Reactions of Fe2(Co)9 with azine derivatives: Discovery of new coordination modes and reactivity of new bimetallic compounds

Article abstract of DOI:10.1021/om0205546

Reaction of N,N′-bis-(3-phenyl-allylidene)-hydrazine (1) with Fe₂(CO)₉ was studied. When the reaction was carried out in refluxing THF, the three mononuclear compounds Fe(CO)₃-[PhCH=CHCH=NN=CHR-trans] (3), Fe(CO)₃[PhCH=CHCH=NN=CHR-cis] (4), and Fe(CO)₃[PhCH=CHCH=N=CHR] (5; R = -CH=CHPh) were obtained. In refluxing toluene, the novel dinuclear compound Fe(CO)₃[PhCH=CHCH=NN=CHCH=CHPh]Fe(CO)₃ (2) was obtained. Further treatment of 3-5 with Fe₂(CO)₉ in refluxing toluene eventually led to 2. A detailed study of the reaction of 3-5 with/without Fe₂(CO)₉ allowed us to establish an overall reaction sequence from 1 to 2. Reaction of the alkyl analogue MeCH=CHCH=NN=CHCH=CHMe (10) with Fe₂(CO)₉ yielded the two dinuclear compounds Fe(CO)₃[MeCH=CHCH=NN=CHCH=CHMeFe(CO)₃ (11 and 11′) or the two mononuclear compounds Fe(CO)₃[MeCH=CHCH=NN=CHR′-trans] (12) and Fe(CO)₃[MeCH=CHCH=NN=CHR′] (13; R′ = -CH=CHMe) and the dinuclear compound anti-Fe(CO)₃[MeCH=CHCH=N-N=CHCH=CHMe]Fe(CO)₃ (14), respectively, depending upon the reaction conditions. Treatment of 2 with MeLi yielded the dimeric compound [PhCH=CHCH=NN=CHCH= CHPh]₂Fe₄(CO)₁₂ (16), containing four iron atoms, and treatment with MeLi followed by Mel afforded the dimethyl adduct Fe(CO)₃[PhCH=CHCHMeN=NCHMeCH=CHPh]Fe(CO)₃ (17). The molecular structures of 3-5, 8, 11, 11′, 14, and 16 were confirmed by X-ray diffraction studies.

Full text of DOI:10.1021/om0205546

5366
Organometallics 2002, 21, 5366-5372
Rea ction s of F e2(CO)9 w ith Azin e Der iva tives: Discover y
of New Coor d in a tion Mod es a n d Rea ctivity of New
Bim eta llic Com p ou n d s
Seung Uk Son, Kang Hyun Park, Il Gu J ung, and Young Keun Chung*
School of Chemistry and Center for Molecular Catalysis, Seoul National University,
Seoul 151-747, Korea
Myoung Soo Lah
Department of Chemistry, College of Sciences, Han Yang University, Ansan 425-170, Korea
Received J uly 11, 2002
Reaction of N,N′-bis-(3-phenyl-allylidene)-hydrazine (1) with Fe2(CO)9 was studied. When
the reaction was carried out in refluxing THF, the three mononuclear compounds Fe(CO)3-
[PhCHdCHCHdNNdCHR-trans] (3), Fe(CO)3[PhCHdCHCHdNNdCHR-cis] (4), and
Fe(CO)3[PhCHdCHCHdNdCHR] (5; R ) -CHdCHPh) were obtained. In refluxing toluene,
the novel dinuclear compound Fe(CO)3[PhCHdCHCHdNNdCHCHdCHPh]Fe(CO)3 (2) was
obtained. Further treatment of 3-5 with Fe2(CO)9 in refluxing toluene eventually led to 2.
A detailed study of the reaction of 3-5 with/without Fe2(CO)9 allowed us to establish an
overall reaction sequence from 1 to 2. Reaction of the alkyl analogue MeCHdCHCHdNNd
CHCHdCHMe (10) with Fe2(CO)9 yielded the two dinuclear compounds Fe(CO)3[MeCHd
CHCHdNNdCHCHdCHMeFe(CO)3 (11 and 11′) or the two mononuclear compounds
Fe(CO)3[MeCHdCHCHdNNdCHR′-trans] (12) and Fe(CO)3[MeCHdCHCHdNNdCHR′]
(13; R′ ) -CHdCHMe) and the dinuclear compound anti-Fe(CO)3[MeCHdCHCHdN-
NdCHCHdCHMe]Fe(CO)3 (14), respectively, depending upon the reaction conditions.
Treatment of 2 with MeLi yielded the dimeric compound [PhCHdCHCHdNNdCHCHd
CHPh]2Fe4(CO)12 (16), containing four iron atoms, and treatment with MeLi followed by
MeI afforded the dimethyl adduct Fe(CO)3[PhCHdCHCHMeNdNCHMeCHdCHPh]Fe(CO)3
(17). The molecular structures of 3-5, 8, 11, 11′, 14, and 16 were confirmed by X-ray
diffraction studies.
In tr od u ction
materials.5 Recently, azines and pyridyl-substituted
azines have been used extensively as ligands for the
design and synthesis of novel organometallic com-
pounds6
In the reaction of iron carbonyls with azines, the N-N
single bond is cleaved in most cases;7 however, if it is
retained, usually only one nitrogen atom is involved in
the coordination of the metal. When benzaldazines
(R(H)CdNNdC(H)R; R ) Ph, p-R′-C6H4) were used, no
Azines are 2,3-diazabutadiene derivatives that can be
viewed as N-N-linked diimines. They can undergo a
wide variety of chemical processes and have interesting
chemical properties. Azines have been receiving in-
creased attention due to their potential utility in bond
formation reactions,1 their biological properties,2 their
use in the design of liquid crystals,3 and other material
applications such as polymers4 and nonlinear optical
(3) (a) Centore, R.; Garzillo, C. J . Chem. Soc., Perkin Trans. 2 1997,
2, 79. (b) Espinet, P.; Etxebarria, J .; Marcos, M.; Pe´res, J .; Remo´n, A.;
Serrano, J . L. Angew. Chem., Int. Ed. Engl. 1989, 28, 1065.
