Nickel complexes of o-amidochalcogenophenolate(2-)/o-iminochalcogenobenzosemiquinonate(1-) π-radical: Synthesis, structures, electron spin resonance, and x-ray absorption spectroscopic evidence

Article abstract of DOI:10.1021/ic034211r

The preparation of complexes trans-[Ni(-SeC₆H₄-o-NH-)₂]^- (1), cis-[Ni(-TeC₆H₄-o-NH-)₂]^- (2), trans-[Ni(-SC₆H₄- o-NH-)₂]^- (3), and [Ni(-SC₆H₄-o-S-)₂]^- (4) by oxidative addition of 2-aminophenyl dichalcogenides to anionic [Ni(CO)(SePh)₃]^- proves to be a successful approach in this direction. The cis arrangement of the two tellurium atoms in complex 2 is attributed to the intramolecular Te...Te contact interaction (Te...Te contact distance of 3.455 A). The UV-vis electronic spectra of complexes 1 and 2 exhibit an intense absorption at 936 and 942 nm, respectively, with extinction coefficient ε > 10000 L mol^-1 cm^-1. The observed small g anisotropy, the principal g values at g₁ = 2.036, g₂ = 2.062, and g₃ = 2.120 for 1 and g₁ = 2.021, g₂ = 2.119, and g₃ = 2.250 for 2, respectively, indicates the ligand radical character accompanied by the contribution of the singly occupied d orbital of Ni(III). The X-ray absorption spectra of all four complexes show L_III peaks at ～854.5 and ～853.5 eV. This may indicate a variation of contribution of the Ni(II)-Ni(III) valence state. According to the DFT calculation, the unpaired electron of complex 1 and 2 is mainly distributed on the 3d_xz orbital of the nickel ion and on the 4p_z orbital of selenium (tellurium, 5p_z) as well as the 2p_z orbital of nitrogen of the ligand. On the basis of X-ray structural data, UV-vis absorption, electron spin resonance, magnetic properties, DFT computation, and X-ray absorption (K- and L-edge) spectroscopy, the monoanionic trans-[Ni(-SeC₆H₄-o-NH-)₂]^- and cis-[Ni(-TeC₆H₄-o-NH-)₂]^- complexes are appositely described as a resonance hybrid form of Ni(III)-bis(o-amidochalcogenophenolato(2-)) and Ni(II)- (o-amidochalcogenophenolato(2-))-(o-iminochalcogenobenzosemiquinonato(1-) π-radical; i.e., complexes 1 and 2 contain delocalized oxidation levels of the nickel ion and ligands.

Full text of DOI:10.1021/ic034211r

Inorg. Chem. 2003, 42, 3925−3933
Nickel Complexes of o-Amidochalcogenophenolate(2−)/
o-Iminochalcogenobenzosemiquinonate(1−) π-Radical: Synthesis,
Structures, Electron Spin Resonance, and X-ray Absorption
Spectroscopic Evidence
,|
Chung-Hung Hsieh,†,‡ I-Jui Hsu,§ Chien-Ming Lee,‡ Shyue-Chu Ke,* Tze-Yuan Wang,§
,§
,‡
Gene-Hsiang Lee,§ Yu Wang,* Jin-Ming Chen, Jyh-Fu Lee, and Wen-Feng Liaw*
Department of Chemistry, National Tsing Hua UniVersity, Hsinchu 30043, Taiwan, Department of
Chemistry, National Taiwan UniVersity, Taipei, Taiwan, Department of Chemistry, National
Changhua UniVersity of Education, Changhua, Taiwan, Department of Physics, National Dong
Hwa UniVersity, Hualien, Taiwan, and Synchroton Radition Research Center,
Hsinchu 30077, Taiwan
Received February 25, 2003
The preparation of complexes trans-[Ni(−SeC H -o-NH−)2]- (1), cis-[Ni(−TeC H -o-NH−)2]- (2), trans-[Ni(−SC H -
6
4
6
4
6 4
o-NH−)2]- (3), and [Ni(−SC H -o-S−)2]- (4) by oxidative addition of 2-aminophenyl dichalcogenides to anionic
6
4
[Ni(CO)(SePh)3]- proves to be a successful approach in this direction. The cis arrangement of the two tellurium
atoms in complex 2 is attributed to the intramolecular Te‚‚‚Te contact interaction (Te‚‚‚Te contact distance of
3.455 Å). The UV−vis electronic spectra of complexes 1 and 2 exhibit an intense absorption at 936 and 942 nm,
respectively, with extinction coefficient ꢀ > 10000 L mol-1 cm-1. The observed small g anisotropy, the principal g
values at g1 ) 2.036, g2 ) 2.062, and g3 ) 2.120 for 1 and g1 ) 2.021, g2 ) 2.119, and g3 ) 2.250 for 2,
respectively, indicates the ligand radical character accompanied by the contribution of the singly occupied d orbital
of Ni(III). The X-ray absorption spectra of all four complexes show L peaks at ∼854.5 and ∼853.5 eV. This may
III
indicate a variation of contribution of the Ni(II)−Ni(III) valence state. According to the DFT calculation, the unpaired
electron of complex 1 and 2 is mainly distributed on the 3d orbital of the nickel ion and on the 4p orbital of
xz
z
selenium (tellurium, 5p ) as well as the 2p orbital of nitrogen of the ligand. On the basis of X-ray structural data,
z
z
UV−vis absorption, electron spin resonance, magnetic properties, DFT computation, and X-ray absorption (K- and
L-edge) spectroscopy, the monoanionic trans-[Ni(−SeC H -o-NH−)2]- and cis-[Ni(−TeC H -o-NH−)2]- complexes
6
4
6 4
are appositely described as a resonance hybrid form of Ni(III)−bis(o-amidochalcogenophenolato(2−)) and Ni(II)−
(o-amidochalcogenophenolato(2−))−(o-iminochalcogenobenzosemiquinonato(1−) π-radical; i.e., complexes 1 and
2 contain delocalized oxidation levels of the nickel ion and ligands.
Introduction
that [-EC6H4-o-E′-]2- acted as a strong π-bonding bidentate
ligand, which allowed a rationalization of the short M-E/
M-E′ bond lengths and simultaneously proved the impor-
tance of π-bonding for stabilization of the unsaturatedly
The recent reports on the preparations of the varieties of
five-coordinated 16-electron transition-metal complexes
[M(CO)n(CN)3-n(-EC6H4-o-E′-)]- (M ) Mn,1,2 Fe,3 W, Cr,
Mo;4 E ) O, S, Se, Te; E′ ) O, S, NH; n ) 3, 2) revealed
(1) (a) Liaw, W.-F.; Hsieh, C.-K.; Lin, G.-Y.; Lee, G.-H. Inorg. Chem.
2001, 40, 3468. (b) Liaw, W.-F.; Lee, C.-M.; Lee, G.-H.; Peng, S.-M.
Inorg. Chem. 1998, 37, 6396.
(2) Hartl, F.; Vlce´k, A., Jr.; deLearie, L. A.; Pierpont, C. G. Inorg. Chem.
1990, 29, 1073.
(3) Liaw, W.-F.; Lee, N.-H.; Chen, C.-H.; Lee, C.-M.; Lee, G.-H.; Peng,
S.-M. J. Am. Chem. Soc. 2000, 122, 488.
(4) (a) Darensbourg, D. J.; Draper, J. D.; Reibenspies, J. H. Inorg. Chem.
1997, 36, 3648. (b) Darensbourg, D. J.; Klausmeyer, K. K.; Reiben-
spies, J. H. Inorg. Chem. 1996, 35, 1535.
