Photochemical reactions of group 6 metal carbonyls with N-salicylidene-2-hydroxyaniline and bis-(salicylaldehyde)phenylenediimine

Article abstract of DOI:10.1016/j.molstruc.2004.12.002

Sunlight irradiation of the reactions of [M(CO)₆], M=Cr, Mo and W with either N-salicylidene-2-hydroxyaniline (shaH₂) or bis-(salicylaldehyde) phenylenediimine (salphenH₂) in THF were investigated. Three complexes with mol

Full text of DOI:10.1016/j.molstruc.2004.12.002

Journal of Molecular Structure 738 (2005) 171–177
www.elsevier.com/locate/molstruc
Photochemical reactions of group 6 metal carbonyls
with N-salicylidene-2-hydroxyaniline and
bis-(salicylaldehyde)phenylenediimine
a,
Samir M. El-Medani , Omyma A.M. Ali , Ramadan M. Ramadan
b
c
*
aChemistry Department, Faculty of Science, Cairo University, El-Faiyum Branch, El-Faiyum, Egypt
bChemistry Department, University College for Girls, Ain Shams University, Cairo, Egypt
cChemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
Received 1 August 2004; revised 1 December 2004; accepted 2 December 2004
Available online 18 January 2005
Abstract
Sunlight irradiation of the reactions of [M(CO)6], MZCr, Mo and W with either N-salicylidene-2-hydroxyaniline (shaH2) or bis-
(salicylaldehyde) phenylenediimine (salphenH2) in THF were investigated. Three complexes with molecular formulas [Cr(shaH2)3], 1,
[MoO2(shaH2)2], 2, and [W2O5(shaH)2], 3 were isolated from the reactions with shaH2. The corresponding reactions with salphenH2
produced the oxo complexes [CrO(salphenH2)], 4, [Mo2O6(salphenH2)2], 5, and [W2O6(salphenH2)], 6. All complexes were characterised by
1
elemental analysis, infrared, mass and H NMR spectroscopy. The UV–vis spectra of the complexes in different solvents showed visible
bands due to either ligand-to-metal or metal-to-ligand charge transfer. Thermal properties of the complexes were investigated by TG
thermogravimetry technique.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Chromium; Molybdenum; Tungsten; Metal carbonyl; Schiff base; Photochemistry; Thermal analysis
1. Introduction
also found to provide catalytic characteristics especially for
epoxidation reactions [12–17].
Reactions of group 6 and 8 metal carbonyls with some
selected Schiff bases having oxygen and nitrogen donors were
investigated [18–20]. Reactions of the two Schiff bases, shaH2
and salphenH2, with [M(CO)6], MZCr, Mo and W gave
complexes with different structural features; [CrO2(CO)2
(shaH2)], [W(CO)2(shaH)2], [Cr(CO)2(salphen)], [MoO
(CO)(salphen)], [MoO(sha)], [Mo2O4(sha)2], [MoO2
(salphenH)2] and [W2O6(salphenH2)] [21,22]. The versitile
chemistry of these reactions has prompted us to investigate the
reactions of Group 6 metal carbonyls with shaH2 and
salphenH2, Scheme 1, under sunlight photolysis.
A large number of Schiff base compounds are often used
as ligands in coordination chemistry for their metal binding
ability. Schiff base-metal complexes are characterised by
interesting and important properties, such as their ability to
reversibly binding oxygen in epoxidation reactions [1],
biological activity [2–5], complexing ability towards some
toxic metals [6], catalytic activity in hydrogenation of
olefines [7] and photochromic properties [8,9]. Polydentate
Schiff bases containing nitrogen and oxygen donor atoms
such as bis-(salicylaldehyde)ethylenediimine (salenH2),
bis-(salicylaldehyde)phenylenediimine (salphenH2), salicy-
lideneimine-2-anisole (salanH), and N-salicylidene-2-
hydroxyaniline (shaH2) are useful for the synthesis of
transition metal complexes which play important role in
biological systems [10,11]. Such classes of ligands were
2. Experimental
2.1. Reagents
[M(CO)6], MZCr, Mo and W were supplied by Aldrich.
The shaH2 and salphenH2 ligands were prepared
* Corresponding author. Tel.: C20 22707860; fax: C20 234567887.
E-mail address: samirmedani@yahoo.com (S.M. El-Medani).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.12.002

172
S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
vacuo for several hours. Table 1 gives the reaction period,
color of complex and % yield.
