Cationic Pb2 Dumbbells Stabilized in the Highly Covalent Lead Nitridosilicate Pb2Si5N8

Due to the weak oxidative force of N-2, nitrides are only typically formed with the less electronegative metals. Meeting this challenge, we here present Pb2Si5N8, the first nitridosilicate containing highly electron-affine cations of a metal from the right side of the Zintl border. By using advanced synchrotron X-ray diffraction, the crystal structure was determined from a tiny single crystal of 1 x 3 x 3 mu m(3) in size, revealing a significantly different bonding situation compared to all other nitridosilicates known so far. Indeed, DFT calculations confirm distinct amounts of covalency not only between Pb and N but also between formal Pb2+ cations. Thus, unprecedented cationic Pb-2 dumbbells with a stretching vibration at 117 cm(-1) were found in Pb2Si5N8, the first representative of a crystallographically elucidated lead nitride, stabilized by high amounts of covalency.