Synthesis and structures of non-cyclic and cyclic mono- and bisphosphonium salts derived from 1,8-bis(diphenylphosphino)naphthalene

Article abstract of DOI:10.1016/j.tet.2012.11.081

A monoalkylated 1,8-bis(diphenylphosphino)naphthalene (dppn) was prepared by treating diphosphine with 1,8-bis(bromomethyl)naphthalene. Unprecedented cyclizations of monophosphonium salts in polar solvents, such as DMF or acetonitrile were elucidated. The mechanistic pathway of the cyclization reaction was postulated and X-ray crystal structure analyses of the resulting 2,2-diphenyl-2,3-dihydro-1H-2-phosphoniaphenalene bromide was performed. 1,8-Bis(diphenylphosphino)naphthalene and α,α′-dibromo-o- xylene afforded - despite unfavorable steric strain - the first dialkylation product of 1,8-bis(phosphino)naphthalene, namely corresponding cyclic bisphosphonium salt. The use of acetonitrile as the solvent was the key for this synthesis. The bromide anions were exchanged in metathesis reaction with hexafluorophosphate anions and the new compound was fully characterized including single crystal X-ray diffraction. The large distance between phosphorus atoms of 3.974 clearly demonstrate a strong proximity effect in this hindered bisphosphonium salt.

Full text of DOI:10.1016/j.tet.2012.11.081

Tetrahedron 69 (2013) 1628e1633
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and structures of non-cyclic and cyclic mono- and
bisphosphonium salts derived from 1,8-bis(diphenylphosphino)
naphthalene
,
b
a
ꢀ c
Krzysztof Owsianik a , Laure Vendier , Jaros1aw B1aszczyk , Les1aw Sieron
*
a
ꢀ ꢀ
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łodz, Poland
b Laboratoire de Chimie de Coordination, CNRS, 205 route de Narbonne, 31077 Toulouse, France
c
_
ꢀ ꢀ
ꢀ ꢀ
Institute of General and Ecological Chemistry, Technical University of Łodz, Zeromskiego 116, 90-924 Łodz, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 August 2012
Received in revised form 6 November 2012
Accepted 26 November 2012
Available online 13 December 2012
A monoalkylated 1,8-bis(diphenylphosphino)naphthalene (dppn) was prepared by treating diphosphine
with 1,8-bis(bromomethyl)naphthalene. Unprecedented cyclizations of monophosphonium salts in polar
solvents, such as DMF or acetonitrile were elucidated. The mechanistic pathway of the cyclization reaction
was postulated and X-ray crystal structure analyses of the resulting 2,2-diphenyl-2,3-dihydro-1H-2-
phosphoniaphenalene bromide was performed. 1,8-Bis(diphenylphosphino)naphthalene and
a,a
0-di-
bromo-o-xylene affordedddespite unfavorable steric straindthe first dialkylation product of 1,8-
bis(phosphino)naphthalene, namely corresponding cyclic bisphosphonium salt. The use of acetonitrile
as the solvent was the key for this synthesis. The bromide anions were exchanged in metathesis reaction
with hexafluorophosphate anions and the new compound was fully characterized including single crystal
X-ray diffraction. The large distance between phosphorus atoms of 3.974 Ǻ clearly demonstrate a strong
proximity effect in this hindered bisphosphonium salt.
Keywords:
peri-Naphthalenes
Bisphosphonium salts
Bisphosphines
peri-Interactions
Phosphorus heterocycles
Strained molecules
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
a bridging metal center,5 but make it difficult to quaternize both
phosphorus atoms.6e9 In some cases, unfavorable steric strain
Bidentate phosphorus ylides are important reagents in co-
ordination chemistry and their utility in synthetic chemistry has
been well documented.1,2 While the coordination chemistry of
carbodiphosphoranes (R3P]C]PR3) is already a fairly well de-
veloped area,2 information about chelating bis-ylides A is limited to
only few examples.3 These ylides with various substituents should
exhibit specific coordination behavior toward certain metal centers.
operating in the mono- or diadduct can be relieved by formation of
products with a bridging geometry.8,9 In view of the geometry of
naphthalene, hydrogen atoms located at these positions are in
ꢁ
much closer proximity (2.5 A) than those located at the ortho-po-
ꢁ
sitions (3.1 A). Therefore, vicinal diphosphoniums derived from the
o-bis(diphenylphosphino)benzene (o-dppb) have been successfully
synthesized (Fig. 1).10 The 2,20-bis(diethylphosphino)-1,10-biphenyl
offers possibilities for the synthesis of quaternary derivatives of
R1
R2R1
R2
R
PPh2
Ph2
P
Ph2
P
R
2P
PR2
Me
(CH2)n
2OTf
2OTf
Me
P
P
PPh2
R
R = Me, Et
2X
Ph2
Ph2
A
X = Cl, I, OTf, PF6
n = 1-3
In the naphthalene molecule the 1- and 8-positions are said to
be peri to each other. The close proximity of the substituents at
these positions has been responsible for the appearance of several
unique properties of peri-substituted naphthalenes.4 Such ‘prox-
imity effects’ enable coordination of the bidentate ligand to
Et2P
PEt2
2Br
Et2P
PEt2
(CH2)n
2Br
n = 1-4
* Corresponding author. Tel.: þ48 42 680 3216; fax: þ48 42 680 3261; e-mail
address: owsianik@cbmm.lodz.pl (K. Owsianik).
