Structure and reactivity of new phosphine ligands containing the hemi-labile sulfone moiety

Article abstract of DOI:10.1039/b513390d

New heterofunctional phosphine ligands have been synthesised, incorporating the substitutionally labile sulfone and sulfonamide moieties as chelating groups, which display activity in the palladium-catalysed Suzuki and amination cross-coupling reactions.

Full text of DOI:10.1039/b513390d

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PAPER
www.rsc.org/dalton | Dalton Transactions
Structure and reactivity of new phosphine ligands containing the
hemi-labile sulfone moiety
Christopher J. Chapman,* Christopher G. Frost and Mary F. Mahon*
Received 21st September 2005, Accepted 22nd December 2005
First published as an Advance Article on the web 9th February 2006
DOI: 10.1039/b513390d
New heterofunctional phosphine ligands have been synthesised, incorporating the substitutionally
labile sulfone and sulfonamide moieties as chelating groups, which display activity in the
palladium-catalysed Suzuki and amination cross-coupling reactions. Single-crystal X-ray diffraction
studies of the complexes formed with [Pd(l-Cl)(dmba)] (dmba-H = N,N-dimethylbenzylamine)
highlight the coordinating nature of these ligands; showing the formation of a bis chelate complex
through a six-membered Pd–P–C–C–S–O ring with the sulfonamide class of ligands.
that of 10-phenyl-10H-9-thia-10-phosphaanthracene-9,9-dioxide,
Introduction
1.6 The six-membered [1,4]-thiaphosphine ring is anticipated to
sit in a boat formation with the terminal anthracene phenyl
groups pinned back. Together with the phenyl phosphine, the
final structure was expected to resemble a crested bird in flight
and predicted to perch on the metal centre, binding through the
phosphine. As one of the sulfone oxygens remains proximate to
the metal centre at all times, it offers the possibility of stabilising
reaction intermediates by coordinating when required (Fig. 1).
The oxygen is predicted to be hemilabile and thus rotation about
the P–[M] bond is expected to occur.
The synthesis of polydentate hybrid ligands, combining both hard
and soft donor functionality, is of considerable interest in the
development of homogeneous catalysts as their chelating ability
promotes increased stability during catalysis.1 Various metal
complexes and ligands have been prepared containing P,O or P,N
binding modes, which are catalytically active in a broad selection
of reactions. Although the use of oxygen as the substitutionally
labile moiety has been utilised in many forms, including amides,2
ethers,3 phosphine oxides4 and ketones,5 the application of the
sulfone oxygen as the coordinating group has yet to be investigated
in any real depth.
Herein we report the synthesis of a variety of ligands containing
the sulfone moiety as a possible weakly coordinating species on
monophosphine backbones. Both rotationally constrained and
unconstrained sulfones have been prepared along with a series of
sulfonamide containing ligands possessing variation of the amine
and phosphine moieties (1–5).
Fig. 1
A number of publications have investigated ortho-lithiation
of sulfonamides, as reviewed by Familoni,7 and these reports
indicate that aryl sulfonamides (like aryl ethers) are ortho directing.
Thus ligand 1 was prepared in 67% yield by the reaction of
diphenyl sulfone 6 with two equivalents of n-butyllithium in
◦
tetrahydrofuran at −78 C followed by the dropwise addition of
dichlorophenylphosphine in tetrahydrofuran (Scheme 1). Whilst
the formation of the phosphine bridged diphenyl sulfone polymer
7 was envisaged to be a major side reaction, no such by-product
was observed in the reaction mixture. However, greater isolated
yields of 1 were achieved with more dilute solutions of sulfone 6
and dichlorophenylphosphine.
Sulfone ligand 2 was similarly prepared via the reaction of 6 with
one equivalent of n-butyllithium and chlorodiphenylphosphine
(Scheme 2). Ligand 2 possesses similar gross structural features to
1, but with less steric and rotational constraints. The formation of
bisphosphinated product 8 was observed in low yield during the
synthesis of 2.
Results and discussion
Sulfone ligands
Initial studies concerned with the application of sulfone oxygens
as hemilabile moieties centred on the structure of an aryl sulfone,
with an adjacent phosphine group. The most elegant design was
Department of Chemistry, University of Bath, Claverton down, Bath, UK
BA2 7AY. E-mail: m.f.mahon@bath.ac.uk; Fax: +44 (0)1225 386231;
Tel: +44 (0)1225 383752
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(dicyclohexylphosphanyl)benzenesulfonamide 5 was also pre-
pared in 65% overall yield from benzenesulfonyl chloride 9 via
the same route.
Scheme 1 Reagents and conditions: (i) n-BuLi, THF, −78 ◦C; (ii) Cl2PPh,
THF, 18 h.
Scheme 3 Reagents and conditions: (i) Cy2NH (4 equiv.), DCM; (ii)
n-BuLi, THF, −78 ◦C; (iii) ClPPh2, THF, 18 h; (iv) ClPCy2, THF, 18 h; (v)
Me2NH (aq.), THF, 0 ◦C, 2 h.
Catalytic results
Preliminary catalytic results indicate that both the sulfone and
sulfonamide ligands are active ligands for the palladium catalysed
Suzuki and amination coupling reactions. Initial experiments
examined the coupling of 4-bromotoluene with phenylboronic
acid (Table 1). The palladium source used in the reaction had a
substantial effect on the catalytic efficiency of the final palladium-
ligand complex. Ligand 1 displayed disappointingly low reactivity
with [Pd2(dba)3] (3%), but the use of [Pd(OAc)2] or the preformed
triflate salt 13 afforded a significant increase in yield of the desired
product isolated (entries 1,2 and 3). The sulfonamide ligands (3–
5) exhibited greatest reactivity with [Pd2(dba)3] as the palladium
source (>99% yield). Interestingly, ligand 2 displays greater activity
Scheme 2 Reagents and conditions: (i) n-BuLi, THF, −78 ◦C; (ii) ClPPh2,
THF, 18 h.
Sulfonamide ligands
As more flexible analogues to the sulfones, the metal binding
properties and catalytic potential of sulfonamides was also studied.
Thus the sulfonamides were prepared in analogous fashion from
benzenesulfonyl chloride 9 through the amination of the chloride
and subsequent phosphination of the sulfonamide. Whilst the
sulfonamide was predicted to bind through an oxygen, coordi-
nation through the tertiary nitrogen could not be ignored as a
possibility, as shown by Hiroi et al.8 Initial attempts to couple
9 with dicyclohexylamine using 4-(N,N-dimethylamino)pyridine
(DMAP) in refluxing dichloromethane led to a disappointing 35%
yield. However, the direct reaction of 9 with an excess of dicyclo-
hexylamine in dichloromethane at ambient temperature afforded
the same product in a more respectable 80% yield. Unfortunately,
the phosphination of 10 with chlorodiphenylphosphine to afford
ligand 3 was only achieved in 34% yield, no doubt due to steric ef-
fects (Scheme 3). It has been shown that ligand phosphine basicity
has a significant impact on the activity of any resultant complex
synthesised, by directly affecting the electronics at the metal centre.
Moreover, typically more basic alkylphosphines possess a higher
catalytic activity when applied to palladium-catalysed reactions.9,10
To this end the synthesis of the more basic N,N-dicyclohexyl-
2-(dicyclohexylphosphanyl)benzenesulfonamide 4 was effected.
Interestingly, the phosphination of 10 proceeded in signif-
icantly higher yield with chlorodicyclohexylphosphine than
previously observed with chlorodiphenylphosphine; 73 and
34%, respectively. The smaller sulfonamide N,N-dimethyl-2-
Table 1 Selected results for the palladium catalysed Suzuki reactions
with phenylboronic acida
Entry
Ligand
Palladium source
Yieldb (%)
1
2
3
4
5
6
7
8
1
[Pd2(dba)3]
[Pd(OAc)2]
13
[Pd(OAc)2]
[Pd2(dba)3]
[Pd(OAc)2]
[Pd2(dba)3]
[Pd2(dba)3]
3
69
65
93
99
75
>99
99
1
—
2
3
3
4
5
a Typical reaction conditions: 1.0 equiv. of aryl halide, 1.5 equiv. of
phenylboronic acid, 2.0 equiv. of Cs2CO3, 2 mol% Pd, 2 mol% ligand,
dioxane (3 mL/mmol halide), 80 ◦C, 3 h. b Isolated yield.
