Synthesis and structure of tridentate bis(phosphinic amide)-phosphine oxide complexes of yttrium nitrate. Applications of 31P,89Y NMR methods in structural elucidation in solution

Article abstract of DOI:10.1039/c1dt10194c

The synthesis and characterisation of a tridentate ligand containing two diphenylphosphinic amide side-arms connected through the ortho position to a phenylphosphine oxide moiety and the 1:1 and 2:1 complexes formed with yttrium nitrate are reported for t

Full text of DOI:10.1039/c1dt10194c

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PAPER
Synthesis and structure of tridentate bis(phosphinic amide)-phosphine oxide
complexes of yttrium nitrate. Applications of 31P,89Y NMR methods in
structural elucidation in solution†
Cristinel Popovici,a Ignacio Ferna´ndez,a Pascual On˜a-Burgos,a Laura Roces,b Santiago Garc´ıa-Grandab and
Fernando Lo´pez Ortiz*a
Received 3rd February 2011, Accepted 11th April 2011
DOI: 10.1039/c1dt10194c
The synthesis and characterisation of a tridentate ligand containing two diphenylphosphinic amide
side-arms connected through the ortho position to a phenylphosphine oxide moiety and the 1 : 1 and
2 : 1 complexes formed with yttrium nitrate are reported for the first time. The free ligand (RP1*,SP3*)-11
is obtained diastereoselectively by reaction of ortho-lithiated N,N-diisopropyl-P,P-diphenylphosphinic
amide with phenylphosphonic dichloride. Complexes [Y((RP1*,SP3*)-11)(NO3)3] and
[Y((RP1*,SP3*)-11)2(NO3)](NO3)2 were isolated by mixing ligand 11 with Y(NO3)3·6H2O in acetonitrile
at room temperature in a ligand to metal molar ratio of 1 : 1 and 2 : 1, respectively. The 1 : 1 derivative is
the product of thermodynamic control when a molar ratio of ligand to yttrium salt of 1 : 1 is used. The
new compounds have been characterised both as the solid (X-ray diffraction) and in solution
(multinuclear magnetic resonance). In both yttrium complexes the ligand acts as a tridentate chelate.
The arrangement of the two ligands in the 2 : 1 complex affords a pseudo-meso structure. Tridentate
chelation of yttrium(III) in both complexes is retained in solution as evidenced by 89Y NMR data
obtained via 31P,89Y-HMQC, and 89Y, 31P-DEPT experiments. The investigation of the solution
behaviour of the Y(III) complexes through PGSE NMR diffusion measurements showed that average
structures in agreement with the 1 : 1 and 1 : 2 stoichiometries are retained in acetonitrile.
Introduction
Reprocessing of spent nuclear fuels is based on the separation of
the different radioactive components obtained by dissolution of
the irradiated material in nitric acid. A critical aspect of the process
is the efficient separation of lanthanides from actinides. This
task is mostly achieved via liquid–liquid extraction procedures.1
Extractants containing strong oxygen donor centers are partic-
ularly attractive for binding to the oxophilic trivalent f-element
ions. In this context, phosphine oxides and carboxamides are
among the preferred functional groups used to form coordination
complexes with lanthanides and actinides. The studies have shown
that polyfunctional ligands are superior extractants in comparison
to monofunctional molecules.2 For instance, carbamoylphosphine
oxides (CMPOs, 1, Fig. 1) are used in the TRUEX (TRansUranium
EXtraction) process and other variants3 to coextract trivalent
Fig. 1 Examples of PO-based ligand architectures used in the complexa-
tion of trivalent lanthanide ions.
a
´
Area de Qu´ımica Orga´nica, Universidad de Almer´ıa, Carretera de Sacra-
mento, 04120, Almer´ıa. E-mail: flortiz@ual.es; Fax: +34 950 015481;
Tel: +34 950 015478
bDepartamento de Qu´ımica F´ısica y Anal´ıtica, Universidad de Oviedo-CINN,
C/Julia´n Claver´ıa 8, 33006, Oviedo, Spain
lanthanide and actinide ions remaining in the waste liquid result-
ing from the application of the PUREX (Plutonium URanium
EXtraction using tri-n-butyl phosphate, TBP, 2, Fig. 1) method.4
The better extracting efficiency of CMPOs is derived from the
presence of the P O and C( O)N linkages in the same molecule.
† CCDC reference numbers 806039 (R*P1,SP3*)-11, 806041 [Y((RP1*,SP3*)-
11)(NO3)2] and 806040 [Y((RP1*,SP3*)-11)2(NO3)](NO3)2. For crys-
tallographic data in CIF or other electronic format see DOI:
10.1039/c1dt10194c
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It has been found that phosphine oxides interact with lanthanide
cations more strongly than amides.5 As a result, one may expect
Results and discussion
Synthesis of yttrium complexes
that replacing the C O group of carboxamides by a P
O
moiety would lead to ligands with enhanced ability for binding
to f-block ions. The coordination of simple phosphine oxides6
and multifunctional7 PO-based ligands with lanthanide salts
has been extensively investigated. Representative examples of
tridentate molecules 3,8 49 and 510 related to the title compound
are given in Fig. 1. In the same vein, adducts formed between
various lanthanide salts and a series of diphenylphosphinamides
(Ph2P(O)NR1R2, R1 = R2 = H,11 Me,12 R1R2 = (CH2CH2)2O,13
R1 = H, R2 = Et14) have been examined, although only in a few
cases structural data at a molecular level have been reported.15
The group 3 metal yttrium exhibit similar chemical behavior as
the lanthanide elements.16,11,12,13 Yttrium(III) shows an ionic radius
intermediate between that of Dy3+ and Ho3+ and is often treated
as part of the rare earth metals group. Contrary to most trivalent
lanthanide ions, complexes of Y3+ are diamagnetic. Moreover, the
Ligand 11 was readily synthesized via ortho deprotonation of
phosphinic amide 6 with the complex [n-BuLi·TMEDA] in toluene
at -90 ◦C.19a,20 The reaction of the ortho anion thus generated with
0.5 equiv of PhP(O)Cl2 leads to the diastereoselective formation
of 11 in an isolated yield of 55% (Scheme 1, reaction 1).
The molecule (RP1*,SP3*)-11 is a meso compound containing
two ortho-substituted phosphinic amide fragments bridged by a
central phosphine oxide core which form a pocket of three P
O
groups suitable for binding to oxophilic metals. The reaction
of Y(NO3)3·6H2O with (RP1*,SP3*)-11 in a 1 : 1 molar ratio
in acetonitrile solution during 4 h afforded a mixture of two
complexes as evidenced by the 31P NMR spectrum (Scheme 1,
reaction 2). Two sets of signals were identified with the aid of a
phase-sensitive 31P COSY 2D experiment (Fig. 3) and assigned to
complexes 12 (dP 33.4, 36.0, and 42.7 ppm) and 13 (dP 34.3, 40.3,
and 42.0 ppm). Interestingly, the most deshielded signal of each
complex showed cross-peaks with two 31P signals. This pattern of
correlations allows assignment of the signals at dP 42.7 and 42.0
ppm to the central phosphine oxide groups of complex 12 and
1
89Y nucleus is a monoisotopic species of spin I = amenable
2
to obtaining high resolution 89Y-NMR spectra. These features
allow the use of Y3+ complexes as models for investigating the
solution behavior of structurally related paramagnetic complexes
of lanthanides including extraction properties.17
13, respectively. The existence of two correlations for these P
O
We have previously shown that diphenylphosphinamides 6 can
be efficiently deprotonated at the ortho position and the anions
obtained act as C–C–P–O pincer ligands in the formation of
five-membered ring metalocycles of lithium, 7,18 tin(IV), 8, and
gold(III),19 9, or in the preparation of b-phosphine–phosphinamide
bidentate ligands 10 (Fig. 2).20 We reasoned that the same
methodology could be readily extended to the preparation of a
new family of phosphine oxide–phosphinamide tridentate ligands
such as 11 (Fig. 2) that could bind to oxophilic cations through
the three P O groups of the molecule. Here we report: 1) the
synthesis of meso-11, 2) the coordination complexes formed with
yttrium nitrate using 1 : 1 and 2 : 1 molar ratios of ligand to yttrium
salt, and 3) the structural characterisation of all new products in
the solid-state and in solution through multinuclear magnetic res-
onance (1H, 13C, 31P, 89Y) techniques. 89Y NMR data derived from
experiments based on the existence of 89Y, 31P coupling constants
(31P,89Y-HMQC, and 89Y, 31P-DEPT) together with PGSE NMR
diffusion studies allowed to identify the structure of the species
present in solution.
signals implies that complexation of (RP1*,SP3*)-11 to yttrium is
accompanied by the lost of symmetry of the ligand.
31P NMR monitoring of this reaction at ambient temperature
showed that the group of signals attributed to complex 12
increased with increasing reaction time, which also produced the
progressive diminution of the relative concentration of complex 13
(Fig. 4). Quantitative conversion to complex 12 was achieved after
4 days under these conditions. These findings support the existence
of a thermodynamic equilibrium between complexes 12 and 13,
with the former being the most stable species for the stoichiometry
employed.
When the reaction between ligand (RP1*,SP3*)-11 and
Y(NO3)3·6H2O was performed using a 2 : 1 molar ratio complex
13 was obtained in a few minutes in quantitative yields (Scheme
1, reaction 3). Furthermore, the formation of the 2 : 1 complex
is diastereospecific. The relative face-to-face binding of the two
tridentate ligands to the cation could afford two diastereoisomers
corresponding to compounds with
a syn arrangement of
the phosphinic amide centers of the same or opposite chirality.
Fig. 2 Chelating ligands and complexes derived from ortho functionalized P,P-diphenylphosphinic amides.
