A Cyclometallated (Azobenzene)palladium(II) complex of 1,4,7- trithiacyclononane: Synthesis and reactivity with thioether-dithiolate metalloligands, single-crystal X-ray diffraction analyses and electrochemical studies

Article abstract of DOI:10.1002/ejic.200900049

The treatment of [jPd(C₆H₄N=NC₆H ₅)(μ-Cl)j₂](5) with AgPF₆/NH ₄PF₆ in acetone, followed by the addition of two molar equivalents of 1,4,7-trithiacyclononane (9S3), giv

Full text of DOI:10.1002/ejic.200900049

FULL PAPER
DOI: 10.1002/ejic.200900049
A Cyclometallated (Azobenzene)palladium(II) Complex of 1,4,7-
Trithiacyclononane: Synthesis and Reactivity with Thioether-Dithiolate
Metalloligands, Single-Crystal X-ray Diffraction Analyses and Electrochemical
Studies
Richard Y. C. Shin,[a] Chun Lian Goh,[a] Lai Yoong Goh,*[a][‡] Richard D. Webster,[b] and
Yongxin Li[b]
Keywords: Palladium / Heterometallic complexes / S ligands / Ruthenium / Crown compounds
The treatment of [{Pd(C6H4N=NC6H5)(µ-Cl)}2] (5) with
AgPF6/NH4PF6 in acetone, followed by the addition of two
molar equivalents of 1,4,7-trithiacyclononane (9S3), gives the
deep red complex [Pd(C6H4N=NC6H5)(9S3)][PF6] (6A) in
high yield, whereas the direct reaction of 5 with two molar
equivalents of 9S3 gives [Pd(C6H4N=NC6H5)(9S3)][Pd-
(C6H4N=NC6H5)Cl2] (6B) in quantitative yield based on 5.
The subsequent reaction of 5 and 6A with the metalloligand
[(HMB)RuII{η3-tpdt}] [3; HMB = η6-C6Me6, tpdt = S(CH2-
CH2S–)2] results in displacement of the chloride and 9S3 li-
gands, respectively, to give the Ru-Pd heterobimetallic com-
plex [{(HMB)RuII(µ-η2:η3-tpdt)}{Pd(C6H4N=NC6H5)}][PF6] (7)
in 85% yield. Similar reactions with the Cp* analogue of 3,
namely [(Cp*)RuIII{η3-tpdt}] (4), give the trinuclear complex
[{Cp*RuIII(µ-η2:η3-tpdt)}2Pd](PF6)2 (8), in which all the li-
gands on palladium have been displaced, in a yield of around
80%. X-ray diffraction analyses of 6A, 6B and its solvates
(6B·H2O and 6B·CHCl3) have shown that short atom–atom
interactions between the cation and the counterion and lat-
tice solvent molecules have a significant effect on the bond
parameters of the molecules, and 1H NMR spectroscopy indi-
cates that these interactions persist even in solution. The sin-
gle-crystal X-ray structure of 7 has also been determined.
Cyclic voltammetry experiments have been performed on
6A, 6B and 7 in CH2Cl2 and CH3CN at GC and Pt electrodes.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
clude the neutral types with halido ligands, such as cis-
[MX2(9S3)] (X = Cl, Br, I),[3] and with alkyl or aryl ligands,
for example cis-[MR2(9S3)] [M = Pt, R2 = Me2, Et2, Ph2,
(CH2CMe3)2, (CH2SiMe3)2, Me(CH2SiMe3) and Cl(CH2Si-
Me3); M = Pd, R2 = Me2 and (CH2SiMe3)2].[4] The cationic
examples contain phosphane co-ligands, for example cis-
[MClL(9S3)](PF6) (L = PPh3 or PCy3), cis-[ML(9S3)]-
(PF6)2 [L = (PPh3)2, Ph2PCH2PPh2 (dppm), Ph2PCH2-
CH2PPh2 (dppe), {(Ph2PCH2)2[Ph2P(O)CH2]CMe}, 1,1Ј-
bis(diphenylphosphanyl)ferrocene (dppf)][5] and diimine co-
ligands, for example cis-[ML(9S3)](PF6)2 [L = 2,2Ј-bipyr-
idine (bipy) or 1,10-phenanthroline (phen)].[5a,6] Grant pre-
pared the first monocationic orthometallated 9S3 com-
plexes of PtII-containing 2-phenylpyridine (ppy),[7a] and
very recently, while this manuscript was in preparation, sim-
ilar cyclometallated complexes of both PdII (1 and 2, in
Figure 1) and PtII were reported.[7b]
Although 9S3 usually acts as a facial tridentate ligand, it
tends to coordinate to Pd or Pt in a bidentate fashion with
an additional weak axial M–S interaction, thus generating
in a bis(9S3) complex either an elongated square-pyramidal
geometry[2a,2b] or elongated octahedral geometry,[2c–2e] cur-
rently denoted by the respective notations [S4 + S1] and [S4
+ S2],[2f,3a,5] as introduced by Schröder.[5a] A central focus
1. Introduction
The coordination chemistry of crown thioethers such as
1,4,7-trithiacyclononane (9S3) has been extensively studied
over the last two decades.[1] The special interest in their
complexes of the group 10 metals lies in the potential cata-
lytic, synthetic and pharmaceutical uses of compounds of
these metals. Additionally, early investigations of the homo-
leptic complexes [M(9S3)2]2+ (M = Ni, Pd and Pt) revealed
interesting structural, spectroscopic and redox features.[2]
Many heteroleptic complexes of Pd and Pt with various
types of co-ligands have since been synthesized. These in-
[a] Department of Chemistry, National University of Singapore,
Kent Ridge, Singapore 117543
[b] Division of Chemistry & Biological Chemistry, School of Physi-
cal & Mathematical Sciences, Nanyang Technological Univer-
sity,
Singapore 637371
[‡] Present address: Division of Chemistry & Biological Chemistry,
School of Physical & Mathematical Sciences, Nanyang Techno-
logical University,
Singapore 637371
Fax: +65-67911961
E-mail: LaiYoongGoh@ntu.edu.sg
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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Cyclometallated (Azobenzene)palladium(II) Complex
2. Results and Discussion
2.1. Synthesis
The µ-dichlorido complex [{Pd(C6H4N=NC6H5)(µ-
Cl)}2] (5) was treated with two molar equivalents of 9S3, via
its solvato derivative [Pd(C6H4N=NC6H5)(OCMe2)2][PF6],
obtained by treatment with AgPF6 or NH4PF6 in acetone.
