Tellurium complexes with new, large-bite dithio ligands. The crystal structures of cis- and trans- [Te{Ph2P(S)-N-P(S)(OPh)2}2] and [(4-MeOC6H4TeCl3)2{μ-iPr2P(S)-Fc-P(S)iPr2}]

Article abstract of DOI:10.1016/S0022-328X(00)00656-2

Reaction of the protonated large-bite bidentate ligand Ph₂P(S)-NH-P(S)(OPh)₂ with [Te{NH₂)₂CS}₄]Cl₂ resulted in the complex [Te(L-L)₂], (1a), where (L-L)^-=Ph₂P(S)-N-P(S)(OPh)₂. When (L-L)^- reacted with 4-MeOC₆H₄TeCl₃, an isomeric complex, 1b, resulted. Reaction between the less basic ligand ⁱPr₂P(S)-Fc-P(S)ⁱPr₂ (Fc=ferrocene) and 4-MeOC₆H₄TeCl₃ yielded the complex [(4-MeOC₆H₄TeCl₃)₂ {μ-ⁱPr₂P(S)-Fc-P(S)ⁱPr₂}], (2). X-ray crystallographic studies show that 1a and 1b both are square planar complexes of Te(II), 1a being asymmetric and `cis' with two short Te-S bonds trans to two long Te-S bonds (average bond lengths being 2.5415 and 2.9050 A?). Isomer 1b is centrosymmetric, `trans', with nearly equal Te-S bond lengths averaging 2.6805 A?. Complex 2 is an addition compound where the large dithio ligand bridges two 4-MeOC₆H₄TeCl₃ units through weak Te-S bonds. The resulting coordination around each Te(IV) atom is ψ-octahedral with the lone pair of electrons and aryl in axial positions relative to the TeCl₃S equatorial plane. Here the Te-S bond lengths are 2.7560(16) and 2.6910(12) A?. The trans influence of the dithio ligand in 2 is smaller than that of Cl^-, resulting in an average Te-Cl bond length trans to sulfur of only 2.4196 A?, while the other Te-Cl bond lengths average 2.4959 A?. The reason for the lower basic nature of the ligand with a P-Fc-P backbone compared to those with P-N-P backbones, is that it lacks a central charge donating group like N?^-.

Full text of DOI:10.1016/S0022-328X(00)00656-2

Journal of Organometallic Chemistry 623 (2001) 124–130
www.elsevier.nl/locate/jorganchem
Tellurium complexes with new, large-bite dithio ligands. The
crystal structures of cis- and trans- [Te{Ph2P(S)ꢀNꢀP(S)(OPh)2}2]
and [(4-MeOC6H4TeCl3)2{m-iPr2P(S)ꢀFcꢀP(S)iPr2}]
Marek Necas a, Josef Novosad a, Steinar Husebye b,*
a Department of Inorganic Chemistry, Faculty of Science, Masaryk Uni6ersity, Kotla´rska´ 2, 611 37 Brno, Czech Republic
b Department of Chemistry, Uni6ersity of Bergen, Alle´gaten 41, N-5007 Bergen, Norway
Received 26 July 2000; accepted 5 September 2000
Abstract
Reaction of the protonated large-bite bidentate ligand Ph2P(S)ꢀNHꢀP(S)(OPh)2 with [Te{NH2)2CS}4]Cl2 resulted in the
complex [Te(LꢀL)2], (1a), where (LꢀL)−=Ph2P(S)ꢀNꢀP(S)(OPh)2. When (LꢀL)− reacted with 4-MeOC6H4TeCl3, an isomeric
i
complex, 1b, resulted. Reaction between the less basic ligand Pr2P(S)ꢀFcꢀP(S)iPr2 (Fc=ferrocene) and 4-MeOC6H4TeCl3 yielded
the complex [(4-MeOC6H4TeCl3)2 {m-iPr2P(S)ꢀFcꢀP(S)iPr2}], (2). X-ray crystallographic studies show that 1a and 1b both are
square planar complexes of Te(II), 1a being asymmetric and ‘cis’ with two short TeꢀS bonds trans to two long TeꢀS bonds
,
(average bond lengths being 2.5415 and 2.9050 A). Isomer 1b is centrosymmetric, ‘trans’, with nearly equal TeꢀS bond lengths
,
averaging 2.6805 A. Complex 2 is an addition compound where the large dithio ligand bridges two 4-MeOC6H4TeCl3 units
through weak TeꢀS bonds. The resulting coordination around each Te(IV) atom is „-octahedral with the lone pair of electrons
,
and aryl in axial positions relative to the TeCl3S equatorial plane. Here the TeꢀS bond lengths are 2.7560(16) and 2.6910(12) A.
