Re(I) and Ag(I) complexes containing the polydentate symmetric diazine derived from 6-acetyl-1,3,7-trimethylpteridine-2,4(1H,3H)-dione in two different binuclear modes

Article abstract of DOI:10.1016/j.poly.2012.10.033

The symmetric diazine derived from 6-acetyl-1,3,7-trimethylpteridine-2, 4(1H,3H)-dione, (6,6′,1,1′-(hydrazine-1,2-diylidene) bis (ethan-1-yl-1-ylidene) bis (1,3,7-trimethylpteridine-2,4(1H,3H)-dione), DHzD) has been prepared and reacted with ReCl(CO)₅ and AgClO₄ to give binuclear complexes with formula [Re₂Cl₂(CO) ₆(DHzD)]·2CH₃CN and [Ag₂(DHzD) ₂](ClO₄)₂·7H₂O. The XRD single-crystal results indicate two quite different binuclear modes depending on the number of ligands and the counteranion coordinative capacities. Thus, the dirhenium complex consists in two fac-ReCl(CO)₃⁺ units attached to the N5-O4 bidentate sites from both pteridine moieties of the Z,Z′ isomer of the ligand (Re-O, 2.185(5) and Re-N5, 2.225(6) A?). The disilver complex displays two crystallographically independent but practically equivalent 3 + 3-coordinated silver centers to N61, N5 and O4 atoms from both DHzD ligands (E,E′ isomer); distances Ag-N range between 2.31 and 2.48 A?, whereas oxygen atoms are weaker bonded (2.65-2.82 A?). In the molecular units there are not M-M bonds, both metal atoms lying farther than the sum of Van der Waals' radii (Re-Re, 7.959(5) A?; Ag-Ag, 4.073(5) A?).

Full text of DOI:10.1016/j.poly.2012.10.033

Polyhedron 50 (2013) 10–15
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Re(I) and Ag(I) complexes containing the polydentate symmetric diazine
derived from 6-acetyl-1,3,7-trimethylpteridine-2,4(1H,3H)-dione in two
different binuclear modes
⇑
Sonia B. Jiménez-Pulido, Nuria A. Illán-Cabeza, Francisco Hueso-Ureña, Miguel N. Moreno-Carretero
Departamento de Química Inorgánica y Orgánica, Facultad de Ciencias Experimentales, Campus Universitario ‘‘Las Lagunillas’’ (B3), Universidad de Jaén, 23071 Jaén, Spain
a r t i c l e i n f o
a b s t r a c t
0
0
Article history:
The symmetric diazine derived from 6-acetyl-1,3,7-trimethylpteridine-2,4(1H,3H)-dione, (6,6 ,1,1 -
hydrazine-1,2-diylidene) bis (ethan-1-yl-1-ylidene) bis (1,3,7-trimethylpteridine-2,4(1H,3H)-dione),
DHzD) has been prepared and reacted with ReCl(CO) and AgClO to give binuclear complexes with for-
mula [Re Cl (CO) CN and [Ag (DHzD) ](ClO ꢀ7H O. The XRD single-crystal results indi-
(DHzD)]ꢀ2CH
cate two quite different binuclear modes depending on the number of ligands and the counteranion
Received 18 June 2012
Accepted 5 October 2012
Available online 2 November 2012
(
5
4
2
2
6
3
2
2
)
4 2
2
Keywords:
Azines
Crystal structure
Pteridines
Rhenium complexes
Silver complexes
+
coordinative capacities. Thus, the dirhenium complex consists in two fac-ReCl(CO)
3
units attached to
0
the N5–O4 bidentate sites from both pteridine moieties of the Z,Z isomer of the ligand (Re–O, 2.185(5)
and Re–N5, 2.225(6) Å). The disilver complex displays two crystallographically independent but practi-
cally equivalent 3 + 3-coordinated silver centers to N61, N5 and O4 atoms from both DHzD ligands
E,E isomer); distances Ag–N range between 2.31 and 2.48 Å, whereas oxygen atoms are weaker bonded
0
(
(
2.65–2.82 Å). In the molecular units there are not M–M bonds, both metal atoms lying farther than the
sum of Van der Waals’ radii (Re–Re, 7.959(5) Å; Ag–Ag, 4.073(5) Å).
Ó 2012 Elsevier Ltd. All rights reserved.
