Novel diazadienes based on 1,3,4-oxadiazines: Ligands in iron carbonyl complexes and substrates in catalytic [2+2+1] cycloaddition reactions

Article abstract of DOI:10.1016/j.jorganchem.2009.07.024

N,N′-(4-methyl-4H-1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives react with Fe₂(CO)₉ to give dinuclear iron carbonyl complexes. One of the iron atoms is bonded symmetrically to both exocyclic imine nitrogen atoms. The second

Full text of DOI:10.1016/j.jorganchem.2009.07.024

Journal of Organometallic Chemistry 694 (2009) 3800–3805
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Novel diazadienes based on 1,3,4-oxadiazines: Ligands in iron carbonyl
complexes and substrates in catalytic [2+2+1] cycloaddition reactions
Katharina Kaleta a, Jan Fleischhauer b, Helmar Görls a, Rainer Beckert b, Wolfgang Imhof a,
*
a Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University Jena, August-Bebel-Str. 2, D-07743 Jena, Germany
b Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich-Schiller-University Jena, Humboldtstr. 10, D-07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
N,N0-(4-methyl-4H-1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives react with Fe2(CO)9 to give
dinuclear iron carbonyl complexes. One of the iron atoms is bonded symmetrically to both exocyclic
imine nitrogen atoms. The second iron atom shows a side-on coordination towards the C@N bond next
to the oxadiazine oxygen atom. In addition, the iron atoms are connected via a metal metal bond. The
same oxadiazine derivatives produce chiral spiro-lactams in a ruthenium catalyzed formal [2+2+1] cyclo-
addition reaction with carbon monoxide and ethylene.
Article history:
Received 15 May 2009
Received in revised form 6 July 2009
Accepted 10 July 2009
Available online 16 July 2009
Keywords:
Iron
Ó 2009 Elsevier B.V. All rights reserved.
Ruthenium
Carbonyl complexes
Catalysis
Cycloaddition
Lactams
1. Introduction
ities compared to the substrates used in preliminary investigations.
We especially wondered whether the N–N bond present in the
Cycloaddition reactions represent one of the most atom eco-
nomic and straightforward synthetic strategies for the production
of carbocyclic or heterocyclic organic compounds. During the last
decades a number of cycloaddition reactions catalyzed by transi-
tion metals have been reported and the progress of this field of re-
search has been thoroughly reviewed [1]. We have been able to
show that chiral diazadienes from the reaction of enantiomerically
pure S-prolinol with N,N0-bis-aryl-oxalimidoylchlorides may be re-
acted either with Fe2(CO)9 under thermal or with Fe(CO)5 under
photochemical activation to give unsymmetrically coordinated
dinuclear iron carbonyl complexes [2]. In addition, the synthesis
of chiral spiro-lactams in a formal [2+2+1] cycloaddition reaction
from the diazadiene derivatives, carbon monoxide and terminal al-
kenes was achieved regioselectively at the imine function next to
the oxazine oxygen atom [3]. The mechanism of this cycloaddition
reaction as well as an explanation for the observed regioselectivity
was elucidated by means of high-level DFT calculations [4]. In this
manuscript we will introduce highly related N,N0-(4-methyl-4H-
1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives [5] into
similar stoichiometric and catalytic reactions. The aim of the inves-
tigation is to see whether the same reaction principles are realized
for these heterocyclic substrates that show additional functional-
oxadiazine ring might cause side reactions or might even be split
under the reaction conditions.
2. Results and discussion
The ligands used in this investigation are N,N0-(4-methyl-4H-
1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives that in
addition to the exocyclic diimine unit show a heterocyclic back-
bone with other functional groups as the ring oxygen atom, a
C@N double bond and a N–N bond. The ligands 1a–e may be pre-
pared in a three-step synthesis from bis-aryloxalimidoylchlorides
(Scheme 1). The latter are reacted with methylhydrazine to
produce
D
2-1,2-diazetines that in a subsequent reaction step
may be acylated with acylchlorides or anhydrides. The acylated
four-membered heterocyclic compounds in a thermally induced
ring enlargement reaction produce the N,N0-(4-methyl-4H-1,3,4-
oxadiazine-5,6-diylidene)-bis-aniline derivatives [5].
Scheme 2 shows the synthesis of dinuclear iron carbonyl com-
plexes from N,N0-(4-methyl-4H-1,3,4-oxadiazine-5,6-diylidene)-
bis-aniline derivatives with different substituents at C2 of the
oxadiazine ring. The thermally induced reactions in n-heptane
(50 °C) first produced an intermediate of deep bluish green colour
that most probably corresponds to a mononuclear intermediate of
the formula LFe(CO)3 in which one iron atom symmetrically binds
both imine nitrogen atoms [6]. Nevertheless, in no case these inter-
* Corresponding author. Tel.: +49 3641 948 185; fax: +49 3641 948 102.
E-mail address: Wolfgang.Imhof@uni-jena.de (W. Imhof).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.07.024

K. Kaleta et al. / Journal of Organometallic Chemistry 694 (2009) 3800–3805
3801
Scheme 1. Synthesis of N,N0-(4-methyl-4H-1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives [6].
