Structural studies of copper(II) complexes derived from di-2-pyridyl-ketone, (py)2CO

Article abstract of DOI:10.1016/j.poly.2012.08.009

Reaction of ArSNC(py)₂ [Ar = 2,4-dinitrophenyl, (O ₂N)₂C₆H₃] with CuCl ₂·2H₂O in DMF yielded the tetranuclear complex [Me₂NH₂][Cu₄Cl₆{py ₂CO₂}{py₂C(OH)O}] (1) through metal-catalysed hydrolysis of both DMF and the thiazyl chain. Notably direct reaction of dipyridylketone (py₂CO) with CuCl₂·2H₂O in DMF yielded the mononuclear pseudo-octahedral complex [CuCl ₂(py₂C(OH)₂)(DMF)]·DMF (2) in which the 1,1-gem diol, py₂C(OH)₂ acts as a tripodal ligand. Heating of 2 in DMF/MeOH promoted aggregation and formation of the polymer [Cu ₂Cl₃{py₂(OMe)O}]_∞ (3). The structures of 1-3 were determined by X-ray diffraction.

Full text of DOI:10.1016/j.poly.2012.08.009

Polyhedron 47 (2012) 16–23
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural studies of copper(II) complexes derived from di-2-pyridyl-ketone,
(py)2CO
⇑
⇑
Rebecca L. Melen , Jeremy M. Rawson , Dana J. Eisler
Department of Chemistry, The University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of ArSN@C(py)2 [Ar = 2,4-dinitrophenyl, (O2N)2C6H3] with CuCl2ꢀ2H2O in DMF yielded the tetra-
nuclear complex [Me2NH2][Cu4Cl6{py2CO2}{py2C(OH)O}] (1) through metal-catalysed hydrolysis of both
DMF and the thiazyl chain. Notably direct reaction of dipyridylketone (py2CO) with CuCl2ꢀ2H2O in DMF
yielded the mononuclear pseudo-octahedral complex [CuCl2(py2C(OH)2)(DMF)]ꢀDMF (2) in which the
1,1-gem diol, py2C(OH)2 acts as a tripodal ligand. Heating of 2 in DMF/MeOH promoted aggregation
Received 5 July 2012
Accepted 6 August 2012
Available online 11 August 2012
Keywords:
Thiazyl ligand
Dipyridylketone
Dipyridyldihydroxymethane
Copper complexes
and formation of the polymer [Cu2Cl3{py2(OMe)O}] (3). The structures of 1–3 were determined by X-
1
ray diffraction.
Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
1. Introduction
C(OMe)O}]1 (3) (Fig. 3). All three complexes bear ligands derived
from dipyridylketone, py2C@O. However the tetranuclear complex
The conducting and superconducting properties [1] of poly(sul-
fur-nitride) (SN)x promoted the development of many C/S/N hetero-
cycles in the mid-1970s as researchers attempted to include
C-functionalised groups into the polymer backbone to facilitate
fine-tuning of the electronic properties [2]. These heterocycles
themselves have spawned research into the development of neutral
radical conductors [3], organic magnets [4] and hetero-spin sys-
tems involving thiazyl radicals coordinated to transition metal ions
[5]. Some years ago we proposed the use of small fragments of (SN)x
as alternatives to conjugated polyenes with applications as molec-
ular wires [6]. Whilst a number of thiazyl chain oligomers, RSxNyR,
are known (Fig. 1), these typically exhibit simple aryl or alkyl cap-
ping groups unsuitable for metal-binding [7–10]. Nevertheless
some thiazyl chains have been shown to bind directly via chain het-
ero-atoms to certain metals [11], or via phosphine-capping groups
[12]. Recently we reported [13] a potential prototype chelate li-
gand, ArS–N@C(py)2 (L, Ar = 2,4-(O2N)2C6H3) which offers several
potential modes for metal-binding (Fig. 2). Here we report that
the imine functionality within L is, like other imines, susceptible
to hydrolysis [14] and attempted coordination of L to CuCl2ꢀ2H2O
affords the CuII complexes, [Me2NH2][Cu4Cl6{py2C(OH)O}{py2CO2}]
1 isolated from reaction of L with CuCl2ꢀ2H2O differs substantially
from the mononuclear complex 2 isolated from the reaction of
dipyridylketone with CuCl2ꢀ2H2O under similar conditions.
2. Experimental
2.1. Chemicals and handling
The reagents Li[N(SiMe3)2], Me3SiCl, py2CO, CuCl2ꢀ2H2O and
2,4-(O2N)2C6H3SCl were used as received (Aldrich). The synthesis
of ligand L was undertaken using standard Schlenk line techniques
and anhydrous solvents under an atmosphere of dry nitrogen
according to the literature method [13]. Whilst L appeared air sta-
ble for periods in excess of several weeks and could be crystallised
from DMF on the open bench, it was stored and manipulated in a
glove box (Saffron Scientific). Subsequent coordination chemistry
did not exclude oxygen or water and solvents (DMF and MeOH)
were used as received.
2.2. Characterisation methods
(1). Attempts to prepare
py2CO afforded [CuCl2{py2C(OH)2}DMF] ꢀDMF (2) and [Cu2Cl3{py2-
1
directly from CuCl2ꢀ2H2O and
NMR spectra were recorded on a Bruker Avance DRX500 Dual
Cryoprobe or Bruker Avance DPX400 QNP probe. Microanalytical
data were determined by combustion using an Exeter CE-440 ele-
mental analyser and mass spectroscopic data collected on a Kratos
MS890-EI instrument. Single crystal X-ray diffraction experiments
were performed using a Nonius Kappa CCD diffractometer with
⇑
Corresponding authors. Current addresses: Department of Chemistry, The
University of Toronto, 80 St George St, Toronto, ON, Canada M5S 3H6 (R.L.Melen).
Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset
Avenue, Windsor, ON, Canada N9B 3P4 (J.M. Rawson).
monochromatic Mo-K
stream which maintained a temperature of 180(2) K. Raw data
a radiation equipped with an Oxford cryo-
E-mail addresses: rmelen@utoronto.ca (R.L. Melen), jmrawson@uwindsor.ca
(J.M. Rawson).
0277-5387/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.009

R.L. Melen et al. / Polyhedron 47 (2012) 16–23
17
Fig. 1. Crystal structure of selected thiazyl chains; (top) PhSeNSNSiMe3; (centre) (p-ClC6H4)2S3N2 and bottom; (p-MeC6H4)2S5N4.
