Trimethyl platinum chloride and related compounds

These compounds are of quite unusual interest because their empirical formulae suggest coordination numbers 4, 5, and 7 for Pt. Platinum forms a number of compounds Pt(CH3)3X, in which X is Cl, I, OH, or SH, which exist as tetrameric molecules (Fig. 27.13(a)) in which Pt and X atoms occupy alternate vertices of a (distorted) cube. These compounds are notable for the facts that the hydroxide was formerly described as the tetramethyl compound and the iodide as Pt2(CH3)6. In the early study of [Pt(CH3)3Cl]4 Pt-Cl was found to be 2-48 the value, 2-58 A determined in [Pt(C2Hs)3Cl] should be more reliable. The following figures for the hydroxide show that there is some distortion from the highest possible cubic symmetry  

A neutron diffraction study of this compound has also been made. Since OH or Cl together provide 5 electrons (one normal and two dative covalent bonds) Pt acquires the same electronic structure as in PtCll 

The molecules of salicylaldehyde, I, and 8-hydroxyquinoline, II, normally form chelate compounds in which two 0 atoms or O and N are bonded to the metal 

In all these compounds there is octahedral coordination of Pt which is achieved in a variety of ways in compounds which present the possibility of coordination numbers of 4, 5, and 7. 

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