Organomercury(II) and tellurium(II) compounds with the "pincer" ligand 2,6-[O(CH2CH2)2NCH2] 2C6H3 - Stabilization of an unusual organotellurium(ii) cationic species

Article abstract of DOI:10.1039/c1dt10414d

The reaction of RH (1) with Hg(OAc)₂, in EtOH, gave the acetate RHgOAc (2) [R = 2,6-[O(CH₂CH₂)₂NCH ₂]₂C₆H₃]. The corresponding RHgCl (3) was obtained from 2 and LiCl. The reaction of 3 with TeCl₄ (1:1 molar ratio), in anhydrous 1,4-dioxane, resulted in the transfer of the organic ligand from mercury to tellurium and the isolation of the unexpected ionic compounds [RTe]₂[Hg₂Cl₆] (4) and [RH ₃][HgCl₄] (5). The molecular structures of 1-4 and 5·H₂O were established by single-crystal X-ray diffraction. The acetate 2 and the chloride 3 are monomeric in solid state. In both mercury and tellurium organometallic compounds the organic group acts as an (N,C,N) "pincer" ligand. This coordination pattern provided stability for the rare [RTe]⁺ cation. Weak cation-anion interactions [Te...Cl 3.869(3) A] are present between [RTe]⁺ and the dinuclear anion [Hg₂Cl₆]^2- in the crystal of 4. Theoretical calculations with DFT methods were performed for models of 3 and 4. The results show that in the cation of 4 the coordination of the nitrogen atoms play an important role for the stabilization of the structure found in the crystal whereas in 3 the coordination of the nitrogen atoms to the metal centre stabilizes to a less extent the structure found in solid state. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt10414d

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Pincers and other hemilabile ligands
Guest Editors Dr Bert Klein Gebbink and Gerard van Koten
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PERSPECTIVE:
Cleavage of unreactive bonds with pincer metal complexes
Martin Albrecht and Monika M. Lindner
Dalton Trans., 2011, DOI: 10.1039/C1DT10339C
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Pincer Ru and Os complexes as efficient catalysts for racemization and deuteration of alcohols
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Mechanistic analysis of trans C–N reductive elimination from a square-planar macrocyclic aryl-
copper(III) complex
Lauren M. Huffman and Shannon S. Stahl
Dalton Trans., 2011, DOI: 10.1039/C1DT10463B
CSC-pincer versus pseudo-pincer complexes of palladium(II): a comparative study on
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Dalton Trans., 2011, DOI: 10.1039/C1DT10269A
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PAPER
Organomercury(II) and tellurium(II) compounds with the “pincer” ligand
2,6-[O(CH2CH2)2NCH2]2C6H3 – stabilization of an unusual
organotellurium(II) cationic species†
Anca Beleaga, Vilma R. Bojan, Alpar Po¨llnitz, Ciprian I. Rat¸* and Cristian Silvestru*
Received 12th March 2011, Accepted 25th May 2011
DOI: 10.1039/c1dt10414d
The reaction of RH (1) with Hg(OAc)2, in EtOH, gave the acetate RHgOAc (2) [R =
2,6-[O(CH2CH2)2NCH2]2C6H3]. The corresponding RHgCl (3) was obtained from 2 and LiCl. The
reaction of 3 with TeCl4 (1 : 1 molar ratio), in anhydrous 1,4-dioxane, resulted in the transfer of the
organic ligand from mercury to tellurium and the isolation of the unexpected ionic compounds
[RTe]2[Hg2Cl6] (4) and [RH3][HgCl4] (5). The molecular structures of 1–4 and 5·H2O were established
by single-crystal X-ray diffraction. The acetate 2 and the chloride 3 are monomeric in solid state. In
both mercury and tellurium organometallic compounds the organic group acts as an (N,C,N) “pincer”
ligand. This coordination pattern provided stability for the rare [RTe]+ cation. Weak cation–anion
+
2-
˚
interactions [Te ◊ ◊ ◊ Cl 3.869(3) A] are present between [RTe] and the dinuclear anion [Hg2Cl6] in the
crystal of 4. Theoretical calculations with DFT methods were performed for models of 3 and 4. The
results show that in the cation of 4 the coordination of the nitrogen atoms play an important role for the
stabilization of the structure found in the crystal whereas in 3 the coordination of the nitrogen atoms to
the metal centre stabilizes to a less extent the structure found in solid state.
Te6a) derivatives. The solid state molecular structure of the sulphur
and of the selenium compounds was established by single-crystal
X-ray diffraction.
Introduction
The chemistry of heavy main group organometallic com-
pounds containing (N,C,N) “pincer” ligands like 2,6-
(Me2NCH2)2C6H3,1,2 2,6-[MeN(CH2CH2)2NCH2]2C6H3,1d or 2,6-
[2¢,6¢-Me2C6H3N C(Me)]2C6H3,3 raised a considerable interest
in recent years mainly due to the capability of such ligands to
provide stability for unusual hypervalent species.4,5 Such ligands
can sterically protect the metal centre by increased coordination,
but also reduce the Lewis acidity at the metal centre through
intramolecular N→M interactions observed both in the solid
state and in solution. Various “pincer” ligands were also used
in the organoselenium and tellurium chemistry, including that
of cationic organochalcogen species.6 Of particular interest, with
respect to the ionic organotellurium(II) species reported in this
work, are the related [2,6-(Me2NCH2)2C6H3E][PF6] (E = S,6c Se,
Organomercury compounds of type R2Hg and RHgX (R =
alkyl or aryl; X = halide) have received considerable attention in
the last three decades mainly related to the search for versatile
reagents in controlled transmetallation reactions.7 Organomer-
cury(II) derivatives have been successfully used to obtain the
desired organometallic compounds of transition metals as well as
main group metals, otherwise inaccessible by classical Grignard
and/or lithiation reactions.8 Although the toxicity of mercury
compounds should always be taken into account, there are
important advantages, e.g. the possibility to prepare functionalized
organomercury derivatives and the high selectivity of the transmet-
allation reaction.9 Some cyclometallated organomercury(II) chlo-
rides containing N-donor functionalized aryl ligands were inves-
tigated in the context of their use as transmetallation reagents.10–12
Few other organomercury(II) compounds with aryl groups with
one pendant arm containing a nitrogen donor atom were re-
ported so far, i.e. [2-(R2NCH2)C6H4]2Hg (R = Me,13,14 Et15), [2-
(Me2NCH2)C6H4]HgCl,13,16 [2-{Me2NC(Me)H}C6H4]HgX (X =
Cl, Br, I),17 2-HgX-3-[Me2NC(Me)H]C10H6 (X = Cl, Br, I).18
Recently the use of [2,6-{2¢-NC5H4}2C6H3]HgCl as a transmet-
allating agent was reported.19
Facultatea de Chimie si Inginerie Chimica, Universitatea Babes-Bolyai,
RO-400028, Cluj-Napoca, Romania. E-mail: cristi@chem.ubbcluj.ro;
Fax: (+40) 264-590818; Tel: (+40) 264-593833
† Electronic supplementary information (ESI) available: X-ray crystallo-
graphic data in CIF format for 1, 2, 3, 4 and 5·H2O; figures representing
the ORTEP representations for 1 and 5·H2O; selected bond distances and
bond angles for 1 and 5·H2O; figures representing the optical isomers as
well as the supramolecular architectures in the crystals of 2, 3, 4 and 5·H2O;
selected calculated (3a, 4a, 4b and 4e) and experimental (3 and 4) bond
lengths and angles as well as the atomic coordinates for the optimized
models. CCDC reference numbers 812968 (1), 812970 (2), 812969 (3),
812967 (4) and 812966 (5·H2O). For ESI and crystallographic data in CIF
or other electronic format see DOI: 10.1039/c1dt10414d
As part of our interest on organometallic compounds with
(N,C,N) “pincer” ligands we focused on the synthesis of potential
transmetallating organomercury(II) compounds with the new
2,6-[O(CH2CH2)2NCH2]2C6H3 ligand. Herein we report on the
8830 | Dalton Trans., 2011, 40, 8830–8838
This journal is
The Royal Society of Chemistry 2011
©

synthesis of the new proligand 1,3-[O(CH2CH2)2NCH2]2C6H4
(1), the acetate [2,6-{O(CH2CH2)2NCH2}2C6H3]HgOAc (2)
and the chloride [2,6-{O(CH2CH2)2NCH2}2C6H3]HgCl (3)
as well as the unusual ionic organotellurium(II) deriva-
tive [2,6-{O(CH2CH2)2NCH2}2C6H3Te]2[Hg2Cl6] (4) and [1,3-
{O(CH2CH2)2NHCH2}2C6H4][HgCl4] (5), isolated as products of
the reaction between 3 and TeCl4.