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Table 2 Palladium catalysed Suzuki reaction of aryl chloride with
provided an isolated product yield of 53% obtained. Interestingly,
the selectivity of the palladium source was reversed for 3 over that
with the other ligands tested. No explanation can be offered at
this time, however any variation is expected to result from minor
interactions between the ligands and the coordinated species on
the palladium complexes.
phenylboronic acida
Application of 4 in the reaction with 4-bromotoluene resulted
in an isolated yield comparable to that obtained by Buchwald
and co-workers, 93 and 92%, respectively (entry 4).10 However, the
activity was significantly reduced when applied to the coupling
of 4-chlorotoluene, 37% (entry 5) compared to 93% achieved
by Buchwald and co-workers. Replacement of the sulfonamide
cyclohexyl groups by the less sterically hindered methyl (ligand 5)
provided a mild increase in catalytic activity (44%).
Entry
Ligand
Palladium source
Yieldb (%)
1
2
3
4
2
4
4
5
[Pd2(dba)3]
[Pd(OAc)2]
[Pd(OAc)2]
[Pd(OAc)2]
32
72
77
3
a Typical reaction conditions: 1.0 equiv. of arylchloride, 1.5 equiv. of
phenylboronic acid, 2.0 equiv. of Cs2CO3, 2 mol% Pd, 2 mol% ligand,
dioxane (3 mL/mmol halide), 80 ◦C, 3 h. b Isolated yield.
Preparation and studies of transition metal–ligand complexes
than the more constrained 1 (entries 2 and 4). Given the similarity
of the groups around the phosphorous centre this variation is
attributed to the increase in rotational freedom of the phenyl
groups about the phosphorus in 2 over those in 1, and the
possibility of a p-interaction between the terminal arene ring and
the palladium centre as observed by Buchwald in related ligands.11
Whilst disappointing results were obtained for the coupling
of chlorotoluene with phenyl boronic acid,12 couplings with 1-
chloro-4-tosylbenzene proceeded in higher yields (Table 2). As
expected the more basic dicyclohexylphosphines, 4 and 5 afforded
higher yields of the desired 1-phenyl-4-tosylbenzene. Contrary to
the activity of palladium sources observed in the coupling of
bromotoluene, use of [Pd(OAc)2] gave superior yields to those
achieved with [Pd2(dba)3].
To investigate the possible binding modes of ligands 1 and 3,
palladium complexes were prepared in a similar fashion to that
used by Braunstein et al., to show hemilability of acetamide-
derived P,O-phosphine ligands.14 Reaction of [Pd(l-Cl)(dmba)]2
(dmba-H = N,N-dimethylbenzylamine) with 2 molar equivalents
of 1 afforded [PdCl(dmba)(1)] 11 as a pale green solid (Scheme 4).
In his earlier work Buchwald and co-workers noted that
triphenylphosphine was an ineffective ligand for the palladium
catalysed amination reaction,13 thus it was no surprise that ligand
1 afforded the desired amination cross coupled product in low
yields, given that it is fundamentally similar to triphenylphosphine
(Table 3, entry 1). In this case, the major product from the
reaction was through dehalogenation. Exchange of the phenyl
group for cyclohexyl in 3 resulted in an increase of basicity at
the phosphorus and concomitant increase in catalytic activity.
The use of this ligand, with [Pd(OAc)2] as the palladium source,
Scheme 4 Reagents and conditions: (i) [Pd(l-Cl)(dmba)]2, DCM, 30 min.
1
31P{ H} NMR spectroscopy at ambient temperature showed
the presence of a single sharp peak at d 16.43, indicative of
a single form in the solution phase. However single-crystal X-
ray crystallography showed the presence of two configurational
isomers, 11a and 11b (Fig. 2), of the complex each having a
distinct geometry (Fig. 3). A selection of intermolecular distances
and angles are presented in Table 4, which illustrate that the two
conformers are markedly different from a geometrical perspective.
Moreover, while no significant variation in the S–O bond distances
was evident in the solid state for the two isomers of 11, solution
phase IR spectrometry indicates two environments for the sulfone
therein. In particular the free ligand, 1, displays stretches at 1312
and 1160 cm−1 while, in 11, stretches are observed at 1317, 1310,
Table 3 Palladium catalysed amination of halotoluenes with
morpholinea
Entry
Ligand
X
Yieldb (%)
1
2
3
4
5
6
1
2
3
4
4
5
Br
Br
Br
Br
Cl
Br
25
67
38
93
37
85
a Typical reaction conditions: 1.0 equiv. of aryl halide, 1.2 equiv. of
morpholine, 1.4 equiv. of NaOt-Bu, 2 mol% [Pd2(dba)3], ligand (1:1 Pd),
toluene (1 mL/mmol halide), 100 ◦C, 6 h. b Isolated yield.
Fig. 2 Configurational isomers of complex 11.
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˚
form 12. Three counterion complexes were prepared: OTf 13, PF6
Table 4 Selected intramolecular distances (A) and angles ( ) for complex
1
1
14 and SbF6 15 (Scheme 5, Selected H and 31P{ H} NMR data
are presented in Table 5). Single-crystal X-ray analysis of 13 and
15 elucidated structures where the sulfone oxygens remain above
the plane (Fig. 4 and 5, respectively, with selected bond distances
11
Pd(1)–P(1)
Pd(1)–N(1)
Pd(1)–Cl(1)
Pd(1)–C(11)
Pd(2)–P(2)
Pd(2)–N(2)
Pd(2)–Cl(2)
Pd(2)–C(81)
2.2454(8)
2.132(3)
2.3872(8)
2.024(3)
2.2650(7)
2.135(2)
2.3856(7)
2.020(3)
Pd(1)–O(2)
S(1)–O(1)
S(1)–O(2)
3.768(2)
1.436(2)
1.434(2)
1
and angles presented in Tables 6 and 7). H NMR spectroscopy
Pd(2)–O(4)
S(2)–O(3)
S(2)–O(4)
3.407(2)
1.439(2)
1.440(2)
of complexes 14 and 15 indicated the presence of water in the
complexes, indeed X-ray analysis of 15 elucidated the complex
with water coordinated in place of the chloride ion of 11. Although
single-crystal X-ray diffraction data were not collected for complex
14, the presence of water coordinated to the palladium centre could
be inferred, due to the presence of a signal in the 1H NMR for water
and the correlation between the data collected for 14 and 15.
N(1)–Pd(1)–P(1)
C(11)–Pd(1)–Cl(1)
C(11)–Pd(1)–N(1)
N(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–Cl(1)
C(11)–Pd(1)–P(1)
P(1)–Pd(1)–O(2)
N(2)–Pd(2)–P(2)
C(81)–Pd(2)–Cl(2)
C(81)–Pd(2)–N(2)
N(2)–Pd(2)–Cl(2)
P(2)–Pd(2)–Cl(2)
C(81)–Pd(2)–P(2)
P(2)–Pd(2)–O(4)
173.50(9)
174.07(9)
81.28(12)
92.81(8)
86.55(3)
99.38(9)
60.52(4)
177.22(7)
173.08(8)
82.03(11)
91.47(7)
85.76(3)
100.74(9)
67.04(4)
C(41)–P(1)–Pd(1)
C(21)–P(1)–Pd(1)
C(31)–P(1)–Pd(1)
C(21)–P(1)–C(31)
C(41)–P(1)–C(21)
C(41)–P(1)–C(31)
109.99(10)
124.02(10)
117.42(10)
99.39(14)
100.18(13)
102.72(14)
C(71)–P(2)–Pd(2)
C(51)–P(2)–Pd(2)
C(61)–P(2)–Pd(2)
C(61)–P(2)–C(51)
C(71)–P(1)–C(51)
C(71)–P(1)–C(61)
112.28(10)
111.97(9)
123.59(9)
98.56(13)
104.11(14)
103.99(14)
Scheme 5 Preparation of palladium complexes 13–15 to investigate
possible coordination through the sulfone oxygen.
Fig. 3 ORTEP plot of one molecule in the asymmetric unit of complex 11
(hydrogen atoms have been omitted for clarity). Ellipsoids are represented
at 30% probability.
Comparison of the data from the X-ray diffraction of complexes
11, 13 and 15 highlighted a significant shift of the proximal sulfone
oxygen toward the palladium centre for weaker coordinating
1170 and 1162 cm−1, indicative of some interaction between the
palladium and sulfone oxygens.
˚
Exchange of the chloride ions with other counter ions by
treatment of 11 with silver salts was expected to yield cationic
PdII salts with the sulfone oxygen bound to the palladium, of the
anions: (Pd–O) 3.407(2)–3.1200(14)–2.9454(12) A.
