Tris(dialkyldithiocarbamato)diazenido(1-) and hydrazido(2-) molybdenum complexes: Synthesis and reactivity in acid medium

Article abstract of DOI:10.1016/S0277-5387(00)00496-4

A series of new molybdenum complexes, [Mo(NNH-CO-Ph){S₂CN (C₂H₅)₂}₃] (1), [Mo(NN-CO-C₆H₄-NO₂){S₂CN (C₂H₅)₂}₃] (2), [Mo(NNH-CO-Ph){S₂CN(CH₃)₂}₃] (3), [Mo(NN-CO-C₆H₄-NO₂){S₂CN (CH₃)₂}₃] (4) have been synthesized, with p-nitrobenzoyldiazenido(1-) and benzoylhydrazido(2-) as ligands, and dialkyldithio-carbamatos as coligands. Reactions of these compounds with aqueous and methanolic HCl were carried out but the attempted separation of the aroyl group was unsuccessful. Only the reaction of 1 and 2 with HCl in methanol gave a product, identified as [Mo{S₂CN(C₂H₅)₂}₄] [MoCl₄(OCH₃)₂]. The complexes were characterized by elemental analysis, IR spectroscopy, ¹H and ¹³C NMR, and mass spectrometry. Single crystals of 2 were obtained and the crystal structure was determined. The Mo atom is heptacoordinated; one diazenido(1-) and three diethyldithiocarbamatos act as ligands. From the latter one sulfur is in trans-position to the diazenido-nitrogen atom and the other five sulfur atoms lie in a plane giving a distorted pentagonal-bipyramidal coordination.

Full text of DOI:10.1016/S0277-5387(00)00496-4

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 2327–2335
Tris(dialkyldithiocarbamato)diazenido(1-) and hydrazido(2-)
molybdenum complexes: synthesis and reactivity in acid medium
Pablo C. Riveros a, Isabel C. Perilla a, Arnulfo Poveda a,*, Heimo J. Keller b,
H. Pritzkow b
a Departamento de Qu´ımica, Uni6ersidad Nacional de Colombia, Santafe´ de Bogota, Colombia
b Anorganisch-Chemiches Institut der Uni6ersita¨t, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Received 1 October 1999; accepted 24 April 2000
Abstract
A series of new molybdenum complexes, [Mo(NNHꢀCOꢀPh){S2CN(C2H5)2}3] (1), [Mo(NNꢀCOꢀC6H4ꢀNO2){S2CN(C2H5)2}3]
(2), [Mo(NNHꢀCOꢀPh){S2CN(CH3)2}3] (3), [Mo(NNꢀCOꢀC6H4ꢀNO2){S2CN(CH3)2}3] (4) have been synthesized, with p-ni-
trobenzoyldiazenido(1-) and benzoylhydrazido(2-) as ligands, and dialkyldithio-carbamatos as coligands. Reactions of these
compounds with aqueous and methanolic HCl were carried out but the attempted separation of the aroyl group was unsuccessful.
Only the reaction of 1 and 2 with HCl in methanol gave a product, identified as [Mo{S2CN(C2H5)2}4][MoCl4(OCH3)2]. The
1
complexes were characterized by elemental analysis, IR spectroscopy, H and 13C NMR, and mass spectrometry. Single crystals
of 2 were obtained and the crystal structure was determined. The Mo atom is heptacoordinated; one diazenido(1-) and three
diethyldithiocarbamatos act as ligands. From the latter one sulfur is in trans-position to the diazenido-nitrogen atom and the
other five sulfur atoms lie in a plane giving a distorted pentagonal-bipyramidal coordination. © 2000 Elsevier Science B.V. All
rights reserved.
Keywords: Molybdenum; Hydrazido; Diazenido; Dialkyldithiocarbamato; Hydrazines
or hydrazido(ꢀNNH2) complexes by breaking the
C(O)ꢀN bond in a solvolysis reaction. All aroyl hy-
drazines used in this work act as monodentate. The
aroyl hydrazine derivatives with dimethyldithiocarbam-
ato coligand are stable to solvolysis whereas those with
diethyldithiocarbamato react under reflux to give tetra-
dithiocarbamato complexes.
1. Introduction
There have been several recent studies concerning the
reactivity of dinitrogen coordinated to transition metal
ions. Besides substitution, the reactions that give rise to
N2 derivatives such as hydrazido(2-), (1-), or di-
azenido(1-) are the most interesting [1–4]. Similar inter-
mediates can be obtained by reaction of hydrazines
with dioxomolybdenum complexes; however, there are
not many reports in the literature of acyl or aroyl
hydrazido or diazenido complexes [5]. These ligands
can act as monodentate or didentate and generate
derivatives that may be considered as intermediates in a
cyclic process of nitrogen fixation, similarly to some
rhenium complexes with phosphine ligands [6]. The
aroyl and acyl derivatives could also give azido(ꢀNNH)
2. Experimental
2.1. Physical measurements
Melting points were obtained with a Melt-Temp II
apparatus, using glass capillaries. Elemental analyses
were performed at the Microanalyses Department of
the Anorganisch-Chemischen Institut of Heidelberg
Universita¨t. IR spectra were recorded for solid disper-
sions of 5% samples in KBr by the reflectance technique
in a Nicolet 510P FT-IR spectrometer. 1H and 13C
NMR spectra were obtained at room temperature (r.t.)
* Corresponding author. Tel.: +57-1-316-5000, ext. 1443; fax:
+57-1-316-5220.
E-mail address: apovedap@ciencias.ciencias.unal.edu.co (A.
Poveda).