3. Results and discussion
3.1. Infrared and NMR studies
Scheme 1.
3.1.1. The shaH2 complexes
Interaction of [M(CO)6], MZCr, Mo and W, with N-
salicylidene-2-hydroxyaniline (shaH2) under sunlight
irradiation resulted in the formation of different complexes
depending on the metal type. While the reaction with
[Cr(CO)6] gave the tris derivative [Cr(shaH2)3], 1, with the
chromium atom in the zero formal oxidation state, the
molybdenum and tungsten hexacarbonyls gave the oxo
derivatives [MoO2(shaH2)2], 2, and [W2O5(shaH)2], 3, with
C4 and C6 formal oxidation states, respectively. It is
expected that the formation of complexes were proceeded via
the M(CO)5 intermediate through M–CO bond dissociation.
This is a general route for the UV photolysis of the
hexacarbonyls of Group 6 [24]. Such intermediate reacts
with either the ligand alone to give the chromium derivative
or with the ligand and oxygen to give the molybdenum and
tungsten products. The source of oxygen in the oxo
complexes could be originated from the dissolved oxygen
in the used solvent. It is well established that both
molybdenum and tungsten have higher affinity to react
with oxygen [24,25]. Numerous oxo molybdenum and
tungsten complexes were previously reported. For example,
interaction of bis-(salicylaldehyde)etylenediimine (salenH2)
and 2-hydroxyacetophenoneethylenediimine (hapenH2)
with Mo(CO)6 in THF under atmospheric pressure gave
Mo(O)(salen) and Mo(O)(hapen) with the metal atom in C4
oxidation state [18,19]. Also, reactions of the Schiff base
salicylideneimine-2-anisole (salanH) with M(CO)6, MZMo
or W, gave the dinuclear oxo complex M2O4(salan)2 [26].
The infrared spectrum of the chromium complex, 1,
displayed the characteristic bands of shaH2 with the
appropriate shifts due to complex formation (Table 2). The
complex showed vibrational bands at 3354, 1379 and
1340 cmK1 due to n(OH) and d(OH) frequencies, respect-
ively (Table 2). In addition, the infrared spectrum of 1
showed an appreciable shifts in the n(C]N) and n(C–O)
as described in literatures [21,23]. All solvents were purified
by distillation before use.
2.2. Instruments
Infrared measurements (KBr pellets) were carried out on a
Unicam–Mattson 1000 FT-IR spectrometer. UV–vis spectra
were measured on a Unicam UV2-300 spectrophotometer.
NMR measurements were performed on a Spectrospin–
Bruker AC 200 MHz spectrometer. Samples were dissolved
in deuterated DMSO using TMS as internal reference.
Elemental analyses were performed on a Perkin–Elmer 2400
CHN elemental analyzer. Mass spectrometry measurements
of the solid complexes (70 eV, EI) were carried out on a
Finnigan MAT SSQ 7000 spectrometer. Thermogravimetric
analysis was performed under nitrogen atmosphere with a
heating rate of 10 8C/min using a Schimadzu DT-50 thermal
analyzer. Table 1 gives the elemental analysis and mass
spectrometry data for the complexes.
2.3. Syntheses of complexes
A general procedure was employed for the synthesis of
the reported complexes. A mixture of equimolar amounts of
[M(CO)6], MZCr, Mo and W, and either shaH2 or
salphenH2 in a sealed tube containing 25 cm3 of THF.
Photolysis of the mixture with sunlight for a certain period
of time (25 8C) was employed (Table 1). (The photoexcita-
tion procedure is expected to be the UV range of light). The
solvent was removed on a vacuum line. The residue was
washed several times by boiling petroleum ether and then
recrystallized from THF. The complex was left to dry in
Table 1
Elemental analysis and mass spectrometry data for the chromium, molybdenum and tungsten complexes
Complex
Color
Reaction
time (h)
% Yield
Elemental analysis
%C
Mass spectrometry
%H
%N
Mol. Wt. m/z (pC
)
Calc.
Found
Calc.
Found
Calc.