(4) (a) Kesslen, E. C.; Euler, W. B. Chem. Mater. 1999, 11, 336. (b)
Hashidzume, A.; Tsuchiya, A.; Morishima, Y.; Kamachi, M. Macro-
molecules 2000, 33, 2397 and references therein.
* To whom correspondence should be addressed.
(1) (a) Grashey, R.; Padwa, A. Azomethine Imines. In 1,3-Dipolar
Cycloaddition Chemistry; Taylort, D. C., Weissberger, A., Eds.; General
Heterocyclic Chemistry Series; Wiley: New York, 1984; Vol. 1, p 733.
(b) Schweizer, E. E.; Cao, Z.; Rheingold, A. L.; Bruch, M. J . Org. Chem.
1993, 58, 4339.
(5) Nalwa, H. S.; Kakatu, A.; Mukoh, A. J . Appl. Phys. 1993, 73,
4743.
(2) Khodair, A. I.; Bertrand, P. Tetrahedron 1998, 54, 4859.
10.1021/om0205546 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/31/2002

Reactions of Fe2(CO)9 with Azine Derivatives
Organometallics, Vol. 21, No. 24, 2002 5367
Sch em e 1
cleavage of the molecule was observed, and the reaction
proceeds with ortho proton rearrangement to the azome-
thine carbon and the metalation of the phenyl ring.8
Aza-dienes have been attracted recent attention due
to their use as ligands in iron carbonyl complexes9 and
their Ru3(CO)12-catalyzed carbocyclization with ethylene
and carbon monoxide to yield lactams and spiropyrro-
lidin-2-ones.10 Very recently, we discovered that (η4-aza-
diene)Fe(CO)3 acted like cyclopentadiene in the reac-
tion.11 As an extension of our previous research, we
studied the reaction of iron carbonyls Fe2(CO)9 with
N,N′-bis(3-phenylallylidene)hydrazine (1). We aimed to
discover whether 1 reacted as an azine and/or azabuta-
diene derivative in the complex formation. We herein
report new reactions of 1 with Fe2(CO)9.
Resu lts a n d Discu ssion
Treatment of 1 with Fe2(CO)9 in refluxing toluene for
5 h gave the unexpected compound 2 in 45% yield (eq
1). The formation of 2 was confirmed by an X-ray
coordinated to the iron atom. Thus, we could see a
characteristic absorption at 1581 cm-1, indicative of a
ν(CdN) stretch in the infrared spectrum of 2. The
bonding mode discovered in 2 is not a new one, but it is
rare.12 The same bonding mode was found in the
reactions of FeCl2(PMe2Ph)2 and cis-Pt(C6F5)2(OC4H8)2
with diphenyldiazomethane, respectively. The formation
of 2 instead of 6 means that the coordination of an iron
tricarbonyl to the carbon-carbon double bond and to
the farther nitrogen atom is more favorable than the
well-known η4 coordination of an iron tricarbonyl. To
obtain some insight into the formation of 2, we tried to
trap intermediates in the reaction by controlling the
reaction time and changing the reaction medium (Table
1). Refluxing 1 with Fe2(CO)9 in toluene for 2 h gave a
mixture of 2-5 in 10%, 68%, 2%, and 10% yields,
respectively (eq 1).
Treatment of 1 with Fe2(CO)9 in refluxing THF for 1
h yielded 3 as the sole product in 41% yield. However,
when the same reaction was carried out in refluxing
THF for 18 h, compounds 3-5 were obtained in 60%,
5%, and 7% yields, respectively. Thus, compounds 3-5
(6) (a) Perera, S. D.; Shaw, B. L.; Thornton-Pett, M. Inorg. Chim.
Acta 2001, 325, 151. (b) Ohff, A.; Zippel, T.; Arndt, P.; Spannenberg,
A.; Kempe, R.; Rosenthal, U. Organometallics 1998, 17, 1649. (c) Shaw,
B. L.; Perera, S. D.; Shenton, D. J .; Thornton-Pett, M. Inorg. Chim.
Acta 1998, 270, 312. (d) Shaw, B. L.; Ike, U. U.; Perera, S. D.; Thornton-
Pett, M. Inorg. Chim. Acta 1998, 279, 95. (e) Perera, S. D.; Shaw, B.
L. Inorg. Chim. Acta 1995, 228, 127. (f) Matsuo, Y.; Mashima, K.; Tani,
K. Bull. Chem. Soc. J pn. 2002, 75, 1291.
(7) Zimniak, A.; Bakalarski, G. J . Mol. Struct. 2001, 597, 211.
Zimniak, A.; Zachara, J . J . Organomet. Chem. 1997, 533, 45.
(8) Bright, D.; Mills, O. S. Chem. Commun. 1967, 245. Zachara, J .;
Zimniak, A. Acta Crystallogr. 1998, C54, 353.
(9) (a) Kno¨lker, H.-J .; Gonser, P. Synlett 1992, 517. (b) Kno¨lker, H.-
J .; Gonser, P.; J ones, P. G. Synlett 1994, 405. (c) Kno¨lker, H.-J .; Baum,
G.; Foitzik, N.; Goesmann, H.; Gonser, P.; J ones, P. G.; Ro¨ttele, H.
