Cyclometalation reactions involving C-Cl bond activation of ortho-chlorinated substrates with imine as anchoring groups by cobalt complexes

Article abstract of DOI:10.1021/om7008793

The aldazines (C₆H₃Cl₂-2,6)CH=N-NH ₂ (la) and (C₆H₃Cl₂-2,6)CH=N-N= CH(C₆H₃Cl₂-2,6) (1b) or the Schiff bases (C₆H₃Cl₂-2,6)CH=N-CH₃) (1c), (C ₆H₃Cl₂-2,6)CH=N(C₆H₅) (1d), and (C₆H₃Cl₂-2,6)CH=N(C ₁₀H₇) (1e) were obtained by condensation of 2,6-dichlorobenzaldehyde with hydrazine, methylamine, aniline, or α-naphthylamine, respectively. Treatment of 1a-1e with [CoMe(PMe ₃)₄] resulted in oxidative addition of me C-Cl bond to afford the ortho-chelated cobalt(III) complexes [CoClMe(PMe₃) ₂-{(C₆H₃Clortho)-CH=N-R)] (2a-2e). The reaction of 1b, 1c with [CoCl(PMe₃)₃] delivered the aryl Co(III) complexes 3b, 3c containing a [C-Co-Cl] fragment, while Co(II) complexes [CoCl(PMe₃)₂((C₆H₃Cl-ortho)CH=N-R)] (3d,3e) were formed through the reaction of Id or 1e with [CoCl(PMe ₃)₃]. Under similar conditions, the ortho-chelated cobalt(III) complex [CoBrCl(PMe₃)₂((C₆H ₃Cl₂-2,6)CH=N-CH₃)] (4c) could be isolated via the reaction of [CoBr(PMe₃)₃] with 1c. The crystal and molecular structures of complexes 2a, 3b, 3e, and 4c were determined by X-ray diffraction.

Full text of DOI:10.1021/om7008793

270
Organometallics 2008, 27, 270–275
Cyclometalation Reactions Involving C-Cl Bond Activation of
ortho-Chlorinated Substrates with Imine as Anchoring Groups by
Cobalt Complexes
Yue Chen,† Hongjian Sun,† Ulrich Flörke,‡ and Xiaoyan Li*,†
School of Chemistry and Chemical Engineering, Shandong UniVersity, Shanda Nanlu 27, 250100 Jinan,
People’s Republic of China, and Anorganische and Analytische Chemie der UniVersität Paderborn,
Warburger Strasse, 33098 Paderborn, Germany
ReceiVed September 2, 2007
The aldazines (C6H3Cl2-2,6)CHdN-NH2 (1a) and (C6H3Cl2-2,6)CHdN-NdCH(C6H3Cl2-2,6) (1b)
or the Schiff bases (C6H3Cl2-2,6)CHdN-CH3 (1c), (C6H3Cl2-2,6)CHdN(C6H5) (1d), and (C6H3Cl2-
2,6)CHdN(C10H7) (1e) were obtained by condensation of 2,6-dichlorobenzaldehyde with hydrazine,
methylamine, aniline, or R-naphthylamine, respectively. Treatment of 1a-1e with [CoMe(PMe3)4] resulted
in oxidative addition of the C-Cl bond to afford the ortho-chelated cobalt(III) complexes [CoClMe(PMe3)2-
{(C6H3Clortho)-CHdN-R}] (2a-2e). The reaction of 1b,1c with [CoCl(PMe3)3] delivered the aryl Co(III)
complexes 3b,3c containing a [C-Co-Cl] fragment, while Co(II) complexes [CoCl(PMe3)2((C6H3Cl-
ortho)CHdN-R)] (3d,3e) were formed through the reaction of 1d or 1e with [CoCl(PMe3)3]. Under
similar conditions, the ortho-chelated cobalt(III) complex [CoBrCl(PMe3)2((C6H3Cl2-2,6)CHdN-CH3)]
(4c) could be isolated via the reaction of [CoBr(PMe3)3] with 1c. The crystal and molecular structures of
complexes 2a, 3b, 3e, and 4c were determined by X-ray diffraction.