0277-5387/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(00)00496-4

2328
P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
in a Brucker Typ AC 300 spectrometer at 300 and 75
MHz respectively, using TMS as standard; CDCl3 was
used as solvent for all samples but [MoO2{S2CN-
(CH3)2}2], which was taken in (CD3)2SO. Mass spectra
were recorded in a Finnigan Mat 8200 spectrometer
using the FAB-Nibeol ionization technique. Small sin-
gle crystals of 2 were obtained from THF solution.
Crystal data were collected at −70°C with a Siemens–
Stoe AED2 diffractometer using Mo Ka radiation, a
graphite monochromator and omega-scan. The struc-
ture was solved by direct methods (SHELXS-86) [7]. The
compound crystallizes with one half THF per molecule.
The THF molecule is disordered. It was not possible to
distinguish the oxygen from the carbon atoms, then the
solvent molecule was refined for five carbon atoms with
restrictions on the bond lengths and angles. The struc-
ture was refined by least-squares methods based on F2
with all measured reflections (SHELXL-97 [8]) using an-
isotropic temperature factors for all non-hydrogen
atoms except those of the THF molecule. Hydrogen
atoms were inserted in calculated positions or as part of
a rigid group (methyl).
3H2O, and 0.60 g (4.4 mmol) of PhCONHNH2 in 20 ml
methanol were boiled under reflux for 2 h with mag-
netic stirring. Longer times of reflux lead to lower yield,
whereas shorter times cause the product to be contami-
nated with the reactants. The solvent was reduced to
about 10 ml in a rotary evaporator and the solution
was cooled to r.t. The orange solid thus obtained was
filtered and washed with methanol, water, and again
with a little methanol. The product was recrystallized in
methanol and dried under vacuum. It can also be
recrystallized in THF. Yield, 82%. The same product
was obtained with 1:0:1 and 1:0:2 molar ratios of
reactants respectively, but the yield decreased to 30 and
38%. Elemental analysis: Anal. Found: C, 38.31; H,
5.17; N, 10.14. Calc.: C, 39.21; H, 5.24; N, 10.39%.
2.3.2. Tris(diethyldithiocarbamato)-p-nitrobenzoyl-
diazenido(1-)molybdenum(IV), [Mo(NNCOꢀC6H4ꢀNO2)
{S2CN(C2H5)2}3] (2)
The procedure described above was employed, using
1.00 g (2.35 mmol) of [MoO2{S2CN(C2H5)2}2], 0.60 g
(2.66 mmol) of NaS2CN(C2H5)2·3H2O, and 0.80 g (4.41
mmol) of O2NꢀC6H4CONHNH2. The red solid was
recrystallized in THF and dried under vacuum for one
h at 35°C. Yield, 80%. With 1:0:2 molar ratio of
reactants the same product was obtained in 35% yield.
(Elemental analysis: Anal. Found: C, 38.27; H, 5.22; N,
11.09; S, 25.15. Calc. for [Mo(NNCOꢀC6H4ꢀNO2)-
{S2CN(C2H5)2}3]·0.5THF: C, 38.18; H, 5.07; N, 11.13;
S, 25.48%). Crystals for X-ray analysis were grown by
dissolving the compound in THF at 20°C and then
filtering. The solution was warmed at about 60°C and
after 12 h red crystals were obtained.
2.2. Synthesis of the dioxocomplexes
2.2.1. Bis(dimethyldithiocarbamato)-
dioxomolybdenum(VI), [MoO2{S2CN(CH3)2}2]
A solution of 9.40 g (50 mmol) of NaS2CN(CH3)2·
2.5H2O in 100 ml H2O was slowly added to a solution
of 8.70 g (7 mmol) of (NH4)6Mo7O24·4H2O in 100 ml
H2O, with strong stirring. The pH was kept at about 2
by adding 1 M HNO3. The obtained yellow precipitate
was filtered off and washed with water, then dried
under vacuum. Yield, 99%. The compound decomposes
between 290–300°C. (Elemental analysis: Anal. Found:
C, 28.13; H, 4.64; N, 6.40. Calc.: C, 28.30; H, 4.75; N,
6.60%).
2.3.3. Benzoylhydrazido(2-)tris(dimethyldithio-
carbamato)molybdenum(V),
[Mo(NNHCOꢀPh){S2CN(CH3)2}3] (3)
The procedure as described above was employed,
using 1.00 g (2.71 mmol) of [MoO2{S2CN(CH3)2}2],
0.55 g (2.92 mmol) of NaS2CN(CH3)2·2.5H2O, and 0.60
g (4.41 mmol) of PhꢀCOꢀNHNH2. The product was
recrystallized in methanol or THF and dried under
vacuum. Yield, 75%. The same product was obtained in
1:0:2 molar ratio of reactants, in 33% yield. (Elemental
analysis: Anal. Found: C, 32.56; H, 4.10; N, 11.61.
Calc: C, 32.59; H, 3.93; N, 11.88%).
2.2.2. Bis(diethyldithiocarbamato)dioxomolybdenum(VI),
[MoO2{S2CN(C2H5)2}2]
The previously described procedure was employed,
using 10.00 g (44 mmol) of NaS2CN(C2H5)2·3H2O in
150 ml H2O, and 10.00 g (8 mmol) of (NH4)6Mo7O24·
4H2O in 150 ml H2O. The yellow compound was
recrystallized in 1:1 benzene: n-hexane. Yield, 95%.
m.p., 133°C. (Elemental analysis: Anal. Found: C,
19.27; H, 3.34; N, 7.62; S, 34.27. Calc.: C, 19.56; H,
3.28; N, 7.60; S, 34.82%).