Table 2 it can be seen that the metal metal bond is slightly elon-
gated for an aromatic substituent at C1 (2b) whereas the coordina-
tion of Fe2 to the imine group C3–N4 is slightly shorter for 2b with
respect to the tert. butyl and ethyl derivative 2a and 2c, respec-
tively. In general, bond lengths and angles correspond to expected
values [7].
In analogy to the related proline based diazadiene substrates
oxadiazines 1a–e produce chiral spiro-lactams 3a–e as a result of
a formal [2+2+1] cycloaddition reaction of one of the exocyclic
imine functions with carbon monoxide and ethylene in the pres-
ence of catalytic amounts of Ru3(CO)12 [2]. Yields of 3a–e decrease
in the same order as it has been observed for the formation of the
dinuclear iron carbonyl complexes 2a–e leading to only trace
amounts of 3d and 3e whereas 3a–c could be purified and fully
characterized. In connection with our DFT calculations on the
mechanism of this type of cycloaddition reaction it has been
pointed out that compounds of the general formula LM(CO)3
(M = Fe, Ru) are both the catalytically active species in the cycload-
dition reaction and the intermediates in the synthesis of com-
pounds of type 2 [3]. So obviously the same electronic effects
that lead to a diminished yield in the order 2a–e by hampering
the attack of another Fe(CO)3 moiety from the basis of square-
pyramidal LFe(CO)3 also prevent the approach of ethylene from
the same direction which has been shown to be the rate determin-
ing step of the catalytic cycloaddition [3].
Scheme 2. Synthesis of dinuclear iron carbonyl complexes 2a–e.
mediates could be isolated. During chromatographic workup albeit
performed under inert conditions the colour of the product fraction
turned deep red. After recrystallization of the products from light
petroleum dichloromethane mixtures the molecular structure of
2a–e could unequivocally be confirmed by their spectroscopic
properties as well as by X-ray structure analyses of 2a, 2b and
2c. Isolated yields decrease from 2a–e which most probably is
due to an increase of the acceptor character of the residue R at
the heterocycle therefore reducing the ability of the oxadiazines
to act as ligands.
Interestingly, the NMR spectra of 3a–c show a strong tempera-
ture dependence thus indicating dynamic processes. In Fig. 2 13C
The pattern of IR bands in the region typical for terminal carbon
monoxide ligands is identical to related [Fe2(CO)6(1,4-diazabutadi-
ene)] complexes [2]. All mass spectra show peaks corresponding to
the molar masses of the complete molecules and fragmentations
corresponding to the loss of CO ligands, the iron atoms and subse-
quent degradation of the ligands. The most significant changes in
the NMR spectra of 2a–e compared to the starting compounds
1a–e are the 13C resonances of the imine carbon atom in 6-position
of the heterocycle. These signals are shifted to higher field upon
coordination of both iron tricarbonyl groups to approx. 90 ppm
whereas the signals of carbon atoms C5 and C2 of the heterocycle
are observed at approx. 156 and 150 ppm, respectively. For all
complexes 2a–e four or three (2b) resonances for terminal CO li-
gands are observed meaning that one of the Fe(CO)3 moieties ro-
tates freely whereas the second Fe(CO)3 unit is fixed. In addition,
CO ligands at both iron centres do not show any interconversion
on the NMR time scale.
The complexes 2a, 2b and 2c could be characterized by means
of X-ray diffraction (Table 1). Fig. 1 shows the molecular structure
of 2a giving the atom labelling scheme for 2a–c, Table 2 summa-
rizes the most important bond lengths and angles of all structurally
characterized compounds.
Since 2a–c only differ concerning the organic substituent at C1
their molecular structure is almost identical. One of the iron atoms
(Fe1) symmetrically binds to both imine nitrogen atoms (N3, N4)
and is situated in a co-planar fashion with respect to the diimine
moiety N3–C2–C3–N4. The second iron tricarbonyl group is at-
tached to the aforementioned plane from below displaying a metal
metal bond and an additional side-on coordination towards the
imine group next to the oxadiazine oxygen atom (C3–N4). From
Table 1
Crystal data and refinement details for the X-ray structure determinations of 2a, 2b
and 2c.
2a
2b
2c
Formula
C28H26Fe2N4O7
642.24
183(2)
monoclinic
P21/n
11.2473(4)
17.6247(4)
16.0443(7)
90
109.574(2)
90
2996.7(2)
4
1.424
10.18
20 969
6827
0.0688
4495
376
0.1045
0.0423
0.956
0.377/ꢀ0.482
C31H24Fe2N4O7
676.13
183(2)
C26H22Fe2N4O7
614.17
183(2)
Formula weight (g molꢀ1
)
T (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
triclinic
ꢀ
ꢀ
P1
P1
9.6469(9)
11.9331(9)
14.682(1)
77.431(4)
72.101(5)
72.540(5)
1519.6(2)
2
1.478
10.08
8845
6240
0.0288
4919
401
0.1475
0.0516
1.019
0.524/ꢀ0.797
8.6009(2)
10.8307(3)
15.6246(5)
106.265(2)
96.666(2)
95.382(2)
1375.56(7)
2
1.483
11.05
9875
6238
0.0235
5001
356
0.0956
0.0367
1.002
0.842/ꢀ0.409
a
(°)
b (°)
(°)
c
Volume (Å3)
Z
qcalc [g cmꢀ3
]
l
(cmꢀ1
)
Measured data
Unique data
Rint
Data with I > 2
r
(I)
Number of parameters
wR2 (all data, on F2)a
R1(I > 2
r
(I))a
Goodness-of-fitb
Res. dens. (e Åꢀ3
)
P
P
P
2
a
Definition of the R indices: R1 ¼ ð kFoj ꢀ jFckÞ= jFoj; wR2
¼
½wðF2o ꢀ F2c Þ ꢁ=
P
2
1=2
2
½wðF2oÞ ꢁ
with wꢀ1
¼
r2ðF2oÞ þ ðaPÞ .
