Easy ketimine formation assisted by heteropolynuclear gold -thallium complexes

Article abstract of DOI:10.1021/om051030j

Treatment of the heterometallic complexes [AuTl(C₆X ₅₂(L¹)] (X = Cl (1a), F (1b), L¹ = ethylenediamine) with ketones at room temperature yields stable amine-imine or diimine complexes with the new ligands bound

Full text of DOI:10.1021/om051030j

Organometallics 2006, 25, 1689-1695
1689
Easy Ketimine Formation Assisted by Heteropolynuclear
Gold-Thallium Complexes
Eduardo J. Ferna´ndez,*,§ Antonio Laguna,*,‡ Jose´ M. Lo´pez-de-Luzuriaga,§
Manuel Montiel,§ M. Elena Olmos,§ and Javier Pe´rez§
Departamento de Qu´ımica, UniVersidad de la Rioja, Grupo de S´ıntesis Qu´ımica de La Rioja, UA-CSIC,
Complejo Cient´ıfico Tecnolo´gico, 26006 Logron˜o, Spain, and Departamento de Qu´ımica Inorga´nica,
Instituto de Ciencia de Materiales de Arago´n, UniVersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
ReceiVed December 2, 2005
Treatment of the heterometallic complexes [AuTl(C6X5)2(L1)] (X ) Cl (1a), F (1b), L1
ethylenediamine) with ketones at room temperature yields stable amine-imine or diimine complexes
with the new ligands bound to the thallium centers. Besides their reactivity in solution, both amine
complexes 1a and 1b react in the solid state with ketone vapors at room temperature in a few seconds.
)
photoluminescent chromophores.15 The classical synthesis of
imines, originally reported by Schiff,16 involves a condensation
of a carbonyl compound with an amine under azeotropic
distillation17 to separate the liberated water. Usually, the reaction
requires high temperatures, prolonged reaction periods, and the
presence of external or in situ dehydrating agents in order to
achieve better yields.18-21 Even the use of metal salts as catalysts
or more specialized methods, as acids under microwave radiation
or ionic liquids, have been reported.22-34 Even so, the efficiency
of these procedures is limited to the reaction of highly
electrophilic carbonyl compounds and strongly nucleophilic
amines. In the particular case of ethylenediamine, the addition
of acetone does not lead to the isolation of the corresponding
diimine ligand because of its low stability. An alternative
pathway consists of the coordination of ethylenediamine to the
chosen metal center and the subsequent addition of the carbonyl-
containing precursor. Nevertheless, the complexes prepared
Introduction
In the last years the synthesis of extended linear chain
compounds has received renewed interest to chemists and
physicists owing to their fascinating and unique chemical and
physical properties.1,2 In fact, heterometallic systems have been
shown as very promising candidates for photophysical studies3
that could lead to their use as light-emitting devices, and some
of them can even be used as VOC sensors,4-11 but their utility
as reagents for organic synthesis now appears as a new
application for these systems. In this regard, nonconjugated
diimines are tailored derivatives of bipyridine or phenanthroline-
type organic ligands and used as a more flexible alternative to
the conventional building blocks in supramolecular architec-
tures,12 in complexes with catalytic activity,13 in complexes that
form supramolecular host-guest assemblies with electrical
transport properties,14 or as stabilizing ligands of copper
(15) Chowdhury, S.; Patra, G. K.; Drew, M. G. B.; Chattopadhyay, N.;
Datta, D. Dalton Trans. 2000, 235-237.
* To whom the correspondence should be addressed. E-mail: alaguna@
posta.unizar.es; eduardo.fernandez@dq.unirioja.es.
§ Universidad de la Rioja.
(16) Schiff, H. Annals 1864, 131, 118.
(17) Moffett, R. B., Rabjohn, N., Eds. Organic Synthesis; John Wiley
& Sons: New York, 1963; Vol. 4, pp 605-608.
‡ Universidad de Zaragoza-CSIC.
(1) Hoffmann, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 846.
(2) Williams, J. M.; Schultz, A. J.; Underhill, A. E.; Carneiro, K.
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1-3.
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Tetrahedron Lett. 1995, 36, 2937-2940.
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2001, 34, 14-19, and references therein.
(21) Vaas, R. S.; Duda’s, J.; Varma, R. S. Tetrahedron 1999, 40, 4951-
4954.
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32, 3246-3249.
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M. A.; Omary, M. A. J. Am. Chem. Soc. 2003, 125, 12072.
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M. E.; Pe´rez, J.; Laguna, A.; Mohamed, A. A.; Fackler, J. P., Jr. J. Am.
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A.; Fackler, J. P., Jr. Inorg. Chem. 2004, 43, 3573.
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10.1021/om051030j CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/18/2006

1690 Organometallics, Vol. 25, No. 7, 2006
Ferna´ndez et al.
in which L2 is bound to the thallium centers through both types
of nitrogen atoms, amine and imine, respectively (see Scheme
2). The analytical and spectroscopic data of both complexes
agree with the proposed stoichiometries, and their IR spectra
in Nujol mulls show, among others, absorptions arising from
Scheme 1. Ligands Bound to Thallium Centers
37
38
the C6Cl5 and C6F5 groups bonded to gold(I) (see Experi-
mental Section) and bands due to the new ligand (L2) at 3356,
3296 cm-1 [ν(N-H)] and 1657 cm-1 [ν(CdN)] for 2a and
3380, 3310 cm-1 [ν(N-H)] and 1656 cm-1 [ν(CdN)] for 2b.
