A phosphenium cation supported by a seven-membered thiophene based ring system

Article abstract of DOI:10.1139/cjc-2013-0015

A novel diamine ligand containing a simple thiophene ring in the backbone has been synthesized. Substitution at the nitrogen atoms with either 2,4,6-trimethylphenyl (Mes) or 2,6-diisopropylphenyl (Dipp) was varied via a condensation reaction between the corresponding aniline and 3,4- diformylthiophene, giving two different ligand derivatives. In onwards chemistry that targeted the cyclic diaminochlorophosphines, the substitution at phosphorus was dependent on the ligand used. For example, when a stoichiometric reaction between PCl₃ and thiophene-3,4 diyldimethaneamine (R = Mes) was carried out, the synthesis of a bis-substituted diphosphino-product was isolated. If the R = Dipp ligand derivative was employed, both a 2:1 and 1:1 stoichiometric reaction between PCl₃ and the diamine was observed. Nevertheless, the cyclic diaminochlorophosphine (i.e., 1:1 stoichiometry) for R = Dipp was isolated in high yields and the synthesis of the corresponding phosphenium cation was achieved and structurally characterized.

Full text of DOI:10.1139/cjc-2013-0015

691
ARTICLE
A phosphenium cation supported by a seven-membered thiophene
based ring system
Jacquelyn T. Price, Nathan D. Jones, and Paul J. Ragogna
Abstract: A novel diamine ligand containing a simple thiophene ring in the backbone has been synthesized. Substitution at the
nitrogen atoms with either 2,4,6-trimethylphenyl (Mes) or 2,6-diisopropylphenyl (Dipp) was varied via a condensation reaction
between the corresponding aniline and 3,4-diformylthiophene, giving two different ligand derivatives. In onwards chemistry
that targeted the cyclic diaminochlorophosphines, the substitution at phosphorus was dependent on the ligand used. For
example, when a stoichiometric reaction between PCl3 and thiophene-3,4 diyldimethaneamine (R = Mes) was carried out, the
synthesis of a bis-substituted diphosphino- product was isolated. If the R = Dipp ligand derivative was employed, both a 2:1 and
1:1 stoichiometric reaction between PCl3 and the diamine was observed. Nevertheless, the cyclic diaminochlorophosphine (i.e.,
1:1 stoichiometry) for R = Dipp was isolated in high yields and the synthesis of the corresponding phosphenium cation was
achieved and structurally characterized.
Key words: thiophene, phosphenium, diaminochlorophosphine, diamine.
Résumé : On a synthétisé un nouveau ligand diamine dont le squelette contient un noyau thiophène simple. On a procédé a` la
substitution d’un groupe 2,4,6-triméthylphényle (Mes) ou d’un groupe 2,6-diisopropylphényle (Dipp) sur les atomes d’azote par
une réaction de condensation entre l’aniline correspondante et le 3,4-diformylthiophène pour obtenir deux dérivés différents du
ligand. Lors de réactions chimiques ultérieures ayant pour cible les diaminochlorophosphines cycliques, la substitution sur
le phosphore dépendait du ligand utilisé. Par exemple, une réaction stœchiométrique entre PCl3 et la thiophène-3,
4 diyldiméthanamine (R = Mes) a donné la synthèse d’un produit diphosphiné bisubstitué. Lorsqu’on a employé le dérivé R = Dipp
du ligand, on a observé une réaction de stœchiométrie 2:1 ainsi qu’une réaction de stœchiométrie 1:1 entre PCl3 et la diamine.
Néanmoins, on a isolé avec un haut rendement la diaminochlorophosphine cyclique (c. a` d. stœchiométrie 1:1) obtenue pour
R = Dipp, et on a synthétisé le cation phosphénium correspondant et caractérisé sa structure. [Traduit par la Rédaction]
Mots-clés : thiophène, phosphénium, diaminochlorophosphine, diamine.
plications in broader arenas. Examples have surfaced within the
past few years in utilizing main group elements in the construc-
Introduction
The utility of the N-heterocyclic carbenes (NHCs) has given rise
to a wide range of chemistries, from functional and structurally
diverse metal coordination complexes to enhancing catalytic
properties within transition metal catalysis, and in some cases
defining new directions in materials chemistry.1–5 The NHCs
share many similarities with their heavier group 15 analogue the
N-heterocyclic phosphenium cations (NHPs), as they are isovalent
and isolobal to each other; however, NHPs are the electronic in-
verse of the NHCs.6,7 The phosphorus atom in an NHP is dicoordi-
nate and cationic, formally possesses a lone pair of electrons and
an empty ␲ orbital, and the central phosphorus is formally in the
+3 oxidation state. The cationic charge at the phosphorus center is
normally stabilized by two flanking amino substituents, and it is
these combined components that dominate the chemistry of the
NHPs. The cations are weak ␴ donors and strong ␲ acceptors, thus
enabling NHPs to be good Lewis acidic ligands for electron-rich
transition metals.8–10
The NHP framework typically consists of four-, five-, or six-
membered rings with phosphorus being the lone reactive site.
