Metal complexes of an N-selenocarbamoyl benzamidine

Article abstract of DOI:10.1016/j.poly.2011.11.008

The N-selenocarbamoyl benzamidine 4-MeC₆H₄N(H)C(Ph) NC(Se)NEt₂ (HL) was prepared from the reaction of the corresponding isoselenocyanate with Et₂NH. The reactivity of HL with various metal compounds including [Ni(OAc)₂], [PdCl₂(^tBu ₂bipy)], H[AuCl₄], [AuCl(SMe₂)] as well as the cyclometallated species [Pd(OAc){κC,N-C₆H₄N(Me)NO}] ₂ was studied. In the case of the Ni(II) and Pd(II) compounds, square planar bis(chelate) complexes were formed in which the deprotonated N-selenocarbamoyl benzamidine acts as a monoanionic [Se,N]^- ligand. Reaction of the gold(III) precursor with two equivalents of HL, resulted in reduction and formation of the gold(I) complex [AuCl(HL)], in which the neutral N-selenocarbamoyl benzamidine coordinates to the metal only via the selenium atom. The same coordination mode of the N-selenocarbamoyl benzamidine is observed in the gold(I) salt [Au(HL)₂]Cl. Both these complexes are also accessible from the reaction of [AuCl(SMe₂)] with one or two equivalents of HL. The electronic structure of the ligand was studied using computational methods.

Full text of DOI:10.1016/j.poly.2011.11.008

Polyhedron 33 (2012) 107–113
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Metal complexes of an N-selenocarbamoyl benzamidine
⇑
Angela Bredenkamp, Xiaoqing Zeng, Fabian Mohr
Fachbereich C, Anorganische Chemie, Bergische Universität Wuppertal, 42119 Wuppertal, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The N-selenocarbamoyl benzamidine 4-MeC6H4N(H)C(Ph)@NC(Se)NEt2 (HL) was prepared from the
reaction of the corresponding isoselenocyanate with Et2NH. The reactivity of HL with various metal com-
pounds including [Ni(OAc)2], [PdCl2(tBu2bipy)], H[AuCl4], [AuCl(SMe2)] as well as the cyclometallated
Received 28 October 2011
Accepted 9 November 2011
Available online 26 November 2011
species [Pd(OAc){jC,N-C6H4N(Me)N@O}]2 was studied. In the case of the Ni(II) and Pd(II) compounds,
square planar bis(chelate) complexes were formed in which the deprotonated N-selenocarbamoyl ben-
zamidine acts as a monoanionic [Se,N]À ligand. Reaction of the gold(III) precursor with two equivalents
of HL, resulted in reduction and formation of the gold(I) complex [AuCl(HL)], in which the neutral N-sel-
enocarbamoyl benzamidine coordinates to the metal only via the selenium atom. The same coordination
mode of the N-selenocarbamoyl benzamidine is observed in the gold(I) salt [Au(HL)2]Cl. Both these
complexes are also accessible from the reaction of [AuCl(SMe2)] with one or two equivalents of HL.
The electronic structure of the ligand was studied using computational methods.
Keywords:
Selenium ligands
Chelating ligands
X-ray crystal structure
NBO analysis
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
In continuation of our exploration of the coordination chemistry
of organoselenium compounds [11–19], we wished to study the
In 1984, the group of Beyer reported that the reaction of
nickel(II) thioureato bis(chelates) react with SOCl2 to give good
yields of N-(amino-thiocarbonyl)benzimido chlorides, which can
be further functionalised by reaction with primary amines to give
the corresponding N-thiocarbamoyl benzamidines (Scheme 1) [1,2].
These N-thiocarbamoyl benzamidines react with various metal
salts to give bis(chelate) complexes in which the deprotonated,
monoanionic N-thiocarbamoyl benzamidine coordinates to the
metal through the sulfur and nitrogen atoms forming M–S–C–N–
C–N heterocycles (Scheme 2). Examples of bis(chelate) complexes
containing N-thiocarbamoyl benzamidines have been reported
with metals including Cu(II), Ni(II), Co(II), Pt(II) and Pd(II) [2–8].
Such compounds can therefore be considered nitrogen analogues
of thioureas, which form M–S–C–N–C–O cycles (Scheme 2).
In marked contrast, the chemistry of their selenium counterparts,
the N-selenocarbamoyl benzamidines, is virtually unexplored.
Beyer reported that whilst the N-(aminoselenocarbonyl)benzimido
chlorides are not accessible from the corresponding Ni(II) bis(sele-
noureato) complexes, they can however be prepared from the
reaction of N-acyl selenoureas with thiophosgene (Scheme 3) [9].
The group of Heimgartner more recently reported an alternative
synthesis procedure which leads directly to N-selenocarbamoyl
benzamidines from the corresponding isoselenocyanates, which
are readily accessible in two-steps from N-aryl benzamides
(Scheme 4) [10].
reactivity of the N-selenocarbamoyl benzamidine 4-MeC6H4N(H)
C(Ph)@NC(Se)NEt2 (HL) with various transition metal compounds.
Some results of this investigation are reported herein.
2. Results and discussion
Following the Heimgartner procedure [10], we prepared isose-
lenocyanate
A in two steps from N-(p-tolyl)benzamide. The
isoselenocyanate was subsequently reacted with Et2NH to afford
4-MeC6H4N(H)C(Ph)@NC(Se)NEt2 (HL) as a stable, orange-yellow
solid in 76% yield (Scheme 5).
