New amino acid ligated yttrium hydroxy clusters

Article abstract of DOI:10.1039/c001464h

The synthesis of the four mixed pentanuclear yttrium hydroxy clusters [Y₅(OH)₅(α-AA)₄(Ph₂acac) ₆] (α-AA = d-phenyl glycine, l-proline, l-valine, and l-tryptophan; Ph₂acac = dibenzoylmethani

Full text of DOI:10.1039/c001464h

View Online / Journal Homepage / Table of Contents for this issue
This article is published as part of the Dalton Transactions themed issue entitled:
New Horizons in Organo-f-element Chemistry
Guest Editor: Geoff Cloke
University of Sussex, UK
Published in issue 29, 2010 of Dalton Transactions
Image reproduced with the permission of Tobin Marks
Articles in the issue include:
PERSPECTIVES:
Organo-f-element catalysts for efficient and highly selective hydroalkoxylation and hydrothiolation
Charles J. Weiss and Tobin J. Marks, Dalton Trans., 2010, DOI: 10.1039/c003089a
Non-classical divalent lanthanide complexes
François Nief, Dalton Trans., 2010, DOI: 10.1039/c001280g
COMMUNICATIONS:
A bimetallic uranium μ-dicarbide complex: synthesis, X-ray crystal structure, and bonding
Alexander R. Fox, Sidney E. Creutz and Christopher C. Cummins
Dalton Trans., 2010, DOI: 10.1039/c0dt00419g
PAPERS:
Coordination polymerization of renewable butyrolactone-based vinyl monomers by lanthanide and
early metal catalysts
Garret M. Miyake, Stacie E. Newton, Wesley R. Mariott and Eugene Y.-X. Chen,
Dalton Trans., 2010, DOI: 10.1039/c001909g
Visit the Dalton Transactions website for more cutting-edge inorganic and
organometallic chemistry research
www.rsc.org/dalton

Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
Volume 39 | Number 29 | 7 August 2010 | Pages 6553–6892
Themed issue: New horizons in organo-f-block chemistry
ISSN 1477-9226
HOT ARTICLE
Roesky et al.
PERSPECTIVE
Nief
New amino acid ligated yttrium
hydroxy clusters
Non-classical divalent lanthanide
complexes
1477-9226(2010)39:29;1-0

PAPER
www.rsc.org/dalton | Dalton Transactions
New amino acid ligated yttrium hydroxy clusters†
a
b
a
Dominique T. Thielemann, Ignacio Fern a´ ndez and Peter W. Roesky*
Received 22nd January 2010, Accepted 1st April 2010
First published as an Advance Article on the web 5th May 2010
DOI: 10.1039/c001464h
The synthesis of the four mixed pentanuclear yttrium hydroxy clusters [Y
5
(OH)
5
(a-AA)
4
(Ph
2
acac)
6
]
(
a-AA = D-phenyl glycine, L-proline, L-valine, and L-tryptophan; Ph
2
acac = dibenzoylmethanide) is
reported. The solid state structures of all compounds were established by single crystal X-ray
diffraction. In these enantiomerically pure chiral clusters the dibenzoylmethanide and amino acid
ligands are accommodated in the coordination spheres of the yttrium atoms. The specific optical
rotations of all four compounds were determined. PGSE NMR diffusion measurements as function of
concentration have been carried out on one model cluster, proving these molecules to be prone to
aggregation in chloroform solutions.
Introduction
In contrast, we and others have established the synthesis of
lanthanide hydroxo complexes in organic solvents in the presence
of an organic base such as triethylamine. Using this approach, the
Biologically active ligands have been employed in lanthanide
chemistry over the recent years because lanthanide complexes
have been used in several biological and medical applications.
These are, for example, the application of certain Gd complexes
as contrast agents for magnetic resonance imaging (MRI), the
use of lanthanide complexes and nanoparticles as luminescent
labels in various fluoroimmunoassays, and the employment of
radioactive lanthanide isotopes as radiopharmaceuticals. More-
over, lanthanide complexes are very active non-enzymatic agents
capable of mediating hydrolysis of DNA and RNA with both high
selectivity and specificity.
In all these different types of applications it deserves mentioning
that the lanthanide complexes can reach the target (e.g. an organ
or a cell) unchanged. Biologically relevant ligands such as amino
acids and peptides have been used among others over the years.
Using amino acids as ligands leads to the formation of not
only mononuclear complexes but also oligo- and polynuclear
reaction of [LnCl
ligand was shown to give nanoscaled cluster compounds in
3
·(H
2
O)
n
] (n = 6, 7) with a suitable supporting
1
–3
3
+
which the lanthanide atoms are versatilely arranged in cage-
4–7
17–21
like coordination polyhedra.
Mechanistically, the cluster for-
mation occurs via a ligand-controlled partial hydrolysis of the
lanthanide salts, i.e. the degree of hydrolysis depends on the
capability of the ligand to serve as ancillary or supporting ligand.