Fig. 1. Bisphosphonium salts of o-dppb and 2,20-bis(diethylphosphino)-1,10-biphenyl.
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.11.081

K. Owsianik et al. / Tetrahedron 69 (2013) 1628e1633
1629
heterocyclic phosphorus compounds, from which free cyclic
phosphines might be obtained by thermal decomposition (Fig. 1).11
Previous attempts at two-fold quaternization of 1,8 bis(dime-
thylphosphino)naphthalene (dmpn) and 1,8-bis(diphenylphosphino)
naphthalene (dppn) (1) using MeI, BnBr or TfMe failed because
of unfavorable steric strain and only products of monoalkylation
have been observed.7,9 On the other hand, excess of strong
Brønsted acids, such as concd H2SO4, tetrafluoroboric acid or tri-
fluoromethanesulfonic acid afforded the symmetrically diprotonated
species as confirmed by 31P NMR spectroscopy.7 Hereinwe report our
attempts at the synthesis of cyclic phosphonium saltsdpotential re-
agents for synthesis of the corresponding type A bis-ylides, through
quaternization of the two phosphorus atoms of dppn with 1,4- and
and 16.7 ppm (JPP¼36 Hz) for the phosphonium group. Moreover,
broad signals at ꢀ13.1 ppm and 19.7 ppm were observed. The JPP
4
value is larger than normal JPP values (up to 10 Hz) and indicates
a considerable through-space coupling associated with the close
proximity of the phosphorus atoms.8,9 The latter signals are
assigned probably to the other conformers, as has been proved for
benzyl-(8-diphenylphosphanylnaphthalen-1-yl)diphenylphospho-
nium bromide.7
Due to the fact that prolongation of the reaction time in boiling
toluene did not produce the desired salt we decided to raise the
temperature of this reaction and apply DMF as a solvent. Treatment
of 1 with 1,8-bis(bromomethyl)naphthalene in DMF at 152 ꢁC for
2 h resulted in the formation of a white precipitate (Scheme 2). The
31P{1H} NMR spectrum of a crude mixture exhibited two singlets at
6.0 ppm and 29.0 ppm, which suggested cleavage of the PeCNph
bond. The products were separated, purified and characterized
initially by FAB mass spectrometry and NMR spectroscopy. These
spectra confirmed the structures of cyclic phosphonium salt 2 and
phosphine oxide 6 formed in a 1:1 ratio.
1,5-dihalo derivatives, such as
a,a
0-dibromo-o-xylene and 1,8-
bis(bromomethyl)naphthalene. These compounds or their chloro
derivatives react readily with reactive phosphorus compounds giving
cyclic monophosphonium salts 2 and 3$X (Fig. 2).12 The use of such
dihalogens should facilitate the bis-alkylation by linking and bridging
two terminal phosphonium groups.
The availability of X-ray structural data plays an essential role in
assessing steric strain and allows critical insight into the bonding in
the peri-substituted naphthalenes. Therefore, even though the
phosphonium salt 212 was previously synthesized and its NMR
spectra were also described we decided to characterize it by X-ray
diffraction. Colorless crystals of 2 were obtained by crystallization
from MeOH/toluene (5:1) and the molecular structure was de-
termined by X-ray analysis (Fig. 3). In the molecular structure of 2
the six-membered heterocyclic ring is found to be in a slightly
distorted sofa conformation with the phosphorus atom deviation of
Ph2
P
Ph2
P
X
Br
2
3 X X = Cl, Br
Fig. 2. The cyclic monophosphonium salts derived from 1,8-bis(bromomethyl)naph-
thalene,
0-dichloro-o-xylene and 0-dibromo-o-xylene.
a,
a
a,a
ꢁ
0.869 A from the C1C2C3C4C5 plane. All the carbon atoms of this
ring are almost coplanar with the naphthalene (C1 and C5 carbon
ꢁ
ꢁ
2. Results and discussion
atoms deviation 0.096 A and 0.017 A). The bridging of the carbon
atoms of the CePeC system by naphthalene lead to straining of the
C1PC5 angle, therefore the phosphorus center adopts a tetrahedral
geometry with C1P1C5 angle 101.3ꢁ substantially narrower than
the normal tetrahedral angle. This one, as well as distances P1C5
1,8-Bis(diphenylphosphino)naphthalene (1) was treated with
1 equiv of 1,8-bis(bromomethyl)naphthalene in boiling toluene.
After 3 h the reaction led to monoadduct 4 in 62% yield and did not
afford the cyclic diphosphonium salt 5$Br2, even after prolonged
heating (Scheme 1).
ꢁ
ꢁ
(1.772 A) and P1C1 (1.768 A) in the ring, are smaller than those of
the cyclic phosphonium salt with a chair conformation of hetero-
14
ꢁ
ꢁ
ꢁ
cyclic ring (103.9 , 1.797 A and 1.794 A, respectively).
