Synthesis and characterization of [Ru(NO)(bpp)Cl · 2H2O] [bpp = N,N′-bis(2-pyridinecarboxamide)-1,3-propane dianion] and [Ru(NO)(bpe)Cl · 2H2O] [bpe = N,N′-bis(2- pyridinecarboxamide)-1,2-ethane dianion]

Article abstract of DOI:10.1016/j.ica.2004.09.060

Two ruthenium nitrosyl bis-pyridyl/biscarboxamido compounds, [Ru(NO)(bpp)Cl · 2H₂O] [bpp = N,N′-bis(2-pyridinecarboxamide)-1,3- propane dianion] and [Ru(NO)(bpe)Cl · 2H₂O] [bpe = N,N′-(bis-2-pyridinecarboxamide)-1,2-ethane dianion] h

Full text of DOI:10.1016/j.ica.2004.09.060

Inorganica Chimica Acta 358 (2005) 2921–2932
www.elsevier.com/locate/ica
Synthesis and characterization of [Ru(NO)(bpp)Cl Æ 2H2O]
[bpp = N,N0-bis(2-pyridinecarboxamide)-1,3-propane dianion] and
[Ru(NO)(bpe)Cl Æ 2H2O] [bpe = N,N0-bis(2-pyridinecarboxamide)-
1,2-ethane dianion]
*
Carol F. Fortney , Steven J. Geib, Fu-tyan Lin, Rex E. Shepherd
Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
Received 20 August 2004; accepted 17 September 2004
Available online 29 December 2004
This paper is dedicated to the memory of my advisor and our friend, Professor Rex E. Shepherd, a gifted educator, a respected chemist and a good
kind man who did what he believed was right
Abstract
Two ruthenium nitrosyl bis-pyridyl/biscarboxamido compounds, [Ru(NO)(bpp)Cl Æ 2H2O] [bpp = N,N0-bis(2-pyridinecarboxa-
mide)-1,3-propane dianion] and [Ru(NO)(bpe)Cl Æ 2H2O] [bpe = N,N0-(bis-2-pyridinecarboxamide)-1,2-ethane dianion] have been
characterized by 1H NMR, 13C{1H} NMR, and IR spectroscopies, electrospray ionizaton mass spectrometry, and X-ray
crystallography.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Carboxamido ligands; {RuNO}6; Ruthenium nitrosyl; Linear nitrosyl; Split NO
1. Introduction
gely due to the Nobel Prize winning discovery [33–36]
that endothelium-derived relaxing factor is actually
nitric oxide and to the realization that nitric oxide is
implicated in a multitude of physiological and patho-
physiological functions. Photolytic activity, exhibited
by some transition metal nitrosyl compounds [37–41],
combines with nitric oxideꢀs various biological functions
to suggest a myriad of applications related to photody-
namic therapy [38,42–54]. As a result of these diverse
and important applications many books [10,36,55–65],
reviews [1–3,29,34,66–69] and special topic papers
[70,71], are devoted to transition metal nitrosyl chemis-
try. Professor Shepherdꢀs contributions to the transition
metal nitrosyl chemical literature include the study of
[RuII(NO+)]3+ and [RuII(NO+)Cl]2+ coordinated to N-
(hydroxyethyl)ethylenediamine triacetate (hedta3ꢀ) [72,73],
bipyridine [74,75], dipyridylamine [76,77], imidazole
The nitrosyl groupꢀs abilities to bind to transition
metals in a linear or a bent fashion [1–9], to behave as
NO+ or NOꢀ [10–12] and to influence, as well as be
influenced by, other ligands in the coordination environ-
ment [13–21] have been of interest to coordination
chemists and theoretical chemists for decades [22–24].
Catalytic applications [25–32] of transition metal nitro-
syl compounds are of current interest to organometallic
and organic chemists. The recent surge of investigations
into the behavior of transition metal nitrosyl com-
pounds by biologists and inorganic biochemists is lar-
*
Corresponding author. Tel.: +1 412 624 1219; fax: +1 412 624
8611.
E-mail address: cffst5@pitt.edu (C.F. Fortney).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.09.060

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C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
donors [78], peptide ligands [Ru(NO)Cl3(gly–gly–
his)]2ꢀ(gly–gly–his = diglycylhistidine) and [Ru(NO)Cl3-
can be tailored to target specific cell types, their failure
to chelate fully under physiological conditions dimin-
ishes their potential as ligands for NO transport. If
peptides are to be used as transporter ligands, they
may have to be connected to synthetic chelates at
the Ru(NO) center via biocompatible linkers.
Since multiple coordination to peptides was found
to be disfavored below pH 7, the viability of the diox-
ocyclam ligand [80] was investigated. The hypothesis
was that the macrocyclic dioxocyclam ligand would
enforce the desired bis-amine/bis-amide chelation.