Found
1
2
3
4
5
6
Brown
3
4
73
68
75
84
61
53
67.7
56.3
35.8
62.5
52.2
30.8
67.4
56.1
35.6
62.3
52.4
30.4
4.8
4.0
2.3
4.2
3.5
2.1
5.0
4.2
2.4
4.5
3.1
1.9
6.1
5.7
3.2
7.3
6.1
3.6
5.9
5.5
3.0
7.1
6.2
3.4
691.7
554.4
872.2
384.4
920.6
780.1
692
555
873
385
921
781
Dark-brown
Light-brown
Brown
10
6
Dark-brown
Light-brown
5
12

S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
173
Table 2
Infrared data for the shaH2, salphenH2 and their chromium, molybdenum and tungsten complexes
Compound
Infrared data (cmK1 a
)
n(C]N)
n(C–O)
d(OH)
1368 (m)
n(OH)
3422(m)
n(M]O)
n(M–O–M)
n(M–O)
n(M–N)
shaH2
1631 (s)
1274 (m)
1243 (m)
1278 (m)
1146 (m)
1281 (m)
1247 (m)
1286 (m)
1241 (m)
1274(s)
–
–
–
–
1
2
3
1607 (s)
1612 (s)
1613(s)
1379 (m)
1340 (m,sh)
1389 (m)
3354 (m,b)
3384 (m,b)
3381(m,b)
–
–
534(m)
551(m)
554(w)
420(m)
477(w)
444(m)
933(s)
912(s)
946(s)
899(m)
–
–
1371 (m,sh)
1385(m)
642(m)
salphenH2
1612(s)
1605(s)
1455 (m)
1441 (m)
1461(m)
1462 (m)
3424 (m)
–
–
–
–
4
1278(s)
3383 (m,b)
853(s)
539(m)
453(m)
5
6
1605(s)
1606(s)
1282 (m)
1256(m)
3283 (m)
3198(m)
937(m)
914(s)
979(s)
895(s)
818(m)
799(m)
652(m)
633(m)
507(w)
548(m)
588(m)
470(w)
444(w)
1454(m)
a
s, strong; m, medium; b, broad; sh, shoulder.
bands. The infrared spectrum of the complex also exhibited
two non-ligand bands at 534 and 420 cmK1 due to Cr–O and
Cr–N bonds, respectively [19,27]. Therefore, it can be
concluded that shaH2 ligand probably coordinated to
chromium atom through phenolic oxygen and azomethine
nitrogen and acting as a bidentate ligand. From the elemental
analysis and spectroscopic data, it can be concluded that the
chromium complex has the tris configuration as shown in
Scheme 2. This structural arrangement would give a
chromium species with zero (d6) oxidation state. Magnetic
studies of the complex showed paramagnetic characteristics.
The magnetic measurement at 298 K gave a value of
2.98 BM for the effective magnetic moment. This value is
close to the spin-only moment of two unpaired electrons
(2.84 BM). Since the UV–vis of the complex [Cr(shaH2)3]
did not display the characteristic band of the high-spin
configuration at 628 nm (vide infra) and the value of the meff
is in the range 2.7–3.4 BM, it is suggested that the complex
has the electronic configuration d2xzdy1zd1xydz1dx02Ky2 [22]. Thus,
this meff value could be due to second order paramagnetism
effects arising from a low lying excited state in an otherwise
diamagnetic compound; the diamagnetism might arise from
further splitting of the t2g orbitals in the low symmetry
complex [19].
Scheme 2. The shaH2 complexes.

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S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
The sun irradiation of a mixture of [Mo(CO)6] and shaH2
the tungsten complex displayed a shift of 18 cmK1 to lower
energy relative to that of ligand (Table 2) indicating the
coordination of the azomethine nitrogen atom to the metal
[12]. The infrared spectrum of 3 also displayed two
vibrational bands at 946 and 899 cmK1 due to symmetric
and asymmetric frequencies of two terminal cis W]O
bonds. In addition, stretching infrared bands were observed
at 642, 554 and 444 cmK1 corresponding to W–O–W, W–O
and W–N bonds, respectively. Interestingly, the infrared
spectrum of the tungsten complex exhibited only one
bending OH band due to one OH group, which is different
from the chromium and molybdenum derivatives (Table 2).