1
In their H NMR spectra in D8-tetrahydrofuran, signals due to
according to this procedure have been reported to present similar
preparation conditions and to be extremely moisture sensitive,35
in agreement with the water-scavenging properties of the
ligand.36
In this paper we report the unprecedented room-temperature
formation of very stable mono- and diimine gold-thallium
complexes starting from perhalophenyl ethylenediamine gold-
thallium precursors and the study of their reactivity. Their
extremely easy formation is illustrated with the complete
conversion of the diamine precursors into the diimine ones when
the former are exposed to ketone vapors at room temperature.
methylene groups appear at 2.86 (R position relative to amine
group) and 3.47 ppm (â position) for 2a and 2.86 (R position)
and 3.48 ppm (â position) for 2b. In addition, nonequivalent
methyl groups at 1.87 (endo) and 1.78 ppm (exo) (partially
masked by THF residual peak) for 2a and 1.89 (endo) and 1.78
ppm (exo) for 2b are observed. These spectra seem to indicate
the absence of a dissociative equilibrium in solution.
Nevertheless, when the reaction is carried out in a 1:2
(ethylenediamine/acetone) molar ratio, or using acetone as
solvent, the complexes obtained are [AuTl(C6X5)2(L3)] (X )
Cl, 3a; F, 3b) (Scheme 1), in which the coordination to the
thallium atoms takes place by two imine groups. Their IR spectra
show absorptions due to the stretching ν(CdN), at 1656 cm-1
(3a) and 1647, 1632 cm-1 (3b), respectively, and those due to
the N-H groups of the previously mentioned complexes 2a and
2b disappear. In the 1H NMR spectra of both complexes in D8-
tetrahydrofuran two signals arising from the endo and exo
methyl groups and one from the methylene groups at 3.47, 1.88,
and 1.81 ppm for 3a and 3.38, 1.92, and 1.85 ppm for 3b.
Results and Discussion
By reacting equimolecular amounts of [AuTl(C6X5)2]n (X )
Cl, F) and ethylenediamine two complexes of stoichiometry
[AuTl(C6X5)2(L1)] (X ) Cl, 1; F, 1b; L1 ) ethylenediamine)
are obtained as white (1a) or green (1b) solids, respectively.
Their spectroscopic data are in agreement with the proposed
formulation. Thus, their IR spectra in Nujol mulls show, among
others, absorptions arising from the C6Cl537 and C6F538 groups
bonded to gold(I) at 837 and 613 for 1a and at 1510, 960, and
The proposed mechanism for each condensation is likely to
be influenced by the acidic characteristics of the thallium centers.
Thus, first a nucleophilic attack of the oxygen of the ketone is
produced to the thallium center. This attack is favored by the
relatively low occupancy of the coordination sphere of the
thallium atoms (four positions taking into account the gold
interaction, two nitrogen atoms, and the stereochemically active
lone pair) (see the crystal structure comments below), as well
as by the formal positive charge on these atoms. Subsequently,
the transfer of a acidic proton of the amine group to the oxygen
center and simultaneous nucleophilic attack of the nitrogen to
the carbonyl carbon produces a hemiacetal intermediate that
evolves to the imine by â-elimination of water (see Scheme 3).
Interestingly, attempts to detect intermediates by NMR experi-
ments at room or at low temperature were unsuccessful,
probably because the reaction is faster than the NMR time scale.
Nevertheless, a signal at 2.52 ppm due to the water formed in
the reation is observed. Although free ethylenediamine displays
in its 1H NMR spectrum a signal due to the NH2 groups at 1.22
ppm, in the case of complexes 1a, 1b, 2a, and 2b these groups
1
768 cm-1 for 1b, respectively; in the H NMR spectra of both
complexes in D8-tetrahydrofuran a unique signal appears at
similar chemical shift, 2.83 ppm [s, CH2], due to the equivalent
protons of the ethylenediamine groups. Significantly, the
position of this resonance differs from that of the free diamine,
indicating that this ligand is bonded to thallium even in solution.
By contrast, the 19F NMR of complex 1b displays three
resonances due to the three types of fluorine atoms of the
perhalophenyl groups, which appear at the same chemical shift
as in the starting material.39 Elemental analyses and mass
spectrometry measurements also agree with these stoichiometries
(see Experimental Section).
Reaction of both complexes with ketones in tetrahydrofuran
leads to new amine-imine or diimine complexes depending on
the stoichiometry (see Scheme 1 (ligands) and Scheme 2). Thus,
when we treated complexes [AuTl(C6X5)2(L1)] (X ) Cl, 1a; F,
1b) with equimolecular amounts of acetone, the evaporation of
the solvent and the addition of dichloromethane led to the
complexes [AuTl(C6X5)2(L2)] (X ) Cl, 2a; F, 2b), respectively,
Scheme 2. Reactions of [AuTl(C6X5)2(L1)] with Acetone

Easy Ketimine Formation
Organometallics, Vol. 25, No. 7, 2006 1691
Figure 1. Crystal structure of complex 2a with the labeling scheme
of the atom positions. Hydrogen atoms have been omitted for clarity.
