Exchange of alkyl and tris(2-mercapto-1-t-butylimidazolyl)hydroborato ligands between zinc, cadmium and mercury

Article abstract of DOI:10.1016/j.jorganchem.2015.04.014

Abstract The tris(2-mercaptoimidazolyl)hydroborato ligand, [Tm^But], has been used to investigate the exchange of alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, [Tm^But]₂Zn reacts with Me₂Zn to yield [Tm^But]ZnMe, while [Tm^But]CdMe is obtained readily upon reaction of [Tm^But]₂Cd with Me₂Cd. Ligand exchange is also observed between different metal centers. For example, [Tm^But]CdMe reacts with Me₂Zn to afford [Tm^But]ZnMe and Me₂Cd. Likewise, [Tm^But]HgMe reacts with Me₂Zn to afford [Tm^But]ZnMe and Me₂Hg. However, whereas the [Tm^But] ligand transfers from mercury to zinc in the methyl system, [Tm^But]HgMe/M^e2Zn, transfer of the [Tm^But] ligand from zinc to mercury is observed upon treatment of [Tm^But]₂Zn with HgI₂ to afford [Tm^But]HgI and [Tm^But]ZnI. These observations demonstrate that the phenomenological preference for the [Tm^But] ligand to bind one metal rather than another is strongly influenced by the nature of the co-ligands.

Full text of DOI:10.1016/j.jorganchem.2015.04.014

Journal of Organometallic Chemistry 792 (2015) 177e183
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Exchange of alkyl and tris(2-mercapto-1-t-butylimidazolyl)
hydroborato ligands between zinc, cadmium and mercury
*
*
Ava Kreider-Mueller, Patrick J. Quinlivan, Yi Rong, Jonathan S. Owen , Gerard Parkin
Department of Chemistry, Columbia University, New York, NY 10027, USA
a r t i c l e i n f o
a b s t r a c t
But
Article history:
Received 13 February 2015
Received in revised form
The tris(2-mercaptoimidazolyl)hydroborato ligand, ½Tm ꢀ, has been used to investigate the exchange of
t
Bu
alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, ½Tm ꢀ Zn
2
But
But
reacts with Me
2
Zn to yield ½Tm ꢀZnMe, while ½Tm ꢀCdMe is obtained readily upon reaction of
7
April 2015
Bu
t
½
Tm ꢀ Cd with Me
2
Cd. Ligand exchange is also observed between different metal centers. For example,
2
Accepted 8 April 2015
Available online 29 April 2015
But
But
But
½
Tm ꢀCdMe reacts with Me
2
Zn to afford ½Tm ꢀZnMe and Me
2
Cd. Likewise, ½Tm ꢀHgMe reacts with
But
But
Me
2
Zn to afford ½Tm ꢀZnMe and Me
2
Hg. However, whereas the ½Tm ꢀ ligand transfers from mercury to
But
But
Dedicated with respect to Mike Mingos on
the occasion of his 70th birthday. Happy
birthday, Mike!
zinc in the methyl system, ½Tm ꢀHgMe=Me Zn, transfer of the ½Tm ꢀ ligand from zinc to mercury is
2
observed upon treatment of ½TmBut ꢀ Zn with HgI to afford ½TmBut ꢀHgI and ½TmBut ꢀZnI. These observations
2
2
But
demonstrate that the phenomenological preference for the ½Tm ꢀ ligand to bind one metal rather than
another is strongly influenced by the nature of the co-ligands.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Zinc
Cadmium
Mercury
Alkyl
Tris(2-mercaptoimidazolyl)hydroborato
Exchange
Introduction
Results and discussion
The exchange of alkyl, aryl and cyclopentadienyl groups be-
tween metal centers is an important method for synthesizing a
variety of organometallic compounds [1]. For example, transition
metal alkyl compounds are often synthesized via metathesis of a
transition metal halide compound with main group metal alkyls
such as RLi, RMgX, and R Zn. In addition to their use in the syn-
2
thesis of organometallic compounds of transition metals, main
group metal alkyl compounds have found other applications. For
While zinc [3e6] and, to a lesser extent, cadmium [5,7] dialkyls
have important applications, the mercury counterparts find little
utility due to their extreme toxicity [8]. One of the factors respon-
sible for the toxicity of organomercury compounds is the high af-
finity of mercury for sulfur [8e10] such that it binds effectively to
the cysteine residues in proteins and enzymes [11], and also dis-
places zinc from cysteine rich structural and catalytic sites [9,12,13].
