Metal complexes of an amine bisphenol with a thiophene side-arm

Article abstract of DOI:10.1135/cccc2010049

Dioxomolybdenum(VI) and oxotungsten(VI) complexes with a new amine bisphenol ligand (H₂L) are reported. The ligand which carries a neutral nitrogen atom, two phenolic oxygen atoms and a thiophene side-arm was synthesized by a simple one-pot Mannich reaction. Further reaction with [MoO₂(acac)₂] yielded a monomeric molybdenum complex [MoO₂(L)(MeOH)] (2a) or a dimeric complex [Mo₂O ₂(μ-O)₂(L)₂] (2b), depending on the reaction conditions. The reaction with a tungsten trisglycolate [W(eg)₃] led to the formation of a monomeric compound [WO(eg)(L)] (3). In these complexes, the potentially tetradentate amine bisphenolate dianion coordinates as a tridentate O,N,O donor while the sulfur side-arm donor remains intact. The solid-state structure of 2a was investigated by X-ray crystallography.

Full text of DOI:10.1135/cccc2010049

Mo and W Amine Bisphenolates
1051
METAL COMPLEXES OF AN AMINE BISPHENOL WITH
A THIOPHENE SIDE-ARM
b
a2,
Eero SALMINENa1, Reijo SILLANPÄÄ and Ari LEHTONEN
*
a
Laboratory of Materials Chemistry and Chemical Analysis, Department of Chemistry,
University of Turku, FI-20014 Turku, Finland; e-mail: essalm@utu.fi, arileh@utu.fi
Laboratory of Inorganic Chemistry, Department of Chemistry,
1
2
b
University of Jyväskylä, FI-40351 Jyväskylä, Finland; e-mail: resillan@jyu.fi
Received May 15, 2010
Accepted July 29, 2010
Published online October 5, 2010
Dedicated to Professor Bohumil Štíbr on the occasion of his 70th birthday in recognition his
outstanding contributions to the field of organometallic chemistry.
Dioxomolybdenum(VI) and oxotungsten(VI) complexes with a new amine bisphenol ligand
(H2L) are reported. The ligand which carries a neutral nitrogen atom, two phenolic oxygen
atoms and a thiophene side-arm was synthesized by a simple one-pot Mannich reaction.
Further reaction with [MoO2(acac)2] yielded
a monomeric molybdenum complex
[MoO2(L)(MeOH)] (2a) or a dimeric complex [Mo2O2(µ-O)2(L)2] (2b), depending on the reac-
tion conditions. The reaction with a tungsten trisglycolate [W(eg)3] led to the formation of
a monomeric compound [WO(eg)(L)] (3). In these complexes, the potentially tetradentate
amine bisphenolate dianion coordinates as a tridentate O,N,O donor while the sulfur
side-arm donor remains intact. The solid-state structure of 2a was investigated by X-ray crys-
tallography.
Keywords: Tungsten; Molybdenum; Phenolate ligands.
In organometallic chemistry, several bulky anionic ligands with hard oxy-
gen donor atoms have been used to control the structure and reactivity of
metal complexes and various phenolate ligands, especially, have shown
great promise towards this goal1. For instance, amine bisphenol molecules
form a group of readily available and versatile chelating ligands2. Espe-
cially, tripodal ligands with an attached side-arm donor are complexed with
several main-group and transition metals to form active catalysts and initia-
tors for various biomimetic processes as well as some industrially valuable
reactions. For example, in studies on bioinorganic chemistry, Cu(II) com-
plexes supported by a tripodal N2O2 donor set are used as functional ana-
logues for galactose oxidase3. Similarly, several Fe(III) complexes containing
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060
© 2010 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc2010049

