Synthesis, structure and properties of delocalized transition metal chelates: Diazoketiminato chelates of Co(III) and Pt(II)

Article abstract of DOI:10.1016/j.poly.2007.08.029

The reactions of HL 1 [where HL is 1N-(2-pyridyl-2-methyl)-2-arylazoaniline and is formulated as ArN = NC₆H₄N(H)(CH₂C₅H₄N); Ar = C₆H₅ (for HL¹) or p-MeC₆H₄ (for HL²) or p-ClC₆H₄ (for HL³)] with K₂PtCl₄ and Co(ClO₄)₃ · 6H₂O afforded the (L)PtCl and [(L)₂Co]ClO₄ complexes, respectively. The HL ligands bind the platinum(II) and cobalt(III) centres in a tridentate (N,N,N) fashion, forming new diazoketiminato chelates upon dissociating the amino proton. The X-ray structures of (L³)PtCl and [(L³)₂Co]ClO₄ were determined. Redox properties of the new complexes have been examined.

Full text of DOI:10.1016/j.poly.2007.08.029

Available online at www.sciencedirect.com
Polyhedron 26 (2007) 5484–5490
www.elsevier.com/locate/poly
Synthesis, structure and properties of delocalized transition
metal chelates: Diazoketiminato chelates of Co(III) and Pt(II)
*
Debprasad Patra, Poulami Pattanayak, Jahar Lal Pratihar, Surajit Chattopadhyay
Department of Chemistry, University of Kalyani, Kalyani, West Bengal 741 235, India
Received 29 June 2007; accepted 10 August 2007
Available online 1 October 2007
Abstract
The reactions of HL 1 [where HL is 1N-(2-pyridyl-2-methyl)-2-arylazoaniline and is formulated as ArN = NC6H4N(H)(CH2C5H4N);
Ar = C6H5 (for HL1) or p-MeC6H4 (for HL2) or p-ClC6H4 (for HL3)] with K2PtCl4 and Co(ClO4)3 Æ 6H2O afforded the (L)PtCl and
[(L)2Co]ClO4 complexes, respectively. The HL ligands bind the platinum(II) and cobalt(III) centres in a tridentate (N,N,N) fashion,
forming new diazoketiminato chelates upon dissociating the amino proton. The X-ray structures of (L3)PtCl and [(L3)2Co]ClO4 were
determined. Redox properties of the new complexes have been examined.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: 1N-(2-Pyridyl-2-methyl)-2-arylazo aniline; Potassium tetrachloroplatinate; Cobalt(III) perchlorate; Diazoketiminato species
1. Introduction
amino protons [14,16,17]. On the other hand, the N-alkyl-
ated derivatives of 2-(arylazo)aniline afforded orthopalla-
dated complexes or delocalized diazoketiminato chelates
of Pd(II) according to the proposed mechanism as shown
in Scheme 1 [17,18].
Syntheses of transition metal chelates incorporating
delocalized ligands have emerged as an active area of chem-
ical research in recent years, to obtain clarification of issues
related to the oxidation states of the metal and ligand, the
nature of electron transfer processes and metal assisted
reactions [1–17].
Ar
N
N
N
Conjugated unsaturated organic ligands have been used
for the preparation of such delocalized transition metal
chelates [1–17]. Often deprotonation of a donor atom
during complexation is necessary for the formation of delo-
calized chelates [14–17]. Earlier we reported that 2-(ary-
lazo)aniline formed delocalized diazoketiminato chelates
of Pd(II) and Pt(II), A, upon dissociation of one of the
M
N
N
N
Ar
M=Pd / Pt
A
Thus the donor atom, i.e. X within the N-alkyl group of
1, plays an important role towards the exclusive formation
of diazoketiminato chelates.
*
Herein, we report the reactions of the ligand 1b with
K2PtCl4 and Co(ClO4)3 Æ 6H2O.
Corresponding author. Fax: +91 33 25828282.
E-mail address: scha8@rediffmail.com (S. Chattopadhyay).
