Synthesis and characterization of novel carbene complexes of phosphorus(V) fluorides with potential liquid-crystalline properties

Article abstract of DOI:10.1016/j.tet.2013.07.062

A series of novel push-push I and push-pull II carbene-stabilized complexes of phosphorus(V) fluorides bearing substituents with liquid-crystalline properties were synthesized by the oxidative addition of difluoroamines to phosphorus(III) halides. These octahedral complexes were characterized by NMR spectroscopy and X-ray analysis.

Full text of DOI:10.1016/j.tet.2013.07.062

Accepted Manuscript
Synthesis and Characterization of Novel Carbene Complexes of Phosphorus(V)
Fluorides with Potential Liquid-Crystalline Properties
Romana Pajkert, Tobias Böttcher, Maksym Ponomarenko, Matthias Bremer, Gerd-
Volker Röschenthaler
PII:
S0040-4020(13)01155-1
10.1016/j.tet.2013.07.062
TET 24643
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 30 May 2013
Revised Date: 15 July 2013
Accepted Date: 16 July 2013
Please cite this article as: Pajkert R, Böttcher T, Ponomarenko M, Bremer M, Röschenthaler G-V,
Synthesis and Characterization of Novel Carbene Complexes of Phosphorus(V) Fluorides with Potential
Liquid-Crystalline Properties, Tetrahedron (2013), doi: 10.1016/j.tet.2013.07.062.
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Synthesis and Characterization of Novel Carbene Complexes of Phosphorus(V)
Fluorides with Potential Liquid-Crystalline Properties
Romana Pajkert,a* Tobias Böttcher,a Maksym Ponomarenko,a Matthias Bremerb and Gerd-Volker
Röschenthalera*
a School of Engineering and Science, Jacobs University Bremen, Campus Ring 1,
28759 Bremen, Germany
b Merck KGaA, 250 Frankfurterstr., 64271 Darmstadt, Germany
b Merck KGaA, 250 Frankfurterstr., 64271 Darmstadt, Germany
*Corresponding Authors: r.pajkert@jacobs-university.de
Tel. +49 421 200-3269
g.roeschenthaler@jacobs-university.de
Tel. +49 421 200-3138
Fax. +49 421 200-3229
Abstract
A series of novel push-push I and push-pull II carbene-stabilized complexes of phosphorus(V)
fluorides bearing substituents with liquid crystalline properties were synthesized by the oxidative
addition of difluoroamines to phosphorus(III) halides. These octahedral complexes were
characterized by NMR spectroscopy and X-Ray analysis.

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1. Introduction
Over the last five decades, carbenes have played an important role as transient intermediates,
however only during the past two decades, the understanding of carbene chemistry has advanced
dramatically with the preparation and isolation of the first stable N-heterocyclic carbene (NHC).1
Since then, nucleophilic diaminocarbenes (push-push carbenes) and their analogues have emerged
as a powerful class of ligands for catalysis which show superior properties in comparison with their
phosphine counterparts.2 Despite the rapid evolution of NHCs as strong σ-donor ligands for
transition metals, their application in other areas has experienced substantial advances only during
the last 10 years. Especially the increased stability of the M-CNHC bond of NHCs complexes as well
as the possibility for structural diversity of NHCs beneficiated for their use in biomedical
applications,3 luminescent components4 or self-assembled structures.5 In the latter case, the self-
assembly of amphiphilic metal-NHC complexes into birefringent materials provides a suitable
approach for preparing metal-containing liquid crystals which are attractive due to the possibility of
combining the physico-chemical metal-like properties (i.e. color, magnetism, polarizability,
spectroscopic properties, redox behavior, etc.) with those of the organic framework. These
complexes (metallomesogens) can be treated as a new kind of materials with many potential
applications in optical and electronic devices.6
Up to now, only a small number of gold(I),7 silver(I)8 and palladium(II)9 N-heterocyclic carbene
complexes with various wingtip chain lengths has been proved for liquid-crystalline behavior.
Generally, these compounds exhibit increased thermal stability connected with the strong covalent
metal bonding to prevent decomposition at the clearing point. Moreover, they possess lower melting
temperatures as well as birefringence. It should be however noted, that limited synthetic routes to
these molecules and the use of expensive reagents hamper their potential application. Therefore, it
is of great interest to design other types of carbene complexes, which are easy to apply, with
exceptionally large dipole moments, a prerequisite for applications as liquid crystals. Usually, the
dipole moment serve to improve their properties, which in turn could lead to increased brilliance in
smarthphone displays or faster circuit time in monitors and flat screens. To fulfill these
requirements, a series of carbene complexes of phosphorus(V) fluorides with potential liquid-
crystalline properties has been investigated. These liquid crystalline properties could be achieved by
the use of different sources of carbene (push-push or push-pull) as well as by variation of the
periphery of carbenes, substituents at nitrogen (the wingtip groups) or at phosphorus. As
substituents with liquid-crystalline properties, 4-propyl-1,1'-bi(cyclohexane) and 1-methyl-4-(4-
propylcyclohexyl)benzene were used. The carbene ligands were introduced via oxidative addition
using difluorobis(dialkylamines) (push-push carbenes), as well as difluoroorganyldialkylamines

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(push-pull carbenes).10 The latter precursor was reported by our group just recently and only a few
examples of main group element compounds coordinated by these carbene ligands are known
because aryl(amino)carbene are highly reactive in their free form and the first isolation was
achieved not before 2001.11
Thus, in this paper we report the preliminary results of these studies as well as structural
investigations of novel carbene complexes of phosphorus(V) fluorides with potential liquid-
crystalline properties.
2. Result and Discussion:
In order to gain an access to difluorinated carbene precursors, the synthetic route to various
N,N-disubstituted or 2-substituted-N,N-dimethyl imidazolidinones was initially investigated. A
symmetrical compound 1, bearing liquid-crystalline wingtip substituents attached to the nitrogen
atoms, was successfully obtained via dibenzylation of the sodium salt of imidazolidinone using two
equivalents of 1-(bromomethyl)-4-(4-propylcyclohexyl)benzene2 in refluxing 1,4-dioxane (Scheme
1). Consecutively, the appropriate bromo derivative 2 was prepared by reducing the carboxylic acid
3 leading to benzyl alcohol 4, which was then brominated with 48% of hydrobromic acid to give 2.
Scheme 1.
The peripheral liquid-crystalline functions were introduced using two different approaches. The 2-
substituted-N,N-dimethyl imidazolidinone precursor 5 was obtained from the corresponding alkene
6 which was firstly brominated as presented in Scheme 2. This step furnished 1,2-dibromoalkane 7,
which was then substituted with 2 equiv. of sodium azide to give compound 8, prior to the reduction
of azide groups to appropriate 1,2-diamine 9. Alkylation of the amino groups was then achieved by
the reaction of 9 with 2 equiv of chloroformate, followed by reduction of the corresponding
formamide 10 with lithium aluminium hydride. Subsequent cyclization of dimethylamine 11 to the
desired imidazolidin-2-one 5 was achieved upon deprotonation of 11 with 2 equiv of n-butyllithium,
followed by addition of ethyl chloroformate (Scheme 2).

