Copper(I) halide complexes of the new 4,4′-bridged heteroaromatic biscarbenes of the 1,2,4-triazole series

Article abstract of DOI:10.1016/j.jorganchem.2007.07.056

The stable biscarbenes, 1,4- and 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-yliden-4-yl]benzenes (4a,b) have been prepared. Treatment of 4b with copper(I) chloride and copper(I) iodide in acetonitrile or acetonitrile/toluene solution afforded the biscarbene copper(I) complexes 5a and 5b, respectively. The reactions of 4a and 4b with diphenyldiazomethane and sulfur resulted in the novel bisazine (6) and bisthione (7) derivatives, respectively. The X-ray crystal structures of 4a and 5b were determined.

Full text of DOI:10.1016/j.jorganchem.2007.07.056

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1405–1411
www.elsevier.com/locate/jorganchem
Copper(I) halide complexes of the new 4,40-bridged heteroaromatic
biscarbenes of the 1,2,4-triazole series
a
a
b,
b
Arthur V. Knishevitsky , Nikolai I. Korotkikh , Alan H. Cowley *, Jennifer A. Moore ,
a
a
b
Tatyana M. Pekhtereva , Oles P. Shvaika , Gregor Reeske
a
The L.M. Litvinenko Institute of Physical Organic and Coal Chemistry, Ukrainian Academy of Sciences, 70, R. Luxemburg, Donetsk 83114, Ukraine
b
The University of Texas at Austin, Department of Chemistry and Biochemistry, 1 University Station A5300, Austin, TX 78712-0165, USA
Received 17 October 2006; received in revised form 20 July 2007; accepted 24 July 2007
Available online 23 August 2007
Abstract
The stable biscarbenes, 1,4- and 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-yliden-4-yl]benzenes (4a,b) have been prepared.
Treatment of 4b with copper(I) chloride and copper(I) iodide in acetonitrile or acetonitrile/toluene solution afforded the biscarbene cop-
per(I) complexes 5a and 5b, respectively. The reactions of 4a and 4b with diphenyldiazomethane and sulfur resulted in the novel bisazine
(6) and bisthione (7) derivatives, respectively. The X-ray crystal structures of 4a and 5b were determined.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Biscarbenes; 1,2,4-Triazoles; Copper complexes
1. Introduction
with a chelating bis-[1,2,4]-triazolium salt gives a norticy-
clyl Rh complex.
Following the syntheses of the first stable carbenes [1–4],
interest began to develop in the possibility of synthesizing
polyfunctional carbenes. It was recognized [5] that carbene
dimerization might render this objective somewhat diffi-
cult. However, it was not long before Dias et al. [6]
reported the synthesis of the first triscarbene ligand of the
imidazole series in which the electronically isolated carb-
enes are linked by a mesitylene moiety. The first syntheses
of biscarbenes of the imidazole series were reported by
Herrmann and co-workers [7]. In these biscarbenes, the
imidazole rings are connected by ethylene bridges at the
nitrogen atoms. However, these carbenes were obtained
in situ and characterized spectroscopically prior to their
use for the synthesis of metal carbene complexes. More
recently, new stable biscarbenes of the 1,2,4-triazole series
have been isolated and characterized [8], as have some
related biscarbenes of the imidazole series [9,10]. Crabtree
et al. [11] have also shown that the reaction of [(nbd)RhCl]2
In the present contribution we describe (i) the synthesis
of two stable heteroaromatic biscarbenes of the 1,2,4-tria-
zole series in which triazole rings are connected by pheny-
lene bridges to the nitrogen atoms in the 4 positions; (ii) the
synthesis of two biscarbene complexes of copper(I) halides;
(iii) the synthesis of two new organic derivatives by treat-
ment of the new carbenes with diphenyldiazomethane
and elemental sulfur; and (iv) the X-ray crystal structures
of the m-phenylene-bridged bistriazolylidene and its com-
plex with copper(I) iodide. In conceiving of this study, it
was assumed that, akin to the 3,30-bonded bistriazolylid-
enes [8], conjugation between the 4,40-bonded biscarbenes
would afford some degree of electronic interaction between
the triazole rings and hence between the two carbene cen-
ters of the molecule.
2. Results and discussion
The ring transformations of 2-phenyl-1,3,4-oxadiazole
(1) into triazoles were effected by treatment of p-phenylen-
ediamine dihydrochloride or m-phenylenediamine with
*
Corresponding author. Tel.: +1 5124717484; fax: +1 5124716822.