Scheme 3. Proposed Condensation Mechanism
Figure 2. Crystal structure of complex 3a with the labeling scheme
of the atom positions. Hydrogen atoms have been omitted for clarity.
Figure 3. Crystal structure of complex 3b with the labeling scheme
of the atom positions. Hydrogen atoms have been omitted for clarity.
are not observed at the NMR time scale. Nevertheless, their
presence is undoubtedly detected in their infrared spectra (see
above).
into account the Au‚‚‚Tl contacts) with typical Au-C bond
lengths ranging from 2.038(7) to 2.062(7) Å (see Tables 2-4).
Each thallium binds two nitrogen atoms of a chelating amine-
imine (2a) or diimine ligand (3a, 3b) with slightly longer Tl-N
distances for the N atoms of the amine in 2a (2.675(8) Å) than
for the nitrogen centers of the imine groups (Tl-Nav ) 2.611
Å) in 2a, 3a, and 3b. Nevertheless, they are still longer than
the Tl-N bond distances observed in the Tl/Fe complex
When the starting product is TlPF6, addition of ethylenedi-
amine in 1:1 molar ratio and subsequent addition of acetone
does not produce the formation of the imine, which is perhaps
indicative of a certain degree of cooperative interaction between
the gold and thallium centers, which modifies the electronic
characteristics of the latter, making the reaction possible.
Crystal structures of complexes 2a, 3a, and 3b were
determined by X-ray diffraction, and all of them show polymeric
chains, which in the case of 3a runs parallel to the crystal-
lographic y-axis, of alternating gold(I) and thallium(I) centers
linked via unsupported Au‚‚‚Tl interactions between 2.9726(3)
and 3.1423(19) Å (see Figures 1-3 and Tables 2-4) similar to
those observed in other related polynuclear Au/Tl systems with
unsupported metal-metal interactions (2.9078(3)-3.3205(3)
Å).9,10,39-46 They all display square-planar gold(I) centers (taking
[{(CO)4Fe(Me2CdCH2CH2CMe2)Tl}2Fe(CO)4] (Tl-Nav
)
2.5475 Å),47 which contains the same diimine ligand as 3a and
3b, but shorter than most of the Tl-N distances found in other
related Au/Tl polymeric systems containing bipy or phen as
N-donor ligands (2.641(9)-2.847(5) Å).41,44,45 The environment
for Tl, considering the intermetallic contacts, is distorted trigonal
bipyramidal with a vacant equatorial coordination site apparently
associated with the stereochemically active lone pair and the
(41) Ferna´ndez, E. J.; Jones, P. G.; Laguna, A.; Lo´pez-de-Luzuriaga, J.
M.; Monge, M.; Olmos, M. E.; Pe´rez, J. Inorg. Chem. 2002, 41, 1056.
(42) Ferna´ndez, E. J.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Mendiza´-
bal, F.; Monge, M.; Olmos, M. E.; Pe´rez, J. Chem. Eur. J. 2003, 9, 456.
(43) Ferna´ndez, E. J.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Montiel,
M.; Olmos, M. E.; Pe´rez, J. Organometallics 2005, 24, 1631.
(44) Ferna´ndez, E. J.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Olmos,
M. E.; Pe´rez, J. Dalton Trans. 2004, 1801.
(45) Ferna´ndez, E. J.; Jones, P. G.; Laguna, A.; Lo´pez-de-Luzuriaga, J.
M.; Monge, M.; Montiel, M.; Olmos, M. E.; Pe´rez, J. Z. Naturforsch. 2004,
59b, 1379.
(46) Ferna´ndez, E. J.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Montiel,
M.; Olmos, M. E.; Pe´rez, J. Inorg. Chim. Acta 2005, 358, 4293-4300.
(47) van Hal, J. W.; Alemany, L. B.; Whitmire, K. H. Inorg. Chem. 1997,
36, 3152-3159.
(35) Paz-Sandoval, M. A.; Dom´ınguez-Dura´n, M. E.; Pazos-Mayen, C.;
Ariza-Castolo, A.; Rosalez-Hoz, M. d. J.; Contreras, R. J. Org. Chem. 1995,
492, 1-9.
(36) Holm, R. T. J. Paint Technol. 1967, 39, 385.
(37) Uso´n, R.; Laguna, A.; Laguna, M.; Manzano, B. R.; Tapia, A. Inorg.
Chim. Acta 1985, 151-153.
(38) Uso´n, R.; Laguna, A.; Laguna, M.; Manzano, B. R.; Jones, P. G.;
Sheldrick, G. M. Dalton Trans. 1984, 285.
(39) Ferna´ndez, E. J.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Monge,
M.; Montiel, M.; Olmos, M. E.; Pe´rez, J. Organometallics 2004, 23, 774.
(40) Crespo, O.; Ferna´ndez, E. J.; Jones, P. G.; Laguna, A.; Lo´pez-de-
Luzuriaga, J. M.; Mend´ıa, A.; Monge, M.; Olmos, M. E. Chem. Commun.
1998, 2233.