Therefore, in addition to examining alkyl group exchange, it is also
pertinent to examine exchange reactions involving sulfur ligands.
example, Et
polymerization for the control of molecular weight distributions
3]; furthermore, it has also been used as an effective means to
2
Zn [2] is an important chain transfer agent in olefin
Previous studies have demonstrated that tris(2-mercaptoimi-
R
[
dazolyl)hydroborato ligands, ½Tm ꢀ [14e18], are a useful class of L
2
X
shuttle growing polymer chains between different catalyst centers,
thereby affording a novel method for forming block copolymers [4].
Here we describe a series of reactions that involve exchange of alkyl
and other ligands between Group 12 metals.
3
[19] [S ] donors that provide a sulfur-rich coordination environ-
ment for a variety of metals (Fig. 1). For example, the t-butyl de-
But
rivative, ½Tm ꢀ, has been used to synthesize a variety of zinc
[20e22], cadmium [21,23] and mercury [21,24] complexes, which
provides a basis for us to investigate alkyl exchange reactions of
these metals [25].
Whereas the aforementioned synthetic use of main group alkyls
involves the exchange of alkyl groups between different metals,
alkyl transfer between centers involving the same metal is also
*
Corresponding authors.
E-mail addresses: jso2115@columbia.edu (J.S. Owen), parkin@columbia.edu
(
G. Parkin).
http://dx.doi.org/10.1016/j.jorganchem.2015.04.014
022-328X/© 2015 Elsevier B.V. All rights reserved.
0

178
A. Kreider-Mueller et al. / Journal of Organometallic Chemistry 792 (2015) 177e183
We have now demonstrated that a similar type of trans-
But
But
formation exists between ½Tm ꢀMMe and ½Tm ꢀ M=Me M, and
2
2
that the reaction lies heavily in favor of the heteroleptic derivative,
But
But
½
Tm ꢀMMe. Thus, treatment of ½Tm ꢀ Zn [22] with Me
2
Zn results
2
But
in the facile formation of ½Tm ꢀZnMe [20a], as illustrated in
But
Scheme 1. Likewise, ½Tm ꢀCdMe [23] is rapidly obtained upon
But
reaction of ½Tm ꢀ Cd [23] with Me
2
Cd.
2
But
But
The formation of ½Tm ꢀZnMe and ½Tm ꢀCdMe by these re-
actions provides a useful method of synthesis from the sodium
But
complex because ½Tm ꢀ M may be generated via the reactions of
2
But
½
Tm ꢀNa [17,27] with MCl
2
(M ¼ Zn, Cd), as illustrated in Scheme 2.
But
But
Specifically, ½Tm ꢀMMe can be obtained from ½Tm ꢀNa in a single
reaction flask via a two-step sequence that involves (i) treatment of
But
Bu
t
2
equivalents of ½Tm ꢀNa with MCl
2
to generate ½Tm ꢀ M, fol-
2
But
lowed by (ii) treatment with Me
2
M to afford ½Tm ꢀMMe (Scheme
Fig. 1. ½Tm ꢀ ligands in their k3-coordination mode.
R
3). An important advantage of this method is that it does not
But
require the use of the thallium reagent ½Tm ꢀTl [27]. Thus,
possible. For example, the Schlenk equilibrium involving the
interconversion of Grignard reagents and the corresponding dialkyl
magnesium compounds provides an excellent illustration of this
type of transformation [26].
But
although ½Tm ꢀMMe may be synthesized directly via the reactions
But
of Me
2
M with ½Tm ꢀTl, the latter compound is also synthesized
But
from ½Tm ꢀNa by treatment with Tl(OAc) [27]. As such, it is evident
But
t
Bu
that the method of synthesis of ½Tm ꢀMMe from ½Tm ꢀNa
t
t
Scheme 1. Formation of ½TmBu ꢀMMe by treatment of ½TmBu ꢀ2M with Me
2
M (M ¼ Zn, Cd).
t
t
Scheme 2. Formation of ½TmBu ꢀ2M from MCl
(M ¼ Zn, Cd) and ½TmBu ꢀNa.