E-mail address: cowley@mail.utexas.edu (A.H. Cowley).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.07.056

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A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
equimolar amounts of trifluoroacetic acid at 180 ꢁC in o-
dichlorobenzene. The solvent choice was dictated by the
high polarity of o-dichlorobenzene (l 2.50 D) and its lack
of reactivity toward oxadiazole 1. Bistriazoles 2a,b were
prepared in isolated yields of 54–56%. The syntheses, spec-
tral data and other characteristics of triazoles 2a,b have
been described by us earlier [12].
in a pure state. In the case of 4a, the reaction was complete
in 40–50 min at room temperature in a yield of 88%. Inter-
estingly, the method employed for the conversion of 3b to
4b is unsuitable for the synthesis of 4b. Even at low temper-
atures the deprotonation of salt 3b is accompanied by
unidentified side reactions that presumably involve carbene
insertion into a C–H bond of acetonitrile to form cya-
nomethylderivatives of the respective bistriazoline [14,15]
and H-complexes of the carbene and the initial salt similar
to those reported by Arduengo and co-workers [16]. How-
ever, biscarbene 4b was prepared in quantitative yield via
the reaction of triazolium salt 3b with an equimolar quan-
tity of sodium tert-butoxide in a 5:1 mixture of toluene and
tert-butanol. The presence of tert-butanol in the reaction
mixture permits complete solubility of the initially formed
triazolium tert-butoxide, thereby facilitating its decomposi-
tion to the biscarbene and tert-butanol by slow solvent
evaporation. Moreover, the tert-butoxide anion is a strong
base (pKa ꢀ 19) with a basicity close to that of triazolylid-
enes. Furthermore, the tert-butyl substituent is a good ste-
rically protecting group and this facilitates the elimination
of the C(5)H proton from the bistriazolium salt and pre-
vents the H-interaction of the biscarbene with unreacted
salt as discussed in reference [16]. Experiments conducted
in the presence of other alcohols (isopropanol, methanol)
showed that, along with carbene 4b, from 40 to 60% of
the relatively stable (to 120–130 ꢁC) triazolium alkoxides
accumulate, thereby preventing isolation of the pure
biscarbenes. It should be noted that 1,4-bis[1-(1-adaman-
tyl-4-phenyl-1,2,4-triazol-5-ylidene-3-yl)benzene [9], which
is isomeric with biscarbenes 4a,b, was obtained in 85%
yield by deprotonation of the precursor salt with potassium
methylate in a 1:1 toluene/methanol mixture. In this case, it
was reported that the corresponding bistriazolium methox-
ide decomposed to form the biscarbene at 70–80 ꢁC.
The quaternization of triazoles 2a,b to the correspond-
ing bistriazolium salts 3a,b was effected via thermal reac-
tion with 1-bromoadamantane in acetic acid or DMF
solution (Scheme 1). In the case of triazole 2b, the reaction
of 1-bromoadamantane in acetic acid afforded 96–100%
yields of 3b after 12–14 h. Under analogous conditions, tri-
azole 2a forms a sparingly soluble bistriazolium acetate
which inhibits the desired quaternization process and
restricts the yields of 3a to 20% even in the presence of a
large excess of 1-bromoadamantane. On the other hand,
if the aprotic polar solvent DMF is employed in the pres-
ence of a 20–30% excess of 1-bromoadamantane, these side
reactions are avoided and almost quantitative yields of 3a
are realized. The bistriazolium bromides 3a,b produced
by the above methods were purified by crystallization from
water, followed by treatment with sodium perchlorate to
precipitate the perchlorate salts. If necessary, perchlorates
3a,b can be recrystallized from 40% aqueous DMF or ace-
tic acid.
The compositions and structures of bistriazolium salts
3a,b were established on the basis of elemental analyses
1
and NMR spectral data. Thus, the H NMR spectra of
salts 3a,b are indicative of the presence of two carbenoid
protons on the triazolium rings and occur in the range d
10.60–10.67 ppm, which is downfield relative to those for
triazoles 2a,b by 1.77 ppm [12] (the atom numbering system
is based on the chemical names of compounds). The reso-
nances for the adamantyl protons are evident at d 1.6–
2.3 ppm.
