Coordination polymers and polygons using di-pyridyl-thiadiazole spacers and substituted phosphorodithioato NiII complexes: Potential and limitations for inorganic crystal engineering

Article abstract of DOI:10.1039/c6ce00991c

Coordinatively unsaturated P-substituted dithiophosphonato, dithiophosphato, and dithiophosphito complexes {[Ni((MeO)₂PS₂)₂] (1), [Ni((EtO)₂PS₂)₂] (2), [Ni(MeOdtp)₂] (3), and [Ni((Ph)₂PS₂)₂] (4)} were reacted with the bis-functional ligands 3,5-di-(4-pyridyl)-1,2,4-thiadiazole (L1) and 3,5-di-(3-pyridyl)-1,2,4-thiadiazole (L2) to give the coordination polymers (1-4·L1)_∞, (3·L2)_∞, and (4·L2·2C₇H₈)_∞ and the discrete dimers (1-2·L2)₂, all characterised by single crystal X-ray diffraction. A comparison of the structures shows that L1 can be exploited for the predictable assembly of undulating chains independent of the nature of the Ni^II complex, while L2 allows for the existence of different supramolecular constructs ensuing from different ligand conformations deriving from the rotation of the pyridyl rings.

Full text of DOI:10.1039/c6ce00991c

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ARTICLE
Coordination polymers and polygons using di-pyridyl-thiadiazole
spacers and substituted phosphorodithioato NiII complexes:
potential and limitations for inorganic crystal engineering
Received 00th January 20xx,
Accepted 00th January 20xx
M. Carla Aragoni,*a Massimiliano Arca,a Simon J. Coles, b Miriam Crespo,a Susanne L. Coles (née
Huth),c Robert P. Davies,*d Michael B. Hursthouse,b Francesco Isaia,a Romina Laia and Vito Lippolisa
DOI: 10.1039/x0xx00000x
www.rsc.org/
Coordinatively unsaturated P-substituted dithiophosphonato, dithiophosphato, and dithiophosphito complexes
[Ni((MeO)2PS2)2] (1), [Ni((EtO)2PS2)2] (2), [Ni(MeOdtp)2] (3), and [Ni((Ph)2PS2)2] (4) were reacted with the bis-functional
ligands 3,5-di-(4-pyridyl)-1,2,4-thiadiazole (L1) and 3,5-di-(3-pyridyl)-1,2,4-thiadiazole (L2) to give the coordination
polymers (1–4·L1)∞, (3·L2)∞, (4·L2·2C7H8)∞ and the discrete dimers (1–2·L2)2, all characterised by single crystal X-ray
diffraction. The comparison of the structures show that L1 can be exploited for the predictable assembly of undulating
chains independent of the nature of the NiII complex while L2 allows for the existence of different supramolecular
constructs ensuing from different ligand conformations deriving from the rotation of the pyridyl rings.
can be used to direct the network assembly, although factors
such as flexibility of the ligand and different accessible
conformations need to be examined and taken into account.
Introduction
The last decades experienced an impressive number of novel
multidentate bridging ligands designed to construct a variety
of discrete metal–organic polygons and polyhedra (MOPs), or
metal–organic frameworks (MOFs) with high dimensionality.
These supramolecular assemblies are of great appeal for a
combination of their intrinsic beauty and promising
applications in fields as varied as gas storage, ion exchange,
chemical sensing, catalysis, energy transfer, and separation.1,‡
The properties of these crystalline materials are critically
dependent on their network structures, and the deliberate
creation of a crystalline network, planned using properly
designed building blocks remains, nowadays, a challenge.
Several aspects need to be evaluated in developing a network
based on coordination polymers: the building blocks, i.e. metal
nodes and organic spacers, metal coordination environments,
formation conditions, and weak secondary interactions. Multi-
topic organic molecules are commonly used as spacers and an
opportune choice of the number and position of donor atoms
The metal coordination environment is exceptionally difficult
to control when “naked” metal ions are used as nodes and, in
view of that, the use of neutral coordination complexes held
together by additional donor molecules or secondary bonding
interactions has gained striking importance.2 In fact, by
reducing the degrees of freedom of the system, for instance by
using cis-protected metal blocks in place of the naked metal
ions, or by using a neutral, coordinatively unsaturated metal
complex, less uncertainty can be expected. Moreover, the use
of neutral synthons leads to self-reliant supramolecular
assemblies which do not require the presence of a counterion
and thus reduce the occurrence of isomerism.
In this respect, we have been developing a synthetic
program based on the ability of neutral dithiophosphonato NiII
–
complexes [Ni(ROdtp)2] [ROdtp = (RO)(4-MeOC6H4)PS2 ; R =
alkyl substituent]3 to assemble coordination polymers in
combination with a variety of polypyridyl donors, in particular
4,4'-bipyridine and its analogues.§,4 This assembly process is
based on the capability of the coordinatively unsaturated NiII
ion of these square-planar complexes to axially bind
monodentate ligands, such as pyridine, to yield discrete
octahedral complexes.5,6 In addition suitable N–L–N bidentate
bipyridyl-based spacers yield 1D coordination polymers of the
type [Ni(ROdtp)2(N–L–N)]∞.7,8 The primary structural motif of
these polymers mainly depends on the features of the spacers
such as length, rigidity and orientation of the donor atoms, as
recently confirmed by the deliberate stereospecific generation
of homochiral polymeric helices built from
enantiopure binaphthyl-based ligand.9
a designed
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water in hexane) was added to KCH2Ph (0.3265 g, 2.5 mmol) in
10 mL of freshly distilled toluene at room temperature. After
10 minutes, the solution was transferred onto dried powdered
N
S
S
S
S
S
R2
R1
R1
P
Ni
P
S8 (0.1588 g,
5 mmol), and the newly-formed brown
N
R2
suspension was transferred onto NiI2 (0.3906 g, 1.25 mmol)
and refluxed for 4 hours. The solvent was removed under
reduced pressure and the resulting brown solid was dissolved
in CH2Cl2 and filtered through a small celite plug. The filtrate
N
N
L1
R1
R2
(1) OMe
(2) OEt
OMe
OEt
N
S
N
was concentrated under vacuum and
4 obtained as purple
(3) 4-MeC6H4
(4) Ph
OMe
Ph
crystals, suitable for X-ray analysis. C24H20P2S4Ni (formula mass
= 557.30 Da, 0.9971 g, 1.8 mmol, 72% yield). M.p.: 253-255 °C
L2
N
N
1
(m). H NMR (400 MHz, D6-DMSO) δ = 7.22 (d, 3H, Ph), 7.94
Scheme 1 General scheme of complexes
1
–
4
(left) and ligands L1
–
L2 (right).