The main focus in this field has been to harness the chemistry of
the P+ centre; however, a shifting philosophy within main group
chemistry as a whole (which includes phosphenium chemistry)
has moved from studying purely the fundamental structure,
bonding, and reactivity of these species to their potential for ap-
tion of OLEDs and within catalysis/small molecule activation by
taking advantage of the unique properties that these main group
centres posses.11–15 Efforts in these fields by ourselves and other
research groups have centred on designing new ligand sets con-
taining thiophene, a ubiquitous building block in the area of
redox active and fluorescent materials.16,17 Ultimately such ar-
chitectures target the photoluminescent and polymerizable prop-
erties of thiophene, yet look to tune the photophysics of the
overall construct by varying the main group element centre. Our
group has recently designed a diamine, which contains a fused
conjugated bithiophene backbone and has demonstrated its abil-
ity to stabilize pnictenium cations (Pn = P, As, and Sb) and NHCs
(Fig. 1, compound i).18,19 Cowely et al. have developed a novel
redox active diimine with pendent thiophene rings in the 2 and 3
position and have used this ligand to coordinate a phosphenium
cation with a triiodide counter ion.20 Furthermore, Cowley and
Bielawski have used that same diimine to synthesize polymers
containing NHCs orthogonal to the polymer backbone (Fig. 1,
compound ii).21,22 Although there are many different ligands able
to support main group elements, there is a void in those that can
combine the unique reactivity of the members of the p-block with
the desired photophysical and polymerizable properties that are
required for the design of new materials. A need exists to develop
Received 8 January 2013. Accepted 1 March 2013.
J.T. Price, N.D. Jones, and P.J. Ragogna. Department of Chemistry and Center for Advanced Materials and Biomaterials Research (CAMBR), The University of Western University, London,
ON N6A 3K7, Canada.
Corresponding author: Paul J. Ragogna (e-mail: pragogna@uwo.ca).
Can. J. Chem. 91: 691–697 (2013) dx.doi.org/10.1139/cjc-2013-0015
Published at www.nrcresearchpress.com/cjc on 19 March 2013.

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Can. J. Chem. Vol. 91, 2013
Fig. 1. Previously synthesized thiophene ligands coordinated to main group elements (i and ii).
ligands that can meet these requirements while continuing to
push main group chemistry into the applied research fields. In
this context, we have synthesized two new chelating diimino-
(2Mes and 2Dipp) and diamino- (3Mes and 3Dipp) ligands with a
thiophene unit in the backbone, where 3Dipp is able to support a
phosphenium cation (7). This is the first synthesis and complete
characterization of a seven-membered phosphenium cation and
aids in identifying new opportunities in the unique structure,
bonding, and reactivity of phosphorus.
subsequent diffraction experiments revealed that the 1:2 stoichi-
ometric reaction of diamine:phosphine occurred and explained
the apparent lack of reactivity upon the addition of the halide-
abstracting agent (Scheme 3).
Utilizing the ligand 3Dipp yielded differing results from those of
3Mes, where a 3:1:1 stoichiometric amount of N-methylmorpholine,
PCl3, and 3Dipp was stirred for 3 h at –78 °C and then warmed to room
temperature and stirring was continued for 48 h. The reaction
progress was monitored by 31P{1H} NMR spectroscopy, where two
separate singlets emerged as the reaction proceeded (␦p = 152 and
Results and discussion
␦
= 155). The signal slightly upfield (␦p = 152) was tentatively
p
Synthesis
assigned to the 1:1 stoichiometric reaction of PCl3 with the di-
amine (3Dipp), ultimately yielding the cyclic diaminochlorophos-
phine (5) in 80%. The more downfield signal (␦p = 155) was assigned
to the 2:1 reaction between PCl3 and the diamine, giving the bis
(amino)dichlorophosphine (6), which was later confirmed by sin-
gle crystal X-ray diffraction experiments. Compounds 5 and 6 had
similar solubilities and the separation of compound 5 from 6
proved to be very difficult. However, changing the solvent to tol-
uene and slowing the addition of a 0.043 mol L−1 toluene solution
of PCl3 (1 mL h−1 over 10 h), the selective synthesis of the cyclic
diaminochlorophosphine (5) was achieved in a 90% isolated yield.
Subsequent dehalogenation of 5 proceeded when an excess of
Me3SiOTf was added. An aliquot from the reaction solution was
examined by 31P{1H} NMR spectroscopy where the original phos-
phorus signal (␦p = 152) was no longer present, and a new peak
appeared farther downfield (␦p = 257), which was tentatively as-
signed to the phosphenium cation (7). The reaction mixture was
then concentrated and washed with Et2O leaving behind a white
powder. A sample of the bulk powder was redissolved and exam-
ined by multinuclear NMR spectroscopy. The 31P{1H} spectrum
revealed a single peak (␦p = 257) consistent with the in situ forma-
tion of the phosphenium cation (Scheme 3).
