Synthesis, structural characterization and alcohol oxidation activity of a new mononuclear manganese(II) complex

Article abstract of DOI:10.1007/s11243-010-9327-4

A manganese(II) complex of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) has been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR, and UV-Vis spectroscopic techniques. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this catalyst using oxone (2KHSO5KH-SO₄K₂SO₄) as an oxidant under biphasic reaction conditions (CH₂Cl₂/H ₂O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature. Easy preparation, mild reaction conditions, high yields of the products, short reaction times, no further oxidation to the corresponding carboxylic acids, high selectivity and inexpensive reagents make this catalytic system a useful oxidation method for aliphatic and benzylic alcohols. Springer Science+Business Media B.V. 2010.

Full text of DOI:10.1007/s11243-010-9327-4

Transition Met Chem (2010) 35:297–303
DOI 10.1007/s11243-010-9327-4
Synthesis, structural characterization and alcohol oxidation
activity of a new mononuclear manganese(II) complex
•
Mohammad Mahdi Najafpour Mojtaba Amini
•
•
Mojtaba Bagherzadeh Davar M. Boghaei
•
Vickie McKee
Received: 11 October 2009 / Accepted: 3 January 2010 / Published online: 20 January 2010
Ó Springer Science+Business Media B.V. 2010
Abstract A manganese(II) complex of 2,4,6-tris(2-pyridyl)-
1,3,5-triazine (tptz) has been synthesized and characterized
by single-crystal X-ray diffraction, elemental analyses, IR,
and UV–Vis spectroscopic techniques. Oxidation of alco-
hols to their corresponding aldehydes and ketones was
conducted by this catalyst using oxone (2KHSO5ÁKH-
SO4ÁK2SO4) as an oxidant under biphasic reaction condi-
tions (CH2Cl2/H2O) and tetra-n-butylammonium bromide
as phase transfer agent under air at room temperature. Easy
preparation, mild reaction conditions, high yields of the
products, short reaction times, no further oxidation to the
corresponding carboxylic acids, high selectivity and
inexpensive reagents make this catalytic system a useful
oxidation method for aliphatic and benzylic alcohols.
current chemistry [1–8]. In this context, the use of transi-
tion metal complexes as homogeneous catalysts is very
effective and selective [9–14]. Since manganese is known
to be catalytically active in a variety of metalloenzymes,
manganese complexes have been widely used as catalysts
to promote oxidation reactions [15–19]. In fact, many
catalytic studies in recent years have found that manganese
complexes can exhibit a diversity of catalytic oxidation
reactions on organic substrates in organic solvents [20, 21].
Numerous complexes of terpyridine and oligopyridines
with manganese have been investigated because of their
interesting structural, redox, photochemical, catalytic, and
water oxidation properties [22–33].
The ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) is a
potential spacer, which functions as a bis-bidentate or
simultaneously as a tridentate and a bidentate bridging unit.
As a ligand, tptz is believed to be stable towards nucleo-
philic attack and has been used as an analytical reagent for
various metal ions [34–37]. It behaves as a tridentate ligand
and forms hepta-coordinate complexes with manganese(II)
with small chelate bite angles [38–40].
Introduction
Finding an efficient catalyst for the selective oxidation of
bulk chemicals into useful products is an interesting field of
One of the most fundamental and important processes in
organic chemistry is oxidation of alcohols to carbonyl
compounds. A number of methods are known for alcohol
oxidation, until recently the traditional oxidation reactions
have been performed with classic reagents such as per-
manganate and dichromate salts [41, 42]. These reagents
are moderately expensive, toxic, corrosive, unstable, show
no selectivity, and require dangerous procedures for prep-
aration as well as over-oxidation to carboxylic acids and
moisture-sensitivity [43, 44].
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-010-9327-4) contains supplementary
material, which is available to authorized users.
