Dehydrogenation of ammonia borane through the third equivalent of hydrogen

Article abstract of DOI:10.1039/c6dt00604c

Ammonia borane (AB) has high hydrogen density (19.6 wt%), and can, in principle, release up to 3 equivalents of H₂ under mild catalytic conditions. A limited number of catalysts are capable of non-hydrolytic dehydrogenation of AB beyond 2 equivalents of H₂ under mild conditions, but none of these is shown directly to derivatise borazine, the product formed after 2 equivalents of H₂ are released. We present here a high productivity ruthenium-based catalyst for non-hydrolytic AB dehydrogenation that is capable of borazine dehydrogenation, and thus exhibits among the highest H₂ productivity reported to date for anhydrous AB dehydrogenation. At 1 mol% loading, (phen)Ru(OAc)₂(CO)₂ (1) effects AB dehydrogenation through 2.7 equivalents of H₂ at 70 °C, is robust through multiple charges of AB, and is water and air stable. We further demonstrate that catalyst 1 has the ability both to dehydrogenate borazine in isolation and dehydrogenate AB itself. This is important, both because borazine derivatisation is productivity-limiting in AB dehydrogenation and because borazine is a fuel cell poison that is commonly released in H₂ production from this medium.

Full text of DOI:10.1039/c6dt00604c

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Zhang, L. Kam
and T. Williams, Dalton Trans., 2016, DOI: 10.1039/C6DT00604C.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/dalton

Please(do(not(adjust(margins(
Dalton Transactions
Page 1 of 7
View Article Online
DOI: 10.1039/C6DT00604C
Dalton'Transactions'
'
ARTICLE(
Dehydrogenation'of'Ammonia'Borane'through'the'Third'
Equivalent'of'Hydrogen'
Xingyue(Zhang,(Lisa(Kam,(and(Travis(J.(Williams*(
Received(00th(January(20xx,(
Accepted(00th(January(20xx(
Ammonia(Borane((AB)(has(high(hydrogen(density((19.6(wt.(%),(and(can,(in(principle,(release(up(to(3(equivalents(of(H2(under(
mild(catalytic(conditions.(A(limited(number(of(catalysts(are(capable(of(nonAhydrolytic(dehydrogenation(of(AB(beyond(2(
equivalents(of(H2(under(mild(conditions,(but(none(of(these(is(shown(directly(to(derivatise(borazine,(the(product(formed(
after(2(equivalents(of(H2(are(released.(We(present(here(a(high(productivity(rutheniumAbased(catalyst(for(nonAhydrolytic(AB(
dehydrogenation( that( is( capable( of( borazine( dehydrogenation,( and( thus( exhibits( among( the( highest( H2( productivity(
reported( to( date( for( anhydrous( AB( dehydrogenation.( ( At( 1( mol%( loading,( (phen)Ru(OAc)2(CO)2( (1)( effects( AB(
dehydrogenation(through(2.7(equivalents(of(H2(at(70°C,(is(robust(through(multiple(charges(of(AB,(and(is(water(and(air(
stable.( We( further( demonstrate( that( catalyst( 1( has( the( ability( both( to( dehydrogenate( borazine( in( isolation( and(
dehydrogenate( AB( itself.( This( is( important,( both( because( borazine( derivatisation( is( productivityAlimiting( in( AB(
dehydrogenation(and(because(borazine(is(a(fuel(cell(poison(that(is(commonly(released(in(H2(production(from(this(medium.
DOI:(10.1039/x0xx00000x(
www.rsc.org/'
only( a( few( catalysts( achieved( a( high( release( extent( of( 2.5(
equivalents( or( greater( (Figure( 1).( Currently,( Baker’s( nickelA
based( system( supported( by( Ender’s( carbene( is( the( highest(
Introduction'
Dehydrogenation( of( ammonia( borane( (AB,( H3NABH3)( has(
been( studied( extensively( as( an( approach( for( highAcapacity(
hydrogen(storage,(because(AB(has(high(hydrogen(density((19.6(
wt%)( and( the( ability( to( release( H2( under( mild( conditions.1(
Although(catalytic(hydrolysis(is(well(known(and(efficient(for(H2(
production( from( AB,2( nonAhydrolytic( dehydrogenation( is( a(
more(desirable(approach,(because(it((1)(enables(more(facile(reA
reduction( of( dehydrogenated( spent( fuel3( and( (2)( minimizes(
evolution( of( ammonia,( a( hydrogen( fuel( cell( poison,( in( the(
eluent( gas( stream.4,( 1b( Several( transition( metal( catalysts( are(
active( for( nonAhydrolytic( AB( dehydrogenation,( including(
complexes(of(iron,5(molybdenum,6(iridium,7(rhodium,8(nickel,9(
palladium,10(and(ruthenium.11,(12'Catalyst(systems(reported(to(
date( fit( one( of( two( classes:13( (1)( those( that( release( 1(
equivalent(of(hydrogen(quickly14,(7(and((2)(those(that(release(2(
or(more(equivalents(slowly.9,(10a,(12,(15(The(latter(are(known(to(
proceed( through( (or( stop( at)( borazine,( N3B3H6,( as( an(
intermediate( with( its( subsequent( conversion( to(
polyborazylene( as( a( slow( step( in( the( overall( mechanism( of(
hydrogen( evolution.16( This( is( problematic( because( (1)( slow(
borazine( derivatization( limits( H2( productivity,12( (2)( borazine,(
which(boils(at(55(oC,(is(poisonous(to(fuel(cells,(and((3)(borazine(
is( known( to( coordinate( metals17( and( deactivate( some( AB(
extent(of(H2(release(from(AB(reported(to(date.(The(Guan(FeA
POCOP( catalyst( uses( inexpensive( iron( but( dehydrogenates(
fairly(slowly(and(reacts(through(2.5(equiv.(H2.(The(Agapie(Mo(
catalyst( has( the( same( productivity,( and( is( limited( by( air( and(
water( sensitivity.( Further,( Wegner( has( recently( presented( a(
metalAfree(catalyst(that(is(capable(of(releasing(ca.(2.5(equiv.(of(
H2.( Despite( high( extent( of( H2( release( observed( with( these(
catalytic(systems,(no(study(of(direct(borazine(consumption(was(
reported(with(any(of(them,(and(borazine(remains(a(significant(
constituent( of( the( reactive( medium( at( the( end( of( the( AB(
dehydrogenation(reaction(for(each.(
(
Baker, 2007
Ni(cod)2
Guan, 2014
H
O
PiPr2
Fe
PMe2Ph
Ph
MeO
N
N
+ 2
C
O
P
N
Ph
iPr2
PMe2Ph
Ph
2.5-2.8 eq. H2, 5 mol% [Ni], 60°C, 4 hr
2.3-2.5 eq. H2, 5 mol%, 60°C, 20 hr
1 M [AB] in C6D6/diglyme
1 M [AB] in THF/diglyme
Wegner, 2015
Agapie, 2014
N2
Cl
B
iPr
iPr
iPr
iPr
dehydrogenation(catalysts.16(
(
P
Mo
P
B
Maximizing(the(H2(release(efficiency(is(highly(desirable,(and(
Cl
2.5 eq. H2, 5 mol%, 60°C, 7 hr
2.5 eq. H2, 5 mol%, 70°C, 12 hr
0.4M [AB] in THF/diglyme
0.25 M [AB] in diglyme
(
Fig.'1'Catalysts(that(dehydrogenate(AB(over(2.5(equiv.(
This(journal(is(©(The(Royal(Society(of(Chemistry(2016!
