Complexes of lanthanide nitrates with tri tert butylphosphine oxide

Article abstract of DOI:10.1021/ic300142r

Reaction of lanthanide nitrates with ^tBu₃PO (=L) lead to the isolation of complexes Ln(NO₃)₃L ₂·H₂O·nEtOH (Ln = La (1), Nd(2)), Ln(NO ₃)₃L₂·nEtOH (Sm(3), Eu(4)), and Ln(NO₃)₃L₂ (Dy(5), Er(6), Lu(7)). These have been characterized by elemental analysis, infrared and NMR(¹H, ¹³C and ³¹P) spectroscopy and single-crystal X-ray diffraction. The structures show L to be positioned on opposite sides of the metal with the nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct molecules are present in the unit cell. A major isomer (70%) has a (P)O-Ln-O(P) angle of less than 180° with one of the nitrate ligands twisted out of the plane of the other nitrates while the lower abundance isomer is more symmetric with the (P)O-Ln-O(P) angle of 180° and the nitrate ligands coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be observed by variable temperature solution ³¹P NMR measurements but are clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln(NO ₃)₂L₃]⁺[PF₆]^- have not been totally successful and led to the isolation of crystals of Lu(NO₃)₃L₂ and Tb(NO₃) ₃L₂.CH₃CN (8).

Full text of DOI:10.1021/ic300142r

Article
pubs.acs.org/IC
Complexes of Lanthanide Nitrates with Tri Tert
Butylphosphine Oxide
Allen Bowden,† Simon J. Coles,‡ Mateusz B. Pitak,‡ and Andrew W. G. Platt*,§
†Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6BT, U.K.
‡School of Chemistry, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, U.K.
§Faculty of Sciences, Staffordshire University, College Road, Stoke-on-Trent, ST4 2DE, U.K.
S
* Supporting Information
t
ABSTRACT: Reaction of lanthanide nitrates with Bu3PO (=L) lead to the
isolation of complexes Ln(NO3)3L2·H2O·nEtOH (Ln = La (1), Nd(2)),
Ln(NO3)3L2 ·nEtOH (Sm(3), Eu(4)), and Ln(NO3)3L2 (Dy(5), Er(6),
Lu(7)). These have been characterized by elemental analysis, infrared and
NMR(1H, 13C and 31P) spectroscopy and single-crystal X-ray diffraction. The
structures show L to be positioned on opposite sides of the metal with the
nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct
molecules are present in the unit cell. A major isomer (70%) has a (P)O−
Ln−O(P) angle of less than 180° with one of the nitrate ligands twisted out of
the plane of the other nitrates while the lower abundance isomer is more
symmetric with the (P)O−Ln−O(P) angle of 180° and the nitrate ligands
coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be
observed by variable temperature solution 31P NMR measurements but are
clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers
do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln(NO3)2L3]+[PF6]− have not been
totally successful and led to the isolation of crystals of Lu(NO3)3L2 and Tb(NO3)3L2.CH3CN (8).
We report here the extension of this study to the more
sterically demanding Bu3PO.
INTRODUCTION
■
t
Complexes between lanthanide nitrates and phosphine oxides
have a long pedigree, with complexes of triphenylphosphine
oxide in particular being extensively studied.1−4
RESULTS AND DISCUSSION
■
The reactions of lanthanide nitrates with tBu3PO (=L) in a 1:3
ratio in ethanol led to the formation of complexes with a 1:2
metal to ligand ratio Ln = La(1), Nd(2), Sm(3), Eu(4), Dy(5),
Er(6), Lu(7). The complexes of the heavier lanthanides were
less soluble and crystallized readily from the reaction mixture.
For the lighter metals (La and Nd) spontaneous crystallization
did not occur on reducing the volume of ethanol and cooling
the solutions. For these complexes, seeding the concentrated
solutions with the solid obtained from evaporating a small
amount of the solution was successful in giving crystalline
complexes. Crystals of the lighter metals (La − Eu) deteriorate
on exposure to the laboratory atmosphere due to loss of
ethanol (see crystal structures), and have a bulk composition
corresponding to Ln(NO3)3L2·H2O. The complexes of the
heavier lanthanides Dy − Lu, crystallized as Ln(NO3)3L2, which
are stable under ambient conditions. In contrast to reactions
with less sterically demanding phosphine oxides, in no cases
could we isolate neutral complexes with a 1:3 metal to ligand
ratio under these conditions.