P
2
1=2
GOF ¼ ½wðF2o ꢀ Fc2Þ ꢁ=ðNo ꢀ NpÞ
.
b

3802
K. Kaleta et al. / Journal of Organometallic Chemistry 694 (2009) 3800–3805
Fig. 1. Molecular structure of 2a.
Table 2
Selected bond lengths (pm) and angles (°)..
2a
2b
2c
2a
2b
2c
Fe1–N4
Fe1–N3
Fe1–Fe2
Fe2–N4
Fe2–C3
O1–C1
O1–C3
N1–C1
195.1(2)
202.1(2)
256.79(6)
192.4(2)
201.1(3)
135.7(3)
140.4(3)
126.7(3)
196.7(2)
202.6(2)
258.92(6)
191.4(2)
199.4(3)
136.6(3)
142.7(4)
128.3(4)
196.1(2)
202.7(2)
256.43(4)
193.5(2)
201.0(2)
135.9(3)
140.8(3)
126.8(3)
N1–N2
N2–C2
N2–C4
N3–C2
N4–C3
C1–C5
C2–C3
141.1(3)
134.2(3)
146.3(3)
130.7(3)
139.3(3)
150.5(4)
147.7(4)
140.8(3)
134.9(4)
146.2(4)
130.5(4)
139.5(4)
147.1(4)
147.7(4)
140.7(3)
134.6(3)
146.1(3)
130.4(3)
139.0(3)
149.6(3)
147.0(3)
N4–Fe1–N3
N4–Fe1–Fe2
N3–Fe1–Fe2
N4–Fe2–C3
N4–Fe2–Fe1
C3–Fe2–Fe1
C1–O1–C3
C1–N1–N2
C2–N2–N1
C2–N2–C4
N1–N2–C4
C2–N3–Fe1
C3–N4–Fe2
C3–N4–Fe1
84.11(9)
48.04(7)
86.08(6)
41.4(1)
48.96(6)
71.21(8)
117.9(2)
118.2(2)
121.5(2)
126.5(2)
111.7(2)
112.5(2)
72.7(2)
83.9(1)
83.60(7)
48.40(5)
86.53(5)
41.22(8)
49.29(5)
71.35(6)
115.9(2)
118.8(2)
121.3(2)
127.1(2)
111.5(2)
112.2(1)
72.3(1)
Fe2–N4–Fe1
N1–C1–O1
N1–C1–C5
O1–C1–C5
N3–C2–N2
N3–C2–C3
N2–C2–C3
N4–C3–O1
N4–C3–C2
O1–C3–C2
N4–C3–Fe2
O1–C3–Fe2
C2–C3–Fe2
83.00(8)
126.0(2)
122.5(3)
111.5(2)
130.6(2)
113.0(2)
116.2(2)
114.4(2)
117.3(2)
115.9(2)
66.0(1)
83.7(1)
82.31(7)
125.7(2)
122.4(2)
111.9(2)
129.9(2)
113.4(2)
116.5(2)
114.2(2)
117.2(2)
116.2(2)
66.5(1)
47.27(7)
88.24(7)
41.8(1)
123.9(3)
120.4(3)
115.6(2)
130.1(2)
113.9(2)
116.0(2)
115.0(2)
116.4(2)
113.9(2)
66.0(2)
49.04(7)
70.86(8)
113.4(2)
117.0(2)
121.1(2)
127.0(3)
111.7(2)
111.6(2)
72.2(2)
115.9(2)
113.3(2)
120.0(2)
117.2(2)
120.0(2)
113.6(2)
106.7(2)
105.7(2)
106.4(1)
NMR spectra of 3a at 223, 300 and 323 K are depicted together
with the assignment of resonances to respective carbon atoms (de-
rived from HMBC/HQMC experiments). It clearly demonstrates
that at lower temperature two sets of signals are observed whereas
at 323 K only one set of signals representing the averaged structure
is visible. At 300 K a broadening of signals appears indicating that
coalescence occurs near room temperature. The carbon atoms that
are highly affected by this dynamic process are the nitrogen bound
methyl group (4), the quarternary carbon atom of the unreacted
imine function (5) and one of the CH functions of one of the tolyl
substituents (16). We therefore interpret these observations as a
E-/Z-interconversion of the unreacted imine moiety due to rela-
tively strong interactions between the methyl group and the tolyl
imine substructure (Scheme 3). In the Z-isomer the tolyl substitu-
ent of the imine group interfers with the NMe function whereas
there should be no interaction in the E-isomer. The free activation
enthalpy of this equilibrium of 3a may be calculated from the res-
onances of carbon atoms 4, 5 and 16 (Fig. 2) and shows a value of
58.7(3) kJ molꢀ1 [8].