Dalton!Trans.,(2016,(00,(1A3(|(1((
Please(do(not(adjust(margins(

Please(do(not(adjust(margins(
Dalton Transactions
Page 2 of 7
ARTICLE(
Journal'Name(
(
and(Tl)(is(undesirable.(Further,(this(reaction(is(not(as(effective(
View Article Online
DOI: 10.1039/C6DT00604C
In( the( absence( of( a( catalyst,( borazine( undergoes( slow(( at(lower(catalyst(loadings.(We(eliminated(the(usage(of(thallium(
dehydrogenative(BN(crossAlinking((48A60(hours(at(70(°C(under( by(replacing(the(chlorine(ligands(with(acetates((1,(Figure(2)22b(
reduced(pressure(with(periodic(degassing)(to(polyborazylene.18( with( the( expectation( that( acetate( groups( should( dissociate(
This( rate( is( insufficient( to( prevent( borazine( accumulation( easily(from(the(metal(centre(in(the(presence(of(an(excess(of(
under(catalytic(hydrogen(evolution(conditions.(Thus,(there(is(a( boron(with(this(dissociation(driven(by(the(strength(of(boronA
(
desire( to( find( a( catalyst( system( that( will( dehydrogenate( acetate(bonds.
borazine(at(a(rate(faster(than((or(commensurate(with)(the(rate(
at(which(it(reacts(with(ammonia(borane(itself.(No(such(system(
(
O
Ph
Ph
Ph
N
N
has( yet( to( be( reported.( We( report( here( the( reactivity( of(
+
[(phen)RuLn]
4
Benzene
70°C, 12-14hrs
Ph
ruthenium(complex(1'(Figure(2)(with(AB(to(produce(H2(gas(with(
high( efficiency.( ( 1' and( its( isomers( are( known( to( catalyse(
hydrogenation( of( ketones,( olefins,( and( alkynes19( and(
CPD
(
Scheme' 1.' Ruthenium( dimer( 4' loses( CPD( in( the( presence( of( bidentate(
nitrogen(ligands(such(as(phen.((
hydroformylate( olefins,20( but( its( reactivity( with( AB( has( not(
been(studied.((1'not(only(dehydrogenates(AB,(but(also(reacts(
with(borazine(to(form(polyborazylene,(therefore(exceeding(the(
extent( of( dehydrogenation( available( with( other( systems( and(
decreasing( the( amount( of( fuel( cell( poison( in( the( gaseous(
eluent( stream( as( less( volatile( polyborazylene.( In( addition( to(
decreasing( the( accumulation( of( borazine( in( the(
dehydrogenation( reactor,( conditions( based( on( 1( yield(
unusually( high( productivity,( 2.7( equivalents( of( H2( at( mild(
reaction(temperature,(and(are(air(and(water(tolerant.''
