Vibrational study of new Pt(II) and Pd(II) complexes with functionalized nitrogen-containing tertiary phosphine oxides. Ab initio study of ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline

Article abstract of DOI:10.1016/S1386-1425(02)00163-4

Vibrational study of new Pt(II) and Pd(II) complexes of functionalized nitrogen-containing tertiary phosphine oxides, namely ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline (o-, m- and p-dpmoa), (CH₃)₂P(O)CH₂O

Full text of DOI:10.1016/S1386-1425(02)00163-4

Spectrochimica Acta Part A 59 (2003) 169Á192
/
www.elsevier.com/locate/saa
Vibrational study of new Pt(II) and Pd(II) complexes with
functionalized nitrogen-containing tertiary phosphine oxides.
Ab initio study of ortho-, meta- and
para-dimethylphosphinylmethyleneoxyaniline
N. Trendafilova a,*, G. Bauer b, I. Georgieva a, T. Tosheva c, S. Varbanov c
a Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
b Institute of Electrochemistry and Solid State Chemistry, Technical University of Vienna, 1060 Vienna, Austria
c Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Received 7 March 2002; accepted 16 April 2002
Abstract
Vibrational study of new Pt(II) and Pd(II) complexes of functionalized nitrogen-containing tertiary phosphine
oxides, namely ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline (o-, m- and p-dpmoa),
(CH3)2P(O)CH2OC6H4NH2, have been presented. Geometry optimization of the ligands was performed at HF/6-
31G* and B3LYP/6-31G* levels of the theory. Harmonic frequencies were calculated at HF/6-31G* optimized
geometries. Relative gas-phase and solution-phase (H2O and CH3CN) basicities of o-, m- and p-dpmoa ligands have
been determined by ab initio calculations at STO-3G level with the Onsager reaction field model. On the basis of the
vibrational study, physical and analytical data it was suggested that the ligands in the complexes studied coordinate
through the amino group and form square-planar platinum and palladium complexes of the general formula ML2Cl2
(Mꢀ
/
Pt, Pd, Lꢀo-, m- and p-dpmoa).
/
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Platinum(II) and palladium(II) complexes; Functionalized nitrogen containing tertiary phosphine oxides; Vibrational
spectra (IR and Raman); Ab initio study
1. Introduction
studied as to their potential antitumor activity [1].
The phosphoryl group of the ligands increases the
solubility of the Pt(II) and Pd(II) complexes in
water and thus improves their pharmacokinetical
The coordination compounds of Pt(II) and
Pd(II) with different phosphine oxides have been
properties. Besides, the presence of a free Pꢀ
/
O
group in the molecule is very important since it
offers possibility for binding the complex to the
biologically active centres by hydrogen bonds.
Recently we have investigated a series of Pt(II)
* Corresponding author. Tel.: ꢁ
2-705024
E-mail address: ntrend@svr.igic.bas.bg (N. Trendafilova).
/
359-2-979-2592; fax: ꢁ359-
/
1386-1425/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 1 3 8 6 - 1 4 2 5 ( 0 2 ) 0 0 1 6 3 - 4

170
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
and Pd(II) complexes with different phosphine
oxides of the general formula, ML2Cl2, where Lꢀ
results from the comparative vibrational study as
well as the physical and chemical data are used to
suggest the stoichiometry of the new complexes.
/
4- and (3-pyridyloxymethylene) dimethylphos-
phine oxides [2], dimethyl(aminomethyl)phosphine
oxide [3] and 1,1-(methylphosphinylidene)bis-
(methanamine) [4,5]. It was shown that the ligands
coordinate to Pt(II) and Pd(II) only through the
pyridine nitrogen [2] or through the amino-nitro-
2. Experimental
gen [3Á5].
/
2.1. Synthesis
The tertiary phosphine oxides functionalized
with primary or secondary amino groups are a
relatively small group of organophosphorus com-
pounds [6]. Due to the high reactivity of the amino
group they form complexes, which may be used to
mimic biologically active centres. Recently, a series
Pt(II) complexes of 2-, 3- or 4-substituted anilines
were synthesized and studied as important biolo-
gical compounds [7]. From them six cis-dichloro
Pt(II) complexes have shown high antitumor
activity against Sarcoma 180 ascites in female
ICR/JCL mice [7].
The ortho-, meta- and para-dimethylphosphi-
nylmethyleneoxyaniline, (o-, m-, and p-dpmoa),
(CH3)2P(O)CH2OC6H4NH2, are relatively new
compounds (synthesis were reported in 1997) and
could be considered as o-, m-, p-substituted ani-
line [6]. The coordination behaviour of the com-
pounds has not been investigated. There is a lack
of information about their structures as well. In
such cases ab initio quantum mechanical and
The starting compounds, o-, m- and p-dpmoa,
(PhCH2NEt3)2PtCl4 and cis-PdCl2(CH3CN)2 were
prepared as described in the literature [6,8,9]. The
high water solubility of [M(o-dpmoa)2Cl2], [M(m-
dpmoa)2Cl2], and [M(p-dpmoa)2Cl2] (MꢀPt, Pd)
/
required preparing these complexes in non-aqu-
eous medium. K2PtCl4, PdCl2 and solvents used
were analytical grade purity products. Acetonitrile
(AN) and ethanol were rigorously dried over
˚
preconditioned 3 A molecular sieves.
The complexes have been synthesized according
to the schemes:
(PhCH2NEt3)2PtCl4 ꢁ2L
0 PtL2Cl2¡ꢁ2PhCH2NEt3Cl
(1)
Pd(CH3CN)2Cl2 ꢁ2L 0 PdL2Cl2¡ꢁ2CH3CN (2)
2.1.1. [Pt(o-dpmoa)2Cl2]
density functional calculations [8Á10] may be
/
(PhCH2NEt3)2PtCl4 (0.4947 g, 0.69 mmol) was
dissolved in 20 ml AN by heating at 50 8C under
constant stirring for 3 h. A solution of o-dpmoa
(0.3004 g, 1.51 mmol) in 6 ml AN was added in
used to predict many properties of the molecules,
such as equilibrium geometries, conformational
energies, IR and Raman spectra and thermoche-
mical properties [11Á14].
/
argon medium to
a
stirring solution of
In this paper we report the synthesis and the
vibrational study of Pt(II) and Pd(II) complexes
with o-, m- and p-dpmoa. To obtain structural
parameters for the ligands, geometry optimization
was performed at HF and DFT levels of the theory
with 6-31G* basis set. The effect of o-, m- and p-
(PhCH2NEt3)2PtCl4. The reaction mixture was
carried out in a dark room, and at ambient
temperature for 4 months. The obtained light
yellow precipitate was separated with filtration,
washed with AN and diethylether and dried. The
[Pt(m-dpmoa)2Cl2] and [Pt(p-dpmoa)2Cl2] com-
plexes were prepared in a similar way.
substituent, (CH3)2P(O)CH2Oꢁ
/
, on the aniline
properties was examined in terms of the obtained
vibrational frequencies and structural parameters.
The vibrational assignment of the complexes
studied was performed on the basis of comparison
with the free ligand vibrational assignment and
literature data about related compounds. The
2.1.2. [Pd(o-dpmoa)2Cl2]
A solution of o-dpmoa (0.1622 g, 0.81 mmol) in
ethanol (5 ml) was added dropwise to a suspension
of PdCl2(CH3CN)2 (0.1007 g, 0.38 mmol) in

N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á
/
192
171
ethanol (5 ml). The prepared mixture was stirred at
room temperature for 40 h in argon atmosphere.
in methanol and only for Pt(m-dpmoa)2Cl2 in
dimethylformamide (DMF).
The obtained yellowÁbrown precipitate was sepa-
/
rated by filtration, washed with ethanol, diethy-
lether and dried under vacuum over P2O5. The
Pd(m-dpmoa)2Cl2 and Pd(p-dpmoa)2Cl2 were pre-
pared in a similar way. The preparation of the
palladium complexes proceeds totally in hetero-
geneous media: the starting and the prepared
complexes are not soluble in ethanol. The high
yields of the Pd(II) complexes indicate the reac-
tions proceed quantitatively.
2.3. Infrared and Raman spectra measurements
The Raman spectra of the ligands and com-
plexes studied were measured in the solid state
with
monochromator with 1152ꢃ
camera detector) in the 200Á
4000 cmꢂ1 frequency
a
SPEX-Ramalog spectrometer (double
/298 pixels CCD-
/
range. An argon ion laser (514.5 nm) and a
krypton ion laser (647.1 nm) were used for
excitation.
The preparative and analytical data for Pt(II)
and Pd(II) complexes are given in Table 1.
The solid-state infrared spectra were recorded in
KBr pellets by FTIR 113V Bruker spectrometer in
the 4000Á
cmꢂ1 frequency regions. In all cases the resolution
was 1 cmꢂ1
/
400 cmꢂ1 and in CsI in the 400Á
150
/
2.2. Physical measurements and analysis
.
The melting points of complexes were obtained
on a Boetius micro-heating plate PHMK 05
¨
(Germany) and were not corrected. The elemental
analysis for N and Cl were performed according to
standard microanalytical procedures. The phos-
phorus content was determined as described in
[14].
The electrical conductivity measurements were
performed using a conductivity meter type OK-
102/1, Radelkis, for 10ꢂ3 mol lꢂ1 solutions at 258
3. Computational procedure
The ab initio calculations of the o-, m- and p-
dpmoa were carried out using GAUSSIAN-98 com-
puter program set [15]. Complete geometry opti-
mization of the compounds was performed using
Table 1
Preparative, analytical and physical data for M(o-dpmoa)2Cl2, M(m-dpmoa)2Cl2, M(p-dpmoa)2Cl2 (MꢀPt,Pd) complexes
/
Complexes
Yield % Reaction Colour
time (d)c
Melting
point ( 8C)
Analysis (%)
P
b
N
Cl
LM
(cm2 Vꢂ1
mol1)
Pt(o-dpmoa)2Cl2 33
Pt(m-dpmoa)2Cl2 51
120
80
Light yellow
White
255Á
/
258
9.38 (9.32)a 4.41 (4.22)
10.20 (10.67) 1.0 (MeOH)
10.97 (10.67) 2.4 (DMF)
270Á
/
272
8.67 (9.32)
4.46 (4.22)
(decomp)
296Á298
(decomp)
Pt(p-dpmoa)2Cl2 42
60
Light grey
/
9.48 (9.32)
4.34 (4.22)
10.48 (10.67) 2.6 (MeOH)
Pd(o-dpmoa)2Cl2 87
Pd(m-dpmoa)2Cl2 99
Pd(p-dpmoa)2Cl2 95
2
2
2
Yellow-brown 255Á
/
258
282
295
10.69 (10.76) 4.83 (4.87)
10.77 (10.76) 5.44 (4.87)
10.91 (10.76) 5.52 (4.87)
12.61 (12.32) 7.3 (MeOH)
11.96 (12.32) 2.6 (MeOH)
12.62 (12.32) 4.4 (MeOH)
Yellow
Yellow-green
280Á
/
292Á
/
a
The calculated values are given in brackets.
10ꢂ3 mol lꢂ1
.
Days.
b
c
At room temperature, cꢀ
/

