Intermetallic bonds in metallophilic mercuraazametallamacrocycles of synthetic design

Article abstract of DOI:10.1021/om100297v

22-Membered mercuraazametallamacrocycles 6, 7, and 12 have been synthesized by dipodal condensation (2 + 2) of bis(o-formylphenyl)mercury (11) and 1,2-disubstituted amines. Reduction of macrocycle 6 with sodium borohydride afforded novel 11-membered mercuraazametallamacrocycle 13. Macrocycle 6, when treated with [Cu(CH₃CN)₄]ClO₄ and Cu(OCOCH ₃)₂/NH₄PF₆, formed orange-colored Cu^I complexes 14 ([6·Cu]ClO₄) and 15 ([6·Cu]PF₆), respectively, whereas red-colored complex 16 ([12·Cu]ClO₄) was obtained from the reaction of 12 with [Cu(CH₃CN)₄]ClO₄. Similarly, complexes 17 ([6·Ag]ClO₄) and 18 ([6·Ag]PF₆) were synthesized by the reaction of 6 with the corresponding silver salts. The reaction of 6 with Hg(OCOCH₃)₂/NH₄PF ₆ led to the formation of hydroxo-bridged complex 19. The reaction of macrocycle 7 with Pd(C₆H₅CN)₂Cl₂ gave access to novel complex 9a. The macrocycles and the complexes have been characterized by elemental analysis, NMR (¹H, ¹³C, ¹⁹⁹Hg), fluorescence spectroscopy, and cyclic voltammetry. The molecular structures of organomercury precursors Hg{1-C₆H ₄-2-(CH₂OH)}₂ (10) and Hg{1-C₆H ₄-2-(CHO)}₂ (11) and macrocycles 6, 7, and 12 show almost linear geometry around mercury; however, 13 shows a bent structure, i.e., significant deviation of the C-Hg-C angle from linearity. 22-Membered mercuraazametallamacrocycles 6, 7, and 12 are stabilized by secondary Hg...N intramolecular interaction and have an hour-glass -like conformation. The molecular structures of 14, 17, and 9a showed metallophilic interactions. The metal ions (Cu^I and Ag^I) are coordinated not only to the four nitrogens but also to two mercury atoms, forming a distorted octahedral geometry around the metal ions.

Full text of DOI:10.1021/om100297v

Organometallics 2010, 29, 4265–4275 4265
DOI: 10.1021/om100297v
Intermetallic Bonds in Metallophilic Mercuraazametallamacrocycles
of Synthetic Design
Upali Patel,† Sagar Sharma,† Harkesh B. Singh,*,† Sandip Dey,‡ Vimal K. Jain,‡
§
Gotthelf Wolmershauser, and Ray J. Butcher
€
†Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India,
‡Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India, §Fachbereich Chemie,
Universita€t Kaiserslautern, Postfach 3049, Kaiserslautern 67653, Germany, and Department of Chemistry,
Howard University, Washington, D.C. 20059
Received April 13, 2010
22-Membered mercuraazametallamacrocycles 6, 7, and 12 have been synthesized by dipodal
condensation (2 þ 2) of bis(o-formylphenyl)mercury (11) and 1,2-disubstituted amines. Reduction of
macrocycle 6 with sodium borohydride afforded novel 11-membered mercuraazametallamacrocycle
13. Macrocycle 6, when treated with [Cu(CH3CN)4]ClO4 and Cu(OCOCH3)2/NH4PF6, formed
orange-colored CuI complexes 14 ([6 Cu]ClO4) and 15 ([6 Cu]PF6), respectively, whereas red-
3
3
colored complex 16 ([12 Cu]ClO4) was obtained from the reaction of 12 with [Cu(CH3CN)4]ClO4.
Similarly, complexes 17 ([6 Ag]ClO4) and 18 ([6 Ag]PF6) were synthesized by the reaction of 6 with
3
3
3
the corresponding silver salts. The reaction of 6 with Hg(OCOCH3)2/NH4PF6 led to the formation of
hydroxo-bridged complex 19. The reaction of macrocycle 7 with Pd(C6H5CN)2Cl2 gave access to
novel complex 9a. The macrocycles and the complexes have been characterized by elemental analysis,
NMR (1H, 13C, 199Hg), fluorescence spectroscopy, and cyclic voltammetry. The molecular structures
of organomercury precursors Hg{1-C6H4-2-(CH2OH)}2 (10) and Hg{1-C6H4-2-(CHO)}2 (11) and
macrocycles 6, 7, and 12 show almost linear geometry around mercury; however, 13 shows a bent
structure, i.e., significant deviation of the C-Hg-C angle from linearity. 22-Membered mercura-
azametallamacrocycles 6, 7, and 12 are stabilized by secondary Hg N intramolecular interaction
3 3 3
and have an “hour-glass”-like conformation. The molecular structures of 14, 17, and 9a showed
metallophilic interactions. The metal ions (CuI and AgI) are coordinated not only to the four
nitrogens but also to two mercury atoms, forming a distorted octahedral geometry around the metal
ions.
Introduction
metallamacrocycles incorporate main group elements such as
tin,2 silicon,3 boron,4 germanium,5 and mercury.6-12 Among
these, the polydentate organomercury macrocycles have
attracted considerable current interest. The organomercury
macrocycles include trimeric-perfluoro-o-phenylenemercury
1,6 [9]mercuracarborand-3 2,7 [12]mercuracarborand-4,7 a
24-membered macrocyclic perfluoroglutarate derivative,8a,b
Metallamacrocycles formed by the self-assembly of Lewis
acids and bases have been studied extensively.1 However, the
metallamacrocycles, where the metal is embedded into the
macrocycle in a preorganized framework through a covalent
linkage, have received less attention. Only a few such exam-
ples have been reported in the literature. Generally, these
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*To whom correspondence should be addressed. E-mail: chhbsia@
chem.iitb.ac.in.
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Published on Web 09/09/2010
pubs.acs.org/Organometallics

4266 Organometallics, Vol. 29, No. 19, 2010
Patel et al.
and a cyclic pentameric [(CF3)2CHg]5 macrocycle.9 Due to
the electrophilic nature of the metal ions, mercuramacro-
cycles act as sensors,10 catalysts,11 and anion receptors.12
The binding of electron-rich species, e.g., anions,7-12 solvent
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interactions between both chemically similar and different
closed-shell metal ions. Compounds with closed-shell
d10-d10/d8/s2 interactions have attracted considerable cur-
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tures, and unusual chemical and physical properties.15 The
types of forces that are involved in the binding of closed-shell
atoms/ions have been a subject of considerable debate.
Theoretical studies suggest that the dispersion forces magni-
fied by relativistic effects16 play a crucial role when these
heavy closed-shell metal ions or atoms are involved in
interactions. The nature of these weak interactions has also
been interpreted in terms of an acid-base or donor-acceptor
interaction.17 As compared to the homometallic18 closed-
shell interactions, heterometallic interactions are rare.19
Furthermore, there are relatively very few of them that
contain three or more consecutive closed-shell ions/atoms.16
In this regard the contributions by the groups of Catalano,20
Braunstein,21 and Gabbaı17 are notable. Catalano and co-
workers20 have reported encapsulation of metal ions or atoms
in metallacryptands (3). These are formed by self-assembly,
resulting in different types of closed-shell d10 d10 interac-
3 3 3
tions. Braunstein and co-workers21 have demonstrated the
capture of metal ions/atoms by a heterometalloligand (4)
leading to heterometallic d10
d
10 interactions. Gabbaı and
3 3 3
co-workers have recently reported a PdII HgII PdII
3 3 3
3 3 3
closed-shell interaction, which is formed by a d8 d10 inter-
molecular interaction (5).17
3 3 3
We envisaged that if the mercuramacrocycles contained
several strong Lewis base donors in addition to the Lewis
acidic organomercury, the metalloligands could prove sui-
table hosts for the closed-shell d10/d8 metal ions and may lead
The interaction of metal ions with these metallamacro-
cycles would normally be expected to be repulsive due to the
electrostatic repulsion between the positively charged metal
ions. However, recent experimental and theoretical investi-
to heterometallic systems with metal metal interaction.
