Lanthanide complexes of the klaeui metalloligand, CpCo(P=O(OR) 2)3: An examination of ligand exchange kinetics between isotopomers by electrospray mass spectrometry

Article abstract of DOI:10.1021/ic301830u

A series of lanthanide complexes, {[CpCo(P=O(OR)₂) ₃]₂Ln(H₂O)_x}⁺Cl ^- (Ln = Nd, 3; Eu, 4; Tb, 5; Yb, 6; R = Et, a; R = Ph, b) bearing two cobalt metalloligands were prepared. Electrospray mass spectrometry and thermogravimetric analysis suggest that the cations are either solvent-free or contain very weakly bound water molecules. The related complex {[CpCo(P=O(OPh)₂)₃]₂Yb}⁺ [CoCl ₃(THF)]^-, 7, was crystallographically characterized, and the cation in this case was confirmed to be 6-coordinate and solvent-free. Ligand exchange rates between the d₀- and d₆₀-isotopomers of 3a-6a and 5b were determined in acetonitrile by electrospray mass spectrometry. The ligand exchange rate was found to increase by almost 4 orders of magnitude from the smallest (Yb, 6a, k = 0.3 M^-1 s^-1) to largest ion (Nd, 3a, >2500 M^-1 s^-1) in acetonitrile. Additionally, the ligand exchange rate increased rapidly for 5a (Tb) with increasing water concentration from 30 M^-1 s^-1 in pure acetonitrile to 268 M^-1 s^-1 in 50:50 (v/v) acetonitrile/water. Changing the phosphite substituent had no significant impact on the rate of ligand exchange for 5b (R = Ph) relative to 5a (R = Et).

Full text of DOI:10.1021/ic301830u

Article
pubs.acs.org/IC
̈
Lanthanide Complexes of the Klaui Metalloligand, CpCo(PO(OR)2)3:
An Examination of Ligand Exchange Kinetics between Isotopomers
by Electrospray Mass Spectrometry
Kevin J. H. Allen, Emma C. Nicholls-Allison, Kevin R. D. Johnson, Rajinder S. Nirwan, David J. Berg,*
Dennis Wester,† and Brendan Twamley‡
Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia, Canada V8W 3V6
S
* Supporting Information
ABSTRACT: A series of lanthanide complexes, {[CpCo(PO(OR)2)3]2Ln(H2O)x}+Cl− (Ln = Nd, 3; Eu, 4; Tb, 5; Yb, 6; R =
Et, a; R = Ph, b) bearing two cobalt metalloligands were prepared. Electrospray mass spectrometry and thermogravimetric
analysis suggest that the cations are either solvent-free or contain very weakly bound water molecules. The related complex
{[CpCo(PO(OPh)2)3]2Yb}+ [CoCl3(THF)]−, 7, was crystallographically characterized, and the cation in this case was
confirmed to be 6-coordinate and solvent-free. Ligand exchange rates between the d0- and d60-isotopomers of 3a−6a and 5b were
determined in acetonitrile by electrospray mass spectrometry. The ligand exchange rate was found to increase by almost 4 orders
of magnitude from the smallest (Yb, 6a, k = 0.3 M−1 s−1) to largest ion (Nd, 3a, >2500 M−1 s−1) in acetonitrile. Additionally, the
ligand exchange rate increased rapidly for 5a (Tb) with increasing water concentration from 30 M−1 s−1 in pure acetonitrile to
268 M−1 s−1 in 50:50 (v/v) acetonitrile/water. Changing the phosphite substituent had no significant impact on the rate of ligand
exchange for 5b (R = Ph) relative to 5a (R = Et).
In this contribution, we report the synthesis of several
lanthanide complexes of the type [(LCoP)2Ln]+Cl− (Ln = Nd,
Eu, Tb, Yb) that appear to be either solvent-free or to contain
very weakly bound water molecules. We have verified
crystallographically that the complex [(LCoP)2Ln]+
[CoCl3(THF)]− contains a 6-coordinate cation without
bound waters. Additionally, since lanthanide complexes of the
INTRODUCTION
■
The cobalt metalloligands, [CpCo(PO(OR)2)3]−, developed
by Klaui function as tripodal oxygen donors to a wide variety of
̈
metals.1 These ligands exhibit a number of interesting
properties that make them attractive for in vivo studies
including exceptionally high stability to oxidizing agents,
water, and aqueous acids.1,2 The solubility of the ligands in
water or polar organic solvents can also be tuned by changing
the phosphite substituents. We are interested in developing
new lanthanide contrast agents for magnetic resonance imaging
that are not based on the polyacetate DOTA-type structure.3
The high affinity of lanthanides for oxygen donors and the
Klaui metalloligand must show relatively low kinetic lability in
̈
aqueous solution to be useful as contrast agents, we investigated
the rate of intermetallic ligand exchange between isotopomers
using electrospray mass spectrometry. To the best of our
knowledge, this is the first reported use of ESI MS to determine
ligand exchange rates in lanthanide chemistry.10
exceptional stability of the Klaui metalloligands suggested that
these ligands might provide a suitable platform to develop new
contrast agents.
̈
RESULTS AND DISCUSSION
■
The Klaui ligands, [CpCo(PO(OR) ) ]− were prepared as
̈
Lanthanide complexes of Klaui metalloligands, LCoP, have
̈
2
3
their sodium salts from Cp2Co or CpCo(CO)(I)2 using
modified literature procedures, for 1a (R = Et) and 1b (R =
Ph), respectively (Scheme 1).11 Any of the paramagnetic
trinuclear cobalt species, [CpCo(PO(OR)2)3]2Co, that
formed were conveniently cleaved by reflux with NaCN in
methanol.
been reported in the past. Included in this group are a number
of mono(ligand) complexes such as (LCoP)Ln(por) (Ln = Nd,
Er, Yb, Y; por = various porphyrin derivatives),4 (LCoP)Y-
(H2Bpz2),5 clusters with molybdenum oxo anions,6 and acetate-
bridged dimers [(LCoP)Ln]2(μ-CH3CO2)4 (Ln = Nd, Y).7
Among the bis(ligand) complexes, both neutral complexes such
Reaction of 2 equiv of the Na+ salts of 1a or 1b with 1 equiv
of LnCl3(H2O)n (n = 7, Ln = Nd; n = 6, Ln = Eu, Tb, Yb) in
THF afforded the bis(ligand) complexes, {[CpCo(PO-
8
−
as (LCoP)2Ln(X) (X = acac, Cr2O7, CH3CO2 ) and salts such
as [(LCoP)2Ln(OH2)n]+X− (Ln = Eu, La; n = 1, 2; X = BF4 ,
−
Cl−)9 have been structurally characterized. Of these, the latter
are expected to have the greatest water solubility and most
potential as contrast agents, particularly since they have water
molecules bound to the metal center.