1
. Introduction
Different metal–ligand binding modes were found depending on
the potential donor atoms supplied by the aldehyde moiety. The
study of the effects of the compounds on the growth of several hu-
man tumor cell lines suggested a modulator behaviour, according
to the concentration, of cell growth due to the estrogen-like char-
acteristics of the compounds. Furthermore, in this paper, the pos-
sibility of isolation of symmetric diazines controlling the
aldehyde/hydrazine stoichiometric ratio in the synthetic method
was also pointed out. Now, the present paper is devoted to report
the synthesis and structural study of the symmetric diazine (here-
after denoted as DHzD, Fig. 1) and its Re(I) and Ag(I) compounds,
which, in accordance with the molecular structure of the ligand
and the flexibility around the –C = N–N = C– segment bridging both
pteridine moieties, are dinuclear complexes, but showing different
metal-binding patterns as function of the stoichiometry of the
reaction and the coordinative capacities of the counteranions used.
Diazines, N–N linked diimines, exhibit a number of interesting
properties from both biological and technological points of view;
thus, they have recently attracted growing attention due to their
activity as anticonvulsant, antidepressant, antiinflammatory, anti-
viral or antitumor agents [1], the design of liquid crystals [2,3],
as non-linear optical materials [4,5], their utility as sensors for sev-
eral metal ions [6–8] and their luminescent properties [9]. The
flexibility of these ligands around the N–N single bond offers sev-
eral possible mono- and binuclear binding modes which can give
rise complexes having different geometries [10–18]. Most of the
diazine ligands are symmetric and the bis-Schiff bases derived
from hydrazine are one of the most important families of organic
molecules designed for the assembly of helicates [13,15,16] or
intercalating ligands to achieve site-specific DNA recognition [12].
Only a paper focused on the structural data of metal-containing
Schiff bases diazines derived from 6-acetyllumazines has been pre-
viously reported [19]; in this paper, a number of asymmetric dia-
zine ligands derived from 6-acetyl-1,3,7-trimethylpteridine-
2. Experimental
2
,4(1H,3H)-dione and either hydrazine or several aromatic alde-
2.1. Materials and instrumentation
hydes and their Re(I) complexes were isolated and characterized.
The metallic sources ReCl(CO)
reactants and solvents are commercially available and were used
without purification. Microanalyses were carried out with a Ther-
5
and Ag(ClO
4
)
2
ꢀH
2
O, the organic
⇑
Corresponding author. Tel.: +34 953 212738; fax: +34 953 211876.
E-mail address: mmoreno@ujaen.es (M.N. Moreno-Carretero).
0
277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.10.033

S.B. Jiménez-Pulido et al. / Polyhedron 50 (2013) 10–15
11
Fig. 1. Synthesis of the DHzD symmetric diazine and the Re(I) and Ag(I) dinuclear compounds. In the free ligand, significant atoms are labelled.
mo Finnigan Flash EA 1112. Mass spectrum of the ligand DHzD was
run on a Thermo DSQ II spectrometer equipped with a direct inlet
probe, operating at 70 eV. The ESI-MS (electrospray ionization
mass spectrometry) spectra of the complexes were recorded in
an ion-trap mass spectrometer Esquire 6000 Bruker Daltonics
equipped with an electrospray interface operating in positive ion
mode (4000 V) in the range m/z 50–3000; the samples were dis-
solved in methanol and analyzed by direct injection. The IR spectra
were recorded on a IR Bruker Tensor 27 apparatus (KBr pellet,
1456m, 1403w, 1373m, 1348m, 1287m, 1260m, 1228m, 1119m,
1
3
1053w, 1033w, 1008w, 969w, 810w, 750m. C NMR (CDCl
3
; d,
ppm): 158.4 (C4), 157.3 (C7), 156.7 (C2), 149.3 (C6), 144.6 (C8A),
144.1 (C61), 122.2 (C4A), 27.8 (C1), 27.4 (C3), 24.4 (C71), 15.0
1
(C62). H NMR (CDCl
3
; d, ppm): 3.75 (s, 3H, N1–CH
), 3.02 (s, 3H, C7–CH ), 2.45 (s, 3H, C61–CH
Cl (CO) (DHzD)]: ReCl(CO) (0.5 mmol) and DHzD
3
), 3.55 (s, 3H,
).