* Authors to whom correspondence should be addressed. E-mail:
wfliaw@mx.nthu.edu.tw (W.-F.L.); yuwang@xtal.ch.ntu.edu.tw (Y.W.);
ke@mail.ndhu.edu.tw (S.-C.K.).
† National Changhua University of Education.
‡ National Tsing Hua University.
§ National Taiwan University.
| National Dong Hwa University.
Synchroton Radition Research Center.
10.1021/ic034211r CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/15/2003
Inorganic Chemistry, Vol. 42, No. 12, 2003 3925

Hsieh et al.
Scheme 1
Scheme 3
Scheme 2
the presence of o-iminothionebenzosemiquinonato(1-) π-rad-
icals in transition-metal complexes and to identify the
oxidation level of metal ions and ligands.9
coordinated [M(CO)n(CN)3-n(-EC6H4-o-E′-)]- systems.1-4
The existence of one π-bond and two σ-bonds between the
[Mn(CO)3]+ and [-SC6H4-o-S-]2- fragments, based on the
qualitative frontier molecular orbital analysis,5 also indicated
that the lone-pair electrons are delocalized among the sulfur-
manganese-sulfur system to stabilize the five-coordinate
complex [Mn(CO)3(-SC6H4-o-S-)]-.5 In fact, the analogous
catecholate and dithiolene ligands have long been suggested
to behave as “noninnocent” ligands to exhibit different
oxidation levels (catecholate(-2), semiquinone(-1), quinone-
(0), ene-1,2-dithiolate(-2), and semidithione radical(-1),
1,2-dithione(0), respectively) as shown in Scheme 1a6 and
b,7 respectively. Although the iron complexes of o-benzene-
dithiolate ([bdt]2-) indicate that [bdt]2- behaves as an
innocent dithiolate based on crystal X-ray diffraction and
Mo¨ssbauer spectra, it is still ascribed as the formation of
dithio-o-benzoquinone which breaks up the aromatic system.8
Interestingly, the recent investigation of the nickel, pal-
ladium, and platinum complexes of o-amidothiophenolates
shows that o-amidothiophenolate also acts as a “noninnocent”
ligand which can exist at three different oxidation levels,
o-amidothiophenolato(2-) (Scheme 2a), the o-iminothion-
ebenzosemiquinonato(1-) π-radical (Scheme 2b), and o-
iminothionequinone (Scheme 2c).9 Meanwhile, the structural
and spectroscopic criteria have been developed to address
The present work was undertaken in order to expand the
scope of transition-metal o-amidochalcogenophenolato de-
rivatives. It may provide valuable evidence concerning the
delocalized oxidation levels of the metal ion and ligands
(resonance hybrid complexes)9 and certainly will provide
comparisons among transition-metal o-amidochalcogenophe-
nolato species [M(-EC6H4-o-NH-)2]- (E ) Te, Se, S).
Specifically, the synthesis and structures of the square planar
trans-[Ni(-SeC6H4-o-NH-)2]- (1) and cis-[Ni(-TeC6H4-o-
NH-)2]- (2) are described. In order to identify the respective
oxidation level unambiguously, the oxidation levels of the
Ni ion and ligands will be investigated by crystal structural
data, electron spin resonance, UV-vis absorption, magne-
tochemistry, and X-ray absorption spectroscopy of Ni K- and
L
III, II-edges.
Results and Discussion
Synthesis. When a THF solution of 2-aminophenyl
diselenide (0.5 mmol, 0.172 g) and [PPN][NiII(CO)(SePh)3]
(0.5 mmol, 0.545 g)10 is stirred under N2, a rapid reaction
ensues over the course of 5 min at ambient temperature to
give, by what may be described as a reductive elimination/
oxidative addition, an extremely air-sensitive intermediate
[Ni(CO)(SePh)(-SeC6H4NH2-)2]- (Scheme 3a). The IR
spectrum (νCO (THF): 2010 cm-1) of such species did match
those of [Ni(CO)(SPh)n(SePh)3-n]- (n ) 0, 1, 2) complexes
as previously established (by IR and X-ray diffraction).10
The dark green Se,N-chelated trans-[PPN][Ni(-SeC6H4-
o-NH-)2] (1) (Scheme 3b) was isolated as a solid from
THF-hexane (0.422 g, 90%) after stirring the solution under
(5) Lee, C.-M.; Lin, G.-Y.; Lee, C.-K.; Hu, C.-H.; Lee, G.-H.; Peng, S.-
M.; Liaw, W.-F. J. Chem. Soc., Dalton Trans. 1999, 2393.
(6) (a) Pierpont, C. G.; Buchanan, R. M. Coord. Chem. ReV. 1981, 38,
45. (b) Attia, A. S.; Pierpont, C. G. Inorg. Chem. 1995, 34, 1172.
(7) Lim, B. S.; Fomitchev, D. V.; Holm, R. H. Inorg. Chem. 2001, 40,
4257.
(8) Sellmann, D.; Geck, M.; Knoch, F.; Ritter, G.; Dengler, J. J. Am. Chem.
Soc. 1991, 113, 3819.
(9) (a) Herebian, D.; Bothe, E.; Bill, E.; Weyhermuller, T.; Wieghardt,
K. J. Am. Chem. Soc. 2001, 123, 10012. (b) Chaudhuri, P.; Verani,
C. N.; Bill, E.; Bothe, E.; Weyhermuller, T.; Wieghardt, K. J. Am.
Chem. Soc. 2001, 123, 2213. (c) Sun, X.; Chun, H.; Hildenbrand, K.;
Bothe, E.; Weyhermuller, T.; Neese, F.; Wieghardt, K. Inorg. Chem.
2002, 41, 4295.
(10) (a) Liaw, W.-F.; Horng, Y.-C.; Ou, D.-S.; Ching, C.-Y.; Lee, G.-H.;
Peng, S.-M. J. Am. Chem. Soc. 1997, 119, 9299. (b) Liaw, W.-F.;
Chen, C.-H.; Lee, C.-M.; Lee, G.-H.; Peng, S.-M. J. Chem. Soc.,
Dalton Trans. 2001, 138.
3926 Inorganic Chemistry, Vol. 42, No. 12, 2003

Synthesis and Characterization of Ni Complexes
air overnight in THF at room temperature. A reasonable
reaction sequence accounting for the formation of complex
1 is shown in Scheme 3a,b. Upon contact with air/O2, the
brown reaction mixture immediately turns to dark green in
THF. The IR ν(N-H) spectrum (3352 br cm-1 (CH2Cl2))
indicated the formation of complex 1 accompanied by
byproducts of H2O and diphenyl diselenide identified by 1H
NMR.10 In this oxidative reaction, the oxidation process is
best assigned to the yield of diphenyl diselenide from
terminal selenolate ligand via radical (•[SePh]) recombination,
the subsequent deprotonation of amine proton of the inter-
mediate [Ni(CO)(SePh)(-SeC6H4-o-NH-)2]- leading to the
formation of H2O, and, presumably, the concomitant oxida-
tion of the Ni(II) yielding Ni(III) resulting in the displacement
of the carbonyl ligand (to our knowledge, no Ni(III)-CO
Figure 1. ORTEP drawing and labeling scheme of trans-[Ni(-SeC6H4-
o-NH-)2]-. The ellipsoid is at 50% probability.