M. M. Najafpour
Department of Chemistry, Institute for Advanced Studies
in Basic Sciences, 45195-1159, Gava Zang, Zanjan, Iran
M. Amini Á M. Bagherzadeh Á D. M. Boghaei (&)
Chemistry Department, Sharif University of Technology,
PO Box 11155-3516, Tehran, Iran
e-mail: dboghaei@sharif.edu
In this work, we report the synthesis and characteriza-
tion of a novel complex of manganese with tptz as ligand.
Also, herein, we demonstrate the efficient and selective
oxidation of alcohols to their corresponding aldehydes and
V. McKee
Department of Chemistry, Loughborough University,
Leicestershire LE11 3TU, UK
123

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Transition Met Chem (2010) 35:297–303
General oxidation procedure
ketones using this complex under mild and biphasic con-
ditions (CH2Cl2/H2O) at room temperature with oxone as
oxidant. Oxone was chosen in this study as a convenient,
readily available, and economical oxidant, which is utilized
for various transformations in organic synthesis [45–50].
In a typical experiment, a solution of oxone (0.2 mmol) in
H2O (5 mL) at room temperature was added to a solution
of alcohol (0.2 mmol), tetra-n-butylammonium bromide,
(0.1 mmol), and [Mn(tptz)(Cl)2(OH2)] (0.01 mmol), in
CH2Cl2 (1 mL), and the biphasic mixture stirred vigor-
ously. Formation of products and consumption of sub-
strates were monitored by gas chromatography. The
identities of the products were determined by comparison
with authentic samples using gas–liquid chromatography.
Oxidation product yields based on the oxidant were
quantified by comparison with chlorobenzene.
Experimental
All reagents and materials used for synthesis were reagent
grade and used without further purification. Elemental
analyses were performed on a Perkin-Elmer 2400 CHNS/O
elemental analyzer. IR spectra (4,000–400 cm-1) were
measured on a FT-IR JASCO 460 spectrophotometer with
KBr pellets and electronic spectra on a JASCO 7850 spec-
trophotometer. EPR Spectra were collected at 4 K on frozen
samples with an X-band Varian E-9 spectrometer equipped
with an Oxford ESR-900 liquid helium cryostat. Typical
instrument settings were the following: modulation ampli-
tude; 20 G, modulation frequency; 100 kHz, and microwave
power; 2.0 mW. The reaction products of oxidation were
determined and analyzed with an HP Agilent 6890 gas
chromatograph equipped with an HP-5 capillary column
(phenyl methyl siloxane 30 l 9 320 lm 9 0.25 lm) and
flame-ionization detector.
Results and discussion
Complex characterization
The elemental analysis and spectral data confirm the
assigned composition of the complex. The IR spectrum of
the complex shows a broad band due to water centered at
3,400 cm-1. Peaks revealing the presence of tppz in the
complex occur in the ranges 3,100–2,900 cm-1 (aromatic
C–H stretching vibrations), 1,580–1,550 cm-1 [m(C=N) and
m(C=C) stretches], 1,470–1,020 cm-1 [m(C–C) ? m(C–N)
vibrations], and 810–710 cm-1 (aromatic C–H deformation
vibrations). In the IR spectrum, the m(C=C/C=N) bands were
shifted from 1,590–1,390 cm-1 in free tptz to higher
wavenumbers in the product [52]. The electronic spectrum
of this complex was taken in water. The absorption bands in
the UV region between 210 and 246 nm are assigned to
ligand-centered p ? p* or n ? p* transitions; the complex
also exhibits one MLCT transition located at 284 nm [53].
Preparation of [Mn(tptz)(Cl)2(OH2)]
The complex was prepared by dissolving manganese(II)
chloride (1 mmol, 126 mg) and tptz (1 mmol, 312 mg) in
water (30 ml); the mixture was stirred for about 1 h at room
temperature under nitrogen. The solution was then evapo-
rated on a steam bath to 10 mL and cooled to room
temperature. Orange crystals separated and were filtered
off, washed with 5 mL of cooled water and then dried
in air (360 mg, 76% yield). Elemental analysis for
C18H16Cl2MnN6O2: Found: C 45.6%, H 3.4%, N 17.7%;
Calcd: C 45.3%, H 3.1%, N 18.0%. IR: 3,400 (b), 3,050 (s),
1,580 (s), 1,470 (m), 800 (w).