The identity of HL was confirmed by NMR spectroscopy (see
Section 4) and also by single crystal X-ray diffraction (Fig. 1).
The solid-state structure of HL is very similar to that of the mor-
pholino derivative reported by Heimgartner [10]. Here too, the NH
proton is located on the nitrogen atom between the two aryl rings
(N3) and not (as is the case in the selenoureas) on the nitrogen
atom adjacent to the C–Se unit (N2). The C–N bond lengths along
the N–C–N–C(Se)–NEt2 backbone also clearly show the presence
of a C@N double bond between C5 and N2. Within the asymmetric
unit hydrogen bonding interactions between the selenium atom of
one molecule and the N(3)–H proton of an adjacent molecule
(SeÁ Á ÁH–N distance of ca. 2.62 Å) can be observed. Such hydrogen
bonding is also observed in the morpholino analogue (SeÁ Á ÁH–N
distance of ca. 2.64 Å).
The reaction of HL with Ni(OAc)2 gave a dark solution out of
which a dark green solid precipitated in moderate yield (Scheme
6). The material was found to be insoluble or poorly soluble in
⇑
Corresponding author.
E-mail address: fmohr@uni-wuppertal.de (F. Mohr).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.11.008

108
A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
R2N
R2N
N
Ph
Ph
R`
R`
S
N
S
HN
S
Cl
S
S
O
O
R`NH2
SOCl2
Ni
R2N
N
H
Ph
R2N
N
Ph
R2N
N
Ph
N
Scheme 1.
environment around the metal. Possible reasons for these differ-
ences will be discussed below. In the selenoureato compound the
selenium atoms are also cis to each other. The Ni–Se and Ni–N bond
distances in complex 1 [2.2784(5) and 1.916(3) Å, respectively] are
similar to those observed in [Ni{PhC(O)NC(Se)NEt2}2] [Ni–Se =
2.244(1) Å] and [Ni{PhC(NPh)NC(S)NEt2}2] [Ni–N = 1.90(1) Å],
respectively.
R2N
N
R2N
R2N
Ph
N
Ar
Ar
R`
Base
Metal precursor
S
N
N
S
O
O
S
HN
R'
M
N
M
N
R`
R2N
N
Ph
S
S
R2N
Ph
We subsequently examined the reactivity of HL with two palla-
dium(II) species: HL reacts with [PdCl2(tBu2bipy)] in the presence
of base to give the cationic species [Pd(L)(tBu2bipy)]+ (2) which
was isolated as the orange-brown PF6 salt in good yield (Scheme
6). The proton NMR spectrum of 2 indicated that deprotonation
of HL had occurred and doubling of all three signals from the tBu2-
bipy protons was consistent with an asymmetric coordination
environment about the metal. The high-resolution electrospray
mass spectrum of the compound showed a strong signal corre-
sponding to the molecular ion of the cation, whose observed isoto-
pic distribution pattern perfectly agreed with the calculated one.
Whilst we were unable to obtain X-ray quality crystals of 2, the
spectral data is consistent with the presence of a heteroleptic salt
in which the deprotonated ligand is coordinated to the tBu2bipyPd
unit via Se and N atoms. We have previously prepared and struc-
turally characterised similar heteroleptic tBu2bipyPd(II) complexes
with deprotonated thio- and selenoureas [18,21].
Scheme 2.
R2N
R2N
N
Ph
Ph
Se
O
Se Cl
Se
Se
O
CSCl
2
SOCl2
Ni
R2N
N
H
Ph
R2N
N
Ph
O
N
Scheme 3.
common solvents including CH2Cl2, CHCl3, MeOH, acetone, dmso
and dmf.
The 1H NMR spectrum recorded in dmso was not very diagnos-
tic. Apart from the disappearance of the NH signal, there was little
change in position and multiplicity of the signals. In order to
unambiguously identify the structure of the compound, an X-ray
diffraction study was carried out (Fig. 2).
The cyclometallated acetato-bridged dimer [Pd(OAc){jC,N-
C6H4N(Me)N@O}]2 reacts with HL to give the yellow compound
(3) in high yield (Scheme 6). No additional base is required since
the acetate ions from the palladacycle are basic enough to deproto-
nate the ligand. The compound was fully characterised by NMR
spectroscopy. The data showed again signals due to the presence
of the deprotonated ligand as well as those of the cyclometallated
nitrosamine. X-ray quality crystals were obtained, which allowed
us to determine the solid-state structure of complex 3 (Fig. 3).
The molecule consists of the deprotonated selenocarbamoyl
benzamidine coordinating to the Pd centre through the selenium
and nitrogen atoms. The square planar geometry about the metal
centre is completed by the nitrosamine ligand which coordinates
through the arene carbon atom and the nitrogen atom of the
In complex 1 two deprotonated selenocarbamoyl benzamidine
molecules coordinate to the nickel atom through the selenium
atom and nitrogen atom (N3); the selenium atoms being cis to each
other (Fig. 2). The coordination geometry about the nickel centre
can be described as distorted square planar, with the six-membered
rings adopting an almost boat-like conformation. These same
structural features are also observed in the sulfur analogue
[Ni{PhC(NPh)NC(S)NEt2}2] [8]. At this point it is also appropriate
to compare complex 1 with the structurally similar nickel(II) sele-
noureato bis(chelate) complex [Ni{PhC(O)NC(Se)NEt2}2] [20]. In
this compound the six-membered rings are, however, virtually
planar, leading to an almost perfect square planar coordination
Se
C
N
Ph
1.SOCl2
2.KSeCN
O
Se HN
N
R`2NH
Ph
N
H
R`2N
Ph
N
R
R
R=H,Me,Cl
R
Scheme 4.
