Synthesis and structural characterization of new piano-stool ruthenium(II) complexes bearing 1-butylimidazole heteroaromatic ligand

Article abstract of DOI:10.1016/j.jorganchem.2012.04.024

New cationic ruthenium(II) complexes with the formula [Ru(η ⁵-C₅H₅)(LL)(1-BuIm)] [Z], with (LL) = 2PPh ₃ or DPPE, and Z = CF₃SO₃^-, PF ₆^-, BPh₄

Full text of DOI:10.1016/j.jorganchem.2012.04.024

Journal of Organometallic Chemistry 713 (2012) 112e122
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Journal of Organometallic Chemistry
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Synthesis and structural characterization of new piano-stool ruthenium(II)
complexes bearing 1-butylimidazole heteroaromatic ligand
,
e
,
b
,
,
Tânia S. Morais a, M. Helena Garcia a , M. Paula Robalo c, M.F.M. Piedade c e, M. Teresa Duarte c,
*
M. José Villa de Brito c e, Paulo J. Amorim Madeira d
,
a Centro de Ciências Moleculares e Materiais, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
b Departamento de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Av. Conselheiro Emídio Navarro, 1, 1959-007 Lisboa, Portugal
c Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
d Centro de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
e Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
a r t i c l e i n f o
a b s t r a c t
New cationic ruthenium(II) complexes with the formula [Ru(h
5-C5H5)(LL)(1-BuIm)] [Z], with
Article history:
(LL) ¼ 2PPh3 or DPPE, and Z ¼ CF3SOꢀ3 , PF6ꢀ, BPh4ꢀ, have been synthesized and fully characterized.
Spectroscopic and electrochemical studies revealed that the electronic properties of the coordinated
1-butylimidazole were clearly influenced by the nature of the phosphane coligands (LL) and also by the
different counter ions. The solid state structures of the six complexes determined by X-ray crystallo-
graphic studies, confirmed the expected distorted three-legged piano stool structure. However the
geometry of the 1-butylimidazole ligand was found considerably different in all six compounds, being
governed by the stereochemistry of the mono and bidentate coligands (PPh3 or DPPE).
Ó 2012 Elsevier B.V. All rights reserved.
Received 15 March 2012
Received in revised form
20 April 2012
Accepted 24 April 2012
Keywords:
Ruthenium(II)
Cyclic voltametry
X-ray crystal structures
Monocyclopentadienyl complexes
1-Butylimidazole
1. Introduction
suitable drug candidates. The families of ruthenium(II) organome-
tallic compounds studied, so far, for this purpose present a half
Ruthenium coordination compounds have attracted much
attention as antitumor agents, since these compounds revealed
already properties that can be an advantage to antitumor plati-
num(II) complexes currently used in clinic [1e 4]. One of the most
significant features is the reduced toxicity of ruthenium compounds,
which is in part due to the ability of ruthenium to mimic the iron in
binding to biological molecules. Besides, the non-cross-resistance
and a novel mechanism of action [5,6] in cisplatin-resistant cancer
cells together with the prospect of a different spectrum of activity
[7,8], make the study of ruthenium complexes a particular attractive
area for the search of new drugs. However coordination compounds
present some problems concerning clinical trials related to their
instabilityand complicated ligand exchange chemistry. To overcome
this situation the organometallic chemistry appeared as an attrac-
tive area of research to provide organo-ruthenium complexes as
sandwich structure mainly based on h
6-arene substituted ligands.
Many results are reported in the literature revealing potent cyto-
toxicity, against a range of tumor cell lines, for two families of these
Ru(II) derivatives [9,10].
Our approach in this field lead us to the synthesis and study of
half sandwich cationic compounds derived of “Ru(h
5-C5H5)” frag-
ment, containing N-heteroaromatic sigma coordinated ligands. The
new studied compounds revealed significant effect of toxicity in
Lovo and MiaPaCa cells [11], human leukemia cancer cells (HL-60)
with IC50 values lower than that of cisplatin [12,13].
Our promising results obtained for compounds with imidazole
[11], which cytotoxicity is in the nanomolar range, encouraged us to
continue these studies and synthesize a set of new compounds
bearing an imidazole derivative molecule. The chosen molecule
was 1-butylimidazole, which flexible side chain can impart ability
to the molecule for different type of interactions. Moreover, in order
to play with the electronic properties of the organometallic frag-
ment and consequently, the electronic density on the ring of
1-butylimidazole, two different phosphanes were used as col-
igands, PPh3 and DPPE. Finally, changes in the counter ion were also
* Corresponding author. Faculdade de Ciências da Universidade de Lisboa, Edifí-
cioC8, Campo Grande, 1749-016 Lisboa, Portugal. Tel.: þ351 217500972; fax: þ351
217500088.
E-mail address: lena.garcia@fc.ul.pt (M.H. Garcia).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.04.024

T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
113
considered, having in mind studies reporting considerable changes
in the biological activity of the compounds. In fact, different counter
ions are expected to lead to diverse ion-pair formation which can
account for a number of physiochemical phenomena involving the
wide-ranging lipophilic parts of the molecule [14e22].
2.2.2. [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][PF6] 2
5-C5H5)(PPh3)2Cl] (0.32 g, 0.5 mmol) in
To a solution of [Ru(
h
dichloromethane (25 mL) was added 1-butylimidazole (0.06 mL,
0.6 mmol) followed by the addition of TlPF6 (0.21, 0.6 mmol). The
reaction is carried out at room temperature with vigorous stirring
during 2 h with the change of color orange to brown. The precipitate
of TlCl was removed by cannula-filtration and the solvent evapo-
rated. The product was washed with n-hexane (2 ꢁ10 mL) affording
brown crystals after recrystallization from dichloromethane/
The structures of the six new compounds [23], here presented,
were determined by X-ray diffraction studies. Spectroscopic and
electrochemical data obtained by cyclic voltammetry were
analyzed in order to get some understanding about the electronic
p-coupling between the
h
5-cyclopentadienylruthenium fragment
n-hexane. Yield: 43%. 1H NMR [(CD3)2CO, Me4Si,
6, Hpara(PPh3)], 7.34 [m, 12, Hmeta(PPh3)], 7.20 [s, 1, H1], 7.13 [m, 14,
d
/ppm]: 7.48 [m,
and the -system of the imidazole ring. The overall results are
p
analyzed in perspective of further studies of interaction of these
compounds with DNA.
Hortho(PPh3) þ H3 þ H2], 4.56 [s, 5,
h
5-C5H5], 3.31 [t, 2, H4,
3JHH ¼ 6.63 Hz], 1.43 [quintet, 2, H5, 3JHH ¼ 7.16 Hz], 0.94 [sextet, 2,
H6, 3JHH ¼ 7.96 Hz], 0.76 [t, 3, H7, 3JHH ¼ 7.27 Hz].13C NMR [(CD3)2CO,
d/ppm]: 143.83 (C1, 1-BuIm), 137.52 (Cq, PPh3), 134.43 (CH, PPh3),
2. Experimental
130.90 (CH, PPh3),129.21 (CH, PPh3),136.60 (C2,1-BuIm),121.55 (C3,
1-BuIm), 83.41 (C5H5), 48.17 (C4, 1-BuIm), 33.04 (C5, 1-BuIm), 19.81
2.1. General procedures
(C6, 1-BuIm), 13.70 (C7, 1-BuIm). 31P NMR [(CD3)2CO,
d/ppm]: 42.23
[s, PPh3], ꢀ144.12 [septet, PF6]. IV [KBr, cmꢀ1]: 3435 (m), 3143 (m),
3051 (m), 2959 (m), 2928 (m), 2856 (w),1518 (w),1480 (m),1420 (s),
1419 (w), 1312 (vw), 1262 (w), 1233 (vw), 1184 (w), 1159 (vw), 1119
(m),1086 (s),1027 (w), 998 (vw), 910 (vw), 839 (vs), 748 (s), 695 (vs),
668 (m), 618 (vw), 587 (w), 557 (m), 520 (s), 463 (w), 419 (w). ESI-
HRMS: calcd. For [Mþ] 815.22653, found 815.22565.