The preparation of biscarbenes 4a,b was carried out by
deprotonation of the respective bistriazolium perchlorates
3a,b by means of sodium hydride in acetonitrile solution
or potassium tert-butoxide in a toluene/t-butanol mixed
solvent as summarized in Scheme 1. This method of synthe-
sis for carbenes 4a,b proved to be very successful. In partic-
ular, the use of acetonitrile as solvent [13,14] permits rapid,
high yield reactions due to the high solubility of the initial
salt and one of the products (sodium perchlorate). More-
over, the solubilities of the biscarbenes in acetonitrile is
low hence they are precipitated from the reaction mixture
Biscarbenes 4a and 4b can be purified easily by recrystal-
lization from toluene and cyclohexane, respectively. Com-
pounds 4a,b were characterized by means of elemental
1
analysis, H and 13C NMR spectroscopy, and in the case
of 4a also by single-crystal X-ray diffraction. The salient
feature that distinguishes the 1H NMR spectra of carbenes
4a,b from those of their precursors 3a,b is the absence of
carbenoid signals in the range d 10.6–10.7 ppm. The ada-
mantyl protons are observed as three multiplets with chem-
ical shifts of d 1.6–1.8, 2.1–2.3 and 2.6–2.8 ppm. As noted
for the monocarbene analogues [9,14], there is a significant
deshielding of the adamantyl protons closest to the triazole
Ph
N
Ph
N
Ph
N
Ph
Ph
Ph
N
N
N
N
AdBr
N
N
t-BuOK
N
N
N
X
X
N
X N
N
N
N
or NaH
N
Ad
Ad
Ad
Ad
2W
2a,b
3a,b
4a,b
Scheme 1. 3a,b: W = ClO4, Br; 2–4: X = 1,4-C6H4 (a) and 1,3-C6H4 (b)

A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
1407
Table 2
rings that is not evident in the precursor bistriazolium salts.
The 13C NMR spectra of biscarbenes 4a,b exhibit a signal
for the carbenic carbon in the range d 206.3–209.2 ppm.
Comparable chemical shifts have been reported for
mono-1,2,4-triazol-5-ylidenes (d 207–214 ppm). These
chemical shift values imply a small degree of conjugation
between the triazole rings and phenylene bridge.
Selected bond distances and angles for 4a and 5b
4a
5b
˚
Bond lengths (A)
C(1)–N(1)
C(1)–N(2)
C(2)–N(1)
C(2)–N(3)
N(2)–N(3)
N(2)–N(3)
1.390(2)
1.338(2)
1.390(2)
1.303(2)
1.394(2)
1.436(2)
Cu(1)–I(1)
Cu(1)–I(2)
Cu(2)–I(1)
Cu(2)–I(2)
Cu(1)–Cu(2)
Cu(1)–C(1)
Cu(2)–C(25)
C(1)–N(1)
C(1)–N(2)
N(1)–N(3)
N(3)–C(2)
C(2)–N(2)
N(2)–C(19)
2.5799(8)
2.6100(9)
2.5058(7)
2.8268(10)
2.6631(12)
1.928(3)
1.918(3)
1.342(4)
1.378(4)
1.383(3)
1.297(4)
1.385(4)
1.443(4)
Crystals of biscarbene 4a suitable for X-ray diffraction
study were grown as colorless prisms by slow cooling of
a hot saturated toluene solution. Biscarbene 4a crystallizes
ꢀ
in the triclinic space group P1 with Z = 2; there are no
unusually short contacts between individual molecules.
Crystal data collection and refinement details are summa-
rized in Table 1 and selected metrical parameters are listed
in Table 2. As illustrated in Fig. 1, the phenyl substituents
at the C(2)-carbon atoms of biscarbene 4a are arranged in a
mutually trans fashion and the metrical parameters for the
triazole rings are similar to those for adamantyl-substituted
monocarbenes of the 1,2,4-triazole series [14]. The aromatic
rings at the C(2) and N(1) positions are twisted by 31.1(3)ꢁ
and 123.5(2)ꢁ, respectively, in relation to the plane of each
triazole ring. The molecule is characterized by significant
delocalization reminiscent of that found for monotriazoly-
lidenes thus confirming the aromatic character of the
biscarbene. As in the case of monocarbenes, a significant
feature of the structure of 4a is a noticeable inequality of
the bond orders in each triazole ring. Thus, the C(1)–
N(2) bond has a particularly high multiplicity (the
Penny–Dirac bond order, p = 1.782 vs. 1.736 for the mono-
carbenes described in Ref. [14]), thus implying a consider-
able contribution of an ylidic structure both in 4a and
also in its monocarbene analogues. It should also be noted
that the Penny–Dirac bond order is p = 1.983 for the C@N
double bond of compound 4a while for the related mono-
Bond angles/dihedral angles (ꢁ)
N(1)–C(1)–N(2)
100.19(3)
I(1)–Cu(1)–I(2)
Cu(1)–I(1)–Cu(2)
I(1)–Cu(2)–I(2)
Cu(1)–I(2)–Cu(2)
N(1)–C(1)–N(2)
C(1)–N(1)–N(3)
N(1)–N(3)–C(2)
N(3)–C(2)–N(2)
C(2)–N(2)–C(1)
107.68(3)
63.10(3)
103.35(3)
58.49(3)
101.8(2)
114.2(2)
104.5(2)
109.8(2)
109.7(2)
C(1)–N(1)–C(2)
N(1)–C(2)–N(3)
C(2)–N(3)–N(2)
N(3)–N(2)–C(1)
N(1)–C(2)–C(3)–C(4)
C(1)–N(1)–C(9)–C(10)
110.58(13)
109.73(13)
103.26(12)
116.24(13)
31.1(3)
ꢁ123.52(17)
Table 1
Crystal data for 4a and 5b
Fig. 1. X-ray structure of biscarbene 4a showing the atom numbering
scheme.