The 13C NMR spectra at different temperatures therefore also
clarify the regioselectivity of the catalytic reaction itself. Since
there is only one resonance for the spiro carbon atom at
94.16 ppm (Fig. 2, 323 K) the reaction proceeds regioselectively
at the imine function next to the oxadiazine oxygen atom. The
imine group at the 5-position of the oxadiazine core remains unre-
acted during the catalytic cycle.
3. Experimental
All procedures were carried out under an argon atmosphere in
anhydrous, freshly distilled solvents. The syntheses of the oxadi-
azine derivatives 1a–e were performed following a literature

K. Kaleta et al. / Journal of Organometallic Chemistry 694 (2009) 3800–3805
3803
Fig. 2. 13C NMR spectra of 3a at different temperatures.
Scheme 3. Formation of chiral spiro-lactams 3a–e.
method [5]. Infrared spectra were recorded on a Perkin Elmer FT-IR
3.2. Synthesis of 2a–e
System 2000 using 0.2 mm KBr cuvettes. NMR spectra were re-
corded on a Bruker DRX 400 spectrometer (1H: 400.13 MHz, 13C:
100.62 MHz, solvent as internal standard). Mass spectra were re-
corded on a Finnigan MAT SSQ 710 instrument. Elemental analyses
were carried out at the laboratory of the Institute of Organic Chem-
istry and Macromolecular Chemistry of the Friedrich–Schiller-Uni-
versity Jena.
A 0.685 mmol (0.25 g) sample of Fe2(CO)9 was stirred together
with 0.825 mmol of the corresponding ligand (1a: 0.299 g, 1b:
0.327 g, 1c: 0.276 g, 1d: 0.264 g, 1e: 0.309 g) in 20 ml of n-heptane
at 50 °C for 2 h. The yellow suspension turned blueish-green. The
solvent was evaporated in vacuo and the solid residue was dis-
solved in 2 ml of CH2Cl2. 200 mg of silanized silica gel was added
and the solvent was again evaporated. Chromatography using a
mixture of light petroleum (b.p. 40–60 °C) and CH2Cl2 as the eluent
with increasing polarity yielded 2a–e as deep red solutions. After
the solvents were evaporated the crude products were recrystal-
lized from a mixture of light petroleum (b.p. 40–60 °C) and CH2Cl2
at ꢀ20 °C. Yields: 1a: 222 mg (50.5%), 1b: 191 mg (41.2%), 1c:
141 mg (33.5%), 1d: 126 mg (30.7%), 1e: 132 mg (29.5%).
3.1. X-ray structure determinations
Intensity data were collected on a Nonius Kappa CCD diffrac-
tometer using graphite-monochromated Mo Ka radiation. Data
were corrected for Lorentz polarization but not for absorption ef-
fects [9,10]. Crystallographic data as well as structure solution
and refinement details are summarized in Table 1. The structures
were solved by direct methods (SHELXS) and refined by full-matrix
least squares techniques against Fo2 (SHELXL-97) [11,12]. The hydro-
gen atoms were included at calculated positions with fixed thermal
parameters. All non-hydrogen atoms were refined anisotropically.
XP (SIEMENS Analytical X-ray Instruments, Inc.) was used for
structure representations.
3.2.1. MS and spectroscopic data for 2a
MS (FAB) [m/z (%)]: 643 (1) [MH+], 627 (2) [M+ꢀMe], 614 (2)
[M+ꢀCO], 586 (10) [M+ꢀ2CO], 571 (2) [M+ꢀMeꢀ2CO], 558 (6)
[M+ꢀ3CO], 530 (12) [M+ꢀ4CO], 507 (8) [M+ꢀ5CO], 474 (5)
[M+ꢀ6CO], 446 (8) [M+ꢀ5COꢀFe], 418 (20) [M+ꢀ6COꢀFe], 363
(100) [MH+ꢀ6COꢀ2Fe], 258 (20) [LH+ꢀC7H7N], 230 (22)

3804
K. Kaleta et al. / Journal of Organometallic Chemistry 694 (2009) 3800–3805
[LH+ꢀC8H7NO]; IR (Nujol, 298 K) [cmꢀ1]: 2059, 2008, 1975, 1943,
146.9 (qCPh), 149.1 (qCPh), 150.5 (N@C–Me), 156.8 (C@N), 203.1
(CO), 210.6 (CO), 214.6 (CO), 217.9 (CO); Anal. Calc. for
C25H20N4O7Fe2: C, 50.00; H, 3.33; N, 9.33. Found: C, 49.39; H,
3.59; N, 8.92%.