This capability is associated with preventing the lanthanide salts
from an uncontrolled polymerization (in terms of hydrolysis) to
structurally undefined oxo/hydroxy species. The dimensions of
the resulting cages generally depend on both the ionic radii of
the lanthanide(III) atoms and the steric demand of the ligands
used. In this context, the synthesis and structure of a pentanuclear
8
9
10
2
lanthanide cluster [Ln
Ph
5
(OH)
5
(Ph
2
acac)10] (Ln = Y, Eu, Dy, Ho;
21–24
2
acac = dibenzoylmethanide) was reported,
in which the
lanthanide atoms build up a square pyramidal scaffold by occupy-
ing its vertices. The {Ln } core is surrounded by ten monoanionic
Ph acac ligands showing two types of coordination behaviour: six
ligands are terminal chelates (h ), whereas each basal lanthanide
atom is chelated by one Ph acac ligand and the apical lanthanide
atom lying on a twofold symmetry axis is chelated by two Ph acac
2,11
lanthanide oxo/hydroxy clusters. While most of the reported
lanthanide amino acid clusters consist of only a few lanthanide
5
2
12,13
atoms,
cluster by using tyrosine as a supporting ligand.
the same group also published a chiral 60-metal sodalite-like Er-
Zheng and coworkers reported a pentadecanuclear
2
14,15
Very recently
2
2
16
structure by using L-threonine as a ligand. In these polynuclear
compounds the carboxylate functions of the amino acids act as
bridges between adjacent metal centers.
2
ligands. The residual four ligands are bridging chelates ((m-O)-h )
acting as linkages between two adjacent metal atoms belonging
to the base of the polyhedron, thus capping all four basal edges
Lanthanide amino acid clusters were usually prepared in water
by adjusting the pH-value carefully. In this manner, highly
sophisticated lanthanide-hydroxo complexes have been obtained
at near neutral pH. Another common feature of this kind of
cluster synthesis is the absence of other organic coligands.
(
Scheme 1).
11
a
Institut f u¨ r Anorganische Chemie, Karlsruher Institut f u¨ r Technologie
(
KIT), Engesserstr. 15, Geb. 30.45, 76131, Karlsruhe, Germany. E-mail:
2 5 5 2
Scheme 1 Coordination of Ph acac ligand in [Ln (OH) (Ph acac)10].
roesky@kit.edu; Fax: (+49) 721-608-4854; Tel: (+49) 721-608-6117
b
A´ rea de Qu ´ı mica Org a´ nica, Universidad de Almer ´ı a, Crta. Sacramento s/n,
Herein we report the synthesis of chiral mixed pentanuclear
0
4120, Almeria, Spain. E-mail: ifernan@ual.es
yttrium hydroxy clusters, in which both dibenzoylmethanide and
amino acid ligands are accommodated in the coordination spheres
†
CCDC reference numbers 762599–762602. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c001464h
This journal is © The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 6661–6666 | 6661

of the yttrium atoms. In comparison to the above mentioned pure
dibenzoylmethanide clusters, the four dibenzoylmethanide ligands
2
serving as bridging chelates adopting the (m-O)-h coordination
modus have selectively and quantitatively been substituted by the
amino acids. In this manner, four proteinogenic and essential
amino acids were attached onto the pyramidal lanthanide scaffolds
to give the corresponding mixed cluster species.
Results and discussion
Dibenzoylmethane (Ph
2
acacH) and the corresponding amino acid
(
a-AAH) were deprotonated in methanol using potassium tert-
Fig. 1 Perspective view of the molecular structure of 1. Hydro-
butoxide. As amino acids we used D-phenyl glycine (D-PhGlyH),
L-proline (L-ProH), L-valine (L-ValH) and L-tryptophan (L-TrpH).
The solutions of the deprotonated ligands were subsequently re-
acted with [YCl
the pentanuclear yttrium clusters [Y
AA = D-PhGly (1), L-Pro (2), L-Val (3), L-Trp (4)) (Scheme 2).
In contrast to our previous studies we used potassium tert-
butoxide instead of triethylamine as base. Thus we preemptively
avoided the formation of triethylammonium chloride, which was
not easily removed from the products in the crystallization step.
The new clusters have been characterized by standard analytical
and spectroscopic techniques and the solid state structures of all
compounds were established by single crystal X-ray diffraction.
gen atoms are omitted for clarity. Selected distances [ A˚ ] and an-
◦
gles [ ]: N1–Y2 2.503(5), N2–Y3 2.484(6), N3–Y4 2.469(6), N4–Y5
2
2
.502(6); O7–Y2 2.394(5), O7–Y5 2.413(5), O11–Y2 2.431(5), O11–Y3
.337(4), O15–Y3 2.416(5), O15–Y4 2.392(5), O19–Y4 2.428(5), O19–Y5
+
-
3
·(H
2
O)
6
], which is in fact [YCl
2
·(H
2
O)
6
] Cl , to give
acac) ] (a-
5
(OH) (a-AA)
5
4
(Ph
2
6
2.330(5); Y2–O7–Y5 96.6(2), Y2–O11–Y3 97.6(2), Y3–O15–Y4 96.4(2),
Y4–O19–Y5 96.8(2).
