Synthesis, structure, and reactivity of two-coordinate mercury alkyl compounds with sulfur ligands: Relevance to mercury detoxification

Article abstract of DOI:10.1021/ic900721g

The susceptibility of two-coordinate mercury alkyl compounds of the type X - Hg - R (where X is a monodentate sulfur donor) towards protolytic cleavage has been investigated as part of ongoing efforts to obtain information relevant to understanding the me

Full text of DOI:10.1021/ic900721g

Inorg. Chem. 2009, 48, 6763–6772 6763
DOI: 10.1021/ic900721g
Synthesis, Structure, and Reactivity of Two-Coordinate Mercury Alkyl Compounds
with Sulfur Ligands: Relevance to Mercury Detoxification
Jonathan G. Melnick, Kevin Yurkerwich, and Gerard Parkin*
Department of Chemistry, Columbia University, New York, New York 10027
Received April 14, 2009
The susceptibility of two-coordinate mercury alkyl compounds of the type X-Hg-R (where X is a monodentate sulfur
donor) towards protolytic cleavage has been investigated as part of ongoing efforts to obtain information relevant
to understanding the mechanism of action of the organomercurial lyase, MerB. Specifically, the reactivity of the
t
t
t
two-coordinate mercury alkyl compounds PhSHgR, [mimBu ]HgR and {[HmimBu ]HgR}þ (HmimBu = 2-mercapto-
1-t-butylimidazole; R = Me, Et) towards PhSH was investigated, thereby demonstrating that the ability to cleave the
Hg-C bond is very dependent on the nature of the system. For example, whereas the reaction of PhSHgMe with
PhSH requires heating at 145 °C for several weeks to liberate CH4, the analogous reaction of PhSHgEt with PhSH
leads to evolution of C2H6 over the course of 2 days at 100 °C. Furthermore, protolytic cleavage of the Hg-C bond by
t
t
PhSH is promoted by HmimBu . For example, whereas the reaction of {[HmimBu ]HgEt}þ with PhSH eliminates C2H6 at
elevated temperatures, the protolytic cleavage occurs over a period of 2 days at room temperature in the presence of
t
t
HmimBu . The ability of HmimBu to promote the protolytic cleavage is interpreted in terms of the formation of a higher
t
coordinate species {[HmimBu ]nHgR}þ that is more susceptible to Hg-C bond cleavage than is two-coordinate
t
{[HmimBu ]HgR}þ. These observations support the notion that access to a species with a coordination number greater
than two is essential for efficient activity of MerB.
Introduction
we have employed the [S3]-donor tris(2-mercapto-1-t-buty-
t
limidazolyl)hydroborato ligand, [TmBu ], to provide insight
into the mechanism of action of the enzyme.4 For example,
we demonstrated that the Hg-C bonds of the tris(2-mercap-
In view of the potent toxicity of organomercury com-
pounds,1 Nature has developed a detoxification procedure
that is achieved by the combined action of two enzymes,
namely (i) organomercurial lyase (MerB), which causes
protolytic cleavage of the otherwise inert Hg-C bond, and
(ii) mercuric ion reductase (MerA), which reduces Hg(II) to
less toxic elemental mercury, Hg(0).1,2 The active site of
MerB features cysteine ligation3 and, to emulate this aspect,
to-1-t-butylimidazolyl)hydroborato mercury alkyl com-
t
plexes [κ1-TmBu ]HgR (R= Me, Et) are readily cleaved by
a thiol (Scheme 1). The facility with which the Hg-C bonds
are cleaved under mild conditions was proposed to be
a consequence of the mercury center of two-coordinate
t
[κ1-TmBu ]HgR being able to access higher coordination
t
numbers because of the multidentate nature of the [TmBu
]
ligand.4,5 Herein, we provide further evidence that supports
this suggestion by describing the susceptibility of a series
of linear two-coordinate mercury alkyl compounds with a
common S-Hg-C coordination environment towards pro-
tolytic Hg-C bond cleavage by PhSH.6
*To whom correspondence should be addressed. E-mail: parkin@colum-
bia.edu.
(1) (a) Clarkson, T. W.; Magos, L. Crit. Rev. Toxicol. 2006, 36, 609–662.
(b) Mutter, J.; Naumann, J.; Guethlin, C. Crit. Rev. Toxicol. 2007, 37, 537–549.
(c) Clarkson, T. W. Environ. Health Perspect. Suppl. 2002, 110, 11–23. (d)
Clarkson, T. W. Crit. Rev. Clin. Lab. Sci. 1997, 34, 369–403. (e) Langford, N. J.;
Ferner, R. E. J. Human Hypertens. 1999, 13, 651–656. (f) Boening, D. W.
Chemosphere 2000, 40, 1335–1351. (g) Magos, L. Met. Ions Biol. Sys. 1997, 34,
321–370. (h) Hutchison, A. R.; Atwood, D. A. J. Chem. Crystallogr. 2003, 33,
631–645. (i) Alessio, L.; Campagna, M.; Lucchini, R. Am. J. Ind. Med. 2007, 50,
779–787. (j) Clarkson, T. W.; Vyas, J. B.; Ballatorl, N. Am. J. Ind. Med. 2007, 50,
757–764. (k) Risher, J. F.; De Rosa, C. T. J. Environ. Health 2007, 70, 9–16. (l)
Onyido, I.; Norris, A. R.; Buncel, E. Chem. Rev. 2004, 104, 5911–5929. (m)
Ozuah, P. O. Curr. Probl. Pediatr. 2000, 30, 91–99.
Results and Discussion
X-ray diffraction studies on [κ1-TmBu ]HgR indicate that
t
But
only one of the sulfur donors of the [Tm ] ligand coordinates
to the mercury in the solid state, such that the metal adopts a
(2) (a) Moore, M. J.; Distefano, M. D.; Zydowsky, L. D.; Cummings, R.
T.; Walsh, C. T. Acc. Chem. Res. 1990, 23, 301–308. (b) Walsh, C. T.;
Distefano, M. D.; Moore, M. J.; Shewchuk, L. M.; Verdine, G. L. FASEB J.
1988, 2, 124–130.
(3) Lafrance-Vanasse, J.; Lefebvre, M.; Di Lello, P.; Sygusch, J.; Omi-
chinski, J. G. J. Biol. Chem. 2009, 284, 938–944.
(4) Melnick, J. G.; Parkin, G. Science 2007, 317, 225–227.
(5) (a) Stradeit, H. Angew. Chem., Int. Ed. Engl. 2007, 46, 2–5. (b) Miller, S.
M. Nat. Chem. Biol. 2007, 3, 537–536. (c) Omichinski, J. G. Science 2007, 317,
205–206.
(6) Some of this research has been previously communicated. See refer-
ence 4.
r
2009 American Chemical Society
Published on Web 06/23/2009
pubs.acs.org/IC

6764 Inorganic Chemistry, Vol. 48, No. 14, 2009
Melnick et al.
Scheme 1
Scheme 2
rapidly by PhSH at room temperature,4 the phenylthiolate
complexes PhSHgR are inert under these conditions. At
elevated temperatures, however, PhSH cleaves the Hg-C
bond of PhSHgR (R = Me, Et) to give (PhS)2Hg11 and
t
RH (Scheme 2).12 The greater reactivity of [κ1-TmBu ]HgR
towards PhSH is, therefore, consistent with the notion that
cleavage of the Hg-C bond is promoted by access to species
with coordination numbers greater than two.
