Ligand-field photolysis of [Mo(CN)8]4- in aqueous hydrazine: Trapped Mo(II) intermediate and catalytic disproportionation of hydrazine by cyano-ligated Mo(III,IV) complexes

Article abstract of DOI:10.1021/ic800053e

The substitutional photolysis of K₄[Mo(CN)₈] ·2H₂O in 98% N₂H₄·H₂O has been investigated in detail. A molybdenum(II) intermediate, K ₅[Mo(CN)₇]·N₂H₄, is isolated in the primary stage of the reaction that involves the oxidation of N ₂H₄ to N₂, as evidenced by the analysis of evolving gases. The powder X-ray crystal structure of K₅[Mo(CN) ₇]·N₂H₄ indicates the pentagonal bipiramidal geometry of the anion and the presence of N₂H₄ in proximity to the CN^- ligands. The salt is characterized by means of EDS, IR, UV-vis, and EPR spectroscopy as well as cyclic voltammetry measurements. The secondary stages of photolysis, involving the catalytic decomposition of N₂H₄ into NH₃ and N ₂, lead to the formation of a molybdenum(IV) complex, [Mo(CN) ₄O(NH₃)]^2-. The monitoring of the amounts of evolving gases combined with UV-vis and EPR spectroscopic measurements at various stages of photolysis indicate that the molybdenum(III,IV) couple is catalytically active. The scheme of the catalytic decomposition of hydrazine is presented and discussed.

Full text of DOI:10.1021/ic800053e

Inorg. Chem. 2008, 47, 5464-5472
Ligand-Field Photolysis of [Mo(CN)8]4- in Aqueous Hydrazine: Trapped
Mo(II) Intermediate and Catalytic Disproportionation of Hydrazine by
Cyano-Ligated Mo(III,IV) Complexes
Janusz Szklarzewicz,* Dariusz Matoga, Agnieszka Kłys´, and Wiesław Łasocha
Faculty of Chemistry, Jagiellonian UniVersity, Ingardena 3, 30-060 Krako´w, Poland
Received January 14, 2008
The substitutional photolysis of K4[Mo(CN)8]·2H2O in 98% N2H4 ·H2O has been investigated in detail. A
molybdenum(II) intermediate, K5[Mo(CN)7]·N2H4, is isolated in the primary stage of the reaction that involves the
oxidation of N2H4 to N2, as evidenced by the analysis of evolving gases. The powder X-ray crystal structure of
K5[Mo(CN)7]·N2H4 indicates the pentagonal bipiramidal geometry of the anion and the presence of N2H4 in proximity
to the CN- ligands. The salt is characterized by means of EDS, IR, UV-vis, and EPR spectroscopy as well as
cyclic voltammetry measurements. The secondary stages of photolysis, involving the catalytic decomposition of
N2H4 into NH3 and N2, lead to the formation of a molybdenum(IV) complex, [Mo(CN)4O(NH3)]2-. The monitoring
of the amounts of evolving gases combined with UV-vis and EPR spectroscopic measurements at various stages
of photolysis indicate that the molybdenum(III,IV) couple is catalytically active. The scheme of the catalytic
decomposition of hydrazine is presented and discussed.
Introduction
transition-metal complexes. Among them, monometallic
molybdenum complexes have quite well-estabilished mech-
anisms of N2 reduction to ammonia.4 One wide group of
these systems is based on a molybdenum in its low oxidation
state [molybdenum(0)], different from biological FeMo-
nitrogenase [where molybdenum(III,IV) is present], whereas
the other distinctive group includes molybdenum in higher
oxidation states [molybdenum(III)-molybdenum(VI)]. How-
ever, the first synthetic complex that could catalytically
reduce dinitrogen under mild conditions and thus mimic
nitrogenase was published only recently. Yandulov and
Schrock reported a molybdenum(III) triamidoamine complex
as a catalyst for the reduction of dinitrogen to ammonia at
room temperature and a pressure of one atmosphere.4c,5 In
relation to these and biological N2-fixing models, the late
stage of dinitrogen fixation, reductive cleavage of the N-N
The natural reduction of dinitrogen to ammonia by
nitrogenases has been attracting considerable attention of
chemists working on alternative systems that perform the
same reaction under mild conditions.1 Despite detailed
crystallographic determination of the structure of molybde-
num nitrogenase even at 1.16 Å resolution, there is still little
known about the site and the mechanism of dinitrogen
reduction.1,2 Recently, trapping of intermediates formed
during the reduction of nitrogenous substrates of nitrogenase
(N2, a diazene, hydrazine) revealed more details in this
complicated process.3 Following the strategy based on
nitrogenase biomimetics, much effort has been made by
researchers on models with relatively simple mononuclear
* To whom correspondence should be addressed. E-mail: szklarze@
chemia.uj.edu.pl.
(1) (a) For recent reviews on dinitrogen fixation, see: Holland, P. L. In
ComprehensiVe Coordination Chemistry II; McCleverty, J. A., Meyer
T. J., Eds.; Elsevier: Oxford U.K., 2004; Vol. 8, Chapter 8.22, p 569.
(b) MacKay, B. A.; Fryzuk, M. D. Chem. ReV. 2004, 104, 385–401.
(c) Barney, B. M.; Lee, H.-I.; Dos Santos, P.; Hoffman, B. M.; Dean,
D. R.; Seefeldt, L. C. Dalton Trans. 2006, 2277–2284. (d) Himmel,
H.-J.; Reiher, M. Angew. Chem., Int. Ed. 2006, 45, 6264–6288.
(2) (a) Einsle, O.; Tezcan, F. A.; Andrade, S. L. A.; Schmid, B.; Yoshida,
M.; Howard, J. B.; Rees, D. C. Science 2002, 297, 1696–1700. (b)
Howard, J. B.; Rees, D. C. Proc. Natl. Acad. Sci. U.S.A. 2006, 103,
17088–17093.
(3) (a) Barney, B. M.; Laryukhin, M.; Igarashi, R. Y.; Lee, H.-I.; Dos
Santos, P.; Yang, T.-C.; Hoffman, B. M.; Dean, D. R.; Seefeldt, L. C.
Biochemistry 2005, 44, 8030–8037. (b) Barney, B. M.; Yang, T.-C.;
Igarashi, R. Y.; Dos Santos, P.; Laryukhin, M.; Lee, H.-I.; Hoffman,
B. M.; Dean, D. R.; Seefeldt, L. C. J. Am. Chem. Soc. 2005, 127,
14960–14961.
