New heterodimetallic platinum(II) complexes potentially useful as molecular switches

Article abstract of DOI:10.1002/ejic.200701181

Four types of platinum(II) complexes of general formulae [Pt(FcCH=NC ₆H₄OH-2)Cl₂(L)] [Fc = (η⁵-C ₅H₅)Fe(η⁵-C₅H₄), L = dmso (2) or PhCN (3)], [Pt(FcCH=NC₆H₄O-2)Cl(dmso)] (4), [Pt{(η⁵-C₅H₃CH=NC₆H ₄O-2)Fe(η⁵-C₅H₅)}(L)] [L = dmso (5) or PPh₃ (6)] or [Pt{(η⁵-C₅H ₃CH=NC₆H₄OH-2)Fe(η⁵-C ₅H₅)}Cl(L)] [L = dmso (7) or PPh3 (8)] have been prepared. These compounds differ in the mode of binding of the ligand: (N) (in 2 and 3), (N,O)^- (in 4), [C(sp², ferrocene),N,O]^2- (in 5 and 6) or [C(sp², ferrocene),N]^- (in 7 and 8). NMR, UV/Vis and electrochemical studies of 2 and 4-8 reveal that these products can be grouped in three pairs [(2c, 4b), (5, 7) and (6, 8)], and one of the compounds of each pair can be easily converted into its partner by a H⁺/OH ^- chemical input. The results obtained revealed that these transformations, that affect the spectroscopic and electrochemical properties, are reversible and robust. A study of the relevancy of the mode of binding of compounds 2 and 4-8 upon their potential utility of the new platinum(II) complexes as molecular switches is reported. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200701181

FULL PAPER
DOI: 10.1002/ejic.200701181
New Heterodimetallic Platinum(II) Complexes Potentially Useful as Molecular
Switches
Sonia Pérez,[a] Concepción López,*[a] Amparo Caubet,[a] Xavier Solans,[b][†] and
Mercè Font-Bardía[b]
Keywords: Platinum(II) complexes / Ferrocene derivatives / Platinacycles / Molecular switches
Four types of platinum(II) complexes of general formulae
[Pt(FcCH=NC6H4OH-2)Cl2(L)] [Fc = (η5-C5H5)Fe(η5-C5H4), L
= dmso (2) or PhCN (3)], [Pt(FcCH=NC6H4O-2)Cl(dmso)] (4),
[Pt{(η5-C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(L)] [L = dmso (5) or
PPh3 (6)] or [Pt{(η5-C5H3CH=NC6H4OH-2)Fe(η5-C5H5)}Cl(L)]
[L = dmso (7) or PPh3 (8)] have been prepared. These com-
pounds differ in the mode of binding of the ligand: (N) (in 2
and 3), (N,O)– (in 4), [C(sp2, ferrocene),N,O]2– (in 5 and 6) or
[C(sp2, ferrocene),N]– (in 7 and 8). NMR, UV/Vis and electro-
chemical studies of 2 and 4–8 reveal that these products can
be grouped in three pairs [(2c, 4b), (5, 7) and (6, 8)], and one
of the compounds of each pair can be easily converted into
its partner by a H+/OH– chemical input. The results obtained
revealed that these transformations, that affect the spectro-
scopic and electrochemical properties, are reversible and ro-
bust. A study of the relevancy of the mode of binding of com-
pounds 2 and 4–8 upon their potential utility of the new plati-
num(II) complexes as molecular switches is reported.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
of acid/base-based molecular switches are scarce. In ad-
dition, ferrocene and its derivatives contain a redox-active
centre, and this property,[7] which is specially interesting in
view of their applications in different areas[8,9] including
bio-organometallic chemistry, bio-technology and medi-
cine,[9] has also been used to prepare electrochemical de-
vices for gene sensors and glucose detection as well as mo-
lecular switches for non-linear optical properties (NLO) or
for the fluorescence of ferrocene derivatives.[9–11]
Despite of these facts, examples of platinum(II) com-
plexes containing ferrocenyl units potentially useful as mo-
lecular switches are still unknown. In this paper we present
several types of platinum(II) complexes where the ferrocen-
ylimine [FcCH=NC6H4OH-2] (1)[12] (Scheme 1) adopts
four different coordination modes, together with a compar-
ative study showing the relevancy of the mode of binding
of 1 in the potential utility of the new products as molecular
devices.
Introduction
The design and development of molecular devices based
on coordination or organometallic complexes is of great im-
portance nowadays due to their applied interest in different
fields.[1–3] Among all types of molecular devices (i.e. clips,
rotors, scissors, switches, twisters, etc.) with different archi-
tectures reported so far, molecular switches are targets of
increasing interest for electronics and optical memory de-
vices.[3] In this type of devices, an external stimulus (i.e.
light, electrons, pH, etc.) produces intra- or intermolecular
changes that affect a characteristic physical or chemical
property of the molecule.[3] To allow their use in the devel-
opment of sensors, information and storage materials, these
transformations should be reversible, to permit the “switch
on” and “switch off” of that property, and fast.
On the other hand, and mainly promoted by the crucial
role of platinum(II) in cancer therapy,[4] several research
groups have foccused their attention in molecular switches
based on platinum(II) complexes.[5,6] A few articles showing
the utility of such compounds as sensors for amino acids
and proteins have been published recently,[6] but examples
Results and Discussion
Synthesis, Characterization and Study of the Reactivity of
the Platinum(II) Complexes
[a] Departament de Química Inorgànica, Facultat de Química,
Universitat de Barcelona
Martí i Franquès 1–11, 08028 Barcelona, Spain
Fax: +34-93-490-77-25
In a first attempt to evaluate the potential coordination
abilities of the ferrocenyl Schiff base [FcCH=NC6H4OH-2]
(1)[12] to platinum(II), its reactivity with the platinum(II)
complexes cis-[PtCl2(L)2] (L = dmso[13] or PhCN) was
studied under different experimental conditions. Due to the
variety of compounds isolated and the number of reactions
E-mail: conchi.lopez@qi.ub.es
[b] Departament de Cristal·lografía Mineralogía i Dipòsits Min-
erals, Facultat de Geología, Universitat de Barcelona
Martí i Franquès s/n, 08028 Barcelona, Spain
[†] In memoriam
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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Scheme 1. (i) X = H. Equimolar amount of cis-[PtCl2(L)2] (with L = dmso or PhCN) (for compounds 2 and 3, respectively) in refluxing
methanol (for 2) or toluene (for 3). (ii) Equimolar amounts of cis-[PtCl2(dmso)2] and NaOAc in refluxing methanol (see text). (iii) For
L = dmso, NaOD in [D4]methanol in a molar ratio NaOD/2 = 0.7. (iv) For L = dmso and X = D, addition of DCl (in a molar ratio
PtII/DCl = 1.0:0.7) in [D4]methanol at 298 K (see text).
studied the most relevant results are presented in Table 1 acts as an N-donor group, and their 195Pt{1H} NMR spec-
and Scheme 1.
tra show a singlet centred at δ = –2868, –2991 and
When 1 was treated with an equimolar amount of cis- –3009 ppm (for 2a–2c, respectively). The positions of these
[PtCl2(dmso)2] in refluxing methanol for 2.5 h [Table 1, En- signals are consistent with the values reported for other
1
try I; Scheme 1, step (A)], the H NMR spectrum of the complexes where the platinum(II) atom has a “Pt(N)Cl2-
crude product of the reaction showed the presence of three (Sdmso)” environment.[16,17]
platinum(II) complexes (2a–2c) and a small amount of fer-
Several isomeric species of 2 could be expected in princi-
rocenecarbaldehyde (hereinafter referred to as FcCHO). pal, these may differ in the conformation of the Schiff base
Examples of partial hydrolysis of related Schiff bases in- [anti-(E) or syn-(Z)] or relative arrangement of the two
1
duced by the presence of platinum(II) complexes have been chlorido ligands (cis or trans). Previous H NMR spectro-
reported.[14,15] The use of column chromatography allowed scopic studies of platinum(II) and palladium(II) complexes
us to separate these products. Elemental analyses of derived from imines have shown that the chemical shift of
2a–2c are consistent with those expected for the methine proton signal is indicative of the conformation
[Pt(FcCH=NC6H4OH-2)Cl2(dmso)] (2) in which the ligand of the ligand in the complexes.[18–20] If the imine is in the
Table 1. Summary of the experimental conditions [reagents, solvents, temperature (T) and reaction time (t)] used to prepare the plati-
num(II) complexes containing the imino alcohol 1 acting as an (N), (N,O)– or [C(sp2,ferrocene),N,O]2– donor ligand.
Entry
Reagent (molar ratio)
Solvent
T
t
Final products (molar ratio)[a]
I
II
III
IV
V
VI
VII
VIII
IX
1 and cis-[PtCl2(dmso)2] (1:1)
1 and cis-[PtCl2(dmso)2] (1:1)
methanol
methanol
toluene
toluene
methanol
reflux
reflux
reflux
reflux
reflux
298 K
298 K
reflux
reflux
2.5 h
16 h
2a/2b/2c/4b (0.4:0.8:1.0[b]
2a/2b/2c/4b (0.1:0.5:1.0[b]
3b/3c (1.0:2.6)
3b/3c (1.0:3.1)
2a/2b/2c/4a/4b[d]
4a
)
)
1 and cis-[PtCl2(PhCN)2] (1:1)
1.5 h
1.5 h
1 and cis-[PtCl2(PhCN)2] (2:1)
1 and cis-[PtCl2(dmso)2] and NaOAc (1:1:1)
2a and NaOD (1:0.7)
2b (or 2c) and NaOD (1.0:0.7)
1 and cis-[PtCl2(dmso)2] and NaOAc (1:1:2)
1 and cis-[PtCl2(dmso)2] and NaOAc (1:1:2)
16 h[c]
[e]
CDCl3/[D4]methanol
CDCl3/[D4]methanol
methanol
[e]
4b
24 h[d]
72 h[d]
4a/4b/5 (1.0:1.0[f])
4a/4b/5 (1.0:1.0:5.5)
toluene/methanol[g]
[a] In all the experiments ferrocenecarbaldehyde (FcCHO) was also isolated as a by-product. [b] The presence of traces of 4b was also
detected by NMR spectroscopy. [c] When the reaction time decreased to 8 h, the reaction gave 2a/2b/2c/4a/4b in a relative abundance of
0.4:0.1:0.1:0.6:1.0. [d] Under these experimental conditions 2a, 2b and 2c were isolated as the minor components (ca. 8 mg), and the
molar ratio 4a/4b was 1:1. [e] This reaction is instantaneous. [f] Only traces of 5 (ca. 5 mg) were isolated. [g] 4:1 mixture.
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New Heterodimetallic Platinum(II) Complexes
anti-(E) form the resonance of the methine proton is high-
Crystals of 2b·CH2Cl2 and 2c suitable for X-ray analyses
field-shifted when compared with that of the free ligand, could be also obtained. ORTEP plots of the heterodimetal-
3
and the value of the coupling constant JPt,H is larger than lic units [Pt(FcCH=NC6H4OH-2)Cl2(dmso)] contained in
if the ligand adopts the syn-(Z) form in the complex.[17,19,20] the unit cells, together with a selection of bond lengths and
The analyses of the signals detected in the 1H NMR angles are depicted in Figures 1 and 2.
spectra of 2 show that for 2a and 2b (i) the resonance due
In the [Pt(FcCH=NC6H4OH-2)Cl2(dmso)] molecules,
to the imine proton [signal at δ = 8.18 ppm (for 2a) and the platinum(II) atom is bound to the imine nitrogen atom,
8.22 ppm (for 2b)] appears at higher field than for the free the sulfur atom of the dmso ligand and two chlorido li-
imine (δ = 8.58 ppm[12]) and complex 2c (δ = 8.56 ppm) and gands [Cl(1) and Cl(2)] in a trans arrangement, as reflected
3
(ii) the values of the coupling constants JPt,H (113.0 Hz in the value of the bond angle Cl(1)–Pt–Cl(2) [176.18(5)°
and 86.0 Hz for 2a and 2b, respectively) are larger than that (2b), 175.59(13)° (2c)].
of 2c (40.2 Hz). These findings suggest, according to the
In the two complexes the bond lengths around the plati-
bibliography,[19,20] that in 2a and 2b the ligand adopts an num(II) atom fall in the range reported for related com-
anti-(E) conformation, while in 2c it has the syn-(Z) form. plexes where the platinum(II) atom has a similar environ-
The existence of NOE peaks between the imine proton and ment.[17,21,22] The C(11)–N bond of 2b [1.285(6) Å] is longer
the 6Ј-H proton of the aryl ring of 2a and 2b confirm these than that in 2c [1.266(14) Å], and the imine group forms an
findings.
angle of 15.5° (2b) and 13.9° (2c) with the C5H4 unit of the
In addition, the [1H-1H] NOESY spectrum of 2a shows ferrocenyl moiety. The value of the torsion angles C(10)–
NOE contacts between the methyl group of the dmso ligand C(11)–N(1)–C(12) of 2b (179.97°) and C(10)–C(11)–N–
and the 2-H and 3-H protons of the C5H4 ring. These NOE C(12) of 2c (3.86°) indicate that the imine adopts the anti-
peaks were not detected for any of the two isomers 2b and (E) conformation in 2b and the syn-(Z) form in 2c, in good
2c. This indicates that in 2a this ring is close to the dmso agreement with the results obtained from the NMR experi-
ligand and consequently the two Cl– ligands should be in ments. The phenyl ring is planar, and its mean plane forms
cis arrangement. Furthermore, since no evidence of the an angle of 72.1° (2b) and 69.6° (2c) with the coordination
existence of NOE peaks between the signals due to the plane of the platinum atom.
methyl protons and those of the Fc or Ph groups were de-
tected in the NOESY spectra of 2b and 2c, we assume that
in these products the relative disposition of the Cl– ligands
is trans.