While the Hg-C bonds of both PhSHgMe and
PhSHgEt are cleaved by PhSH, the facility of these
reactions differ considerably, with the Hg-Et bond
being considerably more susceptible to cleavage than
that of the Hg-Me bond. For example, whereas PhSH
protolytically cleaves the Hg-Et bond of PhSHgEt
over a period of 2 days at 100 °C, the corresponding
reaction of PhSHgMe proceeds only slowly at tempera-
tures of about 145 °C. The greater reactivity of the
Hg-Et bond relative to the Hg-Me bond in this system
is noteworthy because protonolysis of RHgI by HClO4
and H2SO4 exhibits the opposite trend, with the reac-
tivity decreasing in the sequence Me>Et>Pri>But.13
On the other hand, the ease of cleaving the Hg-R bond
of a series of asymmetric dialkyl mercury compounds,
RHgR0, by AcOH decreases in the irregular sequence
Et > Pri > Me > But (for a common spectrator R0
group).14 The observation that the preference for cleav-
ing Hg-Me and Hg-Et bonds in RHgX molecules may
be switched by varying X and/or the acid is particularly
noteworthy, and it is evident that a detailed under-
standing of these effects is of considerable relevance to
linear two-coordinate S-Hg-C coordination geometry.4 In
view of the observation that two-coordinate mercury alkyl
compounds of the type X-Hg-R are generally inert towards
protolytic cleavage of the Hg-C bond,7,8 the high reactivity
t
of [κ1-TmBu ]HgR towards PhSH (as a simple mimic for a
cysteine S-H group) was attributed to the ability of mercury
to access non-linear κ2- or κ3-isomers in which the Hg-C
1
bond is more susceptible to cleavage.4 In this regard, H
t
NMR spectroscopic studies demonstrate that [κ1-TmBu ]HgR
is fluxional and that higher coordination numbers are acces-
sible.4 To provide further evidence for the proposal that
increased coordination number facilitates protolytic cleavage
of Hg-C bonds, it was deemed appropriate to probe the
reactivity of well-defined two-coordinate X-Hg-R com-
plexes in which X is a strictly monodentate sulfur donor.
Therefore, we report here the reactivity of a series of two-
coordinate mercury alkyl compounds, namely, PhSHgR,
mercury detoxification.
t
Reactivity of [mimBu ]HgR towards PhSH. While com-
t
parison of the reactivity of [κ1-TmBu ]HgR and PhSHgR
provides evidence that the additional sulfur donors of the
t
[TmBu ] ligand are responsible for facilitating cleavage of
the Hg-C bond, a better comparison is to evaluate the
t
t
t
t
[mimBu ]HgR, and {[HmimBu ]HgR}þ (HmimBu =2-mercap-
to-1-t-butylimidazole), towards PhSH.
reactivity of [κ1-TmBu ]HgR relative to a two-coordinate
mercury alkyl complex that features a monodentate sulfur
t
ligand that more closely resembles the [κ1-TmBu ] ligand
than does phenylthiolate. Therefore, we sought mercury
alkyl compounds that incorporate the 2-mercapto-1-t-
Reactivity of PhSHgR towards PhSH. As part of an
investigation of thimerosal (sodium ethylmercury thiosali-
cylate), we have recently demonstrated that the phenylthio-
late mercury alkyl complexes, PhSHgMe and PhSHgEt,
possess two-coordinate linear geometries at mercury.9,10 As
such, these complexes provide suitable reference points to
evaluate the reactivity of the Hg-C bond in organomercury
compounds with a two-coordinate linear S-Hg-C coordi-
t
butylimidazolyl ligand, namely, [mimBu ]HgR (R = Me,
Et), which may be hypothetically regarded as being deri-
t
ved from [κ1-TmBu ]HgR by dissociation of the neutral
t
borane, HB(mimBu
conveniently obtained via the reaction of RHgCl with
) (Scheme 3). Such complexes are
2
t
HmimBu in aqueous NaOH solution (Scheme 4).15 The
nation geometry. Significantly, despite the similar coordina-
t
tion geometries (Table 1), [κ1-TmBu ]HgR and PhSHgR
(R =Me, Et) react very differently towards PhSH. Thus,
(11) (PhS)2Hg has been previously reported. See, for example, (a) Carl-
ton, L.; White, D. Polyhedron 1990, 9, 2717–2720. (b) Canty, A. J.; Kishimoto,
R. Inorg. Chim. Acta 1977, 24, 109–122.
t
whereas the Hg-C bonds of [κ1-TmBu ]HgR are cleaved
(12) PhSHgMe has been synthesized by reaction of MeHgCl with PhSH,
but subsequent elimination of methane was not observed; however, the
conditions employed were not reported. In contrast, PhSHgPh has been
reported to react with PhSH to give (PhS)2Hg and PhH. See: Cross, R. J.;
Jenkins, C. M. Environ. Pollut. 1975, 8, 179–184.
(13) Kreevoy, M. M.; Hansen, R. L. J. Am. Chem. Soc. 1961, 83, 626–630.
(14) Nugent, W. A.; Kochi, J. K. J. Am. Chem. Soc. 1976, 98, 5979–5988.
(15) The related methimazole complex (mimMe)HgMe has been reported.
(7) (a) Kreevoy, M. M. J. Am. Chem. Soc. 1957, 79, 5927–5930.
(b) Kreevoy, M. M.; Hansen, R. L. J. Am. Chem. Soc. 1961, 83, 626–630.
(8) Barone, V.; Bencini, A.; Totti, F.; Uytterhoeven, M. G. Organome-
tallics 1996, 15, 1465–1469.
(9) Melnick, J. G.; Yurkerwich, K.; Buccella, D.; Sattler, W.; Parkin, G.
Inorg. Chem. 2008, 47, 6421–6426.
(10) For simplicity, this description does not take into account the longer
ꢀ
ꢀ
distance secondary Hg S interactions that are often observed in mercury
compounds.
See: Norris, A. R.; Taylor, S. E.; Buncel, E.; Belanger-Gariepy, F.;
3 3 3
Beauchamp, A. L. Can. J. Chem. 1983, 61, 1536–1541.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6765
Scheme 3
t
Figure 1. Molecular structure of [mimBu ]HgEt.
Scheme 4
t
molecular structure of [mimBu ]HgEt has been determined
by X-ray diffraction (Figure 1), and the coordination geo-
t
metry at mercury is comparable to that of [κ1-TmBu ]HgEt
(Table 1).
In contrast to the phenylthiolate derivatives, the
t
2-mercapto-1-t-butylimidazolyl complexes [mimBu ]HgR
react rapidly with PhSH at room temperature. How-
ever, instead of cleaving the Hg-C bond, PhSH cleaves
the Hg-S bond to give PhSHgR (Scheme 4). The
different reaction pathway is most likely a consequence
of the presence of the sp2 nitrogen lone pair on the
t
[mimBu ] ligand, protonation of which provides an
alternative mechanism than one involving direct reac-
tion with the Hg-C bond (Scheme 4). Supporting this
t
suggestion, the proposed {[HmimBu ]HgR}þ (R = Me,
Et) intermediates may be synthesized independently via
t
addition of HmimBu to [RHg][BF4],16 as illustrated in
Scheme 5. The molecular structure of the ethyl deriva-
NaSPh generates PhSHgR (Scheme 5), thereby providing
evidence for the second step of the proposed mechanism for
t
tive {[HmimBu ]HgEt}[BF4] has been determined by
t
the reaction of [mimBu ]HgR with PhSH (Scheme 4).
