Synthesis and characterization of allylicdinuclear molybdenum complexes with bridging oxygen and sulfur containing ligands

Article abstract of DOI:10.1246/bcsj.20090148

Complexes of the type [NEt₄][{Mo(CO)₂(η3-C ₃H₅)}₂(μ-L)₃] and [Na(thf) _x][{Mo(CO)₂(η3-C₃H₅)} ₂(μ-L)₃] (L = OC₂H₅,SC ₂H₅, OPh, SPh, OC₆H₄CH₃, and SCH₂Ph) were synthesized using two different methods. The first was by the reaction of the starting material [Mo(CO)₂(CH ₃CN)₂(η3-C₃H₅)Cl]with NaSR or NaOR and [NEt₄]+,using 2:3 (metal:ligand) mole ratio inthf at room temperature. The second was by the insitu reactions of the ligands with the intermediate [Mo(CO)₂(CH₃CN)₂(η3-C ₃H₅)(thf)]+which was generated by reacting the starting material [Mo(CO)₂(CH₃CN)₂(η3-C ₃H₅)C1]with Ag[BF₄]. The complexes were characterized by means of IR, NMR, and elemental analysis. The X-ray structure of the complex [NEt₄][{Mo(CO)₂(η3-C₃H ₅)}₂(μ-SC₆H₅)₃] was determined, and cyclic voltammetery measurements for the complexes [NEt ₄][{Mo(CO)₂(η3-C₃H₅)} ₂(μ-SC₆H₅)₃] and [NEt ₄][{Mo(CO)₂-(η3-C₃H₅)} ₂(μ-OC₆H₄CH₃)₃] were carried out. The OC₆H₄CH₃ complex exhibited a reversibleoxidation wave at ca. 0.1 V whereas the SC₆H₅ complex did not.

Full text of DOI:10.1246/bcsj.20090148

© 2010 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 83, No. 2, 151–156 (2010)
151
Synthesis and Characterization of Allylic Dinuclear Molybdenum
Complexes with Bridging Oxygen and Sulfur Containing Ligands
Mazin Y. Shatnawi,*1 Samer A. Tanash,1,³ Saleem A. Al-Ahmad,2 Paul R. Challen,3 and Gerald Henkel4
1Department of Applied Chemistry, Jordan University of Science and Technology, Irbid 22110, P. O. Box 3030, Jordan
2Lubrizol Corporation, Wickliffe, Ohio, USA
3Department of Chemistry, John Carroll University, Cleveland, Ohio, USA
4University of Paderborn, Paderborn, Germany
Received June 8, 2009; E-mail: shatnawi@just.edu.jo
Complexes of the type [NEt4][{Mo(CO)2(©3-C3H5)}2(®-L)3] and [Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-L)3]
(L = OC2H5, SC2H5, OPh, SPh, OC6H4CH3, and SCH2Ph) were synthesized using two different methods. The first
was by the reaction of the starting material [Mo(CO)2(CH3CN)2(©3-C3H5)Cl] with NaSR or NaOR and [NEt4]+, using
2:3 (metal:ligand) mole ratio in thf at room temperature. The second was by the in situ reactions of the ligands
with the intermediate [Mo(CO)2(CH3CN)2(©3-C3H5)(thf)]+, which was generated by reacting the starting material
[Mo(CO)2(CH3CN)2(©3-C3H5)Cl] with Ag[BF4]. The complexes were characterized by means of IR, NMR, and elemental
analysis. The X-ray structure of the complex [NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] was determined, and cyclic
voltammetery measurements for the complexes [NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] and [NEt4][{Mo(CO)2-
(©3-C3H5)}2(®-OC6H4CH3)3] were carried out. The OC6H4CH3 complex exhibited a reversible oxidation wave at ca.