NO2
NO2
NO2
N
N
O2N
S
O2N
O2N
S
S
N
N
N
N
N
M
N
M
I
II
L
N
Fig. 2. Structure of ligand L (left) and two potential N,N0-coordination modes, I and II for L (right).
were collected [15] and processed using the HKL package and unit
cell parameters refined against all data [16]. Structures were
solved and refined using the SHELXTL package [17] and were visu-
alised using Mercury [18]. Crystallographic data for complexes 1–3
are presented in Table 1. X-band EPR spectra were recorded on a
Bruker ER200D EPR spectrometer at room temperature. Simula-
tions of solid state EPR spectra were undertaken using PIP [19]
with an in-house windows interface, PIP4WIN (J.M. Rawson, Uni-
versity of Cambridge, 2008).
of dipyridylketone (0.500 g, 2.71 mmol) in Et2O (15 mL) was added
to a solution of Li[N(SiMe3)2] (0.450 g, 2.69 mmol) in Et2O (15 mL)
and the resultant orange solution stirred for 16 h at room temper-
ature. Me3SiCl (0.360 mL, 2.85 mmol) was added and the solution
stirred for a further 3 h at room temperature. The solution was fil-
tered, dried in vacuo and redissolved in CH2Cl2 (20 mL). A solution
of 2,4-(O2N)2C6H3SCl (0.680 g, 2.90 mmol) in CH2Cl2 (10 mL) was
added to give a yellow precipitate of 2,4-(O2N)2C6H3SN@C(py)2
(L) which was stirred for a further 18 h to ensure complete reaction
prior to filtration and drying in vacuo. Yield 0.56 g, 1.47 mmol, 54%.
Crystals suitable for X-ray diffraction were obtained by slow evap-
oration of a DMF solution at 40 °C and the structure reported pre-
viously [13]. 1H NMR (400 MHz, d7-DMF): d = 9.10 (d, 8.8 Hz, 1H),
9.03 (d, 2.4 Hz, 1H), 8.97 (dt, 5.2 Hz, 1.2 Hz, 1H), 8.73 (dd, 9.2 Hz,
2.4 Hz, 1H), 8.6 (m, 1H), 8.40 (dt, 8.0 Hz, 1.2 Hz, 1H), 8.08 (m,
2.3. Synthesis
2.3.1. Synthesis of 2,4-(O2N)2C6H3SN@C(py)2, L
This compound was prepared according to the literature meth-
od [13] but full experimental details are provided here; a solution

18
R.L. Melen et al. / Polyhedron 47 (2012) 16–23
OH
N
OH
O
Cu
Cu
Cl
Cl
O
O
Cu
Cu
N
N
N
N
Cl
N
Cl
N
Cl
O
Cl
Cl
Cu
Cu
Cu
O
Cu
Cu
Cl
Cl
O
O
H
Cl
Cu
Cu
N
Cl
N
Fig. 3. Structures of copper complexes 1–3.
2H), 7.77 (dt, 8.0 Hz, 1.2 Hz, 1H), 7.58–7.66 (m, 2H); +EI-MS m/z
382.06 (M+); IR ( max/cmꢁ1): 1502w (
NO2(asym)), 1334w ( NO2(sym)),
1592w ( C@N).
(0.110 g, 0.23 mmol, 23%) which proved suitable for X-ray diffrac-
m
m
m
tion. Anal. Calc. for C17H24CuCl2N4O4: C, 42.29; H, 5.01; N, 11.60.
m
Found: C, 42.16; H, 4.93; N, 11.48%; IR (
OH), 1648s ( CO).
m
max/cmꢁ1) 3354br,m
(m
m
2.3.2. Synthesis of [Me2NH2][Cu4Cl6{py2C(OH)O}{py2CO2})] (1)
slightly more than twofold equivalent of (200 mg,
0.60 mmol) was added to
solution of CuCl2ꢀ2H2O (35 mg,
2.3.4. Synthesis of [Cu2Cl3{py2C(OMe)O}] (3)
A
L
1
Dipyridylketone (18 mg, 0.10 mmol) was added to a solution of
CuCl2ꢀ2H2O (27 mg, 0.20 mmol) in DMF (1 mL) containing two
drops of MeOH. The resultant green solution was stirred at room
temperature for 2 h and then heated to 40 °C. Slow solvent evapo-
ration at 40 °C resulted in dark green crystals of 3 (37 mg,
0.08 mmol, 80%) suitable for X-ray diffraction. Anal. Calc. for C12-
H11Cu2Cl3N2O2: C, 32.12; H, 2.57; N, 6.24. Found: C, 32.67; H,
a
0.26 mmol) in DMF (8 mL). The resultant green solution was stirred
at room temperature for 18 h then allowed to stand for 48 h during
which time a few blue/green crystals of 1 formed which were suit-
able for X-ray diffraction but which appeared to decompose over
ca. 7–14 days. The paucity of crystalline sample precluded other
analytical data.
2.78; N, 6.51%; IR (
m mOH), 1648s (mCO).
max/cmꢁ1) 3354br,m (
2.3.3. Synthesis of [CuCl2{py2C(OH)2}(DMF)] ꢀDMF (2)
Dipyridylketone (0.180 g, 0.98 mmol) was added to a solution of
CuCl2ꢀ2H2O (0.269 g, 2.01 mmol) in DMF (8 mL). The resultant
green solution was stirred at room temperature for 18 h then al-
lowed to stand. After 3 days, large green crystals of 2 had formed
3. Results and discussion
We have previously reported [13] the synthesis of the thiazyl
chain L which exhibits the potential to act as an N,N0-chelate ligand
Table 1
Crystal data and structure refinement details for complexes 1–3.