A dark red crystalline complex [Pd(C6H4N=NC6H5)-
(9S3)][PF6] (6A) was isolated in 80% yield. The direct reac-
tion between 5 and 9S3 led to a quantitative yield of the
[Cl2Pd(C6H4N=NC6H5)]– salt (6B) of the same cationic 9S3
species. Clearly, in this case 9S3 has cleaved two Pd–Cl
bonds in 5 and coordinated to the non-chlorido mono-nu-
clear fragment, but failed to displace the chlorido ligands
Figure 1. Cyclometallated Pd(9S3) complexes.[7b]
of current interest has been the correlation of this axial in- from the PdII anion [Cl2Pd(C6H4N=NC6H5)]– (Scheme 1).
teraction with the electronic and electrochemical properties
The reaction of 5 with [(HMB)RuII{η3-tpdt}] (3) resulted
in cleavage of the Pd–Cl bond to give the thiolate-bridged
of these complexes.[7b]
In recent years, we have reported the high efficacy of the heterobimetallic complex [{(HMB)RuII(µ-η2:η3-tpdt)}{Pd-
RuII and RuIII metalloligands [(HMB)RuII(η3-tpdt)] (3)[8] (C6H4N=NC6H5)}]PF6 (7) in 85% yield after PF6 metathe-
and [(Cp*)RuIII(η3-tpdt)] (4)[9] [HMB = η6-C6Me6, Cp* = sis. Complex 3 can also preferentially displace the 9S3 li-
η5-C5Me5; tpdt = S(CH2CH2S–)2] in the cleavage of metal– gand in 6A to give 7 in 75% yield (Scheme 2).
X bonds (X = chloride, phosphane, solvent ligand) in a
However, when [(Cp*)RuIII{η3-tpdt}] (4) was treated
variety of complexes, leading to di- and trinuclear homo- with 5 or 6A the trinuclear complex [{Cp*RuIII(µ-η2:η3-
and heterometallic derivatives.[10] This paper describes the tpdt)}2Pd](PF6)2 (8) was isolated as the only product in
comparative reactivity of species 3 and 4 with a target cy- 80% and 73% yield, respectively (Scheme 3). In this case,
clometallated (azobenzene)PdII(9S3) complex, the electro- both the azobenzene and 9S3 ligands are displaced by the
chemistry and crystal structure of which are also presented. thiolate sulfur atoms of the tpdt ligand, thus indicating that
Scheme 1.
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R. Y. C. Shin, C. L. Goh, L. Y. Goh, R. D. Webster, Y. Li
FULL PAPER
cies is adsorbed onto the electrode surface on the forward
scan and subsequently stripped off when the potential di-
rection is reversed.
Scheme 2.
complex 4 is a stronger metalloligand than the HMB ana-
logue 3. We have previously obtained 8 from the reaction
of 4 with PdCl2 or [PdCl2(MeCN)2].[11]
Scheme 3.
Figure 2. Cyclic voltammograms of 0.5 m solutions of 6A per-
formed at 1 mm diameter planar GC (···) and Pt (Ϫ) electrodes in
CH2Cl2 or CH3CN (containing 0.25  Bu4NPF6) at a scan rate of
100 mVs–1. CV traces at the Pt electrode are offset by –3 µA.
2.2. Electrochemical Studies
Cyclic voltammograms recorded for 0.5 m solutions of
The voltammetric processes of 6A observed in CH2Cl2 at
6A show significant differences depending on the electrode 243 K on GC were found to be similar to those observed
surface (GC or Pt), the solvent (CH2Cl2 or CH3CN) and at 273 K (Figure 2). On Pt, the reduction process appears
the temperature (Figure 2 and Table 1). CVs performed on to be the same as that observed at higher temperature,
solutions of CH2Cl2 containing 6A at 273 K show a re- whereas the oxidation process is substantially different, with
ox
red
duction process at around –1.2 V vs. Fc/Fc+ that appears smaller ip and ip values and with a wide anodic peak
more chemically reversible on Pt than GC (at v = 0.1 Vs–1), potential (Epox) to cathodic peak potential (Epred) separa-
in the sense that the oxidative (ipox) to reductive (ipred) peak tion (∆Epp) of at least 200 mV (the anodic process was par-
current ratio (ipox/ipred) is equal to unity on Pt (but not on ticularly drawn out).
GC). An oxidation process is evident at around +1 V vs.
The reduction of 6A on GC in CH3CN appears to be
red
ox
Fc/Fc+ with an ip
value at least twice that of the ip
chemically irreversible at a scan rate of 0.1 Vs–1 at high and
value observed for the oxidation process, thereby indicating low temperatures, whilst the oxidation wave split into two
that the reduction process involves the transfer of a higher chemically reversible processes. It is likely that the oxidation
number of electrons. The reverse reductive peak observed process involves two one-electron steps that are resolved in
for the process at around +1 V vs. Fc/Fc+ is very sharp on acetonitrile on GC but appear as one process in CH2Cl2.
both GC and Pt, typical of electrochemical processes that However, caution is required in reaching this conclusion be-
involve strong surface interactions, where the oxidized spe- cause the data in CH3CN may be complicated by coordina-
Table 1. Cyclic voltammetric data for 0.5 m solutions of 6A obtained at a scan rate of 0.1 Vs–1 at 1 mm diameter electrodes at 273 K
with 0.25  Bu4NPF6 as the supporting electrolyte.
Electrode
Solvent
Reduction processes[a]
Oxidation processes[a]
red
ox
ox
red
Ep [V][b] Ep [V][c]
Er1/2 [V][d] ∆E [mV][e]
Ep [V][c]
Ep [V][b] Er1/2 [V][d]
∆E [mV][e]
GC
CH3CN
–1.208
+0.698
+0.814
+0.616
+0.728
+0.66
+0.77
82
86
Pt
CH2Cl2
–1.225
–1.157
–1.19
68
+0.931
+0.839
[a] All potentials are relative to the Fc/Fc+ redox couple. [b] EP = reductive peak potential. [c] Ep = oxidative peak potential.
red
ox
[d] Er1/2 = (Ep + Epox)/2. [e] ∆E = |Ep – Epred|.
red
ox
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Cyclometallated (Azobenzene)palladium(II) Complex
tion of the solvent to Pd, either prior to or immediately
following the electron-transfer steps. The voltammograms
obtained during the reduction of 6A on Pt in CH3CN (at
high and low temperature) were found to be similar to those
observed in CH2Cl2, with a chemically reversible process at
around –1.2 V vs. Fc/Fc+. The oxidation process(es) ob-
served in CH3CN on Pt (at high and low temperatures)
were more drawn out and similar to the voltammograms
observed in CH2Cl2 at 243 K. Therefore, it is likely that
the anodic process on Pt is associated with a slow rate of
heterogeneous electron transfer that decreases with lower-
ing temperatures, and increases the ∆Epp values with respect
to those observed on GC.
