Novel Five-Membered Pallada- and Platinacycles Containing a [C(sp 2, ferrocene), N, S]- Terdentate Ligand. Theoretical Interpretation of Their Electrochemical and Electronic Properties Based on Density Functional Calculations

Article abstract of DOI:10.1021/om030520d

The synthesis of the novel ferrocenyl Schiff base [(η ⁵-C₅H₅)Fe{(η⁵-C ₅H₄)CH=N(C₆H₄-2SMe)}] (1c) and the study of its reactivity versus palladium(II) or platinum(II) salts are reported. These studies have allowed us to isolate and characterize [M{ [(η ⁵-C₅H₃)CH=N(C₆H ₄-2-SMe)]Fe(η⁵-C₅H₅)}Cl] {with M = Pd (2c) or Pt (3c)}, which are the first examples of cyclopallada- and cycloplatinated compounds containing a mer-terdentate [C(sp², ferrocene), N, S]^- ligand. Moessbauer spectroscopic studies and the X-ray crystal structures of 1c-3c are reported. The crystal structures of 2c and 3c confirmed the mode of binding of the ligand and revealed that the molecules are associated in pairs, which interact by C-H...π interactions forming a chain that stacks along the [101] plane. Electrochemical studies, based on cyclic voltammetry, reveal that the ease with which the oxidation of the ferrocenyl moiety occurs increases according to the sequence 1c < 2c < 3c. Molecular orbital calculations at a DFT level have also been carried out to rationalize the influence of the nature of the Pd(II) (in 2c) or Pt(II) in (3c) on the electrochemical properties of these compounds, and theoretical studies using time-dependent density functional theory (TD-DFT) calculations have also been carried out in order to assign the bands observed in the electronic spectra of the cyclometalated compounds.

Full text of DOI:10.1021/om030520d

224
Organometallics 2004, 23, 224-236
Novel F ive-Mem ber ed P a lla d a - a n d P la tin a cycles
Con ta in in g a [C(sp 2, fer r ocen e), N, S]- Ter d en ta te
Liga n d . Th eor etica l In ter p r eta tion of Th eir
Electr och em ica l a n d Electr on ic P r op er ties Ba sed on
Den sity F u n ction a l Ca lcu la tion s
Sonia Pe´rez,† Concepcio´n Lo´pez,*,† Amparo Caubet,† Ramon Bosque,†
Xavier Solans,‡ Merce` Font Bard´ıa,‡ Anna Roig,§ and Elies Molins§
Departament de Qu´ımica Inorga`nica, Facultat de Quı´mica, Universitat de Barcelona,
Martı´ i Franque`s 1-11, 08028-Barcelona, Spain, Departament de Cristal‚lografia,
Mineralogia i Dipo`sits Minerals, Facultat de Geologia, Universitat de Barcelona,
Martı´ i Franque`s s/ n, 08028-Barcelona, Spain, and Institut de Cie`ncia de Materials de
Barcelona (ICMAB-CSIC), Campus de la Universitat Auto`noma de Barcelona,
08193-Bellaterra, Spain
Received J uly 3, 2003
The synthesis of the novel ferrocenyl Schiff base [(η5-C5H5)Fe{(η5-C5H4)CHdN(C6H4-2-
SMe)}] (1c) and the study of its reactivity versus palladium(II) or platinum(II) salts are
reported. These studies have allowed us to isolate and characterize [M{[(η5-C5H3)CHdN(C6H4-
2-SMe)]Fe(η5-C5H5)}Cl] {with M ) Pd (2c) or Pt (3c)}, which are the first examples of
cyclopallada- and cycloplatinated compounds containing a mer-terdentate [C(sp2, ferrocene),
N, S]- ligand. Mo¨ssbauer spectroscopic studies and the X-ray crystal structures of 1c-3c
are reported. The crystal structures of 2c and 3c confirmed the mode of binding of the ligand
and revealed that the molecules are associated in pairs, which interact by C-H‚‚‚π
interactions forming a chain that stacks along the [101] plane. Electrochemical studies, based
on cyclic voltammetry, reveal that the ease with which the oxidation of the ferrocenyl moiety
occurs increases according to the sequence 1c < 2c < 3c. Molecular orbital calculations at
a DFT level have also been carried out to rationalize the influence of the nature of the Pd-
(II) (in 2c) or Pt(II) in (3c) on the electrochemical properties of these compounds, and
theoretical studies using time-dependent density functional theory (TD-DFT) calculations
have also been carried out in order to assign the bands observed in the electronic spectra of
the cyclometalated compounds.
In tr od u ction
A wide variety of pallada- and platinacycle complexes
having monoanionic bidentate [C,N]- or [C,S]- or ter-
dentate [C,N,N′]- or [X,C,X]- (X ) N, S, or P) ligands
and a σ[M-C(sp2, aryl)] or to a lesser extent a σ(M-
Csp3) bond (M ) Pd or Pt) have been described in the
literature.8-12 Some applications of compounds of this
type as building blocks for the synthesis of macromol-
ecules,5 as precursors for the synthesis of organic as well
as organometallic compounds,4a-d,6 or even in homoge-
Transition metal complexes derived from polydentate
ligands containing two or more donor atoms with
different hardness have attracted great interest due to
their potential hemilability,1 which may be particularly
important in view of their potential applications in
different areas, including homogeneous catalysis.2 Be-
sides that, during the past decade the importance and
utility of a wide variety of cyclopalladated and cyclo-
platinated complexes3 in several fields has also in-
creased considerably.4-12
(4) For a general overview concerning the applications of cyclopal-
lada- and cycloplatinated complexes, see for instance: (a) Klaus, A. J .
In Modern Colorants: Synthesis and Structure; Peters, A. E., Freeman,
H. S., Eds.; Blackie Academic: London, U.K., 1995; Vol. 3. (b) Pfeffer,
M. Rec. Trav. Pays-Bas 1990, 109, 567, and references therein. (c)
Ryabov, A. D. Synthesis 1985, 233, and references therein. (d) Spencer,
J .; Pfeffer, M. Adv. Metal-Org. Chem. 1998, 6, 103, and references
therein. (e) Torraca, K. E.; Kuwabe, S. I.; Buchwald, S. L. J . Am. Chem.
Soc. 2000, 122, 12907. (f) Shelby, Q.; Kataoka, N.; Mann, G.; Hartwig,
J . J . Am. Chem. Soc. 2000, 122, 10718. (g) Serrano, J . L., Ed.
Metallomesogens. Synthesis, Properties and Applications; VCH: Wein-
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111, 117, and references therein. (j) Hambley, T. Coord. Chem. Rev.
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† Departament de Qu´ımica Inorga`nica, Universitat de Barcelona.
‡ Departament de Cristal‚lografia, Mineralogia i Dipo`sits Minerals,
Universitat de Barcelona.
§ Institut de Cie`ncia de Materials de Barcelona.
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C. S.; Weinberger, D.; Mirkin, C. A. Prog. Inorg. Chem. 1999, 48, 232.
(2) (a) J olly, P. W., Wilke, G., Kermann, W. A., Cornils, B., Eds.
Applied Homogeneous Catalysis with Organometallic Compounds;
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10.1021/om030520d CCC: $27.50 © 2004 American Chemical Society
Publication on Web 12/19/2003

