A study of competitive coordination of benzochalcogenazole ligands by heteronuclear NMR spectroscopy

Article abstract of DOI:10.1023/B:RUGC.0000018661.83670.2a

Complexes of 2-methyl(phenyl)benzo-1,3-tellurazole and 2-methyl(phenyl) benzo-1,3-selenazole with tungsten pentacarbonyl and boron trifluoride were studied by heteronuclear NMR spectroscopy (¹H, ¹³C, ⁷⁷Se, and ¹²⁵

Full text of DOI:10.1023/B:RUGC.0000018661.83670.2a

Russian Journal of General Chemistry, Vol. 73, No. 11, 2003, pp. 1810 1814. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 11, 2003,
pp. 1910 1914.
Original Russian Text Copyright
2003 by Borodkina, Uraev, Borodkin, Sadekov, Garnovskii, Minkin.
A Study of Competitive Coordination
of Benzochalcogenazole Ligands
by Heteronuclear NMR Spectroscopy
I. G. Borodkina, A. I. Uraev, G. S. Borodkin,
I. D. Sadekov, A. D. Garnovskii, and V. I. Minkin
Reaearch Institute of Physical and Organic Chemistry, Rostov State University, Rostov-on-Don, Russia
Received August 2, 2001
Abstract Complexes of 2-methyl(phenyl)benzo-1,3-tellurazole and 2-methyl(phenyl)benzo-1,3-selenazole
with tungsten pentacarbonyl and boron trifluoride were studied by heteronuclear NMR spectroscopy (1H, 13C,
77Se, and 125Te). The coordination mode of the ambident ligand can be determined from the coordination
shifts of the 125Te and 77Se NMR signals: upfield at coordination via Te and Se atoms and downfield at N
coordination.
Benzochalcogenazoles I containing, along with
nitrogen, donor atoms of sulfur, selenium, or tellurium
(A) are important ambident chalcogen N ligand
systems [1, 2].
MXn
N
N
A
N
MXn
MXn
R
R
R
A
A
MXn
II
I
III
A = S, Se, Te; R = H, Alk, Ar; MXn are Lewis acids.
Most of chalcogenazoles bind a metal via pyridine-
77Se and 125Te NMR spectroscopy turned to be a
powerful tool for elucidating the ligand coordination
mode in the chalcogenazole complexes. The NMR
spectra of I (A = Te, R = Ph) and its complex with
W(CO)5 (III, A = Te, R = Ph) in which the coordina-
tion undoubtedly occurs via the Te atom [7] show that
the complex formation results in an upfield shift of
type N atom (structure II) [1 5]. The exceptions are
complexes of 2-phenylbenzo-1,3-tellurazole with the
Group VI metal pentacarbonyls [6, 7]. According to
X-ray structural analysis, in the complex of 2-phenyl-
benzo-1,3-tellurazole with tungsten pentacarbonyl, the
metal is bound via Te atom [III, A = Te, R = Ph,
MXn = W(CO)5] [7].
the 125Te signal:
842.4 ppm in free ligand I and
654.9 ppm in comTpelex III. Direct Te W bonding is
confirmed by the presence of satellites originating
In this work we showed that the ligand coordina-
tion mode in chalcogenazole complexes can be deter-
mined by heteronuclear NMR spectroscopy (1H, 13C,
77Se, and 125Te).
from the 125Te 183W coupling (1JTeW 90.0 Hz). On
the contrary, in the spectrum of the complex of
2-phenylbenzo-1,3-tellurazole with BF3 (II), with N
coordination of the ligand, the 125Te signal is shifted
As the objects for the study we chose complexes
of 2-methyl(phenyl)benzo-1,3-tellurazole and 2-me-
thyl(phenyl)benzo-1,3-selenazole with soft [W(CO)5]
and hard (BF3) Pearson acids [1, 2, 8 11].
downfield (
914.2 ppm). Thus, the direction of the
125Te signal Tsehift can be used for estimating the co-
ordination mode of Te,N-containing ligands, which
are very actively studied today [1, 2, 12 18].