1921 (vs, m(CO)); 1655 (w, m(C@N)); 1595 (s, m(C@C)); 1508 (w,
m
(C@C)); 1H NMR (400 MHz, THF-d8, 298 K) [ppm]: 0.94 (s, 9H,
CH3 (tBu)), 2.30 (s, 3H, Ph–CH3), 2.37 (s, 3H, Ph–CH3), 2.58 (s, 3H,
N–CH3), 6.96 (m, 2H, CHPh), 7.18 (m, 4H, CHPh), 7.45 (m, 2H, CHPh);
13C NMR (400 MHz, THF-d8, 298 K) [ppm]: 20.9 (Ph-CH3), 27.3
(CH3(tBu)), 36.2 (qC(tBu)), 42.8 (N-CH3), 90.5 (C@N), 124.7 (CHPh),
125.2 (CHPh), 126.8 (CHPh), 130.1 (CHPh), 130.4 (CHPh), 136.7 (qCPh),
137.0 (qCPh), 147.1 (qCPh), 150.5 (qCPh), 155.7 (N@C–tBu), 155.9
(C@N), 202.8 (CO), 210.5 (CO), 214.5 (CO), 217.7 (CO); Anal. Calc.
for C28H26N4O7Fe2: C, 52.34; H, 4.05; N, 8.72. Found: C, 51.27; H,
4.50; N, 8.52%.
3.2.5. MS and spectroscopic data for 2e
MS (DEI) [m/z (%)]: 654 (1) [M+], 626 (2) [M+ꢀCO], 598 (3)
[M+ꢀ2CO], 570 (1) [M+ꢀ3CO], 542 (7) [M+ꢀ4CO], 514 (6)
[M+ꢀ5CO], 486 (3) [M+ꢀ6CO], 458 (2) [M+ꢀ5COꢀFe], 430 (7)
[M+ꢀ6COꢀFe], 374 (7) [M+ꢀ6COꢀ2Fe], 355 (23) [L+-F], 341 (14)
[LH+–FꢀCH3], 281 (73) [C11H7F3FeNO+], 221 (96) [C11H9F2N3+],
207 (100) [C10H7F2N3+], 173 (44) [C10H10N3+]; IR (Nujol, 298 K)
[cmꢀ1]: 2059, 2020, 1992, 1969, 1939 (vs,
(C@N)); 1589 (m, (C@C)); 1502 (m,
m
(CO)); 1684 (w,
3.2.2. MS and spectroscopic data for 2b
m
m
m
(C@C)); 1156 (m, (C–F));
m
MS (DEI) [m/z (%)]: 648 (1) [M+ꢀCO], 620 (3) [M+ꢀ2CO], 592 (2)
[M+ꢀ3CO], 564 (13) [M+ꢀ4CO], 536 (15) [M+ꢀ5CO], 508 (11)
[M+ꢀ6CO], 480 (9) [M+ꢀ5COꢀFe], 452 (25) [M+ꢀ6COꢀFe], 396
(56) [M+ꢀ6COꢀ2Fe], 279 (39) [L+ꢀC8H7N], 146 (37) [C9H10N2+],
119 (100) [C8H7O], 91 (65) [C7H7+]; IR (Nujol, 298 K) [cmꢀ1]:
1H NMR (400 MHz, THF-d8, 298 K) [ppm]: 2.32 (s, 3H, Ph–CH3),
2.38 (s, 3H, Ph-CH3), 2.69 (s, 3H, N–CH3), 6.99 (m, 2H, CHPh), 7.21
(m, 4H, CHPh), 7.47 (m, 2H, CHPh); 13C NMR (400 MHz, THF-d8,
298 K) [ppm]: 20.8 (Ph-CH3), 20.9 (Ph-CH3), 43.7 (N-CH3), 91.2
1
(C@N), 117.4 (q, CF3, JCF = 274 Hz), 124.2 (CHPh), 124.5 (CHPh),
126.3 (CHPh), 130.3 (CHPh), 130.7 (CHPh), 137.2 (qCPh), 137.5 (q,
2063, 2007, 1994, 1981, 1933 (vs,
m
(CO)); 1628 (w,
m(C@N));
(C@C)); 1H NMR
2
N@C–CF3, JCF = 41 Hz), 137.9 (qCPh), 146.0 (qCPh), 149.7 (qCPh),
1594 (m, (C@C)); 1505 (w, (C@C)); 1401(w, m
m
m
(400 MHz, THF-d8, 298 K) [ppm]: 2.28 (s, 3H, Ph–CH3), 2.33 (s,
3H, Ph–CH3), 2.39 (s, 3H, Ph–CH3), 2.75 (s, 3H, N–CH3), 6.98 (m,
2H, CHPh), 7.07 (m, 2H, CHPh), 7.19 (m, 2H, CHPh), 7.24 (m, 2H,
CHPh), 7.42 (m, 2H, CHPh), 7.54 (m, 2H, CHPh); 13C NMR
(200 MHz, THF-d8, 298 K) [ppm]: 20.9 (Ph-CH3), 20.9 (Ph-CH3),
21.3 (Ph-CH3), 43.2 (N-CH3), 91.0 (C@N), 124.8 (CHPh), 125.0
(CHPh), 126,4 (qCPh), 126.7 (CHPh), 126.8 (CHPh), 129.6 (CHPh),
130.1 (CHPh), 130.4 (CHPh), 130.5 (CHPh), 136.8 (qCPh), 137.1 (qCPh),
142.2 (qCPh), 146.9 (qCPh), 147.1 (qCPh), 150.5 (N@C–Ph), 156.8
(C@N), 210.6 (CO), 214.4 (CO), 217.6 (CO); Anal. Calc. for
C31H24N4O7Fe2: C, 55.03; H, 3.55; N, 8.28. Found: C, 54.87; H,
3.62; N, 7.93%.
