Synthesis, catalytic activity and redox properties of palladium(0) complexes with 15-membered triolefinic macrocyclic ligands containing one, two or three ferrocenyl groups

Article abstract of DOI:10.1016/S0040-4039(02)00028-X

A series of 15-membered triolefinic macrocycles containing ferrocenyl groups and their palladium(0) complexes have been synthesized and characterized. Their catalytic activity has been demonstrated in Suzuki-type cross-coupling and in the Heck reaction. Their redox properties have been investigated by means of cyclic voltammetry.

Full text of DOI:10.1016/S0040-4039(02)00028-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 1425–1428
Synthesis, catalytic activity and redox properties of palladium(0)
complexes with 15-membered triolefinic macrocyclic ligands
containing one, two or three ferrocenyl groups
a
a
b
a
Antoni Llobet, Ester Masllorens, Marcial Moreno-Ma n˜ as, Anna Pla-Quintana,
a
a,
Montserrat Rodr ´ı guez and Anna Roglans *
a
Department of Chemistry, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
b
Department of Chemistry, Universitat Aut o` noma de Barcelona, Cerdanyola, 08193 Barcelona, Spain
Received 30 November 2001; revised 27 December 2001; accepted 28 December 2001
Abstract—A series of 15-membered triolefinic macrocycles containing ferrocenyl groups and their palladium(0) complexes have
been synthesized and characterized. Their catalytic activity has been demonstrated in Suzuki-type cross-coupling and in the Heck
reaction. Their redox properties have been investigated by means of cyclic voltammetry. © 2002 Elsevier Science Ltd. All rights
reserved.
1
. Introduction
or three ferrocenyl groups), as well as their palla-
dium(0) complexes 2, in order to understand the inter-
action between palladium metal center and ferrocenyl
groups.
There is currently great interest in ferrocene-containing
complexes owing to their importance in areas of cataly-
sis, asymmetric synthesis, and material science.
1
N SO2 Ar2
N SO2 Ar2
Recently, one of us has published synthetic procedures
for a novel type of triazatriolefinic macrocycles with the
structure of (E,E,E)-1,6,11-tris(arylsulfonyl)-1,6,11-tri-
Ar1 SO2
Ar1 SO2
N
Pd
N
2a,3
azacyclopentadeca-3,8,13-triene,
the preparation and structures of their complexes with
palladium(0), platinum(0) and silver(I). These macro-
1 (Fig. 1), as well as
N SO2 Ar2
N SO2 Ar2
4
2
1
cycles are exceptional, as nitrogen-containing 15-mem-
bered macrocycles featuring internal olefinic double
bonds have been seldom described in the literature. The
few known examples contain only one double bond,
Ar1
Fe
Ar2
Present work
5
and metathesis is the key step for their preparation. On
1aab
H C
3
the other hand, the air-stable palladium(0) complex 2
2aab
1
2
(
when Ar =Ar =2,4,6-triisopropylphenyl) (Fig. 1)
shows high catalytic activity and recovery in certain
2
Suzuki-type cross-coupling reactions.
1
2
abb
abb
H C
3
Fe
Fe
All this led us to undertake the preparation of three
different macrocycles 1aab, 1abb and 1bbb (Fig. 1) (aryl
units in macrocycle 1 have been substituted by one, two
1
2
bbb
bbb
Fe
Keywords: macrocycles; ferrocene; triene palladium(0) complexes;
catalysis.
Figure 1. Structure of macrocycles 1aab, 1abb, and 1bbb and
their palladium(0) complexes 2 prepared in this work.
*
Corresponding author. Tel.: +34-972-418-275; fax: +34-972-418-150;
e-mail: anna.roglans@udg.es
0
040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00028-X

1
426
A. Llobet et al. / Tetrahedron Letters 43 (2002) 1425–1428
2
. Synthesis of macrocyclic ligands, 1, and their
0.5 equiv. of p-toluenesulfonamide 3a and ferrocenesul-
8 8
palladium(0) complexes, 2. Catalytic activity of
complexes 2
fonamide 3b to give 6abb and 6bbb, both in quantita-
tive yields. Deprotection of the three compounds 6aab,
6
abb and 6bbb was carried out with trifluoroacetic acid
8
Macrocycles 1aab, 1abb and 1bbb were prepared by the
sequences outlined in Scheme 1. Compounds 4a and 4b
were prepared from the corresponding sulfonamides 3a
and 3b according to the general method described in
the literature. Reaction of 4a and 4b with 4 equiv. of
E)-1,4-dibromo-2-butene afforded 5a and 5b in 77
and 69% yield, respectively. Reaction of 5a with 0.5
giving the respective deprotected compounds 7aab
(94% yield), 7abb (88% yield) and 7bbb (86% yield).