Me
Se
C
N
Me
1.SOCl2
2.KSeCN
O
Et2NH
Me
Se HN
Ph
N
H
Et2N
N
Ph
Ph
N
A
HL
Scheme 5.

A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
109
for neutral HL. A subsequent X-ray diffraction study revealed the
compound to be a gold(I) chlorido complex containing the neutral
selenocarbamoyl benzamidine acting as a Se-donor ligand (Fig. 4).
As expected for a gold(I) compound, the coordination geometry
about the metal is linear [179.86(4)°] and the angle at the selenium
atom is about 103°, typical for gold compounds containing sele-
nium donor ligands [11]. The same is true for the gold-selenium
distance which is typical for a gold(I) complex containing a neutral
selenium donor ligand [11]. Complex 4 is generated by reduction of
the gold(III) starting material by the selenocarbamoyl benzamidine
which is itself thereby oxidised. The second equivalent of HL then
coordinates to the AuICl unit. This behaviour of HL mimics that of
structurally similar sulfur compounds [4]. In this case too, the
thiocarbamoyl benzamidines reduce the H[AuCl4] forming cyclic
1,2,4-thiadiazolium salts as oxidation products (Scheme 7). A sub-
sequent paper reports the isolation and structural characterisation
of these compounds as their [AuCl2]À salts [22]. Analogous 1,2,4-
selenadiazolium salts are known, however they are reported to
be unstable and readily undergo a rearrangement reaction to give
2H-1,3,5-selenadiazines [23].
Upon standing in CDCl3 for several days samples of 4 deposited
crystals which appeared different than those of the batch used for
the structure determination. An X-ray diffraction study allowed us
to identify the compound as the gold(I) salt [Au(HL)2]Cl in which
two neutral selenocarbamoyl benzamidine ligands coordinate to
the metal (Fig. 5).
Fig. 1. Molecular structure of HL. Ellipsoids show 50% probability levels. Hydrogen
atoms are shown as spheres with arbitrary radii. Selected bond lengths (Å): Se(1)–
C(4) 1.873(3), N(1)–C(4) 1.330(4), N(2)–C(4) 1.346(4), N(2)–C(5) 1.294(4), C(5)–
N(3) 1.353(4). Selected bond angles (°): N(1)–C(4)–Se(1) 123.6(2), C(4)–N(2)–C(5)
126.2(3), N(2)–C(5)–N(3) 118.9(3).
Structurally salt 5 is rather similar to the neutral complex 4.
Two neutral selenocarbamoyl benzamidine ligands coordinate to
the gold(I) centre in a linear fashion. The bond distances and angles
are again typical for gold(I) salts containing neutral Se-donor
ligands [11]. Unfortunately, there was not enough material for
NMR spectroscopy; however the high-resolution electrospray mass
spectrum showed a single peak whose isotopic distribution pattern
corresponds to the molecular ion of the expected cation. The com-
pound is probably formed by displacement of the chlorido ligand
N@O group. The selenium is located trans to the nitrogen atom of
the nitrosamine, an orientation which has previously been
observed in a nitrosamine derived palladacycle containing a depro-
tonated selenourea ligand [15]. In this structure too, the deproto-
nated selenocarbamoyl benzamidine unit is not planar but
adopts a boat-like conformation; the coordination geometry about
the Pd centre is however square planar.
Two equivalents of HL react with H[AuCl4] giving a yellow
material (4) the 1H NMR spectrum of which shows only the signals
N
Ph
NEt2
C
NH
Se
Au
Se
Me
Cl
Et2N
Et2N
N
Ph
Ph
Me
Se
N
Me
HN
Ni
C
Et2N
Ph
N
Se
N
Me
vi
5
( )
i
N
1
( )
HL
v
ii
tBu
tBu
iv
Ph
N
NEt2
C
iii
N
N
Pd
NH
PF6
Se
Au
Cl
Me
N
Se
N
Me
O
N
Me
Me
Et2N
N
Ph
Pd
Se
4
( )
N
2
( )
Et2N
Ph
N
3
( )
Scheme 6. (i) Ni(OAc)2. (ii) [PdCl2(tBu2bipy)], Et3N, NH4PF6. (iii) [Pd(OAc){
jC,N-C6H4N(Me)N@O}]2. (iv) 0.5 eq. H[AuCl4] or [AuCl(SMe2)]. (v) Standing in CDCl3. (vi) 0.5 eq.
[AuCl(SMe2)].

110
A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
Fig. 2. Molecular structure of compound 1. Ellipsoids show 50% probability levels.
Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å): Ni(1)–
Se(1) 2.2784(5), Ni(1)–N(3) 1.916(3), Ni(1)–Se(2) 2.2934(5), Ni(1)–N(6) 1.915(3),
Se(1)–C(5) 1.921(3), N(3)–C(6) 1.310(4), N(2)–C(6) 1.344(4), N(2)–C(5) 1.312(4),
C(5)–N(1) 1.341(4). Selected bond angles (°): Ni(1)–Se(1)–C(5) 94.71(10), Se(1)–
Ni(1)–Se(2) 85.139(19), Se(1)–Ni(1)–N(6) 162.27(8), Se(1)–Ni(1)–N(3) 93.18(8),
Se(1)–C(5)–N(2) 124.1(2), C(5)–N(2)–C(6) 125.0(3), N(2)–C(6)–N(3) 125.9(3).
