Co-ordination chemistry of higher oxidation states. Part 2. Neutral and cationic complexes of platinum(IV) with bi- and multi-dentate ligands

Abstract

Octahedral platinum(IV) complexes [Pt(L–L)X₄][X = Cl or Br, L–L = Me₂NCH₂CH₂NMe₂, Ph₂PCH₂CH₂PPh₂, cis-Ph₂PCHCHPPh₂, Me₂As(CH₂)₃AsMe₂, o-C₆H₄(AsMe₂)₂, o-C₆H₄(AsPh₂)₂, cis-Ph₂AsCHCHAsPh₂, o-C₆H₄(SbPh₂)₂, Me₂Sb(CH₂)₃SbMe₂, or (SbMe₃)₂] have been prepared by oxidation of [Pt(L–L)X₂] with halogen (X₂) in CCl₄. The amine, phosphine, and arsine complexes are very stable thermally and in solution, but the stabines decompose slowly at ambient temperature and immediately in solution. Decomposition of [Pt{Me₂Sb(CH₂)₃SbMe₂}Cl₄] in solution gives [Pt{Me₂Sb(CH₂)₃SbMe₂}Cl₂], Me₂Sb(Cl₂)(CH₂)₃Sb(Cl₂)Me₂, and other products. Several unstable [Pt(L–L)l₄] complexes have been prepared, which lose iodine very easily and are partially dissociated in solution. Chlorine oxidation of [Pt(L′–L′)₂Cl₂][L′–L′=o-C₆H₄(AsMe₂)₂, Me₂PCH₂CH₂PMe₂, or o-C₆H₄(PMe₂)(AsMe₂)] produced trans-[Pt(L′–L′)₂Cl₂]Cl₂, but for L′–L′=o-C₆H₄(AsPh₂)₂ or cis-Ph₂AsCHCHAsPh₂ the product was [Pt(L′–L′)Cl₄] and oxidised ligand. The complex [Pt(Ph₂PCH₂CH₂PPh₂)₂Cl₂] gave [Pt(L–L)Cl₄] on chlorine oxidation in solution, but Pt(L–L)₂Cl₄ when oxidised in a CCl₄ suspension. The syntheses of mer-[Pt{PPh(CH₂CH₂PPh₂)₂}X₃]X, mer-[Pt{AsMe(CH₂CH₂AsMe₂)₂}X₃]X (X = Cl or Br),[Pt{P(CH₂CH₂PPh₂)₃}Cl₂]Y₂, [Pt{As(CH₂CH₂CH₂AsMe₂)₃}Cl₂]Cl₂, [Pt{(CH₂PPhCH₂CH₂PPh₂)₂}Cl₂]Y₂, and [Pt{o-C₆H₄[As(Me)CH₂CH₂CH₂AsMe₂]₂}Cl₂]Cl₂(Y = Cl or ClO₄) are described. Complexes were characterised by i.r., electronic, and ¹H n.m.r. spectroscopy, and conductivity measurements.