Reactivity'of'1'with'AB'
1( dehydrogenates( AB( efficiently( at( low( catalyst( loading,(
down( to( 1( mol%,( producing( 2.4–2.7( equiv.( of( hydrogen,( as(
shown( in( Figure( 3.( The( catalyst( system( is( robust,( capable( of(
producing(a(similarly(high(extent(of(H2(release((2.6,(2.5,(2.4)(in(
each(of(the(multiple(AB(reloadings.(Further,(we(compared(the(
rates( of( catalytic( reactions( prepared( in( the( glove( box( under(
nitrogen(atmosphere(and(an(analogous(sample(of(1(suspended(
in(solvent( and(immersed(in(an(ultrasonic(bath(in(open(air(for(
20(minutes(before(AB(addition.(We(find(that(exposure(of(the(
catalyst(to(air(and(water(in(the(atmosphere(neither(slows(nor(
accelerates( dehydrogenation;( rather,( these( runs( have(
analogous(rates((Supplementary(Information).(
OAc
Cl
CO
CO
CO
CO
N
N
Ru
OAc
Ru
N
N
Cl
1
H
H
2
Ph
CO
O
Ph
Ph
O
Ph
Ph
CO
(
O
Ru
Ph
Ph
Ph
Ph
Ru
OAc
Ph
Ph
Ph
Ph
Ph
Ph
Ru
O
CO
N
Ru
Ru
CO
CO
OC
CO
OC
Ph
N
CO
CO
OAc
3
4
1
(
'
1 mol %
AB
H2 + B-N Byproducts 5 - 9
(
((
Fig.' 2' Ru( catalysts( for( AB( dehydrogenation.( (phen)Ru(OAc)2(CO)2( (1),(
(phen)RuCl2(CO)2((2),(Shvo’s(catalyst((3),(Shvo(oxidised(form(dimer((4).(
3
2.5
2
0.4
Results'and'Discussion'
0.3
0.2
0.1
0
Catalyst'Development'
1.5
1
k
= 8.9(3) x 10-5 s-1
obs
We( have( previously( demonstrated( that( the( Shvo( catalyst(
can( lose( its( tetraphenylcyclopentadienone( (CPD)( ligand( from(
the(metal(centre(in(the(presence(of(bidentate(nitrogen(ligands(
such(as(1,10Aphenanthroline((phen)(shown(in(Scheme(1.21(We(
suspect(that(the(species(produced(by(the(expulsion(of(the(CPD(
ligand( contributes( to( the( increase( in( rate( of( AB(
dehydrogenation.( This( species( potentially( consists( of( a(
ruthenium(centre(supported(by(two(carbonyl(ligands(and(the(
bidentate( bis(nitrogen)( ligand.( We( therefore( investigated(
ruthenium(scaffolds(composed(of(these(constituents.(Whereas(
these( square( planar( ruthenium( complexes( are( not( stable( to(
isolation,( we( generate( analogous( compounds( in( situ.( We(
reasoned( that( treatment( of( the( known( complex(
(phen)RuCl2(CO)2((2)22(with'TlOTf(and(ammonia(borane(would(
generate( a( reactive( (phen)Ru(CO)2Abased( fragment.21( While(
10%( of( 2( with( 2( equivalents( of( TlOTf( will( liberate( 2.5A2.7(
equivalents(of(H2(from(AB,(the(high(loading(of(metals((both(Ru(
0.5
0
0
10
20
30
40
50
60
0
5
10
15
20
25
30
35
Time (Sec x 1000)
Time (Sec x 1000)
(
Fig.'3'Left:(H2(production(from(1%(of(1(at(70°C(in(diglyme(releasing(
2.7(equiv.(Right:(11B(kinetic(profile(of(the(consumption(of(AB(
catalyzed(by(1%(of(1(in(2:1(diglyme/benzeneAd6.((
'
Reactivity'of'1'with'Borazine'
Treatment(of(AB(with(1(results(in(the(formation(of(a(family(
of( AB( dehydrogenation( products( (Scheme( 2)( that( has(
homology( to( those( formed( when( the( dehydrogenation( is(
conducted( with( the( Shvo( catalyst( (3),16( except( that( the(
reaction( does( not( stop( at( borazine,( but( goes( on( to(
2(|(Dalton!Trans.,(2016,(00,(1A3(
This(journal(is(©(The(Royal(Society(of(Chemistry(2016(
Please(do(not(adjust(margins(

Page 3 of 7
Dalton Transactions
Please(do(not(adjust(margins(
Journal'Name'
'ARTICLE'
polyborazylene( materials( (9).( Borazine( (8)( is( the( exclusive(
boronAnitrogen(material(formed(when(3(is(used(as(the(catalyst,(
and( it( is( the( principal( material( that( accumulates( after( two(
equivalents( of( H2( are( produced.( We( expect( that( the( Shvo(
system(can(not(derivatise(borazine(because(it(is(restricted(to(
View Article Online
DOI: 10.1039/C6DT00604C
an(outer(sphere(hydrogen(transfer(mechanism.(
H2
H2
N
H2
N
BH3
H2B
H2N
BH
H2
N
H2
H2B
H2N
BH
N
H2B BH2
H
NH2
+
NH2
B
H2
+
B
H2
AB
70°C
Branched
cyclotetraborazane
Cyclotriborazane
µ-aminodiborane
6
5
7
H
N
HB
N
BH
NH
H
N
H
N
'
B
B
B
N
HB
HN
BH
NH
H2
H2
HN
N
Fig.'4(Reaction(of(1(with(borazine((8)(in(2:1(diglyme/benzeneAd6.(Bottom:(
initial( 11B( spectrum( of( 1( and( borazine( at( room( temperature.( Top:( 11B(
spectrum(of(1(and(borazine(after(24(hrs(at(70°C.(Boron(external(standard(
BF3AOEt2(is(at(0(ppm,(and(borazine(is(the(only(boron(species(present(in(the(
bottom(spectrum(at(31(ppm.(In(the(top(spectrum,(borazine(peak(height(has(
decreased( and( other( broad( boron( species( that( are( indicative( of(
polyborazylene(appear(after(24(hrs.(Areas(under(the(peaks(are(integrated(
relative(to(the(external(standard(BF3AOEt2(peak(set(to(1.00.(
B
N
B
N
B
B
H
NH
HB
N
B
N
B
N
Borazine
B
H
B
BH
NH
8
HN
N
Polyborazylene
9
(
Scheme'2.'Typical(BN(byproducts(seen(in(AB(dehydrogenation(reactions.(
Unlike( 3' and( its( derivatives,21( 1( reacts( with( isolated(
borazine( at( 70°C,( yielding( polyborazylene( as( the( major(
byproduct.(We(can(observe(this(directly(by(11B(NMR((Figure(4).(
In(this(experiment,(borazine(was(isolated(by(a(vacuum(transfer(
of( the( volatiles( in( a( spent( 3Acatalysed( AB( dehydrogenation(
reaction.12a(After(the(transfer(of(borazine(and(solvents(into(a(JA
Young(NMR(tube(preloaded(with(1,(a(11B(NMR(spectrum(was(
taken,(and(the(solution(was(heated(to(70(°C((see(experimental(
section( for( further( details).' After( heating( for( 24( hours,(
borazine( (31( ppm)( was( converted,( ca.( 70%,( relative( to( the(
external(11B(standard((0(ppm)(to(give(signals(consistent(with(
crossAlinked( polyborazylene( and( other( unsaturated( BAN(
byproducts.( These( are( indicated( by( broad( signals( in( the( 11B(
NMR( spectra( from( 24A34( ppm.( Visual( inspection( of( the( NMR(
tube( after( the( reaction( shows( insoluble,( gelatineAlike,( white(
material,(which(is(consistent(with(the(formation(of(polymeric(
BAN( species( and( accounts( for( the( loss( in( integration( of( 11B(
products( observed( by( NMR.( ( In( contrast,( the( background(
thermal(decomposition(reaction(under(these(conditions(gives(
only(ca.(15%(after(24(hours((see(Supplementary(Information).'