172
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
Fig. 1. Atom numbering and total atomic charges for o-, m- and p-dpmoa at HF/6-31G* level.
6-31G* (split-valence Gaussian basis set plus
polarization) basis set at Hartree-Fock and density
functional (B3LYP) levels of the theory [16]. The
start geometries of o-, m- and p-dpmoa were
found with MM2 method. The selected most
stable conformers for o-, m- and p-dpmoa were
optimized at the HF/6-31G* and B3LYP/6-31G*
levels and in any case the nature of the model
(minimum state) was substantiated by evaluation
of vibrational frequencies. Harmonic frequencies
and Cartesian coordinate force field were calcu-
lated at the HF/6-31G* optimized geometries. A
scaling procedure was applied to obtain a better
agreement between the experimental and calcu-
lated frequencies.
sidering the zero-point energy (ZPE), vibration
energy (Evib), and total electronic energy Eo
according to Eq. (4):
/
elec
DH ꢀH(products)ÁH(reactants)
ꢀDEoelec ꢁDZPEꢁDEvib(T)ꢂ5=2RT
(4)
The calculated nitrogen PA values of o-, m- and
p-dpmoa were compared at ambient temperature
(298 K).
4. Results and discussion
4.1. Ab initio study of o-, m- and p-dpmoa
The relative proton affinity (PA) of the nitrogen
base in the studied o-, m- and p-dpmoa in gas
phase and solution (H2O and CH3CN) has been
evaluated by ab initio calculations at STO-3G level
with Onsager reaction field model. PA was defined
as the positive value of the enthalpy change (DH)
for the proton-transfer isodesmic reaction [17]:
4.1.1. Geometry optimization
Selected structural data for o-, m- and p-
dpmoa, obtained at HF/6-31G* and B3LYP/6-
31G* levels are listed in Table 2. Since the ligands
are considered as o-, m- and p-substituted aniline,
ab initio (at HF and B3LYP levels) and experi-
mental [11] data for aniline are also presented in
Table 2. The atom numbering and total atomic
charges for o-, m- and p-dpmoa are shown in Fig.
1. The C3C4, C2C3 and C1N bond lengths of
aniline, calculated at B3LYP/6-31G* level, are in
excellent agreement with the experiment [11]. In
XC6H4NHꢁ3 ꢁC6H5NH2
l XC6H4NH2 ꢁC6H5NH3ꢁ
(3)
where X is OCH2P(O)(CH3)2 substituent. The
enthalpy changes (DH) were estimated by con-

Table 2
Structural parameters and relative energies of aniline, o-, m- and p-dpmoa
Geometrical
parametersa
Aniline
o-dpmoa
m-dpmoa
p-dpmoa
HF6-31G*
[11]
B3LYP6-31G* Exp. [11]
(this work)
HF6-31G*
(this work)
B3LYP6-31G* HF6-31G*
(this work)
B3LYP6-31G* HF6-31G*
(this work)
B3LYP6-31G*
(this work)
(this work)
(this work)
C1ꢁ
C1ꢁ
C3ꢁ
C4ꢁ
C5ꢁ
C2ꢁ
C1ꢁ
C2ꢁ
C3ꢁ
C4ꢁ
C5ꢁ
C6ꢁ
N13ꢁ
N13ꢁ
/
C2
1.392
1.392
1.386
1.386
1.384
1.383
1.398
1.077
1.076
1.075
1.076
1.077
0.997
0.997
1.405
1.405
1.397
1.396
1.393
1.393
1.400
1.088
1.087
1.086
1.087
1.088
1.013
1.013
1.3979
1.3979
1.3969
1.3969
1.3949
1.3949
1.4029
1.0829
1.0839
1.0809
1.0839
1.0829
1.0019
1.0019
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
0.003
0.003
0.002
0.002
0.004
0.004
0.002
0.004
0.002
0.002
0.002
0.004
0.01
1.401
1.383
1.392
1.377
1.389
1.378
1.398
1.414
1.398
1.401
1.391
1.397
1.391
1.399
1.398
1.389
1.391
1.379
1.386
1.383
1.392
1.073
1.408
1.403
1.401
1.391
1.395
1.395
1.397
1.085
1.384
1.396
1.381
1.390
1.377
1.391
1.403
1.076
1.073
1.400
1.407
1.396
1.399
1.389
1.397
1.405
1.088
1.084
/C6
/
/C4
/
/C5
/
/C6
/
/C3
/
/
N13
H14
H14(H15-p)
H15
H16
H17
/
/
/
Á/
Á/
/
/
1.073
1.075
1.075
1.076
0.997
0.998
1.365
1.401
1.834
1.086
1.474
1.814
1.084
118.39
120.65
120.19
119.68
120.01
119.66
121.90
1.084
1.086
1.086
1.088
1.013
1.012
1.383
1.420
1.855
1.099
1.501
1.829
1.094
118.17
120.87
120.01
119.74
120.15
119.44
122.33
Á/
1.073
1.076
Á/
1.085
1.087
/
/
Á/
1.075
1.076
Á/
/
/
1.086
1.088
1.013
1.013
1.381
1.419
1.854
1.100
1.501
1.830
1.094
117.99
121.34
119.91
119.34
/
/
1.076
1.087
/
H26
H27
/
0.997
0.997
1.012
1.013
0.998
0.998
/
/
0.01
C2(C3,C4)ꢁ
O7ꢁC8
C8ꢁP9
C8ꢁH18(H19)
P9ꢁ
P9ꢁ
Cꢁ
C2ꢁ
C1ꢁ
C2ꢁ
C3ꢁ
C4ꢁ
C2ꢁ
C6ꢁ
C1ꢁ
C3ꢁ
C2ꢁ
(H15-p)
C4ꢁC3ꢁ
(H15-p)
/
O7
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
118.6
1.355
1.401
1.376
1.420
1.364
1.399
/
/
1.834
1.086
1.855
1.099
1.834
1.086
/
/O10
1.474
1.814
1.501
1.829
1.474
1.814
/C11
/H(CH3)
1.084
1.094
1.084
/
C1ꢁ
C2ꢁ
C3ꢁ
C4ꢁ
C5ꢁ
C1ꢁ
C1ꢁ
C2ꢁ
C2ꢁ
C3ꢁ
/
C6
118.74
120.38
120.86
118.77
120.86
120.61
120.60
119.59
120.03
119.20
119.439
120.129
120.709
118.929
/
0.20
0.20
0.08
0.08
119.64
119.81
120.86
118.66
121.56
119.55
120.77
118.94
121.24
119.38
119.84
120.94
118.70
121.38
119.82
120.74
119.12
121.04
117.98
121.36
120.01
119.13
120.60
121.40
120.56
119.74
118.90
118.68
/
/C3
120.46
120.79
118.90
120.76
120.68
120.66
119.42
120.13
119.19
/
/
/C4
/
/
/C5
/
/
/C6
Á/
Á/
/
/
N13
N13
H14
H14
H14
120.289
120.289
119.839
Á/
Á/
/
0.20
0.20
0.20
/
/
/
121.18
119.57
119.09
118.97
/
/
/
Á/
Á/
Á/
Á/
/
/
/
/
120.40
120.3
Á/
Á/
/
/
H14
119.94
120.02
119.929
/
0.08
119.42
119.69
Á/
Á/
121.31
121.12

Table 2 (Continued)
Geometrical
parametersa
Aniline
o-dpmoa
m-dpmoa
p-dpmoa
HF6-31G*
[11]
B3LYP6-31G* Exp. [11]
(this work)
HF6-31G*
(this work)
B3LYP6-31G* HF6-31G*
(this work)
B3LYP6-31G* HF6-31G*
(this work)
B3LYP6-31G*
(this work)
(this work)
(this work)
C3ꢁ
C5ꢁ
C4ꢁ
C6ꢁ
C1ꢁ
C5ꢁ
C1ꢁ
C1ꢁ
H26ꢁ
CꢁCꢁ
CꢁCꢁ
Cꢁ
/
C4ꢁ
C4ꢁ
C5ꢁ
C5ꢁ
C6ꢁ
C6ꢁ
N13ꢁ
N13ꢁ
/
H15
H15
H16
H16
H17
H1
120.61
120.62
119.96
119.18
120.53
120.57
120.07
119.16
119.58
120.12
114.56
114.58
111.01
120.549
Á/
Á/
Á/
Á/
Á/
/
0.08
119.55
120.76
120.44
119.55
118.97
119.95
113.45
113.51
110.98
114.96
124.38
119.77
29.04
119.54
120.73
120.37
119.48
118.77
119.38
121.96
119.28
119.16
120.07
120.46
115.00
114.67
111.23
115.64
123.50
120.47
27.60
119.29
122.01
119.34
119.28
119.80
Á
Á/
/
Á
Á/
/
/
/
/
/
118.82
120.59
119.63
117.45
113.68
113.69
109.95
116.07
124.79
119.64
30.74
118.81
120.72
119.57
/
/
/
/
Á/
/
/
120.03
114.23
114.23
110.63
Á/
Á/
Á/
/
/H26
115.94
115.94
114.06
113.57
111.74
114.36
124.76
118.46
27.10
114.75
115.12
111.36
115.47
123.59
118.97
26.80
114.07
114.04
110.39
115.94
124.72
118.27
28.45
/
/H27
/
N13ꢁ
O7
O7
/H27
113.1092
/
/
/
Á/
Á/
Á/
26.97
Á/
Á/
Á/
26.44
Á/
Á/
Á/
/
/
/
O7ꢁ
/
C8
g
37.4/46
Relative energy
(kJ molꢂ1
9.04
4.39
0.0
0.0
11.30
7.61
)
a
Atom numbering is given in Fig. 1.