(4) (a) For reviews, see Barriere, F. Coord. Chem. ReV. 2003, 236, 71–
89. (b) Hidai, M.; Mizobe, Y. Met. Ions Biol. Syst. 2002, 39, 121–
161. (c) Schrock, R. R. Acc. Chem. Res. 2005, 38, 955–962. (d)
Tuczek, F. AdV. Inorg. Chem. 2004, 56, 27–53.
5464 Inorganic Chemistry, Vol. 47, No. 12, 2008
10.1021/ic800053e CCC: $40.75  2008 American Chemical Society
Published on Web 05/15/2008

Ligand-Field Photolysis of [Mo(CN)8]4-
bond in hydrazine leading to ammonia has also been studied,
but the reported complexes (both mono and multimetallic)
that catalyze this process are still very limited.6,7
O(NH3)]2- as a final product. The photolysis is accompanied
by catalytic, quantitative disproportionation of hydrazine into
NH3 and N2.12 However, it was not clear which complexes
(substrates, intermediates, or products) are catalytically
active. For comparison, in the photolysis of aqueous
[Mo(CN)8]4- solution, stepwise cyano ligand release is
observed with the formation of hepta-, hexa-, and penta-
cyano intermediates; and in all described complexes, the
oxidation state of molybdenum remains intact.13
In this work, we report the detailed study on the ligand-
field photolysis of [Mo(CN)8]4- in aqueous hydrazine that
provides a deeper insight in the catalytic mechanism of N2H4
decomposition. The same oxidation state (IV) of the metal
center in the substrate and final products of the photolysis
was intriguing, given that hydrazine transformations are
redox processess, and prompted us to investigate the role of
metal in the catalytic decomposition of the solvent. In
particular, our goal was to find isolable intermediates as well
as to determine which transient species in a route from octa-
to tetra-cyano complexes are catalytically active in the
studied system. These findings were expected to be important
steps in attempts to utilize molybdenum(IV) cyanocomplexes
toward efficient dinitrogen reduction.
In the 1970s, it was shown that tetracyanooxo complexes
of molybdenum(IV) can be precursors for a reduction of
dinitrogen to hydrazine and ammonia, but the efficiency of
these systems under studied conditions was relatively low.8
On the other hand, working with molybdenum complexes
we have observed that several molybdenum(IV) tetracya-
nooxo complexes are involved in redox processes in the
presence of O2 and NO molecules.9,10 In the reactions with
molecular oxygen, the molybdenum(IV) center is oxidized
to molybdenum(VI), and attempts have been made to utilize
this process in the oxidation of other molecules.11 These
attempts to build an efficient catalytic system based on a
cyanooxo molybdenum(IV/VI) redox couple proved to be
unsuccessful so far, and the difficulty of quantitative reduc-
tion of molybdenum(VI) species to molybdenum(IV) was
suggested as a main hindrance.11c Recently, we decided to
further explore the redox chemistry of molybdenum(IV)
cyano complexes, this time under reducing conditions. In
our previous article, it has been shown that a prolonged d-d
photolysis of [Mo(CN)8]4- in N2H4 · H2O leads to an almost
quantitativeformationofmolybdenum(IV)complex[Mo(CN)4-
Experimental Section
(5) (a) Yandulov, D. V.; Schrock, R. R. Science 2003, 301, 76–78. (b)
Yandulov, D. V.; Schrock, R. R.; Rheingold, A. L.; Ceccarelli, C.;
Davis, W. Inorg. Chem. 2003, 42, 796–813. (c) Ritleng, V.; Yandulov,
D. V.; Weare, W. W.; Schrock, R. R.; Hock, A. S.; Davis, W. M.
J. Am. Chem. Soc. 2004, 126, 6150–6163. (d) Yandulov, D. V.;
Schrock, R. R. Inorg. Chem. 2005, 44, 1103–1117. (e) McNaughton,
R. L.; Chin, J. M.; Weare, W. W.; Schrock, R. R.; Hoffman, B. M.
J. Am. Chem. Soc. 2007, 129, 3480–3481. (f) Magistrato, A.;
Robertazzi, A.; Carloni, P. J. Chem. Theory Comput. 2007, 3, 1708–
1720.
K4[Mo(CN)8]·2H2O,12(PPh4)2[Mo(CN)4O(NH3)]·2H2O,12Cs2Na-
[Mo(CN)5O],14 K3Na[Mo(CN)4O2] · 6H2O,15 and K5[Mo(CN)7] ·
H2O16 were prepared according to literature procedures, their
identities and purity confirmed by elemental analyses and IR
spectroscopy. All other chemicals including hydrazine monohydrate
(98%, Aldrich) were of analytical grade and were used as supplied.
Carbon, hydrogen, and nitrogen were determined using Euro EA
3000 elemental analyzer. The UV-vis absorption spectra were
recorded on a Shimadzu UV-2101PC scanning spectrophotometer
in the 200-900 nm range. Diffuse reflectance spectra were
measured in BaSO4 pellets with BaSO4 as a reference using a
Shimadzu 2101 PC spectrometer equipped with an ISR-260
attachment. The IR spectra were recorded as either KBr pellets or
nujol mulls on a Bruker EQUINOX 55 FTIR spectrometer. The
thermogravimetric analyses were performed on a TGA/SDTA
(Mettler Toledo) microthermogravimeter with a quadrupole mass
spectrometer Thermostar GSD 300T (Balzers). X-band ESR spectra
were recorded at liquid nitrogen and at room temperature on a
Bruker ELEXSYS E-500CW-EPR spectrometer operating at 9.1
GHz and a modulation frequency of 100 kHz. Cyclic voltammetry
measurements were carried out under argon in aqueous solutions
with KNO3 (0.10 M) or KCN (0.10 M) as the supporting electrolytes
using a platinum working and counting and Ag/AgCl reference
electrodes on a model EA9 electrochemical analyzer. The redox
potentials were calibrated versus K4[Fe(CN)6], which was used as
(6) (a) For reactions on monometallic sites, see: Chu, W.-C.; Wu, C.-C.;
Hsu, H.-F. Inorg. Chem. 2006, 45, 3164–3166. (b) Hitchcock, P. B.;
Hughes, D. L.; Maguire, M. J.; Marjani, K.; Richards, R. L. J. Chem.
