Au2PbP2, Au2TlP2, and Au2HgP2:: Ternary gold polyphosphides with lead, thallium, and mercury in the oxidation state zero

The polyphosphide Au2PbP2 was prepared by reaction of the elemental components using liquid lead as a reaction medium. Well-developed crystals were obtained after dissolving the matrix in hydrochloric acid. Their crystal structure was determined from four-circle X-ray diffractometer data: Cmcm, a=323.6(1)pm, b=1137.1(2)pm, c=1121.8(1)pm, Z=4, R=0.023 for 478 structure factors and 20 variable parameters. The structure contains zigzag chains of phosphorus atoms with a typical single-bond distance of 219.4(2) pm. The two different kinds of gold atoms are both in linear phosphorus coordination with typical single-bond distances of 232.6(2) and 234.2(2) pm, and the lead atoms have only metal neighbors (7 An and 2 Pb). Accordingly, chemical bonding of the compound may be expressed by the formula (Au+1)(2)Pb+/-0(P-1)(2). The corresponding thalliurn and mercury polyphosphides Au2TIP2 (a=324.1(1)pm, b=1136.1(1)pm, c=1122.1(1)pm) and Au2HgP2 (a=322.1(1) pm, b=1131.4(2) pm, c=1122.6(1) pm) pm) were found to be almost isotypic with Au2PbP2. Their crystal structures were refined from single-crystal X-ray data to R=0.036 (682 F values, 25 variables) and R=0.026 (539 F values, 35 variables), respectively. The structure of these compounds may also be described as consisting of a three-dimensional network of condensed 8- and 10-membered Au2P6 and Au4P6 rings forming parallel channels, which are filled by the lead, thallium, and mercury atoms. The lead atoms are well localized in these channels, while the thallium and even more the mercury atoms occupy additional positions within these channels. Freshly prepared samples of Au2HgP2 show reproducibly slightly different axial ratios and larger cell volumes (DeltaV=0.5%) than those after exposure of the samples to air for several days. (C) 2002 Elsevier Science (USA).