(m, 2H, Ph); 31P NMR (400 MHz, D6-DMSO) δ = 60.22.
The substituents on the phosphorus atoms are responsible
for the connection of the polymers through hydrogen bonds
Synthesis of [Ni((MeO)2PS2)·L1)]∞, (1·L1)∞. Complex
1 (18.6
mg, 0.05 mmol) and L1 (12.0 mg, 0.05 mmol) were reacted at
130 °C in a high pressure Aldrich tube in 30 mL of MeOH. After
complete dissolving of the reagents, the reaction mixture was
and face–to–face or edge–to–face
π–π interactions, thus
influencing the final 3D-architecture.7 As a consequence,
coordination polymers and 3D assemblies with different
structures and architectures can be built up by varying either
the bridging ligands or the substituents on the P atom of the
initial Ni complexes. In order to better understand the process
of molecular recognition between components and how the
steric information contained in the P-substituents and in the
orientation of ligand binding sites combine to give the final
structure, differently P-substituted dithiophosphonato,
slowly cooled at room temperature. After a few days (1·L1
)
∞
(4.0 mg, 0.006 mmol, 13% yield) was obtained as green
crystals suitable for X-ray analysis. M.p.: 170 °C (d). Elemental
analysis found (calc. for C16H20N4O4P2S5Ni; formula mass =
611.9 Da): C, 31.63 (31.33); H, 2.38 (3.29); N, 9.31 (9.14); S,
21.75 (26.14). FT-IR (KBr, 3000-300 cm–1): 2938 w, 2834 vw,
2361 vw, 1608 m, 1462 m, 1411 m, 1335 m, 1290 w, 1210 w,
1176 w, 1130 vs, 827 s, 798 s, 709 m, 691 s, 675 s, 665 m, 530
m, 439 vw, 398 w, 324 m cm–1. FT-Raman (3500-100 cm-1, 600
mW, solid state, relative intensities between parentheses
related to the highest peak taken equal to 10.0): 1922 (6.0),
1894 (6.4), 1877 (6.0), 1811 (6.4), 1758 (4.6), 1612 (10.0), 1513
(8.6), 1459 (9.3), 1410 (9.3), 1335 (6.1), 1293 (6.0), 1020 (6.2)
cm–1.
dithiophosphato,
[Ni((MeO)2PS2)2] (
and
), [Ni((EtO)2PS2)2] (
) were reacted with the bis-functional
dithiophosphito
complexes
1
2), [Ni(MeOdtp)2] (
3
),
and [Ni((Ph)2PS2)2] (
ligands 3,5-di-(4-pyridyl)-1,2,4-thiadiazole (L1
pyridyl)-1,2,4-thiadiazole (L2
10 (Scheme 1).
4
10
)
and 3,5-di-(3-
)
We recently investigated the reactivity of L1 and L2 with I2
and IBr, in both polar and apolar media, thereby elucidating
the role of specific directional interactions, namely NH+···N and
N···I, combined with geometrical features of the molecules, in
the formation of different supramolecular constructs.10 The
investigation of these ligands is extended here to the
formation of coordination polymers.
Synthesis of [Ni((EtO)2PS2)·L1)]∞, (2·L1)∞. Complex
2 (21.4 mg,
0.05 mmol) and L1 (12.0 mg, 0.05 mmol) were reacted at 160
°C in a high pressure Aldrich tube in 30 mL of EtOH. After
complete dissolving of the reagents, the reaction mixture was
slowly cooled at room temperature. After a few days (2⋅L1)
∞
(4.1 mg, 0.006 mmol, 12% yield) was obtained as green
crystals suitable for X-ray analysis by slow evaporation of the
solvent. M.p.: 155 °C (d). Elemental analysis found (calc. for
C20H28N4O4P2S5Ni; formula mass = 668.0 Da): C, 36.31 (35.89);
H, 4.17 (4.22); N, 8.46 (8.37); S, 24.12 (23.95). FT-IR (KBr, 3000-
350 cm–1): 3054 vw, 3032 w, 2934 w, 2893 vw, 2459 vw, 2285
vw, 1931 vw, 1609 s, 1496 vs, 1440 m, 1412 m, 1336 m, 1121
m, 1019 vs, 945 vs, 848 w, 830 m, 805 m, 773 s, 713 m, 673 s,
Experimental
Materials
All commercially available compounds were used as received.
657 s, 644 m, 620 w, 546w, 410 w cm–1. FT-Raman (3500-0 cm-
Bis[O-alkyl-dithiophosphato]Ni complexes {[Ni((RO)2PS2)2] R =
)},5 the dithiophosphonato NiII complex
1
,
150 mW, solid state, relative intensities between
Me
(
1
), Et
(
2
–
[Ni(MeOdtp)2] [MeOdtp = (RO)(4-MeOC6H4)PS2 ],3 and bis-
parentheses related to the highest peak taken equal to 10.0):
3075 (4.8), 3027 (4.2), 2933 (5.1), 2888 (5.0), 1981 (4.1), 1611
(10.0), 1513 (5.7), 1413 (8.5), 1338 (5.9), 1229 (5.3), 1215 (5.5),
1095 (7.7), 1015 (7.7) 999 (5.7), 729 (4.2), 650 (6.1) 548 (8.8),
376 (7.5) cm–1.
functional ligands 3,5-di-(4-pyridyl)-1,2,4-thiadiazole (L1) and
3,5-di-(3-pyridyl)-1,2,4-thiadiazole
(
L2),10 were synthesised
according to previously reported procedures. The solvents
used were freshly distilled over the appropriate drying agent
and used directly from the stills.
Synthesis of [Ni((MeO)(4-MeOC6H4)PS2)2·L1]∞, (3·L1)∞
.
Complex 3 (26.2 mg, 0.05 mmol) and L1 (12.0 mg, 0.05 mmol)
Synthesis
of
bis(diphenyldithiophosphinato)nickel(II),
were reacted at 100 °C in a high pressure Aldrich tube in 30 mL
of CH3OH. After complete dissolving of the reagents, the
reaction mixture was slowly cooled at room temperature.