The trans influence of the dithio ligand in 2 is smaller than that of Cl−, resulting in an average TeꢀCl bond length trans to sulfur
,
,
of only 2.4196 A, while the other TeꢀCl bond lengths average 2.4959 A. The reason for the lower basic nature of the ligand with
a PꢀFcꢀP backbone compared to those with PꢀNꢀP backbones, is that it lacks a central charge donating group like N −. © 2001
8
Elsevier Science B.V. All rights reserved.
Keywords: Tellurium(II) and (IV) complexes; New dithio ligands; Crystal structures
1. Introduction
recently, analogous ligands with PꢀNꢀP backbones of
the type [R2P(E)ꢀNꢀP(E%)R2%]− have been prepared with
a variety of R groups (aryl, alkyl, aryloxy and alkoxy)
and E’s (O,S,Se). These ligands may be symmetric
(R=R% and E=E%), or asymmetric (R " R%, E " E%;
R " R%, E=E%; R=R%, E " E%) [7–12]. Quite re-
cently, a series of Te complexes with such ligands have
been prepared and their structures solved [13,14].
Other, related types of large-bite ligands where the
nitrogen atoms of the PꢀNꢀP backbone of
[Ph2P(S)ꢀNꢀP(S)Ph2]− have been replaced by ꢀCH2ꢀ or
ꢀCH2CH2ꢀ have been found to react with TeCl4 and
ArTeCl3.The reactions are typical addition reactions
and result in Te(IV) complexes [TeCl4(LꢀL)] and
[(ArTeCl3]2·m-(LꢀL)] [13,15]. These ligands have a
smaller basicity than those with a PꢀNꢀP backbone and
form weaker TeꢀS bonds. To extend our studies on Te
The coordination of the flexible, large-bite ligand
[Ph2P(E)ꢀNꢀP(E)Ph2]− (E=S, Se) with Te(II) mostly
results in square planar complexes with a TeE4 coordi-
nation sphere. The two Te(II) complexes with E=S
and Se [1,2] respectively, are isomorphous with the
square planar complexes of divalent Se (E=Se) and Sn
(E=Se) [3,4]. So far, the only Te(IV) complex known
with this ligand is [Ph3Te{Ph2P(S)ꢀNꢀP(S)Ph2}][5]. Ad-
dition of the ligand to ArTeCl3 results in disproportion-
ation and formation of a twelve-membered cyclic
dimer, [TeAr{Ph2P(S)ꢀNꢀP(S)Ph2}]2 with a T-shaped
TeCS2 coordination for each Te(II) atom [2,6]. More
* Corresponding author. Tel.: +47-5558-3551; fax: +47-5558-
9490.
E-mail address: steinar.husebye@kj.uib.no (S. Husebye).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00656-2

M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
125
complexes with large-bite ligands we have prepared
2.6. [(4-MeOC6H4TeCl3)2 {v-iPr2P(S)ꢀFcꢀP(S)iPr2}]
ligands of both types above and studied their reactions
with selected tellurium compounds.
A saturated solution of iPr2P(S)ꢀFcꢀP(S)iPr2 (0.200 g,
0.415 mmol) in dichloromethane was added to a solu-
tion of 4-MeOC6H4TeCl3 (0.290 g, 0.850 mmol) in
acetonitrile (15 ml). The resulting mixture was then
refluxed for 10 min, and an orange solid formed. After
cooling, the precipitate was collected by filtration and
dried in vacuo.