4a
5b
Formula
C
42H44Cl3N6
C45H51Cu2I2N7O
1086.81
Triclinic
Formula weight
Crystal system
Space group
632.83
Triclinic
carbenes the value is 1.994. The other endocyclic bonds
in biscarbene 4a show less or equal multiplicities (C(1)–
N(1) 1.483, C(1)–N(1) 1.483, N(2)–N(3)1.293), than those
for monocarbenes (C(1)–N(1) 1.506, C(2)–N(1) 1.517,
N(2)–N(3) 1.293). The multiplicity of the C(Ar)–C(2) bond
(p = 1.305) is somewhat larger than that for the C(Ar)–
N(1) bond (p = 1.218). This is due to the smaller twist
angle of the C(2)-aromatic ring relative to the triazole ring
than to the N(1)-ring. The bond angle at the carbene car-
bon atom C(1) is almost the same as that for the related
monocarbenes (100.2(1)ꢁ) according to the X-ray diffrac-
tion study.
ꢀ
ꢀ
P1
P1
˚
a/A
6.365(5)
9.952(5)
16.149(5)
102.899(5)
98.185(5)
95.948(5)
977.2(10)
1
13.922(3)
14.203(3)
14.221(3)
66.66(3)
64.70(3)
61.32(3)
2164.6(11)
2
˚
b/A
˚
c/A
a/ꢁ
b/ꢁ
c/ꢁ
3
˚
V/A
Z
Dc/g cmꢁ3
1.075
1.667
Crystal size/mm
h Max/ꢁ
0.13 · 0.10 · 0.05 0.30 · 0.21 · 0.21
2.12–27.49
2.72–27.47
Number of reflections collected
7417
15,020
Biscarbenes 4a,b are among the most stable carbenic
structures. Thus crystalline 4a reacts very slowly with water
and oxygen in a moist atmosphere. However, in order to
explore the reactivities of 4a and 4b somewhat further, 4a
was treated with diphenyldiazomethane, and 4b was
Number of independent
4442 [0.251]
9675 [0.0263]
reflections [Rint
R1 [I > 2r (I)]
]
0.0584
0.1482
0.0338
0.0750
wR2 [I > 2r (I)]
Peak and hole/e A
ꢁ3
˚
0.369 and ꢁ0.305 0.893 and ꢁ0.851

1408
A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
allowed to react with copper(I) chloride, copper(I) iodide,
and elemental sulfur. The synthesis of copper complexes
5a,b was effected in one step by treatment of biscarbene
4b with copper(I) halides in acetonitrile (CuCl) or an aceto-
nitrile–toluene mixture (CuI) under an inert atmosphere
(Scheme 2). The reaction of biscarbene 4b with CuI pro-
ceeds at room temperature and complex 5b precipitates
as a white powder in good yield (72%) after 5–10 min.
The interaction of carbene 4b with CuCl is complicated
by the formation of unidentified side products and is
accompanied by intense coloration of the reaction mixture.
As a result, the yield is reduced to 50%. Complexes 5a,b
were characterized by elemental analysis, 1H and 13C
NMR spectroscopy and, in the case of 5b, by single-crystal
X-ray diffraction. Thus, the elemental analysis data indi-
cate that the overall compositions of 5a and 5b correspond
to the formula (biscarbene)Cu2X2, where O = Cl, I. The 1H
NMR resonances for the adamantyl groups are observed in
the ranges d 1.76–1.84; 2.27–2.36; 2.51–2.53 ppm. The res-
onances for the protons in the 2 position of the phenylene
bridge for 5a and 5b (d 8.21 and 8.94 ppm, respectively) are
the most diagnostic.
N
N
N
2Ph2CN2
PhMe, 50 oC
N
4a
N
N
N
N
N
N
6
Scheme 3.
In the 13C NMR spectra the carbenoid signals (C5) for
complexes 5a,b are observed at d 176.6 and 184.4 ppm
for Cu2Cl2L2 and Cu2I2L2, respectively (L2 = biscarbene
ligand). These signals for 5a,b are 24.6–32.4 ppm upfield
in comparison with those for biscarbenes 4a and 4b and
36–44 ppm downfield in comparison with those of the
1,2,4-triazolium salts.
N
N
N
S8
4b
N
N
PhMe, r.t.
