A new entry into ferraborane chemistry: Synthesis and characterization of heteroferraborane complexes

Article abstract of DOI:10.1016/j.ica.2010.12.033

Reaction of [CpFe(CO)₂I], 1 (Cp = η⁵-C ₅H₅) and di(organyl)dichalcogenides, E₂R ₂ (E = S, Se; R = Ph, CH₂Ph, 2,6-(^tBu) ₂-C₆H₂OH) with

Full text of DOI:10.1016/j.ica.2010.12.033

Inorganica Chimica Acta 372 (2011) 42–46
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Inorganica Chimica Acta
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A new entry into ferraborane chemistry: Synthesis and characterization
of heteroferraborane complexes
⇑
K. Geetharani, Shubhankar Kumar Bose, Debajyoti Basak, Venkata M. Suresh, Sundargopal Ghosh
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 21 December 2010
Reaction of [CpFe(CO)2I], 1 (Cp =
g
5-C5H5) and di(organyl)dichalcogenides, E2R2 (E = S, Se; R = Ph, CH2Ph,
2,6-(tBu)2-C6H2OH) with [LiBH4Áthf] at À70 °C in toluene, followed by stirring at room temperature for
18 h yielded heteroferraboranes, [CpFe(CO)B2H4(l-L)], 2–4 (2: L = SePh; 3: SeCH2Ph and 4: S(2,6-
Dedicated to Professor S.S. Krishnamurthy
on the occasion of his 70th birthday.
(tBu)2-C6H2OH). Compounds 2–4 are highly unstable and concurrent lose of boron atoms yielded orga-
nochalcogenolato-bridged complexes, [CpFe(CO)( -L)]2, 5–7, respectively (5: L = SePh; 6: SeCH2Ph and
7: S(2,6-(tBu)2-C6H2OH). In contrast, the reaction of 1 with di(2-furyl)ditelluride, (C4H3O)2Te2, yielded
organotellurato-bridged complex, [CpFe(CO)( -TeC4H3O)]2, 8 and all of our attempts to isolate the boron
precursor [CpFe(CO)B2H4(
l
Keywords:
Boron
Ferraborane
Chalcogenide ligand
Selenium
l
l
-TeC4H3O)] in pure form failed. The accuracy of these predictions in each case
is established by IR, 1H, 11B, 13C, 77Se, 125Te NMR and mass spectrometry and complex 8 is further struc-
turally confirmed by X-ray crystallography.
Tellurium
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
dimolybdaheteroborane clusters [16], an investigation of metalla-
heterobaranes containing group 8 metal, became of interest. As ferr-
Metallaborane [1,2] and metallaheteroborane [3,4] chemistry is
widespread and has historically developed largely by the incorpo-
ration of one, two, or three atoms other than boron into the borane
cluster. Syntheses of metallaheteroborane clusters are typically af-
fected by the addition of metal complexes to heteroborane clusters
[5], and as a result there is substantial interest in the nature of the
chemistry that may typically result while the transition metals are
from the first row. Metallaheteroborane compounds containing
group 16 elements as cluster constituents [6,7] have mostly been
generated from the reaction of metal centers with preformed poly-
hedral heteroborane substrates [8], and very little attention has
been given to the idea of producing metallaheteroborane by the
addition of the heteroatom to metallaborane clusters [9].
aboranes are rare [17], and known heteroferraboranes [18,19,6b,20]
even more so, we have begun to investigate the use of different
chalcogen sources which generally may result new types of cluster
systems. In this paper, we present a set of small monometallic
heteroferraborane compounds generated from the reaction of
dichalcogenide ligands and an in situ generated intermediate
([CpFe(CO)B3H8]) [21], produced from the reaction between
[CpFe(CO)2I] 1 and [LiBH4Áthf].