X-ray structure of [Mn(tptz)(Cl)2(OH2)]
The molecular structure of the complex is shown in Fig. 1.
Selected bond distances and angles are presented in
Table 2.
Each manganese atom in the structure is hexa-coordi-
nated, with a coordination polyhedron close to octahedral.
Hexa-coordination is achieved by means of three N atoms
belonging to the tptz ligand (N1, N4 and N5), one oxygen
atom from water (O1W) and two Cl (Cl1 and Cl2). The
bond distance of Mn(II) to the middle nitrogen N1 is sig-
nificantly shorter than the Mn1–N4 and Mn1–N5 distances,
which is usually observed in tptz-type ligands [54]. The
tptz ligand is almost planar; the angles between the central
triazine ring and the attached pyridyl rings are 2.93°, 0.32°
and 12.74° which are in accordance with the values
reported in the literature in related systems [55, 56]. In tptz,
the C(sp2)–C(sp2) distances within the ring are normal
X-ray crystallography
The data were collected at 150(2) K on a Bruker Apex II
CCD diffractometer. The structure was solved by direct
methods and refined on F2 using all the reflections [51]. All
the non-hydrogen atoms were refined using anisotropic
atomic displacement parameters and hydrogen atoms
bonded to carbon were inserted at calculated positions
using a riding model. Hydrogen atoms bonded to oxygen
were located from difference maps and refined with ther-
mal parameters riding on their carrier atoms. More infor-
mation is listed in Table 1.
123

Transition Met Chem (2010) 35:297–303
299
Table 1 Crystal data and
structure refinement for the
complex
Empirical formula
C18H16Cl2MnN6O2
474.21
Formula weight
Temperature
150(2) K
˚
0.71073 A
Wavelength
Crystal system
Space group
Monoclinic
P2(1)/n
˚
a = 8.6630(8) A
Unit cell dimensions
a = 90°
b = 98.3700(10)°
c = 90°
˚
b = 11.5311(11) A
˚
c = 20.0243(18) A
3
˚
1979.0(3) A
Volume
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.592 mg/m3
0.965 mm-1
964
0.25 9 0.22 9 0.16 mm3
Crystal size
Crystal description
Theta range for data collection
Index ranges
Yellow block
2.04 to 27.50°
-11 B h B 11, -14 B k B 14, -26 B l B 26
Reflections collected
Independent reflections
Completeness to theta = 27.50°
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2sigma(I)]
R indices (all data)
Largest diff. peak and hole
18,650
4,531 [R(int) = 0.0435]
99.8%
Semi-empirical from equivalents
0.8609 and 0.7944
Full-matrix least-squares on F2
4531/0/274
1.023
R1 = 0.0344, wR2 = 0.0820
R1 = 0.0478, wR2 = 0.0901
-3
˚
0.427 and -0.544 e A
contributing factor in the supramolecular assembly and
stabilization of the lattice; however, the strong O–H–O and
O–H–N interactions are obviously the dominant intermo-
lecular interactions. The significant p–p stacking distance
between the two parallel planar rings of the tptz ligand is
˚
3.6 A.
Catalytic reaction
Due to the importance of aldehydes and ketones as inter-
mediates in organic synthesis as well as their key roles in
the activation of some enzymes, the oxidation of alcohols
to aldehydes and ketones has been extensively studied [57].
Several reagents and oxidative procedures are available for
this transformation but many results in over-oxidation to
carboxylic acids. Control of the reaction conditions, spe-
cifically, time, temperature and the relative amount of
oxidants plays an important role to avoid forming oxidative
side products; however, these requirements are often hard
to meet. Thus, there is still considerable interest in the
development of selective oxidants for this transformation.
