[Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N, I}], a palladium(II) complex with I- and organic iodide as trans ligands

Article abstract of DOI:10.1016/S0020-1693(02)01435-4

The treatment of [Pd(dmba)(Fmes)(OH₂)] with I₂ leads to the formation of [Pd(Fmes)I{NMe₂(CH₂-o-C₆H₄-I)-N, I}]. The X-ray structure shows that a new halocarbon ligand, (2-iodobenzyl)dimethyl

Full text of DOI:10.1016/S0020-1693(02)01435-4

Inorganica Chimica Acta 347 (2003) 49Á52
/
www.elsevier.com/locate/ica
[Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N,I}], a palladium(II) complex
with Iꢀ and organic iodide as trans ligands
´
Camino Bartolome´, Pablo Espinet *, Jose´ Miguel Mart´ın-Alvarez, Fernando Villafane
˜
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
Received 20 February 2002; accepted 7 June 2002
Dedicated to Prof. Rafael Uso´n, whose initiative meant more than one small step on the trail to modern Spanish Organometallic Chemistry
Abstract
The treatment of [Pd(dmba)(Fmes)(OH2)] with I2 leads to the formation of [Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N,I}]. The X-ray
structure shows that a new halocarbon ligand, (2-iodobenzyl)dimethylamine has been formed and is acting as NÁ
different types of iodine, one iodide ligand and one organic iodide coordinated to Pd, are mutually trans and display essentially
identical PdÁI distances.
/I chelate. The two
/
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Palladium complexes; Iodocarbon; Iodide; Six-membered metalacycles
1. Introduction
has been obtained by oxidation of (NnBu4)[Pt(C6Cl5)]
with Cl2.[5] However it fails when applied on
[Pd(dmba)(Fmes)(OH2)] (dmbaꢁdimethylbenzyla-
mine). In this case the PdÁC bond with the dmba ligand
is split, and the new IÁdmba ligand so formed remains
The solid state structures of main group, and of some
transition metal compounds with the bulky ligand 2,4,6-
tris(trifluoromethyl)phenyl (nonafluoromesityl or Fmes)
often show that the ortho-CF3 groups are involved in
/
/
/
coordinated to the Pd center.
Mꢀ ꢀ ꢀF bonding interactions in many structures [1Á
/
3].
On the contrary, the structures of palladium(II) com-
plexes determined so far show structural features and
PdÁF distances suggestive of non interaction, which we
/
attribute to the soft nature of Pd(II) [4]. Since the
structure of the Fmes ligand places F atoms on the Pd
atom and would favor geometrically this interaction, we
planned to oxidize the Pd center with I2 in the hope that
the bulk iodides arising from the redox process might
prefer to remain as external counteranions, while the so
formed hard Pd(IV) center would achieve hexacoordi-
nation by accepting two fluorine donor atoms from the
Fmes ligand (Eq. (1)). A similar strategy has worked
ð1Þ
2. Results and discussion
previously for the synthesis of compounds with MÁ
/
Cl(aromatic) interactions, such as in [Pt(C6Cl5)4] which
The reaction of [Pd(dmba)(Fmes)(OH2)] (1) with I2 in
a 1:1 molar ratio did not afford the corresponding
palladium(IV) complex but led to the formation of
[Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N,I}] (2) according
to Eq. (2):
* Corresponding author. Tel.: ꢂ
013.
E-mail address: espinet@qi.uva.es (P. Espinet).
/
34-983-423-231; fax: ꢂ34-983-423-
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 4 3 5 - 4