The [Ru(NO)(dioxocyclam)Cl] compound induced
(gly–gly–gly)]2ꢀ(gly–gly–gly = triglycine)
[79],
the
p-donating macrocycle dioxocyclam [80] (dioxocyclam =
1,4,8,11-tetraazacylcotetradecane-5,7-dione),methylated
biimidizaole [81] donors in [Ru(NO)Cl(2,20-bis(4,5-dime-
thylimidazole)2)]2+ with the antitumor agent bleomycin
[82], the study of cis-[Ru(NO)Cl(bpy)2]2+ by ESI-MS
[74], and the synthesis and characterization of [Ru(NO)-
(bpb)Cl] (bpb = N,N0-bis(2-pyridinecarboxamide)-1,3-
benzene dianion) [83]. Following a brief discussion of the
development of our current research, this paper will
describe the synthesis, crystal structures and NMR
characterization of two {RuNO}6 compounds [Ru(NO)-
(bpp)Cl] (bpp = N,N0-bis(2-pyridinecarboxamide)-1,3-
propane dianion) and [Ru(NO)(bpe)Cl] (bpe =
lower mNOð1845 cmꢀ1Þ than did the tetra-amino [Ru-
ꢀ
39
(NO)(cyclam)]2+ ðmNO ¼ 1875 cmꢀ1
Þ
(cyclam = 1,4,8,
ꢀ
11-tetraazacyclotetradecane), an effect that illustrates
the significant shift of electron density to NO by the
amido groups in dioxocyclam. The intent was to
derivatize dioxocyclam at the methylene carbon be-
tween the two carbonyl groups with solubilizing and
recognition assisting side chains; however, other strat-
egies were adopted because the dioxocyclam ligand is
too costly for use on a large scale. From results ob-
tained in the ESI-MS investigation of cis-[Ru-
(NO)Cl(bpy)2]2+ it was concluded that, p-acceptor
ligands, by competing with NO+ for electron density,
weaken the Ru–NO bond, and assist the thermal
and gas phase dissociation of NOꢀ. On the other hand
p-donor ligands inhibit thermal and gas phase reac-
tions by strengthening backbonding from RuII to
NO [74]. The opposite applies to photolytic loss of
NOꢀ; p-donor ligands facilitate photolytic loss of
NOꢀ while p-acceptor ligands inhibit photolytic loss
of NOꢀ. p-acceptor ligands, such as aromatic N-het-
erocyclic ligands, inhibit photolytic loss of NOꢀ from
ruthenium nitrosyl complexes because they exhibit
MLCT to the N-heterocyclic p-acceptor and ligand
field excitations which are at lower energy than the
MLCT-to-NO+ state [66,74,89,90].
N,N-bis(2-pyridinecarboxamide)-1,2-ethane
dianion)
which are currently under investigation for photolytic
activity.
It is well known that the nitrosyl moiety, whether it is
bound as NO+, NOꢀ, or NOꢀ, is sensitive to the nature
of the central metal and to the coordination environ-
ment [13,21,84,85] and that the nitrosyl group exerts
an influence on the reactivity of other ligands [1,71,85–
88]. However, the factors that control nitrosyl behavior
are incompletely understood. Nonetheless, trends are
beginning to emerge from the literature. The following
discussion shows how the Shepherd group helped eluci-
date some of those trends and applied them in efforts to
design ruthenium nitrosyl compounds predisposed to
photolytic dissociation of nitric oxide.
The investigation of ruthenium nitrosyl polyamino-
polycarboxylates, including [RuII(NO+)(hedta3ꢀ)] pro-
vided the first comparison of separate RuIINO+,
RuIINOꢀ, and RuIINOꢀ complexes with a constant
secondary ligand field and with a constant oxidation
state for the central metal [73]. The thorough investi-
gation of the [RuNO]3+ complex of bleomycin illus-
trated that ruthenium nitrosyl agents can be tuned
for cell selectivity and revealed that bleomycinꢀs coor-
dination structure depends on the metalꢀs dn count as
well as on the p-acceptor nature and the hydrogen
bonding capacity of NO+ or its replacement [74,82].
Studies of the different structural isomers [72] of
[RuII(NO+)(hedta)(H2O)] illustrated that two nitrogen
p-donating ligands cis to the nitrosyl group push elec-
tron density onto the nitrosyl moiety. Increased elec-
tron density on the nitrosyl group is evidenced by a
decrease in the NO stretching frequency, an effect
which has been correlated with a propensity to lose
NO by photolysis [74,83,89–91]. Because amido groups
also facilitate cell transport [92–97], peptides such as
triglycine (gly–gly–gly) and diglycylhistidine (gly–gly–
his) were investigated as amido donor ligands [79].
One conclusion from the peptide investigations was
that, even though peptides are desirable ligands that
Some observations from the studies described illus-
trate the rationale behind our selection of ligands and
the use of ruthenium as the central metal. Because ruthe-
nium complexes are known to accumulate in tumors
[36,98–103] and because the strength of the Ru–NO
bond [85] increases the probability that the complex will
survive under physiological conditions, ruthenium is the
transition metal of choice for nitrosyl compounds
designed for photodynamic therapy [90]. Nitrosyl phot-
olability may be controlled by altering the p-donor/p-
acceptor character of the ligand set. As one of the best
p-donating groups, a deprotonated amido functionality
should activate the nitrosyl moiety to photolabilization
[90] by pushing electron density onto the nitrosyl group.
The amido groupꢀs propensity toward water solubility
and biocompatibility make chelated amido donors
excellent ligands for transporting the ruthenium nitrosyl
moiety through biological environments [92–97]. Our

C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
2923
current focus is on developing ruthenium nitrosyl com-
plexes bearing tetradentate, bis-pyridyl/bis-amido li-
gands, bis-pyridyl/bis-phenolato ligands and mixed
amido/phenolato ligands. The pyridyl ligands should
help force chelation [90,92,96,104,105] while the strong
p-donating bis-amido/bis-phenolato donors have the
dual purpose of activating the RuII(NO+) moiety toward
photolysis, then stabilizing the RuIII-solvent complex
that remains after photolysis [84,90,106–109]. Although
the compounds described here were designed to examine
the possibility of tuning nitrosyl photolability by modi-
fications of the ligand set in the equatorial plane, we are
also investigating the influence of bis pyridyl/bisamido,
bispyridyl/bisphenolato and mixed bispyridyl/bispheno-
lato ligands in a position trans to the nitrosyl group. It
is well known that ligands trans to the nitrosyl group
influence the behavior of the NO group by direct inter-
action with the p* orbitals of the NO group through the
metal center [13,19,66,110–114].
pellets were obtained on Perkin–Elmer BX FT-IR spec-
trometer. Mass spectrometry was carried out on a
Waters Q-TOF API US instrument using electrospray
ionization or on a 571A HP GC–MS instrument.