0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.08.029

D. Patra et al. / Polyhedron 26 (2007) 5484–5490
5485
R
R
+
2-
Cl
N
N
N
PdCl4
+
Pd
Cl
H
N
N
N
N
Pd
R
N
H
N
5
H
3
[X=N]
N
+
R
N
X
N
R
H
Cl
N
1
H
Pd
2-
PdCl4
+
N
H
N
N
Pd
Cl
x
CH
N
H
N
1a
1b
H
4
2
X=CH
Scheme 1.
ligand has been isolated for the first time. Synthesis, X-
ray structures, redox properties and the plausible nature
of the redox orbitals have been reported in this paper.
R
R
H
HL
HL1
N
N
N
2. Results and discussion
HL2
HL3
CH3
Cl
X
2.1. Syntheses
H
The reaction of 1N-(2-pyridyl-2-methyl)-2-arylazo ani-
line, HL, with K2PtCl4 in methanol afforded a pink com-
plex of platinum (II) of the composition (L)PtCl 6
incorporating the tridentate (N,N,N) ligand (Scheme 2).
Reaction of HL 1b with Co(ClO4)3 Æ 6H2O in refluxing
methanol afforded the blue-violet bis complex of the com-
position [(L)2Co]ClO4 7 where Lꢀ binds the metal in a tri-
dentate (N,N,N) fashion (Scheme 2). In both cases the
1b
HL when X=N of 1b
Formation of a diazoketiminato chelate, like 5, sup-
ported our mechanistic proposal. The bis complex cation
of Co(III) incorporating the tridentate diazoketimine
Ar
Ar
Ar
N
N
N
N
Cl
N
N
N
K2PtCl4
Co(ClO4)3
N
N
N
Pt
ClO4
Co
N
N
N
H
N
N
N
Ar
1b
6
7
Scheme 2.

5486
D. Patra et al. / Polyhedron 26 (2007) 5484–5490
with the structure as determined by X-ray studies (see
1
below). The H NMR data are collected in Section 3.
2.3. X-ray structure of (L3)PtCl
Suitable crystals of (L3)PtCl were grown by the slow
evaporation of a dichloromethane–methanol mixed solu-
tion. The X-ray structure of (L3)PtCl was determined and
the perspective view of the molecule along with the atom
numbering scheme is shown in Fig. 2. Selected bond dis-
tances and angles are collected in Table 1. The geometry
about platinum is distorted square planar where the
(L3)ꢀ binds in a tridentate (N,N,N) fashion. A chloride
ligand satisfies the tetracoordination. The three nitrogen
Fig. 1. UV–Vis spectra of [(L1)2Co]ClO4 (---) and (L1)PtCl (—). The
arrows indicate scales of the corresponding spectra.
deprotonated secondary amino nitrogen binds the metal
forming a six-membered diazoketiminato chelate. Forma-
tion of a six-membered diazoketiminato chelate has been
attributed to the delocalisation of the negative charge
within the ligand backbone [14–17]. Complex 7 is diamag-
netic and is consistent with a low spin t62g configuration.
2.2. Characterization
All the Pt(II) complexes, (L)PtCl, exhibited a character-
istic low energy absorption near 580 nm which has been
assigned to a MLCT transition [14–18]. The low energy
absorption due to a MLCT transition for the [(L)2Co]ClO4
complexes has been observed near 570 nm. Representative
UV–Vis spectra of (L1)PtCl and [(L1)2Co]ClO4 are shown
in Fig. 1. Relevant data are collected in Section 3.
The IR spectra of HL [17] displayed a sharp singlet near
3189 cmꢀ1 for mN–H which was absent for both the com-
plexes (L)PtCl and [(L)2Co]ClO4, indicating the dissocia-
tion of the amino proton upon complexation. The mN@N
of the ligands (ꢁ1510 cmꢀ1) shifted to lower frequency
upon complexation (1400–1410 cmꢀ1), consistent with
coordination of the azo nitrogen [14–18]. The mPt-Cl of the
platinum complexes appeared at 325 cmꢀ1 [19,20]. The
cobalt complexes exhibited a broad absorption near
1100 cmꢀ1, characteristic of uncoordinated ClO4ꢀ. Rele-
vant data are included in Section 3.