1052
Salminen, Sillanpää, Lehtonen:
amine bisphenol ligands with a pyridyl side-arm were reported as synthetic
models for catechol dioxygenases4. A number of transition metal complexes
with this type of ligands have been studied due to their relevance in indus-
trial applications. Such examples are zirconium catalysts for olefin polymer-
ization5 and titanium catalysts for the ring-opening polymerization of
lactones6. Dioxomolybdenum(VI) and dioxotungsten(VI) complexes with
tripodal or linear amine bisphenols resemble the active centres of several
metal based enzymes, thus they can be used as model compounds in bio-
logical oxotransfer reactions7,8. The reactivity of such compounds can be
also employed in industrially important reactions, e.g. in epoxidation of
olefins9. Amine bisphenols with a coordinating side-arm group combine
typically hard nitrogen and oxygen donors to react as dianionic, tetra-
dentate chelators10. In this paper we report a synthesis of a new potentially
tetradentate amine bisphenol with a thiophene side-arm. The final aim was
to combine hard oxygen and nitrogen donors with a soft sulfur donor to
have a biomimetic O2NS donor set around a metal centre. It was found that
the new amine bisphenol molecule reacts with molybdenum(VI) and tung-
sten(VI) precursors as a tridentate O,N,O donor while the sulfur side-arm
donor remains uncoordinated.
RESULTS AND DISCUSSION
Syntheses
The amine bisphenol 1 was prepared straightforwardly by a solvent-free
Mannich reaction11. A mixture of 2,4-di-tert-butylphenol, 2-(aminomethyl)-
thiophene and paraformaldehyde was kept at 120 °C for 16 h and the re-
sulting solid material was recrystallized from acetonitrile (Scheme 1).
SCHEME 1
The product formed in the reaction between [MoO2(acac)2] and a ligand
1 was found to depend on the reaction medium (Scheme 2). When a meth-
anol solution of [MoO2(acac)2] was treated with one equivalent of 1, the re-
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

Mo and W Amine Bisphenolates
1053
action initiated and the reaction mixture subsequently turned yellow in
colour (Scheme 2a). The solution was kept at 4 °C for 24 h to obtain yellow
prismatic crystals, which were characterized by XRD as [MoO2(L)(MeOH)]·
MeOH (2a). The corresponding solvate complex was formed also in dimeth-
ylsulfoxide (DMSO) solution. When the identical reaction was carried out
in the acetonitrile solution, the reaction mixture turned orange-red and
orange microcrystals started to precipitate (Scheme 2b). Elemental analyses
and spectroscopic measurements showed that the crystals were formed of
dimeric complexes [Mo2O2(µ-O)2(L)2] (2b). The slightly air-sensitive 2a is
soluble in DMSO, DMF and hot MeOH, but it reacts in an acetonitrile sus-
pension to form a dimeric complex 2b as a red powder. Similar deformation
occurs also in open air and particularly in vacuum due to the loss of metha-
nol solvate molecules. Air-stable crystals of 2b dissolve in DMSO to yield
yellow solutions, but they are practically insoluble in other common sol-
vents at room temperature. Compound 2b dissolves also in methanol upon
SCHEME 2
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

1054
Salminen, Sillanpää, Lehtonen:
heating while recrystallization from hot methanol produces the methanol
adduct 2a. In conclusion, it is demonstrated that the formation of com-
plexes 2a and 2b can be easily adjusted. Particularly, the monomeric com-
plex is transformed to the dimeric counterpart as a consequence of the
leaving of methanol in the solid state, whereas the dimeric form can be
turned to the monomeric one by recrystallization from MeOH. As MeOH
and MeCN have practically the same steric properties, the coordinating
capability of MeOH and the formation of hydrogen bonds seem to have
significant roles in the formation of the monomeric adduct. This solvent-
dependent reactivity resembles the reactions of [MoO2(acac)2] with related
tridentate dianionic ligands12,13
.
The tungsten complex 3 was prepared by applying the reaction condi-
tions reported earlier for the preparation of related amine bisphenol com-
plexes14. The stirred suspension of a tungsten precursor [W(eg)3] (eg =
1,2-ethanediolate dianion) in toluene was treated with a stoichiometric
amount of the ligand 1 at reflux temperature while the reaction was pro-
moted by fractionating out the liberated 1,2-ethanediol as a toluene azeo-
1
trope (Scheme 3). The H NMR spectrum of the unpurified yellow reaction
mixture shows resonances for 3 along with some uncharacterized minor
components. The oxotungsten(VI) complex 3 was isolated by column chro-
matography and crystallized from hot toluene as bright yellow crystals. As
expected on the grounds of our earlier studies on amine bisphenolate
complexes of tungsten(VI), the coordination of ligand 1 was associated
with the formation of an oxo group14. Although the formation of terminal
oxo group was predictable due to our earlier investigations, the source of
the oxo moiety remains unclear. In principle, high-valent metal alkoxides
can decompose by an elimination process, which yields ether and the corre-
sponding oxometal compounds15. However, water is the most likely source
of oxide, as it is practically impossible to exclude the diminutive amount of
water necessary to carry out the hydrolysis reaction.
SCHEME 3
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

