N-H bond activation of 2-aminobenzophenone by trimethylphosphine complexes of nickel and cobalt

Article abstract of DOI:10.1016/j.poly.2012.12.005

2-Aminobenzophenone (1) reacted with NiMe₂(PMe₃) ₃ and CoMe₃(PMe₃)₃ afforded N-H bond cleavage products, the tetra-coordinate square-planar nickel complex (2), and the hexa-coordinate octahedral dimethyl cobalt(III) complex (3) with a cationic [N, O]-chelate ligand while the reaction of Co(PMe₃)₄ with 2-aminobenzophenone (1) delivered only a π-(CO) coordinate complex (o-NH-C₆H₄-eta²-C(O)-C₆H ₅)Co(PMe₃)₃ (4) in a tetrahedral coordination geometry. The structures of complexes 2-4 were determined by X-ray single crystal diffraction. The formation mechanism of complex 2 was discussed.

Full text of DOI:10.1016/j.poly.2012.12.005

Polyhedron 50 (2013) 571–575
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Polyhedron
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N–H bond activation of 2-aminobenzophenone by trimethylphosphine complexes
of nickel and cobalt
⇑
Zehua Zhang, Hongjian Sun, Wengang Xu, Xiaoyan Li
School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
2-Aminobenzophenone (1) reacted with NiMe2(PMe3)3 and CoMe3(PMe3)3 afforded N–H bond cleavage
Received 12 September 2012
Accepted 7 December 2012
Available online 20 December 2012
products, the tetra-coordinate square-planar nickel complex
hexa-coordinate octahedral dimethyl cobalt(III) complex
(2), and the
(3) with a cationic
[N, O]-chelate ligand while the reaction of Co(PMe3)4 with 2-aminobenzophenone (1) delivered only a p-
Keywords:
(C@O) coordinate complex (o-NH–C6H4–eta2-C(@O)–C6H5)Co(PMe3)3 (4) in a tetrahedral coordination
geometry. The structures of complexes 2–4 were determined by X-ray single crystal diffraction. The for-
mation mechanism of complex 2 was discussed.
2-Aminobenzophenone
N–H activation
Nickel
Cobalt
Trimethylphosphine
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Among the publications on the N–H bond activation of amine
molecules, Hartwig’s work is very conspicuous. He and his cowork-
Amines are important intermediates and starting materials in
the synthesis of natural products, pharmacological agents, fine
chemicals, agrochemicals and some other industrial chemical sub-
stances [1]. N–H bond activation and formation of the N–C bond
are involved in many synthetic methods of amines. In fact, activa-
tion of the N–H bond by the transition metals has always been uti-
lized as the key step in the hydroamination reaction [2], therefore
transition metal complex mediated N–H bond activation and func-
tionalization to various useful intermediates and chemical sub-
ers synthesized pincer-(PCP)IrH2 complexes to activate the N–H
bond of NH3 or aniline. Hartwig concluded that two factors ratio-
nalize the difference in stability of the products from the reactions
of aniline and ammonia. The dative bond in an aniline complex is
weaker than that in an ammonia complex because of lower basi-
city while an M–N bond in an anilide complex is stronger (relative
to the respective H–N bonds) than the M–N bond in an amido com-
plex because of a greater ionic interaction [6].
Recently, several articles regarding the N–H bond activation of
amides were published with different organometallic complexes
[7–15]. Some of them provide new methods of synthesis of amine.
Ir(I)-C3-TUNEPHOS complex can catalyze an intermolecular hydro-
amination of styrene derivatives with various heteroaromatic
amines under solvent free condition [7]. [Rh(COD)2]BF4 can also
be a catalyst in the hydroamination of olefins [8]. Another study
of anti-Markovnikov hydroamination of vinylarenes was disclosed
with [Rh(COD)(DPEphos)]BF4 as catalyst in good yield [9]. Tita-
nium and zirconium amido complexes supported by imidazole-
containing ligands can catalyze hydroamination of alkynes with
aniline via N–H bond activation [10]. Schafer and co-workers has
a broad mechanistic investigation of hydroamination reactions cat-
alyzed by a tethered bis(ureate) zirconium species [11]. We also
reported a new method of carbonylative formation of N-acetyl-
2,6-difluorobenzamide through N–H bond activation of 2,6-difluo-
robenzamide with Ni(II) complex [12]. Lancaster and co-workers
disclosed N–H bond activation by zirconocene and hafnocene
complexes [13]. With pincer Rh(I) complexes the N–H bond of
stances have now become
a hot spot in current chemical
research. For example, the catalytic addition of ammonia to olefins
and the coupling between ammonia and aromatic compounds are
thought to be two of the 10 greatest current challenges for catalytic
chemistry [3]. Unfortunately, many common reactions catalyzed
by transition metal complexes do not occur with ammonia [4]. This
lack of reactivity of ammonia results from several factors. In the
first place, the reactions of ammonia with most of transition metal
complexes generate simple Lewis acid–base complexes. The cata-
lyst is often deactivated by formation of stable Werner’s ammine
complexes. Secondly, the strength of the N–H bond in ammonia
(107 kcal/mol) makes this ‘‘N–H activation’’ by the metal center
difficult. In addition, the moderate basicity and low acidity of
ammonia disfavor proton exchanges, either as a proton donor or
as a proton acceptor [5].