If it is considered that the oxidation process is a two-
electron process in CH2Cl2, the small peak current observed
on Pt at low temperatures might be due to the slow hetero-
geneous electron-transfer rate increasing the overpotential
required to remove a second electron. This would also ex-
plain the lack of a stripping peak for the oxidation of 6A
in CH2Cl2 at 243 K, if the adsorbed species were associated
with the second electron transfer that occurs at a higher
potential (Ͼ +1.2 V vs. Fc/Fc+). In CH3CN, the oxidized
Figure 3. Cyclic voltammograms of 0.5 m solutions of 7 per-
formed at 1 mm diameter planar GC (···) and Pt (Ϫ) electrodes in
species may have improved solubility; hence no stripping CH2Cl2 or CH3CN (containing 0.25  Bu4NPF6) at a scan rate of
peaks are observed.
100 mVs–1. CV traces at the Pt electrode are offset by –3 µA.
The voltammograms obtained for solutions of 6B were
found to be similar to those for solutions of 6A, with oxi-
In CH2Cl2 and CH3CN at high and low temperatures,
dation and reduction processes that vary in appearance de- CV experiments on 7 showed a chemically reversible re-
pending on the temperature and solvent (see Supporting duction process at around –1.3 V vs. Fc/Fc+ (Figure 3 and
Information). CVs performed on solutions of CH2Cl2 con- Table 2). The ∆Epp value is similar to that observed for the
red
taining 7 at 243 K show an oxidation process at +0.50 V vs. oxidation process, as is the ip value, thus indicating that
Fc/Fc+ that appears to be chemically reversible at a scan the reduction is also a one-electron process. On GC elec-
rate of 100 mVs–1 (Figure 3). A second chemically irrevers- trodes a second diffusion-controlled chemically irreversible
ible oxidation process is evident at +0.86 V vs. Fc/Fc+. At reduction process, which was not detected on Pt electrodes,
temperatures above 243 K, the first (least positive) oxi- was evident at around –1.9 V vs. Fc/Fc+. The second re-
dation process becomes less chemically reversible, thus indi- duction process on Pt electrodes appears as a long drawn-
cating the instability of the oxidized states. The anodic to out wave with high currents that are likely due to strong
cathodic peak-to-peak separation (∆Epp) for the first oxi- surface-based (adsorption) interactions.
dation process is similar to that observed for ferrocene un-
Janzen, Grant et al. have described the electrochemistry
der similar conditions, thus suggesting a one-electron pro- of several similar cyclometallated PtII and PdII complexes
cess. In CH3CN solutions the first oxidation process pro- with the 9S3 ligand.[7b] For several compounds, two closely
duces a species that is chemically unstable at low and high spaced oxidation processes were detected at approximately
temperatures, possibly due to irreversible coordination of +0.6 V vs. Fc/Fc+, similar to the values obtained in this
CH3CN to the oxidized form of the compound.
work. The oxidative electrochemistry was interpreted as se-
Table 2. Cyclic voltammetric data for 0.5 m solutions of 7 obtained at a scan rate of 0.1 Vs–1 at a 1 mm diameter GC electrode at 243 K
in CH2Cl2 or CH3CN with 0.25  Bu4NPF6 as the supporting electrolyte.
Solvent
Reduction processes[a]
Oxidation processes[a]
Ep [V][b]
Ep [V][c]
Er1/2 [V][d]
–1.32
∆E [mV][e]
Ep [V][c]
ox
Ep [V][b]
Er1/2 [V][d]
∆E [mV][e]
red
ox
red
CH2Cl2
–1.354
–1.86
–1.279
75
+0.533
+0.86
+0.465
+0.50
68
CH3CN
–1.303
–1.96
–1.234
–1.27
69
+0.43
[a] All potentials are relative to the Fc/Fc+ redox couple. [b] Ep = reductive peak potential. [c] Ep = oxidative peak potential.
red
ox
[d] Er1/2 = [Ep + Epox]/2. [e] ∆E = |Ep – Epred|.
red
ox
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FULL PAPER
quential one-electron oxidation of the metal ion (i.e. PdII/III which also includes selected data for Grant’s cyclometall-
and PdIII/IV).[7b] It is therefore possible that the oxidation ated complexes 1 and 2. There are clear variations in the
processes detected in this study are also associated with the bond parameters of the geometrically identical cations of
sequential one-electron oxidation of Pd ion. However, RuII 6A and the different solvates of 6B. Thus, the Pd–S(1) dis-
complexes can often be oxidized in one- and two-electron tances range from 2.276(2) to 2.3052(6) Å, similar to those
processes to RuIII and RuIV, so there is also a possibility
that the Ru ions are involved in the oxidation (and re-
duction) processes.
2.3 Crystallographic Studies
The molecular structures of complexes 6A, 6B, and its
solvates 6B·H2O and 6B·CHCl3, and 7 have been deter-
mined by X-ray diffraction analyses, and are illustrated for
6A, 6B·CHCl3 and 7 in Figures 4, 5 and 8, respectively. The
cations adopt a structure that is a compromise between the
preference of PdII to adopt a square-planar geometry and
the tendency of the 9S3 ligand to bind to a trigonal face of
an octahedron. The distorted square-pyramidal structure is
in fact a characteristic feature of 9S3 complexes of PdII and
PtII. The coordination geometry around the palladium cen-
tre in these cations is an elongated square pyramid, with
the square plane defined by the C(7) and N(1) atoms of
azobenzene and the sulfur atoms S(1) and S(2) of 9S3. The
bond parameters for these complexes are listed in Table 3, soids, hydrogen atoms are omitted).
Figure 4. ORTEP diagram for 6A (50% probability thermal ellip-
Table 3. Selected bond lengths [Å] and angles [°] in the Ru–Pd complexes.