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Scheme 2.
In contrast, the construction of the imidazolidin-2-one ring 12 was successfully accomplished using
palladium-catalyzed carboamination of N-allylurea 13 with phenyl bromide 14 (Scheme 3).12
Treatment of 12 with phenyl bromide 14 and NaOt-Bu in the presence of 1 mol % of palladium
catalyst and 2 mol % of Xanthos afforded the desired product in good yield. It should be however
noted, that an attempt to scale up this reaction to more than 1 g of 14 provided lower yield of 12.
Scheme 3.
N-Allylurea 13 was readily obtained by the reaction of methyl isocyanate 18 with appropriate N-
allylamine 15 which was prepared 16 via its formylation and subsequent reduction of the
formamide 17 using lithium aluminium hydride (Scheme 4). Methyl isocyanate 18 was synthesized
by reaction of sodium azide 19 with acetyl chloride 20, followed by the Curtius rearrangement of in
situ formed acyl azide to isocyanate in dry diglyme as illustrated at Scheme 4.

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Scheme 4.
The method used to prepare the precursor of aryl(amino)carbene precursor (benzamide) 21 included
the preparation of an appropriate acyl chloride 22 from carboxylic acid 3, followed by the amidation
of 22 with N,N-dimethylamine as presented in Scheme 5.
Scheme 5.
In the next step, appropriate imidazolidinone and benzamides were conveniently
transformed to push-push carbene precursors - 2,2-difluoro-N,N-dimethylimidazolidinones 23a-d
and push-pull carbene source - 1,1-difluoro-N,N-dimethyl-phenylmethyldiamines by the known
procedure.13 This method was based on the halogen exchange reaction of appropriate chlorides 24a-
d, prepared from the respective precursors upon heating with oxalyl chloride, with an excess of
spray-dried potassium fluoride in refluxing acetonitrile (Scheme 6). After filtration of the inorganic
salts (KCl, KF), washing with MeCN or Et2O, DFI was isolated in a pure form from the reaction
mixture by evaporation of the filtrate.
Scheme 6.
Two approaches were applied to the preparation of the corresponding α,α-difluoroamine. Bearing in
mind that various benzamides are able to undergo direct chlorination with using phosgene,14 we
have examined if the similar process for fluorination of amides using difluorophosgene might
proceed. For these reasons, we condensed the appropriate amount of carbonyl difluoride onto the
solution of amide 21a-b in dry acetonitrile. Stirring of the resulting mixture at room temperature for
12 hours, subsequent addition of the catalytic amount of Lewis acid (BF3·Et2O) and refluxing in
acetonitrile led however to the desired difluoroamines 25a-b in only moderate yield (15% for 25a
and 45% for 25b, according to 19F NMR). The main product formed during the reaction was

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probably the more stable ester 25’ (30%), which might form the conjugated system together with
phenyl ring und unreacted carbonyl difluoride as proposed in Scheme 7. Based on these results, we
therefore carried out the fluorination via a modified procedure to improve the yield.15 Consequently,
benzamide 21a,b was chlorinated using oxalyl chloride to chlorides 26a,b, then fluorinated with
triethylamine tris(hydrogen fluoride) in the presence of triethylamine to give α,α-
difluoro(aryl)amines 25a-b in good yield (Scheme 7).
F
O
F
N
F
O
O
F
1. F2CO, MeCN, r.t.
2. BF3 Et2O,
N
N
R
R
R
21a,b
25a (15%)
b (45%)
25'
Scheme 7.
Compounds 23a-d and 25a-b were then used as sources of carbene ligands in the oxidative addition
to phosphorus(III) halides (fluorides or chlorides) to give carbene-stabilized complexes of
substituted and unsubstituted phosphorus(V) fluorides. Noteworthy, difluoroamines are also prone
to halide metathesis, therefore the use of easier-to-handle chlorophosphines instead of
fluorophosphines is sometimes preferred, like in the case of 27.10
Thus, compound 27 was readily obtained from bromo-nPrCP 28 upon treatment with magnesium to
give the corresponding Grignard reagent 29 which was then reacted with ClP(NEt2)2 to furnish 30.
By the substitution of amino groups for chlorine atoms using gaseous anhydrous HCl, the
chlorophosphine 27 was formed conveniently. Noteworthy, attempts to prepare difluorophosphine
31 from chlorophosphine 27 were unsuccessful, however, and led to the oxidation of phosphorus.
Therefore in this case the chlorophosphine 27 was used as a source of trivalent phosphorus (Scheme
8).

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Scheme 8.
As mentioned above, carbene complexes of phosphorus(V) fluorides were obtained by oxidative
addition of 2,2-difluorobis(alkylamines) 23a-d and 25a-b to phosphorus(III) halides. The
complexes series I (push-push carbene complexes) and II (push-pull carbene complexes) were thus
obtained as presented in Scheme 9.
All reactions were carried out under Schlenk conditions in dry diethyl ether or tetrahydrofuran at
-196 or -40 °C for 12 h, giving rise to complexes 32a-e (series I) in very good or 33a-c (series II) in
moderate yield. In a typical procedure, phosphorus fluoride was condensed onto a frozen mixture (-
196) of difluoroamine 23b,c,d; 25b in anhydrous diethyl ether or appropriate dihalophosphine was
added to a cooled (-40 °C) solution of difluoroamine 23a,b; 25a,b in dry Et2O or THF to furnish the
corresponding adducts: 32a,c,d; 33a or 32b,e; 33b,c, respectively (Scheme 9). As observed, the
increased reactivity in the series of diaminocarbenes 23a-d resulted from the donation of the two
strong σ-donors (nitrogen lone pairs) and hence enhanced nucleophilicity of the reaction center
(higher yields of products) when compared to aryl(amino)carbenes. In the case, when
dichlorophosphine 27 was used as a substrate 32e, 33c, the chloroamidinium chloride precipitated
as a by-product was removed by washing with water. All liquid-crystalline complexes 32a-e and
33a-c were obtained as colorless solids, which are stable toward air and moisture. The stability of
hexacoordinated phosphorus(V) fluorides in water is known and was reported some time ago by our
working group.16 A general, plausible mechanism toward the formation of these species is presented
in Scheme 10. Noteworthy, this process could only be conducted when at least a single electron
pair-active substituent is present in the structure of the carbene precursor.