Closer inspection of the three-dimensional structures obtained
for the three complexes indicated that the sulfone oxygen could
Table 5 Selected NMR data for ligand 1 and complexes 11, 13, 14 and 15
1
Compound
Counter ion
Cl−
1H NMR
31P{ H} NMR
1
11
−17.27
2.82 (6H, d, 4JPH = 2.6, N(CH3)2)
4.05 (2H, d, 4JPH = 2.0, CH2)
2.74 (6H, d, 4JPH = 2.9, N(CH3)2)
3.95 (2H, d, 4JPH = 1.9, CH2)
2.70 (6H, d, 4JPH = 2.8, N(CH3)2)
4.01 (2H, d, 4JPH = 2.0, CH2)
2.72 (6H, d, 4JPH = 2.8, N(CH3)2)
4.03 (2H, d, 4JPH = 2.0, CH2)
16.43
13.29
−
13
14
15
CF3SO3
−
PF6
13.47
−142.82 (septet JPF = 1320, PF6)
−
SbF6
12.82
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Table 7 Selected intramolecular distances (A) and angles ( ) for complex
15
Pd(1)–P(1)
Pd(1)–N(1)
Pd(1)–O(3)
Pd(1)–C(1)
2.2462(4)
2.1352(14)
2.2031(13)
1.9793(16)
Pd(1)–O(1)
S(1)–O(1)
S(1)–O(2)
2.9454(12)
1.4402(13)
1.4430(12)
N(1)–Pd(1)–P(1)
C(1)–Pd(1)–O(3)
C(1)–Pd(1)–N(1)
N(1)–Pd(1)–O(3)
P(1)–Pd(1)–O(3)
C(1)–Pd(1)–P(1)
P(1)–Pd(1)–O(1)
165.19(4)
176.47(6)
81.89(6)
94.98(5)
91.91(4)
91.51(5)
78.04(3)
C(10)–P(1)–Pd(1)
C(22)–P(1)–Pd(1)
C(16)–P(1)–Pd(1)
C(16)–P(1)–C(22)
C(10)–P(1)–C(22)
C(10)–P(1)–C(16)
120.20(5)
111.33(5)
110.61(5)
99.53(7)
109.58(7)
103.34(7)
the ligand in very close proximity, possibly over, the phenyl ring
of the dimethylbenzylamine (Fig. 6).
Fig. 4 ORTEP plot of complex 13 (hydrogen atoms have been omitted
for clarity). Ellipsoids are represented at 30% probability.
Fig. 6 Possible interaction between the two phenyl rings, hindering direct
coordination of the sulfone to palladium centre.
The analogous reaction of ligand 3 with [Pd(l-Cl)(dmba)]2
afforded the neutral chloride complex 16 (Scheme 6), as a pale
1
green solid in 92% yield, with a 31P{ H} NMR signal at d 46.07.
Treatment of 16 with silver hexafluoroantimonate (AgSbF6) in
anhydrous DCM for 30 min produced the cationic palladium
1
complex 17 in 91% yield (selected 1H and 31P{ H} NMR data are
1
presented in Table 8). Interestingly the 31P{ H} NMR signal shifts
Fig. 5 ORTEP plot of complex 15 (hydrogens have been omitted for
clarity). Ellipsoids are represented at 30% probability.
◦
˚
Table 6 Selected intramolecular distances (A) and angles ( ) for complex
13
Pd(1)–P(1)
Pd(1)–N(1)
Pd(1)–O(4)
Pd(1)–C(41)
2.2504(4)
2.1408(15)
2.2075(12)
1.9810(17)
Pd(1)–O(1)
S(1)–O(1)
S(1)–O(2)
3.1200(14)
1.4439(13)
1.4397(14)
N(1)–Pd(1)–P(1)
C(41)–Pd(1)–O(4)
C(41)–Pd(1)–N(1)
N(1)–Pd(1)–O(4)
P(1)–Pd(1)–O(4)
C(41)–Pd(1)–P(1)
P(1)–Pd(1)–O(1)
167.79(5)
173.97(6)
81.94(7)
93.02(5)
92.52(4)
93.06(5)
73.06(3)
C(11)–P(1)–Pd(1)
C(31)–P(1)–Pd(1)
C(21)–P(1)–Pd(1)
C(21)–P(1)–C(31)
C(11)–P(1)–C(31)
C(11)–P(1)–C(21)
120.46(6)
114.28(5)
110.72(5)
100.64(8)
105.17(7)
103.26(8)
not bind to the palladium centre due to steric hindrance, caused
by the rigid nature of ligand 1. Modelling studies on 11 show that
rotation about the P–Pd bond would position the phenyl tail of
Scheme 6 Reagents and conditions: (i) [Pd(l-Cl)(dmba)]2, DCM, 30 min;
(ii) AgSbF6, DCM, 30 min.
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Table 8 Selected NMR data for ligand 3 and complexes 16 and 17
1
Compound
Counter ion
Cl−
1H NMR
31P{ H} NMR
3
16
−5.30
2.85 (6H, br s, CH3)
46.07
3.80–4.40 (2H, vbr s, CH2N)
2.85 (6H, d, 4JPH = 2.7, N(CH3)2)
4.09 (2H, s, NCH2)
−
17
SbF6
33.40
upfield, from d 46.07 to d 33.40. Single-crystal X-ray diffraction
studies were performed on both complexes 16 and 17 with selected
intramolecular distances and angles reported in (Tables 9 and
10). Conversely to that observed with ligand 1, exchange of the
chloride salt of 16 with a hexafluoroantimonate anion, results in
the coordination of the sulfone to the palladium centre as shown
in complex 17 (Fig. 7 and 8).
1
Interestingly, the H NMR spectroscopic data for 16 displays
broad signals for protons on carbons adjacent to the nitrogen of
N,N-dimethylbenzylamine. These together with a slightly broad
phosphorus signal suggest dynamic behaviour within the complex
in the solution phase; with the possible formation of the cationic
PdII salt 16ꢀ or merely the coordination and dissociation of the
sulfone oxygen to the palladium centre (Scheme 7). The single-
crystal X-ray diffraction data for 16 exhibits a single structure
with the chloride ion bound to the palladium centre.
Crystal structures
Strain within the metallocyclopentane ring across all crystal
Fig. 7 ORTEP plot of complex 16 (hydrogen atoms have been omitted
for clarity). Ellipsoids are represented at 30% probability.
structures is evidenced by closing down of both the N–Cmethylene
–
Caryl and Pd–Caryl–Cmethylene angles with concurrent opening of the
external Pd–Caryl–Caryl angle which average 109.0, 112.3 and 129.9◦,
respectively.
◦
˚
Table 9 Selected intramolecular distances (A) and angles ( ) for complex
16
Pd(1)–P(1)
Pd(1)–N(1)
Pd(1)–Cl(1)
Pd(1)–C(1)
2.2456(4)
2.1279(14)
2.4233(4)
2.0086(17)
Pd(1)–O(2)
S(1)–O(1)
S(1)–O(2)
2.9399(12)
1.4380(13)
1.4379(13)
N(1)–Pd(1)–P(1)
C(1)–Pd(1)–Cl(1)
C(1)–Pd(1)–N(1)
N(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–Cl(1)
C(1)–Pd(1)–P(1)
172.58(4)
165.73(5)
82.62(6)
91.75(4)
91.914(15)
95.23(5)
P(1)–Pd(1)–O(2)
C(22)–P(1)–Pd(1)
S(1)–O(2)–Pd(1)
O(2)–S(1)–C(27)
C(22)–C(27)–S(1)
C(27)–C(22)–P(1)
68.34(3)
116.67(5)
136.93(7)
107.86(7)
124.05(12)
124.41(12)
Fig. 8 ORTEP plot of the cation in 17 (hydrogen atoms have been omitted
for clarity). Ellipsoids are represented at 30% probability.
◦
˚
Table 10 Selected intramolecular distances (A) and angles ( ) for com-
plex 17
Moreover, in 11, 13, 15 and 16 the configuration of the dmba
methylene fragment relative to a least-squares plane based on the
central metal and the atoms bonded to it (excluding the amine
nitrogen) appears to have bearing on the overall structure. In
particular, the potential for a sulfone oxygen to coordinate to
the palladium as a square-pyramidal apex is enhanced where the
benzyl carbon and the sulfone moiety lie cis to this plane. Thus,
for the molecule based on Pd(2) in 11, as well as for 13, 15 and
Pd(1)–P(1)
Pd(1)–N(1)
Pd(1)–O(1)
2.2486(4)
2.1191(13)
2.1508(11)
Pd(1)–C(1)
S(1)–O(1)
S(1)–O(2)
1.9913(15)
1.4711(12)
1.4307(12)
N(1)–Pd(1)–P(1)
C(1)–Pd(1)–O(1)
C(1)–Pd(1)–N(1)
N(1)–Pd(1)–O(1)
P(1)–Pd(1)–O(1)
C(1)–Pd(1)–P(1)
174.88(4)
166.77(6)
83.22(6)
93.29(5)
82.14(3)
100.71(5)
C(34)–P(1)–Pd(1)
S(1)–O(1)–Pd(1)
O(1)–S(1)–C(39)
C(34)–C(39)–S(1)
C(39)–C(34)–P(1)
113.55(5)
127.68(7)
107.16(7)
125.06(12)
126.22(12)
˚
16 the cis methylenes are situated 0.75, 1.32, 1.36 and 1.30 A
2256 | Dalton Trans., 2006, 2251–2262
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©

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proved to be an effective partner for this reaction with isolated
yields of up to 77% achieved. These results clearly show the
phosphine-sulfone and phosphine-sulfonamide hybrid ligands to
be effective ligands for palladium catalysed cross couplings, further
studies are being performed into the structure and activity of this
novel ligand class.