⇑
Corresponding author. Tel.: +86 531 88361350; fax: +86 531 88564464.
E-mail address: xli63@sdu.edu.cn (X. Li).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.005

572
Z. Zhang et al. / Polyhedron 50 (2013) 571–575
RNH2 was cleavaged [14]. Bohle gave an example of the N–H acti-
vation in N-nitropropionate using IrCl(N2)(PPh3)2 complex [15].
In this paper we present the recent results of our study on N–H
bond activation of 2-aminobenzophenone (o-NH2–C6H4–C(@O)–
C6H5) (1) by NiMe2(PMe3)3, CoMe3(PMe3)3 and Co(PMe3)4. The cor-
2.4. Synthesis of 4
To a solution of Co(PMe3)4 (0.91 g, 2.5 mmol) in 30 mL of THF
was slowly added
a solution of 2-aminobenzophenone (1)
(0.46 g, 2.3 mmol) in 30 mL of THF at 0 °C. The mixture was al-
lowed to warm to ambient temperature. The color of the solution
turned to yellow brown from yellow. After stirring at 40 °C for
72 h, a yellow brown solution was obtained. The solvent was re-
moved under reduced pressure and the brown residue was ex-
tracted with pentane (60 mL). After filtration, the brown spindle
crystals suitable for X-ray diffraction analysis were obtained at
ꢀ18 °C. Yield: 27.9% (0.31 g). Elemental Anal. Calc. for C22H39-
CoNOP3 (485.38): C, 54.44; H, 8.10; N, 2.89. Found: C, 54.24; H,
responding N–H bond cleavage products
(2),
(3) and p-(C@O) coordinated com-
plex (o-NH–C6H4–eta2-C(@O)–C6H5)Co(PMe3)3 (4) were isolated
and structurally characterized.
2. Experimental
8.11; N, 2.95%. IR (Nujol, cmꢀ1): 3432, 3314
(C@O), 937 (PMe3).
m(N–H), 1625
2.1. General procedures and materials
m
m
Standard vacuum techniques were used in manipulations of
volatile and air-sensitive materials. Solvents were dried by known
procedures and distilled under nitrogen before use. Literature
methods were used in the preparation of NiMe2(PMe3)3, CoMe3
(PMe3)3, Co(PMe3)4 and 2-aminobenzophenone [16–19]. Infrared
spectra (4000–400 cmꢀ1), as obtained from Nujol mulls between
KBr disks, were recorded on a Bruker ALPHA FT-IR Spectrometer.
1H, 13C and 31P NMR spectra (300, 75, and 121 MHz, respectively)
were recorded on a Bruker Avance 300 spectrometer. 13C and 31P
NMR resonances were obtained with broadband proton decou-
pling. Elemental analyses were carried out on an Elementar Vario
EL III.
2.5. X-ray structure determination
Intensity data were collected on a Bruker SMART 1000 diffrac-
tometer with graphite-monochromated Mo radiation
(k = 0.71073 Å). Crystallographic data for complexes 2–4 are sum-
marized in Table 1. The structures were solved by direct methods
and refined with full-matrix least-squares on all F2 (SHELXL-97) with
non-hydrogen atoms anisotropic.
K
a
Table 1
Crystallographic data for complexes 2–4.
