Polydentate 4-Pyridyl-terpyridine Containing Discrete Cobalt Phosphonate and Polymeric Cobalt Phosphate as Catalysts for Alcohol Oxidation

Article abstract of DOI:10.1002/zaac.201800091

Mononuclear discrete cobalt phosphonate [Co(pytpy)(tBuPO₃H)₂(H₂O)]·H₂O (1) and 1D zigzag polymeric cobalt phosphate [Co(pytpy)₂(dipp)(MeOH)·2MeOH]_n (2) were prepared from the reactions of tert-butyl phosphonic acid (tBuPO₃H₂) and organic-soluble 2,6-diisopropylphenyl phosphate (dippH₂) ligands with Co(OAc)₂·4H₂O in the presence of 4′-pyridyl 2,2′:6′,2′′-terpyridine in MeOH/CHCl₃(1:1 v/v) solvent mixture at 25 °C. The new compounds were characterized by analytical, thermo-analytical, and spectroscopic techniques. Further, the molecular structures were established by single-crystal X-ray diffraction studies. Mass spectrometry analysis reveal that both the compounds exist in the solution phase as dimers. Compound 1 was employed as homogeneous catalysts for alcohol oxidation reactions using tert-butyl hydroperoxide (TBHP) as the oxidant.

Full text of DOI:10.1002/zaac.201800091

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201800091
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Polydentate 4-Pyridyl-terpyridine Containing Discrete Cobalt
Phosphonate and Polymeric Cobalt Phosphate as Catalysts for
Alcohol Oxidation
Gulzar A. Bhat,[a] Antony Rajendran,[a] and Ramaswamy Murugavel*[a]
Dedicated to Prof. Peter Comba on the Occasion of his 65th Birthday
Abstract.
Mononuclear
discrete
cobalt
phosphonate
were characterized by analytical, thermo-analytical, and spectroscopic
techniques. Further, the molecular structures were established by sin-
[Co(pytpy)(tBuPO3H)2(H2O)]·H2O (1) and 1D zigzag polymeric co-
balt phosphate [Co(pytpy)2(dipp)(MeOH)·2MeOH]n (2) were prepared gle-crystal X-ray diffraction studies. Mass spectrometry analysis reveal
from the reactions of tert-butyl phosphonic acid (tBuPO3H2) and or- that both the compounds exist in the solution phase as dimers. Com-
ganic-soluble 2,6-diisopropylphenyl phosphate (dippH2) ligands with pound 1 was employed as homogeneous catalysts for alcohol oxidation
Co(OAc)2·4H2O in the presence of 4Ј-pyridyl 2,2Ј:6Ј,2ЈЈ-terpyridine in
reactions using tert-butyl hydroperoxide (TBHP) as the oxidant.
MeOH/CHCl3(1:1 v/v) solvent mixture at 25 °C. The new compounds
Introduction
[Co(pytpy)Cl2]·MeOH and [Co(pytpy)Cl2]·2H2O exhibit a
guest dependent 1D spin-crossover phenomenon with thermal
hysteresis.[10] Substitution of 4Ј-position in pytpy with alkoxyl,
hydroxyl or long chain alkyl groups in these complexes im-
parts interesting phase transition properties apart from the ob-
served spin cross over.[11]
Oxidation of alcohols to their corresponding carbonyl com-
pounds is always being appraised as the key functional group
transformation reaction in chemical industry.[1] Conventionally
alcohol oxidation is achieved by using stoichiometric amounts
of toxic inorganic oxidants such as HNO3, KMnO4, and
K2Cr2O7, which contribute to excessive toxic byproducts to
the ecosystem.[2] Thus need for non-toxic, atom economic,
catalytic and environmentally benign approaches for such reac-
tions were realized in the last few decades.[3,4] First row transi-
tion metal (TM) catalysts are renowned as efficient alcohol
oxidation catalysts in the presence of peroxides[5] or in combi-
nation with nitroxyl radicals (e.g., 2,2,6,6-tetramethyl-
piperidyl-1-oxy TEMPO)[6] due to their higher natural abun-
dance and inherent ability to exist in more than one oxidation
state.[5d,7] Thus search to achieve best selectivity and effi-
ciency of such alcohol oxidation catalysts is the main impetus
for continued research in this field.