N
S
S
The reaction of carbene 4a with diphenyldiazomethane
in toluene solution takes place at 50 ꢁC and results in a
good yield (70%) of the yellow-colored azine 6 (Scheme
3). Carbene 4b reacts readily with elemental sulfur to form
the bisthione 7 in 77% yield (Scheme 4). Note, however,
that a short heating period is required for complete decom-
position of the intermediate hypervalent compounds as
described in Ref. [14b].
7
Scheme 4.
downfield with respect to that for azine 6 (e.g., C(3) and
C(5) appear at d 147.7 and 166.2 ppm, respectively).
Crystals of complex 5b suitable for X-ray diffraction
study, were grown from DMF solution. The complex crys-
The most characteristic resonances in the 13C NMR
spectrum of azine 6 are those for the cyclic carbon atoms
C(3) and C(5) which appear at d 149.4 and 155.2 ppm,
respectively. The signal for the C(5) atom of dithione 7 is
ꢀ
tallizes in the space group P1 with Z = 2 and there are no
close intermolecular contacts. There is one molecule of
DMF per formula unit present in the crystal structure.
Crystal data collection and refinement details are summa-
rized in Table 1 and selected metrical parameters are listed
in Table 2.
Individual molecules of 5b (Fig. 2) feature a Cu2I2 core
which is chelated by the biscarbene ligand 4b. However,
there is significant asymmetry in the Cu–I–Cu bridges.
N
N
CuX, r.t.
N
˚
4b
N
Thus, the Cu(2)–I(2) bond distance (2.827(1) A) is notably
CH3CN or
CH3CN/
toluene
˚
N
longer than that for the bond Cu(1)–I(1) (2.580(1) A). Nev-
N
XCu
CuX
ertheless, both values are considerably less than the sum of
˚
ionic radii for copper and iodine (3.15–3.20 A) and closer
to the sum of covalent radii for these atoms (2.60–
˚
˚
2.65 A). The Cu–C(1) bond distance (1.928(3) A) is also
closer to the sum of atomic radii for the indicated atoms
5a,b
X = Cl, I
˚
Scheme 2.
(2.05 A) than to the sum of ionic radii for copper and car-

A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
1409
3.1.1. 4,40-p(m)-Phenylene-bis-[1-(1-adamantyl)-3-phenyl-
1,2,4-triazolium] bromides (3a,b)
A mixture of (1,3-) or (1,4-)-bis-(3-phenyl-1,2,4-triazole-
4-yl)benzene 2a,b (1.5 g, 4.12 mmol) and 1-bromoadaman-
tane (2.12 g, 9.9 mmol) in acetic acid (4 mL) or dimethyl-
formamaide (6 mL) was refluxed for 6 h, followed by the
addition of 1-bromoadamantane (0.27 g, 1.26 mmol) and
heating for 8 h. After the reaction was complete, the mix-
ture was treated with 10–15 mL of diethyl ether and the
resulting precipitate was filtered off, washed with small
amounts of hexane and diethyl ether, then dried. Each bro-
mide salt was converted into the corresponding perchlorate
by treatment with an excess of sodium perchlorate (2.02 g,
16.5 mmol) in aqueous solution.
Fig. 2. X-ray structure of the DMF solvate of copper iodide biscarbene
complex 5b showing the atom numbering scheme.
Perchlorate 3a: yield 96%, m.p. 285–287 ꢁC (DMF–
water, 2:3). 1H NMR (DMSO-d6, 200 MHz): 1.70–1.90
(m, 12H), 2.05–2.55 (m, 18H, Ad), 7.46–7.82 (m, 14H,
Ar), 10.67 (s, 2H, CHN). 13C NMR (DMSO-d6,
50.3 MHz): 28.2; 34.6; 40.3; 62.6 (Ad); 127.8; 128.6;
128.8; 131.6 (Ar); 122.1 (ipso-CC); 133.4 (ipso-CN); 141.8
(C5); 152.0 (C3). Anal. Calc. for C42H46Cl2N6O8: C,
60.50; H, 5.56; Cl, 8.50; N, 10.08. Found: C, 60.60; H,
5.49; Cl, 8.37; N, 10.01%.
˚
bon atom (1.72 A). On the other hand, the Cu(1)–Cu(2)
˚
distance (2.663(1) A) exceeds the sum of atomic radii
˚
(2.56 A) and is significantly larger than the sum of ionic
˚
radii for two copper atoms (1.90 A). Clearly, there is no
direct bonding interaction between the two copper centers.
The metrical parameters for the triazole rings are similar to
those for the monocarbenes [13,14]. The multiplicity of the
C(Ar)–C(2) bond (Penney–Dirac order p = 1.345) calcu-
lated using the linear dependence of p on bond length is
notably larger than that for the C(Ar)–N(2) bond
(p = 1.178). This is probably due to the larger twist angle
of aromatic ring at nitrogen N(2)than at carbon atom C(2).