X-ray diffraction (Figure 2) and the Hg-S and Hg-C
bond lengths are similar to those of the neutral counter-
t
Reactivity of {[HmimBu ]HgEt}[BF4] towards PhSH. Since
t
t
the HmimBu ligand of {[HmimBu ]HgR}þ is not susceptible
t
part, [mimBu ]HgEt (Table 1).
t
to protonation, {[HmimBu ]HgR}þ cannot react with
t
With respect to the reactivity of {[HmimBu ]HgR}[BF4],
t
PhSH in a manner analogous to that of [mimBu ]HgR, and
t
it is significant that treatment of {[HmimBu ]HgR}[BF4]with
the site of reactivity switches from the Hg-S bond to the
t
Hg-C bond. Thus, treatment of {[HmimBu ]HgEt}þ with
PhSH results in elimination of C2H6 (Scheme 6). The initial
(16) Brower, K. R.; Gay, B.; Konkol, T. L. J. Am. Chem. Soc. 1966, 88,
1681–1685.

6766 Inorganic Chemistry, Vol. 48, No. 14, 2009
Melnick et al.
Table 1. Mercury Coordination Environments in Two-Coordinate Mercury Alkyl Complexes with Sulfur Donors
˚
˚
Hg-C/A
Hg-S/A
S-Hg-C/deg
reference
t
[κ1-TmBu ]HgCH3
2.073(7)
2.093(3)
2.068(6)
2.07(1)
2.092(5)
2.088(3)
2.085(3)
2.396(2)
2.405(1)
2.383(2)
2.369(2)
2.377(1)
2.4098(7)
2.3874(7)
176.1(3)
176.5(1)
176.6(2)
178.1(3)
171.8(1)
174.41(8)
176.80(9)
4
4
9
9
t
[κ1-TmBu ]HgCH2CH3
PhSHgCH3
PhSHgCH2CH3
t
[mimBu ]HgCH2CH3
this work
this work
t
{[HmimBu ]HgCH2CH3}[BF4]
Scheme 5
t
Figure 2. Molecular structure of {[HmimBu ]HgEt}[BF4] (only the ca-
tion is shown).
Scheme 6
t
mercury product is postulated to be {[HmimBu ]HgSPh}þ,
although this species has not been isolated because of the
existence of a subsequent exchange equilibrium that
t
results in the formation of, inter alia, {[HmimBu ]2Hg}-
[BF4]2, the molecular structure of which is shown in
Figure 3. In addition, (PhS)2Hg, the accompanying redis-
tribution product, was identified by mass spectrometry
(m/z = 421.1 {M þ 1}þ).11
t
Protolytic Cleavage of PhSHgR and {[HmimBu ]HgR}þ
t
by PhSH is Promoted by HmimBu . The observation that
both neutral and cationic two-coordinate compounds,
t
i.e., PhSHgR and {[HmimBu ]HgR}þ, are less suscep-
tible to protolytic cleavage of the Hg-C bond than is
t
[TmBu ]HgR provides a strong indication that the more
t
facile cleavage reaction of [TmBu ]HgR is a consequence
of the ability of the mercury center to access a higher
coordination number, an effect which has been attributed
to an increase in the negative charge on the carbon
atom.17 Further evidence to support the proposal that
an increase in coordination number enhances protolytic
cleavage of the Hg-C bond is provided by the observa-
tion that cleavage of the Hg-C bond of both PhSHgEt
(17) Ni, B.; Kramer, J. R.; Bell, R. A.; Werstiuk, N. H. J. Phys. Chem. A
2006, 110, 9451–9458.
t
and {[HmimBu ]HgEt}[BF4] by PhSH is promoted by

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6767
Scheme 7
t
Figure 3. Molecular structure of {[HmimBu ]2Hg}[BF4]2 (only the cation
is shown).
t
addition of HmimBu . For example, a mixture of
PhSHgEt and PhSH readily eliminates ethane at
t
18,19
room temperature in the presence of HmimBu
.
t
Likewise, HmimBu promotes elimination of ethane
t
from a mixture of {[HmimBu ]HgEt}[BF4] and PhSH
t
at room temperature (Scheme 7). Since HmimBu alone
does not cleave the Hg-C bond under these condi-
t
tions,20 the ability of HmimBu to promote protolytic
cleavage may be rationalized by the generation of
higher coordinate species that are more susceptible to
Hg-C protolytic cleavage than their two-coordinate
counterparts.21 Other studies also suggest that coordi-
nation of substrates to mercury enhances the suscept-
ibility of protolytic cleavage of Hg-C bonds. For
example, I- catalyzes the protolytic cleavage of allyl
mercury iodide,22 while the nature of the buffer (i.e.,
formate, acetate, phosphate) has been shown to have
an effect on the rate of protolytic cleavage of an aryl-
mercury bond.23
t
(18) In the presence of excess PhSH and HmimBu , the mercury product
could possibly be
a
dynamic mixture of Hg(SPh)2, [Hg(SPh)3]-,
[Hg2(SPh)6]2-, and [Hg(SPh)4]2-. See: (a) Christou, G.; Folting, K.; Huff-
man, J. C. Polyhedron 1984, 3, 1247–1253. (b) Bowmaker, G. A.; Dance, I. G.;
Harris, R. K.; Henderson, W.; Laban, T.; Scudder, M. C.; Oh, S.-W. J. Chem.
Soc., Dalton Trans. 1996, 2381–2388.
t
(19) In view of the observation that coordination of HmimBu has
a significant effect on the facility of protolytically cleaving the Hg-C bond,
it is possible that protolytic cleavage in the absence of this reagent does
not occur with two-coordinate PhSHgR but occurs preferentially via
low concentration species with higher coordination numbers, such as
PhSHgR(PhSH) or [PhSHgR]2.
(20) At elevated temperatures (100 °C), a solution of PhSHgEt and
t
HmimBu eliminates ethane.
(21) The three-coordinate intermediates are represented with
a
“T-shaped”, rather than a “Y-shaped”, geometry on the basis that the
former type of structure is often observed in organomercury compounds.a,b,c
t
Indeed, this geometry is observed in [TmBu ]HgR upon consideration of the
secondary bonding interaction involving one of the mercaptoimidazole
t
Support for the proposal that HmimBu is capable of
coordinating to the mercury centers of PhSHgMe,
groups.d Furthermore, DFT geometry optimization calculations on
t
{[HmimBu ]2HgCH3}þ indicate a structure in which the S-Hg-S and S-
Hg-C angles are 89° and 157°, respectively, which are more in accord with a
“T-shaped”, rather than a “Y-shaped”, geometry. Three-coordinate mer-
cury compounds with “Y-shaped” geometries and 120° bond angles are,
nevertheless, known in situations where the three ligands contribute equally
to the bonding (e.g., [Hg(SBut)3]-).e (a) Casa, J. S.; Garcıa-Tasende, M. S.;
Sordo, J. Coord. Chem. Rev. 1999, 193-195, 283–359. (b) Holloway, C. E.;
Melník, M. J. Organomet. Chem. 1995, 495, 1–31. (c) Holloway, C. E.; Melnik,
M. Main Group Met. Chem. 1994, 17, 799–885. (d) Reference 4. (e) Wright, J.
G.; Natan, M. J.; MacDonnell, F. M.; Ralston, D. M.; O’Halloran, T. V. Prog.
