Rhodium(I) carbonyl complexes of mono selenium functionalized bis(diphenylphosphino)methane and bis(diphenylphosphino)amine chelating ligands and their catalytic carbonylation activity

Article abstract of DOI:10.1016/j.jorganchem.2005.11.069

The chelate complexes of the types (1) and (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the ν(P-Se) bands and downfield shift of the ³¹P-{¹H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation through selenium donor. 1 and 2 show terminal ν(CO) bands at 1977 and 1981 cm^-1, respectively, suggesting high electron density at the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans- to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH₃I to produce acyl complexes (3) and (4), respectively. The kinetics of the OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of methanol was higher than that of the well known species [Rh(CO)₂I₂]^- and 2 shows higher catalytic activity compared to 1.

Full text of DOI:10.1016/j.jorganchem.2005.11.069

Journal of Organometallic Chemistry 691 (2006) 1229–1234
www.elsevier.com/locate/jorganchem
Rhodium(I) carbonyl complexes of mono selenium
functionalized bis(diphenylphosphino)methane
and bis(diphenylphosphino)amine chelating ligands
and their catalytic carbonylation activity
a,
b
b
a
Dipak K. Dutta *, J. Derek Woollins , Alexandra M.Z. Slawin , Dilip Konwar ,
a
b
b
Manab Sharma , Pravat Bhattacharyya , Stephen M. Aucott
a
Material Science Division, Regional Research Laboratory (CSIR), Jorhat 785006, Assam, India
b
School of Chemistry, University of St. Andrews, Fife, Scotland KY16 9ST, UK
Received 20 June 2005; received in revised form 22 November 2005; accepted 29 November 2005
Available online 10 January 2006
Abstract
The chelate complexes of the types
sized and characterized by IR and NMR spectroscopy. The lower shift of the m(P–Se) bands and downfield shift of the 31P–
{1H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation
through selenium donor. 1 and 2 show terminal m(CO) bands at 1977 and 1981 cmꢀ1, respectively, suggesting high electron density at
the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center
of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans-
to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH3I to produce
[Rh(CO)Cl(Ph PN(CH )P(Se)Ph )]
(1) and
(2) have been synthe-
[Rh(CO)Cl(Ph2PCH2P(Se)Ph2)]
2
3
2
[Rh(COCH )ClI(Ph PCH P(Se)Ph )]
[Rh(COCH )ClI(Ph PN(CH )P(Se)Ph )]
(4), respectively. The kinetics of the
3 2 3 2
acyl complexes
(3) and
3
2
2
2
OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of meth-
anol was higher than that of the well known species [Rh(CO)2I2]ꢀ and 2 shows higher catalytic activity compared to 1.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Rhodium(I) carbonyl complexes; Bis(diphenylphosphino)methane selenide; Bis(diphenylphosphino)amine selenide; Oxidative addition;
Carbonylation
1. Introduction
coordinate to the metal center in bidentate or monodentate
way [13,14]. Nature of backbone of these ligands plays an
important role on the stability and reactivity of the com-
plexes. The most promising feature of these ligands is that
they can confer stability to the metal complexes by chelate
formation and may create vacant coordination sites at the
metal center by the cleavage of relatively weaker metal–
chalcogen bond, which is a prerequisite for OA reactions.
Thus, these types of hemilabile ligands have great impact
on OA reactions [15–18], which is a key step in many
catalytic reactions like carbonylation of methanol. Since
the first introduction of the commercial species, i.e.,
[Rh(CO)2I2]ꢀ as an efficient catalyst for carbonylation of
Metal complexes of functionalized phosphines particu-
larly potential chelating ligands like phosphine–phosphine
monochalcogenides with different backbones have
attracted much attention in the recent time because of their
structural novelty, reactivity and catalytic activity [1–12].
Presence of two different types of donor sites makes the
chemistry of these ligands more fascinating as they can
*
Corresponding author. Tel.: +91 376 2370081; fax: +91 376 2370011.
E-mail address: dipakkrdutta@yahoo.com (D.K. Dutta).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.11.069

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D.K. Dutta et al. / Journal of Organometallic Chemistry 691 (2006) 1229–1234
methanol to acetic acid [15,16,19–22], considerable efforts
have been devoted to improve the catalyst by incorporating
different ligands [15–18,23–27] into its coordination sphere.
