Transition‐Metal‐Catalyzed Dehydrocoupling: A Convenient Route to Bonds between Main‐Group Elements

Clark, Timothy; Lee, Kajin; Manners, Ian

doi:10.1002/chem.200600981

Cited by 271 publications

(205 citation statements)

References 112 publications

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“…Crystals suitable for X-ray diffraction were obtained by recrystallisation from difluorobenzene/pentane. 1 Addition of an excess of pentane followed by its evaporation was repeatedly performed until a powdered solid was obtained. Excess pentane was then added and the supernatant filtered off.…”

Section: Methodsmentioning

confidence: 99%

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

Stevens

Dallanegra

Chaplin

et al. 2011

Chemistry A European J

116

167

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The Ir(III) fragment {Ir(PCy(3))(2)(H)(2)}(+) has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H(3)B⋅NMe(2)H (A) to ultimately give dimeric aminoborane [H(2)BNMe(2)](2) (D). Addition of A to [Ir(PCy(3))(2)(H)(2)(H(2))(2)][BAr(F)(4)] (1; Ar(F) = (C(6)H(3)(CF(3))(2)), gives the amine-borane complex [Ir(PCy(3))(2)(H)(2)(H(3)B⋅NMe(2)H)][BAr(F)(4)] (2 a), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy(3))(2)(H)(2)(H(2)B-NMe(2))][BAr(F)(4)] (3). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H(2) loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3. DFT calculations indicate that this involves metal trapping of the monomer-dimer equilibrium, 2 H(2)BNMe(2) ⇌ [H(2)BNMe(2)](2). Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy(3))(2)(H)(2)(NCMe)(2)][BAr(F)(4)] (6) liberating H(2)B-NMe(2) (B), which then dimerises to give D. This is shown to be a second-order process. It also allows on- and off-metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine-borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H(3)B⋅NMe(2)BH(2)⋅NMe(2)H (C), which ultimately was converted to D. These results indicate that the metal is involved in both the dehydrogenation of A, to give B, and the oligomerisation reaction to afford C. A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D, with 3 observed as the final organometallic product, suggesting a B-N bond cleavage mechanism. Complex 6 does not react with C, but in combination with B oligomer C is consumed to eventually give D, suggesting an additional role for free aminoborane in the formation of D from C.

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Section: Methodsmentioning

confidence: 99%

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

Stevens

Dallanegra

Chaplin

et al. 2011

Chemistry A European J

116

167

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“…This of course suggested catalytic approaches that offer the opportunity to increase the rate and decrease the temperature of onset of hydrogen release. R&D performed by the CHSCoE (Baker, Sneddon, Heinekey, Goldberg, Burrell, and their colleagues [74][75][76][77][78][79][80][81][82][83][84][85][86][87] ) and by researchers outside of the Center resulted in the description of many different catalytic processes and catalysts for the dehydrogenation of ammonia borane (Figure 14). In order to perform the catalytic dehydrogenation of ammonia borane, it is necessary to make intimate contact of ammonia borane with the catalyst.…”

Section: Catalytic Release Of Hydrogen From Ammonia Boranementioning

confidence: 99%

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

Klebanoff

Ott

Simpson

et al. 2014

Metallurgical and Materials Transactions E

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A technical review of the progress achieved in hydrogen storage materials development through the U.S. Department of Energy's (DOE) Fuel Cell Technologies Office and the three Hydrogen Storage Materials Centers of Excellence (CoEs), which ran from 2005 to 2010 is presented. The three CoEs were created to develop reversible metal hydrides, chemical hydrogen storage materials, and high-specific-surface-area (SSA) hydrogen sorbents. For each CoE, the approach taken is specified, key outcomes and accomplishments identified, and recommendations for future work are suggested. The Metal Hydride Center of Excellence addresses work on destabilized hydrides, including the LiBH/Mg 2 NiH 4 system, borohydrides, amides, and alanes; and compares the best materials to DOE targets. The Chemical Hydrogen Storage Center of Excellence discusses the classes of materials studied for chemical hydrogen storage, focusing on ammonia borane and examines the progress in developing efficient regeneration schemes. The Hydrogen Sorption Center of Excellence describes the progress in developing high-SSA sorbents and pathways for developing improved materials capable of achieving DOE targets. The phenomenon of spillover is also observed and its importance to ensuring improved measurements is discussed. Through the five-year effort of the Hydrogen Storage Materials Centers of Excellence, significant progress was achieved in developing and understanding hydrogen storage materials.