Complex
2
3
4
2.2. Synthesis of 2
Empirical formula
Formula weight
T (K)
Crystal system
Space group
a (Å)
C
17H22NNiOP
C21H34CoNOP2
437.36
140(2)
C22H39CoNOP3
485.38
293(2)
monoclinic
P2(1)
14.410(2)
9.726(1)
19.064(2)
102.438(2)
2609.0(5)
4
1.236
14922
5795
0.0948
27.52
0.0489
0.1350
346.04
293(2)
monoclinic
P2(1)/c
11.783(2)
15.907(3)
9.671(2)
104.30(3)
1756.5(6)
4
1.194
6243
2055
0.0307
21.70
To a solution of NiMe2(PMe3)3 (0.79 g, 2.5 mmol) in 30 mL of
THF was slowly added a solution of 2-aminobenzophenone (1)
(0.46 g, 2.3 mmol) in 30 mL of THF at 0 °C. The mixture was al-
lowed to warm to ambient temperature. The color of the solution
turned to red slowly from orange. After stirring at 40 °C for 72 h,
a claret solution was obtained. The solvent was removed under re-
duced pressure and the red residue was extracted with pentane
(60 mL). After filtration, the red pale crystals suitable for X-ray dif-
fraction analysis were obtained at ꢀ18 °C. Yield: 64.3% (0.51 g).
Elemental Anal. Calc. for C17H22NNiOP (346.04): C, 59.01; H, 6.41;
N, 4.05. Found: C, 59.21; H, 6.11; N, 3.95%. IR (Nujol, cmꢀ1): 3176
monoclinic
P2(1)/c
7.640(2)
27.333(6)
10.580(2)
108.97(3)
2089.4(7)
4
1.390
16091
4449
0.0486
b (Å)
c (Å)
b (°)
V (Å3)
Z
Dcalc (Mg mꢀ3
)
Reflections measured
Unique reflections
Rint
hmax (°)
26.92
0.0465
0.1279
m(N–H), 1616
m
(C@O), 941 m
(PMe3). 1H NMR (300 MHz, C6D6,
R1 (I > 2r(I))
0.0321
0.0793
294 K, ppm):
d
ꢀ0.29 (d, 3J(PH) = 8.4 Hz, 3H, CH3), 0.76 (d,
wR2 (all data)
2J(PH) = 9.0 Hz, 9H, PCH3), 5.87 (s br, 1H, NH), 6.03–7.45 (m, 9H,
Ar–H); 31P NMR (121.5 MHz, C6D6, 294 K): d ꢀ8.3 (s, PCH3). 13C
NMR (75.5 MHz, C6D6, 294 K, ppm): d ꢀ12.3 (d, 2J(PC) = 35.4 Hz,
CH3), 11.7 (d, 2J(PC) = 26.4 Hz, PCH3), 111.6–185.0 (m, Ar–C).
3. Results and discussion
3.1. Reaction of NiMe2(PMe3)3 with 2-aminobenzophenone (1)
2.3. Synthesis of 3
The reaction of NiMe2(PMe3)3 with 2-aminobenzophenone (1)
afforded four-coordinate Ni(II) complex 2 via N–H bond activation
with the ketone group as the directing group (Eq. (1)).
To a solution of CoMe3(PMe3)3 (0.83 g, 2.5 mmol) in 30 mL of
THF was slowly added a solution of 2-aminobenzophenone (1)
(0.46 g, 2.3 mmol) in 30 mL of THF at 0 °C. The mixture was al-
lowed to warm to ambient temperature. The color of the solution
turned to green slowly from orange. After stirring at 40 °C for
72 h, a dark green solution was obtained. The solvent was removed
under reduced pressure and the green residue was extracted with
pentane (60 mL). After filtration, the green lump crystals suitable
for X-ray diffraction analysis were obtained at ꢀ18 °C. Yield:
72.0% (0.72 g). Elemental Anal. Calc. for C21H34CoNOP2 (437.36):
C, 57.67; H, 7.84; N, 3.20. Found: C, 57.55; H, 7.67; N, 3.05%. IR (Nu-
Me
NH
Me3P
Ni
O
NH2
O
ð1Þ
NiMe (PMe )
3 3
+
2
,
PMe3
CH4
2
2
1
Complex 2 was isolated as red crystals in the yield of 64%. Com-
plex 2 is stable at room temperature in the solid state for more
than 6 h and slowly decomposes in solution when it is exposed
to air. Complex 2 was characterized by elemental analysis, IR and
NMR spectroscopy. In the infrared spectra the characteristic
jol, cmꢀ1): 3175
m(N–H), 1603 m(C@O), 935 m
(PMe3). 1H NMR
(300 MHz, C6D6, 294 K, ppm): d ꢀ0.80 (s, 3H, CH3), ꢀ0.06 (s, 3H,
CH3), 1.02 (s, 18H, PCH3), 3.72 (s br, 1H, NH), 5.67–7.46 (m, 9H,
Ar–H); 31P NMR (121.5 MHz, C6D6, 294 K): d 14.2 (s, PCH3).

