Platinum diarsine complexes

When the apparently penta-coordinated diarsine complexes just described are dissolved in solvents more polar than nitrobenzene, they tend to dissociate into halide ions and bivalent cations, thus becoming 2 1 electrolytes (119). The effect is most marked with the platinum compounds. It has been shown that solvation effects might be less with platinum than with palladium, and so, other things in the equilibria being equal, it can also be concluded that the bonding of further ligands by a square-planar complex is much weaker with platinum than with palladium. Square-planar nickel complexes are of course the most ready to take up further ligands. 

P NMR spectroscopy.53 Steric factors account for the different coordination modes, while the influence of electronic factors is evidenced by the difference in structure between analogous palladium(II) and platinum(II) compounds, for example, the thiocyanates are N- and S-bonded in [Pd(NCS)(SCN)(diars)], but only S-bonded in [Pt(SCN)2(diars)].54 These and other diphosphine or diarsine complexes of palladium(II) with thio- or seleno-cyanate ligands are further discussed in Section 51.8.2.6. 

A ruthenium complex, Ru(CO)2Cl2L, has been reported with ortfto-phenylenebis-(methylphenylarsine) (L) and there is a square-planar platinum complex (As—Pt 2.396 A) with the fully phenylated diarsine in which the metal atom also carries two p-(trifluoromethyl)phenyl groups . ... 

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