A nuclear magnetic resonance study of the binding of trimethylphosphine selenide to cadmium oleate

Article abstract of DOI:10.1021/jp411681f

We report an NMR study on the binding of trimethylphosphine selenide (Se=PMe₃) to cadmium oleate (Cd(OA)₂) in CDCl₃ and toluene-d₈. At room temperature in CDCl₃, Se=PMe₃ binds to Cd(OA)₂ in 1:1 ratio with a binding constant of 20 ± 3 as determined by NMR titration. The Cd-bound and free Se=PMe₃ are in fast exchange on the NMR time scale at room temperature and gives only one ³¹P NMR peak. At ca. 190 K, three ³¹P NMR peaks were observed for a toluene-d₈ solution of 1:1 mixture of Cd(OA)₂ and Se=PMe₃. These three peaks were tentatively assigned to free Se=PMe₃ (9.0 ppm), 1:1 (19.5 ppm), and 2:1 complex between Se=PMe₃ and Cd(OA)₂ (18.8 ppm). (Chemical Equation Presented)

Full text of DOI:10.1021/jp411681f

Article
pubs.acs.org/JPCA
A Nuclear Magnetic Resonance Study of the Binding of
Trimethylphosphine Selenide to Cadmium Oleate
†
Raul
́
García-Rodríguez and Haitao Liu*
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
S Supporting Information
*
ABSTRACT: We report an NMR study on the binding of trimethylphosphine
selenide (SePMe ) to cadmium oleate (Cd(OA) ) in CDCl and toluene-d . At
3
2
3
8
room temperature in CDCl , SePMe binds to Cd(OA) in 1:1 ratio with a
3
3
2
binding constant of 20 ± 3 as determined by NMR titration. The Cd-bound and free
SePMe are in fast exchange on the NMR time scale at room temperature and
3
31
31
gives only one P NMR peak. At ca. 190 K, three P NMR peaks were observed for
a toluene-d solution of 1:1 mixture of Cd(OA) and SePMe . These three peaks
8
2
3
were tentatively assigned to free SePMe (9.0 ppm), 1:1 (19.5 ppm), and 2:1
3
complex between SePMe and Cd(OA) (18.8 ppm).
3
2
INTRODUCTION
syntheses of group II−VI nanocrystals. These early studies
■
focus on the coordination of phosphine chalcogenides to CdX
2
The coordination chemistry of trialkylphosphine chalcogenide
plays a key role in the synthesis of group II−VI and IV−VI
semiconductor nanostructures.
(
X = SbF and AsF ) in liquid SO while semiconductor
6 6 2
1
−12
nanocrystal synthesis typically uses cadmium carboxylate and a
Several studies suggested
1,2,4,7
−
−
hydrocarbon solvent.
to metal ions and can be readily displaced by common
2+
3
While SbF and AsF bind weakly
6 6
that the coordination of trialkylphosphine chalcogenide
precedes the monomer production in the synthesis of CdSe
18
2
,4−7
ligands, carboxylate is a much stronger ligand for Cd .
and PbSe nanocrystals.
Binding of phosphine chalcogenide
Therefore, it is likely that the presence of carboxylate could
to metal precursors (e.g., cadmium carboxylate and lead
carboxylate) was shown to activate the chalcogenide for its
subsequent release of the chalcogen atom, which leads to the
production of monomer.
monomer production was shown to be the rate-limiting step of
the nanocrystal synthesis and plays a key role in the nucleation
affect the coordination of trialkylphosphine chalcogenide to
2+
Cd .
Herein, we report a 31P NMR study of the coordination of
2
,4,5,7,11
In many cases, the rate of
SePMe to Cd(OA) in CDCl and toluene-d . Cd(OA) is
3
2
3
8
2
one of the most commonly used cadmium precursors for the
1,19
synthesis of group II−VI nanocrystals.