2,2Ј:6Ј,2ЈЈ-Terpyridine (tpy), a tridentate chelating oligopyr-
idine ligand, has been extensively employed for making homo
or heteroleptic TM complexes which find potential applica-
tions in research areas such as materials science (e.g. photovol-
taics and magnetic materials), biomedicinal chemistry (e.g.
anti-cancer drugs), and organometallic catalysis.[8]
Interest in cobalt terpyridine complexes mainly arises due to
their ability to act as spin cross over systems.[9] The
one-dimensional cobalt terpyridine complexes such as
We have a long standing interest in metallophosphates,[12]
and have extensively reported on discrete and polymeric cobalt
phosphates, including clusters of different nuclearity.[13] Co-
ligands such as bipyridine, phenanthroline and Cl-tpy have
also been employed to control their nuclearity.[13b,13c,14] Cobalt
phosphates find potential applications as single source precur-
sors for fine particle ceramics, for CO2 adsorption, as molecu-
lar magnets, and as catalysts for water oxidation reac-
tions.[12c,13d,15] Although transition metal complexes of tpy,
pytpy and their derivatives have been implicated recently to
have great potential as catalysts in organic transformation reac-
tions such as asymmetric cyclopropanation of styrenes, alkene
hydroboration, etc., they have rarely been employed as alcohol
oxidation catalysts.[8e,16] To the best of our knowledge only
few examples of terpyridine containing transition metal com-
plexes were investigated as catalysts for alcohol oxidation re-
actions.[17]
In a series of recent investigations, we have employed a
number of transition metal catalysts for selective and efficient
oxidation of alcohols. The catalytic systems that have been
studied include, silica supported Schiff base complexes,[18] di-
nuclear MnII, CoII NiII arylphosphates incorporating 4Ј-chloro-
2,2Ј:6Ј,2ЈЈ-terpyridine (Cl-tpy) ancillary ligand,[14] bulky 2,6-
dibenzhydryl-4-methylaniline derived Schiff base complexes
of PdII, CuII, and CoII,[19] and arylimido hexamolybdates.[20]
Continuing on our earlier efforts, in this article we wish to
report new cobalt terpyridine complexes containing lipophilic
phosphate/phosphonate ligands as homogeneous catalysts for
alcohol oxidation reactions.
* Prof. Dr. R. Murugavel
E-Mail: rmv@chem.iitb.ac.in
[a] Department of Chemistry
Indian Institute of Technology Bombay
Mumbai – 400 076, India
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201800091 or from the au-
thor.
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diate (Scheme 1 and Figure 1). The ESI-MS spectrum of reac-
tions leading to products 1 and 2 exhibit peaks at m/z 1011
Results and Discussion
and 1251, whose isotopic pattern exactly matches with the ex-
Synthesis and Characterization of 1 and 2
Reacting equimolar quantities of [Co(OAc)2.4H2O],
tBuPO3H2 and 4Ј-pyridyl-2,2Ј:6Ј,2ЈЈ-terpyridine (pytpy) in
methanol / chloroform solvent mixture (1:1 v/v) at 25 °C leads
to the formation of monomeric cobalt phosphonate
[Co(pytpy)(tBuPO3H)2(H2O)]·H2O (1), whereas reaction of
2,6-diisopropylphenyl phosphate (dippH2) under similar
reaction conditions leads to the formation of polymeric cobalt
phosphate
[Co(pytpy)2(dipp)(MeOH)·2MeOH]n
(2)
(Scheme 1). Due to the bulkiness of 2,6-diisopropylphenyl
group of dippH2, only one dippH2 is coordinated to the central
metal atom. This permits the coordination of terminal nitrogen
of pytpy (4Ј-pyridyl) to the central metal atom, which in turn
leads to the formation of polymeric complex 2. This phenome-
non is not observed when tBuPO3H2 was used because two
molecules of tBuPO3H2 are coordinated to the central metal
atom leaving no space for the coordination of terminal nitrogen
of pytpy. The crystalline products of 1 and 2 obtained in these
reactions were characterized by different analytical and spec-
troscopic methods.
Surprisingly, the two phosphorus-based diprotic acids
tBuPO3H2 and dippH2 give rise to two different product types
(viz. discrete monomeric complex 1 and a 1D zigzag polymer
2). ESI-MS of the reaction mixtures suggest that the two dif-
Figure 1. Section of experimental and simulated ESI-MS spectra of
ferent products have gone through a similar dinuclear interme- the reaction mixture leading to formation of 1 (a) and 2 (b).
