Synthesis, characterization and crystal structures of 1,2-disubstituted ferrocenyl stibines

Article abstract of DOI:10.1515/znb-2012-0107

New 1,2-disubstituted ferrocenyl stibines containing a-CH₂OR pendant arm were synthesized and characterized by various spectral and analytical methods. Nucleophilic substitution of rac-diphenyl[( 2-trimethylammoniomethylferrocen-1-yl)]stibine iodide by methanol produces compound Fc(CH2OMe)SbPh2 (1). The acetylation of diphenyl(2- dimethylaminomethylferrocen-1-yl)stibine by acetic anhydride affords compound Fc(CH₂OCOCH₃)SbPh₂ (2), which on further reaction with sodium hydroxide affords the alcohol Fc(CH₂OH)SbPh ₂ (3). The molecular structures of the stibines 1, 2 and 3 were determined by X-ray crystallography. None of the heterobimetallic compounds containing a -CH₂OR arm shows hypervalent interactions in the solid state. By contrast, hypervalent interactions were found in ferrocenyl stibines with a -CH₂NR₂ pendant arm.

Full text of DOI:10.1515/znb-2012-0107

Synthesis, Characterization and Crystal Structures
of 1,2-Disubstituted Ferrocenyl Stibines
Diego Pe´reza, Pankaj Sharmaa, Ana M. Ortiza, Armando Cabreraa, Simon Herna´ndeza,
Alfredo Toscanoa, and Rene´ Gutie´rrezb
a Instituto de Qu´ımica, Universidad Nacional Autonoma de Me´xico, 04510, Me´xico D. F.
b Facultad de Ciencias Qu´ımicas, Universidad Auto´noma de Puebla, Puebla 72001, Me´xico
Reprint requests to Dr. Pankaj Sharma. Fax: 52-55-56162217. E-mail: pankajsh@servidor.unam.mx
Z. Naturforsch. 2012, 67b, 36 – 40; received November 4, 2011
New 1,2-disubstituted ferrocenyl stibines containing a -CH2OR pendant arm were synthesized
and characterized by various spectral and analytical methods. Nucleophilic substitution of rac-di-
phenyl[(2-trimethylammoniomethylferrocen-1-yl)]stibine iodide by methanol produces compound
Fc(CH2OMe)SbPh2 (1). The acetylation of diphenyl(2-dimethylaminomethylferrocen-1-yl)stibine
by acetic anhydride affords compound Fc(CH2OCOCH3)SbPh2 (2), which on further reaction with
sodium hydroxide affords the alcohol Fc(CH2OH)SbPh2 (3). The molecular structures of the stib-
ines 1, 2 and 3 were determined by X-ray crystallography. None of the heterobimetallic compounds
containing a -CH2OR arm shows hypervalent interactions in the solid state. By contrast, hypervalent
interactions were found in ferrocenyl stibines with a -CH2NR2 pendant arm.
Key words: 1,2-Disubstituted Ferrocene, Organoantimony, Stibine, X-Ray Structures
Introduction
ferrocenes bonded to antimony atoms in the literature,
and our interest in stibine ligands, this work was un-
dertaken.
