Iminophosphine palladium complexes in catalytic stille coupling reactions: From monomers to dendrimers

Article abstract of DOI:10.1021/om011076m

Palladium complexes of a variety of β- and γ-iminophosphines were prepared and characterized by X-ray diffraction studies. Their properties as catalysts for three different Stille coupling reactions were investigated. Their properties were compared to cat

Full text of DOI:10.1021/om011076m

4680
Organometallics 2002, 21, 4680-4687
Im in op h osp h in e P a lla d iu m Com p lexes in Ca ta lytic Stille
Cou p lin g Rea ction s: F r om Mon om er s to Den d r im er s
Marek Koprowski,† Rosa-Maria Sebastia´n,‡ Vale´rie Maraval,‡ Maria Zablocka,†
Victorio Cadierno,‡ Bruno Donnadieu,‡ Alain Igau,‡
Anne-Marie Caminade,*,‡ and J ean-Pierre Majoral*,‡
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza
112, 90-363, Lodz, Poland, and Laboratoire de Chimie de Coordination du CNRS, 205 Route
de Narbonne, 31077 Toulouse Cedex 4, France
Received December 18, 2001
Palladium complexes of a variety of â- and γ-iminophosphines have been prepared and
characterized by X-ray diffraction studies. Their properties as catalyst for three different
Stille coupling reactions have been investigated and compared to catalytic performances of
a phosphorus-containing dendrimer incorporating analogous γ-iminophosphine palladium
complexes on the surface.
In tr od u ction
and tricyclic â-iminophosphines via a reductive elimina-
tion reaction of R-phosphino zirconocene-iminoacyl
complexes. We envisaged that the corresponding com-
plexes and mainly the palladium complexes should be
active as catalysts. For this purpose, we prepared a
variety of these complexes, most of them being charac-
terized by X-ray diffraction analysis, and compared their
catalytic activity, in typical reactions such as Stille
coupling reactions, with that of metalladendrimers
incorporating γ-iminophosphines. Indeed, transition
metal catalysis based on functionalized dendrimers is
an attractive area of research, not only because metal-
ladendrimers are generally easily recyclable homoge-
neous catalysts but also because they can be more
active, more selective, or more stable than the corre-
sponding monomers. The wide scope of applications of
metalladendrimers has been recently reviewed.12,13
Recently also we demonstrated that phosphorus-con-
taining metalladendrimers of generation 3, with either
24 terminal palladium or ruthenium diphosphine com-
plexes, are efficient, recoverable catalysts in some
classical reactions.14 However this finding does not
reflect the very contrasted results found for the com-
parison between dendritic catalysts and the correspond-
ing monomers in terms of reaction rate or selectivity.
For instance considering only Pd catalysts, some Pd
complexes of dendrimers were found much less active
than models for the hydrovinylation of styrene15,16 or
for hydroformylation.17 An equal activity between mod-
Phosphorus and nitrogen donor ligands are among the
most attractive and useful ligands used in catalysis
because of the presence of both soft and hard donor
atoms, which allows tailoring their complexation prop-
erties.1 Generally, the phosphorus part of these deriva-
tives is constituted by phosphines or phosphites, while
the nitrogen coordinating site involves amines, pyr-
idines, quinolines, pyrazoles, and oxazolines to name a
few. Among these mixed donor ligands, â-iminophos-
phines were found useful ligands and their complexes
very efficient in a number of catalytic reactions as for
example in the Heck reaction,2 the cross-coupling reac-
tion of alkylstannanes with aryl iodides,3 the hydroge-
nation of unsaturated carbon-carbon bonds,4 the enan-
tioselective allylic substitutions using ketene silyl acetals
and others,5-9 and the copolymerization of CO-ethyl-
ene.10 In most of these reactions the behavior of acyclic-
imino phosphines has been investigated.
Very recently11 we reported the synthesis of new bi-
* Corresponding author. Fax: 33 5 61 55 30 03. E-mail: majoral@
lcc-toulouse.fr.
† Centre of Molecular and Macromolecular Studies, Polish Academy
of Sciences.
‡ Laboratoire de Chimie de Coordination du CNRS.
(1) Kwong, F. Y.; Chan, K. S. Organometallics 2001, 20, 2570, and
references therein.
(2) Reddy, K. R.; Surekka, K.; Lee, G. H.; Peng, S. M.; Liu, S. T.
Organometallics 2000, 19, 2637.
(3) Shirakawa, E.; Yoshida, H.; Takaya, H. Tetrahedron Lett. 1997,
21, 3759; 1997, 29, 5177.
(4) Pelagatti, P.; Bacci, A.; Carcelli, M.; Costa, M.; Fochi, A.; Ghidini,
P.; Leporati, E.; Masi, M.; Pelizzi, C.; Pellizi G. J . Organomet. Chem.
1999, 583, 94.
(5) Saitoh, A.; Morimoto, T.; Achiwa, K. Tetrahedron: Asymmetry
1997, 21, 3567.
(6) Shirakawa, E.; Yoshida, H., Kurahashi, T.; Nakao, Y.; Hiyama,
T. J . Am. Chem. Soc. 1998, 120, 2975.
(7) Saitoh, A.; Achiwa, K.; Morimoto, T. Tetrahedron: Asymmetry
1998, 9, 741.
(8) Saitoh, A.; Misawa, M.; Morimoto, T. Synlett. 1999, 4, 483.
(9) Shirakawa, E.; Yamasaki, K.; Yoshida, H.; Hiyama, T. J . Am.
Chem. Soc. 1999, 121, 10221.
(10) Reddy, K. R.; Surekka, K.; Lee, G. H.; Peng, S. M.; Liu S. T.
Organometallics 2000, 19, 2637.
(11) Cadierno, V.; Zablocka, M.; Donnadieu, B.; Igau, A.; Majoral,
J . P.; Skowronska, A. J . Am. Chem. Soc. 1999, 121, 11086.
(12) (a) Oosterom, G. E.; Reek, J . N. H.; Kamer, P. C. J .; van
Leeuwen, P. W. N. M. Angew. Chem., Int. Ed. 2001, 40, 1828. (b)
Astruc, D.; Chardac, F. Chem. Rev. 2001, 101, 2991.
(13) Caminade, A. M.; Maraval, V.; Laurent R.; Majoral, J . P. Curr.
Org. Chem. 2002, 6, 739.