benzenedithiol led to the formation of the known complex
4 which is identified by UV and X-ray diffraction (Scheme
3f).11b
The electronic structures of complexes 1 and 2 are quite
similar since both compounds exhibit an intense absorption
at 936 and 942 nm, respectively, with extinction coefficient
ꢀ > 10000 L mol-1 cm-1, but no absorption bands around
600 nm (π f π* charge-transfer band) and 730-840 nm
(ligand-to-ligand charge-transfer band) were detected.9 As
suggested by Wieghardt and co-workers,9 this result indicates
that complexes 1 and 2 contain at least one o-iminochalco-
genobenzosemiquinonato(1-) π-radical ligand. Obviously,
according to the UV-vis spectra, we cannot assign com-
plexes 1 and 2 exactly as a [NiIII(o-amidoselenophenolato-
(2-))2]- or a [NiIII(o-amidotellurophenolato(2-))2]-. If the
complex contains two o-amidochalcogenophenolato(2-)
ligands, it normally does not exhibit an absorption band at
longer than 400 nm with intensity greater than 500 L mol-1
cm-1.9 The CV of complex 1 measured in CH3CN with 0.1
M [n-Bu4N][PF6] as supporting electrolyte (scan rate 250
mV/s) reveals three pseudoreversible oxidation-reduction
potentials at -0.44, -1.22, and -1.43 V (E1/2) (vs Ag/
AgClO4).
Structure. The molecular structure of trans-[Ni(-SeC6H4-
o-NH-)2]- (1) is depicted in Figure 1; selected bond
distances and angles are summarized in Table 1. Complex 1
possesses a crystallographically imposed center of inversion
symmetry. The geometry around the Ni atom is square planar
with a trans configuration of the two o-amidoselenophenolato
ligands in the solid state. Complex 1 exhibits a shorter
Ni-Se distance (2.2949(3) Å) than those reported in
tetrahedral [Ni(SePh)4]2- (NiII-Seav ) 2.401(3) Å)12 and
[Ni(CO)(SePh)3]- (average NiII-Se ) 2.317(2) Å)10 but a
longer distance than those observed for [(C4H9)4N]-
[Ni(-SeC6H4Se-)2] (average Ni-Se ) 2.259(9) Å)13 and
[Ni(Se(CH2)2N(Me)(CH2)2Se)]2 (average NiII-Se ) 2.255(9)
Å, excluding the bridge Se ones).14 The C-C bond lengths
of phenyl rings range from 1.373(5) to 1.415(4) Å in complex
1.9
1
complex was ever observed and reported).10 The H NMR
spectra of complex 1 at 298 K do not display any observable
signals for the phenyl groups, indicating complex 1 is
paramagnetic (either a Ni(III) or a Ni(II)-(π-radical ligand))
at ambient temperature.
Similarly, the reductive elimination/oxidative addition was
also displayed by the reaction of complex [PPN][NiII(CO)-
(SePh)3] and 2-aminophenyl ditelluride. When a mixed-
solvent THF-CH3CN-CH2Cl2 solution of [PPN][NiII(CO)-
(SePh)3] was treated with 1 equiv of 2-aminophenyl ditelluride
and 2 equiv of triethylamine, an immediate change in color
of the solution from dark red-brown to dark green-brown
was observed. After extended periods of stirring in the
presence of air in CH3CN-CH2Cl2 at room temperature for
1 h, the reaction mixture finally led to the isolation of dark
brown compound cis-[PPN][Ni(-TeC6H4-o-NH-)2] (2)
(Scheme 3a,b). In addition to the X-ray analysis and the
UV-vis spectrum, the lower ν(N-H) (3333, 3327 cm-1)
compared to that of complex 1 (3352 br cm-1) also supports
the formation of complex 2. Crystals suitable for X-ray
diffraction were obtained by diffusion of hexane into its CH2-
Cl2 solution. It can be concluded that replacement of
o-amidoselenophenolato with the o-amidotellurophenolato
ligand in complex 1 has a significant effect on its thermal
stability and sensitivity toward O2. The 1H NMR spectra of
complex 2 at 298 K also indicate the paramagnetic property.
Treatment of 1 equiv of complex 1 with 2 equiv of
2-aminophenylthiol/1,2-benzenedithiol in THF led to the
formation of the known trans-[PPN][Ni(-SC6H4-o-NH-)2]
(3) and [PPN][Ni(-SC6H4-o-S-)2] (4), respectively (Scheme
3c-e),11 although the π-bonding ability of bidentate
[-SeC6H4-o-NH-]2- is stronger than that of [-SC6H4-o-
NH-]2-/[-SC6H4-o-S-]2- ligands. It is known that any
π-bonding containing an amido group is a more effective
donor than the one without an amido group.1,4 Presumably,
the direction of reaction we have observed for the π-bonding
ligand metathesis reactions must depend on the formation
(stability) of the intermediate [Ni(-SeC6H4-o-NH2)2(-SC6H4-
o-EH-)2]- (E ) S, NH) (Scheme 3c), as observed previ-
ously.1 In a similar fashion, reaction of complex 3 with 1,2-
An ORTEP plot of complex 2 is displayed in Figure 2.
The selected bond distances and angles are listed in
(12) Goldman, C. M.; Olmstead, M. M.; Mascharak, P. K. Inorg. Chem.
1996, 35, 2752.
(13) Sandman, D. J.; Allen, G. W.; Acampora, L. A.; Stark, J. C.; Jansen,
S.; Jones, M. T.; Ashwell, G. J.; Foxman, B. M. Inorg. Chem. 1987,
26, 1664.
(14) Choudhury, S. B.; Pressler, M. A.; Mirza, S. A.; Day, R. O.; Maroney,
M. J. Inorg. Chem. 1994, 33, 4831.
(11) (a) Liaw, M.-C.; Lee, G.-H.; Peng, S.-M. Bull Inst. Chem., Acad. Sin.
1993, 40, 23. (b) Ceasar, G. P.; Gray, H. B. J. Am. Chem. Soc. 1969,
91, 191.
Inorganic Chemistry, Vol. 42, No. 12, 2003 3927

Hsieh et al.
Figure 3. ORTEP drawing and labeling scheme of trans-[Ni(-SC6H4-
o-NH-)2]-. The ellipsoid is as in Figure 1.
Figure 2. ORTEP drawing and labeling scheme of cis-[Ni(-TeC6H4-o-
NH-)2]-. The ellipsoid is as in Figure 1.
