Palladium(II), platinum(II), ruthenium(II) and mercury(II) complexes of potentially tridentate Schiff base ligands of (E, N, O) type (E = S, Se, Te): Synthesis, crystal structures and applications in Heck and Suzuki coupling reactions

Article abstract of DOI:10.1016/j.ica.2009.02.031

Schiff bases of 2-hydroxybenzophenone (HBP) (C₆H₅)(2-HOC₆H₄)C{double bond, long}N(CH₂)_nEAr (L1/L2: E = S, Ar = Ph, n = 2/3; L3/L4: E = Se, Ar = Ph, n = 2/3; L5/L6: E = Te, Ar = 4-MeOC₆

Full text of DOI:10.1016/j.ica.2009.02.031

Inorganica Chimica Acta 362 (2009) 3208–3218
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Inorganica Chimica Acta
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Palladium(II), platinum(II), ruthenium(II) and mercury(II) complexes of
potentially tridentate Schiff base ligands of (E, N, O) type (E = S, Se, Te):
Synthesis, crystal structures and applications in Heck and Suzuki
coupling reactions
b
Arun Kumar a, Monika Agarwal a, Ajai K. Singh a, , R.J. Butcher
*
a Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
b Department of Chemistry, Howard University, Washington, DC 20059, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Schiff bases of 2-hydroxybenzophenone (HBP) (C6H5)(2-HOC6H4)C@N(CH2)nEAr (L1/L2: E = S, Ar = Ph,
n = 2/3; L3/L4: E = Se, Ar = Ph, n = 2/3; L5/L6: E = Te, Ar = 4-MeOC6H4, n = 2/3) and their complexes
[PdCl(L-H)] (L = L1ꢀL6; 1, 2, 3, 5, 7, 11), [PtCl(L3-H/L5-H)] (4/8), [PtCl2(L4/L6)2] (6/12), [(p-cymene)R-
uCl(L5/L6)]Cl (9/13) and [HgBr2(L5/L6)2] (10/14) have been synthesized and characterized by proton, car-
bon-13, selenium-77 and tellurium-125 NMR, IR and mass spectra. Single crystal structures of L1, 1, 3, 4,
5 and 7 were solved. The Pd–E bond distances (Å): 2.2563(6) (E = S), 2.3575(6)ꢀ2.392(2) (E = Se);
2.5117(5)ꢀ2.5198(5) (E = Te) are near the lower end of the bond length range known for them. The
Pt–Se bond length, 2.3470(8) Å, is also closer to the short values reported so far. The Heck and Suzuki
reaction were carried out using complexes 1, 3, 5 and 7 as catalysts under aerobic condition. The percent-
age yields for trans product in Heck reaction were found upto 85%.
Received 12 September 2008
Received in revised form 14 February 2009
Accepted 20 February 2009
Available online 9 March 2009
Keywords:
Chalogenated Schiff bases
Tridentate ligands
Metal complexes
Structure elucidation
Homogeneous catalysis
2-Hydroxybenzophenone
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
ware of any chalcogenated Schiff base of 2-hydroxybenzophenone
(HBP), which has been studied so far as a ligand. The presence of
A variety of 2-hydroxybenzophenones have been found suitable
precursors for 3-substituted benzofurans [1]. Hydroxylated benzo-
phenone derivatives used as UV stabilizers and in hair and skin
sunscreen composition [2–4], have estrogenic and anti-androgenic
activities [5–7]. Antiplaque oral composition containing a 2-
hydroxybenzophenone has been reported [8]. Schiff bases of 2-
hydroxybenzophenone are continued to be explored as ligands
[9–15] as some of their complexes have interesting features and
properties like chirality and catalytic activity [16]. Schiff bases of
2-hydroxybenzophenone have also been found to have potential
as corrosion inhibitors [17] and catalyst for polymerization [18].
Schiff bases and related compounds continue to be of current inter-
est for catalyst designing. Thiosemicarbazones [19,20] as well as
salicylaldehyde derived chalcogenated Schiff bases [21,22] are
known as efficient ligands for the palladium-catalyzed Heck and
Suzuki reactions under aerobic condition. Recently use of 2-
hydroxyacetphenone derived selenated Schiff bases as ligands in
Heck reaction has been reported by us [23]. However, we are una-
chalcogen atom may tune the properties of their complexes in a
new direction. Therefore first examples of Schiff bases of 2-
hydroxybenzophenone (HBP) containing chalcogen functionalities,
L1–L6 (Scheme 1) are reported here. Their complexes with Pd(II),
Pt(II), (p-cymene)Ru(II) and Hg(II) have been synthesized. The li-
gands and complexes have been characterized using multinuclei
NMR, IR and mass spectral data. The single crystal structures of
palladium(II) complexes of L1, L3, L4 and L5, platinum(II) complex
of L3 and Schiff base L1 have been solved and reported in this pa-
per. The Pd (II) complexes of L1ꢀL5 show potential as homoge-
neous catalysts for Heck and Suzuki (under aerobic condition)
reactions with good yields (upto ꢁ85%). The results of these inves-
tigations are included in the present paper.
2. Results and discussion
2.1. General
The syntheses of ligands L1–L6 made by further standardizing
general procedures [21,23,24,30,34] and their complexes are given
in Scheme 1. The complexes formed with the four metal ions do
not change on varying the metal:ligand ratio during their synthe-
sis. The complexes 6 and 12 may be mixtures of cis–trans isomeric
* Corresponding author. Tel.: +91 11 26591379; fax: +91 11 26581102.
E-mail addresses: arunkaushik@gmail.com (A. Kumar), monikaiitd@gmail.com
(M. Agarwal), ajai57@hotmail.com, aksingh@chemistry.iitd.ac.in (A.K. Singh),
rbutcher99@yahoo.com (R.J. Butcher).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.02.031

A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
3209
17
16
15
14
6
3
13
8
9
E
2
12
11
7
N
4
5
R
R
OH
1
10
E
(CH2)2
H2N
E = S, R = H (L1)
E = Se, R = H (L3)
E = Te, R = OMe(L5)
r.t
Dry EtOH
/
O
17
16
15
13
H2N
OH
2
(CH2)3
R
3
E
1
14
6
5
8
9
R
12
11
7
E
N
4
a
OH
10
E = S, R = H (L2)
E = Se, R = H (L4)
E = Te, R = OMe(L6)
Acetone / Water (1:1)
Acetone / Water (1:1)
+
Na2PdCl4 / K2PtCl4
L
[Pd / PtCl(L-H)] + 2Na / KCl
+
2HCl
...................1
For Pd: L = L1 in 1; L2 in 2; L3 in 3;
L4 in 5; L5 in 7 and L6 in 11
For Pt : L = L3 in 4 and L5 in 8
+
+
K2PtCl4
2 L
[PtCl (L) ]
+
2 2
2 KCl
...................2
For 6: L = L4 and for 12: L = L6
Dichloromethane
2 [(p-cymene)Ru(L)Cl]Cl
For 9: L = L5 and for 13: L = L6
[(p-cymene)RuCl2]2
2 L
2 L
+
...................3
CHCl3 / Acetone (1:1)
HgBr2
[HgBr2(L)2]
For 10: L = L5 and for 14: L = L6
...................4
N
E
N
O
E
L
L H
OH
In equation 1
In equation 2, 3 and 4
Scheme 1.
(16ꢀ39 cmꢀ1) with respect to that of corresponding ligand, indicat-
ing the involvement of its nitrogen in coordination or weak interac-
tion. The bands at 3300ꢀ3400 cmꢀ1 in IR spectra of ligand and some
forms but attempt to separate them did not succeed. The ligands
and complexes 1ꢀ14 are stable and can be stored under ambient
conditions up to six months. They have good solubility in CHCl3,
CH2Cl2, CH3CN, CH3OH, C2H5OH and acetone but are sparingly sol-
uble in hexane. The complexes are non-ionic in nature except 9 and
13, which have molar conductance values at room temperature in
CH3CN, 44.0 and 52.0 S cm2 molꢀ1, respectively, less than the KM
value expected for a 1:1 electrolyte (120ꢀ160 S cm2 molꢀ1). How-
ever, KM values of 9 and 13 in CH2Cl2 at room temperature are 26.0
and 32.0 S cm2 molꢀ1, respectively (KM = 22.0ꢀ27.0 S cm2 molꢀ1
for a 1:1 electrolyte in CH2Cl2). The L5 and L6 can behave as hemil-
abile ligands. Therefore lower values in MeCN may be due to par-
tial substitution of weak Ruꢂ ꢂ ꢂN (see Section 2.4) bond with Ru–Cl.
The CH3CN is a good coordinating solvent therefore the possibility
of following equilibrium also exists.
complexes are due to m(OH), as they are intramolecularly hydrogen
bonded. The mass spectra of few representative complexes for
which crystals could not be grown were recorded. The appearance
of molecular ion peak in the spectra of 6 and 12 supports their
1:2 (M:L) stoichiometry. The presence of peaks in mass spectra of
complexes 9 and 10 for [MH+ꢀCl] and [M+ꢀBr], respectively, con-
curs with the stoichiometries (M:L) 1:1 for Ru and 1:2 for Hg. The
[MH+ꢀCl] peak in the spectra of Ru-complex, further suggests that
one of Ru–Cl bond is weak and consequently Ru appears to alternate
coordination with Cl and nitrogen of >C@N group, which is sup-
ported by NMR and IR spectral data [25].