These prompted us to synthesize the Rh(I) carbonyl com-
plexes containing P–Se donors ligands of the type
Ph2PCH2P(Se)Ph2 and Ph2PN(CH3)P(Se)Ph2 which are
expected to coordinate to the metal center through P and
Se coordination sites with enhanced electron density on
the metal center that might lower the activation energy
for OA reactions. Moreover, chelate formation through
least strained five-membered ring may increase the stability
of the complexes. As a part of our continuing work
[11,17c,25–30], we report here the synthesis and character-
hence expected to show high nucleophilicity. Recently,
Cole-Hamilton et al. [24] reported a few electron rich com-
plexes of the type [Rh(CO)X(PEt3)2] (X = Cl, Br, I) having
m(CO) ca. 1960 cmꢀ1, which showed high catalytic activity
in the carbonylation of methanol, and postulated that elec-
tron rich centers play a significant role in improving the rate
of the reaction. The 31P–{1H}NMR spectrum of 1 showed a
doublet of doublet centered at d = 51.1 ppm and a doublet at
d = 35.2 ppm for the tertiary and pentavalent P-atoms,
respectively. These two resonances show a downfield shift
compared to the free ligand {d = ꢀ26.4 and d = 31.3 (d,
JPP = 85, JPSe = 725 Hz) ppm} value which indicates chelate
formation through metal phosphorus and selenium bonding.
The complex
2 exhibits a downfield resonance at
ization of electron rich
(1) and
[Rh(CO)Cl(Ph2PCH2P(Se)Ph2)]
d = 119.14 ppm for the tertiary phosphorus and upfield res-
onance at d = 66.42 ppm for the pentavalent phosphorus
atoms compared to the free ligand {d = 55.73 and 76.08 (d,
[Rh(CO)Cl(Ph2PN(CH3)P(Se)Ph2)]
(2) complexes including an
X-ray study of 2; their OA reactions with CH3I; kinetic
behavior and catalytic carbonylation of methanol.
JPP = 96, JPSe = 760 Hz) ppm} while the JPP = 72, JPSe
=
481 Hz values are lower than their corresponding free values
similar to complex 1 indicating chelate formation. The H
2. Results and discussion
1
NMR spectrum of 1 and 2 shows characteristic resonances
d = 4.3 ppm (–CH2–) and d = 2.5 ppm (CH3–), respectively,
along with their Ph protons in the range of 7.2–7.7 ppm. The
m(P–Se) bands of 1 and 2 occur at 513 and 543 cmꢀ1, respec-
tively, which are considerably lower than the corresponding
free ligands and thus substantiate further formation of che-
late through Rh–Se bonds [4].
2.1. Synthesis and characterization
The reaction of the chloro-bridged dimer [Rh(CO)2Cl]2 in
CH2Cl2 with 2 molar equivalents of each of the ligands
Ph2PCH2P(Se)Ph2 and Ph2PN(CH3)P(Se)Ph2 proceeds rap-
idly with the evolution of CO gas to yield the yellow chelated
monocarbonyl complexes
(1)
[Rh(CO)Cl(Ph2PCH2P(Se)Ph2)]
[Rh(CO)Cl(Ph PN(CH )P(Se)Ph )]
and
(2), respectively. 1 and 2
2
3
2
2.2. Single-crystal X-ray structure
show single terminal m(CO) bands at 1977 and 1981 cmꢀ1
,
respectively, which is in the characteristic region for such
rhodium(I) carbonyl complexes. The m(CO) values of the
complexes 1 and 2 are lower relative to the analogous rho-
Suitable crystals of 2 were grown by slow diffusion of
diethyl ether into a solution of CH2Cl2 of the complex, how-
ever, attempts to develop suitable crystal from 1 were unsuc-
cessful. The crystal structure (Fig. 1) was determined by
single-crystal X-ray diffraction studies and the crystal data
are given in Tables 2 and 3. The rhodium atom lies at the
center of an approximately square planar environment
[Rh(CO)Cl(Ph PCH P(O)Ph )]
dium phosphine complexes like
[Rh(CO)Cl(Ph PCH P(S)Ph )]
,
2
2
2
, etc. (Table 1) [14–17,28,31–34]
2
2
2
indicating the metal center is rich in electron density and
Table 1
Comparison of the m(CO) cmꢀ1 of the complexes [Rh(CO)Cl(P\X)] for
different hemilabile phosphine ligands
[Rh(CO)Cl(P\X)] (X = O, S, N, Se)
P\X
m(CO)a
Ref.
