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Heating a solution of Cr(CO) 6 in an aromatic solvent results in replacement of three CO ligands. The reactions are especially favorable for electron-rich arenes: Cr(CO) 6 + C 6 H 5 R → Cr(CO) 3 (C 6 H 5 R) + 3 CO. The products are "piano stool complexes". These species are typically yellow solids. One example is (benzene)chromium tricarbonyl.
Chromium(III) hydroxide (Cr(OH) 3) is amphoteric, dissolving in acidic solutions to form [Cr(H 2 O) 6] 3+, and in basic solutions to form [Cr(OH) 6] 3−. It is dehydrated by heating to form the green chromium(III) oxide (Cr 2 O 3), a stable oxide with a crystal structure identical to that of corundum. [6]
Hexavalent chromium (chromium(VI), Cr(VI), chromium 6) is any chemical compound that contains the element chromium in the +6 oxidation state (thus hexavalent). [1] It has been identified as carcinogenic, which is of concern since approximately 136,000 tonnes (150,000 tons) of hexavalent chromium were produced in 1985. [ 2 ]
The number indicates the degree of oxidation of each element caused by molecular bonding. In ionic compounds, the oxidation numbers are the same as the element's ionic charge. Thus for KCl, potassium is assigned +1 and chlorine is assigned -1. [4] The complete set of rules for assigning oxidation numbers are discussed in the following sections.
The lowest oxidation states are exhibited in metal carbonyl complexes such as Cr(CO) 6 (oxidation state zero) and [Fe(CO) 4] 2− (oxidation state −2) in which the 18-electron rule is obeyed. These complexes are also covalent. Ionic compounds are mostly formed with oxidation states +2 and +3.
Bis(benzene)chromium is the organometallic compound with the formula Cr(η 6-C 6 H 6) 2. It is sometimes called dibenzenechromium. It is sometimes called dibenzenechromium. The compound played an important role in the development of sandwich compounds in organometallic chemistry and is the prototypical complex containing two arene ligands .
An atom (or ion) whose oxidation number increases in a redox reaction is said to be oxidized (and is called a reducing agent). It is accomplished by loss of one or more electrons. The atom whose oxidation number decreases gains (receives) one or more electrons and is said to be reduced. This relation can be remembered by the following mnemonics.
Co(NH 3) 6] 3+, which features 6-coordinate metal centre with octahedral molecular geometry. Chloro(triphenylphosphine)gold(I), which features 2-coordinate metal centre. In chemistry, coordination number, defined originally in 1893 by Alfred Werner, is the total number of neighbors of a central atom in a molecule or ion.