Crystal Structure of Bis(ethylenediphosphinetetraacetic acid)palladium(II) Bis(dihydrogenethylenediphosphinetetraacetato)palladate(II) Tetrahydrate Hydrobromide (1/1): An Unusual Case of Bromide Uncoordinated to Palladium(II)
Synthesis, crystal and molecular structure of the title compound as a representative of the complexes of phosphineacetic acids with soft metal ions is described. Crystal data: triclinic, P1 , a = 10.809(1), b = 14.922(1), c = 10.617(1) A, α = 108.871(7), β = 102.773(9), γ = 102.970(7)°, Z = 1, R = 0.031 for 4 545 observed reflections. The structure is built of layers composed of hydrogen-bonded ligands; the layers are joined, in alternate manner, by Pd(II) ions, water molecules and bromide anions. As an average, one proton of the tetraprotonated ligand is released during complexation even in protic solvent (aqueous acetic acid), resulting in the given ionic composition with non-equivalent Pd(II) centers. The carboxyl groups and, surprisingly, even the bromide ion are not coordinated to Pd. The proton assigned formally to hydrobromic acid was not located and is possibly disordered.