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F
F
F
F
N
N
N
N
23b
23b
PF3
-196 °C, Et2O
PhPF2
-40 C, Et2O
F
F
F
F
F
P
F
F
F
P
N
N
F
N
N
32a (80%)
32b (80%)
N
N
F
F
N
N
F
F
N
N
F
F
23c
23a
23d
Cl2P
PF3
PF3
-196 °C, Et2O
-40 C, THF
-196 °C, Et2O
F
F
F
F
P
F
F
F
F
N
N
N
N
N
N
P
F
P
F
F
F
F
F
32c (81%)
32d
(76%)
32e
(64%)
I
series
F
F
F
F
F
F
N
N
N
25b
25b
25a
Cl2P
PhPF2
PF3
-40 C, THF
-40 C, Et2O
-196 °C, Et2O
F
F
F
P F
F
F
F
F
F
P F
P
N
F
F
N
F
N
33a (53%)
33b
33c
(35%)
(45%)
II
series
Scheme 9.

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Thus, in the first step a fluoride is transferred from the difluoride to phosphorus fluoride to give a
phosphoranide and monofluorinated species. In the second step, the carbon atom at the 2 position of
monofluoride cation undergoes nucleophilic attack by the phosphoranide to give a carbon-
phosphorus bond. In the latter step, the redox-rearrangement takes place, where the electron poor
and highly acidic phosphorus(III) abstracts the second fluoride and is oxidized to give phosphorus
(V), whereas carbon(IV) is reduced to the carbene atom.10
Scheme 10.
1
All products were characterized by H, 13C, 19F and 31P NMR spectroscopy and high resolution
mass spectrometry. The most distinguished features could be observed in 19F and 31P NMR spectra.
Selected chemical shifts and coupling constants were presented in Table 1.
Table 1. Selected chemical shifts [ppm] and coupling constants [Hz] of carbene complexes
32a
32b
32c
32d
32e
33a
33b
33c
δ [ppm], J [Hz]
19F
-53.4
-42.2
-56.6
-56.8
-45.0
-59.4
-47.9
-47.0
(dd)
(d)
(dd)
(dd)
(d)
(dd)
(d)
(d)
J
FP 798
J
FP 871
J
FP 759
J
FP 796
JFP 865
J
FP 815
J
FP 887
J
FP 887
JFF 53.5
JFF 51.0
JFF 50.6
JFF 50.
-75.2
-74.7
-74.6
-73.3
(dquint)
JFP 769
JFF 53.4
(dquint)
JFP 758
JFF 51.0
(dquint)
JFP 796
JFF 50.6
(dquint)
JFP 751
JFF 33.2
31P
-153.3
(dquint)
JPF 800
JPF 770
-138.9
quint
JPF 800
-150.3
(dquint)
JPF 797
JPF 760
-150.4
(dquint)
JPF 796
JPF 758
-139.1
(quint)
JPF 865
-149.8
(dquint)
JPF 815
JPF 744
-140.8
(quint)
JPF 886
-139.1
(quint)
JPF 887
For the diaminocarbene adducts 32a, c, d, two magnetic environments for the fluorine centers could
be distinguished. These two fluorine signals (doublet of doublets and doublet of quintets) occur in a
1:4 ratio and correspond to the axial (opposite to the carbene) and equatorial (adjacent to the
carbene) fluorine sites. Moreover, the larger F-P coupling constants to the equatorial fluorine
substituents than to axial is observed what could be explained by higher s-character of orbitals used
by phosphorus to make its equatorial bonds. The 31P NMR spectra of 32a, c, d show a doublet of

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quintets at about -150 ppm, which clearly indicates the presence of a hexacoordinated phosphorus
center. For the PF4Ph adducts 32b, e, the 19F resonance appears as a doublet at about -42.2 and -
45.0 ppm, suggesting four equatorial fluorine sites whereas 31P NMR spectrum shows a quintet at -
138 and -139 ppm, respectively. Examining the data given for aryl(amino)carbene complexes 33a-c,
the similar coupling pattern in 19F as well as 31P NMR is observed for PF5 (33a) and PF4Ph (33b, c)
complexes when compared to the previously described diaminocarbene adducts. However for the
products derived from the push-push N-heterocyclic carbene source, the phosphorus resonance
occurs at slightly higher field than for the adduct derived from push-pull carbene precursor
indicating, as expected, greater relative electron donating ability of the diaminocarbene. Moreover,
13
analysis of the C NMR chemical shifts of the carbene centers suggests a strong phosphorus bond
to carbene carbon nuclei. Examining the resonance of the corresponding free carbenes, these signals
fall approximately 60 ppm upfield for diaminocarbene complexes and 110 ppm for
aryl(amino)adducts.11,17
As reported above, adducts derived from oxidative addition of difluoroamines to phosphorus(III)
fluorides (chlorides) were stable compounds and compound 32e could conveniently be
recrystallized to produce suitable crystals for X-Ray analysis. Single crystal of 32e was thus
obtained by slow diffusion of diethyl ether into a solution of the adduct in acetonitrile. Compound
32e crystallizes in the triclinic space group P-1 and its X-Ray crystal structure is illustrated in
Figure 1. Selected structural parameters of 32e are given in Table 2.
Table 2. Selected bond lengths [pm] and angles [°C] for 32e
32e
Ccarbene-P
P-Caryl
190.7(5)
181.9(5)
133.4(6)
162.8(3)
179.3(2) °
87.3 °
av Ccarbene-N
av P-F
Ccarbene-P-Caryl
NHC/phenyl
The structure of 32e shows the expected octahedral geometry at the phosphorus atom, with almost
linear C-P-C bond (179.3°). The four equatorial fluorine atoms form a plane with a slight up-down
altering arrangement of the fluorines. Moreover, similarly to the Arduengo carbene adduct,17 the
NHC and the phenyl ring are twisted by 87.3° to perpendicular configuration (Figure 1), what could
be explained by the packing effects of the crystal lattice (Figure 2). As observed, the crystal consists

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of parallel layers of head-to-tail ‘dimers’, where imidazole and phenyl rings are in every layer
parallel to each other.
Figure 1.
Figure 2.
The carbene-phosphorus bond distance in 32e is rather long (190.7 pm), but very similar to the
corresponding NHC carbene adducts described in the literature.10,17,18 The C-P bond length of the
ipso-carbon of the phenyl substituent resembles a normal P-C single bond whereas the C-N bond
distance is typical for NHC complexes but longer as for other push-pull complex.11
3. Conclusions
A series of novel push-push and push-pull carbene complexes of phosphorus(V) fluorides
bearing liquid-crystalline substituents has been prepared and characterized by NMR spectroscopy.
Compound 32e was additionally characterized by X-Ray. Moreover, for the first time 1,1-difluoro-
N,N-dimethyl-1-phenylmethanamine was used in the oxidative addition to phosphorus(III) halides
as a source of aryl(amino)carbene. Further studies including the properties and application of novel
carbene complexes as liquid-crystalline molecules will be reported in due course.