2.2. NMR spectra of ligands
½ðp-cymeneÞRuðTe; NÞClꢃCl ꢀ ½ðp-cymeneÞRuðTeÞCl2ꢃ
þ CH3CN ꢀ ½ðp-cymeneÞRuðTeÞðCH3CNÞClꢃCl
In 77Se{1H}NMR spectra of L3 and L4 the difference in the posi-
tions of signals (Table 1) was found small (ꢁ8 ppm). The signals in
125Te{1H}NMR spectra of L5 and L6 has been found deshielded by
52.5 ppm and unchanged, respectively, with respect to that of pre-
cursor 2-(4-methoxyphenyltelluro)ethylamine and 3-(4-methoxy-
L5=L6 coordinated through Te and N ¼ ðTe; NÞ and Te ¼ ðTeÞ
In IR spectra of all the complexes except those of 6, 10, 12 and 14,
>C@N– stretching frequency has been observed red shifted

3210
A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
Table 1
125Te/77Se NMR of metal complexes of L3ꢀL6.
S. no.
Complex
Chemical shift d (ppm) in 125Te/77Se NMR
Change in chemical shift relative to ligand (ppm)
1
2
PdCl(L3-H)] (3)
[PtCl(L3-H)] (4)
440.0
389.7
+158.5
+108.2
3
4
5
[PdCl(L4-H)](5)
[PtCl2(L4)2] (6)
[PdCl(L5-H)] (7)
273.7
339.2 and 340.1
755.4
ꢀ16.2
+49.3 and +50.2
+308.8
6
[PtCl(L5-H)] (8)
631.2
+184.5
7
8
9
10
11
12
[(p-cymene)RuClL5]Cl (9)
[HgBr2 (L5)2] (10)
[PdCl(L6-H)] (11)
[PtCl2(L6)2] (12)
[(p-cymene)RuClL6]Cl (13)
[HgBr2 (L6)2] (14)
505.5
361.7
472.9
563.4 and 578.5
534.6
+58.9
ꢀ84.9
+11.10
+101.6 and +116.7
+72.8
ꢀ105.7
356.1
phenyltelluro)propylamine which is corroborated by 13C{1H} NMR
spectra. In 13C{1H} NMR spectra of all the six ligands, the position
of signal of C7 has been found shielded by ꢁ26ꢀ27 ppm in compar-
ison to that of precursor 2-hydroxybenzophenone [26]. The posi-
ing. In case of 6 and 12 signal of C14 appears almost unshifted as
>C@N group is not involved in bonding. In the spectra of all Pd-
complexes and Pt-complexes 4 and 8 signals of carbon atom of
@NCH2 group have been always found deshielded (upto
14.03 ppm) with respect to those of corresponding free ligands.
In case of Pt species 6 and 12 no shift in the position of @NCH2 sig-
nal is observed as ligands are coordinating through chalcogen
atom. For ligands having E–(CH2)2–N@ system (1, 3 and 7), the
magnitude of deshielding of @NCH2 (relative to free ligand) is be-
tween 10.19 and 13.00 ppm whereas for E–(CH2)3–N@ (2, 5 and
11), it is between 3.61 and 7.82 ppm. The signal of ꢀOH has not
been observed in 1H NMR spectra of 1ꢀ5, 7, 8 and 11, indicating
that ꢀOH group coordinates in deprotonated form Oꢀ. The signal
of C9 directly attached to OH group also shifts low field (upto
3.43 ppm) in 13C{1H}NMR spectra, on the formation of these com-
plexes. On complexation with Pd/Pt the signal of C4 is expected to
show deshielding (with respect to those of free ligands) as ob-
served for 7 and 11 (4.87 and 5.08 ppm, respectively) and 6, 8
and 12 (1.58–3.38 ppm). Surprisingly shielding was observed in
the case of other Pd/Pt-complexes (1: 6.36; 2: 7.12; 3: 3.91, 4:
4.87 and 5: 3.08 ppm).
tion of N–CH2 carbon signal of precursor amine shows
a
deshielding of the order of ꢁ9 ppm on the formation of Schiff base.
The CH2E carbon signal (E = Chalcogen) in the spectra of ligands
containing E–(CH2)2–N = system appears shielded (<6 ppm) with
respect to that of corresponding precursor amine and the value
of shielding follows the order S < Se < Te. In the spectra of ligands
containing E–(CH2)3–N = system, the position of CH2E signal re-
mains almost unchanged with respect to that of precursor amine.
In spectra of the six ligands the d value of C4 and C5 atom signal fol-
lows the order S > Se > Te. The signal of C14 appears almost at the
same position in the spectra of L1ꢀL6 but shielded (ꢁ4 ppm) with
respect to that of 2-hydroxybenzophenone. The signals of H5 in 1H
NMR spectra of ligands containing E–(CH2)2–N@ system are
deshielded by 0.12ꢀ0.20 ppm with respect to those containing
E–(CH2)3–N@, but their d values are in the order S > Se > Te. The
signal of ꢀOH proton has been observed beyond 15 ppm due to
intramolecular H-bonding OꢀHꢂ ꢂ ꢂN (see Supplementary material).
In all Pd-complexes and Pt-complexes 4 and 8 two protons of
each CH2 group become diastereotopic. The two H5 protons in 1H
NMR spectra of 1, 3, 4, 5, 7, 8 and 11 show two signals (assigned
on the basis of HMQC experiment), each corresponds to one pro-
ton. Generally, one of these two is shielded (upto 1.12 ppm) and
the other is deshielded (upto 0.45 ppm) in comparison to that of
corresponding free ligand, except in the case of 5 in which both
the signals are deshielded with respect to that of free L4. Instead
of expected [26] doublet of doublet of doublet (ddd) for H5 protons,
the 1H NMR spectra of 1, 4, 5, 7 and 8 have one signal as a triplet of
2.3. Palladium and platinum complexes
All palladium complexes are of type [PdCl(L-H)] (L = L1ꢀL6), in
which the ligands coordinate in an uni-negative tridentate mode as
corroborated by single crystal structures of 1, 3, 5 and 7. Plati-
num(II) forms two type of species [PtCl(L-H)] (4 and 8), which
are similar to Pd-complexes and [PtCl2(L)2] (6 and 12), in which
the ligands probably coordinate through chalcogen atom. The
greater softness of Pt(II) may be a possible reason for the differ-
ence. The signals (Table 1) in 77Se{1H} spectra of Pd-complex 3
and Pt-complexes 4 and 6 and 125Te{1H} NMR spectra of Pd-com-
plexes 7 and 11 and Pt-complexes 8 and 12 have been found
deshielded with respect those of free ligands. When one chelate
ring around Pd is five membered, the deshielding is much large
(Table 1) in magnitude. In 77Se{1H} NMR spectrum of 6 and
125Te{1H} NMR spectrum of 12, two signals appear which are close
by (Table 1), probably indicating the presence of both cis and trans
isomeric forms together in solution. The Pd-complex 5 is an excep-
tion as shielding of 16.2 ppm is observed in this case which does
not concur with deshielding (6.9 ppm) observed earlier in a similar
3
2
doublet (two J(HꢀC5ꢀC6ꢀH) are similar but ꢄ J(HꢀC5ꢀH)) and the
other as a doublet of triplet. The dihedral angle ꢁ180° between
one out of four pairs of vicinal protons makes two 3J(HꢀC5ꢀC6ꢀH) dif-
3
2
3
ferent. One J(HꢀC5ꢀC6ꢀH) is ꢅ J(HꢀC5ꢀH) and the other J(HꢀC5ꢀC6ꢀH)
much smaller in magnitude. In 1H NMR spectra of 3 and 11 there
are two multiplets for H5 whereas in the spectra of 2, there is only
one signal for H5 (complex multiplet), which is deshielded by
0.26 ppm in comparison to that of free L2. The two @NCH2 protons
(H6) like H5 protons also give two signals (one for each proton) in
1H NMR spectra of 1, 3, 4, 7, 8 and 11. In the spectra of 2 and 5, sig-
nals of both the protons (H6) appear as one complex multiplet. The
signals of H6 protons in the spectra of 1ꢀ5, 7, 8 and 11 were as-
signed on the basis of HMQC experiments. In 1H NMR spectra of
1, 3 and 4 one signal is shielded (upto 0.22 ppm) and the other is
deshielded (upto 0.74 ppm) in comparison to those of the corre-
sponding ligands. For 7, 8 and 11, both @NCH2 signals are deshield-
ed (upto 1.75 ppm) with respect to those of corresponding free
ligands. Most probably in case of 6 and 12 ligands are coordinating
through chalcogen atom, resulting these complexes in solution as a
case,
[PdCl{PhSe-(CH2)3-N@C(CH3)-C6H4-2-Oꢀ}]
[23].