2. Experimental
2.1. General and instrumental
Yield: 0.300 g (62%); m.p.: 157–160°C (dec.). IR
(cm−1): ws (PS) 629m; was(PS) 586s, 581s. 31P{1H}-
NMR: singlet at 66.56 ppm. Microanalysis calculated
for C36H50Cl6FeO2P2S2Te2: C, 37.12; H, 4.33; S, 5.50.
Found: C, 37.28; H, 4.41; S, 5.83%.
The 31P-NMR spectra were recorded in CH2Cl2 on a
Bruker AVANCE DRX 500 instrument using H3PO4
(85%) as external standard. IR spectra were recorded
on Nujol mulls using a Bruker IFS 28 spectrometer. All
reactions were performed under argon in anhydrous
conditions. [Te(tu)4]Cl2·2H2O (tu=thiourea) and [4-
MeOC6H4TeCl3] were prepared according to literature
[16,17].
2.7. X-ray structure determination
Diffraction data were collected on a KUMA KM-4
s-axis diffractometer fitted with an area detector.
Structures were solved by direct methods and refined by
full-matrix least-squares methods using anisotropic
thermal parameters for the non-hydrogen atoms. The
programs used were: DATPROC9 and KM4RED of the
KM-4 software [21] for the data reduction, SHELXS-86
for the structure solutions [22], SHELXL-93 for the
structure refinement [23]. Crystallographic data and
refinement parameters are given in Table 1.
2.2. Ph2P(S)ꢀNHꢀP(S)(OPh)2
Synthesized according to literature [18].
i
2.3. Pr2P(S)ꢀFcꢀP(S)iPr2
Synthesized according to literature [19].
2.4. Acentric [Te{Ph2P(S)ꢀNꢀP(S)(OPh)2}2], (1a)
A solution of [Te(tu)4]Cl2·2H2O (0.170 g, 0.315
mmol) in MeOH (15 ml) was added to a solution of
Ph2P(S)ꢀNHꢀP(S)(OPh)2 (0.300 g, 0.623 mmol) in
MeOH (10 ml) at room temperature. The mixture was
stirred for 1 h. The yellow precipitate was collected by
filtration and dried in vacuum. Yield: 0.100 g (29%);
m.p.: 241–242°C. IR (cm−1): was(PNP) 1205sh, 1184s;
ws(PS) 593m; was(PS) 542s. 31P-{1H}-NMR: multiplets
43.39 ppm and 35.43 ppm. Anal. Calc. for
C48H40N2O4P4S4Te: C, 52.95; H, 3.70; N, 2.57; S, 11.76.
Found: C, 53.09; H, 3.81; N, 2.66; S, 12.09%.
3. Results and discussion
3.1. Synthesis
The two isomers of [Te{Ph2P(S)ꢀNꢀP(S)(OPh)2}2],
(1a) (acentric) and (1b) (centrosymmetric) were made
by different procedures. 1a was made by a displacement
of
the
thiourea
ligands
in
the
complex
[Te(tu)4]Cl2·2H2O by the protonated form of the ligand
Ph2P(S)ꢀNHꢀP(S)(OPh)2, which was deprotonated in
the process. The centrosymmetric complex, 1b, was a
quite unexpected product resulting from addition of the
anionic form of the ligand to 4-MeOC6H4TeCl3. Nor-
mally, aryl ligands are hard to remove because of the
strong TeꢀC bond. Nevertheless, the only explanation
for the resulting product is that all four monodentate
groups also here are displaced by the large dithiolate
ligands in a process involving disproportionation result-
ing in reduction of Te(IV) to Te(II). Displacement of an
aryl group bonded to tellurium has been observed
before in our labs [20]. The complex [(4-
MeOC6H4TeCl3)2{m-iPrP(S)ꢀFcꢀP(S)iPr2}], (2), was the
result of a simple addition reaction between two 4-
MeOC6H4TeCl3 molecules and the large-bite dithio
ligand.
2.5. Centric [Te{Ph2P(S)ꢀNꢀP(S)(OPh)2}2], (1b)
A solution of 4-MeOC6H4TeCl3 (0.177 g, 0.519
mmol) in MeOH (8 ml) was added to a solution of
Ph2P(S)ꢀNHꢀP(S)(OPh)2 (0.250 g, 0.519 mmol) and
KOtBu (0.058 g, 0.519 mmol) in MeOH (10 ml). A
yellow precipitate appeared after 30 min and the mix-
ture was stirred overnight. The precipitate was collected
by filtration and dried in vacuo.
