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  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
  • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
  • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
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  • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
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  • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
  • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
  • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
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  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
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  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
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  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
  • C07F15/0006—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table compounds of the platinum group
  • C07F15/0046—Ruthenium compounds
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  • C07F17/00—Metallocenes
  • C07F17/02—Metallocenes of metals of Groups 8, 9 or 10 of the Periodic Table
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  • C09B57/10—Metal complexes of organic compounds not being dyes in uncomplexed form
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
  • B01J2231/70—Oxidation reactions, e.g. epoxidation, (di)hydroxylation, dehydrogenation and analogues
  • B01J2231/76—Dehydrogenation
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  • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
  • B01J2531/82—Metals of the platinum group
  • B01J2531/821—Ruthenium
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  • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
  • B01J2531/82—Metals of the platinum group
  • B01J2531/825—Osmium
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
  • B01J2531/84—Metals of the iron group
  • B01J2531/842—Iron
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present invention relates to a process for the production of dihydrogen. More specifically, the invention relates to a process for catalysing the release of dihydrogen from ammonia borane, and derivatives thereof, using a transition metal catalyst.
• the process of the invention has important applications in the field of hydrogen fuel cells.
• Chemical hydrides can be packaged as non-pyrophoric, non-hazardous, solid, slurried or liquid fuels. Hydrogen may then be generated on demand from the chemical hydride under controlled conditions.
• hydrogen storage materials have a high hydrogen content and a low molecular weight.
• ammonia borane, H 3 N-BH 3 which has a very high hydrogen content by weight (19.2 %) and is attracting attention as a means of achieving efficient chemical hydrogen storage.
• Suitable catalyst examples include [Rh(1 ,5-cod)(M-CI)] 2 , [lr(1 ,5-cod)(M-CI)] 2 , RhCI 3 , lrCI 3 , trans-RuMe 2 (PMe 3 ) 4 and trans- PdCI 2 (P(o-tolyl) 3 ) 2 .
• secondary amine-borane adducts, R 2 NH-BH 3 have also been shown to undergo catalytic dehydrocoupling in the presence of Rh(l) or Rh (II) complexes to form cyclic aminoboranes and borazines (Manners et al, Chem. Commun., 2001 , 962-963).
• Baker et al discloses base metal catalysed dehydrogenation of ammonia borane using a nickel catalyst (J. Am. Chem. Soc, 2007, 129, 1844-1845). Similarly, Fagnou et al (J. Am. Chem. Soc, 2008, 103, 14034-14035) disclose ruthenium catalysts containing mixed phosphorus and nitrogen-containing ligands and their use in the dehydrogenation of ammonia boranes.
• US 2009274613 discloses the production of hydrogen from ammonia borane using a catalyst complex of the formula L n -M-X, where M is a base metal such as Fe, Mn, Co, Ni and Cu, X is an anionic nitrogen- or phosphorus-based ligand or hydride, and L is a neutral ancillary ligand that is a neutral monodentate or polydentate ligand.
• US 7,544,837 (Blacquiere et al) describes a method of dehydrogenating an amine- borane of formula R H 2 N-BH 2 R 2 using a base metal catalyst, to generate hydrogen and at least one of a [R 1 HN-BHR 2 ] m oligomer and a [R 1 N-BR 2 ] n oligomer.
• Base metal catalysts are defined as transition metals other than Pt, Pd, Rh, Os and Ru. The method has applications in the field of fuel cells.
• ligand stabilized homogenous catalysts containing Ru, Co, Ir, Ni and Pd to catalyse the release of hydrogen from ammonia borane is also described in WO 2008141439 (Kanata Chemical Technologies Inc.).
• Suitable ligands include phosphines, aminophosphines, heterocyclic ligands, diaminophosphines, diamines, thiophines and thioamines.
• US 20080159949 discloses a method of generating hydrogen from an ammonia borane complex using catalysts including cobalt complexes, noble metal complexes and metallocenes.
• suitable noble metal catalysts include NaRhCle, chlorotris(triphenylphosphine) Rh (I), (NH 4 ) 2 RuCI 6 K 2 PtCI 6 , (NH 4 ) 2 PtCI 6 Na 2 PtCl6, H 2 PtCI 6 , Fe(C 5 H 5 ) 2 and di-p-chlorobis(p-cymene)chororuthenium.