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4. Experimental Part
All reactions were carried out under an atmosphere of dry argon. THF was freshly distilled
from sodium benzophenone ketyl. Reagents obtained from commercial sources (1.3-
dimethylimidazolidinone, N,N-dimethylbenzamide, phosphorus trifluoride), were used without
further purification. All other reagents were distilled or recrystallized, if necessary. DFI was
obtained according to the known procedure.13 Phenyldifluorophosphine was prepared by the method
of Riesel et al.19 Column chromatography was performed using Merck silica gel 60 (230–400 mesh
ASTM) and TLCs using Merck silica gel 60 F254.Visualization was achieved by UV light or by
1
spraying with Ce(SO4)2 solution in 5% H2SO4. H (400 MHz), 13C (100 MHz), 19F (376 MHz) and
31P NMR (161 MHz) spectra were measured on a JEOL ECX 400 MHz spectrometer at room
1
temperature using 5 mm tubes. TMS was the internal standard in H NMR, CFCl3 was used as a
reference for 19F NMR and 85% H3PO4 in 31P NMR. Chemical shifts (δ) are reported in ppm and
coupling constants (J) in Hz. 31P NMR spectra were broadband decoupled from hydrogen nuclei.
High resolution mass spectra were recorded on a MicroTOF-Q fitted with an ESI source. Elemental
analysis was performed by the ‘Microanalytical Laboratory Beller-Matthies’ in Göttingen. Melting
points were determined with an Electrothermal IA9100 Digital Melting Point Apparatus and are
uncorrected.
[4-(4-Propylcyclohexyl)phenyl]methanol (4)
Lithium aluminium hydride (3.1 g, 2 equiv.) was added to a solution of carboxylic acid 3 (10 g, 1
equiv.) in dry THF and the mixture was refluxed for 10 h. The reaction was quenched with water
(10 mL), 15% NaOH (10 mL) and water (30 mL), stirred for 1 hour and then filtered. The filtrate
was dried over Na2SO4, evaporated under reduced pressure to give pure [4-(4-
propylcyclohexyl)phenyl]methanol 4 as a white solid.
1
Yield: 93%; H NMR (400 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz, 3H), 1.1 (m, 2H), 1.3 (m, 8H, CH,
OH), 1.9 (m, 2H), 2.6 (tt, J = 12.2, 3.2 Hz, 1H), 4.7 (s, 2H), 7.2 (d, J = 7.0 Hz, 2H), 7.3 (d, J = 7.0
Hz, 2H)
1-(Bromomethyl)-4-(4-propylcyclohexyl)benzene (2)
Toluene (100 mL) and 48% hydrobromic acid (20 mL) were mixed together with benzyl alcohol 4
(15 g, 65 mmol) and the mixture was stirred at 80°C for 14 hr. After partitioning, the organic layer
was successively washed with water (50 ml), saturated aqueous sodium hydrogen carbonate (50 ml),
water (50 ml) and saturated brine and dried over magnesium sulfate. After filtration and solvent
evaporation, the residue was dried in vacuo to give 2 as a pale-yellow oil.
Yield: 84%; 1H NMR (400 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz, 3H), 1.1 (m, 2H), 1.3 (m, 7H), 1.9 (m,
2H), 2.5 (tt, J = 12.2, 3.2 Hz, 1H), 4.5 (s, 2H), 7.2 (d, J = 7.0 Hz, 2H), 7.3 (d, J = 7.0 Hz, 2H)
1,3-Bis[4-(4-propylcyclohexyl)benzyl]imidazolidin-2-one (1)

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A mixture of cyclic urea (1.5 g, 17 mmol), NaH (0.8 g, 34 mmol) and dioxane (100 mL) was
refluxed for 1.5 h. The suspension was cooled to 20°C and then bromide 2 (10 g, 34 mmol) was
added. The mixture was refluxed for 5 hrs, cooled to r.t. and filtered. The solvent was evaporated
from the filtrate, to afford a white solid 1 which was purified by recrystallization from
dichloromethane-pentane.
1
Yield: 70%; mp 180-190°C. H NMR (399.8 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz), 1.0 (m, 4H), 1.3
(m, 14H), 1.9 (m, 8H), 2.4 (m, 2H), 3.2 (s, 4H), 4.4 (s, 4H), 7.16 (d, J = 8.2 Hz, 4H), 7.19 (d, J = 8.2
Hz, 4H). 13C NMR (100.5 MHz, CDCl3) δ: 14.5, 20.1, 33.7, 34.4, 37.1, 39.8, 44.4, 48.3, 127.1,
128.3, 134.8, 147.2, 161.2 (C=O)
4-(1,2-Dibromoethyl)-4'-propylbi(cyclohexane) (7)
To a solution of 6 (0.2 mol) in hexane (30 mL), 1 equiv. of bromine was added slowly at ambient
temperature, and then the reaction mixture was stirred for 3 hrs. Hexane was removed in vacuo and
the dibromide 7 was obtained as yellow crystals which were used in the next step without further
purification.
Yield: 98%; mp. 51-53 ºC; 1H NMR (399.8 MHz, CDCl3): δ 0.86 (t, J = 6.8 Hz, 3H, CH3), 0.90-
1.44 (m, 14H), 1.62-1.86 (m, 10H), 3.74 (A-part ABX, J = 10.4, 9.6 Hz, 1H), 3.81 (B-part ABX, J
= 10.4, 5.6 Hz, 1H), 4.16 (m, 1H).
4-(1,2-Diazidoethyl)-4'-propylbi(cyclohexane) (8)
o
A mixture of 7 (0.2 mol) and NaN3 (2 mol) in DMSO (30 mL) was stirred at 95 C for 10 h. Than
the mixture was diluted with 150 mL of water and extracted with hexane (5×20 mL). The organic
layers were combined, washed with brine and dried over NaSO4. The solvent was removed and the
residue was purified by column chromatography eluting with n-hexane, giving pure 8 as an yellow
oil.
1
Yield: 65%; H NMR (400 MHz, CDCl3): δ 0.86 (t, J = 6.8 Hz, 3H, CH3), 0.79-1.20 (m, 13H),
1.22-1.34 (m, 2H), 1.45 (m, 1H), 1.62-1.86 (m, 8H), 3.25 (m, 1H), 3.34 (A-part ABX, J = 12.8, 7.8
Hz, 1H), 3.44 (B-part ABX, J = 12.8, 3.7 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 14.5, 20.1, 28.9,
29.4, 29.5, 29.9, 30.1, 33.6, 37.7, 39.9, 40.4, 43.0, 43.3, 53.3, 67.7.
1-[4'-Propylbi(cyclohexan)-4-yl]ethane-1,2-diamine (9)
A mixture of 8 (0.2 mol) and 0.05 equiv. of Pd (10% on C) in EtOH (30 mL) was stirred overnight
under H2 atmosphere at room temperature. The Pd/C was filtered off and EtOH was removed giving
pure 9 as an yellow oil.
1
Yield: 87%; H NMR (400 MHz, CDCl3): δ 0.79-2.0 (m, 31H), 2.44 (m, 2H), 2.77 (m, 1H). 13C
NMR (100 MHz, CDCl3): δ 14.5, 20.1, 28.7, 29.9, 30.0, 30.1, 33.7, 37.7, 39.9, 42.3, 43.4, 46.1,
58.7.
N,N'-1-[4'-Propylbi(cyclohexan)-4-yl)ethane-1,2-diyl]diformamide (10)