Experimental
General considerations
Commercially available solvents and reagents were obtained from
Sigma-Aldrich Company Ltd, Lancaster Synthesis Ltd, Fisher
Scientific Ltd and Strem Chemicals UK and were used without
further purification.
Reactions were routinely carried out under pure dry nitrogen or
argon, using dry dioxygen-free solvents unless otherwise noted.
Melting points were determined using a Bu¨chi 535 melting point
apparatus and are uncorrected. IR spectra (4000 to 600 cm−1) were
recorded on a Perkin Elmer (1600) FT spectrometer with internal
calibration. Elemental analyses were performed with an Exeter
analytical, INC. CE-440 elemental analyzer in the Chemistry
Department at the University of Bath. Fast atom bombardment
(FAB) and electron Impact (EI) mass spectra were obtained using
a Fisons VG Autospec Finnigan MAT 8340 instrument at the
University of Bath.
Scheme 7 Possible fluctional behaviour of complex 16 in solution.
on the sulfone side of the palladium coordination plane defined
above, and the corresponding Pd(2)–O(4), Pd(1)–O(1), Pd(1)–O(1)
and Pd(1)–O(2) distances are 3.407(2), 3.1200(14), 2.9454(12) and
1H, 13C and 31P NMR spectra were recorded on a Varian
Mercury 400, Bru¨ker Avance 300 or a JEOL GX-270 spectrometer.
Chemical shifts (d) are expressed in parts per million (ppm),
referenced to SiMe4 or 85% H3PO4.
˚
2.9399(12) A. Conversely, for the molecule based on Pd(1) in 11,
˚
the methylene lies trans to the sulfone functionality by 1.07 A, and
˚
the accompanying Pd(1)–O(2) distance is 3.768(2) A.
Based on this argument, one might have expected greater metal–
sulfone interaction in compound 13. However, the situation is
more complex in this structure where a chloride ligand has been
replaced by a bulkier triflate.
Overall, the trend observed here may not be altogether surpris-
ing when the steric impact of the dmba ligand is considered, as cis
arrangement of the methylene necessitates movement of the aryl
ring further away from the sulfone moiety.
The palladium complex [Pd(l-Cl)(dmba)]2 was prepared in
accordance to the literature procedure.15
N,N-Dicyclohexylbenzenesulfonamide 10
To a stirred solution of benzenesulfonyl chloride (10 g, 56.6 mmol)
in dichloromethane (60 mL), at room temperature, was added
dicyclohexylamine (36.4 g, 0.2 mol) under an atmosphere of
nitrogen. The reaction mixture was allowed to stir for 72 h,
after which it was poured into NaOH (aq.) (2 M, 75 mL) and
the aqueous layer extracted with dichloromethane (2 × 20 mL).
The combined organics were washed with brine (20 mL), dried
over magnesium sulfate and concentrated in vacuo to yield the
crude product. Purification by column chromatography on silica
(dichloromethane) gave the title compound (15 g, 83%) as a
The structure of compound 17 differs from the others in that
one of the sulfone oxygens is coordinated in the metal square
˚
plane with a Pd(1)–O(1) bond length of 2.1508(13) A. Indeed
this Pd–O distance is shorter than for those observed between the
˚
palladium and triflate oxygen in 13 (2.2077(12) A), and between
˚
the palladium and water ligand in 15 (2.2031(13) A). As a result of
the direct bonding between the sulfone and the palladium in 17 the
S–O bond lengths have altered as predicted, with the coordinating
◦
1
white solid. Rf (dichloromethane) 0.6; mp 98–99 C; H NMR
(300 MHz, CDCl3) d 1.07–1.32 (6H, m, CH2), 1.57–1.83 (14H, m,
CH2), 3.18–3.28 (2H, m, NCH), 7.43–7.53 (3H, m, Ar), 7.87 (2H,
dd, J = 7.8, 1.4, Ar); 13C NMR (75.5 MHz, CDCl3) d 143.1, 131.7,
128.7, 127.0, 58.0, 32.4, 26.5, 25.2; IR (CDCl3, cm−1) m 2934.4,
2856.0, 1446.0, 1321.4, 1219.0, 1200.1, 11.65.4, 1151.8, 1110.7,
1088.0, 1046.7, 981.4; HRMS (FAB+) Calc. for C18H28NO2S
[MH+]: m/z 321.1763; found: m/z 321.1763. Anal. Calc. for
C18H27NO2S: C 67.25, H 8.5, N 4.7. Found: C 67.7, H 8.5, N
4.3%.
˚
oxygen to sulfur bond increasing by approximately 0.04 A and the
˚
unbound O–S bond unaffected at 1.4380(13) A.
Summary
In summary, a selection of novel modular, hybrid ligands have
been synthesised containing the sulfone moiety. The sulfonamide
ligands have been shown to be bidentate in the solid state, in pal-
ladium complexes, with coordination displayed through both the
phosphine and sulfonamide oxygen. The ligands display moderate
activity when applied to the palladium catalysed Suzuki–Miyaura
and amination reactions. Whilst yields for the coupling with
4-chlorotoluene are low, the activated 1-chloro-4-tosylbenzene
N,N-Dimethylbenzenesulfonamide
Prepared in accordance with the literature procedure.16
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Dalton Trans., 2006, 2251–2262 | 2257
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To a solution of benzenesulfonyl chloride (10 g, 56.6 mmol)
in tetrahydrofuran (250 mL) at 0 ◦C, was added dimethylamine
(28.4 mL of 40% aq., 226.4 mmol), over 15 min. After stirring
for 2 h the solution was diluted with diethyl ether (200 mL) and
transferred to a separating funnel, the aqueous layer was extracted
with diethyl ether (2 × 50 mL) the combined organics were
washed with water (2 × 20 mL) and brine, dried over MgSO4 and
evaporated under reduced pressure to afford the title compound
in 87% yield (9.12 g) as a yellow solid. Rf (dichloromethane) 0.55;
mp 47 ◦C lit 47.5 ◦C;17 1H NMR (300 MHz, CDCl3) d 2.71 (6H, s,
CH3), 7.52–7.64 (3H, m, Ar), 7.79 (2H, dt, J = 6.7, 1.7, Ar);
13C NMR (75.5 MHz, CDCl3) d 135.8, 133.1, 129.4, 128.1, 38.3;
IR (CDCl3, cm−1) m 3013.0, 1445.8, 1343.7, 1229.9, 1211.5, 1196.7,
1165.6, 1091.2, 955.8; HRMS (FAB+): calc. for C8H12NO2S [MH+]:
m/z 185.0511; found: m/z 185.0519. Anal. Calc. for C8H11NO2S:
C 51.9, H 6.0, N 7.6. Found: C 52.0, H 6.0, N, 7.4%. Data identical
to those in the literature.18
2.5 M in hexanes, 17.12 mmol) to generate the title compound as
a colourless solid (34% yield, 2.71 g). Rf (dichloromethane) 0.56;
◦
1
mp 75–78 C; H NMR (300 MHz, CDCl3) d 1.08–1.33 (6H, m,
CH2), 1.56–1.62 (2H, m, CH2), 1.77 (12H, m, CH2), 3.61 (2H,
m, NCH), 7.04 (1H, m, Ar), 7.18–7.24 (4H, m, Ar), 7.31–7.37
(7H, m, Ar), 7.43 (1H, dt, J = 7.4, 1.4, Ar), 8.07 (1H, m, Ar);
13C NMR (75.5 MHz, CDCl3) d 147.5, 147.2, 137.8, 137.3, 135.7,
133.9, 133.6, 131.5, 129.8, 128.9, 128.5, 128.4, 57.8, 57.7, 33.0,
1
32.8, 26.6, 25.4; 31P{ H} NMR (121 MHz, CDCl3) d −5.30 (m);
IR (CHCl3, cm−1) 2933.8, 1320.5, 1229.6, 1221.4, 1196.2, 1152.3;
HRMS (FAB+) Calc. for C30H37NO2PS [MH+]: m/z 505.2204;
found: m/z 505.2215. Anal. Calc. for C30H36NO2PS: C 71.3, H
7.2, N 2.8. Found: C 70.5, H 7.0, N 2.5%.
