A General Synthetic Route to NHC-Phosphinidenes: NHC-mediated Dehydrogenation of Primary Phosphines

Article abstract of DOI:10.1002/zaac.202000405

The dehydrocoupling of primary phosphines with N-heterocyclic carbenes (NHCs) to yield NHC-phosphinidenes is reported. The reaction of two equivalents of the NHCs Me₂Im (1,3-dimethylimidazolin-2-ylidene), Me₄Im (1,3,4,5-tetramethylimidazolin-2-ylidene), iPr₂Im (1,3-di-iso-propylimidazolin-2-ylidene) and Mes₂Im (2,4,6-trimethylphenylimidazolin-2-ylidene) with PhPH₂ and MesPH₂ led to the NHC stabilized phosphinidenes (NHC)PAr: (iPr₂Im)PPh (1), (Mes₂Im)PPh (2), (Me₄Im)PPh (3), (Mes₂Im)PMes (4), (Me₂Im)PMes (5), (Me₄Im)PMes (6) and (iPr₂Im)PMes (7). The reaction of tBuPH₂ with two equivalents of the NHCs afforded the corresponding NHC stabilized parent phosphinidenes (NHC)PH: (iPr₂Im)PH (8), (Mes₂Im)PH (9) and (Me₄Im)PH (10). Reaction of 1 with oxygen and sulfur led to isolation of iPr₂Im-P(O)₂Ph (11) and iPr₂Im-P(S)₂Ph (12), whereas the reaction with elemental selenium and tellurium gave (NHC)PPh cleavage with formation of (iPr₂Im)Se (13), iPr₂ImTe (14) and different cyclo-oligophosphines. Furthermore, the complexes [{(iPr₂Im)PPh}W(CO)₅] (15), [Co(CO)₂(NO){(iPr₂Im)PPh}] (16) and [(η⁵-C₅Me₅)Co(η²-C₂H₄){(iPr₂Im)PPh}] (17) have been prepared starting from 1 and a suitable transition metal complex precursor. The complexes 16 and 17 decompose in solution upon heating to ca. 80 °C to yield the NHC complexes [Co(iPr₂Im)(CO)₂(NO)] and [(η⁵-C₅Me₅)Co(iPr₂Im)(η²-C₂H₄)] with formation of cyclo-oligophosphines. The reaction of 1 with [Ni(COD)₂] afforded the diphosphene complex [Ni(iPr₂Im)₂(trans-PhP=PPh)] 18.

Full text of DOI:10.1002/zaac.202000405

Title: A General Synthetic Route to NHC-Phosphinidenes: NHC-
mediated Dehydrogenation of Primary Phosphines
Authors: Udo Radius, Luis Werner, Günther Horrer, Michael Philipp,
Katharina Lubitz, and Maximilian W. Kuntze-Fechner
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
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content of this Accepted Article.
To be cited as: Z. anorg. allg. Chem. 10.1002/zaac.202000405
Link to VoR: https://doi.org/10.1002/zaac.202000405

Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
A General Synthetic Route to NHC-Phosphinidenes: NHC-mediated
Dehydrogenation of Primary Phosphines
[a]
[a]
[a]
[a]
Luis Werner , Günther Horrer , Michael Philipp , Katharina Lubitz , Maximilian W.
[a]
[a]
Kuntze-Fechner and Udo Radius *
[
a]
L. Werner, G. Horrer, M. Philipp, Dr. K. Lubitz, Dr. M. W. Kuntze-Fechner, Prof. Dr. U. Radius,
Institut für Anorganische Chemie,
Julius-Maximilians-Universität Würzburg,
Am Hubland,
97074 Würzburg, Germany.
u.radius@uni-wuerzburg.de
http://www.ak-radius.de
Key-Words: N-Heterocyclic Carbenes, Phosphinidenes, Dehydrocoupling, Transition
Metal Complexes.
Supporting Information Placeholder
th
Dedicated to Prof. Dr. Peter Klüfers on the Occasion of his 70 birthday
ABSTRACT: The dehydrocoupling of primary phosphines with N-heterocyclic
carbenes (NHCs) to yield NHC-phosphinidenes is reported. The reaction of two
equivalents of the NHCs Me
tetramethylimidazolin-2-ylidene), iPr
Mes Im (2,4,6-trimethylphenylimidazolin-2-ylidene) with PhPH
NHC stabilized phosphinidenes (NHC)PAr: (iPr Im)PPh (1), (Mes
Me Im)PPh (3), (Mes Im)PMes (4), (Me Im)PMes (5), (Me Im)PMes (6) and
iPr Im=PMes (7). The reaction of tBuPH with two equivalents of the NHCs afforded
the corresponding NHC stabilized parent phosphinidenes (NHC)PH: (iPr Im)PH (8),
Mes Im)PH (9) and (Me Im)PH (10). Reaction of 1 with oxygen and sulfur led to
isolation of iPr Im–P(O) Ph (11) and iPr Im–P(S) Ph (12), whereas the reaction with
elemental selenium and tellurium gave (NHC)PPh cleavage with formation of
iPr Im)Se (13), iPr Im=Te (14) and different cyclo-oligophosphines. Furthermore, the
Im)PPh}W(CO) ] (15), [Co(CO) (NO){(iPr
Im)PPh}] (16) and [(η5-
2
Im (1,3-dimethylimidazolin-2-ylidene), Me
Im (1,3-di-iso-propylimidazolin-2-ylidene) and
and MesPH led to the
Im)PPh (2),
4
Im (1,3,4,5-
2
2
2
2
2
2
(
4
2
2
4
2
2
2
(
2
4
2
2
2
2
(
2
2
complexes [{(iPr
2
5
2
2
2
5
C Me
5
)Co(η -C
2 4
H ){(iPr
2
Im)PPh}] (17) have been prepared starting from 1 and a
1
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
suitable transition metal complex precursor. The complexes 16 and 17 decompose in
solution upon heating to ca. 80°C to yield the NHC complexes [Co(iPr Im)(CO) (NO)]
)] with formation of cyclo-oligophosphines. The
] afforded the diphosphene complex [Ni(iPr Im) (trans-
2
2
5
2
and [(η -C
5
Me
5
)Co(iPr
2
Im)(η -C
H
2 4
reaction of 1 with [Ni(COD)
PhP=PPh)] 18.
2
2
2
Introduction
[1]
Phosphinidenes represent a group of highly reactive, low-valent, six electron species,
which can be made manageable by terminal coordination on either transition metal
complexes or Lewis-bases.[2,3] In the early 1980s 7-phosphinonorbornadienes were
found to be promising starting materials for the preparation of phosphinidenes in
solution, yet their isolation turned out to be difficult. Coordination to [M(CO) ] (M =
5
group VI metal) complexes made 7-phosphinobornadienes isolable and moreover led
to the discovery of the electrophilic terminal transition metal phosphinidene complex
[
[
(OC)
(OC)
5
W=PPh] by Matthey et al. These complexes with the general formula
M=PPh] are not isolable, but can be generated in situ for further reactions.[2a, 4]
5
All literature known metal carbonyl phosphinidene-complexes of the general formula
[
(OC)
n
M(PR)]
are
unstable
at
room
temperature
except
of
[
{(Dipp
2
ImH/Me)C(Ph)}P]Fe(CO)
4
(Dipp = 2,6-di-iso-propylphenyl) published recently by
Ghadwal and coworkers.[4c] First examples of nucleophilic transition metal
5
phosphinidene complexes, the bent metallocene complexes [(h -C
5 5
H )
2
M=PMes*]
t
[5]
(
Mes* = 2,4,6- BuC
6
H ; M = Mo, W) were presented by Lappert et al. in 1987. These
2
1
8-electron phosphinidene complexes were synthesized using salt metathesis of
5
lithium metallocene hydrides [{(h -C
5 5
H )
2
MHLi}
4
] with dichlorophosphine Mes*PCl
2
under elimination of LiCl. Salt metathesis is the most common route to synthesize
nucleophilic phosphinidene complexes, which resulted in variations of bent
metallocene phosphinidene complexes including early-transition-metal complexes
5
P)(=PMes*)]; (M = Zr, Hf),[6, 7] as well as the uranium complex [[(h5-
[
(h -C
5
H
5
)
2
M(Me
U(Me
PO)(=PMes*)].[8] Lammertsma et al. demonstrated that this synthetic
route is also feasible for late transition metals, e.g., by treating the dichloro complexes
3
C
5
Me
5
)
2
3
5
iPr
Im ) with LiPHMes* to give [(h5-
Me
[
((h -C
5 5 2
H )Ir(L)Cl )] (L = PPh
3
,
2
C H
5 5
)Ir(L)(=PMes*)].[9]
The stabilization of metal-free phosphinidenes was introduced with an early example
by Schmidpeter et al. in 1980 with a report on the isolation of cyanophosphinidene-
2
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
substituted heterocycles.[10] Arduengo et al. reported in 1997 the synthesis and
isolation of the NHC pnictinidene adducts Mes Im=PnR (Mes Im = 1,3-
dimesitylimidazolin-2-ylidene; Pn = P, As; R = C , CF , C ) and related compounds
such as (Me Im)PPh (NHC = N-heterocyclic carbene, Me Im = 1,3,4,5-tetramethyl-
2
2
H
6 6
3
F
5 5
4
4
imidazolin-2-ylidene), and provided thus the first example that NHCs are suitable
molecules for the stabilization of reactive phosphinidenes.[11] Since then, synthesis and
application of NHC-phosphinidenes gained more and more importance.[3]
Several synthetic routes have been developed for the preparation of NHC
[3]
phosphinidene adducts since then (Scheme 1). The aforementioned first ‘bottleable’
NHC-phosphinidenes such as (Me Im)PPh were obtained by reaction of Me Im and
pentaphenyl-cyclo-pentaphosphine (PPh)
.[11] Several NHC-phosphinidenes such as
Mes Im)PPh or (Mes Im)PCF , have been synthesized from (PPh) or similar
compounds such as (PCF
following this methodology (Scheme 1).[3, 11] However the
4
4
5
(
2
2
3
5
)
3 4
scope of this procedure is strongly dependent on the availability of the cyclo-phosphine
used. The synthesis of NHC-phosphinidenes is also feasible via the reaction of two
equivalents of free carbene with dichlorophosphines, which in selected cases leads to
+
- [11a]
the NHC-phosphinidene and [NHC-Cl] Cl .
Instead of using NHC as the chlorine
acceptor, Bertrand et al. presented a reductive pathway, i.e. the reaction of the NHC
with dichlorophosphines and subsequent two electron reduction with potassium
graphite or magnesium powder, which leads to the desired NHC-phosphinidenes
(
Scheme 1).[12] The formation of NHC-phosphinidenes is also known from a variety of
other NHC and phosphinidene precursors aside from the commonly applied routes
starting from chloro-,[11a, 12] and cyclo-polyphosphines.[11] For example, (Me
Im)P(Rind)
was synthesized from the reaction of diphosphenes (Rind)P=P(Rind) (Rind =
,1,3,3,5,5,7,7-octa-R-substituted s-hydrindacen-4-yl; R = Et, Me) and two equivalents
of the free carbene Me with N,N’-1,3-bis(2,6-
Im.[13] The reaction of P(SiMe
diisopropylphenyl)-2,2-difluoroimidazoline led to (Dipp Im)P(SiMe ) and subsequently
to (Dipp
Im)PH upon addition of methanol.[14] Another efficient route to NHC-
4
1
4
)
3 3
2
3
2
phosphinidenes was established by Grützmacher and Gudat et al. by using the
-
phosphaethynolate anion OCP as phosphorus transfer reagent in the reaction with N-
arylated imidazolium salts.[15] Na(OCP) is also a useful reagent for the preparation of
tetrel-substituted phosphaketenes (e.g. Ph E(PCO), E = Sn, Ge), which afforded NHC-
3
phosphinidene adducts upon coordination to NHCs and subsequent thermolysis.[16] An
interesting example of an intramolecular carbene-stabilized phosphinidene was
3
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
provided by Hahn et al., which was synthesized from the reaction of the phosphaalkyne
iPr NCP with Me Im. The bicyclic azaphospholene product of this reaction is formed
by unusual C-H activation at the nitrogen substituent of the NHC.[17] Similar to
polyphosphines, other polyphosphorus compounds such as Na or (Me Si) also
2
4
P
3 7
3
P
3 7
provide access to NHC-phosphinidenes of NHCs of varying steric demand by reaction
with dihydroimidazolium chlorides, as reported by Grützmacher and Gudat et al.[15]
Moreover Hey-Hawkins and co-workers demonstrated that Na
2
(THF)
4
P
4
Mes is a
4
+
- [18]
suitable precursor for (Me
2
Im)PMes, if reacted with Me
2
Im or [Me Im-H] I .