1692 Organometallics, Vol. 25, No. 7, 2006
Table 1. Details of Data Collection and Structure Refinement for Complexes 2a, 3a, and 3b
Ferna´ndez et al.
2a
3a
3b
chemical formula
cryst color
cryst size/mm
cryst syst
space group
a/Å
C34H24Au2Cl20N4Tl2
red
0.23 × 0.2 × 0.1
triclinic
P1h
9.2077(1)
15.2963(2)
20.1556(3)
109.814(1)
93.478(1)
103.581(1)
2565.33(6)
2
C20H16AuCl10N2Tl
red
0.15 × 0.1 × 0.08
triclinic
P1h
11.4427(2)
11.8772(2)
12.8710(2)
64.907(1)
72.058(1)
73.161(1)
1481.23(4)
2
C20H16AuF10N2Tl
yellow
0.2 × 0.15 × 0.1
monoclinic
P21/c
9.0891(1)
23.9641(4)
11.8157(2)
90.0
114.053(1)
90.0
2350.13(6)
4
b/Å
c/Å
R/deg
â/deg
γ/deg
U/Å3
Z
Dc/g cm-3
F(000)
2.590
1832
2.332
960
2.475
1600
T/K
173(2)
53
13.039
31 792
9661
0.0422
0.0334
0.0863
173(2)
56
173(2)
56
13.173
20 523
5564
0.0355
0.0304
0.0576
332
2θmax/deg
µ(Mo KR)/mm-1
no. of reflns measd
no. of unique reflns
Rint
11.296
17 192
6927
0.0531
0.0421
0.1118
309
Ra (I > 2σ(I))
wRb (F2, all reflns)
no. of params
no. of restraints
Sc
575
152
1.016
74
1.036
122
1.118
max. residual electron
3.070
1.653
0.701
density/e‚Å-3
2
2
2
2
2
2
a R(F) ) ∑||Fo| - |Fc||/∑|Fo|. b wR(F2) ) [∑{w(Fo - Fc )2}/∑{w(Fo )2}]0.5; w-1 ) σ2(Fo ) + (aP)2 + bP, where P ) [Fo + 2Fc ]/3 and a and b are
2
2
constants adjusted by the program. c S ) [∑{w(Fo - Fc )2}/(n - p)]0.5, where n is the number of data and p the number of parameters.
Table 2. Selected Bond Lengths [Å] and Angles [deg] for
Complex 2aa
Table 4. Selected Bond Lengths [Å] and Angles [deg] for
Complex 3ba
Au(1)-C(1)
Au(1)-Tl(1)
Au(2)-C(21)
Au(2)-C(31)
Au(2)-Tl(2)
Au(2)-Tl(1)
Au(3)-C(11)
Au(3)-Tl(2)
Tl(1)-N(1)
2.057(7)
2.9726(3)
2.056(7)
2.059(7)
2.9571(11)
3.0258(4)
2.050(6)
3.0365(11)
2.618(6)
Tl(1)-N(2)
Tl(2)-N(3)
Tl(2)-N(4)
N(1)-C(41)
C(42)-N(2)
N(2)-C(43)
N(3)-C(51)
C(52)-N(4)
N(4)-C(53)
2.675(7)
2.520(10)
2.675(8)
1.452(10)
1.463(10)
1.262(11)
1.455(15)
1.482(12)
1.258(13)
Tl-N(2)
2.591(5)
2.603(5)
3.04792(19)
3.14273(19)
2.045(6)
N(1)-C(21)
N(1)-C(27B)
N(1)-C(27A)
N(2)-C(23)
N(2)-C(28B)
N(2)-C(28A)
1.264(7)
1.476(16)
1.517(15)
1.274(8)
1.419(13)
1.608(15)
Tl-N(1)
Tl-Au(1)
Tl-Au(2)
Au(1)-C(11)
Au(2)-C(1)
2.047(6)
N(2)-Tl-N(1)
67.17(16) C(21)-N(1)-Tl
139.204(7) C(27B)-N(1)-Tl
126.1(4)
110.2(7)
113.5(7)
Au(1)-Tl-Au(2)
C(11)-Au(1)-C(11)#1 180.0
C(27A)-N(1)-Tl
C(23)-N(2)-C(28B) 124.0(7)
C(23)-N(2)-C(28A) 114.2(7)
C(23)-N(2)-Tl
C(28B)-N(2)-Tl
C(28A)-N(2)-Tl
C(1)#1-Au(1)-C(1)
Tl(1)-Au(1)-Tl(1)# 1
C(21)-Au(2)-C(31)
Tl(2)-Au(2)-Tl(1)
180.0
180.0
Au(2)-Tl(2)-Au(3) 139.43(4)
C(41)-N(1)-Tl(1)
C(43)-N(2)-C(42)
Tl-Au(1)-Tl#1
180.0
180.0
180.0
122.8(8)
118.2(8)
107.2(5)
119.0(7)
125.4(6)
114.4(5)
111.2(6)
121.8(10)
123.7(7)
114.4(7)
C(1)-Au(2)-C(1)# 2
Tl-Au(2)-Tl#2
178.9(2)
160.15(2) C(43)-N(2)-Tl(1)
125.8(5)
109.7(5)
112.4(5)
C(21)-N(1)-C(27B)
C(21)-N(1)-C(27A)
C(11)#2-Au(3)-C(11) 180.0
C(42)-N(2)-Tl(1)
C(51)-N(3)-Tl(2)
C(53)-N(4)-C(52)
Tl(2)-Au(3)-Tl(2)# 2
N(1)-Tl(1)-N(2)
Au(1)-Tl(1)-Au(2)
N(3)-Tl(2)-N(4)
180.0
66.1(2)
144.26(1) C(53)-N(4)-Tl(2)
67.1(3) C(52)-N(4)-Tl(2)
a Symmetry transformations used to generate equivalent atoms: #1
-x+1, -y, -z+1; #2 -x+2, -y, -z+2.
