Heptacoordinate dithiophosphate Mo(II) and W(II) complexes: Molecular structures of mono and binuclear phosphine complexes

Article abstract of DOI:10.1016/S0022-328X(01)00989-5

The complex [M(CO)₃{S₂P(OEt)₂}₂] (M=Mo, W) can be obtained in situ from the reaction of [MI₂(CO)₃(NCMe)₂] with ammoniumdiethyldithiophosphate, in dichloromethane. One or two carbonyl groups can be replaced by mono and bidentate phosphines, such as Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), or PPh₃, to afford heptacoordinate complexes [M(CO)₂(PPh₃){S₂P(OEt)₂} ₂] (M=Mo, 2a; W, 2b), [M(CO)₂{S₂P(OEt)₂}₂] ₂(μ-dppe) (M=Mo, 3a; W, 3b), [M(CO)(dppm){S₂P(OEt)₂}₂] (M=Mo, 4a; W, 4b), [Mo(CO)(dppe){S₂P(OEt)₂}₂] (5a), [W(CO)₂(dppe){S₂P(OEt)₂}₂] (6b), and [Mo(O)(I)(dppe){S₂P(OEt)₂}] (7a). All these complexes, with the exception of 4b, were structurally characterized by single crystal X-ray diffraction. The capped octahedral geometry was observed in all biscarbonyl species, the CO being the capping ligand. Complex 4a exhibits a pentagonal bipyramidal arrangement, with the carbonyl occupying one axial position, while 7a is an octahedral complex. These complexes were studied by cyclic voltammetry, showing essentially irreversible processes, involving orbitals with a strong d character.

Full text of DOI:10.1016/S0022-328X(01)00989-5

Journal of Organometallic Chemistry 632 (2001) 175–187
www.elsevier.com/locate/jorganchem
Heptacoordinate dithiophosphate Mo(II) and W(II) complexes:
molecular structures of mono and binuclear phosphine complexes
Huizhang Liu a, Maria Jose´ Calhorda a,b,*, Vitor Fe´lix c, Michael G.B. Drew d
a Instituto de Tecnologia Qu´ımica e Biolo´gica (ITQB), A6. da Repu´blica, EAN, Apt 127, 2781-901 Oeiras, Portugal
b Departamento de Qu´ımica e Bioqu´ımica, Faculdade de Cieˆncias da Uni6ersidade de Lisboa, 1749-016 Lisbon, Portugal
c Departamento de Qu´ımica, Uni6ersidade de A6eiro, 3810-193 A6eiro, Portugal
d Department of Chemistry, Uni6ersity of Reading, Whiteknights, Reading RG6 6AD, UK
Received 15 March 2001; accepted 1 May 2001
Dedicated to Professor A. Roma˜o Dias on the occasion of his 60th birthday
Abstract
The complex [M(CO)3{S2P(OEt)2}2] (M=Mo, W) can be obtained in situ from the reaction of [MI2(CO)3(NCMe)2] with
ammoniumdiethyldithiophosphate, in dichloromethane. One or two carbonyl groups can be replaced by mono and bidentate
phosphines, such as Ph2PCH2PPh2 (dppm), Ph2P(CH2)2PPh2 (dppe), or PPh3, to afford heptacoordinate complexes [M(CO)2-
(PPh3){S2P(OEt)2}2] (M=Mo, 2a; W, 2b), [M(CO)2{S2P(OEt)2}2]2(m-dppe) (M=Mo, 3a; W, 3b), [M(CO)(dppm){S2P(OEt)2}2]
(M=Mo, 4a; W, 4b), [Mo(CO)(dppe){S2P(OEt)2}2] (5a), [W(CO)2(dppe){S2P(OEt)2}2] (6b), and [Mo(O)(I)(dppe){S2P(OEt)2}]
(7a). All these complexes, with the exception of 4b, were structurally characterized by single crystal X-ray diffraction. The capped
octahedral geometry was observed in all biscarbonyl species, the CO being the capping ligand. Complex 4a exhibits a pentagonal
bipyramidal arrangement, with the carbonyl occupying one axial position, while 7a is an octahedral complex. These complexes
were studied by cyclic voltammetry, showing essentially irreversible processes, involving orbitals with a strong d character. © 2001
Elsevier Science B.V. All rights reserved.
Keywords: Molybdenum; DFT calculations; Allyl complexes; Crystal structures; Binuclear complexes
1. Introduction
an important role on hydrodesulfurization reactions [3].
The search for new molybdenum chemistry has led to
the synthesis and study of a large variety of Mo(II)
derivatives [4–6]. Heptacoordination of the metal is
observed if the 18 electron count is achieved, as hap-
pens with most of the characterized compounds, al-
though examples of unusual unsaturated 16 electron
carbonyl derivatives are also known [4h]. The seven-co-
ordinate complexes exhibit geometries ranging from the
capped octahedron, capped trigonal prism, and pentag-
onal bipyramid, to the 4:3 geometry [4c]. These struc-
tures and their interconversions pathways have been
examined in detail [7]. We describe the synthesis and
properties of a family of new mixed carbonyl, phos-
phine and dithiophosphate Mo(II) and W(II) com-
plexes, mono- and binuclear. Most of the compounds
have been structurally characterized by single crystal
X-ray diffraction.
Molybdenum plays an important role in metalloen-
zymes. In particular, it has been known for some time
that nitrogenases contain a molybdenum center [1], but
only recently, with the crystal structure determination
of the active center of nitrogenase has its coordination
environment been established [2]. Much uncertainty still
remains about its precise function, though, and it is
therefore important to acquire more knowledge on
related molybdenum complexes where the metal is
bound to sulfur ligands. Besides its role in nitrogen
fixation, molybdenum associated with sulfur also plays
* Corresponding author. Tel.: +351-21-446-9754; fax: +351-21-
441-3969.
E-mail address: mjc@itqb.unl.pt (M.J. Calhorda).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00989-5