2. Results and discussion
2.1. Isolation and characterization of 2–4
As a part of our interest in synthesizing metallaboranes of group
5–9 from various metal precursors and small metallaboranes, re-
cently we have reported several novel metallaborane and metal-
laheteroborane compounds of group 5 and 6 transition metals
[10–14]. Accordingly, in our continuing search for different metal
As shown in Scheme 1, compounds 2–4 have been isolated in
good yields as red brown solids. The 1H and 11B NMR spectra pro-
vided convincing evidence for the structure and bonding of these
complexes. The 11B NMR spectra of 2–4 are very identical consist-
ing of a triplet, which indicates the presence of BH2 group. The IR
spectra show bands due to terminal carbonyl groups. Descriptions
of the characterization of 2–4 from mass spectrometry and IR, 1H,
11B, 13C NMR spectroscopic studies follow.
precursors, containing CpÃM (Cpà =
g
5-C5Me5) fragment, we found
that mono(halo)(cyclopentadienyl)metal carbonyl, [CpÃM(CO)nX],
(when M = Mo or W, X = Cl and n = 3; M = Fe, X = I and n = 2), are
very useful to group 6 and 8 metallaboranes [15]. After it had been
discovered that the reaction of [CpÃMoCl4] with [LiBH4Áthf] in pres-
ence of dichalcogenide ligands yielded a new class of open-cage
2.1.1. arachno-[CpFe(CO)B2H4(l–SePh)] (2)
The composition and structure of 2 is established in comparison
of the spectroscopic data with arachno-[CpÃFe(CO)B3H8] [15] and
related species [22–25]. The composition of 2 is defined by the
mass, an isotopic distribution pattern characteristic of one Fe,
⇑
Corresponding author. Tel.: +91 44 2257 4230; fax: +91 44 2257 4202.
E-mail address: sghosh@iitm.ac.in (S. Ghosh).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.12.033

K. Geetharani et al. / Inorganica Chimica Acta 372 (2011) 42–46
43
2.1.3. arachno-[CpFe(CO)B2H4(l
–S(2,6-(tBu)2-C6H2OH)] (4)
The mass spectrum of 4 in the high m/z range shows a molecu-
lar ion peak at 412 corroborating the composition of C20H30B2
Fe1O2S1 and a single resonance at d = À28.4 ppm in the 11B NMR
spectrum indicates a highly symmetrical structure in solution.
The 11B chemical shift is consistent with hydrogen-bridged rather
than direct Fe–B linkages and the 1H chemical shift with the inten-
sity ratio of 5:2:2, attributed to the Cp, Fe–H–B and B–H protons,
respectively. The IR spectrum of 4 shows a band at 1966 cmÀ1
which is characteristic of terminal carbonyl ligand. However, spec-
troscopic analysis were used to assign 4 as an arachno-metallahe-
teroborane, similar to that of [B4H10], where one of the wing-tips,
that is BH2, has been replaced by [CpFe(CO)] fragment and another
wing-tip BH4 by [S(2,6-(tBu)2-C6H2OH)] fragment.
Scheme 1. Synthesis of heteroferraboranes, 2–4.
two B and one Se atom. It is also evident by the loss of one CO from
the parent ion mass of 330. The 11B NMR spectrum reveals one
equivalent of boron environment associated with one terminal
hydrogen and one bridging hydrogen at d = À25.1 ppm. The
chemical shift and multiplicity of 11B NMR resonance is character-
istic of those observed for metal–B3H8 complexes [22] and
The existence of compounds 2–4 permit comparison of the spec-
troscopic parameters with other metal–B3H8 complexes, which are
listed in Table 1. The 11B resonances, on going from the lighter to
the heavier metal atom, appeared at low field, whereas the 1H chem-
ical shifts (M–H–B) appear at high field. Difference in the 1H and 11
B
NMRchemicalshiftcorrelationof 2–4withother relatedcompounds
may due to the perturbation of the electronic environment of the
boron atoms both by the metal and the chalcogen ligands.
[CpÃRu(PMe3)(
g
2-B2H7)] [23]. Besides the Cp protons, 1H NMR
spectrum reveals four protons associated with boron cage with a
ratio of 1:1. The resonances appeared at d = À16.12 and 1.83 ppm
have been assigned to two equivalents each of Fe–H–B and B–H
terminal protons, respectively. The 77Se NMR of 2 shows single res-
2.2. Isolation and characterization of (5–8)
onance at d = 336 ppm for the bridged
l-SePh group. In addition,
Up to date significant attention has been devoted to the metal
complexes with chalcogenolate ligands [26,27]. The keen interest
in this area stems from the richness of their structural, bonding
and reactivity features [28,29] and their relevance to materials sci-
ence [30,31]. In contrast to the larger number of sulfur containing
clusters, those containing selenium and tellurium have been less
explored [32,33].
the IR spectrum shows band corresponding to terminal carbonyl
group at 1965 cmÀ1. All the spectroscopic data suggest a seven
skeletal electron pair (sep) 2 with molecular formula [CpFe
(CO)B2H4(l-SePh)].