Figure 1. ORTEP plot of trans-[Pt(FcCH=NC6H4OH-2)Cl2(dmso)]·
CH2Cl2 (2b·CH2Cl2). Hydrogen atoms and the CH2Cl2 molecule
Figure 2. ORTEP plot of the isomer 2c of trans-
[Pt(FcCH=NC6H4OH-2)Cl2(dmso)]. Hydrogen atoms have been
have been omitted for clarity. Selected bond lengths [Å] and angles
[°]: Pt–N(1) 2.026(4), Pt–S 2.2135(11), Pt–Cl(1) 2.2828(12), Pt– omitted for clarity. Selected bond lengths [Å] and angles [°]: Pt–N
Cl(2) 2.2986(13), C(10)–C(11) 1.436(7), C(11)–N(1) 1.285(6), N(1)– 2.064(9), Pt–S 2.223(3), Pt–Cl(1) 2.287(4), Pt–Cl(2) 2.290(4),
C(12) 1.439(6), C(12)–C(13) 1.393(7), C(13)–C(14) 1.405(8), C(14)– C(10)–C(11) 1.442(16), C(11)–N 1.266(14), C(12)–C(13) 1.424(17),
C(15) 1.378(8), C(15)–C(16) 1.400(8), C(16)–C(17) 1.384(7), C(17)– C(13)–C(14) 1.503(15), C(14)–C(15) 1.385(16), C(15)–C(16)
O(1) 1.351(6), S–C(18) 1.763(5), S–C(19) 1.779(6), S–O(2) 1.456(4); 1.327(16), C(16)–C(17) 1.394(17), C(17)–O(1) 1.346(16), S–C(18)
S–Pt–Cl(1) 92.05(4), Cl(1)–Pt–N(1) 87.44(11), N(1)–Pt–Cl(2)
89.36(11), Cl(2)–Pt–S 91.31(5), C(10)–C(11)–N(1) 128.7(4), C(11)–
1.773(12), S–C(19) 1.707(12), S–O(2) 1.441(8); S–Pt–Cl(1)
90.26(14), Cl(1)–Pt–N 87.7(3), N–Pt–Cl(2) 89.2(3), Cl(2)–Pt–S
N(1)–C(12) 116.8(4), O(1)–C(17)–C(12) 117.4(4), O(1)–C(17)– 92.92(14), C(10)–C(11)–N 132.6(13), C(11)–N–C(12) 121.1(12),
C(16) 123.0(4).
O(1)–C(17)–C(12) 117.2(14), O(1)–C(17)–C(16) 123.3(17).
Eur. J. Inorg. Chem. 2008, 1599–1612
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S. Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía
Elemental analyses and mass spectra of 4 are consistent
FULL PAPER
Bond lengths and angles of the ferrocenyl moiety in
2b·CH2Cl2 and 2c agree with the values reported for other with those expected for [Pt(FcCH=NC6H4O-2)Cl(dmso)]
monosubstituted ferrocene derivatives.[21] The two pentago- where 1 behaves as a bidentate (N,O)– ligand. The
nal rings are planar, nearly parallel [tilt angles: 2.23° (2b) 195Pt{1H} NMR spectrum of 4 shows two singlets at δ =
and 2.16° (2c)], and they deviate by ca. 2.7° (2b) and 6.1° –2760 and –2818 ppm suggesting the presence of two spe-
(2c) from the ideal eclipsed conformations. The separation cies (hereinafter referred to 4a and 4b) in solution with a
between the platinum(II) and the iron(II) atoms [4.691 Å similar environment around the platinum(II) atom. Two
(2b) and 5.601 Å (2c)] clearly exceeds the sum of the sets of superimposed signals of relative intensities 1:1 can
van der Waals radii[23] of these atoms, thus precluding the also be observed in the 1H and 13C{1H} spectra of 4.
existence of any direct interaction.
Longer reaction times (t) produced a decrease of the molar
In the crystal of 2b the separation between the O(1) atom ratio 2/4. The {1H-1H} NOESY spectrum revealed that the
of one of the molecules of [Pt(FcCH=NC6H4OH-2)- two species (i) did not interchange in solution and (ii) con-
Cl2(dmso)] and the O(2) atom of a neighbouring molecule tained the imine in the syn-(Z) conformation.
suggest the existence of an O(1)–H···O(2) interaction that
Besides, for one of the isomers (4a) the existence of an
connects the molecules forming a chain along the b-axis NOE peak between the protons of the ϾCH=N– and
(Figure 3).
Me(dmso) units indicate that these protons are close. In the
Data presented in Table 1 (Entries I and II) indicate that 13C{1H} NMR spectrum the signal due to the C-2Ј atom
the molar ratio 2a/2b/2c is time-dependent and show that of the two isomers appears at lower field [δ = 167.7 (4a),
longer refluxing times favour the formation of 2c, where the 168.3 ppm (4b)] than for compounds 2 [148.4 (2a), 149.5
ligand has the syn-(Z) conformation.
(2b), 148.6 ppm (2c)], wheras the resonance of the imine
The reaction between equimolar amounts of 1 and cis- carbon atom is shifted in the opposite direction [δ = 163.5
[PtCl2(PhCN)2] in toluene under reflux [Table 1, Entries III (4a), 168.3 (4b), 175.7, 175.4, 176.0 (2a, 2b, 2c, respec-
and IV; Scheme 1, step (B)] produced two isomers of com- tively)]. All these findings suggest that in 4a and 4b the li-
pound [Pt(FcCH=NC6H4OH-2)Cl2(PhCN)] (3) that differ gand behaves as a bidentate (N,O)– group and that the two
in the conformation of the ligand [anti-(E) in 3b and syn- isomers differ in the relative arrangement of the Cl– ligand
(Z) in 3c], and the molar ratios 3c/3b did not change when and the imine nitrogen atom [trans-(Cl,N) in 4a and
the molar ratio 1/PtII was 2:1. Unfortunately, attempts to cis-(Cl,N) in 4b]. Unfortunately, attempts to separate the
separate the two isomers of 3 failed, and the use of column two isomers by either column chromatography or fractional
chromatography allowed us to isolate only the major com- crystallization failed, and it was only possible to
ponent 3c.
obtain fractions enriched in ca. 95% in each one of the
Since previous studies on the reactivity of cis- isomers.
[PtCl2(dmso)2] with N-donor ligands have shown that the
Comparison of the chemical formulae of 2a–2c and those
presence of a base such as NaAcO in the reaction medium of 4a and 4b prompted us to elucidate whether the addition
may induce the formation of the platinacycles,[24] we also of a base could induce the deprotonation of the OH group
studied the effect produced by this salt on the reaction. on the pendant arm of 2 and the formation of compounds
Treatment of equimolar amounts of 1, cis-[PtCl2(dmso)2] 4. Thus, we studied the action of NaOD ([D4]methanol) on
and NaAcO in refluxing methanol for 16 h (Table 1, Entry CDCl3 solutions of 2a–2c and monitored the changes by
V) gave after workup a brown residue. Further SiO2 column NMR spectroscopy (Table 1, Entries VI and VII; Figure 4,
chromatography, using CH2Cl2 as eluant, yielded traces of A–I). In all cases the addition of NaOD (molar ratios
FcCHO and 2, but the subsequent elution with a CH2Cl2/ NaOD/2 in the range 0.4–0.7) produced a change of the
1
MeOH (100:0.2) mixture produced the release of an ad- color of the solution and the H NMR spectra indicate the
ditional band that gave after concentration a red solid of 4. complete transformation of 2 into 4 (Figure 4).
Figure 3. Simplified view of the assembly of the heterodimetallic molecules of trans-[Pt(FcCH=NC6H4OH-2)Cl2(dmso)] in the isomer 2c
through O(1)–H···O(2) forming a chain along the b-axis.
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New Heterodimetallic Platinum(II) Complexes
anol) to solutions of 4b (in CDCl3) gave 2c, and no evidence
of the presence of 2b was detected by NMR spectroscopy,
even when the molar ratio DCl/4b increased. Besides that,
subsequent cycles exposing 2c to basic (or 4b to acidic) con-
ditions showed that the transformations 2c i 4b are repro-
ducible and robust, suggesting that these systems may be
potentially useful as a simple molecular switch[3] (we will
return to this point later on).
In order to compare the reactivity of 4a and 4b, we
treated a CDCl3 solution containing equimolar amounts of
4a and 4b with DCl (in [D4]methanol) (Figure 6). As ex-
pected, the addition of DCl produced the conversion of 4b
into 2c, but the behaviour of 4a was markedly different
since it evolved into 2a and the new intermediate species III
(Figure 5) in a molar ratio 2a/III = 0.4:1.0. NMR spectro-
scopic data suggest that III is a new isomeric form of
[Pt(FcCH=NC6H4OH-2)Cl2(dmso)] (2) in which the ligand
adopts the syn-(Z) conformation and the two Cl– ligands
are in a cis arrangement. The comparison of the results ob-
tained indicate that the isomerization process III Ǟ 2a is
more favoured than the transformation 2c Ǟ 2b.
1
Figure 4. Partial views of the H NMR spectra (400 MHz) of 2a,
2b and 2c before (A, B and C, respectively) and after the addition
of NaOD (in [D4]methanol) in a molar ratio NaOD/2 = 0.4 (D–F)
or 0.7 (G–I).
For 2c the conversion was fast and proceeded in one step
(Figure 4, C, F and I); but the reactions of 2a and 2b [where
the ligand has the anti-(E) form] were more complex than
the process 2c Ǟ 4b and took place in two steps [Figure 4,
A, D and G (2a) or B, E and H (2b)]. When the molar ratio
1
NaOD/[2a (or 2b)] is 0.4 the H NMR spectra (Figure 4, D
and E) indicate the presence of new platinum(II) complexes
[hereinafter referred to as I (2a) and II (2b), Figure 5] which
could be transformed into 4a and 4b, respectively by an
additional supply of NaOD [molar ratio NaOD/PtII = 0.7
(Figure 4, G and H) or 1.0].
NMR spectroscopic data of I and II, suggest that these
intermediate species (i) are isomeric forms of 4 containing
the imine in the anti-(E) form and (ii) differ in the relative
arrangement between the imine nitrogen atom and the Cl–
ligand [trans (I) and cis (II)] (Figure 5). These results sug-
gest that 2a and 2b could be easily transformed into their
partners (4a and 4b, respectively). The reactions presented
in Scheme 1, [steps (C)] constitute an alternative and more
effective path to obtain separately 4a and 4b.
Figure 6. Partial view of the 1H NMR spectra (in the range δ =
8.02–9.02 ppm) of an equimolar solution of compounds 4a and 4b
(A) and after the addition of DCl (in [D4]methanol) in a molar
ratio DCl/PtII = 0.7 (B).
Due to the increasing interest of platinacycles containing
In order to evaluate the potential reversibility of the reac- pincer ligands,[15a,25–28] and since it has been reported that
tions 2 Ǟ 4, the action of DCl on CDCl3 solutions of 4a the formation of metallacycles with (C,N,E)– or (C,N)– li-
and 4b was also studied. The addition of DCl (in [D4]meth- gands is often favoured in the presence of a slight excess of
Figure 5. Intermediate species I–II detected in the reaction of compounds 2a or 2b with NaOD (in [D4]methanol) and the product III
formed when 4a was treated with DCl in [D4]methanol.
