Dithiolate-hydrazido(2-) molybdenum complexes: Synthesis and structure

Article abstract of DOI:10.1016/S0020-1693(03)00051-3

Reaction of [MoO₂(acac)₂] with an excess of X(CH ₂CH₂SH)₂ where X=O, S leads to the formation of mononuclear complexes [MoO₂{X(CH₂CH₂S) ₂}]: (1a) for X=O and (1b) for X=S. The complexes 1a and 1b react with organohydrazines in methanol, MeCN or THF to give the family of hydrazido(2-)-oxo-molybdenum compounds [MoO(NNRR′){X(CH₂CH ₂S)₂}]: (2a) for R=R′=Me and X=O; (2b) for R=R′=Me and X=S; (2c) for R=Me, R′=Ph and X=O; (2d) for R=Me, R′=Ph and X=S. Similar reaction carried out in CH₂Cl ₂ with an excess of NH₂NMe₂ leads to the formation of 2a and hydrazinium salt [NH₂N(CH₂Cl)Me ₂]Cl consisting of tetrahedral cations bonded by hydrogen bonds to chloride ions as shown by X-ray studies. The X-ray crystal structures of 2a and 2b have been determined. These molecules have a distorted trigonal bipyramidal configuration with the hydrazido(2-) ligand bonded linearly in a trans position to either the ether oxygen or the thioether sulfur atoms of the dithiolate ligand. Me₃SiCl causes abstraction of the oxo group in 2a-2d to create the six-coordinate compounds [MoCl₂(NNRR′){X(CH ₂CH₂S)₂}] (3a-3d), respectively. The chlorides in 3d can be easily substituted by oxygen and nitrogen donor ligands to give the new compounds [Mo(di-t-Bu-cat)(NNRR′){X(CH₂CH ₂S)₂}] (4) and [Mo(NNRR′)₂{X(CH ₂CH₂S)₂}] (5), respectively.

Full text of DOI:10.1016/S0020-1693(03)00051-3

Inorganica Chimica Acta 350 (2003) 379ꢀ386
/
www.elsevier.com/locate/ica
Dithiolateꢀ
/
hydrazido(2-) molybdenum complexes:
synthesis and structure
Zofia Janas a, Lucjan B. Jerzykiewicz a, Raymond L. Richards b, Piotr Sobota a,*
a Faculty of Chemistry, University of Wroc law, 14 F. Joliot-Curie Street, PL-50383 Wroc law, Poland
b Department of Chemistry, Physics and Environment Studies, University of Sussex, Brighton BN1 9RQ, UK
Received 5 July 2002; accepted 30 September 2002
Dedicated in honor of Professor Pierre Braunstein
Abstract
Reaction of [MoO2(acac)2] with an excess of X(CH2CH2SH)2 where Xꢁ
[MoO2{X(CH2CH2S)2}]: (1a) for XꢁO and (1b) for XꢁS. The complexes 1a and 1b react with organohydrazines in methanol,
MeCN or THF to give the family of hydrazido(2-)-oxo-molybdenum compounds [MoO(NNRR?){X(CH2CH2S)2}]: (2a) for Rꢁ
R?ꢁMe and XꢁO; (2b) for RꢁR?ꢁMe and XꢁS; (2c) for RꢁMe, R?ꢁPh and XꢁO; (2d) for RꢁMe, R?ꢁPh and XꢁS.
/
O, S leads to the formation of mononuclear complexes
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Similar reaction carried out in CH2Cl2 with an excess of NH2NMe2 leads to the formation of 2a and hydrazinium salt
[NH2N(CH2Cl)Me2]Cl consisting of tetrahedral cations bonded by hydrogen bonds to chloride ions as shown by X-ray studies. The
X-ray crystal structures of 2a and 2b have been determined. These molecules have a distorted trigonal bipyramidal configuration
with the hydrazido(2-) ligand bonded linearly in a trans position to either the ether oxygen or the thioether sulfur atoms of the
dithiolate ligand. Me3SiCl causes abstraction of the oxo group in 2aꢀ
/
2d to create the six-coordinate compounds
[MoCl2(NNRR?){X(CH2CH2S)2}] (3aꢀ3d), respectively. The chlorides in 3d can be easily substituted by oxygen and nitrogen
/
donor ligands to give the new compounds [Mo(di-t-Bu-cat)(NNRR?){X(CH2CH2S)2}] (4) and [Mo(NNRR?)2{X(CH2CH2S)2}] (5),
respectively.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Molybdenum; Thiolate ligands; Hydrazido(2-) complexes; X-ray crystallography
1. Introduction
able to bind small molecules is of great importance in
understanding the mode of action of this enzyme.
Hydrazido(2-) complexes are plausible intermediates
in the protonation of ligating dinitrogen to ammonia [1].