N→Hg interactions, if present, which allows a fast combined
dynamic process (ring inversion and nitrogen inversion) of the six-
membered morpholinyl ring in the molecules of the acetate 2 and
the chloride 3. A similar behaviour was previously described for
[2-{O(CH2CH2)2NCH2}C6H4]2Se2 which contains a related one
pendant arm ligand.20 The resonance for the methylene protons of
1
the pendant arms appeared as a singlet even when the H NMR
spectrum of 3 was recorded at -60 ◦C. A similar behaviour was also
observed for [2-(Me2NCH2)C6H4]HgCl.16 This is consistent either
with the absence of intramolecular N→Hg coordination or with a
fast conformational change of the chelate five-membered HgC3N
rings [assuming a planar (N,C,N)HgX core] in solution even at
this temperature, thus y◦ielding an averaged NMR resonance. On
the other hand, at -60 C the ring protons of the N-substituted
morpholine gave a more complex spectrum consistent with a
Results and discussion
Synthesis and characterization of 1,3-[O(CH2CH2)2NCH2]2C6H4
(1) and [2,6-{O(CH2CH2)2NCH2}2C6H3]HgX [X = OAc (2), Cl
(3)]
The aromatic derivative 1 was prepared by reacting 1,3-
bis(bromomethyl)benzene with morpholine in excess, to trap the
resulted HBr. The acetate 2 was obtained by direct mercuration
of 1 with Hg(OAc)2 in ethanol, while the chloride 3 was isolated
when 2 was treated with a saturated solution of LiCl, in methanol
(Scheme 1). Compounds 1–3 were isolated in good yields as
colourless solids.
1
slower ring inversion process. The H NMR spectrum of 1, at
-60 ◦C, also shows a complex ABCD spectrum due to slow ring
inversion on the NMR timescale. A similar dynamic behaviour
was reported for a range of N-substituted morpholines.21 Since
the morpholinyl ring inversion process can also be stopped by
decreasing the temperature no conclusion concerning possible
Hg–N interactions could be drawn. The 13C NMR spectra show,
in addition to the three aliphatic singlet resonances, the expected
four singlet resonances for the four different carbons of the
aromatic ring. The presence of 199Hg satellites for the carbon of the
methylene pendant arm and for the aromatic resonances due to
the mercury–carbon coupling is consistent with the mercuration
of the aromatic ring. For 2, additional signals were observed at d
23.07 and 176.68 ppm for the methyl and carboxylic carbons of
the acetato group, respectively. For both 2 and 3 the 199Hg NMR
spectra exhibit only one singlet resonance at d -1200 ppm and
-912 ppm respectively, consistent with the presence of only one
mercury-containing species in CDCl3 solutions.
Single crystals suitable for X-ray diffraction studies were
obtained on cooling the colourless oily crude product in the case
of 1, and by slow diffusion of n-hexane into CDCl3 solutions of
2 and 3, respectively. The molecular structures of the acetate 2
and the chloride 3 are shown in Fig. 1 and 2. Selected interatomic
distances and angles for 2 and 3 are listed in Table 1 (the molecular
structure and parameters for 1 are available in the ESI†).
Scheme 1 Preparation of compounds 1–5.
The room-temperature NMR spectra of 1–3 in CDCl3 solutions
confirm the identity of the compounds. The assignment of the 1H
and 13C chemical shifts was made according to the numbering
schemes (a) and (b) for the free ligand and the organomercury(II)
derivatives, respectively (Scheme 2), and are based on 2D experi-
ments.
Scheme 2 Numbering scheme for NMR assignments.
Only one set of resonances was observed at r.t. for both the
organic proligand 1 and the corresponding organomercury(II)
derivatives 2 and 3. This suggests equivalence of the two pendant
arms. The alkyl region in the 1H NMR spectra for 2 and 3 exhibits
two multiplet resonances for H-8,11,13,16 and H-9,10,14,15
protons of the rings and a singlet for the methylene protons
of the pendant arms, as was also observed for the proligand
1. This suggests a considerable weakness of the intramolecular
Fig. 1 ORTEP representation at 30% probability and atom numbering
scheme for the (SN1,RN2) isomer in the crystal of 2. Hydrogen atoms have
been omitted for clarity.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8830–8838 | 8831
©

in [2-(Me2NCH2)C6H4]HgCl.16 The Hg–N distances in 2 and 3
are closer to those found in the di-organomercury(II) derivative
14
˚
[2-(Me2NCH2)C6H4]2Hg [2.89(1) A], and indicate the weakness
of these intramolecular N→Hg interactions, consistent with the
behaviour of these compounds in solution. A structural difference
between 2 and 3 concerns the position of the nitrogen atoms
with respect to the Hg[C(1)–C(6)] plane. In the molecule of 2 the
nitrogen atoms are placed on the same side of the Hg[C(1)–C(6)]
plane, resulting in a N(1)–Hg(1)–N(2) angle of 122.3(3)◦. For 3 the
nitrogen atoms lie on opposite sides of the Hg[C(1)–C(6)] plane
and the trans N(1)–Hg(1)–N(2) angle is opened to 145.8(1)◦.
In both compounds the primary bonds to the mercury atom ex-
hibit an arrangement close to linearity [C(1)–Hg(1)–O(3) 175.4(4)◦
in 2 and C(1)–Hg(1)–Cl(1) 175.13(17)◦ in 3]. In 2 the acetato
group acts as a monodentate ligand, being covalently attached to
the metal atom through one oxygen atom [Hg(1)–O(3) 2.105(8)
Fig. 2 ORTEP representation at 30% probability and atom numbering
scheme for the (RN1,RN2) isomer in the crystal of 3. Hydrogen atoms have
been omitted for clarity.
A, cf. the sum of the covalent radii, Rrcov(Hg, O) 2.10 A22,23].
˚
˚
However it is twisted to bring the second oxygen atom in the close
◦
˚
Table 1 Selected bond distances (A) and angles ( ) for compounds 2 and
˚
proximity of mercury [Hg(1) ◊ ◊ ◊ O(4) 2.871(9) A, cf. the sum of the
3
van der Waals radii, RrvdW (Hg, O) 2.90 A22,23]. The lengths of the
˚
Hg(1)–C(1) and Hg(1)–Cl(1) are typical for organic derivatives of
2
3
mercury.16,19
Hg(1)–C(1)
Hg(1)–O(3)
Hg(1)–N(1)
Hg(1)–N(2)
2.035(4)
2.084(5)
2.787(6)
2.858(6)
Hg(1)–C(1)
Hg(1)–Cl(1)
Hg(1)–N(1)
Hg(1)–N(2)
2.066(6)
2.3152(17)
2.840(6)
2.877(5)
The non-planarity of the condensed five-membered HgC3N
rings, with the nitrogen atom displaced out of the best plane
defined by the residual HgC3 system, induces planar chirality
(with the aromatic ring and the nitrogen atom as chiral plane
and pilot atom, respectively).24 Both compounds crystallize as
racemates, i.e. 1 : 1 mixtures of (SN1,RN2)/(RN1,SN2) isomers for 2,
and (RN1,RN2)/(SN1,SN2) isomers for 3, respectively (with respect
to the two chelate rings in a molecular unit).