Compound
1
2
3
Formula
FW
CCDC deposit number
Crystal system
Space group
a (Å)
C
24H25Cl6Cu4N5O4
C17H24Cl2CuN4O4
482.84
890383
C12H11Cl3Cu2N2O2
448.58
890384
914.35
890382
orthorhombic
P212121
8.4796(3)
19.0914(6)
19.5491(7)
90
triclinic
triclinic
ꢀ
ꢀ
P1
P1
7.9062(2)
9.2306(2)
14.8078(4)
94.2784(8)
97.1989(2)
91.9660(8)
1068.11(5)
2
7.7405(2)
8.8843(2)
11.9126(3)
78.2995(11)
76.1188 (11)
66.9589(10)
726.39(3)
2
b (Å)
c (Å)
a
(°)
b (°)
90
90
c
(°)
V (Å3)
Z
3164.75(19)
4
T (K)
180(2)
1.919
0.71073
3.199
180(2)
1.501
0.71073
1.302
180(2)
2.051
0.71073
3.481
Dcalc (g cmꢁ3
k (Å)
)
l
(mmꢁ1
)
Crystal size (mm)
h range (°)
Reflections collected
Unique reflections
Rint
0.12 ꢂ 0.06 ꢂ 0.06
3.37–21.97
26011
3811
0.2029
0.46 ꢂ 0.32 ꢂ 0.12
1.39–27.45
11465
4840
0.0527
0.32 ꢂ 0.16 ꢂ 0.10
2.91–27.49
10423
3313
0.0580
Parameters
223
1.126
261
1.058
191
1.044
GOF (F2)
R1 [I > 2
r
(I)]
0.072
0.0408
0.0347
wR2 (all data)
0.155
0.1074
0.0917
Flack parameter
0.07(5)
+0.57/ꢁ0.68
–
–
Peak/hole (e Åꢁ3
)
+0.49/ꢁ0.82
+0.50/ꢁ1.04

R.L. Melen et al. / Polyhedron 47 (2012) 16–23
19
Fig. 4. (Top) Crystal structure of 1 (the Me2NH2+ cation and H atoms of the pyridyl rings are omitted for clarity); (bottom) the core structure of 1 highlighting the tetranuclear
nature of 1 and the longer inter-cluster contacts (dotted line) linking these tetranuclear units.
in a variety of modes (Fig. 2). Ligand L appears air stable in the solid
state and crystals suitable for X-ray diffraction were previously
grown from ‘wet’ DMF on the open bench at 40 °C, suggesting that
L exhibits some stability towards hydrolysis, yet the coordination
chemistry of L remained unexplored.
In order to probe its potential coordination chemistry, we
examined its reaction chemistry with CuCl2ꢀ2H2O; when L was
stirred with CuCl2ꢀ2H2O for 18 h in DMF and then permitted to
stand for a further 2–3 days a small number of blue–green crystals
of compound 1 formed whose structure was determined by X-ray
diffraction to be the tetranuclear complex [Me2NH2][Cu4Cl6{py2-
C(OH)O}{py2CO2}] (1) (Fig. 4). The presence of the Lewis acidic cop-
per(II) ion clearly promotes hydrolysis not only of L (which
otherwise appears stable in DMF) but also some hydrolysis of the
solvent itself which acts as a source of the dimethylammonium
counter-ion [Me2NH2]+.
When attempting to prepare 1 directly from py2CO and CuCl2-
ꢀ2H2O in DMF using the crystallographically determined 1:2 ratio
under otherwise identical conditions, the mononuclear complex
[CuCl2{py2C(OH)2}(DMF)]ꢀDMF (2ꢀDMF) was isolated in moderate
yield. The 1,1-gem-diol ligand is generated from hydrolysis of the
dipyridylketone, py2CO. Both hydrolysis [20] and other solvolysis
[21] reactions of this ligand have been reported previously leading
to a range of polynuclear complexes whose magnetism has been
studied extensively. Coordination complexes of the parent dipyr-
idylketone appear more common for the heavier d-block elements
of the second and third row in which the lower Lewis acidity affor-
ded by the larger size and smaller charge reduces the tendency for
solvolysis [22]. In some organometallic complexes, metal coordina-
tion appears to activate the ligand to nucleophilic attack at the car-
bonyl C [23].
An IR spectrum of 2ꢀDMF revealed a broad OH peak at
3345 cmꢁ1 suggesting hydrogen-bonding between a pendant hy-
droxyl of the py2C(OH)2 ligand and the DMF solvate which was
confirmed by the crystallographic analysis. The room temperature
solid state EPR spectrum of 2ꢀDMF at X-band revealed a broad,
near-axial, spectrum with little g-anisotropy (g = 2.23, g\ = 2.21)
k
consistent with significant dipolar line broadening.
The failure of 2 to either aggregate or undergo deprotonation of
the py2C(OH)2 ligand (both processes are required for formation of
1), prompted us to try and drive aggregation by heating 2 in DMF
solution. No clear evidence for reaction was observed upon heating
in DMF. However in the presence of trace MeOH, the polymeric
complex [Cu2Cl3{py2C(OMe)O}] (3) was formed which has previ-
1
ously been characterised by Papadopoulos et al. [24] from the reac-
tion of CuCl2ꢀ2H2O with py2CO in MeOH. Similar copper-polymers
with the {py2(OR)O}ꢁ (R = H, Me, Et) ligands have been reported
[25]. The structures of 1–3 are described below.
3.1. Crystal structure of 1
Complex 1 crystallises in the acentric orthorhombic space group
P212121 with one molecule in the asymmetric unit. The asymmet-
ric unit of 1 contains four independent copper(II) centres (Fig. 4)
with the geometry about each Cu centre summarised in Table 2.
Cu(1) is pseudo-six-coordinate, adopting a strongly distorted octa-
hedral geometry (bond angles between ‘cis’ ligands in the range
(69.6–97.1°)) with an axially elongated Cl3O2N donor set in which

20
R.L. Melen et al. / Polyhedron 47 (2012) 16–23
Table 2
Copper–ligand bond lengths (Å) and angles (°) in complexes 1–3.