Cyclometalation reactions of substrates containing an imine
or a pyridyl anchoring group by iron and cobalt complexes
Introduction
As chloroarenes are widely applied in many fields, the
productive activation of the C-Cl bond in chloroarenes is of
significant industrial interest. Simultaneously, the disposal of
organic wastes containing chloro groups has become a major
environmental and social problem, because most of them are
toxic and thermally stable, accumulating in the surroundings
for a long time. Due to the importance of functionalization or
dechlorination of aromatic chlorides, there is currently a great
deal of interest in the activation of the comparatively inert C-Cl
bond.1 Several methods have been found to successfully activate
a C-Cl bond; however, employing transition-metal complexes
apparently seems to be the most promising and efficient
approach. There have been many examples of catalytic activa-
tion of the C-Cl bond in chloroarenes by palladium,2–6 nickel,7
cobalt,8–11 platinum,12 and rhodium13,14 complexes, which are
utilized in cross-coupling reactions such as the Heck reaction,
the Suzuki coupling, and the Stille coupling. The first key step
in all the above-described catalytic reactions is oxidative addition
of the C-Cl bond at the electron-rich low-valent transition-
metal center. The research of cobalt complexes on this topic
was well reviewed by Caubere15 and Grushin.16
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* To whom correspondence should be addressed. Fax: +86-531-
88564464. E-mail: xli63@sdu.edu.cn.
† Shandong University.
‡ Universität Paderborn.
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10.1021/om7008793 CCC: $40.75
2008 American Chemical Society
Publication on Web 01/05/2008

Cyclometalation Reactions InVolVing C-Cl Bond ActiVation
Organometallics, Vol. 27, No. 2, 2008 271
Table 1. Selected Spectrocopic Data of Complexes 2a-2e, 3b-3e,
Scheme 1
and 4c
IR, cm-1
NMR, ppm
1H
ν(CdC) F(PMe3) PCH3, CoCH3
31P
ν(CdN)
2a 1591
2b 1625,1610 1581,1567
2c 1599
2d 1599
2e 1591
PMe3
1564,1531
945
945
945
945
945
942
940
939
948
941
0.86(t) 0.66(m)
0.94(m) 0.64(m)
0.69(m) 0.57(m)
0.96(m) 0.69(m)
0.86(t) 0.52(m)
1.07(m)
5.3(s)
5.3(s)
5.2(s)
1567,1531
1567,1531
1564,1531
9.4(s)
6.3(s, br)
10.8(s)
-0.9(s)
3b 1624,1615 1568,1558
3c 1594
3d 1596
3e 1592
4c 1592
1562,1531
1.12(m)
1.17(m)
-1.8(s, br)
consisting of a P-Co-P axis and equatorial coordination of
C, C, Cl, and N donor atoms. The crystal structure of complex
2a was elucidated by an X-ray diffraction analysis.
proceed through intramolecular C-H activation.17 Recently we
have reported cyclometalation reactions involving C-F bond
activation at a cobalt(I) center with azine as an anchoring group,
which afforded the first complex containing a C-Co-F
fragment.18
Herein we report on progress in the direction of cyclometa-
lation reactions involving C-Cl bond activation at cobalt(I)
centers with azine or imine as prechelate ligands. The new ortho-
chelated cobalt complexes formed by oxidative addition of an
aromatic C-Cl bond were isolated and characterized. C,C-
coupling reactions have been observed in reactions of [CoMe-
(PMe3)4], while steric crowding in the substrate molecules has
a marked effect on reactions of [CoCl(PMe3)3].
The molecular structure of complex 2a (Figure 1) confirms
the octahedral coordination geometry in the crystal. A five-
membered metallacycle is formed through the coordination
of the N atom of the imine group and the ortho-chelated C
atom. The sum of internal bond angles (540°) of this chelate
ring indicates ideal planarity. Typically, the Cl atom is trans-
oriented to the phenyl-C atom, which is well understood in
terms of mutual trans-influence. The bite angle of the
chelating ligand [C1-Co1-N1 ) 82.41(10)°] is close to that
found in a related compound.13 The two axial trimethylphos-
phine ligands are slightly displaced [P2-Co1-P1 )
173.90(4)°] toward the Co-Me group for steric reasons. The
CdN bond length [N1-C7 ) 1.289(3) Å] is comparable with
that (1.293(8) Å) in the ortho-metalated cobalt(III) fluoride
we have recently reported.18 This can be explained by the
strong electron-withdrawing ability of the fluorine atom,
which makes the cobalt(III) center more electron-deficient,
which strengthens coordination of the N-donor and weakens
the CdN bond.
