The present invention relates to a process for the production of
hydrogen comprising contacting at least one complex of formula (I), (I) wherein: X− is an anion; M is a
metal selected from Ru, Os, Fe, Co and Ni; D is optionally present and is one or more monodentate or multidentate donor ligands; Y1 is selected from CR13, B and N; Z1 and Z2 are each independently selected from ═N, ═P, NR14, PR15, O, S and Se; or Z2 is a direct bond between carbocyclic ring B and
substituent R4; each of A and B is independently a saturated, unsaturated or partially unsaturated carbocyclic
hydrocarbon ring; R3 and R4 are each independently selected from H, C1-6-
alkyl,
aryl and C1-6-haloalkyl, and a
linker group optionally attached to a
solid support; or R3 and R4 together form the following
moiety: (AB) Y2 is a direct
single bond or
double bond, or is CR18; R1, R2, R5-13 and R16-18 are each independently selected from H, C1-6-
alkyl, C2-6-alkenyl, C2-6-alkynyl,
aryl, C1-6-haloalkyl, NR19R20 and a
linker group optionally attached to a
solid support; or two or more of said R1-13 and R16-18 groups are linked, together with the carbons to which they are attached, to form a saturated or
unsaturated hydrocarbon group; R14, R15, R19 and R20 are each independently selected from H, C1-6-
alkyl, C2-6-alkenyl, C2-6-alkynyl,
aryl, C1-6-haloalkyl, and a
linker group optionally attached to a
solid support; with at least one substrate of formula (II), R21R22NH—BHR23R24, wherein R21 to R24 are each independently selected from H, C1-6-alkyl, fluoro-substituted C1-6-alkyl, C6-14-aryl and C6-14-aralkyl, or any two of R21, R22, R23 and R24 are linked to form a C3-10-alkylene group or C3-10-alkenylene group, which together with the
nitrogen and / or
boron atoms to which they are attached, forms a cyclic group; or a substrate comprising two, three or four substrates of formula (II) linked via one or more bridging groups so as to form a dimeric, trimeric or tetrameric species, and wherein the bridging group is selected from straight or branched C1-6-alkylene optionally substituted by one or more fluoro groups,
boron, C6-14-aryl and C6-14-aralkyl; or a substrate comprising two, three or four substrates of formula (II) which are joined so as to form a fused cyclic dimeric, trimeric or tetrameric species. Further aspects of the invention relate to a
hydrogen generation
system comprising a complex of formula (I), a substrate of formula (II) and a
solvent, and to the use of complexes of formula (I) in
fuel cells. Another aspect of the invention relates to novel complexes of formula (I).