Fig. 1 ORTEP structure of the title complex with partial atom
labeling, the ellipsoids enclose 50% of the electronic density
˚
(1.40 A) and the exterior bonds (C1–C4, 1.48(1) A; C2–C9,
˚
˚
˚
1.48(1) A; C3–C14, 1.48(6) A) are also normal. The
structure also contains uncoordinated water molecules in
the lattice. Both hydrogen atoms of the coordinated water
molecule are involved in making hydrogen bonds with the
nitrogen atom of an uncoordinated tptz molecule (N6), the
chlorides, and coordinated water. This hydrogen bonding
network is reinforced by two types of weak Cl–H–O
interactions. This weak hydrogen bonding is possibly a
123

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Transition Met Chem (2010) 35:297–303
Table 2 Selected geometric parameters for the complex
Table 3 The effects of various conditions on the oxidation of benzyl
alcohol by the [Mn(tptz)(Cl)2(OH2)]/oxone/n-Bu4NBr catalytic system
˚
The bond lengths (A)
Entry Amount
Amount
of catalyst of oxone (1 mL)
Solvent Conversion Selectivity to
(%)a
Mn(1)–O(1W)
Mn(1)–N(1)
Mn(1)–N(5)
Mn(1)–N(4)
Mn(1)–Cl(1)
Mn(1)–Cl(2)
C(1)–N(3)
2.1996(17)
2.2303(17)
2.3270(17)
2.3353(18)
2.4235(6)
2.4683(6)
1.331(3)
benzaldehyde
(%)b
(mmol)
(mmol)
1
2
0.01
0.01
0.01
0.01
0.01
0.2
0.2
0.2
0.2
0.2
CH2Cl2 100
100
100
100
100
CH3Cl
CH3CN
C6H6
91
85
60
3
4
5
CH3COCH3 85
C(1)–N(1)
1.337(3)
100
6
The bond angles (8)
0.01
0.01
0
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.05
0.1
0.15
0.2
0.25
CCl4
58
100
100
100
100
100
100
100
100
98
7
n-hexane 41
O(1W)–Mn(1)–N(1)
O(1W)–Mn(1)–N(5)
N(1)–Mn(1)–N(5)
O(1W)–Mn(1)–N(4)
N(1)–Mn(1)–N(4)
N(5)–Mn(1)–N(4)
O(1W)–Mn(1)–Cl(1)
N(1)–Mn(1)–Cl(1)
N(5)–Mn(1)–Cl(1)
N(4)–Mn(1)–Cl(1)
O(1W)–Mn(1)–Cl(2)
N(1)–Mn(1)–Cl(2)
N(5)–Mn(1)–Cl(2)
N(4)–Mn(1)–Cl(2)
84.08(6)
86.38(7)
69.97(6)
85.07(7)
70.15(6)
139.84(6)
83.90(5)
164.32(5)
99.23(4)
118.69(5)
175.75(5)
93.89(5)
96.45(4)
90.72(5)
8
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
18
51
62
75
81
9
0.002
0.004
0.006
0.008
0.01
0.012
0.01
0.01
0.01
0.01
0.01
10
11
12
13
14
15
16
17
18
19
CH2Cl2 100
CH2Cl2 100
CH2Cl2
CH2Cl2
CH2Cl2
54
73
91
100
100
100
100
95
CH2Cl2 100
CH2Cl2 100
Reaction condition: benzylalcohol 0.2 mmol, n-Bu4NBr 0.1 mmol
a
The conversions (%) were measured after 5 min at room temperature
b
Selectivity to benzaldehyde = (benzaldehyde/(benzaldehyde ?
benzoic acid)) 9 100
For finding the optimal conditions for the oxidation of
alcohols, the oxidation of benzyl alcohol under various
conditions was studied and the results are listed in Table 3.