All the experiments were carried out under dinitrogen atmo-
sphere using current Schlenk techniques and solvents used were
dried using standard methods [24]. Starting materials [Ru(h5
-
C5H5)(LL)Cl] were prepared following the methods described in the
literature: LL ¼ 2PPh3 [25] and DPPE [26]. 1H- 13C and 31P NMR
spectra were recorded on a Bruker Avance 400 spectrometer at
probe temperature. 1H and 13C chemical shifts (s ¼ singlet;
d ¼ duplet; t ¼ triplet; quint ¼ quintet; sep ¼ septet; m ¼ multiplet
for 1H) are reported in parts per million (ppm) downfield from
internal Me4Si and 31P NMR spectra are reported in ppm downfield
from external standard H3PO4 85%. FT-IR spectra were recorded in
a Mattson Satellite FT-IR spectrophotometer with KBr; only signifi-
cant bands are cited in the text w ¼ weak; vw ¼ very weak;
m ¼ medium; s ¼ sharp; vs ¼ very sharp. ESI-HRMS spectra were
acquired in an Apex Ultra FTICR Mass Spectrometer equipped with
an Apollo II Dual ESI/MALDI ion source, from Bruker Daltonics, and
a 7T actively shielded magnet fromMagnex Scientific. Electronic
spectra were recorded at room temperature on UV-1603 Shimadzu
UVevisible spectrometer in the range of 200e900 nm.
2.2.3. [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][BPh4] 3
5-C5H5)(PPh3)2Cl] (0.32 g, 0.5 mmol) in
To a suspension of [Ru(
h
methanol (25 mL) was added 1-butylimidazole (0.06 mL, 0.6 mmol)
followed by the addition of NH4BPh4 (0.20, 0.6 mmol). After 3 h and
30 min the yellow powder which separated was filtered, washed
with n-hexane (2 ꢁ 10 mL), and vacuum dried, affording yellow
crystals after recrystallization from dichloromethane/n-hexane.
Yield: 87%. 1H NMR [(CD3)2CO, Me4Si,
d/ppm]: 7.47 [m, 6, Hpara
(PPh3)], 7.33 [m, 20, Hmeta(PPh3) þ Hortho(BPh4)], 7.22 [t, 1, H3,
3JHH ¼ 1.46 Hz], 7.13 [m, 13, H1 þ Hortho(PPh3)], 7.07 [t, 1, H2,
3JHH ¼ 1.48 Hz], 6.92 [m, 8, Hpara(BPh4)], 6.77 [m, 4, Hpara(BPh4)], 4.55
3
[s, 5,
h
5-C5H5], 3.67 [t, 2, H4, JHH ¼ 6.96 Hz], 1.42 [quint, 2, H5,
3JHH ¼ 6.23 Hz], 0.93 [sextet, 2, H6, JHH ¼ 7.45 Hz], 0.76 [t, 3, H7,
3
3JHH ¼ 7.25 Hz]. 13C NMR [(CD3)2CO,
d/ppm]: 143.75 (C1, 1-BuIm),
2.2. Synthesis of the Ru(II) complexes
137.48 (Cq, PPh3), 137.29 (Cq, BPh4), 137.03 (CH, BPh4), 136.61 (C2, 1-
BuIm),134.41 (CH, PPh3),130.90(CH, PPh3),129.21 (CH, PPh3),125.95
(CH, BPh4), 122.21 (CH, BPh4), 121.56 (C3, 1-BuIm), 83.38 (C5H5),
48.21 (C4, 1-BuIm), 33.09 (C5, 1-BuIm), 19.82 (C6, 1-BuIm), 13.75 (C7,
2.2.1. [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][CF3SO3] 1
5-C5H5)(PPh3)2Cl] (0.32 g, 0.5 mmol)
To a stirred solution of [Ru(
h
in dichloromethane (25 mL) was added 1-butylimidazole (0.06 mL,
0.6 mmol) and AgCF3SO3 (0.15, 0.6 mmol). After refluxing for 5 h the
solution turned from orange to yellow. The reaction mixture was
cooled to room temperature, filtered and the solvent removed under
reduced pressure; the product was washed with n-hexane
(2 ꢁ 10 mL) affording yellow crystals after recrystallization from
dichloromethane/diethyl ether. Yield: 77%. 1H NMR [CDCl3, Me4Si,
1-BuIm). 31P NMR [(CD3)2CO, /ppm]: 42.23 [s, PPh3]. IV [KBr, cmꢀ1]:
d
3416 (w), 3140 (w), 3124 (m), 3051 (s), 2997 (m), 2983 (m), 2955 (m),
2929 (m), 2862 (w),1946 (vw),1890 (vw),1818 (vw),1589 (m), 1531
(m),1479 (s),1431 (s),1310 (w),1237 (w),1104 (w),1089 (s),1029 (w),
998 (w), 826 (w), 734 (s), 689 (vs), 612 (m), 535 (s), 522 (vs), 494 (s),
468 (m), 421 (m). ESI-HRMS: calcd. For [Mþ] 815.22653, found
815.22964.
d
/ppm]: 7.62 [s, 1, H1], 7.37 [m, 6, Hpara(PPh3)], 7.22 [m, 12, Hmeta
(PPh3)], 7.01 [m, 12, Hortho(PPh3)], 6.63 [t, 1, H3, 3JHH ¼ 1.72 Hz], 6.59
2.2.4. [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][CF3SO3] 4
5-C5H5)(DPPE)Cl] (0.30 g, 0.5 mmol)
3
[t, 1, H2, JHH ¼ 1.72 Hz], 4.41 [s, 5,
h
5-C5H5], 3.79 [t, 2, H4,
To a stirred solution of [Ru(h
3JHH ¼ 7.01 Hz], 1.43 [quintet, 2, H5, 3JHH ¼ 7.03 Hz], 0.97 [sextet, 2,
in dichloromethane (25 mL) was added 1-butylimidazole (0.06 mL,
0.6 mmol) and AgCF3SO3 (0.15, 0.6 mmol). After refluxing for 10 h
the solution turned from orange to yellow. The reaction mixture
was cooled to room temperature, filtered and the solvent removed
under reduced pressure; the product was washed with n-hexane
(2 ꢁ 10 mL) affording yellow crystals after recrystallization from
dichloromethane/n-hexane. Yield: 83%. 1H NMR [(CD3)2CO, Me4Si,
H6, 3JHH ¼ 7.94 Hz], 0.77 [t, 3, H7, 3JHH ¼ 7.03 Hz]. 13C NMR [CDCl3,
d/ppm]: 143.64 (C1, 1-BuIm), 136.64 (Cq, PPh3), 135.65 (CH, PPh3),
130.01 (CH, PPh3), 128.06 (CH, PPh3), 135.35 (C2, 1-BuIm), 120.14 (C3,
1-BuIm), 82.77 (C5H5), 47.64 (C4, 1-BuIm), 32.57 (C5, 1-BuIm), 19.26
(C6, 1-BuIm), 13.61 (C7, 1-BuIm). 31P NMR [CDCl3,
d/ppm]: 42.48 [s,
PPh3]. IV [KBr, cmꢀ1]: 3433 (m), 3124 (m), 3051 (m), 2960 (m), 2931
(w), 2873 (w), 1969 (vw), 1907 (vw), 1828 (vw), 1637 (vw), 1529
(vw), 1479 (m), 1435 (s), 1344 (vw), 1279 (vs), 1255 (vs), 1223 (m),
1159 (s), 1088 (s), 1030 (vs), 997 (w), 924 (vw), 887 (vw), 843 (w),
816 (w), 742 (s), 696 (vs), 636 (s), 571 (vw), 517 (vs), 420 (w). ESI-
HRMS: calcd. For [Mþ] 815.22653, found 815.22393.
d
/ppm]: 7.70 [t, 4, DPPE], 7.41 [m, 4, DPPE], 6.62 [t, 1, H
,
3
3JHH ¼ 1.37 Hz], 6.57 [s, 1, H1], 6.34 [t, 1, H2, 3JHH ¼ 1.35 Hz ], 4.75 [s,
5,
h
5-C5H5], 3.40 [t, 2, H4, 3JHH ¼ 7.35 Hz], 2.96 [m, 4, CH2 (DPPE)],
1.19 [quint, 2, H5, 3JHH ¼ 7.27 Hz], 0.91 [sextet, 2, H6, 3JHH ¼ 7.64 Hz],
0.76 [t, 3, H7, JHH ¼ 7.30 Hz]. 13C NMR [(CD3)2CO,
d/ppm]: 143.65
3

114
T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
[C1, 1-BuIm], 135.30 [C2, 1-BuIm], 133.86 [CH, DPPE], 131.63 [CH,
DPPE], 131.07 [Cq, DPPE], 129.42 [CH, DPPE], 120.20 [C3, 1-BuIm],
82.96 [C5H5], 47.61 [C4, 1-BuIm], 33.17 [C5, 1-BuIm], 29.12 [CH2,
(s), 530 (s), 520 (s), 496 (m), 469 (w), 441 (w). ESI-HRMS: calcd. For
[Mþ] 689.17932, found 689.17980.