Fig. 3. Molecular structure of compound 3. Ellipsoids show 50% probability levels.
Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å): Pd(1)–
Se(1) 2.3804(7), Pd(1)–N(3) 2.115(4), Pd(1)–C(20) 1.979(5), Pd(1)–N(4) 2.040(5),
Se(1)–C(5) 1.929(6), C(5)–N(2) 1.295(7), N(2)–C(6) 1.369(7), C(6)–N(3) 1.301(7).
Selected bond angles (°): Se(1)–Pd(1)–N(4) 170.72(15), Se(1)–Pd(1)–C(20)
94.35(16), Se(1)–Pd(1)–N(3) 88.53(13), N(4)–Pd(1)–N(3) 96.73(19), Pd(1)–Se(1)–
C(5) 91.42(17), Se(1)–C(5)–N(2) 125.8(4), C(5)–N(2)–C(6) 126.0(5), N(2)–C(6)–N(3)
123.4(6), C(6)–N(3)–Pd(1) 125.9(4).
by free selenocarbamoyl benzamidine in solution. Both complexes
4 and 5 can also be prepared by the direct reaction of HL with one
or two equivalents of the gold(I) compound [AuCl(SMe2)] (Scheme
6). Spectroscopic data for complex 4 prepared by this method is
identical to that for the product obtained using the Au(III) precur-
sor. As would be expected, the proton NMR spectrum of salt 5
shows the same sets of resonances (including a broad NH signal)
as that of complex 4. We were however able to obtain a 77Se
NMR spectrum of 5: the observed chemical shift of 348 ppm occurs
within the same range as those of structurally similar Au(I) seleno-
ureato complexes [24].
As mentioned in the structural discussions above, the coordi-
nated selenocarbamoyl benzamidine ligand is not planar. Given
this marked difference to the selenoureas, which form planar
chelate rings, we studied possible reasons for this difference by
computational methods. Using the coordinates from the X-ray
structures of complex 1 and the selenoureato nickel complex
[Ni{PhC(O)NC(Se)NEt2}2] [20], we carried out an NBO calculation
using GAUSSIAN 03 [25].
Both the Wiberg bond indices and the atomic charges (Fig. 6)
show that in complex 1, the delocalisation is less pronounced when
compared to the selenourea derivative. This is manifested by
Wiberg bond indices indicating delocalised bonding between the
carbon, nitrogen and oxygen atoms in the backbone of the selenou-
rea. In contrast, in the selenocarbamoyl benzamidine bonding in
the C–N–C–N unit alternates between single and delocalised. The
same trend can be observed in the C–N bond distances. One of
the C–N bonds in complex 1 is with 1.344 Å significantly longer
than the other two (1.310 Å). As a consequence of this reduced
delocalisation, the ring does not need to be planar resulting in the
observed puckered structure.
Fig. 4. Molecular structure of compound 4. Ellipsoids show 50% probability levels.
Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å): Au(1)–
Se(1) 2.3672(5), Au(1)–Cl(1) 2.2952(12), Se(1)–C(5) 1.904(5), C(5)–N(2) 1.342(6),
N(2)–C(6) 1.294(6), C(6)–N(3) 1.349(5). Selected bond angles (°): Cl(1)–Au(1)–Se(1)
179.86(4), Au(1)–Se(1)–C(5) 102.99(13), Se(1)–C(5)–N(2) 122.4(3), C(5)–N(2)–C(6)
126.9(4), N(2)–C(6)–N(3) 120.2(4).
ionic [N,Se]À donor. In contrast to the selenoureato complexes,
the metallacycles containing selenocarbamoyl benzamidine are
not planar but form boat-like rings. Furthermore, the compound
may also act as neutral Se-donor in gold(I) complexes. Electronic
structure calculations show that the ligand backbone is not
completely delocalised, thus giving rise to non-planar rings. We
are currently further developing the coordination chemistry of this
new class of ligands with other transition and main-group metals.
3. Conclusions
4. Experimental
In conclusion, we have prepared a selenocarbamoyl benzami-
dine and have explored its coordination chemistry with various
transition metal species. Like the selenoureas the selenocarbamoyl
benzamidine can form both homoleptic and heteroleptic complexes
with divalent metals in which the ligand coordinates as monoan-
4.1. General
1H, 13C{1H} and 77Se NMR spectra were recorded on a 400 or
600 MHz Bruker Avance spectrometer. Chemical shifts are quoted

A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
Ph
NH
111
N
NEt2
Ph
Ar
N
E
Ph
HN
N
NEt2
H[AuCl4]
E
NEt2
X
+
Ar
N
E
Ar
Au
Cl
E=Se,Ar=p-tol(4)
E=S,Ar=Ph
Scheme 7.
NEt2
NEt2
1.06
0.90
1.20
Se
O
C
C
Se
C
C
1.31
N
1.18
N
0.35
0.46
Ni
Ni
1.04
1.28
0.23
0.22
N
1.33
Ph
p-tol
Ph
NEt2
+0.46
NEt2
-0.33
-0.35
Se
Se
C
C+0.42
N
-0.80
Ni+1.21
N
Ni+1.16
-0.75
O
C
N
C
+0.90
Ph
+0.68
Ph
-0.77
p-tol
-0.87
Fig. 6. Computed Wiberg bond indices (top) and atomic charges (bottom) for
complex 1 and [Ni{PhC(O)NC(Se)NEt2}2].
