1H-NMR and EPR studies of the electronic structure of low-spin ruthenium(III) isocyanide porphyrin complexes: Unusual (dxz,dyz)4 (dxy)1 configuration

Article abstract of DOI:10.1016/S0022-328X(01)00830-0

The synthesis and characterization of the perchlorato derivatives of bis(isocyanide)tetrakis(phenyl)porphynatoruthenium(III) [Ru(TPP)(RNC)₂]ClO₄ (1, R=^tBu; 2, R=2,6-xylyl) are reported. The ¹H-NMR isotropic shifts at 298 K of the pyrrole protons of the two complexes, varied from -5.44 ppm for 1 to +2.55 ppm for 2 rather than the expected -31 ppm, based on previously studied aryl complexes of low-spin ruthenium porphyrins. The EPR spectrum of 2 in solution is axial, with g_⊥=2.07 and g_II=1.99 at 4 K, Σg²=12.53. These spectroscopic observations are indicative of a metal-based electron for complex with a (d_xz, d_yz)⁴ (d_xy)¹ ground state at any temperature.

Full text of DOI:10.1016/S0022-328X(01)00830-0

Journal of Organometallic Chemistry 629 (2001) 145–152
www.elsevier.com/locate/jorganchem
1H-NMR and EPR studies of the electronic structure of low-spin
ruthenium(III) isocyanide porphyrin complexes: unusual (dxz,dyz)4
(dxy)1 configuration
Erwan Galardon a, Paul Le Maux a, Christine Paul b, Cyril Poriel a,
Ge´rard Simonneaux a,*
a Laboratoire de Chimie Organome´tallique et Biologique, URA CNRS 415, Uni6ersite´ de Rennes 1, 35042 Rennes Cedex, France
b Groupe de Recherche en Chimie et Me´tallurgie, I.N.S.A., 35043 Rennes Cedex, France
Received 9 January 2001; accepted 4 April 2001
Abstract
The synthesis and characterization of the perchlorato derivatives of bis(isocyanide)tetrakis(phenyl)porphynatoruthenium(III)
1
[Ru(TPP)(RNC)2]ClO4 (1, R=tBu; 2, R=2,6-xylyl) are reported. The H-NMR isotropic shifts at 298 K of the pyrrole protons
of the two complexes, varied from −5.44 ppm for 1 to +2.55 ppm for 2 rather than the expected −31 ppm, based on previously
studied aryl complexes of low-spin ruthenium porphyrins. The EPR spectrum of 2 in solution is axial, with gÞ=2.07 and
gII=1.99 at 4 K, Sg2=12.53. These spectroscopic observations are indicative of a metal-based electron for complex with a (dxz,
dyz)4 (dxy)1 ground state at any temperature. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ruthenium porphyrins; Isocyanides complexes; Paramagnetic complexes; Nuclear magnetic resonance
plexes of ruthenium(III) porphyrins as part of a pro-
gramme concerned with systematic examination of new
probes of heme proteins [6].
1. Introduction
Many heme proteins which have an accessible sixth
coordination position bind molecular oxygen to its
heme iron but exhibit a variety of different functions
such as hemoglobins and P-450 cytochromes [1]. Thus
an attractive attempt regarding the structure-function
relationship is to substitute oxygen by various exogen
ligands [2]. Several small nonphysiological ligands have
been examined by various spectroscopic methods in
hope of gaining information about structural and reac-
tivity perturbations of the heme environment. Examples
include mainly carbon monoxide [3] and to a less extent
isocyanides [4]. These axial-ligand probes have been
discussed in terms of both model studies and utility for
heme protein studies. Since interest in ruthenium por-
phyrin chemistry is inspired by the Periodic Table
relationship of ruthenium to iron [5], we report here the
synthesis and the characterization of isocyanide com-
Low-spin Fe(III) porphyrins are of major interest
because of the relevance of this spin state to a large
number of hemoproteins. It has been accepted that
most of the low-spin Fe(III) hemes have a (dxy)2 (dxz,
dyz)3 ground state [7]. However, it was reported that
when two molecules of tert-butylisocyanide are bound
1
to ferric tetraphenylporphyrin, the H-NMR spectrum
is indicative of a low spin complex with an unusual
pyrrole resonance in the diamagnetic area [8]. The
hyperfine shifts have been separated into their dipolar
and contact contributions. The separated components
reflect the very low magnetic anisotropy of the iron,
and the unusual orientation of the unpaired spin den-
sity when the nitrogen axial ligands are exchanged for
isocyanide ligands leads to complete reverse localiza-
tion. It should be underlined that a similar situation
was very recently reported with low-basicity cyanopy-
ridine complexation to ferriporphyrins [9,10]. The
change in ground state of low-spin Fe(III) from (dxy)2
(dxz, dyz)3 to (dxz, dyz)4 (dxy)1 electron configuration
* Corresponding author. Tel.: +33-2-9928-6285; fax: +33-2-9928-
1646.