The thiophene substituted aryldiimines (2Mes and 2Dipp) were syn-
thesized via a condensation reaction between 3,4-diformylthiophene
(1) and the appropriate arylamine in EtOH. The reaction mixtures
were stirred overnight at room temperature and the yellow pre-
cipitates were isolated by filtration and washed with cold EtOH
1
(Scheme 1). Upon examination of the H NMR spectrum of the
redissolved powders, the proton signal from the aldehyde (␦H
=
10.30) was no longer present and a resonance consistent with an
imine appears (␦H = 8.70). Compounds 2Mes and 2Dipp were iso-
lated in 76% and 80% yields, respectively. Single crystals of 2Mes
suitable for X-ray diffraction studies were grown from a concen-
trated solution of CH2Cl2 confirming the targeted connectivity
(see Fig. 3).
Compounds 2Mes and 2Dipp were then reduced to the diamines
3Mes and 3Dipp using 3 stoichiometric equivalents of LiAlH4 in
Et2O (Scheme 2).23 The reaction mixture was stirred overnight at
room temperature and then quenched with a 10% KOH(aq) solu-
tion. The filtrate was collected and concentrated under reduced
pressure yielding a white solid. The bulk powders were redis-
solved in CDCl3 and the corresponding 1H NMR spectrum revealed
that the aldimine proton was no longer present and a new singlet
(␦H = 4.0) appeared, indicative of the methylene protons adjacent
to the thiophene ring. X-ray quality single crystals of 3Dipp were
grown from a concentrated solution of CH2Cl2 confirming the
synthesis of 3Dipp. The 3Mes and 3Dipp derivatives were isolated in
85% and 80% yields, respectively (Scheme 2).
The chlorophosphine 4 was synthesized using a 3:1:1 stoichio-
metric reaction between N-methylmorpholine, PCl3, and 3Mes in
tetrahydrofuran (THF), which resulted in an immediate formation
of a white precipitate. Reaction progress was monitored by obtain-
ing 31P{1H} NMR spectra of aliquots of the reaction mixture that
indicated that the reaction was complete after 15 h, marked by the
disappearance of PCl3 (␦P = 220) and the appearance of a new
single resonance at ␦P = 153. In the proton 1H NMR spectrum, the
methylene protons in the 3 and 4 positions of the thiophene ring
appear as a doublet because of coupling to phosphorus (J1H−31P =
2.8 Hz) and the methyl protons on the aryl rings were no longer
identical, as distinct signals were observed. Subsequent halide ab-
straction using trimethylsilyl trifluoromethanesulfonate (Me3SiOTf)
surprisingly resulted in no shift of the phosphorus signal in the
31P{1H} NMR spectrum. X-ray quality crystals of 4 were grown from
a concentrated CH2Cl2 solution of 4 layered with CH3CN, and
Photophysical properties
The UV-visible absorption spectra of compounds 2–7 are shown
in Fig. 2, with the ␭
and the extinction coefficients listed in
max
Table 1. Compounds 2–7 were all white to light yellow in colour
and had ␭ values in the range of 220–240 nm, attributed to
max
both ␲–␲* and n–␲* transitions. There was little variation in the
UV-visible absorption spectra between the different compounds
and the photophysical properties were dominated by the thio-
phene functionality in the backbone with no considerable influ-
ence from the phosphorus atom.
X-ray crystallography
Single crystals of compounds 2Mes, 3Dipp, 4, 6, and 7 were grown
either by vapour diffusion using various solvent combinations or
from concentrated solutions of CH2Cl2 layered with either CH3CN
or hexanes. Their solid-state structures were determined by single
crystal X-ray diffraction and the relevant crystallographic data,
metrical parameters, and structures are detailed in Table 2, Table 3
and Fig. 3, respectively.
Published by NRC Research Press

Price et al.
693
Scheme 1. Synthesis of 2Mes and 2Dipp diimines.
Scheme 2. Synthesis of compound 3Mes and 3Dipp diamines.
Scheme 3. Synthesis of compounds, 3, 4, 5, 6, and 7. (i) N-methylmorpholine, PCl3, –78 °C, room temperature; (ii) TMSOTf, CH2Cl2, room
temperature.
Examination of the solid-state structure of 2Mes reveals that the
lack of reactivity with halide-abstracting agents observed in both
C
␤–N bond is consistent with a double bond (1.270(4) Å average)24
compounds 4 and 6, as they are more tightly bound to phos-
corresponding to the diimine, and upon reduction of 2Dipp to
3Dipp, the C␤–N bond is reduced to a single bond with a length of
1.464(3) Å average.25 A comparison of the metrical parameters for
compounds 4 and 6 reveals that the P−Cl bond lengths range from
2.0725(13) to 2.1047(14) Å, which are similar to other aminodichlo-
rophosphines, but much shorter compared with previously syn-
thesized cyclic diaminochlorophosphines, where the P−Cl bonds
can range from 2.2 to 2.7 Å.26 These short P−Cl bonds explain the
phorus.27
The solid-state structure of compound 7 shows a well-separated
cation−anion pair with the distance between the oxygen and phos-
phorus being 3.8 Å, well outside the sum of the van der Waals radii
for P−O (ΑvdW = 3.3 Å). The P−N bond is on average 1.625(1) Å,
which is slightly shorter than compounds 4 and 6, but still con-
sistent with other related NHPs.19,23 The bond angle between the
N(1)–P(1)–N(2) is 111.28(8)° and is much larger than those reported
Published by NRC Research Press

694
Can. J. Chem. Vol. 91, 2013
Fig. 2. UV-visible spectrum of compounds 2–7 in a 5 × 10−5 mol L−1 CH2Cl2 solution.
