Square planar nickel(II) complexes with halogenated o- diiminobenzosemiquinonato ligation: Synthesis, characterization, and redox property

Article abstract of DOI:10.1002/cjoc.201300664

Seven square planar bis(o-diiminobenzosemiquinonato)nickel(II) complexes, [Ni(o-C₆H₄(NH)(NAr))₂] (Ar=Mes, 1; p-F-C ₆H₄, 2; p-Cl-C₆H₄, 3), [Ni(o-4,5-F₂-C₆H₂(NH)(NPh))₂] (4), and [Ni(o-4,5-Cl₂-C₆H₂(NH)(NAr))₂] (Ar=Ph, 5; 2,6-F₂-C₆H₃, 6; 2,6-Cl ₂-C₆H₃, 7), have been synthesized and characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR, IR, UV-Vis-NIR, elemental analyses, HRMS, as well as single-crystal X-ray diffraction studies (1 and 7). The cyclic voltammograms of these complexes exhibit two reversible redox processes of [NiL₂]^0/1- and [NiL₂]^1-/2-, and one irreversible process of [NiL ₂]^0/2+. Substituent effects on the redox properties of these complexes, in addition with those of the known complexes [Ni(o-C ₆H₄(NH)(NPh))₂] (8) and [Ni(o-3,5-Bu ^t₂-C₆H₂(NH)₂) ₂] (9), are identified by comparing the half-wave potentials of the reduction waves, as 1≈9<8≈2<3<4<5<7<6, reflecting the ease of reduction of [NiL₂] parallels the electron-donating and -withdrawing ability of the substituent group. Reduction of 1 with one or two equivalents of sodium metal in THF has led to the isolation of [Na(THF) ₃][1] and [Na(THF)₃]₂[1]. The structure data of these two complexes revealed by low-temperature X-ray crystallography suggest their corresponding electronic structures of [Ni^II(¹L ^·1-)(¹L^2-)]^1- and [Ni ^II(¹L^2-)²]^2-, which are in line with those of [9]ⁿ (n=1-, 2-) suggested by spectroelectrochemical study. Copyright

Full text of DOI:10.1002/cjoc.201300664

FULL PAPER
DOI: 10.1002/cjoc.201300664
Square Planar Nickel(II) Complexes with Halogenated
o-Diiminobenzosemiquinonato Ligation: Synthesis,
Characterization, and Redox Property
Wansheng Zuo,a Long Zhang,b Meihua Xie,*,a and Liang Deng*,b
a Anhui Key Laboratory of Molecular Based Materials, College of Chemistry and Materials Science,
Anhui Normal University, Wuhu, Anhui 241000, China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, China
Seven square planar bis(o-diiminobenzosemiquinonato)nickel(II) complexes, [Ni(o-C6H4(NH)(NAr))2] (Ar＝
Mes, 1; p-F-C6H4, 2; p-Cl-C6H4, 3), [Ni(o-4,5-F2-C6H2(NH)(NPh))2] (4), and [Ni(o-4,5-Cl2-C6H2(NH)(NAr))2] (Ar
1
＝Ph, 5; 2,6-F2-C6H3, 6; 2,6-Cl2-C6H3, 7), have been synthesized and characterized by H NMR, 13C NMR, 19F
NMR, IR, UV-Vis-NIR, elemental analyses, HRMS, as well as single-crystal X-ray diffraction studies (1 and 7).
The cyclic voltammograms of these complexes exhibit two reversible redox processes of [NiL2]0/1− and [NiL2]1−/2−
,
and one irreversible process of [NiL2]0/2＋. Substituent effects on the redox properties of these complexes, in addi-
tion with those of the known complexes [Ni(o-C6H4(NH)(NPh))2] (8) and [Ni(o-3,5-But2-C6H2(NH)2)2] (9), are
identified by comparing the half-wave potentials of the reduction waves, as 1≈9＜8≈2＜3＜4＜5＜7＜6, reflect-
ing the ease of reduction of [NiL2] parallels the electron-donating and -withdrawing ability of the substituent group.
Reduction of 1 with one or two equivalents of sodium metal in THF has led to the isolation of [Na(THF)3][1] and
[Na(THF)3]2[1]. The structure data of these two complexes revealed by low-temperature X-ray crystallography
suggest their corresponding electronic structures of [NiII(1L•1−)(1L2−)]1− and [NiII(1L2−)2]2−, which are in line with
those of [9]n (n＝1−, 2−) suggested by spectroelectrochemical study.
Keywords benzosemiquinonate, nickel, redox property, redox active, substituent effect
using iridium-amidophenolate complexes,[25,26] homoly-
sis of O2 and aerobic alcohol oxidation catalyzed by
oxorhenium-catecholates,[27,28] and cross-coupling of
alkylzinc reagents with alkylhalides with the mediation
of cobalt-amidophenolate compounds.[29,30]
Introduction
Catecholates and their structure analogs with nitro-
gen donor atoms are among the prototype of redox-ac-
tive ligands (Chart 1), and their transition metal chemis-
try has been subjected to extensive study for more than
half a century.[1-10] While early studies on these com-
plexes had been intrigued by their unique redox property
of multiple sequential single-electron transfer proc-
esses,[11-14] further investigations were spurred by the
difficulty of assigning the oxidation states of the metal
center and the ligand because of the presence of redox-
innocent ligands.[1-6] Later, this challenge was resolved
by Wieghardt and Neese et al.[15-22] Upon systematic
spectroscopic and theoretical investigations, they
pointed out the oxidation level of these bidentate ligands
in a complex could be reasoned from high-quality,
low-temperature X-ray crystallography data.[23] Recently,
redox-active ligands have also found applications in
catalysis.[8-10,24] Representative works using these bi-
dentate redox-active ligands include oxidation of H2
X -
X-
X -
X
X
-1e-
-1e-
+1e-
+1e-
X
( X = O, NR)
Chart 1 Redox processes of catecholate and its analogs.
As redox chemistry is the basis on which many
chemical transformations can operate, understanding
factors affecting the redox properties of redox-active
ligands is the necessity of effective catalyst design. Ap-
parently, the electronic property of substitutents on
ligand backbones is among most significant ones. Stud-
ies on catecholate complexes [Ru(acac)2(catecho-
lato)]n[31] and [(Tp)Mo(O)(catecholato)][32] have shown
that the ease of reduction of a given series of complexes
*
E-mail: deng@sioc.ac.cn; Tel.: 0086-021-54925460; Fax: 0086-021-54925460
Received September 2, 2013; accepted September 27, 2013; published online November 4, 2013.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201.00664 or from the author.
Chin. J. Chem. 2013, 31, 1473—1482
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Zuo et al.
FULL PAPER
parallels the electron-donating and -withdrawing ability
of the substituents on the catecholato ligands. Similar
situation could be expected for o-diiminophenolato
ligands, but this conclusion could not be drawn yet be-
cause o-diiminobenzoquinones are always too unstable
to permit measurement,[14] and only a limited number of
o-diiminophenolato complexes with structural resem-
blance are known.[11-22,33-35] Aiming to bring a broad
view on the substituent effects on the redox properties of
o-diiminophenolato ligands, we choose square planar
bis(o-diiminobenzosemiquinonato)nickel complexes as
the platforms because Wieghardt and Neese’s studies
have revealed the single-electron redox processes of
these complexes are mainly ligand-centered.[17-19] In this
regard, we report herein the synthesis, characterization,
and redox property of a series of square planar bis(o-di-
iminobenzosemiquinonato)nickel(II) complexes (1－7
in Chart 2) featuring halogenated diiminobenzosemi-
quinonato backbone and/or halogenated phenyl sub-
stituents on the imino nitrogen. The voltammetry data of
these complexes, in addition with those of the alkyl sub-
stituted complexes reported by Holm and Wieghardt (8
－11 in Chart 2),[14,18] enable us to evaluate substituent
effects on the redox properties of o-diiminophenolato
ligands. Also achieved in this study are the isolation and
structural characterization of two anionic compounds
[Na(THF)3][1] and [Na(THF)3]2[1], which represent the
first structural characterizations for the anionic species
in the [NiL2]n (L＝o-diiminophenolato ligands, n＝2＋,
1＋, 0, 1−, 2−) family as shown below.
chemicals were purchased from either Strem or J&K
Chemical Co. and used as received unless otherwise
1
noted. H NMR, 13C NMR, 19F NMR spectra were re-
corded on a VARIAN Mercury 300 or 400 MHz spec-
trometer. Chemical shifts (δ) were reported with refer-
ences to the residual protons of the deuterated solvents
for proton chemical shifts, the 13C of deuterated solvents
for carbon chemical shifts, and the 19F of the CF3COOH.