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14
A mixture of 9 (0.02 mol), 10 equiv. of ethyl formate in 20 mL of CHCl3 was refluxed for 24 hrs.
All volatiles were removed at reduced pressure and the residue was crystallized from acetone giving
a crystalline product containing ~80% of the desired 10 (according to NMR). This mixture was used
in the next step without further purification.
Yield: 67%; 1H NMR (400 MHz, DMSO-d6): δ 0.80 (t, J = 6.8 Hz, 3H, CH3), 0.77-1.00 (m, 10H),
1.08 (m, 2H), 1.23 (m, 2H), 1.65 (m, 10H), 2.98 (m, 1H), 3.27 (m, 1H), 3.66 (m, 1H), 7.70-8.05 (m,
4H, NH, C(O)H).
N,N-Dimethyl-1-[4'-propylbi(cyclohexan)-4-yl]ethane-1,2-diamine (11)
To a suspension of LiAlH4 (0.035mol) in 50 mL of dry THF, diformamide 10 (0.02 mol) was added
portionwise under stirring and cooling with an ice bath. The reaction mixture was refluxed for 15 h.
Than 5 mL of water was dropwise added. All precipitates were filtered off and washed with diethyl
ether. The organic layers were extracted with water (5×10 mL), dried over NaOH. The solvent was
removed giving 11 as an yellow oil, which was used in the next step without purification.
Yield: 74%; 1H NMR (400 MHz, CDCl3): δ 0.86 (t, J = 6.8 Hz, 3H, CH3), 0.79-1.20 (m, 10H), 1.11
(m, 2H), 1.28 (m, 2H), 1.42 (bs, 2H, NH), 1.61-1.80 (m, 10H), 2.25 (m, 1H), 2.39 (A-part ABX, J =
12.0 Hz, 8.4 Hz, 1H), 2.38 (s, 3H, CH3), 2.40 (s, 3H, CH3), 2.59 (B-part ABX, J = 12.0 Hz, 4.0 Hz,
1H); 13C NMR (100 MHz, CDCl3): δ 14.5, 20.1, 25.7, 28.7, 30.0, 30.2, 33.7, 34.8, 36.9, 37.7, 39.3,
39.9, 43.5, 43.6, 52.5, 64.2, 68.1.
1,3-Dimethyl-4-[4'-propylbi(cyclohexan)-4-yl]imidazolidin-2-one (5)
To a stirred solution of 11 (24 mmol) in 100 mL of THF, two equiv. of 2.5M n-BuLi in hexanes
were dropwise added. The reaction mixture was stirred at ambient temperature for 2 hrs. Then the
reaction mixture was cooled to -30 ºC and one equiv. of ethyl chloroformate (2.61 g, 24 mmol)
dissolved in 10 mL of THF was dropwise added upon stirring. The resulting solution was stirred at
room temperature overnight and filtered through a glass frit. The solution was washed with brine,
and dried over NaSO4. The solvent was removed, and the residue was purified by chromatography
(eluent: CHCl3/AcOEt = 10/1), giving pure 5 as white crystals.
Yield: 56%; mp 69-80 ºC 1H NMR (400 MHz, CDCl3): δ 0.85 (t, J = 6.8 Hz, 3H, CH3), 0.79-1.08
(m, 10H), 1.12 (m, 2H), 1.29 (m, 2H), 1.51-1.82 (m, 10H), 2.73 (s, 3H, CH3), 2.75 (s, 3H, CH3),
2.97 (A-part ABX, J = 8.7, 7.8 Hz, 1H), 3.19 (B-part ABX, J = 8.7, 7.0 Hz, 1H), 3.31 (m, 1H); 13C
NMR (100 MHz, CDCl3): δ 14.5, 20.1, 25.6, 28.8, 29.4, 29.9, 30.1, 31.3, 33.6, 37.7, 38.5, 39.9,
43.4, 43.6, 47.0, 59.7, 161.8.
1-Allyl-1,3-dimethylurea (13)
An oven- or flame-dried round bottom flask equipped with a stirbar was cooled under a stream of
nitrogen and charged with N-allylamine 15 (0.02 mol), the appropriate isocyanate (0.022 mol), and
CH2Cl2 (20 mL). The reaction was stirred at room temperature until the starting amine was

