Structural and spectroscopic studies of Au(III) and Pd(II) chloride complexes and organometallics with 2-benzylpyridine

Article abstract of DOI:10.1016/j.molstruc.2012.08.005

Au(III) and Pd(II) chloride complexes with 2-benzylpyridine (2bzpy) - [Au(2bzpy)Cl₃] and trans-[Pd(2bzpy)₂Cl₂], as well as Au(III) chloride organometallics with monoanionic form of 2bzpy, deprotonated in the benzyl side gr

Full text of DOI:10.1016/j.molstruc.2012.08.005

Journal of Molecular Structure 1032 (2013) 195–202
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structural and spectroscopic studies of Au(III) and Pd(II) chloride complexes
and organometallics with 2-benzylpyridine
Daria Niedzielska a, Tomasz Pawlak b, Maria Bozejewicz a, Andrzej Wojtczak a, Leszek Pazderski a,
,
⇑
Edward Szlyk a
a
´
Faculty of Chemistry, Nicholas Copernicus University, Gagarina 7, PL-87100 Torun, Poland
b Center of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90363 Lodz, Poland
h i g h l i g h t s
"
"
"
Au(III)/Pd(II) complexes/organometallics with 2-benzylpyridine were studied by NMR.
Nitrogen metallation in 2-benzylpyridine results in 15N shielding and 1H deshielding.
2bzpyH+ [AuCl4]- ionic pair was studied by single crystal X-ray diffraction.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 May 2012
Received in revised form 2 August 2012
Accepted 2 August 2012
Available online 13 August 2012
Au(III) and Pd(II) chloride complexes with 2-benzylpyridine (2bzpy) – [Au(2bzpy)Cl3] and trans-
[Pd(2bzpy)2Cl2], as well as Au(III) chloride organometallics with monoanionic form of 2bzpy, deproto-
nated in the benzyl side group at the ortho-carbon C(20) (2bzpyꢀ) – [Au(2bzpyꢀ)Cl2], were studied by
1H, 13C and 15N NMR. 1H, 13C and 15N coordination shifts (i.e. differences of chemical shifts for the same
atom in the complex and ligand molecules) were discussed in relation to the molecular structures and the
coordination modes, as well as to the factors influencing nuclear shielding. Analogous NMR measure-
ments were performed for the new (2bzpyH)[AuCl4] salt, studied also by single crystal X-ray diffraction.
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Au(III) complexes
Pd(II) complexes
Au(III) organometallics
2-Benzylpyridine
15N NMR
X-ray
1. Introduction
[8]). [Au(2bzpyꢀ)Cl2] and its [Au(2-(1,1-dimethylbenzyl)pyri-
dineꢀ)Cl2] analogue are also widely used as precursors for prepara-
2-Benzylpyridine (2bzpy), being an analogue of 2-phenylpyri-
dine (2ppy) (Scheme 1), is an azine ligand, which is known to coor-
dinate transition metal ions, such as Au(III) and Pd(II), in two
alternative ways: as a monodentate N(1)-donor or a N(1),C(20)-
chelating agent 2bzpyꢀ (2bzpyꢀ = monoanionic form of 2bzpy,
deprotonated in the benzyl side group at the ortho-carbon C(20)).
The former complexation mode occurs in [Au(2bzpy)Cl3] [1] and
trans-[Pd(2bzpy)2Cl2] [2,3], while the latter in [Au(2bzpyꢀ)Cl2]
[1,4] (Scheme 2).
These compounds are of increasing interest due to their cata-
lytic properties (trans-[Pd(2bzpy)2Cl2] in hydrogenation of unsatu-
rated functional groups [5], [Au(2bzpyꢀ)Cl2] in introduction of
amine and alkyne substituents into oligosaccharides [6]) and cyto-
toxicity ([Au(2bzpyꢀ)Cl2] is active against cancer [7] and parasites
tion of some other compounds with antitumour, antibacterial,
antifungal or antiviral properties [9–17]. However, they still re-
main insufficiently characterized, as only their IR and 1H (but
not 13C and 15N) NMR spectra were published [1–4]. In contrast
to Au(III) and Pd(II) chloride complexes and organometallics with
2ppy, for which two single crystal X-ray structures were reported
([Au(2ppy)Cl3] – YIDMAA [18], [Au(2ppyꢀ)Cl2] – IJAQEP [19]; all
refcodes derive from the Cambridge Structural Database [20]),
for the studied 2bzpy analogues such data are unavailable.
Recently, we have reported the 1H, 13C and 15N NMR spectra for
[Au(2ppy)Cl3], trans- and cis-[Pd(2ppy)2Cl2] [21], and [Au(2ppyꢀ)Cl2]
[22], assigning all signals by 1H–13C and 1H–15N HMQC and HMBC
methods. In this paper we have applied the same techniques
for [Au(2bzpy)Cl3], trans-[Pd(2bzpy)2Cl2] and [Au(2bzpyꢀ)Cl2].
Additionally, we describe the results of analogous NMR measure-
ments and single crystal X-ray diffraction for the new
(2bzpyH)[AuCl4] salt.
⇑
Corresponding author.
E-mail address: leszekp@chem.umk.pl (L. Pazderski).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.08.005

196
D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
Scheme 1. 2-Phenylpyridine (2ppy) and 2-benzylpyridine (2bzpy), with the numbering scheme.
2. Experimental
2.1. Materials
2bzpy (98% purity) was purchased from Aldrich; Au (99.99%)
from Polish Mint, PdCl2 (99.9%) from POCh Gliwice (Poland). Aque-
ous HAuCl4 solution (ca. 0.05 M) was prepared by dissolving Au in
aqua regia followed by the removal of HNO3 and HCl excess by boil-
ing. Solid NaAuCl4 and K2PdCl4 were prepared in water by the reac-
tions of HAuCl4 with NaOH and PdCl2 with KCl, respectively, and
evaporation to dryness.
Scheme 2. [Au(LL)Cl3] and trans-[Pd(LL)2Cl2] complexes with N(1)-monodentately
bonded neutral LL molecules and [Au(LL⁄)Cl2] organometallics with N(1), C(2⁄)-
chelated LL⁄ monoanionic ligands (LL = various 2-arylpyridines, e.g. 2ppy, 2bzpy).
The 1H NMR spectra are nearly identical with those published
for [Au(2bzpy)Cl3] by Cinellu et al. [1], trans-[Pd(2bzpy)2Cl2] by
Hiraki et al. [2], and [Au(2bzpyꢀ)Cl2] by Cinellu et al. and Shaw
et al. [1,4], which confirms the identity of these compounds; their
detailed data are described in the further part of this paper.