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 225
neous catalysis have been reported.4e,h,9b In addition,
several examples of cyclopalladated as well as cyclo-
platinated complexes having interesting photooptical
properties have been reported in the last five years,7
and some of them have been used as luminiscent centers
in the design of organic light-emiting diodes (OLEDs).8
However, despite the potential interest of the pres-
ence of three atoms [C, N, and X] of different hardness13
bound to the metal, and the prochiral nature of the
ferrocenyl moiety in the cyclometalation process, com-
pounds containing “M[C(sp2, ferrocene), N, X]” (M ) Pd
or Pt and X ) N′ or S) cores are scarce.14-16 Recently a
few pallada- and platinacycles having [C,N,N′]- groups
derived from [(η5-C5H5)Fe{(η5-C5H4)CHdN(CH2)nNMe2]
(n ) 2 or 3) have been reported,14,15 but to the best of
Ch a r t 1
our knowledge, related derivatives containing mer-
terdentate [C(sp2, ferrocene), N, S] ligands are
not known. The cyclopalladation of [(η5-C5H5)Fe{(η5-
C5H4)CHdN[CH(CO2Me)(CH2)2SMe]}] has been previ-
ously studied, but in this case the activation of the
σ(Csp3-H) bond took place, giving [Pd{(η5-C5H5)Fe[(η5-
C5H4)CHdN{C(CO2Me)(CH2)2SMe}]}Cl]2 (Chart 1), in
which each palladium atom is bound to a chlorine, the
imine nitrogen, the stereogenic carbon atom, and the
sulfur atom of half of the molecule.16b
As a part of a project aimed at the synthesis and study
of metallacycles containing [C,N,S]- terdentate groups,
in the last two years we have described a few pallada-
and platinacycles arising from the activation of the ortho
σ[C(sp2, phenyl)-H] bond of the thioimines C6H5CHd
NCH2CH2SEt (1a ) and C6H5CHdN(C6H4-2-SMe) (1b)
(Figure 1).17,18 Among these palladium(II) and platinum-
(II) complexes (2a ,2b and 3a ,3b in Figure 1), compounds
3a and 3b are particularly interesting due to their
luminescence in solution.18b To the best of our knowl-
edge and despite the great proclivity of N-donor ferro-
cenyl ligands to undergo cyclometalation,19,20 palladium-
(II) and platinum(II) complexes having mer-terdentate
[C(sp2, ferrocene), N, S]- ligands are still unknown. In
view of these facts and our previous experience on
cyclometalation of N-donor ferrocenyl ligands,14,20 we
were prompted to extend our studies to the novel
ferrocenyl Schiff base [(η5-C5H5)Fe{(η5-C5H4)CHdN(C6H4-
2-SMe)}] (1c) (Figure 1), which can be visualized as
derived from 1b by replacement of the phenyl ring
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226 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
F igu r e 2. ORTEP plot of the two nonequivalent molecules
found in the crystal structure of the ligand [(η5-C5H5)Fe-
{(η5-C5H4)CHdN(C6H4-2-SMe)}] (1c). Hydrogen atoms are
not shown.
F igu r e 1. Schematic view of the thioimines of general
formulas C6H5CHdN-R′ with R′ ) CH2CH2SEt (1a ) or
C6H4-2-SMe (1b), their cyclopallada- and cycloplatinated
complexes (2a ,b and 3a ,b) reported before, and the novel
complexes prepared in this work (1c-3c).
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Tw o Non equ iva len t Molecu les F ou n d
in th e Cr ysta l Str u ctu r e of Com p lex
[(η5-C5H5)F e{(η5-C5H4)CHdN(C6H4-2-SMe)}], 1c
(sta n d a r d d evia tion p a r a m eter s a r e given in
p a r en th eses)
bound to the imine carbon by a ferrocenyl fragment. In
this work we describe the synthesis, characterization,
molecular structures, and the study of the electrochemi-
cal and spectroscopic properties of 1c and the cyclopal-
ladated and cycloplatinated complexes [M{[η5-C5H3)-
CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] {with M ) Pd (2c)
or Pt (3c)}, shown in Figure 1, which are the first
examples of palladium(II) and platinum(II) complexes
having a terdentate [C(sp2, ferrocene), N, S]- ligand.
Bond Lengths
S(1)-C(17)
S(1)-C(18)
N(1)-C(11)
N(1)-C(12)
C(10)-C(11)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
Fe-C1
1.765(3)
1.800(4)
1.268(4)
1.415(4)
1.454(4)
1.385(5)
1.387(5)
1.371(6)
1.392(5)
1.390(4)
2.03(11)
1.40(4)
S(1A)-C(17A)
S(1A)-C(18A)
N(1A)-C(11A)
N(1A)-C(12A)
C(10A)-C(11A)
C(12A)-C(13A)
C(13A)-C(14A)
C(14A)-C(15A)
C(15A)-C(16A)
C(16A)-C(17A)
Fe-Ca
1.755(3)
1.774(5)
1.268(4)
1.411(4)
1.452(4)
1.390(5)
1.373(5)
1.381(6)
1.375(6)
1.396(4)
2.04(7)
C-Ca
C-Ca
1.412(9)
Resu lts a n d Discu ssion
Bond Angles
Th e Liga n d . Compound [(η5-C5H5)Fe{(η5-C5H4)CHd
N(C6H4-2-SMe)}] (1c) was prepared according to the
general procedure described before for the syntheses of
ferrocenyl Schiff bases of general formula [(η5-C5H5)-
Fe{(η5-C5H4)CHdN-R′}], where R′ represents a phenyl,
benzyl, or naphthyl group.20 This procedure consists of
the reaction of equimolar amounts of ferrocenecarbal-
dehyde and the corresponding amine in refluxing ben-
zene. The synthesis is usually carried out using a Dean-
Stark apparatus to remove the benzene-water azeotrope
formed in the course of the reaction. For the preparation
of 1c, 2-mercaptoaniline was used and the reaction
yielded deep red crystals suitable for X-ray diffraction
(see below). Compound 1c was also characterized by
elemental analyses, FAB+ mass spectra, and infrared,
visible, and ultraviolet spectroscopy as well as one- and
two-dimensional {NOESY, COSY, HSQC, and HMBC}
NMR spectroscopy. The most outstanding feature ob-
served in the infrared spectrum is the presence of a
C(10)-C(11)-N(1) 122.8(3)
C(11)-N(1)-C(12) 117.6(3)
N(1)-C(12)-C(17) 118.1(3)
C(12)-C(17)-S(1) 116.3(2)
C(10A)-C(11A)-N(1A) 122.2(2)
C(11A)-N(1A)-C(12A) 118.9(2)
N(1A)-C(12A)-C(17A) 118.4(3)
C(12A)-C(17A)-S(1A) 116.0(2)
C(17)-S(1)-C(18) 104.20(19) C(17A)-S(1A)-C(18A) 103.3(2)
a
Average value for the ferrocenyl moiety.
group of three intense bands in the range 1540-1600
cm-1. The band at higher wavenumber is assigned,
according to the literature, to the stretching of the >Cd
N- group, while the remaining two bands are due to
the stretchings of the >CdC< groups of the aromatic
ring. One- and two-dimensional NMR experiments
suggested that only one isomer [anti-(E) form)] of 1c was
present in solution.
The two nonequivalent molecules (herein after re-
ferred to as A and B) of 1c present in the unit cell
together with the atom labeling schemes are depicted
in Figure 2, and a selection of bond lengths and angles
is presented in Table 1.

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 227
The >CdN- bond lengths [1.268(4) Å in the two
molecules] are similar to those found for related Schiff
bases of general formula [(η5-C5H5)Fe{(η5-C5H4)CHdN-
R}], with R ) phenyl, benzyl, or naphthyl groups.20 The
values of the torsion angles C(10)-C(11)-N(1)-C(12)
[177.79°] and C(10A)-C(11A)-N(1A)-C(12A) [179.13°]
indicate that in the two molecules the imine adopts the
anti-(E) form.
Bond lengths and angles of the ferrocenyl moiety
agree with those reported for most ferrocene deriva-
tives.21 In the two molecules the pentagonal rings of the
ferrocenyl fragments are planar and nearly parallel (tilt
angles: 1.41° and 1.22° for the two molecules), and they
deviate by ca. 1.47° and 8.66° from the ideal eclipsed
conformation.
In the crystal the two nonequivalent molecules are
packed in such a way that the distance between the
sulfur [S(1) or S(1A)] of a given molecule and one of the
hydrogen atoms of the methyl groups [H(18A) or H(18)]
of a close molecule [2.21(6) and 2.20(5) Å] is indicative
of a weak C-H‚‚‚S intermolecular interaction. Besides
that, the distances between (a) the C(14)-H(14) bond
of one molecule and the ring defined by the set of atoms
[C(1A)-C(5A)] [2.917Å] and (b) the C(5)-H(5) bond and
the phenyl ring of a close nonequivalent molecule [2.947
Å] suggest the existence of C-H‚‚‚π intermolecular
interactions.22 Similar interactions have also been re-
ported for other ferrocene-based heterobimetallic com-
plexes.23
F igu r e 3. View of the arrangement of the two types of
nonequivalent molecules of ligand 1c in the crystal.
Sch em e 1a
It is generally recognized that although C-H‚‚‚π
interactions have energies that are in the range 2-20
kJ /mol,24 they play an important role in the assembly
of small molecules to form supramolecular struc-
tures.22,25 In the crystals of 1c four discrete molecules
[two of each type] are associated through the two types
of intermolecular interactions [C-H‚‚‚π and C-H‚‚‚S]
mentioned above (Figure 3).
Cyclopalladation an d Cycloplatin ation of Ligan d
1c. When ligand 1c was treated with equimolar amounts
of Na2[PdCl4] and Na(CH3COO)‚3H2O in methanol at
room temperature for 24 h, a deep blue solid formed
(Scheme 1). Its characterization data (see below) were
consistent with those expected for [Pd{[η5-C5H3)CHd
N(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] (2c). This compound
arises from the coordination of the two heteroatoms of
the ligand (N and S) and the activation of the σ[C(sp2,
ferrocene)-H] bond, thus indicating that in this case
the ligand acts as a [C(sp2, ferrocene), N, S]- terdentate
group. The crystal structure of this complex (vide infra)
confirms these results.
a
(i) Equimolar amounts of Na2[PdCl4] and sodium acetate
in methanol at room temperature. (ii) SiO2 column chroma-
tography. (iii) Equimolar amount of cis-[PtCl2(PhCN)2] in
refluxing toluene.
agent.19,27 In particular, this was the method used to
prepare the first platinacycle having a terdentate [C(sp2,
ferrocene), N, N′]- ligand.15 In view of this we decided
to study whether the treatment of ligand 1c with cis-
[PtCl2(dmso)2] in refluxing methanol could lead to the
cycloplatinated derivative. When stoichiometric amounts
of ligand 1c and cis-[PtCl2(dmso)2] were refluxed in
methanol (HPLC-grade) for varying refluxing times
(from 30 min to 3 days), the formation of metallic
platinum was detected and the 1H NMR spectrum of
the crude of the reaction indicated the formation of large
amounts of ferrocenecarboxaldehyde, which may form
through a hydrolysis process. This is similar to the
Recently, some authors have demonstrated the ad-
vantages of using cis-[PtCl2(dmso)2]26 as metallating
(21) Allen, T. H.; Kennard, O. Chem. Des. Automat. News 1993, 8,
128.
(22) Nishio, N.; Hirota, M.; Umezakwo, Y. The CH‚‚‚‚π Interaction;
Wiley-VCH: New York, 1988.
(23) Dong, G.; Yu-jing, L.; Chung-ying, D.; Hong, M.; Qing-jin, M.
Inorg. Chem. 2003, 42, 2519.
(24) (a) Steiner, T.; Starikov, E. B.; Tamm, M. J . Chem. Soc., Perkin
Trans. 2 1996, 67. (b) Steiner, T.; Stariko, E. B.; Amado, A. M.; Texeira-
Dias, J . J . C. T. J . Chem. Soc., Perkin Trans. 2 1995, 1321.
(25) (a) Lehn, J . M. Supramolecular Chemistry; VCH: Weinheim,
Germany, 1995. (b) Fabbrizi, L.; Poggi, A. Transition Metals in
Supramolecular Chemistry; Kuwer: Dordecht, Germany, 1994; Vol.
448. (c) Eddaouli, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, M.;
O’Keefe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319.
(26) Price, J . H.; Williamson, A. N.; Schramm, F. R.; Wayland, B.
Inorg. Chem. 1972, 11, 1280.
(27) (a) Ryabov, A. D.; Payanskina, I. M.; Polyakov, V. A.; Fischer,
A. Organometallics 2002, 21, 1633. (b) Wu, J . Y. J .; Ding, L.; Wang,
H. X.; Liu, Y. H.; Yuan, H. Z.; Mao, X. A. J . Organomet. Chem. 1997,
535, 49.

