Synthesis, structure and solution NMR properties of (Ph 4P)[M(SeC{O}Tol)3], M = Zn, Cd and Hg

Article abstract of DOI:10.1039/b409621e

Metal selenocarboxylate salts (PPh₄)[M(SeC{O}Tol)₃] (M = Zn (1), Cd (2) and Hg (3); Tol = C₆H₄-p-CH ₃) have been synthesized by reacting Zn(NO₃) ₂·6H₂O, Cd(NO₃

Full text of DOI:10.1039/b409621e

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F U L L P A P E R
Synthesis, structure and solution NMR properties of
(Ph4P)[M(SeC{O}Tol)3], M = Zn, Cd and Hg
Meng Tack Ng,a Philip A. W. Dean*b and Jagadese J. Vittal*a
a
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore,
117 5 43. E-mail: chmjjv@nus.edu.sg
Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7,
b
Canada. E-mail: pawdean@uwo.ca
Received 24th June 2004, Accepted 9th August 2004
First published as an Advance Article on the web 23rd August 2004
Metal selenocarboxylate salts (PPh4)[M(SeC{O}Tol)3] (M = Zn (1), Cd (2) and Hg (3); Tol = C6H4-p-CH3) have been
synthesized by reacting Zn(NO3)2·6H2O, Cd(NO3)2·4H2O or HgCl2 with Na+TolC{O}Se− and PPh4Cl in the ratio of
1:4:1. The structures of these compounds were determined by single-crystal X-ray diffraction methods. The crystal
structures contain discrete cations and anions. In the each anion, the metal center is bound to three TolC{O}Se
ligands, primarily through Se, though some long MO interactions also occur. NMR spectra (113Cd, 199Hg and
77Se, as appropriate) are reported for solutions of [M(SeC{O}Tol)3]−, and of [M(SeC{O}Tol)3]−–[M(SC{O}Ph)3]−
mixtures (M = Zn–Hg), in CH2Cl2 at reduced temperatures. In addition, ESI-MS data have been obtained for
[M(SeC{O}Tol)3]−–[M(SC{O}Ph)3]− mixtures (M = Zn–Hg) in acetone and in CH2Cl2. The NMR and ESI-MS
studies show that the complexes [M(SeC{O}Tol)n(SC{O}Ph)3−n]− (n = 3–0) persist in solution.
question, as well as to extend the chemistry of selenobenzoates
Introduction
generally, we have carried out a synthetic and structural study
In the recent years, there has been significant interest in the
of the monoselenocarboxylate complexes [M(SeC{O}Tol)3]−
development of the chemistry of metal–thiocarboxylate
(M = Zn–Hg). In addition, 77Se, 113Cd and 199Hg NMR have
complexes, stemming not only from their interesting structural
been utilized to characterize the new complexes in solution.
chemistry1–4 but also from the fact that many of them can be
Further, ligand exchange between [M(SeC{O}Tol)3]− and
used as molecular single precursors for the low-temperature
[M(SC{O}Ph)3]− in solution has been monitored by both
synthesis of bulk metal sulfides, thin films and nanoparticles.5–8
ESI-MS and metal NMR studies.
Monothiocarboxylates (RC{O}S−) represent an interesting
class of organic ligands equipped with both hard and soft
Experimental
donor sites.1 These donor sites enable the incorporation of a
combination of hard and soft metal centers into a coordination
compound, as illustrated by the claw-like [M(SC{O}Ph)3]−
metalloligands of the complexes (Me4N)[A{M(SC{O}Ph)3}2]
(A = Na, K; M = Cd, Hg).2 In these metalloligands, the metal
centers have a trigonal planar MS3 kernel, a situation attributed
tothepresenceof thehardalkalimetals,whichbindtotheoxygen
atoms of the carbonyl groups. Similar trigonal planar MS3
geometry, but with the support of weak intermolecular MO
interactions, was observed for the anions in alkali-metal-free
salts of [M(SC{O}Ph)3]− (M = Zn, Cd or Hg).3 The structures
of the latter anions contrast with those of the homoleptic
transition metal complexes [M(SC{O}Ph)3]− (M = Co, Mn or
Ni) which were found to contain discrete octahedral anions with
MO3S3 kernels as a result of O,S-chelation.4
All materials were obtained commercially and were used as
received except for p-toluoyl chloride, which was purified by
distillation under N2. Acetonitrile was distilled from calcium
hydride under N2. Na2Se was prepared according to the literature
method.14 All reactions were performed under an atmosphere of
argon using Schlenk techniques.
Synthesis of (PPh4)[Zn(SeC{O}Tol)3], 1
To the solution of Na+−SeC{O}Tol (4.0 mmol) in MeCN,
prepared as described above, Zn(NO3)2·6H2O (0.30 g,
1.01 mmol) and PPh4Cl (0.38 g, 1.01 mmol) were added.
This solution was stirred for 1.5 h, then the insoluble NaNO3
was separated by filtration. The solvent from the filtrate was
removed using vacuum, then the yellow–orange sticky product
was dissolved in 5 mL of CH2Cl2. The CH2Cl2 solution was
layered with ca. 20 mL of hexane and left at 278 K overnight
to obtain a yellow sticky product. Yellow rod like crystals of 1
were obtained by layering Et2O onto a solution of the product
in an MeCN–acetone (1:1 v/v) solution. Yield 0.63 g (63%).