Eur. J . Inorg. Chem. 1998, 993. (d) Imhof, W. Orgaometallics 1999,
18, 4845. (e) Kno¨lker, H.-J .; Ahrens, B.; Gonser, P.; Heininger, M.;
J ones, P. G. Tetrahedron 2000, 56, 2259. (f) Zhang. S.; Xu, Q.; Sun, J .;
Chen, J . Organometallics 2001, 20, 2387.
(10) (a) Berger, D.; Imhof, W. Chem. Commun. 1999, 1457. (b) Go¨bel,
A.; Imhof, W. Chem. Commun. 2001, 593.
(11) Son, S. U.; Park, K. H.; Chung, Y. K. Organometallics 2002,
21, 5072.
(12) Louie, J .; Grubbs, R. H. Organometallics 2001, 20, 481.
Fornide`s, J .; Menjo´n, B.; Go´mez, N.; Toma´s, M. Organometallics 1992,
11, 1187.
diffraction study. Due to its poor crystallinity, we failed
to obtain good X-ray diffraction data suitable for pub-
lication; however, we could confirm the molecular
structure shown in Scheme 1. The imine carbon is not

5368 Organometallics, Vol. 21, No. 24, 2002
Son et al.
Ta ble 1. P r od u ct Distr ibu tion
reactant
yield (%)a
amt of
reac- Fe2(CO)9
temp time
entry tant (equiv) solvent (°C)
(h)
2
3
4
5
1
2
3
4
5
6
7
8
1
1
1
1
3
3
4
4
5
5
2.0
2.0
2.0
2.0
none
1.5
none
1.5
none
1.5
toluene 110
toluene 110
5
2
1
18
8
7
2
7
2
4
45
10
68
41
60
2
10
7
THF
THF
60
60
5
toluene 110
toluene 110
toluene 110
toluene 110
toluene 110
toluene 110
n.r.b
50
20
F igu r e 2. ORTEP view of complex 4.
79
72
55
9
10
68
22
8
a
b
Isolated yield. n.r. ) no reaction.
F igu r e 3. ORTEP view of complex 5.
nitrogen atoms which is far away from the CdC bond.
Thus, the bonding mode found in 2 was confirmed by
X-ray diffraction studies of 3 and 4. The bond distances
between Fe and the coordinated nitrogen atoms range
from 2.006(5) to 2.068(2) Å, slightly shorter than those
of (η4-1-azabuta-1,3-diene)Fe(CO)3.13 Compound 5 has
the well-known η4 bonding mode, as found for tricarbo-
nyliron complexes of 1-azabuta-1,3-diene, buta-1,3-
diene, and cyclohexa-1,3-dienes.9c-e,13 The bond lengths
found in the tricarbonyliron complexes of 3-5, compared
to those of cyclohexa-1,3-dienes and buta-1,3-dienes,
correlate very well with the concept of increased back-
bonding from the filled iron d orbitals into the π*
orbitals of the organic ligand for the heterodiene com-
plexes.
F igu r e 1. ORTEP view of complex 3.
seemed to be intermediates on the way to 2. Interest-
ingly, the expected formation of 6 was not observed.
These observations suggest that the bonding mode in
2-4 is thermodynamically more favorable than that in
5. To confirm this speculation, we heated 3-5 and
observed their transformation.
When 4 and 5 were further heated, they were con-
verted to 3. However, a thermal transformation of 3 to
4 or 5 was not observed. These observations confirmed
that the coordination mode in 2-4 is thermodynamically
more favorable than that in 5 and that the trans isomer
3 is thermally more stable than the cis isomer 4. We
can temporarily conclude that 2 is synthesized by the
following sequences (Scheme 1). The first step is the
usual coordination of Fe(CO)3 to azabutadiene to form
5. The second step is a change of bonding mode from η4
to π and σ mode via the use of a distant nitrogen atom
instead of a nearby nitrogen atom. This change may be
responsible for the energy difference between 3 and 5.
Then, 3 isomerized to 4. The final step is another
coordination of Fe(CO)3 to a free CdC bond and a
nitrogen atom to form 2.
Treatment of 7 with Fe2CO)9 in refluxing toluene for
2 h yielded 8 as the sole product (77%) (eq 2).
Compounds 3- 5 were characterized by X-ray dif-
fraction studies (Figures 1-3). Crystal data and refine-
ment details are given in Table 2, and selected bond
distances and angles are given in Table 3. The X-ray
crystal structure determinations of 3 and 4 confirm the
tetragonal-pyramidal coordination of the iron atom. Two
basal positions are occupied by the CdC bond and a
nitrogen atom, and the others are occupied by carbonyl
ligands. The third carbonyl ligand adopts the apical
position of these complexes. Other structural features
are similar to those of (η4-1-azabuta-1,3-diene)Fe(CO)3
derivatives.9,11 Compounds 3 and 4 are related to each
other as cis and trans isomers. The Fe(CO)3 moiety in
3 and 4 coordinates to a CdC bond and one of the
Formation of 8 was confirmed by an X-ray diffraction
study (Figure 4). The molecular structure of 8 was quite
similar to that of the parent complex (η4-PhCHCHCHN-
Ph)Fe(CO)3.14a,b As expected, transformation of 8 to 9
was not observed, presumably due to the steric effect.
Thus, we expect that the substituent on the free imine
(13) Imhof, W.; Gobel, A.; Braga, D.; De Leonardis, P.; Tedesco, E.
Organometallics 1999, 18, 736-747.