2
N
1
/5 (PPh)5
N
N
C
P
N
Ph
N
N
N
Na (THF) P Mes
4
2
4
4
2
2
P
P
C
N
Mes
Mes
Mes
Mes
Cl
Cl
N
N
N
PhPCl2
+
C
Ph
N
N
N
Mes
R1
Mes
Mes
R1
R
Cl
N
R
Cl
N
PhPCl2
C
P
R
N
R1
R
N
Ph
R1
2
KC8
or 2 Mg
R1
R
R
N
C
P
N
Ph
R1
2
N
N
R PH
2
C
P
2
R2
N
-iPr2ImH2
N
Scheme 1. Major synthetic routes to NHC-phosphinidenes.
We recently explored the reactivity of NHCs and related molecules with group 13 to 15
main group element hydrides[19] and other main group element compounds.[20] We
demonstrated that the reaction of iPr Im (1,3-diisopropylimidazolin-2-ylidene) with
2
substrates such as hydrostannanes[19d] or primary and secondary phosphines[19b] leads
to dehydrogenative element element coupling. P-P coupling was exemplified by the
4
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
stoichiometric reaction of iPr
2
Im with secondary phosphines, e.g. Ph
ImH and the P-P coupled product Ph in 89% yield.
A similar reaction protocol with primary phosphines ArPH (Ar = Ph, pTol) leads to the
P-P coupled rings P Ph , P Ph and P Ph . In contrast, using primary phosphines in
sub-stoichiometric amounts, i.e. a 1:2 ratio regarding to iPr Im, yields the
dihydroaminal iPr ImH and the NHC-phosphinidene (iPr Im)PAr (Ar = Ph, pTol)
2
PH, which
afforded the dihydroaminal iPr
2
2
4 2
P
2
4
4
5
5
6
6
2
2
2
2
quantitatively as judged from NMR spectroscopy. In this reaction, the ambiphilic
character of the NHC is exploited i) as an activator of the primary phosphine P-H bond
and ii) as a hydrogen acceptor. Thus, we considered the NHC mediated
dehydrogenation of phosphines as a very interesting approach for the selective
synthesis of NHC-phosphinidenes (Scheme 1, bottom) and we report herein on
primary phosphine dehydrocoupling using different NHCs as a general and convenient
synthetic approach to prepare NHC-phosphinidenes in moderate to high isolated yields
(
up to 71%). Furthermore, we also report a novel synthesis to different parent NHC-
phosphinidenes (NHC)PH and preliminary investigations concerning the reactivity of
iPr Im)PPh towards chalcogenides and selected transitions metals complexes.
(
2
Results and Discussion
Our previous work demonstrated that the reaction of the primary aryl-substituted
phosphines PhPH
2:1 led selectively to the formation of the NHC-phosphinidene adduct (iPr
1) and (iPr Im)PTol in good isolated yield. One equivalent of the NHC serves as a
hydrogen acceptor leading to the dihydroaminal iPr ImH and the other equivalent is
2
and p-TolPH
2
with iPr
2
Im in a stoichiometric ratio NHC:phosphine
=
2
Im)PPh
(
2
2
2
needed to stabilize the phosphinidene generated. [19b] As this approach represents a
convenient way to access NHC-phosphinidenes we were interested to explore this
preparative route in more detail. Thus, we reacted two equivalents of different NHCs
with PhPH
primary phosphines, i.e. PhPH
different phosphines (Scheme 2).
2
to probe their ability to act as hydrogen-acceptor as well as different
2
, MesPH
2
and tBuPH
2
with different NHCs to probe
5
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
R1
R1
R
R
N
2
R
R
N
N
R PH2
2
C
P
1
R
-
R Im H2
R2
N
R1
R1
iPr
C
Mes
N
Me
Me
N
N
N
P
C
P
C
P
Ph
N
Ph Me
N
Ph
iPr
Mes
Me
1
2
3
Mes
Me
Me
iPr
Me
N
N
N
N
N
C
N
C
P
C
P
P
C
P
N
Mes
N
Mes Me
Mes
Mes
Mes
Me
Me
iPr
4
5
6
7
R1
R1
R
R
tBuPH2
R
R
N
N
N
2
C
P
1
R
-
R Im H2
N
H
-
C4H8
R1
R1
iPr
Mes
Me
Me
N
N
N
N
N
N
C
P
C
P
C
P
H
H
Me
H
iPr
Mes
Me
8
9
10
Scheme 2. Dehydrogenative synthesis of NHC-phosphinidenes (NHC)PAr (1–7, top) and (NHC)PH (8-
0, bottom).
1
Thus, we applied the same reaction protocol on the primary phosphines PhPH ,
2
MesPH
2
and tBuPH
2
2
in combination with iPr Im, Mes
2
Im, Me
2
Im and the backbone
methylated NHC, Me
4
Im. The reaction of two equivalents Mes
2
Im and Me Im with one
4
equivalent phenyl phosphine in xylene or toluene at 135°C and 110°C, respectively,
31
was monitored via P NMR spectroscopy. During the reactions new species were
31
31
detected in the P NMR spectra, the corresponding P resonances were significantly
downfield shifted in comparison to phenyl phosphine (c.f. -124.2 ppm). The signals at
-
23.7 ppm ((Mes
2
Im)PPh (2)) and -52.9 ppm ((Me Im)PPh (3)) were assigned
4
accordingly to the corresponding NHC-phosphinidenes and are in good agreement
with those reported earlier by Arduengo et al. and by Layfield and coworkers
(
Table 1).[11, 21] For the reaction of Mes
corresponding P-P coupling products were observed. After the reaction reached
2
Im with PhPH
2
no NMR signals for
31
quantitative conversion without any side products formed, as judged from P NMR
spectroscopy, the solvent was evaporated, and the residue suspended in n-hexane.
Subsequent filtration and washing with portions of n-hexane to remove the residual
dihydroaminal NHCH
2
led to the isolation of (Mes Im)PPh (2) as a bright yellow solid
2
in good yield (61%). The reaction of two equivalents Me
4 2
Im with PhPH , however,
6
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
afforded aside from the product (Me
4
Im)PPh (3) cyclo-oligophosphines P
4
Ph
4 5
, P Ph
5
and P
equivalents). Thus, (Me
low yields of approximately 14 % judged from the integration of the P NMR signals
of the isolated yellow solid, which contained a mixture of (Me Im)PPh (3) and different
oligophosphines. We did not try to separate the cyclo-oligophospines from (Me Im)PPh
3).
6
Ph
6
as major side products, even in presence of an excess of NHC (i.e. 2.1
4
Im)PPh (3) was also formed using this procedure, but only in
31
4
4
(
As the primary aryl phosphines seem to be suitable sources for the dehydrogenative
route to NHC-phosphinidenes, we also investigated the reaction of mesityl phosphine
MesPH
2
towards NHCs. MesPH was reacted in a 1:2 ratio with the four different NHCs
2
31
at higher temperatures. After the phosphine was completely consumed (judged on P
NMR spectroscopy) and subsequent work up, the literature known NHC-
phosphinidenes (Mes
2
Im)PMes (4), (Me
2
Im)PMes (5) and (Me Im)PMes (6) were
4
isolated in moderate to fair yields (4: 33%, 5: 53%, 6: 47%). Layfield and coworkers
reported an iron- and cobalt-catalyzed synthesis for the NHC-phosphinidenes
(
Mes
with MesPH
under otherwise catalytic conditions. Upon heating Mes
at 80°C in deutereobenzene for several days, these authors observe no reaction,
2
Im)PMes (4) and (Me
to exclude formation of the NHC-phosphinidene without any catalyst
Im and Dipp Im with MesPH
4
Im)PMes (6).[21] Layfield et al. also reacted Mes
Im directly
2
2
2
2
2
1
31
whereas H and P NMR spectra of the combination Me
4
Im/MesPH showed that
2
MesPH , MesP(H)Me, and IMe ·PMes are present in an approximate ratio of 7:1:1 and
2
4
the mixture is thus dominated by starting materials.[21] However, using more elevated
temperatures up to 110°C or higher, dehydrocoupling is feasible even without the need
for a catalyst with formation of (Mes
and (iPr Im)PMes (6), the direct reaction of two equivalents
Im)PMes (7).[19a] For (Me
of Me Im with one equivalent of MesPH results in the complete consumption of
2
Im)PMes (4), (Me
2
Im)PMes (5), (Me Im)PMes (6)
4
2
4
4
2
starting materials after 10 days at 110°C. This simple, yet efficient synthetic route
represents an alternative, even though long reaction times are required. It is
remarkable that these simple reactions are in some cases (i.e. for Me Im=PMes 6)
4
high in yield compared to the catalyzed analogues.[21] Due to limited rotations around
1
the C–P bond some signals in the H NMR spectrum of (Me
4
Im)PMes (6) are
significantly broadened at room temperature, which was also observed by Layfield et
al.[21] Hence, temperature dependent NMR spectra in THF-d
were recorded which
8
show splitting into sharp signals at 248 K (see Figure S11 in the SI). This is in good
7
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
agreement to the data reported before.[21] In a similar fashion, the hitherto unknown
(
(
iPr
iPr
2
Im)PMes (7) was synthesized and isolated as a sticky oil. The formation of
1
13
C{ H} and 31P NMR
1
2
Im)PMes (7) was unambiguously verified by H,
Im)PMes (7)shows a single resonance at -81.0 ppm in the P NMR
spectrum, similar to other (NHC)PMes species such as (Mes Im)PMes (4) (-50.0 ppm),
Me Im)PMes (5) (-73.5 ppm) and (Me Im)PMes (6) (-74.8 ppm) (see Table 1).
31
spectroscopy. (iPr
2
2
(
2
4
However, the NMR spectra of the isolated yellow oil show small amounts of different,
unassigned side products, which could not be separated. A doublet resonance for the
13
1
NHC carbene carbon atom of (iPr Im)PMes (7) in the C{ H} NMR spectrum at a
2
chemical shift of 168.4 ppm with a 1JCP coupling constant of 105.0 Hz to the adjacent
phosphorus atom verifies the formation of the NHC-phosphinidene. Compared to the
free NHC, this resonance is noticeably shifted to higher field and is also in perfect
13
1
agreement to the C{ H} NMR spectroscopic data for the carbene carbon atom of
(
iPr
2
Im)PPh (1) at 168.2 ppm (Table 1).
Table 1. Important 31P and 13C{ H} chemical shifts (P=CNHC) and 1JCP coupling constants recorded in
1
C
6
D and isolated yields of compounds 1-7.
6
δ
NCN
δ P 1JCP yield
3
1
1
3
1
C{ H}
ppm]
Compound
[ppm] [Hz]
[%]
[
(
iPr
Mes
Me Im)PPh (3)
Mes Im)PMes (4)
2
Im)PPh (1)
168.2 -59.9 104
169.8 -23.7 103
88
61
14
33
53
47
-
(
(
(
(
(
(
2
Im)PPh (2)
4
168.9 -52.9
97
2
170.3 -59.0 103
170.4 -73.5 101
169.5 -74.8 100
168.4 -79.5 105
Me
Me
2
Im)PMes (5)
Im)PMes (6)
4
iPr Im)PMes (7)
2
In addition to the characterization by NMR spectroscopy and high-resolution mass
spectrometry, the NHC-phosphinidene (Me Im)PMes (6) was also structurally
4
characterized. Single-crystals of 6 suitable for X-ray diffraction were obtained by
storing a saturated solution of this compound in n-pentane at room temperature for
several days (see Figure 1).
8
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Zeitschrift für anorganische und allgemeine Chemie
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4
Figure 1. Molecular structure of (Me Im)PMes (6) in the solid state. Hydrogen atoms are omitted for
clarity. Atomic displacement ellipsoids are set at the 50% probability level. Selected bond lengths (Å)
and angles (°) for 6: P1–C1 1.791(2), C1–N1 1.363(3), C1–N2 1.358(3), P1–C2 1.842(2), C2–C3
1.425(3), C2–C4 1.409(3); C2–P1–C1 102.3(1), N1–C1–N2 104.8(2); N–C–P–C 67.4(2).