Compounds 2–4 are highly unstable and sensitive to both air
and moisture. As a result they slowly converted to corresponding
organochalcogenolato-bridged complexes, 5–7 from a hexane solu-
tion (Scheme 2, vide infra) even at low temperature. Identification
of 5 is based on a comparison of its spectral features and a solid
state X-ray structure which is reported earlier [34]. The mass spec-
trometry measurements of 6 and 7 gave molecular ions corre-
sponding to C26H24Fe2O2Se2 and C40H52Fe2O4S2, respectively. The
IR spectra of 6 and 7 (6: 1955; 7: 1956 cmÀ1) are indicative of ter-
minal CO groups. The 1H spectra show Cp resonances at d = 4.68
and 5.25 ppm for 6 and 7, respectively. Consistent with this obser-
vation, the 13C NMR spectra of 6 and 7 show resonances corre-
sponds to the Cp and CO groups.
2.1.2. arachno-[CpFe(CO)B2H4(l–SeCH2Ph)] (3)
The parent ion in the mass spectrum fragments by the loss of
CO molecule and the molecular mass corresponds to [CpFe(CO)
B2H4(SeCH2Ph)]. The IR spectrum of compound 3 supports the
presence of a terminal carbonyl ligand appeared at 1953 cmÀ1
.
The 11B NMR spectrum of
3 shows a singlet resonance at
d = À24.1 ppm approximating to a triplet and the chemical shift
is similar to that observed for 2. The 1H NMR spectrum reveals
the presence of one Cp resonance and a single broad resonance
at d = À16.1 ppm due to Fe–H–B. The terminal boron hydrogen
atoms resonate at d = 1.78 ppm. The 13C NMR spectrum indicates
the presence of carbonyl ligand appeared at d = 216.4 ppm. The
77Se NMR spectrum of 3 shows a single peak, in the region nor-
mally associated with l-Se ligand (d = 332 ppm). Despite many at-
tempts to grow X-ray-quality crystals of 3 were unsuccessful,
however, the molecular formula as well as the spectroscopic prop-
erties of 3 are best fit with the proposed structure as shown in
Scheme 1.
2.3. Compound 8
In an attempt to synthesize telluroferraborane [CpFe(CO)B2H4
(l-TeC4H3O)], 1 was treated with [LiBH4Áthf] and di(2-furyl)ditellu-
Table 1
Comparision of selected spectroscopic parameters of compounds 2–4, 6–8 and related species.
Compound
1H NMR (ppm)[M–H–B]
11B NMR (ppm)a
77Se NMR (ppm)
mCO (cmÀ1
)
Ref.
2
3
4
À16.12
À16.10
À15.66
À15.4
À11.1
À12.01
À9.50
À10.3
–
À25.1
À24.1
À28.4
À41.3
À21.4
À34.6
À36.5
À39.9
–
336
332
–
–
–
–
–
–
1965
1953
1966
1967
–
–
–
–
This work
This work
This work
[15]
[23]
[24]
[22a]
[25]
This work
This work
This work
[CpÃFe(CO)B3H8]
[CpÃRu(PMe3)(
g
2-B2H7)]
[CpÃRu(PMe3)B3H8]
[(
g
6-C6Me6)Ru(Cl)B3H8)]
[CpÃRe(H3)B3H8]
6
7
8
333
–
1955
1956
1923
–
–
–
–
373b
a
11B NMR of hinge boron (M–H–B).
125Te NMR.
b

44
K. Geetharani et al. / Inorganica Chimica Acta 372 (2011) 42–46
Scheme 2. Reaction pathway for the formation of 5–7 from heteroferraboranes, 2–4.
ride in toluene for 4 h. However, a rather unexpected observation,
not seen with analogous S and Se systems, was the direct forma-
tion of organotellurato-bridged complex 8. Compound 8 has been
characterized spectroscopically, as well as by a single crystal
X-ray diffraction study. Mass spectral data of 8 suggest a molecular
formula of C20H16Fe2O4Te2. The IR spectrum of 8 in the carbonyl re-
gion displays band at 1923(m) cmÀ1 due to terminal carbonyl
groups. The 1H NMR shows single resonance for Cp ligands at
d = 4.89 ppm. The 13C NMR spectrum shows four resonances at
d = 108.4, 110.2, 143.7 and 144.6 ppm for furyl ligands. In addition
to these, resonances at d = 213.6 and 210.2 ppm are due to the CO
groups. The 125Te NMR spectrum of 8 shows a signal at d = 373
ppm, which is in well agreement with the reported organotellura-
to-bridged complex [35].