They may also be involved in the process catalysed by
nitrogenase enzymes [2], in which the cofactor FeMco
The interaction of complexes possessing
molybdenumꢀthiolate core with organohydrazine has
been extensively investigated by Chatt, Zubieta, Dil-
worth and coworkers [7ꢀ15]. Recently a rich chemistry
a
/
/
of the molybdenum [16] and vanadium [17,18] with the
tripodal sulfur-donor ligand N(CH2CH2S)33ꢂ has been
developed. It proved the ability of Mo and V carrying
this ligand to bind species such as N2H, N2H2 and N2H4
and their derivatives. Similar trend has been demon-
(Mꢁ
/
Mo, V, Fe) has been considered the site respon-
sible for the conversion of N2 into NH3 [3ꢀ
/5]. The X-ray
crystallography showed FeMoco to contain an MoFe7S9
cluster with the Mo atom ligated by one histidine
nitrogen, three sulfides and two oxygen atoms from
homocitrate [6]. Research on the coordination chemistry
of molybdenum complexes as models which mimic the
molybdenum centre (MoS3O2N) in nitrogenase and are
strated for
V
with the tridentate dithiolate
O(CH2CH2S)22ꢂ [18].
As part of this continuing investigation, we report
here
[MoO2{X(CH2CH2S)2] (Xꢁ
drazines. The crystal structures of [MoO(N-
NMe2)({X(CH2CH2S)2}] (2a) for XꢁO and (2b) for
the
synthesis
and
reactivity
of
/
O, S) towards organohy-
* Corresponding author. Fax: ꢃ
E-mail address: plas@wchuwr.chem.uni.wroc.pl (P. Sobota).
/48-71-328 2348.
/
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00051-3

380
Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ386
/
Xꢁ
/
S and the substitution reactions of the oxo group by
to that used to prepare 1a. Elemental analysis: Anal.
Found: C, 17.0; H, 2.8; S, 33.5. Calc. for C4H8O2S3Mo:
C; 17.1; H, 2.9; S, 34.3%. IR (Nujol mulls, cmꢂ1):
chloride, catecholate and imide ligands are also de-
scribed.
n(MoÄ/O) 948(s), 912(s).
2. Experimental
2.5. Preparation of [MoO(NNMe2){O(CH2CH2S)2}]
(2a) and [NH2N(CH2Cl)Me2]Cl
2.1. General procedures
2.5.1. Method (a)
All operations were carried out under a dry dinitrogen
atmosphere, using standard Schlenk techniques. All the
solvents were distilled under dinitrogen from the appro-
priate drying agents prior to use. The compounds
[MoO2(acac)2] [19] and [MoO(NNMePh)(acac)2] [20]
were prepared by literature methods. The sodium salt
of 2,5-di-tert-butylcatechol Na2(di-t-Bu-cat) was pre-
pared by treating it with NaH in THF. All other starting
materials were obtained from the Aldrich chemical Co.
and used without further purification unless stated
A suspension of 1a (1.38 g, 5.2 mmol) and NH2NMe2
(0.31 g, 5.2 mmol) in MeCN (50 ml) was heated under
refluxed for 6 h. The resulting mixture was filtered from
a brown solid (which was characterised as the unreacted
substrate), to give an orangeꢀred solution. This was
/
concentrated to about 10 ml in vacuum then allowed to
stand overnight at r.t., whereupon yellow crystals
suitable for X-ray analysis deposited. Yield 23%. Ele-
mental analysis: Anal. Found: C, 23.2; H, 4.3; N, 9.0; S,
19.7. Calc. for C6H14O2N2S2Mo: C; 23.5; H, 4.6; N, 9.2;
otherwise. Infrared spectra were recorded on
a
S, 21.0%. IR (Nujol mulls, cmꢂ1): n(MoÄ
/O) 920(s).
PerkinꢀElmer 180 spectrophotometer in Nujol mulls.
/
NMR spectra were performed on a Bruker ARX 300E
spectrometer. Microanalysis were conducted with a
ASA-1 (GDR, Karl-Zeiss-Jena) instrument (in-house).
2.5.2. Method (b)
The compound NH2NMe2 (0.21 g, 3.5 mmol) was
added dropwise to a stirred suspension of [MoO(N-
NMe2)(acac)2] (1.29 g, 3.5 mmol) in MeOH (30 ml) and
the mixture was stirred for 14 h. The resulting micro-
crystalline yellow solid was filtered off, washed with
methanol, recrystallized from hot acetonitrile and dried
in vacuum. Yield 96%.