(
Me
asymmetric unit. The P-C distance of 1.791(2) Å is similar to those of P–CCarbene bonds
observed in the molecular structures of other NHC-phosphinidenes (Me Im)PR
reported earlier, which lie in a range of 1.77 to 1.79 Å for a variety of substituents at
the P atom with different steric bulk ((Me Im)PH 1.7721(14) Å, (Me Im)PPh 1.794(3)
Å, (Me Im)PMes
Im)P(Dmp) 1.786(4) Å).[3a] The angle C1–P1–C2 of 102.3(1)° for (Me
6) matches the C–P–C angle of (Me
Im)PPh (102.34(14)°),[3a] whereas the torsion
angle N–C–P–C of 6 of 67.4(2)° is widened compared to (Me Im)PPh (51.0(3)°) and
Me
Im)P(Dmp) (55.5(4)°).[3a]
4
Im)PMes (6) crystallizes in the space group Cc with one molecule in the
4
4
4
4
4
(
4
4
(
4
In comparison to aryl phosphinidenes, there are far less examples for alkyl substituted
NHC-phosphinidenes and unsubstituted, i.e. parent NHC-phosphinidenes. One
example for a CF
substituted species was presented by Arduengo et al.,[11a] while
3
NHC adducts of the parent phosphinidene (:PH) include examples of NHCs with
different steric properties as well as saturated and unsaturated NHC backbones. The
first synthesis of such a compound was reported by Driess et al. in 2013. These authors
obtained (Dipp
Dipp
Im, which results in a room temperature transfer of the PH moiety.[22] The
synthesis of (Dipp Im)PH (II) is also feasible starting from the [HCl] salt of the carbene
III) and react it with phosphaethynolate, Na(OCP), or TMS as “P” transfer reagent
as described by Grützmacher et al.[23] Another synthetic route presented by Tamm et
al. uses N,N’-1,3-bis(2,6-diisopropylphenyl)-2,2-difluoroimidazoline (IV) and P(SiMe
2
Im)PH (II) (Scheme 3) by treating phospasilene I with the carbene
2
2
(
P
3 7
)
3 3
which forms the (NHC)PSiMe
3
adduct. Subsequent treatment of (NHC)PSiMe
3
with
methanol furnishes II in good yield (Scheme 3).[14]
9
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Dipp
Dipp
N
H
N
N
F
Cl
F
N
Dipp
III
Dipp
IV
Dipp
N
Dipp
N
Na(OCP)
-CO
-NaCl
or
Si PH +
Dipp
TMS3P7
- Me3SiCl
P(SiMe3)3
2 Me3SiF
N
N
-
Dipp
I
Dipp
Dipp
N
C6D6, rt
Dipp
N
Si
N
C
P
MeOH
C
P
N
H
N
SiMe3
Dipp
Dipp
-
II
N
Dipp
R
R
N
C
R1
R1
1/3 Na3P7
THF
R1
R1
R = Me, R1 = H
1
N
H
X
P
H
R = Me, R = Me
R = iPr, R1 = H
N
- NaCl
N
1
R
V
R
VI
R = Mes, R = H
Dipp
Dipp
Dipp
N
C
P
PH3
NaOtBu
thf
N
N
H
quinone
H
PH2
- hydro-
chinone
thf
N
N
N
H
Cl
Dipp
VII
Dipp
VIII
Dipp
IX
Mes
Mes
N
N
[
Na(1,4-dioxane)2.5PCO]
0 °C, thf
H
C
P
6
N
N
H
Cl
Mes
X
Mes
XI
Scheme 3. Synthetic routes to NHC-phosphinidenes (NHC)PH.
Grützmacher and Gudat and coworkers reported an alternative synthesis for NHC=PH
compounds mainly of sterically less demanding NHCs in 2016. Whereas the reaction
of the imidazolium salts V with P
and polyphosphorous side products, the reaction of V with Na
NHC-phosphinidenes (VI) selectively.[24] For the synthesis of (sDipp
4
and KOtBu only led to unselective product formation
in THF afforded the
Im)PH (IX)
Im = 1,3-Bis-(2,6-di-iso-propylphenyl)-imidazolidin-2-ylidene) either PH or
[Na(OtBu)]2.5[Na(PH )]} can be used as phosphinidene source, and treatment with the
P
3 7
2
(
{
sDipp
2
3
2
[
HCl]-salt (VII) and dehydrocoupling of the intermediate VIII with quinone afforded the
desired compound. Dehydrogenation to the phosphinidene-carbene adduct VIII was
achieved using an ortho-quinone as hydrogen acceptor.[25] Recently von Hänisch et al.
reported a synthesis for (sMes
ylidene) applying a slightly modified reaction protocol based on the synthesis for
Dipp
Im)PH (II) developed by Grützmacher (Scheme 3).[23, 26]
2
Im)PH (XI) (sMes Im = 1,3-Dimesityl-imidazolidin-2-
2
(
2
Treating tBuPH
2
with two equivalents of iPr Im in xylene at 125°C for 5 days resulted
2
in complete consumption of the primary phosphine. After workup, a pale-yellow solid
31
31
1
was isolated and P and P{ H} spectroscopy revealed a resonance at -149.9 ppm
with a 1JPH coupling constant of 166 Hz, which is consistent with the existence of a
10
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
phosphorous bound hydrogen atom. These data obtained match perfectly with the data
reported earlier by Grützmacher and Gudat and coworkers for (iPr Im)PH (8)
Table 2).[24] Thus, the reaction did not afford the expected tert-butyl substituted NHC-
2
(
phosphinidene, but the parent NHC phsophinidene (iPr Im)PH (8) was isolated in 28%
2
yield instead. To gain a better insight into the course of the transformation we repeated
the reaction in a temperature range between -78°C and 0°C, but only starting material
3
1
31
in form of tBuPH
NMR resonance of (iPr
of iPr Im and tBuPH to 50°C, and an intermediate tert-butyl substituted phosphinidene
species was never isolated or observed for this reaction spectroscopically.
Also (Mes Im)PH (9) and (Me Im)PH (10) can be synthesized from the reaction of
2
was detected by means of P NMR spectroscopy. However, a P
2
Im)PH (8) was already observed when heating the 2:1 mixture
2
2
2
4
tBuPH
2
and two equivalents NHC (Mes
2
Im: 135°C in xylene, Me Im: 110°C in toluene).
4
t
The primary phosphine BuPH
2
was completely consumed after five days and the NHC-
Im)PH (9) (δ 31P = -147.2 ppm) and (Me
Im)PH (10)
δ P = -149.9 ppm) were isolated as off-white and colorless solids in yields of 71%
phosphinindenes (Mes
2
4
31
(
and 51 %, respectively (Table 2). Formation of the H substituted species was also
supported by the observation of the corresponding P–H vibrations in the IR spectra of
-
1
-1
-1
the compounds 8-10 (8: 2302 cm , 9: 2269 cm , 10: 2293 cm , Table 2). Compared
to other established synthetic routes for (Mes Im)PH (9) and (Me Im)PH (10), these
reactions are remarkably high yielding using a standard primary phosphine,[24] but also
limited in the NHC used. As an example, we have found that the reaction of Me Im
with tBuPH in a 2:1 ratio in toluene at 115°C leads to (Me Im)PH (11) only in traces
2
4
2
2
2
31
even after 10 days and the mixture is dominated by starting material (according to P
NMR spectroscopy).
Table 2. Important 31P, H and C{ H} chemical shifts (P=CNHC) and coupling constants recorded in
1
13
1
6 6
C D , IR data and isolated yields of compounds 8-10.
δ
NCN
3
1
1
1
1
δ P
δ
PH
H
J
PH
J
CP
yield
[%]
1
3
1
C{ H}
-1
ṽ
PH [cm ]
Compound
[ppm]
[ppm]
[Hz]
[Hz]
[
ppm]
(
iPr
Mes
Me Im)PH (10)
2
Im)PH (8)
173.7
176.3
174.6
-149.9
-147.2
-149.9
2.64
2.07
2.49
166
164
165
93
85
88
2302
2269
2293
28
71
51
(
(
2
Im)PH (9)
4
11
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Figure 2. Molecular structure of (iPr
2
Im)PH (8) in the solid state. Hydrogen atoms are omitted for clarity
with exception of H1. Atomic displacement ellipsoids are set at the 50% probability level. Selected bond
lengths (Å) and angles (°) for 8: P1–H1 1.3504(4), P1–C1 1.7788(4), C1–N1 1.3636(3), C1–N2
1.3613(3); H1–P1–C1 92.886(9), N1–C1–N2 105.278(16); H1–P1–C1–N1) 2.612.
Single crystals of (iPr
by storing a saturated solution of the compound in n-hexane at room temperature (see
Figure 2). NHC-phosphinidene 8 crystallizes in the space group P2 with one
molecule in the asymmetric unit. The P-C distance of 1.7788(4) Å observed for 8 is
similar to that of the Me Im analogue (Me
Im)PH (1.7721(14) Å) reported previously.[3a]
2
Im)PH (8) suitable for X-Ray diffraction analysis were obtained
1
2
2
1 1
4
4
The angle C–P–H of 92.886(9)° and the torsion angle H–P–C–N of 2.612° reveal an
almost ideal eclipsed conformation between the phosphinidene moiety and the NHC
ligand.
iPr
iPr
E
N
N
N
N
O or S
2
8
E
C
P
P
P
E = O (11),
S (12)
Ph
Ph
Ph
iPr
iPr
iPr
iPr
N
N
N
N
Se or Te
C
C
E
E = Se (13),
Te (14)
iPr
iPr
Scheme 4. Reactions of NHC-phosphinidene 1 with chalcogenids.
The dehydrocoupling route presented here allows the synthesis and isolation of
(
iPr
2
Im)PPh (1) on a multigram (here: 4 g) scale with an excellent yield of 88%. With
this NHC-phosphinidene at hand we were interested in first reactivity studies. To probe
12
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oxygen sensitivity, we initially reacted the NHC-phosphinidene (iPr
2
Im)PPh (1) with dry
oxygen (0.5 bar) in toluene. Directly after addition of oxygen, the reaction mixture
changes its color from orange to colorless with formation of a colorless precipitate.
After workup, compound iPr
yield. NMR spectroscopic investigations revealed a significant downfield shift of the P
NMR resonance at -0.8 ppm in CD CN compared to the NHC-phosphinidene 1, similar
as observed for the NHC adducts of phenyldioxophosphorane presented previously by
Tamm et al. (Me Im-P(O) Ph: -1.0 ppm, Mes Im-P(O) Ph: -23.0 ppm, Dipp Im-
P(O)
Ph: -18.9 ppm).[27] Further, the doublet resonance for the NHC carbene carbon
atom is noticeably shifted in the C{ H} NMR spectrum, i.e. iPr
rise to a signal at 147.9 ppm (1JCP = 94.5 Hz), whereas the resonance for (iPr
1) is located at 168.2 ppm (1JCP = 104 Hz).
Similarly, the reaction between equimolar amounts of (iPr
sulfur (S ) in THF afforded the NHC adduct of phenyldithiophosphorane iPr
P(S) Ph (12), which gives rise to a P NMR resonance at 54.1 ppm in CDCl
2
Im–P(O)
2
Ph (11) was isolated as a colorless solid in 55%
31
3
4
2
2
2
2
2
13
1
2
Im–P(O)
2
Ph (11) gives
2
Im)PPh
(
2
Im)PPh (1) and elemental
Im–
. This
8
2
31
2
3
compound is well soluble and sufficiently stable in acetonitrile and chloroform which
allows full characterization by NMR spectroscopy. A doublet for the NHC carbene
13
1
carbon atom was detected in the C{ H} NMR spectrum at 147.2 ppm with a coupling
constant 1JPC of 40.4 Hz, which is much smaller than 1JPC coupling observed for iPr
2
Im–
Ph (11) (1JPC(NHC) = 94.5 Hz). Similarly, the 1JPC coupling constant of the C{ H}
13
1
P(O)
2
NMR resonance at 142.3 ppm for the phenyl Cipso attached to phosphorous of 91.0 Hz
is much smaller compared to 11 (1JPC(Ph) = 145.6 Hz). Furthermore, the compound
iPr
2
Im–P(S) Ph (12) was also characterized by X-ray diffraction (see Figure 3).
2
Figure 3. Molecular structure of iPr
2
Im–P(S) Ph (12) in the solid state. Hydrogen atoms are omitted for
2
clarity. Atomic displacement ellipsoids are set at the 50% probability level. Selected bond lengths (Å)
and angles (°) for 12: P1–C1 1.8732(14), P1–S1 1.9739(5), P1–S2 1.9626(5), P1–C2 1.8247(14); C1–
P1–S1 107.17(5), C1–P1–S2 104.29(4); C1–P1–C2 99.33(6), S1–P1–S2 119.29(2), S2–P1–C2
112.45(4), S1–P1–C2 107.17(5).
