Synthesis of doubly-bridged Fe/Se and Fe/Te complexes via reactions of the [MgX]+ salts of anions [(μ-RE)(μ-CO)Fe2(CO)6]- (E=Se,Te).: Crystal structure of (μ-p-MeC6H4Te)(μ-PhC=NPh)Fe2(CO) 6

Article abstract of DOI:10.1016/S0022-328X(98)00886-9

The reactions of Grignard reagents RMgX with elemental Se or Te in THF, followed by treatment of the intermediates RSeMgX or RTeMgX with Fe₃(CO)₁₂ at room temperature (r.t.), were found to give [MgX]⁺ salts of anions [(μ-RSe)(μ-CO)Fe₂(CO)₆]^- (2) and [(μ-RTe)(μ-CO)Fe₂(CO)₆]^- (3), respectively. Furthermore, the [MgX]⁺ salts of anions 2 (R=Et) reacted in situ with the electrophile Ph₂AsCl to afford (μ-EtSe)(μ-Ph₂As)Fe₂(CO)₆ (4), whereas the [MgX]⁺ salts (R=p-MeC₆H₄) reacted with the electrophile PhNCS, followed by treatment with another electrophile MeI to give (μ-p-MeC₆H₄Se)(μ-PhN(Me)C=S)Fe₂(CO) ₆ (5). Similarly, the [MgX]⁺ salts of anions 3 (R=Et, t-Bu, i-Bu) were found to react sequentially with the electrophiles PhCCPh and CF₃COOH to yield (μ-RTe)(μ-σ,π-PhC=CHPh)Fe₂(CO)₆ (6a, R=Et; 6b, R=t-Bu; 6c, R=i-Bu), whereas reactions of the [MgX]⁺ salts of anions 3 (R=Et, Ph, p-MeC₆H₄) with the electrophiles Ph₂AsCl or PhC(Cl)NPh produced (μ-RTe)(μ-Ph₂As)Fe₂(CO)₆ (7a, R=Et; 7b, R=p-MeC₆H₄) and (μ-RTe)(μ-PhC=NPh)Fe₂(CO)₆ (8a, R=a(axial)-Ph; 8b, R=e(equatorial)-Ph; 9a, R=a-p-MeC₆H₄; 9b, R=e-p-MeC₆H₄), respectively. The reaction courses for the formation of Fe/Se and Fe/Te complexes 4-9 were discussed briefly and the structures of these new complexes, along with two other new Fe/Te complexes (μ-RTe)₂Fe₂(CO)₆ (R=Et, i-Bu), were characterized by elemental analysis and spectroscopy, as well as for complex 9b, whose structure was confirmed further by X-ray diffraction analysis.

Full text of DOI:10.1016/S0022-328X(98)00886-9

Journal of Organometallic Chemistry 571 (1998) 55–63
Synthesis of doubly-bridged Fe/Se and Fe/Te complexes via reactions
of the [MgX]+ salts of anions [(v-RE)(v-CO)Fe2(CO)6]− (E=Se,Te).
Crystal structure of (v-p-MeC6H4Te)(v-PhCꢀNPh)Fe2(CO)6
Li-Cheng Song a,*, Guo-Liang Lu a, Qing-Mei Hu a, Xiang-Dong Qin a, Cui-Xiang Sun a,
Jing Yang a, Jie Sun b
a Department of Chemistry, Nankai Uni6ersity, Tianjin 300071, People’s Republic of China
b Laboratory of Organometallic Chemistry at Shanghai Institute of Organic Chemistry, Shanghai 200032, People’s Republic of China
Received 28 April 1998; received in revised form 27 July 1998
Abstract
The reactions of Grignard reagents RMgX with elemental Se or Te in THF, followed by treatment of the intermediates
RSeMgX or RTeMgX with Fe3(CO)12 at room temperature (r.t.), were found to give [MgX]+ salts of anions [(v-RSe)(v-
CO)Fe2(CO)6]− (2) and [(v-RTe)(v-CO)Fe2(CO)6]− (3), respectively. Furthermore, the [MgX]+ salts of anions 2 (R=Et) reacted
in situ with the electrophile Ph2AsCl to afford (v-EtSe)(v-Ph2As)Fe2(CO)6 (4), whereas the [MgX]+ salts (R=p-MeC6H4) reacted
with the electrophile PhNCS, followed by treatment with another electrophile MeI to give (v-p-MeC6H4Se)(v-Ph-
N(Me)CꢀS)Fe2(CO)6 (5). Similarly, the [MgX]+ salts of anions 3 (R=Et, t-Bu, i-Bu) were found to react sequentially with the
electrophiles PhCꢁCPh and CF3COOH to yield (v-RTe)(v-|,y-PhCꢀCHPh)Fe2(CO)6 (6a, R=Et; 6b, R=t-Bu; 6c, R=i-Bu),
whereas reactions of the [MgX]+ salts of anions 3 (R=Et, Ph, p-MeC6H4) with the electrophiles Ph2AsCl or PhC(Cl)NPh
produced (v-RTe)(v-Ph2As)Fe2(CO)6 (7a, R=Et; 7b, R=p-MeC6H4) and (v-RTe)(v-PhCꢀNPh)Fe2(CO)6 (8a, R=a(axial)-Ph;
8b, R=e(equatorial)-Ph; 9a, R=a-p-MeC6H4; 9b, R=e-p-MeC6H4), respectively. The reaction courses for the formation of
Fe/Se and Fe/Te complexes 4–9 were discussed briefly and the structures of these new complexes, along with two other new Fe/Te
complexes (v-RTe)2Fe2(CO)6 (R=Et, i-Bu), were characterized by elemental analysis and spectroscopy, as well as for complex
9b, whose structure was confirmed further by X-ray diffraction analysis. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Selenium; Tellurium; Iron; CO-bridged anions; Electrophiles; X-ray structure
1. Introduction
neutral products in which the organic or inorganic
group replaced the v-CO ligand, such as in Refs. ([1]a)
and ([2]a). In the other type, reactions with the elec-
trophiles without a leaving group, initially gave another
anions and finally produced the neutral products
through further reaction of the anions with additional
electrophiles, such as in Refs. ([1]b) and ([2]b). In order
to further develop the chemistry of anion 2 and, partic-
ularly, anion 3, we recently prepared some of the new
[MgX]+ salts of 2 and 3, and explored their reactions
with various electrophiles. Interestingly, these reactions
yielded a series of new doubly-bridged Fe/Se and Fe/Te
complexes. In this report, we describe the synthesis and
As is well-known, the reactions of anions [(v-RE)(v-
CO)Fe2(CO)6]− (1, E=S [1,2]; 2, E=Se [2]; 3, E=Te
[3]) are of considerable interest and have been utilized
extensively in the synthesis of a variety of organometal-
lic complexes containing one or more (v-RE)Fe2(CO)6
structural units. For anions 1–3 most of the reactions
so far studied, according to the electrophiles employed,
might be divided into two types. In one type, reactions
with the electrophiles having a leaving group afforded
* Corresponding author. Fax: +86 22 23504853.