(14) Maraval, V.; Laurent, R.; Caminade A. M.; Majoral J . P.
Organometallics 2000, 19, 4025.
(15) Eggeling, E. B.; Hovestad, N. J .; J astrzebski, J . T. B. H.; Vogt,
D.; van Koten, G. J . Org. Chem. 2000, 65, 8857.
(16) Hovestad, N. J .; Eggeling, E. B.; J astrzebski, J . T. B. H.; Kragl,
U.; Keim, W.; Vogt, D.; van Koten, G. Angew. Chem., Int. Ed. 1999,
38, 1665.
(17) de Groot, D.; Emmerink, P. G.; Coucke, C.; Reek, J . N. H.;
Kamer, P. C. J .; van Leeuwen, P. W. N. M. Inorg. Chem. Commun.
2000, 3, 711.
10.1021/om011076m CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/01/2002

Iminophosphine Palladium Complexes
Organometallics, Vol. 21, No. 22, 2002 4681
Sch em e 1
F igu r e 1. ORTEP drawing of 6 (50% probability of the
thermal ellipsoids). Selected bond distances (Å) and angles
(deg): P-Pd 2.2322 (11), P-C(9) 1.801(4), N-Pd 2.056(3),
C(1)-N 1.292(5), C(1)-C(9) 1.459(5), N-Pd-P 86.02(9),
C(1)-N-Pd 119.0(3), C(9)-P-Pd 99.18(13), N-C(1)-C(9)
120.8(3), C(1)-C(9)-P 115.0(3).
els and Pd metalladendrimers was found for allylic
amination.18 In contrast a higher activity for the den-
drimer compared to the monomer model was found for
the hydrogenation of olefins19 and for Heck reactions.20
Different explanations were given for these findings.
The decreased activity of Pd complexes of some den-
drimers was ascribed to decomposition due to the close
proximity of the metallic centers, which could facilitate
the formation of elemental Pd.15 On the other hand, the
significantly higher activity compared to monomeric
parent compounds obtained with some other dendrimers
which are also Pd complexes was attributed to a higher
thermal stability, inducing the absence of formation of
elemental Pd.20
Sch em e 2
A deeper insight into dendritic effects observed in
catalysis is also required. Therefore, it is necessary to
investigate the catalytic properties of more metalla-
dendrimers and to compare their activity with that of
related monomers in the hope of offering additional
information which might help to understand the role
of dendrimer complexes and their scope and limitations.
Hereafter we present some preliminary results concern-
ing the use of dendrimers incorporating γ-iminophos-
phine Pd complexes on the surface and that of some
related monomers in three different classical Stille
coupling reactions.
prepared according to previously reported procedures.
The γ-iminophosphine chain end dendrimer 17 was
prepared via a substitution reaction between 15, bearing
six terminal P(S)Cl2 units, and the phenol 16 in the
presence of cesium carbonate: the reaction proceeded
cleanly at room temperature for 12 h, leading to 17,
isolated in 93% yield (Scheme 3).
Resu lts a n d Discu ssion
The â-iminophosphines 5 and 10 (Schemes 1 and 2)
were readily prepared by thermolysis of diphenylzir-
conocene 1, which leads to the benzyne zirconocene 2,
in the presence of either the acetylenic phosphine 3 or
the phospholene 8, followed by treatment of the result-
ing phosphinozircona fused bi- or tricyclic phosphines
4 and 9 with the isocyanide 2,6-Me2C6H3-NC.11 The
γ-iminophosphine 1321 and the dendrimer 1522 were
P a lla d iu m Com p lexes. The â-iminophosphine 5
(δ31P ) -23.8 ppm) in solution in dichloromethane was
first reacted with PdCl2(COD). The resulting complex
6, obtained in 84% yield, was characterized by means
of 31P (δ ) +19 ppm), 1H NMR, and elemental analysis.
An X-ray diffraction study corroborated the postulated
structure in which the PdCl2 unit is linked both to the
imino nitrogen atom and to the phosphino group (Figure
1, Table 1).
(18) de Groot, D.; de Waal, B. F. M.; Reek, J . N. H.; Schenning, A.
P. H. J .; Kamer, P. C. J .; Meyer, E. W.; van Leeuwen, P. W. N. M. J .
Am. Chem. Soc. 2001, 123, 8453.
(19) Mizugaki, T.; Ooe, M.; Ebitani, K.; Kaneda, K. J . Mol. Catal. A
1999, 145, 329.
(20) Reetz, M. T.; Lohmer, G.; Schwickardi, R. Angew. Chem., Int.
Ed. Engl. 1997, 36, 1526.
(21) Wehman, P.; van Donge, H. M. A.; Hagos, A.; Kamer P. C. J .;
van Leeuwen, P. W. N. M. J . Organomet. Chem. 1997, 535, 183.
(22) Launay, N.; Caminade, A. M.; Lahana, R.; Majoral, J . P. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1589.

4682 Organometallics, Vol. 21, No. 22, 2002
Koprowski et al.
Sch em e 3
Addition of the isocyanide 2,6-Me2C6H3-NC to the
complex 6 afforded the new complex 7 (δ31P ) +15.5
ppm), also characterized by single-crystal X-ray diffrac-
tion studies (Figure 2, Table 1). As expected, the
isocyanide group is a better ligand than the imino
nitrogen atom, and the PdCl2 unit in 7 is now linked to
the carbon atom of the isocyanide as well as to the
phosphino group.
The same type of complex could be obtained from the
fused tricyclic â-iminophosphine 10. Complexes with
PdCl2 (11a ), RuCl2(PPh3) (11b), and Mo(CO)4 (11c) were
isolated in high yield. Single crystals of 11a suitable
for X-ray structure determination were obtained from
a dichloromethane pentane solution. The structure
(Figure 3, Table 1) undoubtedly proved the coordination
of the PdCl2 unit to the imino nitrogen atom and to
phosphorus. A ligand exchange readily occurred when
11a was reacted with 2,6-Me2C6H3-NC, affording the
new complex 12, which was also subjected to an X-ray
structure analysis (Figure 4, Table 1). The course of the
reaction, i.e., the 10 f 11a f 12 transformations, was
monitored by 31P NMR (δ ) +9, +34.8, and +52.2 ppm,
respectively, for 10, 11a , and 12). The palladium
complex 14 of the γ-iminophosphine 13 was prepared
in quantitative yield using a classical procedure. 14 was
also characterized by X-ray diffraction studies (Figure
5, Table 1).