176
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
In the analogous reaction with dppe, a 2:1 ratio of 1a
2. Results and discussion
2.1. Chemical results
(1b) to dppe was used, with the aim of obtaining
binuclear complexes of Mo or W with bridging dppe.
The products obtained (3a, 3b) still exhibited two wCꢀO
stretching modes (1937, 1850 cm−1, for Mo, and 1925,
1831 cm−1, for W), suggesting that two carbonyl
groups remained coordinated to the metal center. The
1H-NMR spectra in CD3CN show peaks assigned to
phenyl protons (l=7.55–7.62 for Mo, 7.59 for W),
CH2 from dppe (l=2.66–2.73 for Mo, 2.66–2.72 for
W), CH2 from OEt (l=3.87–4.28 for Mo, 3.96–4.24
for W), and CH3 from OEt (l=1.12–1.39 for Mo,
1.22–1.37 for W). These peaks are all broad multiplets
making an integration extremely difficult. The structure
of each compound was confirmed by single crystal
X-ray diffraction studies to be a binuclear complex with
the two metals bridged by a dppe ligand, [M(CO)2-
{S2P(OEt)2}2]2(m-dppe).
The reaction of 1a (1b) with dppm in a 1:1 ratio,
should in principle lead to substitution of two car-
bonyls by the bidentate ligand. For Mo, one broad
band at 1806 cm−1 with a shoulder is assigned to the
wCꢀO stretching mode. The 1H-NMR spectrum in
CD3CN is compatible with the composition
[Mo(CO)(dppm){S2P(OEt)2}2] (4a), which was confi-
rmed by X-ray diffraction studies. For the W complex,
the band corresponding to the wCꢀO stretching mode is
partially split in two, at 1809 and 1790 cm−1, but the
IR spectrum is almost superimposable with that of 4a.
This split band is, however, quite distinct from the two
well-defined bands observed for complexes 2a, 2b, 3a,
and 3b. The IR spectrum of an acetonitrile solution of
the complex was also recorded and showed only one
band, indicating the coordination of only one carbonyl.
Therefore, the complex can be formulated as
[W(CO)(dppm){S2P(OEt)2}2] (4b).
The reaction of the well known complexes
[MI2(CO)3(NCMe)2] (M=Mo, W) [4] with ammonium
diethyldithiophosphate, in dichloromethane, led to the
new species [M(CO)3{S2P(OEt)2}2] (M=Mo (1a), W
(1b)), a procedure related to that described by other
authors [4h].
These materials were used as precursors in situ for all
the other complexes, as shown in Scheme 1, which were
prepared in reactions involving substitution of car-
bonyls by several different phosphines (Ph2PCH2-
PPh2=dppm; Ph2P(CH2)2PPh2=dppe; PPh3) in differ-
ent proportions.
The reaction of 1a with PPh3 led to the substitution
of one carbonyl, as suggested by the presence of two
wCꢀO stretching modes in 2a, at 1939 and 1860 cm−1
,
assigned to the symmetric and antisymmetric modes of
two coordinated carbonyl groups. The H-NMR spec-
1
trum in CD3CN shows three broad peaks for the
phenyl protons (l=7.41 ppm), the methylenic protons
of the ethyl group (l=1.28 ppm), and the methylic
protons of the ethyl group (l=4.11 ppm), respectively,
integrating approximately as 15:12:8, respectively. The
peaks are too broad to allow for an accurate integra-
tion. The complex 2a was confirmed by a single crystal
X-ray study (see Section 2.2) as the heptacoordinate
Mo(II) complex [Mo(CO)2(PPh3){S2P(OEt)2}2]. The
same reaction was carried out, using the W analog as
starting reagent. A similar product, 2b, was obtained,
which exhibited two wCꢀO stretching modes at 1927 and
1
1840 cm−1, and three H-NMR peaks (multiplets) at l
7.32–7.51 ppm, 1.26–1.31 ppm, and 4.14 ppm, for the
phenyl, methylene, and methyl protons, respectively.
This spectroscopic evidence and a single crystal X-ray
study led to the assignment of this complex as
[W(CO)2(PPh3){S2P(OEt)2}2].
The reactions of 1a (1b) with dppe in a 1:1 ratio were
expected to follow similar trends. Indeed, for Mo, a
sharp band at 1811 cm−1 indicated unequivocally the
Scheme 1.

H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
177
presence of only one coordinated carbonyl, the 1H-
NMR spectrum in CD3CN being compatible with the
formulation [Mo(CO)(dppe){S2P(OEt)2}2] (5a). This
structure was confirmed by single crystal X-ray diffrac-
tion. The IR spectrum of the complex, obtained when
the same reaction was repeated with the W precursor,
showed two well defined bands in the region of wCꢀO
stretching vibrations, at 1943 and 1862 cm−1, suggest-
ing that a different product might have been formed.
have seven-coordinate environments, while complex 7a,
obtained from an alternative process, is six-coordinate.
The crystal structures of 2a and 2b consist of discrete
monomers molecules of [Mo(CO)2(PPh3){S2P(OEt)2}2]
(2a), and [W(CO)2(PPh3){S2P(OEt)2}2] (2b), respec-
tively. The bond lengths and angles in the metal coordi-
nation spheres are given in Table 1 for both complexes.
From a comparison of the unit-cell dimensions (see
Table 6) and molecular geometry parameters, it is clear
that these two complexes are isomorphous. The molec-
ular structure of 2a together with the atomic notation
scheme used is shown in Fig. 1. 2b, not shown, is
equivalent. In each structure the metal center is coordi-
nated to two carbonyls, four sulfur donor atoms from
two dithiolate bidentate ligands, and one phosphorus
atom of the triphenylphosphine ligand. The coordina-
tion polyhedra can be described as distorted capped
octahedra. The carbonyl group comprising the atoms
C(200) and O(200) occupies the capping position on the
triangular face defined by the atoms S(4), P(7), and
C(100), intersecting this face nearly on the perpendicu-
lar, at an angle of 88.6° for 2a and 2b. Atoms S(1), S(3),
and S(6) occupy the uncapped face. The MꢁS(4) bond
1
The H-NMR spectrum in CD3CN is not of sufficient
quality to assign another structure, since multiplets
assignable to phenyl groups, methylene protons from
dppe and OEt, and methyl protons are observed with
chemical shifts comparable to those of the Mo complex
5a. The single crystal X-ray study showed this new
tungsten complex to be [W(CO)2(dppe){k1-S2P(OEt)2}-
{k2-S2P(OEt)2}] (6b), where one S2P(OEt)2 coordinates
in the usual bidentate mode but the other is monoden-
tate, so that the heptacoordination of the metal is
maintained. In an attempt to prepare a second batch of
5a, the reaction was repeated but accidentally the work
up period was longer. In particular, the recrystallization
period took place over a period of several days rather
than overnight. Although the IR spectrum was surpris-
ingly similar to that of 6b, with two peaks at 1944 and
1879 cm−1, the single crystal X-ray diffraction revealed
a completely different compound, [Mo(O)(I)(dppe)-
{S2P(OEt)2}] (7a), without any coordinated carbonyl.
From the reasons given above, namely badly defined
multiplets, 1H-NMR does not give much structural
information. The most likely explanation is that a Mo
analog of 6b may form 6a and under exposure to some
air and water during the long crystallization process,
oxidation to 7a takes place. Indeed, compounds such as
[MI(CO)2(dppe){S2P(OEt)2}] [8], may be the intermedi-
ates in the oxidation to 7a. Their presence may be
assigned to incomplete removal of iodide in the parent
precursor [MI2(CO)3(NCMe)2]. There are possible equi-
libria between different species where bidentate ligands
dppe and S2P(OEt)2 change their bonding mode, lead-
ing to expulsion of the second carbonyl. The final
product is probably a mixture of 6a and 7a, as sug-
gested by the IR spectrum, the crystal of 7a having
been selected. The intensity of the carbonyl stretching
bands is much smaller than in all the other compounds.
Table 1
,
Bond lengths (A) and angles (°) in the metal coordination spheres of
2a, 2b, 3a and 3b
2a
2b
3a
3b
Bond lengths
MꢁC(100)
MꢁC(200)
MꢁS(1)
MꢁS(4)
MꢁS(3)
1.937(10) 1.955(4)
1.934(16) 1.898(12)
1.960(14) 1.947(13)
1.960(9)
2.599(3)
2.553(3)
2.651(3)
2.643(4)
2.520(3)
1.935(4)
2.585(3)
2.551(3)
2.653(3)
2.620(4)
2.514(3)
2.595(5)
2.551(5)
2.659(4)
2.655(5)
2.513(4)
2.594(4)
2.535(4)
2.655(4)
2.637(4)
2.500(2)
MꢁS(6)
MꢁP(7)
Bond angles
S(1)ꢁMꢁS(3)
S(4)ꢁMꢁS(3)
P(7)ꢁMꢁS(4)
P(7)ꢁMꢁS(1)
S(1)ꢁMꢁS(4)
P(7)ꢁMꢁS(3)
C(100)ꢁMꢁS(6)
C(100)ꢁMꢁC(200)
C(200)ꢁMꢁS(6)
S(6)ꢁMꢁS(4)
75.7(1)
78.0(1)
122.5(1)
79.9(1)
150.4(1)
153.8(1)
168.0(2)
71.0(3)
120.4(2)
75.9(1)
89.0(1)
104.2(2)
71.3(2)
84.0(1)
83.9(2)
135.1(2)
106.0(2)
74.0(2)
82.8(2)
134.0(2)
86.1(1)
76.4(1)
76.7(1)
123.5(1)
79.3(1)
149.6(1)
153.7(18) 153.78(7) 148.6(1)
74.6(1)
77.5(2)
129.4(1)
74.9(1)
74.4(1)
76.8(1)
129.6(1)
75.2(1)
149.2(1)
148.0(1)
167.6(1)
70.9(2)
121.3(1)
76.3(1)
87.9(1)
103.8(1)
72.1(1)
83.8(1)
84.0(1)
135.3(1)
106.6(1)
74.6(1)
83.4(1)
133.4(1)
85.6(1)
170.3(4)
74.0(6)
115.4(4)
76.2(1)
89.9(1)
101.0(4)
74.0(4)
84.5(1)
84.0(4)
137.3(4)
105.5(4)
73.1(4)
83.0(4)
135.7(4)
88.2(2)
170.0(3)
72.8(5)
116.9(3)
76.1(1)
88.8(1)
101.5(3)
74.4(3)
84.2(1)
84.8(3)
137.3(3)
105.6(3)
74.4(3)
83.4(3)
135.6(3)
87.4(1)
S(6)ꢁMꢁS(1)
2.2. Crystal structures
C(100)ꢁMꢁP(7)
C(200)ꢁMꢁP(7)
P(7)ꢁMꢁS(6)
C(100)ꢁMꢁS(1)
C(200)ꢁMꢁS(1)
C(100)ꢁMꢁS(4)
C(200)ꢁMꢁS(4)
C(100)ꢁMꢁS(3)
C(200)ꢁMꢁS(3)
S(6)ꢁMꢁS(3)
The structures of complexes [Mo(CO)2(PPh3)-
{S2P(OEt)2}2] (2a), [W(CO)2(PPh3){S2P(OEt)2}2] (2b),
[Mo(CO)2{S2P(OEt)2}2]2(m-dppe)
(3a),
[W(CO)2-
{S2P(OEt)2}2]2(m-dppe) (3b), [Mo(CO)(dppm){S2P-
(OEt)2}2] (4a), [Mo(CO)(dppe){S2P(OEt)2}2] (5a),
[W(CO)2(dppe){S2P(OEt)2}2] (6b), and [Mo(O)(I)-
(dppe){S2P(OEt)2}] (7a), were determined by single
crystal X-ray diffraction. The first six complexes all