2.2. Preparation of [MoO(NNMe2)(acac)2]
This compound was prepared by identical procedure
to that reported in reference [20]. To a stirred suspension
of [MoO2(acac)2] (5.54 g, 17 mmol) in dry methanol (50
ml) was added NH2NMe2 (1.02 g, 17 mmol). The
reaction mixture was stirred for 24 h at room tempera-
ture (r.t.). The resulting light orange precipitate was
filtered off and washed with methanol and diethyl ether
and dried in vacuum. Yield 97%. Elemental analysis:
Anal. Found: C, 38.5; H, 5.3; N, 7.3. Calc. for
C12H20N2O5Mo: C; 39.1; H, 5.5; N, 7.6%. IR (Nujol
2.5.3. Method (c)
To a stirred suspension of [MoO2{O(CH2CH2S)2}]
(3.29 g, 1.24 mmol) in CH2Cl2 (50 ml) was added
NH2NMe2 (5 ml, 6.6 mmol). After stirring for 48 h at
r.t. a light-brown crude [NH2N(CH2Cl)Me2]Cl precipi-
tated from a dark brown solution. It was filtered off,
washed with CH2Cl2, recrystallized from hot MeCN and
dried in vacuo. Yield 22%. Elemental analysis: Anal.
Found: C, 24.5; H, 6.9; Cl, 48.0; N, 19.3. Calc. for
C3H10N2Cl2: C; 24.8; H, 7.0; Cl, 48.9; N, 19.3%. IR
mulls, cmꢂ1): n(MoÄ
/
O) 942(s).
2.3. Preparation of [MoO2{O(CH2CH2S)2}] (1a)
(Nujol mulls, cmꢂ1): n(NÃ
/
H) 3258(s), 1582(m).
A suspension of [MoO2(acac)2] (2.4 g, 7.37 mmol) and
O(CH2CH2SH)2 (1.02 g, 7.37 mmol) in methanol (30 ml)
was stirred for approximately 10 h, during which time
the brick-brown solid precipitated. It was filtered off,
washed with methanol, diethyl ether and dried under
vacuum. Yield 43%. Elemental analysis: Anal. Found:
C, 18.2; H, 3.0; S, 23.7. Calc. for C4H8O3S2Mo: C; 18.2;
The dark brown filtrate was evaporated to dryness
and washed with Et2O to give, after recrystallisation,
light yellow crystals of [MoO(NNMe2){O(CH2CH2S)2}]
(2a). Yield 61.4%.
2.6. Preparation of [MoO(NNMe2){S(CH2CH2S)2}]
(2b), [MoO(NNMePh){O(CH2CH2S)2}] 2c,
[MoO(NNMePh){S(CH2CH2S)2}] (2d)
H, 3.1; S, 24.3%. IR (Nujol mulls, cmꢂ1): n(MoÄ
/O)
948(s), 912(s).
These compounds were obtained by identical proce-
dure to route 2.3(b) using appropriate quantities of
[MoO(NNMe2)(acac)2] or [MoO(NNMePh)(acac)2] and
dithiol. Elemental analysis for: [MoO(NNMe-
Ph){O(CH2CH2S)2}]: Anal. Found: C, 35.2; H, 4.3; N,
7.2; S, 17.0. Calc. for C11H16O2N2S2Mo: C; 35.9; H, 4.4;
2.4. Preparation of [MoO2{S(CH2CH2S)2}] (1b)
This compound was obtained in 39% yield as a
burgundyꢀred solid from appropriate quantities of
[MoO2(acac)2] and S(CH2CH2SH)2 by a method similar
/

Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ
/386
381
N, 7.6; S, 17.4%. IR (Nujol muls, cmꢂ1): n(MoÄ
[MoO(NNMe2){S(CH2CH2S)2}]: Anal. Found: C, 22.0;
H, 4.3; N, 8.2; S, 29.0. Calc. for C6H14ON2S3Mo: C;
22.4; H, 4.4; N, 8.7; S, 29.8%. IR (Nujol muls, cmꢂ1):
/
O) 922;
2.9. Preparation of [Mo(NNMePh)2{O(CH2CH2S)2}]
(5)
To a suspension of 3a (1.35 g, 3.73 mmol) in MeCN
(50 ml) was added NH2NMe2 (0.22 g, 3.73 mmol). After
stirring for 24 h an orange solid was isolated by
filtration, washed with MeCN, Et2O and dried in vacuo.
Yield 78%. Elemental analysis: Anal. Found: C, 27.1; H,
5.6; N, 15.8; S, 17.5. Calc. for C8H20ON4S2Mo: C; 27.6;
H, 5.8; N, 16.1; S, 18.4%.
n(MoÄ
/
O)
918;
Anal. Found: C, 34.0; H, 4.3; N, 7.0; S, 24.2. Calc. for
[MoO(NNMePh){S(CH2CH2S)2}]:
C11H16ON2S3Mo: C; 34.4; H, 4.2; N, 7.3; S, 25.0%. IR
(Nujol muls, cmꢂ1): n(MoÄ
/
O) 921.
2.7. Preparation of
[MoCl2(NNMe2){O(CH2CH2S)2}] (3a),
[MoCl2(NNMePh){O(CH2CH2S)2}] (3b) and
[MoCl2(NNMePh){S(CH2CH2S)2}] (3c)
2.10. Crystal structure determinations
Crystal data collection and refinement are summar-
ized in Table 1. Preliminary examination and intensity-
data collections were carried out on a Kuma KM-4 k-
axis diffractometer with graphite-monochromated Mo
Ka and with scintillation counter or CCD camera. All
data were corrected for Lorentz and polarization effects.