Ca ta lytic Tests. The catalytic activity of complexes
6, 11a , 14, and 18 was examined for three Stille cou-
pling reactions. Complexes 5-P d (OAc)2 (δ31P (DMF) )
28.2 ppm), 10-P d (OAc)2 (δ31P (DMF) ) 30.4 ppm), 13-
P d (OAc)2 (δ31P (DMF) ) 31.5 ppm), and 17-P d (OAc)2

Iminophosphine Palladium Complexes
Organometallics, Vol. 21, No. 22, 2002 4683
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p ou n d s 6, 7, 11a , 12, a n d 14
6
7
11a
12
14
formula
C
29H24Cl2NPPd
C38H33Cl2N2PPd,
CH2Cl2
810.86
C
25H24Cl2NPPd
C34H33Cl2N2PPd,
CHCl3
797.26
160
C
25H20Cl2NPPd,
CH2Cl2
627.62
180
fw
temp (K)
594.76
293
546.72
150
160
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
11.381(2)
17.129(2)
13.558(2)
90.0
96.930(17)
90.0
2623.9(6)
4
1.506, 0.990
20 251
4459
309
0.901
triclinic
P1h
orthorhombic
P212121
12.631(2)
8.6180(8)
20.653(2)
90.0
monoclinic
P21/c
10.459(2)
14.405(3)
24.422(5)
90.0
102.04(3)
90.0
3598.5(13)
4
1.472, 0.958
20 845
5161
428
0.914
triclinic
P1h
10.161(2)
10.305(2)
17.860(4)
84.88(2)
75.58(2)
84.43(2)
1798.5(6)
2
9.002(5)
10.159(5)
14.252(5)
78.586(5)
80.303(5)
89.794(5)
1258.7(10)
2
R (deg)
â (deg)
90.0
90.0
γ (deg)
V (Å)
2248.0(4)
4
1.615, 1.147
13 048
3198
Z
Dc (g/cm3), µ (mm-1
no. of reflns collcd
no. of reflns unique
no. of variables
GOF
)
1.497, 0.889
14 049
5668
428
1.096
1.656, 1.242
12 354
4566
298
1.011
274
0.988
R1 (all data)
wR2 (all data)
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
0.0671
0.0724
0.0328
0.0637
0.0379
0.0905
0.0348
0.0886
0.0707
0.1103
0.0504
0.1023
0.0795
0.1335
0.0485
0.1177
0.0377
0.0839
0.0319
0.0805
F igu r e 2. ORTEP drawing of 7 (50% probability of the
thermal ellipsoids). Selected bond distances (Å) and angles
(deg): P-Pd 2.2631(9), P-C(1) 1.792(3), C(9)-N(1) 1.271-
(4), C(18)-Pd 1.921(3), C(18)-N(2) 1.146(4), C(18)-Pd-P
93.92(9), C(1)-P-Pd, 109.41(9).
F igu r e 3. ORTEP drawing of 11a (50% probability of the
thermal ellipsoids). Selected bond distances (Å) and angles
(deg): P-Pd 2.225(2), N-Pd 2.044(7), C(1)-N 1.311(12),
P-C(11) 1.820(9), C(1)-C(11) 1.534(4), N-Pd-P 81.9(2),
C(1)-N-Pd 118.7(6), Pd-P-C(11) 101.7(3).
(δ31P ) 30.4 ppm for terminal P-Pd units) were
prepared “in situ” by mixing 5, 10, 13, or 17 with Pd-
(OAc)2 in a P/Pd ratio ) 1.
cases and that the metalladendrimer appeared to be
more efficient than the corresponding monomer (Table
2, entries 9, 11, and Figure 6). Moreover the metalla-
dendrimer can be reused several times.23 Indeed 18 can
be recovered via precipitation with dry ether, while no
precipitation of monomers 6, 11a , and 14 occurred under
the same experimental conditions. Furthermore no
undesired formation of elemental Pd was observed.
Complexes 5-P d (OAc)2, 10-P d (OAc)2, 13-P d (OAc)2,
and 17-P d (OAc)2 were also used, but they have shown
lower activity (except for 17-P d (OAc)2) (Table 2, entries
1, 4, 6, 10) than the corresponding PdCl2 complexes.
Moreover they were found unstable (abundant forma-
The first reaction investigated was the Stille coupling
of iodobenzene with tributylvinyltin (Figure 6, Table 2).
The catalytic properties of the PdCl2 monomers were
first analyzed under the same conditions, i.e., 5 mol %
Pd, for 20 h at 50 °C with THF as solvent (Table 2,
entries 2, 5, 7). It clearly appeared that the reaction is
faster with the monomer 14 (90% conversion) than with
the fused “tricyclic” system 11a (30% conversion), which
in turn is more effective than the fused bicyclic ligand
complex 6 (20% conversion). Precipitation of Pd was
frequently observed. To try to avoid this, DMF was used
as solvent instead of THF, and the activity of the best
catalyst, i.e., 14, was compared with that of dendrimer
18, bearing on the surface the same complexed units.
Reactions were performed with only 2 mol % Pd during
5 h at 50 °C in DMF. Under these conditions, it can be
noticed that the rate of conversion is very high in all
(23) All the amount of dendritic catalyst was precipitated during
the recycling procedure. No detectable traces of the catalyst were found
in the solution. However it was always difficult during the workup
(filtration) not to lose a small amount of catalyst, as we were working
with a very small quantity of it. We do believe that this fact explains
why we observed the slight decrease of activity of the dendritic catalyst
18 when reused. Obviously several other options (membrane reactors,
etc.) can be envisaged.

4684 Organometallics, Vol. 21, No. 22, 2002
Koprowski et al.
Ta ble 2. Stille Cou p lin g of Iod oben zen e w ith
Tr ibu tylvin yltin
mol % time
conversion
entry
catalyst
Pd
(h) T (°C) solvent %
1
2
3
4
5
6
7
8
5-P d (OAc)2
6
6
10-P d (OAc)2
11a
13-P d (OAc)2
14
14
14
17-P d (OAc)2
18 first run
18 second run
18 third run
5
5
5
5
5
5
5
5
2
2
2
2
2
20
20
37
20
20
20
20
5
5
5
5
5
50
50
50
50
50
50
50
50
50
50
50
50
50
THF
THF
THF
THF
THF
THF
THF
DMF
DMF
DMF
DMF
DMF
DMF
10a
20
48
20a
30a
65a
90a
91
9
83
10
11
12
13
98a
98
92
86
5
a
Pd precipitate observed.
