Complexes of diaminomaleonitrile with nickel, palladium and platinum, and the crystal structure of bis-(diaminomaleonitrile)dichloropalladium

Diaminomaleonitrile (DMN) reacts with PdII and PtII in acidic solution to give the complexes [M(DMN)2Cl2], (M = Pd, Pt). A single crystal X-ray study has been made of the Pd complex. The crystals are monoclinic with unit cell parameters, a = 7·41, b = 7·89, c = 12·25 Å, β = 102·8°. The spacegroup is P21a and there are two centrosymmetric molecules per cell. The complex has the expected square planar geometry, with monodentate DMN ligands coordinating through one amine group. The possibility of further interaction between the metal atom d orbitals and the ligand π-system is discussed.In basic or neutral solutions, DMN react with NiII, PdII and PtII to give the highly coloured complexes [M(C4H2N4)2]. With [Pt0(Ph3P)4], DMN forms the complex [Pt(Ph3P)2C4H2N4]. The structures of these complexes are discussed.