Chromium, powder tris

Copper(II) bis[(0-alkyl)-4-ethoxyphenyldithiophosphonato] and chromium(III) tris[(0-alkyl)-4-ethoxyphenyldithiophosphonato] complexes (alkyl = Me, Et, Pr1) were prepared and studied by magnetic measurements, and electronic, IR, and EPR spectroscopy. The valence vibrations of the PS2 group show that this group coordinates as isobidentate. The powder EPR spectra are typical for square-planar monomeric species and present hyperfine and superhyperfine structure. The EPR bands of the chromium(III) complexes may be attributed to metal ions in a pseudo-octahedral environment, coupled by dipole-dipole interaction.123... 

Tris(0-ethyl dithiocarbonato)chromium(III) is obtained as a dark blue crystalline powder which decomposes at 100 to 140°. The indium(III) ethylxanthate complex forms small colorless crystals which decompose at 130 to 150°.16,17 The cobalt (III) ethylxanthate complex is isolated as a dark green crystalline powder whose decomposition temperature determined by use of a thermal balance is 135 to 137° (lit. value, 117° 2 118 to 119°8). These compounds decompose slowly in air and more rapidly when heated in solution. The tripositive chromium, indium, and cobalt complexes are insoluble in water but are soluble in many organic solvents (Table T). 

X-ray powder diagrams obtained by the Guinier method show the tris (O-ethyl dithiocarbonato) complexes of chro-mium(III), indium(III), cobalt(III), iron(III), arsenic(III), and antimony(III) to be isomorphous. Carrai and Gottardi have determined the structure of the arsenic(III)18 and anti-mony(III)19 complexes. Crystallographic data for the cobalt(III) and chromium(III) ethylxanthate complexes are given by Derenzini20 and Franzini and Schiaffino,21 respectively. 

Sievers and his coworkers have used the volatility of the metal diketonates in the separation and analysis of heavy metals and have done interesting stereochemical work on a few of them. They have achieved at least partial resolution of the optical isomers of tris(hexafluoroacetyl-acetonato)chromium(III) by passing the vapor through a column of quartz powder at 55 °C, and have separated the facial and meridional isomers of tris(trifluoroacetylacetonato)chromium(III) by gas chromatography at 115 °C.40... 

To a mixture of 11.0 g. (0.031 mole) of tris(2,4-pentanedio-nato) chromium (III)2 and 4.0 g. (0.12 mole) of powdered paraformaldehyde in 150 ml. of glacial acetic acid is added 12.5 ml. (0.12 mole) of iV iVW -tetramethyldiaminomethane, prepared according to Lindsay and Hauser.3 After stirring for 12 hours at room temperature, the acid is neutralized by slow addition to 700 ml. of saturated aqueous potassium carbonate. Sufficient quantities of ice are added periodically to keep the neutralization solution below room temperature. An excess of ammonium hydroxide is then added to make the solution basic. The triamine is extracted into chloroform from which it is recovered as a red-purple tar by evaporation (end of step a). 

Eleven and two-tenths grams (0.05 mol) of 1,3-diphenyl-1,3-propanedione is ground in a mortar with 5.84 g. (0.017 mol) of tris(2,4-pentanedionato)chromium(III) until a fine homogeneous powder is obtained. The mixture is transferred to an Erlenmeyer flask equipped with a gas inlet tube. The flask is heated slowly in an oil bath or with a heating mantle, in a hood, with a slow stream of nitrogen (about 0.5 1./minute) flowing over the mixture. The mixture melts at about 75° at about 150°, 2,4-pentanedione is... 

After cooling, the brown reaction product is broken up, heated briefly with 100 ml. of methanol to extract unchanged starting materials, and cooled to room temperature. The solid is filtered from the extract, washed with 50 ml. of cold acetone, and air-dried at room temperature. The yield is 11 to 11.5 g. (91 to 95 %). For purification, the solid is dissolved in 500 ml. of warm benzene. The solution is filtered while warm, and, after cooling, 800 ml. of cyclohexane is added. Tris(l,3-diphenyl-l,3-propanedionato)-chromium(III) slowly separates as a microcrystalline powder. The product is filtered and dried in a vacuum desiccator. Yield, 9 to 9.5 g. (74.4 to 78.6%). Anal. Calcd. for [Cr(Ci6Hu02)3l Cr, 7.21 C, 74.88 H, 4.61. Found Cr, 7.2, C, 74.9 H, 4.2. 

There is some controversy concerning the existence of the a isomers of these tris complexes, Israily reported a purple complex to be or-[Cr(gly)3] however, subsequent workers have shown that this substance most probably was the dihydroxy dimer [Cr2(gly)4(OH)2]. Careful chromatography, on potato starch, of solutions from chromium(III)/glycine reactions yielded red and purple fractions,the electronic spectra of which were consistent with jS and a isomers respectively. Solutions of the a complex were unstable even in the dark and cold. Hoggard has recently claimed the preparation of the a isomer of the glycine complex by a fractional crystallization. The complex was anhydrous, unlike its cobalt(III) analogue. X-Ray powder methods could hence not be used to confirm the identity of the complex the luminescence spectra were held to be consistent with meridional coordination. There have been a number of studies of the physical properties of /S-[Cr(gly)3], summarized in Table 99. 

After some experience with surfacing materials, various combinations of materials can be tried to improve product performance. For example, on a part which is normally surfaced with a tough, semiaustenitic electrode, it may be possible to get additional abrasion resistance without sacrificing resistance to cracking. A little of the powdered chromium carbide material can be fused to critical areas where additional protection is needed. 

A study of the properties of (C Hs)3C HF)3 demonstrates how n-arene complexes may be formed from bonded aryl conqdexes. If the tris-tetrahydrofuranate is washed with ether the tetrahydrofuran is removed and a black powder is formed. This powder is at first strongly paramagnetic and the paramagnetism decreases with time. Hydrolysis of the powder forms 7r-arene chromium complexes. These properties suggest that the black powder contains radical species and the formulations, exemplified in Figure 57, have been suggested [91]. The formation of diphenyl has been proposed to occur by the /u>rn-coupling of phenyl radicals, within the environment of the chromium atom [95]. 

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