Received: August 21, 2012
Published: October 26, 2012
© 2012 American Chemical Society
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°C at which point it loses mass consistent with the loss of ethyl
chloride (or ethene and HCl); steady mass loss due to further
decomposition occurs beyond 210 °C. A TGA of 5a (Ln = Tb)
shows very similar behavior with loss of ca. 2 water molecules
by ca. 65 °C and loss of ethyl chloride beginning at only 135
°C. Presumably greater steric crowding at the smaller Tb3+
center in 5a destabilizes the complex relative to Nd3+ complex
5a. Interestingly, Nolan et al. reported a neutral, dimeric
complex, {[CpCo(PO(OEt)2)3][μ-CpCo(PO(OEt)2)2(P-
(O)2(OEt)]Y}2 containing one bridging [CpCo(PO-
(OEt)2)(PO2(OEt)]2− ligand.12 The authors obtained this
complex by refluxing the Na+ salt of 1a with anhydrous YCl3 in
THF and given the low temperature required for loss of ethyl
chloride from 3a and 5a by TGA, it is reasonable to speculate
that ligand fragmentation occurs after complex formation at the
temperatures used.
Scheme 1. Synthesis of Ligands, [CpCo(P
a
O(OR)2)3]−Na+, 1a (R = Et) and 1b (R = Ph)
The phenyl-substituted complex 6b (Ln = Yb) also shows
low-temperature loss of two water molecules (complete by 50
°C), but in this case, the anhydrous complex remains stable to
more than 220 °C. Above this temperature, there is a clear mass
loss consistent with loss of a phosphite arm (OP(OPh)2)
followed by further decomposition at temperatures above 250
°C. The ease with which these complexes dehydrate on heating
during TGA strongly suggests that the water molecules present
are not bonded to the metal ions. This is confirmed
crystallographically for the {[CpCo(PO(OPh)2)3]2Yb}+
cation in 7 discussed below.
During the initial synthesis of yellow microcrystalline 6b, a
small amount of green X-ray quality crystals were obtained that
correspond to the expected {[CpCo(PO(OPh)2)3]2Yb}+
cation with a tetrahedral {CoCl3(THF)}− counterion, 7.
Recrystallization of 7 from acetone containing NaCl resulted
in a pale yellow solid corresponding to 6b. Complex 7 shows
absorptions at 592, 623, and 684 (ε = 22 L mol−1 cm−1) which
are consistent with the blue, distorted tetrahedral
[CoCl3(THF)]− anion;13 6b on the other hand shows only a
peak tailing into the visible at ca. 400 nm.
a
Conditions: (a) 130 °C, 18 h, 78% yield; (b) NaCN, MeOH, reflux in
air, 18 h, 95% yield; (c) NaH, THF, 0 °C; (d) reflux, THF, 18 h, 73%
yield; (e) NaCN, toluene−MeOH, reflux in air, 18 h.
An ORTEP3 plot14 of 7 is shown in Figure 1, while selected
bond distance and angles are collected in Table 1. At this
(OR)2)3]2Ln(H2O)x}+Cl− (Ln = Nd, 3; Eu, 4; Tb, 5; Yb, 6; R
= Et, a; R = Ph, b) as microcrystalline solids (Scheme 2). The
Scheme 2. Synthesis of Lanthanide Complexes, {[CpCo(P
O(OR)2)3]2Ln}+ Cl−
water content of these complexes varies from 2 to more than 20
equiv, but the average value for most complexes is about 8
equiv of water. Most samples remain hydrated with 2−4 waters
after exposure to vacuum at room temperature.
Thermogravimetric analysis of complex 3a shows a steady
loss of ca. 4 water molecules until the anhydrous complex is
reached at 65 °C. Anhydrous 3a remains stable until about 185
Figure 1. ORTEP314 plot of {[CpCo(PO(OPh)2)3]2Yb}+
{CoCl3(THF)}−·2C6H6, 7 (50% probability ellipsoids; phosphite
phenyl groups and benzenes of solvation omitted for clarity).
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a
Table 1. Selected Bond Lengths and Angles for {[CpCo(PO(OPh)2)3]2Yb}+ {CoCl3(THF)}−·2C6H6, 7
Cation
Yb(1)−O(3)
Yb(1)−O(12)
P(1)−O(3)
2.227(4)
2.220(4)
1.512(5)
1.509(5)
2.160(2)
2.161(2)
1.694
Yb(1)−O(6)
Yb(1)−O(15)
P(2)−O(6)
P(5)−O(15)
Co(1)−P(2)
Co(2)−P(5)
Co(2)−Cp(2)
2.207(4)
2.205(4)
1.521(5)
1.506(4)
2.150(2)
2.162(2)
1.736
Yb(1)−O(9)
Yb(1)−O(18)
P(3)−O(9)
P(6)−O(18)
Co(1)−P(3)
Co(2)−P(6)
Co(1)−C(Cp1)ave
2.213(4)
2.207(4)
1.517(5)
1.502(5)
2.159(2)
2.171(2)
2.075
P(4)−O(12)
Co(1)−P(1)
Co(2)−P(4)
b
b
c
Co(1)-Cp(1)
c
Co(1)-C(Cp2)ave
2.110
Yb(1)−O(3)−P(1)
Yb(1)−O(12)−P(4)
Co(1)−P(1)−O(3)
Co(2)−P(4)−O(12)
128.3(3)
Yb(1)−O(6)−P(2)
Yb(1)−O(15)−P(5)
Co(1)−P(2)−O(6)
Co(2)−P(5)−O(15)
131.1(3)
Yb(1)−O(9)−P(3)
Yb(1)−O(18)−P(6)
Co(1)−P(3)−O(9)
Co(2)−P(6)−O(18)
128.4(3)
132.7(3)
118.9(2)
119.8(2)
132.6(2)
119.2(2)
120.1(2)
133.5(3)
120.0(2)
119.3(2)
Anion
Co(3)−Cl(1)
Co(3)−O(19)
2.245(2)
2.037(5)
Co(3)−Cl(2)
2.223(2)
Co(3)−Cl(3)
2.238(2)
Cl(1)−Co(3)−Cl(2)
Cl(2)−Co(3)−Cl(3)
113.56(11)
113.3(10)
Cl(1)−Co(3)−Cl(3)
Cl(2)−Co(3)−O(19)
117.44(11)
105.7(2)
Cl(1)−Co(3)−O(19)
102.3(2)
102.4(2)
Cl(3)−Co(3)−O(19)
a
b
c
Estimated standard deviation in parentheses. Cp designated the centroid of the cyclopentadienyl C5 ring. Average distance from cobalt to the
cyclopentadienyl ring carbons.
writing, there are 24 reports of crystallographically charac-
terized lanthanide complexes containing Klaui ligands, although
̈
in all cases, the phosphite substituents are aliphatic, making this
the first example of an aryl substituted Klaui lanthanide
̈
complex.4−9 The bond lengths within the Klaui ligand of 7 are
̈
unremarkable; however, the Yb−O distances are at the long
end of the range of distances in the previously reported
complexes after adjustment for lanthanide ionic radius and
coordination number (lit:4−9 2.10−2.24 Å, mean = 2.17 Å; 7:
2.205(4)−2.227(4) Å, mean = 2.213 Å). This observation, the
fact that 7 is the only six-coordinate complex containing two
Klaui ligands and the lack of chloride or water coordination,
̈
suggests that the ytterbium center in 7 is relatively crowded.