2.2. Syntheses and identification by far-IR and 1H NMR
The (2bzpyH)[AuCl4] salt, although simple, is new. It was ob-
tained by stirring aqueous HAuCl4 solution with 2bzpy in ethanol
(1:1; 5 h, 20 °C). After concentration, the overnight-formed
precipitate was washed with ethanol and diethyl ether, giving
yellow crystals suitable for X-ray structural analysis (yield
ca. 90%); elemental analysis: C 28.3%, H 2.7%, N 2.8% (calculated
for AuC12H12NCl4: C 28.3%, H 2.4%, N 2.8%). The far-IR spectrum
(measured in polyethylene by a Perkin–Elmer Spectrum 2000
FT-IR spectrometer with a triglycerin sulphate detector) exhibited
the characteristic mAuCl stretching mode at 352 cmꢁ1, consistent
with the literature data for free [AuCl4]ꢁ anions (350 cmꢁ1 [23]).
The [Au(2bzpy)Cl3] and trans-[Pd(2bzpy)2Cl2] complexes, as
well as the [Au(2bzpyꢀ)Cl2] organometallic are known. Both Au(III)
compounds were synthesized by the method of Cinellu et al. [1],
i.e. by stirring NaAuCl4 in water with 2bzpy in ethanol (1:1) for
1 h at 20 °C or for 5 h at 80 °C, respectively, while the Pd(II) species
by the method of Hiraki et al. [2], i.e. by stirring K2PdCl4 in water
with 2bzpy in ethanol (1:2) for 3 h at 20 °C. Their composition
was confirmed by elemental analysis: [Au(2bzpy)Cl3]: C 30.2%, H
2.4%, N 3.4% (calculated for AuC12H11NCl3: C 30.5%, H 2.3%, N
3.0%); trans-[Pd(2bzpy)2Cl2]: C 56.0%, H 4.6%, N 5.6% (calculated
for PdC24H22N2Cl2: C 55.9%, H 4.3%, N 5.4%); [Au(2bzpyꢀ)Cl2]: C
32.6%, H 2.5%, N 3.4% (calculated for AuC12H10NCl2: C 33.1%, H
2.3%, N 3.2%).
2.3. NMR measurements
1H–13C and 1H–15N two-dimensional NMR spectra were mea-
sured at 303 K in CDCl3, CD2Cl2, CD3CN or DMSO-d6, by a Bruker
Avance III 700 MHz NMR spectrometer. The 1H–13
C
HMQC,
1H–13C HMBC and 1H–15N HMBC experiments were adjusted for
n
n
1JH–C = 150 Hz, JH–C = 10 Hz, JH–N = 5 Hz, with the following
parameters:
p
/2 pulse lengths for 1H: 9–10
l ls,
s, 13C: 12–13
15N: 23–24
l
s; acquisition time for 1H–13C HMQC and HMBC:
0.2–0.3 s, for 1H–15N HMBC: 0.07–0.08 s; relaxation delay for
1H–13C HMQC and HMBC: 1.5 s, for 1H–15N HMBC: 2 s. As refer-
ences were used: TMS for 1H and 13C (with residual 1H and 13C sol-
vent signals as primary references – in CDCl3: 7.24 ppm and
77.2 ppm, in CD2Cl2: 5.32 ppm and 54.0 ppm, in CD3CN:
1.94 ppm and 1.4 ppm, in DMSO-d6: 2.50 ppm and 39.5 ppm); neat
nitromethane for 15N.
2.4. X-ray diffraction studies
X-ray data for the single crystal of (2bzpyH)[AuCl4], obtained
directly from the synthesis by slow evaporation of the ethanol–
water solvent, was collected with an Oxford Sapphire CCD diffrac-
The far-IR spectra revealed the following mAuCl or mPdCl stretch-
ing vibrations: [Au(2bzpy)Cl3]: 360 cmꢁ1 (Cinellu et al.: 362 cmꢁ1
[1]) – a broad band, being probably an overlap of three
mAuCl modes
tometer, using MoKa radiation, by x–2h method with numerical
(2A1 + B1) predicted by group theory for MXY3 square-planar mol-
ecules with C2v symmetry [23]; trans-[Pd(2bzpy)2Cl2]: 340 and
336 cmꢁ1 (Hiraki et al.: 352 and 344 cmꢁ1 [2]) – two maxima,
deriving, most likely, from both rotational isomers discovered by
Hiraki et al. [2], each giving one mPdCl mode (B2u) predicted for
trans-MX2Y2 square-planar molecules with D2h symmetry [23];
[Au(2bzpyꢀ)Cl2]: 355 and 348 cmꢁ1 (Cinellu et al.: 358 cmꢁ1 [1])
– two mAuCl modes (A1 + B2) predicted for M(XX)Y2 square-planar
molecules of cis-geometry with C2v symmetry [23].
absorption correction [24]; further experimental details are listed
in Table 1. The structure was solved with direct methods and re-
fined with the full-matrix least-squares method on F2 using
SHELX-97 [25] and PLATON [26], without extinction correction.
Hydrogen atoms were located from the difference maps and con-
strained. The space group was determined basing on the system-
atic absences. The respective CIF file is available at Cambridge
Crystallographic Data Centre with deposition number CCDC
873251.

D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
197
Table 1
Crystal structure data and X-ray experimental details for (2bzpyH)[AuCl4].
Compound
(2bzpyH)[AuCl4]
C12H12AuCl4N
508.99
Orthorhombic
Pbca
7.4262(3)
15.8385(7)
25.3806(11)
90
Empirical formula
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
90
c
(°)
90
2985.3(2)
8
2.265
10.552
V (Å3)
Z
Density (Mg/m3)
l
(mmꢁ1
)
Temperature (K)
293(2)
Wavelength (Å)
0.71073
Crystal size (mm)
Max. and min. transmission
h Range
Reflections collected/unique/Rint
Final R1/wR2 indices [I > 2r(I)]
0.48 ꢃ 0.30 ꢃ 0.06
0.5890 and 0.0799
2.57–28.44
18972/3526/0.0472
0.0305/0.0738
0.0500/0.0799
0.966
Fig. 1. The (2bzpyH)[AuCl4] salt (PLATON [26]).
