N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide (L1): Synthesis, oxidation by ruthenium(III) chloride and ligation with ruthenium(II). Crystal structures of L1, its oxidized product and of [RuCl2(p-cymene)·L1]

Article abstract of DOI:10.1016/S0022-328X(00)00250-3

N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide (L¹) synthesized by reacting ArTe^- (generated in situ) with N-(2-bromoethyl)phthalimide, has been characterized structurally. The Te-C(alkyl) (2.147(5) ?) is somewhat longer than Te-C(aryl) (2.111(4) ?). The L¹ on reaction with RuCl₃·xH₂O results in a novel heterocycle, Te-chloro,Te-anisyl-1a-aza-4-oxa-3-tellura-1H,2H,4aH-9-fluorenone (1), which is characterized structurally and is a unique example of a tellura heterocycle containing oxygen as well as nitrogen in the same ring. The oxidation state of Te changes to +IV in the formation of 1. The Te-Cl and Te-O bond lengths in 1 are 2.604(2) and 2.038(4) ?, respectively. The reaction of L¹ with [RuCl₂(p-cymene)]₂ gives [RuCl₂(p-cymene)·L¹] (2) which is characterized structurally. The Ru-C (av), Ru-Cl and Ru-Te bond lengths are 2.192(1), 2.417(1)-2.434(1) and 2.651(5) ?, respectively. The difference in Te-C(alkyl) and Te-C(aryl) bond lengths is not affected on the ligation of L¹ with ruthenium(II).

Full text of DOI:10.1016/S0022-328X(00)00250-3

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 605 (2000) 39–44
N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide (L1): synthesis,
oxidation by ruthenium(III) chloride and ligation with
ruthenium(II). Crystal structures of L1, its oxidized product and of
[RuCl2(p-cymene)·L1]
Ajai K. Singh a,*, M. Kadarkaraisamy a, G.S. Murthy b, J. Srinivas b, B. Varghese b,
R.J. Butcher c
a Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
b Department of Physics and Regional Sophisticated Instrumentation Centre, Indian Institute of Technology, Chennai 600 036, India
c Department of Chemistry, Howard Uni6ersity, Washington DC 20059, USA
Received 19 February 2000; accepted 16 April 2000
Abstract
N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide (L1) synthesized by reacting ArTe− (generated in situ) with N-(2-bro-
,
moethyl)phthalimide, has been characterized structurally. The TeꢀC(alkyl) (2.147(5) A) is somewhat longer than TeꢀC(aryl)
1
,
(2.111(4) A). The L on reaction with RuCl3·xH2O results in a novel heterocycle, Teꢀchloro,Teꢀanisyl-1a-aza-4-oxa-3-tellura-
1H,2H,4aH-9-fluorenone (1), which is characterized structurally and is a unique example of a tellura heterocycle containing
oxygen as well as nitrogen in the same ring. The oxidation state of Te changes to +IV in the formation of 1. The TeꢀCl and
1
,
TeꢀO bond lengths in 1 are 2.604(2) and 2.038(4) A, respectively. The reaction of L with [RuCl2(p-cymene)]2 gives [RuCl2(p-
cymene)·L1] (2) which is characterized structurally. The RuꢀC (av), RuꢀCl and RuꢀTe bond lengths are 2.192(1), 2.417(1)–
2.434(1) and 2.651(5) A, respectively. The difference in TeꢀC(alkyl) and TeꢀC(aryl) bond lengths is not affected on the ligation
,
of L1 with ruthenium(II). © 2000 Elsevier Science S.A. All rights reserved.
Keywords: N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide; Teꢀchloro,Teꢀanisyl-1a-aza-4-oxa-3-tellura-1H,2H,4aH-9-fluorenone; Rutheni-
um(III); Ruthenium(II); Complex; Crystal structure
1. Introduction
and its palladium complexes, we have now solved the
reported single crystal structure of L1 so that its ligation
characteristics are understood better, and synthesized
Ru(II) complex, [Ru(p-cymene)Cl2(L1)], which is also
structurally characterized. The reaction of L1 with
RuCl3·xH2O results in its oxidation, giving a Te, O and
N containing novel heterocycle, Teꢀchloro,Teꢀanisyl-
1a-aza-4-oxa-3-tellura-1H,2H,4aH-9-fluorenone, char-
acterized by crystal structure determination. These
results are the subject of this paper.
The chemistry [1–7] of organotellurium ligands in-
cluding hybrid ones is of some current interest. The
main reason for interest in the hybrid ones is the fact
that they can make us understand better the ligation of
noblest metalloid tellurium vis a vis other very well
known
donor
sites.