The solid state structure of 7 suggested that complexes 3−6
also exist as salts containing a {[CpCo(PO(OR)2)3]2Ln}+
cation. Indeed, electrospray MS in positive ion mode from
acetonitrile or a mixture of acetonitrile and water readily gave
the expected isotopic pattern for the intact cation as shown, for
example, for 3a in Figure 2. No higher mass peaks were
observed, suggesting that the cations are not solvated, at least
under ESI MS conditions.
Figure 2. Observed (a) and simulated (b) isotopic distribution for the
cation, {[CpCo(PO(OEt)2)3]2Nd}+, of 3a.
The utility of complexes like 3−6 as possible MRI relaxation
agents depends, in part, on the lability of the Klaui
̈
metalloligand in aqueous solution at blood pH (ca. 7.4).3,15
formation of the d30-[CpCo(PO(OR)2)3]− ligand from
which the corresponding d60-{[CpCo(PO(OR)2)3]2Ln}+
analogues of 3−6 were prepared. The ligand exchange reaction
was followed by mixing equimolar amounts of d0 3−6 with
their d60 analogues in acetonitrile and following the rate of
disappearance of either the d0 or d60 cation or the appearance of
the d30 ligand exchange product with time as illustrated in
Figure 3 for {[CpCo(PO(OEt)2)3]2Tb}+ Cl−, 5a.16
Although we expected the unmodified Klaui ligands used here
̈
to be quite labile, there is no information available in the
literature regarding the lability of a tridentate ligand set such as
that presented by a Klaui ligand. Therefore, to provide a
̈
baseline for any future work, we set out to determine the
lability of the ligands used here as a function of metal size and
ligand substituent. In addition, since these complexes are only
soluble in polar solvents containing limited amounts of water,
we also examined how increasing water in a polar solvent
changes the rate of ligand exchange.
The reaction between the d0- and d60-{[CpCo(PO-
(OR)2)3]2Ln}+ complexes follow first-order behavior in each
complex (2nd order overall), so a plot of 1/[d60] or 1/[d0]
versus time initially follows a straight line of slope k. Good
linear behavior is observed until at least 25% conversion, but
eventually, the back reaction becomes significant and the
apparent rate declines (Figure 4). As expected, the reaction
mixture eventually reaches a thermodynamic 1:2:1 mixture of
d0:d30:d60 isotopomers (Figure 3).
The ease with which we obtained a mass spectrum for the
cations of 3−6 by positive ESI suggested a straightforward
method to measure the rate of ligand exchange. The Klaui
̈
ligands were easily deuterated at every position except the
cyclopentadienyl ring by using either d6-ethanol or d6-phenol
when preparing the phosphite. In both cases, this allows
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Figure 4. Plot of 1/[d60-5a] versus time for the reaction between d0
and d60-{[CpCo(PO(OEt)2)3]2Tb}+ Cl− (5a) in acetonitrile
monitored by ESI MS (7.905 × 10−6 M each).
Table 2. Summary of Rate Constant Data for Ligand
Exchange between d0- and d60-{[CpCo(PO(OR)2)3]2Ln}+
Cl−
a
b
compd
Ln
R
ACN/H2O
k (M−1 s−1
)
3a
4a
5a
5a
5a
5a
5a
5a
5b
5b
6a
6a
Nd
Eu
Tb
Tb
Tb
Tb
Tb
Tb
Tb
Tb
Yb
Yb
Et
Et
Et
Et
Et
Et
Et
Et
Ph
Ph
Et
Et
100:0
100:0
100:0
90:10
80:20
70:30
60:40
50:50
100:0
50:50
100:0
>2500
575
30
55
67
74
166
268
34
100
0.3
11
50:50
a
b
Acetontrile/water ratio in v/v percentages. Estimated error ca. 10%.
Figure 3. Electrospray mass spectra (positive mode, acetonitrile)
showing the evolution of the d0, d30, and d60 isotopic manifolds over
time for the cation of {[CpCo(PO(OEt)2)3]2Tb}+ Cl−, 5a, after
mixing equimolar amounts of the d0- and d60-isotopomers (7.905 ×
10−6 M).
The observed rate constants for ligand exchange derived
from electrospray MS are summarized in Table 2. We estimate
an error of roughly 10% in these values based on the
reproducibility between runs. Obviously, our ability to handle
very fast reactions is limited by the time required to mix the d0-
and d60-isotopomers and inject them into the mass
spectrometer (ca. 1−2 min). In the case of {[CpCo(P
O(OEt)2)3]2Nd}+ Cl−, 3a, this meant that we could only
estimate a lower limit for the rate constant k. Fortunately, in
most of the cases studied here, the rate was sufficiently slow
that reliable values for k could be determined.
Figure 5. Plot of rate constant k versus ionic radius (Å) for the
reaction between d0 and d60-{[CpCo(PO(OEt)2)3]2Ln}+ Cl− (3a−
6a) in acetonitrile monitored by ESI MS.
roughly linear (Figure 6). This observation is consistent with an
associative mechanism where ligand exchange occurs within a
dimeric aggregate through bridging interactions. The X-ray
structure of the related neutral yttrium dimer, {[CpCo(P
O(OEt)2)3][μ-CpCo(PO(OEt)2)2(P(O)2(OEt)]Y}2, men-
The rate constant for ligand exchange increases sharply as the
ionic radius of the lanthanide increases (Figure 5).17 In fact, a
plot of log k vs lanthanide ionic radius in six-coordination is
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This is not surprising if steric effects dominate the exchange
process, because the substituents are relatively far away from
the metal center and the size differences between an Et and Ph
group are not that extreme. On the other hand, Klaui and co-
̈
workers have found that changing from Et to Ph causes a
change from a dimeric [CpCo(PO(OEt)2)3]2Rh2(CO)3 to a
monomeric [CpCo(PO(OPh)2)3]Rh(CO)2.18
CONCLUDING REMARKS
■
We have shown that the complexes {[CpCo(PO-
(OR)2)3]2Ln}+ Cl− (R = Et, Ph) are isolated as salts with
good solubility in acetonitrile and limited solubility in water.