Fig. 5. Molecular structure of compound 5. Ellipsoids show 50% probability levels.
Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å): Au(1)–
Se(1) 2.3843(6), Au(1)–Se(2) 2.3932(6), Se(1)–C(5) 1.903(5), Se(1)–C(24) 1.901(5),
C(5)–N(2) 1.328(7), N(2)–C(6) 1.305(6), C(6)–N(3) 1.344(7). Selected bond angles
(°): Se(1)–Au(1)–Se(2) 176.66(2), Au(1)–Se(1)–C(5) 104.32(16), Au(1)–Se(2)–C(24)
100.40(16), Se(1)–C(5)–N(2) 122.7(4), C(5)–N(2)–C(6) 127.2(5), N(2)–C(6)–N(3)
118.7(5).
20.80 (Me), 45.26, 48.43 (CH2N), 122.81 (p-tol), 128.13 (m-Ph),
129.30 (o-Ph), 129.47 (p-tol), 130.56 (p-Ph), 134.39 (ipso p-tol),
135.30 (ipso Ph), 136.17 (p-tol), 157.37 (C@N), 183.27 (C@Se).
77Se NMR (76 MHz, CDCl3): d 322. Anal. Calc. for C19H23N3Se
(372.27): C, 61.28; H, 6.23; N, 11.28. Found: C, 61.34; H, 6.11; N,
11.07%. X-ray quality crystals were obtained from recrystallisation
of the compound from EtOH.
relative to external SiMe4 (1H, 13C) or Me2Se (77Se). Elemental anal-
yses were performed by staff of the microanalytical laboratory of
the University of Wuppertal. High-resolution electrospray mass
spectra were recorded on a Bruker Daltonics MicroTOF instrument
in positive ion mode using MeCN solutions of the samples. All reac-
tions were carried out under aerobic conditions unless stated
otherwise. Isoselenocyanate A [10] as well as the metal precursors
4.3. [Ni(L)2] (1)
To a solution of [Ni(OAc)2]Á4H2O (0.068 g, 0.275 mmol) in warm
EtOH (10 mL) was added a solution of HL (0.205 g, 0.55 mmol) in
EtOH (10 mL). After 30 min the dark precipitate was isolated by fil-
tration, washed with H2O, EtOH and dried in air. Yield: 0.084 g
(40%). 1H NMR (400 MHz, CDCl3): d 1.32–1.47 (br. m, 12 H,
CH3CH2N), 2.25 (s, 6 H, Me), 3.63, 4.14 (br. m, 8 H, NCH2), 6.79–
6.86 (m, 8 H, p-tol, Ph), 6.93–7.06 (m, 6 H, Ph), 7.52 (d, J = 7.9 Hz,
4 H, p-tol). Anal. Calc. for C38H44N6Se2Ni (801.41): C, 56.95; H,
5.53; N, 10.49. Found: C, 57.03; H, 5.59; N, 10.65%. X-ray quality
crystals were grown by slow evaporation of the mother liquor.
[PdCl2(tBu2bipy)] [26] [Pd(OAc){
jC,N-C6H4N(Me)N@O}]2 [15] and
[AuCl(SMe2)] [27] were prepared as described in the literature.
All other chemicals and solvents (HPLC grade) were sourced
commercially and used as received.
4.2. HL
To a solution of isoselenocyanate A (2.0 g, 6.7 mmol) in acetone
(20 mL) was added Et2NH (0.8 mL, 7.4 mmol). After stirring for
30 min the orange brown solution was filtered into water
(100 mL), causing an orange-yellow solid to precipitate. The mate-
rial was subsequently isolated by filtration, washed with water and
dried in air. The compound was obtained in 84% yield (2.1 g). 1H
NMR (400 MHz, CDCl3): d 1.27 (t, J = 7.1 Hz, 3 H, CH3CH2N), 1.34
(t, J = 7.1 Hz, 3 H, CH3CH2N), 2.26 (s, 3 H, Me), 3.86 (q, J = 7.1 Hz,
2 H, CH2N), 4.07 (q, J = 7.1 Hz, 2 H, CH2N), 6.82 (d, J = 8.3 Hz, 2 H,
p-tol), 6.98 (d, J = 8.3 Hz, 2 H, p-tol), 7.27–7.32 (m, 2 H, m-Ph),
7.36-7.41 (m, 1 H, p-Ph), 7.57–7.51 (m, 2 H, o-Ph), 11.29 (br. s, 1
H, NH). 13C{1H} NMR (100 MHz, CDCl3): d 12.31, 13.31 (CH3CH2N),
4.4. [Pd(L)(tBu2bipy)]PF6 (2)
To a suspension of [PdCl2(tBu2bipy)] (0.050 g, 0.108 mmol) in
MeOH (5 mL) containing NH4PF6 (0.023 g, 0.141 mmol) was added
HL (0.042 g, 0.113 mmol) and Et3N (1 mL). The mixture was heated
to reflux for 15 min by which time an orange-red solution had
formed. The solution was filtered and the solvent removed in
vacuum. The resulting residue was washed with water and Et2O,
filtered and dried to give the product as a red-brown solid. Yield:
0.87 g (91%). 1H NMR (400 MHz, CDCl3): d 1.26–1.34 (m, 6 H,

112
A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
CH3CH2N), 1.39 (s, 9 H, tBu), 1.46 (s, 9 H, tBu), 2.21 (s, 3 H, Me), 3.76
(q, J = 7.0 Hz, 2 H, CH2N), 3.90 (q, J = 7.0 Hz, 2 H, CH2N), 6.95 (d,
