Catalytic Dehydrogenation of Amine-Boranes using Geminal Phosphino-Boranes

Article abstract of DOI:10.1002/zaac.201900313

The reaction of the intramolecular frustrated Lewis pair (FLP) tBu₂PCH₂BPh₂ with the amine-boranes NH₃·BH₃ and Me₂NH·BH₃ leads to the formation of the corresponding FLP-H₂

Full text of DOI:10.1002/zaac.201900313

Title: Catalytic Dehydrogenation of Amine-Boranes using Geminal
Phosphino-Boranes
Authors: Chris Slootweg
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10.1002/zaac.201900313
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Catalytic Dehydrogenation of Amine-Boranes using Geminal
Phosphino-Boranes
Devin H. A. Boom,[a] Ewoud J. J. de Boed,[a] Emmanuel Nicolas,[a] Martin Nieger,[b] Andreas W.
Ehlers,[a,c] Andrew R. Jupp,[a] and J. Chris Slootweg*[a]
Dedicated to Professor Manfred Scheer on the Occasion of his 65th Birthday
Abstract: The reaction of the intramolecular frustrated Lewis pair
(FLP) tBu2PCH2BPh2 with the amine-boranes NH3·BH3 and
Me2NH·BH3 leads to the formation of the corresponding FLP-H2
adducts as well as novel 5-membered heterocycles that result from
capturing the in situ formed amino-borane by a second equivalent of
FLP. The sterically more demanding tBu2PCH2BMes2 does not form
such a 5-membered heterocycle when reacted with Me2NH·BH3 and
its H2 adduct liberates dihydrogen at elevated temperatures,
promoting the metal-free catalytic dehydrogenation of amine-boranes.
reported as efficient TM-free catalysts for amine-borane
dehydrogenation.[8]
The first FLP catalyst for ammonia-borane dehydrogenation
was reported by Stephan and Erker (I, Figure 1) utilizing a transfer
hydrogenation step for catalyst regeneration.[9] After this, Uhl and
co-workers and some of us reported on the catalytic
dehydrogenation of dimethylamine-borane (DMAB) by
phosphino-alane II.[10] In 2016, Rivard and co-workers extended
the field and showed that iminoborane IV can dehydrogenate
methylamine-borane (MAB) at 70 °C, utilizing 2 mol% of IV.[11] In
the same year, Aldridge et al. reported that the xanthene-based
phosphino-borane V is capable of dehydrogenating AB, MAB and
DMAB with catalysts loadings down to 1 mol%.[12] Recently Uhl
and co-workers found that the gallium analogue of II, phosphino-
galane III, can be applied for ammonia- and dimethylamine-
borane dehydrogenation too.[13] At the same time, the group of
Bourissou showed that phosphino-borane VI rapidly converts a
variety of amine-borane substrates to the corresponding
dehydrogenated products.[14]
Introduction
During the past decades tremendous breakthroughs were
made in main-group mediated chemical transformations and new
strategies for single bond activations were discovered. The notion
that frustrated Lewis pairs (FLPs) can heterolytically cleave
dihydrogen[ 1 ] spawned a new research field for metal-free
stoichiometric and catalytic chemical transformations, such as
hydrogenation and dehydrogenation reactions.[2]
As a substrate for catalytic dehydrogenation, amine-
boranes gained a lot of attention due to their potential application
as dihydrogen storage material;[3] in particular ammonia-borane
(AB) is of interest as is contains a high weight percentage of
dihydrogen (19.6%).[ 4 ] Furthermore, the products resulting of
amine-borane dehydrogenation are valuable, with many potential
applications in material science.[5] To date, a lot of research has
been conducted on the catalytic dehydrogenation of amine-
boranes by transition metal (TM) complexes.[ 6 ] Alternatively,
efforts have been made in the development of group 1 and 2
catalysts,[ 7 ] and recently frustrated Lewis pairs have been
Figure 1. FLP catalysts for amine-borane dehydrogenation.
[a]
Dr. D. H. A. Boom, E. J. J. de Boed, Dr. E. Nicolas, Dr. A. W. Ehlers,
Dr. A. R. Jupp, Assoc. Prof. Dr. J. C. Slootweg
Van ’t Hoff Institute for Molecular Sciences (HIMS)
University of Amsterdam, P.O. Box 94157,
1090 GD Amsterdam (The Netherlands)
We developed geminal phosphino-borane FLP VII (R =
tBu, R’ = Ph; 1) bearing a methylene linker, which shows
reactivity towards a variety of small molecules and metal
15
, 16 ]
complexes.[
Herein, we describe the (catalytic)
E-mail: j.c.slootweg@uva.nl
dehydrogenation of amine-boranes by such geminal frustrated
Lewis pairs using a rational catalyst design approach targeting
increased reactivity.
[b]
[c]
Dr. M. Nieger
Department of Chemistry, University of Helsinki
A. I. Virtasen aukio 1, PO Box 55, 00014 University of Helsinki
(Finland)
Dr. A. W. Ehlers
Department of Chemistry, Science Faculty
University of Johannesburg
PO Box 254, Auckland Park, Johannesburg (South Africa)
Results and Discussion
Treatment of 2 equivalents of tBu2PCH2BPh2 (1) with 1
equivalent of ammonia-borane (H3N·BH3, AB) in THF at room
Supporting information for this article is given via a link at the end of
the document.
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temperature resulted in immediate consumption of AB, along with
formation of dihydrogen adduct 2 (δ31P{1H}ꢀ=ꢀ59.0 ppm) and 5-
membered heterocycle 3 (δ31P{1H}ꢀ=ꢀ56.7 ppm) in a 1:1 ratio. The
products can be separated by extraction of 3 into n-pentane
(leaving pure 2 as residue in 57% yield) and subsequent filtration
of the combined extracts over alumina to remove trace amounts
of 2 from the extract, giving 3 as colorless solid in 74% yield. H2
adduct 2 displays a double multiplet in the 31P NMR spectrum with
Å, respectively), suggesting that the trapped H2N=BH2 fragment
is more tightly bound to the FLP in 3.