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Fig. 4 31P NMR (121.49 MHz) monitoring of the reaction of equimolar
amounts of (RP1*,SP3*)-11 and Y(NO3)3·6H2O in CD3CN at room
temperature. NMR spectra acquired at reaction times of 4, 12, 36, and
84 h.
Complex 13 proved to be stable in acetonitrile solution
over several weeks without any sign of decomposition. Moreover,
for ligand : yttrium stoichiometries greater than 2 : 1, i.e. 3 : 1 or
4 : 1, the 31P NMR spectra showed the coexistence of complex 13
and free ligand in agreement with an stable complex not prone
to dissociate and/or aggregate (see diffusion NMR studies).
The preference for the formation of the 2 : 1 complex 13 with
respect to the 1 : 1 species 12 is somewhat surprising8d,e,9a due to
intraligand interactions.5d,e However, this behavior is precedented
in the lanthanide literature.8c,21
Scheme 1 Reaction schemes for (1) the diastereoselective synthesis of the
tridentate bis(phosphinic amide)-phosphine oxide ligand (RP1*,SP3*)-11,
(2) synthesis of complex [Y((RP1*,SP3*)-11)(NO3)3], 12, and (3) synthesis
of complex [Y((RP1*,SP3*)-11)2(NO3)](NO3)2, 13.
Solid state characterisations
Solid state structural characterisation of the new compounds
synthesized was achieved by single crystal X-ray diffraction
analysis. Crystals of (RP1*,SP3*)-11 were grown by layering
diethyl ether over a concentrated chloroform solution of 11.
The molecular structure is shown in Fig. 5, and allows the
unequivocal assignment of the relative stereochemistry of the
chiral phosphorus atoms as (RP1*,SP3*), i.e., the optically inactive
meso form. Selected data are summarized in Tables 1 and 2.
The molecule may be described as a triphenylphosphine oxide
derivative with two P-phenyl rings bearing a phenylphosphinic
amide ortho substituent. The ortho substituted rings adopt a
quasi-perpendicular arrangement (torsion angle C1–C2–P2–C19
of 165.1(2)◦) that places the three phosphorus atoms in a plane
and one phosphinic amide P O vector (P1–O1) oriented anti
with respect to the P O of the phosphine oxide group, P2–
O2. P2 and P3 are quasi coplanar with the oxygen atom of the
second phosphinic amide moiety, O3, almost aligned with the
P2–C25 vector (deviation from plane P2–O3–P3–C20 of 0.9(1)◦)
Fig. 3 2D 31P COSY (121.49 MHz) of the reaction crude resulting
from the equimolecular mixture of (RP1*,SP3*)-11 and Y(NO3)3·6H2O in
CD3CN at room temperature after 30 min of reaction.
˚
Interestingly, the O3 ◊ ◊ ◊ P2 distance of 2.990(2) A is significantly
shorter than the sum of the corresponding van der Waals radii
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Table 1 Selected crystal data for (RP1*,SP3*)-11 and complexes 12 and 13
Compound
11
12
13
Empirical formula
M
C42 H51 N2 O3 P3
724.76
Monoclinic
P21/c
13.567(2)
19.623(3)
14.296(2)
90
90.334(4)
90
3806.1(9)
0.198
1.265
0.20 ¥ 0.17 ¥ 0.06
4
150
1544
1.50 to 25.71
19397
6271 (Rint = 0.0711)
541/0
0.877
0.0446
C44 H54 N6 O12 P3 Y
1040.75
Monoclinic
P21/c
21.5641(7)
20.9926(8)
24.1037(8)
90
119.372(2)
90
9508.8(6)
1.395
1.454
0.20 ¥ 0.17 ¥ 0.13
8
100
4320
1.08 to 24.46
49562
15665(Rint = 0.0912)
1189/0
0.825
0.0426
C86 H105 N8 O15 P6 Y
1765.51
Triclinic
P-1
14.831(2)
15.879(2)
23.473(3)
74.596(2)
73.845(3)
62.892(3)
4663.7
0.792
1.257
0.42 ¥ 0.22 ¥ 0.10
2
150
1852
0.92 to 24.45
24286
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
m/mm-1
Dc/g cm-3
Crystal dimensions/mm
Z
T/K
F(000)
q range for data collection/◦
Refls measured
Refls unique
Parameters/restraints
GOF on F2
15189(Rint = 0.0547)
1016/3
0.804
0.0576
0.1293
1.178/-0.729
R1 [I ≥ 2s(I)]
wR2 (all data)
max./min. res. elec. dens./e A
0.0623
0.349/-0.333
0.0754
0.501/-0.823
-3
˚
◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for (RP1*,SP3*)-11 and complexes 12 and 13
(RP1*,SP3*)-11
12
13
P1–O1
P1–N1
P1–C1
P1–C7
P2–O2
P2–C2
P2–C19
P2–C25
P3–O3
P3–N2
P3–C20
P3–C31
O1–P1–N1
O1–P1–C1
O1–P1–C7
O2–P2–C2
O2–P2–C19
O2–P2–C25
O3–P3–N2
O3–P3–C20
O3–P3–C31
1.507(2)
1.588(2)
1.858(3)
1.844(3)
1.4232(16)
1.843(3)
1.927(3)
1.795(3)
1.537(2)
Y1–O1
Y1–O1N1
Y1–O2
Y1–O2N1
Y1–O3
Y1–O1N2
Y1–O2N2
Y1–O2N3
Y1–O1N3
P1–N4
P1–O1
P2–O2
P3–N3
P3–O3
O1–Y1–O2
O1–Y1–O3
O2–Y1–O3
O1–P1–N4
O3–P3–N3
Y1–O1–P1
Y1–O2–P2
Y1–O3–P3
2.378(3)
2.484(3)
2.250(3)
2.412(3)
2.233(3)
2.417(3)
2.461(3)
2.451(3)
2.459(3)
1.647(4)
1.513(3)
1.500(3)
1.641(4)
1.494(3)
77.81(10)
80.81(9)
76.08(9)
117.98(18)
117.29(18)
152.25(16)
133.82(17)
158.24(17)
Y1–O1
Y1–O2
Y1–O3
Y1–O4
Y1–O5
Y1–O6
Y1–O7
Y1–O8
P1–O1
P1–N1
P2–O2
P3–O3
P3–N2
P4–O4
P4–N3
P5–O5
2.283(3)
2.335(3)
2.314(3)
2.330(3)
2.319(3)
2.261(3)
2.431(3)
2.485(3)
1.502(3)
1.637(4)
1.493(3)
1.498(3)
1.631(4)
1.507(3)
1.639(4)
1.489(3)
1.498(3)
1.631(4)
73.05(10)
97.79(11)
88.97(11)
89.73(10)
161.87(10)
71.72(11)
122.89(11)
112.6(2)
118.0(2)
154.45(19)
138.95(18)
172.95(18)
166.39(19)
140.38(18)
156.60(18)
1.594(2)
1.865(3)
1.792(3)
108.34(12)
112.21(12)
108.39(12)
113.57(12)
113.42(11)
110.00(11)
120.18(12)
115.40(12)
109.77(13)
P6–O6
P6–N4
O1–Y1–O2
O1–Y1–O3
O1–Y1–O4
O1–Y1–O5
O1–Y1–O6
O1–Y1–O7
O1–Y1–O8
O1–P1–N1
O3–P3–N2
Y1–O1–P1
Y1–O2–P2
Y1–O3–P3
Y1–O4–P4
Y1–O5–P5
Y1–O6–P6
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that the particular arrangement of the P O groups in (RP1*,SP3*)-
11 is the result of electrostatic rather than covalent bonding
interactions. Also relevant is the positioning of the oxygen atom
of the phosphinic amide with respect to the nitrogen substituents,
staggered for P3 and eclipsed with a methyl carbon for P1. As
far as we know, (RP1*,SP3*)-11 is the first example of a tridentate
pincer ligand combining two P(O)N side arms connected to one
PO group through a scaffold of ortho-substituted phenyl rings that
has been ever characterised in the solid state.
The infrared spectrum of complex 12 (KBr disk) displays bands
at 1190 (s) and 986 (m) cm-1 assigned to the P O and P–
N stretching vibrations, respectively.11–13,16,29 The shift of these
absorptions to lower frequencies for the P O (~ 20–36 cm-1)30
and to higher frequencies for the P–N (~8 cm-1) with respect to
the corresponding bands in the free ligand, support the binding
to the yttrium cation. Absorptions typical of coordinated nitrate
were observed at 1482 (s), 1295 (s), 1058 (w) and 817 (w) cm-1.
However, the unequivocal identification of the coordination mode
Fig. 5 ORTEP view of the crystal structure of (RP1*,SP3*)-11 including
the numbering scheme used. Thermal ellipsoids are shown at the 50% level.
-
of NO3 groups to the metal is not possible.
Single crystals of the 1 : 1 complex [Y(RP1*,SP3*)-11)(NO3)3], 12,
were prepared from an acetonitrile solution layered with diethyl
ether. After 12 h at room temperature crystalline material suitable
for X-ray diffraction was obtained. A view of the molecule is
shown in Fig. 6. Selected crystal data and bond lengths and angles
are given in Tables 1 and 2, respectively, as the two independent
molecules in the asymmetric unit do not differ significantly, we use
one of them on the structural discussion. The Y(III) is coordinated
to three bidentate NO3 and one tridentate ligand (RP1*,SP3*)-
11 resulting in a nine-coordinate polyhedron that approximates
to a tricapped trigonal prism (Fig. 7a).31 Similar coordination
polyhedra have been reported for 1 : 1 complexes of a meso
diphosphine dioxide ligand of type 3 (Fig. 2) with Nd(NO3)3
and Er(NO3)3.32 Replacing conceptually the nitrate groups by an
hypothetical monoatomic ligand transforms the nine-coordinated
polyhedron into a pseudo-octahedron that can be viewed as a fac
isomer, i.e. the three P O moieties define a face of an octahedron
with all three groups ca. 90◦ apart from each other (Fig. 6b).