N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á
/
192
175
contrast to HF/6-31G*, the DFT methods over-
estimate the C1C6 and NH bonds and the average
pair is localized over the nitrogen atom [18].
Thus, it is expected that the nitrogen basicity of
o-, m- and p-dpmoa isomers are higher then that
of aniline. The calculated positive values of the
relative PA for the dpmoa isomers in gas-phase (at
HF/6-31G*) and in aqueous- and AN solution (at
STO-3G) confirmed the suggestion made above
(Table 3). A survey of the results in Table 3 shows
that the relative nitrogen PA of dpmoa isomers
increased in the sequence (1) in gas-phase: p-
˚
0.008 and 0.012 A, respectively. Both
errors are Â
/
methods (HF and DFT) and experiment give the
same relationships between CarꢁCar and Carꢁ
bond lengths in aniline: C1ꢁC2 and C1ꢁC6 bond
lengths (Table 2) are larger than the other Cꢁ
bond distances; the CꢁN is shorter than the Cꢁ
/
/N
/
/
/C
/
/C
bond distances; the net atomic charges are nega-
tive for the carbon atoms, except for C2, which has
a positive charge [10,11]. Since the B3LYP/6-31G*
method reproduced reliably the structural data for
aniline we used it further to study the aniline
derivatives, o-, m- and p-dpmoa. Both HF and
DFT levels with 6-31G* basis set predicted the
pyramidal conformation around the amino-nitro-
gen atom in o-, m-, p-dpmoa as it was experimen-
tally established for aniline [11]. The obtained
angle values, ‘g’ (between NH2 plane and ring
dpmoaB
solution: p-dpmoaB
AN: m-dpmoaBp-dpmoaB
/
m-dpmoaB
m-dpmoaB
o-dpmoa. The calcu-
/
o-dpmoa; (2) in aqueous
/
/o-dpmoa; (3) in
/
/
lations showed the highest nitrogen basicity for o-
dpmoa as compared to that obtained for m- and
p-dpmoa in gas- and solution-phases. As seen
from the results in Table 3, there is a variation of
the nitrogen base strength going from gas- to
solution-phase: the nitrogen basicity decreases for
o-dpmoa and increases for m- and p-dpmoa. As
noted previously, strong polarizability effects in
solution probably lead to different basicities in
gas-phase and solution [19].
plane) in o-, m- and p-dpmoa (26.8Á30.78) are in
/
agreement with the reported in the literature value
for this angle in aniline (Table 2). The calculations
showed that the Cꢁ
and shorter for m-dpmoa, compared with that one
for o-dpmoa and aniline. The CarꢁO bond length
/
N bond is longer for p-dpmoa
/
for m-dpmoa is shorter than that for p- and o-
dpmoa (Table 2). The net atomic charges for the
carbon atoms are negative, except for C1 and C2 in
o-dpmoa, C1 and C3 in m-dpmoa and C1 and C4 in
p-dpmoa, which have positive charges, Fig. 1. The
relative energies for o-, m- and p-dpmoa at HF/6-
31G* and DFT/6-31G* levels are reported in
Table 2. Both methods suggested the lowest energy
for m-dpmoa, followed by o- and p-dpmoa. The
resonance and inductive effects, provoked by the
p-donor substituent, (OCH2P(O)(CH3)2), at o-, m-
or p-position in aniline, are thought to be respon-
4.1.3. Vibrational assignment of the free ligands
The calculated frequencies, IR relative intensi-
ties, Raman activities and experimental IR and
Raman data for o-, m- and p-dpmoa are given in
Tables 4Á
/
6 and Figs. 2Á4, respectively. The
/
calculated frequencies were scaled with two factors
and the RMS deviation is 1.27% for o-dpmoa,
1.45% for m-dpmoa and 1.45% for p-dpmoa. The
vibration modes have been analyzed by means of
the displacement vectors for all the normal modes
determined at Hartree-Fock level with 6-31G*
basis set. The assignment was assisted by literature
data about their positions in related compounds
[2,3,11,20].
First, detailed assignment of the NH2 stretching
and bending vibrational modes will be presented.
It is important to determine the positions of these
modes in o-, m- and p-dpmoa, since they are
expected to shift in the complexes studied and to
confirm the coordination of the ligands through
the amino-nitrogen.
sible for the variable Carꢁ
/
Car bond lengths in o-,
m- and p-dpmoa (Table 2).
4.1.2. Nitrogen PA of o-, m- and p-dpmoa in gas-
and solution- (aqueous and AN) phases
The total electronic energy and nitrogen PA
(basicity) for o-, m- and p-dpmoa (relative to
aniline) in gas- and solution phase (aqueous and
AN) are given in Table 3. Since the p-donor
substituent (ꢁ
/
OCH2P(O)(CH3)2) decreases the
pp(N)Ápp(Car) electron conjugation, the p-lone
/

176
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
4.1.4. NH2 stretching (3460Á
Two bands due to the NH stretching modes in
anilines are expected to appear in the 3509Á3460
mꢂ1 and 3416Á3382 cmꢂ1 regions [20]. The
/
3290 cmꢂ1
)
/
/
observed negative shift of the NH stretching
modes for the compounds studied could be
explained by the electron-donating properties of
the ring substituent, O-CH2-P(O)-(CH3)2 (Tables
4Á
charge density (in comparison with aniline) the ‘s’
H bonds in the studied isomers
/
6). Due to the increased p-electron nitrogen
character of the Nꢁ
/
decreases and they become weaker [20,21].
On the basis of ab initio (HF/6-31G*) calcula-
tions we have studied the effect of the substituent
position upon the p-electron charge density of the
amino-nitrogen and respectively upon the posi-
tions of the NH vibrations in o-, m- and p-dpmoa.
The calculated net population of nitrogen pz basis
function (0.69306 for p-dpmoa, 0.65243 for m-
dpmoa and 0.62234 for o-dpmoa) showed that the
p-electron density of the nitrogen decreases in the
order: p-dpmoaꢀ
/
m-dpmoaꢀo-dpmoa. The low-
/
est p-electron charge density of the nitrogen atom
(the strongest s-character of the NH bond) in o-
dpmoa is expected to produce the highest asym-
metric NH stretching frequency as compared to p-
and m-dpmoa. This correlation was observed in
the vibrational spectra of o-, m- and p-dpmoa.
The highest asymmetric NH frequency was ob-
served for o-dpmoa and the experimental fre-
quency separation of the asymmetric and
symmetric NH bands is highest for o-dpmoa,
Doꢀ
/
167 cmꢂ1, followed by p-dpmoa, Dpꢀ
/85
cmꢂ1, and m-dpmoa, Dmꢀ
/
67 cmꢂ1
.
The o-, m- and p-dpmoa showed in addition a
third band in the NH region at relatively lower
frequencies, 3179, 3224, 3229 cmꢂ1, respectively.
These bands could originate from NH absorption
of the NH2 group involved in intermolecular
hydrogen bonds of the type NH2. . .NH2 or
NH2. . .O(P). Interactions of the second type
probably occur in p-dpmoa since the position of
Pꢀ
cmꢂ1. In o- and m- isomers the positions of the
Pꢀ
O absorption (1172, 1164 cmꢂ1) are in agree-
ment with the positions of a free (uncoordinated)
PꢀO groups [2] and therefore the observed third
/O band was found at lower frequency, 1148
/
/