Ph2P(CH2)2SMe
Ph2P(CH2)2SEt
Ph2P(CH2)2SPh
2-Ph2PC6H4SMe
Ph2P(CH2)2OEt
Ph2PCH2P(S)Ph2
Ph2PCH2P(O)Ph2
Ph2P(CH2)2P(O)Ph2
Ph2PCH2P(O)(OPh)2
Ph2PCH2P(O)(Oi-Pr)2
2-Ph2PC6H4N(Me)2
Ph2P(CH2)2C5H4N
Ph2PCH2P(Se)Ph2
Ph2PN(CH3)P(Se)Ph2
1990
1985
2000b
1998c
1990b
1992b
1985
1995
1990b
1990b
2005
1990
1977
1981
[31]
[28]
[14]
[15a]
[32]
[16a]
[17]
[17]
[32]
[32]
[33]
[34]
This work
This work
a
In KBr.
In CH2Cl2.
Medium not mentioned.
b
c
Fig. 1. Molecular structure of 2 showing atomic labeling.

D.K. Dutta et al. / Journal of Organometallic Chemistry 691 (2006) 1229–1234
1231
Table 2
Crystal data and structure refinement details for 2
2.3. OA reaction and their kinetics
Empirical formula
Formula weight
Temperature (K)
C26H23ClNOP2RhSe
644.71
125(2)
0.71073
Orthorhombic
Pbca
The OA reactions of 1 and 2 with CH3I yield
[Rh(COCH3)ClI(Ph2PCH2P(Se)Ph2)]
complexes
(3) and
˚
[Rh(COCH )ClI(Ph PN(CH )P(Se)Ph )]
Wavelength (A)
(4), respectively, through
3
2
3
2
Crystal system
Space group
Unit cell dimensions
their corresponding unisolable rhodium(III) alkyl inter-
mediates (Scheme 1). The 31P–{1H}NMR spectrum of 3
shows a doublet of doublet centered at d = 50.2 and a
doublet at d = 33.3 ppm. Similarly, 4 shows a doublet of
doublet centered at d = 117.0 ppm along with a doublet
at d = 68.4 ppm, these reveal that, like in 1 and 2, in the
oxidized products the ligands also remain in metal–Se che-
˚
a (A)
17.5618(19)
15.8421(17)
18.906(2)
90
90
90
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
1
lating mode. The H NMR spectra of 3 and 4 show a new
3
˚
Volume (A )
5260.0(10)
singlet at d = 2.18 and d = 2.81 ppm, respectively, along
with the other characteristic resonances for the ligands,
which are in consistent with the formation of the acyl
group (–COCH3).
Kinetic studies for the OA reaction of CH3I with 1
and 2 were carried out in order to understand the effect
of ligand backbone. Fig. 2a shows a plot of absorbance
against time for the disappearance of the terminal m(CO)
band of 1 (1977 cmꢀ1) and formation of a new terminal
m(CO) band at higher energy 2063 cmꢀ1 which is a char-
acteristic band [35,36] for Rh(III) alkyl intermediate
Z
8
Crystal size (mm3)
Reflections collected
Independent reflections [Rint
Refinement method
Final R indices [I > 2r(I)]
.1 · .1 · .1
33751
4734 [0.1302]
Full-matrix least-squares on F2
R1 = 0.0440, wR2 = 0.0897
]
Table 3
Selected bond lengths (A) and angles (ꢁ) for 2
˚
Rh(1)–C(26)
Rh(1)–Se(1)
C(26)–O(26)
P(1)–N(1)
P(1)–C(7)
N(1)–P(2)
1.810(5)
2.464(6)
1.158(6)
1.654(4)
1.789(5)
1.717(4)
1.818(5)
Rh(1)–P(2)
Rh(1)–Cl(1)
Se(1)–P(1)
P(1)–C(1)
N(1)–C(25)
P(2)–C(13)
2.201(12)
2.381(11)
2.153(13)
1.784(5)
1.495(5)
1.807(5)
[Rh(CO)(CH )ICl(Ph PCH P(Se)Ph )]
(
(10)) (Scheme 1) along
3
2
2
2
with the formation of acyl m(CO) band at around
1700 cmꢀ1. The decay of the terminal m(CO) band of 1