Table 5. Hydrogen Bonds for Complex 2a [Å and deg]a
a Symmetry transformations used to generate equivalent atoms: #1 -x,
-y, -z; #2 -x-1, -y, -z+1.
D-H‚‚‚A
d(D-H) d(H‚‚‚A) d(D‚‚‚A)
(DHA)
N(1)-H(1A)‚‚‚Cl(5)# 1
N(1)-H(1B)‚‚‚Cl(15)
N(3)-H(3A)‚‚‚Cl(20)
N(3)-H(3B)‚‚‚Cl(15)
a Symmetry transformations used to generate equivalent atoms: #1 -x,-
y,-z.
0.92
0.92
0.92
0.92
2.72
2.73
2.96
2.68
3.625(7)
3.530(7)
3.410(10)
3.579(8)
167.8
145.3
112.1
164.1
Table 3. Selected Bond Lengths [Å] and Angles [deg] for
Complex 3aa
Au(1)-C(1)
Au(1)-Tl
Au(2)-C(11)
Au(2)-Tl
Tl-N(2)
2.041(7)
3.0519(3)
2.062(7)
3.0877(3)
2.641(10)
Tl-N(1)
2.694(9)
1.230(19)
1.56(2)
1.247(19)
1.45(2)
N(1)-C(21)
N(1)-C(27)
N(2)-C(24)
N(2)-C(28)
Table 5), which may contribute to the stabilization of the system,
but do not give rise to two- or three-dimensional arrays.
C(1)#1-Au(1)-C(1)
Tl-Au(1)-Tl#1
C(11)#2-Au(2)-C(11)
180.0
180.0
180.0
Tl#2-Au(2)-Tl
N(2)-Tl-N(1)
Au(1)-Tl-Au(2)
180.0
68.5(4)
150.59(1)
The crystal structure of complex 1a was also determined by
X-ray diffraction methods (see Supporting Information), al-
though the crystals were not good enough to give the desired
degree of accuracy and the thallium center is also disordered
over two different positions (75:25). It consists of discrete
dinuclear molecules [AuTl(C6Cl5)2(L1)] with an intramolecular
Au-Tl distance of approximately 3.1 Å and an intermolecular
Au-Tl distance of ∼4.04 Å with the neighboring molecules,
a Symmetry transformations used to generate equivalent atoms: #1
-x+1, -y+1, -z; #2 -x+1, -y, -z.
gold centers occupying the apical positions (Au-Tl-Au angles
from 139.20(1)° to 150.59(1)°).
Finally, in complex 2a, a series of N-H‚‚‚Cl hydrogen bonds
are present between atoms of the same polymeric chain (see

Easy Ketimine Formation
Organometallics, Vol. 25, No. 7, 2006 1693
giving rise to a “discontinuous polymer” extended parallel to
the crystallographic y-axis.
Different results are obtained when the precursor gold-
thallium ethylenediamine complexes 1a and 1b react with the
stronger acceptor acetophenone, because they both lead to the
double imine formation L4 (see Scheme 1), independently of
the molar ratio employed, 1:1 (as in complexes 2a and 2b) or
1:2 (as in complexes 3a and 3b). Consequently, when the
reactions are carried out in a 1:1 molar ratio, complexes 4a,b
and unreacted 1a,b are isolated from the reaction medium.
However, when the stoichiometry is 1:2, complexes 4a and 4b
are obtained as the only products in higher yields.
As before, their analytical and spectroscopic data are also in
accordance with the proposed stoichiometry, [AuTl(C6X5)2-
(L4)]n, and, for instance, their IR spectra show only absorptions
due to the stretching CdN vibrations and the 19F NMR spectrum
of 4a shows three resonances due to the three types of fluorine
atoms of the perfluorophenyl groups at a chemical shift similar
Figure 4. Photograph showing the sequence of the transformation
of a powder sample of compound [AuTl(C6F5)2(L1)], 1b (upper
left), deposited in a flask and subjected to acetone vapors. The
arrows indicate the steps of the conversion.
produced. Thus, bands at 1647 and 1632 cm-1, corresponding
to the second condensation, appear and their intensity increase
at the same time as the previous bands, at 3380, 3310 and 1656
cm-1, diminish. Significantly, bands assigned to the three
complexes do not coexist at the same time in any moment of
the process.