Inorg. Chem. 1990, 38, 323–412.
t
PhSHgEt, and {[HmimBu ]HgMe}þ is provided by the
observation that the 1H NMR spectroscopic signals
for the mercury alkyl groups of these complexes shift
t
in the presence of HmimBu . For example, 1H NMR
spectra of PhSHgMe and PhSHgEt in the presence of
t
variable concentrations of HmimBu are illustrated in
t
Figures 4 and 5,24 thereby demonstrating that HmimBu
(22) Kreevoy, M. M.; Goon, D. J. W.; Kayser, R. A. J. Am. Chem. Soc.
1966, 88, 5529–5534.
(23) Gopinath, E.; Bruice, T. C. J. Am. Chem. Soc. 1987, 109, 7903–7905.
2
(24) Note that JHg-H (235 Hz) for PhSHgMe does not change signifi-
t
cantly in the presence of HmimBu
.

6768 Inorganic Chemistry, Vol. 48, No. 14, 2009
Melnick et al.
t
Figure 6. Molecular structure of {[HmimBu ]4Hg}[BF4]2 (only the cation
is shown).
Figure 4. 1H NMR spectra of PhSHgMe in the presence of increasing
t
amounts of HmimBu (*=mesitylene internal reference).
Figure 7. Molecular structure of [p-ButC6H4S]2Hg.
t
of HmimBu to PhSHgR. For example, the 199Hg NMR
spectroscopic signal for PhSHgMe progressively shifts
from -557 ppm25 to -540 ppm upon increasing the con-
t
centration of HmimBu . Likewise, the 199Hg NMR spectro-
scopic signal for PhSHgEt progressively shifts from -730
t
ppm25 to -680 ppm in the presence of HmimBu . O’Halloran
and co-workers have noted that 199Hg NMR chemical shifts
of mercury thiolate complexes typically become deshielded
as coordination number increases,21e and thus the observed
variation of 199Hg chemical shifts are in accord with co-
t
ordination of HmimBu to PhSHgR generating three-coor-
dinate species that are in rapid equilibrium with the two-
coordinate species in solution.
Further evidence for the existence of three-coordinate
mercury species in solution is provided by mass spectro-
t
metric studies that suggest that {[HmimBu ]2HgSPh}þ
(m/z = 623.3)} is a component of the product mixture
t
resulting from the reaction of {[HmimBu ]HgEt}[BF4] with
t
PhSH in the presence of HmimBu , although ligand redis-
t
tribution giving {[HmimBu ]4Hg}[BF4]2 and (PhS)2Hg11 is
facile (Scheme 7). Likewise, the corresponding reaction of
t
Figure 5. 1H NMR spectra of PhSHgEt in the presence of increasing
{[HmimBu ]HgEt}[BF4] with p-ButC6H4SH in the presence
t
amounts of HmimBu (*=mesitylene internal reference).
t
t
of HmimBu liberates ethane and yields {[HmimBu ]4Hg}[BF4]2
binds rapidly, and reversibly, to the mercury centers of
these two-coordinate compounds, such that the observed
chemical shifts are a weighted average of two- and three-
coordinate species.
(25) The 199Hg NMR chemical shifts for PhSHgR are within the range
observed for two-coordinate mercury thiolate compounds. See
ꢀ
references 9, 21d, and (a) Almagro, X.; Clegg, W.; Cucurull-Sanchez, L.;
In addition to 1H NMR spectroscopy, 199Hg NMR
spectroscopy also provides evidence for coordination
ꢀ
Gonzalez-Duarte, P.; Traveria, M. J. Organomet. Chem. 2001, 623, 137–148.
(b) Carlton, L.; White, D. Polyhedron 1990, 9, 2717–2720.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6769
and [p-ButC6H4S]2Hg.26 The molecular structures of
δ=-3106).30 Coupling constants are given in hertz. IR spectra
were recorded as KBr pellets on a Nicolet Avatar DTGS
spectrometer, and the data are reported in reciprocal centi-
meters. Mass spectra were obtained on a JMS-HX110/110
t
{[HmimBu ]4Hg}[BF4]2 (Figure 6) and [p-ButC6H4S]2-
Hg (Figure 7) have been detemined by X-ray diffraction.27
As expected, the Hg-S bond lengths in tetrahedral
But
Double Focusing mass spectrometer using fast atom bombard-
ment (FAB). Hmim
{[Hmim ]4Hg}2þ (2.54 A average) are substantially lon-
˚
But 31
,
PhSHgMe9 and PhSHgEt9 were ob-
ger than the corresponding values in two-coordinate
t
tained by the literature methods. HgI2 (Aldrich), MeHgCl
(Aldrich), EtHgCl (Strem), PhSH (Aldrich), PhSNa (Fluka)
and AgBF4 (Strem) were obtained commercially. Caution! All
mercury compounds are toxic and appropriate safety precautions
must be taken in handling these compounds.
{[HmimBu ]2Hg}2þ (2.35 A average). For comparison, these
˚
bond lengths are virtually identical to the mean values for
˚
˚
two-coordinate (2.34 A) and four-coordinate (2.55 A)
mercury thiolate compounds listed in the Cambridge Struc-
tural Database.28
Reactivity of PhSHgEt towards PhSH in the Presence and
t
Absence of HmimBu . (a) A solution of PhSHgEt (25 mg,
0.074 mmol) in C6D6 (0.7 mL) was treated with PhSH (20 μL)
and heated at 100 °C for a period of 2 days. The solution was
allowed to cool to room temperature, thereby depositing a white
precipitate over a period of 3 days. The mother liquor was
decanted, and the white solid was washed with pentane (2 ꢀ
1 mL) and dried in vacuo to give (PhS)2Hg as a white solid (9 mg,
29%). (PhS)2Hg was identified by comparison of the 1H NMR
spectrum of a solution in d6-DMSO with that of an authentic
Conclusions
In summary, comparison of the reactivity of the two-
t
coordinate mercury alkyl compounds [κ1-TmBu ]HgR,
t
t
PhSHgR, [mimBu ]HgR, and {[HmimBu ]HgR}þ towards
PhSH indicates that the susceptibility towards cleavage of
the Hg-C bond is very dependent on the nature of the
t
system. Thus, whereas the Hg-C bond of [κ1-TmBu ]HgR is
3
sample.11a 1H NMR (d6-DMSO) 7.06 [t, 2H, JH-H= 7 Hz
readily cleaved by PhSH at room temperature, the Hg-C
(C6H5S)2Hg], 7.15 [t, 4H, 3JH-H= 7 Hz (C6H5S)2Hg], 7.36 [d,
3JH-H= 4 Hz, 4H of (C6H5S)2Hg]; 1H NMR (C6D6) 6.85 [m, 6H
of (C6H5S)2Hg], 7.25 [m, 4H of (C6H5S)2Hg].
t
bonds of PhSHgR and {[HmimBu ]HgR}þ are inert under
t
comparable conditions. On the other hand, [mimBu ]HgR is
reactive towards PhSH at room temperature, but it is the
(b) A solution of PhSHgEt (40 mg, 0.12 mmol) in C6D6 (3 mL)
was treated with PhSH (40 μL) and mesitylene (10 μL) as an
internal standard. The resulting solution was divided equally
Hg-S bond that is preferentially cleaved to give PhSHgR.
t
Although {[HmimBu ]HgEt}þ does not react with PhSH at
t
t
room temperature, addition of HmimBu promotes cleavage
of the Hg-C bond, thereby supporting the notion that access
to geometries with a coordination number greater than two is
required for the efficient activity of MerB.