Z. Zhang et al. / Polyhedron 50 (2013) 571–575
573
phine ligand, one methyl group, the carbonyl group and the –NH
group at the four vertices. The four angles (N1–Ni1–
O1 = 91.2(1)°, N1–Ni1–C17 = 90.9(2)°, O1–Ni1–P1 = 88.55(8)° and
C17–Ni1–P1 = 89.5(1)°) between adjacent coordination bonds
around nickel center atom make 360.15°. This suggests that the
four coordination atoms [P1, O1, N1 and C17] and the central Ni
atom are nearly in a plane. N1–Ni1 distance (1.861(3) Å), O1–Ni1
distance (1.911(2) Å) and C17–Ni1 distance (1.929(4) Å) are within
the range of the corresponding bond lengths. Bond angles O1–Ni1–
C17 (174.6(2)°) and N1–Ni1–P1 (178.55(9)°) deviate from 180°.
This indicates the distortion of this square. The sum of the three
bond angles around N1 atom (H1–N1–Ni1 = 114.9°, H1–N1–
C8 = 114.9° and Ni1–N1–C8 = 130.2°) is 360°. This signifies N1
has planar geometry in an sp2 hybrid state.
It is proposed that the oxidative addition of N–H bond of 1 on
nickel center is the initial step to form an intermediate nickel(IV)
species (1a) (path A, Scheme 1). The nickel(IV) intermediate (1a)
is unstable and transforms into nickel(II) complex 2 by reductive
elimination with the escape of a methane molecule. An alternative
reaction pathway (path B) is protonolysis of Ni-methyl group to af-
ford anionic intermediate 1b and the nickel coordination cation 1c
by acidic amino proton. The second step is the substitution of two
trimethylphosphine ligands by the anionic chelate ligand to form
the final product 2.
Similar investigation was realized through the reaction of 2,6-
difluorobenzamide (C6H3F2-2,6)C(O)NH2 with NiMe2(PMe3)3 in
THF (Eq. (2)). A tetra-coordinate nickel(II) complex in square-pla-
nar coordination configuration with two trans-orientated trimeth-
ylphosphine ligands was isolated as N–H bond cleavage product
[12].
Fig. 1. Molecular structure of 2 (all hydrogen atoms were omitted for clarity).
Selected distances (Å) and angles (°): Ni1–N1 1.861(3), Ni1–O1 1.911(2), Ni1–C17
1.929(4), Ni1–P1 2.160(1), O1–C7 1.271(4), N1–C8 1.334(4); N1–Ni1–O1 91.2(1),
N1–Ni1–C17 90.9(2), O1–Ni1–P1 88.55(8), C17–Ni1–P1 89.5(1), C7–O1–Ni1
129.6(2), C8–N1–Ni1 130.2(2).
m
(
(C@O) band was recorded at 1616 cmꢀ1. Comparing with that
m
(C@O) 1630 cmꢀ1) of the free ligand 2-aminobenzophenone (1)
there is a red shift because of the coordination of the oxygen atom
of the ketone group to the central nickel atom. This coordination
makes the C@O bond weaker than the uncoordinated. The two IR
vibration bands (3434 and 3314 cmꢀ1) of –NH2 group in free ligand
1 disappeared while the N–H band of complex 2 is registered at
3176 cmꢀ1. In the 1H NMR spectra the proton resonances of the
NH and methyl groups in complex 2 are recorded as singlet at
5.87 ppm and a doublet at ꢀ0.29 ppm with the coupling constant
3J(PH) = 8.4 Hz. The 31P NMR signal is observed at ꢀ8.3 ppm as a
singlet. In the 13C NMR spectra the C atom resonance of the methyl
group in complex 2 is registered at ꢀ12.3 ppm while the signal of
the ketone C atom is located at 185 ppm. All of the spectroscopic
data imply a tetra-coordinate Ni(II) complex with one chelate li-
gand and one methyl as well as one trimethylphosphine ligand.