Mass spectra were recorded with a Waters Miscromas
GCT instruments for EI-MS, and IonSpec 4.7 Tesla
FTMS for MALDI/DHB. Elemental analysis was per-
formed by the Analytical Laboratory of Shanghai Insti-
tute of Organic Chemistry (CAS). Infrared spectra were
obtained from KBr pellets on a Perkin-Elmer 1600 Fou-
rier transform spectrometer. Electronic spectra were re-
corded with a Shimadzu UV-3600 UV-vis spectro-
photometer. Magnetic moments were measured at 23 ℃
by the method originally described by Evans with stock
and experimental solutions containing a known amount
of a (CH3)3SiOSi(CH3)3 standard.[44] Cyclic voltam-
metry measurements were made with a CHI 600D po-
tentiostation in THF solutions using a glassy carbon
working electrode, 0.1 mol/L (Bu4N)(PF6) supporting
electrolyte, and a SCE reference electrode. Under these
＋
conditions, E1/2＝0.55 V for the [Cp2Fe]0,1 couple.
Preparation of 4,5-dichloro-2-(2',6'-difluoroanilido)-
nitrobenzene
To a mixture of 4,5-dichloro-2-fluoronitrobenzene
(5.00 g, 23.8 mmol) and 2,6-difluoroaniline (5.1 mL,
47.6 mmol) cooled in ice bath was added sodium
tert-butoxide (4.60 g, 47.6 mmol). After stirred for 12 h
at this temperature, the reaction mixture was raised to
room temperature, and then quenched with water (200
mL). The organic phase was extracted with dichloro-
methane (100 mL×3), and dried with anhydrous so-
dium sulfate. After filtration, removal of all the volatiles
under vacumm, and washed with ethanol, 4,5-dichloro-
2-(2',6'-difluoroanilido)-nitrobenzene was obtained as an
H
N
Ar
N
Ar = Mes, 1;
Ni
Ni
Ni
Ar = p-F-C6H4, 2;
Ar = p-Cl-C6H4, 3
N
N
H
Ar
H
N
Ar
N
X = F, Ar = Ph, 4;
X = Cl, Ar = Ph, 5;
X = Cl, Ar = 2,6-F2-C6H3, 6;
X = Cl, Ar = 2,6-Cl2-C6H3, 7
X
X
X
X
N
N
H
Ar
1
orange solid. Yield 4.6 g, 60%. H NMR (CDCl3, 400
H
N
Ph
N
MHz) δ: 8.97 (br, 1H, NH), 8.32 (s, 1H, ArCH), 7.36－
7.26 (m, 1H, ArCH), 7.10－7.06 (m, 2H, ArCH), 6.80－
6.78 (m, 1H, ArCH); 13C NMR (CDCl3, 100 MHz) δ:
158.1 (dd, J＝250.6, 3.8 Hz), 140.9 (d, J＝9.6 Hz),
132.1, 128.1 (t, J＝9.6 Hz), 127.3, 121.7, 116.9 (t, J＝
1.8 Hz), 114.6 (t, J＝15.8 Hz), 112.4 (m). 19F NMR
(CDCl3, 282 MHz) δ: −117.7 (m). HRMS (EI) calcd for
C12H6Cl2F2N2O2 317.9774, found 317.9778.
8
N
N
H
Ph
R
H
N
H
N
R'
R = R' = Bu-t, 9;
R = R' = H, 10;
Ni
R'
N
H
N
H
R = H, R' = Pr-i, 11
R
Chart 2 Square planar bis(o-diiminobenzosemiquinonato)-
Preparation of 4,5-dichloro-2-(2',6'-dichloroanilido)-
nitrobenzene
nickel(II) complexes.
This compound was prepared using similar proce-
dures as described for 4,5-dichloro-2-(2',6'-difluoroani-
lido)nitrobenzene, from the reaction of 4,5-dichloro-2-
fluoronitrobenzene (5.00 g, 23.8 mmol), 2,6-dichloro-
aniline (7.70 g, 47.6 mmol), and sodium tert-butoxide
(4.60 g, 47.6 mmol). Yield 4.2 g, 50%. 1H NMR (CDCl3,
400 MHz) δ: 9.19 (br, 1H, NH), 8.35 (s, 1H, ArCH),
Experimental
General procedures
2-Nitrodiphenylamines[42,43] and the substituted
1
5
2-aminodiphenylamine ligands, H2 L to H2 L[36,37] were
6
prepared according to literature methods. Ligands H2 L
7
and H2 L were obtained using similar procedures. All
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Square Planar Nickel(II) Complexes with Halogenated o-Diiminobenzosemiquinonato Ligation
1
7.49 (d, J＝6.3 Hz, 2H, ArCH), 7.30 (t, J＝6.0 Hz, 1H,
ArCH), 6.53 (s, 1H, ArCH); 13C NMR (CDCl3, 75 MHz)
δ: 140.8, 140.7, 134.2, 132.5, 131.7, 129.2, 129.1, 127.5,
121.6, 116.8. HRMS (EI) calcd for C12H6Cl4N2O2
349.9183, found 349.9182.
as blue crystals. Yield 330 mg, 66%. H NMR (C6D6,
300 MHz) δ: 6.88 (s, 2H, ArCH), 6.37－6.28 (m, 4H,
ArCH), 6.00 (br, 1H, NH), 2.28 (s, 6H, o-Mes-CH3),
2.21 (s, 3H, p-Mes-CH3); 13C NMR (CDCl3, 75 MHz) δ:
154.7, 154.1, 144.3, 135.4, 134.9, 128.2, 123.0, 122.7,
118.1, 115.3, 21.1, 18.4; IR (KBr): υN H＝3334 (m)
－
cm−1. HRMS (EI) calcd for C30H32N4Ni 506.1980,
found 506.1984. Anal. calcd for C30H32N4Ni: C 71.03, H
6.36, N 11.04; found C 71.22, H 6.39, N 11.07.
Preparation of N-(2',6'-difluorophenyl)-4,5-dichloro-
1,2-phenylenediamine (H2 L)
6
To a mixture of 4,5-dichloro-2-(2',6'-difluoroani-
lido)nitrobenzene (12.7 g, 40.0 mmol) and Pd/C (5 wt%,
0.15 g) in THF (100 mL) was added sodium boro-
hydride (5.90 g, 156 mmol) in portions under stirring.
When the bubble-releasing process ceased, methanol (50
mL) was then added slowly to the mixture. The reaction
mixture was kept stirring until its color faded to gray.
After filtrated through a celite pad, then removal of
volatiles, the red residue was further treated with an
aqueous ammonium chloride solution (100 mL, 6.8
mol/L), and extracted with dichloromethane (70 mL×3).
