Synthesis and crystal structure of Na[Pd(Hpba)]center dot 2H(2)O [H(4)pba = 1,3-propylenebis(oxamic acid)]. The first bis(oxamato)palladium(II) complex and an unexpected trideprotonated form of the ligand

The complex of formula Na[Pd(Hpba)]. 2H(2)O, in which H(4)pba is 1,3-propyl enebis(oxamic acid), was obtained by reaction of the diethyl ester of the 1 ,3-propylenebis(oxamic acid) and Na2PdCl4 in basic conditions. The X-ray st ructure consists of [N,N'-(1,3-propanediyl)bis(oxamato-N,O)]palladate(II) d ihydrate anions, sodium cations and water molecules coordinated to the sodi um cations, linked together to give rise to polymeric chains [Na(H2O)(2)Pd( Hpba)](n). Within the [Pd(Hpba)](-) anions, Pd(II) atom occupies the N2O2 i nner-site of the ligand displaying a distorted square-planar coordination. Interestingly, the Ligand coordinates to Pd(II) in an unexpected trideproto nated fashion; the remaining hydrogen atom being located on an amide oxygen atom. (C) 1999 Elsevier Science S.A. All rights reserved.