Ferrocenyl ligands with one or more heteroatom
donor centers are of interest because of their ap-
plications in enantioselective catalysis, rigid confor-
mational behavior and planar chirality combination
[1 – 7]. In this regard, 1,2-disubstituted ferrocenyl
phosphines are well known compounds which are
synthesized from N,N-dimethylaminomethylferrocene
(Ugi amine) and have a number of industrial applica-
tions [8]. However, the number of reports decreases as
we go from lighter to higher pnicogens, and there exist
only a few examples of ferrocenyl stibines in the liter-
ature [9, 10]. Very recently our group has reported the
synthesis of some 1,2-disubstituted ferrocenyl stibines,
by nucleophilic substitution on quaternary ferrocenyl
stibine ammonium salts with different primary amines
and heterocyclic secondary amines [11], and some of
these ferrocenyl stibines present Sb-N hypervalent in-
teractions. Our group has also reported the synthesis
of ether and thioether derivatives from quaternary fer-
rocenyl stibine ammonium salts by nucleophilic sub-
stitution with different phenols and thiols [12]. In these
stibines, intramolecular Sb-O coordination was not ob-
served. Considering the vast number of ferrocene lig-
ands, the unique stereoelectronic properties of the fer-
Results and Discussion
rac-diphenyl[(2-trimethylammoniomethylferrocen-
1-yl)]stibine iodide and rac-diphenyl(2-dimethyl-
aminomethylferrocen-1-yl)stibine were obtained as re-
ported in the literature [11, 12]. Compound 1 was
prepared by a nucleophillic attack of MeOH on the
ammonium salt (Scheme 1), and compound 2 was
synthesized by an acetylation of the amine. A sub-
sequent saponification reaction of the acetate with
2 M NaOH in a methanol/THF mixture finally afforded
compound 3 (Scheme 2).
rocene framework, the existence of very few reports on Scheme 1. Synthetic route to compound 1.
c
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D. Pe´rez et al. · 1,2-Disubstituted Ferrocenyl Stibines
37
Scheme 2. Synthetic procedure for compounds 2 and 3.
All three stibines 1 – 3 are air stable, melt without
decomposition and are soluble in polar organic sol-
vents, e. g. chloroform or dichloromethane, and are in-
soluble in water and show little solubility in non polar
solvents, e. g. hexane or pentane.
For all three new compounds, in the (+)-FAB spec-
tra molecular ion peaks were observed along with frag-
ments corresponding to the successive loss of organic
entities attached to the antimony atoms. The assign-
ment of individual proton signals in the 1H NMR spec-
tra was based on signal integral values and confirmed
by COSY and HETCOR experiments.
Fig. 1. ORTEP view of diphenyl(2-methoxymethylferrocen-
1-yl)stibine (1).
1
In the H spectra a similar chemical shift pattern
was observed for the ferrocene fraction and the phenyl
rings. The methylene protons of the FcCH2O moieties
are not magnetically equivalent. This phenomenon has
1
been observed in the H NMR spectra of complexes
containing both monodentate and bidentate 1,2-disub-
stituted ferrocenyl ligands as well [9 – 11, 13, 14]. The
stereoheterotopic methylene protons give rise to two
AB doublets. A singlet observed at ca. 4.1 ppm in the
1H spectra of the stibines can be assigned to the unsub-
stituted Cp ring protons. Higher chemical shifts were
observed for both aromatic and ferrocenyl protons ad-
jacent to the Sb–C bond in all compounds in compar-
ison to those of similar ferrocenyl phosphines [15].
Such higher chemical shifts are also observed in the
13C NMR spectra with respect to phosphines.
Fig. 2. ORTEP view of diphenyl[(2-acetoxymethylferrocen-
1-yl)]stibine (2).
Single crystals of compounds 1 – 3 were obtained
by slow diffusion of hexane in chloroform solutions. X-ray diffraction. The antimony atoms adopt distorted
The molecular structures of 1, 2 and 3 have been trigonal pyramidal structures without considering the
confirmed by X-ray crystallography and are shown lone pairs of electrons with bond angles at Sb smaller
in Figs. 1 – 3. Crystal data for all structural analyses than 100◦. compound 1 presents an average Sb–C bond
˚
are given in Table 1. Selected bond lengths and an- length of 2.148(3) A. The crystal structure of com-
gles for all compounds are listed in Table 2. Com- pound 2 presents disorder in the acetate fragment and
pounds 1 and 2 are monomeric in nature, and no sig- was modeled in two major contributions. The average
˚
nificant inter- or intramolecular interactions were ob- Sb–C bond length is 2.144(3) A. Compound 3 also
˚
served, while compound 3 presents hydrogen bonding presents an Sb–C average bond length of 2.144(3) A
interactions. It is worth noting that all compounds pos- and shows hydrogen bonding with an H(1A)···O(1)
˚
sess planar chirality as a consequence of the 1,2-di- distance of 2.49 A and an O(1)–H(1A)···O(1)#1 an-
substitution on the ferrocenyl Cp ring. Few other fer- gle of 126.9◦. The average Sb–Cferrocenyl bond length
˚
rocenyl stibines have previously been characterized by found in the ferrocenyl stibines is 2.126(3) A, which
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38
D. Pe´rez et al. · 1,2-Disubstituted Ferrocenyl Stibines
Table 1. Crystallographic data for
Compounds
1
2
3
compounds 1 – 3.
