Cent. Eur. J. Chem. • 6(1) • 2008 • 55-64
DOI: 10.2478/s11532-007-0063-3
Central European Journal of Chemistry
H, 13C, 15N NMR and 13C, 15N CPMAS studies
of cobalt(III)-chloride-pyridine complexes,
spontaneous py → Cl substitution in
trans-[Co(py)4Cl2]Cl, and a new synthesis
of mer-[Co(py)3Cl3]
1
Research article
Leszek Pazderski1*, Andrzej Surdykowski1, Małgorzata Pazderska-Szabłowicz1,
Jerzy Sitkowski2,3, Lech Kozerski2,3, Bohdan Kamieński3, Edward Szłyk1
1
Faculty of Chemistry, Nicholas Copernicus University,
Gagarina 7, PL-87100, Toruń, Poland
2
National Drug Institute, Chełmska 30/34,
PL-00725, Warsaw, Poland
3
Institute of Organic Chemistry, Polish Academy of Sciences,
Kasprzaka 44/52, PL-01224, Warsaw, Poland
Received 5 September 2007; Accepted 23 November 2007
Abstract: trans-[Co(py)4Cl2]Cl·6H2O, mer-[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl] were studied by UV-Vis, far-IR and 1H, 13C,
15
N NMR. The formation of Co-N bonds lead to variable in sign and magnitude changes of 1H NMR chemical
shifts, heavily dependent on proton position, coordination sphere geometry and character of auxiliary ligands.
13
C nuclei were deshielded upon Co(III) coordination, while 15N NMR studies exhibited ca. 85-110 ppm shielding effects (ca. 15-25 ppm more expressed for nitrogens trans to N than trans to Cl or O). 13C and 15N CPMAS
spectra revealed a slight inequivalency of formally identical Co-py bonds in trans-[Co(py)4Cl2]Cl·6H2O and mer[Co(py)3Cl3], suggesting for the latter complex an existence of distortion isomers. In chloroform, a spontaneous
trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction was monitored by 1H NMR and UV-Vis. This process of py
→ Cl substitution allowed the design of a more convenient and efficient method of mer-[Co(py)3Cl3] preparation.
Keywords: Co(III) complexes • Pyridine complexes • 15N NMR • 15N CPMAS • NMR coordination shifts
© Versita Warsaw and Springer-Verlag Berlin Heidelberg.
1. Introduction
Co(III) chloride complexes with pyridine (py), trans[Co(py)4Cl2]Cl·6H2O [1] and mer-[Co(py)3Cl3] [2], have
been known for years. Owing to the lability of py ligands,
the former compound, readily prepared by oxidation
of trans-[Co(py)4Cl2] [3,4] with gaseous chlorine [5,6],
is widely used as a facile and versatile precursor for
synthesis of more complicated Co(III) species [7]. In
contrast, mer-[Co(py)3Cl3] is unwillingly applied by
inorganic chemists because its preparation requires
as many as three time-consuming steps: (a) reaction
of CoCl2 with KHCO3 + H2O2 to K3[Co(CO3)3] [8]; (b)
its reaction with py + HCl to mer-[Co(py)3(CO3)Cl] [9];
(c) its reaction with HCl to mer-[Co(py)3Cl3] [2]; their
efficiency (especially of stage (b)) is heavily dependent
on appropriate conditions, resulting in a relatively low
overall yield (ca. 15%). Other attempts to manufacture
mer-[Co(py)3Cl3], e.g. from [Co(H2O)6]3+, have been
unsuccessful due to the instability of the latter cation,
which oxidises water molecules (Eo[Co(H2O)6]3+/[Co(H2O)6]2+
= 1.83 V [10]). Moreover, mer-[Co(py)3Cl3] cannot be
* E-mail: [email protected]
55
Unauthenticated
Download Date | 6/18/17 6:43 AM
H,
1
C,
13
directly prepared by oxidation of aqueous CoCl2 + py
mixtures (which is a common procedure for obtaining
Co(III) chloride-azine complexes, e.g. those of cis[Co(LL)2Cl2]Cl formula, where LL = 2,2’-bipyridine
or 1,10-phenanthroline [11,12]), because the only
product is again trans-[Co(py)4Cl2]+ [1,5,6,13]. In the
past, Shevchenko et al. reported mer-[Co(py)3Cl3] as
the main product of trans-[Co(py)4Cl2]Cl·6H2O thermal
decomposition at 50-80oC [14], however, this technique
was unsuitable for preparative purposes due to the
formation of some other by-products. Thus, alternative
methods of mer-[Co(py)3Cl3] manufacture are interesting
from the practical point of view. In this paper we
describe a new, more convenient and efficient method
of its synthesis from easily available trans-[Co(py)4Cl2]
Cl·6H2O. We have monitored this process, occurring
spontaneously in chloroform, by 1H NMR and UV-Vis
spectroscopies.
Besides its potential utility as a reactant in inorganic
syntheses, mer-[Co(py)3Cl3] is a relatively rare example
of a cobalt(III) complex containing three identical azine
ligands, in contrast to the more prevalent tetrakis- and
hexakis- derivatives. To the best of our knowledge,
only a few species having exactly three py molecules
inside Co(III) coordination sphere have been previously
described– [Co(py)3Br3] [14], [Co(py)3(CO3)Cl] [2],
[Co(py)3(CO3)(H2O)]+ [2,15], [Co(py)3(H2O)3]3+ [2,15,16],
[Co(py)3Cl(H2O)2]2+
[2,16,17],
[Co(py)3Cl2(H2O)]+
[2], [Co(py)3F(H2O)2]2+ [2], [Co(py)3F2(H2O)]+ [2,18],
[Co(py)3ClF(H2O)]+ [2], [Co(py)3(NCS)2Cl] [19] (their
geometry being uncertain, although mer- configurations
have been usually proposed), and mer-[Co(py)3(N3)3].
The latter compound was previously investigated
by single crystal X-ray diffraction (JOZNAN [20]; all
reference codes in this paper are from the Cambridge
Structural Database [21]), which proved the meridional
arrangement of the py and azide ligands. In contrast,
the X-ray structure of mer-[Co(py)3Cl3] has not yet been
described, its geometry being proposed on the basis of
X-ray powder diffraction pattern similarity [2,22] to mer[Cr(py)3Cl3] (QQQFYV01 [23]) and mer-[Mo(py)3Cl3]
(CLPYMO10 [22]).
The aim of the present work was the confirmation
of meridional geometry for mer-[Co(py)3Cl3] (by farIR and 1H NMR), as well as multinuclear (1H, 13C, 15N)
magnetic resonance studies of trans-[Co(py)4Cl2]+, mer[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl] – both in solution
and as a solid phase. Particularly, we have obtained 1H13
C and 1H-15N HMBC spectra of all the above species,
as well as those of 13C and 15N CPMAS for trans[Co(py)4Cl2]Cl·6H2O and mer-[Co(py)3Cl3]. We discuss
the Co(III)-induced NMR coordination shifts in respect
to the assumed molecular structures of the studied and
15
N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine
complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl,
and a new synthesis of mer-[Co(py)3Cl3]
related coordination compounds, completing our recent
reports on similar diamagnetic transition metal chlorideazine complexes [24-28]. Finally, an additional result
of these NMR experiments was the discovery of the
trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction,
occurring spontaneously in CDCl3.