In order to gain more insight into the mechanism of this
dehydrogenation reaction, FLP 1 was reacted with the deuterated
analogue of AB, H3N·BD3, which resulted in selective N–H to P
and B–D to B transfer according to 31P and 11B NMR spectroscopy.
This suggests a similar double hydrogen transfer mechanism
being operative as was observed previously by Manners et al. for
dihydrogen transfer from ammonia-borane to sterically
encumbered amino-boranes.[18] Analysis of the formation of 2 by
density functional theory (DFT) calculations at the ωB97X–D/6-
311G** level of theory revealed that the interaction of ammonia-
borane with FLP 1 leads to the formation of a three-center-two-
electron adduct 4 as intermediate (Figure 2), which enables
dihydrogen transfer from H3N·BH3 in a concerted manner via a 7-
membered transition state, forming phosphonium-borate 2 and
one equivalent of amino-borane H2N=BH2. The overall process is
exergonic, and the low barrier (ΔG‡ = 13.1 kcal·mol-1, ΔE‡ = 14.3
kcal·mol-1) for TS4-2 is in good agreement with the experimentally
observed facile reaction (instantaneous at 0 °C). Additionally,
trapping of the amino-borane H2N=BH2 fragment by a second
equivalent of FLP 1 makes the overall reaction even more
exergonic (ΔGtrapping = –17.5 kcal·mol-1, ΔEtrapping = –34.7
kcal·mol-1).
a
1JP,H coupling of 453.2 Hz, and a doublet in the 11B NMR
spectrum (1JB,H = 83.5 Hz), which is characteristic for a P–H and
B–H bond, respectively. Single crystals suitable for X-ray
diffraction analysis of 2 were obtained from n-pentane at 4 °C,
which confirmed the formation of the FLP-H2 adduct that was
previously obtained from the reaction of 1 with dihydrogen.[15a] In
the solid state, the boron center in 2 is strongly pyramidalyzed
(Σ(CB1C) 330.5°), which also resembles the upfield 11B NMR shift
(δ11B{1H}ꢀ=ꢀ–10.1 ppm). In contrast to the o-phenylene-bridged
P/B FLP-H2 adduct reported by Bourissou and co-workers,[14]
dihydrogen adduct 2 is stable at room temperature in the solid
state and in solution, and only slowly released dihydrogen at
elevated temperatures (2 hours at 80 °C).
Scheme 1. Reaction of 2 equivalents of FLP 1 with 1 equivalent of ammonia-
borane (top) and the molecular structures (bottom) of 2 (left) and 3 (right)
(ellipsoids at 50% probability, FLP-hydrogens, and a toluene molecule for 2 are
omitted for clarity). Selected bond lengths (Å) and angles (°) for 2: P1−C1
1.7759(16), B1−C1 1.683(2), P1−C1−B1 113.48(11), Σ(CB1C) 330.5 3: P1−C1
1.8155(10), C1−B1 1.6626(14), B1−N1 1.6321(13), N1−B2 1.5898(14), B2−P1
1.9606(11).
The formation of the 5-membered heterocycle 3 is believed
to be the result of trapping of the highly polarized amino-borane
intermediate H2N=BH2 by the second equivalent of FLP 1. In the
11B{1H} NMR spectrum, 3 displays a singlet resonance (δ = –1.95
ppm) for the FLP’s boron moiety together with a characteristic
doublet (δ = –20.7 ppm, 1JB,P = 85.5 Hz) that can be ascribed to
the amino-borane fragment. The corresponding 31P{1H} NMR
spectrum supports this notion as a broad signal was observed at
δ = 56.7 ppm, which is common for such B–P interactions.[17] X-
ray diffraction analysis of suitable single crystals of 3, obtained by
layering a solution of 3 in DCM with pentane, unambiguously
established the formation of the P-C-B-N-B based 5-membered
heterocycle (Scheme 1, bottom right). Compared to the previously
reported Al- and Ga-based 5-membered heterocycles formed by
H2N=BH2 trapping using the corresponding FLPs,[10,13] 3 contains
a shorter P1–B2 bond (1.9606(11) Å; c.f. 1.9984(14) and 2.004(2)
Figure 2. Gibbs free energy and (energy) profile calculated for dehydrogenation
of ammonia-borane by FLP 1 in kcal·mol-1.
Under the same conditions, the reaction of 2 equivalents of
1 with the bulkier dimethylamine-borane (Me2NH·BH3, DMAB)
resulted in rapid formation of the known FLP-H2 adduct 2 together
with the methylated analogue of 3, compound 5 (Scheme 2).
31P{1H} NMR spectroscopy of the reaction mixture revealed
comparable resonance signals as for the reaction of 1 with AB
(δ31P{1H}ꢀ=ꢀ59.0 ppm for the FLP-H2 adduct, and a broad
resonance signal for the methylated heterocycle; δ31P{1H}ꢀ=ꢀ43.0
ppm). In contrast to 3, the 1JB,P coupling in 5 is significantly smaller
and no clear doublet was observed in the 11B{1H} NMR spectrum.
DFT calculations at the ωB97X–D/6-311G** level of theory
suggest that the same mechanism takes place. With an overall
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barrier (ΔG) of only 14.1 kcal·mol-1 (ΔE‡ = 14.5 kcal·mol-1), the
experimentally observed reaction rate is in good agreement with
the DFT calculations (see ESI). Interestingly, when a sample of
the reaction mixture was kept for a prolonged period at room
temperature signals of the dimeric (Me2NBH2)2 started to appear
in the 11B{1H} NMR spectrum due to release of the Me2N=BH2
fragment from 5 and subsequent dimerisation. This indicates that
increasing the steric bulk of the substrate reduces the bond
strength of the amino-borane fragment to FLP 1, which suggests
that increasing the steric bulk of the FLP’s substituents should
also prevent adduct formation.
Scheme 3. Synthesis of FLP 6 (top) and its molecular structure (bottom;
ellipsoids at 50% probability, hydrogen atoms are omitted for clarity). Selected
bond lengths (Å) and angles (°) for 6: P1−C1 1.8605(17), C1−B1 1.582(3),
P1−C1−B1 124.21(12), P1−C1−B1−C11 168.94(12), Σ(CB1C) 359.8.