Fig. 2. Perspective view of (L3)PtCl with the atom numbering scheme.
Hydrogen atoms are omitted.
Table 1
3
˚
Selected bond distances (A) and angles (°) for (L )PtCl
Bond distances
Pt(1)–N(1)
Pt(1)–N(3)
Pt(1)–N(4)
N(1)–N(2)
N(2)–C(7)
N(1)–C(1)
N(3)–C(12)
C(13)–C(14)
Pt(1)–Cl(1)
2.004(13)
1.957(11)
2.054(12)
1.265(19)
1.44(2)
1.38(2)
1.345(19)
1.50(2)
C(7)–C(12)
C(11)–C(12)
N(3)–C(13)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.40(2)
1.49(2)
1.44(2)
1.37(2)
1.39(3)
1.37(2)
1.43(2)
1.352(19)
The N–H resonance of the free ligands (d 9.37–
1
9.55 ppm) [17] were absent in the H NMR spectra of the
C(7)–C(8)
N(4)–C(14)
platinum and cobalt complexes, signifying the dissociation
of the N–H proton upon complexation. The resonance of
the methylene protons appeared in the platinum complexes
as a singlet (d 5.29–5.48 ppm), in contrast to the doublet of
the ligands (d 4.68–4.69 ppm), indicating the lack of vicinal
coupling due to the absence of the N–H proton [17]. The
resonances of the pair of methylene protons in the
[(L)2Co]+ ion appeared as two doublets signifying the sub-
stantial difference in chemical shielding within the pair.
Resonances for the other aromatic protons are consistent
2.540(3)
Bond angles
Cl(1)–Pt(1)–N(1)
Cl(1)–Pt(1)–N(4)
N(1)–Pt(1)–N(4)
N(3)–Pt(1)–N(4)
N(2)–C(7)–C(12)
C(12)–N(3)–C(13)
Pt(1)–N(4)–C(14)
92.6(4)
93.0(3)
174.2(5)
82.0(5)
127.4(13)
117.7(12)
113.0(9)
Cl(1)–Pt(1)–N(3)
N(1)–Pt(1)–N(3)
N(1)–C(1)–C(2)
Pt(1)–N(1)–N(2)
N(1)–N(2)–C(7)
Pt(1)–N(3)–C(12)
N(3)–C(13)–C(14)
173.5(4)
92.5(5)
117.3(14)
127.7(11)
122.5(14)
125.0(10)
110.1(12)

D. Patra et al. / Polyhedron 26 (2007) 5484–5490
5487
Table 2
donors are azo (N(azo)), pyridyl (N(py)) and deprotonated
amino (N(am)) nitrogens. The Pt–N(azo), Pt–N(py) and
Pt–Cl lengths (2.004(13), 2.054(12) and 2.540(3) A, respec-
3
˚
Selected bond distances (A) and angles (°) of [(L )2Co]ClO4
˚
Bond distances
Co–N(1)
Co–N(3)
Co–N(4)
Co–N(5)
1.919(3)
1.910(3)
1.980(3)
1.924(3)
1.915(3)
1.977(3)
1.413(5)
1.347(6)
1.410(6)
1.355(6)
1.420(5)
1.452(5)
1.468(4)
1.329(4)
1.449(4)
N(4)–C(18)
N(4)–C(14)
N(1)–N(2)
1.346(4)
1.344(4)
1.277(4)
1.292(3)
1.431(5)
1.345(6)
1.381(8)
1.374(5)
1.424(5)
1.421(6)
1.451(5)
1.343(4)
1.342(5)
1.358(4)
1.444(5)
tively) are within the normal range [15,19,20]. The geome-
˚
try about platinum is planar (mean deviation 0.067 A)
consistent with a dipositive oxidation state of platinum
and the uninegative ligand, since the complex is non-
electrolyte.