OAc
CO
CO
N
Ru
OAc
N
1
O
Ph
H
H
Ph
O
Ph
Ph
Ph
Ru
Ph
Ph
Ph
Ru
CO
OC
CO
CO
3
a.(
(
15
10
5
15
10
5
0
0
0
5
10
15
20
25
0
5
10
15
20
25
Time ( x 1000 sec)
Time (Sec x 1000)
b.
'
Fig.' 5( a.( Comparison( of( endAofAreaction( 11B( NMR( spectra( under(
representative( conditions.( Top:( AB( dehydrogenation( catalysed( by( 10%( Ru(
atom(of(1'after(1.75(hours(in(2:1(diglyme/benzeneAd6!at(70°C.(Bottom:(AB(
dehydrogenation( catalysed( by( 10%( Ru( atom( of( 3( after( 1.75( hours( in( 2:1(
diglyme/benzeneAd6!at(70°C.(Note(the(larger(proportion(of(polyborazylene(
in( the( top( spectra( (24A34( ppm)( compared( to( the( bottom( spectra.( Boron(
standard( (BF3AOEt2( inset( tube)( is( at( 0( ppm.( Areas( under( the( peaks( are(
integrated( relative( to( the( external( standard( BF3AOEt2( peak( set( to( 1.00.( b.(
Peak(height(of(borazine(over(time(catalysed(by(10%(Ru(atom(of(1((left)(and(3(
(right).((
This(journal(is(©(The(Royal(Society(of(Chemistry(2016!
Dalton!Trans.,(2016,(00,(1A3(|(3(
Please(do(not(adjust(margins(

Please(do(not(adjust(margins(
Dalton Transactions
Page 4 of 7
ARTICLE(
Journal'Name(
Reaction'Intermediates'
up(to(2.7(equiv.(of(H2(at(low(catalyst(loading.(It(Vhieaws(AdrteicsleirOanblinlee (
kinetic(properties,(air(and(water(toleranDceO,I(:a1n0d.1(0r3e9u/sCa6bDiTli0t0y6.(0W4Ce(
also(show(that(this(catalyst(has(reactivity(with(borazine(itself,(
thus( minimizing( borazine( concentration( in( the( gas( eluent(
stream(of(the(H2(generation(reactor.(
We( observe( by( 11B( NMR( that( reactions( catalysed( by( 1(
generate(boron(intermediates(common(in(AB(dehydrogenation(
reactions(with(catalysts(outlined(in(Figure(1,(which(include(μA
aminodiborane( (5),( cyclotriborazane( (6),( aminoborane( cyclic(
tetramer( (7),( and( borazine( (8)( (Scheme( 2).( However,( at( 1%(
loading(of(1,(we(observe(the(appearance(of(polyborazylene((9)(
as( early( as( the( first( 20( minutes( into( AB( consumption,( along(
with( intermediates( 6R8.( ( This( suggests( that( as( borazine( is(
Experimental'
All(air(and(water(sensitive(procedures(were(carried(out(either(
in( a( Vacuum( Atmosphere( glove( box( under( nitrogen( (0.5A10(
ppm( O2( for( all( manipulations)( or( using( standard( Schlenk(
techniques( under( nitrogen.( Deuterated( NMR( solvents( were(
purchased(from(Cambridge(Isotopes(Laboratories.((BenzeneAd6(
and( diethylene( glycol( dimethyl( ether( (diglyme,( Alfa( Aesar)(
were(dried(over(sodium(benzophenone(ketyl(and(distilled(prior(
to( use.( ( Ammonia( borane( (NH3BH3,( AB)( was( purchased( from(
Sigma( Aldrich( and( used( under( N2( atmosphere( only( without(
further(purifications.(RuCl3!3H2O(was(purchased(from(Pressure(
Chemical( Co.( and( used( without( further( purifications.( Shvo’s(
catalyst( (3)( was( purchased( from( Strem( Chemicals( and( used(
without(further(purifications.(Acetic(acid(was(purchased(from(
EMD( Millipore( and( used( without( further( purification.( Formic(
acid,(1,10Aphenanthroline,(and(silver(acetate(were(purchased(
from( Alfa( Aesar( and( used( without( further( purification.(
[RuCl2(CO)2]n,( (phen)RuCl2(CO)2( (2)( and( (phen)Ru(OAc)2(CO)2(
(1)(were(synthesized(according(to(literature(procedures((more(
details(in(the(Supplementary(Information)23.22(1H(and(11B(NMR(
spectra(were(obtained(on(Varian(600(MHz((600(MHz(in(1H,(192(
MHz( in( 11B),( 500( MHz,( and( 400( MHz( spectrometers( ( with(
chemical(shifts(reported(in(units(of(ppm.(All(1H(chemical(shifts(
were(referenced(to(the(residual(1H(solvent((relative(to(TMS).(
All(11B(chemical(shifts(were(referenced(to(a(BF3AOEt2(in(diglyme(
in( a( coAaxial( external( standard( (0( ppm).( ( 11B( spectra( are(
phased,(baseline(corrected,(and(backwards(linear(predicted(3A
8( points.( NMR( spectra( were( taken( in( 8”( JAYoung( tubes(
(Wilmad)(with(Teflon(valve(plugs.((FTIR(were(taken(on(KBr(salt(
plate,(or(KBr(pellet(on(a(Bruker(Vertex(80(FTIR.(((
produced,(
another(
mechanism(
is(
concurrently(
dehydrogenating( it( into( polyborazylene.( The( borazine(
concentration(builds(steadily(until(approximately(50%(of(AB(is(
consumed,(and(then(the(growth(of(the(borazine(peak(tapers(
off( followed( by( its( conversion( to( polyborazylene.( When( we(
