Synthesis and characterization of [4-{(CH2O)2CH}C6H4]2Hg, [4-(O=CH)C6H4]2Hg and [(E)-4-(RN=CH)C6H4]2Hg (R = 2′-py, 4′-py, 2′-pyCH

Article abstract of DOI:10.1002/aoc.6339

The reaction of 4-[(CH₂O)₂CH]C₆H₄Br (1) with n-BuLi, followed by addition of HgCl₂ to the in situ formed organolithium derivative, affords [4-{(CH₂O)₂CH}C₆H₄

Full text of DOI:10.1002/aoc.6339

Received: 28 April 2021
DOI: 10.1002/aoc.6339
Revised: 4 June 2021
Accepted: 6 June 2021
R E S E A R C H A R T I C L E
Synthesis and characterization of [4-{(CH2O)2CH}C6H4]2Hg,
[4-(O=CH)C6H4]2Hg and [(E)-4-(RN=CH)C6H4]2Hg
(R = 20-py, 40-py, 20-pyCH2, 40-pyCH2)
Levente Kiss1
Cristian Silvestru1
| Alexandra Pop1
| Sergiu Shova2
| Ciprian I. Raț1
|
1Supramolecular Organic and
Abstract
Organometallic Chemistry Centre,
Department of Chemistry, Faculty of
Chemistry and Chemical Engineering,
Babes¸-Bolyai University, Cluj-Napoca,
Romania
2Department of Inorganic Polymers,
Institute of Macromolecular Chemistry
“Petru Poni”, Ias¸i, Romania
The reaction of 4-[(CH2O)2CH]C6H4Br (1) with n-BuLi, followed by addition of
HgCl2 to the in situ formed organolithium derivative, affords [4-{(CH2O)2CH}
C6H4]2Hg (2). Deprotection of the formyl groups of 2 in presence of p-TsOH
(p-Ts = 4-MeC6H4SO3) leads to [4-(O=CH)C6H4]2Hg (3). Condensation
reactions of 3 with 2-aminopyridine (2-pyNH2), 4-aminopyridine (4-pyNH2),
2-aminomethylpyridine
(2-pyCH2NH2),
and
4-aminomethylpyridine
(4-pyCH2NH2), in CH2Cl2, affords the novel diorganomercury(II) compounds
of type [(E)-4-(RN=C)C6H4]2Hg [R = 20-py (4), 40-py (5), 2'-pyCH2- (6),
40-pyCH2 (7)]. Compounds 2 and 3 were useful precursors for the preparation
of the corresponding homocoupling products [4-{(CH2O)2CH}C6H4]2 (8) and
[4-(O=CH)C6H4]2 (9) in presence of catalytic amounts of palladium(II) acetate.
Compounds 2–9 were characterized by multinuclear magnetic resonance
(NMR) (1H, 13C{1H}, and 199Hg{1H}, when appropriate) and infrared
(IR) spectroscopy and by mass spectrometry. The molecular structures of 3, 5,
Correspondence
Cristian Silvestru, Supramolecular
Organic and Organometallic Chemistry
Centre, Department of Chemistry, Faculty
of Chemistry and Chemical Engineering,
Babes¸-Bolyai University, 11 Arany Janos,
RO-400028 Cluj-Napoca, Romania.
Email: cristian.silvestru@ubbcluj.ro
Funding information
Consiliului National al Cercetarii
Stiintifice din Invatamantul Superior,
Grant/Award Number: PN-II-ID-PCCE-
2011-2-0050
6, 8, and 9 were determined by single-crystal X-ray diffraction.
Highlights
• A quick, easy, and economic synthesis was optimized for bis
(4-formylphenyl)mercury(II).
• Syntheses of novel homoleptic diorganomercury(II) compounds with imine
functional groups were optimized to give good to excellent yields in mild
conditions with easy workup.
• All diorganomercury(II) compounds were characterized by multinuclear
(1H, 13C{1H}, and 199Hg{1H} NMR) and IR spectroscopy as well as mass spec-
trometry and, for three compounds with imine functional groups, the
molecular structure was determined by single-crystal X-ray diffraction.
• The use of diorganomercury(II) compounds as starting materials for homo-
coupling reactions, in presence of catalytic amounts of palladium(II) acetate,
was investigated.
K E Y W O R D S
199Hg NMR spectroscopy, catalysis, homocoupling, organomercury(II), structural investigation
Appl Organomet Chem. 2021;e6339.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6339

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KISS ET AL.
1 | INTRODUCTION
Organomercury(II) compounds containing ortho-
substituted (imino)aryl groups attached to the metal
were generally prepared by Schiff base condensation
reactions between [2-(O=CH)C6H4]2Hg or [2-(O=CH)
C6H4]HgX (X = halogen) and primary amines.
This includes mercuramacrocycles with at least two
metal atoms per heterocycle and their metal
complexes,[1e,f,9a–c] as well as monometallic molecular
species as [2-(imino)aryl]2Hg,[1e,16b,19] and [2-(imino)aryl]
HgX (X = Cl, Br).[20] In addition, some [2-(imino)aryl]
mercury(II) chlorides were isolated as side products
during transmetallation reactions, often through split-
ting of a macrocycle during complexation of transition
Despite the very well-known toxicity of mercury com-
pounds the organomercury chemistry continues to
receive notable interest regarding both fundamental
and applied topics. Thus, for example, a field of
particular
development
was
that
related
to
mercuramacrocycles,[1] that is, (i) studies on supramo-
lecular aspects based on interactions between Lewis
acidic mercuramacrocycles and neutral electron-rich
substrates as solvents,[2] oxygeneous Lewis bases, for
example, carbonylic derivatives, esters, amides, phos-
phoramides, sulfoxides, nitroxide and nitronyl-nitroxide
organic radicals, and crown-ethers,[2e,3] sulfur-
containing compounds,[4] azacrowns,[5] or aromatic
hydrocarbons, alkynes, and related species,[2c,f,g,6] neu-
tral inorganic metal complexes and organometallics,[7]
metal ions.[1e,9b,c,16b,18,21]
A
few other related
organomercury(II) compounds containing (oxazolynyl)
aryl[14h,17a] or (imino)ferocenyl[17c,22] substituents were
also reported. By contrast, organomercury(II) com-
pounds containing the [4-(RN=C)C6H4]Hg fragment
have not been described so far, while only a few reports
on related compounds containing the [4-(RCH=N)
C6H4]Hg fragment, prepared either by direct mer-
curation of Schiff bases[23] or by condensation of
[4-(H2N)C6H4]HgX (X = OAc, Cl) with aromatic
aldehydes, are available.[24] Very recently, an article on
the synthesis of 4-(40-HO-C6H4CH=N)-5-F-2-NO2-C6H4]
HgCl and its use as transmetallating agent in a reaction
and anions[2g,8]
; (ii) investigation of metallophilic
Hg(II) ꢀꢀꢀM [M = Hg(II), Cu(I), Ag(I), Au(I), Pd(II),
Pt(II), and Sb(III)] interactions[1e,f,2d,7a,9]; (iii) potential
applications as sensors,[8b,10] anion receptors,[8] molecu-
lar recognition,[11] catalysts,[4a,12] and new luminescent
materials.[1d,6a–d]
The use of organomercury compounds as precursors
in organic and organometallic synthesis also raised con-
siderable interest,[13] mainly due to (i) easy mercuration
of functionalized arenes and arene-transition metal
complexes using common inorganic mercury(II) salts as
Hg(OAc)2, Hg(TFA)2, or HgCl2,[14] and (ii) high selec-
tivity of the transmetallation reaction to either main
group or transition metals thus providing organometal-
lic species, which are often inaccessible by classical
Grignard and/or lithiation reactions.[14a,15–17] Related to
the topic of the present research, organomercury com-
pounds containing aryl groups with at least one substit-
uent with a potential donor nitrogen available for an
intramolecular N!M interaction are of interest to be
mentioned here. Thus, both homoleptic, Ar2Hg[14b,c,16]
or ArHgX,[1e,9b,c,14c–h,l,16b,d,17] with ortho-substituted aro-
matic groups containing either sp3 nitrogen[14b,g,16a,b,17a,d–f]
or sp2 nitrogen[1e,9b,c,14c–f,h,16b–d,17a–c,f] as donor atom
were used as transmetallating agents to obtain organo-
metallic compounds of other metals, for example,
Sn,[17c,18] Te,[14g] Ru,[14e,16a,d,17d–f] Pd,[9b,c,14b–d,f,h,l,16c]
Pt,[1e,17b] or Au.[16b,17a] It should also be noted that the
unusual reverse transmetallation process, that is, the
transfer of an ortho-substituted (imino)aryl group from
a transition metal to mercury, was reported when a
with TeBr4, to afford
published.[14m]
a RTeBr3 derivative, was
Within our interest for organometallic supramolecu-
lar architectures, we have designed several new
organotin(IV),[25]
organophosphorus(V),[26]
and
organobismuth(V)[27] compounds, which might be used
as tectons of different geometry for construction of
molecular heterometallic species or coordination poly-
mers with different dimensionality. In addition, we have
improved the preparation of di(4-pyridyl)mercury(II),
which was used as a new organometallic linear tecton in
crystal engineering of coordination polymer supramolec-
ular solid-state architectures.[28]
As an extension of this work, we have decided to
investigate new related organomercury(II)-based tectons
useful as spacers of different dimension and directional-
ity. Herein, we report the synthesis and the spectro-
scopic characterization of [4-{(CH2O)2CH}C6H4]2Hg (2),
[4-(O=CH)C6H4]2Hg (3) and conversion of the later
into various imine derivatives [(E)-4-(RN=CH)
C6H4]2Hg [R = 20-py (4), 40-py (5), 20-pyCH2 (6),
40-pyCH2 (7)], as well as on the use of compounds
2 and 3 as precursors for conversion into the homo-
coupling products [4-{(CH2O)2CH}C6H4]2 (8) and
[4-(O=CH)C6H4]2 (9), in presence of catalytic amounts
of palladium(II) acetate.
reaction
was
carried
out
between
an
organopalladium(II) chloride and elemental mercury,
resulting in the isolation of the organomercury(II)
chloride.[18]