3 3 3
The attractive interaction of the bases with the guest metal
ions should facilitate interaction of the guest ions with metal
atoms of the host metallamacrocycle. Accordingly, we de-
signed and synthesized mercuraazamacrocycle 6. The CuI
gations have revealed the presence of weak metal metal
3 3 3
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Article
Organometallics, Vol. 29, No. 19, 2010 4267
Scheme 1. Synthetic Route to the Macrocycles 6, 7, and 12
the PdII ion with 7 led to a facile transmetalation and the
formation of a novel helical trimetallic complex (9) with a
HgII PdII HgII interaction.22b Extending the concept,
Scheme 2. Synthesis of 11-Membered Mercuraazamacrocycle 13
3 3 3
3 3 3
we now report the synthesis and characterization of some
new Schiff base metallophillic mercuraazamacrocycles and
their metal complexes with CuI, AgI, PdII, and PtII that exhi-
bit d10 d10/d10 d8 interactions. In particular, we draw
3 3 3
3 3 3
and hexane; however, they were highly soluble in chloroform
and dichloromethane and moderately soluble in acetone,
acetonitrile, DMSO, and DMF.
attention to HgII AgI HgII as a closed-shell interaction
3 3 3
3 3 3
involving three atoms in a colinear bond with short inter-
nuclear distances. The metal metal interactions have been
3 3 3
In order to get a more stable and flexible tetraamino
derivative of 6, its reduction with an excess of NaBH4 was at-
tempted. The reduction resulted in the formation of an
unexpected reduced macrocycle, 13 (Scheme 2). The 11-
membered macrocycle presumably results from the cleavage
of the Hg-C bond during reduction. This type of demer-
curation and skeletal rearrangement have been earlier obser-
ved in the reduction of organomercury compounds.25 Com-
pound 13 was recrystallized from a dichloromethane and
confirmed by X-ray crystallography. We also describe our
attempts to synthesize the a trimetallic complex with a
HgII HgII HgII closed-shell interaction, which furn-
3 3 3
3 3 3
ished a cleaved compound with a Hg-O-Hg bond. The
reduction of the mecuraazamacrocycle 6 with NaBH4 is
shown to furnish an 11-membered mercuraazamacrocycle,
unprecedented in its C-Hg-C angle of 135.5ꢀ.
hexane mixture as square-shaped crystals. The IR and 1H, 13
C
Results and Discussion
and 199Hg NMR spectroscopic data confirm the total reduc-
tion of the Schiff base macrocycle. ESI-MS and X-ray crys-
tallographic studies (vide infra) unambiguously establish the
formation of the 11-membered reduced macrocycle with a
significantly bent C-Hg-C angle (see Figure 6).
The reaction of ligand 6 with Cu(CH3CN)4ClO4 and Cu-
(OCOCH3)2/NH4PF6 afforded orange-colored CuI com-
plexes 14 ([6 CuI]ClO4) and 15 ([6 CuI]PF6) (Scheme 3).22a
Synthesis of the mercuraazamacrocycles and their precur-
sors is outlined in Scheme 1. Benzyl alcohol, upon lithiation
followed by the reaction with HgCl2 at -78 ꢀC, gave bis-
(o-hydroxymethylphenyl)mercury (10). Bis(o-formylphe-
nyl)mercury (11) was obtained by the oxidation of 10 with
PCC (pyridinium chlorochromate). The synthesis of 11 has
been earlier reported by Flower et al.23 and Rickard et al.24
by slightly different routes. In our modification, coupling of
the organomercury halide with NaI and protection of the
alcohol groups is avoided. In an attempt to synthesize the
mercurous analogue of 11, when the lithiated benzyl alcohol
was reacted with Hg2Cl2, the reaction afforded only 10.
Reactions of 1,2-diaminoethane, 1,2-diaminobenzene, and
trans-1,2-diaminocyclohexane with 11 afforded ligands 6, 7,
and 12, respectively, in good yields without recourse to a
metal ion template or high dilution techniques. The synthesis
of macrocycle 7 required refluxing, whereas 6 and 12 formed
3
3
The reaction of ligand 12 with Cu(CH3CN)4ClO4 in a 1:1
ratio under nitrogen gave the red-colored complex 16
([12 CuI]ClO4), which showed a base peak at m/z 1041
3
corresponding to [M - ClO4]þ in the ES-MS. Complex 16
is soluble in chloroform and dichloromethane. Upon addi-
tion of solvents such as acetonitrile, acetone, DMF, and DMSO,
the complex decomposes to give a white residue. Complexes 14,
15, and 16 are soluble in acetonitrile. The reaction of ligand 6
with AgClO4 or AgNO3/NH4PF6 afforded complexes 17
([6 Ag]ClO4) and 18 ([6 Ag]PF6), respectively. In the ES-
3
3
at room temperature. Secondary intramolecular Hg
N
3 3 3
MS both the complexes exhibited a peak at m/z 977 corre-
sponding to [M - X]þ (X = ClO4-, PF6-). The reactions of
CuII and AgI salts with 12 were unsuccessful. Although the
cavity size of 12 is nearly the same as that of 6, the conforma-
tional constraints introduced by use of a cyclic diamine may
prevent coordination of Ag(I) with 12. It is interesting to note
coordination (vide infra) plays an important role in the
formation of the (2 þ 2) macrocycles. In general, all these
compounds show poor solubility in solvents such as pentane
€
(22) (a) Patel, U.; Singh, H. B.; Wolmershauser, G. Angew. Chem.,
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Butcher, R. J. Angew. Chem., Int. Ed. 2009, 48, 1987–1990.
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Warren, J. E.; McGown, A. T. Inorg. Chem. 2002, 41, 1907–1912.
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Wright, L. J. J. Organomet. Chem. 2001, 619, 293–298.
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Tetrahedron Lett. 1998, 39, 59–62.

4268 Organometallics, Vol. 29, No. 19, 2010
Patel et al.
Scheme 3. Synthesis of CuI and AgI Complexes of 6 and 12
Table 1. 199Hg NMR Chemical Shifts (in ppm) of Synthesised
Compounds
compound
199Hg NMR
compound
199Hg NMR
Ph2Hg
Ph2Hg
10
11
6
12
7
13
-745a
-806b
-690b
-750a
-690a
-667a
-750a
-572a
14
15
16
17
18
19
20
21
-559b
-537c
-495a
-552c
-555c
-1013b
-1045b
-1043b
a CDCl3. b d6-DMSO. c CD3CN.
The reactions of macrocycles 6 and 7 with Pd(C6H5CN)2-
Cl2/Pt(COD)Cl2 in dichloromethane led to the formation of
trimetallic complexes 20, 21, and 9, respectively, having
HgII PdII/PtII HgII interactions (Scheme 5).22b The
3 3 3
3 3 3
ES-MS spectra of 20 and 21 showed peaks for [M - Cl]þ
at m/z 1011 and 1100, respectively. The recrystallization of 9
with acetone gave a pseudopolymorph (9a) of the complex.
All the complexes are quite stable in air. However, these are
stable only for a few days in solution, after which they begin
to decompose.
