NOVELTY - Production (P1) of hydrogen involves contacting at least one transition metal complex (I) with at least one ammonia borane substrate (II).    USE - For production of hydrogen use in fuel cell (claimed) and combustion engines.    ADVANTAGE - The transition metal complex is a bifunctional dual site complex that is robust and stable over long periods. The method safely releases hydrogen at constant rate; and provides a constant flow rate of high purity hydrogen for use in fuel cells or combustion engines, which in combination with atmospheric oxygen emit only water. No external heating, light or electricity is required to initiate the catalytic dehydrogenation process. Hydrogen has been shown to carry an extremely energy to mass ratio of 120 MJ kg-1 as compared to conventional gasoline products (44 MJ kg-1).    DETAILED DESCRIPTION - Production (P1) of hydrogen involves contacting at least one transition metal complex of formula (I) with at least one ammonia borane substrate of formula R1R2-NH-BH-R3R4 (II).    X-=anion;    Y'=N or CR6;    M=Ru, Os or Fe;    A and B'=saturated, unsaturated or partially unsaturated carbocyclic ring;    R5-R7=H, NR24R25, 1-6C alkyl or 1-6C haloalkyl;    R8-R25=H, 1-6C alkyl, 1-6C haloalkyl, or linker group (optionally attached to a solid support);    R1-R4=H, 1-20C alkyl, fluoro-substituted-1-20C alkyl, 6-14C aryl or 6-14C aralkyl.    At last two of R5-R7 are linked, together with the carbons to which they are attached, to form (un)saturated carbocyclic group. At last two of R1-R4 are linked to form 2-10C alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group. INDEPENDENT CLAIMS are included for the following:    (1) a hydrogen generation system comprising the complex (I), the substrate (II), and a solvent;    (2) a fuel cell comprising the complex (I);    (3) a method of thermolytically dehydrogenating the substrate (II) involving: contacting the substrate (II) with the complex (I) in the presence of a solvent;    (4) a method of using a hydrogen generation system involving: modulating the hydrogen pressure in the system to modulate activity of the complex (I); and    (5) new transition metal complex of formulae (I1)-(I7).