The morpholinyl rings exhibit a chair conformation which
prevents further intramolecular coordination to the mercury
atom of the oxygen atom. This oxygen atom could however
be used in coordination to another metal centre thus providing
heterometallic systems. The bulkiness of the organic groups
in the pendant arms also prevents further association of the
molecules through intermolecular interactions between heavy
atoms. A closer inspection of the crystal structures of 2 and
3 revealed different supramolecular architectures built through
weak intermolecular contacts (for details, see ESI†).
C(17)–O(3)
C(17)–O(4)
1.282(10)
1.215(9)
C(1)–Hg(1)–O(3)
C(1)–Hg(1)–N(1)
C(1)–Hg(1)–N(2)
O(3)–Hg(1)–N(1)
O(3)–Hg(1)–N(2)
N(1)–Hg(1)–N(2)
175.0(2)
72.0(2)
71.0(2)
103.2(2)
113.2(2)
122.3(2)
C(1)–Hg(1)–Cl(1)
C(1)–Hg(1)–N(1)
C(1)–Hg(1)–N(2)
Cl(1)–Hg(1)–N(1)
Cl(1)–Hg(1)–N(2)
N(1)–Hg(1)–N(2)
175.13(17)
72.9(2)
72.9(2)
106.2(1)
107.9(1)
145.8(1)
O(3)–C(17)–O(4)
O(3)–C(17)–C(18)
O(4)–C(17)–C(18)
125.0(8)
114.3(8)
120.7(8)
Hg(1)–O(3)–C(17)
111.0(5)
Hg(1)–N(1)–C(7)
Hg(1)–N(1)–C(8)
Hg(1)–N(1)–C(11)
92.4(4)
115.8(5)
115.4(5)
Hg(1)–N(1)–C(7)
Hg(1)–N(1)–C(8)
Hg(1)–N(1)–C(11)
92.9(4)
116.1(4)
114.3(4)
Hg(1)–N(2)–C(12)
Hg(1)–N(2)–C(13)
Hg(1)–N(2)–C(16)
91.3(5)
118.0(4)
111.1(4)
Hg(1)–N(2)–C(12)
Hg(1)–N(2)–C(13)
Hg(1)–N(2)–C(16)
91.1(4)
112.9(4)
119.9(4)
Reaction of [2,6-{O(CH2CH2)2NCH2}2C6H3]HgCl
(3) with TeCl4
The main structural feature to be noted for the molecule
of 1 is that the pendant arms are twisted to diminish steric
stress. By contrast in both organomercury compounds, 2 and
3, the pendant arms are twisted to allow the organic group
to act as an N,C,N-ligand, i.e. the metal centre is coordinated
by both nitrogen atoms from the pendant arms resulting in
two five-membered HgC3N rings. The Hg–N distances [Hg(1)–
To investigate the potential of 3 as a transmetallating agent,
its reaction with TeCl4, in 1 : 1 molar ratio, was carried out
in anhydrous toluene and 1,4-dioxane, under argon atmosphere
(Scheme 1). The reaction solvents were chosen in order to afford
the solubility of TeCl4 used as a starting material. When toluene
was used as the reaction solvent the NMR spectrum of the
crude product indicated the presence of a complex mixture of
products which was not further investigated. By contrast, the 1H
NMR spectrum of the crude product obtained from the reaction
carried out in 1,4-dioxane, recorded in DMSO-d6, indicated the
presence of two species in ca.1 : 5 molar ratio. After working
up the reaction mixture the minor product (4) and the major
product (5) were isolated as a yellow–orange solid and a white
solid, respectively. For both compounds the 13C NMR spectra
˚
N(1)/Hg(1)–N(2) 2.857(9)/2.771(9) A in 2 and 2.840(6)/2.877(5)
˚
A in 3] are considerably shorter than the sum of the van der
Waals radii for Hg and N [RrvdW(Hg, N) 3.05 A].22,23 However they
˚
are longer than the values observed for mono-organomercury(II)
compounds containing related organic ligands with one pen-
17
˚
dant arm, e.g. 2.65(1) A in (S)-[2-{Me2NC(Me)H}C6H4]HgCl,
16
˚
˚
2.725(4) A in [2-(Me2NCH2)C6H4]HgS(S)PPh2, or 2.764(6) A
8832 | Dalton Trans., 2011, 40, 8830–8838
This journal is
The Royal Society of Chemistry 2011
©

do not exhibit resonances surrounded by mercury satellites, thus
suggesting that Hg–C bond in the starting material was broken.
For the minor product 4 the 125Te NMR spectrum in DMSO-
d6 shows one resonance at d 1525 ppm (cf. dTe 1950 ppm
for [2,6-(Me2NCH2)2C6H3Te][PF6] in CD3CN, in ref. 6a), while
in the ESI+ MS a peak for [RTe+] was observed. However,
the elemental analysis does not indicate the formation of the
desired RTeCl3 derivative or of an ionic species of the type
[RTeCl2][HgCl3]. The later might be suggested by the previously
reported [R¢R¢¢TeCl][HgCl3] species obtained by reacting R¢TeCl3
(R¢ = 4-EtOC6H4) with R¢¢HgCl [R¢¢ = 2-(2-C5H4N)C6H4,25,26 2-
(Me2NCH2)C6H4,27]. Surprisingly, the elemental analysis corre-
sponds to the formula [2,6-{O(CH2CH2)2NCH2}2C6H3]TeHgCl3,
although an 199Hg resonance could not be observed in the NMR
spectrum recorded for this compound. The RTeHgCl3 species can
be formed from RTeCl and HgCl2 during the transmetallation
IV
process. This result indicates that a reduction from Te to
II
VI
Te took place, probably with simultaneous oxidation to Te .
However the redox process cannot be explained at present time
and further investigations are envisaged. Attempts to prepare
an organotellurium(II) species by reacting RHgCl or RLi with
TeCl2(thiourea)2 failed and the resulted black material indicated
decomposition to elemental Hg and/or Te.
1
Only one set of H and 13C resonances were observed for the
Fig. 3 ORTEP representation at 30% probability and atom numbering
scheme for the (RN1,RN2) cation and the dinuclear dianion in the crystal of
4 [symmetry equivalent atoms (1 - x, -y, -z) are given by “a”].
two pendant arms of the organic ligand attached to the tellurium
atom, thus suggesting their equivalence on the NMR time scale.
However, in contrast to the starting material 3, the H spectrum
1
◦
a
˚
Table 2 Selected bond distances (A) and angles ( ) for compound 4
of 4 exhibits four multiplet resonances for the methylene protons
of the morpholinyl rings, consistent with their non-equivalence
induced by the (N,C,N) coordination pattern in solution, at room
temperature. These intramolecular N→Te interactions prevent a
fluxional behavior which would result in equivalent N-CH2-CH2
and -CH2-CH2-O protons, respectively.20 Consequently, the four
1H multiplet resonances were assigned to Hpro-trans-/Hpro-cis-8, 11,
13, 16 and Hpro-trans-/Hpro-cis-9, 10, 14, 15, respectively, with respect
to the position of the tellurium atom in relation with the rigid
morpholinyl ring (for details, see ref. 20).
Te(1)–C(1)
Te(1)–N(1)
2.074(8)
2.392(7)
Te(1)–N(2)
2.354(7)
Hg(1)–Cl(1)
Hg(1)–Cl(3)
2.373(3)
2.586(3)
Hg(1)–Cl(2)
Hg(1)–Cl(3a)
2.382(3)
2.748(3)
C(1)–Te(1)–N(1)
N(1)–Te(1)–N(2)
75.1(3)
150.4(2)
C(1)–Te(1)–N(2)
75.3(3)
Te (1)–N(1)–C(7)
Te(1)–N(1)–C(8)
Te(1)–N(1)–C(11)
104.4(5)
108.9(5)
115.2(6)
Te(1)–N(2)–C(12)
Te(1)–N(2)–C(13)
Te(1)–N(2)–C(16)
103.6(5)
111.6(6)
113.0(5)
1
The H NMR spectrum of the major product 5 suggests that
this species contains a dication resulted from the protonation of
the nitrogen atoms from both pendant arms of the proligand 1.