Intramolecular ligand exchange was followed by ESI MS using
the d0- and d60-isotopomers of the cation. The kinetic results
are consistent with an associative process. The rate of exchange
increases rapidly with increasing lanthanide ionic radius and
water content, but the phosphite substituents have compara-
tively little effect. The rate of ligand exchange is sufficiently high
that lanthanide complexes of the simple [CpCo(PO-
(OR)2)3]− ligands are not likely to be suitable for medical
uses; however, incorporating chelating functionality into the
phosphite groups may lower the ligand exchange rate to an
acceptable level, especially for complexes of the later
lanthanides.
Figure 6. Plot of log k versus ionic radius (Å) for the reaction between
d0 and d60-{[CpCo(PO(OEt)2)3]2Ln}+ Cl− (3a−6a) in acetonitrile
monitored by ESI MS.
tioned above, is noteworthy in this regard because it shows that
dimer formation is feasible in a similar system.12 Although there
are no structurally characterized examples of intact [CpCo(P
O(OEt)2)3]− units bridging two lanthanide centers, it is
reasonable to assume that such a dimer could form, particularly
if one PO arm dissociates from the lanthanide center.
Addition of water to the acetonitrile solvent was investigated
to the limit of solubility (ca. 50% water) in the case of the Tb
complexes 5a and 5b. The rate of exchange increased rapidly
with increasing water content in the solvent, as illustrated for 5a
in Figure 7. Overall, the rate constant increased about 8-fold for
EXPERIMENTAL SECTION
All experiments were performed under an inert argon atmosphere
using standard glovebox (Braun MB150-GII) or Schlenk techniques in
■
Table 3. Summary of Crystallographic Data for 7
formula
fw
C98H90Cl3Co3O19P6Yb
2213.70
cryst syst
space group
a (Å)
orthorhombic
P212121 (no. 19)
19.6632(7)
19.7358(7)
24.5563(9)
9529.5(6)
4
b (Å)
c (Å)
V (Å3)
Z
ρcalc (g cm−3
)
1.543
μ (mm−1
)
1.739
2θmax (deg)
meas. refl.
unique refl.
50.5
123863
17278
a
b
R , Rw
0.048, 0.101
1.023
Figure 7. Plot of rate constant k versus water content (v/v) for the
reaction between d0 and d60-{[CpCo(PO(OEt)2)3]2Tb}+ Cl− (5a)
in acetonitrile monitored by ESI MS.
GOF
a
b
R = Σ(|Fo| − |Fc|)/Σ|Fo|. Rw = [Σw(|Fo| − |Fc|2)/Σw(|Fo|)2]1/2
.
flame-dried glassware unless otherwise noted. THF and ether were
freshly distilled from sodium/benzophenone before use; dichloro-
methane was distilled from calcium hydride unless stated otherwise.
CpCo(I)2CO was synthesized from commercially available (Aldrich)
CpCo(CO)2 according to the literature procedure.19 The deuterated
phosphites d10-diethylphosphite and d10-diphenylphosphite were
prepared from PCl3 in two steps: initial reaction of PCl3 with t-
butanol (1 equiv) followed by addition of commercially available d6-
ethanol or d6-phenol (2 equiv) by a modification of a literature
procedure.20 Acetonitrile for ESI MS studies was HPLC grade. All
other chemicals were purchased from Sigma-Aldrich and used as is.
Samples for NMR spectroscopy were recorded on Bruker AMX-300
MHz or 360 MHz NMR. FT-IR spectra were recorded on a Perkin-
Elmer Spectrum 1000 FT-IR. An Omega Engineering model 199
melting point apparatus was used for melting point data. Kinetic +ESI-
MS data was collected on a Q-TOF II by MicroMass.
the Et complex 5a and about 3-fold for the Ph complex 5b on
going from pure acetonitrile to a 50:50 acetonitrile/water
mixture. The reason for this strong water dependence is not
clear, but it could be that water competes with PO binding
and dissociation of one arm of the Klaui ligand facilitates bridge
̈
formation. We have not investigated the effect of changing pH
on the rate of exchange, but it is quite likely that labile hydroxo
bridges could form at slightly basic pH and that these could
facilitate dimer formation.
There does not appear to be a strong rate dependence on the
phosphite substituent. The rate constants for the Et and Ph
complexes of Tb, 5a and 5b, are essentially the same within
experimental error in pure acetonitrile, although 5a is
noticeably faster in 50:50 acetonitrile/water (ca. 2.7 times).
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Synthesis. OP(H)(OC2D5)2. Anhydrous t-butanol (3.5 g, 48.0
mmol) was dissolved in dichloromethane (10 mL) and the mixture
was added to freshly distilled PCl3 (6.59 g, 48.0 mmol) dissolved in
dichloromethane (50 mL) at 0 °C. The solution was stirred 1 h, then
allowed to warm to room temperature, and deuterated ethanol (5.0 g,
96 mmol) was added dropwise over 0.5 h. This solution was stirred for
1.5 h at room temperature and then refluxed for 18 h. Removal of the
solvent under reduced pressure and vacuum distillation afforded pure
deuterated diethylphosphite as a clear and colorless oil. Yield: 5.3 g
(75%). 1H NMR (CDCl3, 300 MHz, 22 °C): δ 6.79 (d, 1H, 1JPH = 694
Hz, 1H). 31P{1H} NMR (121.5 MHz): δ 6.43 s.
1H NMR (CDCl3, 300 MHz, 22 °C) δ 6.85−6.77 (m, 30H, arylH),
5.59 (s, 5H, C5H5). 31P{1H} NMR (CDCl3, 121.5 MHz): δ 103.20 s.
13C{1H} NMR (CDCl3, 75.5 MHz): δ 152.69 (m, ipso-aryl), 128.78 (s,
m-aryl), 122.99 (s, p-aryl), 121.90 (s, o-aryl), 90.72 (s, C5H5).