N-[2-(4-methoxyphenyltel-
luro)ethyl]phthalimide (L1) is one such ligand, which
may behave as a (Te, N) type of donor [8] easily in
mononuclear complexes. Its palladium(II) complexes
are reported [8] but characterized only spectroscopi-
cally. Crystal structure of L1 has also not been reported
so far. In continuation of our earlier studies [8] on L1
* Corresponding author. Fax: +91-11-6862037.
E-mail address: aksingh@chemistry.iitd.ernet.in (A.K. Singh).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00250-3

40
A.K. Singh et al. / Journal of Organometallic Chemistry 605 (2000) 39–44
2. Experimental
(0.82 g, 2 mmol) made in 10 ml of chloroform was
added to it dropwise. The mixture was stirred for 1 h
and solvent was removed on a rotary evaporator under
reduced pressure. The residue was redissolved in 10 ml
of acetonitrile, filtered and layered with 20 ml of diethyl
ether. The pale brown crystals appeared after three
days were separated and air-dried. Yield ca. 35%; m.p.
192–194°C.
Anal. Calc. for C17H16ClNO3Te: C, 45.85; H, 3.59;
N, 3.14; Te, 28.65. Found: C, 47.16; H, 3.04; N, 2.92;
Te, 29.05%. 1H-NMR (CDCl3): l, 3.51–3.68 (t, 2H,
TeCH2), 3.91 (s, 3H OCH3), 4.48–4.81 (t, 2H, NCH2),
5.54 (s, 1H, CH), 7.19–7.22 (d, 2H, ArH m to Te),
7.46–7.60 (m, 4H, phthalimide ring protons), 8.09–8.12
(d, 2H, ArH o to Te). 13C{1H}-NMR (CDCl3) l, 37.6
(C7), 53.8 (C6), 55.6 (C1), 83.8 (NꢀCꢀH), 115.7 (C3),
123.5–135.4 (ArꢀC of phthalimide ring), 143.9 (C4),
162.2 (C2), 168.7 (C8).
The C and H analyses were carried out with a
Perkin–Elmer elemental analyzer 240 C. The H- and
1
13C{1H}-NMR spectra were recorded on a Bruker
Spectrospin DPX-300 NMR spectrometer at 300.13
and 75.47 MHz, respectively. IR spectra in the range
4000–250 cm−1 were recorded on a Nicolet Prote´ge
460 FTIR spectrometer as KBr or CsI pellets. Molecu-
lar weights were determined in chloroform using a
Knauer vapour pressure osmometer model A028 at a
concentration ꢀ1 mM. The conductance measure-
ments were made using an ORION conductivity meter
model 162. The melting points determined in open
capillary are reported as such. Bis(4-methoxyphenyl)-
ditelluride was prepared by the published method [9].
N-(2-bromoethyl)phthalimide was used as received
from Aldrich (USA). Tellurium estimation was made
by a standard method [10].
2.3. Synthesis of [RuCl2(p-cymene) L1] (2)
2.1. Synthesis of N-[2-(4-methoxyphenyltelluro)-
ethyl]phthalimide (L1)
The [RuCl2(p-cymene)]2 (0.62, 1 mmol) was dissolved
in 10 ml of dichloromethane. The solution of L1 (0.966
g, 2 mmol) made in 20 ml of dichloromethane was
added to it with vigorous stirring. The mixture was
stirred further for 3 h. The solvent was removed on a
rotary evaporator under reduced pressure. The residue
was dissolved in acetone (5 ml) and layered with 25 ml
of petroleum ether (40–60°C). The dark red microcrys-
talline solid was separated and dried in vacuo. The half
of this solid was dissolved in 5 ml of dichloromethane
and layered with 25 ml of petroleum ether (40–60°C).
The dark red coloured single crystals were separated.
Yield ca. 75%; m.p. 180°C. Molecular weight: Found
736.3 (Calc. 714.8)
The published method [8] was used after some mod-
ifications. It is detailed below.
Bis(4-methoxyphenyl)ditelluride (1 g, 2.13 mmol) was
refluxed in methanol (50 ml) under nitrogen atmo-
sphere. Sodium borohydride (0.2 g in 2 ml of 1 M
NaOH) was added drop wise until the solution became
colourless. A solution of N-(2-bromoethyl)phthalimide
(1.08 g, 4.26 mmol) made in 5 ml of THF was added
and the mixture refluxed further for 30 min. It was
cooled to room temperature and poured into 100 ml of
water. L1 from the aqueous phase was extracted into
100 ml of chloroform. The extract was dried over
anhydrous sodium sulphate and concentrated to ca. 20
ml on a rotary evaporator under reduced pressure. The
concentrate was mixed with hexane (25–30 ml). The
resulting precipitate was recrystallized with chloro-
form–petroleum ether mixture (1:2) to grow single
crystals (yellow needle type) of L1. Yield ca. 71%; m.p.