Scheme 4. Synthesis of Hydroxo-Bridged Compound 19
In solution, the ligands and the complexes were characterized
by UV-vis, fluorescence, cyclic voltammetry, and detailed
NMR (1H, 13C, 199Hg) studies. The 199Hg NMR data for all
the compounds are given in Table 1 and are reported relative
to diphenyl mercury as external standard (-745 ppm). The
199Hg NMR chemical shifts are sensitive to the solvent and
also to the electronic and steric substituents on mercury.27
The 199Hg signals for the ligands 10, 6, and 12 are shifted
downfield relative to Ph2Hg. This shift may be attributed to
the þI effect of -CH2OH and the imino groups. A weak
Scheme 5. Synthesis of 9/9a, 20, and 21
intramolecular Hg O/N interaction is also possible in
3 3 3
solution (vide infra). In the case of the imine derivatives 6
and 12, such interactions are quite prominent in the solid
state. Although the structure of 11 indicates a weak interac-
tion between -CHO and Hg, in the solid state (vide infra),
the 199Hg NMR data are not indicative of any significant
Hg OCH interaction. This may be due to two opposing
3 3 3
effects, viz., the -I of -CHO and an intramolecular Hg
O
3 3 3
interaction. Interestingly, the 199Hg signal for 13 is observed
at ca. -572 ppm, which is downfield shifted by ∼120 ppm
with respect to the parent compound 6, indicating a much
stronger coordination between Hg and N. The structural
analysis (vide infra) of 13 further supports a change in the
coordination geometry around Hg with the formation of
strong Hg-N bonds. The 199Hg NMR signal of 16 at -495
ppm is ∼220 ppm upfield shifted as compared to the free
ligand 12 (Table 1). Complexes 17 and 18 exhibited a single
peak at around -552 ppm in the 199Hg NMR spectra,
whereas compound 19 showed a peak at -1013 ppm in the
199Hg NMR spectrum. Also the 199Hg NMR signals for 20
and 21 appear at -1045 and -1043 ppm, respectively (Table 1).
Such a large downfield shift in the 199Hg NMR with respect
to the simple metal complexes 14-16 is indicative of the
formation of organomercury chloride. However, such a
downfield shift in a polar solvent such as DMSO-d6 should
be taken with caution, as the observed chemical shift differ-
ences may be also due to the coordination of polar solvent
molecules to the Hg atom in solution.
that the reaction of 6 with CuII afforded the reduced CuI
complex and not the expected CuII complex. This reduction
is probably accompanied by the oxidation of methanol
present in the system to either formaldehyde or formic acid;
however, attempts to characterize the oxidized species were
not successful. Lai and co-workers26 have observed a similar
reduction of a CuII ion when treated with a quinquedentate
macrocycle, and they suggested that the autoreduction was
due to the electron-donating properties of the ligand or the
geometry of the complex formed.
A similar reaction of Hg(OCOCH3)2/NH4PF6 with 6 to
get the HgII analogue, with a HgII HgII HgII interac-
3 3 3
3 3 3
tion, led to the cleavage of the macrocycle to give the cationic
complex 19, where the hydroxide ion is bridged between the
two mercury atoms (Scheme 4). In view of the identical mass
and number of electrons for hydroxide ion and fluoride ion,
the possibility of the fluoro-bridged complex was also con-
sidered. However, this could be ruled out on the basis of the
19F NMR spectrum, which showed only one peak for the
PF6- anion.
(26) Vetrichelvan, M.; Lai, Y.; Mok, K. F. Dalton Trans. 2003, 295–
303.
(27) Wrackmeyer, B.; Contreras, R. Annu. Rep. NMR Spectrosc.
1992, 24, 267–329.

Article
Organometallics, Vol. 29, No. 19, 2010 4269
Figure 1. Crystal structure of 10 (50% ellipsoids). Selected
bond lengths (A) and angles (deg): Hg-C1B 2.085(4), Hg-C1A
2.089(4), Hg-O1A, 3.098(4), Hg-O1B 3.232(4), C1B-Hg-
C1A 177.88(16).
Figure 4. Crystal structure of 7 (50% ellipsoids, H atoms
omitted for clarity). Selected bond lengths (A) and angles
(deg): Hg1-C1A 2.079(5), Hg1-C20B 2.073(5), Hg1-N1A
2.750(4), Hg2-N1B 2.760(4), C1A-Hg1-C20B 177.4(2),
C1B-Hg2-C20A 175.07(19), C20A-Hg2-N2A 71.93(17),
C20A-Hg2-N1B 109.08(17), N2A-Hg2-N1B 143.35(12).
Figure 2. Crystal structure of 6 (50% ellipsoids, H atoms
omitted for clarity). Selected bond lengths (A) and angles
(deg): Hg1-N1B 2.65(2), Hg1-N1A 2.70(2), Hg2-N2B 2.65(3),
Hg2-N2A 2.72(2), C1A-Hg1-C1B 175.2(7), C16A-Hg2-
C16B 175.1(7), N1A-Hg1-N1B 107.6(7), N2A-Hg2-N2B
108.6(7).
Figure 5. Crystal structure of 12 (50% ellipsoids, H atoms
omitted for clarity). Selected bond lengths (A) and angles
(deg): Hg-C10A 2.077(3), Hg-C10B 2.077(3), Hg-N1A
2.676(3), Hg-N1B 2.716(2), C10A-Hg-C10B 177.89(11),
C10A-Hg-N1A 74.49(10), C10A-Hg-N1B 108.20(9),
N1A-Hg-N1B 109.51(7).
For complex 16, by exciting at 475 nm in the solid state, the
emission peak is obtained at 530 nm. The cyclic voltam-
metric study of 16 shows a quasi-reversible system with
oxidation at 0.807 V and reduction at 0.476 V with a ΔE of
0.331 V. The cyclic voltammogram of 17, as expected for
AgI complexes, shows irreversible oxidation at 0.364 V and
reduction at 0.100 V with a ΔE of 0.264 V, and for 18 the
oxidation occurs at 0.124 V and reduction at 0.397 V, with a
ΔE of 0.273 V.
Molecular structures of 10, 11, 6, 7, 12, 13, 17, 19, and 9a
are depicted in Figures 1-11. Compounds 10 and 11 crystal-
lized in the monoclinic crystal system and triclinic system,
respectively. The C-Hg-C bond angles for 10 and 11 are
almost linear, with bond angles of 177.88(16)ꢀ (Figure 1) and
179.0(6)ꢀ, respectively (Figure S25). Compound 10 exhibits
weak intramolecular interactions between mercury and oxy-
Figure 3. Packing diagram of 6 showing intramolecular
Hg Hg interaction.
3 3 3
The electronic spectra of macrocycles 6, 7, 12, and 13 and
the complexes were recorded in solution and in the solid
state. In solution the macrocycles exhibit a high-energy
feature at ∼290 nm corresponding to the π-π* transition.
Macrocycle 7 shows an additional absorption at 375 nm
corresponding to the n-π* transition. In the solid state 6, 12,
and 13 exhibit a π-π* absorption at ∼336 nm, whereas 7
shows an absorption at 418 nm. Similar to the copper
complexes of 6,22a complex 16 also shows a metal to ligand
charge-transfer band at 450 nm in solution and at 475 nm in
the solid state in addition to the high-energy transition at
∼336 nm. Palladium complex 20 has a broad absorption in
the range 460-489 nm in the solid state. Macrocycles 6, 7,
and 12 are found to be luminescent. Macrocycles 6 and 12,
upon excitation at 336 nm, show emission peaks at 422, 460,
and 530 nm in the solid state. Macrocycle 7 shows strong
emission peaks at 484 and 524 nm when excited at 418 nm.
gen of the hydroxyl group with Hg O distances of 3.098(4)
3 3 3
and 3.232(4) A, respectively. The distances are greater than
the sum of the covalent radii;28 however, these are close to the
sum of the van der Waals radii of mercury (1.73-2.05 A29a-c
)
and oxygen (1.52 A29d). For compound 11, the Hg1 O11
and Hg1 O12 distances are 2.870(14) and 2.855(14) A,
3 3 3
3 3 3

4270 Organometallics, Vol. 29, No. 19, 2010
Patel et al.
Figure 6. Crystal structure of 13 (50% ellipsoids). Selected
bond lengths (A) and angles (deg): Hg1-C1 2.079(7), Hg1-N1
2.684(5), C1-Hg1-C1 135.5(3), C1-Hg1-N1 125.57(17),
N1-Hg1-N1 54.0(2).