Trialkylphosphine oxide complexes have received less
attention. The complexes Nd(NO3)3(R3PO)3 (R = Me, Et)5
were characterized by elemental analysis, infrared, and electronic
spectroscopy. More extensive studies of the lanthanide series
similarly revealed that the 1:3 composition Ln(NO3)3(R3PO)3
(R = butyl, octyl) is common6 and Am(NO3)3(R3PO)3 and Cm-
(NO3)3(R3PO)3 were also deduced to have been formed in the
solvent extraction with Bu3PO and Oct3PO.7 The main tech-
nological interest in these complexes stems from their potential
application in nuclear fuels reprocessing where the chemically
robust nature of phosphine oxides is advantageous. In addition,
there has been considerable research aimed at optimizing the
solvent extraction properties of phosphine oxides by altering their
peripheral structure.8−13 Mixed trialkylphosphine oxides R3PO
(R = hexyl, heptyl, and octyl) have been used as extractants for
lanthanide ions either alone14,15 or in synergy with alkylphosphinic
acids.16
We have previously examined the formation and properties
of lanthanide nitrate complexes with R3PO (R = cyclohexyl,17
iBu3PO18) and find that the structural theme for these complexes
is Ln(NO3)3(R3PO)3 as expected, with subtle variations in struc-
ture as the ionic radius decreases.
Received: January 19, 2012
Published: March 13, 2012
© 2012 American Chemical Society
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Figure 1. Molecular structure of La(NO3)3(tBu3PO)2·H2O·2EtOH (1) (H atoms and the lattice ethanol molecules have been omitted for clarity).
Figure 2. Molecular structure of Eu(NO3)3(tBu3PO)2·EtOH (4). (H atoms and the lattice ethanol molecules have been omitted for clarity).
The X-ray crystal structures show interesting transitions from
La to Lu. Nine-coordinate species Ln(NO3)3L2(H2O)·2EtOH
(Ln = La, Nd) form for the larger ions, whereas 8-coordinate
complexes Ln(NO3)3L2·xEtOH where the ethanol is not directly
bound to the metal, are found for Ln = Sm (x = 0.5) and Eu (x = 1).
The ethanol molecules are not directly coordinated to the
lanthanide ion in any of the complexes. The unsolvated complexes
Ln(NO3)3L2 are obtained for Ln = Dy, Er, Lu. The structures of
each type of complex are shown in Figures 1−3 respectively.
Details of the data collection and refinement for these complexes
and Tb(NO3)3L2·0.5CH3CN are given in Tables 1a and 1b and
selected bond distances in Table 2. The crystal structures are all
O···N3 plane distances. These distances average from 0.712 Å
(range 0.158−1.029 Å) (La, Nd) reducing to about 0.2 Å (Sm,
Eu). The Dy, Er, and Lu complexes exist as two isomers, with a
lower abundance (30%) form having a highly symmetric structure
(local C3v symmetry) with the nitrates adopting a planar
arrangement (maximum deviation of O from the N3 plane of
0.063 Å). In the higher abundance (70%) isomer one of the
nitrate ligands is twisted with its oxygen atoms at approximately
90° to the N3 plane. The (P)O−Ln−O(P) angle varies with the
size of the lanthanide ion. For the larger ions (La, Nd) this angle is
bent significantly from linearity at 151.9°, whereas for the smaller
Sm and Eu it is almost linear at about 177°. These changes are
accompanied by the reduction in the puckering of the nitrate
ligands described above. The low abundance isomers of the Dy −
Lu complexes have a linear (P)O−Ln−O(P) geometry, whereas
the twisting of the nitrate out of plane in the more abundant form
induces a bending of this angle to minimize the unfavorable steric
interactions.
t
similar in that the Bu3PO ligands lie on opposite sides of the
lanthanide ion in an axial arrangement, as would be expected on
steric grounds, with the bidentate nitrates occupying an equatorial
belt. The lanthanide ions lie close to the N3 plane in all cases, the
greatest deviation being for the Eu complex where the metal ion is
situated 0.188 Å from the plane. The nitrates generally have a
puckered arrangement of their oxygen atoms relative to the N3
plane. The degree of puckering can be gauged in the average
The Ln−O distances for both nitrate and phosphine oxide
show an approximately linear decrease with atomic number of
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Figure 3. Molecular structures of the two isomers of Lu(NO3)3(tBu3PO)2 (7); a) the 70% isomer, b) the 30% isomer (H atoms have been omitted
for clarity).
the lanthanide, as expected from the lanthanide contraction.