In addition to
5
and shape evolution of the nanocrystals. In other related
understanding their coordination chemistry, another major
goal of this study is to probe the kinetics and thermodynamics
associated with the formation of the coordination complex.
This information is critical to modeling the kinetics of
nanocrystal nucleation and growth but has been long missing
studies, the structure of phosphine was shown to have a strong
impact on the reactivity of precursors by Ruberu et al. and
5
,13
Owen et al. Finally, the impact of chalcogen exchange on the
8
,13
nanocrystal synthesis has also been reported.
2
0,21
The coordination chemistry between phosphine chalcoge-
nides and cadmium salts has been reported by several
in the literature.
1
4−17
studies.
Dean and co-workers have shown that R PE
RESULTS AND DISCUSSION
3
■
31
and R P(Se)(CH ) P(Se)Ph (R = phenyl, cyclohexyl; n = 1, 2,
2
2 n
2
Binding of SePMe to Cd(OA) at Room Temper-
3
2
3
; E = S, Se) bind to CdX (X = SbF and AsF ) in liquid
2
6
6
ature. P NMR spectroscopy is a sensitive tool to probe the
1
6
SO2. At 209 K, a solution of 4.1: 1 mixture of Ph PSe and
3
coordination of SePMe to metal ions because metal binding
3
3
1
Cd(SbF ) gave well-resolved P NMR peaks for the free and
31
16,17
31
6
2
causes a large change in its P chemical shift.
The
P
metal-bound phosphine chalcogenide. For the metal bound
NMR spectrum of SePMe in toluene-d gives a sharp singlet
3
8
2
1
Ph PSe, its J
was observed to be 48 Hz; its J
(585 Hz)
77
3
Cd−P
P−Se
at 5.74 ppm (Figure 1A) with characteristic Se satellites
was significantly smaller than that of free R PE (655 Hz). At
1
31
3
( J
= 720 Hz). In the presence of Cd(OA) , the
P
P−Se
2
room temperature or at 209 K but in the presence of excess
metal ion, fast ligand exchange was observed, as indicated by
the absence of coupling between P and Cd atoms. These results
chemical shift of SePMe increased along with a decrease in
3
1
the
J
and both spectroscopic changes increase with
P−Se
1
13
as well as additional Cd NMR studies support the formation
2
+
15,17
Special Issue: Kenneth D. Jordan Festschrift
of [Cd(Ph PSe) ] complex at low temperature.
3
4
Although these early studies provided important insight into
the coordination chemistry of phosphine chalcogenides, the
systems they studied are very different from those used in the
Received: November 27, 2013
Revised: January 9, 2014
Published: January 10, 2014
©
2014 American Chemical Society
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The Journal of Physical Chemistry A
Article
SePMe + Cd(OA) = (OA) Cd(SePMe )
(1)
3
2
2
3
Figure 1. 31P{ H} spectra (toluene-d , T = 293 ± 1 K) of (A) pure
1
8
1
SePMe (δ = 5.74 ppm, J
= 720 Hz), (B) 4: 1 mixture of Se
= 676 Hz), (C) 1: 1 mixture of
P−Se
3
P−Se
1
PMe : Cd(OA) (δ = 9.49 ppm J
3
2
1
SePMe : Cd(OA) (δ = 11.54 ppm, J
= 648 Hz), (D) 0.2: 1
3
2
P−Se
1
mixture of SePMe : Cd(OA) (δ = 16.14 ppm, J
= 586 Hz),
P−Se
3
2
and (E) ca. 1: 1 mixture SePMe and Cd(OTf) (δ = 21.28 ppm,
3
2
1
J
= 533 Hz). Note: spectrum E was taken in CD Cl due to
P−Se
2 2
solubility reasons; similar chemical shift was observed in acetone-d for
Figure 2. Job plot suggesting a 1:1 binding stoichiometry between
SePMe and Cd(OA) .
6
a ca. 1: 1 mixture of SePMe and Cd(OTf) (see Experimental
3
2
3
2
Section).