J = 8.1 Hz, 2 H, p-tol), 7.19–7.24 (m, 5 H, Ph), 7.36 (d, J = 8.3 Hz, 2
H, p-tol), 7.42 (dd, J = 6.0, 1.9 Hz, 1 H, H5-bipy), 7.61 (dd, J = 6.1,
2.0 Hz, 1 H, H5-bipy), 7.97 (d, J = 6.0 Hz, 1 H, H6-bipy), 8.05 (d,
J = 1.7 Hz, 1 H, H3-bipy), 8.10 (d, J = 1.9 Hz, 1 H, H3-bipy), 9.05 (d,
J = 6.1 Hz, 1 H, H6-bipy). 13C{1H} NMR (400 MHz, CDCl3): d 12.98,
14.46 (CH3CH2N), 20.88 (Me), 30.05, 30.08 (tBu), 45.00, 48.93
(CH2N), 119.70, 120.49 (C3-bipy), 124.25, 124.57 (C5-bipy),
127.31 (Ph), 127.83 (p-tol), 128.95 (Ph), 129.18 (p-Ph), 129.41 (p-
tol), 136.07 (quart. p-tol), 136.09 (ipso Ph), 144.86 (ipso p-tol),
148.07, 151.99 (C6-bipy), 154.25, 156.52 (C2-bipy), 158.85 (CSe),
165.93, 166.30 (C4-bipy), 172.22 (NCN). 77Se NMR (CDCl3, 114
MHz): d = 233.7. HR-ESMS (m/z): 746.1962 [M]+. Anal. Calc. for
4.6. [AuCl(HL)] (4) from H[AuCl4]
To a solution of H[AuCl4] (0.050 g, 0.133 mmol) in EtOH (10 mL)
was added a solution of HL (0.099 g, 0.0266 mmol) in the same sol-
vent (10 mL). The mixture was heated to reflux for ca. 10 min. The
resulting brownish solution was taken to dryness and the residue
was extracted into CH2Cl2. The solution was subsequently passed
through celite to remove some metallic gold. Concentration of
the filtrate in vacuum and addition of hexanes gave yellow crystals
of the product (0.078 g, 97% yield) after several days. 1H NMR
(400 MHz, CDCl3): d 1.19 (br. m, 3 H, CH3CH2N), 1.33 (br. m, 3 H,
CH3CH2N), 2.39 (s, 3 H, Me), 3.61 (br. m, 2 H, CH2N), 3.81 (br. m,
2 H, CH2N), 7.13 (d, J = 8.0 Hz, 2 H, p-tol), 7.18 (d, J = 8.0 Hz, 2 H,
p-tol), 7.31–7.51 (m, 5 H, Ph), 8.80 (br. s, 1 H, NH). 13C{1H} NMR
(CDCl3, 100 MHz): d = 12.91 (CH3CH2N), 20.61 (Me), 46.70, 49.06
(CH2N), 126.76 (p-tol), 128.56 (Ph), 130.61 (p-tol), 130.96 (Ph),
132.16 (Ph), 134.41 (ipso Ph), 140.46 (quart. p-tol), 158.63 (ipso
p-tol), 166.41(NCN), 179.79 (CSe). Anal. Calc. for C19H23N3SeAuCl
(604.79): C, 37.73; H, 3.83; N, 6.95. Found: C, 37.64; H, 4.01; N,
6.93%. X-ray quality crystals were picked from the bulk sample.
Crystals of [Au(HL)2]Cl (5) deposited from the CDCl3 NMR sample
solution after several days. Whilst there were insufficient crystals
of 5 to obtain any NMR spectra, the HR mass spectrum showed
the molecular ion peak [M]+ for the cation at m/z 943.1789 (calcu-
lated for C38H46N6Se2Au: 943.1780).
C37H46N5PSeF6Pd (891.14): C, 49.87; H, 5.20; N, 7.86. Found: C,
50.01; H, 5.33; N, 7.66%.
4.5. [Pd(L){jC,N-C6H4N(Me)N@O}] (3)
To a solution of [Pd(OAc){
jC,N-C6H4N(Me)N@O}]2 (0.049 g,
0.082 mmol) in MeOH (10 mL) was added a solution of HL
(0.061 g, 0.164 mmol) in the same solvent (10 mL). A yellow solid
deposited almost instantly upon mixing the two solutions. The pre-
cipitate was isolated by filtration, washed with MeOH and dried in
air. The product was obtained as a yellow solid. Yield: 0.060 g
(61%). 1H NMR (400 MHz, CDCl3): d 1.15 1.40 (m, 6 H, CH3CH2N),
2.24 (s, 3 H, Me), 3.34 (s, 3 H, NMe), 3.69 (br. m, 2 H, CH2N), 3.96
(br. m, 2 H, CH2N), 6.84–6.93 (m, 3 H, p-tol, H6-CM ring), 7.05–
7.15 (m, 6 H, H5 CM ring, Ph), 7.17–7.24 (m, 3 H, p-tol, H4 CM ring),
7.83 (dd, J = 7.5, 1.1 Hz, 1 H, H3 CM ring). 13C{1H} NMR (CDCl3,
100 MHz): d = 13.01, 14.37 (CH3CH2N), 20.96 (Me), 30.16 (NMe),
44.41, 47.43 (CH2N), 112.71 (C6 CM ring), 125.28 (C4 CM ring),
125.48 (C5 CM ring), 126.58 (o-Ph), 127.17 (m-Ph), 127.49 (p-Ph),
128.03 (p-tol), 129.12 (p-tol), 133.12 (quart. p-tol), 136.76 (C3
CM ring), 139.46 (ipso Ph), 140.64 (C-Pd), 144.10 (C2 CM ring),
148.17 (ipso p-tol), 158.15 (CSe), 165.26 (NCN). 77Se NMR (CDCl3,
114 MHz): d = 147.6. Anal. Calc. for C26H29N5OSePd (612.92): C,
50.95; H, 4.77; N, 11.43. Found: C, 51.22; H, 5.04; N, 11.39%. X-
ray quality crystals were grown by slow evaporation of the mother
liquor.