Compounds
6A
6B
6B·H2O
6B·CHCl3 1[a]
2[a]
7
Pd(1)–S(1)
Pd(1)–S(2)
Pd(1)–S(3)
Pd(1)–N(1)
Pd(1)–C(7)
C(1)–N(1)
N(1)–N(2)
N(2)–C(12)
Pd(2)–Cl(1)
Pd(2)–Cl(2)
Pd(2)–C(19)
Pd(2)–N(3)
N(3)–C(25)
N(3)–N(4)
N(4)–C(24)
Pd(2)···S(1)
Pd(2)···S(2)
Pd(2)···S(3)
2.3052(6)
2.3781(7)
2.7113(8)
2.0353(19) 2.083(4)
1.990(2)
1.436(3)
1.267(3)
1.395(3)
–
–
–
–
–
–
–
–
–
–
2.2773(14)
2.4130(13)
2.8458(14)
2.3004(4)
2.4035(5)
2.7299(5)
2.0586(15) 2.073(7)
1.9940(17) 1.994(9)
1.428(2)
1.273(2)
1.397(2)
2.3164(5)
2.4194(5)
1.9711(18) 1.968(8)
2.0262(14) 2.030(7)
1.436(2)
1.269(2)
1.397(2)
4.852
2.276(2)
2.418(2)
2.784(2)
2.2985(9)
2.3842(9)
2.8705(10)
2.0614(18) [2.0289(18)] 2.080(3)
2.0614(18) [2.0289(18)] 2.023(3)
2.2657(10) Ru(1)–S(1)
2.3714(10) Ru(1)–S(2)
3.0066(12) Ru(1)–S(3)
2.3537(15)
2.3184(18)
2.3742(16)
2.2850(15)
2.4178(16)
2.086(5)
1.988(6)
1.403(9)
1.277(8)
1.371(9)
Pd(1)–S(1)
Pd(1)–S(3)
Pd(1)–N(1)
Pd(1)–C(7)
C(1)–N(1)
N(1)–N(2)
N(2)–C(12)
2.002(5)
1.439(6)
1.267(6)
1.411(7)
2.3059(13)
2.4346(14)
1.971(5)
2.044(4)
1.446(6)
1.268(6)
1.390(7)
5.046
1.451(11)
1.251(11)
1.409(12)
2.305(2)
2.428(2)
1.442(11)
1.285(10)
1.389(11)
4.553
3.947
3.455
3.646
6.948
4.124
3.478
S(1)–Pd(1)–S(2)
S(1)–Pd(1)–S(3)
S(2)–Pd(1)–S(3)
S(3)–Pd(1)–N(1)
S(3)–Pd(1)–C(7)
S(1)–Pd(1)–C(7)
S(2)–Pd(1)–N(1)
N(1)–Pd(1)–C(7)
Cl(1)–Pd(2)–Cl(2)
Cl(1)–Pd(2)–C(19)
Cl(2)–Pd(2)–N(3)
N(3)–Pd(2)–C(19)
Dihedral angles[b] in the
cation/anion
88.70(3)
87.07(3)
84.80(3)
102.20(6)
94.93(8)
95.86(8)
97.26(6)
78.31(9)
–
87.80(5)
87.44(5)
81.67(4)
88.331(16) 87.68(8)
88.533(16) 89.59(8)
84.145(15) 83.42(7)
87.96(3)
85.95(3)
82.50(3)
88.94(4)
S(1)–Ru(1)–S(2) 85.76(7)
S(1)–Ru(1)–S(3) 82.82(5)
S(2)–Ru(1)–S(3) 85.76(9)
S(1)–Pd(1)–S(3) 83.31(5)
S(1)–Pd(1)–C(7) 95.13(19)
S(3)–Pd(1)–N(1) 102.56(15)
N(1)–Pd(1)–C(7) 78.9(2)
91.44(12)
107.35(15)
90.96(15)
103.03(12)
78.77(19)
90.08(5)
92.18(15)
98.79(13)
78.94(19)
42.63/49.34
97.16(4)
94.80(5)
93.45(5)
100.06(4)
78.26(7)
87.6(2)
96.6(3)
93.0(3)
102.3(2)
77.1(3)
93.64(6)
97.01(5)
81.14(7) [81.14(7)]
91.75(10)
97.54(8)
81.91(12)
91.323(17) 90.28(8)
–
–
–
93.03(5)
96.48(4)
78.80(7)
92.0(3)
99.3(2)
78.2(3)
58.59/NA
44.39/50.26 44.99/50.09
40.38
[a] See Figure 1 and ref. [7b]. [b] Between phenyl rings.
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Cyclometallated (Azobenzene)palladium(II) Complex
in 1 and 2[7b] and in non-cyclometallated complexes;[5e,6a,6b]
the Pd–S(2) distances range from 2.3781(7) to 2.418(2) Å
(those of 1 and 2 are within this range and slightly lower,
respectively). The Pd(1)–S(3) bonds are significantly longer
(by 0.32–0.56 Å), more variable (variation of 0.1345 Å), and
are slightly shorter than those in Grant’s compounds. The
Pd–N distances range from 2.0353(19) Å in 6A to
2.083(4) Å in 6B (those of 1 and 2 lie within this range). The
relative order of magnitude of the bond lengths of Pd(1) to
S(1) and S(2) in all these cyclometallated complexes is in
agreement with the expected higher trans influence of the
aryl C(7) vs. the diazo or pyridyl N, since the aryl C is a
stronger σ-donor. While the Pd–N distances in the diazo-
benzene complexes and in 1 or 2 are very similar, there is a
large difference in the Pd–C distances in the two sets of
compounds, as expected as they are components of dif-
ferent types of five-membered ring systems (PdC2N2 and
PdC3N). The same rationale explains the difference in the
N–Pd–C angles of the two sets of complexes. The phenyl
rings are planar and the dihedral angles are also listed in
Table 3. The ring attached to N(1) is twisted away from the
plane of the cyclometallated (chelate) ring, undoubtedly
due to steric effects. This “twist” would reduce the conjuga-
tion of the phenyl ring with the planar phenylazo moiety
and lengthen C(1)–N(1) relative to C(12)–N(2) [1.436(3)
and 1.395(3) Å, respectively, in 6A].
There are only slight variations in the bond parameters
of the anion of 6B and its solvates. As in the cation, the
Figure 5. ORTEP diagram for 6B·CHCl3 (50% probability thermal
ellipsoids, hydrogen atoms are omitted).
Figure 6. Packing diagram of 6A, viewed along the c-axis. Short contacts between the F atoms of the PF6 anion and the phenyl ring
hydrogen atoms of the cation are shown.
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FULL PAPER
Figure 7. Packing diagram of 6B·H2O, viewed along the c-axis. Short contacts between the anion and cation are shown.
greater trans influence of C(19) vs. N(3) in the anions is S4 in the Supporting Information. These contacts (although
reflected in the relative Pd–Cl distances, with the Pd(2)– of comparative qualitative significance, since the hydrogen
Cl(2) distances being 0.10–0.13 Å longer than those of atoms are not refined in the structure analyses) are shorter
Pd(1)–Cl(1). The non-bonding length for Pd(2)···S(x) (x = than their van der Waal’s distances by 0.037–0.202 (F···H),
1, 2, 3) is shortest for x = 2 in 6B and for x = 3 in the 0.039–0.223 (C···H), 0.001–0.404 (Cl···H), 0.002–0.193
solvato analogues 6B·H2O and 6B·CHCl3.