N(5)–N(6)
Co–N(7)
Co–N(8)
C(25)–C(26)
C(26)–C(27)
C(27)–C(28)
C(28)–C(29)
C(29)–C(30)
C(25)–C(30)
N(7)–C(31)
N(7)–C(30)
N(8)–C(32)
N(8)–C(36)
N(5)–C(19)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
C(7)–C(12)
N(3)–C(13)
N(3)–C(12)
N(1)–C(1)
˚
The C(12)–N(3) length (1.345(19) A) is shorter com-
˚
pared to a C–N single bond (N(1)–C(1) 1.38(2) A) in the
same molecule and is similar to the imine (C@N) distance
[14–17]. The effect of imine formation due to delocalisation
has been reflected in the adjacent phenyl ring (C(7)–C(12))
˚
which is distorted with two short (ꢁ1.37 A) and four long
˚
(ꢁ1.43 A) bonds [14–17]. Thus, the formation of a diazoke-
timinato chelate could be inferred from the X-ray results
and the structural formula of (L3)PtCl has been drawn
accordingly in 6 of Scheme 2 (vide supra). All the non-
hydrogen atoms of (L3)PtCl, excluding the pendant phenyl
ring (C(1)–C(6)), make a good plane (mean deviation
Bond angles
N(1)–Co–N(3)
N(1)–Co–N(5)
N(3)–Co–N(4)
N(2)–C(7)–C(12)
N(1)–Co–N(4)
N(5)–N(6)–C(25)
Co–N(3)–C(12)
N(3)–Co–N(7)
91.67(11)
88.09(12)
83.37(11)
126.3(3)
175.04(11)
122.5(3)
N(1)–N(2)–C(7)
N(5)–Co–N(3)
Co–N(1)–N(2)
N(8)–Co–N(7)
N(7)–Co–N(1)
C(14)–N(4)–C(18)
Co–N(4)–C(14)
N(5)–Co–N(7)
123.7(3)
93.19(12)
128.30(19)
83.32(12)
93.82(11)
118.7(3)
˚
0.220 A).
127.7(2)
172.68(14)
114.0(2)
91.83(12)
2.4. X-ray structure of [(L3)2Co]ClO4
Suitable crystals of [(L3)2Co]ClO4 were obtained from
the methanolic mother liquor. The X-ray structure of
[(L3)2Co]ClO4 was determined and the perspective view
of the [(L3)2Co]+ cation along with the atom numbering
scheme is shown in Fig. 3. Selected bond distances and
angles are collected in Table 2. The geometry about the
Co(III) centre is distorted octahedral, where the two anio-
nic ligands, [L3]ꢀ, coordinated meridionally give rise to a
[(L3)2Co]+. The relative orientations of N(py), N(azo) and
N(am) pairs are cis, cis and trans, respectively. Extensive
electron delocalisation along the ligand backbone is also
observed in this case. As a result, the C(12)–N(3) length
˚
˚
(1.329(4) A) and C(30)–N(7) length (1.343(4) A) are shorter
˚
compared to the C–N single bonds (N(1)–C(1) 1.449(4) A;
˚
N(5)–C(19) 1.444(5) A) in the same molecule and are sim-
CoN6 coordination sphere. A perchlorate ðClOꢀÞ ion satis-
4
ilar to the imine (C@N) distance [19–22]. The effect of
imine formation due to delocalisation has also been
reflected in the adjacent phenyl ring (C(7)–C(12)) which
fies the unipositive charge of the complex cation,
˚
is distorted with two short (ꢁ1.35 A) and four long
˚
(ꢁ1.42 A) bonds, consistent with the formation of a dia-
zoketiminato chelate [14–17,23]. The structural formula
of [(L3)2Co]ClO4 has been drawn accordingly in 7 of
Scheme 2 (vide supra).
2.5. Redox processes and nature of redox orbitals
(L3)PtCl and [(L3)2Co]ClO4 displayed one and two irre-
versible oxidative responses, respectively, in their cyclic
voltammograms (0.924 V versus SCE for the Pt(II) com-
plex and 0.78, 1.14 V versus SCE for the Co(III) complex).