228 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
results obtained when equimolar amounts of cis-[PtCl2-
(dmso)2] and ligand 1b (which can be visualized as
derived from 1c by replacement of the ferrocenyl moiety
by a phenyl ring) were refluxed.18b Since this strategy
failed to achieve the synthesis of the platinacycle, we
decided to replace (a) the starting platinum(II) reagent
by cis-[PtCl2(PhCN)2] and (b) the methanol by a non-
protic solvent such as toluene. When 1c was treated
with the stoichiometric amount of cis-[PtCl2(PhCN)2] in
refluxing toluene, the initial red color of the reaction
mixture changed gradually to give a deep green solution.
After a refluxing period of 5.5 h, the reaction mixture
was filtered out and evidence of the formation of a small
platinum mirror on the bottom of the reaction flask was
detected. The concentration of the filtrate and the
workup of an SiO2 column led to small amounts of
ferrocenecarboxaldehyde and a deep green solid, whose
characterization data were consistent with those ex-
pected for [Pt{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-
C5H5)}Cl] (3c), which is formally identical to 2c except
for the nature of the metal ion.
F igu r e 4. Molecular structure and atom-labeling scheme
for [Pd{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] (2c).
Hydrogen atoms have been omitted for clarity.
Ch a r a cter iza tion of Com p ou n d s 2c a n d 3c. Com-
pounds 2c and 3c were characterized by the usual
techniques: elemental analyses, FAB+ mass spectrom-
etry, infrared, one-, and two-dimensional NMR spec-
troscopy, and X-ray diffraction (vide infra). The most
relevant feature observed in the infrared spectra of 2c
and 3c is the shift of the band due to the asymmetric
stretching of the functional >CdN- to lower frequen-
cies than for 1c. This trend, also reported for related
cyclopalladated and cycloplatinated complexes14,17-19,28-30
derived from aldimines and ketimines, suggests the
binding of the imine nitrogen to the palladium(II) (in
2c) or the platinum(II) (in 3c).
Proton and 13C{1H} NMR data for compounds under
study are presented in the Experimental Section. One-
and two-dimensional NMR spectra {HSQC and HMBC}
of 2c and 3c provided conclusive evidence of the mode
of binding of the ligand 1c in the metal complexes. In
1H NMR spectra of 2c and 3c the signals due to the
protons of the >CHdN- and the SMe moieties ap-
peared downfield shifted when compared with the free
ligand, and for 3c these resonances exhibited the typical
satellites due to coupling with the 195Pt-nucleus, thus
suggesting the coordination of the imine nitrogen and
the sulfur to the M(II) ions. In addition, a group of four
signals of relative intensities 5:1:1:1 was also observed
in the region 4.0-5.5 ppm, which is consistent with the
typical pattern reported for cyclopalladated and cyclo-
platinated complexes containing a [C(sp2, ferrocene), N]-
ligand.15,19,27b,30
F igu r e 5. ORTEP plot of the molecular structure of [Pt-
{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] (3c). Hy-
drogen atoms have been omitted for clarity.
2c) and 91.8 ppm (for 3c)], the imine carbon {δ ) 167.1
(for 2c) and 167.7 ppm (for 3c)}, and the methyl carbon
of the thioether group {δ ) 25.4 (for 2c) and 26.8 ppm
(for 3c)} when compared to those of the free ligand
{δ(C2) ) 69.3 ppm, δ(>CdN-) ) 161.4 ppm and δ(Me)
) 14.7 ppm}, in good agreement with the results
reported for related pallada- and platinacyles reported
before.14,15,18, 27b,30
The 195Pt{1H} NMR spectrum of 3c showed one signal
at δ ) -3488 ppm, which is consistent with the range
expected for complexes containing a [(C,N,S,Cl] environ-
ment around the platinum(II).18,31,32 According to the
literature,31 an upfield shift of the 195Pt{1H} NMR
chemical shift is related to a strong donor interaction,
since compounds 3b and 3c differ only in the nature of
the group bound to the imine nitrogen (a phenyl in 3b
or a ferrocenyl fragment in 3c); the differences observed
in their 195Pt NMR spectra (δ ) -3716 ppm for 3b18b
and δ ) -3488 for 3c) can be ascribed to different donor
abilities of the (C,N,S)- terdentate group.
The most relevant feature observed in the 13C{1H}
NMR spectra of 2c and 3c is the downfield shift of the
signals due to the metalated carbon, C2 {δ ) 107.4 (for
Descr ip t ion of t h e Molecu la r St r u ct u r es of
[M{[(η5-C5H 3)CH dN(C6H 4-2-SMe)]F e(η5-C5H 5)}Cl]
{w ith M ) P d (2c) or P t (3c)}. The molecular
structures of 2c and 3c together with their atom-
labeling schemes are shown in Figures 4 and 5, respec-
tively, and a selection of bond lengths and angles as well
as other relevant structural parameters are presented
in Table 2.
(28) (a) Onue, H.; Moritani, I. J . Organomet. Chem. 1972, 43, 431.
(b) Onue, H.; Moritani, K. Bull. Chem. Soc. J pn. 1970, 43, 3480.
(29) (a) Albert, J .; Granell, J .; Sales, J .; Font-Bard´ıa, M.; Solans, X.
Organometallics 1995, 14, 1393. (b) Benito, M.; Lo´pez, C.; Solans, X.;
Font-Bard´ıa, M. Tetrahedron: Asymm. 1998, 9, 4219. (c) Vila, J . M.;
Gayoso, E.; Pereira, T.; Marin˜os, M.; Mart´ınez, J .; Ferna´ndez, J . J .;
Ferna´ndez, A.; Lo´pez-Torres, M. J . Organomet. Chem. 2001, 637-639,
577.
(30) (a) Wu, Y. J .; Cui, X.; Du, C. X.; Wang, W. L.; Guo, R. Y.; Chen,
R. F. J . Chem. Soc., Dalton Trans. 1998, 3727. (b) Caubet, A.; Lo´pez,
C.; Bosque, R.; Solans, X.; Font-Bard´ıa, M. J . Organomet. Chem. 1999,
577, 292. (c) Wu, Y. J .; Ding, L.; Wang, H. X.; Liu, Y. H.; Yuan, H. Z.;
Mao, X. A. J . Organomet. Chem. 1997, 535, 49.
(31) Pregosin, P. S. Coord. Chem. Rev. 1982, 44, 247.
(32) (a) Riera, X.; Lo´pez, C.; Caubet, A.; Moreno, V.; Solans, X. Eur.
J . Inorg. Chem. 2001, 2135. (b) Ding, L.; Wu, Y. J .; Zhou, D. P.
Polyhedron 1998, 17, 1725.

