Bis(fluoromesityl) palladium complexes, archetypes of steric crowding and axial protection by ortho effect - Evidence for dissociative substitution processes - Observation of 19F-19F through-space couplings

Article abstract of DOI:10.1002/ejic.200300756

Bisarylated complexes trans-[Pd(Fmes)₂(SR₂) ₂](SR₂)₂] [Fmes = 2,4,6-tris(trifluoromethyl) phenyl (fluoromesityl); SR₂ = SMe₂, tht; tht = tetrahydrothiophene] are precursors for various bisarylated fluoromesityl palladium(II) complexes by ligand-substitution reactions. Boiling under reflux in acetonitrile gives the mixed complexes trans-[Pd(Fmes)₂(NCMe) (SR₂)], whereas boiling under reflux in toluene leads to trans-[PdCl₂L₂] (L = PMe₃, tBuNC, pTol-NC, 4-MePy), in the presence of neutral monodentate ligands, or to (NnBu ₄)[trans-Pd(Fmes)₂I(SR₂)] when treated with (NnBu₄)I. trans-[Pd(Fmes)₂(SMe₂)₂] reacts with bidentate ligands, also boiling under reflux in toluene, to give [Pd(Fmes)₂(L-L)] [L-L = Me₂bipy, 2,2′-biquinolyl, κ²N,N′-OCPy₂, dppe (Ph₂PCH ₂CH₂PPh₂), pte (PhSCH₂CH ₂SPh), κ²S,N-SPPh₂Py, κ²O,N-OPPhPy₂], or the bimetallic complex [Pd(Fmes)₂(μ-1κN:1,2κO:2κN-Py ₂MeCO)Pd(Fmes)(SMe₂)] (characterized by X-ray diffractometry) when treated with (OH)(CH₃)CPy₂. The crowding associated with two Fmes groups produces several interesting features: (1) trans complexes are preferred over cis complexes, against the expected electronic preferences; (2) the low-temperature NMR spectra of several complexes, or the X-ray diffraction structure of Pd(Fmes)₂(2, 2′-biquinolyl)], reveal significant structural distortions associated with steric crowding; (3) the need for boiling under reflux in the synthesis suggests a dissociative substitution mechanism, which is unknown so far for Pd; (4) some of the complexes show ¹⁹F-¹⁹F through-space couplings. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300756

