Synthesis of cobalt(II) and iron(II) complexes with the ligand bis(2-diphenylphosphinoethyl)methylamine and their catalytic action on ethylene oligomerization. X-ray crystal structure of

Article abstract of DOI:10.1016/S0022-328X(01)01341-9

Complexes [MCl₂{CH₃N(CH₂CH₂PPh₂)₂}] (1, M = Co; 2, Fe) were prepared by a modified procedure. The X-ray structural determination of 1 reveals that the cobalt(II) complex is four-coordinate with a distorted tetrahedral coordination geometry. The tertiary amine CH₃N(CH₂CH₂PPh₂)₂ acts as a bidentate ligand through two phosphorus atoms. The Co-P distances of 2.3666(14) and 2.3731(15) ? found in 1 are significantly longer than general Co-P bond lengths. The incoordinate N atom of the ligand locates at the apical position trans to one of the chlorides. The catalytic properties of 1 and 2 in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization were studied. The activities of 89.4 kg oligomers mol^-1 Co h^-1 for 1 and 81.2 kg oligomers mol ^-1 Fe h ^-1 for 2 (100 equivalents of EAO, 180 °C and 1.8 MPa ethylene) were observed with high selectivity to linear C_4-10 olefins.

Full text of DOI:10.1016/S0022-328X(01)01341-9

Journal of Organometallic Chemistry 645 (2002) 127–133
www.elsevier.com/locate/jorganchem
Synthesis of cobalt(II) and iron(II) complexes with the ligand
bis(2-diphenylphosphinoethyl)methylamine and their catalytic
action on ethylene oligomerization. X-ray crystal structure of
[CoCl2{CH3N(CH2CH2PPh2)2}]
Mei Wang a,*, Xiaomin Yu a, Zhan Shi b, Mingxing Qian a, Kun Jin a, Jiesheng Chen b,
Ren He a
a State Key Laboratory of Fine Chemicals, Dalian Uni6ersity of Technology, Zhongshan Road 158-46,
Dalian 116012, People’s Republic of China
b Key Laboratory of Inorganic Synthesis and Preparati6e Chemistry, Jilin Uni6ersity, Jiefang Road 119,
Changchun 130023, People’s Republic of China
Received 18 July 2001; received in revised form 2 October 2001; accepted 4 October 2001
Abstract
Complexes [MCl2{CH3N(CH2CH2PPh2)2}] (1, M=Co; 2, Fe) were prepared by a modified procedure. The X-ray structural
determination of 1 reveals that the cobalt(II) complex is four-coordinate with a distorted tetrahedral coordination geometry. The
tertiary amine CH3N(CH2CH2PPh2)2 acts as a bidentate ligand through two phosphorus atoms. The CoꢀP distances of 2.3666(14)
,
and 2.3731(15) A found in 1 are significantly longer than general CoꢀP bond lengths. The incoordinate N atom of the ligand
locates at the apical position trans to one of the chlorides. The catalytic properties of 1 and 2 in combination with
ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization were studied. The activities of 89.4 kg oligomers mol−1
Co h−1 for 1 and 81.2 kg oligomers mol−1 Fe h−1 for 2 (100 equivalents of EAO, 180 °C and 1.8 MPa ethylene) were observed
with high selectivity to linear C4–10 olefins. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Cobalt and iron complexes; Bis(2-diphenylphosphinoethyl)methylamine; Ethylene oligomerization
1. Introduction
tate iminophosphine (N,P) ligands has been reported
[7]. It is noteworthy that the oligomerization of ethyl-
ene catalyzed by the palladium(II) complexes with
diphosphine (P,P) ligands gives only dimers [8], whereas
palladium(II)-based uni-component catalysts with a-di-
imine (N,N) ligands catalyzes the reaction of ethylene
to high polymers at 25 °C [9]. The sharply contrasting
results show that proper combinations of the soft P and
the hard N donor atoms in the ligands and subtle
ligand modifications have an effect on tuning product
distributions in ethylene oligomerization and poly-
merization.