Moreover, the protonation prevents a fast conformational change
of the six-membered morpholinyl ring since again four multiplet
1H resonances were observed for the methylene protons. The 199Hg
NMR spectrum of 5 exhibits one resonance at d -1167 ppm, which
is indicative for a [HgCl4]2- counter-anion (cf. dHg -1152 ppm for
[HgCl4]2- in ref. 28). Therefore, compound 5 can be formulated as
an ionic species, [1,3-{O(CH2CH2)2NHCH2}2C6H4][HgCl4].
Yellow single-crystals were obtained from a solution of 4 in
acetonitrile, while slow evaporation of an acetone solution gave
colourless crystals of 5·H2O. The structures of both compounds
were established by X-ray diffraction and confirmed their ionic
nature. The cation and the anion found for 4 are depicted in Fig.
3. Selected interatomic distances and angles for 4 are listed in Table
2 (the molecular structure and parameters for 5·H2O are available
in the ESI†).
Cl(1)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–Cl(3)
Cl(1)–Hg(1)–Cl(3a)
133.02(11) Cl(2)–Hg(1)–Cl(3)
111.90(11) Cl(2)–Hg(1)–Cl(3a)
101.62(11) Cl(3)–Hg(1)–Cl(3a)
107.06(10)
105.47(9)
87.34(8)
Hg(1)–Cl(3)–Hg(1a)
92.66(8)
a Symmetry equivalent atoms (1 - x, -y, -z) are given by “a”.
(Me2NCH2)2C6H3Te][PF6] was previously reported.6a The tel-
lurium atom in 4 is strongly coordinated by both nitrogen atoms,
the (N,C,N)-pincer coordination pattern of the organic ligand
providing stability for the rare [RTe]+ cation. The nitrogen atoms
are placed on opposite sides of the Te[C(1)-C(6)] plane (as also
observed in the molecule of 3), in an almost trans arrangement
[N(1)–Te(1)–N(2) 150.4(2)◦]. The coordination geometry around
the Te atom can be described as distorted T-shaped (hypervalent
10-Te-3 species).29 The deviations of the bond angles at the
tellurium atom from the ideal values are obviously due to
the constraints imposed by the coordinated amine arms. The
The crystal of 4 contains the first structurally charac-
terized tellurenium cation [2,6-{O(CH2CH2)2NCH2}2C6H3Te]+,
with [Hg2Cl6]2- as the counter-anion. The preparation
and the spectroscopic characterization of the related [2,6-
˚
two tellurium-nitrogen bonds [Te(1)–N(1) 2.392(7) A, Te(1)–
˚
N(2) 2.354(7) A] are stronger than observed in the neutral
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The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8830–8838 | 8833
©

30
˚
[2-(Me2NCH2)C6H4]TeS(S)PPh2 [2.439(2) A]. Due to the non-
planarity of the five-membered TeC3N rings which induces planar
chirality, the crystal of 4 contains both (RN1,RN2) and (SN1,SN2
)
isomers of the [RTe]+ cation.
In the dinuclear anion the mercury atoms are asymmetrically
˚
bridged by chlorine atoms [Hg(1)–Cl(3) 2.586(3) A, Hg(1)–Cl(3a)
˚
2.748(3) A] and the terminal mercury–chlorine bonds are consid-
˚
erably shorter than the bridging ones [Hg(1)–Cl(1) 2.373(3) A,
˚
˚
˚
Hg(1)–Cl(2) 2.382(3) A]. Weak Te(1) ◊ ◊ ◊ Cl(1a) [3.869(3) A, cf.
the sum of the van der Waals radii, RrvdW (Te, Cl) 3.90 A22,23],
˚
˚
Cl(1) ◊ ◊ ◊ H(10Aa) (2.92 A) and Cl(3) ◊ ◊ ◊ H(13Ba) (2.98 A) contacts
are established between the dianion and the (RN1,RN2) and
(SN1,SN2) isomers of the [RTe]+ cation (for details, see ESI†).
The structure of 5·H2O confirms the presence of a dication
resulted from the protonation of both nitrogen atoms of a
proligand 1 molecule. A closer inspection of the crystal structure of
5·H2O revealed the formation of a supramolecular arrangement
through hydrogen bonding which involves the hydrogens of the
water and those attached to the nitrogen atoms of the cation (for
details, see ESI†).
Theoretical calculations
To understand the bonding and structure of 3 and 4, theoretical
calculations at DFT theory level were carried out on several
models of the compounds (Schemes 3 and 4). In order to have
a better approximation of the molecular structure of 4 as found
in the crystal, a model (4a) consisting of the cation [RTe]+ and the
dinuclear anion [Hg2Cl6]2- was chosen for the theoretical studies.
An argument for the use of the model 4a was the possibility to
preserve the coordination geometry of mercury in the solid state
without applying any constraints.
Scheme 4 Models of the anion [(RTe)(Hg2Cl6)]- (4a), of [RTe]+ cations
(4b–4d) and of the [Hg2Cl6]2- dianion (4e) calculated at DFT level.
bond length is only slightly overestimated (0.6%) with respect to
the experimental value.
In the theoretical model for 4a, the Te(1) ◊ ◊ ◊ Cl(1a) distance
is 16.3% shorter than the determined value. Consequently, the
Hg(1a)–Cl(1a) bond and the Cl(1a)–Hg(1a)–Cl(2a) bond angle
are also overestimated by 9.5 and 14.8%, respectively. The large
difference between the theoretical and the experimental values
is likely to emerge from the choice of the model, 4a. In the
crystal structure the attraction between a cation [RTe]+ and
the dianion [Hg2Cl6]2- is compensated by the attraction to the
symmetry generated cation [RTe]+. In the theoretical model, 4a,
where the symmetry generated cation was omitted in order to
reduce the computation time, this effect is no longer present
and causes an overestimation of the interaction between the two
charged fragments. Therefore, for a better evaluation of the cation–
dianion interaction energy a model was used (4A) where the
coordinates of the atoms except hydrogens were retained from the
crystallographic data. In 4A only the coordinates of the hydrogen
atoms were optimized.
The theoretical calculations reveal a strong interaction between
the cation and the dianion in 4. Using the model 4a, the uncor-
rected interaction energy is 123.68 kcal mol-1 (517.50 kJ mol-1).
Taking into account that the distance between the two charged
fragments is overestimated by ca. 7% (calculated considering the
distance between the tellurium atom and the weight centre of the
dianion), using the model based on the crystallographic data 4A
a slightly smaller value of 110.92 kcal mol-1 (464.12 kJ mol-1) is
obtained for the uncorrected interaction energy.
The stabilization of 3 and of the cation [RTe]+ of 4, brought by
the internal coordination of nitrogen atoms from the morpholinyl
groups, was investigated using the conformers 3b, 4c, 3c and
4d (Scheme 3 and 4). The 3b conformer is 1.39 kcal mol-1
(5.83 kJ mol-1) and 3c is 4.66 kcal mol-1 (19.51 kJ mol-1) higher
Scheme 3 Models of RHgCl (3a–3c) calculated at DFT level.
Most of the bond lengths and bond angles obtained by
theoretical calculations are in good agreement with those obtained
by X-ray diffraction on the single crystal (see ESI, Tables S3 and
S4†). In the calculated models the M–C [M = Hg (3a); Te (4a)] bond
lengths are slightly overestimated. In both theoretical models 3a
and 4a the M–N bonds are larger [3a: 3.9 and 4.6%; 4a: 3.5 and
4%] than those measured. Large differences between the calculated
and experimental structures of 3a and of the cation of 4a were also
found for the torsion angles Ci–Co–Cmethylene–N. In 3a the Hg–Cl
8834 | Dalton Trans., 2011, 40, 8830–8838
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The Royal Society of Chemistry 2011
©

in energy than 3a. In contrast, the calculations reveal that for
the stabilization of the [RTe]+ cation the coordination of the
morpholinyl groups plays an important role. Thus, conformer 4c is
20.26 kcal mol-1 (84.78 kJ mol-1) higher in energy than 4b whereas
the structure 4d is 39.22 kcal mol-1 (164.11 kJ mol-1) higher in
energy than 4b. For both compounds the stabilization energies of
3 and 4 are consistent with the NMR data which show that in
solution the pendant arms are not coordinated to the metal centre
in the first but are strongly coordinated in the later.