The nitrates are symmetrically coordinated to Y(III) and the
˚
(3.32 A), which suggests the existence of a contact between these
atoms. A similar interaction seems to be present in ortho phenyl-22
and -naphthylbis(diphenylphosphine) dioxides23 as well as in the
solid state structure of the HI3 adduct of the triphosphine trioxide
ligand 5.24 The phosphorus atom geometries are tetrahedral,
with min/max bond angles variations of 106.5(1)◦–113.2(1)◦ for
P1, 100.3(1)◦–113.6(1)◦for P2, and 101.5(1)◦–120.2(1)◦ for P3.
The O3 ◊ ◊ ◊ P2 contact noted above together with the almost
linear arrangement of O3–P2–C25 (angle of 171.5(1)◦) could be
appropriate for considering P2 as a pentacoordinated atom with
a trigonal bipyramid (tbp) geometry. However, several features
indicate that the configuration of this atom is best described as
tetrahedral: the O3–P2 distance is too long (2.990(2) A), the sum of
the bond angles comprising the equatorial atoms C2, C19, and O2
of the hypothetical tbp is only 339.0(3) , the displacement of 0.41 A
of the P2 atom with respect to the quasi basal plane of the tbp, and
perhaps most importantly, the lack of elongation of the P2–C25
˚
◦
˚
˚
bond anti to the O2 atom. The distance of 1.795(3) A observed
for this bond is of the same order24 or even slightly shorter than
those found in P-phenyl rings of related compounds.22 As in other
triarylphosphine oxides, the aromatic rings linked to P2 adopt
a propeller-like arrangement. The nitrogen atoms show trigonal
configuration as deduced from values of 350.7(6)◦ and 352.8(6)◦
for the sum of the bond angles of N1 and N2, respectively.
Bond distances in the phosphorus-containing functional groups
are remarkable. The P–N bond lengths (average distance of
Y–O(nitrates) distances (av. 2.448 A) are comparable to those
˚
in [Y(R3PO)3(NO3)3] (R3PO = Ph3PO, Ph2MePO, Me3PO)16c
and related structures of complexes of lanthanide nitrate and
phosphine oxides.6a,e,33 As expected, the geometry shows that the
nitrate coordinated oxygen atoms have longer N–O distances
˚
(average 1.258 A) than the uncoordinated or “free” N–O and that
the O–N–O angles are close to the idealized 120◦ of isolated NO3
anions (min/max variation of 115.4(4)◦–122.8(4)◦). In complex
12 the tripodal ligand is coordinated by the three phosphinoyl
moieties with Y–O–P angles of 152.2(2)◦, 133.8(2)◦, and 158.2(2)◦
for P1, P2 and P3 respectively. The complex has C1 symmetry
as is evidenced by the different conformation of the two seven-
membered metallacycles formed by binding the P O groups of
ligand 11 to the Y(III) ion. Although both metallacycles acquire
a slightly twisted envelope conformation in the crystal, the “flap”
of the envelope is defined only by the yttrium atom for the ring
involving P2, O2, P3, and O3, whereas this flap includes the O1–
Y1–O2 moiety for the ring containing the P1 O1 and P2 O2
groups.34 The asymmetry of the complex is also reflected in the
˚
1.590(2) A) are notably shorter than the values reported in
25
˚
N,N-dialkylphosphinic amides (average distance of 1.662 A),
including some ortho-functionalised19a,26 and N,N-diisopropyl
derivatives.20 As expected, the reduction in the P–N distance is
accompanied by an appreciable increase of the P O bond length
˚
(average distance of 1.522(2) A) in the P(O)N linkage as compared
with the mean value of 1.484 A reported for analogue phosphinic
amide moieties.20,25,26 Significantly, the P3–O3 distance (1.537(2) A)
is slightly longer than that of P1–O1 as one would expect from the
existence of a O3 ◊ ◊ ◊ P2.27 Surprisingly, such interaction apparently
produced a shortening of the P2–O2 bond in the phosphine
˚
˚
˚
˚
˚
oxide linkage (cf. the value of 1.423(2) A vs. 1.489 A in C3P
O
large difference in the intraligand O ◊ ◊ ◊ O distances (2.908(4) A
systems),28 when a lengthening was expected. These facts suggests
for O1 ◊ ◊ ◊ O2 vs. 2.763(4) A for O2 ◊ ◊ ◊ O3). The phosphorus
˚
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Fig. 6 a) ORTEP view of the crystal structure of complex [Y((RP1*,SP3*)-11)(NO3)3], 12 including the numbering scheme used (ellipsoids drawn at 50%
probability). b) Coordination sphere drawing of 12.
˚
(distance of centroids of 3.592 A, angles between centroids and
the para carbons C11 and C16 of 88.1◦ and 98.8◦, respectively).
The asymmetry of the molecule also extends to the P O and
Y–O(P) distances, which are all different. The Y–O(P) distances,
˚
2.378(3), 2.250(3) and 2.233(3) A for O1, O2 and O3, respectively,
are comparable with the related bond lengths found in complexes
of yttrium nitrate and phosphine oxides.16c It is worthy of note that
the binding to both phosphinic amide groups is clearly different
˚
(D = 0.145 A). Interestingly, the expected lengthening of the P–
O bonds produced by the coordination of the P O groups5b,e,35
to the Y3+ cation is only observed for P1–O1 (1.513(3) A) and
˚
˚
P2–O2 (1.500(3) A). Furthermore, the increase is notably larger
˚
for the phosphine oxide linkage (D = 0.0768 A) than for the
˚
phosphinic amide P1–O1 bond (D = 0.006 A). In sharp contrast,
˚
the P3–O3 bond distance (1.494(3) A) in complex 12 decreases
˚
markedly (D = -0.043 A) with respect to the length found in the
free ligand 11. This behaviour has no precedent in the coordination
of tridentate ligands such as 3,8 4,9 and 510 with lanthanide
cations. Curiously, the P–N distances in 12 are larger than in
11 and comparable to those described for uncomplexed N,N-
dialkylphosphinic amides.25,26 The variations in P O bond lengths
mentioned suggest that the phosphine oxide P O of tridentate
ligand 11 binds to the Y3+ cation more strongly than the P
O
linkage of the P(O)N groups. A definite explanation for these
observations is not available at the moment.
The infrared spectrum of the 2 : 1 complex [Y((RP1*,SP3*)-
11)2(NO3)](NO3)2, 13, in KBr showed similar features to that
of the 1 : 1 complex 12 for the P O (1173 cm-1) and P–N (986
Fig. 7 Shape of the coordination polyhedron of a) 12 and b) 13.
cm-1) stretching absorptions. Bands for coordinated NO3 are
-
atoms retain the characteristics observed in the free ligand, i.e.,
tetrahedral configuration (range of bond angles of 103.8(2)◦ to
117.4(2)◦) and propeller-like arrangement of the aryl rings linked
to P2. Tridentate chelation of 11 with Y(III) involves a rotation
around the P1–C1 bond of the ligand. This reorganization of
the chelate chain places the phenyl ring bonded to P1 almost
parallel to the ortho substituted ring connected to P2 and P3
observed at 1469 (m), 1310 (m), 1057 (w) and 817 (w) cm-1.
Characteristic bands for the unbound nitrate group appear at
1384 (s) and 829 (w) cm-1. As for 12, crystals of 13 suitable
for X-ray analysis were obtained by layering diethyl ether on a
concentrated acetonitrile solution of 13. A view of the molecule
is shown in Fig. 8. Selected crystal data and bond lengths
6696 | Dalton Trans., 2011, 40, 6691–6703
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Fig. 8 a) ORTEP view of the crystal structure of cation [Y((RP1*,SP3*)-11)2(NO3)]2+ of 13 including the numbering scheme used (50% thermal ellipsoids).
Hydrogens, the two outer nitrate ions and one molecule of acetonitrile used in the recrystallization were omitted for clarity. b) Coordination sphere
drawing of 13.
and angles are presented in Tables 1 and 2. The solid-state
structure confirms that two ligands (RP1*,SP3*)-11 bound to the
Y3+ cation by displacing two nitrate ions and all water molecules
from the inner coordination sphere of Y(NO3)3·6H2O. The outer
coordination sphere consists of two nitrate ions and one molecule
of acetonitrile used in the recrystallization. The eight-coordinate
polyhedron formed by the two tridentate chelates and the bidentate
nitrate represents a dodecahedron of triangular faces.31 The oxygen
atoms of the phosphine oxide linkages occupy A edges whereas
those of the P(O)N groups are placed in adjacent B positions
of an ideal dodecahedron (Fig. 8b).36 The two meso ligands
show a face-to-face syn arrangement of the phosphorus atoms
of opposite relative configuration. The remaining two A positions
of the dodecahedron are occupied by the oxygen atoms of the
bidentate nitrate ion. A simplified view of the coordination mode
of the tridentate ligands can be obtained by artificial elimination
of nitrate coordination to yttrium. The resulting coordination
polyhedron (Fig. 8b) would approximate to a distorted octahedron
with a fac coordination of the ligands in which phosphine oxides
and chiral phosphinic amide moieties of opposite configuration
from each ligand are arranged syn to each other.
The complex has C1 symmetry. The conformation adopted by
the tridentate ligands bound to Y3+ in complex 13 is analogous
to that found in the 1 : 1 complex 12, i.e., twisted envelope
seven-membered matallacycles. Taking as reference the O3–Y1–
O6 atoms defining a plane, the oxygen atoms O2 and O1 bisect the
angles O6–Y1–O5 and O5–Y1–O4, respectively, and are allocated
perpendicularly above those planes.