Empirical formula
Formula weight
Crystal system
Space group
C24H23FeOSb
505.02
C25H23FeO2Sb
533.03
C23H21FeOSb
491.00
triclinic
P1
triclinic
P1
triclinic
¯
P1
¯
¯
Crystal size, mm3
0.34×0.22×0.18 0.244×0158×0.152 0.22×0.10×0.04
˚
a, A
7.6488(13)
10.3899(17)
13.429(2)
76.262(2)
88.746(2)
83.095(2)
1029.1(3)
2
7.919(1)
10.311(1)
13.440(1)
92.351(2)
92.507(2)
95.767(2)
1089.7(2)
2
1.62
1.9
532
9, 12, 16
1.99 – 25.36
7.4987(10)
10.4577(13)
13.1717(17)
70.984(2)
82.760(2)
84.154(2)
966.7(18)
2
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
3
˚
V, A
Z
Dcalcd, g cm−3
µ (MoKα ), cm−1
F(000), e
hkl range
2θ, deg
1.63
2.0
504
9, 12, 16
2.03 – 25.37
1.69
2.1
488
−8 → 9, 12, 15
1.64 – 25.38
a R1 = ΣꢀFo|−|Fcꢀ/Σ|Fo|;
Refl.measured / unique / Rint 8536 / 5759 / 0.038 12117 / 3994 / 0.024 8025 / 3527 / 0.054
wR2 = [Σw(Fo − Fc2)2/Σw(Fo2)2]1/2
,
b
2
Param. refined
245
310
245
w = [σ2(Fo2) + (AP)2 + BP]−1, where
R(F) / wR(F2)a,b (all refl.) 0.0347 / 0.0598
0.0308 / 0.0645
1.039
0.52 / −0.24
0.0319 / 0.0621
1.000
0.78 / −0.48
P = (Max(Fo2,0) + 2Fc2)/3; GoF =
c
GOF(F2)c
∆ρfin (max / min), e A
0.954
0.47 / −0.36
2
[Σw(Fo −Fc2)2/(nobs −nparam)]1/2
.
−3
˚
˚
Table 2. Selected bond lengths (A) and angles (deg) for 1, 2,
and 3 with estimated standard deviations in parentheses.
1
2
3
Sb-C1
2.130(3) Sb-C1
2.157(3) Sb-C14
2.159(3) Sb-C20
1.491(3) C2-C11
1.391(4) C2-C11B
1.429(4) O1-C11
2.123(3) Sb-C1
2.157(3) Sb-C11
2.153(3) Sb-C17
1.500(5) C2-C23
1.498(6) C23-O1
2.125(3)
2.153(3)
2.154(3)
1.494(5)
1.408(4)
Sb-C11
Sb-C17
C2-C23
C23-O1
O1-C24
1.457(8) C23-O1A 1.401(6)
C11-Sb-C17 96.3(1) C1-Sb-C20 95.7(1) C1-Sb-C11 94.2(1)
C1-Sb-C11 98.0(1) C1-Sb-C14 94.4(1) C1-Sb-C17 95.8(1)
C11-Sb-C17 96.3(1) C20-Sb-C14 98.0(1) C11-Sb-C17 97.2(1)
these ferrocenyl stibines 1, 2 and 3 have been deter-
mined by X-ray crystallography. None of these het-
erobimetallic compounds possesses hypervalent inter-
action in the solid state. This type of interaction was
found previously in similar compounds with -CH2NR2
pendant arms.