Scheme 2. Reaction of 2 equivalents of FLP 1 with dimethylamine-borane.
Encouraged by these findings, we set out to design a FLP
system that disfavors amino-borane adduct formation. DFT
calculations at the ωB97X–D/6-311G** level of theory showed
that only a slight change of the system could already prevent
adduct formation. FLP tBu2PCH2BMes2 (6) bearing the bulkier
mesityl substituents on boron was found to disfavor adduct
formation with Me2N=BH2 (ΔG = 15.8 kcal·mol-1), which makes 6
an interesting synthetic target for catalytic dehydrogenation.
Following the same synthetic strategy used for our previously
reported FLP 1,[15a] the reaction of tBu2PCH2Li with 1 equivalent
of ClBMes2 cleanly afforded 6 that after work up was isolated as
an orange solid in 99% yield. The 31P{1H} and 11B{1H} NMR
resonances of 6 are rather similar compared to 1, namely a sharp
singlet at 26.9 ppm and a broad singlet at 82.5 ppm, respectively.
X-ray diffraction analysis of orange crystals obtained by cooling a
saturated heptane solution of 6 to –20 °C showed that the boron
empty p-orbital is rotated away from the phosphorus lone-pair
(torsion angle P1–C1–B1–C11 = 168.9°) and that the boron
center bears a planar geometry (∑(CB1C) = 359.8°), making any
LA···LB type of interaction negligible in the solid state (Scheme
3). The physical appearance of FLP 6 is noteworthy; whereas
phenyl-substituted FLP 1 is an oil at room temperature, the
mesityl-substituted analogue 6 is a solid, which facilitates the
handling of the compound.
Under similar conditions, FLP 6 (2 equivalents) was reacted
with
1
equivalent of ammonia-borane in 2-MeTHF (2-
methyltetrahydrofuran) at room temperature. After approximately
1 hour at room temperature, the 11B{1H}ꢀ and 31P{1H} NMR spectra
of the reaction mixture revealed that 6 was fully converted into
FLP-H2 adduct 7 (δ31P{1H}ꢀ=ꢀ56.5 (s); 11B{1H}ꢀ= –15.0 (s)) and the
5-membered heterocycle 8 (δ31P{1H}ꢀ=ꢀ58.1 (br. s); 11B{1H}ꢀ= 1.95
(s), –23.2 (s)), along with the formation of traces of
dehydrogenation products such as borazine, cyclotriborazane
(CTB) and B-(cyclodiborazanyl)aminoborohydride (BCDB) and a
few unidentified products (Scheme 4).
Scheme 4. The reaction of 2 equivalents of 6 with dimethylamine-borane.
Interestingly, heating the reaction mixture to 70 °C led to
almost complete disappearance of H2-adduct 7 and heterocycle
8, concomitant with an increase of dehydrogenation products
together with the formation of degradation products, such as
Mes2B=NH2 (δ11B{1H}ꢀ= 44.1 (br. s))[ 19 ] and tBu2PCH3·BH3
(δ31P{1H}ꢀ=ꢀ39.9 (m); 11B{1H}ꢀ= –40.8 (d, 1JB,P = 57.8 Hz)), as was
observed by 11B{1H}ꢀ and 31P{1H} NMR spectroscopy. In addition,
regeneration of FLP 6 was observed, suggesting that 6 could play
a role in catalytic amine-borane dehydrogenation, which is
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significant as only a few FLPs are reported to catalyze the
dehydrogenation of AB.[12,13,14]
Under our standard catalytic conditions (4 mol% of 6, 70 °C,
2.1 M DMAB, in 2-MeTHF) dimethylamine-borane was set for
dehydrogenation (Scheme 5). Initial formation of the FLP-H2
adduct 7 was observed by 31P{1H} NMR spectroscopy, while upon
heating to 70 °C this species disappeared and the formation of
dimeric (Me2NBH2)2 was observed in the 11B NMR spectrum,
along with traces of other dehydrogenation products as well as
the evolution of dihydrogen gas. Prolonging the reaction time
resulted in an increase of (Me2NBH2)2 formation which was
monitored by 11B NMR spectroscopy utilizing a sealed capillary
filled with B(OMe)3 as internal standard. Over time, FLP 6
continuously consumed the Me2NH·BH3 substrate, while
producing the amino-borane dimer. Concomitant to the catalytic
dehydrogenation, slow decomposition of the FLP catalyst 6 to
tBu2PCH3·BH3 and several other unknown degradation products
was observed. Eventually after 6 days at 70 °C, 6 was completely
degraded and the production of (Me2NBH2)2 stopped. Important
to note is that in the absence of FLP 6, no dehydrogenation was
observed under the same reaction conditions.
The labile character of both the FLP-H2 adduct 7 and the 5-
membered heterocycle 8 inspired us to investigate the possibility
to apply 6 as a catalyst for ammonia-borane dehydrogenation.
When 4 mol% of 6 was added to a suspension of H3N·BH3 in 2-
MeTHF, 6 was directly converted to H2-adduct 7 and heterocycle
8 according to 11B{1H}ꢀ and 31P{1H} NMR spectroscopy. When the
reaction mixture was heated to 70 °C, a modest evolution of
dihydrogen gas was visually observed as bubbles appeared from
the reaction mixture. After 20 minutes at 70 °C, a mixture of
dehydrogenation products was formed, yet the H2-adduct 7 was
still observable in both the 11B{1H}ꢀ and 31P{1H} NMR spectrum,
suggesting that this H2-adduct is the resting state of the catalytic
cycle. Prolonging the reaction time to 2 hours at 70 °C resulted in
an increase of dehydrogenation B–N products and full
degradation of the catalyst to tBu2PCH3·BH3 and Mes2B=NH2,
and neither free FLP 6 nor the dihydrogen adduct 7 were
observed by NMR spectroscopy.