In
13C{1H}NMR spectra of all Pd and Pt-complexes signals of C5
(CH2E; E = S, Se or Te) show deshielding (upto 12.42 ppm) with re-
spect those of free ligands, supporting bonding through chalcogen
atom as indicated by 77Se{1H} and 125Te{1H} NMR spectra. The sig-
nal of C14 shows deshielding upto 3.42 ppm (relative to corre-
sponding ligand) on formation of all Pd-complexes and Pt-
complexes 4 and 8 indicating involvement of >C@N group in bond-

A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
3211
mixture of cis and trans isomeric forms. Thus signals of H5 and H6
protons appear as complex multiplet, virtually unshifted with re-
spect to those of free ligands in 1H NMR spectra of 6 and 12. For de-
tails of proton NMR spectral data see Supplementary material.
C5
C6
C7
C18
C19
2.4. Ruthenium and mercury complexes
C4
The deshielding of signals in 125Te{1H}NMR spectra of Ru-com-
plexes (with respect to those of free ligands) is in the order 13 > 9
(Table 1). The signals of C4 and C5 (CH2Te) in 13C{1H}NMR spectra
are deshielded in the spectra of both Ru-complexes (upto
11.54 ppm) in comparison to those of free ligands, supporting the
ligation of Ru through Te. The signal of carbon atom of @NCH2
group shows shielding (upto 3.30 ppm) with respect to those of
free ligands, for 9 and 13 both and the signals of C14 appear almost
at positions similar to those of free ligands, ruling out coordination
of Ru with >C@N. However presence of [MH+ꢀCl] ion peak in high
resolution mass spectra and molar conductances of 9 and 13 indi-
cate the possibility of weak interaction between Ru and >C@N. The
presence of OH signal in the 1H NMR spectra and almost unshifted
signal of C9 in 13C{1H}NMR spectra for both 9 and 13 (relative to
corresponding free ligands), suggest that OH group does not coor-
dinate with Ru in both the species.
C9
C2
C20
C21
C17
C3
C1
C10
C8
C16
S
N
C15
C14
C11
C13
C12
H
O
Fig. 1. ORTEP diagram of L1 with 50% probability ellipsoids.
the earlier reports of 104.1(3)° for PhS-(CH2)2-N@C(CH3)-C6H4-2-
OH [30]. The intramolecular hydrogen bonding OꢀHꢂ ꢂ ꢂN exists in
the structure of L1. The molecular structure of 1 with its selected
bond distances and angles related to Pd is shown in Fig. 2. The
coordination geometry around Pd is almost square planar. The li-
gand coordinated with Pd in a monoanionic tridentate (S, N, Oꢀ)
mode forms six membered chelate ring via Oꢀ and N and five
membered via S and N. The Pd–N bond length (2.002(2) Å) in 1 is
longer than 1.965(2) Å reported [20] for [PdCl{EtNHC(@S)NH-
N@CH-C6H4-2-Oꢀ}] (15) but the Pd–O distance (1.9862(16) Å) in
1 is slightly shorter than 2.019(2) Å reported [20] for 15. The bond
distances Pd–S (2.2563(6) Å) and Pd–Cl (2.3159(7) Å) of 1 are con-
sistent with the earlier reported values [20] for 15 [Pd–S = 2.2456
(9) and Pd–Cl = 2.3078(8) Å] and [PdCl2{4-MeO-C6H4TeCH2CH2-
SEt}] [Pd–S = 2.268(4) and Pd–Cl 2.316(4) Å] [31]. The Pd–S bond
distance of cis-Pd(SNNMe2-S)(AsPh3)Cl2 (2.249(1) Å) [32] is also
in agreement with that of 1. The Pd–S bond length (2.352 Å) of
trans-[Pd(SCN)2[P(OPh)3]2] [33], is longer than that of 1, probably
due to the trans influence of sulphur.
In 1H NMR spectra of 9 and 13, H5 protons give two multiplets,
assigned on the basis of HMQC experiments. In case of 9, the two
multiplets of H5 are deshielded (ꢁ0.20ꢀ0.43 ppm) but for 13, one
is almost unshifted while the other is deshielded by 0.43 ppm in
comparison to those of corresponding free ligands. The @NCH2
protons (H6) give two different signals in case of 9 but both are
shielded (0.12 and 0.35 ppm) in comparison to those of free L5.
In the spectrum of 13, signals of both the protons of @NCH2 appear
as a complex multiplet, which is slightly shielded (0.08 ppm) with
respect to that of free ligand. This supports possible weak interac-
tion between Ru and nitrogen of >C@N group mentioned earlier.
For details of proton NMR spectral data see Supplementary
material.
In 125Te{1H}NMR spectra of Hg-complexes shielding of signals
(Table 1) relative to those of free ligands has been observed as re-
ported earlier for d10 systems [27–29]. The signal of C4 is slightly
deshielded in 13C{1H} NMR spectra of both 10 (1.74 ppm) and
14(1.45 ppm) but signal of C5 (CH2E) is deshielded (relative to that
of free ligand) by 11.64 and 13.20 ppm, respectively, for 10 and 14,
indicating formation of TeꢀHg bond. The deshielding (upto
0.46 ppm) of H5 signals in 1H NMR spectra of both the complexes
relative to those of free ligands further supports it. In 13C{1H}NMR
spectra, of 10 and 14, the signals of C14 appear almost unshifted.
The signals of C6 (@NCH2) show shielding (upto 2.66 ppm) with re-
spect to those of free ligands. Both these observations rule out the
possibility of Hgꢂ ꢂ ꢂN interaction which is supported by 1H NMR
spectra of 10 and 14, as triplet of @NCH2 (H6) is nearly unshifted
or shielded in both the cases in comparison to those of free ligands.
The presence of OH signal in the 1H NMR spectra and no change in
the position of C9 signal (relative to those of free L5 and L6) in
13C{1H}NMR spectra of both 10 and 14 suggest that OH group
probably does not coordinate with Hg in these species. For details
of proton NMR spectral data see Supplementary material.
The molecular structures of 3 and 5 with selected bond lengths
and angles related to Pd are shown in Figs. 3 and 4, respectively.
C12
C11
C13
C18
C10
C17
C14
C15
C8
C9
C5
C16
C19
C7
C6
N
C20
S
C21
C4
2.5. Crystal structures
Pd
C2
Cl
Molecular structure of L1 is shown in Fig. 1 and bond lengths
and angles are available in supplementary crystallographic data
(CIF files). S–C bond lengths 1.764(4)/1.833(4) Å are consistent
with the earlier reports 1.771(6)/1.794(6) Å on PhS-(CH2)2-
N@C(CH3)-C6H4-2-OH [30]. The bond distances S–C(Ar) is some-
what shorter than S–C(alkyl) distance as expected. C(16)–S(1)–
C(15) was found to be 105.39(18)° which is also consistent with
C1
O
C3
0
Fig. 2. ORTEP diagram of 1 with 50% probability ellipsoids; bond lengths (ÅA): Pd–S,
2.2563(6); Pd–O, 1.9862(16); Pd–N, 2.002(2); Pd–Cl, 2.3159(7); bond angles (°): O–
Pd–N 93.26(7); O–Pd–S, 175.26(5); N–Pd–S, 89.00(6); O–Pd–Cl, 88.75(5); N–Pd–Cl,
176.77(5); S–Pd–Cl, 89.18(2).

3212
A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
C5
C5A
C6A
C7A
C4A
C4
C6
C22A
Pd1A
C3A
C2A
C18
C3
C17
C21
C18A
C19A
C17A
C21A
C14
N
C15
Pd
C15A
C14A
N1A
C7
C2
C16A
C1
C1A
C8A
Se
C9A
C19
C9
C16
C8
Se1A
C10A
C20A
C20
C10
C13A
Cl1A
O1A
O
C13
Cl
C11A
C12A
C11
C12
Fig. 5. ORTEP diagram of 5 with 50% probability ellipsoids; bond lengths (Å):
Pd(1A)–Se(1A), 2.3855(19); Pd(1A)–N(1A), 1.986(6); Pd(1A)–O(1A), 1.995(6);
Pd(1A)–Cl(1A), 2.284(3); bond angles (Å): N(1A)–Pd(1A)–Se(1A), 94.25(19);
Cl(1A)–Pd(1A)–Se(1A), 86.19(7); O(1A)–Pd(1A)–Se(1A), 173.95(17); N(1A)–
Pd(1A)–O(1A), 89.1(3); N(1A)–Pd(1A)–Cl(1A), 178.12(19); O(1A)–Pd(1A)–Cl(1A),
90.66(17).