into four NMR tubes, to which three were treated with HmimBu
(2 mg, 0.013 mmol; 10 mg, 0.064 mmol; 20 mg, 0.13 mmol), and
the reactions were monitored by H NMR spectroscopy. The
1
formation of small quantities of C2H6 was observed immedi-
t
ately for all three samples which contained HmimBu , but
complete elimination required a period of several days: the
t
Experimental Section
mixture containing 2 mg of HmimBu went to completion over
a period of 12 days at room temperature, while the mixtures
General Considerations. All manipulations were performed
using a combination of glovebox and Schlenk techniques under
a nitrogen or argon atmosphere. Solvents were purified and
degassed by standard procedures. Reactions monitored by
NMR spectroscopy were prepared in an NMR tube equipped
with a J. Young valve. NMR spectra were measured on Bruker
300 DRX, Bruker 400 DRX and Bruker Avance 500 DMX
spectrometers. 1H NMR spectra are reported in ppm relative to
SiMe4 (δ = 0) and were referenced internally with respect to
the protio solvent impurity (δ 7.16 for C6D5H, and 2.50 for
d6-Me2SO).29 13C NMR spectra are reported in parts per
million relative to SiMe4 (δ=0) and were referenced internally
with respect to the solvent (δ 128.06 for C6D6).29 199Hg NMR
chemical shifts are reported relative to HgMe2 (δ = 0) but in
view of the toxicity of the latter compound, the spectra were
referenced externally with respect to HgI2 (1 M in d6-DMSO,
t
containing 10 and 20 mg of HmimBu were complete after
t
1 week. In contrast, the solution to which no HmimBu was
added proceeded to only about 50% conversion over a period of
2 weeks at room temperature, and complete elimination of C2H6
required heating for 1 day at 145 °C.
Reactivity of PhSHgMe towards PhSH in the Presence and
t
Absence of HmimBu . A solution of PhSHgMe (20 mg,
0.062 mmol) in C6D6 (1.5 mL) was treated with PhSH (20 μL)
and mesitylene (20 μL) as an internal standard. The resulting
solution was divided equally into two NMR tubes, to which one
t
was treated with HmimBu (10 mg, 0.064 mmol). The reactions
were heated at 145 °C and monitored by 1H NMR spectroscopy.
t
In the presence of HmimBu , elimination of methane was com-
t
plete after two days, whereas in the absence of HmimBu
,
elimination of methane proceeded only to about 90% comple-
tion after 3 weeks.
Comparison of the Reactivity of PhSHgMe and PhSHgEt
towards PhSH. A solution of PhSHgMe (10 mg, 0.031 mmol)
and PhSHgEt (10 mg, 0.030 mmol) in C6D6 (0.7 mL) was treated
with PhSH (20 μL) and mesitylene (20 μL) as an internal
standard. The reactions were heated at 145 °C and were
(26) The dithiolate complex [p-ButC6H4S]2Hg can also be independently
prepared via reaction of p-ButC6H4SH with HgO, a method analogous to
that for other Hg(SR)2 complexes. See: Carlton, L.; White, D. Polyhedron
1990, 9, 2717–2720.
(27) For other structurally characterized (ArS)2Hg compounds, see:
::
1
(a) Alsaadi, B. M.; Sandstrom, M. Acta Chem. Scand. 1982, A36, 509–512.
monitored by H NMR spectroscopy, thereby demonstrating
(b) Gruff, E. S.; Koch, S. A. J. Am. Chem. Soc. 1990, 112, 1245–1247.
(c) Block, E.; Brito, M.; Gernon, M.; McGowty, D.; Kang, H.; Zubieta, J. Inorg.
Chem. 1990, 29, 3172–3181. (d) Kato, M.; Kojima, K.; Okamura, T.; Yamamoto,
H.; Yamamura, T.; Ueyama, N. Inorg. Chem. 2005, 44, 4037–4044. (e) Chen, J.
X.; Zhang, W.-H.; Tang, X.-Y.; Ren, Z.-G.; Zhang, Y.; Lang, J.-P. Inorg. Chem.
2006, 45, 2568–2580. (f) Ueyama, N.; Taniuchi, K.; Okamura, T.; Nakamura, A.;
Maeda, H.; Emura, E. Inorg. Chem. 1996, 35, 1945–1951. (g) Chen, J.-X.; Zhang,
W.-H.; Tang, X.-Y.; Ren, Z.-G.; Li, H.-X.; Zhang, Y.; Lang, J. P. Inorg. Chem.
the complete formation of C2H6 after heating the solution
for 1 day. In contrast, liberation of CH4 required a period of
3 weeks.
Synthesis of [mimBu ]HgMe. A solution of HmimBu (200 mg,
1.28 mmol) in aqueous NaOH (30 mL of 75 mM) was added to a
suspension of MeHgCl (321 mg, 1.28 mmol) in water (20 mL)
t
t
ꢀ
2006, 45, 7671–7680. (h) Almagro, X.; Clegg, W.; Cucurull-Sanchez, L.;
(30) Kidd, R. G.; Goodfellow, R. J. In NMR and the Periodic Table;
Harris, R. K.; Mann, B. E., Eds.; Academic Press: New York, 1978; p 268.
(31) Cassidy, C. S.; Reinhardt, L. A.; Cleland, W. W.; Frey, P. A. J. Chem.
Soc., Perkin Trans. 1999, 2, 635–641.
ꢀ
Gonzalez-Duarte, P.; Traveria, M. J. Organomet. Chem. 2001, 623, 137–148.
(28) Manceau, A.; Nagy, K. L. Dalton Trans. 2008, 1421–1425.
(29) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997, 62,
7512–7515.

6770 Inorganic Chemistry, Vol. 48, No. 14, 2009
Melnick et al.
over 15 min resulting in the immediate formation of a white
precipitate. The suspension was stirred for 3 h, allowed to settle
for 30 min, and filtered. The precipitate was dried in vacuo to
[C(CH3)3]S}HgMe], 6.75 [d, 1H, 3JH-H= 2 Hz, H{C3N2H2[C-
(CH3)3]S}HgMe], 12.07 [br, 1H, H{C3N2H2[C(CH3)3]S}-
HgMe]. 13C{1H} NMR (C6D6) 8.9 [1C, H{C2N2H2[C(CH3)3]
CS}HgCH3], 28.6 [3C, H{C2N2H2[C(CH3)3]CS}HgMe], 58.8
[1C, H{C2N2H2[C(CH3)3]CS}HgMe], 118.4 [1C, H{C2N2H2-
[C(CH3)3]CS}HgMe], 119.8 [1C, H{C2N2H2[C(CH3)3]CS}HgMe],
147.6 (tentative) [1C, H{C2N2H2[C(CH3)3]CS}HgMe]. IR Data
(KBr pellet, cm-1): 3191 (m), 2981 (m), 2919 (m), 2736 (w), 1574 (s),
1469 (s), 1420 (m), 1374 (s), 1325 (m), 1246 (s), 1220 (s), 1139 (s),
t
give [mimBu ]HgMe as a white powder (290 mg, 61%). 1H NMR
2
(C6D6) 0.42 [s, 3H, JHg-H = 176 Hz, {C3N2H2[C(CH3)3]S}-
HgMe], 1.45 [s, 9H, {C3N2H2[C(CH3)3]S}HgMe], 6.66 [br d,
1H, 3JH-H= 2 Hz, {C3N2H2[C(CH3)3]S}HgMe], 6.92 [br d, 1H,
3JH-H= 2 Hz, {C3N2H2[C(CH3)3]S}HgMe]. 13C{1H} NMR
(C6D6) 8.6 [1C, {C2N2H2[C(CH3)3]CS}HgCH3], 29.6 [3C,
{C2N2H2[C(CH3)3]CS}HgMe], 55.8 [1C, {C2N2H2[C(CH3)3]
CS}HgMe], 117.8 [1C, {C2N2H2[C(CH3)3]CS}HgMe], 125.9
[1C, {C2N2H2[C(CH3)3]CS}HgMe], 144.4 (tentative) [1C,
{C2N2H2[C(CH3)3]CS}HgMe]. IR Data (KBr pellet, cm-1):
3172 (w), 3111 (w), 2970 (m), 2908 (m), 1679 (w), 1561 (w),
1511 (m), 1475 (w), 1468 (w), 1447 (w), 1438 (w), 1417 (s), 1404
(m), 1393 (m), 1367 (s), 1343 (vs), 1297 (m), 1251 (vs), 1230 (m),
1221 (m), 1180 (w), 1141 (w), 1123 (vs), 1043 (s), 1021 (m), 914
(w), 843 (w), 817 (w), 771 (m), 720 (s), 690 (vs), 632 (w). Mass
spectrum: m/z = 373.1 {Mþ1}þ.