Anal. Calc. for C48H41ZnPO3Se3 (mol. wt 999.10): C, 57.70; H,
4.14. Found: C, 57.48; H, 3.99%. dH (CDCl3): 2.27 (9H, S, CH3–
C6H4C{O}Se), 6.99–7.01 (6H, d, J = 6 Hz, meta-H), 7.89–7.91
(6H, d, J = 6 Hz, ortho-H), 7.52–7.83 (20 H, PPh4). dC (CDCl3):15
207.2 (TolC{O}Se), 141.5 (C4), 140.7 (C1), 128.5 (C2/6 or C3/5),
127.9 (C3/5 or C2/6), 21.3 (CH3–C6H4C{O}Se). ESI-MS (acetone):
m/z 660.9 ([M(SeC{O}Tol)3]−, 100%), 199.5 (TolC{O}Se−, 15%),
In contrast, little is known about the chemistry of metal-
selenocarboxylate complexes to date. A major impediment
to the development of this chemistry has been the difficulty
of synthesizing the metal selenocarboxylate starting
materials. Thus, for example, monoselenocarboxylate anions,
RC{O}Se−, are highly air and moisture-sensitive. Several
years ago, Kato et al. reported a general synthesis of alkali
metal selenocarboxylates,9,10 including p-tolylmonoselenocarb
oxylate (TolC{O}Se−). This provided an opportunity to study
the chemistry of certain copper selenocarboxylate complexes.11
The study revealed that the chemistry of monoselenobenzoates
is distinct from that of the monothiocarboxylates. This
raises a question about selenocarboxylate complexes of the
Group 12 elements: will planar MSe3 geometry also occur
in [M(SeC{O}R)3]− (M = Zn, Cd, Hg), as it does in the
+
339.0 (PPh4 , 100%).
Synthesis of (PPh4)[Cd(SeC{O}Tol)3], 2
−
corresponding [M(SC{O}Ph)3 anions? To date, only two
examples of MSe3 planar geometry have been reported,
The initial sticky crude product was obtained from Na+−SeC-
{O}Tol (4.0 mmol), Cd(NO3)2·4H2O (0.31 g, 1.01 mmol) and
neither involving selenocarboxylate ligands.12,13 To answer the
2 8 9 0
D a l t o n T r a n s . , 2 0 0 4 , 2 8 9 0 – 2 8 9 4
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

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Table 1 Crystal data and experimental details
PPh4Cl (0.38 g, 1.01 mmol), as described for 1. The crude
product was dissolved in 20 mL of MeCN–acetone (1:1 v/v),
and the resulting yellow solution was then layered with ca.
50 mL of Et2O. Following refrigeration at 278 K overnight,
yellow rod like crystals of 2 were obtained. These crystals were
separated by filtration and washed with MeOH and Et2O. Yield
0.57 g (54%). Anal. Calc. for C48H41CdPO3Se3 (mol. wt 1046.12):
C, 55.11; H, 3.95. Found: C, 55.10; H, 3.80%. dH (CDCl3): 2.29
(9H, s, CH3–C6H4C{O}Se), 7.01–7.03 (6H, d, J = 6 Hz, meta-H),
7.89–7.91 (6H, d, J = 6 Hz, ortho-H), 7.57–7.83 (20 H, m, PPh4).
dC (CDCl3):15 207.3 (TolC{O}Se), 141.5 (C4), 140.8 (C1), 128.9
(C2/6 or C3/5), 127.9 (C3/5 or C2/6), 21.3 (CH3–C6H4C{O}Se).
ESI-MS (acetone): m/z 708.9 ([M(SeC{O}Tol)3]−, 100%), 199.5
1
2
3
Formula
M
k/Å
C48H41O3PSe3Zn C48H41O3PSe3Cd C48H41O3PSe3Hg
999.03
1046.06
0.71073
P21/c
1134.25
0.71073
P21/c
18.4603(6)
12.7772(4)
19.6026(6)
109.362(1)
4362.2(2)
4
1.727
6.108
0.0450
0.0869
0.71073
Space group P21/c
a/Å
b/Å
c/Å
18.6651(7)
18.6691(6)
12.5193(4)
19.9006(7)
110.581(1)
4354.4(2)
4
1.596
3.086
0.0476
0.0846
12.3597(5)
20.0688(8)
110.862(2)
4326.2(3)
4
1.534
3.169
b/°
V/Å3
Z
Dc/g cm−3
l/mm−1
R1a
+
(TolC{O}Se−, 10%), 339.0 (PPh4 , 100%).
0.0521
0.0960
wR2a
Synthesis of (PPh4)[Hg(SeC{O}Tol)3], 3
a R1 = (||Fo| − |Fc||)/(|Fo|); wR2 = [(w(Fo2 − Fc2)/wFo )]1/2
.
4
To the solution of Na+−SeC{O}Tol (4.0 mmol), an ice-cold
solution of HgCl2 (0.28 g, 1.01 mmol) and PPh4Cl (0.38 g,
1.01 mmol) in 5 mL MeCN was added by syringe very close
to the surface (to prevent the formation of black precipitate,
HgSe3), to produce a yellow solution. This solution was stirred
for 1.5 h and the insoluble NaCl was filtered off. This solution
was concentrated by 50% and then refrigerated at 278 K
overnight. The crystals of 3 were collected by filtration, washed
with ice-cold MeOH and Et2O, and dried in vacuum. Yield
0.35 g (31%). Anal. Calc. for C48H41HgPO3Se3 (mol. wt 1134.30):
C, 50.83; H, 3.64. Found: C, 50.85; H, 3.55%. dH (CDCl3): 2.31
(9H, s, CH3–C6H4C{O}Se), 7.05–7.07 (6H, J = 6 Hz, d, meta-H),
7.96–7.98 (6H, d, J = 6 Hz, ortho-H), 7.48–7.79 (20 H, m, PPh4).
dC (CDCl3):15 199.7 (TolC{O}Se), 141.7 (C4), 140.8 (C1), 128.7
(C2/6 or C3/5), 128.2 (C3/5 or C2/6), 21.4 (CH3–C6H4C{O}Se).