Results and Discussion
1. Reaction of [CoMe(PMe3)4] with Aryl Chlorides. Reac-
tions of [CoMe(PMe3)4] with ortho-chlorinated substrates
containing imine anchoring groups (1a-1e) proceed by oxida-
tive addition of the C-Cl bond to give rise to the ortho-
metalated diorgano cobalt(III) chlorides 2a-2d, respectively.
In every reaction [CoCl(PMe3)3] was found as a byproduct. The
formation of the respective methyl arene derivatives via C,C-
coupling through reductive elimination was verified by LC-MS
analysis (Scheme 1). No spontaneous elimination of chlo-
romethane was observed. It appears that initial coordination of
the N-donor should be the key step. With HCdN as an
anchoring group the oxidative addition reactions proceed
smoother, and products are more stable owing to the chelate
effect.
The selected IR and NMR data of complexes 2a-2e, 3b-3e,
and 4c were collected in Table 1. Compared with the (CdN)
band of 1a-1e (1622–1655 cm-1), a substantial red shift upon
coordination of the N-donor atom indicates a weakening of the
CdN double bond.
In the 13C NMR spectra, we found that the PMe3 group gives
rise to a virtual triplet signal between 11.6 and 11.9 ppm with
3
the coupling constant |1J(PC) + J(PC)| ) 25.5–28.5 Hz. The
coordinated HCdN group shows a singlet in the region of
167.7–172.6 ppm. All spectroscopic data are compatible with
an octahedral configuration around the cobalt atom in solution,
(15) Caubere, V. V. ReV. Heteroatom. Chem. 1991, 4, 78.
(16) Grushin, V. V.; Alper, H. Top. Organomet. Chem. 1999, 3, 193.
(17) (a) Klein, H.-F.; Camadanli, S.; Beck, R.; Leukel, D.; Flörke, U.
Angew. Chem., Int. Ed. 2005, 44, 975. (b) Klein, H.-F.; Camadanli, S.;
Beck, R.; Flörke, U. Chem. Commun. 2005, 381–382.
(18) Li, X.; Sun, H.; Yu, F.; Flörke, U.; Klein, H.-F. Organometallics
2006, 25, 4695.
Figure 1. Molecular structure of 2a. Selected bond distances (Å)
and angles (deg): Co1-C1 1.913(3), Co1-N1 1.991(2), Co1-C8
2.044(2), N1-C7 1.289(3), Co1-Cl1 2.3679(8), Co1-P2 2.2161(9),
Co1-P1 2.176(9); C1-Co1-N1 82.41(10), C8-Co1-Cl1 93.33(8),
P2-Co1-P1 173.90(4), N1-C7-C6 113.8(2), C1-C6-C7
115.1(2), C6-C1-Co1 112.66(19), C7-N1-Co1 115.98(19).

272 Organometallics, Vol. 27, No. 2, 2008
Chen et al.
Figure 2. Molecular structure of 3b. Selected bond distances (Å)
and angles (deg): C7-N1 1.313(3), C8-N2 1.204(3), C1-C7
1.394(3), C8-C9 1.441(3), Co1-C6 1.944(2), Co1-N1 1.9997(18),
Co1-Cl1 2.2885(7), Co1-P2 2.3377(9), Co1-P1 2.3392(8),
Co1-Cl5 2.3748(8), C6-Co1-N1 79.12(8), N1-C7-C1 114.2(2),
C7-N1-Co1 117.79(14), C1-C6-Co1 114.68(15), C7-C1-C6
113.58(19), P2-Co1-P1 172.89(2).
Figure 3. Molecular structure of 4c. Selected bond distances (Å)
and angles (deg): Co1-C1 1.925(10), Co1-N1 1.929(9), Co1-P2
2.255(3), Co1-P1 2.259(3), Co1-Br1 2.3941(18), Co1-Cl1
2.420(2), N1-C3 1.295(13); C1-Co1-N1 82.5(4), C3-N1-Co1
116.1(7), N1-C3-C2 114.9(9), C1-C2-C3 112.4(8), C2-C1-Co1
114.0(7), P2-Co1-P1 173.09(12).