compare(11B(NMR(spectra(of(1Acatalysed(AB(dehydrogenation(
(10( mol%( Ru( atom( loading)( with( our( previouslyAreported(
reaction(catalysed(by(the(same(loading(of(3,12a(we(observe(less(
borazine( (31( ppm)( buildAup( and( more( polyborazylene( (24A34(
ppm)( in( the( reaction( catalysed( by( 1' (Figure( 5a).( ( Plotting(
normalized(peak(height(of(borazine(against(time(for(reactions(
catalysed(by(10(mol(%(of(1'and(3'(Figure(5b),(we(observe(the(
decrease(of(borazine(over(time(with(1,(while(the(borazine(peak(
rises(in(the(reaction(catalysed(by(3.(
(
Homogeneity'
In(order(to(probe(the(homogeneity(or(heterogeneity(of(the(
dehydrogenation( catalysis,( we( conducted( several( tests.( We(
added( ca.( 100( µL( of( elemental( mercury( to( the( reaction(
conducted( at( 10%( catalyst( loading( and( monitored( AB(
consumption( via( 11B( kinetics( in( a( mercury( drop( test( of(
homogeneity.( While( there( was( a( small( drop( in( rate,( the(
reaction( proceeded( similarly( to( the( parent( reaction,(
completing(in(approximately(the(same(amount(of(time((Figure(
6).((This(result(suggests(homogeneous(catalysis,(even(though(
there(are(observable(heterogeneous(materials(in(the(reaction.(
We( therefore( suspect( that( we( have( a( homogeneous( active(
species(working(in(a(heterogeneous(suspension.(
(
10% 1 with Hg
10% 1
Hydrogen'Quantification'
0.4
0.3
0.2
0.1
0
In( a( typical( reaction,( 7.7( mg( AB( (0.25( mmol)( was( combined(
with( catalyst( (1A10( mol%)( in( a( 2( mL( Schlenk( bomb( equipped(
with( a( Teflon( stir( bar( while( in( a( glove( box( under( nitrogen.(
Diglyme( (0.6( mL)( was( added( to( the( flask( to( create( a( light(
yellow( mixture.( The( eudiometer( was( constructed( as( follows:(
The(side(arm(of(the(valve(was(connected(to(a(piece(of(Tygon(
tubing,(which(was(connected(to(a(3Away(valve.((Center(of(the(
3Away( valve( was( connected( to( the( Schlenk( line( to( allow(
vacuum(and(nitrogen(purge(of(the(apparatus.((The(last(valve(
was(connected(to(Tygon(tubing(that(was(adapted(to(20(gauge(
(0.03”)(Teflon(tubing(with(a(needle.(The(tubing(was(threaded(
through(open(end(of(a(burette(that(was(sealed(with(a(Teflon(
stopcock(on(the(other(end.((The(burette(was(filled(with(water.(
The( entire( apparatus( was( then( inverted( into( a( 500( mL(
Erlenmeyer( filled( with( water( and( clamped( onto( a( metal( ring(
stand.( ( Opening( the( 3AwayAvalve( to( the( Schlenk( line( and( the(
bomb( (reaction( still( closed( and( wrapped( in( foil( at( room(
0
4
8
12
16
Time (Sec x 1000)
'
Fig.'6((Hg(addition(homogeniety(test(in(2:1(diglyme/benzeneAd6!at(70°C.((
Black(circles:(10(mol%(of(1(with(Hg.(Blue(squares:(10%(of(1.(
Conclusions'
In( summary( we( present( here( a( high( productivity( nonA
hydrolytic(ammonia(borane(dehydrogenation(system(releasing(
4(|(Dalton!Trans.,(2016,(00,(1A3(
This(journal(is(©(The(Royal(Society(of(Chemistry(2016(
Please(do(not(adjust(margins(

Page 5 of 7
Dalton Transactions
Please(do(not(adjust(margins(
Journal'Name'
'ARTICLE'
temperature),( the( space( in( the( 3Away( valve( and( tubing( was( overlap(in(the(11B(spectrum(and(integrations(could(not(be(done(
View Article Online
DOI: 10.1039/C6DT00604C
vacuumed(and(refilled(with(N2(for(5(minutes(twice(and(then( accurately.( The( procedure( for( the( borazine( background(
opening( all( 3( valves( to( the( line,( N2( purge( was( conducted( reaction( was( the( same,( except( for( the( absence( of( 1( in( the(
through(out(the(burette(for(10(minutes.((Then(the(3Away(valve( receiving( tube( (See( Supplementary( Information( for( graphical(
was(turned(so(that(only(the(bomb(and(the(side(connected(to( representation).(
the(burette(were(open,(and(N2(was(turned(off.((The(water(in(
the(burette(was(pulled(upwards(by(a(pipette(filler(bulb(and(the(
initial(volume(was(recorded.((The(bomb(was(then(submerged(
into(a(70(°C(oil(bath(for(2(minutes(to(allow(the(temperature(of(
the(system(to(equilibrate.((The(reactor’s(valve(was(opened(to(
release( gas( from( the( reactor( headspace( while( heating( in( a(
regulated(oil(bath.(The(volume(of(liberated(gas(was(recorded(
periodically( until( gas( evolution( ceased.( Liberated( hydrogen(
was( quantified( by( recording( its( volume( displacement( in( the(