178
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
C(100) triangular face, making with it angles of 89.7° in
3a and 89.6° in 3b.
The crystal structure of 6b consists of
[W(CO)2(dppe){S2P(OEt)2}2] and CH2Cl2 crystallisa-
tion solvent molecules. Table 2 lists the selected bond
lengths and angles for 6b while Fig. 3 shows the molec-
ular structure with the atomic numbering scheme
adopted.
The tungsten center is bonded to two carbonyl
groups, two phosphorus atoms from dppe, and three
sulfur atoms of two thiolate ligands. The chelation of
tungsten atom by two phosphorus donors of the dppe
ligand prevents the coordination of a sulfur atom of the
second S2P(OEt)2 bidentate ligand. The sulfur atom
S(3) is clearly displaced from the tungsten coordination
sphere, giving rise to a WꢁS(1)ꢁP(2)ꢁS(3) torsion angle
of 137.6(3)° and an intermolecular distance S(3)···W of
,
5.478(6) A. In addition, the P(2)ꢁS(3) bond length of
,
1.938(6) A is shorter than the remaining three PꢁS bond
,
lengths of 2.014(6), 1.985(6) and 1.991(6) A between
Fig. 1. An ORTEP view of [Mo(CO)2(PPh3){S2P(OEt)2}2] (2a), with
thermal ellipsoids drawn at 30% probability. The atom numbering
scheme of the phenyl and ethoxy groups is omitted for clarity. The
analogous tungsten complex 2b is isomorphous.
phosphorus and coordinated sulfur atoms. Thus, the
bond P(2)ꢁS(3) retains some double bond character,
while in the other three it is reduced by the coordina-
tion of their sulfur atoms to the metal center. Complex
6b also exhibits a distorted capped octahedral geome-
try, with the carbonyl capping the triangular face
defined by the atoms C(100), S(4) and P(7). The angle
between the carbonyl group and the C(100), S(4), P(7)
triangular face is 89.9°. The WꢁS, WꢁP and WꢁC
distances are comparable to those for 2b and 3b and in
addition it is apparent that WꢁP(7) in the capped face
to the sulfur atom in the capped face is the shortest
bond. The next shortest bond is MꢁS(1), where S(1) is
trans to S(4), rather than S trans to P(7) and C(100), as
are S(3) and S(2), respectively.
The crystal structures of 3a and 3b consist of dimeric
discrete molecules of [Mo(CO)2{S2P(OEt)2}2]2(m-dppe)
(3a), and [W(CO)2{S2P(OEt)2}2]2(m-dppe) (3b), respec-
tively. As for 2a and 2b, these two complexes are also
isomorphous. The structures contain a crystallographic
center of symmetry. A complete picture of the molecu-
lar structure of 3a (3b is equivalent) is shown in Fig. 2a.
The first molecular diagram is a general view of the
overall structure of the molybdenum binuclear complex
and Fig. 2b is a side view of the crystallographic
asymmetric unit, emphasizing the geometry of the metal
coordination polyhedron.
,
is much shorter at 2.480(4) A than WꢁP(10) in the
,
uncapped face at 2.568(4) A.
The crystal structure of 4a consists of discrete
molecules of [Mo(CO)(dppm){S2P(OEt)2}2] and CH2Cl2
solvent crystallization molecules, while that of 5a only
contains discrete molecules of [Mo(CO)(dppe)-
{S2P(OEt)2}2]. Selected bond lengths and angles in the
molybdenum coordination sphere are compared in
Table 3. The molecular structures of 4a and 5a, to-
gether with atomic numbering scheme used are shown
in Figs. 4 and 5, respectively.
Two M(CO)2{S2P(OEt)2}2 structural units (M=
Mo(II) or W(II)) are linked by a dppe bridge, which
,
holds the two metal centers at 8.789(2) A in 3a and
In contrast with the five structures described above,
the complexes 4a and 5a display a distorted pentagonal
bipyramidal coordination environment around the
molybdenum, with the equatorial coordination defined
by three sulfur atoms of two S2P(OEt)2 bidentate lig-
ands and two phosphorus atoms from dppm in 4a or
from dppe in 5a. Seven coordination is completed with
two axial atoms, the remaining sulfur of a S2P(OEt)2
ligand and the carbon atom of the carbonyl group, with
a C(100)ꢁMoꢁS(6) angle of 172.30(20) and 169.90(30)°,
respectively, in 4a and 5a. In both complexes, the atoms
that define the equatorial plane show significant devia-
tions from the least-squares plane calculated with their
,
8.783(1) A in 3b. The bridge adopts an anti conforma-
tion with a PꢁCꢁCꢁP torsion angle of 180° due to the
presence of a crystallographic inversion center. The
molecular dimensions of the two structural
M(CO)2{S2P(OEt)2}2 fragments in these two complexes,
also listed in Table 1, compare quite well with those
found for the analogues 2a and 2b. In fact, the differ-
ences between the four X-ray determinations are less
,
than 0.04 A in bond lengths and 3° in the angles.
Therefore, the complexes 3a and 3b also exhibit a
capped octahedral geometry with identical disposition
of the ligands. Furthermore, the capping carbonyl lig-
and is again almost perpendicular to the S(4), P(7),
,
atomic positions. These deviations are in A: −0.181(1)