(N···H), 0.028 (O···H) and 0.023 Å (N···S). Most of these
Our serendipitous isolation and structure determination interactions appear to be much stronger than those re-
of the anionic variants of 6 (6A and 6B) and the solvato ported for the [Pt(9S3)2]2+ and [Pt(18S6)]2+ complexes,
variants of 6B provided us with an opportunity to observe
the effect of both anion and lattice solvent molecules on the
crystal packing in the structures of these heteroleptic 9S3
complexes of Pd. The variations found in the cation bond
parameters in these various species of 6 bring to mind the
reports of Schröder[2c] and Grant[2f] on the influence of
anions on the coordination geometry (S4+S1 vs. S4+S2) of
the thioether ligand in the [Pt(18S6)]2+ and [Pt(9S3)2]2+ cat-
ions, as well as those of Grant[12] and McAuley[13] on the
effect of solvents on “positional linkage” isomerism of
[Pd(10S3)2](PF6)2. Atom–atom contact interactions be-
tween the anion and cation in the crystal lattice of 6A are
shown in Figure 6, and Figure 7 also includes interactions
between the anion and cation and H2O in 6B·H2O. Colour
versions of these and other packing diagrams are depicted
in Figures S1–S4 in the Supporting Information. These il-
lustrate interactions between the cation and anion {F atoms
–
of PF6 in 6A and atoms of [Pd(C6H4N=NC6H5)Cl2]– in
the various 6B species}, and interactions between the cation
and anion of the complex and lattice solvent molecules
(H2O or CHCl3). The MERCURY software provided lis-
tings of atom–atom contacts, which are listed in Tables S1– soids, hydrogen atoms are omitted for clarity).
Figure 8. ORTEP diagram for 7 (50% probability thermal ellip-
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Eur. J. Inorg. Chem. 2009, 2282–2293

Cyclometallated (Azobenzene)palladium(II) Complex
–
–
wherein S···F contacts in the PF6 or BF4 salts, and the 2.89–3.39 ppm, respectively, with a “dispersion” or separa-
S···O contact (of solvent MeNO2), are just above or below
tion (∆) of 0.12 ppm in 6A and around four times larger in
6B (0.50 ppm at 298 K and 0.54 ppm at 193 K). The reso-
nances of 6B in both the aromatic and 9S3 regions are bet-
ter resolved at low temperature. This characteristic AAЈBBЈ
splitting pattern, which arises due to the magnetic inequiva-
lence of the methylene protons caused by their different
spatial orientations, has been observed previously for al-
most all known 9S3 complexes of PdII and PtII.[2b,3,4,5a,5c,7]
In 6A, this multiplet is less resolved in acetone and acetoni-
trile, probably because of the greater interaction of the 9S3
ligand with these solvent molecules. In [D6]acetone, the 9S3
proton resonance is a single symmetrical multiplet at δ =
3.16–3.34 ppm (∆ = 0.03 ppm), centred at δ = 3.25 ppm,
while in CD3CN this resonance is a broad unresolved mul-
tiplet at δ = 2.87–3.03 ppm, with intense “spikes” at δ =
2.94 and 2.95 ppm. Variations in the magnitude of the “dis-
persion” have ranged from 0–0.84 ppm for [Pd(9S3)(L2)]-
PF6, with ∆ in increasing order for L2: bipy Ͻ phen Ͻ
dppm Ͻ (PPh3)2 Ͻ Cl[P(C6H11)3].[5a] In a recent paper,
Grant also reported a single multiplet for 9S3 (i.e. ∆ =
0 ppm) for cyclometallated Pd and Pt 7,8-benzoquinolinate
complexes.[7b] The present observations show the sensitivity
of the splitting of the AAЈBBЈ pattern to both the counter-
ion and the solvent.
the sum of their van der Waal’s distances.[2f]
The molecular structure of 7 shows a [(HMB)RuII{η3-
tpdt}] unit ligated to a Pd(C6H4N=NC6H5) fragment via
the thiolate sulfurs S(1) and S(3), with the Pd atom in a
four-coordinate planar environment (Figure 8). As in the
structures of the variants of species 6, a higher trans influ-
ence of the aryl C(7) vs. N(1) atom results in a substantially
longer Pd(1)–S(3) bond [2.4178(16) Å] compared to Pd(1)–
S(3) [2.2850(15) Å]. Due to steric repulsion imposed by the
phenyl ring attached to N(1), the S(3)–Pd(1)–N(1) angle
[102.56(15)°] is much larger than the other three angles at
Pd [78.9(2)–95.13(19)°; see Table 3].
2.4 Spectral Characteristics
The NMR characteristics of 6A and the solvent variants
of 6B are in agreement with their determined solid-state
structures. As expected, the proton resonances in the aro-
matic region for the phenyl ring protons of the cyclometall-
ated azobenzene are very different in 6A (multiplets in the
range δ = 7.26–8.16 ppm in CD2Cl2) and 6B (unresolved
multiplets in the range δ = 7.22–8.13 ppm in CD2Cl2; see
Figures 9 and 10) The twelve methylene protons of the 9S3
ligand in 6A and 6B are observed as two sets of second
order AAЈBBЈ multiplets (8-lines) at δ = 2.86–3.09 and
The 13C NMR spectra of 6A in CD3CN and 6B in
CDCl3 show one intense peak at δ = 33.9 and 34.2 ppm,
respectively, for the six carbon atoms of the 9S3 ligand, thus
1
Figure 9. H NMR spectra of 6A in (i) CD2Cl2, (ii) (CD3)2CO and (iii) CD3CN. ∆ = “dispersion”.
Eur. J. Inorg. Chem. 2009, 2282–2293
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R. Y. C. Shin, C. L. Goh, L. Y. Goh, R. D. Webster, Y. Li
FULL PAPER
1
Figure 10. H NMR spectra of 6B·CHCl3 in CD2Cl2 at 298 and 186 K. ∆ = “dispersion”.
–
indicating the rapid intramolecular exchange of the three counterions PF6 (6A) and [Pd(azobenzene)Cl2]– (6B). The
inequivalent S atoms, presumably via a 1,4-metallotropic crystal data for complexes 6A and 6B, and the latter’s solv-
shift, as observed in all 9S3 complexes of PdII and ate derivatives, show that the molecular structures are influ-
PtII.[4,6,14] The phenyl carbon atoms of azobenzene in 6A enced by atom–atom contacts between the counterions and/
are seen as ten resonances (range δ = 165.1–123.2 ppm), in or lattice solvent molecules. These effects are reflected in
agreement with the pairs of magnetically equivalent ortho the variation of the fine structure of the 9S3 proton reso-
and meta carbons in the non-metallated phenyl ring. Only nance with both counterion and the NMR solvent. A semi-
twelve resonances (range δ = 164.6–122.6) are observed for quantitative estimation of atom–atom contact distances was
the two cyclometallated azobenzene moieties in 6B, presum- obtained by calculations using the MERCURY software.
ably due to overlapping of some resonances.