KISS ET AL.
3 of 15
2 | EXPERIMENTAL
2.1 | Materials and procedures
All reactions were carried out using standard Schlenk
techniques under argon atmosphere. Work-ups were
done in air using freshly distilled solvents. All chemicals
were purchased from commercial sources and used as
supplied. THF was pre-dried on KOH pellets, distilled,
and refluxed with metallic potassium for 24 h prior to
use. Dichloromethane was pre-dried and neutralized by
stirring over anhydrous sodium carbonate for 2 days
followed by distillation and drying for 24 h over 10%
(m/v) 4-Å molecular sieves.[29] Multinuclear magnetic
resonance (NMR) (1H, 13C, 199Hg) spectra were recorded
in solution at room temperature (r.t.) on Bruker Avance
1
III 400- or 600-MHz instruments. The H chemical shifts
are reported in δ units (ppm) relative to the residual peak
of the deuterated solvent (CDCl3, 7.26 and DMSO-d6
2.50 ppm), while the 13C chemical shifts are reported in δ
units (ppm) relative to the peak of the deuterated solvent
(CDCl3, 77.16 ppm and DMSO-d6 39.52 ppm).[30] 1H and
13C resonances were assigned using 2-D NMR experi-
ments (COSY, HSQC, and HMBC) according to the num-
bering scheme displayed in Scheme 1. The 199Hg
chemical shifts are reported in δ units (ppm) relative to
Me2Hg using the chemical shift of the lock solvent as a
reference. The NMR spectra were processed using the
MestReNova software package.[31] The MS APCI+ and
ESI+ spectra were recorded on a Thermo Scientific
Orbitrap XL spectrometer. Data analysis and calculations
of the theoretical isotopic patterns were carried out with
the Xcalibur software package.[32] Infrared spectra were
recorded in the 4000- to 500-cmꢁ1 range as KBr pellets
on a Bruker FT IR Vector 22 spectrometer or on an
FT-IR Bruker Alpha II spectrometer with ATR module.
Melting points were recorded in capillary tubes on a
Gallenkamp Melting Point Apparatus (MFB 595 030 G).
SCHEME 1 Numbering scheme for 1H and 13C NMR
assignments. In compounds 8 and 9 only non-equivalent positions
were labeled
was stirred for 30 min. After filtration, the solvent was
evaporated to leave colorless oil. Distillation of the crude
product at reduced pressure (1 ꢃ 10ꢁ3 mbar), at 140ꢄC,
afforded the title compound 1 as colorless oil, which
solidified on standing. Yield 20.25 g (89%; cf. 69% in
Mei et al.[33]), m.p. 36–37ꢄC (cf. 37–38ꢄC in Wu et al.[34]
;
34–35ꢄC in Dhayalan et al.[35]). 1H NMR (CDCl3,
400.13 MHz): δ 3.80–4.15 [m, 4H, (CH2O)2CH], 5.77
[s, 1H, (CH2O)2CH], 7.33–7.37 (m, 2H, H-3, C6H4),
7.49–7.53 (m, 2H, H-2, C6H4). 13C{1H} NMR (CDCl3,
100.62 MHz):
δ
65.42 [s, (CH2O)2CH], 103.12
2.2 | Syntheses
[s, (CH2O)2CH], 123.34 (s, C-1), 128.30 (s, C-3), 131.60
(s, C-2), 137.08 (s, C-4).
2.2.1 | Synthesis of 4-[(CH2O)2CH]
C6H4Br (1)
2.2.2 | Synthesis of [4-{(CH2O)2CH}
C6H4]2Hg (2)
The protected aryl bromide 1 was prepared using a
slightly modified literature method.[33] A reaction mix-
ture of 4-(O=CH)C6H4Br (18.520 g, 100 mmol), ethylene
glycol (9.311 g, 150 mmol) and p-toluenesulfonic acid
(0.344 g, 2 mmol) in toluene (100 ml) was refluxed with a
Dean-Stark apparatus until the expected amount of water
(ꢂ1.8 ml) was separated. The remained solution was
cooled to r.t., Na2CO3 was added, and the mixture
A solution of n-BuLi (14.5 ml, 1.5 M) in hexane was
added under argon to anhydrous THF (40 ml) cooled to
ꢁ78ꢄC. Then, under stirring,
a
solution of
4-[(CH2O)2CH]C6H4Br (1) (5 g, 21.83 mmol) in THF
(40 ml) was added dropwise during about 15 min, and
the stirring was continued for 1 h, maintaining the