Mo and W Amine Bisphenolates
1055
Solution and Solid-State Structures
In the solid state, complex 2a is formed of mononuclear units, in which the
amine bisphenolate is coordinated to the dioxomolybdenum(VI) ion as a
tridentate ligand. In the solid state, complex 2a is formed of mononuclear
units, in which the amine bisphenolate is coordinated to the dioxo-
molybdenum(VI) ion as a tridentate ligand. The coordination sphere
around the central metal presents distorted octahedral geometry with the
terminal oxo ligands cis to each other. Two anionic phenolate oxygens and
two neutral donor atoms of the ligands are trans and cis, respectively, as ex-
pected for octahedral dioxo complexes. The Mo1–O5 and Mo1–N8 bonds
are relatively long (2.338(2) and 2.499(2) Å, respectively), which can be
explained by the strong trans-effect of the oxo ligands7. A thiophene side-
arm donor does not coordinate to the metal centre. Instead, a molecule of
solvent methanol is located trans to the oxo group to complete the coordi-
nation sphere (Fig. 1). Another molecule of methanol is attached to the co-
FIG. 1
Molecular structure of [MoO2(L)(MeOH)]·MeOH (2a). Thermal ellipsoids have been drawn at
30% probability level. Selected bond lengths (in Å) and angles (in °): Mo1–O1 1.7114(19),
Mo1–O2 1.6945(19), Mo1–O3 1.9241(18), Mo1–O4 1.9153(18), Mo1–O5 2.338(2), Mo1–N8
2.499(2); O1–Mo1–O2 105.06(10), O1–Mo1–N8 168.34(9), O2–Mo1–O5 166.14(8)
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

1056
Salminen, Sillanpää, Lehtonen:
ordinated methanol through hydrogen bonding (coordinated MeOH as an
acceptor) with the O···O distance of 2.597 Å. The uncoordinated MeOH
molecule forms a hydrogen bond with terminal oxygen atom O1 of the ad-
jacent unit, the O···O distance being 2.731 Å. The O=Mo=O angles and the
Mo=O bonds are typical for cis-dioxomolybdenum(VI) phenolates7,9,12,16–18
.
Also the Mo–O(phenolate) bond lengths (1.9241(18) and 1.9153(18) Å) and
Mo–O–C angles (134.80(16) and 140.18(17)°) are similar to those reported
for other dioxomolybdenum(VI) phenolate complexes. According to our
earlier investigations on the related complexes of tridentate amine
bisphenols12, we may suggest that complex 2b consists of dinuclear, doubly
bridged units of Mo2O2(µ-O)2(L)2. The IR spectrum of 2a presents strong
bands at 900 and 922 cm–1, which are distinctive absorption maxims for
2+
MoO2 moiety19. Bands at ~3440 and 3640 cm–1 are due to the presence of
coordinated and hydrogen bonded methanol molecules. Complex 2b has
generally similar IR spectrum although it presents a strong IR absorption at
834 cm–1, which is typical for a non-symmetrically bridged Mo–O–Mo
core20. Furthermore, complexes 2b show only a single stretch at 941 cm–1
instead of a characteristic doublet for cis-MoO2 moieties in complexes 2a.
1H NMR spectrum of 2a in DMSO shows typical resonances for Cs-symmet-
ric amine bisphenolate complexes together with resonances for free metha-
nol, which indicates that DMSO can replace MeOH molecules from the first
coordination sphere around Mo(VI) ion. The DMSO-d6 solutions of com-
1
pounds 2a and 2b show identical H and 13C NMR resonances for the che-
late ligand, so it seems evident that the supposed dimeric structure of 2b
1
breaks down upon dissolution in DMSO. In both cases, the H NMR spec-
trum shows doublets for the methylene protons bridging the phenolates
and the central amine nitrogen. This confirms that these protons are
diastereotopic, i.e. on each methylene group one proton faces towards the
thiophene and the other faces away from it. A singlet for the methylene
protons adjacent to the thiophene group indicates that these protons are
equivalent, so the thiophene sulfur seems not to coordinate to the metal
centre to form a chelate ring.
Spectroscopic analyses of yellow product 3 indicate that the simple
alkoxide displacement reaction of trisglycolate [W(eg)3] is associated with
some other modification in the ligand environment, i.e. the formation of
1
an oxo group. H NMR spectrum showed anticipated resonances for coordi-
nated amine bisphenolate ligand. The CH2 protons were seen as broad over-
lapping signals at 3.7–4.0 ppm. Similar resonances are found earlier for
structurally well-characterized amine bisphenolate complexes of oxo-
tungsten(VI) with a cis-orientation of phenolate moieties. In the aliphatic
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