The P–X (X = O, N) distances show the same features noted
in complex 12. Perhaps the most relevant characteristic is the
very small differences of lengths among bonds of the same type:
4.9b,c The Y–O distances are all different and fall in the same
˚
ranges found in 12 for O(P) (2.261(3)–2.335(3) A) and O(N)
˚
(2.431(3) and 2.485(3) A) oxygen atoms. Curiously, the shortest
Y–O distances arise from the oxygen atoms of phosphinic amide
˚
groups of relative R configuration (values of 1.283(3) A for Y1–O1
˚
and 2.261(3) A for Y1–O6). The intraligand O ◊ ◊ ◊ O distances are
quite regular, with the same ligand showing the two extreme values
˚
˚
(2.712(4) A (O2 ◊ ◊ ◊ O3) to 2.748(5) A (O1 ◊ ◊ ◊ O2)). The geometry of
the phosphorus and nitrogen atoms can be described as tetrahedral
and trigonal, respectively. Notwithstanding, some bond angles
depart notably from ideal values of these configurations. The
maxima deviations are observed for P5 (range of values of
103.5(2)◦–119.5(2)◦) and N3 (range of values of 113.35◦–129.88◦).
Solution state characterisations
The structure of compound 11 in CD3CN solution was established
based on standard NMR spectroscopic methods. The presence of
two phosphinic amide fragments connected through a phosphine
oxide bridge was readily deduced from the two signals observed
in the 31P NMR spectrum, one triplet at dP 37.16 and one doublet
at dP 31.61 ppm in a ratio of 1 : 2 and a mutual coupling constant
3JPP of 8.1 Hz. The prochirality of the molecule turns the methyl
protons of the N-isopropyl groups into diastereotopic ones. They
appear in the 1H NMR spectrum as two doublets at dH 1.12
and 1.15 ppm due to the coupling with the adjacent CH proton
(3JHH 6.9 Hz). The four equivalent methynes show a characteristic
double heptet at dH 3.51 ppm originating from the coupling of
the methyl protons and the phosphorus nucleus (3JHH 6.9 Hz, 3JPH
6.8 Hz). The corresponding carbons are observed in the 13C NMR
spectrum at dC 23.22 and 23.81 ppm for the methyl carbons and
dC 47.7 ppm for the methyne groups. The aromatic region of this
spectrum is characterised by 14 resonances in the range of dC
126–139 ppm.
˚
˚
1.498(4)–1.507(4) A and 1.631(4)–1.639(4) A for P–O and P–
˚
N bonds of P(O)N groups, respectively, and 1.493(3) A and
˚
1.489(3) A for the respective phosphine oxide P2–O2 and P5–O5
The 31P NMR analysis of [Y((RP1*,SP3*)-11)(NO3)3] (12) indi-
cated that the asymmetry of the ligand established in the solid
state was retained in solution. The 31P spectrum of a ca. 0.1 M
bonds. The latter are similar to those reported for 2 : 1 complexes
of Eu3+,8b,37 Nd3+,8c,32 Th3+, and Yb3+ nitrates8a with tridentate
ligands 3 as well as complexes of cerium(III) nitrate with ligand
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acetonitrile solution of 12 at room temperature consisted of three
signals with the same integral: a double triplet at dP 42.67 (3JPP
7.7, JYP 5.4 Hz) ppm, and two broad triplets at dP 35.98 and
involving the P(O)N linkages are occurring rapidly on the NMR
time scale. Binding of the ligand to Y3+ at this temperature is
2
2
evidenced by the 89Y, 31P coupling shown by P1 (3JPP = JYP
=
33.44 ppm. The multiplicity pattern observed clearly indicates
that the ligand is acting as a tridentate chelate. The signal at
dP 42.67 ppm can be unequivocally assigned to the 31P of the
phosphine oxide linkage coupled to two P(O)N groups and one
Y3+ cation. As for the phosphinic amide phosphorus, the coupling
constants with the vicinal P O group and the yttrium ion seem
to be of approximately the same magnitude. The inequivalence of
the phosphinic amide substructures in 12 is also ascertained in
7.7 Hz). P1 and P3 exhibit different behaviour at low temperature.
In both cases, the coupling information is apparently lost. P1
undergoes deshielding and achieves the minimum line width at
0
◦C (W1/2 = 26 Hz), while P3 is shifted to lower frequencies
and the sharpest signals is obtained at -40 ◦C (W1/2 = 23 Hz).
Aggregation effects could be discarded by repeating the study
using a very dilute sample. Using a ca. 10 mM solution of 12 in
acetonitrile afforded the same results, thus confirming the absence
of concentration dependent processes. At the end of the study, the
room temperature spectrum is recovered showing that the dynamic
processes observed are fully reversible.
1
the H NMR spectrum. The N-isopropyl groups afford two sets
of signals. One appears as a relatively broad pair of doublets (dH
0.77, 0.94 ppm, 3JHH = 6.0 Hz) and one heptet (dH 3.36 ppm, 3JHH
=
6.0 Hz) as expected for two diastereotopic methyl groups and
one methyne proton, respectively. The second group of isopropyl
signals shows the methyl (dH 1.05 and 1.18 ppm) and methyne
(dH 3.67 ppm) resonances as very broad signals without resolvable
homo- or hetero-nuclear coupling constants.38 The features noted
Perhaps the most relevant NMR issue in yttrium complexes
is 89Y NMR. The large chemical shift range reported for this
metal nucleus, ca. 1300 ppm, suggests that should be a good
reporter of small changes in its coordination sphere.39 The 89Y
nucleus combines attractive properties for high resolution NMR,
i.e., spin I = 1/2, 100% natural abundance, with severe limitations
for rapid accessing to NMR data: low receptivity (DC = 0.7) and
long T1 relaxation times.39,40 The need to use long recovery delays
in standard excitation–acquisition 89Y NMR experiments has been
overcome by transferring polarization from 1H to 89Y via INEPT41
and DEPT42 schemes or using inverse detection through proton.43
Recently, we have reported the application of inverse 31P detection
experiments for obtaining 89Y NMR data of yttrium(III) complexes
with triphenylphosphine oxide.44
1
in the H and 31P NMR spectra indicate the existence of some
dynamic process in complex 12. This dynamic behaviour is even
more pronounced in the 13C NMR spectrum, where the signals
of one NiPr2 fragment seem to have reached coalescence at room
temperature and could not be detected.
A variable temperature 31P NMR study was undertaken to
get some insight into the dynamic behaviour of 12 (Fig. 9). For
simplicity, the 31P signals were labelled with the same numbers
employed in the solid-state structure. Increasing the temperature
to 75 ◦C produced the collapse of P1 and P3 into a single
average broad signal at dP 34.7 ppm. This means that at this
temperature any hindered rotations around the P–N linkages
and conformational exchange processes between metallacycles
The 31P,89Y{ H} HMQC spectrum of 12 measured at 20 ◦C,
1
0 ◦C and -40 ◦C is displayed in Fig. 10. At 20 ◦C only P2 shows
a correlation with a Y3+ cation at dY of -2.5 ppm. Most probably,
the rather large line width of P1 and P3 prevents the detection
of any 31P,89Y correlation due to rapid transverse relaxation. This
hypothesis is confirmed by acquiring the spectrum at 0 ◦C and
-40 ◦C, the temperatures corresponding to the narrowest P1 and
P3 signals, respectively (see above). Under these conditions the
correlations of P1/P2 and P1/P3 with the 89Y nucleus are clearly
observed, which also reveal a very small temperature dependence
1
Fig. 10 31P,89Y{ H} HMQC (202.5 MHz) spectra of a sample of 12 ca.
0.1 M in CD3CN measured at 20 ◦C (a), 0 ◦C (b), and -40 ◦C (c). Top
projections correspond to 31P NMR spectra acquired at the temperature
indicated in the inset of the 2D spectrum. Experimental time ca. 3 h.
Fig. 9 31P NMR (202.5 MHz) spectra as a function of temperature for a
ca. 0.1 M sample of 12, in CD3CN.
6698 | Dalton Trans., 2011, 40, 6691–6703
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of dY (DdY = -1.8 ppm for a DT= -60 ◦C). These results are
Table 3 Diffusion coefficient (D) and hydrodynamic radius (rH) values for
ligand (RP1*,SP3*)-11 and complexes 12 and 13 at room T/K in CD3CN
3
consistent with an Y3+ cation coordinated in a k -O fashion to
((RP1*,SP3*)-11, in agreement with the solid-state structure.
The 31P NMR spectrum of the 2 : 1 complex 13 consist of three
signals: a double triplet for P2 (dP 42.01 ppm, 3JPP 8.4, 2JYP 5.6 Hz)
b
c
˚
˚
Compounds
Da ¥ 1010 m2 s-1
rH (A)
rX-ray (A)
12
13
7.912
6.636
7.4
8.8
5.8
1.7
6.6
8.2
5.9
2
and two triplets for P1 (dP 40.30 ppm, 3JPP = JYP 8.4 Hz) and P3
(RP1*,SP3*)-11
CH3CN
10.138
3
2
(dP 34.28 ppm, JPP = JYP 8.4 Hz) (see Fig. 4). This pattern is
comparable to the spectrum obtained for the 1 : 1 derivative. In
this case, only P3 appears significantly broadened probably due
to rapid transverse relaxation induced by the 14N of the nitrate
ligand. As for 12, P2 is readily assigned based on the double triplet
produced by the coupling with two 31P of the P(O)N linkages and
the 89Y nucleus. The presence of only three signals in the spectrum
indicates that the two ligands in 13 are equivalent. This means that
the solid-state structure is retained in solution and the flexibility of
the ligands produces an average structure that can be considered
as a meso species with a plane of symmetry including the nitrate
ligand. The binding of all P O groups to Y3+ is demonstrated
by the 89Y, 31P coupling displayed by all resonances. The existence
of these couplings are the basic requirement for performing the
34.330d
a The experimental error in the D values is 2%. b The viscosity h used in
the Stokes–Einstein equation was taken from Perry’s Chemical Engineers’
Handbook 8th Edition (www.knovel.com) and is 0.3635 ¥ 10-3 kg m-1
s-1. 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. d Average value
considering the same signal in the three different samples based on
(RP1*,SP3*)-11, 12 and 13.