Fig. 2 Perspective view of the molecular structure of 2. Hydro-
gen atoms are omitted for clarity. Selected distances [ A˚ ] and an-
◦
gles [ ]: N1–Y2 2.510(9), N2–Y3 2.529(10), N3–Y4 2.535(11), N4–Y5
2
2
2
.525(10), O7–Y2 2.385(8), O7–Y5 2.375(7), O11–Y2 2.380(8), O11–Y3
.391(8), O15–Y3 2.395(9), O15–Y4 2.408(7), O19–Y4 2.390(7), O19–Y5
.378(8); Y2–O7–Y7 97.3(2), Y2–O11–Y3 97.0(3), Y3–O15–Y4 97.1(3),
Y4–O19–Y5 97.6(3).
linked by one m -O atom each. All these linking oxygen atoms
3
depict fragments of the hydroxo bridges stabilizing the pyramidal
shape inwardly. In 1–4 each yttrium ion is coordinated to eight
oxygen atoms displaying a square antiprismatic coordination
polyhedron. A similar pentanuclear pyramidal lanthanide core
2
5,26
was reported earlier,
e.g. in [Ln
5
(OH)
(OH) (Ph
-O = o-nitro-phenolate),
(NCCH ]. To the best of our
5
(Ph
acac)
2
acac)10] (Ln =
21–24
+
Y, Eu, Dy, Ho),
HNEt
3
[Ln
N-C
-2,6)
5
4
2
7
(o-O N-C
2
6
H
4
-
-
20
O)
3
Cl] (Ln = Er, Tm; o-O
2
6
H
4
2
7
and H
5
[Eu
5
O
5
(OC
6
H
3
iPr
2
6
)
3 8
knowledge, a neutral pentanuclear motif with two different organic
supporting ligands including amino acids has not been reported
yet.
Scheme 2 Synthesis of mixed pentanuclear yttrium clusters with amino
acids as coligands.
2
In compounds 1–4 the six h -coordinating chelating diben-
Compounds 1–4 having chiral amino acids in their coordination
zoylmethanide ligands remain in the same terminal posi-
spheres could be obtained as enantiopure compounds. They all
tions as compared to the pure dibenzoylmethanide clusters
21–24
21–24
crystallize in the orthorhombic space group P2
1
2
1
2
1
having four
[Ln
5
(OH)
5
(Ph
2
acac)10
]
with Ln = Y, E u , D y, H o.
In
2
molecules in the unit cell. All compounds form pentayttrium
cores in a square-based pyramidal arrangement, i.e. the metal
atoms occupy the vertices of the pyramid (Fig. 1–4). In the
contrast, the four bridging and chelating (m-O)-h -coordinating
dibenzoylmethanide ligands are now formally substituted by the
amino acids, acting as coligands. The amino acids, which were
deprotonated under basic reaction conditions at the acid function,
are coordinated via the nitrogen atom of the amino group and one
square base face four yttrium atoms are linked by one m
4
-O
atom, whereas in the four triangular faces three metal atoms are
6
662 | Dalton Trans., 2010, 39, 6661–6666
This journal is © The Royal Society of Chemistry 2010

Scheme 3 Selective substitution of Ph
ligands in (m-O)-h modus.
2
acac ligands with amino acid
2
results, we are now able to predict the position in which the amino
acids coordinate to the pentanuclear yttrium core.
The specific optical rotations of the four enantiopure com-
Fig. 3 Perspective view of the molecular structure of 3. Hydrogen
◦
pounds 1–4 were determined in CH
2
2
Cl . As expected, they always
atoms are omitted for clarity. Selected distances [ A˚ ] and angles [ ]:
show negative values for the clusters containing the L-configured
amino acids (L-Pro (2), L-Val (3) and L-Trp (4)) and a positive
value for the cluster with the D-configured one (D-PhGly (1)). In
N1–Y2 2.483(6), N2–Y3 2.453(5), N3–Y4 2.455(6), N4–Y5 2.452(6),
O7–Y2 2.370(4), O7–Y5 2.335(4), O11–Y2 2.324(4), O11–Y3 2.401(4),
O15–Y4 2.357(4), O15–Y3 2.364(4), O19–Y4 2.334(4), O19–Y5 2.377(4);
Y2–O7–Y5 97.38(15), Y2–O11–Y3 96.51(15), Y3–O15–Y4 96.90(14),
Y4–O19–Y5 97.2(2).
1
the H NMR spectra, few unambiguous signals are observed for
the Ph
2
acac ligand in the aromatic region, but two sets of singlets
acac
in a 1 : 2 ratio are observed for the methyne bridges of the Ph
2
ligands. This indicates two different coordination environments
for this ligand. The more intense signal can be ascribed to those
methyne bridges of the Ph acac ligands coordinating to the basal
2
metal atoms (four ligands), whereas the minor one can be assigned
to those binding to the apical metal atom (two ligands). The signals
of each amino acid were observed in the expected region. We could
not assign the OH and NH
2
protons in all compounds. In the IR
spectra the hydroxyl groups of the cluster core showed broad peaks
-
1
between 3350 and 3650 cm .
The nuclearity of these pentanuclear yttrium clusters in solution
has not been evaluated so far. A partial answer to this question
stems from diffusion measurements. Table 1 shows pulsed gradient
spin-echo (PGSE) diffusion data for the model cluster 3 in
chloroform solution as a function of concentration.