13
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iPr
2
Im–P(S)
2
Ph (12) crystallizes in the monoclinic space group P2
1
/c with one molecule
in the asymmetric unit. The molecular structure of 12 reveals a distorted tetrahedral
geometry at phosphorus with a large S–P–S angle of 119.29(2)°. The the P–CCarbene
bond length of 1.8732(14) Å is significantly longer than the P–CPhenyl bond of
1
.8247(14) Å and the C=P bond observed in NHC-phosphinidenes (vide supra).
However, the bond lengths and angles obtained for 12 are in good agreement with the
data reported by Tamm et al. for Me Im–P(S)
Ph previously.[27]
4
2
The reaction of 1 with elemental (grey) selenium and tellurium did not lead to the
selenium and tellurium analogues of 11 and 12, but yielded (NHC)PPh cleavage with
formation of the isolated compounds (iPr
cyclo-oligophospines, according to NMR spectroscopy ( P-NMR: P
22.0, P Ph -3.6 to -2.7 ppm). The NMR data of 13 are in good agreement to those
reported by Ganter et al.,[28] most characteristic is the C{ H} NMR resonance of the
2
Im)Se (13) and (iPr
2
Im)Te (14) and different
31
4
Ph -48.2, P Ph
4
6
6
-
5
5
13
1
77
1
NHC carbene carbon atom at 153.5 ppm and a singlet at -19.7 ppm in the Se{ H}
NMR spectrum. Tamm and coworkers reported the isolation of Me Im substituted
diselenophosphorane from the analogous reaction of (Me Im)PPh with grey selenium
Im)Te (14) shows a characteristic
4
4
in THF at room temperature.[27] The compound (iPr
2
resonance at -184.6 ppm in the 123Te{ H} NMR spectrum which is in agreement with
1
the 123Te NMR spectrum reported for closely related iPr
Im =Te at -167.8 ppm as
Me
2
reported by Kuhn and Henkel et al.[29]
Figure 4. Molecular structure of (iPr Im)Te (14) in the solid state. Hydrogen atoms are omitted for clarity.
2
Atomic displacement ellipsoids are set at the 50% probability level. Selected bond lengths (Å) and
angles (°) for 14: C1–Te1 2.092(4), N1–C1 1.340(6), C1–N2 1.355(6).
(
iPr
2
Im)Te (14) crystallizes in the triclinic space group P 1¯ with two molecules in the
asymmetric unit. The molecular structure shows as expected a Te atom bonded to the
14
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10.1002/zaac.202000405
NHC iPr
2
Im. The bond length C1–Te1 of 2.092(4) Å is identical within standard
Me
[29b]
deviation to the closely related C-Te distance reported for (iPr
2
Im )Te.
The developed synthetic protocol for NHC-phosphinidenes of the general formula
(
(
(
NHC)PR paired with the observation of (NHC)PPh cleavage by treatment of
iPr
2
Im)PPh (1) with elemental selenium and tellurium to yield (iPr
Im)Te (14) is particularly useful to determine the electronic properties of NHCs by
77Se NMR spectroscopy as demonstrated by Bertrand and Ghadwal
2
Im)Se (13) and
iPr
2
31P and
recently.[12, 30]
Several transition metal complexes of NHC-phosphinidenes have been reported so far
in the literature. Larocque and Lavoie provided an early example in 2014 and reported
the reaction of a first-generation ruthenium benzylidene Grubbs complex with
(
Mes
2
Im)PPh. Ligand exchange of one PPh ligand occurred and led to the formation
3
of a ruthenium NHC-phosphinidene complex, maintaining the NHC-phosphinidene.[31]
Tamm et al. reported the synthesis of NHC-phosphinidene coinage metal complexes
from the reaction of the NHC-phosphinidene (Dipp
Au)[32] and a series of tungsten and molybdenum pentacarbonyl complexes of NHC-
phosphinidenes.[33] Different complexes [{(Dipp
Im)PR}M(CO) ] (R = H, Ph, Mes, M =
Mo, W) of NHC-phosphinidenes of the sterically demanding Dipp Im have been
2
Im)PPh with MCl (M = Cu, Ag,
2
5
2
synthesized and it has been demonstrated that NHC phospinidenes are good donor
ligands. For example, the CO band for the CO stretch in the IR spectrum of
-
1
[
{(Dipp
2
Im)PPh}Rh(CO)
2
Cl] at 2006 cm lies much lower compared to those of other
Cl], e.g. phosphines (PPh : 2052
Im: 2037 cm-1).[33] These results encouraged
us to study the ligation properties of the sterically less demanding NHC-phosphinidene
iPr Im)PPh (1) with respect to selected transition metal complexes (Scheme 5). The
tetrahydrofuran adduct [W(CO) (thf)], which was in situ generated by photolysis of
] in THF, was reacted with (iPr Im)PPh (1) and yielded [{(iPr Im)PPh}W(CO)
5 in quantitative yield according to P NMR spectroscopy. This complex was isolated
important ligand classes in complexes [(L)Rh(CO)
2
3
-
1
-1
cm ) or NHCs (Mes
2
Im: 2038 cm , Dipp
2
(
2
5
[
W(CO)
6
2
2
5
]
31
1
31
as a yellow solid in 54% yield. The P NMR resonance of the NHC-phosphinidene
tungsten complex was observed at -81.1 ppm, significantly shifted from -60.1 ppm for
(
iPr
2
Im)PPh (1), and coupling of the phosphorus nucleus with the tungsten center with
a coupling constant of 1JPW = 112.3 Hz was observed. Tamm et al. reported a wide
15
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
31
range of P NMR chemical shifts for similar compounds, e.g. -57.7 ppm in THF-d
{(Dipp Im)PPh}W(CO)
] with a coupling constant of 1JPW = 120 Hz, close to our
data.[33]
8
for
[
2
5
Scheme 5. Reaction of (iPr Im)PPh (1) with selected transition metal complexes.
2
We recently reported the reaction of [Co(CO)
to replacement of carbonyl ligands and to formation of either [Co(NHC)(CO)
Co(NHC)
(CO)(NO)] in overall good yields.[35] The use of the sterically demanding
NHCs Dipp
complexes of the type [Co(NHC)(CO)
3
(NO)][34] with different NHCs, which leads
(NO)] or
2
[
2
Me
2
Im, Mes Im and the cyclic (alkyl)(amino)carbene cAAC selectively led to
2
2
(NO)], even if an excess of NHC was provided.
i
Similarly, NHC phosphine complexes [Co(Pr
2
Im)(PR
3
)(CO)(NO)] (PR = PMe , PEt ,
3
3
3
i
i
Me
PHPr ) and [Co(NHC)(PMe )(CO)(NO)] (NHC = Me Im, MePrIm, MetBuIm, iPr
2
Im )
2
3
4
are available from the reaction of [Co(NHC)(CO)
Co(CO) (NO)] might be a suitable precursor for either a cobalt NHC-phosphinidene
complex [Co{(NHC)PR}(CO) (NO)] or a NHC-stabilized cobalt phosphinidene complex
Co(NHC)(PR)(CO)(NO)] or [Co(NHC)(PR)(CO)
].[35] However, the reaction of
iPr Im)PPh (1)with [Co(CO) NO] resulted with CO release in the formation of the red
complex [Co{(iPr
2
(NO)] and phosphines.[35b] Therefore,
[
3
2
[
2
(
2
3
2
Im)PPh}(CO) (NO)] (16) in 42% yield. Complex 16 reveals
2
1
significantly shifted H NMR data as compared to the analogous NHC complex
16
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10.1002/zaac.202000405
[35]
[
Co(CO) (NO)(iPr Im)] (XII), i.e. a doublet at 0.82 ppm (XII: 0.92 ppm) for the methyl
2 2
protons and a doublet of septets at 5.02 ppm (XII: 4.60 ppm) for the methine protons
of the iPr substituent as well as a broad doublet at 6.07 ppm (XII: 6.40 ppm) for the
NHC-backbone protons. The resonances of the NHC carbene carbon atom in the
13
1
1
C{ H} NMR spectrum of 16 at 163.7 ppm (XII: 219.8 ppm) reveals a JCP coupling
constant to the phosphorus atom of 91.2 Hz, which is in accordance with an intact
NHC-phosphinidene unit and thus confirms the formation of the NHC-phosphinidene
59
ligated complex 16. The large quadrupole moment of Co affects the NHC carbene
13
1
carbon and the carbonyl carbon resonance in the C{ H} NMR spectrum, the latter
31
was not observed, but also the P NMR resonance, which appears as a broadened
signal at -45.5 ppm. This resonance is also in good agreement with other reported
31
NHC-phosphinidene carbonyl complexes, which show P resonances typically in the
range between -25 to -164 ppm.[33] In addition, an intense NO (1694 cm ) and two CO
-1
-
1
-1
(
1925 cm and 1992 cm ) stretching modes were observed in the IR spectrum of 16,
which indicate a high electron density at the cobalt atom. However, heating of 16 in
solution led to decomposition of this complex with formation of [Co(iPr Im)(CO) (NO)]
2
2
and cyclo-oligophosphines and not to the formation of an NHC-stabilized cobalt
phosphinidene complex, as might expected.
Various group 8 and 9 half sandwich phosphinidene complexes of the type [(ƞ6-
, NHC)[37] or [(ƞ -C
5
R ,
)M(L)(=PAr)] (Co[38a]
C
6
R
6
)M(L)(=PAr)] (M= Ru, Os; L= PR
3
5
5
Rh[38a], Ir[9a, 2b]; L= PR
3
, NHC) as well as related NHC-phosphinidene metal complexes
are known.[38] Therefore, we envisioned the synthesis of NHC-stabilized
5
phosphinidene complexes [(ƞ -C
5
R
5
)Co(NHC)(=PAr)] starting from (iPr Im)PPh (1)
2
2
and [(C
5
R
5
)Co]-synthons such as [(C
5
R
5
)Co(η -C
2
H
4
) ]. We have reported previously
2
5
different complexes with the [(η -C R )Co(NHC)] complex moiety on several
5
5
occasions.[36] The reaction of [(C
)Co(η -C
2
H
)
] with (iPr
Me )Co{(iPr
)Co(iPr
Im)PPh (1) afforded the
5
Me
5
2
4
2
2
5
2
NHC-phosphinidene cobalt complex [(ƞ -C
5
5
2
Im)PPh}(ƞ -C
2
H )] (17)
4
5
2
(
Scheme 5). Complexes 17 and [(ƞ -C
5
Me
5
2
Im)(ƞ -C
2 4
H )] (XIII) reported
previousely[36a] can be easily distinguished by NMR spectroscopy. The H NMR
1
spectrum of 17, for example, reveals a resonance at 1.93 ppm (XIII: 1.78 ppm)
characteristic for C
5
Me
5
protons and the iso-propyl methine protons give rise to a
broadened doublet of septets at 4.57 ppm (XIII: one septet at 6.20 ppm). The NHC
13
1
carbene carbon atom resonance at 163.7 ppm (XIII: 193.8 ppm) in the C{ H} NMR
17
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
spectrum shows 1JCP coupling of 98.7 Hz, and P NMR resonance at +25.8 ppm is
31
shifted compared to the NMR resonance of 1 at -60.1 ppm.
Similar as observed for 16, complex 17 decomposes upon heating in solution. At room
temperature, both NHC-phosphinidene complexes are stable in solution for a
prolonged period of time. However, after gradually heating both complexes up to 80°C
5
2
the NHC complex [(η -C
5
Me
5
)Co(iPr
2
Im)(η -C
2
H )] was formed together with cyclo-
4
oligophosphines.
To support these experimental observations, additional quantum-mechanical DFT
calculations on the BP86/def2-TZVP level of theory were performed. According to
these calculations the decomposition of [Co{(iPr Im)PPh}(CO) (NO)] 16 to yield
2
2
298
[
Co(iPr
2
Im)(CO) (NO)] and cyclo-P Ph is exergonic by ΔG = -37.46 kJ·mol,
2
5
5
whereas the formation of [Co(iPr
2
Im)(PPh)(CO)(NO)] (and CO) is endergonic by
298
ΔG = +129.43 kJ·mol (Figure 5). Thus, the calculations clearly predict [PPh]
cleavage from 16 and oligophosphine formation, a transfer to the cobalt atom with
substitution of a CO ligand seems not to be feasible.