1070-3632/03/7311-1810$25.00 2003 MAIK Nauka/Interperiodica

A STUDY OF COMPETITIVE COORDINATION OF BENZOCHALCOGENAZOLE LIGANDS
1811
1
Table 1. Chemical shifts ( , ppm) and coupling constants (J, Hz) in the H, 13C, and 125Te NMR spectra of compounds
I III [A = Te, R = Me, Ph; MXn = W(CO)5, BF3]
1
N
1
N
7
7
8
9
8
6
5
6
5
R MXn
R
A
A
9
4
4
3
3
I
II, III
Compound
Atom numbersa
Nu-
cleus
Solvent
ipsoc
no. R MXn
2{3}b
4
5
6
7
8
9
o
m
p
{Me}d
1H
I
Ph
III Ph W(CO)5
Ph
III Ph W(CO)5
125Te I Ph
III Ph W(CO)5
7.49 6.84 7.18 8.23
7.04 6.77 7.03 7.89
166.66 131.76 125.02 127.13 127.02 162.89 141.73 134.90 128.90 129.10 130.86 C6D5CD3
172.56 132.59 126.87 129.94 127.42 160.90 137.05 134.98 129.84 129.75 131.90 C6D5CD3
7.79 7.06 7.71 C6D5CD3
7.59 7.04 7.12 C6D5CD3
13C
I
{842.4}
{654.9
C6D5CD3
C6D5CD3
(JTeW) (90)}
1H
I
Ph
II Ph BF3
Ph
II Ph
Ph
II Ph BF3
Me
8.18 7.22 7.56 8.14
8.40 7.52 7.77 8.36
7.98 7.52 7.50 C2D6CO
8.18 7.67 7.81 C2D6CO
13C
I
166.66 131.76 125.02 127.13 127.02 162.89 141.73 134.90 128.90 129.10 130.86 C6D5CD3
191.76 133.47 127.87 129.80 122.94 149.47 135.43 128.40 129.77 130.90 135.49 C6D5CD3
{852.74}
I
C6D5CD3
C6D5CD3
CD3CN
{914.25}
1H
I
7.95 7.15 7.44 8.01
8.16 7.46 7.67 8.06
{2.80
(14.2)}
{3.06
(7.3)}
(JHSe
)
II Me BF3
Me
CD3CN
CD3CN
(JHSe) (14.2)}
13C
I
171.20 132.20 124.66 126.75 125.25 161.20 135.40 {30.02}
JCSe 331.2 27.2 15.2 6.7 279.8 {45.0}
195.89 132.52 127.30 129.03 120.67 145.58 127.30 {25.29}
JCSe 445.5
{914.0}
II Me BF3
125Te I Me
CD3CN
CD3CN
CD3CN
CD3CN
17.3 17.0
8.4
318.5 {12.1}
II Me BF3
{971.2}
a
b
c
Numbering of hydrogen atoms corresponds to that of carbon atoms. Values for atoms in 3-position are given in braces. ipso-, o,
m- and p-carbon atoms in 2-phenyl group.
d
Values for atoms in the methyl group are given in braces.
Changes in the chemical shifts are also observed
most pronounced changes in the 13C chemical shifts
1
in the H NMR spectra. The signals of all the protons
in complex III [A = Te, R = Ph, MXn = W(CO)5]
show upfield shift as compared to free ligand I (A =
Te, R = Ph) (Table 1). At the same time, the proton
signals in the spectrum of II (A = Te, R = Ph, MXn =
BF3) are shifted downfield compared to I (A = Te,
R = Ph) (Table 1).
relative to free ligand I (A = Te, R = Ph,
C
166.66 ppm) are observed for the C2 atoms in com-
plexes III [A = Te, R = Ph, MXn = W(CO)5;
C
172 ppm] and II (A = Te, R = Ph, MXn = BF3;
C
191.76 ppm). Unlike the 125Te and 1H chemical shifts,
the direction of the shift of the 13C signals is in-
dependent of the nature of the complex-forming com-
pound (Lewis acid).