Final R1/wR2 indices all data
Goodness of fit
Residual density peaks (e Åꢁ3
)
1.308/ꢁ0.910
3. Results and discussion
3.1. Crystal and molecular structure of 2-benzylpyridinium
tetrachloraurate(III)
The perspective view of the (2bzpyH)[AuCl4] salt is presented at
Fig. 1, its packing in the crystal lattice – at Fig. 2. The crystal struc-
ture data are collected in Table 1, the bond lengths and angles
within the 2bzpyH+ cation – in Table 2.
The symmetry of (2bzpyH)[AuCl4] (orthorhombic, Pbca) is high-
ꢀ
er than for (2bzpyH)4[Sb2Cl10] (LUHVOZ; Triclinic, P1 [27]). The
geometry of pyridine and phenyl rings is similar for both salts, as
their bond lengths and angles are nearly the same; in contrast,
their orientation is different: in (2bzpyH)[AuCl4] the dihedral angle
between both rings is uniform for all molecules (57.7°; it results
from the N(1)–C(2)–C(7)–C(10), C(3)–C(2)–C(7)–C(10), C(2)–C(7)–
C(10)–C(20), C(2)–C(7)–C(10)–C(60) torsion angles of 37.2(8)°,
34.1(6)°, 32.6(8)°, and 28.2(5)°), while in (2bzpyH)4[Sb2Cl10] it
was specific for each of 4 crystallographically independent cations
(65.6°, 71.9°, 88.1°, 89.6° [27]). For comparison, in (2-(2,4-dinitrob-
enzyl)pyridineH)Cl (TAVMEJ) both rings were nearly perpendicular
(89.1° [28]). Thus, this structural feature is heavily dependent on
the type of substituents and counterions.
The comparison of both salts to unprotonated 2-arylpyridines
containing a bridge between pyridine and phenyl ring exhibits
the increase of the C(6)–N(1)–C(2) angle upon protonation:
118.8(2)° in 2-(1-phenylbenzyl)pyridine (YANRAG) [29], 116.8(2)°
in 2-benzoylpyridine (NOGCIV) [30] or 117.5(2)° in 2-phenylami-
nopyridine (NARYEK) [31] ? 124.0(5)° or 123.8(5)° [27] in
2bzpyH+.
Fig. 2. The packing of the (2bzpyH)[AuCl4] salt in the crystal lattice (PLATON [26]).
(2,9-di-n-butyl-1,10-phenanthrolineH)[AuCl4] and (2,9-di-sec-bu-
tyl-1,10-phenanthrolineH)[AuCl4] [37].
In the crystal lattice, the chain of nearly linear intermolecular
N(1)–H(1)ꢂ ꢂ ꢂCl(2) [x + 1,y,z] hydrogen bonds along the crystallo-
graphic X axis is formed, with the N(1)ꢂ ꢂ ꢂCl(2) distance of 3.320 Å
and the N(1)-H(1)ꢂ ꢂ ꢂCl(1) angle of 165.4°. Some other interactions
are: C(5)–H(5)ꢂ ꢂ ꢂCl(1) [ꢁ1/2 + x,y,1/2ꢁz] (with C(5)ꢂ ꢂ ꢂCl(1) 3.595 Å,
C(5)–H(5)ꢂ ꢂ ꢂCl(1) 150.4°) and C(30)–H(30)ꢂ ꢂ ꢂCl(1) [1ꢁx,1ꢁy,ꢁz]
(with C(30)ꢂ ꢂ ꢂCl(30) 3.713 Å, C(30)–H(30)ꢂ ꢂ ꢂCl(1) 155.1°), as well
as C(7)–H(7a)ꢂ ꢂ ꢂC(40) [1ꢁx,1ꢁy,ꢁz] (with C(7)ꢂ ꢂ ꢂC(40) 3.858 Å,
C(7)–H(7a)ꢂ ꢂ ꢂC(40) 171.4°; this contact concerns only one of the
two methylene protons).
3.2. 1H NMR spectroscopy
The (2bzpyH)[AuCl4] salt is slightly soluble in CDCl3, CD2Cl2 and
CD3CN, and much better in DMSO-d6. Its 1H NMR spectra in all sol-
vents (Table 3) are noticeably different from those of unprotonated
2bzpy; however, addition of the free ligand results in only one set
of 1H signals at intermediate chemical shifts, indicating fast proton
exchange between 2bzpyH+ and 2bzpy.
The AuClꢁ4 anions are square-planar; the mean Au–Cl bond
lengths are 2.276(2) Å, being nearly the same as in (pyridineH)
[AuCl4] (BENYAU: 2.270(2) Å [32]), (3-phenylpyridineH)[AuCl4]
(PUHYIB: 2.276(1) Å [33]) and (2,6-diphenylpyridineH)[AuCl4]
(ZAKXIS: 2.276(1) Å [34]). Generally, the presently studied
(2bzpyH)[AuCl4] salt is similar also to some other (azineH)[AuCl4]
ionic pairs, consisting of distinct N-protonated azinium cations
and tetrachloraurate anions, the best examples being the X-ray
studied species (2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)pyridi-
neH)[AuCl4] [35], (1,3-bis(2-pyridyl)benzeneH)[AuCl4] [36],
The 2bzpy protonation results in the moderate 1H deshielding
Hð3ÞꢁHð6Þ;Hð20ÞꢁHð60Þ
(mean
D
: 0.28–0.35 ppm), analogous to that
prot
for (2bzpyH)[B(3,5-bis(trifluoromethyl)phenyl)4] (mean
0
0
DHprðo3tÞꢁHð6Þ;Hð2 ÞꢁHð6 Þ: 0.13 ppm, as deduced from the unassigned
1H NMR data: 8.23, 8.05, 7.74, 7.55, 3 ꢃ (7.39 ꢁ 7.42),

198
D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
Table 2
Geometry of (2bzpyH)+, in crystalline (2bzpyH)[AuCl4] and (2bzpyH)4[Sb2Cl10] [27].