E-mail address: simonnea@univ-rennes1.fr (G. Simonneaux).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00830-0

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E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
occurs softly through the series of pyridine complexes
of both TPPFe(III) and TMPFe(III) complexes [9,10],
the low-basicity pyridines stabilizing the unusual (dxz,
dyz)4 (dxy)1 state. Finally, it has been confirmed from
X-ray studies that complexation of isocyanides to fer-
riporphyrins leads to a compound with a pure (dxz,
dyz)4 (dxy)1 ground state [6,11]. The axial EPR spectra,
with gÞ\gII are also indicative of a (dxz, dyz)4 (dxy)1
state. In these systems, the X-ray structure shows an
extensively S4-ruffled porphyrin core which is related to
electronic factors rather than steric factors. This elec-
tronic contribution may be due to the partial delocal-
ization of the (dxy)1 unpaired electron into the 3a2u(p)
orbital of the porphyrin ring, which is made possible by
the twisting of the nitrogen pz orbitals of the nitrogen
out of the plane of the porphyrin ring, as suggested
recently by Walker et al. [11].
Here we report the preparation of a new low-spin
ruthenium porphyrin bis-isocyanide compound showing
also such unusual electronic structure. It is different
from the electronic structure of low-spin ruthenium
porphyrin alkyl and aryl analogues [12]. Although there
are many EPR informations available on low-spin fer-
ric porphyrins, very little has been reported for the
low-spin ruthenium(III) porphyrins [13] due to the
difficulty to prepare ruthenium porphyrins in this oxi-
dation state [14–18]. It should be underlined however
that the ordering of the energy levels is also changed in
the carbonyl and chloro complexes of ruthenium(III)
Schiff bases [19].
porphyrins occurs at the ring to give a p-cation radical
species [22–24]. Both situations were previously re-
ported by Collman [25], James and Dolphin [26] with
the synthesis of Ru alkyl and aryl complexes providing
a new class of ruthenium(III) porphyrins. The use of
ferric perchlorate as oxidant and a p-acceptor axial
ligand, such as an isocyanide, allowed us to prepare
new low-spin ruthenium(III) porphyrins.
The bis(isocyanide) ruthenium(II) porphyrins were
first synthetized by stirring Ru(TPP)(CO) [27] in
dichloromethane or chloroform in the presence of an
excess of tert-butyl isocyanide or 2,6-xylyl isocyanide as
described previously [28–30]. They were all character-
1
ized by H-NMR, IR, UV–vis and mass spectrometry.
Subsequent addition under argon of an excess of ferric
perchlorate (large excess) to Ru(TPP)(tBuNC)2 in
dichloromethane affords the hexacoordinated com-
pound [Ru(TPP)(tBuNC)2]ClO4 (1) (Scheme 1). Thus,
the color of the solution readily changes from purple to
dark brown, and after 1 h, precipitation of a purple
powder occurred and the product was collected by
filtration (80% yield). For the preparation of the other
ruthenium derivatives with the 2,6-xylyl isocyanide lig-
and, [Ru(TPP)(2,6-xylylNC)2]ClO4 (2), the same proce-
dure can be used with the corresponding rurhenium(II)
analogues in dichloromethane solvent.