In order to choose a suitable solvent, the oxidation of
benzylalcohol was carried out in dichloromethane, chlo-
roform, acetonitrile, benzene, acetone, carbon tetrachloride
and n-hexane. Among the solvents examined, dichloro-
methane was found to be the best (Table 3, entries 1–7).
The conversion of benzyl alcohol monotonously increases
with the addition of catalyst between 0.002 to 0.01 mmol.
When the amount of catalyst was increased to 0.012 mmol,
the selectivity of benzylalcohol oxidation reduces from 100
to 98% (Table 3, entries 9–14). The reaction without
catalyst was found to proceed only very slightly (Table 3,
entry 8). The amount of oxone could also significantly
affect the conversion and benzaldehyde selectivity. When
the amount of oxone was increased from 0.05 to 0.2 mmol,
the conversion of benzyl alcohol increased from 54 to
100%. With a further increase of oxone to 0.25 mmol, the
selectivity to benzaldehyde decrease from 100 to 95%
(Table 3, entries 15–19). Next, we investigated the ability
of this homogenous manganese(II) complex, as a catalyst
for the oxidation of a range of alcohols in the presence
of oxone and tetra-n-butylammonium bromide as phase
transfer agent. Reactions were performed at room tem-
perature under air in CH2Cl2/H2O containing [Mn(tptz)
(Cl)2(OH2)], tetra-n-butylammonium bromide, substrate
and oxone in 1:20:10:20 molar ratio, respectively. The
system was applicable for the oxidation of a wide variety of
primary and secondary aliphatic and benzylic alcohols to
the corresponding aldehydes and ketones (Table 4).
As shown in Table 4, substituted benzyl alcohols were
converted to their corresponding aldehydes efficiently
without marked affecting the functional groups. Further-
more, all primary and secondary alcohols were selectively
oxidized to aldehydes and ketones, respectively. In addi-
tion, the reaction of aromatic alcohols to the corresponding
carbonyl compounds (Table 4, entries 1–8) was fast and
efficient, whereas aliphatic alcohols all reacted more
slowly (Table 4, entries 9–19).
The reactivity of the complex toward oxone in the
reaction solutions was investigated by measuring the EPR
spectrum of the brown species resulting from the reaction
between the complex and oxone (Fig. 2). The 16-line
123

Transition Met Chem (2010) 35:297–303
301
Table 4 Oxidation of alcohols
by the [Mn(tptz)(Cl)2(OH2)]/
oxone/n-Bu4NBr catalytic
system
Entry
Substrate
Product
Yield%a TONc
CH2OH
CH3
CH2OH
OMe
CH2OH
CHO
CH3
CHO
OMe
CHO
1
2
100
100
20
20
3
4
100
100
20
20
MeO
MeO
MeO
CH2OH
CHO
CHO
MeO
CH2OH
5
6
100
98
20
NO2
CH2OH
NO2
CHO
19.6
N
CHO
CHO
O2N
Cl
CH2OH
O2
7
98
19.6
CH2OH
OH
Cl
8
9
97
65
79
19.4
13
O
CH3
OH
CH3
10
15.8
O
H3C
H3C
OH
OH
O
11
12
76
93
15.2
18.6
O
H3C
HO
CH3
CH3
H3C
CH3
CH3
13
14
81b
95
16.2
19
O
OH
O
The molar ratios for
OH
O
[Mn(tptz)(Cl)2(OH2)]:phase
transfer agent: substrate:
oxidant are 1:10:20:20,
respectively. The reactions were
run for 5 min at room
15
83
16.6
O
OH
16
17
18
19
72
71
14.4
14.2
18
OH
O
temperature in a biphasic
medium (CH2Cl2/H2O)
a
CH3
The yields are based on GC
data using an internal standard
method
CH3
O
90
OH
CH3
CH3
b
67b
The reactions were run for
30 min at room temperature
13.4
OH
O
c
TON = (mmol of product)/
mmol of catalyst
H3C
CH3
H3C
CH3
spectrum observed is characteristic of MnI2II,IV di-l-oxo
complexes [58–60]. This experiment shows that the
mononuclear complex is oxidized to a MnI2II,IV di-l-oxo
species by oxone. This dinuclear complex is also observed
as a pre-catalyst in the reactions of other mononuclear
manganese complexes with tridentate ligands incorporating
oxone [59].