Table 2. Selected Bond Distances (Å) and Angles (deg) of Complex 3
Table 1. Selected Bond Distances (Å) and Angles (deg) of Complexes
1 and 2
Ni-N(1)
1.8135(19)
1.369(3)
1.401(3)
1.410(3)
1.376(4)
Ni-S(1)
2.1713(6)
1.735(2)
1.391(3)
1.372(3)
1.378(4)
C(2)-N(1A)
C(1)-C(2)
C(2)-C(3)
C(4)-C(5)
S(1)-C(1)
C(1)-C(6)
C(3)-C(4)
C(5)-C(6)
Complex 1
Ni-N(1)
1.814(3)
1.373(4)
1.415(4)
1.378(4)
1.376(4)
Ni-Se(1)
2.2949(3)
1.877(3)
1.403(4)
1.373(5)
1.391(4)
C(1)-N(1)
C(1)-C(2)
C(2)-C(3)
C(4)-C(5)
Se(1)-C(6)
C(1)-C(6)
C(3)-C(4)
C(5)-C(6)
N(1)-Ni-S(1)
N(1)-Ni-S(1A)
C(2A)-N(1)-Ni
92.14(6)
87.86(6)
122.22(17)
C(1)-S(1)-Ni
N(1A)-C(2)-C(3)
98.03(9)
125.1(2)
N(1)-Ni-Se(1)
N(1)-Ni-Se(1A)
C(1)-N(1)-Ni
88.24(8)
91.76(8)
124.8(2)
N(1)-C(1)-C(2)
C(6)-Se(1)-Ni
N(1)-C(1)-C(6)
124.4(4)
94.04(12)
117.4(4)
Table 3. Comparisons of the Selected Bond Distances (Å) and Angles
(deg) for Complexes 1, 2, and 3
E ) S (3)
E ) Se (1)
E ) Te (2)
Complex 2
Ni-N(2)
1.852(4)
2.4441(6)
2.100(4)
1.366(5)
1.412(6)
1.389(6)
1.377(7)
1.404(6)
1.400(6)
1.394(8)
Ni-N(1)
1.859(3)
2.4450(7)
2.080(5)
1.357(5)
1.412(6)
1.371(6)
1.372(6)
1.410(7)
1.363(8)
1.357(7)
Ni-N
1.8135(19)
2.1713(6)
1.369(3)
1.814(3)
2.2949(3)
1.373(4)
1.877(3)
1.859(3), 1.852(4)
2.4441(6), 2.4450(7)
1.366(5), 1.357(5)
2.100(4), 2.080(5)
94.9(2)
Ni-Te(1)
Ni-Te(2)
Ni-E
Te(1)-C(2)
C(1)-N(1)
C(1)-C(2)
C(2)-C(3)
C(4)-C(5)
C(7)-C(8)
C(8)-C(9)
C(10)-C(11)
Te(2)-C(8)
C(7)-N(2)
C(1)-C(6)
C(3)-C(4)
C(5)-C(6)
C(7)-C(12)
C(9)-C(10)
C(11)-C(12)
N-C
E-C
N-Ni-N
E-Ni-E
N-Ni-E
1.735(2)
89.92(2)
87.86(6)
88.24(8)
87.85(11), 87.59(11)
2.4450(7) and 2.4441(6) Å in complex 2 are shorter than
the Ni(II)-Te bond distance of 2.4804(6) Å in the complex
CpNi(TePh)(PPh3).17 Alternation in C-C bond lengths of
phenyl rings, spanning the range from 1.357(7) to 1.412(6)
Å, are observed.9
N(2)-Ni-N(1)
N(2)-Ni-Te(2)
N(2)-Ni-Te(1)
C(2)-Te(1)-Ni
N(1)-C(1)-C(2)
94.9(2)
Te(2)-Ni-Te(1)
N(1)-Ni-Te(2)
N(1)-Ni-Te(1)
C(1)-N(1)-Ni
C(3)-C(2)-Te(1)
89.92(2)
174.30(11)
87.85(11)
129.2(3)
87.59(14)
175.74(11)
90.00(13)
118.6(4)
The structure of trans-[Ni(-SC6H4-o-NH-)2]- (3) is
shown in Figure 3. The selected bond distances and angles
are given in Table 2.11 Further appropriate comparisons lie
in the N-C and Ni-N parameters (Table 3); the N-C bond
distances (1.369(3) Å for complex 3, 1.373(4) Å for 1 and
1.362(5) Å (average) for 2) are not disturbed by the change
of donor sets (S, Se, Te) in complexes 1, 2, and 3. The
variation of Ni-E bond lengths (E ) S, Se, Te; 2.1713(6)
Å for 3, 2.2949(3) Å for 1 and 2.4450(7) Å for 2) gives 3 <
1 < 2 (Table 3). However, the N-Ni-E bond angles (E )
Se, Te, S) of these three complexes are essentially the same
(88.24(8)°, 87.72(11)°, and 87.86(6)°) (Table 3). It is worth
noticing that the C(1)-N(1) distance of 1.373(4) Å in
complex 1 and C(1)-N(1)/C(7)-N(2) distances of 1.367-
(7)/1.377(7) Å in complex 2, respectively, are slightly longer
than those observed for the transition-metal o-iminothion-
ebenzosemiquinonato(1-) π-radical complexes (average
C-N bond lengths of 1.356 Å) but significantly shorter than
those observed for the transition-metal o-amidothiophenolato-
(2-) complexes (average C-N bond lengths of 1.413 Å).9
Obviously, the UV-vis spectrum and X-ray structural data
lend support to the notion, developed by Wieghardt and
125.0(4)
Table 1. Nickel is best described as in a distorted square
planar coordination surrounded by two o-amidotellurophe-
nolato ligands with the bite angles of 87.85(11)° and
87.59(11)°, respectively. Two tellurium atoms are disposed
in a cis arrangement while trans to the nitrogen atoms. The
intramolecular Te‚‚‚Te contact distance of 3.455 Å is
considerably longer than that of a typical single bond length
15
of 2.7574(3) Å in H2N-o-C6H4Te-TeC6H4-o-NH2 but
comparable to the Te‚‚‚Te contact distance of 3.495 Å in a
Cs2Te5 complex16 which is considered to be a significant
interchain interaction. This intramolecular Te‚‚‚Te contact
interaction may contribute to the stabilization of complex 2
with a cis configuration having 89.92(3)° for Te(2)-Ni-
Te(1) and 94.9(2)° for N(2)-Ni-N(1) , respectively. In
contrast, the structure of [Pd(LAP)2][HNEt3][CH3CO2] ([LAP]1-
) o-aminothiophenolate) adopts a cis configuration deriving
from both cis coordinated NH2 groups of cis-[Pd(LAP)2]
binding weakly to two oxygen atoms of an acetate
[CH3CO2]-.9 The Ni-Te(1) and Ni-Te(2) bond lengths of
(15) Liaw, W.-F.; Ou, D.-S.; Li, Y.-S.; Lee, W.-Z.; Chuang, C.-Y.; Lee,
Y.-P.; Lee, G.-H.; Peng, S.-M. Inorg. Chem. 1995, 34, 3747.
(16) Burns, R. C.; Gillespie, R. J.; Luk, W. C.; Slim, D. R. Inorg. Chem.
1979, 18, 3086.
(17) Hsieh, C.-K.; Lo, F.-C.; Lee, G.-H.; Peng, S.-M.; Liaw, W.-F. J. Chin.
Chem. Soc. (Taipei) 2000, 47, 103.
3928 Inorganic Chemistry, Vol. 42, No. 12, 2003

Synthesis and Characterization of Ni Complexes
) 2.021, g2 ) 2.119, and g3 )2.250 due to larger spin-
orbit coupling of the heavier chalcogen atom, Te.9c
Three possible spin configurations exist for these monoan-
ionic complexes 1 and 2, namely, L*-Ni(I)-L*, L-Ni(III)-
L, and L-Ni(II)-L*; here, the L* denotes the o-imino-
(seleno/telluro)benzosemiquinonato ligand with a radical
residing on the ligand (Scheme 2b), and L denotes the amido-
(seleno/telluro)phenolato ligand(2-) (Scheme 2a). According
to the X-ray absorption spectroscopy and magnetic measure-
ment of complexes 1 and 2, it seems rather unlikely to
support the presence of a Ni(I) oxidation state, which will
be discussed in the following section. Therefore, the pos-
sibility of the three-spin coupled L*-Ni(I)-L* spin con-
figuration (1/2, 1) is ruled out.9,18 It leaves (1/2, 0) and (1/2,
1/2) as the ground state of the L-Ni(III)-L and L-Ni(II)-
L* spin configurations, respectively; here the spin states (St,
S*) are labeled by their total spin St ) Sligand1 + SNi + Sligand2
19
and a subspin of the ligand S* ) Sligand1 + Sligand2
.