2. Reaction of CoX(PMe3)3 (X ) Cl, Br) with Aryl
Chlorides. When [CoCl(PMe3)3] was used instead of [CoMe-
(PMe3)4] in reactions with 1b or 1c in THF with stirring for
18 h at room temperature, a similar oxidative addition reaction
also happened. ortho-Metalated cobalt(III) chloride 3b or 3c
(eq 1) was formed. Complexes 3b and 3c were isolated by
crystallization from diethyl ether at -27 °C. Both complexes
are stable under ambient condition and can be handled in the
air for at least 2 h. Under argon, decomposition begins above
120 °C.
conjugation in the cobaltocycle. The sum of internal bond angles
(539.3°) indicates planarity of the chelating ring. The longer
bond Co1-Cl5 (2.3748(8) Å), when compared with Co1-Cl1
(2.2885(7) Å), reflects the stronger trans-influence of the carbon
atom (C6) than that of the nitrogen atom (N1).
The reaction of [CoBr(PMe3)3] with 1c under similar condi-
tions afforded a violet-red solution. Complex 4c could be
isolated from diethyl ether at -27 °C as violet-red crystals
suitable for X-ray diffraction analysis (eq 2). The other possible
isomer with the position exchange of Cl/Br atoms was not found.
(1)
In the 13C NMR spectrum, the PMe3 group gives rise to a
(2)
pseudotriplet resonance at 12.7 ppm (3b) or at 12.3 ppm (3c)
1
3
An X-ray diffraction study reveals that complex 4c attains a
molecular structure (Figure 3) that is closely related with that
of complex 3b. The bite angle C1-Co1-N1 ) 82.9(2)° almost
matches that in 2a (82.41(10)°), while both bite angles are
substantially larger than that in complex 3b (79.12(8)°).
Reactions of [CoCl(PMe3)3] with 1d,1e did not afford the
expected Co(III) complexes according to eq 1 or 2, but formed
aryl Co(II) chloride 3d or 3e, while [CoCl2(PMe3)3] was isolated
as a second fraction of crystals and identified through the
comparation of the IR data with those in the literature19 (Scheme
2). Complexes 3d and 3e are paramagnetic and were character-
ized by elemental analysis and IR.
A mechanism of formation is proposed in Scheme 2. With
the nitrogen atom of the imine function serving as anchoring
group, an oxdative addition of the C-Cl bond to the cobalt
center occurs, affording intermediate aryl Co(III) complexes that
are similar to 3b and 3c. Owing to the electron-withdrawing
effect of the phenyl or naphthyl group, the Co(III) intermediates
with coupling constants J(PC) + J(PC) ) 29.2 or 25.5 Hz,
respectively. The spectroscopic data are in line with an
octahedral configuration around the cobalt atom with two trans-
oriented trimethylphosphine ligands and a five-membered che-
late ring [C, C, C, N, Co].
Crystals of 3b were obtained from diethyl ether and were
analyzed by X-ray diffraction. The molecular structure of 3b is
shown in Figure 2. The cobalt atom attains an octahedral
coordination with two cis-chloro ligands (Cl1-Co1-Cl5 )
86.87(3)°), opposite to the planar [C:N]-chelate ring of a diazine
ligand with the bite angle C6-Co1-N1 ) 79.12(8)°. The two
axial trimethylphosphine ligands are slightly displaced
(P2-Co1-P1)172.89(2)°) toward the midpoint Cl1-Cl5 by
the bulky diazine ligand. The CdN bond length with the
coordinated nitrogen, C7-N1 (1.313(3) Å), is longer than that
of the uncoordinated CdN, C8-N2 (1.204(3) Å), indicating
significant bond weakening upon coordination of the nitrogen
donor atom. C1-C7 (1.394(3) Å) is shorter than C8-C9
(1.441(3) Å), which could be due to back-donation from the
cobalt atom into the π*-orbital of the ligand and a considerable
(19) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1976, 109, 1453.

Cyclometalation Reactions InVolVing C-Cl Bond ActiVation
Organometallics, Vol. 27, No. 2, 2008 273
Scheme 2
Thermally stable crystalline materials were isolated and structur-
ally characterized. Likely routes of formation are in accord with
the notion that intially the N-donor function is coordinated to
the cobalt center, folowed by activation of the C-Cl bond and
oxidative addition. In the reactions of CoMe(PMe3)4, the aryl
Co(III) complexes (2a-2e) show a trend to undergo subsequent
reductive elimination accompanied by C,C-coupling to give
monochlorinated arene derivatives. Reactions of 1b or 1c with
[CoCl(PMe3)3] or [CoBr(PMe3)3] afforded ortho-metalated
cobalt(III) chlorides (3b, 3c, and 4c), while Co(II) complexes
(3d and 3e) were formed by reactions of [CoCl(PMe3)3] with
reactants containing bulky groups.