2.3.4. Tris(dimethyldithiocarbamato)-p-
nitrobenzoyldiazenido(1-)molybdenum(IV),
2.3. Synthesis of the aroylhydrazine deri6ati6es
[Mo(NNCOꢀC6H4ꢀNO2) {S2CN(CH3)2}3] (4)
The procedure described above was employed, using
1.50 g (4.07 mmol) of [MoO2{S2CN(CH3)2}2], 0.90 g
(4.79 mmol) of NaS2CN(CH3)2·2.5H2O, and 1.20 g
(6.63 mmol) of O2NꢀC6H4ꢀCOꢀNHNH2. The product
was recrystallized in THF and dried under vacuum.
Yield, 81%. The same product was obtained in 30%
2.3.1. Benzoylhydrazido(2-)tris(diethyldithiocarbamato)-
molybdenum(V), [Mo(NNH-COꢀPh){S2CN(C2H5)2}3]
(1)
A suspension of 1.00 g (2.36 mmol) of [MoO2{S2CN-
(C2H5)2}2], 0.60 g (2.66 mmol) of NaS2CN(C2H5)2·

P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
2329
yield when a 1:0:2 molar ratio of reactants was used.
(Elemental analysis: Anal. Found: C, 30.85; H, 3.75;
N, 13.10; S, 29.90. Calc.: C, 30.28; H, 3.49; N, 13.24;
S, 30.31%).
brown solid was suspended in 50 ml water and stirred
for 30 min to dissolve and thus eliminate the excess of
reactants. The precipitate was filtered and then washed
with water, ethanol, and n-hexane. The product was
recrystallized in ethanol; after three days brown micro-
crystals precipitated, which were filtered and washed
with n-hexane, and diethyl ether. The product was
2.4. Sol6olysis of the hydrazido(2-) and diazenido(1-)
deri6ati6es
1
dried under vacuum. Yield, 65%. H NMR lH(solvent
The solvolysis of 1, 2, 3, and 4 was attempted in 5%
and 10% NaOH in water and in methanol at r.t. for 24
h but no reaction was observed. The reactants decom-
posed when refluxed at 60°C for 2 h. The same com-
pounds did not react with 37% HCl in water at r.t. for
24 h, neither with 5% HCl below 50°C. At 60°C decom-
position of the reactants was observed. IR spectroscopy
was used as a probe to monitor the course of the
reactions.
CDCl3) 1.12–1.35 (18H, m, 6CH3), 1.95–2.20 (1H, br s,
NꢀH), 2.17 (3H, s, CH3ꢀCO), 3.65–3.85 (12H, m,
6CH2).
2.7. Trisdiethyldithiocarbamatophenyldiazenido(1-)-
molybdenum(IV), [Mo(NNPh){S2CN(C2H5)2}3].
This compound was prepared following a published
procedure [10].
Only the reaction of the diethyldithiocarbamato
derivatives 1 and 2 with 2.5% HCl in methanol under
reflux gave an identifiable product.
3. Results and discussion
2.5. Tetrakis(diethyldithiocarbamato)molybdenum(V)-
tetrachlorobis(methoxy) molybdate(V),
3.1. Synthesis of the compounds
[Mo(S2CN(C2H5)2)4][MoCl4(OCH3)2] (5)
The dioxocomplexes were synthesized by a modifica-
tion of the procedure published by Moore and Larson
[11]; the pH was kept below 2.0 with diluted HNO3 in
order to avoid contamination with the violet Mo(V)
complex, [{Mo(S2CNR2)2O}2O].
A suspension of 0.30 g of 1 in 15 ml of a solution of
concentrated HCl 2.5% 6/6 in methanol was placed
under reflux; after 45 min a green precipitate formed,
that was filtered and washed with water, diethyl ether
and n-hexane. Its m.p. (143°C) and mass spectra
showed it to be the unstable known compound
[Mo{S2CN(C2H5)2}4] [9]. After refluxing for 2 h, the
resultant brown solution was evaporated in a rotary
evaporator until about 4 ml, then it was warmed and
diethyl ether added drop to drop, until a brown solid
precipitated. The solid was filtered and washed at 0°C
with diethyl ether and methanol. Then it was recrystal-
lized in methanol and dried under vacuum. Yield, 27%.
The product is insoluble in acetone, diethyl ether, chlo-
roform, and dimethyl sulfoxide (Elemental analysis:
Anal. Found: C, 26.72; H, 4.69; Cl, 14.34; N, 5.67; S,
25.94; Calc. for [Mo{S2CN(C2H5)2}4][MoCl4(OCH3)2]:
C, 26.80; H, 4.74; Cl, 13.37; N, 6.44; S, 25.63). When 2
was allowed to react by the above described procedure
the same products were obtained under the same condi-
tions but in lower yield (5 was formed in 20% yield).
It has been published that the reactivity of dioxocom-
plexes against substituted hydrazines depends on sev-
eral factors, such as the nature of the coligands and of
the hydrazines, and the molar ratio of the reactants; for
example, the number of substituents and the basicity of
the hydrazines play an important role in the number of
these that coordinate to the metal center [12–15]. In
this work we found that condensation reactions be-
tween the dioxocomplexes and the hydrazides in the
presence of the corresponding dialkyldithiocarbamate
in methanol always give tris(dialkyldithiocarbamato)
complexes of the type [Mo(NNHCOꢀPh)(S2CNR2)3]
and [Mo(NNCOꢀC6H4ꢀNO2)(S2CNR2)3] (R=ꢀCH3 or
ꢀC2H5). The same compounds are formed when no
dialkyldithiocarbamate is added although in lower
yield, since the additional dithiocarbamate has to be
provided by decomposition of the original dithicarbam-
ato complex.
The acyldiazenido- and acylhydrazido- ligands may
be either monodentate when they are bound to the
metal through the terminal nitrogen, or didentate when
they are bound through the nitrogen and the oxygen. In
addition, the monodentate ligand can bind the metal
center in three different ways depending on the hydra-
zide from which it originates, as diazenido(1-), hy-
drazido(1-), or hydrazido(2-) [12,13]. These binding
modes are shown in Fig. 1. In our case the two hy-
drazides act as monodentate ligands; p-nitrobenzohy-
2.6. Tris(diethyldithiocarbamato)acetylhydrazido(2-)-
molybdenum(V), [Mo(NNHCOꢀCH3){S2CN(C2H5)2}3].
