Department of Chemistry, Loughborough University, Loughborough, UK LE11 3TU.
Dalton Trans. 2010 Aug 14;39(30):7136-46. doi: 10.1039/c0dt00200c. Epub 2010 Jun 24.
The three-step synthesis of new, air-stable, PNN'O-tetradentate ligands 3a x HH-3c x HH by Schiff base condensation of the primary amines 2a-2c with 2-Ph2PC6H4(CHO) in refluxing EtOH is described. The racemic ligand 3d x HH, isolated in 79% yield, was successfully prepared from 2-C6H4(OH){C(O)NHCH2CH(Me)NH2} 2d and 2-Ph2PC6H4(CHO) in absolute EtOH. Upon careful choice of metal precursor, ligands 3a x HH-3d x HH display various coordination modes. Reaction of 3a x HH with AuCl(tht) (1:1 molar ratio) affords AuCl(3a x HH), 4a, in which kappa(1)-P-complexation of the functionalised ligand is observed. In contrast, reaction of 3a x HH (or 3d x HH) with MCl2(cod) (M = Pt, Pd) affords MCl2(3a x HH) (M = Pt, 5a; M = Pd, 5b) or MCl2(3d x HH) (M = Pt, 5c; M = Pd, 5d) in which ligand chelation is achieved using both P and imine N donor atoms. Moreover kappa(2)-P,N-chelation was also observed when 3a x HH-3c x HH were separately allowed to react with [PdCl(eta(3)-C3H5)]2 in CH2Cl2 affording new cationic eta(3)-allyl complexes [Pd(eta(3)-C3H5)(3a x HH-3c x HH)]Cl, 6a-6c. Two neutral (methyl)chloropalladium(II) complexes, 7a/7c, were isolated in high yields from 3a x HH or 3c x HH and Pd(CH3)Cl(cod). Elimination of cod and single methyl protonation from Pt(CH3)2(cod) with 1 equiv. of 3a x HH, 3b x HH or 3d x HH in toluene, at room temperature, afforded square-planar complexes Pt(CH3)(kappa(3)-3a x H/3b x H/3d x H), 8a/8b/8d, containing monoanionic kappa(3)-PNN'-tridentate ligands. The kappa(3)-PNN'-tridentate mode was likewise observed for Pd(CH3)(3a x H/3c x H), 10a/10c, upon treatment of a methanolic solution of Pd(CH3)Cl(3a x HH/3c x HH) with tBuOK. Similarly the monohapto (allyl)Pd(II) compounds Pd(CH2CHCH2)(3a x HH-3c x HH), 9a-9c, were obtained cleanly from 6a-6c and tBuOK via an eta(3)-->eta(1) allyl isomerisation. Both amide and phenolic protons in 5a-5d were smoothly deprotonated, with base, to give the kappa(4)-PNN'O-tetradentate complexes 11a/11b and 11d/11e containing the dianionic ligands 3a(2-)/3d(2-) respectively. The Ni(II) complexes 11c and 11f were synthesised directly from NiCl2 x 6 H2O, 3a x HH (or 3d x 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 x HH, 3c x HH, 4a, 7c, 8a, 8b, 8d and 11a-11d.
三步法合成新的、空气稳定的 PNN'O-四齿配体 3a x HH-3c x HH，通过在回流的 EtOH 中用 2-Ph2PC6H4(CHO)与仲胺 2a-2c 的席夫碱缩合来实现。外消旋配体 3d x HH，收率为 79%，成功地由 2-C6H4(OH){C(O)NHCH2CH(Me)NH2} 2d 和 2-Ph2PC6H4(CHO)在绝对 EtOH 中制备。通过仔细选择金属前体，配体 3a x HH-3d x HH 显示出各种配位模式。3a x HH 与 AuCl(tht)（1:1 摩尔比）反应得到 AuCl(3a x HH)，4a，其中观察到功能化配体的 kappa(1)-P-络合。相比之下，3a x HH（或 3d x HH）与 MCl2(cod)（M = Pt，Pd）反应得到 MCl2(3a x HH)（M = Pt，5a；M = Pd，5b）或 MCl2(3d x HH)（M = Pt，5c；M = Pd，5d），其中配体螯合使用 P 和亚胺 N 供体原子。此外，当 3a x HH-3c x HH 分别与[PdCl(eta(3)-C3H5)]2 在 CH2Cl2 中反应时，也观察到 kappa(2)-P，N-螯合，得到新的阳离子 eta(3)-烯丙基配合物[Pd(eta(3)-C3H5)(3a x HH-3c x HH)]Cl，6a-6c。从 3a x HH 或 3c x HH 和 Pd(CH3)Cl(cod) 以高产率分离出两种中性（甲基）氯化钯（II）配合物 7a/7c。用 1 当量的 3a x HH、3b x HH 或 3d x HH 在室温下用甲苯处理 Pt(CH3)2(cod)和 cod 的单甲基质子化，得到含有单阴离子 kappa(3)-PNN'-三齿配体的正方形平面配合物 Pt(CH3)(kappa(3)-3a x H/3b x H/3d x H)，8a/8b/8d。当用 tBuOK 处理 Pd(CH3)Cl(3a x HH/3c x HH)的甲醇溶液时，也观察到 Pd(CH3)(3a x H/3c x)的 kappa(3)-PNN'-三齿模式 10a/10c。类似地，通过 6a-6c 和 tBuOK 之间的 eta(3)-->eta(1) 烯丙基异构化，得到了纯的单膦基（烯丙基）Pd(II)化合物 Pd(CH2CHCH2)(3a x HH-3c x HH)，9a-9c。5a-5d 中的酰胺和酚质子都能在碱的作用下顺利脱质子，得到含有二阴离子配体 3a(2-)/3d(2-)的 kappa(4)-PNN'O-四齿配合物 11a/11b 和 11d/11e。Ni(II)配合物 11c 和 11f 直接由 NiCl2 x 6 H2O、3a x HH（或 3d x HH）和 tBuOK 在 CH3OH 中合成。所有新化合物均通过多核 NMR、FT-IR、质谱和微量分析进行了表征。对化合物 3a x HH、3c x HH、4a、7c、8a、8b、8d 和 11a-11d 进行了单晶 X 射线研究。