Experimental Section
General Procedures and Materials. Standard vacuum tech-
niques were used in manipulations of volatile and air-sensitive
materials. Literature methods were used in the preparation of N,N′-
bis(2,6-dichlorobenzylidene)hydrazine,20 methyltetrakis(trimeth-
ylphosphine)cobalt(I),21 chlorotris(trimethylphosphine)cobalt(I),
and bromotris(trimethylphosphine)cobalt(I).22 Schiff bases were
obtained by condensation of 2,6-dichlorobenzaldehyde with amines.
The other chemicals were used as purchased. Infrared spectra
(4000–400 cm-1), as obtained from Nujol mulls between KBr disks,
were recorded on a Nicolet 5700. 1H, 13C, and 31P NMR (300, 75,
and 121 MHz, respectively) spectra were recorded on a Bruker
Avance 300 spectrometer. 13C and 31P NMR resonances were
obtained with broadband proton decoupling. Elemental analyses
were carried out on an Elementar Vario EL III. Melting points were
measured in capillaries sealed under argon and are uncorrected.
X-ray crystallography was performed with a Bruker Smart 1000
diffractometer.
are readily reduced by [CoCl(PMe3)3] to afford the pentacoor-
dinate Co(II) complexes 3d,3e. Our efforts to isolate the Co(III)
intermediates were not successful.
By recrystallization from pentane at 4 °C brown-red prisms
of 3e were obtained, which proved suitable for X-ray
diffraction analysis. The molecular geometry is shown in
Figure 4. It can be described as a distorted square-pyramidal
coordination of a cobalt(II) center with the N atom in the
apical position. The angles N1-Co1-P1 (98.23(4)°) and
N1-Co1-P2 (97.33(4)°) are larger than 90° because the
bulky naphthyl ring is almost in plane with atoms [N1, P1,
P2] and perpendicular to the five-membered chelate ring. This
metallacycle with the internal bond angles (539.9°) is
perpendicular to the square coordination plane.
Synthesis of 2a. A solution of 0.44 g (1.16 mmol) of [CoMe-
(PMe3)4] in 30 mL of pentane was combined with a solution of 1a
0.21 g (1.14 mmol) in pentane (20 mL) at -80 °C. The reaction
mixture was allowed to warm to ambient temperature and stirred
for 18 h. During this period, the reaction mixture turned red-brown
in color. After filtering, the red solid residue was extracted with
diethyl ether (60 mL). Repeated recrystallization from diethyl ether
at 4 °C yielded orange single crystals suitable for X-ray structure
analysis. Yield: 0.19 g (42.0%). Dec > 120 °C. Anal. Calcd for
C14H27Cl2CoN2P2 (415.15 g/mol): C, 40.47; H, 6.55; N, 6.74.
Found: C, 40.78; H, 6.80; N, 6.57. IR (Nujol): 1591 ν(CdN), 1564,
1531 ν(CdC), 945 F(PMe3) cm-1. 1H NMR (300 MHz, C6D6, 296
K): δ 0.66 (m, 3H, CH3), 0.86 (t, 2J(PH) + 4J(PH) ) 7.8 Hz, 18H,
PCH3), 6.33 (s, 2H, NH2), 6.74-7.07 (m, 3H, Ar-H), 7.97(s, 1H,
Conclusion
Reactions of ortho-chlorinated aromatic compounds bearing
imine as anchoring groups with [CoMe(PMe3)4], [CoCl(PMe3)3],
or [CoBr(PMe3)3] were investigated. By activation of the C-Cl
bond novel ortho-chelated cobalt(III) complexes were obtained.
1
CHdN). 13C NMR (75 MHz, C6D6, 296 K): δ 11.6 (t, J(PC) +
3J(PC) ) 26.6 Hz, PCH3), 121.7 s, 126.3 s, 127.6 s, 136.2 s, 141.3
s, 145.5 s. 31P NMR (121 MHz, C6D6, 300 K): δ 5.3 s.