DPPE], 19.96 [C6, 1-BuIm], 13.70 [C7, 1-BuIm]. 31P NMR [(CD3)2CO,
d/
2.3. Electrochemical studies
ppm]: 83.35 [s, DPPE]. IV [KBr, cmꢀ1]: 3415 (w), 3136 (m), 3053 (w),
2950 (m), 2933 (m), 2867 (w), 1968 (vw), 1896 (vw), 1825 (vw),
1571 (w), 1530 (w), 1478 (w), 1435 (m), 1372 (vw), 1352 (vw), 1268
(vs), 1224 (m), 1186 (w), 1149 (s), 1093 (m), 1030 (vs), 994 (w), 916
(vw), 875 (w), 807 (m), 752 (m), 689 (s), 637 (vs), 674 (m), 531 (s),
517 (s), 497 (m), 440 (m). ESI-HRMS: calcd. For [Mþ] 689.17932,
found 689.17777.
Cyclic voltammograms were obtained using a EG&G Princeton
Applied Research Potentiostat/Galvanostat Model 273A equipped
with Electrochemical PowerSuite v2.51 software for electro-
chemical analysis, in anhydrous dichloromethane or acetonitrile
with tetrabutylammonium hexafluorophosphate (0.1e0.2 M) as
supporting electrolyte. The electrochemical cell was a homemade
three electrode configuration cell with a platinum-disc working
electrode (1.0 mm) probed by a Luggin capillary connected to
a silver-wire pseudo-reference electrode and a platinum wire
auxiliary electrode. All the experiments were performed in
nitrogen atmosphere at room temperature. All the potentials
reported were measured against the ferrocene/ferrocenium redox
couple as internal standard and normally quoted relative to SCE
(using the ferrocenium/ferrocene redox couple E1/2 ¼ 0.46 or
0.40 V versus SCE for dichloromethane or acetonitrile respectively
[27]).
2.2.5. [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][PF6] 5
5-C5H5)(DPPE)Cl] (0.30 g, 0.5 mmol) in
To a solution of [Ru(
h
dichloromethane (25 mL) was added 1-butylimidazole (0.06 mL,
0.6 mmol) followed by the addition of TlF6 (0.21, 0.6 mmol). After
refluxing for 5 h the solution turned from orange to yellow. The
reaction mixture was cooled to room temperature, filtered and the
solvent removed under reduced pressure; the product was washed
with n-hexane (2 ꢁ 10 mL) affording yellow crystals after recrys-
tallization from dichloromethane/n-hexane. Yield: 78%. 1H NMR
[(CD3)2CO, Me4Si,
d
/ppm]: 7.69 [t, 4, DPPE], 7.39 [m, 4, DPPE], 6.63
Both the sample and the electrolyte (Fluka) were dried under
vacuum for several hours prior to the experiment. Reagent grade
solvents were dried, purified by standard procedures and distilled
under nitrogen atmosphere before use.
[t, 1, H
,
3JHH ¼ 1.49 Hz], 6.53 [s, 1, H1], 6.36 [t, 1, H2,
3
3JHH ¼ 1.48 Hz], 4.75 [s, 5,
h
5-C5H5], 3.39 [t, 2, H4, JHH ¼ 7.33 Hz],
3
3
2.96 [m, 4, CH2 (DPPE)], 1.19 [quint, 2, H5, JHH ¼ 7.34 Hz], 0.90
[sextet, 2, H6, JHH ¼ 7.64 Hz], 0.76 [t, 3, H7, JHH ¼ 7.11 Hz]. 13C
3
3
NMR [(CD3)2CO,
d
/ppm]: 143.62 [C1, 1-BuIm], 135.35 [C2, 1-BuIm],
2.4. Crystal structure determination
133.85 [CH, DPPE], 131.63 [CH, DPPE], 131.09 [Cq, DPPE], 129.46
[CH, DPPE], 120.30 [C3, 1-BuIm], 82.88 [C5H5], 47.62 [C4, 1-BuIm],
33.15 [C5, 1-BuIm], 29.15 [CH2, DPPE], 20.07 [C6, 1-BuIm], 13.69 [C7,
X-ray data were collected on a Brucker AXS APEX CCD are
detector diffracometer at 150(1) K using graphite-monochromated
1-BuIm]. 31P NMR [(CD3)2CO,
d
/ppm]: 83.37 [s, DPPE], ꢀ144.24
Mo K
a
(
l
¼ 0.71073 Å) radiation. Intensity data were corrected for
[septet, PF6]. IV [KBr, cmꢀ1]: 3426 (w), 3151 (m), 3058 (w), 2959
(m), 2922 (m), 2862 (w), 1965 (vw), 1890 (vw), 1814 (vw), 1654
(vw), 1521 (m), 1479 (m), 1435 (s), 1416 (m), 1307 (vw), 1240 (m),
1181 (w), 1096 (s), 1028 (w), 999 (m), 918 (w), 837 (vs), 752 (m),
733 (m), 697 (s), 675 (m), 645 (w), 587 (vw), 557 (s), 529 (s), 517
(m), 497 (m), 438 (m). ESI-HRMS: calcd. For [Mþ] 689.17932, found
689.17982.
Lorentz polarization effects. Empirical absorption correction using
SADABS [28] was applied and data reduction was done with SMART
and SAINT programs [29].
The structures were solved by direct methods with the
programs SIR97 [30] and SHELXS97 [31] and refined by full-matrix
least squares on F2 with SHELXL97 [32] both included in the
package of programs WINGX-Version 1.70.01 [33]. Non-hydrogen
atoms were refined with anisotropic thermal parameters whereas
H-atoms placed in idealized positions and allowed to refine riding
on the parent C atom. Graphical representations were prepared
using ORTEP [34] and Mercury 1.1.2 [35].
2.2.6. [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][BPh4] 6
5-C5H5)(DPPE)Cl] (0.30 g, 0.5 mmol) in
To a solution of [Ru(
h
methanol (25 mL) was added 1-butylimidazole (0.06 mL, 0.6 mmol)
followed by the addition of NH4BPh4 (0.20, 0.6 mmol).
A summary of the crystal data, structure solution and refine-
ment parameters for all structures are givens in Tables 1 and 2.
After refluxing for 4 h the solution was filtered and the solvent
removed under reduced pressure. The yellow powder was dissolved
in acetone and the precipitate of NH4Cl was removed by cannula-
filtration and the solvent evaporated. The product was washed
with n-hexane (2 ꢁ 10 mL) affording yellow crystals after recrys-
tallization from dichloromethane/n-hexane. Yield: 81%. 1H NMR
3. Results and discussion
3.1. Synthesis of the Ru(II) complexes
[(CD3)2CO, Me4Si,
d
/ppm]: 7.68 [t, 4, DPPE] 7.38 [m, 24,
The novel cationic complexes of general formula [Ru(h5
-
DPPE þ Hortho(BPh4)], 6.60 [t,1, H3, 3JHH ¼1.37 Hz], 6.50 [s,1, H1], 6.35
C5H5)(LL)(1-BuIm)][Z], with (LL) ¼ 2PPh3 or DPPE, and Z ¼ CF3SOꢀ3 ,
[t, 1, H2, 3JHH ¼ 1.34 Hz], 6.92 [m, 8, Hpara (BPh4)], 6.77 [m, 4, Hpara
PFꢀ6 , BPh4ꢀ, were prepared by halide abstractionwith AgCF3SO3, TlPF6
(BPh4)], 4.74 [s, 5,
h
5-C5H5], 3.37 [t, 2, H4, 3JHH ¼ 7.17 Hz], 2.93 [m, 4,
or NH4BPh4, from the neutral complexes [Ru(h
5-C5H5)(LL)Cl], in
3
CH2 (DPPE)], 1.18 [quint, 2, H5, JHH ¼ 6.96 Hz], 0.89 [sextet, 2, H6,
dichloromethane or methanol, in the presence of a slight excess of
the 1-butylimidazole ligand (Scheme 1). The reactions were carried
out at reflux or stirring at room temperature. The compounds were
recrystallized by slow diffusion of diethyl ether or n-hexane in
dichloromethane solutions. The new compounds were fully char-
acterized by FT-IR, 1H, 13C, and 31P NMR spectroscopies. The solid
state FT-IR spectra of the complexes present the characteristic band
of the cyclopentadienylligand in the range 3051e3058 cmꢀ1, the PF6ꢀ
(840 and 560 cmꢀ1), CF3SO3ꢀ anion (1250 cmꢀ1) or BPhꢀ4 anion
(730e745 cmꢀ1) and the imidazole ring (CH stretch) in the range
3124e3151 cmꢀ1 All the new compounds were also characterized by
X-ray diffraction studies.