[Ni((C6H5)2PS2)2] (4). Complex
4
was synthesised and firstly X-
However, in this work we
11
ray characterised in 1968.
developed a new high yielding and clean synthetic route,
which starts from primary phosphines: Ph2PH (6.7 mL, 10%
After a week, (
3⋅
L1)
(29.5 mg, 0.39 mmol, 77% yield) was
∞
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obtained as green crystals suitable for X-ray analysis. M.p.: peak taken equal to 10.0): 3075 (4.8), 3027 (4.2), 2933 (5.1),
160°C (d). Elemental analysis found (calc. for C28H28N4O4P2S5Ni; 2888 (5), 1981 (4.1), 1611 (10), 1513 (5.7), 1413 (8.5), 1338
formula mass = 764.0 Da): C, 44.73 (43.98); H, 3.38 (3.69); N, (5.9), 1229 (5.3), 1215 (5.5), 1095 (7.7), 1015 (7.7), 999 (5.7),
7.53 (7.32); S, 21.08 (20.94). FT-IR (KBr, 1800-300): 1214 w, 729 (4.2), 650 (6.1), 548 (8.8), 376 (7.5) cm-1.
1179 mw, 1130 vw, 1114 s, 1065 w, 1029 vs, 1020 vs, 909 vw, Synthesis of [Ni((MeO)(4-MeOC6H4)PS2)2·L2]∞, (3·L2)∞.
851 vw, 830 ms, 779 vs, 754 w, 733 vw, 709 w, 690 vw, 654 Complex
3 (26.3 mg, 0.05 mmol) and L2 (24.0 mg, 0.10 mmol)
ms, 640 s, 625 mw, 546 vs, 520 mw, 508 w, 457 vw, 442 w, 398 were reacted at 100 °C in a high pressure Aldrich tube in 25 mL
vw, 369 vw, 326 ms cm-1. FT-Raman (3500-100 cm-1, 150 mW, of MeOH. After complete dissolving of the reagents, the
solid state, relative intensities between parentheses related to reaction mixture was slowly cooled at room temperature.
the highest peak taken equal to 10.0): 3054 (2.8), 2924 (2.8), After a week, (3⋅L2) (29.5 mg, 0.031 mmol, 62% yield) was
∞
1615 (10.0), 1582 (5.7), 1420 (7.8), 1310 (3.6), 1280 (4.2), 1110 obtained as green crystals suitable for X-ray analysis. M.p.: 160
(5.7), 1020 (5.0), 1000 (5.0), 547 (6.4), 102 (6.4) cm-1.
°C (d). Elemental analysis found (calc. for C28H28N4O4P2S5Ni;
Synthesis of [Ni((C6H5)2PS2)2·L1]∞, (4·L1)∞. A mixture of
4
(5.5 formula mass = 764.0 uma): C, 44.73 (43.93); H, 3.38 (3.69); N,
mg, 0.01 mmol) and L1 (2.4 mg, 0.01 mmol) in 3 mL of toluene 7.53 (7.32); S, 21.08 (20.94). FT-IR (KBr, 1600-350 cm–1): 1593
was heated to 100 °C in a sealed 5 mL screw-top glass bottle s, 1569 mw, 1499 s, 1474 ms, 1432 w, 1406 m, 1331 w, 1294 s,
for 3 days. The mixture was allowed to cool to room 1254 vs, 1175 ms, 1113 vs, 1021 vs, 827 mw, 775 vs, 730 w,
temperature and the resulting green crystals of (
from the reaction mixture; (5.1 mg, 0.007 mmol, 64% yield) Raman (4000-0 cm-1, 100 mW, solid in KBr, relative intensities
M.p.: 230 °C. Elemental analysis found (calc. for between parentheses related to the highest peak taken equal
4⋅L1)
∞ filtered 654 vs, 623 s, 545 vs, 525 w, 436 w, 406 vw, 327 ms cm–1. FT-
>
C36H28N4P2S5Ni; formula mass = 797.57 Da): C, 44.88 (54.21); H, to 10.0): 3054 (0.7), 2850 (0.4), 2670 (0.3), 1618 (5.2), 1477
3.45 (3.54); N, 4.93 (7.02)%. FT-IR (KBr, 4000- 400 cm-1): 3448 (2.6), 1418 (2.0), 1199 (6.0), 1156 (10.0), 1031 (2.6), 642 (0.8),
vw, 3045 w, 1607 s, 1465 s, 1435,09 s, 1408 s, 1329 m, 1304 w, 545 (1.2), 125 (4.2), 104 (2.4) cm–1.
1285 w, 1226 w, 1099 s, 1061 m, 999 m, 833 m, 823 m, 746 s, Synthesis of [Ni((C6H5)2PS2)2·L2]∞, (4·L2)∞. A mixture of
4 (5.5
707 vs, 699 vs, 612 vs, 571 s, 565 vs, 518 m, 483 m, 443 w, 420 mg, 0.01 mmol) and L2 (2.4 mg, 0.01 mmol) in 3 mL toluene
w cm-1.
was heated to 100 °C in a sealed 5 mL screw-top glass bottle
Synthesis of [Ni((MeO)2PS2)·L2)]2, (1·L2)2. Complex
1
(18.6 mg, for 3 days. The mixture was allowed to cool to room
0.05 mmol) and L2 (18.0 mg, 0.07 mmol) were reacted at 140 temperature and the resulting green crystals filtered from the
°C in a high pressure Aldrich tube in 30 mL of MeOH. After reaction mixture; (4.3 mg, 0.0042 mmol, 42% yield). M.p.: 233
complete dissolving of the reagents, the reaction mixture was °C (d). Elemental analysis found (calc. for C48H36N8P2S6Ni;
slowly cooled at room temperature. After a few days (
1
⋅
L2
)
formula mass = 1037.86 Da): C, 54.2 (55.6); H, 3.5 (3.5); N, 10.8
2
(5.5 mg, 0.008 mmol, 18% yield) was obtained as green (7.1)%. FT-IR (KBr, 4000- 400 cm-1): 3432 vw, 1637 w, 1587 m,
crystals suitable for X-ray analysis by slow evaporation of the 1497 s, 1471 vs, 1415 s, 1325 s, 1289 s, 1096 m, 1048 m, 1024
solvent. M.p.: 180 °C (d). Elemental analysis found (calc. for m, 998 m, 902 m, 815 s, 730 s, 693 s, 650 s, 611 m, 566 vs, 489
C16H20N4O4P2S5Ni; formula mass = 611.9 Da): C, 31.55 (31.33); vs, 415 w cm-1.
