Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination

Article abstract of DOI:10.1039/c8sc00348c

Diphosphene Ter^MesP = PTer^Mes (1; Ter^Mes = 2,6-Mes₂C₆H₃; Mes = 2,4,6-Me₃C₆H₂) and NHC^Me₄2 (NHC^Me₄ = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHC^Me₄-coordinated diphosphene 3. While uncoordinated 1 is inert to hydrolysis, the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHC^Me₄. On this basis, conditions suitable for the catalytic use of NHC^Me₄ were identified. Similarly, while the hydrogenation of free diphosphene 1 with H₃N·BH₃ is very slow, 3 reacts instantaneously with H₃N·BH₃ at room temperature to afford a dihydrodiphosphane.

Full text of DOI:10.1039/c8sc00348c

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S. Mondal, S. Narayanan, K. Mote, V. Huch, M. Zimmer, C. B. B. Yildiz, D. Scheschkewitz, V. Chandrasekhar
and A. Jana, Chem. Sci., 2018, DOI: 10.1039/C8SC00348C.
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DOI: 10.1039/C8SC00348C
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EDGE ARTICLE
Reactivity Enhancement of a Diphosphene by Reversible N-
Heterocyclic Carbene Coordination
Debabrata Dhara,a Pankaj Kalita,b Subhadip Mondal,a Ramakirushnan Suriya Narayanan,a
Kaustubh R. Mote,a Volker Huch,c Michael Zimmer,c Cem B. Yildiz,*d David Scheschkewitz,*c
Vadapalli Chandrasekhar*a,e and Anukul Jana*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
Diphosphene TerMesP=PTerMes (1; TerMes = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) and NHCMe 2 (NHCMe = 1,3,4,5-
tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHCMe4-coordinated diphosphene 3. While
uncoordinated 1 is inert to hydrolysis; the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted
4
4
phosphine oxide under liberation of NHCMe4. On this basis conditions suitable for the catalytic use of NHCMe were
4
identified. Similarly, while the hydrogenation of free diphosphene 1 with H3N·BH3 is very slow, 3 reacts instantaneously
with H3N·BH3 at room temperature to afford a dihydrodiphosphane.
reports followed including the reversible coordination/binding
6
of ethylene with distannynes,5 phosphines with CO2, N-
Introduction
heterocyclic carbenes with cyclotrisilenes,7 and reversible
Reversible coordination/binding between substrate and
catalyst is pivotal to catalytic reactions. This paradigm has
been the raison d'être for the use of a vast number of
transition metal complexes in catalysis as exemplified by many
celebrated compounds such as the Wilkinson's catalyst.1
Another crucial feature of many catalytic reactions is the role
of auxiliary Lewis bases/donors in the activation of the
catalyst to facilitate product formation.2 While transition metal
complexes are a strong mainstay in this field, there have been
efforts to examine if systems based on main-group elements
can also be useful in catalytic reactions. An important
challenge in this endeavor is the design of compounds that,
like their transition metal counter parts, are involved in
reversible reactions with substrates and auxiliary activators
such as bases.3 An important breakthrough in this area has
been the seminal report of Stephan and co-workers on the
reversible activation of dihydrogen by the frustrated Lewis pair
effect of a compound containing a P-B motif.4 Numerous other
oxidative addition of organoboronate esters at the carbon(II)
center of cyclic alkyl amino carbene.8 Main-group compounds
can indeed display
a transition metal-like behavior as
exemplified by the stoichiometric activation of small
molecules9 as well as ligand exchange at the reactive low-
valent centers.10
In the above context, recently Bertrand et al. reported a
singlet (phosphino)phosphinidene, I, which is electrophilic
despite its P‒P multiple bond character and the presence of a
formal negative charge at the phosphinidene center.11 It was
also shown that ligand exchange could occur at the
phosphinidene centre of
I
(Scheme 1).12 On the other hand,
Robinson's NHCDip-stabilized P2, II (Scheme 1)13 which can be
considered as a interconnected bis-phosphinidene dimer does
not undergo ligand exchange with more nucleophilic NHCs
such as NHCMe4 and NHCiPr Me 14
.
2
2
a.Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad-
500107, Telangana, India. E-mail: ajana@tifrh.res.in
b.School of Chemical Sciences, National Institute of Science Education and Research,
Bhimpur-Padanpur, Jatni, Khurda, Bhubaneswar-752050, Odisha, India
c. Krupp-Chair of General and Inorganic Chemistry, Saarland University, 66123
Saarbrücken, Germany. E-mail: scheschkewitz@mx.uni-saarland.de
d.Department of Medicinal and Aromatic Plants, University of Aksaray, Aksaray,
Turkey. E-mail: cemburakyildiz@aksaray.edu.tr
Scheme 1 Chemical structures of phosphino phosphinidene I, donor stabilized
diphosphorus(0) II, and diphosphene III (Ar* = 2,6-CHPh2-4-tBuC6H2, NHCDip = 1,3-
(2,6-iPr2C6H3)2-imidazole-2-ylidene, R = General monoanionic ligand).
e. Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016,
India. E-mail: vc@iitk.ac.in
†Electronic Supplementary Information (ESI) available: Thermodynamic data of
equilibrium between
NMR simulation of compound
CCDC 1588456 ( ), 1588457 (
1
and
3
, solution and solid state NMR spectra, UV/vis spectra,
, X-ray crystallographic data and theoretical details.
), 1588458 ( ), 1588459 ( ) and 1588460 ( ). For ESI
6
4
The intriguing difference of reactivity between I and II and
3
5
6
7
most importantly the fact that reversible coordination of Lewis
and crystallographic data in CIF see DOI: 10.1039/x0xx00000x.
bases to multiply bonded main group species are limited,7
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prompted us to investigate the coordination behaviour of an theory clearly indicate elongation and polarization of the P=P
View Article Online
DOI: 10.1039/C8SC00348C
NHC as an auxiliary base towards a diphosphene III as well as bond upon coordination of NHC.23
the influence on its reactivity. In this context, it may be
mentioned that Matsuo and co-workers recently reported the
cleavage of the P-P double bond of Rind-substituted
diphosphene (Rind
= 1,1,3,3,5,5,7,7-octa-R-substituted s-
hydrindacen-4-yl) by an NHC to yield two NHC-coordinated
phosphinidene fragments. The mechanism was proposed to
proceed via the formation of an NHC-coordinated, highly
polarized diphosphene as transient intermediate.15 The
coordination of NHC to the heteronuclear and thus naturally
polarised P=C bond of phosphaalkenes has been studied by
Gates et. al.16
Results and discussion
Figure 1 Molecular structure of 3 (thermal ellipsoids at 50 % probability; hydrogen
atoms omitted for clarity).
Since the isolation of the sterically protected diphosphene,
Mes*P=PMes* (Mes* = 2,4,6–tBu3-C6H2) by Yoshifuji and
coworkers17 several other diphosphenes have been isolated
and characterized.18 We deliberately chose the relatively
The two nonbonding electron pairs at P2 implied by the
ylidic nature of
3 correspond to the HOMO and HOMO−1
unreactive diphosphene TerMesP=PTerMes
,
119 and probed its
with a
2 at room temperature resulted in
(Figure 2). While the HOMO almost exclusively consists of a p-
orbital centered at the formally negatively charged P center,
the HOMO−1 and the HOMO−2 are delocalized across the P-P
unit and therefore correspond to the s-type lone pairs at the
phosphorus centers (Figure 2). The LUMO is mainly delocalized
over the P‒C bond between the carbenic carbon and P1.
binding with NHCMe
, . The treatment of 1
2 20
4
stoichiometric amount of
an immediate colour change from yellow to deep red (Scheme
2). The 31P{1H} NMR of the reaction mixture showed two
upfield doublets of equal intensity at
0.78 ppm (1J(P,P) = 423 Hz) along with the signal of the free
diphosphene at = 492 ppm in about 70:30 ratio. As this
 = 95.36 ppm and