Fig. 3. ORTEP view of diphenyl[(2-hydroxymethylferrocen-
1-yl)]stibine (3).
Experimental Section
is shorter than the average Sb–Cphenyl bond length
of these compounds (2.156(3) A) and is also slightly
˚
General
shorter than Sb–Cphenyl bond lengths in other ter-
tiary stibines. A similar observation was reported ear-
lier [11, 12]. This shortening of the Sb–Cferrocenyl bond
lengths is ascribed to the electron-donating ability of
the ferrocenyl group [11].
All solvents were distilled immediately prior to use,
and the reactions were performed under an atmosphere of
oxygen-free dry nitrogen. Melting points were obtained on
a MEL-TEMP II Fisher instrument and are uncorrected.
(+)-FAB mass spectra were recorded on a Jeol SX102
double-focusing mass spectrometer with reverse geometry
using a 6 kV xenon beam and nitrobenzyl alcohol as ma-
In summary, three new 1,2-disubstituted ferrocenyl
stibines containing a -CH2OR pendant arm have been
synthesized and characterized. Molecular structures of trix. 1H and 13C NMR spectra were recorded in CDCl3
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D. Pe´rez et al. · 1,2-Disubstituted Ferrocenyl Stibines
39
on a Jeol Eclipse 300 spectrometer (1H: 300.5311 MHz; m/z (%) = 533 (100 %) [M]+, 473 (24) [M–C2H3O2]+, 275
13C: 75.5757 MHz).
(10) [SbPh2]+). – Elemental analyses (%): calcd. C 56.31,
H 4.35; found C 56.03, H 4.22.
Diphenyl[(2-methoxymethylferrocen-1-yl)]stibine (1)
Diphenyl[(2-hydroxymethylferrocen-1-yl)]stibine (3)
In a Schlenk tube, under N2, 10 mL of methanol was
added to a mixture of 0.645 g (1 mmol) of rac-diphen-
In a Schlenk tube, under N2, 10 mL of an aqueous NaOH
yl[(2-trimethylammoniomethylferrocen-1-yl)]stibine iodide solution (2 M) was added to a solution of 0.533 g (1 mmol)
of compound 2 in 2 mL of methanol and 15 mL of THF.
and 1.38 g (10 mmol) of ◦K2CO3 in 5 mL of acetonitrile. Af-
After stirring for 6 h at 80 ◦C the solvents were evapo-
rated, and the mixture was extracted with chloroform and
dried with anhydrous Na2SO4. Compound 3 was obtained
as yellow crystals after recrystallization from a chloroform/
hexane mixture. Yield: 78 %. – IR film: ν = 3049 (C–H
aromatic), 3464 (C–O), 1214 (C–O), 451 (Sb–C) cm−1. –
1H NMR(300 MHz, CDCl3): δ = 1.44 (s, 1 H, OH), 4.02
(t, 1 H, CH, C3H5), 4.10 (s, 5 H, C5H5), 4.29 (d, 1 H, CH,
C3H5), 4.39 (broad, 1 H, CH, C3H5), 4.34, 4.45 (AB, 2 H,
J = 10.7 Hz, CH2), 7.29 – 7.36 (m, 10 H, Ph). – 13C NMR
(75 MHz, CDCl3): δ = 63.52 (CH2), 74.7 (CFc-CH2OH),
61.57 (CFc), 68.37 (C5H5), 70.92 (CFc), 71.38 (CFc),
93.19 (CFc-Sb), 137.17 (CPh-Sb), 136.71(CPh), 135.92(CPh),
128.74 (CPh), 166.50 (OC). – MS (EI, 70 eV): m/z (%) =
490 (100) [M]+, 472 (2) [M–H2O]+, 413 (6) [M–C6H5]+,
394 (26) [M–H2O–C6H5]+, 275 (10) [SbPh2]+. – Elemental
analyses (%): calcd. C 56.24, H 4.31; found C 57.03, H 4.18.