The dichloromethane phase was separated and dried
with sodium sulfate. Removal of all the solvent gave the
Synthesis of [Ni(o-C6H4(NH)(NC6H4-p-F))2] (2)
This complex was prepared using procedures similar
to those of 1 by the reaction of o-C6H4(NH2)(NHC6H4-
2
p-F) (H2 L) (404 mg, 2.00 mmol) with NiCl2•6H2O (240
mg, 1.00 mmol) in aqueous ammoniacal solution in air.
Yield 270 mg, 60%. 1H NMR (CDCl3, 300 MHz) δ: 7.60
－7.56 (m, 2H, ArCH), 7.25－7.19 (m, 2H, ArCH), 6.70
－6.63 (m, 4H, ArCH), 6.00 (br, 1H, NH); 13C NMR
(CDCl3, 100 MHz) δ: 158.3 (d, J＝241.7 Hz), 152.1,
142.7, 126.8, 126.8, 121.1 (d, J＝25.5 Hz), 116.3, 113.5,
112.5 (d, J＝21.4 Hz); 19F NMR (CDCl3, 282 MHz) δ:
1
−117.3 (m); IR (KBr): υN H＝3352 (m) cm−1. HRMS
product as a red solid. Yield 11.5 g, 99%. H NMR
－
(CDCl3, 400 MHz) δ: 6.98－6.92 (m, 3H, ArCH), 6.83
(s, 1H, ArCH), 6.72 (s, 1H, ArCH), 5.10 (br, 1H, NH),
3.79 (br, 2H, NH2); 13C NMR (CDCl3, 100 MHz) δ:
155.3 (dd, J＝245.1, 4.8 Hz), 137.8, 130.9, 125.8, 122.6
(m), 121.7, 120.1 (t, J＝13.3 Hz), 119.5 (t, J＝1.9 Hz),
116.9, 111.9 (m); 19F NMR (CDCl3, 376 MHz) δ:
−123.0 (m). HRMS (EI) calcd for C12H8Cl2F2N2
289.0111, found 289.0108.
(EI) calcd for C24H18F2N4Ni 458.0853, found 458.0855.
Anal. calcd for C24H18F2N4Ni: C 62.79, H 3.95, N 12.20;
found C 62.75, H 4.24, N 12.21.
Synthesis of [Ni(o-C6H4(NH)(NC6H4-p-Cl))2] (3)
This complex was prepared using procedures similar
to those of 1 by the reaction of o-C6H4(NH2)(NHC6H4-
3
p-Cl) (H2 L) (500 mg, 2.00 mmol) with NiCl2•6H2O
(240 mg, 1.00 mmol) in aqueous ammoniacal solution in
air. Yield 200 mg, 41%; 1H NMR (300 MHz, CDCl3) δ:
7.58－7.49 (m, 4H, ArCH), 6.74－6.66 (m, 4H, ArCH),
6.01 (br, 1H, NH); 13C NMR (100 MHz, CDCl3) δ:
154.8, 154.1, 147.9, 131.5, 129.2, 128.3, 123.8, 123.6,
118.9, 115.9; IR (KBr): υN−H＝3344 (m) cm−1. HRMS
(EI) calcd for C24H18Cl2N4Ni 490.0262, found 490.0264.
Anal. calcd for C24H18Cl2N4Ni: C 58.59, H 3.69, N
11.39; found C 59.19, H 4.05, N 11.52.
Preparation of N-(2',6'-dichlorophenyl)-4,5-dichloro-
7
1,2-phenylenediamine (H2 L)
This compound was obtained as a red solid using
similar procedures described for N-(2',6'-dichlorophe-
nyl)-4,5-dichloro-1,2-phenylenediamine, from the reac-
tion
of
4,5-dichloro-2-(2',6'-dichloroanilido)nitro-
benzene (14.0 g, 40.0 mmol) with Pd/C (5 wt%, 0.15 g),
and sodium borohydride (5.90 g, 156 mmol) in metha-
1
nol (50 mL). Yield 8.80 g, 99%. H NMR (CDCl3, 300
MHz) δ: 7.34 (d, J＝8.1 Hz, 2H, ArCH), 7.01 (t, J＝8.1
Hz, 1H, ArCH), 6.85 (s, 1H, ArCH), 6.51 (s, 1H, ArCH),
5.36 (br, 1H, NH), 3.69 (br, 2H, NH2); 13C NMR (CDCl3,
75 MHz) δ: 138.6, 137.4, 130.5, 128.9, 128.6, 126.2,
124.4, 121.2, 120.5, 116.6. HRMS calcd for C12H8Cl4N2
322.9490, found 322.9479.
Synthesis of [Ni(4,5-F2-o-C6H4(NH)(NPh))2] (4)
4
To a solution of 4,5-F2-o-C6H4(NH2)(NHPh) (H2 L)
(220 mg, 1.00 mmol) in THF (5 mL) was added n-BuLi
(1.6 mol/L in hexane, 1.2 mL, 2.00 mmol) at –78 ℃.
The mixture was further stirred for 30 min, then a sus-
pension of NiCl2(DME) (110 mg, 0.5 mmol) in THF (5
mL) was added. The mixture was warmed to room tem-
perature and stirred overnight to give a brown solution.
After passing a stream of pure oxygen through the solu-
tion for 30 min, and removal of solvents by vacuo, the
blue residue was repeatedly extracted with diethyl ether
(10 mL×3). The ether phase was combined and filtrated.
Complex 4 was isolated as blue crystals by standing the
ether solution at room temperature overnight. Yield 120
mg, 48%. 1H NMR (CDCl3, 400 MHz) δ: 7.55－7.52 (m,
5H, ArCH), 6.47－6.36 (m, 2H, ArCH), 5.75 (br, 1H,
NH); 13C NMR (CDCl3, 100 MHz) δ: 162.5, 160.0,
Synthesis of [Ni(o-C6H4(NH)(NMes))2] (1)
1
To a solution of o-C6H4(NH2)(NHMes) (H2 L) (452
mg, 2 mmol) in water/ethanol mixture (1∶1 vol, 30 mL)
was added NiCl2•6H2O (240 mg, 1.0 mmol) and aque-
ous NH3 (25%, 2 mL) at room temperature. The resul-
tant blue mixture was heated to 70 ℃ in air for 3 h, and
then cooled down to room temperature to give dark blue
microcrystalline precipitate. The blue solid was col-
lected by filtration, washed with cold water (20 mL) and
ethanol (20 mL), and then dried in vacuo. After recrys-
tallization from CH2Cl2, the final product was obtained
Chin. J. Chem. 2013, 31, 1473—1482
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Zuo et al.
FULL PAPER
Synthesis of [Na(THF)3][Ni(o-C6H4(NH)(NMes))2]
155.0, 154.8, 151.6, 150.4 (m), 149.1, 148.8, 148.9,
147.9, 128.6, 128.4, 127.8, 126.7 (m), 116.8, 116.7,
112.4, 112.3, 102.4 (m). Attempts to assigning the 13C
NMR have not been made; 19F NMR (CDCl3, 282 MHz)
([Na(THF)3][1])
To a solution of 1 (122 mg, 0.24 mmol) in THF was
added Na (7.0 mg, 0.3 mmol) at room temperature, the
resulting mixture was stirred for 2 d. The mixture was
filtered and the solvent was concentrated for about 5 mL.
Layering n-hexane (15 mL) on the green solution af-
forded the product as green crystals. Yield 106 mg, 60%.
Magnetic susceptibility (d8-THF): μeff＝1.8(3) μB; IR
δ: −138.9 (m), −139.3 (m); IR (KBr): υN H＝3358 (m)
－
cm−1. HRMS (EI) calcd for C24H16F4N4Ni 494.0665,
found 494.0663. Anal. calcd for C24H16F4N4Ni: C 58.22,
H 3.26, N 11.32; found C 57.42, H 3.55, N 10.84.