Fig. 4 Perspective view of the molecular structure of 4. Hydro-
This diffusion methodology allows one to estimate molecular
gen atoms are omitted for clarity. Selected distances [ A˚ ] and an-
28–30
volumes and ion pairing in solution.
From the measured D
◦
gles [ ]: N1–Y2 2.477(8), N2–Y3 2.522(7), N3–Y4 2.510(8), N4–Y5
value at 6 mM, we estimate (via the Stokes–Einstein equation)
2
2
2
.500(8), O7–Y2 2.395(6), O7–Y5 2.385(6), O11–Y2 2.347(5), O11–Y3
.391(6), O15–Y3 2.371(6), O15–Y4 2.415(6), O19–Y4 2.379(7), O19–Y5
.381(6); Y2–O7–Y5 96.4(2), Y2–O11–Y3 97.1(2), Y3–O15–Y4 97.0(2),
˚
to be 8.6 A, which is in good
the hydrodynamic radius r
H
˚
agreement with the ca 8.6 A derived from our crystallographic
data. Increasing the concentration up to 44 mM provides a
Y4–O19–Y5 98.1(2).
2
-1
significant decrease on the D value (3.701 m s ) and consequently
˚
to 10.0 A. Although there is
results in a marked increase of r
a change of viscosity at higher concentrations, the remarkable
H
oxygen atom of the carboxyl group in a chelating fashion to one
basal metal atom each. Concomitantly the carboxyl groups are
also bridging two adjacent basal metal atoms via the same oxygen
atom, hence, the amino acid ligands simultaneously also cap each
˚
difference in radii (Dr
aggregation. The formation of a hydrogen bond might decrease the
H
1.4 A, 16%) seems likely to be due to
2
basal edge and are thus (m-O)-h -coordinating.
Table 1 Diffusion coefficient (D) and hydrodynamic radius (r
H
) values
Although the amino acids have a significantly different steric
demands and different Lewis basicities (primary (1, 3, 4) and
secondary amino nitrogen atoms (2)), there are no significant
differences in bond lengths and angles of compounds 1–4. For
example, the bond distances of the yttrium atoms to the amino acid
for cluster 3 as a function of concentration at 292 K in CDCl as solvent
3
a
10
2
-1
˚
b
rX-ray/A
˚
c
Concentration/mM
6
D ¥ 10 m s
r
H
/A
4.314
4.262
4.183
3.701
8.6
8.7
8.9
10.0
1
2
2
2
8
.6
˚
˚
˚
˚
ligands vary only very slightly (av. Y–Na-AA 2.490 A (1), 2.525 A
(
(
˚
˚
44
2), 2.461 A (3), and av. Y–Oa-AA 2.393 A (1), 2.388 A (2), 2.358 A
3)). Obviously there is a high tolerance of the coordination
a
b
The experimental error in the D values is ±2%. The viscosity h used in
chemistry of these cluster compounds towards the bulkiness and
the electronic nature of the amino acid ligands (Scheme 3).
None of the clusters have a crystallographic symmetry element,
but a non-crystallographic C2-axis can be drawn through the
the Stokes–Einstein equation was taken from Perry’s Chemical Engineers’
-3
-1 -1
Handbook 8th Edition (www.knovel.com) and is 0.5737 ¥ 10 kg m s .
c
Deduced from the X-ray structure by considering the volume of the
crystallographic cell divided by the number of contained asymmetric units,
the latter one is assumed to be spherical in shape.
yttrium atom of the apex and the m
4
-oxygen atom. Based on these
This journal is © The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 6661–6666 | 6663

D value of a certain molecule from that expected (with regard to its
size) in a given medium at a given temperature. Considering a rapid
exchange on the measurement timescale between sites, we suggest
a clear hydrogen bond aggregation at relatively concentrated
solutions since the large amount of XH (X = O, N) moieties
in cluster 3 are capable of providing intermolecular hydrogen
bonding, resulting in an averaged D value.
and the solvents were used as purchased from commercial sources
without further purification.
Preparation of [Y
(1), L-Pro (2), L-Val (3) L-Trp (4)
5
(OH)
5
(a-AA)
4
(Ph
2
acac)
6
] (a-AA = D-PhGly
The general procedure for preparing the pentanuclear amino acid
compounds is as follows. To a stirred solution of KOtBu (1.168 g,
9
.89 mmol, 3 eq.) in 20 mL of methanol, the a-amino acids
2.64 mmol, 0.8 eq.) D-PhGlyH (1) (399 mg), L-ProH (2) (304
mg), L-ValH (3) (309 mg) or L-TrpH (4) (539 mg) were added.