ter stirring for 8 h at 80 C the solvent was evaporated, and
the mixture was extracted with chloroform and dried with
anhydrous Na2SO4. Compound 1 was obtained as orange-
yellow crystals after recrystallization from a chloroform/
hexane mixture. Yield: 38 %. – IR (film): ν = 3048 (C–H
aromatic), 1261 (C–O), 1093 – 1020 (C–O-C), 455 cm−1
(Sb–C). – 1H NMR (300 MHz, CDCl3, ppm): δ = 4.55
(s, 1 H, CH, C3H5), 4.16, 4.37 (AB, 2 H, J = 10.6 Hz,
CH2), 7.25 – 7.56 (m, 10 H, Ph), 4.04 (s, 5 H, C5H5); 3.14
(s, 3 H, OCH3). – 13C NMR (75 MHz, CDCl3): δ = 57.7
(OCH3), 69.1 (C5H5), 70.7 (CH2), 71 (CFc-Sb), 71.3 (CFc),
72.0 (CFc), 74.6 (CFc), 89.5 (CFc-O), 128.1 (CPh), 128.6
(CPh), 136.9 (CPh), 139.8 (CPh-Sb). – MS ((+)-FAB): m/z
(%) = 504 (100) [M]+, 473 (100) [M–CH3O]+, 427 (10)
[M–C6H5]+, 275 (10) [SbPh2]+. – Elemental analysis (%):
calcd. C 57.06, H 4.59; found C 56.87, H 4.48.
Diphenyl[(2-acetoxymethylferrocen-1-yl)]stibine (2)
Crystal structure determinations
In a Schlenk tube, under N2, 7 mL of acetic anhydride
was added to a mixture of 0.516 g (1 mmol) of rac-diphenyl-
(N,N-dimethylaminomethylferrocenyl)stibine and 15 mL of
CHCl3. After stirring for 8 h at 80 ◦C the solvent was
evaporated, and the mixture was extracted with chloro-
form and dried with anhydrous Na2SO4. compound 2 was
obtained as yellow crystals after recrystallization from a
chloroform/hexane mixture. Yield: 89%. – IR film: ν =
3043 (C–H aromatic), 1730 (C=O), 1220 – 1060 (C–O), 454
The X-ray intensity data were measured at 293 K on a
Bruker SMART APEX CCD-based X-ray diffractometer by
using monochromatized MoKα radiation (λ = 0.71073 A).
˚
The detector was placed at a distance of 4.837 cm from the
crystals in all cases. Empirical absorption corrections were
applied. The program SHELXTL (version 6.12) was used for
all calculations.
CCDC 806069–806071 contain the supplementary crys-
tallographic 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.
1
(Sb–C) cm−1. – H NMR (300 MHz, CDCl3): δ = 3.15 (s,
3 H, COCH3), 3.78 (1 H, d, CH, C3H5), 4.10 (s, 5 H, C5H5),
4.31 (1 H, t, CH, C3H5), 4.49 (1 H, d (broad), CH, C3H5),
4.93, 5.05 (AB, 2 H, J = 10.4 Hz, CH2), 7.26 – 7.39 (m, 10 H,
Ph). – 13C NMR (75 MHz, CDCl3): δ = 87.21 (CFc-Sb),
75.34 (CFc-CH2OAc), 73.28 (CFc), 71.31 (CFc), 63.52 (CFc),
69.17 (C5H5), 136.76 (CPh-Sb), 135.91 (CPh), 128.69 (CPh),
128.31 (CPh), 63.52 (CH2), 166.50 (OC). – MS ((+)-FAB):
Acknowledgement
We gratefully acknowledge financial support by the Di-
reccion General De Asuntos para Academicos (DGAPA,
UNAM, project no. IN206809).
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