3JHH ¼ 7.60 Hz], 0.76 [t, 3, H7, 3JHH ¼ 7.29 Hz]. 13C NMR [(CD3)2CO,
d/
ppm]: 143.51 [C1, 1-BuIm], 135.37 [C2, 1-BuIm], 137.03 (CH, BPh4),
133.84 [CH, DPPE], 131.63 [CH, DPPE], 131.10 [Cq, DPPE], 130.56 (Cq,
BPh4),129.36[CH, DPPE],125.95(CH, BPh4),122.21(CH, BPh4),120.23
[C3, 1-BuIm], 82.73 [C5H5], 47.63 [C4, 1-BuIm], 33.14 [C5, 1-BuIm],
29.11 [CH2, DPPE], 19.97[C6, 1-BuIm], 13.70 [C7, 1-BuIm]. 31P NMR
[(CD3)2CO, d
/ppm]: 83.46 [s, DPPE]. IV [KBr, cmꢀ1]: 3433 (w), 3125
(m), 3053 (m), 3038 (m), 2998 (w), 2932 (w), 2873 (vw), 1946 (vw),
1886 (vw), 1804 (vw), 1578 (m), 1529 (w), 1481 (m), 1434 (s), 1408
(m), 1236 (w), 1184 (vw), 1091 (s), 1030 (w), 1000 (w), 989 (w), 868
(w), 840 (w), 799 (m), 746 (s), 732 (s), 699 (vs), 672 (s), 641 (m), 611

T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
115
Table 1
Data collection and structure refinement parameters for [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][CF3SO3] 1, [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][PF6] 2, [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][BPh4] 3.
Compound
1
2
3
Empirical formula
Formula weight
T (K)
C
49.50H48ClF3N2O3P2RuS
C49H49Cl2F6N2P3Ru
1044.78
150(2)
C72H67BN2P2Ru
1134.10
296(2)
1006.42
150(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
0.71073
Monoclinic
P21/c
0.71069
Triclinic
P-1
0.71073
Orthorhombic
P c a 21
14.3039(16)
43.934(4)
14.6701(17)
90
97.339(5)
90
9143.5(17)
8
1.462
10.7473(4)
11.3403(4)
21.2344(8)
78.882(2)
79.672(2)
71.227(2)
2385.12(15)
2
23.5845(5)
18.5011(5)
26.0889(7)
90
90
90
11,383.6(5)
8
1.323
0.378
4736
1.10e27.52
ꢀ30 ꢃ h ꢃ 18,
ꢀ24 ꢃ k ꢃ 23,
ꢀ33 ꢃ l ꢃ 33
63,147/25,594
[R(int) ¼ 0.0438]
b (Å)
c (Å)
a
Β (ꢂ)
G
Volume (Å3)
(ꢂ)
(ꢂ)
Z
Calculated density (Mgmꢀ3
)
1.455
0.601
1068
Absorption Coefficient (mmꢀ1
F (000)
)
0.574
4136
q
Range for data collection (ꢂ)
1.44e27.52
ꢀ18 ꢃ h ꢃ 17
ꢀ57 ꢃ k ꢃ 55
ꢀ16 ꢃ l ꢃ 19
74,424/20,934
[R(int) ¼ 0.1890]
2.99e26.78
ꢀ13 ꢃ h ꢃ 13,
ꢀ14 ꢃ k ꢃ 11,
ꢀ26 ꢃ l ꢃ 26
36,624/10,064
[R(int) ¼ 0.0680]
Limiting indices
Reflections collected/unique
Completeness to Refinement method
Refinement method
q
¼ 27.52 [99.5%]
q
¼ 26.78 [98.7%]
q
¼ 27.52 [99.7%]
Full-matrix least-squares on F2
20,934/0/1126
0.874
Full-matrix least-squares on F2
10,064/6/571
Full-matrix least-squares on F2
15,594/1/1405
1.047
Goodness-on-fit on F2
1.006
Final R indices [I > 2
s
(I)]
R1 ¼ 0.0716
R1 ¼ 0.0451
R1 ¼ 0.0375
wR2 ¼ 0.1448
R1 ¼ 0.2054
wR2 ¼ 0.0820
R1 ¼ 0.0781
wR2 ¼ 0.0875
R1 ¼ 0.0554
R indices (all data)
wR2 ¼ 0.2068
1.012 and ꢀ0.965
wR2 ¼ 0.0926
0.689 and ꢀ0.723
wR2 ¼ 0.1113
0.659 and ꢀ0.663
Largest diff. peak and hole (eÅ)ꢀ3
Table 2
Data collection and structure refinement parameters for [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][CF3SO3] 4, [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][PF6] 5, [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][BPh4] 6.
Compound
4
5
6
Empirical formula
Formula weight
T (K)
C
39H41F3N2O3P2RuS
C38H41F6N2P3Ru
833.71
150(2)
C62H57BN2P2Ru
1003.92
150(2)
837.81
150(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
0.71073
Monoclinic
P21/n
0.71073
Monoclinic
P21/n
0.71073
Monoclinic
P21/n
14.2788 (10)
16.4575(11)
16.6624(12)
90
107.585(2)
90
3732.6(5)
4
1.491
13.6741(10)
16.5051(12)
16.8448(12)
90
106.711(4)
90
3641.2(5)
4
1.521
9.925
21.064
24.132
90
95.17
90
5024.5
4
b (Å)
c (Å)
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
Volume (Å3)
Z
Calculated density (Mgmꢀ3
)
1.327
0.418
2088
Absorption coefficient (mmꢀ1
F (000)
)
0.617
1720
0.624
1704
q
Range for data collection (ꢂ)
2.83e27.99
ꢀ18 ꢃ h ꢃ 16,
ꢀ21 ꢃ k ꢃ 20,
ꢀ21 ꢃ l ꢃ 20
34,811/8925
[R(int) ¼ 0.0952]
2.58e25.02
ꢀ16 ꢃ h ꢃ 16,
ꢀ19 ꢃ k ꢃ 19,
ꢀ20 ꢃ l ꢃ 20
83,462/6378
[R(int) ¼ 0.0520]
2.49e28.37
ꢀ13 ꢃ h ꢃ 13
ꢀ28 ꢃ k ꢃ 28
ꢀ32 ꢃ l ꢃ 32
48,511/12,473
[R(int) ¼ 0.0748]
Limiting indices
Reflections collected/unique
Completeness to refinement method
Refinement method
q
¼ 27.99 [99.1%]
q
¼ 25.02 [99.2%]
q
¼ 28.37 [99.2%]
Full-matrix least-squares on F2
8925/0/460
Full-matrix least-squares on F2
6378/1/451
Full-matrix least-squares on F2
12,473/0/613
Data/restraints/parameters
Goodness-on-fit on F2
0.952
1.042
0.998
Final R indices [I > 2
R indices (all data)
s
(I)]
R1 ¼ 0.0384
R1 ¼ 0.0441
R1 ¼ 0.0488
wR2 ¼ 0.0753
R1 ¼ 0.0671
wR2 ¼ 0.1111
R1 ¼ 0.0553
wR2 ¼ 0.1106
R1 ¼ 0.0845
wR2 ¼ 0.0840
1.062 and ꢀ0.682
wR2 ¼ 0.1175
2.136 to ꢀ0.790
wR2 ¼ 0.1275
1.279 and ꢀ0.750
Largest diff. peak and hole (eÅ)ꢀ3

116
T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
Scheme 1. Reaction scheme for the synthesis of Ru (II) complexes [Ru(h
5-C5H5)(LL)(1-BuIm)][Z] with numbering scheme for NMR purposes.