156.5 (C@N), 202.4 (CO), 210.0 (CO), 213.6 (CO), 217.2 (CO); Anal.
Calc. for C25H17N4O7Fe2: C, 45.87; H, 2.60; N, 8.56. Found: C, 46.39;
H, 2.89; N, 8.08%.
3.3. Synthesis of 3a–e
About 0.25 mmol of the corresponding N,N0-(4-methyl-4H-
1,3,4-oxadiazine-5,6-diylidene)bis(4-methylaniline) (for 3a: 91 mg,
3b: 99 mg, 3c: 84 mg, 3d: 80 mg, 3e: 94 mg) were transferred
together with 0.01 mmol (26 mg) Ru3(CO)12 into a 75 ml stainless
steel autoclave. After evaporation of the autoclave, 3 ml of toluene
were added under an argon atmosphere. Afterwards the autoclave
was pressurized with 12 atm CO and 8 atm ethylene and the
reaction mixture was heated to 140 °C for 16 h or 3d, respectively.
After the autoclave was cooled down to room temperature the
pressure was released and the solution transferred into a Schlenk
tube. After evaporation of toluene a brown oily residue was
obtained. This residue was used to determine the conversion of
the educt by NMR spectroscopy. In the case of 3a–d products were
purified by HPLC using pentane/methanol (3a, 3b) or pentane/
THF mixtures (3c, 3d) as eluent. Yields: 3a: 61 mg (58%), 3b:
70 mg (62%), 3c: 51 mg (52%), 3d: 13 mg (14%). In case of 3e con-
version rates were too low to allow purification by HPLC methods
(see Table 3).
3.2.3. MS and spectroscopic data for 2c
MS (DEI) [m/z (%)]: 586 (1) [M+ꢀCO], 558 (1) [M+ꢀ2CO], 530 (1)
[M+ꢀ3CO], 502 (1) [M+ꢀ4CO], 474 (1) [M+ꢀ5CO], 446 (1)
[M+ꢀ6CO], 418 (1) [M+ꢀ5COꢀFe], 390 (1) [M+ꢀ6COꢀFe], 334 (4)
[M+ꢀ6COꢀ2Fe], 319 (3) [L+ꢀCH3], 243 (11) [L+ꢀC7H7], 217 (100)
[L+-C8H7N]; IR (Nujol, 298 K) [cmꢀ1]: 2058, 2007, 1976, 1935 (s,
m(CO)); 1682 (w, m(C@N)); 1584 (m, m(C@C)), 1504 (m, m(C@C)).
1H NMR (400 MHz, THF-d8, 298 K) [ppm]: 1.29 (br, 3H, CH3), 2.06
(br, 2H, CH2), 2.30 (s, 3H, Ph-CH3), 2.37 (s, 3H, Ph-CH3), 2.59 (s,
3H, N-CH3), 6.96 (m, 2H, CHPh), 7.18 (m, 4H, CHPh), 7.43 (m, 2H,
CHPh); 13C NMR (400 MHz, THF-d8, 298 K) [ppm]: 9.8 (CH3), 20.8
(Ph-CH3), 20.9 (Ph-CH3), 30.5 (CH2), 42.7 (N-CH3), 90.5 (C@N),
124.8 (CHPh), 125.1 (CHPh), 126.5 (CHPh), 130.1 (CHPh), 130.4
(CHPh), 136.6 (qCPh), 137.0 (qCPh), 147.0 (qCPh), 150.5 (qCPh), 152.1
(N@C–Et), 156.7 (C@N), 202.8 (CO), 210.4 (CO), 214.4 (CO), 217.5
(CO); Anal. Calc. for C26H22N4O7Fe2: C, 50.81; H, 3.58; N, 9.12.
Found: C, 50.32; H, 4.01; N, 8.65%.
3.3.1. MS and spectroscopic data for 3a
MS (DEI): m/z (%) = 418 (100) [M+], 361 (13) [M+ꢀC(CH3)3], 312
(24) [M+ꢀC7H7NH], 290 (48) [C19H18N2O+], 262 (40) [C18H18N2+],
247 (12) [C17H15N2+], 233 (2) [C16H13N2+], 144 (26) [C10H10N+],
117 (11) [C8H7N+], 91 (16) [C7H7+]; IR (Nujol, 298 K) [cmꢀ1]:
3021 (w,
m
(CHAr)), 2969 (w,
m
as(CH3)), 2918 (w,
mas(CH2)), 2874
3.2.4. MS and spectroscopic data for 2d
(w, s(CH2)), 1722 (s,
m
m(C@O)), 1632 (s, m
(C@N)), 1513 (m,
MS (DEI) [m/z (%)]: 600 (1) [M+], 572 (13) [M+ꢀCO], 544 (20)
[M+ꢀ2CO], 516 (14) [M+ꢀ3CO], 488 (50) [M+ꢀ4CO], 460 (100)
[M+ꢀ5CO], 432 (50) [M+ꢀ6CO], 404 (25) [M+ꢀ5COꢀFe], 376 (92)
[M+ꢀ6COꢀFe], 320 (28) [M+ꢀ6COꢀ2Fe], 216 (30) [LH+ꢀC7H7N],
203 (21) [L+ꢀC7H7NC], 146 (13) [C9H10N2+], 91 (13) [C7H7+]; IR (Nu-
jol, 298 K) [cmꢀ1]: 2055, 2011, 1990, 1982, 1962, 1939, 1926 (vs,
m
(C@C)), 1458 (w, d(CH2)), 1164, 1142 (s, m
as(C–O–C)); 1H NMR
(200 MHz, THF-d8, 323 K) [ppm]: 1.15 (s, 9H, CH3 (tBu)), 2.23 (s,
Table 3
Conversion of 1a–e and isolated yields of 3a–e after HPLC.