Lo¨wdin molecular orbitals reduced population of 4b (Fig. 4)
reveals the largest contributions to the HOMO are from the p
orbitals of the Te atom (px: 56.8%, py: 3.6%) and the LUMO
corresponds to a combination out of phase with the largest
contributions from the p orbitals of the Te atom (px: 45.1%) and
N atoms (py: 9.7% and py: 9.6%). The contributions of Te (px:
20.6%), Cipso (px: 20.8%) and Cpara (px: 20.4%) to the HOMO-5
orbital suggest that the charge is partly delocalized also on the
phenyl group of the cation. The orbital HOMO-8 corresponds to
the s bonding orbital between Te (pz: 23.6%) and Cipso (pz: 11.8%).
the six-membered morpholinyl rings. By contrast, the room-
temperature H NMR data provided evidences for the presence
1
of the intramolecular N→Te interactions in the case of the cation
in 4, the dynamic process (ring inversion and nitrogen inversion)
being frozen at this temperature. The bond lengths and bond
angles found by theoretical calculations at BP86/def2-TZVP level
of theory on 3 are close to the experimental values. At the same
theory level using models of 4 the molecular parameters are
reproduced to a less extent. For the latter a strong interaction exists
between the charged fragments. The strength of the intramolecular
N→M coordination obtained from DFT calculations for both
compounds is consistent with the spectroscopic data.
Experimental section
General procedures
Multinuclear NMR spectra were recorded on a Bruker Avance 300
instrument. The 1H chemical shifts are reported in d units (ppm)
relative to the residual peak of the deuterated solvent (ref. CDCl3:
1
1H 7.26 ppm; DMSO-d6: H 2.50 ppm). The 13C chemical shifts
are reported in d units (ppm) relative to the peak of the solvent
(ref. CDCl3: 13C 77.0 ppm; DMSO-d6: 13C 39.43 ppm). 1H and 13
C
resonances were assigned using 2D NMR experiments (COSY,
HSQC and HMBC). The 199Hg and 125Te spectra were obtained
using HgCl2 (in DMSO) and Ph2Te2 as external standards. Chem-
ical shifts are reported relative to Me2Hg and Me2Te (d 0 ppm) by
assuming that the resonance of the standard is at d -1501.6 ppm31,32
and 422 ppm,33 respectively. The NMR spectra were processed
using the MestReC and MestReNova software.34 Mass spectra
were recorded on an Agilent 6320 Ion Trap instrument. Melting
points were measured on an Electrothermal 9200 apparatus
and are not corrected. Elemental analyses were performed at
Facultatea de Farmacie, Universitatea de Medicina si Farmacie
“Iuliu Hatieganu”, Cluj-Napoca (Romania). All manipulations
were carried out under an inert atmosphere of argon using Schlenk
techniques. Solvents were dried and freshly distilled under argon
prior to use. All common reagents were obtained from Aldrich or
Merck, and were used as received.
Fig. 4 Selected molecular orbitals (isolevel 0.04 au) of the cation model
4b calculated at the BP86/def2-TZVP theory level.
In 3a, the HOMO is localized mainly on the nitrogen atoms with
the largest contributions from their py orbitals whereas the LUMO
consists of an out-of-phase combination between the px orbitals
of Cipso and Cpara and px orbital of Hg, respectively. The HOMO-10
corresponds to a s in-phase combination mainly between the Hg
(s: 20.7%) and Cl (pz: 30.0%) atomic orbitals.
Synthesis
of
1,3-[O(CH2CH2)2NCH2]2C6H4
(1). 1,3-
bis(bromomethyl)benzene (10 g, 38 mmol) and morpholine
(13.18 g, 152 mmol) were dissolved in benzene (80 mL). The
reaction mixture was refluxed for 12 h, then the white precipitate
of O(CH2CH2)2NH·HBr was filtered off and the solvent was
removed under vacuum from the clear solution. The remaining
colourless oil crystallizes on cooling to give 8.48 g (81%) of
compound 1, mp 55 ◦C. Anal. Calcd. for C16H24N2O2 (276.37):
C, 69.53; H, 8.75; N 10.14; Found: C, 69.26; H, 8.86; N 10.26%.
1H NMR (300 MHz, CDCl3, r.t.): d 2.33 (8 H, t, H-8, 11, 13, 16,
N–CH2–CH2–O, 3JHH 4.3 Hz), 3.39 (4 H, s, H-7, 12, C6H4–CH2–
Conclusions
The organomercury(II) acetate 2 and chloride 3 are the first
compounds of their classes for which the crystal structures were
established. The new 2,6-[O(CH2CH2)2NCH2]2C6H3 group acts
as an (N,C,N) “pincer” ligand in solid state. When the chloride 3
was reacted with TeCl4 in anhydrous 1,4-dioxane, transmetallation
occurred with the organic ligand being transferred from mercury
to tellurium. The unexpected ionic compound [RTe]2[Hg2Cl6]
(4) was isolated and a single-crystal X-ray diffraction study
provided evidences for the capacity of this pincer ligand to
stabilize the rare [RTe]+ cation. The solution NMR studies revealed
a different behaviour for these organometallic species. For 2
and 3 a considerable weakness of the intramolecular N→Hg
interactions, if present, allows a fast conformational change of
3
N), 3.59 (8 H, t, H-9, 10, 14, 15, N–CH2–CH2–O, JHH 4.6 Hz),
7.14 (4 H, m, H-2, 4–6, C6H4). 1H NMR (300 MHz, CDCl3, -60
◦
3
C): d 2.18 (4 H, dd, H-8, 11, 13, 16, N–CH2–CH2–O, 2JHH ª JHH
10.6 Hz), 2.69 (4 H, d, H-8, 11, 13, 16, N–CH2–CH2–O, 2JHH 11.1
Hz), 3.47 (4 H, s, H-7, 12, C6H4–CH2–N), 3.60 (4 H, dd, H-9, 10,
14, 15, N–CH2–CH2–O, 2JHH ª JHH 11.0 Hz), 3.81 (4 H, d, H-9,
3
2
10, 14, 15, N–CH2–CH2–O, JHH 10.8 Hz), 7.24 (3 H, m, H-3–5,
C6H3). 13C NMR (75.5 MHz, CDCl3, r.t.): d 53.19 (s, C-8, 11, 13,
Dalton Trans., 2011, 40, 8830–8838 | 8835
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©

3
3
16), 62.92 (s, C-7, 12), 66.50 (s, C-9, 10, 14, 15), 127.62 (s, C-4, 6),
127.74 (s, C-5), 129.52 (s, C-2), 137.28 (s, C-1, 3).
ª JH
12.7, JH
2.7 Hz), 3.13 (4 H, d, Hpro-cis
-
H
H
pro-cis pro-trans
pro-cis pro-cis
2
8, 11, 13, 16, N–CH2–CH2–O, JH
12.5 Hz), 3.65 (4
H
pro-cis pro-trans
H, dd, Hpro-trans-9, 10, 14, 15, N–CH2–CH2–O, 2JH
ª
H
pro-cis pro-trans
Synthesis of [2,6-{O(CH2CH2)2NCH2}2C6H3]HgOAc (2).