N3–CH
[Re
3
3
3
2
2
6
5
(0.25 mmol) were put into a flask containing hot toluene (20 mL)
and refluxed for 12 h; a orange powdered compound was isolated
(yield referred to DHzD, ca. 35%). Anal. Calc. for C14H12ClN O Re
5 5
ꢁ1
1
13
4
000–400 cm ). H and C NMR spectra of the ligand were re-
corded on a Bruker DPX-400 instrument in CDCl
at room temperature. For the complexes, the solubility in CDCl
and DMSO-d
at room temperature and 120 °C. Only the H NMR spectra in CDCl
3
and DMSO-d
6
(M = 551.93): C, 30.47; H, 2.19; N, 12.69. Found: C, 30.21; H,
2.14; N, 12.24%. ESI-MS (m/z, abundance): 1127, 18%; 821, 100%;
515, 45%. IR bands (cm ): 2032vs, 1919vs, 1899vs, 1731s,
3
ꢁ1
6
is not too high and the NMR experiments were made
1
3
1680s, 1561s, 1532m, 1451w, 1398w, 1374w, 1300w, 1246w,
1
3
13
show quality enough to make some assignments, whereas the
C
3
1190w, 1139w, 1082w, 1007w, 807w, 748w. C NMR (CDCl ; d,
NMR spectra of the complexes show no clear resonances; then, re-
ported data were obtained by simulation on a 1H/ C HMBC-cus-
tom (heteronuclear multiple bond correlation) experiment.
ppm): 171.3 (C4), 165.9 (C7), 163.4 (C61), 149.3 (C6), 148.4 (C2).
13
1
H NMR (CDCl
N3–CH ), 2.86 (s, 3H, C7–CH
recrystallization from acetonitrile afforded red crystals of
(DHzD)]ꢀ2CH
[Re Cl (CO) CN.
Ag (DHzD) ](ClO AgClO (0.25 mmol) and DHzD
3
; d, ppm): 3.83 (s, 3H, N1–CH
3
), 3.71 (s, 3H,
3
3
), 2.53 (s, 3H, C61–CH
3
). The
2.2. Synthesis of the ligand and complexes
2
2
6
3
[
2
2
4
)
2
:
4
ꢀH
2
O
CAUTION! Perchlorate salts are potentially explosive and
(0.25 mmol) were refluxed in hot EtOH (20 mL) during 24 h; a yel-
should only be used in small quantities and handled with the nec-
essary precautions.
low solid precipitates (yield referred to DHzD, ca. 55%). Anal. Calc.
for C22
8
H24ClN10O Ag (M = 699.81): C, 37.76; H, 3.46; N, 20.02.
The synthetic pathway used to isolate the symmetric diazine
DHzD used as ligand is briefly outlined in the Fig. 1.
Found: C, 37.87; H, 3.45; N, 20.23%. ESI-MS (m/z, abundance):
ꢁ1
599, 85%; 393, 100%; 260, 55%. IR bands (cm ): 1722s, 1678vs,
1553s, 1489m, 1456w, 1406w, 1373w, 1348m, 1288w, 1260w,
1231w, 1142m, 1120s, 1086m, 952w, 809w, 749w. 13C NMR
Ligand: the proligand 6-acetyl-1,3,7-trimethyllumazine (DLMA-
ceM) was synthesized from 6-amino-1,3-dimethyl-5-nitrosouracil
and acetylacetone following a reported method [20]. The title sym-
metric diazine (hereafter denoted as DHzD) was prepared by react-
ing dropwise an ethanolic solution (5 mL) of hydrazine
monohydrate (5 mmol) with the lumazine derivative (DLMAceM)
(CDCl
29.8 (C1), 29.3 (C3), 25.3 (C71), 20.0 (C62). H NMR (CDCl
ppm): 3.73 (s, 3H, N1–CH ), 3.41 (s, 3H, N3–CH ), 2.87 (s, 3H,
C7–CH ), 2.62 (s, 3H, C61–CH ). Some days later, from the mother
3
; d, ppm): 164.9 (C7), 160.1 (C61), 150.2 (C2), 142.2 (C6),
1
3
; d,
3
3
3
3
(
(
10 mmol) in ethanol (25 mL). Acetic acid was used as catalyst
ca. 1 mL). The mixture was refluxed for 5 h until the yellow prod-
liquor, orange crystals of the compound [Ag
can be isolated.