ESI-MS (acetone): m/z 795.0 ([M(SeC{O}Tol)3]−, 80%), 199.5
Cd(ClO4)2 (aq), and neat HgMe2 at 299 K for 77Se, 113Cd and
1
199Hg, respectively. Temperatures were calibrated using the H
NMR spectrum of MeOH19 when no decoupling was used, and
the heating effect of decoupling was measured using 50:50 v/v
CCl4–Me2CO.20 To measure the spectra of the selenocarboxylate
samples, proton-decoupling was continuous for 77Se and 199Hg
but inverse-gated for 113Cd, which has a negative Overhauser
effect. Typically, the pulse-widths used for 77Se and 199Hg
were 5.0 ls (39°) and 12.7 ls (52.7°), and the in both cases the
acquisition time and re-cycle time was 1 s. For 113Cd, the pulse
width used was 9.5 ls (68°), the acquisition time was 1 s and the
re-cycle time was 4 s. After each temperature change, 30 min
was allowed to reach a steady state before the spectrum was
measured; this was particularly important for the 199Hg NMR
spectra, since the chemical shifts show a large temperature
dependence.
+
(TolC{O}Se−, 100%), 339.4 (PPh4 , 100%).
Compounds 1–3 were stored at 278 K under N2. However,
they are air stable as solids under ambient laboratory condi-
tions, except for 3, which is only stable under these conditions
for about 2 h.
ESI-MS studies
Positive- and negative-ion ESI-MS spectra were measured
using a Finnigan/Mat LCQ spectrometer. Equimolar amounts
X-Ray crystallography
−
−
of [M(SeC{O}Tol)3 ] and [M(SC{O}Ph)3 ] (M = Zn–Hg)
were mixed in acetone or CH2Cl2 under ambient conditions.
Immediately after mixing, a small portion of the solution was
injected into the mass spectrometer, with the temperature of
the ionization chamber preset at 323 K. Individual species were
detected in the mass spectra and confirmed from their simulated
isotopic envelopes. The m/z values listed in this paper are those
of the principal ions. The positive-ion spectra gave only the
Single crystals were obtained during the synthesis. The
diffraction experiments were carried out at 223 K on a Bruker
SMART CCD diffractometer with a Mo-Ka sealed tube. The
program SMART16 was used for collecting frames of data,
indexing reflection and determination of lattice parameters,
SAINT16 for integration of the intensity of reflections and
scaling. SADABS17 was used for absorption correction and
SHELXTL18 for space group and structure determination
and least squares refinements on F2. A brief summary of the
crystallographic data is given in Table 1.
+
signal from PPh4 ; therefore these are not discussed further in
this paper.
CCDC reference numbers 242797–242799.
See http://www.rsc.org/suppdata/dt/b4/b409621e/ for crystal-
lographic data in CIF or other electronic format.
Results and discussion
Sodium p-tolylmonoselenocarboxylate was allowed to react
with PPh4Cl and appropriate metal salt in the ratio 4:1:1
in MeCN to obtain analytically pure salts of homoleptic
selenocarboxylato anions containing Group 12 metal ions,
(PPh4)[M(SeC{O}Tol)3].
NMR studies
Samples for 77Se, 113Cd or 199Hg NMR spectroscopy were
prepared in 10 mm od NMR tubes under an atmosphere of
Ar(g), using CH2Cl2 that had been dried by standing over
3 Å molecular sieves then, just before use, sparged with Ar(g).
Because of the thermal instability of the solutions, the NMR
tube containing the prospective solute(s) was chilled in ice
prior to addition of sufficient solvent to give a concentration
of 0.1 mol of solute(s)/litre of CH2Cl2 at ambient laboratory
temperature. Each sample was transferred to the pre-cooled
NMR probe directly after it had been prepared.
NMR spectra were measured using a Varian INOVA 400
Spectrometer System, at 76.240, 88.663 and 71.60 MHz for
77Se, 113Cd and 199Hg, respectively, without a field-frequency
lock; negligible field drift was measured. External referencing
was carried out by sample interchange using neat Me2Se, 0.1 M
NMR spectra
Metal (113Cd or 199Hg, as appropriate) and 77Se NMR spectra
have been measured for solutions of [M(SeC{O}Tol)3]− and
[M(SeC{O}Tol)3]−–[M(SC{O}Ph)3]− mixtures (M = Zn–Hg) in
CH2Cl2, atreducedtemperatures;solutionsof [M(SeC{O}Tol)3]−
decompose on standing at ambient probe temperature. The
results of these measurements are summarized in Table 2.