Mo and W Amine Bisphenolates
1057
region of the spectra two distinct multiplets for the ethanediolate groups
are observed implying that there are two different environments for these
methylene protons. The different signals for the axial and equatorial hydro-
gen atoms are indications of a rigid glycolate chelate ring, which prevents
the fast transformations of the ligand configuration. IR spectrum shows
a strong absorption band at 953 cm–1, which is typical for a W=O moiety.
CONCLUSIONS
A new amine bisphenolate, which carries a neutral nitrogen atom, two phe-
nolic oxygen atoms and a thiophene side-arm, was synthesized by a simple
one-pot Mannich reaction. The reaction of a new ligand with [MoO2(acac)2]
in a methanol solution yields a monomeric molybdenum complex
[MoO2(L)(MeOH)], whereas a dimeric complex [Mo2O2(µ-O)2(L)2] is formed
in acetonitrile. The reaction with a tungsten trisglycolate [W(eg)3] in tolu-
ene leads to the formation of a monomeric compound [WO(eg)(L)]. In all
cases, the amine bisphenolate dianion coordinates as a tridentate O,N,O
donor while the sulfur side-arm donor remains intact.
EXPERIMENTAL
Starting complexes [MoO2(acac)2] and [W(eg)3] were prepared according to the literature
procedures21,22. Other chemicals and solvents were obtained from commercial sources and
were used as purchased. IR spectra (ν, cm–1) were measured in KBr using a diffusion reflect-
ance attachment. The NMR spectra (δ, ppm; J, Hz) were recorded at 25 °C with a Bruker
Avance 400 spectrometer (1H at 399.75 MHz, 13C at 100.52 MHz) equipped with a broad-
band observe probe (BBO-5mm-Zgrad) and referenced internally to TMS.
6,6′-(Thiophen-2-ylmethylazanediyl)bis(methylene)bis(2,4-di-tert-butylphenol) (1)
2,4-Di-tert-butylphenol (8.25 g, 40.0 mmol), 2-(aminomethyl)thiophene (2.26 g, 20 mmol)
and paraformaldehyde (1.32 g, 44 mmol) were mixed in an open vessel and the reaction
mixture was kept at 120 °C for 16 h. The sticky mixture was cooled to the room tempera-
ture, mixed with 15 ml of acetonitrile and then kept overnight at –18 °C. Colorless crystal-
line material was separated by filtration and washed with cold acetonitrile to obtain 5.11 g
(47%) of amine bisphenol 1, m.p. 126 °C. 1H NMR (CDCl3): 1.303 s, 18 H (t-Bu); 1.439 s,
18 H (t-Bu); 3.718 s, 4 H (CH2); 3.875 s, 2 H (CH2); 6.97–7.44, five partially overlapping sig-
nals, 5 H (ArH + thiophene); 10.5 s (br.), 2 H (ArOH). 13C NMR (CDCl3): 29.67 (CMe3);
31.64 (CMe3); 34.19 (CMe3); 34.91 (CMe3); 51.73 (CH2); 56.37 (CH2); 121.16, 123.67,
125.23, 126.06, 127.15, 127.98, 136.04, 139.37, 141.52, 152.28. For C35H51NO2S (549.87)
calculated: 76.45% C, 9.35% H, 2.55% N; found: 76.73% C, 9.02% H, 2.56% N.
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