Conclusion
In conclusion, the new complex [Mn(tptz)(Cl)2(OH2)] has
been synthesized and characterized by physico-chemical
methods. In this study, we have demonstrated the effec-
tiveness of this manganese(II) complex as catalyst for the
oxidation of different types of alcohols to carbonyl
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Transition Met Chem (2010) 35:297–303
15. Bagherzadeh M, Latifi R, Tahsini L (2006) J Mol Catal A
260:163
16. Bagherzadeh M, Tahsini L, Latifi R (2008) Catal Commun
9:1600
17. Bagherzadeh M, Latifi R, Tahsini L, Amini M (2008) Catal
Commun 10:196
18. Wieghardt K (1989) Angew Chem Int Ed Engl 28:1153
19. Kessissoglou DP (1999) Coord Chem Rev 185/186:837
20. Koek JH, Kohlen EWMJ, Russell SW, van der Wolf L, ter Steeg
PF, Hellemons JC (1999) Inorg Chim Acta 295:189
21. Bagherzadeh M (2003) Tetrahedron Lett 44:894322
22. Limburg J, Vrettos JS, Liable-Sands LM, Rheingold AL, Crab-
tree RH, Brudvig GW (1999) Science 283:1524
23. Das S, Incarvito CD, Crabtree RH, Brudvig GW (2006) Science
312:1941
24. Chiswell B, McKenzie ED, Lindoy LF (1987) In: Wilkinson G,
Gillard RD, McCleverty JA (eds) Comprehensive coordination
chemistry, vol 4. Pergamon Press, Oxford
25. Louloudi M, Nastopoulos V, Gourbatsis S, Perlepes SP, Hadjil-
iadis N (1999) Inorg Chem Commun 2:479
26. Drummond J, Wood JS (1970) J Chem Soc A 226
27. Andrew JE, Blake AB, Fraser LR (1975) J Chem Soc Dalton
Trans 800
Fig. 2 EPR spectrum of the reaction between the complex (1 mM)
and oxone (0.023 M), frozen within 10 s of mixing
28. Milinski N, Ribar B, Culum Z, Djuric S (1977) Acta Crystallogr
B 33:1678
29. Mikuriya M, Hatano Y, Asato E (1997) Bull Chem Soc Jpn
70:2495
30. Hughes BB, Haltiwanger RC, Pierpont CG, Hampton M,
Blackmer GL (1980) Inorg Chem 19:1801
31. Reid HON, Kahwa IA, White AJP, Williams DJ (1998) Inorg
Chem 37:3868
compounds with oxone. Easy preparation, mild reaction
conditions, high yields of the products, short reaction
times, no further oxidation to the corresponding carboxylic
acids, high selectivity and inexpensive reagents make this
catalytic system a useful method for the oxidation of
alcohols.
32. Vaira MD, Mani F, Stoppioni P (1992) J Chem Soc Dalton Trans
1127
33. Hagen KS (1992) Angew Chem Int Ed Engl 31:764
34. Collins P, Diehl H (1960) Anal Chem Acta 2:125
35. Diehl H, Buchanan EB, Smith GF (1960) Anal Chem 32:1117
36. Embry WA, Ayres GH (1968) Anal Chem 40:1499
37. Janmohamed MJ, Ayres GH (1972) Anal Chem 44:2263
38. Majumder A, Choudhury CR, Mitra S, Marschner C, Baum-
gartner J (2005) Z Naturforsch 60b:99
Acknowledgements We are grateful to the Research Council of
Sharif University of Technology and National Elite Foundation for
their financial support.