F igu r e 4. ORTEP drawing of 12 (50% probability of the
thermal ellipsoids). Selected bond distances (Å) and angles
(deg): P-Pd 2.2358(16), C(1)-N(2) 1.265(8), C(1N)-N(1)
1.169(8), P-Pd-C(1N) 88.64(18), Pd-C(1N)-N(1) 177.9-
(5).
Ta ble 3. Stille Cou p lin g of Meth yl-2-iod oben zoa te
w ith 2-(Tr ibu tylsta n n yl)th iop h en e
mol % time
T
conversion
(%)
entry catalyst
Pd
(h)
(°C) solvent
1
2
3
4
5
6
6
11a
14
18
5
5
5
5
5
4
30
4
4
3
50
67
50
50
50
DMF
THF
DMF
DMF
DMF
65
91
73a
99
100
a
Pd precipitate observed.
F igu r e 5. ORTEP drawing of 14 (50% probability of the
thermal ellipsoids). Selected bond distances (Å) and angles
(deg): P-Pd 2.2205(10), N-Pd 2.053(2), N-C(1) 1.275(4),
C(1)-C(2) 1.470(4), C(2)-C(7) 1.399(4), C(7)-P 1.819(3),
N-Pd-P 86.34(8), C(1)-N-Pd 125.39(18), Pd-P-C(7)
103.84(10).
F igu r e 7. Stille coupling of methyl-2-iodobenzoate with
2-(tributylstannyl)thiophene at 50 °C in DMF in the
presence of 5 mol % Pd of catalyst 14, 18, or recycled 18.
The Stille coupling of methyl-2-iodobenzoate with
2-(tributylstannyl)thiophene was then investigated (Table
3). Reactions were performed in DMF at 50 °C with 5
mol % Pd. The metalladendrimer 18 and the monomer
14 exhibited close catalytic activities: 100% conversion
was reached after 3-4 h depending on the complex
(Figure 7), while a lower activity was observed for 11a
(Table 3, entries 3, 4, 5). The metalladendrimer 18 was
also found to be efficient with a slightly decreased
activity when recycled (Figure 7). In contrast here again,
the â-iminophosphine complex 6 is poorly efficient when
used in the same experimental conditions (Table 3,
entry 1). However 91% conversion was observed using
6 as catalyst (5 mol % Pd) in THF but at 67 °C and for
30 h (Table 3, entry 2).
F igu r e 6. Stille coupling of iodobenzene with tributyl-
vinyltin at 50 °C in DMF in the presence of 2 mol % Pd of
catalyst 14, 17-P d (OAc)2, or 18.
tion of elemental Pd), and recycling of 5-P d (OAc)2, 10-
P d (OAc)2, and 13-P d (OAc)2 failed. The recycling of 17-
P d (OAc)2 was possible (precipitation with dry ether)
but was accompanied by formation of elemental Pd and
by a dramatic decrease of the catalytic activity.
The catalytic activity of the PdCl2 complexes coordi-
nated with â- or γ-iminophosphines 5, 10, and 13 and
dendrimer 17 was also demonstrated in the cross-

Iminophosphine Palladium Complexes
Organometallics, Vol. 21, No. 22, 2002 4685
Ta ble 4. Stille Cou p lin g of
4-(Tr iflu or om eth yl)iod oben zen e w ith
P h en yleth yn yltr ibu tyltin
mol % time
T
conversion
(%)
entry catalyst
Pd
(h)
(°C) solvent
1
2
3
4
5
6
6
6
11a
11a
14
18
1
2.5
1
2.5
1
1
20
4
20
20
10
15
20
20
20
20
20
20
DMF
DMF
DMF
DMF
DMF
DMF
65
90
70
90
90
75
F igu r e 9. Conformation of the palladium five- and six-
membered ring in complexes 6, 11a , and 14. For clarity
only the location of the substituents (and not the substit-
uents themselves) on phosphorus, nitrogen, and carbon are
represented. The largest deviation of the carbon atoms of
the palladium ring from the mean PPdCl2 plane is 0.05 Å
for 6, 1.46 Å for 11a , and 1.69 Å for 14.
Con clu sion
It clearly appears from these preliminary experiments
concerning cross-coupling reactions that palladium com-
plexes of the γ-iminophosphine 13 and the correspond-
ing metalladendrimer 18 are better catalysts than the
complexes formed from bi- or tricyclic â-iminophos-
phines. The catalytic performances of the metalladen-
drimer depend on the reagents involved in the investi-
gated Stille coupling reactions: besides the fact that it
can be easily recycled, it also allowed improvement of
the catalytic activity of γ-iminophosphine palladium
complexes in the case of the reaction of iodobenzene with
tributylvinyltin. Such an unpredictable and versatile
behavior of metalladendrimers in catalysis brings new
examples reflecting the very contrasted results already
reported in the literature. It is clear that numerous
investigations have to be performed in order to clarify
the role of metalladendrimers and their usefulness in
addition to recycling. In the continuation of the present
work further investigations in understanding the role
of steric effects and electronic influence of ligands, the
effect of the size of dendrimers (number of generations),
and the role of the complex inside the dendrimer or on
the surface are presently underway.
F igu r e 8. Stille coupling of 4-(trifluoromethyl)iodobenzene
with phenylethynyltributyltin at 20 °C in DMF in the
presence either of 1 mol % Pd of catalyst 14 or 18 or of 2.5
mol % Pd of catalyst 6 or 11a .
coupling reaction of 4-(trifluoromethyl)iodobenzene with
phenylethynyltributyltin (Table 4, Figure 8). The con-
version was readily monitored by 19F NMR spectroscopy
of the reaction mixture. Reactions were performed in
DMF at 20 °C using 1 mol % Pd. The monomer 14 is
more efficient than the corresponding metalladendrimer
18 (Figure 8). Conversion was 75% with 18 for 15 h of
reaction (Table 4, entry 6), whereas it reached 90% for
10 h with 14, respectively, with 1 mol % Pd in all cases.