This could be probably due to coordination of one OH group
to the metal with proton displacement, i.e., the ligand
reacted oxidatively. The presence of OH bands in the
infrared spectrum of the complex due to the other OH group
with low frequency shift indicated the presence of
intramolecular hydrogen bonding (Scheme 2).
in THF produced the mononuclear dioxo complex [MoO2
(shaH2)2], 2, with the metal atom in C4 formal oxidation
state. The corresponding thermal reaction gave a dinuclear
derivative [Mo2O4(sha)2] with the molybdenum in the C6
formal oxidation state [21]. The infrared spectrum of 2
displayed the ligand bands with the corresponding shifts due
to complex formation, Table 2. In addition, two stretching
bands were observed at 933 and 912 cmK1 due to symmetric
and asymmetric frequencies of two terminal cis Mo]O
bonds [28]. The infrared spectrum of the molybdenum
complex also displayed non-ligand bands at 551 and
477 cmK1 due to Mo–O and Mo–N bonds, respectively.
Furthermore, the infrared spectrum showed a broad band at
3384 cmK1 due to stretching OH frequencies, and two
bands at 1389 and 1371 cmK1 due to bending OH
1
frequencies. The H NMR spectrum of 2 displayed two
signals at 13.69 and 10.67 ppm indicating the presence of
two OH groups. The latter signal showed lower field shift
and indicated that the shaH2 ligand coordinated to the
molybdenum atom through the OH group, which is cis to the
azomethine group. The other OH signal at 13.69 ppm was
broad and showed a higher field shift relative to that of
ligand, which may indicate the presence of hydrogen
bonding as in Scheme 2.
3.1.2. The salphenH2 complexes
Interaction of [M(CO)6], MZCr, Mo and W, with bis-
(salicylaldehyde)-phenylenediimine (salphenH2) in THF
under sunlight irradiation gave the oxo complexes
[CrO(salphenH2)], 4, [Mo2O6(salphenH2)2], 5, and [W2O6
(salphenH2)], 6. Scheme 3 gives the proposed structures for
the complexes. The infrared spectrum of salphenH2 dis-
played the characteristic bands due to OH, C–O, and C]N
function groups (Table 2). The infrared spectrum of the
chromium complex, 4, exhibited the ligand bands with the
corresponding shifts, Table 2. It also displayed two bands at
1441 and 1461 cmK1 due to d(OH) vibrations and a broad
Interaction of [W(CO)6] with shaH2 under sunlight
irradiation resulted in the formation of a light-brown
complex with a molecular formula of [W2O5(shaH)2], 3.
The infrared spectrum of the tungsten complex showed the
ligand bands with appropriate shifts as a result of complex
formation (Table 2). The C]N stretching vibration of
Scheme 3. The salphenH2 complexes.

S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
175
band at 3383 cmK1 due to a n(OH) stretching frequency. The
shift in these OH bands relative to those of ligand indicated
that the two OH groups may be coordinated to chromium
atom without proton displacement and forming hydrogen
bonding with the oxygen atom. In addition, the infrared
spectrum of 4 showed additional bands at 539 and 453 cmK1
due to n(Cr–O) and n(Cr–N), respectively. The appearance of
a strong infrared band at 853 cmK1 could be attributed to
n(Cr]O) stretching vibration. Investigation of the chro-
mium complex by 1H NMR spectroscopy gave no signals due
to its paramagnetic properties. It is expected that chromium
would have a Cr(II) d4 electronic configuration (Scheme 3).
Magnetic measurement of 4 at 298 K gave a value of an
effective magnetic moment of 3.9 BM. This value is less than
the spin only value for four unpaired electrons (4.8 BM).
Many paramagnetic chromium complexes exhibited effec-
tive magnetic moment values less than the spin-only ones
[22]. Magnetic studies of the two complexes [Mo(O)(salen)]
[18] and [Mo(O)(hapen)] [19] with metal atom in C4 formal
oxidation state gave meff values less than the spin-only value
of two unpaired electrons.
Table 3
1H NMR data of shaH2 and salphenH2 and their chromium, molybdenum
and tungsten complexes
Compound
shaH2
1H NMR data (ppm)a
13.75 (s, OH), 9.70 (s, OH), 9.03 (s, N]CH),
7.55 (m, Ph), 7.06 (m, Ph)
2
13.69 (s, OH), 10.67 (s, OH), 9.66 (s, N]CH),
7.36–6.84 (m, Ph)
3
salphenH2
9.27 (s, N]CH), 7.87–6.88 (m, Ph)
12.86 (s, OH), 8.93 (s, CH), 7.65 (m, Ph),
7.43 (m, Ph), 6.94 (m, Ph)
5
10.70 (s, OH), 10.25 (s, OH), 9.11 (s, N]CH),
7.67–7.72 (m, Ph)
6
9.95 (s, OH), 9.08 (s, N]CH), 7.65–6.70 (m, Ph)
a
s, singlet; m, multiplet.