For the L-Ni(III)-L configuration with an unpaired
electron localized at the metal ion, the EPR g tensor generally
exhibits considerable anisotropies and a large deviation from
the free electron g value as described in detail by Holm et
al.20,21 and Lovecchio et al.,22 respectively (Table 4). Thus,
the observed small g anisotropy with gav)2.073 for com-
plex 1 does not support the single metal centered (Ni(III))
unpaired electron. However, such a conclusion is not so
straightforward for complex 2. Although the g anisotropy
of 2 is much bigger than that of 1, the anisotropy of 2 could
be due to the large spin-orbital coupling of Te through M-L
π-interaction.
Figure 4. EPR spectra of complex 1 (top) and 2 (bottom) frozen in CH2-
Cl2 (4.2 K), respectively.
Scheme 4
The ligand radical stabilized by the Ni(II) configuration,
L-Ni(II)-L*, produces a typical radical EPR signal with
an isotropic g value closed to 2.00 (Table 4). Apparently,
the EPR spectrum of complex 1 is indicative of the ligand
radical characters but with a contribution of the Ni(III) d
orbital leading to the observed small g anisotropy.
co-workers,9 that complexes 1 and 2 contain delocalized
oxidation levels of the nickel ion and ligands, namely a
resonance hybrid of A (a paramagnetic NiIII (d7) central ion
with two dianionic o-amidochalcogenophenolato(2-)) and
B (a diamagnetic NiII (d8) central ion with o-amidochalco-
genophenolato(2-) as well as o-iminochalcogenobenzosemi-
quinonato(1-) π-radical ligands), as shown in Scheme 4a,b.
EPR Spectroscopy. The ground state electronic structures
of complexes 1 and 2 have also been investigated by the
variable temperature (4-300 K) EPR measurements. EPR
spectra of complex 1 (top) and complex 2 (bottom) frozen
in CH2Cl2 at 4.2 K are shown in Figure 4. The EPR signal
remains unchanged from room temperature down to 4.2 K.
The unresolved EPR spectrum of complex 1 exhibits an
observable but rather small g-tensor anisotropy, with all g
values greater than 2.0023. The slight rhombic distortion in
complex 1 is not obvious enough to be discerned from the
experimental EPR spectra directly and is obtained by com-
puter simulations with simulated principal g values at g1 )
2.036, g2 ) 2.062, and g3 )2.120. Complex 2 exhibits a
rhombic EPR spectrum and larger principal g values at g1
Since none of the configurations discussed here could,
alone, fully account for the observed EPR spectra, we suggest
that the spin configuration is better described as delocalized
systems described for the low spin Ni(III) d7 square planar
complex [Ni(S2C2(CN)2)2]-, for which a 3dyz/dxz (dyz/dxz-
pπ) ground state and spin delocalization were deduced.23-25
The delocalization of unpaired spin density was further
(18) Wang, H.; Ralston, C. Y.; Patil, D. S.; Jones, R. M.; Gu, W.; Verhagen,
M.; Adams, M.; Ge, P.; Riordan, C.; Marganian, C. A.; Mascharak,
P.; Kovacs, J.; Miller, C. G.; Collins, T. J.; Brooker, S.; Croucher, P.
D.; Wang, K.; Stiefel, E. I.; Cramer, S. P. J. Am. Chem. Soc. 2000,
112, 10544.
(19) Kambe, K. J. Phys. Soc. Jpn. 1950, 5, 48.
(20) Forbes, C. E.; Gold, A.; Holm, R. H. Inorg. Chem. 1971, 10, 2479.
(21) Holm, R. H.; Balch, A. L.; Davison, A.; Maki, A. H.; Berry, T. E. J.
Am. Chem. Soc. 1967, 89, 2866.
(22) Lovecchio, F. V.; Gore, E. S.; Busch, D. H. J. Am. Chem. Soc. 1974,
96, 3109.
(23) Maki, A. H.; Edelstein, N.; Davison, A.; Holm, R. H. J. Am. Chem.
Soc. 1964, 86, 4580.
(24) Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H. Inorg. Chem.
1964, 3, 814.
(25) (a) Lim, B. S.; Fomitchev, D. V.; Holm, R. H. Inorg. Chem. 2001,
40, 4257. (b) Stein, M.; van Lenthe, E.; Baerends, E. J.; Lubitz, W. J.
Phys. Chem. A 2001, 105, 416.
Inorganic Chemistry, Vol. 42, No. 12, 2003 3929

Hsieh et al.
Table 4. Electronic (g Tensor) Parameters for Square Planar Ni Complexes
oxidation state
characterization
complex
g1
g2
g3
giso
1
2
2.036
2.021
2.062
2.119
2.120
2.250
Ligand Radical with Metal d Characters (Delocalized System)
[1a/1b]-
2.0282
2.028
2.14
2.0055
2.005
2.04
2.1147
2.126
1.99
ligand ladical +
2 2
9
Ni(I) dx -y character
ligand radical +
[Ni(S(NH)C6H4)2]-
[NiS4C4(CN)4]-
[Ni(S2C2Me2)2]-
metal character21
delocalized spin with
Ni(III) dyz character23-25
delocalized spin with
2.118
2.041
2.000
Ni(III) dyz character23-25
Ligand Radical
[NiMe2[14]1,3-dieneN4]-
[NiMe6[14]1,3,7,11-tetraeneN4]-
[1a/1b]+
2.004
2.003
2.0014
ligand radical22
ligand radical22
ligand radical9
1.9970
1.9901
2.0172
Metal Centered Oxidation State
[NiMe6[14]1,4,8,11-tetraeneN4]-
[NiMe6[14]4,11-dieneN4]-
2.053
2.055
2.186
2.199
2.180
2.053
2.055
2.186
2.199
2.180
2.195
2.226
2.018
2.024
2.016
Ni(I)22
Ni(I)22
[NiMe6[14]1,4,8,11-tetraeneN4]+
[NiMe6[14]4,11-dieneN4]+
Ni(III)22
Ni(III)22
Ni(III)22
[NiMe6[14]1,3,7,11-tetraeneN4]+
Figure 5. X-ray absorption near edge spectroscopy (XANES) of Ni:
K-edge spectra of Ni foil and Ni complexes 1, 2, 3, 4 [t-Bu4P][Ni(-SC6H4-
o-S-)2], and 5 Ni(S2CNBu2)2.
characterized by ENDOR26 and ESEEM26 of 13C and 14,15N
isotopomers of such a complex. The fact that the unpaired
electron is delocalized onto the ligands supports the observed
small anisotropy of the g factor and the decreases in g values
for complex 1.
Figure 6. X-ray absorption spectroscopy of Ni LIII, II-edge spectra of some
Ni complexes 1-5 are as in Figure 5.
Ni(II) complex, 5. The main LIII peak at ∼854.5 eV, an
indication of Ni(III) oxidation state, was observed with a
shoulder at ∼853.5 eV for complexes 1-4, individually.
Recently, it was reported that the average centroids of the
X-ray Absorption Spectroscopy. In order to clarify the
detailed electronic structure (oxidation state) of the central
nickel ion in complexes 1-4, the X-ray absorption measure-
ments were undertaken. The K-edge absorption spectra of
complexes 1-4 are displayed in Figure 5. A typical Ni(0)
of Ni foil and a square planar, low spin, diamagnetic d8 Ni-
(II) complex 5, Ni(S2CNBu2)2, are included for references.
As shown in Figure 5, the absorption edge E0 of Ni(II)
complex 5 is higher than that of Ni(0). The even higher
energy E0 of 1-4 than that of 5 implies a higher oxidation
state of Ni in these complexes. Among them, the E0 values
of 1 and 3 are slightly higher than those of 2 and 4.