4 of 15
KISS ET AL.
temperature at ꢁ78ꢄC. Solid HgCl2 (2.370 g, 8.73 mmol)
was added at once, and the reaction mixture was stirred
for 1 h at low temperature and then left to reach
r.t. overnight. The obtained THF solution was filtered
through celite, and the solvent was removed under vac-
uum. The remaining slightly yellow solid was extracted
with CHCl3 (3 ꢃ 50 ml), and the organic phase was
washed with H2O (2 ꢃ 50 ml) and then dried over anhy-
drous Na2SO4. After filtration, the solvent was removed
under vacuum and the obtained yellowish solid was
suspended in ethanol (50 ml), sonicated for 15 min, fil-
tered, washed with ethanol (2 ꢃ 25 ml), and dried at
reduced pressure to give the title compound as a colorless
solid. Yield 3.97 g (91%; cf. 50% in Drefahl and
Lorenz[36]), m.p. 185–188ꢄC (cf. 184–186ꢄC in ref. Drefahl
and Lorenz[36]). 1H NMR (CDCl3, 400.13 MHz): δ
4.01–4.19 [m, 4H, (CH2O)2CH], 5.82 [s, 1H, (CH2O)2CH],
7.9 Hz), 7.87 (d, 2H, H-3, C6H4, 3JHH 8.0 Hz), 9.96 (s, 1H,
CH=O). 13C{1H} NMR (DMSO-d6, 100.62 MHz): δ
3
128.22 (s, C-3, JHgC 102 Hz), 134.95 (s, C-4), 138.80
2
(s, C-2, JHgC 80 Hz), 179.10 (s, C-1), 193.54 (s, CH=O).
199Hg{1H} NMR (DMSO-d6, 71.61 MHz): δ ꢁ908.8. IR
(KBr pellet, υ, cmꢁ1): 3802(w), 3745(w), 3613(w),
3501(w), 1715(s), 1686(vs), 1583(w), 1555(w), 1516(w),
1493(w), 1423(m), 1394(w), 1300(s), 1182(w), 1128
(w), 1067(w), 999(w), 984(w), 935(w), 814(w), 812(w), 754
(m), 687(m), and 565(w). MS (ESI+, MeCN), m/z
(relative intensity, %): 413.04 (100) [M + H]+. HRMS
(APCI+, MeCN): [M + H]+ calcd. For C14H11HgO2
413.04598. Found: 413.04241.
2.2.4 | General synthesis of [4-(RN=CH)
C6H4]2Hg
3
7.45 (d, 2H, H-2, C6H4, JHH 8.0 Hz), 7.57 (d, 2H, H-3,
C6H4, 3JHH 8.0 Hz). 13C{1H} NMR (CDCl3, 100.62 MHz):
δ 65.43 [s, (CH2O)2CH], 103.80 [s, (CH2O)2CH], 126.62
A Schlenk tube of 50 ml was charged with 1 g of 4-Å
molecular sieves, which were then activated for 2 h at
250ꢄC and 1 ꢃ 10ꢁ3 mbar. Compound 3 was then intro-
duced under argon atmosphere in the flask and anhy-
drous CH2Cl2 (10 ml) was added. The obtained
suspension was stirred for 15 min, and then the
corresponding amine (50% excess) was added. The work-
ing up of the reaction mixture is described below:
3
2
(s, C-3, JHgC 99.6 Hz), 137.57 (s, C-2, JHgC 86.9 Hz),
137.73 (s, C-4), 171.43 (s, C-1, JHgC 1187 Hz). 199Hg{1H}
1
NMR (CDCl3, 71.61 MHz): δ ꢁ751.9 (s). IR (KBr pellet,
υ, cmꢁ1): 3302(w), 2953(w), 2883(w), 2853(w), 2752(w),
1595(w), 1477(w), 1414(s), 1375(w), 1310(w), 1219(m),
1103(w), 1082(s), 1061(vs), 1020(m), 959(m), 939(s), 806
(vs), and 677(w). MS (APCI+, MeCN), m/z (relative
intensity, %): 211.07 (4) [M–Hg–C4H7O2]+, 255.10
(24) [M–Hg–C2H3O]+, 299.13 (100) [M–Hg + H]+, 457.07
(2) [M–C2H3O]+, 501.10 (27) [M]+. HRMS (APCI+,
MeCN): [M + H]+ calcd. For C18H19HgO4 501.09848.
Found: 501.09841.
[(E)-4-(20-pyN=CH)C6H4]2Hg (4): from 3 (0.1 g,
0.243 mmol) and 2-pyNH2 (0.069 g, 0.733 mmol). After
stirring overnight, a colorless precipitate was obtained
and was filtered off, then washed with acetonitrile
(3 ꢃ 10 ml) and dried in vacuum to obtain the title
compound as a colorless solid. Yield 0.113 g (83%),
m.p. 190–200ꢄC (decomp.). Elemental analysis calcd.
For C24H18HgN4 (MW 563.03): C, 51.20; H, 3.22; N,
9.95%. Found: C, 49.09; H, 3.09; N, 8.80%. 1H NMR
2.2.3 | Synthesis of [4-(O=CH)C6H4]2Hg (3)
3
(CDCl3, 400.13 MHz): δ 7.19 (t, 1H, H-8, NC5H4, JHH
3
p-Toluenesulfonic acid (0.200 g, 1.16 mmol) was added to
a solution of 2 (2.000 g, 4 mmol) in THF (35 ml)/H2O
(15 ml) mixture. The reaction mixture was stirred over-
night resulting in a colorless precipitate. The precipitate
was filtered off and washed with small amounts of cold
THF and ethanol and then dried to get 3 as a colorless
solid. Yield 1.35 g (82%; cf. 90% in Drefahl and
Lorenz[36]), m.p. 260–270ꢄC (decomp.) (cf. 262–264ꢄC in
Drefahl and Lorenz[36]). Elemental analysis calcd. For
C14H10HgO2 (MW 410.82): C, 40.93; H, 2.45%. Found: C,
6.4 Hz), 7.35 (d, 1H, H-6, NC5H4, JHH 7.9 Hz), 7.59
3
(d, 2H, H-2, C6H4, JHH 7.6 Hz), 7.77 (t, 1H, H-7, NC5H4,
3
3JHH 7.7 Hz), 8.08 (d, 2H, H-3, C6H4, JHH 7.6 Hz), 8.51
3
(d, 1H, H-9, NC5H4, JHH 5.5 Hz), 9.16 (s, 1H, CH=N).
13C{1H} NMR (CDCl3, 100.62 MHz): δ 120.01 (s, C-6),
122.01 (s, C-8), 129.39 (s, C-3), 135.81 (s, C-4), 137.97
(s, C-2), 138.28 (s, C-7), 149.04 (s, C-9), 161.32 (s, C-5),
163.18 (s, CH=N), and 175.11 (s, C-1). 199Hg{1H} NMR
(CDCl3, 71.61 MHz): δ ꢁ777.9 (s). IR (KBr pellet, υ, cmꢁ1):
3298(w), 3044(w), 2988(w), 1620(vs), 1582(vs), 1562(vs),
1547(vs), 1391(w), 1360(w), 1310(w), 1258(m), 1198(m),
1175(m), 1140(w), 1092(w), 1015(w), 989(w), 887(m),
816(s), 787(m), 739(m), and 579(m). MS (APCI+,
MeCN), m/z (relative intensity, %): 181.08 (100) [R]+,
565.13 (50) [M + H]+, [R = 4-(20-pyN=CH)C6H4].
HRMS (APCI+, MeCN): [M + H]+ calcd. For
C24H19HgN4 565.13105. Found: 565.13019.
1
41.29; H, 2.44%. H NMR (CDCl3, 400.13 MHz): δ 7.64
3
(d, 2H, H-2, C6H4, JHH 8.0 Hz), 7.96 (d, 2H, H-3, C6H4,
3JHH 8.0 Hz), 10.02 (s, 1H, CH=O). 13C{1H} NMR
(CDCl3, 100.62 MHz): δ 129.45 (s, C-3), 136.21 (s, C-4),
138.15 (s, C-2), 177.61 (s, C-1), 192.72 (s, CH=O). 199Hg
1
{1H} NMR (CDCl3, 71.61 MHz): δ ꢁ813.7 (s). H NMR
3
(DMSO-d6, 400.13 MHz): δ 7.82 (d, 2H, H-2, C6H4, JHH