m
(CO)); 1670 (w, m(C@N)); 1589 (m, m(C@C)); 1504 (m, m(C@C));
Compound
Conversion after 16 h
(%)
Conversion after 3 day
(%)
Isolated yields
(%)
1H NMR (400 MHz, THF-d8, 298 K) [ppm]: 1.30 (s, 3H, N@–CH3),
2.30 (s, 3H, Ph–CH3), 2.38 (s, 3H, Ph–CH3), 2.59 (s, 3H, N–CH3),
6.94 (m, 2H, CHPh), 7.19 (m, 4H, CHPh), 7.43 (m, 2H, CHPh); 13C
NMR (400 MHz, THF-d8, 298 K) [ppm]: 17.1 (CH3), 20.8 (Ph-CH3),
42.6 (N-CH3), 90.7 (C@N), 124.8 (CHPh), 125.1 (CHPh), 126.5 (CHPh),
130.2 (CHPh), 130.4 (CHPh), 130.5 (CHPh), 136.6 (qCPh), 137.0 (qCPh),
3a
3b
3c
3d
3e
ꢂ100
45
n.d.
45
58
62
52
14
>95
>95
20
6
7

K. Kaleta et al. / Journal of Organometallic Chemistry 694 (2009) 3800–3805
3805
3H, Ph-CH3), 2.31 (s, 3H, Ph–CH3), 2.09–2.39 (m, 1H, CH2), 2.49–
2.67 (m, 2H, CH2), 2.79 (s, 3H, N–CH3), 2.86–2.97 (m, 1H, CH2),
6.47 (m, 2H, CHPh), 6.95 (m, 2H, CHPh), 7.14 (m, 4H, CHPh); 13C
NMR (50 MHz, THF-d8, 323 K) [ppm]: 20.6 (Ph–CH3), 20.9 (Ph-
CH3), 27.7 (CH3 (tBu)), 29.1 (CH2), 33.2 (CH2), 36.1 (qC (tBu)), 42.2
(N-CH3), 94.1 (spC), 121.0 (CHPh), 128.4 (CHPh), 129.3 (CHPh),
129.5 (CHPh), 131.4 (qCPh), 134.6 (qCPh), 137.5 (qCPh), 143.0 (C@N),
147.3 (qCPh), 153.9 (N@C–tBu), 173.5 (C@O); Anal. Calc. for
C25H30N4O2: C, 71.77; H, 7.18; N, 13.40. Found: C, 70.68; H, 7.22;
N, 13.16%.
m
s(CH2)), 1716 (s,
m
(C@O)), 1624 (s,
m
(C@N)), 1606 (s,
m
(C@C)),
1445 (m, d(CH2)), 1212 (s,
m
as(C–O–C)); 1H NMR (400 MHz, THF-
d8, 323 K) [ppm]: 1.82 (s, 3H, CH3), 2.23 (s, 3H, Ph–CH3), 2.31 (s,
3H, Ph-CH3), 2.14–2.38 (m, 2H, CH2), 2.46–2.52 (m, 1H, CH2),
2.68 (s, 3H, N–CH3), 3.13–3.16 (m, 1H, CH2), 6.57 (m, 2H, CHPh),
6.97 (m, 2H, CHPh), 7.12 (m, 4H, CHPh); 13C NMR (100 MHz, THF-
d8, 323 K) [ppm]: 18.0 (CH3), 20.6 (Ph-CH3), 21.0 (Ph–CH3), 29.1
(CH2), 32.7 (CH2), 41.9 (N–CH3), 94.0 (spC), 119.2 (qCPh), 121.1
(CHPh), 129.0 (CHPh), 129.6 (CHPh), 129.7 (CHPh), 131.5 (qCPh),
134.4 (qCPh), 138.4 (qCPh), 145.9 (C@N), 147.4 (C@N), 173.5
(C@O); Anal. Calc. for C22H24N4O2: C, 70.21; H, 6.38; N, 14.89.
Found: C, 69.84; H, 6.86; N, 14.27%.
3.3.2. MS and spectroscopic data for 3b
MS (DEI): m/z (%) = 452 (84) [M+], 346 (23) [M+-C7H7NH], 320
(16) [C20H22N3O+], 290 (76) [C19H18N2O+], 275 (38) [C18H15N2O+],
262 (50) [C18H18N2+], 247 (18) [C17H15N2+], 163 (14) [C9H11N2O+],
146 (69) [C9H10N2+], 119 (95) [C8H7O+], 107 (70) [C7H7O+], 91
3.3.5. MS and spectroscopic data for 3e
MS (DEI): m/z (%) = 430 (1) [M+], 402 (1) [M+ꢀCO], 335 (2)
[C20H21N3O2+].