H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
179
Fig. 2. The structure of [Mo(CO)2{S2P(OEt)2}2]2(m-dppe) (3a): (a) a PLATON view showing the centrosymmetric arrangement of two
Mo(CO)2{S2P(OEt)2}structural units linked by the dppe bridge; the symmetry operation * −x+2, −y+1, −z+2 is used to generate the
equivalent atoms; (b) an ORTEP view of the asymmetric unit of 3a, showing the molybdenum coordination. The thermal ellipsoids are drawn at
20% probability and the atom numbering scheme of the phenyl and ethoxy groups is omitted for clarity. The analogous tungsten complex 3b is
isomorphous.
reflected in the widening of the PꢁMoꢁP angle: 66.70(8)
in 4a and 77.55(11)° in 5a. This also affects most of the
other angles subtended at the metal center, including
those not involving the phosphorus atoms, which
changed by ca. 3–16°. In both complexes, the MoꢁS
distance involving the axial sulfur is longer than the
[P(7)], −0.123(1) [P(9)], 0.357(1) [S(4)], −0.455(2)
[S(1)] and 0.402(1) [S(3)] in 4a and −0.448(2) [P(7)],
0.598(2) [P(10)], −0.466(2) [S(4)], 0.175(2) [S(1)] and
0.141(2) [S(3)] in 5a. This distortion of the equatorial
plane can be ascribed to the steric requirements of the
bulky ligands, such as S2P(OEt)2 and dppm in 4a or
dppe in 5a. On the other hand, the cis angles on the
equatorial plane are close to the ideal value of 72°. The
largest shift from this value is of 5.3° in 4a, being
reduced to only 2.6° in 5a. It is noteworthy that in both
cases this difference is due to the PꢁMoꢁP chelating
angle. The increased size of dppe in 5a over dppm 4a is
,
,
equatorial ones, by ca. 0.04 A in 4a and 0.06 A in 5a.
The crystal structure 7a is built from an asymmetric
unit composed of one discrete molecule of [Mo(O)(I)-
(dppe){S2P(OEt)2}]. The molecular structure of 7a and
the labelling scheme adopted are shown in Fig. 6. The
bond lengths and angles listed in Table 4 indicate that