• the method is suitable for use in polymer electrolyte membrane fuel cells (also known as proton exchange or PEMFCs).
• PEMFCs polymer electrolyte membrane fuel cells
• the first is the high cost associated with the iridium or rhodium metal catalysts reported to date.
• the second problem is sensitivity to atmospheric oxygen, which at low levels significantly deactivates iridium and rhodium-based systems.
• the present invention seeks to provide a new method of generating hydrogen that alleviates one or more of the above problems. Specifically, the invention seeks to provide a means for storing hydrogen that allows for the controlled and safe release of dihydrogen at a constant rate.
• the present invention broadly relates to a process for the catalytic dihydrogen decoupling of ammonia boranes and derivatives thereof.
• a first aspect of the invention relates to a process for the production of dihydrogen comprising contacting at least one complex of formula (I),
• X " is an anion
• Y is N or CR 6 ;
• M is selected from Ru, Os and Fe
• each of A and B is independently a saturated, unsaturated or partially unsaturated carbocyclic ring
• R 5 , R 6 and R 7 are each independently selected from H, NR 24 R 25 , C 1-6 -alkyl and C 1-6 - haloalkyl, or two or more of R 5 , R 6 and R 7 are linked, together with the carbons to which they are attached, to form a saturated or unsaturated carbocyclic group;
• R 8 -R 25 are each independently selected from H, C 1-6 -alkyl, C 1-6 -haloalkyl and a linker group optionally attached to a solid support;
• R 1 , R 2 , R 3 and R 4 are each independently selected from H, C -2 o-alkyl, fluoro- substituted-C 1-2 o-alkyl, and C 6 . 14 -aryl, or any two of R 1 , R 2 , R 3 and R 4 are linked to form a C 2 -io-alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group.
• the presently described process provides a homogenous catalyst that activates gaseous dihydrogen.
• Ab initio calculations and experimental evidence have shown that a bifunctional mechanism is operative for the decoupling of ammonia borane.
• Preliminary studies have also indicated that at elevated pressure and temperature the process is reversible.
• the unique dual site design of the ⁇ -diketiminato-metal complex offers the possibility for reversible H 2 coupling, thereby regenerating the original ammonia borane and eliminating the need for external removal and reloading of the energy storage medium.
• a second aspect of the invention relates to a hydrogen generation system comprising: (a) at least one complex of formula (I)
• X " is an anion
• Y is N or CR 6
• M is selected from Ru, Os and Fe
• each of A and B is independently a saturated, unsaturated or partially unsaturated carbocyclic ring
• R 5 , R 6 and R 7 are each independently selected from H, NR 2 R 25 , C -6 -alkyl and C 1-6 - haloalkyl, or two or more of R 5 , R 6 and R 7 are linked, together with the carbons to which they are attached, to form a saturated or unsaturated carbocyclic group;
• R 8 -R 25 are each independently selected from H, C ⁇ e-alkyl, d_ 6 -haloalkyl and a linker group optionally attached to a solid support;
• R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-2 o-alkyl, fluoro- substituted-C 1-2 o-alkyl and C 6 -i 4 -aryl, or any two of R 1 , R 2 , R 3 and R 4 are linked to form a C 2- io-alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group; and
• a third aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a fuel cell.
• a fourth aspect of the invention relates to a fuel cell comprising at least one complex of formula (I) as defined above.
• a fifth aspect of the invention relates to a method of thermolytically dehydrogenating a substrate of formula (II) as described above, said method comprising contacting at least one substrate of formula (II) with a complex of formula (I) in the presence of a solvent.
• a sixth aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a method of thermolytically dehydrogenating a substrate of formula (II) as described above.
• a seventh aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a method of producing hydrogen.
• An eighth aspect of the invention relates to complexes of formula (I).
• a ninth aspect of the invention relates to a method of using a hydrogen generation system as defined above which comprises modulating the hydrogen pressure in said system so as to modulate activity of the at least one complex of formula (I).