To have an insight into the nature of the redox orbitals, the
EHMO results have been taken into account (Supplemen-
tary material). The HOMO of (L)PtCl and [(L)2Co]ClO4
(Figs. S20 and S22) were found to be primarily ligand orbi-
tals. Thus, the oxidative responses have been attributed to
ligand oxidations as given in
ꢀe
½ðLÞPtIIClꢂ ꢀꢀ! ½ðLÅÞPtClꢂþ
ð1Þ
ð2Þ
Fig. 3. Perspective view of [(L3)2Co]+ with the atom numbering scheme.
Hydrogen atoms and the perchlorate ion are omitted.
2þ
3þ
ꢀe
ꢀe
½ðLÞ2CoIIIꢂþ ꢀꢀ! ½ðLꢀÞðLÅÞCOꢂ ꢀꢀ! ½ðLÅÞðLÅÞCoꢂ

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D. Patra et al. / Polyhedron 26 (2007) 5484–5490
1
3. Experimental
3.1. Materials
pellets, cmꢀ1): mN@N 1400, mPt-Cl 324. H NMR (CDCl3,
ppm): d 9.72 (d, 1H); 7.97 (m, 2H); 7.90 (t, 1H); 7.67 (m,
2H); 7.60 (d, 1H); 7.37–7.29 (m, 3H); 7.04 (d, 1H); 6.67
(t, 1H); 5.47 (s, 2H).
The solvents used in the reactions were of reagent grade
obtained from E. Merck, Kolkata, India, and were purified
and dried by reported procedures [23,24]. 2-(Arylazo) ani-
lines and 1N-(2-pyridyl-2-methyl)-2-arylazoaniline were
prepared according to reported procedures [14,15,17].
Chloroplatinic acid, cobalt carbonate, potassium carbon-
ate, perchloric acid and potassium chloride were purchased
from E. Merck, Kolkata, India. 2-(Chloromethyl) pyridine
hydrochloride was purchased from Lancaster, England.
Potassium tetrachloroplatinate was prepared by reported
procedures [25]. Cobalt(III) perchlorate was prepared by
oxidation of Co(II) perchlorate with H2O2 [26].
3.3. Syntheses of the Co(III) complexes
The complexes [(L1)2Co]ClO4, [(L2)2Co]ClO4 and
[(L3)2Co]ClO4 were prepared by a similar procedure. A
representative example for [(L1)2Co]ClO4, is given below.
3.3.1. [(L1)2Co]ClO4
A solution of HL1 (0.2 g, 0.70 mmol) in 10 cm3 metha-
nol was added to a 5 cm3 methanolic solution of
Co(ClO4)3 Æ 6H2O (0.150 g, 0.35 mmol). The mixture was
refluxed for 1 h. The colour of the solution became blue-
violet. It was kept for five days. Pure crystalline solid of
[(L1)2Co]ClO4 was obtained. Yield: 65%. Anal. Calc. for
C36H30N8CoClO4, [(L1)2Co]ClO4: C, 58.98; H, 4.12; N,
15.28. Found: C, 59.00; H, 4.17; N, 15.25%. Electronic
spectrum (kmax/nm (ꢀ/dm2 molꢀ1), dichloromethane): 552
(5000), 368 (7300), 300 (21900). IR (KBr pellets, cmꢀ1):
3.2. Syntheses of the Pt(II) complexes
The complexes (L1)PtCl, (L2)PtCl and (L3)PtCl were
prepared by a similar procedure. A representative example
for (L1)PtCl, is given below.
1
mN@N 1409, mCl–O 1102. H NMR (CDCl3, ppm): d 7.76
3.2.1. (L1)PtCl
(t, 1H); 7.67 (d, 1H); 7.52–7.48 (m, 2H); 7.29–7.26 (m,
1H); 7.21–7.17 (m, 2H); 7.05 (t, 2H); 6.88 (d, 1H); 6.57
(t, 1H); 6.33 (d, 2H); 5.28 (d, 1H); 4.42 (d, 1H).