180
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
Table 2
Table 3
,
,
Bond lengths (A) and angles (°) in the metal coordination spheres of
6b
Bond lengths (A) and angles (°) in the metal coordination sphere of
4a and 5a
Bond lengths
4a
5a
WꢁC(100)
WꢁS(1)
WꢁS(6)
1.920(5)
2.617(5)
2.619(4)
2.568(4)
WꢁC(200)
WꢁS(4)
WꢁP(7)
1.938(6)
2.601(5)
2.480(4)
(x=9)
(x=10)
Bond lengths
MoꢁC(100)
MoꢁS(1)
MoꢁS(3)
MoꢁS(4)
MoꢁS(6)
MoꢁP(7)
MoꢁP(x)
WꢁP(10)
1.904(8)
2.650(3)
2.618(3)
2.577(3)
2.688(3)
2.471(2)
2.462(2)
1.919(14)
2.670(4)
2.628(4)
2.579(4)
2.730(4)
2.526(4)
2.462(3)
Bond angles
S(4)ꢁWꢁS(1)
P(7)ꢁWꢁP(10)
P(7)ꢁWꢁS(1)
C(100)ꢁWꢁS(6)
C(200)ꢁWꢁS(6)
C(100)ꢁWꢁP(7)
C(100)ꢁWꢁP(10)
C(100)ꢁWꢁS(4)
P(7)ꢁWꢁS(6)
78.9(2)
75.5(1)
159.2(1)
159.0(6)
131.9(2)
115.8(2)
83.5(2)
110.3(2)
79.6(1)
78.8(2)
82.9(1)
P(7)ꢁWꢁS(4)
107.2(1)
92.6(1)
161.7(1)
68.6(2)
75.8(2)
73.0(2)
121.8(2)
75.6(2)
87.1(2)
127.6(2)
P(10)ꢁWꢁS(1)
P(10)ꢁWꢁS(4)
C(100)ꢁWꢁC(200)
S(4)ꢁWꢁS(6)
C(200)ꢁWꢁP(7)
C(200)ꢁWꢁP(10)
C(200)ꢁWꢁS(4)
P(10)ꢁWꢁS(6)
C(200)ꢁWꢁS(1)
Bond angles
P(x)ꢁMoꢁP(7)
P(x)ꢁMoꢁS(4)
S(4)ꢁMoꢁS(1)
S(3)ꢁMoꢁS(1)
P(7)ꢁMoꢁS(3)
S(4)ꢁMoꢁS(6)
P(x)ꢁMoꢁS(6)
P(7)ꢁMoꢁS(4)
P(x)ꢁMoꢁS(3)
S(4)ꢁMoꢁS(3)
P(x)ꢁMoꢁS(1)
P(7)ꢁMoꢁS(1)
C(100)ꢁMoꢁP(7)
C(100)ꢁMoꢁP(x)
C(100)ꢁMoꢁS(4)
C(100)ꢁMoꢁS(3)
C(100)ꢁMoꢁS(1)
C(100)ꢁMoꢁS(6)
S(3)ꢁMoꢁS(6)
P(7)ꢁMoꢁS(6)
S(1)ꢁMoꢁS(6)
66.70(8)
74.97(7)
76.68(7)
73.69(8)
73.21(8)
74.55(11)
73.98(13)
73.70(13)
73.39(10)
73.18(9)
C(100)ꢁWꢁS(1)
S(6)ꢁWꢁS(1)
75.49(9)
95.81(7)
74.75(10)
109.80(2)
136.96(10)
139.44(11)
145.86(11)
138.87(10)
145.66(11)
99.30(30)
77.90(30)
101.90(30)
83.80(30)
84.60(30)
169.90(30)
93.72(11)
89.27(9)
141.27(7)
138.90(7)
142.62(8)
146.88(8)
141.37(8)
85.00(20)
85.40(20)
97.60(20)
100.10(20)
81.70(20)
172.30(20)
83.96(10)
102.41(8)
93.33(7)
85.27(10)
by the bite angles of the bidentate ligand, dppe or
S2P(OEt)2. The bond distances MoꢁS and MoꢁP can-
not be compared with those found for the related
complexes described above, owing to the different for-
mal oxidation states of the metal, namely IV in 7a and
II in all the remaining ones. These distances, as well as
,
the distances MoꢁI of 2.963(3) A and MoꢁO of 1.695(6)
Fig. 3. An ORTEP view of [W(CO)2(dppe){S2P(OEt)2}2] (6b), with
thermal ellipsoids drawn at 30% probability. The atom numbering
scheme of the phenyl and ethoxy groups is omitted for clarity.
,
A, are within the expected values [9].
In general, the MꢁS and MꢁP distances are compara-
ble to those observed in related heptacoordinate Mo(II)
and W(II) complexes, as described in Refs. [4d,4g,5a],
for instance. It is more interesting to compare com-
plexes 2a, 2b, 3a, and 3b with those described by Baker
et al. [4h], which are hexacoordinate complexes contain-
ing two carbonyl groups, two monodentate phosphines
and a bidentate dithiolate, and adopting a trigonal
prismatic geometry. The MoꢁS in particular are shorter
the molybdenum displays a distorted octahedral geome-
try with the equatorial plane defined by two sulfur
atoms from the S2P(OEt)2 ligand and two phosphorus
atoms from dppe. Six-coordination is completed axially
by one iodine atom and one oxygen atom from an oxo
group, with an IꢁMoꢁO angle deviating from 180° by
12°. The cis angles are within 10° of the ideal octahe-
dral value of 90°. The PꢁMoꢁP angle is only slightly
larger than that found for dppe in 6b [75.5(1)°] and in
5a [74.55(11)°]. The SꢁMoꢁS angle of 79.12(10)° is also
larger by ca. 4–3° than the equivalent angles reported
for the previous structures. This comparison suggests
that the value of these two chelating angles is imposed
,
(2.386–2.430 A). These are formally 16 electrons spe-
cies and it can be assumed that the sulfur ligand acts as
a p-donor, leading to some double bond character and
therefore a stronger MꢁS bond. In the saturated hepta-
coordinate complexes described in this work, this
should not happen.

H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
181
electrolyte. The cyclic voltammograms of 2a, 2b, 3a and
3b are similar, but the resolution is better in the case of
the W complexes. The basic pattern consists of two
irreversible oxidation processes, and an irreversible re-
duction wave.
Complex 4a exhibits a slightly different behavior,
which is not surprising owing to the different coordina-
tion environment of the metal. The two oxidations are
observed at less positive potentials and the reduction
counterparts are observed, although the processes are
still by far irreversible. The same reductions at very
negative potentials are found (−1408 mV). Complex
5a, on the other hand, exhibits a quasi-reversible oxida-
tion (210, 136 mV) superimposed in the usual pattern:
two irreversible oxidations and an irreversible
reduction.
Fig. 4. An ORTEP view of [Mo(CO)(dppm){S2P(OEt)2}2] (4a), with
thermal ellipsoids drawn at 30% probability. The atom numbering
scheme of the phenyl and ethoxy groups is omitted for clarity.
Fig. 6. An ORTEP view of [Mo(O)(I)(dppe){S2P(OEt)2}] (7a), with
thermal ellipsoids drawn at 20% probability. The atom numbering
scheme of the phenyl and ethoxy groups is omitted for clarity.
Table 4
,
Bond lengths (A) and angles (°) in the metal coordination spheres of
7a
Fig. 5. An ORTEP view of [Mo(CO)(dppe){S2P(OEt)2}2] (5a), with
thermal ellipsoids drawn at 20% probability. The atom numbering
scheme of the phenyl and ethoxy groups is omitted for clarity.
Bond lengths
MoꢁO(100)
MoꢁS(3)
MoꢁP(4)
S(3)ꢁMoꢁS(1)
1.695(6)
2.496(3)
2.509(2)
79.12(10)
MoꢁI
MoꢁS(1)
MoꢁP(7)
2.963(3)
2.507(3)
2.529(3)
2.3. Cyclic 6oltammetry studies
Bond angles
The redox behavior of complexes [Mo(CO)2(PPh3)-
{S2P(OEt)2}2] (2a), [W(CO)2(PPh3){S2P(OEt)2}2] (2b),
[Mo(CO)2{S2P(OEt)2}2]2(m-dppe) (3a), [W(CO)2{S2P-
(OEt)2}2]2(m-dppe) (3b), [Mo(CO)(dppm){S2P(OEt)2}2]
(4a), [Mo(CO)(dppe){S2P(OEt)2}2] (5a), and [Mo(O)-
(I)(dppe){S2P(OEt)2}] (7a), was studied in dichloro-
methane containing [NBu4][PF6] as the supporting
O(100)ꢁMoꢁS(3)
O(100)ꢁMoꢁP(4)
S(3)ꢁMoꢁP(4)
S(3)ꢁMoꢁP(7)
P(4)ꢁMoꢁP(7)
S(3)ꢁMoꢁI
99.5(3)
91.1(3)
97.9(1)
170.7(1)
70.0(1)
89.4(1)
79.4(1)
O(100)ꢁMoꢁS(1)
O(100)ꢁMoꢁP(7)
S(1)ꢁMoꢁP(4)
S(1)ꢁMoꢁP(7)
O(100)ꢁMoꢁI
S(1)ꢁMoꢁI
102.5(3)
89.6(3)
166.4(1)
100.9(1)
167.8(2)
87.2(1)
81.3(1)
P(4)ꢁMoꢁI
P(7)ꢁMoꢁI