In summary, we have synthesized representatives of a
new class of stable biscarbenes of the 1,2,4-triazole series,
namely the 4,40-arylene-bis-1,2,4-triazol-5-ylidenes 4a,b.
Two copper(I) halide complexes have been prepared along
with two new organic derivatives, 6 and 7.
Perchlorate 3b: yield 100%, m.p. 266–267 ꢁC (acetic
acid–water, 2:1); 1H NMR (DMSO-d6, 200 MHz):
1.59–1.97 (m, 12H), 2.02–2.44 (m, 18H, Ad), 7.39–7.93
(m, 14H, Ar), 10.59 (s, 2H, CHN). 13C NMR
(DMSO-d6, 50.3 MHz): 28.7; 35.0; 40.9; 63.2 (Ad);
125.6; 129.2 (enhanced int.); 130.0; 131.7; 132.2 (Ar);
122.3 (ipso-CC); 133.0 (ipso-CN); 142.3 (C5); 152.6
(C3). Anal. Calc. for C42H46Cl2N6O8: C, 60.50; H,
5.56; Cl, 8.50; N, 10.08. Found: C, 60.72; H, 5.37; Cl,
8.52; N, 10.18%.
3.1.2. 1,4-Bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-
yliden-4-yl]benzene (4a)
Sodium hydride (0.31 g, 0.72 mmol) in a 55% mineral oil
suspension was added to a solution of 0.3 g (0.36 mmol) of
4,40-p-phenylene-bis-[1-(1-adamantyl)-3-phenyl-1,2,4-tria-
zolium] perchlorate in 6 mL of acetonitrile at ꢁ78 ꢁC and
the resulting reaction mixture was stirred for 40–50 min,
during which time the temperature rose gradually to
25 ꢁC. The progress of the reaction was monitored by the
volume of hydrogen evolved (8.1 mL). When the reaction
was complete, the precipitate was filtered off, washed 2–3
times with small quantities of acetonitrile, and vacuum
dried at 80 ꢁC for 1 h. Yield 0.2 g (88%), m.p. 186–
188 ꢁC (toluene). 1H NMR spectrum (Py-d5, 200 MHz):
1.55–1.92 (m, 12H), 2.04–2.25 (m, 6H), 2.43–2.62 (m,
12H, Ad); 7.15–7.55 (m, Ar). 1H NMR (benzene-d6):
1.70–1.92 (m, 12H), 2.00–2.10 (m, 6H), 2.40–2.82 (m,
12H, Ad); 6.50–8.12 (m, 14H, Ar). 13C NMR (Py-d5,
50.3 MHz): 30.6; 37.0; 44.3; 60.2 (Ad); 125.8; 127.9;
128.7; 129.2; 129.8 (Ar); 130.0 (ipso-CC); 141.2 (ipso-
CN); 151.4 (C3); 206.2 (C5). Anal. Calc. for C42H44N6:
C, 79.71; H, 7.01; N, 13.28. Found: C, 79.89; H, 7.21; N,
13.54%.
3. Experimental
3.1. General
All experiments with biscarbenes 4a,b were carried out
under an argon atmosphere. All solvents were dried by
standard methods prior to use. 1H and 13C NMR chemical
shifts are reported relative to tetramethylsilane (TMS,
d = 0.00) as internal standard. IR spectra were measured
as Nujol mulls and thin-layer chromatography was per-
formed on silica gel with chloroform or a 10:1 mixture of
chloroform and methanol as eluent, followed by develop-
ment with iodine. Elemental analyses were carried out at
the Analytical Laboratory of the Litvinenko Institute of
Physical Organic and Coal Chemistry. Triazoles 2a,b were
obtained by the ring transformation of the respective
oxadiazole 1 with p-phenylenediamine dihydrochloride or
m-phenylenediamine in the presence of trifluoroacetic acid.
Both reactions were carried out in o-dichlorobenzene at
180 ꢁC according to the literature method [12].

1410
A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
3.1.3. 1,3-Bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-
yliden-4-yl]benzene (4b)