H, 2.21 (3.29); N, 9.13 (9.14); S, 24.69 (26.14). FT-IR (KBr, 4000-
400 cm–1): 2938 w, 2834 vw, 2361 vw, 1608 m, 1462 vm, 1411
Characterisation
m, 1335 m, 1290 w, 1210 w, 1176 w, 1130 vs, 827 s, 798 s, 709
m, 691 s, 675 s, 665 m, 530 m, 439 vw, 398 w, 324 m cm-1. FT-
Raman (4000-0 cm-1, 200 mW, solid in KBr, relative intensities
between parentheses related to the highest peak taken equal
to 10.0): 1922 (6), 1894 (6.4), 1877 (6), 1811 (6.4), 1758 (4.6),
1612 (10), 1513 (8.6), 1459 (9.3), 1410(9.3), 1335 (6.1), 1293
(6), 1020 (6.2) cm-1.
1H- and 31P-NMR spectra were recorded at 25°C in D6-DMSO
on
a Bruker DPX400 NMR spectrometer with internal
standards. Elemental analyses were performed with an
EA1108 CHNS-O Fisons instrument. FT-Infrared spectra were
recorded on a Thermo Nicolet 5700 spectrometer at room
temperature using a flow of dried air. Middle IR spectra
(resolution 4 cm-1) were recorded as KBr pellets, with a KBr
Synthesis of [Ni((EtO)2PS2)·L2)]2, (2·L2)2. A solution of L2 (10
mg, 0.042 mmol) in 10 mL of EtOH was slowly diffused into a
beam-splitter
determinations and crystallographic data for compounds
1·L1)∞, (2·L1)∞, (3·L1)∞, (1·L2)2, and (3·L2)∞, were collected at
and
KBr
windows.
X-ray
structure
of CH2Cl2 solution of
stand at room temperature for several weeks. Green crystals
of ( L2)2 (16.9 mg, 0.025 mmol, 50% yield) suitable for X-ray
2 (10 mg, 0.023 mmol, 0.5 mL) and left to
(
2⋅
120(2) K by means of combined phi and omega scans on a
Bruker-Nonius Kappa CCD area detector, situated at the
analysis were obtained. M.p.: 159-162 °C (m). Elemental
analysis found (calc. for C20H28N4O4P2S5Ni; formula mass =
668.0 Da): C, 34.84 (35.89); H, 4.53 (4.22); N, 8.11 (8.37); S,
24.15 (23.95). FT-IR (KBr, 4000-50 cm–1): 3054 vw, 3032 w,
2934 w, 2893 vw, 2459 vw, 2285 vw, 1931 vw, 1609 s, 1496 vs,
1440 m, 1412 m, 1336 m, 11215 m, 1019 vs, 945 vs, 848 w,
830 m, 805 m, 773 s, 713 m, 673 s, 657 s, 644 m, 620 w, 546 w,
410 w cm-1. FT-Raman (3500-0 cm-1, 600 mW, solid state,
relative intensities between parentheses related to the highest
window of a FR591rotating anode (graphite Mo-Kα radiation,
λ
= 0.71073Å). Data for compound (2·L2)2, were collected at
120(2) K by means of fine-slice/omega scans on Bruker SMART
APEX2 CCD diffractometer with Daresbury SRS station 9.8
synchrotron source (silicon 111, λ = 0.6893Å). Data for
compound (4·L1)∞, were collected at 173(2) K by means of
combined phi and diffractometer with enhance X-ray source
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Table 1 Selected bond lengths (Å), bond and torsion angles (°), and angles
between pyridyl (Py)/thiadiazole (Tdz) ring mean planes (°) for (1·L1)∞,
(2·L1)∞, (3·L1)∞, and (4·L1)∞. Numbering scheme according to Fig. S1.b
(1·L1)∞
(2·L1)∞
(3·L1)∞
(4·L1)∞
Ni–N1
Ni–N4
Ni–S1
Ni–S2
P1–S1
P1–S2
2.095(3)
2.100(3)
2.1042(16)
2.1042(16)
2.4846(5)
2.4683(5)
1.9693(8)
1.9884(8)
2.1343(18)
2.137(2)
2.1376(16)
2.1052(16)
2.4836(5)a
2.4940(6)a
2.0001(8)a
2.0025(7)a
2.5041(12)a
2.4585(11)a
1.9735(15)a
1.9814(15)a
2.4876(6)a
2.4662(6)a
1.9993(9)a
1.9974(9)a
N1–Ni–S1
N1–Ni–S2
S1–Ni–S2
S1–P1–S2
91.02(8)
89.58(9)
82.04(4)a
110.95(7)a
89.72(5)
90.39(5)
82.010(17)
110.39(3)
90.94(5)
89.12(5)
82.55(2)a
109.70(4)a
91.22(4)
88.76(5)
82.42(2)a
110.2(4)a
C2–C3–C6–N2
C9–C8–C7–N2
19(3)
17(3)
31.9(3)
31.9(3)
34.2(3)
20.3(3)
4.7(3)
11.0(3)
Py(N1)^Py(N4)
Py(N1)^Tdz
Py(N4)^Tdz
25.8
20.1
17.3
63.7
32.9
32.9
31.9
36.5
20.0
16.1
4.9
11.4
a Average of the bond parameters for the two symmetry independent fragments
b
(P1S1S2Ni1) and (P2S3S4Ni2). Due to the different space groups own by the
polymers, as a consequence, to the different equivalent atoms imposed by
symmetry, each structure had to be solved with different labels. In order to
compare structural parameters of differently labelled polymers, Table 1 refers to
the common artificial numbering scheme shown in Fig. S1.
(graphite Mo-Kα radiation). Data for compound (4·L2·2C7H8)∞,
were collected at 173(2) K by means of omega scans on an
Oxford Diffraction Xcalibur PX Ultra diffractometer with
enhance ultra (Cu) X-ray source (graphite Cu-Kα radiation,
λ =
1.54184Å). The structures were solved by direct methods,
SHELXS-97 and refined on F2 using SHELXL-97.12,13 Anisotropic
displacement parameters were assigned to all non-hydrogen
atoms. Hydrogen atoms were included in the refinement, but
thermal parameters and geometry were constrained to ride on
the atom to which they are bonded. The data of (1·L1)∞,
(
2·L1
)
∞ and (3·L1
)
∞ were corrected for absorption effects using
and (4·L2 ∞ were refined
SADABS V2.10.14 The data for (4·L1
)
∞
)
using CrysAlis RED,15 implemented in SCALE3 ABSPACK scaling
algorithm for empirical absorption correction using spherical
harmonics. Structures have been deposited with the
Cambridge Crystallographic Data Centre: deposition numbers
Fig. 2 Polymeric and protonated chains involving ligand L1 in the compounds
(1·L1) (a), (2·L1) (b), (3·L1) (c), (4·L1) (d (e; ref. 10).