0
Fig. 3. ORTEP diagram of 3 with 50% probability ellipsoids; bond lengths (ÅA): Pd–Se,
2.3575(6); Pd–O, 1.993(3); Pd–N, 2.010(4); Pd–Cl, 2.3150(13); bond angles (°): Se–
Pd–O, 173.92(9); Se–Pd–N, 89.98(11); Se–Pd–Cl, 87.97(4); O–Pd–N, 93.32(14); O–
Pd–Cl, 89.03(10); N–Pd–Cl, 176.02(11).
reports [Pd–N = 2.01(1), Pd–O = 2.03(1), Pd–Cl = 2.290(4) Å] for
Pd(II) complex of a (Te, N, Oꢀ) type ligand [34]. The Pd–Se bond
lengths of complexes 3 and 5, 2.3575(6) and 2.3855(19) Å, respec-
tively, are shorter than those reported for [Pd(PEt3)2(SePh)(-
PO(OPh)2)] (2.518(9) Å) [35] and [Pd(Me2PCH2CH2PMe2)(Me)
(SeC6H4-4-Cl)] (2.4483(8) Å) [36]. The possible reason for shorten-
ing of Pd–Se bond in 3 and 5 may be the tridentate-coordination
mode of L3 and L4 which makes two chelate rings and conse-
quently forces Se to bind with Pd(II) some what more strongly in
comparison to those complexes in which selenium ligand is mono-
dentate one. Similar observations have been made for (N, Se, Oꢀ)
ligands earlier [22–23]. However, it is also noticeable that Pd–Se
bond length 2.3575(6) Å in 3 is shorter than Pd–Se bond distance
of 2.392(2)/2.3789(18) Å of 5, where both chelate rings are six
membered. The bond angles at N (114.58(15)–12.09 (16)°) are con-
sistent with its trigonal pyramidal geometry (see Fig. 5).
In 7 also the ligand is coordinated with Pd in a tridentate (Te, N,
Oꢀ) mode forming a six membered chelate ring with Oꢀ and N and
a five membered ring with Te and N (see ORTEP diagram in Fig. 6
with selected bond lengths and angles related to Pd). The unit cell
of 7 has two nearly similar molecules and therefore given bond
lengths/angles are average values. The lengths of Pd–Te, Pd–N,
Pd–O and Pd–Cl bonds of 7, 2.5158(5), 2.020(3), 2.026(3),
2.3222(12) Å, respectively, are consistent with the earlier report
[34] for [PdCl{MeO-p-C6H4-Te-(CH2)2-N@C(CH3)-C6H4-2-Oꢀ}]
[Pd–Te = 2.504(1), Pd–N = 2.01(1), Pd–O = 2.03(1) and Pd–
Cl = 2.290(4) Å]. The Pd–Te bond length in the present complex
2.5158(5) Å is shorter in comparison to earlier reports,
2.5873(2) Å for di[bis(2-{1,3-dioxan-2-yl}ethyl)telluride)dichloro-
palladium(II) [37] and 2.5865(2)–2.6052(2) Å for di[N-{2-(4-meth-
oxyphenyltelluro)ethyl} morpholine]dichloropalladium(II) [38].
This is due to combined effect of tridentate nature of present ligand
and the absence of strong trans influence in 7. On comparing Pd–N,
Pd–O, Pd–Cl, Pd–Se and Pd–Te bond lengths of 1, 3, 5 and 7 with
sum of their covalent radii 2.03, 2.01, 2.27, 2.44 and 2.64 Å, respec-
tively, the bonding between L3/L4/L5/L5 and Pd seems to be strong
in nature. The geometry around chalcogen atoms in 1, 3, 5 and 7 is
pyramidal [bond angles (°): S, 94.87 (8) to 107.01 (9); Se, 91.93(15)
to 107.9; Te, 88.05 to 101.74(12)].
C5
C4
C6
C3
C15
C7
C14
Pt
C18
C17
C2
C1
C8
N
C16
C9
Se
C10
C11
C19
C21
C20
C13
O
Cl
C12
Fig. 4. ORTEP diagram of 4 with 50% probability ellipsoids; bond lengths (Å): Pt–Se,
2.3470(8); Pt–N, 1.992(5); Pt–O, 2.005(4); Pt–Cl, 2.3132(19); bond angles (°): N–Pt–
Se, 89.75(15); O–Pt–Se, 174.63(15); Cl–Pt–Se, 89.22(6); N–Pt–O, 93.6(2); N–Pt–Cl,
177.41(17); O–Pt–Cl, 87.56(14).
The unit cell of 5 has two nearly similar molecules and therefore
given bond lengths/angles are average values in this case. The coor-
dination geometry around Pd is nearly square planar in 3 and 5
both. The ligands are coordinated with Pd via Se, N and Oꢀ in both
the complexes forming a six membered chelate ring with Oꢀ and
N@C< and a five membered with Se and N@C< in 3, and two six
membered chelate rings in the case of 5. The Pd–Se, Pd–N, Pd–O
and Pd–Cl bond distances 2.3575(6), 2.010(4), 1.993(3),
2.3150(13) Å, respectively, in case of 3 and 2.3855(19), 1.986(6),
1.995(6), 2.284(3) Å, respectively, in case of 5, are consistent with
the earlier reports [23] for [PdCl{PhSe-(CH2)2-N@C(CH3)-C6H4-2-
Oꢀ}] [Pd–Se@2.3669(11), Pd–N = 2.003(7), Pd–O = 1.977(6) and
Pd–Cl = 2.305(2) Å] and [PdCl{PhSe-(CH2)2-N = C(CH3)-C6H3-3-R-
2-Oꢀ}] [R = CH(CH2CH3)2; Pd–Se = 2.365(1), Pd–N = 1.985(4), Pd–
O = 2.017(4) and Pd–Cl = 2.323(2) Å] [22]. The Pd–N, Pd–O and
Pd–Cl bond distances of 3 and 5 are also consistent with the earlier
In Fig. 6 the molecular structure of 4 with its selected bond
lengths and angles related to Pt is given. The geometry around Pt

A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
3213
length of 4, 2.005(4) Å is comparable with earlier reports [23,42]
2.034 and 1.976(10) Å. On comparing Pt–N, Pt–O, Pt–Cl and Pt–Se
bond lengths with the sum of their covalent radii 2.05, 2.03, 2.29
and 2.46 Å, respectively, it appears that the observed bond distances
are shorter than these values, except in the case of Pt–Cl where the
observed values are marginally higher. This indicates that coordina-
tion of L3 is quite strong with Pt also. Some more Pd/Pt–E distances
from the literature reports are compiled in Table 2. These distances
are sensitive to trans influence as well as chelate ring size. On com-
paring our values with these reports, it appears that our Pd–S, Pd–
Se, Pd–Te and Pt–Se bond distances are some what shorter than
the literature values [43–61].
It is interesting to note the effect on bond lengths/angles of sul-
phated Schiff base L1 when it coordinates with metal ion Pd(II).
The C(alkyl)–S–C(aryl) bond angle of 105.39(18)° in L1 gets some
what lowered to 102.81(12)° on the formation of 1. The SꢀC(aryl)
and SꢀC(alkyl) bond distances in L1 are 1.764(4) and 1.833(4) Å,
respectively, but on formation of 1, the distances for these bonds
also change (1.789(2) and 1.808(2) Å, respectively). The >C@N–
bond distance in L1 is 1.293(4) Å. However, this distance remains
almost unchanged on complexation with Pd(II) [1.296(3) Å in 1].
However, NꢀCH2 bond distance of 1.481(5) Å in L1 gets slightly in-
creased on the formation of 1 and becomes 1.496(3) Å. The O–C
distance of 1.341(4) Å for L1 is shortened on the formation of 1
and becomes 1.314(3) Å. Generally S/Se/Te–C(alkyl) is longer than
S/Se/Te–C(aryl).
C4A
C3A
C5A
C6A
O2A
C18A
C14A
C17A
C16A
C2A
C1A
C7A
C9A
C22A
C15A
C19A
C20A
C8A
N1A
C21A
C10A
Te1A
Pd1A
C13A
C11A
O1A
Cl1A
C12A
Fig. 6. ORTEP diagram of 7 with 70% probability ellipsoids; bond lengths (Å):
Pd(1A)–Te(1A), 2.5158(5); Pd(1A)–N(1A), 2.020(3); Pd(1A)–O(1A), 2.026(3);
Pd(1A)–Cl(1A), 2.3222(12); bond angles (°): Te(1A)–Pd(1A)–N(1A), 90.91(10);
Te(1A)–Pd(1A)–O(1A), 175.18(8); Te(1A)–Pd(1A)–Cl(1A), 86.76(3); N(1A)–Pd(1A)–
O(1A), 92.27(13); N(1A)–Pd(1A)–Cl(1A), 175.93(10); O(1A)–Pd(1A)–Cl(1A),
90.27(9).
is nearly square planar. The Pt–Se bond length, 2.3470(8) Å, is con-
sistent with the earlier reported values in the case of
[(CH3SeCH2CH2CH(COOMe)NH2)PtCl2] (2.3697(8) Å) [39] and
[PtCl{C6H5-Se-(CH2)2-N@C(CH3)-C6H4-2-Oꢀ}] (2.3543(16) Å) [23],
but is shorter than those reported for cis-[Pt(SePh)2(PPh3)2]
(2.4970(9)/2.4604(10) Å) [40] and trans- [Pt(SePh)2(2,9-dimethyl-
1,10-phenanthroline)(MeOOCCH@CHCOOMe)] (2.5197/2.5142 Å)
[41]. This may be attributed to tridentate-coordination mode of L3
in 4, as in the case of Pd(II) complexes. The absence of the trans
influence may also contribute, particularly in comparison to
trans-[Pt(SePh)2(2,9-dimethyl-1,10-phenanthroline)-(MeOOCCH@
CHCOOMe)]. The Pt–N and Pt–Cl bond distances of 4, 1.992(5) and
2.3132(19) Å, respectively, are consistent with the earlier reports
for PtCl2{CH3-Se-(CH2)2-CH(COOMe)-NH2} (Pt–N, 2.043(5); Pt–Cl,
2.294(2)/2.322(2) Å) [36] and PtCl{C6H5-Se-(CH2)2-N@C(CH3)-
C6H4-2-Oꢀ} (Pt–N 1.988(12); Pt–Cl 2.306(4) Å) [23]. The Pt–O bond
2.6. Applications in Heck and Suzuki reaction
The palladium complexes are expected to be active for Heck and
Suzuki reactions which were carried out using complexes 1, 3, 5
and 7 as summarized in Scheme 2. The percentage yields were
found upto 85 (Table 3).