Compound 1 (2.4 g, 8.7 mmol) was added to a slurry of mercury(II)
diacetate (2.8 g, 8.8 mmol) in EtOH (125 mL). The mixture was
stirred overnight and the insoluble product◦was filtered off. The
filtrate was concentrated and stored at -20 C to give colourless
crystals of 2. Further removal of the solvent in vacuum gave a
second crop of crystals. The total amount of 2 collected was 3.5 g
(75%), mp 134–135 ◦C. Anal. Calcd. for C18H26HgN2O4 (535.00):
C, 40.41; H, 4.90; N 5.24; Found: C, 40.26; H, 4.86; N 4.96%. 1H
NMR (300 MHz, CDCl3, r.t.): d 2.08 (3 H, s, O2C–CH3), 2.52 (8
3JH
11.0 Hz), 3.93 (4 H, d, Hpro-cis-9, 10, 14, 15, N–CH2–
H
pro-cis pro-trans
CH2–O, 2JH
12.7 Hz), 4.20 (4 H, s, H-7, 12, C6H4–CH2–
H
pro-cis pro-trans
N), 7.38 (3 H, m, H-3–5, C6H3). 13C NMR (75.5 MHz, DMSO-d6):
d 56.48 (s, C-8, 11, 13, 16), 64.90 (s, C-7, 12), 65.90 (s, C-9, 10, 14,
15), 122.31 (s, C-1), 126.57 (s, C-3, 5), 128.96 (s, C-4), 137.17 (s,
C-2, 6). 125Te NMR (94.8 MHz, DMSO-d6): d 1525. MS (ESI+),
m/z (%): 404.3 (100) [RTe+].
The remaining solid was again washed with acetonitrile
(30 mL) and the solution was discarded since it contained
both species 4 and 5. Then hot acetonitrile (100 mL) was
added, the solution was separated, the solvent removed to
dryness to give a white solid which was proved to be [1,3-
{O(CH2CH2)2NHCH2}2C6H4][HgCl4] (5) (0.47 g, 81.5% with
respect to RHgCl), mp 98–99 ◦C (dec.). Anal. Calcd. for
C16H26Cl4HgN2O2 (620.80): C, 30.96; H, 4.22; N 4.51; Found: C,
30.76; H, 4.49; N 4.65%. 1H NMR (300 MHz, DMSO-d6): d 3.21
(4 H, br s, Hpro-trans-8, 11, 13, 16, N–CH2–CH2–O), 3.35 (4 H, d,
3
H, t, H-8, 11, 13, 16, N–CH2–CH2–O, JHH 4.3 Hz), 3.42 (4 H,
s, H-7, 12, C6H4–CH2–N), 3.73 (8 H, t, H-9, 10, 14, 15, N–CH2–
3
3
CH2–O, JHH 4.0 Hz), 7.04 (2 H, d, H-3, 5, C6H3, JHH 7.1 Hz),
7.13 (1 H, m, H-4, C6H3). 13C NMR (75.5 MHz, CDCl3, r.t.): d
23.07 (s, O2C–CH3), 53.02 (s, C-8, 11, 13, 16), 64.61 (s, C-7, 12,
3JHgC 115.1 Hz), 66.57 (s, C-9, 10, 14, 15), 128.37 (s, C-4, 4JHgC 23.4
Hz), 128.47 (s, C-3, 5, 3JHgC 185.2 Hz), 143.21 (s, C-2, 6, 2JHgC 72.6
1
Hz), 145.25 (s, C-1, JHgC 2655 Hz), 176.68 (s, O2C–CH3). 199Hg
Hpro-cis-8, 11, 13 ,16, N–CH2–CH2–O, 2JH
11.7 Hz), 3.68
H
pro-cis pro-trans
NMR (53.7 MHz, CDCl3, r.t.): d -1200.
2
(4 H, dd, Hpro-trans-9, 10, 14, 15, N–CH2–CH2–O, JH
ª
H
pro-cis pro-trans
3JH
11.7 Hz), 3.97 (4 H, d, Hpro-cis-9, 10, 14, 15, N–CH2–
H
pro-cis pro-trans
Synthesis of [2,6-{O(CH2CH2)2NCH2}2C6H3]HgCl (3). A so-
lution of LiCl (0.2 g, 4.7 mmol, excess ca. 40%) in MeOH (10
mL) was added to a solution of 2 (1.6 g, 3.4 mmol) in EtOH (100
mL). The solution was stirred overnight and the resulting solid
was filtrated and dried in air to give 3 as a colourless solid (1.4 g,
92%), mp 178–180 ◦C. Anal. Calcd. for C16H23ClHgN2O2 (511.40):
C, 37.58; H, 4.53; N 5.48; Found: C, 37.26; H, 4.86; N 5.16%. 1H
NMR (300 MHz, CDCl3, r.t.): d 2.53 (8 H, br s, H-8, 11, 13, 16,
N–CH2–CH2–O), 3.41 (4 H, s, H-7, 12, C6H4–CH2–N), 3.79 (8
H, t, H-9, 10, 14, 15, N–CH2–CH2–O, 3JHH 4.5 Hz), 7.07 (2 H, d,
CH2–O, 2JH
11.9 Hz), 4.45 (4 H, s, H-7, 12, C6H4–CH2–
H
pro-cis pro-trans
N), 7.65 (4 H, m, H-2, 4–6, C6H4), 10.00 (2 H, s, N–H). 13C NMR
(75.5 MHz, DMSO-d6): d 50.90 (s, C-8, 11, 13, 16), 58.84 (s, C-7,
12), 63.19 (s, C-9, 10, 14, 15), 129.39 (s, C-5), 129.49 (s, C-1, 3),
132.74 (s, C-4, 6), 134.74 (s, C-5). 199Hg NMR (53.7 MHz, CDCl3):
d -1167.
Crystal structures
Crystals of 1 were obtained on cooling the oily reaction product.
Crystals of 2 were obtained from an EtOH solution at -20 ◦C,
while crystals of 3 were grown by slow diffusion using a CHCl3-
n-hexane system (1 : 5 by volume). Yellow crystals of 4 were
obtained from a CH3CN solution. Colourless crystals of 5·H2O
were grown by slow evaporation of the solvent from an acetone
solution. The details of the crystal structure determination and
refinement are given in Table 3. The crystals were mounted with
Paratone N oil on cryoloops and the data were collected at room
temperature on a Bruker SMART APEX diffractometer, using
3
1
H-3, 5, C6H3, JHH 6.7 Hz), 7.15 (1 H, m, H-4, C6H3). H NMR
(300 MHz, CDCl3, -60 ◦C): d 2.44 (4 H, br s, H-8, 11, 13, 16,
N–CH2–CH2–O), 2.69 (4 H, d, H-8, 11, 13, 16, N–CH2–CH2–O,
2JHH 11.2 Hz), 3.43 (4 H, s, H-7, 12, C6H4–CH2–N), 3.82 (8 H, br
s, H-9, 10, 14, 15, N–CH2–CH2–O), 7.14 (3 H, m, H-3–5, C6H3).
13C NMR (75.5 MHz, CDCl3, r.t.): d 53.02 (s, C-8, 11, 13, 16),
64.59 (s, C-7, 12, 3JHgC 109.3 Hz), 66.37 (s, C-9, 10, 14, 15), 128.43
(s, C-4, 4JHgC 24 Hz), 128.56 (s, C-3, 5, 3JHgC 180.3 Hz), 143.36 (s,
C-2, 6, 2JHgC 71.1 Hz), 150.96 (s, C-1, 1JHgC 2560 Hz). 199Hg NMR
(53.7 MHz, CDCl3, r.t.): d -912.
˚
graphite-monochromated Mo-Ka radiation (l = 0.71073 A). The
Reaction of [2,6-{O(CH2CH2)2NCH2}2C6H3]HgCl (3) with
TeCl4. Compound 3 (0.95 g, 1.85 mmol) was added to a stirred
solution of TeCl4 (0.50 g, 1.85 mmol) in anhydrous 1,4-dioxane (80
mL), under argon atmosphere. The reaction mixture was refluxed
for 5 h, then cooled to room temperature and left overnight under
stirring. The solvent was completely removed under vacuum. The
1H NMR spectrum of the crude product indicated the presence
of two species identified as RTeHgCl3 (4) and RH3HgCl4 (5).
