Zhang Shuanming, Pattacini Roberto, Braunstein Pierre, De Cola Luisa, Plummer Edward, Mauro Matteo, Gourlaouen Christophe, Daniel Chantal
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS/UdS), Université de Strasbourg , 4 rue Blaise Pascal, F-67081 Strasbourg, France.
Inorg Chem. 2014 Dec 15;53(24):12739-56. doi: 10.1021/ic501566u. Epub 2014 Nov 24.
New square-planar complexes [Pt(1(-H))2] (2a) [1(-H) = (oxazolin-2-yl)bis(diphenylphosphino)methanide] and [Pd(1(-H))2] (2b), of general formula [M{(Ph2P)2C---C---NCH2CH2O}2] (M = Pt, 2a; M = Pd, 2b), result from deprotonation of 2-{bis(diphenylphosphino)methyl}oxazoline (1) at the PCHP site. The new, functionalized dppm-type ligand 4-{bis(diphenylphosphino)methyl}pyridine, (Ph2P)2CH(4-C5H4N) (4), was prepared by double lithiation and phosphorylation of 4-picoline. In the presence of NEt3, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [Pd(acac)2] (acac = acetylacetonate) afforded [Pt(4(-H))2] (5a) [4(-H) = bis(diphenylphosphino)(pyridin-4-yl)methanide] and [Pd(4(-H))2] (5b), of general formula [M{(Ph2P)2C(4-C5H4N)}2] (M = Pt, 5a; M = Pd, 5b), respectively. In the absence of base, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [PdCl2(NCPh)2] afforded (5a·2HCl) (6a) and (5b·2HCl) (6b), respectively, in which the PCHP proton of 4 has migrated from carbon to nitrogen to give a pyridinium derivative of general formula [M{(Ph2P)2C(4-C5H4NH)}2]Cl2 (M = Pt, 6a; M = Pd, 6b). The complexes 3a, 5a·2MeOH, and 6b·4CH2Cl2 have been structurally characterized by X-ray diffraction. The absorption/emission properties of the Pt(II) complexes 2a and 5a and the Pd(II) complexes 2b and 5b have been investigated by UV-vis spectroscopy and theoretical analysis based on density functional theory. The UV-vis absorption spectra of the neutral complexes recorded in dilute N,N'-dimethylformamide solutions are dominated by intense spin-allowed intraligand transitions in the region below 350 nm. The complexes exhibit charge-transfer bands between 350 and 500 nm. The experimental and theoretical absorption spectra agree qualitatively and point to two low-lying ligand-to-metal charge transfer states that contribute to the bands observed between 350 and 500 nm. The complexes are emissive in frozen solutions at 77 K, in the pure solid state, and when doped into films of poly(methyl methacrylate) but are nonemissive in solution. A red shift is observed when Pt(II) is replaced by Pd(II).
通式为[M{(Ph₂P)₂C---C---NCH₂CH₂O}₂]（M = Pt，2a；M = Pd，2b）的新型平面正方形配合物[Pt(1(-H))₂]（2a）[1(-H) = (恶唑啉-2-基)双(二苯基膦基)甲烷化物]和[Pd(1(-H))₂]（2b），是由2-{双(二苯基膦基)甲基}恶唑啉（1）在PCHP位点去质子化得到的。新型功能化双膦配体4-{双(二苯基膦基)甲基}吡啶，(Ph₂P)₂CH(4-C₅H₄N)（4），是通过4-甲基吡啶的双锂化和磷酸化制备的。在三乙胺存在下，2当量的4与[PtCl₂(NCPh)₂]和[Pd(acac)₂]（acac = 乙酰丙酮）反应，分别得到通式为[M{(Ph₂P)₂C(4-C₅H₄N)}₂]（M = Pt，5a；M = Pd，5b）的[Pt(4(-H))₂]（5a）[4(-H) = 双(二苯基膦基)(吡啶-4-基)甲烷化物]和[Pd(4(-H))₂]（5b）。在无碱条件下，2当量的4与[PtCl₂(NCPh)₂]和[PdCl₂(NCPh)₂]反应，分别得到(5a·2HCl)（6a）和(5b·2HCl)（6b），其中4的PCHP质子从碳迁移到氮，得到通式为[M{(Ph₂P)₂C(4-C₅H₄NH)}₂]Cl₂（M = Pt，6a；M = Pd，6b）的吡啶鎓衍生物。配合物3a、5a·2MeOH和6b·4CH₂Cl₂已通过X射线衍射进行了结构表征。通过紫外可见光谱和基于密度泛函理论的理论分析，研究了Pt(II)配合物2a和5a以及Pd(II)配合物2b和5b的吸收/发射性质。在稀N,N'-二甲基甲酰胺溶液中记录的中性配合物的紫外可见吸收光谱，在350 nm以下区域主要由强烈的自旋允许的配体内跃迁主导。配合物在350至500 nm之间表现出电荷转移带。实验和理论吸收光谱定性一致，表明有两个低能的配体到金属的电荷转移态，它们对在350至500 nm之间观察到的谱带有所贡献。这些配合物在77 K的冷冻溶液、纯固态以及掺杂到聚甲基丙烯酸甲酯薄膜中时会发光，但在溶液中不发光。当用Pd(II)取代Pt(II)时，观察到红移。