2. Experimental
2.1. Materials
CoCl2·6H2O (99%), KHCO3 (98.5%), py (99%) and 30%
H2O2 were purchased from POCh Gliwice, Poland.
Two types of chloroform were used: CHCl3 (a) – 99.8%
“for spectroscopic analyses” (POCh) and CHCl3 (b) –
98% “pure for laboratory purposes” (Chempur Piekary
Śląskie, Poland). The NMR solvents: CDCl3 (99.8% 2H
(or D) ), DMSO-d6 (99.8% D) and D2O (99.95% D) were
supplied by Armar Chemicals Switzerland.
2.2. Instruments
UV-Vis spectra were recorded with a Hewlett-Packard
8453 spectrophotometer, in 4⋅10-4 M (visible region)
and 3.2-4⋅10-5 M (UV range) aqueous or CHCl3 (a)
solutions, at 298 K. IR spectra were measured by a
Perkin-Elmer Spectrum 2000 FT-IR spectrometer, using
KBr (400-4000 cm-1) and polyethylene discs (100-400
cm-1). 1H and 13C NMR spectra were detected with a
Bruker Avance 300-MHz NMR spectrometer, at 298
K in 0.01-0.1 M CDCl3, DMSO-d6 or D2O solutions, in
respect to TMS. 1H-15N HMBC-NMR measurements
were performed in CDCl3 or DMSO-d6 by a Varian
INOVA 500 MHz-NMR spectrometer, equipped with an
inverse 1H{31P/15N} 5 mm Z-SPEC Nalorac probe with an
actively shielded z-gradient coil, in respect to external
CH3NO2. 13C and 15N CPMAS spectra were acquired on
a Bruker AVANCE DRX 500-MHz spectrometer using
a Bruker MASVTN500SB BL4 probehead and 4 mm
zirconia rotors, using a 12 kHz spinning speed, at 297 K.
They were referenced to solid glycine and recalculated
to TMS (δ(CH2 in glycine) = 43.3 ppm) or nitromethane
(δ(NH2 in glycine) = -347.6 ppm).
2.3. Synthesis
trans-[Co(py)4Cl2]Cl·6H2O was obtained by modification
of the Babayeva and Elgy method [5,6]. 23.8 g of
CoCl2·6H2O (0.1 mol) was dissolved in 250 cm3 of water,
and 32 cm3 of py (31.3 g, 0.4 mol) added. The blue
solution was stirred for 1h at 20oC and cooled to 5oC. The
pink precipitate of neutral trans-[Co(py)4Cl2] [3,4] was
filtered and washed with water. Gaseous Cl2 was passed
through the prepared aqueous suspension (250 cm3) for
56
Unauthenticated
Download Date | 6/18/17 6:43 AM
L. Pazderski et al.
6 h, with intense stirring. When the solution changed its
colour to brown-green, 100 cm3 of 4 M HCl was added,
and the reaction mixture filtered. The green filtrate
containing trans-[Co(py)4Cl2]+ cations was evaporated
at 60oC to 25 cm3 and diluted with ethanol to 100
cm3. The dark-green precipitate of trans-[Co(py)4Cl2]
Cl·6H2O was filtered, washed with ethanol and dried
in air. The crude product was purified by dissolution
in water at 40oC, fine filtration and re-precipitation by
cooling to 5oC. Yield was 41.0 g (70%).
mer-[Co(py)3(CO3)Cl] and mer-[Co(py)3Cl3] were
prepared following the modified Laier and Springborg
method [2,9]. 23.8 g of CoCl2·6H2O (0.1 mol) was
dissolved in 500 cm3 of water, then 25 cm3 of 30% H2O2
and 150 g of solid KHCO3 (1.5 mol) added. The darkgreen solution containing [Co(CO3)3]3- anions [8] was
cooled to 0-2oC. A mixture of 20 cm3 of py (19.5 g, 0.25
mol) and 60 cm3 of 12 M HCl was added by drops, with
rapid evolution of CO2. The red-violet solution was left
for 1 week to evaporate in air. The blue-violet residue
of mer-[Co(py)3(CO3)Cl] was washed with water and
ethanol, then dried in air; yield was 7.8 g (20%).
In another synthetic procedure, the whole amount
of mer-[Co(py)3(CO3)Cl] was further used as reactant.
It was dissolved in 20 cm3 of 12 M HCl, with intensive
liberation of CO2; from the green solution immediately
precipitated a light-green powder of mer-[Co(py)3Cl3].
The precipitate was filtered, washed with water and
ethanol, then dried in air; yield was 4.0 g (50% in
respect to mer-[Co(py)3(CO3)Cl], i.e. 10% to CoCl2).
Both crude products were purified by dissolution in
CHCl3 (a), fine filtration and evaporation.
A new method of mer-[Co(py)3Cl3] synthesis started
from trans-[Co(py)4Cl2]Cl·6H2O. 0.59 g (1 mmol) was
dissolved in 100 cm3 of CHCl3 (a). The green-blue
solution was left in darkness for 1 week, at 20oC,
resulting in its colour changing to deep green. This
solution was filtered and evaporated under a stream
of cold air. The use of high quality chloroform, as
well as the absence of heating and sunlight were
crucial in order to obtain a pure product (vide infra).
The light-green powder was washed with water (in
order to remove residual trans-[Co(py)4Cl2]Cl) and
dried in air. The yield was 0.35 g (87% in respect to
trans-[Co(py)4Cl2]Cl·6H2O, i.e. 61% to CoCl2); hence,
the new procedure was ca. 6-fold more efficient than
the old one. After purification, IR, far-IR and UV-Vis
spectra of the obtained solid were identical with those
(vide infra) of the previously prepared mer-[Co(py)3Cl3]
sample, confirming the identity of both coordination
compounds.
We tried to hasten the above procedure by heating
to 50oC or by addition of small amounts of 12 M HCl
(0.05 cm3 into 100 cm3 of CHCl3 (a)), assuming that the
trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py substitution
process might be catalysed by an excess of Cl- anions.
However, upon such conditions the formed product was
contaminated by some blue species (probably containing
Co(II)), easily detected by 1H NMR spectroscopy due
to their paramagnetic character. Similarly polluted mer[Co(py)3Cl3] samples were obtained when the reaction
mixture was exposed to sunlight or when CHCl3 (b) of
lower purity was used (it concerned also long-standing
CHCl3 (a)). In contrast, very pure mer-[Co(py)3Cl3] was
formed in CDCl3 during NMR measurements (vide
infra).
3. Results and discussion
3.1. UV-Vis spectra of trans-[Co(py)4Cl2]Cl and
mer-[Co(py)3Cl3]
In order to study the trans-[Co(py)4Cl2]Cl → mer[Co(py)3Cl3] reaction, we characterised both the reactant
and the product by UV-Vis, IR and far-IR spectroscopy.
trans-[Co(py)4Cl2]Cl·6H2O in water exhibits two d-d
transitions in the visible region (λmax = 508 nm, ε = 32
M-1·cm-1; λmax = 636 nm, ε = 44 M-1·cm-1), in agreement
with reports of Glerup (λmax = 505 nm, ε = 30 M-1·cm-1;
λmax = 631 nm, ε = 43 M-1·cm-1; in 0.01 M HCl [18]) and
Schevchenko (λmax = 510 nm, ε = 37 M-1·cm-1; λmax =
640 nm, ε = 42 M-1·cm-1; in H2O [14]), as well as two
other bands in the UV range (λmax = 232 nm, ε ≈ 40000
M-1·cm-1; λsh = 295 nm, ε ≈ 10000 M-1·cm-1), which are
probably charge-transfer or π → π* transitions. An
accurate determination of those spectral parameters
in CHCl3 (a) has been more difficult because trans[Co(py)4Cl2]Cl dissolves very slowly in chloroform, while
its conversion into mer-[Co(py)3Cl3] starts immediately.