2.3. Syntheses
Trichloronitrosylruthenium (1) was prepared using a
modification of the procedure of Fletcher et al. [117]
[RuCl3 Æ xH2O] (207.43 g/mol, 2.00 g, 0.0096 mol, 1
equiv.) was dissolved in HCl (1 M, 15.0–18.0 ml, >1
equiv.) and heated to 100 ꢁC in an oil bath. At 100
ꢁC, an aqueous solution of NaNO2 (68.9 g/mol, 1.99 g,
3 equiv.) was added dropwise over 1 h. The dark red/
black solution began to turn purple as NO2 was re-
leased. After 1 h the water was removed from the reac-
tion mixture under vacuum (rotary evaporator, 90 ꢁC).
The remaining dark purple solid was dissolved in etha-
nol to separate 1 from NaCl formed in the reaction.
NaCl was removed via vacuum filtration. Ethanol was
removed under vacuum (rotary evaporator, 65–70 ꢁC).
The extremely hygroscopic purple solid was stored in a
desiccator with Drierite.
With the above principles in mind we synthesized and
characterized the {RuNO}6 compound [Ru(NO)(bpb)-
Cl] [83,110] (bpb = N,N0-bis(2-pyrdinecarboxamide)-
1,2-benzene) [104,115,116] by ESI-MS and NMR (1H,
13C, HH COSY, HMQC and HMBC) spectroscopy.
Publication was delayed due to Professor Shepherdꢀs
lengthy illness and unexpected passing. After our paper
was submitted, the synthesis, crystal structure and pho-
tochemistry of [Ru(NO)(bpb)Cl] were reported by the
Mascharak group [89]. The crystal structure reveals a
linear Ru–N–O moiety (172.37(14)ꢁ), as we expected
N,N0-bis(2-pyridine carboxamide)-1,2-ethane (bpeH2)
(2) (270.29 g/mol, 14.06 g, 0.0520 mol, 87% yield) was
prepared according to a literature procedure [118]. 1,2-
Diaminoethane (60.10 g/mol, d = 0.899 g/ml, 3.66 g,
0.060 mol, 1 equiv.) in pyridine (ꢁ12.0 ml) was added
to a stirred solution of picolinic acid (123.11 g/mol,
14.76 g, 0.119 mol, 2 equiv.) in pyridine (ꢁ48.0 ml). After
Triphenyl phosphite (310.29 g/mol, d = 1.184 g/ml, 31.5
ml, 0.119 mol, 2 equiv.) was added slowly, the reaction
mixture was heated for 4 h in an oil bath (100 ꢁC). Pale
yellow crystals formed overnight at room temperature.
White crystals were obtained by recrystallization from
for a {RuNO}6 compound [89] Our IR data (mNO
=
1867 cmꢀ1) is in excellent agreement with theirs and is
within the range characteristic of similar linear Ru–N–O
complexes [41,42].
This paper discusses the next compounds in a series of
Ru(NO) bispyridylbiscarboxamido compounds we are
investigating, [Ru(NO)(bpe)Cl Æ 2H2O] (3) (bpe = N,N0-
bis(2-pyridinecarboxamide)-1,2-ethane dianion) and
[Ru(NO)(bpp)Cl Æ 2H2O] (5) (bpp = N,N0-bis(2-pyridin-
ecarboxamide)-1,3-propane dianion).
1
Chloroform. H NMR (500 MHz, DMSO-d6): d 8.95
(s, 2H, NH2) 8.62 (d, 2H, H-1); 8.01 (d, 2H, H-4); 7.97
(td, 2H, H-3); 7.57 (td, 2H, H-5), 3.52 (m, 2H, H-5 &
6); (1H NMR 500 MHz, CDCl3) d 8.52 (d, 2H, H-1),
8.37 (s, 2H, NH2), 8.16 (d, 2H, H-4), 7.80 (td, 2H, H-
3), 7.38 (td, 2H, H-2), 3.73 (m, 2H, H-5 & 6). 13C {1H}
NMR (125 MHz, DMSO-d6): d 164.16 (C@O), 149.92
(Pyridyl-ipso), 148.31 (C-1), 137.66 (C-3), 126.39 (C-2),
121.81 (C-4), 38.84 (C-5 & 6); 13C {1H} NMR (125
MHz, CDCl3 chloroform): d 164.96 (C@O), 149.77 (Pyr-
idyl-ipso), 148.10 (C-1), 137.25 (C-3), 126.14 (C-2),
122.21 (C-4), 39.51 (C-5 & 6).
Chloro-nitrosyl-N,N0-bis(2-pyridinecarboxamido)-1,
3-ethane-ruthenium(II). [Ru(NO)(bpe)Cl Æ (H2O)2] (3)
(434.84 g/mol, 0.247g, 5.68 · 10ꢀ4 mol, 31% yield) was
prepared using an adapted procedure from Vagg and
co-worker [119] 1 (0.500 g, 0.0018 mol, 1 equiv.) was
added to a stirred solution of 2 (0.494 g, 0.0018 mol, 1
equiv.) in an ethanol/water solution (95%, ꢁ60.0 ml,
ꢁ85 ꢁC). After 12 h at reflux, a fine brown solid was
filtered from the reaction mixture. Upon reduction of
2. Experimental
2.1. Materials and measurements
[RuCl3 Æ xH2O], NaNO2, picolinic acid, 1,2-diamino-
propane, 1,2-diaminoethane, pyridine, triphenylphosph-
ite, chloroform and ethanol were obtained from Aldrich
and used without further purification.