0.1 V whereas the SC6H5 complex did not.
There is an extensive chemistry of molybdenum compounds
containing sulfur and oxygen ligands.1-12 Those compounds
are important in some industrial processes such as hydro-
desulfurization and polymerization of certain dienes,2 and in
the biological reduction of dinitrogen to ammonia using the
active site of molybdenum in nitrogenase enzyme.3-5 Although,
many thiolato-bridged complexes with a variety of CO-ligands
have been reported, the use of the allyl moiety as supporting
ligand remains relatively unexploited.6 Examples of molyb-
denum allyl complexes, where the bridging ligands are
-SR or -OR, are those complexes of the general formula
[Mo2(CO)4(©3-C3H5)2L3] in which L is either a thiol or an
alkoxide. These complexes are produced from the reaction
of the corresponding ligands with the starting material
[Mo(CO)2(©3-C3H5)Y2X] in which X is a halide or pseudo-
halide and Y is a monodentate ligand.4,5b,5c
These complexes found to act as catalysts for the poly-
merization of certain dienes7 and the organic synthesis for
allylic alkylation.8 Molybdenum complexes of the formula
[Mo(CO)2(CH3CN)2(©3-C3H5)X] have been extensively used
for the synthesis of many allylic derivatives. These derivatives
can be obtained by the replacement of the weakly bonded
nitriles by nitrogen,9,10 phosphorus,11 arsenic,12 or carboxylic13
ligands. However, examples reported with sulfur ligands are
much rarer and involve (S, S) anionic donors.14,15
coordination chemistry of unsaturated 1,2-dithiolate ligands has
been thoroughly investigated and reviewed regularly.16-18 All
molybdenum oxotransferase and hydroxylase enzymes which
catalyze the overall reaction
X þ H2O ꢀ XO þ 2Hþ þ 2eꢀ
ð1Þ
are now recognized to contain a molybdenum cofactor, Moco.
In these compounds, a molybdenum atom is coordinated to one
or two pterin dithiolene ligands Figure 1.19
DuBois and co-workers reported the synthesis of a series of
complexes in which sulfur ligands bonded to the molybdenum
atom in a bridging form.20,21 They were interested in
investigating the effect of the electron-withdrawing substituents
on the sulfide ligand reactivity toward olefins and hydrogen.
They found that the electron-withdrawing cyclopentadiene (Cp)
substituent leads to an enhancement of the acceptor properties
of the bridging sulfur ligands.
Mo
O
S
H
N
S
HN
O
O
OR
H2N
N
N
H
O
P
1,2-Dithiolate ligands are examples where the (S, S) ligands
may be bonded to molybdenum. During the past decades the
O
Figure 1. Molybdenum oxotransferase and hydroxylase
enzyme cofactor.
³ Present address: Department of Chemistry, Stuttgart University,
Stuttgart, Germany
Published on the web January 20, 2010; doi:10.1246/bcsj.20090148

152
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
©3-C3H5 Mo2 Complexes with ®-O and ®-S
reported in the literature.8 The following procedure was used for
the preparation: Under nitrogen atmosphere, 5.28 g (20 mmol) of
[Mo(CO)6] were placed in a 250-mL three-neck flask fitted with a
condenser, vacuum adapter and a septum. At room temperature and
with continuous stirring, two aliquots (40 mL each) of toluene and
acetonitrile were then added to the flask through the septum. To the
resulting mixture, 2.5 mL of allyl chloride (2.3 g, 30 mmol) were
then added. The mixture was heated to reflux under nitrogen. After
about 30 min, the color became yellow, and then changed to
orange. Upon cooling to room temperature and vacuum reduction
of the mixture’s volume to 2/3 of its original volume, a yellow
solid was obtained. The solid was filtered under nitrogen and
washed with hexane to afford 5.8 g of a yellow powder, yield 93%,
and melting point 168 °C.
Green and Ng reported the synthesis of a series of
binuclear thiolato-bridged Mo complexes [(©-C7H3R1 )Mo-
4
(®-SR2)3Mo(©-C7H3R1 )][BF4] (R1 = H or Me; R2 = Et, Pr,
4
Bu, Ph, or CH2Ph).22 Cyclic voltammetry measurements of
these compounds exhibited two reversible reduction waves
due to the cleavage of the Mo-Mo bond to give the anion
¹
[(©-C7H3R4)Mo(®-SR)3Mo(©-C7H3R4)] .
Borgmann and co-workers reported the synthesis of several
complexes with (©3-allyl)Mo-units in oxygen-rich coordination
¹
spheres containing RO ligands.4 These compounds are
important as models for catalytic intermediates in industrial
processes. They started with the neutral complex [Mo(CO)2-
(CH3CN)2(©3-C3H5)Cl] and reacted it with Ag[BF4], to produce
the cationic complex [Mo(CO)2(CH3CN)2(©3-C3H5)(thf)]+.