1

ratio remained unaltered even after 2 h, we suspected that the
coordination of NHC might indeed be reversible. The
remarkable difference in the chemical shifts accompanied by a
large coupling constant proves the presence of two non-
equivalent phosphorus nuclei in different electronic
environments, which is consistent with the formation of the
NHC-diphosphene adduct 3 (Scheme 2).
HOMO
HOMO−1
Scheme 2 Reaction of 1 and 2 under the reversible formation of 3 (TerMes = 2,6-
Mes2C6H3, Mes = 2,4,6-Me3C6H2, LA = Ph3B and ZnCl2).
HOMO−2
LUMO
Figure 2 Frontier molecular orbitals of the compound 3 at 0.04 atomic units.
The single crystal X-ray diffraction analysis of 3 reveals that
NHCMe is coordinated to one of the P-centres of the former
4
The carbenic carbon C1 is connected to the P1 center with
diphosphene moiety (Figure 1). The P‒P bond length in 3 is
an angle of 113.26(18)
The two terphenyl ligands adopt a trans-arrangement with a
torsion angle of C8 P1 P2 C32 = 166.8(2) . The bond distance
between carbenic carbon and coordinated phosphorus of is
 with respect to P1‒P2 bond vector.
2.134(2) Å and thus longer than that observed in
1 (2.029(1) Å
),21 but still substantially shorter than the P‒P single bond of
diphosphanes, e.g. (6-Me-2-pyridyl)(SiMe3)2CPH]2 (2.222(3)
Å).22 The calculated Wiberg Bond Order (WBO) (1: 1.812; 3:




3
1.876(2) Å and hence slightly larger than the corresponding
1.116) and the partial NBO charges (
1: P1 = 0.280, P2 = 0.326;
distance in NHCMe4-coordinated phosphaalkene, MesP=CPh2
3
: P1 = 0.494, P2 = −0.116) at the B3LYP/6-311G(d,p) level of
(
1.8512 Å).16b
2 | Chem. Sci., 2018, 00, 1-3
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To substantiate our assertion of reversible coordination of
ARTICLE
Due to the pronounced polarization of theViPew=APrticmleoOinelitnye
NHC to the P=P moiety, we recorded the 31P{1H} NMR of a 1:1 upon coordination of NHCMe , an enhanced reactivity was
4
DOI: 10.1039/C8SC00348C
mixture of
1
and
2
(0.0805 M solution in toluene-d8) at anticipated. We probed the addition reactions of water and
variable temperatures (253 to 293 K). Indeed, the proportion dihydrogen in the presence of NHCMe as benchmarks as free
4
of adduct
grounds of entropic arguments. We calculated the Gibbs (Scheme 3). Thus far, only the hydrolysis of Lewis acid-
enthalpy of formation of to G298 11.2
1.1 kJmol-1.23 In coordinated diphosphene and heteroleptic diphosphenes has
order to check the solvent dependency of the equilibrium, we been reported.24
recorded the solution NMR of 1:1 mixture of and in C6D6
and THF-d8 at room temperature. While diphosphene and
3 increases at lower temperature as expected on diphosphene 1 is inert towards hydrolysis or hydrogenation
3

=


1
2
1
NHC-adduct
3 are observed in an almost 3:7 ratio along with
free NHCMe in the comparatively apolar C6D6, the more polar
THF-d8 leads to a shift of equilibrium in favour of the polarized
4
adduct
3
(90 %). As expected on grounds of the law of mass
action, the addition of 2 equivalents of NHCMe to
1
shifts the
3. On the
4
equilibrium almost completely towards the adduct
other hand, when equivalent amounts of Lewis acids such as
Ph3B or ZnCl2 are added, NHCMe is effectively scavenged and
4
free diphosphene
1 regenerated (Scheme 2). In order to
confirm the exclusive presence of
3 in the solid state, we also
measured a CP-MAS 31P{1H} NMR.23 This reversible addition of
NHCMe
,
2
to diphosphene,
1
has similarities with the reactivity
4
of transition metal complexes in terms of ligand exchange.3
In order to further substantiate the reversibility of NHC
coordination, we monitored the changes in the absorption of
(in THF) with increasing concentrations of by UV-vis
spectroscopy. A THF solution of free diphosphene
1
Scheme 3 Reaction of 3 with H2O (TerMes = 2,6-Mes2C6H3, Mes = 2,4,6-Me3C6H2).
2
1
absorbs at
Addition of one equivalent of H2O to a THF solution of
3
λmax = 448, 372, and 317 nm. Upon gradual addition of NHCMe
4
,
(1:1 mixture of
1 and 2) at RT, led to an immediate colour
2
, the absorbance at 448 nm increases while the absorbance at
change from red to yellow (Scheme 3). Presence of four new
372 nm decreases in intensity as the equilibrium is shifted
multiplets in 31P NMR spectrum with each two of equal
towards
3
. The absorbance at λ = 317 nm is shifted to λ = 324
intensity at
 = 9.55 and 77.36 ppm and  = 28.50 and 46.76
nm when the NHCMe concentration exceeds more than 1.11
4
ppm indicate complete conversion to two new species.
equivalents (1.33, 2.22, and 4.44 equivalents).
isosbestic point is revealed at λ = 392 nm (Figure 3). From the
UV/vis studies the Gibbs enthalpy of formation of , is
estimated to G298
13.30 kJ mol-1, which is close to the
A clear
3