indicates that the course of the reaction proceeds in an
exponential manner while the initial formation and then
decay of the terminal m(CO) band of 10 indicates that at
a reaction time of about 5 min the concentration of the
intermediate reaches a maximum after which it follows
a similar kinetics to that of 1. Similar type of plot
(Fig. 2b) was also obtained for 2 in which the decay
of the terminal m(CO) band at 1981 cmꢀ1 accompanies
with the growth and decay of another new terminal
m(CO) band at around 2060 cmꢀ1 which is due to forma-
tion of a hexacoordinated Rh(III) alkyl intermediate
P(2)–C(19)
C(26)–Rh(1)–P(2)
P(2)–Rh(1)–Cl(1)
P(2)–Rh(1)–Se(1)
O(26)–C(26)–Rh(1)
N(1)–P(1)–C(1)
C(1)–P(1)–C(7)
C(25)–N(1)–P(1)
P(1)–N(1)–P(2)
N(1)–P(2)–Rh(1)
C(19)–P(2)–Rh(1)
90.55(15)
177.14(5)
92.44(3)
175.5(4)
110.7(2)
107.2(2)
118.4(3)
122.1(2)
112.89(13)
116.52(15)
C(26)–Rh(1)–Cl(1)
C(26)–Rh(1)–Se(1)
Cl(1)–Rh(1)–Se(1)
P(1)–Se(1)–Rh(1)
N(1)–P(1)–C(7)
N(1)–P(1)–Se(1)
C(25)–N(1)–P(2)
N(1)–P(2)–C(13)
C(13)–P(2)–Rh(1)
C(13)–P(2)–C(19)
91.83(15)
170.14(15)
85.46(3)
98.64(4)
106.7(2)
109.71(14)
119.5(3)
102.1(2)
114.75(16)
106.2(2)
([Rh(CO)(CH3)ICl(Ph2PN(CH3)P(Se)Ph2)] (20)). From Fig. 2b,
it is clear that the concentration of the intermediate
increases up to a period of about 15 min and then starts
decreasing in a manner similar to that of the decaying
curve of 2. The rate of decay of the terminal m(CO) band
of 2 was slower than 1 and the course of the reaction
proceeds exponentially. The growth of the acyl m(CO)
formed by the P, Se, C (of CO) and Cl atom. The ligand
forms a chelate (bite angle P–Rh–Se 92.44ꢁ) through phos-
phorous and selenium donors and maintains a five-mem-
bered less strained ring structure. The longer bond length
in Rh–Se (2.46 A) than in Rh–P (2.20 A) may indicate a
weaker interaction in the former and is likely to cleave easily
during catalytic reaction.
˚
˚
I
OC
Cl
OC
Cl
P
I
P
CH3OC
Cl
P
Migratory
insertion
Fast
OA
Rh
Se
Rh
CH3I
+
Rh
Slow
Se
Se
CH3
Complex
Acyl complex
Alkyl intermediate
1′ or 2′
P Se = Ph2PCH2P(Se)Ph2
Ph2PN(CH3)P(Se)Ph2,
Scheme 1. OA and migratory insertion reactions of 1 and 2 with CH3I.

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D.K. Dutta et al. / Journal of Organometallic Chemistry 691 (2006) 1229–1234
Table 4
120
100
80
Results of carbonylation of methanol
a
Catalyst precursor Acetic
Methyl
Total
TONb
acida (%) acetatea (%) conversion (%)
[Rh(CO)2I2]ꢀ1c
3.34
9.6
9.1
7.2
6.8
30.74
29.2
27.8
35.2
33.8
34.08
38.8
36.9
42.4
40.6
648
870
827
901
863
1977 cm-1 (1)
× 2063 cm-1 (1/)
1700 cm-1 (3)
1
1d
2
2d
60
a
Yields of methyl acetate and acetic acid were obtained from GC
analyses.
b
40
TON = [amount of product (mol)]/[amount of catalyst (Rh mol)].
Formed from added [Rh(CO)2Cl]2 under the catalytic condition.