a
a
Bond length
(2bzpyH)[AuCl4]/(2bzpyH)4[Sb2Cl10
]
[27] (Å)
Angle
(2bzpyH)[AuCl4]/(2bzpyH)4[Sb2Cl10] [27] (°)
N(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–N(1)
C(2)–C(7)
C(7)–C(10)
C(10)–C(20)
C(10)–C(60)
C(20)–C(30)
C(60)–C(50)
C(30)–C(40)
C(50)–C(40)
1.351(6)/1.33(1)
1.371(8)/1.37(1)
1.363(8)/1.37(1)
1.381(9)/1.36(1)
1.356(8)/1.35(1)
1.334(7)/1.33 (1)
1.491(7)/1.50(1)
1.498(7)/1.50(1)
Meanb
N(1)–C(2)–C(3)
C(2)–C(3)–C(4)
C(3)–C(4)–C(5)
C(4)–C(5)–C(6)
C(5)–C(6)–N(1)
C(6)–N(1)–C(2)
N(1)–C(2)–C(7)
C(3)–C(2)–C(7)
C(2)–C(7)–C(10)
116.5(5)/117(1)
120.9(5)/120(1)
120.5(6)/121(1)
118.0(7)/118(1)
120.0(6)/120(1)
124.0(5)/124(1)
119.8(5)/117(1)
123.7(5)/126(1)
118.0(5)/116(1)
1.390(7)/1.38(1)
Meanb
C(7)–C(10)–C(20)
C(7)–C(10)–C(60)
C(20)–C(10)–C(60)
Meanb
121.5(5)/121(1)
116.6(5)/118(1)
1.368(8)/1.38(1)
Meanb
1.376(9)/1.35(1)
C(10)–C(20)–C(30)
C(10)–C(60)–C(50)
C(20)–C(30)–C(40)
C(60)–C(50)–C(40)
C(30)–C(40)–C(50)
Meanb
121.6(6)/121(1)
Meanb
120.6(7)/120(1)
118.8(6)/120(1)
a
Averaged for four crystallographically different 2bzpyH+ cations and round to 0.01 Å or 1°.
b
Averaged for the formally equivalent (due to the rotation around the C(7)–C(10) bond) C(10)–C(20)–C(30)–C(40) and C(10)–C(60)–C(50)–C(40) halves of the phenyl ring.
Table 3
1H chemical and protonation/coordination shifts (in parentheses) for 2bzpy, (2bzpyH)[AuCl4], [Au(2bzpy)Cl3], trans-[Pd(2bzpy)2Cl2], [Au(2bzpyꢀ)Cl2].
Compound
H(3)
H(4)
H(5)
H(6)
H(20)
H(30)
H(40)
H(50)
H(60)
CH2
2bzpyCDCl3
2bzpyCD2Cl2
2bzpyCD3CN
7.09
7.18
7.21
7.55
7.63
7.64
7.08
7.15
7.16
8.53
8.55
8.50
7.25
7.31
7.30
7.28
7.33
7.31
7.20
7.24
7.23
4.15
4.18
4.13
2bzpyDMSO-d6
7.25
7.71
7.69
8.42
7.20
7.89
8.48
8.85
7.27
7.30
7.28
7.42
7.18
7.39
4.08
4.56
(2bzpyH)[AuCl4]CDCl3
(+0.62)
7.77
(+0.59)
7.82
(+0.61)
7.83
(+0.87)
8.46
(+0.83)
8.47
(+0.83)
8.41
(+0.81)
7.92
(+0.77)
7.86
(+0.70)
7.84
(+0.32)
8.80
(+0.25)
8.50
(0.00)
8.81
(+0.05)
7.37
(+0.06)
7.32
(+0.02)
7.34
(+0.14)
7.45
(+0.12)
7.42
(+0.11)
7.37
(+0.19)
7.42
(+0.18)
7.38
(+0.15)
7.29
(+0.41)
4.56
(+0.38)
4.42
(+0.29)
4.35
(2bzpyH)[AuCl4]CD2Cl2
(2bzpyH)[AuCl4]CD3CN
(2bzpyH)[AuCl4]DMSO-d6
(+0.58)
(+0.72)
(+0.64)
(+0.33)
(+0.07)
(+0.09)
(+0.11)
(+0.27)
[Au(2bzpy)Cl3]CDCl3 a
7.36
7.96
7.54
8.67
7.27
7.40
7.33
4.72
(+0.27)
(+0.41)
(+0.46)
(+0.14)
(+0.02)
(+0.12)
(+0.13)
(+0.57)
trans-[Pd(2bzpy)2Cl2]CDCl3 b
A 6.94
(ꢁ0.15)
B 6.88
(ꢁ0.21)
A + B 7.57
(+0.02)
A 7.20
(+0.12)
B 7.17
(+0.09)
A 9.04
(+0.51)
B 8.89
(+0.36)
A + B 7.32
(+0.07)
A + B 7.43
(+0.15)
A + B 7.40
(+0.20)
A 5.27
(+1.12)
B 5.42
(+1.27)
A + B 1:1
[Au(2bzpyꢀ)Cl2]CDCl3
[Au(2bzpyꢀ)Cl2]CD2Cl2 c
[Au(2bzpyꢀ)Cl2]CD3CN
[Au(2bzpyꢀ)Cl2]DMSO-d6 d
7.68
(+0.59)
7.72
(+0.54)
7.81
(+0.60)
8.00
8.01
(+0.46)
8.04
(+0.41)
8.11
(+0.47)
8.26
7.50
(+0.42)
7.52
(+0.37)
7.56
(+0.40)
7.71
9.32
(+0.79)
9.27
(+0.72)
9.16
(+0.66)
9.17
No proton
No proton
No proton
No proton
7.60
(+0.32)
7.55
(+0.22)
7.48
(+0.17)
7.41
7.08
7.16
7.11
4.55, 4.03
(ꢁ0.12)
(ꢁ0.12)
(ꢁ0.14)
(+0.40/ꢁ0.12)
7.09
7.18
7.18
4.56, 4.07
(ꢁ0.15)
7.08
(ꢁ0.15)
7.18
(ꢁ0.13)
7.22
(+0.38/ꢁ0.11)
4.56, 4.20
(+0.43/+0.07)
4.60, 4.36
(ꢁ0.15)
(ꢁ0.13)
(ꢁ0.08)
7.07
7.18
7.25
(+0.75)
(+0.57)
(+0.51)
(+0.69)
(+0.13)
(ꢁ0.11)
(ꢁ0.10)
(ꢁ0.02)
(+0.52/+0.28)
Literature data for:
a
[Au(2bzpy)Cl3] in CDCl3: H(6) 8.69, CH2 4.73 ppm [1].
b
c
trans-[Pd(2bzpy)2Cl2] in CDCl3: H(6) 8.89/8.74, CH2 5.35/5.20 ppm [2].
[Au(2bzpyꢀ)Cl2] in CD2Cl2: H(6) 9.27, others 7.1–8.1, CH2 4.56, 4.08 ppm [1].
d
[Au(2bzpyꢀ)Cl2] in DMSO-d6: H(3) 7.99, H(4) 8.26, H(5) 7.71, H(6) 9.17, C6H5: 7.41, 2 ꢃ (7.14–7.28), 7.07, CH2 4.62, 4.34 ppm [4].