Subsequently, Ph acacH (905 mg, 3.96 mmol, 1.2 eq.) was added
to this mixture, which turn its colour from colourless to pale
yellow. After stirring for 15 min, a solution of [YCl O)
(
Conclusions
The first yttrium-based amino acid clusters with accessory organic
coligands were synthesized and structurally characterized. Pre-
liminary PGSE NMR diffusion experiments have been performed
with such species for the first time proving the clusters’ tendency to
aggregate in chloroform solution. It could also be shown that the
amino acids coordinate via the nitrogen atom of the amino group
and one oxygen atom of the carboxyl group in a chelating fashion
to one basal metal atom each. Concomitantly the carboxyl groups
are also bridging two adjacent basal metal atoms via the same
oxygen atom. Based on these results, we are now able to predict
the position in which the amino acids will coordinate within a
pentanuclaer structural motive. Targeting a further expansion of
the scope of applications for these pentanuclear structures, we are
currently conducting analogous syntheses as mentioned above by
substituting the yttrium salts with the corresponding europium,
terbium and dysprosium salts.
2
3
·(H
2
6
]
(1.00 g, 3.30 mmol, 1 eq.) in 20 mL of methanol was added
dropwise and a flaky white precipitate was formed. The reaction
was stirred overnight at room temperature. Then the precipitate
was filtered off, washed with methanol (3 ¥ 20 mL) and air-dried.
The resulting yellow solids of compounds 1–4 were extracted with
20 mL of dichloromethane. The solutions were filtered and cooled
◦
to -80 C. Layering these solutions with 80 mL of n-hexane (not
precooled) yielded yellowish rhombic crystals suitable for single
crystal X-ray analysis after one day.
20
1
.
Yield (single crystals): 22%. [a] = 754.92 (CH
2
Cl
2
, c =
2
1
0
.60). H NMR (CDCl
3
, 400 MHz): d 5.29 (2H, s, CH
2
Cl ), 6.15
(
6
7
(
4H, t, J = 10.3 Hz, CH (PhGly)), 6.23 (4H, s, CH (Ph
2
acacbas)),
acacap)), 6.71 (10H, m, Ph), 6.84 (8H, m, Ph),
.04 (10H, m, Ph), 7.11 (10H, m, Ph), 7.16 (10H, m, Ph), 7.36
.42 (2H, s, CH (Ph
2
This work was supported by the Landesstiftung Baden-
W u¨ rttemberg gGmbH, the DFG and the Center for Functional
Nanostructures (CFN). I. F. thanks the Ram o´ n y Cajal program
for financial support.
13
1
12H, m, Ph), 7.62 (20H, m, Ph), 7.82 (8H, br s, NH
2
). C{ H}
NMR (CDCl
3
, 400 MHz): d 60.7 (a-CH), 95.3 (CH (Ph acac)),
2
1
27.2 (Ar-C), 127.4 (Ar-C), 127.7 (Ar-C), 128.2 (Ar-C), 129.0 (Ar-
C), 130.7 (p-Ar-C), 131.1 (p-Ar-C), 140.0 (i-Ar-C), 141.6 (i-Ar-
C), 180.7 (carboxyl-C), 182.4, 183.5, 185.7 (CO (Ph
2
acacap/bas)).
Experimental
-1
IR [cm ]: 3348, 3285, 3060, 1593, 1552, 1517, 178, 1453, 1395,
-
1
1
1
311, 1024, 1009, 943, 597. Raman [cm ]: 3055, 1594 (nCO), 1487,
General considerations
439, 1288, 1283, 1175, 1059, 1004, 998, 939, 780, 669, 604, 396.
CDCl
3
was obtained from Chemotrade Chemiehandelsge-
C122H103N O Y ·CH Cl (2554.60) Anal Calcd: C 57.83, H 4.14
4
25
5
2
2
sellschaft mbH (≥ 99 atom% D). NMR spectra were recorded on a
Bruker Avance 400 or an Avance II 300 MHz spectrometer. Chem-
ical shifts are referenced relative to internal solvent resonances
in ppm and are reported relative to tetramethylsilane. Diffusion
measurements were performed using the Stimulated Echo Pulse
Sequence on a Bruker Avance 500 without spinning. The shape
of the gradient pulse was rectangular, and its strength varied
automatically in the course of the experiments. The calibration
of the gradients was carried out via a diffusion measurement
N 2.19. Found: C 57.76, H 4.25, N 1.87.
2
0
2
.
Yield (single crystals): 31%. [a] = -782.01 (CH
2
Cl
2
, c =
1
0
.63). H NMR (CDCl
3
, 400 MHz): d 1.48, 1.60 (8H, 2 m, g -
CH
8H, 2 m, d-CH
CH (Ph acacap)), 6.22 (4H, s, CH (Ph
.73 (8H, m, Ph), 7.01 (4H, m, Ph), 7.13 (3H, m, Ph), 7.20 (4H,
m, Ph), 7.30 (10H, m, Ph), 7.37 (6H, m, Ph), 7.41 (5H, m, Ph),
2
), 1.80 (4H, br s, NH), 2.06, 2.21 (8H, 2 m, b-CH
), 4.09 (4H, q, J = 8.3 Hz, a-CH), 5.87 (2H, s,
acacbas)), 6.65 (4H, m, Ph),
2
), 2.62, 2.81
(
2
31
2
2
6
1
3
1
7
.49 (8H, d, Ph), 7.92 (8H, m, Ph). C{ H} NMR (CDCl
MHz): d 26.2 (g -CH ), 30.4 (b-CH ), 46.6 (d-CH ), 62.9 (a-CH),
acac)), 126.8 (Ar-C), 127.5 (Ar-C), 127.8 (Ar-C),
28.1 (Ar-C), 130.6 (p-Ar-C), 131.0 (p-Ar-C), 138.3 (i-Ar-C), 139.5
3
, 400
-
4
of HDO in D O, which afforded a slope of 2.022 ¥ 10 . To
2
2
2
2
check reproducibility, three different measurements with different
diffusion parameters (d and/or D) were always carried out. The
gradient strength was increased in 8% steps from 10% to 98%.