Data reduction and analysis were carried out with the
Kuma Diffraction programs [21,22]. The structures were
solved by direct methods [23] and refined by the full-
matrix least-squares method on all F2 data using the
SHELXL-97 software [24]. After refinement with isotropic
displacement parameters for all atoms, absorption
To a solution of 2a (1.05 g, 3.4 mmol) in THF was
added Me3SiCl (0.74 g, 7.0 mmol) via a syringe to afford
an intense green solution. The reaction mixture was
stirred for 24 h during which time a dark-green solid
precipitated. It was filtered off, washed with THF and
dried under vacuum. Yield 87%. Elemental analysis for
[MoCl2(NNMe2){O(CH2CH2S)2}] (3a): Anal. Found:
C, 19.8; H, 3.7; Cl, 19.2; N, 7.5; S, 17.2. Calc. for
C6H14ON2S2Cl2Mo: C; 20.0; H, 3.9; Cl, 19.6; N, 7.8; S,
17.8%. IR (Nujol mulls, cmꢂ1): n(MoÃ
[MoCl2(NNMePh){O(CH2CH2S)2}]
[MoCl2(NNMePh){S(CH2CH2S)2}] (3c) were prepared
/Cl) 366, 304.
(3b) and
correction based on least-squares fitted against jFcjꢂ
/
jFoj differences was also applied [25] to the data for
structure 2a and 2b. Carbon bonded hydrogen atoms
were included in calculated positions and refined in the
riding mode using SHELXL-97 default parameters. Other
hydrogen atoms were located in a difference map and
refined freely. All non-hydrogen atoms were refined
with anisotropic displacement parameters.
by an identical procedure in approximately 80% yield.
Elemental
analysis
for
[MoCl2(NNMe-
Ph){O(CH2CH2S)2}] (3c): Anal. Found: C, 30.9; H,
3.78; Cl, 16.1; N, 6.4; S, 14.9. Calc. for C11H16ON2-
S2Cl2Mo: C; 31.2; H, 3.8; Cl, 16.8; N, 6.6; S, 15.5%. IR
(Nujol mulls, cmꢂ1): n(MoÃ
[MoCl2(NNMePh){S(CH2CH2S)2}]
/
Cl) 364(m), 302(m).
(3d):
Anal.
Found: C, 30.0; H, 3.7; Cl, 15.9; N, 6.4; S, 19.9. Calc.
for C11H16N2S3Cl2Mo: C; 30.1; H, 3.7; Cl, 16.1; N, 6.4;
3. Results and discussion
S, 21.9%. IR (Nujol mulls, cmꢂ1): n(MoÃ
305(m).
/
Cl) 366(m),
The molybdenum(VI) complexes MoO2L, Lꢁthio-
/
lates are usually synthesised by either of two possible
routes: (1) reaction of [MoO2(acac)2] with the appro-
2.8. Preparation of [Mo(di-t-Bu-
cat)(NNMePh){S(CH2CH2S)2}] (4)
priate ligand or (2) reaction of Na2MoO4×
/
2H2O with a
stoichiometric amount of the ligand [26]. In our
investigation the route (1) appeared to be the most
convenient to reach the research aim summarised in
Scheme 1. The reaction of [MoO2(acac)2] with an excess
of X(CH2CH2SH)2 in MeOH yielded diamagnetic
To a suspension of 3c (0.83 g, 1.9 mmol) in THF (30
ml) was added Na2(di-t-Bu-cat) [generated in situ from
H2(di-t-Bu-cat) (0.42 g, 1.9 mmol) and NaH (0.1 g, 3.8
mmol) in THF]. After stirring for 24 h the solvent was
removed in vacuo to give a dark oil, which was solidified
by stirring with n-hexane. The solid was filtered, washed
with n-hexane and extracted with CH2Cl2 to separate
the product from LiCl. The extract was layered with n-
hexane and allowed to stand for 2 days at r.t. to afford
microcrystalline
[MoO2{X(CH2CH2S)}], which are redꢀ
O (1a) and burgundyꢀred for XꢁS (1b). These com-
solids
of
formula
/
brown for Xꢁ
/
/
/
plexes are air sensitive as the solid; they are insoluble
except sparingly and with fast (few hours) decomposi-
tion in dimethyl sulfoxide. Their IR spectra exhibit the
characteristic bands at approximately 910 and 950 cmꢂ1
due to the molybdenum-terminal oxygen vibrations
the greenꢀbrown crystalline product. Yield 61%. Ele-
/
mental analysis: Anal. Found: C, 49.2; H, 5.8; N, 4.7.