The reactions of 6A with the metalloligands [(HMB)-
1
The H NMR spectrum of 7 in CD3CN shows peaks for RuII{η3-tpdt}] and [(Cp*)RuIII{η3-tpdt}] show that the tri-
the phenyl ring protons of the cyclometallated azobenzene dentate 9S3 ligand is more readily displaced than the biden-
at δ = 7.30–7.99 ppm and seven sets of resolved multiplets tate cyclometallated azobenzene ligand.
at δ = 1.79–3.34 ppm for the methylene protons of the tpdt
Compounds 6A, 6B and 7 can be electrochemically oxid-
ligand and a singlet at δ = 2.10 ppm for the C6Me6 protons. ized and reduced. However, while 6A and 6B behave simi-
Similar to 6A, the 13C NMR spectrum of 7 shows 10 peaks larly, a significantly different CV was obtained for 7 at the
at δ = 124.2–166.0 ppm for the azobenzene ligand while res- different electrode surfaces (GC and Pt) and in the different
onances at δ = 15.9 and 101.6 ppm belong to the methyl solvents (CH3CN and CH2Cl2) as the temperature was var-
and ring carbons of the C6Me6 ligand, respectively. Four ied.
signals in the range δ = 27.5–45.5 ppm are also observed
for the four SCH2 carbons.
4. Experimental Section
3. Conclusion
4.1. General Procedures: All reactions were carried out using con-
ventional Schlenk techniques under an inert atmosphere of nitro-
taining azobenzene and 9S3 ligands has been isolated, with gen or under argon in an M. Braun Labmaster 130 Inert Gas Sys-
A new cationic heteroleptic complex of palladium con-
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Eur. J. Inorg. Chem. 2009, 2282–2293

Cyclometallated (Azobenzene)palladium(II) Complex
tem. Other procedures were as described previously.[11] 1,4,7-Trithi-
acyclononane was obtained from Aldrich and used as supplied.
study in CD2Cl2 showed that the azobenzene multiplets were most
resolved at 263 K, while the SCH2 resonances sharpened to υ1/2
≈
The compounds [(HMB)RuII{η3-tpdt}] (3), [(Cp*)RuIII{η3-tpdt}] 30 Hz at δ = 3.41 and 2.78 ppm, respectively, at 263 K. These sig-
(4) and [{Pd(C6H4N=NC6H5)(µ-Cl)}2] (5) were prepared as pre-
nals resolved into overlapping doublets at δ = 3.29 and 2.73 ppm,
respectively, at 193 K. ESI+ MS: m/z 467 [M+]. ESI– MS: m/z 358
[M–], with higher mass “clusters” at m/z 665 and 972. MALDI-
TOF MS+: m/z 467 [M]+. MALDI-TOF MS–: m/z 359 [M–]. IR
viously reported.[8,9,15]
4.2. Reaction of [Pd(C6H4N=NC6H5)(µ-Cl)]2 (5)
(i) With AgPF6, Followed by 1,4,7-Trithiacyclononane (9S3): Solid
AgPF6 (86 mg, 0.34 mmol) was added, with stirring, to a suspen-
sion of 5 (100 mg, 0.15 mmol) in acetone (15 mL). Precipitation of
white AgCl occurred almost immediately as the solution gradually
changed from red to orange-yellow. After 1 h the solution was fil-
tered and 9S3 (56 mg, 0.31 mmol) was added to the filtrate. An
instantaneous colour change to deep red was observed. This mix-
ture was stirred for 1 h and then filtered to remove some insoluble
black solids. The dark red filtrate was evaporated to dryness and
the residue extracted with MeCN (10 mL) and filtered again. Ad-
dition of diethyl ether to the filtrate, followed by cooling at –30 °C
for 24 h, led to the formation of red orthorhombic crystals of
[(9S3)Pd(C6H4N=NC6H5)]PF6 (6A; 151 mg, 80%). Concentration
of the mother liquor and addition of diethyl ether gave a second
crop of 6A (25 mg, 13%) after 2 days at –30 °C. Diffraction-quality
crystals were obtained by the slow diffusion of diethyl ether into a
concentrated solution of complex 6A in acetone at –10 °C after
three days.
(KBr): ν = 3047 (w), 2976 (m), 2959 (w), 2909 (w), 1574 (s), 1551
˜
(w), 1481 (w), 1456 (w), 1445 (m), 1393 (s), 1316 (sh w), 1300 (m),
1258 (m), 1238 (m), 1217 (vw), 1200 (w), 1155 (w), 1109 (w), 1072
(w), 1040 (w), 1020 (w), 1001 (w), 891 (w), 829 (w), 814 (w), 764
(vs), 741 (m), 712 (w), 694 (s), 665 (w), 737 (vw), 611 (vw), 579
(vw), 550 (w), 523 (w), 494 (w), 440 (m) cm–1. C31H31Cl5N4Pd2S3
(945.92): calcd. C 39.4, H 3.3, N 5.9; found C 39.1, H 3.3, N 5.7.
(iii) With [(HMB)RuII{η3-tpdt}] (3): Complex
0.019 mmol) was added to stirred solution of
5
(12 mg,
a
3 (15 mg,
0.036 mmol) in methanol (10 mL). A gradual colour change from
red to brown occurred over 30 min. After stirring for 6 h, the solu-
tion was filtered to remove unreacted 5. NH4PF6 (20 mg,
0.12 mmol) was added and, after stirring for 15 min, the precipi-
tated brown solids were filtered. The brown product was then dis-
solved in MeCN (6 mL) and filtered to remove NH4Cl and the
excess NH4PF6. Addition of diethyl ether to the filtrate and subse-
quent cooling to –30 °C for 24 h gave brown needle-shaped crystals
of [{(HMB)RuII(µ-η2:η3-tpdt)}{Pd(C6H4N=NC6H5)}]PF6 (7;
26 mg, 85%).
Data for 6A: 1H NMR (300 MHz, CD3CN): δ = 8.18–8.15 (m, 1
H, Ph), 7.60 (unresolved m, 5 H, Ph), 7.47–7.31 (16-line m, 3 H,
Ph), 2.95–2.86 (8-line m, 6 H, SCH2), 3.08–2.98 (8-line m, 6 H,
SCH2) ppm. 13C NMR (300 MHz, CD3CN): δ = 165.1, 163.7,
154.3, 135.1, 133.9, 131.8, 131.7, 130.0, 127.6, 123.2 (all Ph),
33.9 ppm (SCH2). FAB+ MS: m/z 467 [M – PF6]+. FAB– MS: m/z
Data for 7: 1H NMR (400 MHz, CD3CN): δ = 8.00–7.99 (5-line m,
1 H, Ph), 7.76–7.74 (5-line m, 2 H, Ph), 7.63–7.61 (4-line m, 1 H,
Ph), 7.58–7.56 (5-line m, 3 H, Ph), 7.37–7.30 (11-line m, 2 H, Ph),
3.34–3.28 (6-line m, 1 H, SCH2), 3.13–3.06 (7-line m, 1 H, SCH2),
2.90–2.83 (5-line m, 1 H, SCH2), 2.71–2.65 (7-line m, 1 H, SCH2),
2.50–2.42 (8-line m, 1 H, SCH2), 2.27–2.15 (14-line m, 2 H, SCH2),
1.88–1.82 (8-line m, 1 H, SCH2), 2.11 (s, 18 H, C6Me6) ppm. 13C
NMR (400 MHz, CD3CN): δ = 166.0, 160.5, 152.3, 134.6, 133.6,
131.8, 131.4, 129.7, 127.4, 124.2 (all Ph), 101.6 (C6Me6), 45.5, 42.9,
34.0, 27.5 (all SCH2), 15.9 ppm (C6Me6). FAB+ MS: m/z 703 [M –
145 [PF ]–. IR (KBr): ν = 2960 (vw), 2936 (vw), 2860 (vw), 1635
˜
6
(w), 1485 (w), 1447 (w), 1432 (w), 1411 (w), 1394 (m), 1302 (w),
1239 (w), 1130 (vw), 1112 (vw), 1076 (vw), 1040 (vw), 869 (m), 839
[vs. (PF6)], 776 (s), 762 (m), 712 (m), 700 (m), 668 (vw), 557 [s
(PF6)], 375 (w) 354 cm–1. C18H21F6N2PPdS3 (612.96): calcd. C
35.3, H 3.5, N 4.6, S 15.7; found C 35.0, H 3.4, N 4.3, S 16.0.