1
to that in the starting material. Interestingly, in the H NMR
spectra of 4a and 4b signals due to the methyl, phenyl, and
methylene groups appear at different chemical shifts than those
observed for the free ligand (7.86-7.29 (10H, Ph), 3.86 (s, 4H,
CH2), 2.25 (s, 6H, CH3) in THF-D8), indicating the coordination
of the thallium center in the same way as the commented
ethylenediamine in the precursor complexes. However, the
spectra show only signals corresponding to one isomer of the
ligand, which indicates that, as in the other complexes, there is
no dissociative equilibrium in solution. The data also show that
all the methyl protons are equivalent (see Experimental Section),
suggesting the cis disposition of the substituents. NMR studies
of a molybdenum complex about the disposition of these groups
inward toward or outward from the coordination sphere of the
metal center suggest that in this case the chemical shifts of the
methyl groups are in agreement with their inward disposition.35
This proposal with the smaller methyl groups situated toward
the thallium center seems to be in agreement with the suggested
mechanism in that, first, the condensation is produced with the
diamine ligand bonded to the thallium center and, second, the
[Au(C6X5)2]- groups probably interact with the thallium atoms
since the bulkier phenyl groups lie at the less sterically hindered
positions.
Similarly, complex 1a follows similar exchange and the final
solid does not show bands due to the remaining amine ν(N-
H) vibrations, and instead, the expected ν(CdN) appears. Also
1
the H NMR and mass spectra do not show any evidence of
the presence of starting materials, indicating a complete conver-
sion into the diimine products. As in the solids obtained in
solution, these materials are stable to air and moisture indefi-
nitely, in contrast to other reported imine complexes, whose
stability to moisture is very low.35,47 This behavior could perhaps
make these diamine products appropriate for their use as
irreversible sensors of ketone groups, for instance, in the food
industry.
Addition of ethylenediamine to a solution of the diimine
complexes 3a,b and 4a,b leads to the displacement of the
diimine ligand by the diamine one and formation of the starting
products 1a,b quantitatively. In the case of complexes 3a,b,
addition of ethylenediamine allows us to identify in the solution
the precursors ethylenediamine and acetone, while in the case
of the complexes 4a,b the more stable PhMeCdN(CH2)2Nd
CMePh (L4) evolves only to the decomposition products amine
and acetone by the presence of water in the reaction medium.
This result agrees with the data obtained from the mass spectra
of the diimine derivatives, in which for 3a,b no peak due the
isolated diimine L3 is found, while in the case of 4a,b a peak
at m/z ) 265 corresponding to [L4+H]+ appears. In this case,
this synthetic pathway can be used for the easy formation of
this imine ligand by displacement with ethylenediamine and,
thus, recovering the starting product, which, to some extent,
can be considered a catalytic cycle.
Finally, as can be expected from their structures and colors
under visible radiation, all the complexes exhibit a bright
luminescence in the solid state (see Supporting Information),
but not in deoxygenated tetrahydrofuran solutions, where, in
addition, their absorption spectra display only high-energy
structureless absorptions assigned to the perhalophenyl rings.43,46
Thus, they show single emissions at 515 (exc. 395) 1a, 505
(exc. 430) 1b, 670 (exc. 510) 2a, 625 (exc. 515) 2b, 640 (exc.
540) 3a, 675 (exc. 455) 3b, 560 (exc. 360) 4a, and 575 nm
(exc. 465 nm) 4b at room temperature. The assignation of the
excited states responsible for the luminescence in these com-
plexes is made on the basis of similar extended heteropoly-
Very interestingly, the ethylenediamine complexes 1a and
1b can also react in the solid state with ketone vapors at room
temperature. The transformation of the ethylenediamine com-
plexes in the corresponding diimine ones takes place in a few
seconds (about 10 s) when a flask containing [AuTl(C6X5)2-
(en)] (X ) Cl, 1a; F, 1b) is subjected to a saturated atmosphere
of the ketone. Thus, a very rapid change of color of the solids
from white (1a) to red (acetone) or orange (acetophenone) and
from green (1b) to yellow for both ketones is observed (see
Figure 4). A detailed observation of the photograph that shows
several moments of the transformation indicates a change from
green [AuTl(C6F5)2(L1)], 1b, to orange and yellow. These colors
are similar to those observed for the solids [AuTl(C6F5)2(L2)]n,
2b, and [AuTl(C6F5)2(L3)]n, 3b, respectively, which could
indicate that the conversion is produced in two steps. The study
of this process for complex 1b by infrared spectroscopy in the
solid state agrees with this assumption. Thus, the intensities of
the original bands of the ethylenediamine complex, placed at
3388 and 3322 cm-1, decrease as the new ones, at 3380, 3310,
and 1656 cm-1, due to amine ν(N-H) and imine ν(CdN),
increase. These appear at wavenumbers similar to those in
[AuTl(C6F5)2(L2)]n, 2b. The conversion to the double imine
complex does not begin until the first condensation has been

1694 Organometallics, Vol. 25, No. 7, 2006
Ferna´ndez et al.
and 2.86 (s, 2H, R-CH2), 3.48 (s, 2H, â-CH2), 1.89 (s, 6H, CH3),
1.78 (s, 3H, CH3) for 2b. ES(+) m/z: 203/205 [Tl]+, 263/265 [Tl-
(en)]+ for 2b. ES(-) m/z: 695 [Au(C6Cl5]- for 2a and 531
[Au(C6F5]- for 2b.
nuclear gold-thallium chains prepared in this laboratory with
similar44,45 or different10 donor centers, and therefore, we assign
them to delocalized excitons along the heterometallic chains
influenced by the coordination environment of the thallium
centers.