(KBr): υN H＝3333 (m) cm−1. Anal. calcd for C42H56N4-
Synthesis of [Ni(4,5-Cl2-o-C6H4(NH)(NPh))2] (5)
－
NaNiO3: C 67.57, H 7.56, N 7.50; found C 66.68, H
7.11, N 7.94.
This complex was prepared using procedures similar
to those of 1 by the reaction of 4,5-Cl2-o-C6H4(NH2)-
5
(NHPh) (H2 L) (380 mg, 1.50 mmol) with NiCl2•6H2O
Synthesis of [Na(THF)3]2[Ni(o-C6H4(NH)(NMes))2]
([Na(THF)3]2[1])
(180 mg, 0.75 mmol) in aqueous ammoniacal solution in
air. Yield 130 mg, 30%; 1H NMR (CDCl3, 400 MHz) δ:
7.57－7.53 (m, 5H, ArCH), 6.81 (s, 1H, ArCH), 6.73 (s,
1H, ArCH), 5.89 (br, 1H, NH); 13C NMR (CDCl3, 100
MHz) δ: 153.0, 152.8, 148.4, 128.7, 127.9, 127.8, 127.8,
To a solution of 1 (122 mg, 0.24 mmol) in THF was
added Na (14.0 mg, 0.6 mmol) at room temperature, the
resulting mixture was stirred for 2 d. The mixture was
filtered and the solvent was concentrated for about 5 mL.
Layering n-hexane (15 mL) on the brown solution af-
forded the product as pale brown crystals. Yield 98.0 mg,
126.9, 118.1, 115.9; IR (KBr): υN H＝3350 (m) cm−1.
－
MALDI-FTMS HRMS (DHB) calcd for C24H16Cl4N4Ni
557.9483, found 557.9477. Anal. calcd for C24H16Cl4-
N4Ni: C 51.39, H 2.88, N 9.99; found C 52.32, H 3.16,
N 9.67.
1
42%. H NMR (d8-THF, 400 MHz) δ: 6.82－6.77 (m,
2H), 6.31－6.28 (m, 1H), 5.73－5.59 (m, 2H), 5.29－
5.12 (m, 1H), 2.71 (br, 1H), 2.47 (s, 3H), 2.41 (s, 3H),
2.17 (s, 3H); 13C NMR (d8-THF, 100 MHz) δ: 157.1,
151.6, 150.9, 148.6, 146.2, 136.2, 135.9, 130.5, 130.3,
128.9, 128.3, 127.1, 126. 6, 123.5, 112.3, 109.9, 109.1,
107.9, 106.3, 105.6, 67.2, 25.4, 20.2, 18.4, 18.2; IR
Synthesis of [Ni(4,5-Cl2-o-C6H4(NH)(NC6H3-2',6'-
F2))2] (6)
This complex was prepared using procedures similar
to those of 1 by the reaction of 4,5-Cl2-o-C6H4(NH2)-
＝ 3333 (m) cm−1. Anal. calcd for
6
(KBr): υN
－
H
(NHC6H3-2',6'-F2) (H2 L) (280 mg, 1.00 mmol) with
C54H80N4Na2NiO6: C 65.78, H 8.18, N 5.68; found C
65.21, H 7.94, N 6.02.
NiCl2•6H2O (120 mg, 0.50 mmol) in aqueous ammo-
1
niacal solution in air. Yield 94 mg, 30%. H NMR
(CD2Cl2, 300 MHz) δ: 7.57－7.53 (m, 1H, ArCH), 7.26
－7.21 (m, 2H), 6.89 (s, 1H, CH), 6.58 (s, 1H, CH),
6.26 (br, 1H, NH); 13C NMR (CD2Cl2, 100 MHz) δ:
162.1, 159.7, 154.8, 154.5, 145.4, 129.4, 129.4, 123.7,
123.7, 118.7, 116.0, 115.1, 114.9, 110.0; 19F NMR
X-ray structure determinations
The structures of the four compounds in Table 1
were determined. Diffraction-quality crystals were ob-
tained as 1 in CH2Cl2 and 7•0.5toluene in THF/toulene.
Crystallizations were performed at room temperature.
Crystals were coated with Paratone-N oil and mounted
on a Bruker APEX CCD-based diffractometer equipped
with an Oxford low-temperature apparatus. Data were
collected with scans of 0.3 s/frame for 30 s. Cell pa-
rameters were retrieved with SMART software and re-
fined using SAINT software on all reflections. Data in-
tegration was performed with SAINT, which corrects for
Lorentz polarization and decay. Absorption corrections
were applied using SADABS.[45] Space groups were
assigned unambiguously by analysis of symmetry and
systematic absences determined by XPREP. All struc-
tures were solved and refined using SHELXTL.[46]
Metal and first coordination sphere atoms were located
from direct-methods E-maps; other non-hydrogen atoms
were found in alternating difference Fourier synthesis
and least-squares refinement cycles and during final
cycles were refined anisotropically. Hydrogen atoms
were placed in calculated positions employing a riding
model. Final crystal parameters and agreement factors
are reported in Table 1. CIF files giving X-ray crystallo-
graphic data for 1, [Na(THF)3][1], [Na(THF)3]2[1], and
(CD2Cl2, 282 MHz) δ: −116.3 (m); IR (KBr): υN
＝
－
H
3344 (m) cm−1. MALDI-FTMS HRMS (DHB) calcd for
C24H12Cl4F4N4Ni 629.9106, found 629.9102. Anal.
calcd for C24H12Cl4F4N4Ni: C 45.55, H 1.91, N 8.85;
found C 46.24, H 2.20, N 9.24.
Synthesis of [Ni(4,5-Cl2-o-C6H4(NH)(NC6H3-2',6'-
Cl2))2] (7)
This complex was prepared using procedures similar
to those of 1 by the reaction of 4,5-Cl2-o-C6H4(NH2)-
7
(NHC6H3-2',6'-Cl2) (H2 L) (320 mg, 1.00 mmol) with
NiCl2•6H2O (120 mg, 0.50 mmol) in aqueous ammo-
1
niacal solution in air. Yield 101 mg, 29%. H NMR
(CDCl3, 400 MHz) δ: 7.61－7.45 (m, 3H, ArCH), 6.81
(s, 1H, ArCH), 6.30 (s, 1H, ArCH), 5.94 (br, 1H, NH);
13C NMR (CDCl3, 100 MHz) δ: 153.3, 152.4, 142.9,
142.9, 134.1, 129.5, 128.5, 128.4, 118.6, 114.9; IR
(KBr): υN H＝3341 (m) cm−1. MALDI-FTMS HRMS
－
(DHB) calcd for C24H12Cl8N4Ni 693.7924, found
693.7918. Anal. calcd for C24H12Cl8N4Ni•0.5toluene: C
44.35, H 2.17, N 7.52; found C 44.17, H 2.18, N 8.15.