DFT calculations at the ωB97X–D/6-311G** level of theory
confirm that dihydrogen adduct 7 is a plausible resting state in the
catalytic dehydrogenation of AB. Similar to 1, the calculations
suggest that the initial interaction via a three-center-two-electron
adduct is followed by a concerted double hydrogen abstraction
step (ΔG‡ = 25.1 kcal·mol-1, ΔE‡ = 16.3 kcal·mol-1; Figure 3). This
reaction step forming H2-adduct 7 and H2N=BH2 was found to be
exergonic by 6.13 kcal·mol-1 (ΔG) and 4.70 kcal·mol-1 (ΔE). The
energy barrier for dihydrogen release from 7 is the rate-
determining step (ΔG‡ = 27.3 kcal·mol-1, ΔE‡ = 28.6 kcal·mol-1),
which explains why H2-adduct 7 can be observed by NMR
spectroscopy during the reaction and why release of dihydrogen
is observed after the reaction mixture is heated to elevated
temperatures.
Scheme 5. Catalytic dehydrogenation of dimethylamine-borane by FLP 6.
The highest turnover number (TON) was obtained with 4
mol% catalyst loading at 70 °C, reaching 23 turnovers after 6 days.
For comparison, a range of Ru pincer complexes performed the
same reaction with TONs of between 2 and 99 after 24 hours.[20]
The turnover frequency (TOF) after approximately 10%
conversion of the dimethylamine-borane substrate at 50 °C was
found to be 0.62 h-1, which is not high, but is comparable with
several transition metal complexes reported by Travieso-Puente
and co-workers.[21] As expected, higher TOFs were obtained at
higher temperatures and after approximately 10% conversion at
60, 70 and 80 °C TOFs of 1.89, 2.65 and 4.36 h-1 were obtained,
respectively. At these elevated temperatures faster catalyst
decomposition was observed resulting in lower turnover
frequencies as the conversion increases.
Since
a
minor modification of our original FLP
tBu2PCH2BPh2 (1) affords tBu2PCH2BMes2 (6) that changed the
reactivity towards dimethylamine-borane from stoichiometric to
catalytic dehydrogenation, we envision that additional changes of
the P- and B-substituents might further increase the activity of the
FLP catalyst, which is an ongoing endeavor in our laboratories.
Figure 3. Gibbs free energy and (energy) profile calculated for AB
dehydrogenation by 6 in kcal·mol-1.
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g, 74%). X-ray quality crystals were obtained from a solution of 3 (289 mg)
in a pentane/DCM mixture (7.5 mL : 0.54 mL) which was stored at 4 °C.
Mp. (nitrogen, sealed capillary): 128 °C. 1H NMR (400.13 MHz, THF-d8,
293 K): δ 7.29 (d, 3JH,H = 7.1 Hz, 4H; o-PhH), 7.03, (t, 3JH,H = 7.4 Hz, 4H;
Conclusions
tBu2PCH2BPh2 (1) conveniently dehydrogenates ammonia-
borane and dimethylamine-borane to form the FLP-H2 adduct 2
and a new 5-membered heterocycle 3. DFT calculations revealed
that the underlying mechanism operates via formation of a three-
center-two-electron adduct, which is followed by a concerted
double hydrogen abstraction step involving a 7-membered
transition state. The bulkier tBu2PCH2BMes2 (6) was designed
and subsequently synthesized in excellent yields, and shows
catalytic activity towards ammonia-borane and dimethylamine-
borane.
3
m-PhH), 6.89 (t, JH,H = 7.2 Hz, 2H, p-PhH), 3.37 (br. s, 2H; NH2), 2.80–
1.75 (br. m, 2H; BH2), 1.19–1.13 (m, 20H; PCH2B, C(CH3)3). 13C{1H} NMR
(100.62 MHz, THF-d8, 293 K): δ 157.0 (br. s; ipso-PhC), 132.1 (s; o-PhC),
127.2 (s; m-PhC), 124.4 (s; p-PhC), 31.8 (d; 1JC,P = 25.8 Hz; C(CH3)3), 28.1
2
(d; JC,P = 1.2 Hz; C(CH3)3), 9.0 (s; PCH2B). 31P{1H} NMR (162.0 MHz,
THF-d8, 293 K): δ 56.7 (br. m). 11B{1H} NMR (128.4 MHz, THF-d8, 293 K):
1
δ –1.95 (s; BPh2), –20.7 (d, JB,P = 85.5 Hz; PBH2N). HR‒MS (ESI):
352.2554 [3–H]+, calcd for: C21H33B2NP+ 352.25312.