Figure 9. Crystal structure of cation 19 (50% ellipsoids, H
atoms and anion omitted for clarity). Selected bond lengths
(A) and angles (deg): Hg1-C1, 2.042(8), Hg1-N1 2.669(8),
Hg1-O1 2.069(6), Hg1-O1-Hg1 109.3(4), C1-Hg1-N1
74.9(3), C1-Hg1-O1 178.5(3).
Mercuraazamacrocycle 6 crystallizes in the monoclinic
crystal system. To our knowledge, this is the first single-
crystal X-ray structure (Figure 2) of a metallamacrocycle
containing covalently linked mercury and nitrogen in its
molecular framework. The geometry about each mercury
atom is nearly linear. The —C1A-Hg1-C1B (175.2(7)ꢀ) is
only slightly deviated from linearity. The notable feature of
the molecular structure is the presence of the intramolecular
interaction of the imine nitrogens with the Hg1 and Hg2
atoms. All four nitrogen atoms interact with the two mercury
atoms, having bond distances [Hg1-N1B 2.65(2) A, Hg1-
N1A 2.70(2) A, Hg2-N2B 2.65(3) A and Hg2-N2A
2.72(2) A] that are much less than the sum of the van der
Waals radii,29 but close to the sum of covalent radii, i.e.,
2.03 A (Hg 1.32 þ N 0.71 A).
Figure 7. Crystal structure of cation 17 (50% ellipsoids, H
atoms and anion omitted for clarity). Selected bond lengths
(A) and angles (deg): Hg1-Ag 2.8741(7), Hg2-Ag 2.9472(7),
Ag-N1A 2.222(6), Ag-N1B 2.380(6), Ag-N2A 2.502(7),
Ag-N2B 2.241(7), Hg1-Ag-Hg2 166.50(3), C1B-Hg1-C1A
178.9(3), C16A-Hg2-C16B 176.3(3).
The observed Hg-N distances are shorter than the Hg-N
distance observed for related acyclic Schiff base compounds
of 11 with aromatic monoamines (2.85-2.71 A).23 These are
also less than the Hg-N distances (2.860-3.126 A) observed
in σ-alkynyl complexes of orthomercurated Schiff bases of
substituted benzylideneanilines and anthracenylmethylene-
anilines.30 The Hg-N intramolecular interactions probably
force the macrocycle into an “hour-glass” conformation. The
transannular distance between two Hg atoms is 4.992(2) A. The
packing diagram reveals the presence of the intermolecular
d10 d10 interaction between Hg1 and Hg2# (3.1643(14) A)
3 3 3
(Figure 3). This distance is longer than the intermolecular
Hg Hg distance of 3.101(2) A reported for methyl(2-
3 3 3
mercapto-4-methylpyrimidinato)mercury(II).18j,29b
Compound 7 crystallizes in the monoclinic crystal system
and in the P21/c space group. One of the important features
of the mercuracycle 7 is the short distance between Hg1 and
Hg2, which is 3.654 A (Figure 4).
Figure 8. Crystal structure of cation 14 (30% ellipsoids, H
atoms and anion omitted for clarity). Selected bond lengths
(A) and angles (deg): Hg1-Cu1 2.9212(7), Hg2-Cu1 2.9198(7),
Cu1-N1 2.114(4), Cu1-N2 2.071(5), Cu1-N3 2.100(4), Cu1-
N(4) 2.062(4), Hg2-Cu1-Hg1 177.88(3), C27-Hg2-C28
177.23(18), C11-Hg1-C12, 177.80(18).
The distance between Hg1 and Hg2 in 7 is much less than
the Hg Hg distance in 6 (4.992 A) as well as in 12 (4.924 A).
3 3 3
All four nitrogen atoms strongly interact with the two mer-
cury atoms, having bond distances Hg1 N1A (2.750(4) A),
respectively, which are comparable to the reported value
of 2.827(7) A for HgCl{1-C6H4-2-(CHO)} (for details see
Figure S25 in the Supporting Information).24
3 3 3
(29) (a) Canty, A. J.; Deacon, G. B. Inorg. Chim. Acta 1980, 45, L255–
€
L227. (b) Pyykko, P.; Straka, M. Phys. Chem. Chem. Phys. 2000, 2, 2489–
2493. (c) Batsanov, S. S. Inorg. Mater. 2001, 36, 1031–1046. (d) Bondi, A.
J. Phys. Chem. 1964, 68, 441–451.
(30) Wong, W.-Y.; Lu, G.-L.; Liu, L.; Shi, J.-X.; Lin, Z. Eur. J. Inorg.
ꢀ
ꢀ
(28) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.;
a, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans.
ꢀ
Echeverrı
´
2008, 2832–2838.
Chem. 2004, 2066–2077.

Article
Organometallics, Vol. 29, No. 19, 2010 4271
Figure 10. (a) Crystal structure of 9a (50% ellipsoids, one of the molecules in the asymmetric unit is shown, H atoms and the other three
molecules in the asymmetric unit are omitted for clarity). Selected bond lengths (A) and angles (deg): Hg1C-Pd1C 3.1496(9),
Hg2C-Pd1C 3.2201(9), Hg1C-N4C 2.777(9), Hg2C-N2C 2.663(10), Pd1C-N1C 2.158(8), Pd1C-N3C 2.178(11), Hg1C-
Pd1C-Hg2C 162.22(3), C40C-Hg1C-Cl1C 165.8(3), C20C-Hg2C-Cl2C 168.3(4). (b) Simplified ORTEP picture of 9a showing
a helical structure.
nitrogen atoms (Figure 6). The most noteworthy feature of
the structure is the nonlinearity of the geometry about
mercury. In a recent review on Lewis acid behavior of
organomercurials, Gabbaı and co-workers13f have noted
that a nearly linear C-Hg-C geometry in organomercury
adducts indicates an extremely weak ligandfHg interaction.
This behavior has been interpreted in terms of the unfavorable
energy of mercury orbitals for overlap with donor orbitals. The
observed bond angle of C1-Hg1-C1 (135.5(3)ꢀ) in 13 devi-
ates significantly from linearity and is the maximum obser-
ved for any diorganomercury derivative.
This deviation is significantly greater than the deviation
observed for the chloride complex of [12]mercuracarborane-
4 (162ꢀ).31 In diorganomercury compounds, HgII can be also
considered as sp hybridized (although participation of d
orbitals is also expected) and forms two linear covalent
bonds while retaining two empty and mutually perpendi-
cular p-orbitals. The two filled orbitals of two nitrogen
Figure 11. Hg π interaction in acetone solvate of 9a.
3 3 3
atoms interact with the two empty orbitals of mercury. The
Hg-N bond distance observed is 2.684(5) A. Interestingly,
Hg1 N2B (2.777(4) A), Hg2 N2A (2.772(4) A), and
3 3 3
3 3 3
3 3 3
the Hg-N distances are on the same order as those ob-
served in macrocycles 6 and 12. Thus, the significant
deviation of the C-Hg-C bond angle in 13 may also be
due to the small size of the ring. The deviation of the
C-Hg-C bond from linearity requires mixing of some
additional p-character into the sp-hybrid mercury orbitals
involved in bonding to aromatic carbon atoms. The C7-
N1 and C8-N1 bond distances are 1.460(9) and 1.487(10)
A, respectively, compared to the CdN bond distances,
∼1.30 A,28 in 6, confirming complete reduction of the
CdN bonds. Compound 13 also exhibits a weak intra-
Hg2 N1B (2.760(4) A). The C1A-Hg1-C20B bond angle
is almost linear, at 177.4(2)ꢀ. The molecular structure depicts
the mutual stacking of the phenyl rings attached to mercury
atoms.