• C 1-n alkyl means straight or branched chain, saturated alkyl groups containing from one to n carbon atoms and includes (depending on the identity of n) methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, 2,2-dimethylbutyl, n-pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, n-hexyl and the like, where the variable n is an integer representing the largest number of carbon atoms in the alkyl group.
• the C 1-n alkyl group is a C 1-20 -alkyl group, more preferably a C 1-6 -alkyl group.
• C 1-n -haloalkyl refers to a C 1-n -alkyl group as defined above in which one or more hydrogens are replaced with a halogen atom selected from Br, F, CI and I.
• the C 1-n -haloalkyl group is a C 1-2 o-haloalkyl group, more preferably a C 1-10 -haloalkyl group, even more preferably, a C 1-s -haloalkyl group.
• the C -n -haloalkyl group is a C 1-n -fluoroalkyl group, more preferably, a C _ 2 o-fluoroalkyl group, even more preferably a d.io-fluoroalkyl group, even more preferably still, a C 1-6 -fluoroalkyl group.
• CF 3 is a particularly preferred C -6 - fluoroalkyl group.
• C 6-n aryl means a monocyclic, bicyclic or tricyclic carbocyclic ring system containing from 6 to n carbon atoms and at least one aromatic ring and includes, depending on the identity of n, phenyl, naphthyl, anthracenyl, 1 ,2- dihydronaphthyl, 1 ,2,3,4-tetrahydronaphthyl, fluorenyl, indanyl, indenyl and the like, where the variable n is an integer representing the largest number of carbon atoms in the aryl group.
• the C 6 - n aryl group is a C 6 -i4-aryl group, more preferably, a C 6-10 -aryl group, even more preferably, a phenyl group.
• aralkyl means a conjunction of C 1-n alkyl or d-n-haloalkyl and C 6-n aryl as defined above.
• Preferred aralklyl groups include benzyl.
• the term "carbocyclic group” means a carbon-containing ring system, that includes monocycles, fused bicyclic and polycyclic rings, bridged rings and metallocenes. Where specified, the carbons in the rings may be substituted or replaced with heteroatoms. Preferably, the carbocyclic group is cyclohexyl.
• each of A and B is independently an unsaturated carbocyclic ring, more preferably a phenyl ring.
• Carbocyclic ring A is substituted by groups R 8 -R 12 as defined above, whereas carbocyclic ring B is substituted by groups R 13 -R 17 as defined above.
• fluoro-substituted means that one or more, including all, of the hydrogens in the group have been replaced with fluorine.
• the suffix "ene” added on to any of the above groups means that the group is divalent, i.e. inserted between two other groups.
• a first aspect of the invention relates to a process for the production of hydrogen comprising contacting at least one complex of formula (I), with at least one substrate of formula (II) as defined above.
• the process is carried out in the presence of a suitable solvent.
• the invention consists of a catalyzed chemical process for the controlled and safe release of hydrogen at constant rate from the substrate ammonia borane or related organic ⁇ , ⁇ -substituted derivatives.
• the overall purpose of the process is to provide 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 ).
• the presently described process provides a homogenous catalyst that activates gaseous dihydrogen.
• Ab initio calculations and experimental evidence have shown that a bifunctional mechanism is operative for the decoupling of ammonia borane.
• the reaction mechanism is illustrated in Figures 1 and 2.
• the complex of formula (I) e.g. denoted as complex A in Figures 1 and 2 extracts one equivalent of gaseous hydrogen from the substrate of formula (II) to form a hydride complex (e.g. denoted complex B in Figures 1 and 2).
• the resulting hydride complex is unstable and readily releases hydrogen at room temperature and pressure to reform the complex of formula (I) (e.g. complex A).
• the process of the invention uses a substrate of formula (II), R 1 R 2 -NH-BH-R 3 R 4 , wherein R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-20 -alkyl, fluoro- substituted-d-20-alkyl, C 6- 4 -aryl and C 6 _ 14 -aralkyl or any two of R , R 2 , R 3 and R 4 are linked to form a C 2- io-alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group.