A suspension of 0.50 g (1.18 mmol) of [MoO2{S2CN-
(C2H5)2}2], 0.50 g (2.22 mmol) of NaS2CN(C2H5)2·
3H2O, and 0.22 g (2.97 mmol) of CH3ꢀCOꢀNHNH2 in
15 ml methanol was stirred for 12 h at r.t. The solution
thus obtained was filtered and then evaporated until
dryness in a rotary evaporator at 48°C. The resultant

2330
P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
Fig. 1. Types of ligation and binding modes of the hydrazido ligands.
drazide is bound to the metal as diazenido(1-), and
benzohydrazide as hydrazido(2-). A plausible explana-
tion for this difference is that when the ꢀNO2 group is
present, electron density is withdrawn from the nitrogen
atom and therefore the NꢀH bond is unstable. Then the
oxidation state of molybdenum is different with these
ligands; it acts as Mo(IV) in diazenido(1-) complexes,
and as Mo(V) in hydrazido(2-) complexes. The para-
magnetism of the latter was proven by EPR, in which a
signal at gav=1.980 is seen.
[9,16,17]. The presence of the anion [MoCl4(OCH3)2]−
is proposed mainly on the basis of elemental analysis,
since the compound is not soluble enough to allow to
take NMR spectra; this anion has also been isolated
from the reaction between [Mo2Cl10] and CH3OH [16].
3.3. IR spectroscopy
As expected, the dialkyldithiocarbamato coligands
show IR bands due to the CꢁN stretching mode be-
tween 1540 and 1506 cm−1, indicating a double bond
character; bands due to CꢀS stretching are found be-
tween 1010 and 999 cm−1; the CꢀH stretching for ethyl
and methyl groups is shown in the region 2981–2858
cm−1, the CꢀH bending modes appear as two bands
around 1460 and 1380 cm−1 in the diethyldithiocar-
bamato complexes, and as only one band around 1395
cm−1 in the dimethyldithiocarbamato complexes
[9,11,18]. The p-nitrobenzoyldiazenido and benzoylhy-
drazido ligands show bands for the ꢁCꢀH stretching of
the aromatic ring between 3071 and 3053 cm−1, and
also the out-of-plane ꢁCꢀH bending modes of the aro-
matic rings around 700 cm−1. Tables 1 and 2 show the
positions of some selected bands. Two strong bands in
the region 870–915 cm−1 assigned to cis-MoꢁO
stretchings are present in the dioxocomplexes, but dis-
appear in the benzoylhydrazido- and p-nitrobenzoyldi-
azenidocomplexes, as expected.
3.2. Reacti6ity of p-nitrobenzoyldiazenido(1-) and
benzoylhydrazido(2-) complexes with acids and bases in
aqueous and methanolic media
Compounds 1 and 3 are neither protonated nor
deprotonated on the nitrogens of the diazenido or
hydrazido ligands when boiled under reflux with base
or acid in methanolic or aqueous medium. On the other
hand, the same nitrogen atoms in compounds 2 and 4
are not protonated when reacting with acid in
methanol, or in water. When 1 is allowed to react with
HCl in methanol (2.5 ml concentrated HCl in 95 ml
MeOH) under reflux, a green solid precipitates after 45
min. This precipitate is insoluble in water but soluble in
chloroform, dichloromethane and acetone, indicating a
non-ionic or slightly polar nature. In the solid state this
compound is unstable to air, and even more in solution,
and this makes difficult to take NMR spectra. The MS
indicates this compound to be [Mo(dedtc)4]1, which is
confirmed by its m.p., 143°C, similar to that reported in
the literature [9]. The same compound was also ob-
tained in 24% yield when 2 was allowed to react by the
same procedure.
At longer reaction time (2 h) the oxidation product
of [Mo(dedtc)4], [Mo{S2CN(C2H5)2}4][MoCl4(OCH3)2]
(5) was isolated, being the metal of the cation in the
5+ oxidation state. Similar types of oxidation reac-
tions have already been reported and are used for the
synthesis of the cation [9,16]. Several ionic compounds
that contain the [Mo(S2CN(C2H5)2)4]+ cation have
been reported, which have been prepared from
[Mo2O2Cl6] and {(C2H5)2NH2}{S2CN(C2H5)2}, or by
oxidation of the corresponding Mo(IV) compounds
The shift of the w(CꢀO) and w(NꢀN) IR bands ac-
cording to the change in the CO bond order allows to
determine whether the hydrazido and diazenido ligands
act as mono- or didentate. If the IR spectrum shows
bands assignable to w(CꢁO) and w(NꢁN), the ligand is
acting as monodentate; on the other hand, if the
w(CꢁO) band disappears and the w(NꢁN) band is
Table 1
Selected IR bands for the hidrazido and diazenido ligands
a
Complex
w(ꢁCꢀH) l(ꢁCꢀH)
w(CꢁO)
1618.5
1621.4
1622.3
1636.8
w(NꢁN)
1574.1
1591.5
1571.2
1593.4
[Mo(NNHꢀCOꢀC6H5)
(S2CN(C2H5)2)3]
[Mo(NNꢀCOꢀC6H4ꢀ
NO2)(S2CN(C2H5)2)3]
[Mo(NNHꢀCOꢀC6H5)-
(S2CN(CH3)2)3]
3053.7
3070.1
3056.6
3070.1
706.0
712.8
696.4
709.9
1 The MS shows a multiplet at m/z 690 which corresponds to the
molecular ion, its isotopic distribution is consistent with only one
molybdenum atom. Other multiplets appear at m/z 542 and 426, that
correspond to [Mo{S2CN(C2H5)2}3]+ and MoS{S2CN(C2H5)2}2+, re-
spectively.