Macrocycle 12 crystallizes in the orthorhombic crystal
system. Although the reaction of bis(o-formylphenyl)-
mercury 11 with racemic trans-1,2-cyclohexane diamine can give
product 12 as three different stereoisomers (viz., (R,R)-(R,
R); (S,S)-(S,S); (R,R)-(S,S)), the crystal structure shows the
presence of a 1:1 ratio of (R,R)-(R,R) and (S,S)-(S,S) isomers
formed from the (R,R) and (S,S) enantiomers of the diamine,
respectively. Here also the geometry around each Hg atom is
nearly linear, with an intramolecular interaction between the
imine nitrogen atoms and Hg atoms (Figure 5). All four
nitrogens interact with the two mercury atoms, having bond
distances Hg-N1B of 2.716(2) A and Hg-N1A of 2.676(3) A.
The —C10A-Hg-C10B is almost linear (177.89(11)ꢀ). The
deviation of the C-Hg-C angle from linearity is more in the
case of 6 as compared to 12. The transannular distance between
the two Hg atoms is 4.924(0) A.
molecular C-H Hg van der Waals interaction at a distance
3 3 3
(3.131 A) close to the sum of the van der Waals radii of Hg
and H.
Complex 17 crystallizes in the monoclinic crystal system.
The silver ion is coordinated to four nitrogen and two
mercury atoms of the macrocycle, forming a distorted octa-
hedral geometry (Figure 7). To our knowledge, this is the
first structural example of the encapsulation of a silver ion in
a metallamacrocycle cavity. In the literature there are very
Compound 13 crystallizes in the orthorhombic crystal
system and space group Cmc21. The geometry around Hg
is distorted tetrahedral, where Hg is coordinated to two sp3
(31) Yang, X.; Knobler, C. B.; Hawthorne, M. F. Angew. Chem., Int.
Ed. Engl. 1991, 30, 1507–1508.

4272 Organometallics, Vol. 29, No. 19, 2010
Patel et al.
few reports of a six-coordinated AgI ion.32 The Hg1-Ag-Hg2
bond angle is 166.50(3)ꢀ and deviates from linearity. The
Hg1 Ag (2.8741(7) A) and Hg2 Ag (2.9472(7) A) dis-
and co-workers.8c However, this distance is longer than the
Hg-O distance in the hydrated [(PhHg)2OH]þ cation.34 The
observed distance is close to the sum of covalent radii (Hg
1.32 A þ O 0.66 A = 1.98 A). The geometry around the
oxygen atom in 19 is bent, with the Hg1-O-Hg1 bond angle
being 109.3(4)ꢀ. This value is larger than the Hg-O-Hg
value reported for [(PhHg)2OH]þ (126ꢀ), but is smaller than
the value of 119.8(4)ꢀ reported for [(1,7-C2B10H10)2Hg4(OH)2]-
[CF3CO2]2.33b Two fluoro groups of the anion are involved in
hydrogen bonding with the hydrogen of the μ-hydroxo group
3 3 3
3 3 3
tances are less than the sum of the van der Waals radii of Ag
(1.72) þ Hg (1.73-2.05 A) and close to the sum of Hg-Ag
covalent radii (Hg 1.32 A þ Ag 1.45 A).28 The observed
Hg-Ag distances indicate a strong HgII AgI d10-d10
3 3 3
metallophilic interaction. The observed Hg Ag bond dis-
tances are less than the nonbonded Hg Ag distances
3 3 3
3 3 3
(3.101(1), 3.386(1) A) in [HgAg2(mes)2(O3SCF3)2]2.19d They
are comparable to Hg-Ag distances of 2.805(2) and 2.85(3)
with an F2 H distance of 2.388 A. The Hg1-Hg1 distance
3 3 3
19e
A observed in [AgHg2(μ-dppm)3](O3SCF3)3 and similar
(3.3753(7) A) in 19, though less than the sum of van der
Waals radii (3.46-4.1 A; rvwd Hg = 1.73-2.05 A), may not
be a case of d10-d10 interaction. The close distance between
the two mercury atoms may be a consequence of geometrical
constraint.
Hg/Ag clusters.19f The C-Hg-C bond angles [—C1B-
Hg1-C1A 178.9(3)ꢀ and —C16A-Hg2-C16B 176.3(3)ꢀ]
are close to 180ꢀ. The packing diagram reveals that out of
the four oxygens of the ClO4-, two oxygens interact with one
mercury atom and one of the hydrogens of the macrocycle.
A comparison of the structure of the copper complex
(14)22a (Figure 8) with the structure of the silver complex
(17) reveals close similarities. The geometry around both the
guest metal ions is distorted octahedral. The —Hg-Ag-N
angles are in the range ∼63.63-72.99ꢀ as compared to the
—Hg-Cu-N angles, ∼69.69-73.04ꢀ. Similarly, —N1A-
Ag-N2A (76.0(2)ꢀ), —N1B-Ag-N2B (76.1(2)ꢀ), —N1-
Cu-N2 (83.81ꢀ), and —N3-Cu-N4 (83.57ꢀ) are compar-
able. However, —Hg1-Ag-Hg2 (166.50(3)ꢀ) is quite dif-
ferent from —Hg1-Cu-Hg2 (177.88(3)ꢀ).
In the reactions of macrocycles 6 and 7 with PdII, a facile
transmetalation of the aryl group from mercury to palladium
takes precedence over coordination by nitrogen/mercury
and results in the formation of 20 and 9, respectively, with
cis disposition of the aryl groups to the palladium. The
crystal structure of the dichloromethane solvate of 9 showed
a unique HgII PdII HgII interaction.22b Crystallization
3 3 3
3 3 3
of 9 from acetone gave the pseudopolymorph 9a in small
amount that contains four molecules of 8 in an asymmetric
unit and acetone as solvent of crystallization. Compounds 9
and 9a have low solubility in common organic solvents such
Colorless crystals of 19 were obtained by slow evaporation
of a chloroform/hexane solution. It crystallizes in the orthor-
hombic crystal system, in the Pnma space group. The mole-
cule has a 2-fold axis that passes through the ethane bridge,
and only half the molecule represents the asymmetric unit
with the μ-hydroxo group located at the special position. The
C8 carbon, which is disordered, is refined by taking two posi-
tions with 0.5 occupancy for each. The molecular structure
confirmed cleavage of the macrocycle and formation of a
cationic bis(Lewis acid), which traps a hydroxo group.
Cleavage of the macrocycle in the case of 19 might be due to
the larger size and higher charge on mercury(II). There are
no reports in the literature on the complexation of dicationic
metal ions with metallamacrocycles/metallacryptands con-
taining dicationic metal ions through a metallophillic inter-
action. It is worth noting that Catalano and co-workers were
unable to synthesize a metallocryptand with a Au(1þ)-Pb-
as acetone, dichloromethane, and DMSO. The Hg Pd
3 3 3
distances in the asymmetric unit of 9a are Hg1A Pd1A
3 3 3
3.1054(9), Hg2A Pd1A 3.2181(10), Hg1B Pd1B 3.1524(9),
3 3 3
3 3 3
Hg2B Pd1B 3.1896(10), Hg1C Pd1C 3.1496(9), Hg2C
3 3 3 3 3 3
3 3 3
Pd1C 3.2201(9), Hg1D Pd1D 3.1092(9), and Hg2D Pd1D
3 3 3
3 3 3
3.2150(10) A. The corresponding distances in the dichloro-
methane solvate were 3.1020(3) A (Hg1 Pd) and 3.2337(3)
3 3 3
A (Hg2 Pd), which are close to those observed by Gabbaı
3 3 3
and co-workers in the PdII HgII PdII intermolecular
3 3 3
3 3 3
system.17 The Hg Pd distances in 9a as well as 9 are not
identical within the same molecule, and the difference be-
3 3 3
tween the two Hg Pd distances in 9a is 0.1127 A. The
helical nature of the molecule may be responsible for the dif-
ference in the two Hg Pd distances. The HgII P-
3 3 3
3 3 3
3 3 3
dII HgII angles in the acetone solvate are —Hg1A
3 3 3
3 3 3
Pd1A Hg2A 164.98(3)ꢀ, —Hg1B
Pd1B Hg2B
3 3 3
3 3 3
3 3 3
161.22(3)ꢀ, —Hg1C
—Hg1D Pd1D Hg2D 165.10(3)ꢀ as compared to
3 3 3
Pd1C Hg2C 162.22(3)ꢀ, and
3 3 3
3 3 3
(
2þ) interaction.20b They were able to isolate only systems
3 3 3
with (1þ)-(0) and (2þ)-(0) charged metallophillic interac-
tions. In addition to the cleavage of the mercury-carbon
bond, the other important aspect of this structure is trapping
of the hydroxo group between two Lewis acidic mercury
centers. There are very few reports of such complexes that
incorporate a hydroxo group between two Hg(II) ions.33,34
The geometry about each mercury atom is T-shaped,
having bonds with carbon, nitrogen, and oxygen (Figure 9).