To explore the impact of mixed nitrogen–phospho-
rus polydentate ligands on ethylene oligomerization, a
cobalt(II) and an iron(II) complex containing the ligand
bis(2-diphenylphosphinoethyl)methylamine were pre-
pared by a modified procedure [4]. Here we wish to
The synthesis and chemistry of transition metal com-
plexes containing mixed nitrogen–phosphorus polyden-
tate ligands have received considerable attention for
decades. The preparation and magnetic as well as spec-
troscopic properties of the complexes were extensively
studied in the sixties and the seventies [1–4]. Afterward
interest in the transition metal complexes containing
nitrogen–phosphorus polydentate ligands arises mainly
from their potential as homogeneous or water-soluble
catalysts [5,6]. Recently, the oligomerization of ethylene
to C6–C16 olefins catalyzed by a series of uni-compo-
nent catalysts of palladium(II) complexes with biden-
* Corresponding author. Fax: +86-411-263-3041.
E-mail address: symbueno@mail.dlptt.ln.cn (M. Wang).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01341-9

128
M. Wang et al. / Journal of Organometallic Chemistry 645 (2002) 127–133
report the synthesis, characterization of the complexes,
the X-ray crystal structure of [CoCl2{CH3N(CH2-
CH2PPh2)2}], and the catalytic action of the complexes
in combination with ethylaluminoxane (EAO) as cocat-
alyst for ethylene oligomerization. So far as we know,
although many complexes of the potentially tridentate
ligands RN(CH2CH2PPh2)2 (RꢀPNP, R=H, alkyl)
with a wide variety of transition metals have been
prepared and characterized, none of the stereostruc-
tures of these complexes has been well established by
X-ray crystallographic evidences, and the iron complex
with an RꢀPNP ligand has not been known.
water and oxygen. Decomposition occurred gradually
for complex 1 and quickly for 2 when they are dissolved
in untreated solvents. The magnetic properties of com-
plexes 1 and 2, being paramagnetic and having a high
spin electronic configuration, are the same as the re-
ported iron(II) and cobalt(II) complexes bearing 2,6-
bis(imino)pyridyl ligands, which are known to be highly
active catalysts for ethylene polymerization [10].
(1)
Although some complexes of [MX2{RN(CH2-
CH2PPh2)2}] (M=Co, Ni; X=Br, I; R=H, CH3, Cy)
were prepared in the late sixties [3,4], no IR and NMR
data relative to these complexes have been reported. All
typical bands in the IR spectrum of the free ligand
appeared with small shifts in the spectra of complexes 1
and 2. The common characters of the IR spectra of 1
and 2 were that the band at 1490 cm−1 was split and
the intensity of the bands in the 1000–1200 cm−1
region increased evidently. The 31P{1H}-NMR spec-
trum of 1 showed an intense singlet at l 23.2, which
differs by 43.6 ppm from the resonance (l −20.4) of
the phosphorus atoms in the 31P{1H}-NMR spectrum
of the ligand [6], indicating that in solution the two
coordinating phosphorus atoms of the complex are
eqivalent on the NMR time scale. In the 1H-NMR
spectrum of 1, besides the signals (l 7.60–7.40) for the
phenyl groups of the ligand, there were a broad singlet
at l 2.71 for the methyl group on the nitrogen atom
and two broad humps without clear fine structures
centered at ca. l 4.63 and 2.92. The Co(II) complex 1
manifested a considerable downfield shift of the reso-
nance (l 4.63) for the protons of CH2 groups attached
to the diphenylphosphino groups (l 2.9 for the same
protons in the free ligand) [6], which is caused by the
coordination of the two phosphorus atoms to the
Co(II) center. In contrast, the resonance for the protons
of CH2 groups attached to the nitrogen atom in com-
plex 1 shifted downfield only by ca. 0.4 ppm compared
with the signal arising from the same protons (l 2.5) in
2. Results and discussion
2.1. Preparation and spectroscopic characterization of
[MCl2{CH3N(CH2CH2PPh2)2}] (1, M=Co; 2, Fe)
The title complexes 1 and 2 were prepared directly by
simple assembly of one equivalent of MCl2 and the free
tertiary amine in absolute ethanol (Eq. (1)). Since the
complexes 1 and 2 have rather low solubility in ethanol,
the products can directly precipitate in the ethanolic
solution during the reactions. The advantages of conve-
nient separation and high yields of products encour-
aged us to use ethanol as solvent, instead of 1-butanol
which was used in the literature [4] for the preparations
of analogous Co(II) and Ni(II) complexes. The Co(II)
complex is blue and the Fe(II) complex is colorless.