Figure 5. Free reaction enthalpies (ΔG298, at 298 K) calculated at the def2-TZVP/BP86-level of theory
for the formation of [Co(iPr
2
Im)(CO)
2
(NO)] II and cyclo-P
Ph
5 5
(top) or [Co(iPr Im)(PPh)(CO)(NO)]
2
(
bottom) starting from [Co(CO)
2
(NO){(iPr
2
Im)PPh}] (16).
Over the past years we investigated the chemistry of different NHC-stabilized nickel
complexes in stochiometric and catalytic reactions in some detail.[39] As NHC-
phosphinidenes have not been used as ligands in any nickel complex so far, we
became interested to use (iPr Im)PPh (1) in nickel chemistry. Wolf and Goicoechea
2
reported the reaction of the paramagnetic nickel(I) NHC complex [(η-C
5
H
5
)Ni(Mes Im)]
2
18
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
with [Na(dioxane)1.8][PCO] which led to the isolation of carbene-phosphinidenyl-
2
2
Im)Cp.[40]
bridged dimer (µ -CO)[µ -P(Mes
The reaction of (iPr Im)PPh (1) with the nickel(0) precursor [Ni(COD)
ratio in toluene at room temperature led to isolation of a diphosphene complex
Ni(iPr Im) (trans-PhP=PPh)] (18) (Scheme 5), which was characterized using NMR
2
Im)]Ni
2
(Mes
2
2
2
] in a 2:1 molar
[
2
2
spectroscopy, elemental analysis, and high-resolution mass spectroscopy. In contrast
to the transition metal complexes of 1 with tungsten and cobalt reported here, no η1-
coordination of (iPr
nickel center with coupling of the phoshinidene units occurred instead. Thus, complex
8 is formed by formal NHC-phosphinidene cleavage and phosphinidene coupling in
2
Im)PPh (1) was observed but direct coordination of iPr Im to the
2
1
the coordination sphere of nickel with coordination of the NHC and the diphosphene to
the nickel atom. However, independent on the stoichiometry and temperature we were
using, we could not detect any intermediate for this reaction. For 18, a single resonance
31
in the P NMR spectrum was detected at -40.9 ppm in C
, which lies in a similar region as observed for the palladium and platinum derivatives
Pd(dppe)(trans-PhP=PPh)] (d = -34 ppm) and [Pt(dppe)(trans-PhP=PPh)] (d = -24
6
D
6
and -42.9 ppm in toluene-
d
8
[
ppm) previousely.[41] The resonance of the NHC carbene carbon atoms in the C{ H}
NMR spectrum of 18 appear as a triplet at 193.9 ppm, in the typical range for this kind
of NHC nickel complexes,[39] with a 2JCP coupling constant of 8.3 Hz, which is much
smaller than the 1JCP coupling constant typically observed for NHC-phosphinidene
13
1
1
complexes (typically ca. 90 Hz, vide supra). The H NMR resonances of the NHC
ligands in 18 are broadened at room temperature, consistent with a hindered rotation
of the ArP=PAr ligand around the Ni-(PP)centroid vector and/or of the NHC ligands
around the Ni-C bonds. Cooling to -50 °C resolved the spectra into four iPr methyl and
two iPr methine resonances, as typically found for a pseudo-C2v type structure in
solution. At 90°C, two iPr methyl resonances and a single iPr methine signal were
observed, which were still broadened (see Figure S66 of the SI).
Conclusion
The dehydrocoupling of primary phosphines with NHCs to yield NHC-phosphinidenes
was investigated and we demonstrate here that dehydrocoupling of primary phosphine
using NHCs is a general and convenient synthetic approach to prepare NHC-
phosphinidenes in moderate to high isolated yields. The reaction of primary
phosphines ArPH (Ar = Ph, pTol, Mes) with NHCs led to addition of hydrogen to the
2
19
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
NHC carbene carbon atom with formation of the dihydroaminal NHCH
2
and the NHC-
phosphinidene (NHC)PAr. The NHC phosphinidenes (iPr
2
Im)PPh (1), (Mes
Im)PMes (5), (Me Im)PMes (6) and
Im)PMes (7) have been synthesized using this approach. If tBuPH is used as the
2
Im)PPh
(
(
2), (Me
iPr
4
Im)PPh (3), (Mes
2
Im)PMes (4), (Me
2
4
2
2
phosphine source, the parent NHC-phosphinidenes (NHC)PH were obtained, as
exemplified by the preparation of (iPr Im)PH (8), (Mes Im)PH (9) and (Me Im)PH (10).
The NHC-phosphinidene (iPr Im)PPh (1) is oxygen-sensitive, as the reaction of 1 with
oxygen led to the isolation of iPr Im–P(O) Ph (11). The reaction with elemental sulphur
afforded iPr Im–P(S) Ph (12). Treatment of 1 with elemental selenium and tellurium
did not lead to the selenium and tellurium analogues of 11 and 12, but to (NHC)PPh
cleavage with formation of (iPr Im)Se (13) and (iPr Im)Te (14) and different cyclo-
oligophospines. Furthermore, several transition metal complexes of the NHC-
phosphinidene 1 were synthesized. In situ prepared [W(CO) (thf)] reacts with 1
quantitatively to yield [{(iPr Im)PPh}W(CO) ] (15), the reaction of 1 with [Co(CO) NO]
(NO)] (16) and the
)Co{iPr
Im)PPh}(ƞ2-
(NO)] (16) and [(ƞ5-
2
2
4
2
2
2
2
2
2
2
5
2
5
3
results with CO release in the formation of [Co{(iPr
2
Im)PPh}(CO)
2
2
5
reaction of [(C
5
Me
5
)Co(η -C
2 4
H )
2
] with 1 afforded [(ƞ -C
5
Me
5
2
2 4
C H )] (17). Both cobalt complexes, [Co{(iPr
2
Im)PPh}(CO)
2
2
5
C Me
5
)Co{iPr
2
Im)PPh}(ƞ -C
H
2 4
)] (17) are stable in the solid state and in solution at
Im)(CO) (NO)] and
)], respectively, and cyclo-oligophosphines upon
heating to 80°C in solution. A different behavior was observed for the reaction of
iPr Im)PPh (1) with the common nickel(0) precursor [Ni(COD) ], which afforded the
diphosphene complex [Ni(iPr Im) (trans-PhP=PPh)] (18). This complex was formed by
room temperature, but decompose to the NHC complexes [Co(iPr
2
2
5
2
[
(η -C
5
Me
5
)Co(iPr
2
Im)(η -C
H
2 4
(
2
2
2
2
formal NHC-phosphinidene cleavage, NHC coordination to nickel and phosphinidene
coupling in the coordination sphere of the nickel atom.
Experimental Section
General considerations
All reactions and subsequent manipulations involving organometallic reagents were
performed under argon atmosphere by using standard Schlenk techniques or in a
Glovebox (Innovative Technology Inc. and MBraun Uni Lab) as reported previously.[39]
All reactions were carried out in oven-dried glassware. Toluene, n-hexane and THF
were obtained from a solvent purification station (Innovative Technology) by previous
purification through alumina columns. The deuterated benzene solvent was purchased
20
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
from Sigma-Aldrich and dried thoroughly over molecular sieves. The carbene ligands
iPr Im, Me Im, Me
Im[42] and IMes[43] were prepared according to published
2
2
4
procedures. Elemental analyses were performed in the microanalytical laboratory of
the University of Würzburg with an Elementar vario micro cube. Infrared spectra were
recorded on a Bruker alpha spectrometer as solids by using an ATR unit. NMR spectra
1
13
were recorded at 298 K using Bruker Avance 400 ( H, 400.1 MHz; C, 100.6 MHz,
31
1
13
31
P, 162.0 MHz) and Bruker Avance 500 ( H, 500.1 MHz; C, 125.8 MHz, P, 202.5
1
MHz) spectrometers. H NMR chemical shifts are listed in parts per million (ppm) and
reported relative to TMS and were referenced via residual proton resonances of the
6 5 6 6 7 7
deuterated solvent (C D H: 7.16 ppm (C D ); C D H: 2.08, 6.97, 7.01, 7.09 ppm (tol-
d
8 4
); C D
7
HO: 1.72, 3.58 ppm (thf-d
8
); C
2
D
2
HN: 1.94 (CD
3
CN); CHCl : 7.26 (CDCl ))
3
3
whereas 13C{ H} NMR spectra are reported relative to TMS using the natural-
1
abundance carbon resonances (C
28.87, 137.48 ppm; thf-d : 25.31, 67.21; CD
Synthesis of (iPr Im)PPh (1): Phenyl phosphine (2.00 g, 18.2 mmol) was added at
room temperature to a solution of iPr Im (5.80 g, 36.3 mmol) in 20 mL of toluene and
6 6
D : 128.06 ppm; tol-d
8
: 20.43, 125.13, 127.96,
1
8
3
CN: 1.92, 118.26; CDCl
3
: 77.16).[44]
2
2
the clear solution was heated to 105 °C for 3 h. All volatiles were removed in vacuo
and a light orange residue was suspended in 20 mL of n-hexane. After filtration, the
yellow solid was washed with n-hexane (3 x 10 mL) and dried in vacuo to afford 4.15
1
g (15.9 mmol; 88 %) of a yellow solid. H NMR (400.1 MHz, C
6
D , 298 K): d = 0.90 (d,
6
1
6
2
2 H, 3JHH= 6.7 Hz, iPr-CH
.19 (s, 2 H, CHCH), 6.91, 7.07, 7.64 (m, 5 H, aryl-H). C{ H} NMR (100.6 MHz, C
98 K): d = 21.8 (s, iPr-CH
), 49.9 (d, 3JCP = 10 Hz, iPr-CH), 115.4 (d, 1JCC = 3 Hz,
3
), 5.06 (dsept, 2 H, 3JHH =6.7 Hz, 4JPH = 4.0 Hz, iPr-CH),
13
1
6 6
D ,
3
CHCH), 122.2, 128.1 (aryl-CH), 132.1 (d, 2JCP = 19 Hz, aryl-CHortho), 150.3 (d, 1JCP
=
0 Hz, aryl-CHipso), 168.2 (d, 1JCP = 104 Hz, NCN). P NMR (162.0 MHz, C
31
D , 298
5
6
6
K): d = -59.9 (s, P). C15
H
21
N P (260.32 g/mol): calcd.: 69.21, H 8.13, N 10.76; found:
2
+
C 69.80, H 7.91, N 10.60 HRMS LIFDI (m/z): calculated for C15
H
21
N
2
P [M ]: 260.1437;
found: 260.1429. IR (ATR[cm ]): 458 (m), 493 (m), 583 (w), 658 (w), 676 (s), 693 (vs,
CH), 738 (vs, dCHoop), 878 (w), 1021 (w, dPAroop), 1070 (m), 1198 (s), 1300 (m), 1370
m, dCH), 1406 (m, dCH), 1466 (m, dCH), 1574 (m, nCC), 2010 (vw), 2183 (vw), 2970 (vw,
CH), 3050 (vw, nCH).
Synthesis of (Mes Im)PPh (2): Phenyl phosphine (150 mg, 1.36 mmol) was added at
room temperature to a solution of Mes Im (871 mg, 2.86 mmol) in 12 mL of xylene and
the clear solution was heated to 135 °C for 3 d. All volatiles were removed in vacuo
-
1
d
(
n
2
2
21
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
and the pale-yellow residue was suspended in 11 mL of n-hexane. After filtration, the
yellow solid was washed with 8 mL of n-hexane and dried in vacuo to afford 340 mg
1
(
824 µmol; 61 %) of a yellow solid. H NMR (400.1 MHz, C
6
D , 298 K): d = 2.03 (s, 6
6
H, mesityl-CH3para), 2.24 (s, 12 H, mesityl-CH3ortho), 5.83 (s, 2 H, CHCH), 6.57 (s, 4 H,
13
1
mesityl-CHmeta), 6.68, 6.75 (m, 3 H, aryl-H), 7.45 (m, 2 H, aryl-H). C{ H} NMR (100.6
MHz, C
, 298 K): d = 18.5 (d, 5JCP = 2.88 Hz, mesityl-CH3ortho), 21.0 (s, mesityl-
D
6 6
CH3para), 118.6 (d, 3JCP = 3.5 Hz, CHCH), 124.8 (s, Ph-Cpara), 126.5 (d, 3JCP = 3.8 Hz,
Ph-Cmeta), 129.4 (s, Mes-Cmeta), 134.4 (s, Mes-Cipso), 135.9 (d, 4JCP = 1.9 Hz, Mes-
C
ortho), 137.5 (d, 2JCP = 14.3 Hz, Ph-Cortho), 138.4 (s, Mes-Cpara), 139.4 (d, 1JCP = 42.0
Hz, Ph-Cipso), 169.8 (d, 1JCP = 102.5 Hz, NCN). P NMR (162.0 MHz, C
31
D , 298 K): d
6
6
=
-23.7 (s, P). C27
H
29
N P (412.52 g/mol): calcd.: 78.61, H 7.09, N 6.79; found: C 78.11,
2
+
H 7.05, N 6.59. HRMS LIFDI (m/z): calculated for C27
H N
29 2
P [M ]: 412.2063; found:
-
1
4
12.2051. IR (ATR[cm ]): 405 (w), 466 (m), 485 (m), 517 (w), 566 (m), 577 (s), 668
(
m, nPC), 699 (vs, dCHoop), 738 (m, dCHoop), 850 (s, dCHoop), 921 (m, dCHoop), 1031 (w),
1
1
038 (w), 1117 (vw, nPAr), 1217 (m), 1264 (w), 1290 (m), 1327 (vs), 1394 (m, dCH),
437 (m, dCH), 1482 (s, dCH), 1590 (m, nCC), 1604 (m, nCC), 1990 (vw), 2151 (vw), 2206
(
w), 2907 (vw, nCH), 2942 (vw, nCH), 2999 (vw, nCH), 3136 (w, nCH).