N,N-Dicyclohexyl-2-(dicyclohexylphosphanyl)benzenesulfonamide
4
N,N-Dicyclohexylbenzenesulfonamide 10 (1.80 g, 5.60 mmol) and
chorodicyclohexylphosphine (1.55 mL, 7.00 mmol) were coupled
as stated by the general protocol with n-butyllithium (2.64 mL
2.5 M in hexanes, 6.16 mmol) to generate the title compound as
a colourless foam (73% yield, 2.12 g). Rf (dichloromethane) 0.26;
mp 133–135 ◦C; 1H NMR (300 MHz, CDCl3) d 1.05–1.39 (16H,
m), 1.52–1.82 (22H, m), 1.90 (4H, m), 3.62 (2H, m), 7.38 (1H, dt,
J = 1.5, 7.5, Ar), 7.43 (1H, dt, J = 1.5, 7.2, Ar), 7.56 (1H, d,
J = 7.2, Ar), 8.08 (1H, dm, J = 7.5, Ar); 13C NMR (75.5 MHz,
CDCl3) d 149.4, 137.8, 137.3, 133.9, 130.5, 128.5, 58.3, 58.3, 35.7,
35.5, 33.5, 30.9, 30.7, 30.2, 30.0, 27.9, 27.8, 27.7, 27.6, 27.1, 26.8,
25.8; 31P{ H} NMR (121 MHz, CDCl3) d −3.29; H{ P} NMR
(300 MHz, CDCl3) d 1.01–1.35 (16H, m), 1.52–1.81 (22H, m),
1.84–1.96 (4H, m), 3.59–3.63 (2H, m), 7.40 (2H, app. quintet, J =
7.6), 7.56 (1H, app. d, J = 7.6), 8.08 (1H, app. d, J = 7.6); IR
(Nujol, cm−1) m 1322, 1149, 1102, 1049, 980, 893, 850, 818, 752,
723; HRMS (FAB+) Calc. for C30H49NO2PS [MH+]: m/z 518.3222;
found: m/z 518.3238. Anal. Calc. for C30H48NO2PS: C 69.6, H 9.3,
N 2.7. Found: C 69.3, H 9.3, N 2.5%.
General procedure for the phosphination of benzene sulfonamides
with chlorophosphines
An oven-dried round-bottomed flask was cooled to room
temperature under a nitrogen purge and charged with N,N-
dialkylbenzenesulfonamide (15.6 mmol). The flask was purged
with nitrogen and tetrahydrofuran (250 mL) was added. The
◦
solution was cooled to −78 C with stirring, and n-butyllithium
(2.5 M in hexanes, 1.1 equiv.) was added dropwise. The solution
was stirred at −78 ◦C for 30 min, followed by the dropwise addition
of chlorophosphine (19.5 mmol, 1.25 equiv.) in tetrahydrofuran
(50 mL) to the reaction vessel. The reaction mixture was stirred
at −78 ◦C and allowed to warm slowly to room temperature
overnight. After 20 h the reaction was quenched with saturated
NH4Cl (100 mL), diluted with ether (100 mL), and poured into
a separatory funnel. The layers were separated and the aqueous
phase was extracted with ether (50 mL). The combined organic
layers were dried over anhydrous magnesium sulfate, filtered, and
concentrated to give a solid. The crude material was purified
by flash chromatography (dichloromethane) to afford the title
compound.
1
1
31
N,N-Dimethyl-2-(dicyclohexylphosphanyl)benzenesulfonamide 5
Diphenyl(2-(phenylsulfonyl)phenyl)phosphine 2
N,N-Dimethylbenzenesulfonamide (1.04 g, 5.60 mmol) and
chorodicyclohexylphosphine (1.55 mL, 7.00 mmol) were coupled
as stated by the general protocol with n-butyllithium (2.64 mL
2.5 M in hexanes, 6.20 mmol) to generate the title compound as
a colourless◦solid (75% yield, 1.61 g). Rf (dichloromethane) 0.32;
Diphenyl sulfone 6 (5.00 g, 22.90 mmol) and chorodiphenylphos-
phine (5.14 mL, 28.63 mmol) were coupled as stated by the
general protocol with n-butyllithium (10.07 mL 2.5 M in hexanes,
25.20 mmol) to generate the title compound as a colourless solid
(48% yield, 4.43 g). Rf (light petroleum–ethyl acetate 5 : 1) 0.39;
1
mp 98–100 C; H NMR (300 MHz, CDCl3) d 1.00–1.32 (10H,
◦
m), 1.46 (2H, m), 1.65 (4H, m), 1.78 (2H, m), 1.91 (4H, m), 2.83
(6H, s, CH3), 7.44 (1H, dt, J = 1.1, 7.5, Ar), 7.50 (1H, dt, J =
1.5, 7.5, Ar), 7.70 (1H, d, J = 7.5, Ar), 8.05 (1H, dm, J = 7.5,
Ar); 13C NMR (75.5 MHz, CDCl3) d 144.8, 138.5, 135.0, 131.6,
1
mp 146–149 C; H NMR (300 MHz, CDCl3) d 7.08 (5H, m),
7.27 (5H, m), 7.40–7.56 (6H, m), 8.05 (2H, d, J = 7.2), 8.35 (1H,
m); 13C NMR (75.5 MHz, CDCl3) d 145.7, 145.4, 141.8, 138.2,
137.8, 137.0, 136.7, 136.5, 133.7, 133.4, 133.2, 132.9, 130.1, 129.5,
1
131.0, 128.7, 38.0, 35.9, 30.6, 30.3, 27.7, 27.5, 26.7; 31P{ H} NMR
1
128.7, 128.6, 128.5, 128.4; 31P{ H} NMR (121 MHz, CDCl3)
1
31
(121 MHz, CDCl3) d −4.69; H{ P} NMR (300 MHz, CDCl3)
d 1.05–1.30 (10H, m), 1.47 (2H, br d, J = 11.1), 1.63–1.66 (4H,
m), 1.76–1.80 (2H, m), 1.86–1.94 (4H, m), 2.83 (6H, s, 2 × CH3),
7.45 (1H, app. dt, J = 1.1, 7.6), 7.52 (1H, app. dt, J = 1.1, 7.6),
7.71 (1H, app. dd, J = 1.1, 7.6), 8.05 (1H, app. dd, J = 1.1, 7.6);
IR (Nujol, cm−1) m 1320, 1207, 1151, 1094, 1039, 956, 751, 719,
696; HRMS (FAB+) Calc. for C20H33NO2PS [MH+]: m/z 382.1970;
found: m/z 382.1975.
d −10.65; HRMS (FAB+): Calc. for C24H20O2PS [MH+]: m/z
403.0922; found: m/z 403.0930.
N,N-Dicyclohexyl-2-(diphenylphosphanyl)benzenesulfonamide 3
N,N-Dicyclohexylbenzenesulfonamide 10 (5.00 g, 15.60 mmol)
and chorodiphenylphosphine (3.50 mL, 19.50 mmol) were coupled
as stated by the general protocol with n-butyllithium (6.85 mL
2258 | Dalton Trans., 2006, 2251–2262
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10-Phenyl-10H-9-thia-10-phosphaanthracene-9,9-dioxide 1
1202.2, 1195.0, 1189.8, 1164.1, 1099.1, 1015.6. Anal. Calc. for
C27H25ClNO2PPdS: C 54.0, H 4.2, N 2.3. Found: C 53.6, H 4.3, N
2.3%.
An over dried round-bottomed flask was cooled to room temper-
ature under a nitrogen purge and charged with diphenyl sulfone
6 (5.00 g, 22.91 mmol). The flask was purged with nitrogen and
tetrahydrofuran (150 mL) was added. The solution was cooled
to −78 ◦C with stirring, and n-butyllithium (20.2 mL 2.5 M in
hexanes, 50.4 mmol) was added dropwise. The solution was stirred
at −78 ◦C for 30 min, then dichlorophenylphosphine (4.51 g,
25.2 mmol) in tetrahydrofuran (100 mL) was added dropwise to
the reaction vessel. The reaction mixture was stirred at −78 ◦C
and allowed to warm slowly to room temperature overnight. After
20 h the reaction was quenched with saturated NH4Cl (150 mL),
diluted with ether (100 mL), and poured into a separatory funnel.