When these distances are corrected for the effect of the
lanthanide contraction by subtraction of the appropriate ionic
radius the residual values are essentially constant. This implies
that the changes in observed Ln−O distances are accountable
entirely by the lanthanide contraction. This is summarized in
Figure 4.
This was further confirmed by single factor ANOVA analysis
over all the residual Ln-O distances described above where no
statistically significant differences were observed.
In Ln(NO3)3L2(H2O)·2EtOH (Ln = La, Nd) the metal
is 9-coordinate bound to two phosphine oxides and
three bidentate nitrate ligands with a water molecule
completing the coordination sphere. The three nitrogen
atoms and the oxygen atom of the coordinated water lie
approximately in the same plane (the maximum deviation is
for the oxygen, which is 0.093 Å from the mean plane) and
these structures can be envisaged as somewhat distorted
octahedra if the nitrates are considered as pseudomono-
dentate ligands.
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Table 2. Selected Bond Distances /Å in Compounds (1) to (8)
La(1)
Nd(2)
Sm(3)
Eu(4)
Tb(8)
Dy(5)
Er(6)
Lu(7)
O1−Ln1
O2−Ln1
O3−Ln2
O4−Ln2
O11−Ln1
O12−Ln1
O21−Ln1
O22−Ln1
O31−Ln1
O32−Ln1
O41−Ln2
O42−Ln2
O51−Ln2
O52−Ln2
O61−Ln2
O62−Ln2
H2O−Ln1
O1−P1
2.418(2)
2.396(2)
2.3688(18)
2.3451(18)
2.255(3)
2.258(3)
2.259(3)
2.272(3)
2.469(4)
2.478(4)
2.493(4)
2.481(4)
2.487(4)
2.488(4)
2.468(4)
2.469(4)
2.480(4)
2.486(4)
2.478(4)
2.495(4)
2.2438(16)
2.2413(16)
2.2145(19)
2.2200(19)
2.2127(19)
2.2232(18)
2.436(2)
2.441(2)
2.454(2)
2.444(2)
2.452(2)
2.448(2)
2.423(2)
2.441(2)
2.459(2)
2.467(2)
2.447(2)
2.448(2)
2.207(5)
2.212(5)
2.193(9)
2.206(8
2.206(3)
2.199(3)
2.187(5)
2.196(5)
2.385(3)
2.391(3)
2.367(3)
2.428(3)
2.434(3)
2.382(3)
2.407(3)
2.417(3)
2.168(2)
2.176(2)
2.159(4)
2.166(4)
2.363(3)
2.363(3)
2.329(3)
2.397(3)
2.400(3)
2.341(3)
2.387(3)
2.397(3)
2.633(2)
2.616(3)
2.582(3)
2.633(3)
2.615(3)
2.653(2)
2.5660(19)
2.5559(19)
2.527(2)
2.566(2)
2.548(2)
2.587(2)
2.4572(19)
2.456(2)
2.415(5)
2.416(5)
2.394(5)
2.453(5)
2.453(5)
2.418(5)
2.431(5)
2.445(5)
2.4816(19)
2.4885(19)
2.4705(19)
2.4815(19)
a
a
a
a
2.533(3)
1.523(2
1.521(3)
2.475(2)
1.520(2)
1.5184(19)
1.522(4)
1.527(4)
1.516(4)
1.518(3)
1.5245(17)
1.5206(17)
1.522(2)
1.526(2)
1.522(2)
1.5267(19)
1.516(5)
1.512(5)
1.508(3)
1.518(3)
1.531(6)
1.519(3)
1.514(3)
1.527(5)
O2−P2
O3−P3
O4−P4
1.530(10
Symmetry transformations used to generate equivalent atoms:
a
b
−x + y + 1, −x + 2, z. −y + 2, x − y + 1, z.