Both of the complexes are air-stable in the solid state,
but in solution they are sensitive to a trace amount of
Table 1
X-ray crystallographic data for 1
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C29H31Cl2CoNP2
585.32
293
Orthorhombic
P212121
,
a (A)
8.7267(7)
15.3372(13)
20.8864(16)
2795.5(4)
4
1.391
0.938
13 787
4012
1
the free ligand. Attempts to obtain the H- and 31P-
,
b (A)
NMR spectra of the Fe(II) complex 2 were thwarted
because of the poor solubility of 2 in organic solvents
and quick decomposition in solution.
,
c (A)
3
,
V (A )
Z
Dcalc (g cm−3
)
Absorption coefficient (mm−1
Total reflections
)
2.2. Molecular structure of
[CoCl2{CH3N(CH2CH2PPh2)2}] (1)
Observed reflections [I\2|(I)]
Goodness-of-fit on F2
1.044
R (observed data, %)
R1=0.0479 a,
wR2=0.1224 b
R1=0.0564 a,
wR2=0.1291 b
The stereostructures of the complexes and the prob-
lem whether CH3N(CH2CH2PPh2)2 acts as a tridentate
or as a bidentate ligand in the complexes could not be
determined by the obtained spectroscopic data. A crys-
tal of [CoCl2{CH3N(CH2CH2PPh2)2}] was subjected to
R (all data, %)
a R1=(ꢀꢁFoꢂ−ꢂFcꢁ)/(ꢀꢂFoꢂ).
b wR2=[ꢀw(Fo2−Fc2)2/ꢀw(Fo2)2]1/2
.

M. Wang et al. / Journal of Organometallic Chemistry 645 (2002) 127–133
129
Table 2
result is not in agreement with the early suggestion that
the [CoX2{CH3N(CH2CH2PPh2)2}] (X=Br, I) com-
plexes each be five-coordinate with a distorted square-
pyramidal coordination polyhedron in the solid state
[4]. In spite of the presence of three potentially coordi-
nating atoms, the CH3ꢀPNP ligand is bidentate through
two phosphorus atoms to the center Co(II) of complex
1. The CoꢀP bond lengths of 2.3666(14) and 2.3731(15)
,
Selected bond lengths (A) and bond angles (°) for 1
Bond lengths
CoꢀCl(1)
CoꢀP(1)
P(1)ꢀC(6)
P(1)ꢀC(12)
P(1)ꢀC(1)
NꢀC(2)
2.2483(16)
2.3666(14)
1.820(6)
1.826(6)
1.836(7)
1.330(12)
1.375(11)
1.362(11)
CoꢀCl(2)
CoꢀP(2)
P(2)ꢀC(24)
P(2)ꢀC(18)
P(2)C(4)
NꢀC(5)
2.2817(16)
2.3731(15)
1.820(5)
1.824(5)
1.825(6)
1.349(10)
1.329(12)
NꢀC(3)
C(3)ꢀC(4)
C(1)ꢀC(2)
,
A are considerably longer than the general CoꢀP bond
,
lengths (2.1–2.3 A) reported for many cobalt(II) phos-
Bond angles
phine complexes [2,11–13]. Only a few examples of
cobalt(II) complexes with CoꢀP coordination
Cl(1)ꢀCoꢀCl(2)
Cl(2)ꢀCoꢀP(1)
Cl(2)ꢀCoꢀP(2)
C(6)ꢀP(1)ꢀC(12)
C(12)ꢀP(1)ꢀC(1)
C(12)ꢀP(1)ꢀCo
104.73(7)
102.15(6)
98.71(6)
105.8(2)
103.8(3)
120.08(18)
Cl(1)ꢀCoꢀP(1)
Cl(1)ꢀCoꢀP(2)
P(1)ꢀCoꢀP(2)
C(6)ꢀP(1)ꢀC(1)
C(6)ꢀP(1)ꢀCo
C(1)ꢀP(1)ꢀCo
113.04(7)
120.04(7)
114.57(6)
106.6(3)
110.46(18)
109.3(2)
,
bonds longer than 2.35 A were reported, such as
,
the CoꢀP length of 2.369(5) A for [Cy3PCo(dmgH)2-
,
Cl] (dmgH=dimethylglyoximate), 2.418(1)
[Ph3PCo(dmgH)2CH3] [14], and 2.520(2)
A
for
for
,
A
C(24)ꢀP(2)ꢀC(18) 102.7(2)
C(24)ꢀP(2)ꢀC(4) 104.9(3)
[CoL2(O3SCF3)2] (L=P(CH2Ph)(CH2CH2OC2H5)2 [13].