182
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
The differences are concentrated on the OH positions
as quantified by the SPOH torsion angles, no doubt
because of replacement of the bulky groups by ꢁOH.
However, these differences are so small with respect to
the metal environment, that for the other complexes
only single point calculations were carried out. The full
optimization process was very slow owing to the re-
quirement of optimizing the peripheric atoms, but these
atoms did not contribute significantly to a better
knowledge of the frontier orbitals. The energy and
composition of the frontier orbitals of the complexes
studied is given in Table 5.
The first conclusion is that the difference between
Mo and W complexes, from comparing 2a and 2b, is
much smaller than that produced by replacing a phos-
phine, keeping the octahedral capped coordination en-
vironment (2a and 3a). The fourth complex, 5a, exhibits
a different geometry (pentagonal bipyramid), as well as
containing only one carbonyl and a bidentate phos-
phine. It is not surprising that the energy and composi-
tion of the frontier orbitals for this complex are rather
different from that of the others, the same happening
with the redox behavior.
The two oxidations observed for the W complex 2b
can be assigned as metal oxidations, as both the
HOMO and HOMO−1 are strongly concentrated on
the metal atom, as well as on the sulfur ligand and on
the carbonyls. As these orbitals are bonding, the loss of
an electron leads to bond weakening and further reac-
tion, and the accompanying reduction is not observed.
The reduction process starts by populating a level with
less (but still significant) contribution of the metal, but
more localized on all the ligands. Its metal–ligand
antibonding character leads to further reactivity. The
pattern is similar for the binuclear species 3a and 3b. In
Fig. 7. The structure of model [Mo(CO)2(PH3){S2P(OH)2}2] (2a): (a)
optimized structure from DFT calculations; (b) X-ray structure with
hydrogen atoms replacing ethyl and phenyl groups.
2.4. Theoretical calculations
DFT calculations [10] (ADF program [11]) were per-
formed on several of the complexes (2a, 2b, 3a, 3b, and
5a; details in Section 4), in order to find some explana-
tion for their redox behavior. 5a differs from the other
complexes as the geometry is a pentagonal bipyramid,
rather than a capped octahedron. The phenyl groups of
the amines, as well as the ethyl groups of the dithio-
phosphate, were replaced by hydrogen atoms, in order
to reduce the size of the calculations. The structures of
the models for complexes 2a and 2b, respectively
[Mo(CO)2(PH3){S2P(OH)2}2] and [W(CO)2(PH3){S2P-
(OH)2}2], were fully optimized. The results are shown in
Fig. 7 for the molybdenum complex and are analogous
for tungsten. The calculated distances, angles, and the
coordination environment (left) are very similar to the
experimental X-ray structure with hydrogen atoms re-
placing alkyls and phenyls (right).
Table 5
The energy (kJ mol−1) and composition (%) of the frontier orbitals of model complexes 2a, 2b, 3a, 3b, and 5a
Complex
Orbital
Energy
Composition (%)
Mo
S2P(OH)2
Phosphine
CO
[Mo(CO)2(PPh3){S2P(OH)2}2]
[W(CO)2(PPh3){S2P(OH)2}2]
[Mo(CO)2{S2P(OH)2}2]2(m-dppe)
[W(CO)2{S2P(OH)2}2]2(m-dppe)
[Mo(CO)(dppe){S2P(OH)2}2]
2a
2b
3a
3b
5a
HOMO−1
HOMO
LUMO
HOMO−1
HOMO
LUMO
HOMO−1
HOMO
LUMO
HOMO−1
HOMO
LUMO
−514.84
−501.65
−280.90
−504.44
−490.02
−263.97
−482.46
−482.23
−283.13
−469.28
−469.02
−266.41
−407.85
−386.03
−211.84
51.0
45.5
36.8
49.3
44.4
29.5
48.4
48.5
34.7
47.1
47.3
30.2
59.6
58.3
34.7
22.1
26.2
29.9
20.1
23.6
28.0
18.1
18.0
26.4
17.2
17.1
23.5
14.5
14.9
26.9
3.1
4.4
9.3
3.8
5.4
11.5
1.4
1.3
10.4
1.9
1.7
20.0
20.1
21.0
23.2
23.1
28.0
22.9
22.8
20.1
25.6
25.6
23.8
16.5
13.0
2.9
12.8
7.1
10.9
29.4
HOMO−1
HOMO
LUMO

H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
183
4.2. Preparation of [Mo(CO)2(PPh3){S2P(OEt)2}2] (2a)
these, the HOMO and HOMO−1 are very similar,
owing to the dimeric nature of the complexes. The
energies of the frontier orbitals are lower than for 2a,
suggesting more difficult oxidations and easier reduc-
tions. The almost degeneracy of the two highest levels
makes direct comparison difficult. As far as reduction is
concerned, however, the LUMO+1 is similar to the
LUMO, and the easiest reductions are indeed observed.
The different geometry of [Mo(CO)(dppe)-
{S2P(OEt)2}2] (5a), is reflected in the different energies
and compositions of the frontier orbitals. The HOMO
is much more localized on the metal and its energy is
much higher than for the previous complexes. In this
case, the first oxidation occurs at lower potentials and
is reversible.
[MoI2(CO)3(NCMe)2] (0.103 g, 0.2 mmol) was dis-
solved in CH2Cl2 (10 ml), and solid NH4[S2P(OEt)2]
(0.084 g, 0.4 mmol) was added with vigorous stirring.
The color of the solution changed from dark-red to
red-brown, and a white precipitate formed gradually
(30 min). The reaction mixture was filtered, solid PPh3
(0.052 g, 0.2 mmol) was added to the red–brown
filtrate, rapid gas evolution occurred, and the color of
the solution immediately turned to red. The solution
was stirred for further 30 min, and then concentrated to
about one fourth of its original volume. Hexane (20 ml)
was added, the solution was cooled down (−20 °C)
overnight, to afford red crystals of the compound
[Mo(CO)2(PPh3){S2P(OEt)2}2] (2a). The yield was 0.13
g (83%). One of the crystals was used for a single
crystal X-ray diffraction analysis.
3. Conclusions
Anal. Found: S, 16.05; C, 42.24; H, 4.19%. Calc. for
C28H35MoO6P3S4: S, 16.35; C, 42.87; H, 4.46%. 1H-
NMR: l 7.41 (s, 15H, C6H5), 4.11 (s, 8H, OCH2CH3),
1.28 (s, 12H, OCH2CH3).
A family of complexes of Mo(II) and W(II) contain-
ing the dithiophosphate ligand and carbonyls or phos-
phines, displaying a coordination number seven, has
been prepared and characterized. The coordination ge-
ometry adopted by the metal is either a capped octahe-
dron, with a carbonyl ligand in the capping position,
when two carbonyl groups are present, or a pentagonal
bipyramid in the monocarbonyl derivative. The car-
bonyl group occupies one axial position. These com-
plexes are relatively reactive, since irreversible processes
are found to take place during cyclic voltammetric
studies and a longer crystallization time led to the
formation of an oxidized six-coordinate species.
4.3. Preparation of [W(CO)2(PPh3){S2P(OEt)2}2] (2b)
[WI2(CO)3(NCMe)2] (0.121 g, 0.2 mmol) was dis-
solved in CH2Cl2 (10 ml), and solid NH4[S2P(OEt)2]
(0.084 g, 0.4 mmol) was added with vigorous stirring.
The color of the solution changed from dark-red to
orange, and a white precipitate formed gradually (30
min). The reaction mixture was filtered, solid PPh3
(0.052 g, 0.2 mmol) was added to the filtrate, and the
color of the solution turned to red quickly. The solu-
tion was stirred for further 30 min, and then concen-
trated to about one fourth of its original volume.
Hexane (20 ml) was added, the solution was cooled
down (−20 °C) overnight, to afford red crystals of the
compound [W(CO)2(PPh3){S2P(OEt)2}2] (2b). The yield
was 0.14 g (80%). One of the crystals was used for a
single crystal X-ray diffraction analysis.
4. Experimental
4.1. Synthesis
Commercially available reagents and all solvents
were purchased from standard chemical suppliers. All
solvents were used without further purification except
MeCN (dried over CaH2), CH2Cl2 (dried over CaH2),
and THF, which was distilled over sodium/benzophe-
none ketyl and used immediately. NH4[S2P(OEt)2]
(Aldrich) was recrystallized from THF. The complexes
[MI2(CO)3(NCMe)2] (M=Mo, W) were synthesized ac-
cording to literature procedures [4a].
Anal. Found: S, 14.46; C, 38.31; H, 3.67%. Calc. for
C28H35O6P3S4W: S, 14.70; C, 38.55; H, 4.01%. 1H-
NMR: l 7.32–7.51 (m, 15H, C6H5), 4.14 (s, 8H,
OCH2CH3), 1.26–1.37 (m, 12H, OCH2CH3).
The other Mo and W compounds, [Mo(CO)2-
{S2P(OEt)2}2](m-dppe) (3a) [W(CO)2{S2P(OEt)2}2]-
(m-dppe) (3b), [Mo(CO)(dppm){S2P(OEt)2}2] (4a),
[W(CO)(dppm){S2P(OEt)2}2] (4b), [Mo(CO)(dppe)-
{S2P(OEt)2}2] (5a), [W(CO)2(dppe){S2P(OEt)2}2] (6b),
[Mo(O)(I)(dppe){S2P(OEt)2}] (7a), were prepared in a
similar way, and also crystallized in a similar way
(except 7a). All appeared as red crystals. The reactive
mixture which gave 5a, as we mentioned before, was
put in a cold room (0 °C) for about 2 weeks, leading to
7a as red–purple crystals.
1H-NMR spectra were recorded on a Bruker AMX-
300 (300 MHz) spectrometer in d3-CD3CN (l 1.93),
using TMS as internal reference, and 31P shifts were
measured with respect to external 85% H3PO4. Elemen-
tal analyses were carried out at ITQB. The IR spectra
were recorded on a Unicam Mattson 7000 FTIR spec-
trometer. Samples were run as KBr pellets.