120°C.
Anal. Calc. for C17H15NO3Te: C, 49.93; H, 3.70; N,
3.43; Te, 31.20. Found: C, 50.25; H, 3.65; N, 3.40; Te,
30.65%. 1H-NMR (CDCl3): l, 3.06–3.11 (t, 2H,
TeCH2), 3.75 (s, 3H OCH3), 4.05–4.09 (t, 2H, NCH2),
6.67–6.70 (d, 2H, ArH m to Te), 7.60–7.80 (m, 6H,
ArH o to Te+phthalimide ring protons). 13C{1H}-
NMR (CDCl3) l, 5.2 (C6), 39.9 (C7), 55.0 (C1), 99.4
(C5), 115.2 (C3), 123.2 (C10), 132.1 (C9), 133.8 (C4),
140.8 (C4), 159.8 (C2), 167.9 (C8).
Anal. Calc. for C27H29NO3TeRuCl2 C, 45.35; H,
4.06; N, 1.95; Te, 17.84. Found: C, 45.28; H, 4.59; N,
1
1.76; Te, 18.46%. H-NMR (CDCl3): l, 1.25–1.27 (d,
6H, CH3 of i-Pr), 2.11 (s, 3H, CH3 p to i-Pr), 2.78–2.90
(sp, 1H, CH of i-Pr), 3.72 (s, 3H, OCH3), 3.81ꢀ4.01 (m,
4H, TeCH2+NCH2), 5.25–5.39 (m, 4H, ArH of p-
cymene), 6.83–6.86 (d, 2H, ArH m to Te).7.53–7.79
(m, 4H, ArH of phthalimide ring), 7.84–7.87 (d, 2H,
ArH, o to Te). 13C{1H}-NMR (CDCl3) l 16.4, 16.7
(C6), 18.5 (CH3 of i-Pr), 22.1, 22.4 (CH3), 30.8 (CH),
36.7, 38.6 (C7), 55.3 (C1), 80.5, 81.0, 81.3, 81.7, 85.0,
85.5 (ring C of p-cymene o and m to i-Pr), 97.9–98.3
(ArC linked to i-Pr), 104.4 (C5), 115.2, 115.4 (C3),
122.2–123.5 (C10), 131.8–132.0 (C9), 133.8 (C11),
136.8–137.2 (C4), 143.8 (ArC linked to CH3), 161.3
(C2), 167.4 (C8).
2.2. Reaction of L1 with RuCl3·xH2O (1)
2.4. X-ray diffraction
Ruthenium(III) chloride hydrate (0.21 g, 1 mmol)
The X-ray data were collected on an Enraf–Nonius
was dissolved in methanol (25 ml). The solution of L1
CAD-4 automated four circle diffractometer for L1 and

A.K. Singh et al. / Journal of Organometallic Chemistry 605 (2000) 39–44
41
Table 1
Crystallographic data measurements and refinements of L1, 1 and 2
Compound
L1
1
2
Empirical formula
Formula weight
T (K)
C17H15NO3Te
408.90
293(2)
C17H16ClNO3Te
445.36
293(2)
C17H15Cl2NO3RuTe
580.87
295(2)
Crystal system
Space group
Monoclinic
P21/c
Triclinic
Monoclinic
P21/c
(
P1
Unit cell dimensions
,
a (A)
7.116(2)
16.368(4)
13.756(3)
90
99.30
90
1581.1(6)
4
7.5497(10)
8.0185(10)
14.6195(10)
93.369(10)
92.928(10)
112.961(10)
810.9(2)
2
12.3942(8)
21.7609(14)
10.3092(7)
90
95.889(1)
90
2765.8(3)
4
1.395
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.718
18.93
800.0
1.824
20.13
436
v (cm−1
F(000)
)
18.05
1112
Reflections collected
Independent reflections
Absorption
3017
3085
30 483
6718 (Rint=0.0936)
None
2780 (Rint=0.0230)
None
2848 (Rint=0.0060)
None
Corrections
Data/restraint/parameters
Final R indices [I\2|(I)]
2780/0/259
R1=0.0324, wR2=0.059
2840/0/273
R1=0.0277, wR2=0.0932
6718/0/351
R1=0.0355,
wR2=0.0866
R1=0.0572,
wR2=0.0950
1.040
R indices (all data)
R1=0.0613, wR2=0.0748
R1=0.0306, wR2=0.1404
Goodness-of-fit on F2
Largest difference peak and hole (e A
1.157
0.601 and −0.481
1.087
0.696 and −1.108
−3
,
)
0.778 and −0.766
1 using graphite monochromated Mo–Ka radiation
plexes. However none of the bimetallic complexes of L1
synthesized by us so far, has given crystals suitable for
X-ray diffraction.