Compound 1
Cu(1)
Cu(2)
Cu(3)
Cu(4)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–N(1)
Cu(1)–O(2)
Cu(1)–O(3)
Cu(1)–Cl(5)0
2.214(5)
2.290(4)
2.00(1)
1.97(1)
2.75(1)
3.082(5)
Cu(2)–O(2)
Cu(2)–Cl(3)
Cu(2)–N(5)
Cu(2)–O(3)
Cu(2)–O(1)
Cu(2)–Cl(2)
1.99(1)
2.237(4)
1.97(1)
1.97(1)
2.72(1)
2.682(5)
Cu(3)–O(1)
Cu(3)–Cl(4)
Cu(3)–N(2)
Cu(3)–Cl(5)
1.94(1)
2.238(5)
1.97(1)
2.269(5)
Cu(4)–Cl(6)
Cu(4)–O(1)
Cu(4)–N(4)
Cu(4)–O(3)
Cu(4)–Cl(5)
2.217(4)
1.96(1)
1.97(1)
1.96(1)
2.840(4)
Compound 2
Cu(1)
Compound 3
Cu(1)
Cu(2)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–O(2)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–O(1S)
2.2775(7)
2.2791(7)
2.678(2)
2.042(2)
2.044(2)
2.340(2)
Cu(1)–Cl(3)
Cu(1)–Cl(3)0
Cu(1)–N(1)
Cu(1)–O(1)
Cu(1)–Cl(2)
2.2542(7)
Cu(2)–Cl(1)
Cu(2)–Cl(1)0
Cu(2)–Cl(2)
Cu(2)–O(1)
Cu(2)–N(2)
2.2424(8)
2.7084(8)
2.325(1)
1.963(2)
1.983(3)
2.7132(8)
1.997(3)
1.943(2)
2.320(1)
Compound 1
Cu(1)
Cu(2)
Cu(3)
Cu(4)
Cl(1)Cu(1)Cl(2)
Cl(1)Cu(1)N(1)
Cl(1)Cu(1)O(2)
Cl(1)Cu(1)O(3)
Cl(2)Cu(1)N(1)
Cl(2)Cu(1)O(2)
Cl(2)Cu(1)O(3)
N(1)Cu(1)O(2)
N(1)Cu(1)O(3)
O(2)Cu(1)O(3)
96.4(2)
96.9(4)
Cl(2)Cu(2)Cl(3)
Cl(2)Cu(2)O(1)
Cl(2)Cu(2)O(2)
Cl(2)Cu(2)N(5)
Cl(2)Cu(2)O(3)
Cl(3)Cu(2)O(1)
Cl(3)Cu(2)O(2)
Cl(3)Cu(2)N(5)
Cl(3)Cu(2)O(3)
O(1)Cu(2)O(2)
O(1)Cu(2)O(3)
O(2)Cu(2)N(5)
O(2)Cu(2)O(3)
N(5)Cu(2)O(3)
108.6(2)
Cl(4)Cu(3)Cl(5)
Cl(4)Cu(3)O(1)
Cl(4)Cu(3)N(2)
Cl(5)Cu(3)O(1)
Cl(5)Cu(3)N(2)
O(1)Cu(3)N(2)
95.8(2)
170.7(3)
95.2(4)
87.9(3)
168.6(4)
80.8(5)
Cl(5)Cu(4)Cl(6)
Cl(5)Cu(4)O(1)
Cl(5)Cu(4)N(4)
Cl(5)Cu(4)O(3)
Cl(6)Cu(4)O(1)
Cl(6)Cu(4)N(4)
Cl(6)Cu(4)O(3)
O(1)Cu(4)N(4)
O(1)Cu(4)O(3)
N(4)Cu(4)O(3)
98.4(2)
72.7(3)
105.1(4)
100.6(3)
93.6(3)
96.2(4)
160.6(3)
170.2(5)
88.5(4)
82.5(5)
127.7(2)
74.6(3)
99.5(4)
93.6(3)
92.5(2)
92.5(3)
98.7(4)
157.2(3)
56.8(3)
69.3(4)
168.6(5)
88.8(4)
81.8(5)
166.5(3)
97.1(3)
166.7(4)
84.8(3)
85.2(3)
81.9(5)
92.0(5)
69.6(4)
Compound 2
Cu(1)
Compound 3
Cu(1)
Cu(2)
Cl(2)Cu(1)Cl(1)
Cl(2)Cu(1)O(2)
Cl(2)Cu(1)N(1)
Cl(2)Cu(1)N(2)
Cl(2)Cu(1)O(1s)
Cl(1)Cu(1)O(2)
Cl(1)Cu(1)N(1)
Cl(1)Cu(1)N(2)
Cl(1)Cu(1)O(1s)
O(2)Cu(1)N(1)
O(2)Cu(1)N(2)
O(2)Cu(1)O(1s)
N(1)Cu(1)N(2)
N(1)Cu(1)O(1s)
N(2)Cu(1)O(1s)
93.79(3)
104.13(4)
175.74(6)
91.54(6)
93.00(5)
102.38(4)
89.13(6)
170.83(6)
97.44(5)
72.17(7)
69.02(7)
152.69(6)
85.17(8)
89.70(8)
89.72(8)
Cl(3)Cu(1)Cl(2)
Cl(3)Cu(1)O(1)
Cl(3)Cu(1)N(1)
Cl(3)Cu(1)Cl(3)
Cl(2)Cu(1)O(1)
Cl(2)Cu(1)N(1)
Cl(2)Cu(1)Cl(3)
O(1)Cu(1)N(1)
O(1)Cu(1)Cl(3)
N(1)Cu(1)Cl(3)
95.44(3)
176.07(7)
98.62(7)
85.05(3)
82.38(6)
151.12(8)
109.52(3)
81.99(9)
98.76(6)
96.78(7)
Cl(2)Cu(2)Cl(1)
Cl(2)Cu(2)O(1)
Cl(2)Cu(2)N(2)
Cl(2)Cu(2)Cl(1)
Cl(1)Cu(2)O(1)
Cl(1)Cu(2)N(2)
Cl(1)Cu(2)Cl(1)
O(1)Cu(2)N(2)
O(1)Cu(2)Cl(1)
N(2)Cu(2)Cl(1)
96.45(3)
81.83(6)
156.01(8)
109.29(3)
81.83(6)
96.74(8)
86.87(3)
82.2(1)
101.36(6)
91.37(8)
the final Cl atom to complete the coordination sphere arises from
another tetra-nuclear unit which is symmetry-related via transla-
tion parallel to x (1 + x, y, z). The ‘axial’ bond lengths Cu(1)–O(3)
and Cu(1)–Cl(5)0 (2.75(1) and 3.082(5) Å) are substantially longer
than the equatorial distances (1.97(1)–2.290(4) Å) consistent with
a substantial Jahn–Teller elongation. Notably the Cu(1)–Cl(5)0 dis-
tance is longer than other axially elongated Cu–Cl bonds observed
in 1–3 (Table 2) and it is arguable whether the geometry is best de-
scribed as octahedral or square pyramidal. Cu(2) is also six-coordi-
nate but exhibits a Cl2O3N donor set. Two of the donor O atoms to
Cu(2) are provided by the same ligand leading to a strained 4-
membered ring and a more substantial distortion from octahedral
symmetry (bond angles at Cu(2) for ‘cis’ ligands fall in the range
56.8(3)–124.4(5)°). This Cu-centre is also axially elongated along
a ClCuO axis. The ‘axial’ bond lengths Cu(2)–O(1) and Cu(2)–Cl(2)
(2.72(1) and 2.682(5) Å) are substantially longer than the equato-
rial distances (1.97(1)–2.237(4) Å) consistent with a Jahn–Teller
elongation. Unlike Cu(1) and Cu(2), Cu(3) is square planar with a
Cl2NO donor set with ‘cis’ bond angles in the range 80.7(5)–
95.8(2)° (sum 359.6°, compared with 360° for a perfectly planar
4-coordinate geometry). Cu(4) exhibits a square-based pyramidal
geometry with a Cl2NO2 donor set with one Cl atom in the axial po-
sition. Again the axial Cu–Cl bond length (2.840(4) Å) is substan-
tially longer than the equatorial distances (1.96(1)–2.217(4) Å).