= 
value obtained from the VT-NMR study (
G298 = 11.2  1.1 kJ
mol-1).23
Figure 4 Molecular structures of 4 at thermal ellipsoids of 50 % probability level; all the
hydrogen atoms are omitted for clarity except P-H.
Indeed, the molecular structure determination reveals that
the formation of phosphino substituted phosphine oxide 4
(Figure 4) and phosphido phosphine oxide
5 (Figure 5) in the
course of reaction (Scheme 3). The solid state structures of
these two compounds match well with that of solution state
Figure 3 UV/vis spectra of 1 (black line) in THF with increasing concentrations of 2.
NMR data. The P-P distances involved are 2.1946 (8) Å for
4
and 2.1099(11) Å for . These distances are longer than those
5
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in
4
1
or 3 (1: 1.985(2), 3: 2.134 Å). The P-O bond length found in parent diphosphene
1 only reacts sluggishly with NH3·BH3
View Article Online
is 1.478(2) Å, which is shorter compared with that of
5
taking more than 7 days to afford thDeOIp: r1o0.d10u3c9t/Cin8SCm0o03d4e8sCt
(1.492(2) Å) presumably because of a H-bonding interaction yields.
with an imidazolium cation.25 The P-P distance in
4
(2.1946 (8)
Å) is slightly longer than that observed in metal carbonyl
(Lewis acid) free phospha-Wittig-Horner reagent, (Mes*PH-
P(O)(OEt)2) (2.1854 Å).26
Scheme 4 Reaction of 3 with NH3·BH3 (TerMes = 2,6-Mes2C6H3, Mes = 2,4,6-Me3C6H2).
The 31P NMR spectra of d/l-6 and meso-6 exhibit an AA'XX'
pattern with the peaks centered at
 = 109.9 and 101.4
ppm, respectively (Figure 6). To determine the magnitudes of
the coupling constants of the AA′XX′ spin system, a simulation
of the 1H and 31P NMR spectra was performed (Figure 6).28
Previously, Erickson et al. reported the formation of one of the
diastereomers of compound
6
by the tin-catalyzed
dehydrocoupling of TerMesPH2.29 Based on the current study it
can be concluded that the previously reported diastereomer
had the meso configuration. The initially formed racemic
mixture of d/l-6 is slowly converted to the meso-isomer, meso-
Figure 5 Molecular structures of 5 at thermal ellipsoids of 50 % probability level; all the
hydrogen atoms are omitted for clarity except P-H and imidazolium C-H.
6
, reaching equilibrium within 12 hrs at room temperature.
This has been confirmed by performing the reaction and
measuring 31P{1H} NMR at
50 C. DFT calculations at B3LYP-
D3/6-311G(d,p) level of theory indeed show that meso-6
−
°
Lewis acid free phospha-Wittig-Horner reagent, (Mes*PH-
P(O)(OEt)2), is known to be readily deprotonated to the
isomer is lower in free energy than d/l-6, by a ΔG298 = 2.3 kcal
mol-1.23
lithiated
phospha–Wittig–Horner
reagent,
Mes*P=P(OLi)(OEt)2.26 Similarly, the phosphino substituted
phosphine oxide
pair
complete formation of
equivalents of
are added. The 31P NMR spectrum of the
phosphino substituted phosphine oxide exhibits two
doublets at δ = 9.55 and
77.36 ppm with a 1JP–P of 230 Hz. In
the corresponding resonances are observed at = 28.50 and
4
is transformed to the corresponding ion
5
through deprotonation by NHCMe
,
2
(Scheme 3). The
4
5
from 4 is observed when 2
2
4

5

1

46.76 ppm with a JP–P of 464 Hz. These trends are similar to
those observed in Mes*PH-P(O)(OEt)2 (1JP–P = 222 Hz) and
Mes*P=P(OLi)(OEt)2 (1JP–P = 615 Hz).26 Despite, the imidazolium
character of NHC moiety in
scavenger results in the liberation of free
observed for standard NHC-coordinated main group species
(Scheme 3).27 The exclusive formation
has also been
5
, the addition of BPh3 as NHC
Figure 6 Comparison between the experimental (black, upper curve) and simulated
(red, lower curve) 31P NMR spectrum of A) meso-6 and B) d/l-6 compounds. The scalar
couplings used for the simulations are shown at the lower right.
4
as previously
4
achieved by the addition of Et3N·HCl to the reaction mixture. In
view of the apparent equilibrium, we expected the hydrolysis
Single crystal X-ray diffraction on crystalline samples of
6
exclusively resulted in a structural model in line with meso-6
(Figure 7). As this model depends on the somewhat ambiguous
determination of the hydrogen positions H1P and H1P*, we
cannot exclude the presence of a mixture of isomers in the
solid state. Indeed, the CP-MAS 31P{1H} NMR of a crystalline
sample shows the presence of both diastereomers.
of
relative free energy for the formation of
+ 2) is determined to be ΔG298 = −12.1 kcal mol−1 at the B3LYP-
D3/6311-G(d,p) level of theory.23 Indeed, treatment of
at 78
1
to be catalytic in NHCMe4. In addition, the calculated
4
from 3 (3 + H2O → 4
1