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FULL PAPER
a base,[15,17,26a,26b,27–29] we also studied the reactions of 1,
Characterization data of 5 agree with the proposed for-
1
cis-[PtCl2(dmso)2] and NaAcO in amolar ratio of 1:1:2 mulae. In the H NMR spectrum of 5 the resonance of the
(Table 1, Entries VIII and IX). When the reaction was per- imine proton appears as a singlet at δ = 7.94 ppm and
formed in methanol (Table 1, Entry VIII), four different shows the typical satellites due to the 195Pt nucleus (3JPt,H
products were isolated. Three of them were FcCHO, 4a = 163.2 Hz), suggesting the coordination of the imine nitro-
and 4b (in a 1.6:1.0:1.0 molar ratio). The minor component gen atom. In addition, the presence of a group of four sig-
(5) was a purple solid whose elemental analysis is con- nals of relative intensities 5:1:1:1 in the range δ = 4.20–
sistent with that expected for the platinacycle [Pt{(η5- 4.90 ppm indicates the existence of a σ-[Pt–C(sp2,ferro-
C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(dmso)] (5) (Scheme 2). cene)] bond. The comparison of the 13C{1H} NMR spec-
This compound arises from the activation of the σ- trum of 5 and that of the free ligand reveals that the reso-
[C(sp2,ferrocene)–H] and the σ-(O–H) bond of 1.
nances due to the C-2 and the C-2Ј atoms are shifted to the
low-field region. This trend has also been observed for
other pallada- and platinacyles containing terdentate
(C,N,O)2– ligands.[28b,28c,28f] The 195Pt{1H} NMR spectrum
shows a singlet at higher fields (δ = –4031 ppm) than that
of 2 and 4.
One of the main interests of pallada- and platinacycles
containing terdentate (C,N,E)– ligands arises from the po-
tential hemilability[30] of the σ-(M–E) bond and the study
of the factors that may induce the formation and cleavage
of this bond. These processes may play an important role
in view of their applications in homogeneous catalysis.[26c,31]
In view of this and in order to study the lability of the Pt–
O bond of 5, additional experiments were performed. The
first one [Scheme 2, step (A)] consisted of the treatment of
5 with an equimolar amount of PPh3 in benzene. This reac-
tion gave after workup [Pt{(η5-C5H3CH=NC6H4O-2)-
Fe(η5-C5H5)}(PPh3)] (6), which arises from 5 by replace-
ment of the dmso ligand by the phosphane ligand. It should
be noted that (i) the formation of 6 does not modify the
coordination mode of the ligand and (ii) the presence of a
larger excess of PPh3 did not produce the cleavage of the
Pt–O bond. This suggests that the Pt–O bond exhibits a
low lability. This finding has also been detected for related
pallada- and platinacycles with dianionic (C,N,O)2– li-
gands.[28b–28d,28f]
Scheme 2. (i) Equimolar amount of PPh3 in benzene at 343 K for
1 h, followed by SiO2 column chromatography. (ii) X = D if the
reaction is performed on an NMR scale using CDCl3 as solvent
and DCl (in [D4]MeOH) or X = H if non-deuterated solvents and
reagents were used. The molar ratios (DCl or HCl)/PtII were 0.8
and 0.7 for 5 and 6, respectively.
On the other hand and in view of the results obtained in
the reactions of 4 with DCl, we decided to explore whether
the mode of binding of the ligand in 5 could be affected by
The replacement of the methanol by a mixture toluene/ the acidity of the medium. In a first stage, this process was
methanol (4:1) (Table 1, Entry IX) produced 5 (in higher studied on an NMR scale by treatment of a CDCl3 solution
yield), and traces of compounds 4 were detected by NMR of 5 with DCl (in [D4]methanol). The addition of DCl pro-
spectroscopy of the crude product of the reaction. The com- duced a change of the color of the solution (from deep-
parison of data presented in Table 1 (Entries VIII and IX) purple to reddish) and of the 1H NMR spectrum. The
shows that in methanol the formation of compounds 4 is analysis of the 1H, 13C{1H}, 195Pt{1H} NMR spectra as
preferred over that of complex 5, whereas a decrease of the well as the cross-peaks detected in the {1H-1H} NOESY
polarity of the reaction medium favours the cycloplati- and {1H-13C} HSQC and HMBC spectra suggest that the
nation of the ligand and inhibits the formation of 4, indicat- DCl produced the protonation of the alkoxido unit, the
ing that the proper selection of the solvents permits to con- cleavage of the Pt–O bond with the subsequent opening of
trol selectively the formation of the two types of plati- the five-membered chelate and the binding of the Cl–
num(II) complexes (4 or 5). Besides that since in 4 the li- ligand to the platinum(II) atom, suggesting the formation
gand is in the syn-(Z) form, none of the two ortho-σ- of [Pt{(η5-C5H3CH=NC6H4OD-2)Fe(η5-C5H5)}Cl(dmso)]
[C(sp2,ferrocene)–H] bonds of the ferrocenyl unit have the [Scheme 2, step (B)]. When this reaction was carried out
proper orientation in relation to the platinum(II) atom as on a larger scale and using non-deuterated reagents and
to allow the cycloplatination. Thus, the transformation 4 Ǟ solvents, complex [Pt{(η5-C5H3CH=NC6H4OH-2)Fe(η5-
5 is unlikely to occur, unless a complex process [involving C5H5)}Cl(dmso)] (7) was isolated.
(i) the decoordination of the oxygen atom and (ii) the isom-
erization of the ligand] takes place.
Further treatment of 7 with an equimolar amount of
PPh3 yielded [Pt(η5-C5H3CH=NC6H4OH-2)Fe(η5-C5H5)-
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New Heterodimetallic Platinum(II) Complexes
Cl(PPh3)] (8) [Scheme 2, step (C)]. This product and its ana- ligand [dmso (7) or PPh3 (8)]. The spectra of the platinacy-
logue with a deuterated hydroxy group can also be obtained cles 5 and 6 where the ligand acts as a (C,N,O)– terdentate
by reaction of 6 with HCl (in MeOH) or DCl (in [D4]meth- group show a band at ca. 582 nm. According to previous
anol) [Scheme 2, step (D)]. Characterization data of 8 indi- studies on pallada- and platinacycles with a terdentate
cate that the ligand behaves as a monoanionic and biden- [C(sp2,ferrocene),N,O]– or
a
terdentate [C(sp2,ferro-
tate [C(sp2,ferrocene),N]– group, and the phosphane is in cene),N,S] ligand such as [Pd{(η5-C5H3CH=NC6H4CH2O-
a trans arrangement to the imine nitrogen atom, in good 2)Fe(η5-C5H5)}(L)] or [Pd{(η5-C5H3CH=NC6H4SMe-2)-
agreement with the “transphobia effect”.[32]
Fe(η5-C5H5)}Cl] (Figure 7),[28c,28d] this band is due to a
metal-to-ligand charge-transfer transition [5d(Pt)Ǟπ*].
Spectroscopic and Electrochemical Studies
In order to elucidate the effects induced by the mode of
coordination of the Schiff base to the platinum(II) atom on
the electronic environment of the iron(II) atom, we decided
(i) to compare the UV/Vis spectra of 1, 2, and 4–8 in
CH2Cl2 solutions and (ii) to perform electrochemical stud-
ies of these products.
A summary of the results obtained from the spectro-
scopic studies of 10–4  solutions of 1, 2, 4, 5 and 7 or
5ϫ10–5  solutions of 6 and 8 in CH2Cl2 at 298 K is pre-
sented in Table 2. The UV/Vis spectrum of the free ligand
Figure 7. Pallada- and platinacycles of general formula [M{(η5-
C5H3CH=NC6H4SMe-2)Fe(η5-C5H5)}Cl] reported previously.[26b]
In order to elucidate the effect induced by the mode of
1 shows two intense bands at 344 (ε = 11940) and 467 (ε coordination of 1 and the nature and relative arrangement
= 1718) nm. Their positions fall in the range reported for of the ligands bound to the platinum(II) atom on the redox
ferrocenylketimines of general formula [FcCH=NR1] (R1 = properties of the iron(II) atom in 2 and 4–8, we also per-
substituted phenyl ring) and have been attributed to intrali- formed electrochemical studies based on cyclic voltamme-
gand transitions (ILT) [3d(Fe)Ǟπ* and πǞπ*, respec- try. In all cases, the cyclic voltammograms of freshly pre-
tively].[26b,33]
pared solutions (10–3 ) of 2, and 4–8 in acetonitrile[35]
The UV/Vis spectra of the platinum(II) complexes where using (Bu4N)[PF6] as supporting electrolyte were recorded.
the imine behaves as an (N)-donor group (2) or as a biden- Cyclic voltammograms are presented in Figures 8 and 9,
tate [(N,O)– (4) or (C,N)– (7 and 8)] ligand exhibit two and the most relevant electrochemical parameters obtained
bands in good agreement with the results reported for re- for the complexes and those reported for the free ligand
lated metal complexes derived from ferrocenyl Schiff bases under identical experimental conditions are summarized in
for which these bands have been assigned to metal-per- Table 2.
turbed intraligand πǞπ* transitions (MPILCT).[33] Parallel
As shown in Figures 8 and 9 the cyclic voltammograms
studies on cyclopalladated derivatives of general formulae show one anodic peak with a directly associated reduction
[Pd{(η5-C5H3CH=NR1)Fe(η5-C5H5)}X(L)] with [C(sp2,fer- peak in the reverse scan. For the compounds under study
rocene),N]– ligands have shown that the positions of these the ∆E values depart appreciably from the constant value
bands are sensitive to the changes of the nature of the re- of 59 mV (theoretically expected for an electrochemically
maining ligands (X and L) bound to the PdII atom,[34] as reversible one-electron-step oxidation-reduction process)
occurs for compounds 7 and 8 that differ in the neutral suggesting that a structural reorganization takes place upon
Table 2. UV/Vis spectroscopic data (wavelengths, λi [nm], extinction coefficients, εi [–1 cm–1] together with the assignment of the
bands[a]) and electrochemical data {anodic (Epa) and cathodic (Epc) potentials, and separation of the peaks (∆E) [mV] at a scan speed
v = 100 mV/s}[b] for the free ligand 1 and compounds 2 and 4–8.
Complex Binding mode
UV/Vis spectroscopical data
Electrochemical data
λi (εi)
λ2 (ε2)
λ3 (ε3)
Epa
Epc
∆E
1[c]
2a
2b
2c
4a
4b
5
–
(N)
(N)
(N)
344 (11940), ILT
363 (3060), MPILCT
364 (2273), MPILCT
359 (2671), MPILCT
391 (5361), MPILCT
366 (3900), MPILCT
354 (6250), MPILCT
368 (10000)[d], MPILCT
381 (2570), MPILCT
387 (3020), MPILCT
467 (1718), ILT
–
–
–
–
–
–
258
415
474
448
396
416
67
12
116
151
178
294
323
316
228
265
–32
–92
15
80
489 (2249), MPILCT
488 (17163), MPILCT
488 (1890), MPILCT
498 (4051), MPILCT
494 (3215), MPILCT
516 (4579), MILCT
522 (5155), MPILCT
541 (2008), MPILCT
525 (2535), MPILCT
121
151
132
168
200
95
104
101
155
(N,O)–
(N,O)
(C,N,O)2–
(C,N,O)2–
(C,N)–
(C,N)–
584 (3400), 5d(Pt)Ǟπ*
6
582 (3690)[d], 5d(Pt)Ǟπ*
7
8
–
–
–3
[a] ILT = Intraligand transitions 3d(Fe)Ǟπ* and πǞπ*; MPILCT = metal-perturbed intraligand charge-transfer transition and
5d(Pt)Ǟπ* = metal-to-ligand charge-transfer transition. [b] In all cases the Epa and Epc values are referenced to the Fc/Fc+ couple. [c]
Data from ref.[12] [d] This band appears as a shoulder.
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FULL PAPER
palladium(II) and platinum(II) complexes containing a
monodentate (N) or bidentate (N,E) (E = NЈ, O or S) ferro-
cenyl ligand.[38] In contrast with these results, the cycloplati-
nated derivatives 5–8 are less resistant to undergo oxidation.
This trend is similar to those described for other metall-
acycles with a σ-[M–C(sp2,ferrocene)] bond (M = PdII or
PtII).[26b,39] Furthermore, the comparison of the Epa values
for the pairs of compounds (5,6 and 7,8) indicate that
changes of the nature of the remaining ligands bound to
the PtII atom at a three-bond-length distance from the
iron(II) atom also affect the electrochemical properties of
the ferrocenyl unit.
In order to clarify the effect induced by the H+/OH–
chemical input on the electrochemical properties of the new
products, we performed some additional studies. First of
all, and once the cyclic voltammogram of the solutions of
4b, 5 and 6 had been recorded, we added an equimolar
amount of HCl and studied the electrochemistry of the
solution obtained inmediately after the addition of the acid.
In all cases the shape of the voltammograms and the posi-
tion of the peaks coincided with those obtained from their
corresponding partners (2c, 7 and 8, respectively). Besides
that, the transformations 2c Ǟ 4b, 5 Ǟ 7 or 6 Ǟ 8 were
easily reverted upon the addition of NaOH in in the range
of molar ratios platinum(II) complex/NaOH = 0.7–1.0.
In order to confirm the reversibility of the protonation/
deprotonation process, titrations with HCl were carried out
and monitored by UV/Vis spectroscopy and cyclic voltam-
metry. Once the spectrum of a freshly prepared solution of
5 or 6 in CH2Cl2 had been recorded, aliquots containing
HCl [in a molar ratio HCl/(5 or 6) = 0.2] were succesively
added. The UV/Vis spectra were registered after each ad-
dition, and the comparison of the spectra obtained reveals
that the band due to the 5d(Pt)Ǟπ* transition vanishes
gradualy. After the fourth addition the spectrum obtained
is superimbosable with those of compounds 7 and 8, respec-
tively. Afterwards, we investigated the effect induced by the
Figure 8. Cyclic voltammograms of compounds 2a–2c and 4a,b in
acetonitrile at 298 K and at a scan speed v = 100 mV/s.