Table 4
Experimental (IR and Raman) and calculated frequencies of o-dpmoa, Pd(o-dpmoa)2Cl2 and Pt(o-dpmoa)2Cl2, (n, cmꢂ1
)
o-dpmoa
Pd(o-dpmoa)2Cl2
Pt(o-dpmoa)2Cl2
Approximate
description
Experimental
IR
Calculated (HF/6-31G*)
Freqa IR intensity
IR
Raman
IR
Raman*
Raman
Raman activity
(A4 AMUꢂ1
)
(km molꢂ1
)
3460 m
3293 m
3179 w
3068 w
3057 w
Á
Á/
Á/
Á/
/
3468
3377
20.6
15.2
57.6
120.8
3295 s
3198 w
Á
Á/
Á/
/
3278 s
3194 w
3295 w
3173 w
NH2 str. (nas NH2)
NH2 str. (ns NH2)
H-bonded (N)H. . .O(P)
Á/
3028
3013
Á/
9.7
36.2
Á/
136.5
129.9
Á/
Á/
Á/
Á/
Á/
Á/
Á/
3100 w
3086 m
3116 w
3079 w,
3073 w
3027 w
3016 w
2979 w
2958 w
2922 m
2911 w
2890 w
2874 w
2866 w
2855 w
1603 w
1594 m
1573 w
1503 m
1464 m
1437 w
1427 w
Car
ꢁ
/
H-str. (nCar
ꢁ
/
H)
Á/
Car
Car
Car
ꢁ
/
H-str. (nCar
H-str. (nCar
H-str. (nCar
ꢁ
/
H)
H)
H)
3034 w, sh
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
2998
2982
2946
2942
2934
2932
2905
2866
2864
2856
1634
1605
1598
1501
1462
1449
1436
1428
1423
1420
1346
1331
1327
11.2
12.2
14.3
3.6
86.3
66.8
89.2
21.8
139.8
39.5
40.2
234.0
8.8
Á/
3051 vw
2996 w
2982 w
3028 w
2991 s
2978 s
ꢁ
/
ꢁ
/
Á/
2992 s
2976 s
ꢁ
/
ꢁ
/
2960 vw
CH3 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH2 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH2 str. (nCH)
Á/
Á/
Á/
Á/
2919 w
10.5
3.5
2915 m
2919 m
2915 w
2895 w
2914 m
Á/
Á/
Á/
2903 sh, w
18.5
2.1
2892 m, sh
2892 m, sh
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
3.1
2852 w
1622 m
1600 w
1588 w
1509 s
17.5
92.5
15.9
7.5
52.4
22.2
8.8
2834 w
1605 m
1594 m
1573 vw
1500 s
2836 w
1603 m
1599 s
2833 w
1609 m
1603 m
1577 w
1500 s
1623 m
1602 m
1591 m
1513 m
1461 w
1433 w
NH2 scissor (dsNH2)
Car
Car
Car
ꢁ
/
Car str. (nCar
Car str. (nCar
Car str. (nCar
ꢁ
/
Car)
Car)
Car)
23.5
2.6
Á/
ꢁ
/
ꢁ
/
181.5
33.4
14.1
16.2
4.8
1501 m
1463 w
1432 w
ꢁ
/
ꢁ
/
1458 m
1438 m
6.8
2.0
1461 m
1438 m
1461 m
1437 m
d(HCH) (CH2)
Car Car str. (nCar Car)
ꢁ
/
ꢁ
/
Á/
Á/
2.6
Á/
Á/
Á/
d(HCH) (CH3)
d(HCH) (CH3)
d(HCH) (CH3)
d(HCH) (CH3)
d(HCH) (CH2)
d(HCH) (CH3)
d(HCH) (CH3)
1417 w, sh
1422 w
26.7
29.6
3.0
1418 w
1421 vw
1417 w
Á/
Á/
Á/
2.0
1.5
Á/
Á/
Á/
1410 w
1357 w
1344 w
1338 w
1405 w
1404 w
1410 w
1410 w
1357 vw
1339 w
1321 m
1405 w
1364 w
1346 w
1322 w
Á/
29.6
8.4
2.3
0.4
Á/
Á/
1346 m
1337 w
1321 m
1342 m
1323 w
1321 w
1290 m
Á/
31.2
0.5
1298 m
1290 w
1308
35.4
6.5
1298 m
1291 s, d
1261 sh
1248 s
1298 m
1291 s, d
1254 sh
1247 m
1302 w
1293 w
Car
ꢁ
/
Car str. (nCarꢁCar)
/
1285 m
1230 m
1277 w
1231 w
1271
1226
163.0
46.9
13.2
2.2
Á/
Á/
CH i.p. bend (dCH)ꢁ
/
nCarꢁO
/
1246 vs
1245 m
nCar
ꢁN
/

Table 4 (Continued)
o-dpmoa
Pd(o-dpmoa)2Cl2
Pt(o-dpmoa)2Cl2
Approximate
description
Experimental
Calculated (HF/6-31G*)
Freqa IR intensity
Raman activity
IR
Raman
IR
Raman*
IR
Raman
(km molꢂ1
)
(A4 AMUꢂ1
)
1207 m
1209 w
1189 w
1168 m
1161 m
1147 vw
1080 m
1050 m
1030 m
1206
1186
1176
1133
1100
1060
1034
1016
972
11.0
30.3
363.8
3.6
7.4
1.9
4.3
8.2
6.4
8.0
1.3
13.4
0.3
1.3
1.6
2.2
3.8
2.0
6.3
1.1
21.0
0.9
0.7
13.3
1.5
6.7
5.5
17.9
3.1
1205 m
1215 vw
1180 m
1165 m
1150 m
1214 m
1185 w, sh
1160 s
1215 w
1187 w
1167 m
1158 m
1146 m
1106 w
1053 m
1032 w
981 w
d(OCH)
CH i.p. bend (dCH)
PO str. (nPO)
Á/
Á/
1172 s
1165 s
1154 m
1129 sh
1081 w
1048 w
1029 w
1157 s
Á/
CH i.p. bend (dCH)
CH i.p. bend (dCH)
NH2 rock (dasNH2)
ring breathing
ring i.p. def. (dr)
CH o.p. bend (gCH)
d(OCH)
82.5
20.4
18.5
10.2
0.1
1123 m
1100 m
1050 m
1032 m
Á/
1129 sh
1104 m
1051 m
1032 m
1114 s
1053 w
1035 w
995 w
Á/
Á/
Á/
Á/
Á/
942 m
930 m, sh
941
939
56.0
72.2
29.5
56.9
4.2
941 s
926 w, sh
Á/
942 s
926 sh, m
943 w
920 w
921 w
929 w
913 w
891 w
854 w
837 s
d(PCH)
CH o.p. bend (gCH)
d(PCH)
Á/
Á/
925
910
Á/
Á/
Á/
888 m
852 w
848 w
826 w
886 w
906 m
857 m
841 w
820 w
905 m
857 m
843 w
816 w
909 w
850 m
844 m
818 m
801 w
780 w
764 m
748 w
724 w
682 w
643 w
620 w
599 w
585 w, d
Á/
856
853
CH o.p. bend (gCH)
d(PCH)
846 w
826 w
800 w
781 m
752 m
742 w
731
26.4
20.1
11.8
8.6
822
817 m
ring i.p. def. (dr)
Á/
799
780
Á/
Á/
Á/
n (OC)ꢁ
d(PCH)
CH o.p. bend (gCH)
d(COC)ꢁn(OC)
ring o.p.def (xr)
n(CP)ꢁ d(PCH)
NH2 wag (gsNH2)
n (CP)ꢁ d(PCH)
/d(OCH)
779 w
760 s
748 m
784 w
757 s
747 s
784 w
765 m
755 m
722 w
684 w
783 w
758 s
747 s
751
740
111.4
41.2
46.5
21.2
213.0
4.1
/
743 m, sh
683 w
719
708
722 vw
683 w
722 vw
683 w
649 w
617 w
589 w
683 w
/
632 br, w
591 vw
569 vw
Á/
667
635
Á/
Á/
595 s
595 w
596 w
/
573 w
578
6.2
580 w
573 s
OC i.p. bend
536 vw
538 w
520 w
549
516
12.1
2.4
0.7
1.7
Á
Á/
/
Á
Á/
/
Á
Á/
/
Á
/
ring o.p.def (xr)
Á/
520 w
545 m
508 w
497 w
480 w
435 w
410 w
375 w
366 vw
342 w
d(OCO)ꢁring i.p.def.
/
544 w
512 w
490 w
542 m
500 w
489 m
547 w
514 w
494 w
Mꢁ
/
N
Á/
Á/
Á/
479
Á/
9.9
Á/
4.5
Mꢁ
/
N
ring i.p. def (dr)
493 w
493 w
460 w
397 w
460 w
397 w
382 w
368 w
446
404
380
374
6.8
12.5
28.4
23.7
0.8
2.4
1.8
0.3
433 w
393 w
378 w
368
423 m
435 w
ring o.p.def (xr)
CN i.p. bend
d(CPC)
Á/
Á/
Á/
Á/
Á/
376 vw
362 vw
370 w
d(CPC)
Á/
Á/
Á/
Á/
Á/
356 m
Á/
349 m
MꢁCl
/

Table 4 (Continued)
o-dpmoa
Pd(o-dpmoa)2Cl2
Pt(o-dpmoa)2Cl2
Approximate
description
Experimental
Calculated (HF/6-31G*)
Freqa IR intensity
IR
Raman
IR
Raman*
IR
Raman
Raman activity
(A4 AMUꢂ1
(km molꢂ1
)
)
Á
/
Á
/
Á
/
Á
/
Á
/
339 m
Á
Á/
/
338 m
339 w
330 w
311 w
Mꢁ
CN o.p.bend
d(CPC)ꢁd(CPO)
NH2 twist (gasNH2)
d(CPC)ꢁd(CPO)
d(CPO)
/
Cl
333 w
333 w
297 w
278 ww
264 w
329
287
271
266
240
208
193
184
172
113
82
5.6
4.2
39.1
2.1
3.0
6.1
0.2
5.2
0.5
6.6
4.8
1.0
1.2
2.2
1.0
2.1
0.3
2.3
1.5
0.3
0.8
0.1
0.6
0.3
3.2
4.3
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
295 vw
280 vw
265 vw
253 w
303 w
289 w
274 w
257 w
209 w
209
298 w, sh
293 w
274 w
/
Á/
274 w
265 vw
/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
219 vw
205 vw
179 w
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
CO o.p bend
d(PCH)
d(PCH)
185 w
159 w
168 w
d(PCH)
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
40
25
Á/
Á/
Á/
s, strong; m, medium; w, weak; vs, very strong; vw, very weak; br, broad; i.p., in plane; o.p., out of plane; str., stretch; sh, shoulder; d, doublet.
a
Scaling factors for the calculated frequencies: from 3468 to 446 cmꢂ1, 0.89; from 404 to 25 cmꢂ1, 1.00.
* Raman bands of Pt(o-dpmoa)2Cl2 are very weak.