2 ꢃ (7.10 ꢁ 7.13) ppm, in CDCl3 [38]). This effect is much stronger
for the pyridine ring (mean DHprðo3tÞꢁHð6Þ: 0.53–0.66 ppm) than the phe-
of the positive (+1) electric charge within the whole pyridine ring.
The latter hypothesis is supported by the fact that similarly
0
0
nyl one (mean DHprðo2tÞꢁHð6 Þ: 0.08–0.11 ppm). The deshielding of the
moderate H(6) deshielding was noted for some other 2-substituted
Hð6Þ
Hð6Þ
nitrogen-adjacent H(6) atom (
D
= 0.00–0.33 ppm, depending on
pyridinium cations (
D
= 0.21–0.40 ppm for 2-methylpyridineH+,
prot
prot
the solvent; a surprising difference between CD3CN and the other
media should be mentioned) is weaker than for more far-distant
2-(tert-butyl)pyridineH+, 2-(tert-butylmethyl)pyridineH+, 2-(1,1-
dimethylbenzyl)pyridineH+ [1,39,40]); Table S1.
Hð3Þ
Hð5Þ
pyridine ring protons (
D
–D
= 0.58–0.83 ppm, depending on
The methylene protons in (2bzpyH)[AuCl4] are moderately
deshielded (DCprHo2t = 0.27–0.41 ppm, depending on the solvent), which
is again comparable to (2bzpyH)[B(3,5-bis(trifluoromethyl)phenyl)4]
prot
prot
the solvent). These phenomena and dependencies are probably
caused by the electron density decrease due to the delocalization

D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
199
CH2
prot
(D
¼ 0:23 ppm, as dCH2 = 4.32 ppm for 2bzpyH+ and dCH2 = 4.19 -
account in this NMR solvent. For example, Fuchita et al., who stud-
ied [Au(2-phenoxypyridine)Cl3] and [Au(2-(phenylsulfanyl)pyri-
dine)Cl3] just in DMSO-d6, erroneously attributed the observed
proton signals to the above molecules, although they appeared at
the chemical shifts of free ligands, and the same concerned (2-phe-
noxypyridineH)[AuCl4] and (2-(phenylsulfanyl)pyridine)[AuCl4]
salts [46]. Most likely, both [AuLCl3] complexes and LH+ cations
decomposed due to their reactions with DMSO and residual water.
The [Au(2bzpyꢀ)Cl2] organometallic is slightly soluble in CDCl3,
CD2Cl2 and CD3CN, and well soluble in DMSO-d6; in contrast to
[Au(2bzpy)Cl3] it does not decompose in the latter solvent. Its
dH6 and dCH2 parameters in CD2Cl2 and DMSO-d6 are in agreement
to the literature values [1,4]. A similar behaviour was reported
for analogous [Au(LLꢀ)Cl2] organometallics with many other
2-arylpyridines (LL = 2ppy [19,22,47,48], 2-benzoylpyridine [7,49],
2-phenoxypyridine and 2-phenylsulfanylpyridine [46], 2-phenyla-
minopyridine and 2-phenyl(N-methyl)aminopyridine [46,50]).
In all solvents the 1H NMR pattern of [Au(2bzpyꢀ)Cl2] corre-
sponds well to the N(1),C(20)-cyclometallated structure, revealing
eight aromatic protons (four doublets: H(3), H(6), H(30), H(60) and
four triplets: H(4), H(5), H(40), H(50), with the absence of H(20)
and inequivalency of all other phenyl ring hydrogens), as well as
two distinct CH2 atoms. The pyridine ring protons are significantly
deshielded (mean DHcoðo3rÞdꢁHð6Þ: 0.51–0.63 ppm, depending on the
solvent). In DMSO-d6, their average deshielding is similar to that
ppm for 2bzpy, both in CDCl3 [38]).
The [Au(2bzpy)Cl3] and trans-[Pd(2bzpy)2Cl2] complexes are sol-
uble and stable in CDCl3, their dH6 and dCH2 parameters being in
agreement to the literature values [1,2]. The latter molecule
appears in two forms (ca. 1:1), being probably rotameric isomers
formed by steric hindrance of the bulky 2bzpy ligands, which re-
stricts free rotation around the Pd–N(1) bonds. Such a phenomenon
was already mentioned for this compound and its bromide analogue
(trans-[Pd(2bzpy)2Br2] [2]), as well as many other trans-[PdL2Cl2]
complexes with 2-alkyl- or 2-arylpyridines (L = 2-methylpyridine
[41], 2,3-dimethylpyridine and 2,4-dimethylpyridine [42], 2-(2-
chloroethyl)pyridine [43], 2-(1-methylbenzyl)pyridine [44]). We de-
note as A and B the species with the H(6) signal at the higher and the
lower chemical shift, respectively (dH6(A) > dH6(B)); the order of other
proton peaks may be different (e.g. dCH2(A) < dCH2(B)). In our further
discussion concerning trans-[Pd(2bzpy)2Cl2] we will use the
weighted (1:1) averages of the
For [Au(2bzpy)Cl3] the pyridine ring protons are moderately
deshielded (mean DcHoðo3rÞdꢁHð6Þ: 0.32 ppm), similarly to [Au(2ppy)Cl3]
(mean DcHoðo3rÞdꢁHð6Þ: 0.36 ppm [21]); this effect is weaker for H(6) than
1H
coord
D
parameters for A and B.