(14) (a) De Cian, A.; Weiss, R. J . Chem. Soc., Chem. Commun. 1968,
348. (b) De Cian, A.; Weiss, R. Acta Crystallogr. 1972, 28, 3264. (c)
Kno¨lker, H.-J .; Baum, G.; Gonser, P. Tetrahedron Lett. 1995, 36, 8191.
(d) Kno¨lker, H.-J .; Goesmann, H.; Gonser, P. Tetrahedron Lett. 1996,
37, 6543.

Reactions of Fe2(CO)9 with Azine Derivatives
Organometallics, Vol. 21, No. 24, 2002 5369
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t Deta ils for 3-5, 8, 11, 11′, 14, a n d 16
3
4
5
8
11
11′
14
16
formula
C
21H16Fe-
N2O3
C
21H16Fe-
N2O3
C
21H16Fe-
N2O3
C
19H14Fe-
N2O3
C
14H12Fe2-
N2O3
C
14H12Fe2-
N2O3
C
14H12Fe2-
N2O3
C
50H38Fe4-
N4O12
fw
400.21
orthorhombic triclinic
400.21
400.21
triclinic
P1h
374.17
415.96
415.96
415.96
1110.24
orthorhombic
P212121
13.273(1)
13.226(1)
28.646(1)
90
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic monoclinic monoclinic triclinic
P21/c
Pcba
P1h
P21/a
P21/n
P1h
6.984(1)
22.873(1)
23.788(1)
90
90
90
8.067(1)
9.629(1)
12.783(1)
80.289(2)
78.102(2)
83.271(2)
954.19(17)
2
9.561(1)
9.986(1)
10.494(1)
85.192(1)
72.765(1)
81.1620(1)
944.80(16)
2
13.166(1)
7.444(1)
17.807(1)
90
92.573(2)
90
1743.5(3)
4
1.426
10.821(1)
12.681(1)
12.716(1)
90
96.262(1)
90
1734.5(3)
4
1.593
7.041(1)
13.638(1)
8.952(1)
90
96.008(1)
90
854.89(7)
4
1.616
7.511(1)
10.217(1)
11.508(1)
79.250(2)
89.994(2)
89.980(2)
867.62(16)
2
R, deg
â, deg
90
90
γ, deg
V, Å3
3800.0(6)
8
5028.8(6)
4
1.466
Z
D(calcd), Mg/m3
θ range, deg
no. of data collected
no. of unique data
1.399
1.393
1.407
1.592
1.71-24.14
16 301
3011
1.65-27.58 2.03-27.52 1.14-27.51 1.61-27.49 2.73-27.58 1.80-27.45 3.38-25.26
5879
6294
4321
6849
3989
7090
3979
3469
1953
5865
3933
8825
8835
4309
no. of params refined 244
244
244
226
219
110
219
658
R1(I > σ(I))
wR2(I > σ(I))
R1(all data)
wR2(all data)
GOF
0.0411
0.0514
0.1259
0.1131
0.1692
0.938
0.0385
0.1162
0.0529
0.1336
1.150
0.0430
0.1021
0.0892
0.1348
1.031
0.0452
0.1217
0.0705
0.1472
1.058
0.0351
0.0874
0.0644
0.1128
1.004
0.0456
0.1052
0.0703
0.1211
0.950
0.0443
0.0853
0.1450
0.0994
0.794
0.0966
0.1318
0.1690
0.944
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for 3-5, 8, 11, 11′, 14, a n d 16
Compound 3
Fe-C(21)
1.784(8)
Fe-C(7)
2.102(5)
N(1)-N(2)
1.434(6)
Fe-N(2)
2.006(5)
C(21)-Fe-N(2)
172.8(2)
C(20)-Fe-N(2)
88.4(2)
C(19)-Fe-N(2)
95.2(2)
C(8)-Fe-C(7)
40.0(2)
Compound 4
Fe-C(19)
1.763(14)
172.8(6)
Fe-C(20)
1.84(2)
Fe-C(7)
2.063(12)
N(1)-N(2)
1.375(17)
118.4(12)
C(19)-Fe-N(2)
C(21)-Fe-N(2)
88.5(7)
C(9)-N(1)-N(2)
107.4(11)
C(7)-C(8)-C(9)
Compound 5
Fe-C(19)
1.781(3)
Fe-N(1)
2.0685(19)
Fe-C(8)
2.070(2)
112.6(2)
N(1)-N(2)
1.390(3)
117.5(2)
C(21)-Fe-C(7)
164.56(10)
C(19)-Fe-N(1)
160.75(10)
C(9)-N(1)-N(2)
C(7)-C(8)-C(9)
Compound 8
Fe-C(19)
1.796(3)
Fe-N(1)
2.077(3)
Fe-C(8)
2.067(3)
113.1(2)
N(1)-N(2)
1.397(3)
117.8(3)
C(19)-Fe-C(7)
164.49(12)
C(17)-Fe-C(8)
94.93(14)
C(9)-N(1)-N(2)
C(7)-C(8)-C(9)
Compound 11
Fe(1)-C(14)
N(2)-C(5)
1.769(4)
1.279(4)
C(6)-C(7)
C(5)-C(6)
1.419(5)
1.457(5)
Fe(1)-N(1)
C(5)-C(6)
1.999(3)
1.457(5)
N(1)-N(2)
Fe(1)-C(6)
1.424(4)
2.050(3)
C(13)-Fe(1)-N(1)
90.51(14)
C(5)-C(6)-C(7)
118.5(3)
C(6)-C(5)-N(2)
123.2(3)
N(1)-N(2)-C(5)
111.1(3)
Compound 11′
Fe-C(7)
N(1)-N(1)#1
1.762(4)
1.435(5)
C(2)-C(3)
C(2)-C(1)
1.434(4)
1.446(4)
C(1)-N(1)
Fe-C(2)
1.284(4)
2.055(3)
Fe-N(1)#1
Fe-C(3)
2.082(3)
2.063(3)
C(3)-C(2)-C(1)
117.3(3)
C(7)-Fe-N(1)
175.10(15)
N(1)-Fe-C(3)
85.86(12)
C(2)-Fe-C(3)
40.76(12)
Compound 14
Fe-N(1)
2.082(3)
118.3(4)
Fe-C(4)
2.054(3)
Fe-C(2)
2.131(3)
N(1)-N(1)#1
1.442(5)
179.0(4)
C(2)-C(3)-C(4)
C(3)-C(4)-N(1)
114.8(4)
C(10)-Fe-C(2)
91.71(16)
Fe-C(10)-O(2)
Compound 16
Fe(1)-C(7)
N(1)-N(2)
2.106(6) C(7)-C(8)
1.280(6) C(11)-C(30)
1.399(9) C(8)-C(9)
1.562(6) Fe(1)-N(2)
1.510(10) C(9)-N(1)
1.984(5) Fe(2)-N(1)
1.501(7)
1.941(5)
C(7)-C(8)-C(9) 119.4(7)
C(8)-C(9)-N(1) 107.1(6)
N(1)-N(2)-C(11) 114.0(5)
C(10)-C(11)-C(12) 114.9(5)
nitrogen may play an important role in the transforma-
tion of 5 to 3.