2.2. IR and UV-6is spectroscopy
The [Ru(TPP)(tBuNC)2]ClO4 compound exhibited an
electronic spectrum with a Soret band at 398 nm (m=90
dm3 mmol−1 cm−1). To get further insight into the
reaction, the evolution of the UV–vis spectra of
Ru(TPP)(tBuNC)2 (umax=417 nm) was studied during
oxidation (Fig. 1). The titration curve reveals an
isobestic point (u=407 nm) with less intense absorp-
tion, similar to those of carbonyl ruthenium(II) por-
phyrin p-cation radicals, with a blue-shifted Soret band
and a broad absorption in the 500–700 region [22–24].
The IR spectra of the new complexes [Ru(TPP)-
(CNR)2]ClO4 are different to those of Ru(TPP)(CO)
[27] since they all exhibit a major additional band at
ꢀ2170 cm−1, w¯(CꢀN) in KBr, and the disparition of
the CO band. The w¯(CꢀN) stretching frequency of CNR
is increased upon coordination of the isocyanide to the
metal, increasing from 2130 cm−1 for the free ligand to
2170 cm−1 in [Ru(TPP)(tBuNC)2]ClO4. Isocyanide lig-
ands are both good s donnor and good p acceptor
ligands [31,32]. In the case of a formal positive charge,
this increase of the frequency indicates a higher bond
order in the complex than in the free ligand which is
attributed to the good donor properties of isocyanides
and to the concomitant decrease in the s* population
of the CN bond. In contrast, the isocyanide frequency
decreases in the reduced complex such as
Ru(II)(TPP)(tBuNC)2 (w¯(CꢀN)=2116 cm−1).
2. Results and discussion
2.1. Synthesis
Two major difficulties may be encountered in prepar-
ing ruthenium(III) complexes of porphyrins. First, the
rapid disproportionation of the Ru(III) complex to
Ru(IV) and Ru(II) complexes may occur, as it was
reported previously with amine and porphyrin ligands
[20,21]. Second, oxidation of carbonyl ruthenium(II)
Scheme 1.

E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
147
Che and coworkers [30]. The one-electron oxidation of
the ruthenium(II) tetraphenylporphyrin complexes con-
taining the axial thiocarbonyl ligand led also to the
formation of the porphyrin p-cation radical [15]. Since
the nature of the axial ligand in ruthenium porphyrin
systems can regulate electron transfer between metal
and porphyrin [33] and isocyanide ligands are both
good s donnor and good p-acceptor ligands [4], the
complexes were investigated by 1H-NMR and EPR
spectroscopies to discriminate between a porphyrin rad-
ical and a Ru(III) species.
2.4. NMR spectroscopy
1
The signals in the paramagnetic H-NMR spectra of
Ru(P)(CNR)2ClO4 complexes are sharp and shifted
1
considerably from their diamagnetic positions. The H-
NMR spectrum of [Ru(TPP)(tBuNC)2]ClO4 is shown in
Fig. 2 (293 K) and the isotropic shifts are listed in
Table 2 (293 K). The isotropic shifts of [Ru(TPP)(2,6-
xylylNC)2]ClO4 are listed in Table 3 (293 K). The peaks
for the phenyl protons of the porphyrin ring are as-
signed completely by methyl substitution and in combi-
nation with proton decoupled experiments. For
isocyanide axial ligands, measurements of the relative
intensities completely determine the assignment. The
shift of the isocyanide ligand is totally independent of
the presence of excess ligand. Hence axial ligand disso-
ciation is not expected to become significant at ambiant
Fig. 1. Oxidation of Ru(TPP)(tBuNC)2 (0.8 mM) with an excess of
Fe(ClO4)3 in dichloromethane.
Table 1
Electrochemical data (V vs. SCE) for ruthenium porphyrin complexes
Complex
E1/2 (1)
E1/2 (2)
1
temperature. H-NMR magnetic measurements [34,35]
Ru(TPP)(CO) a
0.82
0.21
0.28
0.58
0.58
0.51
1.21
1.26
0.92
were made for 0.03M CD2Cl2 solutions of
[Ru(TPP)(CNR)2]ClO4 employing Me4Si as the refer-
ence (293 K). The solution magnetic moment (v=
1.90vB) is compatible with a low-spin state S=1/2.
