1,2-Bis(dimethylarsino)benzene
Encyclopedia
1,2-Bisbenzene is the organoarsenic compound
with the formula
C6H4(As(CH3)2)2. The molecule consists of two dimethylarsino groups attached to adjacent carbon centers of a benzene
ring. It is a chelating ligand
in coordination chemistry. This colourless oil is commonly abbreviated "diars." Related, but non-chelating organoarsenic ligands include triphenylarsine
and trimethylarsine
. Work on diars led to the development of the |chelating diphosphine ligands such as dppe, which are now prevalent in homogeneous catalysis
.
for its ability to stabilize metal complexes with unusual oxidation states and coordination numbers, e.g. TiCl4(diars)2. High coordination numbers arise because diars is fairly compact and the As-M bonds are long, which relieves crowding at the metal center. In terms of stabilizing unusual oxidation states, diars stabilizes Ni(III), as in [NiCl2(diars)2]Cl.
Of historical interest is the supposedly diamagnetic [Ni(diars)3](ClO4)2, obtained by heating nickel perchlorate with diars. Octahedral d8 complexes characteristically have triplet ground states, so the diamagnetism of this complex was puzzling. Later by X-ray crystallography
, the complex was shown to be pentacoordinate with the formula [Ni(triars)(diars)](ClO4)2, where triars is the tridentate ligand [C6H4As(CH3]2As(CH3), arising from the elimination of trimethylarsine
.
and sodium dimethylarsenide:
It is a colorless liquid. Oxygen quickly converts diars to the dioxide, C6H4(As(CH3)2O)2.
Organoarsenic compound
Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fungicides. In general these applications are declining in...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
C6H4(As(CH3)2)2. The molecule consists of two dimethylarsino groups attached to adjacent carbon centers of a benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
ring. It is a chelating ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
in coordination chemistry. This colourless oil is commonly abbreviated "diars." Related, but non-chelating organoarsenic ligands include triphenylarsine
Triphenylarsine
Triphenylarsine is the chemical compound with the formula As3. This organoarsenic compound, often abbreviated AsPh3, is a colorless crystalline solid that is used as a ligand and a reagent in coordination chemistry and organic synthesis...
and trimethylarsine
Trimethylarsine
Trimethylarsine is the chemical compound with the formula 3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination...
. Work on diars led to the development of the |chelating diphosphine ligands such as dppe, which are now prevalent in homogeneous catalysis
Homogeneous catalysis
In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
.
Coordination chemistry
Diars is a bidentate ligand used in coordination chemistry. It was first described in 1939, but was popularlized by R. S. NyholmRonald Sydney Nyholm
Sir Ronald Sydney Nyholm was an Australian chemist, born on 29 January 1917 at Broken Hill, New South Wales, Australia, as the fourth in a family of six children. Broken Hill is a mining town whose streets are named after minerals, a fit place for to sire an inorganic chemist. Beryl-and-Sulphide...
for its ability to stabilize metal complexes with unusual oxidation states and coordination numbers, e.g. TiCl4(diars)2. High coordination numbers arise because diars is fairly compact and the As-M bonds are long, which relieves crowding at the metal center. In terms of stabilizing unusual oxidation states, diars stabilizes Ni(III), as in [NiCl2(diars)2]Cl.
Of historical interest is the supposedly diamagnetic [Ni(diars)3](ClO4)2, obtained by heating nickel perchlorate with diars. Octahedral d8 complexes characteristically have triplet ground states, so the diamagnetism of this complex was puzzling. Later by X-ray crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
, the complex was shown to be pentacoordinate with the formula [Ni(triars)(diars)](ClO4)2, where triars is the tridentate ligand [C6H4As(CH3]2As(CH3), arising from the elimination of trimethylarsine
Trimethylarsine
Trimethylarsine is the chemical compound with the formula 3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination...
.
Preparation and handling
Diars is prepared by the reaction of ortho-dichlorobenzene1,2-Dichlorobenzene
1,2-Dichlorobenzene, or orthodichlorobenzene , is an organic compound with the formula C6H4Cl2. This colourless liquid is poorly soluble in water but miscible with most organic solvents...
and sodium dimethylarsenide:
- C6H4Cl2 + 2 NaAs(CH3)2 → C6H4(As(CH3)2)2 + 2 NaCl
It is a colorless liquid. Oxygen quickly converts diars to the dioxide, C6H4(As(CH3)2O)2.