Table 1. UV-visible absorption and ex-
tinction coefficients of compounds 2–7.
photophysical properties of these compounds and there was very
little variation in the UV-visible spectrum.
Compound
␭ (nm) (3 (M−1 cm−1))
General experimental
2Mes
240 nm (2.5 × 104)
332 nm (2.8 × 103)
242 nm (2.8 × 104)
333 nm (2.1 × 103)
223 nm (1.6 × 104)
242 nm (1.6 × 104)
289 nm (2.4 × 103)
241 nm (1.0 × 104)
281 nm (2 × 103)
All manipulations were performed under N2 atmosphere using
standard Schlenk or glovebox techniques unless otherwise stated.
Reagents where obtained from Sigma-Alrich and Alfa Aesar.
CDCl3 was dried over calcium hydride, distilled prior to use, and
stored in the glovebox over 4 Å molecular sieves. All solvents were
dried using an MBraun controlled-atmosphere solvent purifica-
tion system and stored in Straus flasks under a N2 atmosphere or
over 4 Å molecular sieves with the exception of CH3CN, which was
stored over 3 Å molecular sieves in the glovebox. All NMR spectra
were recorded on a Varian INOVA 400 MHz spectrometer (1H =
399.76,13 C = 100.52 MHz, 19F = 376.15 MHz, 31P = 161.85 MHz). All
31P{1H} NMR spectra were recorded relative to an external stan-
dard (85% H3PO4, ␦ = 0.00) at room temperature unless otherwise
stated). UV-visible absorption spectra were recorded over a range
of 220–600 nm using a Varian Cary 300 spectrometer in CH2Cl2.
X-ray diffraction data were collected on a Nonius Kappa CCD or a
Bruker ApexII CCD area detector using graphite monochromatic
Mo−K␣ radiation (␭ = 0.71073 Å). Single crystals were selected un-
der Paratone-N, mounted on nylon loops, and immediately placed
in a cold stream of N2. Structures were solved by direct methods
and refined using full matrix least squares on F2. Hydrogen atom
positions were calculated. FT−IR spectra were collected on sam-
ples as a KBr pellet using a Bruker Tensor 27 spectrometer with a
resolution of 4 cm−1. FT−Raman spectra were collected in flame-
sealed capillary tubes on a Bruker RFS 100/s spectrometer with
a resolution of 4 cm−1. Decomposition/melting points were re-
corded in flame-sealed capillary tubes using a Gallenkamp
Variable Heater. High resolution mass spectrometry (HRMS)
data were collected using a Finnigan MAT 8200 instrument.
2Dipp
3Mes
3Dipp
4
5
226 nm (2.5 × 104)
240 nm (1.8 × 104)
270 nm (7.9 × 102)
226 nm (1.9 × 104)
226 nm (7.1 × 103)
241 nm (4.1 × 103)
6
7
for five-membered23 and six-membered NHPs,28 which are ap-
proximately 90° and 105°. In the solid state, the thiophene ring
sits at a 110.80(5)° angle from the C2N2P ring in an open book
conformation.
Conclusions
A new class of thiophene-substituted diimine (2Mes and 2Dipp
)
and diamine (3Mes and 3Dipp) ligands has been synthesized and
their reactivity with PCl3 was explored. Due the inherent flexibil-
ity of the seven-membered ring system, there were difficulties
controlling the degree of substitution at phosphorus. When Ar =
Mes, a 1:2 stoichiometry of diamine:phosphine was observed
(i.e., compound 4); however, when Ar = Dipp, both the 1:1 (5)
and 1:2 (6) products were isolated. When the solvent was changed
from THF to toluene and the rate of addition of PCl3 to 2Dipp was
decreased, the cyclic diaminochlorophosphine (5) was success-
fully isolated. Compound 5 can be converted to NHP using the
halide abstraction/metathesis reagent Me3SiOTf, where the isola-
tion and solid-state structure of a seven-membered NHP (7) was
achieved. The thiophene ring in the backbone dominated the
Synthesis
General synthesis for compounds 2Mes and 2Dipp
To a 20 mL EtOH solution of 3,4-diformylthiophene (1.00 g,
7.24 mmol), 2,6-diisopropylaniline (2.65 g, 14.28 mmol) or 2,3,6-
trimethylaniline (1.93 g, 14.28 mmol) was added. The solution
turned dark orange and a yellow solid precipitated from the reac-
Published by NRC Research Press

Price et al.