50
C. Bartolome´ et al. / Inorganica Chimica Acta 347 (2003) 49Á52
/
Table 1
Selected bond lengths (A) and bond angles (8) for
[Pd(Fmes)I{NMe2(CH2 Áo-C6H4-I)-N,I}] (2)
˚
/
ð2Þ
Bond lengths
Pd(1)Á
Pd(1)Á
Pd(1)Á
Pd(1)Á
/
C(11)
N(1)
I(1)
1.93(3)
2.16(2)
I(1)Á
C(11)Á
I(2)Á
N(1)Á
/
Pd(1)Á
Pd(1)Á
Pd(1)
Pd(1)
/
I(2)
170.40(12)
175.1(13)
91.8(9)
/
/
/
N(1)
/
2.607(3) C(1)Á
2.636(3) C(7)Á
/
/
/
I(2)
/
/
119.1(17)
The characterization of 2 was not unequivocal from
Bond angles
C(11)ÁPd(1)Á
N(1)ÁPd(1)ÁI(1)
C(11)Á
N(1)ÁPd(1)Á
its analytical and spectroscopic data only, and its solid
structure was determined by X-ray diffraction. A
perspective view of one of the molecules in the asym-
metric unit is shown in Fig. 1. Selected distances and
angles are listed in Table 1.
/
/
I(1)
83.4(8)
95.1(6)
89.4(8)
92.6(7)
C(6)Á
C(1)Á
C(6)Á
C(12)Á
/
C(7)Á
C(6)Á
C(1)Á
/
N(1)
C(7)
I(2)
112(3)
121(3)
120(3)
112(3)
/
/
/
/
/
Pd(1)Á/I(2)
/
/
/
/
I(2)
/C(11)ÁC(16)
/
Both molecules of 2 in the asymmetric unit display the
same structural features. The palladium atom is ap-
proximately square planar, coordinated by a new
halocarbon ligand, (2-iodobenzyl)dimethylamine, which
is acting as a chelating bidentate ligand, with its iodine
atom cis to the fluoromesityl ligand. This ligand forms
with the palladium a six-membered cycle that shows a
boat conformation. A iodide ligand is coordinated trans
to the iodine atom, and the coordination plane is
completed by a Fmes ligand. The fluoromesityl ligand
lays essentially perpendicular (90.08) to the pseudoplane
inversion of (2-iodobenzyl)dimethylamine ligand which
is fast at room temperature but slow at ꢀ
expected for a six-membered metalacycle.
The Pd(1)ÁI(1) distance is 2.607(3)Á
remarkably similar to the Pd(1)Á
2.624(4) A) distance, in spite of the very different nature
of the two iodine atoms. Moreover, both distances are
similar to those found in complexes with iodide co-
ordinated to palladium as terminal ligand [9], and to
/
60 8C, as
˚
/
/
2.600(4) A,
/
I(2) (2.636(3)Á
/
˚
that found for PtÁ
/
I in [Pt(C6F5)2{(RÁ
/
I)Á
/
C,I}] (RÁ
/
Iꢁ
/
defined by the metal and the donor atoms. The shortest
...
Pd F3C-ortho distance found in 2 is 2.987 A (between
1,2-iodoaniline) [7a]. The fact that the two iodine atoms
in 2 are mutually trans and the metalacycle is six-
membered makes our observation of equality in dis-
tances particularly significant, as they are not affected
by effects coming from different trans ligands, or by
strain in a shorter cycle.
˚
Pd(1) and F(3)), longer than those found in palladiu-
m(II) [Pd(Fmes)2L2] complexes, confirming that these
are non bonding contacts [4].
Chelating halocarbon ligands are not uncommon and
a number of structures have been reported [6,7].
However, they are observed usually when involved in
the formation of particularly stable five-membered
metalacycles. Only one example of a six-membered
metalacycle involving a halogen as donor has been
reported, in a Mo complex [8]. Obviously there are not
NMR experiments in CDCl3 at low temperature were
carried out in order to suggest a possible mechanism for
the formation of 2, but no intermediate was detected.
The clean formation of 2 suggests that the reaction
might be initiated by electrophilic substitution at the
easily accessible metalated carbon of the dmba, followed
by coordination of the iodide and the iodocarbon, with
water displacement. In such case the reaction would not
involve a Pd(IV) intermediate, and the bulky iodine
would not need to approach the Pd center, which is
somewhat protected by the ortho effect of the CF3
groups above and below the coordination plane.
Attempts at extending these results to Cl2 or Br2
resulted in mixtures that could not be well characterized.
Considering that the chelating N,X-coordination of the
2-halodimethylbenzylamine is expected to be less fa-
vored when X is Cl, or Br (both worse donors than I),
the spectroscopic data of the crude products suggest the
existence of halogen bridged binuclear compounds,
possibly [Pd2(m-X)2(Fmes)2{NMe2(CH2-o-C6H4-X)}2]
where the halocarbon ligand is coordinated only by
the nitrogen. However, the mixture contains also other
products revealing that the reaction is not as clean as it
was for I2.
precedents of six-membered metalacycles with a PdÁ
/
I
bond. The 19F NMR spectra of 2 show a boat to boat
Fig. 1. Molecular structure of [Pd{NMe2(CH2Ã
/
OÃ
/
C6H4I)ÃN,I}(F-
/
mes)I] (2) showing the atom numbering scheme. The elipsoids are
drawn at 30% probability level.