The reaction in boiling acetonitrile at 92 ꢁC for 3 h also leads to
the conversion of 4 into 2 and 6, but probably because of a low
boiling point of the solvent the reaction is slower and it does not
occur until the end.
Br
Br
Br
P
Ph2
PPh2
Subsequently, the alkylation of 1 with another bis-halide, such as
Ph
2P
PPh2
a,a
0-dibromo-o-xylene in different solvents was also examined
toluene
110 oC, 3 h
(Scheme 3). In this case, depending on the conditions used, the re-
action leads to various products. In a polar solvent as DMF the cyclic
phosphonium salt 3$Br,12,13 analogous to the salt 2, was formed.
However, a completely different result was obtained when aceto-
nitrile has been used in place of DMF. Surprisingly, instead of the
cyclic monophosphonium salt 3$Br, the bis-alkylationproduct 5$Br2
was obtained as a white solid after 5 h heating in boiling acetonitrile.
Metathesis of the salt 5$Br2 with an excess of KPF6 in methanol gave
the corresponding hexafluorophosphate 5$[PF6]2. The reaction in
toluene at different temperatures leads tothe formation of a mixture
of both monoalkylation 7 and dialkylation 5$Br2 products. Un-
fortunately, all attempts to isolate the compounds 7 in a pure form
from the reaction mixture were unsuccessful.
Br
1
4
2Br
Ph2
Ph
2P
P
5 Br2
Compound 5$[PF6]2 crystallizes from acetone/hexane mixture
in a tetragonal system, space group I(ꢀ4)2d (Fig. 4). The asym-
metric unit contains a half of the dication moiety, a half of the first
PF6ꢀ ion, a half of the second PF6ꢀ ion, and a quarter of the acetone
molecule, that lies at the special position and has positional dis-
order (see Experimental section). The presence of an acetone
molecule in the crystal has been experimentally confirmed by 1H
NMR spectroscopy (one singlet from CH3 groups at 2.13 ppm).
Scheme 1. Synthesis of (8-bromomethylnaphthalen-1-ylmethyl)-(8-diphenylphos-
phanylnaphthalen-1-yl)diphenylphosphonium bromide (4).
The structure of the product 4 has been studied by NMR spec-
troscopy, mass spectrometry and elemental analysis. In the 31P
NMR spectrum, two characteristic AB-patterns were observed.
The spectrum displays sharp doublets at ꢀ14.6 ppm for the PPh2

1630
K. Owsianik et al. / Tetrahedron 69 (2013) 1628e1633
Br
Br
, H2O
Ph
Br
2P
PPh2
DMF
Ph2
P
152 oC, 2 h
O
2P
1
Ph
+
Br
DMF, 2 h
2
6
H2O, 152 oC
Ph
2P
PPh2
Br
or MeCN, 92 oC
3 h
4
Scheme 2. Conversion of 1 and 4 into cyclic monophosphonium salt 2 and phosphine oxide 6 using 1,8-bis(bromomethyl)naphthalene.
The P/P distance of 3.974 Ǻ is larger than in the parent bis-
ꢁ
ꢁ
phosphine 1 (3.052 A) and monophosphonium salt 10 (3.192 A)
(Fig. 5). As in the structures of other 1,8-P,P0-disubstituted naph-
thalenes the proximity of the two bulky substituents leads to in-
plane and out-of-plane displacement of both phosphorus atoms
with respect to the naphthalene ring system. The in-plane distor-
tion takes the form of a widening of the bay angles P1eC31eC36
(126.49ꢁ) and C31eC36eC310 (129.60ꢁ) while the out-of-plane
distortion can be assessed from pseudo-torsion angle
P1eC31/C310eP10 (60.2ꢁ), or from the distance between the
phosphorus atoms P1 and P10, which reside above and below the
ꢁ
naphthalene mean plane (1.124 A). These values distinctly dem-
onstrate an extremely strong repulsive interaction between the
phosphorus atoms in this cyclic bisphosphonium salt 5$[PF6]2.
2.1. Mechanistic postulations
As a starting point to study of the mechanism of peri ring closure,
the reaction of 1 with 1,8-bis(bromomethyl)naphthalene in DMF
was monitored by 31P NMR spectroscopy. The spectra showed the
disappearance of the signal due to diphosphine 1 (
d
¼ꢀ14.0 ppm)
Fig. 3. Crystal structure of 2. The displacement ellipsoids are drawn at the 50%
probability level and the H atoms are omitted for clarity.
and the appearance of two doublets at
d
¼ꢀ14.6 ppm and 16.7 ppm
Br
Ph Ph
P
Br Br
Ph
2P
PPh2
toluene, 110 o
4 h
C
DMF, 152 o
1 h
C
Ph
2P
PPh2
5 . Br2
+
+
6
Br
+
Br
3 . Br
1
MeCN, 92 oC, 5 h
55%
7
KPF6
Ph2P
PPh2
2Br
Ph2P
PPh2
MeOH
95%
2PF6
5. Br2
5. [PF6]2
Scheme 3. Reaction of diphosphine 1 with a,a
0-dibromo-o-xylene in different solvents.