Nevertheless, after ca. 30 minutes three d-d bands
have been observed in the visible region (λmax = 519
nm, ε ≈ 30 M-1·cm-1; λsh = 613 nm, ε ≈ 50 M-1·cm-1; λmax
= 637 nm, ε ≈ 60 M-1·cm-1).
mer-[Co(py)3Cl3] reveals in CHCl3 (a) three d-d
bands (λsh = 610 nm, ε = 99 M-1·cm-1; λmax = 633 nm, ε =
116 M-1·cm-1; λsh = 667 nm, ε = 98 M-1·cm-1), consistent
with the report of Laier (λsh = 600 nm, ε = 49 M-1·cm-1;
λmax = 640 nm, ε = 60 M-1·cm-1; λsh = 670 nm, ε = 58
M-1·cm-1 [2]); however, we have found molar absorption
coefficients ca. twice as large. Two charge-transfer or
π → π* transitions appear at λmax ≈ 250 nm (ε ≈ 21000
M-1·cm-1) and λsh = 307 nm (ε ≈ 7400 M-1·cm-1), the
former values being relatively uncertain due to the
solvent absorption starting below 250 nm. Another wellshaped maximum is present at λmax = 433 nm (ε = 682
57
Unauthenticated
Download Date | 6/18/17 6:43 AM
H,
1
C,
13
M-1·cm-1), being entirely absent in trans-[Co(py)4Cl2]
Cl·6H2O; this band allows for an easy distinction of both
complexes.
3.2. IR and far-IR spectra of trans-[Co(py)4Cl2]
Cl and mer-[Co(py)3Cl3]
IR spectra of trans-[Co(py)4Cl2]Cl·6H2O and mer[Co(py)3Cl3] in the 400-1700 cm-1 range are very similar,
exhibiting a large number of py ring skeletal vibrations
(1636, 1604, 1481, 1445, 1348, 1236, 1213, 1155, 1067,
1016, 870, 764, 697, 646, 475 cm-1 and 1633, 1601,
1479, 1442, 1347, 1232, 1214, 1147, 1066, 1014, 872,
762, 694, 645, 466 cm-1, respectively).
The far-IR spectrum of trans-[Co(py)4Cl2]Cl·6H2O
reveals an intense absorption band at 388 cm-1,
assigned to the only IR-active Co-Cl stretching vibration
(A2u, assuming D4h symmetry of the trans-MCl2N4
chromophore [29]). This νCo-Cl parameter is higher by ca.
25 cm-1 than νRh-Cl in trans-[Rh(py)4Cl2]Cl (362-364 cm-1
[30-32]) and by ca. 55 cm-1 than νIr-Cl in trans-[Ir(py)4Cl2]
Cl (335 cm-1 [30]), following the rule that energies of
metal-chlorine stretching modes diminish with the
increase of the central atom mass. It is also ca. 25-35
cm-1 higher than νCo-Cl in several other Co(III) chloride
complexes (trans-[Co(py)4Cl2][Co(py)Cl3] – 353 cm-1 [13],
trans-[Co(NH3)4Cl2]Cl – 352 cm-1 [33], trans-[Co(en)2Cl2]
Cl – 365 cm-1 [33]), whereas as much as ca. 180 cm-1
higher when compared to the respective Co(II) species
(trans-[Co(py)4Cl2] – 210 cm-1 [34]). The only IR-active
Co-N stretching mode (Eu [29]) appears at 248 cm-1,
this νCo-N value being similar to that in trans-[Co(py)4Cl2]
[Co(py)Cl3] (256 cm-1 [13]), and ca. 15-35 cm-1 higher
than in trans-[Co(py)4Cl2] (221-232 cm-1 [34,35]) or
trans-[Co(py)4(NCS)2] (212-215 cm-1 [34,35]). Hence,
the respective νCo-Cl and νCo-N frequencies are generally
higher for Co(III) than Co(II) coordination compounds.
mer-[Co(py)3Cl3] exhibits three νCo-Cl bands (2A1+B1,
assuming C2v symmetry of the mer-MCl3N3 chromophore
[29]) at 381, 360 and 329 cm-1. These values are again
higher by ca. 25-40 cm-1 than in mer-[Rh(py)3Cl3] (νRh= 355-358, 332-334, 290-297 cm-1 [30,31,36]), and
Cl
by ca. 25-55 cm-1 than in mer-[Ir(py)3Cl3] (νIr-Cl = 329,
318, 307 cm-1 [30]), as well as by ca. 15-25 cm-1 when
compared to mer-[Cr(py)3Cl3] (νCr-Cl = 364, 341, 307 cm-1
[30]). The three νCo-N bands (2A1+B2) appear at 278, 250
and 237 cm-1, corresponding well to those reported for
mer-[Co(py)3(N3)3] (255, 235 and 215 cm-1 [20]).
15
N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine
complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl,
and a new synthesis of mer-[Co(py)3Cl3]
3.3. 1H, 13C, 15N NMR spectra of trans[Co(py)4Cl2]Cl, mer-[Co(py)3Cl3] and mer[Co(py)3(CO3)Cl]
trans-[Co(py)4Cl2]Cl·6H2O readily dissolves in D2O or
DMSO-d6, and sparingly in CDCl3, exhibiting in these
solvents only one set of 1H resonances within ca. 7.28.25 ppm, ca. 7.55-8.35 ppm and ca. 7.35-8.4 ppm range,
respectively (Table 1, Fig. 1 top). The presence of exactly
three proton signals in each NMR spectrum proves an
equivalency of all py ligands in the trans-[Co(py)4Cl2]+
cation or the trans-[Co(py)4Cl2]Cl ion pair (we assume
dissociation of this chloride salt in D2O and DMSO-d6 but
rather not in CDCl3). Comparing to free py in DMSO-d6
or CDCl3 (remarks (a) and (b) under Table 1), H(2) atoms
are moderately shielded (by ca. 0.2-0.25 ppm), whereas
H(3) and H(4) are deshielded (by ca. 0.1-0.2 ppm and
ca. 0.3-0.4 ppm, respectively); nevertheless, the order
of proton signals remains the same (H(2) > H(4) > H(3),
decreasing chemical shifts). We have not determined 1H
coordination shifts in D2O because, in our opinion, the
comparison to the spectrum of the uncoordinated ligand
in an aqueous medium would be unreliable – mainly due
to the fact that this free azine forms strong hydrogen
bonds with water molecules (this solvation results in a
large variability of δ1H parameters, heavily depending
on concentration). Hence, the observed changes of 1H
chemical shifts in D2O would rather reflect the difference
between Co(III) coordination and H-bond formation,
than the real complexation effect.