,
(u=0.71073 A) whereas for 2 Bruker-AXS SMART2K
CCD diffractometer was used. The unit cell was deter-
mined from 25 randomly selected selected reflections
using the automatic search index and least-squares rou-
tine. The structure solutions were made by the pro-
gramme SHELXS-86 [11] and for structure refinement
SHELXL-93 programme [12] was used. Some details of
data collection and refinement are given in Table 1. The
full details about coordinates, bond lengths and angles,
structure factors and thermal parameters may be re-
trieved from Cambridge crystallographic data base.
(1)
3. Results and discussion
3.1. Crystal structures
The L1 is formed by the reactions given in Eq. (1)
and characterized structurally. The molecular structure
of L1 as determined by single crystal X-ray diffraction
is shown in Fig. 1. It may act as a (Te, N) donor easily
and perhaps (Te, N, O) donor also in bimetallic com-
Fig. 1. Molecular structure of N-[2-(4-methoxyphenyltelluro)phthali-
mide (L1)

42
A.K. Singh et al. / Journal of Organometallic Chemistry 605 (2000) 39–44
Table 2
,
Selected bond lengths (A) and angles (°)
L1
1
2
TeꢀC(1)
TeꢀC(8)
C(9)ꢀN
C(10)ꢀN
2.111(4)
2.147(5)
1.454(5)
1.393(5)
1.394(5)
1.208(5)
1.213(5)
1.485(6)
1.488(6)
97.4(2)
Te(1)ꢀC(1)
Te(1)ꢀC(8)
Te(1)ꢀO(2)
Te(1)ꢀCl(1)
C(13)ꢀO(2)
C(13)ꢀN
C(10)ꢀN
C(9)ꢀN
2.106(5)
2.132(6)
2.038(4)
2.604(2)
1.426(7)
1.450(8)
1.369(8)
1.433(8)
1.218(8)
1.530(9)
87.9(2)
92.0(2)
100.0(2)
82.2(2)
92.4(2)
RuꢀCl(1)
RuꢀCl(2)
RuꢀC(1C)
RuꢀC(2C)
RuꢀC(3C)
RuꢀC(4C)
RuꢀC(5C)
RuꢀC(6C)
RuꢀTe
TeꢀC(10)
TeꢀC(11)
C(9)ꢀC(10)
NꢀC(9)
NꢀC(6)
NꢀC(5)
C(6)ꢀO(2)
Cl(1)ꢀRuꢀCl(2)
Cl(1)ꢀRuꢀTe
TeꢀRuꢀCl(2)
Cl(1)ꢀRuꢀC(1C)
Cl(2)ꢀRuꢀC(1C)
TeꢀRuꢀC(1C)
Cl(1)ꢀRuꢀC(2C)
Cl(2)ꢀRuꢀC(2C)
TeꢀRuꢀC(2C)
RuꢀTeꢀC(10)
RuꢀTeꢀC(11)
C(10)ꢀTeꢀC(11)
2.417(1)
2.434(1)
2.211(3)
2,215(3)
2.194(4)
2.196(4)
2.157(3)
2.1849(3)
2.651(8)
2.156(4)
2.111(3)
1.523(5)
1.438(5)
1.353(5)
1.464(5)
1.221(4)
88.50(4)
90.40(2)
81.31(3)
149.75(9)
90.36(10)
119.28(10)
112.80(10)
97.04(10)
157.02(10)
104.57(10)
106.58(9)
94.29(15)
C(13)ꢀN
C(10)ꢀO(3)
C(13)ꢀO(2)
C(10)ꢀC(11)
C(12)ꢀC(13)
C(1)ꢀTeꢀC(8)
NꢀC(10)ꢀO(3)
NꢀC(13)ꢀO(2)
NꢀC(10)ꢀC(11)
NꢀC(10)ꢀC(13)
C(10)ꢀO(1)
C(9)ꢀC(8)
124.0(4)
124.0(4)
106.4(3)
111.1(3)
C(1)ꢀTe(1)ꢀCl(1)
C(1)ꢀTe(1)ꢀO(2)
C(1)ꢀTe(1)ꢀC(8)
C(8)ꢀTe(1)ꢀCl(1)
C(8)ꢀTe(1)ꢀO(2)
O(2)ꢀTe(1)ꢀCl(1)
O(2)ꢀC(13)ꢀN
C(13)ꢀNꢀC(9)
NꢀC(9)ꢀC(8)
C(9)ꢀC(8)ꢀTe(1)
174.4(1)
111.9(5)
120.2(5)
111.5(5)
112.1(4)
The selected bond lengths and angles of L1 are given
in Table 2. The TeꢀC(1) is shorter than TeꢀC(8), as is
generally reported [13] for TeꢀC(aryl) in comparison to
TeꢀC(alkyl). The C(1)ꢀTeꢀC(8) angle is consistent with
the literature reports made earlier for a similar angle, in
the case of alkyl aryl tellurides [13].