Soc., Dalton Trans. 1997, 4747–4752. (c) Block, E.; Ofori-Okai, G.;
Kang, H.; Zubieta, J. J. Am. Chem. Soc. 1992, 114, 758–759. (d)
Schrock, R. R.; Glassman, T. E.; Vale, M. G.; Kol, M. J. Am. Chem.
Soc. 1993, 115, 1760–1772. (e) Schrock, R. R.; Glassman, T. E.; Vale,
M. G. J. Am. Chem. Soc. 1991, 113, 725–726. (f) Vale, M. G.; Schrock,
R. R. Inorg. Chem. 1993, 32, 2767–2772.
(7) (a) For reactions on multimetallic sites, see: Demadis, K. D.; Malinak,
S. M.; Coucouvanis, D. Inorg. Chem. 1996, 35, 4038–4046. (b)
Coucouvanis, D.; Demadis, K. D.; Malinak, S. M.; Mosier, P. E.;
Tyson, M. A.; Laughlin, L. J. J. Mol. Catal. 1996, 107, 123–135. (c)
Malinak, S. M.; Demadis, K. D.; Coucouvanis, D. J. Am. Chem. Soc.
1995, 117, 3126–3133. (d) Demadis, K. D.; Coucouvanis, D. Inorg.
Chem. 1995, 34, 3658–3666. (e) Demadis, K. D.; Coucouvanis, D.
Inorg. Chem. 1994, 33, 4195–4197. (f) Coucouvanis, D.; Mosier, P. E.;
Demadis, K. D.; Patton, S.; Malinak, S. M.; Kim, C. G.; Tyson, M. A.
J. Am. Chem. Soc. 1993, 115, 12193–12194.
(8) (a) Robinson, P. R.; Moorehead, E. L.; Weathers, B. J.; Ufkes, E. A.;
Vickrey, T. M.; Schrauzer, G. N. J. Am. Chem. Soc. 1976, 98, 2815–
2822. (b) Schrauzer, G. N.; Robinson, P. R.; Moorehead, E. L.;
Vickrey, T. M. J. Am. Chem. Soc. 1975, 97, 7069–7076. (c)
Moorehead, E. L.; Robinson, P. R.; Vickrey, T. M.; Schrauzer, G. N.
J. Am. Chem. Soc. 1976, 98, 6556–6601. (d) Robinson, P. R.;
Moorehead, E. L.; Weathers, B. J.; Ufkes, E. A.; Vickrey, T. M.;
Schrauzer, G. N. J. Am. Chem. Soc. 1977, 99, 3657–3662.
(9) (a) Matoga, D.; Szklarzewicz, J.; Samotus, A.; Lewin´ski, K. J. Chem.
Soc., Dalton Trans. 2002, 3587–3592. (b) Matoga, D.; Szklarzewicz,
J.; Samotus, A.; Burgess, J.; Fawcett, J.; Russell, D. R. Polyhedron
2000, 19, 1503–1509.
(12) Szklarzewicz, J.; Matoga, D.; Lewin´ski, K. Inorg. Chim. Acta 2007,
360, 2002–2008.
(13) (a) Szklarzewicz, J.; Matoga, D.; Niezgoda, A.; Yoshioka, D.;
Mikuriya, M. Inorg. Chem. 2007, 46, 9531–9533. (b) Matoga, D.;
Szklarzewicz, J.; Samotus, A.; Burgess, J.; Fawcett, J.; Russell, D. R.
Transition Met. Chem. 2001, 26, 404–411. (c) Samotus, A.; Szklarze-
wicz, J. Coord. Chem. ReV. 1993, 125, 63–74.
(10) Matoga, D.; Szklarzewicz, J.; Fawcett, J. Polyhedron 2005, 24, 1533–
1539.
(14) Dudek, M.; Samotus, A. Transition Met. Chem. 1985, 10, 271–274.
(15) Samotus, A.; Dudek, M.; Kanas, A. J. Inorg. Nucl. Chem. 1975, 37,
943–948.
(11) (a) Arzoumanian, H.; Petrignani, Jean, F.; Pierrot, M.; Ridouane, F.;
Sanchez, J. Inorg. Chem. 1988, 27, 3377–3381. (b) Arzoumanian, H.
Coord. Chem. ReV. 1998, 178, 191–202. (c) Matoga, D. Ph.D. Thesis,
Jagiellonian University, Krako´w, Poland, 2003.
(16) Drew, M. G. B.; Mitchell, P. C. H.; Pygall, C. F. J. Chem. Soc., Dalton
Trans. 1977, 1071–1077.
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Szklarzewicz et al.
an internal potential standard to avoid the influence of liquid
5-85° (2θ) with 0.02° resolution, measuring time 14 s/step, applied
lamp voltage 40 kV, with 30 mA cathodic current. The space group
and cell parameters were determined with PROSZKI package with
TREOR and VISSER software.17 The lattice parameters were refined
with APPLE software using type I net extinctions h + k + l ) 2n
+ 1 according to the found space group.18 Because of the
similarities between structures of 1 and K4[Mo(CN)7]·H2O, data-
base data for the latter compound were used as a starting model in
FOX software and in calculations within the Rietveld method.16,19
junction potential. E0 values were calculated from the average
1/2
anodic and cathodic peak potentials, E01/2 ) 0.5(Ea + Ec); the final
values of potentials were reported versus standard hydrogen
electrode (SHE). The scanning electron microscope JSM 5410 JEOL
(at 20 keV) was used to verify purity of samples as well as to
estimate the K/Mo ratio using an EDS 679A-3SES energy dispersive
X-ray spectrometer (Noran Instruments Inc.); K4[Mo(CN)8]·2H2O
and KI were used as standards.
Continuous photolyses for synthetic purposes were performed
using a low-pressure mercury lamp. Spectral changes were recorded
for solutions irradiated with a low-pressure mercury lamp in glass
conical flasks to prevent them from UV irradiation. The amount of
N2 released during photolysis was measured in a gas burette using
1.0 M HCl as an NH3 trap. The yield of conversion of N2H4 into
NH3 was established on the basis of the amount of evolved N2 and
NH3. To estimate the amount of released NH3 the reacting mixtures,
each was photolyzed for a certain period of time, and was alkalized
with 6.0 M NaOH and heated until boiling. The evolving gas (NH3)
was passing through an NH3 trap filled with 25.00 mL of 0.1000
M HCl. Such solutions were subsequently transferred quantitatively
to Erlenmeyer flasks and subjected to potentiometric titrations
carried out with 0.0971 M NaOH on a Schott Titroline Alpha
titrator.
