Group 3 metal complexes of radical-anionic 2,2'-bipyridyl ligands

A new method for generating group 3 metal complexes containing radical-anionic 2,2'-bipyridyl (bipy) ligands is described that relies on hydrogen-atom abstraction from dearomatized biheterocyclic complexes. This method does not involve electron transfer to neutral 2,2'-bipyridyl or salt metathesis between the lithium salt of the 2,2'-bipyridyl radical anion and group 3 metal halides. The new metal complexes were characterized by single-crystal X-ray diffraction, electron paramagnetic resonance, and absorption spectroscopy. Density functional theory (DFT) calculations were used to probe the electronic structure of these compounds. All these methods support the radical-anionic character of bipy in all bipy compounds presented.     

硅桥连双环戊二烯基ⅣB族金属二氯化物的反应

研究了标题化合物[(Me~2Si)~n(C~5H~4)~2MCl~2, n=1,2,3;M=Ti, Zr, Hf]与酚的反应, 水解反应以及与卤素的相互置换反应。结果表明, 由于硅桥的不同它们表现出不同的反应活性。通过这些反应制备了十种新化合物, 用元素分析, 'H NMR 以及质谱鉴定了它们的结构。     

Reactions of group IVB metal dihalides with η1-allyl complexes of η5-cyclopentadienyldicarbonyliron

The reactions of tin(II) chloride in tetrahydrofuran with the η¹-allyl systems, [η⁵-Cp(CO)₂Fe allyll, have been reexamined, and an extension made to SnBr₂ and GeCl₂.dioxan. The insertion compounds, [η⁵-Cp(CO)₂FeMX₂ allyl], which contain the Group IVB element bound to iron, are the major products, but, in the presence of excess metal dihalide, these slowly react to form the trihalometal compounds [η⁵-Cp(CO)₂FeMX₃]. The insertion reactions are inhibited by small amounts of a radical scavenger, and occur initially with allylic rearrangement. In methanol, the process is more complex; an unknown species, possibly an iron-olefin dipolar intermediate, and substantial amounts of trihalometal-iron compounds are formed additionally. A mechanistic scheme for the processes is discussed.     

Phosphorescence of lyophilized complexes between cyclodextrins andβ-arylpropiophenones

-Arylpropiophenones do not phosphoresce in homogeneous solution as a result of excited state quenching by the -aryl group. In the presence of cyclodextrins the parent substrate, -phenylpropiophenone, shows readily detectable phosphorescence. The complexes show strong phosphorescence after lyophilization to dryness. The phosphorescence intensity of ring-substituted derivatives is strongly dependent upon molecular size and cavity dimensions, suggesting that the -arylpropiophenones can be used to probe these properties.Issued as NRCC-23907     

Facile alcoholysis of L-lactide catalysed by Group 1 and 2 metal complexes

Alkyl (S)-lactate and alkyl (S,S)-lactyllactate were rapidly and conveniently synthesized from L-lactide using Group 1 and 2 metal complexes as catalyst in alcohol.     

Group 12 metal complexes of [26]hexaphyrin(1.1.1.1.1.1)

Metalation of meso-hexakis(pentafluorophenyl)-substituted [26]hexaphyrin(1.1.1.1.1.1) (1) has been explored with group 12 metal ions Zn(II), Cd(II), and Hg(II). Zn(II) and Cd(II) ions afforded dinuclear gable-shaped complexes 2 and 3 in good yields, while Hg(II) ion provided bis-Hg(II) and mono-Hg(II) planar complexes (4 and 5) via C-H bond cleavage.     

Phosphorescence sensitization via heavy-atom effects in d10 complexes

Heavy atom-induced phosphorescence of organic chromophores that originates from spin?Corbit coupling (SOC) is always accompanied by fluorescence quenching concomitant with a reduction of the triplet excited state lifetime. However, such changes are typically manifest by fluorescence quenching at room temperature and phosphorescence sensitization at cryogenic temperatures. Herein we overview our efforts over the past decade in which both internal and external heavy-atom effects (HAEs) can trigger room temperature phosphorescence (RTP) with dramatic shortening of the phosphorescence radiative lifetime by several orders of magnitude. Such spectral properties render new classes of phosphorescent materials for potential use in organic light-emitting diodes (OLEDs). The molecular systems described in this paper are organic fluorophores that are ??-complexed or ??-bonded to a multinuclear d¹⁰ transition metal center, the presence of which leads to phosphorescence sensitization because of the significant SOC in such materials.     

