Synthesis of Novel Amidinato(amidine) Complexes of Molybdenum via Bis(amidine) Complexes

Article abstract of DOI:10.1246/bcsj.77.303

The molybdenum complex [Mo(η³-allyl)Cl(CO) ₂(NCMe)₂] (1) reacted with two equivalents of amidines, ArN=C(R)NHAr (R = H, CH₃; Ar = C₆H₅, p-CH ₃-C₆H₄) (2), to give corresponding bis(amidine) complexes, [Mo(η³-allyl)Cl(CO)₂(amidine) ₂] (3). Upon a treatment of bis(amidine)molybdenum complexes (3) with a base, such as n-butyllithium, complexes (4) bearing both amidinato and amidine ligands were formed and isolated as a yellow solid. The amidine ligand in complexes 4 was easily substituted by PEt₃ to give amidinato(phosphine) complexes of molybdenum (5) as a red solid. These complexes were characterized spectroscopically as well as by X-ray analyses.

Full text of DOI:10.1246/bcsj.77.303

ꢀ 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 303–309 (2004)
303
Synthesis of Novel Amidinato(amidine) Complexes of Molybdenum
via Bis(amidine) Complexes
ꢀ
ꢀ
Yoshitaka Yamaguchi, Kenichi Ogata, Kimiko Kobayashi,1 and Takashi Ito
Department of Materials Chemistry, Graduate School of Engineering, Yokohama National University,
79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501
1The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198
Received July 25, 2003; E-mail: t-ito@ynu.ac.jp
The molybdenum complex [Mo(ꢀ3-allyl)Cl(CO)2(NCMe)2] (1) reacted with two equivalents of amidines,
ArN=C(R)NHAr (R = H, CH3; Ar = C6H5, p-CH3–C6H4) (2), to give corresponding bis(amidine) complexes,
[Mo(ꢀ3-allyl)Cl(CO)2(amidine)2] (3). Upon a treatment of bis(amidine)molybdenum complexes (3) with a base, such
as n-butyllithium, complexes (4) bearing both amidinato and amidine ligands were formed and isolated as a yellow solid.
The amidine ligand in complexes 4 was easily substituted by PEt3 to give amidinato(phosphine) complexes of molybde-
num (5) as a red solid. These complexes were characterized spectroscopically as well as by X-ray analyses.
The amidinato ligand is known to play an important role as
an ancillary ligand to stabilize complexes of transition metals,
main-group elements, or rare earth metals because of its ability
to act as both a chelating and bridging ligand toward metals.1,2
In respect concerning amidinato complexes of molybdenum,
much effort has been made for their syntheses and reactivities.
In particular, an excellent study was developed by Cotton and
co-workers concerning quadruply bonded dinuclear molybde-
num complexes utilizing a bridging amidinato ligand,3 and
numerous investigations have been undertaken by Vrieze,4
Kilner,5 and Brunner,6 independently, relating to mononuclear
molybdenum complexes bearing a chelating amidinato ligand,
[Mo(ꢀ5-C5H5)(amidinato)(CO)2]. Although miscellaneous
types of complexes of this kind have also been studied,1,2 typi-
cal amidinato complexes of molybdenum are limited in num-
ber, as mentioned above. In order to prepare the new type of
amidinato complex of Mo, our effort focused on the combina-
tion of the Mo(allyl)(CO)2 fragment with an amidinato ligand.
[Mo(allyl)Cl(CO)2(NCMe)2], which has two labile acetoni-
trile ligands and one chloride ligand, is a most useful starting
material for the synthesis of a series of allyl complexes of mo-
lybdenum,7 and is known to be a key compound for a Mo-cat-
alyzed allylic alkylation reaction.8 Although a series of allyl
complexes of molybdenum have been studied using 4-electron
donating neutral nitrogen9 or phosphorus-containing ligands10
as well as anionic oxygen11 or sulfur containing ligands,12 to
our best knowledge there has been no investigation concerning
the amidinato ligand. In this paper, we report on the syntheses
and crystal structures of novel amidinato(amidine) complexes
of molybdenum possessing the Mo(ꢀ3-allyl)(CO)2 fragment.
is easily prepared by the treatment of 1,3-disubstituted carbo-
diimido with appropriate alkyllithium.1 In order to prepare an
unprecedented type of amidinato complex of molybdenum,
we first chose [Mo(ꢀ3-allyl)Cl(CO)2(NCMe)2] (1-Mo) as the
starting material, and examined its reaction with Li(amidinate).
However, the reaction resulted in the formation of complicated
products, and the desired complex was not obtained. We next
examined the reaction of 1-Mo and its tungsten analogue (1-
W) with amidines, since amidine, which is a precursor of ami-
dinate, has been reportedly known to coordinate to a transition
metal by its imine nitrogen.13
Upon a treatment of the yellow complex of 1-Mo with two
equivalents of N,N0-diphenylformamidine 2a in THF at room
temperature, a clean substitution reaction took place, and after
a work-up, a two-amidines coordinated molybdenum complex,
3a-Mo, was isolated as a yellow powder in quantitative yield
(Eq. 1). In a similar fashion, complexes 3b-Mo, 3c-Mo, 3d-
Mo, and 3a-W were successfully prepared and isolated in quan-
titative yield (Eq. 1).
R
2eq.