Synthesis of (Me Im)PPh (3): Phenyl phosphine (50 mg, 454 µmol) was added at
room temperature to a solution of Me Im (119 mg, 954 µmol) in 10 mL of toluene and
4
4
the clear solution was heated to 110 °C for 7 d. All volatiles were removed in vacuo
and the residue was suspended in 12 mL of n-pentane. After filtration, the yellow solid
was washed with 8 mL of n-pentane and dried in vacuo to afford 88 mg (379 µmol; 14
1
%, P
n
Ph
n
impurities) of a yellow solid. H NMR (400.1 MHz, C
6
D , 298 K): d = 1.25 (s,
6
6
H, CH
3
), 3.02 (s, 6 H, NCH
3
), 6.95, 7.13 (m, 3 H, aryl-H), 7.63 (m, 2 H, aryl-H).
, 298 K): d = 8.4 (s, CH
), 33.5 (d, 3JCP = 10.4 Hz,
), 122.1 (s, aryl-CH), 122.4 (d, 1JCC = 3.2 Hz, C=C), 127.9 (d, JCP = 5.6 Hz, aryl-
CH), 132.5 (d, JCP = 19.0 Hz, aryl-CH), 149.6 (d, JCP = 48.7 Hz, aryl-CH), 168.9 (d, 1JCP
13
1
C{ H} NMR (100.6 MHz, C
6
D
6
3
NCH
3
31
=
97.3 Hz, NCN). P NMR (162.0 MHz, C
D
6 6
, 298 K): d = -52.9 (s, P). HRMS LIFDI
+
-1
(
m/z): calculated for CHNP [M ]: 232.1124; found: 232.1121. IR (ATR[cm ]): 413 (w),
4
48 (m), 481 (s), 546 (w), 621 (vw), 662 (m), 695 (vs, dCH), 734 (vs, nPC), 856 (m), 990
(
(
w), 1021 (m, nCH), 1064 (s), 1094 (m, nPAr), 1170 (m), 1209 (wdCH), 1364 (s, dCH), 1425
m, dCH), 1470 (m, dCH), 1576 (s, nCC), 1651 (m, nCC), 1981 (w, nCC), 2008 (w, nCC),
2
151 (m, nCC), 3048 (vw, nCH).
22
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
Synthesis of (Mes
2
Im)PMes (4): Mesityl phosphine (50 mg, 329 µmol) was added at
room temperature to a solution of Mes
2
Im (210 mg, 690 µmol) in 10 mL of xylene and
the clear solution was heated to 135 °C for 12 d. All volatiles were removed in vacuo
and the residue was suspended in 10 mL of n-pentane. After filtration, the orange solid
was washed with 8 mL of n-pentane and dried in vacuo to afford 50 mg (110 µmol; 33
1
%
) of an orange solid. H NMR (400.1 MHz, THF-d
8
, 298 K): d = 2.03 (s, 6 H, mesityl-
CH3para), 2.08 (s, 6 H, mesityl-CH3ortho), 2.13 (sbr, 3 H, mesityl-CH3para), 2.29 (s, 12 H,
mesityl-CH3ortho), 6.34 (s, 2 H, mesityl-CHmeta), 6.48 (sbr, 2 H, mesityl-CHmeta), 6.66 (s,
1
1
H, CHCH), 6.98 (s, 1 H, CHCH), 7.02 (s, 2 H, mesityl-CHmeta). H NMR (500.1 MHz,
THF-d
8
, 248 K): d = 2.04 (s, 3 H, mesityl-CH3para), 2.10 (s, 6 H, mesityl-CH3ortho), 2.13
s, 3 H, mesityl-CH3para), 2.28 (s, 12 H, mesityl-CH3ortho), 2.32 (s, mesityl-CH3para), 6.35
s, 2 H, mesityl-CHmeta), 6.48 (s, 2 H, mesityl-CHmeta), 6.72 (s, 1 H, CHCH), 6.85 (s, 1
(
(
1
3
1
H, CHCH), 7.01 (s, 2 H, mesityl-CHmeta). C{ H} NMR (100.6 MHz, THF-d
17.7 (d, mesityl-CH3ortho, 3JCP = 48.5 Hz), 18.9 (s, mesityl-CH3para), 21.1 (s, mesityl-
CH3para), 25.7 (s, mesityl-CH3ortho), 124.0 (s, CHCH), 127.7 (s, mesityl-CHmeta), 129.5
s, CHCH), 129.9 (s, mesityl-CHmeta), 134.8 (sbr, mesityl-Cpara), 136.1 (d, 1JCP = 43.0
8
, 298 K): d
=
(
Hz, mesityl-Cipso), 144.4 (d, J = 8.9 Hz, mesityl-Cortho), 170.5 (d, 1JCP = 103.2 Hz, NCN).
31P NMR (162.0 MHz, C
D
, 298 K): d = -59.0 (s, P). P NMR (202.5 MHz, THF-d ,
31
6
6
8
31
2
98 K): d = -60.6 (s, P). P NMR (202.5 MHz, THF-d , 248 K): d = -63.2 (s, P).
8
30
C H
35
N
2
P (454.60 g/mol): calcd.: 79.26, H 7.76, N 6.16; found: C 76.84, H 8.27, N
+
6
.57. HRMS LIFDI (m/z): calculated for C30
35
H N
2
P [M ]: 454.2532; found: 454.2519.
-
1
IR (ATR[cm ]): 481 (s), 577 (m), 654 (m, nPC), 703 (vs, dCHoop), 805 (m), 842 (s), 919
m), 1078 (s, nPAr), 1113 (s, nPAr), 1213 (w), 1264 (m), 1288 (s), 1321 (vs), 1390 (m,
CH), 1482 (m, dCH), 1606 (vw, nCC), 2004 (m), 2061 (w), 2126 (vw), 2222 (vw), 2911
w), 3129 (w, nCH).
Synthesis of (Me
room temperature to a solution of Me
(
d
(
2
Im)PMes (5): Mesityl phosphine (50 mg, 329 µmol) was added at
2
Im (66 mg, 690 µmol) in 10 mL of toluene and
the clear solution was heated to 115 °C for 7 d. All volatiles were removed in vacuo
and the residue was suspended in 10 mL of n-pentane. After filtration, the yellow solid
was washed with 8 mL of n-pentane and dried in vacuo to afford 43 mg (175 µmol; 53
1
%
) of a yellow solid. H NMR (400.1 MHz, C
6
D , 298 K): d = 2.24 (s, 3 H, mesityl-
6
3
CH3para), 2.67 (d, 6 H, NCH ), 2.67 (s, 6 H, mesityl-CH3ortho), 5.57 (s, 2 H, CHCH), 6.95
13
1
(
s, 2 H, mesityl-CHmeta). C{ H} NMR (100.6 MHz, C
6
D , 298 K): d = 21.2 (s, mesityl-
6
CH3para), 25.0 (d, 3JCP = 12.0 Hz, mesityl-CH3ortho), 35.6 (d, 3JCP = 10.6 Hz, NCH
3
),
23
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
1
18.1 (d, 3JCP = 3.3 Hz, CHCH), 134.3 (s, Mes-Cpara), 138.7 (d, 1JCP = 44.8 Hz, Mes-
ipso), 143.3 (d, 2JCP = 10.0 Hz, Mes-Cortho), 170.4 (d, 1JCP = 101.2 Hz, NCN). P NMR
31
C
(
162.0 MHz, C
6
D
6
, 298 K): d = -73.5 (s, P). C14 P (246.29 g/mol): calcd.: 68.27, H
H
19
N
2
7
.78, N 11.37; found: C 62.37, H 7.57, N 14.05. HRMS LIFDI (m/z): calculated for
+
-1
14
C H
19
N P [M ]: 246.12870; found: 246.1275. IR (ATR[cm ]): 460 (w), 475 (m), 503
2
(
(
(
vs), 552 (m), 570 (vs), 634 (vs), 723 (s, dCH), 752 (m, dCHoop), 846 (m, dCHoop), 1048
m), 1097 (s, nPAr), 1147 (m), 1186 (w), 1233 (m), 1329 (m, dCH), 1382 (m, dCH), 1457
m, nCC), 1568 (w, nCC), 1602 (w, nCC), 1924 (vw), 1963 (vw), 2169 (w).
Synthesis of (Me
4
Im)PMes (6): Mesityl phosphine (50 mg, 329 µmol) was added at
room temperature to a solution of Me
4
Im (86 mg, 690 µmol) in 10 mL of toluene and
the clear solution was heated to 110 °C for 10 d. All volatiles were removed in vacuo
and the residue was suspended in 10 mL of n-pentane. After filtration, the solid was
washed with 8 mL of n-pentane and dried in vacuo to afford 42 mg (153 µmol; 47 %)
1
of a pale yellow solid. H NMR (400.1 MHz, C
6
D
6
, 298 K): d = 1.25 (s, 6 H, CCH ), 2.28
3
(
s, 3 H, mesityl-CH3para), 2.71 (s, 6 H, mesityl-CH3ortho), 2.81 (d, 6 H, 2JHN = 0.8 Hz,
13
1
NCH
3
), 7.00 (m, 2 H, mesityl-CHmeta). C{ H} NMR (100.6 MHz, C
), 21.3 (s, mesityl-CH3para), 25.1 (d, 3JCP = 12.5 Hz, mesityl-CH3ortho), 32.3 (d,
3JCP = 11.6 Hz, NCH ), 120.9 (d,1JCC = 3.4 Hz, CHCH), 133.6 (s, mesityl-CH), 140.5
d, JCP = 47.8 Hz, mesityl-CH), 142.6 (d, JCP = 10.2 Hz, mesityl-CH), 169.5 (d, 1JCP
6
D
6
, 298 K): d = 8.4
(
s, CH
3
3
(
=
3
1
-1
9
4
9.6 Hz, NCN). P NMR (162.0 MHz, C
6
D , 298 K): d = -74.8 (s, P). IR (ATR[cm ]):
6
03 (w), 450 (vs), 479 (vs), 517 (w), 564 (m), 617 (m), 636 (w, nPC), 699 (m, nCH), 725
(
(
m, nCH), 829 (w, dCHoop), 850 (s, dCHoop), 1046 (s, nCH), 1092 (vs, nPAr), 1194 (vs), 1384
m, dCH), 1449 (m, dCH), 1574 (s, nCC), 1651 (w), 1994 (m), 2049 (m), 2141 (s, nCC),
2
194 (m, nCC), 2208 (m, nCC), 2518 (w), 2840 (w, nCH), 2875 (w, nCH), 3615 (w).