3.2. Spectroscopic studies by NMR
DPPE containing compounds this value was w83 ppm. In
compounds 2 and 5 was also found the characteristic septuplet
signal of PFꢀ6 at ꢀ144.1 ppm.
1H NMR resonances of the cyclopentadienyl ring are in the
characteristic range of monocationic ruthenium(II). The coordi-
nated 1-BuIm ligand displays a general shielding of the protons as
3.3. UVevisible studies
result of
p backdonation from de organometallic moiety, with
special relevance for H1, which up field shift was about 1 ppm for
compounds 4, 5 and 6 (see Scheme 1 for protons identification).
Compounds with PPh3 (1, 2 and 3) showed only an up field shift of
w0.4 ppm on that proton H1, being these results in good agreement
with the better donor character of DPPE. Moreover, the remaining
protons of the coordinated heteroaromatic ring, H2 and H3, display
The optical absorption spectra of all the synthesized new
complexes were recorded in w5 ꢁ 10ꢀ5 mol dmꢀ3 solutions of
dichloromethane and are presented on Table 4.
The spectra of the compounds are essentially analogous to the
ruthenium starting material complexes and are characterized by
intense absorption bands in the UV region, at w250 nm charac-
a slight deshielding (w0.3 ppm) revealing that the income of
p
teristic of pep* transitions of the aromatic ligands. This band was
electronic density did not compensate the effect of sigma coordi-
nation on this side of the ring, which is the longest way between
the two N atoms. Furthermore, also an increased electronic density
was found at the coordinated 1-butylimidazole pendent arm. In
fact, protons H4 and H5 are shielded up to 0.6 and 0.5 ppm rela-
tively to the free ligand values. Nevertheless, this shielding effect
might be explained by the influence of the anisotropic effect of the
neighbor phosphino aromatic rings. Table 3 compares the 1H NMR
chemical shifts of the free and coordinated 1-butylimidazole for the
followed by one or two broad and less intense bands, which
maximum is place between 300 and 400 nm. Fig.1 is representative
of the electronic spectra of this family of compounds.
Comparison of the electronic spectra of the studied compounds
in solvents of different polarity, namely acetonitrile, acetone and
dichloromethane revealed little effect of the solvent.
3.4. Electrochemical studies
family [Ru(h
5-C5H5)(LL)(1-BuIm)][Z] (1e6) in (CD3)2CO.
The electrochemical behavior of the redox-active compounds
1e6 have been studied at room temperature by cyclic voltammetry
13C NMR spectra for this family of compounds confirm the
evidence found for proton spectra. The Cp ring chemical shifts are
in the range usually observed for Ru(II) cationic derivatives. All
carbons of 1-butylimidazole ligand were only slightly deshielded or
remained almost unchanged for the entire family of compounds.
31P NMR spectra of the complexes showed a single sharp signal
for the phosphine coligands revealing the equivalence of the two
phosphorus atoms, and an expected deshielding upon coordination
Table 4
Optical spectra data for complexes [Ru(
ligand, in dichloromethane, acetone and acetonitrile solutions.
h
5-C5H5)(LL)(1-BuIm)][Z] (1e6) and the free
Compound
lmax (nm) (ε Mꢀ1 cmꢀ1
)
CH2Cl2
(CH3)2CO
CH3CN
according to the
s donor character of these ligands. For compounds
[Ru(
[CF3SO3] (1)
h
5-C5H5)(PPh3)2(1-BuIm)]
233 (40,700)
e
e
205 (99,800)
e
with the PPh3 coligand this resonance occurred at w42 ppm and for
e
364 (2980)
236 (21,600)
291 (3670)
364 (2230)
239 (38,000)
271 (sh)
367 (2290)
e
363 (2790)
202 (9350)
230 (sh)
364 (2020)
204 (11,900)
234 (sh)
[Ru(
h
5-C5H5)(PPh3)2(1-BuIm)]
[PF6] (2)
e
Table 3
363 (2240)
e
Selected 1H NMR data for compounds [Ru(
h
5-C5H5)(LL)(1-BuIm)][Z] (1e6) and the
[Ru(h
5-C5H5)(PPh3)2(1-BuIm)]
free ligand in (CD3)2CO.
[BPh4] (3)
e
364 (3120)
234 (34,300)
291 (sh)
363 (2300)
e
364 (2040)
203 (60,200)
298 (sh)
Compound
Proton number
[Ru(
[CF3SO3] (4)
h
5-C5H5)(DPPE)(1-BuIm)]
H1
H2
H3
H4
H5
H6
H7
Cp
e
1-BuIm
7.56
7.22
7.20
7.13a
6.57
6.53
6.50
7.09
7.13
7.13a
7.07
6.34
6.36
6.35
6.94
7.18
7.13a
7.22
6.62
6.63
6.60
3.99
3.73
3.71
3.67
3.40
3.39
3.37
1.72
1.44
1.43
1.42
1.19
1.19
1.18
1.26
0.94
0.94
0.93
0.91
0.90
0.89
0.90
0.76
0.76
0.76
0.76
0.76
0.76
e
377 (1790)
236 (23,900)
290 (sh)
377 (1450)
248 (50,300)
306 (sh)
381 (1850)
e
380 (1170)
201 (77,800)
302 (sh)
380 (1340)
211 (78,900)
316 (sh)
1
2
3
4
5
6
4.56
4.56
4.55
4.75
4.75
4.74
[Ru(
[PF6] (5)
h
5-C5H5)(DPPE)(1-BuIm)]
e
381 (1322)
e
[Ru(h
5-C5H5)(DPPE)(1-BuIm)]
[BPh4] (6)
e
385 (1990)
381 (1550)
382 (1630)
a
Overlap with PPh3.
sh: shoulder.

T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
117
Fig. 2. Cyclic voltammogram of complex [Ru(
h
5-C5H5)(DPPE)(1-BuIm)][PF6] in
dichloromethane (____) and acetonitrile ( _ _ _) tipyfying the electrochemical behavior of
these family of compounds.
Fig. 1. Electronic spectra of [Ru(
h
5-C5H5)(PPh3)2(1-BuIm)][CF3SO3] (1) (ꢀ), [Ru(h5
-
C5H5)(PPh3)2Cl] (ꢄꢄꢄꢄꢄ) and 1-BuIm ̶(̶̶) in w5 ꢁ 10ꢀ5 mol dmꢀ3 dichloromethane
Table 6
solutions. Inset: detail of the charge transfer band.
Selected bond lengths and bond and torsion angles for [Ru(
BuIm)][CF3SO3] 1, [Ru(
h
h
5-C5H5)(PPh3)2(1-
5-C5H5)(PPh3)2(1-
h
5-C5H5)(PPh3)2(1-BuIm)][PF6] 2, [Ru(
BuIm)][BPh4] 3.
(CV) at a platinum disk electrode in dichloromethane and aceto-
nitrile with tetrabutylammonium hexafluorophosphate as sup-
porting electrolyte. The results are summarized on Table 5 and
typical CV’s are showed on Fig. 2.
Compound
1
2
3
Molecule 1 Molecule 2
Molecule 1 Molecule 2
Bond lengths (Å)
RueCpa
RueP(1)
1.846 (1)
2.370 (2)
2.338 (2)
2.149(5)
1.853(1)
2.338(2)
2.337 (2)
2.131(6)
1.856 (3) 1.853(7)
1.856(7)
2.319 (1)
2.349 (1)
2.131(3)
Upon scanning anodically, all the complexes (1e6) exhibit, in
2.3472(7) 2.366(1)
2.344 (1) 2.320(1)
2.127(3) 2.126(3)
dichloromethane, onereversible oxidativeresponse(
D
E ¼ 80 mV), in
RueP(2)
the potential range 0.90e1.05 V at the scan rate 200 mV sꢀ1 assigned
RueN(1)
to the couple RuII/RuIII. These results are within the range observed
Angles (ꢂ)
before for the related complexes [Ru(h
5-C5H5)(PPh3)2(ImH)][PF6]
CpaeRueP(1)
CpaeRueP(2)
CpaeRueN(1)
121.74(5)
118.57(5)
117.85(5)
123.85(5)
119.22(2) 125.79(11) 122.26(8)
124.60(2) 120.43(7)
117.94(3)
125.05(11)
124.1(3)
130.8(3)
104.55(3)
87.85(9)
92.07(9)
121.04(14) 124.78(15) 124.17(6) 119.42(3)
RueN(1)eC(11) 133.5(5)
RueN(1)eC(13) 121.8(5)
125.3(5)
129.8(5)
102.31(7)
124.8(2) 125.9(3)
130.0(2) 128.7(3)
100.60(3) 106.24(3)
91.76(6) 90.50(9)
88.26(7) 87.07(8)
Table 5
Electrochemical data for complexes [Ru(
methane and acetonitrile.
h
5-C5H5)(PP)(1-BuIm)][Z] in dichloro-
P(1)eRueP(2)
N(1)eRueP(1)
N(1)eRueP(2)
97.99(7)
95.20(16) 92.75(16(
96.70(16) 87.78(16)
Epa (V)
Epc (V)
E1/2 (V)
EpaeEpc (mV)
ic/ia
a
Centroid of the h
5-cyclopentadienyl ligand.