K. Owsianik et al. / Tetrahedron 69 (2013) 1628e1633
1631
This involves an SNi(Ar) displacement for the phosphonium
group in the phosphine 4 with the formation of a positively
charged four membered cyclic species 9 and phosphine 8. It is
possible that the strained four-membered ring of salt 9 opens in
the presence of water giving the phosphine oxide 6 while the
monophosphine
8 immediately undergoes an intramolecular
quaternization reaction under the reaction conditions giving the
six-membered cyclic monophosphonium salt 2. Inactivity of the
halogen group at a nucleophilic displacement stage suggests
that monobenzylated 1,8-bis(diphenylphosphino)naphthalene 10
should be a good starting material for the synthesis of salt 9.
Having this in mind, the above mentioned monophosphonium salt
10 was heated for 3 h in boiling DMF, but neither compound 9,
phosphine oxide 6 nor the benzyldiphenylphosphine have been
obtained. From this experiment, we can conclude that the forma-
tion of a stable six-membered ring presented in Scheme 2 is the
driving force of this reaction and leads to 2. The influence of the
solvent nature on the reaction course sometimes provides useful
clues regarding the structure of the solvated molecule. Many an-
ions formed during nucleophilic aromatic substitution reactions
are expected to be highly polarizable and should strongly interact
with polarizable dipolar aprotic solvents like HMPT, DMSO, and
DMF.15 The difference between molecular polarizability values of
Fig. 4. A view of the structure of 5$[PF6]2. The asymmetric unit contains a half of the
complete assembly shown in Figure. The symmetry operations that generate the complete
assemblyare given in Experimental section. The displacementellipsoids for atoms are drawn
at the 50% probability level. The PF6 anion, H atoms and acetone are omitted for clarity.
3
ꢁ
3
ꢁ
acetonitrile (a(mol)¼4.45 A ) and DMF (a(mol)¼7.91 A ) suggests an
SNi(Ar) mechanism and formation of the zwitterionic complex 11
s
(Fig. 5) stabilized by DMF. The dependence of the obtained product
on the nature of the solvent is evident for the synthesis of cation
3$Br, but ambiguous for the synthesis of cation 2, when cyclic
monophosphonium salt 2 was formed during reaction in acetoni-
trile. Presumably, the structure of dihalogens also has an effect on
the reaction course. Such thermal decomposition of 4 appears to
be a further example of a general SNi(Ar) mechanism,11 although
due to the lack of conclusive evidence we cannot exclude an al-
ternative mechanism involving ‘electropositive’ halogen. Such re-
actions are known in the literature as halophilic reactions.16 We can
assume that non-bonded pair on phosphorus is attacking the
Br
Ph
2P
PPh2
Ph
2P
PPh2
Br
Br
11
10
Fig. 5. Monophosphonium salt 10 and intermediate 11.
antibonding orbital d*CeBr, which results in breaking of the CeBr
bond and the formation of a benzylic carbanion 12, which sub-
sequently leads to cyclic phosphonium salt 2 and intermediate 13
(Scheme 5).
Probably, carbanion 13 in the presence of traces of water gives
stable phosphine oxide 6 or is transformed into the unstable four-
membered cyclic product 9.17 However, the latter intermediate was
not detected when the reactions were monitored by 31P NMR
spectroscopy.
with JPP¼36 Hz for 4. After 1 h, besides these doublets two singlets
characteristic of the cyclic phosphonium salt 2 (dP¼6.0 ppm) and
phosphine oxide 6 (29 ppm) were observed. Finally, after 2 h two
singlets due to the formation of 2 and 6 were only visible in the
spectrum. As the characteristic doublets in the 31P NMR spectrum
were assigned to monophosphonium salt 4, we can propose for-
mation of this product as the initial step of this reaction. In fact,
heating of 4 in DMFat 152 ꢁC after 2 h also led to formation of 2 and 6
(Scheme 2). On the basis of the literature information11 and our
experimental results, we can suggest two possible pathways for the
formation of 2 and 6, one of them is presented in Scheme 4.
3. Conclusions
In conclusion, we have successfully performed the first alkyl-
ation reaction of 1,8-bis(phosphino)naphthalene on both phos-
phorus atoms by reacting this bisphosphine with
xylene in acetonitrile. We have shown that the reaction of 1,8-
bis(bromomethyl)naphthalene or
0-dibromo-o-xylene with
a,a
0-dibromo-o-
Br
PPh2
Ph Ph
P
Br
a,a
DMF
152 oC, 2 h
dppn in toluene proceeds through conventional alkylation reaction
giving the monoalkylation product or a mixture of mono- and
dialkylation products. Unprecedented conversion of these mono-
salts into the corresponding cyclic products 2, 3$Br and oxide 6
with PeC bond cleavage in DMF takes place. Their formation was
the subject of mechanistic studies and two possible mechanisms
have been proposed. We can assume that reaction conditions and
particularly the type of solvent, its polarizability as well as the
structure of the dihalides are predominant factors affecting the
reaction course. The structures of the products 2 and 5$[PF6]2 have
been confirmed by X-ray crystallographic analysis and strong re-
pulsive Pþ/Pþ interactions in 5$[PF6]2 are expressed by the large
value of the peri-distance of 3.974 Ǻ. Our current efforts are focused
+
Br
Ph
2P
PPh2
9
8
Br
moist solvent
- HBr
4
Ph Ph
P
O
Ph2P
Br
2
6
Scheme 4. Proposed stepwise mechanism for the formation of
termediate 8 and 9.