2.2. Instrumentation
1H, 13C{1H} NMR, HMQC, and HMBC spectra
were obtained on a Bruker AVANCE DRX 500 digital
NMR spectrometer. Infrared spectra of KBr or KCl

2924
C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
solvent volume under vacuum (rotary evaporator,
30 ꢁC) an orange solid precipitated from the filtrate.
The solid was rinsed with small amounts of ethanol
and dried at ꢁ100 ꢁC. X-ray quality crystals were
obtained from a concentrated solution of [Ru(NO)-
(bpe)Cl Æ (H2O)2] in ethanol. 1H NMR (500 MHz,
DMSO-d6): d 9.23 (d, 2H, H-1), 8.34 (td, 2H, H-3),
8.08 (d, H-4), 7.90 (ddd, 2H, H-2), 4.02 (m, 2H, H-50
& 6), 3.91 (m, 2H, H-5 & 60); 13C {1H} NMR (125
MHz, DMSO-d6): d 166.56 (C@O), 157.76 (Pyridyl-
ipso), 152.40 (C-1), 141.44 (C-3) 127.70 (C-2), 125.53
ꢀ
2.4. Crystallographic data collection
X-ray quality crystals were obtained for 3 and 5 by
slow evaporation of solvent from the reaction mixture
filtrate. Crystals of 5 were also obtained from DMSO
after the reaction mixture filtrate was reduced in volume
and taken up on DMSO. The crystal structure shown
for 5 is from a crystal obtained in DMSO. Data collec-
tions were performed at room temperature on a Bruker
Smart Apex CCD diffractometer using graphite-mono-
˚
chromated Mo Ka (k = 0.71073 A) radiation. Full crys-
(C-4), 51.62 (C-5 & 6); IR (KBr): mNO ¼ 1825 cmꢀ1
;
tallographic details are deposited with Cambridge
Structural Database (CCD 245015 and CDC 245016).
Crystal and intensity collection data can be seen in
Table 1.
ESI-MS M + Na+ 457.95 (M+ꢀ = 434.77).
N,N0-bis(2-pyridine carboxamide)-1,2-propane(bppH2)
(4) (284.33 g/mol, 6.75 g, 0.024 mol, 47% yield) was pre-
pared according to a literature procedure [118]. 1,2-Dia-
minopropane (74.13 g/mol, d = 0.888 g/ml, 4.71 ml, 3.71
g, 0.050 mol, 1 equiv.) in pyridine (ꢁ20.0 ml) was added
to a stirring solution of picolinic acid (123.11 g/mol, 12.3
g, 0.099 mol, 2 equiv.) in pyridine (ꢁ40 ml). After tri-
phenyl phosphite (310.29 g/mol, d = 1.18 g/ml, 26.27
ml, 31.0 g, 0.099 mol, 2 equiv.) was added slowly, the
reaction mixture was heated for 4 h in an oil bath
ꢁ100 ꢁC. A brown oil was obtained after solvent evap-
oration (rotary evaporator, ꢁ80 ꢁC). The oil was dis-
solved in chloroform (ꢁ50 ml), washed with water
(ꢁ50 ml, 3 times), saturated sodium bicarbonate solu-
tion (ꢁ50 ml, 4 times), and finally with water (ꢁ50 ml,
3 times).
The chloroform solution was dried over magnesium
sulfate and concentrated under vacuum (rotary evapora-
tor, ambient temperature). A powdery white precipitate
formed as the concentrated solution was added dropwise
over 1 h to diethyl ether (ꢁ70 ml, 0 ꢁC) with stirring.
Recrystallization from chloroform yielded white crys-
tals. 1H NMR (500 MHz, DMSO-d6): 8.99 (t, 2H,
NH2) 8.61 (d, 2H, H-1), 8.03 (d, 2H, H-4), 7.95 (t, 2H,
H-3); 7.57 (td, 2H, H-2), 3.34 (q, 4H, H-5), 1.75 (qn,
2H, H-6). 13C{1H} NMR (125 MHz, DMSO-d6): d
163.91 (C@O), 150.05 (Pyridyl-ipso), 148.31 (C-1),
137.68 (C-3), 126.35 (C-2), 121.79 (C-4), 36.29 (C-5),
29.42 (C-6); GC–MS m/z 284.
Chloronitrosyl-N,N0-bis(2-pyridinecarboxamido)-1,3-
propane-ruthenium(II), [Ru(NO)(bpp)Cl Æ (H2O)2] (5)
(448.86 g/mol, 0.080 g, 1.78 · 10ꢀ4 mol, 10% yield), was
prepared with the same procedure as described above
for 3. Recrystallization from an ethanol/water solution
as well as from DMSO provided X-ray quality crystals.
1H NMR (500 MHz, DMSO-d6): d 9.24 (d, 2H, H-1),
8.38 (t, 2H, H-3), 8.18 (d, H-4), 7.91(t, 2H, H-2), 3.78
(m, 2H, H-5), 3.54 (t, 2H, H-50), 2.10 (m, 2H, H-60), 1.77
(q, 2H, H-6); 13C{1H} NMR (125 MHz, DMSO-d6): d
168.83 (C@O), 154.23 (Pyridyl-ipso), 150.21 (C-1),
141.67 (C-3), 127.31 (C-2), 125.20 (C-4), 46.23 (C-5),
30.19 (C-6); IR (KBr): ðꢀmNO ¼ 1838 cmꢀ1Þ; ESI-MS
M + Na+ 471.97.