By using a similar approach, we have also determined the
equilibrium constant of eq 1 by NMR titration. In this case, we
increasing Cd: Se ratio (Figure 1B−D); a similar downfield
7
7
shift was also observed in the Se spectra (Figure S1,
Supporting Information). For a sample having a 5: 1 ratio of
varied the ratios of Cd(OA)
2
and SePMe
3
and recorded their
3
1
Cd(OA) and SePMe , the P NMR peak shifted to δ =
2
3
1
1
6.14 ppm and the J
decreased to 586 Hz. In no cases did
P−Se
we observe satellite peaks that could be assigned to coupling to
1
11
113
31
77
Cd or Cd. The downfield shift of P and Se NMR peaks
1
and the decrease in J
SePMe to Cd(OA) .
are consistent with the binding of
The fact that we observed only a
P−Se
1
6,17
3
2
single 31P peak and the absence of Cd satellites both suggest
that the exchange between metal-bound and free SePMe is
3
16,17
faster than the NMR time scale,
in our case, ca. 1 μs to 100
2
2
ms.
To evaluate the role of oleate on the binding of SePMe to
3
2+
Cd , we also prepared a 1:1 mixture of SePMe and
3
Figure 3. 31P{ H} NMR spectra (243 MHz, 298 K, CDCl
1
3
1
3
) of Se
cadmium triflate (Cd(OTf) ). The P NMR spectrum of this
2
PMe upon addition of Cd(OA) showing the progressive downfield
shift of SePMe resonance.
3
2
mixture is shown in Figure 1E. It can be seen that Cd(OTf)2
3
produced the largest downfield shift (to 21.28 ppm) and the
1
largest decrease in JP−Se (to 533 Hz) in this series of
experiments. This result suggests that the binding of SePMe
3
3
3
1
1
P NMR spectra at 298 K (Figure 3). Because the measured
P chemical shift is a weighted average of the bound and
to Cd(OTf) is significantly stronger than to Cd(OA) , as
2
2
expected due to the fact that triflate is a much weaker Cd ligand
1
8
than oleate.
unbound SePMe , we can calculate the concentration of
3
Binding Stoichiometry and Equilibrium Constant at
Room Temperature. To evaluate the binding stoichiometry
between SePMe and Cd(OA) , we used the method of
bound and unbound SePMe if the chemical shift of the pure
3
species is known. In this case, the chemical shift of free Se
PMe can be measured directly; a 1:1 mixture of Cd(OTf) and
3
2
3
2
23
31
continuous variation, also known as the Job’s method. Briefly,
we prepared a series of solutions of SePMe and Cd(OA) in
SePMe which has a P chemical shift of 21.3 ppm, is a
3,
good approximation of the Cd-bound SePMe because
3
2
3
CDCl in which we kept their total molar concentration
triflate is a weak ligand and can be easily displaced by Se
3
constant but varied their mole fractions (χ and χ ). At room
PMe . From the calculated concentrations, we then determined
Se
Cd
3
3
1
temperature, the P NMR chemical shift of SePMe is a
the equilibrium constant for eq 1 to be 20.2 ± 3.1. At 298 K,
this equilibrium constant corresponds to a free energy change
of −(7.4 ± 0.4) kJ·mol .
Low-Temperature NMR Studies. Variable temperature
(VT) NMR spectroscopy was carried out in order to gain
additional insight into the binding dynamics between Se
PMe and Cd(OA) . For these experiments, we prepared three
3
weighted average of that of metal-bound and free species and
therefore is a function of the solution composition. Addition of
−1
3
1
Cd(OA) will induce an increase in the P chemical shift
2
relative to that of pure SePMe (Δδ). To determine the
3
binding stoichiometry, the product of Δδ and χ is plotted
Se
against χ ; the maximum of the plot would correspond to the
Se
3
2
stoichiometry of the complex. As shown in Figure 2, a clear
toluene-d solutions having different Cd: Se ratios: 4:1 (sample
8
31
1
maximum was observed at 50% mole fraction of SePMe ,
A), 1: 1 (sample B), and 1: 4 (sample C). Their P{ H}spectra
were recorded in the range of 190 to 296 K and a subset of
them are shown in Figure 4.