Calc. for C25H36N2O2S3Mo: C; 51.0; H, 6.2; N, 4.8; S,
16.3%.
n(MoÄ
/
O) and agree with those observed for mono-
nuclear
MoO2(L), Lꢁ
/

382
Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ386
/
Table 1
Crystal data and structure refinement for 2a, 2b and [NH2N(CH2Cl)Me2]Cl
Compound
2a
2b
[NH2N(CH2Cl)Me2]Cl
C3H10Cl2N2
145.03
Chemical formula
Formula weight
Crystal color; habit
Crystal size (mm)
Space group
C6H14MoN2O2S2
306.25
yellow, block
C6H14MoN2OS3
322.31
yellow, block
colorless, plate
0.5ꢄ
P21/n
/
0.5ꢄ
/0.5
0.4ꢄ
P21/c
/
0.4ꢄ
/0.3
0.4ꢄ
/
0.4ꢄ0.2
/
P21/n
Crystal system
˚
monoclinic
7.036(3)
20.480(4)
7.748(3)
93.80(4)
1114.0(7)
4
monoclinic
13.725(3)
7.219(2)
11.863(3)
101.46(8)
1152.0(5)
4
monoclinic
7.052(1)
10.527(3)
8.792(2)
90.49(3)
652.7(3)
4
a (A)
˚
b (A)
˚
c (A)
b (8)
3
V (A )
˚
Z
Dcalc (g cmꢂ3
F(000)
)
1.826
616
1.858
648
1.476
304:0
m (mmꢂ1
)
1.525
semi-empirical
1.648
semi-empirical
0.880
none
Absorption correction
Max. and min. transmission
Diffractometer
0.982 and 0.791
KM-4 four circle k-geometry
Mo Ka, 0.71073
0.8472 and 0.5151
Kuma KM-4 CCD k-geometry
Mo Ka, 0.71073
v
Kuma KM-4 CCD k-geometry
Mo Ka, 0.71073
v
˚
Radiation type, l (A)
Data collection method
T (K)
v ꢀ
100(1)
2.82ꢀ25.06
total: 1931; unique 1858
Rint 0.0146
1784 [I ꢀ2s(I)]
R1ꢁ0.0206, wR2ꢁ
R1ꢁ0.0219, wR2ꢁ
1.195
0.534 and ꢂ
/2u
100(1)
100(1)
uRange (8)
Number of reflections measured
/
3.50ꢀ
total: 6993; unique: 2654
Rint 0.0539
2454 [I ꢀ2s(I)]
R1ꢁ0.0372, wR2ꢁ
R1ꢁ0.0408, wR2ꢁ
1.095
0.768 and ꢂ
/
28.37
3.48ꢀ
total: 4217; unique: 1542
Rint 0.0338
1322 [I ꢀ2s(I)]
R1ꢁ0.0335, wR2ꢁ
R1ꢁ0.0468, wR2ꢁ
1.104
0.247 and ꢂ
/
28.40
ꢁ/
ꢁ/
ꢁ/
Number of observed reflections
Final R indices [F2ꢀ
/
/
/
/
4s(Fo2)] a,b
/
/
0.0542
0.0558
/
/
0.0974
/
/
0.0623
R indices (all data) a,b
/
/
/
/0.1002
/
/0.0658
Goodness-of-fit (S)
˚
Largest difference peak and hole (e A
ꢂ3
)
/
0.556
/1.034
/0.294
a
R1ꢁ
wR2ꢁ
/
SjjFojꢂ
/
jFcjj/SjFoj.
b
/
{S[w(Fo2ꢂ
/
Fc2)2]/S[w(Fo2)2]}1/2
.
(SCH2CH2NMe(CH2)nNMeCH2CH2S)2ꢂ, nꢁ
[27]. No MoÃOÃMo bridge absorptions at approxi-
mately 740 and 440ꢀ
495 cmꢂ1 were detected for 1a and
1b, characteristic for an Mo2O34ꢃ core in [Mo2(m-
O)2(O)2{X(CH2CH2S)2}2] (XꢁO, S), which was ob-
/
2 or 3
2a and 2b have essentially distorted trigonal bipyramidal
geometry with the two sulfur-donor ligands and the oxo
group in the trigonal plane and the hydrazido(2-) ligand
trans to the apical ether oxygen (2a) or thioether sulfur
/
/
/
/
(2b) of the thiolate ligands. The short MoÃ
/
N and NÃ
/N
tained via route (2) by Zubieta et al. [28].