3. Results and discussion
3.1. Infrared data
The infrared spectrum of a pure sample of 3 in KBr
showed a split nitrosyl stretch with one peak at 1852
cmꢀ1 and the other at 1825 cmꢀ1. Split NO peaks have
been observed for complexes having only one NO
group. For example, splitting of the absorbance associ-
ated with the NO stretching mode has been observed
for cis-[RuCl(en)2(NO)]Cl2, [RuBr(en)2(NO)]Br2, [RuI-
(en)2(NO)]I2 [114], [Ru(NH3)5(NO)]Cl3 Æ H2O [120] and
mer-[RuX3(en)(NO)] where X = Cl, Br, and I [121] For
the complex ions the splitting has been attributed to
an interaction between the counterion and the NO
group [21,120] Where there is no counterion, the split-
ting has been explained by a slight difference in the con-
formation of the ethylenediamine ligand induced in
sample preparation [114] Unexpected peaks in infrared
spectra, particularly with KBr pellets, have also been
attributed to reactions with KBr and to interactions
with KBr. To eliminate the possibility of some interac-
tion with KBr as the cause of the extra NO stretch, a
spectrum was obtained using a KCl pellet. With KCl
the IR spectrum (Fig. 1(a)) exhibited only one NO
stretch at 1825 cm1 and a shoulder of another at 1850
cmꢀ1. It might be concluded from these data that bro-
mide might displace chloride when the sample is pre-
pared in KBr. Hence, only one NO peak is observed
when the sample is prepared in KCl. However, the
Ru–Cl bond is quite strong, especially when it is trans
to NO. Moreover, if Brꢀ had displaced Clꢀ the peak
that should remain when the spectrum is obtained in
KCl should be the one with the highest stretching fre-
quency. Since the lower frequency peak remains, ex-
change with bromide was not the cause of the
splitting. Another spectrum of the same KCl pellet of
3, obtained after several days of being exposed to air,
(Fig. 1(b)) showed two NO peaks of equal intensity.

C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
2925
Table 1
Crystal data and structure refinements for [Ru(NO)(bpp)Cl] 3 and [Ru(NO)(bpe)Cl] 5
3
5
Chemical formula
Formula weight
Temperature (K)
C15H18ClN5O5Ru
484.86
293(2)
C14H16ClN5O5Ru
470.84
295(2)
˚
Wavelength (A)
0.71073
triclinic
0.71073
triclinic
Crystal system
Space group
ꢀ
ꢀ
P1
7.6860 (15)
P1
˚
a (A)
7.3057(7)
11.0170(10)
11.7851(11)
79.900(2)
74.622(2)
74.29(2)
874.93(14)
2
˚
b (A)
11.180(2)
11.462(2)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
80.47(3)
74.99(3)
72.58(3)
903.6(3)
3
˚
Volume (A )
Z
2
1.767
Dcalc Mg/m3
1.787
1.086
Absorption coefficient (mmꢀ1
F(0 0 0)
)
1.054
480
472
0.38 · 0.18 · 0.13
1.80–32.54
Crystal size (mm3)
0.37 · 0.34 · 0.21
1.85–32.59
h Range for data collection (ꢁ)
Index ranges
Reflections collected
ꢀ11 6 h 611; ꢀ16 6 k 6 16; ꢀ17 6 l 6 17
11 590
6118 (0.0395)
ꢀ10 6 h 610; ꢀ16 6 k 6 16; ꢀ176 l 617
11 486
5976 (0.0348)
Independent reflections (Rint
Completeness
Data/restraints/parameters
)
92.7% (h = 32.59ꢁ)
6118/0/244
94.2% (h = 32.54ꢁ)
5976/0/235
Maximum and minimum transmissions
Refinement method
Goodness-of-fit on F2
0.8091 and 0.6965
full-matrix least-squares on F2
1.167
0.8717 and 0.6831
full-matrix least-squares on F2
1.092
Final R indices [I > 2r(I)]
R indices (all data)
Largest differential peak and hole (e A )
R1 = 0.0790; wR2 = 0.2595
R1 = 0.0886; wR2 = 0.2656
4.009 and ꢀ1.477
R1 = 0.0615; wR2 = 0.1487
R1 = 0.0870; wR2 = 0.1606
1.682 and ꢀ0.0598
3
˚
Fig. 1. IR spectrum of KCl pellet of 3: (a) immediately after preparation; (b) after several days in air at ambient temperature; (c) after two days in
120 ꢁC oven.

2926
C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
Fig. 2. (a) Fresh KBr pellet of 5; (b) KBr pellet after 3 h at 120 ꢁC.
The extra peak along with an increase in the intensity of
the peak representing the O–H stretching mode sug-
gested that water might be the cause of the splitting. A
final IR spectrum (Fig. 1(c)), obtained after the same
KCl pellet was stored for two days at 120 ꢁC to drive
off water, exhibited only one NO peak at 1825 cmꢀ1
and lacked the O–H peak. Therefore it was concluded
that water caused the split NO peak. Only one NO peak
was observed in the infrared spectrum of 5 at 1868 cmꢀ1
.
Given the similarity in N–O bond length, the stretching
frequency for 5 seemed a little high compared to that for
3. To test whether the one observed peak was actually
two overlapping peaks, the KBr pellet of 5 was also
stored at 120 ꢁC. Fig. 2 shows that after about 3 h
drying, the peak representing the NO stretching fre-
quency had shifted to 1838 cmꢀ1. In addition, as the
Fig. 3. Pyridyl region of HH COSY spectrum of 2.
Fig. 4. Pyridyl region of HMQC spectrum of 2.