Compared with the metal NMR signals of the complexes
[M(SC{O}Ph)3]− (M = Cd or Hg), with the primary kernel
MS3, those of [M(SeC{O}Tol)3]−, with the primary kernel
MSe3 (see below) are more shielded. This is expected, as both
113Cd and 199Hg are known21–23 to exhibit an “inverse chalcogen
D a l t o n T r a n s . , 2 0 0 4 , 2 8 9 0 – 2 8 9 4
2 8 9 1

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Table 2 Metal and 77Se NMR spectral parameters of [M(SeC{O}Tol)n(SC{O}Ph)3−n]− in CH2Cl2a
M
n
T/K
dM (Dmꢀ, approx./Hz)
dSeb (Dmꢀ, approx./Hz))
1J(M–Se)/Hz
Zn
3
2
1
223
223
223
342.4 (70),c 340.3 (200)
320.4 (80)
305.9 (70)
e
Cdd
Hgg
3
2
1
0
193
193
193
193
250.1 (140),c 250.0 (200)
264.9 (100)
363.6 (60),c 361.7 (130)
354.1 (75)
346.1 (90)
—
—
—
e
e
275.3 (70)
283.0 (50)f
3
2
1
0
193
193
193
193
−729.6 (70),c,h −729.8 (100)
427.3 (10),b 427.0 (20)
424.2 (25)
421.0 (20)
1060 ± 10i,j
945 ± 15i
825 ± 15i
k
—
—
k
−672.8 (70),c,l −671.9 (80)
a In mixtures containing [M(SeC{O}Tol)3]−–[M(SC{O}Ph)3]− = 1:1, except as noted. b Measured relative to neat Me2Se at 299 K. c In a solution
containing [M(SeC{O}Tol)3]− or [M(SC{O}Ph)3]− alone (as appropriate). d M = 113Cd, measured relative to 0.1 M Cd(ClO4)2(aq) at 299 K. e Not
observed in either 77Se or 113Cd NMR spectrum. f dCd (Dmꢀ, approx.) = 287 (7 Hz) at 295 K.7 g M = 199Hg, measured relative to neat HgMe2 at 299 K;
the 199Hg chemical shifts show a large temperature dependence (see text). h dHg (Dmꢀ, approx.) = −799 (250 Hz) at 253 K. i In the 77Se NMR spectrum.
j Also observed in the 199Hg NMR spectrum of the parent [Hg(SeC{O}Tol)3]− alone. k See text. l dHg (Dmꢀ, approx.) = −749 (200 Hz) at 298 K.7
dependence” (shielding depending on the attached atom in the
order Te > Se > S), analogous to the better-known24 inverse
halogen dependence (shielding order with attached atom I >
Br > Cl). Determination of the size of this effect is complicated
for 199Hg by the very large temperature dependences that we
observe for the shielding of both [Hg(SeC{O}Tol)3]− and
[Hg(SC{O}Ph)3]−, +1.2ppmK−1 (193–253K)and +0.72ppmK−1
(193–298 K), respectively (see Table 2). However, at 193 K,
dM([M(SC{O}Ph)3]−) − dM([M(SeC{O}Tol)3]−) = 58 and 33, for
M = 199Hg and 113Cd, respectively, in concert with the larger
chemical shift range known for 199Hg than for 113Cd.25 At
temperatures below approximately 233 K, 77Se satellites are
observed in the 199Hg NMR spectrum of [Hg(SeC{O}Tol)3]−.
However, the value of 1J(77Se–199Hg) can be measured more
accurately in the corresponding 77Se NMR spectrum, where the
signals are sharper (see Table 2 and below).
mixed ligands, as shown in the Table 2. The redistribution of the
ligands is evidently close to statistical. At 253 K, the 77Se NMR
spectra of the mixtures containing Cd or Hg have collapsed to
a single very broad line, but three very broad signals are observed
in the Zn-containing mixtures; it is clear that inter-complex
exchange of [SeC{O}Tol]− is occurring for all complexes at this
temperature, the exchange rates being Cd, Hg > Zn.
Consistent with the reduced-temperature 77Se NMR spectra
of mixtures of [Cd(SC{O}Ph)3]− and [Cd(SeC{O}Tol)3]−, the
reduced temperature 113Cd NMR spectra of these mixtures
show a total of four signals, corresponding to the four possible
−
anions [M(SeC{O}Tol)n(SC{O}Ph)3−n
]
(n = 3–0). Once again
the signal intensities confirm a close to statistical distribution of
ligands. The signals attributed to the complexes with n = 3, 2, 1
and 0 have relative intensities that are approximately 1, 3, 3 and 1
in a mixture where [Cd(SC{O}Ph)3]−:[Cd(SeC{O}Tol)3]− = 1:1.
Strangely, the 199Hg NMR spectra of mixtures of [Hg(SC-
{O}Ph)3]− and [Hg(SeC{O}Tol)3]− show a total of only three
signals, at −672, −721, and −730 ppm (Dm1/2 values approxi-
mately 110, 170 and 170 Hz), with intensities approximately
1:3.5:3.5 for a 1:1 mixture at 213 K. The 77Se NMR spectrum
The 77Se NMR chemical shifts of [M(SeC{O}Tol)3]− vary with
M in the order Zn < Cd < Hg. This contrasts with the irregular
order Cd < Hg < Zn observed for both directly and indirectly
bound 77Se nuclei in [M(Se4)2]2−.26 The 77Se NMR chemical shifts
of [M(SeC{O}Tol)3]− show only slight temperature dependence
for M = Cd and Hg; DdSe = +1.1 and −0.6 ppm, respectively, as
the temperature is changed from 193 to 233 K. The complex
[Zn(SeC{O}Tol)3]− shows a change in DdSe of −1.8 ppm over the
same temperature range: the values of dSe (Dmꢀ, approx./Hz) are
344.6 (100), 344.3 (340), 342.2 (180), 342.4 (70) and 342.8 (30)
at 193, 203, 213, 223 and 233 K, respectively. These changes are
reversible. A plausible explanation is that a change in confor-
mation is occurring around 203–213 K, with both conformers
present, and exchanging, in the region where the line width is
greatest.