8
8
8
8
8
Then, macrocycles 1aab, 1abb and 1bbb were formed
in 84, 84 and 89% yield by reaction of equimolar
amounts of compounds 7 and (E)-1,4-dibromo-2-
butene using potassium carbonate as a base in refluxing
acetonitrile.
6
7
3
8
(
equiv. of ferrocenesulfonamide 3b in refluxing acetoni-
trile and potassium carbonate as a base, gave 6aab in
quantitative yield. Under the same conditions as for
compound 5a, compound 5b reacts, respectively, with
8
Tetrakis(triphenylphosphine)palladium(0) was used as a
8
source of palladium(0) to prepare complexes 2aab,
8
8
2abb and 2bbb (Scheme 1). Thus, macrocycles 1aab,
i
ii
Ar SO NH
Ar SO NHBoc
2
2
2
(
(
92%) for 4a
81%) for 4b
(77%) for 5a
(69%) for 5b
3a, 3b
4a, 4b
Boc
N SO2 Ar2
Boc
iii
Ar SO2
N
Ar1 SO2
N
Br
(
Quantitative yields)
5a, 5b
N SO2 Ar2
Boc
From 5a: 6aab
From 5b: 6abb, 6bbb
H
N SO2 Ar2
iv
v
Ar1 SO2
N
(84%) for 1aab
(84%) for 1abb
(89%) for 1bbb
(94%) for 7aab
(88%) for 7abb
(86%) for 7bbb
N SO2 Ar2
H
7aab, 7abb, 7bbb
N SO2 Ar2
N SO2 Ar2
vi
Ar1 SO2 N
Ar1 SO2
Pd
N
(
95%) for 2aab
95%) for 2abb
(
N SO2 Ar2
aab, 2abb, 2bbb
N SO2 Ar2
(72%) for 2bbb
2
1
aab, 1abb, 1bbb
1
2
See Figure 1 for Ar and Ar
a
b
Ar =H C
3
Ar =
Fe
t
Scheme 1. (i) ( BuOCO) O, Et N, DMAP, CH Cl , 2.5 h.; (ii) 4 equiv. (E)-1,4-dibromo-2-butene, K CO , CH CN, reflux, 6 h (for
2
3
2
2
2
3
3
5
a), 21 h (for 5b); (iii) to give 6aab and 6bbb: 0.5 equiv. ferrocenesulfonamide 3b, K CO , CH CN, reflux, 7 h (for 6aab), 18 h
2 3 3
(
for 6bbb); to give 6abb: 0.5 equiv. p-toluenesulfonamide 3a, K CO , CH CN, reflux, 24 h; (iv) TFAA, CH Cl , rt, 2 h; (v) 1 equiv.
2 3 3 2 2
(
E)-1,4-dibromo-2-butene, K CO , CH CN, reflux, 23 h (for 1aab), 20 h (for 1abb), and 23 h (for 1bbb); (vi) 1.5 equiv. Pd(PPh ) ,
2
3
3
3 4
THF, reflux, 2 days (for 2aab), 26 h (for 2abb) and 7 h (for 2bbb).

A. Llobet et al. / Tetrahedron Letters 43 (2002) 1425–1428
1427
1abb and 1bbb were treated with 1.5 equiv. of Pd(PPh3)4
Acknowledgements
in refluxing THF to give the three complexes in 95, 95
and 72% yield, respectively. The three complexes 2aab,
Financial support from MEC of Spain (Projects PB98-
902 and BQP2000-0458) and ‘Generalitat de
Catalunya’ (Projects SGR2000-0062 and SGR1999-166)
2abb and 2bbb are air-stable and have been purified by
0
recrystallization from ethyl acetate/hexane giving cor-
1
rect elemental analysis. Their H NMR spectra are
is gratefully acknowledged.
similar to others already published showing a strong
displacement of the signals of the olefinic protons to
4
higher fields with respect to the free ligands 1.