2
t
t
Scheme 3. Synthesis of ½TmBu ꢀMMe from ½TmBu ꢀNa by sequential reaction with MCl
and Me
2
2
M (M ¼ Zn, Cd).

A. Kreider-Mueller et al. / Journal of Organometallic Chemistry 792 (2015) 177e183
179
t
Fig. 2. van't Hoff plot for the reaction of ½TmBu ꢀZnMe with Me
2
Cd.
The above thermodynamic data indicate that there is a
But
phenomenological preference for the ½Tm ꢀ ligand to coordinate
Scheme 4. Formation of ½TpMe ꢀZnMe from ½TpMe ꢀ2Zn and Me
2
2
Zn.
2
to zinc rather than to cadmium in this system. However, this
t
Bu
observation does not, per se, mean that the Znꢂ½Tm ꢀ bond
t
Bu
dissociation energy (BDE, D) is greater than the Cdꢂ½Tm ꢀ BDE
presented in Scheme 3 is more direct and does not require the use
of a thallium reagent.
because it is also necessary to take into account the MeMe BDEs in
But
½
Tm ꢀMMe and Me
2
M.
The Schlenk-type redistribution reaction illustrated in Scheme 1
t
Specifically,
(1), where L ¼ ½Tm ꢀ:
D
H for the reaction may be expressed by Equation
Bu
is not restricted to the ½Tm ꢀ ligand, and we have also observed it
But
Me
2
to occur with the tris(pyrazolyl)hydroborato ligand, ½Tp ꢀ. Spe-
Me
2
Me
2
cifically, ½Tp ꢀ Zn [28] reacts with Me Zn to form ½Tp ꢀZnMe
2
2
h
[
28], as illustrated in Scheme 4.
DH ¼ 2DðCdꢂMeÞ
þ DðZnꢂMeÞ
Me
2
Cd
LZnMe
In addition to examining Schlenk-type equilibria involving
i
h
t
½
TmBu ꢀMMe complexes, we have also investigated alkyl exchange
þ DðZnꢂLÞLZnMe ꢂ 2DðZnꢂMeÞ
þ DðCdꢂMeÞLCdMe þ DðCdꢂLÞLCdMe
(1)
2
Me Zn
between two different metals. For example, treatment of the zinc
i
t
Bu
methyl compound, ½Tm ꢀZnMe, with Me
2
Cd results in the rapid
2
Zn. However, the reaction does
But
formation of ½Tm ꢀCdMe and Me
Alternatively,
Equation (2):
D
H may be expressed in the form shown in
not proceed to completion, but rather results in the generation of
an equilibrium mixture, which has been confirmed by examining
t
Bu
the reverse reaction between ½Tm ꢀCdMe and Me
2
Zn (Scheme 5).
But
ꢀ
ꢁ
The equilibrium constant for the reaction between ½Tm ꢀZnMe
DH ¼ DðZnꢂLÞ
ꢂ DðCdꢂLÞLCdMe
LZnMe
1
h
i
i
and Me
.0(5) ꢁ 10 at 300 K [
2
Cd, as determined by
H NMR spectroscopy, is
ꢂ2
ꢂ1
þ 2DðCdꢂMeÞ
ꢂ DðCdꢂMeÞ
7
D
G ¼ 1.6(1) kcal mol ]. Furthermore,
Me
2
Cd
LCdMe
(2)
h
measurement of the temperature dependence of the equilibrium
ꢂ 2DðZnꢂMeÞ
2
Me Zn
ꢂ DðZnꢂMeÞLZnMe
ꢂ1
constant (Fig. 2) allows determination of
and
D
H [1.82(7) kcal mol
]
D
S [0.9(3) e.u.]. The latter value is close to zero, which is to be
Bu
t
Thus,
D
H will only correspond to the difference in Znꢂ½Tm
ꢀ
expected for the entropy change associated with a redistribution
reaction of this type [29].