with differing linewidths. Signals for the major isomer are
assigned to peaks at 78.2 and 79.2 ppm, whereas those for the
minor isomer are at 80.5 and 81.8 ppm. The integrated peak
areas from the deconvoluted spectra vary depending on the
temperature and probably are influenced by differing relaxation
rates for the nuclei in different crystallographic environ-
ments. The 15N spectra show two signals of differing line width
at −7.5 ppm (sharp) and −9.6 ppm (broad). These are tenta-
tively assigned to the nitrate twisted out of plane in the most
abundant isomer and the in plane nitrates for both isomers,
respectively. The sharp signal arises as there is only one
crystallographic environment for this nitrate ligand, whereas the
in plane nitrates have a total of three independent environ-
ments (two for the 70% isomer and one for the 30%) and
would thus be expected to give broader signals. The 15N spectra
recorded with different contact times of 1, 3, and 5 ms are
shown in the insert to part d of Figure 6 and show that the two
signals have different cross-polarization behavior. Thus, the
signal intensities do not necessarily relate directly to the
abundance of the environments in the sample. There is no
observable exchange between the phosphorus or nitrogen
environments such as coalescence of signals on increasing the
temperature to 100 °C. A 31P EXSY experiment conducted at
100 °C did show low intensity cross peaks linking the two
peaks for the major isomer. These could arise from chemical
exchange or spin diffusion between the two environments in
the major isomer. No such correlations are seen for the peaks in
the minor isomer most probably as a result of the longer P···P
distance and the lower intensity of the signals. It thus seems
that in the solid state there is no interconversion of the isomers
or a change in their relative abundance. The changes observed
in the high-temperature NMR spectra are reversible and
probably due to differing relaxation rates as a function of
temperature.
Figure 4. Ln−O distances and the distances corrected for the
lanthanide contraction.
A network of hydrogen bonds involving the coordinated
water molecules, nitrate ligands and noncoordinated ethanol
molecules exists as shown in Figure 5. A dimeric unit is formed
by H-bonding between the coordinated water molecules and
the terminal oxygen of the nitrate on an adjacent molecule
giving a 12-membered ring. An 8-membered ring is formed by
H-bonding between the coordinated water, two lattice ethanol
molecules and the O of a nitrate ligand. The O···O distances
vary between 2.718−2.907 Å, which is within the range
expected for hydrates.19
The solid-state 31P and 15N NMR spectra of Lu(15NO3)3L2
have been obtained over a range of temperatures and are shown
in Figure 7. The 31P spectra show the 4 signals expected from
the crystallographically independent phosphorus atoms but
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Figure 5. Hydrogen bonding network in La(NO3)3(tBu3PO)2H2O·2EtOH (1) (tBu groups and all hydrogen atoms have been omitted for clarity).
O5−H5···O6i = 2.727(4) Å, O6−H6···O12ii = 2.838(4) Å, O41−H42···O33iii = 2.907(4) Å, O41−H41···O5 = 2.718(4)2.718(4) Å; Symmetry
3
1
3
3
1
3
transformations used to generate equivalent atoms: (i) −x+ /2, y + /2, −z + /2, (ii) −x + /2, y − /2, −z + /2, (iii) −x + 1, −y + 1, −z + 2.
Figure 6. CPMAS 31P and 15N NMR spectra of Lu(NO3)3(tBu3PO)a.
aA 31P at 25 °C, B 31P at 50 °C, C 31P at 100 °C, D 15N at 25 °C (inset spectra recorded with 1, 3, and 5 ms contact time respectively).
In addition to single crystal X-ray diffraction, the complexes
were characterized by elemental analyses, electrospray mass
spectrometry, and solution NMR spectroscopy. The infrared
spectra of the isolated solids show the expected bands with OH
stretches between 3500−3300 cm−1 for complexes with
lanthanide coordinated water (La, Nd) and lattice ethanol
(Sm, Eu). Three bands typical of coordinated nitrate are seen as
a series of absorptions between 1460 and 1444 (La) − 1512
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Figure 7. Observed and theoretical isotope profiles for [Er(NO3)2L2]+.
and 1471 cm−1 (Lu), and single peaks at 1300 (La) − 1280
cm−1 (Lu) and 1030 (La) − 1022 cm−1 (Lu), whereas the
PO stretch is observed between 1065 cm−1(La) and
1085 cm−1(Lu) compared with 1107 cm−1 for the free ligand.