In this paper we report the synthesis and characterization of
some anionic complexes of the type [{Mo(CO)2(©3-C3H5)}2-
General Procedure for the Preparation of [NEt4][{Mo(CO)2-
(©3-C3H5)}2(®-L)3] (L = OC2H5, OC6H5, SC6H5, OC7H7,
SC2H5, and SCH2C6H5): The sodium salts of the respective
anionic ligands (NaL) were prepared by the reaction of sodium
metal (3.0 mmol) with the ligand (L) (3.0 mmol) in 15 mL of thf.
The suspension was stirred for 7 h at room temperature. A solution
of I (2 mmol) in 70 mL of thf was placed in a 250-mL Schlenk
flask. With stirring, 3 mmols of the ligand and 1 mmol of NEt4Cl
were then added. The reaction mixture was stirred at room
temperature for 2 h. An orange solution formed and NaCl
precipitated. The solution was filtered over celite. The solvent
was removed under vacuum at 25 °C and the resulting yellow solid
was washed three times with 15 mL aliquots of hexane. The solid
product was recrystallized from thf/hexane (ca. 1:5 ratio) at ca.
0 °C. All products were yellow solids and found as follows.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-OC2H5)3] (1a); Yield 72%.
Mp 75-77 °C (decomp.). IR (thf solution, cm¹1) ¯(co): 1922(s),
1823(s). 1H NMR (DMSO-d6): allyl protons {¤ 0.85 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; NEt4+ protons
{1.2 (t, 12H, CH3) and 3.1 (q, 8H, CH2)}; ethoxide ligand protons
{1.3 (t, 9H, CH3) and 5.1 (q, 6H, CH2)}. Anal. Calcd for
C24H45Mo2NO7: C, 44.3; H, 7.0%. Found: C, 44.0; H, 6.8%.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-OC6H5)3] (2a); Yield 84%.
Mp 157-160 °C (decomp.). IR (thf solution, cm¹1) ¯(co): 1922(s),
¹
(®-L)3] (L = OC2H5, SC2H5, OPh, SPh, OC6H4CH3, and
SCH2Ph). These complexes were synthesized using two differ-
ent methods. The first was by the reaction of the starting
material [Mo(CO)2(CH3CN)2(©3-C3H5)Cl] with sulfur or oxy-
gen containing ligands and [NEt4]+ using 2:3 (metal:ligand)
mole ratio in thf at room temperature. The second was by
the in situ reactions of the ligands with the intermediate
[Mo(CO)2(CH3CN)2(©3-C3H5)(thf)]+, which was generated by
reacting the starting material [Mo(CO)2(CH3CN)2(©3-C3H5)Cl]
with Ag[BF4].
Experimental
Materials and Methods. All reactions were carried out using
standard Schlenk and vacuum line techniques under an inert
atmosphere of dinitrogen (N2). Tetrahydrofuran (thf) was pur-
chased from Scharlau. Toluene and hexane were obtained from
Avonchem. Toluene, thf, and hexane were distilled over sodium
with benzophenone. Acetonitrile was purchased from Gainland
Chemical Co., dried over phosphorus pentaoxide and distilled
before use. Allyl chloride was freshly distilled before use.
Molybdenum hexacarbonyl, ethanol, p-cresol, phenol, sodium,
ethanethiol, thiophenol, and allyl chloride were purchased from
Aldrich. Silver tetrafluoroborate was obtained from Acros Co.
Proton nuclear magnetic resonance (1H NMR) spectra were
recorded on a Bruker AC-200 MHz spectrometer and tetramethyl-
silane (TMS) was used as internal reference. Infrared (IR) spectra
were carried out with a Nicolet-impact 410 FT-IR spectrophotom-
eter. Elemental analysis was performed by Laboratoire D’Analyze
Elementaire Universite de Montreal, Montreal, Canada. Cyclic
voltammetery measurements were performed using a BAS CV-
50W. X-ray crystallographic single crystal structural determina-
tion was carried out on a Syntex P21 four circle diffractometer
(graphite monochromator, scintillation counter, low-temperature
device LT-1).