NHAr
ArN
2
Cl
OC
OC
NCMe
NCMe
OC
OC
NHAr
H
M
M
N
THF
(quant.)
ArN
Cl
Ar
H
ð1Þ
ArHN
1-Mo (M = Mo)
1-W (M = W)
3a-Mo 3a-W
3b-Mo
3c-Mo
3d-Mo
Ar
Ph
p-tolyl
R
H
H
Results and Discussion
a
b
c
d
Preparation of Bis(amidine) Complexes, [Mo(ꢀ3-allyl)-
Cl(CO)2(amidine)2]. One of the most convenient synthetic
procedures for amidinato complexes is a reaction of the metal
halide precursor with the lithiated amidinate compound, which
Me Ph
p-tolyl
Me
Published on the web February 10, 2004; DOI 10.1246/bcsj.77.303

304 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Amidinato(amidine) Complexes of Molybdenum
Table 1. IR Spectral Data for Starting Materials and Bis(amidine) Complexes 3
1-Mo
3a-Mo
3b-Mo
3c-Mo
3d-Mo
1-W
3a-W
ꢁCO
/cmꢁ1
1942
1849
1937
1844
1931
1836
1932
1832
1932
1822
1933
1836
1914
1810
ꢁCN
/cmꢁ1
2317
2285
2317
2286
In the IR spectra, the starting complex, 1-Mo, showed two
stretching bands (2317, 2285 cmꢁ1) due to CH3CN and two
stretching bands (1942, 1849 cmꢁ1) due to CO ligands. In the
complex 3a-Mo, the former bands fully disappeared and the
latter bands were shifted slightly to lower frequencies (1937,
1844 cmꢁ1) than those for complex 1-Mo. A similar tendency
was observed for the rest of complexes 3b-Mo, 3c-Mo, 3d-Mo,
and 3a-W. The IR spectral data for starting compounds 1 and
amidine complexes 3 are summarized in Table 1. In the
1H NMR spectra, the bis(formamidine) complex 3a-Mo
showed broadened signals in the temperature range from ꢁ80
ꢂC to 70 ꢂC. In other bis(amidine) complexes 3, similar broad-
ened signals were observed at room temperature. These fea-
tures might have come from the low isomerization energy bar-
rier for the trigonal twist mechanism of these complexes.14,15
Although we could not confirm the structure of complex 3 in
solution to be bis(amidine) complexes, [Mo(ꢀ3-allyl)Cl(CO)2-
Fig. 1. ORTEP drawing of 3a-Mo with thermal ellipsoids
drawn at the 30% probability level. Some hydrogen atoms
and toluene molecule are omitted for clarity.
{N(C6H5)=C(H)N(H)C6H5}2] 1/2toluene
(3a-Mo 1/2tol-
ꢃ
ꢃ
uene) was characterized by a single-crystal X-ray diffraction
study. An ORTEP drawing of 3a-Mo 1/2toluene is shown in
Fig. 1. The crystal data and the selected bond distances and an-
ꢃ
Table 2. Summary of Crystal Data for 3a-Mo, 4a-Mo, and 5a-Mo
3a-Mo 1/2toluene
ꢃ
4a-Mo
5a-Mo
Empirical formula
Formula weight
Crystal color, Habit
Crystal size/mm
Crystal system
C34:50H33ClMoN4O2
667.06
C31H28MoN4O2
584.53
yelow, prismatic
0:20 ꢄ 0:08 ꢄ 0:08
orthorhombic
P212121 (#19)
C24H31MoN2O2P
506.43
dark-orange, prismatic
0:50 ꢄ 0:23 ꢄ 0:13
monoclinic
yellow, plate
0:30 ꢄ 0:10 ꢄ 0:05
monoclinic
Space group
Lattice parameters
P21=n (#14)
P21=n (#14)
ꢀ
a/A
18.39(1)
22.64(1)
7.545(3)
97.87(5)
3112(3)
4
13.532(9)
17.00(1)
11.967(6)
90
2753(3)
12.255(2)
14.787(2)
13.670(1)
100.501(9)
2435.6(4)
4
ꢀ
b/A
ꢀ
c/A
ꢂ/deg
ꢀ 3
V/A
Z value
Dcalc/g cmꢁ3
4
1.410
1.423
1.381
F000
1372.00
5.44
7043
1342 (Rint ¼ 0:160)
368
8.41
1200.00
5.10
1048.00
6.25
7676
7106 (Rint ¼ 0:016)
316
22.56
ꢃ(Mo-Kꢄ)/cmꢁ1
Reflections measured
Independent reflections
No. Variables
2771
2747 (Rint ¼ 0:679)
344
7.99
Reflection/parameter ratio
Residuals: R; Rw
Residuals: R1
0.226; 0.287
0.138
0.155; 0.166
0.077
0.053; 0.110
0.033
No. of reflections to calc R1
Goodness of Fit Indicator
2411 (I > 2:0ꢅðIÞÞ
2.80
1.53
ꢁ2:39
1375 (I > 2:0ꢅðIÞÞ
1.14
1.17
ꢁ0:83
5258 (I > 2:0ꢅðIÞ)
1.26
0.53
ꢁ0:36
ꢀ ꢁ3
Maximum peak in Final Diff. Map/e A
ꢀ ꢁ3
Minimum peak in Final Diff. Map/e A