Heck reaction is very important in organic synthesis for carbon–
carbon bond formation. The complexes used as catalysts are based
on phosphorus ligands as well as involve phosphorus-free ligands.
The improved catalytic activity of transition metal complexes with
hemilabile ligands has been reported [62,63]. The present ligands
Table 2
M–E (E = S, Se or Te) bond lengths.
0
S. no.
Bond
Length (AÅ)
Charge on E
Trans group/atom
Ref.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Pd–S
Pd–S
Pd–S
Pd–S
2.3305(11)
2.306(5)
Neutrala
Neutralb
Neutrala
Neutrala
Neutralb
Negative
Negative
Neutrald
Neutrald
Negative
Negative
Neutrale
Negative
Neutralc
Neutralc
Neutralc
Neutralc
Neutralc
Neutralc
Neutralc
Neutralc
Neutralc
S
I
[43]
[44]
[45]
[46]
[46]
[47]
[48]
[49]
[50]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[57]
[57]
[58]
[59]
[60]
[61]
2.3204(10)ꢀ2.3430(13)
2.3208(8)ꢀ2.3225(19)
2.251(2)ꢀ2.429(2)
2.401(3)ꢀ2.416(3)
2.4049(13) ꢀ2.4363(12)
2.4307(5)
ArC
ArC
C, O or S
Se
Se
PPh3
Cl
PPh3
PPh3
Cl
PPh3
Cl
Pd–S
Pd–Se
Pd–Se
Pd–Se
Pd–Se
Pt–Se
Pt–Se
Pt–Se
Pt–Se
Pd–Te
Pd–Te
Pd–Te
Pd–Te
Pd–Te
Pd–Te
Pd–Te
Pd–Te
Pd–Te
2.3725(3)
2.4565(5)ꢀ2.5009(13)
2.4371(6)ꢀ2.372(6)
2.366(3)ꢀ2.368(2)
2.4301(7)ꢀ2.4595(7)
2.5606(8)
2.5040(4)
2.534(2)
2.517(6)
2.5007(6)/2.5101(6)
2.4914(7)/2.5005 (7)
2.538(2)/2.517(2)
2.5301(1)/2.5313(9)
2.5951(7)/2.5872(7)
Cl
SMe
SMe
Cl
Oꢀ
TeRR’
Py
TeRR’
a
>C@S Group.
b
c
Sulphide.
Telluride
Selenide.
Diselenide.
d
e

3214
A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
Complex 1/3/5/7
R
R
Br
+
+
(OH)2B
K2CO3, DMF/H2O, 24h, 100oC
Ar
Complex 1/3/5/7
Na2CO3, DMF, N2 atm, 24h at 100oC
Scheme 2.
Ar
X
Y
Y
Table 3
Yields (%) in Suzuki and Heck reactions.
Substituents on reactants
Complex
1
3
5
7
Heck reaction
Ar-X
Y
Yield of trans product (%)
COOH
COOH
COOH
Ph
78
85
80
35
83
78
33
74
65
33
78
68
30
70
60
30
72
70
35
O2N
Cl
I
70
I
25
O2N
O2N
Cl
Br
I
74
Ph
70
I
Ph
28
O2N
Br
Suzuki reaction
R
Yield (%)
OMe
H
NO2
30
50
80
20
45
87
15
30
84
10
35
80
L1ꢀL6 are also potent hemilabile ligands. However, many phos-
phine based catalysts are often water- and air-sensitive. Therefore,
catalysis under phosphine-free conditions is a challenge of high
importance, and a number of Pd-complexes of phosphine-free li-
gands [64–69] have been reported to exhibit promising catalytic
activity for Heck reaction. Recently Pd–Se bond containing com-
plexes [70] have found very promising for Heck reaction. This
has motivated us to examine palladium(II) complexes 1, 3, 5 and
7 for Heck coupling. The advantage of using them is that they are
air stable and moisture insensitive. Not much investigations on
Pd(II) complexes of tellurated ligands for Heck reaction have been
made and present results show promise of such species also. A
good selectivity for trans-products has been observed. The catalytic
activity depends on the halide, while electron-withdrawing groups
on the aryl ring increase the reaction rate. The reactivity decreases
drastically in the order ArI > ArBr > ArCl. For Aryl bromides
(1 mmol) also, a very little amount (0.001 mmol) of a complex
was found sufficient to catalyze the Heck reaction.
Suzuki–Miyaura reaction is also among the most important pal-
ladium-catalyzed cross-coupling reactions of both academic and
industrial interest [20,23,71–77]. In view of air and moisture
sensitivity of complexes of phosphorus ligands there is an interest
in phosphine-free ligands for the Suzuki–Miyaura reaction also.
Complexes 1, 3, 5 and 7 have been explored for Suzuki–Miyaura
reaction as they offer the advantage of stability under ambient con-
ditions. For carrying out Suzuki–Miyaura reactions of aryl bro-
mides with phenylboronic acid the reaction conditions used were
similar to those used for analogous phosphine-free systems
[20,22–24,30]. Aryl bromides and phenylboronic acid were reacted
under aerobic conditions at 100 °C for 24 h, using K2CO3 as a base,
without addition of free ligand or any promoting additive and in
the presence of a small amount of water (ꢁ1 equivalent with re-
spect to the substrates). Homocoupling of phenylboronic acid to
give unsubstituted biphenyl was negligible. The reaction was per-
formed using a 1:1000 catalyst: aryl halide molar ratio. The cata-
lytic activity was dependent on the halide, and also electron-
withdrawing groups present on the aryl ring increased the reaction
rate. The activity follows in the order NO2 > H > OMe. For the acti-
vated 1-bromo-4-nitrobenzene the yields were usually about 80%
or higher. Not many evaluations of palladium complexes of tellu-
rated ligands for Suzuki–Miyaura reaction have been made so far
and present results are promising. Thus palladium complexes of
chalcogenated Schiff base ligands of HBP can be efficient catalysts
for both Suzuki–Miyaura cross-coupling and Heck reactions. The
advantage of using them is that they are air stable and also not
moisture sensitive. A 1:1000 catalyst:aryl halide molar ratio was
found optimum for Heck as well as Suzuki reactions. The difference
in the catalytic activities of 1, 3, 5 and 7 is not much and can not be
explained unequivocally.
3. Experimental
The recording of melting points and IR spectra
(4000ꢀ250 cmꢀ1, in KBr), C and H analyses and conductivity

A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
3215
measurements in CH3CN (concentration ca 1 mM) were carried out
by earlier reported method [23–24]. The 1H, 13C{1H}, 77Se{1H} and
125Te{1H} NMR spectra were recorded on a Bruker Spectrospin
DPX-300 NMR spectrometer at 300.13, 75.47, 57.24 and
94.69 MHz, respectively. Mass spectra (ion spray) were recorded
on Hybrid Quadrupole-TOF LC/MS/MS mass spectrometer (QSTAR
XL System), Model 1011273/A, AB Sciex Instruments (Applied Bio-
systems, Canada). PhE(CH2)2NH2, PhE(CH2)3NH2 (E = S, Se), Ar-
Te(CH2)2NH2 and ArTe(CH2)3NH2 [Ar = ꢀC6H4–4–OCH3] were
synthesized by the literature methods [78–81].
(C9), 174.65 (C7); 77Se {1H}NMR (57.24 MHz CDCl3, 25 °C, vs Me2Se)
d = 281.48. IR (KBr, cmꢀ1): 3436, 1612, 738, 474.
L4: Yield 1.82 g (ꢁ92%); KM = 0.6 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C22H21NOSe: C, 67.01; H, 5.37; N, 3.55. Found C, 67.08; H,
5.31; N, 3.59. 13C{1H}NMR (75.47, CDCl3, 25 °C): d = 24.90 (C5),
30.86 (Ca), 50.71 (C6), 117.10 (C12), 117.78 (C10), 119.50 (C8),
126.61 (C1), 126.98 (C16), 128.55 (C15), 128.81 (C17), 128.86 (C2),
129.67 (C4), 131.26 (C13), 132.26 (C11), 132.31 (C3), 133.61 (C14),
163.20 (C9), 174.46 (C7); (77Se {1H}NMR (57.24 MHz, CDCl3, 25 °C,
vs Me2Se): d = 289.90. IR (KBr, cmꢀ1): 3438, 1612, 743, 476.