Bu
t
and Cdꢂ½Tm ꢀ BDEs if the combined term {[2D(CdeMe)Me Cd
e
2
D(CdeMe)LCdMe
] e [2D(ZneMe)Me Zn e D(ZneMe)LZnMe]} is
2
t
Scheme 5. ½TmBu ꢀ Ligand transfer between zinc and cadmium.

180
A. Kreider-Mueller et al. / Journal of Organometallic Chemistry 792 (2015) 177e183
t
Scheme 6. ½TmBu ꢀ Ligand transfer from mercury to zinc or cadmium.
coincidentally zero, i.e. 2[D(ZneMe)Me Zn e D(CdeMe)Me Cd] ¼
[24a], as illustrated in Scheme 7. Thus, it is evident that the ther-
modynamics of ligand exchange reactions in this system depend
strongly on the nature of co-ligands.
2
2
[
D(ZneMe)LZnMe e D(CdeMe)LCdMe].
Employing the literature values for the average MeMe BDEs of
ꢂ1
ꢂ1
Me
2
Zn (42.0 kcal mol ) and Me
2
Cd (33.3 kcal mol ) [30,31] and
ꢂ1
the experimental value of 1.8 kcal mol determined for
DH, the
But
Bu
t
difference in Znꢂ½Tm ꢀ and Cdꢂ½Tm ꢀ BDEs may be expressed in
the form shown in Equation (3), which clearly indicates how
determination of its value is linked to the difference in ZneMe and
CdeMe BDEs.
ꢀ
ꢁ
DðZnꢂLÞ
ꢂ DðCdꢂLÞLCdMe
LZnMe
ꢀ
ꢁ
¼
19:2 ꢂ DðZnꢂMeÞ
ꢂ DðCdꢂMeÞ
(3)
LZnMe
LCdMe
ꢂ1
Bu
Thus, a difference of less than 19.2 kcal mol bt etween the
ZneMe and CdeMe BDEs corresponds to a Znꢂ½Tm ꢀ interaction
t
Bu
that is stronger than the Cdꢂ½Tm ꢀ interaction, whereas a greater
t
Bu
difference corresponds to a Cdꢂ½Tm ꢀ interaction that is stronger
But
1
than the Znꢂ½Tm ꢀ interaction . For reference, we are aware of
few comparisons between ZneX and CdeX BDEs, but note that the
ꢂ1
ZneN BDE of Zn[N(SiMe
3
)
2
]
2
is 15.6 kcal mol stronger than the
corresponding CdeN bond in Cd[N(SiMe
3
)
2
]
2
[32], while the ZneC
ꢂ1
BDE of Me
2
Zn is 8.7 kcal mol stronger than the corresponding
CdeC bond in Me
2
Cd [30]. Thus, if the difference in ZneMe and
But
CdeMe BDEs of ½Tm ꢀMMe were to be of a comparable value to
t
Bu
the above ZneX and CdeX BDEs, the Znꢂ½Tm ꢀ interaction would
But
be predicted to be stronger than the Cdꢂ½Tm ꢀ interaction.
t
Bu
In addition to observing transfer of the ½Tm ꢀ ligand from
cadmium to zinc, we have also observed the analogous transfer
t
Bu
from mercury to both cadmium and zinc. Thus, ½Tm ꢀHgMe [24a]
But
reacts with Me
and ½Tm ꢀCdMe (Scheme 6).
2
Zn and Me
2
Cd to give, respectively, ½Tm ꢀZnMe
But
But
While the transfer of the ½Tm ꢀ ligand from mercury to zinc
and cadmium may seem unexpected in terms of the often discussed
thiophilicity of mercury [8e10], it is important to emphasize that,
as discussed above, the thermodynamics of the exchange reactions
require due consideration to be given to all MeX bonds. As such, a
contributing factor to the observed exchange reaction is that the
t
1
Bu
mercury methyl compound ½Tm ꢀHgMe exhibits
k -coordination
But
of the ½Tm ꢀ ligand [24a], whereas both the zinc and cadmium
3
counterparts exhibit
k -coordination.
