576
M. K. KHOSA ET AL.
RESULTS AND DISCUSSION
values between 323–347 cm21, indicating stronger inter-
actions between the carbonyl oxygen atoms of the carboxylates
groups and the antimony atom in the former and weaker inter-
actions or no interaction between the antimony atom and the
carbonyl oxygen atoms of carboxylates of the latter
groups.[15] In addition, the frequencies n(Sb-C) appeared
The different triorganogermyl substituted propionic
acids have been synthesized according to the reported
method.[8] The title compounds (1–11) were synthesized
as shown in (Eq. (1)) by stirring 2:1 molar ratio of triorg-
anigermyl substituted propionic acid and triarylantimony(V)
dibromide in the presence of triethylamine in toluene under
mild conditions.[9]
[16]
between 459–484 cm21 consistent with literature.
NMR SPECTROSCOPY
Et3N
21R3GeCHR2CH2CO2HþAr3SbBr2ꢀꢀ!
Toluene
r:t:8h
1H NMR
The chemical shift of various protons in the compounds is
listed in Table 3. All protons in the compounds have been
identified by intensity and multiplicity pattern and the total
number of protons calculated from the integeration curve is
in agreement with the expected molecular composition. The
signals of the aromatic protons of substituted phenyl group of
the germyl and antimony moiety are complex and are
observed as multiplet in the region 6.8–7.2 ppm, while the sub-
stituent on the phenyl group observed as sharp singlet in the
region 2.14–2.54 ppm, respectively. Another characteristic
feature of these compounds is presence of GeCH chiral
center and CH2 is a prochiral center and three hydrogen of
the unit GeCHCH2, corresponds to an ABX system. The sub-
spectral analysis of the ABX spectra revealed that the eight-
lines portion (two pseudo-quartets) of the spectrum is made
up of two AB sub-spectra in the range of 2.12–2.81 ppm,
whereas the X part of the spectrum consists of four detectable
lines with equal intensity in the range of 3.15–3.82 ppm. The
interesting observation for this ABX system is diasterotopy.
The two protons of methylene group (A, B) being diasterotopic,
coupled to the third proton (X) of the chiral center giving three
chemical shifts, yA, yB and yX and three suitable coupling
constants, JAB, JAX and JBX, as shown in Table 3.[17]
1
ð R3GeCHR2CH2CO2Þ2SbðArÞ3 þEt3NꢁHCl
ð1Þ
R1 ¼ Ph; Ar ¼ pꢀCH3C6H4 ð1ꢀ6Þ
R1 ¼ pꢀCH3C6H4; Ar ¼ Ph ð7ꢀ11Þ
R2 ¼ pꢀClC6H4 ð1Þ;oꢀCH3OC6H4 ð2Þ;
pꢀCH3OC6H4 ð3;8Þ;mꢀCH3OC6H4 ð9Þ
pꢀCH3C6H4 ð4;7Þ;nꢀC3H7 ð5Þ;CH3 ð6;10Þ;C6H5 ð11Þ:
TheproductswerepurifiedbycrystallizationfromCH2Cl2 and
petroleum ether. The yield obtained is 70–80%. All compounds
are white powder, which are easily soluble in CHCl3, CH2Cl2
and DMSO. They are unaffected by atmospheric moisture
showing no decomposition over a period of several weeks. The
physical data of synthesized compounds are given in Table 1.
Infrared Spectroscopy
The infrared spectra of these compounds have been
recorded in the range of 4000–400 cm21. Tentative assign-
ments have been made on the basis of earlier publications,[10,11]
and the important data are listed in Table 2. The formation of
the complex is evidenced by the absence of the broad band
of n(OH) in the 3500–3300 cm21 region by deprotonation
and coordination of germyl substituted propionic acid with
antimony. Further, the IR data support the molecular consti-
tution of title compounds. In the majority of organoantimony
(V) compounds, the antimony has generally a coordination
number of five. Because of the vacant 5d orbital, antimony
atom can accept lone electron pairs of ligands and may have
a coordination number of six or seven.[12,13] When there are
interactions between the antimony atom and carbonyl oxygen
atoms of the carboxylates groups, the asymmetric absorption
vibration frequencies nasy(CO2) of carbonyl groups decrease,
and the symmetric absorption vibration frequencies
13C NMR
13C NMR spectral data of triorganoantimony carboxylates
containing germanium is given in Table 4. The number of
signals found corresponds with the presence of magnetically
non-equivalent carbon atoms, which was assigned by compari-
son with the experimental chemical shift with those calculated
from the incremental method.[18] The position of carboxylate
carbon in all synthesized compounds move to a lower field,
as compared with the germyl substituted propionic acid
ligand indicating participation of carboxylic group in coordi-
nation to antimony atom. The group with strong electron with-
drawing effect e.g., methoxy group attached to phenyl ring (R1)
resonate at low field, while the methyl substituent on the
phenyl group of germyl and antimony moiety appear at
21.21–22.05 ppm and 21.56–22.85 respectively.
n
sym(CO2) increase. Therefore, the difference, Dn(CO2)
decrease.[14] In the IR spectra of synthesized compounds, the
carboxylates bands are observed in the characteristic regions:
n(CO2)asym between 1603 to 1666 cm21 and n(CO2)sym
between 1308 to 1360 cm21, respectively. On the basis of
the difference Dn(CO2), these compounds can be divided into
two classes. Compounds (4) show low Dn value,
MASS SPECTROMETRY
The main mass spectral data of representative compounds
ca.279 cm21, while all other compounds show high Dn (1, 10) are listed in Table 5. Mass spectral data support the
Khosa, Muhammad Kaleem