The definitive assignment of the structure of 8 was obtained by
X-ray crystallography (Fig. 1). The iron atom is bonded to a car-
bonyl and cyclopentadienyl ligand, which together with the two
Te contacts yield a distorted tetrahedral environment (82.42–
127.31°) about Fe. On the other hand, the tellurium atom is also
bonded to a 2-furyl ligand, which together with the two iron con-
tacts, gives rise to a distorted trigonal–pyramidal arrangement
(93.30–106.64°) in which Te lies at the apex of the pyramid. The
cyclopentadienyl ligands on the iron atoms are trans disposed with
respect to each other and 2-furyl ligands on the tellurium atoms
are also in trans configuration.
Fig. 1. Molecular structure and labeling diagram for [CpFe(CO)(l-TeC4H3O)]2 8.
Relevant bond lengths (Å) and angles (°): Fe(1)–Te(1) 2.5567(9), Fe(1)–Te(2)
2.5435(8), Fe(2)–Te(1) 2.5606(9), Fe(2)–Te(2) 2.5690(9), C(11)–Te(1) 2.108(5),
C(15)–Te(2) 2.121(5); Fe(1)–Te(1)–Fe(2) 93.30(3), Fe(1)–Te(2)–Fe(2) 93.42(3),
C(11)–Te(1)–Fe(1) 102.68(14), C(15)–Te(2)–Fe(1) 106.57(15), C(11)–Te(1)–Fe(2)
102.50(14), C(15)–Te(2)–Fe(2) 106.83(16).
An interesting piece of structural data can be found by compar-
ing the geometry of 8 with different organotellurato-bridged com-
plexes [35–37]. The FeÁ Á ÁFe separations are found to be 3.721 Å and
apparently depend mainly on the size of the chalcogen atoms. It is
reasonable to assume that interaction and communication be-
tween the two metals is essentially transferred through the two
Te(2-furyl) bridges. The Te–Te bond distance is too long to consider
the existence of any TeÁ Á ÁTe bonding interaction. The angles at the
metal (Te–Fe–Te, 81–82°) are generally more acute than those at
the chalcogen (Fe–Te–Fe, 93°), although they are comparable
(93–94°) in the p-ethoxyphenyltellurolato complex, [CpFe(CO)
(TeC6H4OC2H5)]2 [37]. The mean Fe–Te bond distance (2.5574 Å)
is slightly longer than the Fe–Te bond distance of 2.5495 Å in
distances of 2.108(5) and 2.121(5) Å, compare favorably with other
Te–C distances, e.g., 2.136(8) Å in 2-biphenyltellurium tribromide
[39].
2.4. Reaction pathways
The mechanism for the formation of 5–7 is not fully implicit;
however a plausible sequence of actions is shown in Scheme 2. It
is reasonable to consider that compounds 2–4 are the primary
products of the oxidative attack of dichalcogenide ligands to the
ferraborane, arachno-[CpFe(CO)B3H8] [21]. The ER (E = S, Se) in 2–
4 is a five-skeletal electron donor isoelectronic with the BH4 unit;
therefore the replacement of wing-tip boron hydride in ferrabora-
ne necessitates the formation of 2–4. As shown in Scheme 2, a
three-step mechanism has been suggested to account for the for-
mation 5–7 from 1. Further, to evaluate the ultimate fate of the
[Fe2(CO)6(l-TeCH3)2] [38]. The Fe–C (carbonyl) distances of
1.748(6) Å and the Fe–C (Cp) distances of 2.07–2.10 Å are compa-
rable with distances in similar iron compounds. The carbonyl
groups in 8 are very close to linear. Tellurium–carbon (furyl)

K. Geetharani et al. / Inorganica Chimica Acta 372 (2011) 42–46
45
released boron atoms in the last step, low temperature reaction of
2–4 was performed in the presence of Lewis base, PMe2Ph. The
reaction was monitored by 11B NMR spectroscopy, which revealed
the formation of borane base adduct (BH3ÁPMe2Ph), as indicated by
the presence of a single resonance in the 11B{1H} NMR spectrum at
d = À36.2 ppm [40]. Thus it is possible that upon slow release of
BH3 from 2 to 4, compounds 5–7 are formed. On the other hand,
in order to verify further the formation of telluroferraborane,
the similar reaction conditions, PhCH2Se–SeCH2Ph (0.52 g,
1.53 mmol) and (2,6-(tBu)2-C6H2OH)2S2 (0.74 g, 1.56 mmol)
yielded 3 (0.07 g, 51%) and 4 (0.05 g, 30%), respectively. Note that,
reaction of 1 with [LiBH4Áthf] and (C4H3O)2Te2 (0.6 g, 1.54 mmol) in
toluene for 4 h, under the same reaction conditions yielded 8
(0.08 g, 29%).