C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
2927
2
O
2
1
3
3
1
N
4
N
N
N
N
N
4
ipso-carbon
7
ipso-carbon
NH
O
N
O
HN
O
O
Cl
6
5
carbonyl
carbonyl
5
6
2
3
O
N
2
ipso-carbon
1
O
O
3
5
6
N
N
N
N
1
4
N
N
Ru
H
H
2
3
ipso-carbon
6
4
N
N
O
O
carbonyl
carbon
7
Cl
5
carbonyl
carbon
4
5
1H and 13C Chemical Shiftsa for 2b, 3c, 4d, and 5e
1H
1
2
3
4
5
3.52
5' f
*
6
3.52
6' f
*
3.91
*
7
8.95
*
8.99
*
8.62
9.23
8.61
9.24
7.57
7.90
7.57
7.91
7.97
8.34
7.95
8.38
8.01
8.08
8.03
8.18
2
3
4
5
3.91 4.02 4.02
3.34
3.78
*
3.54
1.75
1.77
2.10
13C
2
C=O
Py-ipso
148.31 126.39 137.66 121.81 38.48
152.40 127.70 141.44 125.53 51.62
148.31 126.35 137.68 121.79 36.29
150.21 127.31 141.67 125.20 46.23
*
*
*
*
38.48
51.62
29.42
30.19
*
*
*
*
*
*
*
*
149.92 164.16
157.76 166.56
150.05 163.91
154.23 168.83
3
4
5
500 MHz for 1H; 125 MHz for 13C; dmso-d6
N,N -bis(2-pyridinecarboxamide)-1,2-ethane (bpeH2)
[Ru(NO)(bpe)Cl] (bpe = N,N -bis(2-pyridinecarboxamide)-1,2-ethane dianion)
N,N -bis(2-pyridinecarboxamide)-1,2-propane (bppH2)
a
b
c
d
e
f
′
[Ru(NO)(bpp)Cl] (bpp = N,N -bis(2-pyridinecarboxamide)-1,2-propane dianion)
Prime indicates methylene proton oriented toward the Ru-NO moiety
* Not applicable
Fig. 5. 1H and 13C labeling scheme and chemical shifts for 2, 3, 4 and 5.
water peak decreased in size, splitting of the NO peak
became apparent. A peak at about 1384 cmꢀ1 is charac-
teristic of all RuNO compounds derived from [Ru
(NO)Cl3(H2O)2] is observed in the spectra for both com-
pounds and is assigned to the Ru–NO bending mode
[80].
shown in Figs. 3 and 4, respectively. Fig. 3 depicts the
correlations between H-2, H-3 and H-1 and between
H-3 and H-4. A correlation (not shown) also exists be-
tween the ethylene protons at 3.52 ppm and the amide
protons at 8.95 ppm.
The HMQC spectrum in Fig. 4 shows the correlation
of each proton resonance with its respective carbon res-
onance. Quaternary carbon signals at 149.77 and 164.96
ppm in the HMQC spectrum are assigned to the pyridyl-
ipso carbon and the carbonyl carbon, respectively, based
3.2. NMR data
1
upon the HMBC spectrum. The most downfield 13C
Fig. 5 shows the numbering schemes for 2, 3, 4 and 5
as well as the 1H and 13C NMR data obtained in
signal that exhibits a proton correlation appears at
1
DMSO-d6. H and 13C assignments are based on the
HH COSY and HMQC spectra. The HH COSY and
HMQC spectra for the pyridyl resonances of 2 are
1
HMBC Spectrum can be seen in the supplementary information.

2928
C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
148.10 ppm and corresponds to H-1. H-1 is also the
most downfield doublet by virtue of its proximity to
electron withdrawing the pyridyl nitrogen. The next
most downfield doublet, H-4, correlates with the second
most upfield 13C resonance. This may be rationalized by
considering the magnetic anisotropy induced by the ring
current as well as the different resonance forms of the
pyridine ring [122,123]. Except for the extra carbon
and proton signals associated with the extra methylene
carbon in 4, the NMR data for 4 is almost exactly the
same as that for 2.
Fig. 5 compares the 1H and 13C data for 2, 3, 4 and 5.
The lack of an N–H signal in the 1H NMR spectra for 3
and 5 indicates that each ligand coordinates in its
deprotonated form. Due to the electron withdrawing
nature of the Ru–NO center [80], all proton and carbon
resonances shift downfield upon coordination to ruthe-
nium. The ethylene carbon atoms are undifferentiated
in the 13C spectrum of 3, however the protons associated
with them, H-5 and H-6, are differentiated by their prox-
imity to the nitrosyl group [69,121]. Fig. 6 illustrates
how the ethylene protonsꢀ signal splits into two down-
field shifted multiplets upon formation of 3. The most
downfield multiplet at 4.02 ppm is assigned to H-50,
the axial proton on carbon 5 and to H-6, the equatorial
proton on C-6. The signal at 3.90 ppm represents H-5
and H-60, which are on the chloride face of the com-
pound and farthest from the NO group. It may be help-
ful to refer to the crystal structure of 3 in Fig. 7; but be
aware of the different numbering scheme.
In 4 the protons on C-5, which are bonded to the ami-
do nitrogens, are identical to each other; however, they
are in different environments than those on the central
methylene carbon, C-6. Thus the spectrum exhibits a
triplet at 3.34 ppm for protons labeled H-5 and a multi-
plet at 1.75 ppm for protons labeled H-6. Coordination
of 4 causes both methylene signals to shift downfield and
split into two groups of two signals. One of the signals, a
doublet of doublets, at 3.78 ppm, has been assigned to
Fig. 7. Molecular structure of 3 [Ru(NO)(bpe)Cl] (bpe = N,N0-bis(2-
pyridinecarboxamide)-1,2-ethane dianion).
the protons that are directed toward the nitrosyl group;
the other signal, an apparent triplet at 3.54 ppm has
been assigned to those oriented toward the chloride.