2
(DHzD)
2
(ClO
4
)
2
2
]ꢀ7H O
uct precipitates. Note that hydrazine must be added in stoichiom-
etric ratio, not in excess, to avoid the appearance of the previously
reported azine DLMHz [19] containing only one pteridine moiety.
2.3. XRD experimental details
The ligand was filtered off and recrystallized in CH
2
Cl
2
(yield ca.
Details of the crystallographic data collection and refinement
parameters are given in Table 1. The structures were solved by di-
rect methods and refined using SHELXL97 program inside the WINGX
package employing full-matrix least-squares methods on F2
[21,22]. Lorentz, polarization and multi-scan absorption corrections
7
5%). Anal. Calc. for C22 Cl (M = 660.10): C, 43.52;
H
24
N
10
O
4
ꢀ2CH
2
2
H, 4.26; N, 21.15. Found C, 43.65; H, 4.40; N, 21.18%. MS (m/z,
abundance): 492, 5%; 247, 20%; 246, 100%; 206, 5%; 177, 3%; 146,
ꢁ1
4
%; 107, 11%. IR bands (cm ): 1723vs, 1676vs, 1555vs, 1487s,

1
2
S.B. Jiménez-Pulido et al. / Polyhedron 50 (2013) 10–15
Table 1
Crystallographic and refinement data.
Compound
Re
885224
24Cl
1179.93
red prism
2
Cl
2
(CO)
6
(DHzD)ꢀ2CH
3
CN
Ag
885223
48Cl
1511.66
orange prism
2
(DHzD)
2
(ClO
4
)
2
ꢀ7H
2
O
CCDC number
Empirical formula
Formula weight (g molꢁ1)
Color, habit
C
32
H
2
N
12
O
10Re
2
C
44
H
2
N
20
O
23Ag
2
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
a (Å)
0.42 ꢂ 0.38 ꢂ 0.02
orthorhombic
Pbca
0.26 ꢂ 0.20 ꢂ 0.14
monoclinic
1
P2 /c
11.856(2)
27.069(6)
12.291(1)
90
3944(1)
4
1.987
6.338
2256
26.156(2)
14.785(5)
15.895(3)
101.130(8)
6031(2)
4
1.655
0.832
3056
b (Å)
c (Å)
b (°)
Volume (Å )
3
Z
D
calc Mg m 3
ꢁ
)
Absorption coefficient (mmꢁ1)
F(000)
Diffractometer
Radiation
Temperature (K)
Bruker Nonius Kappa CCD
Graphite-monochromated Mo K
120(2)
a
(k = 0.71073 Å)
120(2)
h
range (°)
2.50 to 27.50
5.01 to 27.54
ꢁ33 6 h 6 33
–19 6 k 6 19
–20 6 l 6 20
82491/13752/9470
0.0865
Index ranges
ꢁ12 6 h 6 15
–
–
35 6 k 6 34
12 6 l 6 15
Reflections collected/independent reflections/I > 2
R
Weighting scheme (P = (F
w = 1/[
r(I)
42892/4525/2935
0.0856
int
2
o c
+ 2F
2)/3)
2
2
) + (xP)2 + yP]
r
(F
o
x = 0.0634/y = 24.0423
4525/0/257
1.050
x = 0.0585/y = 62.9737
13752/0/787
1.069
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2 (I)] R/wR
R indices (all data) R/wR
0.0479/0.0919
0.1135/0.1353
3.395 and ꢁ1.802
0.0826/0.1861
0.1227/0.2098
2.089 and ꢁ1.359
Largest difference peak and hole (e Åꢁ3)
were applied with SADABS [23]. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms from methyl groups were put at
calculated ideal positions following riding models. For the Ag com-
pound, the final Fourier map shows eight main free peaks which
were assigned to oxygen atoms from disordered water molecules.
Graphics and calculations were performed with MERCURY [24] and
PLATON [25].
coordinative capacity, perchlorate anions leaving outside the coor-
dination sphere. By contrast, the presence in the starting Re(I)
+
material of the very stable fac-ReCl(CO)
3
moiety leaves in the
Re(I) only two cis unsaturated coordinative sites that are occupied
by two pairs of donor atoms N5,O4 from bidentate lumazine frag-
ments, which probably provides the sterically more favorable
structural solution to the system.