1
1820(s). H NMR (DMSO-d6): allyl protons {¤ 0.9 (dd, 4H, CH2
anti), 2.8 (dd, 4H, CH2 syn), and 3.6 (m, 2H, CH)}; NEt4+ protons
{1.15 (t, 12H, CH3) and 3.2 (q, 8H, CH2)}; phenoxide ligand
protons {6.7 and 7.2 (m, 15H)}. Anal. Calcd for C36H45Mo2NO7:
C, 54.4; H, 5.7%. Found: C, 54.0; H, 5.5%.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] (3a); Yield 85%.
Mp 145-147 °C (decomp.). IR (thf solution, cm¹1) ¯(co): 1933(s),
1838(s). 1H NMR (DMSO-d6): allyl protons {¤ 0.75 (dd, 4H, CH2
anti), 2.8 (dd, 4H, CH2 syn), and 3.6 (m, 2H, CH)}; NEt4+ protons
{1.15 (q, 12H, CH3) and 3.2 (q, 8H, CH2)}; thiophenolate ligand
{7.2, 7.7 (m, 15H)}. Anal. Calcd for C36H45Mo2NO4S3: C, 51.2;
H, 5.4; S, 11.4%. Found: C, 51.6; H, 6.0; S, 11.0%.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-OC7H7)3] (4a); Yield 85%.
Mp 93-95 °C (decomp.). IR (thf solution, cm¹1) ¯(co): 1919(s),
1822(s). 1H NMR (DMSO-d6): allyl protons {¤ 0.75 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.6 (m, 2H, CH)}; NEt4+ protons
{1.15 (t, 12H, CH3) and 3.2 (q, 8H, CH2)}; cresolate ligand
{2.2 (s, 9H, CH3) and 6.6, 7.0 (dd, 12h, Ph)}. Anal. Calcd for
C39H51Mo2NO7: C, 55.9; H, 6.1%. Found: C, 55.4; H, 5.9%.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC2H5)3] (5a); Yield 76%.
Mp 76-78 °C (decomp.). IR (thf solution, cm¹1) ¯(co): 1924(s),
1821(s). 1H NMR (DMSO-d6): allyl protons {¤ 0.85 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; NEt4+ protons
{1.2 (t, 12H, CH3) and 3.1 (q, 8H, CH2)}; ethanethiolate ligand
Crystallographic data have been deposited with Cambridge
Crystallographic Data Centre: Deposition number CCDC-720896
for the [NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3]. Copies of the
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge, CB2 1EZ, U.K.; Fax:
+44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).
Synthesis of Complexes.
General Procedure for the
Preparation of the Complex [Mo(CO)2(CH3CN)2(©3-C3H5)Cl]
(I): This complex was used as a starting material and prepared as

M. Y. Shatnawi et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
153
{1.4 (t, 9H, CH3) and 5.3 (q, 6H, CH2)}. Anal. Calcd for
C24H45Mo2NO4S3: C, 41.2; H, 6.5; S, 13.8%. Found: C, 41.6; H,
6.7; S, 13.9%.
Anal. Calcd for C35H39Mo2NaO8, (x ¹ 1)thf molecules lost on
drying: C, 52.4; H, 4.9%. Found: C, 52.5; H, 5.0%.
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-SC2H5)3] (5b);
Yield
78%. Mp 74-76 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-SCH2C6H5)3] (6a);
Yield
:
87%. Mp 135-138 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
:
1924(s), 1824(s). (DMSO-d6): allyl {¤ 0.85 (dd, 4H, CH2 anti), 2.9
(dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; thf {3.1 (q, 8H, CH2)};
ethanethiolate ligand {1.2 (t, 9H, CH3) and 1.5 (q, 6H, CH2)}.
Anal. Calcd for C20H33Mo2NaO5S3, (x ¹ 1)thf molecules lost on
drying: C, 36.2; H, 5.0; S, 14.5%. Found: C, 36.8; H, 5.2; S,
14.6%.
1
1916(s), 1824(s). H NMR (DMSO-d6): allyl protons {¤ 0.75 (dd,
4H, CH2 anti), 2.8 (dd, 4H, CH2 syn), and 3.6 (m, 2H, CH)};
+
NEt4 protons {1.15 (q, 12H, CH3) and 3.2 (q, 8H, CH2)}; ligand
{3.8 (m, 6H, CH2), 7.4, 7.3 (m, 15H, Ph)}. Anal. Calcd for
C39H51Mo2NO4S3: C, 53.0; H, 5.8; S, 10.9%. Found: C, 52.8; H,
5.4; S, 10.7%.