The 1H NMR spectrum in D2O does not vary with
time (for at least 1 week), while in DMSO-d6 some new
signals (up to 10% intensity) appear within 24 hours,
probably due to the substitution of py or chlorides by
solvent molecules (DMSO is well-known to have its own
ligating ability); in CDCl3 the trans-[Co(py)4Cl2]Cl → mer[Co(py)3Cl3] + py transformation starts immediately (vide
infra).
The comparison to literature data for some other
diamagnetic transition metal complexes of octahedral
geometry and trans-[M(py)4Cl2]n+ formulae (n = 0-2),
which contain four equatorial py molecules and two axial
chlorides, exhibited a similar shielding of H(2), although
the effect was usually weaker, while effects at H(3)
and H(4) were of variable sign and magnitude: trans[Ru(py)4Cl2] – δH(2) = 8.5-8.57 ppm, δH(3) = 7.0-7.06 ppm,
δH(4) = 7.5-7.60 ppm (in CDCl3) [37,38] and δH(2) = 8.54
ppm, δH(3) = 7.11 ppm, δH(4) = 7.66 ppm (in CD2Cl2) [39];
trans-[Pt(py)4Cl2](NO3)2 – δH(2) = 8.45 ppm, δH(3) = 7.54
ppm, δH(4) = 8.23 ppm (in D2O) [40]. A larger influence
of cobalt(III) than ruthenium(II) or platinum(IV) chloride
coordination (all these ions having the same d6 low-spin
electron configuration) may be explained by the smaller
58
Unauthenticated
Download Date | 6/18/17 6:43 AM
L. Pazderski et al.
Table 1.
H, 13C, 15N NMR chemical shifts (δ1H, δ13C, δ15N; ppm) for trans-[Co(py)4Cl2]Cl, mer-[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl], in D2O (A),
DMSO-d6 (B), CDCl3 (C); the relevant coordination shifts (in parentheses: ∆coord = δcomplex - δligand) were determined in respect to free py
in the same solvent (except for D2O).
1
Compound
H(2)
H(3)
H(4)
C(2)
C(3)
C(4)
Trans-[Co(py)4Cl2]Cl•6H2OA
8.23
7.21
7.86
157.4
125.3
140.6
Trans-[Co(py)4Cl2]Cl•6H2OB,a
8.33
(-0.23)
7.54
(+0.17)
8.13
(+0.36)
157.3
(+7.6)
125.5
(+1.7)
140.9
(+4.8)
-172.9
(-109.8)
Trans-[Co(py)4Cl2]Cl•6H2OC,b
8.37
(-0.23)
7.36
(+0.08)
8.00
(+0.33)
Mer-[Co(py)3Cl3] (axial py)C,b
9.01
(+0.41)
7.24
(-0.04)
7.76
(+0.09)
158.7
(+8.8)
123.4
(-0.4)
138.4
(+2.5)
ca. -172
(ca. -103)
Mer-[Co(py)3Cl3] (equatorial py)C,b
8.67
(+0.07)
7.22
(-0.06)
7.83
(+0.16)
156.7
(+6.8)
124.1
(+0.3)
139.1
(+3.2)
ca. -157
(ca. -88)
Mer-[Co(py)3(CO3)Cl] (axial py)C,b
8.46
(-0.14)
7.24
(-0.04)
7.73
(+0.06)
152.6
(+2.7)
123.2
(-0.6)
137.2
(+1.3)
-168.9
(-100.2)
Mer-[Co(py)3(CO3)Cl] (equatorial py)C,b
9.05
(+0.45)
7.52
(+0.24)
7.98
(+0.31)
152.5
(+2.6)
124.8
(+1.0)
138.1
(+2.2)
-153.9
(-85.2)
a
b
N(1)
Free py in DMSO-d6: δH(2) = 8.56 ppm, δH(3) = 7.37 ppm, δH(4) = 7.77 ppm; δC(2) = 149.7 ppm, δC(3) = 123.8 ppm, δC(4) = 136.1 ppm; δN(1) = -63.1 ppm.
Free py in CDCl3: δH(2) = 8.60 ppm, δH(3) = 7.28 ppm, δH(4) = 7.67 ppm; δC(2) = 149.9 ppm, δC(3) = 123.8 ppm, δC(4) = 135.9 ppm; δN(1) = -68.7 ppm.
ionic radius of Co(III) (0.55 Å) than Ru(II) (ca. 0.700.75 Å) or Pt(IV) (0.63 Å) [41], and, in consequence,
by a shorter Co-py distance (for trans-[Co(py)4Cl2]+ in
trans-[Co(py)4Cl2][Co(py)Cl3] (HEDVER [13]) and trans[Co(py)4Cl2](dibenzoylmonohydrogentartrate) (SICWEG
[42]) they varied within 1.974(5)-1.984(4) Å and 1.9661.989 Å ranges, respectively), in comparison to Ru-py (for
trans-[Ru(py)4Cl2]: 2.079(2) Å (WIBNIE [43]) or 2.073(3) Å
(WIBNIE01 [44]), and Pt-py (for trans-[Pt(py)4F2]2+ in trans[Pt(py)4F2](B(C6H5)4)2·2H2O: 2.008(9) Å (TULKAM [45]);
X-ray data of trans-[Pt(py)4Cl2]2+ are unavailable [21]).
mer-[Co(py)3Cl3] is insoluble in D2O, while in DMSOd6 it immediately decomposes and forms a large
number of unidentified products (most likely, due to py
→ DMSO-d6 and/or Cl → DMSO-d6 substitutions). This
decomposition seems to be much faster than for trans[Co(py)4Cl2]Cl. The neutral complex, however, is soluble
and very stable (for at least 1 week) in CDCl3, where two
sets of 1H signals with 2:1 intensity ratio, corresponding
to axial and equatorial py molecules, are detected
(Table 1, Fig. 1 bottom). The comparison to free py in
CDCl3 exhibits that, unlike for trans-[Co(py)4Cl2]Cl, both
types of H(2) atoms are evidently deshielded (this effect
being much more pronounced for axial (ca. 0.4 ppm)
than equatorial (ca. 0.1 ppm) ligands – δH(2)ax > δH(2)eq),
while H(3) nuclei are very slightly shielded (by ca. 0.05
ppm), and H(4) – weakly deshielded (by ca. 0.1-0.15
ppm).
mer-[Co(py)3(CO3)Cl] does not dissolve in D2O and
decomposes in DMSO-d6, while in CDCl3 it reveals two
sets (2:1) of proton signals (Table 1); in contrast to mer[Co(py)3Cl3], however, the pattern of 1H coordination
shifts is entirely different. Particularly, axial H(2) atoms
are slightly shielded (by ca. 0.15 ppm), whereas those
equatorial are significantly deshielded (by ca. 0.45
ppm). In consequence, the former 1H resonance is ca.