The Hg-N distances are 2.669(8) A. Hg1-O1 bond distance
of 2.069(6) A is less than the Hg-O bond distance observed
in the tetradentate Lewis acid (2.08(1) A) reported by Wuest
162.898(7)ꢀ observed in the dichloromethane solvate. Com-
plex 9a has a metallohelicate structure along the HgII
3 3 3
PdII HgII axis and is deviated from linearity due to sec-
ondary N Hg interactions.
3 3 3
3 3 3
A closer look at the crystal structure of 9a reveals that two
molecules in the asymmetric unit are linked by an intermo-
lecular Hg π interaction (3.773 A) (Figure 11)
3 3 3
Conclusion
Using the approach of intramolecular coordination, we
have achieved a convenient template-free synthesis of mer-
curaazametallamacrocycles in good yield. The 22-membered
macrocycles have a twisted conformation (“hour glass” or
figure 8). These macrocycles easily trap CuI and AgI ions and
exhibit strong HgII CuI HgII and HgII AgI HgII
(32) (a) Burini, A.; Fackler, J. P., Jr.; Galassi, R.; Pietroni, B. R.;
Staples, R. J. Chem. Commun. 1998, 95–96. (b) Silong, S. B.; Kildea, J. D.;
White, A. H. Aust. J. Chem. 1989, 42, 1387–1391.
ꢁ
ꢀ
ꢀ
ꢀ
(33) (a) Grdenic, D.; Matkovic-Calogovic, D.; Sikirica, M. J. Orga-
nomet. Chem. 1987, 319, 1–8. (b) Zheng, Z.; Knobler, C. B.; Curtis, C. E.;
Hawthorne, M. F. Inorg. Chem. 1995, 34, 432–435.
(34) Nicholson, B. K.; Whitton, A. J. J. Organomet. Chem. 1986, 306,
139–144.
3 3 3
3 3 3
3 3 3
3 3 3
metallophilic interactions. With PdII and PtII, transmetala-
tion leads to cleavage of the macrocycles. We have also suc-
ceeded in isolating an 11-membered mercuraazamacrocycle

Article
Organometallics, Vol. 29, No. 19, 2010 4273
in which the —C-Hg-C angle is ∼135ꢀ and is most deviated
from linearity compared to any diorganomercury com-
pound. Interestingly, attempted coordination of HgII with
6 leads to facile cleavage of the ring and entrapment of a
hydroxide ion. This entrapment is facilitated by inadvertent
formation of a cationic, chelating bis(Lewis acid) based on
an organomercury derivative.
(%) 979 (100) [M]þ, 491 (60). UV/vis (CHCl3; λmax (ε)): 270
(14 000), 294 nm (8400 M-1 cm-1). UV/vis (solid, λmax): 330 nm.
Emission (solid, λex 330 nm): λmax 422, 460, 485, 530 nm. Anal.
Calcd for C40H40Hg2N4: C, 49.13; H, 4.12; N, 5.73. Found: C,
49.12; H, 4.12; N, 5.67.
Synthesis of Compound 13. Schiff base macrocycle 6 (0.435 g,
0.500 mmol) was taken in 50 mL of dry methanol. An excess of
sodium borohydride was slowly added over a period of 2 h at
0 ꢀC. The reaction mixture was stirred at room temperature for
5 h. After refluxing it for 2 h, the solvent was evaporated under
vacuum. The residue was quenched with water to destroy the
unreacted sodium borohydride and then extracted with dichloro-
methane (3 ꢀ 15 mL) and dried over sodium sulfate. The
workup afforded the crude compound, which was recrystallized
from dichloromethane and petroleum ether. Yield: 0.052 g (0.12
Experimental Section
General Experimental Procedures. All reactions were carried
out under nitrogen or argon using standard vacuum-line tech-
niques. The solvents were purified by standard procedures and
were freshly distilled prior to use. Cu(CH3CN)4ClO4 was pre-
pared by a reported procedure.35 Synthesis of compounds 6, 7,
10, and 11 has been earlier described in the literature.22 AgClO4
and trans-1,2-diaminocyclohexane were purchased from Aldrich.
All the other reagents and solvents used for the reactions were of
reagent grade.
1
mmol, 11%), mp 166-168 ꢀC. H NMR (300 MHz, CDCl3):
δ 7.58 (d, 2H, J = 7.32 Hz), 7.26 (m, 4H) 7.15 (t, 2H, J = 7.32
Hz), 3.89 (s, 4H), 2.80 (s, 4H). 13C NMR (75.42 MHz, CDCl3):
δ 168.2, 148.2, 139.1, 128.1, 126.9, 126.4, 48.3, 55.0. 199Hg NMR
(53.05 MHz, CDCl3): δ -572 ppm. IR (KBr): 3312 ν(N-H)
cm-1. ESI-MS: m/z (%) 441.8 (55) [M þ 2]þ. Anal. Calcd for
C16H16HgN2: C, 43.99; H, 3.69; N, 6.41. Found: C, 43.57; H,
3.93; N, 6.03.
Caution: The reactions involving mercury compounds were
carried out in a well-ventilated fume hood with proper precautions
due to their hazardous nature.
Instrumentation. Melting points were recorded in capillary
tubes. Elemental analyses were performed on a Carlo-Erba
model 1106 elemental analyzer. IR spectra were recorded as
KBr pellets on a Nicolet Impact 400 and Perkin FT-IR spectro-
meter. All UV-vis spectra were recorded on a Jasco-570 spec-
trophotometer. Emission spectra were recorded by using a
Synthesis of Compound 16. To a two-necked round-bottomed
flask containing Schiff base 12 (0.195 g, 0.199 mmol) in dry
methanol (30 mL) was added [Cu(CH3CN)4]ClO4 (0.065 g,
0.199 mmol). The color of the suspension changed to red
immediately. On stirring the reaction mixture for 4 h, a red-
colored precipitate was obtained. The precipitate was filtered,
washed with methanol, and dried to obtain 16. The orange-
colored filtrate was concentrated, and further slow evaporation
gave 16 as a red, crystalline solid. Yield: 0.18 g (0.16 mmol,
79%). 1H NMR (400 MHz, CDCl3): δ 8.10 (s, 4H), 7.56 (m, 8H),
7.46 (t, 4H, J = 9.20 Hz), 7.30 (d, 4H, J = 10.4 Hz), 2.80 (s, br,
4H), 2.02 (s, br, 4H), 1.75 (s, br, 4H), 1.19 (s, 8H). 13C NMR
(100.05 MHz, CDCl3): δ 169.1, 166.8, 143.8, 137.9, 132.6, 132.6,
128.1, 68.5, 32.1, 24.2. 199Hg NMR (53.05 MHz, CDCl3): δ
1
Perkin-Elmer LS55 luminescence spectrometer. H (300.4 and
400.5 MHz) and 13C (100.5 MHz, 75.4 MHz) NMR spectra were
recorded on a Varian VXR 300S and a Varian 400 MHz spec-
trometer, and the 199Hg (199Hg, 53.7 MHz) NMR spectra were
recorded on a Bruker DPX300-NMR spectrometer at the indi-
cated frequencies. 19F (470.3 MHz) NMR was recorded on a
Varian 500 MHz spectrometer with C6F6 as external standard.