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“…In particular, the lightweight complex metal hydrides (MAlH 4 and MBH 4 , M: alkali metal) enhanced by 3d-transition metal (TM) compounds offer a promising opportunity as solid-state hydrogen storage media for transportation applications due to Bogdanovic and Schwickardis breakthrough discovery with Ti-doped NaAlH 4 . [9] The discovery stimulated a large number of studies aimed at unraveling the role played by Ti as well as the mechanism of hydrogen adsorption and desorption in Ti-catalyzed NaAlH 4 . Great efforts have also been devoted to reduce the hydrogen release and recharging temperatures by improving the kinetics of the NaAlH 4 -based systems.…”

Section: Introductionmentioning

confidence: 99%

“…[1,2] Over the past decades, many advanced materials including complex metal hydrides, [3] chemical hydrides, [4,5] and metal-organic frameworks [6][7][8] have been explored as potential on-board hydrogen storage candidates. In particular, the lightweight complex metal hydrides (MAlH 4 and MBH 4 , M: alkali metal) enhanced by 3d-transition metal (TM) compounds offer a promising opportunity as solid-state hydrogen storage media for transportation applications due to Bogdanovic and Schwickardis breakthrough discovery with Ti-doped NaAlH 4 . [9] The discovery stimulated a large number of studies aimed at unraveling the role played by Ti as well as the mechanism of hydrogen adsorption and desorption in Ti-catalyzed NaAlH 4 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH₄

Han

2009

Chemistry A European J

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Periodic density functional theory calculations with plane-wave basis set and projector-augmented wave potentials have been carried out to investigate the stability and hydrogen interaction in the NaAlH(4)(001) surfaces doped with 3d transition-metal (TM) elements. A complex structure, TMAl(3)H(12), in which the TM atom occupies the interstitial position formed from three AlH(4)(-) groups, is the most stable structure for TM = Sc to Co. The stability of the complex structure, as well as the hydrogen desorption energies from different positions of the complex structure, was found to follow the 18-electron rule in general. The electron-deficient TMAl(3)H(x) tends to get more electrons by coordinating with the surrounding Al-H bonds and H-H bond, or by losing the "outside" hydrogen atoms. On the other hand, the electron-rich complex loses its excess electrons easily by releasing AlH(x), which resulted in the formation of a new catalytic center, or by desorbing H(2). By cycling between the electron-deficient and electron-rich states, TMAl(3)H(x) acted as an active center in reversible hydrogen release/uptake processes. Electronic structure analysis revealed that the electron transfer between hydrogen and Al groups mediated by the d orbitals of TMs played important roles in hydrogen release/uptake from alanate-based materials. The exchange of ligands can be described as a sigma-bond metathesis process catalyzed by transition metals through a dihydrogen complex. Early transition metals are more efficient to reduce hydrogen desorption energy and break H-H and Al-H bonds as a result of balanced electron-accepting/backdonating abilities, making them better candidates as catalysts. The present analyses are consistent with the experimental observations.

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Transition‐Metal‐Catalyzed Dehydrocoupling: A Convenient Route to Bonds between Main‐Group Elements

Cited by 271 publications

References 112 publications

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH₄

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Transition‐Metal‐Catalyzed Dehydrocoupling: A Convenient Route to Bonds between Main‐Group Elements

Cited by 271 publications

References 112 publications

[Ir(PCy3)2(H)2(H2BNMe2)]+ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H3B⋅NMe2H and Retrodimerisation of [H2BNMe2]2

[Ir(PCy3)2(H)2(H2BNMe2)]+ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H3B⋅NMe2H and Retrodimerisation of [H2BNMe2]2

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH4

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[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH₄