3.2. UV–vis studies
The electronic absorption studies of shaH2, salphenH2
and their complexes were studied in DMSO, CH2Cl2,
acetone, benzene and methanol (Table 4). The UV–vis
spectra of the shaH2 ligand displayed two absorption bands
in all solvents. The first absorption band ranged from 268 to
278 nm was corresponded to p–p* electronic transitions.
The second band at 349–357 nm was due to n–p* transition.
In the complexes, a bathochromic shift in the p–p*
electronic transition was observed, Table 4. On the other
hand, the n–p* electronic transitions exhibited hypsochro-
mic shifts. The complexes showed additional absorption
bands in the range 404–480 nm which could be due to
charge transfer transitions, Table 4. In the chromium
complex, metal-to-ligand charge transfer (shaH2 p*)Cr
dp) could be assigned while in molybdenum and tungsten
complexes, ligand-to-metal charge transfer (M dp)shaH2
p*) might be present [31].
Similar to those of shH2, the UV–vis absorption spectra
of salphenH2 gave two absorption bands in all solvents. The
first absorption band referred to p–p* electronic transitions
and ranged from 260 to 274 nm. On the other hand, the
second absorption band ranged from 328 to 348 nm was
corresponded to n–p* electronic transition. On going from
salphenH2 ligand to its complexes a bathochromic shifts
were exerted in the p–p* electronic transitions, Table 4. On
the other hand, the n–p* electronic transitions exhibited
hypsochromic shifts (Table 4). All complexes displayed
additional absorption bands in the range 359–540 nm
corresponding to (M dp)salphenH2 p*) charge transfer
[28].
Reaction of [Mo(CO)6] with salphenH2 under sunlight
irradiation resulted in the formation of the dark-brown oxo
complex [Mo2O6(salphenH)2], 5. The infrared spectrum of 5
displayed the ligand bands with the proper shifts indicating
complex formation (Table 2). In addition, the infrared
spectrum exhibited two bands at 937 and 914 cmK1 due to
symmetric and asymmetric stretching vibrations of
O]Mo]O indicating that the two oxygen atoms were
coordinated to the metal in cis positions. Further more,
another two bands at 799 and 652 cmK1 were observed due
to n(Mo–O–Mo) frequencies [29,30]. The infrared spectrum
of [Mo2O6(salphenH)2] displayed a band at 3283 cmK1 due
to n(OH) and a band at 1462 cmK1 due to d(OH). The
presence of the OH groups was also confirmed by 1H NMR
spectroscopy. The OH signals displayed shifts to the higher
1
field. The shift in the H NMR signals and the IR bands
indicated that the OH groups formed intra- and intermole-
cular hydrogen bonding (Scheme 3). Magnetic measure-
ments showed diamagnetic properties for 5. According to
the proposed structure, molybdenum may have C6 formal
oxidation state with d0 electronic configuration.
On comparison between the complex formed from
sunlight irradiation reaction, [Mo2O6(salphenH)2], and the
corresponding derivative formed via thermal reaction,
[MoO2(salphenH)2], different structural arrangement were
observed [22]. The former complex is a dinuclear with the
two salphenH moieties bound to the metal through their
nitrogen atoms while the later complex is a mononuclear
with the two salphenH moieties bound to the metal through
nitrogen and oxygen atoms [22].
3.3. Thermogravimetric analysis
In order to give more insight into the structure of the
complexes, the thermal studies of the complexes were
carried out using thermogravimetry (TG) technique. The TG
plot of Cr(shaH2)3 displayed three resolved and well-
defined decomposition steps. The first decomposition step
occurred in the temperature ranges 298–502 K, with a net
Reaction of [W(CO)6] with salphenH2 under sunlight
irradiation gave the light brown oxo complex [W2O6
1
(salphenH2)], 6. The infrared and H NMR spectra of the
complex showed that the complex is identical to that
isolated from the thermal reaction [22] (Table 3).