PF6]+. FAB– MS: m/z 145 [PF ]–. IR (KBr): ν = 3040 (vw), 2956
˜
6
(ii) With 1,4,7-Trithiacyclononane (9S3): Dichloromethane (15 mL)
was added to a solid mixture of 5 (130 mg, 0.20 mmol) and 9S3
(72 mg, 0.40 mmol). A deep red solution was obtained almost im-
mediately. After stirring for 18 h, the solvent was removed in vacuo
and the product was extracted with MeOH (10 mL). The extracts
were filtered through a glass sinter (Por. 4) and the deep red filtrate
evacuated to dryness. The oily residue obtained was then recrystal-
lised from CHCl3 and hexane at room temperature to give
6B·CHCl3 as black needles (94 mg, 0.10 mmol, 100% based on 5)
after 3 days. Single crystals were obtained by layering a concen-
trated solution of this complex in non-dried chloroform with hex-
ane at room temperature. After 3 days, diffraction-quality black-
red needles of 6B·H2O and black needles of 6B·CHCl3 were ob-
tained. Another attempt to obtain single crystals from a solution
in MeCN/diethyl ether gave red crystals of 6B.
Data for 6B·CHCl3: 1H NMR (400 MHz, CDCl3 or 300 MHz,
CD2Cl2): δ = 8.12 (d, J = 7.2 Hz, 1 H, Ph), 7.85 (unresolved m, 4
H, Ph), 7.54 (unresolved m, 5 H, Ph), 7.43 (unresolved m, 3 H,
Ph), 7.32 (unresolved m, 2 H, Ph), 7.29–7.22 (unresolved m, 3 H,
Ph), 3.43 (br. s, υ1/2 = 70–100 Hz, 6 H, SCH2), 2.86 ppm (br. s,
υ1/2 = 70–100 Hz, 6 H, SCH2). These broad resonances shifted to
δ = 3.64 and 2.80 ppm, respectively, with a slight increase in CHCl3
content. A resonance at δ = 7.26 ppm (s, CHCl3) is clearly visible
in CD2Cl2 solution. 13C NMR (400 MHz, CDCl3): δ = 164.6,
133.9, 133.2, 131.6, 131.1, 130.2, 129.4, 127.9, 126.8, 125.2, 124.6,
122.6 (all Ph), 34.2 ppm (SCH2). A VT 1H NMR (298–193 K)
(vw), 2922 (w), 2853 (vw), 1459 (w), 1389 (m), 1304 (w), 1253 (w),
1236 (w), 1158 (vw), 1109 (w), 1072 (w), 1016 (w), 842 [vs. (PF6)],
772 (m), 712 (w), 693 (w), 558 [m (PF6)] cm–1.
C28H35F6N2PPdRuS3 (848.25): calcd. C 39.7, H 4.2, N 3.3, S 11.3;
found C 40.0, H 4.3, N 3.4, S 11.4.
(iv) With [Cp*RuIII{η3-tpdt}] (4): MeOH (10 mL) was added to a
mixture of 4 (20 mg, 0.051 mmol) and 5 (17 mg, 0.026 mmol). A
colour change from dark purple to dark brown was observed after
5 min. After stirring for 2 h, the solution was filtered through a
glass sinter (Por. 4) to remove some unreacted Pd complex 5.
NH4PF6 (25 mg, 0.15 mmol) was added to the dark brown filtrate
and, after stirring for 15 min, the reaction mixture was evacuated
to dryness. The residue was then extracted with MeCN (2ϫ3 mL)
and the extracts filtered through a Por. 4 glass sinter. Diethyl ether
was added to the filtrate to give a dark brown solid after 24 h at
–30 °C. This solid was further purified by recrystallization from
MeCN/diethyl ether to give [{Cp*RuIII(µ-η2:η3-tpdt)}2Pd](PF6)2
(8; 26 mg, 80%) as a black crystalline solid.
Data for 8: 1H NMR (300 MHz, CD3CN): δ = 3.03 (br. s, 8 H,
SCH2), 2.74–2.66 (6-line m, 8 H, SCH2), 1.77 ppm (s, 30 H,
C5Me5). FAB+ MS: m/z 1028 [M – PF6 + H]+, 883 [M – 2PF6 +
H]+, 827 [M – PF6 – 4CH2]+. FAB– MS: m/z 145 [PF6]–.
4.3. Reaction of [(9S3)Pd(C6H4N=NC6H5)]PF6 (6A)
(i) With 3: A mixture of 6A (23 mg, 0.038 mmol) and 3 (16 mg,
0.039 mmol) in MeOH (8 mL) was stirred for 1 h to give a brown
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R. Y. C. Shin, C. L. Goh, L. Y. Goh, R. D. Webster, Y. Li
FULL PAPER
solid. The reaction mixture was then concentrated to half volume
and the brown solid was filtered off and washed with MeOH
(2ϫ3 mL). It was then recrystallised from MeCN/diethyl ether to
give brown needle-shaped crystals of 7 (24 mg, 75% yield) after
12 h at –30 °C.
pancy ratio). There is also one diethyl ether molecule present as
space filling solvent in complex 7.
Crystal and refinement data are summarized in Table 4. The Ortep
drawings and packing diagrams were plotted using SHELX/XP.
The short atom–atom contact distances were calculated using
MERCURY (CCDC, UK).
(ii) With 4: A mixture of 6A (16 mg, 0.026 mmol) and 4 (10 mg,
0.026 mmol) in MeOH (8 mL) was stirred for 2 h. The reaction
mixture was then filtered to remove some insoluble blackish solid.
The solvent was removed from the filtrate under vacuum and re-
placed by MeCN. Layering the solution with diethyl ether gave
black orthorhombic crystals of 8 (11 mg, 73% yield) after 1 week
at –30 °C.
