LOW-TEMPERATURE SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF 3 NOVEL MAGNESIUM PLATINUM INTERMETALLICS, T-MGPTCXHY, T-MG2PTCXHY, M-MG2PTCXHY

Reactions between catalytically prepared solid or solubilized magnesiu m hydride (MgH2) and various transition metal species in organic solve nts under mild conditions (< 25-degrees-C) can be used to prepare amor phous binary magnesium intermetallics containing hydrogen. Within a pa rticular binary system, a series of crystalline intermetallic compound s can be purposely synthesized by controlling the molar ratio of the r eactants in the initial low temperature synthesis step and the subsequ ent thermal handling. In the magnesium platinum system, three novel co mpounds, t-MgPtC(x)H(y), t-Mg2PtCxHy and m-Mg2PtCxHy, have been isolat ed through this route, which were not previously obtained via metallur gical techniques. These crystalline intermetallics were structurally c haracterized via X-ray powder diffraction. t-MgPtC(x)H(y) crystallizes with a tetragonal cell (P4/mmm: a = 2.966(5), c 3.509(1) angstrom) an d the metal atom framework is isostructural with the HgMn structure ty pe t-Mg2PtCxHy crystallizes with a tetragonal cell (I4/mcm: a = 6.3338 (3), c = 5.6191(3)angstrom) and the metal atom substructure was refine d on the basis of a Al2Cu structural model. m-Mg2PtCxHy reveals a mono clinic unit cell C2/c: a = 7.214(l), b = 7.199(2), c = 6.9008(9) angst rom, beta = 106.05(1). The structure Of m-Mg2PtCxHy was refined in a s ubcell C2/m: a = 4.2451(4), b = 7.1945(9), c = 2.8200(2) angstrom, bet a = 92.638(9) and represents a new distorted variant of the high press ure form of titanium, omega-Ti.