The rates of N2 evolution were measured in 1.00 cm quartz
cuvettes. K4[Mo(CN)8]·2H2O (0.200 g) was dissolved in N2H4 ·H2O
(98%, 1.5 mL) and irradiated as described above for a certain period
of time. The irradiation was stopped, and a cuvette was connected
to a gas burette. After that, the cuvette with solution was heated to
90 ( 1 °C, thermostatted for 5 min, and then the rate of N2 evolution
was measured. The procedure was repeated for various irradiation
times.
Results and Discussion
General Description of the Photolysis. It has been
previously observed that the irradiation of K4[Mo(CN)8] ·
2H2O solution in 98% N2H4 · H2O yields the color change
from yellow to orange-yellow, green, and finally blue.12 From
the final blue solution, the [Mo(CN)4O(NH3)]2- complex can
be isolated nearly quantitatively. It has also been found that
during the [Mo(CN)8]4- photolysis, N2H4 decomposes with
N2 and NH3 formation.12 In this work, we have found that
the proper modification of conditions leads to the precipita-
tion of an orange-yellow product (1) at the very early stage
of the photolysis. The formation of the solid primary
photoproduct K5[Mo(CN)7] · N2H4 has been observed both
in the presence of electrolytes such as KCl, KI, K2CO3 or
K2SO4 as well as when the concentration of starting
K4[Mo(CN)8] · 2H2O in 98% N2H4 · H2O has been relatively
high (c > 0.3 M). The photolytic formation of 1 is
represented by eqs 1-3.
hν
[Mo(CN)8]4 98 *[Mo(CN)8]4-
(1)
A catalytic activity of K4[Mo(CN)8]·2H2O and that of its
photoproducts (including K5[Mo(CN)7]·N2H4, Cs2Na[Mo(CN)5],
(PPh4)2[Mo(CN)4O(NH3)]·2H2O, and K3Na[Mo(CN)4O2]·6H2O)
was investigated under the same conditions as described for
irradiated K4[Mo(CN)8]·2H2O solutions (with the same concentra-
tion of molybdenum complexes), except that the solutions were
not exposed to irradiation prior to thermostatting.
*[Mo(CN)8]4- f [Mo(CN)7]3-+ CN-
(2)
[Mo(CN)7]3-+ 1/2 N2H4 f [Mo(CN)7]5-+ 1/2 N2+ 2H+
(3)
The introduction of salts with other countercations than
K+ (e.g., NaCl, CsCl, LiCl) to the photolyzed system also
results in the precipitation of a yellow-orange product at the
early stage of photolysis but the most suitable crystals for
X-ray diffraction experiment have been obtained in the
presence of KI. The oxidation of N2H4 to N2 has been
demonstrated by the volumetric measurements of the evolved
N2 combined with the determination of the amount of
produced NH3. It has been found that at the early stage of
photolysis (when 1 is formed) almost pure N2 is evolved.
The traces of NH3 are formed due to the catalytic activity
of 1, which is discussed later in this article.
Synthesis of K5[Mo(CN)7]·N2H4 (1). K4[Mo(CN)8]·2H2O (1.01
g, 2.03 mmol) and KI (2.00 g, 12.1 mmol) were dissolved in
N2H4 ·H2O (98%, 7.5 mL, 0.15 mol). The solution in an Erlenmeyer
flask was exposed to sunlight for a period of one day or was
irradiated with the low-pressure mercury lamp for 30 min. The
resulting product of 1 (yield: 0.71 g, 69%) was filtered off, washed
with EtOH and Me2CO, and dried. All manipulations were
performed under argon.
Synthesis of K5[Mo(CN)7]·H2O (2). The salt was prepared
according to two different methods, one described in the literature16
and the other presented below. K5[Mo(CN)7]·N2H4 (0.50 g, 0.99
mmol) was dissolved in 50% N2H4(aq) (5.0 mL) and precipitated
with acetone. The crystalline product of 2 (yield: 0.40 g 82%) was
filtered off, washed with acetone, diethyl ether and dried. All of
the manipulations were performed under argon. Anal. Calcd for
C7H2K5MoN7O: C, 17.1; H, 0.4; N, 20.0. Found: C, 17.5; H, 0.5;
N, 19.7%. The purity of the compound was verified using IR and
UV-vis spectroscopy.
Characterization of the Primary Photoproduct. Isolated,
diamagnetic 1 is a crystalline yellow-orange solid that is
soluble in water, merely soluble in hydrazine hydrate, and
(17) (a) Łasocha, W.; Lewin´ski, K. J. Appl. Crystallogr. 1994, 27, 437–
438. (b) Werner, P. E.; Eriksson, L.; Westdahl, M. J. Appl. Crystallogr.
1985, 18, 367–370. (c) Visser, J. W. J. Appl. Crystallogr. 1969, 2,
89–95.
(18) Appleman D. E., Jr. Indexing and least squares refinement of powder
diffraction data. U.S. National Technical Information Service, Docu-
ment PB 216-188, 1973, Job 9214.
(19) Favre-Nicolin, V.; Cerny, R. J. Appl. Crystallogr. 2002, 35, 734–
743.
Caution! During handling and photolysis of the cyano com-
plexes, care should be taken because of HCN release. N2H4 is
carcinogenic and contact with it should be limited.
Crystal structure determination of 1. The polycrystalline
samples of 1 were measured on a Bruker D5005 and a Philips X’pert
diffractometer under mineral oil. The angle measuring range was
5466 Inorganic Chemistry, Vol. 47, No. 12, 2008

Ligand-Field Photolysis of [Mo(CN)8]4-
Figure 1. Scanning electron microscope photographs of (a) KI, (b) K5[Mo(CN)7]·N2H4, and (c) K4[Mo(CN)8]·2H2O.
Figure 3. Diffractogram of K5[Mo(CN)7]·N2H4 (1) and differential curve
obtained by Rietveld calculations.
Figure 2. EDS spectrum of K5[Mo(CN)7]·N2H4 (1). In the upper right
corner, the EDS spectrum of KI is presented for comparison.
insoluble in organic solvents. It is unstable in air and it
becomes green. At room temperature, the salt is stable when
kept under N2H4 · H2O, and the dry compound undergoes
slow decomposition with NH3 release even under argon. This
process has considerably affected the results of elemental
analyses, making them not repeatable. Each measurement
performed on samples of 1 has shown that carbon and
nitrogen contents are between those calculated for 1 and 2.
