Synthesis divalent halides

Typically, the synthesis of the precursor iron(II) and cobalt(II) halide complexes proceeds by treatment of an anhydrous or hydrated divalent iron or cobalt halide (e.g. MX2 jcH20 or MX2 X = Cl or Br) with 1 (and also 2-4) in... 

Other catalytic uses of rare-earth compounds have not reached the same development. Neodymium salts are, however, used for mbber manufacturing (22). Divalent samarium halides are employed in organic synthesis (23). 

Among the electrochemical syntheses related to the change of metal oxidation number, we emphasize obtaining acetylacetonates of divalent iron, cobalt, and nickel [551,623]. The method of alternating-current electrochemical synthesis was applied to isolate Ji-complexes of monovalent copper with allylamines, allylimines, and ally-lurea from the salts of divalent copper [624-628], We note that the same method was used for preparation of analogous ji-complexes with copper(II) halides (X = Cl, Br) [629a]. Other electrochemical syntheses with participation of metal salts and complexes are described in monographs [201,202] and literature cited therein. 

In this chapter we will review the synthesis, structural aspects, and basic chemical properties of formally divalent and trivalent titanium and zirconium metallocene complexes. We have restricted our coverage to the low-valent bis(rj-cyclopentadienyl) and related metallocenes metal halide complexes and organometallic mixed metal systems will not be discussed here. We have not attempted to present an exhaustive coverage of the field. Rather, our aim has been to describe critically and to evaluate the often confusing chemistry that has been reported for the reactive low-valent titanium and zirconium metallocenes. More general reviews (7) and a book (2) on the organometallic chemistry of titanium, zirconium, and hafnium have been published. 

As in synthesis of 7r-bonded divalent compounds, the principal method of synthesis is nucleophilic displacement of halogen from the divalent metal halide as shown in Eq. (34). 

Vinyl cations [1], the dicoordinated unsaturated analogs of divalent carbenium ions, were first detected by Grob and coworkers in the early 1960s in solvolysis reactions of a-aryl vinyl halides [2]. The direct NMR detection of vinyl cations in superacidic media was achieved in 1992 at temperatures below -100 °C [3]. We recently reported a convenient synthesis of unusually stable vinyl cations at room temperature [4, 5]. One reason for the unusual high thermodynamic stabilization of these vinyl cations is the presence of two 3-silyl substituents. [4]. We report here details of the X-ray structure of the vinyl cation 1 and discuss the structural and spectroscopic consequences of 3-SiC hyperconjugation [6]. 

Kagan, H. B., Namy, J. L., Girard, P. Divalent lanthanide derivatives in organic synthesis. II. Mechanism of Sml2 reactions in presence of ketones and organic halides. Tetrahedron, Supplement, 175-180. 

In this paper, we present the metastable a-polymorph of strontium carbodiimide as a novel pseudochalkogenide host lattice for divalent europium ions. Because of the high thermal inertness and cationic nitrogen coordination of this compound looks like a promising candidate for future applications. Furthermore, Sr-based compounds are ideal host lattices for divalent rare-earth-ions, simply because Sr " " is spectroscopically inactive, and Sr and Eu have comparable ionic rachi and identical charge. As a synthetic challenge, however, the preparation of phase-pure samples is required. Inspired by the reaction of EuN, BN, and NaN3 to form Eu3(NBN)2, and the synthesis of In2.24(NCN)3 from InBr and NaCN, we developed a new flux route based on the metal halide, alkaline cyanide, and alkaline azide, which act as precursors for the synthesis of structurally rather complex rare-earth and alkaline-earth cyanamides and... 

A one-pot variation of the thioether generation, applicable to the formation of cyclic sulfones, involves reaction of a dihalide (or halide equivalent) with a divalent sulfide, such as sodium sulfide. This methodology was used in the synthesis of conduritols, whereby sodium sulfide reacted with diepoxy stereoisomers 13 in a one-step thioether formation fScheme 8.5). The resulting thiapane isomers 14 were separated (HPLC) and then individually methylated and oxidized with m-CPBA to a set of isomeric sulfones, 15. 

Aryls Alkyl Homogeneous Catalysis The Electronic Stmcture of the Lanthanides Variable Valency Solvento Complexes of the Lanthanide Ions Lanthanides Coordination Chemistry The Divalent State in Solid Rare Earth Metal Halides Lanthanides Comparison to 3d Metals Trivalent Chemistry Cyclopentadienyl Tetravalent Chemistry Organometallic Organic Synthesis. 

The synthesis of compounds of the lanthanides containing cluster complexes follows in general the same routes as described in The Divalent State in Solid Rare Earth Metal Halides, the conproportionation route and the metallothermic reduction route, for example... 

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