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Chin. J. Chem. 2013, 31, 1473—1482

Square Planar Nickel(II) Complexes with Halogenated o-Diiminobenzosemiquinonato Ligation
Table 1 Crystal data and summary of data collection and refinement for 1, [Na(THF)3][1], [Na(THF)3]2[1], and 7•0.5toluenea
1
[Na(THF)3][1]
C42H56N4NaNiO3
746.61
[Na(THF)3]2[1]
C54H80N4Na2NiO6
985.91
7•0.5toluene
C31H20Cl8N4Ni
790.82
Formula
C30H32N4Ni
507.31
Fw
Crystal system
triclinic
P-1
monoclinic
P2(1)/c
triclinic
triclinic
P-1
Space group
a/Å
P-1
10.521(2)
13.239(3)
15.886(3)
66.110(4)
71.776(4)
83.178(4)
1921.7(7)
3
21.955(4)
15.557(2)
24.743(4)
90.00
11.138(3)
11.338(3)
12.351(3)
67.306(3)
87.495(4)
66.894(4)
1312.8(5)
1
10.7617
11.9036
13.6725
69.893(2)
75.087(2)
88.112(2)
1586.4(3)
2
b/Å
c/Å
α/(°)
β/(°)
γ/(°)
112.113(2)
90.00
V/Å3
Z
7830(2)
8
d
calcd/(g•cm–3)
1.315
1.267
1.245
1.656
2θ range/(°)
GOF (F2)
3.36－54.0
1.055
2.0－52.0
0.990
3.6－52.0
1.073
3.66－60.92
1.044
b
R1
0.0513,d 0.0692e
0.1547,d 0.1916e
0.0669,d 0.1539e
0.1509,d 0.1849e
0.0663,d 0.0842e
0.0521,d 0.0747e
0.1517,d 0.1724e
c
wR2
0.1946,d 0.2248e
a Collected using Mo Kα radiation (λ＝0.71073 Å). b R1＝Σ[(Fo–Fc)]/Σ(Fo). c wR2＝Σ[w(Fo –Fc2)2/Σ[w(Fo ) ]] . d I＞2σ(I). e All data.
2
2 2 ½
7•0.5toluene have been deposited in the Cambridge
Crystallographic Data Centre (CCDC 917983 －
917986).
Scheme 1 Preparation of the ligands
NO2
NO2
R
R
R
+ H2NAr
condition:
a, b or c
NHAr
R
F
Results and Discussion
cat. Pd/C
NaBH4
CH3OH
a) KF (1 equiv.), 180 oC, 48 h
b) NaOBut (2 equiv.),
0 oC to r.t., 12 h, THF
c) NaH (1 equiv.),
THF
Synthesis and characterization of [NiL2] complexes
1
NH2
R
R
The substituted 2-aminodiphenylamine ligands, H2 L
5
to H2 L, were prepared according to reported procedures
0 oC to r.t., 12 h, THF
shown in Scheme 1.[36,37] Without further purification,
these 2-aminodiphenylamine compounds generally dis-
NHAr
Cl
NH2
NHAr
F
NH2
NH2
1
play a dark brown or red color, but H NMR analyses
have confirmed their purity. Using similar synthetic
procedures, new compounds, H2 L and H2 L, have been
NHPh Cl
NHAr
Ar = Mes, H21L;
F
H24L
Ar = Ph, H25L;
6
7
p-F-C6H4, H22L;
p-Cl-C6H4, H23L
2,6-F2-C6H4, H26L;
2,6-Cl2-C6H4, H27L
1
synthesized in good yields, and characterized by H
NMR, 13C NMR and high resolution mass spectroscopy.
By the reactions of nickelous chloride with the
2-aminodiphenylamines in aqueous ammoniacal solu-
tion in air,[14] complexes 1－3, and 5－7 were prepared
in moderate yields (Scheme 2). The reaction with the
ether, and insoluble in n-hexane. They display a deep
blue color in the solid state and solution phase. Resem-
bling the known square planar bis(o-diiminobenzosemi-
quinonato)nickel(II) complexes (9－11 in Chart 2),[14,18]
the electronic spectra of 1－7 in THF feature intense
ligand-to-ligand charge-transfer bands (LLCT) in the
4
difluoro-substituted ligand, H2 L, under this condition
failed to give the desired product. Therefore, salt me-
tathesis reaction between Li2[4L] and NiCl2(DME) fol-
lowed by oxidation with dioxygen was tried, which has
led to the isolation of [Ni(4L)2](4) in 48% yield (Scheme
2).
Complexes 1－7 are quite soluble in chloroform and
dichloromethane, moderately soluble in THF and diethyl
1
range 700 to 1000 nm (Table 2). The NMR spectra, H
NMR, 13C NMR, and 19F NMR, of these complexes are
indicative of their diamagnetism. The chemical shifts of
their 1H NMR resonances locate in the δ range 0.0 to 7.5,
and those of amino protons appear near δ 6.0. The
Chin. J. Chem. 2013, 31, 1473—1482
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Zuo et al.
FULL PAPER
Scheme 2 Preparation of the nickel complexes
crystallographically independent molecules), and qui-
noid-type distortion of the six-membered carbon rings
with two short C＝C bonds and four longer C－C bonds
(Table 3), which accord well with those observed in 8
reported by Wieghardt et al.[18] It is interesting to note
that, despite the presence of different substitutes in 1
and 7, the corresponding Ni－N, and N－C distances of
the five membered Ni-N-C-C-N rings and C－C dis-
tances of the six-membered carbon rings in the two
complexes are close to each other (Table 3).
0.5NiCl2 6H2O
NH2
R
xs. NH3 H2O, air
ethanol/H2O (1:1)
70 oC, 3 h
1 - 3, 5 - 7
R
NHAr
H21L-H23L, H25L-H27L
1) 2BunLi
2) 0.5NiCl2(DME)
NH2
F
F
3) O2
THF
4
NHPh
H24L
19F NMR spectra of 2, 4, and 6 feature one, two, and one
sets of signals at δ –117.3, –138.9 and –139.3, and
–116.3, respectively. These chemical shifts are typical
for fluorines attached on sp2-carbons. Characteristic N－
H stretching resonances around 3340 cm–1 are observed
in their IR spectra. In addition to these, complexes 1－7
have been characterized by high-resolution mass spec-
troscopy and elemental analysis.
Table 2 Absorption spectra data of 1－7, measured in THF
–
–
1
Figure 1 Molecular structure of 1, showing one of the two
crystallographically independent molecules in the unit cell with
30% probability ellipsoids.
1
λmax/nm [ε/(104 L•mol •cm )]
228 (3.7), 287 (1.6), 338 sh (1.0), 439 (0.2), 545 sh (0.1),
646 (0.4), 700 (0.5), 847 (3.6)
1
244 (4.5), 340 sh (1.0), 450 (0.7), 555 sh (0.2), 609 (0.3),
1137 (1.9)
–
–
11
12
2
242 (4.0), 27 9(3.1)
233 (3.3), 281 (2.0), 336 sh (1.0), 433 (0.3), 543 sh (0.2),
636 (0.5), 687 (0.7), 828 (4.4)
235 (5.2), 275 (3.4), 340 sh (2.2), 434 (0.6), 542 sh (0.3),
631 (0.5), 690 (0.8), 828 (4.7)
3
4
5
6
7
232 (2.5), 282 (1.6), 344 sh (0.7), 424 (0.3), 532 sh (0.3),
649 (0.5), 687 (0.7), 827 (3.3)
226 (2.7), 283 (1.6), 363 sh (0.6), 427 (0.3), 530 sh (0.3),
624 (0.4), 666 (0.5), 870 (3.1)
Figure 2 Molecular structure of 7, showing one of the two
crystallographically independent molecules in the unit cell with
30% probability ellipsoids.
259 (5.6), 284 (2.1), 368 sh (1.0), 446 (0.3), 557 sh (0.2),
665 (0.4), 708 (0.5), 875 (4.1)
Cyclic voltammetry of [NiL2]
251 (4.7), 287 (3.5), 328 sh (2.3), 428 (0.7), 554 sh (0.3),
630 (0.4), 696 (0.6), 847 (4.9)
Cyclic voltammograms of 1－7, in addition with the
known complex 8 for comparison, have been measured
in THF solutions with 0.10 mol/L [Bun N][PF6] as sup-
4
As the representatives for this series of complexes,
porting electrolyte at a glassy carbon working electrode
and a saturated calomel reference electrode. Figure 3
reproduces the voltammograms, and Table 4 summa-
rizes their potentials.
