Stabilization of the (η4-COD)Pt-fragment (COD = η2,η2-cyclo-octa-1,5-diene) by a bistriazenide: Synthesis and X-ray structural characterization of [(η4-COD) Pt(NNN-Ph)2C6H4], a neutral 1,2-bis(phenyltriazenido)benzene complex of platinum(II)

Article abstract of DOI:10.1016/j.jorganchem.2005.09.018

After exchange of Cl against NO₃ by reaction with AgNO ₃ [(COD)PtCl₂] reacts with the sodium salt of 1,2-bis(phenyltriazene)benzene to give [(η⁴-COD)Pt(NNN-Ph) ₂C₆H₄], the first example of a π-fragment of platinum(II) stabilized by two symmetrical triazenide chains. The new complex belongs to the monoclinic space group C2/c and corroborates the ability of the (COD)Pt fragment to be stabilized by bidentate ligands. The odd flying dragon structure of the title compound retains the C_2v symmetry of the free anion 1,2-bis(phenyltriazenide)benzene.

Full text of DOI:10.1016/j.jorganchem.2005.09.018

Journal of Organometallic Chemistry 691 (2006) 251–254
www.elsevier.com/locate/jorganchem
Note
Stabilization of the (g4-COD)Pt-fragment (COD = g2,g2-cyclo-
octa-1,5-diene) by a bistriazenide: Synthesis and X-ray structural
characterization of [(g4-COD)Pt(NNN-Ph)2C6H4], a neutral
1,2-bis(phenyltriazenido)benzene complex of platinum(II)
a,
a,
a
Manfredo Horner *, Gelson Manzoni de Oliveira *, Julieta Saldanha de Oliveira ,
¨
Wagner Magno Teles b,1, Carlos Alberto Lombardi Filgueiras , Johannes Beck
c
d
a
Departamento de Quı´mica, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
Departamento de Quı´mica, ICE, Universidade Federal de, Juiz de Fora, 36036-330 Juiz de Fora, MG, Brazil
b
c
Instituto de Quı´mica, Universidade Federal do Rio de, Janeiro, 21949-900 Rio de Janeiro, RJ, Brazil
Institut fu¨r Anorganische Chemie der Rheinischen, Friedrich-Wilhelms-Universita¨t, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
d
Received 1 September 2005; received in revised form 13 September 2005; accepted 13 September 2005
Available online 13 October 2005
Abstract
After exchange of Cl against NO3 by reaction with AgNO3 [(COD)PtCl2] reacts with the sodium salt of 1,2-bis(phenyltriazene)ben-
zene to give [(g4-COD)Pt(NNN-Ph)2C6H4], the first example of a p-fragment of platinum(II) stabilized by two symmetrical triazenide
chains. The new complex belongs to the monoclinic space group C2/c and corroborates the ability of the (COD)Pt fragment to be
stabilized by bidentate ligands. The odd flying dragon structure of the title compound retains the C2v symmetry of the free anion
1,2-bis(phenyltriazenide)benzene.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Triazenes; Triazenide-complexes; (COD)Pt-fragment
1. Introduction
small number of complexes is known in which the (COD)Pt
fragment is stabilized by an heteroatom. There are only
six crystallographically characterized [14–19] examples of
compounds with two nitrogen atoms acting as co-ligands,
like for example (g2,g2-cyclo-octa-1,5-diene)-bis(3,5-bis(tri-
fluoromethyl)pyrazole-N)-platinum(II) [14] and (N,N0-1,
2-phenylenebis(benzenesulfonamido))(g2,g2-cyclo-octa-1,5-
diene)-platinum(II) [15].
None of the described examples exhibits a triazene chain
as co-ligand. On the basis of their structures and biological
activity [20], triazenes are well important and interesting
substances. As ligands, the N–N–N moieties – with single
or twofold nitrogen chains, neutral or anionic (triazenides)
– can act as mono, bidentate or chelate ligands, showing a
remarkable ability to support the stereochemical requisites
of a wide variety of metal transition complexes [21–23].
Organoplatinum(II) complexes [(COD)Pt(R)2] (R = al-
kyl or aryl) are well known since decades and have been
widely used as precursors for mono- and polynuclear orga-
nometallic platinum(II) compounds [1–10]. They are also
of interest for the generation of organoplatinum reaction
centres on catalyst surfaces for heterogeneous catalysis
[11] or as potential precursors for chemical vapour deposi-
tion (CVD) of platinum [12]. In contrast, with exception of
some classical examples like [(COD)PtCl2] [13], a very
*
Corresponding authors. Tel.: +55 55 3220 8056; fax: +55 55 3220 8031.
E-mail addresses: hoerner@smail.ufsm.br (M. Ho¨rner), manzoni@
quimica.ufsm.br (G.M. de Oliveira).
1
In memoriam.
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.09.018