Figure 9. Cyclic voltammograms of compounds 5–8 in acetonitrile
at 298 K and at a scan speed v = 100 mV/s.
oxidation.[36] According to the general rules established for addition of aliquots of a base; thus, we repeated the whole
ferrocene derivatives, the presence of electron-withdrawing process but replaced the aliquots of HCl by aliquots of
groups inhibits the oxidation of the iron(II) atom in con- NaOH. In these cases the spectrum obtained after four ad-
trast to electron-donor groups that facilitate the oxi- ditions of the NaOH aliquots was also superimposable to
dation.[37]
those of 5 and 6. It should be noted that the comparison
The comparison of the plots depicted in Figures 8 and 9 of the sets of spectra obtained after one cycle (5 Ǟ 7 Ǟ 5)
shows that for 1, 2, 4, 7 and 8, the Epa values are larger than reveals the existence of an isostbestic point at λ = 410 nm,
that of ferrocene, thus suggesting that the effect induced by whereas for the process 6 Ǟ 8 Ǟ 6 two isosbestic points
the CH=NC6H4OH-2 unit in 1 or its binding of the PtII are found.[40] These transformations were also monitored
atom reduces the proclivity of the iron(II) atom to be oxid- by cyclic voltammetry, and the comparison of the voltam-
ized. Besides that, the shift of the position of the peaks to mograms along the whole process (Supporting Infor-
the more anodic region is strongly affected by the mode of mation) also provides conclusive proof of the reversibility
binding of the ligand. In general the Epa values increase of the reactions 5 i 7 or 6 i 8 in acetonitrile. It should be
according to the sequence 6 Ͻ 5 Ͻ 7 Ͻ 8 Ͻ 1 Ͻ 4a Ͻ 4b noted that subsequent additions of HCl an NaOH did not
≈ 2a Ͻ 2c Ͻ 2b [in the range 12 mV (6) to 474 mV (2b)]. produce significant variations in the cyclic voltammograms
This trend is closely related to the coordination mode of of the complexes. This indicates that the reactions 5 i 7 or
the ligand (N) (2), (N,O)– (4), [C(sp2,ferrocene),N]– (7 and 6 i 8 are reversible and robust.
8) or [C(sp2,ferrocene),N,O]2– (5 and 6) and indicates that
Unfortunately, a similar study with ligand 1 could not be
in compounds without a σ-[Pt–C(sp2,ferrocene)] bond (2 carried out because of its low stability in the presence of
and 4) the FeII atom is less prone to be oxidized than in the HCl and NaOH. When a CDCl3 solution of 1 was treated
free ligand. This agrees with the results reported for related with NaOD or DCl (in MeOD) [in molar ratios (NaOD or
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New Heterodimetallic Platinum(II) Complexes
1
DCl)/1 = 0.2]. In both cases, the H NMR spectra of the [C(sp2,ferrocene),N,O]2– to [C(sp2,ferrocene),N]– produced
resulting mixtures reveal the formation of ferrocenecarbal- a greater variation of the Epa values [49 mV for the couple
dehyde (Supporting Information). In addition, when DCl (5,7) or 139 mV for the pair (6,8)]. Consequently, these
was used the color of the initially orange solution turned studies constitute the first step of a further work centred on
purple, the signals became broader and the peak due to the (i) the synthesis and the study of the properties of the chem-
imine proton of 1 could not be detected. This suggests that ical products formed in the oxidation of 5–8 and (ii) the
in this case hydrolysis of the ligand took place.
investigation of their practical utility as molecular switches.
Moreover, since it is well known that cyclopallada- and
cycloplatinated complexes containing bi- or terdentate li-
gands are useful precursors in organometallic synthesis and
in homogeneous catalysis,[41,42] compounds 5–8 are particu-
Conclusions
The results presented here have allowed us to establish larly interesting in view of their potential applications in
the best experimental conditions to selectively control the this field.
mode of binding {(N), (N,O)–, [C(sp2,ferrocene),N]– or
[C(sp2,ferrocene),N,O]2–} of ligand 1 to a platinum(II) atom
Experimental Section
and the formation of several different isomers of the hetero-
dimetallic complexes trans-[Pt(FcCH=NC6H4OH-2)Cl2-
(dmso)] (2) and [Pt(FcCH=NC6H4O-2)Cl(dmso)] (4) that
differ in the conformation of the ligand (2a–2c) or in the
relative arrangement of the imine nitrogen atom and the
dmso ligand (2 and 4).
General: cis-[PtCl2(dmso)2] and ligand [FcCH=NC6H4OH-2] (1)
were prepared as described,[12,13] and the remaining reagents were
obtained from Aldrich and used as received. The methanol was
HPLC-grade,[43] and the remaining solvents used, except benzene,
were dried and distilled before use.[44] Elemental analyses were car-
ried out at the Serveis Científico-Tècnics (Universitat de Barcelona)
and Servei de Recursos Científics i Tècnics (Univ. Rovira i Virgili,
Tarragona). Infrared spectra were obtained with a Nicolet Impact
400 instrument using KBr discs. 1H and the two-dimensional NMR
({1H-1H} COSY and NOESY and the {1H-13C} HSQC and
HMBC) experiments were run at 500 MHz with either a Varian
500 or a Bruker Avance 500DMX instrument. Except where
The study of the reactivity of 2 and 4–8 in the presence
of H+ or OH– indicates that the interconversion between
the two compounds of each one of the sets of products
(2c,4b), (5,7) or (6,8) can be easily achieved by a simple and
reversible chemical reaction. The transformations 2c i 4b,
5 i 7 and 6 i 8 are instantaneous and clearly faster than
1
1
the time required to register the H NMR or UV/Vis spec-
quoted, the solvent used for the H NMR experiments was CDCl3
(99.9%), and SiMe4 was the internal reference. 195Pt{1H} NMR
spectra as well as 31P{1H} NMR spectra, were recorded with a
Bruker 250DXR instrument using CDCl3 (99.9%) as solvent
tra.
On the other hand, electrochemical studies provide a
method for fine-tunning the oxidation potential of the
ferrocenyl unit in a wide range [from 12 mV (6) to 474 mV
(2b)] by modifying the mode of binding of the ligand in the
complexes. In addition, the results obtained from UV/Vis
spectroscopy and the electrochemical studies of the pairs of
complexes (2c,4b), (5,7) or (6,8) in the presence of NaOH
or HCl, indicate that the reactions 2c i 4b, 5 i 7 and 6 i
8 (i) affect the proclivity of the iron(II) atom to be oxidized
and (ii) are reversible and can be performed for several cy-
cles without a significant variation of the electronic spectra
or the intensity of the anodic or cathodic peaks detected in
the cyclic voltammograms (Supporting Information), thus
indicating that they are robust from an electrochemical
point of view. These findings are particularly outstanding
since examples of heterodimetallic complexes containing
simultaneously PtII atoms and ferrocenyl units with a sim-
ilar behaviour have not been reported so far and are espe-
and H2[PtCl6] {δ195Pt(H2[PtCl6])
= 0.0 ppm} and P(OMe)3
{δ31P[P(OMe)3] = 140.17 ppm} as references, respectively. In order
to evaluate the stability of compounds 2 and 4–8 in the solvent
1
used for the electrochemical studies, the H NMR spectra of these
compounds in CD3CN (99.8%) were also recorded at 298 K. In all
cases the chemical shifts (δ) are given in ppm and the coupling
constants (J) in Hz. Mass spectra (FAB+, MALDI-TOF+ or elec-
trospray) were registered at the Servei de Espectrometria de Masses
(Universitat de Barcelona) with a VG-Quattro, Voyager DE-RP or
Waters Micromass instrument, respectively. The matrix used for
FAB+ and MALDI-TOF+ mass spectra were 3-nitrobenzyl alcohol
(NBA) and 2-hydroxybenzoic acid (DHB), respectively. The UV/
Vis spectra of 10–4  solutions of 2, 4, 5 and 7 or 5.0ϫ10–5  of 6
and 8 in CH2Cl2 were recorded at 298 K with a Shimadzu 160A
spectrophotometer.
Preparation of the Compounds
trans-[Pt(FcCH=NC6H4OH-2)Cl2(dmso)] (2): Three isomeric forms
cially relevant in view of their potential utility as molecular of this product (2a, 2b and 2c) were isolated. These isomers differ
in the conformation of the ferrocenyl ligand [anti-(E) (2a and 2b)
or syn-(Z) (2c)] or in the relative arrangement of the two Cl– ligands
[cis (2a) or trans (2b and 2c)]. cis-[PtCl2(dmso)2] (250 mg,
5.92ϫ10–4 mol) was suspended in methanol (40 mL) and the mix-
ture refluxed until complete dissolution. The hot and yellow solu-
tion was filtered, and the filtrate was added to a solution containing
1 (189 mg, 5.92ϫ10–4 mol) and methanol (10 mL). The resulting
mixture was protected from light with aluminium foil, refluxed for
2.5 h and filtered. The filtrate was concentrated in a rotary evapora-
tor to dryness, and the residue obtained was dissolved in the mini-
switches.
Among the three pairs of compounds, those involving
the platinacycles containing a bi- (7 and 8) or a terdentate
(5 and 6) ligand appear to be the most relevant for different
reasons. First, the H+/OH– chemical input produces more
spectacular variations in their UV/Vis spectra which involve
the presence or absence of an additional band at λ ≈ 583 nm
which is characteristic of compounds 5 and 6 with a ter-
dentate [C(sp2,ferrocene),N,O]2– group. In addition, the
changes of the mode of binding of the ligands from mum amount (ca. 5 mL) of CH2Cl2/n-hexane (100:5) and passed
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S. Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía
FULL PAPER
through an SiO2 column (5.0 cmϫ2.0 cm) using the same solution
as eluant. The first band released gave after concentration FcCHO
(ca. 10 mg), and the second band produced after workup com-
pound 2a (15 mg). Once these bands were collected, a CH2Cl2/n-
hexane (100:2) solution was used as eluant. This produced the re-
lease of a wide orange band that was collected in ca. 25-mL por-
tions. Concentration of the first portions gave 2b (28 mg), the fol-
lowing two fractions produced a solid containing a mixture of 2b
and 2c, while the final portions gave isomer 2c (36 mg). The subse-
quent elution with CH2Cl2/MeOH (100:0.2) allowed to isolate
traces of complex 4b. 2a: C19H21Cl2FeNO2PtS (649.3): calcd. C
35.15, H 3.25, N 2.16, S 4.93; found C 35.1, H 3.3, N 2.1, S 4.9.
1 H,CH=N) ppm. 13C{1H} NMR:[45] CDCl3: δ = 43.7, 44.0 (2 Me,
dmso), 71.1 (C5H5), 71.9 (C-1), 75.0 (C-2), 74.7 (C-3), 73.6 (C-4),
71.4 (C-5), 134.4 (C-1Ј), 148.6 (C-2Ј), 118.6 (C-3Ј), 129.5 (C-4Ј),
121.2 (C-5Ј), 125.3 (C-6Ј), 176.0 (CH=N) ppm. 195Pt{1H} NMR:
CDCl3: δ = –3009 ppm.
trans-[Pt(FcCH=NC6H4OH-2)Cl2(PhCN)] (3): A suspension of cis-
[PtCl2(PhCN)2] (200 mg, 4.23ϫ10–4 mol) in toluene (25 mL) was
refluxed until complete dissolution of the platinum(II) complex.