), and (L1H+)∞
∞ ∞ ∞ ∞
CCDC 1474147, 1474143, 1474148, 1474145, 1474150,
1474144, 1474146, and 1474149, for (1·L1 2·L1 3·L1)∞,
4·L2·2C7H8)∞,,
)
,
(
) , (
∞
∞
(
4·L1)∞,
(
1·L2)2,
(
2·L2)2,
(
3·L2)∞, and
(
respectively. Theoretical calculations based on Density
Functional Theory (DFT)16 were carried out on L1 and L2 with
the Gaussian0917 commercial suite of software by adopting the
mPW1PW18 functional and Schäfer, Horn, and Ahlrichs double-
zeta plus polarisation (pVDZ) all-electron basis sets (BSs) for all
atomic species.19 A potential energy surface was carried out by
rotating by an angle
τ one of the pyridine rings (-180.0° ≤ τ ≤
180.0°; ꢀτ = 5.0°). The programmes GaussView 5.0.8 and
Molden 5.2 were used to investigate the charge distributions
and MO shapes.20
Results
Fig. 1 Relative electronic energy variation ΔE as a function of the rotation angle τ
of one pyridine ring (rotation step 5.0°) calculated at DFT level for L1 (red) and L2
(blue). In the inset the two possible cisoids (A) and transoid (B) L2 conformers
The bis-functional ligands L1 and L2 (Scheme 1) were first
isolated by Meltzer et al. in 1955,21 but their complexing ability
are depicted. ΔEB–ΔEA = 0.39 kcal mol–1
.
4 | J. Name., 2016, 00, 1-3
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Me (
[MeOdtp
dithiophosphito
1
), Et (
2
); Scheme 1]; dithiophosphonato [Ni(MeOdtp)2]
–
(CH3O)(4-MeOC6H4)PS2 , Scheme 1], and
(
3)
=
[Ni(Ph2PS2)2]
(4
)
complexes
under
solvothermal conditions afforded solid, crystalline compounds,
which were isolated and identified by means of single crystal
X-ray diffraction as coordination polymers of formula (
1·L1)∞,
(
2·
L1)∞, ( L1)∞, and (4·L1)∞, respectively. Crystallographic
3
·
data and selected bond lengths and angles are reported in
Tables S1 and 1 respectively. With the exception of compound
(4·L1)∞, the L1 molecules are found in two different but
essentially superimposable orientations, arising from a 180°
rotation of the molecule about the direction passing through
the midpoint of the N-S bond and through the remaining
nitrogen atom of the penta-atomic ring (Figs. S1–S3). As a
consequence, the nitrogen and the adjacent sulfur atoms show
fractional occupancies refined at values of about 60% and 40%,
respectively, and only the major orientation of the molecule is
illustrated in the figures. In the case of compound (2·L1) the
∞
L1 molecule is located about a crystallographic two-fold axis
and therefore the resulting disorder is modelled with
occupancies of 50% for each orientation.
Fig. 3 Packing view of (1·L1) showing parallel chains interacting through C–H···S
; H···S distanc∞es and C–H···S angles: a, C9i–H9i···S2 2.89(3), 120(2);
interactions (
a
i
b, C8i –H8i ···S5 2.85(3), 122(2); c, C15i–H15i···S3 2.91(4) Å, 126(2)°. x, –1+y, z);
(b) view along the 010 direction with polymeric chains coloured in blue and
involved in the described H-bonds (d, C6ii–H6ii···O3 2.37(4), 3.288(5), 155(3); e,
yellow according to their orientation. The NiII ions and the O and H atoms
C5ii –H5ii ···O4 2.60(4) Å, 3.419(5) Å, 148(3)°; x, 1.5-y, 0.5+z) have been left of
the conventional colours.
ii
towards metal ions, or as Lewis donors, has not been
investigated to date. In fact, a search in the Cambridge
Crystallographic Data Base revealed only a recent work by
Ondrejkovicova et al.22 Both L1 and L2 contain two pyridyl
groups linked by a 1,2,4-thiadiazole ring acting as a rigid, non-
reactive spacer. Compared with the popular 4,4'-bipyridine
linker, the pyridyl rings in L1 and L2 feature different geometry
and separation lengths (9.95 and 9.60 Å, respectively).
Moreover, due to the different position of the nitrogen atoms
in L1 and L2 and to the different rotational conformations
possible for the pyridyl rings, several orientations of the
binding sites can be expected. A Potential Energy Surface (PES)
analysis carried out on L1 and L2 at DFT level in the gas phase
by rotating one pyridyl substituent by an angle τ ranging
between -180 and 180° clearly shows that both donors display
an energy minimum when the central 1,2,4-thiadiazole ring is
coplanar with the pyridine moieties (Fig. 1). In the case of L2
,
two planar isomers, cisoid and transoid, are possible, differing
in energy by less than 1 kcal mol–1 and showing similar metric
parameters. As previously described, L1 and L2 feature the
highest Kohn-Sham molecular orbitals localized on the
negatively charged nitrogen atoms of the two pyridine
moieties, which are therefore available to behave as donor
sites towards Lewis unsaturated metal complexes.10 The
reactions of L1 with nickel dithiophosphato [Ni((RO)2PS2)2] [R =
Fig. 4 Packing view along the 001 direction of (2·L1) showing polymeric chains
∞
differently coloured according to their orientation. The NiII ions and the H atoms
involved in the described H-bonds [a, C2–H2a···N3i/S3i 2.54(4)/2.73(3),
i
3.426(10)/3.617(5), 147(2)/148(2); C5–H5···S2ii 2.85(2) Å, 3.364(2) Å, 115(2)°; x,
–y, 0.5+z; –0.5+x, 0.5–y, 1-z] have been left of the conventional colours. H-
ii
atoms not involved in showed interactions have been omitted for clarity. The
labels used for the described interactions refer to the original numbering scheme
(Fig. S2).