Synthesis of (iPr Im)PMes (7): Mesityl phosphine (200 mg, 1.31 mmol) was added
at room temperature to a solution of iPr Im (420 mg, 2.76 mmol) in 10 mL of xylene
2
2
and the clear solution was heated to 135 °C for 5 d. All volatiles were removed in vacuo
and the sticky residue was washed with n-hexane (3 x 10 ml) and dried in vacuo to
1
D =
, 298 K): d = 0.90 (d, 12 H, 3JHH
afford a sticky orange oil. H NMR (400.1 MHz, C
6
6
i
6
.7 Hz, Pr-CH
3
), 2.24 (s, 3 H, mesityl-CH3para), 2.72 (s, 6 H, mesityl-CH3ortho) 4.69
dsept, 2 H, 3JHH = 4.1 Hz, 4JPH = 2.6 Hz, Pr-CH), 6.12 (s, 2 H, CHCH), 6.97 (s, 2 H,
i
(
1
3
1
mesityl-CHmeta). C{ H} NMR (100.6 MHz, C
6 6
D , 298 K): 21.2 (s, mesityl-CH3para), 21.6
i
), 25.0 (d, 3JCP = 12.2 Hz, mesityl-CH3ortho), 49.0 (d, 3JCP = 11.1 Hz, Pr-CH),
i
(
s, Pr-CH
3
1
14.3 (d, 1JCC = 3.6 Hz, CHCH), 128.5 (s, mesityl-CHmeta), 133.7 (s, mesityl-Cpara),
24
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
1
40.4 (d, 1JCP = 48.4 Hz, mesityl-Cipso), 142.6 (d, 2JCP = 10.4 Hz, mesityl-Cmeta), 168.4
d, 1JCP = 105.0 Hz, NCN). P NMR (162.0 MHz, C
Synthesis of (iPr Im)PH (8): tert-Butyl phosphine (169 mg, 1.88 mmol) was added at
room temperature to a solution of iPr Im (600 mg, 3.94 mmol) in 10 mL of xylene and
31
D , 298 K): d = -79.5 (s, P).
(
6
6
2
2
the clear solution was heated to 125 °C for 5 d. All volatiles were removed in vacuo
and the residue was suspended in 10 mL of n-hexane. After filtration, the solid was
washed with 8 mL of n-hexane and dried in vacuo to afford 97 mg (530 µmol; 28 %) of
1
D
, 298 K): d = 0.95 (d, 12 H, 3JHH = 6.7
a pale yellow solid. H NMR (400.1 MHz, C
6
6
i
), 2.64 (d, 1 H, 1JPH = 166.1 Hz, PH), 4.49 (dsept, 2 H, 3JHH = 6.7 Hz, 4JPH
Hz, Pr-CH
3
i
13
1
=
2
1
2.7 Hz, Pr-CH), 6.09 (s, 2 H, CHCH). C{ H} NMR (100.6 MHz, C
6
D
6
, 298 K): d =
i
), 48.8 (d, 3JCP = 7.9 Hz ,Pr-CH), 113.1 (d, JCP = 3.0 Hz , CHCH),
i
3
1.1 (s, Pr-CH
3
73.7 (d, 1JCP = 92.9 Hz, NCN). P{ H} NMR (162.0 MHz, C
31
1
D
6 6
, 298 K): d = -149.9 (s,
, 298 K): d = -149.9 (d, 1JPH = 166.1 Hz, PH). C
184.22 g/mol): calcd.: 58.68, H 9.30, N 15.21; found: C 58.67, H 9.30, N 15.02. HRMS
31
P). P NMR (162.0 MHz, C
D
6 6
9
H
17
N P
2
(
+
-1
LIFDI (m/z): calculated for C
9 17
H N
2
P [M ]: 184.1124; found: 184.1122. IR (ATR[cm ]):
4
1
2
60 (vs), 638 (s, nPC), 670 (m, dCHoop), 736 (s, dCHoop), 884 (s, nPH), 1066 (s), 1131 (m),
174 (m), 1217 (s), 1329 (m, dCH), 1364 (s, dCH), 1408 (vs, dCH), 1464 (w), 1566 (w),
179 (vw), 2302 (m, nPH), 2968 (m, nCH), 3070 (m, nCH).
Synthesis of (Mes
2
Im)PH (9): tert-Butyl phosphine (50 mg, 555 µmol) was added at
room temperature to a solution of Mes
2
Im (355 mg, 1.17 mmol) in 10 mL of xylene and
the clear solution was heated to 135 °C for 5 d. All volatiles were removed in vacuo
and the residue was suspended in 10 mL of n-hexane. After filtration, the off-white solid
was washed with 8 mL of n-hexane and dried in vacuo to afford 132 mg (392 µmol; 71
1
D
, 298 K): d = 2.07 (d, 1 H, 1JPH =164
%
) of an off-white solid. H NMR (400.1 MHz, C
6
6
Hz, PH), 2.09 (s, 6 H, mesityl-CH3para), 2.21 (s, 12 H, mesityl-CH3ortho), 5.92 (s, 2 H,
13
1
CHCH), 6.76 (s, 4 H, mesityl-CHmeta). C{ H} NMR (100.6 MHz, C
6 6
D , 298 K): d = 18.2
(
d, 5JCP = 1.9 Hz, mesityl-CH3ortho), 21.1 (s, mesityl-CH3para), 117.7 (d, mesityl-CH, JCP
=
2.9 Hz), 129.8 (s, mesityl-CHmeta), 134.7 (s, mesityl-CH), 136.5 (s, CHCH), 138.9 (s,
mesityl-CH), 176.3 (d, NCN, 1JCP = 85.4 Hz). P{ H} NMR (162.0 MHz, C
31
1
D
, 298 K):
, 298 K): d = -147.2 (d, 1JPH =164 Hz, PH).
P (336.42 g/mol): calcd.: 74.98, H 7.49, N 8.33; found: C 71.47, H 7.17, N
6
6
31
d = -147.2 (s, P). P NMR (162.0 MHz, C
D
6 6
21
C H
25
N
2
+
7
.65. HRMS LIFDI (m/z): calculated for C21
H
25
N
2
P [M ]: 336.1750; found: 336.1738.
IR (ATR[cm ]):477 (m), 501 (m), 572 (s), 603 (m), 666 (s, nPC), 697 (vs, dCHoop), 762
m, dCHoop), 852 (vs), 872 (s), 929 (w, nPH), 1033 (m), 1099 (m), 1143 (w), 1225 (vs),
-
1
(
25
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
1
339 (vs, dCH), 1355 (vs, dCH), 1398 (m, dCH), 1437 (m, dCH), 1484 (s, dCH), 1588 (m,
CC), 2269 (m, nPH), 2913 (vw, nCH), 2944 (vw, nCH), 3021 (vw, nCH), 3138 (vw).
Synthesis of (Me Im)PH (10): tert-Butylphosphine (50 mg, 555 µmol) was added at
room temperature to a solution of Me Im (145 mg, 1.17 mmol) in 10 mL of toluene and
n
4
4
was heated to 110 °C for 5 d. All volatiles were removed in vacuo and the residue was
suspended in 10 mL of n-pentane. After filtration, the solid was washed with 8 mL of
1
n-pentane and dried in vacuo to afford 44 mg (282 µmol; 51 %) of a colorless solid. H
NMR (400.1 MHz, C
PH), 2.84 (s, 6 H, NCH
1.6 (d, 3JCP = 7.8 Hz, NCH
6
D
6
, 298 K): d = 1.26 (s, 6 H, CH
3
), 2.49 (d, 1 H, 1JPH = 165 Hz,
). C{ H} NMR (100.6 MHz, C , 298 K): d = 8.4 (s, CH ),
), 120.2 (d, 1JCC = 3.1 Hz, CHCH), 174.6 (d, 1JPC = 88.0
13
1
3
D
6 6
3
3
3
31
1
31
Hz, NCN). P{ H} NMR (162.0 MHz, C
6
D
6
, 298 K): d = -149.9 (s, P). P NMR (162.0
MHz, C D
6 6
, 298 K): d = -149.9 (d, 1JPH =165 Hz, PH). C
7 13 2
H N P (156.17 g/mol): calcd.:
5
3.84, H 8.39, N 17.94; found: C 51.22, H 7.98, N 16.64. HRMS LIFDI (m/z): calculated
+
-1
for C H N
7 13 2
P [M ]: 156.0811; found: 156.0809. IR (ATR[cm ]): 436 (s), 481 (m), 621
(
w), 833 (w, dCHoop), 921 (m, dPHoop), 1064 (m, nCH), 1099 (s, nCC), 1164 (m), 1209 (m,
CH), 1260 (vw, dCH), 1345 (m, dCH), 1384 (vs, dCH), 1433 (m), 1457 (m), 1576 (m, nCC),
663 (w, nCC), 2014 (vw), 2155 (vw, nCC), 2208 (vw, nCC), 2293 (m, nPH), 3019 (vw,
d
1
nCH).
2
Synthesis of iPr Im–P(O)
2
Ph (11): A solution of (iPr
2
Im)PPh (1) (100 mg, 384 µmol,
1
.0 eq) in 5 mL toluene was thoroughly stirred under an atmosphere of 0.5 bar O
2
at
room temperature for 1 h. The resulting solid was filtered off, washed with n-hexane
1
(
3x 5 mL) and dried in vacuo. Yield : 61.2 mg (209 µmol, 55%) of a colorless solid. H
NMR (500.1 MHz, CD
3
CN, 298 K): δ = 1.31 (d, 12 H, 3JHH = 6.8 Hz, iPr-CH
sept, 2 H, 3JHH = 6.8 Hz, iPr-CH), 7.43 (d, 2 H, 4JHP = 1.2 Hz, CHCH), 7.38 – 7.43 (m,
3
), 6.28
(
1
3
2
H, aryl-H), 7.71 – 7.77 (m, 2 H, aryl-H) ppm. 13C{ H} NMR (125.8 MHz, CD
3
CN,
98 K): δ = 23.3 (iPr-CH
3
), 51.5 (iPr-CH), 120.3 (d, 3JCP = 3.6 Hz, CHCH), 129.2 (d,
2JCP = 12.7 Hz, aryl-CH), 131.6 (d, 4JCP = 2.8 Hz, aryl-CH), 132,2 (d, 3JCP = 9.8 Hz,
aryl-CH), 140.8 (d, 1JCP = 145.6 Hz, aryl-CP), 147.9 (d, 1JCP = 94.5 Hz, NCN) ppm.
31
1
31
P{ H} NMR (202.5 MHz, CD
CD
CN, 298 K): δ = -0.8 (t, 3JPH = 12.3 Hz, P) ppm. C15
calcd.: 61.63, H 7.24, N 9.58; found: C 61.09, H 7.23, N 9.17. HRMS LIFDI (m/z):
3
CN, 298 K): δ = -0.8 (s) ppm. P NMR (202.5 MHz,
3
H
21
N
2
PO (292.32 g/mol):
2
+
-1
calculated for C15H N
21 2
PO
2
: 292.3188; found [M+H ]: 293.1413. IR (ATR[cm ]): 436
(
m), 447 (w), 494 (m), 555 (s), 579 (s), 614 (w), 630 (w), 673 (vs), 699 (s), 743 (w),
7
65 (w), 787 (vw), 881 (vw), 995 (vw), 1024 (vw), 1071 (vw), 1092 (w), 1136 (w), 1158
26
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10.1002/zaac.202000405
(
vw), 1173 (vw), 1201 (m), 1305 (vw), 1373 (vw), 1399 (vw), 1419 (vw), 1436 (w), 1462
vw), 1562 (vw), 2297 (vw), 2929 (vw), 2980 (vw), 3045 (vw), 3078 (vw), 3100 (vw),
139 (vw), 3182 (vw).
Synthesis of iPr Im-P(S)
and S (14.0 mg, 436 µmol) in 5 mL THF was heated for 24 h at 65°C. The precipitate
(
3
2
2
Ph (12): A solution of (iPr Im)PPh (1) (100 mg, 384 µmol)
2
8
was filtered off and washed with THF (3x 5 mL) and n-hexane (1x 5 mL). The product
1
was dried in vacuo to afford 41.2 mg (126 µmol, 33%) of a light yellow solid. H NMR
, 298 K): δ = 1.28 (d, 12 H, 3JHH = 6.8 Hz, Pr-CH
i
(
500.1 MHz, CDCl
3
3
), 6.08 (sept, 2 H,
3JHH = 6.6 Hz, Pr-CH), 7.16 (d, 2 H, JPH = 1.1 Hz, CHCH), 7.41 – 7.48 (m, 3 H, aryl-
i
4
13
1
H), 8.19- 8.27 (m, 2 H, aryl-H) ppm. C{ H} NMR (125.8 MHz, CDCl
3
, 298 K): δ = 23.0
(
s, iPr-CH
3
), 51.2 (d, 3JCP = 1,0 Hz, iPr-CH), 118.5 (d, 3JCP = 1.2 Hz, CHCH), 128.4 (d,
2JCP = 13.6 Hz, aryl-CH), 131.0 (d, 4JCP = 3.4 Hz, aryl-CH), 131.1 (d, 3JCP = 12.0 Hz,
aryl-CH), 142.3 (d, 1JCP = 91.0 Hz, aryl-CP), 146.9 (d, 1JCP = 38.9 Hz, NCN) ppm.