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S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
weight loss of 13.05%, probably due to elimination of three
C2H6 moieties, Table 5. The second decomposition step
occurred in the temperature range 502–626 K with a net
weight loss of 15.23% due to the loss of a NO2 and C4H11
moieties. The third decomposition step (626–1141 K,
62.31%) was due to the elimination of C29H4N2O3 species
to leave the metallic residue CrO (Table 5).
The TG plot of the MoO2(shaH2)2 complex displayed
four decomposition steps in the temperature range 365–
1000 K (Table 5). The first decomposition step occurred in
the temperature range 365–413 K with a net weight loss of
8.50% corresponding to elimination of a C3H11. The second
decomposition peak occurred in the temperature range 413–
548 K with a weight loss of 17.34% and corresponded to the
material decomposition of C6H8O. The third decomposition
step in the temperature range 548–714 K is corresponded to
the elimination of a NO species. The last decomposition step
at the temperature range 714–1000 K is due to the
elimination of C17H3 and NO2 moieties to give finally the
metallic residue MoO2.
The W2O5(shaH)2 complex was found to thermally
decompose in three well-defined steps in the temperature
range 323–965 K (Table 5). The first decomposition step
at 323–590 K with a net weight loss of 66.98%
corresponded to elimination of C5H7 species molecules.
The second decomposition step (590–735 K, 16.60%)
was due to elimination of C6H10O species and NO2
molecule. The third decomposition step occurred in the
temperature range 735–965 K (weight loss 22.61%)
probably due to the elimination of a C15H3N moiety to
leave WO3 as a residue.
The TG plot of CrO(salphenH2) showed that it decom-
posed in two steps. The first decomposition step (323–
603 K, 15.62%) was due to the elimination of two NO
molecules. The second step at 603–703 K with a net weight
loss of 70.87% was due to material decomposition to leave
the chromium metal as a residue (13.53%).
The complex Mo2O6(salphenH2) was decomposed in
three steps. In the range 348–713 K, the complex was firstly
decomposed with a net weight loss of 30.98% due to the
elimination of C15H13 moiety in addition to two NO2
molecules. The second decomposition step in the range
713–933 K was found to be due to the elimination of C13H12
species and two NO2 molecules. The third decomposition
step at 933–1073 K was corresponded to the elimination of
C12H7 species leaving MoO as metallic residue.
The TG plot of W2O6(salphenH2) complex gave five
decomposition steps in the range 328–1073 K. The first
three steps at 328–693 K were overlapped and unresolved.
They could be corresponded to the elimination of C5H6
moiety and NO2 molecule (14.37%). The fourth decompo-
sition step at 693–833 K corresponded to the elimination of
C4H7 species (7.06%), while the fifth step (833–1073 K)
was corresponded to the elimination of C11H3 moiety and
NO2 molecule leaving WO2 as metallic residue.

S.M. El-Medani et al. / Journal of Molecular Structure 738 (2005) 171–177
177
Table 5
Thermal analysis data for the chromium and molybdenum complexes of shaH2 and salphenH2
Complex
Decomposition step, K
% Weight loss
Mol. wt.
Species eliminated
% Solid residue
9.43 (CrO)
Cr(C39H33O6N3)
298–502
502–626
626–1141
365–413
413–548
548–714
714–1000
323–590
590–735
735–965
323–603
603–703
348–713
713–933
933–1073
328–693
693–833
833–1073
13.04
15.23
62.31
8.50
90.21
105.35
431.00
47.14
3C2H6
NO2CC4H11
C29H4N2O3
C3H11
Mo(C26H22O6N2)
W2(C26H20O9N2)
23.10 (MoO2)
53.11 2(WO3)
17.34
5.41
96.13
C6H8O
30.00
NO
45.67
7.68
253.21
66.98
C17H3CNO2
C5H7
16.60
22.61
15.62
70.87
30.99
28.27
16.42
14.37
7.06
144.78
197.20
60.03
C6H10OCNO2
C15H3N
2NO
Cr(C20H16N2O3)
13.53 (Cr)
272.40
285.27
260.24
151.19
112.10
55.10
C20H16
C15H13C2NO2
13H12C2NO2
O
Mo2(C40H32O10N4)
24.33 2(MoO)
C
C12H7
W2(C20H16N2O8)
C5H6CNO2
C4H7
55.34 2(WO2)
23.22
181.15
C11H3CNO2
[15] C.P. Horwitz, S.E. Creager, R.W. Murray, Inorg. Chem. 29 (1990)
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