695
Table 2. Crystal data for compounds 2Mes, 3Dipp, 4, 6, and 7.
2Mes
3Dipp
4
6
7
Empirical formula
FW (g mol−1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
␣ (°)
␤ (°)
C24H26N2S1
374.53
Monoclinic
P21/c
8.116 (1)
15.946 (3)
16.190 (3)
90
91.76 (3)
90
2094.2 (7)
1.188
C30H42N2S1
462.72
Monoclinic
C2/c
26.186 (1)
13.392
16.408
90
106.997 (5)
90
5502.7 (6)
1.117
0.0469
0.1458
C24H28N2S1Cl4P2
580.28
Triclinic
P⌺1
9.547 (1)
10.435 (2)
14.707 (3)
84.69 (3)
80.09 (3)
75.51 (3)
1395.6 (5)
1.381
C30H40N2S1Cl4P2
664.44
Triclinic
P⌺1
9.983 (2)
13.907 (3)
25.630 (5)
75.91 (3)
84.28 (3)
83.86 (3)
3421.3 (12)
1.290
C31H40N2S2F3O3P1
640.74
Triclinic
P⌺1
10.227 (3)
10.949 (4)
15.625 (5)
75.021 (9)
75.056 (9)
85.202 (9)
1632.8 (9)
1.303
)
␦ (°)
V (Å3)
Dc (g cm−3
)
R1[I > 2⌠I]a
0.0631
0.2237
1.069
0.049
0.1631
1.060
0.0546
0.1473
0.974
0.0419
0.0908
1.023
wR2(F2)a
GOF(S)
0.868
Scan range
Completeness
2.60–25.48
0.993
2.60–25.48
0.993
1.00–27.28
0.982
1.00–27.48
0.994
2.64–26.35
0.999
aR1(F[I > 2(I)]) = Α࿣ |Fo| – |Fc| ࿣/Α |Fo|; wR2(F2 [all data]) = [w(Fo2 – Fc2)2]1/2; S(all data) = [w(Fo2 – Fc2)2/(n – p)]1/2 (n = no. of data; p = no. of
parameters varied; w = 1/[⌠2 (Fo2) + (aP)2 + bP], where P = (Fo2 + 2Fc2)/3 and a and b are constants suggested by the refinement.
Table 3. Selected average bond lengths (Å) and angles (°).
removed by filtration and the colourless filtrate was dried over
MgSO4 and concentrated under reduced pressure to obtain the
diamine.
2Mes
3Dipp
4
6
7
N–C␤
P–Cl
N–P
N–P–Cl
N–P–N
1.270 (4)
1.464 (3)
1.487 (3)
2.095 (2)
1.646 (4)
103.07 (18)
1.491 (7)
2.090 (3)
1.648 (5)
103.1 (2)
1.511 (3)
Compound 3Mes
1.625 (1)
Yield: 0.85% (0.86 g, 1.85 mmol); mp 104–105 °C. FT−IR (ranked
intensity (cm−1)): 569 (8), 698 (13) 756 (15), 804 (2), 856 (7), 1025 (14),
1065 (5), 1154 (9), 1226 (3), 1300 (10), 1329 (12), 1480 (1), 2910 (4), 3108
(11), 3348. (6) FT−Raman (ranked intensity (cm−1)): 139 (15), 492 (12),
576 (1), 841 (14), 957 (9), 1066 (11), 1155 (13), 1228 (8), 1301 (3), 1379 (5),
1446 (7), 1608 (4), 2912 (2), 30109 (10). 1H NMR (CDCl3 ␦ (ppm)): 7.23
(s, 2H, thienyl), 7.83 (s, 4H, aryl), 4.03 (s, 4H, alkyl), 2.24 (s, 6H,
methyl), 2.22 ppm (s, 12H, methyl). 13C{1H} NMR (CDCl3 ␦ (ppm)):
143.1, 139.9, 131.7, 130.2, 129.4, 123.4, 46.7, 20.5, 18.2. HRMS C24H28N2S
calcd. (found): 378.2130 (378.2139); ␭max = 223 nm (1.6 × 104 M−1 cm−1)
242 nm (1.6 × 104 M−1 cm−1), 289 (sh) nm (2.4 × 10−3 M−1 cm−1).
111.28 (8)
tion mixture. The reaction was stirred overnight at room temper-
ature and the yellow powder was isolated by filtration. The
product was washed with 5 × 5 mL of cold EtOH.