The lengthenings of CoꢀP distances in these octahedral
cobalt complexes are caused by the trans effect of other
ligands. In contrast to these cobalt complexes, the trans
effect of ligands on the CoꢀP bond lengths does not
exist in complex 1 with a tetrahedral coordination
configuration. It is reasonable to assume that the sig-
nificant lengthening of CoꢀP bonds in complex 1 is
provoked by the steric size of two phosphorus terminals
in the CH3ꢀPNP ligand. To our knowledge, the CoꢀP
distances found in complex 1 are the largest values so
C(18)ꢀP(2)ꢀC(4)
C(18)ꢀP(2)ꢀCo
C(2)ꢀNꢀC(5)
C(5)ꢀNꢀC(3)
C(1)ꢀC(2)ꢀN
C(3)ꢀC(4)ꢀP(2)
105.5(3)
116.69(18)
111.0(13)
108.3(12)
135.9(8)
111.4(5)
C(24)ꢀP(2)ꢀCo
C(4)ꢀP(2)ꢀCo
C(2)ꢀNꢀC(3)
C(2)ꢀC(1)ꢀP(1)
C(4)ꢀC(3)ꢀN
114.86(19)
111.10(18)
108.5(14)
112.1(5)
129.8(9)
Fig. 1. Perspective view of complex 1. ORTEP diagram showing 30%
probability ellipsoids.
an X-ray diffraction study. Crystallographic details and
structure refinements are summarized in Table 1. Se-
lected bond lengths and angles for 1 are shown in Table
2. The molecular structure of 1 with the atom-number-
ing scheme is depicted in Fig. 1. The complex 1 crystal-
lizes with four molecules in an orthorhombic unit cell.
It is interesting to note that the molecular packing of 1,
viewed from the a-axis, is in a perfect stacking of
phenyl rings and of all bonds of the same kinds (see
Fig. 2). The well-laid-out structure in the solid state is
formed by the self-assembly of molecules, presumably
driven by intermolecular p···p stacking interactions of
the neighboring phenyl groups.
As shown in Fig. 1, the Co(II) complex 1 is four-co-
ordinate with a distorted tetrahedral geometry. The
Fig. 2. A view of the crystal packing for complex 1, projected along
the a-axis.

130
M. Wang et al. / Journal of Organometallic Chemistry 645 (2002) 127–133
Table 3
Results of ethylene oligomerization by 1 and 2 in toluene a
Compound no.
Temperature (°C)
Activity (kg mol−1 M−1 h−1
)
Olefins b
Linear olefins b
Cꢁ4–10/ꢀCꢁ4–10
h
Cꢁ4–10/ꢀCꢁ
a-Cꢁ6–10/ꢀCꢁ6–10
1
1
1
1
1
2
2
2
150
160
170
180
210
150
180
210
38.6
63.7
88.1
89.4
85.4
36.0
81.2
66.1
90.2
90.7
91.9
92.9
95.5
89.8
90.3
94.9
97.0
97.2
97.3
93.6
97.9
95.3
96.5
97.9
73.2
75.5
74.7
63.6
38.5
64.4
62.3
35.4
0.63
0.64
0.57
0.54
0.42
0.60
0.53
0.40
a Reaction conditions: [MCl2{CH3N(CH2CH2PPh2)2}] (M=Co, Fe) 0.05 mmol, Al/M=100, reaction time 2 h, pressure of ethylene 1.8 MPa,
toluene 30 ml.