[Mo(NNꢀCOꢀC6H4ꢀ
NO2)(S2CN(CH3)2)3]
a Out-of-plane bending.

P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
2331
Table 2
Selected IR bands for the dialkyldithiocarbamato ligands
Complex
w(CꢁN)
w(CꢀS)
w(ꢀCꢀH)
w(ꢀCꢀH)
w(ꢀCꢀH)
[Mo(NNHꢀCOꢀC6H5)(S2CN(C2H5)2)3]
[Mo(NNꢀCOꢀC6H4ꢀNO2)(S2CN(C2H5)2)3]
[Mo(NNHꢀCOꢀC6H5)(S2CN(CH3)2)3]
[Mo(NNꢀCOꢀC6H4ꢀNO2)(S2CN(CH3)2)3]
1506.6
1511.4
1539.4
1524.9
1002.1
1009.9
999.2
2980.4
2979.4
2928.3
2931.2
2935.1
2935.1
2858.9
2861.0
2873.3
2872.4
1008.9
shifted to lower frequency, the ligand is didentate. The
IR spectra of 1, 2, 3, and 4 show two bands in the
region 1640–1570 cm−1 that may be assigned to either
w(CꢁO), w(NꢁN), l(NꢀH), or w(CꢁC) of the aromatic
ring. This fact does not allow to establish the binding
mode of the above mentioned ligands. In order to make
range l=3.26–3.40. In 1 and 3 the hydrogens of the
benzyl ring of the benzoylhydrazido(2-) appear as two
triplets and one doublet in the region l=7.27–8.12, as
expected [14]. In 2 and 4, the hydrogens of the aromatic
ring from the p-nitrobenzoyldiazenido display a multi-
plet at l=8.05–8.25.
1H NMR allows to determine whether the ligand is
hydrazido or diazenido, since the number of hydrogens
bound to the nitrogens determine the kind of ligand.
The spectra of 1 and 3 show a broad signal at l=
1.60–1.85 that disappears when D2O is used. This
behavior suggests that the band corresponds to the H
bound to the non-coordinated N, then in these com-
pounds the ligand is bound as benzoyl-hydrazido(2-); a
similar signal was reported for [MoO(NNHPh)-
{S2CN(C2H5)2}2] [14]. When the hydrogen is bound to
the coordinated nitrogen the signal is seen at higher
chemical shift due to weaker binding, as found for
a
correct assignment, [Mo(NNHCOꢀCH3){S2CN-
(C2H5)2}3] and [Mo(NNꢀPh){S2CN(C2H5)2}3] were syn-
thesized, the former lacking the aromatic group and the
latter, the CꢁO group. The IR spectrum of the former
also has the above mentioned bands, therefore it can be
concluded that they do not originate from the w(CꢁC)
of the aromatic ring of the p-nitrobenzoyldiazenido or
benzoylhydrazido ligand. The IR spectrum of the latter
does not have the band around 1620 cm−1 that is
present in the p-nitrobenzoyldiazenido- and benzoylhy-
drazido complexes, and therefore it should correspond
to w(CꢁO). On the other hand, the band around 1580
cm−1 can still be assigned to l(NꢀH) or w(NꢁN).
Compounds 2 and 4 do not have H bound to N, as is
[Mo(NHNPh2)(NNPh2)(acac)Cl2]
and
[Mo(NHN-
MePh)(NNMePh)(acac)Cl2], where the signals appear
by l=12 [13]. Compounds 2 and 4 do not show signals
assignable to hydrogen bound to nitrogen, and further-
more there are not changes in the spectra with D2O,
1
concluded from the H NMR spectra but the IR spec-
tra still show this band that can then be assigned to
w(NꢁN). With the assignment of these bands we can
conclude that the p-nitrobenzoyldiazenido and benzoyl-
hydrazido ligands are acting as monodentate in all the
complexes prepared. The band corresponding to
w(NꢁN) is found at higher energy in the p-nitrobenzoyl-
diazenido(1-) complexes (around 1592 cm−1) than in
the benzoylhydrazido(2-)complexes (around 1572
cm−1). This can be interpreted in terms of the decreas-
ing NꢁN bond order when the ligand also has an NꢀH
bond, since part of the electron density that is involved
in the NꢁN bond is shifted to NꢀH.
then the ligand is bound as
diazenido(1-).
a p-nitrobenzoyl-
Compound 2 shows a quintuplet at l=1.80–1.90
that corresponds to one of the signals of THF, from the
hydrogens bound to the carbons distant from oxygen.
This quintuplet is not observed when the compound
has not been recrystallized. The hydrogens bound to
the carbons next to oxygen show a signal at l=3.70–
3.80 that overlaps with the signals from the coligands.
The integration ratios for compounds 1, 2, 3, and 4
are in agreement with the presence of three di-
alkyldithiocarbamato coligands and one p-nitroben-
zoyldiazenido or benzoylhydrazido ligand.