CCDC-714923 (for 6A), -714924 (for 6B), -714925 (for 6B·H2O),
-714926 (for 6B·CHCl3), -714927 (for 7) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
4.5. Electrochemistry: Voltammetric experiments were conducted
with a computer-controlled Eco Chemie µAutolab III potentiostat
with a 1-mm diameter glassy carbon (GC) and Pt working elec-
trodes. Potentials were referenced to the ferrocene/ferrocenium (Fc/
Fc+) redox couple, which was added as an internal standard at the
end of the electrochemical experiments. The electrochemical cell
was jacketed in a glass sleeve and cooled to between 243–293 K
using a Lauda RL6 variable-temperature methanol-circulating
bath.
4.4. X-ray Crystal Structure Determinations: The crystals were
mounted on glass fibres and X-ray data were collected on a Bruker
AXS SMART APEX CCD diffractometer (for 6A and 7) or Bruker
X8 CCD diffractometer (for 6B, 6B·H2O, 6B·CHCl3) using Mo-Kα
radiation (graphite monochromator, λ = 0.71073 Å) at 223 and
173 K, respectively. SAINT[16] was used for integration of the inten-
sity of reflections and scaling; SADABS[17] was used for absorption
correction.
The structures were solved by direct methods to locate the heavy
atoms, and refined by full-matrix least-squares against F2 using
SHELXL-97.[18] All non-hydrogen atoms were refined anisotropi-
cally, whereas hydrogen atoms were introduced at calculated posi-
tions and refined riding on their carrier atoms. The asymmetric
unit of the crystal of 7 contains one cation which shows disorder
in the ethylene carbons (C3–C4) of the tpdt ligand (60:40 occu-
Supporting Information (see footnote on the first page of this arti-
cle): Tables S1–S4 list selected atom–atom contact distances (ob-
tained by the MERCURY software) in the crystal lattices of 6A,
6B, 6B·H2O and 6B·CHCl3, respectively. Figures S1–S4 show the
packing diagrams (in color) of 6A, 6B, 6B·H2O and 6B·CHCl3,
respectively, viewed along selected axes. Figure S5 shows the cyclic
voltammograms of 6B.
Table 4. Data collection and processing parameters.
6A
6B
6B·H2O
6B·CHCl3
7
Formula
Mr
Temperature [K]
C18H21F6N2PPdS3 C30H30Cl2N4Pd2S3
C30H32Cl2N4OPd2S3
844.48
173(2)
C31H31Cl5N4Pd2S3
945.83
173(2)
C32H45F6N2OPPdRuS3
922.32
223(2)
612.92
223(2)
826.46
173(2)
Crystal color and habit
red, orthorhombic red blocks
black red, needle
0.30ϫ0.10ϫ0.05
triclinic
black needles
0.30ϫ0.04ϫ0.03
monoclinic
P21/n
brown, cuboid
0.40ϫ0.10ϫ0.08
orthorhombic
Pna2(1)
Crystal size [mm3]
0.18ϫ0.16ϫ0.10
0.12ϫ0.10ϫ0.10
Crystal system
Space group
triclinic
P1
triclinic
P1
¯
¯
¯
P1
a [Å]
b [Å]
c [Å]
α [°]
9.4590(4)
10.7392(4)
12.1331(5)
71.8760(10)
89.6170(10)
72.8130(10)
1114.11(8)
2
11.5311(5)
11.6861(6)
13.1943(6)
80.782(3)
74.533(2)
63.970(2)
1537.86(12)
2
10.1248(3)
10.6328(3)
15.1670(4)
99.796(2)
90.060(2)
95.750(2)
1600.63(8)
2
1.752
1.518
844
18.8678(13)
10.0045(6)
20.5907(15)
90
115.678(2)
90
3502.9(4)
4
1.793
1.617
18.4238(11)
21.5491(13)
9.1320(6)
90
90
90
3625.6(4)
4
β [°]
γ [°]
V [Å3]
Z
Density [gcm–3]
Absorption coeff. [mm–1]
F(000)
1.827
1.245
612
1.785
1.575
824
1.690
1.190
1864
1880
θ range for data collection
Index ranges
1.77 to 27.50
–12 Յ h Յ 12
–13 Յ k Յ 13
–15 Յ l Յ 15
14667
1.60 to 27.83
–15 Յ h Յ 14
15 Յ k Յ 15
–17 Յ l Յ 17
27245
2.46 to 31.19
–14 Յ h Յ 14
–15 Յ k Յ 15
–22 Յ l Յ 22
63438
1.22 to 26.41
–23 Յ h Յ 23
12 Յ k Յ 12
–25 Յ l Յ 25
36584
1.45 to 27.50
–23 Յ h Յ 23
–28 Յ k Յ 28
–11 Յ l Յ 11
46172
Number of reflections collected
Independent reflections
5103
7182
10335
7196
8321
Max. and min. transmission
0.8856 and 0.8070 0.8584 and 0.8335
0.9280 and 0.6588
10335/2/387
R1 = 0.0242
wR2 = 0.0549
R1 = 0.0341
wR2 = 0.0592
1.030
0.9531 and 0.6426
7196/0/406
R1 = 0.0617
wR2 = 0.1661
R1 = 0.0884
wR2 = 0.1897
1.124
0.9108 and 0.6476
8321/7/430
R1 = 0.0585
wR2 = 0.1353
R1 = 0.0624
wR2 = 0.1377
1.173
Number of data/restraints/params. 5103/0/348
7182/0/370
Final R indices [I Ͼ 2σ(I)][a,b]
R1 = 0.0317
wR2 = 0.0753
R1 = 0.0339
wR2 = 0.0765
1.064
R1 = 0.0439
wR2 = 0.1184
R1 = 0.0689
wR2 = 0.1461
1.123
R Indices (all data)
Goodness-of-fit on F2[c]
Largest diff. peak and hole [eÅ–3] 0.820 and –0.486
2.961 and –1.673
1.201 and –0.528
2.237 and –1.447
3.461 and –0.856
[a] R = (Σ|Fo| – |Fc|)Σ|Fo|. [b] wR2 = [(Σω|Fo| – |Fc|)2/Σω|Fo|2]1/2. [c] GoF = [(Σω|Fo| – |Fc|)2/(Nobs – Nparam)]1/2
2292 Eur. J. Inorg. Chem. 2009, 2282–2293
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Cyclometallated (Azobenzene)palladium(II) Complex
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Acknowledgments
We thank the National University of Singapore for a grant (R143-
000-209-112) to L. Y. G., a research graduate scholarship to
R. Y. C. S., and support for G. C. L. (Honours Year Project), and
Dr. L. L. Koh, Ms. G. K. Tan and Ms. E. L. Goh for technical
assistance. Support from the Nanyang Technological University is
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Received: January 15, 2009
Published Online: April 20, 2009
Eur. J. Inorg. Chem. 2009, 2282–2293
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2293