0.6 ppm low-frequency shifted in respect to the latter,
this δH(2)ax < δH(2)eq sequence being opposite to that in
mer-[Co(py)3Cl3]. Furthermore, H(3) and H(4) equatorial
resonances are moderately shifted to higher frequency
(by ca. 0.25-0.3 ppm), while the axial resonances
remain at nearly the same positions (with variations up
to ca. ±0.05 ppm). Hence, the mer-[Co(py)3Cl3] → mer[Co(py)3(CO3)Cl] transition, following the replacement,
within Co(III) coordination sphere, of two chlorides by a
carbonate anion, leads to noticeable in magnitude and
variable in sign changes of δH(2) parameters: 0.55 ppm
shielding of axial H(2) (9.01 ppm → 8.46 ppm) contrasts
to 0.38 ppm deshielding of equatorial H(2) (8.67 ppm
→ 9.05 ppm). Moreover, upon such ligand exchange
(2Cl- → CO32-)the equatorial H(3) and H(4) atoms are
deshielded by 0.30 ppm and 0.15 ppm (7.22 ppm →
7.52 ppm, and 7.83 → 7.98 ppm, respectively), while
the variations concerning axial H(3) and H(4) nuclei are
negligible (0.00-0.03 ppm). This relatively complicated
dependence of δ1H parameters on proton position,
orientation of py rings and character of auxiliary ligands
suggests the significance of either inductive effects (as
electron-acceptor/donor properties of Cl- and CO32- are
different) or anisotropic phenomena (associated with
π-bonds in carbonate anions).
13
C NMR spectra of trans-[Co(py)4Cl2]+ cations in
D2O or DMSO-d6 exhibit three signals in the same order
observed for free py (C(2) > C(4) > C(3)), their chemical
shifts being nearly independent of the solvent (variations
up to ±0.3 ppm); analogous measurements in CDCl3
have not been performed due to the low solubility of this
ionic complex and the conversion of trans-[Co(py)4Cl2]
Cl into mer-[Co(py)3Cl3]. Compared to uncoordinated py
in DMSO-d6, all carbons are deshielded by ca. 2-8 ppm,
59
Unauthenticated
Download Date | 6/18/17 6:43 AM
H,
1
Figure 1.
C,
13
15
N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine
complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl,
and a new synthesis of mer-[Co(py)3Cl3]
H NMR spectral changes during trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction in CDCl3.
1
this effect decreasing also in the C(2) > C(4) > C(3)
order. Such a pattern of ∆13Ccoord parameters is different
from that reported for trans-[Pt(py)4Cl2]2+ cations, where
the deshielding phenomenon surprisingly increased with
the distance from the coordination site, i.e. in sequence
C(2) < C(3) < C(4) (for trans-[Pt(py)4Cl2](NO3)2 in D2O:
δC(2) = 154.1 ppm, δC(3) = 130.2 ppm, δC(4) = 146.3 ppm
[40]; thus the ∆13Ccoord values, determined by us versus
free py in DMSO-d6, have been found as: ∆C(2)coord =
+4.4 ppm, ∆C(3)coord = +6.4 ppm, ∆C(4)coord = +10.2 ppm).
Similar 13C deshielding effects and their diminishing
in the C(2) > C(4) > C(3) series are observed for mer[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl] in CDCl3. The
most characteristic C(2) high-frequency coordination
shifts are much larger for the former complex (ca. 7-9
ppm) than the latter one (ca. 2-3 ppm); in both species
they are more pronounced for axial than equatorial py.
In these two compounds, also C(4) signals are slightly
shifted to higher frequency (by ca. 1-3 ppm), while
those of C(3) remain at nearly the same positions (with
variations up to ca. ± 1 ppm).
The only 15N signal of trans-[Co(py)4Cl2]+ cation in
DMSO-d6 appears at δN(1) = -172.9 ppm, being ca. 110
ppm shifted to lower frequency when compared to free
py in the same solvent. Thus, the 15N coordination shift
is negative, its absolute magnitude being larger than in
the cases of [Pd(py)4]2+ and [Pt(py)4]2+ ions (ca. 94 ppm
[24]). For mer-[Co(py)3Cl3] in CDCl3, two 15N resonances
are detected at δN(1)ax ≈ -172 ppm (axial py) and δN(1)eq ≈
-157 ppm (equatorial py), the respective low-frequency
shifts being ca. 103 ppm and ca. 88 ppm. For mer[Co(py)3(CO3)Cl] in CDCl3, the axial nitrogens appear at
60
Unauthenticated
Download Date | 6/18/17 6:43 AM
L. Pazderski et al.
δN(1)ax = -168.9 ppm, while the equatorial one at δN(1)eq
= -153.9 ppm, which correspond to ca. 100 ppm and
ca. 85 ppm low-frequency shifts, respectively. The
comparison of these ∆N(1)coord parameters for all three
complexes exhibits that the 15N nuclei trans to N (i.e. all
in trans-[Co(py)4Cl2]+ and the axial in mer-[Co(py)3Cl3]
or mer-[Co(py)3(CO3)Cl] – ∆15Ncoord being from ca. -100
ppm to ca. -110 ppm) are ca. 15-25 ppm more shielded
than those trans to Cl or O (i.e. the equatorial in mer[Co(py)3Cl3] or mer-[Co(py)3(CO3)Cl] – ∆15Ncoord being
from ca. -85 ppm to ca. -88 ppm). It follows a similar
tendency noted for trans-/cis-[Pt(py)2Cl2] or trans-/cis[Pt(py)2Cl4] geometric isomers, where δN(1) (and ∆N(1)
) values also decreased by ca. 15-30 ppm upon the
coord
cis → trans transition [24]. Finally, in both meridional
isomers the 2Cl- → CO32- replacement weakens the 15N
shielding effects by ca. 3 ppm for both types of N atoms
(i.e. the ca. 15 ppm separation of axial and equatorial
resonances remains nearly the same).
Another possible reason for the decrease of the 15N
coordination shifts’ absolute magnitude upon N(axial)
→ N(equatorial) transitions, observed for both mer[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl], is a probable
elongation of the equatorial Co-N bonds when compared
to those axial. Unfortunately, single crystal X-ray data are
unavailable for these two chloride complexes, however,
such a structural effect was already reported for a
similar azide species – mer-[Co(py)3(N3)3] (JOZNAN), in
which the Co-pyeq bonding was ca. 0.015 Å longer than
the Co-pyeq one [20]. The same dependency was also
observed for its analogues – mer-[Co(4-methyl-py)3(N3)3]
(VOZSIM, VOZSIM01) [20,46], mer-[Co(3,4-dimethylpy)3(N3)3] (NOKJAY) [47] and mer-[Co(3,5-dimethylpy)3(N3)3] (NOKJEC) [47]; their Co-N bond lengths are
listed below (see 13C CPMAS discussion).