4.7. [AuCl(HL)] (4) from [AuCl(SMe2)]
To a solution of [AuCl(SMe2)] (0.050 g, 0.169 mmol) in CH2Cl2
(10 mL) was added HL (0.063 g, 0.169 mmol). The mixture was
stirred at room temperature for ca. 2 h. The resulting brownish
solution was passed through celite to remove some metallic gold.
Concentration of the filtrate in vacuum and addition of hexanes
gave the product (0.048 g, 47% yield) as yellow solid. Spectral data
for this material was identical to that given above.
4.8. [Au(HL)2]Cl (5)
This was prepared as described above using [AuCl(SMe2)]
(0.050 g, 0.169 mmol) and HL (0.126 g, 0.338 mmol). The product
Table 1
Crystallographic and refinement details for compounds HL, 1, 3, 4 and 5.
HL
1
3
4
5
Empirical formula
Colour
C
19H23SeN3
C38H44N6Se2Ni
reddish-brown
801,42
monoclinic
P21/c
11.2134(6)
18.4090(10)
18.1157(11)
90.0
95.449(5)
90.0
C26H29ON5SePd
orange
612.90
monoclinic
P21/c
7.0460(4)
21.1674(13)
17.1503(15)
90.0
92.664(8)
90.0
2555.1(3)
4
1.593
2.179
C19H23AuClN3Se
yellow
604.78
C38H46AuClN6Se2
yellow
977.14
yellow
372.36
monoclinic
P21/n
9.4692(3)
19.6150(9)
10.0270(4)
90.0
96.264(4)
90.0
1851.29(12)
4
Mr (g molÀ1
)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
triclinic
ꢀ
ꢀ
P1
P1
9.2191(4)
10.8783(4)
11.1442(5)
64.067(5)
80.580(4)
86.032(3)
991.54(8)
2
10.0780(3)
11.7138(4)
18.5026(7)
89.112(3)
87.691(3)
70.839(3)
2061.57(12)
2
a
(°)
b (°)
c
(°)
V (Å3)
3722.7(4)
4
1.430
Z
Dcalc (g cmÀ3
)
1.336
2.031
2.026
9.395
1.574
5.431
l
(mmÀ1
)
2.511
F(000)
768
1640
1232
576
960
h Range
3.00–28.73°
10251
3920
2.98–29.43°
22457
8784
3.04–29.30°
12776
6692
3.05–29.42°
6282
4432
3.12–29.31°
12077
9510
Reflections collected
Independent reflections
Parameters
211
430
312
229
439
Goodness-of-fit (GOF)
1.098
1.036
1.012
1.033
1.070
R1 [I > 2
r
(I)]
0.0450
0.1003
0.875/À0.467
0.0503
0.1335
1.404/À1.053
0.0522
0.1340
1.983/À1.618
0.0319
0.0609
1.027/À1.034
0.0443
0.1109
2.269/À1.299
wR2 (all data)
Largest difference peak/hole (e ÅÀ3
)

A. Bredenkamp et al. / Polyhedron 33 (2012) 107–113
113
was obtained as yellow solid in 82% yield (0.136 g). 1H NMR
(400 MHz, dmso-d6): d 1.14 (br. m, 12 H, CH3CH2N), 2.31 (s, 3 H,
Me), 3.62 (br m, 8 H, CH2N), 7.07–7.20 (m, 4 H, p-tol), 7.37–7.65
(m, 14 H, p-tol, Ph), 10.91 (br. s, 1 H, NH). 13C{1H} NMR (dmso-
d6, 100 MHz): d = 12.16, 12.61 (CH3CH2N), 20.61 (Me), 46.31,
48.87 (CH2N), 122.35 (p-tol), 128.53, 128.81 (Ph), 129.51 (p-tol),
130.40 (Ph), 131.96 (ipso Ph), 132.60 (Ph), 134.98, 135.39 (quart.
p-tol), 158.13 (NCN), 173.59 (CSe). 77Se NMR (dmso-d6, 114
MHz): d = 348.5. HR-ESMS (m/z): 943.1783 [M]+. Anal. Calc. for
and 5. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
References
[1] L. Beyer, J. Hartung, R. Widera, Tetrahedron 40 (1984) 405.
[2] J. Hartung, G. Weber, L. Beyer, R. Kirmse, J. Stach, J. Prakt. Chem. 332 (1990)
359.
C
38H46N6Se2AuCl (977.15): C, 46.71; H, 4.74; N, 8.60. Found: C,
[3] E. Guillon, I. Déchamps-Olivier, A. Mohamadou, J.P. Barbirt, Inorg. Chim. Acta
268 (1998) 13.
[4] R. Richter, U. Schröder, M. Kampf, J. Hartung, L. Beyer, Z. Anorg. Allg. Chem. 623
(1997) 1021.
