1,2-Bis(dimethylarsino)benzene
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477203033
| ImageFile = Diars.png
| ImageFile_Ref = {{chemboximage|correct|??}}
| ImageName = Stereo, Kekulé, skeletal formula of 1,2-bis(dimethylarsino)benzene with some implicit hydrogens shown
| ImageFile1 = Diars-3D-balls-A.png
| ImageFile1_Ref = {{chemboximage|correct|??}}
| ImageName1 = Ball and stick model of 1,2-bis(dimethylarsino)benzene
| PIN = (1,2-Phenylene)bis(dimethylarsane)
|Section1={{Chembox Identifiers
| Abbreviations = DAS, Diars
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 13246-32-7
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = K3C0GW5M57
| PubChem = 83261
| ChemSpiderID = 75125
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 236-227-9
| MeSHName = 2-Phenylene-bis-dimethylarsine
| ChEBI = 30628
| ChEBI_Ref = {{ebicite|correct|EBI}}
| Beilstein = 2937031
| Gmelin = 3780
| SMILES = C[As](C)c1ccccc1[As](C)C
| SMILES1 = C[As](C)C1=CC=CC=C1[As](C)C
| StdInChI = 1S/C10H16As2/c1-11(2)9-7-5-6-8-10(9)12(3)4/h5-8H,1-4H3
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/C10H16As2/c1-11(2)9-7-5-6-8-10(9)12(3)4/h5-8H,1-4H3
| StdInChIKey = HUBWRAMPQVYBRS-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = HUBWRAMPQVYBRS-UHFFFAOYAM
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|Section2={{Chembox Properties
| Formula = {{Chem|C|10|As|2|H|16}}
| MolarMass = 286.0772 g mol{{sup|−1}}
| Appearance = Colourless liquid
| Density = 1.3992 g cm{{sup|−3}}
| BoilingPtC = 97 to 101
| BoilingPt_notes = at 150 Pa
}}
|Section3={{Chembox Hazards
| MainHazards = Toxic
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1,2-Bis(dimethylarsino)benzene (diars) is the organoarsenic compound with the formula C{{sub|6}}H{{sub|4}}(As(CH{{sub|3}}){{sub|2}}){{sub|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."Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.
Coordination chemistry
Related, but non-chelating organoarsenic ligands include triphenylarsine and trimethylarsine. Work on diars preceded the development of the chelating diphosphine ligands such as dppe, which are now prevalent in homogeneous catalysis.
Diars is a bidentate ligand used in coordination chemistry. It was first described in 1939,Chatt, J.; Mann, F. G. "The Synthesis of Ditertiary Arsines. Meso- and Racemic Forms of Bis-4-Covalent-Arsenic Compounds" Journal of the Chemical Society, 1939, 610–615. {{doi|10.1039/JR9390000610}} but was popularized by R. S. Nyholm for its ability to stabilize metal complexes with unusual oxidation states and coordination numbers, e.g. TiCl{{sub|4}}(diars){{sub|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 [NiCl{{sub|2}}(diars){{sub|2}}]Cl.
Of historical interest is the supposedly diamagnetic [Ni(diars){{sub|3}}](ClO{{sub|4}}){{sub|2}}, obtained by heating nickel perchlorate with diars. Octahedral d{{sup|8}} 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)](ClO{{sub|4}}){{sub|2}}, where triars is the tridentate ligand [C{{sub|6}}H{{sub|4}}As(CH{{sub|3}}){{sub|2}}]{{sub|2}}As(CH{{sub|3}}), arising from the elimination of trimethylarsine.B. Bosnich, R. S. Nyholm, P. J. Pauling, M. L. Tobe "A nickel(II)-catalyzed synthesis of a triarsine from a diarsine" J. Am. Chem. Soc. 1968, volume 90, pp 4741–4742. {{doi|10.1021/ja01019a049}}Anthony Nicholl Rail; Some new reactions of a ditertiary arsine ligand; Ph.D. Thesis; University College London; 1973
Preparation and handling
Diars is prepared by the reaction of ortho-dichlorobenzene and sodium dimethylarsenide:Feltham, R. D.; Silverthorn, W. "o-Phenylenebis(dimethylarsine)" Inorganic Syntheses 1967, Vol. X, pp. 159–164. {{doi|10.1002/9780470132418.ch24}}
:C{{sub|6}}H{{sub|4}}Cl{{sub|2}} + 2 NaAs(CH{{sub|3}}){{sub|2}} → C{{sub|6}}H{{sub|4}}(As(CH{{sub|3}}){{sub|2}}){{sub|2}} + 2 NaCl
It is a colorless liquid. Oxygen converts diars to the dioxide, C{{sub|6}}H{{sub|4}}(As(CH{{sub|3}}){{sub|2}}O){{sub|2}}.
References
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