[CpCo(PO(OC6D5)2)3]− Na+, d30-1b. The same procedure was
used to prepare d30-1b as that used to prepare 1b except that d10-
diphenylphosphite was used in place of diphenylphosphite. Yield: 1.13
g (46%). Mp. 311 °C (dec). IR (thin film, NaCl): 2276w, 1557s,
1375s, 1204m, 1156s, 1140s, 962w, 889m, 847m, 799s, 772w, 680w
1
2
cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 5.59 (s, C5H5). H
(CHCl3, 55.3 MHz): δ 7.02 (s, br, 30D, arylD). 31P{1H} NMR
(CDCl3, 121.5 MHz): δ 102.57 s. 13C{1H} NMR (CDCl3, 75.5 MHz):
OP(H)(OC6D5)2. Anhydrous t-butanol (1.85 g, 24.96 mmol)
dissolved in 10 mL dichloromethane was added to freshly distilled
PCl3 (3.43g, 24.96 mmol) dissolved in dichloromethane (30 mL) at 0
°C. The solution was stirred for 1 h, then allowed to warm to room
temperature. Deuterated phenol (5.0 g, 49.92 mmol) dissolved in
dichloromethane (30 mL) was added dropwise over 0.5 h, and the
solution stirred for 1.5 h at room temperature and then refluxed for 18
h. Removal of the solvent under reduced pressure left a yellow oil
containing up to 5% of the monoaryl substituted phosphite as a
contaminant. The crude product was redissolved in dichloromethane
(30 mL) and ammonia was bubbled through the solution for 10 min
resulting in a milky white suspension. Filtration through Celite and
removal of the solvent under reduced pressure afforded pure
deuterated diphenylphosphite as a clear colorless oil. Yield: 5.43 g
1
δ 152.65 (m, ipso-aryl), 128.78 (t, JCD = 22 Hz, m-aryl), 122.51 (t,
1JCD = 20 Hz, p-aryl), 121.56 (t, 1JCD = 22 Hz, o-aryl), 90.72 (s, C5H5).
[CpCo(PO(OEt)2)3]2Co, 2a. Freshly sublimed cobaltocene (2.30
g, 12.2 mmol) was added to a Schlenk tube under an inert atmosphere
and diethylphosphite (4.66 mL, 5.0 g, 36.2 mmol) was injected by
syringe. The resulting mixture was heated at 130 °C for 18 h, cooled to
room temperature, and diluted with 25 mL of methanol. After stirring
for 0.5 h, the suspension was filtered to isolate 2a as a pale yellow
solid. Yield: 3.57 g (78%). Mp. 254−257 °C. IR (thin film, NaCl):
2973m, 2920w, 2892w, 1422w, 1385m, 1263s, 1126s, 1039s, 922s,
1
833w, 748m, 719m cm−1. H NMR (CDCl3, 360 MHz, 22 °C): δ
33.84 (s, 10H, C5H5, ν1/2 = 21 Hz), −12.09 (s, 36H, CH3, ν1/2 = 21
Hz), −23.00 (s, 12H, CHAHB, ν1/2 = 71 Hz), −29.43 (s, 12H, CHAHB,
ν1/2 = 103 Hz).
1
1
(89%). H NMR (CD2Cl2, 300 MHz, 22 °C): δ 7.34 (d, 1H, JPH
732 Hz). 31P{1H} NMR (CD2Cl2, 121.5 MHz): δ 0.91 s.
=
[CpCo(PO(OEt)2)3]− Na+, 1a. Solid NaCN (0.95 g, 19.3 mmol)
was added to a slurry of 2a (3.57g, 3.20 mmol), described below, in 30
mL methanol. The mixture was refluxed in air for 18 h, and the
solution cooled to room temperature, filtered through Celite, and
washed with dichloromethane leaving behind insoluble Na3[Co-
(CN)6]. The filtrate was evaporated to dryness under reduced pressure
and the residue was recrystallized from hot acetone to yield pure 1a.
Yield: 3.21 g (95%). Mp. 188−189 °C. IR (thin film, NaCl): 2974m,
2927w, 2894w, 1384w, 1161s, 1047s, 929s, 830w, 759m, 723m cm−1.
1H NMR (CDCl3, 300 MHz, 22 °C): δ 4.99 (s, 5H, C5H5), 3.98−3.89
[CpCo(PO(OC2D5)2)3]2Co, d60-2a. The deuterated complex was
prepared by the same procedure as for 2a but with d10-
diethylphosphite substituted for diethylphosphite. Yield: 2.19 g
(74%). Mp. 239−241 °C. IR (thin film, NaCl): 2224m, 2143w,
2101w, 1422w, 1265s, 1177s, 1135s, 1090s, 1060m, 1008s, 906w,
821m, 739s, 690w, 671w cm−1. 1H NMR (CDCl3, 300 MHz, 22 °C): δ
2
33.78 (s, 10H, C5H5, ν1/2 = 20 Hz). H NMR (CHCl3, 55.3 MHz): δ
−11.99 (s, 36H, CH3, ν1/2 = 7 Hz), −22.37 (s, 12H, CHAHB, ν1/2 = 13
Hz), −28.80 (s, 12H, CHAHB, ν1/2 = 12 Hz).
{[CpCo(PO(OEt)2)3]2Nd}+ Cl−, 3a. The ligand salt 1a (0.40g, 0.72
mmol) and NdCl3(H2O)7 (0.139g, 0.36 mmol) were stirred in 20 mL
reagent-grade THF in air for 18 h. The solution was filtered through
Celite and the solvent was removed to leave a yellow solid. The solid
was redissolved in dichloromethane, filtered through Celite once more,
and the filtrate evaporated to dryness. The residue was redissolved in a
minimum of dichloromethane and precipitated with hexanes to afford
3a as a yellow solid. Yield: 0.23 g (90%). Mp. 188−190 °C. IR (thin
film, NaCl): 2976m, 2927w, 2898w, 1385w, 1125s, 1041s, 933s, 832w,
3
(m, 12H, CH2), 1.21 (t, JHH = 7.3 Hz, 18H, CH3). 31P{1H} NMR
(CDCl3, 121.5 MHz): δ 105.89 s. 13C{1H}(CDCl3, 75.5 MHz): δ
89.67 (s, C5H5), 58.64 (m, CH2), 16.70 (s, CH3).
[CpCo(PO(OC2D5)2)3]− Na+, d30-1a. The deuterated complex was
prepared in the same manner as 1a from NaCN and d60-2a. Yield: 2.06
g (99%). Mp 188−190 °C. IR (thin film, NaCl): 2224m, 2144w,
2101w, 1426w, 1183s, 1163s, 1099m, 1061m, 1007s, 908w, 814m,
733w, 687m, 667m cm−1. 1H NMR (CDCl3, 300 MHz, 22 °C) δ 4.96
2
(s, C5H5). H NMR (CHCl3, 55.3 MHz): δ 3.93 (s, 12D, CD2), 5.56
1
769w, 727w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 10.40 (s,
(s, 18D, CD3). 31P{1H} NMR (CDCl3, 121.5 MHz): δ 105.66 s.