3
. Results and discussion
3.2. Spectroscopy
3
.1. Synthesis
The analytical and spectral data of the free ligand are in accor-
dance with the structure found in the title metal complexes. Mass
spectrum shows the signal at m/z = 492 assignable to the molecu-
The reactions carried out to obtain the symmetric diazine DHzD
+
and the Re(I) and Ag(I) complexes are depicted in the Fig. 1. The
synthesis of the ligand was already somehow mentioned in a pre-
vious paper [19]; in the last step, it is a conventional carbonyl-pri-
mary amine condensation to afford the corresponding azomethine
C@N bond. As the aim is to isolate the symmetric diazine, the use
of a hydrazine/DLMAceM ratio near but slightly lower than 1/2
should be stressed. In view of the obtained results on preparing
the metal complexes, it is clear that the DHzD is not isolated in a
pure isomeric form. Therefore, it should be noted that the yields
obtained in the synthesis of the complexes are limited by the both
isomers abundance (Z,Z and E,E ) in the isolated product; in this
way, the found yield for the Ag(I) compound (55%) is bigger than
the Re(I) one (35%), in accordance with the lower steric impedi-
ments to build the E isomer if compared with the Z ones.
On the other hand, the structural results clearly reflect the influ-
ence of the used metallic starting material, the metal/ligand ratio
for such synthesis as well as the higher coordinative capacity of
the chloride if compared with the perchlorate counteranions. In
this way, Ag(I) ions make available to the DHzD ligand their full
lar peak (M ); the peak at m/z = 246 corresponds just to a half of
+
the initial molecule (M/2) , broken through the N–N bond and, fi-
nally, the fragment at m/z = 206 may be assignable to the loss of
+
the substituent in 6 position (M/2-C(CH
3
)N) . The IR bands and
NMR signals are in accordance with those published for related
compounds [19,26].
ESI-MS spectrum of the Re(I) compounds shows the molecular
+
peak at m/z = 1127 assignable to (M + Na) ; other important peaks
at m/z = 821 and 515 are assignable to the successive loss of two
+
ReCl(CO)
3
fragments. In the spectrum of the Ag(I) compound,
0
0
2+
2 2
the molecular peak corresponding to the dimeric [Ag (DHzD) ]
cation does not appear and only the peak at m/z = 599 can be as-
+
signed to the monomer (DHzD + Ag) .
The tentative assignment of the infrared bands is not easy due
to large number of bands shown in the spectrum of the ligand.
Thus, upon complexation, some shifts are found in the stretching
ꢁ1
carbonyl range, two bands between 1730 and 1675 cm due to
the combination of (C2@O2) and (C4@O4) modes. The strong
bands at ca. 1490–1560 cm may be assigned to (C@N) vibration
m
m
ꢁ1
m

S.B. Jiménez-Pulido et al. / Polyhedron 50 (2013) 10–15
13
and a set of bands of medium-to-weak intensity ranging from 1460
ꢁ1
to 1200 cm are due to
m(C@C) + m(C–N) mode. The vibrations
m
(C@N–N@C) cannot be clearly identified because they are hidden
ꢁ1
by the C@O and C@N stretching vibrations (ca. 1600 cm ); due to
the electronic delocalization with adjacent C@N double bonds,
bands due to
number than expected for a simple N–N bond (900–1000 cm
and cannot be safely identified due to their weakness and the exis-
tence of bands assignable to (C@C) and (C–N). Finally, as typical
features, three very strong bands (2032–1899 cm ) in the Re(I)
m(N–N) vibrations become shifted to higher wave-
ꢁ1
)
m
m
ꢁ1
+
spectrum from the fac-Re(CO)
3
moiety and a set of medium-to-
ꢁ1
strong bands (ca. 1120 cm ) in the Ag(I) spectrum due to the pres-
ence of free perchlorate anions can be cited.
More detailed information about the structure of ligand is pro-
vided by a series of 1D and 2D NMR experiments and specific
assignments of protons and carbons are given in the experimental
section. As it has been indicated in the Experimental part, the com-
plexes are very soluble in neither CDCl
spectra in CDCl show quality enough to make some assignments.
The signals for the protons C61–CH and C7–CH were shifted as
3 6
nor DMSO-d and only
3
3
3
]2+ unit, showing only the encapsu-
Fig. 3. Ball-and-stick picture for [Ag
2
(DHzD)
2
consequence of the coordination from 2.45 and 3.02 in the ligand
to 2.53 and 2.86 ppm in the Re(I) complex and 2.62 and
lated perchlorate anion (the other perchlorate anion, hydrogen atoms and solvent
molecules are omitted for clarity). The two DHzD ligands are built as pte(A) = N–
N = pte(B) and pte(C) = N–N = pte(D). Atoms are labelled as pte(A) followed by the
pte(X) corresponding letter.
