Inter- and intra-molecular condensation patterns of (en)Pd-II with trans-[a(2)PtL(2)](2+)(a=am(m)ine, L=2-aminopyridine) : PtPd3 and Pt2Pd4 species with multiple amide bridges : unexpected trapping of a pair of nitrate ions by a Pt2Pd4 double cone

Reaction of trans-[a(2)Pt(Hampy)(2)] X-2 (a = NH3, 2; a = MeNH2, 3; Hampy = 2-aminopyridine; X = NO3 or ClO4) with an excess of [(en) Pd(H2O)(2)](2+) in aqueous solution leads to two types of condensation products: (i) tetranuclear PtPd3 species, in which the deprotonated " a" ligands (mu-NH2, mu-MeNH) and the deprotonated amino group of the 2-aminopyridine (ampy) ligands are chelated by two (en) Pd-II entities and in addition a single Pd-II ion (without en) cross-links the amido functions of ampy in a nearly linear fashion. The four metal ions thus form a diamond arrangement with a short (< 2.5 &ANGS;) Pt-->Pd dative bond. (ii) Hexanuclear Pt2Pd4 species, in which (en) Pd-II moieties bridge exclusively amido groups of four ampy ligands in such a way that an open rectangular box ( or double cone) is formed. This allows two nitrate counter ions to become inserted in the cavity of the +8 charged cation. Thus in both cases the ampy ligand acts as a mu(3)-ligand, either in an intramolecular or an intermolecular fashion.