We also studied compounds I III [A = Te; R =
Me, Ph; MXn = W(CO)5, BF3] by 13C NMR spec-
troscopy. Their 13C chemical shifts and coupling
constants with 125Te nuclei are listed in Table 1. The
With the complex of 2-methylbenzo-1,3-tellurazole
1
with BF3, the pattern of changes in the H, 13C, and
125Te chemical shifts relative to the free ligand (I, A =
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 11 2003

1812
BORODKINA et al.
Te, R = Me) was similar to that observed with the
complex of 2-phenylbenzo-1,3-tellurazole with BF3
(Table 1).
13C2,8,9 signals are shifted upfield relative to the free
ligand (I, A = Se; R = Me, Ph) (Table 2).
It is noteworthy that, as in the tellurazole com-
plexes, complexation causes significant changes in the
13C 77Se coupling constants (Table 2). In complexes
II [A = Se; R = Me, Ph; MXn = W(CO)5, BF3], the
A characteristic feature of these complexes is that
1
the 13C2 125Te coupling constant increases from J
1
333.2 Hz in I (A = Te, R = Ph) to J 445.5 Hz in II
(A = Te, R = Ph, MXn = BF3), whereas the 13C(CH3)
77Se 13C2 coupling constant increases, and the 77Se
13
2
125Teconstant decreases from J 14.2 Hz in I (A = Te,
C
constant decreases (Table 2) as compared to the
Me
2
free ligand (I, A = Se; R = Me, Ph).
R = Ph) to J = 7.3 Hz in II (A = Te, R = Ph, MXn =
BF3).
Thus, comparison of changes in the chemical shifts
of protons located near donor centers of benzotellur-
(selen)azoles with related changes in the 125Te and
We also applied heteronuclear NMR spectroscopy
to studying competitive coordination of benzoseleno-
diazoles I III [A = Se; R = Me, Ph; MXn = W(CO)5,
BF3]. Previous 14N NMR data [19, 20] suggested oc-
currence of an equilibrium between isomers II and III
differing in the binding mode for the complexes of
2-methylbenzo-1,3-selenazoles (A = Se, R = Me) with
Group VI metal pentacarbonyls M(CO)5, where M =
Cr, Mo, W. The presence of two signals in the 77Se
NMR spectrum of II (A = Se, R = Me, MXn =
77Se shifts shows that the coordination mode of the
compounds in complexes with Pearson’s acid can also
1
be determined from the H NMR spectra.
EXPERIMENTAL
1
The H, 13C, 125Te, and 77Se NMR spectra were
recorded on a Varian UNITY-300 spectrometer with
2
W(CO)5] at
this assumptiSoen. However, we found that the first of
the above signals ( 646.34 ppm) belongs to free
646.34 and 677.13 ppm might support
internal field stabilization by the H signal of the
corresponding deuterated solvent.
Se
1
For reliable assignment of peaks in the H and 13C
ligand I (A = Se, R = Me). This observation allows us
to conclude that the binding mode in this complex is
unique. A downfield shift of the 77Se signal in com-
plex II [A = Se, R = Me, MXn = W(CO)5],
677.13 ppm, as compared to free ligand I (A = SSee,
NMR spectra, we used two-dimensional homonuclear
1
(1H H COSY) and heteronuclear (1H 13C HETCOR)
correlation spectroscopy [21].
The chemical shifts in the 125Te NMR spectra are
R = Me),
646.34 ppm, as well as the absence of
satellites inStehe 77Se spectrum originating from cou-
pling with 183W suggest the N coordination of W in
the complex [structure II, A = Se, R = Me, MXn =
W(CO)5].
given relative to Me2Te (
0.00 ppm) taken as a
Te
reference (Table 1) [22]. In the 77Se NMR spectra,
Me2Se (
0.00 ppm) was taken as a reference
(Table 2) Se[22].