Table 5
Experimental (IR and Raman) and calculated frequencies of m-dpmoa, Pd(m-dpmoa)2Cl2 and Pt(m-dpmoa)2Cl2, (n, cmꢂ1
)
m-dpmoa
Pd(m-dpmoa)2Cl2
Pt(m-dpmoa)2Cl2
Aproximate
description
Experimental
IR
Calculated (HF/6-31G*)
IR
Raman
IR
Raman*
Raman
Freqa
IR intensity
(km molꢂ1
Raman activity
(A4 AMUꢂ1
)
)
3409 m
3342 m
3224 m
3099 w
Á
Á/
Á/
Á/
/
3499
3409
15.5
22.1
63.0
129.9
3261 m
3216 br
3266 m
3243 m
3195 br
3240 w
NH2 str. (nasNH2)
NH2 str. (nsNH2)
Á/
Á/
Á/
3051
3046
9.0
7.8
123.6
57.7
3096 w
3059 w
3023 w
3098 w
3075 m
3058 w
3090 w
3057 w
3028
3090 w
3084 w
3047 w
3041 w
3027 w
3013 w
2985 w
2972 w
2933 w
2914 w
2872 w
2857 w
2826 w
2812 w
1614 w
1607 w
1592 w
1498 w
1481 w
1460 w
Car
Car
ꢁ
/
H str. (nCarH)
H str. (nCarH)
3051 w
3029 w
Á/
ꢁ
/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
3030
3014
2974
2971
2960
2959
2932
2891
2889
2885
1654
1621
1610
1506
1475
1467
1448
1441
1435
1434
1358
1343
1339
1320
1307
1215
1209
1199
30.1
10.8
13.4
1.5
117.7
67.6
91.9
16.8
148.0
35.6
37.8
240.1
3.3
3035 w
2992 w
2985 m
CarH str. (nCarH)
CarH str. (nCarH)
CH3 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH2 str. (nCH)
CH3 str. (nCH)
CH3 str. (nCH)
CH2 str. (nCH)
NH2 scissor (ds NH2)
CarCar str. (nCarCar)
CarCar str. (nCarCar)
CarCar str. (nCarCar)
d(HCH) (CH2)
Á/
Á/
Á/
2981
2986 w
2982 m
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
11.8
3.6
2914 w
2884 w
2852 w
2911 m
2870 w
2852 w
2915 m
2875 m
2919
19.2
1.9
Á/
Á/
2850 w
Á/
Á/
Á/
3.3
Á/
2820 w
2816 sh
1612 s
Á/
Á/
2823 w
1634 m
1608 s
15.2
147.7
237.0
95.5
112.2
45.7
31.6
17.8
5.2
48.2
16.7
29.1
8.5
2815 w
1611 s
1598 m
1623 m
1609 w
1586 w
1494 w
1485 w
1476 w
1423 m
1415 w
1611 s
1600 sh
1597 w
1587 w
1498 w
1480 w
1468 m
1431 w
1420 m
1413 w
1405 w
1316 m
1313 m
1301 w
1587 m
1496 s
Á/
Á/
0.4
6.3
1496 m
1480 sh
1498 m
1487 m
1468 w
1474 w
1467 w
1428 m
1413 m
3.5
1.6
1468 w, sh
1433 m, sh
1420 w
CarCar str. (nCarCar)
d(HCH) (CH3)
d(HCH) (CH3)
1423 w, sh
1420 w
Á/
27.7
30.9
1.8
1423 w
1412 w
1394 w
1325 w
1314 w
1301 w
1280 w
1264 w
1229 vw
1195 w
1180 w
Á/
Á/
1.7
1.9
Á/
Á/
d(HCH) (CH3)
d(HCH) (CH3)
1402 w
1335 m
1404 w
1336 w
1322 w
1300 w
1400 w, sh
1313 m
1409 vw
1312 w
33.5
6.3
2.8
0.8
d(HCH) (CH2)
d(HCH) (CH3)
Á/
Á/
Á/
1304 m
32.6
0.1
0.5
0.6
1292 m
1284 m
1271 m
1223 w
1289 m
1281 m
1271 m
1225 w
d(HCH) (CH3)
CarCar str.(nCarCar)
Á/
Á/
Á/
1294 m
1223 m
1292 w
1222 w
1202 w
1188 w
160.4
10.2
60.4
122.1
13.9
7.6
1268 s
1221 w
1203
nCarNꢁ
/
nCarOꢁnCarCar
/
d(OCH)
Á/
1.3
0.2
1200 w
1180 w, sh
1190 w
1172 w, sh
CH i.p. bend (dCH)
CH i.p. bend (dCH)
1194 m
1181 m

Table 5 (Continued)
m-dpmoa
Pd(m-dpmoa)2Cl2
Pt(m-dpmoa)2Cl2
Aproximate
description
Experimental
Calculated (HF/6-31G*)
IR
Raman
IR
Raman*
IR
Raman
Freqa
IR intensity
(km molꢂ1
Raman activity
(A4 AMUꢂ1
)
)
1164 s
1168 m
1146 w
1121 w
1088 w
1079 w
1012 vw
992 m
922 w
1188
1140
1088
1063
1051
986
970
951
948
946
917
864
860
844
794
788
777
766
754
726
683
676
324.8
32.9
26.5
21.9
16.0
0.7
5.8
5.2
1.4
2.5
5.2
1.0
27.0
1.2
3.3
1.4
3.4
2.4
3.0
2.3
11.8
0.2
1.3
13.7
6.8
0.7
4.3
18.9
1157 s
1168 m
1156 s
1165 w
1153 vw
1144 w
1095 vw
1058 w
PO str.(n PO)
CH i.p. bend (dCH)
CH i.p. bend (dCH)
1157 s, sh
1135 m, sh
1089 w
Á/
Á/
Á/
1137 s
1095 w
1056 m
1131 vs
1097 w
1079 w
1147 s
1095 w
1055 m
d(COC)ꢁd(OCH)
/
1053 w
NH2 rock (das NH2)
CH o.p. bend (gCH)
ring i.p. def (dr)
ring breathing
d(PCH)
Á/
Á/
Á/
Á/
Á/
991 w
938 s
0.8
998 w
945 s
999 s
931 m
997 w
943 s
1001 m
945 vw
928 w
92.0
70.3
37.2
39.1
39.0
2.3
923 sh
904 vw
886 w
911 w
895 w
889 w
923 sh
899 m
880 vw
Á/
927 m, sh
897 m
883 vw
904 m
882 w
870 w
851 w
901 w
888 vw
d(OCH)
d(PCH)
873 w
853 w
880 w
Á/
Á/
Á/
d(PCH)
CH o.p. bend (gCH)
CH o.p. bend (gCH)
Á/
859 m
844 w, sh
819 w
858 m
854 vw
838 m
822 w
830 w
820 w
790 w
779 w
765 m
751 w
739 w
698 w
687 m
88.9
13.3
3.5
Á/
Á/
Á/
Á/
Á/
822 w
804 w
n(CP)ꢁ
/
d(PCH)
787 vw
774 m
760 m
752 m, sh
740 w
Á/
782 w
776 w
773 w
748 w
730 s
784 w
776 w
769 vw
742 w
739 w
702 w
674 w
656 w
635 w
590 w
555 w
502 w
480 w
453 w
435 w
407 w
374 w
d(PCH)
59.0
27.9
26.7
3.5
788 m, sh
778 m
789 w, sh
776 m
CH o.p. bend (gCH)
ring o.p. def (xr)
d(PCH)
Á/
Á/
745
744 m
689 m
ring o.p. def (xr)
ring o.p. def (xr)
d(CPC)
697 m
689 w, sh
139.3
11.9
691 w
676 m
690 m
672 w, sh
668 w, sh
639 w
671 w, sh
666 w, sh
632 vw
588 w
632 w
587 w
630 w
586 w
618
587
218.1
7.9
5.2
1.1
629 m
588 w
548 s
NH2 wag (gsNH2)
CO i.p. bend
589 w
Á/
Á/
Á/
Á/
Á/
550 w
520 w
554 w
526 w
Mꢁ
/
N
N
506 w
Mꢁ
/
520 vw
485 w
460 w
397 w
376 w
357 w
532 m
481 m
446 w
395 w
383 w
345 w
544
499
475
414
382
361
10.4
0.4
4.8
0.5
0.4
1.1
1.8
0.2
Á/
Á/
Á/
ring i.p. def (dr)
d(COC)
471 w
441 w
470 w
438 w
382 w
372 w
473 w
442 w
12.4
32.0
29.3
10.4
ring o.p. def(xr)
CN i.p. bend (bCN)
d(CPO)
Á/
374
Á/
Á/
Á/
Á/
Á/
Á/
d(CPO)
Á
/
Á
/
Á
/
Á
/
Á
/
360 m
340 m
355 m
354 m
330 m
358 w
331 w
309 w
297 w
Mꢁ
Mꢁ
/
Cl
Cl
Á/
/
304 vw
291 vw
Á/
309
283
8.8
18.7
2.4
0.2
Á/
Á/
296 w
289 w
Á/
Á/
d(CPC)
NH2 twist (gasNH2)
294 w

Table 5 (Continued)
m-dpmoa
Pd(m-dpmoa)2Cl2
IR Raman
Pt(m-dpmoa)2Cl2
IR Raman*
Aproximate
description
Experimental
Calculated (HF/6-31G*)
IR
Raman
Freqa
IR intensity
(km molꢂ1
Raman activity
(A4 AMUꢂ1
)
)
277 vw
266 vw
252 vw
242 vw
229 vw
181 vw
170 vw
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
272
259
250
242
196
177
169
117
86
8.9
7.0
2.1
3.5
0.02
0.7
3.0
6.9
5.8
0.8
2.4
2.4
2.5
2.3
0.6
0.1
0.1
1.2
0.6
0.04
2.9
4.6
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
277 w
CN o.p. bend (gCN)
ring o.p. def (xr)
d(CPO)
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
CO o.p. bend
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
39
34
Á/
Á/
s, strong; m, medium; w, weak; vs, very strong; vw, very weak; br, broad; i.p., in plane; o.p., out of plane; sh, shoulder; d, doublet.
a
Scaling factors for the calculated frequencies: from 3467 to 447 cmꢂ1, 0.898; from 722 to 447, 0.946; from 414 to 169 cmꢂ1, 1.00.
* Raman bands of Pt(m-dpmoa)2Cl2 are very weak.