The complexes formed with the cyclic â-iminophos-
phines 5 and 10, i.e., 6 and 11a , are again less active:
it is necessary to use a larger amount of catalyst (2.5
mol % Pd) and generally longer reaction times to observe
a comparable conversion (Table 4, entries 1-4). The
more efficient catalyst was 6 (2.5 mol % Pd), which
allowed 90% conversion for 4 h at room temperature.
Exp er im en ta l Section
At this stage of this preliminary study, it is difficult
to rationalize the catalytic activity of the monomer
ligands. One might evoke that the difference of activity
of the corresponding Pd complexes can be due to the
difference of geometry of the palladium five-membered
rings (compounds 5-P d (OAc)2, 6, 10-P d (OAc)2, 11a )
or six-membered rings (compounds 13-P d (OAc)2, 14,
17-P d (OAc)2, 18), and therefore to the more or less easy
access of the reagents to the palladium center. Pal-
ladium cycles for compounds 6, 11a , and 14 are repre-
sented in Figure 9. Complex 6 appears practically
planar, while an envelope form can be detected for 11a
and a quite distorted chair form for 14. Anyway these
differences in geometry do not preclude other effects
responsible for the activities for the different complexes,
as for example electronic properties of the ligands.
Therefore at the present state of the art, discussion
appears only speculative.
Gen er a l P r oced u r es. All manipulations were carried out
with standard high-vacuum and dry-argon techniques. 1H, 13C,
and 31P NMR and 19F spectra were recorded with Bruker
AC200, AC250, DPX300, or AMX 400 spectrometers. Refer-
ences for NMR chemical shifts are 85% H3PO4 for 31P NMR,
SiMe4 for 1H and 13C NMR, and CF3CO2H for 19F. The
attribution of 13C NMR signals has been done using J mod, two-
dimensional HBMC and HMQC, broad band, or CW 31P
decoupling experiments when necessary. The numbering used
for NMR of compounds 14, 16, 17, and 18 is depicted in Figure
10. Iminophosphines 5 and 1011 as well as 1321 were prepared
according to literature procedures. Dendrimer 15 was prepared
in our lab, according to the procedure that we developed.22
Complexes 5-P d (OAc)2, 10-P d (OAc)2, 13-P d (OAc)2, and 17-
P d (OAc)2 were prepared “in situ” by mixing 5, 10, 13, or 17
with Pd(OAc)2 (P/Pd ) 1).
Syn th esis of Com p lex 6. To a solution of the â-iminophos-
phine 5 (0.417 g, 1 mmol) in 10 mL of CH2Cl2 was added
(COD)PdCl2 (0.291 g, 1 mmol) in solution in 20 mL of CH2Cl2.
The resulting solution was stirred for 2 h at room temperature,

4686 Organometallics, Vol. 21, No. 22, 2002
Koprowski et al.
3
9.7 Hz, CH), 145.5 (s, CCCdN), 155.9 (d, J CP ) 4.3 Hz, CCd
2
N), 184.1 (d, J CP ) 5.0 Hz, CdN), Cipso-P not detected. Anal.
Calcd for C43H39Cl2NP2Ru (803.7): C, 64.26; H, 4.89; N, 1.74.
Found: C, 64.09; H, 4.78; N, 1.70.
Syn th esis of Com p lex 11c. To a solution of 10 (0.044 g,
0.12 mmol) in CH2Cl2 (5 mL) was added bicyclo[2.2.1]hepta-
2,5-diene molybdenum tetracarbonyl in solution in CH2Cl2 (2
mL). The resulting solution was stirred for 1 h at room
temperature and then evaporated to dryness. The resulting
brown powder was washed with 2 × 5 mL of pentane, then
with 1 mL of Et2O, to give 11c as a yellow powder in 58% yield
F igu r e 10. Numbering used for NMR.
then the solvent was evaporated to give a yellow solid, which
was washed two times with a 1:10 CH2Cl2/pentane solution.
Yellow crystals suitable for X-ray diffraction studies were
obtained from a CH2Cl2/pentane/ether solution of 6. 31P{1H}
NMR (CH2Cl2) δ: 19.0. 1H NMR (CD2Cl2) δ: 2.28 (s, 6H, CH3),
6.85-7.70 (m, 13H, Harom), 7.8-8.3 (m, 5H, Harom). The
compound was not soluble enough to be characterized by 13C
NMR. Anal. Calcd for C29H24Cl2NPPd (594.8): C, 58.56; H,
4.06; N, 2.35. Found: C, 58.27; H, 3.89; N, 2.25.
1
(0.040 g). 31P{1H} NMR (CDCl3) δ: 51.4. H NMR (CDCl3) δ:
1.85 (s, 3H, CH3), 1.96-2.68 (m, 4H, CH2), 2.35 (s, 3H, CH3),
2
3
4.04 (m, 1H, CH), 4.52 (dd, J HP ) 7.3 Hz, J HH ) 7.0 Hz, 1H,
3
CHP), 5.99 (d, J HH ) 8.1 Hz, 1H, Harom), 6.95-7.20 (m, 5H,
H
arom), 7.35-7.38 (m, 2H, Harom), 7.45-7.55 (m, 2H, Harom),
7.60-7.82 (m, 2H, Harom). 13C{1H} NMR (CDCl3) δ: 17.9 (s,
2
CH3), 18.2 (s, CH3), 31.4 (d, J CP ) 13.1 Hz, CH2), 33.7 (d,
1J CP ) 5.3 Hz, CH2), 45.4 (s, CH), 63.8 (d, 1J CP ) 20.9 Hz, CH),
124.6 (s, CH), 124.9 (s, Cquat), 125.6 (s, CH), 126.0 (s, CH), 127.8
4
Syn th esis of Com p lex 7. To a solution of complex 6 (0.059
g, 0.1 mmol) dissolved in 20 mL of CH2Cl2 was added the
isocyanide 2,6-Me2C6H3-NC (0.013 g, 0.1 mmol) in 5 mL of CH2-
Cl2. The solution was stirred for 2 h at room temperature, then
evaporated, and the residue was washed with EtOH (2 × 10
mL) and then pentane (2 × 10 mL) and dried in a vacuum.