Cu(4) is approximately square-based pyramidal with a
s value of
0.16 (0 for perfectly square pyramidal and 1 for a trigonal bipyra-
mid [26]) and a CuClNO2 square base. The Cu(4)–O bond lengths at
1.96(1) Å are comparable with the Cu(4)–N 1.97(1) Å and are a lit-
tle shorter than the Cu(4)–Cl(6) bond length (2.217(4) Å). The axial
Cu(4)–Cl(5) bond length is markedly longer at 2.840(4) Å. Notably
each CuII centre is N,O-chelated by a py2C(OH)Oꢁ or {py2CO2}2ꢁ li-
gand with a Cl located trans to the O donor. A combination of bridg-

R.L. Melen et al. / Polyhedron 47 (2012) 16–23
21
These tetranuclear clusters are additionally linked via longer
2-bridges (Cu(1). . .Cl(5) at 3.082(5) Å) generating a
Cu–Clꢀ ꢀ ꢀCu
l
one-dimensional polymer structure (Fig. 4, bottom).
3.2. Crystal structure of 2
ꢀ
Complex 2 crystallises in the triclinic space group P1 with one
molecule of 2 and a DMF solvent molecule in the asymmetric unit
(Fig. 5). The copper(II) centre occupies a distorted octahedral envi-
ronment (cis bond angles fall in the region 69.02–102.34°) with a
hydroxyl group of the py2C(OH)2 ligand and the DMF O-atom lo-
cated in the axially-elongated positions (Table 2).
The tridentate N,N0,O coordination geometry of 2 is similar to a
number of other mononuclear copper(II) complexes of the neutral
py2C(OH)2 ligand which have previously been reported in which
the py2C(OH)2 ligand invariably acts as a tridentate N2O donor
[27]. The DMF lattice solvent appears hydrogen-bonded to the
complex (O(2)ꢀ ꢀ ꢀO(2S) = 2.711(3) Å).
3.3. Crystal structure of 3
Fig. 5. Asymmetric unit of 2 including hydrogen-bonded DMF solvate molecule.
ꢀ
Complex 3 also crystallises in the triclinic space group P1 with
ing
l
2- and
l
3-O atoms plus
l
2-Cl atoms link the four cupric
two five-coordinate copper(II) ions in the asymmetric unit. There
are three crystallographically independent Clꢁ ions and a py2-
C(OMe)Oꢁ ligand which exhibits an unusual N,N0,l2-O bridging
mode between the two metal ions (Fig. 6), compared to 2 (above).
The geometry at both Cu(1) and Cu(2) appear intermediate be-
tween square-based pyramidal and trigonal bipyramidal based
2ꢁ
ions together. With one py2CO2
and one py2C(OH)Oꢁ ligand
along with six Clꢁ ions, the net negative charge on the complex
is charge balanced by an Me2NH2+ counterion (formed by hydroly-
sis of DMF) which is weakly hydrogen bonded to the
O(2) and Cl(4).
l2-O atom
Fig. 6. Part of the polymeric structure of 3, [Cu2Cl3(py2C(OMe)O)]1, illustrating interchain Cl. . .H contacts.

22
R.L. Melen et al. / Polyhedron 47 (2012) 16–23
on Addison0s
s values; s = 0.42 for Cu(1) and 0.26 for Cu(2) (s = 1.0
[9] (a) F.P. Olsen, J.C. Barrick, Inorg. Chem. 12 (1973) 1353;
(b) J. Leitch, S.C. Nyburg, D.A. Armitage, M.J. Clarke, J. Cryst. Mol. Struct. 3
(1973) 337;
for trigonal bipyramidal and 0.0 for square-based pyramidal [26]),
suggesting Cu(2) adopts a geometry somewhat closer to square-
based pyramidal. In both cases one Cu–Cl bond length is substan-
tially longer than the others, consistent with a Jahn–Teller elonga-
tion of the five-coordinate geometry.
The structure of 3 has been reported previously [24] along with
several other halo- and pseudo-halogen variants and alkoxy deriv-
atives [25]. The one-dimensional polymeric chains are linked via
weak C–H. . .Cl contacts (C(23). . .Cl(1) at 3.440(4) Å, C–H. . .Cl
131.5(2)°, Fig. 6).
(c) K. Tersago, I.Y. Bagryanskaya, Y.V. Gatilov, S.A. Gromilov, A.Y. Makarov, M.
Mandado, C. Van Alesnoy, A.V. Zibarev, F. Blockhuys, Eur. J. Inorg. Chem. (2007)
1958;
(d) A.G. Makarov, I.Y. Bagryanskaya, Y.V. Gatilov, N.V. Kuratieva, A.Y. Makarov,
M.M. Shakirov, A.V. Alexeyev, K. Tersago, C. Van Alsenoy, F. Blockhuys, A.V.
Zibarev, Eur. J. Inorg. Chem. (2010) 4801.
[10] (a) W. Isenburg, R. Mews, G.M. Sheldrick, Z. Anorg. Allg. Chem. 525 (1985) 54;
(b) H.W. Roesky, J. Sundermeyer, M. Noltemeyer, G.M. Sheldrick, K. Meyer-
Base, P.G. Jones, Z. Naturforsch., B 41 (1986) 53;
(c) E.M. Holt, S.L. Holt, K.J. Watson, Dalton Trans. (1974) 1357;
(d) J.J. Mayerle, J. Kuyper, G.B. Street, Inorg. Chem. 17 (1978) 2610;
(e) J. Konu, A. Maaninen, K. Paananen, P. Ingman, R.S. Laitinen, T. Chivers, J.