Complexes 2b-2e were synthesized according to the method
given above for 2a.
Synthesis of 2b. Yield: 36%. Dec > 135 °C. Anal. Calcd for
C21H29Cl4CoN2P2 (572.33 g/mol): C, 44.07; H, 5.11; N, 4.89.
Found: C, 44.58; H, 5.30; N, 4.57. IR (Nujol): 1625, 1610 ν(CdN),
1581, 1567 ν(CdC), 945 F(PMe3) cm-1 1H NMR (300 MHz,
.
C6D6, 296 K): δ 0.64 (m, 3H, CH3), 0.94 (m, 18H, PCH3),
6.50-7.00 (m, 6H, Ar-H), 9.45 (s, 1H, CHdN), 10.46 (s, 1H,
CHdN). 31P NMR (121 MHz, C6D6, 300 K): δ 5.3 s.
Synthesis of 2c. Yield: 61%. Dec > 120 °C. Anal. Calcd for
C15H28Cl2CoNP2 (414.17 g/mol): C, 43.50; H, 6.81; N, 3.38. Found:
C, 43.78; H, 6.80; N, 3.57. IR (Nujol): 1599 ν(CdN), 1567, 1531
Figure 4. Molecular structure of 3e. Selected bond distances (Å)
and angles (deg): Co1-C1 1.9046(15), Co1-N1 2.0770(13),
Co1-P2 2.2235(5), Co1-P1 2.2337(5), Co1-Cl2 2.2826(5),
N1-C7 1.2964(19); C1-Co1-N1 82.90(6), N1-Co1-P1 98.23(4),
N1-Co1-P2 97.33(4), N1-Co1-C1 82.90(6), N1-Co1-Cl2
105.09(4), P2-Co1-P1 163.13(18), N1-C7-C6 116.74(13),
C1-C6-C7 115.46(13), C6-C1-Co1 113.15(11), C7-N1-Co1
111.66(10).
1
ν(CdC), 945 F(PMe3) cm-1. H NMR (300 MHz, C6D6, 296 K):
(20) Dönnecke, D.; Halbauer, K.; Imhof, W. J. Organomet. Chem. 2004,
689, 2707.
(21) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1975, 108, 944–955.
(22) Klein, H.-F.; Karsch, H. H. Inorg. Chem. 1975, 14, 473–477.

274 Organometallics, Vol. 27, No. 2, 2008
Chen et al.
Table 2. Crystallographis Data for Complexes 2a, 3b, 3e, and 4c
2a
3b
3e
4c
empirical formula
fw
C14H27Cl2CoN2P2
415.15
C20H26Cl5CoN2P2
592.55
C23H29Cl2CoNP2
511.24
C14H25BrCl2CoNP2
479.03
cryst dimens, mm3
temp, K
0.35 × 0.23 × 0.13
0.35 × 0.23 × 0.13
0.48 × 0.45 × 0.39
0.25 × 0.20 × 0.19
120(2)
150(2)
120(2)
273(2)
cryst syst
space group
a, Å
b, Å
c, Å
orthorhombic
Pbca
10.4280(12)
14.2733(17)
26.233(3)
90
90
90
3904.5(8)
8
1.412
monoclinic
P2(1)/c
10.646(2)
17.194 (3)
14.953(3)
90
101.15(3)
90
2685.4(9)
4
orthorhombic
P2(1)2(1)2(1)
8.8928(13)
15.554(2)
18.083(3)
90
90
90
2495.1(6)
4
1.361
orthorhombic
P2(1)2(1)2(1)
8.7058(5)
10.7403(5)
22.1671(13)
90
90
90
2072.7(2)
4
1.535
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
Dc, g cm-3
no. of rflns collected
no. of indep rflns
Rint
1.412
16 363
5646
0.0520
32 793
4653
0.1090
19 103
5956
0.0205
9281
3650
0.0304
θmax, deg
R1 (I > 2σ(I))
wR2 (all data)
27.87
0.0471
0.0943
28.53
0.0471
0.0943
27.87
0.0228
0.0599
25.00
0.0683
0.2204
δ 0.57 (m, 3H, CH3), 0.69 (m, 18H, PCH3), 3.42 (s, 3H, N-CH3),
6.66–7.07 (m, 3H, Ar-H), 8.57(s, 1H, CHdN). 13C NMR (75 MHz,
C6D6, 296 K): δ 11.9 (t, 1J(PC) + 3J(PC) ) 25.5 Hz, PCH3), 121.5
s, 123.1 s, 127.1 s, 130.7 s, 136.5 s, 142.3 s, Ar; 167.7 s, CHdN.