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Coordination polymers (
Journal Name
1–4·L1)∞ show similar coordination in the [10(1/2)] (yellow and green in Fig. 4) and [–10(1/2)]
environments: the nickel ions display distorted octahedral (blue and grey in Fig. 4) directions, respectively, interact
geometries with the equatorial plane occupied in iso-bidentate through weak H-bonds involving the P-substituents and the
bonds with two dithiophosphoric ligands and the pyridine rings central thiadiazole ring of L1 (“a” in Fig. 4) form 2D layers
belonging to spacer L1 axially bridging adjacent NiII ions to which stack along the [010] direction leading to a very dense
form infinite polymeric chains. The relevant bond lengths and packing with no voids.
angles (Table 1) are similar to those found in analogous
The coordination polymers (3·L1)∞ and (4·L1)∞ (Figs. 2c, 2d,
coordination polymers.7,8,9 The structures of the coordination S5 and S6) are characterised by the presence of aryl
polymers share the presence of neutral undulated polymeric substituents at the phosphorous atoms which are expected to
chains with very similar pitches: Ni-Ni distances, through engender additional intra
coordinate bonds, of 13.70, 14.15, 13.97, and 14.02 Å for interactions. Similarly to those described previously herein, the
L1)∞, ( L1)∞, ( L1)∞, and ( L1)∞, respectively (Fig. 2). asymmetric units of compounds ( L1 and ( L1 contain
ꢁꢂ
- and inter-molecular aromatic
(
1·
2
·
3·
4
·
3·
)
4· )
∞
∞
These chains are closely analogous to the ꢀꢁ 12 chains of two independent NiII ions located on crystallographic inversion
type [···(Py
PyH+···Py PyH+)n···] built up through the centres and differing only in the orientation of the aryl P-
moderate NH+···N bonds derived by the protonation of L1 substituents. In the coordination polymer
L1 the
ꢃ
∩
∩
(3· )
∞
molecules, reported for comparison in Fig. 2e.10 This confirms interactions involving the aromatic rings are intramolecular in
that the orientation of the nitrogen atoms para-positioned in nature (edge-to-face interaction “a” in Fig. 5). Weak
the outwards pyridyl rings of L1 self-govern the geometry of interactions between the methoxy groups (interactions “b”
the resulting supramolecular aggregates, leading to similar and “c” in Fig. 5) connect the chains in layers which pack
shapes independent of the nature of the interacting Lewis parallel to each other, forming a three-dimensional network
acid. The asymmetric unit of compound (1·L1)∞ (Fig. S2, Fig 2a) through C–H···S interactions mainly involving the coordinated
contains two independent NiII ions, namely Ni1 and Ni2, lying sulphur atoms and the methoxy substituents (interactions “d”-
on crystallographic inversion centres with coordination sites “g” in Fig. 5Sb).
differing in the orientation of the methoxy substituents at the
phosphorous atoms. The two coordination sites are bridged by
L1 molecules thus forming 1D parallel chains propagating
along the 101 direction. These chains interact to each other
through C–H···S short contacts, involving the pyridine rings and
the coordinated sulphur atoms, leading to the 2D layers shown
in Fig. 3a. The polymeric chains pack in two different
orientations (coloured blue and yellow in Fig. 3b and S3)
generated by inversion along the screw axes parallel to the 010
direction. As a consequence, symmetry related 2D layers
formed by differently oriented chains alternate when packed
and interact through synergic C–H···O bonds (“d” and “e” in
Fig. 3b and S3a) involving the pyridine rings and the methoxy
P-substituents belonging to Ni1b coordination sphere in a
ꢄꢅꢅꢂ7ꢃ motif. This packing arrangement enables the formation
of “rippled” void channels of about 60 Å3 corresponding to
2.2% of the unit cell volume (Fig. S3b). The presence of OEt P-
substituents in place of the OMe ones in the compound
Fig. 5 Packing views of (
3
·
L1
)
showing layers of undulated chains; a, C2–
∞
(2·L1)∞ (Fig. 2b, Fig. S4) does not result in significant changes in
H2···CntPy(N1) 2.62 Å; b, C8–H8c···O3i 2.24, 3.171(3), 158.0; c, C15–H15a···O4ii
either the NiII coordination environment or in the primary
motif of the polymer and no relevant intramolecular
interactions are worthy of note. The polymeric chains assume
four symmetry related orientations as illustrated in the colour
scheme in Fig. 4. Pairs of symmetry related chains propagating
i
2.53 Å, 3.237(3) Å, 129.0°; –1+x, –1+y, z; ii 2–x, 2–y, –z. H-atoms not involved in
showed interactions have been omitted for clarity. The labels used for the
described interactions refer to the original numbering scheme (Fig. S5).
6 | J. Name., 2016, 00, 1-3
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Table 2 Selected bond lengths (Å), bond and torsion angles (°), and angles
between pyridyl (Py)/thiadiazole (Tdz) ring mean planes (°) for (1·L2)2,
(2·L2)2, (3·L2)∞, and (4·L2·2C7H8)∞. Numbering scheme according to Fig. S7.
(1·L2)2
2.093(5)
2.099(5)
(2·L2)2
(3·L2)∞
2.160(2)
2.160(2)
2.4915(6) 2.4809(15)
2.4871(6) 2.4995(17)
1.9974(8) 2.0059(19)
1.9915(9) 1.997(2)
(4·L2)∞·2C7H8)∞
2.129(6)
2.129(6)
Ni–N1
Ni–N4
Ni–S1
Ni–S2
P1–S1
P1–S2
2.103(5)b
2.100(5)b
2.4928(18)a 2.500(2)b
2.4846(18)a 2.487(2)b
1.979(2)a
1.981(2)a
1.969(3)b
1.976(3)b
N1–Ni–S1
N1–Ni–S2
S1–Ni–S2
S1–P1–S2
N1–Ni–N4
90.66(15)
88.99(15)
81.89(10)a
89.93(19)b 88.91(5)
89.76(18)b 90.52(5)
90.82(11)
89.35(11)
83.00(5)
81.98(8)b
81.86(2)
109.71(4) 111.08(8)
110.93(10)a 112.0(2)b
175.7(2)
176.3(2)b
180.00
180.00
N2–C6–C3–C2
N2–C7–C8–C9
9.6(3)
17.9(3)
1.4(11)b
4.4(11)b
11.7(3)
11.7(3)
0.0
0.0
Fig.