Dichloromethane
1-BuIm
1.35
0.96
1.58
0.56
1.03
0.87
1.10
1.49
0.94
1.59
0.98
1.64
0.85
1.49
e
e
e
e
1
2
3
PP ¼ 2PPh3
Z ¼ CF3SO3
PP ¼ 2PPh3
Z ¼ PF6
0.88
e
0.92
e
80
e
1.0
e
(E1/2
¼
1.04 V) and [Ru(h
5-C5H5)(PPh3)2(1-BI)][CF3SO3] (E1/
0.48
0.95
e
0.52
0.99
e
80
80
e
0.9
0.9
e
¼ 0.90 V)in the same experimental conditions [12,13] indicating
2
that the chemically linked alkyl pendent arm have a negligible
contribution on the ruthenium(II) oxidation process. In addition,
another redox process was also found w1.5 V for all the studied
compounds attributed to the oxidation at imidazole coordinated
molecule. Unexplainably, anotheroxidationprocess, at a muchlower
potential, was found for complexes 2 and 3 which was postulated to
occur in the 1-butylimidazole coordinated ligand and may possibly
PP ¼ 2PPh3
Z ¼ BPh4
1.02
e
1.04
e
80
e
1.0
e
4
5
6
PP ¼ Dppe
Z ¼ CF3SO3
PP ¼ Dppe
Z ¼ PF6
0.86
e
0.90
e
80
e
0.95
e
0.90
e
0.94
e
80
e
0.91
e
PP ¼ Dppe
Z ¼ BPh4
0.76
e
e
90
e
0.4
e
e
Acetonitrile
1-BuIm
1.48
e
e
e
e
e
e
e
e
e
70
e
e
e
e
e
e
e
e
70
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
0.95
Table 7
Selected bond lengths and bond and torsion angles for [Ru(
BuIm)][CF3SO3] 4, [Ru(
BuIm)][BPh4] 6.
h
h
5-C5H5)(DPPE)(1-
5-C5H5)(DPPE)(1-
ꢀ0.66
ꢀ1.55
e
e
h
5-C5H5)(DPPE)(1-BuIm)][PF6] 5, [Ru(
e
e
1
2
PP ¼ 2PPh3
0.98
1.45
e
e
Z ¼ CF3SO3
e
e
Compound
4
5
6
ꢀ0.77
0.56
e
e
PP ¼ 2PPh3
Z ¼ PF6
0.63
1.01
1.33
e
0.60
e
Bond lengths (Å)
RueCpa
RueP(1)
RueP(2)
RueN(1)
Angles (ꢂ)
1.863 (1)
1.861 (1)
1.860(1)
2.269(1)
2.289(1)
2.133(2)
e
e
2.275(1)
2.283 (1)
2.131(2)
2.278(1)
2.286 (1)
2.141(3)
ꢀ0.80
e
e
3
PP ¼ 2PPh3
Z ¼ BPh4
0.79
0.95sh
1.22
e
e
e
e
e
e
CpaeRueP(1)
CpaeRueP(2)
CpaeRueN(1)
RueN(1)eC(11)
RueN(1)eC(13)
P(1)eRueP(2)
N(1)eRueP(1)
N(1)eRueP(2)
128.65(2)
126.04(2)
123.59(6)
130.49(17)
124.97(17)
84.04(3)
123.37(8)
127.54(3)
127.09(3)
130.7(3)
124.2(3)
84.04(3)
89.41(8)
93.43(9)
124.80(2)
127.05(2)
122.68(7)
124.9(2)
130.0(2)
84.50(3)
92.39(7)
94.70(7)
ꢀ0.13
ꢀ0.75
0.74
e
e
e
4
5
6
PP ¼ Dppe
Z ¼ CF3SO3
PP ¼ Dppe
Z ¼ PF6
0.81
0.78
0.82
0.90
0.75
0.70
0.79
70
1.0
88.23(6)
94.28(6)
PP ¼ Dppe
Z ¼ BPh4
e
200
0.43
a
Centroid of the h
5-cyclopentadienyl ligand.

118
T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
Fig. 3. Molecular diagrams depicting the cationic moieties for complexes 1e3. Hydrogen atoms were omitted for clarity. The different conformation of the aliphatic side chain of the
1-butylimidazole can be clearly observed. For compounds 1 and 3 only one molecule is depicted.
Fig. 4. Molecular diagrams depicting the cationic moieties for complexes 4e6. Hydrogen atoms were omitted for clarity. The different conformation of the aliphatic side chain of the
1-butylimidazole is again clearly evidenced.
reflect some modification of the electronic features of the 1-BuIm
ligand through metal complexation. In effect, complex 2 (with PF6
as counter ion), showed a quasi reversible oxidation at E1/2 ¼ 0.52 V,
while this process was irreversible for complex 3 (with BPh4 as
counter ion) with an anodic wave at Epa ¼ 0.87 V. The cyclic volta-
mograms obtained in acetonitrile for complexes 1e3 were charac-
terized, at positive potentials, by the RuII/RuIII irreversible process in
the range 0.95e1.01 V. As observed in dichloromethane, also the
process occurring at lower potentials attributed to the coordinated
imidazole was found quasi reversible for complex 2 (E1/2 ¼ 0.60 V)
and irreversible for complex 3 (Epa ¼ 0.79).
The anodic scan gives for complexes 4 and 5, a reversible RuII/
RuIII redox wave at 0.81 and 0.82 V, respectively. The similarity of
these oxidation potentials indicates the negligible contribution of
the non-coordinating anions PFꢀ6 and CF3SO3ꢀ on the ruthenium
redox potentials. Ratios of reverse to forward currents (ic/ia) of 1.0
and 0.95 V at a scan rate of 200 mV sꢀ1 presented by complexes 4
and 5, showed that the oxidized forms display high chemical
stability on the time scale of the cyclic voltammetry experiment.
The lower stability of compound 6 presenting the BPhꢀ4 as counter
ion (Epa ¼ 0.90 V), with the value of ic/ia ratio of 0.4 is in agreement
with the result also found in dichloromethane.
Fig. 5. Superimposition of the cationic fragments of CpRu(1-BuIm)(PPh3)2. Phenyl
rings and H atoms have been omitted for clarity. Perfectly evidenced is the different
geometries adopted by the N-heterocyclic rings and the butyl chains. (dark blue:
molecule 1 of 1; red: molecule 2 of 1; pale blue: compound 2; green: molecule 1 of 3
and magenta: molecule 2 of 3). (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
Our electrochemical studies reveal that the DPPE derivatives
present redox potentials for the RuII/RuIII couple slightly lower than
those of the correspondent triphenylphosphine analogs, particu-
larly in acetonitrile. This can be expected on the basis of the greater
electro-withdrawing power of triphenylphosphine in comparison

T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
119
Scheme 2. Definition of the angles 41, 42 and
s : for details see text above.
with the bidentate DPPE and the reduced
the ruthenium center.
p-backdonation ability of
3.5. X-ray structural studies of complexes
Inthisfamilyofruthenium complexes bearinga 1-butylimidazole
ligand, we are looking for the influence of the mono and bidentate
phosphine ligand in the overall coordination geometry of the Ru
core. The effect of the counter ionnot only in the geometry but also in
the overall packing, governing the behavior of the newlysynthesized
compounds is also studied here.