1058
Salminen, Sillanpää, Lehtonen:
[MoO2(L)(MeOH)]·MeOH (2a)
[MoO2(acac)2] (163 mg, 0.50 mmol) and a ligand 1 (275 mg, 0.50 mmol) were dissolved in
10 ml of methanol by a gentle heating. The yellow reaction mixture was stored at –18 °C
for 2 days. Yellow crystals formed were isolated and washed with cold methanol to obtain
243 mg (72%) of molybdenum complex 2a. The NMR sample was prepared by adding the
complex in excess, and then filtering away the undissolved part, thus the amounts of MeOH
in a sample was not stoichiometric. 1H NMR (DMSO-d6): 1.290 s, 18 H (t-Bu); 1.409 s, 18 H
(t-Bu); 3.17 d, J = 5.2, 18 H (MeOH); 3.368 d, J = 13.2, 2 H (ArCH2); 4.057 s, 2 H
(thiophene-CH2); 4.09 q, J = 5.2, 6 H (MeOH); 4.240 d, J = 13.2, 2 H (ArCH2); 6.557 d, J =
2.4, 1 H (thiophene); 7.012 s, 1 H (ArH); 7.025, overlapping s + t, 3 H (ArH + thiophene);
7.250 s, 2 H (ArH); 7.665 d, J = 5.2, 1 H (thiophene). 13C NMR (DMSO-d6): 30.02 (CMe3);
31.36 (CMe3); 33.88 (CMe3); 34.60 (CMe3); 48.50 (CH2); 55.99 (CH2); 122.81 (arom.); 122.89
(arom.); 125.89 (thiophene); 126.16 (arom.); 127.88 (thiophene); 131.69 (thiophene); 133.13
(thiophene); 135.91 (arom.); 140.79 (arom.); 159.34 (arom.). IR: 470 w, 570 m, 712 m, 760 s,
801 m, 815 m, 844 vs, 855 m, 883 s, 900 vs, 912 vs, 922 vs, 958 m, 1006 vs, 1012 m,
1080 w, 1124 m, 1168 s, 1208 m, 1236 s, 1257 vs, 1311 m, 1342 m, 1360 m, 1474 s,
2867 m, 2909 s, 2959 vs, 3406 s, 3638 s. For C37H57MoNO6S (739.86) calculated: 60.07% C,
7.77% H, 1.89% N; found: 59.74% C, 7.36% H, 1.94% N. Elemental analyses gave erroneous
results for 2a due to the partial loss of solvent molecules upon work-up.
[Mo2O2(µ-O)2(L)2] (2b)
[MoO2(acac)2] (98 mg, 0.30 mmol) and ligand 1 (165 mg, 0.30 mmol) were mixed with
10 ml of acetonitrile. The orange-red reaction mixture was kept at room temperature over-
night. The solid product was filtered and washed with acetonitrile to obtain 190 mg (94%)
of 2b as orange-red microcrystals. 1H NMR (DMSO-d6): 1.290 s, 18 H (t-Bu); 1.411 s, 18 H
(t-Bu); 3.370 d, J = 13.2, 2 H (ArCH2); 4.054 s, 2 H (thiophene-CH2); 4.242 d, J = 13.2, 2 H
(ArCH2); 6.556 d, J = 2.4, 1 H (thiophene); 7.009 s, 1 H (ArH); 7.022, overlapping s + t, 3 H
(ArH + thiophene); 7.250 s, 2 H (ArH); 7.666 d, J = 5.2, 1 H (thiophene). 13C NMR
(DMSO-d6): 30.00 (CMe3); 31.38 (CMe3); 33.87 (CMe3); 34.59 (CMe3); 48.52 (CH2); 55.99
(CH2); 122.82 (arom.); 122.92 (arom.); 125.90 (thiophene); 126.20 (arom.); 127.88 (thio-
phene); 131.68 (thiophene); 133.12 (thiophene); 135.92 (arom.); 140.81 (arom.); 159.32
(arom.). IR: 475 w, 572 m, 700 m, 712 m, 760 s, 807 s, 815 m, 834 vs, 844 vs, 850 vs, 867 s,
882 m, 911 m, 925 m, 941 s, 970 m, 1085 w, 1012 m, 1065 m, 1125 m, 1168 s, 1202 m,
1235 s, 1256 vs, 1309 m, 1342 m, 1359 m, 1390 m, 1474 s, 2865 m, 2900 s, 2952 vs. For
C
70H98Mo2N2O8S2 (1351.55) calculated: 62.21% C, 7.31% H, 2.07% N; found: 62.11% C,
7.45% H, 2.06% N.
[WO(eg)(L)] (3)
[W(eg)3] (182 mg, 0.50 mmol) and ligand 1 (275 mg, 0.50 mmol) were mixed with 30 ml of
toluene. The reaction mixture was stirred under reflux for 2 h. The most of solvent and
other volatiles were then removed by distillation and the yellow product was isolated by sil-
ica column chromatography using toluene as an eluent. The solid material was crystallized
from 5 ml of hot acetonitrile to obtain 254 mg (63%) of 3 as bright yellow crystals. 1H NMR
(CDCl3): 1.313 s, 18 H (t-Bu); 1.527 s, 18 H (t-Bu); 3.7–4.0, several peaks, 4 H (ArCH2);
4.134 s, 2 H (thiophene-CH2); 5.082 m, 2 H (OCH2); 5.294 m, 2 H (OCH2); 6.984 overlap-
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