In accord to the voltammogram recorded in
CH2Cl2,[18] the voltammogram of 8 obtained in THF
consists of two reversible one-electron redox waves, and
one irreversible two-electron redox wave with large
peak-potential-separation (410 mV). The voltammo-
grams of 1－7 resemble that of 8 (Figure 3). The two
the molecular structures of 1 and 7 in solid state have
been established by single-crystal X-ray crystallography
at 133(2) K. Selected bond distances for 1 and 7 are
compiled in Table 3. As shown in Figures 1 and 2, both
neutral complexes adapt a square planar geometry in
which the nickel centers are coordinating with two
o-diiminobenzosemiquinonato π-radical anions in a
transoid fashion. Characteristic structure features for the
π-radical anions in 1 and 7 are reflected by the C－N
bond distances of 1.34 and 1.35 Å (in average from two
1478
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Chin. J. Chem. 2013, 31, 1473—1482

Square Planar Nickel(II) Complexes with Halogenated o-Diiminobenzosemiquinonato Ligation
Table 3 Selected bond distances (Å) of the [NiL2]n fragments in
1, [Na(THF)3][1], [Na(THF)3]2[1], and 7
reversible waves of their voltammograms have the half-
wave potentials in the range −1.62 to −0.92 for E1
,
1/2
and −0.85 to −0.26 for E21/2, and the separations of
E11/2−E21/2 between 790 to 630 mV (Table 4). Following
Wieghardt’s assignment for 8, these reduction waves are
attributed to ligand-based one-electron transfer proc-
esses of [NiL2]2−/1− and [NiL2]1−/0 (Scheme 3).[18] Be-
sides the global resemblances of the reduction waves of
1－8, it should be noted that the intensity of the redox
waves with the lowest half-wave-potential (E11/2) in the
voltammograms of 6 and 7 increased when more scans
were performed. This phenomenon implies the dianions
[Ni(4,5-Cl2-o-C6H4(NH)(NAr)2)]2− might dissociate its
diamido ligands [4,5-Cl2-o-C6H4(NH)(NAr)]2− in solu-
right wing
Ar
H
C5
C2
C5
N2
N1
C4
C3
C6
C1
C1
C6
C3
C4
Ni
N1
H
N2
Ar
C2
left wing
11− a
Rightb
1a
7a
12−
Left
Ni－N1 1.824(4) 1.826(2) 1.846(4) 1.832(4) 1.870(3)
Ni－N2 1.863(3) 1.864(2) 1.865(4) 1.880(4) 1.899(3)
N1－C1 1.337(5) 1.340(3) 1.346(6) 1.367(6) 1.375(4)
N2－C6 1.349(5) 1.350(3) 1.360(6) 1.368(6) 1.374(4)
C1－C2 1.417(6) 1.408(4) 1.412(7) 1.394(7) 1.387(5)
C2－C3 1.378(6) 1.376(4) 1.366(7) 1.383(7) 1.404(5)
C3－C4 1.417(7) 1.416(4) 1.410(7) 1.388(7) 1.374(6)
C4－C5 1.369(6) 1.376(4) 1.389(7) 1.376(7) 1.403(5)
C5－C6 1.417(6) 1.412(4) 1.396(7) 1.392(7) 1.390(5)
C6－C1 1.431(6) 1.435(4) 1.438(7) 1.436(7) 1.440(5)
tion phase, and the E1 redox waves might correspond
1/2
to [4,5-Cl2-o-C6H4(NH)(NAr)]2−/1−
.
The irreversible two-electron redox waves with large
peak-potential-separations (230－390 mV) are assigned
to the redox couple of [NiL2]0/2＋. The large peak-poten-
tial-separation of these two-electron redox processes
might be caused by an ECE mechanism involving elec-
tron-transfer between the nickel center (NiII/III) and the
redox active ligands (o-diiminobenzosemiquinonato to
a
＋
o-diiminobenzoquinonato) within the cations [NiL2]1
Distances in average from two crystallographically independent
molecules in the unit cell. b The wing coordinating with Na＋.
and [NiL2]2＋, as suggested for the irreversible two-
electron oxidation wave of [Ni(4,6-But2-o-C6H2(O)-
Table 4 Redox potentials of 1－8 in THFa
＋
(NPh))2]0/2 [16] Noting two well separated one-electron
.
redox couples of [NiL2]0/1 and [NiL2]1 ＋, instead of
the two-electron redox of [NiL2]0/2＋, were observed in
the voltammograms of 9－11,[14-18] the different substi-
tutents on the imino nitrogen atoms (N－Ar and N－H
for 1－8 and N－H moieties for 9－11) should be the
structural cause.
＋ ＋
/2
1
2
3
4
5
6
7
8
E1
E2
−1.62 −1.34 −1.28 −1.21 −1.05 −0.92 −1.03 −1.38
−0.83 −0.68 −0.65 −0.58 −0.39 −0.26 −0.31 −0.71
0.79 0.66 0.63 0.63 0.66 0.66 0.72 0.67
0.55 0.41 0.44 0.45 0.57 0.66 0.70 0.40
0.68 0.60 0.61 0.59 0.68 0.74 0.87 0.60
0.43 0.21 0.26 0.31 0.45 0.58 0.53 0.19
1/2
1/2
b
∆
E3
E3
E3
c
1/2
d
pa
e
pc
Scheme 3 Ligand-based one-electron transfer processes of
[NiL2]0/1−/2−
a Volts vs. SCE, scan rate: 100 mV/s, room temperature. b ∆＝
E11/2−E2
.
c Two-electron process. d E3pa: anodic peak potential.
1/2
H
N
Ar
N
H
N
Ar
N
Xn
e E3pc: cathodic peak potential.
1−
Xn
+ e−
- e−
NiII
NiII
N
Xn
N
H
N
Xn
N
H
E2
Ar
1/2
Ar
+ e− - e−
E1
1/2
H
N
Ar
N
2−
Xn
NiII
N
Xn
N
H
Ar
These voltammetry data provide an opportunity to
examine the substitutent effects on the redox properties
of bis(o-diiminobenzosemiquinonato)nickel(II) com-
plexes. Comparisons among [Ni(o-4,5-X2-C6H2(NH)-
(NPh))2] (X＝H, 8;[18] F, 4; Cl, 5) and [Ni(o-3,5-But2-
C6H4(NH)2)2] (9)[38] reveal that the reduction potentials
are significantly affected by the substituents attached on
the o-diiminobenzosemiquinonato backbone with those
of 9 being the lowest and those of 5 the highest. The
ease of reduction roughly parallels the electron-donating
and -withdrawing ability of the substituent group as both
Figure 3 Cyclic voltammograms of ca. 1 mmol/L THF solution
prepared from 1－8.
Chin. J. Chem. 2013, 31, 1473—1482
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Zuo et al.
FULL PAPER
E11/2 and E21/2 increase in the order of 9＜8＜4＜5 when
the substituent goes from But to H to F to Cl. The lower
reduction potentials of the difluoro-subsituted complex
4, when compared to those of its chloride analog 5, hint
the contribution of conjugation effect of the fluoro sub-
stituents. The effects of the imino substituents are re-
vealed by the reduction potentials of E1 and E2
1/2
1/2
within the series of [Ni(o-C6H4(NH)(NAr))2] (Ar＝Mes,
1; Ph, 8; p-F-C6H4, 2; p-Cl-C6H4, 3) with the order of 1
＜ 8 ≈ 2 ＜ 3, and those of [Ni(o-4,5-Cl2-C6H2(NH)-
(NAr))2] (Ar＝Ph, 5; 2,6-F2-C6H3, 6; 2,6-Cl2-C6H3, 7)
with order of 5＜7＜6. These trends, again, suggest the
ease of reduction for [NiL2]0 and [NiL2]1− is in line with
the electron-donating and -withdrawing ability of the
substituent group on the imino nitrogen. Taking all to-
gether, the ease of reduction of these nickel complex
shows the order of 1≈9＜8≈2＜3＜4＜5＜7＜6.