Preparation of Mes2BOMe:[23] A solution of MesMgBr (1 M in THF, 27 mL,
27 mmol, 2.1 equiv.) was added dropwise to a solution of B(OMe)3 (1.45
mL, 1.35 g, 13 mmol, 1.0 equiv.) in THF (15 mL), which resulted in a grey
suspension that turned into a brown solution after heating to 55 °C for 5h
and subsequent stirring at room temperature overnight. The volatiles were
removed in vacuo and the mixture was extracted into n-pentane (40 + 18
mL). The combined extracts were dried in vacuo to yield a colorless solid
(2.98 g, 82%). Crystallization of this compound was possible from a
solution in hot methanol (10 mL/g product) to afford colorless crystals upon
cooling. 1H NMR (500.23 MHz, CDCl3, 293 K): δ 6.79 (s, 4H; MesH), 3.75
(s, 3H; OCH3), 2.27 (s, 6H; p-MesCH3), 2.22 (s, 12H; o-MesCH3). 13C{1H}
NMR (125.80 MHz, CDCl3, 293 K): δ 128.3 (br. s; m-MesC), 54.3 (s; OCH3),
22.4 (s; o-MesCH3), 21.3 (s; p-MesCH3), the signals for ipso-MesC, o-
MesC and p-MesC are unresolved. 11B{1H} NMR (128.38 MHz, CDCl3,
293 K): δ 45.0 (br. s).
Experimental Section
Materials and Methods: All manipulations were carried out under an
atmosphere of dry nitrogen, using standard Schlenk and drybox
techniques. Solvents were purified, dried and degassed according to
standard procedures and stored under 3Å molecular sieves or a sublimed
sodium mirror. 1H and 13C{1H} NMR spectra were recorded on a Bruker
Avance 400 or Brucker Avance 500 and internally referenced to the
residual solvent resonances (CDCl3: 1H δ 7.26, 13C{1H} δ 77.2; THF-d8: 1H
δ 3.58, 1.72, 13C{1H} δ 67.2, 25.3; C6D6: 1H δ 7.16, 13C{1H} 128.1; Tol-d8:
1H δ 7.09, 7.01, 6.97, 2.08, 13C{1H} δ 137.48, 128.87, 127.96, 125.13,
20.43). 31P{1H}, 31P, 11B{1H} and 11B NMR spectra were recorded on a
Bruker Avance 400 and externally referenced (85% H3PO4, BF3·OEt2,
respectively). High resolution mass spectra were recorded on a Bruker
MicroTOF with ESI nebulizer (ESI). Melting points were measured in
sealed capillaries and are uncorrected. tBu2PCH2Li,[22] and tBu2PCH2BPh2
(1)[15a] were synthesized following literature procedures. 2-MeTHF was
purchased from Sigma Aldrich and subsequently degassed and dried with
3Å molecular sieves. NH3·BH3, NHMe2·BH3, PBr3, MesMgBr (1M in THF),
LiAlH4, n-BuLi (1.6M in hexane), t-BuLi (1.7M in pentane), MeLi (1.6M in
Et2O), BCl3 (1 M in heptane) and B(OMe)3 were purchased from Sigma
Aldrich, and all were used without any further purification.
Preparation of Mes2BCl:[24] A solution of BCl3 (1 M in heptane, 19 mL, 19
mmol, 1.3 equiv.) was added dropwise to a solution of Mes2BOMe (4.13 g,
14.8 mmol, 1.0 equiv.) in heptane (20 mL) at room temperature, after which
the mixture was heated overnight at 60 °C. The reaction mixture was
cooled to room temperature and the volatiles were removed in vacuo to
offer pinkish solids that were extracted into n-pentane (12 + 20 mL). The
combined extracts were dried in vacuo, which afforded a colorless solid
(3.86 g, 92%). X-ray quality crystals were obtained by recrystallization from
hot pentane (2.6 mL/g crude Mes2BCl) and subsequent washing with
pentane (0.5 mL/g crude) at –80 °C to afford colorless crystals. Mp.
(nitrogen, sealed capillary): 80–84 °C (trajectory). 1H NMR (500.23 MHz,
CDCl3, 293 K): δ 6.83 (s, 4H; Mes-H), 2.30 (s, 12H; o-MesCH3), 2.28 (s,
6H; p-MesCH3). 13C{1H} NMR (125.80 MHz, CDCl3, 293 K): δ 140.9 (s; o-
MesC), 140.5 (s; p-MesC), 129.0 (s; m-MesC), 23.4 (s; o-MesCH3), 21.4
(s; p-MesCH3), the signal for ipso-MesC is unresolved. 11B{1H} NMR
(128.38 MHz, CDCl3, 293 K): δ 69.9 (br. s).
Preparation of tBu2PCH2BPh2-H2 adduct 2:[15a] A THF stock solution of
ammonia-borane (28.84 mL, 0.1 M, 2.88 mmol, 1.0 equiv.) was added to
a solution of tBu2PCH2BPh2 (1, 1.87 gr, 5.77 mmol, 2.0 equiv.) in THF (15
mL) at 0 °C. After addition, the reaction mixture was warmed to room
temperature and all volatiles were removed in vacuo. The obtained
colorless solid was thoroughly washed with n-pentane (3 x 20 mL) and the
solids were subsequently dried in vacuo to afford 2 as a colorless solid
(0.536 g, 57%). Colorless X-ray quality crystals were obtained from a
solution of 2 in n-pentane which was stored at 4 °C. 1H NMR (400.13 MHz,
Preparation of tBu2PCH2BMes2 (6): A solution of Mes2BCl (3.47 g, 12.2
mmol, 1.0 equiv.) in Et2O (15 mL) was added dropwise to a suspension of
tBu2PCH2Li (2.72 g, 16.4 mmol, 1.3 equiv.) in Et2O (15 mL) at –80 °C and
after addition the reaction mixture was warmed to room temperature. After
2.5 days of stirring at room temperature, the suspension was concentrated
in vacuo which afforded an orange foam. The foam was extracted into n-
pentane (25 mL) and filtered over a Schlenk filter packed with Celite.
Subsequently, the Celite layer was extracted into pentane (3 x 10 mL) and
the combined extracts were concentrated in vacuo, which afforded an
orange solid (4.94 g, 99%). X-ray quality crystals were obtained from a
solution of 0.45 g of 6 in 1 mL of hot heptane (80–85 °C) and subsequent
slow cooling to –20 °C. Mp. (nitrogen, sealed capillary): 79–87 °C
(trajectory). 1H NMR (400.13 MHz, C6D6, 293 K): δ 6.77 (s, 4H; MesH),
2.43 (s, 12H; o-MesCH3), 2.15 (s, 6H; p-MesCH3), 2.09 (d, 2JH,P = 4.7 Hz,
2H; PCH2B), 1.08 (d, 2JH,P = 10.5 Hz, 18H; C(CH3)3). 13C{1H} NMR (100.62
3
THF-d8, 293 K): δ 7.32 (d, JH,H = 7.1 Hz, 4H; o-PhH), 6.97 (t, 3JH,H = 7.4
Hz, 4H; m-PhH), 6.82 (t, 3JH,H = 7.3 Hz, 2H; p-PhH), 4.96 (dt, 1JH,P = 453.2
Hz, 3JH,H = 4.8 Hz, 1H; PH), 3.12–2.29 (br. m, 1H; BH), 1.26 (d, 3JH,P = 14.8
Hz, 18H; C(CH3)3), 1.19–1.10 (br. m, 2H; PCH2B). 31P{1H} NMR (162.0
MHz, THF-d8, 293 K): δ –10.1 (s). 11B{1H} NMR (128.4 MHz, THF-d8, 293
K): δ 59.0 (s).
