Sr4PbPt4O11, the first platinum oxide containing Pt26+ ions

We report the synthesis and crystal structure of the new compound Sr4PbPt4O11, containing platinum in highly unusual square pyramidal coordination. The crystals were obtained in molten lead oxide. The structure was solved by X-ray single crystal diffraction techniques on a twinned sample, the final R factors are R=0.0260 and wR=0.0262. The symmetry is triclinic, space group P1-bar , with a=5.6705(6)A, b=9.9852(5)A, c=10.0889(5)A, α=90.421(3)o, β=89.773(8)o, γ=90.140(9)o and Z=2. The structure is built from dumbell-shaped Pt2O9 entities formed by a dinuclear metal-metal bonded Pt26+ ion with asymmetric environments of the two Pt atoms, classical PtO4 square plane and unusual PtO5 square pyramid. Successive Pt2O9 entities deduced from 90o rotations are connected through the oxygens of the PtO4 basal squares to form [Pt4O108-]∼ columns further connected through Pb2+ and Sr2+ ions. Raman spectroscopy confirmed the peculiar platinum coordination environment