Bromopentacarbonylrhenium(I)
Encyclopedia
Bromopentacarbonylrhenium(I) is an inorganic compound
of rhenium
, commonly used for the syntheses of other rhenium complexes.
with bromine
:
It was first prepared by the "reductive carbonylation" of rhenium(III) bromide:
Copper(I) bromide
is a side-product.
and acetic acid
to give pentacarbonylhydridorhenium
(ReH(CO)5).
It also reacts with tetraethylammonium bromide
in diglyme
to give [NEt4]2[ReBr3(CO)3)], an important precursor to compounds containing the rhenium tricarbonyl fragment.
Refluxing bromopentacarbonylrhenium(I) in water also provides access to the rhenium tricarbonyl fragment:
This route avoids the formation of the tetraethylammonium bromide byproduct when the tetraethylammonium complex is used. This is desirable because the tetraethylammonium bromide is often difficult to remove from reaction mixtures.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
of rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
, commonly used for the syntheses of other rhenium complexes.
Preparation
Bromopentacarbonylrhenium(I) is commercially available. It is also easily and inexpensively synthesized by the oxidation of dirhenium decacarbonylDirhenium decacarbonyl
Dirhenium decacarbonyl is an inorganic compound with the formula Re210. Commercially available, it is used as a starting point for the synthesis of many rhenium carbonyl complexes. It was first reported in 1941 by Walter Hieber who prepared it by carbonylation of Re2O7. The compound consists of a...
with bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
:
- Re2(CO)10 + Br2 → 2 ReBr(CO)5
It was first prepared by the "reductive carbonylation" of rhenium(III) bromide:
- ReBr3 + 2 Cu + 5 CO → BrRe(CO)5 + 2 CuBr
Copper(I) bromide
Copper(I) bromide
Copper bromide is the chemical compound with the formula CuBr. This diamagnetic solid adopts a polymeric structure akin to that for zinc sulfide. The compound is widely used in the synthesis of organic compounds....
is a side-product.
Reactions
Bromopentacarbonylrhenium(I) is a useful intermediate to other rhenium complexes. For example, it reacts with zincZinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
to give pentacarbonylhydridorhenium
Pentacarbonylhydridorhenium
Pentacarbonylhydridorhenium is a chemical compound with the formula ReH5. This colorless liquid is a weak acid and represents one of the most important derivatives of dirhenium decacarbonyl...
(ReH(CO)5).
- Re(CO)5Br + Zn + HO2CCH3 → ReH(CO)5 + ZnBrO2CCH3
It also reacts with tetraethylammonium bromide
Tetraethylammonium bromide
Tetraethylammonium bromide is a quaternary ammonium salt. It is a common source for the tetraethylammonium cation. Currently, no NFPA 704 for TEABr has been established. Industrially, it can be used to determine the epoxide value of various adhesives....
in diglyme
Diglyme
Diglyme, or bis ether, is a solvent with a high boiling point. It is an organic compound which is the dimethyl ether of diethylene glycol. It is a clear, colorless liquid with a slight ether-like odor...
to give [NEt4]2[ReBr3(CO)3)], an important precursor to compounds containing the rhenium tricarbonyl fragment.
Refluxing bromopentacarbonylrhenium(I) in water also provides access to the rhenium tricarbonyl fragment:
- ReBr(CO)5 + 3 H2O → [Re(H2O)3(CO)3]Br + 2 CO
This route avoids the formation of the tetraethylammonium bromide byproduct when the tetraethylammonium complex is used. This is desirable because the tetraethylammonium bromide is often difficult to remove from reaction mixtures.