Chemical shifts cited were referenced to TMS (1H, 13C) as
internal and Ph2Hg (199Hg) as external standard. The electron
spray mass spectra (ESI-MS) were performed on a Q-Tof micro
(YA-105) mass spectrometer. Mass spectra were obtained with a
Platform II single quadrupole mass spectrometer (Micromass,
Altrincham, UK) using a CH3OH mobile phase. Cyclic voltam-
metric measurements were carried out using a PAR model 273A
electrochemistry system. A platinum wire working electrode, a
platinum wire auxiliary electrode, and saturated calomel refer-
ence electrode were used in a standard three-electrode config-
uration. Tetraethylammonium perchlorate was the supporting
electrolyte, the scan rate used was 50 mV s-1, and ferrocene was
used as standard. All of the electrochemical experiments were
carried out under a nitrogen atmosphere, and all of the redox
potentials are uncorrected for junction potentials.
-495 ppm. IR (KBr): 1627 ν(CdN), 1092, 626 ν(ClO4-) cm-1
.
ESI-MS: m/z (%) 1041 (100) [M - ClO4]þ. UV/vis (CHCl3; λmax
(ε)): 269 (10 000), 294 (7800), 421 nm (960 M-1cm-1). UV/vis
(solid, λmax): 340, 475 nm. Emission (solid, λex 475 nm): λmax 530
nm. Anal. Calcd for C40H40ClCuHg2N4O4: C, 42.11; H, 3.53; N,
4.91. Found: C, 41.93; H, 3.43; N, 4.87.
Synthesis of Compound 17. A similar reaction of Schiff base
ligand 6 (0.219 g, 0.252 mmol) with silver perchlorate (0.052 g,
0.252 mmol) in methanol (20 mL) afforded a white precipitate of
complex 17. Yield: 0.17 g (0.16 mmol, 63%). 1H NMR (400 Hz,
CD3CN): δ 8.28 (s, 4H), 7.55 (m, 8H), 7.32 (m, 4H), 7.17 (d, 4H),
3.64 (s, 8H). 13C NMR (75.42 MHz, CD3CN): δ 172.5, 144.7,
139.1, 133.1, 132.5, 128.3, 165.8, 66.7. 199Hg NMR (53.05 MHz,
CDCl3): δ -552 ppm. IR (KBr): 1627 ν(CdN) cm-1. ESI-MS:
m/z (%) 977 (30) [M - ClO4]þ. UV/vis (CH3CN, λmax (ε)): 270
(14 000), 294 nm (9400 M-1cm-1). Emission (solid, λex 336 nm):
λmax 422, 460, 485, 530 nm. Anal. Calcd for C32H28AgClHg2-
N4O4: C, 35.68; H, 2.62; N, 5.20. Found: C, 34.62; H, 2.75; N,
5.29.
Synthesis of Compound 18. To a two-necked round-bottomed
flask with 30 mL of degassed methanol was added ligand 6
(0.219 g, 0.252 mmol). After some time AgNO3 (0.042 g, 0.252
mmol) was added and the reaction mixture stirred at room
temperature overnight. To the reaction mixture was added an
excess of ammonium hexafluorophosphate. The resulting white
precipitate was filtered off, and the filtrate was kept for crystal-
lization. After evaporation of the solvent, a pale white precipi-
tate of 18 was obtained. Yield: 0.16 g (0.14 mmol, 57%), mp
210-212 ꢀC. 1H NMR (400 MHz, CD3CN): δ 8.36 (s, 4H), 7.56
(d, 8H, J = 5.2), 7.34 (m, 4H), 7.17 (d, 4H, J = 9.60), 3.71 (s,
8H). 13C NMR (100.05 MHz, CD3CN): δ 172.5, 168.8, 144.7,
139.1, 133.1, 132.5, 128.4, 60.7. 199Hg NMR (53.05 MHz,
CDCl3): δ -555 ppm. IR (KBr): 1627 ν(CdN) cm-1. ESI-MS:
Synthesis of Compound 12. A solution of 11 (0.41 g, 0.99
mmol) in methanol (100 mL) was added dropwise to a stirred
solution of trans-1,2-diaminocyclohexane (0.11 g, 0.96 mmol) in
methanol (200 mL) over a period of 5-6 h. The mixture was
stirred overnight, and the precipitated white powder was filtered
off. The filtrate was evaporated under reduced pressure, and the
residue obtained was washed with methanol 2-3 times. It was
recrystallized from a chloroform and hexane mixture to give
square-shaped white crystals of 12. Yield: 0.33 g (0.34 mmol,
68%), mp 280-282 ꢀC. 1H NMR (400 MHz, CDCl3): δ 7.54 (d,
4H, J = 9.2 Hz), 7.42 (t, 4H, J = 9.40 Hz), 7.26 (t, 4H, J = 9.60
Hz), 7.05 (s, 4H), 6.96 (d, 4H, J = 9.60 Hz), 3.0 (s, 4H),
1.25-1.65 (m, 16H). 13C NMR (100.05 MHz, CDCl3 with 2
drops of d6-DMSO): δ 166.8, 166.6, 144.2, 137.9, 132.8, 130.4,
126, 71.7, 35.2, 25.0. 199Hg NMR (53.05 MHz, CDCl3): δ -667
ppm. IR (KBr): 1632 ν(CdN), 1561, 1446 cm-1. ESI-MS: m/z
(35) Simmons, M. G.; Merrill, C. L.; Wilson, L. J.; Bottomley, L. A.;
Kadish, K. M. J. Chem. Soc., Dalton Trans. 1980, 1827–1837.

4274 Organometallics, Vol. 29, No. 19, 2010
Table 2. Crystallographic Data of 6, 7, 10, and 12
Patel et al.