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00886-9

56
L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
anion 2 (R=p-MeC6H4) reacted in situ with elec-
trophilic PhNCS, followed by further treatment with
another electrophile MeI to afford a doubly-bridged
Fe/Se complex 5 in a 35% yield (Scheme 1).
characterization of such Fe/Se and Fe/Te complexes, as
well as the single-crystal molecular structure of a dou-
bly-bridged Fe/Te complex (v-p-MeC6H4Te)(v-
PhCꢀNPh)Fe2(CO)6.
Mechanistically, product 4 could be viewed as
formed via a simple SN2 process with attack of the
negatively-charged Fe of anion 2 at the As atom of
Ph2AsCl to eliminate chloride ion and subsequent coor-
dination of the lone electron pair of As and concurrent
loss of the v-CO ligand; product 5 might be similarly
envisioned as produced through the nucleophilic Fe
attack at the carbon of PhNCS, followed by coordina-
tion of the lone electron pair of S and the concomitant
loss of the v-CO ligand to generate a nitrogen-centered
anion. Subsequent electrophilic reaction of this nitrogen
anion with MeI gave the final N-methylation product 5
(Scheme 1).
It is worth pointing out that the above synthetic
method for doubly-bridged Fe/Se complexes based on
2·[MgX] salts is more convenient and more feasible
than that based on 2·[Et3NH] salts. This is because the
alkylselenols RSeH, particularly their lower homo-
logues, such as EtSeH, used for making 2·[Et3NH]
salts, are highly toxic and are much more difficult to
prepare than the alkylselenate RSeMgX utilized for the
preparation of 2·[MgX] salts. In addition, it is impossi-
ble to prepare product 5 from 2·[Et3NH] (R=p-
MeC6H4) since the intermediate nitrogen anion will be
protonated preferentially by the proton of the counte-
rion [Et3NH] to give another product (v-p-
MeC6H4Se)[v-PhN(H)CꢀS]Fe2(CO)6 [5].
2. Results and discussion
2.1. Synthesis and characterization of
(v-EtSe)(v-Ph2As)Fe2(CO)6 (4) and
(v-p-MeC6H4Se)[v-PhN(Me)CS]Fe2(CO)6 (5)
We found that the RSeMgX (R=Et, p-MeC6H4,
X=Br) prepared from an insertion reaction of Grig-
nard reagents RMgX with elemental selenium reacted
with Fe3(CO)12 in THF at r.t. to give a THF solution of
the salts [(v-RSe)(v-CO)Fe2(CO)6][MgX] (denoted as
2·[MgX]; R=Et, p-MeC6H4, X=Br) (Eq. 1). It was
believed that such salts had been formed since the IR
spectrum of the THF solution of 2·[MgX] (R=Et)
showed a medium absorption band at 1735 cm−1 for
its v-CO ligand, which was similar to that of the
[Et3NH]+ salt of anion 2 (R=Ph) showing a corre-
sponding absorption band at 1740 cm−1 [4].
(1)
Interestingly, we further found that the intermediate
salt of anion 2 (R=Et) reacted in situ with elec-
trophilic Ph2AsCl to give a doubly-bridged Fe/Se com-
plex 4 in a 22% yield, whereas the intermediate salt of
Products 4 and 5 are air-stable red solids, which have
been characterized by elemental analysis and spec-
troscopy. In principle, 4 would exist, similar to its
sulfur analogs [6], as only one isomer, in which the R
Scheme 1.

L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
57
Scheme 2.
We further found that the in situ reaction of the THF
solution of 3·[MgX] (R=Et, t-Bu, i-Bu) with the
electrophile diphenylacetylene, followed by treatment
with excess CF3COOH, gave doubly-bridged Fe/Te
complexes (v-RTe)(v-|,y-PhCꢀCHPh)Fe2(CO)6 (6a,
R=Et; 6b, R=t-Bu; 6c, R=i-Bu) in 25, 31 and 39%
yields, respectively (Scheme 3). The reaction mechanism
is similar to that proposed for the reaction of 3·[Li]
with PhCꢀCH [3], except that in this case the proton
used for protonation of the carbanion intermediates is
from the extra added electrophile CF3COOH (Scheme
3).
group is attached to Se atom by an equatorial bond to
minimize its steric repulsion with an axial Ph group
located on the As atom. In fact, the 1H-NMR spectrum
of 4 did show that the ethyl group is oriented equatori-
ally, since its SeCH2 proton NMR consists of only one
set of quartets at 2.48 ppm [6] (Scheme 2).