Compounds I (A = Se, Te; R = Me, Ph) were
prepared by procedures described in [23, 24].
The downfield shift of the 77Se signal in the NMR
spectrum of the 2-methylbenzo-1,3-selenazole com-
plex with BF3 (II, A = Se, R = Me, MXn = BF3),
671.67 ppm, relative to the free ligand (I, A = SSee,
R = Me), Se 653.27 ppm, suggests the N coordination
of BF3.
(2-Phenylbenzo-1,3-tellurazole)pentacarbonyl-
tungsten [III, A = Te, R = Ph, MXn = W(CO)5]. A
solution of 3 mmol of W(CO)6 in 100 ml of absolute
THF saturated with argon was illuminated with a
mercury lamp. Then 3 mmol of the free benzotellura-
zole was added, and the mixture was stirred for 1 h.
The solution was filtered, and the solvent was distilled
off on a rotary evaporator. The solid residue was
transferred into a sublimer, and unchanged tungsten
carbonyl was removed in a high vacuum. The solid
was twice recrystallized from hexane. Complex III
[A = Te, R = Ph, MXn = W(CO)5] is a yellow crystal-
line powder. Found, %: C 33.95; H 1.58; N 2.80.
C18H9NO5TeW. Calculated, %: C 34.27; H 1.44;
N 2.22.
A similar change in the 77Se chemical shift in the
NMR spectrum of 2-phenylbenzo-1,3-selenazole com-
plex with BF3 (II, A = Se, R = Ph, MXn = BF3),
631.81 ppm, relative to the free ligand (I, A = SSee,
R = Ph),
616.29 ppm, also suggests binding of
Se
BF3 via nitrogen atom.
1
In the H NMR spectra of complexes II and III
(A = Se; R = Me, Ph; MXn = W(CO)5, BF3], all the
signals are shifted downfield relative to the free ligands
(I, A = Se; R = Me, Ph). However, in the 13C NMR
spectrum not all the signals are shifted in the same
direction. The signals of the 13C4 7 nuclei in the
benzene ring are shifted downfield, whereas the
(2-Phenylbenzo-1,3-tellurazole)trifluoroboron
(II, A = Te, R = Ph, MXn = BF3). To 1 mmol of the
free benzotellurazole, 1 mmol of a boron trifluoride
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 11 2003

A STUDY OF COMPETITIVE COORDINATION OF BENZOCHALCOGENAZOLE LIGANDS
1813
1
Table 2. Chemical shifts ( , ppm) and coupling constants (J, Hz) in the H, 13C, and 77Se NMR spectra of compounds I
and II [A = Se; R = Me, Ph; MXn = W(CO)5, BF3]
Compound
Atom numbersa
Nuc-
leus
Solvent
ipsoc
no. R MXn
2{3}b
4
5
6
7
8
9
o
m
p
{Me}d
1H
I
Me
(JSe)
7.98 6.93 7.13 7.45
8.35 7.46 7.68 8.04
{2.34
(8.1)}
{2.44
(10.8)}
C6D5CD3
C6D5CD3
II Me W(CO)5 (JSe)
13C
77Se
1H
I
Me
II Me W(CO)5
Me
II Me W(CO)5
Me
169.22 124.70 122.90 123.80 123.60 154.44 138.68 {21.83}
182.20 126.90 124.50 125.86 125.20 154.80 134.64 {26.91}
{646.34}
{677.13}
C6D5CD3
C6D5CD3
C6D5CD3
I
I
7.96 7.30 7.45 7.92
8.16 7.60 7.71 8.04
{2.80
CD3CN
CD3CN
CD3CN
C6D5CD3
(JHSe
(JHSe
)
)
(12.0)}
(3.06)}
(7.8)}
II Me BF3
Me
II Me BF3
13C
I
171.58 125.25 124.98 126.12 123.79 155.22 139.49 {23.13}
JCSe 130.5 14.1 7.00 2.70 100.3 {24.1}
185.85 126.20 127.66 128.79 119.72 143.52 134.40 {20.73}
JCSe 152.1 11.7 8.10 109.3 {12.9}
{653.27}