The assignments were confirmed by the preparation of
Lu(15NO3)3L2, which shows the N−O vibrations shifted to
lower wavenumber particularly for the stretching modes as
expected. Full infrared data and assignments are given in the
Supporting Information. The electrospray mass spectra from
dichloromethane/acetonitrile solution show that ligand redis-
tribution occurs extensively during the electrospray process and
it is interesting in this regard that [Ln(NO3)2L3]+ is always the
most abundant lanthanide containing ion, with the expected
parent ion [Ln(NO3)2L2]+ always present, but represented by a
significantly lower intensity signal in all cases. The assignments
are supported by the excellent agreement between observed
and calculated m/z values (all within 10 ppm) and the match
between the experimental and predicted isotope distribution
profiles. An example for [Er(NO3)2L2]+ is shown in Figure 7.
Full details of the spectra and the assignments are given in the
Supporting Information.
complex spectra are observed with a sharp peak assignable to
Lu(NO3)3L2 at 79.7 ppm by comparison with the spectrum of a
solution of an authentic sample in CD2Cl2, and also on the basis
of the weighted average of the chemical shifts in the solid-state
NMR spectrum (79.4 ppm) and other major signals at 77.9
(sharp) and 82.0 ppm (broad). Crystallization of the reaction
mixtures yielded only Lu(NO3)3L2 and Tb(NO3)3L2·0.5CH3CN
(8) from the corresponding reaction with Tb(NO3)3. Here, it
seems that the isolated mixture contains crystals of the
Ln(NO3)3L2 complexes with any cationic species being present
as non crystalline material.
Solution structures and dynamics have been investigated
in CD2Cl2 solution by multinuclear NMR spectroscopy.
Full details of the NMR parameters are given in the Supporting
Information and are as expected for the ligand coordinated to a
lanthanide center. The 31P NMR spectra generally show a
single signal at 20 °C. On cooling the solutions the shifts of the
paramagnetic complexes show a pronounced temperature
dependence, particularly Dy for which the shift decreases by
approximately 12 ppm/°C. At −90 °C the complexes of the
lighter metals (La − Sm) show several additional low intensity
signals which imply that a dynamic equilibrium exists between
different structures in solution. The Eu − Lu complexes show a
single resonance at all temperatures. This is despite the fact that
in the solid state the complexes of Dy, Er, and Lu exist as two
distinct isomers. Thus in CD2Cl2 it seems that either rapid
exchange occurs between the two isomers or only one is pres-
ent on dissolution and that in the solid state the two forms are
of very similar energy and the isomers arise as a result of crystal
packing effects.
Given the abundance of [Ln(NO3)2L3] + in the mass spectra it
seemed logical to attempt the synthesis of complexes containing
this ion. The reaction of Ln(NO3)3 (Ln = Pr, Tb, and Lu) and
three equivs of L with a suspension of KPF6 in CH3CN led to
the isolation of crystalline materials which contained the [PF6]−
ion. The infrared spectra show strong bands at 790 and 550 cm−1
assigned to [PF6]− and the 31P NMR spectra show the expected
1
binomial septet at about δ −144 ppm JPF = 707 Hz. The 31P
NMR spectra in CD3CN also indicate that the isolated materials
contain Ln(NO3)3L2 and at least one other complex. At 80 °C
the spectra of the solid from Lu reaction shows, in addition to
[PF6]−, a single peak as a result of rapid exchange on the NMR
time scale. On cooling, this band broadens and at −40 °C more
Exchange between free and bound ligand was examined by
addition of a small quantity of L to CD2Cl2 solutions of the
complexes. For the complexes of La − Sm a single peak at an
average position is observed at 20 °C, which is indicative of
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Figure 8. Shift ratio plots of A δC/δP vs δCH3 /δP and B δP/δC vs δCH3/δC at 20 °C and −30 °C.
rapid exchange between free and bound ligand. At lower
temperatures separate signals for free and bound ligand are
observed in addition to other low intensity peaks. These are
tentatively assigned to the presence of 1:3 complexes formed in
solution, although we have not been able to isolate these
species. For the complexes of the heavier metals exchange is
slower at 20 °C and two broad signals are observed. This
behavior is understandable on the basis that the ligands will be
more tightly bound as a result of the higher charge density on
the smaller ions toward the right of the lanthanide series.