3.4. NMR spectroscopy
1
3.4.1. H NMR
1
3.4.2. 13C NMR
The H NMR spectra of 1 and 2 show the signals of
The 13C NMR spectra of 1 and 3 show four signals in
the region l=127–135 that correspond to the aromatic
carbons from the benzoylhydrazido. In compounds 2
and 4, four similar signals from the p-nitrobenzoyldi-
azenido are shown at 122–150. All four compounds
show a signal at l=180 that corresponds to C from the
carbonyl group. The diethyldithiocarbamato coligands
the hydrogens from the diethyldithiocarbamates as
complex multiplets at l=1.15–1.35 and at l=3.62–
3.93, which are the result of overlapping of some
triplets and quadruplets, respectively; this fact suggests
that these coligands are not equivalent in solution. In 3
and 4 the hydrogens of the methyl groups from the
dimethyldithiocarbamates give rise to four peaks in the

2332
P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
from 1 and 2 give signals around l=12 and 42–45
from the ethyl groups, whereas the methyl groups from
3 and 4 give signals at l=37–41. All four compounds
show two signals around l=200 and 206 that corre-
spond to the carbons bound to sulfur in the di-
alkyldithiocarbamates; of these, the former signal is
approximately twice as intense as the latter, suggesting
that only two of the coligands are equivalent and
located on the same plane, which is consistent with a
nearly decaedric geometry obtained for a seven coordi-
nation number.
The mass spectrum of 5 shows a multiplet with the
most intense peak at m/z 690, that can be assigned to
the [Mo{S2CN(C2H5)2}4]+ ion, its isotopic distribution
corresponds to a complex with one molybdenum atom;
there are also multiplets at m/z 574, assigned to [Mo-
S{S2CN(C2H5)2}3]+; m/z 542, assigned to [Mo{S2CN-
(C2H5)2}]+3 ; m/z 426, assigned to [MoS{S2CN-
(C2H5)2}2]+; and m/z 394, that corresponds to
[Mo{S2CN(C2H5)2}2]+.
3.6. X-ray structure of
[Mo(NNCO-C6H4-NO2){S2CN(C2H5)2}3]·(0.5)THF (2)
3.5. Mass spectrometry
The X-ray structure of this compound is shown in
Fig. 2. Crystal data are listed in Table 3 and the
selected bond lengths and angles, in Table 4. The
complete atomic coordinates, bond lengths and angles
have been deposited as Supporting Information. The
Mo atom is heptacoordinated, the donor atoms are
arranged in a distorted pentagonal bipyramid. The
atoms N5 and S1 occupy the axial positions
(N5ꢀMo1ꢀS1 166.1(2)°), while the atoms S2, S3, S4, S5,
and S6 are located in the equatorial plane. S2 con-
nected via C1 to the axial atom S1 deviates strongly
Compound 2 shows a Mo-isotopic multiplet with the
most intense peak at m/z 721 which can be assigned to
the protonated molecular ion, [Mo(NNHCOꢀC6H4-
NO2){S2CN(C2H5)2}3]+. At m/z 542 another similar
multiplet is found, that corresponds to the loss of the
protonated ligand ꢀNNHCOꢀC6H4ꢀNO2. The addi-
1
tional proton is not found in the H NMR spectrum of
the complex, therefore it is gained in the ionization
process; these proton additions are common when the
FAB-Nibeol ionization technique is used [19].
Fig. 2. Molecular structure of [Mo(NNꢀCOꢀC6H4ꢀNO2)(S2CN(C2H5)2)3] (2).

P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
2333
Table 3
from the plane through Mo1, S3, S4, S5 and S6. The
MoS2CNC2 fragment from the diethyldithiocarbamato
coligands is nearly planar as expected, and the bond
distances lie in the expected ranges [9,20]. The
MoꢀN5ꢀN4 group is nearly linear (175.4(9)°) indicating
extensive electronic delocalization i.e., the MoꢀN and
NꢀN have double bond character or, in terms of the
valence bond model, the N bound to Mo has sp
hybridization. The MoꢀN and NꢀN bond lengths
Crystal data for [Mo(NNꢀCOꢀC6H4ꢀNO2)(S2CN(C2H5)2)3] (2)
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
C22H34MoN6O3S6·0.5C4H8O
754.9
0.05×0.25×0.50
monoclinic
P21/a
,
a (A)
10.546(5)
27.084(14)
12.251(6)
90
110.78(4)
90
3437(3)
4
1.46
7.8
1560
23
−115h511, 05k529,
05l513
4786
4786
[I\2|(I)] 3247
372
,
b (A)
,
c (A)
,
(1.756(5) and 1.278(7) A, respectively), are consistent
h (°)
i (°)
k (°)
with this character. Unfortunately, from X-ray studies
it is not possible to establish whether the binding occurs
as diazenido(1-) or hydrazido(2-), since comparison of
bond lengths and angles (MoꢀNꢀNꢀR1 or 2 fragment)
for this ligands in similar compounds (Table 5) indi-
cates that these values are within the same range.
However, the double character of the MoꢁN and NꢁN
bonds is certain. There is a noticeable difference be-
tween these values and those observed for the hy-
drazido(1-) complexes, MoꢀNHꢀNR2, where the MoꢀN
and NꢀN bonds are single in character as indicated by
3
,
V (A )
Z
Dcalc (g cm−3
)
v (cm−1
F(000)
qmax
)
hkl range
Reflections collected
Reflections unique
Reflections observed
Parameters
R1 (for observed data only)
wR2 (for all data)
,
the longer distances (1.95 and 1.38 A, respectively), and
smaller MoꢀNꢀN angles (between 120 and 140°).
0.051
0.124
Largest difference peak and hole
+0.6; −0.6
−3
,
(e A
)
4. Conclusions
In the compounds prepared in this work, we found
that bis(dialkyldithiocarbamato)-dioxocomplexes react
with p-nitrobenzohydrazide and benzohydrazide to
yield always seven-coordinate complexes, in which one
oxo ligand is substituted by a hydrazide independently
of the molar ratios of the hydrazide used, and the other
oxoligand is substituted by an additional dialkyldithio-
carbamato, even when this coligand is not added in the
condensation reaction.
The aroyl hydrazines used in this work act as
monodentate ligands, differently from the behavior re-
ported for rhenium with phosphines as coligands, where
the aroyl hydrazine preferentially coordinates in a di-
dentate fashion.