Scheme 1. Synthesis of compounds 1 and 2.
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pected pattern for the dimeric intermediates depicted in
The Co–N bond lengths fall in the expected range, in which
Scheme 1. Similarly, the ESI-MS analysis of the isolated single the central-Py Co–N2 bond length is shorter [2.058(2) Å] than
crystals of 1 in solution yields once again the spectra depicted the lateral-Py Co–N1 [2.153(2) Å] and Co–N3 [2.196(2) Å]
in Figure 1. These results clearly indicate that the dinuclear bond lengths of the pytpy unit. The bond lengths for 1 are
species is present in the solution for both the compounds, consistent with those typical for high-spin CoII compounds re-
whereas in the solid-state (see below) they assume either a ported earlier.[21] The Co–O bond lengths varies from
mononuclear or polymeric structure depending on the organic 2.011(2) Å (Co–O5) to 2.123(2) Å (Co–O7), which are again
(tert-butyl or bulky aryloxy) substituent on the phosphorus.
comparable with similar literature reported values for cobalt
The FT-IR spectra of 1 and 2 recorded as KBr diluted discs phosphonates.[22] The trans angle between axial coordination
exhibit broad absorptions bands centered around 3400 cm–1 sites (O7–Co–O5 177.07°) is slightly smaller than the ideal
due to the coordinated and lattice water molecules in 1 and value for octahedral arrangement (180°). Both the tBuPO3H2
[23]
methanol molecules in 2. The weak absorptions appearing molecules are mono deprotonated (Harris notation 1.100)
around 3056, 2968 cm–1 in 1 and 3060, 2967 cm–1 in 2, corre- with free P–OH groups [further supported by the presence of
sponds to C–H stretching vibrations of pytpy and phosphonate/ a broad absorption at around 2300 cm–1(P–OH) in the FT-IR
phosphate ligands. The absence of any absorption band at spectrum, vide supra]. Strong hydrogen bonding interactions
around 2350 cm–1 in 2 indicates complete neutralization of all occur between the hydrogen atoms of the coordinated water
P–OH groups on aryl phosphate (dippH2), whereas in case of molecule (H7A and H7B) and the phosphoryl oxygen atom of
1, the broad absorption band centered around 2364 cm–1 im- the phosphate ligand (O7–H7B···O1 2.662(2) Å, 158.4(5)°]
plies the presence of residual P–OH group on tBuPO3H2 li- and pendant pyridine nitrogen atom pytpy [O7–H7A···N4
gand. The absorption bands appearing at 1147, 1105, and 2.549(2) Å, 159.9(2)°]. The free P–OH and phosphoryl oxygen
1053 cm–1 in 1 and 1187, 1093, and 992 cm–1 in 2, arise due atoms of adjacent tBuPO3H2 molecules also show P–OH···O=P
to the O–P–O stretching vibrations and M–O–P asymmetric complimentary hydrogen bonding with each other
and symmetric stretching vibrations, respectively (Figure S1, [O2–H2A···O1 2.739(2) Å, 169.5(7)°]. This pattern of
Supporting Information).
hydrogen bonding leads to the formation of hydrogen bond
aided water dimers as shown in Figure 3.
Crystal Structures of 1 and 2
Red X-ray diffraction quality single crystals of 1 and 2 were
directly obtained from the reaction mixture by slow evapora-
tion of solvent (MeOH/CHCl3 1:1 v/v) at room temperature
over two weeks. Discrete cobalt phosphonate 1 crystallizes in
¯
the triclinic space group P1, whereas 1D polymeric cobalt
phosphate 2 crystallizes in the monoclinic P21/n space group.
The asymmetric part of the unit cell of 1 contains one pytpy
molecule, one di-cationic CoII ion, two mono-deprotonated
tBuPO3H2, and one coordinated aqua ligand besides one lattice
water molecule (Figure 2). The arrangement around CoII is dis-
torted octahedral. The CoN3O3 octahedron exhibits meridio-
nal-isomeric form around the metal (Figure 2).
Figure 3. Water dimer formation via O–H···O inter and intra molecular
hydrogen bonding interaction in 1 above ball and stick model and
Figure 2. Molecular structure of 1 (lattice water molecule and below space filling model (hydrogen atoms except those involved in
hydrogen atoms and are omitted for clarity).
hydrogen bonding are omitted for clarity).