Table 6
Experimental (IR and Raman) and calculated frequencies of p-dpmoa, Pd(p-dpmoa)2Cl2 and Pt(p-dpmoa)2Cl2, (n, cmꢂ1
)
p-dpmoa
Pd(p-dpmoa)2Cl2
Pt(p-dpmoa)2Cl2
Approximate
description
Experimental
IR
Calculated (HF/6-31G*)
Freq.a IR intensity
IR
Raman
IR
Raman*
Raman
Raman activity
(A4 AMUꢂ1
)
(km molꢂ1
)
3428 m
3343 m
3229 sh
3030 w
3020 w
2990 w
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
3438
3353
11.1
14.4
68.3
150.4
3224 m
3185 m
Á
Á/
/
3265 m
3198 m
3220 vw
3175 vw
NH2 str.(nasNH)
NH2 str.(nsNH)
H-bond (N)H..O(P)
CarH str.(nCarH)
3018
3001
2977
2976
2938
2934
2924
2922
2887
2856
2853
2844
1638
1620
1590
10.7
10.8
21.3
23.2
14.5
1.5
84.1
103.8
79.0
79.4
92.8
16.8
149.8
34.3
40.3
233.1
3.3
3125 w
3057 w
2991 w
Á/
3050 w
3047 w
3074 m
3060 m
3036 w
3010 w
2922 m
2910 m
Á/
Á/
Á/
CarHÁstr.(nCarH)
/
3003 w
CarH-str.(nCarH)
CarH-str.(nCarH)
CH3 str.(nCH)
Á/
Á/
Á/
Á/
3026 w
2941 vw
2923 w
2912 m
2960 w
2954 m
Á/
2920 m
2902 w
CH3 str.(nCH)
CH3 str.(nCH)
2921 w
12.3
3.5
2924 m
Á/
Á/
Á/
Á/
Á/
Á/
CH3 str.(nCH)
CH2 str.(nCH)
2886 w
2848 w
22.2
2.1
2884 w
2853 w
2892 w
2898 w
2865 w
Á/
Á/
Á/
Á/
2854 m
CH3 str.(nCH)
CH3 str.(nCH)
Á/
3.3
Á/
Á/
Á/
Á/
2821 w
18.1
48.6
30.8
5.8
58.6
46.0
26.4
3.2
2830 w
2822 vw
CH2 str.(nCH)
1674 m
1637 m
1590 w,sh
1676 w
1633 w
1617 m
1661 br,w
1611 m
1592 sh
1662 br,w
1617 m
1592 sh
Á/
NH2 scissor (dsNH2)
CarCar str.(nCarCar)
CarCar str.(nCarCar)
1614 s
1606 m,sh
1616 m,sh
1604 m
1598 m
1519 w
1513 s
1513 w
1487 w
1444 w
1430 w
1411 w
1401 w
1356 w
1334 w
1321 w
1502
1459
1431
1425
1424
1418
1417
1341
1326
1323
1307
1252
1229
1200
287.5
47.6
17.3
0.9
0.3
6.1
1507 s
1509 m
1494 w,sh
1444 m
1421 w
1507 s
1468 w
1460 w
1437 w
1415 w
CarCar str.(nCarCar)
d(HCH) (CH2)
d(HCH) (CH3)
CarCar str.(nCarCar)
d(HCH) (CH3)
d(HCH) (CH3)
d(HCH) (CH3)
d(HCH) (CH2)
d(HCH) (CH3)
d(HCH) (CH3)
CarCar str.(nCarCar)
Á/
1465 vw
1443 w
1431 w
1411 w,sh
1495 w
1443 w,sh
1431 w
1414 w,sh
1.4
1.4
1478 vw
1434 vw
1419 vw
4.6
1.5
28.9
31.7
1.0
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
1367 vw
1345 vw
1323 w
2.1
1375 vw
1342 vw
27.2
11.3
32.5
1.5
1.9
0.3
1341 vw
1315 w
1323 w
Á/
Á/
1305 m
Á/
0.5
2.1
Á/
1295 w
1279 w
1248 w
1304 m,sh
1293 m
1246 m
1301 m
1273 w
1244 w
1215 w
1209 m
1204 m
1189 m
1294 m,sh
1286 m,sh
1238 m
1295 w
1277 w
1231 w
1222 w
1297 m
1245 m
1230 m
1204 m
161.1
233.5
10.6
21.6
2.5
nCarNꢁnCarO
/
Á/
Á/
CH i.p. bend (dCH)
d(OCH)
1220 m
7.7
1203 m
1200 m,d
1177 m,sh
1210 m
1178 sh
1178 m
1175 m
1180
61.0
5.0
1173 m,sh
CH i.p. bend (dCH)

Table 6 (Continued)
p-dpmoa
Pd(p-dpmoa)2Cl2
Pt(p-dpmoa)2Cl2
Approximate
description
Experimental
Calculated (HF/6-31G*)
Freq.a IR intensity
IR
Raman
IR
Raman*
IR
Raman
1143 m
Raman activity
(A4 AMUꢂ1
(km molꢂ1
)
)
1148 s
1172
247.4
3.8
1162 s
1164 m
1156 m,d
1124 w
1106 m
1160 s
1176 m
PO stretch (nPO)
1137 sh
1085 vw
1123 w
1089 w
1080 w
1033 w
1012 w
999 w
979 w
945 w
989 w
889 w
851 m
832 w
822 w
797 w
765
1154
1067
1062
1040
983
952
939
938
926
907
852
837
824
814
781
778
739
707
701
663
633
626
511
1.3
39.0
19.9
30.4
3.0
6.4
0.4
2.3
2.1
0.1
0.6
0.02
2.0
5.2
4.0
4.3
1.5
40.4
3.5
4.6
0.3
5.2
7.0
2.6
3.1
21.1
6.1
1.1
1126 sh
1105 w
1125 sh
1107 w
Á/
CH i.p. bend (dCH)
CH i.p. bend (dCH)
1105 vw
Á/
Á/
Á/
Á/
Á/
d(COC)ꢁn(CO)
/
1056 m
1011 vw
1048 m
1013 vw
1048 w
1014 w
1004 w
981 w
1034 m
1015 vw
1038 vw
1014 w
983 vw
960 w
NH2 rock (dasNH2)
ring i.p. def (dr)
CH o.p. bend (gCH)
CH o.p. bend (gCH)
d(PCH)
Á/
Á/
0.9
Á/
Á/
Á/
Á/
23.5
103.3
13.8
57.5
39.5
124.0
5.4
938 m
914 w,sh
888 w
941 m
914 w,sh
900 m
852 w
946 m
939 m
927 w,sh
902 m
851 w
930 vw
929 vw
886 vw
854 vw
Á/
Á/
CH o.p. bend (gCH)
d(PCH)
861 w
850 m
d(PCH)
826 m
827 m
824 w
834 m
Á/
CH o.p. bend (gCH)
ring breathing
Á/
Á/
Á/
Á/
828 w
807 vw
797 w
761 w
754 w
742 m
698 w
684 w
668 w
620 w
574 w,br
528 w
4.8
800 w
786 vw
759 m
807 w
807 w
796 vw
754 m
ring o.p. def. (xr)
11.9
0.4
Á/
Á/
d(OCH)ꢁ
/
n(PC)
Á/
755 m
727 w
712 w
683 w
661 w
641 w
558 m
757 vw
731 w
712 w
695 m
d(PCH)
ring i.p. def. (dr)
d(CPC)
731 w
700 w
688 w
642 w
607 vw
581 w
529 vw
16.1
25.9
84.6
320.7
3.2
Á/
Á/
700 vw
678 w
667 w
711 w
Á/
ring o.p. def. (xr)
NH2 wag (gs NH2)
667 w
637 w
583 w
Á/
Á/
642 m
578 m
d(CPC)ꢁd(CPO)
/
0.1
29.7
563 w
ring i.p. def. (dr)
ring o.p. def. (xr)
M-N
Á/
Á/
Á/
Á/
529 w
518 m
532 w
531 m
516 w
520 vw
502
5.8
1.7
Á
/
Á
/
Á
/
Á
/
CN i.p.bend (b CN)
M-N
496 w
465 w
409 w
491 m
460 w
420 w
410 w
390 w
368 w
360 vw
500 w
460 w
413 w
506 w
462 w
418 m
404 m
384 w
370 w
360 vw
461 w
420 vw
396 w
382 w
366 vw
348 w
450 w
419 w
442
412
397
395
372
359
2.7
0.9
0.7
0.2
2.7
1.4
2.2
0.2
CO i.p.bend
ring o.p. def. (xr)
CO o.p.bend
CN o.p.bend
393 vw
381 vw
368 vw
350 vw
29.0
14.5
20.5
15.5
Á/
Á/
Á/
Á/
Á/
388 m
373 w
d(CPC)ꢁ
/
d(CPO)
Á/
d(CPC)ꢁd(CPO)ꢁd(COC)
/
/

Table 6 (Continued)
p-dpmoa
Pd(p-dpmoa)2Cl2
Pt(p-dpmoa)2Cl2
Approximate
description
Experimental
Calculated (HF/6-31G*)
Freq.a IR intensity
IR
Raman
IR
Raman*
IR
Raman
Raman activity
(A4 AMUꢂ1
(km molꢂ1
)
)
Á
Á/
/
Á
Á/
/
Á
Á/
/
Á
Á/
/
Á
Á/
/
368 m
339 m
298 w
372 w
331 w
291 w
287 w,d
354 m
330 m
350 w
331 w
M-Cl
M-Cl
d(CPO)
305 w
298 w
296
8.4
2.3
Á/
Á/
260 vw
239 vw
210 vw
194 vw
169 vw
269 w
261
242
192
187
180
176
169
106
82
3.2
3.6
0.1
29.0
1.7
2.7
0.7
7.0
4.8
1.7
0.7
0.3
2.9
0.1
0.8
0.1
0.9
0.1
0.2
0.1
4.9
4.4
268 w
221 w
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
Á
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
d(PCH)ꢁ
d(CPO)ꢁd(CPC)
d(PCH)
/
d(CPC)
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
/
Á/
185
154
NH2(gasNH2)
d(PCH)
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
Á/
42
26
s-strong, m-medium, w-weak, vs-very strong, vw-very weak, br-broad, i.p.-in plane, o.p.-out of plane, str.-stretch, d-doublet.
a
Scaling factors for the calculated frequencies: from 3450 to 414 cmꢂ1, 0.887, from 404 to 26 cmꢂ1, 0.982.
* Raman bands of Pt(p-dpmoa)2Cl2 are very weak.