C. Bartolome´ et al. / Inorganica Chimica Acta 347 (2003) 49Á
/
52
51
3. Experimental
Table 2
Empirical formula
Formula weight
Crystal system
Space group
C18H14F9I2NPd
775.50
triclinic
The reactions were carried out under dinitrogen
atmosphere. The solvents were purified according to
standard procedures [10]. [Pd(dmba)(Fmes)(OH2)] (1)
was prepared as described elsewhere [11]. Infrared
¯
P1
˚
a (A)
8.684(6)
13.370(8)
20.358(13)
95.969(13)
98.026(12)
102.104(13)
2267(2)
4
˚
b (A)
spectra were recorded in PerkinÁElmer 883 or 1720X
/
˚
c (A)
apparatuses, as Nujol mulls between polystyrene films,
from 4000 to 200 cmꢀ1. NMR spectra were recorded on
an ARX-300 instrument in CDCl3, and chemical shifts
are referred to TMS, or CFCl3. Coupling constants are
given in Hz. Elemental analyses were performed on a
a (8)
b (8)
g (8)
V (A )
Z
Dcalc (g cmꢀ3
3
˚
)
2.273
3.621
1448
PerkinÁElmer 2400B microanalyzer.
/
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm3)
Temperature (K)
0.09ꢃ
293(2)
1.02 to 20.83
0.71073 (Mo Ka)
85h 58, ꢀ135
05l 520
8306
/
0.05ꢃ
/
0.02
3.1. Synthesis of [Pd(Fmes)I{NMe2(CH2-o-C6H4I)-
N,I}] (2)
u range for data collection (8)
˚
Wavelength (A)
I2 (0.026 g, 0.1 mmol) was added to a solution of 1
(0.054 g, 0.1 mmol) in CH2Cl2 (10 ml). The colorless
solution became deep orange instantaneously. The
solution was stirred at room temperature for 2 min
and then filtered on dry Celite. Hexane (ca. 30 ml) was
added to the filtrate, which was concentrated, and
Index ranges
ꢀ/
/
/
/
/
k 513,
/
/
/
Reflections collected
Independent reflections
4693 (Rint
1605
ꢁ/0.1299)
Observed reflections [I ꢀ2s(I)]
/
Absorption correction
Max. transmission
Min. transmission
SADABS
1.000
0.682
cooled to ꢀ
decanted, washed with hexane (3ꢃ
vacuum. Yield 0.041 g (53%). 19F RMN: d ꢀ
ortho-CF3, 6F), ꢀ
63.09 (s, para-CF3, 3F). 19F RMN
(ꢀ60 8C): d ꢀ56.61 (s, ortho-CF3, 3F), ꢀ56.95 (s,
ortho-CF3, 3F), ꢀ62.63 (s, para-CF3, 3F). H RMN: d
7.79 (d, Jꢁ
8 Hz, H3, NMe2(CH2-o-C6H4I), 1H), 7.74
(s, C6H2(CF3)3, 2H), 7.52 (t, Jꢁ
7.5 Hz, H5,
/
20 8C. The orange crystals obtained were
5 ml), and dried in
56.65 (br,
/
Data/restraints/parameters
Goodness-of-fit on F2
4693/0/523
0.761
/
Final R indices [I ꢀ
R indices (all data)
/
2s(I)]
R1ꢁ
R1ꢁ
1.344 and ꢀ
/
0.0676, wR2ꢁ
0.1890, wR2ꢁ
0.830
/
0.1303