These results indicate weak bonding of the N2H4 molecule
and its release during handling. Repeated crystallizations of
1 from water or diluted N2H4 solutions always lead to the
quantitative formation of K5[Mo(CN)7]·H2O, which confirms
the weak bonding of N2H4 group and indicates that N2H4 is
released upon dissolving, thus it acts as an outer-sphere
solvent molecule in the adduct 1. In aqueous solutions, 1
undergoes dissociation and the [Mo(CN)7]2- anion is stable
under anaerobic conditions (no spectral changes observed),
whereas in the presence of dioxygen the solution changes
color from yellow to red. In spite of many efforts, we were
not able to get single crystals of 1 suitable for X-ray
measurements, thus the structure was refined using powder
diffractograms. To verify the purity of the sample, and in
particular to exclude the presence of KI cocrystallizing with
salt 1, we used the scanning electron microscope equipped
with an energy dispersive X-ray spectrometer. The salts KI
and K4[Mo(CN)8] · 2H2O were used as references. The SEM
photograph of 1 presented in Figure 1 indicates that the
sample is uniform. The EDS spectra show that 1 does not
contain KI (Figure 2) and that the salt composition is the
same in crystals and within studied surfaces.
Figure 4. Structure of the [Mo(CN)7]5- ion in 1.
The established K/Mo ratio for 1 was found to be 5.6,
and this value was estimated on the basis of the K/Mo ratio
(4.0) for the K4[Mo(CN)8] · 2H2O standard. The difference
between the observed and expected value (5.0) for 1 is the
result of complicated surface morphology. The surface of
the sample is not flat, and thus the results of quantitative
EDS measurements can only be interpreted tentatively.
Structure of K5[Mo(CN)7] · N2H4. The powder diffrac-
togram of 1 is presented in Figure 3, and the structure of
the complex anion in 1 is presented in Figure 4. Because of
the pseudoregular symmetry of the unit cell, the unusual
instability of the Rietveld method as well as the softness of
the molecule and easy deformation of the M-CN angles are
observed (angles even as low as 140° are observed if very
soft restraints are introduced in calculations). The attempts
to solve the structure using higher symmetry (for example
Imm2 or I222) were unsuccessful. On the other hand,
Inorganic Chemistry, Vol. 47, No. 12, 2008 5467

Szklarzewicz et al.
Figure 5. IR spectra of K5[Mo(CN)7]·N2H4 (1) and K5[Mo(CN)7]·H2O
(2) (in KBr).
similarity of the composition and unit cell dimensions of 1
suggest its close relation to the structure of the compound
described by Drew et al.16 The literature cell volume for the
latter was 754.08, whereas for 1 it was found as 768.1(2)
Å3. This similarity was confirmed by the Rietveld method
using for computation the parameters of the net, line shape,
scale factor, and zero 2θ scale parameters. The resulting
factors are: RF ) 11.5, Rwp (weight profile) ) 14.2%. On
the basis of the partially refined model, the differential
Fourier maps were calculated and localization of atoms was
obtained, for N11 they are 0.000, 0.261, and 0.0. The site
occupancy of N11 is equal to 50%. The Fourier maps indicate
the possibility of other atom locations, for instance in (0,x,0)
or (0,0,z) positions.
Figure 6. (a) Electronic spectra of K5[Mo(CN)7]·N2H4 (1): in aqueous
solution (dotted line, c ) 1.5 × 10-3 M, d ) 1.00 cm) and diffuse reflectance
(solid line, after Kubelka-Munk transformation). (b) UV-vis spectra of
K5[Mo(CN)7]·N2H4 (1) in H2O (c ) 5.0 × 10-3 M, d ) 0.500 cm): initial
spectrum (dotted line); after short exposure to dioxygen (dashed line), final
spectrum (solid line). (c) Spectral changes of oxidized aqueous solution of
1 induced by the addition of KCN. The arrows indicate direction of the
changes (c ) 5.0 × 10-3 M, d ) 0.500 cm, spectra recorded every 180 s).
The observed small shift of these bands in comparison to
that of N2H4 · H2O is the result of the interaction of N2H4
with cyano ligands, probably via a network of hydrogen
bonds.
The cell parameters were found as a ) 9.167(1), b )
9.187(13), and c ) 9.121(3) Å; R ) ꢀ ) γ ) 90°. The
calculated unit cell volume 768.1(2) Å3 indicates the presence
of a molecule bigger than H2O and giving a more compli-
cated hydrogen-bond network. The ion symmetry is a
distorted pentagonal bipyramid, close to the structure of the
anion found by Drew et al.16 The cyano ligands are almost
linear, with not more than 10° deviations of the Mo-CN
bonds from linearity.
The isolated salt 1 is formed only in concentrated
N2H4 · H2O. It was found earlier that the photolysis of
K4[Mo(CN)8] · 2H2O in diluted aqueous N2H4 solutions is
very similar to the one without hydrazine, and a salt of
formula Cd2[Mo(CN)8]·2N2H4 ·4H2O was isolated and struc-
turally characterized from such solutions.20
IR Spectra. The IR spectrum of 1 is presented in Figure
5, and the spectrum of K5[Mo(CN)7] · H2O is given for
comparison. The band at 523 cm-1 can be assigned to the
νMo-C absorption, and the other bands below 650 cm-1 can
be attributed to δMoCN vibrations. The characteristic bands
of N2H4 are observed in the 650-900 cm-1 range (out-of-
plane νN-H), at 1081 cm-1 (νN-N stretching), at 1610 and
1660 cm-1 (δNH2), and in the 3000-3650 cm-1 range (νN-H).
In the νCN range, there are seven bands at 1958, 1985,
2019, 2034, 2078, 2107, and 2125 cm-1. In the literature,
there are different IR data on 2, probably due to problems
with purification and proper handling with that very unstable
salt.16,21 Our investigations indicate that samples of salt 2
prepared by us in two different methods have the same IR
and UV-vis spectra, and these were taken for comparison
with the respective spectra of 1. It can be seen that in the
νCN range there is a significant difference between 1 and 2
(Figure 5). Salt 1 has seven bands with two new bands above
2100 cm-1, not observed in 2. The presence of seven bands
in this region indicates low symmetry of the anion in 1 (C1),
very similar to that observed in K5[Mo(CN)7] · H2O. On the
other hand, band positions are closer to those found for
Na5[Mo(CN)7] · 10H2O (ranging from 1968 to 2142
cm-1).16,21
UV-vis Spectra. The aqueous solution electronic spec-
trum of 1, presented in Figure 6, is almost identical with the
spectrum of a solution of K4[Mo(CN)8]·2H2O in N2H4 ·H2O,
irradiated for 10 min. It has a shoulder at 420 nm, and at
higher energies a continuous increase of absorbance, not
featuring any bands, is observed, similarly as it is for 2. The
shoulder at 420 nm is attributable to a d-d transition due to
(20) Chojnacki, J.; Grochowski, J.; Lebioda, Ł.; Oleksyn, B.; Stadnicka,
(21) Soares, A. M.; Griffith, W. P. J. Chem. Soc., Dalton Trans. 1981,
K. Rocz. Chem., Ann. Soc. Chim. Polonorum 1969, 43, 273–280.
1886–1891.