2 and 6 via in-

1632
K. Owsianik et al. / Tetrahedron 69 (2013) 1628e1633
Br
Ph Ph
Br
Ph2P
P
Br
2P
+
Ph
P
2
PPh2
Br
Ph
PPh2
Br
Br
13
2
12
4
moist solvent
- HBr
O
Ph Ph
P
Ph2P
H2O
- HBr
Br
6
9
Scheme 5. Proposed stepwise mechanism for the formation of 2 and 6 via intermediate 12.
now on further application of the diphosphonium salt 5$[PF6]2 for
the synthesis of the corresponding stabilized mono- and bis-ylides.
for X-ray analysis were obtained by crystallization from methanol/
toluene (5:1). 1H NMR (200 MHz, DMF-d7):
d 8.40e7.54 (m, CHarom),
5.36 (d, J 15.0 Hz, 2ꢂ CH2), 31P{1H} NMR (81 MHz, DMF-d7):
d 11.0.
4. Experimental
13C NMR (50 MHz, DMF-d7):
d 135.5,133.6,133.3, 130.9, 130.6, 129.9,
127.0 (s, Carom), 126.2 (d, J 5.7 Hz, Carom), 24.8 (d, J 51.3 Hz, CH2). FAB-
MS 339 [MꢀBrꢀ]. The filtrate was concentrated to dryness. The
resulting solid residue was extracted with diethyl ether and filtered.
The volatiles were evaporated and product 6 was obtained as white
powder (0.042 g, 35%), mp 179e180 ꢁC. 31P{1H} NMR (CDCl3):
4.1. General information
All reactions and manipulations were carried out an atmosphere
of argon using standard Schlenk and vacuum-line techniques. The
solvents were dried, distilled under argon, and degassed before use.
1,8-Bis(diphenylphosphino)naphthalene (1) was prepared by lit-
erature methods.18 All commercial reactant were purchased from
SigmaeAldrich. IR spectra were measured on an Ati Mattson In-
finity FTIR 60. MS-FAB spectra were registered on a Finnigan MAT
95 spectrometer. The melting points were measured using a PHMK
Boetius (VEB Analytik Dresden) apparatus.
d
33.5. EI-MS 328 [M].
4.1.3. Bisphosphonium salt 5$Br2. To
bis(diphenylphosphino)naphthalene 1 (0.200 g, 0.403 mmol) in
acetonitrile (5 mL) was added solution of
0-dibromo-o-xylene
a
suspension of 1,8-
a,a
(0.128 g, 0.484 mmol) in acetonitrile (2 mL). The mixture was
stirred at 92 ꢁC for 5 h. The precipitate was separated and washed
with acetone; yield 0.168 g (55%) of white powder of 5$Br2, mp
4.1.1. (8-Bromomethylnaphthalen-1-ylmethyl)-(8-diphenylphospha-
nylnaphthalen-1-yl)diphenylphosphonium bromide (4). To a suspen-
sion of 1,8-bis(diphenylphosphino)naphthalene
198e199 ꢁC. 1H NMR (200 MHz, CD3OD):
d 8.92e7.00 (m, 30H,
CHarom) 5.21 (d, J 14.2 Hz, 4H, 2ꢂ CH2), 31P{1H} NMR (81 MHz,
1
(0.210 g,
CD3OD): d d 143.4 (d, J 7.2 Hz,
29.5 (s). 13C NMR (50 MHz, DMSO-d6):