A solution of HL1 (0.1 g, 0.35 mmol) in 10 cm3 metha-
nol was added to a solution of K2PtCl4 (0.145 g,
0.35 mmol) in 5 cm3 water. The mixture was stirred for
15 h. The dark solid precipitate that formed was purified
by washing with benzene–petroleum ether (80:20) mixed
solvent. The pure solid was then dissolved in dichlorometh-
ane with a few drops of methanol and kept for crystallisa-
tion. Pure crystalline solid of (L1)PtCl was obtained. Yield:
50%. Anal. Calc. for C18H15N4PtCl, (L1)PtCl: C, 41.75; H,
2.92; N, 10.82. Found: C, 41.73; H, 2.90; N, 10.85%. Elec-
tronic spectrum (kmax/nm (e/dm2 molꢀ1), dichlorometh-
ane): 578 (2200), 359 (5000), 259 (14260). IR (KBr
3.3.2. [(L2)2Co]ClO4 and [(L3)2Co]ClO4
Complexes [(L2)2Co]ClO4 and [(L3)2Co]ClO4 were pre-
pared using the ligands HL2 and HL3 in place of HL1,
respectively. Yield: [(L2)2Co]ClO4, 70% and [(L3)2Co]ClO4,
60%.
Anal. Calc. for C38H34N8CoClO4, [(L2)2Co]ClO4: C,
59.96; H, 4.50; N, 14.72. Found: C, 59.90; H, 4.53; N,
14.70%. Electronic spectrum (kmax/nm (ꢀ/dm2 molꢀ1),
dichloromethane): 569 (6340), 368 (11000), 310 (22750).
1
1
pellets, cmꢀ1): mN@N 1405, mPt–Cl 326. H NMR (CDCl3,
IR (KBr pellets, cmꢀ1): mN@N 1410, mCl–O 1085. H NMR
ppm): d 9.67 (d, 1H); 7.99 (d, 1H); 7.88–7.83 (m, 2H);
7.66–7.62 (m, 1H); 7.59 (d, 1H); 7.42–7.39 (m, 3H); 7.36–
7.27 (m, 2H); 7.03 (d, 1H); 6.65 (t, 1H); 5.48 (s, 2H).
(CDCl3, ppm): d 7.88 (t, 1H); 7.64 (d, 1H); 7.53–7.50 (m,
2H); 7.33–7.26 (m, 2H); 6.83 (d, 3H); 6.61 (t, 1H); 6.19
(d, 2H); 5.15 (d, 1H); 4.44 (d, 1H); 2.25 (s, CH3).
Anal. Calc. for C36H28N8CoCl2ClO4, [(L3)2Co]ClO4: C,
53.91; H, 3.52; N, 13.97. Found: C, 53.88; H, 3.55; N,
13.95%. Electronic spectrum (kmax/nm (ꢀ/dm2 molꢀ1),
dichloromethane): 570 (5560), 363 (10120), 304 (21660).
3.2.2. (L2)PtCl and (L3)PtCl
Complexes (L2)PtCl and (L3)PtCl were prepared using
the ligands HL2 and HL3 in place of HL1. Yield: (L2)PtCl,
50% and (L3)PtCl, 55%, respectively.
1
IR (KBr pellets, cmꢀ1): mN@N 1408, mCl–O 1089. H NMR
Anal. Calc. for C19H17N4PtCl, (L2)PtCl: C, 42.89; H,
3.19; N, 10.53. Found: C, 42.92; H, 3.23; N, 10.50%. Elec-
tronic spectrum (kmax/nm (ꢀ/dm2 molꢀ1), dichlorometh-
ane): 579 (1230), 358 (2750), 259 (7483). IR (KBr pellets,
(CDCl3, ppm): d 7.78 (t, 1H); 7.67 (d, 1H); 7.53 (d, 1H);
7.45 (d, 1H); 7.35 (t, 1H); 7.24 (d, 1H); 7.01 (d, 2H); 6.94
(d, 1H); 6.61 (t, 1H); 6.27 (d, 2H); 5.37 (d, 1H); 4.47 (d,
1H).