An alkyl analogue 10 shows a reaction pattern similar
to that of 1 (eq 3). However, when 10 was reacted with
Fe2(CO)9 in refluxing toluene for 7 h, two compounds
having quite similar 1H NMR patterns in the ratio of
3:1 were observed in the 1H NMR spectrum. This means
that there may be two structural isomers in the solution.
Fortunately, two compounds, 11 and 11′, were separated
by recrystallization. Both compounds were characterized
F igu r e 4. ORTEP view of complex 8.

5370 Organometallics, Vol. 21, No. 24, 2002
Son et al.
F igu r e 5. ORTEP view of complex 11.
F igu r e 7. ORTEP view of complex 14.
Treatment of 10 with Fe2(CO)9 in refluxing THF for
7 h yielded 12-14 in 27%, 10%, and 7% yields, respec-
tively (eq 1). Comparison of the 1H NMR spectrum with
that of 3 and 5 allowed the assignment of the products
to 12 and 13, and the formation of 14 was verified by
an X-ray diffraction study (Figure 7). The two Fe(CO)3
moieties coordinate to the azine ligand in an anti
fashion, and the structure of each half of 14 is quite
similar to that of the parent complex (η4-PhCHCHCHN-
Ph)Fe(CO)3.14a,b When we considered the chemistry of
1, the formation of 14 was not expected. This seemed
to be reflected in its poor yield. When a mixture of 12
and 13 was treated with Fe2(CO)9 in refluxing toluene,
a mixture of 11 and 11′ in the ratio 3:1 was obtained in
75% yield. However, refluxing 14 in toluene gave no
reaction product.
F igu r e 6. ORTEP view of complex 11′.
by an X-ray diffraction study (Figures 5 and 6). As
expected, both compounds are related to the structural
isomers, due to the difference in the bonding modes of
the two iron metals. The structure of 11 is almost the
same as that of 2, the two iron metals coordinating to
the same face of the azine ligand. In 11′, each iron metal
is coordinated to a different face of the azine ligand. This
contrast seems to be due to the steric difference between
methyl and phenyl groups.
Next we investigated the reactivity of 2 having a new
bonding mode. To determine whether the bimetallic core
of 2 may act as a η6-ligand through C-H activation of
the benzyl group, 2 was heated with Cr(CO)6 at 110 °C
(eq 4). However, no C-H activation was observed.
Instead, the Cr(CO)3 fragments were coordinated to the
free phenyl groups to yield the tetrametallic Cr2Fe2
compound 15.
Compound 2 has two free imine carbons. Thus, we
expected a nucleophilic addition to the free imine

Reactions of Fe2(CO)9 with Azine Derivatives
Organometallics, Vol. 21, No. 24, 2002 5371
nucleophile and an electrophile. Thus, we investigated
the reaction of 2 with MeLi and MeI (eq 6). As expected,
the dimethyl adduct 17 was obtained in 91% yield.
Con clu sion
We have demonstrated that, using 1 and 10 as
ligands, new mono-, bi-, and tetrametallic compounds
can be synthesized in good yields. This study discloses
new bonding modes in the coordination of 1 and 10 to
the iron metal. We expect that these new bonding modes
can be expanded to other transition-metal systems.
Exp er im en ta l Section
F igu r e 8. ORTEP view of complex 16.
Gen er a l Con sid er a tion s. All reactions were conducted
under nitrogen using standard Schlenk-type flasks. Workup
procedures were done in air. All solvents were dried and
distilled according to standard methods before use. THF was
freshly distilled from sodium benzophenone ketyl prior to use.
Reagents were purchased from Aldrich Chemical Co. and
Strem Chemical Co. and were used as received. IR spectra
were obtained in solution or measured as films on NaCl by
evaporation of solvent. 1H NMR spectra were obtained with a
Bruker 300 or 500 spectrometer. Elemental analyses were
done at the National Center for Inter-University Research
Facilities, Seoul National University. High-resolution mass
spectra were measured at the Korea Basic Science Institute.
Rea ction of 1 w ith F e2(CO)9. Compounds 1, 7, and 10
were previously reported.16 The general procedure for the
reaction between 1 and Fe2(CO)9 in Table 1 is as follows.