0.423 mmol) in toluene (8 mL) was added solution of 1,8-
bis(bromomethyl)naphthalene (0.133 g, 0.423 mmol) in toluene
(3 mL). The mixture was stirred at 110 ꢁC for 3 h and then the pre-
cipitate was separated and washed with toluene (3ꢂ2 mL); yield
0.213 g (62%) of yellowish powder, mp 185e186 ꢁC. 1H NMR
Carom), 137.8, 133.7, 131.7, 131.7, 129.2, 128.9 (s, Carom), 128.3 (d, J
13.1), 128.0 (s, Carom), 126.7 (d, J 12.0), 112.5 (d, J 83.3), 29.2 (d, J
43.8). IR (KBr, cmꢀ1): 1484,1436,1098, 996, 826, 892, 750, 690. FAB-
MS 601 [Mꢀ2Brꢀ]. Anal. Calcd for C42H34Br2P2 (760.50): C, 66.33; H,
4.51. Found: C, 66.82; H, 4.58.
(200 MHz, MeOD): d 8.85e5.80 (m, 32H, CHarom), 4.55e4.10 (m, 4H,
2ꢂ CH2). 31P{1H} NMR (81 MHz, MeOD):
d
19.7 (br m, P(IV), A2-part),
4.1.4. Bisphosphonium salt 5$[PF6]2. To a solution of 5$Br2 (0.168 g,
0.221 mmol) in MeOH (1 mL) was added a solution of KPF6 (0.049 g,
0.265 mmol) in MeOH (5 mL). The solution was stirred at room
temperature for 2 h and the white precipitate was filtered and
washed with MeOH (3 mL); yield 0.187 g (95%) of white powder of
5$[PF6]2, mp 204e205 ꢁC. The crystals suitable for X-ray analysis
were obtained by recrystallization from acetone/hexane (5:1). 1H
16.7 (d, J 36.0 Hz, P(IV), A1-part), ꢀ13.1 (br m, P(III), B2-part), ꢀ14.6
(d, J 36.0 Hz, P(III), B1-part).13C NMR (50 MHz, MeOD):
d 143.7,140.4,
134.9, 134.5 (s, Carom),133.1,133.0 (d, J 8.3 Hz),130.9, 129.9 (s, Carom),
129.5 (d, J 5.5 Hz, Carom), 129.3, 126.3, 126.0, 115.1 (s, Carom), 36.3 (s,
BrCH2), 30.2 (d, J 45.2 Hz, PCH2). IR (KBr, cmꢀ1): 1437,1268,1107, 826,
771, 731, 695. FAB-MS 731 [MꢀBrꢀ]. Anal. Calcd for C46H36Br2P2
(810.56): C, 68.16; H, 4.48. Found: C, 68.06; H, 4.53.
NMR (200 MHz, CD3OD):
d 8.65e7.00 (m, 30H, CHarom), 5.08 (d, J
14.2 Hz, 4H, 2ꢂ CH2). 31P{1H} NMR (81 MHz, CD3OD):
d 25.6 (s,
4.1.2. 2,2-Diphenyl-2,3-dihydro-1H-2-phosphoniaphenalene
bro-
PPh), ꢀ143.4 (septet, J 708.2 Hz, PF6). 13C NMR (125 MHz, DMSO-
mide (2)12 and 1-naphthyldiphenylphosphine oxide (6).19 To a sus-
pension of 1,8-bis(diphenylphosphino)naphthalene 1 (0.180 g,
0.363 mmol) in DMF (5 mL) was added solution of 1,8-
bis(bromomethyl)naphthalene (0.114 g, 0.363 mmol) in DMF
(2 mL). The mixture was stirred at 152 ꢁC for 2 h and then the
precipitate was separated and washed with toluene; yield 0.067 g
(44%) of white powder of 2, mp 258e259 ꢁC. The crystals suitable
d6): d 144.7 (d, J 7.7 Hz, CHarom), 139.2 (s, CHarom), 136.5, 136.4 (d, J
9.1 Hz, Carom), 135.0 (s, CHarom), 133.2 (br m, Carom),132.9 (s, CHarom),
131.3, 131.2 (d, J 5.0 Hz, Carom), 130.4 (d, J 13.8 Hz, CHarom), 129.6 (s,
Carom), 129.4 (s, CHarom), 127.9 (d, J 13.7 Hz, CHarom), 113.3 (d, J
84.2 Hz, Carom), 30.5 (d, J 43.9 Hz, PCH2). 19F{1H} NMR (CD3OD):
d
ꢀ73.2 (d, J 708.2 Hz). IR (KBr, cmꢀ1): 1493, 1440, 1104, 999, 838,
809, 744, 690, 557. FAB-MS 601 [Mꢀ2PF6ꢀ]. Anal. Calcd for

K. Owsianik et al. / Tetrahedron 69 (2013) 1628e1633
1633
C42H34F12P4$1/2 acetone (919.69): C, 56.81; H, 4.06. Found: C, 57.21;
H, 4.11.
generated by applying symmetry operation (2ꢀx, 1ꢀy, z) (to gen-
erate complete conformer A) and (0.5þy, 1.5ꢀx, 0.5ꢀz and 1.5ꢀy,
ꢀ0.5þx, 0.5ꢀz) (to generate conformer B).
Crystallographic data for structures 2 and 5$[PF6]2 in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication numbers CCDC 792140 and
859561. Copies of the data can be obtained, free of charge, from the
CCDC via www.ccdc.cam.ac.uk/data_request/cif.
4.2. X-ray crystal structure
Crystallographic measurements of compound 2 were performed
at low temperature (180 K) on an Xcalibur Oxford Diffraction dif-
fractometer using graphite-monochromated Mo
K
a
radiation
ꢁ
(l¼0.71073 A) (Table 1). The final unit cell parameters have been
Supplementary data
obtained by means of a least-squares refinement. The structure has
been solved by direct methods using SIR9220 and refined by means
of least-squares procedures on F2 with the aid of the program
SHELXL9721 included in the softwares package WinGXversion
1.63.22 Drawing of molecule was performed with the program
ORTEP3223 with 30% probability displacement ellipsoids for non-
hydrogen atoms.