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15
completely consumed as monitored by TLC analysis. The reaction mixture was then concentrated in
vacuo and the crude product was purified by column chromatography on silica gel giving 13 as an
yellow oil (eluent: CH2Cl2).
Yield: 82%; 1H NMR (400 MHz, CDCl3): δ 2.84 (s, 3H, CH3), 2.78 (d, J = 6.0 Hz, 3H, CH3), 3.85
(dm, J = 6.5 Hz, 2H, CH2), 4.39 (bs, 1H, NH), 5.12 (m, 1H), 5.15 (s, 1H), 5.76 (m, 1H).
1,3-Dimethyl-4-[4-(4-propylcyclohexyl)benzyl]imidazolidin-2-one (12)
An oven- or flame-dried Schlenk tube equipped with a stirbar was cooled under a stream of nitrogen
and charged with Pd2(dba)3 (1 mol % complex, 2 mol % Pd), Xantphos (2 mol %), NaOtBu (1.2
equiv), N-allylurea 13 (1.0 equiv), and the aryl bromide 14 (1.2 equiv). The tube was purged with
nitrogen and toluene (4ml/mmol of urea) was then added. The urea was added at the same time as
toluene. The Schlenk tube was then heated to 110 °C with stirring until total consumption of the
starting materials as judged by GC of the reaction mixture. The mixture was then cooled to r.t.,
saturated aqueous NH4Cl (4–6 mL/mmol substrate) was added, and the mixture was extracted with
methylene chloride (3×7 mL). The combined organic extracts were dried over Na2SO4, filtered and
concentrated in vacuo. The crude product was purified by chromatography on silica gel (eluent:
CH2Cl2) to give 12 as an yellow oil.
Yield: 56%; 1H NMR (400 MHz, CDCl3): δ 0.89 (t, J = 7.3 Hz, 3H, CH3), 1.02 (m, 2H), 1.16-1.48
(m, 7H), 1.8-1.9 (m, 4H), 2.43 (tt, J = 11.9, 3.2 Hz, 1H), 2.55 (dd, J = 13.7, 9.2 Hz, 1H), 2.71 (s,
3H, CH3), 2.79 (s, 3H, CH3), 2.91 (dd, J = 8.7, 7.8 Hz, 1H), 3.08 (dd, J = 15.6, 4.6 Hz, 1H), 3.17 (t,
13
J = 8.7 Hz, 1H), 3.57 (m, 1H), 7.05 (d, J = 8.0 Hz, 2H), 7.13 (d, J = 8.0 Hz, 2H); C NMR (100
MHz, CDCl3): δ 14.5, 20.1, 29.8, 31.3, 33.6, 34.4, 37.1, 38.4, 39.8, 44.3, 50.8, 57.2, 127.2, 129.1,
134.1, 146.5, 161.8.
General procedure for the synthesis of chloroamidinium chlorides (24a-d): N,N´-Disubstituted
cyclic urea (6 mmol) was dissolved in toluene (50 mL) and oxalyl chloride (7.6 g, 5.2 mL, 60
mmol) was added. The resulting mixture was stirred at 80 °C for 12 hrs. The white precipitate was
then filtered off under an inert atmosphere, washed with anhydrous Et2O and dried in vacuo to give
the pure chloride as a white solid.
2-Chloro-1,3-bis[4-(4-propylcyclohexyl)benzyl]-4,5-dihydro-1H-imidazol-3-ium chloride (24b)
Yield: 82%; 1H NMR (400 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz), 1.0 (m, 4H), 1.3 (m, 14H), 1.9 (m,
8H), 2.4 (m, 2H), 3.4 (s, 4H), 4.9 (s, 4H), 7.18 (d, J = 8.2 Hz, 4H), 7.22 (d, J = 8.2 Hz, 4H). 13C
NMR (100 MHz, CDCl3) δ: 14.5, 20.1, 33.6, 34.4, 37.1, 39.8, 44.3, 47.7, 53.2, 127.5, 128.7, 131.7,
148.4, C2 not observed.
2-Chloro-1,3-dimethyl-4-[4-(4-propylcyclohexyl)benzyl]-4,5-dihydro-1H-imidazol-3-ium chloride
(24c)

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16
Yield: 89%; 1H NMR (400 MHz, CDCl3): δ 0.86 (t, J = 7.3 Hz, 3H, CH3), 0.80-1.18 (m, 13H), 1.29
(m, 2H), 1.49 (m, 1H), 1.61-1.90 (m, 8H), 3.27 (s, 3H), 3.30 (s, 3H), 3.69 (m, 1H), 4.55 (m, 1H),
4.69 (m, 1H).
2-Chloro-1,3-dimethyl-4-[4'-propyl-1,1'-bi(cyclohexyl)-4-yl]-4,5-dihydro-1H-imidazol-3-ium
chloride (24d)
Yield: 79%; 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 7.3 Hz, 3H, CH3), 1.03 (m, 2H), 1.16-1.48
(m, 7H), 1.80-1.90 (m, 4H), 2.43 (tm, J = 8.7 Hz, 1H), 3.05 (A-part ABX, J = 14.2, 7.8 Hz, 1H),
3.15 (B-part ABX, J = 14.2, 5.0 Hz, 1H), 3.15 (s, 3H, CH3), 3.30 (s, 3H, CH3), 3.77 (dd, J = 11.0
6.9 Hz, 1H), 4.40 (t, J = 11.5 Hz, 1H), 4.93 (m, Hz, 1H), 7.10 (d, J = 8.2 Hz, 2H), 7.16 (d, J = 8.2
Hz, 2H);
N-{Chloro[4-(4-propylcyclohexyl)phenyl]methylene}-N-methylmethanaminium chloride (26b)
Yield: 82%; 1H NMR (400 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz, 3H), 1.1 (m, 2H), 1.3 (m, 8H, CH),
1.9 (m, 2H), 2.5 (t, J = 12.4 Hz, 1H), 3.3 (s, 6H), 7.2 (d, J = 8.2 Hz, 2H), 7.3 (d, J = 8.2 Hz, 2H)
General procedure for the synthesis of difluorides (23b-d):
To a solution of imidazolium chloride 24b-d (3.5 mmol) in anhydrous acetonitrile 60 mL, (10
equiv.) of spray dried potassium fluoride were added. The reaction mixture was heated with stirring
at 85 ºC under argon for 12 hours. After cooling to room temperature, insoluble solids (KCl, KF)
were filtered off under an inert atmosphere. The solids were washed three times with anhydrous
Et2O. The filtrate was concentrated in vacuo to give pure difluoride.
2,2-Difluoro-1,3-bis[4-(4-propylcyclohexyl)benzyl]imidazolidine (23b)
Yield: 76%; white hygroscopic solid; 1H NMR (400 MHz, CDCl3) δ: 0.9 (t, J = 7.3 Hz), 1.0 (m,
4H), 1.3 (m, 14H), 1.9 (m, 8H), 2.4 (m, 2H), 2.9 (s, 4H), 4.1 (s, 4H), 7.16 (d, J = 8.2 Hz, 4H), 7.19
(d, J = 8.2 Hz, 4H). 19F NMR (376 MHz, CDCl3) δ: -67.3 (s, 2F).
2,2-Difluoro-1,3-dimethyl-4-[4-(4-propylcyclohexyl)benzyl]imidazolidine (23c)
Yield: 86%; colorless oil; 19F NMR (376 MHz, CDCl3): δ -73 (bs)
2,2-Difluoro-1,3-dimethyl-4-[4'-propyl-1,1'-bi(cyclohexyl)-4-yl]imidazolidine (23d)
Yield: 83%; colorless oil; 19F NMR (376 MHz, CDCl3): δ -73 (bs)
General procedure for the synthesis of difluorides (25a,b):
A solution of benzamide 21a or b (67 mmol) in dichloromethane (60 mL) was placed into a 2-neck
250 mL flask equipped with a reflux condenser. Oxalyl chloride (74 mmol) was slowly added and
the reaction mixture was refluxed for 1 h. After reaching room temperature, triethylamine
trihydrofluoride (50 mmol) was added, followed by dropwise addition of triethylamine (100 mmol).
The reaction mixture was diluted with 40 mL of dichloromethane and stirred for 3 hrs. Compounds
25a or b were obtained by fractional distillation of the reaction mixture under reduced pressure.
1,1-Difluoro-N,N-dimethyl-1-phenylmethanamine (25a)