Extraction of the crude product with 5 mL of acetonitrile and
addition of diethyl ether (5 mL) to the resulting solution afforded
the isolation of an yellow–orange solid which was proved to be
[2,6-{O(CH2CH2)2NCH2}2C6H3Te]2[Hg2Cl6] (4) (0.085 g, 12.9%
with respect to RHgCl), mp 160 ◦C (dec.). Anal. Calcd. for
C16H23Cl3HgN2O2Te (709.90): C, 27.07; H, 3.27; N 3.95; Found: C,
26.86; H, 3.47; N 3.65%. 1H NMR (300 MHz, DMSO-d6): d 2.97
structures were refined with anisotropic thermal parameters. The
hydrogen atoms from the water molecule and those attached to
nitrogen’s in 5·H2O were located from the difference map. The
other hydrogen atoms were refined with a riding model and a
mutual isotropic thermal parameter. For structure solving and
refinement the software package SHELX-97 was used.35 The
drawings were created with the Diamond program.36 CCDC
reference numbers 812968 (1), 812970 (2), 812969 (3), 812967 (4)
and 812966 (5·H2O).
Computational details
Theoretical calculations were carried out with the ORCA 2.8
(Rev: 2287) software package.38 The geometries of the investi-
gated models have been optimized at density functional theory
level using BP86 functional. For all the calculations the RI
2
(4 H, ddd, Hpro-trans-8, 11, 13, 16, N–CH2–CH2–O, JH
H
pro-cis pro-trans
8836 | Dalton Trans., 2011, 40, 8830–8838
This journal is
The Royal Society of Chemistry 2011
©

Table 3 Crystallographic data for compounds 1–4 and 5·H2O
1
2
3
4
5·H2O
Empirical formula
M
T
C16H24N2O2
276.37
297(2)
C18H26HgN2O4
535.00
297(2)
C16H23ClHgN2O2
511.40
297(2)
C16H23Cl3HgN2O2Te
709.90
297(2)
C16H28Cl4HgN2O3
638.79
297(2)
Crystal system
Space group
Monoclinic
P21/c
14.380(9)
11.502(7)
9.591(6)
90.00
94.558(11)
90.00
1581.2(18)
4
Orthorhombic
Pbcn
19.823(14)
10.425(8)
18.926(14)
90.00
90.00
90.00
3911(5)
8
25 719
Monoclinic
P21/n
9.7841(8)
10.0718(8)
18.2607(15)
90.00
99.3760(10)
90.00
1775.4(2)
4
Monoclinic
P21/n
9.9793(13)
20.080(3)
10.5966(13)
90.00
96.489(3)
90.00
2109.8(5)
4
Orthorhombic
P212121
7.7037(5)
16.9650(12)
17.1737(12)
90.00
90.00
90.00
2244.5(3)
4
16 296
3949 (Rint = 0.0480)
Multi-Scan37
7.351
0.0339
0.0727
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
Z
No. of reflections collected
No. of independent reflections
Absorption correction
m(Mo-Ka)/mm-1
R1 [I > 2s(I)]
10 272
12 456
10 990
2744 (Rint = 0.0899)
Multi-Scan37
0.077
0.1566
0.3664
3451 (Rint = 0.0659) 3121 (Rint = 0.0324)
3710 (Rint = 0.0548)
Multi-Scan37
9.043
0.0538
0.1102
Multi-Scan37
7.894
Multi-Scan37
8.827
0.0334
0.0680
1.186
0.0469
0.0828
1.143
wR2
GOF on F2
1.119
1.134
1.092
approximation was used and relativistic effects were treated using
the ZORA approximation. The modified def2-TZVP basis set
designed for the use in conjunction with ZORA approximation
was used for all calculations.39 All the geometries were optimized
using the TightOpt option and requesting that all convergence
criteria to be fulfilled (ConvCheckMode 0). Throughout Grid
4 and NoFinalGrid option were used. For the structures of 4b,
4c and 4e tight convergence criteria for the SCF were sufficient
for the localization of the equilibrium geometries. For all the
other investigated structures VeryTightSCF convergence criteria
were used. All the equilibrium geometries were confirmed by
frequency calculations (no imaginary frequencies were obtained).
In all calculated models the labelling of the atoms is consistent to
that used for the crystallographic data.
Due to large overestimation of the distances between the cation
and the anion in the calculated model 4a an optimization of the
position of the hydrogens atoms only was carried out also. In this
model, designated in discussions as 4A, except for the position of
the hydrogen atoms that were optimized, the coordinates of all the
other atoms were taken from the crystallographic data.
de Chimie Mole´culaire, Universite´ Joseph Fourier, Grenoble)
for helpful discussions regarding the theoretical calculations.
Theoretical calculations were performed using the computational
facilities of Data Center of National Institute for Research
and Development of Isotopic and Molecular Technologies –
INCDTIM (Cluj-Napoca).
Notes and references
1 (a) L. Bala´zs, H. J. Breunig, E. Lork, A. Soran and C. Silvestru, Inorg.
Chem., 2006, 45, 2341; (b) A. P. Soran, C. Silvestru, H. J. Breunig,
G. Bala´zs and J. C. Green, Organometallics, 2007, 26, 1196; (c) H. J.
Breunig, L. Ko¨nigsmann, E. Lork, M. Nema, N. Philipp, C. Silvestru,
A. Soran, R. A. Varga and R. Wagner, Dalton Trans., 2008, 1831 and
references cited therein; (d) A. Soran, H. J. Breunig, V. Lippolis, M.
Arca and C. Silvestru, Dalton Trans., 2009, 77; (e) H. J. Breunig, M. G.
Nema, C. Silvestru, A. P. Soran and R. A. Varga, Dalton Trans., 2010,
39, 11277.
2 (a) R. Jambor, B. Kasˇna´, K. N. Kirschner, M. Schu¨rmann and K.
Jurkschat, Angew. Chem., Int. Ed., 2008, 47, 1650; (b) L. Dosta´l, R.
Jambor, A. Ru˚zˇicˇka and J. Holecˇek, Organometallics, 2008, 27, 2169;
(c) L. Dosta´l, R. Jambor, A. Ru˚zˇicˇka, A. Lycˇka, J. Brus and F. de Proft,
Organometallics, 2008, 27, 6059; (d) L. Dosta´l, R. Jambor, A. Ru˚zˇicˇka,
M Erben, R. Jira´sko, A. Cernosˇkova´ and J. Holecˇek, Organometallics,
2009, 28, 2633; (e) J. Martincova´, R. Jambor, M. Schu¨rmann, K.
Jurkschat, J. Honz´ıcˇek and F. A. Almeida Paz, Organometallics, 2009,
28, 4778; (f) J. Martincova´, R. Dosta´lova´, L. Dosta´l, A. Ru˚zˇicˇka and
R. Jambor, Organometallics, 2009, 28, 4823; (g) A. Fridrichova´, T.
Svoboda, R. Jambor, Z. Padeˇlkova´, A. Ru˚zˇicˇka, M. Erben, R. Jira´sko
and L. Dosta´l, Organometallics, 2009, 28, 5522; (h) L. Dosta´l, R.
Jambor, A. Ru˚zˇicˇka, R. Jira´sko, E. Cernosˇkova´, L. Benesˇ and F. de
Proft, Organometallics, 2010, 29, 4486.
The energy of all the arrangements was obtained by single point
calculations on the coordinates of the equilibrium geometries at
the theory level described above and using VeryTightSCF criteria.
For the Lo¨wdin reduced orbital population analysis the molecules
were moved in a position where metal is located in the centre of
the coordinate system and the metal–Cipso bond positioned along
the z axis.
ˇ
3 P. Simon, F. de Proft, R. Jambor, A. Ru˚zˇicˇka and L. Dosta´l, Angew.
Chem., Int. Ed., 2010, 49, 5468.
Acknowledgements
4 Chemistry of Hypervalent Compounds, ed. K.-y. Akiba, Wiley-VCH,
New York, 1999.
5 The Chemistry of Pincer Compounds, ed. D. Morales-Morales and C.
Jensen, Elsevier, Amsterdam, 2007.