0.1661
/
/
/
/
/
/
Largest difference Peak and hole (e
ꢀ3
/
1
/
˚
A
)
/
/
˚
0.71073 A) [12].
fractometer with Mo Ka radiation (lꢁ
/
NMe2(CH2-o-C6H4I), 1H), 7.30 (m, NMe2(CH2-o-
C6H4I), 2H), 3.69 (br, NMe2(CH2-o-C6H4I), 2H), 2.85
Intensities were integrated [13] from several series of
exposures, each exposure covering 0.38 in v, and the
total data set being a hemisphere. Absorption correc-
tions were applied, based on multiple and symmetry-
equivalent measurements [14]. The structure was solved
by direct methods and refined by least squares on
weighted F2 values for all reflections (see Table 2) [15].
All non-hydrogen atoms were refined without positional
constraints and assigned anisotropic displacement para-
meters except for C(12), C(18), C(31), C(34), C(35),
C(37), C(39) and N(2). Hydrogen atoms were con-
strained to ideal geometries and refined with fixed
isotropic displacement parameters. Refinement pro-
ceeded to give residuals shown in Table 2, the poor
quality of the crystal preventing a better result. Complex
neutral-atom scattering factors were used [16].
1
(br, N(CH3)2(CH2-o-C6H4I), 6H). H RMN (ꢀ
/
60 8C):
7.79 (d, Jꢁ
(s, C6H2(CF3)3, 2H), 7.52 (t, Jꢁ
NMe2(CH2-o-C6H4I), 1H), 7.37 (t, Jꢁ
NMe2(CH2-o-C6H4I, 1H), 7.31 (t, Jꢁ
7.8 Hz, H4,
NMe2(CH2-o-C6H4I), 1H), 3.87 (d, Jꢁ12.4 Hz,
NMe2(CH2-o-C6H4I), 1H),3.56 (d, Jꢁ12.4 Hz,
/
8 Hz, H3, NMe2(CH2-o-C6H4I), 1H), 7.75
7.5 Hz, H5,
7.4 Hz, H6,
/
/
/
/
/
NMe2(CH2-o-C6H4I), 1H), 3.15 (s, N(CH3)2(CH2-o-
C6H4I), 3H), 2.53 (s, N(CH3)2(CH2-o-C6H4I), 3H). IR:
2020 vw(br), 1868 vw(br), 1787 vw(w), 1615 m, 1568 w,
1298 vs, 1278 vs, 1180 s, 1144 s, 1082 m, 1023 m, 929 w,
914 m, 833 w, 757 m, 695 w, 683 m, 667 w, 654 d, 531
w(br), 437 w(br), 290 w(br). Anal. Calc. for
C18H14NF9I2Pd: C, 27.88; H, 1.82; N, 1.81. Found: C,
28.16; H, 1.89; N, 1.71%.
4. X-ray crystallography
5. Supporting material
Suitable crystals of 2 were grown by slow diffusion of
a concentrated dichloromethane solution of the complex
Crystallographic data (excluding structure factors) for
the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC No.
179640. Copies of this information may be obtained free
into n-hexane at ꢀ
/
20 8C. X-ray measurements were
made using a Bruker SMART CCD area-detector dif-

52
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