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The asymmetric part of the unit cell of 2 contains one CoII Catalytic Studies
ion, one doubly deprotonated aryl phosphate (dipp), one pytpy
ligand, and one coordinated methanol molecule besides two
lattice methanol molecules (Figure 4). The CoII ion has a dis-
torted octahedral arrangement with square base of the octahe-
dron occupied by three nitrogen atoms of pytpy (N1–N3) and
one oxygen atom of dipp (O2) ligand; the axial coordination
sites are provided by oxygen atom (O5) of coordinated meth-
anol and pendant pyridine nitrogen (N4) of another pytpy li-
gand. The Co–N bond lengths varies from 2.079(4) to
2.163(4) Å [av. 2.136(4) Å], whereas the Co–O distances vary
from 1.957(3) to 2.224(3) Å [av. 2.090(3) Å]. The Co–N bond
metrics are comparable with those reported for high spin CoII
complexes.[21] The pendant pyridine and the terpy units are not
coplanar but are tilted by a dihedral angle of 37.16°. The aryl
phosphate ligand is doubly deprotonated and coordinates to
CoII ion through O2 (Harris notation 1.100).[23] Coordination
of chelating terpy unit of one pytpy molecule and pendant pyr-
idine moiety of another pytpy molecule results in the formation
of 1D zigzag polymer (Figure 5).
The soluble phosphonate 1 was further investigated as
alcohol oxidation catalysts for diverse substrates. The initial
optimization was performed by using benzyl alcohol as sub-
strate and discrete mononuclear cobalt phosphonate 1 as cata-
lyst. We have used three different catalytic doses (0.25, 0.5,
and 1 mol%) in separate catalytic runs to find out the optimum
catalytic dose in presence of TBHP as oxidant (see Supporting
Information). We have obtained better results with 0.5 mol%
of the catalyst (67% conversion with 94% benzaldehyde selec-
tivity). Meanwhile we have run catalytic reactions in different
solvents, temperatures and time to ascertain the optimum sol-
vent, temperature, and reaction time for higher selectivity and
catalytic activity. Solvent optimization studies by employing
water, methanol, acetonitrile, hexane, and toluene reveal that
the use of acetonitrile as solvent medium results in maximum
conversion (67%) with 94% benzaldehyde selectivity (Fig-
ure 6). The solvent free reaction shows 64% conversion but
with poor selectivity (61% benzaldehyde). Thus we have cho-
sen acetonitrile as the solvent for further catalytic studies.
Figure 6. Oxidation of benzyl alcohol in different solvents using cata-
lyst 1 [substrate (2.5 mmol), oxidant (1 equiv.) and catalyst (0.5 mol%)
Figure 4. Asymmetric unit of 2 (hydrogen atoms, isopropyl groups on
phosphate, and two lattice methanol molecules are omitted for clarity). at 80 °C for 3 h].
Figure 5. 1D zigzag polymeric view of 2 (hydrogen atoms and isopropyl groups on phosphate are omitted for clarity).
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To arrive at the optimum reaction time, aliquots of the reac- 1-pentanol and benzyl alcohol. Owing to the significance of
tion mixture were taken at regular intervals of time and sub- pyridine carboxaldehydes in drug synthesis, we have per-
jected to GC-MS analysis. The conversion percentage of formed the oxidation of a few pyridine containing alcohols.
benzyl alcohol increases up to 3 h; further continuation of reac- Though our catalyst yields moderate conversion, here again
tion does not produce any noticeable increase in the conversion 100% selectivity (aldehyde) is achieved. Blank experiments
(Figure 7). Moreover, it should also be noted that running the (without catalyst or without oxidant) result in no conversion
reaction beyond 3 h also destroys the benzaldehyde selectivity. of benzyl alcohol. With the motive to use the polymeric com-
Therefore it can be concluded that running the alcohol oxid- plex 2 as the heterogeneous catalyst, we have carried out the
ation for 3 h is necessary to obtain maximum conversion and benzyl alcohol oxidation (52% conversion with 78% benzal-
selectivity. Further in order to probe the optimum reaction tem- dehyde selectivity). However, under optimized reaction condi-
perature, the catalysis was carried out at different temperatures tions, polymeric complex 2 completely dissolves in the me-
and it was observed that 80 °C is the optimal temperature for dium.
the current catalytic system (Figure 8).