of the same mixture shows that [Hg(SeC{O}Tol)n(SC{O}-
−
Ph)3−n
]
(n = 1–3) are present in an approximately statistical
ratio. To be consistent with the intensity data in the 77Se NMR
spectrum, [Hg(SC{O}Ph)3]− must also be present, which is also
in agreement with the ESI MS data (see below). Therefore four
199Hg NMR signals should be observed for the 1:1 mixture; some
signal overlap must be occurring. The small relative intensity of
the signal at −672 ppm, together with its position means that it
can be assigned to [Hg(SC{O}Ph)3]−. The signal at −730 ppm
is in the correct position to be assigned to [Hg(SeC{O}Ph)3]−,
but its relative intensity is too high for the known binomial
concentration distribution. Tentatively, we suggest that the
resonance at −721 ppm is that of [Hg(SeC{O}Tol)(SC{O}-
Ph)2]−, and that the resonance at −730 ppm is a superimposition
of those of [Hg(SeC{O}Tol)n(SC{O}Ph)3−n]−, n = 3 and 2.
At 253 K, no sharp199Hg satellites are observed in the 77Se
NMR spectrum of [Hg(SeC{O}Tol)3]−, but the satellites are
1
evident below 233 K. The size of J(77Se–199Hg), 1060 Hz, is
of the same order of magnitude as other such couplings in the
literature, e.g. 1270 Hz in [Hg(SePPh3)3]2+.22 We were unable to
observe any 113Cd–77Se coupling in the 77Se (or 113Cd) NMR
spectrum of [Cd(SeC{O}Tol)3]−, or corresponding mixed-ligand
complexes; since clear slow-exchange 77Se and 113Cd NMR
spectra are observed for [Cd(SeC{O}Tol)n(SC{O}Ph)3−n]− (see
following), we attribute the lack of an observable one-bond
coupling to the relative broadness of the signals in both 77Se
and 113Cd NMR spectra, which could easily obscure a one-bond
coupling that is expected to be of order 50–200 Hz.21,27
Overall, the metal and 77Se NMR spectra confirm that the
−
complexes [M(SeC{O}Tol)n(SC{O}Ph)3−n
]
(M = Zn–Hg, n =
3–0) persist in solution, and that ligand exchange is slow (relative
to the appropriate chemical shift differences) at or below
approximately 253 K for M = Zn, and at or below approximately
233 K for M = Cd or Hg.
ESI-MS studies
When the reduced-temperature 77Se NMR spectra of mixtures
of [M(SC{O}Ph)3]− and [M(SeC{O}Tol)3]− are examined for
M = Zn, Cd or Hg, a total of three signals is observed (see
Table 2). One is that of the parent [M(SeC{O}Tol)3]− and for
the intensities to be consistent with the known compositions of
the solutions, the other two must be assigned to complexes with
Negative-ion ESI-MS data have been obtained for acetone
solutions containing equimolar amounts of [M(SeC{O}Tol)3]−
and [M(SC{O}Ph)3]− (M = Zn–Hg) at 323 K. In each case,
signals from the four distinct species [M(SeC{O}Tol)n(SC{O}-
Ph)3−n]− (n = 0, 1, 2 and 3; M = Zn–Hg) occur in the spectrum.
2 8 9 2
D a l t o n T r a n s . , 2 0 0 4 , 2 8 9 0 – 2 8 9 4

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Table 3 Table showing the m/z of the products of ligand exchange,
[M(SeC{O}Tol)n(SC{O}Ph)3−n]−, in ESI-MS spectra of mixtures of
[M(SC{O}Ph)3]− and [M(SeC{O}Tol)3]− (M = Zn–Hg) in acetone
Table 4 Selected bond distances (Å), angles (°) and deviations (Å)
from the Se3 and O3 planes in the anions of 1–3
1 (M = Zn)
2 (M = Cd)
3 (M = Hg)
M
Principal ions (m/z, %)
Zn
Cd
Hg
n = 0 (475, 38), n = 1 (537, 100), n = 2 (599, 46), n = 3 (661, 8)
n = 0 (525, 56), n = 1 (585, 100), n = 2 (647, 70), n = 3 (707, 12)
n = 0 (613, 52), n = 1 (673, 100), n = 2 (735, 62), n = 3 (795, 12)
M(1)–Se(1)
M(1)–Se(2)
M(1)–Se(3)
M(1)–O(1)
M(1)–O(2)
M(1)–O(3)
Se(1)–C(1)
Se(2)–C(2)
Se(3)–C(3)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
C(1)–C(11)
C(2)–C(21)
C(3)–C(31)
2.3973(6)
2.4738(5)
2.4114(5)
3.263(2)
2.217(2)
2.973(2)
1.920(3)
1.885(3)
1.921(4)
1.217(4)
1.244(4)
1.213(4)
1.485(5)
1.486(5)
1.490(4)
2.5686(4)
2.6178(4)
2.6036(4)
3.280(3)
2.535(2)
2.836(3)
1.914(3)
1.887(3)
1.913(3)
1.200(4)
1.230(3)
1.219(4)
1.508(4)
1.493(4)
1.485(4)
2.5433(5)
2.5728(5)
2.5867(5)
3.317(6)
2.927(4)
3.106(4)
1.898(5)
1.897(5)
1.926(4)
1.204(6)
1.206(5)
1.210(5)
1.516(6)
1.499(6)
1.468(6)
The m/z values of the principal ions for these species are given
in Table 3. Surprisingly, the relative intensities of the four species
arenotconsistentwiththeapproximatelybinomialconcentration
distribution suggested by the 77Se NMR spectra (see above). In
each case, more selenium-rich species are under-represented.