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-SCH2C6H5)3]
Yield 87%. Mp 135-138 °C (decomp.). IR (thf solution, cm
(6b);
¹1
General Procedure for the Preparation of [Mo(CO)2-
(CH3CN)2(©3-C3H5)(thf)][BF4] (II): To a stirred solution of I
(0.487 g, 1.5 mmol) in thf, a solution of 0.292 g (1.5 mmol)
Ag[BF4] in 5 mL of thf was added using a cannula. Immediately,
AgCl precipitated as a grayish solid. After 5 min of stirring, the
suspension was filtered and the orange filtrate stored for 14 h at
¹20 °C. The resulting yellow solid was separated by filtration in
the cold and dried at high vacuum.1 Yield 61%, Mp 127 °C
decomposition.
)
1
¯
(co): 1918(s), 1826(s). H NMR (DMSO-d6): allyl {¤ 0.9 (dd, 4H,
CH2 anti), 2.9 (dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; thf {1.6
(t, 4H, CH2) and 3.5 (m, 4H, CH2)}; ligand {3.8 (m, 6H, CH2) and
7.3, 7.5 (m, 15H)}, 1.7, 3.7 (thf). Anal. Calcd for C35H39Mo2-
NaO5S3, (x ¹ 1)thf molecules lost on drying: C, 49.4; H, 4.6; S,
11.3%. Found: C, 49.1; H, 4.5; S, 11.3%.
Cyclic Voltammetry Measurements.
measurements were carried out for the complexes [NEt4]-
[{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3]
and [NEt4][{Mo(CO)2-
Cyclic voltammetry
General Procedure for the Preparation of [Na(thf)4][{Mo-
(CO)2(©3-C3H5)}2(®-L)3] (L = OC6H5, SC6H5, OC7H7, OC2H5,
SCH2C6H5, and SC2H5): The sodium salts of the respective
anionic ligands NaL were prepared by the reaction of sodium metal
(3.0 mmol) with the ligand (L) (3.0 mmol) in 15 mL of thf. The
suspension was stirred for 7 h at room temperature. A solution of
the cation of II (prepared in situ, I (1.5 mmol) and Ag[BF4]
(1.5 mmol) in 5 mL of thf, as reported in Ref. 1) was added to the
above suspension via a cannula. A fine white precipitate formed
and the color of the solution brightened-up. After 2 h of stirring the
solution was filtered over celite. The filtrate was overlaid with
100 mL of light petroleum ether and stored at ¹20 °C for 14 h. The
yellow product was dried at high vacuum that resulted in a loss of
some of the thf coordinated to the cation. The following yellow
compounds were obtained and found to be as follows:
(©3-C3H5)}2(®-OC6H4CH3)3] in CH3CN solvent with Glassy
Carbon working electrode and Ag/Ag+ as reference electrode.
The supporting electrolyte was 0.1 M tetrabutylammonium per-
chlorate (TBAP).
X-ray Crystallographic Structure Determination.
X-ray
crystallographic structure determination of the complex [NEt4]-
[{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] was performed. The cell
constants and reflections were measured at a temperature of
150 K on a Syntex P21 four circle diffractometer with graphite
¹1
monochromator, - = 0.71069 ¡, ® (Mo K¡) = 0.87 mm and an
½ scan with scan range 4° < 2ª < 54° (+h,+k,«l) and a scan
speed of 3-29° min¹1, intensity dependent. Structure solution and
refinement were done using direct methods in combination with
Fourier procedures (SHELXTL PLUS); full-matrix least squares
on F2, non-hydrogen atoms with anisotropic temperature factors,
[NEt4]+-counter ions disordered.
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-OC2H5)3] (1b);
68%. Mp 74-76 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
Yield
:
1923(s), 1822(s). 1H NMR (DMSO-d6): allyl {¤ 0.85 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; thf {1.8 and
3.6}; ethoxide ligand {1.3 (t, 9H, CH3) and 3.2 (q, 6H, CH2)}.
Anal. Calcd for C20H33Mo2NaO8, (x ¹ 1)thf molecules lost on
drying: C, 39.0; H, 5.4%. Found: C, 38.5; H, 5.2%.