Preparation of tBu2PCH2BPh2-NH2BH2 adduct 3: A THF stock solution
of ammonia-borane (28.84 mL, 0.1 M, 2.88 mmol, 1.0 equiv.) was added
to a solution of tBu2PCH2BPh2 (1, 1.87 gr, 5.77 mmol, 2.0 equiv.) in THF
(15 mL) at 0 °C. After addition, the reaction mixture was warmed to room
temperature and all volatiles were removed in vacuo. The obtained white
solid was thoroughly extracted in n-pentane (3 x 20 mL). The combined
extracts were filtered over a pad of alumina, which was subsequently
flushed with 250 mL eluent (cyclohexane/ethyl acetate 20:1, resp.). The
collected filtrate was dried in vacuo to afford 3 as a colorless solid (0.754
3
MHz, C6D6, 293 K): δ 143.4 (only observed in the HMBC spectrum, JC,H
coupling with MesH, o-MesCH3, and PCH2B; ipso-MesC), 139.1 (s; o-
1
MesC), 138.3 (s; p-MesC), 129.2 (s; m-MesC), 31.5 (d, JC,P = 25.1 Hz;
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1
C(CH3)3), 30.0 (d, JC,P = 14.1 Hz; C(CH3)3), 28.1 (only observed in the
b = 8.776(1) Å, c = 17.801(2) Å, β = 118.75(1)°, V = 4459.8(10) Å3, Z = 8,
ρ =1.109 Mg/m-3, µ(Mo-Kα) = 0.13 mm-1, F(000) = 1624, 2θmax = 55°, 25741
reflections, of which 5128 were independent (Rint = 0.039), 243 parameters,
38 restraints, R1 = 0.049 (for 4179 I > 2σ(I)), wR2 = 0.123 (all data), S =
1.03, largest diff. peak / hole = 0.88 / -0.44 e Å-3.
1
HSQC spectrum, JC,H coupling with PCH2B; PCH2B), 24.1 (2 x s; o-
MesCH3), 21.2 (s; p-MesCH3). 31P{1H} NMR (161.97 MHz, toluene-d8, 293
K): δ 26.9 (s). 11B{1H} NMR (128.38 MHz, toluene-d8, 293 K): δ 82.0 (br.
s). HR‒MS (ESI): 409.3200 [6+H]+, calcd for C27H43BP+ 409.3190.
Stability of tBu2PCH2BPh2-H2 adduct (2) towards heating: A NMR
sample containing a solution of 2 in 2-MeTHF was heated to 50 °C for 3
hours, after which 31P{1H} spectroscopy revealed no formation of
tBu2PCH2Ph2 and only 2% decomposition to tBu2PCH3. Subsequent
heating to 80 °C for 2 hours resulted in liberation of dihydrogen and 17%
conversion to tBu2PCH2Ph2 as well as 18% decomposition to tBu2PCH3.
3: colorless crystals, C21H34B2NP, Mr = 353.08, crystal size 0.48 x 0.48 x
0.36 mm, triclinic, space group P-1 (no.2), a = 9.0523(5) Å, b = 10.2844(6)
Å, c = 13.0205(8) Å, α = 100.971(2)°, β = 108.436(2)°, γ = 104.693(2)°, V
= 1062.92(11) Å3, Z = 2, ρ = 1.103 Mg/m-3, µ(Mo-Kα) = 0.13 mm-1, F(000)
= 384, 2θmax = 55°, 36356 reflections, of which 4902 were independent
(Rint = 0.022), 239 parameters, 4 restraints, R1 = 0.032 (for 4554 I > 2σ(I)),
wR2 = 0.085 (all data), S = 1.05, largest diff. peak / hole = 0.35 / -0.28 e Å-
3
.
Reaction of tBu2PCH2BMes2 (6) with 0.5 equiv. of NH3BH3: A screw-
cap NMR tube was charged with ammonia-borane (0.0054 g, 0.175 mmol,
1.0 equiv.), tBu2PCH2BMes2 (6, 0.1428 g, 0.350 mmol, 2.0 equiv.) and 2-
MeTHF (6 mL). The reaction mixture was kept at room temperature and
analyzed after 1 hour with 31P{1H}, 11B{1H} and 11B NMR spectroscopy,
showing a mixture of dehydrogenated ammonia-borane products (11B{1H}
NMR: δ 30.8 (borazine), –4.94 (BCDB), –11.2 (CTB)), along with the
formation of the H2-adduct 7 (11B NMR: δ –15.0 (d, 1JB,H = 81.1 Hz); 31P{1H}
NMR: δ 56.5 (s)) and 5-membered heterocycle 8 (11B NMR: δ 1.92 (s), –
6: orange crystals, C27H42BP, Mr = 408.38, crystal size 0.60 x 0.45 x 0.40
mm, monoclinic, space group P21/c (no.14), a = 12.842(1) Å, b = 10.033(1)
Å, c = 20.516(2) Å, β = 104.46(1)°, V = 2559.6(4) Å3, Z = 4, ρ = 1.060
Mg/m-3, µ(Mo-Kα) = 0.12 mm-1, F(000) = 896, 2θmax = 55°, 24882
reflections, of which 5871 were independent (Rint = 0.054), 268 parameters,
R1 = 0.050 (for 4666 I > 2σ(I)), wR2 = 0.135 (all data), S = 1.04, largest diff.
peak / hole = 0.40 / -0.35 e Å-3.
1
23.3 (t, JB,H = 72.9 Hz); 31P{1H} NMR: δ 58.1 (br. s)). Subsequently, the
reaction mixture was heated to 70 °C overnight and a white suspension
was obtained (solids are postulated to be polyborazine) and 31P{1H}, 11B
and 11B{1H} NMR spectroscopy revealed complete consumption of the H2-
adduct 7 and heterocycle 8, as well as an increase in formation of borazine,
polyborazine (11B NMR: δ 24.8 (s)), formation of two unidentified products
(11B NMR: δ –23.4 (s) and –29.8 (s)), decomposition to Mes2B=NH2 (11B
CCDC-1967181 (2), CCDC-1967182 (3), and CCDC-1967183 (6) contain
the supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Computational details: All structures were optimized at the ωB97X−D
level of theory,[ 27 ] using Gaussian 09, Revision D01.[ 28 ] Geometry
optimizations were performed using the 6-311G(d,p) basis set,[29,30] and
the nature of each stationary point was confirmed by frequency
calculations.