Table 4
Selected bond lengths (A) and angles (°) for [Mo(NNꢀCOꢀ
C6H4ꢀNO2)(S2CN(C2H5)2)3] (2)
Mo(1)ꢀN(5)
Mo(1)ꢀS(2)
Mo(1)ꢀS(5)
Mo(1)ꢀS(3)
Mo(1)ꢀS(6)
Mo(1)ꢀS(4)
Mo(1)ꢀS(1)
C(16)ꢀC(22)
C(22)ꢀO(1)
C(22)ꢀN(4)
N(4)ꢀN(5)
1.756(5)
2.490(2)
2.516(2)
2.522(2)
2.527(2)
2.531(2)
2.576(2)
1.513(9)
1.208(8)
1.382(9)
1.278(7)
Benzohydrazide and p-nitrobenzohydrazide have dif-
ferent behavior, the former gives ligands of hy-
drazido(2-) type while the latter, ligands of
diazenido(1-) type. A plausible explanation for this
difference is that when the ꢀNO2 group is present,
electron density is withdrawn from the nitrogen atom
and therefore the NꢀH bond is unstable. Molybdenum
is reduced in this reactions, but the oxidation state of
the metal is different in each ligand, thus Mo(V) com-
plexes are obtained starting from Mo(VI) and benzohy-
drazide, while Mo(V) complexes are formed from
p-nitrobenzohydrazide.
N(5)ꢀMo(1)ꢀS(2)
N(5)ꢀMo(1)ꢀS(5)
N(5)ꢀMo(1)ꢀS(3)
N(5)ꢀMo(1)ꢀS(6)
N(5)ꢀMo(1)ꢀS(4)
N(5)ꢀMo(1)ꢀS(1)
S(2)ꢀMo(1)ꢀS(1)
S(5)ꢀMo(1)ꢀS(1)
S(3)ꢀMo(1)ꢀS(1)
S(6)ꢀMo(1)ꢀS(1)
S(4)ꢀMo(1)ꢀS(1)
O(1)ꢀC(22)ꢀN(4)
O(1)ꢀC(22)ꢀC(16)
N(4)ꢀC(22)ꢀC(16)
N(5)ꢀN(4)ꢀC(22)
N(4)ꢀN(5)ꢀMo(1)
96.26(18)
101.27(18)
98.86(18)
90.51(17)
91.00(17)
166.11(17)
69.86(6)
90.11(7)
2.10(6)
86.33(7)
85.22(7)
125.1(7)
121.6(7)
113.3(6)
116.0(6)
174.9(5)
The study of IR spectra of the diazenido(1-) and
hydrazido(2-) complexes, supported by the results of X
1
ray diffraction and H and 13C NMR allows to make a

2334
P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
.
Table 5
Complex
MoꢀN
NꢀN
NꢀC
MoꢀNꢀN
NꢀNꢀC
Reference
Diazenido (1-)
[Mo(NCO2Et)(dtc)3]
1.732(5)
1.770(6)
1.781(4)
1.765(9),
1.776(9)
1.274(7)
1.262(9)
1.233(6)
1.268(13),
1.256(13)
1.382(10)
1.410(10)
1.417(7)
1.421(15),
1.400(14)
178.9(5)
170.6(6)
171.5(4)
170.0(9),
171.2(8)
117.0(6)
117.9(7)
120.5(5)
118.0(1.0),
117.8(1.0)
118.0(32),
120.5(28)
120.3(14),
118.8(15)
111.9(8) b
[21]
[22]
[23]
[23]
[Mo(NNC6H4-3-NO2)(S2CNMe2)3]
[Mo(NNPh)(dmdtc)3],CH2Cl2
[Mo{NNC6H4(m-NO2)}(dmdtc)3]2,
1/2CH2Cl2, 1/2H2O
[Mo(NNC6H4Me-p)2(acac)2]
1.80(3), 1.75(3) 1.27(3), 1.31(3) 1.37(4), 1.45(4) 176.0(28),
[10]
[10]
[24]
177.8(25)
1.80(2), 1.75(2) 1.24(2), 1.23(2) 1.45(2), 1.44(2) 176.8(14),
174.9(13)
[Mo(NNC6H4OMe)2(acac)2]
[Mo(PPh3)(N aNCOPh)
1.785(8) b
1.29(1) b
1.40(1) b
171.0(6) b
b(N aNCO aPh)(C10H11N2O)]
Hidrazido (2-)
[Mo(NNMePh)(NHNMePh)-
1.752(10)
1.799(8)
1.74(1)
1.285(14)
1.288(10)
1.31(1)
169.6(7)
168.0(7)
[25]
[26]
[27]
(S2CNMe2)2]+
[Mo(NnMe2)O(S2CNMe2)2]
1.485(13),
1.529(12)
121.9(8),
117.3(9)
118.8(5),
118.7(7)
118, 116
118.3(3),
119.5(5)
118.7(5),
120.2(5)
120(1)
[Mo(NNPh2)2(S2CNMe2)2]
1.43(1), 1.45(1) 169.9(8)
[Mo(NNEtPh)(S2CN(CH2)5)3]+
[MoO(NNMePh)(acac)2]
1.715(16)
1.789(3)
1.37(2)
1.281(4)
170(2)
[28]
[29]
1.468(4),
1.419(4)
1.466(8),
1.423(6)
1.505(17)
175.6(2)
165.5(4)
174(1)
[{MoO(NNMePh)(acac)(m-OPr-n)}2]
1.780(4)
1.292(6)
[29]
[30]
[MoI(NNHC8H17)(dppe)2]+
1.801(11)
1.259(14)
c
Hidrazido (1-)
[Mo(NHNPh2) c(NNPh2) d(acac)-
Cl2]
1.948(5) c
1.752(4) d
1.359(6) c
1.313(6) d
1.339(3) e
1.301(3) f
1.412(7),
1.432(7) c
1.433(7) d
140.5(4) c
171.9(4) d
142.9(2) e
173.8(2) f
119.4(5),
118.7(5) c
118.1(4),
118.4(4) d
117.9(3),
118.7(3) e
116.9(2),
120.3(2) f
[11]
[11]
[Mo(NHNMePh) e(NNMePh) f(acac)- 1.948(2) e
Cl2]
1.443(4),
1.416(4) e
1.460(4),
1.419(4) f
1.750(2) f
a Coordinated atoms.