Compound 2. 11B NMR (128 MHz, CDCl3, 22 °C): d À25.1 (br s,
2B); 1H{11B} NMR (400 MHz, CDCl3, 22 °C): d 7.60–7.01(m, 5H,
Ph), 4.63 (s, 5H, Cp), 1.83 (partially collapsed quartet (pcq), 2
BHt), À16.12 (s, 2Fe–H–B); 13C NMR (100 MHz, CDCl3, 22 °C): d
223.3 (s, Fe–CO), 131.6, 129.3, 128.6, 127.8 (s, C6H5), 78.7 (s,
C5H5); 77Se NMR (95.38 MHz, CDCl3, 22 °C): d 336 (s, Se); MS
(FAB+): m/z (%) = 330 [M]+, 302 [MÀCO]+; IR (hexane cmÀ1): 2496
(w, BHt), 1965 (s, Fe–CO); C12H14B2FeOSe: Calc. C, 43.59; H, 4.27.
Found: C, 44.06; H, 4.64.
[CpFe(CO)B2H4(l-TeC4H3O)] as an intermediate in the formation
of 8, low temperature reaction of 1 and di(2-furyl)ditelluride with
[LiBH4Áthf] was monitored by 11B NMR spectroscopy, which re-
vealed the formation (almost immediately) of a new boron con-
taining compound, as indicated by the presence of a resonance at
d = –29.2 ppm. The peak at d = –29.2 ppm slowly decreases as the
reaction progresses and finally disappears after the reaction mix-
ture stirred for 4 h at room temperature. Thus, we assume that tell-
uroferraborane is an intermediate in the formation of 8.
Compound 3. 11B NMR (128 MHz, CDCl3, 22 °C): d À24.1 (br s,
2B); 1H{11B} NMR (400 MHz, CDCl3, 22 °C): d 7.69–7.26 (m, 5H,
Ph), 4.61 (s, 5H, Cp), 2.76 (s, PhCH2Se), 1.78 (pcq, 2 BHt), À16.10
(s, 2Fe–H–B); 13C NMR (100 MHz, CDCl3, 22 °C): d 216.4 (s, Fe–
CO), 129.2, 128.8, 128.5, 128.3 (s, C6H5), 79.8 (s, C5H5), 34.5 (s,
PhCH2Se); 77Se NMR (95.38 MHz, CDCl3, 22 °C): d 332 (s, Se); MS
(FAB+): m/z (%) = 344 [M]+, 316 [MÀCO]+; IR (hexane cmÀ1): 2417
(w, BHt), 1953 (s, Fe–CO).
3. Conclusions
In conclusion, the synthesis and characterization of heteroferr-
aboranes have been described, which on slow decomposition gen-
erate organochalcogenolato-bridged complexes, 5–8. Apparently,
these results highlight the possibility of practical application in
the synthesis of a new class of mixed transition metal/chalcogen/
boron complexes. Efforts to assess the scope, limitations, as well
the solid state structure of these novel heteroferraboranes 2–4
are now in process.