However, the spectrum of [Ru(TPP)(CNR)2]ClO4
shows unexpected behavior for a Ru(III) species in that
the pyrrole proton signal is found in a downfield posi-
tion at 2.55 ppm (R=2,6-Me2Ph) and -5.44 ppm (R=
tBu) (293 K). It contrasts with the pyrrole proton of
that of Ru(III)(TPP)Phe (l= −30.9 ppm) [12] and
provides an essential proof for a different electronic
structure in these derivatives. The chemical shifts of
[Ru(TPP)(2,6-xylylNC)2]ClO4 are similar to those re-
ported for Br2 oxidation of Ru(TPP)(CO) (pyrrole:
l=3.35 ppm) [36]. Thus the description of the elec-
tronic structure should account for a large spin density
at the meso position. Two alternative electronic struc-
tures can be considered: a (dxz, dyz)4 (dxy)1 Ru(III)
species and a porphyrin a2u radical Ru(II). However,
the sharpness of the 1H-NMR signals is inconsistent
with a porphyrin radical.
a
Ru(TPP)(py)2
Ru(T(o,o%-OMe)PP)(tBuNC)2
Ru(TPP)(tBuNC)2
1.37
Ru(TPP)(2,6-xylylNC)2
Ru(TTP)(2,6-xylylNC)2
1.31 b
1.20 b
a Ref. [22].
b Non reversible system.
2.3. Electrochemical studies
As indicated by cyclic voltammograms in
dichloromethane, the first reversible oxidation potential
of the low-spin complexes (E1/2=0.51 V for 1 and 0.58
V for 2 vs. SCE) is between the potentials observed
with s-donor ligands (E1/2=0.21 V for Ru(TPP)(py)2)
and strong p-acceptor ligand (E1/2=0.82
V for
Ru(TPP)(CO)) [22]. In the latter case, the electron
location is on the macrocycle ring (porphyrin p-cation
radical), while in the former the unpaired electron is
metal-based. It can be seen from Table 1 that the
complexes also exhibit a second oxidation potential
which is reversible for 1 at 1.37 V versus SCE. These
second oxidation couples can be tentatively assigned to
a Ru(III)–cation radical complex due to an oxidation
of the porphyrin ring as it was previously suggested by
Also analysis of the curve in the Curie plot was made
for the [Ru(TTP)(2,6-xylylNC)2]ClO4 compound (Fig.
3). The isotropic shifts vary linearly with 1/T, but the
extrapoled lines do not pass through the origin at
1/T=0 and the pyrrole protons show an anti-Curie

148
E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
Fig. 2. Proton NMR spectrum of [Ru(TPP)(tBuNC)2]ClO4 in CDCl3 at 293 K. Assignment of the various resonances are indicated; x marks the
residual solvent and impurity peaks.
Table 2
behavior. As reported previously [7], the pattern of
Observed shifts and separation of the isotropic shift into contact and
isotropic shifts observed and the anti-Curie behavior of
dipolar contributions in [Ru(TPP)(tBuNC)2]ClO4 (ppm)
the pyrrole protons are indicative of a (dxz, dyz)4 (dxy)1
a
b
ground state. The chemical shifts observed for the axial
ligands (2,6-xylylNC: 8.0 (4H, d, Hm); 6.4 (2H, t, Hp);
3.5 (s, 12H, CH3) (Table 3) are close to those expected
for groups located in the diamagnetic region. Thus
there is essentially no spin density on the axial ligands,
as expected because the orthogonality of the isocyanide
pp orbitals and the metal dxy orbital that contains the
unpaired electron.
Proton type
DH/H
(DH/H)iso
(DH/H)dip (DH/H)con
Ho
Hm
m-CH3
Hp
p-CH3
Hpyrr
−4.97
17.2
0.22
−0.46
14.4
−5.44
−13.1
9.51
−2.50
−8.16
11.6
6.50
3.17
2.15
2.91
2.13
−19.6
6.33
−4.6
−11.1
9.51
−25.9
−13.8
12.1
t
a Chemical shift at 298 K with TMS as internal reference. BuNC:
Analysis of the chemical shifts were made according
to the method of La Mar et al. [37]. In this method, the
plot (DH/H)iso versus (3 cos2 q−1)/r3 for proton meso-
aryl positions (and methyl substituents) permits a quan-
titative separation of the dipolar and contact
contribution. The results are summarized in Tables 2
and 3. It is clearly observed that there is a large contact
contribution to the meso-phenyl-H resonance. This
contribution is about 30% higher in [Ru(TPP)(2,6-xy-
lylNC)2]ClO4 than in [Ru(TPP)(tBuNC)2]ClO4. This is
in contrast with previous work on low-spin rutheniu-
m(III) derivatives as Ru(TPP)Phe complex for example
[12]. As previously reported for ferric porphyrin com-
plexes, this pattern of observed isotropic shifts and the
anti-Curie behavior of the pyrrole protons are indica-
tive of a (dxz, dyz)4 (dxy)1 ground state. This can be
ascribed to the electronic interaction between (dp) and
isocyanide(pp*) orbitals. The interaction stabilizes the
dp orbitals and induces (dxz, dyz)4 (dxy)1 configuration.