Tentatively, we suggest that the parent [M(SeC{O}Tol)3]− anions
undergo decomposition under the conditions used in the ESI-
MS experiments. When the solvent was changed from acetone
to CH2Cl2, signals from three extra species appeared in the ESI-
MS spectra of Zn mixtures: those of [Zn(SeC{O}Ph)n(SC{O}-
Ph)2−nCl]− (n = 0, 1 and 2) (m/z values: 375.4, 435.5 and 480.4).
Analogous species are not observed for Cd- or Hg-containing
mixtures, perhaps because Cl− is a relatively hard donor, and
Cd(II) and Hg(II) are softer acceptors than Zn(II).
Se(1)–M(1)–Se(2)
Se(1)–M(1)–Se(3)
Se(2)–M(1)–Se(3)
Se(1)–M(1)–O(1)
Se(2)–M(1)–O(2)
Se(3)–M(1)–O(3)
C(1)–Se(1)–M(1)
C(2)–Se(2)–M(1)
C(3)–Se(3)–M(1)
C(1)–O(1)–M(1)
C(2)–O(2)–M(1)
C(3)–O(3)–M(1)
O(1)–C(1)–C(11)
O(1)–C(1)–Se(1)
C(11)–C(1)–Se(1)
O(2)–C(2)–C(21)
O(2)–C(2)–Se(2)
C(21)–C(2)–Se(2)
O(3)–C(3)–C(31)
O(3)–C(3)–Se(3)
C(31)–C(3)–Se(3)
118.87(2)
117.80(2)
119.32(2)
55.86(5)
70.50(6)
60.30(5)
99.6(1)
73.9(1)
91.9(1)
81.7(2)
96.4(2)
123.34(2)
117.91(1)
117.81(1)
54.50(5)
63.79(5)
60.17(5)
97.1(1)
79.4(1)
86.4(1)
84.7(2)
96.1(2)
126.04(2)
116.55(2)
117.34(2)
54.09(7)
59.21(6)
56.78(6)
98.3(2)
88.7(1)
93.1(1)
82.9(4)
89.8(3)
Structures of [M(SeC{O}Tol)3]− (M = Zn–Hg)
The crystal structure of each compound consists of discrete
anions and cations. These compounds are isomorphous. The
structures of the cations in 1–3 are unexceptional and will not
be discussed further. The structures of the anions in 1 and 3
are shown in Figs. 1 and 2, while selected distances, angles and
deviations of M from Se3 and O3 planes are given in Table 4.
85.9(2)
92.3(2)
88.7(3)
120.3(3)
121.6(3)
118.1(2)
120.8(3)
119.0(2)
120.1(2)
121.4(3)
120.8(3)
117.8(2)
120.1(3)
122.4(3)
117.4(2)
120.5(3)
120.3(2)
119.1(2)
121.6(3)
120.0(2)
118.5(2)
118.5(5)
123.5(4)
117.8(3)
121.0(4)
121.9(4)
117.1(3)
122.0(4)
120.4(3)
117.6(3)
Deviations of M from Se3 plane
0.2826
−0.1451
−0.1451
−0.0372
−0.0372
Deviations of M from O3 plane
0.2826
In each of the anions, the three TolC{O}Se− ligands are
bonded to the metal atom primarily through selenium, each
metal atom being located roughly in the plane of the three
selenium atoms. In addition, weak metaloxygen interactions
occur in these anions, as is also observed for the corresponding
benzenemonothiocarboxylate complexes.7 In the TolC{O}Se−
ligands, the COSe planes are twisted from the aromatic rings;
dihedral angles of these two planes vary from 10.4 to 24.1°.
In compound 1, the Zn–Se distances range from 2.397 to
2.474 Å, which are longer than the 2.377 and 2.378 Å observed
in [Zn(SeC6H2Me3-2,4,6)2(C5H5N)2].28 The three Zn–O bond
distances (2.217, 2.973 and 3.263 Å) in 1 are quite different
from each other. Only one of the Zn–O distances (Zn(1)–O(2))
is found to be less than the sum of van der Waals radii for Zn
and O (2.9 Å).29 Thus a ZnO interaction is present in 1, so that
the geometry of the Zn(II) center can be considered as distorted
tetrahedral. The Zn atom is only 0.057 Å out of the O3 plane;
the sum of the O–Zn–O angles is 359.7°.30 The dihedral angle
between the O3 and Se3 planes in 1 is 62.2°.
Fig. 1 Diagram showing the numbering scheme and 50% probability
thermal ellipsoids of the [Zn(SeC{O}Tol)3]− anion in 1. Hydrogen
atoms are omitted for clarity.
The Cd–Se bond distances in 2 (2.569–2.618 Å; mean
2.597 Å) appear to be slightly longer than those found in
[Cd(Se-2,4,6-iPr3C6H2)2(bpy)]31 (2.549–2.557 Å; mean 2.553 Å)
but shorter than those presence in [Cd{N(PPh2Se)2-Se,Se}2]32
(2.617–2.642 Å; mean 2.634 Å) and (Me4N)2[(l-SePh)6(CdBr)4]33
(2.627–2.654 Å; mean 2.638 Å) Two of the Cd–O bond distances
in 2 (Cd(1)–O(2) and Cd(1)–O(3)) are found to be less than the
sum of van der Waals radii for Cd and O (3.10 Å). When these
two Cd…O interactions are included in the coordination kernel,
the geometry of Cd may be described as distorted trigonal
Fig. 2 Diagram showing the numbering scheme and 50% probability
thermal ellipsoids of the [Hg(SeC{O}Tol)3]− anion in 3. The same
numbering scheme is used as for anions of 1. Hydrogen atoms are
omitted for clarity.