13
2
.87 ppm in the Ag(I) complex. In the C NMR spectrum of the free
ligand, the signals at 144.1 ppm and 157.3 ppm were assigned to
the C61 and C7 atoms, respectively. In the 13C NMR spectra of
the complexes, no resonances were found; for this reason, the re-
ported data were obtained by simulation on a 1H/ C HMBC-cus-
tom spectrum. Although a general deshielding is observed, the
main spectral change is found for the C61 signal which is down-
field shifted to 163.4 ppm in the Re(I) complex and 160.1 ppm in
the Ag(I) complex due to the coordination.
13
Table 2
Bond lengths (Å) and angles (°) around the metal center.
2 2 6
[Re Cl (CO) (DHzD)]
Re–C2X
Re–C1X
Re–C3X
1.892(9)
1.922(9)
1.971(9)
Re–O4
Re–N5
Re–Cl
2.185(5)
2.225(6)
2.448(3)
C2X–Re–C1X
C2X–Re–C3X
C1X–Re–C3X
C2X–Re–O4
C1X–Re–O4
C3X–Re–O4
C2X–Re–N5
C1X–Re–N5
87.7(4)
90.4(4)
89.9(4)
177.8(3)
92.7(3)
91.8(3)
103.7(3)
168.6(3)
C3X–Re–N5
O4–Re–N5
C2X–Re–Cl
C1X–Re–Cl
C3X–Re–Cl
O4–Re–Cl
N5–Re–Cl
91.0(3)
75.9(2)
92.7(3)
93.8(3)
175.3(3)
85.1(1)
84.9(2)
3
.3. Structure of Re(I) and Ag(I) complexes
The molecular units of the title complexes are shown in Figs. 2
and 3. Distances and angles around the metal ions are given in
Table 2.
The structure of the rhenium complex (Fig. 2) consists in cen-
trosymmetric dinuclear units in which two fac-ReCl(CO)
3
frag-
2 2 4 2
[Ag (DHzD) ](ClO )
Ag1–N5A
Ag1–N5C
Ag1–N61C
Ag1–N61A
Ag1–O4A
Ag1–O4C
2.323(6)
2.371(6)
2.374(5)
2.453(6)
2.649(6)
2.816(6)
Ag2–N5D
Ag2–N5B
Ag2–N61B
Ag2–N61D
Ag2–O4D
Ag2–O4B
2.310(5)
2.348(6)
2.391(6)
2.479(6)
2.656(6)
2.791(6)
ments are attached in both N5,O4-bidentate cavities of the DHzD
ligand (Z,Z isomer). To get this, the organic ligand rotates around
0
the C6-C61 bond until the mean plane of each lumazine moiety be-
comes perpendicular to the azine bridge (C6–C61 = N61–
0
0
0
N61 = C61 –C6 ) one. Then, both pteridine planes are parallel and
distanced by 3.359 Å, but they cannot establish intramolecular
p
-
N5A–Ag1–N5C
N5A–Ag1–N61C
N5C–Ag1–N61C
N5A–Ag1–N61A
N5C–Ag1–N61A
N61C–Ag1–N61A
O4A–Ag1–N5A
O4A–Ag1–N5C
O4A–Ag1–N61C
O4A–Ag1–N61A
O4A–Ag1–O4C
O4C–Ag1–N5A
O4C–Ag1–N5C
O4C–Ag1–N61C
O4C–Ag1–N61A
151.9(2)
140.0(2)
67.8(2)
66.6(2)
115.9(2)
106.9(2)
66.5(2)
106.3(2)
107.2(2)
133.1(2)
88.8(2)
88.7(2)
63.5(2)
131.3(2)
92.1(2)
N5D–Ag2–N5B
N5D–Ag2–N61B
N5B–Ag2–N61B
N5D–Ag2–N61D
N5B–Ag2–N61D
N61B–Ag2–N61D
O4D–Ag2–N5D
O4D–Ag2–N5B
O4D–Ag2–N61B
O4D–Ag2–N61D
O4D–Ag2–O4B
O4B–Ag2–N5D
O4B–Ag2–N5B
O4B–Ag2–N61B
O4B–Ag2–N61D
152.5(2)
139.0(2)
68.3(2)
67.3(2)
108.6(2)
105.1(2)
67.0(2)
112.3(2)
108.2(2)
134.2(2)
92.7(2)
88.6(2)
63.9(2)
132.2(2)
87.5(2)
stacking interactions because the mutual conformation of pteri-
dine residues left as closest to both pyrazine rings with their cen-
troids lying ca. 7 Å to each other; in the same way, the Re–Re
distance is 7.959(5) Å. Consequently, the dimetallic molecule be-
3
haves as two independent octahedral ReCl(CO) (N5,O4-pteridine)
centers linked by the diazine bridge.