References
Palladium(0) complex 2aab catalyses the Suzuki-type
cross-coupling reaction of iodobenzene (8) with ben-
zeneboronic acid (9) to afford biphenyl (10) (70% yield)
and the Heck reaction of ethyl acrylate (11) with
iodobenzene (8) leading to ethyl cinnamate (12) in
quantitative yield (Scheme 2). In both cases complex
1
2
. Togni, A.; Hayashi, T. Ferrocenes: Homogeneous Cataly-
sis, Organic Synthesis, Materials Science; VCH: Wein-
heim, 1995.
. (a) Cort e` s, J.; Moreno-Ma n˜ as, M.; Pleixats, R. Eur. J.
Org. Chem. 2000, 239–243; (b) Estrine, B.; Blanco, B.;
Bouquillon, S.; H e´ nin, F.; Moreno-Ma n˜ as, M.; Muzart,
J.; Pena, C.; Pleixats, R. Tetrahedron Lett. 2001, 42,
7055–7057.
2
aab was recovered by column chromatography on
silica gel in 95 and 55% yield, respectively. For the
Heck reaction the rest of the macrocycle is recovered as
uncomplexed 2aab.
3. Cerezo, S.; Cort e` s, J.; Galvan, D.; Lago, E.; Marchi, C.;
Molins, E.; Moreno-Ma n˜ as, M.; Pleixats, R.; Torrej o´ n,
J.; Vallribera, A. Eur. J. Org. Chem. 2001, 329–337.
4
. Cerezo, S.; Cort e` s, J.; Lago, E.; Molins, E.; Moreno-
Ma n˜ as, M.; Parella, T.; Pleixats, R.; Torrej o´ n, J.; Vallrib-
era, A. Eur. J. Inorg. Chem. 2001, 1999–2006.
9
3
. Redox properties
Macrocyclic ferrocenyl ligands 1aab, 1abb and 1bbb,
5. (a) Ripka, A. S.; Bohacek, R. S.; Rich, D. H. Bioorg.
Med. Chem. Lett. 1998, 8, 357–360; (b) Goldring, W. P.
D.; Weiler, L. Org. Lett. 1999, 1, 1471–1473.
display a reversible wave at approximately 700 mV in
III
II
acetonitrile, which can be associated to the Fe /Fe
10
6. Slocum, D. W.; Achermann, W. Synth. React. Inorg.
ferrocenyl moiety couple. Their corresponding Pd(0)
III
II
Met. Org. Chem. 1982, 12, 397–405.
complexes 2aab, 2abb and 2bbb, besides the Fe /Fe
couple, display a new chemically irreversible wave
Ep,a=1.3 V) due to the irreversible oxidation of Pd(0).
7
8
. Neustadt, B. R. Tetrahedron Lett. 1994, 35, 379–380.
. Selected data for all new compounds:
(
4b, mp 149–151°C; 5b, mp 122–124°C; 6aab, mp 57–
In the specific case of 2abb, both waves exhibit similar
59°C; 6abb, 65–67°C; 6bbb, mp 82–84°C; 7aab, mp 46–
intensities. For the corresponding Pd(0) complexes, not
2
,3
49°C; 7abb, mp 54–56°C; 7bbb, mp 71–74°C.
aab, (E,E,E)-1-Ferrocenylsulfonyl-6,11-bis[(4-methyl-
containing the ferrocenyl group (palladium(0) com-
1
1
2
plex 2 with Ar =Ar =2,4,6-triisopropylphenyl, see
Fig. 1), this wave is also observed but with very low
intensity. Thus, the ferrocenyl group in 2aab, 2abb and
phenyl)sulfonyl] - 1,6,11 - triaza cyclopentadeca - 3,8,13-
triene: mp 195–197°C; IR (KBr) 2922, 2859, 1338, 1151
−1
1
cm ; H NMR (CDCl , 200 MHz): l 2.44 (s, 6H),
3
2bbb is responsible for inducing an enhancement of the
3
4
.55–3.66 (m, 12H), 4.39 (apparent t, J=1.8 Hz, 2H),
heterogeneous electron transfer rate constant in the Pd
based wave. These experiments clearly reveal that the
ferrocenyl group is not simply acting as a spectator
ligand, but on the contrary is strongly influencing the
Pd(0) redox properties. We are at the moment investi-
gating the potential origins of this phenomena which
will be reported as a full paper in the near future.