• R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-20 -alkyl, fluoro- substituted-d-20-alkyl, C 6- 4 -aryl and C 6 _ 14 -aralkyl or any two of R , R 2 , R 3 and R 4 are linked to form a C 2- io-alkylene group, which
• R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-10 -alkyl, fluoro-substituted-C ⁇ o-alkyl, C 6- i 0 -aryl and C 6 --io-aralkyl, or any two of R 1 , R 2 , R 3 and R 4 are linked to form a C 2- 6-alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group.
• R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-6 -alkyl, fluoro-substituted-Ci-e-alkyl, C 6 -aryl and C 6-10 -aralkyl, or any two of R 1 , R 2 , R 3 and R 4 are linked to form a C 2 - 6 -alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group.
• R 3 and R 4 are both H.
• R 3 and R 4 are both H, and R and R 2 are each independently selected from H, C 1-10 -alkyl, fluoro-substituted-C -10 -alkyl, C 6- i 0 -aryl and C 6-10 -aralkyl, or R 1 and R 2 are linked to form a C 2-6 -alkylene group, which together with the nitrogen atom to which they are attached, forms a cyclic group.
• R 3 and R 4 are both H and R 1 , R 2 are each independently selected from H, C ⁇ o-alkyl, fluoro-substituted-C 1-10 -alkyl and C6--io-aryl.
• R 1 , R 2 , R 3 and R 4 are each independently selected from H and C 1 _ 2 o-alkyl.
• R 3 and R are both H, one of R 1 and R 2 is H and the other is selected from H, C - 0 -alkyl, C -10 -fluoroalkyl, C 6 . 10 -aryl and C 6 .io-aralkyl.
• one of R and R 2 is H and the other is selected from H, methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, tert-butyl, CF 3 , sec-butyl, phenyl and benzyl.
• R 3 and R 4 are both H, and R 1 and R 2 are each independently selected from H, methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, tert- butyl, sec-butyl, phenyl and benzyl, CF 3 , or R 1 and R 2 are linked to form a C 2-6 -alkylene group, which together with the nitrogen atom to which they are attached, forms a cyclic group.
• the C 2 . 6 - alkylene group is a C 4 -alkylene group.
• the substrate of formula (II) is selected from ammonia borane, methylamine borane, dimethylamine borane, di-isopropylamine borane, isopropylamine borane, tert-butylamine borane, isobutylamine borane, phenylamine borane and pyrrolidine borane.
• the substrate of formula (II) is ammonia borane, H 3 B-NH 3 , i.e. R 1 , R 2 , R 3 and R 4 are all H.
• Ammonia borane is a non- combustible, industrially inexpensive, low molecular weight solid substrate that carries multiple molecular equivalents of hydrogen. Ammonia borane has a high hydrogen carrying capacity of 19.6% per weight and is not flammable. This is consistent with the objectives set forth by the American department of energy of 5.5 wt% in vehicles by 2015.
• a molecular catalyst consisting of a metal and supporting organic ligands
• the process of the invention utilises a complex of formula (I), as defined above, as a catalyst.
• the catalyst is a bifunctional dual site complex consisting of a transition metal and a ligand that is robust and stable over long periods of time.
• M is Ru
• the catalyst is a modified r -arene ⁇ -diketiminato- ruthenium complex of formula (I), i.e. M is Ru.
• the catalyst can be synthesized in a single step process in high yield from commercially available precursors and can be stored in the solid state under nitrogen indefinitely.
• the complex of formula (I) is derived from a precursor that is a ⁇ - diketiminate-type ligand.
• Deprotonation of the structure shown on the left below gives rise to a ⁇ -diketiminate-type ligand as shown on the right below, that is conventionally represented with the dashed lines showing a delocalisation of the negative charge.
• the negative charge may of course be further delocalised over the molecule, depending on the nature of the A and B rings.
• the ⁇ -diketiminate-type ligand is capable of forming a complex with Ru(ll), Os(ll) or Fe(ll), for example, an r -arene ⁇ -diketiminato-ruthenium complex, an r -arene ⁇ - diketiminato-osmium complex or an r
• Ru(ll), Os(ll) or Fe(ll) for example, an r -arene ⁇ -diketiminato-ruthenium complex, an r -arene ⁇ - diketiminato-osmium complex or an r
• the coordination between the metal M and the r -arene group is represented as a dashed line.
