Group 6 chromium

The main oxidation states of chromium are - -6, - -3 and -1-2. A few compounds of Cr(V) and Cr(IV) are known, but are unstable with respect to disproportionation. Chro-mium(O) is stabilized by rr-acceptor ligands (see Chapter 23). [Pg.606]

Chromium(VI) oxide dissolves in base to give yellow solutions of [Cr04]. This is a weak base and forms [HCr04] and then H2Cr04 as the pH is lowered (H2Cr04 pKj(l) = 0.74 pKj(2) = 6.49). In solution, these equilibria are comphcated by the formation of orange dichromate(VI), [Cr207p (equation 21.27). [Pg.606]

Chromium(VI) compounds are highly toxic (suspected carcinogens) and must be stored away from combustible materials violent reactions occur with some organic compounds. [Pg.607]

Simple vanadium(II) complexes include [V(CN)6] , the K salt of which is made by reducing K4[V(CN)7] with K metal in liquid NH3. The magnetic moment of 3.5 for [V(CN)6] is close to the spin-only value of 3.87 /rg- Octahedral [V(NCMe)6] has been isolated in the [ZnC ] salt from the reaction of VCI3 with Et2Zn in MeCN. Treatment of VC12-4H20 with phen gives [V(phen)3]Cl2, for which Meff = 3.82/Tg (300 K), consistent with octahedral. [Pg.699]

The octahedral complex IVL3I where HL = CF3COCH2COCH3 (related to Hacac) exists as fac and mer isomers in solution. Draw the structures of these isomers, and comment on further isomerism exhihited hy this complex. [Pg.699]

The vanadate Vi4036Cl] is an open cluster with a guest Cl ion. (a) What are the formal oxidation states of the V centres (h) The electronic spectrum exhibits intense charge transfer bands. Explain why these are likely to arise from LMCT rather than MLCT transitions. [Pg.699]

The only halide of chromium(VI) to have been reported is yellow CrFg, produced by fluorination of the metal at 670 K and 200 bar followed by rapid chilling. The material so prepared reacts violently in moist air and decomposes at 173 K into CrF5 and F2 whether or not CrFg actually exists and, if it does, the question of whether it is octahedral or trigonal prismatic, are controversial topics. The oxohalides Cr02F2 and Cr02Cl2 are much more stable. [Pg.699]

KCl solution, K[Cr03Cl] precipitates. Structure 21.11 shows the [Cr03Cl] ion. [Pg.731]

Further conciensation occurs at high [H ] to give [Cr30io] and [Cr40i3l. The stmctures (determined for solid [Pg.731]

In the sixth group, chromium, molybdenum, tungsten, and uranium constitute Family A. In their trioxides they show the characteristic valence of the sixth group and resemble in properties the non-metals of Family B, of which sulphur is the type. In their lower oxides they possess none of the characteristics of Group VI but show the general base-f orming properties of the heavy metals. [Pg.320]

Cadmium group Chromium group Cadmium sulfide Chromium oxide hydrate Cadmium yellow, Viridian Heaton (1928) 380 Kittel (1953)... [Pg.68]

Chromium group Chromium oxide hydrate Gypsum Viridian Bersch (1901) 261 Coffignier (1924) 456 Zerr Rubencamp (1906/ 1908)241... [Pg.87]

Cobalt group Tin group Chromium aluminium cobalt oxide Cobalt tin oxide Bleu celeste-, Caeruleum Coelin Coeruleum Hopjner blue-. New blue... [Pg.91]

Chromates group Chromium oxides aud hydroxides group Lead carbonates group Lead chromates group Lead phosphates group Lead sulfates group Baryte Chalk Chromium oxide Gypsum Lead... [Pg.100]

Alumimum group Chromium group Cobalt group Cerulean blue Turkish green Turquoise green... [Pg.100]

Chromium group Chromium oxide Eskolaite Amaudon s chrome... [Pg.102]

Chromium group Chromium oxides and hydroxides group... [Pg.106]

Cobalt group Chromium aluminium cobalt oxide Cobalt aluminium oxide Cobalt arsenate Cobalt arsenic oxide hydrate Cobalt chromate Cobalt hexacyanoferrate(II) Cobalt iron oxide Cobalt magnesium oxide Cobalt tin oxide Cobalt tungstate Cobalt zinc oxide Cobalt(III) oxide Erythrite Cobalt black Cobalt blue Cobalt violet... [Pg.115]

Aluminium oxides and hydroxides group Chromium oxide Colour Index (1971) Montagna (1993) 141... [Pg.216]

Hexacyanoferrate group Chromium aluminium cobalt oxide Ultra-marine Cerulean blue Cobalt blue Prussian blue Heaton (1928) 382 Mayer (1991) 52 Salter (1869) 216... [Pg.275]

Chromium group Chromium oxide hydrate Viridian Church (1901) Riffault et al. (1874) 563... [Pg.289]

Chromium group Chromium oxide Heaton (1928) 383 Newman (1997)... [Pg.318]

Chromates group Chromium oxides and hydroxides group Zinc chromates group Barium chromate(VI) Cadmium chromate ... [Pg.355]

Zinc chromates group Chromium oxide Strontium chromate Zinc chromate hydroxide Zinc potassium chromate hydrate Chrome green Citron Yellow Permanent green Permanent yellow Ultramarine yellow Victoria green... [Pg.409]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...