Elemental analyses were carried out with an Elementar Vario
EL. IR spectra were obtained on a Bruker IFS 113 v spectrometer
via the Attenuated Total Reflection method (ATR). Raman spectra
were measured on a Jobin Yvon Labram spectrometer. Optical
rotations were determined with a Jasco P-2000 spectrometer (Na,
9
1
4.3 (CH (Ph
2
(
i-Ar-C), 181.5 (carboxyl-C), 182.7, 183.6 (CO (Ph acacap/bas)). IR
2
-
1
[cm ]. 3614 (nOH), 1702, 1597 (nCO), 1553, 1521, 1479, 1456,
-
1
1
391, 1108, 1025, 751, 721, 689, 642. Raman [cm ]: 3055, 1594
(
nCO), 1486, 1439, 1288, 1283, 1174, 1057, 998, 988, 916, 781,
779, 665, 363. C110
H
103
N
4
O
25
5
Y (2325.54) Anal Calcd: C 56.81, H
4
.46 N 2.41. Found: C 56.68, H 4.54, N 2.06.
5
89 nm). The yttrium salt was synthesized from its corresponding
2
0
oxide by neutralizing with concentrated hydrochloric acid, fol-
lowed by evaporation to dryness. Dibenzoylmethane, potassium
tert-butoxide, D-phenyl glycine, L-proline, L-valine, L-tryptophane
3. Yield (single crystals) 28%. [a] = -818.76 (CH
2
Cl
2
, c =
1
0.71). H NMR (CDCl
3
, 400 MHz): d 0.64, 0.85 (24H, 2 d, J =
6.9 Hz, CH
3
), 2.31 (4H, m, CH-(CH ) ), 3.45 (4H, m, a-CH), 4.36,
3 2
6
664 | Dalton Trans., 2010, 39, 6661–6666
This journal is © The Royal Society of Chemistry 2010

5
.10 (8H, 2 br s, NH
CH (Ph acacbas)), 6.72 (5H, m, Ph), 6.82 (5H, br s, OH), 6.95 (4H,
m, Ph), 7.21 (12H, m, Ph), 7.29 (8H, m, Ph), 7.41 (5H, m, Ph),
2
), 6.18 (2H, s, CH (Ph
2
acacap)), 6.37 (4H, s,
Crystal data 1.
C
122
H
103
N
4
O
˚
25
Y
5
·3(CH
2
Cl
2
), M = 2724.41,
˚
2
orthorhombic, a = 18.175(5) A, b = 19.080(5) A, c = 33.846(5)
3
˚
˚
A, V = 11737(5) A , T = 200(2) K, space group P2
1
2
1
2
1
, Z =
1
3
1
-1
7
.48 (10H, m, Ph), 7.74 (8H, m, Ph), 7.88 (8H, m, Ph). C{ H}
NMR (CDCl , 400 MHz): d 16.4 (CH ), 20.1 (CH ), 30.4 (iPr-
CH), 61.2 (a-CH), 93.2 (CH (Ph acacap)), 94.5 (CH (Ph
26.8, 127.4, 127.6 (m-Ar-C), 127.7, 127.9, 128.0 (o-Ar-C), 130.8
p-Ar-C), 139.0, 139.9, 140.2 (i-Ar-C), 180.9 (carboxyl-C), 182.4,
4, m(Mo-Ka) = 2.657 mm , 82578 reflections measured, 16835
3
3
3
independent reflections (Rint = 0.0733). The final R
1
values were
2
2
2
acacbas)),
0.0449 (I > 2s(I)). The final wR(F ) values were 0.1314 (all data).
2
1
(
The goodness of fit on F was 1.054. Flack parameter = -0.026(5).
-
1
Crystal data for 2.
C
110
H
103
N
4
O
25
Y
5
, M = 2325.51, or-
1
1
7
1
83.2, 183.7, 184.7 (CO (Ph
680, 1597 (nCO), 1554, 1521, 1479, 1456, 1391, 1102, 1032, 751,
21, 689, 642. Raman [cm ]: 3055 (nOH), 1595 (nCO), 1488, 1440,
290, 1283, 1176, 1061, 1002, 998, 939, 789, 782, 671, 604, 372.
2
acacap/bas)). IR [cm ]: 3615 (nOH),
˚
˚
thorhombic, a = 16.587(3) A, b = 20.348(4) A, c = 31.568(6)
3
˚
˚
-
1
A, V = 10655(4) A , T = 203(2) K, space group P2
1
2
1
2
1
, Z =
-
1
4
, m(Mo-Ka) = 2.768 mm , 37542 reflections measured, 18159
independent reflections (Rint = 0.1522). The final R
1
values were
C
110
H
111
N
4
O
25
Y
5
(2333.60) Anal Calcd: C 56.62, H 4.79, N 2.40.