5468 Inorganic Chemistry, Vol. 47, No. 12, 2008

Ligand-Field Photolysis of [Mo(CN)8]4-
its low intensity. In diluted deoxygenated aqueous solutions,
spectra of 1 and 2 are identical, which indicates weak
interactions of N4H4 with the [Mo(CN)7]5- ion and its release
upon dissolving.
The diffuse reflectance spectrum of 1, shown in part a of
Figure 6, reveals bands at 325, 365, and 430 nm, and in this
region the spectrum is similar to that of K5[Mo(CN)7]·H2O.16
The increase of absorbance above 700 nm, neither observed
in the reflectance spectrum of 2 nor in that of aqueous
solution of 1, is associated with the interaction of the N2H4
molecule with cyano ligands and suggests its SMCT (solvent-
to-metal charge transfer) origin.
Reaction of K5[Mo(CN)7] · N2H4 with O2. The complex
ion in 1 is stable in deoxygenated aqueous solution. In the
presence of dioxygen, the originally yellow solution turns
red. The electronic spectra of an aqueous solution of 1
reacting with O2 are presented in part b of Figure 6. When
the reaction is completed, the spectrum shows bands of
relatively low intensities at 500 and 600 nm. The latter can
be attributed to the formation of tetracyanooxocomplexes of
molybdenum(IV), whereas the band at 500 nm, observed also
in irradiated solutions of K4[Mo(CN)8] · 2H2O, is associated
with heptacyanomolybdates(IV). The appearance of these
bands indicates that the reaction with dioxygen results in
the oxidation of molybdenum(II) to molybdenum(IV) species
with subsequent partial decomposition and cyano ligands
release. Such an interpretation is also confirmed by spectral
changes induced by the addition of KCN excess to an
oxidized solution of 1 (part c of Figure 6). The observed
reaction leads to a decrease of the band at 500 nm
accompanied by the formation of new bands at 367 and 427
nm, typical for the [Mo(CN)8]4- anion. This reaction does
not affect the band at 630 nm corresponding to tetracya-
nooxomolybdates(IV), which is in agreement with the fact
that they are relatively stable under these conditions. The
presence of an isosbestic point at 446 nm additionally
confirms the explanation.
Thermogravimetic Measurements. Thermogravimetic
measurements combined with a quadrupole mass spectrom-
etry indicate that a decomposition process of salt 1 begins
almost at room temperature (Figure 7). This explains the
instability of 1 mentioned earlier and problems with its
elemental analysis. Analysis of gases evolving during ther-
molysis shows that NH3 molecules are released in the first
step (up to 250 °C). The loss of mass in this step (3.44%) is
close to that calculated for a corresponding amount of N2H4
present in 1 (3.17%). Further decomposition, observed above
300 °C, is associated with a stepwise cyano ligands release.
This process results in the formation of HCN and (CN)2,
detected by mass spectrometry.
Figure 7. Thermogravimetric curve for K5[Mo(CN)7]·N2H4 (1) (solid line)
with NH3 and HCN signals in mass spectrometry.
Figure 8. (a) Cyclic voltammetry of K5[Mo(CN)7]·N2H4 (1) in 0.10 M
KNO3, scan speed 100 mV/s. In the left upper corner the voltammogram
after addition of K4[Mo(CN)8]·2H2O is shown for comparison. (b) Cyclic
voltammetry of 1 in 0.10 M KCN (scan speed 100 mV/s).
At a first glance, peak 1 seems to be associated with an
irreversible oxidation process because its corresponding
reduction wave is not well resolved. However, the oxidation
potential shows only little dependence on a scan speed; it
shifts from 7 to 54 mV upon a 100 to 1000 mV/s scan-
speed change. This indicates that the observed irreversibility
is a result of a chemical reaction that follows the electro-
chemical oxidation. The process associated with peak 1 can
be attributed to the oxidation of molybdenum(II) to molyb-
denum(III) moieties. The unknown molybdenum(III) hep-
tacyano complex undergoes fast decomposition, which
accounts for the lack of the reduction wave (part a of
Figure 8).
It has been observed that shoulder 2 at 127 mV (100 mV/
s) disappears with repeated scanning, whereas all other peaks
(1, 3, 4) remain unaltered. This peak is associated with
transient decomposition products of unstable molybdenu-
m(III) species, formed at lower potential as evidenced in
measurements with excess of KCN described below. The
positions of both oxidation and reduction waves (peak 3)
remain unchanged within 50-1000 mV/s scan speed range,
Cyclic Voltammetry Measurements. The electrochemical
properties of 1 were investigated in aqueous solutions using
cyclic voltammetry measurements. In the studied range
(-600 to 1200 mV), four oxidation and three reduction peaks
are observed (part a of Figure 8). Each peak was measured
separately at different scan speeds to confirm its origin and
reversibility.
Inorganic Chemistry, Vol. 47, No. 12, 2008 5469

Szklarzewicz et al.
the corresponding half-wave potential, E1/2, is equal to 380
mV. The presence of oxidation and reduction peaks, the
independence of E1/2 on scan speed, and the symmetry of
anodic and cathodic peaks (Ia/Ic ) 0.98 at 100 mV/s) indicate
a reversible process. The anodic and cathodic peak separation
(86 mV at 100mV/s) correlates well with a one-electron
process attributed to a molybdenum(III)/molybdenum(IV)
system.
tetracyanooxomolybdates(IV) accountable for the appearance
of peak 5.