6
Packing view of
(
4
·
L1
)
showing layers built up by the aromatic
∞
interactions a-g: a, CntPh(C24-C29)···CntPh(C24-C29)' 4.16, 0; b, CntPy(N1)···H26i–C26i 3.32,
Py(N1)^Py(N4) 12.3
Py(N1)^Tdz
5.0b
3.0b
7.2b
19.2
14.7
14.7
0.0
0.0
0.0
49; c, CntPy(N15)···H21ai–C21i 3.08, 133; d, CntPy(N15)···Cntii
3.67, 11; e,
Ph(C36-C41)
3.58, 109; g, C19iv–
CntPh(C30-C35)···CntiPh(C18-C23) 3.90, 19; f, C34–H34a···Cntiii
4.3
20.3
Py(N1)
H19aiv···CntPy(N1) 3.90 Å, 129°. Symmetry codes: i –x, 1–y, 1–z; ii 1–x, 1–y, 2–z; iii x,
–1+y, z; –x, 2–y, –z. H-atoms not involved in showed interactions have been
Py(N4)^Tdz
a
iv
Average of the bond parameters for the two fragments (P1S1S2Ni) and
(P2S3S4Ni). Average of the bond parameters for the symmetry independent
coordination environment around Ni1 and Ni2.
b
omitted for clarity. The labels used for the described interactions refer to the
original numbering scheme (Fig. S6).
Aromatic interactions become prevalent in polymer (4·L1)
∞
In the case of compound (3·L2)∞ the L2 molecule is located
about a crystallographic two-fold axis and therefore the
resulting disorder is modelled with occupancies of 50% for
due to the presence of phenyl substituents at the phosphorous
atoms, so that the polymeric chains pack in layers built up by
face-to-face and edge-to-face interactions only (“a”-“g” in Fig.
each orientation. The asymmetric unit of the dimer (
contains two independent units featuring differently oriented
ligands L2 (Fig. 7b). Both dimers ( L2 and polymers (
L2
display octahedral NiII coordination environments
2·L2)
2
6). The layers pack parallel to the
a axis through weak C–H···S
interactions (“h”-“j” in Fig. 6Sb). Despite the fact that all the
coordination polymers featuring L1 as a spacer exhibit the
same primary motif found in the supramolecular aggregates of
L1H+ (Fig. 2e), the presence and orientation of the P-
substituents influences the final architecture of the polymers
1–
2·
)
2
3–
4· )
∞
similar to those previously discussed, with two iso-bidentate
dithiophosphoric ligands in the equatorial plane and the axial
positions occupied by the pyridine rings of L2 bridging spacers.
The bond lengths and angles (Table 2) are also similar to those
via aromatic or C-H···S intramolecular interactions. The main
consequence is the loss of planarity of the bridging L1 ligands
(Table 1), probably ascribable to the conformational
arrangement the pyridine rings adopt to optimize these
interactions. It is interesting to note that in the H-bonded
chains built up by protonated L1 molecules, where such
interactions are not present, the ligands retain planarity.10
found in the analogous coordination polymers (
1–4·L1)∞.
Notwithstanding similarities with the results obtained with L1
,
the use of L2 as a linker leads to different constructs. In fact, as
evidenced by DFT calculations (see above), L2 can exist either
as a transoid or cisoids isomer and a convergent or a divergent
conformation can be distinguished depending on the
orientation of N-atoms of the pyridyl rings that can point
The reactions of L2 with the nickel complexes 1–4 under
solvothermal conditions afforded crystalline compounds
recognised by means of single crystal X-ray diffraction as the
inwards or outwards with respect to the pinch angle. In (
1·L2)
2
and (2·L2) the pyridyl rings of ligand L2 are oriented in a
2
dimers (
1
·L2)2, (
2·L2)2, and the coordination polymers (
3·L2)∞,
convergent fashion leading to closed rings rather than
polymeric chains (Fig. 7a-b). It is interesting to note that this
construct is far from predictable in its behaviour since a
convergent fashion does not necessarily lead to closed rings.
This is demonstrated by the formation of the mono-
and ( L2
4
·
)
in the compound (4·
L2·2C7H8)∞, respectively (Figs.
∞
7–10, S8–S11). The two different constructs reflect the
different conformations of L2 behaving as a convergent linker
in the dimeric structures and as divergent linker in the
polymers. Crystallographic data and selected bond lengths and
angles are reported in Tables S2 and 2. Similarly to the
ꢁꢂ
ꢃ
dimensional ꢀꢁ 10 spirals found in the two structures of
(HL2)I3 and (HL2)I3 assembled through NH+···N bonds between
protonated L2 molecules exhibiting a convergent cisoids
previously discussed cases of polymers (
structures of the dimer ( L2)2 and the polymers (3–4· )
∞
1–
3
·L1)∞, in the crystal
1·
L2 the
conformation.10 In dimers (
1·L2) and (2·L2) two spacers
2 2
spacer L2 is located in two essentially superimposable
orientations. As a consequence, the nitrogen and the adjacent
sulfur atoms show fractional occupancies refined at values of
bridge two dithiophosphato nickel complexes through axial
coordination generating eicos-atomic planar wheels with
openings of about 8
7.77, and 7.58 Å for (
L2)2, respectively.
ꢀ
8 Å2, and inner Ni···Ni distances of 7.73,
68.8 and 31.2% for (1·L2)2, and 61.5 and 31.5% for (4·L2)∞ (the
1
·
L2)2 and the two independent units of
figures represent the molecules in the major orientation only).
(2·
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Journal Name
and intermolecular C–H···O interactions with the oxygen
belonging to the MeO P-substituents which connect the chains
in layers (interactions a and b in Fig. S12a). The layers pack in
parallel through C–H···S interactions involving the para
-
methoxy group of the Ar-P substituents and the coordinated
sulphur atoms (interactions c-e in Fig. S12b), thus forming an
overall three-dimensional network. Solvent accessible voids of
69 Å3 (in blue in the inset of Fig. S12), correspond to 4% of the
unit cell volume. In polymer (4·L2) the exclusive presence of
∞
phenyl substituents at the phosphorous atoms results in the
aromatic interactions becoming prevalent such that the
parallel polymeric chains pack through edge-to-face
interactions only (Fig. 10a). The resulting network features
empty channels suitable for the inclusion of toluene molecules
which engage in π-interactions with the phenyl rings (Fig. 10b–
c). It is interesting to note that, in contrast to the previously
discussed structures (see also Tables 1 and 2), (4·L2)∞ contains
perfectly planar L2 ligands.
Fig. 7 Dimeric units and polymeric chains for (1·L2) (a), (2·L2) (b), (3·L2) (c),
2 2 ∞
and (
4
·
L2
)
in compound (4·L2·2C7H8)∞ (d). The labels reported refer to the
∞
original numbering schemes (Figs. S8–S12). H-atoms have been omitted for
clarity. Only the labels used in the discussion are here reported.