1
NMR: δ 43.7 (s)) and tBu2PCH3·BH3 (11B NMR: δ –41.6 (dq, JB,H = 96.4
1
Hz, JB,P = 57.9 Hz; 31P{1H} NMR: δ 39.9 (br. q), and lastly also
regeneration of FLP 6.
Reaction of tBu2PCH2BMes2 (6) with 25 equiv. of NH3BH3: A screw-cap
NMR tube was charged with ammonia-borane (0.031 g, 1.357 mmol, 25.0
equiv.), tBu2PCH2BMes2 (6, 0.022 g, 0.054 mmol, 1.0 equiv.) and 2-
MeTHF (6 mL). The reaction mixture was mixed at room temperature and
directly analyzed by 31P{1H}, 11B{1H} and 11B NMR spectroscopy, which
revealed formation of the H2-adduct 7 and the 5-membered heterocycle 8.
Subsequently, the NMR tube was heated to 70 °C and analyzed by NMR
spectroscopy after 20 and 120 minutes, after which complete consumption
of FLP 6 and H2-adduct 7 was observed, along with the formation of
dehydrogenation products and dihydrogen gas.
Supporting Information (see footnote on the first page of this article):
Cartesian coordinates for all computed structures and a video of the
catalytic dehydrogenation of DMAB with 6 are given as Supporting
Information available online.
Acknowledgements
This work was supported by the Council for Chemical Sciences of
The Netherlands Organization for Scientific Research (NWO/CW)
by a VIDI grant (J.C.S.) and a VENI grant (A.R.J.). J.C.S.
acknowledges the Alexander von Humboldt Foundation for a
Humboldt Research Fellowship for Experienced Researchers.
We gratefully acknowledge Ed Zuidinga for mass spectrometric
analyses and Ibrahim Aydin for obtaining suitable crystals of
compound 3.
X-ray Crystallography: The single-crystal X-ray diffraction studies were
carried out on a Bruker-Nonius KappaCCD diffractometer at 123(2) K
using Mo-Kα radiation (λ = 0.71073 Å) (2, 6) or Bruker D8 Venture
diffractometer with Photon100 detector at 123(2) K using Mo-Kα radiation
(λ = 0.71073 Å) (3). Direct Methods (SHELXS-97)[ 25 ] were used for
structure solution and refinement was carried out using SHELXL-
2013/2014 (full-matrix least-squares on F2).[ 26 ] Hydrogen atoms were
localized by difference electron density determination and refined using a
riding model (H(B, N, P) free). Semi-empirical absorption corrections were
applied. For 3 an extinction correction was applied.
Keywords: frustrated Lewis pairs • amine-boranes •
dehydrogenation • main-group catalysis • density functional
calculations
2: colorless crystals, C21H32BP · 0.5(C7H8), Mr = 372.31, crystal size 0.50
x 0.30 x 0.20 mm, monoclinic, space group C2/c (no.15), a = 32.562(4) Å,
[1]
[2]
G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science, 2006,
314, 1124–1126.
For an overview of developments in FLP chemistry, see: a) D. W.
Stephan, G. Erker, Angew. Chem. Int. Ed. 2010, 49, 46–76. b) D. W.
Stephan, Acc. Chem. Res. 2015, 48, 306–316. c) D. W. Stephan,
Science 2016, 354, 1248. d) A. R. Jupp, D. W. Stephan, Trends Chem.
2019, 1, 35–48.
C. W. Hamilton, R. T. Baker, A. Staubitz, I. Manners, Chem. Soc. Rev.
2009, 38, 279–293.
[3]
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[19] a) N. M. D. Brown, F. Davidson, J. W. Wilson, J. Organomet. Chem. 1980,
192, 133−138. b) R. A. Bartlett, H. Chen, V. R. Dias, M. M. Olmstead, P.
P. Power, J. Am. Chem. Soc. 1988, 110, 446−449.
[20] M. J. Sgro, D. W. Stephan, Dalton Trans. 2013, 42, 10460−10472.
[21] D. García‐Vivó, E, Huergo, M. A. Ruiz, R. Travieso‐Puente, Eur. J. Inorg.
Chem. 2013, 4998−5008.
[22] F. Eisenträger, A. Göthlich, I. Gruber, H. Heiss, C. A. Kiener, C. Krüger,
J. U. Notheis, F. Rominger, G. Scherhag, M. Schultz, B. F. Straub, M. A.
O. Volland, P. Hofmann, New. J. Chem. 2003, 27, 540−550.
[23] N. M. D. Brown, F. Davidson, R. McMullan, J. W. Wilson, J. Organomet.
Chem. 1980, 193, 271−282.
[24] A. Sundararaman, F. Jäkle, J. Organomet. Chem. 2003, 681, 134−142.
[25] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112–122.
[26] G. M. Sheldrick, Acta Crystallogr. 2015, C71, 3–8.
[4]
a) T. B. Marder, Angew. Chem. Int. Ed. 2007, 46, 8116–8118. b) A.
Staubitz, A. P. M. Robertson, M. E. Sloan, I. Manners, Chem. Rev. 2010,
110, 4023–4078. c) A. Staubitz, A. P. M. Robertson, I. Manners, Chem.
Rev. 2010, 110, 4079–4124.
E. M. Leitao, T. Jurca, I. Manners, Nat. Chem. 2013, 5, 817–829.
For reviews about transition metal based amine-borane dehydrogenation
catalysts, see: a) N. C. Smythe, J. C. Gordon, Eur. J. Inorg. Chem. 2010,
509–521. b) N. E. Stubbs, A. P. M. Robertson, E. M. Leitao, I. Manners,
J. Organomet. Chem. 2013, 730, 84–89. c) A. Rossin, M. Peruzzini,
Chem. Rev. 2016, 116, 8848−8872. d) S. Bhunya, T. Malakar, G.