Cyclic voltammetry findings on redox processes occurring
in [Mo(CN)7]5- aqueous solutions can be illustrated with eqs
(4-11):
peak 1: [MoII(CN)7]5- f [MoIII(CN)7]4-+ e-
(4)
[MoIII(CN)7]4- f [MoIII(CN)x](x-3)-+ (7-x)CN- (5)
peak 2: [MoIII(CN)x](x-3)- f [MoIV(CN)x](x-4)-+ e- (6)
The oxidation peak 4, observed in the 700-1000 mV
range, has the corresponding reduction wave and the
calculated E1/2 equal to 0.780 V (part a of Figure 8). The
anodic and cathodic peak separation is 59 mV, which is a
value typical for a one-electron process. This redox process
does not seem to be fully reversible, but it has been observed
that the addition of K4[Mo(CN)8] · 2H2O to the studied
solution results in an increase of peak 4 (inset in part a of
Figure 8). Thus, it is attributable to the [Mo(CN)8]3-/
[Mo(CN)8]4- redox couple (with E° equal to 0.78 V).22 The
ill-defined reduction wave is caused by the fact that the
strongly oxidizing [Mo(CN)8]3- anion oxidizes CN- ions
present in solution. The assignment of peak 4 for the
[Mo(CN)8]3-/4- redox couple was additionally corroborated
with cyclic voltammetry measurements for pure
K4[Mo(CN)8]·2H2O under similar conditions. The reversible
one-electron [Mo(CN)8]3-/4- redox system (with the same
E1/2, Ea, and Ec values as peak 4) after the addition of small
amounts of KCN shows the same behavior as the studied
system in part a of Figure 8 (with unsymmetrical oxidation
and reduction peaks).
The cyclic voltammogram for 1 in 0.10 M aqueous KCN
solution is presented in part b of Figure 8. In general, a
recorded curve is similar to that observed for 1 in a 0.10 M
aqueous KNO3 solution (part a of Figure 8). The significant
difference is the formation of a new peak (peak 5) at a lower
potential (0.656 V) than that of the [Mo(CN)8]3-/4- redox
couple. Similarly, as in the measurements with a nitrate
electrolyte, the addition of K4[Mo(CN)8]·2H2O results in an
increase of peak 4, which is in agreement with its previous
assignment. The addition of [Mo(CN)4O(L)]n- anions (L )
OH-, CN-, or NH3) together with test cyclic voltammetry
measurements of K3Na[Mo(CN)4O2]·6H2O in 0.10 M KNO3
or 0.10 M KCN indicate that peak 5 is attributable to the
oxidation of tetracyanooxomolybdate(IV). Because tetracy-
ano complexes of molybdenum can exist in the form of either
[Mo(CN)4O(OH)]3- or [Mo(CN)4O(H2O)]2- (depending on
pH, pK ) 9.7) common formula, [Mo(CN)4O(L)]2-, was
introduced. The tetracyano complex exists also in equilibrium
with [Mo(CN)5O]3- and [Mo(CN)6]2- ions. However, under
studied conditions a tetracyano- complex is a predominant
species.13a The presence of tetracyanooxomolybdates(IV) in
solution of 1 confirms that decomposition processes occurring
at potentials higher than peak 1 (part b of Figure 8) result in
formation of complexes with a lower number of cyano
ligands, which, under an excess of CN- ions, convert into
[MoIV(CN)x](x-4)-+ (4-x)CN-+ L + OH- f
[MoIV(CN)4O(L)]n-+ H+ (7)
peak 3: [MoIII(CN)7]4- f [MoIV(CN)7]3-+ e-
[MoIV(CN)7]3-+ CN- f [MoIV(CN)8]4-
(8)
(9)
peak 4: [MoIV(CN)8]4- f [MoV(CN)8]3- + e- (10)
peak 5: [MoIV(CN)4O(L)]n- f [MoV(CN)4O(L)](n-1)- + e-
(11)
where L ) H2O, OH- or CN-.
The cyclic voltammogram presented in part a of Figure 8
indicates that dissolving of 1 and its subsequent electro-
chemical oxidation or reduction result in a release of cyano
ligands and a formation of numerous products. Most of those
products were recognized and attributed to octa- and hepta-
cyano ions undergoing redox processes. The formation of
octacyanomolybdates(IV) from heptacyano complexes in-
dicates a presence of free CN- ions in solution and their
coordination upon oxidation to hepacyanomolybdate. Thus,
complexes with a number of cyano ligands lower than seven
must be formed, but these are not observed in voltammo-
grams (except for a transient peak 2). The lack of the peak
5 in part a of Figure 8, attributable to tetracyano complexes
and its appearance upon KCN addition indicate a cyanation
process. Thus, it is reasonable to suggest a presence of
complexes with less than four cyano ligands per molybdenum
center. Up until now, there are not any representatives of
monomeric molybdenum complexes of this type. Only were
the trimeric [Mo3O4(CN)9-x(H2O)x]n- complexes reported,
but these were isolated in much more acidic conditions.23
The complex accountable for the formation of a transient
peak 2 in the voltammogram cannot be attributed to any of
the isolated earlier cyano complexes of molybdenum, and
thus eqs 5-8 contain complexes with an unspecified number
of cyano ligands, x.
Catalytic Decomposition of Hydrazine. As it was shown
earlier, the irradiation of K4[Mo(CN)8] · 2H2O in N2H4 · H2O
results in quantitative N2 and NH3 formation according to
an overall equation:
3N2H4 f N2+ 4NH3
(12)
The detailed study shows that N2H4 can be totally
converted into N2 and NH3, and the amount of formed
products is only limited by the starting amount of N2H4.
(22) Szklarzewicz, J.; Samotus, A.; Kanas, A. Polyhedron 1986, 11, 1733–
1740.
(23) Szklarzewicz, J.; Samotus, A. Polyhedron 1993, 12, 1471–1475.
5470 Inorganic Chemistry, Vol. 47, No. 12, 2008

Ligand-Field Photolysis of [Mo(CN)8]4-
Thus, hydrazine is catalytically decomposed in the presence
of molybdenum complexes during photolysis. The calculated
turnover numbers (as moles of hydrazine consumed per one
mole of starting [Mo(CN)8]4- complex) exceed 103, and we
did not aim in determining its upper limit.