Further studies of the gold-thallium precursors in solution
with different donor-acceptor amines and ketones in order to
obtain imine ligands, including those whose preparation requires
very strong reaction conditions, as well as in solid/vapor media,
to test the capabilities of these materials for sensing applications
are now under current research in this laboratory.
Preparation of [AuTl(C6X5)2(L3)]n (X ) Cl (3a), F (3b)). Two
solutions of [AuTl(C6X5)2(L1)] (0.20 mmol; 192 mg for X ) Cl,
159 mg for X ) F) in 20 mL of tetrahydrofuran were treated with
acetone (0.40 mmol, 29 µL) and stirred at room temperature. After
5 min, the evaporation of the solvent and the addition of dichlo-
romethane give a red precipitate for 3a and yellow for 3b. The
solids were filtered off and washed with dichloromethane (3 × 5
mL). Yield: 78% for 3a and 87% for 3b. Anal. (%) Calcd for 3a
(C20H16AuCl10N2Tl): C, 23.09; H, 1.55; N, 2.69. Found: C, 23.06;
H, 1.55; N, 2.70; for 3b (C20H16AuF10N2Tl): C, 27.43; H, 1.84;
N, 3.20. Found: C, 27.34; H, 1.86; N, 3.21. FT-IR (Nujol mulls):
ν(C6Cl5) at 836 and 616 cm-1, ν(CdN st) 1656 cm-1 for 3a; ν(C6F5)
at 1502, 957, and 783 cm-1, ν(CdN st) 1647 and 1632 cm-1 for
3b. 1H NMR (THF-D8, room temperature, ppm): 3.47 (s, 4H, CH2),
1.88 (s, 6H, CH3), 1.81 (s, 6H, CH3) for 3a and 3.38 (s, 4H, CH2),
1.92 (s, 6H, CH3), 1.85 (s, 6H, CH3) for 3b. ES(+) m/z: 203/205
[Tl]+, 483/485 [Tl(L3)2]+ for 3b. ES(-) m/z: 695 [Au(C6Cl5]- for
3a and 531 [Au(C6F5]- for 3b.
Preparation of [AuTl(C6X5)2(L4)]n (X ) Cl (4a), F (4b)). Two
solutions of [AuTl(C6X5)2(L1)] (0.20 mmol; 192 mg for X ) Cl,
159 mg for X ) F) in 20 mL of tetrahydrofuran were treated with
acetophenone (0.40 mmol, 47 µL) and stirred at room temperature.
After 5 min, the evaporation of the solvent and the addition of
dichloromethane give an orange precipitate for 4a and yellow for
4b. The solids were filtered off and washed with dichloromethane
(3 × 5 mL). Yield: 65% for 4a and 76% for 4b. Anal. (%) Calcd
for 4a (C30H20AuCl10N2Tl): C, 30.95; H, 1.73; N, 2.41. Found:
C, 30.84; H, 1.76; N, 2.42; for 4b (C30H20AuF10N2Tl): C, 36.04;
H, 2.02; N, 2.80. Found: C, 35.97; H, 2.04; N, 2.79. FT-IR (Nujol
mulls): ν(C6Cl5) at 833 and 610 cm-1, ν(CdN st) 1633 cm-1 for
4a; ν(C6F5) at 1497, 960, and 758 cm-1, ν(CdN st) 1621 cm-1 for
4b. 1H NMR (THF-D8, room temperature, ppm): 7.63-7.32 (10H,
Ph), 3.89 (s, 4H, CH2), 2.33 (s, 6H, CH3) for 4a and 7.67-7.36
(10H, Ph), 3.89 (s, 4H, CH2), 2.33 (s, 6H, CH3) for 4b. ES(+)
m/z: 203/205 [Tl]+, 265 [L4+H]+. ES(-) m/z: 695 [Au(C6Cl5]-
for 4a and 531 [Au(C6F5]- for 4b.
Experimental Section
Instrumentation. Infrared spectra were recorded in the range
4000-200 cm-1 on a Perkin-Elmer FT-IR Spectrum 1000 spec-
trophotometer using Nujol mulls between polyethylene sheets. C,
H, S analyses were carried out with a Perkin-Elmer 240C
microanalyzer. Mass spectra were recorded on a HP59987 A
1
electrospray. H and 19F NMR spectra were recorded on a Bruker
ARX 300 in D8-THF solutions. Chemical shifts are quoted relative
to SiMe4 (1H, external) and CFCl3 (19F, external). UV-visible
absorption spectra were obtained on a Hewlett-Packard 8453 diode
array UV-visible spectrophotometer in tetrahydrofuran solutions
(1 × 10-5 M). Corrected excitation and emission spectra were
recorded with a Jobin-Yvon Horiba Fluorolog 3-22 Tau-3 spec-
trofluorimeter.
General Comments. Ethylenediamine, acetone, and acetophe-
none are commercially available and were purchased from Aldrich.
The precursor complexes [AuTl(C6F5)2]39 and [AuTl(C6Cl5)2]9 were
obtained according to literature procedures. CAUTION: Thallium
salts have been found to be toxic to living organisms.