given in Table 2. The C(1)ꢀTeꢀC(8) angle in 1 is a little
more than that of L1. The TeꢀC bond lengths are also
somewhat shortened on the formation of 1. So far no
tellurium heterocycle containing three heteroatoms is
known and therefore 1 is the first such example. The
TeꢀO(2) and TeꢀCl(1) bond lengths are concurrent with
(2)
The L1 on reaction with RuCl3·xH2O results in 1, in
which Te is oxidized to the +IV oxidation state and a
novel heterocycle ring containing N, Te, and O is
generated (Eq. (2)). The structure of Te-chloro,Te-ani-
syl-1a-aza-4-oxa-3-tellura-1H,2H,4aH-9-fluorenone (1)
established by determining its single crystal structure
with X-ray diffraction is shown in Fig. 2. The geometry
of Te in 1 is typically that of a Te(IV) species, which
may be derived from a trigonal bipyramidal arrange-
ment by placing at one corner of the trigonal plane a
lone pair. The oxygen and chlorine atoms are trans to
each other. The selected bond lengths and angles are
Fig. 2. Molecular structure of Te-chloro,Te-anisyl-1a-aza-4-oxa-3-tel-
lura-1H,2H,4aH-9-fluorenone (1)

A.K. Singh et al. / Journal of Organometallic Chemistry 605 (2000) 39–44
43
Fig. 3. Molecular structure of [RuCl2(p-cymene)·L1] (2)
ppm) with respect to those of free L1. Similarly 13C-
NMR spectrum of 2 has deshielded CH2Te (ꢀ11 ppm)
and C5 (ꢀ6 ppm) signals with respect to that of free
L1. Both these observation suggest that the ligation of
L1 with Ru in solution is also through Te only as
shown in Fig. 3 for the crystal.
,
the values 1.890(8)–2.116(8) and 2.315(5)–2.564(1) A,
respectively, reported in the literature [14,15] for these
bonds. The reaction of [(p-cymene)RuCl2]2 with L1
results in 2, which is also characterized structurally
(Fig. 3). The coordination of L1 in 2 is through Te only.
The RuꢀTe and RuꢀCl bond lengths in 2 are normal,
and in agreement with the literature values, 2.636(1)–
,
2.655(1) and 2.467(4) A [5c, 16], respectively. The half
sandwich compound 2 has p-cymene in a h6 bonding
Acknowledgements
,
mode (RuꢀC(av.) 2.192(1) A). The TeꢀC(alkyl) in 2 has
also been found to be longer than TeꢀC(aryl) as it is in
Authors thank Department of Science and Technol-
ogy (India) for financial support.
L1 and 1.
3.2. H- and 13C{1H}-NMR spectra
1
References
The L1 exhibits characteristic 1H- and 13C-NMR
spectra. The two NMR spectra of 1, formed through
oxidation of tellurium of L1, are also characteristic. The
1H-NMR spectrum of 1 has a CH signal at 5.54 ppm,
and also exhibits ca. 0.4–0.5 ppm deshielded TeCH2,
NCH2 and ArTe signals (with respect to that of free
L1), as expected due to oxidation of tellurium from
+II to +IV oxidation state and cyclization. In 13C-
NMR spectrum of 1 also, signal due to TeCH2 shows
ca. 50 ppm down field shift with respect to that of free
L1, concurring well with the formation of Te(IV). The
1H-NMR spectrum of 2 exhibits a deshielding in
CH2Te (ꢀ0.74 ppm) and ArH signals (ꢀ0.17 to 0.20
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