References
39. Zhang M, Fang R, Zhao Q (2008) J Chem Crystallogr 38:601
40. Das A, Rosair GM, Fallah MS, Ribas J, Mitra S (2006) Inorg
Chem 45:3301
¨
1. Backvall JE (ed) (2004) Modern oxidation methods. Wiley-VCH,
Weinheim
41. Rankin KN, Liu Q, Hendry J, Yee H, Noureldin NA, Lee DG
(1998) Tetrahedron Lett 39:1095
2. Roberts SM (2007) Catalysts for fine chemical synthesis. Wiley-
VCH, Weinheim
42. Ley SV, Madin A (1991) In: Trost BM, Flemming I (eds)
Comprehensive organic synthesis, vol 7. Pergamon Press,
Oxford, 251 pp
43. Ley SV, Norman J, Griffith WP, Marsden SP (1994) Synthesis
639
44. Stevens RV, Chapman KT, Waiter HN (1980) J Org Chem
45:2030
45. Wozniak LA, Stec WJ (1999) Tetrahedron Lett 40:2637
46. Wozniak LA, Koziolkiewicz M, Kobylanska A, Stec WJ (1998)
Bioorg Med Chem Lett 8:2641
3. Olason G, Sherrington DC (1999) React Funct Polym 42:163
4. Davies JA, Watson PL, Liebman JF, A. Greenberg A (eds) (1990)
Selective hydrocarbon oxidation, principles and progress. VCH,
New York
5. Simadi LI (ed) (1991) Dioxygen activation and homogeneous
catalytic oxidation. Elsevier, New York
6. Sheldon RA, Kochi JK (1981) Metal-catalyzed oxidation of
organic compounds. Academic Press, New York
7. Jacobsen EN (1993) In: Ojima I (ed) Catalytic asymmetric syn-
thesis, VCH, Weinheim
47. Webb KS, Levy D (1995) Tetrahedron Lett 36:5117
48. Webb KS, Ruszkay SJ (1998) Tetrahedron 54:401
49. Trost BM (1981) Tetrahedron Lett 22:1287
50. Baumstark AL, Beeson M, Vasquez PC (1989) Tetrahedron Lett
30:5567
8. Katsuki T (1995) Coord Chem Rev 140:189
9. Holm RH (1987) Chem Rev 87:1401
10. Collman JP, Hegedus LS, Norton JR, Finke RG (eds) (1987)
Principles and applications of organotransition metal chemistry.
University Science Books, Mill Valley
51. Sheldrick GM (2001) SHELXTL version 6.12. Bruker AXS,
Madison
52. Nakamoto K (1986) Infrared and Raman spectra of inorganic and
coordination compounds, 4th edn. Wiley-Interscience Publica-
tion, New York
11. Boghaei DM, Mohebi S (2002) J Mol Catal A 179:41
12. Bagherzadeh M, Amini M (2009) Inorg Chem Commun 12:21
13. Boghaei DM, Mohebi S (2002) Tetrahedron 58:5357
14. Bagherzadeh M, Tahsini L, Latifi R, Ellern A, Woo LK (2008)
Inorg Chim Acta 361:2019
123

Transition Met Chem (2010) 35:297–303
303
53. Campos Fernandez CS (2001) Ph.D thesis, Michigan state
University
54. Majumder A, Choudhury CR, Mitra S, Marschner C, Baum-
gartner J (2005) Z Naturforsch 60b:99
55. Kim J, Han S (2002) Acta Crystallogr C 58:m521
56. Janiak C (2000) J Chem Soc Dalton Trans 3885
57. Mallat, Baiker A (2004) Chem Rev 104:3037
58. Limburg J, Crabtree RH, Brudvig GW (2000) Inorg Chim Acta
297:301
59. Limburg J, Brudvig GW, Crabtree RH (1997) J Am Chem Soc
119:2761
60. Thorp HH, Brudvig GW (1991) New J Chem 15:479
123