.41 (s, 5H), 4.57 (apparent t, J=1.8 Hz, 2H), 5.53–5.55
13
(
m, 6H), 7.31 (m, 4H), 7.65 (m, 4H); C NMR (CDCl3,
5
1
0 MHz): l 21.5, 50.5, 50.6, 50.7, 68.6, 70.6, 70.8, 86.2,
27.2, 129.0, 129.4, 129.6, 129.8, 136.1, 143.5; ESI-MS
+
+
+
(m/z) 786 [M+Na] , 781 [M+NH ] , 764 [M+H] , 763
[M] . C H FeN O S (763.8) calcd: C, 56.61; H, 5.41;
4
+
36
41
3
6 3
N, 5.50. Found: C, 56.57 and 56.47; H, 5.29 and 5.39; N,
5.50 and 5.42.
1abb, (E,E,E)-1,6-Bis(ferrocenylsulfonyl)-11-[(4-methyl-
phenyl)sulfonyl] - 1,6,11 - triazacyclopentadeca - 3,8,13-
i
triene: mp 103–105°C; IR (KBr) 2921, 2853, 1338, 1157
I
+
B(OH)2
−
1
1
(
70%)
cm ; H NMR (CDCl
.55–3.64 (m, 12H), 4.39 (s, 10H), 4.10–4.42 (m, 4H), 4.56
apparent t, J=1.9 Hz, 4H), 5.50–5.52 (m, 6H), 7.31 (m,
3
, 200 MHz): l 2.44 (s, 3H),
3
(
8
9
10
ii
COOEt
13
2
H), 7.64 (m, 2H); C NMR (CDCl , 50 MHz): l 21.9,
COOEt
3
I
+
(quantitative)
50.5, 50.6, 50.7, 68.6, 70.6, 70.8, 86.2, 127.1, 128.9, 129.2,
12
+
11
129.6, 129.8, 136.0, 143.5; ESI-MS (m/z) 880 [M+Na] ,
8
+
8
57 [M] . C H Fe N O S (857.7) calcd: C, 54.62; H,
39
43
2
3
6 3
Scheme 2. (i) 2aab (0.043 mmol), 8 (0.99 mmol), 9 (1.22
5.05; N, 4.90. Found: C, 54.74 and 54.78; H, 5.43 and
5.44; N, 4.54 and 4.57.
mmol), K CO3 (8.84 mmol), acetone (5 mL)/water (5 mL),
2
6
0°C, 5 h; (ii) 2aab (0.05 mmol), 8 (0.87 mmol), 11 (1.82
1bbb, (E,E,E)-1,6,11-Tris(ferrocenylsulfonyl)-1,6,11-tri-
azacyclopentadeca-3,8,13-triene: mp 225–226°C; IR
(KBr) 2919, 2850, 1332, 1187, 1131 cm ; H NMR
mmol), KOAc (1.76 mmol), Bu NBr (0.96 mmol), DMF (10
mL), 60°C, 2.5 h.
4
−
1
1

1
428
A. Llobet et al. / Tetrahedron Letters 43 (2002) 1425–1428
(
(
CDCl , 200 MHz): l 3.57 (br absorption, 12H), 4.42
45.1, 48.1, 48.2, 49.4, 49.5, 68.4, 68.5, 70.5, 70.6, 70.8,
78.0, 78.2, 78.3, 78.4, 78.7, 82.4, 82.7, 82.8, 85.5, 85.9,
127.0, 127.1, 129.7, 129.8, 135.4, 136.1, 143.3, 143.5;
3
apparent t, J=1.9 Hz, 6H), 4.44 (s, 15H), 4.60 (apparent
13
t, J=1.9 Hz, 6H), 5.46 (br. absorption, 6H); C NMR
CDCl , 50 MHz): l 50.6, 68.6, 70.6, 70.8, 86.4, 129.2;
+
+
(
ESI-MS
(m/z)
963
[M] ,
857
[M−Pd] .
3
+
+
+
ESI-MS (m/z) 968 [M+Na] , 952 [M+H] , 951 [M] .
C H Fe N O PdS (964.1) calcd: C, 48.59; H, 4.50; N,
39
43
2
3
6
3
C H Fe N O S (951.5) calcd: C, 53.01; H, 4.77; N,
4.36. Found: C, 48.91 and 49.06; H, 4.67 and 4.65; N,
4.11 and 4.09.
42
45
3
3
6 3
4
4
2
.42. Found: C, 53.27 and 53.48; H, 4.82 and 4.88; N,
.41 and 4.42.