KISS ET AL.
5 of 15
[(E)-4-(40-pyN=CH)C6H4]2Hg (5): from 3 (0.1 g,
[R = 4-(20-pyCH2N=CH)C6H4].
HRMS
(APCI+,
0.243 mmol) and 4-pyNH2 (0.069 g, 0.733 mmol). The
reaction mixture was stirred for 5 days when a precipitate
is formed. Then the solid was filtered off, washed with
acetonitrile (2 ꢃ 5 ml) and dried in vacuum to obtain
5 as a colorless solid. Yield 0.081 g (59%), m.p. 200–205ꢄC
(decomp.). Elemental analysis calcd. For C24H18HgN4
(MW 563.03): C, 51.20; H, 3.22; N, 9.95%. Found: C,
MeCN): [M + H]+ calcd. For C26H13HgN4 593.16235.
Found: 593.16311.
[(E)-4-(40-pyCH2N=CH)C6H4]2Hg
(7):
from
3
(0.100 g, 0.243 mmol) and 4-pyCH2NH2 (0.079,
0.731 mmol). The reaction mixture was stirred overnight,
and then the obtained colorless solution was concen-
trated to ꢂ5 ml and acetonitrile (20 ml) was added. The
resulted solid was filtered off and washed with acetoni-
trile (2 ꢃ 5 ml) and diethyl ether (2 ꢃ 5 ml), then dried
in vacuum to obtain 7 as a colorless solid. Yield 0.10 g
(70%), m.p. 190–200ꢄC (decomp.). Elemental analysis
calcd. For C26H22HgN4 (MW 591.08): C, 52.83; H,
1
49.88; H, 3.23; N, 8.89%. H NMR (CDCl3, 400.13 MHz):
δ 7.04 (d, 2H, H-6, NC5H4, 3JHH 6.1 Hz), 7.60 (d, 2H, H-2,
3
3
C6H4, JHH 7.9 Hz), 7.99 (d, 2H, H-3, C6H4, JHH 7.9 Hz),
3
8.39 (s, 1H, CH=N), 8.59 (d, 2H, H-7, NC5H4, JHH
6.1 Hz). 13C{1H} NMR (CDCl3, 100.62 MHz): δ 115.86
(s, C-6), 129.06 (s, C-3), 135.27 (s, C-4), 138.10 (s, C-2),
150.93 (s, C-7), 159.17 (s, C-5), 163.09 (s, CH=N), 175.33
(s, C-1). 199Hg{1H} NMR (CDCl3, 71.61 MHz): δ ꢁ786.6
(s). IR (KBr pellet, υ, cmꢁ1): 3749(w), 3674(w), 3613(w),
3587(w), 1690(w), 1626(m), 1580(s), 1543(s), 1522(m),
1491(w), 1420(w), 1394(w), 1198(w), 1175(w), 1082(m),
1001(vs), 885(w), 831(w), 687(w), and 590(w). MS
(APCI+, MeCN), m/z (relative intensity, %): 182.08 (100)
[R + H]+, 363.16 (14) [M–Hg + H]+, 565.13 (70)
[M + H]+, [R = 4-(40-pyN=CH)C6H4]. HRMS (APCI+,
MeCN): [M + H]+ calcd. For C24H19HgN4 565.13105.
Found: 565.12988.
1
3.75; N, 9.48%. Found: C, 49.94; H, 3.91; N, 7.15%. H
NMR (CDCl3, 600.13 MHz): δ 4.83 (s, 2H, CH2), 7.30
(d, 2H, H-6, NC5H4, 3JHH 5.4 Hz), 7.53 (d, 2H, H-2, C6H4,
3JHH 7.9 Hz), 7.88 (d, 2H, H-3, C6H4, JHH 8.0 Hz), 8.41
3
3
(s, 1H, CH=N), 8.58 (d, 2H, H-7, NC5H4, JHH 5.9 Hz).
13C{1H} NMR (CDCl3, 150.92 MHz): δ 63.69 (s, CH2),
122.90 (s, C-6), 128.29 (s, C-3), 135.65 (s, C-4), 137.91
(s, C-2), 148.62 (s, C-5), 150.03 (s, C-7), 163.46
(s, CH=N), 173.98 (s, C-1). 199Hg{1H} NMR (CDCl3,
71.61 MHz): δ ꢁ770.8 (s). IR (KBr pellet, υ, cmꢁ1):
3022(w), 2874(w), 2839(w), 1641(s), 1599(vs), 1587(s),
1551(m), 1481(w), 1420(m), 1414(s), 1379(w), 1348(w),
1302(w), 1217(w), 1065(w), 1016(w), 993(w), 837(w), 808
(vs), 795(s), 727(w), and 609(w). MS (APCI+, MeCN),
m/z (relative intensity, %): 197.11 (90) [R + H]+, 389.18
(30) [M–Hg–H]+, 593.16 (76) [M + H]+, [R = 4-(40-pyC-
H2N=CH)C6H4]. HRMS (APCI+, MeCN): [M + H]+
calcd. For C26H23HgN4 593.16235. Found: 593.16322.
[(E)-4-(20-pyCH2N=CH)C6H4]2Hg
(6):
from
3 (0.100 g, 0.243 mmol) and 2-pyCH2NH2 (0.079 g,
0.731 mmol). The reaction mixture was stirred over
night, when a colorless precipitate was obtained. It was
filtered off, then washed with acetonitrile (3 ꢃ 5 ml)
and dried in vacuum to obtain 6 as a colorless solid.
Yield 0.126 g (88%), m.p. 205–210ꢄC (decomp.).
Elemental
analysis
calcd.
For
C26H22HgN4
(MW 591.08): C, 52.83; H, 3.75; N, 9.48%. Found: C,
50.75; H, 3.80; N, 8.07%. 1H NMR (CDCl3,
600.13 MHz): δ 4.98 (s, 2H, CH2), 7.19 (dd, 1H, H-8,
2.2.5 | Synthesis of [4-{(CH2O)2CH}
C6H4]2 (8)
3
3
NC5H4, JHH 7.7, JHH 4.7 Hz), 7.45 (d, 1H, H-6, NC5H4,
A mixture of 2 (0.234 g, 0.5 mmol) and a catalytic amount
of Pd(OAc)2 (0.010 g, 0.0445 mmol) in 10 ml CH2Cl2 was
stirred overnight, under protection against light. The
obtained dark suspension was mixed with anhydrous
MgSO4 and then filtered. The solvent was evaporated
from the clear solution providing a colorless solid, which
was washed with 3 ꢃ 5 ml EtOH, followed by extraction
with 2 ꢃ 10 ml Et2O. The solvent was removed in
vacuum from the resulting clear solution to provide
0.105 g of 8 as a colorless crystalline product (yield 70%
of isolated pure product), m.p. 281–283ꢄC. 1H NMR
(CDCl3, 600.13 MHz): δ 4.01–4.20 [m, 4H, (CH2O)2CH],
3
3JHH 7.9 Hz), 7.51 (d, 2H, H-2, C6H4, JHH 7.7 Hz), 7.69
3
(t, 1H, H-7, NC5H4, JHH 7.7 Hz), 7.89 (d, 2H, H-3,
3
C6H4, JHH 7.8 Hz), 8.48 (s, 1H, CH=N), 8.58 (d, 1H,
3
H-9, NC5H4, JHH 5.2 Hz). 13C{1H} NMR (CDCl3,
150.92 MHz): δ 67.03 (s, CH2), 122.17 (s, C-8), 122.45
(s, C-6), 128.34 (s, C-3), 136.00 (s, C-4), 136.81 (s, C-7),
137.83 (s, C-2), 149.45 (s, C-9), 159.51 (s, C-5), 163.36
(s, CH=N), 173.76 (s, C-1). 199Hg{1H} NMR (CDCl3,
71.61 MHz): δ ꢁ765.3 (s). IR (KBr pellet, υ, cmꢁ1): 3045
(w), 2889(w), 2895(w), 2870(w), 2839(w), 1691(w), 1634
(vs), 1587(s), 1570(m), 1549(w), 1475(w), 1433(m), 1335
(w), 1302(w), 1263(w), 1215(w), 1096(w), 1051(w), 1045
(w), 1018(m), 995(m), 872(w), 833(m), 818(m), 775(s),
752(w), and 615(w). MS (ESI+, MeCN), m/z (relative
intensity, %): 198.10 (58) [C14H14O]+, 503.10 (100)
3
5.87 [s, 1H, (CH2O)2CH], 7.55 (d, 2H, H-2, C6H4, JHH
3
8.3 Hz), 7.61 (d, 2H, H-3, C6H4, JHH 8.3 Hz). 13C{1H}
NMR (CDCl3, 150.92 MHz): δ 65.50 [s, (CH2O)2CH],
103.70 [s, (CH2O)2CH], 127.03 (s, C-3), 127.38 (s, C-2),
137.25 (s, C-4), 141.86 (s, C-1). IR (ATR, υ, cmꢁ1): 2941
[M–C6H6N + OH]+,
593.16
(40)
[M + H]+,