Results and Discussion
Characterization of the Complexes. The complexes of the
¹
type [{Mo(CO)2(©3-C3H5)}2(®-L)3] (L = ethoxide, ethane-
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-OC6H5)3] (2b);
Yield
thiolate, phenolate, thiophenolate, cresolate, and benzylthio-
late) were synthesized in good yields by the displacement of
the labile ligands thf and CH3CN from the starting mate-
rials [Mo(CO)2(CH3CN)2(©3-C3H5)Cl] and the intermediate
[Mo(CO)2(CH3CN)2(©3-C3H5)(thf)]+ (the intermediate was
generated in situ by the reaction of [Mo(CO)2(CH3CN)2-
(©3-C3H5)Cl] with Ag[BF4] in thf) by the sodium thiolate or
sodium alkoxide salts of the forms [Na][SR] (RSH = ethane-
thiol, thiophenol, and benzylthiol) and [Na][OR] (ROH =
ethanol, phenol, and 4-methylphenol). The reactions were
carried out at room temperature as shown in Schemes 1 and
2. The mole ratio employed for the preparation of these
complexes was 2:3 (metal:ligand).
Complexes 1a to 6a and 1b to 6b are soluble in highly polar
solvents such as DMSO and slightly soluble in less polar
solvents such as thf and chlorinated solvents. The color of these
complexes is yellow. They are air sensitive in both solution and
solid states. Complexes containing thiol ligands are of very
high sensitivity to air.
83% Mp 156-158 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
:
1
1921(s), 1827(s). H NMR (DMSO-d6): allyl {¤ 0.8 (dd, 4H, CH2
anti), 2.7 (dd, 4H, CH2 syn), and 3.2 (m, 2H, CH)}; thf {1.8 (4H, t,
CH2) and 3.6 (m, 4H, CH2)}; phenolate ligand {6.8, 7.3 (m, 15H)}.
Anal. Calcd for C32H33Mo2NaO8, (x ¹ 1)thf molecules lost on
drying: C, 50.5; H, 4.4%. Found: C, 50.0; H, 4.7%.
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] (3b);
Yield
87%. Mp 148-150 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
:
1
1924(s), 1836(s). H NMR (DMSO-d6): allyl {¤ 0.9 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.4 (m, 2H, CH)}; thf {1.6 (4H, t,
CH2) and 3.5 (m, 4H, CH2)}; thiophenolate ligand {7.3, 7.7 (m,
15H)}. Anal. Calcd for C32H33Mo2NaO5S3, (x ¹ 1)thf molecules
lost on drying: C, 47.5; H, 4.1; S, 11.9%. Found: C, 47.1; H, 3.9; S,
11.5%.
[Na(thf)x][{Mo(CO)2(©3-C3H5)}2(®-OC7H7)3] (4b);
Yield
85% Mp 92-95 °C (decomp.). IR (thf solution, cm¹1) ¯(co)
:
1
1917(s), 1823(s). H NMR (DMSO-d6): allyl {¤ 0.8 (dd, 4H, CH2
anti), 2.9 (dd, 4H, CH2 syn), and 3.2 (m, 2H, CH); thf {2.0 (t, 4H,
CH2) and 3.6 (m, 4H, CH2)}; cresolate ligand {6.6, 6.9 (m, 12H)}.

154
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
©3-C3H5 Mo2 Complexes with ®-O and ®-S
2[Mo(CO)2(C3H5)(CH3CN)2Cl] + 3NaL + NEt4Cl
2[Mo(CO)2(CH3CN)2(C3H5)(thf)] BF4 + 3NaL
OC
OC
Na(thf)x
L
CO
CO
OC
OC
NEt4
L
CO
CO
L
L
L
L
Mo
Mo
Mo
Mo
L = OCH2CH3, SCH2CH3, OC6H5,
SC6H5, OC6H4CH3, SCH2C6H5
L = OCH2CH3, SCH2CH3, OC6H5,
SC6H5, OC6H4CH3, SCH2C6H5
Scheme 2.
Scheme 1.
The IR spectra of these complexes show strong bands in the
¹1
range 1915-1925 and 1815-1830 cm which are assigned to
the stretching frequencies of the terminal carbonyl groups.