Y. Yamaguchi et al.
Table 3. Selected Bond Distances (A) for 3a-Mo, 4a-Mo, and 5a-Mo
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
305
ꢀ
3a-Mo
Mo(1)–C(29)
4a-Mo
Mo(1)–C(29)
5a-Mo
Allyl
CO
2.34(2)
2.22(2)
2.36(2)
1.92(2)
1.91(2)
1.18(2)
1.21(2)
2.36(2)
2.24(1)
1.29(2)
1.37(2)
1.58(4)
1.09(3)
2.29(2)
2.21(2)
2.25(2)
1.94(2)
1.94(2)
1.18(2)
1.17(2)
2.21(1)
2.27(1)
2.25(2)
1.31(2)
1.37(2)
1.32(2)
1.29(2)
Mo(1)–C(22)
Mo(1)–C(23)
Mo(1)–C(24)
Mo(1)–C(14)
Mo(1)–C(15)
O(1)–C(14)
O(2)–C(15)
Mo(1)–N(1)
Mo(1)–N(2)
N(1)–C(1)
2.339(3)
2.224(3)
2.327(3)
1.953(3)
1.959(3)
1.155(3)
1.148(3)
2.237(2)
2.243(2)
1.317(3)
1.320(3)
Mo(1)–C(30)
Mo(1)–C(31)
Mo(1)–C(27)
Mo(1)–C(28)
O(1)–C(27)
O(2)–C(28)
Mo(1)–N(1)
Mo(1)–N(3)
N(1)–C(1)
Mo(1)–C(30)
Mo(1)–C(31)
Mo(1)–C(14)
Mo(1)–C(15)
O(1)–C(14)
O(2)–C(15)
Mo(1)–N(1)
Mo(1)–N(2)
Mo(1)–N(3)
N(1)–C(1)
Amidinato
or
Amidine
N(2)–C(1)
N(3)–C(14)
N(4)–C(14)
N(2)–C(1)
N(2)–C(1)
N(3)–C(16)
N(4)–C(16)
Others
Mo(1)–Cl(1)
2.608(6)
Mo(1)–P(1)
2.5621(6)
Table 4. Selected Bond Angles (deg) for 3a-Mo, 4a-Mo, and 5a-Mo
3a-Mo
4a-Mo
5a-Mo
CO
Mo(1)–C(27)–O(1)
Mo(1)–C(28)–O(2)
Mo(1)–N(1)–C(1)
Mo(1)–N(1)–C(2)
N(1)–C(1)–N(2)
177(2)
173(2)
130(1)
119(1)
124(2)
111(2)
127(2)
137(1)
120(1)
102(1)
103(4)
104(4)
Mo(1)–C(14)–O(1)
Mo(1)–C(15)–O(2)
N(1)–Mo(1)–N(2)
Mo(1)–N(1)–C(1)
Mo(1)–N(1)–C(2)
C(1)–N(1)–C(2)
Mo(1)–N(2)–C(1)
Mo(1)–N(2)–C(8)
C(1)–N(2)–C(8)
Mo(1)–N(3)–C(16)
Mo(1)–N(3)–C(17)
C(16)–N(3)–C(17)
C(16)–N(4)–C(23)
N(1)–Mo(1)–N(3)
N(1)–Mo(1)–C(14)
N(1)–Mo(1)–C(15)
N(2)–Mo(1)–N(3)
N(2)–Mo(1)–C(14)
N(2)–Mo(1)–C(15)
N(3)–Mo(1)–C(14)
N(3)–Mo(1)–C(15)
C(14)–Mo(1)–C(15)
172(2)
176(1)
59.3(5)
96(1)
144(1)
119(1)
92(1)
145(1)
122(2)
121(2)
121(1)
117(2)
121(2)
83.7(5)
168.0(7)
106.5(6)
79.0(5)
113.2(7)
164.2(7)
85.6(7)
93.2(6)
79.4(8)
Mo(1)–C(14)–O(1)
Mo(1)–C(15)–O(2)
N(1)–Mo(1)–N(2)
Mo(1)–N(1)–C(1)
Mo(1)–N(1)–C(2)
C(1)–N(1)–C(2)
Mo(1)–N(2)–C(1)
Mo(1)–N(2)–C(8)
C(1)–N(2)–C(8)
N(1)–C(1)–N(2)
N(1)–C(1)–H(1)
N(2)–C(1)–H(1)
179.1(3)
179.5(3)
58.76(6)
94.3(1)
140.7(1)
124.9(2)
94.0(1)
141.1(1)
124.8(2)
112.9(2)
120(1)
Amidinato
or
Amidine
C(1)–N(1)–C(2)
C(1)–N(2)–C(8)
Mo(1)–N(3)–C(14)
Mo(1)–N(3)–C(15)
C(14)–N(3)–C(15)
N(3)–C(14)–N(4)
C(14)–N(4)–C(21)
126(1)
Mo
Cl(1)–Mo(1)–N(1)
Cl(1)–Mo(1)–N(3)
Cl(1)–Mo(1)–C(27)
Cl(1)–Mo(1)–C(28)
N(1)–Mo(1)–N(3)
N(1)–Mo(1)–C(27)
N(1)–Mo(1)–C(28)
N(3)–Mo(1)–C(27)
N(3)–Mo(1)–C(28)
88.8(4)
84.1(4)
93.5(5)
166.8(5)
78.8(5)
169.2(7)
98.4(7)
91.0(7)
86.6(7)
P(1)–Mo(1)–N(1)
P(1)–Mo(1)–N(2)
P(1)–Mo(1)–C(14)
P(1)–Mo(1)–C(15)
N(1)–Mo(1)–C(14)
N(1)–Mo(1)–C(15)
N(2)–Mo(1)–C(14)
N(2)–Mo(1)–C(15)
C(14)–Mo(1)–C(15)
80.68(5)
84.53(5)
89.29(9)
86.42(9)
165.0(1)
109.4(1)
109.38(9)
166.2(1)
80.9(1)
gles for 3a-Mo 1/2toluene are listed in Tables 2–4, respective-
was allowed to warm to room temperature. After a work-up,
amidinato(amidine) complex 4a-Mo was isolated as a yellow
solid in 64% yield. A similar reaction of complex 3b-Mo with
nBuLi yielded complex 4b-Mo as a yellow solid (79%) (Eq. 2).