3.36 ppm.
b Isotropic shift with diamagnetic Ru(TPP)(tBuNC)2 complex as
reference.
Table 3
Observed shifts and separation of the isotropic shift into contact and
dipolar contributions in [Ru(TPP)(2,6-xylylNC)2]ClO4 (ppm)
a
b
Proton type
DH/H
(DH/H)iso
(DH/H)dip
(DH/H)con
Ho
Hm
(m-CH3)
Hp
(p-CH3)
Hpyrr
−10.7
21.5
−0.82
−4.63
19.9
−18.9
13.8
−3.46
−12.3
17.2
9.12
4.47
3.00
3.99
3.09
17.2
−28.0
9.30
−6.46
−16.3
14.1
2.55
−5.97
−23.1
a Chemical shift at 298 K with TMS as internal reference. 8.0 (4H,
d, Hm ligand); 6.4 (2H, t, Hp ligand); 3.5 (s, 12H, CH3, ligand).
b Isotropic shift with diamagnetic Ru(TPP)(2,6-xylylNC)2 complex
as reference.

E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
149
were imputed to the localisation of the unpaired elec-
tron in the dxy orbital of the metal, leading to a (dxz,
dyz)4 (dxy)1 electronic ground state of the iron(III). The
relative energies of the three t2g d-orbitals can be calcu-
lated from the g values in solution, using a general
theory elaborated by Taylor [43]. Thus, D/u is negative
(−26.3) for [Ru(TPP)(2,6-xylylNC)2]ClO4, indicating
that the ground state is largely (dxz, dyz)4 (dxy)1. Conse-
quently, we propose, in accordance with previously
reported EPR results, a (dxz, dyz)4 (dxy)1 electron
configuration both at low and room temperatures for
bis(isocyanide) ruthenium porphyrin complexes.
3. Conclusion
In conclusion, these spectroscopic observations are
indicative of a metal-based electron in the dxy orbital
for [Ru(TPP)(CNR)2]ClO4 compounds at any tempera-
ture. In contrast, it should be underlined the coordina-
Fig. 3. Curie plot for protons resonances of [Ru(TPP)(2,6-xy-
lylNC)2]ClO4 in CD2Cl2.
Such interpretation was recently proposed by Naka-
mura et al. for the ground state of bis(cyano) complexes
of ferric porphyrins [38]. In order to explain the anti-
Curie behavior, the presence of excited states has been
recently proposed in several model heme systems hav-
ing unsymmetrical substitution patterns [39]. The same
two level approach [40] could also be applied to our
system but the theoretical treatment is beyond this
current work.
t
tion of BuNC to iron(III) isobacteriochlorin induces a
reversible electronic rearrangement resulting in the re-
duction of iron(III) to iron(II) with the formation of a
p-radical due to the presence of the tetrahydropor-
phyrin macrocycle [44] and one electron oxidation of
Ru(TPP)CS led also to the formation of the p-cation
radical [15].
Different reasons have also been suggested to explain
this large spin delocalization on the meso position, such
as an increasing p delocalization on the meso carbon
positions [41] or a partial delocalization of the unpaired
electron into the (dxz, dyz) orbitals [7]. However, a
possible contribution of a partial porphyrin p cation
radical character to the electronic configurations of
these derivatives has been also suggested [9]. although,
to our knowledge, the typical visible spectrum of such
radical cation has never been observed with the ferric
isocyanide porphyrin complexes.