46.68; H, 4.80; N, 8.43%.
4.9. Computational details
[5] R. del Campo, J.J. Criado, E. García, M.R. Hermosa, A. Jiménez-Sánchez, J.L.
Manzano, E. Monte, E. Rodríguez-Fernández, F. Sanz, J. Inorg. Biochem. 89
(2002) 74.
Single point natural bond order (NBO) analyses [28] were per-
formed for the two complexes using the Hartree–Fock (HF) method
based using X-ray structure data. The double-f basis set LANL2DZ
with Hay and Wadt effective core potential (ECP) [29,30] for the
heavy atoms (Ni and Se) and the 6-31GÃ basis set for the remaining
atoms (H, C, N, and O) were used. The NBO analyses were per-
formed with the NBO 3.1 program incorporated in the GAUSSIAN 03
package [25].
[6] U. Schröder, R. Richter, L. Beyer, J. Angulo-Cornejo, M. Lino-Pacheco, A. Guillen,
Z. Anorg. Allg. Chem. 629 (2003) 1051.
[7] W. Hernández, E. Spodine, R. Richter, K.H. Hallmeier, U. Schröder, L. Beyer, Z.
Anorg. Allg. Chem. 629 (2003) 2559.
[8] J. Sieler, R. Richter, L. Beyer, O. Lindqvist, L. Andersen, Z. Anorg. Allg. Chem. 515
(1984) 41.
[9] G. Weber, J. Hartung, L. Beyer, Tetrahedron Lett. 29 (1988) 3475.
[10] Y. Zhou, A. Linden, H. Heimgartner, Helv. Chim. Acta 83 (2000) 1576.
[11] A. Molter, F. Mohr, Coord. Chem. Rev. 254 (2010) 19.
[12] P. Bippus, A. Molter, D. Müller, F. Mohr, J. Organomet. Chem. 695 (2010) 1657.
[13] M. Ben Dahman Andaloussi, F. Mohr, J. Organomet. Chem. 695 (2010) 1276.
[14] D. Gallenkamp, T. Porsch, A. Molter, E.R.T. Tiekink, F. Mohr, J. Organomet.
Chem. 694 (2009) 2380.
4.10. X-ray crystallography
[15] F. Fuge, C. Lehmann, F. Mohr, J. Organomet. Chem. 694 (2009) 2395.
[16] D. Gallenkamp, E.R.T. Tiekink, F. Mohr, Phosphorus Sulfur Silicon 183 (2008)
1050.
Diffraction data were collected at 150 K using an Oxford Diffrac-
tion Gemini E Ultra diffractometer, equipped with an EOS CCD area
detector and a four-circle kappa goniometer. For the data collec-
[17] A. Molter, F. Mohr, Dalton Trans. 40 (2011) 3754.
[18] A. Molter, J. Rust, C.W. Lehmann, F. Mohr, ARKIVOC VI (2011) 10.
[19] A. Molter, J. Rust, C.W. Lehmann, G. Deepa, P. Chiba, F. Mohr, Dalton Trans. 40
(2011) 9810.
tion the Mo source emitting graphite-monochromated MoKa radi-
ation (k = 0.71073 Å) was used. Data integration, scaling and
empirical absorption correction was carried out using the CRYSALIS-
PRO program package.[31] The structure was solved using Direct
Methods and refined by Full-Matrix-Least-Squares against F2. The
non-hydrogen atoms were refined anisotropically and hydrogen
atoms were placed at idealised positions and refined using the rid-
ing model. All calculations were carried out using the program
OLEX2.[32] Important crystallographic data and refinement details
are summarised in Table 1. The dataset of compound 3 showed
signs of twinning. The data was therefore processed using the twin
integration module in CRYSALIS. After refinement convergence of the
data for complex 5 there remained two high (ca. 2 e ÅÀ3) electron
density peaks within 1 Å of the chlorine atom, for which we could
not find a plausible model.
[20] W. Bensch, M. Schuster, Z. Anorg. Allg. Chem. 620 (1994) 177.
[21] S. Pisiewicz, J. Rust, C.W. Lehmann, F. Mohr, Polyhedron 29 (2010) 1968.
[22] U. Schröder, R. Richter, J. Hartung, U. Abram, L. Beyer, Z. Naturforsch. 52b
(1997) 620.
[23] R.N. Butler, A. Fox, J. Chem. Soc., Perkin Trans. 1 (2001) 394.
[24] A. Molter, Ph.D. Thesis, University of Wuppertal, 2011.
[25] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery, T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Yengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson,
H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian,
J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O.
Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, GAUSSIAN 03, Revision D.01, Gaussian Inc., Wallingford CT, 2004.
[26] F.R. Hartley, Organomet. Chem. Rev. A 6 (1970) 119.
[27] A. Tamaki, J.K. Kochi, J. Organomet. Chem. 64 (1974) 411.
[28] A.E. Reed, L.A. Curtiss, F. Weinhold, Chem. Rev. 88 (1988) 899.
[29] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299.
Acknowledgments
We wish to thank RETORTE GmbH for a generous donation of
selenium metal as well as the DFG for a grant to purchase the
diffractometer.
[30] W.R. Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284.
[31] CRYSALISPRO 171.33.49, Oxford Diffraction Ltd., 2009.
[32] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl.
Cryst. 42 (2009) 339.
Appendix A. Supplementary data
CCDC 848199, 831978, 831979, 831980 and 831981 contain the
supplementary crystallographic data for HL and compounds 1, 3, 4