1243220-87-2Relevant academic research and scientific papers
Flexible κ4-PNN′O-tetradentate ligands: Synthesis, complexation and structural studies
Durran, Sean E.,Elsegood, Mark R. J.,Hammond, Shelly R.,Smith, Martin B.
, p. 7136 - 7146 (2010)
The three-step synthesis of new, air-stable, PNN′O-tetradentate ligands 3a·HH-3c·HH by Schiff base condensation of the 1°amines 2a-2c with 2-Ph2PC6H4(CHO) in refluxing EtOH is described. The racemic ligand 3d·HH, isolated in 79% yield, was successfully prepared from 2-C6H4(OH){C(O) NHCH2CH(Me)NH2} 2d and 2-Ph2PC 6H4(CHO) in absolute EtOH. Upon careful choice of metal precursor, ligands 3a·HH-3d·HH display various coordination modes. Reaction of 3a·HH with AuCl(tht) (1:1 molar ratio) affords AuCl(3a·HH), 4a, in which κ1-P-complexation of the functionalised ligand is observed. In contrast, reaction of 3a·HH (or 3d·HH) with MCl2(cod) (M = Pt, Pd) affords MCl 2(3a·HH) (M = Pt, 5a; M = Pd, 5b) or MCl 2(3d·HH) (M = Pt, 5c; M = Pd, 5d) in which ligand chelation is achieved using both P and imine N donor atoms. Moreover κ2-P, N-chelation was also observed when 3a·HH-3c·HH were separately allowed to react with [PdCl(η3-C3H5)] 2 in CH2Cl2 affording new cationic η3-allyl complexes [Pd(η3-C3H 5)(3a·HH-3c·HH)]Cl, 6a-6c. Two neutral (methyl)chloropalladium(ii) complexes, 7a/7c, were isolated in high yields from 3a·HH or 3c·HH and Pd(CH3)Cl(cod). Elimination of cod and single methyl protonation from Pt(CH3)2(cod) with 1 equiv. of 3a·HH, 3b·HH or 3d·HH in toluene, at room temperature, afforded square-planar complexes Pt(CH3) (κ3-3a·H/3b·H/3d·H), 8a/8b/8d, containing monoanionic κ3-PNN′-tridentate ligands. The κ3-PNN′-tridentate mode was likewise observed for Pd(CH3)(3a·H/3c·H), 10a/10c, upon treatment of a methanolic solution of Pd(CH3)Cl(3a·HH/3c·HH) with tBuOK. Similarly the monohapto (allyl)PdII compounds Pd(CH2CHCH2)(3a·HH-3c·HH), 9a-9c, were obtained cleanly from 6a-6c and tBuOK via an η 3→η1 allyl isomerisation. Both amide and phenolic protons in 5a-5d were smoothly deprotonated, with base, to give the κ4-PNN′O-tetradentate complexes 11a/11b and 11d/11e containing the dianionic ligands 3a2-/3d2- respectively. The NiII complexes 11c and 11f were synthesised directly from NiCl2·6H2O, 3a·HH (or 3d·HH) and tBuOK in CH3OH. All new compounds were characterised by multinuclear NMR, FT-IR, mass spectrometry and microanalysis. Single crystal X-ray studies have been undertaken on the compounds 3a·HH, 3c·HH, 4a, 7c, 8a, 8b, 8d and 11a-11d. The Royal Society of Chemistry 2010.