The layers were separated and the aqueous phase was extracted
with ether (50 mL). The combined organic layers were dried
over anhydrous magnesium sulfate, filtered, and concentrated
to give a colourless solid. The crude material was purified by
flash chromatography (dichloromethane as eluent), followed by
recrystallisation from hot ethanol to afford the title compound
(5.00 g, 67%) as white prisms. Rf (dichloromethane) 0.59; mp 155–
[Pd(O3SCF3)(dmba)(10-phenyl-10H-9-thia-10-
phosphaanthracene-9,9-dioxide)] 13
Complex 11 (150 mg, 0.25 mmol), was treated with Ag[O3SCF3]
(64 mg, 0.25 mmol) in dichloromethane (20 mL) at ambient
temperature and stirred for 20 min. The solution was filtered
and the solvent was removed under reduced pressure. The
residue was washed with pentane (10 mL), crystallization from
dichloromethane–hexane generated pale yellow–green prisms suit-
◦
able for X-ray diffraction study (153 mg, 86%); mp 206–208 C;
1H NMR (300 MHz, CDCl3) d 2.74 (6H, d, 4JP–H = 2.9, N(CH3)2),
3.95 (2H, d, 4JP–H = 1.9, CH2), 6.54 (1H, t, J = 6.7, Ar), 6.63 (1H,
t, J = 6.7, Ar), 6.81 (2H, m, Ar), 7.42 (4H, m, Ar), 7.58 (4H, m,
Ar), 7.74 (1H, m, Ar), 8.05 (2H, dd, J = 13.0, 7.4, Ar), 8.23 (2H,
dd, J = 7.6, 2.9, Ar); 13C NMR (75.5 MHz, CDCl3) d 148.2, 148.2,
141.3, 141.3, 137.4, 137.2, 134.5, 134.4, 133.6, 133.3, 132.7, 131.8,
131.7, 130.8, 130.8, 129.8, 129.7, 125.8, 125.8, 124.9, 123.2, 117.5,
◦
1
1
71.8 (d, JP–C = 3), 49.7 (d, JP–C = 2); 31P{ H} NMR (121 MHz,
156 C; H NMR (300 MHz, CDCl3) d 7.08 (2H, dt, J = 5.9,
0.7, Ar), 7.37 (2H, tt, J = 7.6, 1.4, Ar), 7.46–7.65 (7H, m, Ar),
8.24 (2H, dt, J = 7.8, 1.5, Ar); 13C NMR (75.5 MHz, CDCl3)
d 142.9, 142.6, 138.4, 138.2, 137.7, 137.4, 133.8, 133.6, 131.7,
31
CDCl3) d 13.29; 1H{ P} NMR (300 MHz, CDCl3) d 2.74 (6H, s,
CH3), 3.95 (2H, s, CH2), 6.53 (1H, t, J = 6.7, Ar), 6.63 (1H, d,
J = 7.6, Ar), 6.80 (2H, m, Ar), 7.44 (4H, m, Ar), 7.61 (4H, m, Ar),
7.73 (1H, d, J = 7.2, Ar), 8.05 (2H, d, J = 7.3, Ar), 8.23 (2H, d,
J = 7.7, Ar); IR (CHCl3, cm−1) m 2963.7, 1452.3, 1438.4, 1313.8,
1260.3, 1234.1, 1221.9, 1212.0, 1203.8, 1193.0, 1185.8, 1164.6,
1108.2, 1016.0. Anal. Calc. for C28H25F3NO5PPdS2: C 47.1, H
3.5, N 2.0. Found: C 46.7, H 3.5, N 1.95%.
1
131.2, 131.2, 131.1, 129.6, 129.5, 128.1, 124.9; 31P{ H} NMR
(121 MHz, CDCl3) d −17.27 (m); IR (CHCl3, cm−1) m 3012.5,
1577.7, 1445.7, 1436.3, 1311.1, 1292.6, 1255.9, 1216.0, 1209.3,
1202.2, 1197.8, 1159.2, 1130.1, 1109.8, 1038.4; HRMS (FAB+)
Calc. for C18H13O2PS [MH+]: m/z 324.0374; found: m/z 324.0367.
Anal. Calc. for C18H13O2PS: C 66.7, H 4.0, N 0.0. Found: C 66.6,
H 4.0, N 0.0%.
[Pd(H2O)(dmba)(10-phenyl-10H-9-thia-10-phosphaanthracene-
9,9-dioxide)][PF6] 14
Complex 11 (150 mg, 0.25mmol), was treated withAg[PF6] (63 mg,
0.25 mmol) in dichloromethane (20 mL) at ambient temperature
and stirred for 20 min. The solution was filtered and the solvent
was removed under reduced pressure. The residue was washed with
pentane (10 mL), crystallization from dichloromethane–hexane
generated pale green prisms (157 mg, 88%). Mp 168–171 ◦C
[PdCl(dmba)(10-phenyl-10H-9-thia-10-phosphaanthracene-9,9-
dioxide)] 11
10 - Phenyl - 10H - 9 - thia - 10 - phosphaanthracene - 9,9 - dioxide 1
(163 mg, 0.5 mmol) was added to a solution of [Pd(l-Cl)(dmba)]2
(139 mg, 0.25 mmol) in dichloromethane (13 mL) at ambient
temperature. The mixture was stirred for 30 min, filtered, and
the volatiles evaporated to leave a pale green powder, which
was washed with diethyl ether (5 mL) and pentane (2 × 5 mL)
and dried under vacuum. Crystallization from dichloromethane–
hexane afforded pale green prisms sui◦table for X-ray diffraction
1
4
(decomp.); H NMR (300 MHz, CDCl3) d 2.70 (6H, d, JP–H
=
2.8, N(CH3)2), 4.01 (2H, d, 4JP–H = 2.0, CH2), 6.49 (1H, t, J = 5.4,
Ar), 6.56 (1H, t, J = 5.4, Ar), 6.88 (1H, t, J = 5.1, Ar), 6.93 (1H,
dd, J = 5.7, 1.2, Ar), 7.54–7.72 (9H, m, Ar), 7.78 (1H, dd, J = 9.9,
0.9, Ar), 7.79 (1H, d, J = 9.9, Ar), 7.27 (2H, ddd, J = 6.0, 2.4, 0.9,
Ar); 13C NMR (75.5 MHz, CDCl3) d 148.3, 141.6, 141.0, 140.9,
136.5, 136.3, 136.0, 135.9, 135.3, 135.2, 133.7, 133.2, 133.1, 131.9,
131.5, 130.2, 130.1, 126.5, 126.5, 126.2, 126.2, 125.8, 124.6, 123.9,
1
study. Yield 271 mg (90%). Mp 207 C; H NMR (300 MHz,
CDCl3) d 2.82 (6H, d, 4JP–H = 2.6, N(CH3)2), 4.05 (2H, d, 4JP–H
=
2.0, CH2), 6.10 (1H, t, J = 7.4, Ar), 6.35 (1H, t, J = 7.4, Ar),
6.76 (1H, t, J = 7.1, Ar), 6.92 (1H, d, J = 7.1, Ar), 7.43 (2H, m,
Ar), 7.52 (3 H, m, Ar), 7.65 (4H, m, Ar), 8.00 (2H, dd, J = 12.5,
1.5, Ar), 8.24 (2H, dd, J = 7.7, 1.7, Ar);13C NMR (75.5 MHz,
CDCl3) d 151.9, 148.2, 141.7, 137.1, 136.9, 135.4, 135.2, 132.7,
132.1, 131.6, 131.5, 131.2, 128.7, 128.6, 125.4, 125.3, 124.1, 122.6,
1
71.6, 50.3; 31P{ H} NMR (162 MHz, CDCl3) d 13.47, −142.82
(sep JP–F = 713, PF6); IR (CHCl3, cm−1) m 2963.0, 1314.7, 1260.6,
1238.1, 1230.2, 1217.5, 1208.4, 1202.2, 1193.3, 1171.8, 1108.0,
1036.3, 1012.6. Anal. Calc. for C27H25F6NO2P2PdS·H2O: C 44.55,
H 3.7, N 1.9. Found: C 44.6, H 3.75, N 1.9%.
