Synthesis of new Group III fluoride-ammonia adducts in supercritical ammonia:: structures of AlF3(NH3)2 and InF2(NH2)(NH3)

The reaction of NH4F with AlN and InN in supercritical ammonia at 400 degrees C leads to the formation of two new metal fluoride amine complexes AlF3(NH3)(2) (I) and InF2(NH2)(NH3) (II). Both compounds were characterized by single-crystal X-ray diffraction. Compound I crystallizes in space group Immm, with Z = 2 and unit cell dimensions: a = 3.7184(8), b = 7.001 (1), c = 7.307(2) Angstrom, V = 190.22(7) Angstrom(3). Compound II crystallizes in the monoclinic space group P2(1)/n, with Z = 4 and unit cell dimensions: a = 7.723(3), b = 5.394(2), c = 8.638(2) Angstrom, beta = 95.52(2)degrees, V = 358.2(2) Angstrom(3). Both are completely new structural types and consist of extended arrays of distorted metal octahedra linked by bridging fluorides. In compound I, all octahedra are corner sharing with linear bridging fluorides. The resultant parallel chains are linked together by N-H ... F hydrogen bonding between terminal fluorides and coordinated amines. In II, there is a combination of distorted edge and corner-sharing octahedra with fluorides acting as edge-bridging groups and amides acting as corner-sharing units. The arrays form layers which are held together by hydrogen bonding. (C) 1999 Elsevier Science S.A. All rights reserved.