Yield: 0.060 g (21%); m.p.: 214–215°C. IR (cm−1):
was(PNP) 1200s, 1184s; ws(PS) 576m; was(PS) 542s.
31P{1H}-NMR: doublets 27.18 ppm and 51.14 ppm,
2J(PꢀP) 28.96 Hz. Microanalysis calculated as for 1a.
Found: C, 52.81; H, 3.73; N, 2.71; S, 11.93%.

126
M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
P(S)Ph2}] [13]. Thus the neutral, potentially bidentate
3.2. Crystal structures
i
ligand, Pr2P(S)ꢀFcꢀP(S)iPr2, acts as a bridge between
two 4-MeOC6H4TeCl3 groups, its two sulfur atoms
attaching to two different Te(IV) atoms. Both tellurium
atoms have „-octahedral coordination with the aryl
group and the lone pair of electrons in axial positions
relative to the TeCl3S equatorial plane. The eclipsed
ferrocene moiety in the center of the molecule is con-
nected to the two Pr2P(S) groups of the ligand in a
‘trans’ fashion, where each group is connected to a
different cyclopentadienyl ring (Fig. 2).
The structures of 1a and 1b are shown in Fig. 1. Both
complexes are square planar complexes [TeIIL2], where
L=Ph2P(S)ꢀNꢀP(S)(OPh)−2 . L is bidentate, forming
six-membered chelate rings, TeS2P2N, in both com-
plexes. The two lone pairs of electrons on tellurium are
located above and below the coordination planes. The
acentric or cis isomer 1a is more distorted compared to
its centrosymmetric, trans isomer, 1b. In 1a the greatest
deviation from planarity in the coordination plane, is
i
,
0.148 A, the maximum difference in TeꢀS bond lengths
,
is 0.406 A, compared to absolute planarity and a
,
maximum TeꢀS bond length difference of only 0.009 A
3.3. Tellurium-ligand bonding
in 1b. Furthermore the chelate rings of 1a have differ-
ent conformations, the Te(1) to N(1) ring having the
chair form while the Te(1) to N(2) ring has the boat
form. In 1b, the rings are required by symmetry to have
the same form, which is the chair form, the most
common form in chelate complexes with such ligands.
The structure of 2, shown in Fig. 2, is similar to the
structure of [(4-MeOC6H4TeCl3)2{m-Ph2P(S)ꢀCH2CH2ꢀ
The TeꢀS bonds are quite asymmetric in 1a, there are
two
long
bonds
[Te(1)ꢀS(1)=2.8728(8)
and
,
Te(1)ꢀS(3)=2.9372(12) A] trans to two short bonds
[Te(1)ꢀS(4)=2.5311(8) and Te(1)ꢀS(2)=2.5520(10) A].
,
Also the coordination angles differ, ꢁS(1)ꢀTe(1)ꢀ
S(3):ꢁS(2)ꢀTe(1)ꢀS(4):95° while ꢁS(1)ꢀTe(1)ꢀ
S(2):ꢁS(3)ꢀTe(1)ꢀS(4):85°.