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17
1
Yield: 83%; colorless liquid; bp 50-51 °C/0.001 Bar; H NMR (400 MHz, CDCl3) δ: 2.5 (s, 6H,
CH3), 7.4-7.6 (m, 5H, Ph); 19F NMR (376 MHz, CDCl3) δ: -85.7 (s, 2F).
1,1-Difluoro-N,N-dimethyl-1-[4-(4-propylcyclohexyl)phenyl]methanamine (25b)
Yield: 90%; colorless liquid; bp 100-102 °C/0.001 Bar; 19F NMR (376 MHz, CDCl3) δ: -67.5 (s,
2F)
N,N,N',N'-Tetraethyl-1-[4-(4-propylcyclohexyl)phenyl]phosphinediamine (30)
A solution of 28 (10g, 36 mmol) in dry THF (40 mL) was slowly added into a 250 mL 2-neck flask
equipped wit a reflux condenser, to a suspension of magnesium turnings (0.87 g, 36 mmol) in THF
(20 mL). The reaction mixture was refluxed for 1h and then cooled to -20 °C. A solution of
ClP(NEt2)2 (7.6 g, 36 mmol) in THF (15 mL) was slowly added. The reaction mixture was stirred
for 16 h, during which it was allowed to reach room temperature. After removing of all volatiles
under reduced pressure, the residue was dissolved in Et2O (100 mL) and filtered through a celite to
give a pale yellow solution of 30.
31P NMR (161 MHz, Et2O): δ 98.1 (s)
Dichloro[4-(4-propylcyclohexyl)phenyl]phosphine (27)
Dry gaseous HCl was passed through a solution of 30 (11g, 36 mmol) in Et2O (100 mL) at r.t. until
the reaction was completed (monitoring by 31P NMR). The reaction mixture was then passe through
a P4 glass frit and all volatile components were removed under reduced pressure. The residue was
washed with small amount of Et2O. Drying in vacuo gave 27 as a pale yellow solid.
Yield: 88%; 31P NMR (161 MHz, Et2O): δ 162.6 (s)
General procedure for the synthesis of PF5 carbene complexes (32a,c,d) and (33a): Onto a frozen
solution (-196 °C) of an appropriate difluoride 23b,c,d ; 25b (5 mmol) in dry diethyl ether (20 mL),
an equimolar amount of phosphorus trifluoride was condensed using a vacuum line. The resulting
mixture was then left with stirring overnight and concentrated in vacuo. The precipitate was filtered
off, washed with cold ether, ethanol and hexane to give the corresponding adduct which was
additionally recrystallized from acetonitrile.
1,3-Bis[4-(4-propylcyclohexyl)benzyl]imidazolin-2-ylidene – phosphorus(V) pentafluoride adduct
(32a)
1
Yield: 80%; white crystals; mp 235-245°C; H NMR (400 MHz, CDCl3): δ 0.9 (t, J = 7.3 Hz), 1.0
(m, 4H), 1.3 (m, 14H), 1.9 (d, J = 11.0 Hz, 8H), 2.5 (m, 2H), 3.4 (s, 4H), 4.9 (s, 4H), 7.18 (d, J =
8.2 Hz, 4H), 7.23 (d, J = 8.2 Hz, 4H); 13C NMR (100 MHz, CDCl3): δ 14.5, 20.1, 33.6, 34.4, 37.1,
39.8, 44.3, 48.2, 52.5, 127.9, 128.7, 149.3, 155.0, C2 not observed; 19F NMR (376 MHz, CDCl3): δ -
75.2 (dquint, JFP = 768.7 Hz, JFF = 53.4 Hz, PF4F), -53.4 (dd, JPF = 797.6 Hz, JFF = 53.5 Hz, PF4F);
31P NMR (161 MHz, CDCl3): δ -153.3 (dquint, JPF = 800.4 Hz, JPF = 770.4 Hz, PF4F); HRMS (ESI,
positive): Calcd for C36H55F5N2PNa 664.3920 [M+Na]+, found: 664.3914.

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18
1,3-Dimethyl-4-{4'-propyl-[1,1'-bi(cyclohexan)]-4-yl}imidazolin-2-ylidene
-
phosphorus(V)
pentafluoride adduct (32c)
Yield: 76%; white crystals; mp 180-182 °C; 1H NMR (400 MHz, Acetone-d6): δ 0.84 (t, J = 7.3 Hz,
3H, CH3), 0.91-1.18 (m, 13H), 1.29 (m, 2H), 1.43 (m, 1H), 1.57 (m, 1H), 1.65-1.85 (m, 7H), 3.20
(s, 6H), 3.64 (m, 1H), 3.89 (m, 1H), 4.02 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 13.9, 19.7, 26.1,
29.3, 29.9, 30.8, 31.5, 31.9, 34.5, 37.7, 38.2, 40.5, 41.4, 43.1, 53.5 (d, JCP = 11.0 Hz), 61.2 (d, JCP
=
10.3 Hz); 31P NMR (162 MHz, Acetone-d6): δ -150.27 (quint,d, J = 796.6, 760.1 Hz); 19F NMR
(376 MHz, Acetone-d6): δ -56.6 (dd, JFP = 758.6 Hz, JFF = 50.6 Hz, 4F), -74.7 (dquint, JFP = 758.2
Hz, JFF = 50.6 Hz, 1F); Anal. Calc. for C20 H36 F5 N2 P: C, 55.80%; H, 8.43%; N, 6.51%. Found: C,
55.91%; H, 8.36%; N(6.41%).
1,3-Dimethyl-4-[4’-(4-propylcyclohexyl)benzyl]imidazolin-2-ylidene - phosphorus(V) pentafluoride
adduct (32d)
1
Yield: white crystals; mp 192-195 °C; H NMR (400 MHz, Acetone-d6): δ 0.88 (t, J = 7.3 Hz, 3H,
CH3), 1.07 (m, 2H), 1.00-1.11 (m, 2H), 1.15-1.23 (m, 2H), 1.31 (m, 3H), 1.47 (m, 2H), 1.83 (m,
4H), 2.45 (tm, J = 12.4 Hz, 1H), 2.82 (dd, J = 13.7 Hz, 8.7 Hz, 1H), 3.07 (s, 3H, CH3), 3.21 (dd, J =
13.7 Hz, 4.1 Hz, 1H), 3.33 (s, 3H, CH3), 3.55 (dd, J = 11.9 Hz, 6.4 Hz, 1H), 3.85 (t, J = 11.5 Hz,
1H), 4.33 (m, Hz, 1H), 7.12-7.25 (m, 4H); 13C NMR (101 MHz, Acetone-d6): δ 13.8, 19.8, 33.5,
34.3, 34.3, 36.6, 36.9, 39.7, 44.2, 55.7 (d, JCP = 10.6 Hz), 63.4 (d, JCP = 9.7 Hz), 127.1, 129.5,
133.0, 146.6; 31P NMR (162 MHz, Acetone-d6): δ -150.47 (quint,d, J = 796.5, 758.8 Hz); 19F NMR
(376 MHz, Acetone-d6): δ -56.8 (dd, JFP = 796.2 Hz, JFF = 50.6 Hz, 4F), -74.6 (dquint, JFP = 796.2
Hz, JFF = 50.6 Hz, 1F); Anal. Calc. for C21 H32 F5 N2 P: C, 57.53%; H, 7.36%; N, 6.39%. Found: C,
57.45%; H, 7.28%; N, 6.32%.
Dimethylamino[4-(4-propylcyclohexyl)phenyl]methylidene - phosphorus(V) pentafluoride adduct
(33a)
1
Yield: 53 %; white solid, mp 170–172°C. H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 7.3 Hz, 3H,
CH3), 1.04 (m, 2H), 1.19-1.49 (m, 7H), 1.8-1.9 (m, 4H), 2.53 (tt, J = 11.9, 3.2 Hz, 1H), 3.1 (s, 3H,
CH3), 3.9 (s, 3H, CH3), 7.1 (d, J = 7.8 Hz, 2H), 7.3 (d, J = 8.2 Hz). 19F NMR (376 MHz, CDCl3): δ
-59.4 (dd, JFP 814.9 Hz, JFF 49.1 Hz); -73.3 (dquint, JFP 751.4 Hz, JFF 33.2 Hz). 31P NMR (161
MHz, CDCl3): δ -149.8 (dquint, JPF 815.4 Hz, JPF 744.2 Hz); HRMS (ESI, positive): Calcd for
C18H28F5NPNa 407.1777 [M+Na]+, found: 407.1772.
General procedure for the synthesis of PF4Ph carbene complexes (32b, 33b):
Phenyldifluorophosphine (3.4 mmol) was added to a solution of difluoride (3.2 mmol) in 30 mL of
anhydrous Et2O or THF at -40°C. After warming to room temperature the solid formed was
collected by filtration yielding 32b or 33b.