Hence, it can be reasonably inferred that the ease of
oxidation of the o-diiminophenolato ligands decreases in
the order of [1L]2−≈[9L]2−＞[8L]2−≈[2L]2−＞[3L]2−＞
[4L]2−＞[5L]2−＞[7L]2−＞[6L]2−, in which [8L]2− and
[9L]2− are referring to [o-C6H4(NH)(NPh)]2− and
[o-3,5-But2-C6H2(NH)2]2−, respectively.
Figure 4 Molecular structure of [Na(THF)3][1], showing one of
the two crystallographically independent molecules in the unit
cell with 30% probability ellipsoids.
[1.846(4) and 1.832(4) Å] and Ni－NMes bond distances
[1.865(4) and 1.880(4) Å] in the anion are close to those
in 1. The geometrical details of the two ligands are dif-
ferent as the one having interaction with [Na(THF)3]＋
features long N－C bonds, and averaged C－C dis-
tances, whereas, the other has shorter N－C bonds, and
a four longer and two shorter C－C separations of its
six-membered carbon ring (Table 3). These structure
features, when compared with the structures of the
Synthesis and characterization of [Ni(1L)2]1−,2− com-
plexes
Electrochemical studies have suggested five oxida-
tion states for square planar bis(o-diiminophenolato)
nickel complexes [Ni(L)2]n (n ＝ 2 ＋ , 1 ＋ , 0, 1−,
2−).[14,18] Among these five categories of species, known
examples of neutral complexes [Ni(L)2]0 are
plenty[5,11-22,33] and their geometrical[18,33,39] and elec-
tronic structures have been well-established.[18] Starting
from neutral complexes, spectroelectrochemical studies
in solution phase have disclosed the electronic structures
of cationic and anionic species, [Ni(L)2]n (n＝2＋, 1＋,
1−, 2−).[14,18] But, their molecular structures in solid
state are rarely known. To our knowledge, the dimeric
complex {cis-[Ni(o-3,5-But2-C6H2(NH)2)]2}Cl2 proba-
bly represents the solely known example of them.[18]
Aiming to establish the structures of anionic complexes,
the reactions of 1 with one or two equivalents of sodium
have been performed, which have led to the isolation of
the mono- and dianionic complexes, [Na(THF)3][1] and
[Na(THF)3]2[1], as green and pale brown crystals, re-
spectively, in good yields.
An X-ray crystallographic study has shown there are
two crystallographically independent molecules in the
unit cell of [Na(THF)3][1]. As the structures of these
two molecules are nearly identical, Figure 4 shows only
one of them as the representative. The ionic complex
contains a square planar motif of [Ni(o-C6H4(NH)-
(NMes))2]1− that is coordinating with one cation
[Na(THF)3]＋ via its o-diiminophenolato ligand in an
η4-fashion. The long Na－C [2.725 (5) to 2.938(5) Å]
and Na－N distances [2.571(5) to 2.938(5) Å] indicate
the interaction between the cation and the o-diimino-
phenolato ligand is ionic. The Ni－NH distances
known o-diiminophenolato complexes, [Bun N][TcO(o-
4
C6H4(NH)2)2][40]
and
[Mo(o-C6H4(NH)2)(CO)2-
(PPh3)2][41], and the o-diiminobenzosemiquinonato com-
plexes, 1, 7, and 8－10,[18,33] imply the structure of [1]1−
can be described as [NiII(1L•1−)(1L2−)]1−. This assign-
ment is further supported by the magnetic moment
[1.8(3) μB] and the presence of strong mixed valent
charge-transfer band (1138 nm with absorption coeffi-
ciency of 19000 L•mol−1•cm−1) of [Na(THF)3][1] in so-
lution phase, which are consistent with those of
[NiII(9L•1−)(9L2−)]1− established by spectroelectrochemi-
cal studies.[18]
The molecular structure of [Na(THF)3]2[1] in solid
state has also been established by single-crystal X-ray
diffraction. As shown in Figure 5, the molecule displays
centrosymmetry in which the square planar dianion
[Ni(o-C6H4(NH)(NMes))2]2− has interactions with two
[Na(THF)3]＋ cations via its C－NH moieties. The dian-
ion [Ni(o-C6H4(NH)(NMes))2]2− has the Ni－N bond
distances of 1.872(3) and 1.898(3) Å, and the N－C
bond distances around 1.375(4) and 1.374(4) Å, which
are slightly longer than the corresponding ones in 1 and
[1]1− (Table 3). The C－C separations of the
six-membered carbon rings within the bidentate ligands
display characters of o-diiminophenolato dianion as five
averaged C－C bonds [1.374(4) to 1.404(5) Å] and one
longer C－C bond [1.440(5) Å] are observed.[40,41]
Based on these, the structure of [1]2− can be established
as [NiII(1L2−)2]2−. This assignment is consistent with the
diamagnetic nature of this complex in solution phase
1480
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 1473—1482

Square Planar Nickel(II) Complexes with Halogenated o-Diiminobenzosemiquinonato Ligation
lution magnetic moment and UV-vis-NIR spectra of
these ionic complexes are consistent with the assign-
ments.
Acknowledgement
We thank the financial supports from the National
Natural Science Foundation of China (Nos. 20923005,
21002114, and 21121062) and the Science and Tech-
nology Commission of Shanghai Municipality (No.
11PJ1412100).
References
[1] Pierpont, C. G.; Lange, C. W. Prog. Inorg. Chem. 1994, 41, 331.
[2] Lever, A. B. P.; Gorelsky, S. I. Coord. Chem. Rev. 2000, 208, 153.
[3] Pierpont, C. G. Coord. Chem. Rev. 2001, 216, 99.
[4] Ward, M. D.; McCleverty, J. A. J. Chem. Soc., Dalton Trans. 2002,
275.
Figure 5 Molecular structure of [Na(THF)3]2[1], showing 30%
probability ellipsoids.
[5] Butin, K. P.; Beloglazkina, E. K. Russ. Chem. Rev. 2005, 74, 531.
[6] Lever, A. B. P. Coord. Chem. Rev. 2010, 254, 1397.
[7] Kaim, W. Inorg. Chem. 2011, 50, 9752.
and the absence of LLCT band in its absorption spec-
trum.
[8] Praneeth, V. K. K.; Ringenberg, M. R.; Ward, T. R. Angew. Chem.,
Int. Ed. 2012, 51, 10228.
Conclusions
[9] Lyaskovskyy, V.; de Bruin, B. ACS Catal. 2012, 2, 270.
[10] van der Vlugt, J. I. Eur. J. Inorg. Chem. 2012, 363.
[11] Schrauzer, G. N.; Mayweg, V. J. Am. Chem. Soc. 1962, 84, 3221.
[12] Gray, H. B.; Williams, R.; Bernal, I.; Billig, E. J. Am. Chem. Soc.
1962, 84, 3596.
[13] Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H. Inorg. Chem.
1963, 2, 1227.
[14] Balch, A.; Holm, R. H. J. Am. Chem. Soc. 1966, 88, 5201.
[15] Jüstel, T.; Bendix, J.; Metzler-Nolte, N.; Weyhermüller, T.; Nuber,
B.; Wieghardt, K. Inorg. Chem. 1998, 37, 35.
[16] Chaudhuri, P.; Verani, C. N.; Bill, E.; Bothe, E.; Weyhermüller, T.;
Wieghardt, K. J. Am. Chem. Soc. 2001, 123, 2213.