1055 (s), 914 (m), 734 (m), 686 (m). Mass spectrum: m/z = 373.1
t
{M}þ (M = {[HmimBu ]HgMe}).
t
Synthesis of {[HmimBu ]HgEt}[BF4]. A mixture of EtHgCl
(500 mg, 1.89 mmol) and AgBF4 (367 mg, 1.89 mmol) was
treated with CH2Cl2 (25 mL) resulting in the immediate deposi-
tion of a white precipitate. The suspension was stirred 3 h and
t
filtered into a flask containing HmimBu (221 mg, 1.42 mmol).
The resulting solution was stirred 1 h at room temperature, and
the volatile components removed in vacuo. The residue was
extracted into C6H6 (20 mL) and filtered. The volatile compo-
t
nents were removed by lyophilization to give {[HmimBu ]HgEt}-
[BF4] as a white powder (480 mg, 72%). Crystals suitable for
X-ray diffraction were obtained by vapor diffusion of pentane
into a tetrahydrofuran (THF) solution of the compound.
1H NMR (C6D6) 1.15 [s, 9H, H{C3N2H2[C(CH3)3]S}Hg], 1.17
[m, 3H, HgCH2CH3], 1.61[m, 2H, H{C3N2H2[C(CH3)3]S}
t
t
Synthesis of [mimBu ]HgEt. A solution of [HmimBu ] (200 mg,
1.28 mmol) in aqueous NaOH (30 mL of 40 mM) was added to a
suspension of EtHgCl (339 mg, 1.28 mmol) in water (20 mL)
over 15 min resulting in the immediate formation of a white
precipitate. The suspension was stirred for 16 h, allowed to settle
for 30 min, and filtered. The precipitate was dried in vacuo to
3
t
give [mimBu ]HgEt as a white powder (263 mg, 53%). Crystals of
HgCH2CH3], 6.33 [d, 1H, JH-H= 2 Hz, H{C3N2H2[C-
(CH3)3]S}HgEt], 6.90 [d, 1H, JH-H= 2 Hz, H{C3N2H2[C-
3
t
composition [mimBu ]HgEt suitable for X-ray diffraction were
obtained from CH3CN. 1H NMR (C6D6) 1.07 [t, 3H, 3JH-H=8 Hz,
{C3N2H2[C(CH3)3]S}HgCH2CH3], 1.27 [q, 2H, JH-H = 8 Hz,
{C3N2H2[C(CH3)3]S}HgCH2CH3], 1.46 [s, 9H, {C3N2H2[C-
(CH3)3]S}HgEt], 12.27 [br, 1H, H{C3N2H2[C(CH3)3]S}HgEt].
13C{1H} NMR (C6D6) 13.8 [1C, H{C2N2H2[C(CH3)3]CS}-
HgCH2CH3], 28.5 [1C, H{C2N2H2[C(CH3)3]CS}HgCH2CH3],
59.9 [1C, H{C2N2H2[C(CH3)3]CS}HgEt], 119.7 [1C, H-
{C2N2H2[C(CH3)3]CS}HgEt], obscured by solvent [1C, H-
{C2N2H2[C(CH3)3]CS}HgEt], 145.1 [1C, H{C2N2H2[C(CH3)3]
CS}HgEt]. IR Data (KBr pellet, cm-1): 3287 (m), 3183 (m), 3158
(m), 2984 (m), 2928 (m), 2868 (m), 2742 (w), 1730 (w), 1618 (w),
1577 (s), 1480 (m), 1460 (m), 1431 (w), 1408 (w), 1373 (m), 1338
(m), 1284 (w), 1250 (m), 1222 (s), 1182 (s), 1143 (vs), 1129 (s),
1106 (vs), 1068 (vs), 1044 (vs), 958 (s), 913 (m), 818 (w), 785 (w),
3
3
(CH3)3]S}HgEt], 6.66 [br d, 1H, JH-H= 2 Hz, {C3N2H2-
[C(CH3)3]S}HgEt], 6.93 [br d, 1H, 3JH-H= 2 Hz, {C3N2H2[C-
(CH3)3]S}HgEt]. 13C{1H} NMR (C6D6) 13.8 [1C, {C2N2H2[C-
(CH3)3]CS}HgCH2CH3], 25.7 [1C, {C2N2H2[C(CH3)3]CS}
HgCH2CH3], 29.6 [3C, {C2N2H2[C(CH3)3]CS}HgEt], 55.8
[1C, {C2N2H2[C(CH3)3]CS}HgEt], 117.7 [1C, {C2N2H2[C
(CH3)3]CS}HgEt], 126.0 [1C, {C2N2H2[C(CH3)3]CS}HgEt],
144.7 [1C, {C2N2H2[C(CH3)3]CS}HgEt]. IR Data (KBr pellet,
cm-1): 3165 (w), 3103 (w), 2988 (w), 2970 (m), 2926 (w), 2864
(w), 1683 (w), 1566 (w), 1476 (w), 1445 (w), 1418 (m), 1406 (m),
1394 (m), 1368 (s), 1338 (vs), 1295 (m), 1248 (vs), 1232 (m), 1178
(m), 1141 (m), 1123 (vs), 1044 (s), 1022 (s), 966 (w), 952 (w),
913 (w), 845 (w), 800 (m), 722 (s), 692 (vs), 682 (s), 633 (w). Mass
755 (s), 696 (m). Mass spectrum: m/z = 387.1 {M}þ (M =
t
{[HmimBu ]HgEt}).
t
Reactivity of {[HmimBu ]HgMe}þ towards NaSPh. A mixture
t
of {[HmimBu ]HgMe}[BF4] (25 mg, 0.055 mmol) and NaSPh
(10 mg, 0.076 mmol) was treated with C6D6 (0.7 mL). The
reaction was monitored by using 1H NMR spectroscopy which
spectrum: m/z = 387.1 {M þ 1}þ.
t
demonstrated the formation of PhSHgMe and HmimBu within 20
min at room temperature.
t
Reactivity of [mimBu ]HgMe towards PhSH. A solution of
t
[mimBu ]HgMe (10 mg, 0.027 mmol) in C6D6 (0.7 mL) was
treated with PhSH (10 μL) and mesitylene (10 μL) as an internal
standard. The reaction was monitored by 1H NMR spectrosco-
t
Comparison of the Reactivity of {[HmimBu ]HgEt}[BF4] to-
t
wards PhSH in the Presence and Absence of HmimBu . A solution
t
of {[HmimBu ]HgEt}[BF4] (15 mg, 0.032 mmol) in C6D6
py, thereby demonstrating the formation of PhSHgMe and
t
HmimBu in quantitative yield over a period of 1.5 h.