The molecular structure of 2 reveals aforementioned configura-
tion analysis (Fig. 1). The tetra-coordinate nickel(II) complex has a
square-planar coordination geometry with one trimethylphos-
F
O
F
O
PMe3
NH2
ð2Þ
N
H
Ni Me
PMe3
NiMe (PMe )
3 3
+
2
PMe3, CH4
F
F
3.2. Reaction of CoMe3(PMe3)3 with 2-aminobenzophenone (1)
The reaction of 2-aminobenzophenone (1) with CoMe3(PMe3)4
afforded the dimethyl cobalt(III) complex 3 via N–H bond activa-
tion with the elimination of methane (Eq. (3)). Crystallization at
Me
Ni Me
NH
H
Me3P
O
CH4
2
PMe3
1a
path A
Me
NH
Me3P
Ni
O
NH2
O
NiMe (PMe )
3 3
+
2
1
2
path B
CH4
_
2
PMe3
NH
O
+
NiMe(PMe3)3
+
1c
1b
Scheme 1. Proposed reaction mechanism for the reaction shown in Eq. (1).

574
Z. Zhang et al. / Polyhedron 50 (2013) 571–575
ꢀ18 °C from pentane delivered dark green crystals in the yield of
72%. Complex 3 is stable at room temperature in the solid state
for more than 4 h but quickly decomposes in solution when it is ex-
posed to air.
free 2-aminobenzophenone (1) molecule transforms into sp2-N in
the complex 3 after deprotonation and coordination. This change
is also compensated by the conjugation of the p-orbital of N1 atom
with the chelate ring and phenyl (C16–C21) group.
Me
Me
3.3. Reaction of Co(PMe3)4 with 2-aminobenzophenone (1)
Me3P
Co PMe3
The reaction of Co(PMe3)4 with 2-aminobenzophenone (1) did
not afford the N–H bond cleavage product. The isolated product
of this reaction is only a p-(C@O) coordinated cobalt(0) complex
4 (Eq. (4)).
NH
O
NH2
O
ð3Þ
CoMe (PMe )
3 3
+
3
,
PMe3
CH4
3
1
Me3P
O
PMe3
In the IR spectra of complex 3 the characteristic
was found at 1603 cmꢀ1. Comparing with that of the free ligand
2-aminobenzophenone (1) (
(C@O) 1630 cmꢀ1) this is also a red
m(C@O) band
O
Co
PMe3
ð4Þ
m
Co(PMe )
+
PMe3
3
4
+
shift because of the coordination of the O atom of the ketone group.
The two IR vibration bands (3434 and 3314 cmꢀ1) of –NH2 group in
free ligand 1 disappeared while the N–H band of complex 2 is reg-
istered at 3175 cmꢀ1. In the 1H NMR spectra the proton resonance
of the NH in complex 3 is recorded as a broadening singlet at
3.72 ppm. The signals of the two methyl groups are situated at
ꢀ0.80 and ꢀ0.06 ppm respectively as broadening singlet. The 31P
NMR signal is observed at 14.2 ppm as singlet for the two trimeth-
ylphosphine ligands in the same chemical environment. The spec-
troscopic data are compatible with an octahedral configuration
around the cobalt atom center with two axial phosphine ligands.
The molecular structure of complex 3 was confirmed by single
crystal X-ray diffraction analysis. The molecular structure of com-
plex 3 is shown in Fig. 2. The cobalt center has a distorted octahe-
dral coordination geometry with two P-donor atoms in the axial
positions, one anionic [N, O]-chelate ligand and two methyl groups
in the equatorial plane. If the two trimethylphosphine ligands are
considered as axial ligands with the angle of 175.76(2)° deviated
from 180°, the sum of the four angles between the coordination
bonds (N1–Co1–O1 = 87.69(7)°, O1–Co1–C4 = 88.40(9)°, C5–Co1–
C4 = 91.4(1)° and N1–Co1–C5 = 92.52(9)°) in the equatorial plane
is 360.01°. This indicated the co-planarity of the four coordination
atoms (C4, C5, N1 and O1) with the central cobalt atom while the
phenyl ring (C10–C15) is not in the chelate plane due to the pack-
ing effect in the crystal cell. N1 atom has planar configuration
(C21–N1–Co1 (130.88°) + C21–N1–HN1 (110.15°) + Co1–N1–HN1
(118.97°) = 360°). This means that the sp3-N in the amide in the
H2N
H2N
1
4
The relatively low yield (28%) might result from the equilibrium
between the reactants and the product. The complex 4 is stable in
the solid state at room temperature for more than 6 h and slowly
decomposes in solution when it is exposed to air. In the infrared
spectra of complex 4 the characteristic
1273 cmꢀ1. Comparing with that ( (C@O) 1630 cmꢀ1) of the free
2-aminobenzophenone ligand (1) there is significant red shift be-
cause of the -coordination of the C@O bond to the cobalt atom
[20–24]. The
(C@O) (1715 cmꢀ1) of free acetone shifted to
1230 cmꢀ1 after 2-coordination in the tungsten complex
(W(
2-(O@CMe2))(PMePh2)2Cl2) [20]. This red shift (357 cmꢀ1) in
m(C@O) is recorded at
m
p
m
g
g
complex 4 is remarkably larger than the red shifts in complexes
both 2 (14 cmꢀ1) and 3 (27 cmꢀ1). This explains that the C@O bond
in complex 4 is much more strongly activated by
than those in complexes 2 and 3 with
g
2-coordination
r
-coordination. The IR vibra-
tion bands (3432 and 3314 cmꢀ1) of –NH2 group in complex 4 are
the same as those of the free ligand 2-aminobenzophenone (1).