°
C with one equivalent of H2O in the presence of 10 mol % of 2
leads to > 90 % of
4
(TON = 9, Scheme 3).23 At higher
temperatures, the hydrolysis of NHCMe becomes competive
4
significantly reducing the yield of
The reaction of with H2 does not proceed at ambient
conditions. On the other hand, reacts instantaneously with
NH3·BH3 as dihydrogen source affording two diastereomers
d/l-6 and meso-6) of dihydrodiphosphane, (Scheme 4). The
4 and thus the TON.
3
3
(
4 | Chem. Sci., 2018, 00, 1-3
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The formation of
7
from
3
is strong experimental
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DOI: 10.1039/C8SC00348C
corroboration for the mechanism proposed by Matsuo and co-
workers for the cleavage of a P=P bond in a diphosphene.15
Conclusions
In summary, we have demonstrated for the first time that the
coordination of an N-heterocyclic carbene to a heavier double
bond results in
reversible coordination of the NHC to
a
striking reactivity enhancement. The
diphosphene
a
significantly enhances the reaction rate of hydrolysis and
hydrogenation by the ammonia-borane complex. In case of
hydrolysis, we have demonstrated that the reaction is catalytic
in NHC.
Figure 7 Molecular structure of meso-6 (thermal ellipsoids of 50 % probability level;
hydrogen atoms are omitted for clarity).
Experimental
Finally, to address the complete cleavage of the P
present in , we monitored the 1:2 reaction between
‒
1
P bond General
3
and
2.
All experiments were carried out under argon atmosphere
After four days a colour change from deep red to yellow
occurred and we observed the appearance of a new 31P
using standard Schlenk techniques or in
a PL-HE-2GB
resonance at
stabilized phosphinidene.30 Subsequently we heated the
reaction mixture at 105 C for 30 hrs to ensure complete
 = 77 ppm, which is in the range for a carbene- Innovative Technology GloveBox. n-Hexane, diethyl ether, THF,
and toluene were dried by PS-MD-5 Innovative Technology
solvent purification system. Benzene was refluxed over

dissociation resulting in the formation of
7 (Scheme 5).
sodium/benzophenone, then distilled and stored under argon.
Starting compounds TerMes2P2, 119 and NHCMe
,
220 were
4
prepared according to known literature procedures. Benzene-
d6 was dried and distilled over potassium under argon. NMR
spectra were recorded with Bruker NanoBay 300 MHz NMR
1
machine. H and 13C{1H} NMR spectra were referenced to the
peaks of residual protons of the deuterated solvent (1H) or the
deuterated solvent itself (13C{1H}). Solid-state 31P{1H} NMR
Scheme 5 Reaction of 3 with NHCMe (TerMes = 2,6-Mes2C6H3, Mes = 2,4,6– Me3C6H2).
4
spectra were obtained on
a
Bruker Avance 400 MHz
spectrometer with
a
wide-bore magnet and operating
The distance between phosphorus and the carbenic carbon is
1.786 (2) Å (Figure 8), which is comparable with that reported
for a NHC-stabilized phosphinidene.31 However it is shorter
than that of distance between phosphorus and carbenic
at 400.13 MHz (1H) and 163.32 MHz (31P). Powdered samples
were packed in a 4 mm o.d. zirconia rotor. Diameter of the
Probe is 89 mm with spinning speed of 13 KHz. 31P{1H} CP MAS
experiment was performed using 1H 90° pulse for 3.3
s, with
carbon of 3 (1.8306(19) Å).
contact time 5 ms, CPD Spinal64 as decoupling scheme, and a
recycle delay of 3 s. UV/vis spectra were acquired using a Jasco
V-670 spectrometer using quartz cells with a path length of 0.1
cm. Elemental analyses were performed on a Leco CHN-900
analyzer. Melting points were determined in closed NMR tubes
under argon atmosphere and are uncorrected.
Synthesis of 3
10 mL of THF are added to a Schlenk flask containing
1 (0.357
g, 0.518 mmol) and (0.084 g, 0.673 mmol) at room
2
temperature. After stirring for about 5 minutes, all volatiles
are removed under vacuum. The resulting residue is extracted
with 10 mL of n-pentane (2 times) and the combined filtrate
kept at −30 °C overnight resulting in the formation of bright
red crystals are. Yield: 0.211 g (51.9 %). In solution compound
Figure 8 Molecular structure of 7 at thermal ellipsoids of 50 % probability level; all
hydrogen atoms are omitted for clarity.
3
is in equilibrium with 1 and 2. NMR data from 1:1
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stoichiometric ratio of
1
and
2
in C6D6 at RT (almost 30% of
1
Inside the glovebox, 0.019 g (0.08 mmol) of VieBwPArhti3clewOnelirnee
and 2 and 70% of 3
): M.P.: 185 °C (decomposed). 1H NMR (300 weighed into an NMR tube. A benzene–d6 solution of 0.010 g
DOI: 10.1039/C8SC00348C
MHz, C6D6, 298K): δ = 1.25 (s, 3H, C‒CH3 of NHCMe4), 1.30 (s, (0.08 mmol, in 0.5 ml C6D6) of
1 was added at room
3H, C‒CH3 of NHCMe4), 1.57 (s, 2H, C‒CH3 of
2
), 1.89 (br, 14H, temperature. Measurement of H NMR confirm the formation
1
6H from CH3 of Mes and remaining 8H from CH3 of Mes of
2.17 (s, 18H, CH3 of Mes), 2.21 (s, 16H, 12H from CH3 of Mes
and remaining 4H from CH3 of Mes of ), 2.66 (s, 3H, N‒CH3 of
NHCMe4), 3.35 (br, 5H, 3H from N‒CH3 and 2H from N‒CH3 of
), 6.53 (s, br, 2 H, Ar‒H), 6.62‒6.67 (m, 4H, Ar‒H), 6.78‒7.04
(m 13H, 8H from Ar‒H and 5H from Ar‒H of ) ppm. NMR data
in C6D6 at RT to get
1H NMR (300 MHz, C6D6,
1), of 2·BPh3.
1H NMR (300 MHz, C6D6, 298K): δ = 1.11 (s, 6H,
CH3C-CCH3), 2.63 (s, 6H, NCH3), 7.187.27( m, 3H, Ar-H), 7.34
(t, 3J(H, H) = 7.40 Hz, 6H, ArH), 7.68 (d, 3J(H, H) = 6.95 Hz, 6H, ArH)
1
ppm.
2
Reaction of 3 with ZnCl2
1
from 1:2 stoichiometric ratio of
unambiguous 1H NMR data of
1 and 2
Inside the glovebox,
1 (0.024 g, 0.035 mmol) and 2 (0.0056 g,
3
.
0.045 mmol) were dissolved in THF (0.2 mL) in an NMR tube.
After about 5 minutes ZnCl2 (0.0061 g, 0.045 mmol, in 0.2 mL
THF) was added leading to an instant colour change from red
to yellow. After addition of 0.1 mL C6D6, a 31P NMR spectrum
298K): δ = 1.28 (s, 3H, C-CH3 of NHCMe4), 1.33 (s, 3H, C-CH3 of
NHCMe4), 1.82 (br, 6H, CH3 of Mes), 2.16 (s, 18H, CH3 of Mes),
2.21 (s, 12H, CH3 of Mes), 2.66 (s, 3H, N-CH3 of NHCMe4), 3.36
(s, br, 3H, N-CH3 of NHCMe4 and 6H, N‒CH3 of
2), 6.52 (s, br, 2
was recorded showing complete conversion of 2 into 1.
H, Ar-H), 6.62‒6.66 (m, 4H, Ar‒H), 6.78 (s, br, 4H, Ar‒H),
6.86‒7.04 (m, 4H, Ar‒H) ppm. 13C{1H} NMR (75.43 MHz, C6D6,
298K): δ = 7.73 (1C, C‒CH3 of NHCMe4), 8.29 (1C, C‒CH3 of
NHCMe4), 21.07 (3C, CH3 of Mes), 21.37 (4C, CH3 of Mes), 21.92
(3C, CH3 of Mes), 22.66 (1C, CH3 of Mes), 22.88 (1C, CH3 of
Synthesis of 4
In a 50 mL Schlenk flask, 0.392 g (0.57 mmol) of compound
and 0.080 g (0.64 mmol) of were dissolved in 15 mL of THF.
The reaction mixture was stirred for 10 minutes. Subsequently,
degassed water (12 L, 0.65 mmol) was added at room
1
2
3
Mes), 30.46 (1C, d, J(P, C) = 26.85 Hz, N‒CH3 of NHCMe4), 32.83
(1C, d, 3J(P, C) = 19.39 Hz, N‒CH3 of NHCMe4), 120.00 (1C, Ar‒CH),
123.04 (1C, CH3‒C of NHCMe4), 125.82 (1C, CH3‒C of NHCMe4),
126.89 (1C, Ar‒CH), 127.31 (2C, Ar‒CH), 127.63 (2C, Ar‒CH),
127.98 (2C, Ar‒CH), 128.29 (1C, Ar‒CH), 128.58 (3C, Ar‒CH),
130.46 (1C, Ar‒CH), 130.51 (1C, Ar‒CH), 133.77 (2C, Ar‒Cquat),
135.55 (2C, Ar‒Cquat), 135.70 (3C, Ar‒Cquat), 137.46 (2C,
Ar‒Cquat), 138.22 (1C, Ar‒Cquat), 138.40 (1C, Ar‒Cquat), 138.78
(2C, Ar‒Cquat), 140.95 (2C, Ar‒Cquat), 142.78 (1C, Ar‒Cquat),
142.84 (2C, Ar‒Cquat), 146.93 (1C, Ar‒Cquat), 147.18 (1C,
Ar‒Cquat), 150. 17 (1C, Ar‒Cquat), 150.28 (1C, NCN), 151.83 (1C,