ꢃ
ly. An X-ray study revealed that complex 3a-Mo has two ami-
dine ligands; one is located in trans position to the ꢆ-allyl li-
gand and the other to the CO ligand.16 An elemental analysis
supported the formation of complex 3a-Mo containing 0.5
molecule of toluene.
Ar
Cl
nBuLi
N
OC
OC
NHAr
H
OC
OC
Conversion of Bis(amidine) Complexes 3 into Amidinato-
(amidine) Complexes 4. It is reported that the amidine com-
plex of iron, having a halogen ligand, was successfully convert-
ed into the amidinato complex by alkyllithium.13b We therefore
examined the reaction of bis(amidine) complexes 3 with a base,
Mo
Mo
H
N
N
THF
-78 °C → r.t.
ArN
ArN
Ar
Ar
H
H
ð2Þ
ArHN
ArHN
n
such as BuLi, to prepare the amidinato complex.
After bis(formamidine) complex 3a-Mo was treated with
one equivalent of nBuLi in THF at ꢁ78 ꢂC, the reaction mixture
3a-Mo (Ar = Ph)
3b-Mo (Ar = p-tolyl)
4a-Mo (Ar = Ph)
4b-Mo (Ar = p-tolyl)

306 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Amidinato(amidine) Complexes of Molybdenum
In IR spectra, complexes 4a-Mo and 4b-Mo showed two CO
stretching bands (1927, 1826 cmꢁ1 for 4a-Mo and 1926, 1832
cmꢁ1 for 4b-Mo, respectively), which are lower frequency than
those for the starting complexes 3a-Mo (1937, 1844 cmꢁ1) and
3b-Mo (1931, 1836 cmꢁ1). In 1H NMR spectra, both com-
plexes showed complicated signals, possibly due to the fluxio-
nal geometrical rearrangement of the molecule in solution.14,17
Complex 4a-Mo was characterized by a single-crystal X-ray
diffraction study (vide infra).
Ar
N
Ar
N
PEt3
OC
OC
OC
OC
Mo
H
Mo
H
N
N
CH2Cl2, r.t.
ArN
Ar
Ar
Et3P
H
ð5Þ
ArHN
4a-Mo (Ar = Ph)
4b-Mo (Ar = p-tolyl)
5a-Mo (Ar = Ph)
5b-Mo (Ar = p-tolyl)
Next, we examined the reaction of complexes 3c-Mo and
3d-Mo, having acetamidine ligands, with nBuLi (Eq. 3). In
these reactions, the desired reaction did not occur and uniden-
tified products were formed. The employment of another base,
such as KH or KOtBu, in the place of nBuLi also resulted in the
formation of uncharacterized products. These complicated re-
sults might have come from abstraction of the hydrogen atom
of the methyl group on the acetamidine ligand, though there
is no compelling evidence to support it. In the case of a tungsten
complex, the desired product (4a-W) was also not obtained by
the reaction of 3a-W with an equimolar amount of nBuLi (Eq.
4). A further investigation of the preparation of these com-
pounds is now in progress.
The IR spectrum of 5a-Mo showed two CO stretching bands
at 1921 and 1836 cmꢁ1. In 31P NMR, a singlet signal was ob-
served at 13.7 ppm, which suggests that PEt3 binds to the mo-
1
lybdenum center. In the H NMR spectrum, methyl and meth-
ylene groups in PEt3 were observed at 1.04 ppm as a double
1
triplet and at 1.75 ppm as quintet, respectively. The H NMR
spectrum also showed a doublet at 8.79 ppm (J ¼ 4:0 Hz)
due to a formamidinato CH proton. This pattern resulted from
coupling with coordinated PEt3. The 13C NMR spectrum
2
showed a doublet signal at 227.4 ppm with JPC ¼ 14:7 Hz
due to the carbonyl carbons. Two signals being assignable to
the allyl ligand were observed at 60.5 ppm as a singlet and at
86.2 ppm as a doublet, and four sets of singlets due to phenyl
carbons were observed. These results suggest that the phos-
phine is located in the cis position to two CO ligands and in
the trans position to the allyl ligand in solution. Similar spectra
were obtained for complex 5b-Mo.
nBuLi, KH,
or KOtBu
Ar
N
Cl
OC
OC
NHAr
CH3
OC
OC
Mo
Mo
CH3
N
N
Crystal Structures of Molybdenum Complexes 4a-Mo
and 5a-Mo. X-ray structure analyses of complexes 4a-Mo
and 5a-Mo were undertaken. ORTEP drawings of 4a-Mo and
5a-Mo are displayed in Figs. 2 and 3, respectively. The crystal
data and the selected bond distances and angles for 4a-Mo and
5a-Mo are listed in Tables 2–4, respectively.