The formation of 1 in the reaction:
[MoIV(CN)7]3-+ 1/2N2H4 f [MoII(CN)7]5-+ 1/2N2+ 2H+
(13)
was confirmed by the measurements of N2 and NH3 released
at the very early stage of photolysis. The irradiation of
K4[Mo(CN)8]·2H2O (0.1173 g) in N2H4 ·H2O (0.50 mL) until
light-green color appears, gives the molar ratio Mo/N2/NH3
equal 1.2/1/1, which means a 4-fold increase of the amount
of N2 compared to that expected from (12). The formation
of H+ ions (13) was ascertained through pH measurements,
which reveal that pH of irradiated solutions decreases rapidly
and comes close to 5.6 once the [Mo(CN)7]5- complex has
been formed. Upon further irradiation, the solution turns deep
green. At this stage, our attempts to isolate pure products
were unsuccessful. However, when the green solution was
dried under vacuum the resulting residue was found to be
paramagnetic. The green residue has ESR, IR, and UV-vis
spectra (peak positions) similar to those of molybdenum(III)
cyano complexes described in the literature.21,24,25 However,
the residue is likely to be a mixture of products, thus it is
not possible to determine the molar extinction coefficients
(in the UV-vis spectra). It can be assumed that the
molybdenum(III) complex is formed in the reaction:
Figure 9. Rate of N2 formation versus irradiation time (at 90 °C).
solution (irradiation time >40 min). At this stage, the activity
toward N2H4 remains constant up until its almost total
decomposition.
The observed thermal catalytic activity was compared with
that of K4[Mo(CN)8] · 2H2O and isolated photoproducts
(including 1, 2, [Mo(CN)4O(NH3)]2-, [Mo(CN)5O]3-, and
[Mo(CN)4O(OH)]3-) under the same conditions. It has been
shown that the [Mo(CN)8]4- ion is catalytically inactive,
whereas salts 1 and 2 show activity at the level of 0.13 mL
N2/min. This value is in agreement with the data presented
in Figure 9 because 1 is being formed up until 10 min of
irradiation, under studied conditions.
The solutions containing [Mo(CN)4O(L)]n- ions (L )
CN-, OH-, NH3) dissolved in N2H4 · H2O (98%), indepen-
dently on L, turn dark green upon temperature increase, and
show activity at a level of 2.0 mL N2/min. This observation
confirms that the final photoproducts are the most active
complexes, which can be easily converted into a molybde-
num(III) species in a strongly reducing medium. The activity
of tetracyanooxomolybdates(IV) is the same as that observed
within a plateau in Figure 9, which indicates the same origin
of active centers in both photolyzed and nonphotolyzed
systems.
2Mo2++ N2H4+ 2H+ f 2Mo3++ 2NH3v
(14)
The further photolysis of the green solution does not affect
the UV-vis spectrum of the solution, but the intense
evolution of N2 and NH3 gases is observed at this stage. At
the end of photolysis, when hydrazine is nearly completely
decomposed, the concentrated NH3(aq) solution is formed,
and the solution turns blue due to the formation of
[Mo(CN)4O(NH3)]2- according to the reaction:
2Mo3++ N2H4+ 2H+ f 2Mo4++ 2NH3v
(15)
The photolysis affords molybdenum(II) complex (eq 13),
which is subsequently oxidized to molybdenum(III) species
(eq 14). This low-cyano molybdenum(III) product partici-
pates in a catalytic cycle, involving molybdenum(IV) com-
plex, represented by reactions (15) and (16).
To study the activity of primary, transient, and final
photoproducts, the rate of N2 formation during photolysis
was measured and it is presented in Figure 9. The activity
presented in Figure 9 represents a thermal (and not a
photochemical) activity of the series of equimolar
[Mo(CN)8]4- solutions, each irradiated for a certain period
of time before being subjected to an analysis. This activity
refers to all photoproducts present in each solution after
irradiation is stopped. The procedure described in the
Experimental Section allowed us to avoid the influence of
photochemical processes on the thermal catalytical activity
of photoproducts.
4Mo4++ N2H4 f 4Mo3+ + N2 + 4H+
(16)
Thus, in the catalytic cycle, we observe a reduction of the
molybdenum(IV) complex with the indication of a molyb-
denum(III) species formation and its reoxidation to the
molybdenum(IV) complex. The same cycle can be observed
when reaction with hydrazine begins directly from tetracya-
nooxomolybdates(IV) and not via the photolytical route.
Because the redox cycle can be achieved starting from
[Mo(CN)4O(L)]n- ions, it can be assumed that N2H4 replaces
labile ligand L, and then the resulting complex can be
reduced, yielding coordinatively unsaturated molybdenu-
m(III) species (eq 16). The latter can oxidize N2H4 to NH3
It can be clearly seen that the catalytic activity increases
during photolysis with the maximum at the stage of the green
(24) Rossman, G. R.; Tsay, F. D.; Gray, H. B. Inorg. Chem. 1973, 12,
824–829.
(25) Mockford, M. J.; Griffith, W. J. Chem. Soc., Dalton Trans. 1985, 717–
722.
Inorganic Chemistry, Vol. 47, No. 12, 2008 5471

Szklarzewicz et al.
Scheme 1. Molybdenum-Based Catalytic Decomposition of Hydrazine
strongly reducing media it is possible to reduce both primary
and final photoproducts of [Mo(CN)8]4- photolysis and to
isolate an unstable molybdenum(II) intermediate. The pro-
duced molybdenum(II) species can reduce N2H4, yielding
molybdenum(III) and molybdenum(IV) complexes that can
be further reduced by N2H4, thus closing the catalytic cycle,
whose turnover number exceeds 103. There is strong evidence
of low activity of the molybdenum(II) and high activity of
the molybdenum(IV) complexes. The same catalytic cycle
can be achieved in a thermal way, starting from tetra- or
penta-cyano complexes of molybdenum(IV). There are also
strong indications of a presence of molybdenum(III) during
the catalytic cycle. It also seems that proper modifications
of the system could make these complexes act as competitive
catalysts with nitrogenase-like activity, which will be the
subject of further investigations. A facile and efficient method
of cyanomolybdates(II) synthesis, presented in this article,
can also be used for exploration of molybdenum(II) chem-
istry.
with accompanying recovery of the molybdenum(IV) com-
plex. The overall molybdenum-based catalytic mechanism
of N2H4 decomposition is presented in Scheme 1.
Concluding Remarks. For the first time, we have been
able to obtain an efficient catalytic system based on molyb-
denum(III/IV) cyano complexes. It has been shown that in
Supporting Information Available: CIF file for 1 and additional
cyclic voltammograms for 1. This material is available free of
charge via the Internet at http://pubs.acs.org.
IC800053E
5472 Inorganic Chemistry, Vol. 47, No. 12, 2008