temperature and allowed to stir for 1.5 h. The red colour of
the solution slowly transformed into orange. The 31P NMR
showed complete formation of compound
mixture was then added into a THF (5 mL) suspension of
Et3N HCl (0.094 g, 0.68 mmol) and allowed to stir for 30
4. This reaction

minutes resulting in the gradual fading of the colour. All
volatiles were then evaporated and extracted with hot n-
hexane (15 mL). Incipient crystallization happened at room
temperature. Isolated yield 0.310 g (78%). M.P.: > 190 
C. 1H
1
d, J(C, P) = 9.50 Hz, Ar‒Cquat), 152.33 (1C, Ar‒Cquat) ppm. 31P
NMR (300 MHz, C6D6, 298K): δ = 1.79 (s, 6H, CH3 of Mes),
1
NMR (121.5 MHz, C6D6, 298K): δ = −95.35 (d, J(P, P) = 423 Hz),
1.93(s, 6H, CH3 of Mes), 2.05 (s, 6H, CH3 of Mes), 2.28 (s, 6H,
1
= 423 Hz) ppm. CP-MAS 31P{1H} NMR
1

0.78 (d, J(P,
P)
CH3 of Mes), 2.31 (s,12 H, CH3 of Mes), 3.21 (ddd, J(P,H)
=
1
2
3
(163.32 MHz, 298K): δ =

99.07 (d, J(p, p)= 430 Hz, 1P), 3.99
248.70 Hz, J(H,P) = 13.34 Hz, J(H,H) = 8.10 Hz, 1H, HP(O)‒P‒H),
(d, 1J(p, p)= 430 Hz, 1P) ppm. UV/vis (n-hexane): IR (KBr, cm ): ῡ
= 405 (s), 414 (vs), 422 (s), 435 (w), 449 (vs), 474 (vw) 489 (vw),
501 (vw), 530 (m), 548 (vw), 576 (m), 588 (m), 657 (vw), 669
(m), 712 (s) 738 (br, s), 768 (w), 788 (s), 802 (s), 846 (vs), 872
(vw), 907(br, vw), 998 (vw), 1030 (s), 1080 (w), 1107(w), 1178
(m), 1239 (w), 1363 (m), 1439 (m), 1569 (w), 1607 (w), 1652
(w), 2356 (w).
1
7.19 (ddd, 1J(P,H) = 473.31 Hz, 2J(H,P) = 32.35 Hz, J(H,H) = 8.10 Hz,
3
1H, H‒P(O)‒PH), 6.70–6.74 (m, 4H, Ar‒H). 6.77 (br, 1H, Ar‒H),
6.79–6.81 (m, 3H, Ar‒H), 6.87 (s, 4H, Ar‒H), 6.96–7.07 (m, 2H,
Ar‒H) ppm. 13C{1H} NMR (75.43 MHz, C6D6, 298K): δ = 21.03
(2C , CH3 of Mes), 21.37 (2C, CH3 of Mes), 21.63 (1C, CH3 of
Mes), 21.72 (6C, CH3 of Mes), 21.79 (1C, CH3 of Mes), 129.01
(2C, Ar‒CH), 129.04 (2C, Ar‒CH), 129.14 (2C, Ar‒CH), 129.36
(2C, Ar‒CH), 129.47 (1C, Ar‒CH), 129.87 (1C, Ar‒CH), 129.98
Reaction of 3 with BPh3
4
(3C, Ar‒CH), 132.58 (d, J(C,P) = 2.27Hz,1C, Ar‒CH), 133.42 (d,
1
1J(P,C) = 4.52 Hz, 1C, Ar‒Cquat), 134.51 (d, J(P,C) = 4.52 Hz, 1C,
In a glovebox,
1 (0.020 g, 0.029 mmol) and 2 (0.0047 g, 0.037
Ar‒Cquat), 136.74 (2C, Ar‒Cquat), 136.75 (2C, Ar‒Cquat),
136.77(2C, Ar‒Cquat), 137.93 (1C, Ar‒Cquat), 139.50 (2C,
Ar‒Cquat), 145.70 (1C, Ar‒Cquat), 145.83 (1C, Ar‒Cquat), 147.58
(d, 1C, J(C,P) = 5.28 Hz), 147.73 (d,1C, J(C,P) = 4.52 Hz) ppm. 31P
mmol) were dissolved in THF (0.2 mL) in an NMR tube. After
about 5 minutes BPh3 (0.0091 g, 0.037 mmol, in 0.2 mL THF)
was added resulting in an instant colour change from red to
yellow. Subsequent addition of 0.1 mL C6D6 allowed for the
recording of a 31P NMR spectrum, which revealed the
NMR (121.5 MHz, C6D6, 298K): δ = 9.55 (ddd, 1J(P,P) = 248.70 Hz,
2
1J(P,H) = 473.31 Hz, J(H,P) = 13.34 Hz, HP(O)‒PH),