Compound 4. 11B NMR (128 MHz, CDCl3, 22 °C): d À28.4 (br s,
2B); 1H{11B} NMR (400 MHz, CDCl3, 22 °C):
d 7.04 (s, 2H,
C6H2OH), 5.08 (s, C6H2OH), 4.79 (s, 5H, Cp), 2.08 (br, 2BHt), 1.35
(s, 18H, (CH3)3C), À15.66 (s, 2Fe–H–B); 13C NMR (100 MHz, CDCl3,
22 °C): d 221.1 (s, Fe–CO), 154.3, 136.8, 127.8 (s, C6H2OH), 79.4 (s,
C5H5), 34.6 (s, –C(CH3)3), 30.3 (s, C(CH3)3); MS (FAB+): m/z (%) = 412
[M]+, 384 [MÀCO]+; IR (hexane cmÀ1): 2432 (w, BHt), 1966 (s, Fe–
CO).
4. Experimental
Compound 8. 1H NMR (400 MHz, CDCl3, 22 °C): d 7.72–6.55 (s,
3H, C4H3O), 4.89 (s, 5H, Cp); 13C NMR (100 MHz, CDCl3, 22 °C): d
213.6, 210.2 (s, Fe–CO), 144.6, 143.7, 110.2, 108.4 (s, C4H3O), 80.1
(s, C5H5); 125Te NMR: d 373 (s, 2Te); MS (ESI+): m/z (%) = 688
[M]+, 660 [MÀCO]+, 632 [MÀ2CO]+; IR (hexane cmÀ1): 1923 (s,
Fe–CO). C20H16Fe2O4Te2: Calc. C, 34.95; H, 2.35. Found: C, 34.41;
H, 2.06.
4.1. General procedures and instrumentation
All the operations were conducted under an Ar/N2 atmosphere
using standard Schlenk techniques and glove box. Solvent were
distilled prior to use under Argon. [CpFe(CO)2]2, [LiBH4Áthf] (Al-
drich) were used as received. The external reference [Bu4N(B3H8)]
for the 11B NMR, was synthesized with the literature method [41].
The [CpFe(CO)2I] [42], (C4H3O)2Te2 [43], (PhCH2)2Se2 [44], Ph2Se2
[45] and (2,6-(tBu)2-C6H2OH)2S2 [46] were prepared as described
in the literature. Thin layer chromatography was carried on
250 mm diameter aluminum supported silica gel TLC plates
(MERCK TLC Plates). NMR spectra were recorded on a 400 and
500 MHz Bruker FT-NMR spectrometer. Residual solvent protons
were used as reference (d, ppm, CDCl3, 7.26), while a sealed tube
containing [Bu4N(B3H8)] in C6D6 (dB, ppm, À30.07) was used as
an external reference for the 11B NMR. Microanalyses for C, H
and N were performed on Perkin-Elmer Instruments series II model
2400. Infrared spectra were obtained on a Nicolet 6700 FT-IR spec-
trometer. Mass spectra were obtained on ESI Q-Tof Micro mass
Spectrometer and Jeol SX 102/Da-600 mass spectrometer/Data
System using Argon/Xenon (6kv, 10 mÅ) as the FAB gas.
4.3. Generation of 5–7 from 2 to 4
In a 50 mL Schlenk tube, containing 0.2 g (0.6 mmol) of 2 in
3 mL of hexane was kept at 4 °C for 5 days. The solvent was dried
and the residue was extracted into hexane and passed through Cel-
ite. After removal of solvent, the residue was subjected to chro-
matographic work up using silica gel TLC plates. Elution with a
hexane/CH2Cl2 (95:05 v/v) mixture yielded reddish brown 5
(0.24 g, 65%). Under identical conditions, 3 (0.3 g, 0.87 mmol) and
4 (0.2 g, 0.49 mmol) yielded 6 (0.26 g, 47%) and 7 (0.18 g, 48%),
respectively. Note that the optimized reaction time for the conver-
sion of 2–4 into the respective organochalcogenolato-bridged com-
plexes 5–7 was 5 days.Compound
5 was characterized by
comparison of its spectroscopic data and an X-ray structure re-
ported earlier [34].
