Chromium trihalides

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

We could show further that not only methoxy(organo)carbene complexes react with boron trihalides in the above-mentioned sense. For instance, it was found that b aws-(bromo)tctracarbonyl(phenylcarbyne)chromium(0) and -tungsten(0) are also accessible from pentacarbonyl[hydroxy (phenyl)-carbene [[chromium (0) (02) and from pentacarbonyl[methoxycarbonyl-... 

Ziegler-Natta Catalysts (Heterogeneous). These systems consist of a combination of a transition metal compound from groups IV to VIII and an organometallic compound of a group I—III metal.23 The transition metal compound is called the catalyst and the organometallic compound the cocatalyst. Typically the catalyst is a halide or oxyhalide of titanium, chromium, vanadium, zirconium, or molybdenum. The cocatalyst is often an alkyl, aryl, or halide of aluminum, lithium, zinc, tin, cadmium, magnesium, or beryllium.24 One of the most important catalyst systems is the titanium trihalides or tetra-halides combined with a trialkylaluminum compound. 

These are listed in Table 17-C-2. The anhydrous Cr11 halides are obtained by action of HF, HC1, HBr, or I2 on the metal at 600 to 700°C or by reduction of the trihalides with H2 at 500 to 600°C. Chromium dichloride is the most common and most important of these halides, dissolving in oxygen-free water to give a blue solution of Cr2+ ion. 

Chromium forms trihalides with all four halogens. The colour of a CrClg solution varies with temperature and chloride ion concentration. In cold dilute solution the octahedral [Cr(H20)g] + ion gives a violet colour. Addition of chloride ion, particularly if accompanied by heat, produces a green solution due to the [Cr(H20)5Cl]2+ ion ... 

Bisarene chromium compounds have been shown to undergo reversible exchange with aromatic hydrocarbons in the presence of aluminum trihalides (207). The exchange reaction has been used to improve the preparation of the bisbenzene chromium cation via the more readily prepared bismesitylene chromium cation 157b). 

Pyridazine forms a stable adduct with iodine, with semiconductor properties. " Similar complexes were prepared from iodine mono-ehloride, bromine, and nickel(II) ethyl xanthate. Complexes of pyrida-zines with iron carbonyls and with iron carbonyls and triphenylphosphine have been prepared and investigated. " Complexes of pyridazines with boron trihalides, silver salts, mercury(I) salts, iridium salts, " ruthenium salts, and chromium carbonyls are re-... 

Anhydrous chromium dihalides are conveniently prepared by reduction of the trihalides with H2 at 300-5()0 C, or by the action of HX (or h for the diiodide) on the metal at temperatures of the order of 1000°C. They are all deliquescent and the hydrates can be obtained by reduction of the trihalides using pure chromium metal and aqueous HX. All have distorted octahedral structures as anticipated for a metal ion with the d configuration which is particularly susceptible to Jahn-Teller distortion. This is typified by Crp2, which adopts a distorted rutile structure in which... 

The dihalides of Mn, Fe, Co and Ni are readily available. Trihalides of vanadium and chromium can be used, but an excess of NaCgHg is then required as a reducing agent. Alternatively MX, can be reduced in situ to MX, using zinc or magnesium before NaC5Hg is added. 

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