Preparation of [AuTl(C6X5)2(L1)] (X ) Cl (1a), F (1b)). To a
tetrahydrofuran solution (20 mL) of [AuTl(C6X5)2]n (0.20 mmol;
180 mg for X ) Cl, 147 mg for X ) F) was added ethylenediamine
(0.20 mmol, 14 µL). The solution was stirred for 10 min, and the
solvent was removed under reduced pressure. The addition of
dichloromethane gave a white precipitate for 1a and green for 1b.
The solids were filtered off and washed with dichloromethane (3
× 5 mL). Yield: 92% for 1a and 87% for 1b. Anal. (%) Calcd for
1a (C14H8AuCl10N2Tl): C, 17.51; H, 0.84; N, 2.92. Found: C,
17.52; H, 0.84; N, 2.91; for 1b (C14H8AuF10N2Tl): C, 21.14; H,
1.01; N, 3.52. Found: C, 21.19; H, 1.01; N, 3.52. FT-IR (Nujol
mulls): ν(C6Cl5) at 837 and 613 cm-1, ν(N-H st) at 3365 and
3290 cm-1 for 1a; ν(C6F5) at 1510, 960, and 768 cm-1, ν(N-H st)
at 3388 and 3322 cm-1 for 1b. 1H NMR (THF-D8, room
temperature, ppm): δ 2.83 (s, CH2) for 1a and 2.83 (s, CH2) for
1b. 19F NMR (THF-D8, room temperature, ppm): δ -114.9 (m,
2F, Fo); δ -163.3 (t, 1F, Fp, 3J(Fp-Fm) ) 18.8 Hz)); δ -164.4 (m,
2F, Fm) for 1b. ES(+) m/z: 263/265 [Tl(en)]+. ES(-) m/z: 695
[Au(C6Cl5]- for 1a and 531 [Au(C6F5]- for 1b.
Crystallography. The crystals were mounted in inert oil on glass
fibers and transferred to the cold gas stream of a Nonius Kappa
CCD diffractometer equipped with an Oxford Instruments low-
temperature attachment. Data were collected by monochromated
Mo KR radiation (λ ) 0.71073 Å). Scan type: ω and φ. Absorption
corrections: numerical (based on multiple scans). The structures
were solved by direct methods and refined on F2 using the program
SHELXL-97.48 All non-hydrogen atoms were anisotropically
refined, and hydrogen atoms were included using a riding model.
Further details on the data collection and refinement methods can
be found in Table 1. Selected bond lengths and angles are shown
in Tables 2-4, and crystal structures of 2a, 3a, and 3b can be seen
in Figures 1-3. CCDC-291380-291382 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Center, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk).
Preparation of [AuTl(C6X5)2(L2)]n (X ) Cl (2a), F (2b)). Two
solutions of [AuTl(C6X5)2(L1)] (0.20 mmol; 192 mg for X ) Cl,
159 mg for X ) F) in 20 mL of tetrahydrofuran were treated with
acetone (0.20 mmol, 15 µL) and stirred at room temperature. After
5 min, the evaporation of the solvent and the addition of dichlo-
romethane give a orange precipitate in both cases. The solids were
filtered off and washed with dichloromethane (3 × 5 mL). Yield:
75% for 2a and 82% for 2b. Anal. (%) Calcd for 2a (C17H12-
AuCl10N2Tl): C, 20.42; H, 1.21; N, 2.80. Found: C, 20.43; H,
1.20; N, 2.80; for 2b (C17H12AuF10N2Tl): C, 24.44; H, 1.45; N,
3.35. Found: C, 24.40; H, 1.45; N, 3.36. FT-IR (Nujol mulls): ν(C6-
Cl5) at 834 and 605 cm-1, ν(N-H st) at 3356 and 3296 cm-1, ν(Cd
Special Details. In compound 2a Tl(2) is disordered over two
different positions (75:25). For this reason its bond lengths and
angles are referred to the thallium atom with higher occupancy. In
complex 3b the methylenic carbon atoms of one of the diimine
ligands (C(27) and C(28)) are disordered over two different
positions (50:50).
N st) 1657 cm-1 for 2a; ν(C6F5) at 1502, 955, and 787 cm-1
,
ν(N-H st) at 3380 and 3310 cm-1, ν(CdN st) 1656 cm-1 for 2b.
1H NMR (THF-D8, room temperature, ppm): 2.86 (s, 2H, R-CH2),
3,47 (s, 2H, â-CH2), 1.87 (s, 3H, CH3), 1.78 (s, 3H, CH3) for 2a
(48) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.

Easy Ketimine Formation
Organometallics, Vol. 25, No. 7, 2006 1695
structure of this complex. Figure S2 shows the emission spectra in
the solid state of the complexes 1a-4a and 1b-4b. Figures S3-
S8 display the structures of 2a, 3a and 3b viewed perpendicular
and parallel to the polymetallic chains. This material can be
obtained, free of charge, via the Internet at http://pubs.acs.org.
Acknowledgment. This work was supported by the DGI-
(MEC)/FEDER (CTQ2004-05495). M.M. thanks CAR for a
grant.
Supporting Information Available: Tables S1 and S2 show
details of data collection, structure refinement, and selected bond
lengths and angles for complex 1a. Figure S1 shows the molecular
OM051030J