6 of 15
KISS ET AL.
(w), 2871(m), 2351(vs), 2332(vs), 1607(m), 1499(w), 1406
(m), 1310(m), 1216(m), 1065(s), 1016(m), 961(m), 930(m),
879(w), 812(vs), 718(w), and 526(w). MS (APCI+,
MeCN), m/z (relative intensity, %): 255.10 (10)
[M–C2H4O]+, 299.13 (100) [M + H]+. HRMS (APCI+,
MeCN): [M + H]+ calcd. For C18H19O4 299.12779.
Found: 299.12722.
structure solution program and refined by full-matrix
least squares on F2 with SHELXL-2015.[40] For structure
solving and refinement of 8 and 9, the Bruker APEX3
Software Package was used.[40] Atomic displacements for
non-hydrogen atoms were refined using an anisotropic
model. Hydrogen atoms have been placed in fixed, ideal-
ized positions accounting for the hybridation of the
supporting atoms. The crystal structure of 5ꢀ3H2O con-
tains large channels hosting severely disordered water
molecules. Nevertheless, their positional parameters were
successfully determined from difference Fourier maps
and refined isotropically with fractional s.o.f. In the struc-
tures of 5 and 6, the molecules lie on a center of inver-
sion. The asymmetric unit of 8 contains two complete
molecules and two molecules located on inversion cen-
ters, thus the overall value of Z is 12. The drawings were
created with the Diamond program.[41]
2.2.6 | Synthesis of [4-(O=CH)C6H4]2 (9)
A mixture of 3 (0.205 g, 0.5 mmol) and a catalytic amount
of Pd(OAc)2 (0.010 g, 0.0445 mmol) in 10 ml CH2Cl2 was
stirred overnight, under protection against light. The
resulted dark suspension was mixed with anhydrous
MgSO4 and then filtered. The solvent was evaporated
from the clear solution providing a colorless solid, which
was extracted with 4 ꢃ 5 ml EtOH. Then the solvent was
removed and the solid was dried in vacuum for 3 h to
give 0.062 g of 9 as a colorless microcrystalline product
(yield 59% of isolated pure product), m.p. 146–147ꢄC
(cf. 146–148ꢄC in Dwivedi et al.[37a], 150–151ꢄC in
3 | RESULTS AND DISCUSSION
3.1 | Synthesis
1
Kaboudin et al.[37b]). H NMR (CDCl3, 400.13 MHz): δ
3
7.81 (d, 2H, H-2, C6H4, JHH 8.3 Hz), 8.00 (d, 2H, H-3,
Compounds 1–3 were prepared according to Scheme 2.
The aryl bromide 4-[(CH2O)2CH]C6H4Br (1) was
obtained from 4-bromobenzaldehyde and ethylene glycol
using a slightly modified literature method[33]: to avoid
the contact with water (i.e., extraction with cold water/
ethyl acetate mixture and treatment with brine) and
acidic media (i.e., separation by silica gel column chro-
matography), which might decompose the desired prod-
uct, the crude material was distilled at reduced pressure.
This resulted in considerable (ꢂ20%) increased yield in
pure 1, isolated as a viscous colorless oil which solidified
on standing; the solid was kept under argon atmosphere
at ꢁ24ꢄC, to reduce its decomposition. Alternative
methods for the preparation and working-up of 1 were
also reported.[34,35]
3
C6H4, JHH 8.3 Hz), 10.09 (s, 1H, CH=O). 13C{1H} NMR
(CDCl3, 100.62 MHz): δ 128.19 (s, C-2), 130.53 (s, C-3),
136.13 (s, C-4), 145.72 (s, C-1), 191.88 (s, CH=O). IR
(ATR, υ, cmꢁ1): 3337(w), 2826(w), 2733(w), 1683(vs),
1596(s), 1556(m), 1384(w), 1308(w), 1207(m), 1165(w),
1003(w), 857(w), 829(w), 809(m), 656(w), 548(w), and 498
(w). MS (APCI+, MeCN), m/z (relative intensity, %):
155.09 (95) [C12H11]+, 211.07 (100) [M + H]+. HRMS
(APCI+, MeCN): [M + H]+ calcd. For C14H11O2
211.07536. Found: 211.07495.
2.3 | Crystal structure determination
Single crystals of 3, 5ꢀ3H2O, 6, 8, and 9 were obtained by
slow evaporation of the solvent from solutions of 3 in ace-
tone, 5 in CH2Cl2, 6 in CHCl3, and 8 and 9 in CH2Cl2/
EtOH (1:1) mixture, in open atmosphere. Table S1 (see
Supporting Information) provides a summary of the crys-
tallographic data together with refinement details for
compounds. Crystallographic measurements were carried
out with Rigaku Oxford-Diffraction XCALIBUR E CCD
(3, 5ꢀ3H2O, and 6) or Bruker D8 VENTURE (8 and 9) dif-
fractometers equipped with graphite-monochromated
Mo-Kα radiation (λ = 0.71073 Å). The unit cell determi-
nation and data integration for 3, 5ꢀ3H2O, and 6 were car-
ried out using the CrysAlis package of Oxford
Diffraction,[38] and the structures were solved by direct
methods using Olex2 software[39] with the SHELXT
In an earlier work, compound [4-{(CH2O)2CH}
C6H4]2Hg (2) was obtained in 50% yield through a
SCHEME 2 Synthesis of compounds 2 and 3