The geometry around the Re atoms are practically octahedral
with the sterical restraints imposed by the bite O4–Re–N5 angle
of the pteridine (75.9(2)°) which is quite far from the ideal 90° ex-
pected for a regular octahedron. The metal–ligand distances are in
the ranges reported for Re–Cl (2.47 ± 0.02 Å), Re–N (2.18 ± 0.04 Å)
and Re–O (2.18 ± 0.01 Å) distances in eight related mononuclear
Re(I) compounds [19,27–29].
2 2 6
Fig. 2. Labelled ball-and-stick drawing for [Re Cl (CO) (DHzD)] (hydrogen atoms
and solvent molecules are omitted for clarity).

1
4
S.B. Jiménez-Pulido et al. / Polyhedron 50 (2013) 10–15
The structure of the silver compound (Fig. 3) also consists in
Table 3
Geometrical details of Y–X anionꢀ ꢀ ꢀring interactions.
dinuclear units, but due to the 1:1 M/L ratio employed in the syn-
thesis and the low coordinative ability of the perchlorate countera-
nions, two Ag(I) ions are binucleated by two ligands (E,E isomer).
d(Xꢀ ꢀ ꢀCg) (Å) d (°) \Y–Xꢀ ꢀ ꢀCg (°)
0
[
2 2 6
Re Cl (CO) (DHzD)]
3
The whole set is arranged around a central Ag1–N61C–N61D–Ag2–
N61B–N61A six-membered boat-shaped ring, the prow and poop
sites being occupied by N61B and N61C atoms. Each metal ion is
chelated by two tridentate N61,N5,O4-pteridine moieties, from dif-
ferent DHzD ligands, in a roughly perpendicular mer-conformation.
In the dinuclear unit, the silver atoms are almost equivalent, being
surrounded by four nitrogen atoms at 2.31–2.48 Å and two oxy-
gens quite longer distanced at 2.64–2.82 Å (see Table 2), but short-
er than the sum of the Van der Waals’ radii (3.24 Å); the long Ag–O
bonds are consistent with those found for other complexes of met-
als of the first and second transition rows [30,31]. Although the
Ag(I) centers are nearer than in the Re(I) compound, the Ag1–
Ag2 distance (4.073(5) Å) is longer than the sum of Van der Waals’
radii (3.44 Å), thus preventing the existence of M–M bonds. There-
fore, as in the Re(I) complex, the disilver unit also behaves as two
independent 5 + 1-coordinated centers mutually assembled by two
N61–N61 azine groups.