Hð6Þ
Hð3Þ
Hð5Þ
H(3)–H(5) (
D
= 0.14 ppm vs
D
–D
= 0.27–0.46 ppm). It is
coord
coord
coord
worth noting that the same coordination shifts pattern was ob-
served for analogous [AuLCl3] complexes with 2-alkylpyridines
(L = 2-methylpyridine [41], 2,3-dimethylpyridine and 2,4-dimeth-
ylpyridine [42]). The small H(6) deshielding is comparable to that
for [Au(2ppy)Cl3] (
for [Au(2ppyꢀ)Cl2] (mean DcHoðo3rÞdꢁHð6Þ: 0.63 ppm vs 0.55 ppm [22]),
Hð6Þ
Hð6Þ
D
¼ 0:15 ppm [21]) and [Au(2-(1-methyl-
and the same concerns H(6) (
D
: 0.69 ppm vs 0.86–0.87 ppm
coord
coord
Hð6Þ
benzyl)pyridine)Cl3] (
nomena and dependencies are probably caused by an inductive
D
¼ 0:08 ppm [1]); Table S2. These phe-
[19,22,47,48]). In CDCl3, H(6) is much more deshielded that
coord
Hð6Þ
in [Au(2bzpy)Cl3]
(
D
:
0.79 ppm vs 0.14 ppm), such
relation being also noted for
coord
Hð3Þ
Hð6Þ
effect of three electronegative chlorides. 0The phenyl ring protons
D
ꢅ
D
coord;½AuðLLꢀÞCl2ꢄ
coord;½AuðLLÞCl3ꢄ
0
are slightly deshielded (mean DHcoðo2rdÞꢁHð6 Þ: 0.08 ppm). In conse-
[Au(2ppyꢀ)Cl2] vs [Au(2ppy)Cl3] (0.86–0.87 ppm ꢅ 0.15 ppm
quence, all heterocyclic ring protons are, on average, deshielded
[19,21,22,47,48]), and for (R)/(S)-[Au(2-(1-methylbenzyl)pyri-
0
0
as well (mean DHcoðo3rÞdꢁHð6Þ;Hð2 ÞꢁHð6 Þ: 0.19 ppm).
dineꢀ)Cl2]
vs
[Au(2-(1-methylbenzyl)pyridine)Cl3]
(0.72/
For trans-[Pd(2bzpy)2Cl2] the pyridine ring protons are variously
affected (with differences between both rotamers reaching
0.15 ppm); on average, they are slightly deshielded (mean
0.82 ppm ꢅ 0.08 ppm [1]); Table S3.
Hð6Þ
Similarly high
D
values were reported for some other
coord
[Au(LLꢀ)Cl2] organometallics with derivatives of 2ppy (LL = 2-(4-meth-
DHcoðo3rÞdꢁHð6Þ: 0.10 ppm). The comparison to trans-[Pd(2ppy)2Cl2] and
ylphenyl)pyridine, 4-(n-propyl)-2-phenylpyridine, 2-(2,4-difluoro-
Hð3ÞꢁHð6Þ
Hð6Þ
cis-[Pd(2ppy)2Cl2] (mean
D
:
ꢁ0.04 ppm and ꢁ0.47 ppm
phenyl)pyridine:
D
= 0.86–1.13 ppm [4,48,51]) or 2bzpy (LL =
coord
coord
[21]) exhibits the similarity rather to the former than the latter iso-
3-methyl-2-benzylpyridine, 4-methyl-2-benzylpyridine, 5-methyl-2-
benzylpyridine, 2-(6-methylbenzyl)pyridine, 2-(5-methylbenzyl)
pyridine, 2-(4-methylbenzyl)pyridine, 2-(4-phenylbenzyl)pyridine,
mer, being in favour of the assumed trans-geometry. On the other
Hð6Þ
hand, H(6) is highly deshielded (
D
= 0.44 ppm), in contrast to
coord
Hð6Þ
its slight shielding in trans-[Pd(2ppy)2Cl2] (
very large shielding in cis-[Pd(2ppy)2Cl2] (
Table S2. For comparison, cis-[Pt(2ppy)2Cl2] (this complex was orig-
inally supposed to have trans-geometry but later proved, by single
D
= ꢁ0.12 ppm) and
2-(4-chlorobenzyl)pyridine, 2-(1,1-dimethylbenzyl)pyridine, 2-(1-
coord
Hð6Þ
Hð6Þ
D
= ꢁ0.86 ppm) [21];
phenylbenzyl)pyridine:
D
= 0.45–0.82 ppm [1,7]); Table S3. Thus,
coord
coord
this parameter can be regarded as a tool to identify Au(III) cyclometal-
lation of such 2-arylpyridine ligands.
crystal X-ray studies, to be cis-isomer (CCDC 799847 [45]) revealed
The changes for phenyl ring protons in [Au(2bzpyꢀ)Cl2] are of
Hð6Þ
nearly no effect at H(6) (
D
= ꢁ0.04 ppm [21]). So complicated
variable sign and moderate or0 small absolute magnitude, although
coord
0
1H NMR coordination shifts patterns derive probably from combina-
tion of an inductive effect of two electronegative chlorides and vari-
able anisotropic interactions of the adjacent 2bzpy heterocyclic
rather shielding (mean DHcoðo3rdÞꢁHð6 Þ: from ꢁ0.05 to ꢁ0.01 ppm,
depending on the solvent). The H(30) atom, adjacent to the
metallated C(20) carbon, is moderately deshielded while the other
Hð30Þ
Hð40Þ
rings, heavily dependent on complex geomet0ry. The phenyl ring pro-
protons are weakly shielded (
D
= 0.13–0.32 ppm vs
D
–
coord
coord
0
Hð60Þ
tons are slightly deshielded (mean DHcoðo2rdÞꢁHð6 Þ: 0.13 ppm). In conse-
D
= ꢁ0.15 to ꢁ0.02 ppm, depending on the solvent). A similar
coord
quence, all heterocyclic ring proto0ns are, on average, slightly
coordination shifts pattern was observed for [Au(2ppyꢀ)Cl2]
0
Hð30Þ
Hð40Þ
deshielded as well (mean DHcoðo3rÞdꢁHð6Þ;Hð2 ÞꢁHð6 Þ: 0.11 ppm).
(D
= 0.36 ppm vs
D
= ꢁ0.11 to 0.02 ppm [22]). On average,
coord
coord
The methylene protons in both presently studied complexes are
all heterocyclic0 ring protons are moderately deshielded (mean
0
significantly deshielded, much more in trans-[Pd(2bzpy)2Cl2] than
DHcoðo3rÞdꢁHð6Þ;Hð3 ÞꢁHð6 Þ: 0.23–0.30 ppm, depending on the solvent), again
0
0
[Au(2bzpy)Cl3] (
D
: 1.20 ppm vs 0.57 ppm). A similar depen-
similarly to [Au(2ppyꢀ)Cl2] (mean DcHoðo3rÞdꢁHð6Þ;Hð3 ÞꢁHð6 Þ: 0.30 ppm
[22]).
CH2
coord
dency was reported for CH protons in trans-[Pd(2-(1-methylben-
zyl)pyridine)2Cl2] and [Au(2-(1-methylbenzyl)pyridine)Cl3]
: 2.32 ppm vs 1.02 ppm [1,44]); Table S2. The difference be-
Both methylene protons in [Au(2bzpyꢀ)Cl2] become inequivalent
CH
coord
(D
and appear as two doublets separated by 0.24–0.52 ppm (dCH2
:
tween CH2 signals in both rotamers of trans-[Pd(2bzpy)2Cl2]
(ꢁ0.15 ppm) has the same absolute magnitude but an opposite
sign than in case of H(6).