Although 5 might exist theoretically as two isomers
(Scheme 2) (one with an equatorial R and the other
with an axial R since no axial substituent in bridged
Ph(Me)NCS ligand), they would probably exist also as
one isomer either the e(p-MeC6H4) or the a(p-MeC6H4)
1
isomer (Scheme 2), since the p-Me H-NMR signal in
Although products 6a–c might be present theoreti-
cally as four isomers [a(R)endo(H), e(R)endo(H),
a(R)exo(H) and e(R)exo(H) (Scheme 4)], they actually
p-MeC6H4 group attached to Se in 5 showed only one
singlet at 2.25 ppm. However, we could not establish it
as the e(p-MeC6H4) or the a(p-MeC6H4) isomer due to
1
exist only as one isomer since the H-NMR spectra of
1
lack of comparable H-NMR data associated with this
CH2 in Et of 6a, CH2 in i-Bu of 6c and CH3 in t-Bu of
6b showed only one quartet, one doublet and one
singlet, respectively, and those of the HC group in the
ligand PhCHꢀCPh of 6a–c exhibit only one singlet. It
was reported ([1]c) that reactions of 1·[Et3NH] salts
with acetylenes also each afforded one isomer product,
in which the proton on the CꢀC double bond lies in an
endo position and the R group is bonded to S atom in
an equatorial orientation. Therefore, the type of isomers
for products 6a–c yielded from the similar reaction
shown in Scheme 3 would belong to e(R)endo(H).
While the reaction of anions 1 [5] and 2 (vide supra)
with Ph2AsCl are known to give doubly-bridged Fe/S
and Fe/Se compounds of the type (v-RE)(v-
Ph2As)Fe2(CO)6 (E=S, Se), no study concerning the
reaction of anions 3 with Ph2AsCl are reported so far.
Interestingly, we found that the [MgX]+ salts of anions
3 (R=Et, p-MeC6H4) could react also with Ph2AsCl,
under similar conditions to those with anions 1 or 2, to
give the type of products (v-RTe)(v-Ph2As)Fe2(CO)6
(7a, R=Et, 7b, R=p-MeC6H4) in 13 and 18% yields,
respectively (Scheme 5). It appears that the nucleo-
philicity of anions 2 is much greater than that of anions
3, since the yields of (v-EtSe)(v-Ph2As)Fe2(CO)6 (4)
and (v-EtTe)(v-Ph2As)Fe2(CO)6 (7a) are 22 and 13%,
respectively.
assignment.
2.2. Synthesis and characterization of
(v-RTe)(v-|,y-PhCꢀCHPh)Fe2(CO)6 (6a–c),
(v-RTe)(v-Ph2As)Fe2(CO)6 (7a,b) and
(v-RTe)(v-PhCꢀNPh)Fe2(CO)6 (8a,b, 9a,b)
Since we reported the first preparation of Te-contain-
ing anions [(v-RTe)(v-CO)Fe2(CO)6]− (3) [3], it is pos-
sible to make comparative studies for the anionic series
[(v-RE)(v-CO)Fe2(CO)6]− (E=S, Se, Te). Now, we
have found that anions 3 not only can be prepared as
their [Li]+ salts, but also as their [MgX]+ salts. The
preparation of 3·[MgX] salts, similar to that of 3·[Li]
salts, involved an insertion reaction of elemental Te
with Grignard reagents RMgX (R=Et, t-Bu, i-Bu, Ph,
p-MeC6H4; X=Cl, Br) followed by reaction of the
intermediates RTeMgX with Fe3(CO)12 (Eq. 2). The
formation of [MgX]+ salts of anion 3 had been also
demonstrated by IR spectrum of the THF solution of
3·[MgX] (R=Ph) showing a medium v-CO absorption
band at 1620 cm−1
.
(2)
Products 7a,b like their analogs (v-RE)(v-
Ph2As)Fe2(CO)6 [E=S [6], Se (vide supra)] exist as only
one e(R) isomer. This has been demonstrated by their
1H-NMR spectra, in which TeCH2 of 7a showed only

58
L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
23% yield, respectively). However, since Grignard
reagents are generally more readily accessible than
lithium reagents, this synthetic route based on 3·[MgX]
salts, compared to that based on 3·[Li] salts [3], would
be more convenient and more applicable in the synthe-
sis of numerous corresponding organometallics.
one quartet at 2.78 ppm and the p-Me subsituent of 7b
exhibited only one singlet at 2.29 ppm, respectively.
We found also that reaction of 3·[MgX] (R=Ph,
p-MeC6H4) with N-phenylbenzimidoyl chloride,
PhC(Cl)ꢀNPh afforded the corresponding Fe/Te com-
plexes 8a,b and 9a,b in 21 and 28% yields, respectively
(Scheme 5). Products 8a,b and 9a,b are two pairs of
isomers, in which 8a and 9a were assigned to have an
axial R, whereas 8b and 9b were assigned to have an
2.3. Crystal structure of 9b
1
In order to confirm the types of structures of 8a,b
and 9a,b, an X-ray diffraction analysis of 9b was under-
taken. The molecular structure of 9b is shown in Fig. 1;
Table 1 lists its selected bond lengths and angles. As
seen in Fig. 1, both p-MeC6H4Te and PhCꢀNPh lig-
ands are indeed bridged to two Fe atoms of the two
Fe(CO)3 units; in addition, the p-MeC6H4 group at-
tached to Te atom lies in an equatorial position,
whereas the two phenyl groups bonded to a CꢀN bond
are located in a cis manner. The C(14)–N bond in
equatorial R (Scheme 5), since the H-NMR spectra of
the former, compared to those of the latter, appeared in
higher field [3]. In addition, the single-crystal X-ray
diffraction analysis for 9b (vide infra) has confirmed
further such assignments. The IR spectra of 8a,b and
9a,b showed one medium absorption band at 1535–
1547 cm−1 for their CꢀN double bonds, so that the IR
spectra of CꢀN double bonds of 8a,b and 9a,b are
similar to those of (v-RS)(v-R%CꢀNPh)Fe2(CO)6 (wCꢀN
1555–1570 cm−1) prepared by the Seyferth group
([1]d). This means that the CꢀN double bond in 8a,b
and 9a,b might be involved basically in coordination of
the nitrogen lone electron pair with iron atom, but not
in coordination of the CꢀN double bond. In fact, this
coordination mode of v-iminoacyl has also been confi-
rmed by the single-crystal X-ray diffraction analysis of
9b (vide infra). The reaction mechanism for the forma-
tion of 7a,b is obviously the same as that described for
the production of 4, whereas production of 8a,b and
9a,b can be viewed, similar to that of (v-MeS)(v-
PhCꢀNPh)Fe2(CO)6 ([1]d), as through a simple SN2
process with attack of an iron-centered anion at the
imino carbon and subsequent bridging of the iminoacyl
ligand by the nitrogen lone electron pair with the
concomitant loss of the v-CO ligand (Scheme 5).