C42H44Cu2I2N6: C 49.76; H 4.37; Cu 12.54; I 25.04; N
8.29. Found: C 49.67; H 4.41; Cu 12.29; I 24.78; N 8.51%.
A mixture of 4,40-m-phenylene-bis-[1-(1-adamantyl)-3-
phenyl-1,2,4-triazolium] perchlorate (0.6 g, 0.72 mmol)
and 99% potassium tert-butoxide (0.16 g, 1.44 mmol) in
6 mL of toluene and 1.5 mL of tert-butanol was stirred at
room temperature for 15 min. The reaction mixture was fil-
tered and the resulting precipitate was washed with small
quantities of toluene, following which the mother liquor
was vacuum evaporated. The crude carbene was dried
under vacuum at 50–60 ꢁC for 30–40 min, triturated with
4 mL of hexane, then filtered off and dried. Yield 0.41 g
3.1.6. 1,4-Bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-
(2,2-diphenylazin)-4-yl]benzene (6)
A mixture of carbene 4a (0.15 g, 0.24 mmol), diphe-
nyldiazomethane (0.092 g, 0.48 mmol) and toluene
(1.5 mL) was heated at 50 ꢁC for 10 h. The reaction
mixture was stirred with hexane (5 mL), the precipitate
formed was filtered off, washed with small amounts of
hexane and dried. Yield 0.17 g (70%), m.p. 268–270 ꢁC
(DMF). 1H NMR (CDCl3, 200 MHz): 1.43–1.77 (m,
12H), 2.03–2.36 (m, 18H, Ad); 6.90–7.55 (m, 14H,
Ar). 13C NMR (CDCl3, 50.3 MHz): 29.7; 36.1; 39.4;
60.1 (Ad); 126.5; 127.4; 127.6; 128.1; 128.2; 129.0;
129.3; 129.7 (Ar); 126.7; 137.2; 139.2; 145.3 (ipso-C);
149.4 (C3); 155.2 (C5). Anal. Calc. for C68H64N10: C,
79.97; H, 6.32; N, 13.71. Found: C, 80.21; H, 6.18;
N, 13.66%.
1
(90%), m.p. 140 ꢁC (cyclohexane). H NMR (benzene-d6,
200 MHz): 1.72–1.95 (m, 12H), 2.08–2.37 (m, 6H), 2.51–
2.96 (m, 12H, Ad); 6.96–7.83 (m, 14H, Ar). 13C NMR (ben-
zene-d6, 50.3 MHz): 30.0; 36.6; 43.9; 59.7 (Ad); 101.9;
125.3; 127.90; 128.7; 129.2; 129.8 (Ar); 130.0 (ipso-CC);
140.9 (ipso-CN); 150.8 (C3); 209.2 (C5). Anal. Calc. for
C42H44N6: C, 79.71; H, 7.01; N, 13.28. Found: C, 79.78;
H, 7.06; N, 13.44%.
3.1.7. 1,3-Bis-[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-
thion-4-yl]benzene (7)
3.1.4. Complex of 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-
triazol-5-yliden-4-yl]benzene with copper(I) chloride (5a)
A mixture of carbene 4b (0.15 g, 0.24 mmol) and cop-
per(I) chloride (0.047 g, 0.48 mmol) in 3 mL of acetonitrile
was stirred for 1.5 h. The solvent was evaporated and the
resulting precipitate was triturated with diethyl ether. Fol-
lowing filtration, the isolated product was purified by flash
chromatography on silica gel (the eluent is chloroform).
The solvent was evaporated and the residue was triturated
with hexane, filtered off and dried. The resulting complex
was crystallized from DMF. Yield 0.1 g (50%), m.p. 271–
A mixture of carbene 4b (0.2 g, 0.32 mmol), elemental
sulfur (0.04 g, 1.26 mmol) and toluene (2 mL) was stirred
at room temperature for 8 h. A further 0.03 g (0.94 mmol)
of sulfur was then added and the reaction mixture was
refluxed for a short time. Then hexane (5 mL) was added
to the cooled reaction mixture, and the resulting precipitate
was filtered off, washed with small amounts of hexane, and
1
dried. Yield 0.17 g (77%), m.p. >310 ꢁC (DMF). H NMR
(CDCl3, 200 MHz): 1.60–1.96 (m, 12H), 2.07–2.43 (m, 6H),
2.56–2.90 (m, 12H, Ad); 7.00–7.64 (m, 13H), 7.85 (s, 1H,
Ar). 13C NMR (CDCl3, 50.3 MHz): 29.6; 35.8; 39.1; 63.5
(Ad); 125.0; 128.3; 128.5; 128.9; 130.1; 130.4 (Ar); 131.8;
135.6 (ipso-C); 147.7 (C3); 166.2 (C5). Anal. Calc. for
C42H44N6S2: C, 72.38; H, 6.36; S, 9.20; N, 12.06. Found:
C, 72.54; H, 6.40; S, 9.09; N, 12.22%.