The 13C CPMAS spectrum of trans-[Co(py)4Cl2]
Cl·6H2O exhibits exactly three signals (δC(2) = 158.1 ppm,
δC(3) = 127.1 ppm, δC(4) = 142.8 ppm), their assignment
being based on the spectral pattern similarity between
the solid state and the solution (in crystalline phase,
δ13C values have increased ca. 1-2 ppm comparing
to DMSO-d6). The respective 15N CPMAS spectrum
unexpectedly reveals not one, but four signals at -168.2,
-170.8, -175.0, -176.9 ppm, exhibiting an inequivalency
of all nitrogen atoms, and, in consequence, of the four
py molecules. Such slight structural differences between
formally equivalent equatorial Co-N bonds were already
reported for trans-[Co(py)4Cl2]+ cations in the two salts
studied by X-ray: trans-[Co(py)4Cl2][Co(py)Cl3] (HEDVER
– 1.974(5), 1.976(5), 1.978(4), 1.984(4) Å [13]) and
trans-[Co(py) 4Cl 2](dibenzoylmonohydrogentartrate)
(SICWEG – 1.966, 1.970, 1.979, 1.989 Å [42]). In case
of the studied trans-[Co(py)4Cl2]Cl·6H2O complex, this
phenomenon is caused, most likely, by unsymmetrical
interactions of the trans-[Co(py)4Cl2]+ moiety with the
respective counterions (Cl-) and/or solvated molecules
(H2O). Such symmetry-distorting influences (host-guest
interactions) of various additional species, present
in the crystal lattice, was in the past exemplified by
X-ray studies of several octahedral Co(II) chloride-py
complexes; particularly, various Co-py bond lengths
were found in trans-[Co(py)4Cl2]·H2O (QELMEZ – 2.188,
2.192, 2.193, 2.223 Å [48]) and trans-[Co(py)4Cl2]·CHCl3
(ZIZQAA – 2.171(3), 2.179(3), 2.203(2), 2.235(2) Å [49]),
in contrast to unsolvated trans-[Co(py)4Cl2], where they
were identical (TPYRCO01 – 2.183(4) Å [50]). A similar
differentiation of Co-N bondings was also reported for a
number of trans-[Co(py)4X2]·2py clathrates, containing
axial ligands other than Cl (X = Br, EYULEP; X = I, EYULIT;
X = ONO2, EYULOZ [51]; X = NCO, SEJQED01 [52]), as
well as for analogous Rh(III) and Ir(III) chloride cationic
complexes (trans-[Rh(py)4Cl2]+ in trans-[Rh(py)4Cl2]
NO3·HNO3 – TPYRRH, TPYRRH01 [53,54] and trans[Rh(py)4Cl2][Ag(NO3)2] – KIJMEV [55]; trans-[Ir(py)4Cl2]+
in trans-[Ir(py)4Cl2]Cl·6H2O – CUHWOR [56]). Recently,
we have exhibited that even slight differences between
metal-nitrogen bond lengths in the solid state can lead
to noticeable variations of 15N CPMAS chemical shifts
(e.g. for [Zn(purine-N(7))2Cl2] (ZAYDAE) the two Zn-N(7)
interatomic distances differed by only 0.006 Å (2.027(3)
and 2.033(4) Å [57]), resulting in ca. 2 ppm various δN(7)
parameters (-188.0 and -185.8 ppm [58])).
The 13C CPMAS spectrum of mer-[Co(py)3Cl3]
exhibits distinct peaks for each of three py molecules
(δC(2)ax = 158.2/156.0 ppm, δC(3)ax = 125.2/123.7 ppm,
δC(4)ax = 139.7/138.7 ppm; δC(2)eq = 161.4 ppm, δC(3)eq
= 127.7 ppm, δC(4)eq = 141.4 ppm); in contrast to the
CDCl3 solution, in the solid state all equatorial carbons
are more deshielded than the axial ones. This pattern
indicates an inequivalency of all azine ligands, similar
to those already revealed by X-ray structural studies
for a number of Co(III)-py-azide complexes (mer[Co(py)3(N3)3] (JOZNAN – Co-pyax: 1.970(2)/1.975(2)
Å, Co-pyeq 1.986(3) Å [20]); mer-[Co(4-methylpy)3(N3)3] (VOZSIM – Co-pyax: 1.926(10)/1.956(10)
Å, Co-pyeq 1.972(11) Å [46] or VOZSIM01 – Co-pyax:
1.961(6)/1.971(6) Å, Co-pyeq 1.986(6) Å [20]); mer[Co(3,4-dimethyl-py)3(N3)3] (NOKJAY – Co-pyax:
1.995(4)/1.955(3) Å, Co-pyeq 1.994(3) Å [47]); mer[Co(3,5-dimethyl-py)3(N3)3] (NOKJEC – Co-pyax:
1.973(3)/1.985(3) Å, Co-pyeq 1.990(3) Å [47])), as well
as for various chloride coordination compounds having
a general mer-[M(py)3Cl3] formula (M = Al, BODZAV
[59]; M = V, WEHZUE [60]; M = Cr, QQQFYV01 [23], M
= Mo, CLPYMO01 [22]; M = Rh, CILYOL [61]).
The 15N CPMAS spectrum of mer-[Co(py)3Cl3]
61
Unauthenticated
Download Date | 6/18/17 6:43 AM
H,
1
C,
13
reveals even more sophisticated differences between py
molecules. The problem is that the signals, appearing in
the range from ca. -157 to ca. -177 ppm, are heavily
overlapped, making evaluation of their exact number
difficult. We suppose there are six of them, however, this
number is not fully certain. Nevertheless, a significant 15N
shielding effect, comparable to that for trans-[Co(py)4Cl2]
Cl·6H2O, is again evident.
A surprisingly increased number of 15N CPMAS
resonances suggests either sample polymorphism,
or the appearance of two discrete types of mer[Co(py)3Cl3] molecules within the crystal lattice, differing
in packing and details of the coordination polyhedron
(such a phenomenon being usually named as distortion
isomerism [62]), by analogy to [Zn(py)2Cl2] (ZNPYRC01)
[63] or [Pd(dpphen)Cl2] (FURKUY) [64].
The comparison of 13C and 15N CPMAS spectra,
for each studied complex, leads to the conclusion that
the latter technique is a more sensitive tool for detection
of slight variations in the coordination mode. The
differences between distinct 15N resonances, reaching
ca. 9 ppm for trans-[Co(py)4Cl2]Cl·6H2O and ca. 20 ppm
for mer-[Co(py)3Cl3] confirm a large dependence of the
δ15N parameter on the crystal packing and intermolecular
interactions in the solid phase.
3.4. 1H NMR studies of trans-[Co(py)4Cl2]Cl
mer-[Co(py)3Cl3] + py reaction
15
N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine
complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl,
and a new synthesis of mer-[Co(py)3Cl3]
The integration of both types of proton peaks ((A)
– shared by trans-[Co(py)4Cl2]Cl and free py versus
(B) – corresponding to the sum of axial and equatorial
ligands in mer-[Co(py)3Cl3]) allows the calculation of a
time-variable molar ratio of both studied complexes.
Generally, at each stage of the substitution process,
the relative concentrations of trans-[Co(py)4Cl2]Cl, mer[Co(py)3Cl3] and py can be expressed as (1-x), x and x
(where x denotes a degree of the reaction advancement),
respectively. Hence, the relevant (A) and (B) areas, for a
given type of hydrogen, correspond to 4·(1-x)+x and 3x.
Our integrations, performed for the best separated H(2)
resonances (those of H(3) and H(4) heavily overlapping
to one another, and also to the peak of residual CHCl3)
have lead to the following results: after 24h – (A) : (B) ≈
6.5 : 1.5 (thus, x ≈ 0.25, and trans-[Co(py)4Cl2]Cl : mer[Co(py)3Cl3] ≈ 3 : 1); after 48h – (A) : (B) ≈ 2.5 : 1.5 (thus,
x ≈ 0.5, and trans-[Co(py)4Cl2]Cl : mer-[Co(py)3Cl3] ≈ 1
: 1). Within 120h, the content of mer-[Co(py)3Cl3] has
reached nearly 100% ((A) : (B) ≈ 0.5 : 1.5, thus x ≈ 1);
the final reaction mixture, however, contains also free
py, whose peaks are even more broadened (ν1/2 = ca.