184
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
4.10. [Mo(O)(I)(dppe){S2P(OEt)2}] (7a)
4.4. [Mo(CO)2{S2P(OEt)2}2](v-dppe) (3a)
Anal. Found: S, 7.80; C, 44.96; H, 4.09%. Calc. for
C30H34IMoO3P3S2: S, 7.78; C, 43.78; H, 4.13%. 1H-
NMR: l 7.37–7.86 (m, 20H, C6H5), 3.97–4.44 (m, 4H,
OCH2CH3), 2.73–2.96 (m, 4H, CH2CH2 from dppe),
1.23–1.48 (m, 6H, OCH2CH3). 31P{1H}-NMR: l 77.4
(s, S2P(OEt)2), 53.1 (s, dppe). Phosphine used: 0.080 g,
0.2 mmol. Weight of 6b: 0.050 g. Yield 31%.
Anal. Found: S, 17.15; C, 37.98; H, 4.03%. Calc. for
C46H64Mo2O12P6S8: S, 17.78; C, 38.25; H, 4.43%. H-
NMR: l 7.55–7.62 (m, 20H, C6H5), 3.87–4.28 (m,
16H, OCH2CH3), 2.66–2.73 (m, 4H, CH2CH2 from
dppe), 1.12–1.39 (m, 24H, OCH2CH3). Phosphine used:
0.040 g, 0.1 mmol. Weight of 3a: 0.250 g. Yield 87%.
1
4.5. [W(CO)2{S2P(OEt)2}2](v-dppe) (3b)
4.11. Crystal structure determinations
Anal. Found: S, 16.06; C, 33.92; H, 3.73%. Calc. for
C46H64O12P6S8W2: S, 15.81; C, 34.10; H, 3.95%. 1H-
NMR: l 7.59 (s, 20H, C6H5), 3.96–4.24 (m, 16H,
OCH2CH3), 2.66–2.72 (m, 4H, CH2CH2 from dppe),
1.22–1.37 (m, 24H, OCH2CH3). Phosphine used: 0.040
g, 0.1 mmol. Weight of 3b: 0.230 g. Yield 71%.
The pertinent crystal data and refinement details are
listed in Table 6. The X-ray data for all complexes were
collected on a MAR research plate system using
graphite Mo–Ka radiation at Reading University. The
crystals were positioned at 70 mm from the image plate.
95 frames were measured at 2° intervals using an ade-
quate counting time between 2 and 5 min. Data analy-
sis was carried out with the XDS program [12].
Intensities of the complexes 3a, 3b, 6b and 7a were
corrected empirically for absorption effects with the
DIFABS program [13].
4.6. [Mo(CO)(dppm){S2P(OEt)2}2] (4a)
Anal. Found: S, 14.19; C, 43.54; H, 4.43%. Calc. for
C34H42MoO5P4S4·CH2Cl2: S, 13.29; C, 43.62; H, 4.57%.
1H-NMR: l 7.42 (s, 20H, C6H5), 5.44 (s, 2H, CH2Cl2),
3.90–4.31 (m, 8H, OCH2CH3), 2.92 (s, 2H, CH2 from
dppm), 0.86–1.39 (m, 12H, OCH2CH3). Phosphine
used: 0.077 g, 0.2 mmol. Weight of 4a: 0.140 g. Yield
78%.
The structures were solved by direct methods. All
non-hydrogen atoms were refined with anisotropic ther-
mal parameters. The hydrogen atoms were introduced
in the refinement at the geometric idealized positions
giving isotropic thermal parameters equal 1.2 times
those of the carbon atom they were attached. Then, the
structures were refined by full matrix least-squares on
F2 using a weighting scheme with a standard form until
convergence. The X-ray determinations of 2b, 4a, 5a,
6b, and 7a showed positive peaks for residual electronic
4.7. [W(CO)(dppm){S2P(OEt)2}2] (4b)
Anal. Found: S, 12.90; C, 41.26; H, 4.27%. Calc. for
C34H42O5P4S4W: S, 13.25; C, 42.23; H, 4.35%. 1H-
NMR: l 7.34–7.56 (m, 20H, C6H5), 4.02–4.79 (m, 8H,
OCH2CH3), 3.28 (s, 2H, CH2 from dppm), 0.86–1.36
(m, 12H, OCH2CH3). Phosphine used: 0.077 g, 0.2
mmol. Weight of 4b: 0.140 g. Yield 71%.
density greater than 1 e A−3, but in all cases the
,
corresponding peak was within the metal coordination
sphere. The structure of 3b shows a residual electronic
density in the range −0.57–1.74 e A−3, with the
,
,
positive peak of 1.46 A having two coordinates equiva-
4.8. [Mo(CO)(dppe){S2P(OEt)2}2] (5a)
lent to those of the tungsten atom.
All calculations required to solve and refine the struc-
tures were carried out with SHELXS and SHELXL from
the SHELX97 package [14]. Molecular diagrams were
performed with the PLATON graphical interface [15].
Anal. Found: S, 13.75; C, 48.10; H, 5.20%. Calc. for
MoC35H44O5P4S4: S, 14.34; C, 47.07; H, 4.93%. 1H-
NMR: l 7.33–7.87 (m, 20H, C6H5), 3.85–4.42 (m, 8H,
OCH2CH3), 2.67–2.73 (m, 4H, CH2CH2 from dppe),
1.16–1.48 (m, 12H, OCH2CH3). Phosphine used: 0.080
g, 0.2 mmol. Weight of 5a: 0.250 g. Yield 87%.
4.12. Electrochemistry
All electrochemical instrumentation was from BAS
and consisted of a CV-50W Voltammetric Analyzer
connected to a BAS/Windows data acquisition software
and a three electrode VC-2 voltammetry cell assembly
in a C-2 Cell Stand, enclosed in a Faraday Cage. Also
from BAS were the MF-2013 Platinum Working elec-
trode, MW-1032 Platinum Wire Auxiliary Electrode
and MF-2079 Ag/AgCl Reference Electrode. The work-
ing electrode was polished on 1 mM diamond, then on
alumina and finally sonicated. Between each CV scan it
4.9. [W(CO)2(dppe){S2P(OEt)2}2] (6b)
Anal. Found: S, 11.69; C, 40.51; H, 4.13%. Calc. for
C36H44O6P4S4W·CH2Cl2: S, 11.71; C, 40.61; H, 4.21%.
1H-NMR: l 7.59 (s, 20H, C6H5), 5.44 (s, 2H, CH2Cl2),
3.87–4.04 (m, 8H, OCH2CH3), 2.66–2.71 (m, 4H,
CH2CH2 from dppe), 1.16–1.28 (m, 12H, OCH2CH3).
Phosphine used: 0.080 g, 0.2 mmol. Weight of 6b: 0.230
g. Yield 71%.