ArN
ArN
Ar
Ar
ð3Þ
CH3
CH3
ArHN
ArHN
3c-Mo (Ar = Ph)
3d-Mo (Ar = p-tolyl)
4c-Mo (Ar = Ph)
4d-Mo (Ar = p-tolyl)
Both complexes have a pseudo octahedral geometry around
the Mo atom, and the amidinato ligand is located on a coplanar
with two CO ligands. The amidine ligand in 4a-Mo, which is
coordinated to molybdenum through an imine nitrogen, is posi-
tioned trans to the ꢀ3-allyl ligand. In 5a-Mo, the PEt3 ligand is
also positioned trans to the ꢀ3-allyl ligand, whose geometrical
structure coincide with that suggested by NMR spectroscopy
(vide supra).
Ph
nBuLi
Cl
N
OC
OC
NHPh
H
OC
OC
W
W
H
N
N
PhN
PhN
Ph
Ph
ð4Þ
H
H
PhHN
PhHN
3a-W
4a-W
Reaction of Amidinato(amidine) Complexes of Molybde-
num with Triethylphosphine. We next examined the reaction
of amidinato(amidine) complexes of molybdenum (4a-Mo, 4b-
Mo) with triethylphosphine (PEt3), hoping that the substitution
reaction of the amidine with PEt3 might proceed. In a treatment
of complex 4a-Mo with one equimolar amount of PEt3 in
CH2Cl2 at ambient temperature, an initial yellow solution
changed to a homogenous red solution. The product was isolat-
ed by column chromatography as a red solid (70%). Elemental
analysis as well as IR and 1H, 13C, and 31P NMR spectra estab-
lished the formation of an amidinato complex of molybdenum
bearing PEt3 (5a-Mo). In a similar procedure, complex 5b-Mo
was isolated as a red solid in 61% yield, whose complex was
also characterized spectroscopically as well as by elemental
analysis (Eq. 5). Complex 5a-Mo was determined by a sin-
gle-crystral X-ray diffraction study (vide infra).
Fig. 2. ORTEP drawing of 4a-Mo with thermal ellipsoids
drawn at the 30% probability level. Some hydrogen atoms
are omitted for clarity.

Y. Yamaguchi et al.
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
307
SICAPENT (Merck Co., Inc.), by using a standard Schlenk tube or
high-vacuum techniques. All solvents were distilled over appropri-
ate drying agents prior to use. Mo(CO)6 and W(CO)6 were pur-
chased from Kanto Chemical Co., Inc., and used as received. nBuLi
in a hexane solution was purchased from Kanto Chemical Co., Inc.
and titrated prior to use. Other reagents employed in this research
were used without further purification. [Mo(ꢀ3-allyl)Cl(CO)2-
(NCMe)2] (1-Mo),7 [W(ꢀ3-allyl)Cl(CO)2(NCMe)2] (1-W),7
N,N0-disubstituted formamidines,19 (N(C6H5)=C(H)N(H)C6H5
(2a) and N(C6H4–p-CH3)=C(H)N(H)C6H4–p-CH3 (2b), and
N,N0-disubstituted acetamidines,19 N(C6H5)=C(CH3)N(H)C6H5
(2c) and N(C6H4–p-CH3)=C(CH3)N(H)C6H4–p-CH3 (2d)), were
prepared according to the literature methods.
1H, 13C{1H}, and 31P{1H} NMR spectra were recorded on a
JEOL EX-270 spectrometer at ambient temperature, unless other-
Fig. 3. ORTEP drawing of 5a-Mo with thermal ellipsoids
drawn at the 30% probability level. Some hydrogen atoms
are omitted for clarity.
1
wise mentioned. H and 13C{1H} NMR chemical shifts were re-
ported in ppm relative to internal Me4Si. 31P{1H} NMR chemical
shifts were recorded in ppm relative to external H3PO4. All cou-
pling constants were recorded in Hz. The splitting patterns are in-
dicated as s, singlet; d, doublet; t, triplet; quint, quintet. IR spectra
were recorded on a Perkin-Elmer 1600 FT-IR spectrometer. Melt-
ing points were measured using a YAZAWA Micro Melting Point
BY-2 apparatus. Column chromatography was performed under
air.
In complex 4a-Mo, the Mo(1)–N(3) (amidine nitrogen) bond
ꢀ
distance is 2.25(2) A, which is similar to that found for Mo–
ꢀ
amidinato N bond distances (Mo(1)–N(1); 2.21(1) A and
ꢀ
Mo(1)–N(2); 2.27(1) A). The amidinato N–C bond distances
ꢀ
ꢀ
are 1.34(2) A for N(1)–C(1) and 1.31(2) A for N(2)–C(1). This
result indicates that the amidinato N–C–N bond electrons are
delocalized. Furthermore, the nitrogen atoms in the amidinato
ligand have a trigonal-planar structure; the sum of the angles
is 359.0ꢂ for N(1) and 358.0ꢂ for N(2), respectively. The N–
Preparation of [Mo(ꢀ3-allyl)Cl(CO)2{N(C6H5)=C(H)N(H)-
C6H5}2] (3a-Mo).