The central methylene resonance is also split into two
multiplets. Again, the most downfield shifted signal at
2.10 ppm has been assigned to the proton which is direc-
ted toward the nitrosyl group while the negligibly shifted
resonance at 1.77 ppm is assigned to the proton directed
away from the NO group.
1
As previously mentioned, all H and 13C signals for
shift downfield upon coordination. However there are
some interesting differences in the magnitude of the shift
for 3 and 5. For 3 both carbons which are bonded to the
amido nitrogen atoms (C-5) resonate 13.14 ppm more
downfield than those of the free ligand. This compares
to a downfield shift of 9.94 ppm for the analogous car-
bon atoms in 5. Also, C-1 and the pyridyl ipso signals
are more affected upon coordination in 3 than they are
in 5. For 3 for C-1 shifts 4.09 ppm, while that for 5 C-
1 shifts only 1.9 ppm. A difference of similar magnitude
is seen for the pyridyl ipso carbon which is downfield
shifted 7.84 ppm in 3 and only 4.18 ppm for 5. The car-
bonyl signal, on the other hand, is less responsive to
coordination in 3 than it is in 5. In 3 the carbonyl carbon
Fig. 6. Ethylene protonsꢀ signal for 2 splits into two multiplets upon
formation of 3.
Fig. 8. Molecular structure of 5 [Ru(NO)(bpp)Cl] (bpp = N,N0-bis(2-
pyridinecarboxamide)-1,2-propane dianion).

C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
2929
Table 2
Selected bond distances (A) and bond angles (ꢁ) for 3
Table 3
Selected bond distances (A) and angles (ꢁ) for 5
˚
˚
O(3)–N(5)
Ru–N(5)
Ru–Cl
1.140(5)
1.742(4)
2.3833(12)
2.118(3)
2.127(4)
1.980(3)
1.983(4)
O(2)–C(9)
O(1)–C(6)
N(2)–C(7)
C(7)–C(8)
N(3)–C(8)
N(3)–C(9)
N(2)–C(6)
1.238(5)
1.231(5)
1.471(6)
1.532(8)
1.456(6)
1.315(6)
1.329(6)
O(3)–N(5)
Ru–N(5)
Ru–Cl
1.143(8)
1.732(6)
2.3683(19)
2.129(5)
2.147(7)
2.039(6)
2.034(6)
O(1)–C(6)
O(2)–C(10)
N(2)–C(6)
N(3)–C(10)
N(2)–C(7)
C(7)–C(8)
C(8)–C(9)
N(3)–C(9)
1.246(8)
1.252(9)
1.321(9)
1.298(10)
1.460(9)
1.517(11)
1.522(13)
1.468(10)
Ru–N(1)
Ru–N(4)
Ru–N(3)
Ru–N(2)
Ru–N(1)
Ru–N(4)
Ru–N(3)
Ru–N(2)
O(3)–N(5)–Ru
N(5)–Ru–Cl
177.0(4)
N(3)–Ru–N(4)
N(3)–Ru–N(1)
N(2)–Ru–N(4)
C(8)–N(3)–Ru
N(3)–C(8)–C(7)
C(7)–N(2)–Ru
N(2)–C(7)–C(8)
N(3)–C(9)–C(10)
N(2)–C(6)–C(5)
79.51(15)
162.58(15)
161.11(15)
112.5(3)
110.4(4)
113.4(3)
109.3(4)
112.2(4)
112.7(4)
174.18(13)
92.53(16)
92.81(16)
96.39(16)
98.48(17)
84.20(15)
115.04(14)
79.70(14)
O(3)–N(5)–Ru
N(5)–Ru–Cl
177.5(7)
176.4(2)
93.2(3)
93.3(3)
93.7(3)
95.9(3)
95.4(3)
107.3(2)
78.3(2)
N(3)–Ru–N(4)
N(3)–Ru–N(1)
N(2)–Ru–N(4)
N(2)–C(7)–C(8)
C(7)–C(8)–C(9)
C(9)–N(3)–Ru
C(7)–N(2)–Ru
N(3)–C(10)–C(11)
N(2)–C(6)–C(5)
77.9(3)
N(5)–Ru–N(1)
N(5)–Ru–N(4)
N(5)–Ru–N(3)
N(5)–Ru–N(2)
N(3)–Ru–N(2)
N(1)–Ru–N(4)
N(2)–Ru–N(1)
171.1(2)
169.0(2)
112.6(6)
115.8(7)
123.4(5)
123.5(5)
114.1(6)
113.5(6)
N(5)–Ru–N(1)
N(5)–Ru–N(4)
N(5)–Ru–N(3)
N(5)–Ru–N(2)
N(2)–Ru–N(3)
N(1)–Ru–N(4)
N(2)–Ru–N(1)
Fig. 9. Close contacts in the crystal lattices of [Ru(NO)(bpe)Cl] 3 and [Ru(NO)(bpp)Cl] 5.

2930
C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
13C signal shifts downfield 2.40 ppm while in 5 it shifts
4.92 ppm.
Finally, as Fig. 9 shows, there are short close contacts
between the chloride ion and the hydrogen atom on the
pyridyl ring that is para to the nitrogen of the heterocy-
cle. This interaction is significant enough to pull the
hydrogen atoms attached to C-10 in 3 and C-12 in 5
slightly out of the plane of the rest of the pyridyl hydro-
gen atoms.