Ganguly, A. Paul, ACS Catal. 2016, 6, 7907−7934.
[5]
[6]
[7]
For reviews on group
1
and
2
metal-based amine-borane
dehydrogenation catalysts, see: a) R. J. Less, R. L. Melen, D. S. Wright,
RSC Adv. 2012, 2, 2191–2199. b) R. L. Melen, Chem. Soc. Rev. 2016,
45, 775–788.
[27] J.-D. Chai, M. Head-Gordon, M. Phys. Chem. Chem. Phys. 2008, 10,
6615–6620.
[28] Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P.
Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery,
Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N.
Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K.
Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J.
Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma,
V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich,
A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J.
Fox, Gaussian, Inc., Wallingford CT (USA), 2013.
[29] a) R. Ditchfield, W. J. Hehre, J. A. Pople, J. Chem. Phys. 1971, 54, 724–
728. b) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys. 1972, 56,
2257–2261. c) P. C. Hariharan, J. A. Pople, Theor. Chem. Acc. 1973, 28,
213–222. d) P. C. Hariharan, J. A. Pople, Mol. Phys. 1974, 27, 209–214.
e) M. S. Gordon, Chem. Phys. Lett. 1980, 76, 163–168. f) M. M. Francl,
W. J. Pietro, W. J. Hehre, J. S. Binkley, D. J. DeFrees, J. A. Pople, M. S.
Gordon, J. Chem. Phys. 1982, 77, 3654–3665. g) R. C. Binning, Jr., L.
A. Curtiss, J. Comp. Chem. 1990, 11, 1206–1216. h) J.-P. Blaudeau, M.
P. McGrath, L. A. Curtiss, L. Radom, J. Chem. Phys. 1997, 107, 5016–
5021. i) V. A. Rassolov, J. A. Pople, M. A. Ratner, T. L. Windus, J. Chem.
Phys. 1998, 109, 1223–1229. j) V. A. Rassolov, M. A. Ratner, J. A. Pople,
P. C. Redfern, L. A. Curtiss, J. Comp. Chem. 2001, 22, 976–984.
[30] For the polarization functions, see: M. J. Frisch, J. A. Pople, J. S. Binkley,
J. Chem. Phys. 1984, 80, 3265–3269.
[8]
[9]
For a recent review, see: D. H. A. Boom, A. R. Jupp, J. C. Slootweg,
Chem. Eur. J. 2019, 25, 9133−9152.
a) D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2010, 49, 46–76. b)
D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2015, 54, 6400–6441.
[10] C. Appelt, J. C. Slootweg, K. Lammertsma, W. Uhl, Angew. Chem. Int.
Ed. 2013, 52, 4256–4259.
[11] M. W. Lui, N. R. Paisley, R. McDonald, M. J. Ferguson, E. Rivard, Chem.
Eur. J. 2016, 22, 2134–2145.
[12] Z. Mo, A. Rit, J. Campos, E. L. Kolychev, S. Aldridge, J. Am. Chem. Soc.
2016, 138, 3306−3309.
[13] J. Possart, W. Uhl, Organometallics, 2018, 37, 1314−1323.
[14] M. Boudjelel, E. D. S. Carrizo, S. Mallet−Ladeira, S. Massou, K. Miqueu,
G. Bouhadir, D. Bourissou, ACS Catal. 2018, 8, 4459−4464.
[15] Reactivity towards small molecules: a) F. Bertini, V. Lyaskovskyy, B. J.
J. Timmer, F. J. J. de Kanter, M. Lutz, A. W. Ehlers, J. C. Slootweg, K.
Lammertsma, J. Am. Chem. Soc. 2012, 134, 201−204. b) E. R. M.
Habraken, L. C. Mens, M. Nieger, M. Lutz, A. W. Ehlers, J. C. Slootweg,
Dalton Trans. 2017, 46, 12284−12292. c) D. H. A. Boom, A. R. Jupp, M.
Nieger, A. W. Ehlers, J. C. Slootweg, Chem. Eur. J. 2019, 25, 13299–
13308.
[16] Reactivity towards transition metals: a) D. H. A. Boom, A. W. Ehlers, M.
Nieger, J. C. Slootweg, Z. Naturforsch., B: Chem. Sci. 2017, 72, 781−784.
b) D. H. A. Boom, A. W. Ehlers, M. Nieger, M. Devillard, G. Bouhadir, D
Bourissou, J. C. Slootweg, ACS Omega, 2018, 3, 3945–3951.
[17] For examples of cyclic phosphine-boranes see: H. Schmidbaur, M. Sigl,
A. Schier, J. Organomet. Chem. 1997, 529, 323–327.
[18] a) A. P. M. Robertson, E.M. Leitao, I. Manners, J. Am. Chem. Soc. 2011,
133, 19322–19325. b) E. M. Leitao, N. E. Stubbs, A. P. M. Robertson, H.
Helten, R. J. Cox, G. C. Lloyd-Jones, I. Manners, J. Am. Chem. Soc.
2012, 134, 16805−16816.
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Entry for the Table of Contents
FULL PAPER
An intramolecular P/B frustrated
Lewis pair (FLP) has been shown
to effect the catalytic
dehydrogenation of ammonia-
borane and other amine-boranes.
The catalyst could be rationally
tuned by enhancing the steric bulk
at the Lewis acidic centre to
improve the catalytic activity.
Devin H. A. Boom, Ewoud J. J. de
Boed, Emmanuel Nicolas, Martin
Nieger, Andreas W. Ehlers, Andrew
R. Jupp, and J. Chris Slootweg*
Page No. – Page No.
Catalytic Dehydrogenation of
Amine-Boranes using Geminal
Phosphino-Boranes
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Additional Author information for the electronic version of the article.
J. Chris Slootweg: ORCID 0000-0001-7818-7766
Andrew R. Jupp:
ORCID 0000-0003-4360-5838
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