Homogeneous Ziegler–Natta catalysis. II. Ethylene polymerization by IVB transition metal complexes/methyl aluminoxane catalyst systems

Homogeneous Ziegler-Natta systems for the ethylene polymerization, deriving from R₂R_2′M complexes (R = cyclopentadienyl; R′ = alkyl, aryl; M = Ti, Zr, Hf) and oligomeric oxoalane compounds, were studied. Further results concerning the methyl aluminoxane synthesis and the related chemistry are reported. On the basis of spectroscopic data a delocalized electronic structure could be inferred for these compounds. Results from polymerization experiments showed that the highest productivities are obtained only by oxoalane cocatalysts having a high degree of oligomerization. The catalytic activity of the systems under investigation was strongly affected also by changing both the σ-alkyl and the π-cyclo-pentadienyl ligands. Furthermore, it was found that in the presence of methyl aluminoxane, the homoleptic σ-alkyl derivatives of IVB transition metals, such as Zr(CH₂C₆H₅)₄, are also able to polymerize ethylene with a fairly high productivity. Active species containing Zr? O? Al bonds have been postulated.     

Porphyrazinediols: Synthesis, Characterization, and Complexation to Group IVB Metallocenes

The first metalated porphyrazinediols 11 have been prepared from (L)-(+)-dimethyl tartrate via conversion into the corresponding dispoke or 2,3-dimethoxy-2,3-butanediyl protected 2,3-dihydroxymaleonitrile, Linstead macrocyclization, transmetalation, and deprotection. Their stability is very dependent on the nature of the metal ion in the cavity of the porphyrazine. Reaction of these porphyrazinediols with metallocene dichlorides led to new solitaire porphyrazines 12 while DDQ oxidation followed by trapping with diaminomaleonitrile afforded new porphyrazine dinitriles 14.     

Group 10 metal complexes of meso-aryl-substituted [26]hexaphyrins with a metal-carbon bond

Nickel(II), palladium(II), and platinum(II) complexes of meso-aryl-substituted [26]hexaphyrin have been prepared and structurally characterized. In mono-metalated complexes, the metal ion is commonly bound with three pyrrolic nitrogen atoms and one pyrrolic beta-carbon, whereas a bis-Pd(II) complex exhibits a unique structure involving a Pd-C(alpha) bond. These results reveal novel coordination abilities of the hexaphyrin that lead to a metal-carbon bond at either pyrrolic C(beta) or C(alpha) position.     

Thiosulfate metal complexes

The electronic structure of the thiosulfate ions was determined, which made it possible to predict and confirm experimentally for the first time the nature of their ³³S NMR spectra containing two signals of functionally different sulfur atoms. The results of NMR study on different nuclei and the EPR data indicated that the thiosulfate ions as bifunctional ligands enter the coordination sphere of metals with different nature in accordance with the principle of hard and soft acids and bases. The general scheme of the redox transformations of the thiosulfate ions as a result of homo-and heterolytic cleavage of the S-S bonds or the charge transfer in a metal-ligand system was proposed.     

桥环二茂钛、锆、铁金属衍生物的研究

本文用β,β'-双环戊二烯基乙醚二钠与TiCl4, ZrCl4, (C5H5)TiCl3和FeCl2在四氢呋喃中反应合成了新型氧桥环戊二烯基钛、锆和铁衍生物。在企图合成硫桥环戊二烯基化合物时, 得到的却是四亚甲基桥联双环戊二烯基金属衍生物。(苯二亚甲基)双环戊二烯基二钠与FeCl2反应合成了对、间(苯二亚甲基)二茂铁。讨论了新化合物的X射线光电子能谱和Mossbauer谱。