Yield: 94% (0.068 g). Yellow crystals suitable for X-ray
diffraction studies were obtained from a 2:1 CH2Cl2/pentane
solution. 31P{1H} NMR (CDCl3) δ: 15.5. 1H NMR (CDCl3) δ:
(s, CH), 128.4 (s, Cquat), 128.8 (d, J CP ) 4.1 Hz, CH), 129.1 (d,
3J CP ) 18.2 Hz, CH), 130.3 (s, CH), 131.1 (d, J CP ) 12.4 Hz,
2
CH, o-C6H5P), 132.1 (s, Cipso-N), 132.9 (s, CH), 149.1 (s,
3
2
CCCdN), 154.8 (d, J CP ) 3.0 Hz, CCdN), 183.4 (d, J CP
)
2
10.3 Hz, CdN), 208.0 (d, J CP ) 10.0 Hz, CdO), 209.7 (d,
2J CP ) 10.1 Hz, CdO), 215.0 (d, J CP ) 36.2 Hz, CdO), 224.1
2
2
(d, J CP ) 7.8 Hz, CdO), Cipso-P not detected. Anal. Calcd for
29H24NO4MoP (577.4): C, 60.32; H, 4.19; N, 2.43. Found: C,
C
60.06; H, 4.11; N, 2.30.
3
1.92 (s, 6H, CH3), 2.06 (s, 6H, CH3), 6.43 (d, J HP ) 7.4 Hz,
Syn th esis of Com p lex 12. To a solution of 11a (0.203 g,
0.37 mmol) in 20 mL of CH2Cl2 was added the isocyanide 2,6-
Me2C6H3-NC (0.049 g, 0.37 mmol) in 5 mL of CH2Cl2. The
resulting solution was stirred for 1 h at room temperature,
then evaporated, and the residue was washed with Et2O (2 ×
10 mL) and pentane (2 × 10 mL) and dried in a vacuum to
give 12 in 88% yield (0.220 g). Crystals were obtained from a
1:1 CH2Cl2/pentane solution. 31P{1H} NMR (CD2Cl2) δ: 52.2.
1H NMR (CD2Cl2) δ: 1.67 (s, 3H, CH3), 2.03 (s, 6H, CH3), 2.07-
1H, dCH), 6.85-7.95 (m, 20H, Harom). The compound was not
soluble enough to be characterized by 13C NMR. Anal. Calcd
for C38H33Cl2N2PPd (726): C, 62.87; H, 4.58; N, 3.86. Found:
C, 62.71; H, 4.51; N, 3.79.
Syn th esis of Com p lex 11a . To a solution of 10 (0.077 g,
0.21 mmol) in CH2Cl2 (5 mL) was added (COD)PdCl2 (0.060 g,
0.21 mmol) in CH2Cl2 (5 mL). The resulting orange solution
was stirred for 1 h at room temperature, then evaporated, and
the residue was washed with Et2O (2 × 10 mL) and pentane
(2 × 10 mL), to give 11a in 82% yield (0.094 g). Crystals were
obtained from a 1:1 CH2Cl2/pentane solution. 31P{1H} NMR
(CD2Cl2) δ: 34.8. 1H NMR (CD2Cl2) δ: 2.12-2.40 (m, 1H), 2.31
(s, 6H, CH3), 2.43-2.63 (m, 2H), 2.75-2.93 (m, 1H), 3.90-3.98
2
2.65 (m, 4H, CH2), 2.66 (s, 3H, CH3), 4.25 (dd, J HP ) 7.8 Hz,
2
2
2J HH ) 8.0 Hz, 1H, CHP), 4.29 (dd, J HH ) 8.0 Hz, J HP ) 9.8
3
Hz, 1H, CHP), 6.60 (d, J HH ) 8.0 Hz, 1H, Harom), 6.93-7.58
(m, 12H, Harom), 7.94-8.04 (m, 2H, Harom). The compound was
not soluble enough to be characterized by 13C NMR. Anal.
Calcd for C34H33Cl2N2PPd (677.9): C, 60.24; H, 4.90; N 4.13.
Found: C, 60.01; H, 4.81; N, 4.07.
3
4
2
(m, 1H), 5.11 (ddd, J HH ) 1.1 Hz, J HH ) 5.4 Hz, J PH ) 6.9
3
Hz, 1H, CH-CdN), 5.95 (d, J HH ) 8.1 Hz, 1H, Harom), 7.01-
7.37 (m, 6H, Harom), 7.38-7.68 (m, 3H, Harom), 7.90-8.00 (m,
2H, o-C6H5P). The compound was not soluble enough to be
characterized by 13C NMR. Anal. Calcd for C25H24Cl2NPPd
(546.7): C, 54.90; H, 4.42; N, 2.56. Found: C,54.71; H,4.40;
N, 2.47.
Syn th esis of Com p lex 14. To a solution of the phosphine
13 (0.372 g, 1 mmol) in 10 mL of CH2Cl2 was added (COD)-
PdCl2 (0.291 g, 1 mmol) in solution in 25 mL of CH2Cl2. The
resulting solution was stirred for 3 h at room temperature,
then the solvent was evaporated to give a yellow solid, which
was washed three times with a 1:10 CH2Cl2/pentane solution.
Slow evaporation of a CH2Cl2/pentane/ether solution of 14 gave
yellow crystals. 31P{1H} NMR (DMSO-d6) δ: 36.3. 1H NMR
Syn th esis of Com p lex 11b. To a solution of 10 (0.053 g,
0.14 mmol) in 5 mL of CH2Cl2 was added (Ph3P)3RuCl2 (0.138
g, 0.14 mmol) in 5 mL of CH2Cl2. The resulting deep brown
solution was stirred for 1 h at room temperature, then
evaporated to dryness. The resulting brown powder was
dissolved in CH2Cl2 (1 mL) then precipitated with 10 mL of
pentane. 11b was obtained as a brown powder in 78% yield
3
3
(DMSO-d6) δ: 7.15 (dd, J HH ) 7.7 Hz, J HP ) 17.9 Hz, 1H,
arom), 7.40-8.10 (m, 17H, Harom), 8.30 (m, 1H, Harom), 8.80 (s,
H
1H, CHdN). The compound was not soluble enough to be
characterized by 13C NMR. Anal. Calcd for C25H20Cl2NPPd
(542.7): C, 55.33; H, 3.71; N, 2.58. Found: C, 55.08; H, 3.62;
N, 2.49.
