PbP7 - a polyphosphide with a three-dimensional [P7](2-) network of condensed and P-bridged P6 hexagons

The first lead polyphosphide PbP7 was synthesized from the elements in a lead flux through a low-temperature route. The PbP7 structure was determined from single crystal X-ray diffractometer data: new type, P21/c, a = 970.70(11), b = 673.34(10), c = 1243.89(18) pm, β = 122.55(1)°, wR = 0.0488, 2022 F(2) values and 74 variables. PbP7 exhibits a pronounced three-dimensional phosphorus substructure that derives from the modification of black phosphorus: rows of trans-edge-sharing P6 hexagons in chair conformation are condensed via P bridges. Two of the seven crystallographically independent phosphorus atoms have two and five of them have three P neighbours, leading to an electron-precise Zintl-like description Pb(2+)P(-)P(-)P(0)P(0)P(0)P(0)P(0). The P-P distances lie in a small range of 219 to 225 pm, indicating P-P single bond character. The lead atoms fill large cages left by the phosphide substructure. Each lead atom is coordinated to six P atoms (283-333 pm Pb-P) in the form of a half-shell (capped pentagon). The opposite side claims the space for the lead lone pair (L) leading to very long Pb-Pb distances of 473 pm between adjacent P6PbL pairs. Consistent with the crystal structure, (31)P magic-angle spinning (MAS) NMR spectra show seven distinct signal components with equal peak areas.