[17] Bachler, V.; Olbrich, G.; Neese, F.; Wieghardt, K. Inorg. Chem.
2002, 41, 4179.
[18] Herebian, D.; Bothe, E.; Neese, F.; Weyhermüller, T.; Wieghardt, K.
J. Am. Chem. Soc. 2003, 125, 9116.
[19] Herebian, D.; Wieghardt, K.; Neese, F. J. Am. Chem. Soc. 2003, 125,
10997.
[20] Bill, E.; Bothe, E.; Chaudhuri, P.; Chlopek, K.; Herebian, D.; Ko-
katam, S.; Ray, K.; Weyhermüller, T.; Neese, F.; Wieghardt, K.
Chem. Eur. J. 2005, 11, 204.
[21] Chlopek, K.; Bothe, E.; Neese, F.; Weyhermüller, T.; Wieghardt, K.
Inorg. Chem. 2006, 45, 6298.
[22] Khusniyarov, M. M.; Harms, K.; Burghaus, O.; Sundermeyer, J.;
Sarkar, B.; Kaim, W.; van Slageren, J.; Duboc , C.; Fiedler, J. Dalton
Trans. 2008, 1355.
[23] Ray, K.; Petrenko, T.; Wieghardt, K.; Neese, F. Dalton Trans. 2007,
1552.
[24] Chirik, P. J.; Wieghardt, K. Science 2010, 327, 794.
[25] Ringenberg, M. R.; Kokatam, S. L.; Heiden, Z. M.; Rauchfuss, T. B.
J. Am. Chem. Soc. 2008, 130, 788.
[26] Ringenberg, M. R.; Rauchfuss, T. B. Eur. Inorg. Chem. 2012, 490.
[27] Lippert, C. A.; Arnstein, S. A.; Sherrill, C. D.; Soper, J. D. J. Am.
Chem. Soc. 2010, 132, 3879.
[28] Lippert, A.; Riener, K.; Soper, J. D. Eur. Inorg. Chem. 2012, 554.
[29] Smith, A. L.; Hardcastle, K. I.; Soper, J. D. J. Am. Chem. Soc. 2010,
132, 14358.
[30] Smith, A. L.; Clapp, L. A.; Hardcastle, K. I.; Soper, J. D. Polyhedron
2010, 29, 164.
[31] Das, D.; Sarkar, B.; Kumbhakar, D.; Mondal, T. K.; Mobin, S. M.;
Starting from a series of substituted 2-aminodiphe-
nylamine ligands, we have achieved the synthesis of
seven new bis(o-diiminobenzosemiquinonato)nickel(II)
complexes, [Ni(o-C6H4(NH)(NAr))2] (Ar ＝ Mes, 1;
p-F-C6H4, 2; p-Cl-C6H4, 3), [Ni(o-4,5-F2-C6H2(NH)-
(NPh))2] (4), [Ni(o-4,5-Cl2-C6H2(NH)(NAr))2] (Ar＝Ph,
5; 2,6-F2-C6H3, 6; 2,6-Cl2-C6H3, 7), bearing halogenated
diiminobenzosemiquinonato backbone and/or halo-
genated phenyl substituents on the imino nitrogen.
Spectroscopic characterization (1H NMR, 13C NMR, 19
F
NMR, IR, and UV-Vis-NIR) for all the complexes and
single-crystal X-ray diffraction studies for 1 and 7 sug-
gest a square planar geometry for them and a π-radical
anion nature for their bidentate ligands. The cyclic
voltammograms of these complexes resemble that of the
known complex [Ni(o-C6H4(NH)(NPh))2] (8),[18] and
exhibit three redox waves, [NiL2]0/1−, [NiL2]1−/2−, and
[NiL2]0/2＋, of which the two reduction processes are
reversible, and the oxidation process is irreversible.
Comparing the half-wave potentials of the reduction
waves of these complexes, in addition with those of 8
and [Ni(o-3,5-But2-C6H2(NH)2)2] (9),[18] revealed the
substituent effect on the redox property of these bis(o-
diiminobenzosemiquinonato)nickel(II) complexes as
the ease of reduction of [NiL2] parallels the electron-
donating and -withdrawing ability of the substituent
group. Since these reduction processes are ligand-based,
the ease of oxidation of the o-diiminophenolato ligands
can be reasoned as [1L]2−≈[9L]2−＞[8L]2−≈[2L]2−＞
[3L]2− ＞[4L]2− ＞[5L]2− ＞[7L]2- ＞[6L]2−. Furthermore,
we have also achieved the synthesis and structure char-
acterization of two anionic complexes [Na(THF)3][1]
and [Na(THF)3]2[1]. Analyzing the metric data of the
square planar anions has revealed their electronic struc-
tures as [NiII(1L•1−)(1L2−)]1− and [NiII(1L2−)2]2−. The so-
Chin. J. Chem. 2013, 31, 1473—1482
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
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Zuo et al.
FULL PAPER
Fiedler, J.; Urbanos, F. A.; Jiménez-Aparicio, R.; Kaim, W.; Lahiri,
G. K. Chem. Eur. J. 2011, 17, 11030.
[39] Cheng, H.-Y.; Lin, C.-C.; Tzeng, B.-C.; Peng, S.-M. J. Chin. Chem.
Soc. 1994, 41, 775.
[32] Basu, P.; Bruck, M. A.; Li, Z.; Dhawan, I. K.; Enemark, J. H. Inorg.
Chem. 1995, 34, 405.
[40] Gerber, T. I. A.; Kemp, H. J.; du Preez, J. G. H.; Bandoli, G.; Dol-
mella, A. Inorg. Chim. Acta 1992, 202, 191.
[33] Hall, G. S.; Soderberg, R. H. Inorg. Chem. 1968, 7, 2300.
[34] Christoph, G. G.; Goedken, V. L. J. Am. Chem. Soc. 1973, 95, 3869.
[35] Elder, R. C.; Koran, D.; Mark, H. B. Inorg. Chem. 1974, 13, 1644.
[36] Bianchi, M.; Butti, A.; Rossi, S. Eur. J. Med. Chem. 1981, 16, 321.
[37] O’Neill, D. J.; Adedayo, A.; Alfinito, P. D.; Bray, J. A.; Cosmi, S.;
Deecher, D. C.; Fensome, A.; Harrison, J.; Leventhal, L.; Mann, C.;
McComas, C. C.; Sullivan, N. R.; Spangler, T. B.; Uveges, A. J.;
Trybulski, E. J.; Whiteside, G. T.; Zhang, P. J. Med. Chem. 2010, 53,
4511.
[41] Anillo, A.; Obeso-Rosete, R.; Lanfranchi, M. A.; Tiripicchio, T. J.
Organomet. Chem. 1993, 453, 71.
[42] Kulagowski, J. J.; Rees, C. W. Synthesis 1980, 215.
[43] Zhu, Y.-F.; Lin, G.-Q.; Chen, Y.-Q. Synthesis 1990, 430.
[44] Evans, D. F. J. Chem. Soc. 1959, 2003.
[45] Sheldrick, M. SADABS: Program for Empirical Absorption Correc-
tion of Area Detector Data, University of Göttingen, Germany,
1996.
[46] Sheldrick, M. SHELXTL 5.10 for Windows NT: Structure Determi-
nation Software Programs, Bruker Analytical X-ray Systems, Inc.,
Madison, Wisconsin, USA, 1997.
[38] The voltammogram of 9 in CH2Cl2 has E11/2＝−1.76 V and E2
−1.07 V (vs. SCE), see, reference 18.
＝
1/2
(Lu, Y.)
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Chin. J. Chem. 2013, 31, 1473—1482