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 229
Ta ble 2. Selected Bon d Len gth s (Å), An gles (d eg),
a n d Oth er Releva n t Str u ctu r a l P a r a m eter s for
Com p ou n d s [M{[(η5-C5H3)CHdN(C6H4-2-SMe)]-
F e(η5-C5H5)}Cl], M ) P d (2c) or P t (3c)
Each molecule contains a [5,5,5,6] tetracyclic system
formed by the metalated pentagonal ring of the ferro-
cenyl fragment, a five-membered pallada- (in 2c) or
platinacycle (in 3c), a chelate ring formed by the
coordination of the two heteroatoms (N and S) of the
ligand to the metal, and the aryl group.
In the two cases, the five-membered metallacycle,
which is defined by the atoms C(6), C(10), C(11), N and
the metal ion, is nearly planar38 and contains the >Cd
N- functional group (endocyclic). In the two structures,
the >CdN- bond lengths are larger than the average
value for the two nonequivalent molecules of ligand 1c
[1.268(4) Å] present in the crystal structure, and the
variations observed in the >CdN- bond lengths of
1.296(4) and 1.326(11) Å in 2c and 3c, respectively, may
be related to the different effect produced by the binding
of the palladium(II) (in 2c) or the platinum(II) (in 3c)
to the imine nitrogen.
The value of the torsion angles defined by the atoms
C(10), C(11), N, and C(12) are 178.99° in 2c and
179.26°in 3c, in good agreement with the anti-(E)
conformation of the ligand in these compounds.
In the two structures the five-membered chelate rings
formed by the binding of the palladium (in 2c) or
platinum (in 3c) to the nitrogen and sulfur atoms have
an envelope-like conformation.
2c
3c
M ) Pd
M ) Pt
Selected Bond Lengths
1.978(5)
M-C(6)
1.985(10)
1.998(7)
2.302(4)
2.328(3)
1.795(9)
1.821(11)
1.326(11)
1.430(11)
1.396(12)
1.408(14)
1.444(15)
2.037(17)
1.417(23)
M-N(1)
M-Cl
2.020(3)
2.2851(14)
2.3653(11)
1.776(4)
1.805(5)
1.296(4)
1.408(4)
1.391(5)
1.417(5)
1.417(7)
M-S
S-C(17)
S-C(18)
N(1)-C(11)
N(1)-C(12)
C(12)-C(17)
C(11)-C(10)
C(10)-C(6)
Fe-Ca
2.031(9)
1.409(12)
C-Ca
Selected Bond Angles
84.72(8)
S-M-N(1)
85.6(2)
80.8(4)
96.3(4)
97.60(13)
122.9(8)
N(1)-M-C(6)
C(6)-M-Cl
Cl-M-S
81.38(16)
95.52(15)
98.83(6)
124.9(3)
C(11)-N-C(12)
Other relevant parameters
Twist angle (in deg.)
Tilt angle (in deg.)
1.8
0.92
3.5350
2.2
0.89
3.5761
Fe...M distance (in Å)
a
The phenyl rings are planar and form angles of ca.
9.99° (for 2c) and 9.78° (for 3c) and 4.99° (for 2c) and
8.03° (for 3c) with the coordination plane of the metal
and with the mean plane of the metalated C5H3 ring,
respectively.
Bond lengths and angles of the ferrocenyl moiety
agree with those reported for most ferrocene deriva-
tives.21 The two pentagonal rings are planar39 and
nearly parallel (tilt angles 0.93° and 0.89° for 2c and
3c, respectively), and they deviate by ca. 1.8° in 2c or
2.2° in 3c from the ideal eclipsed conformation.
The separation between the Fe and the Pd(II) [3.5350
Å] in 2c or Pt(II) in 3c [3.5761 Å] is greater than the
sum of their van der Waals radii,40 thus suggesting that
there is no direct interaction between the two metal
ions.
Average value for the ferrocenyl unit.
In both cases the structures contain molecules of
[M{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] {with
M ) Pd (2c) or Pt (3c)}, in which the ligand binds to
the metal ion through the sulfur, the nitrogen, and the
C(6) atom of the ferrocenyl moiety, thus confirming the
results obtained by NMR spectroscopy, which suggested
a [C(sp2, ferrocene), N, S] mode of binding of the ligand
in the metal complexes. The remaining coordination site
is occupied by a chlorine. The palladium(II) in 2c or the
Pt(II) in 3c are in a sligthly distorted square-planar
environment.33
The Pd-S and Pt-S bond lengths [2.3653(11) Å (in
2c) and 2.328(3) Å (in 3c)] are clearly greater than the
value usually reported for palladium(II) and platinum-
(II) thioether derivatives.34,35 This variation can be
explained in terms of the strong trans-influence of the
metalated carbon.36 In general terms, all the M-ligand
(M ) Pd in 2c or Pt in 3c) bond distances and angles
are similar to those found in 2a ,b, 3a ,b,17,18 or [Pd{(4-
Cl)C6H3)CHdNCH2CH2SEt}Cl].37
In the crystals of 2c and 3c the molecules of [M{[(η5-
C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] {with M )
Pd (2c) or Pt (3c)} are associated in pairs, forming head-
to-tail dimers (Figure 6). Each molecule of the dimer is
related to its partner by a center of inversion. For this
arrangement of groups in 2c and 3c the sulfur of one
molecule lies over the imine bond of the other molecule
of the dimeric unit and vice versa. In 2c the S‚‚‚C and
(33) The least-squares equation of the plane defined by the atoms
N, S, Cl, and C(6) in 2c is (0.3171)XO + (-0.7093)YO + (0.6296)ZO )
-5.8470 (deviations from the plane: Cl, 0.077; S, -0.083; N, 0.112;
and C(6), -0.106 Å) and for 3c (0.2899)XO + (-0.7029)YO + (0.6495)ZO
) -1.065 (deviations from the plane: Cl, 0.078; S, -0.087; N, 0.115;
and C(6), -0.106 Å).
(34) (a) Al-Shami, E. M.; Abru-Surrah, A. S.; Kling, M.; Hobali, H.
A. Z. Anorg. Allg. Chem. 2002, 628, 1433. (b) Go´mez, M.; J ansat, S.;
Muller, G.; Maestro, M. A.; Mahia, J . Organometallics 2002, 21, 1077.
(c) Battaglia, L. P.; Corradi, A. B.; Palmier, C. G.; Nardelli, M.; Tany,
M. E. V. Acta Crystallogr. Sect. B 1973, 29, 762. (d) Enders, D.; Peters,
R.; Runsink, J .; Bats, J . W. Org. Lett. 1999, 1, 1863. (e) Okoroafor, M.
O.; Ward, D. L.; Brubakerjr, C. H. Organometallics 1988, 7, 1504.
(35) (a) Wheman, E.; van Koten, G.; Knaap, C. T.; Ossor, H.; Pffefer,
M.; Spek, A. L. Inorg. Chem. 1988, 27, 4409. (b) Orpen, A. G.; Brammer,
L.; Allen, F. H.; Kennard, O.; Watson, D. G.; Taylor, R. J . Chem. Soc.,
Dalton Trans. 1989, S1.
(37) Ferna´ndez, A.; Va´zquez-Diaz, D.; Ferna´ndez, J . J .; Lo´pez-
Torres, M.; Sua´rez, A.; Castro-J uiz, S.; Ortigueira, J . M.; Vila, J . M.
New J . Chem. 2002, 26, 105.
(38) In 2c and 3c, the least-squares equations of the planes defined
by the atoms C(6), C(10), C(11), N, and M are as follows: for 2c (M )
Pd) is (0.2624)XO + (-0.6680)YO + (0.6964)ZO ) -5.6281 (deviations
from the plane: Pd, 0.004; C(6), 0.008; C(10), 0.006; C(11), -0.020;
and N, -0.020 Å) and for 3c (M ) Pt) (0.2449)XO + (-0.6579)YO +
(0.7122)ZO ) -1.0097 (deviations from the plane: Pt, 0.010; C(6),
-0.006; C(10), -0.003; C(11), -0.016; and N, -0.017 Å).
(39) The least-squares equations of the planes defined by the sets
of atoms [C(1)-C(5)] and [C(6)-C(10)] are (0.2699)XO + (-0.7019)YO
+ (0.6591)ZO ) 2.0374 and (0.2699)XO + (-0.7019)YO + (0.6591)ZO
) 2.0374 for 2c and (0.2591)XO + (-0.7058)YO + (0.6593)ZO )
-3.0460 and (0.2588)XO+ (-0.7112)YO + (0.6537)ZO ) -1.4580 for
3c.
(36) (a) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem.
Rev. 1973, 10, 335. (b) Elder, R. C.; Curea, R. D. P.; Morrison, R. F.
Inorg. Chem. 1976, 15, 1623.
(40) (a) Bondi, A. J . Phys. Chem. 1964, 64, 441. (b) Kitaigorodskii,
A. I. Molecular Crystals and Molecules; Academic Press: London, U.K.,
1973.

230 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
F igu r e 6. View of the arrangement of the molecules of
compound 2c in the crystal. A similar distribution of
structural units is also found for 3c.
S‚‚‚N intermolecular separations are 3.415(4) and
3.440(3) Å, respectively, while in 3c, they are equal to
3.458(1) Å.
Several authors have postulated that for cycloplati-
nated and cyclopalladated complexes having terdentate
ligands, the planarity of the terdentate group, the
π-stacking of the aryl rings of the ligand, and the
intermolecular M‚‚‚M separation are particularly im-
portant in view of their potential photoluminiscent
properties.7,41 In these compounds the M‚‚‚M intradimer
separation in 2c is larger than the sum of the van der
Waals radii of the palladium(II) atoms,40 while for 3c
the distance between the two platinum(II) atoms of the
dimeric unit [4.490(4) Å] is clearly larger than the value
reported for 2c [4.216(3) Å] and related platinacycles
holding [C(sp2,aryl), N, N′] and [C(sp2, aryl), N, S]-
terdentate ligands for which intramolecular Pt‚‚‚Pt
interactions have been proposed.7e,41
F igu r e 7. Mo¨ssbauer spectra of the free ligand 1c and
compounds 2c and 3c.
Another outstanding feature of the structures of 2c
and 3c is the existence of C-H‚‚‚π(ring) interactions22
between one of the hydrogen atoms of the methyl group
bound to the sulfur {H(15)} of one of the molecules
forming the dimers and the C5H3 ring of a neighboring
molecule belonging to a different dimer. This leads to a
chain that stacks along the [101] plane.
Ta ble 3. Ir on -57 Mo1ssba u er Hyp er fin e P a r a m eter s
(a t 80 K): Isom er Sh ift, δ, Qu a d r u p ole Sp littin g,
∆Eq, a n d F u ll-Wid th a t Ha lf-Heigth , Γ (in m m s-1
(sta n d a r d d evia tion p a r a m eter s a r e given in
p a r en th eses)
)
compound
δ
∆Eq
Γ
Mo1ssba u er Sp ectr a . In all cases, 57Fe Mo¨ssbauer
spectra of the compounds consist of a single quadrupole
1c
2c
3c
0.502(2)
0.485(2)
0.495(2)
2.2541(4)
2.087(4)
2.06(2)
0.361(6)
0.33(1)
0.33(3)
(41) (a) Ratilla, E.; Scott, B. K.; Moxness, M. S.; Kostic, N. M. Inorg.
Chem. 1990, 29, 918. (b) Bailey, J . A.; Miskovskii, V. M.; Gray, H. B.
Inorg. Chem. 1993, 21, 369. (c) J ovanovic, B.; Manojlovic, L. J .; Muir,
K. J . Chem. Soc., Dalton Trans. 1972, 1178. (d) Constable, E. C.;
Henney, R. P. G.; Leese, T. A.; Tocher, D. A. Chem. Commun. 1990,
513. (e) Lai, S. W.; Lam, H. W.; Lu, W.; Cheung, K. K.; Chen, C. M.
Organometallics 2002, 21, 226. (f) Wong, K. H.; Chan, M. C. W.; Che,
C. M. Chem. Eur. J . 1999, 5, 2845. (g) Lu, W.; Mi, B. X.; Chan, M. C.
W.; Hui, Z.; Zhu, N.; Lee, S. T.; Che, C. M. Chem. Commun. 2002,
206. (h) Lu, W.; Zhu, W.; Che, C. M. Chem. Commun. 2002, 900.
doublet (Figure 7), indicating a unique iron site. The
isomer shifts, δ, quadrupole splittings, ∆Eq, and line
widths, Γ, are summarized in Table 3.
It is well known that for substituted ferrocene deriva-
tives electron-donating substituents cause an increase
in the quadrupole splittings relative to ferrocene, whereas
electron-pulling groups produce a decrease in the ∆Eq