˚
bond distances of 1.79(2) and 1.276(3) A for 2a and
Upon treatment with NH2NRR? in MeOH or MeCN,
THF, complexes 1 give a family of hydrazido(2-)
compounds [MoO(NNRR?){X(CH2CH2S)2}] where
˚
1.824(3) and 1.271(4) A for 2b, respectively, together
with the MoÃ
/
NÃ
/
N bond angles of 169.7(2) for 2a and
163.2(2) for 2b are in normal range for five-coordinate
Rꢁ
/
R?ꢁ
/
Me, Xꢁ
/
O (2a); Rꢁ
/
R?ꢁ
/
Me, Xꢁ/S (2b);
hydrazido(2-) complexes of this type e.g., [MoO(N-
Rꢁ
/
Me, R?ꢁ
/
Ph, Xꢁ
/
O (2c); Rꢁ
/
Me, R?ꢁ
/
Ph, XꢁS
/
NMe2)(SPh)3}]ꢃ has MoÃ
/
N and NÃ
1.806 and 1.30 A, respectively, and MoÃ
176.78 [13] and [MoCl(NNMe2)2(PPh3)3]ꢃ has MoÃ
/
N distances of
(2d) in reasonable yields. Almost quantitative yields of
these compounds were obtained via reactions of
[MoO(NNRR?)(acac)2] with appropriate thiols (see
Scheme 1). Compounds 2a and 2b are mentioned in
[14], however, there are no details of their preparation,
˚
/
NÃN angle of
/
/N
˚
and NÃ
and MoÃ
extensive delocalisation through the MoÃ
/
N distances of 1.761 and 1.25 A, respectively,
NÃN angle of 173.98 [29]. These data indicate
NÃN unit and
/
/
/
/
crystal structures and reactivity. Only the MoÃ
/
N, NÃ
/
N
are consistent with the description of the hydrazido(2-)
˚
distances of 1.79, 1.29 A and MoÃ
/
NÃ
/
N angle of 174.38,
ligand acting as the four-electron donor to the Mo atom.
˚
S thiolate distances 2.358(2), 2.38(1) A for 2a
˚
for [MoO(NNMe2){O(CH2CH2S)2] and 1.78, 1.29 A
and 176.28 for [MoO(NNMe2){S(CH2CH2S)2}], respec-
tively, are presented. Since complexes 2a and 2b gave us
X-ray quality crystals, we have determined their struc-
tures to allow us to make more detailed comparison
with other systems as below. The structures are shown in
Figs. 1 and 2; molecular dimensions are in Table 2. Both
The MoÃ
/
˚
and 2.383(2), 2.373(1) A for 2b are close to the range of
MoÃS thiolate distances found in the related trigonal
bipyramidal complexes [MoO(N-
NHPh){O(CH2CH2S)2}] [14], and [Mo(NS3)(NNR)]
RꢁMe, Ph; NS3ꢁ
[N(CH2CH2S)]3ꢂ [16].
/
/
/

Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ
/386
383
Scheme 1.
The 1H NMR spectra at room temperature consist of
one singlet at 3.60 ppm for 2a and two singlets at 3.73
and 3.70 ppm for 2b for the methyl groups of the
dimethylhydrazido ligand. At 203 K (coalescence point)
one singlet at 3.74 ppm due to the NMe2 group is
observed for 2b. As well as these, three multiplets at
4.63, 3.57, 3.20 ppm for 2a and 4.05, 3.10, 2.15 ppm for
2b for the CH2 groups of the dithiolate ligands are
observed.
structure analysis showed the solid to be a hydrazinium
salt [NH2N(CH2Cl)Me2]Cl consisting of approximately
tetrahedral cations [NH2N(CH2Cl)Me2]ꢃ, bonded by
hydrogen bonds to chloride ions. The central nitrogen in
the cation is surrounded by one amino, two methyl and
one chloromethane groups (Fig. 3). The average angle
between the central nitrogen and the terminal atoms in
the cation equals the tetrahedral angle. The NÃ
/
N
distance of 1.460(2) A is similar to the value of 1.45(3)
˚
˚
A found for 1,1-dimethylhydrazine [30] and is in the
Attempts to prepare [MoO(NNMe2){X(CH2CH2S)2}]
from [MoO2{X(CH2CH2S)2}] and NH2NMe2 in
CH2Cl2 led after work-up to a light beige solid. IR
range of single bonds [31]. Internuclear distances and
angles are listed in Table 3. The distances between the
chloride ions and the amino hydrogens 2.42(2) and
data showed a NÃ
/
H bands at 3258 and 1582 cmꢂ1 while
the 1H NMR spectrum contained three singlet reso-
nances assigned to the CH3, CH2 and HO groups at
3.48, 5.54 and 6.54 (broad) ppm, respectively. The X-ray
2.36(2) A (Table 4) are shorter than the minimum
Hꢀ ꢀ ꢀCl nonbonded distance, indicating that both amino
˚
hydrogens form hydrogen bonds to chloride ions. The

384
Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ
/386
Table 2
˚
Selected bond distances (A) and angles (8) for (2a) and (2b)
2a
2b
Bond lengths
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
S(1)Ã
S(2)Ã
S(3)Ã
S(3)Ã
N(1)Ã
N(2)Ã
N(2)Ã
C(1)Ã
C(3)Ã
O(2)Ã
O(2)Ã
/
S(1)
S(2)
S(3)
O(1)
O(2)
N(1)
2.358(2)
2.380(1)
2.383(2)
2.373(1)
2.514(2)
1.703(2)
/
/
/
1.695(2)
2.221(2)
1.790(2)
1.820(3)
1.819(3)
/
/
1.824(3)
1.823(3)
1.824(4)
1.808(4)
1.819(3)
1.271(4)
1.465(4)
1.465(4)
1.511(4)
1.514(4)
/
C(1)
C(4)
C(2)
C(3)
/
/
/
/
N(2)
C(6)
C(5)
1.276(3)
1.453(3)
1.454(4)
1.489(4)
1.498(4)
1.451(3)
1.457(3)
/
/
/C(2)
/C(4)
/
C(3)
C(2)
/
Bond angles
Fig. 1. The molecular structure of 2a with atom numbering scheme.