Recycled.
c
d
20
0
2.4. Catalytic activity of 1 and 2 for carbonylation of
methanol
0
20
40
60
80
100
120
b
The results of batch carbonylation of methanol to acetic
acid and its ester in the presence of 1, 2, and [Rh(CO)2Cl]2
as catalyst precursors are shown in Table 4. GC analyses of
the products reveal that 2 exhibits a maximum conversion
of 42.4% with the highest turn over number (TON) 901
compared to the other complexes. Under the same experi-
mental condition, the well-known catalyst precursor
[Rh(CO)2I2]ꢀ generated in situ [37,38] from [Rh(CO)2Cl]2
shows 34.08% conversion with a TON 648 while 1 exhibits
38.8% conversion with TON 870. Data from Table 4, in
general, reveal an order of efficiency of the catalytic activity
of the precursors as 2 > 1 > [Rh(CO)2I2]ꢀ. It is well known
that OA step plays a key role in enhancing the catalytic effi-
cacy of such reaction. As expected from higher OA reac-
tion rate of 1 over 2, the former should act more
efficiently over the latter in the carbonylation reaction.
But in practice, the reverse situation was observed. To
explain this, one must consider the fact that higher electron
donating ligands make the metal center more nucleophilic
and may lead to the formation of stronger Rh–C (acyl)
bond [36b] which may cause retardation of the rate of
the reductive elimination reaction required for completion
of the catalytic cycle. On examining the catalytic reaction
mixture by IR spectroscopy at different time intervals and
at the end of the catalytic reactions, the m(CO) bands com-
pared well with the m(CO) values of a solution containing a
mixture of the parent rhodium(I) carbonyl complexes and
the rhodium(III) acyl complexes. Thus, it may be inferred
that the ligands remained bound to the metal centre during
the entire course of the catalytic reactions. It is worth to
mention that the catalysts showed almost the same efficacy
for their recycled experiments (Table 4), indicating ade-
quate stability of the catalysts.
100
80
60
40
20
0
1981 cm-1 (2)
× 2060 cm-1 (2/)
1717 cm-1 (4)
0
20
40
60
80
100
Time (min)
Fig. 2. Absorbance of m(CO) against time for different carbonyl species:
decay (m) of terminal m(CO) band (a) for the complexes 1 and (b) for 2;
variation (·) of terminal m(CO) band (a) for intermediate (10) and (b) for
(20); and the growth (j) of the acyl m(CO) band (a) for the complex 3 and
(b) for 4 during the course of OA reactions with CH3I.
bands at 1700 and 1717 cmꢀ1 for 3 and 4 were also
found to follow a similar type of kinetics as that of
decay of terminal m(CO) bands for 1 and 2. Kinetics
measurements were done by applying pseudo-first-order
conditions, i.e., at high concentration of CH3I. A linear
fit of pseudo-first-order was observed for the entire
course of the OA reactions of CH3I with 1 and 2 as is
evidenced from the plot of ln(A0/At) versus time, where
A0 and At are the absorbance at time t = 0 and t, respec-
tively. From the slope of the plot, the rate constants for
both the reactions were calculated and found to be
24.67 · 10ꢀ4 and 5.47 · 10ꢀ4 sꢀ1 for 1 and 2, respectively.
The values of the rate constants clearly indicate that the
OA reaction of 1 is almost 4.5 times faster than that of
2. This can be substantiated by higher electron density,
i.e., higher nucleophilicity of 1 over 2 as indicated from
the m(CO) stretching values of the complexes (Table 1).
3. Experimental
3.1. General procedure
The reagents were procured from M/s Aldrich Chemi-
cals, USA and M/s Lancaster, UK. All solvents were

D.K. Dutta et al. / Journal of Organometallic Chemistry 691 (2006) 1229–1234
1233
distilled under N2 prior to use. All operations were carried
out under oxygen-free nitrogen atmosphere using standard
Schlenk technique. Microanalyses were performed by St.
Andrews University service (Chemistry Department). FT-
IR spectra (4000–400 cmꢀ1) were recorded using a Per-
kin–Elmer 2000 spectrometer in CHCl3 and as KBr discs.
The 1H NMR (270 MHz), 13C (67.94 MHz) and
31P{1H}NMR (109.36 MHz) spectra were recorded in
CDCl3 solution on a Jeol Delta 270 MHz Spectrometer.