KISS ET AL.
7 of 15
reaction between the Grignard reagent 4-[(CH2O)2CH]
C6H4MgBr and HgBr2, in THF, at r.t., but no spectro-
scopic characterization was reported.[36] We have carried
out the preparation of the same compound 2 using the
organolithium reagent 4-[(CH2O)2CH]C6H4Li and HgCl2,
in anhydrous THF, at ꢁ78ꢄC. After working up the crude
reaction mixture, 2 was isolated in excellent yield (90%).
The deprotection of 2 was achieved using a standard pro-
cedure (i.e., hydrolysis with THF/H2O mixture, in pres-
ence of p-toluenesulfonic acid, at r.t.) resulting in a high
yield of pure [4-(O=CH)C6H4]2Hg (3), a useful interme-
diate in the synthesis of the target [4-(RN=CH)C6H4]2Hg
compounds.
Imines of type [(E)-4-(RN=C)C6H4]2Hg [R = 20-py
(4), 40-py (5), 20-pyCH2 (6), 40-pyCH2 (7)] were obtained
in good to excellent yield (60%–90%) by reacting 3 with
an excess of the corresponding amine, in dry and acid
free CH2Cl2, at r.t. (Scheme 3). All four compounds 4–7
were isolated as colorless solids. Satisfactory analytical
results and HRMS data were obtained for all these
organomercury(II) compounds. Compounds 4–6 exhibit
good stability in the solid state, but slowly decompose in
solution, in non-anhydrous solvents, to starting material
3 and the corresponding amine, as was easily observed by
NMR studies. Compound 7 was found to decompose after
few days even in solid state, when unidentified yellow
oily products were formed.
The solution characterization of compounds 2–7 was
achieved by multinuclear (1H, 13C{1H} and 199Hg{1H})
NMR spectroscopy, the spectra being recorded in CDCl3
at r.t.. Owing to the low solubility in CDCl3, the spectra
for compound 3 were also recorded in DMSO-d6, without
significant changes in terms of chemical shifts of the
observed resonance signals. The 199Hg{1H} NMR spectra
for compounds 2–7 exhibit one singlet resonance, thus
indicating the presence of only one organomercury(II)
species in CDCl3 solution. The δHg chemical shifts range
from ꢁ751.9 ppm for 2 to ꢁ813.7 ppm for 3, with inter-
1
mediate values for the imines 4–7. The H and 13C{1H}
NMR spectra show in all cases only one set of expected
resonances both in the aliphatic and the aromatic
regions, thus being consistent with the equivalence of the
organic groups attached to the same mercury atom. An
indicative 1H chemical shift for compounds 2–7 is that of
the resonance signal assigned to the hydrogen of the CH
group placed in position 4 of the aromatic substituent.
Thus, the change in this chemical shift from δ 5.82 ppm
for 2 [(CH2O)2CH] to δ 10.02 ppm for 3 (CH=O) is useful
to follow the deprotection of the carbonyl function in 2,
while the shift of the corresponding resonance to δ
9.16 ppm for 4, δ 8.39 ppm for 5, δ 8.48 ppm for 6, and
δ 8.41 ppm for 7 (CH=N) can be used for easy
1
monitorization by H NMR spectroscopy of the conver-
sion of the aldehyde function to the imine one. A similar
significant shift of the singlet resonance for the carbon of
the same CH group was observed in the 13C NMR spectra
3.2 | Spectroscopic characterization
of compounds 2–7, that is,
[(CH2O)2CH], 192.72 ppm for
δ
103.80 ppm for
(CH=O), and
2
3
Compounds 2–7 were investigated by mass spectrometry,
IR, and NMR spectroscopy. In the APCI+ or ESI+ mass
spectra (see Supporting Information) the protonated
molecular ions [M + H]+ was observed for all the com-
pounds. In the IR spectra of 2 and 3, typical medium to
very strong bands were assigned to the acetal moiety
163.18 ppm for 4, 163.09 ppm for 5, 163.36 ppm for 6, or
163.46 ppm for 7 (CH=N), respectively.
3.3 | Solid-state structures
(959, 939 cmꢁ1
)
and C=O stretching vibration
The molecular structures of the diorganomercury(II)
compounds 3, 5, and 6 were established by single-crystal
X-ray diffraction. The ORTEP-like representations of the
molecular structure of these compounds, with the atom
numbering scheme, are depicted in Figures 1–3. Selected
interatomic distances and bond angles, as well as dihe-
dral angles, are listed in Tables 1 and 2.
(1686 cmꢁ1).[42] For compounds 4–7, a strong band in the
region 1620–1641 cmꢁ1 was assigned to the stretching
vibration of the C=N double bond as typical for com-
pounds containing Schiff-base ligands.[42]
FIGURE 1 Molecular structure of [4-(O=CH)C6H4]2Hg (3).
SCHEME 3 Synthesis of compounds 4–7
Thermal ellipsoids are drawn at 40% probability

8 of 15
KISS ET AL.
FIGURE 2 Molecular structure of [(E)-
4-(40-pyN=CH)C6H4]2Hgꢀ3H2O (5ꢀ3H2O).
Thermal ellipsoids are drawn at 40% probability
(water molecules are not shown)
FIGURE 3 Molecular structure of [(E)-4-
(20-pyCH2N=CH)C6H4]2Hg] (6). Thermal
ellipsoids are drawn at 40% probability
TABLE 1 Selected interatomic
Hg1–C1
2.073(8)
2.066(8)
C1–Hg1–C8
178.3(3)
distances (Å) and angles (ꢄ) in
Hg1–C8
compound 3
C4–C7–O1
124.9(9)
118
C7–O1
1.187(11)
1.217(12)
C4–C7–H7
C14–O2
O1–C7–H7
118
C11–C14–O2
C11–C14–H14
O2–C14–H14
126.3(9)
117
117
Dihedral angles
{C1–C6}/{C8–C13}
9.4
5.0
{C1–C6}/{C7,H7,O1}
7.1
7.2
{C4,C7,H7,O1}/{C11,C14,H14,O2}
{C8–C13}/{C14,H14,O2}
Common structural features for these organomercury
compounds are (i) the lengths of the covalent Hg–C
bonds, which fit in the reported range (2.06–2.15 Å) for
diarylmercury compound[43]; (ii) the expected linear
arrangement of the Hg–C bonds within a molecule, that is,
C–Hg–C 178.3(3)ꢄ for 3, and 180ꢄ for 5 and 6, respectively;
and (iii) the isolation as E-imino isomers of compounds
5 and 6, as consequence of the existence of the inversion
centers. In the molecule of 3, the two aromatic rings
attached to a mercury atom are slightly twisted to each
other (dihedral angle {C1–C6}/{C8–C13} of 9.4ꢄ), as are
the carbonyl (O=CH–C) groups (dihedral angle {C4,C7,
H7,O1}/{C11,C14,H14,O2} of 5.0ꢄ). By contrast, both
corresponding systems, that is, aromatic rings attached to
mercury atom and the imino (C–N=CH–C) groups, are
co-planar within a molecular unit of 5 and 6 (see Tables 1
and 2 for the corresponding dihedral angles). The pyridyl
rings are twisted (33.0ꢄ and 77.5ꢄ for 5 and 6, respec-
tively) with respect to the planar Ar2Hg skeleton.
A major structural difference that should be noted is
the relative orientation of the C=E (E = O, N) double
bonds with respect to the quasi planar arrangement of
the aromatic rings attached to mercury: they are trans in
the molecule of 3, but cis in those of the di(imino)
arilmercury compounds 5 and 6.
A closer check of the crystal structures of these
diorganomercury(II) compounds revealed different
supramolecular architectures. For both compounds 3 and
5, the planar (or almost planar) molecules are stacked to
allow the formation of chain polymers through two
Hgꢀꢀꢀπ interactions per metal atom (with almost orthogo-
nal HgꢀꢀꢀArcentroid vectors as evaluated through the γ
angle between the normal to the aromatic ring and the
line defined by the metal atom and Arcentroid): Hg(1)ꢀꢀꢀ