3
1
1
, 298 K): δ = 53.9 (s) ppm. 31P NMR (202.5 MHz,
P{ H} NMR (202.5 MHz, CDCl
CDCl
, 298 K): δ = 53.9 (t, 3JPH = 14.7 Hz, P) ppm. C15
5.53, H 6.52, N 8.63; found: C 55.25, H 6.72, N 8.55. HRMS LIFDI (m/z): calculated
3
3
21
H N
2
PS (324.44 g/mol): calcd.:
2
5
+
-1
21
for C15H N
2
PS [M ]: 324.0884; found: 324.0878. IR (ATR[cm ]): 410 (vw),432 (vw),
2
4
61 (w), 524 (vs), 548 (vs), 589 (vw), 669(vw), 702 (s), 722 (vw), 754 (w), 803 (w), 885
(
m), 907 (vw), 940 (vw), 979 (vw), 1003 (vw), 1024 (vw), 1050 (m), 1067 (m), 1081 (w),
1
1
132 (m), 1150 (vw), 1179 (w), 1213 (w), 1252 (s), 1350 (w), 1373 (vw), 1393 (vw),
417 (vw), 1434 (vw).
Synthesis of (iPr
2
Im)Se (13): A suspension of (iPr Im)PPh (1) (100 mg, 384 µmol)
2
and black selenium (30.3 mg, 384 µmol) in 5 mL toluene was heated for 24 h at 85°C.
The resulting Solution was filtered off and all volatiles were removed in vacuo. The
remaining residue was suspended in 5 mL n-hexane. The suspension was filtered off,
washed n-hexane (2x 5 mL) and dried in vacuo to afford 38.3 mg (165 µmol, 43%) of
1
, 298 K): δ = 1.39 (d, 12 H, 3JHH = 6.9
a colorless solid. H NMR (500.1 MHz, CDCl
3
13
1
Hz, iPr-CH
NMR (125.8 MHz, CDCl
CHCH), 153.5 (s, NCN) ppm. Se{ H} NMR (95.4 MHz, CDCl
ppm. C
.16, N 8.26. HRMS LIFDI (m/z): calculated for C15
found: 232.0474.
3
), 5.30 (sept, 2 H, 3JHH = 6.8 Hz, iPr-CH), 6.92 (s, 2 H, CHCH) ppm. C{ H}
3
, 298 K): δ = 22.2 (s, iPr-CH ), 50.7 (s, iPr-CH), 115.4 (s,
3
77
1
3
, 298 K): δ = -19.7 (s)
9
H
16
N Se (231.21 g/mol): calcd.: 46.75, H 6.98, N 12.12; found: C 49.97, H
2
+
6
21
H N
2
Se [M ]: 232.0479
27
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
2
Synthesis of (iPr Im)Te (14): A suspension of (iPr
2
Im)PPh (1) (100 mg, 384 µmol)
and amorphous tellurium (75.0 mg, 588 µmol) in 5 mL toluene was heated for 24 h at
5°C. The resulting solution was filtered and all volatiles of the filtrate were removed
8
in vacuo. The remaining residue was suspended in 5 mL hexane, filtered and washed
with n-hexane (2x 5mL) and dried in vacuo to afford 27.4 mg (98.0 µmol, 26%) of an
1
D
, 298 K): δ = 0.93 (d, 12 H, 3JHH = 6.8 Hz,
off-white solid. H NMR (500.1 MHz, C
6
6
), 5.45 (sept, 2 H, 3JHH = 6.8 Hz, iPr-CH), 6.26 (s, 2 H, CHCH) ppm. C{ H}
13
1
iPr-CH
3
6 6 3
NMR (125.8 MHz, C D , 298 K): δ = 21.8 (s, iPr-CH ), 54.0 (s, iPr-CH), 116.7 (s,
CHCH), 131.5 (s, NCN) ppm. 123Te{ H} NMR (130.9 MHz, C
1
6 6
D , 298 K): δ = -184.6 (s,
9 16
Te) ppm. C H N
2
Te (279.84 g/mol): calcd.: 38.63, H 5.76, N 10.01; found: C 40.62, H
+
6
2
.16, N 8.26. HRMS LIFDI (m/z): calculated for C15
21
H N
2
Te [M ]: 282.0376; found:
82.03693.
Synthesis of [(W(CO)
suspended in THF (7 mL) and irradiated with UV light for 16 h. To this solution,
iPr Im)PPh (1) (100 mg, 384 µmol) dissolved in THF (5 mL) was added. The reaction
5 2
){(iPr Im)PPh}] (15): W(CO)
6
(135 mg, 384 µmol) was
(
2
mixture stirred at room temperature overnight. All volatiles were removed in vacuo and
the residue was suspended in 10 mL of n-pentane. After filtration, the solid was washed
with n-pentane (2 x 6 mL) and dried in vacuo to afford 122 mg (208 µmol; 54 %) of a
1
D
, 298 K): d = 0.80 (d, 12 H, 3JHH = 6.7 Hz, Pr-
i
yellow solid. H NMR (400.1 MHz, C
6
6
i
CH
3
), 4.98 (dsept, 2 H, Pr-CH), 6.00 (s, 2 H, CHCH), 7.02 (m, 3 H, aryl-H), 7.63 (m, 2
1
3
1
i
), 50.9 (d, 3JCP
H, aryl-H). C{ H} NMR (100.6 MHz, C
6
D
6
, 298 K): d = 22.2 (s, Pr-CH
12.9 Hz, Pr-CH), 117.3 (d, JCC = 2.2 Hz, CHCH), 126.1 (d, 4JCP = 1.1 Hz, aryl-
CHpara), 128.7 (d, 3JCP = 4.0 Hz, aryl-CHmeta), 135.3 (d, 2JCP = 15.6 Hz, aryl-CHortho),
3
i
1
=
1
4
41.0 (d, 1JCP = 26.3 Hz, aryl-Cipso), 164.3 (d, 1JCP = 86.4 Hz, NCN), 200.5 (d, 2JCP
=
31
, 298 K): d = -80.9 (m, 1JPW = 112.3 Hz, P).
.1 Hz, CO). P NMR (162.0 MHz, C
D
6 6
20
C H
21
N
2
O
5
PW (584.21 g/mol): calcd.: 41.12, H 3.62, N 4.80; found: C 40.97, H 3.16,
+
N 4.02. HRMS LIFDI (m/z): calculated for C20
H
21
N
2
O
5
PW [M ]: 584.0692; found:
-
1
5
84.0685. IR (ATR[cm ]): 405 (m), 438 (m), 491 (m), 579 (s), 605 (m), 691 (m), 738
(
(
(
(
s, nCH), 801 (m, dCHoop), 1023 (w), 1131 (vw), 1194 (vw), 1207 (m), 1260 (w), 1319
vw), 1370 (w), 1396 (w), 1431 (m), 1464 (w), 1561 (w), 1578 (w), 1810 (vs, nCO), 1833
vs, nCO), 1855 (s, nCO), 1880 (s), 1969 (s), 1996 (m), 2051 (w, nCC), 2968 (vw), 3140
vw, nCH), 3168 (vw, nCH).
Synthesis of [Co(CO)
2 2
(NO){(iPr Im)PPh}] (16): A solution of (iPr
2
Im)PPh (1)
(
224 mg, 861 µmol) in 6 mL THF was added to a pre-cooled (-78°C) solution of
28
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.202000405
[
Co(CO) (NO)] (149 mg, 861 µmol) in 6 mL THF. The mixture was allowed to warm up
3
to room temperature and the solvent was removed under vacuum. The residue was
suspended in n-pentane and filtered and the remaining solid was washed with n-
pentane (2x 5 mL) and dried in vacuo to afford 144 mg (357 µmol, 42%) of a red
1
, 25 °C): δ = 0.81 (d, 12 H, 3JHH = 6.7 Hz, iPr-CH
),
solid. H NMR (500.1 MHz, C
D
6 6
3
5
6
.02 (dsept, 2 H, 3JHH = 6.7 Hz, 4JPH = 1.35 Hz, iPr-CH), 6.07 (dbr, 2 H, CHCH), 6.59 −
.99 (m, 1 H, p-CHAr), 7.04 − 7.07 (m, 2 H, o-CHAr), 7.46 − 7.67 (m, 2 H, m-CHAr) ppm.
13
1
, 298 K): δ = 22.3 (iPr-CH
), 50.9 (d, 3JPC = 12.4 Hz,
C{ H} NMR (126 MHz, C
D
6 6
3
iPr-CH), 117.6 (d, 4JPC = 2.24 Hz, CHCH), 125.5 (d, 4JPC = 1.24 Hz, p-CHAr), 128.4 (o-
CHAr), 133.9 (d, 3JPC = 15.4 Hz, m-CHAr), 144.1 (d, 1JPC = 31.9 Hz, q.-CAr), 163.7 (d,
1JPC = 91.2 Hz, NCN), the carbonyl carbon atom were not detected. P NMR (202
31
6 6
MHz, C D ) δ = -45.5 (br, P). C17H21CoN
3
O P (405.3 g/mol): calcd.: 50.38, H 5.22, N
3
1
1.97; found: C 49.55, H 5.35, N 9.93. HRMS LIFDI (m/z): [M]+ for C17
H21CoN
3
O P
3
-
1
calcd.: 405.0647, found: 405.0639. IR (ATR): ꢀꢁ [cm ] = 499 (vs), 581 (vs), 670 (m),
6
1
99 (vs), 744(vs), 801 (w), 833 (w), 1023 (m), 1066 (m), 1135 (m), 1176 (m), 1209 (s),
374 (m), 1435 (m), 1464 (m), 1560 (m), 1576 (m), 1694 (vs,ꢂνN≡O, str.), 1925 (vs, νC≡
O, str.(B1)), 1992 (vs, νC≡O, str.(A1)), 2873 (w, νC-H, str.), 2934 (w, νC-H, str.),2981 (m,ꢂνC-H, str.),
3
059 (w, νC-H, str.), 3144 (w, νC-H, str.), 3171 (w, νC-H, str.).
5
Synthesis of [(ƞ -C
5
Me
5
)Co(C
2
H
4
){iPr
2
Im)PPh}] (17): (iPr
2
Im)PPh (1) (157 mg,
] (150 mg, 599 µmol) in 15
mL toluene at room temperature and the mixture was stirred for additional 16 h.
Immediately the formation of gaseous C and a color change to red was observed.
5
5
99 µmol) was added to a solution of [(ƞ -C
5
Me
5 2 4 2
)Co(C H )
2
H
4
The solvent was removed and the residue was suspended in 5 mL n-pentane, filtered
off and washed with n-pentan (2x 5 mL) and dried in vacuo to afford 98.3 mg (203.7
1
µmol, 34%) of a dark brown solid. H NMR (500.1 MHz, C
6
D , 298 K): δ = 0.71 (dbr, 2
6
2
), 0.95 (d, 12 H, 3JHH = 6.59 Hz, iPr-CH ), 1.37 (d, 2 H, 3JHH = 8.08 Hz, η2-
H, η -C
H
2 4
3
5
) ,
), 4.57 (sept, 2 H, 3JHH = 5.80 Hz, iPr-CH), 6.04 (dbr
C
2
H
4
), 1.93 (s, 15 H, η -C
5
(CH
3
5
2
H, CHCH), 7.05 – 7.09 (m, 1 H, p-CHAr.), 7.19 – 7.23 (m, 2 H, m-CHAr.), 8.30 – 8.33
1
3
1
, 25 °C): δ = 9.88 (d, 3JPC = 5.07
), 49.1 (d, 2JPC = 12.7 Hz, iPr-CH), 87.9
(
m, 2 H, o-CHAr.) ppm. C{ H} NMR (126 MHz, C
D
6 6
5
2
Hz, η -C
5 3
(CH )
5
), 22.5 (iPr-CH
3
), 28.2 (η -C
H
2 4
d, 2JPC = 3.02 Hz, η -C
5
Me
), 116.3 (d, 3JPC = 2.73 Hz,CHCH), 125.5 (d, 4JPC = 0.9 Hz,
(
5
5
p-CHAr.), 127.6 (d, 3JPC = 3.24 Hz, m-CHAr.), 136.4 (d, 2JPC = 14.6 Hz, o-CHAr.), 142.3
d, 1JPC = 33.2 Hz, q-CAr.), 163.7 (d, 1JPC = 98.5 Hz, NCN). P NMR (202 MHz, C
31
(
6 6
D )
δ = 25.8 (br, P). C27
H
40CoN P (482.53 g/mol): calcd.: 67.21, H 8.36, N 5.81; found: C
2
29
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