1
1
31
73.3, 50.7; 31P{ H} NMR (121 MHz, CDCl3) d 16.43; H{ P}
NMR (300 MHz, CDCl3) d 2.82 (6H, s, CH3), 4.05 (2H, s, CH2),
6.11 (1H, d, J = 7.7, Ar), 6.35 (1H, t, J = 7.3, Ar), 6.75 (1H,
t, J = 7.3, Ar), 6.92 (1H, d, J = 7.2, Ar), 7.42 (2H, m, Ar),
7.52 (3H, m, Ar), 7.65 (4H, m, Ar), 7.99 (2H, d, J = 7.5, Ar),
8.24 (2H, d, J = 7.7, Ar); IR (CHCl3, cm−1) m 2962.0, 1719.8,
1453.9, 1314.4, 1261.1, 1236.2, 1229.7, 1222.1, 1215.7, 1212.0,
[Pd(H2O)(dmba)(10-phenyl-10H-9-thia-10-phosphaanthracene-
9,9-dioxide)][SbF6] 15
Complex 11 (150 mg, 0.25 mmol), was treated with Ag[SbF6]
(86 mg, 0.25 mmol) in dichloromethane (20 mL) at ambient
temperature and stirred for 20 min. The solution was filtered
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and the solvent was removed under reduced pressure. The
residue was washed with pentane (10 mL), crystallization from
dichloromethane–hexane generated pale yellow–green prisms suit-
able for X-ray diffra◦ction study (189 mg, 95%). Mp 123 ◦C softens,
changes colour 130 C melts 168 ◦C; 1H NMR (300 MHz, CDCl3)
dichloromethane–hexane generated pale yellow–green prisms suit-
able◦for X-ray diffraction study (167 mg, 91%). Mp 179 ◦C softens,
195 C decomposes; 1H NMR (300 MHz, CDCl3) d 0.86–1.10 (6H,
4
m), 1.48–1.61 (2H, m), 1.62–1.85 (12H, m), 2.85 (6H, d, JP–H
=
2.7, N(CH3)2), 2.89–3.06 (2H, m, NCH), 4.09 (2H, s, NCH2), 5.93
(1H, t, J = 7.2, Ar), 6.39 (1H, t, J = 7.5, Ar), 6.87 (1H, t, J = 7.2,
Ar), 6.98 (1H, d, J = 6.0, Ar), 7.18 (1H, t, J = 9.4, Ar), 7.49–7.63
(10H, m, Ar), 7.69 (1H, t, J = 7.5, Ar), 7.84 (1H, t, J = 7.7, Ar),
8.02 (1H, dd, J = 4.5, 7.2, Ar); 13C NMR (75.5 MHz, CDCl3) d
148.3, 148.2, 143.8, 143.6, 142.4, 136.5, 136.5, 134.9, 133.9, 133.0,
132.7, 132.6, 130.0, 129.8, 129.6, 129.6, 126.0, 126.0, 125.5, 123.6,
4
4
d 2.72 (6H, d, JP–H = 2.8, N(CH3)2), 4.03 (2H, d, JP–H = 2.0,
CH2), 6.63–6.64 (2H, m, Ar), 6.91–6.98 (2H, m, Ar), 7.53–7.63
(6H, m, Ar), 7.70–7.74, (3H, m, Ar), 7.84 (2H, dd, J = 9.9, 6.0,
Ar), 8.29–8.32 (2H, m, Ar); 13C NMR (75.5 MHz, CDCl3) d 148.1,
141.4, 140.6, 140.5, 136.7, 134.6, 133.1, 132.9, 132.4, 131.8, 131.5,
1
130.1, 129.9, 126.1, 126.0, 125.6, 123.7, 123.2, 77.2, 50.0; 31P{ H}
NMR (121 MHz, CDCl3) d 12.82; IR (CHCl3, cm−1) m 2971.8,
1516.5, 1508.1, 1314.3, 1261.3, 1236.0, 1230.0, 1226.1, 1221.5,
1209.2, 1204.0, 1195.4, 1186.0, 1172.0, 1108.4, 1036.3. Anal. Calc.
for C27H25F6NO2PPdSSb·H2O: C 39.6, H 3.3, N 1.7. Found: C
39.5, H 3.3, N 1.6%.
70.3 (J = 4), 59.3, 50.3 (J = 2), 31.8, 29.7, 26.0, 24.7; 31P{ H}
1
NMR (121 MHz, CDCl3) d 33.40; IR (Nujol, cm−1) m 2923, 2854,
2724, 2725, 1583, 1461, 1377, 1293, 1264, 1166, 1140, 1117, 1098,
1042, 1024, 982, 892, 846, 765, 748, 720; MS (FAB+): m/z 745.4
(M − SbF6). Anal. Calc. for C39H48F6N2O2PPdSSb: C 47.7, H 4.9,
N 2.85. Found: C 47.9, H 4.8, N 2.8%.
[PdCl(dmba)(N,N-dicyclohexyl-2-
(diphenylphosphanyl)benzenesulfonamide)] 16
Typical procedure for the palladium-catalysed Suzuki–Miyaura
cross coupling
Ligand 3 (253 mg, 0.5 mmol) was added to a solution of [Pd(l-
Cl)(dmba)]2 (139 mg, 0.25 mmol) in dichloromethane (13 mL) at
ambient temperature. The mixture was stirred for 30 min, filtered,
and the volatiles evaporated to leave a pale yellow powder, which
was washed with diethyl ether (5 mL) and pentane (2 × 5 mL)
and dried under vacuum. Crystallisation from dichloromethane–
hexane afforded pale green prisms suitable for X-ray diffracti◦on
An oven-dried Schlenk tube, cooled to room temperature under
a nitrogen atmosphere, was charged with aryl halide (1 mmol),
Cs2CO3 (1.4 mmol), boronic acid (1.5 mmol) [Pd(OAc)2] (20 lmol,
2 mol%), ligand (20 lmol, 2 mol%) and 1,4-dioxane (3 mL). The
tube was sealed and heated at 80 ◦C for 3 h. The mixture was
allowed to cool to room temperature before either being purified
directly by flash chromatography (petrol), or filtered through a pad
of Celite, concentrated, and then purified by flash chromatography
to afford analytically pure title compound.
◦
study: Yield 359 mg (92%). Mp 170–172 C softens 198–200 C
1
(decomp.); H NMR (300 MHz, CDCl3) d 0.85 (1H, t, J = 6.4),
1.03 (2H, m), 1.27 (4H, m), 1.44–1.84 (13H, m), 2.85 (6H, br s,
CH3), 3.44 (2H, br s, NCH), 3.80–4.40 (2H, br s, CH2N), 6.31
(1H, t, J = 6.8, Ar), 6.40 (1H, t, J = 7.5, Ar), 6.83 (1H, t, J = 7.2,
Ar), 6.98 (1H, d, J = 7.2, Ar), 7.06 (1H, ddd, J = 1.1, 7.9, 10.9,
Ar), 7.29–7.47 (9H, m, Ar), 7.50–8.20 (3H, br m, Ar), 7.91 (1H,
ddd, J = 1.1, 4.1, 7.9, Ar); 13C NMR (75.5 MHz, CDCl3) 149.3,
148.4, 144.5, 144.3, 137.8, 137.6, 137.0, 136.4, 134.1, 134.0, 130.7,
130.6, 130.4, 130.1, 130.1, 129.5, 127.9, 124.5, 124.5, 123.7, 122.3,
4-Methylbiphenyl
4-Bromotoluene (171 mg, 1 mmol) and phenylboronic acid
(183 mg, 1.5 mmol) were coupled under the standard protocol
to afford the titled compound as a colourless solid (158 mg, 94%).
1H NMR (300 MHz) d 2.39 (3H, s, CH3), 7.25 (2H, d, J = 8.3,
Ar), 7.31 (1H, tt, J = 1.8, 7.5, Ar), 7.42 (2H, tm, J = 7.5, Ar), 7.49
(2H, d, J = 8.3, Ar), 7.57 (2H, dm, J = 6.9, Ar); 13C NMR (75.5
MHz) d 141.1, 138.3, 137.0, 129.5, 128.7, 128.7, 127.2, 127.0, 21.1;
IR (film, cm−1) m 3056, 3027, 2920, 2864, 1948, 1903, 1804, 1659,
1601, 1568, 1519, 1488, 1445, 1403, 1380, 1266, 1217, 1112, 1075,
1038, 1008, 912, 822, 757, 697, 668; HRMS (EI+) Calc. for C13H12
[M+]: m/z 168.0939; found: m/z 168.0937. Data identical to those
in the literature.19
1
77.23, 73.4, 56.2, 53.4, 50.5, 34.7, 31.8, 26.0, 25.3; 31P{ H} NMR
31
(121 MHz, CDCl3) d 46.07; 1H{ P} NMR (300 MHz, CDCl3) d
0.85 (1H, t, J = 7.3), 1.03 (2H, m), 1.28 (4H, m), 1.46–1.88 (13H,
m), 2.88 (6H, br s, CH3), 3.45 (2H, br s, NCH), 3.80–4.40 (2H, br s,
CH2N), 6.31 (1H, d, J = 6.9, Ar), 6.40 (1H, dt, J = 1.1, 7.4, Ar),
6.83 (1H, dt, J = 0.8, 7.3, Ar), 6.99 (1H, dd, J = 1.1, 7.6, Ar), 7.07
(1H, dd, J = 1.1, 8.0, Ar), 7.25–7.47 (9H, m), 7.50–8.20 (3H, br m,
Ar), 7.91 (1H, dd, J = 1.1, 7.6, Ar); IR (Nujol, cm−1) m 2922, 2857,
2221, 1577, 1558, 1455, 1438, 1406, 1378, 1334, 1311, 1262, 1186,
1151, 1121, 1103, 1095, 1042, 1022, 992, 974, 912, 907, 891, 865,
851, 818, 760, 734, 725; MS (FAB+): m/z 745.1 (M − Cl). Anal.