KISS ET AL.
9 of 15
TABLE 2 Selected interatomic distances (Å) and angles (ꢄ) in compounds 5ꢀ3H2O and 6
5ꢀ3H2Oa
6 b
Hg1–C1
2.100(11)
1.27(2)
1.403(17)
1.34(2)
1.36(2)
180
Hg1–C1
2.090(5)
N1–C7
N1–C7
1.262(6)
1.475(7)
1.338(7)
1.302(9)
180
N1–C8
N1–C8
N2–C10
N2–C9
N2–C11
C1–Hg1–C10
N2–C13
C1–Hg1–C10
C4–C7–N1
C4–C7–H7
N1–C7–H7
C7–N1–C8
C9–N2–C13
C4–C7–N1
122.9(13)
119
124.3(5)
118
C4–C7–H7
N1–C7–H7
118
118
C7–N1–C8
120.3(12)
114.8(14)
117.0(5)
116.1(5)
C10–N2–C11
Dihedral angles
{C1-C6}/{C10–C60}
{C1–C6}/{C7,H7,N1,C8}
{C1–C6}/{C8-C12,N2}
{C7,H7,N1,C8}/{C8–C12,N2}
{C4,C7,H7,N1,C8}/{C40,C70,H70,N10,C80}
{C8–C12,N2}/{C80–C120,N20}
0.0
{C1–C6}/{C10–C60}
0.0
6.8
{C1–C6}/{C7,H7,N1,C8}
4.7
33.0
36.6
0.0
{C1–C6}/{C9–C13,N2}
77.5
80.8
0.0
{C7,H7,N1,C8}/{C9–C13,N2}
{C4,C7,H7,N1,C8}/{C40,C70,H70,N10,C80}
{C9–C13,N2}/{C90–C130,N20}
0.0
0.0
aSymmetry equivalent atoms (1–x, ꢁ3–y, 3–z) are given by “prime.”
bSymmetry equivalent atoms (ꢁx, ꢁy, ꢁz) are given by “prime.”
FIGURE 5 View of the supramolecular chain polymer
association build through Hgꢀꢀꢀπ interactions in the crystal of [(E)-
4-(40-pyN=CH)C6H4]2Hgꢀ3H2O (5ꢀ3H2O) (only hydrogen atoms of
the imino groups and those involved in intermolecular interactions
are shown; due to disorder, water molecules are not shown)
[symmetry equivalent atoms (1–x, ꢁ3–y, 3–z), (x,–1+y, z), (x, 1+y,
z) and (1–x, ꢁ2–y, 3–z) are given by “prime,” “a,” “b,” and “b
prime”]
FIGURE 4 View along c axis of the supramolecular chain
polymer association build through Hgꢀꢀꢀπ interactions in the crystal
of [4-(O=CH)C6H4]2Hg (3) (only hydrogen atoms of the carbonyl
groups and those involved in intermolecular interactions are
shown) [symmetry equivalent atoms (ꢁ1+x, y, z) and (1+x, y, z) are
given by “a” and “b”]
Arcentroid{C(1a)–C(6a)} 3.48 Å (γ = 5.0ꢄ) and Hg(1)ꢀꢀꢀ
Arcentroid{C(8b)-C(13b)} 3.50 Å (γ = 14.1ꢄ) for 3 (Figure 4),
and Hg(1)ꢀꢀꢀArcentroid{C(1a)-C(6a)} 3.43 Å (γ = 2.7ꢄ) for
5 (Figure 5). Although somewhat longer than other
reported intra- or intermolecular Hgꢀꢀꢀπ interactions in
organomercury(II) compounds,[43–45] these HgꢀꢀꢀArcentroid
distances in the crystals of 3 and 5 are shorter than the
sum of the van der Waals radii of mercury (recently
reported as 2.45 Å)[46] and that estimated for an arene
ring, that is, 1.9 Å.[47]
The resulting chains of molecules of 3 are connected
through HgꢀꢀꢀO interactions [Hg(1)ꢀꢀꢀO(1b”) 3.01 Å, c.f.
ΣrvdW (Hg,O) 3.95 Å[46]] into a 3-D network supported by
further C–HarylꢀꢀꢀO contacts [range 2.57–2.61 Å,
cf. ΣrvdW(O,H) 2.70 Å[46]; see Figures S44 and S45]. The
C2HgO core has a slightly distorted T-shape [C(1)-Hg

10 of 15
KISS ET AL.
(1)ꢀꢀꢀO(1b00) 92.8ꢄ; C(8)-Hg(1)ꢀꢀꢀO(1b00) 88.9ꢄ], while the
overall C2HgO(Arcentroid 2 core is distorted square
)
pyramidal.
By contrast, in the crystal of 5 there are no further
interactions between heavy atoms, but the chain poly-
mers based on Hgꢀꢀꢀπ interactions are connected into a
layer through C–HarylꢀꢀꢀN contacts [C(6)–H(6)arylꢀꢀꢀN
(1A) 2.78 Å, cf. ΣrvdW(N,H) 2.86 Å[46]; see Figures S46
and S47].
No Hgꢀꢀꢀπ interactions or other interactions between
heavy atoms are present in the crystal of 6, but a network
of C–Himinoꢀꢀꢀπ interactions [C(7)–H(7)iminoꢀꢀꢀArcentroid{C
(9a)–C(13a), N(2a)} 2.90 Å, γ = 3.9ꢄ; cf. HꢀꢀꢀArcentroid con-
tacts shorter than 3.1 Å and an angle γ between the nor-
mal to the aromatic ring and the line defined by the H
atom and Arcentroid smaller than 30ꢄ][48] connects the
molecules into a layer (Figure 6). Further, C–Haryl ꢀꢀꢀπ
and C–HPyꢀꢀꢀπ interactions between layers result in a 3-D
supramolecular architecture (see Figures S48–S50).
3.4 | Investigation of transmetallation
versus homocoupling
As pointed out in Section 1, the imine derivatives 4–7
might be useful as divergent, linear organometallic
tectons in crystal engineering of coordination polymers,
as was already proved for di(4-pyridyl)mercury(II).[28] On
the other hand, the use of organomercury(II) is well
known as transmetallating agents of organic substituents
to either main group or transition metals,[14–18] for exam-
ple, several homoleptic Ar2Hg,[49] including compounds
with ortho-substituted aromatic groups,[14b,c,16c] were
reported as source for aryl substituents in the synthesis of
organopalladium(II) compounds. This potential reactivity
should be also taken into account when synthesis of coor-
dination polymers is designed.
Therefore, we have performed reactions between
Pd(OAc)2 and several diarylmercury(II) compounds
reported in this work, in 1:1 molar ratio, in order to
check the potential use of the title diorganomercury com-
pounds as linkers between Pd-containing nodes or as
transmetallating agents. The reaction carried out with
the imino derivative 6 produced a complex reaction mix-
ture, including some black material suggesting decompo-
sition to naked metal, and its work-up did not resulted in
pure compounds. When the reaction was carried using
the compounds 2 or 3, the NMR data recorded on the
crude reaction mixture suggested that instead of a coordi-
nation polymer or a transmetallation of the aryl substitu-
ent from mercury to palladium, a C–C coupling reaction
occurred to produce the homocoupling products
[4-{(CH2O)2CH}C6H4]2 (8) and [4-(O=CH)C6H4]2 (9)
FIGURE 6 View along c axis of the supramolecular layer build
through C–Himinoꢀꢀꢀπ interactions in the crystal of [(E)-4-(20-
pyCH2N=CH)C6H4]2Hg (6) (only hydrogen atoms of the imino
groups and those involved in intermolecular interactions are
shown) [symmetry equivalent atoms (ꢁx, ꢁy, ꢁz), (x, 1+y, z), (x,
ꢁ1+y, z), (ꢁ1–x, 0.5+y, 0.5–z), (1–x, 0.5 y, ꢁ0.5–z), (ꢁ1–x, ꢁ0.5+y,
0.5–z) and (1–x, ꢁ0.5+y, ꢁ0.5–z) are given by “prime,” “A,” “B,”
“a,” “b,” “Ba,” and “Bb”)
SCHEME 4 Synthesis of compounds 8 and 9 via
homocoupling reactions
(Scheme 4). In fact, such a reaction pathway should have
been also anticipated taking into account previous
reports regarding the use of some arylmercury com-
pounds as starting materials for synthesis of pure organic