b Determined by GC analysis (OV 101, 30 m×0.25 mm) with n-heptane as an internal standard and GC–MS spectra.
far reported for the CoꢀP coordination bonds without
the influence of the trans effect. These data practically
show the importance of steric effect on the MꢀL bond
lengths in transition metal complexes. Although the
nitrogen atom of the ligand stays very close to the
Cl(1) towards the Cl(2) atom. If the nitrogen atom is
considered into the coordination sphere, the
stereostructure of complex 1 is a pseudo-trigonal
bipyramid with the Cl(2) and the N atom at each apex
of the bipyramid, which may give a rational expression
,
,
to the fact that the CoꢀCl(2) distance is 0.0334 A longer
Co(II) center, the distance of 2.665 A between the
cobalt(II) and the nitrogen atom is out of the range
than the CoꢀCl(1) bond. Although, the nitrogen atom
of the CH3ꢀPNP ligand does not directly bind with the
center cobalt in complex 1, it indeed plays an important
role in the coordination configuration of the complex.
,
(1.9–2.3 A) expected for a direct coordination bond
donating from a nitrogen atom to a Co(II) center [15].
This bidentate coordination model of the CH3ꢀPNP
ligand is similar with those of the CH3ꢀNNN ligands
(CH3N(CH2CHꢁNAr)2) in the analogous Co(II) and
Fe(II) dichloride complexes, which proved to be active
catalysts for ethylene polymerization [16]. Considering
the outer-electron configuration of Co(II) with a P2X2
donor set, the center cobalt(II) has only 15 electrons in
its valence shell and it should be quite electron-defi-
cient. Therefore, the cause for the fact that the amine
CH3N(CH2CH2PPh2)2 in complex 1 acts as a bidentate
ligand should be attributed to the steric effect of the
methyl group and the relative low coordinating power
of the tertiary nitrogen. The CoꢀCl distances of
2.3. Ethylene oligomerization
It has been reported that the analogous iron(II) and
cobalt(II) complexes containing CH3ꢀNNN ligands
with MAO as cocatalyst are highly active catalysts for
ethylene polymerization [16]. Ethylene oligomerization
catalyzed by LFeCl2, LCoCl2 (L=N,N,N-tridentate
ligands)/MAO affords oligomers with high average
molecular weight [10b], while a-diimine iron(II) and
cobalt(II) complexes in combination with EAO are
moderately active for ethylene oligomerization with
good selectivity to C4–10 olefins [18]. It has been found
that in comparison with LMCl2 (M=Fe, Co)/MAO
catalysts, the catalytic systems formed by the replace-
ment of MAO with EAO has a preference for low-car-
bon olefins. One of the unrevealed problems in this field
is the influence by the replacement of hard N donor
atoms with soft ones on the catalytic activity and
selectivity of the iron(II) and cobalt(II) complexes. The
catalytic activities and product distributions of 1 and 2
in combination with EAO as cocatalyst for ethylene
oligomerization were tested, respectively, at different
temperatures. The results are collected in Table 3.
Without cocatalyst, complexes 1 and 2 are inactive in
ethylene oligomerization. The active catalysts were gen-
erated in situ by the addition of 100 equivalents of
EAO to the precursor complexes in toluene. The cata-
lytic reactions were carried out under a constant pres-
,
2.2483(16) and 2.2817(16) A fall well within the range
of CoꢀCl bond lengths reported for cobalt complexes
[11,14,17].