The displacement ellipsoids are drawn at the 50% probability level.
S(1)Ã
S(1)Ã
S(2)Ã
O(1)Ã
O(1)Ã
O(1)Ã
O(1)Ã
O(1)Ã
O(2)Ã
O(2)Ã
N(1)Ã
N(1)Ã
N(1)Ã
N(1)Ã
MoÃN(1)Ã
/
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
/
S(2)
S(3)
S(3)
135.49(3)
130.52(4)
82.20(5)
82.34(4)
/
/
/
/
/
/
N(1)
O(2)
S(3)
S(1)
S(2)
S(1)
S(2)
107.27(11)
100.03(9)
106.58(12)
/
/
/
/
96.12(9)
114.83(9)
113.39(8)
/
/
108.35(7)
113.11(8)
78.88(6)
78.71(6)
152.62(9)
90.41(8)
92.24(8)
/
/
/
/
/
/
/
/
O(2)
S(1)
S(2)
S(3)
N(2)
/
/
88.12(9)
88.58(9)
/
/
/
/
157.30(10)
163.2(2)
/
/
169.7(2)
Fig. 2. The molecular structure of 2b with atom numbering scheme.
The displacement ellipsoids are drawn at the 50% probability level.
two hydrogen bonds H(1N)ꢀ ꢀ ꢀCl(2) and Cl(2)aꢀ ꢀ ꢀH(2N)
link the cations. This results in zigzag chains running
parallel to the [010] direction (Fig. 4). Hydrogen bonds
have also been reported in the structures of the salts of
Fig. 3. The molecular structure of [NH2N(CH2Cl)Me2]Cl with atom
numbering scheme. The displacement ellipsoids are drawn at the 50%
probability level.
hydrazinium
[CH3)3NNH2]Cl [33].
Further substitution of the oxo ligand in complexes
2aꢀ2d by either dimethyl- and methylphenylhydrazines
cations;
e.g.,
N2H6Cl2
[32],
/
or monosubstituted derivatives such as methyl- and

Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ
/386
385
Table 3
reaction pathway, in contrast to the system based on
[MoO2{(SCH2CH2)2NCH2CH2NMe2}] in which
˚
Selected bond distances (A) and angles (8) for [NH2N(CH2Cl)Me2]Cl
NH2NMePh replaces only one oxo group but
NH2NHPh forms bis[hydrazido(2-)] complex [15]. We
consider that the reactivity of oxo-molybdenum pre-
cursors depends on various factors, that include the
basicity of hydrazines, the identity of coligands which
influence profoundly the geometry of the complexes and
the overall electronic effects. Because of this the
products of the reactions are not always predictable.
Bond lengths
Cl(1)Ã
N(1)Ã
N(1)Ã
N(1)Ã
N(1)Ã
/
C(1)
1.758(2)
1.460(2)
1.494(2)
1.500(2)
1.501(2)
/
N(2)
C(3)
C(2)
C(1)
/
/
/
Bond angles
N(2)ÃN(1)Ã
N(2)ÃN(1)Ã
C(3)ÃN(1)Ã
N(2)ÃN(1)Ã
C(3)ÃN(1)ÃC(1)
C(2)ÃN(1)Ã
N(1)ÃC(1)Ã
/
/C(3)
107.60(13)
111.89(13)
110.69(14)
102.56(13)
111.37(13)
112.39(14)
111.77(12)
/
/C(2)
/
/C(2)
The replacement of the oxo group in 2aꢀ2d by two
/
/
/C(1)
chlorides occurs in reaction with an excess of Me3SiCl in
methanol to regenerate the six-coordinate compounds
/
/
/
/C(1)
[MoCl2(NNRR?){X(CH2CH2S)2}] Rꢁ
(3a); RꢁR?ꢁMe, XꢁS (3b); RꢁMe, R?ꢁ
(3c), RꢁMe, R?ꢁPh, Xꢁ
common organic solvents. The IR bands at approxi-
Cl)
/
R?ꢁ
/
Me, Xꢁ
/O
/
/Cl(1)
/
/
/
/
/
Ph, Xꢁ
/O
/
/
/S (3d), which are insoluble in
Table 4
˚
mately 360 and 300 cmꢂ1, attributed to n(MoÃ
/
Hydrogen bonds for [NH2N(CH2Cl)Me2]Cl] (A and 8)
confirm the presence of Cl ligands in the cis position,
while the absence of bands of significant intensity in the
DÃ
/
H...A
d(DÃ
/
H) d(H...A) d(D...A)
Ú(DHA)
/
850ꢀ
the terminal oxo-unit. This means that treatment of the
oxoꢀhydrazido(2-) complexes (3aꢀ3d) with acid does
not involve reactions at the hydrazidoꢀnitrogens to give
hydrazido(1-) or other protonated nitrogenous pro-
ducts. Similar trend was observed for other oxoꢀ
/
1000 cmꢂ1 region is consistent with the absence of
N(2)Ã
N(2)Ã
/
H(1N)...Cl(2)
H(2N)...Cl(2)
0.91(2)
0.81(2)
2.36(2)
2.42(2)
3.258(2) 168(2)
3.228(2) 175(2)
a
/
/
/
a
Symmetry transformations used to generate equivalent atoms: ꢂ
3/2, yꢃ1/2, ꢂzꢃ3/2.