The 13C spectra show the expected features of the coordina-
ted ligand with a doublet (1JPC∼ 49 Hz) due to the CMe3 and a
singlet due to the methyl groups. At low temperatures the
signals from the CH3 groups broaden and at −90 °C two
separate peaks are observable, where the line width permits, in
an approximately 2:1 ratio. This could possibly be due to
on the observation of three nuclei20,21 in a complex offer a
model independent method of evaluating whether solution
structures remain the same across a series, although the analysis
is less sensitive to small structural changes. We have been able
to observe the 31P and two 13C signals at 20 and −30 °C. The
shift ratio plots are shown in Figure 8 indicate that there are no
large changes in structure in solution. This, at first sight, might
seem strange as the X-ray structures show clear differences.
However as the solution NMR spectra show average structures
and as the differences in the solid state structures are generally
small it may well be that the shift ratio plots are not sufficiently
sensitive to detect relatively small changes in the averaged
structures.
CONCLUSIONS
■
t
The complexes of L = Bu3PO with lanthanide nitrates form
t
restricted rotation of the Bu groups leading to the inequiva-
Ln(NO3)3L2 for all Ln studied in contrast to the Ln(NO3)3-
(R3PO)3 formulation found in other trialkylphosphine oxide
complexes. This difference is readily explained by the steric
requirements of the ligand. Attempts to observe in solution and
isolate cationic species such as [Ln(NO3)3L3]+, which are clearly
seen in the gas phase have given ambiguous results an no com-
plexes which contain these cations have been prepared free from
Ln(NO3)3L2. While attempts to prepare pure samples containing
[Ln(NO3)2L3]+ have not been successful, the preliminary results
are encouraging and further work in this area is presently under
lence of the methyl groups, or the presence of other isomers in
solution as indicated by the low-temperature 31P NMR spectra.
1
The H NMR spectra were not easily interpretable for all the
complexes. Where good spectra were obtained, La − Eu and Lu,
the methyl signal in the 1H NMR spectra broadens at −90 °C, but
no further splitting was observed in any instance.
Analysis of lanthanide induced shifts has previously been
used to deduce whether structures remain constant across the
lanthanide series in solution. Analyses of shift ratio plots based
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Nd(NO3)3(tBu3tPO)2·H2O: Nd(NO3)36H2O (0.11 g 0.25 mmol) in
0.6 g ethanol and Bu3PO (0.14 g 0.64 mmol) in 0.50 g ethanol were
mixed and heated to 70 °C for 30 min. Cooling the solution to −30 °C
did not produce any solid complex. Reducing the volume by approxi-
mately 50% and cooling similarly was unsuccessful. A small volume of
the solution was evaporated to give a lilac power. On seeding the cold
solution with this powder and maintaining at −30 °C for 2 days gave
the title compound as lilac crystals. These were filtered, washed with
cold ethanol and dried at the pump. The crystals rapidly became
opaque on exposure to the normal laboratory atmosphere. Yield 0.13 g
(66%) Analysis Observed (required) C 37.03(36.98) H, 7.14(7.24), N
t
investigation particularly as the cone angle of Bu3PO is only 12°
larger than that of Cy3PO for which 1:3 complexes have been
isolated.
EXPERIMENTAL SECTION
■
Crystallography. Suitable crystals were selected and single-crystal
X-ray diffraction analyses were performed using a Bruker APEXII
CCD diffractometer mounted at the window of a Bruker FR591
rotating anode (Mo Kα, λ = 0.71073 Å) and equipped with an Oxford
Cryosystems Cryostream device at 120K. Data were processed using
the COLLECT package22 and unit cell parameters were refined against
all data. An empirical absorption correction was carried out using
SADABS.23
−
+
5.35(5.39). Mass spectrometry (ESMS) [M-NO3
(calculated), 704.2459 (704.2456).