˚
v-iminoacyl ligand of 9b (1.293(5) A) could be best
assigned to a CꢀN double bond, but not a C–N single
bond, since the normal bond lengths of a C–N single
˚
bond and a CꢀN double bond are 1.47 and 1.28 A [7],
respectively. In fact, such a type of CꢀN double bond
was also observed in other v-iminoacyl bridged transi-
tion metal complexes, such as (v-H)(v-p2-
˚
PhCꢀNCH3)Os3(CO)10
(1.278(10)
A)
[8]
and
(v-H)(v-p2-HCꢀNPh)Os3(CO)9 (P(OMe)3) (1.320(10)
A) [9]. It follows that this is consistent with the assign-
˚
ment of its structure (according to IR data) being the
nitrogen lone electron pair coordination, but not the
CꢀN double bond coordination. However, in (v-H)(v3-
2
˚
p -HCꢀNPh)Os3(CO)9 (1.415(1) A) [9], the CꢀN double
bond is much longer than C(14)–N bond in 9b and has
approached a normal C–N single bond, due to the
CꢀN double bond coordinated to the third Os atom in
this triosmium compound.
It is worth noting that the nucleophilicity of 3·[MgX]
salts is probably similar to that of 3·[Li] salts towards
PhCꢁCPh, Ph2AsCl or PhC(Cl)NPh, since the yield of
8a,b are comparable in both reactions of N-phenylbenz-
imidoyl chloride with 3·[MgX] and with 3·[Li] (21 and
˚
The Fe(1)–N bond length of 9b is 1.993(4) A, which
is almost the same as those in (v-H)(v3-p2-
Scheme 3.

L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
59
Scheme 4.
˚
CH3CꢀNH)Fe3(CO)9 2.001(2)
A
(Fe(1)–N) and
3.1. Standard in situ preparation of intermediate salts
[(v-RSe)(v-CO)Fe2(CO)6][MgX] (2 ·[MgX]; R=Et,
p-MeC6H4; X=Br)
˚
1.931(2) A (Fe(2)–N) [10]. The Fe(2)–C(14) bond
˚
length (1.985(4) A) of 9b is reasonable for the bond
length of a |-bond between an sp2-carbon atom and an
iron atom of Fe(CO)3, such as those in (v-PhSe)(v-
A 100 ml three-necked flask equipped with a mag-
netic stir-bar, a rubber septum and a nitrogen inlet tube
was charged with 0.237 g (3.00 mmol) of selenium
powder, 30 ml of THF and 3.00 mmol of Grignard
reagents RMgX (R=Et, p-MeC6H4; X=Br) in Et2O
or THF. The mixture was stirred at r.t. for ca. 20 min
and at this time the selenium powder completely disap-
peared to give a yellowish solution. To the solution was
added 1.50 g (2.98 mmol) of Fe3(CO)12 and the mixture
was stirred at r.t. for ca. 30 min, resulting in brown–red
solutions of salts 2·[MgX] (R=Et, p-MeC6H4; X=
Br), which were utilized immediately in the following
preparations.
˚
PhCH2SCꢀS)Fe2(CO)6 (1.98(1) A) ([2]a), (v-t-BuS)[v-
˚
EtOC(ꢀCH2)CꢀO]Fe2(CO)6 (1.930(3) A) [11].
In addition, the Fe(1)–Fe(2) bond length of 2.616(1)
˚
A of 9b is basically the same as those in other similar
Fe/Te complexes, such as 2.61(1)
˚
A
in [(v-
˚
PhTe)Fe2(CO)6]2(v-Te–Te-v] [3], 2.614(4) A) in [(v-
Te)(v-Te)2Fe2(CO)6]−2 [12] and 2.634(5)
A
in
˚
[(v-MeTe)2Fe2(CO)6 [13]. Likewise, the average Fe–Te
bond length (2.535 A) of 9b agrees well with those in
[(v-PhTe)Fe2(CO)6]2(v-Te–Te-v] (2.536 A) [3], (v-
˚
˚
˚
MeTe)2Fe2(CO)6 (2.549 A) [13] and [(v-Te)(v-
Te)2Fe2(CO)6]−2 (2.572 A) [12]. The dihedral angle
˚
between the two wings [Fe(1)–Te–Fe(2) and Fe(1)–N–
C(14)–Fe(2)] of the butterfly skeleton of 9b is equal to
82.29°, which is much smaller than those between the
two Fe2Te wings in [(v-PhTe)2Fe2(CO)6]2(v-Te–Te-v)
(100.82 and 100.95°) [3] and in (v-MeTe)2Fe2(CO)6
(99.66°) [13].
3.1.1. Preparation of (v-EtSe)(v-Ph2As)Fe2(CO)6 (4)
To the above prepared solution of 2·[MgX] (R=Et,
X=Br) was added 0.29 ml (1.51 mmol) of Ph2AsCl.