13C{1H} NMR (CDCl3, 75.5 MHz): δ 89.60 (s, C5H5), 57.74 (quin,
10H, C5H5, ν1/2 = 8 Hz), 2.05 (s, CHAHB, ν1/2 = 29 Hz), 1.79 (s, 12H,
CHAHB, ν1/2 = 28 Hz), −0.15 (s, 36H, CH3, ν1/2 = 18 Hz), −2.54 (s,
∼12 equiv H2O, ν1/2 = 19 Hz). 31P{1H} NMR (CDCl3, 121.5 MHz): δ
−189.45 (s, ν1/2 = 72 Hz).
1
1JCD = 21 Hz, CD2), 15.62 (sept, JCD = 20 Hz, CD3).
[CpCo(PO(OPh)2)3]− Na+, 1b. A solution of diphenylphosphite
(7.65 g, 32.7 mmol) in freshly distilled THF (100 mL) was added
dropwise to a slurry of NaH (0.98g, 60% dispersion in mineral oil, 24.5
mmol) in THF (60 mL) at 0 °C. This suspension was stirred for 0.5 h
at 0 °C and then allowed to warm to room temperature. CpCo(I)2CO
(1.70 g, 4.19 mmol) dissolved in THF (50 mL) was then added
dropwise over 1 h resulting in an orange solution. The orange solution
was allowed to stir for 1 h and then refluxed for 18 h. After cooling to
room temperature, a small amount of water was added to quench the
reaction and the solvent was removed under reduced pressure leaving
an orange solid. The orange residue was dispersed in hexanes, filtered,
and the solid washed with water (50 mL), followed by cold methanol
(50 mL) to leave crude 1b as a yellow powder. 1H NMR revealed ∼5%
impurity consistent with the presence of [CpCo(PO(OPh)2)3]2Co,
2b. To remove this impurity, the crude product was dissolved in a
mixture of toluene (50 mL) and methanol (10 mL) containing NaCN
(0.05 g) and the mixture was refluxed in air overnight. After filtration
through Celite to remove any unreacted NaCN and insoluble
Na3[Co(CN)6], pure 1b was recovered as a yellow solid. Yield: 3.37
g (73%). Mp. 302 °C (dec). IR (thin film, NaCl): 3065w, 1591s,
1489s, 1213s, 1193m, 1157w, 1068w, 1023w 872s, 763w, 690m cm−1.
{[CpCo(PO(OC2D5)2)3]2Nd}+ Cl−, d60-3a. The deuterated complex
was prepared according to the same procedure as 3a using d30-1a
instead of 1a. Yield: 0.102 g (84%). Mp. 177−178 °C. IR (thin film,
NaCl): 2226s, 2143m, 2102m, 1425w, 1187s, 1133s, 1086s, 1059s,
1
1008s, 928m, 829s, 731w, 683m, 673m cm−1. H NMR (CDCl3, 300
MHz, 22 °C): δ 10.44 (s, C5H5, ν1/2 = 7 Hz), −10.53 (s, ∼4 equiv
2
H2O, ν1/2 = 51 Hz). H NMR (CHCl3, 55.3 MHz): δ 2.06 (s, 12D,
CDADB, ν1/2 = 4 Hz), 1.74 (s, 12D, CDADB, ν1/2 = 5 Hz), −0.15 (s,
36D, CD3, ν1/2 = 3 Hz). 31P{1H} NMR (CDCl3, 121.5 MHz): δ
−189.33 (s, ν1/2 = 66 Hz).
{[CpCo(PO(OPh)2)3]2Nd}+ Cl−, 3b. Complex 3b was prepared as a
yellow solid using the same procedure as 3a but starting from 1b and
NdCl3(H2O)7. Yield: 0.356 g (91%). Mp. 291 °C (dec). IR (thin film,
NaCl): 3065w, 1589s, 1488s, 1208s, 1183m, 1163m, 1134s, 1071w,
1
1024w, 910s, 888s, 847w, 757m, 689m cm−1. H NMR (CDCl3, 300
MHz, 22 °C): δ 10.48 (s, 10H, C5H5, ν1/2 = 8 Hz), 5.38 (s, 12H, p-
arylH, ν1/2 = 9 Hz), 4.88 (s, 24H, o/m-arylH, ν1/2 = 21 Hz), 3.96 (s,
24H, o/m-arylH, ν1/2 = 20 Hz), −3.99 (s, 7 equiv H2O, ν1/2 = 45 Hz).
31P{1H} NMR (CDCl3, 121.5 MHz): δ 195.40 (s, ν1/2 = 55 Hz).
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{[CpCo(PO(OC6D5)2)3]2Nd}+ Cl−, d60-3b. The deuterated com-
plex was prepared according to the same procedure as 3a using d30-1b
instead of 1a. Yield: 0.091 g (85%). Mp. 285 °C (dec). IR (thin film,
NaCl): 2277w, 1556s, 1372s, 1155s, 1132s, 964w, 898s, 853m, 804s,
9.68 (s, 12D, CDADB, ν1/2 = 5 Hz), 5.56 (s, 36D, CD3, ν1/2 = 4 Hz).
31P{1H} NMR (CDCl3, 121.5 MHz): δ 67.89 (s, ν1/2 = 71 Hz).
{[CpCo(PO(OPh)2)3]2Yb}+ Cl−, 6b. Complex 6b was prepared as a
yellow solid using the same procedure as 3b starting from 1b and
YbCl3(H2O)6. Yield: 0.204 g (93%). Mp. 283 °C (dec). IR(thin film,
NaCl): 3040w, 1590s, 1487s 1208s, 1185m, 1162m, 1081s, 1069m,
1024w, 913s, 888s, 847w, 770w, 757m, 689m cm−1. 1H NMR (CDCl3,
300 MHz, 22 °C): δ 15.72 (s, 24H, o/m-arylH, ν1/2 = 20 Hz), 11.44 (s,
24H, o/m-arylH, ν1/2 = 20 Hz), 10.30 (s, 12H, p-arylH, ν1/2 = 14 Hz),
1.40 (s, ∼9 equiv H2O, ν1/2 = 9 Hz), −6.01 (s, 10H, C5H5, ν1/2 = 10
Hz). 31P{1H} NMR (CDCl3, 121.5 MHz): δ 48.40 (s, ν1/2 = 51 Hz).
{[CpCo(PO(OC6D5)2)3]2Yb}+ Cl−, d60-6b. Complex d60-6b was
prepared using the same procedure as 3b starting from d30-1b and
YbCl3(H2O)6. Yield: 0.096 g (88%). Mp. 278 °C (dec). IR (thin film,
NaCl): 2273w, 1556m, 1370s, 1155m, 1129m, 1080s, 960w, 905s,
1
770w, 703w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 10.61 (s,
C5H5, ν1/2 = 8 Hz), −7.62 (s, 4 equiv H2O, ν1/2 = 143 Hz). 31P{1H}
NMR (CDCl3, 121.5 MHz): δ 194.79 (s, ν1/2 = 56 Hz).