The Ni LIII, II-edge absorption spectra of complexes 1-4
are depicted in Figure 6 together with that of a typical
L
III edge of Ni(I), Ni(II, high spin)/Ni(II, low spin), and Ni-
(III) complexes are at 852.5, 853.4/853.5, and 854.5 eV,
respectively.18,27,28 However, it was also realized that a Ni(III)
absorption is often accompanied by the presence of Ni(II)
due to the charge transfer (LMCT) mechanism.29 Apparently,
complexes 1, 3, and 4 all have the main LIII and LII absorption
peaks at ∼854.5 and ∼871.5 eV, respectively, which is a
(27) Ralston, C. Y.; Wang, H.; Ragsdale, S. W.; Kumar, M.; Spangler, N.
J.; Ludden, P. W.; Gu, W.; Jones, R. M.; Patil, D. S.; Cramer, S. P.
J. Am. Chem. Soc. 2000, 122, 10553.
(28) Wang, H.; Patil, D. S.; Gu, W.; Jacquamet, L.; Friedrich, S.; Funk,
T.; Cramer, S. P. J. Electron Spectrosc. Relat. Phenom. 2001, 114-
116, 855-863.
(29) De Nada¨ı, C.; Demourgues, A.; Grannec, J.; de Groot, F. M. F. Phys.
ReV. B 2001, 63, 125123.
(26) Huyett, J. E.; Choudhury, S. B.; Eichhorn, D. M.; Bryngelson, P. A.;
Maroney, M. J.; Hoffman, B. M. Inorg. Chem. 1998, 37, 1361.
3930 Inorganic Chemistry, Vol. 42, No. 12, 2003

Synthesis and Characterization of Ni Complexes
Figure 7. Plots of µeff vs T for complexes 1 and 2, respectively.
typical Ni(III). A shoulder peak at this energy is also
observed in complex 2. Taking a closer look of the absorption
spectra, an additional absorption peak at ∼853.5 eV is
observed for all complexes. A plausible interpretation of these
spectra is mixed Ni(II) T Ni(III) states existing in all these
complexes, where the major component is Ni(III) for 1, 3,
and 4. No Ni(I) state is observed between the edges of Ni
foil and of 5. The LIII-edge absorption spectrum of complex
1 is similar to that of K3NiF6,18 and the simulated spectra
using a ligand field multiplet calculation on the basis of
Ni(III) in D4h symmetry with the charge-transfer effect being
taken into account;18,29,30 i.e., it contains a 3d7 and 3d8L mixed
state where L means an electron hole at a ligand site.29,30 In
fact, this is consistent with what was found in the EPR
measurement, where a L-Ni(III)-L and a L-Ni(II)-L* (or
Figure 8. SOMO of (a) complex 1 and (b) complex 2. Solid and mesh
surfaces are of opposite sign.
As seen in Figure 8a,b, the unpaired electron is indeed
delocalized between the Ni and the ligands. The ligand π*-
orbital is mainly contributed by the following orbitals: 4pz
of selenium, 5pz of tellurium, and 2pz of nitrogen. This MO
can be realized as metal-to-ligand back-bonding, and thus,
the ligand is serving as a π-acceptor. Mu¨lliken population
analysis gave the atomic spin density of each selenium
(tellurium), nitrogen, and nickel atom as 0.083 (0.144), 0.138
(0.104), and 0.345 (0.339), respectively. The residual spin
density of ∼0.21 (∼0.16) is dissipated equally onto the two
phenyl rings. The total unpaired spin density of ∼0.78 and
∼0.75 of the core of complexes 1 and 2, respectively, is
comparable with that of the [NiS4] core of [Ni(S2C2(CN)2)2]-
(∼0.85 and ∼0.75 derived from ENDOR and DFT,26
respectively) and of [Ni(S2C2Me2)2]- (∼0.79 derived from
DFT25).
1
L*-Ni(II)-L) with a spin state of (1/2, 0) and (1/2, /2) as a
ground state, respectively.
The magnetic measurements of complexes 1 and 2 are
shown in Figure 7. It is roughly in accord with one net
unpaired electron of µeff ∼ 1.6µB and ∼1.7µB for complexes
1 and 2, respectively; however, the temperature dependence
is very small though detectable. It is unlikely to be described
as three unpaired electrons coupled together to yield a net
one unpaired electron, i.e., a (1/2, 1) state which supposedly
will give a large temperature dependence. Therefore, a mixed
1
spin state of (1/2, 0) and (1/2, /2) is ascribed for such a
magnetic measurement.
Summary. Complex [Ni(CO)(SePh)3]- provides a con-
venient preparative entry to the complexes trans-
[Ni(-SeC6H4-o-NH-)2]- (1), cis-[Ni(-TeC6H4-o-NH-)2]-
(2), trans-[Ni(-SC6H4-o-NH-)2]- (3), and [Ni(-SC6H4-o-
S-)2]- (4). Square planar structures of complexes 1-3 have
been characterized by X-ray analysis. The anisotropy in g
values of these complexes from EPR measurement as well
as the magnetic measurement is consistent with the spin
located either at the Ni site or at one of the ligand sites, i.e.,
L-Ni(III)-L or L-Ni(II)-L* with probable (1/2, 0) or (1/2,
1/2) as the ground state. The spin exchange between Ni and
L could be accomplished through the Ni-L π bond, namely
pz-dxz/dyz -pz molecular orbitals as realized by DFT calcula-
tion. Ni LIII-peaks at ∼853.5 and ∼854.5 eV for complexes
1-4 also indicate the existence of the Ni(II) and Ni(III)
valence state. On the basis of the X-ray structural data,
DFT Computation. In order to compare the SOMOs25,26
of these complexes with those of the [Ni(S2C2Me2)2]- and
[Ni(S2C2(CN)2)2]- complexes, a density functional theory
based on MO calculation at unrestricted ZORA scalar
relativistic BP/TZ2P level was performed. The derived
SOMOs of complexes 1 and 2 are depicted in Figure 8a,b,
respectively, which shows an antibonding π-character be-
tween the 3dxz orbital of the nickel ion and the π*-orbital of
the ligand in both complexes. The outcome is consistent with
the SOMOs of [Ni(S2C2(CN)2)2]- and [Ni(S2C2Me2)2]-
which reconfirms the L-Ni(III)-L and L-Ni(II)-L* con-
figuration and in accord with EPR measurements and X-ray
absorption spectra.
(30) Hu, Z.; Kaindl, G..; Warda, S. A.; Reinen, D.; de Groot, F. M. F.;
Mu¨ller, B. G. Chem. Phys. 1998, 232, 63.
Inorganic Chemistry, Vol. 42, No. 12, 2003 3931

Hsieh et al.
Table 5. Crystal Data of Complexes 1, 2, and 3
magnetic measurements, and UV-vis, EPR, and X-ray K-
and L-edge absorption spectroscopy, a delocalized oxidation
level of the nickel ion and ligands is proposed for complexes
1-4, as shown in Scheme 4. We noticed that the monoan-
ionic complex [Pt(LISQ)2]- (LISQ ) o-iminobenzosemiquinon-
ate(1-)), reported by Wieghardt and co-workers very
recently,9c is best described as a delocalized mixed-valence
system where the unpaired electron is mainly located on the
ligands and the delocalized SOMO acquires some metal d
character by mixing with the d orbital of the Pt (the observed
g anisotropy). This elucidation may further explain the
observations of this study in complexes 1-4, especially
complex 2 with the suspected large spin-orbit coupling of
the Te through M-L π-interaction.