The reaction mixture was stirred at r.t. for 12 h. Upon
cooling to r.t., the mixture was filtered through a ca. 5
cm high bed of 200–300 mesh silica gel to remove
insoluble materials. The filtrate was evaporated under
reduced pressure to remove all volatiles and then the
residue was subjected to TLC separation using 1:20
(v/v) CH2Cl2/petroleum ether as eluent. The first main
band gave 0.207 g (28%) of (v-EtSe)2Fe2(CO)6, which
has been identified by comparison of its m.p. and
1H-NMR spectrum with those of an authentic sample
[18]. The third main band afforded 0.204 g (22%) of 4
as a red solid, m.p. 92–93°C. Anal. Found: C, 38.79;
H, 2.20%. C20H15AsFe2O6Se Calc.: C, 38.93; H, 2.45%.
IR (KBr disk): terminal CꢁO, 2049s, 2016s, 1983vs,
3. Experimental
All reactions were carried out under an atmosphere
of prepurified nitrogen using standard Schlenk and
vacuum-line techniques. THF was distilled from
sodium-benzophenone ketyl under nitrogen. Elemental
Se and Te, PhNCS, MeI, CF3COOH and PhCꢁCPh
were chemically pure reagents and were used without
further purification. Grignard reagents RMgX [14],
Fe3(CO)12 [15], Ph2AsCl [16] and PhC(Cl)NPh [17] were
prepared according to the literature. The products were
separated by TLC (20×25×0.25 cm, silica gel G) and
further purified by recrystallization from CH2Cl2/hex-
ane. The yields of the products were calculated based
on the electrophiles Ph2AsCl, PhNCS, PhCꢁCPh and
PhC(Cl)NPh employed. IR spectra were recorded on a
Nicolet FT-IR 170 X spectrophotometer; 1H-NMR
spectra were obtained on either a Jeol FX-90 Q or a
Brucker Ac-200 NMR spectrometer. Combustion
analyses were performed on a Yanaco CHN Corder
MT-3 analyzer and melting points were determined on
a Yanaco Mp-500 apparatus.
1
1959vs cm−1. H-NMR (CDCl3): l 1.15(t, J=7.2Hz,
3H, CH3), 2.48(q, J=7.2Hz, 2H, CH2), 6.96–7.40(m,
10H, 2C6H5) ppm.
3.1.2. Preparation of (v-p-MeC6H4Se)
[v-PhN(Me)CS]Fe2(CO)6] (5)
To the above prepared solution of 2·[MgX] (R=p-
MeC6H4, X=Br) cooled to −10°C, was added 0.18 ml
(1.50 mmol) of PhNCS. The reaction mixture was
stirred at −10°C for 0.5 h and then at r.t. for 1 h.
After 0.19 ml (3.02 mmol) of MeI was added, the

60
L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
Scheme 5.
temperature for about 12 h and then 0.24 ml (3.12
mmol) of CF3COOH was added followed by stirring
the reaction mixture for an additional 2 h. The same
workup as that for 4 was then carried out, except for
TLC using neat petroleum ether as eluent. From the
first main band 0.270 g (30%) of (v-EtTe)2Fe2(CO)6
was obtained as a red oil. Anal. Found: C, 20.27; H,
reaction mixture was stirred continuously at this tem-
perature for 15 h. After the same workup as that for 4,
the first main band gave 0.182 g (20%) of (v-p-
MeC6H4Se)2Fe2(CO)6, which has been identified by
comparison of its m.p. and 1H-NMR spectrum with
those given in literature ([2]a). The second main band
afforded 0.318 g (35%) of 5 as a red solid, m.p. 111°C
(dec). Anal. Found: C, 42.20; H, 2.67; N, 2.33%.
C21H15Fe2NO6SSe Calc.: C, 42.03; H, 2.52%; N, 2.33%.
IR (KBr disk): terminal CꢁO, 2063vs, 2022vs, 2004vs,
1
1975vs cm−1. H-NMR (CDCl3): 2.25(s, 3H, ArCH3),
3.55(s, 3H, NCH3), 6.94–7.50(m, 9H, C6H4, C6H5)
ppm.
3.2. Standard in situ preparation of intermediate salts
[(v-RTe)(v-CO)Fe2(CO)6][MgX] (3 ·[MgX]; R=Et,
t-Bu, i-Bu, Ph, p-MeC6H4, X=Cl, Br)
A 100 ml three-necked flask equipped with a mag-
netic stir-bar, a rubber septum, and a reflux condenser
topped with a nitrogen inlet tube was charged with
0.383 g (3.00 mmol) of tellurium powder, 40 ml of THF
and 3.00 mmol of RMgX (R=Et, t-Bu, i-Bu, Ph,
p-MeC6H4; X=Cl, Br) in Et2O or THF. The mixture
was refluxed for 0.5 h (in the cases of aryl Grignard
reagents) or 8 h (in the cases of aliphatic Grignard
reagents) to give a light gray solution with very small
amounts of tellurium powder. Upon cooling the solu-
tion to r.t., 1.50 g (2.98 mmol) of Fe3(CO)12 was added
and the reaction mixture was stirred for ca. 0.5 h to
produce brown–red solution of salts 3·[MgX] (R=Et,
t-Bu, i-Bu, Ph, p-MeC6H4; X=Cl, Br), which was
utilized immediately in the following preparations.
3.2.1. Preparation of (v-EtTe)(v-|,y-PhCꢀCHPh)-
Fe2(CO)6 (6a)
To the above prepared solution of 3·[MgX] (R=Et,
X=Br) was added, at r.t., 0.267 g (1.50 mmol) of
PhCꢁCPh. The reaction mixture was stirred at this
Fig. 1. Molecular structure of 9b showing the atom labeling scheme.

L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
61
Table 1
Selected bond lengths (A) and bond angles (°) for 9b
produced 0.375 g (39%) of 6c as a red solid, m.p.
102–103°C. Anal. Found: C, 44.52; H, 3.02%.
C24H20Fe2O6Te Calc.: C, 44.78; H, 3.13%. IR (KBr
disk): terminal CꢁO, 2054s, 2022s, 1978vs, 1965vs
˚
˚
Bond length (A)
Te–Fe(1)
Te–Fe(2)
Te–C(7)
Fe(1)–Fe(2)
Fe(1)–N
2.5309(8) N–C(14)
1.293(5)
1.782(5)
1.791(5)
1.466(5)
1.144(6)
1.136(7)
cm−1 1H-NMR (CDCl3): l 1.18(d, J=6.0Hz, 6H,
.