{[CpCo(PO(OEt)2)3]2Eu}+ Cl−, 4a. Complex 4a was isolated as a
yellow solid using the same procedure as 3a starting from 1a and
EuCl3(H2O)6. Yield: 0.21 g (82%). Mp. 158−160 °C. IR (thin film,
NaCl): 2976m, 2927w, 2899w, 1386w, 1125s 1040s, 934s, 832w,
1
770w, 727w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 5.95 (s,
12H, CHAHB, ν1/2 = 24 Hz), 5.64 (s, 12H, CHAHB, ν1/2 = 26 Hz), 2.96
(s, ∼30 equiv H2O, ν1/2 = 10 Hz), 2.45 (s, 36H, CH3, ν1/2 = 13 Hz),
0.72 (s, 10H, C5H5, ν1/2 = 10 Hz). 31P{1H} NMR (121.5 MHz): δ
−12.79 (s, ν1/2 = 51 Hz).
1
856w, 807m, 770w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ
{[CpCo(PO(OC2D5)2)3]2Eu}+ Cl−, d60-4a. Complex d60-4a was
prepared using the same procedure as 3a starting from d30-1a and
EuCl3(H2O)6. Yield: 0.091 g (74%). Mp. 161−162 °C. IR (thin film,
NaCl): 2226m, 2144w, 2103w, 1424w, 1187s, 1136s, 1088s, 1060s,
−5.91 (s, C5H5, ν1/2 = 7 Hz), 1.48 (s, ∼9 equiv H2O, ν1/2 = 10 Hz).
31P{1H} NMR (CDCl3, 121.5 MHz): δ 47.68 (s, ν1/2 = 42 Hz).
{[CpCo(PO(OPh)2)3]2Yb}+ {CoCl3(THF)}−·2 C6H6, 7. Complex 7
was isolated as a teal green crystalline solid in yields ranging from 10%
to 65% in various trials as a byproduct in the synthesis of 6b from 1b
and YbCl3(H2O)6. Recrystallation of green 7 from acetone containing
NaCl results in isolation of yellow 6b in quantitative yield. Mp. 218−
222 °C. IR (thin film, KBr): 2980w, 2929w, 1719w, 1590m, 1488s,
1454w, 1423w, 1204s, 1162m, 1081m, 1024m, 914s, 889s, 766m,
689m cm−1. 1H NMR (CDCl3, 300 MHz, 22 °C): δ 12.49 (s, 24H, o/
m-arylH), 10.55 (s, 24H, o/m-arylH), 9.62 (s, 12H, p-arylH), −3.09 (s,
10H, C5H5). MS (+LSIMS): 1820.1 amu.
1
1010s, 829s, 732w, 693m, 674m cm−1. H NMR (CDCl3, 300 MHz,
22 °C): δ 6.05 (s, ∼9 equiv H2O, ν1/2 = 20 Hz), 0.73 (s, C5H5, ν1/2 = 7
2
Hz). H NMR (CHCl3, 55.3 MHz): δ 5.97 (s, 12D, CDADB, ν1/2 = 5
Hz), 5.62 (s, 12D, CDADB, ν1/2 = 5 Hz), 2.42 (s, 36D, CD3, ν1/2 = 3
Hz). 31P{1H} NMR (121.5 MHz): δ −12.33 (s, ν1/2 = 65 Hz).
{[CpCo(PO(OEt)2)3]2Tb}+ Cl−, 5a. Complex 5a was prepared as a
yellow solid using the same procedure as 3a starting from 1a and
TbCl3(H2O)6. Yield: 0.19 g (73%). Mp. 145−147 °C. IR (thin film,
NaCl): 2976m, 2927w, 2899w, 1386w, 1128s, 1042s, 935s, 834w,
Kinetic Experiments. The following procedure describes the
kinetic experiment for the d0-6a and d60-6a crossover experiment; all
other kinetic runs were performed in an analogous fashion using the
appropriate lanthanide, ligand, and solvent combination.
1
770w, 729w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 146.89 (s,
10H, C5H5, ν1/2 = 150 Hz), −40.47 (s, 36H, CH3, ν1/2 = 124 Hz),
−58.50 (s, 12H, CHAHB, ν1/2 = 418 Hz), −66.80 (s, 12H, CHAHB, ν1/2
= 410 Hz), −125.43 (s, ∼2 equiv H2O, ν1/2 = 1527 Hz).
Solutions of 6a and d60-6a (10 mg of each) in HPLC-grade
acetonitrile (10.00 mL) were prepared separately and then diluted
100-fold to give solutions with a final concentration of 10 μg/mL. A
0.500 mL aliquot of each solution was added to a vial and mixed for 10
s, and samples of this mixture were injected into the Q-TOF II mass
spectrometer running in +ESI MS mode. Spectra were collected every
5 min for the first hour, followed by every 30 min for the next 6 h, and
then every hour for the next 18 h. For other complexes, the sampling
rate was adjusted as appropriate. In all cases, the reaction was followed
until thermodynamic equilibrium (1:2:1 ratio of d0/d30/d60 iso-
topomers) was established. The total counts for the major mass
peaks of each isotopomer were used to establish the relative
concentrations of each species. The mass spectrometer response was
assumed to be identical for the different isotopomers of the complex in
all cases. The effect of water content in the acetonitrile solvent on the
exchange rate was examined for 5a using solvent mixtures containing
0%, 10%, 20%, 30%, 40%, and 50% (v/v) water to acetonitrile. The
maximum water content of 50% was dictated by the solubility limit of
5a in the mixed solvent.
X-ray Crystallography. Crystals of compound 7 were grown from
benzene. A suitable crystal was selected, attached to a glass fiber, and
data were collected at 90(2) K using a Bruker/Siemens SMART APEX
instrument (Mo Kα radiation, λ = 0.71073 Å) equipped with a
Cryocool NeverIce low-temperature device. Data were measured using
omega scans 0.3° per frame for 30 s, and a full sphere of data was
collected. A total of 2400 frames were collected with a final resolution
of 0.83 Å. Cell parameters were retrieved using SMART21 software and
refined using SAINTPlus22 on all observed reflections. Data reduction
and correction for Lp and decay were performed using the
SAINTPlus22 software. Absorption corrections were applied using
SADABS.23 The structure was solved by direct methods and refined by
least-squares method on F2 using the SHELXTL24 program package.
The structure was solved in the space group P212121 (no. 19) by
analysis of systematic absences. Various phenyl rings (C12, 61:39%;
C53, 50%; C59, 66:34%), one Cp ring (C42, 54:46%) and solvents
(C87, 70:30%; C93, 69:31%) were disordered. Disordered atoms were
held isotropic and some restraints (distance and displacement) were
applied. All other non-hydrogen atoms were refined anisotropically.