Table 1
Crystal data and refinement parameters for complexes 1a, 1b and 2
Complex
1a
1b
2
Empirical formula
Formula weight
Temperature (K)
C48H40N2O4P4S4Te
1088.54
130(2)
C48H40N2O4P4S4Te
1088.54
120(2)
C36H50C16FeO2P2S2Te2
1164.57
130(2)
,
Wavelength (A)
0.71073
Triclinic, P1
0.71073
Triclinic, P1
0.71073
Triclinic, P1
Crystal system, space group
Unit cell dimensions
,
a (A)
10.575(2)
12.787(3)
19.796(4)
71.48(3)
76.87(3)
69.55(3)
2357.9(9)
2
10.878(2)
10.955(2)
11.336(2)
107.55(3)
106.96(3)
96.71(3)
1200.5(4)
1
10.511(2)
14.855(3)
16.135(3)
63.25(3)
79.63(3)
81.66(3)
2207.1(7)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.533
0.990
1100
1.506
0.972
550
1.752
2.199
1152
Absorption coefficient (mm−1
F (000)
)
Crystal size (mm)
Theta range for data
collection (°)
0.50×0.50×0.20
3.41–29.31
0.40×0.40×0.05
3.30–28.43
0.20×0.20×0.10
3.25–28.59
Index ranges
−130h013, −160k017,
−2601010
−140h014, −140k014,
−1401015
−140h06, −190k019,
−2101021
Reflections collected/unique
Completeness to 2
11773/8948 [R(int)=0.0197]
82.4
8394/5248 [R(int)=0.0438]
97.0
14403/9622 [R(int)=0.0436]
96.3
theta=25.00 (%)
Max/min transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\| (I)]
R indices (all data)
0.8265, 0.6373
0.9530, 0.6971
0.8100, 0.6674
Full-matrix least-squares on F2
8948/0/728
Full-matrix least-squares on F2
5248/0/286
Full-matrix least-squares on F2
9622/0/470
1.069
1.188
1.041
R1=0.0312, wR2=0.0816
R1=0.0337, wR2=0.0830
R1=0.0532, wR2=0.1468
R1=0.0694, wR2=0.1542
1.264 and −1.224
R1=0.0383, wR2=0.1018
R1=0.0547, wR2=0.1052
0.963 and −0.798
Largest diff. peak and hole (e 1.027 and −1.846
−3
,
A
)

M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
127
Fig. 1. The molecular structures of 1a (top) and 1b (bottom). Anisotropic displacement parameters are drawn at the 50% probability level.
Fig. 2. The molecular structure of 2. Anisotropic displacement parameters are drawn at the 50% probability level.

128
M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
,
A similar asymmetry in TeꢀS bonding is found in
[Te{Et2P(S)ꢀNꢀP(S)(OPh)2}2] where the long bonds are
1.64 A found for most square-planar Te(II) complexes
with monodentate ligands and for asymmetric com-
plexes with bidentate small bite ligands like di-
alkyldithiocarbamates and alkylxanthates [24]. A radius
,
,
close to 2.91 A and the short ones are close to 2.52 A
[14]. This difference in bonding was therein explained
as being a result of the difference in electronic proper-
ties of the substituents on the phosphorus atoms con-
nected to sulfur. In both complexes, the (PhO)2P(S)
part of the ligand forms the longer (weaker) TeꢀS
,
of 1.64 A usually corresponds to symmetric, linear
3-center, four-electron bonding based on overlap be-
tween a 5p orbital on tellurium and suitable orbitals on
two ligands. In a square planar complex, there are two
such systems at right angles to each other. It is also
found that the apparent Te(II) radius increases with
increasing asymmetry in such systems [24].
Complex 1b is centrosymmetric with nearly identical
TeꢀS bond lengths [Te(1)ꢀS(1)=2.6759(16) and
Te(1)ꢀS(2)=2.6851(12) A] averaging 2.681 A, corre-
sponding to a normal Te(II) radius of 1.64 A. Here, the
,
bonds. The average TeꢀS bond length is 2.723 A in 1a,
nearly the same as in the similar complex above. Sub-
,
tracting the covalent radius of 1.04 A for sulfur gives a
,
radius for Te(II) of 1.68 A. This may be compared to
Table 2
,
,
,
Selected bond lengths (A) and angles (°) for 1a and 1b
,
bidentate ligands are identical to those of 1a, with
identical thiol groups trans to each other in each of the
two 3-center 4-electron SꢀTeꢀS systems in 1b, the TeꢀS
1a
1b
Bond lengths
Te(1)ꢀS(1)
Te(1)ꢀS(2)
Te(1)ꢀS(3)
Te(1)ꢀS(4)
P(1)ꢀS(1)
P(2)ꢀS(2)
P(3)ꢀS(3)
P(4)ꢀS(4)
P(1)ꢀN(1)
P(2)ꢀN(1)
P(3)ꢀN(2)
P(4)ꢀN(2)
P(1)ꢀO(1)
P(1)ꢀO(2)
P(3)ꢀO(3)
P(3)ꢀO(4)
P(2)ꢀC(13)
P(2)ꢀC(19)
P(4)ꢀC(37)
P(4)ꢀC(43)
2.8728(8)
2.5520(10)
2.9372(12)
2.5311(8)
1.9719(10)
2.0554(10)
1.9736(10)
2.0604(10)
1.5744(19)
1.5793(19)
1.5665(19)
1.5795(19)
1.6000(19)
1.5992(16)
1.6092(17)
1.590(2)
2.6759(16)
2.6851(12)
,
bond lengths are all expected to be close to 2.68 A [24].
