Organoarsenic dihalides

More extensive catenation occurs in the cyc/o-polyarsanes (RAs) which can readily be prepared from organoarsenic dihalides or from arsonic acids as follows ... 

Several methods are available for the synthesis of cycloarsoxanes (a) hydrolysis of organoarsenic(III) dihalides RASX2 (X = Cl, Br, I), (b) reduction of arsonic acids RAsO(OH)2 and (c) oxidation of primary arsines RASH2 or cyclopolyarsines (RAs) . The tetramer cyclo-(MeAsO)4 exhibits the boat-chair conformation, whereas the mesityl derivative cyclo-(MesAsO)4 adopts the crown conformation (Figure 11.24). The As-O bond distances are in the range 1.77-1.82 A, typical for single bonds. 

Protonolysis of triorganoarsenic compounds by mineral acids gives organoarsenic(III) dihalides (equation 105) °°. 

Several organoarsenic(III) compounds containing arsenic(III)-transition metal bonds have been oxidized by halogen-based electrophiles or by elemental sulfur to give the corresponding dihalides or sulfides (equations 365 , 366 and 367 - ). 

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