2
(0.088 g). 31P{1H} NMR (CDCl3) δ: 55.1 (d, J PP ) 43.9 Hz,
CH-P-CH2), 79.5 (d, 2J PP ) 43.9 Hz, PPh3). 1H NMR (CDCl3)
δ: 2.02 (s, 3H, CH3), 2.05-2.52 (m, 3H, CH2), 2.52 (s, 3H, CH3),
2.61-2.89 (m, 1H, CH2-P), 3.58-3.72 (m, 1H, CH), 5.37 (dd,
Syn th esis of Com p ou n d 16. To a solution of 2-(diphen-
ylphosphino)benzaldehyde (0.29 g, 1 mmol) in hot ethanol (2
mL) was added a hot solution of 4-aminophenol (0.11 g, 1
mmol) in ethanol (2 mL). The resulting solution was refluxed
in a sealed Schlenk for 2 h. Then the solution was concentrated
and cooled at 5 °C for 3 h. Compound 16 precipitated as a
yellow solid in 83% yield (0.31 g). 31P{1H} NMR (CDCl3) δ:
-13.3. 1H NMR (CDCl3) δ: 5.40 (s, 1H, OH), 6.70-7.45 (m,
2
3
3J HH ) 6.0 Hz, J HP ) 7.1 Hz, 1H, CHP), 6.23 (d, J HH ) 7.7
Hz, 1H, Harom), 6.93-7.73 (m, 26H, Harom). 13C{1H} NMR
(CDCl3) δ: 19.9 (s, CH3), 21.2 (s, CH3), 25.6 (d, J CP ) 24.6
Hz, CH2P), 32.4 (s, CH2CH2P), 41.9 (s, CH), 65.3 (d, J CP
2
1
)
31.9 Hz, dCCHP), 124.5 (s, CH), 125.9 (s, CH), 126.3 (s, CH),
127.1 (d, J CP ) 8.9 Hz, CH), 127.4 (s, CH), 128.0 (d, J CP ) 9.3
Hz, CH), 128.3 (d, J CP ) 7.5 Hz, CH), 128.6 (d, J CP ) 11.4 Hz,
CH), 128.7 (s, CH), 129.1 (s, CH), 130.0 (s, CH), 131.0 (s, Cquat),
3
3
12H, Harom), 6.72 (d, J HH ) 8.8 Hz, 2H, HC2), 6.88 (d, J HH
)
8.8 Hz, 2H, HC3), 6.91 (m, 1H, HC9), 8.16 (ddd, 3J HH ) 7.6 Hz,
4
4
131.1 (d, J CP ) 7.6 Hz, CH), 131.4 (s, Cipso-N), 131.8 (s, CH),
4J HP ) 3.8 Hz, J HH ) 1.25 Hz, 1H, HC6), 9.07 (d, J HP ) 5.2
2
131.9 (d, J CP ) 9.4 Hz, CH), 133.4 (s, Cquat), 134.3 (d, J CP
)
Hz, 1H, CHdN). 13C{1H} NMR (CDCl3) δ: 115.7 (s, C2), 122.5

Iminophosphine Palladium Complexes
Organometallics, Vol. 21, No. 22, 2002 4687
4
(s, C3), 127.9 (d, J CP ) 4 Hz, Cp), 128.6 (s, C7 or C6), 128.7 (s,
ment of the Flack parameters led to a value close to 0.5, which
denotes the presence of the racemic twin. The refinement has
been carried out using the following twin matrix: -1 0 0 0-1
0 0 0-1.
Drawings of molecules were performed with the program
ORTEP3228 with 50% probability displacement ellipsoids for
non-hydrogens.
C6 or C7), 128.8 (d, J CP ) 15 Hz, Cm), 130.6 (s, C8), 133.6 (s,
3
C9), 134.0 (d, J CP ) 19.6 Hz, C0), 136.4 (d, J CP ) 10 Hz, Ci),
2
1
138.3 (d, J CP ) 17 Hz, C10), 139.5 (s, C5), 144.5 (s, C4), 154.8
1
(s, C1), 156.9 (d, 3J CP ) 21.6 Hz, CHdN). Anal. Calcd for C25H20
-
NOP (381.4): C, 78.72; H, 5.28; N, 3.67. Found: C, 78.59; H,
5.17; N, 3.59.
Syn th esis of Den d r im er 17. To a solution of the den-
drimer 1522 (0.110 g, 0.06 mmol) in THF (5 mL) was added
the phosphine 16 (0.300 g, 0.78 mmol) dissolved in THF (5
mL). After stirring overnight at room temperature, the solvent
was evaporated under reduced pressure. The residue was
washed with a 1:10 THF/pentane solution, giving rise to a
white powder. Yield: 93% (0.326 g). 31P{1H} NMR (CDCl3) δ:
Gen er a l Con d ition s for Ca ta lytic Exp er im en ts. Stille
Cou p lin g w ith Com p lexes 6, 11a , 14, a n d 18. Complexes
6 (5% molar, 32 mg, 0.054 mmol), 11a (1% molar, 6 mg, 0.011
mmol; 2.5% molar, 15 mg, 0.027 mmol; 5% molar, 29 mg, 0.054
mmol), 14 (1% molar, 6 mg, 0.011 mmol; 2% molar, 12 mg,
0.021 mmol; 5% molar, 29 mg, 0.054 mmol), and 18 (1% molar
[Pd], 7 mg, 0.0008 mmol; 2% molar [Pd], 13 mg, 0.0016 mmol;
5% molar [Pd], 34 mg, 0.0042 mmol) were dissolved in 5 mL
of distilled THF or DMF. The iodo derivative (1.07 mmol) was
added, and the mixture was stirred 15 min at room temper-
ature. Then the tin derivative (1.07 mmol for tributylvinyltin
or 1.18 mmol for tributylstannyl thiophene and phenylethyn-
yltributyltin) was added and the mixture was stirred at 20,
50, or 67 °C. Reactions were monitored either by 1H NMR
(integration of the signals due to the vinyl protons in the case
of the coupling of iodobenzene with tributylvinyltin, integra-
tion of the signals due to methyl groups in the case of coupling
of methyl-2-iodobenzoate with 2-(tributylstannyl)thiophene) or
by 19F NMR (coupling of 4-(trifluoromethyl)iodobenzene with
phenylethynyltributyltin).