Fig. 8 Packing views showing the (
and (b) packing of intercalating layers evidenced in different colours; in the inset
a) layers formed by interacting (1·L2) dimers
2
Despite the analogies in their structures, the dimers (
and ( L2)2 show different packing arrangements. The dimers
L2)2 are arrayed in regular perforated layers assembled by
N···H and S···H interactions (Fig. 8a). Symmetry related parallel
1·L2)
2
the intercalating layers packing along the 010 direction are presented. All the
hydrogen atoms with the exception of those involved in the showed interactions
have been omitted. Interactions: a: C14i–H14i···N3, 2.70(9), 3.331(13), 124; b:
C15ii–H15ii···S2, 2.93(9), 3.618(8), 127; c: C1iii–H1biii···N2, 2.57, 3.365(19), 138; d:
C2iii–H2aiii···S5, 2.88, 3.542(8), 126; e: C8iv–H8iv···O3, 2.59 Å, 3.504(9) Å, 161°.
2
·
(1·
i
ii
layers pack in an off-set compact arrangement along the
direction showed in Fig. 8.
b
Symmetry codes: –1+x, y, –1+z; 1–x, 1–y, 1–z; iii –x, 0.5+y, 0.5–z; iv x, 1.5–y,
0.5+z.
In the crystal packing of
(
2·L2)
the two symmetrical
2
independent units (containing Ni1 and Ni2 ions) that, as
previously observed differ in the orientation of the thiadiazole
ring (Tdz), interact with each other through π–π interactions
involving the pyridine and Tdz rings forming puckered ribbons
Conclusions
The reaction of L1 with the differently P-substituted
dithiophosphonato, dithiophosphato, and dithiophosphito
complexes
1
–
4
yielded the corresponding coordination
L1 featuring polymeric assemblies
[···(Py∩ ∩
PyH+···Py PyH+)n···] built up through the moderate
(Fig. 9a). A view along the
a axis (Fig. 9b) shows the ribbons
polymers
(1–4· )
∞
aligned in a parallel arrangement through H-bonds and weaker
interactions mainly involving the sulphur atoms and the
pyridine hydrogens. A cisoid but divergent conformation of L2
NH+···N bonds derived by the protonation of L1 molecules.
These results indicate that L1 can be used as a spacer for the
predictable assembly of smoothly undulating chains
independent of the nature of the interacting Lewis acid, since
the orientation of the nitrogen atoms para-positioned in the
outwards pyridyl rings of L1 self-governs the geometry of the
resulting supramolecular construct. On the contrary, L2 allows
for the existence of different supramolecular constructs
ensuing from different ligand conformations deriving from the
rotation of the pyridyl rings.
leads to the coordination polymers (3·L2) and (4·L2) (Figs.
∞ ∞
7c–d, S10–S12). The asymmetric units of both compounds
contain one independent NiII ion situated on a crystallographic
inversion centre in the first case and on a mirror plane in the
latter. The polymeric supramolecular constructs present close
ꢁꢂ
ꢃ
analogies with the ꢀꢁ 10 chains formed by head-to-tail
NH+···N bonds between adjacent pyridine rings of protonated
L2 molecules featuring a trans conformation.10 Both complexes
3
and
type interactions which govern the assembly of the relevant
polymers. In ( L2 the aromatic P-substituents engage in
4 feature aromatic substituents that are involved in π-
3
· )
∞
intramolecular π-π interactions with the facing pyridine rings
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In particular, the results suggest that aromatic P-
substituents capable of π-interacting with the aromatic rings of
the ligand tend to favour divergent constructs. The influence
of secondary interactions involving the P-substituents is
confirmed by the loss of planarity of L1 and L2 in order to
enhance inter-molecular packing interactions.
Acknowledgements
MCA, MA, FI and VL kindly acknowledge the Dipartimento di
Scienze Chimiche e Geologiche of the Università degli Studi di
Cagliari and Banco di Sardegna for financial support (PRID
2015).
Fig. 9 Packing views showing (a) the ribbons formed by π-π interacting (2·L2)
2
dimers and (b) packing view along 100 direction of interacting ribbons. All the
hydrogen atoms with the exception of those involved in the showed interactions
have been omitted. Showed π–π interactions (iaii, b), weak contacts (c, d, e, g, h),
and the H-bond (f): a, CntPy(N8)···CntPy(N1) 3.58, Py(N5)^Py(N4)iii 1; b,
iii
CntTdz(S15)···Cnt Tdz(S5)iii 3.44 Å, Tdz(S15)^ Tdz(S5) 1°; c, C38–H38···O3iii 2.40 Å; d, C6iii–
H6ciii···C38, 2.78; e, C12ii–H12ii···S2, 2.89; g, C1ix–H1aix···S12, 2.99; h, C2ix–
H2aix···S13, 3.04 Å; f, C32viii–H32viii···S12, 2.77 Å, 3.596(9) Å, 146°. Symmetry
Notes and references
‡ The 112 issue of Chem. Rev. (2012) and the 16 issue of Chem. Soc. Rev. (2014)
were entirely devoted to the synthesis and applications of MOF’s showing how
rapidly this branch of solid state materials chemistry is being evolving.
i
ii
codes: 2–x, –y, 1–z; 1–x, 1–y,–z; iii x, –1+y, z; iv –1+x, y, –1+z; v 1–x,–y, –z; vi –x,
1–y, –1–z; vii –1+x, –1+y, –1+z; viii 2–x, 1–y, 1–z; ix 1+x, y, 1+z.
§ Among the ligands most commonly employed as spacers the choice of using 4,4'-
bipyridine and its analogues is due to their versatility. In fact, by introducing
different groups between the two pyridyl rings a wide variety of either linear or
bent, rigid or flexible spacers are available. See for example ref. 4.
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N
S
Coordination polymers and polygons using di-
Differently P-substituted phosphorodithioato
NiII complexes were reacted with bis-pyridyl
thiadiazole spacers L1 and L2 differing for the
position of the donor atoms obtaining either
polymeric or discrete supramolecular
constructs.
pyridyl-thiadiazole spacers and substituted
phosphorodithioato NiII complexes: potential
and limitations for inorganic crystal engineering
N
N
N
L1
N
S
M. C. Aragoni, M. Arca, S. J. Coles, M. Crespo, S.
L. Coles (née Huth), R. P. Davies, M. B.
Hursthouse, F. Isaia, R. Lai, V. Lippolis
N
L2
N
N