Compounds 1 (0.30 g, 1.2 mmol) and Fe2(CO)9 (predetermined
amounts in Table 1) were dissolved in 25 mL of THF or
toluene. The solution was heated to reflux for the predeter-
mined time. After the solution was cooled to room temperature,
the solvent was evaporated by a rotary evaporator. Chroma-
tography of the residue on a silica gel column yielded the
compound(s) in Table 1. 2: 1H NMR (CDCl3) δ 7.97 (d, J )
3.6 Hz, 2 H), 7.26-7.06 (m, 1 H), 3.99 (dd, J ) 3.7, 9.0 Hz, 2
H), 3.62 (d, J ) 9.0 Hz, 2 H); 13C NMR (CDCl3) δ 177.6, 144.3,
carbons. As expected, 2 reacted with a nucleophile. MeLi
was added to one of the free imine carbons (eq 5).
Surprisingly, the dimeric compound 16, having four iron
tricarbonyl moieties, was obtained as the sole products
in 58% yield. This is quite a rare example of a dimer-
ization induced by MeLi. Several years ago, Thomas et
128.5, 125.5, 125.1, 63.3, 52.1; IR ν(CO) 2036, 1949 cm-1
,
ν(CN) 1581 cm-1; HRMS m/z calcd 539.9707, obsd 539.9097.
Anal. Calcd for C24H16Fe2N2O6: C, 53.37; H, 2.99; N, 5.19.
Found: C, 53.39; H, 2.98; N, 5.16. 3: 1H NMR (CDCl3) δ 8.34
(d, J ) 9.8 Hz, 1 H), 7.94 (br s, 1 H), 7.64-7.21 (m, 11 H),
7.07 (br s, 1 H), 4.58 (d, J ) 6.7 Hz, 1 H), 3.68 (d, J ) 8.7 Hz,
1 H); 13C NMR (CDCl3) δ 173.1, 169.1, 149.2, 144.6, 134.9,
131.0, 129.2, 128.3, 128.2, 125.2, 124.0, 63.0, 56.3; IR ν(CO)
2029, 1937 cm-1, ν(CN) 1593 cm-1; HRMS m/z calcd 400.0510,
obsd 400.0515. Anal. Calcd for C21H16FeN2O3: C, 63.02; H,
4.03; N, 7.00. Found: C, 63.22; H, 4.06; N, 7.08. 4: 1H NMR
(CDCl3) δ 8.00 (br s, 1 H), 7.97 (br s, 1 H), 7.51-7.211 (m, 10
H), 7.03 (br s, 2 H), 4.36 (d, J ) 6.6 Hz, 1 H), 3.86 (d, J ) 8.4
Hz, 1 H); 13C NMR (CDCl3) δ 174.8, 164.9, 145.5, 144.9, 134.7,
130.7, 129.0, 128.3, 128.2, 125.2, 124.9, 119.8, 63.7, 55.6; IR
ν(CO) 2030, 1935 cm-1, ν(CN) 1593 cm-1; HRMS m/z calcd
400.0510, obsd 400.0506. Anal. Calcd for C21H16FeN2O3: C,
63.02; H, 4.03; N, 7.00. Found: C, 63.24; H, 4.04; N, 7.05. 5:
1H NMR (CDCl3) δ 7.88 (d, J ) 8.1 Hz, 1 H), 7.45-7.28 (m, 10
H), 6.92 (d, J ) 12.0 Hz, 2 H), 6.78 (d, J ) 11.0 Hz, 1 H), 5.57
(d, J ) 7.2 Hz, 1 H), 3.20 (d, J ) 8.5 Hz, 1 H); 13C NMR (CDCl3)
δ 161.1, 140.6, 139.3, 136.5, 129.4, 129.3, 128.9, 127.5, 127.3,
al.15 reported pyrrole formation from the reaction of
(1-azabutadiene)tricarbonyliron(0) with methyllithium.
Thus, we first expected a pyrrole derivative as a product.
The molecular structure of 16 confirmed that the methyl
group has been added to the free imine carbon, and the
coupling of the resulting diiron species leads to a dimeric
structure (Figure 8). The structure of each half of 16 is
similar to that of 2, although the detailed structure of
16 is different from that of 2.
Owing to the two free imine carbons of 2, we expected
that there would be a sequential reaction of 2 with a
126.9, 125.5, 106.2, 72.2, 60.2; IR ν(CO) 2046, 1972 cm-1
;
(15) Danks, T. N.; Thomas, S. E. Tetrahedron Lett. 1988, 29, 1425-
1426.
(16) For the synthesis of 1: Elguero, J .; et al. Bull. Soc. Chim. Fr.
1967, 3005-3019. Mlochowski, J .; Abdel-Latif, F. F.; Kubicz, E.; Said,
S. B. Pol. J . Chem. 1993, 67, 711-722. For the synthesis of 7: Freche,
P.; et al. Tetrahedron 1997, 33, 2069-2077. For the synthesis of
10: Brun, P.; et al., Tetrahedron 1985, 41, 5019-5030.

5372 Organometallics, Vol. 21, No. 24, 2002
Son et al.
HRMS m/z calcd 400.0510, obsd 400.0510. Anal. Calcd for
to -78 °C. To the cold solution was added MeLi (0.40 mmol).