{671.67}
77Se
1H
I
Me
II Me BF3
Ph
II Ph BF3
Ph
CD3CN
CD3CN
8.06 7.54 7.52 CD3CN
8.09 7.70 7.83 CD3CN
I
8.03 7.36 7.52 8.04
8.27 7.66 7.79 8.18
13C
I
172.66 125.53 125.74 126.84 124.81 156.18 138.52 136.41 128.05 129.54 131.54 CD3CN
JCSe 128.2 14.9 7.80 99.0 8.8
183.37 126.78 128.21 129.55 120.12 144.06 133.42 135.46 129.07 130.47 135.46 CD3CN
JCSe 147.3 12.1 8.7 110.9 54.4 8.7
{616.29}
{631.81}
II Ph BF3
77Se
I
Ph
CD3CN
CD3CN
II Ph BF3
a
b
For structural formulas, see Table 1. Numbering of hydrogen atoms corresponds to that of carbon atoms. Values for atoms in
c
d
3-position are given in braces. ipso-, o, m- and p-carbon atoms in 2-phenyl group. Values for atoms in the methyl group are
given in braces.
etherate solution in absolute ether was added dropwise.
The reaction mixture was stirred for 1 h at room
temperature. The precipitate was filtered off, washed
with ether, and dried in a vacuum.
transferred into a sublimer, and unchanged metal
carbonyl was removed in a high vacuum. Then the
solid was twice recrystallized from a benzene hexane
mixture. The complex [II, A = Se, R = Me, MXn =
W(CO)5] is a yellow crystalline powder. Found, %: C
29.83; H 1.95; N 2.93. C13H7NO5SeW. Calculated,
%: C 30.03; H 1.35; N 2.63.
(2-Methylbenzo-1,3-tellurazole)trifluoroboron
(II, A = Te, R = Me, MXn = BF3) was prepared
similarly.
(2-Methylbenzo-1,3-selenazole)pentacarbonyl-
tungstenl [II, A = Se, R = Me, MXn = W(CO)5]. A
solution of 1 mmol of W(CO)6 and 1 mmol of the free
benzoselenazole in 100 ml of absolute THF saturated
with argon was illuminated under a mercury lamp.
The solution was filtered, and the solvent was distilled
off on a rotary evaporator. The solid residue was
(2-Methylbenzo-1,3-selenazole)trifluoroboron
(II, A = Se, R = Me, MXn = BF3). To 1 mmol of
2-methylbenzo-1,3-selenazole dissolved in absolute
ether ( 10 C), boron trifluoride etherate was added
dropwise. The mixture was stirred for 30 min. The
precipitate was filtered off, washed with ether, and
dried in a vacuum.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 11 2003

1814
BORODKINA et al.
(2-Phenylbenzo-1,3-selenazole)trifluoroboron
10. Garnovskii, A.D., Koord. Khim., 1980, vol. 6, no. 12,
(II, A = Se, R = Ph, MXn = BF3) was prepared
p. 1779.
similarly.
11. Garnovskii, A.D. and Sadimenko, A.P., Zhestko-
myagkie vzaimodeistviya v koordinatsionnoi khimii
(Hard Soft Interactions in Coordination Chemistry),
Rostov-on-Don: Rostov. Gos. Univ., 1986.
ACKNOWLEDGMENTS
This work was financially supported by the Rus-
sian Foundation for Basic Research (project nos. 99-
03-33132, 99-03-33505, 00-15-97320).
12. Singh, A.K., Srivastava, V., and Khandelwal, B.L.,
Polyhedron, 1990, vol. 9, no. 6, p. 851.
13. Khandelwal, B.L., Singh, A.K., Srivastava, V., Po-
veley, D.C., and Smith, G.W., Polyhedron, 1990,
vol. 9, no. 17, p. 2041.
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