The bond angles subtended at the cobalt atom vary
from 98.71 to 120.04°. It is noticeable that enlarged are
the angles of P(1)ꢀCoꢀP(2) (114.57(6)°), P(2)ꢀCoꢀCl(1)
(120.04(7)°) and Cl(1)ꢀCoꢀP(1) (113.04(7)°), which
form a wide cone with the bottom facing to the coordi-
nation ring of the molecule, while the remaining angles
(P(2)ꢀCoꢀCl(2) 98.71(6)°, P(1)ꢀCoꢀCl(2) 102.15(6)° and
Cl(1)ꢀCoꢀCl(2) 104.73(7)°) concerning with the
CoꢀCl(2) bond of complex 1 are all decreased from the
value in a standard tetrahedral configuration. The
eight-membered ring of complex 1 may be primarily
responsible for the large distortion of the coordination
configuration. Furthermore, the cobalt atom is dis-
,
placed of 0.4780 A from the plane of P(1), P(2) and

M. Wang et al. / Journal of Organometallic Chemistry 645 (2002) 127–133
131
sure of ethylene (1.8 MPa). At the temperature below
120 °C, the activities of catalytic systems 1/EAO and
2/EAO were very low. The activities of 1 and 2, which
increased apparently as the reaction temperature was
raised from 150 to 180 °C, are comparable to those of
the cobalt(II) and iron(II) dichloride complexes with an
N,N-ligand (PhHCꢁNCH2CH2NꢁCHPh) in this tem-
perature range. The further enhancement of tempera-
ture resulted in a trend of decreased activities for the
catalytic systems of 1 and 2. In contrast, the activities
of a-diimine cobalt(II) and iron(II) complexes with
EAO kept a strongly growing trend even at 200 °C,
which was found in our previous studies [18]. The
results imply that the active catalysts derived from the
cobalt and iron dichloride complexes with a CH3ꢀPNP
ligand are less thermostable than those derived from
the complexes with a-diimine ligands. Complexes 1 and
2 both displayed high selectivities to the low-carbon
olefins. A Schulz–Flory distribution of olefin oligomers
was observed in all catalytic runs (GC analysis). The
data presented in Table 3 illustrate that the a-value,
which represents the probability of chain propagation,
is sensitive to the reaction temperature. For example,
the a-value changed from 0.63 to 0.42 for 1/EAO and
from 0.6 to 0.4 for 2/EAO when the reaction tempera-
ture was increased from 150 to 210 °C. The experimen-
tal facts showed that the replacement of an a-diimine
ligand PhHCꢁNCH2CH2NꢁCHPh with CH3N(CH2-
CH2Ph2)2 in cobalt(II) and iron(II) dichloride precur-
sors led to a higher selectivity to the low-carbon linear
olefins in ethylene oligomerization reaction, but with no
obvious improvement of the selectivity to linear a-
olefins.
Infrared spectra were recorded from KBr disk by
using a Nicolet AVATAR-360 IR spectrophotometer.
31P- and 1H-NMR spectra were recorded on
a
JEDLFX-90Q apparatus. The 31P-NMR spectra were
1
referenced to external 85% H3PO4 and the H-NMR
spectra to internal Me4Si. Elemental analyses were per-
formed on a CARLO ERBA MOD-1106 elemental
analyzer and GC–MS analyses of oligomers were made
by using an HP6890GC/5973MS instrument.
3.2. Preparation of the ligand CH3N(CH2CH2PPh2)2
The starting compound CH3N(CH2CH2Cl)2 was ob-
tained from the reaction of SOCl2 and CH3N(CH2-
CH2OH)2 [20], which was prepared by Eschweiler–
Clarke reaction from HN(CH2CH2OH)2. Instead of
KPPh2 as reported in the literature [4,6], LiPPh2 was
used in the preparation of the ligand CH3N(CH2-
CH2PPh2)2. The free tertiary amine CH3N(CH2CH2Cl)2
(7.8 g, 0.05 mol) was dissolved in THF (40 ml) and
added dropwise at −5–0 °C to a deep red solution of
LiPPh2, which was obtained freshly through the reac-
tion of lithium (1.4 g, 0.2 mol) with PPh3 (26.2 g, 0.1
mol) in THF at 0–5 °C. The further operations were
made according to the published procedure [6]. The
ligand CH3N(CH2CH2PPh2)2 in its hydrochloride form
was obtained (yield, 18 g, 75%); m.p. 121–123 °C. IR
(KBr, cm−1): 3447 (w), 3009 (m), 2989 (w), 2964 (m),
2921 (w), 2565 (m), 2458 (s br), 2396 (m), 1490 (m),
1432 (s), 749 (s), 698 (s), 509 (m), 481 (m), 415 (m).
31P{1H}-NMR (CHCl3): l −20.4 (s).