The resulting solution was stirred at -78 °C for 10 h. After
the solution was warmed to room temperature, the solution
was quenched by addition of 0.2 mL of water. After the solution
was dried over anhydrous MgSO4, the solution was filtered,
evaporated to dryness, and chromatographed on a silica gel
column. Yield: 58% (0.06 g). 16: 1H NMR (CDCl3) δ 7.31-
7.10 (m, 20 H), 6.19 (s, 2 H), 5.79 (d, J ) 6.9 Hz, 2 H), 4.26 (d,
J ) 11.0 Hz, 2 H), 3.69 (d, J ) 11.0 Hz, 2 H), 3.07 (d, J ) 10.0
Hz, 2 H), 2.85 (d, J ) 11.0 Hz, 2 H), 2.00 (d, J ) 6.6 Hz, 6 H);
13C NMR (CDCl3) δ 142.6, 141.9, 128.6, 128.5, 126.1, 125.9,
93.4, 88.7, 77.9, 61.1, 60.9, 53.2, 47.5, 20.7; IR ν(CO) 2026,
1972, 1944 cm-1; HRMS (M + H) m/z calcd 1110.9962, obsd
1110.9972. Anal. Calcd for C50H38Fe4N4O12: C, 54.09; H, 3.45;
N, 5.05. Found: C, 54.07; H, 3.57; N, 5.01.
C
21H16FeN2O3: C, 63.02; H, 4.03; N, 7.00. Found: C, 63.25;
H, 4.07; N, 7.00.
Rea ction of 7 w ith F e2(CO)9. Compounds 7 (0.20 g, 0.85
mmol) and Fe2(CO)9 (0.62 g, 1.7 mmol) were dissolved in 20
mL of toluene. The solution was heated to reflux for 2 h. After
the solution was cooled to room temperature, the solvent was
evaporated to dryness and chromatographed on a silica gel
1
column. Yield: 77%. H NMR (CDCl3): δ 8.06 (s, 1 H), 7.62-
7.27 (m, 10 H), 5.58 (d, J ) 7.8 Hz, 1 H), 3.21 (d, J ) 7.8 Hz,
1 H). 13C NMR (CDCl3): δ 158.7, 138.9, 134.1, 130.2, 128.8,
128.7, 127.3, 126.9, 126.4, 106.2, 71.6, 59.7. IR: ν(CO) 2044,
1975 cm-1, ν(CN) 1597 cm-1. HRMS m/z calcd 374.0354, obsd
374.0357. Anal. Calcd for C19H14FeN2O3: C, 60.99; H, 3.77;
N, 7.49. Found: C, 60.99; H, 3.81; N, 7.37.
Rea ction of 10 w ith F e2(CO)9. Compounds 10 (0.30 g, 2.2
mmol) and Fe2(CO)9 (1.60 g, 4.4 mmol) were dissolved in 25
mL of THF or toluene. The solution was refluxed for 7 h. After
the solution was cooled to room temperature, the solvent was
evaporated to dryness and chromatographed on a silica gel
column. When the reaction medium was toluene, a mixture of
11 and 11′ in the ratio of 3:1 was obtained in 58% yield. In
THF, 12-14 were isolated in 27%, 10% and 7% yield, respec-
Syn th esis of 17. A solution of 2 (0.10 g, 0.19 mmol) in 10
mL of diethyl ether was cooled to -78 °C. To the cold solution
was added MeLi (0.29 mmol). After the solution was stirred
at -78 °C for 2 h, an excess of MeI was added. The resulting
solution was stirred at -78 °C for 2 h. After the solution was
warmed to room temperature, the reaction was quenched by
addition of 0.1 mL of water. After the solution was dried over
anhydrous MgSO4 (0.5 g), it was filtered and evaporated to
dryness. Chromatography of the residue on a silica gel column
with n-hexane as eluent gave 17 in 91% yield (0.096 g). 17:
1H NMR (CDCl3) δ 7.26-7.05 (m, 10 H), 5.38 (q, J ) 6.6 Hz,
2 H), 3.97 (d, J ) 11.0 Hz, 2 H), 2.89 (d, J ) 11.0 Hz, 2 H),
1.67 (d, J ) 6.7 Hz, 6 H); 13C NMR (CDCl3) δ 143.6, 128.9,
126.6, 125.9, 86.9, 59.0, 54.4, 19.6; IR ν(CO) 2024, 1968, 1940
cm-1; HRMS m/z calcd 570.0177, obsd 570.0175. Anal. Calcd
for C26H22Fe2N2O6: C, 54.77; H, 3.89; N, 4.91. Found: C, 55.18;
H, 4.03; N, 4.87.
X-r a y Str u ctu r e Deter m in a tion s of 3-5, 8, 11, 11′, 14,
a n d 16. Single crystals of 3-5, 8, 11, 11′, 14, and 16 suitable
for X-ray diffraction study were grown by slow diffusion of the
dichloromethane solutions of 3-5, 8, 11, 11′, 14, and 16 into
hexane in a freezer (at -15 °C). X-ray data for single crystals
were collected on an Enraf-Nonius CCD single-crystal X-ray
diffractometer at room temperature using graphite-monochro-
mated Mo KR radiation (λ ) 0.710 73 Å). The structures were
solved by direct methods (SHELXS-97) and refined against all
F2 data (SHELXS-97). All non-hydrogen atoms were refined
with anisotropic thermal parameters, and the hydrogen atoms
were treated as idealized contributions. The crystal structure
of 16 was assigned as the noncentric P212121 space group on
the basis of the systematic absences of the reflection data.
However, the refinement of the structure with either enan-
tiomeric configuration gave a Flack parameter of around 0.5.
The refinement of the structure as a racemic twinned structure
gave better agreement. Crystal data, details of the data
collection, and refinement parameters are listed in Table 2.