• counterion X " in the complex of formula (I) is selected from OTf, BF “ , PF e “ , BPh 4 " and BArF “ (B((3,5-CF 3 ) 2 C 6 H 3 )4T More preferably, counterion X " is OTf.
• R 5 , R 6 and R 7 are each independently selected from H, NR 24 R 25 , C 1-6 -alkyl and C 1-6 - alkyl, or two or more of R 5 , R 6 and R 7 are linked, together with the carbons to which they are attached, to form a saturated or unsaturated carbocyclic group.
• the CLis-haloalkyl group is a C ⁇ -fluoroalkyl group.
• R 5 , R 6 and R 7 are each independently NR 24 R 25 , preferably, R 24 and R 25 are each independently H or C -6 -alkyl.
• R 5 , R 6 and R 7 are each independently selected from H, NR 24 R 25 and C -6 -alkyl, or two or more of R 5 , R 6 and R 7 are linked, together with the carbons to which they are attached, to form a saturated or unsaturated carbocyclic group.
• R -R are each independently selected from H, Ci -6 -alkyl, C haloalkyl and a linker group optionally attached to a solid support.
• the group is a C 1-6 -fluoroalkyl group.
• R 8 -R 25 are each independently selected from H, Ci assign 6 -alkyl and a linker group optionally attached to a solid support.
• R 8 -R 25 are each independently selected from H, methyl, CF 3 and isopropyl and a linker group optionally attached to a solid support.
• R 8 -R 25 are each independently selected from H, methyl, CF 3 and isopropyl.
• R 7 is selected from H, C -6 -alkyl, C 1-6 - haloalkyl, and R 5 and R 6 are linked together with the carbon atoms to which they are attached to form a 6-membered carbocyclic group.
• the ( ⁇ .e-haloalkyl group is a C ⁇ e-fluoroalkyl group. More preferably, R 5 and R 6 are linked together with the carbon atoms to which they are attached to form a 6-membered unsaturated group.
• Y is CR 6 .
• Y is CR 6
• R 6 is H
• R 5 and R 7 are each independently selected from C 1 _ 6 -alkyl, C 1-B -haloalkyl and N(C . 6 -alkyl) 2 . More preferably R 5 and R 7 are each independently selected from methyl, CF 3 and NMe 2 .
• Y is CR 6
• R 6 is H and R 5 and R 7 are each independently selected from C 1-6 -alkyl, and N(Ci. 6 -alkyl) 2 . More preferably R 5 and R 7 are each independently selected from methyl and NMe 2
• Y is N. In one preferred embodiment, Y is N and R 5 and R 7 are each independently selected from C 1-6 -alkyl, C 1-6 -haloalkyl and More preferably R 5 and R 7 are each independently selected from methyl, CF 3 and NMe 2 . In one preferred embodiment, Y is N and R 5 and R 7 are each independently selected from C -6 -alkyl and N(C 1 . 6 -alkyl) 2 . More preferably R 5 and R 7 are each independently selected from methyl and NMe 2 .
• R 8 , R 12 , R 13 and R 17 are each independently selected from C 1-6 -alkyl, C 1-6 -haloalkyl, and R 9 , R 10 , R 11 , R 14 , R 15 and R 16 are all H.
• R 18 -R 23 are each independently selected from H, C -6 - alkyl, C 1-6 -haloalkyl.
• R 18 -R 23 are all H.
• R 18 -R 23 are all each independently C ⁇ -alky!, more preferably, Me.
• R 8 and R 2 are C -6 -alkyl, and R 9 , R 20 , R 22 and R 23 are all H.
• R 18 is Me
• R 21 is isopropyl
• R 19 , R 20 , R 22 and R 23 are all H.
• the complex of formula (I) is selected from the following:
• the complex of formula (I) is anchored to a solid support, for example, a polymer, thereby facilitating easy separation of the spent materials.
• a solid support for example, a polymer
• suitable solid supports will be familiar to one of ordinary skill in the art.
• suitable linker groups for attaching the complex of formula (I) to the solid support will also be familiar to the skilled artisan.