L5: Yield 2.20 g (ꢁ95%); KM = 0.6 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C22H21NO2Te: C, 57.57; H, 4.61; N, 3.05. Found C, 57.51; H,
4.57; N, 3.09%. 13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): d = 8.66
(C5), 52.50 (C6), 54.82 (OMe) 99.66 (C4), 114.90 (C2), 117.14 (C12),
117.70 (C10), 119.49 (C8), 126.90 (C16), 128.43 (C15), 128.69 (C17),
131.32 (C13), 132.20 (C11), 133.53 (C14), 140.84 (C3), 159.49 (C1),
162.85 (C9), 173.97 (C7); 125Te {1H} NMR (94.69 MHz CDCl3,
25 °C, vs Me2Te): d = 446.63. IR(KBr, cmꢀ1): 3440, 1612, 513.
L6: Yield 2.15 g (ꢁ90%); KM = 0.8 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C23H23NO2Te: C, 58.40; H, 4.90; N, 2.96. Found: C, 58.37; H,
4.83; N, 2.91%. 13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 5.58
(C5), 32.58 (Ca), 52.76 (C6), 55.05 (OMe), 100.05 (C4), 115.09 (C2),
117.14 (C12), 117.96 (C10), 119.59 (C8), 127.17 (C16), 128.67 (C15),
128.93 (C17), 131.36 (C13), 132.38 (C11), 133.74 (C14), 140.92 (C3),
159.66 (C1), 163.48 (C9), 174.46 (C7); 125Te {1H} NMR (94.69 MHz
CDCl3, 25 °C, vs Me2Te) d = 461.80. IR(KBr, cmꢀ1): 3440, 1640, 508.
Single crystal diffraction data for L1, 3, 4, 5 and 7 were collected
on a Bruker AXS SMART Apex CCD diffractometer using Mo K
a
radiations (0.71073 Å) at 298 (2) K. The software SADABS was used
for absorption correction (if needed) and SHELXTL for space group,
structure determination and refinements [82,83] as detailed earlier
[23] The data for 1 was collected on Oxford Diffraction Gemini-R
CCD diffractometer (one degree u and
x scans were used with a
0.8 mm collimator) at 200 (2) K. CRYSALIS RED, Oxford Diffraction
Ltd., Version 1.171.32.5 was used for solutions. Supplementary
material consists of crystal data, structural refinements (Tables
S.1 and S.2) selected bond lengths and angles (Table S.3). Proton
NMR spectral details of all newly synthesized ligand (L1ꢀL6) and
their complexes 1ꢀ14 are given in Supplementary material.
3.1. Synthesis of L1 and L2
2-(Phenylsulphanyl)ethylamine (0.765 g, 5.0 mmol)/3-(phenyl-
sulphanyl)propylamine (0.835 g, 5.0 mmol) was stirred in dry
ethanol (20 mL) at room temperature for 0.5 h. 2-hydroxybenzo-
phenone (0.9911 g, 5.0 mmol), dissolved in dry ethanol (20 mL),
was added dropwise with stirring. The mixture was stirred further
at room temperature for 2 h. The solvent was evaporated off on a
rotary evaporator resulting in a yellow precipitate of L1 or dark
yellow viscous oil in case of L2. The L1 on recrystallization from
chloroform–hexane mixture (1:1), gave yellow coloured single
crystals.
3.3. Synthesis of palladium(II) complexes [PdCl(L-H)
Na2[PdCl4] (0.294 g, 1 mmol) dissolved in water (5 mL) and a
solution of any ligand L1–L6 (1 mmol) prepared in acetone
(10 mL) were stirred together vigorously. An orange precipitate
of palladium(II) complex was immediately obtained, which was fil-
tered, washed with hexane (10 mL) and dried in vacuo. The recrys-
tallization of the complex from chloroform–hexane (60:40)
mixture was made. Single crystals were obtained in case of
[PdCl(L1-H)] (1), [PdCl(L3-H)](3), [PdCl(L4-H)] (5) and [PdCl(L5-
H)] (7).
L1: Yield 1.50 g (ꢁ90%); m.p. 42 °C. KM = 0.8 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C21H19NOS: C, 75.64; H, 5.74; N, 4.20. Found C, 75.61;
H, 5.71; N, 4.26%. 13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 34.38
(C5), 50.43 (C6), 117.48 (C12), 117.90 (C10), 119.79 (C8), 126.12 (C1),
127.16 (C16), 128.72 (C15), 128.90 (C2), 128.98 (C17), 129.37 (C3),
131.57 (C13), 132.50 (C11), 133.80 (C14), 135.50 (C4), 162.88 (C9),
175.02 (C7). IR (KBr, cmꢀ1): 3483, 783, 1612.
[PdCl(L1-H)] (1): Yield 0.39 g (ꢁ82%); m.p. 162 °C.
KM = 6.0 cm2 molꢀ1 ohmꢀ1
. Anal. Calc. for C21H18NOSPdCl: C,
53.18; H, 3.83; N, 2.95. Found: C, 53.13; H, 3.89; N, 2.91%.
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): d = 41.01 (C5), 60.62 (C6),
115.41 (C12), 121.26 (C8), 121.39 (C10), 128.38 (C4), 126.84,
127.08, 129.17, 129.27, 129.32 (ArC: C15, C16 and C17), 129.82
(C2), 130.70 (C1), 133.01 (C3), 134.42 (C11), 134.68 (C13), 135.81
(C14), 165.15 (C9), 169.71 (C7); IR (KBr, cmꢀ1): 1592, 741.
L2: Yield 1.50 g (ꢁ85%); KM = 0.6 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C22H21NOS: C, 76.05; H, 6.09; N, 4.03. Found C, 76.01; H,
6.03; N, 4.09%. 13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): d = 29.89
(Ca), 31.03 (C5), 49.75 (C6), 117.16 (C12), 117.87 (C10), 119.51 (C8),
125.83 (C1), 127.04 (C16), 128.61 (C15), 128.75 (C2), 128.90 (C17),
129.07 (C3), 131.34 (C13), 132.38 (C11), 133.80 (C14), 135.50 (C4),
163.32 (C9), 174.64 (C7). IR (KBr, cmꢀ1): 3426, 788, 1612.
[PdCl(L2-H)] (2): Yield 0.36 g (ꢁ73%); m.p. 158 °C.
KM = 8.0 cm2 molꢀ1 ohmꢀ1
. Anal. Calc. for C22H20NOSPdCl: C,
54.11; H, 4.13; N, 2.87. Found: C, 54.18; H, 4.11; N, 2.81%.
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): d = 25.31 (Ca), 33.89 (C5),
53.36 (C6), 115.30 (C12), 121.11 (C10), 126.43 (C8), 127.55, 128.80
(ArC: C15, C16), 129.14 (C4), 129.62 (C2), 129.69 (C17), 129.93 (C1),
132.23 (C3), 134.34 (C13), 134.63 (C11), 136.10 (C14), 165.40 (C9),
171.04 (C7); IR (KBr, cmꢀ1): 1588, 746.
3.2. Synthesis of L3–L6
2-(Phenylseleno)ethylamine (1.00 g, 5.0 mmol), 2-(phenylsele-
no)propylamine (1.07 g, 5.0 mmol), 2-(4-methoxyphenyltell-
uro)ethylamine (1.39 g, 5.0 mmol) and 3-(4-methoxyphenyl
telluro)propylylamine (1.46 g, 5.0 mmol) were, respectively, re-
acted with 2-hydroxybenzophenone (0.991 g, 5.0 mmol) by the
method given in Section 3.1, to prepare L3, L4, L5 and L6 as dark
yellow viscous oil.
[PdCl(L3-H)] (3): Yield ꢁ 0.42 g (ꢁ81%); m.p. 148 °C
KM = 8.0 cm2 molꢀ1 ohmꢀ1
. Anal. Calc. for C21H18NOSePdCl: C,
48.40; H, 3.48; N, 2.69. Found: C, 48.37; H, 3.41; N, 2.63%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 32.32 (C5), 62.50 (C6),
115.18 (C12), 121.09 (C10), 122.16 (C8), 125.40 (C4), 126.93,
127.46, 128.95, 129.13 (ArC: C15, C16, C17), 129.91 (C2), 130.19
(C1) 133.66 (C3), 134.09 (C11), 135.09 (C13), 136.03 (C14), 165.36
(C9), 169.77 (C7); 77Se {1H}NMR (57.24 MHz, CDCl3, 25 °C, vs
Me2Se) d = 440.0. IR (KBr, cmꢀ1): 1573, 463, 748.
