Diarsine chromium

Diarsine forms the low-spin, tram octahedral chromium(ll) complexes [CrX2(diars)2] (X = Cl, Br, I) the magnetic moments are in the range 2.85 to 2.99 BM and independent of temperature (84-298 K). Reflectance spectra have been recorded, but no assignments made.40... 

Although the n bond is used for coordination in all four compounds, the As—As separation (ca 2.36 A) points to retention of double-bond character. A diarsene carrying a Cp Fe(CO)2 substituent in addition to the well known tri(t-butyl)phenyl group has been isolated as a chromium pentacarbonyl complex, 20, from treatment of Cp Fe(CO)2 As(SiMe3)2 with tri(t-butyl)phenylarsenic dichloride and (cyclo-octene)Cr(CO)5. The compound, which is isostructural with the corresponding diphosphene and phospha-arsene, has an As—As separation of 2.259 A and As—Cr and As—Fe distances of 2.492 and 2.387 A, respectively. On the other hand, the As—As distance in [CpFe(CO)2]-(PhAs—AsPh)[(CO)2FeCp] is 2.456 A and the compound is probably best described as a tetrasubstituted diarsine, rather than a diarsene complex . 

Photochemical addition of dimethylarsine to the olefin MeaAs-CFa-CClrCFs gives a quantitative yield of diarsine Me2As CF2 CHCl-CF2-AsMe2, which forms complexes of chromium and molybdenum carbonyls. ... 

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