Compound 2Dipp
Yield: 76% (2.51 g, 5.46 mmol); mp 192–194 °C. FT−IR (ranked
intensity (cm−1)): 758 (7), 796 (11), 822 (3), 851 (3), 876 (12), 933 (16),
1166 (5), 1323 (9), 1384 (10), 1435 (4), 1470 (15), 1513 (8), 1634 (1), 2962
(2), 3074 (14). FT−Raman (ranked intensity (cm−1)): 169 (13), 273 (2),
528 (6), 799 (3), 857 (11), 957 (1), 1042 (12), 1110 (8), 1159 (4), 1247 (14),
2861 (9), 2905 (7), 2937 (5), 2961 (15), 3089 (10). 1H NMR (CDCl3
␦ (ppm)): 8.72 (s, 2H), 8.04 (s, 2H, thienyl), 7.08 (m, 6H, phenyl),
Compound 3Dipp
Yield: 80% (0.81 g, 1.75 mmol); mp 109–110 °C. FT−IR (ranked
intensity (cm−1)): 527 (9), 573 (11), 732 (1), 803 (5), 856 (8), 932 (7),
1055 (4), 1114 (13), 1195 (6), 1258 (14), 1302 (10), 1382 (12), 1459 (3),
2961 (2), 3090 (15). FT−Raman (ranked intensity (cm−1)): 150 (4), 170
(5), 222 (10), 273 (14), 677 (9), 857 (13), 889 (8), 1043 (12), 1248 (11),
1448 (6), 1590 (7), 2908 (2), 2936 (1), 2960 (3). 1H NMR (CDCl3
␦ (ppm)): 7.34 (s, 2H, thienyl), 7.10 (m, 6H, aryl), 4.03 (s, 4H, alkyl), 3.26
(sept., 4H, 3JHH = 6.8 Hz), 1.23 (d, 24H, 3JHH = 6.8 Hz); 13C{1H} NMR
(CDCl3 ␦ (ppm)): 143.1, 139.8, 124.4, 123.8, 123.2, 50.3, 28.0, 24.5.
3
3
2.94 (sept., 4H, JHH = 6.8 Hz), 1.10 (d, 24H, JHH = 6.8 Hz). 13C{1H}
NMR (CDCl3 ␦ (ppm)): 157.8, 149.5, 138.8, 137.9, 131.7, 124.6, 123.4,
28.4, 23.9. HRMS C30H28N2S calcd. (found): 458.2756 (458.2764).
␭
max = 240 nm (2.5 × 104 M−1 cm−1), 273 (sh) nm (8.7 × 103 M−1 cm−1),
332 (sh) nm (2.8 × 10−3 M−1 cm−1).
HRMS C30H32N2S calcd. (found): 462.3069 (462.3065). ␭
=
Compound 2Mes
max
241 nm (1.0 × 104 M−1 cm−1), 281 (2.0 × 103 M−1 cm−1).
Yield: 80% (2.13 g, 5.60 mmol); mp 139–141 °C. FT−IR (ranked
intensity (cm−1)): 733 (13), 819 (2), 859 (8), 878 (12), 1138 (9), 1174 (5),
1212 (6), 1448 (15), 1476 (3), 1513 (10), 1629 (1), 2859 (4), 2916 (11), 3078
(7), 3100 (14). FT−Raman (ranked intensity (cm−1)): 124 (4), 573 (6),
1139 (7), 1174 (5), 1213 (15), 1297 (10), 1354 (8), 1379 (14), 1405 (11), 1449
Compound 4
A 20 mL THF solution of PCl3 (0.11 mL, 1.33 mmol) was cooled to
–78 °C. A 10 mL THF solution of 3Mes (0.50 g, 1.33 mmol) was then
added dropwise via cannula and a white precipitate formed im-
mediately. The reaction mixture was stirred at –78 °C for 2 h, then
warmed to room temperature, and then stirred for 15 h. The white
precipitate was removed by centrifuge and the resulting colour-
less solution was concentrated. Acetonitrile (5 mL) was then added
to the residue resulting in the formation of a white precipitate.
The CH3CN was decanted and the product dried under vacuum.
Yield: 34% (0.23 g, 0.45 mmol); mp 125–128 °C. FT−IR (ranked in-
tensity (cm−1)): 434 (10), 481 (5), 508 (12), 525 (4), 568 (2), 683 (8), 808
(3), 855 (11), 883 (6), 1061 (1), 1120 (13), 1207 (7), 1346 (15), 1474 (9),
2917 (14). FT−Raman (ranked intensity (cm−1)): 191 (5), 240 (1), 418
(12), 456 (3), 513 (2), 560 (15), 574 (6), 633 (9), 859 (14), 1178 (11), 1307
1
(12), 1513 (3), 1604 (2), 1628 (2), 2918 (9), 3078 (13). H NMR (CDCl3
␦ (ppm)): 8.73 (s, 2H), 8.00 (s, 2H, thienly), 6.86 (s, 4H, aryl), 2.26
(s, 6H, methyl), 2.12 (s, 12H, methyl). 13C{1H} NMR (CDCl3 (ppm)):
␦ 158.0, 148.6, 138.5, 132.9, 130.6, 128.6, 126.9, 20.7, 18.3. HRMS
C24H26N2S calcd. (found): 374.1817 (374.1824). ␭max = 242 nm (2.8 ×
104 M−1 cm−1), 269 (sh) nm (1.1 × 104 M−1 cm−1), 333 (sh) nm (1.1 ×
10−3 M−1 cm−1).