The reaction mixture was stirred at room temperature for
about 1 h and the solvent was evaporated under reduced
pressure in a rotavapor to obtain a light brown solid.
The compound so obtained was washed with diethyl ether
and stored over silica gel in a desiccator. Yield 0.49 g. IR
data (KBr) m(CO) = 1981 cmꢀ1, m(P–Se) = 543 cmꢀ1 1H
.
NMR: d = 2.48(d, JHH = 6, 10 Hz, 3H, –CH3), 7.24–7.60
(m, 20H, Ph) ppm. 31P NMR d = 119.14 (dd, JPP = 72,
JRhP = 169.50 Hz), 66.42 (d, JPP = 72.17, JPSe
=
The chemical shifts for H and 13C NMR are quoted rela-
481.18 Hz) ppm. 13C NMR: d = 35.63 (s, –CH3), 128.60–
134.08 (m, Ph), 181.42 (s, CO) ppm. Free ligand: IR: m(P–
1
tive to SiMe4 as internal standard and for 31P relative to
85% H3PO4 as external standard. The carbonylation reac-
tions of alcohol were carried out in a 100 cm3 teflon coated
high pressure reactor (HR-100 Berghof, Germany) fitted
with a pressure gauge and the reaction products were
analyzed by GC (Chemito 8510, FID). The ligands
(C6H5)2PCH2P(Se)(C6H5)2 and (C6H5)2PN(CH3)P(Se)-
(C6H5)2 were prepared by the literature methods [39,40].
The starting complex [Rh(CO)2Cl]2 was prepared by
known method [41].
Se) = 551 cmꢀ1
.
31P NMR: d = 55.73 (d), 76.08 (d, JPSe
=
1
760.03, JPP = 96.23 Hz) ppm. H NMR: d = 2.65 (d, 3H,
–CH3–), 7.41–7.90 (m, Ph) ppm. 13C NMR: d(ppm) 33.02
(t, –CH3), 127.87–133.90 (m, Ph) ppm. C26H23ClNOP2-
RhSe: found C 48.23, H, 3.50, N 2.07; calc. C 48.45, H
3.57, N 2.17%.
[Rh(CH CO)ClI(Ph PCH P(Se)Ph ]
3.4. Synthesis of
(3)
2
3
2
2
The complex 1 (0.115 g, 0.182 mmol) was dissolved in
CH2Cl2 (10 cm3) and to this CH3I (6 cm3) was added.
The reaction mixture was then stirred at room temperature
under nitrogen atmosphere for about 3 h and the solvent
was evaporated under vacuum. Yellow-reddish colored
compound so obtained was washed with diethyl ether
and stored over silica gel in a desiccator. Yield 0.12 g. IR
[Rh(CO)Cl(Ph PCH P(Se)Ph ]
3.2. Synthesis of
(1)
2
2
2
[Rh(CO)2Cl]2 (0.100 g, 0.257 mmol) was dissolved in
CH2Cl2 (10 cm3) and was added dropwise to the solution
of ligand (Ph2PCH2P(Se)Ph2) (0.238 g, 0.514 mmol in
10 cm3 CH2Cl2) with constant stirring under nitrogen
atmosphere. The reaction mixture was stirred at room tem-
perature for about 1 h and the solvent was evaporated
under reduced pressure in a rotavapor to obtain a yellow
solid. The compound so obtained was washed with diethyl
ether and stored over silica gel in a desiccator. Yield:
0.31 g. IR data (KBr) m(CO) = 1977 cmꢀ1; m(P–Se) =
data (KBr): m(CO)acyl = 1700 cmꢀ1
(t, 2H, –CH2–), 7.26–7.81 (m, 20H, Ph), 2.18 (s, 3H,
–CH3) ppm. 31P NMR: d = 50.2 (dd, JPP = 43 Hz, JRhP
.
1H NMR: d = 4.42
=
145 Hz), 33.3 (d, JPP = 43 Hz) ppm. C27H25ClIOP2RhSe:
calc. C 42.03, H 3.24; found C 41.88, H 3.20%.
513 cmꢀ1
.
