Stereoselective oxidative-addition reactions of dihalogens and copper(II) halides to square-planar organoplatinum(II) complexes containing hard N and C donor atoms. Molecular structures of [bc,de-bis(8-dimethylamino-1-naphthyl)]-af-diiodoplatinum(IV) and ab-dibromo[cf,de-bis(8-dimethylamino-1-naphthyl)]platinum(IV)

Abstract

Oxidative additions of electrophiles X₂(X = Br or I) and CuX₂(X = Cl or Br) to the complexes cis-bis[2-(dimethylaminomethyl)phenyl]platinum(II)1 and cis-bis(8-dimethylamino-1-naphthyl)-platinum(II)3 have been investigated. Those with X₂ afford the respective trans-X₂ platinum(IV) products, whereas with CuX₂ the cis-X₂ platinum(IV) products are obtained, except for the reaction of 1 with CuBr₂ which yields the trans-dibromo product. There is no evidence for cis-trans or trans-cis isomerizations of these octahedral platinum(IV) products in solution. On the basis of these stereoselective products formations (and earlier results) the proposed mechanisms are an S_N2 type for the reactions with dihalogens and an inner-sphere ligand-transfer oxidation for the reactions with copper(II) halides. The mechanisms of the reactions of X₂ and CuX₂ with trans-bis[2(dimethylaminomethyl)phenyl]platinum(II)2 are the same as with 1(and 3) but lead to other geometrical isomers. The stereochemistry of two of the oxidative addition products, i.e.[bc,de-bis(8-dimethylamino-1-naphthyl)]-af-diiodoplatinum(IV)5c and ab-dibromo[cf,de-bis(8-dimethylamino-1-naphthyl)]platinum(IV)5e, have been established by X-ray crystal structure determinations. Crystals of 5c are orthorhombic, space group Pbca, with a= 7.825(3), b= 17.803(2), c= 37.873(6)Å, Z= 8 and R= 0.032 for 2962 reflections with I > 2.5σ(I). Crystals of 5e are monoclinic, space group P2₁/c, with a= 9.696(2), b= 9.722(6), c= 26.81(3)Å, β= 90.46(4)°, Z= 4 and R= 0.083 for 3060 reflections with I > 2.5σ(I).