2.539(2)
2.124(4)
2.616(1)
1.993(4)
1.985(4)
Fe(1)–C(1)
Fe(2)–C(4)
N–C(21)
O(1)–C(1)
O(4)–C(4)
2CH3), 2.00(m, 1H, CH), 2.87(d, J=6.0Hz, 2H, CH2),
3.35(s, 1H, HCꢀ), 6.50–7.44(m, 10H, 2C6H5) ppm.
Fe(2)–C(14)
3.2.4. Preparation of (v-EtTe)(v-Ph2As)Fe2(CO)6 (7a)
To the prepared solution of 3·[MgX] (R=Et, X=
Br) was added 0.3 ml (1.50 mmol) of Ph2AsCl. The
mixture was stirred for 8 h at r.t. and for 15 min at
reflux. The same procedure as that for 4a gave the first
band, from which 0.267 g (29%) of (v-EtTe)2Fe2(CO)6
was obtained. From the third band 0.129 g (13%) of red
solid 7a was obtained, m.p. 84–85°C. Anal. Found: C,
36.18; H, 2.15%. C20H15AsFe2O6Te Calc.: C, 36.09; H,
2.27%. IR (KBr disk): terminal CꢁO, 2041s, 2008vs,
Bond angle (°)
Fe(1)–Te–Fe(2)
Fe(2)–Te–C(7)
Te–Fe(1)–N
Fe(2)–Fe(1)–N
Te–Fe(2)–Fe(1)
Te–Fe(2)–C(14)
62.13(2)
107.1(1)
80.4(1)
70.4(1)
58.78(3)
81.0(1)
Fe(1)–Fe(2)–C(14)
Fe(1)–N–C(21)
Fe(2)–C(14)–N
Te–Fe(1)–Fe(2)
Fe(1)–N–C(14)
C(14)–N–C(21)
70.8(1)
126.2(3)
109.4(3)
59.09(3)
109.4(3)
124.3(3)
1.66%. C10H10Fe2O6Te2 Calc.: C, 20.24; H, 1.69%. IR
1
1959vs cm−1. H-NMR (CDCl3): l 1.36(t, J=7.2Hz,
(KBr disk): terminal CꢁO, 2050s, 2009vs, 1972vs cm−1
.
3H, CH3), 2.78(q, J=7.2Hz, 2H, CH2), 6.93–7.52(m,
10H, 2C6H5) ppm.
1H-NMR (CDCl3): l 1.21–1.66(m, 6H, CH3), 2.52–
2.64(m, 4H, CH2) ppm. The third main band gave
0.231 g (25%) of 6a as a red solid, m.p. 124–125°C.
Anal. Found: C, 42.89; H, 2.82%. C22H16Fe2O6Te
Calc.: C, 42.92; H, 2.62%. IR (KBr disk): terminal
3.2.5. Preparation of
(v-p-MeC6H4Te)(v-Ph2As)Fe2(CO)6 (7b)
The same procedure as that for 7a was followed, but
a solution of 3·[MgX] (R=p-MeC6H4, X=Br) was
used instead of the solution of 3·[MgX] (R=Et, X=
Br). From the first main band was obtained 0.384 g
(36%) of (v-p-MeC6H4Te)2Fe2(CO)6, which has been
identified by comparison of its m.p. and 1H-NMR
spectrum with those of an authentic sample [3]. The
third main band gave 0.195 g (18%) of 7b as a red solid,
m.p. 110–111°C. Anal. Found: C, 41.40; H, 2.39%.
C25H17AsFe2O6Te Calc.: C, 41.27; H, 2.35%. IR (KBr
disk): terminal CꢁO, 2046s, 2010s, 1982s, 1965vs,
CꢁO, 2060s, 2028vs, 1990vs, 1968vs cm−1. H-NMR
1
(CDCl3): l 1.62(t, J=7.2Hz, 3H, CH3), 2.83(q, J=
7.2Hz, 2H, CH2), 3.27(s, 1H, HCꢀ), 6.43–7.23(m, 10H,
2C6H5) ppm.
3.2.2. Preparation of
(v-t-BuTe)(v-|,y-PhCꢀCHPh)Fe2(CO)6 (6b)
The same procedure as that for 6a was followed, but
a solution of 3·[MgX] (R=t-Bu, X=Cl) was used
instead of the solution of 3 (R=Et, X=Br). The first
main band showed that it consisted of (v-t-
BuTe)2Fe2(CO)6 together with some unconsumed
PhCꢁCPh. The third main band afforded 0.297 g (31%)
of 6b as a red solid, m.p. 125–126°C. Anal. Found: C,
44.86; H, 3.06%. C24H20Fe2O6Te Calc.: C, 44.78; H,
3.13%. IR (KBr disk): terminal CꢁO, 2051s, 2013vs,
1
1951vs cm−1. H-NMR (CDCl3): l 2.29(s, 3H, CH3),
6.80–7.58(m, 14H, C6H4, 2C6H5) ppm.
3.2.6. Preparation of (v-PhTe)(v-PhCꢀNPh)Fe2(CO)6
(8a,b)
To the above prepared solution of 3·[MgX] (R=Ph,
X=Br) cooled to ca. −78°C, it was transferred slowly
by a cannula 0.323 g (1.50 mmol) of PhC(Cl)ꢀNPh in
10 ml of THF (also cooled to −78°C) and then the
reaction mixture was stirred for 15 min at −78°C and
for 12 h at r.t. After the same workup as that for 4,
from the first band was produced 0.495 g (48%) of
(v-PhTe)2Fe2(CO)6, which has been identified by com-
1968vs, 1939s cm−1. H-NMR (CDCl3): l 1.73(s, 9H,
(CH3)3C), 3.60(s, 1H, HCꢀ), 6.56–7.43(m, 10H, 2C6H5)
ppm.