Mo and W Amine Bisphenolates
1059
ping s + t, 3 H (ArH + thiophene); 7.127 m, 1 H (thiophene); 7.025, overlapping s + t, 3 H
(ArH + thiophene); 7.414 d, J = 2.4, 1 H (ArH); 7.465 d, J = 5.2, 1 H (thiophene). 13C NMR
(CDCl3): 30.10 (CMe3); 31.62 (CMe3); 34.54 (CMe3); 35.13 (CMe3); 51.38 (thiophene-CH2);
55.99 (ArCH2); 80.11 (OCH2); 123.66 (arom.); 125.68 (thiophene); 126.78 (arom.); 127.34
(thiophene); 132.04 (thiophene); 133.02 (thiophene); 135.91 (arom.); 140.23 (arom.); 145.55
(arom.); 154.02 (arom.). IR: 513 m, 562 m, 604 m, 621 s, 715 s, 739 w, 828 m, 869 vs (br);
896 w, 919 s, 953 vs, 968 m, 999 w, 1029 w, 1080 m, 1063 vs, 1170 s, 1021 s, 1129 m,
1238 vs, 1290 m, 1339 m, 1360 s, 1390 m, 1464 s, 1476 s, 2865 m, 2900 s, 2952 vs. For
C
37H53NO5SW (807.73) calculated: 55.02% C, 6.61% H, 1.73% N; found: 54.88% C,
6.85% H, 1.72% N.
X-ray Crystallography
The crystallographic data were collected at 173 K on an Enraf Nonius Kappa CCD area detec-
tor diffractometer using graphite monochromatized MoKα radiation (λ = 0.71073 Å). Data
collection was performed using
ϕ and ω scans and the data were processed using
DENZO-SMN v0.93.0 23. SADABS 24 absorption correction was applied to the data of all com-
pounds. The structures were solved by direct methods using the SHELXS97 program and
full-matrix least-squares refinements on F2 were performed using the SHELXL97 program25
.
Structure figures were drawn using Ortep-3 for Windows26. Summary of crystallographic
data for 2a: Yellow crystals, formula C37H57MoNO6S, crystal system monoclinic, space group
P21/n, a = 11.8839(3) Å, b = 19.6243(4) Å, c = 16.5166(5) Å, β = 101.9920(10)°, V =
3767.83(17) Å3, Z = 4, R1 = 0.0616, wR2 = 0.0883, GOF = 1.026.
CCDC 777096 contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge, CB2 1EZ, UK;
fax: +44 1223 336033; or deposit@ccdc.cam.ac.uk).
REFERENCES
1. For recent reviews, see: a) Lamberti M., Mazzeo M., Pappalardo D., Pellecchia C.: Coord.
Chem. Rev. 2009, 253, 2082; b) Licini G., Mba M., Zonta C.: Dalton Trans. 2009, 5265;
c) Homden D. M., Redshaw C.: Chem. Rev. 2008, 108, 5086; d) Kawaguchi H., Matsuo T.:
J. Organomet. Chem. 2004, 689, 4228.
2. For example, see: Kerton F. M., Holloway S., Power S. A., Soper R. G., Sheridan K.,
Lynam J. M., Whitwood A. C., Willans C. E.: Can. J. Chem. 2008, 86, 435; and references
therein.
3. John A., Shaikh M. M., Ghosh P.: Dalton Trans. 2008, 2815.
4. Velusamy M., Palaniandavar M., Gopalan R. S., Kulkarni G. U.: Inorg. Chem. 2003, 42,
8283.
5. Tshuva E. Y., Goldberg I., Kol M., Goldschmidt Z.: Organometallics 2001, 20, 3017.
6. Sarazin Y., Howard R. H., Hughes D. L., Humphrey S. M., Bochmann M.: Dalton Trans.
2006, 340.
7. Wong Y.-L., Yan Y., Chan E. S. H., Yang Q., Mak T. C. W., Ng T. K. P.: J. Chem. Soc.,
Dalton Trans. 1998, 3057.
8. Whiteoak C. J., Britovsek G. J. P., Gipson V. C., White A. J. P.: Dalton Trans. 2009, 2337.
9. Wong Y.-L., Tong L. H., Dilworth J. R., Ng T. K. P.: Dalton Trans. 2010, 4602.
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