D a l t o n T r a n s . , 2 0 0 4 , 2 8 9 0 – 2 8 9 4
2 8 9 3

View Article Online
Table 5 Bond valences parameters of Zn–Hg in 1–3
P. A. W. Dean and J. J. Vittal, Inorg. Chem., 1994, 72, 1127;
(c) P. A. W. Dean and J. J. Vittal, Polyhedron, 1998, 17, 1937;
(d) P. A. W. Dean, J. J. Vittal, D. C. Craig and M. L. Scudder, Inorg.
Chem., 1998, 37, 1661.
Total bond
Compound
valence, Vi of M
% of M–Se
% of M–O
2 (a) T. C. Deivaraj, P. A. W. Dean and J. J. Vittal, Inorg. Chem.,
2000, 39, 3071; (b) P. A. W. Dean and J. J. Vittal, Inorg. Chem.,
1993, 32, 791.
3 P. A. W. Dean and J. J. Vittal, Inorg. Chem., 1996, 35, 3089.
4 R. Devy, J. J. Vittal and P. A. W. Dean, Inorg. Chem., 1998, 37,
6939.
1
2
3
2.048
2.129
2.351
85.5
86.0
93.7
14.5
13.4
6.3
bipyramidal (s = 0.76).34 The O(1) atom in 2 is located much
closer to the Se3 plane compared to 1, and this interaction leads
to the large Se(1)–Cd(1)–Se(2) angle (123.34°). The sum of the
O–Cd–O angles is 359.8° with the Cd atom displaced from the
O3 plane by 0.049 Å, and the dihedral angle between the O3 and
Se3 planes is 59.4°.30
The Hg–Se distances in 3 (2.543–2.587 Å) are comparable with
those presence in the reported compound, (Bu4N)[Hg(SePh)3]12
(2.536–2.600 Å). The large Se(1)–Hg(1)–Se(2) angle (126.04°)
is consistent with the location of the C(1)–O(1) carbonyl group
between Se(1) and Se(2). The sum of the van der Waals radii of
Hg and O (4.02 Å) indicates that there are interactions between
the Hg atom and all three carbonyl oxygen atoms. Neverthe-
less, a bond valence calculation (see below) suggests that this
interaction contributes only weakly to the overall metal–ligand
bonding in the anion. The sum of the Se–Hg–Se angles, 359.93°
supports trigonal planar geometry at the metal centre. Further,
the Hg atom in 3 is located much further from the O3 plane
(0.164 Å; the sum of the O–Hg–O angles is 308.2°)30 than is
found for Zn and Cd, in 1 and 2.
The relatively longer M–Se(2) distances as compared to
M–Se(1) and M–Se(3), and shorter C–Se bonds found for ligand
2 in 1 and 2 suggest larger C–Se double bond character. This is
reflected in relatively longer C(2)–O(2) distances, indicating the
possibility of electron delocalization in this selenocarboxylate
ligand (Table 4). As a result the carbonyl oxygen atom O(2)
binds most strongly to M. The extent of electron delocalization
is in the order 1 > 2 > 3. In addition, the MO(2) bonding in
1 and 2 is further confirmed from the fact that M–Se(2)–C(2)
angles are smaller than the other two and M–O(2)–C(2) angles
are larger than the other two.
5 (a) G. Shang, M. J. Hampden-Smith and E. N. Duesler, Chem.
Commun., 1996, 1733; (b) G. Shang, K. Kunze, M. J. Hampden-
Smith and E. N. Duesler, Chem. Vap. Deposition, 1996, 2, 242;
(c) M. D. Nyman, M. J. Hampden-Smith and E. N. Duesler, Chem.
Vap. Deposition, 1996, 2, 171.
6 (a) M. D. Nyman, K. Jenkins, M. J. Hampden-Smith, T. T. Kodas,
E. N. Duesler, A. L. Rheingold and M. L. Liable-Sands, Chem.
Mater., 1998, 10, 914; (b) M. D. Nyman, M. J. Hampden-Smith and
E. N. Duesler, Inorg. Chem., 1997, 36, 2218.
7 (a) T. C. Deivaraj, J.-H. Park, M. Afzaal, P. O’Brien and J. J. Vittal,
Chem. Mater., 2003, 15, 2383; (b) T. C. Deivaraj, J.-H. Park,
M. Afzaal, P. O’Brien and J. J. Vittal, Chem. Commun., 2001, 2304.
8 (a) T. C. Deivaraj, M. Lin, K. P. Loh, M. Yeadon and J. J. Vittal,
J. Mater. Chem., 2003, 13, 1149; (b) M. Lin, K. P. Loh, T. C. Deivaraj
and J. J. Vittal, Chem. Commun., 2002, 1400.
9 S. Kato, H. Kageyama, K. Takagi, K. Mizoguchi and T. Murai,
J. Prakt. Chem., 1990, 332, 898.
10 O. Niyomura, K. Tani and S. Kato, Heteroat. Chem., 1999, 10, 373.
11 L. Zheng, W. Huang and J. J. Vittal, New J. Chem., 2002, 26, 1122.
12 E. S. Lang, M. M. Dias, U. E. Abram and M. Z. Vázquez-López,
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13 U. Behrens, K. Hoffman and G. Klar, Chem. Ber., 1977, 110,
3672.
