SYNTHESIS AND STRUCTURE OF 2 NEW STRONTIUM GERMANIUM NITRIDES - SR3GE2N2 AND SR2GEN2

We report the structures of two new strontium germanium nitrides synth esized as crystals from the elements in sealed Nb tubes at 750 degrees C using liquid Na as a growth medium. Sr3Ge2N2 is isostructural with the previously reported Ba analogue. It crystallizes in P2(1)/m (No. 1 1), with a = 9.032(2) Angstrom, b = 3.883(1) Angstrom, c = 9.648(2) An gstrom and beta = 112.42(3)degrees, and has two formula units per unit cell. It contains GeN24- units and additionally (1)(infinity)\Ge2- zi gzag chains. Sr2GeN2 crystallizes in P4(2)/mbc (No. 135) with a = b = 11.773(2) Angstrom and c = 5.409(1) Angstrom and has Z = 8. It also co ntains GeN24- units which have 18 valence electrons and, consequently are bent, like the isoelectronic molecule SO2.