Table 6
Crystal data and structure refinement details for complexes 2a–7a
Compound
2a
2b
3a
3b
4a
5a
6b
7a
Empirical formula
C
28H35MoO6P3S4 C28H35O6P3S4W C46H64Mo2O12
-
C46H64O12P6-
S8W2
C35H44Cl2Mo-
O5P4S4
C35H44MoO5-
P4S4
C37H46Cl2O6-
P4S4W
C30H34IMoO3-
P3S2
P6S8
Formula weight
Crystal system
Space group
784.65
monoclinic
P21/n
872.56
monoclinic
P21/n
1443.15
monoclinic
P21/c
1618.97
monoclinic
P21/c
963.66
monoclinic
P21/n
892.76
triclinic
1093.61
monoclinic
P21/n
822.44
Monoclinic
P21/n
/
(
P1
Unit cell dimensions
,
a (A)
9.850(13)
23.871(27)
15.482(17)
9.820(12)
23.721(26)
15.553(17)
15.330(20)
11.255(17)
19.827(29)
15.257(21)
11.232(14)
19.798(25)
10.580(11)
20.740(16)
20.152(20)
10.712(14)
12.035(17)
17.642(22)
94.42(1)
21.226(27)
11.128(15)
21.703(25)
17.971(22)
10.028(14)
20.258(27)
,
b (A)
,
c (A)
h (°)
i (°)
95.52(1)
95.72(1)
110.10(1)
109.79(1)
99.59(1)
92.46(1)
117.11(1)
107.53(1)
k (°)
113.57(1)
2072
2
1.431
920
3
,
V (A )
3623
4
1.438
1608
3605
4
1.608
1736
3213
2
1.492
1476
3192
2
1.684
1604
4360
4
1.468
1976
4563
3481
Z
4
4
Dcalc (Mg m−3
F(000)
)
1.590
1.569
2192
1640
Absorption coefficient (mm−1
q range (°)
)
0.761
3.606
0.851
4.064
0.800
0.711
3.013
1.550
632
2.16–26.07
05h511
−295k529
−195l518
9602
2.16–26.08
05h511
−285k528
−195l518
11536
2.11–26.08
05h518
−135k513
−245l522
8821
2.12–25.90
−185h517
05k513
−245l524
9516
1.96–26.12
05h512
−255k525
−245l52
15163
1.86–25.96
05h513
−135k513
−215l521
6571
2.14–26.19
05h526
05k512
−265l523
8099
2.11–25.96
−225h522
05k511
−245l524
Index ranges hkl
(
175
Reflections collected
Unique reflections (Rint
)
5759 (0.0469)
5759/0/383
1.121
6344 (0.0306)
6344/0/366
1.111
5563 (0.0956)
5563/0/336
0.967
5648 (0.0482)
5648/0/332
1.020
7925 (0.0303)
7925/0/465
1.064
6571 (0.0000)
6571/0/440
0.952
8099 (0.0000)
8099/0/473
1.538
10 002 (0.0504)
6100/0/352
1.078
187
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)] R1 and wR2
R indices (all data) R1 and wR2
0.0671, 0.1551
0.1181, 0.1762
) 0.551/−0.823
0.0535, 0.1176
0.0722, 0.1308
1.858/−2.031
0.0820, 0.1977
0.2550, 0.2507
0.550/−0.668
0.0562, 0.1202
0.1157, 0.1388
1.741/−0.574
0.0795, 0.1817
0.1090, 0.1967
1.888/−0.709
0.1024, 0.2404
0.1999, 0.2845
1.604/−1.395
0.0975, 0.3207
0.1197, 0.366
2.934/−3.003
0.0730, 0.2136
0.1218, 0.2501
1.784/−1.340
−3
,
Largest difference peak and hole (e A

186
H. Liu et al. / Journal of Organometallic Chemistry 632 (2001) 175–187
was electrocleaned as a routine procedure. All experi-
ments were run under Argon and at room temperature
(2392 °C). Solutions were typically 1 mM in solute
and 0.1 M in supporting electrolyte, tetrabutylammo-
nium hexafluorophosphate (Aldrich), which was recrys-
tallized from EtOH. Potentials were referred to the
Ag ꢀ AgCl electrode, which was calibrated with a fer-
rocene solution [16].
Acknowledgements
We thank Zara Miravent Tavares for the elemental
analysis (ITQB) and cyclic voltammetric experiments.
H.L. thanks Praxis XXI for a postdoctoral grant. V.F.
thanks FCT for a sabbatical leave grant. The Univer-
sity of Reading and EPSRC are thanked for funds for
the Image Plate system.
4.13. DFT calculations
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Vosko, Wilk and Nusair’s local exchange correlation
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