• the post-grafting of the catalyst to an insoluble solid surface is preferably achieved via attachment through the r -arene, i.e. one or more of R 18 -R 23 is a linker group optionally attached to a solid support.
• the insoluble solid surface is mesoporous silica, e.g. MCM-41 containing hexagonal channels.
• the complex of formula (I) is anchored to the solid surface via a linear silanol alkyl tether.
• the complex of formula (I) may be prepared and isolated prior to use in the process of the invention, or may be generated in situ.
• Another aspect of the invention relates to a complex of formula (lb), (Ic), (Id), (le), (If) (Ig) or (1 h) as defined above.
• the process of the reaction is typically carried out using a suitable solvent system.
• the substrate of formula (II) is dissolved or slurried in a polar, non-protic solvent.
• suitable solvents include toluene, chlorinated solvents such as methylene chloride and 1 ,2-dichlorobenzene, and ethereal solvents such as tetrahydrofuran (THF), ,2-dimethoxyethane, diglyme and polyethylene glycol dimethyl ethylene.
• solvents may be used either individually or in combination with each other.
• Particularly preferred solvents include 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3- methylimidazolium trifluoromethanesulfonate.
• Particularly preferred fluorinated solvents include ⁇ , ⁇ , ⁇ -trifluorotoluene.
• the process of the invention uses a non-volatile solvent, so that only dihydrogen is liberated during the reaction.
• the process of the invention takes place in a homogeneous mixture, i.e. preferably the complex of formula (I) is essentially soluble in the reaction solvent(s) and remains essentially in solution through the reaction process with minimal amounts of precipitation.
• the solvent is a mixture of THF and dimethoxyethane.
• the ratio of THF and dimethoxyethane is from about 4:1 to about 3:1.
• the complex of formula (I) is dissolved or slurried in solution with the same solvent as that used to dissolve or slurry the substrate of formula (II).
• the process involves mixing a concentrated slurry of ammonia borane with an inert solvent mixed with a small amount of the r -arene ⁇ - diketiminato-metal complex.
• the system remains inert until a flow valve is open and the catalytic process operates until the substrate is spent or the valve is closed. Studies showed that elevated temperatures did not significantly increase the static pressure of hydrogen.
• the catalyst to substrate ratio directly controls the rate of hydrogen released. For example, 0.5 mol% of the catalyst dissolved in solution (THF, dimethoxyethane) will release one substrate equivalent of hydrogen within 60 seconds. This is comparable to yielding from 1 g of H 3 BNH 3 , a sustained rate of 779 cm 3 of H 2 per min at 1 atm pressure or 13 cc per second.
• the catalyst is capable of extracting up to two equivalents of hydrogen from the ammonia borane substrate.
• the activity of the catalyst is controlled by hydrogen pressure and liberates hydrogen from ammonia borane until a pressure of 3 atm is obtained. At pressures over 3 atm, the catalyst is deactivated, but is re-activated upon pressure release.
• the system dramatically reduces the amount of free hydrogen within the system during static storage periods.
• a 235 L H2 tank weighting 64 kg with 340 atm of pressure is required to be fixed onboard.
• the invention does not require a pressurized container; the material construction of the cell can consist of light weight plastics.
• the weight of the ammonia borane cell would be about 50 kg, but with a significantly more compacted volume of 65 L.
• the process of the invention is carried out at reduced pressure.
• the process can be carried out without the need for an external heat source.
• the process of the invention is carried out at a temperature of at least 0°C.
• the hydrogen that is generated in the process of the invention may be optionally captured using any known means.
• the reaction produces, in addition to hydrogen gas, easily recyclable and environmentally friendly ammonium borate salts as the only detectable boron-containing residue.
• the reaction may be performed in air, but may also be performed in an inert atmosphere, for example, under argon or neon, or under hydrogen.
• the process of the invention is carried out in the absence of oxygen.
• the process of the invention is carried out in an inert atmosphere. Hydrogen Generation System
• the process of the invention is used to generate hydrogen, which is supplied to a hydrogen fuel cell, such as a PEMFC.
• Hydrogen generators may include a first compartment holding a catalyst-comprising solution and a second compartment holding the one or more substrates of formula (II) as defined above.