1
3.2.3. Preparation of
(v-i-BuTe)(v-|,y-PhCꢀCHPh)Fe2(CO)6 (6c)
The same procedure as that for 6a was followed, but
a solution of 3·[MgX] (R=i-Bu, X=Br) was used
instead of the solution of 3·[MgX] (R=Et, X=Br).
From the first main band, was obtained 0.225 g (23%)
of (v-i-BuTe)2Fe2(CO)6 as a red oil. Anal. Found: C,
25.81; H, 2.62%. C14H18Fe2O6Te2 Calc.: C, 25.90; H,
2.79%. IR (KBr disk): terminal CꢁO, 2083s, 2048vs,
1
parison of its m.p. and H-NMR spectrum with those
of an authentic sample [3]. From second and third
bands were afforded 0.057 g (6%) of 8a and 0.144 g
(15%) of 8b. 8a and 8b could be also prepared by using
the 3·[Li] (R=Ph) salt [3] instead of the 3·[MgX]
through the same procedure. The yields of (v-
PhTe)2Fe2(CO)6, 8a and 8b are 0.433 (41), 0.076 (8) and
0.144 g (15%), respectively. Isomers 8a and 8b are red
solids.
2009vs, 1970vs cm−1 1H-NMR (CDCl3): l 0.96–
.
1.40(m, 12H, 4CH3), 1.68–2.00(m, 2H, 2CH), 2.44–
2.96(m, 4H, 2CH2) ppm. The third main band

62
L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
Table 2
Table 3
Crystal data and experimental details for 9b
The positional parameters and temperature factors for non-hydrogen
atoms of 9b
Formula
C26H17Fe2NO6Te
Formula weight
Crystal system
Space group
678.72
Atom
x
y
z
Beq
Monoclinic
P21/c (no. 14)
16.493(3)
8.467(3)
19.100(5)
90.78(2)
2666(1)
4
1.690
1328.00
21.99
Rigaku AFC7R
20.0
Mo–Kh (u=0.71069)
ꢀ−2q
50.0
3324
326
0.031
0.040
1.68
0.00
0.51
Te()
0.81508(2)
0.67111(4)
0.77695(4)
0.5398(2)
0.5762(2)
0.7047(3)
0.8272(3)
0.9225(3)
0.6727(3)
0.6668(2)
0.5918(3)
0.6144(3)
0.6924(3)
0.8094(3)
0.8652(3)
0.7130(3)
0.8879(3)
0.8731(3)
0.9246(4)
0.9885(4)
1.0036(3)
0.9540(3)
1.0424(5)
0.7183(2)
0.7257(3)
0.7927(4)
0.8004(5)
0.7429(5)
0.6757(4)
0.6664(3)
0.6162(3)
0.6522(3)
0.6051(4)
0.5223(4)
0.4869(3)
0.5329(3)
0.13396(3)
0.17841(7)
0.40858(8)
0.3810(4)
0.52791(1)
0.48476(3)
0.48539(3)
0.4329(2)
0.5304(2)
0.3464(2)
0.3408(2)
0.5368(3)
0.4356(2)
0.5758(2)
0.4525(2)
0.5134(2)
0.3998(3)
0.3976(3)
0.5178(3)
0.4557(3)
0.4494(2)
0.4259(3)
0.3783(3)
0.3512(3)
0.3747(3)
0.4241(3)
0.2966(3)
0.5755(2)
0.6294(2)
0.6715(3)
0.7189(3)
0.7238(3)
0.6816(3)
0.6345(3)
0.6356(2)
0.6990(2)
0.7534(2)
0.7454(3)
0.6837(3)
0.6280(2)
3.375(8)
2.95(1)
3.31(1)
5.15(9)
5.46(10)
6.6(1)
7.2(1)
7.9(1)
6.3(1)
3.76(9)
3.4(1)
3.6(1)
4.2(1)
4.8(1)
4.8(1)
4.0(1)
3.43(10)
4.6(1)
5.8(2)
5.5(2)
5.4(1)
4.6(1)
9.6(2)
2.41(t
3.37(10)
5.6(1)
7.3(2)
6.9(2)
6.2(2)
4.6(1)
3.07(9)
4.3(1)
5.1(1)
5.6(2)
5.8(2)
4.5(1)
˚
a (A)
Fe(1)
Fe(2)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
N()
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
˚
b (A)
˚
c (A)
i (°)
V (A )
−0.0962(4)
0.0433(5)
0.3590(5)
0.5740(6)
0.6661(5)
0.2932(4)
0.3025(5)
0.0086(6)
0.0948(6)
0.3739(6)
0.5113(6)
0.5652(6)
0.0300(5)
−0.1218(6)
−0.1898(7)
−0.1110(8)
0.0401(8)
0.1106(6)
−0.184(1)
0.4084(4)
0.5286(5)
0.5371(7)
0.6607(9)
0.7744(8)
0.1657(7)
0.6423(6)
0.2519(5)
0.2108(6)
0.1563(7)
0.1466(7)
0.1910(8)
0.2417(6)
3
˚
Z
Dcalc. (g cm−3
F(000)
)
v(Mo–Kh) (cm−1
Diffractometer
)
Temperature (°C)
˚
Radiation (A)
Scan type
2qmax (°)
No. of observed reflections, n
No. of variables, p
R
Rw
Goodness-of-fit indicator
Max shift in final cycle
Largest peak (e A
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
−3
˚
)
8a: m.p. 180° (dec). Anal. Found: C, 45.16; H, 2.14;
N, 2.15%. C25H15Fe2NO6Te Calc.: C, 45.17; H, 2.27; N,
2.11%. IR (KBr disk): terminal CꢁO, 2058vs, 2015vs,
1986vs, 1964s cm−1; CꢀN 1535m cm−1 1H-NMR
.
(CDCl3): l 5.93–7.57(m, 15H, 3C6H5) ppm.