Calc. for C39H48ClN2O2PPdS·H2O: C 58.6, H 6.3, N 3.5. Found:
C 58.2, H 6.0, N 3.4%.
(4-Diphenyl)-p-tolyl sulfone
(4-Chlorophenyl)-p-tolyl sulfone (133 mg, 0.50 mmol) and phenyl-
boronic acid (91 mg, 0.75 mmol) were coupled under the standard
protocol to afford the titled compound as a colourless solid (50 mg,
32%). 1H NMR (300 MHz) d 2.39 (3H, s, CH3), 7.31 (2H, d, J =
8.3, Ar), 7.39–7.48 (3H, m, Ar), 7.55 (2H, m, Ar), 7.68 (2H, dt,
J = 1.9, 8.7, Ar), 7.87 (2H, d, J = 8.3, Ar), 7.99 (2H, dt, J =
1.9, 8.7, Ar); 13C NMR (75.5 MHz) d 146.4, 144.6, 140.9, 139.6,
139.2, 130.4, 129.4, 128.9, 128.4, 128.3, 128.1, 127.7, 22.0; IR
(film, cm−1) m 3019, 1594, 1319, 1309, 1292, 1215, 1155, 1109, 758;
HRMS (EI+) Calc. for C19H16O2S [M+]: m/z 308.0871; found: m/z
308.0870. Anal. Calc. for C19H16O2S: C 74.0, H 5.2, N 0.0. Found:
C 73.6, H 5.4, N 0.0%.
[Pd(dmba)(N,N-dicyclohexyl-2-
(diphenylphosphanyl)benzenesulfonamide)][SbF6] 17
Complex 16 (154 mg, 0.19 mmol), was treated with Ag[SbF6]
(65 mg, 0.19 mmol) in dichloromethane (15 mL) at ambient
temperature and stirred for 30 min. The solution was filtered
and the solvent was removed under reduced pressure. The
residue was washed with pentane (10 mL), crystallization from
2260 | Dalton Trans., 2006, 2251–2262
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Table 11 Crystal data and structure refinement for compounds 11, 13, 15, 16 and 17
Compound
11
13
15
16
17
Empirical formula
M
C27H25ClNO2PPdS C28H25F3NO5PPdS2
C27H27F6NO3PPdSSb C41.25H50Cl3N2O2PPdS C39H48F6N2O2PPdSSb
600.36
150(2)
Triclinic
¯
P1
713.98
150(2)
Monoclinic
P21/n
818.68
150(2)
881.61
150(2)
981.97
150(2)
T/K
Crystal system
Space group
Monoclinic
P21/n
Triclinic
P1
Monoclinic
P21/n
¯
˚
a/A
10.4250(1)
13.7540(2)
17.6450(3)
79.8910(5)
88.0700(5)
81.0550(8)
2460.41(6)
4
9.4590(1)
12.1110(1)
25.6990(2)
—
100.0270(3)
—
2899.06(4)
4
1.636
13.7950(1)
14.2050(1)
15.4340(2)
—
104.108(1)
—
10.6200(1)
15.3270(1)
15.3980(1)
108.523(1)
100.290(1)
108.962(1)
2133.66(3)
2
18.4920(2)
12.2630(1)
18.5860(2)
—
102.396(1)
—
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
˚
U/A
2933.19(5)
4
4116.44(7)
4
Z
Dc/g cm−3
1.621
1.854
1.729
1.372
0.745
1.584
1.245
l/mm−1
1.039
0.898
Crystal size/mm
Reflections collected
Independent reflections
Rint
R1, wR2 [I > 2r(I)]
R Indices (all data)
0.15 × 0.15 × 0.15
0.20 × 0.18 × 0.18
0.30 × 0.30 × 0.08
0.37 × 0.25 × 0.25
0.30 × 0.30 × 0.13
40344
56679
59819
43431
80179
10805
0.0408
0.0334, 0.0890
0.0454, 0.0986
8465
0.0367
0.0256, 0.0769
0.0310, 0.0857
11173
0.0399
0.0252, 0.0580
0.0359, 0.0617
12423
0.0329
0.0310, 0.0837
0.0381, 0.0872
12008
0.0425
0.0244, 0.0609
0.0305, 0.0646
Typical procedure for the synthesis of 4-p-tolylmorpholine via the
palladium catalysed amination reaction
Convergence was routine throughout with the exception of the
observations below.
The water hydrogens (H3A and H3B) in 15 were readily located
and refined at a distance of 0.89 A from O3. Indeed, there is
significant evidence for implicating these protons in hydrogen-
An oven-dried pressure tube was cooled to room temperature
under an atmosphere of nitrogen, and charged with bromotoluene
(171 mg, 1.0 mmol), morpholine (105 lL, 1.2 mmol), sodium
tert-butoxide (135 mg, 1.4 mmol), [Pd2dba3] (9.2 mg, 10 lmol,
2 mol% Pd), ligand (20 lmol, 2 mol%) and toluene (1 mL, 0.5
M). The tube was sealed and heated at 100 ◦C for 6 h, after which
time it was allowed to cool to room temperature. The resulting
mixture was diluted with ethyl acetate and filtered through a Celite
plug. Purification by flash chromatography (light petroleum–ethyl
acetate) afforded the title compound in 93% yield (165 mg). Rf
˚
bonding within the gross structure (H3A · · · O2 2.219, H3A · · · F2
˚
2.352, H3B · · · F6 2.045 A; O3–H3A–O2 135.8, O3–H3A–F2
137.8, O3–H3B–F6 166.5◦).
In 16, the asymmetric unit consists of one palladium complex
molecule, one molecule of dichloromethane and one half of
a pentane molecule, the latter exhibiting 50% occupancy. As
the pentane is disordered, the associated hydrogen atoms are
not included in refinement. Metric data for this structure also
indicate the possibility of an interaction between H40B and Cl1
1
(light petroleum–ethyl acetate, 4 : 1) 0.49; H NMR (300 MHz)
d 2.27 (3H, s, CH3), 3.10 (4H, t, J = 4.7, CH2N), 3.85 (4H, t,
J = 4.7, CH2O), 6.84 (2H, d, J = 8.7, CHCN), 7.09 (2H, d,
J = 8.7, CHCCH3); 13C NMR (75.5 MHz) d 149.19 (CN), 129.70
(CHCCH3), 129.56 (CCH3), 116.02 (CHCN), 66.98 (CH2O), 49.92
(CH2N), 20.42 (CH3); IR (film, cm−1) m 2976, 2956, 2853, 2829,
2748, 2695, 1971, 1894, 1612, 1577, 1515, 1452, 1379, 1364, 1327,
1312, 1297, 1259, 1237, 1168, 1118, 1064, 1048, 1031, 922, 857,
818, 755, 706, 666, 608, 530; HRMS (EI+) Calc. for C11H15NO
[M+]: m/z 177.1154; found: m/z 177.1154. Data identical to those
in the literature.20
◦
˚
(H40B · · · Cl1 2.634 A; C40–H40B–Cl1 162.06 ).
Four fluorine atoms (F1, F3, F5 and F6) in the anion displayed
positional disorder in the ratio 72 : 28 in compound 17. This
disorder was successfully modelled.
CCDC reference numbers 232452–232456.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b513390d
Acknowledgements
We are grateful to Johnson-Matthey for a CASE award to C. J. C.
and for the loan of transition metal salts.
Crystallography
Single-crystals of compounds 11, 13, 15, 16 and 17 were analysed
on a Nonius Kappa CCD diffractometer using molybdenum
radiation throughout. Details of the data collections, solutions
and refinements are given in Table 11. The structures were solved
using SHELXS-9721 and refined using SHELXL-97.22 Absorption
corrections (semi-empirical from equivalent reflections) were
applied to data for 11, 13, 16 and 17 (max./min. transmission
factors 0.88 0.79, 0.46 0.43, 0.85 0.75 and 0.86 0.78, respectively).
An absorption correction based on face-indexing the crystal was
applied to data for 15 (max./min. transmission factors; 0.86, 0.62).
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©