186
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
low frequency band was explained by NH2. . .NH2
intermolecular interactions.
NH2 wagging mode) and asymmetric mode,
gasNH2 (related to the NH2 twisting or torsional
mode), respectively (Tables 4Á
/
6, Figs. 2Á4).
/
4.1.5. NH2 ‘in-plane’ bending
The medium intensity bands at 1622 (o-dpmoa),
1634 (m-dpmoa), 1674 cmꢂ1 (p-dpmoa) are as-
signed to the symmetric mode dsNH2 designated
as scissoring vibration and the bands at 1081 (o-
dpmoa), 1053 (m-dpmoa) and 1056 cmꢂ1 (p-
dpmoa) to the asymmetric mode dasNH2 denoted
4.1.7. CN mode
The bands at 1230, 1294 and 1286 cmꢂ1 in the
IR spectra of o-, m- and p-dpmoa, respectively,
were assigned to Carꢁ/N stretching mode on the
basis of calculated displacement vectors, and in
agreement with the CN mode in aniline (1279
cmꢂ1) [11].
as rocking vibration (Tables 4Á6). The dsNH2
/
mode for p-dpmoa appears at higher frequencies
(as compare to o- and m-dpmoa) and it suggested
once again that the NH2 group is probably
involved in intermolecular (N)H. . .O(P) hydrogen
bond.
4.1.8. Phenyl-ring modes
The phenyl-ring modes are affected by the
position
(CH3)2P(O)CH2Oꢁ
of
the
p-donor
) in o-, m- and p-dpmoa.
substituent
4.1.6. NH2 ‘out-of-plane’ bending (torsions)
/
In the 670Á
/
630 cmꢂ1 and 295Á
frequency regions appeared vibrations due to
/
190 cmꢂ1
Thus, they are characteristic and could be used
to characterize the compound with their vibra-
tional spectra.
symmetric mode, gsNH2 (corresponding to the
Fig. 2. FTIR spectra of o-dpmoa, Pt(o-dpmoa)2Cl2 and Pd(o-dpmoa)2Cl2 in the 2000Á
400 cmꢂ1 frequency range.
/

N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á
/
192
187
Fig. 3. FTIR spectra of m-dpmoa, Pt(m-dpmoa)2Cl2 and Pd(m-dpmoa)2Cl2 in the 2000Á
400 cmꢂ1 frequency range.
/
4.1.9. Carꢁ
2990 cmꢂ1
In substituted benzenes a characteristic triplet
due to the CarꢁH stretching vibrations is expected
to appear in this frequency range [20]. In agree-
ment with literature data our calculations con-
firmed the assignment of the three weak
absorptions to these stretching vibrations (Tables
/
H stretching modes, nCarꢁ
/
H (3100Á
/
are strong to medium for meta and weak for ortho
and para. In the Raman spectra these bands are
weak for meta but with higher intensity for o- and
)
/
p-dpmoa (Tables 4Á
/
6, Figs. 2Á4). A correlation
/
between the positions of the ring substituents, their
electronic properties and the band IR intensities of
the first and second ring stretching modes was
observed in the studied spectra. When the electron-
4Á/6).
donor
substituents,
ꢁ
/
NH2
and
ꢁ
/
Oꢁ
/
CH2P(O)(CH3)2, are in para-position, there is a
very small dipole-moment change during the ring-
stretching vibrations and the resulting bands are
very weak. The intensity in this case is related to
the algebraic difference between the electronic
effects of the substituents as measured by their
Hammett s values [20]. As expected for para-
substitution, the ring stretching vibrations ap-
peared as very weak bands (Fig. 4 and Table 6).
When the donor substituents are in meta-posi-
tion, they reinforce each other and increase the
dipole-moment change so that the intensity is
4.1.10. Ring stretching modes, nCarꢁ
/
Car (1640Á
/
1290 cmꢂ1
Due to the ring substitutions, the degenerate
)
skeletal ring vibrations of benzene, which appear
in the 1650Á
1450 cmꢂ1 frequency range, are split
/
to four. The intensity variations for the first and
second bands and the position of the third one are
very informative and helped to distinguish among
the ortho, meta and para isomers. The first and
second bands were observed, as usual, in the
1650Á
1585 cmꢂ1 frequency range. The IR bands
/

188
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
related to the algebraic sum of their effects. In
agreement with this correlation, clearly separated
and high intensity bands were observed for the
ring-stretching modes of the m-dpmoa (Table 5,
Fig. 3).
As stated in the literature the ortho-substitution
leads to more complex correlations and the trends
are often intermediate between those observed for
para- and meta-ligands [20]. In o-dpmoa IR
spectrum the bands are well separated but with
low intensities (Table 4, Fig. 2).
cmꢂ1 for para di-substituted benzenes [20]. The
bands are strong in all the tree IR spectra.
The intensity of the fourth ring-stretching band
(observed at 1431 cmꢂ1 for para and at 1467
cmꢂ1 for meta) is relatively low for para, as it was
found for aniline and it is of medium intensity for
o-dpmoa (observed at 1438 cmꢂ1).
On the basis of ab initio calculations the peaks
at 1298 cmꢂ1, 1292 cmꢂ1 (calculated) and 1294
cmꢂ1 in IR spectra of o-, m-, p-dpmoa, respec-
tively, were assigned also to the Carꢁ/Car stretching
The position of the third band due to the ring-
stretching vibrations is directly related to the
position of the substituent, ortho, meta or para.
The bands at 1509 cmꢂ1 for o-dpmoa, at 1496
cmꢂ1 for m-dpmoa, and at 1513 cmꢂ1 for p-
dpmoa, are in full agreement with the suggested
vibrations. This ring-stretching mode shows an
uncharacteristic band with variable intensity
[11,22].
The CH in-plane bending modes, dCH, were
observed at their usual positions for o-, m-, p-
substituted aniline in the 1285Á
1085 cmꢂ1 fre-
quency range. The CH out-of-plane bending
/
regions in the literature: 1510Á
/
1460 cmꢂ1 for
1480
1470 cmꢂ1 for meta and 1520Á
/
modes are more informative to distinguish be-
ortho, 1495Á
/
Fig. 4. FTIR spectra of p-dpmoa, Pt(p-dpmoa)2Cl2 and Pd(p-dpmoa)2Cl2 in the 2000Á
400 cmꢂ1 frequency range.
/

N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á
/
192
189
tween o-, m- and p-isomers and they will be
discussed in details below. The strong band at
760 cmꢂ1 (752 cmꢂ1 in Raman) was assigned to
the CH out-of-plane bending vibration for o-
dpmoa, where four adjacent ring hydrogen atoms
are present. This assignment on the basis of ab
initio calculations is in full agreement with the
quency (1148 cmꢂ1). As stated before, the low-
ering of the PꢀO frequency in p-dpmoa could be
explain by intermolecular hydrogen bonds.
/
4.2. Characterization of the complexes
The isolated complexes, M(o-dpmoa)2Cl2,
expected position (770Á
/
735 cmꢂ1) and intensity of
M(m-dpmoa)2Cl2 and M(p-dpmoa)2Cl2 (MꢀPt,
/
this band in 1,2-substituted benzenes (ortho-sub-
stitution) [20]. The bands at 972 (calculated), 925
(calculated) and 852 w cmꢂ1 were assigned also to
these modes (Table 4). In m-dpmoa (1,3-substi-
tuted benzene) two bands with medium intensity
Pd), with the analytical data, melting point and
molar electric conductivity values are listed in
Table 1. The complexes were obtained as micro-
crystalline colored powders, partially soluble in
water, methanol and DMF and insoluble in Et2O,
THF, CHCl3. The LM values for the complexes
are in agreement with values for nonelectrolytes
and indicate a non-ionic structure of the com-
plexes. The analytical data and molar electrical
conductivity values are in accord with the sug-
gested general formula, ML2Cl2 [26]. Unfortu-
nately, it was not possible to obtain crystals of
good quality for X-ray structure determination.
are expected in the 840Á
750 cmꢂ1 region. They
/
are observed at 838 and 774 cmꢂ1. The CH
absorption of the isolated ring hydrogen atom
was observed at 853 w cmꢂ1 in full agreement
with the expected position (900Á
850 cmꢂ1) in 1,3
/
substituted benzenes. In the IR spectrum of p-
dpmoa, where two free adjacent hydrogen atoms
are present in the ring, the absorption due to the
CH out-of-plane mode is shifted to higher fre-
quencies in comparison with the position of this
absorption in o- and m-dpmoa spectra. The strong
band at 826 cmꢂ1 in the p-dpmoa IR spectrum is
4.2.1. Vibrational study of M(o-dpmoa)2Cl2,
M(m-dpmoa)2Cl2 and M(p-dpmoa)2Cl2
complexes, MꢀPt, Pd
/
in agreement with the expected position (860Á
/
800
cmꢂ1) and intensity of the CH absorption in 1,4-
substituted benzenes (para-position) [20].
The IR and Raman spectra of Pt(II) and Pd(II)
complexes with o-, m-, p-dpmoa ligands are listed
in Tables 4Á6 and they are shown in Fig. 2, Fig. 3
/
and Fig. 4. The experimental results for aniline
indicate that NH2 stretching, NH2 bending and
4.1.11. Ring in-plane deformations, dr (1030Á520
/
cmꢂ1) and ring out-of-plane deformations gr (760Á
/
Cꢁ
/
N(NH2) stretching vibrations shift to lower
460 cmꢂ1
)
wavenumbers upon complex formation, whereas
the NH2 rocking and wagging vibrations shift to
The strong band, observed in the 1010Á
/
990
cmꢂ1 Raman region is a very characteristic one
for 1,3-ring substitution [20]. The weak IR band at
991 cmꢂ1 (medium in Raman at 992 cmꢂ1) was
assigned on the basis of our ab initio calculations
to i.p. ring deformation and it is in agreement with
literature data [11].
higher wavenumbers [27Á30]. Previous studies
/
have shown the presence of two opposite effects
that arose upon coordination of the ligands to a
metal ion: (i) the coupling of the internal vibra-
tional modes of the ligand with Mꢁ
/N bond
vibrations, which caused the upward shift; (ii) the
effect of hybridization changes as a result of the
coordination through nitrogen lone pairs, which
caused a decrease in the NH2 stretching and
bending force constants [22]. Recently, both effects
on the aniline modes were investigated and the
results could be used to explain the assignment of
NH2 modes in our complexes [22].
4.1.12. Pꢀ/O stretching
The calculated high IR intensities and displace-
ment vectors confirmed the assignment of the
strong peaks at 1172, 1164 and 1148 cmꢂ1 to the
Pꢀ
full agreement with the literature data about the
nPꢀO position [23Á25]. Only the PꢀO stretching
mode of p-dpmoa was observed at lower fre-
/O stretching mode. These assignments are in
/
/
/
In the NH stretching region two bands due to
asymmetric and symmetric NH stretching modes,