1
273 ꢁC (DMF). H NMR (CDCl3, 200 MHz): 1.76–2.00
(m, 12H), 2.30–2.48 (m, 6H), 2.53 (m, 12H, Ad); 7.07–
7.68 (m, 13H), 8.21 (s, 1H, Ar). 13C NMR (CDCl3, 50.3
MHz): 29.7; 35.8; 43.8; 62.0 (Ad); 124.0; 125.6; 128.2;
129.3; 129.4; 130.7 (Ar); 131.0 (ipso-CC); 138.8 (ipso-
CN); 151.9 (C3); 178.6 (C5). Anal. Calc. for
C42H44Cl2Cu2N6: C, 60.72; H, 5.34; Cl, 8.53; Cu, 15.30;
N, 10.11. Found: C, 60.51; H, 5.28; Cl, 8.42; Cu, 15.10;
N, 10.16%.
3.2. X-ray crystallography
Crystals of 4a and 4b were removed from sealed
vials, placed on glass slides, covered with degassed
hydrocarbon oil, and mounted on thin nylon loops.
The X-ray diffraction data were collected at 153(2) K
on a Nonius Kappa CCD area detector diffractometer
equipped with an Oxford Cryostream low-temperature
device and a graphite-monochromated Mo Ka radia-
3.1.5. Complex of 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-
triazol-5-ylidene-4-yl]benzene with copper(I) iodide (5b)
A mixture of carbene 4b (0.13 g, 0.21 mmol) and cop-
per(I) iodide (0.078 g, 0.41 mmol), in 3 mL of acetonitrile
and 1.5 mL of toluene was stirred for 1.5 h. The precipi-
tated complex 5b was filtered off, washed with small
amounts of acetonitrile and diethyl ether, then dried. The
isolated product was purified by flash chromatography
on silica gel (chloroform eluent). Yield 0.15 g (72%), m.p.
˚
tion source (k = 0.71073 A). Corrections were applied
for Lorentz and polarization effects. Both structures
were solved by direct methods and refined by full-
matrix least-squares cycles on F2 [17]. All non-hydro-
gen atoms were refined with anisotropic thermal
parameters and hydrogen atoms were placed in fixed,
1
263–265 ꢁC (DMF). H NMR (CDCl3, 200 MHz): 1.61–
1.88 (m, 12H), 2.05–2.41 (m, 6H), 2.41–2.72 (m, 12H,
Ad); 6.76–7.54 (m, 13H), 8.94 (s, 1H, Ar). 13C NMR
(CDCl3, 50.3 MHz): 29.9; 36.1; 42.9; 62.0 (Ad); 122.8;
126.5; 128.4; 129.1; 129.5; 130.8 (Ar); 125.6 (ipso-CC);
138.4 (ipso-CN); 150.5 (C3); 184.5 (C5). Anal. Calc. for
calculated positions using
a
riding model (C–H
˚
0.96 A). Pertinent experimental data are listed in Table
1 and selected metrical parameters are compiled in
Table 2.

A.V. Knishevitsky et al. / Journal of Organometallic Chemistry 693 (2008) 1405–1411
1411
[5] I.P. Shvaika, N.I. Korotkikh, A.F. Aslanov, Chem. Heterocycl.
Comp. (Latvia) (1992) 1155–1170.
Acknowledgements
[6] H.V.R. Dias, W. Jin, Tetrahedron Lett. 35 (1994) 1365–
1366.
[7] W.A. Herrmann, M. Elison, J. Fischer, K. Kocher, G.R.J. Artus,
Chem. Eur. J. (1996) 1627–1636.
We thank the Ukrainian Academy of Sciences for finan-
cial support and the Robert A. Welch Foundation for
financial support of the X-ray diffraction studies.
[8] N.I. Korotkikh, A.V. Kiselyov, G.F. Rayenko, N.M. Olyinik, O.P.
Shvaika, Rep. Ukr. Acad. Sci. 6 (2002) 142–146.
[9] M. Albrecht, R.H. Crabtree, J. Mata, E. Peris, Chem. Commun.
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[10] V.C. Vargas, R.J. Rubio, T.K. Hollis, M.E. Salcido, Org. Lett. 5
(2003) 4847–4849.
[11] J.A. Mata, C. Incarvito, R.H. Crabtree, Chem. Commun. (2003)
184–185.
[12] N.I. Korotkikh, A.V. Kiselyov, A.V. Knishevitsky, G.F. Rayenko,
O.M. Pekhtereva, I.P. Shvaika, Chem. Heterocycl. Comp. (Latvia)
7 (2005) 1026–1032.
[13] N.I. Korotkikh, G.F. Rayenko, O.P. Shvaika, Rep. Ukr. Acad. Sci. 2
(2000) 135–140.
[14] (a) N.I. Korotkikh, G.F. Rayenko, O.P. Shvaika, T.M. Pekhtereva,
A.H. Cowley, J.N. Jones, C.L.B. Macdonald, J. Org. Chem. 68
(2003) 5762–5765;
Appendix A. Supplementary material
CCDC 623045 and 623046 contain the supplementary
crystallographic data for 4a and 5b. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.07.056.
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