1
31P,89Y{ H} HMQC experiment. The spectrum acquired using a
compromise delay of 41.7 ms (appropriate for 2JYP 12 Hz) for the
preparation of anti-phase magnetization is given in Fig. 10a.45 In
this way, the three phosphorus signals show a correlation with an
yttrium at a dY -23.5 ppm. This value represents a shielding of the
yttrium nucleus of 21 ppm as compared with 12, in agreement with
the empirical group contributions to dY estimated for phosphine
oxide ligands.39b The 1H NMR spectrum of 13 also exhibited
averaged signals for the two ligand molecules incorporated in the
1
complex. The analysis, in combination with the H,31P gHMQC
Fig. 11 (a) 31P,89Y{ H} HMQC (202.5 MHz) spectrum of 13 ca. 0.1 M
1
spectrum, allowed the assignment of the proton signals of the
different phosphinic amide fragments.
The different 89Y chemical shift of the 1 : 1 and 2 : 1 complexes is
an indirect evidence of yttrium coordination to two tridentate
ligands in the latter. An unequivocal proof of the number of
in CD3CN measured at 20 ◦C, experimental time 3 h. (b) 89Y, 31P{ H}
1
DEPT (24.507 MHz) spectrum of 13 ca. 0.1 M in CD3CN measured at
ambient temperature without 31P decoupling during acquisition, (10240
scans, experimental time of 14 h). (c) The same experiment as (b) acquired
with 31P decoupling (1299 scans, experimental time 2 h).
P
O groups bound to yttrium(III) in 13 would be provided by
the multiplicity of the 89Y signal. This information was readily
ments is that experimental parameters such as temperature or
concentration can be adapted to the requirements. In addition, the
sequences needed are available in a standard NMR spectrometer
facilitating the performance of the experiment. Table 3 shows
pulsed field gradient spin-echo (PGSE) diffusion data for 12 and
13 in acetonitrile solution. For the diffusion studies presented,
two model system with different steric hindrance were employed,
i.e., the partially deuterated acetonitrile as an internal standard,
and the neutral ligand 11 as an external one. In the traditional
Stejskal–Tanner plots (Fig. 12), the less the attenuation, the lower
the diffusion coefficient, the larger the molecular size.
obtained from the 89Y, 31P{ H} DEPT experiments. The heptet
1
observed in the spectrum acquired without using 31P decoupling
during acquisition clearly demonstrated the coupling of Y3+ to
six 31P, as expected in complex 13 (Fig. 11b). The multiplet
collapsed to a singlet when the spectrum was measured including
31P decoupling, thus confirming that the splitting observed arises
from 89Y, 31P coupling (Fig. 11c). As far as we know, these
experiments represent the first application of direct observation
of 89Y NMR with intensity enhancement through polarization
transfer from 31P. Besides the increment of intensity afforded by the
polarization transfer technique, the repetition delay is determined
by the relaxation time of the 31P, much shorter than that of 89Y.
Both factors contribute to reduce the experimental time required
for accessing to 89Y NMR data as compared with the standard
excitation scheme.
From the measured D value at ca. 0.1 M samples for 12
and 13, and saturated solution in the case of 1148 we estimate
(via the Stokes–Einstein equation) the hydrodynamic radius rH
˚
to be 7.4, 8.8 and 5.8 A, for complexes 12, 13, and ligand 11,
respectively, which are in reasonable agreement with the values
derived from the crystallographic data given that solvent molecules
and non-bonded nitrates included in the solid-state lattice cannot
be excluded from the rX-ray calculation.
For two spherical molecules, in which one has twice the volume
of the other, one expects the ratio of the slopes (or D-values) to be
(2)1/3 ª 1.26. Assuming that the smaller is of spherical shape and the
larger species has an elongated shape (the longer axis being twice
Additional insights into the solution structure of the yttrium
complexes 12 and 13 were obtained via diffusion studies. The
measurement of diffusion constants via pulsed gradient spin-echo
(PGSE) NMR methods46 has recently attracted increasing interest
as this technique provides data on molecular volumes, and thus
indirectly, on structural characteristics.47 The major advantage of
this method compared with, for instance, colligative measure-
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solution of both 12 and 13. Extension of the present chemistry to
f-block elements is currently under study in our laboratories.
Methods and materials
Unless stated otherwise, all operations were performed using
standard Schlenk techniques under an inert atmosphere of ni-
trogen. The solvents were dried prior to use in a Pure Solv 400-
4-MD system, according to the procedure described by Pangborn
and Grubbs.50 Commercial reagents, except n-butyllithium, were
distilled prior to use. TMEDA was distilled from KOH.
1H (300.13 MHz), 13C (75.47 MHz), and 31P (121.47 MHz)
NMR spectra were recorded in CDCl3 and CD3CN except
otherwise stated, on a Bruker Avance DPX300 equipped with
1
1
a QNP H/13C/19F/31P probe. 2D 31P,89Y{ H} HMQC and 1D
1
89Y, 31P{ H} DEPT spectra were acquired on a Bruker Avance
500 spectrometer (89Y, 24.5 MHz; 31P, 202.4 MHz) using a direct
TBO (1H/31P/BB) probe head. Chemical shifts are reported in
ppm with respect to tetramethylsilane for H and 13C using the
1
1
Fig. 12 Stejskal–Tanner plots from H PGSE diffusion experiments in
CD3CN at room temperature using the stimulated echo sequence of
solvent signal as reference, to external 85% H3PO4 for 31P and to
external Y(NO3)3·6H2O for 89Y. Standard Bruker software was
used for acquisition and processing routines. Infrared spectra
were recorded in a Mattson–Genesis II FTIR equipment. High
resolution mass spectra were recorded on Agilent Technologies
LC–MSD TOF and HP 1100 MSD equipment with electrospray
ionization. Compounds 6,19a,51 has been described previously.
Melting points were recorder on a Bu¨chi B-540 capillary melting
point apparatus and were uncorrected.
Diffusion measurements were performed using the Stimulated
Echo Pulse Sequence52 on a Bruker Avance 500 without spin-
ning. 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 of HDO in D2O, which afforded a slope of 2.022 ¥
10-4. To 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%.
complexes 12 ( ) and 13 ( ), precursor 11 (ꢀ), and partially deuterated
᭹
᭺
acetonitrile (ꢁ), the latter as internal standard. The solid lines represent
linear least-squares fits to the experimental data.
that of the smaller), the ratio is then of ca. 1.18.49 The experimental
ratio of D-values of 1.19 (Table 3) is consistent with 13 having ca.
twice the volume of 12. The small fluctuation can be rationalised
by taking into account the possible contributions of the nitrate
ions. They can be completely separated by solvent or at least
partially paired regarding the cationic entity. Together with this
the exchange between free and bound nitrates can not be excluded,
which could represent a source of uncertainty. The diffusion data
obtained for 11 fit reasonably well with the radius calculated from
the solid-state structure, and provide a clear picture of how the
size of the molecule increases when the ligand itself binds to one
Y(NO3)3 fragment.
Conclusions
The diastereoselective synthesis of the meso tridentate ligand
(RP1*,SP3*)-11 containing two ortho-substituted diphenylphos-
Preparation of (RP1*,SP3*)-11
phinic amides connected through
a
PhP
O
moiety and
To a solution of TMEDA (0.55 mL, 3.7 mmol) and phosphinic
amide 6 (1 g, 3.32 mmol) in dry toluene (50 mL), at -90 ◦C, was
added n-BuLi (2.28 mL, 3.6 mmol, 1.6 M in hexane) dropwise.
After one hour of deprotonation, PhP(O)Cl2 (0.26 mL, 1.66 mmol)
was added and the reaction was stirred overnight out of the
cold bath. Then, the solvent was evaporated under vacuum and
the residue was poured into water (100 mL) and extracted with
dichloromethane (3 ¥ 25 mL). The organic layers collected were
washed five times with 50 mL of distilled water, dried with
Na2SO4, filtered, and concentrated in vacuum to give a yellow–
brown residue from which a brown precipitate was obtained upon
addition of Et2O (150 mL). The product was filtered and washed
up three times with Et2O providing 660 mg (55% isolated yield)
of a white solid that was used further in complexation reactions.
Mp 168–169 ◦C. IR (KBr disk): nmax/cm-1 979 (s), 1102 (s), 1111
its successful coordination to yttrium(III) nitrate to give
1 : 1, [Y((RP1*,SP3*)-11)(NO3)3] 12, and 2 : 1, [Y((RP1*,SP3*)-
11)2(NO3)](NO3)2 13, complexes is described for the first time.