1
-13.1 (s, PPh2), 8.5 (s, N3P3), 63.2 (s, PdS). H NMR (CDCl3)
3
3
δ: 3.18 (d, J HP ) 10.3 Hz, 18H, CH3), 6.79 (d, J HH ) 8.8 Hz,
24H, Harom), 6.88 (m, 12H, Harom), 7.01 (d, 3J HH ) 8.7 Hz, 12H,
3
4
H
arom), 7.08 (dd, J HH ) 8.8 Hz, J HP ) 1.2 Hz, 24H, Harom),
3
7.22-7.42 (m, 144H, Harom), 7.50 (d, J HP ) 2.0 Hz, 6H, CHd
NN), 7.58 (d, J HH ) 8.7 Hz, 12H, C30), 8.09 (ddd, J HH ) 1.2
3
4
Hz, J HP ) 3.9 Hz, J H-H ) 7.7 Hz, 12H, HC6), 8.95 (d, J HP
)
4
3
4
5.2 Hz, 12H, CHdNC). Anal. Calcd for C348H276N27O18P21S6
(5967): C, 70.05; H, 4.66, N, 6.34. Found: C, 69.69; H, 4.59;
N, 6.23.
Syn th esis of Meta lla d en d r im er 18. To a solution of the
dendrimer 17 (0.198 g, 0.03 mmol) in CH2Cl2 (30 mL) was
added (COD)PdCl2 (0.114 g, 0.4 mmol) in solution in CH2Cl2
(20 mL). The resulting mixture was stirred for 3 h at room
temperature, then the solvent was evaporated, and the residue
was washed with a 1:1 THF/pentane solution (20 mL). 18 was
obtained as a yellow solid in 99% yield (0.268 g). 31P{1H}
(DMF-d7) δ: 12.8 (s, N3P3), 35.5 (s, PPh2), 66.9 (s, PdS). 1H
Stille Cou p lin g w ith Com p lexes 5-P d (OAc)2, 10-P d -
(OAc)2, 13-P d (OAc)2, a n d 17-P d (OAc)2 (P /P d ) 1). Five
percent molar ligand 5 (22 mg, 0.053 mmol), or 5% molar
ligand 10 (20 mg, 0.054 mmol), or 5% molar of ligand 13 (20
mg, 0.054 mmol), or 2% molar phosphine of dendrimer 17 (10
mg, 0.0017 mmol) and Pd(OAc)2 (2%: 4.7 mg; 5%: 12 mg) were
dissolved in 5 mL of distilled THF or DMF. The mixture was
stirred 15 min at 50 °C. After cooling to room temperature,
iodobenzene (1.07 mmol) was added and the mixture was
stirred 15 min at room temperature. Then tributylvinyltin
(1.07 mmol) was added, and the mixture was stirred at 50 °C.
3
NMR (DMF-d7) δ: 3.41 (d, J HP ) 10.4 Hz, 18H, CH3), 6.80-
8.02 (m, 234 H, Harom and CHdNN), 8.29 (m, 12H, HC6), 8.70
(s, 12H, CHdNC). Anal. Calcd for C348H276Cl24N27O18P21Pd12S6
(8094.9): C, 51.63; H, 3.44; N, 4.67. Found: C, 51.40; H, 3.36;
N, 4.49.
X-r a y An a lysis. Data were collected at low temperature
for 7, 11a , 12, and 14 and at room temperature for 6 on a IPDS
STOE diffractometer equipped with an Oxford Cryosystems
Cryostream cooler device and using a graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å). Final unit cell parameters
were obtained by means of a least-squares refinement of a set
of well-measured reflections, and crystal decay was monitored
during the data collection. No significant fluctuations of
intensities have been observed. Structures have been solved
by direct methods using SIR9224 and refined by least-squares
procedures on F2 with the aid of SHELXL9725 included in the
program package WinGX version 1.64,26 and atomic scattering
factors were taken from International Tables for X-Ray
Crystallography.27 All hydrogen atoms were located on a
difference Fourier map refined by using a riding model. For
all structures non-hydrogen atoms were anisotropically re-
fined, and in the last cycles of refinement a weighting scheme
was used, where weights are calculated from the following
1
Reactions were monitored by H NMR.
Ca ta lyst Recyclin g. Degassed and distilled ether (100 mL)
was added to the DMF solution to precipitate the catalyst when
the reaction was performed in the presence of 17-P d (OAc)2
or 18. After filtration, the dendrimer complex was washed with
ether (15 mL) and dried under vacuum. For reuse, the
resulting powder was solubilized in DMF and the starting
reagents were added to the resulting solution. It can be noted
that the recycling of monomer 5-P d (OAc)2, 6, 10-P d (OAc)2,
11a , 13-P d (OAc)2, or 14 cannot be done using this procedure
since no precipitation of these complexes occurred by adding
degassed and distilled ether to the DMF or the THF solution
containing reagents and final products involved in the different
Stille coupling reactions.
Ack n ow led gm en t. This work was completed with
support of the European Associate Laboratory financed
by CNRS (France) and the Polish Committee for Sci-
entific Research (KBN Grant 3TO9A03619). Thanks are
due to the foundation Ramon Areces (Spain) for a grant
to R.M.S., and to NATO for a grant to M.K.
2
formula w ) 1/[σ2(Fo2) + (aP)2 + bP], where P ) (Fo + 2Fc2)/
3. Compound 11a crystallizes in the non-centrosymmetric
space group P212121; however it was not possible to properly
define the absolute configuration for this structure, as refine-
(24) (a) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.
SIR92-A program for crystal structure solution. J . Appl. Crystallogr.
1993, 26, 343. (b) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano,
G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. SIR97. J . Appl. Crystallogr. 1999, 32, 115.
(25) Sheldrick, G. M. SHELX97 [Includes SHELXS97, SHELXL97,
CIFTAB]-Programs for Crystal Structure Analysis; 1998 (Release 97-
2).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, data collection, structure refinement, atomic coordinates,
full list of bond lengths and angles, and anisotropic displace-
ment parameters for complexes 6, 7, 11a , 12, and 14. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(26) Farrugia, L. WinGX-1.64.03 Integrated System of Windows
Programs for the Solution, Refinement and Analysis of Single-Crystal
X-Ray Diffraction Data. J . Appl. Crystallogr. 1999, 32, 837.
(27) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, England, 1974; Vol IV.
OM011076M
(28) Farrugia, L. J . ORTEP32 for Windows. J . Appl. Crystallogr.
1997, 30, 565.