In this regard, it is noteworthy that we have also observed
But
transfer of the ½Tm ꢀ ligand from zinc to mercury and from cad-
t
Bu
mium to mercury upon treatment of ½Tm ꢀ MðM ¼ Zn; CdÞ with
2
But
But
HgI
2
to afford ½Tm ꢀMI (M ¼ Zn [20a], Cd [23]) and ½Tm ꢀHgI
1
ꢂ1
Adopting a value of 44.5 kcal mol for the average BDE of Me
2
Zn (reference
ꢂ1
ꢂ1
Scheme 7. ½TmBu ꢀ Ligand transfer from zinc or cadmium to mercury.
t
3
1), the threshold difference is 24.2 kcal mol rather than 19.2 kcal mol
.

A. Kreider-Mueller et al. / Journal of Organometallic Chemistry 792 (2015) 177e183
181
t
Summary
In summary, a variety of ligand exchange reactions between
Reaction of ½ TmBu ꢀ2 Zn with Me
2
Zn
But
A solution of ½Tm ꢀ Zn (2.7 mg, 0.0026 mmol) in C
6
D
6
(0.7 mL)
2
zinc, cadmium and mercury centers has been investigated for
in an NMR tube equipped with a J. Young valve was treated with
Me Zn (150 L of a 0.082 M solution in C , 0.0123 mmol) The
reaction was monitored by H NMR spectroscopy, which demon-
t
Bu
compounds of the type ½Tm ꢀMXðM ¼ Zn; Cd; HgÞ. For example,
2
m
6 6
D
t
Bu
1
ligand redistribution is facile between ½Tm ꢀ M and Me
2
M to
2
But
But
afford ½Tm ꢀMMe (M ¼ Zn, Cd). Ligand exchange is also observed
strated the immediate formation of ½Tm ꢀZnMe [20a].
t
Bu
between different metal centers. Thus, ½Tm ꢀCdMe reacts with
But
t
Me
2
Zn to afford ½Tm ꢀZnMe and Me
2
Cd, while the corresponding
Reaction of ½ TmBu ꢀ2 Cd with Me
2
Cd
t
But
Bu
reaction between ½Tm ꢀHgMe and Me
2
Zn affords ½Tm ꢀZnMe
t
But
Bu
and Me
2
Hg. In contrast to the transfer of the ½Tm ꢀ ligand from
A solution of ½Tm ꢀ Cd (2.4 mg, 0.0022 mmol) in C
6 6
D (1 mL) in
2
t
Bu
mercury to zinc in the methyl system, ½Tm ꢀHgMe=Me Zn,
an NMR tube equipped with a J. Young valve was treated with
excess Me Cd (60 L of a 0.111 M solution in C , 0.0067 mmol).
2
transfer from zinc to mercury is observed upon treatment of
2
m
6 6
D
But
Bu
t
Bu
t
1
½
Tm ꢀ Zn with HgI
2
to afford ½Tm ꢀHgI and ½Tm ꢀZnI. These
The reaction was monitored by H NMR spectroscopy, which
demonstrated the immediate formation of ½Tm ꢀCdMe [23].
2
But
observations demonstrate that the phenomenological preference
But
for the ½Tm ꢀ ligand to bind mercury or zinc is strongly influenced
Reaction of ½ TpMe ꢀ2 Zn with Me
2
by the nature of the co-ligands, which is a reflection of the fact that
all metaleligand bond energies need to be considered when pre-
dicting exchange reactions of this type.
2
Zn
Me
2
A solution of ½Tp ꢀ Zn (4 mg, 0.006 mmol) in C
6
D
6
(1 mL) in an
2
NMR tube equipped with a J. Young valve was treated with excess
1
Me
which demonstrated the immediate formation of ½Tp ꢀZnMe [28].
The sample was lyophilized to remove solvent and excess Me Zn
2
Zn. The reaction was monitored by H NMR spectroscopy,
Me
2
Experimental section
2
General considerations
and the residue was dissolved in benzene. The solution was allowed
to crystallize by slow evaporation at room temperature to afford
½Tp ꢀZnMe as a white solid (3.2 mg, yield 71%).