The new compounds have been characterised in the solid-
state through X-ray diffraction analysis. A detailed multinuclear
magnetic resonance study afforded key aspects of the synthesis
and solution structure of 12 and 13. Complex 12 is the product
of thermodynamic control of the 1 : 1 reaction between ligand
11 and yttrium nitrate, whereas the derivative 13 is formed
diastereospecifically in about 5 min when a 2 : 1 molar ratio of
ligantd to Y(III) salt is used. Both complexes retain in solution
the same structure found in the solid-state. Binding of one or two
ligands to Y3+ has been ascertained through 31P,89Y-HMQC and
89Y, 31P-DEPT NMR experiments, which provided rapid access to
89Y NMR data making use of 31P for inverse detection or as source
of polarization transfer, respectively. In addition, NMR diffusion
measurements contributed to the understanding the nuclearity in
1
3
(s), 1209 (s), 1227 (s). H NMR (CDCl3 d): 1.12 (d, 12H, JHH
3
6.9 Hz, 4CH3), 1.16 (d, 12H, JHH 6.9 Hz, 4CH3), 3.54 (dh, 4H,
3JHH 6.8 Hz, 3JPH 6.8 Hz, 4CH), 6.98 (ddd, 2H, 3JHH 7.3 Hz, 3JHH
6700 | Dalton Trans., 2011, 40, 6691–6703
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3
2
7.2 Hz, 4JPH 3 Hz, ArH), 7.12 (m, 1H, ArH), 7.23 (m, 4H, ArH),
(br), 22.42 (d, JPC 4.3 Hz), 22.93 (br), 47.34 (br), 47.97 (d, JPC
6.2 Hz), 138.25–127.5 (60CAr) 31P NMR (CD3CN, d): 34.28 (bt,
7.3 (m, 2H, ArH), 7.32 (m, 2H, ArH), 7.44 (m, 2H, ArH), 7.53
3
3
3
3
(m, 2H, ArH), 7.55 (m, 4H, ArH), 7.99 (dddd, 2H, JHH 7.6 Hz,
3JPP 8.4 Hz), 40.3 (t, JPP 8.4 Hz), 42.01 (dt, JPP 8.4 Hz, JYP
5.6 Hz) 89Y NMR (via HMQC and DEPT, CD3CN, d): -23.7.
MS, m/z: 1661 (M–NO3), 1599 (M–(NO3)2). Analysis: calcd (%)
for C84H102N7O15P6Y: C, 58.50; H, 5.96; N 5.69. Found: C, 57.01;
H, 5.28; N, 5.48.53
4JHH 0.9 Hz, 4JPH 4 Hz, 3JPH 12 Hz, ArH), 8.11 (m, 2H, ArH). 13
C
NMR (CDCl3 d): 23.22 (d, 3JPC 3 Hz, 4CH3), 23.81 (d, 3JPC 3 Hz,
4CH3), 47.7 (d, 2JPC 4.8 Hz, 4CH), 126.41 (d, 3JPC 13.2 Hz, 2CAr),
127.41 (d, 3JPC 12.6 Hz, 4CAr), 129.63 (dd, 4JPC 3 Hz, 3JPC 11.4 Hz,
2CAr), 129.68 (dd, 4JPC 3 Hz, 3JPC 12.4 Hz, 2CAr),130.14 (d,,43JPC
3 Hz, CAr), 130.54 (d, 4JPC 2.4 Hz, 2CAr), 132.63 (d, 2JPC 10.2 Hz,
X-ray crystallographic studies of 11–13. A suitable crystal of
11, 12 and 13 was covered in mineral oil (Aldrich) and mounted
onto a glass fiber. The crystal was transferred directly to the
cold N2 stream at 150 K for complex 11 and 13 and 100 K for
complex 12 of a Bruker Smart 1000 CCD diffractometer with
2
2
2CAr), 132.89 (d, JPC 9.8 Hz, 4CAr), 134.06 (dd, JPC 10.1 Hz,
3JPC 10.1 Hz, 2CAr), 134.67 (d, JPC 118.3 Hz, 2Cipso), 136.24 (d,
1
1JPC 104.6 Hz, Cipso), 137.7 (dd, JPC 124.4 Hz, JPC 9 Hz,2Cipso),
137.77 (dd, 2JPC 11.4 Hz, 3JPC 11.4 Hz,C-8/C-5), 138.89 (dd, 1JPC
102.6 Hz, 2JPC 10.6 Hz,2Cipso). 31P NMR (CDCl3 d): 31.61 (d, 3JPP
1
2
˚
Mo-Ka (l = 0.71073 A). The intensities were measured using the
3
oscillation method. The crystal structures were solved by Patterson
methods for 11 and 13 and Charge Flipping method for 12. The
refinement was performed using full-matrix least squares on F2.
All non-H atoms were anisotropically refined. All H atoms were
geometrically placed riding on their parent atoms with isotropic
displacement parameters set to 1.2 times the Ueq of the atoms to
which they are attached (1.5 for methyl groups).
Crystallographic calculations were carried out by the X-Ray
Group, at the University of Oviedo, using the following programs:
Bruker Smart54 for data collection and cell refinement; Bruker
Saint52 for data reduction; DIRDIF-200855 for 11, SUPERFLIP56
for 12 and SHELX-8657 for 13 for structure solution; XABS258
for refined absorption correction; SHELXL-9757 for structure
refinement and to prepare materials for publication; Mercury59
and PLATON60 for the geometrical calculations; ORTEP-361
for windows for molecular graphics. Crystal data and structure
refinement details for complexes 11–13 are outlined on Table 1.
Crystallographic data (excluding structure factors) for the struc-
tures reported in this paper have been deposited in The Cambridge
Crystallographic Data Centre no. CCDC:806039 (complex 11),
CCDC:806041 (complex 12) and CCDC:806040 (complex 13).
These data can be obtained free of charge from the CCDC via
http://www.ccdc.cam.ac.uk/products/csd/request/
6.1 Hz), 37.16 (t, JPP 6.1 Hz). MS m/z: 725(M + 1). Analysis:
calcd (%) for C42H51N2O3P3: C, 69.60; H, 7.09; N 3.87. Found: C,
69.64; H, 7.30; N, 3.88. Crystals suitable for X-ray analysis were
obtained from a chloroform solution (20 mg in 0.5 mL) layered
with diethyl ether (1 mL).
General procedure for the preparation of complexes
[Y((RP1*,SP3*)-11)(NO3)3] (12) and
[Y((RP1*,SP3*)-11)2(NO3)](NO3)2 (13)
To a suspension of (RP1*,SP3*)-11 (58 mg, 0.08 mmol) in 0.75 mL
MeCN was added Y(NO3)3·6H2O (15.3 mg (0.04 mmol) for 12;
or 30.6 mg, 0,08 mmol for 13). After 15 min of stirring (for 13)
or 4 days (for 12) the reaction was complete. Slow evaporation of
the corresponding solutions afforded the complexes 12 and 13 as
air stable solids in more than 97% of purity. Crystals suitable for
X-ray analysis were obtained from acetonitrile solutions layered
with diethyl ether.
[Y((RP1*,SP3*)-11)(NO3)3] (12). Mp 220–221 ◦C (dec.). IR
(KBr disk): nmax/cm-1 817 (w), 985 (m), 1057 (w), 1190 (s), 1295
(s), 1384 (m), 1482 (s). 1H NMR (CD3CN, d): 0.75 (br, 6H, 2CH3),
0.92 (br, 6H, 2CH3), 1.01 (br, 6H, 2CH3), 1.17 (br, 6H, 2CH3), 3.35
(br, 2H, 2CH), 3.65 (br, 2H, 2CH), 6,31 (br, 2H, ArH), 6.46 (br, 1H,
ArH), 6.62 (br, 1H, ArH), 7,22 (br, 6H, ArH), 7.51 (br, 2H, ArH),
7.75 (br, 6H. ArH), 8.02 (br, 1H, ArH), 8.31 (br, 3H, ArH), 8.53
(br, 1H, ArH). 13C NMR (CD3CN, d): 22.25 (br, 2CH3), 22.93
(br, 2CH3), 48.93 (br, 2CH), 137.79–127.89 (30CAr). 31P NMR
(CD3CN, d): 33.44 (br), 35.98 (br, J 7.7 Hz), 42.67 (dt, 3JPP 7.7 Hz,
3JYP 5.4 Hz) 89Y NMR (via HMQC, CD3CN, d): -1.5. MS, m/z:
937 (M–NO3). Analysis: calcd (%) for C42H51N5O12P3Y: C, 50.46;
H, 5.14; N 7.01. Found: C, 50.07; H, 5.26; N, 7.26.
Acknowledgements
Dedicated to the memory of Prof. R. Suau. Financial sup-
port by the Ministerio de Ciencia e Innovacio´n (MICINN)
(project CTQ2008-117BQU, MAT2006-01997 and ‘Factor´ıa de
Cristalizacio´n’ Consolider-Ingenio 2010) and the Ramo´n y Cajal
program (I.F.) is gratefully acknowledged.
[Y((RP1*,SP3*)-11)2(NO3)](NO3)2 (13). Mp 217–218 ◦C (dec.).
IR (KBr disk): nmax/cm-1 817 (w), 829 (w), 986 (m), 1102 (s), 1173
(s), 1384 (s), 1469 (m). 1H NMR (CD3CN, d): 0.63 (d, 12H, 3JHH
Notes and references
1 (a) K. L. Nash, R. E. Barrans, R. Chiarizia, M. L. Dietz, M. P. Jensen,
P. G. Rickert, B. A. Moyer, P. V. Bonnesen, J. C. Bryan and R. A.
Sachleben, Solvent Extr. Ion Exch., 2000, 18, 605; (b) H. Eccles, Solvent
Extr. Ion Exch., 2000, 18, 633; (c) W. Li, X. Wang, H. Zhang, S. Meng
and D. Li, J. Chem. Technol. Biotechnol., 2007, 82, 376; (d) M. Nilsson
and L. Nash, Solvent Extr. Ion Exch., 2007, 25, 665; (e) P. V. Achuthan
and C. Janardanan, J. Radioanal. Nucl. Chem., 2011, 287, 753.
2 (a) T. S. Lobana, inThe Chemistry of Organophosphorus Compounds, ed.