eudiometer.((Reaction(proceeds(from(initial(yellow(to(gray,(to(
black(suspension.(
(
Catalyst'Reuse'Reactions'
To(test(the(reusability(of(catalyst(1,(we(studied(the(production(
of( H2( gas( by( eudiometry( for( successive( runs( with( 1.0( mol%(
catalyst.(For(run(1,(we(added(7.7(mg(AB,(1.2(mg(1,'and(0.6(mL(
diglyme(to(a(2(mL(Schlenk(flask(equipped(with(a(small(stir(bar.(
The(reaction(was(heated(at(70(°C!in(a(regulated(oil(bath(and(
reaction(progress(monitored(by(displacement(of(water(by(H2(
gas( in( an( inverted( 50( mL( burette.( For( successive( runs,( we(
added( 7.7( mg( AB( and( 0.2( mL( diglyme( and( repeated( the(
reaction( at( 70( °C.( PseudoAfirst( order( rate( constants( for( H2(
productions(over(these(runs(are(12.1,(10.8,(and(7.0(x(10A5(sA1.(
(
(
Kinetic'Profiles'of'AB'Dehydrogenation'Recorded'via'11B'NMR'
In(a(typical(reaction,(7.7(mg(of(AB(was(combined(with(catalyst(
(1.0(–(10.0(mol%)(in(a(JAYoung(NMR(tube(while(in(a(glove(box(
under( nitrogen.( The( AB( concentration( and( catalyst(
concentrations(may(be(varied.(Diglyme((0.4(mL)(and(benzeneA
d6( (0.2( mL)( were( added( to( the( tube.( The( sample( tube( was(
immediately(inserted(into(a(temperatureAequilibrated((70(°C),(
preAshimmed,(and(preAlocked(NMR,(and(the(kinetic(monitoring(
commenced.( Disappearance( of( AB( in( the( solution( was(
monitored(by(the(relative(integration(of(its(characteristic(peak(
in( the( 11B( spectrum( (−22( ppm)( and( the( BF3AOEt2( (0( ppm)(
standard.(The(acquisition(involved(a(1.84(s(pulse(sequence(in(
which(16,384(complex(points(were(recorded,(followed(by(1(s(
relaxation(delay.(To(eliminate(B−O(peaks(from(the(borosilicate(
NMR( tube( and( probe,( the( 11B( FIDs( were( processed( with(
backward( linear( prediction.( Safety! note:! caution! should! be!
used! when! carrying! out! these! reactions,! as! the! release! of!
hydrogen!can!lead!to!sudden!pressurization!of!reaction!vessels.(
(
Acknowledgements'
This(work(was(sponsored(by(the(National(Science(Foundation(
(CHEA1054910)(and(the(Hydrocarbon(Research(Foundation.(We(
are(grateful(to(the(National(Science(Foundation((DBIA0821671,(
CHEA0840366),( the( National( Institutes( of( Health( (1( S10(
RR25432),( and( the( University( of( Southern( California( for(
sponsorship( of( NMR( spectrometers.( ( Fellowship( assistance(
from( The( Sonosky( Foundation( of( the( USC( Wrigley( Institute(
(X.Z.),(Dornsife(College((L.K.),(and(USC(undergraduate(research(
fellowship(program((L.K.)(is(gratefully(acknowledged.(
Notes'and'references'
‡(No(competing(financial(interests(have(been(declared.((
(
Reactivity'of'1'with'Borazine'
Borazine( was( generated( in( a( J.( Young( NMR( tube( by( the(
reaction(of(Shvo’s(catalyst((6.7(mg,(2.5%,(0.0062(mmol)(with(
AB((7.7(mg,(0.25(mmol)(in(2:1(diglyme/benzeneAd6(((0.4(mL(and(
0.2(mL(respectively)(in(a(70°C(oil(bath(for(16A20(hours.12a,16(The(
NMR(tube(was(connected(via(a(flameAdried(UAtube(to(another(
J.( Young( NMR( tube( containing( 1( (1.2( mg,( 0.0025( mmol),(
diglyme((0.4(mL),(and(11B(external(standard.((The(volatiles((H2,(
borazine,( benzeneAd6)( were( transferred( under( static( vacuum(
while(the(borazineAcontaining(tube(was(heated(gently(with(a(
heat(gun(while(the(receiving(tube(was(submerged(in(liquid(N2(
until(all(of(the(ca.(0.2(mL(of(benzene(was(transferred(to(the(
receiving(tube.(The(J.(Young(valves(were(closed(and(the(UAtube(
system(was(flushed(with(N2.(While(the(N2(line(was(closed(and(
the(UAtube(is(under(N2,(the(receiving(tube(was(opened(briefly(
to(return(it(to(atmospheric(pressure.(1H(and(11B(NMR(spectra(
were( taken,( and( then( the( borazineAcontaining( tube( was(
submerged( in( a( 70( °C( oil( bath( for( 24( hours.( Peak( heights(
relative(to(the(external(standard((BF3AOEt2(in(diglyme((0(ppm))(
were( compared( since( polyborazylene( and( borazine( peaks(
1
(a)(A.(Staubitz,(A.(P.(M.(Robertson,(I.(Manners,(Chem.!Rev.(
2010,( 110,( 4079A4124.( (b)( F.( H.( Stephens,( V.( Pons,( R.( T.(
Baker,( Dalton! Trans.( 2007,( 2613A2626.( (c)( T.( B.( Marder,((
Angew.! Chem.! Int.! Ed.( 2007,( 46,( 8116A8118.( (d)( C.( W.(
Hamilton,( R.( T.( Baker,( A.( Staubitz,( I.( Manners,( Chem.! Soc.!