3
suggesting the formation of a 1:1 complex at room temperature
(
eq 1).
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315
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Figure 4. Selected 31P VT-NMR spectra (toluene-d ) of a mixture of 1 equiv of Cd(OA) and (A) 0.25 equiv, (B) 1 equiv, and (C) 4 equiv of Se
8
2
PMe3.
All three samples gave a single 31P resonance at room
temperature. Upon cooling, all samples showed a slight
downfield shift and significant peak broadening; the Se satellites
disappeared at ca. 240 K. At ca. 200 K, the single resonance
evolved into two at ca. 19 and 9 ppm. The temperature at
which this peak splitting occurs appears to increase with
decreasing Se:Cd ratio, being 194 K, 200 K, and 217 K for
sample A, B, and C, respectively. Upon further cooling,
additional changes were observed for the newly emerged peak
at 19 ppm. For sample A, the peak remained broad; however,
for sample B and C, the peak at 19 ppm split into two that are
separated by 0.7 ppm (e.g., for sample B, the two peaks are
located at 19.5 and 18.8 ppm). The relative intensity of the two
peaks depends on the Cd: Se ratio, with excess Se increasing
the high field (lower ppm) peak. On the other hand, the peak at
peaks merge into one, eq 2 can be used to estimate the
exchange rate:
24
1
2
k =
πΔν
(2)
Here k is the exchange rate constant, Δν is the difference in the
chemical shift of the bound and free SePMe (in Hz). In our
3
experiment, the coalescence temperature is estimated to be
around 220 K for the sample with 1:1 Cd:Se ratio (Figure 2B).
3
The Δν value was measured to be 2.1 × 10 Hz from the
spectrum taken at 193 K. The exchange rate constant was thus
3
−1
calculated to be 4.7 × 10 s at 220 K. Note that eq 2 assumes
that the two exchanged species are of equal population, which is
not strictly the case in our experiments. Therefore, the
calculated exchange rate constant should be considered as an
order-of-magnitude estimate. Nevertheless, from this rate
constant and the corresponding temperature, the activation
free energy of the exchange process can be estimated by the
9
ppm remained as a sharp singlet at 190 K. For sample A, the
signal-to-noise ratio was too low to determine if there were Se
satellites. For samples B and C, however, Se satellite peaks were
−
1
1
following equation to be 38 kJ·mol , where T is the
clearly visible at ca. 190 K with a J
sample B and C, respectively.
= 708 and 692 Hz for
C
Se−P
25
coalescence temperature and R is gas constant.
We assign the peak at 9 ppm to free SePMe based on the
3
⎡
⎤
⎥
⎛
T ⎞
1
‡
C
following evidence: its chemical shift and J
are close to
ΔG = R × T × 22.96 + ln
⎜
⎟
Se−P
C
⎢
⎣
⎝Δν ⎠⎦
those measured for pure SePMe (Figure 1A); the small
3
difference could be attributed to temperature and the effect of
Using the same VT-NMR data, we have also calculated the
ΔH and ΔS of the complex formation by analyzing the
ligand exchange. In addition, its intensity also increased with
R
R
increasing amount of SePMe in the solution. The two peaks
3
temperature dependence of the binding equilibrium for sample
B (Cd: Se = 1: 1) in the range of 248−290 K. In the analysis,
we only considered the formation of 1:1 complex; this
simplification is justified because the Job plot indicates that
such complex is formed at room temperature. Noting that the
Cd/Se ratio is 1 in this case, the equilibrium constant (K) for
eq 1 can be expressed by the following equation:
near 19 ppm were assigned to Cd-bound SePMe . The fact
3
that their relative intensity also depends on the Cd: Se ratio
suggests that the high field peak and low field peak could
correspond to coordination complexes having 1:2 and 1:1 Cd/
Se ratios, respectively. However, this assignment will require
additional study to confirm. Although our result suggests the
formation of both 1:1 and 1:2 complexes at <200 K, it is worth
noting that the Job plot (Figure 2) clearly indicated the
formation of 1:1 complex at room temperature. This should not
come as a surprise given that low temperature will favor
molecular association processes.