31P NMR (121 MHz, C6D6, 300 K): δ 5.2 s.
6.98-7.71 (m, 3H, Ar-H), 8.14 (s, 1H, CHdN). 13C NMR (75
1 3
MHz, CDCl3, 296 K): δ 12.3 (t, J(PC) + J(PC)) ) 25.5 Hz),
48.75 s, 123.5 s, 129.9 s, 130.9 s, 138.5 s, 142.3 s; 172.0 (s CHdN).
31P NMR (121 MHz, CDCl3, 296 K): δ -0.87 s.
Synthesis of 3d. Chlorotris(trimethylphosphane)cobalt(I) (0.90
g, 2.79 mmol) was dissolved in 40 mL of THF. To this solution
was added 1d (0.69 g, 2.79 mmol) in 20 mL of THF at -80 °C.
The mixture was allowed to warm to 20 °C and stirred for 18 h,
turning violet-red. This was filtered and the filtrate was evaporated
in vacuo. The residue was extracted with pentane (60 mL) and
diethyl ether (60 mL), respectively. Crystallization in pentane at
-27 °C afforded complex 3c as brown-red crystals. Yield: 0.33 g
(57.0%). Dec > 135 °C. Anal. Calcd for C19H27Cl2CoNP2 (461.18
g/mol): C, 49.48; H, 5.90; N, 3.04. Found: C, 50.08; H, 5.80; N,
Synthesis of 2d. Yield: 37%. Dec > 120 °C. Anal. Calcd for
C20H30Cl2CoNP2 (476.24 g/mol): C, 50.44; H, 6.35; N, 2.94. Found:
C, 50.98; H, 6.56; N, 2.57. IR (Nujol): 1599 (CdN), 1567, 1531
1
(CdC), 945 (PMe3) cm-1. H NMR (300 MHz, C6D6, 296 K): δ
0.69 (m, 3H, CH3), 0.96 (m, 18H, PCH3), 6.65–7.74 (m, 8H, Ar-
H), 8.15(s, 1H, CHdN). 13C NMR (75 MHz, C6D6, 296 K): δ 12.6
(t, 1J(PC) + 3J(PC)) ) 28.5 Hz, PCH3), 124.9 s, 126.5 s, 127.1 s,
127.7 s, 128.3 s, 129.6 s, 137.7 s, 138.9 s, 145.1 s, 149.5 s; 172.6
(s, CHdN). 31P NMR (121 MHz, C6D6, 300 K): δ 9.4 s.
3.27. IR (Nujol): 1596 (CdN), 939 (PMe3) cm-1
.
Synthesis of 2e. Yield: 34%. Dec > 110 °C. Anal. Calcd for
C24H32Cl2CoNP2 (526.30 g/mol): C, 54.77; H, 6.13; N, 2.66. Found:
C, 54.98; H, 6.30; N, 2.57. IR (Nujol): 1591 (CdN), 1564, 1531
Synthesis of 3e. Complexes 3e were synthesized according to
the method given above for 3d. Yield: 42%. Dec > 135 °C. Anal.
Calcd for C23H29Cl2CoNP2 (511.24 g/mol): C, 54.04; H, 5.72; N,
2.74. Found: C, 54.24; H, 5.89; N, 2.57. IR (Nujol): 1592 (CdN),
1
(CdC), 945 (PMe3) cm-1. H NMR (300 MHz, C6D6, 296 K): δ
0.52 (m, 3H, CH3), 0.86 (t, 2J(PH) +4J(PH) ) 7.2 Hz, 18H, PCH3),
6.77–8.53 (m, 10H, Ar-H), 9.31 (s, 1H, CHdN). 31P NMR (121
MHz, C6D6, 300 K): δ 6.3 s (br).
948 (PMe3) cm-1
.
Synthesis of 4c. Bromotris(trimethylphosphane)cobalt(I) (0.43
g, 1.17 mmol) was dissolved in 20 mL of THF. To this solution
was added 1c (0.22 g, 1.16 mmol) in 20 mL of THF at -80 °C.