In DMSO-d6 both coordination compounds immediately decom-
pose, yielding free 2bzpy. This problem often occurs for Au(III) and
Pd(II) chloride–azine complexes and must be always taken into
4.45–4.60 ppm vs 4.03–4.36 ppm), due to their different orientation
in respect to the planes of both rings and the AuCl2 moiety. The same
phenomenon was reported for [Au(4-methyl-2-benzylpyridineꢀ)
Cl2] (4.57 ppm vs 4.23 ppm), [Au(5-methyl-2-benzylpyridineꢀ)Cl2]
(4.53 ppm vs 4.04 ppm) and [Au(6-methyl-2-benzylpyridineꢀ)Cl2]
(4.61 ppm vs 4.40 ppm); only in case of [Au(3-methyl-2-benzylpyr-

200
D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
idineꢀ)Cl2] both peaks overlapped (2 ꢃ 4.43 ppm) [7]. A similar ineq-
uivalency was noted for the two C(CH3)2 methyl groups in [Au(2-
(1,1-dimethylbenzyl)pyridineꢀ)Cl2] (dCH3: 2.35 ppm vs 2.06 ppm),
being also proved by single crystal X-ray studies (ZETYAY [1]). Thus,
one can suggest that in [Au(2bzpyꢀ)Cl2] the methylene protons are
not positioned symmetrically in respect to the remaining part of
Table 5
15N chemical and protonation/coordination shifts (in parentheses) for 2bzpy,
(2bzpyH)[AuCl4], [Au(2bzpy)Cl3], trans-[Pd(2bzpy)2Cl2], [Au(2bzpyꢀ)Cl2].
Compound
N(1)
2bzpyCDCl3
ꢁ64.7
2bzpyDMSO-d6
ꢁ60.9
(2bzpyH)[AuCl4]DMSO-d6
[Au(2bzpy)Cl3]CDCl3
trans-[Pd(2bzpy)2Cl2]CDCl3
A + B 1:1
ꢁ158.8 (ꢁ97.9)
ꢁ148.6 (ꢁ83.9)
A ꢁ159.4 (ꢁ94.7)
B ꢁ158.7 (ꢁ94.0)
ꢁ151.8 (ꢁ90.9)
the molecule. On average, they are moderately deshielded (mean
CH2
D
: 0.14–0.40 ppm, depending on the solvent), however, much
coord
CH2
less than in [Au(2bzpy)Cl3] (
D
: 0.57 ppm).
coord
[Au(2bzpyꢀ)Cl2]DMSO-d6
3.3. 13C and 15N NMR spectroscopy
13C and 15N NMR chemical and protonation/coordination shifts
are collected in Tables 4 and 5, respectively.
deprotonation and its subsequent auration; it is weaker than for
Cð20Þ
[Au(2ppyꢀ)Cl2] (
D
= 26.2 ppm [22]). This effect is different from
coord
The protonation of 2bzpy results in variable effects within the
pyridine ring: the nitrogen-adjacent C(2) and C(6) atoms are
shielded by ca. 4–7 ppm, while those of C(3)–C(5) are deshielded
by ca. 3–9 ppm, the net result being slight deshielding (mean
DCpðr2otÞꢁCð6Þ: 1.0 ppm); this pattern is similar to that for pyH+ cat-
ions in (pyH)[GeCl3] (IKOFOD) and (pyH)[As(N3)6] (CAFRAD)
[52–55]). Within the phenyl ring, C(10) is shielded by ca.
that for cis-[Pt(2bzpy)(C6F5)2], where the same C(20) atom re-
mained protonated and the 2bzpy molecule was bound to Au(III)
by g2-arene interaction (HASMUJ [56]), which resulted in C(20)
shielding by ca. 13 ppm [56]. The other phenyl ring carbons are
variously affected: the quartenary C(10) atom is shielded by ca.
8–9 ppm, while the CH ones can be either deshielded or shielded;
Cð10ÞꢁCð60Þ
the net result for the whole ring is deshielding (mean
D
:
coord
3 ppm, while the other carbons are deshielded up0 to ca. 1 ppm,
1.5–1.6 ppm). Within the pyridine ring, the quarternary C(2)
0
the net result being nearly zero (mean DCprð1otÞꢁCð6 Þ: ꢁ0.1 ppm).
atom is shielded by ca. 5 ppm, while the CH ones are deshielded
Cð1ÞꢁCð6Þ
The average effect for both heterocyclic rings is negligible (mean
by ca. 3–7 ppm; the net result is deshielding (mean
D
:
coord
Cð2ÞꢁCð6Þ;Cð10ÞꢁCð60Þ
D
:
0.4 ppm), while the methylene carbon is
2.0–2.3 ppm). On average, all heterocyclic ring carbons are
prot
0
0
shielded by ca. 5 ppm.
deshielded as well (mean DCcoð2oÞrꢁdCð6Þ;Cð1 ÞꢁCð6 Þ: 1.7–1.8 ppm). The same
phenomenon was noted for [Au(2ppyꢀ)Cl2], where the average
carbon deshielding was ca. 6.3 ppm for the phenyl ring, ca.
4.1 ppm for the pyridine ring, and ca. 5.3 ppm for the whole
molecule [22].
The Au(III) or Pd(II) complexation of 2bzpy results in the desh-
ielding of pyridine ring carbons, up to ca. 5 ppm and ca. 3 ppm,
Cð2ÞꢁCð6Þ
respectively (mean
D
: 3.2 ppm for [Au(2bzpy)Cl3] and
coord
2.4 ppm for trans-[Pd(2bzpy)2Cl2]). Within the phenyl ring, the
quarternary C(10) atoms have not been detected, while those of
C(20)–C(60) are deshielded, up to ca. 3 ppm and ca. 1 ppm. The
The methylene carbon is deshielded by ca. 2–3 ppm, this effect
being comparable to some [Au(2bzpyꢀ)(XX)] organometallics
methylene carbons are deshielded up to ca. 1 ppm, similarly to
(XX = phtalimidate, saccharinate, isatinate, benzene-1,2-diacetam-
CH2
CH2
cis-[Pt(2bzpy)(CO)(C6F5)2] and [Pt(2bzpy)(C6F5)3]ꢁ
(D
= 0.2–
idate;
D
= 2.7–2.9 ppm [15,16]).
coord
coord
0.3 ppm [56,57]).