For 2, a complex of Te(IV), the tellurium-ligand
bonding is more complex. The TeꢀC bonds are nearly
,
identical, averaging 2.111 A which is normal for such a
2.0061(16)
2.0134(16)
,
bond [25]. The TeꢀS bond lengths differ by 0.065 A
being Te(1)ꢀS(1)=2.7560(16) and Te(2)ꢀS(2)=
2.6910(13) A. These sulfur atoms are trans to Cl
ligands, the corresponding TeꢀCl bond lengths are
−
,
1.554(3)
1.585(4)
Te(1)ꢀCl(11)=2.4215(15)
and
Te(2)ꢀCl(22)=
,
2.4176(13) A. The remaining TeꢀCl bonds are pairwise
trans to each other with an average length of 2.496 A,
1.596(3)
1.590(3)
,
close to the lower quartile of TeꢀCl bonds [25]. That
the TeꢀCl bonds trans to sulfur are significantly shorter
than the other TeꢀCl bonds is due to the trans influ-
ence. Since the large dithio ligand is neutral and lacks a
central electron donating group like the ligand in 1a
and 1b, it is a weak donor with a smaller trans influence
than Cl−. This is comparable to what is found in the
analogous complex, [(4-MeOC6H4TeCl3)2{m-Ph2P(S)ꢀ
CH2CH2ꢀP(S)Ph2}] [13]. There the central part of the
ligand is ꢀCH2CH2ꢀ instead of Fc in 2. The average
1.806(2)
1.804(2)
1.804(2)
1.798(2)
1.809(4)
1.809(4)
Bond angles
S(1)ꢀTe(1)ꢀS(2)
S(1)ꢀTe(1)ꢀS(2a)
S(1)ꢀTe(1)ꢀS(3)
S(2)ꢀTe(1)ꢀS(4)
S(3)ꢀTe(1)ꢀS(4)
S(1)ꢀTe(1)ꢀS(4)
S(2)ꢀTe(1)ꢀS(3)
Te(1)ꢀS(1)ꢀP(1)
Te(1)ꢀS(2)ꢀP(2)
Te(1)ꢀS(3)ꢀP(3)
Te(1)ꢀS(4)ꢀP(4)
S(1)ꢀP(1)ꢀN(1)
S(2)ꢀP(2)ꢀN(1)
S(3)ꢀP(3)ꢀN(2)
S(4)ꢀP(4)ꢀN(2)
P(1)ꢀN(1)ꢀP(2)
P(3)ꢀN(2)ꢀP(4)
P(1)ꢀO(1)ꢀC(1)
P(1)ꢀO(2)ꢀC(7)
P(3)ꢀO(3)ꢀC(25)
P(3)ꢀO(4)ꢀC(31)
O(1)ꢀP(1)ꢀO(2)
O(3)ꢀP(3)ꢀO(4)
85.30(3)
87.11(4)
92.89(4)
95.08(3)
95.53(3)
84.61(3)
175.65(2)
173.08(2)
94.19(4)
98.52(4)
94.95(4)
98.40(4)
119.11(8)
118.17(8)
118.83(8)
117.52(8)
133.75(14)
140.77(12)
121.52(13)
124.02(13)
120.25(13)
129.27(16)
99.06(9)
,
TeꢀCl bond length trans to S is 2.432 A while the
,
average TeꢀS bond length is 2.797 A. A similar relation
is found in the octahedral complex, [TeCl4{Ph2P(S)ꢀ
CH2ꢀP(S)Ph2}] [15]. Comparison with the Te(IV) com-
plexes [4-MeOC6H4TeCl2{iPr2P(S)ꢀNꢀP(S)iPr2}] and [4-
MeOC6H4TeCl2{iPr2P(S)ꢀNꢀP(S)Ph2}] shows that in
these two complexes, the large bidentate dithio ligand is
a stronger base than the corresponding ligand in 2 [14].