]
observed
Sm(NO3)3(tBu3PO)2·H2O: Sm(NO3)36H2O (0.10 g 0.22 mmol) in
t
0.5 g ethanol and Bu3PO (0.11 g 0.50 mmol) in 0.6 g ethanol were
The crystal structure was solved by direct methods and full-matrix
2
least-squares refinement on Fo was carried out using SHELX-97
mixed and heated to 70 °C for 30 min. Cooling the solution to −30 °C
for 5 days a small quantity of colorless crystals formed. These were
filtered, washed with a small quantity of cold ethanol and dried at the
pump to give 0.10 g (57%) colorless crystals. Analysis Observed
(required) C 36.50(36.44), H 7.36(7.14), N 5.26(5.31). Mass spectro-
software package.24 All non-hydrogen atoms were refined anisotropi-
cally, with all hydrogen atoms placed geometrically using standard
riding models. All hydrogen atoms were added at calculated positions
and refined using a riding model with isotropic displacement
parameters based on the equivalent isotropic displacement parameter
(Ueq) of the parent atom.
−
+
metry (ESMS) [M-NO3
(712.2547).
]
observed (calculated) 712.2545
Eu(NO3)3(tBu3PO)2·H2O: Eu(NO3)36H2O (0.09 g 0.25 mol) in
0.5 g ethanol and Bu3PO (0.15 g 0.69 mmol) in 0.6 g ethanol were
Crystal structures of (4) and (8) contain disordered solvent
molecules. In (4) disordered ethanol was modeled over two positions
with distance restraints (DFIX) used to maintain sensible C−C and
C−O bond lengths and molecular geometry. In (8) the disordered
acetonitrile molecule was located. The atomic displacement
parameters were refined as isotropic only.
t
mixed and heated to 70 °C for 30 min. Cooling the solution to −30 °C
for 5 days a small quantity of colorless crystals formed. These were
filtered, washed with a small quantity of cold ethanol and dried at the
pump to give 0.13 g (66%) colorless crystals. Analysis Observed
(required) C 36.59(36.36), H 7.20(7.12), N 5.28(5.30). Mass spectro-
Crystal structures of (5), (6) and (7) have been refined as racemic
twins in noncentrosymmetric spacegroup R3.
−
+
metry (ESMS) [M-NO3
(713.2562).
]
observed (calculated) 713.2560
Crystallographic data (excluding structure factors) for the structures
in this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication numbers CCDC
834847−834853 for compounds (1)−(7) and CCDC 857253 for (8).
Copies of the data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +44(0)−
1223−336033 or e-mail: deposit@ccdc.cam.ac.uk
Dy(NO3)3(tBu3PO)2: Dy(NO3)36H2O (0.11 g 0.24 mol) in 0.3 g
ethanol and Bu3PO (0.11 g 0.50 mmol) in 0.4 g ethanol were mixed
t
and heated to 70 °C for 30 min. Cooling the solution to −30 °C for 5
days a small quantity of colorless crystals formed. These were filtered,
washed with a small quantity of cold ethanol and dried at the pump to
give 0.12 g (64%) colorless crystals. Analysis Observed (required) C
36.67(36.71) H 7.18(6.93) N 5.34(5.35). Mass spectrometry (ESMS)
Mass spectra were obtained on a Thermofisher LTQ Orbitrap XL at
the EPSRC National Mass Spectrometry Service Centre at Swansea
University. Samples (∼10 mg) were dissolved in 300 μL CH2Cl2 and
were loop injected into a stream of actetonitrile.
−
[M-NO3 ]+ observed (calculated) 724.2644 (724.2642).
Er(NO3)3(tBu3PO)2: Er(NO3)36H2O (0.10 g 0.21 mol) in 0.7 g
t
ethanol and Bu3PO (0.13 g 0.61 mmol) in 0.5 g ethanol were mixed
Infrared spectra were recorded with a resolution of 2 cm−1on a
Thermo Nicolet Avatar 370 FTIR spectrometer operating in ATR
mode. Samples were compressed onto the optical window and spectra
recorded without further sample pretreatment.
and heated to 70 °C for 30 min. Cooling the solution to −30 °C for 5
days pale pink crystals formed. These were filtered, washed with a
small quantity of cold ethanol and dried at the pump to give 0.13 g
(78%) colorless crystals. Analysis Observed (required) C 36.48(36.49)
NMR spectra were recorded on a JEOL EX 400 in CD2Cl2 solutions
approximately 20 mg of complex dissolved in about 0.75 mL of
solvent.