Conclusions
Discrete cobalt phosphonate 1 and 1D polymeric cobalt
phosphate 2 were isolated by employing pytpy co-ligand in the
presence of phosphorus acids tBuPO3H2 and dippH2. The crys-
tal structures of both the compounds were established by sin-
gle-crystal X-ray diffraction studies. ESI-MS analyses reveal
that both the compounds exist as dimers in solution. These
compounds were further employed as homogeneous alcohol
oxidation catalysts and the optimization studies reveal that our
catalysts show better conversion and selectivity in acetonitrile
at 80 °C in 3 h. The substrate scope reveals that our catalysts
exhibit promising results in the oxidation of pyridine contain-
ing alcohols which can lead to the pharmaceutically interesting
pyridine carboxaldehye with 100% selectivity. Compounds
such as 1 and 2 have a strong potential for exhibiting solvent
Figure 7. Oxidation of benzyl alcohol at different reaction times using
catalyst 1 [substrate (2.5 mmol), oxidant (1 equiv.) and the catalyst
(0.5 mol%) at 80 °C].
dependent spin cross over behaviour, which we are currently
investigating.
Experimental Section
Material, methods, and instruments: All the reactions were carried
out in open atmospheric conditions inside a fumehood, without any
special precaution to exclude air and moisture. Melting points were
measured in glass capillaries and are reported uncorrected. Infrared
spectra were obtained with a Perkin-Elmer Spectrum One FT-IR spec-
trometer as KBr diluted discs. Microanalyses were performed with a
Thermo Finnigan (FLASH EA 1112) microanalyzer. Thermogravime-
tric analyses were carried out with a Perkin-Elmer Pyris thermal analy-
sis system under a stream of nitrogen gas at the heating rate of
10 K·min–1. The ESI-MS studies were carried out with a Bruker MaXis
impact mass spectrometer.Solvents were purified according to standard
procedures prior to their use. Commercially available starting materials
such as Co(OAc)2·4H2O (S.D Fine) were used as procured. 4Ј-Pyridyl
2,2Ј:6Ј,2ЈЈ-terpyridine (pytpy),[24] 2,6-diisopropylphenyl phosphate
(dippH2)[25] and tert-butyl phosphonic acid (tBuPO3H2)[26] were syn-
thesized by following reported literature procedures.
Figure 8. Oxidation of benzyl alcohol at different temperatures using
catalyst 1 [substrate (2.5 mmol), oxidant (1 equiv.) and catalyst
(0.5 mol%) at 80 °C].
Synthesis of 1 and 2: To a stirred solution of pytpy (61 mg, 0.2 mmol)
and phosphate ligand either tBuPO3H2 (27 mg, 0.2 mmol) in case of
1, or dippH2 (51 mg, 0.2 mmol) in case of 2 in MeOH/CHCl3 (1:1
v/v) solvent mixture Co(OAc)2·4H2O (49 mg, 0.2 mmol) in MeOH
was added under constant stirring at room temperature. The red color
clear solutions obtained in each case was further stirred for 2 h and
filtered and kept for crystallization at room temperature. Red diffrac-
By applying the optimized reaction conditions, we have ex-
tended the present catalytic study to the different substrates,
ranging from aliphatic to aromatic alcohols. As can be seen
from Table 1, it is possible to attain 100% selectivity (ketone /
aldehyde) for the oxidation of all the substrates excepting tion quality single crystals of 1 and 2 were obtained in one week.
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a)
Table 1. Oxidation of alcohols catalyzed by compound 1 in presence of TBHP
.
a) Reaction conditions: substrate (2.5 mmol), oxidant (1 equiv.) and the catalyst (0.5 mol%) at 80 °C for 3 h.
[Co(pytpy)(tBuPO3H)2(H2O)]·H2O (1): Yield 198 g (56% based on
tBuPO3H2) Mp: Ͼ 250 °C. C28H38N4O8P2Co: found (calcd.): C 48.93
(49.49); H 5.34 (5.64), N 8.08(8.25)%. FT-IR (KBr) ν˜ = 3400 (br),
3056 (w), 2968 (vs), 2364 (br), 1147 (s), 1105 (s), 1053 (s), 769 (s)
cm–1. ESI-MS: calcd. for C48H46N8O6P2Co2 (dimeric form Mr =
1010) [M + H]: m/z 1011 found m/z 1011.
cally. The hydrogen atoms were refined isotropically as rigid atoms in
their idealized locations. Crystal data and structure refinement details
for 1 and 2 are given in Table 2
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting the de-
pository numbers CCDC-1829567 (1) and CCDC-1829568 (2)
(Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk, http://
www.ccdc.cam.ac.uk).