• a further aspect of the invention therefore relates to a hydrogen generation system comprising: (a) at least one complex of formula (I)
• X " is an anion
• Y is N or CR 6
• M is selected from Ru, Os and Fe
• each of A and B is independently a saturated, unsaturated or partially unsaturated carbocyclic ring
• R 5 , R 6 and R 7 are each independently selected from H, NR 24 R 25 , C 1-6 -alkyl and d. 6 - haloalkyl, or two or more of R 5 , R 6 and R 7 are linked, together with the carbons to which they are attached, to form a saturated or unsaturated carbocyclic group;
• R 8 -R 25 are each independently selected from H, C 1-6 -alkyl, C-
• R 1 R -NH-BH-R 3 R 4 wherein R 1 , R 2 , R 3 and R 4 are each independently selected from H, C 1-2 o-alkyl, fluoro- substituted-Ci cognitive2cralkyl and C 6-14 -aryl, or any two of R 1 , R 2 , R 3 and R 4 are linked to form a C 2 -io-alkylene group, which together with the nitrogen and/or boron atoms to which they are attached, forms a cyclic group; and
• the hydrogen generation system comprises a first compartment comprising the at least one complex of formula (I), a second compartment comprising the at least one substrate of formula (II), wherein the first or second compartment further comprises a solvent and/or a means for combining the contents of the first compartment with the contents of the second compartment such that when the contents are combined, hydrogen is generated.
• the hydrogen generation system further comprises at least one flow controller to control a flow rate of the at least one complex of formula (I) or the at least one substrate of formula (II).
• control electronics are coupled to catalyst mass flow controllers and hydrogen mass flow controllers.
• Catalyst mass flow controllers control the flow of the catalyst solution, which enters second compartment to achieve a desired hydrogen flow generated by the hydrogen generator.
• the at least one substrate of formula (II) is stored in a second compartment as a solid or as a solution in the solvent.
• control electronics send a signal to a mass flow controller (or a flow controller) to allow a predetermined flow rate of the at least one complex of formula (I) in a solvolytic and/or hydrolytic solvent in a first compartment to flow into the second compartment which holds the substrate of formula (II).
• a mass flow controller or a flow controller
• the substrate of formula (II) can be provided in the first compartment and be pumped into the second compartment holding the complex of formula (I) in the solvent.
• the hydrogen generation system is preferably in the form of a self-contained reaction vessel that is attached via a vent to any application requiring a source of hydrogen gas, for example, a chemical reaction, a fuel cell, or the like.
• Suitable fuel cells will be familiar to one skilled in the art and include any fuel cells that can use hydrogen as a fuel source, for example, internal combustion engines (ICE), solid oxide fuel cells (SOFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC) and molten carbonate fuel cells (MCFC).
• ICE internal combustion engines
• SOFC solid oxide fuel cells
• PAFC phosphoric acid fuel cells
• AFC alkaline fuel cells
• MCFC molten carbonate fuel cells
• the hydrogen generation system is connected to a proton exchange membrane fuel cell (PEMFC). More preferably, a coupling connector delivers hydrogen generated by hydrogen generator to the anode of a PEMFC.
• PEMFC proton exchange membrane fuel cell
• a coupling connector delivers hydrogen generated by hydrogen generator to the anode of a PEMFC.
• the hydrogen generators disclosed herein are capable of delivering PEMFC grade hydrogen at low reaction temperatures, safely and reliably. Such hydrogen PEM fuel cells are optimal for applications where batteries and internal combustion engines do not deliver cost-effective and convenient power generation solutions.
• the hydrogen generators disclosed herein provide a constant source of power in a compact size that does not require electrical recharging.
• Another aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a fuel cell.
• Another aspect of the invention relates to a fuel cell comprising at least one complex of formula (I) as defined above.
• the fuel cell further comprises a substrate of formula (II) as defined above, and optionally a suitable solvent.
• Another aspect of the invention relates to a method of thermoiytically dehydrogenating a substrate of formula (II) as described above, said method comprising contacting at least one substrate of formula (II) with a complex of formula (I) in the presence of a solvent.
• Another aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a method of thermoiytically dehydrogenating a substrate of formula (II) as described above.