Valkonen, Inorg. Chem. 41 (2002) 1430;
(f) J.A.K. Howard, I. Lavender, J.M. Rawson, E.A. Swain, Main Group Chem. 1
(1996) 317;
4. Conclusions
(g) A.V. Zibarev, A.O. Miller, Y.V. Gatilov, G.G. Furin, Heteroat. Chem. 1 (1990)
443;
(h) C.M. Aherne, A.J. Banister, I. Lavender, S.E. Lawrence, J.M. Rawson, W.
Clegg, Polyhedron 15 (1996) 1877;
(i) G. Wolmershäuser, P.R. Mann, Z. Naturforsch., B 46 (1991) 315;
(j) A.V. Zibarev, Y.V. Gatilov, I.Yu. Bagryanskaya, S.N. Konchenko, Polyhedron
11 (1992) 2787.
Whilst the thiazyl ligand py2C@NSAr appears air and moisture
stable both in the solid state and in solution, the presence of a Le-
wis-acidic metal appears to promote hydrolytic decomposition,
leading to isolation of the tetranuclear complex [Me2NH2][Cu4Cl6{-
py2C(O)OH}(py2CO2)] (1). Whilst it is not clear why complex 1 can-
not be accessed directly from CuCl2ꢀ2H2O, DMF and
dipyridylketone, both mononuclear (2) and polymeric (3) copper
complexes can be isolated in this fashion. Further studies with
milder Lewis acidic metal complexes are required to probe the po-
tential of L as a ligand to metal ions and these are currently
underway.
[11] (a) H. van der Meer, D. Heijdenrijk, Cryst. Struct. Commun. 5 (1976) 401;
(b) A.Y. Makarov, I.G. Irtegove, N.V. Vasilieva, I.Y. Bagryanskaya, T. Borrmann,
Y.V. Gatilov, E. Lork, R. Mews, W.-D. Stohrer, A.V. Zibarev, Inorg. Chem. 44
(2005) 7194;
(c) N.P.C. Walker, M.B. Hursthouse, C.P. Warrens, J.D. Woollins, Chem.
Commun. (1985) 227;
(d) R.T. Kops, E. van Aken, H. Schenk, Acta Crystallogr., Sect. B 29 (1973) 913;
(e) M. Limmert, I.-P. Lorenz, J. Neubauer, H. Nöth, T. Habereder, Eur. J. Inorg.
Chem. (2001) 1593.
[12] (a) T. Chivers, C. Lensink, J.F. Richardson, Organometallics 5 (1986) 819;
(b) M. Herberhold, W. Buhlmeyer, A. Gieran, T. Hubner, J. Organomet. Chem.
321 (1987) 37.
Appendix A. Supplementary data
[13] C.E. Bacon, D.J. Eisler, R.L. Melen, J.M. Rawson, Chem. Commun. (2008) 4924.
[14] See for example: M.E. Belowich, J.F. Stoddart, Chem. Soc. Rev. 41 (2012) 2003.
[15] COLLECT, Nonius B.V., Delft, The Netherlands, 1998.
[16] Z. Otwinski, W. Minor, Methods Enzymol. 276 (1997) 307.
[17] SHELXTL, v. 6.14, Bruker AXS, Ó 2000–2003.
[18] Mercury CSD, v. 3.0, Cambridge Crystallographic Data Centre. Available from:
<http://www.ccdc.cam.ac.uk/mercury/>.
[19] PIP for simulation of anisotropic EPR spectra; M. Nilges, Illinois EPR Research
Centre, University of Illinois, USA; J.M. Rawson, PIP4WIN, v. 1.2, University of
Windsor, 2011.
CCDC 890382–890384 contains the supplementary crystallo-
graphic data for 1–3. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
[20] (a) See for example: N. Lalioti, C.P. Raptopoulou, A. Terzis, A.E. Aliev, I.P.
Gerothanassis, E. Manessi-Zoupa, S.P. Perlepes, Angew. Chem., Int. Ed. 40
(2001) 3211;
References
[1] (a) A.J. Banister, I.B. Gorrell, Adv. Mater. 10 (1998) 1415;
(b) M.M. Labes, P. Love, L.F. Nichols, Chem. Rev. 79 (1979) 1.
[2] I. Ernest, W. Hollick, G. Rihs, D. Schomburg, G. Shoham, D. Weakert, R.B.
Woodward, J. Am. Chem. Soc. 103 (1981) 1540.
[3] A.W. Cordes, R.C. Haddon, R.T. Oakley, Phosphorus, Sulfur Silicon Relat. Elem.
179 (2004) 673.
[4] A. Alberola, J.M. Rawson, A.L. Whalley, J. Mater. Chem. 16 (2006) 2560.
[5] K.E. Preuss, Dalton Trans. (2007) 2357.
[6] J.M. Rawson, J.J. Longridge, Chem. Soc. Rev. (1997) 53.
[7] (a) V. Busetti, Acta Crystallogr., Sect. B 38 (1982) 665;
(b) I.Y. Bagryanskaya, Y.V. Gatilov, A.V. Zibarev, Mendeleev Commun. (1999)
157;
(b) G.S. Papaefstathiou, A. Escuer, R. Vicente, M. Font-Bardia, X. Solans, S.P.
Perlepes, Chem. Commun. (2001) 2414;
(c) W. Oloo, P.Y. Zavalij, J. Zhang, E. Khaskin, A.N. Vedernikov, J. Am. Chem.
Soc. 132 (2010) 14400;
(d) A.K. Boudalis, B. Donnadieu, V. Nastopoulos, J.M. Clemente-Juan, A. Mari, Y.
Sanakis, J.-P. Touchagues, S.P. Perlepes, Angew. Chem., Int. Ed. 43 (2004) 2266;
(e) T.C. Stamatatos, K.A. Abboud, W. Wernsdorfer, G. Christou, Angew. Chem.,
Int. Ed. 47 (2008) 6694;
(f) Z.E. Serna, L. Lezama, M.K. Urtiaga, M.I. Arriortua, M.G. Barandika, R. Cortes,
T. Rojo, Angew. Chem., Int. Ed. 39 (2000) 344;
(g) A.K. Boudalis, C.P. Raptopoulou, B. Abarca, R. Ballesteros, M. Chadlaoui, J.-P.