(1.5 mL) was treated with PhSH (15 μL) mesitylene (2 μL) as
an internal standard. The solution was divided into two NMR
t
Reactivity of [mimBu ]HgEt towards PhSH. A solution of
t
tubes, to which one was treated with HmimBu (5 mg), and the
t
[mimBu ]HgEt (10 mg, 0.027 mmol) in C6D6 (0.7 mL) was treated
with PhSH (10 μL) and mesitylene (10 μL) as an internal
standard. The reaction was monitored by 1H NMR spectrosco-
two samples were monitored by 1H NMR spectroscopy. For the
t
sample that was treated with HmimBu , 1H NMR spectroscopy
demonstrated the complete loss of the mercury ethyl signal and
the formation of ethane over a period of 2 days. For the sample
py, thereby demonstrating the formation of PhSHgEt and
t
HmimBu in quantitative yield over a period of 1.5 h. Over the
period of a day, PhSHgEt reacts further with excess PhSH to
yield (PhS)2Hg (see above).
t
without added HmimBu , 1H NMR spectroscopy demonstrated
t
that {[HmimBu ]HgEt}þ was unperturbed, and there was no
formation of ethane over a period of 2 days and only small
amounts (<5%) could be detected after a period of 10 days at
room temperature. However, quantitative elimination of ethane
was achieved over a period of 10 days at 60 °C.
t
Synthesis of {[HmimBu ]HgMe}[BF4]. A mixture of MeHgCl
(750 mg, 2.99 mmol) and AgBF4 (582 mg, 2.99 mmol) was
treated with CH2Cl2 (15 mL) resulting in the immediate deposi-
tion of a white precipitate. The suspension was stirred 3 h,
t
t
Synthesis of {[HmimBu ]2Hg}[BF4]2. {[HmimBu ]HgEt}[BF4]
(15 mg, 0.032 mmol) was treated with a solution of PhSH (20 μL)
in C6D6 (0.7 mL) and heated at 60 °C for a period of 3 days.
A white precipitate was deposited upon cooling to room
temperature. The mother liquor was decanted, and the solid
allowed to settle for 30 min, and filtered into a solution
t
of [HmimBu ] (466 mg, 2.98 mmol) in CH2Cl2 (15 mL). The
resulting solution was stirred for 1 h and solvent removed
t
in vacuo to give {[HmimBu ]HgMe}[BF4] as a white powder
(680 mg, 50%). 1H NMR (C6D6) 0.48 [s, 3H, 2JHg-H = 194 Hz,
H{C3N2H2[C(CH3)3]S}HgMe], 1.24 [s, 9H, H{C3N2H2[C-
was washed with pentane (2ꢀ0.5 mL) and dried in vacuo to give
t
{[HmimBu ]2Hg}[BF4]2 as a white powder (4 mg, 37% yield).
3
(CH3)3]S}HgMe], 6.15 [d, 1H, JH-H= 2 Hz, H{C3N2H2-

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6771
Table 2. Crystal, Intensity Collection, and Refinement Data
t
t
t
t
[mimBu ]HgEt {[HmimBu ]HgEt}[BF4] {[HmimBu ]2Hg}[BF4]2 {[HmimBu ]4Hg}[BF4]2 0.25(C6H6) [p-ButC6H4S]2Hg
3
lattice
formula
monoclinic
C9H16HgN2S
384.89
monoclinic
C18H34B2F8Hg2N4S2
945.41
monoclinic
C14H24B2F8HgN4S2
686.70
P21/c
8.429(1)
12.910(1)
21.383(2)
90.00
98.8040(10)
90.00
2299.4(4)
4
125(2)
triclinic
C29.5H49.5B2F8HgN8S4
1018.72
P1
14.647(2)
17.583(2)
19.839(2)
96.814(2)
111.056(2)
113.285(2)
4172.6(8)
4
triclinic
C20H26HgS2
531.12
P1
6.128(3)
12.040(6)
13.715(7)
87.132(7)
80.368(7)
83.006(7)
989.7(8)
2
formula weight
space group
P21/c
P21/c
˚
a/A
7.0504(6)
7.4019(7)
21.629(2)
90.00
91.331(1)
90.00
1128.42(18)
4
125(2)
0.71073
2.266
13.784
17.7657(7)
10.9903(5)
15.9175(7)
90.00
114.537(1)
90.00
2827.2(2)
4
125(2)
0.71073
2.221
11.063
32.54
47848
9940
325
0.0223
0.0471
0.0357
0.0509
1.044
˚
b/A
˚
c/A
R/deg
β/deg
γ/deg
3
˚
V/A
Z
temperature (K)
125(2)
125(2)
0.71073
1.782
˚
radiation (λ, A)
0.71073
1.984
6.948
30.52
36426
0.71073
1.622
3.957
30.70
68377
25691
946
0.0439
0.0771
F (calcd.), g cm-3
μ (Mo KR), mm-1
θ max, deg.
7.984
32.60
30.710
15931
6068
no. of data collected 18521
no. of data used
no. of parameters
R1 [I > 2σ(I)]
wR2 [I > 2σ(I)]
R1 [all data]
3924
118
7028
280
209
0.0314
0.0678
0.0506
0.0678
1.026
0.0275
0.0584
0.0394
0.0625
1.018
0.0435
0.0646
0.0783
0.0731
1.010
0.0830
0.0866
1.101
wR2 [all data]
GOF
t
1H NMR (C6D6) 1.25 [s, 18 H, {HC3N2H2[C(CH3)3]S}2Hg],
5.97 [t, 2H, JH-H=2 Hz, {HC3N2H3[C(CH3)3]S}2Hg], 6.32 [t,
2H, JH-H=2 Hz, {HC3N2H2[C(CH3)3]S}2Hg], 12.11 [br, 2H,
and successive portions of HmimBu (4 ꢀ 2 mg, 0.01 mmol). The
resulting solution was monitored by 1H NMR spectroscopy, thereby
demonstrating that the chemical shift of the mercurymethyl signal is
t
t
{N-HC3N2H2[C(CH3)3]S}2Hg] (note: the chemical shifts are
a function of the concentration of HmimBu (0 mg HmimBu , δCH
=
3
t t
t
influenced by HmimBu because of exchange). The accompany-
0.081; 2 mg HmimBu , δCH =0.099; 4 mg HmimBu , δCH =0.126; 6
3 3
t t
ing redistribution product, (PhS)2Hg, was observed by 1H
NMR spectroscopic analysis of the sample prior to isolating
mg HmimBu , δCH =0.145; 8 mg HmimBu , δCH =0.172) because of
3
3
t
rapid and reversible coordination of HmimBu
.
t
{[Hmim Bu ]2Hg}[BF4]2.