/
/
xꢃ
/
/
/
/
/
hydrazido(2-)molybdenum compounds [34].
Both chloride atoms in 3c were successfully substi-
tuted by a catecholate ligand in a stoichiometric reaction
with Na2(di-t-Bu-cat) (di-t-Bu-catꢁ2,5-di-tert-butylca-
/
techolate) in THF to give brown microcrystals of
[Mo(di-t-Bu-cat)(NNMePh){S(CH2CH2S)2}] (4), identi-
1
fied by elemental analysis, IR and H NMR spectro-
scopy. Compound 4 is stable as the solid in an inert
atmosphere; soluble in CH2Cl2, THF, MeCN and
1
insoluble in hydrocarbons. In its H NMR spectrum,
complex 4 shows three multiplet resonances for CH2
groups at d 3.89, 3.30 and 2.84 ppm and a singlet at d
3.30 ppm and multiplet at d 6.89 ppm for the Me and Ph
groups of the hydrazido(2-) ligand, respectively, and
also the following resonances for the coordinated di-
tert-butylcatecholate: a singlet at d 1.74 ppm for tert-
butyl and multiplet at d 7.3 ppm for phenyl group.
The reaction of 3a with dimethylhydrazine in MeCN
gave an orange, insoluble in common organic solvents
bis[hydrazido(2-)]
NMe2)2{O(CH2CH2S)2}] (5). Its IR spectrum does not
show MoÃCl frequencies indicating the substitution of
chlorides in 3a. Treatment of 5 with an excess of HCl
causes the formation of untractable molybdenum pro-
duct containing chloride and the liberation of
compound
[Mo(N-
Fig. 4. The crystal packing of [NH2N(CH2Cl)Me2]Cl viewed down the
a-axis. Hydrogen bonds are indicated by dashed lines.
/
phenylhydrazines does not give bis[hydrazido(2-)] com-
plexes even after prolonged refluxing. This indicate that
NH2NMe2×
/
HCl at 1:1 molar ratio suggesting the
in the case of complexes 2aꢀ
hydrazine does not play a crucial role in dictating the
/
2d the basicity of the
protonation of only one hydrazido(2-) ligand.

386
Z. Janas et al. / Inorganica Chimica Acta 350 (2003) 379ꢀ386
/
[4] R.L. Richards, in: C. Elmerlich, A. Kondorosi, W.E. Newton
(Eds.), Biological Nitrogen Fixation in the 21st Century, Kluwer,
Dordrecht, 1997, p. 1.
4. Conclusions
The reaction of the MoÄ
organohydrazines generates hydrazido(2-)-oxo-molyb-
denum compounds [MoO(NNRR?){X(CH2CH2S)2}]
/
O unit in complexes 1 with
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[MoCl2(NNRR?){X(CH2CH2S)2}] (3aꢀ
compounds
3d). The forma-
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/
tion of compounds 3 indicates that acids do not
protonate the hydrazido(2-) ligand in 2 but instead
attack the molybdenum centre. The chlorides in 3 can be
easily substituted by oxygen or nitrogen donor ligands
to create the new hydrazido(2-) compounds [Mo(di-t-
Bu-cat)(NNMePh){S(CH2CH2S)2}] (4) and [Mo(N-
NMe2)2{O(CH2CH2S)2}] (5).
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5. Supplementary material
Supplementary material is available from the Cam-
bridge Crystallographic Data Centre and comprises
experimental data for the X-ray diffraction studies
including atom coordinates, thermal parameters and
remaining bond lengths and angles for compounds 2a,
2b and [NH2N(CH2Cl)Me2]Cl. Copies of this informa-
tion may be obtained from The Director, CCDC
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Acknowledgements
Crystal Structures, University of Gottingen, Gottingen, Germany,
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University of Wroclaw, Wroclaw, Poland, 1999.
The authors thank the State Committee for Scientific
Research (Poland) for financial support of this work
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