The hot solution was then filtered, and ligand
1 (129 mg,
4.23ϫ10–4 mol) was added. The reaction mixture was protected
from light with aluminium foil and refluxed for 1.5 h. After this
period, the undissolved materials were removed by filtration and
discarded, and the filtrate was concentrated to dryness in a rotary
evaporator. The 1H NMR spectrum of the solid formed revealed
the coexistence of the two isomeric forms 3b and 3c {which differ
in the conformation of the ligand [anti-(E) (3b) and syn-(Z) (3c)]}
in a molar ratio 3c/3b = 2.6. Attempts to separate the two isomers
by fractional crystallization failed. When a solution of the mixture
containing 3b and 3c was passed through an SiO2 column
(3.5 cmϫ2.3 cm) using CH2Cl2 as eluant two colored bands were
collected. The first one contained FcCHO and the second one gave,
after concentration to dryness, 3c (70 mg). 3c: C24H20Cl2FeN2OPt
(674.3): calcd. C 42.75, H 2.99, N 4.15; found C 42.3, H 2.9, N
MS (ESI+): m/z = 614 [M – Cl]+. IR: ν = 1590 [ν(ϾC=N–)], 3260
˜
1
3
[ν(–OH)] cm–1. H NMR:[45] CDCl3: δ = 3.37 (s, JPt,H = 20.5 Hz,
3 H, Me, dmso), 3.39 (s, 3JPt,H = 20.2 Hz, 3 H, Me, dmso), 4.49 (s,
5 H, C5H5), 6.97 (s, 1 H, 2-H), 4.98 (s, 1 H, 3-H), 4.82 (s, 1 H, 4-
H), 4.86 (s, 1 H, 5-H), 7.05 (dd, 3J = 8.0 and, 4J = 1.5 Hz, 1 H, 3Ј-
3
4
3
H), 7.24 (td, J = 8.0, J = 1.5 Hz, 1 H, 4Ј-H), 6.95 (td, J = 8.0,
4J = 1.5 Hz, 1 H, 5Ј-H), 7.57 (dd, J = 8.0, J = 1.5 Hz, 1 H, 6Ј-
H), 7.68 (s, 1 H, OH), 8.28 (s, 3JPt,H = 113.0 Hz, 1 H, CH=N) ppm;
[D3]acetonitrile: δ = 3.37 (s, 3JPt,H = 19.2 Hz, 3 H, Me, dmso), 3.30
3
4
3
(s, JPt,H = 20.8 Hz, 3 H, Me, dmso), 4.50 (s, 5 H, C5H5), 6.51 (s,
1 H, 2-H), 5.31 (s, 1 H, 3-H), 4.92 (s, 1 H, 4-H), 5.03 (s, 1 H, 5-
3
3
4.21. MS (FAB+): m/z = 639 [M – Cl]+, 535 [M – Cl – PhCN]+.
H), 7.02 (d, J = 7.8 Hz, 1 H, 3Ј-H), 7.25 (t, J = 7.8 Hz, 1 H, 4Ј-
3
3
1
IR: ν = 1595 [ν(ϾC=N–)] cm–1. H NMR:[45] CDCl3: δ = 4.37 (s,
H), 6.99 (d, J = 7.8 Hz, 1 H, 5Ј-H), 7.52 (d, J = 7.8 Hz, 1 H, 6Ј-
˜
3
5 H, C5H5), 4.11 (s, 1 H, 2-H), 4.52 (t, 3J = 2.8 Hz, 1 H, 3-H), 4.50
H), 7.73 (s, 1 H, OH), 8.45 (s, JPt,H = 120.0 Hz, 1 H, CH=N).
13C{1H} NMR:[45] CDCl3: δ = 44.8, 44.7 (2 Me, dmso), 71.1
(C5H5), 74.3 (C-1), 70.1 (C-2), 75.6 (C-3), 72.5 (C-4), 76.2 (C-5),
139.8 (C-1Ј), 148.4 (C-2Ј), 119.6 (C-3Ј), 129.5 (C-4Ј), 121.1 (C-5Ј),
125.7 (C-6Ј), 175.7 (CH=N) ppm. 195Pt{1H} NMR: CDCl3: δ =
–2868 ppm. 2b: C19H21Cl2FeNO2PtS (649.3): calcd. C 35.15, H
(t, 3J = 2.8 Hz, 1 H, 4-H), 3.64 (s, 1 H, 5-H), 7.10 (dd, J = 8.0, J
3
4
3
4
= 2.0 Hz, 1 H, 3Ј-H), 7.29 (td, J = 8.0, J = 2.0 Hz, 1 H, 4Ј-H),
6.94 (td, J = 8.0, J = 2.0 Hz, 1 H, 5Ј-H), 7.16 (dd, J = 8.0, J =
2.0 Hz, 1 H, 6Ј-H), 7.14 (s, 1 H, OH), 8.58 (s, JPt,H = 40.2 Hz, 1
3
4
3
4
3
H, CH=N), 7.50–7.80 (m, 5 H, aromatic protons of PhCN) ppm.
3.25, N 2.16, S 4.93; found C 35.3, H 3.5, N 2.1, S 4.9. MS (FAB+): 13C{1H} NMR:[45] CDCl3: δ = 71.5 (C5H5), 72.7 (C-1), 73.7 (C-2),
m/z = 649 [M]+. IR: ν = 1589 [ν(ϾC=N–)], 3300 [ν(–OH)] cm–1.
74.7 (C-3), 75.1 (C-4), 71.6 (C-5), 135.4 (C-1Ј), 148.9 (C-2Ј), 119.2
(C-3Ј), 129.8 (C-4Ј), 121.6 (C-5Ј), 125.5 (C-6Ј), 177.1 (CH=N),
110.4, 129.8, 133.9, 135.3 (four types of aromatic carbon atoms of
the PhCN ligand) ppm. 195Pt{1H} NMR: CDCl3: δ = –2144 ppm.
˜
3
1H NMR:[45] CDCl3: δ = 3.36 (s, JPt,H = 20.0 Hz, 6 H, 2 Me,
3
dmso), 4.44 (s, 5 H, C5H5), 5.75 (t, J = 1.8 Hz, 2 H, 2-H, 5-H),
4.86 (t, J = 1.8 Hz, 2 H, 3-H, 4-H), 7.02 (d, J = 7.0 Hz, 1 H, 3Ј-
3
3
3
3
H), 7.22 (t, J = 7.0 Hz, 1 H, 4Ј-H), 6.91 (t, J = 7.0 Hz, 1 H, 5Ј-
H), 7.23 (d, 3J = 7.0 Hz, 1 H, 6Ј-H), 7.19 (s, 1 H, OH), 8.22 (s,
3JPt,H = 86.0 Hz, 1 H, CH=N) ppm; [D3]acetonitrile: δ = 3.32 (s,
3JPt,H = 15.2 Hz, 6 H, 2 Me, dmso), 4.48 (s, 5 H, C5H5), 5.81 (s, 2
H, 2-H, 5-H), 4.92 (s, 2 H, 3-H, 4-H), 7.00 (dd, 3J = 7.6, 4J =
1.6 Hz, 1 H, 3Ј-H), 7.27 (td, 3J = 7.6, 4J = 1.6 Hz, 1 H, 4Ј-H), 6.96
(td, 3J = 7.0, 4J = 1.6 Hz, 1 H, 5Ј-H), 7.37 (dd, 3J = 7.0, 4J =
[Pt(FcCH=NC6H4O-2)Cl(dmso)] (4): Two different isomers of this
product (4a and 4b) were obtained. In both cases the ligand exhib-
its syn-(Z) conformation, but they differ in the relative arrangement
between the imine nitrogen atom and the dmso ligand (cis in 4a and
trans in 4b). These complexes could be isolated using two different
procedures [Methods (a) and (b), respectively]. Method (a) gave an
equimolar mixture of the two isomers (4a and 4b), whereas Method
(b) allowed to isolate 4a and 4b separately. Method (a): cis-
[PtCl2(dmso)2] (200 mg, 4.73ϫ10–4 mol) was suspended in meth-
anol (40 mL) and the mixture refluxed until complete dissolution.
The resulting hot solution was filtered, and then equimolar
amounts of 1 (147 mg) and NaAcO (39 mg) were added. The flask
was then protected from light with aluminium foil, and the mixture
was refluxed for 16 h. After this period, the deep-red solution was
filtered, and the filtrate was concentrated to dryness in a rotary
evaporator. The residue was dissolved in the minimum amount of
CH2Cl2 and passed through an SiO2 column (4.5 cmϫ2.5 cm).
Elution with CH2Cl2 produced the release of two orange bands
which gave after concentration FcCHO (20 mg) and traces (8 mg)
of a solid containing 2a, 2b and 2c (in a molar ratio 2a/2b/2c =
0.3:0.3:0.2). The subsequent elution with CH2Cl2/MeOH (100:0.2)
produced a red band that was concentrated to dryness in a rotary
evaporator to give 75 mg of 4. C19H21Cl2FeNO2PtS·1/2CH2Cl2
(634.3): calcd. C 36.47, H 3.26, N 2.21, S 5.05; found C 36.8, H
3
1.6 Hz, 1 H, 6Ј-H), 7.34 (s, 1 H, OH), 8.39 (s, JPt,H = 81.6 Hz, 1
H, CH=N) ppm. 13C{1H}:[45] CDCl3: δ = 43.8 (2 Me, dmso), 71.0
(C5H5), 73.8 (C-2, C-5), 75.5 (C-3, C-4), 138.7 (C-1Ј), 149.5 (C-2Ј),
118.8 (C-3Ј), 129.3 (C-4Ј), 121.1 (C-5Ј), 126.1 (C-6Ј), 175.4 (CH=N)
ppm. The signal due to C-1 was not observed. 195Pt{1H} NMR:
CDCl3: δ = –2991 ppm. 2c: C19H21Cl2FeNO2PtS (649.3): calcd. C
35.15, H 3.25, N 2.16, S 4.93; found C 35.1, H 3.5, N 2.2, S 4.9.
MS (FAB+): m/z = 649 [M]+. IR: ν = 1594 [ν(ϾC=N–)], 3313
˜
1
3
[ν(–OH)] cm–1. H NMR:[45] CDCl3: δ = 3.35 (s, JPt,H = 20.0 Hz,
6 H, 2 Me, dmso), 4.36 (s, 5 H, C5H5), 4.55 (s, 1 H, 2-H), 4.52 (s,
1 H, 3-H), 4.03 (s, 1 H, 4-H), 3.65 (s, 1 H, 5-H), 7.09 (dd, 3J = 8.0,
4J = 2.0 Hz, 1 H, 3Ј-H), 7.29 (td, 3J = 8.0, J = 2.0 Hz, 1 H, 4Ј-
H), 6.93 (td, J = 8.0, J = 2.0 Hz, 1 H, 5Ј-H), 7.13 (dd, J = 8.0,
4J = 2.0 Hz, 1 H, 6Ј-H), 6.95 (s, 1 H, OH), 8.53 (s, 3JPt,H = 40.2 Hz,
1 H, CH=N) ppm; [D3]acetonitrile: δ = 3.29 (s, JPt,H = 19.2 Hz, 6
H, 2 Me, dmso), 4.38 (s, 5 H, C5H5), 4.62 (t, J = 2.0 Hz, 2 H, 2-
H, 5-H), 3.91 (s, J = 2.0 Hz, 2 H, 3-H, 4-H), 7.04 (dd, J = 8.0,
4J = 1.6 Hz, 1 H, 3Ј-H), 7.33 (td, 3J = 8.0, J = 1.6 Hz, 1 H, 4Ј-
4
3
4
3
3
3
3
3
4
3.2, N 2.2, S 4.8. MS (FAB+): m/z = 613 [M]+. IR: ν = 1560
˜
3
4
3
H), 7.00 (td, J = 8.0, J = 1.6 Hz, 1 H, 5Ј-H), 7.17 (dd, J = 8.0,
4J = 1.6 Hz, 1 H, 6Ј-H), 6.93 (s, 1 H, OH), 8.62 (s, 3JPt,H = 39.2 Hz,
[ν(ϾC=N–)] cm–1. Method (b). Synthesis of 4a: 2a (8.6 mg,
1.32ϫ10–5 mol) was dissolved in CDCl3 (0.7 mL), then an NaOD
1608
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1599–1612

New Heterodimetallic Platinum(II) Complexes
3
4
solution (0.265  in [D4]methanol) (35 µL) was added. The reaction
mixture was stirred at 298 K for ca. 10 min and then filtered. Con-
centration of the filtrate in a rotary evaporation produced an red
oil that was later treated with n-hexane to give 4a as a red solid
that was collected and dried in vacuo for 3 d (yield: 7 mg, 86%).
4J = 2.0 Hz, 1 H, 5Ј-H), 7.10 (dd, J = 8.0, J = 2.0 Hz, 1 H, 6Ј-
3
H), 7.94 (s, JPt,H = 163.2 Hz, 1 H, CH=N) ppm; [D3]acetonitrile:
δ = 3.38 (s, JPt,H = 29.5, 6 H, 2 Me, dmso), 4.33 (s, 5 H, C5H5),
3
3
3
4.53 (d, J = 2.5, 1 H, 3-H), 4.77 (t, J = 2.5, 1 H, 4-H), 4.63 (d,
3J = 2.5, 1 H, 5-H), 6.47 (dd, J = 8.0, J = 1.0, 1 H, 3Ј-H), 6.95
3
4
C19H20ClFeNO2PtS·1/4C6H14 (634.3): calcd. C 38.72, H 3.53, N (td, 3J = 8.0, 4J = 1.0, 1 H, 4Ј-H), 6.37 (td, 3J = 8.0, J = 1.0, 1 H,
4
2.20, S 5.05; found C 38.6, H 3.6, N 2.2, S 4.9. MS (FAB+): m/z =
5Ј-H), 7.20 (dd, 3J = 8.0, 4J = 1.0, 1 H, 6Ј-H), 8.13 (s, JPt,H
=
3
613 [M]+. IR: ν = 1560 [ν(ϾC=N–)] cm–1. H NMR:[45] CDCl3: δ 103.52, 1 H, CH=N). 13C{1H} NMR:[46] CDCl3: δ = 46.5, 47.2 (2
1
˜
= 3.59 (s, 3JPt,H = 22.0, 6 H, 2 Me, dmso), 4.32 (s, 5 H, C5H5), 4.61
Me, dmso), 71.1 (C5H5), 78.0 (C-1), 91.4 (C-2), 72.1 (2JC,Pt
=
(s, 2 H, 2-H, 5-H), 4.65 (s, 2 H, 3-H, 4-H), 7.00 (m, 1 H, 3Ј-H), 45.7 Hz, C-3), 69.5 (C-4), 77.0 (C-5), 137.1 (C-1Ј), 170.5 (C-2Ј),
6.99 (m, 1 H, 4Ј-H), 6.29 (m, 1 H, 5Ј-H), 7.30 (d, 3J = 7.0, 1 H, 6Ј-
121.3 (3JC,Pt = 33.1 Hz, C-3Ј), 130.3 (C-4Ј), 115.6 (C-5Ј), 115.4 (C-
6Ј), 161.4 (2JC,Pt = 72.2 Hz, CH=N) ppm. 195Pt{1H} NMR: CDCl3:
3
H), 8.78(s, JPt,H = 58.2, 1 H, CH=N) ppm; [D3]acetonitrile: δ =
3.52 (s, 3JPt,H = 18.0, 6 H, 2 Me, dmso), 4.37 (s, 5 H, C5H5), 4.75(t, δ = –4031 ppm.