1
2
3
chem formula
C48H40N3-
P2Se2Ni
937.40
monoclinic
C2/c
0.7107
18.1779(12)
11.3673(8)
20.4646(14)
90
99.485(2)
90
4170.9(5)
4
1.493
2.325
C52H50ON3-
P2Te2Ni
1108.80
monoclinic
P21/n
C48H40N3-
P2S2Ni
843.60
monoclinic
C2/c
0.7107
18.2656(12)
11.1299(7)
20.3728(14)
90
99.713 (1)
90
4082.3(5)
4
1.373
0.695
fw
cryst syst
space group
λ(Mo KR), Å
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
0.7107
16.7321(9)
13.0594(7)
22.4392(13)
90
96.892(1)
90
4867.8(5)
4
1.513
Z
d
calcd, g cm-3
µ, mm-1
T, K
1.679
293(2)
293(2)
293(2)
Experimental Section
R
0.0398a
0.0455b
1.048
0.0342a
0.0759b
1.039
0.0334a
0.0654b
0.829
Rw(F2)
GOF
Manipulations, reactions, and transfers of samples were con-
ducted under nitrogen according to standard Schlenk techniques
or in a glovebox (argon gas). Solvents were distilled under nitrogen
from appropriate drying agents (diethyl ether from CaH2, acetonitrile
from CaH2-P2O5, methylene chloride from P2O5, hexane and
tetrahydrofuran (THF) from sodium-benzophenone) and stored in
dried, N2-filled flasks over 4 Å molecular sieves. Nitrogen was
purged through these solvents before use. Solvent was transferred
to a reaction vessel via a stainless steel cannula under positive
pressure of N2. The reagents iron pentacarbonyl, cyclopentadi-
enylnickel carbonyl dimer, bis(triphenylphosphoranylidene)ammonium
chloride (Lancaster/Aldrich), triethylamine (TCI), 2-aminophe-
nylthiol, diphenyl diselenide, 2-aminophenyl diselenide (Arcos), and
1,2-benzenedithiol (Fluka) were used as received. The compound
2-aminophenyl ditelluride was synthesized and characterized by
published procedures.31 Infrared spectra of the ν(NH) stretching
frequencies were recorded on a Bio-Rad model FTS-185 spectro-
photometer with sealed solution cells (0.1 mm) and KBr windows.
UV-vis spectra were recorded on a Hewlett-Packard 71 spectro-
photometer. Cyclic voltammograms were obtained from 2 mM
analyte concentration in CH3CN using 0.1 M [n-Bu4N][PF6] as
supporting electrolyte (scan rate 250 mV/s). Analyses of carbon,
hydrogen, and nitrogen were obtained with a CHN analyzer
(Heraeus).
Preparation of trans-[PPN][Ni(-SeC6H4-o-NH-)2] (1). The
compounds [PPN][Ni(CO)(SePh)3] (0.5 mmol, 0.545 g) and 2-ami-
nophenyl diselenide (0.5 mmol, 0.172 g) were dissolved in 5 mL
of THF and stirred at ambient temperature overnight. Upon contact
with air, the color of the reaction mixture immediately turned from
dark brown to dark green. The solution was then filtered through
Celite, and hexane (15 mL) was added to precipitate the dark green
solid trans-[PPN][Ni(-SeC6H4-o-NH-)2] (1) (0.422 g, 90%).
Diffusion of hexane into a CH2Cl2 solution of complex 1 at -15
°C for 4 weeks led to dark green crystals suitable for X-ray
crystallography. IR (CH2Cl2): 3352 br (νNH) cm-1. Absorption
spectrum (CH2Cl2) [λmax, nm (ꢀ, M-1 cm-1)]: 312(21520), 372(8800),
405(6960) (sh), 623(1600), 693(2297), 936(13603). Anal. Calcd
for C48H40NiN3Se2P2: C, 61.50; H, 4.30; N, 4.48. Found: C, 61.08;
H, 4.27; N, 4.26.
a R ) ∑|(Fo-Fc)|/∑Fo. b Rw(F2) ) {∑w(Fo - Fc )2/∑[w(Fo )2]}1/2
.
2
2
2
(1 mmol, 139 µL) and CH3CN-CH2Cl2 (2 mL + 2 mL) solvent
were then added by syringe to the reaction mixture, respectively.
Upon contact with air, the color of reaction mixture immediately
turned from dark red-brown to dark green-brown. The resulting
mixture was filtered through Celite, and then, hexane was added
to precipitate the dark brown solid cis-[PPN][Ni(-TeC6H4-o-NH-
)2] (2). Recrystallization from saturated CH2Cl2 solution of complex
2 with hexane diffusion at ambient temperature gave dark brown
crystals (0.285 g, 53%) suitable for X-ray crystallography. IR (CH2-
Cl2): 3333, 3327 (νNH) cm-1. Absorption spectrum (CH2Cl2) [λmax
,
nm (ꢀ, M-1 cm-1)]: 331(12485), 413(4485), 552(1353), 707(1745),
847(5351), 942(10105). Anal. Calcd for C48H40NiN3Te2P2: C,
54.66; H, 4.20; N, 3.98. Found: C, 55.77; H, 4.63; N, 4.31.
Preparation of trans-[PPN][Ni(-SC6H4-o-NH-)2] (3). 2-Ami-
nophenylthiol (0.5 mmol, 50 µL) was added dropwise by syringe
to a solution containing 0.468 g (0.5 mmol) of complex 1 in CH2Cl2
(5 mL). The reaction solution was then stirred at ambient temper-
ature overnight. The solution was filtered through Celite, and
hexane (15 mL) was added to precipitate the dark green solid trans-
[PPN][Ni(-SC6H4-o-NH-)2] (3) (0.262 g, 62%).11a Diffusion of
hexane into a CH2Cl2 solution of complex 3 at -15 °C for 4 weeks
yielded dark green crystals suitable for X-ray crystallography. IR
(CH2Cl2): 3357 (νNH) cm-1. Absorption spectrum (CH2Cl2) [λmax
,
nm (ꢀ, M-1 cm-1)]: 326(11649), 411(4828), 628(1741), 912(12118)
(sh), 945(12573).
Reaction of 1,2-Benzenedithiol and Complex 1. Initially, 1.2-
benzenedithiol (0.2 mmol, 24 µL) was added dropwise by syringe
to a solution containing 0.187 g (0.2 mmol) of complex 1 in CH2-
Cl2 (5 mL). After the reaction solution was stirred for 1 h at room
temperature, hexane was added to precipitate the known dark green
solid trans-[PPN][Ni(-SC6H4-o-S-)2] (4).11b The stable product
4 was washed twice with CH2Cl2-hexane and dried under vacuum.
Crystals suitable for X-ray crystallography were grown by vapor
diffusion of hexane into a concentrated CH2Cl2 solution of 4 at
-15 °C. Absorption spectrum (CH2Cl2) [λmax, nm (ꢀ, M-1 cm-1)]:
312(17049), 357(7107), 663(1217), 818(5306) (sh), 879(9401).