4. Experimental
4.1. General procedures
UV–vis spectra were recorded on an Uvikon 941
spectrophotometer in dichloromethane. Infrared spec-
tra were obtained on a Bruker IFS 28 FT-IR spec-
trophotometer. 1H-NMR spectra were recorded in
CDCl3 on a Bruker 200 DPX (200 MHz) and chemical
shifts are referenced to internal TMS. EPR spectra were
recorded in CH2Cl2 on a Bruker EMX 8/2,7 spectrome-
ter operating at X-band frequencies. Samples were
cooled to 4.2 K in a stream of helium gas in frozen
CH2Cl2, the temperature of which was controlled by an
Oxford Instruments ESR 900 cryostat. Cyclic voltam-
metric measurements were performed using an EG&G
Princeton Applied Research Model 273 potentiostat. A
three-electrode cell was utilized and consisted of a
platinum working electrode, a platinum counter elec-
trode, and a saturated calomel reference electrode
(SCE). All electrochemical experiments were carried out
in dichloromethane, with 0,1 M {nBu4N}{PF6} acting
as the supporting electrolyte (scan rate 0.1 V s−1).
Abbreviations used: TTP=5,10,15,20-tetra-para-
tolylporphyrin dianion, TPP=5,10,15,20-tetraphenyl-
porphyrin dianion, OEP=octaethylporphyrin dianion.
2.5. EPR spectroscopy
1
As expected from H-NMR results, no radical-like
EPR spectrum is observed at room temperature. In
contrast, the complex [Ru(TPP)(2,6-xylylNC)2]ClO4
displays
a
broad EPR spectra (4 K, frozen
dichloromethane) with two g-values (2.07 and 1.99)
with axial symmetry (Fig. 4). This rules out the possi-
bility of a ruthenium(II) porphyrin p-cation radical,
which typically displays a single sharp signal with g=
2.00 [24,42]. It should be underlined that an axial
spectrum was also observed with [Fe(III)(TPP)-
(tBuNC)2]ClO4 (g=2.21 and 1.93) and [Fe(OEP)-
(tBuNC)2]ClO4 (g=2.28 and 1.83) [11]. These results

150
E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
4.2. Ru(TPP)(tBuNC)2
Purple crystals of Ru(TTP)(tBuNC)2 were collected by
filtration and washed with hexane. The yield was 49 mg
The complex was prepared by a modified procedure
[28,30]. To a solution of 50 mg (67 mmol) of of
Ru(TPP)CO in 3 cm3 of dichloromethane was added
four equivalents of tert-butyl isocyanide (tBuNC) under
stirring at room temperature (r.t.). After filtration, 10
cm3 of pentane was added and the solution was set
aside 1 day for crystallization at 0°C. Purple crystals of
Ru(TPP)(tBuNC)2 were collected by filtration and
washed with hexane. The yield was 52 mg (88%).
UV–vis (CH2Cl2): umax/nm 399 (m 40 dm3 mmol−1
(83%). UV–vis (CH2Cl2): umax/nm 398 (m 40 dm3
1
mmol−1 cm−1), 417 (m 264), 527 (m 12). H-NMR (l,
CDCl3, ppm) 8.46 (s, 8H, Hpyrr); 8.06 (8H, d, Ho); 7.52
(8H, d, Hm); 2.72 (s, 12H, CH3, porphyrin); −0.42
(18H, s, H ligand). FAB MS (m/z): 936, [M]+; 853
[M−tBuNC]+. IR w¯(CN)=2116 cm−1 in KBr.
4.4. Ru(II)(TPP)(2,6-xylylNC)2
To a solution of 50 mg (67 mmol) of Ru(TPP)CO in
3 cm3 of dichloromethane was added four equivalents
of 2,6-xylyl isocyanide under stirring at r.t. After filtra-
tion, 10 cm3 of pentane was added and the solution was
set aside 1 day for crystallization at 0°C. Purple crystals
of Ru(TPP)(2,6-xylylNC)2 were collected by filtration
and washed with hexane. The yield was 54 mg (82%).