General synthesis for compounds 3Mes and 3Dipp
Solid LiAlH4 (0.248 g, 6.55 mmol) was added portion-wise to
a 50 mL Et2O solution of diimine (2.18 mmol). The suspension
was stirred overnight at room temperature. Excess LiAlH4 was
quenched with 10 mL of a 10% KOH(aq) solution. The salts were
1
(4), 1379 (10), 1606 (8), 2917 (7), 3112 (3). H NMR (CDCl3 ␦ (ppm)):
Published by NRC Research Press

Fig. 3. Solid state structures of compounds 2Mes, 3Dipp, 4, 5, 6, and 7. Thermal ellipsoids are drawn to 50% probability and hydrogen atoms have been omitted for clarity with the
exception of 3Dipp. For compound 7, the triflate anion has been omitted for clarity and a side on view of the molecule is shown in 7b in which the Dipp groups have been omitted.

Price et al.
697
2
3
6.99 (s, 2H, thienyl), 6.83 (s, 4H, aryl), 4.04 (d, 4H, JHP = 2.8 Hz
alkyl), 2.27 (s, 3 H, methyl), 2.26 (s, 3H, methyl), 1.87 (s, 6H, methyl),
1.86 (s, 6H, methyl). 13C{1H} NMR (CDCl3 ␦ (ppm)): 138.8, 138.7,
6.8 Hz), 1.07 (d, 12H, JHH = 6.8 Hz). 13C{1H} (CDCl3 ␦ (ppm)):
147.4, 134.9, 134.7, 134.2, 131.4, 126.7, 125.4, 58.8, 28.7, 25.1, 24.2.
31P{1H} (CDCl3 ␦ (ppm)): 257.1. ␭max = 224 nm (7.1 × 103 M−1 cm−1),
241 nm (4.1 × 103 M−1 cm−1). Elemental analysis (%) calcd. for
C31H40F3O3N2S2P1: C 57.88, H 6.51, N 4.38, S 10.07; found: C 58.11,
H 6.29, N 4.37, S 10.01.
1
138.6, 136.0, 135.5, 129.8, 128.7, 127.5, 44.4 (d, JCP = 28 Hz), 20.9,
18.6. 31P{1H} NMR (CDCl3 ␦ (ppm)): 153.8. ␭max = 224 nm (2.5 × 104 M−1
cm−1). Elemental analysis (%) calcd. for C24H28N2S1Cl4P2: C 49.67, H
4.86, N 4.83, S 5.53; found: C 50.11, H 5.12, N 4.84, S 5.72.
Supplementary material
Compound 5
Supplementary data are available with the article through the
journal Web site at http://nrcresearchpress.com/doi/suppl/10.1139/
cjc-2013-0015. CCDC 929309-929313 contain the crystallograhic
data in CIF format for this article. These data can be obtained,
free of charge, via http://www.ccdc.cam.ac.uk/products/csd/
request (or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1E2, UK; fax: +44 1223 33603;
e-mail: deposit@ccdc.cam.ac.uk).
A 10 mL toluene solution of 3Dipp (0.20 g, 0.43 mmol) was cooled
to –78 °C in a dry ice − acetone bath. To this, a 10 mL toluene
solution of PCl3 (34 ␮L, 0.43 mmol) was added via a syringe pump
at a rate of 1 mL h−1. The reaction mixture was then warmed to
room temperature and stirred for 24 h. Upon completion, the
reaction was concentrated under reduced pressure and then
taken up in 10 mL of Et2O. The Et2O solution was then centrifuged to
remove the ammonium salt and was then concentrated yielding
the desired product. Yield: 90% (0.20 g, 0.38 mmol); mp 98–100 °C.
FT−IR (ranked intensity (cm−1)): 526 (5), 573 (8), 731 (10), 802 (2), 932
(13), 1055 (4), 1113 (14), 1194 (7), 1258 (6), 1302 (15), 1382 (11), 1459 (3),
1587 (9), 2961 (1), 3090 (12). (12) FT-Raman (ranked intensity (cm−1)):
149 (4), 169 (9), 274 (15), 676 (8), 857 (10), 889 (5), 1042 (7), 1110 (11),
1247 (6), 1446 (2), 1589 (3), 2862 (13), 2906 (14), 2961 (1), 3089.
1H NMR (CDCl3 ␦ (ppm)): 7.33 (s, 2H, thienyl), 7.11 (m, 6H, aryl), 4.04
(d, 4H, 1JHP = 7.37 Hz, alkyl), 3.26 (sept. 4H, 3JHH = 6.8 Hz), 1.14 (d,
24H, 3JHH = 6.8 Hz). 13C{1H} NMR (CDCl3 ␦ (ppm)): 142.9, 142.8, 124.1,
123.5, 122.9, 50.0, 27.8, 24.2. 31P{1H} NMR (CDCl3 ␦ (ppm)): 152.2.