The two complexes both have a „-octahedral coordina-
tion sphere like in 2 with the aryl ligand and the lone
pair of electrons in axial positions relative to an equato-
rial TeCl2S2 plane where each S atom is trans to a Cl
atom. The average TeꢀS bond length in these com-
97.85(6)
97.03(6)
120.48(15)
118.23(14)
141.4(2)
120.4(3)
123.0(3)
,
plexes is ca. 0.1 A shorter and the average TeꢀCl bond
,
length ca. 0.1 A longer than the corresponding bond
100.57(16)
lengths found in 2. Selected bond lengths and angles are
93.47(9)
given in Tables 2 and 3.

M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
129
Table 3
some double bond character related to the delocaliza-
tion of the negative charge on nitrogen towards the
sulfur atoms, especially those more strongly bonding to
tellurium [13]. The PꢀNꢀP angles are different,
133.75(14)° for P(1)ꢀN(1)ꢀP(2) and 140.77(12)° for
P(3)ꢀN(2)ꢀP(4), but both are within the normal range
for such flexible ligands [13].
,
Selected bond lengths (A) and angles (°) for 2
Bond lengths
Te(1)ꢀS(1a)
Te(1)ꢀCl(11)
Te(1)ꢀCl(12)
Te(1)ꢀCl(13)
Te(1)ꢀC(1c)
Te(2)ꢀS(2a)
Te(2)ꢀCl(21)
Te(2)ꢀCl(22)
Te(2)ꢀCl(23)
Te(2)ꢀC(1d)
P(1a)ꢀS(1a)
P(2a)ꢀS(2a)
P(1a)ꢀC(1a)
P(2a)ꢀC(5b)
PꢀC(iPr, ave)
CꢀC(Fc, ave)
CꢀFe(Fc, ave)
2.7560(16)
2.4215(15)
2.4995(13)
2.4863(13)
2.109(4)
2.6910(12)
2.4521(15)
2.4176(13)
2.5457(15)
2.112(4)
In 1b, the dithio ligands are approximately symmetri-
cally bonded to the central tellurium atom, conse-
quently the PꢀS and PꢀN bonds are similar. The
,
average bond lengths are 2.010 and 1.570 A, respec-
tively. These values are close to the average values
found in 1a. The PꢀNꢀP angle is large. The observed
value, 141.4(2)° is at the upper end of the range for
such ligands in complexes [13].
2.0062(17)
1.9994(16)
1.768(4)
1.771(4)
1.818(13)
1.415(19)
2.037(17)
i
The dithio ligand in 2 has two Pr2P(S) groups con-
nected through PꢀC bonds via a disubstituted ferrocene
(Fig. 2). There is no through-conjugation involving
electron donating groups connecting the sulfur atoms
like in 1a and 1b. Also this ligand is neutral. It is so
weakly basic that it adds to the 4-MeOC6H4TeCl3
molecules instead of displacing any Cl− ligands. This is
reflected in the weak TeꢀS bonding and the medium
strong PꢀS bonds [P(1a)ꢀS(1a)=2.0062(17) and
Bond angles
S(1a)ꢀTe(1)ꢀCl(11)
S(1a)ꢀTe(1)ꢀCl(12)
S(1a)ꢀTe(1)ꢀCl(13)
S(1a)ꢀTe(1)ꢀC(1c)
Cl(11)ꢀTe(1)ꢀCl(12)
Cl(11)ꢀTe(1)ꢀCl(13)
Cl(12)ꢀTe(1)ꢀCl(13)
Cl(12)ꢀTe(1)ꢀC(1c)
S(2a)ꢀTe(2)ꢀCl(21)
S(2a)ꢀTe(2)ꢀCl(22)
S(2a)ꢀTe(2)ꢀCl(23)
S(2a)ꢀTe(2)ꢀC(1d)
Cl(21)ꢀTe(2)ꢀCl(22)
Cl(21)ꢀTe(2)ꢀCl(23)
Cl(21)ꢀTe(2)ꢀC(1d)
Cl(22)ꢀTe(2)ꢀCl(23)
Te(1)ꢀS(1a)ꢀP(1a)
S(1a)ꢀP(1a)ꢀC(1a)
Te(2)ꢀS(2)ꢀP(2)
173.57(4)
94.90(4)
87.25(4)
82.91(11)
89.41(5)
88.39(4)
177.72(4)
89.76(12)
91.09(6)
169.14(4)
86.25(5)
80.04(12)
91.21(6)
177.00(5)
90.97(13)
91.66(6)
,
P(2a)ꢀS(2a)=1.9994(16) A]. This is a bit shorter than