6
7
10
12
empirical formula
fw
C32H28Hg2N4
869.76
C40H28Hg2N4
965.84
C14H14HgO2
414.84
C40H40Hg2N4
977.94
cryst syst
space group
a (A)
b (A)
c (A)
R (deg)
β (deg)
monoclinic
Pc
9.3680(19)
9.2432(19)
16..261(3)
90
91.123(4)
90
1407.8(5)
2
2.052
monoclinic
P21/c
18.3577(16)
8.6721(8)
41.832(4)
90
100.7450(10)
90
6542.9(10)
8
1.961
monoclinic
P21/n
4.9461(5)
18.807(2)
12.9982(15)
90
94.976(2)
90
1204.5(2)
4
2.288
orthorhombic
Pcan
12.8247(8)
15.5549(9)
17.1838(10)
90
90
90
3427.9(4)
4
1.895
γ (deg)
V (A3)
Z
d(calcd) (Mg/m3)
temp (K)
λ (A)
293(2)
293(2)
103(2)
103(2)
0.71073
2.17 to 28.30
10.920
0.71073
2.09 to 30.93
9.409
0.71073
1.91 to 28.31
12.763
0.71073
2.38 to 28.29
8.981
range of θ (deg)
abs coeff (mm-1
)
obsd reflens [I > 2σ]
final R(F) [I > 2σ(I)]
wR(F2) indices [I > 2σ]
data/restraints/params
goodness of fit on F2
10 499
0.0679
0.1753
4801/182/296
1.106
19 140
0.0415
0.0924
19 140/0/ 829
1.010
9182
0.0203
0.0498
2905/0/154
1.063
25 199
0.0222
0.0517
4177/0/209
0.953
Table 3. Crystallographic Data of 13, 17, 19, and 9a
17
13
19
9a(acetone solvate)
empirical formula
fw
cryst syst
space group
a (A)
b (A)
c (A)
R (deg)
β (deg)
C
16H18HgN2
C32H28AgClHg2N4O4
1077.08
monoclinic
P21/c
14.9546(16)
10.5319(11)
19.534(2)
90
90.001(2)
90
3076.5(6)
4
2.325
C16H15F6Hg2N2OP
797.45
orthorhombic
Pnma
8.7266(5)
17.9057(11)
12.5696(8)
90
90
90
C83H62Cl4Hg4N8OPd2
2344.37
monoclinic
C2/c
41.2863(7)
19.3267(2)
41.0150(7)
90
109.957(2)
90
30761.7(8)
16
2.025
438.91
orthorhombic
Cmc21
21.7105(18)
7.1769(8)
8.9718(8)
90
90
90
1397.9(2)
4
2.085
γ (deg)
V (A3)
1964.1(2)
4
2.697
Z
d(calcd) (Mg/m3)
temp (K)
λ (A)
193(2)
100(2)
293(2)
200(2)
0.71073
2.99 to 26.69
10.998
7261
0.0245
0.0584
1517/2/92
1.092
0.71073
1.36 to 28.27
10.718
23 361
0.0428
0.1035
7461/0/397
1.029
0.71073
3.06 to 26.73
15.764
2148
0.0297
0.0651
2148/41/144
0.947
1.54184
4.10 to 73.78
19.336
29 988
0.0488
0.1202
29 888/0/ 1841
0.934
range of θ (deg)
abs coeff (mm-1
)
obsd reflens [I > 2σ]
final R(F) [I > 2σ(I)]
wR(F2) indices [I > 2σ]
data/restraints/params
goodness of fit on F2
m/z (%) 977 (18) [M - PF6]þ, 565 (10) [1/2 Mþ]. UV/vis
Pd(C6H5CN)2Cl2 (0.096 g, 0.252 mmol) in chloroform. After
stirring for 2 h, the reaction mixture was filtered and kept at 0 ꢀC
to afford a precipitate of the complex 20. Yield: 0.14 g (0.13
mmol, 54%), mp 225 ꢀC (dec). IR (KBr): 1640, 1618 cm-1
ν(CdN). ESI-MS: m/z (%) 1011 (45) [M - Cl]þ. 199Hg NMR
(53.05 MHz, d6-DMSO): δ -1045 ppm. Anal. Calcd for
C32H28Cl2Hg2N4Pd: C, 36.72; H, 2.69; N 5.34. Found: C,
36.57; H, 2.28; N, 6.27.
Synthesis of Compound 21. To a solution of 6 (0.219 g, 0.252
mmol) in chloroform was added dropwise, a solution of Pt-
(COD)Cl2 (0.102 g, 0.273 mmol) in chloroform. It was stirred
for 4 h, and the precipitate formed was filtered and washed with
acetonitrile several times. The yellow powder formed was char-
acterized as 21. Yield: 0.17 g (0.15 mmol, 60%), mp 230 ꢀC (dec).
IR (KBr): 1642 cm-1 (br) ν(CdN). ESI-MS: m/z (%) 1100 (30)
[M - Cl]þ. 199Hg NMR (53.05 MHz, d6-DMSO): δ -1043 ppm.
Anal. Calcd for C32H28Cl2Hg2N4Pt: C, 33.84; H, 2.48; N, 4.93.
Found: C, 34.55; H, 2.29; N, 5.06.
-1
(CH3CN, λmax (ε)): 270 (14 000), 294 nm (9500
M-1cm-1).
Emission (solid, λex 336 nm): λmax 422, 460, 485, 530 nm. Anal.
Calcd for C32H28AgF6Hg2N4P: C, 34.24; H, 2.51; N, 4.99.
Found: C, 33.98; H, 2.60; N, 4.89.
Synthesis of Compound 19. To a solution of 6 (0.219 g, 0.252
mmol) in methanol (25 mL) was added Hg(OCOCH3)2 (0.080 g,
0.252 mmol) in dichloromethane (10 mL) and the reaction
mixture stirred for 3 days. After that, an excess of NH4PF6
was added to give a white precipitate, which was crystallized
1
from acetonitrile. Yield: 0.083 g (0.10 mmol, 42%). H NMR
(400 MHz, d6-DMSO): δ 8.74 (s, 2H), 7.65 (d, 2H, J = 7.6), 7.56
(m, 4H), 7.44 (t, 2H, J = 7.6) 3.9 (s, 4H). 13C NMR (100.05
MHz, d6-DMSO): δ 166.2, 148.1, 140.6, 137.9, 133.0, 132.2,
128.6, 61.1. 19F NMR (470 MHz, d6-DMSO): δ -67.9 (d, 6F,
J(31P-19F) = 711 Hz). 199Hg NMR (53.05 MHz, d6-DMSO): δ
-1013 ppm. IR (KBr): 1622 ν(CdN) cm-1. ESI-MS: m/z (%)
651 (100) [M - PF6]þ, 1285 (10). Anal. Calcd for C16H15-
F6Hg2N2OP: C, 24.10; H, 1.90; N, 3.51. Found: C, 23.85; H,
1.63; N, 3.79.
Synthesis of Compound 9a. To a solution of macrocycle 7
(0.201 g, 0.208 mmol) in dichloromethane (25 mL) was added
Pd(C6H5CN)2Cl2 (0.080 g, 0.208 mmol), and the reaction
mixture was stirred for 5 h at room temperature. The yellow
Synthesis of Compound 20. To a chloroform (10 mL) solution
of 6 (0.219 g, 0.252 mmol) was added dropwise a solution of

Article
Organometallics, Vol. 29, No. 19, 2010 4275
precipitate obtained was filtered, and the filtrate was kept at
room temperature for slow evaporation to obtain orange-colored
crystals of 9 (0.052 mmol, 0.060 g, 60%). On crystallization of
50 mg of yellow precipitate in acetone, 9a was obtained in small
amount (0.008 g), mp 220-222 ꢀC. IR (KBr): 1617, 1598 cm-1
ν(CdN). Anal. Calcd for C83H62Cl4Hg4N8OPd2: C, 42.52; H,
2.67; N, 4.78. Found: C, 43.02; H, 2.46; N, 5.06.
X-ray Crystallography. The diffraction measurements for
compounds 6, 7, 10, 11, 12, 14,22a and 17 were performed on a
Bruker P4 and Bruker SMART 1000 CCD and for 13 and 19 on
a Stoe IPDS with graphite-monochromated Mo KR radiation
(λ = 0.7107 A). The crystal data for 9a were collected on a
Oxford Diffraction X-Calibur diffractometer using Cu radiation
(λ=1.5418A). The structures were solved by direct methods and full
matrix least-squares refinement on F2 (program SHELXL-97).36a,b
Hydrogen atoms were localized by geometrical means. A riding
model was chosen for refinement. The isotropic thermal para-
meters of the H atoms were fixed at 1.5 times (CH3 groups) or 1.2
times U(eq) (Ar-H) of the corresponding C atom. The crystals
of 6 were invariably found to be pseudomerohedrally twinned. It
was solved in Pc with SIR92.36c The twin law was obtained using
ROTAX (1 0 0 0 -1 0 0 0 -1).
Acknowledgment. H.B.S. is grateful to the Department
of Science and Technology (DST), New Delhi, for fund-
ing and S.S. thanks UGC for SRF.
Supporting Information Available: Spectral data (1H, 13C,
199Hg NMR, emission spectra, and ES-MS) for 13, 16, 18, and
19; CV of 17; X-ray crystallographic data of 6, 7, 10, 11, 12, 13,
17, 19, and 9a in CIF format. This material is available free of
charge via the Internet at http://pubs.acs.org.
(36) (a) Sheldrick, G. M. SHELXS-97, Program for Crystal Structures
€
€
Solution; University of Gottingen: Gottingen, Germany, 1997. (b) Sheldrick,
G. M. SHELXL-97, Program for Crystal Structures Refinement; University
€
€
of Gottingen: Gottingen, Germany, 1997. (c) Altomare, A.; Cascarano, G.;
Giacovazzo, C.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M.
J. Appl. Crystallogr. 1994, 27, 435–436.