77.36 (dt,
complete conversion of 2 into 1.
1J(P,P) =1J(P,H) = 248.70 Hz, J(H,P) = 32.35 Hz , Ter-P-H) ppm.
2
31P{1H} NMR (121.5 MHz, C6D6, 298K): δ = 9.55 (d, J(P,P)
=
1
Synthesis of 2·BPh3
6 | Chem. Sci., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
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1
1
cm ): ῡ = 750 (s), 844 (s), 907(s), 988 (vs), 1157(w), 1216 (w),
248.70 Hz, HP(O)‒PH), 77.36 (d, J(P,P) = 248.70 Hz, Ter-P-H)
View Article Online
ppm. CP-MAS 31P{1H} NMR (163.32 MHz, 298K): δ = 9.64 (d,
DOI: 10.1039/C8SC00348C
1270 (w), 1369 (m), 1426 (vw), 1444 (w), 1466 (m), 1485 (m),
1
1J(p, p)= 230 Hz, HP(O)‒PH),

78.48 (d, J(p,p) = 230 Hz, Ter-P-H)
1548 (m), 1563 (w), 1582(w), 1642 (s), 1657 (s), 1688 (s), 1707
(m), 1723 (s), 1754 (m), 1779 (m), 1809 (vw), 1838 (s), 1857 (s),
1879 (m), 1900 (m), 1926 (w), 1951 (w), 1979 (w), 2352 (m P-
H), 2380 (m, P-H), 2921 (br). Elemental Analysis: Calcd. for
C55H64N2OP2 (831.06): C, 79.49; H, 7.76; N, 3.37. Found: C,
79.60; H, 7.89; N, 3.73.
ppm. IR (KBr, cm 1): ῡ = 1131(s),1187(s), 1232 (s), 1307 (w),
1370 (m), 1412 (w), 1431 (m), 1450 (m), 1466 (w), 1482 (w),
1501 (m), 1513 (w), 1534 (s), 1553 (s), 1564(m), 1605 (m),
1633 (w), 1677 (m), 1691 (m), 1712 (m), 1726 (m), 1764 (w),
1785 (w), 1820 (w), 1841 (w), 1862 (w), 1886 (w), 1500(w),
1555 (s), 1570 (m), 1610 (m), 1641 (m), 1676 (m) 1711 (m),
1727 (m), 2313 (m, P-H), 2352 (s, P-H), 2727 (m), 2849 (w).
Elemental Analysis: Calcd. for C48H52OP2 (706.87): C, 81.56; H,
7.41. Found: C, 80.81; H, 7.17.
Catalytic hydrolysis of 1
0.277 g (0.402 mmol) of
were dissolved in about 10 mL of THF (10 mL) and cooled
down to 78 C. Subsequently, 8 L (0.45 mmol) of water were
added and the reaction mixture allowed to warm to room
temperature. Subsequent measurement of 31P{1H} NMR shows
1 and 0.005 g (0.0402 mmol) of 2



Synthesis of 5
In a 50 mL Schlenk flask, 0.510 g (0.740 mmol) of compound
and 0.120 g (0.960mmol) of were dissolved in 15 mL of THF.
Water (17.4 L, 0.960 mmol) was added at room temperature
and allowed to stir for 1.5 h. The red colour of the solution
slowly transformed into orange. The reaction mixture was then
evaporated and extracted with hot toluene (20 mL).
Crystallization happens upon cooling at room temperature.
1
the formation of 4 in about 95% spectroscopic yield.
2

Synthesis of 6
In a 50 mL Schlenk flask, 0.334 g (0.49 mmol) of compound
and 0.080 g (0.64 mmol) of were dissolved in 15 mL of THF.
The reaction mixture was stirred for 10 minutes. Afterwards,
10 mL of a THF solution of NH3 BH3 (0.020g, 0.64 mmol) were
added at room temperature. The reaction mixture was allowed
to stir for 30 minutes during which the red colour of the
solution slowly faded to colourless. The 31P NMR showed
complete formation of compound
All volatiles were evaporated and the residue extracted with
hot n-hexane (15 mL). Crystallization happens at room
1
2
Isolated yield 0.530 g (86.13 %). M. P.: > 190
C (decomposed)