Therefore, that the –NH2 group did not coordinate to the cobalt
atom was proved by the X-ray crystal diffraction analysis.
The molecular structure of 4 (Fig. 3) reveals that the tetra-coor-
dinate cobalt(0) complex (4) has a distorted tetrahedron coordina-
tion geometry with three trimethylphosphine ligands and one
p-
coordinate carbonyl group in the four vertices. All the distances
of the coordination bonds are within the range of the correspond-
ing bond lengths. C7–O1 distance (1.362 Å) is between the length
of C–O single bond (1.43 Å) and the length of C@O double bond
Fig. 2. Molecular structure of 3 (all hydrogen atoms were omitted for clarity).
Selected distances (Å) and angles (°): Co1–N1 192.8(2), Co1–C5 196.3(2), Co1–O1
196.4(2), Co1–C4 196.8(2), Co1–P2 217.63(6), Co1–P1 218.82(6), C9–O1 1.240(3);
N1–Co1–C5 92.52(9), N1–Co1–O1 87.69(7), C5–Co1–C4 91.4(1), O1–Co1–C4
88.40(9), N1–Co1–P2 92.92(5), C5–Co1–P2 88.37(7), O1–Co1–P2 92.25(5), C4–
Co1–P2 87.97(7), N1–Co1–P1 88.21(5), C5–Co1–P1 87.50(7), O1–Co1–P1 91.88(5),
C4–Co1–P1 91.18(7).
Fig. 3. Molecular structure of 4 (all hydrogen atoms were omitted for clarity).
Selected distances (Å) and angles (°): Co1–O1 1.891(3), Co1–C7 2.037(5), Co1–P1
2.193(2), Co1–P2 2.219(2), Co1–P3 2.256(2); O1–Co1–C7 40.4(2), O1–Co1–P1
137.7(1), C7–Co1–P1 106.7(2), O1–Co1–P2 93.3(1), C7–Co1–P2 132.0(2), P1–Co1–
P2 103.86(6), O1–Co1–P3 113.1(1), C7–Co1–P3 108.7(2), P1–Co1–P3 101.80(7), P2–
Co1–P3 100.03(7).

Z. Zhang et al. / Polyhedron 50 (2013) 571–575
575
(1.23 Å) [24]; and is longer than the corresponding C7–O1
(1.271(1) Å (2)) and C9–O1 (1.240(3) Å (3)) in complexes 2 and 3.
This result is in line with the inference from the comparison of
bridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk.
the
m(C@O) data of the IR spectra of complexes 2–4 in the previous
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4. Conclusions
With the keto-O atom as an anchoring group the reaction of 2-
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afforded N–H bond cleavage products, the tetra-coordinate
square-planar nickel complex 2 and the hexa-coordinate octahe-
dral dimethyl cobalt(III) complex 3 with a anionic [N, O]-chelate li-
gand while the reaction of Co(PMe3)4 with 2-aminobenzophenone
(1) delivered only a p-(C@O) coordinated complex 4 in tetrahedral
coordination geometry. The formation mechanism of complex 2
was discussed. The molecular structures of complexes 2–4 were
determined by X-ray single crystal diffraction.
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6
6
pp. CODEN:JKXXAF;
pp. CODEN:JKXXAF;
We gratefully acknowledge the financial support by NSF China
No. 20972087/21172132 and the support from Prof. Dr. Dieter
Fenske and Dr. Olaf Fuhr (Karlsruhe Nano-Micro Facility) on the
determination of the crystal structures.
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Appendix A. Supplementary data
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CCDC 892475–892477 contain the supplementary crystallo-
graphic data for 2–4. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-