252
M. Ho¨rner et al. / Journal of Organometallic Chemistry 691 (2006) 251–254
With the aim, to investigate alternative ways to stabilize the
(COD)Pt fragment, as well as the ability of double-chained
triazenes to act as co-ligands in this compound type, we
report the synthesis and the X-ray characterization of
metallacyclic [(g4-COD)Pt(NNN-Ph)2C6H4], the first p-
fragment of platinum(II) stabilized by two symmetrical
triazenide chains, which achieve a heterocyclic five-
membered ring with the metallic center. There is only one
comparable complex reported up to date [15].
3. Results and discussion
In the X-ray studies of the monoclinic title complex the
space group C2/c was chosen on the basis of statistics and
later justified by the successful refinements. Crystal data
and experimental conditions are given in Table 1. Selected
Table 1
Crystal data and structure refinement for [(g4-COD)Pt(NNN-Ph)2C6H4]
Empirical formula
Formula weight
T (K)
C26H26N6Pt
617.62
293(2)
2. Experimental
Radiation
k (A)
Crystal system,
Space group
Mo Ka
0.71073
Monoclinic
C2/c
˚
All manipulations were carried out under nitrogen by
use of standard Schlenk techniques.
2.1. [(g4-COD)Pt(NNN-Ph)2C6H4],[(g2,g2-cyclo-octa-
1,5-diene)bis(phenyltriazenide)-benzene-platinum(II)]
Unit cell dimensions
˚
a (A)
16.657(9)
˚
b (A)
12.048(8)
13.141(6)
˚
c (A)
1,2-Bis(phenyltriazene)benzene (85.4 mg, 0.27 mmol)
was dissolved in 15 ml of absolute tetrahydrofuran and
treated with small portions of metallic sodium powder until
H2 evolution stopped. The resulting intense-red mixture
was filtered to remove excess of metallic sodium.
C8H12PtCl2 (101.0 mg, 0.27 mmol) was dissolved in 15 ml
of absolute tetrahydrofuran and treated with a solution
of 91.7 mg (0.54 mmol) AgNO3 in 10 ml of absolute aceto-
nitrile. The resulting mixture was filtered to remove the
precipitate of AgCl. To this solution the intense-red mix-
ture was added slowly with continuous stirring. After stir-
ring at room temperature for 3 h, a dark-gray precipitate
was filtered off. The combined organic solvents were evap-
orated. The resulting orange solid was dried in vacuo.
Orange prism-shaped single crystals suitable for X-ray
diffraction were obtained at room temperature within two
weeks by slow diffusion of n-hexane into a THF solution
of the title complex.
Properties: air stable, crystalline substance; C26H26N6Pt
(617.62); Yield: 148.2 mg (0.24 mmol), 89% based on
C8H12PtCl2. Melting point: 96 ꢁC.
IR (KBr): the typical band observed at 1412.7 for the
free ligand (m, mas(N@N)) is substituted for a stretching
at 1259.8 cmꢀ1 in the spectrum of the complex (decreasing
of the N–N bond order of the ligand). The band at
3292.8 cmꢀ1 in the spectrum of the free ligand (m, mas(N–
H)) is suppressed in the spectrum of [(g4-COD)Pt(NNN-
Ph)2C6H4].
a (ꢁ)
b (ꢁ)
c (ꢁ)
V (A )
Z
90
121.24(4)
90
2255(2)
3
˚
4
Calculated density (g cmꢀ3
Absorption coefficient (mmꢀ1
F(000)
Crystal size (mm)
h Range (ꢁ)
Index ranges
)
1.819
6.250
1208
0.2 · 0.04 · 0.02
3.30–25.49
ꢀ20 6 h 6 20, ꢀ14 6 k 6 9,
ꢀ13 6 l 6 14
4833
1953 [0.0684]
93.0%
)
Reflections collected
Reflections unique [Rint
]
Completeness to h max.
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Analytical
0.9121 and 0.3679
Full-matrix least-squares on F2
1953/0/150
0.917
R1 = 0.0417, wR2 = 0.0734
R1 = 0.0716, wR2 = 0.0794
0.749 and ꢀ0.661
ꢀ3
˚
Largest diff. peak and hole (e A
)
Table 2
Selected bond lengths (A) and angles (ꢁ) for [(g4-COD)Pt(NNN-
˚
Ph)2C6H4]
˚
Bond lengths (A)
Pt(1)–N(11)
Pt(1)–C(31)
Pt(1)–C(34)
N(11)–N(12)
N(11)–C(11)
N(12)–N(13)
N(13)–C(21)
2.025(8)
2.163(11)
2.193(10)
1.364(10)
1.418(12)
1.252(11)
1.404(12)
2.2. Crystallography
Bond angles (ꢁ)
X-ray data were collected with a STOE-IPDS diffrac-
tometer. The structure of [(g4-COD)Pt(NNN-Ph)2C6H4]
was solved by direct methods (SHELXS-97) [24]. Refinements
were carried out with the SHELXL-97 [25] package. All
refinements were made by full-matrix least-squares on F2
with anisotropic displacement parameters for all non-
hydrogen atoms. Hydrogen atoms were included in the
refinement in calculated positions.
N(11)#1–Pt(1)–C(31)#1
N(11)–Pt(1)–C(31)#1
N(11)#1–Pt(1)–C(34)
N(11)–Pt(1)–C(34)
C(11)–N(11)–Pt(1)
C(11)#1–C(11)–N(11)
160.0(3)
97.3(4)
163.3(3)
98.3(3)
114.5(6)
115.6(5)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, y,
ꢀz + 1/2.

M. Ho¨rner et al. / Journal of Organometallic Chemistry 691 (2006) 251–254
253
Fig. 1. ZORTEP [26] plot with atom-labeling scheme of the molecular structure of [(g4-COD)Pt(NNN-Ph)2C6H4]; displacement ellipsoids at the 50%
level. Symmetry transformations used to generate equivalent atoms: #1 ꢀx, y, ꢀz + 1/2.
bond distances and angles of [(g4-COD)Pt(NNN-Ph)2-
C6H4] are listed in Table 2; Fig. 1 displays the ZORTEP
[26] representation of the molecule.
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