2bbb,(E,E,E)-1,6,11-Tris(ferrocenylsulfonyl)-1,6,11-triaza-
cyclopentadeca-3,8,13-trienepalladium(0): mp 178–180°C
aab,
(E,E,E)-1-Ferrocenylsulfonyl-6,11-bis[(4-methyl-
−
1
1
phenyl)sulfonyl] - 1,6,11 - triaza cyclopentadeca - 3,8,13-
(dec.); IR (KBr) 2917, 1332, 1132, 900, 611 cm ; H
trienepalladium(0): mp 127–129 (dec.); IR (KBr) 2918,
NMR (CDCl , 200 MHz): l 1.42–1.59 (m, 4H), 2.64 (t,
3
−
1 1
1
333, 1157, 901, 655 cm ; H NMR (CDCl , 200 MHz):
J=11 Hz, 2H), 2.90 (dd, J=14 and 11 Hz, 2H), 3.47–
3.73 (m, 2H), 3.74–3.88 (m, 2H), 4.24–4.47 (m, 18H), 4.34
3
l 1.50–1.70 (m, 4H), 2.38 (s, 6H), 2.76 (apparent t, J=12
Hz, 2H), 3.03 (apparent q, J=12 Hz, 2H), 3.70 (m, 2H),
1
3
(s, 15H); C NMR (CDCl
49.8, 68.8, 68.9, 70.9, 71.0, 71.2, 78.5, 78.8, 83.0, 85.9,
, 62.5 MHz): l 45.6, 48.6,
3
3
4
4
7
1
.93 (m, 2H), 4.41 (s, 5H), 4.32–4.80 (m, 10H), 7.26 (m,
13
+
+
H), 7.68 (m, 4H); C NMR (CDCl , 50 MHz): l 21.4,
86.3; ESI-MS (m/z) 1080 [M+Na] , 1075 [M+NH
4
] ,
1057 [M] , 951 [M−Pd] . C42H45Fe N O PdS (1057.9)
3 3 6 3
3
+
+
5.1, 48.1, 48.2, 49.3, 49.4, 68.3, 68.4, 70.6, 70.7, 78.1,
8.2, 78.3, 78.4, 78.6, 78.7, 82.5, 82.6, 82.9, 85.4, 85.8,
26.9, 127.1, 129.7, 129.8, 135.3, 136.0, 143.3, 143.5;
calcd: C, 47.68; H, 4.29; N, 3.97. Found: C, 47.27 and
47.61; H, 4.39 and 4.43; N, 3.84 and 3.89.
+
+
+
ESI-MS (m/z) 892 [M+Na] , 887 [M+NH ] , 869 [M] ,
9. The redox properties have been investigated by means of
cyclic voltammetry experiments. Those CV experiments
have been carried out using approximately 1 mM sample
complexes in a standard three-electrode cell using aceto-
nitrile, dichloromethane or mixtures of them as solvent
4
+
+
+
7
81 [M−Pd+NH ] , 764 [M−Pd+H] , 763 [M−Pd] .
4
C H FeN O PdS (870.2) calcd: C, 49.69; H, 4.75; N,
36
41
3
6
3
4
4
2
.83. Found: C, 49.50 and 49.66; H, 4.84 and 4.87; N,
.45 and 4.47.
abb, (E,E,E)-1,6-Bis(ferrocenylsulfonyl)-11-[(4-methyl-
under Ar or N atmospheres. Glassy carbon disks (3 mm
2
phenyl)sulfonyl] - 1,6,11 - triazacyclopentadeca - 3,8,13-
diameter) were used as the working electrode, platinum
wire as auxiliary and SSCE as the reference electrode. All
E1/2 redox potentials are thus reported versus SSCE.
trienepalladium(0): mp 144–146°C (dec.); IR (KBr) 2920,
−
1 1
1
337, 1136, 900, 614 cm ; H NMR (CDCl , 200 MHz):
3
l 1.48–1.70 (m, 4H), 2.38 (s, 3H), 2.73 (apparent t, J=12
Hz, 2H), 3.02 (apparent q, J=11 Hz, 2H), 3.68 (m, 2H),
10. E1/2=706 mV, Ep,a=756 mV, Ep,c=656 mV, DE=100
mV for 1aab; E1/2=711 mV, Ep,a=762 mV, Ep,c=660
mV, DE=102 mV for 1abb; E1/2=713 mV, Ep,a=762
mV, Ep,c=664 mV, DE=102 mV for 1bbb.
3
2
.89 (m, 2H), 4.41 (s, 10H), 4.30–4.80 (m, 14H), 7.26 (m,
13
H), 7.67 (m, 2H); C NMR (CDCl , 50 MHz): l 21.5,
3