Me
2
All manipulations were performed using a combination of glo-
vebox, high-vacuum, and Schlenk techniques under a nitrogen or
argon atmosphere [33], except where otherwise stated. Solvents
were purified and degassed by standard procedures. NMR solvents
were purchased from Cambridge Isotope Labs and stored over 3 Å
molecular sieves. NMR spectra were measured on Bruker 300 DPX,
Bruker 400 Avance III, Bruker 400 Cyber-enabled Avance III, and
Bruker 500 DMX spectrometers. H NMR chemical shifts are re-
ported in ppm relative to SiMe
internally with respect to the protio solvent impurity (
t
Reaction of ½ TmBu ꢀZnMe with Me Cd
2
But
(a) A solution of ½Tm ꢀZnMe (5.8 mg, 0.0104 mmol) in C D
6 6
(0.7 mL) in an NMR tube equipped with a J. Young valve was
treated with Me Cd (50
2
6 6
mL of a 0.111 M solution in C D ,
1
1
0.0056 mmol). The reaction was monitored by H NMR spectros-
copy, which demonstrated the immediate formation of an equi-
4
(
d
¼ 0) and were referenced
But
d
¼ 7.16 for
librium mixture with ½Tm ꢀCdMe [23] and Me Zn.
2
But
C
6
D
6
, 2.08 for C
7
D
8
, and 1.94 for CD
3
CN) [34]. Me
2
Cd and Me
2
Zn
(b) A solution of ½Tm ꢀZnMe (3.8 mg, 0.0068 mmol) in C D
7
8
t
t
Bu
2
Bu
were obtained from Strem, while ½Tm ꢀNa [17] , ½Tm ꢀ Zn [22],
(1 mL) in an NMR tube equipped with a J. Young valve was treated
2
But
Me
Bu
t
2
½
Tm ꢀ Cd [23], ½Tp ꢀ Zn [28] and ½Tm ꢀHgMe [24a] were pre-
2 6 6
with Me Cd (50 mL of a 0.111 M solution in C D , 0.0056 mmol).
2
2
1
pared by literature methods. CAUTION: Mercury and cadmium
compounds are toxic, and appropriate safety precautions must be
taken in handling these compounds.
The reaction was monitored by H NMR spectroscopy, which
demonstrated the immediate formation of an equilibrium mixture
But
with ½Tm ꢀCdMe [23] and Me Zn. The equilibrium constant was
2
measured as a function of temperature, thereby allowing deter-
mination of
D
H and DS.
t
But
Formation of ½ TmBu ꢀ2 Zn upon treatment of ½ Tm ꢀNa with ZnCl
2
t
Reaction of ½ TmBu ꢀCdMe with Me
Zn
2
But
A mixture of ½Tm ꢀNa (31 mg, 0.0619 mmol) and ZnCl
2
(4.0 mg,
0
.0293 mmol) in C
6
D
6
(1.5 mL) in an NMR tube equipped with a J.
2 6 6
A solution of Me Zn (1 mL of a 0.0143 M solution in C D ,
ꢃ
1
Young valve was heated at 80 C for 20 h and monitored by H NMR
spectroscopy, thereby demonstrating the formation of, inter alia,
0.0143 mmol) was added to an NMR tube equipped with a J. Young
But
valve that contained ½Tm ꢀCdMe (6.1 mg, 0.0101 mmol). The re-
But
1
½
Tm ꢀ2Zn.
action was monitored by H NMR spectroscopy, which demon-
But
strated the immediate formation of ½Tm ꢀZnMe [20a] and Me
2
Cd.
t
t
Formation of ½ TmBu ꢀ2 Cd upon treatment of ½ TmBu ꢀNa with CdCl
Reaction of ½ TmButꢀHgMe with Me Zn
2
2
But
But
A mixture of ½Tm ꢀNa (19 mg, 0.0380 mmol) and CdCl
2
(3.3 mg,
A solution of ½Tm ꢀHgMe (2.4 mg, 0.0035 mmol) in C
6 6
D
0
.0180 mmol) in C
6
D
6
(1.5 mL) in an NMR tube equipped with a J.