190
N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á192
/
were observed for Pd(II) and Pt(II) complexes.
These bands are shifted to lower frequencies (Dꢀ
204Á
98 cmꢂ1) in comparison with their position in
the free ligands.
Pt(II) and Pd(II) complexes through the amino-
nitrogen. At the same time the PꢀO spectral
behavior showed that the PꢀO group is free and
does not coordinate to the metal ions.
As seen from Figs. 2Á4 the vibrational features
of the ligands in the mid-frequency region are
retained in all the complex spectra. Some of the
ligand bands were observed as doublets and this
finding is in agreement with the presence of two
ligands in the complexes studied, suggested for-
mula, ML2Cl2. The similarity of the observed
spectra showed that the coordination of the
ligands to Pt(II) and Pd(II) is identical.
/
/
/
/
The NH bending or scissors vibrations shift also
to lower frequencies on complex formation and
/
the shift value is between ꢂ
/
13 and ꢂ .
23 cmꢂ1
/
The changes observed in the NH stretching and
bending mode positions confirmed that the co-
ordination in the complexes studied occur through
the nitrogen atom [11,22].
The coordination of the ligands to Pd(II) and
Pt(II) ions was confirmed also by the shift of the
other NH bending modes (rocking, wagging and
twisting). As expected, changes were found in the
In the far-IR region the MÁL stretching fre-
/
quencies are expected to occur and their positions
could supply additional information about the
Carꢁ
/
N stretching positions in the studied com-
plexes. The bands at 1294 cmꢂ1(m-dpmoa) and
1286 cmꢂ1 (p-dpmoa) shifted to lower frequencies
in the m- and p-complexes: 1271 cmꢂ1 for Pd(m-
dpmoa)2Cl2, 1271 cmꢂ1 for Pt(m-dpmoa)2Cl2 and
1245 cmꢂ1 for Pd(p-dpmoa)2Cl2, 1246 cmꢂ1 for
Pt(p-dpmoa)2Cl2. Such a negative shift was not
observed for the o-dpmoa complexes.
complex structure. As seen from Tables 4Á
/6 two
bands for MÁN and two bands for MÁCl stretch-
/
/
ing modes were observed and this finding is in
agreement with cis-coordination of the studied
ligands [31,32]. In general, Pt(o-dpmoa)2Cl2,
Pt(m-dpmoa)2Cl2 and Pt(p-dpmoa)2Cl2 showed
very similar vibrational spectra as compared to
those of Pd(o-dpmoa)2Cl2, Pd(m-dpmoa)2Cl2 and
Pd(p-dpmoa)2Cl2, although the last three com-
plexes were obtained using different strategy.
Thus, on the basis of similarity observed in the
IR and Raman spectra we may suggest that both
metals Pt(II) and Pd(II) formed complexes with
the same general formula ML2Cl2 and identical
metal environment.
The vibrational investigation of the ligands and
complexes studied indicated that NH2 stretching
and NH2 bending (scissor) modes are affected only
by the hybridization changes, while the Cꢁ
/N
stretching, NH2 rocking, NH2 wagging and NH2
twisting modes are affected by two opposite
effects: hybridization changes and coupling with
Pd(Pt)ÁN vibrations.
/
In o-dpmoa and m-dpmoa IR spectra the Pꢀ
/
O
absorption appeared at 1172 cmꢂ1 (1168 cmꢂ1
Raman) and 1164 cmꢂ1 (1168 cmꢂ1 Raman),
respectively. These peaks were not significantly
changed in the Pt(II) and Pd(II) complex spectra.
5. Conclusions
In p-dpmoa IR spectrum, the Pꢀ
observed at 1148 cmꢂ1. This position is signifi-
cantly lower as compared to the PꢀO positions in
/
O absorption was
Both HF and DFT levels of the theory predicted
pyramidal conformation around the amino-nitro-
gen atom in o-, m- and p-dpmoa. Ab initio
calculations have shown that due to the presence
of p-donor substituents, the o-, m- and p-dpmoa
have stronger nitrogen PA as compared to aniline.
It was found that the relative nitrogen basicities of
dpmoa isomers increased in the sequence (1) in
/
m- and o-dpmoa. Probably the lowering is due to
the intermolecular (N)H. . .O(P) hydrogen bond in
p-dpmoa. In the Pd and Pt complexes with p-
dpmoa this band shows the usual position for
uncoordinated Pꢀ
dpmoa)2Cl2 and 1160 cmꢂ1 for Pt(p-dpmoa)2Cl2
[2Á4].
/
O: 1162 cmꢂ1 for Pd(p-
gas-phase: m-dpmoaB
HF/6-31G*); (2) in aqueous solution: p-dpmoaB
m-dpmoaBo-dpmoa; (3) in AN: m-dpmoaBp-
/
p-dpmoaB/o-dpmoa (at
/
/
The observed shift of all NH2 vibrational modes
confirmed the coordination of the ligands in the
/
/

N. Trendafilova et al. / Spectrochimica Acta Part A 59 (2003) 169Á
/
192
191
[10] M.A. Mora, L. Galicia, H. Vazquez, Int. J. Quant. Chem.
78 (2000) 99.
dpmoaBo-dpmoa. The spectral shifts of NH2
/
stretching and bending modes in Pd(II) and Pt(II)
complexes with o-, m-, p-dpmoa confirmed the
coordination of the ligands through the NH2
[11] M. Castella-Ventura, E. Kassab, Spectrochim. Acta 50A
(1994) 69 (ref. therein).
[12] N. Dodoff, Spassovska, S. Varbanov, Z. Naturforsch. B 44
(1989) 1323.
group. The Pꢀ
complexes studied correspond to a free Pꢀ
and thus coordination of the ligands through the
PꢀO is not expected. The observed doublets for
/
O stretching vibrations in the
[13] F.R. Hartley, The Chemistry of Platinum and Palladium,
Applied Science Publishers, London, 1973, p. 462.
[14] S. Varbanov, E. Russeva, N. Nikolov, Bulg. Chem.
Commun. 26 (1993) 91.
/
O group
/
some ligand modes are in agreement with the
presence of two ligands in the complexes according
to the formula ML2Cl2. The analytical and physi-
cal data confirmed also the suggested complex
formula.
[15] Gaussian 98, Revision A.6, M.J. Frisch, G.W. Trucks,
H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R.
Cheeseman, V.G. Zakrzewski, J.A. Montgomery, Jr.,
R.E. Stratmann, J.C. Burant, S. Dapprich, J.M. Millam,
A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas,
J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci,
C. Pomelli, C. Adamo, S. Clifford, J. Ochterski,
G.A. Petersson, P.Y. Ayala, Q. Cui, K. Morokuma,
D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B.
Foresman, J. Cioslowski, J.V. Ortiz, B.B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.
Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A.
Al-Laham, C.Y. Peng, A. Nanayakkara, C. Gonzalez,
M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen,
M.W. Wong, J.L. Andres, C. Gonzalez, M. Head-Gordon,
E.S. Replogle J.A. Pople, Gaussian, Inc, Pittsburgh PA,
1998.
Acknowledgements
N. Trendafilova is grateful to the Technical
University of Vienna for the financial support
during her stay at the Institute of Technical
Electrochemistry and Solid State Chemistry as
well as for the computational facilities and services
provided. The authors are grateful to Assoc.
Professor Dr D. Stoilova for some IR spectra
measurements, to Doz. Dr Hristoskova for the
conductivity measurements and to Assoc. Profes-
sor Dr E. Russeva for the phosphorus determina-
tions.
[16] (a) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988)
785;
(b) A.D. Becke, Phys. Rev. A 38 (1988) 3098;
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(d) A.D. Becke, J. Chem. Phys. 98 (1993)
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Am. Chem. Soc. 92 (1970) 4796;
(b) W.J. Hehre, L. Radom, P.V.R. Schleyer, J.A. Pople,
Ab initio molecular orbital theory, Wiley, New York,
1986.
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