3.3. Crystal structure data
Figs. 7 and 8 display the molecular structures of 3
and 5, respectively. Tables 2 and 3 show selected bond
lengths and angles for 3 and 5, respectively. That 3
and 5 are crystallographic isomorphs facilitates a direct
comparison of the two structures. Both the pyridyl and
deprotonated amido nitrogen atoms of the tetradentate
bpe2ꢀ and bpp2ꢀ ligands coordinate to the ruthenium
center in the equatorial plane to form a slightly distorted
octahedral compound with axial chloride and nitrosyl
substituents. The Ru–N amido and the Ru–N pyridyl
bonds are all shorter in 3 than in 5. The C–O bond
lengths are shorter in 3 than in 5 as well. The Ru–N–
O angle in each compound is essentially linear at
177.0(4) for 3 and 177.5(6) for 5. It follows that the
4. Conclusions
The {RuNO}6 compounds, [Ru(NO)(bpe)Cl Æ 2H2O]
and [Ru(NO)(bpp)Cl Æ 2H2O], are distorted octahedral
compounds with the chloride ligand trans to a linearly
1
bound NO group. The H and 13C spectra suggest that
the compounds maintain the same coordination geome-
try in solution as they do in the solid state. The crystal
structure reveals that all of the ruthenium nitrogen
bonds in the equatorial plane are shorter for 3 than
for 5. Accordingly 13C and 1H NMR analyses show that
nitrogen bound carbons and their respective protons are
more downfield shifted in 3 than in 5 upon coordination.
An exception is the 13C signal of the carbonyl carbon
which is less downfield shifted in upon coordination of
3 than it is upon coordination of 5.
The nitrosyl stretching frequencies of 1825 cmꢀ1 for 3
1838 cmꢀ1 for 5 are in good agreement with literature
values for similar compounds [12,44,89,114]. That the
NO stretching frequencies of 3 and 5 are less than that
for the [Ru(NO)(bpb)Cl] compound (1867 cmꢀ1) indi-
cates that more electron density is pushed on to the
NO group by the bpe2ꢀ and the bpp2ꢀ ligand than by
the bpb2ꢀ ligand.
The infrared spectrum of 3 exhibited a distinctly split
NO peak. Split NO peaks have been observed and
attributed to interactions with counter ions, slight vari-
ations in NO and ligand conformation, solvent when
the sample is prepared in solution, and with reactions
with KBr in KBr pellets [10,124,125]. The split NO peak
exhibited by 3 is attributed to a hydrogen bonding inter-
action with water in the KBr pellet. Drying the KBr pel-
let of 5 revealed that there was a split NO peak for 5 as
well. Drying of a KBr pellet of [Ru(NO)(bpb)Cl] re-
moved water but the NO peak remained unchanged.
This may indicate that the nitrosyl oxygen atoms in 3
and in 5 exhibit a higher basicity, therefore an increased
propensity to hydrogen bond [126], compared to that in
[Ru(NO)(bpb)Cl]. Photolysis and electrochemical stud-
ies of 3 and 5 are in progress.
˚
N–O bond length for 3 (1.140(5) A) is very similar to
˚
that for 5 (1.143(8) A). That the Ru–NO (1.732(6) A)
˚
˚
and Ru–Cl (2.368(3) A) bond lengths for 5 are slightly
˚
shorter those in 3 Ru–NO (1.742(4)) A and Ru–Cl
˚
(2.3833(12) A) may indicate that the NO group exerts
a slightly stronger trans strengthening effect in 3 than
in 5. The longer Ru–Cl and Ru–N(5) bonds in 3 may
also be due to the smaller bite angles of the bpe2ꢀ ligand
as discussed below.
The ruthenium center is displaced toward the nitrosyl
group from the plane defined by the nitrogen atoms
˚
˚
(0.145 A in 5 and 0.167 A in 3) due to the different bite
angles of the ligands. More displacement is required to
alleviate the steric interaction with the rings in 3 because
the five member chelate ring has a smaller bite angle
(84.20(15)ꢁ) [19]. The smaller N(2)–Ru–N(3) angle in 3
also allows a larger N(1)–Ru–N(4) angle of 115.04(14)
˚
A. The six member chelate ring in 5, which has a bite an-
gle of 95.4(3)ꢁ, forces a smaller N(1)–Ru–N(4) angle of
107.3(2)ꢁ. The smaller N(1)–Ru–N(4) in 5 causes the
pyridyl groups to tip out of the plane slightly more in
5 than in 3 to minimize steric interaction between H-1
and H-14. Tilting of chelated pyridyl groups has been
observed by others [89]. Both pyridyl rings involving
N(1) on 3 and 5 exhibit less of a tilt than do those
involving N(4).
The carbon–carbon bonds in the 5 member ring
formed by the diamide in 3 exhibit typical bond lengths
and angles. The N(5)–Ru–N(2) angle is 98.48(17)ꢁ while
the N(5)–Ru–N(3) angle is a little less at 96.35(16)ꢁ. The
six member ring formed upon chelation of the bpp2ꢀ li-
gand exhibits angles that are little larger than those of a
six member ring. The largest deviation from the typical
value of 112ꢁ is the C(8)–C(9)–N(3) angle which is
115.87ꢁ. In 5 the N(5)–Ru–N(2) and N(5)–Ru–N(3) an-
gles, at 95.9(3)ꢁ and 93.7(3)ꢁ, respectively, deviate less
from 90ꢁ than do those in 3.
Acknowledgements
Support from the Petroleum Research Fund is grate-
fully acknowledged. C.F.F. also wishes to thank the
University of Pittsburghꢀs Chemistry Department for

C.F. Fortney et al. / Inorganica Chimica Acta 358 (2005) 2921–2932
2931
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´
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Appendix A. Supplementary data
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Supplementary data associated with this article can
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