3
3J = 2.0, 2 H, 2-H, 5-H), 4.62(t, J = 2.0, 2 H, 3-H, 4-H), 6.77(d,
[Pt{(η5-C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(PPh3)] (6): Compound
5 (62 mg, 1.01ϫ10–4 mol) was suspended in benzene (10 mL), then
an equimolar amount of PPh3 was added. The reaction mixture
was stirred at 343 K for 1 h and then filtered. The filtrate was con-
centrated to dryness in a rotary evaporator, and the residue was
dissolved in the minimum amount of CH2Cl2 and passed through a
short SiO2 column (2.0 cmϫ2.3 cm). Elution with CH2Cl2/MeOH
(100:0.01) produced a violet band that was collected and concen-
trated to dryness. The solid formed was collected and dried (yield:
57 mg, 71%). C35H28FeNOPPt (760.5): calcd. C 55.27, H 3.71, N
3
3
3J = 8.0, 1 H, 3Ј-H), 7.00(t, J = 8.0, 1 H, 4Ј-H), 6.33 (t, J = 8.0,
3
3
1 H, 5Ј-H), 7.35 (d, J = 8.0, 1 H, 6Ј-H), 8.83 (s, JPt,H = 56.0, 1
H, CH=N) ppm. 13C{1H} NMR:[45] CDCl3: δ = 46.3 (2 Me, dmso),
71.8 (C5H5), 76.6 (C-1), 72.4 (C-2, C-5), 74.0 (C-3, C-4), 138.5 (C-
1Ј), 167.7 (C-2Ј), 121.1 (C-3Ј), 130.3 (C-4Ј), 114.8 (C-5Ј), 118.6 (C-
6Ј), 163.5 (CH=N) ppm. 195Pt{1H} NMR: CDCl3: δ = –2760 ppm.
Synthesis of 4b: Prepared according to the same procedure but
using 2c (8.2 mg, 1.26ϫ10–5 mol) and an NaOD solution (0.252 
in [D4]methanol) (35 µL) (yield: 6.6 mg, 85%). C19H20Cl-
FeNO2PtS·1/4C6H14 (634.3): calcd. C 38.72, H 3.53, N 2.20, S 5.04;
1.84; found C 55.2, H 4.0, N 2.0. MS (FAB+): m/z = 760 [M]+. IR:
found C 39.4, H 3.7, N 2.3, S 4.7. MS (FAB+): m/z = 613 [M]+.
1
ν = 1561 [ν(ϾC=N–)] cm–1. H NMR:[46] CDCl3: δ = 4.07 (s, 5 H,
˜
1
IR: ν = 1560 [ν(ϾC=N–)] cm–1. H NMR:[45] CDCl3: δ = 3.48 (s,
˜
3
3
C5H5), 3.08 (d, J = 2.2 Hz, 1 H, 3-H), 4.41 (t, J = 2.2 Hz, 1 H,
3JPt,H = 22.0 Hz, 6 H, 2 Me, dmso), 4.37 (s, 5 H, C5H5), 4.68 (br.,
4 H, 2-H–5-H), 6.87 (d, 3J = 7.0 Hz, 1 H, 3Ј-H), 6.94 (t, 3J =
7.0 Hz, 1 H, 4Ј-H), 6.32 (t, J = 7.0 Hz, 1 H, 5Ј-H), 7.42 (d, J =
7.0 Hz, 1 H, 6Ј-H), 8.47 (s, JPt,H = 40.2 Hz, 1 H, CH=N) ppm;
[D3]acetonitrile: δ = 3.37 (s, JPt,H = 14.4 Hz, 6 H, 2 Me, dmso),
4-H), 4.38 (d, 3J = 2.2 Hz, 1 H, 5-H), 6.67 (dd, 3J = 8, 4J = 1.0 Hz,
3
4
3
1 H, 3Ј-H), 6.99 (td, J = 8, J = 1.0 Hz, 1 H, 4Ј-H), 6.39 (dd, J
3
3
4
3
4
= 8, J = 1.0 Hz, 1 H, 5Ј-H), 7.14 (dd, J = 8, J = 1.0 Hz, 1 H,
3
4
3
6Ј-H), 8.14 (d, JP,H = 10.8, JPt,H = 86.8 Hz, 1 H, CH=N), 7.30–
7.80 (m, 15 H, aromatic protons of PPh3) ppm; [D3]acetonitrile: δ
= 4.06 (s, 5 H, C5H5), 3.06 (d, 3J = 2.0, 1 H, 3-H), 4.43 (t, 3J =
3
3
4.40 (s, 5 H, C5H5), 4.79 (t, J = 2.0 Hz, 2 H, 2-H, 5-H), 6.74 (t,
3J = 2.0 Hz, 2 H, 3-H, 4-H), 6.77 (d, J = 8.0 Hz, 1 H, 3Ј-H), 6.96
3
3
3
4
2.0, 1 H, 4-H), 4.46 (d, J = 2.0, 1 H, 5-H), 6.45 (dd, J = 8, J =
1.5, 1 H, 3Ј-H), 6.93 (td, J = 8, J = 1.5, 1 H, 4Ј-H), 6.37 (dd, J
= 8, J = 1.5, 1 H, 5Ј-H), 7.26 (dd, J = 8.0, J = 1.5, 1 H, 6Ј-H),
3
3
(t, J = 8.0 Hz, 1 H, 4Ј-H), 6.36 (t, J = 8.0 Hz, 1 H, 5Ј-H), 7.47
3
4
3
3
3
(d, J = 8.0 Hz, 1 H, 6Ј-H), 8.52 (s, JPt,H = 36.4 Hz, 1 H, CH=N)
ppm. 13C{1H}:[45] CDCl3: δ = 43.9 (Me, dmso), 71.9 (C5H5), 72.6
(C-2, C-5), 74.2 (C-3, C-4), 143.3 (C-1Ј), 168.3 (C-2Ј), 121.7 (C-3Ј),
129.8 (C-4Ј), 115.0 (C-5Ј), 118.2 (C-6Ј), 163.8 (CH=N) ppm; the
signal due to C-1 was not observed. 195Pt{1H} NMR: CDCl3: δ =
–2818 ppm.
4
3
4
4
3
8.33 (d, JP,H = 11.5, JPt,H = 88.7, 1 H, CH=N), 7.30–7.85 (m, 15
H, aromatic protons of PPh3). 13C{1H} NMR:[46] CDCl3: δ = 70.8
(C5H5), 75.9 (C-1), 92.7 (C-2), 76.8 (C-3), 71.4 (C-4), 68.2 (3JPt,C
= 41.2 Hz, C-5), 137.2 (C-1Ј), 172.6 (C-2Ј), 121.9 (C-3Ј), 130.2 (C-
4Ј), 114.7 (C-5Ј), 115.5 (C-6Ј), 159.2 (CH=N) ppm and four ad-
ditional doublets centred at δ = 128.0, 130.9, 131.0, 135.1 ppm due
to the aromatic carbon atoms of the PPh3 ligand. 31P{1H} NMR:
CDCl3: δ = 15.5 (s, 1JPt,P = 3974 Hz). 195Pt{1H}: CDCl3: δ = –3955
[Pt{(η5-C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(dmso)] (5): Ligand 1
(181 mg, 5.92ϫ10–4 mol) and an equimolar amount of cis-
[PtCl2(dmso)2] were dissolved in toluene (20 mL). Then a solution
of NaAcO (97 mg, 1.18ϫ10–3 mol) and methanol (5 mL) was
added. The resulting mixture was protected from light and refluxed
for 3 d. After this period, the hot solution was filtered, and the
filtrate was concentrated to dryness in a rotary evaporator. The
nearly black residue was dissolved in the minimum amount of
CH2Cl2 and passed through an SiO2 column (4.5 cmϫ2.0 cm).
Elution with CH2Cl2 produced a band that gave after concentra-
tion FcCHO. Afterwards, a CH2Cl2/MeOH (100:0.2) mixture pro-
duced the release of a red band that gave after workup a small
amount (ca. 28 mg) of a solid containing the two isomers of 4 in a
molar ratio of 1:1. Once this band was collected, the polarity of
the solvent was increased, and the use of CH2Cl2/MeOH (100:1.0)
gave a deep-purple band that was collected and concentrated to
dryness to give 5 (144 mg). C19H19FeNO2PtS (575.0): calcd. C
1
(d, JPt,P = 3974 Hz) ppm.
[Pt{(η5-C5H3CH=NC6H4OH-2)Fe(η5-C5H5)}Cl(dmso)]
(7):
[Pt{(η5-C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(dmso)] (5) (54 mg,
9.37ϫ10–5 mol) was dissolved in CHCl3 (5 mL). Then a 0.145 
solution of HCl in methanol (0.52 mL) was added. The resulting
mixture was stirred at room temperature for 1 h. The undissolved
materials were removed by filtration and discarded, and the filtrate
was concentrated to dryness in a rotary evaporator to give a purple
solid which was collected and dried (yield: 50 mg, 94%).
C19H20ClFeNO2PtS·3/4CHCl3 (702.3): calcd. C 33.77, H 2.98, N
1.99, S 4.56; found C 33.5, H 3.2, N 2.1, S 4.8. MS (ESI): m/z =
1
577 [M – Cl]+. IR: ν = 1563 [ν(ϾC=N–)], 3275 [ν(–OH)] cm–1. H
˜
NMR:[46] CDCl3: δ = 3.59 (s, JPt,H = 24.0 Hz, 3 H, Me, dmso),
3.56 (s, JPt,H = 20.8 Hz, 3 H, Me, dmso), 4.38 (s, 5 H, C5H5), 4.63
3
3
3
3
39.95, H 3.33, N 2.43, S 5.56; found C 40.1, H 3.4, N 2.3, S 6.3.