[Mo(ꢀ3-allyl)Cl(CO)2(NCMe)2] (1-Mo)
(130 mg, 0.42 mmol) and formamidine, N(C6H5)=C(H)N(H)C6H5
(2a), (170 mg, 0.87 mmol) were put into a Schlenk tube and then
THF (10 mL) was added via a syringe. The mixture was stirred
over-night at ambient temperature. After removing the volatiles
under reduced pressure, a residual yellow powder was washed with
hexane several times and dried in vacuo to give spectroscopically
pure 3a-Mo as a yellow powder (250 mg, 0.40 mmol, yield 95%).
For the purpose of elemental analysis, the product was further pu-
rified recrystallization from toluene to give yellow crystals of 3a-
ꢀ
C bond distances in the amidine ligand are 1.32(2) A for
ꢀ
N(3)–C(16) and 1.29(2) A for N(4)–C(16) and are in good
agreement with the mean value of the N–C double bond
1
ꢀ
ꢀ
(1.24 A) and the N–C single bond (1.48 A). These observa-
tions stand for the delocalized nature of the two N–C bonds
in amidine ligand. Similar results were reported for a tantalum
complex bearing both amidine and amidinato ligands.13c
ꢀ
The Mo(1)–P(1) distance (2.5621(6) A) of 5a-Mo is in good
Mo 0.5toluene. Found: C, 62.38; H, 5.04; N, 8.41%. Calcd for
ꢃ
C31H29ClMoN4O2 0.5C7H8: C, 62.12; H, 4.99; N, 8.40%. Mp
ꢂ
agreement with the reported value for the normal Mo–P dative
18
ꢃ
ꢀ
bond distances falling in the range of 2.40–2.57 A. Other
105.0–107.0 C.
Preparation of [Mo(ꢀ3-allyl)Cl(CO)2{N( p-CH3C6H4)=C-
(H)NH( p-CH3C6H4)}2] (3b-Mo). Complex 3b-Mo was pre-
pared from 1-Mo (125 mg, 0.40 mmol) and formamidine,
N(C6H4–p-CH3)=C(H)N(H)C6H4–p-CH3 (2b), (215 mg, 0.96
mmol) in the same manner as that for 3a-Mo. 3b-Mo was isolated
as a yellow powder (270 mg, 0.40 mmol, yield quant.). Analytical-
ly pure sample was obtained by recrystallization from toluene.
Found: C, 61.66; H, 5.70; N, 7.99%. Calcd for C35H37ClMoN4O2:
bond distances and angles concerning the molybdenum frag-
ment, Mo(ꢀ-allyl)(amidinato)(CO)2, in complex 5a-Mo bore
a close parallel to those of the parent complex, 4a-Mo.
Conclusion
In an examination of the preparative method of a new type of
amidinato complexes possessing the Mo(ꢀ-allyl)(CO)2 frag-
ment, we found an effective method utilizing the bis(amidine)
complex as a starting material. Conversion of the bis(amidine)
complex of molybdenum to the amidinato(amidine) complex
was successfully achieved by abstraction of HCl with a base,
ꢂ
C, 62.09; H, 5.51; N, 8.27%. Mp 106.0–107.0 C.
Preparation of [Mo(ꢀ3-allyl)Cl(CO)2{N(C6H5)=C(CH3)-
N(H)(C6H5)}2] (3c-Mo). Complex 3c-Mo was prepared from
1-Mo (200 mg, 0.64 mmol) and acetamidine, N(C6H5)=C(CH3)-
N(H)C6H5 (2c), (275 mg, 1.31 mmol) in the same manner as that
for 3a-Mo. 3c-Mo was isolated as a yellow powder (400 mg, 0.62
mmol, yield 97%). Correct elemental analysis data could not be ob-
tained.
n
such as BuLi. However, in cases of acetamidine complexes
of molybdenum (3c-Mo, 3d-Mo), or a tungsten analogue (3a-
W), the desired products were not obtained. The observed fac-
ile displacement of the amidinato ligand in amidinato(amidine)
complexes (4) by tertiary phosphine allows us to expect novel
reactions involving these complexes. A further investigation
along this line is under progress in our laboratory.
Preparation of [Mo(ꢀ3-allyl)Cl(CO)2{N(C6H4–p-CH3)=C-
(CH3)N(H)C6H4–p-CH3}2] (3d-Mo). Complex 3d-Mo was pre-
pared from 1-Mo (80 mg, 0.26 mmol) and acetamidine, N(C6H4–
p-CH3)=C(CH3)N(H)C6H4–p-CH3 (2d), (155 mg, 0.65 mmol) in
the same manner as that for 3a-Mo. 3d-Mo was isolated as a yel-
low powder (180 mg, 0.26 mmol, yield quant.). Correct elemental
analysis data could not be obtained.