1H NMR: d = 4.32 (t, JPH = 10 Hz, 2H,
3.5. Synthesis of
[Rh(CH CO)ClI(Ph PN(CH )P(Se)Ph ]
(4)
2
3
2
3
–CH2–), 7.19–7.43 (m, 10 H, Ph), 7.60–7.69 (m, 10 H,
Ph) ppm. 31P NMR: d = 51.1(dd, JPP = 56 Hz, JRhP
=
The complex 2 (0.106 g, 0.164 mmol) was dissolved in
CH2Cl2 (10 cm3) and to this CH3I (6 cm3) was added.
The reaction mixture was then stirred at room temperature
under nitrogen atmosphere for about 5 h and the solvent
was evaporated under vacuum. Yellow-reddish colored
compound so obtained was washed with diethyl ether
and stored over silica gel in a desiccator. Yield 0.11 g. IR
164 Hz), 35.2 (d, JPP = 56 Hz, JPSe = 561 Hz) ppm. 13C
1
NMR: d = 44.84 (dd, JCP = 17, 50 Hz), 133.15 (1JCP
=
12 Hz), 132.97 (1JCP = 3 Hz), 132.25 (1JCP = 10 Hz),
130.98 (1JCP = 2 Hz), 129.15 (1JCP = 12 Hz), 128.56
(1JCP = 10 Hz), 126.35 (1JCP = 5), 125.28 (1JCP = 5),
183.06 (s, CO) ppm. Free ligand: IR: m(P–Se) = 527 cmꢀ1
;
=
31P NMR: d = ꢀ26.4d, 31.3d (JPSe = 725 Hz, JPP
(KBr): m(CO)acyl = 1717 cmꢀ1. H NMR: d = 2.52 (d, 3H,
1
2
85Hz) ppm, 1H NMR: d = 3.49 (d, 2H, JHP(Se) =
–CH3), 7.11–7.87 (m, 20H, Ph), 2.81 (s, 3H, –CO-
1
13 Hz, –CH2–) ppm. 13C NMR: d = 34.98 (dd, JCP(Se)
=
CH3) ppm. 31P NMR: d = 117.0 (dd, JPP = 41, JRhP
=
1
47.4, JCP = 31 Hz, –CH2–), 128.42–133.21 (m, Ph) ppm.
C26H22ClOP2RhSe: found C 49.12, H 3.42; calc. C 49.60,
H 3.49%.
169 Hz), 68.4 (d, JPP = 41 Hz) ppm. C27H26ClINOP2RhSe:
calc. C 41.23, H 3.31, N 1.78; found C 41.01, H 3.30, N
1.73%.
[Rh(CO)Cl(Ph PN(CH )P(Se)Ph ]
3.3. Synthesis of
(2)
2
3.6. Reaction kinetics
2
3
[Rh(CO)2Cl]2 (0.154 g, 0.396 mmol) was dissolved in
CH2Cl2 (15 cm3) and was added dropwise to the solution
of ligand (Ph2PN(CH3)P(Se)Ph2) (0.380 g, 0.792 mmol in
15 cm3 CH2Cl2) with constant stirring under nitrogen
atmosphere. Reaction took place immediately with effer-
vescence and color changes from pale yellow to deep red.
The OA reactions of 1 and 2 with CH3I were monitored
by using IR spectroscopy in a solution cell (1.0 mm path
length). The complexes 1 and 2 (10 mg) were added to neat
CH3I (1 cm3) at room temperature. An aliquot (0.5 ml) of
the reaction mixture was transferred by syringe into the
IR cell. Then the kinetic measurement was made by

1234
D.K. Dutta et al. / Journal of Organometallic Chemistry 691 (2006) 1229–1234
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m(CO) of 3 and 4 in the range 1700–1720 cmꢀ1 and also the
terminal m(CO) of the intermediate Rh(III)-complexes. A
series of spectra were taken at regular intervals. The OA
reactions of CH3I with 1 and 2 were found to be concentra-
tion dependent on the complexes as well as on CH3I.
Therefore, in order to provide a pseudo-first-order condi-
tion, the reaction was carried out in a large excess of CH3I.
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Acknowledgments
The authors are grateful for the financial support by
UK–India Science & Technology Research Fund. Thanks
are also due to DST, New Delhi, OST, UK, RRL Jorhat
(CSIR) and University of St. Andrews, UK for various
supports.
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