Crystallography. Crystallographic data of complexes 1-3 are
summarized in Table 5, and in the Supporting Information. The
crystals of 1-3 are chunky. The crystals of 1-3 chosen for X-ray
diffraction studies measured 0.42 × 0.32 × 0.30 mm3, 0.30 × 0.28
× 0.25 mm3, and 0.34 × 0.30 × 0.16 mm3, respectively. Each
crystal was mounted on a glass fiber and quickly coated in epoxy
Preparation of cis-[PPN][Ni(-TeC6H4-o-NH-)2] (2). 2-Ami-
nophenyl ditelluride (0.5 mmol, 0.220 g) was added to a THF (10
mL) solution containing 0.545 g (0.5 mmol) of [PPN][Ni(CO)-
(SePh)3] and stirred at ambient temperature for 1 h. Triethylamine
(31) Engman, L.; Stern, D.; Cotgreave, I. A.; Andersson, C. M. J. Am.
Chem. Soc. 1992, 114, 9737.
3932 Inorganic Chemistry, Vol. 42, No. 12, 2003

Synthesis and Characterization of Ni Complexes
resin. Unit cell parameters were obtained by least-squares refine-
ment. Diffraction measurements for complexes 1-3 were carried
out on a SMART CCD diffractometer with graphite-monochro-
mated Mo KR radiation (λ ) 0.7107 Å) and θ between 2.02° and
27.52° for complex 1, between 1.44° and 27.50° for complex 2,
and between 2.03° and 27.55° for complex 3. Least-squares
refinement of the positional and anisotropic thermal parameters of
all non-hydrogen atoms and fixed hydrogen atoms was based on
F2. A SADABS32 absorption correction was made. The SHELXTL33
structure refinement program was employed.
X-ray Absorption Measurements. All X-ray absorption experi-
ments were carried out at the Synchrotron Radiation Research
Center (SRRC), Hsinchu, Taiwan. Both Ni K-edge and L-edge data
were recorded at room temperature. Samples of [PPN][Ni(EC6H4-
o-NH)2] (E ) Se, Te, S) are single crystals, and those of [t-Bu4P]-
[Ni(SC6H4-o-S)2] and NiII(S2CNBu2)2 were purchased from TCI.
For Ni K-edge measurements, the experiments were performed in
transmission mode at the BL-17C X-ray Wiggler beamline with a
double crystal Si(111) monochromator. The higher X-ray harmonics
were minimized by detuning the double-crystal monochromator to
80% of the maximum. The spectra were scanned from 8.132 to
9.326 keV using a gas-ionization detector. A reference Ni foil is
always used simultaneously for the calibration of energy. The ion
chambers used to measure the incident (I0) and transmitted (I)
intensities were filled with a mixture of N2 and He gases and a
mixture of N2 and Ar gases, respectively.
Magnetic Measurements. The magnetization data were recorded
on a SQUID magnetometer (MPMS7 Quantum Design company)
with an external 1.0 T magnetic field in the temperature range from
2-300 K. The magnetic susceptibility of the experimental data was
corrected for diamagnetism by the tabulated Pascal’s constants.
Computational Details. The spin-unrestricted DFT calculations
were carried out using the ADF2002.0234 package. All electrons
were included in the calculation. The zero-order regular approxima-
tion (ZORA)35 Hamiltonian was used to include the relativistic
effects referred to as scalar relativistic (SR) effects and spin-orbit
(SO) coupling. The local density approximation (LDA) utilized the
Vosko-Wilk-Nusair (VWN)36 functional, and the nonlocal cor-
rections were the Becke exchange37 and Perdew correlation38
functionals (BP) which were shown to yield the best magnetic
resonance parameters of the pure generalized gradient approxima-
tion (GGA).39 The basis sets are essentially Slater type with
relativistic ZORA/TZ2P, characterized by a core double-ú, valence
triple-ú and doubly polarized basis. The SOMO was drawn by
MOLEKEL4.3.40
Acknowledgment. This work was supported by the
National Science Council (Taiwan). We gratefully acknowl-
edge Prof. Hong-Chang Yang, Instrumentation Center, for
the magnetic measurements, and the Synchrotron Radiation
Research Center for X-ray absorption experiments.
For Ni L-edge measurements, the data were collected at the 6-m
high-energy spherical grating monochromator (HSGM) beamline
with 40 µm opening slits, corresponding to ∼0.3 eV energy
resolution for the Ni L-edge energy range. All samples were ground
to powder from single crystals, stuck to conducting tape, and then
subjected to an ultrahigh vacuum chamber (10-9 Torr). The spectra
were recorded in total electron yield mode with a microchannel
plate as detector. Each spectrum was calibrated by using the known
LIII-edge absorption peak at 853.2 eV of NiO.
EPR Measurements. EPR measurements were performed at
X-band using a Bruker EMX spectrometer equipped with a Bruker
TE102 cavity and a Bruker VT2000 temperature control unit (120-
300 K). For liquid helium temperature measurements, an Oxford
ESR910 continuous flow cryostat (4-200 K) was used. X-band
EPR spectra of complexes 1 and 2 frozen in CH2Cl2 were obtained
with a microwave power of 2 mW, frequency at 9.468 GHz (Figure
4 (top), complex 1) and 9.416 GHz (Figure 4 (bottom), complex
2), and modulation amplitude of 0.1 mT at 100 kHz (temperature
) 4.2 K).
Supporting Information Available: X-ray crystallographic data
in CIF format for the structure determinations of trans-[PPN][Ni-
(-SeC6H4-o-NH-)2], cis-[PPN][Ni(-TeC6H4-o-NH-)2], and trans-
[PPN][Ni(-SC6H4-o-NH-)2]. This material is available free of
charge via the Internet at http://pubs.acs.org.
IC034211R
(34) (a) te Velde, G.; Bickelhaupt, F. M.; van Gisbergen, S. J. A.; Guerra,
C. F.; Baerends, E. J.; Snijders, J. G.; Ziegler, T. J. Comput. Chem.
1999, 22, 931. (b) Guerra, C. F.; Snijders, J. G.; te Velde, G.; Baerends,
E. J. Theor. Chem. Acc. 1998, 99, 391. (c) ADF2002.02; SCM
Theoretical Chemistry, Vrije Universiteit: Amsterdam, The Nether-
lands; http://www.scm.com.
(35) (a) Chang, C.; Pelissier, M.; Durand, M. Phys. Scr. 1986, 34, 394. (b)
van Lenthe, E.; Baerends, E. J.; Snijders, J. G. J. Chem. Phys. 1993,
99, 4597. (c) van Lenthe, E.; Baerends, E. J.; Snijders, J. G. J. Chem.
Phys. 1994, 101, 9783. (d) van Lenthe, E.; van Leeuwen, R.; Baerends,
E. J.; Snijders, J. G. Int. J. Quantum Chem. 1996, 57, 281.
(36) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200.
(37) (a) Becke, A. D. J. Chem. Phys. 1986, 84, 4524. (b) Becke, A. D.
Phys. ReV. 1988, A38, 3098.
(38) (a) Perdew, J. P. Phys. ReV. 1986, B33, 8822. (b) Perdew, J. P. Phys.
ReV. 1986, B34, 7406.
(39) Belanzoni, P.; Baerends, E. J.; Gribnau, M. J. Phys. Chem. A 1999,
103, 3732.
(40) Flu¨kiger, P.; Luthi, H. P.; Portmann, S.; Weber, J. Molekel4.3; Swiss
Center for Scientific Computing: Manno, Switzerland, 2000-2002.
(32) Sheldrick, G. M. SADABS, Siemens Area Detector Absorption Cor-
rection Program; University of Go¨ttingen: Go¨ttingen, Germany, 1996.
(33) Sheldrick, G. M. SHELXTL, Program for Crystal Structure Determi-
nation; Siemens Analytical X-ray Instruments Inc.: Madison, WI,
1994.
Inorganic Chemistry, Vol. 42, No. 12, 2003 3933