UV–vis (CH2Cl2): umax/nm 399 (m 42 dm3 mmol−1
1
cm−1), 417 (m 260), 527 (m 13). H-NMR (l, CDCl3,
ppm) 8.42 (s, 8H, Hpyrr); 8.17 (8H, d, Ho); 7.70 (12H,
m, Hm+Hp); −0.42 (18H, s, H ligand). FAB MS
(m/z): 880, [M]+; 797 [M−tBuNC]+. IR w¯(CN)=2116
cm−1 in KBr.
4.3. Ru(TTP)(tBuNC)2
1
cm−1), 417 (m 250), 528 (m 12). H-NMR (l, CDCl3,
To a solution of 50 mg (63 mmol) of Ru(TTP)CO in
3 cm3 of dichloromethane was added four equivalents
of tert-butyl isocyanide (tBuNC) under stirring at r.t.
After filtration, 10 cm3 of pentane was added and the
solution was set aside 1 day for crystallization at 0°C.
ppm) 8.52 (s, 8H, Hpyrr); 8.19 (8H, d, Ho); 7.72 (12H,
m, Hm+Hp); 6.47 (2H, t, Hp ligand); 6.26 (4H, d, Hm
ligand); 0.29 (s, 12H, CH3). FAB MS (m/z): 976, [M]+;
845 [M−2,6-xylyl NC]+. IR w¯(CN)=2087 cm−1 in
KBr.
Fig. 4. EPR spectrum of [Ru(TPP)(2,6-xylylNC)2]ClO4 in a CH2Cl2 glass, recorded at 4 K.

E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
151
4.5. Ru(II)(TTP)(2,6-xylylNC)2
crystallization at 0°C. Purple crystals of [Ru(TTP)(2,6-
xylyl NC)2]ClO4 were collected by filtration and washed
with hexane. The yield was 26 mg (78%). UV–vis
(CH2Cl2): umax/nm 397 (m 90 dm3 mmol−1 cm−1), 515
(m 5.8). FAB MS (m/z): 976, [M]+; 845 [M−2,6-xylyl
NC]+. IR w¯(CRN)=2160 cm−1 in KBr.
To a solution of 50 mg (62 mmol) of Ru(TTP)CO in
3 cm3 of dichloromethane was added a four equivalents
of 2,6-xylyl isocyanide under stirring at r.t. After filtra-
tion, 10 cm3 of pentane was added and the solution was
set aside 1 day for crystallization at 0°C. Purple crystals
of Ru(TTP)(2,6-xylylNC)2 were collected by filtration
and washed with hexane. The yield was 50 mg (78%).
UV–vis (CH2Cl2): umax/nm 400 (m 40 dm3 mmol−1
4.9. [Ru(TTP)(tBuNC)2]ClO4
cm−1), 418 (m 240), 528 (m 11). H-NMR (l, CDCl3,
1
To a solution of 30 mg (32 mmol) of Ru(TTP)-
(tBuNC)2 in 3 cm3 of dichloromethane was added a
large excess of ferric perchlorate (Fe(ClO4)3·nH2O) un-
der stirring at r.t. After filtration, 10 cm3 of pentane
was added and the solution was set aside 2 days for
crystallization at 0°C. Purple crystals of [Ru(TTP)-
(tBuNC)2]ClO4 were collected by filtration and washed
with hexane. The yield was 22 mg (66%). UV–vis
(CH2Cl2): umax/nm 398 (m 90 dm3 mmol−1 cm−1), 515
ppm) 8.54 (s, 8H, Hpyrr); 8.06 (8H, d, Ho); 7.52 (8H, d,
Hm); 6.44 (2H, t, Hp ligand); 6.24 (4H, d, Hm ligand);
2.72 (s, 12H, CH3, porphyrin); 0.27 (s, 12H, CH3,
ligand). FAB MS (m/z): 1032, [M]+. IR w¯(CN)=2086
cm−1 in KBr.
4.6. Ru(T(o,o%-OMe)PP)(tBuNC)2
1
(m 5.7). H-NMR (l, CDCl3, ppm) 18.7 (8H, s, Hm);
To a solution of 50 mg (51 mmol) of Ru(T(o,o%-
OMe)PP)CO in 3 cm3 of dichloromethane was added a
four equivalents of tert-butyl isocyanide (tBuNC) under
stirring at r.t. After filtration, 10 cm3 of pentane was
added and the solution was set aside 1 day for crystal-
lization at 0°C. Purple solid of Ru(T(o,o%-
OMe)PP)(tBuNC)2 was collected by filtration and
washed with hexane. The yield was 48 mg (84%).