F. R. Hartley, Wiley, New York, 1992, vol. 2, ch. 8, pp. 409–566; (b) H.
H. Dam, D. N. Reinhoudt and W. Verboom, Chem. Soc. Rev., 2007, 36,
367; (c) A. N. Turanov, V. K. Karandashev and V. E. Baulin, Solvent
Extr. Ion Exch., 2007, 25, 165; (d) A. N. Turanov, V. K. Karandashev, V.
E. Baulin, A. N. Yarkevich and Z. Safronova, Solvent Extr. Ion Exch.,
2009, 27, 551.
3
6.8 Hz, 4CH3), 0.77 (br, 6H, 2CH3), 0.81 (d, 24H, JHH 6.8 Hz,
3
8CH3), 1.01 (br, 6H, 2CH3), 3.32 (dh, 4H, JHH 6.8 Hz, 4CH),
4
3
3.54 (br, 4H, 4CH), 6.48 (dddd, 2H, JHH 0.7 Hz, JHH 7.9 Hz,
JPH 7.6 Hz, JPH 16.6 Hz, ArH), 6.9 (m, 4H, ArH), 7.0 (m, 6H,
ArH), 7.14 (m, 6H, ArH), 7.48 (m, 2H, ArH), 7.65 (ddt, 2H, 4JHH
1.2 Hz, 3JHH 7.6 Hz, JPH 3.2 Hz, ArH). 7.79 (m, 6H, ArH), 7.9 (m,
4
3
4H, ArH), 7.98 (ddt, 2H, JHH 1.2 Hz, JHH 7.6 Hz, JPH 3.2 Hz,
ArH), 8.07 (dd, 2H, 3JHH 7.4 Hz, JPH 1.5 Hz, ArH), 8.13 (m, 4H,
ArH), 8.38 (dddd, 2H, 4JHH 1.2 Hz, 3JHH 7.7 Hz, JPH 4.3 Hz, JPH
12.1 Hz, ArH), 8.58 (m, 2H, ArH). 13C NMR (CD3CN, d): 20.69
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 6691–6703 | 6701
©

View Article Online
3 (a) E. P. Horwitz, D. G. Kalina, H. Diamond, G. F. Vandegrift and W.
W. Schulz, Solvent Extr. Ion Exch., 1985, 3, 75; (b) J. N. Mathur, M. S.
Murali and K. L. Nash, Solvent Extr. Ion Exch., 2001, 19, 357; (c) J.
L. Gregg, V. G. Artem and F. V. George, Solvent Extr. Ion Exch., 2010,
28, 287.
4 (a) W. B. Lanham and T. C. Runion, USAEC Report ORNL-479, Oak
Ridge, Tennessee, 1949; (b) D. D. Sood and S. K. Patil, J. Radioanal.
Nucl. Chem., 1996, 203, 547; (c) A. P. Paiva and P. Malik, J. Radioanal.
Nucl. Chem., 2004, 261, 485.
Z. Anorg. Allg. Chem., 2001, 627, 2323; (g) N. J. Hill, W. Levason, M.
C. Popham, G. Reid and M. Webster, Polyhedron, 2002, 21, 445.
17 L. Fuks and M. Majdan, Miner. Proces. Extr. Metall. Rev., 2000, 21,
25.
18 I. Ferna´ndez, P. On˜a-Burgos, J. M. Oliva and F. Lo´pez-Ortiz, J. Am.
Chem. Soc., 2010, 132, 5193.
19 (a) I. Ferna´ndez, P. On˜a-Burgos, G. Ruiz-Gomez, C. Bled, S. Garc´ıa-
Granda and F. Lo´pez-Ortiz, Synlett, 2007, 611; (b) P. On˜a-Burgos, I.
Ferna´ndez, L. Roces, L. Torre-Ferna´ndez, S. Garc´ıa-Granda and F.
Lo´pez-Ortiz, Organometallics, 2009, 28, 1739.
5 (a) T. M. Ward, I. W. Allcox and G. H. Wahl Jr., Tetrahedron Lett.,
1971, 12, 4421; (b) F. Berny, N. Muzet, L. Troxler, A. Dedieu and
G. Wipff, Inorg. Chem., 1999, 38, 1244; (c) M. Baaden, F. Berny, C.
Boehme, N. Muzet, R. Schurhammer and G. Wipff, J. Alloys Compd.,
2000, 303–304, 104; (d) C. Boehme and G. Wipff, Inorg. Chem., 2002,
41, 727; (e) B. Coupez, C. Boehme and G. Wipff, Phys. Chem. Chem.
Phys., 2002, 4, 5716.
6 For recent references see: (a) M. Bosson, W. Levason, T. Patel, M. C.
Popham and M. Webster, Polyhedron, 2001, 20, 2055; (b) J. Fawcett,
A. W. G. Platt and D. R. Russell, Polyhedron, 2002, 21, 287; (c) J.-C.
Berthet, M. Nierlich and M. Ephritikhine, Polyhedron, 2003, 22, 3475;
(d) M. J. Glazier, W. Levason, M. L. Matthews, P. L. Thornton and M.
Webster, Inorg. Chim. Acta, 2004, 357, 1083; (e) A. P. Hunter, A. M.
J. Lees and A. W. G. Platt, Polyhedron, 2007, 26, 4865; (f) S. Mishra,
Coord. Chem. Rev., 2008, 252, 1996; (g) A. Bowden, A. W. G. Platt, K.
Singh and R. Townsend, Inorg. Chim. Acta, 2010, 363, 243.
7 For recent references see: (a) A. M. J. Lees and A. W. G. Platt, Inorg.
Chem., 2003, 42, 4673; (b) A. M. J. Lees and A. W. G. Platt, Polyhedron,
2005, 24, 427; (c) Z. Spichal, M. Necas and J. Pinkas, Inorg. Chem.,
2005, 44, 5673; (d) K. Matloka, A. K. Sah, M. W. Peters, P. Srinivasan,
A. V. Gelis, M. Regalbuto and M. J. Scott, Inorg. Chem., 2007, 46,
10549; (e) Z. Spichal, V. Petricek, J. Pinkas and M. Necas, Polyhedron,
2008, 27, 283; (f) M. A. Subhan, Y. Hasegawa, T. Suzuki, S. Kaizaki
and Y. Shozo, Inorg. Chim. Acta, 2009, 362, 136.
8 (a) B. M. Rapko, E. N. Duesler, P. H. Smith, R. T. Paine and R. R.
Ryan, Inorg. Chem., 1993, 32, 2164; (b) E. M. Bond, E. N. Duesler,
R. T. Paine and H. No¨th, Polyhedron, 2000, 19, 2135; (c) X. Gan, R.
T. Paine, E. N. Duesler and H. No¨th, Dalton Trans., 2003, 153; (d) X.
Gan, B. M. Rapko, E. N. Duesler, I. Binyamin, R. T. Paine and B. P.
Hay, Polyhedron, 2005, 24, 469; (e) S. Pailloux, C. E. Shirima, A. D.
Ray, E. N. Duesler, R. T. Paine, J. R. Klaehn, M. E. McIlwain and B P.
Hay, Inorg. Chem., 2009, 48, 3104.
9 (a) R. T. Paine, Y.-C. Tan and X.-M. Gan, Inorg. Chem., 2001, 40, 7009;
(b) A. G. Matveeva, E. I. Matrosov, Z. A. Starikova, G. V. Bodrin, S. V.
Matseev, P. V. Petrovskii and E. E. Nifant’ev, Russ. Chem. Bull., 2005,
54, 2519; (c) A. G. Matveeva, E. I. Matrosov, Z. A. Starikova, G. V.
Bodrin, S. V. Matseev and E. E. Nifant’ev, Russ. J. Inorg. Chem., 2006,
51, 253.
20 C. Popovici, P. On˜a-Burgos, I. Ferna´ndez, L. Roces, S. Garc´ıa-Granda,
M. J. Iglesias and F. Lo´pez-Ortiz, Org. Lett., 2010, 12, 428.
21 (a) P. Caravan, T. Hedlund, S. Liu, S. Sjobergand and C. Orvig, J. Am.
Chem. Soc., 1995, 117, 11230; (b) A. Fujiwara, Y. Nakano, T. Yaita and
K. Okuno, J. Alloys Compd., 2008, 456, 429.
22 M. F. Davis, W. Levason, G. Reid and M. Webster, Polyhedron, 2006,
25, 930.
23 M. A. Bennett, C. J. Cobley, A. D. Rae, E. Wenger and A. C Willis,
Organometallics, 2000, 19, 1522.
24 F. Bigoli, P. Deplano, M. L. Mercuri, M. A. Pellinghelli and E. F. Trogu,
Phosphorus, Sulfur Silicon Relat. Elem., 1992, 70, 145.
25 Ph2P(O)NMe2: (a) M. ul-Haque and C. N. Caughlan, J. Chem. Soc.,
Perkin Trans. 2, 1976, 1101; Ph2P(O)NMe(CH2)2Ph: (b) F. Cameron
and F. D. Duncanson, Acta Crystallogr., Sect. B: Struct. Crystallogr.
Cryst. Chem., 1981, 37, 1604; Ph2P(O)N(CH2)2: (c) B. Davidowitz, T.
A. Modro and M. L. Niven, Phosphorus Sulfur Relat. Elem., 1985, 22,
255.
26 (a) I. Ferna´ndez, A. Force´n-Acebal, S. Garc´ıa-Granda and F. Lo´pez-
Ortiz, J. Org. Chem., 2003, 68, 4472; (b) H. De Bod, D. B. G. Williams,
A. Roodt and A. Muller, Acta Crystallogr., Sect. E: Struct. Rep. Online,
2004, 60, o1241.
˚
27 A P–O bond distance of 1.506(2) A has been reported for an ortho-
stannyl N,N-diisopropylphosphinic amide showing intramolecular
oxygen–tin interaction. See reference 19b.