• Another aspect of the invention relates to the use of at least one complex of formula (I) as defined above in a method of producing hydrogen.
• the complex of formula (I) is used in conjunction with a substrate of formula (II) as defined above.
• Another aspect of the invention relates to a method of using a hydrogen generation system as defined above which comprises modulating the hydrogen pressure in said system so as to modulate activity of the at least one complex of formula (I).
• Figure 1 shows the schematic relationship between complex A and complex B, together with the structure of complex B.
• Figure 2A shows the schematic reaction between complex A and H 3 B-NH 3 to form complex B.
• Figure 2B shows the corresponding energy profile.
• Figure 3 shows the results of an NMR study of hydrogen release (intensity versus time (min)).
• Figure 4 shows the results of a volume flow study (hydrogen equivalents released versus time (s)). Two catalyst types liberate 1.0 equivalent of hydrogen from ammonia borane.
• Figure 5 shows the synthetic route for preparing a catalyst according to the invention.
• Figure 6 shows an idealized onboard regenerative system based on ammonia borane.
• the concept is broken down as follows: (a) the reactor is loaded with the active complex solubilised in medium which is not volatile, or with vapour pressure that is low. The reactor is next filled with an ammonia borane or similar hydrogen containing substrate. The reaction is initiated and H 2 is released according to the cycle shown in Figure 6.
• the synthesis is straightforward and implements cheap starting materials.
• the catalyst is made in a single pot procedure (see Figure 5).
• the complex of the invention uses non-toxic ruthenium metal which is significantly cheaper than Ir or Rh.
• the round bottom flask was equipped with a Dean-Stark reflux condenser to allow for collection of water.
• the mixture was allowed to reflux at 130 °C over night.
• the yellow solution was reduced in volume and stored at -20 °C over night, after which an off-white solid formed.
• the solid was filtered off and added to 200 ml of distilled water and 100 ml of concentrated Na 2 C0 3 (80 g) in a large 500 ml beaker. After stirring the solution for about 1 hour, the two phases were separated.
• the aqueous solution was extracted twice with 70 ml of dichloromethane.
• the combined organic phases were dried over MgS0 4 and filtered.
• the filtrate was reduced in volume until a dark yellow oil is formed.
• the solution containing the diketiminate ligand was transferred to the solid sodium trifluoromethanesulfonate bis(dichloro(n 6 -benzene)ruthenium(ll)) mixture by canula.
• the reaction was allowed to stir for 24 hours under nitrogen at room temperature.
• the solution was filtered overtitiite under nitrogen to remove sodium chloride.
• Dichloromethane was removed from the filtrate under vacuum and the crude product was washed several times with degassed pentane and decanted. After drying the brown-red solid under vacuum for 3 days, 380 mg (80%) of the title compound were obtained.
• the synthesis was performed similar to the one for (n 6 -benzene)-ruthenium(ll)-n 2 -/V,/V- bis(2,6-dimethylphenyl)-2,4-pentanediketiminato trifluoromethanesulfonate, which yielded 353 mg (66%) of (n 6 -hexamethylbenzene)-ruthenium(ll)-r
• trifluoromethanesulfonate was obtained as a dark red-brown solid (81%).
• the crude solid was dissolved in dried and degassed dichloromethane and transferred into a 50 ml Schlenk flask containing 457 mg (0.9 mmol) of bis(dichloro(n 6 -benzene)ruthenium(ll)) and 409 mg (2.4 mmol) of sodium trifluoromethanesulfonate.
• the reaction was stirred at room temperature under an atmosphere of nitrogen for 48 hours to afford a black-purple solution.
• the mixture was filtered under nitrogen over celite to remove solid lithium chloride.
• Dichloromethane was removed from the filtrate in vacuo and the crude solid was washed with dried and degassed diethyl ether to afford 640 mg (56 %) of the title compound as a dark red solid.
• Figure 3 shows the results of an NMR study of dihydrogen release (intensity versus time (min)).
• complex A enables a rapid release of H 2 from ammonia borane, then a slow down when the solvent is saturated with H 2 due to pressure build up.
• complex A is deactivated at high pressure, but reactivated at low pressure, which is an important safety feature.

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• 2010
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