14 D. P. Thompson and P. Boudjouk, J. Org. Chem., 1988, 53, 2109.
15 13C NMR of the cation, PPh4+ (CDCl3): d 135.6 (C4, 4J(P–C) = 2 Hz),
134.3 (C2,6, 2J(P–C) = 10 Hz), 130.68 (C3, 5, 3J(P–C) = 13 Hz), 117.87
(C1, 1J(P–C) = 89 Hz).
16 SMART & SAINT Software Reference manuals, Version 6.22,
Bruker AXS, Analytical Instrumentation, Madison, Wisconsin,
USA, 2001.
17 G. M. Sheldrick, SADABS; software for empirical absorption
correction, University of Göttingen, Göttingen, Germany, 2000.
18 SHELXTL Reference Manual, Version 5.1; Bruker AXS, Analytical
Instrumentation, Madison, WI, 2000.
19 C. Amman, P. Meier and A. E. Merbach, J. Magn. Reson., 1982,
46, 319.
20 J. Led and S. B. Petersen, J. Magn. Reson., 1978, 32, 1.
21 G. K. Carson and P. A. W. Dean, Inorg. Chim. Acta, 1982, 66, 37.
22 P. A. W. Dean and V. Manivannan, Can. J. Chem., 1990, 68, 214.
23 P. A. W. Dean and V. Manivannan, Inorg. Chem., 1990, 29, 2997.
24 R. G. Kidd, Annu. Rep. NMR Spectrosc., 1980, 10a, 6.
25 R. J. Goodfellow, inMultinuclear NMR, ed. J. Mason, Plenum,
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26 M. A. Ansari, C. H. Mahler, G. S. Chorghade and J. Ibers, Inorg.
Chem., 1990, 29, 3832.
27 U. Rajalingam, P. A. W. Dean and H. A. Jenkins, Can. J. Chem.,
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MS3 trigonal planar geometry is well known for thiolate
species having bulky ligands.35,36 Thus, a plausible explanation
to the MSe3 trigonal planar geometry in compounds 1–3 is the
presence of relatively ‘inactive’carboxylate groups. Interestingly,
the mean M–Se bond distances in these compounds (Table 4)
follow the unexpected trend, Zn < Hg < Cd. The analogous
trend was found for the corresponding [M(SC{O}Ph)3]−, and is
known in other instances for Zn–Hg.37
The bond valence approach38 was used to estimate the
contribution of metaloxygen interaction toward the overall
bonding in the anions of 1–3. The results of the bond valence
calculation are shown in Table 5 and suggest that compound
3 could be a better oxygen donor metalloligand (oxygen
atoms more available for “outside” coordination) than 1 or 2.
Overall, the monoselenocarboxylatometallate anions in 1–3
contain structural features very similar to those found in their
sulfur analogues, [M(SC{O}Ph)3]−; these appear to be due to
geometrical restraints imposed by the presence of the carbonyl
groups once the three Se or S are bound to the metal.
28 M. A. Malik, M. Notevalli and P. O’Brien, Polyhedron, 1999, 18,
1259.
29 A. Bondi, J. Phys. Chem., 1964, 68, 441.
30 A similar feature occurs in all three anions [M(SC{O}Ph)3]−
(M = Zn, Cd, Hg)3.
31 R. Subramanian, N. Govindaswamy, R. A. Santos, S. A. Koch and
G. S. Harbison, Inorg. Chem., 1998, 37, 4929.
32 V. García-Montalvo, J. Novosad, P. Kilian, J. D. Woollins, A. M. Z.
Slawin, P. G. Y. García, M. López-Cardoso, G. Espinosa-Pérez and
R. Cea-Olivares, J. Chem. Soc., Dalton Trans., 1997, 1025.
33 P. A. W. Dean, J. J. Vittal and N. C. Payne, Inorg. Chem., 1987, 26,
1683.
34 (a) A. W. Addision, T. N. Rao, J. Reedjik, J. van Jijn and G. C.
Verschoor, J. Chem. Soc., Dalton Trans., 1984, 1349; (b) A. W.
Addision, R. N. Rao and R. Sinn, Inorg. Chem., 1984, 23, 1957;
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Chem., 1998, 37, 240; (d) D. S. Marlin, M. M. Olmstead and
P. K. Mascharak, Inorg. Chem., 2001, 40, 7003.
35 E. S. Gruff and S. A. Koch, J. Am. Chem. Soc., 1990, 112, 1245.
36 R. A. Santos, E. S. Gruff and G. S. Harbison, J. Am. Chem. Soc.,
1991, 113, 469.
Acknowledgements
J. J. V. thanks the National University of Singapore for financial
support. P. A. W. D. thanks Dr. Chris Kirby, Manager, NMR
Facility, UWO, for expert assistance in obtaining the 77Se, 113Cd
and 199Hg NMR spectra. We would like to thank Mr Zheng Lu
for his help in synthesis and his interest.
37 J. C. Bollinger, L. C. Roof, D. M. Smith, J. M. McConnachie and
J. A. Ibers, Inorg. Chem., 1995, 34, 1430.
38 I. D. Brown and D. Alternatt, Acta Crystallogr., Sect. B, 1985,
41, 244.
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2 8 9 4
D a l t o n T r a n s . , 2 0 0 4 , 2 8 9 0 – 2 8 9 4