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 231
parameter.42 For the free ligand, the quadrupole split-
ting is smaller than that of ferrocene43 (∆Eq ) 2.37 mm
s-1 at room temperature or 2.41 at 80 K) and of the
Schiff base [(η5-C5H5)Fe{(η5-C5H4)CHdN(C6H5)}]44 (∆Eq
) 2.28 mm s-1), which can be visualized as derived from
1c by replacement of the SMe group by a hydrogen, thus
indicating that the electron-withdrawing character of
the substituent increases according to the sequence
H , -CHdN(C6H5) < -CHdN(C6H4-2SMe).
The ∆Eq values for 2c and 3c are smaller than that
of the free ligand, and the extent of this variation seems
to be dependent on the “MCl” (M ) Pd or Pt) unit, since
the diference observed in the q.s. values when compared
with that of the parent ligand [∆ ) ∆Eq(ligand) - ∆Eq-
(complex)] is greater for 3c than for 2c, thus suggesting
a greater electron-pulling contribution of the “PtCl”
moiety.
As a first approach one could expect that the “MCl”
units may pull electronic density through three different
pathways: (a) directly from the C5H3 ring, (b) through
the imine nitrogen, or (c) a combination of both.
The comparison of the structural data of 2c and 3c
presented in Table 2 reveals that the differences ob-
served in the M-C(6) bond distance do not clearly
exceed 3σ. However, the C(11)-N(11) bond length
increases in the order 1c [1.268(4) Å] < 2c [1.296(4) Å]
e 3c [1.326(11) Å], thus suggesting that the formation
of the cyclometalated complexes reduces the strength
of the imine bond.
Electr och em ica l a n d Sp ectr oscop ic Stu d ies. In
a first attempt to elucidate the effect produced by the
coordination of the Schiff base to the palladium(II) or
platinum(II) upon the electronic environment of the
iron(II), we decided to carry out electrochemical studies
and to register the ultraviolet-visible spectra of 1c-
3c.
Electrochemical data for compounds under study were
obtained from cyclic voltammetric studies of freshly
prepared solutions (10-3 M) in acetonitrile using (Bu4N)-
[PF6] as supporting electrolyte. Cyclic voltammograms
of 1c-3c are presented in Figure 8, and the most
relevant electrochemical data are summarized in Table
4.
F igu r e 8. Cyclic voltammograms of the free ligand [(η5-
C5H5)Fe{(η5-C5H4)CHdN(C6H4-2-SMe)}], 1c, and com-
pounds [M{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl]
with M ) Pd (2c) or Pt (3c).
Ta ble 4. Electr och em ica l Da ta : An od ic (Ep a ) a n d
Ca th od ic P oten tia ls (Ep c), Ha lf-Wa ve P oten tia ls
Refer r ed to F er r ocen e E1/2(Fc), a n d Sep a r a tion of
th e P ea k s (∆E) for th e Sa m p les a n d for F er r ocen e
{∆E′} {w h ich w a s u sed a s sta n d a r d } (in m V) for
th e F r ee Liga n d a n d Com p ou n d s
[M{[(η5-C5H3)CHdN(C6H4-2-SMe)]F e(η5-C5H5)}Cl]
w ith M ) P d (2c) or P t (3c) a t a Sca n Sp eed υ ) 10
m V s-1
In all cases, the voltammograms exhibited an anodic
peak with a directly associated reduction in the reverse
scan. In all cases the Ipa/Ipc molar ratio was close to 1.
For the three compounds the experiments were carried
out at different scan rates, υ {from 0.05 to 1.0 V s-1},
and a linear relationship between the Ipa and υ1/ 2 was
obtained in all cases. According to the literature, all
these findings are consistent with those expected for a
simple reversible one-electron-transfer process.45
For the free ligand and complex 2c the ∆E values
(Table 4) depart appreciably from the constant value of
59 mV (theoretically expected for an electrochemically
Epa
Epc
E1/2(Fc)
∆E
∆E’
1c
2c
3c
250
199
72
191
103
6
184
104
39
132
96
66
83
83
86
reversible one-electron-step oxidation-reduction pro-
cess45), suggesting that a structural reorganization
takes place on oxidation. However, it must be stated
that for compounds under study the highest occupied
molecular orbital (HOMO) is not solely iron based. We
will return to this point later on.
The half-wave potentials E1/2 are presented in Table
4. For the free ligand the E1/2 is greater than the values
reported for related ferrocenyl Schiff bases of general
formula [(η5-C5H5)Fe{(η5-C5H4)CHdN-R}], with R )
phenyl groups,46 thus suggesting that the incorporation
of the -SMe group on the ortho site reduces the
proclivity of the iron(II) to oxidize. For 2c, the E1/2(Fc)
value {104 mV} is smaller than that obtained for the
(42) (a) Houlton, A.; Miller, J . R.; Silver, J .; J asim, N.; Ahmet, M.
T.; Axon, T. L.; Bloor, D.; Cross, G. H. Inorg. Chim. Acta 1993, 205,
65. (b) Houlton, A.; Miller, J . R.; Roberts, R. G. M.; Silver, J . J . Chem.
Soc., Dalton Trans. 1991, 467.
(43) Houlton, A.; Bishop, P. T.; Roberts, R. M. G.; Silver, J .;
Herberhold, M. J . Organomet. Chem. 1989, 364, 381.
(44) Bosque, R.; Font-Bard´ıa, M.; Lo´pez, C.; Sales, J .; Silver, J .;
Solans, X. J . Chem. Soc., Dalton Trans. 1994, 747.
(45) Brown, E. R.; Sandifer, J . R. Physical Methods in Chemistry.
Electrochemical Methods; Rossiter, B. W., Hamilton, J . H, Eds.;
Wiley: New York, 1986; Vol. 4, Chapter 4.
(46) Bosque, R.; Lo´pez, C.; Sales, J . Inorg. Chim. Acta 1996, 244,
141.

232 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
Ta ble 5. Exp er im en ta l Visible-Ultr a violet Sp ectr oscop ic Da ta : Wa velen gth s, λi (in n m ), Mola r Extin ction
Coefficien ts, Ei, in Mol-1 d m 2 (in p a r en th eses), Togeth er w ith th e Ca lcu la ted Wa velen gth s (in n m ) a n d th e
Tr a n sition s Th a t Ha ve th e Gr ea ter Con tr ibu tion to th e Given Ba n d for Com p ou n d s
[M{[(η5-C5H3)CHdN(C6H4-2-SMe)]F e(η5-C5H5)}Cl] w ith M ) P d (2c) or P t (3c)
experimental
calculated
compound
λi
ꢀi
λi
transition
assignment
2c
584
3023
586
(HOMO)f(LUMO+3)
(HOMO-1)f(LUMO+3)
(HOMO-3) f (LUMO)
(HOMO-2) f (LUMO)
(HOMO-5) f (LUMO)
(HOMO-4) f (LUMO)
(HOMO) f (LUMO+4)
(HOMO-7) f (LUMO+3)
(HOMO-5) f (LUMO +1)
(HOMO-1) f (LUMO+1)
(HOMO-1) f (LUMO +2)
(HOMO-6) f (LUMO)
(HOMO) f (LUMO+2)
(HOMO-1) f (LUMO+2)
(HOMO-2) f (LUMO)
(HOMO-4) f (LUMO)
(HOMO) f (LUMO+3)
(HOMO-6) f (LUMO)
(HOMO) f (LUMO+1)
4dxz(Pd) f π*
4dyz(Pd) f π*
MPILCTb
435a
449
MPILCTb
428
413
389
369
360
346
MPILCTb
394
359
4753
8826
4dz2(Pd) f π*
4dyz(Pd) f π*
MPILCTb
MPILCTb
MPILCTb
MPILCTb
343
593
MPILCTb
3c
600
3233
5dxz(Pt) f π*
5dyz(Pt) f π*
MPILCTb
454
412
2935
5993
452
430
2
5dz (Pt) f π*
5dyz (Pt) f π*
344
8466
345
342
MPILCTb
MPILCTb
a
b
Shoulder. MPILCT ) metal perturbed intraligand charge transfer transition (π f π*).
free ligand {E1/2(Fc) ) 184 mV}. This finding is in good
agreement with the results obtained for related palla-
dacycles of general formula [Pd{[(η5-C5H3)C(H)dN-R′]-
Fe(η5-C5H5)}Cl(L)] (with R′ ) phenyl, benzyl, or naph-
thyl groups and L ) pyridine or phosphine ligands)46,47
when compared with the corresponding free ligand.
Besides that, the half-wave potential for 3c {E1/2(Fc) )
39 mV} is smaller than that of 2c {E1/2(Fc) ) 94 mV},
thus indicating that the proclivity of the cyclometalated
complexes to oxidize is markedly dependent on the
nature of the central metal ion Pd(II) (in 2c) or Pt(II)
(in 3c). For compounds under study the E1/2(Fc) de-
creases according to the sequence 1c > 2c > 3c, thus
suggesting that the binding of the nitrogen, the sulfur,
and the C2 atom of the ferrocenyl ligand to the platinum-
(II) center (in 3c) produces a greater enhancement of
the proclivity of the ferrocenyl moiety to oxidize than
for the palladium(II) analogue (in 2c).
600 nm (for 3c)], and its position was dependent on the
nature of the M(II) ion. This band was not detected
before in the UV-vis spectra of other ferrocenylketimines
or their cyclometalated derivatives containing [C(sp2,
ferrocene), N]- ligands.
Th eor etica l Ap p r oa ch es to Cla r ify th e In flu en ce
of th e P a lla d iu m (II) a n d P la tin u m (II) in th e Cy-
clom eta la ted Com p lexes u p on th e Electr on ic En -
vir on m en t of th e Ir on (II). As a first attempt to
explain why the cycloplatinated complex 3c is more
prone to undergo oxidation of the Fe(II) than the
palladium(II) analogue, 2c, we decided to undertake
DFT calculations of the free ligand as well as of the two
cyclometalated compounds (2c and 3c). The first step
of the theoretical studies consisted in the optimization
of the geometries, taking the experimental ones (deter-
mined by X-ray diffraction) as input. For each com-
pound, two geometry optimizations have been per-
formed: the first one has been done in vacuo, using the
LANL2DZ basis set,48 while for the second one solvent
effects have been included via the polarizable conductor
calculation model, CPCM;49 in this case the TZV basis
set50 has been used for all the atoms except Pd and Pt,
for which LANL2DZ has been employed.
The ultraviolet-visible spectrum of a 10-5 M solution
of 1c in CH2Cl2 at ca. 20 °C showed two intense bands
at 364 (ꢀ ) 6544) and 464 (ꢀ ) 1262) nm. Their positions
fall in the range reported for related ferrocenylketimines
of general formula [(η5-C5H5)Fe{(η5-C5H4)CHdN-R′}]
with R′ ) substituted phenyl ring20c and have been
attributed to intraligand transitions (ILT) [3d(Fe) f π*
and πfπ*, respectively].
A summary of the results obtained from the spectro-
scopic studies of 10-4 M solutions of 2c and 3c in CH2-
Cl2 at ca. 20 °C is presented in Table 5. In these cases
four absorption bands were observed in the spectrum,
and three of them appeared in the range 300-400 nm.
Previous studies focused on cyclopalladated derivatives
of general formula [Pd{[(η5-C5H3)C(H)dN-R′]Fe(η5-
C5H5)}Cl(L)] (with R′ ) phenyl groups and L ) pyridine
or phosphine), which contain a bidentate [C(sp2, fer-
rocene), N]- ligand, have shown that this sort of
compound also exhibits bands in this region and that
their position is strongly sensitive to changes in the
nature of the neutral L group.47
Although the inclusion of the solvent, as well as the
use of a better basis set, results in a slight improvement
of the geometry, some discrepancies between the ex-
perimental and calculated geometries remain, mainly
in the >CdN- bond length and in the environment
(47) (a) Lo´pez, C.; Bosque, R.; Solans, X.; Font-Bard´ıa, M. New J .
Chem. 1998, 22, 977. (b) Riera, X.; Caubet, A.; Lo´pez, C.; Moreno, V.
Polyhedron 1999, 19, 2555. (c) Lo´pez, C.; Bosque, R.; Solans, X.; Font-
Bard´ıa, M.; Tramuns, D.; Fern, G.; Silver, J . J . Chem. Soc., Dalton
Trans. 1994, 3039.
(48) (a) Hay, P. J .; Wadt, W. R. J . Chem. Phys. 1985, 82, 270. (b)
Wadt, W. R.; Hay, P. J . J . Chem. Phys. 1985, 82, 284. (c) Hay, P. J .;
Wadt, W. R. J . Chem. Phys. 1985, 82, 299. (d) For C, H, and N, the
D95 basis set is used; Dunning, T. H., J r.; Hay, P. J . In Modern
Theoretical Chemistry; Schaefer, H. F., III, Ed.; Plenum Press, New
York, 1976; Vol. 3, p 1.
(49) Barone, V.; Cossi, M. J . Phys. Chem. A 1998, 1995.
(50) (a) Schaefer, A.; Horn, H.; Ahlrichs, R. J . Chem. Phys. 1992,
97, 2571. (b) Schaefer, A.; Huber, C.; Ahlrichs, R. J . Chem. Phys. 1994,
100, 5829.
The spectra of 2c and 3c showed an additional and
symmetric band at lower energies [λ ) 584 (for 2c) and