Tuchagues, A. Terzis, Angew. Chem., Int. Ed. 45 (2006) 432;
(h) C. Hemmert, M. Renz, H. Gornitzka, S. Soulet, B. Meunier, Chem. Eur. J. 5
(1999) 1766;
(i) M.G. Barandika, Z. Serna, R. Cortes, L. Lezama, M.K. Urtiaga, M.I. Arriortua, T.
Rojo, Chem. Commun. (2001) 45;
(j) A.K. Boudalis, Y. Sanakis, J.M. Clemente-Juan, B. Donnadieu, V. Nastopoulos,
A. Mari, Y. Coppel, J.-P. Tuchagues, S.P. Perlepes, Chem. Eur. J. 14 (2008) 2514;
(k) G.S. Papaefstathiou, S.P. Perlepes, A. Escuer, R. Vicente, M. Font-Bardia, X.
Solans, Angew. Chem., Int. Ed. 40 (2001) 884;
(l) A. Tsohos, S. Dionyssopoulou, C.P. Raptopoulou, A. Terzis, E.G. Bakalbassis,
S.P. Perlepes, Angew. Chem., Int. Ed. 38 (1999) 983;
(m) C.J. Milios, E. Kefalloniti, C.P. Raptopoulou, A. Terzis, R. Vicente, N. Lalioti,
A. Escuer, S.P. Perlepes, Chem. Commun. (2003) 819;
(n) V. Tangoulis, C.P. Raptopoulou, A. Terzis, S. Paschalidou, S.P. Perlepes, E.G.
Bakalbassis, Inorg. Chem. 36 (1997) 3996;
(o) C.M. Zaleski, E.C. Depperman, C. Dendrinou-Samara, M. Alexiou, J.W.
Kampf, D.P. Kessissoglou, M.L. Kirk, V.L. Pecoraro, J. Am. Chem. Soc. 127 (2005)
12862;
(p) S.R. Breeze, S. Wang, J.E. Greedan, N.P. Raju, Inorg. Chem. 35 (1996) 6944;
(q) C.C. Stoumpos, R. Inglis, O. Roubeau, H. Sartzi, A.A. Kitos, C.J. Milios, G.
Aromi, A.J. Tasiopoulos, V. Nastopoulos, E.K. Brechin, S.P. Perlepes, Inorg.
Chem. 49 (2010) 4388;
(c) H. Munsterer, G. Kresze, V. Lamm, A. Gieran, J. Org. Chem. 48 (1983) 2833;
(d) M. Herberhold, W. Ehrenreich, A. Gieren, H. Betz, T. Hubner, Chem. Ber. 118
(1985) 1476;
(e) I.Y. Bagryanskaya, Y.V. Gatilov, E. Lork, R. Mews, M.M. Shakirov, P.G.
Watson, A.V. Zibarev, J. Fluorine Chem. 116 (2002) 149;
(f) E. Lork, R. Mews, M.M. Shakirov, P.G. Watson, A.V. Zibarev, Eur. J. Inorg.
Chem. (2001) 2123;
(g) E. Lork, R. Mews, M.M. Shakirov, P.G. Watson, A.V. Zibarev, J. Fluorine
Chem. 115 (2002) 165.
[8] (a) I.Y. Bagryanskaya, Y.V. Gatilov, M.M. Shakirov, A.V. Zibarev, Mendeleev
Commun. (2002) 167;
(b) A.Y. Makarov, E. Lork, R. Mews, A.V. Zibarev, J. Fluorine Chem. 127 (2006)
437;
(c) I.Y. Bagryanskaya, Y.V. Gatilov, M.M. Shakirov, A.V. Zibarev, Mendeleev
Commun. (1994) 136;
(d) D. Leusser, J. Henn, N. Kocher, B. Engels, D. Stalke, J. Am. Chem. Soc. 126
(2004) 1781;
(e) M. Herberhold, S. Gerstmann, W. Milius, B. Wrackmeyer, H. Borrmann,
Phosphorus, Sulfur Silicon Relat. Elem. 112 (1996) 261;
(f) R. Jones, D.J. Williams, P.T. Wood, J.D. Woollins, Polyhedron 8 (1989) 91;
(g) A.Y. Makarov, I.Y. Bagryanskaya, F. Blockhuys, C. Van Alsenoy, Y.V. Gatilov,
V.V. Knyazev, A.M. Maksimov, T.V. Mikhalina, V.E. Platonov, M.M. Shakirov,
A.V. Zibarev, Eur. J. Inorg. Chem. (2003) 77;
(r) C.C. Stoumpos, O. Roubeau, G. Aromi, A.J. Tasiopoulos, V. Nastopoulos, A.
Escuer, S.P. Perlepes, Inorg. Chem. 49 (2010) 359;
(s) V. Tangoulis, S. Paschalidou, E.G. Bakalbassis, S.P. Perlepes, C.P.
(h) A.Y. Makarov, I.Y. Bagryanskaya, Y.V. Gatilov, T.V. Mikhalina, M.M.
Shakirov, L.N. Shchegoleva, A.V. Zibarev, Heteroat. Chem. 12 (2001) 563.

R.L. Melen et al. / Polyhedron 47 (2012) 16–23
23
Raptopoulou, A. Terzis, Chem. Commun. (1996) 1297;
(t) C.M. Zaleski, T.-C. Weng, C. Dendrinou-Samara, M. Alexiou, P. Kanakaraki,
W.-Y. Hsieh, J. Kampf, J.E. Penner-Hahn, V.L. Pecoraro, D.P. Kessissoglou, Inorg.
Chem. 47 (2008) 6127;
(g) F. Zhang, E.M. Prokopchuk, M.E. Broczkowski, M.C. Jennings, R.J.
Puddephatt, Organometallics 25 (2006) 1583;
(h) G. Volpi, C. Garino, L. Salassa, J. Fiedler, K.I. Hardcastle, R. Gobetto, C. Nervi,
Chem. Eur. J. 15 (2009) 6415.
(u) C. Dendrinou-Samara, M. Alexiou, C.M. Zaleski, J.W. Kampf, M.L. Kirk, D.P.
Kessissoglou, V.L. Pecoraro, Angew. Chem., Int. Ed. 42 (2003) 3763;
(v) T.C. Stamatatos, V. Nastopoulos, A.J. Tasiopoulos, E.E. Moushi, W.
Wernsdorfer, G. Christou, S.P. Perlepes, Inorg. Chem. 47 (2008) 10081;
(w) M.-L. Tong, H.K. Lee, Y.-X. Tong, X.-M. Chen, T.C.W. Mak, Inorg. Chem. 39
(2000) 4666.