8b: m.p. 133°C (dec). Anal. Found: C, 45.02; H, 2.15;
N, 1.98%. C25H15Fe2NO6Te Calc.: C, 45.17; H, 2.27; N,
2.11%. IR (KBr disk): terminal CꢁO, 2061vs, 2015vs,
1987vs, 1966s cm−1; CꢀN 1536m cm−1 1H-NMR
.
(CDCl3): l 6.51–7.58(m, 15H, 3C6H5) ppm.
3.2.7. Preparation of
(v-p-MeC6H4Te)(v-PhCꢀNPh)Fe2(CO)6 (9a,b)
(CDCl3): l 2.32(s, 3H, CH3), 6.53–7.45(m, 14H, C6H4,
2C6H5) ppm.
The same procedure as that for 8a,b was followed,
but a solution of 3·[MgX] (R=p-MeC6H4, X=Br)
was used in place of the solution of 3·[MgX] (R=Ph,
X=Br). The first band gave 0.449 g (41%) of (v-p-
MeC6H4Te)2Fe2(CO)6 [3]. The second and third bands
afforded 0.090 g (9%) of 9a and 0.192 g (19%) of 9b,
both isomers as red solids.
3.3. Single crystal structure determination of 9b
Single crystals of 9b suitable for X-ray diffraction
were grown from its CH2Cl2/hexane solution at −
20°C. A crystal measuring 0.20×0.20×0.30 mm was
mounted on a glass fiber and placed on a Rigaku
AFC7R diffractometer with graphite monochromator
with graphite-monochromated Mo–Kh radiation (u=
9a: m.p. 164°C (dec). Anal. Found: C, 45.89; H, 2.66;
N, 2.18%. C26H17Fe2NO6Te Calc.: C, 46.01; H, 2.52; N,
2.06%. IR (KBr disk): terminal CꢁO, 2058s, 2017vs,
˚
0.71069 A) and a 12 kW rotating anode generator. A
1997vs, 1978s cm−1; CꢀN 1544m cm−1 1H-NMR
.
total of 4335 independent reflections were collected at
20°C by the ꢀ−2q scan mode, of which 3324 indepen-
dent reflections I]3|(I) were considered to be ob-
served and used in subsequent refinement. The data
were corrected for Lorentz polarization factors. Crystal
data are listed in Table 2. Table 3 lists the positional
parameters and temperature factors for non-H atoms.
(CDCl3): l 2.32(s, 3H, CH3), 5.95–7.44(m, 14H, C6H4,
2C6H5) ppm.
9b: m.p. 142°C (dec). Anal. Found: C, 45.95; H, 2.57;
N, 2.15%. C26H17Fe2NO6Te Calc.: C, 46.01; H, 2.52; N,
2.06%. IR (KBr disk): terminal CꢁO, 2060s, 2010vs,
1987vs, 1967vs cm−1; CꢀN 1547m cm−1 1H-NMR
.

L.-C. Song et al. / Journal of Organometallic Chemistry 571 (1998) 55–63
63
[2] (a) L.-C. Song, C.-G. Yan, Q.-M. Hu, R.-J. Wang, T.C.W. Mak,
Organometallics 14 (1995) 5513. (b) L.-C. Song, C.-G. Yan,
Q.-M. Hu, R.-J. Wang, T.C.W. Mak, X.-Y. Huang,
Organometallics 15 (1996) 1535. (c) L.-C. Song, C.-G. Yan,
Q.-M. Hu, B.-M. Wu, T.C.W. Mak, Organometallics 16 (1997)
632.
[3] L.-C. Song, C.-G. Yan, Q.-M. Hu, X.-Y. Huang, Organometal-
lics 16 (1997) 3769.
[4] L.-C. Song, C.-G. Yan, Q.-M. Hu, R.-J. Wang, H.-G. Wang,
Acta Chim. Sin. 53 (1995) 402.
[5] L.-C. Song, et al., unpublished work.
[6] L.-C. Song, R.-J. Wang, Y. Li, H.-G. Wang, J.-T. Wang, Acta
Chim. Sin. 48 (1990) 867.
[7] Special Publication: Chem. Soc. (1965) No. 18—C. Sandorfy, in:
S. Patai (Ed.), The Chemistry of the Carbon Nitrogen Double
Bond, Wiley, New York, 1970, Ch. 1.
The structure was solved by direct methods and
expanded using Fourier techniques. The non-hydrogen
atoms were refined anisotropically, and H atoms were
included but not refined. The final refinement by a
full-matrix least-squares method for non-H atoms con-
verged to give the unweighted and weighted agreement
factors of 0.031 (R) and 0.040 (Rw). The highest peak
on the final difference Fourier map has a height of 0.51
e A−3. All calculations were performed using the
˚
TEXSAN program system crystallographic software of
the Molecular Structure Corporation.
[8] R.D. Adams, N.M. Golembeski, Inorg. Chem. 17 (1978) 1969.
[9] R.D. Adams, N.M. Golembeski, J. Am. Chem. Soc. 101 (1979)
2579.
Acknowledgements
We are grateful to the National Natural Science
Foundation of China, the Laboratory of Organometal-
lic Chemistry and the State Key Laboratory of Struc-
tural Chemistry for financial support of this work.
[10] M.A. Andrews, G. van Buskirk, C.B. Knobler, H.D. Kaesz, J.
Am. Chem. Soc. 101 (1979) 7245.
[11] D. Seyferth, J.B. Hoke, J.C. Dewan, P. Hofmann, M. Schnell-
bach, Organometallics 13 (1994) 3452.
[12] B.W. Eichhorn, R.C. Haushalter, J.S. Merola, Inorg. Chem. 29
(1990) 728.
[13] R.E. Bachman, K.H. Whitmire, Organometallics 12 (1993) 1989.
[14] H. Gilman, E.A. Zoellner, J.B. Dickey, J. Am. Chem. Soc. 51
(1929) 1576.
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