The reaction mixture was allowed to warm to ambient temperature
and stirred for 18 h. During this period, the reaction mixture turned
violet-red. The filtrate was evaporated in vacuo, and the residue
was extracted with pentane (40 mL) and diethyl ether (30 mL),
respectively. Crystallization in diethyl ether at -27 °C afforded
complex 4c as violet-red crystals suitable for X-ray diffraction
analysis. Yield: 0.20 g (35.8%). Dec > 130 °C. Anal. Calcd for
C14H25BrCl2CoNP2 (479.03 g/mol): C, 35.10; H, 5.26; N, 2.92.
Found: C, 35.37; H, 5.50; N, 2.77. IR (Nujol): 1592 (CdN) 941
Synthesis of 3b. Chlorotris(trimethylphosphane)cobalt(I) (0.83
g, 2.57 mmol) was dissolved in 40 mL of THF. To this solution
was added 1b (0.89 g, 2.57 mmol) in 20 mL of THF at -80 °C.
The reaction mixture was allowed to warm to ambient temperature
and stirred for 18 h. During this period, the reaction mixture turned
violet-red. The filtrate was evaporated in vacuo, and the residue
was extracted with pentane (60 mL) and diethyl ether (60 mL),
respectively. Crystallization from diethyl ether at -27 °C afforded
complex 3b as brown-red crystals suitable for X-ray diffraction
analysis. Yield: 0.64 g (41.8%). Dec > 120 °C. Anal. Calcd for
C20H26Cl5CoN2P2(592.55 g/mol): C, 40.54; H, 4.42; N, 4.72. Found:
C, 40.76; H, 4.60; N, 4.57. IR (Nujol): 1624, 1615 (CdN), 1568,
1
(PMe3) cm-1. H NMR (300 MHz, CDCl3, 296 K): δ 1.17 (m,
1
1558 (CdC), 942 (PMe3) cm-1. H NMR (300 MHz, C6D6, 296
18H, PCH3), 3.20 (s, 3H, CH3), 7.00–7.92 (m, 3H, Ar-H), 8.26 (s,
1H, CHdN). 31P NMR (121 MHz, CDCl3, 300 K): δ -1.8 (b).
X-ray Structure Determinations. Intensity data were collected
on a Bruker SMART diffractometer with graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å). Crystallographic data for
complexes 2a, 3b, 3e, and 4c are summarized in Table 2. 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): δ 1.07 (m, 18H, PCH3), 6.42-8.15 (m, 6H, Ar-H), 8.39 (s,
1H, C8HdN2), 9.28 (s, 1H, C7HdN1). 13C NMR (75 MHz, C6D6,
1
3
296 K): δ 12.7 (t, J(PC) + J(PC)) ) 29.2 Hz, PCH3), 123.8 s,
125.6 s, 127.6 s, 128.0 s, 129.2 s, 129.6 s, 131.2 s, 136.0 s, 137.8
s, 139.1 s, 140.2 s; 166.6 s, 177.2 s (CHdN). 31P NMR (121 MHz,
C6D6, 300 K): δ 10.8 s.
Synthesis of 3c. Complex 3c was prepared according to the
method given above for 3b. Yield: 0.85 g (57.0%). Anal. Calcd
for C14H25Cl3CoNP2 (434.48 g/mol): C, 38.70; H, 5.80; N, 3.22.
Found: C, 38.28; H, 6.00; N, 3.51. IR (Nujol): 1594 (CdN), 1562,
1531 (CdC), 940 (PMe3) cm-1. Dec >120 °C. 1H NMR (300
MHz,CDCl3, 296 K): δ 1.12 (m, 18H, PCH3), 3.26 (s, 3H, CH3),
CCDC-667085 (2a), CCDC-667084 (3b), CCDC-667086 (3e)
and CCDC-667083 (4c) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge on

Cyclometalation Reactions InVolVing C-Cl Bond ActiVation
Organometallics, Vol. 27, No. 2, 2008 275
application to CCDC, 12 Union Road, Cambridge CB21EZ, UK
(fax: (+44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
Program of Ministry of Education of China (MOE) Nos.
20050422010 and 20050422011.
Acknowledgment. We gratefully acknowledge support by
NSF China No. 20572062/20772072 and The Doctoral
OM7008793