Suitable crystals for X-ray diffraction studies of the complexes
with triphenylphosphine ligands (1e3), crystallized in different
crystalline systems and space groups (monoclinic, P21/c for 1,
triclinic, P-1 for 2 and orthorhombic P c a 21 for 3). Complexes with
DPPE (4e6) all crystallized in the same crystalline systems and
space group monoclinic, P21/n.
All compounds present the usual distorted three-legged piano
Fig. 7. Supramolecular packing showing the intermolecular hydrogen bonds of the
butylimidazole ligand to the counter ion. (turquoise: intermolecular interactions
described in the text). (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)
stool geometry for
by PeMeP angles of 97.99(7)ꢂ to 106.24(3) and NeMeP angles
varying from 87.07(8)ꢂ to 96.70(16), with the remaining h5
h
5-monocyclopentadienyl complexes confirmed
-
Cp(centroid)eMeX (with X ¼ N or P) angles between 117.85(5)ꢂ
and 125.05(11)ꢂ for complexes 1e3 (see Table 6). In complexes 4e6
the geometry is restricted by the stereochemical imposition of the
bite angle of the bidentate phosphine, with PeMeP angles below
90ꢂ, 84.04(3) to 84.50(3) and NeMeP angles varying from 88.23(6)ꢂ
The distances Ru-h
5-Cp(centroid), ranging from 1.846(1) to
1.863(2) Å, and RueN ranging from 2.126(3) and 2.149(5) Å are well
within the values expected for this family of compounds [36].
Also expected are the slightly longer RueP distances in compounds
to 94.70(7), with the remaining
h
5-Cp(centroid)eMeX (with X ¼ N
or P) angles between 122.68(7)ꢂ and 128.65(2)ꢂ (see Table 7).
Fig. 6. Supramolecular packing showing the intermolecular hydrogen bonds of the
butylimidazole ligand to the counter ion. (BuIm fragment of molecule 2 is green and
gray: turquoise: intermolecular interactions described in the text). (For interpretation
of the references to color in this figure legend, the reader is referred to the web version
of this article.)
Fig. 8. Supramolecular packing showing the structural involvement of the 1-BuIm
fragment in the two different molecules.

120
T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
studies of Ru derivatives with h
6 arene with imidazole ligands, and
as expected the longer the chain the higher is the distortion [25,39].
Comparing the conformation of the 1-butylimidazole (1-BuIm)
within the CpRu(PPh3)2 complexes we can see in Fig. 5, that they
are very different. To better characterize the geometry and distor-
tion of the fragment we have defined the angles 4 , 4 and s : 4 is
1
2
1
the dihedral angle between the plane containing Ru, h
5-Cp(cent-
roid), and the coordinated N atom of the imidazole ring and the ring
plane of the heterocycle; 4 is the angle between the first plane and
2
the plane containing the four carbon atoms of the butyl chain;
s is
the angle, between the N-heterocycle ring and the plane of the
butyl chain, defining the geometry within the ligand. These angles
are illustrated in Scheme 2 (Fig. 6).
In complex 1 there are two molecules in the asymmetric unit
and the two of them have completely different conformations, with
4 ¼ 53.8ꢂ, 4 ¼ 66.0ꢂ and
s
¼ 60.9ꢂ for molecule 1 and 4 ¼ 21.5ꢂ,
1
2
1
4
2
¼ 83.8ꢂ and
s
¼ 82.5ꢂ for molecule 2. Observing the neighbor-
hood of the two fragments we can see that in molecule 1 the 1-
Fig. 9. Superimposition of the cationic fragments of CpRu(1-BuIm)(DPPE). H atoms
have been omitted for clarity. Phenyl rings are represented to show the restrictions
imposed. Geometries adopted by the N-heterocyclic rings and the butyl chains are
shown. (gray: compound 4; purple: compound 5; green: compound 6). (For inter-
pretation of the references to color in this figure legend, the reader is referred to the
web version of this article.)
BuIm interacts with two CF3SO3 anions through CHbuim
ring
-
.Oanion (2.47 and 2.60 Å) while in molecule 2 the fragment is iso-
lated. This can explain the different geometries of the fragment in
the two molecules of compound 1.
In compound
2 the 1-BuIm conformation is defined by
4 ¼ 23.9ꢂ, 4 ¼ 65.5ꢂ and
s
¼ 83.2ꢂ and we can see that there is an
1
2
interaction of the type CHbuim ring.Fanion of 2.56 Å, the aliphatic
chain having no shorter intermolecular interactions. (Fig. 7)
In compound 3 the different conformation of the 1-BuIm ligand,
1e3 when compared with the ones in 1e4, respectively
2.319(1)e2.370(2) Å versus 2.269(1) and 2.289(1) Å [11,23,37].
In Fig. 3 we present the ORTEP moleculardiagrams of compounds
1e3 and in Fig. 4 the corresponding ones for 4e6, for sake of
comparison thesamelabelingis usedin the1-butylimidazoleligand.
While the overall coordination geometry of the cations is similar
4 ¼ 20.5ꢂ, 4 ¼ 81.5ꢂ and
s
¼ 88.3ꢂ for molecule 1 and 4 ¼ 14.4ꢂ,
1
2
1
4
2
¼ 52.7ꢂ and
s
¼ 42.0ꢂ for molecule 2, is mainly due to stereo-
chemical hindrance imposed by the bulkiness of the anion and has
a more pronounced effect on 42 and s, assessing the relative posi-
tioning of the alkyl chain. (Fig. 8)
and comparable to other h5 h6 aryl Ru complexes [11,24,38], the
,
geometry of the 1-butylimidazole ligand is considerably different in
all six compounds. The occurrence of different conformations
within imidazole derivatives was already noticed in previous
As can be seen the supramolecular arrangement, stereochemical
hindrance and intermolecular interactions are determinant in the
final conformation of the ligand.
Fig. 10. a) Inset showing the stereochemical imposition of the phenyl rings b) Supramolecular packing showing the intermolecular hydrogen bonds of the butylimidazole ligand to
the CF3SO3 counter ion.
Fig. 11. a) Inset showing the stereochemical imposition of the phenyl rings b) Supramolecular packing showing the intermolecular hydrogen bonds of the butylimidazole ligand to
the PF6 anion.

T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
121
interaction compound 2 could reversibly be oxidized at the coor-
dinated 1-butylimidazole.
The major interest of the present study, besides the enlargement
of the family of the general formula [Ru(h5-C5H5)(LL)(L0)][Z] that
revealed already potential cytotoxic properties against tumor cells,
is the finding that the electronic properties of the effective ligand
(L0) can significantly be influenced by the coligands (LL) and the
couter ions (Z). Thus, important interaction with serum proteins
and/or DNA are envisaged to occur preferentially for compounds
with PPh3 namely the series [Ru(h
5-C5H5)(PPh3)2(1-BuIm)][Z].
Acknowledgments
We thank to Fundação para a Ciência e Tecnologia for financial
support (PTDC/QUI/66148/2006 and REDE/1501/REM/2005). Tânia
S. Morais thanks FCT for her Ph.D Grant (SFRH/BD/45871/2008).
Fig. 12. a) Inset showing the stereochemical imposition of the phenyl rings b)
Supramolecular packing showing the intermolecular hydrogen bonds of the butyli-
midazole ligand to the PF6 anion.
Appendix A. Supplementary material
Crystallographic data for the structural analysis of compounds
1e6 was deposited at the Cambridge Crystallographic Data Centre
under the numbers CCDC 865875e865880. These data can be
obtained free of charge via www.ccdc.cam.ac.uk or from the
Cambridge Crystallographic Data Centre,12 Union Road, Cambridge
CB21EZ, U.K., e-mail deposit@ccdc.cam.ac.uk.
Analyzing the compounds bearing the DPPE ligand we can see
that the conformation of the ligand is more restricted due to the
stereochemistry of the DPPE fragment, with the phenyl rings
reducing the possible geometries adopted by the 1-BuIm, with the
4
angle showing a less significant variation than previously, 5.0ꢂ,
1
3.8ꢂ and 20.6ꢂ, in compounds 4 to 6 respectively.