50-100 Hz) and shifted as much as to δH(2) ≈ 6.8 ppm,
δH(3) ≈ 5.4 ppm, δH(4) ≈ 5.3 ppm. In our opinion, this
suggests minor contamination by Co(II) paramagnetic
by-products.
→
H NMR spectral changes of trans-[Co(py)4Cl2]Cl·6H2O
solution in CDCl3 are drawn in Fig. 1, exhibiting its
gradual conversion into mer-[Co(py)3Cl3].
After dissolving, we observe the peaks of pure trans[Co(py)4Cl2]Cl (8.37 ppm – 8 x H(2), 8.00 ppm – 4 x
H(4), 7.36 ppm – 8 x H(3)), which, however, immediately
start to decay and, in a few minutes, lose their multiplet
structure appearing as slightly broadened (ν1/2 = ca. 3050 Hz) singlets; then, with increasing time, they become
more and more low-frequency shifted: 24h – δH(2) = 8.19
ppm, δH(3) = 7.12 ppm, δH(4) = 7.68 ppm; 48h – δH(2) = 7.95
ppm, δH(3) = 6.79 ppm, δH(4) = 7.25 ppm). Simultaneously,
the new proton signals, identical with those of pure mer[Co(py)3Cl3] (9.01 ppm – 4 x H(2)ax, 8.67 ppm – 2 x H(2)
eq
, 7.83 ppm – 1 x H(4)eq, 7.76 ppm – 2 x H(4)ax, 7.24 ppm
– 4 x H(3)ax, 7.22 ppm – 2 x H(3)eq) start to arise. With
increasing time they increase in intensity but remain at
nearly the same chemical shifts. Despite liberation of
py molecules, 1H resonances of the free ligand do not
appear distinctly in these NMR spectra, which suggests
that the above mentioned singlets are averaged for
trans-[Co(py)4Cl2]Cl + py, probably due to the fast azine
exchange between the Co(III) coordination sphere and
the solution.
1
Figure 2.
Absorbance changes during the trans-[Co(py)4Cl2]Cl →
mer-[Co(py)3Cl3] + py reaction in CHCl3.
3.5. UV-Vis studies of the trans-[Co(py)4Cl2]Cl
→ mer-[Co(py) Cl ] + py reaction
3 3
Absorbance changes corresponding to the trans[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction in CHCl3
are shown at Fig. 2.
Along with time, the 519 nm maximum decreases,
whereas those at 613 nm and 637 nm increase, being
slightly shifted to ca. 610 nm and ca. 630 nm, respectively.
The isosbestic point appears at ca. 580 cm-1. After 120
h, the spectrum becomes quite similar to that of freshly
dissolved mer-[Co(py)3Cl3], but it is not identical. Some
differences, concerning both λmax and ε parameters
are probably caused by a simultaneous formation of
62
Unauthenticated
Download Date | 6/18/17 6:43 AM
L. Pazderski et al.
Co(II) by-products detected by NMR; the liberation of
free py and water (from the dissolved reactant, which
is a hexahydrate) must be also taken into account. The
previously mentioned dependence of the substitution
process on chloroform quality and absence of sunlight
has resulted in an insufficient reproducibility of the
kinetic runs; this is why we have not studied the reaction
rates quantitatively.
The mechanism of py → Cl substitution during the
trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction
(illustrated at Fig. 3) remains unknown. In our opinion,
this process, generally absent in aqueous media (in
water-alcoholic solutions some solvolysis reactions
were generally reported for trans-[Co(py)4Cl2]+ cations
[6,65,66]) seems to be favoured just in chloroform
due to the two principal reasons: (1) the lack of trans[Co(py)4Cl2]Cl dissociation in this solvent enables
stronger interactions between the Co(III) central ion or
coordinated py molecules, and the Cl atom located in
the outer coordination sphere; (2) the presence of small
amounts of HCl (which is well-known to be formed in
CHCl3 upon daylight exposure) may catalyse Cl → py
substitution.
4. Conclusions
Far-IR and 1H NMR studies of mer-[Co(py)3Cl3]
confirm the meridional geometry of this complex,
earlier suggested on the basis of its X-ray diffraction
pattern, in both solid state and solution. Co(III) chloride
complexation of pyridine (in trans-[Co(py)4Cl2]Cl·6H2O,
mer-[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl]) leads to
variable changes in both sign and magnitude of 1H NMR
chemical shifts, heavily dependent on proton position,
Figure 3.
The trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction, occurring spontaneously in CHCl3.
coordination sphere geometry and character of auxiliary
ligands. Particularly, significant differences between
axial and equatorial py, as well as noticeable changes
following 2Cl → CO32- replacement are observed for
both meridional complexes.
13
C NMR spectra of all coordination compounds
exhibit a general carbon deshielding effect, decreasing
in the order C(2) > C(4) > C(3). 15N nuclei are shielded
by ca. 85-110 ppm, this effect being ca. 15-25 ppm more
pronounced for nitrogens located trans to N than trans
to Cl or O. 13C and 15N CPMAS measurements for trans[Co(py)4Cl2]Cl·6H2O and mer-[Co(py)3Cl3] reveal slight
variations in formally equivalent Co-N bonds; in the
case of the latter complex, they additionally suggest the
appearance of distortion isomerism.
In chloroform, a spontaneous trans-[Co(py)4Cl2]Cl
→ mer-[Co(py)3Cl3] + py reaction is followed by large
changes of 1H NMR and UV-Vis spectral properties. This
process of py → Cl substitution is probably favoured by
the lack of reactant dissociation in CHCl3 and catalysed
by small amounts of HCl. A new, more efficient method
of mer-[Co(py)3Cl3] manufacture has been designed,
allowing for a convenient preparation of this potentially
important synthetic precursor, although restrictive
conditions must be employed in order to avoid formation
of Co(II) by-products.
References
[1] A. Werner, R. Feenstra, Ber. 39, 1538 (1906) (in German)
[2] T. Laier, C.E. Schäffer, J. Springborg, Acta Chem.
Scand. A 34, 343 (1980)
[3] L.I. Katzin, J.R. Ferraro, E. Gebert, J. Am. Chem.
Soc. 72, 5471 (1950)
[4] M. Gerloch, R.F. McMeeking, A.M. White, J. Chem.
Soc. Dalton Trans. 655 (1976)
[5] A.V. Babayeva, I.B. Baranovskii, Zh. Neorg. Khim. 4,
755 (1959) (in Russian)
[6] C.N. Elgy, C.F. Wells, J. Chem. Soc. Dalton Trans.
2405 (1980)
[7] W.L. Purcell, Inorg. Chem. 25, 4068 (1986)
[8] M. Mori, M. Shibata, E. Kyuono, T. Adachi, Bull.