Experimental
General Procedures. All manipulations involving air and
moisture-sensitive organometallic compounds were carried out un-
der an atmosphere of dry argon or nitrogen, which was purified by
Preparation of [W(ꢀ3-allyl)Cl(CO)2{N(C6H5)=C(H)N(H)-

308 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Amidinato(amidine) Complexes of Molybdenum
C6H5}2] (3a-W). Complex 3a-W was prepared from [W(ꢀ3-
allyl)Cl(CO)2(NCMe)2] (1-W) (75 mg, 0.19 mmol) and formami-
dine, N(C6H5)=C(H)N(H)C6H5 (2a), (75 mg, 0.38 mmol) in the
same manner as that for 3a-Mo. 3a-W was isolated as a yellow
powder (130 mg, 0.18 mmol, yield 95%). Analytically pure sample
was obtained by recrystallization from toluene. Found: C, 54.40;
CH). 13C{1H} NMR (ꢈ, in CDCl3) 7.7 (d, J ¼ 2:4 Hz, PCH2CH3),
15.6 (d, J ¼ 19:5 Hz, PCH2), 20.7 (s, C6H4CH3), 60.5 (s, allyl-
CH2), 86.2 (d, J ¼ 6:1 Hz, allyl-CH), 117.4, 129.7, 130.9, 143.7
(s, Ph), 151.2 (d, J ¼ 4:9 Hz, amidinato-CH), 227.5 (d, J ¼ 14:6
Hz, CO). 31P{1H} NMR (ꢈ, in CH2Cl2) 13.7 (s).
Experimental Procedure for X-ray Crystallography. Suita-
ble single crystals were obtained by recrystallization from toluene
(3a-Mo), toluene/hexane (4a-Mo), or from hexane (5a-Mo), and
were mounted on glass fibers.
H, 4.68; N, 7.26%. Calcd for C31H29ClN4O2W 0.5C7H8: C,
ꢃ
ꢂ
54.89; H, 4.41; N, 7.42%. Mp 114.0–115.0 C.
Preparation
of
[Mo(ꢀ3-allyl){(NC6H5)2CH}(CO)2-
{N(C6H5)=C(H)N(H)C6H5}] (4a-Mo). A solution of complex
3a-Mo (430 mg, 0.69 mmol) in THF (20 mL) was cooled to
A diffraction measurement of 3a-Mo was made on a Rigaku
RAXIS IV imaging plate area detector with Mo Kꢄ radiation
ꢁ78 ꢂC, and then a hexane solution of nBuLi (1.50 mol dmꢁ3
,
(ꢉ ¼ 0:71069 A). Indexing was performed from four oscillation
ꢀ
0.46 mL, 0.69 mmol) was added. The mixture was stirred at ꢁ78
ꢂC for 2 h and then allowed to warm to room temperature. After
several hours, the volatiles were removed under reduced pressure.
The residual solid was extracted with toluene. The filtrate was
evaporated off under high vacuum. The residue was washed with
hexane several times, and dried in vacuo to give 4a-Mo as a yellow
powder (260 mg, 0.44 mmol, yield 64%). Found: C, 63.20; H, 4.49;
N, 9.37%. Calcd for C31H28MoN4O2: C, 63.70; H, 4.83; N, 9.59%.
images, which were exposed for 22 min. The crystal-to-detector
distance was 100 mm. The data were collected at a temperature
of ꢁ50 ꢂC to a maximum 2ꢊ value of 60ꢂ. A total of 28 5.00ꢂ os-
cillation images were collected, each being exposed for 22 min.
Readout was performed in the 0.100 mm pixel mode. The data
processing was performed on an SGI Indy computer.
Diffraction measurements of 4a-Mo and 5a-Mo were made on a
Rigaku AFC-7R automated four-circle diffractometer by using
Mp 116.0–117.0 ꢂC. IR (ꢁCO, KBr) 1927, 1826 cmꢁ1
.
graphite-monochromated Mo Kꢄ radiation (ꢉ ¼ 0:71069 A). The
ꢀ
Preparation of [Mo(ꢀ3-allyl){(NC6H4–p-CH3)2CH}(CO)2-
{N( p-CH3C6H4)=C(H)NH ( p-CH3C6H4)}] (4b-Mo). Complex
4b-Mo was prepared from complex 3b-Mo (550 mg, 0.81 mmol)
and a hexane solution of nBuLi (1.50 mol dmꢁ3, 0.55 mL, 0.83
mmol) in the same manner as that for 4a-Mo. 4b-Mo was isolated
as a yellow powder (410 mg, 0.64 mmol, yield 79%). Found: C,
66.18; H, 5.88; N, 8.27%. Calcd for C35H36MoN4O2: C, 65.62;
data collections were carried out at 23 ꢂC using the !–2ꢊ scan
technique to a maximum 2ꢊ value of 50.0ꢂ for 4a-Mo, and 60.0ꢂ
for 5a-Mo, respectively. Cell constants and an orientation matrix
for data collection were determined from 11 reflections with 2ꢊ an-
gles in the range 22.40–24.21ꢂ for 4a-Mo and from 25 reflections
with 2ꢊ angles in the range 29.73–29.99ꢂ for 5a-Mo. Three stand-
ard reflections were monitored at every 150 measurements. The da-
ta processing (data collection) was performed on a personal com-
puter. In the reduction of data, Lorentz and polarization corrections
and an empirical absorption correction (ꢁ scan) were made.