1060
Salminen, Sillanpää, Lehtonen:
10. Dean R. K., Granville S. L., Dawe L. N., Decken A., Hattenhauer K. M., Kozak C. M.:
Dalton Trans. 2010, 548; and references therein.
11. Riisiö A., Wichmann O., Sillanpää R.: Lett. Org. Chem. 2010, 7, 298.
12. Lehtonen A., Sillanpää R.: Polyhedron 2005, 24, 257.
13. Głowiak T., Jerzykiewicz L., Sobczak J. M., Ziółkowski J. J.: Inorg. Chim. Acta 2003, 356,
387.
14. Lehtonen A., Sillanpää R.: Inorg. Chem. 2004, 43, 6501.
15. a) Turova N. Ya., Kessler V. G., Kucheiko S. I.: Polyhedron 1991, 10, 2617; b) Shcheglov
P. A., Drobot D. V., Seisenbaeva G. A., Gohil S., Kessler V. G.: Chem. Mater. 2002, 14,
2378.
16. Hanna T. A., Incarvito C. D., Rheingold A. L.: Inorg. Chem. 2000, 39, 630.
17. Dinda R., Sengupta P., Ghosh S., Sheldrick W. S.: Eur. J. Inorg. Chem. 2003, 363.
18. Rao C. P., Sreedhara A., Rao P. V., Verghese M. B., Rissanen K., Kolehmainen E.,
Lokanath N. K., Sridhar M. A., Prasad J. S.: J. Chem. Soc., Dalton Trans. 1998, 2383.
19. Judmaier M. E., Wallner A., Stipicic G. N., Kirchner K., Baumgarter J., Belaj F.,
Mösch-Zanetti N. C.: Inorg. Chem. 2009, 48, 10211.
20. Wilson A. J., Penfold B. R., Wilkins C. J.: Acta Crystallogr., Sect. C: Cryst. Struct. Commun.
1983, 39, 329.
21. Chen G. J.-J., McDonald J. W., Newton W. E.: Inorg. Chem. 1976, 15, 2612.
22. Schröder F. A., Scherle J.: Z. Naturforsch. 1973, 28b, 46.
23. Otwinowski Z., Minor W.: Methods Enzymol. 1997, 276, 307.
24. Sheldrick G. M.: SADABS. University of Göttingen, Göttingen 2002.
25. Sheldrick G. M.: SHELXS97 and SHELXL97, Programs for Refinement of Crystal Structures.
University of Göttingen, Göttingen 1997.
26. Farrugia L. J.: J. Appl. Crystallogr. 1999, 32, 837.
Collect. Czech. Chem. Commun. 2010, Vol. 75, No. 10, pp. 1051–1060

Copyright of Collection of Czechoslovak Chemical Communications is the property of Institute of Organic
Chemistry & Biochemistry, Academy of Sciences of the Czech Republic, v.v.i. and its content may not be
copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written
permission. However, users may print, download, or email articles for individual use.