Rev.(2009,(38,(279A293.((e)(F.(Baitalow,(J.(Bauman,(G.(Wolf,(
K.(JaenickeARossler,(G.(Leitner,(Thermochim.!Acta(2002,(391,(
159A168.((f)(G.(Wolf,(J.(Baumann,(F.(Baitalow,(F.(P.(Hoffmann,(
Thermochim.! Acta( 2000,( 343,( 19A25.( (g)( J.( S.( Wang,( R.( A.(
Geanangel,(Inorg.!Chim.!Acta(1988,(148,(185A190.((h)(M.(E.(
Bluhm,( M.( G.( Bradley,( R.( III( Butterick,( U.( Kusari,( L.( G.(
Sneddon,(J.!Am.!Chem.!Soc.(2006,(128,(7748A7749.((i)(S.(G.(
Rassat,( C.( L.( Aardahl,( T.( Autrey,( R.( S.( Smith,( Energy! Fuels(
2010,( 24,( 2596A2606.( (j)( H.( A.( Kalviri,( F.( Gartner,( G.( Ye,( I.(
Korobkov,(R.(T.(Baker,(Chem.!Sci.(2015,(6,(618A624.(
2
(
(a)(J.(M.(Yan,(X.(B.(Zhang,(T.(Akita,(M.(Haruta,(Q.(Xu,(J.!Am.!
Chem.!Soc.(2010,(132,(5326A5327.((b)(H.(L.(Jiang,(T.(Umegaki,(
T.(Akita,(X.(B.(Zhang,(M.(Haruta,(Q.(Xu,(Chem.!Eur.!J.(2010,(
16,(3132A3137.((c)(P.V.(Ramachandran,(P.(D.(Gagare,(Inorg.!
This(journal(is(©(The(Royal(Society(of(Chemistry(2016!
Dalton!Trans.,(2016,(00,(1A3(|(5(
Please(do(not(adjust(margins(

Please(do(not(adjust(margins(
Dalton Transactions
Page 6 of 7
ARTICLE(
Journal'Name(
(
(
View Article Online
DOI: 10.1039/C6DT00604C
Chem.(2007,(46,(7810A7817.(D.(J.(Nelson,(B.(J.(Truscott,(J.(D.( 17 T.( J.( Carter,( Z.( M.( Heiden( and( N.( K.( Szymczak,( Chem.! Sci.,(
Egbert,(S.(P.(Nolan,(Organometallics(2013,(32,(3769A3772.( 2015,(6,(7258–7266.(
(a)( Davis,( B.( L.,( Dixon,( D.( A.,( Garner,( E.( B.,( Gordon,( J.( C.,( 18 (a)( P.( J.( Fazen,( E.( E.( Remsen,( J.( S.( Beck,( P.( J.( Carroll,( A.( R.(
3
Matus,(M.(H.,(Scott,(B.(Angew.!Chem.!Int.!Ed.!2009,(48,(6812A
6816.((b)(Sutton,(A.(D.,(Burrell,(A.(K.,(Dixon,(D.(A.,(Garner,(E.(
McGhie( and( L.( G.( Sneddon,( Chem.! Mater.( 1995,( 7,( 1942–
1956.((b)(A.(T.(Lynch,(Ph.D.,(University(of(Pennsylvania,(1989.(
B.,(III,(Gordon,(J.(C.,(Nakagawa,(T.,(Ott,(K.(C.,(Robinson,(J.(P.,( 19 P.( Frediani,( M.( Bianchi,( A.( Salvini,( R.( Guarducci,( L.( C.(
Vasiliu,(M.(Science(2011,(331,(1426A1429.( Carluccio,(F.(Piacenti,(J.!Organomet.!Chem.(1995,(498,(187.(
(a)(N.(C.(Smythe,(J.(C.(Gordon,(Eur.!J.!Inorg.!Chem.(2010,(509A 20 P.(Frediani,(M.(Bianchi,(A.(Salvini,(L.(C.(Carluccio,(L.(Rosi,(J.!
521.((b)(A.(D.(Sutton,(A.(K.(Burrell,(D.(A.(Dixon,(E.(B.(Gardner,( Organomet.!Chem.(1997,(547,(35.(
J.(C.(Gordon,(T.(Nakagawa,(K.C.(Ott,(J.(P.(Robinson,(M.(Vasiliu,( 21 X.(Zhang,(Z.(Lu,(L.(K.(Foellmer,(T.(J.(Williams,(Organometallics(
Science(2011,(331,(1426A1429.( 2015,(34,(3732.(
(a)(J.(R.(Vance,(A.(P.(M.(Robertson,(K.(Lee,(I.(Manners,(Chem.! 22 (a)( G.( N.( Krishnamurthy,( N.( Shashikala,( J.! Serb.! Chem.! Soc.(
4
5
Eur.!J.(2011,(17,(4099A4103.((b)(R.(T.(Baker,(J.(C.(Gordon,(C.(
W.( Hamilton,( N.( J.( Henson,( P.( H.( Lin,( S.( Maguire,( M.(
Murugesu,(B.(L.(Scott,(N.(C.(Smythe,(J.!Am.!Chem.!Soc.(2012,(
134,(5598A(5609.((c)(P.(Bhattacharya,(J.(A.(Krause,(H.(Guan,(J.!
Am.! Chem.! Soc.( 2014,( 136,( 11153A11161.( ( (d)( A.( Glüer,( M.(
Förster,( V.( R.( Celinski,( J.( Schmedt( auf( der( Günne,( M.( C.(
Holthausen(and(S.(Schneider,(ACS!Catal.(2015,(5,(7214–7217.(
J.(A.(Buss,(G.(A.(Edouard,(C.(Cheng,(J.(Shi,(T.(Agapie,(J.!Am.!
