Commonly Used and Abbreviations

Chelate complexes could only be prepared in the case of platinum(II) as the metal ion, while the group V atom alone acted as a donor toward palladium(II) and mercury(II). The coordinated olefin in the chelate complexes was found to be readily displaced by monodentate ligands such as tertiary arsines, -toluidine and the thiocyanate ion. It was suggested by these workers that chelation would take place more readily if the olefinic phosphine or arsine were subject to greater steric restrictions than was the pentenyl ligand. 

For this reason Long (7, 8) and Erskine 8—11) prepared two series of ligands the ortho, meta and para-styryl dimethyl arsines Long), and the o, m and -allylphenyldimethylarsines Erskine) and studied the bromination of these compounds, their methiodides and their platinum (II) and rhodium(III) complexes. 

The ligands react with two equivalents of bromine, the first stage of the reaction being the rapid oxidation of the arsenic atom. This is followed by the slower addition of bromine to the double bond (Fig. 4). 

A spectrophotometric technique showed that the isomeric vinyl phenyl dimethyl arsines reacted at similar rates in carbon tetrachloride solution, as did the isomeric allylphenyl dimethyl arsines 8). The bromination of the methiodides of the allyl compounds was studied to see if the presence of the positively charged group affected the reactivity of the 

The rhodium(III) complexes of the isomeric st oryl dimethyl arsines were all of the type RhBrs (arsine) 3 and all reacted with an excess of bromine ( 6 mols) giving complexes of the t3 e RhBrs (arsine Br2)3, in which all the double bonds of the ligands have been saturated by addition of bromine. No difference in reactivity between any of the isomers was noted (5). 

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