UV–vis (CH2Cl2): umax/nm 417 (m 250 dm3 mmol−1
14.36 (s, 12H, CH3, porphyrin); −3.2 (s, 8H, Hpyrr); 3.7
(s, 18H, ligand); −6.0 (8H, s, Ho). FAB MS (m/z):
936, [M]+; 853 [M−tBuNC]+. IR w¯(CN)=2163 cm−1
in KBr.
4.10. [Ru(TTP)(2,6-xylyl NC)2]ClO4
1
cm−1), 529 (m 13). H-NMR (l, CDCl3, ppm) 8.28 (s,
To a solution of 30 mg (29 mmol) of Ru(TTP)(2,6-xy-
lylNC)2)2 in 3 cm3 of dichloromethane was added a
large excess of ferric perchlorate (Fe(ClO4)3·nH2O) un-
der stirring at r.t. After filtration, 10 cm3 of pentane
was added and the solution was set aside two days for
crystallization at 0°C. Purple crystals of [Ru(TTP)(2,6-
xylyl NC)2]ClO4 were collected by filtration and washed
with hexane. The yield was 26 mg (79%). UV–vis
(CH2Cl2): umax/nm 398 (m 92 dm3 mmol−1 cm−1), 515
8H, Hpyrr); 7.65 (4H, t, Hp); 7.03 (8H, d, Hm); 3.55
(24H, s, OMe); −0.34 (18H, s, H ligand). IR w¯(CN)=
2105 cm−1 in KBr.
4.7. [Ru(TPP)(tBuNC)2]ClO4
To
Ru(TPP)(tBuNC)2 in 3 cm3 of dichloromethane was
added large excess of ferric perchlorate
a
solution of 30 mg (34 mmol) of
1
(m 5.9). H-NMR (l, CDCl3, ppm) 22.7 (8H, s, Hm);
a
19.9 (s, 12H, CH3, porphyrin); 7.8 (4H, d, Hm ligand);
6.7 (2H, t, Hp ligand); 4.2 (s, 8H, Hpyrr); 3.3 (s, 12H,
CH3, ligand); −13.2 (8H, s, Ho). FAB MS (m/z): 1032,
[M]+. IR w¯(CN)=2158 cm−1 in KBr.
(Fe(ClO4)3·nH2O) under stirring at r.t. After filtration,
10 cm3 of pentane was added and the solution was set
aside 2 days for crystallization at 0°C. Purple solid of
[Ru(TPP)(tBuNC)2]ClO4 was collected by filtration and
washed with hexane. The yield was 28 mg (84%).
UV–vis (CH2Cl2): umax/nm 398 (m 90 dm3 mmol−1
cm−1), 515 (m 5.7). FAB MS (m/z): 880, [M]+; 797
[M−tBuNC]+. IR w¯(CRN)=2170 cm−1 in KBr.
For the preparation of the meta-methylated deriva-
tives of tetraphenylporphyrin, the same procedure can
be used with the corresponding ruthenium perchlorate
analogues in dichloromethane solvent and the suitable
ligand. However for meta-methyl derivatives, a partial
decomposition was observed; the solutions were re-
duced in volume to ensure precipitation, due to the
high solubility of meta-methyl derivatives in
dichloromethane. These complexes were not isolated
but used directly for NMR experiments.
4.8. [Ru(TPP)(2,6-xylyl NC)2]ClO4
To a solution of 30 mg (31 mmol) of Ru(TPP)(2,6-xy-
lylNC)2)2 in 3 cm3 of dichloromethane was added a
large excess of ferric perchlorate (Fe(ClO4)3·nH2O) un-
der stirring at r.t. After filtration, 10 cm3 of pentane
was added and the solution was set aside 2 days for
Caution: perchlorate ions are susceptible to sponta-
neous detonation and should be handled in quantities
of less than 50 mg.

152
E. Galardon et al. / Journal of Organometallic Chemistry 629 (2001) 145–152
[18] M. Barley, J.Y. Becker, G. Domazetis, D. Dolphin, B.R. James,
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