(b) A solution PhSHgMe (about 50 mg, 0.15 mmol) in C6D6
t
t
(0.7 mL) was treated with successive portions of HmimBu (2 ꢀ
10 mg, 0.06 mmol). The resulting solution was monitored by
199Hg NMR spectroscopy, thereby demonstrating that the
chemical shift of the mercury signal is a function of the con-
Synthesis of {[HmimBu ]4Hg}[BF4]2. (a)
A solution of
t
{[HmimBu ]HgEt}[BF4] (15 mg, 0.032 mmol) in C6D6 (0.7 mL)
t
was treated with HmimBu (5 mg, 0.032 mmol) and PhSH
(5 μL). Over a period of several days crystals of composition
t
t
t
centration of HmimBu (0 mg HmimBu , -557 ppm; 10 mg
{[HmimBu ]4Hg}[BF4]2 suitable for X-ray diffraction were depos-
ited. The formation of (PhS)2Hg and ethane was demonstrated by
t
t
HmimBu , -542 ppm; 20 mg HmimBu , -540 ppm).
t
1H NMR spectroscopy. 1H NMR for {[HmimBu ]4Hg}[BF4]2
(C6D6): 1.47 [s, 36H, {HC3N2H2[C(CH3)3]S}4Hg], 5.95 [d, JH-H=
1H NMR Spectroscopic Evidence for Reversible Binding of
t
HmimBu to PhSHgEt. (a) PhSHgEt (7 mg, 0.02 mmol) in C6D6
2 Hz, 4H of {HC3N2H3[C(CH3)3]S}4Hg], 6.06 [d, JH-H = 2 Hz,
4H, {HC3N2H2[C(CH3)3]S}4Hg], 12.1 [br, 4H of {N-HC3N2-
H2[C(CH3)3]S}4Hg] (note: the chemical shifts are influenced by
(0.7 mL) was treated with mesitylene (10 μL) and successive
t
portions of HmimBu (4 ꢀ 2 mg, 0.01 mmol). The resulting
solution was monitored by 1H NMR spectroscopy, thereby
demonstrating that the chemical shifts of the mercury ethyl
t
HmimBu because of exchange).
t
t
(b) A solution of {[HmimBu ]HgMe}[BF4] (5 mg, 0.011 mmol)
signals are a function of the concentration of HmimBu (0 mg
t
t
t
in C6D6 (0.7 mL) was treated HmimBu (5 mg, 0.032 mmol) and
HmimBu , δCH = 0.944, δCH = 0.825; 2 mg HmimBu , δCH
=
=
2
3
2
t
PhSH (5 μL). The solution was heated at 110 °C for a period of
0.958, δCH = 0.837; 4 mg HmimBu , δCH = 0.986, δCH
3 2 3
t
t
2 weeks resulting in the formation of {[HmimBu ]4Hg}[BF4]2.
0.863; 6 mg HmimBu , δCH = 1.019, δCH = 0.8923; 8 mg
2
3
t
t
HmimBu , δCH = 1.066, δCH = 0.930).
Reactivity of {[HmimBu ]HgEt}[BF4] towards p-ButC6H4SH in
2
3
t
t
the Presence and Absence of HmimBu ]. A solution of {[HmimBu ]-
HgEt}[BF4] (12 mg, 0.03 mmol) and mesitylene (10 μL) in C6D6
(b) A solution PhSHgEt (200 mg, 0.59 mmol) in C6D6 (0.7
t
mL) was treated with successive portions of HmimBu (2 ꢀ
25 mg, 0.16 mmol). The resulting solution was monitored by
199Hg NMR spectroscopy, thereby demonstrating that the
chemical shift of the mercury signal is a function of the con-
(1.5 mL) was treated with p-ButC6H4SH (20 μL). The solution was
t
split into two NMR tubes, one of which contained HmimBu (3 mg,
t
0.02 mmol). The solution to which HmimBu was added reacted
over a period of 1 day at room temperature to eliminate ethane and
t
t
centration of HmimBu (0 mg HmimBu , -730 ppm; 25 mg
t
t
t
HmimBu , -684 ppm; 50 mg HmimBu , -680 ppm).
generate [p-ButC6H4S]2Hg and {[HmimBu ]4Hg}[BF4]2, as demon-
strated by 1H NMR spectroscopy. In contrast, in the absence of
1H NMR Spectroscopic Evidence for Reversible Binding of
t
t
t
t
additional HmimBu , elimination of ethane was very slow, with
<10% after 3 days at room temperature. The sample was heated at
60 °C, resulting in about 60% conversion over 12 days. Complete
HmimBu to {[HmimBu ]HgMe}þ. A solution of {[HmimBu ]Hg-
t
Me}[BF4] in C6D6 was titrated with a solution of HmimBu in
C6D6 and was monitored by 1H NMR spectroscopy. Evidence
for rapid reversible binding is provided by the observation that
elimination of ethane was achieved by heating at 110 °C for 3 h,
t
t
and [p-ButC6H4S]2Hg and {[HmimBu ]2Hg}2[BF4] were identified
the signals due to the [mimBu ] and alkyl groups shift, while no
t
by 1H NMR spectroscopy.
signals due to uncoordinated HmimBu are observed.
1H NMR Spectroscopic Evidence for Reversible Binding
Synthesis of [p-ButC6H4S]2Hg. HgO (1.00 g, 4.62 mmol) was
treated with a solution of p-ButC6H4SH (1.59 mL, 9.3 mmol) in
EtOH (30 mL). The resulting orange suspension turned white over
t
of HmimBu to PhSHgMe. (a) A solution PhSHgMe (7 mg,
0.02 mmol) in C6D6 (0.7 mL) was treated with mesitylene (10 μL)

6772 Inorganic Chemistry, Vol. 48, No. 14, 2009
Melnick et al.
a period of 1 h and was stirred for an additional 3 h at room
temperature. After this period, the mixture was filtered and the
precipitate was washed with EtOH (30 mL) and dried in vacuo to
give [p-ButC6H4S]2Hg as a white powder (2.30 g, 94% yield).
Crystals of composition [p-ButC6H4S]2Hg suitable for X-ray
X-ray Structure Determinations. Single crystal X-ray diffrac-
tion data were collected on either a Bruker Apex II diffract-
ometer or a Bruker P4 diffractometer equipped with a SMART
CCD detector. Crystal data, data collection, and refinement
parameters are summarized in Table 2. The structures were
solved using direct methods and standard difference map tech-
niques and were refined by full-matrix least-squares procedures
on F2 with SHELXTL (Version 6.10).32
1
diffraction were obtained from CH3CN. H NMR (C6D6) 1.15
3
[s, 18H, [p-ButC6H4S]2Hg], 6.99 [d, JH-H = 8 Hz, 4 H [p-
3
ButC6H4S]2Hg], 7.33 [d, JH-H = 8 Hz, 4 H [p-ButC6H4S]2Hg].
13C NMR (C6D6) 31.4 [6 C, [p-{(CH3)3C}C6H4S]2Hg], 34.4 [2 C [p-
{(CH3)3C}C6H4S]2Hg], 126.4 [4 C SCC4H4CBut], 131.0 [2 C
SCC4H4CBut], 133.2 [4 C SCC4H4CBut], 149.2 [2 C SCC4H4CBut].
IR Data (KBr pellet, cm-1): 3071 (w), 2961 (vs), 2901 (m), 2866
(m), 1491 (s), 1461 (m), 1396 (m), 1361 (m), 1268 (m), 1200 (w),
1119 (s), 1080 (w), 1009 (m), 829 (m), 820 (m), 807 (m), 737 (m),
722 (w). Mass spectrum: m/z = 530.6 {M }þ.
Acknowledgment. We thank the National Institutes of
Health (GM046502) for support of this research. The National
Science Foundation (CHE-0619638) is thanked for acquisition
of an X-ray diffractometer.
Supporting Information Available: Experimental details,
computational data, and crystallographic data in CIF format.
This material is available free of charge via the Internet at http://
pubs.acs.org.
(32) (a) Sheldrick, G. M. SHELXTL, An Integrated System for Solving,
Refining and Displaying Crystal Structures from Diffraction Data; University
of Gottingen: Gottingen, Germany, 1981. (b) Sheldrick, G. M. Acta Crystallogr.
2008, A64, 112–122.
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