(d, J = 2.4 Hz, 1 H, 3-H), 4.79 (t, J = 2.4 Hz, 1 H, 4-H), 5.41 (d,
1
3
MS (FAB+): m/z = 576 [M]+. IR: ν = 1544 [ν(ϾC=N–)] cm–1. H
3J = 2.4 Hz, 1 H, 5-H), 7.04 (d, J = 8.0 Hz, 1 H, 3Ј-H), 7.22–7.26
˜
NMR:[46] CDCl3: δ = 3.48 (s, JPt,H = 22.0 Hz, 6 H, 2 Me, dmso),
(m, 2 H, 4Ј-H, 5Ј-H), 6.99 (br. s, 1 H, 6Ј-H), 5.62 (br. s, 1 H, OH),
3
4.35 (s, 5 H, C5H5), 4.79 (s, 1 H, 3-H), 4.47 (t, 3J = 2.8 Hz, 1 H, 8.23 (s, JPt,H = 95.2 Hz, 1 H, CH=N) ppm; [D3]acetonitrile: δ =
3
3
4
3
4-H), 4.81 (s, 1 H, 5-H), 6.65 (dd, J = 8.0, J = 2.0 Hz, 1 H, 3Ј- 3.52 (s, JPt,H = 16.0 Hz, 6 H, 2 Me, dmso), 4.46 (s, 5 H, C5H5),
H), 7.02 (td, J = 8.0, J = 2.0 Hz, 1 H, 4Ј-H), 6.42 (td, J = 8.0,
3
4
3
4.76 (s, 1 H, 3-H), 4.83 (s, 1 H, 4-H), 5.31 (s, 1 H, 5-H), 7.15 (d,
1609
Eur. J. Inorg. Chem. 2008, 1599–1612
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org

S. Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía
FULL PAPER
3J = 8.0 Hz, 1 H, 3Ј-H), 6.90 (m, 2 H, 4Ј-H, 5Ј-H), 7.03 (d, J =
3
3
H, 5Ј-H), 6.96 (d, J = 8.0 Hz, 1 H, 6Ј-H), 6.54 (br. s, 1 H, OH),
3
4
3
8.0 Hz, 1 H, 6Ј-H), 6.13 (s, 1 H, OH), 8.26 (s, JPt,H = 93.6 Hz, 1
8.51 (d, JP,H = 8.4, JPt,H = 70.4 Hz, 1 H, CH=N), 7.40–7.90 (m,
H, CH=N) ppm. 13C{1H} NMR:[46] CDCl3: δ = 47.2, 47.0 (2 Me,
15 H, aromatic protons of PPh3) ppm. 13C{1H} NMR:[46] CDCl3:
dmso), 70.9 (C5H5), 85.8 (C-1), 103.4 (C-2), 69.0 (C-3), 73.7 (C-4), δ = 70.7 (C5H5), 87.0 (C-1, C-2), 77.4 (C-3), 73.0 (C-4), 67.8 (C-5),
77.9 (C-5), 138.8 (2JPt,C = 76.2 Hz, C-1Ј), 149.2 (C-2Ј), 118.9 (C-
140.2 (C-1Ј), 149.8 (C-2Ј), 119.4 (C-3Ј), 128.4 (C-4Ј), 122.0 (C-5Ј),
3Ј), 129.1 (C-4Ј), 121.9 (C-5Ј), 123.7 (C-6Ј), 180.6 (CH=N) ppm. 123.3 (C-6Ј), 177.5 (CH=N) ppm and four additional doublets cen-
195Pt{1H} NMR: CDCl3: δ = –3831 ppm.
tered at δ ≈ 128.1, 130.8, 131.0, 134.9 ppm due to the four types of
13C nuclei of the PPh3 ligand. 31P{1H} NMR: CDCl3: δ = 16.2 (s,
1JPt,P = 4266 Hz) ppm. 195Pt{1H} NMR: CDCl3: δ = –4206 (d,
1JPt,P = 4266 Hz) ppm.
[Pt{(η5-C5H3CH=NC6H4OH-2)Fe(η5-C5H5)}Cl(PPh3)] (8): This
product can be obtained by using two alternative proce-
dures [Methods (a) and (b)]. Method (a): Compound
[Pt{(η5-C5H3CH=NC6H4O-2)Fe(η5-C5H5)}(PPh3)] (6) (48 mg, Electrochemical Studies: Electrochemical data for the compounds
6.31ϫ10–5 mol) was dissolved in CHCl3 (0.5 mL), and then a
0.181  solution of HCl in methanol (25 mL) was added. The reac-
tion mixture was shaken for 2 min and then filtered. The filtrate
was concentrated to dryness in a rotary evaporator, and the solid
formed was collected and air-dried (yield: 46 mg, 92%). Method
(b): To a suspension of 7 (37 mg, 6.04ϫ10–5 mol) in benzene
(10 mL), PPh3 (16 mg, 6.10ϫ10–5 mol) was added. The reaction
mixture was stirred at 343 K for 1 h. After this period, the resulting
solution was filtered, and the filtrate was concentrated to dryness
in a rotary evaporator. The residue was dissolved in the minimum
amount of CH2Cl2 and passed through an SiO2 column
(3.0 cmϫ2.0 cm). Elution with CH2Cl2 released a purple band,
that was collected and concentrated to dryness in a rotary evapora-
tor to give 8 (yield: 30 mg, 62.5%). C35H29ClFeNOPt·2H2O
(802.0): calcd. C 50.46, H 3.99, N 1.68; found C 50.5, H 4.2, N 1.5.
under study were obtained by cyclic voltammetry under nitrogen
at 298 K by using HPLC-grade acetonitrile as solvent and tetrabu-
tylammonium hexafluorophosphate {(Bu4N)[PF6]} (0.1 ) as sup-
porting electrolyte and an M263A potentiostat from EG&G instru-
ments. The measured potentials E were referenced to an Ag/AgNO3
(0.1  in acetonitrile) electrode separated from the solution by a
medium-porosity fritted disk. A platinum wire auxiliary electrode
was used in conjunction with a platinum disk working Tacussel
EDI rotatory electrode (3.14 mm2). Cyclic voltammograms of fer-
rocene were recorded before and after each sample to ensure the
stability of the Ag/AgNO3 electrode. Cyclic voltammograms of
freshly prepared solutions (10–3 ) of the samples were run, and
average values of the measured potentials were then referenced to
ferrocene [E(Fc)] which was used as internal reference. In all the
experiments, the cyclic voltammograms were registered using scan
speeds varying from v = 10 mV/s to 100 mV/s. For the study of the
effect induced by the acidity of the medium on the electrochemical
properties of 2 and 4–8, an equimolar amount of NaOH (20 µL of
MS (MALDI-TOF+): m/z = 761 [M – Cl]+. IR: ν = 1552
˜
[ν(ϾC=N–)], 3414 [ν(–OH)] cm–1. 1H NMR:[46] CDCl3: δ = 3.95
(s, 5 H, C5H5), 3.54 (s, 1 H, 3-H), 4.36 (s, 1 H, 4-H), 4.56 (s, 1 H,
3
5-H), 6.98–7.03 (m, 3 H, 3Ј-H, 4Ј-H, 6Ј-H), 7.19 (t, J = 7.0 Hz, 1 a 1.0  solution) was added to the solutions containing 2, 7 or 8
4
3
H, 5Ј-H), 6.23 (br. s, 1 H, OH), 8.38 (d, JP,H = 8.0, JPt,H
=
(10–3 ), the supporting electrolyte and acetonitrile. Then the re-
sulting mixture was stirred at room temperature under N2 for a
few minutes, and afterwards its cyclic voltammetry was registered.
75.4 Hz, 1 H, CH=N), 7.35–7.80 (m, 15 H, aromatic protons of
PPh3) ppm; [D3]acetonitrile: δ = 3.99 (s, 5 H, C5H5), 3.46 (s, 1 H,
3
3-H), 4.17 (s, 1 H, 4-H), 4.76 (s, 1 H, 5-H), 7.13 (d, J = 8.0 Hz, 1 Similarly, a solution of (Bu4N)[PF6] and compounds 4, 5 or 6 was
3
3
H, 3Ј-H), 7.18 (t, J = 8.0 Hz, 1 H, 4Ј-H), 6.99 (t, J = 8.0 Hz, 1 treated with an HCl solution (1.0  in CH3CN) (20 µL).
Table 3. Crystallographic data and details of the refinement for the crystal structures of the two isomeric forms of complex trans-
[Pt(FcCH=NC6H4OH-2)Cl2(dmso)] (2b·CH2Cl2 and 2c). Standard deviation parameters are given in parentheses.
2b·CH2Cl2
2c
Empirical formula
Formula mass
C20H23Cl4FeNO2PtS
734.19
C19H21Cl2FeNO2PtS
649.27
T/K
λ/Å
293(2)
0.71069
293(2)
0.71069
Crystal size [mm]
Crystal system
0.1ϫ0.1ϫ0.2
monoclinic
0.1ϫ0.1ϫ0.2
monoclinic
Space group
a/Å
P21/n
13.893(1)
P21/c
13.679(4)
b/Å
c/Å
11.955(1)
14.613(1)
9.157(6)
17.082(6)
β/°
95.476(1)
2416.0(3)
102.77(2)
2086.7(17)
V/Å3
Z
4
4
Dcalcd./gcm–3
2.018
6.931
2.067
7.762
µ [mm–1]
F(000)
1416
2.58–33.14
15071
6441 [R(int) = 0.0523]
6441
1248
2.44–29.99
6061
6061 [R(int) = 0.0613]
6061
θ range for data collection/°
No. of reflections collected
No. of unique reflections
No. of data
No. of parameters
Goodness of fit on F2
Final R indices [IϾ2σ(I)]
Final R indices (all data)
Largest diff. peak and hole/eÅ–3
275
1.023
244
0.769
R1 = 0.0368, wR2 = 0.0939
R1 = 0.0742, wR2 = 0.1024
0.634 and –0.798
R1 = 0.0477, wR2 = 0.0939
R1 = 0.2977, wR2 = 0.1110
0.816 and –0.945
1610
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1599–1612

New Heterodimetallic Platinum(II) Complexes
mun. 2006, 1169–1178; d) T. Bell, N. M. Herst, Chem. Soc. Rev.
2004, 33, 589–598; e) V. Balzani, P. Ceroni, B. Ferrer, Pure
Appl. Chem. 2004, 76, 1887–1901.
B. Feringa (Ed.), Molecular Switches, Wiley-VCH, Weinheim,
Germany, 2001.
Crystallography: A prismatic crystal of 2b·CH2Cl2 (size in Table 3)
was selected and mounted on a Mar345 diffractometer with an
image plate detector. Unit-cell parameters were determined from
15901 reflections (in the range 3° Ͻ θ Ͻ 31°) and refined by least-
squares methods. For 2c, a crystal (size in Table 3) was selected and
mounted on an Enraf-CAD4 four-circle diffractometer, and the
unit cell parameters were determined from 25 automatically cen-
tered reflections (in the range 12° Ͻ θ Ͻ 21°). In both cases inten-
sities were collected with graphite-monochromated Mo-Kα radia-
tion. For 2b·CH2Cl2, the number of reflections measured was 15071
(in the range 2.58° Յ θ Յ 33.14°), of which 6441 were non-equiva-
lent by symmetry [Rint(on I) = 0.0523], and 4487 were assumed as
observed by applying the condition I Ͼ 2σ(I). For 2c, 6061 reflec-
tions were measured (in the range 2.44° Յ θ Յ 29.99°), and 1729
were assumed as observed by applying the condition I Ͼ 2σ(I). In
this case, three reflections were measured every 2 h as orientation
and intensity control, and no significant intensity decay was ob-
served. Lorentz polarization and absorption corrections were ap-
plied in the two cases. The structures were solved by direct meth-
ods, using the SHELXS computer program[47] and refined by a full-
matrix least-squares method with the SHELX97 computer pro-
gram[48] using 6010 reflections for 2b·CH2Cl2 and 6061 for 2c (very
negative intensities were not assumed). The function minimized
was Σw||Fo|2 – |Fc|2|2, where w = [σ2(I) + (0.0629P)2]–1 (for
2b·CH2Cl2) or [σ2(I) + (0.0183P)2]–1 (for 2c) and P = (|Fo|2 + 2|Fc|2)/
3; ƒ, ƒЈ and ƒЈЈ were obtained from the bibliography.[49] In both
cases, all hydrogen atoms were computed and refined using a riding
model with an isotropic temperature factor equal to 1.2 times the
equivalent temperature factor of the atom to which is attached.
The final R(on F) factors were 0.041 (for 2b·CH2Cl2) and 0.047
(for 2c). Further details concerning the resolution and refinement
of these crystal structures are presented in Table 3. CCDC-655221
and -655222 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[3]
[4]
For recent advances on this field, see for instance: a) T. W.
Hambley, J. Chem. Soc., Dalton Trans. 2001, 2711–2718; b) J.
Reedijk, Proc. Natl. Acad. Sci. USA 2003, 100, 3611–3616; c)
J. de Mier-Vinue, A. M. Montaña, V. Moreno, Metal Com-
pounds in Cancer Chemotherapy, Research Signpost, Kerala, In-
dia, 2005, chapter 3, pp. 47–150; d) C. S. Allardyce, A. Docier,
C. Scolaro, P. S. Dyson, Appl. Organomet. Chem. 2005, 19, 110;
e) A. S. Abu-Surrah, M. Kettunen, Curr. Med. Chem. 2006, 13,
1337–1357.
a) V. G. Vaidyanathan, B. U. Nair, Eur. J. Inorg. Chem. 2005,
3756–3759; b) C. M. Che, J. L. Zhang, L. R. Lin, Chem. Com-
mun. 2002, 2556–2557; c) P. K. M. Siu, D. L. Ma, C. M. Che,
Chem. Commun. 2005, 1025–1027.
a) C. K. Koo, B. Lam, S. K. Leung, M. H. W. Lam, W. Y.
Wong, J. Am. Chem. Soc. 2006, 128, 16434–16435; b) J. Müller,
F. Glahé, E. Freisinger, B. Lippert, Inorg. Chem. 1999, 38,
3160–3166.
a) A. Togni, T. Hayashi (Eds.), Ferrocenes, Homogeneous Catal-
ysis, Organic Synthesis and Materials Science, VCH, Weinheim,
Germany, 1995; b) H. Plenio, D. Burth, Organometallics 1996,
15, 4054–4062; c) H. Plenio, A. Aberle, Organometallics 1997,
16, 5950–5957.
For latest advances in this field, see for instance: a) L. Sun, S.
Wang, H. Tian, Chem. Lett. 2007, 36, 250–251; b) A. Cabal-
lero, V. Lloberas, D. Curiel, A. Tárraga, A. Espinosa, R.
García, J. Vidal-Gancedo, C. Rovira, K. Wurst, P. Molina, J.
