Selective B–H versus N–H Bond Activation in Ammonia Borane by [Ir(dppm)<sub>2</sub>]OTf

Rossin, Andrea; Caporali, Maria; Gonsalvi, Luca; Guerri, Annalisa; Lledós, Agustı́; Peruzzini, Maurizio; Zanobini, Fabrizio

doi:10.1002/ejic.200900465

Cited by 45 publications

(31 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the Rh systems H 2 was lost after aminoborane formation, whereas in the present Ir systems H 2 loss occurs between the B À H and N À H activation steps. B À H activation followed by N À H activation has also been suggested to be the favoured pathway in the dehydro- [19] Retrodimerisation of [H 2 BNMe 2 ] 2 : The tight Ir···B interaction present in 3 can be harnessed to drive the equilibrium between B and D towards the monomer, which otherwise at room temperature strongly favours the dimer (Scheme 1). [28,29] Thus heating a 2:1 mixture of 1 and D to 60 8C in C 6 H 5 F solution results in the formation of 3 after 12 h (Scheme 4).…”

Section: (H) 2 (H 2 -H 3 B·nme 2 H)]a C H T U N G T R E N N U N G [Bar Fmentioning

confidence: 99%

“…[4] There are now a good number of transition-metal and main group [5] systems that effect this transformation, some releasing hydrogen rapidly at low catalyst loadings [6][7][8] or giving polymeric materials of useful molecular weight and polydispersities. [4] Progress has also been made in understanding the mechanism of dehydrocoupling, [9] with intermediate and model complexes studied empirically, [10][11][12][13][14][15][16][17][18][19] kinetically [8,20,21] and through computational studies. [15,[22][23][24] Much of this work has centred upon the dehydrocoupling of H 3 B·NMe 2 H (A), which although it neither gives polymer (but rather dimeric [H 2 BNMe 2 ] 2 D instead) nor has high % H capacity, is attractive as it does afford a relatively straightforward set of products and intermediates that are soluble in common solvents.…”

Section: Introductionmentioning

confidence: 99%

“…[19] Retrodimerisation of [H 2 BNMe 2 ] 2 : The tight Ir···B interaction present in 3 can be harnessed to drive the equilibrium between B and D towards the monomer, which otherwise at room temperature strongly favours the dimer (Scheme 1). [28,29] Thus heating a 2:1 mixture of 1 and D to 60 8C in C 6 H 5 F solution results in the formation of 3 after 12 h (Scheme 4).…”

mentioning

confidence: 99%

See 2 more Smart Citations

[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

View full text Add to dashboard Cite

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.

show abstract

Section: (H) 2 (H 2 -H 3 B·nme 2 H)]a C H T U N G T R E N N U N G [Bar Fmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

[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

View full text Add to dashboard Cite

show abstract

“…Hydrogenation of [Ir(dppm) 2 ]OTf. [39] Homogeneous catalysts are more amenable to facile study, but from an engineering point of view, a heterogeneous dehydrogenation catalyst is preferable as it would allow easy separation of the spent fuel. In this vein, Burrell and co-workers recently reported on the dehydrogenation of AB using platinum, palladium, and ruthenium supported on alumina, activated carbon, and alumina respectively.…”

Section: New Catalyst Developmentsmentioning

confidence: 99%

Ammonia Borane as a Hydrogen Carrier: Dehydrogenation and Regeneration

2010

View full text Add to dashboard Cite

Interest in sustainable non‐hydrocarbon‐based fuels for transportation has grown as the realization that the supply of fossil fuels is limited and the deleterious environmental effects of burning them has come into public focus. The use of hydrogen (H2) has been proposed as an alternative, but its use in pure form is undesirable due to the high pressures or low temperatures required to store useful quantities. Approaches to ameliorate this issue, which stem from the low volumetric energy density of H2, include the pursuit of sorbents capable of containing H2 in greater density than liquid H2 at reasonable temperatures and pressures, metal hydrides such as NaBH4, and chemical hydrides such as ammonia borane (AB, NH3BH3). AB contains 19.6 wt.‐% H2, which is well suited to practical applications, but issues with extracting the optimal quantities of H2 at reasonable temperatures and at useful rates as well as recycling of the spent fuel back into AB with good efficiency and reasonable cost remain to be solved. These problems are inextricably intertwined, as the needs of the regeneration process dictate which catalysts are used (i.e. what kind of spent fuel is generated). This Microreview focuses on recent developments in transition metal complexes for the catalytic dehydrogenation of AB. Neither solvolysis of AB nor thermolysis of AB in the absence of a catalyst are covered in this review.

show abstract

“…This is contrast to the facile oxidative addition of the B-H σ-bond of ammonia-borane to the Ir(I) complex. [14] The third is the P-ONO cooperation pathway, in which the phosphorus centre and one atom of the ONO ligand cooperatively react with ammonia-borane. The P-O cooperation pathway is the most favorable with a moderate ∆G 0≠ value of 27.1 kcal/mol, which is much smaller than those of the aforementioned pathways.…”

mentioning

confidence: 99%

Catalytic Transfer Hydrogenation by a Trivalent Phosphorus Compound: Phosphorus‐Ligand Cooperation Pathway or P^III/P^V Redox Pathway?

et al. 2014

View full text Add to dashboard Cite

Main‐group‐element catalysts are a desirable alternative to transition‐metal catalysts because of natural abundance and cost. However, the examples are very limited. Catalytic cycles involving a redox process and E‐ligand cooperation (E=main‐group element), which are often found in catalytic cycles of transition‐metal catalysts, have not been reported. Herein theoretical investigations of a catalytic hydrogenation of azobenzene with ammonia–borane using a trivalent phosphorus compound, which was experimentally proposed to occur through PIII/PV redox processes via an unusual pentavalent dihydridophosphorane, were performed. DFT and ONIOM(CCSD(T):MP2) calculations disclosed that this catalytic reaction occurs through a P‐O cooperation mechanism, which resembles the metal‐ligand cooperation mechanism of transition‐metal catalysts.

show abstract

Selective B–H versus N–H Bond Activation in Ammonia Borane by [Ir(dppm)₂]OTf

Cited by 45 publications

References 33 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

Ammonia Borane as a Hydrogen Carrier: Dehydrogenation and Regeneration

Catalytic Transfer Hydrogenation by a Trivalent Phosphorus Compound: Phosphorus‐Ligand Cooperation Pathway or P^III/P^V Redox Pathway?

Contact Info

Product

Resources

About

Selective B–H versus N–H Bond Activation in Ammonia Borane by [Ir(dppm)2]OTf

Cited by 45 publications

References 33 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

Ammonia Borane as a Hydrogen Carrier: Dehydrogenation and Regeneration

Catalytic Transfer Hydrogenation by a Trivalent Phosphorus Compound: Phosphorus‐Ligand Cooperation Pathway or PIII/PV Redox Pathway?

Contact Info

Product

Resources

About

Selective B–H versus N–H Bond Activation in Ammonia Borane by [Ir(dppm)₂]OTf

[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

Catalytic Transfer Hydrogenation by a Trivalent Phosphorus Compound: Phosphorus‐Ligand Cooperation Pathway or P^III/P^V Redox Pathway?