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2012.11.081.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
References and notes
Table 1
Crystal data and experimental details for compounds 2 and 5$[PF6]2
1. (a) Urriolabeitia, E. P. Top. Organomet. Chem. 2010, 30, 15e48; (b) Urriolabeitia,
E. P. Dalton Trans. 2008, 5673e5686; (c) Kolodiazhnyi, O. I. Tetrahedron 1996, 52,
1855e1929; (d) Cristau, H. J. Chem. Rev. 1994, 94, 1299e1313; (e) Schmidbaur, H.
Angew. Chem. 1983, 95, 980e1000; Angew. Chem., Int. Ed. Engl. 1983, 22, 907e927.
2. Petz, W.; Frenking, G. Top. Organomet. Chem. 2010, 30, 49e92.
3. (a) Schmidbaur, H.; Herr, R.; Zybill, C. E. Chem. Ber. 1984, 117, 3374e3380; (b)
Abdalilah, M.; Canac, Y.; Lepetit, C.; Chauvin, R. C. R. Chim. 2010,13,1091e1098; (c)
Maaliki, C.; Abdalilah, M.; Barthes, C.; Duhayon, C.; Canac, Y.; Chauvin, R. Eur. J.
Inorg. Chem. 2012, 4057e4064; (d) Canac, Y.; Lepetit, C.; Abdalilah, M.; Duhayon,
C.; Chauvin, R. J. Am. Chem. Soc. 2008, 130, 8406e8413; (e) Vicente, J.; Chicote, M.
T.; Saura-Llamas, I. Organometallics 1988, 7, 997e1006; (f) Costa, T.; Schmidbaur,
H. Chem. Ber. 1982, 115, 1367e1373; (g) Holy, N.; Deschler, U.; Schmidbaur, H.
Chem. Ber. 1982, 115, 1379e1388; (h) Spannenberg, A.; Baumann, W.; Rosenthal,
U. Organometallics 2000, 19, 3991e3993; (i) Falvello, L. R.; Margalejo, M. E.;
Navarro, R.; Urriolabeitia, E. P. Inorg. Chim. Acta 2003, 347, 75e85.
Compound
2
5$[PF6]2
Molecular formula
Formula weight
C24H20BrP
419.28
Monoclinic
P21/c
9.206(2)
12.957(3)
16.757(4)
1976.1(8)
4
(C42H36P4F12)*C3H6O
950.70
Crystallographic system
Space group
Tetragonal
I(ꢀ4)2d
20.3806(2)
20.3806(2)
20.7970(2)
8638.4(2)
8
1.462
296(2)
3904
2.396
ꢁ
a [A]
ꢁ
b [A]
ꢁ
c [A]
3
ꢁ
V [A ]
Z
Dcalcd [g/cm3]
T [K]
1.409
180(2)
856
4. Kilian, P.; Knight, F. R.; Woollins, D. Chem.dEur. J. 2011, 17, 2302e2328.
5. (a) Jackson, R. D.; James, S.; Orpen, A. G.; Pringle, P. G. J. Organomet. Chem. 1993,
F(000)
m
[mmꢀ1
]
2.166
€
ꢀ
458, C3eC4; (b) Karac¸ ar, A.; Freytag, M.; Thonnessen, H.; Omelanczuk, J.; Jones,
P. G.; Bartsch, R.; Schmutzler, R. Z. Anorg. Allg. Chem. 2000, 626, 2361e2372; (c)
Karac¸ ar, A.; Freytag, M.; Jones, P. G.; Bartsch, R.; Schmutzler, R. Z. Anorg. Allg.
Chem. 2001, 627, 1571e1581.
Reflections measured
Reflections unique (all)
Rint
13,018
3749
0.1585
235
0.1108
0.2355
0.825
114,239
4372
0.0279
300
0.1391
0.0466
1.053
0.499
Parameters refined
€
ꢀ
6. Karac¸ ar, A.; Freytag, M.; Thonnessen, H.; Omelanczuk, J.; Jones, P. G.; Bartsch, R.;
wR2
Schmutzler, R. Heteroat. Chem. 2001, 12, 102e113.
7. Karac¸ ar, A.; Klaukien, V.; Freytag, M.; Thonnessen, H.; Omelanczuk, J.; Jones, P.
R1 (all data)
Goodness-of-fit
Residual density max [e A
€
ꢀ
G.; Bartsch, R.; Schmutzler, R. Z. Anorg. Allg. Chem. 2001, 627, 2589e2603.
ꢁꢀ3
]
0.614
ꢀ
8. Owsianik, K.; Chauvin, R.; Balinska, A.; Wieczorek, M.; Cypryk, M.; Miko1ajczyk,
M. Organometallics 2009, 28, 4929e4937.
9. Costa, T.; Schmidbaur, H. Chem. Ber. 1982, 115, 1374e1378.
10. Abdalilah, M.; Zurawinski, R.; Canac, Y.; Laleu, B.; Lacour, J.; Lepetit, C.; Magro,
G.; Bernardinelli, G.; Donnadieu, B.; Duhayon, C.; Mikolajczyk, M.; Chauvin, R.