(100) [C7H7+]; IR (Nujol, 298 K) [cmꢀ1]: 3035 (w,
(w, as(CH2)), 2856 (w, s(CH2)), 1719 (s,
(C@N)), 1606 (s, (C@C)), 1449 (m, d(CH2)), 1211 (s, m
m
(CHAr)), 2922
(C@O)), 1625 (s,
as(C–O–
m
m
m
Appendix A. Supplementary material
m
m
C)); 1H NMR (400 MHz, THF-d8, 323 K) [ppm]: 2.25, 2.26 (2s, 6H,
Ph-CH3), 2.35 (s, 3H, Ph–CH3), 2.22–3.33 (m, 1H, CH2), 2.64–2.75
(m, 2H, CH2), 2.81 (s, 3H, N-CH3), 3.16–3.25 (m, 1H, CH2), 6.61
(m, 2H, CHPh), 7.03 (m, 6H, CHPh), 7.18 (m, 2H, CHPh), 7.65 (m,
2H, CHPh); 13C NMR (100 MHz, THF-d8, 323 K) [ppm]: 20.6 (Ph-
CH3), 20.9 (Ph-CH3), 21.2 (Ph-CH3), 29.1 (CH2), 32.5 (CH2), 42.5
(N–CH3), 94.2 (spC), 121.1 (CHPh), 126.4 (CHPh), 128.8 (CHPh),
129.0 (qCPh), 129.2 (qCPh), 129.5 (CHPh), 129.6 (CHPh), 129.7 (CHPh),
131.8 (qCPh), 134.3 (qCPh), 138.2 (qCPh), 140.9 (qCPh), 145.1 (C@N–
Ar), 147.2 (C@N–Ar), 173.7 (C@O); Anal. Calc. for C28H29N4O2: C,
74.17; H, 6.40; N, 12.36. Found: C, 73.52; H, 6.54; N, 11.90%.
CCDC 725446, 725447 and 725448 contain the supplementary
crystallographic data for 2a, 2b and 2c in this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.07.024.
References
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3.3.3. MS and spectroscopic data for 3c
MS (DEI): m/z (%) = 390 (100) [M+], 320 (10) [C20H21N3OH+], 290
(23) [C19H18N2O+], 275 (14) [C18H15N2O+], 262 (15) [C18H18N2+],
247 (6) [C17H15N2+], 217 (31) [C12H15N3O+], 146 (15) [C9H8NO+],
107 (20) [C5H3N2O+], 91 (12) [C7H7+]; IR (Nujol, 298 K) [cmꢀ1]:
3030 (w,
(w, s(CH3)), 1720 (m,
(C@C)), 1450 (m, d(CH2)), 1201 (s,
m
(CHAr)), 2940 (w,
(C@O)), 1633 (s,
as(C–O–C)); 1H NMR
m
as(CH3)), 2925 (w,
mas(CH2)), 2872
m
m
m(C@N)), 1606 (s,
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(400 MHz, THF-d8, 323 K) [ppm]: 1.00 (t, 3H, CH3), 1.13 (t, 3H,
CH3), 2.24 (s, 3H, Ph-CH3), 2.31 (s, 3H, Ph-CH3), 2.14–2.37 (m, 4H,
CH2), 2.46–2.55 (m, 1H, CH2), 2.72 (s, 3H, N–CH3), 3.09 (m, 1H,
CH2), 6.56 (m, 2H, CHPh), 7.00 (m, 4H, CHPh), 7.45 (m, 2H, CHPh);
13C NMR (100 MHz, THF-d8, 323 K) [ppm]: 9.7 (CH3), 10.0 (CH3),
20.6 (Ph-CH3), 21.0 (Ph-CH3), 25.7 (N@C–CH2), 26.0 (N@C–CH2),
29.1 (CH2), 30.5 (CH2), 32.8 (CH2), 42.0 (N–CH3), 94.0 (spC), 119.8
(qCPh), 121.1 (CHPh), 128.9 (CHPh), 129.5 (CHPh), 129.6 (CHPh),
131.5 (qCPh), 134.4 (qCPh), 138.2 (C@N), 138.3 (C@N), 147.4 (qCPh),
149.4 (C@N), 173.5 (C@O); Anal. Calc. for C23H26N4O2: C, 70.77;
H, 6.67; N, 14.36. Found: C, 70.08; H, 6.56; N, 14.06%.
(b) A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, R. Taylor, J.
Chem. Soc., Dalton Trans. (1989) S1.
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3.3.4. MS and spectroscopic data for 3d
MS (DEI): m/z (%) = 376 (17) [M+], 335 (3) [MH+–CO–CH2], 290
(5) [C19H18N2O+], 262 (5) [C18H18N2+], 246 (49) [C13H16N3O2+],
232 (13) [C13H17N3OH+], 203 (19) [C11H13N3O+], 149 (63)
[C9H10NOH+], 133 (32) [C7H7NCO+], 117 (26) [C7H7NC+], 107
(100) [C5H3N2O+], 91 (35) [C7H7+]; IR (Nujol, 298 K) [cmꢀ1]: 3028
(w,
m(CHAr)), 2975 (w, mas(CH3)), 2922 (w, mas(CH2)), 2858 (w,