Chem. Soc. Jpn. 29, 883 (1956)
[9] J. Springborg, C.E. Schäffer, Acta Chem. Scand. 27,
3312 (1973)
[10] N.N. Greenwood, A. Earnshaw, In: Chemistry of the
Elements (Pergamon Press, Oxford, 1984) 1301
[11] A.V. Ablov, Zh. Neorg. Khim., 6, 309 (1961) (in Russian)
[12] A.A. Vlček, Inorg. Chem. 6, 1425 (1967)
[13] H. Xu, J. Ji, Z. Wu, J. Zou, Z. Xu, X. You, Polyhedron 12, 2261 (1993)
[14] Yu.N. Shevchenko, N.B. Golub, Ukr. Khim. Zh. 48,
345 (1982) (in Russian)
[15] T. Mallen, K.E. Hyde, Inorg. Chim. Acta 130, 177
(1987)
[16] K.E. Hyde, G.M. Harris, J. Phys. Chem. 82, 2204
(1978)
63
Unauthenticated
Download Date | 6/18/17 6:43 AM
H,
1
C,
13
[17] D.A. Gooden, H.A. Ewart, K.E. Hyde, Inorg. Chim.
Acta 166, 263 (1989)
[18] J. Glerup, C.E. Schäffer, J. Springborg, Acta Chem.
Scand. A 32, 673 (1978)
[19] A.V. Babayeva, I.B. Baranovskii, Zh. Neorg. Khim.
6, 225 (1961) (in Russian)
[20] M.A.S. Goher, R.J. Wang, T.C.W. Mak, Polyhedron
11, 829 (1992)
[21] Cambridge Structural Database (Cambridge Crystallographic Data Centre, Cambridge, 2007)
[22] J.V. Brencic, Z. Anorg. Allg. Chem. 403, 218 (1974)
(in German)
[23] S.A. Howard, K.I. Hardcastle, J. Crystallogr. Spectrosc. Res. 15, 643 (1985)
[24] L. Pazderski, E. Szłyk, J. Sitkowski, B. Kamieński,
L. Kozerski, J. Toušek, R. Marek, Magn. Reson.
Chem. 44, 163 (2006)
[25] L. Pazderski, Polish J. Chem. 80, 1083 (2006)
[26] L. Pazderski, J. Toušek, J. Sitkowski, L. Kozerski,
R. Marek, E. Szłyk, Magn. Reson. Chem. 45, 24
(2007)
[27] L. Pazderski, J. Toušek, J. Sitkowski, L. Kozerski, E.
Szłyk, Magn. Reson. Chem. 45, 1045 (2007)
[28] L. Pazderski, J. Toušek, J. Sitkowski, L. Kozerski, E.
Szłyk, Magn. Reson. Chem. 45, 1059 (2007)
[29] K. Nakamoto, In Infrared and Raman Spectra of Inorganic and Coordination Compounds Part A Ed.
5th, (Wiley, New York 1997), 346.
[30] R.J.H. Clark, C.S. Williams, Inorg. Chem. 4, 350 (1965)
[31] F. Herbelin, J.D. Herbelin, J.P. Mathieu, H. Poulet,
Spectrochim. Acta 22, 1515 (1966)
[32] R.D. Gillard, T. Heaton, J. Chem. Soc. A 451 (1969)
[33] G. Daffner, D.A. Palmer, H. Kelm, Inorg. Chim. Acta
61, 57 (1982)
[34] M. Goldstein, W.D. Unsworth, Spectrochim. Acta A
28, 1297 (1972)
[35] D.A. Thornton, Coord. Chem. Rev. 104, 251 (1990)
[36] I.I. Bhayat, W.R. McWhinnie, Spectrochim. Acta 28,
743 (1972)
[37] F. Bottomley, M. Mukaida, J. Chem. Soc. Dalton
Trans. 1933 (1982)
[38] A.M. El-Hendawy, W.P. Griffith, F.I. Taha, M.N.
Moussa, J. Chem. Soc. Dalton Trans. 901 (1989)
[39] B.J. Coe, T.J. Meyer, P.S. White, Inorg. Chem. 34,
593 (1995)
[40] K.R. Seddon, J.E. Turp, E.C. Constable, O. Wernberg, J. Chem. Soc. Dalton Trans. 293 (1987)
[41] In Handbook of Chemistry and Physics, Ed. 85th
(CRC Press, Boca-Raton, 2004-05) 12, 14.
[42] N.C. Payne, M.E. Tkachuk, Chirality 1, 284 (1989)
15
N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine
complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl,
and a new synthesis of mer-[Co(py)3Cl3]
[43] W.T. Wong, T.C. Lau, Acta Crystallogr. C 50, 1406
(1994)
[44] M.R.J. Elsegood, D.A. Tocher, Acta Crystallogr. C
51, 40 (1995)
[45] H.H. Drews, W. Preetz, Z. Anorg. Allg. Chem. 623,
509 (1997) (in German)
[46] F.A. Mautner, Cryst. Res. Technol. 26, 883 (1991)
[47] M.A.S. Goher, N.A. Al-Salem, F.A. Mautner, Polyhedron 16, 3747 (1997)
[48] G.F. Wang, F. Ji, X.L. Zhu, G.X. Wang, K.B. Yu,
Wuji Huaxue Xuebao 15, 435 (1999) (in Chinese)
– Chem. Abstr. 131, 193324 (1999)
[49] D.V. Soldatov, Y. Lipkovski, Zh. Strukt. Khim. 36,
905 (1995) (in Russian)
[50] G.J. Long, P.J. Clarke, Inorg. Chem. 17, 1394 (1978)
[51] D.V. Soldatov, Y. Lipkovski, Zh. Strukt. Khim. 36,
1070 (1995) (in Russian)
[52] D.V. Soldatov, V.A. Logvinenko, Y.A. Dyadin, Y.
Lipkowski, K. Suvinska, Zh. Strukt. Khim. 40, 935
(1999) (in Russian)
[53] G.C. Dobinson, R. Mason, D.R. Russell, Chem.
Commun. 62 (1967)
[54] J. Roziere, M.S. Lehman, J. Potier, Acta Crystallogr.
B 35, 1099 (1979)
[55] R.D. Gillard, L.R. Hanton, S.H. Mitchell, Polyhedron
9, 2127 (1990)
[56] R.D. Gillard, S.H. Mitchell, P.A. Williams, R.S. Vagg,
J. Coord. Chem. 13, 325 (1984)
[57] H.L. Laity, M.R. Taylor, Acta Crystallogr. C. 51, 1791
(1995)
[58] E. Szłyk, L. Pazderski, I. Łakomska, A. Wojtczak, L.
Kozerski, J. Sitkowski, B. Kamieński, H. Günther,
Polyhedron 22, 391 (2003)
[59] P. Pullmann, K. Hensen, Z. Naturforsch. B 37, 1312
(1982) (in German)
[60] K.L. Sorensen, J.W. Ziller, N.M. Doherty, Acta Crystallogr. C 50, 407 (1994)
[61] K.R. Acharya, S.S. Tavale, T.N. Guru Row, Acta
Crystallogr. C 40, 1327 (1984)
[62] M. Melnik, Coord. Chem. Rev. 47, 239 (1982)
[63] W.L Steffen, G.J. Palenik, Acta Crystallogr. B 32,
298 (1976)
[64] J. Anbei, C. Krüger, B. Pfeil, Acta Crystallogr. C 43,
2334 (1987)
[65] C.N. Elgy, C.F. Wells, J. Chem. Soc. Dalton Trans.
1617 (1982)
[66] C.N. Elgy, C.F. Wells, J. Chem. Soc. Faraday Trans
I 79, 2367 (1983)
64
Unauthenticated
Download Date | 6/18/17 6:43 AM