f
K =
2
C (1 − f )
(3)
0
where C is the overall concentration of SePMe and f is the
0
3
molar fraction of Cd-bound SePMe . After taking the
Kinetics and Thermodynamics of the Formation of
Coordination Complex. From the VT-NMR data, we can
estimate the rate of exchange between bound and free Se
3
logarithm of both sides of eq 3 and recognizing that
ΔH − TΔS = − RT ln K
R
R
PMe . Specifically, at the coalescence temperature, which is
3
defined as the temperature at which the two exchanged NMR
we obtained
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ΔHR
RT
ΔSR
R
f
that were previously degassed, dried with 4 Å molecular sieves
−
+
+ ln C = ln
0
2
and stored in a glovebox. Acetone-d and CD Cl (1 mL
6
2
2
(1 − f )
ampules, Aldrich) were used as received.
2
Thus plotting ln(f/(1 − f) ) against 1/T will give a straight
line (Figure 5), and from the slope and intercept we obtained
Solution NMR spectra were obtained on Bruker Avance III
500 MHz and Bruker Avance III 600 MHz spectrometers.
1
13
Chemical shift values are given in ppm. H and C chemical
31
shifts are referenced to TMS, and for P spectra 85% H PO
3
4
77
was used as external reference; Se shifts were referenced to
the lock signal. 31P NMR spectra were acquired with inverse
gated decoupling. Coupling constants (J) are given in Hertz
(
Hz). The temperature of the NMR spectrometer was
calibrated with methanol and ethylene glycol standards.
Cadmium Triflate, Cd(OTf) . This compound was
2
synthesized by dissolving CdO in triflic acid following literature
29−31
procedures.
Briefly, Cd(OTf) in the form of a white
2
powder was prepared by carefully mixing cadmium oxide (2.55
g, 20 mmol), triflic acid (4 mL, 45 mmol) and H O. The
2
mixture was gently heated at 45 °C for 22 h resulting in a
solution which was subsequently concentrated by heating.
Anhydrous diethyl ether was added dropwise to obtain a
precipitate. The precipitate was washed several times with ether
and stored in an oven at 140 °C.
Figure 5. Thermodynamic analysis of SePMe binding to Cd(OA) .
3
2
Please see text for an explanation of the terms.
−
1
ΔH = (−14.5 ± 0.4) kJ·mol and ΔS = (−27.5 ± 1.2) J·
SePMe . This compound was synthesized as we
R
R
3
−
1
−1
−1
2,4
mol ·K . These values predict ΔG = (−6.3 ± 0.8) kJ·mol
previously reported.
Briefly, trimethylphosphine (2.50 g,
R
at 298 K, in good agreement with the result (−(7.4 ± 0.4) kJ·
32.86 mmol) was added to a vial and cooled to −30 °C. Se
powder (2.725 g, 34.51 mmol) was then added slowly to the
vial inside a glovebox. The mixture was stirred for 24 h at room
−1
mol ) obtained from the NMR titration experiment.
CONCLUSION
■
temperature to give a white precipitate. CH Cl (5 mL) was
2 2
In conclusion, we have studied the coordination of SePMe
added to dissolve the white precipitate and unreacted Se was
removed by filtration. Addition of hexane and slow evaporation
3
to Cd(OA) in CDCl and toluene-d . Our result indicates that
2
3
8
SePMe binds to Cd(OA) in 1:1 ratio at room temperature
at reduced pressure gave white microcrystals which were stored
3
2
1
with a binding constant of 20 ± 3. The ΔH and ΔS of the
in a glovebox. H NMR (500.16 MHz, CDCl , r.t.) δ = 1.93
R
R
3
1
3
1
complex formation were calculated from the temperature
[d(13.3), 9H, CH ]. C( H) NMR (125.77 MHz, CDCl , r.t.)
