechanism involving the solvent is proposed. Under the same conditions, analogous complexes of platinum (2a, 2c, 2d) proved to be unstable, and release of the N approximately N' ligand was observed. Complexes 1b and 2b show temperature-variable 1H NMR spectra without any evidence accounting for enantiomeric exchange or decoordination. DFT calculations on models of 1a and 1b show that diastereomeric exchange Sdelta/Slambda is a process where the complex with the higher sterical hindrance, 1b, has a lower energy barrier.

Palladium(II) complexes of quinolinylaminophosphonates: Synthesis, structural characterization, antitumor and antimicrobial activity

“…S3). The chelate ring geometries observed in the similar chelate dichloride palladium(II) complexes with α-aminomethylpyridin-2-yl derivatives were analogous to ones described in this work [48][49][50][51]. Two symmetrically independent molecules of complex 1 are connected by the π-π interactions of quinoline rings (Table S1, Fig.…”

Isomeric Preference in Complexes of Palladium(II) with Chelating P,N‐Donor Ligands

“…planarity of the six-membered chelating ring gives rise to twist-boat (δ/λ) [22] chirality in the molecule. [23][24][25][26][27][28][29][30] Taking into account this source of chirality, it is possible to propose two enantiomers for these complexes. …”

Synthesis, Spectral Characterization and Biological Screening of Potentially Active 1, 3-Diones and its Transition Metal Complexes

“…There is continue interest in synthesizing 1, 3-diones 4(L A -L B ) and its metal complexes 5(a-e) because of their potential applications, applied sciences and importance area of coordination chemistry [18][19][20][21] . The synthesized ligands and its transition metal complexes have been screened for in vitro antibacterial activity against S. aureus, B. subtilis, E. coli and P. aeruginosacompared with tetracycline and chloramphenicol as standard drugs.…”