3.3. Preparation of [MCl2{CH3N(CH2CH2PPh2)2}] (1,
M=Co; 2, Fe)
3. Experimental
Bis(2-diphenylphosphinoethyl)methylamine hydro-
chloride (9.2 g, 18.8 mmol) was treated with a stoichio-
metric amount of 10% NaOH. The insoluble oil was
separated and the inorganic layer was extracted with
toluene (10 ml×3). The merged organic portion was
dried with Na2SO4 overnight. The free amine (7.0 g,
15.4 mmol) was obtained as a light-yellow dense oil
after the solvent was removed in vacuo. The ligand was
dissolved in absolute EtOH (15 ml) and dropped with
stirring to a deep blue solution of CoCl2 (1.8 g, 13.8
mmol) in the same solvent. The mixture was stirred at
20 °C for 30 min and then refluxed for 1 h. A large
amount of blue microcrystalline was precipitated during
the reaction. After the solution was concentrated in
vacuo and cooled to −5 °C, the crude product was
filtered off, washed with cold EtOH (10 ml×3) and
dried in vacuo at 60 °C. The pure blue crystal (rectan-
gular prism) of [CoCl2{CH3N(CH2CH2PPh2)2}] was
obtained by recrystallization from CH2Cl2–petroleum
ether (60–90 °C). Yield: 6.0 g (75%), m.p. 162–164 °C.
3.1. General procedures
The reactions and operations related to organometal-
lic complexes were carried out under a dry, oxygen-free
dinitrogen atmosphere with standard Schlenk tech-
niques. Toluene and THF were distilled from sodium–
benzophenone ketyl and methylene chloride from
phosphorus pentoxide. Anhydrous EtOH was further
dried by distillation from sodium–diethyl phthalate
before use. Ethylene was purified by passage through a
,
column of molecular sieves (4 A). Triethyl aluminum
was carefully distilled in vacuo and then partially hy-
drolyzed by the reaction with Al2(SO4)3·18H2O (AlEt3–
H2O=1:1, mol mol−1
)
in toluene at 0–5 °C.
Anhydrous CoCl2 was obtained by dehydration of
CoCl2·6H2O in vacuo at 120–130 °C for 6 h. Iron(II)
dichloride was prepared as the method reported in the
literature [19]. Other commercially available chemical
reagents were used without further purification.

132
M. Wang et al. / Journal of Organometallic Chemistry 645 (2002) 127–133
IR (KBr, cm−1): 3081 (m), 2975 (w), 2913 (w), 2866
(w), 1486 (m), 1438 (s), 1162 (m), 1118 (m), 1098 (m),
749 (s), 697 (s), 504 (m), 486 (w), 422 (w). H-NMR
Data Centre, CCDC no. 167311 for compound 1.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
1
(Me2SO-d6): l 7.58–7.46 (m, 20H, 4Ph), 4.63 (br., 4H,
2CH2P), 2.92 (br., 4H, 2CH2N), 2.71 (s, 3H, NCH3).
31P{1H}-NMR (Me2SO-d6): l 23.2 (s). Anal. Calc. for
C29H31NP2Cl2Co: C, 59.54; H, 5.35; N, 2.39. Found: C,
59.58; H, 5.41; N, 2.26%.
The analogous iron(II) complex (2) was prepared by
the same procedure as above. The colorless microcrys-
talline of [FeCl2{CH3N(CH2CH2PPh2)2}] was obtained
in 61% yield (4.9 g), m.p. 170 °C (dec.). IR (KBr,
cm−1): 3048 (m), 2973 (w), 2908 (w), 2815 (m), 1480
(m), 1459 (m), 1430 (s), 1306 (m), 1184 (m), 1097 (m),
746 (s), 696 (s), 504 (s), 472 (m), 431 (m). Anal. Calc.
for C29H31NP2Cl2Fe: C, 59.84; H, 5.38; N, 2.41. Found:
C, 59.76; H, 5.27; N, 2.29%.
Acknowledgements
We gratefully acknowledge the Chinese National
Natural Science Foundation (Grant no. 20173006) and
the Key Laboratory of Inorganic Synthesis and Prepar-
ative Chemistry, Jilin University, for financial support
of this research.
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