Chem.!Soc.(2014,(136,(11272A11275.(
M.( C.( Denny,( V.( Pons,( T.( J.( Hebdon,( M.( Heinekey,( K.( I.(
Goldberg,(J.!Am.!Chem.!Soc.(2006,(128,(12048A12049.(
C.(A.(Jaska,(K.(Temple,(A.(J.(Lough,(I.(Manners,(J.!Am.!Chem.!
Soc.(2003,(125,(9424A9434.((b)(C.(A.(Jaska,(I.(Manners,(J.!Am.!
Chem.!Soc.(2004,(126,(1334−1335.((c)(R.(P.(Shrestha,(H.(V.(K.(
Diyabalanage,(T.(A.(Semelsberger,(K.(C.(Ott,(A.(K.(Burrell,(Int.!
J.!Hydrogen!Energy.!2009,(34,(2616A2621.((d)(T.(M.(Douglas,(
A.( B.( Chaplin,( A.( S.( Weller,( J.! Am.! Chem.! Soc.( 2008,( 130,(
14432A14433.((e)(G.(Alcaraz,(S.(SaboAEtienne,(Angew.!Chem.(
Int.(Ed.(2010,(49,(7170A7179.(
2009,( 74,( 1085–1096.( (b)( D.( Black,( G.( Deacon,( N.( Thomas,(
Aust.!J.!Chem.(1982,(35,(2445A2453.((c)(R.(Colton,(R.(Farthing,(
Aust.! J.! Chem.! 1967,( 20,( 1283.( (d)( P.( A.( Anderson,( G.( B.(
Deacon,( K.( H.( Haarmann,( F.( R.( Keene,( T.( J.( Meyer,( D.( A.(
Reitsma,(B.(W.(Skelton,(G.(F.(Strouse,(N.(C.(Thomas,(Inorg.!
Chem.( 1995,( 34,( 6145A6157.( (e)( P.( Frediani,( M.( Bianchi,( A.(
Salvini,( R.( Guarducci,( L.( C.( Carluccio,( F.( Piacenti,( J.!
Organomet.!Chem.!1994,(476,(7.(
6
7
8
(
9
R.(J.(Keaton,(J.(M.(Blacquiere,(R.(T.(Baker,(J.!Am.!Chem.!Soc.(
2007,(129,(1844A1845.(
10 (a)(S.AK.(Kim,(W.AS.(Han,(T.AJ.(Kim,(T.AY.(Kim,(S.(W.(Nam,(M.(
Mitoraj,(Ł.(Piecos,)A.(Michalak,(S.AJ.(Hwang,(S.(O.(Kang,(J.!Am.!
́
Chem.!Soc.(2010,(132,(9954A9955.((b)(S.AK.(Kim,(S.AA.(Hong,(
H.AJ.(Son,(W.AS.,(A.(Han,(S.AJ.(Hwang,(S.(O.(Kang,(Dalton!Trans.(
2015,(44,(7373A7381.((c)(S.AK.(Kim,(S.AA.(Hong,(H.AJ.(Son,(W.A
S.( Han,( A.( Michalak,( S.AJ.( Hwang( and( S.( O.( Kang,( Dalton!
Trans.,(2015,(44,(7373–7381.(
11 (a)( N.( Blaquiere,( S.( DialloAGarcia,( I.( Gorelsky,( A.( Black,( K.(
Fagnou,( J.! Am.! Chem.! Soc.( 2008,( 130,( 14034A14035.( (b)( M.(
Kaβ̈,(A.(Fridrich,(M.(Drees,(S.(Schneider,(Angew.!Chem.!Int.!
Ed.( 2009,( 48,( 905A907.( (c)( Z.( Lu,( T.( J.! Williams,( Chem.!
Commun.(2014,(50,(5391A5393.(
12 (a)( Conley,( B.( L.,( Williams,( T.( J.(Chem.! Commun.( 2010,(46,(
4815A4817.((b)(Conley,(B.(L.,(PenningtonABoggio,(M.(K.,(Boz,(
E.,(Williams,(T.(J.(Chem.!Rev.(2010,(110,(2294A2312.(
13 V.(Pons,(R.(T.(Baker,(N.(K.(Szymczak,(D.(J.(Heldebrant,(J.(C.(
Linehan,( M.( H.( Matus,( D.( J.( Grant,( D.( A.( Dixon.( Chem.!
Commun.!2008,(48,(6597A5999.(
14 (a)( N.( Blaquiere,( S.( DialloAGarcia,( I.( Gorelsky,( A.( Black,( K.(
Fagnou,( J.! Am.! Chem.! Soc.! 2008,( 130,( 14034A14035.( (b)( M.(
Käβ,(A.(Friedrich,(M.(Drees,(S.(Schneider,(Angew.!Chem.!Int.!
Ed.!2009,(48,(905A907.((
15 (a)(A.(M.(Chapman,(M.(F.(Haddow,(D.(F.(Wass,(J.!Am.!Chem.!
Soc.! 2011,( 133,( 8826A8829.( (b)( W.( R.( H.( Wright,( E.( R.(
Berkeley,( L.( R.( Alden,( R.( T.( Baker,( L.( G.( Sneddon,( Chem.!
Commun.!2011,(47,(3177A3179.((c)(Z.(Lu,(L.(Schweighauser,(
H.( Hausmann( and( H.( A.( Wegner,( Angew.! Chem.! Int.! Ed.,(
2015,(54,(15556–15559.(
16 Z.(Lu,(B.(L.(Conley,(T.(J.(Williams,(Organometallics(2012,(31,(
6705−6714.(
(
6(|(Dalton!Trans.,(2016,(00,(1A3(
This(journal(is(©(The(Royal(Society(of(Chemistry(2016(
Please(do(not(adjust(margins(

Page 7 of 7
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT00604C
Robust, water and air stable catalyst (phen)Ru(OAc)2(CO)2 dehydrogenates ammonia borane through 2.7
equivalents of H2 and derivatises fuel cell poison borazine.