Veciana, Inorg. Chem. 2007, 46, 825–838; c) A. E. Radi, J. L.
Acero Sánchez, E. Baldrich, C. K. O’Sullivan, J. Am. Chem.
Soc. 2006, 128, 117–124; d) A. Sagi, J. Rishop, D. Shabat, Anal.
Chem. 2006, 78, 1459–1461; e) U. Siemeling, D. Rother, C.
Bruhm, Chem. Commun. 2007, 427–4229; f) K. Heinze, S. Rein-
hart, Organometallics 2007, 26, 5406–5414; g) V. C. Gibson,
C. K. A. Gregson, C. M. Halliway, N. J. Long, P. J. Oxford,
A. T. P. White, D. J. Williams, J. Organomet. Chem. 2005, 690,
6271–6283; h) K. Kowalski, J. Zakrzewski, N. J. Long, S. Dom-
agala, A. J. P. White, J. Organomet. Chem. 2006, 691, 3902–
3908.
D. R. van Staveren, N. Metzler-Nolte, Chem. Rev. 2004, 104,
5931–5986.
M. Malaun, Z. R. Reeves, R. L. Paul, J. C. Jeffery, J. A. McCle-
verty, M. D. Ward, I. Asselberghs, K. Clays, A. Persoons,
Chem. Commun. 2001, 49–50.
R. Martínez, I. Ratera, A. Tárraga, P. Molina, J. Veciana,
Chem. Commun. 2006, 3809–3811.
C. López, R. Bosque, S. Pérez, A. Roig, E. Molins, X. Solans,
M. Font-Bardía, J. Organomet. Chem. 2006, 691, 475–484.
J. H. Price, A. N. Williamson, R. F. Schramm, B. B. Wayland,
Inorg. Chem. 1972, 11, 1280–1284.
J. Bravo, C. Cativiela, R. Navarro, E. P. Urriolabeitia, J. Or-
ganomet. Chem. 2002, 650, 157–172.
a) S. Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía,
New J. Chem. 2003, 27, 975–982; b) C. López, A. Caubet, S.
Pérez, X. Solans, M. Font-Bardía, Chem. Commun. 2004, 540–
541.
P. S. Pregosin, Coord. Chem. Rev. 1982, 44, 247–291.
a) X. Riera, A. Caubet, C. López, V. Moreno, X. Solans, M.
Font-Bardía, Organometallics 2000, 19, 1384–1390; b) X. Ri-
era, C. López, A. Caubet, V. Moreno, X. Solans, Eur. J. Inorg.
Chem. 2001, 2135–2141; c) L. Ding, Y. J. Wu, D. P. Zhou, Poly-
hedron 1998, 17, 1725–1728; d) A. Caubet, C. López, X. Solans,
M. Font-Bardía, J. Organomet. Chem. 2003, 669, 164–171.
a) J. Albert, M. Gómez, J. Granell, J. Sales, X. Solans, Organo-
metallics 1990, 9, 1405–1413; b) J. Albert, R. M. Ceder, M.
Gómez, J. Granell, J. Sales, Organometallics 1992, 11, 1536–
1541.
[5]
[6]
[7]
[8]
Supporting Information (see footnote on the first page of this arti-
cle): Graphical plots showing the variations of the UV/Vis spectra
(in CH2Cl2) and cyclic voltammograms (in CH3CN) of compounds
5, 6, 7 and 8 during the titration with HCl (for 5 and 6) or with
NaOD (for 7 and 8) (Figures S1 and S2) and 1H NMR spectra
(400 MHz) of 1 in CDCl3 at 298 K and after the addition of DCl
or NaOD (in [D4]methanol) (B and C, respectively) (Figure S3).
[9]
[10]
[11]
[12]
[13]
[14]
[15]
Acknowledgments
This work was supported by the Ministerio de Ciencia y Tecnologia
(Spain).
[1] For a general overview on this topic, see for instance: a) Special
issue devoted to “Molecular Machines”: Acc. Chem. Rev. 2001,
34; b) T. Kelly (Ed.), “Molecular Machines”, Topics in Current
Chemistry, Springer, New York, USA, 2005, vol. 262; c) A. Bal-
zani, A. Credi, M. Venturi, Molecular Devices and Machines –
A Journey into the Nanoworld, Wiley-VCH, Weinheim, Ger-
many, 2003.
[2] For recent reviews on this area, see for instance: a) S. Saha, J. F.
Stoddart, Chem. Soc. Rev. 2007, 36, 77–92; b) V. Amendola, L.
Fabbrizzi, F. Foti, M. Licchelli, C. Mangano, P. Pavallicini, A.
Poggi, D. Sacchi, A. Taglietti, Coord. Chem. Rev. 2006, 250,
273–299; c) D. Gust, T. A. Moore, A. L. Moore, Chem. Com-
[16]
[17]
[18]
Eur. J. Inorg. Chem. 2008, 1599–1612
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1611

S. Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía
FULL PAPER
[19] R. G. Miller, R. D. Stauffer, D. R. Fahey, D. R. Parnell, J. Am. [32]
Chem. Soc. 1970, 92, 1511–1521.
J. Vicente, J. A. Abad, E. Martínez-Viviente, P. G. Jones, Orga-
nometallics 2002, 21, 4454–4467.
C. López, R. Bosque, X. Solans, M. Font-Bardía, New J.
Chem. 1996, 20, 1285–1292.
C. López, R. Bosque, X. Solans, M. Font-Bardía, New J.
Chem. 1998, 22, 977–982.
NMR spectra of 2 and 4–8 in [D3]acetonitrile at 298 K indicate
that these compounds are stable in this solvent. However, for
5, the presence of residual water in the solvent induces the
cleavage of the σ-(Pt–O) bond. Thus, for the electrochemical
studies the use of HPLC-grade acetonitrile is strongly recom-
mended.
[20] a) M. Crespo, Polyhedron 1996, 15, 1981–1988; b) M. Crespo,
M. Font-Bardía, J. Granell, M. Martínez, X. Solans, Dalton
Trans. 2003, 3763–3769.
[21] T. H. Allen, Acta Crystallogr., Sect. B Struct. Sci. 2002, 58,
380–388.
[22] A. D. Ryabov, G. M. Kazankov, I. M. Panyashkina, O. V. Gro-
zovsky, O. G. Dyachenko, V. A. Polyakov, L. G. Kuz’mina, J.
Chem. Soc., Dalton Trans. 1997, 4385–4392.
[33]
[34]
[35]
[23] a) A. Bondi, J. Phys. Chem. 1964, 64, 441–451; b) A. I. Kitaigo-
rodskii, Molecular Crystals and Molecules, Academic Press,
London, UK, 1973.
[36]
[37]
[24] a) Y. Wu, S. Huo, J. Gong, X. Cui, L. Ding, K. Ding, C. Du,
Y. Liu, M. Song, J. Organomet. Chem. 2001, 637–639, 27–46
and references cited therein; b) A. Capapé, M. Crespo, J.
Granell, A. Vizcarro, J. Zafrilla, M. Font-Bardía, X. Solans,
Chem. Commun. 2006, 4128–4130.
[25] a) M. Albrecht, G. van Koten, Angew. Chem. Int. Ed. 2001, 40,
3750–3781; b) M. E. van der Boom, D. Milstein, Chem. Rev.
2003, 103, 1759–1792.
E. R. Brown, J. R. Sandifer, Physical Methods in Chemistry:
Electrochemical Methods (Eds.: B. W. Rossiter, J. H. Hamilton),
Wiley, New York, USA, 1986, vol. 4, chapter 4.
a) N. F. Blom, E. W. Neuse, H. G. Thomas, Trans. Met. Chem.
1987, 12, 301–306; b) W. F. Little, C. N. Reilley, J. D. Johnson,
A. P. Sanders, J. Am. Chem. Soc. 1964, 86, 1382–1386; c)
G. L. K. Hoh, W. E. McEwen, J. Kleinberg, J. Am. Chem. Soc.
1961, 83, 3949–3953.
[26] For recent advances on pallada- and platinacycles with terdent-
ate (C,N,S)– ligands, see for instance: a) C. López, S. Pérez, X.
Solans, M. Font-Bardía, J. Organomet. Chem. 2002, 650, 258–
267; b) S. Pérez, C. López, A. Caubet, R. Bosque, X. Solans,
M. Font-Bardía, A. Roig, E. Molins, Organometallics 2004, 23,
224–236; c) C. López, S. Pérez, X. Solans, M. Font-Bardía, A.
Roig, E. Molins, P. W. N. M. van Leeuwen, G. P. F.
van Strijdonck, Organometallics 2007, 26, 571–576.
[27] For recent advances on pallada- and platinacycles with terdent-
ate (C,N,NЈ)– ligands, see for instance: a) I. Favier, M. Gómez,
J. Granell, M. Martínez, X. Solans, M. Font-Bardía, Dalton
Trans. 2005, 123–132; b) S. Pérez, C. López, A. Caubet, A.
Pawełczyk, X. Solans, M. Font-Bardía, Organometallics 2003,
22, 2396–2408.
[28] For recent pallada- and platinacycles with terdentate (C,N,O)
q– (q = 1 or 2) ligands, see for instance: a) G. Zhao, Q. G. Wang,
T. C. W. Mak, Organometallics 1998, 17, 3437–3441; b) A.
Fernández, D. Vázquez-García, J. J. Fernández, M. López-
Torres, A. Suárez, S. Castro-Juiz, J. M. Vila, New J. Chem.
2002, 26, 398–404; c) C. López, A. Caubet, S. Pérez, X. Solans,
M. Font-Bardía, J. Organomet. Chem. 2003, 681, 82–90; d) S.
Pérez, C. López, A. Caubet, X. Solans, M. Font-Bardía, A.
Roig, E. Molins, Organometallics 2006, 25, 596–601; e) D. Solé,
S. Díaz, X. Solans, M. Font-Bardía, Organometallics 2006, 25,
1995–2001; f) S. Pérez, C. López, A. Caubet, X. Solans, M.
Font-Bardía, M. Gich, E. Molins, J. Organomet. Chem. 2007,
692, 2402–2414 and references cited therein.
[38]
[39]
a) E. M. McGale, R. E. Murray, C. J. McAdam, J. L. Morgan,
B. H. Robinson, J. Simpson, Inorg. Chim. Acta 2003, 352, 129–
135; b) X. Riera, A. Caubet, C. López, V. Moreno, Polyhedron
1999, 18, 2549–2555.
a) R. Bosque, C. López, J. Sales, Inorg. Chim. Acta 1996, 244,
141–145; b) J. C. Kotz, E. E. Getty, L. Lin, Organometallics
1985, 4, 610–612; c) A. Moyano, M. Rosol, R. M. Moreno, C.
López, M. A. Maestro, Angew. Chem. Int. Ed. 2005, 44, 1865–
1869.
[40]
For the cycle 6 Ǟ 8 Ǟ 6,The isosbestic points appear at λ =
405 and 374 nm.
[41] K. Godula, D. Sames, Science 2006, 312, 67–72 and references
cited therein.
[42] a) J. Dupont, C. S. Consorti, J. Spencer, Chem. Rev. 2005, 105,
2527–2572; b) I. Omae, J. Organomet. Chem. 2007, 692, 2608–
2632 and references cited in these two articles.
[43] The success of the preparations of compounds 2, 4–6 and 8 is
strongly dependent on the quality of the methanol used. The
presence of small amounts of water induces the formation of
larger amounts of FcCHO and reduces the yields. Thus, the
use of HPLC-grade MeOH is strongly recommended.
[44] D. D. Perrin, W. L. F. Amarego, Purification of Laboratory
Chemicals, 4th ed., Butterworth-Heinemann, Oxford, UK,
1996.
[45] The labelling of the atoms refers to those shown in Scheme 1.
[46] The labelling of the atoms refers to those shown in Scheme 2.
[47] G. M. Sheldrick, SHELXS – A computer program for determi-
nation of crystal structures, University of Göttingen, Germany,
1997.
[29] M. Crespo, M. Font-Bardía, X. Solans, J. Organomet. Chem.
2006, 691, 1897–1906.
[30] a) A. Bader, E. Lindner, Coord. Chem. Rev. 1991, 108, 27–110;
b) C. S. Slone, D. A. Weinberger, C. A. Mirkin, Prog. Inorg.
Chem. 1999, 48, 233–350.
[48] G. M. Sheldrick, SHELX97 – A computer program for determi-
nation of crystal structures, University of Göttingen, Germany,
1997.
[31] a) I. Omae, Applications of Organometallic Compounds, John
Wiley, Chichester, UK, 1998; b) P. W. Jolly, G. Wilke, W. A. [49] International Tables of X-ray Crystallography, Kynoch Press,
Hermann, B. Cornils (Eds.), Applied Homogeneous Catalysis
with Organometallic Compounds, VCH, Weinheim, Germany,
1996.
Birmingham, UK, 1974, vol. IV, pp. 99–100, 149.
Received: November 2, 2007
Published Online: February 13, 2008
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