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19
1,3-Bis[4-(4-propylcyclohexyl)benzyl]imidazolin-2-ylidene
adduct (32b)
–
tetrafluoro(phenyl)phosphorane
1
Yield: 80%; white solid, mp 133–136 °C; H NMR (400 MHz, CDCl3) δ: 0.89 (t, J = 7.3 Hz, 6H,
CH3), 1.04 (m, 4H), 1.18-1.48 (m, 14H), 1.8 (m, 8H), 2.4 (tt, J = 11.9 Hz, 3.2 Hz, 2H), 3.4 (s, 2H),
3.5 (s, 2H), 7.14-7.1 (m, 11H), 7.7 (d, J = 7. Hz, 1H), 7.8 (d, J = 6.8 Hz, 1H); 19F NMR (376 MHz,
CDCl3): δ -42.2 (d, JFP 871.4 Hz); 31P NMR (161 MHz, CDCl3): δ -138.9 (quint, JPF 800.4 Hz);
HRMS (ESI, positive): Calcd for C42H60F4N2PNa 722.4327 [M+Na]+, found: 722.4321.
Dimethylamino[4-(4-propylcyclohexyl)phenyl]methylidene
-
tetrafluoro(phenyl)phosphorane
adduct (33b)
1
Yield: 45 %; white crystals; m.p. 164–167 °C; H NMR (400 MHz, CDCl3): δ 0.89 (t, J = 7.3 Hz,
3H, CH3), 1.04 (m, 2H), 1.18-1.48 (m, 7H), 1.8 (m, 4H), 2.4 (tt, J = 11.9, 3.2 Hz, 1H), 3.1 (s, 3H,
19
CH3), 3.9 (s, 3H, CH3), 7.15-7.28 (m, 7H), 7.64 (d, J = 7.6 Hz, 1H), 7.69 (d, J = 6.8 Hz, 1H). F
NMR (376 MHz, CDCl3) δ: -47.9 (d, JFP = 887.2 Hz); 31P NMR (161 MHz, CDCl3): δ -140.8
(quint, JPF 886.4 Hz); HRMS (ESI, positive): Calcd for C24H33F4NPNa 465.2184 [M+Na]+, found:
465.2178.
General procedure for the synthesis of carbene complexes using dichlorophosphines (32e, 33c)
A solution of 27 (17 mmol) in dry THF (70 mL) was placed into a 2-neck 250 mL flask equipped
with a septum. At -40 °C a solution of difluoride 23a; 25a (49 mmol) in THF (15 mL) was slowly
added through the septum. During a period of 18 hrs the reaction was allowed to reach r.t. All
volatiles were then removed under reduced pressure and the residue was treated with cold water
(100 mL) and stirred for an additional 1 h. The aqueous solution was decanted and the insoluble
residue was washed with addition portion of water, followed by ethanol and diethyl ether. Drying in
vacuo gave the desired product 32e or 33c. Compound 32e was additionally crystallized by slow
diffusion of diethyl ether into a solution of 32e in acetonitrile.
1,3-Dimethylimidazolin-2-ylidene - tetrafluoro[4-(4-propylcyclohexyl)phenyl]phosphorane adduct
(32e)
Yield: 64%; white crystals; mp 165-166 °C (dec.); 1H NMR (400 MHz, CDCl3): δ 0.9-1.0 (m, 3H),
0.9-1.1 (m, 2H), 1.1-1.2 (m, 2H), 1.3-1.4 (m, 2H), 1.4-1.5 (m, 2H), 1.8-1.9 (m, 4H), 2.4-2.5 (m,
1H), 3.3 (s, 6H), 3.7 (s, 4H), 7.1-7.2 (m, 2H), 7.6-7.7 (m, 2H); 19F NMR (376 MHz, CDCl3): δ -45.0
(d, JFP = 865 Hz); 31P NMR (161 MHz, CDCl3): δ -139.1 (quint, JPF 885 = Hz).
(Dimethylamino)(phenyl)methylidene
–
tetrafluoro[4-(4-propylcyclohexyl)phenyl]phosphorane
(33c)
Yield: 64%; white crystals; mp 110-111 °C (dec.); 1H NMR (400 MHz, CDCl3): δ 0.8-0.9 (m, 3H),
0.9-1.1 (m, 2H), 1.1-1.5 (m, 6H), 1.8-1.9 (m, 4H), 2.3-2.5 (m, 1H), 3.1 (s, 3H), 4.0 (s, 3H), 7.0-7.1

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20
(m, 2H), 7.2-7.3 (m, 2H), 7.4-7.5 (m, 3H), 7.5-7.6 (m, 2H); 19F NMR (376 MHz, CDCl3): δ -47.1
(d, JFP = 886 Hz); 31P NMR (161 MHz, CDCl3): δ -140.1 (quint, JPF 887 = Hz).
4. Acknowledgements
We gratefully acknowledge Dr. Bassem Bassil (Jacobs University Bremen) for the X-Ray
measurement and Ms. Anja Müller (Jacobs University Bremen) for measuring mass spectra.
5. References
(1) For general reviews on transient carbenes, see: (a) Carbene Chemistry; Kirmse, W., Ed.;
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