Synthesis and chemical behavior of [MFe4(CO)16]n(M=Au, Zn, Cd, Hg) clusters: X ray structure of [NMe3CH2Ph]2[Au{Fe2(CO)8Cl and [PPh4]2[Cd{Fe2(CO)6(H-CO)2}2]2CH3CN

The metastable hexagonal form of MoO3 has been successfully prepared starting from the ammonium molybdate. using a "Chimie Douce" reaction with NO2 gas. The lattice parameters of the as-prepared material were determined by XRD analysis to be: a = 10.633(2) A and c = 3.719(1) A. The composition of this material obtained by physical and chemical analysis is MoO3, 0.09 H2O, showing that a small amount of water molecules remained while there were no more ammonium ions in this structure. The structural transformation from hexagonal to stable orthorhombic (alpha)-MoO3 phase was observed at 350 °C. It was also shown that NC2 reaction is a very useful method to remove topotactically ammonium ions from a parent structure at low temperature. This "Chimie Douce" process appears to be very promising for obtaining new metastable oxides with large tunnels or interlayer distances.