[Co(pytpy)2(dipp)(MeOH)·2MeOH]n (2): Yield 180 mg (52% based
on dippH2) Mp: Ͼ 250 °C. C35H43N4O7P1Co: found (calcd.): C 57.82
(58.25); H 6.37 (6.00), N 7.97 (7.76)%. FT-IR (KBr) ν˜ = 3400 (br),
3060(w), 2967(vs), 1187(s), 1093(s), 992(s) cm–1. ESI-MS: calcd. for
C64H62N8O8P2Co2 (dimeric form Mr = 1250) [M + H]: m/z 1251 found
m/z 1251.
Oxidation of Alcohols: Oxidation of alcohols was carried out in a
two necked round-bottomed flask. Prior to the reaction, the flask was
equipped with a magnetic bar followed by the sequential addition of
acetonitrile, substrate, catalyst and tert-butylhydrogen peroxide
(TBHP). The obtained catalytic mixture was stirred at 80 °C and the
aliquots were taken out to monitor the progress of reaction using GC-
MS, where helium was used as the carrier gas.
X-ray Crystallography: Single crystal X-ray diffraction data were
collected with a Rigaku Saturn 724+ CCD diffractometer with a Mo-
Kα radiation source (λ = 0.71075 Å) at 150 K. Rigaku Crystal Clear-
SM Expert software was used for data collection. Data integration and
indexing were performed with the CrysAlisPro software suite. WinGX
module was used to perform all the calculations.[27] The structures
were solved by direct methods (SIR-92).[28] The final structure refine-
ment was carried out using full-least-squares methods on F2 using
SHELXL-2014.[29] All non-hydrogen atoms were refined anisotropi-
Supporting Information (see footnote on the first page of this article):
Supporting information contains FT-IR, additional ESI-MS, TGA for
compounds 1 and 2, and packing diagram of 2.
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Table 2. Crystallographic details of compounds 1 and 2.
1
2
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Identification code
Empirical formula
FW
GB-654
C28H38CoN4O8P2
679.49
GB-077
C35H43CoN4O7 P
721.63
T /K
150(2)
150(2)
Crystal system
Space group
triclinic
P1
monoclinic
P21/n
¯
a /Å
b /Å
c /Å
α /°
8.8810(7)
11.7155(8)
16.5459(9)
75.241(5)
89.714(5)
70.565(6)
1563.85(2)
2
11.0802(4)
17,4009(6)
20.1537(8)
90
104.215(4)
90
3766.8(2)
4
1.272
β /°
γ /°
V /Å3
Z
D(calcd.) /mg·cm–3
1.443
0.705
μ /mm–1
0.547
Θ range /°
No. of reflns. collected
Independent reflns.
GOF
2.655 to 24.999
17909
5496
2.085 to 24.999
28081
6627
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1.054
1.065
R1 [I0Ͼ2σ(I0)]
wR2 (all data)
0.0354
0.0937
0.0716
0.1992
¯
[10] S. Hayami, K. Hashiguchi, G. Juhász, M. Ohba, H. Okawa, Y.
Acknowledgements
Maeda, K. Kato, K. Osaka, M. Takata, K. Inoue, Inorg. Chem.
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R. M. thanks SERB, New Delhi for a J. C. Bose Fellowship research
grant (SB/S2/JCB-85/2014). G.A.B. thank UGC New Delhi for re-
search fellowship. R. A. thanks the Department of Science and Tech-
nology (DST), SERB for a National Postdoctoral Fellowship (NPDF/
2016/00037).
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Keywords: Phosphates; Phosphonates; Alcohol oxidation;
Cobalt; Catalysis
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Published online: ᭿
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
G. A. Bhat, A. Rajendran, R. Murugavel* ....................... 1–9
Polydentate 4-Pyridyl-terpyridine Containing Discrete Cobalt
Phosphonate and Polymeric Cobalt Phosphate as Catalysts for
Alcohol Oxidation
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