Diarsine halogenation

Comparison with data (mainly obtained from EXAFS measurements) on osmium diarsine complexes (Table 1.14) shows that as the oxidation state increases, osmium—halogen bonds shorten whereas Os-P and Os—As bonds lengthen. Bond shortening is predicted for bonds with ionic character,... 

With the halogens, As-As bonds are cleaved in the diarsine to produce the monohaloarsine and in the cyclopolyarsine... 

Haloarsines are obtained from a number of cleavage reactions of compounds with As—As bonds. Halogens react very readily with diarsines, a result which has been of value in characterizing these compounds 308). 

Besides ligand exchange and further substitution (not to mention decomposition), few reactions have been noted for these complexes. One interesting example is halogenation, first studied by Nyholm in the case of diarsine complexes 143, 144). The products are sometimes novel seven-coordinate species, depending on conditions [Eqs. (3-10), diarsine = D] 143, 144). The tendency to lose carbon monoxide in these reactions... 

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