3
3
3
1
1
dependence of the equilibrium constant to be (−14.5 ± 0.4) kJ·
δ = 23.08 [d(49.1), CH ]. P{ H} NMR (202.47 MHz,
3
−
1
−1 −1
1
mol and (−27.5 ± 1.2)J·mol ·K , respectively. The Cd-
CDCl , r.t.) δ = 8.77 ( J
= 682 Hz)
3
P−Se
bound and free SePMe are in fast exchange at room
Cadmium Oleate, Cd(OA) . This compound was prepared
3
2
31
temperature at the NMR time scale but can be resolved by P
by dissolving CdO in oleic acid and subsequent precipitation
3
1
2,4
NMR at T < 220 K. At ca. 190 K, P NMR data suggests the
with acetone. In a typical synthesis, CdO (1.036 g, 8.07
formation of complexes having 1:1 and 2:1 ratio of SePMe
mmol) was added to 10.2 mL of oleic acid (32.2 mmol, 90%
tech grade, Aldrich) in a 3-neck flask. The mixture was degassed
at 100 °C and then heated at 190 °C until a colorless solution
was observed. The solution was cooled to room temperature
3
to Cd(OA) .
2
Our study highlights the usefulness of NMR spectroscopy in
understanding the kinetic and thermodynamics of processes
relevant to the synthesis of CdSe nanocrystals. Among other
things, understanding the binding kinetics and thermodynamics
will allow us to quantify the degree of activation of chalcogen
precursors by the metal. Such information will be useful to
design new precursor pairs that offer targeted reactivity and to
match precursors for the synthesis of multicomponent
and acetone was added to precipitate Cd(OA) as a white solid,
2
which was filtered off and dried in vacuo overnight to remove
acetone.
Job Plot Experiment. The method of continuous variation,
also known as Job plot was used to study the stoichiometry of
2
3,32
the coordination of SePMe to Cd(OA)2.
A stock
3
1
3,26
nanocrystals.
Given that similar precursor combinations
solution of SePMe (0.10 M) in CDCl was prepared by
3
3
have been used in the synthesis of other nanocrystals (e.g., CdS
dissolving 186 mg of SePMe in 12 mL of CDCl . A stock
3
3
2
6−28
and CuInSe2),
we expect that the approaches outlined
solution of cadmium oleate in the same concentration was
prepared by dissolving 270 mg of Cd(OA) in 4 mL of CDCl .
here may be useful in the mechanistic studies of these material
systems as well.
2
3
Both stock solutions were prepared inside a glovebox. A total of
1 NMR samples were prepared by mixing the stock solutions
and Cd(OA) in the following quantities: 0.6 and
1
EXPERIMENTAL SECTION
■
of SePMe
3
2
Unless otherwise noted all operations were performed under an
atmosphere of dry nitrogen using Schlenk and vacuum
techniques, or in a nitrogen filled glovebox.
0 mL; 0.5 and 0.1 mL; 0.45 and 0.15 mL; 0.4 and 0.2 mL; 0.35
and 0.25 mL, 0.3 and 0.3 mL; 0.25 and 0.35 mL; 0.2 and 0.4
mL; 0.15 and 0.45 mL; 0.1 and 0.5 mL; and 0.05 and 0.55 mL.
The NMR spectrum was collected immediately after the sample
Chemicals. Selenium powder (Aldrich, ≥99.5%), CdO
99.5%, Aldrich), trioctylphosphine (TOP, 97%, Aldrich),
(
being prepared to avoid reaction between SePMe and
3
trimethylphosphine (99%, Strem), oleic acid (Aldrich, 90%),
Cd(OA) .