and at 175

C color changes slowly towards white. 1H NMR
(300 MHz, THF-D8, 298K): δ = 1.80 (s, 6H, 6H, CH3 of Mes), 1.81
(s, 6H, CH3 of Mes), 1.92 (s, 6H, C‒CH3 of NHCMe4), 2.00 (s, 6H,
CH3 of Mes ), 2.18 (s, 12H, CH3 of Mes), 2.22 (s, 6H, CH3 of
Mes), 3.51(s, 6H, N-CH3 of NHCMe4), 6.32 (s, 1H, Ar‒H), 6.34
(s,1H, Ar‒H), 6.44 (s, 2H, Ar‒H ), 6.47 (s, 2H, Ar‒H), 6.50‒6.54
(m, 3H, Ar‒H), 6.57 (s, 3H, Ar‒H), 6.74 (s, 2H, Ar‒H), 7.08 (t,
1H, 3J(H, H) = 7.60 Hz, Ar‒H), 6.96 (d, 1H, 1J(P, H)= 464.15 Hz, P‒H),
10.65 (s, br, 1H, N‒CH‒N of NHCMe4) ppm. 13C{1H} NMR (75.43
MHz, C6D6, 298K): δ = 7.66 (2C, C‒CH3 of NHCMe4), 21.02 (1C,
CH3 of Mes ), 21.05 (1C, CH3 of Mes), 21.34 (2C, CH3 of Mes),
21.44 (2C, CH3 of Mes), 21.58 (1C, CH3 of Mes) 21.61 (1C, CH3
of Mes), 22.14 (1C, CH3 of Mes), 22.32 (1C, CH3 of Mes), 22.47
(1C, CH3 of Mes), 22.55 (1C, CH3 of Mes), 33.42 (2C, CH3‒C of
NHCMe4), 119.82 (2C, Ar‒CH), 126.31 (2C, 4,5-C of NHCMe4),
127.56 (3C, Ar‒CH), 128.04 (2C, Ar‒CH), 128.18 (2C, Ar‒CH),
128.37 (2C, Ar‒CH), 128.52 (1C, Ar‒CH), 129.63 (1C, Ar‒CH),
129.72 (1C, Ar‒CH), 134.42 (2C, Ar‒Cquat), 134.90(2C, Ar‒Cquat),
136.66 (2C, Ar‒Cquat), 137.26 (2C, Ar‒Cquat), 137.56 (2C,
Ar‒Cquat), 137.87 (2C, Ar‒Cquat), 141.51 (1C, Ar‒Cquat), 141.55
(1C, Ar‒Cquat), 142.90 (1C, Ar‒Cquat), 142.95 (1C, Ar‒Cquat),
143.04 (1C, Ar‒Cquat), 143.08 (1C, Ar‒Cquat), 143.25 (1C,
Ar‒Cquat), 144.63(1C, Ar‒Cquat), 144.65(1C, Ar‒Cquat), 144.72(1C,
6 as d/l and meso isomers.
temperature, a second crop was obtained at
yield 0.300g (89%). M.P.: > 190
(300 MHz, C6D6, 298K): δ = 1.90 (s, 12H, CH3 of Mes), 2.05 (s,
12H, CH3 of Mes), 2.28 (s, 12H, CH3 of Mes), 3.02 (centre of the
20 C. Isolated

C. 1H NMR of meso isomer
1
AA'XX' multiplet pattern, 2H, PH

PH, fitted with J(31P,
=
31P)
3
1
2
94.5 Hz, J(1H, 1H) = 17.0 Hz, J(31P, 1H) = 216 Hz, J(31P, 1H) = 10.9 Hz),
6.74 (s, 2H, Ar H), 6.76 (s, 2H, Ar H), 6.81 (s, 4H, Ar H), 6.83
(s, 4H, Ar H), 6.98 (t, J(H,H) = 7.41, 2H, Ar
H) ppm. Selected 1H
NMR of d/l isomer (300 MHz, C6D6, 298K): δ = 1.91 (s, 12H),
1.96 (s, 12H), 2.30 (s, 12H), 4.01(centre of the AA'XX' multiplet



3


1
3
pattern, 2H, PHPH, fitted with J(31P, 31P) = 260.8 Hz, J(1H, 1H) =
12.9 Hz, J(31P, 1H) = 201 Hz, J(31P, 1H) = 13 Hz) ppm. 13C{1H} NMR
(75.43 MHz, C6D6, 298K): δ = 21.35 (1C, CH3 of Mes), 21.38 (2C,
CH3 of Mes), 21.41 (1C, CH3 of Mes), 21.48 (1C, CH3 of Mes),
21.55 (2C, CH3 of Mes), 21.61 (1C, CH3 of Mes), 21.71 (4C, CH3
of Mes), 128.69 (2C, Ar‒CH), 128.79 (2C, Ar‒CH), 128.92 (2C,
Ar‒CH), 129.08 (2C, Ar‒CH), 129.02 (2C, Ar‒CH), 129.12 (2C,
Ar‒CH), 129.37 (2C, Ar‒CH), 134.14 (1C, Ar‒Cquat), 134.27 (1C,
Ar‒Cquat), 134.41 (1C, Ar‒Cquat), 136.12 (1C, Ar‒Cquat), 136.36
(3C, Ar‒Cquat), 136.54(1C, Ar‒Cquat), 136.65 (3C, Ar‒Cquat),
136.76 (3C, Ar‒Cquat), 139.88 (3C, Ar‒Cquat), 140.05 (1C,
Ar‒Cquat), 140.70 (1C, Ar‒Cquat), 146.78 (2C, Ar‒Cquat), 146.87
(1C, Ar‒Cquat) ppm. 31P NMR (121.5 MHz, C6D6, 298K): δ =
1
2
Ar‒Cquat), 144.76 (1C, NCN) ppm. 31P NMR (121.5 MHz, C6D6,
298K): δ = 28.50 (t, 1P, J(P, P) = 1J(P,H) 464.15Hz, P‒P‒O),

46.76
1
(d,1P, J(P, = 464.15 Hz, P‒P‒O) ppm. 31P{1H} NMR (121.5
1
P)
1
MHz, C6D6, 298K): δ = 28.50 (d, J(P, P) = 464.15 Hz, P‒P‒O),
1

46.76 (d, J(P, P) = 464.15 Hz, P‒P‒O) ppm. CP-MAS 31P{1H}
NMR (163.32 MHz, 298K): δ = 27.04 (d, 1J(p, p)= 465 Hz, P‒P‒O),