L3: Yield 1.80 g (ꢁ94%); KM = 0.8 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C21H19NOSe: C, 66.33; H, 5.04; N, 3.68. Found: C, 66.39; H,
5.01; N, 3.61%. 13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): d = 27.86
(C5), 51.07 (C6), 117.34 (C12), 117.82 (C10), 119.65 (C8), 126.83
(C1), 127.04 (C16), 128.60 (C15), 128.87 (C17), 128.94 (C2), 129.31
(C4), 131.46 (C13), 132.39 (C11), 132.55 (C3), 133.66 (C14), 162.86
[PdCl(L4-H)] (5): Yield ꢁ 0.41 g (ꢁ77%); m.p. 144 °C
KM = 6.0 cm2 molꢀ1 ohmꢀ1
. Anal. Calc. for C22H20NOSePdCl: C,
49.38; H, 3.77; N, 2.62. Found: C, 49.31; H, 3.71; N, 2.69%.

3216
A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 26.61 (Ca), 29.75 (C5),
55.45 (C6), 115.13 (C12), 121.01 (C10), 126.48 (C8), 126.59 (C4),
127.03, 128.02, 128.54, 128.89, 129.54 (ArC: C15, C16, C17), 129.79
(C2, C1), 133.28 (C3), 134.35 (C13), 134.52 (C11), 136.23 (C14),
165.55 (C9), 171.04 (C7); 77Se{1H}NMR (57.24 MHz, CDCl3, 25 °C,
vs Me2Se): d = 273.7. IR(KBr, cmꢀ1): 1578, 743, 474.
128.86 (C15), 129.07 (C17), 129.54 (C2), 130.14 (C1), 131.56 (C3),
132.50 (C4), 132.96 (C13), 133.02 (C11), 133.70 (C14), 162.86 (C9),
175.13 (C7); 77Se{1H}NMR (57.24 MHz, CDCl3, 25 °C, vs Me2Se):
d = 339.2, 340.1. HRMS (ESI+) calcd. for C44H42N2O2Se2PtCl2 (M+)
1055.0602, found m/z 1055.0631 (
3438, 1596, 467, 338.
D
2.7862 ppm). IR(KBr, cmꢀ1):
[PdCl(L5-H)]
(7):
Yield ꢁ 0.53 g
(ꢁ89%);
m.p.171 °C.
[PtCl2(L6)2] (12): Yield ꢁ 0.98 g (ꢁ81%); m.p. 158 °C
KM = 8.0 cm2 molꢀ1 ohmꢀ1. Anal. Calc. for C46H46N2O4Te2PtCl2: C,
45.59; H, 3.83; N, 2.31. found: C, 45.51; H, 3.83; N, 2.37%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 16.40, 16.88, 18.00
(C5), 28.14, 29.08 (Ca), 51.87 (C6) 55.17, 55.21, 55.25, 55.27
(OCH3), 101.65, 102.38, 103.43 (C4), 115.10, 115.15, 115.22,
115.48 (C2), 117.30, 117.38 (C12), 117.83 (C10), 119.93 (C8),
125.56, 127.09, 127.77 (C16), 128.28, 128.74, 128.78 (C15), 129.06,
129.15, 129.19 (C17), 131.67, 132.70 (C13), 133.23 (C14), 133.85,
134.32 (C11), 136.98, 137.82, 138.36 (C3), 160.96, 161.24, 161.28
(C1), 163.19, 163.76, 167.59 (C9), 175.07 (C7); 125Te{1H}NMR
(94.69 MHz, CDCl3, 25 °C, vs Me2Te): d = 563.4, 578.5. HRMS
(ESI+) calcd for C46H46N2O4Te2PtCl2 (M+) 1215.0607, found m/z
KM = 8.0 cm2 molꢀ1 ohmꢀ1. Anal. Calc. for C22H20NO2TePdCl: C,
44.05; H, 3.36; N, 2.34. Found: C, 44.01; H, 3.39; N, 2.37%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 14.70 (C5), 55.29
(OMe), 65.50 (C6), 104.36 (C4), 114.61 (C12), 115.77 (C2), 121.19
(C10), 123.62 (C8), 127.08, 128.01, 128.66, 128.96, 129.02 (ArC:
C15, C16, C17), 133.82 (C11), 135.56 (C13) 136.13 (C14), 138.78 (C3),
161.23 (C1), 166.28 (C9), 170.40 (C7); 125Te{1H}NMR (94.69 MHz,
CDCl3, 25 °C, vs Me2Te) d = 755.4. IR(KBr, cmꢀ1): 1589, 512, 293.
[PdCl(L6-H)] (11): Yield ꢁ 0.47 g (ꢁ76%); m.p. 172 °C
KM = 8.0 cm2 molꢀ1 ohmꢀ1. Anal. Calc. for C23H22NO2TePdCl: C,
45.00; H, 3.61; N, 2.28. Found: C, 45.07; H, 3.68; N, 2.21%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 16.72 (C5), 27.50 (Ca),
55.25 (OMe), 60.58 (C6), 105.13 (C4), 114.43 (C12), 115.57 (C2),
121.06 (C10), 126.05 (C8), 127.06, 128.28, 128.72, 129.06 (ArC:
C15, C16, C17) 134.02 (C11), 134.79 (C13), 136.73 (C14), 138.46
(C3), 160.86 (C1), 165.33 (C9), 170.83 (C7); 125Te{1H}NMR
(94.69 MHz, CDCl3, 25 °C, vs Me2Te): d = 472.9. IR (KBr, cmꢀ1):
1596, 512, 293.
1215.0636 (
695, 586, 516, 414, 306.
D
2.3811 ppm). IR (KBr, cmꢀ1): 3450, 1592, 794, 740,
3.6. Synthesis of [(p-cymene)RuClL5/L6]Cl (9/13)
The [RuCl2(p-cymene)]2 (0.306 g, 0.5 mmol) dissolved in dichlo-
romethane (10 mL) and a solution of L5 (0.459 g, 1 mmol) or L6
(0.473 g, 1 mmol) prepared in dichloromethane (20 mL) were stir-
red together vigorously for 3 h. The solvent was removed on a ro-
tary evaporator which gave 9 or 13 as an orange coloured solid. It
was washed with hexane and dried in vacuo.
3.4. Synthesis of platinum(II) complex [Pt(L-H)Cl]
K2[PtCl4] (0.415 g, 1 mmol) dissolved in water (5 mL) and a
solution of L3 or L5 (1 mmol) prepared in acetone (10 mL) were
stirred together vigorously. A precipitate of 4 (yellow) or 8 (orange)
was immediately obtained. The precipitate was filtered, dried and
recrystallized from chloroform–hexane (60:40) mixture. Single
crystals were obtained in the case of 4.
[PtCl(L3-H)] (4): Yield ꢁ 0.54 g (ꢁ89%); m.p. 157 °C;
KM = 5.0 cm2 molꢀ1 ohmꢀ1 Anal. Calc. for C21H18NOSePtCl: C,
41.37; H, 2.98; N, 2.30. Found: C, 41.31; H, 2.91; N, 2.33%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 33.89 (C5), 63.75 (C6),
116.18 (C12), 121.64 (C10), 122.41 (C8), 124.44 (C4), 126.24,
126.96, 128.83, 129.06, 129.12 (ArC: C15, C16, C17), 129.56 (C2),
130.30 (C1), 133.16 (C3), 133.50 (C11), 134.43 (C13), 136.89 (C14),
163.30 (C9), 165.47 (C7); 77Se{1H}NMR (57.24 MHz, CDCl3, 25 °C,
vs Me2Se): d = 389.7. IR (KBr, cmꢀ1): 1578, 462, 746.
[PtCl(L5-H)] (8): Yield ꢁ 0.59 g (ꢁ86%); m.p. 181 °C;
KM = 9.0 cm2 molꢀ1 ohmꢀ1. Anal. Calc. for C22H20NO2TePtCl: C,
38.38; H, 2.93; N, 2.03. Found: C, 38.31; H, 2.97; N, 2.09%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 13.76 (C5), 55.32
(OCH3), 66.53 (C6), 101.24 (C4), 115.32 (C2), 115.79 (C12), 121.64
(C10), 123.15 (C8), 126.69, 127.17, 128.75, 128.98, 129.14 (ArC:
C15, C16, C17), 133.56 (C11), 134.76 (C13), 136.95 (C14), 138.35 (C3),
161.44 (C1), 164.37 (C9), 166.64 (C7); 125Te{1H}NMR (94.69 MHz,
CDCl3, 25 °C, vs Me2Te): d = 631.2. IR(KBr, cmꢀ1): 1584, 512, 287.
9: Yield ꢁ 0.64 g (ꢁ83%); m.p. 163 °C KM = 44 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C32H35NO2TeRuCl2: C, 50.18; H, 4.57; N,
1.83. Found: C, 50.13; H, 4.59; N, 1.87%. 13C{1H}NMR
(75.47 MHz, CDCl3, 25 °C): d = 18.43 (p-cymene CH3), 20.20 (C5),
22.00, 22.34 (CH3 of i-Pr of p-cymene), 30.73 (CH of i-Pr of p-cym-
ene), 49.20 (C6), 55.16 (OMe), 81.13, 81.33, 84.93 and 85.08 (ArC
of p-cymene m and o to i-Pr), 97.79 (ArC of p-cymene attached to
CH3), 104.34 (ArC of p-cymene attached to i-Pr), 106.27 (C4),
115.24 (C2), 117.41(C12), 117.53 (C10), 119.63 (C8), 126.81 (C16),
128.56 (C15), 128.83 (C17), 131.54 (C13), 132.30 (C11), 133.50
(C14), 137.70 (C3), 161.21 (C1), 162.40 (C9), 174.79 (C7);
125Te{1H}NMR (94.69 MHz, CDCl3, 25 °C, vs Me2Te): d = 505.5.