Dalton. Trans. 2009, 8493e8508.
Crystallization of the product 5$[PF6]2 from acetone/hexane
(5:1) resulted in colorless crystals. The data were collected with
Bruker APEX-II CCD diffractometer at room temperature using
11. Allen, D. W.; Millar, I. T.; Mann, F. G. J. Chem. Soc. C 1967, 1869e1875.
CuKa
radiation.24 An experimental absorption correction was ap-
€
12. Schmidbaur, H.; Mortl, A. J. Organomet. Chem. 1983, 250, 171e182.
plied, with transmission min¼0.45 and max¼0.65.25 Structure was
solved by direct methods with SHELXS-97 and refined with
SHELXL-97 using full-matrix least-squares with F2.26 The H atoms
were found in a difference Fourier map and their geometry was
regularized. Then all H atoms were positionally constrained to ride
on their parent atoms. The isotropic thermal displacement pa-
rameters for all H atoms were refined. All nonhydrogen atoms were
refined anisotropically. For all data, the final wR2 was 0.1391,
13. (a) Maerkl, G. Angew. Chem. 1963, 75, 859e860; Angew. Chem., Int. Ed. Engl. 1963,
2, 620; (b) Snider, T. E.; Berlin, K. D. Phosphorus Relat. Group V Elem.1971,1, 59e60.
14. Gallucci, J. C.; Holmes, R. R. J. Am. Chem. Soc. 1980, 102, 4379e4386.
15. (a) Parker, A. J. Chem. Rev. 1969, 69, 1e32; (b) Artamkina, G. A.; Egorov, M. P.;
Beletskaya, I. P. Chem. Rev. 1982, 82, 427e459.
16. Zefirov, N. S.; Makhon’kov, D. I. Chem. Rev. 1982, 82, 615e624.
17. Wawrzyniak, P.; Slawin, A. M. Z.; Fuller, A. L.; Woollins, J. D.; Kilian, P. Dalton
Trans. 2009, 7883e7884.
18. van Soolingen, J.; de Lang, R.-J.; den Besten, R.; Klusener, P. A. A.; Veldman, N.;
Spek, A. L.; Brandsma, L. Synth. Commun. 1995, 25, 1741e1744.
19. Zhang, X.; Liu, H.; Hu, X.; Tang, G.; Zhu, J.; Zhao, Y. Org. Lett. 2011, 13,
3478e3481.
20. SIR92, A Program for Crystal Structure Solution. Altomare, A.; Cascarano, G.;
Giacovazzo, C.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J. Appl.
Crystallogr. 1994, 27, 435e436.
ꢁꢀ3
R1¼0.0466, S¼1.053, max Dr¼0.50 e A (Table 1).
The COOT and MERCURY programs were used for model build-
ing and structure visualization.27 The asymmetric unit contains
a half of the molecule. The following atoms lie on the special po-
sitions: naphthalene carbons C35 and C36, phosphorus P2 and
21. Sheldrick, G. M. SHELXL97. Program for the Refinement of Crystal Structures;
University of Gottingen: Germany, 1997.
22. WINGX-1.63 Integrated System of Windows Programs for the Solution, Re-
finement and Analysis of Single Crystal X-ray Diffraction Data Farrugia, L. J. J.
Appl. Crystallogr. 1999, 32, 837e838.
ꢀ
fluorides F23 and F24 of the first PF6 ion, phosphorus P3 of the
second PF6ꢀ ion, and oxygen O51A with carbon C51A of the acetone
moiety. The complete structure (shown in Fig. 4) could be assem-
bled by applying the respective symmetry operations to the fol-
lowing items that are present in the asymmetric unit: (xþ1, 1.5ꢀy,
0.25ꢀz: for 1,8-bis(diphenylphosphino)naphthalene moiety), (1ꢀx,
23. ORTEP3 for Windows Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565e566.
24. (a) APEX2 Version 2010.3-0, Bruker AXS. (b) SAINT Version 7.68A; Bruker AXS:
2009.
€
25. SADABS Version 2008/1 (Sheldrick, G.M., University of Gottingen, Germany,
and Bruker AXS).
ꢀ
26. Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112e122.
27. (a) COOT Version 0.6.1 Emsley, P.; Lohkamp, B.; Scott, W. G.; Cowtan, K. Acta
Crystallogr. 2010, D66, 486e501; (b) Macrae, C. F.; Bruno, I. J.; Chisholm, J. A.;
Edgington, P. R.; McCabe, P.; Pidcock, E.; Rodriguez-Monge, L.; Taylor, R.; van de
Streek, J.; Wood, P. A. J. Appl. Crystallogr. 2008, 41, 466e470.
1ꢀy, z: for the first PF6 ion with phosphorus atom labeled as P2),
ꢀ
(1.5ꢀx, y, 0.75ꢀz: for the second PF6 ion with phosphorus atom
labeled as P3). The complete coordinates for both conformers of
positionally disordered solvent (acetone) molecule could be