Crystallographic data and the results of measurements are sum-
marized in Table 2. The structures were solved by heavy-atom Pat-
terson methods (PATTY)20 for 3a-Mo or by direct methods (SIR
92)21 for 4a-Mo and 5a-Mo, and expanded using Fourier tech-
niques.22 All of the non-hydrogen atoms, except for the toluene sol-
ꢂ
H, 5.66; N, 8.75%. Mp 86.0–87.0 C. IR (ꢁCO, KBr) 1926, 1832
cmꢁ1
.
Preparation of [Mo(ꢀ3-allyl){(NC6H5)2CH}(CO)2PEt3] (5a-
Mo). To a solution of complex 4a-Mo (103 mg, 0.18 mmol) in
CH2Cl2 (10 mL) was added PEt3 (28 mL, 0.19 mmol) at room tem-
perature. After being stirred for 1.5 h, the volatiles were removed
under reduced pressure. The residual material was loaded on an
alumina column (ꢇ14 mm ꢄ 40 mm) and eluted with CH2Cl2/hex-
ane (1/1 v/v %). The eluted red band was collected and solvent
was removed in vacuo to give a red powder of 5a-Mo (63 mg,
0.12 mmol, yield 67%). Found: C, 56.77; H, 6.03; N, 5.46%. Calcd
for C24H31MoN2O2P: C, 56.92; H, 6.17; N, 5.53%. Mp 108.0–
109.0 ꢂC. IR (ꢁCO, KBr) 1921, 1836 cmꢁ1. 1H NMR (ꢈ, in CDCl3)
1.04 (dt, J ¼ 14:2, 7.6 Hz, 9H, CH3), 1.70 (d, J ¼ 9:9 Hz, 2H, al-
lyl-CH2), 1.75 (quint, J ¼ 7:6 Hz, PCH2), 3.77 (m, 1H, allyl-CH),
3.84 (dd, J ¼ 7:3, 1.7 Hz, 2H, allyl-CH2), 6.93 (d, J ¼ 7:3 Hz, 4H,
Ph), 7.23 (m, 6H, Ph), 8.79 (d, J ¼ 4:0 Hz, 1H, amidinato-CH).
13C{1H} NMR (ꢈ, in CDCl3) 7.6 (d, J ¼ 2:5 Hz, CH3), 15.5 (d,
J ¼ 19:5 Hz, PCH2), 60.5 (s, allyl-CH2), 86.2 (d, J ¼ 4:9 Hz, al-
lyl-CH), 117.7, 121.6, 129.2, 146.0 (s, Ph), 151.5 (d, J ¼ 6:1 Hz,
amidinato-CH), 227.4 (d, J ¼ 14:7 Hz, CO). 31P{1H} NMR (ꢈ,
in CH2Cl2) 13.7 (s).
vates in 3a-Mo 1/2toluene, were refined anisotropically. Except
ꢃ
for complex 5a-Mo, all hydrogen atoms were located at the calcu-
ꢀ
lated positions (C–H 0.95 A) and not refined. In complex 5a-Mo,
the hydrogen atoms were located from difference Fourier maps and
refined isotropically, except for the ethyl hydrogen atoms, which
ꢀ
were located calculated positions (C–H 0.95 A). All calculations
were performed on an SGI Indy computer using the teXsan crystal-
lographic software package of Molecular Structure Corporation.23
Crystallographic data have been deposited at the CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK and copies can be obtained on re-
quest, free of charge, by quoting the publication citation and the
deposition numbers 219635–219637.
The authors are grateful to Prof. Kohtaro Osakada (Tokyo
Institute of Technology) for his kind help in the elemental anal-
yses. This work was partially supported by a Grant-in-Aid for
Encouragement of Young Scientists from Japan Society for
the Promotion of Science (No. 13740413), Japan and by the
DAINIPPON INK AND CHEMICALS Inc. Award in Synthet-
ic Organic Chemistry, Japan through The Society of Synthetic
Organic Chemistry, Japan, granted to Y.Y.
Preparation of [Mo(ꢀ3-allyl){(NC6H4–p-CH3)2CH}(CO)2-
PEt3] (5b-Mo). Complex 5b-Mo was prepared from complex
4b-Mo (115 mg, 0.18 mmol) and PEt3 (28 mL, 0.19 mmol) in
the same manner as that for 5a-Mo. 5b-Mo was isolated as a red
powder (58 mg, 0.11 mmol, yield 61%). Found: C, 58.00; H,
6.24; N, 5.31%. Calcd for C26H35MoN2O2P: C, 58.43; H, 6.60;
ꢂ
N, 5.24%. Mp 125.0–126.0 C. IR (ꢁCO, KBr) 1921, 1837 cmꢁ1
.
1H NMR (ꢈ, in CDCl3) 1.04 (dt, J ¼ 14:8, 7.6 Hz, 9H, CH3),
1.67 (d, J ¼ 9:9 Hz, 2H, allyl-CH2), 1.74 (quint, J ¼ 7:6 Hz,
6H, PCH2), 2.28 (s, 6H, PhCH3) 3.74 (m, 1H, allyl-CH), 3.84 (d,
J ¼ 6:9 Hz, 2H, allyl-CH2), 6.82 (d, J ¼ 8:3 Hz, 4H, Ph), 7.03
(d, J ¼ 8:3 Hz, 4H, Ph), 8.73 (d, J ¼ 3:6 Hz, 1H, amidinato-
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