the corresponding average bond lengths in 1a and b,
but very close to the PꢀS bond length in the similar
complex with the ligand Ph2P(S)ꢀCH2CH2ꢀP(S)Ph2,
,
where the average value is 2.000 A [13]. The higher
frequency for the PꢀS stretch in 2 as compared to 1a
and b supports this. The bond lengths and angles of the
eclipsed Fc group are normal. The average FeꢀC bond
105.69(6)
110.30(15)
111.69(6)
110.54(16)
165.46(18)
,
length of 2.037(17) A is close to the lower quartile of
,
the average for such bonds (2.052 A), the average CꢀC
S(2)ꢀP(2a)ꢀC(10a)
C(1a)ꢀFeꢀC(5b)
,
bond length of 1.415(19) A is equal to the upper
quartile (1.415 A) for these bonds [26].
,
For all thio ligands in the three complexes, the PꢀC,
PꢀO and CꢀC bonds are quite normal. The same
holds for the CꢀC and CꢀO bonds in the aryl ligands of
2.
3.4. Bonding in the ligands
In 1a, the asymmetry in the TeꢀS bonds is reflected in
the PꢀS bonds. To the weak TeꢀS bonds, there corre-
spond strong PꢀS bonds and vice versa. The strong PꢀS
bonds [P(1)ꢀS(1), P(3)ꢀS(3)] have an average bond
3.5. Packing
There are no especially short intermolecular contacts
in the complexes 1a and 1b, but the asymmetry in the
TeꢀS bonds (being of the 3-center 4-electron type with
average bond order only :1/2) is probably partly due
to packing effects. In 2 there are intermolecular con-
,
length of 1.973 A, somewhat longer than a double bond
,
,
[1.913(14) A] [26]. It may also be compared to 1.965 A,
the average in the similar asymmetric complex with a
Et2P(S)ꢀNꢀP(S)(OPh)−2 dithio ligand [14]. The weak
,
,
tacts CꢀH···Cl [Cl(23)ꢀH(6b) (x+1, y, z)=2.77(5) A,
,
and H(3d1)ꢀCl(12) (x−1, y−1, z+1)=2.88(6) A.
PꢀS bonds have an average bond length of 2.058 A,
close to the value of 2.050 A found in the other
asymmetric complex [14]. The PꢀN bonds are, however,
quite similar ranging from 1.5665(19) to 1.5795(19) A.
H(6b) is bonded to C(6)/(iPr) and H(3d1) is bonded to
C(3d)/(Ph)]. This indicates weak Cl···HꢀC hydrogen
bonding connecting the molecules of 2 into a three-di-
mensional network in the solid state.
,
,
This is a normal range for such ligands and indicates

130
M. Necas et al. / Journal of Organometallic Chemistry 623 (2001) 124–130
[6] S. Husebye, K. Maartmann-Moe, Ø. Mikalsen, Acta Chem.
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Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre (CCDC) CCDC no. 147427-147429.
Copies of data may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).
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Acknowledgements
The present work was supported by the Grant
Agency of the Czech Republic (Grants No. 203/98/0676
and 203/99/0067) and by the Ministry of Education of
the Czech Republic (MSM 143100011).
[19] M. Necas, J. Novosad, Polyhedron, accepted.
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