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 233
The LUMO (Figure 9, D and F) of 2c and 3c is mainly
a combination of a π orbital of the aryl ring, the dyz
2
2
orbital of the M(II) atom, and the dxz, dx -y and dxy
orbitals of the iron.
On the other hand, and in order to elucidate the origin
of the band detected in the UV-vis spectra of 2c and
3c in the range 590-600 nm, we decided to undertake
a study, based on the time-dependent DFT (TD-DFT)
methodology,51 to achieve the assignment of all the
bands detected in the UV-vis spectra of the cyclometa-
lated complexes. After the optimization of the geom-
etries at the B3LYP/LANL2DZ level (see above), the
excitation energies and the corresponding oscillator
strengths were calculated. A summary of the results
obtained from these calculations is presented in Table
5.
In general all the bands arise from a combination of
several transitions, among which those having the
greater contributions are presented in Table 5. The
study of the molecular orbitals involved in these transi-
tions has been very useful to assign the bands, in
particular, to distinguish between those due to intra-
ligand transitions (ILT) and those due to metal to ligand
charge transfer transitions (MLCT).
The position of the band at λ ) 584 nm (for 2c) shifts
to lower energies in the platinum(II) analogue (3c), thus
suggesting a significant character of metal to ligand
charge transfer. The results obtained from the calcula-
tions indicate that these absorption bands are mainly
a combination of two electronic transitions [from (HOMO)
or (HOMO-1) to the (LUMO+3) for (2c) or to the
(LUMO+2) (for 3c)]. Since in the two cases the virtual
orbital is mainly π* ferrocene in character with a small
contribution of the aryl ring, the observed absorption
bands can be attributed predominantly to a dxz(M) or
dyz(M)fπ* (ligand) charge transfer transition. The
comparison of the UV-vis spectroscopic data for 3c and
for [Pt{C6H3CHdN(C6H4-2SMe}Cl] (3b) {λ ) 530 nm}
(which can be visualized as derived from 3c by replace-
ment of the metalated ferrocenyl fragment by a 1,2-
disubstituted phenyl ring) also supports this assign-
ment, since the greater σ-donating ability of the
ferrocenyl group in 3c compared with that of the aryl
ring52 in 3b is expected to desestabilize the HOMO
orbital, giving rise to a lower energy metal to ligand
charge transfer transition.
F igu r e 9. HOMO and LUMO for [(η5-C5H5)Fe{(η5-C5H4)-
CHdN(C6H4-2-SMe)}], 1c (A and B), compound [Pd{[(η5-
C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] (2c) (C and D),
and [Pt{[(η5-C5H3)CHdN(C6H4-2-SMe)]Fe(η5-C5H5)}Cl] (3c)
(E and F).
around the sulfur atoms; these differences could be
ascribed to the existence in the crystal of intermolecular
interactions that involve these atoms. No significant
improvement of the calculated geometries was achieved
by including polarization functions in the basis set.
The calculations performed on the free ligand, at the
B3LYP/LANL2DZ level, show that the HOMO (Figure
2
2
9, A) is mainly formed by the 3dx -y orbital of the iron-
(II), the pz orbitals of the nitrogen and sulfur, and a π
orbital of the aryl ring, while the LUMO (Figure 9, B)
consists of a mixture of a π orbital centered on the imine
bond and the ipso carbon of the aryl ring and a small
contribution of the 3dxy orbital of the iron(II).
The bands centered at λ ) 394 nm (for 2c) or 412 nm
(for 3c), with extinction coefficients (ꢀ) between 2000
and 5000, arise mainly from two transitions, one of them
being the (HOMO-4) f (LUMO) (for 2c and 3c). Since
the (HOMO-4) is mainly a M(II)-centered orbital, these
bands (which are not present in the spectrum of the free
ligand) are assigned to metal to ligand charge transfer
transitions (MLCT). The second component of the
observed band is due to the (HOMO) f (LUMO+4) (for
2c) or (LUMO+3) (for 3c) transition. As mentioned
above in the two cases the HOMO is mainly centered
on the M(II), the iron, and the chlorine atom (Figure 9,
The HOMO and LUMO of 2c and 3c are shown in
Figure 9, C-F. In the two cases, the HOMO (Figure 9,
C and E) is mainly formed by the contribution of the
3dxy orbital of the iron, a 3pz orbital of the chloride, and
the dyz orbital of the M(II) center (M ) Pd or Pt). These
findings confirm that for the compounds under study
the HOMO is not only iron based. The replacement of
the palladium(II) (in 2c) by a platinum(II) (in 3c)
produces an increase of the contribution of the atomic
orbitals of the M(II) in the HOMO [from 0.11 (in 2c) to
0.16 (in 3c)] and a decrease of the participation of the
atomic orbitals of the Fe(II) [from 0.26 (in 2c) to 0.23
(in 3c)].
(51) (a) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J . Chem. Phys.
1998, 109, 8218. (b) Bauernschmitt, R.; Ahlrichs, R. Chem. Phys. Lett.
1996, 256, 454. (c) Casida, M. E.; J amorski, C.; Casida, K. C.; Salahub,
D. R. J . Chem. Phys. 1998, 108, 4439.
(52) Hansch, C.; Leo, A.; Koekman, D. Exploring QSAR. Hydropho-
bic, Electronic and Steric Constants; American Chemical Society:
Washington, DC, 1995.
In 3c, the HOMO of the platinum(II) derivative is
0.105 eV higher in energy than in the palladium(II)
analogue. This trend is consistent with the results
obtained from the electrochemical studies which re-
vealed that 3c is more prone to oxidize than 2c.