Financial support from the Ministry of Education and Research of
Romania (Excellency Research Program, Research Project CEx-
D11-16/2005; Project 19/2006) and National University Research
Council (CNCSIS, Romania; Research Project No. A-709/2006) is
greatly appreciated. The support provided by the National Center
for X-Ray diffraction (Babes-Bolyai University, Cluj-Napoca,
Romania) for the solid state structure determinations is highly
acknowledged. We thank Dr Marius Retegan (De´partement
6 (a) H. Fujihara, H. Mima and N. Furukawa, J. Am. Chem. Soc., 1995,
117, 10153; (b) N. Furukawa, K. Kobayashi and S. Sato, J. Organomet.
Chem., 2000, 611, 116 and references therein; (c) V. P. Singh, H. B.
Singh and R. J. Butcher, Eur. J. Inorg. Chem., 2010, 637 and references
therein; (d) K. Selvakumar, H. B. Singh and R. J. Butcher, Chem.–Eur.
J., 2010, 16, 10576 and references therein.
7 (a) J. L. Wardell, in Comprehensive Organometallic Chemistry, ed.
G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon Press,
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8830–8838 | 8837
©

Oxford, 1982, Vol. 2, p. 863, 902; (b) K. Brodersen, H.-U. Hummel, in
Comprehensive Coordination Chemistry, ed. G. Wilkinson, R. Gillard
and J. A. McCleverty, Pergamon Press, Oxford, 1987, Vol. 5, p. 1047;
Vol. 6, p. 1026; (c) Organometallic Compounds of Zn, Cd and Hg, ed. J.
L. Wardell, Chapman and Hall Ltd., New York, 1985.
8 (a) P. A. Bonnardel, R. V. Parish and R. G. Pritchard, J. Chem. Soc.,
Dalton Trans., 1996, 3185; (b) N. Gul and J. H. Nelson, Organometallics,
1999, 18, 709; (c) N. Gul and J. H. Nelson, Polyhedron, 1999, 18,
1835; (d) A. Berger, A. de Cian, J.-P. Djukic, J. Fischer and M.
Pfeffer, Organometallics, 2001, 20, 3230; (e) A. Berger, J.-P. Djukic,
M. Pfeffer, J. Lacour, L. Vial, A. de Cian and N. Kyritsakas-Gruber,
Organometallics, 2003, 22, 5243; (f) Q.-F. Zhang, K.-M. Cheung, I. D.
Williams and W.-H. Leung, Eur. J. Inorg. Chem., 2005, 4780; (g) J.-P.
Djukic, M. Duquenne, A. Berger and M. Pfeffer, Inorg. Chim. Acta,
2006, 359, 1754.
20 M. Kulcsar, A. Beleaga, C. Silvestru, A. Nicolescu, C. Deleanu, C.
Todasca and A. Silvestru, Dalton Trans., 2007, 2187.
21 L. Lunazzi, D. Casarini, M. A. Cremonini and J. E. Anderson,
Tetrahedron, 1991, 47, 7465.
22 J. Emsley, Die Elemente, Walter de Gruyter, Berlin, 1994.
23 N. Wiberg, Holleman-Wiberg – Lehrbuch der Anorganischen Chemie,
Walter de Gruyter, Berlin, 1995.
24 IUPAC Nomenclature of Organic Chemistry, Pergamon Press, Oxford,
1979.
25 N. Al-Salim, A. A. West, W. R. McWhinnie and T. A. Hamor, J. Chem.
Soc., Dalton Trans., 1988, 2363.
26 T. S. Lobana, S. A. Mbogo, W. R. McWhinnie, W. C. Patalinghug and
A. H. White, J. Organomet. Chem., 1990, 390, 29.
27 H. B. Singh, N. Sudha, A. A. West and T. A. Hamor, J. Chem. Soc.,
Dalton Trans., 1990, 907.
9 (a) R. C. Larock, Organomercury Compounds in Organic
SynthesisSpringer-Verlag, New York, 1985, Ch. 1; (b) K. L. Ding, Y. J.
Wu, Y. Wang, Y. Zhu and L. Yang, J. Organomet. Chem., 1993, 463, 77;
(c) M. Pfeffer, J.-P. Sutter and E. P. Urriolabeitia, Inorg. Chim. Acta,
1996, 249, 63; (d) Y. J. Wu, L. Ding, Z. X. Zhou, C. X. Du and W. L.
Wang, J. Organomet. Chem., 1998, 564, 233; (e) S. D. Dreher and J. L.
Leighton, J. Am. Chem. Soc., 2001, 123, 341; (f) M. T. Crimmins and
B. H. Brown, J. Am. Chem. Soc., 2004, 126, 10264.
28 G. Klose, F. Volke, G. Peinel and G. Knobloch, Magn. Reson. Chem.,
1993, 31, 548.
29 The N-X-L nomenclature system has been previously described: N
valence shell electrons about a central atom X with L ligands in C.
W. Perkins, J. C. Martin, A. J. Arduengo III, W. Lau, A. Alegria and
K. Kochi, J. Am. Chem. Soc., 1980, 102, 7753.
30 J. E. Drake, M. B. Hursthouse, M. Kulcsar, M. E. Light and A. Silvestru,
J. Organomet. Chem., 2001, 623, 153.
31 M. A. Sens, N. K. Wilson, P. D. Ellis and J. D. Odom, J. Magn. Reson.,
1975, 19, 323.
10 M. Ali, W. R. McWhinnie and T. A. Hamor, J. Organomet. Chem.,
1989, 371, C37.
11 E. C. Constable, T. A. Leese and D. A. Tocher, J. Chem. Soc., Chem.
Commun., 1989, 570.
12 E. C. Constable, A. M. W. Cargill Thompson, T. A. Leese, D. G. F.
Reese and D. A. Tocher, Inorg. Chim. Acta, 1991, 182, 93.
13 A. F. M. J. van der Ploeg, C. E. M. van der Kolk and G. van Koten, J.
Organomet. Chem., 1981, 212, 283.
32 R. E. Taylor, C. T. Carver, R. E. Larsen, O. Dmitrenko, S. Bai and C.
Dybowski, J. Mol. Struct., 2009, 930, 99.
33 H. C. E. McFarlane and W. McFarlane, J. Chem. Soc., Dalton Trans.,
1973, 2416.
34 MestReC and MestReNova, Mestrelab Research S.L., A Corun˜a
15706, Santiago de Compostela.
14 J. L. Atwood, D. E. Berry, S. R. Stobart and M. J. Zaworotko, Inorg.
Chem., 1983, 22, 3480.
35 G. M. Sheldrik, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
A64, 112.
15 H. Schumann, S. Freitag, F. Girgsdies, H. Hemling and G. Kociok-
Kohn, Eur. J. Inorg. Chem., 1998, 245.
16 O. Bumbu, C. Silvestru, M. C. Gimeno and A. Laguna, J. Organomet.
Chem., 2004, 689, 1172.
17 S. Attar, J. H. Nelson and J. Fischer, Organometallics, 1995, 14,
4476.
18 N. Gul and J. H. Nelson, J. Mol. Struct., 1999, 475, 121.
19 B. Soro, S. Stoccoro, G. Minghetti, A. Zucca, M. A. Cinellu, S. Gladiali,
M. Manassero and M. Sansoni, Organometallics, 2005, 24, 53.
36 DIAMOND-Visual Crystal Structure Information SystemCrystal Im-
pact, Postfach 1251, D-53002 Bonn, Germany, 2001.
37 G. M. Sheldrick, SADABS, Program for area detector adsorption
correction, Institute for Inorganic Chemistry, University of Go¨ttingen,
Germany, 1996.
38 F. Neese, ORCA-an ab initio, Density Functional and Semiempirical
Program Package, 2.8Universita¨t Bonn, Bonn, Germany, 2010.
39 D. A. Pantazis, X. Y. Chen, C. R. Landis and F. Neese, J. Chem. Theory
Comput., 2008, 4, 908.
8838 | Dalton Trans., 2011, 40, 8830–8838
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