(
0.7 mL) in an NMR tube equipped with a J. Young valve was treated
with Me Zn (100 L of a 0.082 M solution in C , 0.0082 mmol).
The reaction was monitored by H NMR spectroscopy, which
demonstrated the immediate formation of ½Tm ꢀZnMe [20a] and
ꢃ
1
Young valve was heated at 80 C for 20 h and monitored by H NMR
spectroscopy, thereby demonstrating the formation of, inter alia,
2
m
6 6
D
1
But
But
½
Tm ꢀ2Cd.
2
Me Hg.
2
TmBu ꢀNa may be obtained in both solvated and non-solvated forms (see
t
Reaction of ½ TmButꢀHgMe with Me
½
2
Cd
reference 17). The non-solvated form was used herein. The molecular structure of
But
non-solvated ½Tm ꢀNa has not been determined by X-ray diffraction and the
But
3
A solution of ½Tm ꢀHgMe (2.7 mg, 0.0039 mmol) in C
6 6
D
monomeric
to be illustrative.
k
-coordination geometry shown in Schemes 2 and 3 is only intended
(0.7 mL) in an NMR tube equipped with a J. Young valve was treated

182
A. Kreider-Mueller et al. / Journal of Organometallic Chemistry 792 (2015) 177e183
with Me
2
Cd (85
m
L of a 0.111 M solution in C
6
D
6
, 0.0094 mmol). The
References
1
reaction was monitored by H NMR spectroscopy, which demon-
t
strated the immediate formation of ½TmBu ꢀCdMe [23] and Me
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2
Hg.
Metal-Carbon Bond, John Wiley & Sons, 1982.
[
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b) P.D. Hustad, R.L. Kuhlman, D.J. Arriola, E.M. Carnahan, T.T. Wenzel, Mac-
t
Reaction of ½ TmBu ꢀ2 Zn with HgI
2
7
(
But
A solution of ½Tm ꢀ Zn (1.5 mg, 0.0015 mmol) in CD
3
CN (1 mL)
2
3
(
2
was added to HgI (0.7 mg, 0.0015 mmol) and the solution was
transferred to an NMR tube equipped with a J. Young valve. The
reaction was monitored by H NMR spectroscopy, which demon-
romolecules 40 (2007) 7061e7064;
(c) T.T. Wenzel, D.J. Arriola, E.M. Carnahan, P.D. Hustad, R.L. Kuhlman, Top.
Organomet. Chem. 26 (2009) 65e104.
1
But
strated the immediate formation of a 1:1 mixture of ½Tm ꢀHgI
But
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[24a] and ½Tm ꢀZnI [20a].
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t
Reaction of ½ TmBu ꢀ2 Cd with HgI
2
[7] C.B. Murray, D.J. Norris, M.G. Bawendi, J. Am. Chem. Soc. 115 (1993)
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8
But
A solution of ½Tm ꢀ Cd (4.4 mg, 0.0041 mmol) in CD
3
CN (1 mL)
2
(
(
b) J. Mutter, J. Naumann, C. Guethlin, Crit. Rev. Toxicol. 37 (2007) 537e549;
c) J.G. Dorea, M. Farina, J.B.T. Rocha, J. Appl. Toxicol. 33 (2013) 700e711;
2
was added to HgI (1.8 mg, 0.0040 mmol) and the solution was
transferred to an NMR tube equipped with a J. Young valve. The
(d) T. Syversen, P. Kaur, J. Trace Elem. Med. Biol. 26 (2012) 215e226.
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1
reaction was monitored by H NMR spectroscopy, which demon-
But
strated the immediate formation of a ca. 1:1 mixture of ½Tm ꢀHgI
(
b) G. Guzzi, C.A.M. La Porta, Toxicology 244 (2008) 1e12.
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But
[
24a] and ½Tm ꢀCdI [23].