2
trifluoromethanesulfonic acid (98%, Aldrich) were used as
Titration Experiments of SePMe and Cd(OA) in
3
2
received. NMR samples were prepared in CDCl or toluene-d8
CDCl . The binding of SePMe to Cd(OA) was investigated
3
3
3
2
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The Journal of Physical Chemistry A
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by NMR titrations. A stock solution of SePMe in CDCl
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3
3
3
■
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3
(
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3
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2
3
2
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solution was monitored for possible reaction between Se
PMe and Cd(OA) , and if such reaction was detected, which
3
2
(
was indicated by the formation of OPMe , a fresh sample
3
was prepared.
In order to estimate the chemical shift of SePMe
3
(
2
+
coordinated to Cd , equimolar amounts of SePMe and
3
Cd(OTf) were combined in CD Cl . Although the mixture
2
2
2
3
1
was not very soluble, a P resonance of SePMe was
3
1
observed at δ = 21.3 ppm ( J
= 533 Hz), suggesting that in
P−Se
the system the equilibrium is shifted to the coordination of
SePMe to cadmium. This is expected from the excellent
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3
leaving-group properties of the OTf ligand and the use of a
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2
3
6
(
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the system was more soluble. After mixing equimolar amounts
The Formation Mechanism of Binary Semiconductor Nanomaterials:
Shared by Single-Source and Dual-Source Precursor Approaches.
Angew. Chem., Int. Ed. 2013, 52, 11034−11039.
of SePMe and Cd(OTf) , a resonance was observed at δ =
3
2
1
2
2.94 ppm ( J
= 518 Hz) along with a small amount of
P−Se
precipitate, which disappeared upon the addition of a second
(
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1
1
resonance in the P NMR spectrum at δ = 23.10 ppm ( J
=
P−Se
517 Hz).
(
VT-NMR Experiments. The following three samples were
used in the VT experiments: 88 mg of Cd(OA) and 5 mg of
2
Se=PMe dissolved in 1 mL of toluene-d , 22 mg of Cd(OA)
3
8
2
and 5 mg of Se=PMe dissolved in 1 mL of toluene-d , and 22
3
8
mg of Cd(OA) and 20 mg of Se=PMe dissolved in 1 mL of
2
3
toluene-d8.
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ASSOCIATED CONTENT
Supporting Information
Se NMR spectra of free trioctylphosphine selenide (TOPSe)
■
*
S
7
7
and TOPSe with 1 equiv of Cd(OA) . This material is available
free of charge via the Internet at http://pubs.acs.org.
2
(
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(H-1, C-13, Cd-113) Nuclear Magnetic-Resonance and Magnetic
Circular-Dichroism Spectroscopic Study of Thiolate Complexes of
AUTHOR INFORMATION
■
*
Cadmium. Inorg. Chim. A: Bioinorg. 1981, 56, 59−71.
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Corresponding Author
Mailing Address: Department of Chemistry, University of
Pittsburgh, Pittsburgh, PA 15260, U.S.A.
Resonance Spectroscopic Study of Complexes of Cadmium(II) with
Some Phosphine Oxides, Sulfides, and Selenides. Can. J. Chem. 1980,
5
8, 180−190.
Present Address
University of Cambridge, Department of Chemistry, Lensfield
Road, Cambridge, CB2 1EW. U.K.
(17) Dean, P. A. W.; Polensek, L. A P-31 Nuclear Magnetic-
†
Resonance Spectroscopic Study of Some 2−1, 3−1, and 4−1
Complexes of Phosphine Sulfides and Selenides with Cadmium(Ii),
Including Some Complexes with Mixed-Ligands. Can. J. Chem. 1980,
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The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
■
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R.G.-R. acknowledges Fundacio
postdoctoral fellowship. H.L. acknowledges ONR
N000141310575) and AFOSR (FA9550-13-1-0083) for
partial support of this work.
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