Selected bond distances and angles are given in Table 3.
tively. IR of a mixture 11 and 11′: ν(CO) 2025, 1941 cm-1
,
ν(CN) 1578 cm-1. 11: 1H NMR (CDCl3) δ 7.65 (d, J ) 3.4 Hz,
2 H), 3.14 (dd, J ) 3.7, 8.6 Hz, 2 H), 2.48 (qd, J ) 6.3, 8.6 Hz,
2 H), 1.62 (d, J ) 6.3 Hz, 6 H); 13C NMR (CDCl3) δ 176.8, 60.3,
59.4, 23.3; HRMS m/z calcd 415.9394, obsd 415.9391. Anal.
Calcd for C14H12Fe2N2O6: C, 40.43; H, 2.91; N, 6.73. Found:
C, 40.54; H, 2.91; N, 6.68. 11′: 1H NMR (CDCl3) δ 7.86 (d, J
) 3.3 Hz, 2 H), 3.36 (dd, J ) 3.2, 8.6 Hz, 2 H), 2.59 (qd, J )
6.3, 8.6 Hz, 2 H), 1.62 (d, J ) 6.3 Hz, 6 H); 13C NMR (CDCl3)
δ 180.2, 61.1, 60.4, 23.6; HRMS m/z calcd 415.9394, obsd
415.9391. Anal. Calcd for C14H12Fe2N2O6: C, 40.43; H, 2.91;
N, 6.73. Found: C, 40.71; H, 2.99; N, 6.64. 12: 1H NMR (CDCl3)
δ 8.03 (d, J ) 10.0 Hz, 1 H), 7.74 (d, J ) 3.3 Hz, 1 H), 6.83
(dd, J ) 10.0, 15.0 Hz, 1 H), 6.52 (dq, J ) 6.9, 15.0 Hz, 1 H),
3.80 (dd, J ) 3.3, 9.0 Hz, 1 H), 2.58 (m, 1 H), 2.08 (d, J ) 6.9
Hz, 3 H), 1.62 (d, J ) 6.3 Hz, 3 H); 13C NMR (CDCl3) δ 214.4,
172.4, 168.7, 149.7, 128.9, 63.5, 59.8, 22.7, 19.7; IR ν(CO) 2021,
1931 cm-1, ν(CN) 1597 cm-1; HRMS m/z calcd 276.0197, obsd
276.0201. 13: 1H NMR (CDCl3) δ 7.56 (d, J ) 9.0 Hz, 1 H),
6.70 (d, J ) 2.7 Hz, 1 H), 6.08 (m, 2 H), 4.86 (dd, J ) 2.9, 8.9
Hz, 1 H), 2.18 (m, 1 H), 1.82 (d, J ) 6.2 Hz, 3 H), 1.46 (d, J )
6.4 Hz, 3 H); 13C NMR (CDCl3) δ 214.4, 160.9, 139.6, 129.1,
106.2, 66.3, 56.6, 19.1, 18.8; IR ν(CO) 2048, 1964 cm-1; HRMS
m/z calcd 276.0197, obsd 276.0194. 14: 1H NMR (CDCl3) δ 6.61
(d, J ) 3.0 Hz, 2 H), 4.70 (dd, J ) 2.8, 9.0 Hz, 2 H), 1.80 (qd,
J ) 6.5, 9.0 Hz, 2 H), 1.33 (d, J ) 6.5 Hz, 6 H); 13C NMR
(CDCl3) δ 109.9, 77.1, 55.9, 18.2; IR ν(CO) 2036, 1960 cm-1
.
Anal. Calcd for C14H12Fe2N2O6: C, 40.43; H, 2.91; N, 6.73.
Found: C, 40.55; H, 2.87; N, 6.66. HRMS m/z calcd 415.9394,
obsd 415.9394.
Syn th esis of 15. Compounds 2 (0.10 g, 0.19 mmol) and Cr-
(CO)6 (0.21 g, 0.95 mmol) were dissolved in a solvent mixture
of dibutyl ether (25 mL) and THF (5 mL). The solution was
heated to reflux for 3 days. After the solution was cooled to
room temperature, the solvent was evaporated to dryness and
chromatographed on a silica gel column. Yield: 93% (0.14 g).
15: 1H NMR (CDCl3) δ 7.99 (d, 4.1 Hz, 2 H), 5.54 (m, 4 H),
5.41 (t, 6.7 Hz, 2 H), 5.14 (m, 2 H), 4.71 (d, 6.8 Hz, 2 H), 3.62
(dd, 4.7, 8.9 Hz, 2 H), 2.87 (d, 8.9 Hz, 2 H); 13C NMR (CD2Cl2)
δ 177.3, 116.0, 94.2, 93.1, 91.1, 88.6, 84.4, 58.6, 50.2; IR ν(CO)
2044, 1952, 1872 cm-1, ν(CN) 1574 cm-1. Anal. Calcd for
Ack n ow led gm en t. Y.K.C. acknowledges financial
support from KOSEF (Grant No. 1999-1-122-001-5) and
KOSEF through the Center for Molecular Catalysis at
Seoul National University; S.U.S., K.H.P., and I.G.J .
acknowledge receipt of the Brain Korea 21 fellowship.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
positions, anisotropic thermal parameters, bond lengths and
angles, and hydrogen coordinates for 3-5, 8, 11, 11′, 14, and
16 and IR spectra of 2-5, 8, 11, 11′, and 12-15. This material
is available free of charge via the Internet at http://pubs.ac-
s.org. Structure factor tables are available from the authors.
C
24H16Cr2Fe2N2O12: C, 44.37; H, 1.99; N, 3.45. Found: C,
43.94; H, 2.00; N, 3.20.
Syn th esis of 16. Compound 2 (0.10 g, 0.19 mmol) was
dissolved in 20 mL of diethyl ether. The solution was cooled
OM0205546