The protonation of 2bzpy results in significant N(1) shielding
Nð1Þ
For [Au(2bzpyꢀ)Cl2] the 13C NMR spectra were measured in all
(|D
| = 97.9 ppm), which is typical for azines [58]. It proves that
coord
solvents. The most characteristic is the large deshielding of C(20)
the 2bzpyH+ cations remain stable in DMSO-d6, and do not under-
go hydrolysis with residual water present in this NMR solvent.
C20
coord
(D
= ca. 12–13 ppm), being the overall result of carbon
Table 4
13C chemical and protonation/coordination shifts (in parentheses) for 2bzpy, (2bzpyH)[AuCl4], [Au(2bzpy)Cl3], trans-[Pd(2bzpy)2Cl2], [Au(2bzpyꢀ)Cl2].
Compound
C(2)
C(3)
C(4)
C(5)
C(6)
C(10)
C(20)
C(30)
C(40)
C(50)
C(60)
CH2
2bzpyCDCl3
161.1
161.5
162.1
160.5
123.2
123.4
124.0
123.0
136.7
136.8
137.6
136.6
121.4
121.7
122.4
121.4
149.5
149.8
150.3
149.1
139.6
140.4
141.3
139.8
129.2
129.6
130.1
128.9
128.7
129.0
129.5
128.3
126.5
126.8
127.3
126.1
44.9
45.1
45.2
43.7
2bzpyCD2Cl2
2bzpyCD3CN
2bzpyDMSO-d6
(2bzpyH)[AuCl4]DMSO-d6
155.9
(ꢁ4.6)
161.8
(+0.7)
126.9
(+3.9)
145.6
(+9.0)
124.6
(+3.2)
142.6
(ꢁ6.5)
149.7
(+0.2)
136.4
(ꢁ3.4)
n.d.
n.d.
128.9
0
129.0
(+0.7)
127.3
(+1.2)
38.9
(ꢁ4.8)a
[Au(2bzpy)Cl3]CDCl3
128.5
(+5.3)
142.0
(+5.3)
125.8
(+4.4)
130.4
(+1.2)
129.8
(+1.1)
129.5
(+3.0)
45.2
(+0.3)
trans-
A
A + B
126.2
(+3.0)
A + B
138.5
(+1.8)
A + B
122.8
(+1.4)
A + B
152.4
(+2.9)
A + B
130.4
(+1.2)
A + B
129.2
(+0.5)
A + B
127.4
(+0.9)
A 45.6
[Pd(2bzpy)2Cl2]CDCl3
163.9
(+2.8)
B
(+0.7)
B 46.5
A + B 1:1
163.6
(+2.5)
(+1.6)
48.1
[Au(2bzpyꢀ)Cl2]CDCl3
[Au(2bzpyꢀ)Cl2]CD2Cl2
[Au(2bzpyꢀ)Cl2]CD3CN
[Au(2bzpyꢀ)Cl2]DMSO-d6
156.2
(ꢁ4.9)
156.5
(ꢁ5.0)
157.0
(ꢁ5.1)
155.7
(ꢁ4.8)
126.2
(+3.0)
126.8
(+3.4)
127.6
(+3.6)
126.4
(+3.4)
142.4
(+5.7)
143.0
(+6.2)
144.3
(+6.7)
143.3
(+6.7)
124.7
(+3.3)
125.1
(+3.4)
125.6
(+3.2)
124.5
(+3.1)
152.4
(+2.9)
152.6
(+2.8)
153.0
(+2.7)
152.1
(+3.0)
130.5
141.9
133.5
(+4.8)
133.6
(+4.6)
133.9
(+4.4)
132.7
(+4.4)
128.1
(+1.6)
128.1
(+1.3)
128.3
(+1.0)
126.9
(+0.8)
128.6
128.6
(ꢁ9.1) (+12.7)
131.4 142.3
(ꢁ9.0) (+12.7)
132.9 142.5
(ꢁ8.4) (+12.4)
131.9 141.1
(ꢁ7.9) (+12.2)
(ꢁ0.1) (ꢁ0.6) (+3.2)
128.9 129.1 48.3
(ꢁ0.1) (ꢁ0.5) (+3.2)
129.3 129.8 47.9
(ꢁ0.2) (ꢁ0.3) (+2.7)
127.9 128.6 46.1
(ꢁ0.4) (ꢁ0.3) (+2.4)
a
Signal overlapping with residual DMSO peak (38.9–40.1 ppm), was observed by DEPT.

D. Niedzielska et al. / Journal of Molecular Structure 1032 (2013) 195–202
201
15N
The Au(III) and Pd(II) complexation also leads to large N(1)
the comparison of their
D
parameters to the literature values for
coord
Nð1Þ
shielding (|
D
| = 83.9 and 94.0/94.7 ppm, respectively), this ef-
analogous Pd(II) complexes having the known structure allows to
prove trans-geometry suggested previously on the basis of far-IR
studies.
coord
fect being ca. 10 ppm weaker for [Au(2bzpy)Cl3] than trans-
[Pd(2bzpy)2Cl2]. The same dependency was reported for many
other [AuLCl3] and trans-[PdL2Cl2] complexes with N(1)-monoden-
tately bonded azines (L = pyridine; 2-, 3- and 4-methylpyridine;
2,3-, 2,4-, 3,5- and 2,6-dimethylpyridine; 2,4,6-trimethylpyridine;
Appendix A. Supplementary material
2-, 3- and 4-phenylpyridine [21,41,42,59,60]).
Nð1Þ
In case of [Pd(2bzpy)2Cl2], the difference of dN(1) (or
D
)
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.molstruc.2012.08.
005.
coord
parameters between both forms is less than 1 ppm, which excludes
the possibility these are two different geometric isomers. Further-
more, their N(1) shielding is much closer to that for trans-
Nð1Þ
[Pd(2ppy)2Cl2] than cis-[Pd(2ppy)2Cl2] (|
D
| = 94.0/94.7 ppm vs
References
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90.4 ppm and 82.9 ppm [21]), confirming the suggested trans-
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being larger for trans-[PdL2Cl2] than cis-[PdL2Cl2] species [61,62].
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are probably rotamers, for which anisotropic effects have only a
slight influence at 15N shielding. Hence, the 15N NMR spectrum
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not measured because of low solubility [21]), but finally proved
to be cis-[Pt(2ppy)2Cl2] (by single crystal X-ray studies, CCDC
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