KISS ET AL.
11 of 15
compounds, in the presence of catalytic amounts of palla-
dium salts.[50] Indeed, treatment of compounds 2 and
3 with a catalytic amount of Pd(OAc)2 allowed isolation
in good yields of compounds 8 and 9.
In fact, treatment of compounds 2 and 3 with a cata-
lytic amount of Pd(OAc)2 allowed isolation in good yields
of 8 and 9 as colorless, crystalline solids. Their identity
was confirmed by multinuclear NMR and MS studies.
While our work was under preparation a report was pub-
lished[51] on unexpected boronic acid homocoupling
products, including compounds 8 and 9, formed during
Suzuki–Miyaura cross-coupling reactions of 2-bromo-1,-
3-(CF3)2C6H3Br with various arylboronic acids, using Pd
complexes. Our spectroscopic data fit very well with
those reported in this recent article. It should be noted
here that 8 was prepared in good yield (74%) by nickel-
catalyzed Ullmann coupling of 4-[(CH2O)2CH]C6H4Br,
but no spectroscopic characterization was provided.[52]
For compound 9, there were previously reported different
synthetic procedures based on (i) [4-(O=CH)C6H4]B (OH)2
via a Suzuki cross-homocoupling reaction mediated
by Pd(OAc)2,[37a,53a] or CuSO4[37b]; (ii) 4-[(CH2O)2CH]
C6H4I via an Ullmann cross-homocoupling reaction
using palladium on activated charcoal as catalyst,[53b]
or Suzuki-coupling reaction between 4-[(CH2O)2CH]
C6H4Br and [4-(O=CH)C6H4]B(OH)2 in the presence of
Pd(PPh3)4.[53c]
FIGURE 7 Molecular structure of [4ꢁ{(CH2O)2CH}C6H4]2
(8a). Thermal ellipsoids are drawn at 40% probability
The molecular structures of both compounds 8 and
9 were established by single-crystal X-ray diffraction.
Their molecular structures as ORTEP-like representa-
tions, with the atom numbering scheme, are depicted in
Figures 7 and 8. Selected interatomic distances and bond
angles are listed in Table 3.
The crystal of 8 contains four independent, very simi-
lar, molecules noted as 8a (Figure 7) to 8d. The molecules
FIGURE 8 Molecular structure of [4ꢁ(O=CH)C6H4]2 (9).
Thermal ellipsoids are drawn at 40% probability
TABLE 3 Selected interatomic
8aa
9
distances (Å) and angles (ꢄ) in
C1–C10
1.486(4)
1.430(3)
1.416(3)
1.416(3)
1.431(3)
105.5(2)
111.2(2)
111.2(2)
110
C1–C8
C7–O1
1.463(3)
1.222(2)
compounds 8 and 9
C7–O1
C7–O2
C16–O3
C14–O2
1.223(2)
C16–O4
O1–C7–O2
C4–C7–O1
C4–C7–O1
124.48(19)
118
C4–C7–O2
C4–C7–H7
C4–C7–H7
O3–C16–O4
106.2(2)
111.1(2)
111.1(2)
109
C13–C16–O3
C13–C16–O4
C13–C16–H16
Dihedral angles
{C1–C6}/{C10–C15}
{C1–C6}/{C7,O1,O2}
{C10–C15}/{C16,O3,O4}
{C7,O1,O2}/{C16,O3,O4}
C11–C14–O2
C11–C14–H14
124.35(19)
118
27.1
84.8
82.3
3.5
{C1–C6}/{C8–C13}
32.3
5.0
{C1–C6}/{C7,H7,O1}
{C8–C13}/{C14,H14,O2}
{C7,H7,O1}/{C14,H14,O2}
3.7
26.2
aThe molecular parameters are given for molecule 8a of the four independent molecules from the unit cell.

12 of 15
KISS ET AL.
[(E)-4-(RN=CH)C6H4]2Hg [R = 20-py (4), 40-py (5), 20-
pyCH2 (6), 40-pyCH2 (7)]. Compounds 4–7 might be used
as divergent organometallic tectons in crystal engineering
of coordination polymers as previously shown.
Oxidative demercuration reactions of 2 and 3 in pres-
ence of catalytic amounts of palladium(II) acetate affords
[4-{(CH2O)2CH}C6H4]2 (8) and [4-(O=CH)C6H4]2 (9),
respectively. This approach represents an alternative syn-
thetic pathway for the two useful organic derivatives.
FIGURE 9 View along a axis of the supramolecular chain
polymer association build through OꢀꢀꢀHcarbonyl interactions in the
crystal of [4-(O=CH)C6H4]2 (9) (only hydrogen atoms involved in
intermolecular interactions are shown) [symmetry equivalent
atoms (0.5–x, 1–y, 0.5+z) and (0.5–x, 1–y, ꢁ0.5+z) are given by “a”
and “b”]
labeling is consistent to the atom labels. Two
molecules in the asymmetric unit (8a and 8c) are com-
plete, whereas the other two (8b and 8d) lie on inversion
centers. The molecular parameters in Table 3 refer only
to molecule 8a.
ACKNOWLEDGMENT
This work was supported by the National Council for
Scientific Research (Consiliului National al Cercetarii
Stiintifice) (PN-II-ID-PCCE-2011-2-0050).
In the molecules located on the inversion centers, the
torsion angles between the aryl groups are 180ꢄ, in con-
trast to those complete (8a: 27.1ꢄ, 8c: 29.4ꢄ). The C–C
bond lengths between the two aryl groups are slightly
longer in the residues with planar diaryl unit (8b: 1.496
(3), and 8d: 1.497(4) Å), than in 8a or 8d (1.486(4), and
1.473(4) Å, respectively).
AUTHOR CONTRIBUTIONS
Levente Kiss: Investigation; methodology. Alexandra
Pop: Data curation; formal analysis. Shova Sergiu: Data
curation; formal analysis. Ciprian Rat: Project adminis-
tration; visualization. Cristian Silvestru: Project admin-
istration; supervision.
In the crystal of 8, the four independent molecules
are connected through a network of C–HꢀꢀꢀO (range 2.31–
2.51 Å, cf. ΣrvdW(O,H) 2.70 Å[46]) and C–Hꢀꢀꢀπ (range
2.55–2.93 Å, cf. HꢀꢀꢀArcentroid contacts shorter than
3.1 Å[48]) interactions into a complex 3-D supramolecular
architecture (for details, see Figure S51).
In the crystal of 9, the molecules are associated
through C–HcarbonylꢀꢀꢀO hydrogen bonds [C(14b)–H
(14b)carbonylꢀꢀꢀO(1) 2.44 Å] into chain polymers (Figure 9),
which are connected into a 2-D layer through additional
inter-chains C–HcarbonylꢀꢀꢀO interactions [C(7a00)–H
(7a00)carbonylꢀꢀꢀO(2) 2.51 Å] (see Figure S52). Further, wea-
ker inter-layers C–HarylꢀꢀꢀO contacts (range 2.55–2.60 Å)
resulted in a 3-D supramolecular association (for details,
see Figure S53).
DATA AVAILABILITY STATEMENT
Data are available upon request from the authors. CCDC-
2027584 for 3, 2027585 for 5ꢀ3H2O, 2027586 for 6,
2027587 for 8 and 2027588 for 9 contain the supplemen-
tary crystallographic data for this contribution. These
data can be obtained free of charge from the Cambridge
Crystallographic Data Centre (via www.ccdc.cam.ac.uk/
data_request/cif). Represented in the supporting informa-
tion are the 1H, 13C{1H} and 199Hg{1H} (where applicable)
NMR spectra of compounds 1–9 (Figures S1–S27), the
high-resolution mass spectra (Figures S28–S35), and
the IR spectra (Figures S36–S43) of compounds 2–9.
ORCID
Levente Kiss https://orcid.org/0000-0002-9811-5679
Alexandra Pop https://orcid.org/0000-0002-2355-3682
Sergiu Shova https://orcid.org/0000-0002-1222-4373
Ciprian I. Raț https://orcid.org/0000-0002-1154-8130
Cristian Silvestru https://orcid.org/0000-0001-5124-
9525
It is worth to mention here the recent report of the
crystal structure of a supramolecular complex which con-
sists of an octacarbene-based tetranuclear silver(I)
metallacage and a molecule of 9 located outside of the
cavity and connected to it through multiple C–HꢀꢀꢀO
interactions.[54]
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SUPPORTING INFORMATION
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How to cite this article: L. Kiss, A. Pop, S. Shova,
C. I. Raț, C. Silvestru, Appl Organomet Chem 2021,
e6339. https://doi.org/10.1002/aoc.6339