234 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
tively. High-resolution 1H NMR spectra and the two-dimen-
sional [{1H-1H}-NOESY and COSY, {1H-13C}-heteronuclear
single quantum coherence (HSQC), and heteronuclear multiple
bond coherence (HMBC)] NMR experiments were recorded
with either a Varian VRX-500 or a Bruker Advance-DMX 500
instrument at 20 °C. The 195Pt{1H} NMR spectrum of 3c was
registered at 20 °C with a Bruker 250-DXR instrument and
Na2[PtCl6] [δ195Pt ) 0.00 ppm] as reference. In all cases the
solvent used for the NMR experiments was CDCl3 (99.8%), and
SiMe4 was used as internal reference for the spectra in CDCl3.
To check the stability of 1c-3c in the solvent used for the
electrochemical studies, the 1H NMR spectra of these com-
pounds in CD3CN (99.8%) were also recorded. In all cases, the
chemical shifts (δ) are given in ppm and the coupling constants
(J ) in Hz. Visible-ultraviolet spectra of 10-5 M solutions of
compounds under study in CH2Cl2 were registered at 20 °C
with a Hewlett-Packard 8452A spectrophotometer.
C and E). The (LUMO +4) (in 2c) is very similar to the
(LUMO+3) (in 3c), and in the two cases they consist of
a combination of the 2pz orbital of the imine nitrogen
and π* orbitals of the ferrocenyl fragment and the aryl
ring, thus suggesting that also in this case the band can
be mainly due to a metal to ligand charge transfer
transition. This interpretation also explains why the
position of this band depends on the nature of the
substituents on the imine nitrogen and of the remaining
ligands bound to the M(II) ion.
The remaining two absorption bands [at λ ) 359 and
435 nm (for 2c) or 344 and 454 nm (for 3c)], also
observed for related metal complexes derived from Schiff
bases,53 correspond to the metal-perturbed intraligand
π f π* transitions.
P r epar ation of th e Com pou n ds. [(η5-C5H5)Fe{(η5-C5H4)-
CHdN(C6H4-2-SMe)}], 1c. A suspension formed by ferrocen-
ecarboxaldehyde (1.024 g, 4.78 × 10-3 mol) and 50 mL of
benzene was stirred at room temperature (ca. 20 °C) for 20
min and filtered out. Then H2N(C6H4-2-SMe) (0.666 g, 4.78 ×
10-3 mol) was added to the filtrate. The reaction flask was
connected to a condenser equipped with a Dean-Stark ap-
paratus. The mixture was refluxed until ca. 15 mL of the
benzene-water azeotrope had condensed on the Dean-Stark
apparatus. The hot solution was then filtered out and concen-
trated on a rotary evaporator to ca. 10 mL. Slow evaporation
of the solvent produced orange prisms of 1c (yield: 1.326 g,
Con clu sion s
The results presented here have allowed the prepara-
tion and characterization of the two first examples of
cyclopallada- and cycloplatinated complexes (2c and 3c)
containing a [C(sp2, ferrocene), N, S]- ligand. The
electrochemical studies of the three compounds under
study provide a method for fine-tuning the oxidation
potential of the ferrocenyl fragment from 184 mV in the
free ligand to 104 mV (for 2c) or 39 mV (for 3c) by
modifying the nature of the M(II) ion [Pd or Pt] in the
cyclometalated complexes. The theoretical studies based
on the DFT methodology revealed that for these systems
the HOMO is not solely iron(II) based and have ex-
plained why the half-wave potentials of compounds 2c
and 3c are so sensitive to changes in the nature of the
M(II) ion in the two cyclometalated complexes. In
particular for the palladium(II) complex (2c), the energy
level of the HOMO is smaller than that of 3c, in good
agreement with the variations observed in their half-
wave potentials. On the other hand, the UV-vis spectra
calculated using the TD-DFT methodology show a
reasonable agreement with the experiment and have
allowed the assignation of the main absorptions.
85%). Anal. Calcd: C, 64.50; H, 5.20; N, 4.0; S, 9.6. C18H17
-
NSFe requires: C, 64.49; H, 5.11; N, 4.18; S, 9.56. MS
(FAB+): m/z 355 [{M}+]. IR: 1625 cm-1, ν(>CdN-). 1H NMR
3
(in CDCl3): δ 4.27(s, 5H, C5H5), 4.84(t, 2H, H2 and H5, J (H-H)
3
) 2), 4.49(t, 2H, H3 and H4, J (H-H) ) 2), 2.46(s, 3H, -SMe),
3
8.26(s, 1H, -CHdN-), 6.84(t, 1H, H3′, J (H-H) ) 2.5), 7.16(d,
3
3
1H, H4′, J (H-H) ) 2.5), 7.13(d, 1H, H5′, J (H-H) ) 2.5), 7.16(t,
3
1H, H6′, J (H-H) ) 2.5); in CD3CN: δ 4.28(s, 5H, C5H5), 4.80(s,
2H, H2 and H5), 4.53(t, 2H, H3 and H4), 2.44(s, 3H, -SMe),
8.30(s, 1H, -CHdN-), 6.94(dd, 1H, H3′, J (H-H) ) 7.5, J (H-H)
3
4
) 1.5), 7.22(td, 1H, H4′, J (H-H) ) 7.5, J (H-H) ) 1.5), 7.16(td,
3
4
3
4
3
1H, H5′, J (H-H) ) 7.5, J (H-H) ) 1.5), 7.16(d, 1H, H6′, J (H-H)
)
7.5,4J (H-H) ) 1.5). 13C{1H} NMR: δ 69.5(C5H5), 80.2(C1), 69.2-
(C2 and C5), 71.3(C3 and C4), 14.7(Me), 161.4(-CHdN-), 150.2-
(C1′), 132.6(C2′), 117.6(C3′), 124.1(C4′), 125.1(C5′), 125.4(C6′).
[P d {[(η5-C5H3)CHdN(C6H4-2-SMe)]F e(η5-C5H5)}Cl], 2c.
Compound 1c (0.507 g, 1.51 × 10-3 mol), Na2[PdCl4] (0.440 g,
1.49 × 10-3 mol), and Na(CH3COO)‚3H2O (0.207 g, 1.51 × 10-3
mol) were dissolved in 20 mL of methanol. The reaction
mixture was protected from the light with aluminum foil and
stirred at room temperature (ca. 20 °C) for 24 h. The deep blue
solid formed was filtered out and washed with small portions
of methanol, until the mother liquor became nearly colorless.
The resulting solid was air-dried and then dried in a vacuum
(yield: 0.520 g, 72%). Anal. Cacld: C, 44.9; H, 3.53, N, 2.8; S,
6.1. C18H17NFeSPdCl 1/2 H2O requires: C, 44.6; H, 3.53; N,
2.9; S, 6.6. MS (FAB+): m/z 477[{M}+], 441[{M - Cl}+]. IR:
1530 cm-1, ν(>CdN-). 1H NMR data (in CDCl3): δ 4.40(s, 5H,
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. All the reagents used for the
preparations described in this work were obtained from Aldrich
and used as received except for Na2[PdCl4], which was
prepared according to the literature.54 The solvents, except
benzene, were dried and distilled before use.55 Some of the
preparations described below require the use of HIGHLY
HAZARDOUS MATERIALS, such as benzene and toluene,
which should be handled with CAUTION.
Elemental analyses (C, H, N, and S) were carried out at
the Serveis Cientifico-Te`cnics (Universitat de Barcelona) and
at the Serveis de Recursos Cientifics i Te`cnics (Universitat de
Rovira i Virgili, Tarragona). FAB+ mass spectra were per-
formed at the Servei d’Espectrometria de Masses (Universitat
de Barcelona) using 3-nitrobenzyl alcohol (NBA) as matrix.
Infrared spectra were obtained with a Nicolet 400-FTIR
instrument using KBr pellets. Routine 1H NMR spectra and
13C{1H} NMR spectra were obtained with a Gemini-200 MHz
and a Bruker 250-DXR or a Mercury-400 instruments, respec-
3
3
C5H5), 4.74(d, 1H, H3, J (H-H) ) 2.5), 4.61(t, 1H, H4, J (H-H)
)
2.5), 5.36(d, 1H, H5, J (H-H) ) 2.5), 2.78(s, 3H, -SMe), 8.82(s,
3
1H, -CHdN-), 7.62(d, 1H, H3′, J (H-H) ) 7.5), 7.32(t, 1H, H4′,
3
3J (H-H) ) 7.5), 7.39(t, 1H, H5′, J (H-H) ) 7.5), 7.54(d, 1H, H5,
3
3J (H-H) ) 7.5); in CD3CN: δ 4.38(s, 5H, C5H5), 4.72(s, 1H, H3),
4.72(s, 1H, H4), 5.08(s, 1H, H5), 2.76(s, 3H, -SMe), 9.03(s, 1H,
-CHdN-), 7.83(dd, 1H, H3′, J (H-H) ) 8, J (H-H) ) 1), 7.40(td,
3
4
1H, H4′, J (H-H) ) 8, J (H-H) ) 1), 7.48(td, 1H, H5′, J (H-H) ) 8,
3
4
3
4J (H-H) ) 1), 7.68(dd, 1H, H5, J (H-H) ) 8, J (H-H) ) 1). 13C{1H}
NMR: δ 71.4(C5H5), 90.2(C1), 107.4(C2), 68.6(C3), 72.5(C4),
78.23(C5), 25.4(-SMe), 167.1(>CdN-), 148.4(C1′), 130.8(C2′),
116.3(C3′), 128.0(C4′), 130.7(C5′), 135.3(C6′).
3
4
(53) Bosque, R.; Caubet, A.; Lo´pez, C.; Espinosa, E.; Molins, E. J .
Organomet. Chem. 1997, 544, 233.
(54) Brauer, G. Handbook of Preparative Inorganic Chemistry;
Academic Press: New York, 1965; Vol. 2, p 1584.
(55) Perrin, D. D.; Amarego, W. F. L.; Perrin, D. L. Purification of
Laboratory Chemicals, 3rd ed.; Pergamon: London, UK, 1988.
[P t{[(η5-C5H3)CHdN(C6H4-2-SMe)]F e(η5-C5H5)}Cl], 3c.
cis-[PtCl2(PhCN)2] (0.100 g, 2.12 × 10-4 mol) was suspended