The terminal CO bands in all these complexes are shifted
to lower values compared to those of the starting complex
[Mo(CO)2(CH3CN)2(©3-C3H5)Cl] (1955 and 1867 cm¹1).1 This
is due to the strong ³-back donation from the metal to the CO
ligands. This ³-bonding is a result of the increased electron
density around the metal atom due to the strong ability of the
¹
¹
RS and RO ligands to donate electrons.
The 1H NMR spectroscopic data of the synthesized com-
plexes includes the characteristic protons in their expected
chemical shift regions. The protons of the allyl ligands in all
complexes appear as a doublet in the range 0.75-0.90 ppm for
anti, 2.7-2.9 ppm for syn protons and multiplet in the range
3.2-3.6 ppm for CH protons of the allyl groups.
X-ray Structure Analysis for [NEt4][{Mo(CO)2(©3-
C3H5)}2(®-SC6H5)3] (3a). The new complexes are of special
interest to inorganic chemists and biochemists. Complexes of
molybdenum with sulfur containing ligands are important due
to the presence of the Mo-S and Mo-SR bonds in several
enzymes and co-enzymes (such as Nitrogenase).
In order to prove the structure, we were successful in
obtaining single crystals of the SC6H5-containing complex.
Crystals suitable for the X-ray study was obtained by
recrystallization from thf. The complex 3a (Mo2C36H45O4NS3),
relative formula mass 843.82 g mol¹1; crystallizes in the
monoclinic system, space group P21/n with a = 10.946(2) ¡,
Figure 2. X-ray structure of the [NEt4][{Mo(CO)2(©3-
C3H5)}2(®-SC6H5)3] (3a) complex.
The structure was solved by the use of direct methods in
combination with Fourier procedures (SHELXTL PLUS pro-
gram); full-matrix least squares on F2, 454 variables, aniso-
tropic temperature factors for all non-H atoms, hydrogen atoms
riding at idealized positions with common isotropic temper-
ature factors. The refinement converged at R1 = 0.0372 for all
reflections. The values for wR2 and GOF are 0.1003 and 1.060,
respectively.
Description of the Crystal Structure of Complex [NEt4]-
[{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3]. The complex consists
of a monoclinic crystal containing arrays of Mo dimers that
have three (SC6H5) ligands bonded to two Mo atoms in a
bridging form, Figure 2. The distance between the Mo atom
and the S atom ranges between 2.507 and 2.654 ¡. The angle
between Mo-S-Mo is ca. 90°. Each Mo atom is bonded to two
carbonyl moieties and one allyl moiety. The allyl moiety is
bonded to Mo in an ©3-fashion with Mo-C bond distance
ranging between 2.222 and 2.340 ¡. The angle S-Mo-S ranges
b = 20.613(3) ¡, c = 16.227(3) ¡, and ¢ = 90.48(1)°; V =
¹1
3667.2 ¡3; dcalcd = 1.528 g cm¹3, Z = 4, ® = 0.87 mm
.
The cell constants and reflections were measured at
a temperature of 150 K on a Syntex P21 Four Circle
Diffractometer with graphite monochromator, - = 0.71069 ¡,
¹1
®(Mo K¡) = 0.87 mm and an ½ scan with scan range 4° <
2ª < 54° (+h,+k,«l). There were 8037 unique reflections
(7288 with I > 1.96·(I)).

M. Y. Shatnawi et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
155
Table 1. Crystal Date of [NEt4][{Mo(CO)2(©3-C3H5)}2(®-
SC6H5)3] (3a)
Bond distances/¡
Bond angles/°
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(1)-C(19)
Mo(1)-C(20)
Mo(1)-C(21)
Mo(1)-C(22)
Mo(1)-C(23)
2.615(1)
S(1)-Mo(1)-S(2)
S(1)-Mo(1)-S(3)
S(1)-Mo(1)-C(19)
S(1)-Mo(1)-C(20) 161.9(1)
S(1)-Mo(1)-C(21) 125.3(1)
S(1)-Mo(1)-C(22)
S(1)-Mo(1)-C(23)
S(2)-Mo(1)-S(3)
78.2(1)
74.9(1)
93.2(1)
2.634(1)
2.507(1)
1.951(3)
1.942(3)
2.340(4)
2.222(4)
2.316(3)
91.9(1)
83.7(1)
70.7(1)
S(2)-Mo(1)-C(19) 159.6(1)
S(2)-Mo(1)-C(20) 103.3(1)
Figure 3. Cyclic voltammogram for the [NEt4][{Mo(CO)2-
(©3-C3H5)}2(®-OC6H4CH3)3] (4a) complex.