2
0
.0839 (I > 2s(I)). The final wR(F ) values were 0.1662 (all data).
Found: C 56.35, H 4.81, N 2.13.
2
The goodness of fit on F was 1.037. Flack parameter = -0.014(9).
2
0
4.
Yield (single crystals) 13%. [a] = -702.69 (CH
.47). H NMR (CDCl
, 400 MHz): d 3.03 (4H, dd, J = 9.4 Hz,
4.6 Hz, CH ), 3.34 (4H, m, CH ), 4.02 (br s, NH ), 4.37 (4H, br s,
acac)),
.66 (4H, m, Ar-H), 6.77 (10H, m, Ar-H), 6.93 (4H, m, Ar-H),
2
Cl
2
, c =
1
Crystal data for 3. C110H111N O Y , M = 2333.58, or-
0
1
3
4
25
5
˚
˚
thorhombic, a = 16.792(3) A, b = 20.108(4) A, c = 31.541(6)
2
2
2
3
˚
˚
A, V = 10650(4) A , T = 203(2) K, space group P2
1
2
1
2
1
, Z =
NH), 5.18 (4H, t, J = 9.3 Hz, a-CH), 6.24 (6H, s, CH (Ph
2
-
1
4
, m(Mo-Ka) = 2.769 mm , 74142 reflections measured, 20101
6
7
7
7
independent reflections (Rint = 0.1599). The final R
1
values were
.02 (4H, m, Ar-H), 7.07 (6H, m, Ar-H), 7.17 (8H, m, Ar-H),
.22 (4H, m, Ar-H), 7.35 (14H, m, Ar-H), 7.49 (10H, m, Ar-H),
2
0
.0564 (I > 2s(I)). The final wR(F ) values were 0.1265 (all data).
2
1
3
1
The goodness of fit on F was 1.073. Flack parameter = -0.018(5).
.80 (14H, m, Ar-H). C{ H} NMR (CDCl
), 40.7 (a-CH), 94.5 (CH (Ph acac)), 110.7 (g -C
C), 126.9 (Ar-C), 127.1 (Ar-C), 127.3 (Ar-C), 127.7 (Ar-C), 127.9
Ar-C), 128.1 (Ar-C), 128.3 (Ar-C), 128.7 (Ar-C), 136.1 (i-Ar-
C), 140.2 (i-Ar-C), 181.4 (carboxyl-C), 181.9 (carboxyl-C), 184.5,
3
, 400 MHz): d 26.9
(
CH
2
2
q
), 118.6 (Ar-
Crystal data for 4.
C
134
H
115
N
8
O
25
Y
5
·3(CH
2
Cl
2
)·CH
4
O·H
2
O,
˚
˚
M = 2986.73, orthorhombic, a = 19.306(4) A, b = 23.271(5) A, c =
(
3
˚
˚
3
0.474(6) A, V = 13691(5) A , T = 150(2) K, space group P2
1
2
1
1
2 ,
-
1
Z = 4, m(Mo-Ka) = 2.287 mm , 86650 reflections measured,
-
1
1
1
1
3
6
4
85.2 (CO(Ph
2
acacap/bas)). IR [cm ]: 3628 (nOH), 3449, 3056, 1653,
2
4156 independent reflections (Rint = 0.1278). The final R
1
values
596, 1551, 1517 (nCO), 1478, 1453, 1417, 1392, 1311, 1223, 1180,
069, 1024, 1000, 942, 784, 720, 687, 656, 609, 524. Raman [cm ]:
056, 1594 (nCO), 1487, 1439, 1290, 1285, 1175, 1058, 998, 937,
69. C134
2
were 0.0784 (I > 2s(I)). The final wR(F ) values were 0.1992 (all
-
1
2
data). The goodness of fit on F was 1.071. Flack parameter =
0
.027(7).
H
115
N
8
O
25
Y
5
(2681.91) Anal Calcd: C 60.01, H 4.32, N
.18. Found: C 59.76, H 4.47, N 3.93.
Notes and references
X-ray crystallographic studies of 1–4
1
2
H. Tsukube and S. Shinoda, Chem. Rev., 2002, 102, 2389–2404.
C. Kremer, J. Torres, S. Dom ´ı nguez and A. Mederos, Coord. Chem.
Rev., 2005, 249, 567–590.
Suitable crystal of compounds 1–4 were covered in mineral
oil (Aldrich) and mounted onto a glass fiber. The crystal was
3 K. Wang, R. Li, Y. Cheng and B. Zhu, Coord. Chem. Rev., 1999, 190–
192, 297–308.
◦
◦
transferred directly to the -73 C or -123 C cold N stream
2
4
5
L. Helm and A. E. Merbach, Chem. Rev., 2005, 105, 1923–1960.
P. Caravan, J. J. Ellison, T. J. McMurry and R. B. Lauffer, Chem. Rev.,
of a Stoe IPDS 2 or a Bruker Smart 1000 CCD diffractometer.
Subsequent computations were carried out on an Intel Pentium
Core2Duo PC.