b Values correspond to this part of molecule.
c Values correspond to this part of molecule.
d Values correspond to this part of molecule.
e Values correspond to this part of molecule.
f Values correspond to this part of molecule.
conclusive assignment of w(CꢁO) and w(NꢁN) vibra-
tions, which in turn allows to establish the type of
binding of the hydrazines as mono o didentate.
A singular behavior is observed for the dialkyldithio-
carbamato coligands, since the number of these in the
complexes successively increases in each step of the
syntheses.
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
Acknowledgements
This work has been supported by COLCIENCIAS
and the Universidad Nacional de Colombia. The au-
thors also gratefully acknowledge the DAAD–Ger-
many for the financial support given to Dr Poveda for
a three-month visit to Heidelberg Universita¨t, where
most of the analyses were made.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 137508. Copies of this infor-
mation may be obtained free of charge from: The

P.C. Ri6eros et al. / Polyhedron 19 (2000) 2327–2335
2335
.
References
[15] A. Nakamura, M. Nakayama, K. Sugihashi, S. Otsuka, Inorg.
Chem. 18 (1979) 394.
[1] M. Hirano, M. Akita, T. Morikita, H. Kubo, A. Fukoka, S.
Komiya, J. Chem. Soc., Dalton Trans. (1997) 3453.
[2] G.L. Leigh, Acc. Chem. Res. 254 (1992) 177.
[3] J. Chatt, G.A. Heath, G.J. Leigh, J. Chem. Soc., Chem. Commun.
(1972) 444.
[4] M. Hidai, Y. Mizobe, Chem. Rev. 95 (1995) 1115.
[5] See Table 5.
[6] J. Chatt, J.R. Dilworth, G.J. Leigh, V.D. Gupta, J. Chem. Soc.
A (1971) 2631.
[7] G.M. Sheldrick, SHELXL-86, Program for the solution of crystal
structure, University of Go¨ttingen, 1986
[8] G.M. Sheldrick, SHELXL-97, Program for the refinement of crystal
structure, University of Go¨ttingen, 1997.
[9] A.G. Sykes, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty
(Eds.), Comprehensive Coordination Chemistry, Pergamon Press,
Oxford, 1987, p. 1229.
[10] M.W. Bishop, G. Butler, J. Chatt, J.R. Dilworth, G.J. Leigh, J.
Chem. Soc., Dalton Trans. (1979) 1843.
[16] M. Decoster, F. Conan, J.E. Guerchais, Y. Le Mest, J. Sala Pala,
Polyhedron 14 (1995) 1741.
[17] J. Yang, J. Cryst. Spectr. Res. 19 (1989) 929.
[18] T.C. Hsieh, J.A. Zubieta, Polyhedron 5 (1986) 305.
[19] M. Barber, R.S. Bardoli, G.J. Elliot, R.D. Sedgwick, A.N. Taylor,
Anal. Chem. 54 (1982) 645A.
[20] J.M. Berg, K.O. Hodgson, Inorg. Chem. 19 (1980) 2180.
[21] G. Butler, J. Chatt, W. Hussain, G.J. Leigh, Inorg. Chim. Acta
30 (1978) L287.
[22] G. Butler, J. Chatt, G.J. Leigh, A.R.P. Smith, G.A. Williams,
Inorg. Chim. Acta 28 (1978) L165.
[23] G.A. Williams, A.R.P. Smith, Aust. J. Chem. 33 (1980) 717.
[24] E. Uhlemann, E. Ludwig, W. Banße, F. Weller, Z. Anorg. Allg.
Chem. 620 (1994) 955.
[25] J. Chatt, J.R. Dilworth, P.L. Dahlstrom, J. Zubieta, J. Chem. Soc.,
Chem. Commun. (1980) 786.
[26] M.W. Bishop, J. Chatt, J.R. Dilworth, M.B. Hursthouse, M.
Motevalli, J. Chem. Soc., Dalton Trans. (1979) 1600.
[27] J. Chatt, B.A.L. Crichton, J.R. Dilworth, P. Dahlstrom, R.
Gutkoska, J.A. Zubieta, Transition Met. Chem. 4 (1979) 271.
[28] F.C. March, R. Mason, K.M. Thomas, J. Organomet. Chem. 96
(1975) C43.
[11] F.W. Moore, M.L. Larson, Inorg. Chem. 6 (1967) 998.
[12] J. Li-Kao, C. Bustos, D. Carrillo, F. Robert, P. Gouzerh,
Transition Met. Chem. 18 (1993) 265.
[13] C. Bustos, C. Manzur, D. Carrillo, F. Robert, P. Gouzerh, Inorg.
Chem. 33 (1994) 1427.
[29] D. Carrillo, F. Robert, P. Gouzerh, Inorg. Chim. Acta 197 (1992)
209.
[14] J. Chatt, B.A. Crichton, J.R. Dilworth, P. Dahlstrom, R.
Gutkoska, J. Zubieta, Inorg. Chem. 21 (1982) 2383.
[30] V.W. Day, T.A. George, S.D.A. Iske, Jr., S.D. Wagner, J.
Organomet. Chem. 112 (1976) C55.