HRMS (ESI+) calcd. for C32H35NO2TeRuClH (MH+ꢀCl) 733.0540,
found m/z 733.0520 (D
2.7746 ppm). IR (KBr, cmꢀ1): 3436,
1598, 761, 705.
13: Yield ꢁ 0.62 g (ꢁ79%); m.p. 145 °C. KM = 52 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C33H37NO2TeRuCl2: C, 50.82; H, 4.75; N,
1.80. Found: C, 50.87; H, 4.79; N, 1.83%. 13C{1H}NMR (75.47 MHz,
CDCl3, 25 °C): d = 15.62 (C5), 18.31 (p-cymene CH3), 21.83 and
22.28 (CH3 of i-Pr of p-cymene), 29.70 (Ca), 30.64 (CH of i-Pr of
p-cymene), 52.19 (C6), 55.18 (OMe), 80.94, 81.62, 84.49 and
85.37 (ArC of p-cymene m and o to i-Pr), 97.38 (ArC of p-cymene
attached to CH3), 104.12 (ArC of p-cymene attached to i-Pr),
106.23 (C4), 115.41 (C2), 117.11 (C12), 117.75 (C10), 119.49 (C8),
126.95 (C16), 128.65 (C15), 128.92 (C17), 131.38 (C13), 132.28
(C11), 133.37 (C14), 136.97 (C3), 161.18 (C1), 163.18 (C9), 174.62
(C7); 125Te{1H}NMR (94.69 MHz, CDCl3, 25 °C, vs Me2Te):
d = 534.6. IR (KBr, cmꢀ1): 3440, 1592, 763, 712.
3.5. Synthesis of platinum(II) complexes [PtCl2(L)2]
K2[PtCl4] (0.415 g, 1 mmol) dissolved in water (5 mL) and a
solution of L4 (0.788 g, 2 mmol) or L6 (0.946 g, 2 mmol) prepared
in acetone (10 mL) were stirred together vigorously. A yellow pre-
cipitate of 6 or orange precipitate of 12 was immediately obtained,
which was filtered, washed with hexane (10 mL), dried and recrys-
tallized from chloroform–hexane (60:40) mixture.
3.7. Synthesis of [HgBr2 (L5/L6)2] (10/14)
[PtCl2(L4)2] (6): Yield ꢁ 0.92 g (ꢁ87%); m.p. 153 °C;
KM = 7.6 cm2 molꢀ1 ohmꢀ1; Anal. Calcd. for C44H42N2O2Se2PtCl2:
C, 50.12; H, 4.01; N, 2.66. Found: C, 50.16; H, 4.07; N, 2.69%.
13C{1H}NMR (75.47 MHz, CDCl3, 25 °C): d = 28.34 (C5), 31.42 (Ca),
50.83 (C6), 117.47 (C12), 117.81 (C10), 119.70 (C8), 127.07 (C16),
The HgBr2 (0.360 g, 1.0 m mol) was dissolved in 5 mL of ace-
tone. The solution of L5 (0.918 g, 2.0 mmol) or L6 (0.946 g,
2.0 mmol) made in 10 mL of chloroform was added to it with stir-
ring. The mixture was stirred further for 3 h. The solvent was evap-
orated off on a rotary evaporator. The resulting residue was

A. Kumar et al. / Inorganica Chimica Acta 362 (2009) 3208–3218
3217
washed with acetone, redissolved in minimum amount of chloro-
form and mixed with hexane. The resulting precipitate of 10 or
14 was filtered, washed with hexane (10 mL) and dried in vacuo.
10: Yield ꢁ 1.00 g (ꢁ78%); m.p.165 °C KM = 9.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C44H42N2O4Te2HgBr2: C, 41.30; H, 3.29; N,
2.19. Found: C, 41.38; H, 3.21; N, 2.11%. 13C{1H}NMR (75.47 MHz,
CDCl3, 25 °C): d = 20.30 (C5), 49.84 (C6), 55.35 (OMe), 101.40 (C4),
116.17 (C2), 117.81 (C12), 117.86 (C10), 119.71 (C8), 127.04 (C16),
128.93 (C15), 129.23 (C17), 131.95 (C13), 132.87 (C11), 133.57
(C14), 139.52 (C3), 161.34 (C1), 162.56 (C9), 175.85 (C7);
125Te{1H}NMR (94.69 MHz, CDCl3, 25 °C, vs Me2Te): d = 361.7.
HRMS (ESI+) calcd for C44H42N2O4Te2HgBr (M+ꢀBr) 1203.0159,
>C@N group and Se/Te. When these Schiff bases act as a tridentate
uni-negative ligand the binding with the Pd or Pt is very strong as
indicated by various M–L distances which are shorter than the sum
covalent radii. Palladium complexes have potential for catalyzing
Heck and Suzuki reactions (yield upto 85%). The advantage of using
them is that they are not air and moisture sensitive. Optimum cat-
alyst: aryl halide molar ratio was found be 1:1000 for Heck and Su-
zuki reactions both.
Acknowledgements
Authors thank Department of Science and Technology (India)
for Research Project No. SR/S1/IC-23/06 and for partial financial
assistance given to establish single crystal X-ray diffraction facility
at IIT Delhi, New Delhi (India) under its FIST programme. A.K.
thanks Council of Scientific and Industrial Research (India) for
the award of Junior/Senior Research Fellowship. M.A. thanks
Department of Science and Technology (India) for financial
support.
found m/z 1203.0138 (
1590, 584, 513, 420, 324.
D
1.7326 ppm). IR (KBr, cmꢀ1): 3412,
14: Yield ꢁ 1.10 g (ꢁ84%); m.p.172 °C KM = 8.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C46H46N2O4Te2HgBr2: C, 42.25; H, 3.52; N,
2.14. Found: C, 42.29; H, 3.58; N, 2.19%. 13C{1H}NMR (75.47 MHz,
CDCl3, 25 °C): d = 18.78 (C5), 30.58 (Ca), 52.36 (C6), 55.24 (OMe),
101.50 (C4), 116.08 (C2), 117.37 (C12), 117.87 (C10), 119.63 (C8),
127.14 (C16), 128.89 (C15), 129.12 (C17), 131.59 (C13), 132.54
(C11), 133.53 (C14), 139.07 (C3), 161.24 (C1), 163.12 (C9), 175.13
(C7); 125Te{1H}NMR (94.69 MHz, CDCl3, 25 °C, vs Me2Te):
d = 356.10. IR (KBr, cmꢀ1): 3424, 1594, 692, 586, 513, 416.
Appendix A. Supplementary material
CCDC 694461, 694462, 694463, 694464, 694465 and 694466
contains the supplementary crystallographic data for 1, 3, 4, 5, 7
and L1. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.ica.2009.02.031.
3.8. Procedure for catalytic Suzuki reaction
Bromobenzene or its derivative (1 mmol), benzeneboronic acid
(0.183 g, 1.5 mmol), K2CO3 (0.276 g, 2 mmol), distilled water
(0.5 mL), DMF (4 mL) and catalyst (complex 1/3/5/7) (0.001 mmol)
were taken in a two necked round bottom. The mixture was stirred
under reflux over an oil bath for 24 h at 100 °C under ambient con-
ditions. Thereafter, it was cooled to room temperature and mixed
with 20 mL of water. The product was extracted from the mixture
with hexane/diethyl ether (25ꢀ50 mL). The solvent was partly
evaporated on a rotary evaporator to get white crystalline solid
products, which were filtered and washed with 3ꢀ4 mL of hexane.
The NMR (1H and 13C{1H}) spectra of products were characteristic.
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A mixture of alkene (1.5 mmol), aryl halide (1 mmol), Na2CO3
(0.212 g, 2.0 mmol), DMF (4.0 mL) and catalyst (complex 1/3/5/7)
(0.001 mmol) was stirred under reflux on oil bath for 24 h at
100 °C under nitrogen atmosphere. After cooling the reaction mix-
ture to room temperature 20 mL of water was added to it and
products were extracted into dichloromethane (40 mL) and fil-
tered. To obtain (E)-1-(4-chloro/nitrophenyl)-2-phenylethene, the
filtrate was washed with water (3 ꢆ 25 mL) and evaporated on ro-
tary-evaporator. The residue was purified by silica gel column
chromatography using hexane–ethylacetate mixture (9:1) to ob-
tain the product. In case of (E)-3-(4-chloro/nitrophenyl)acrylic
acid, the cooled reaction mixture was further mixed with NaHCO3
(0.50 g) and water (30 mL) and stirred for 1 h at room temperature.
It was filtered and the filtrate was washed with CH2Cl2 (3 ꢆ 20 mL).
The aqueous phase was acidified with 5 N HCl and cooled to 0 °C.
The resulting solid precipitate of pure product was filtered, washed
and air dried.
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