1
(
t
Synthesis of ½ TmBu ꢀCdMe
[12] (a) S.J. Lippard, J.M. Berg, Principles of Bioinorganic Chemistry, University
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t
(b) J.J.R. Fraústo da Silva, R.J.P. Williams, The Biological Chemistry of the El-
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3
1
0 mL) was treated with CdCl
25 C with stirring in a pressure vessel for 19 h. After this period,
the reaction mixture was allowed to cool to room temperature,
thereby depositing a white precipitate. Me Cd (120 L, 1.67 mmol)
was added and the mixture was stirred at room temperature for 1 h
2
(193.5 mg, 1.06 mmol) and heated at
ꢃ
(e) G. Roesijadi, Cell. Mol. Biol. 46 (2000) 393e405.
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and filtered. The white precipitate was extracted with benzene (ca.
2
ꢁ 5 mL), and the extracts were combined with the filtrate from
(
2
the reaction. A white precipitate started to form and was redis-
solved by addition of benzene (ca. 10 mL). The solution was trans-
ferred to a Schlenk flask and the volatile components removed in
[
14] (a) M.D. Spicer, J. Reglinski, Eur. J. Inorg. Chem. (2009) 1553e1574;
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But
vacuo to yield ½Tm ꢀCdMe as a white solid (984 mg, 77%) which
1
was identified by H NMR spectroscopy [23].
[
[
15] (a) G. Parkin, New J. Chem. 31 (2007) 1996e2014;
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t
(c) G. Parkin, Chem. Commun. (2000) 1971e1985.
Synthesis of ½ TmBu ꢀZnMe
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(
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0852e10865.
A suspension of ½TmBut ꢀNa (384.5 mg, 0.768 mmol) in benzene
5
(
(
2
ca. 10 mL) was treated with ZnCl (51.2 mg, 0.376 mmol) and
stirred vigorously at room temperature for 2 days, resulting in the
formation of thick white suspension. Me Zn (157.8 mg,
.65 mmol) was added and the mixture was stirred at room tem-
1
a
2
[
18] R. Rajesekharan-Nair, S.T. Lutta, A.R. Kennedy, J. Reglinski, M.D. Spicer, Acta
1
Cryst. C70 (2014) 421e427.
perature for 1 day. After this period, the reaction mixture was
centrifuged and the mother liquor was filtered. The solid isolated
from the centrifugation was extracted with benzene (8 mL) and the
extract was combined with the above filtrate. The volatile compo-
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11481e11503;
t
Bu
nents were removed in vacuo to yield ½Tm ꢀZnMe as a white solid
(d) M.L.H. Green, G. Parkin, J. Chem. Educ. 91 (2014) 807e816.
1
[20] (a) J.G. Melnick, A. Docrat, G. Parkin, Chem. Commun. (2004) 2870e2871;
(
[
235.0 mg, 56%), which was identified by H NMR spectroscopy
20a].
(
b) J.G. Melnick, G. Zhu, D. Buccella, G. Parkin, J. Inorg. Biochem. 100 (2006)
147e1154.
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987e2991.
[22] M. Tesmer, M. Shu, H. Vahrenkamp, Inorg. Chem. 40 (2001) 4022e4029.
1
[
2
Acknowledgments
[
[
23] J.G. Melnick, G. Parkin, Dalton Trans. (2006) 4207e4210.
24] (a) J.G. Melnick, G. Parkin, Science 317 (2007) 225e227;
Research reported in this publication was supported by the
National Institute of General Medical Sciences of the National In-
stitutes of Health under Award Number R01GM046502 (GP) and
the Department of Energy under Grant No. DEeSC0006410 (JSO).
The content is solely the responsibility of the authors and does not
necessarily represent the official views of the National Institutes of
Health.
(b) J.G. Melnick, K. Yurkerwich, G. Parkin, Inorg. Chem. 48 (2009) 6763e6772;
(c) J.G. Melnick, K. Yurkerwich, G. Parkin, J. Am. Chem. Soc. 132 (2010)
647e655.
R
[
25] (a) For other recent examples of {[Tm ]M} (M ¼ Zn, Cd, Hg) complexes, see
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1
3874e13882;
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(

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1
(
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2
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[
1
(
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(
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[
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31] For consistency, we are using BDE values for Me
2 2
Zn and Me Cd from the same
source (reference 30), but we note that a slightly larger BDE has been recently