S(2)-Mo(1)-C(21)
S(2)-Mo(1)-C(22)
88.9(1)
94.5(1)
S(2)-Mo(1)-C(23) 126.2(1)
S(3)-Mo(1)-C(19)
S(3)-Mo(1)-C(20)
89.3(1)
88.5(1)
S(3)-Mo(1)-C(21) 148.5(1)
S(3)-Mo(1)-C(22) 161.7(1)
S(3)-Mo(1)-C(23) 149.5(1)
Mo(2)-S(1)
Mo(2)-S(2)
Mo(2)-S(3)
Mo(2)-C(24)
Mo(2)-C(25)
Mo(2)-C(26)
Mo(2)-C(27)
Mo(2)-C(28)
2.603(1)
2.654(1)
2.520(1)
1.934(3)
1.942(3)
2.333(4)
2.225(4)
2.331(4)
S(1)-Mo(2)-S(2)
S(1)-Mo(2)-S(3)
S(1)-Mo(2)-C(24) 161.4(1)
S(1)-Mo(2)-C(25)
S(1)-Mo(2)-C(26)
S(1)-Mo(2)-C(27)
S(1)-Mo(2)-C(28) 126.6(1)
S(2)-Mo(2)-S(3) 70.1(1)
78.1(1)
74.9(1)
95.4(1)
83.6(1)
92.8(1)
S(2)-Mo(2)-C(24) 104.7(1)
S(2)-Mo(2)-C(25) 166.3(1)
S(2)-Mo(2)-C(26) 119.0(1)
Figure 4. Cyclic voltammogram for the [NEt4][{Mo(CO)2-
(©3-C3H5)}2(®-SC6H5)3] (3a) complex.
S(2)-Mo(2)-C(27)
S(2)-Mo(2)-C(28)
S(3)-Mo(2)-C(24)
S(3)-Mo(2)-C(25)
87.6(1)
85.0(1)
88.7(1)
96.7(1)
Conclusion
We prepared complexes of the general formula [{Mo(CO)2-
S(3)-Mo(2)-C(26) 154.5(1)
S(3)-Mo(2)-C(27) 156.2(1)
S(3)-Mo(2)-C(28) 143.5(1)
¹
(©3-C3H5)}2(®-L)3] (L = OC2H5, SC2H5, OC6H5, SC6H5,
OC7H7, and SCH2C6H4) in good yields using two reaction
paths. Except for the difference of the counter cation, the two
methods used gave the same dinuclear anions and almost
the same yields. The X-ray crystal structural determination
confirms the presence of the three ligands in bridging modes
between the two Mo atoms. Cyclic voltammetry measurements
indicated that the OPh complexes exhibit reversible oxidation
while the SPh has irreversible oxidation modes.
Mo(1)-S(1)-Mo(2)
Mo(1)-S(2)-Mo(2)
Mo(1)-S(3)-Mo(2)
90.3(1)
88.8(1)
94.8(1)
from 70.1-78.2 according to the position of phenyl group.
Table 1 shows selected bond distances and angles for the
complex above.
Cyclic Voltammetry Measurements for the Complexes
Financial and technical supports from the Deanship of
Research and the Department of Applied Chemical Sciences at
the Jordan University of Science and Technology are highly
acknowledged.
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-OC6H4CH3)3] (4a) and
[NEt4][{Mo(CO)2(©3-C3H5)}2(®-SC6H5)3] (3a).
To study
the electrochemical behavior of these complexes, cyclic
voltammetry (CV) for the [NEt4][{Mo(CO)2(©3-C3H5)}2-
(®-OC6H4CH3)3] (4a) and [NEt4][{Mo(CO)2(©3-C3H5)}2(®-
SC6H5)3] (3a) complexes were carried out. As shown in
Figures 3 and 4 the 4a complex exhibits reversible oxidation
around +0.1 V. On the other hand, the 3a complex displays an
irreversible oxidation wave in CV. This might be due to the
cleavage of the S-Mo bond upon oxidation of the SPh-complex
(S atom oxidizes). While in the OPh-complex the oxidation
takes place on the metal atom.
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