LA3OS2O10 A NEW COMPOUND CONTAINING ISOLATED CLUSTERS OS2O10 WITH METAL-METAL BONDS

The formula of a new compound isolated in the LaOsO system has been established by means of crystal structure determination. There are two La3Os2O10 units in a face-centered monoclinic unit cell (S.G. C2 m); a = 7.911(2) Å, b = 7.963(2) Å, c = 6.966(2)Å, β = 115.76(2)°;. For 1082 intensities, collected on an automated single-crystal diffractometer, the final R value was 0.025 after absorption corrections. The structure consists of isolated Os2O10 clusters composed of two edge-shared OsO6 octahedra. These dimeric units are connected together by two types of La3+ ions in eightfold coordination. In view of the OsOs distance inside the pair (2.462 Å), La3Os2O10 provides an example of metal-metal bonding involving a transition metal in a half-integral formal oxidation state of 5.5. © 1979.