A closest view of the coordination environment around the sil-
ver atoms is shown in the Fig. 4. Both polyhedra are really distorted
and can be described as square-based pyramids with one farther
oxygen atom (O4C and O4B) capping the quasi-planar N61A–
N5A–N5C–O4A (Ag1) and N61D–N5D–N5B–O4D (Ag2) faces. The
analysis of five-coordination following Holmes [32] indicates that
the pivot atoms that best describe a Berry pseudo-rotation are
N61C (Ag1) and N61B (Ag2); in both polyhedra, the percentage
along Berry pseudorotation coordinate D3h(TBP) ? C2v ? C4v(SP)
being ca. 54%, which indicates a just intermediate geometry be-
C2X–O2Xꢀ ꢀ ꢀpyz (½ + x,y, / ꢁ z)
3.087(7)
2.924(9)
14.1 110.4(5)
4.0 103.6(8)
2
C1S–N1Sꢀ ꢀ ꢀpym
2
2
4 2
[Ag (DHzD) ](ClO )
C2B–O2Bꢀ ꢀ ꢀpymD (2 ꢁ x,ꢁy,1 ꢁ z)
3.076(8)
2.711(7)
24.5 153.3(6)
8.8 173.5(6)
18.6 157.7(6)
15.0 109.1(5)
25.5 101.9(5)
C2C–O2Cꢀ ꢀ ꢀpymA (1 ꢁ x, ꢁy, 1 ꢁ z)
3
C2D–O2Dꢀ ꢀ ꢀpymB (2ꢁꢂ,½ + y, /
Cl1P–O3Pꢀ ꢀ ꢀpyzB (x,1 + y,z)
Cl1P–O3Pꢀ ꢀ ꢀpyzC (x,1 + y,z)
Cl1P–O4ꢀ ꢀ ꢀpyzB (x,1 + y,z)
Cl2P–O6Pꢀ ꢀ ꢀpyzA
2
ꢁ z) 2.899(7)
3.096(9)
3.461(9)
3.432(9)
3.090(7)
3.045(6)
3.520(7)
3.598(6)
3.768(7)
26.0
94.2(4)
9.0 117.2(3)
13.5 104.2(3)
Cl2P–O7Pꢀ ꢀ ꢀpyzD
Cl2P–O8Pꢀ ꢀ ꢀchel2D
18.7
20.3 111.6(3)
27.9 74.9(2)
90.3(3)
Cl2P–O8Pꢀ ꢀ ꢀpymD
Cl2P–O8Pꢀ ꢀ ꢀpyzD
Rings are labelled as follows: pym, pyrimidine; pyz, pyrazine; chel, Ag–O4–N5–C4–
C4A. d(Xꢀ ꢀ ꢀCg): distance between the X atom and the centroid of the ring; d: slip-
ping angle between the X-centroid vector and the normal to the ring.
3
2
(½ + x,y, / ꢁ z) interactions, whereas the acetonitrile molecules
occupy the solvent accesible voids of the cell in a quasi-perpendic-
ular C–C„Nꢀ ꢀ ꢀpym arrangement.
Despite the single-crystal XRD measurements have allowed a
good knowledge of the disilver units and perchlorate countera-
nions, several disordered non-coordinated water molecules, which
of course contribute to the crystal packing through H-bonds, have
been found. In this way, the analysis with PLATON [25] indicates that
3
the structure contains solvent accessible voids of 41 Å , as conse-
quence of minor unassigned diffraction peaks. In addition to this,
tween the extreme shapes. Furthermore, the Addison’s
s
parameter
several Y–Xꢀ ꢀ ꢀring
r–p interactions have been also found (see Ta-
[
33] (Ag1, = 0.20; Ag2, = 0.22) describes a more tetragonalized
s
s
ble 3), the most important being those encapsulating the perchlo-
rate (Cl2P) between the pteridine moieties A and D as shown in
Fig. 3.
nearer-to-SP shape for both coordination polyhedra.
In both cases, the geometry of the pteridine moieties are in
according with bibliographic data [19,21,30,31], although it is
noteworthy that, in the Ag(I) compound, the endocyclic C4@O4
carbonyl groups are slightly shorter than in most of the examples
previously reported. Also, the distances in the azine bridge (C6–
Acknowledgements
Thanks are due to the Universidad de Jaén (Plan de Apoyo a la
Investigación, al Desarrollo Tecnológico y a la Innovación de la Uni-
versidad de Jaén) and Junta de Andalucía (FQM-273) for financial
support.
0
C61, ca. 1.48 Å; C61@N61, ca. 1.26–1.29 Å; N61–N61 , ca. 1.39 Å)
clearly denote only a little electron delocalization due to the lack
of coplanarity between the bridge and the pteridine cores, the
N5–C6–C61–N61 dihedral angles being about 90° (Re) and 33°
(
Ag).
Data for intermolecular interactions, calculated by means of PLA-
TON [25] and examined following the criteria reported by Janiak
34], are given in Table 3. In the crystal structure of Re compound,
the molecules are placed with the pteridine planes normal to the
Appendix A. Supplementary material
CCDC 885223 and 885224 contain the supplementary crystallo-
graphic data for Ag and Re compounds. Supplementary data asso-
ciated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.poly.2012.10.033. These data include
MOL files and InChiKeys of the most important compounds de-
scribed in this article.
[
ꢀ
[102] direction. There are no classical H-bonds and the mole-
cules interact to each others mainly through C2X–O2Xꢀ ꢀ ꢀpyz
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