4.2. General procedure for the synthesis of 2–4
Compound 6. 1H NMR (400 MHz, CDCl3, 22 °C): d 7.43–7.25 (s,
10H, C6H5CH2), 4.68 (s, 10H, Cp), 2.43 (s, 4H, C6H5CH2); 13C NMR
(100 MHz, CDCl3, 22 °C): d 218.1, 213.6 (s, Fe–CO), 137.8, 129.4,
128.3, 125.4 (s, C6H5CH2), 91.1 (s, C5H5), 25.3 (s, C6H5CH2); 77Se
NMR (95.38 MHz, CDCl3, 22 °C): d 333 (s, 2Se); MS (FAB+): m/z
(%) = 638 [M]+, 610 [MÀCO]+, 582 [MÀ2CO]+; IR (hexane cmÀ1):
1955 (s, Fe–CO). C26H24Fe2O2Se2: Calc. C, 48.94; H, 3.79. Found:
C, 49.16; H, 4.18.
In a typical reaction, 1 (0.120 g, 0.39 mmol) was loaded in a
100 mL Schlenk tube and freshly distilled toluene (10 mL) was
added to generate a brown solution and the mixture cooled to
À70 °C. LiBH4 (0.78 mL, 1.56 mmol) was added dropwise and stir-
red at room temperature in presence of an excess of PhSe–SePh
(0.48 g, 1.54 mmol) for 18 h. The solvent was dried and the residue
was extracted into hexane and passed through Celite. After re-
moval of solvent, the residue was subjected to chromatographic
work up using silica gel TLC plates. Elution with a hexane/CH2Cl2
(95:05 v/v) mixture yielded reddish brown 2 (0.06 g, 46%). Under
Compound 7. 1H NMR (400 MHz, CDCl3, 22 °C): d 7.19 (s, 4H,
C6H2OH), 5.25 (s, 10H, Cp), 5.18 (s, 2H, C6H2OH), 1.35–1.32 (s,
36H, (CH3)3C); 13C NMR (100 MHz, CDCl3, 22 °C):
d
214.1
(s, Fe–CO), 136.8, 127.9, 127.0 (s, C6H2OH), 82.1 (s, C5H5), 34.6 (s,

46
K. Geetharani et al. / Inorganica Chimica Acta 372 (2011) 42–46
–C(CH3)3), 30.29 (s, C(CH3)3); MS (FAB+): m/z (%) = 772 [M]+, 744
[MÀCO]+, 716 [MÀ2CO]+; IR (hexane cmÀ1): 1956 (s, Fe–CO).
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(d) M.J. Carr, M.G.S. Londesborough, A.R.H. Mcleod, J.D. Kennedy, Dalton Trans.
(2006) 3624.
C
40H52Fe2O4S2: Calc. C, 62.18; H, 6.78. Found: C, 62.86; H, 7.27.
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4.4. X-ray structure determination
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Crystal data were collected and integrated using Bruker Apex II
CCD area detector system equipped with graphite monochromated
Mo Ka (k = 0.71073 Å) radiation at 173 K. The structure was solved
by heavy atom methods using SHELXS-97 [47] and refined using
SHELXL-97 [48] (G.M. Sheldrick, University of Göttingen). X-ray
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Crystal data for 8: formula, C20H16Fe2O4Te2; M = 687.23 g/mol;
crystal system, space group: orthorhombic, Pbca; unit cell dimen-
sions: a = 13.234(3) Å, b = 17.198(3) Å, c = 18.514(4) Å; Z = 8;
density (calculated) 2.167 Mg/m3; final R indices [I > 2
r(I)] R1 =
0.0329, wR2 = 0.0925; index ranges: À12 <= h <= 17, À15 <= k <=
22, À24 <= l <= 20; crystal size: 0.22 Â 0.16 Â 0.09 mm3; reflec-
tions collected 17,415; independent reflections: 5145; [R(int) =
0.0405], goodness-of-fit on F2 0.737.
ˇ
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Acknowledgements
Generous support of the Department of Science and Technology
(DST), Grant No. SR/S1/IC-19/2006, New Delhi, is gratefully
acknowledged. K.G. and S.K.B. thank the Council of Scientific and
Industrial Research (CSIR) and University Grants Commission
(UGC), India, for a Junior and Senior Research Fellowship, respec-
tively. The authors thank V. Ramkumar for X-ray crystallography
analysis. The authors also thank SAIF, CDRI, Lucknow 226001 for
FAB mass and SAIF, IIT Madras for multinuclear NMR.
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Appendix A. Supplementary material
CCDC 789116 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.12.033.
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