−
H 6.84(6.89) N 5.20(5.32). Mass spectrometry (ESMS) [M-NO3 ]+
observed (calculated) 726.2643 (726.2653).
Lu(NO3)3(tBu3PO)2: Lu(NO3)36H2O (0.10 g 0.22 mol) in 0.5 g
Synthesis. tBu3PO: tBu3P (1.26 g 6.23 mmol) in 5 mL acetone was
added to a stirred solution of H2O2 (0.82 g 30% aqueous solution) in
50 mL acetone. The temperature rose to 35 °C during the addition.
The solution was stirred overnight and evaporated to dryness and the
residue dried in vacuo over KOH to give 1.34 g of a waxy colorless
solid. NMR (CD2Cl2) 31P (161.8 MHz) δ 66.64, 13C (100.5 MHz)
CMe3 δ 39.32(d) 1JCP 50.7 Hz, Me δ 29.17 (s), 1H (399.8 MHz) Me δ
t
ethanol and Bu3PO (0.13 g 0.60 mmol) in 0.6 g ethanol were mixed
and heated to 70 °C for 30 min. Cooling the solution to −30 °C for 5
days colorless crystals formed. These were filtered, washed with a small
quantity of cold ethanol and dried at the pump to give 0.16 g (91%)
colorless crystals. Analysis Observed (required) C 36.08(36.14) H
−
6.94(6.82) N Mass spectrometry (ESMS) [M-NO3 ]+ observed
3
(calculated) 735.2747 (735.2758)
1.36 (d) JPH 12.3 Hz.
La(NO3)3(tBu3PO)2·H2O: La(NO3)36H2O (0.10 g 0.22 mmol) in
1.0 g ethanol and Bu3PO (0.14 g 0.66 mmol) in 0.40 g ethanol were
Attempted synthesis of [Ln(NO3)2L3][PF6] Ln = Tb, Lu
Tb(NO3)36H2O) (0.07 g 0.15 mmol), KPF6 (0.04 g 0.21 mmol)
t
t
and Bu3PO (0.11 g 0.51 mmol) were stirred in 0.70 g CH3CN for
mixed and heated to 70 °C for 30 min. Cooling the solution to −30 °C
did not produce any solid complex. Reducing the volume by approxi-
mately 50% and cooling similarly was unsuccessful. A small volume of
the solution was evaporated to give a white power. On seeding, the
cold solution with this powder and maintaining at −30 °C for 2 days
gave the title compound as colorless crystals. These were filtered,
washed with cold ethanol and dried at the pump. The crystals rapidly
became opaque on exposure to the normal laboratory atmosphere.
Yield 0.10 g (58%) Analysis Observed (required), C 36.65(36.72), H
16 h. Evaporation of the solvent to a small volume led to the formation
of colorless crystals which were removed mechanically from the
reaction mixture. Crystals selected for X-ray diffraction analysis proved
to be the !:2 complex Tb(NO3)3(tBu3PO)2 ·0.5CH3CN (8)
Lu(NO3)36H2O (0.07 g 0.14 mmol), KPF6 (0.04 g 0.22 mmol) and
tBu3PO 0.11 g 0.52 mmol) were stirred in 0.75 g CH3CN for 16 h.
Evaporation of the solvent to a small volume led to a white powder
containing some crystalline material which were removed mechanically
from the bulk. Crystals selected for X-ray analysis proved to be the
previously characterized Lu complex (7).
−
7.25(7.19), N 5.28(5.35). Mass spectrometry (ESMS) [M-NO3 ]+
observed (calculated) 699.2403 (699.2414).
4388
dx.doi.org/10.1021/ic300142r | Inorg. Chem. 2012, 51, 4379−4389

Inorganic Chemistry
Article
ASSOCIATED CONTENT
* Supporting Information
Additional material as noted in the text. This material is
available free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: a.platt@staffs.ac.uk.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful to the EPSRC for the use of the National Mass
Spectrometry Service at Swansea University, the National
Crystallography Service at Southampton University,25 the solid
state NMR facility at Durham University and access to the CDS
facility at Daresbury. We also wish to thank Dr’s Sandra Van
Meuse and Robin Stein of Bruker UK Ltd for the initial solid
state 31P NMR spectra of Lu(NO3)3L2.
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