Novel Five-Membered Pallada- and Platinacycles
Organometallics, Vol. 23, No. 2, 2004 235
Ta ble 6. Cr ysta l Da ta a n d Deta ils of th e Refin em en t of th e Cr ysta l Str u ctu r es of th e F r ee Liga n d
[(η5-C5H5)F e{(η5-C5H4)CHdN(C6H4-2-SMe)}], 1c, a n d Com p ou n d s
[M{[(η5-C5H3)CHdN(C6H4-2-SMe)]F e(η5-C5H5)}Cl] {w ith M ) P d (2c) or P t (3c)}
1c
2c
3c
empirical formula
fw
temperature/K
cryst size/mm× mm × mm
cryst syst
space group
unit cell params
C
18H17FeNS
C18H16ClFeNPdS
476.06
C18H16ClFeNPtS
564.77
335.23
293(2)
293(2)
293(2)
0.1 × 0.1 × 0.2
0.1 × 0.1 × 0.2
monoclinic
P21/n
0.1 × 0.1 × 0.2
monoclinic
P21/n
triclinic
P1h
a ) 10.5900(10) Å
b ) 10.7490(10) Å
c ) 14.0280(10) Å
R ) 94.90°
â ) 98.8590(10)°
γ ) 94.79°
1564.4
a ) 7.9010(10) Å
b ) 13.6820(10) Å
c ) 15.8700(10) Å
R ) 90.0°
â ) 93.5000(10)°
γ ) 90°
a ) 8.033(8) Å
b ) 13.710(4) Å
c ) 15.753(8) Å
R ) 90.0°
â ) 92.71(6)°
γ ) 90°
V/Å3
1712.4(3)
4
1733(2)
Z
2
4
Dcalc/Mg m-3
1.423
1.847
2.165
abs coeff/mm-1
F(000)
1.089
2.172
9.172
696
944
1072
θ range for data collection/deg
no. of collected reflns
1.96 to 28.87
10 329
2.97 to 31.60
11 179
3.17 to 30.02
5184
no. of unique reflns [Rint
no. of data
]
6393 [0.0215]
6393
511
1.093
5038 [0.0344]
5038
209
1.106
4993 [0.415]
4993
208
0.949
no. of params
goodness of fit on F2
final R indices [I > 2σ(I)]
R1 ) 0.0440,
wR2 ) 0.1296
R1 ) 0.0649,
wR2 ) 0.1508
R1 ) 0.0453,
wR2 ) 0.118
R1 ) 0.0772,
wR2 ) 0.11312
0.0013(9)
0.555 and -0.878
R1 ) 0.05065,
wR2 ) 0.1094
R1 ) 0.1751
wR2 ) 0.397
final R indices (all data)
extinction coeff
largest diff peak and hole/e Å-3
0.415 and -0.491
0.517 and -0.382
in 20 mL of toluene. The reaction mixture was refluxed until
complete dissolution of the starting platinum(II) reagent,
which was filtered out. Then the filtrate was treated with 0.070
g (2.09 × 10-4 mol) of ligand 1c, and the mixture was refluxed
for 5.5 h. The resulting dark solution was concentrated to
dryness on a rotary evaporator. The residue was washed with
small portions of n-hexane to remove small amounts of
ferrocenecarboxaldehyde formed in the course of the process.
Finally the resulting solid was dissolved in the minimum
amount of CH2Cl2. The addition of n-hexane followed by the
slow evaporation of the solvents at room temperature (ca. 20
°C) produced green monocrystals of 3c, which were collected
and air-dried (yield: 0.069 g, 59%). Anal. Calcd: C, 38.40; H,
2.90; N, 2.40; S, 6.0. C18H17NFeSPtCl requires: C, 38.28; H,
2.86; N, 2.48; S, 5.68. MS (FAB+): m/z 564[{M}+]. IR: 1531
cm-1, ν(>CdN-). 1H NMR (in CDCl3): δ 4.35(s, 5H, C5H5),
4.72(s, 1H, H3), 4.96(s, 1H, H4), 5.26(s, 1H, H5), 2.98(s, 3H,
recorded before and after each sample to ensure the repeat-
ability of the results, in particular to test and monitor the
stability of the Ag-AgNO3 electrode. Cyclic voltammograms
of freshly prepared solutions (10-3 M) of the samples in
acetonitrile were run, and average E1/2 values measured were
then referred to ferrocene, E1/2(Fc), which was used as internal
reference. In these experimental conditions the standard error
of the measured potentials is (5 mV. In all experiments, the
cyclic voltammograms were registered using scan speeds
varying from υ ) 10 mV s-1 to 100 mV s-1
.
Mo1ssba u er Sp ectr a . Mo¨ssbauer spectra were recorded
using powdered solid samples. The spectra were collected at
80 K with the sample placed inside an Oxford Instrument
cryostat. The samples were placed in liquid N2 quenched to
80 K and transferred to a cryostat. The spectra were obtained
using a constant acceleration Mo¨ssbauer spectrometer with a
57Co/Rh source. The source was moved via triangular velocity
wave and the γ-counts were collected in a 512 multichannel
analyzer. The data were folded, plotted, and fitted by a
computer procedure. Velocity calibration was done using a 25
µm thick metallic Fe foil, and the Mo¨ssbauer spectral param-
eters (presented in Table 3) are given relative to this standard
at room temperature.
Cr ysta llogr a p h y. A prismatic crystal of 1c, 2c, or 3c (sizes
in Table 6) was selected and mounted on a MAR345 diffrac-
tometer (for 1c and 2c) with an image plate detector or on a
Enraf-CAD4 four-circle diffractometer (for 3c). Unit cell
parameters were determined from automatic centering of
10 329 reflections (in the range 3° < θ < 21°) for 1c or 6787
reflections (3° < θ < 31°) for 2c, while for 3c, unit cell
parameters were determined from automatic centring of 25
reflections in the range 12° < θ < 21° and refined by a least-
squares full-matrix method. In the three cases intensities were
collected with graphite-monochromatized Mo KR radiation.
The number of reflections collected was 10 329 (in the range
1.96° e θ e 28.87°) for 1c, 11 179 (2.97° e θ e 31.60°) for 2c,
and 5184 (in the range 3.17° e θ e 30.02°) for 3c; among these
reflections 6393 (for 1c), 5038 (for 2c), and 4993 (for 3c) were
nonequivalent by symmetry [Rint (on I) ) 0.021, 0.034, and
0.41 for 1c-3c, respectively]. The number of reflections
assumed as observed applying the condition I > 2σ(I) was 4870
3
4
-SMe, J (H-Pt) ) 22), 9.02(s, 1H, -CHdN-, J (H-Pt) ) 119),
3
3
7.64(d, 1H, H3′, J (H-H) ) 7), 7.37(t, 1H, H4′, J (H-H) ) 7), 7.39-
(t, 1H, H5′, J (H-H) ) 7), 7.58(d, 1H, H6′, J (H-H) ) 7); in CD3-
CN: δ 4.32(s, 5H, C5H5), 4.79(s, 1H, H3), 4.89(s, 1H, H4), 4.95(s,
1H, H5), 2.90(s, 3H, -SMe, 3J (H-Pt) ) 22), 9.24(s, 1H, -CHdN-,
3
3
4J (H-Pt) ) 119), 7.86(td, 1H, H3′, J (H-H) ) 7.5, J (H-H) ) 1.5),
3
4
3
3
7.41(t, 1H, H4′, J (H-H) ) 7.5, J (H-H) ) 1.5), 7.46(td, 1H, H5′,
3J (H-H) ) 7.5, J (H-H) ) 1.5), 7.73 (dd, 1H, H6′, J (H-H) ) 7.5,
4J (H-H) ) 1). 13C{1H} NMR: δ 71.1(C5H5), 91.8(C2), 69.2(C3),
74.5(C4), 77.5(C5), 26.8 (-SMe), 167.7(>CdN-), 149.7(C1′),
132.6(C2′), 116.4(C3′), 128.4(C4′), 130.8(C5′), 134.8(C6′) (the signal
due to the C1 carbon atom could not be detected in this case).
195Pt{1H} NMR: δ -3488.
4
3
Electr och em ica l Stu d ies. Electrochemical data for com-
pounds under study were obtained by cyclic voltammetry
under nitrogen at ca. 20 °C using acetonitrile HPLC-grade as
solvent, tetrabutylammonium hexafluorophosphate, {(Bu4N)-
[PF6]}, (0.1 M) as supporting electrolyte, and a M263A poten-
tiostat from EG&G instruments. The half-wave potentials E1/2
were referred to an Ag-AgNO3 (0.1 M 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 ferrocene were

236 Organometallics, Vol. 23, No. 2, 2004
Pe´rez et al.
for 1c, 3318 for 2c, and 2462 for 3c. Lorentz-polarization
corrections were made in the three cases, and absorption
corrections were also performed for 2c and 3c.
Dunning-Huzinaga full double basis set48d for H, C, N, and S
atoms, while for Pd and Pt the LANL2DZ basis set was
used.48a-c
Solvent effects have been taken into account using the
polarizable conductor calculation model49 also at the B3LYP
level; in this case, the basis set was chosen as follows:
LANL2DZ for Pd and Pt and TZV50 for the other atoms.
Time-dependent DFT calculations have been performed at
the B3LYP/LANL2DZ level using the geometries previously
optimized in the same conditions.
The structures were solved by direct methods, using the
SHELXS computer program,56 and refined by a full-matrix
least-squares method with the SHELX97 computer program,57
using 6393 (for 1c), 5038 (for 2c), and 4993 (for 3c) reflections
(very negative intensities were not assumed). The function
2
2 2
minimized was ∑w ) ||Fo| - |Fc| | , where w ) [σ2(I) +
(0.0912P)2 + 0.5827P]-1 (for 1c), w ) [σ2(I) + (0.0602P)2
+
1.4499P]-1 (for 2c), and w ) [σ2(I) + (0.0618P)2]-1 (for 3c) and
P ) (|Fo| + 2|Fc|)/3; f, f ′, and f ′′ were taken from International
Tables of X-Ray Crystallography.58 For 1c, 33 hydrogen atoms
were located from a difference synthesis and refined with an
overall isotropic temperature factor, and one hydrogen was
computed and refined using a riding model, with an isotropic
temperature equal to the equivalent temperature factor of the
atom linked to it, while for 2c and 3c all the 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 it is linked.
Ack n ow led gm en t. We are grateful to the Ministe-
rio de Ciencia y Tecnolog´ıa of Spain and to the Gener-
alitat de Catalunya for financial support (projects
BQU2003-00906 and 2001-SGR-00045). S.P. is also
grateful to the Generalitat de Catalunya for a predoc-
toral fellowship.
Su p p or tin g In for m a tion Ava ila ble: Tables containing
a selection of bond lengths and angles for the optimized
geometries (Table S1), crystal data and structure refinement
details, atomic coordinates and equivalent isotropic param-
eters, all bond lengths and angles, hydrogen bond lengths and
angles, anisotropic displacement parameters, and hydrogen
coordinates for compounds 1c-3c: Tables S2-S16. This
material is available free of charge via the Internet at
http://pubs.acs.org.
The final R(on F) factors were 0.044, 0.045, and 0.056 for
1c, 2c, and 3c, respectively. Further details concerning the
resolution and refinement of the crystal structures of 1c-3c
are presented in Table 6.
Com p u ta tion a l Deta ils. Calculations were carried out at
the B3LYP computational level59 with the Gaussian 98 pack-
age,60 using the LANL2DZ basis set.48 Geometry optimizations
were performed without symmetry restrictions. To improve the
calculated geometry, polarization functions were added to the
OM030520D
(60) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J . R.; Zakrzewsi, V. G.; Montgomery, J . A.,
J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Menucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Salvador, P.; Dannenberg, J . J .; Malick, D. K.; Rabuck,
A. D.; Raghavachari, K.; Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.;
Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.;
Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J .; Keith, T.; Al-
Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill,
P. M. W.; J ohnson, B.; Chen, W.; Wong, M. W.; Andres, J . L.; Gonzalez,
C.; Head-Gordon, M.; Replogle, E. S.; Pople, J . A. Gaussian 98, Revision
A.11; Gaussian, Inc.: Pittsburgh, PA, 2001.
(56) Sheldrick, G. M. SHELXS. A computer program for determi-
nation of crystal structure; University of Go¨ttingen: Germany, 1997.
(57) Sheldrick, G. M. SHELX97. A computer program for determi-
nation of crystal structure; University of Go¨ttingen: Germany, 1997.
(58) International Tables of X-Ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. IV, pp 99-100 and 149.
(59) (a) Becke, A. D. J . Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.