1
999, 99, 2293–2352.
6 A. Datta and K. N. Raymond, Acc. Chem. Res., 2009, 42, 938–947.
7
8
M. Bottrill, L. Kwok and N. J. Long, Chem. Soc. Rev., 2006, 35, 557–
71.
J. Shen, L.-D. Sun and C.-H. Yan, Dalton Trans., 2008, 5687–5697.
All structures were solved by the Patterson method (SHELXS-
7). The remaining non-hydrogen atoms were located from
5
32
9
successive difference Fourier map calculations. The refinements
9 D. Nayak and S. Lahiri, J. Radioanal. Nucl. Chem., 1999, 242, 423–432.
10 S. J. Franklin, Curr. Opin. Chem. Biol., 2001, 5, 201–208.
11 Z. Zheng, Handbook on the Physics and Chemistry of Rare Earths Ele-
ments, ed. K. A. Gschneidner, Jr., J. C. G. B u¨ nzli and V. K. Pecharsky,
Elsevier, Amsterdam, 2010, vol. 40, pp. 109–239.
12 R. Wang, H. Liu, M. D. Carducci, T. Jin, C. Zheng and Z. Zheng,
Inorg. Chem., 2001, 40, 2743–2750.
3 R. Wang, M. D. Carducci and Z. Zheng, Inorg. Chem., 2000, 39, 1836–
2
were carried out using full-matrix least-squares techniques on F ,
2
minimizing the function (F
o
- F
and F
structure factor amplitudes using the program SHELXL-97.
c
) , where the weight is defined
2
2
as 4F
o
/2(F
o
) and F
o
c
are the observed and calculated
32
Carbon-bound hydrogen atom positions were calculated and
allowed to ride on the carbon atoms to which they are bonded. The
hydrogen atom contributions of compounds 1–4 were calculated,
but not refined. The locations of the largest peaks in the final
difference Fourier map calculation as well as the magnitude of
the residual electron densities in each case were of no chemical
significance.
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as a supplementary
publication no. CCDC-762599-762602.†
1
1
1
1
1
837.
4 R. Wang, Z. Zheng, T. Jin and R. J. Staples, Angew. Chem., Int. Ed.,
1999, 38, 1813–1815.
5 R. Wang, H. D. Selby, H. Liu, M. D. Carducci, T. Jin, Z. Zheng, J. W.
Anthis and R. J. Staples, Inorg. Chem., 2002, 41, 278–286.
6 X.-J. Kong, Y. Wu, L.-S. Long, L.-S. Zheng and Z. Zheng, J. Am. Chem.
Soc., 2009, 131, 6918–6919.
17 P. C. Andrews, T. Beck, C. M. Forsyth, B. H. Fraser, P. C. Junk, M.
Massi and P. W. Roesky, Dalton Trans., 2007, 5651–5654.
1
8 V. Baskar and P. W. Roesky, Z. Anorg. Allg. Chem., 2005, 631, 2782–
2
785.
19 V. Baskar and P. W. Roesky, Dalton Trans., 2006, 676–679.
This journal is © The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 6661–6666 | 6665

2
2
2
2
2
0 S. Datta, V. Baskar, H. Li and P. W. Roesky, Eur. J. Inorg. Chem., 2007,
216–4220.
1 P. W. Roesky, G. Canseco-Melchor and A. Zulys, Chem. Commun.,
004, 738–739.
2 R.-G. Xiong, J.-L. Zuo, Z. Yu, X.-Z. You and W. Chen, Inorg. Chem.
Commun., 1999, 2, 490–494.
26 D. C. Bradley, H. Chudzynska, D. M. Frigo, M. E. Hammond, M. B.
Hursthouse and M. A. Mazid, Polyhedron, 1990, 9, 719–726.
27 W. J. Evans, M. A. Greci and J. W. Ziller, Inorg. Chem., 2000, 39,
3213–3220.
4
2
28 Y. Cohen, L. Avram and L. Frish, Angew. Chem., Int. Ed., 2005, 44,
520–554.
3 M. T. Gamer, Y. Lan, P. W. Roesky, A. K. Powell and R. Clerac, Inorg.
Chem., 2008, 47, 6581–6583.
29 T. Brand, E. J. Cabrita and S. Berger, Prog. Nucl. Magn. Reson.
Spectrosc., 2005, 46, 159–196.
30 P. S. Pregosin, P. G. A. Kumar and I. Fernandez, Chem. Rev., 2005,
105, 2977–2998.
31 P. Stilbs, Prog. Nucl. Magn. Reson. Spectrosc., 1987, 19, 1–45.
32 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
64, 112–122.
4 P. C. Andrews, T. Beck, B. H. Fraser, P. C. Junk, M. Massi, B.
Moubaraki, K. S. Murray and M. Silberstein, Polyhedron, 2009, 28,
2
123–2130.
2
5 O. Poncelet, W. J. Sartain, L. G. Hubert-Pfalzgraf, K. Folting and K. G.
Caulton, Inorg. Chem., 1989, 28, 263–267.
6
666 | Dalton Trans., 2010, 39, 6661–6666
This journal is © The Royal Society of Chemistry 2010