28 F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and
R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
29 (a) D. R. Cousins and F. A. Hart, J. Inorg. Nucl. Chem., 1967, 29,
1745; (b) D. R. Cousins and F. A. Hart, J. Inorg. Nucl. Chem., 1968, 30,
3009.
30 The free ligand shows two P O stretching bands at 1227 and 1209
cm-1, whereas only a broad band is observed for complex 12.
31 (a) M. G. B. Drew, Coord. Chem. Rev., 1977, 24, 179; (b) R. M.
Hartshorn, E. Hey-Hawkins, R. Kalio and G. J. Leigh, Pure Appl.
Chem., 2007, 79, 1779.
32 X.-M. Gan, E. N. Duesler and R. T. Paine, Inorg. Chem., 2001, 40,
4420.
33 W. Levason, E. H. Newman and M. Webster, Polyhedron, 2000, 19,
10 K. Miyata, Y. Hasegawa, Y. Kuramochi, T. Nakagawa, T. Yokoo and
T. Kawai, Eur. J. Inorg. Chem., 2009, 4777.
2697.
34 An analogous arrangement is found in europium complexes of
tridentate triphosphine trioxides. See reference 10.
35 L. Troxler, A. Dedieu, F. Hutschka and G. Wipff, THEOCHEM, 1998,
431, 151.
11 (a) G. Vicentini and P. O. Dunstan, J. Inorg. Nucl. Chem., 1971, 33,
1749; (b) G. Vicentini and J. C. Prado, J. Inorg. Nucl. Chem., 1972, 34,
1309; (c) L. B. Zinner and G. Vicentini, Inorg. Chim. Acta, 1975, 15,
235; (d) L. R. F. Carvalho, G. Vicentini and K. Zinner, J. Inorg. Nucl.
Chem., 1981, 43, 1088; (e) J. R. Matos, L. B. Zinner, K. Zinner, G.
Vicentini and P. O. Dunstan, Thermochim. Acta, 1993, 219, 173.
12 (a) G. Vicentini and L. S. P. Braga, J. Inorg. Nucl. Chem., 1971, 33,
2959; (b) G. Vicentini and P. O. Dunstan, J. Inorg. Nucl. Chem., 1972,
34, 1303; (c) G. Vicentini, L. B. Zinner and L. Rothschild, Inorg. Chim.
Acta, 1974, 9, 213; (d) G. Vicentini and L. C. Machado, J. Inorg. Nucl.
Chem., 1981, 43, 1676.
36 J. L. Hoard and J. V. Silverton, Inorg. Chem., 1963, 2, 235.
37 E. M. Bond, X. Gan, J. R. FitzPatrick and R. T. Paine, J. Alloys Compd.,
1998, 271–273, 172.
38 Although the coupling of the isopropyl protons with 31P could not
be resolved, its existence was evidenced by the narrowing of the
corresponding signals when the 1H NMR spectrum was measured
under 31P decoupling. Additionally, this coupling allowed us to
establish the connectivity within the P(O)NiPr2 frameworks through
the correlations observed in the 1H, 31P-HMQC spectrum for the methyl
protons.
13 L. B. Zinner, G. Vicentini and L. Rothschild, J. Inorg. Nucl. Chem.,
1974, 36, 2499.
14 A. R. de Aquino, G. Bombieri, P. C. Isolani, G. Vicentini and J.
Zucherman-Schpector, Inorg. Chim. Acta, 2000, 306, 101.
15 E. E. Castellano, G. Oliva and J. Zuckerman-Schpector, Inorg. Chim.
Acta, 1985, 109, 33.
16 Phosphine oxide complexes: (a) M. J. McGeary, P. S. Coan, K. Folting,
W. E. Streib and K. G. Caulton, Inorg. Chem., 1991, 30, 1723; (b) W. A.
Herrmann, R. Anwander, V. Dufaud and W. Scherer, Angew. Chem.,
Int. Ed. Engl., 1994, 33, 1285; (c) L. Deakin, W. Levason, M. Popham,
G. Reid and M. Webster, J. Chem. Soc., Dalton Trans., 2000, 2439;
(d) W. Levason, B. Patel, M. C. Popham, G. Reid and M. Webster,
Polyhedron, 2001, 20, 2711; (e) Y.-C. Tan, X.-M Gan, J. L. Stanchfield,
E. N. Duesler and R. T. Paine, Inorg. Chem., 2001, 40, 2910; (f) A.
Tutab, M. Goldner, H. Hu¨cksta¨dt, U. Cornelissen and H. Homborg,
39 (a) D. Rehder, in Transition Metal Nuclear Magnetic Resonance, ed. P.
S. Pregosin, Elsevier, Amsterdam, 1991, pp. 1–58; (b) R. E. White and
T. P. Hanusa, Organometallics, 2006, 25, 5621.
40 (a) J. Kronenbitter and A. Schwenk, J. Magn. Reson., 1977, 25,
147; (b) R. M. Adam, G. V. Fazakerley and D. G. Reid, J. Magn.
Reson., 1979, 33, 655; (c) G. C. levy, P. L. Rinaldi and J. T. Bailey, J.
Magn. Reson., 1980, 40, 167; (d) J. Epinger, M. Spiegler, W. Hieringer,
W. A. Herrmann and R. Anwander, J. Am. Chem. Soc., 2000, 122,
3080.
41 D. L. Reger, J. A. Lindeman and L. Lebioda, Inorg. Chem., 1988, 27,
1890.
42 K. C. Hultzsch, P. Voth, K. Beckerle, T. P. Spaniol and J. Okuda,
Organometallics, 2000, 19, 228.
6702 | Dalton Trans., 2011, 40, 6691–6703
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
43 (a) M. Zimmermann, N. A. Frøystein, A. Fischbach, P. Sirsch, H. M.
Dietrich, K. W. To¨rnroos, E. Herdtweck and R. Anwander, Chem.–
Eur. J., 2007, 13, 8784; (b) M. Zimmermann, F. Estler, E. Herdtweck,
K. W. To¨rnroos and R. Anwander, Organometallics, 2007, 26, 6029;
(c) M. Zimmermann, D. Rauschmaier, K. Eichele, K. W. To¨rnroos and
R. Anwander, Chem. Commun., 2010, 46, 5346.
44 I. Ferna´ndez, V. Yan˜ez-Rodr´ıguez and F. Lo´pez Ortiz, Dalton Trans.,
2011, 40, 2425.
45 The spectrum obtained using a delay of 83.3 ms corresponding to the
experimental 2JYP of ca. 6 Hz does not show the correlation between P3
and 89Y due to the rapid transverse relaxation of the relatively broad
P3 signal.
46 (a) P. Stilbs, Prog. Nucl. Magn. Reson. Spectrosc., 1987, 19, 1; (b) C. S.
Johnson Jr., Prog. Nucl. Magn. Reson. Spectrosc., 1999, 34, 203; (c) F.
Stallmach and P. Galvosas, Annu. Rep. NMR Spectrosc., 2007, 61, 51.
47 (a) Y. Cohen, L. Avram and L. Frish, Angew. Chem., Int. Ed., 2005,
44, 520; (b) T. Brand, E. J. Cabrita and S. Berger, Prog. Nucl. Magn.
Reson. Spectrosc., 2005, 46, 159; (c) P. S. Pregosin, P. G. A. Kumar
and I. Fernandez, Chem. Rev., 2005, 105, 2977; (d) A. Macchioni, G.
Ciancaleoni, C. Zuccaccia and D. Zuccaccia, Chem. Soc. Rev., 2008, 37,
479; (e) G. Bellachioma, G. Ciancaleoni, C. Zuccaccia, D. Zuccaccia
and A. Macchioni, Coord. Chem. Rev., 2008, 252, 2224.
48 Satisfactory results were obtained by using saturated solutions due to
the very poor solubility of 11 in acetonitrile.
49 (a) K. G. Spears and L. E. Cramer, Chem. Phys., 1978, 30, 1; (b) P.
Schurtenberger and M. E. Newman, in Environmental Particles, ed. J.
Buffle and H. P. van Leeuwen, Lewis, Boca Raton, FL, 1993, vol. 2,
pp. 37; (c) K. W. Mattison, U. Nobbmann and D. Dolak, Am. Biotech.
Lab., 2001, 19, 66.
50 A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen and F. J.
Timmers, Organometallics, 1996, 15, 1518.
51 B. Burns, N. P. King, H. Tye, J. R. Studley, M. Gamble and M. Wills,
J. Chem. Soc., Perkin Trans. 1, 1998, 1027.
52 P. Stilbs, Prog. Nucl. Magn. Reson. Spectrosc., 1987, 19, 1.
53 The relatively large deviations of the elemental analysis found with
respect to the calculated values might be due to the presence of small
amounts of yttrium hydroxide that could not be eliminated through
four purification cycles.
54 Area-Detector Software Package, SMART & SAINT, Bruker, 2007.
55 P. T. Beurskens, G. Beurskens, R. de Gelder, S. Garcia-Granda, R.
O. Gould and J. M. M. Smits, The DIRDIF2008 program system,
Crystallography Laboratory, University of Nijmegen, The Netherlands,
2008.
56 L. Palatinus and G. Chapuis, J. Appl. Crystallogr., 2007, 40, 786.
57 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2007,
64, 112.
58 S. Parkin, B. Moezzi and H. J. Hope, J. Appl. Crystallogr., 1995, 28, 53.
59 C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock, G. P. Shields,
R. Taylor, M. Towler and J. J. van de Streek, J. Appl. Crystallogr., 2006,
39, 453.
60 (a) A. L. Spek, Acta Crystallogr. A, 1990, A46, C34; (b) PLATON, A
Multipurpose Crystallographic Tool, Utrecht University, Utrecht, The
Netherlands, A. L. Spek, 1998.
61 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 6691–6703 | 6703
©