1
cmꢀ1): mN@N 1402, mPt–Cl 325. H NMR (CDCl3, ppm): d
9.61 (d, 1H); 8.13 (d, 1H); 7.97–7.96 (m, 2H); 7.35–7.29
(m, 3H); 7.26–7.21 (m, 3H); 7.17–7.23 (m, 1H); 6.62 (m,
1H); 5.29 (s, 2H); 2.40 (s, 3H).
3.4. Physical measurements
Microanalyses (C, H, N) were performed using a Per-
kin–Elmer 240C elemental analyzer. Infrared spectra were
recorded on a Perkin–Elmer L120-00A FT-IR spectrome-
ter with the samples prepared as KBr pellets. Electronic
spectra were recorded on a Shimadzu UV- 2401 PC
Anal. Calc. for C18H14N4PtCl2, (L3)PtCl: C, 39.14; H,
2.56; N, 10.14. Found: C, 39.10; H, 2.60; N, 10.20%. Elec-
tronic spectrum (kmax/nm (ꢀ/dm2 molꢀ1), dichlorometh-
ane): 581 (3200), 359 (7050), 258 (18380). IR (KBr

D. Patra et al. / Polyhedron 26 (2007) 5484–5490
5489
Table 3
hypothetical mechanism of reaction between HL and metal
substrates has been further supported with the formation
of diazoketiminato chelates of Pt(II) and Co(III). The
redox properties of the complexes have been assumed to
be due predominantly to ligand centered.
Crystallographic data for (L3)PtCl and [(L3)2Co]ClO4
Chemical
formula
(C18H14Cl2N4Pt) Æ 0.5CH2Cl2 C36H28Cl2CoN8 Æ ClO4
Formula weight
Crystal system
Space group
594.78
801.94
triclinic
triclinic
ꢀ
ꢀ
P1 (no. 2)
P1 (no. 2)
˚
Acknowledgement
a (A)
11.2488(4)
11.9115(4)
16.0851(5)
89.647(2)
78.830(2)
69.847(2)
0.71073
1980.67(12)
4
10.9360(7)
11.5597(7)
14.9478(14)
100.236(2)
99.415(2)
106.886(2)
0.71073
1732.3(2)
2
˚
b (A)
˚
c (A)
We are thankful to the DST (New Delhi) for funding
and fellowship to J.P. under DST-SERC Project (No.
SR/S1/IC-09/2003). The necessary laboratory and infra-
structural facilities are provided by the Dept. of Chemistry,
University of Kalyani. The support of DST under FIST
program to the Department of Chemistry, University of
Kalyani is acknowledged. We acknowledge Prof. Jui-Hsien
Huang, National Changhua University of Education,
Changhua, Taiwan for X-ray studies.
a (°)
b (°)
c (°)
˚
k (A)
3
˚
V (A )
Z
F(000)
1132
820
Temperature (K) 293
qcalc. (Mg/m3)
1.995
l (mmꢀ1
R (all data)
wR2 [I > 2r(I)]
Goodness-of-fit
293
1.538
)
7.499
0.0537
0.1882
1.26
0.781
0.0493
0.1550
0.98
Appendix A. Supplementary material
CCDC 652204 and 652203 contain the supplementary
crystallographic data for (L3)PtCl and [(L3)2Co]ClO4.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-
ciated with this article can be found, in the online version,
at doi:10.1016/j.poly.2007.08.029.
spectrophotometer. 1H NMR spectra were obtained on
Brucker Avance RPX 500 NMR spectrometers in CDCl3
and in DMSO, using TMS as the internal standard. Elec-
trochemical measurements were performed using a PAR
Versastat II potentiostat, a platinum disk working elec-
trode, a platinum wire auxiliary electrode and aqueous sat-
urated calomel (SCE) as the reference, (0.1 M) Bu4NClO4
supporting electrolyte, and in acetonitrile solvent. Electro-
chemical measurements were carried out under a dinitro-
gen atmosphere at 298 K and were uncorrected for
junction potentials.
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