REACTIVITY OF THE P-N BOND IN THE HALIDE SALTS OF BIS[BIS(DIPHENYLPHOSPHINO)METHYLAMINE]PLATINUM(II)

Conductivity measurements and P-31-{H-1} NMR spectroscopy suggested th at the chloride and iodide salts of bis[bis(diphenylphosphino)methylam ine]platinum(II) [Pt(dppma)(2)](2+) 1 exist in solution equilibrium wi th the five-co-ordinate complexes [Pt(dppma)(2)X](+) (X = Cl or I). Th e magnitude of the interaction of the iodide ion with 1 is greater tha n that of the chloride ion. The extent of formation of the halide-asso ciated species is dependent upon the nature of the solvent. Associatio n equilibrium constants K-assoc = 0.0718 and 0.315 mol dm(-3) respecti vely were calculated for the chloride and iodide salts of 1 in MeNO(2) . Addition of trace quantities of water to solutions of the chloride o r iodide salts of 1 effected cleavage of both P-N bonds of one of its dppma ligands giving [Pt(dppma){(Ph(2)PO)(2)H}](+) 2. The structure of the cation was investigated crystallographically as a mixture of the iodide and tetrafluoroborate salts of the form I-0.21[BF4](0.79). The analogous reaction of the chloride salt of 1 with MeOH produces cleava ge of only one P-N bond to give [Pt(dppma)(Ph(2)POMe)(Ph(2)PNHMe)](2+) 3 as the chloride salt. Phosphorus-nitrogen bond solvolysis of both l igands of 1 occurs to give the complex trans-[Pt(Ph(2)POMe)(2)(CN)(2)] 4 upon addition of 2 equivalents of sodium cyanide to methanolic solv ent mixtures of [Pt(dppma)(2)]X(2) (X = BF4, Cl or I). The product was characterised crystallographically. Possible mechanisms bf formation of these complexes are discussed.