NOVELTY - Preparing a metal hydride comprises: (a) heating an alkyl and/or aryl transition metal compound in a solvent in the absence of hydrogen to form a precipitate; (b) optionally isolating the precipitate; (c) hydrogenating the precipitate; and (d) optionally isolating the hydrogenated precipitate.    USE - The method is useful for preparing a metal hydride, which is used: in a composition, metal hydride storage material, in a battery or fuel cell, and for hydrogen storage (all claimed); for methane adsorption, and in compressed natural gas storage, and propellants.    ADVANTAGE - The method provides metal hydride with improved purity, that exhibits enhanced hydrogen storage capacity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a metal hydride prepared by the process;    (2) metal hydride of formulae (M1(M2)zHxR1yL1n) (I) or M11(M2)zHx1R11yL1n(H2)a (II);    (3) purifying the metal hydride comprising subjecting the metal hydride to at least one hydrogen adsorption-desorption cycles;    (4) method of storing hydrogen comprising providing the metal hydride, adding hydrogen to the metal hydride, and allowing the hydrogen to coordinate to the metal hydride, optionally where the hydrogen is stored in a storage system, such that the method comprises providing the metal hydride in the storage system, adding hydrogen to the metal hydride in the storage system, and allowing the hydrogen to coordinate to the metal hydride in the storage system;    (5) a hydrogen storage system comprising a storage system and the metal hydride within the storage system;    (6) a storage for a gas including hydrogen, methane or compressed natural gas comprising a storage system and the metal hydride within the storage system; and    (7) a storage system for producing electricity using a fuel-cell or heat using an oxidant, comprising a storage system and the metal hydride within the storage system.    M1 = Ti or V (when x is 4.6-13), or Cr (when x is 4.6-12) or Fe (when x is 4.6-10), Co or Ni (when x is 4.6-8), Cu (when x is 4.6-6) or Mn;    M2 = at least one additional metal;    R1 = if present, is an organic group, preferably alkyl, silylated alkyl, alkenyl, arylalkyl, heteroaryl or aryl;    L1 = Lewis base;    n = 0-1;    y = 0-0.5, preferably 0-0.05; and    z = 0-1;    M11 = Ti, V, Cr, Fe, Co, Ni, or Cu; and    a = greater than 1, preferably 3-5, preferably when M1 is Ti, x is greater than 7, preferably 12.5-13, when M1 is V, x is greater than 7, preferably 12.5-13, when M1 is Cr, x is greater than 6, preferably 11.5-12, when M1 is Fe, x is greater than 6, preferably 9.5-10, when M1 is Co, x is greater than 6, preferably 7.5-8, or when M1 is Ni, x is greater than 6, preferably 7.5-8, preferably when M11 is Ti, x1 is 3, and a is 3-5, when M11 is V, x1 is 3, and a is 3-5, when M11 is Cr, x1 is 2, and a is 3-5, when M11 is Fe, x1 is 2, and a is 3-5, when M11 is Co, x1 is 2, and a is 3, or when M11 is Ni, x1 is 2, and a is 3.