Acknowledgements
The authors would like to thank the Natural Sciences and Engi-
neering Research Council of Canada, the Canada Foundation for
Innovation, the Ontario Ministry of Research and Innovation, and
Western University for their generous funding.
References
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(15) Chen, C.; Roland, F.; Kehr, G.; Erker, G. Chem. Commun. 2010, 46, 3580.
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␭
= 240 nm (1.8 × ×
104 M−1 cm−1), 280 (sh) nm (2.1
max
103 M−1 cm−1).
Compound 6
A 10 mL Et2O solution of 3Dipp (0.20 g, 0.43 mmol) was cooled to
–78 °C. To this, a 10 mL Et2O solution of PCl3 was added dropwise
via cannula. A white precipitate formed immediately and the re-
action mixture was stirred at –78 °C for 2 h. The reaction was then
warmed to room temperature and left to stir for an additional
24 h. Upon completion, the solvent was removed in vacuo leaving
an orange residue, which was then taken up in CH3CN. The orange
solution was then concentrated again under reduced pressure
yielding a yellow solid. The yellow solid was washed with 3 × 5 mL
of CH3CN yielding the product as a white solid. Yield 42% (0.12 g,
0.18 mmol); mp 157–159 °C. FT−IR (ranked intensity (cm−1)): 454
(10), 515 (7), 637 (2), 692 (15), 751 (14), 810 (5), 857 (9), 895 (13), 1028
1
(3), 1113 (11), 1169 (8), 1256 (1), 1467 (6), 1587 (12), 2970 (4). H NMR
(CDCl3 ␦ (ppm)): 7.21 (m, 2H, aryl), 7.03 (d, 4H, 3JHH = 7.6 Hz, aryl),
6.30 (s, 2H, thienyl), 4.61 (d, 4H, 2JHP = 2.4 Hz, alkyl), 2.79 (sept. 4H,
3JHH = 6.8 Hz), 1.02 (d, 12H, 3JHH = 6.8 Hz), 0.90 (d, 12H, 3JHH = 6.8 Hz).
13C{1H} NMR (CDCl3 ␦ (ppm)): 149.9, 135.4, 134.1, 129.4, 126.7, 124.3,
46.3 (1JC-P = 28.4 Hz), 28.8, 26.7, 22.6. 31P{1H} NMR (CDCl3 ␦ (ppm)): 154.9.
␭
max = 226 nm (1.9 × 104 M−1 cm−1), 270 (sh) nm (7.9 × 102 M−1 cm−1). HRMS
C30H40SN2Cl4P2 calcd. (found): 662.1142 (662.1135).
Compound 7
To a 5 mL CH2Cl2 of 5 (0.200 g, 0.38 mmol), neat (CH3)3SiOTf
(0.20 mL, 0.1.14 mmol) was added. The reaction mixture stirred
was at room temperature for 2 h until all of the chlorophosphine
was converted to the phosphenium cation. Upon completion, the
reaction mixture was concentrated under reduced pressure yield-
ing a white solid. The product was then washed with 3 × 5 mL of
Et2O and dried under vacuum. Yield: 32% (0.08 g, 0.12 mmol); mp.
FT−IR (ranked intensity (cm−1)): 454 (10), 515 (7), 637 (2), 692 (15), 751
(14), 810 (5), 857 (9), 895 (13), 1028 (3), 1113 (11), 1169 (8), 1256 (1), 1467
(6), 1587 (12), 2970 (4). FT−Raman (ranked intensity (cm−1)): 201 (10),
308 (8), 693 (1), 720 (11), 882 (7), 1027 (3), 1043 (6), 1116 (2), 1239 (5),
(23) Caputo, C. A.; Price, J. T.; Jennings, M. C.; McDonald, R.; Jones, N. D. Dalton
Trans. 2008, 3461. doi:10.1039/B801684D.
(24) Berger, S.; Baumann, F.; Scheiring, T.; Kaim, W. Z. Anorg. Allg. Chem. 2001,
627, 620. doi:10.1002/1521-3749(200104)627:4<620::AID-ZAAC620>3.3.CO;2-B.
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E: Struct. Rep. Online 2008, 64, o135. doi:10.1107/S1600536807061648.
(26) These bond lengthes were found from a survey of cyclic diaminochlorophos-
phines in the cambridge structual database.
(27) Brazeau, A. L.; Hänninen, M. M.; Tuononen, H. M.; Jones, N. D.;
Ragogna, P. J. J. Am. Chem. Soc. 2012, 134, 5398. doi:10.1021/ja300587z.
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doi:10.1039/B617434E.
1586 (4), 2870 (9), 2980 (12). 1H NMR (CDCl3 ␦ (ppm)): 7.36 (t, 2H, 1JHH
=
1
8 Hz, aryl), 7.27 (s, 2H, thienyl), 7.19 (d, 4H, JHH = 8 Hz, aryl),
3
5.48 (br. s, 4H, alkyl), 3.18 (br. sept., 4H), 1.28 (d, 12H, JHH
=
Published by NRC Research Press