[23] (a) See for example: C. Godard, S.B. Duckett, S. Parsons, R.N. Perutz, Chem.
Commun. (2003) 2332;
(b) D. Zuccaccia, E. Foresti, S. Pettirossi, P. Sabatino, C. Zuccaccia, A. Macchioni,
Organometallics 26 (2007) 6099;
(c) A. Basu, S. Bhaduri, N.Y. Sapre, P.G. Jones, Chem. Commun. (1987) 1724;
(d) Y. Li, S. Xiang, T. Sheng, J. Zhang, S. Hu, R. Fu, X. Huang, X. Wu, Inorg. Chem.
45 (2006) 6577;
[21] (a) See for example: G.R. Newkome, H.C.R. Taylor, F.R. Fronczek, V.K. Gupta,
Inorg Chem. 25 (1986) 1149;
(e) T.C. Stamatatos, K.A. Abboud, W. Wernsdorfer, G. Christou, Inorg. Chem. 48
(2009) 807.
(b) A.N. Georgopoulou, C.P. Raptopoulou, V. Psycharis, R. Ballesteros, B.
Abarca, A.K. Boudalis, Inorg. Chem. 48 (2009) 3167;
(c) M.-L. Tong, M. Monfort, J.M.C. Juan, X.-M. Chen, X.-H. Bu, M. Ohba, S.
Kitagawa, Chem. Commun. (2005) 233;
(d) H. Kumagai, M. Endo, M. Kondo, S. Kawata, S. Kitagawa, Coord. Chem. Rev.
237 (2003) 197;
(e) A. Dimitrakopoulou, V. Psycharis, C.P. Raptopoulou, A. Terzis, V. Tangoulis,
D.P. Kessissoglou, Inorg. Chem. 47 (2008) 7608;
(f) C. Tsiamis, A.G. Hatzidimitiou, L. Tzavellas, Inorg. Chem. 37 (1998) 2903;
(g) B.F. Abrahams, T.A. Hudson, R. Robson, Chem. Eur. J. 12 (2006) 7095;
(h) A.D. Katsenis, R. Inglis, A.M.Z. Slawin, V.G. Kessler, E.K. Brechin, G.S.
Papaefstathiou, CrystEngComm 11 (2009) 2117;
(i) V. Tangoulis, C.P. Raptopoulou, S. Paschalidou, A.E. Tsohos, E.G. Bakalbassis,
A. Terzis, S.P. Perlepes, Inorg. Chem. 36 (1997) 5270;
[24] A.N. Papadopoulos, V. Tangoulis, C.P. Raptopoulou, A. Terzis, D.P. Kessissoglou,
Inorg. Chem. 35 (1996) 559.
[25] (a) H. Sartzi, G.S. Papaefstathiou, V. Psycharis, A. Escuer, S.P. Perlepes, C.C.
Stoumpos, Polyhedron 29 (2010) 100;
(b) A.C. Deveson, S.L. Heath, C.J. Harding, A.K. Powell, Dalton Trans. (1996)
3173;
(c) A.K. Boudalis, C.P. Raptopoulou, V. Psycharis, Y. Sanakis, B. Abarca, R.
Ballesteros, M. Chadlaoui, Dalton Trans. (2007) 3582;
(d) T.C. Stamatatos, V. Tangoulis, C.P. Raptopoulou, A. Terzis, G.S.
Papaefstathiou, S.P. Perlepes, Inorg. Chem. 47 (2008) 7969;
(e) C.-M. Liu, D.-Q. Zhang, D.-B. Zhu, Inorg. Chim. Acta 362 (2009) 1383.
[26] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc.,
Dalton Trans. (1984) 1349.
(j) Z.E. Serna, M.K. Urtiaga, M.G. Barandika, R. Cortes, S. Martin, L. Lezama, M.I.
Arriortua, T. Rojo, Inorg. Chem. 40 (2001) 4550;
[27] (a) S.-L. Wang, J.W. Richardson Jr., S.J. Briggs, R.A. Jacobsen, W.P. Jensen, Inorg.
Chim. Acta 111 (1986) 67;
(k) N. De la Pinta, Z. Serna, G. Madariaga, M.K. Urtiaga, M.L. Fidalgo, R. Cortes,
Cryst. Growth Des. 11 (2011) 1458.
[22] (a) See for example: M.J. Rauterkus, B. Krebs, Angew. Chem., Int. Ed. 43 (2004)
1300;
(a) P.J. Steel, C.J. Sumby, Dalton Trans. (2003) 4505;
(b) K. Latham, K.F. White, K.B. Szpakolski, C.J. Rix, J.M. White, Inorg. Chim. Acta
362 (2009) 1872;
(c) F.S. Delgado, F. Lahoz, F. Lloret, M. Julve, C. Ruiz-Perez, Cryst. Growth Des. 8
(2008) 3219;
(d) J.L. Manson, H.I. Sutherland, B. Twamley, R. Rai, J.L. Musfeldt, Dalton Trans.
(2007) 5655;
(e) F. Mautner, M.S. El Fallah, S. Speed, R. Vicente, Dalton Trans. 39 (2010)
4070;
(b) C.M. Kepert, G.B. Deacon, N. Sahely, L. Spiccia, G.D. Fallon, B.W. Skelton,
A.H. White, Inorg. Chem. 43 (2004) 2818;
(c) K.N. Crowder, S.J. Garcia, R.L. Burr, J.M. North, M.H. Wilson, B.L. Conley, P.E.
Fanwick, P.S. White, K.D. Sienerth, R.M. Granger II, Inorg. Chem. 43 (2004) 72;
(d) F.R. Keene, D.J. Szalda, T.A. Wilson, Inorg. Chem. 26 (1987) 2211;
(e) S. Sarkar, B. Sarkar, N. Chanda, S. Kar, S.M. Mobin, J. Fiedler, W. Kaim, G.K.
Lahiri, Inorg. Chem. 44 (2005) 6092;
(f) Z. Serna, M.G. Barandika, R. Cortes, M.K. Urtiaga, M.I. Arriortua, Polyhedron
18 (1999) 249;
(f) F. Zhang, C.W. Kirby, D.W. Hairsine, M.C. Jennings, R.J. Puddephatt, J. Am.
Chem. Soc. 127 (2005) 14196;
(g) O.J. Parker, S.L. Aubol, G.L. Breneman, Polyhedron 19 (2000) 623.