{[CpCo(PO(OC2D5)2)3]2Tb}+ Cl−, d60-5a. Complex d60-5a was
prepared using the same procedure as 3a starting from d30-1a and
TbCl3(H2O)6. Yield: 0.10 g (81%). Mp. 130−131 °C. IR (thin film,
NaCl): 2225s, 2144m, 2102m, 1425w, 1186s, 1136s, 1089m, 1060m,
1008s, 928m, 829m, 731w, 692m, 673m cm−1. 1H NMR (CDCl3, 300
MHz, 22 °C): δ 141.42 (s, C5H5, ν1/2 = 1800 Hz), −84.72 (s, ∼2 equiv
H2O, ν1/2 = 1354 Hz).
{[CpCo(PO(OPh)2)3]2Tb}+ Cl−, 5b. Complex 5b was prepared as a
yellow solid using the same procedure as 3b starting from 1b and
TbCl3(H2O)6. Yield: 0.083 g (85%). Mp. 281 °C (dec). IR (thin film,
NaCl): 3039w, 1590s, 1488s 1207s, 1185m, 1163m, 1138s, 1111m,
1024w, 913s, 893s, 844w, 763m, 729m, 690m cm−1. 1H NMR (CDCl3,
300 MHz, 22 °C): δ 180.44 (s, 10H, C5H5, ν1/2 = 841 Hz), −44.55 (s,
12H, p-arylH, ν1/2 = 153 Hz), −62.60 (s, 24H, o/m-arylH, ν1/2 = 242
Hz), −112.68 (s, 24H, o/m-arylH, ν1/2 = 1174 Hz).
{[CpCo(PO(OC6D5)2)3]2Tb}+ Cl−, d60-5b. Complex d60-5b was
prepared using the same procedure as 3b starting from d30-1b and
TbCl3(H2O)6. Yield: 0.067 g (68%). Mp. 284 °C (dec). IR (thin film,
NaCl): 2277w, 1557m, 1373s, 1155s, 1136s, 963w, 898s, 853m, 805s,
771w cm−1. 1H NMR (CDCl3, 300 MHz, 22 °C): δ 174 (s, C5H5, ν1/2
= 2243 Hz).
{[CpCo(PO(OEt)2)3]2Yb}+ Cl−, 6a. Complex 6a was prepared as a
yellow solid using the same procedure as 3a starting from 1a and
YbCl3(H2O)6. Yield: 0.382 g (83%). Mp. 190−191 °C. IR (thin film,
NaCl): 2977m, 2928w, 2899w, 1387w, 1110s, 1038s, 937s, 835w,
1
772w, 728w cm−1. H NMR (CDCl3, 300 MHz, 22 °C): δ 9.81 (s,
24H, CH2, ν1/2 = 42 Hz), 5.55 (s, 36H, CH3, ν1/2 = 14 Hz), 4.06 (s,
∼2 equiv H2O, ν1/2 = 18 Hz), −4.79 (s, 10H, C5H5, ν1/2 = 7 Hz).
31P{1H} NMR (121.5 MHz): δ 67.77 (s, ν1/2 = 76 Hz).
{[CpCo(PO(OC2D5)2)3]2Yb}+ Cl−, d60-6a. Complex d60-6a was
prepared using the same procedure as 3a starting from d30-1a and
YbCl3(H2O)6. Yield: 0.174 g (76%). Mp. 199−200 °C. IR (thin film,
NaCl): 2226m, 2143w, 2116w, 1423w, 1187w, 1123s, 1086m, 1055m,
1006s, 986s, 824w, 694w, 675w cm−1. 1H NMR (CDCl3, 300 MHz, 22
°C): δ 1.72 (s, ∼8 equiv H2O, ν1/2 = 7 Hz), −4.81 (s, C5H5, ν1/2 = 7
2
Hz). H (CHCl3, 55.3 MHz): δ 9.79 (s, 12D, CDADB, ν1/2 = 5 Hz),
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No decomposition was observed during data collection. Details of the
data collection and refinement are given in Table 3. Further details are
provided in the Supporting Information.
(11) (a) Klaui, W.; Neukomm, H.; Werner, H.; Huttner, G. Chem.
̈
Ber. 1977, 110, 2283. (b) Klaui, W. Z. Naturforsch. 1979, 34B, 1403.
̈
(12) Li, L.; Stevens, E. D.; Nolan, S. P. Organometallics 1992, 11,
3452.
(13) Solari, E.; Corazza, F.; Floriani, C.; Chiesi-Villa, A.; Guastini, C.
J. Chem. Soc., Dalton Trans. 1990, 1345.
(14) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
ASSOCIATED CONTENT
* Supporting Information
■
S
Tables of atomic coordinates, bond distances, and angles, and
anisotropic thermal parameters for 7; plots of 1/[d60] vs time
(4a, 5a from 10% to 50% H2O in ACN, 5b and 6a in ACN and
50% H2O in ACN); TGA plots (3a, 5a, 6b); variable
temperature 1H NMR for 6b and molecular ion isotope
pattern/simulation comparisons for the cations of 3a−6a. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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Magnetic Resonance Imaging and Spectroscopy, Young, I. R., Ed.; John
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(16) The response factor of the mass spectrometer to the d0-, d30-,
and d60-isotopomers is assumed to be identical in all cases. Starting
concentrations were selected to ensure good signal-to-noise ratio
without overloading the instrument.
̈
̈
(17) Shannon, R. D. Acta Crystallogr. 1976, 32, 751.
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Sheldrick, G. M.; Jones, P. G.; Schroeder, T. Angew. Chem. 1985, 97,
AUTHOR INFORMATION
Corresponding Author
*E-mail: djberg@uvic.ca.
■
697. (b) Klaui, W.; Asbahr, H. O.; Schramm, G.; Englert, U. Chem. Ber.
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1997, 130, 1223.
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(21) SMART v 5.632; Bruker AXS Inc., Madison, WI, 2005.
(22) SAINTPlus v 7.23a; Data Reduction and Correction Program;
Bruker AXS Inc., Madison, WI, 2004.
(23) SADABS v 2004−1; Empirical Absorption Correction Program;
Bruker AXS Inc., Madison, WI, 2004.
Present Addresses
†Nordion Inc., 4004 Westbrook Mall, Vancouver, BC, Canada
V6T 2A3.
‡University Research Office, 109 Morrill Hall, University of
Idaho, Moscow, ID, USA 83844−3010.
(24) Sheldrick, G. M. SHELXTL v 6.14; Structure Determination
Software Suite; Bruker AXS, Madison, WI, 2004.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
D.J.B. (Discovery Grant) gratefully acknowledges the support
of the Natural Sciences and Engineering Research Council of
Canada.
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