47.00 (d, 1J(P, P) = 465 Hz, P‒P‒O) ppm. UV/vis (THF): max
() =

101.38 (meso isomer, centre of the AA'XX' pattern as seen in
330 (5244), 390 (9754), 445 (4410) nm (Lmol−1cm−1). IR (KBr,
1H decoupled spectrum; non-decoupled spectrum fit with 1J(31P,
This journal is © The Royal Society of Chemistry 20xx
Chem. Sci., 2018, 00, 1-3 | 7
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3
1
2
31P) = 94.5 Hz, J(1H, 1H) = 17.0 Hz, J(31P, 1H) = 216 Hz, J(31P, 1H) = 10.9
Acknowledgements
View Article Online
DOI: 10.1039/C8SC00348C
1
Hz (same as that for the corresponding H spectrum), 109.9
This work is supported by the Tata Institute of Fundamental
Re-search Hyderabad, Gopanpally, Hyderabad-500107,
Telangana, India, SERB-DST (EMR/2014/001237), India,
Research Group Linkage Programme of Alexander von
Humboldt Foundation, Germany, and Saarland University,
Germany. VC is thankful to the Department of Science and
Technology, New Delhi, India, for a National J. C. Bose
fellowship. We thank the reviewers for their comments to
(d/l Isomer, centre of the AA'XX' pattern as seen in 1H
1
decoupled spectrum; non-decoupled spectrum fit using J(31P,
3
1
2
31P) = 260.8 Hz, J(1H, 31H) = 12.9 Hz, J(31P, 1H) = 201 Hz, J(31P, 1H) = 13
Hz (same as that for the corresponding 1H NMR spectrum)
ppm. 31P{1H} NMR (121.5 MHz, C6D6, 298K): δ =

101.38 (s,
meso isomer),
NMR (163.32 MHz, 298K) ): δ =

109.9 (s, d/l Isomer ) ppm. CP-MAS 31P{1H}

101.38 (s, meso isomer), 
104.13 (s, d/l Isomer ) ppm. IR (KBr, cm 1): ῡ = : 845 (s), 1398 improve the manuscript
(w), 1432 (w), 1457 (w), 1485 (w), 1567 (s), 1610 (s), 1647
(vw), 1726 (m), 1757 (vw), 1804 (vw), 1866 (m), 1932 (m),
2325 (s, P-H), 2403 (Vw, P-H), 2727 (s), 2855 (w), 2907 (w).
Elemental Analysis: Calcd. for C48H52P2 (690.87): C, 83.45; H,
Notes and references
1
(a) J. A. Osborn, F. H. Jardine, J. F. Young and G. Wilkinson, J.
Chem. Soc. A, 1966, 1711‒1732; (b) P. Meakin, J. P. Jesson
and C. A. Tolman, J. Am. Chem. Soc., 1972, 94, 3240–3242;
(c) S. K. Tanielyan, R. L. Augustine, N. Marin and G. Alvez, ACS
7.59. Found: C, 82.56; H, 7.27.
Synthesis of 7
Catal., 2011, 1, 159–169.
In a 25 mL Schlenk flask 0.202 g (0.293 mmol) of compound
1
2
(a) N. H. Park, E. V. Vinogradova, D. S. Surry and S. L.
Buchwald, Angew. Chem., Int. Ed., 2015, 54, 8259 –8262; (b)
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and 0.072 g (0.586 mmol) of
toluene. The red reaction mixture was heated at 105
h. During the course of reaction, the color of the reaction
mixture changed from red to yellow. After 12 h at 0 C yellow
crystals of are obtained. The resulting mother liquor was
concentrated to 5 mL and kept at 20 C. After one day a
2
were dissolved in 10 mL of

C for 30
Organometallics, 2004, 23, 33983416; (d) B. Su, T. –G.

Zhou, X. W. Li, X. R. Shao, P. L. Xu, W. L. Wu, J. F. Hartwig and
Z. J. Shi, Angew. Chem., Int. Ed., 2017, 56, 1092–1096; (e) X.
Jiang, J. J. Beiger and J. F. Hartwig, J. Am. Chem. Soc., 2017,
139, 87−90.
7


second crop of crystals was collected. Total yield: 0.225 g (81.8
%). Single crystals suitable for X-ray diffraction analysis were
obtained from a saturated solution of toluene at 0 °C after one
day. M.P.: > 200 °C. 1H NMR (300 MHz, C6D6, 298K): δ = 1.25 (s,
6H, C‒CH3 of NHCMe4), 2.17 (6H, p‒CH3 of Mes), 2.40 (12H,
o‒CH3 of Mes,), 2.84 (s, 6H, N‒CH3 of NHCMe4), 6.78 (4H, Ar‒H),
6.99‒7.08 (m, 3H Ar‒H) ppm. 13C{1H} NMR (75.43 MHz, C6D6,
298K): δ = 8.83 (2C, C‒CH3 of NHCMe4), 21.51 (4C, CH3 of Mes),
21.56 (2C, CH3 of Mes), 34.12 (N‒CH3 of NHCMe4), 34.24 (N‒CH3
of NHCMe4), 122.50 (1C, Ar‒CH), 122.55 (2C, CH3‒C of NHCMe4),
128.53 (4C, Ar‒CH), 128.98 (2C, d, J(C, P) = 1.38, Ar‒CH), 134.37
(1C, Ar‒Cquat), 136.26 (1C, Ar‒Cquat), 142.78 (1C, Ar‒Cquat),
142.82 (1C, Ar‒Cquat), 144.68 (1C, Ar-Cquat), 144.86 (1C,
Ar‒Cquat), 150.67 (1C, Ar‒Cquat), 151.42 (1C, Ar‒Cquat), 167.40
(1C, Ar‒Cquat), 168.70 (1C, Ar‒Cquat) ppm. 31P NMR (121.5 MHz,
3
4
P. P. Power, Nature, 2010, 463, 171–177.
G. C. Welch, R. R. S. Juan, J. D. Masuda and D. W. Stephan,
Science, 2006, 314, 1124–1126.
Y. Peng, B. D. Ellis, X. Wang, J. C. Fettinger and P. P. Power,
Science, 2009, 325, 1668–1670.
5
6
7
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C6D6, 298K):
(163.32 MHz, 298K) ): δ =
max
) = 446 (11244), 382 (5375), 310 (2553) nm (Lmol−1cm−1).
δ
=
76.92 ppm. CP-MAS 31P{1H} NMR
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
(

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(m), 1185 (w), 1234 (w), 1660 (m), 1705 (m), 1856 (m), 1876
(w), 2346 (br, w), 2372 (w). Elemental Analysis: Calcd. for
C31H37N2P (468.62): C, 79.45; H, 7.96; N, 5.98 Found: C,79.24;
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Conflicts of interest
There are no conflicts to declare.
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DOI: 10.1039/C8SC00348C
TOC Scheme
The reversible coordination of N-heterocyclic carbene (NHC), a Lewis base to a diphosphene leads to the
reactivity enhancement of diphosphene moiety, resulting in ready hydrolysis and hydrogenation
reaction. We were able to show that the hydrolysis reaction is catalytic.