References
In compounds 4 and 5, due to the small values of 4 , the two
1
remaining angles are very similar, as expected (4 ¼ 86.6ꢂ and
2
[1] J.M. Rademaker-Lakhai, D. van den Bongard, D. Pluim, J.H. Beijnen,
J.H.M. Schellens, Clin. Cancer Res. 10 (2004) 3717.
[2] C.G. Hartinger, S. Zorbas-Seifried, M.A. Jakupec, B. Kynast, H. Zorbas,
B.K. Keppler, J. Inorg. Biochem. 100 (2006) 891.
[3] W.H. Ang, P.J. Dyson, Eur. J. Inorg. Chem. (2006) 2003.
[4] P.J. Dyson, Chimia 61 (2007) 698.
[5] W.J. Zeller, S. Fruhauf, G. Chen, B.K. Keppler, E. Frei, M. Kaufmann, Eur. J. Cancer
27 (1991) 62.
[6] M. Coluccia, G. Sava, F. Loseto, A. Nassi, A. Boccarelli, D. Giordano, E. Alessio,
G. Mestroni, Eur. J. Cancer 29A (1993) 1873.
[7] M.J. Clarke, Coord. Chem. Rev. 236 (2003) 209.
[8] E. Alessio, G. Mestroni, A. Bergamo, G. Sava, in: A. Sigel, H. Sigel (Eds.), Metal
Ions in Biological Systems. Metal Complexes in Tumor Diagnosis and as
Anticancer Agents, vol. 42, Marcel Dekker, New York, 2004, pp. 323e351.
[9] Y.K. Yan, M. Melchart,A. Habtermariam,P.J. Sadler, Chem. Comm.38(2005)4764.
[10] S.J. Dougan, P.J. Sadler, Chimia 61 (2007) 704.
s
¼ 87.0ꢂ for 4 and 4 ¼ 74.8ꢂ and
s
¼ 78.6ꢂ for 5), showing that the
2
tilting of the N-heterocyclic ring is restricted but that the relative
positioning of the aliphatic chain is due to its intermolecular inter-
actions. In 4 there is one short CHbuim ring.Oanion of 2.52 Å and also
a CHbuim chain. Oanion of 2.66 Å, governing the torsion of the mole-
cule. In 5 the same type of interaction with the counter ion is noticed
and the same carbon atoms from both the ring and alkyl moiety of
buim are involved, atoms C13 and C14, with distances of CHbuim
ring.Fanion of 2.38 Å and also a CHbuim chain.Fanion of 2.52 Å. Figs. 9
and 10 show the supramolecular arrangements (Fig. 11).
Compound 6 is shown to have a particular conformation,
different from all the others, 4 ¼ 20.6, 4 ¼ 25.7ꢂ and
s
¼ 5.6ꢂ due
1
2
[11] M.H. Garcia, T.S. Morais, P. Florindo, M.F.M. Piedade, V. Moreno, C. Ciudad,
V. Noe, J. Inorg. Biochem. 103 (2009) 354.
[12] V. Moreno, J. Lorenzo, F.X. Aviles, M.H. Garcia, J. Ribeiro, T.S. Morais,
P. Florindo, M.P. Robalo, Bioinorg. Chem. Appl. (2010).
to the “phenylic surrounding” of the fragment imposing strong
stereochemical restrictions. (Fig. 12)
[13] V. Moreno, M. Font-Bardia, T. Calvet, J. Lorenzo, M.H. Garcia, T.S. Morais,
A. Valente, M.P. Robalo, J. Inorg. Biochem. 105 (2011) 24.
[14] B. Fromenty, D. Pessayre, Pharmacol. Ther. 67 (1995) 101.
[15] R.K. Kutty, G. Santostasi, J. Horng, G. Krishna, Toxicol. Appl. Pharmacol. 107
(1991) 377.
[16] R.E. Heikkila, J. Hwang, S. Ofori, H.M. Geller, W.J. Nicklas, J. Neurochem. 54
(1990) 743.
[17] T. Aiuchi, Y. Shirane, H. Kinemochi, Y. Arai, K. Nakaya, Y. Nahamura, Neuro-
chem. Int. 12 (1988) 525.
[18] L.M.Sayre, F.Wang, C.L.Hoppel, Biochem.Biophys.Res. Commun. 161(1989)809.
[19] R.R. Rqamsay, R.J. Mehlhom, T.P. Singer, Biochem. Biophys. Res. Commun. 159
(1989) 983.
[20] A. Berson, V. De Beco, P. Letteron, M.A. Robin, C. Moreau, J. El Kahwaji,
N. Verthier, G. Feldmann, B. Fromenty, D. Pessayre, Gastroenterology 114
(1998) 764.
[21] A. Berson, V. Descatoire, A. Sutton, D. Fau, B. Maulny, N. Vadrot, G. Feldmann,
B. Berthon, T. Tordimann, D. Pessayre, Pharmacol. Ther. 299 (2001) 793.
[22] B.T. Loughrey, P.C. Healy, P.G. Parsons, M.L. Williams, Inorg. Chem. 47 (2008)
8589.
[23] M.H. Garcia, T.S. Morais, A.I. Tomaz, F.M. Marques, F. Mendes, “Transition metal
complexes for pharmaceutical applications”, Patent application PT105890;
[24] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, in: Purification of Laboratory
Chemicals, second ed. Pergamon, New York, 1980.
4. Conclusions
We here have described the synthesis of new ruthenium(II)
organometallic complexes with the formula [Ru(h
5-C5H5)(LL)(1-
BuIm)] [Z], with (LL) ¼ 2PPh3 or DPPE, and Z ¼ CF3SOꢀ3 , PF6ꢀ, BPh4ꢀ,
with coordinated 1-butylimidazole. 1H NMR spectroscopic data
revealed the electron-donor effect of the organometallic fragments
{RuCp(LeL)}þ to the ring of the coordinated 1-butylimidazole
through an effect of
p-backdonation. This effect was also
extended to the pendent arm, as revealed by the significant values
of shielding of these protons. The magnitude of this effect is more
evident for the compounds with DPPE as coligand than with 2PPh3,
this showing the different contribution of these two coligands for
the electronic properties of the {RuCp(LeL)}þ fragment. The influ-
ence of these mono and bidentate phosphanes was also evidenced
by means of X-ray structural studies, which revealed that the
presence of these two coligands definitely influences the occur-
rence of different conformations for the 1-butylimidazole coordi-
nated ligand, within this family of compounds. Moreover, the
presence of DPPE or 2PPh3 clearly controls the interaction of
1-butylimidazole with the counter ion. As a result of this important
[25] M.I. Bruce, N.J. Windsor, Aust. J. Chem. 30 (1977) 1601.
[26] G.S. Ashby, M.I. Bruce, I.B. Tomkins, R.C. Walli, Aust. J. Chem. 32 (1979) 1003.
[27] N.G. Conelly, W.E. Geiger, Chem. Rev. 96 (1996) 877.
[28] SABADS, Area-detector Absorption Correction, Brucker AXS Inc., Madinson,
WI, 2004.

122
T.S. Morais et al. / Journal of Organometallic Chemistry 713 (2012) 112e122
[29] SAINT, Area-detector Integration Software (Version 7.23), Brucker AXS Inc.,
Madinson, WI, 2004.
[35] C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor,
M. Towler, J. Van de Streek, J. Appl. Cryst. 39 (2006) 453.
[30] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, G. Giacovazzo, A. Guagliardi,
A.G.G. Moliterini, G. Polidoro, R. Spagna, J. Appl. Cryst. 32 (1999) 115.
[31] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
[32] G.M. Sheldrick, SHELXL-97: Program for the Refinement of Crystal Structure,
University of Gottingen, Germany, 1997.
[36] F.H. Allen, Acta Cryst. B58 (2002) 380.
[37] M.H. Garcia, P. Florindo, M.F.M. Piedade, M.T. Duarte, M.P. Robalo,
E. Goovaerts, W. Wemseleers, J. Organomet. Chem. 694 (3) (2009) 433.
[38] C.A. Vock, C. Scolaro, A.D. Phillips, R. Scopelliti, G. Sava, P.J. Dyson, J. Med.
Chem. 49 (2006) 5552.
[33] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.
[34] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[39] M. Groessl, E. Reisner, C.G. Hartinger, R. Eichinger, O. Semenova, A.R. Timerbaev,
M.A. Jakupec, V.B. Arion, B.K. Keppler, J. Med. Chem. 50 (2007) 2185.