FULL PAPER
Bis(fluoromesityl) Palladium Complexes, Archetypes of Steric Crowding and
Axial Protection by ortho Effect ؊ Evidence for Dissociative Substitution
19
Processes ؊ Observation of F؊19F Through-Space Couplings
[a]
[a]
[a]
´
´
´
Camino Bartolome, Pablo Espinet,* Jose M. Martın-Alvarez, and
[a]
˜
Fernando Villafane
Keywords: Palladium / Dissociative substitution / Fluorine / Bulky ligands / Steric crowding / Through-space coupling
Bisarylated complexes trans-[Pd(Fmes)2(SR2)2] [Fmes = 2,4,6-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)] (characterized
tris(trifluoromethyl)phenyl (fluoromesityl); SR2 = SMe2, tht; by X-ray diffractometry) when treated with (OH)(CH3)CPy2.
tht = tetrahydrothiophene] are precursors for various bisaryl-
ated fluoromesityl palladium(II) complexes by ligand-substi-
The crowding associated with two Fmes groups produces
several interesting features: (1) trans complexes are pre-
tution reactions. Boiling under reflux in acetonitrile gives the ferred over cis complexes, against the expected electronic
mixed complexes trans-[Pd(Fmes)2(NCMe)(SR2)], whereas preferences; (2) the low-temperature NMR spectra of several
boiling under reflux in toluene leads to trans-[PdCl2L2] (L = complexes, or the X-ray diffraction structure of
PMe3, tBuNC, pTol-NC, 4-MePy), in the presence of neutral [Pd(Fmes)2(2,2Ј-biquinolyl)], reveal significant structural dis-
monodentate ligands, or to (NnBu4)[trans-Pd(Fmes)2I(SR2)]
tortions associated with steric crowding; (3) the need for boil-
when treated with (NnBu4)I. trans-[Pd(Fmes)2(SMe2)2] ing under reflux in the synthesis suggests a dissociative sub-
reacts with bidentate ligands, also boiling under reflux in
stitution mechanism, which is unknown so far for Pd; (4)
toluene, to give [Pd(Fmes)2(L−L)] [L−L = Me2bipy, 2,2Ј-bi-
some of the complexes show 19F−19F through-space coup-
quinolyl, κ2N,NЈ-OCPy2, dppm (Ph2PCH2PPh2), dppe lings.
(Ph2PCH2CH2PPh2), pte (PhSCH2CH2SPh), κ2S,N-SPPh2Py,
κ2O,N-OPPhPy2], or the bimetallic complex [Pd(Fmes)2(µ-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
2,4,6-Tris(trifluoromethyl)phenyl (nonafluoromesityl or
Fmes) is an interesting ligand for main group and transition
metals.[1,2] It combines steric bulk with a certain electron-
withdrawing character, and lacks hydrogens susceptible to
H-elimination. The latter two features may facilitate the
preparation of stable derivatives where the consequences
(structural or otherwise) of steric crowding can be tested.
However, its bulkiness limits direct arylation as a method
of obtaining organometallics that contain more than one
Fmes group. Our initial studies on the coordination of
Fmes in palladium() complexes by arylation indicated that
bisarylated complexes are only accessible for small ancillary
ligands.[2a] After the first arylation (Scheme 1), the coordi-
nated Fmes exerts a high axial protection (ortho effect)
against subsequent nucleophilic attack, which can progress
reasonably well only when the spatial requirements of the
ancillary ligands are small, so that the initially coordinated
Fmes can tilt and facilitate the approach of the entering
FmesϪ nucleophile. In kinetic terms, the activation enthalpy
Scheme 1. Associative mechanism for an arylation reaction
for the second arylation (∆G2‡) is noticeably higher than
∆G1‡, its value increasing as the hindrance of the ancillary
ligands to the tilting of the coordinated Fmes increases.
However, ligand substitution on bisarylated complexes
obtained by arylation might allow the synthesis of a wider
range of bisarylated species. Here we describe the synthesis
and characterization of different bisarylated Fmes pal-
[a]
´
´
Departamento de Quımica Inorganica, Facultad de Ciencias,
Universidad de Valladolid,
47005 Valladolid, Spain
E-mail: espinet@qi.uva.es
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DOI: 10.1002/ejic.200300756
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Bis(fluoromesityl) Palladium Complexes
FULL PAPER
ladium() complexes obtained by treating trans- rivatives they resist displacement, even in the presence of a
[Pd(Fmes)2(SR2)2] (SR2 ϭ SMe2, tht; tht ϭ tetrahydrothio- large excess of the entering ligand. Displacement is achieved
phene) with monodentate or bidentate ligands. The reac- only when the mixture is submitted to reflux in high-boiling
tions must be carried out in either toluene or acetonitrile temperature solvents such as toluene or MeCN.
boiling under reflux, suggesting a dissociative ligand substi-
Thus, neutral monodentate ligands L replace SMe2 from
tution mechanism, which is unusual for Pd. Some of the cis- 1a, in refluxing toluene, to give the corresponding neutral
bisarylated complexes obtained show interesting structural mononuclear complexes trans-[Pd(Fmes)2L2] (L ϭ 4-pic, 1c;
features associated with their steric crowding. Several com- PMe3, 1d; tBuNC, 1e, pTol-NC, 1f). The reactions do not
plexes exhibit 19FϪ19F through-space couplings between proceed under milder conditions. Boiling under reflux 1a or
both Fmes. References on such couplings in organometallic 1b in NCMe produced trans-[Pd(Fmes)2(NCMe)(SMe2)]
compounds are scarce,[3] even though many cis-bisarylated (2a).
fluoroaryl complexes are known.[4]
Treatment of 1a or 1b with excess (NnBu4)I did not lead
to the substitution of both thioether ligands by iodide, but
to the formation of the monoanionic (NnBu4)[trans-
Pd(Fmes)2I(SMe2)] (3a) or (NnBu4)[trans-Pd(Fmes)2I(tht)]
(3b), respectively.
Boiling under reflux in toluene was also required to re-
place the thioether ligands when 1a was treated with neutral
bidentate ligands L-L. This produced [Pd(Fmes)2(L-L)] (L-
L ϭ Me2bipy (4,4Ј-Me2-2,2Ј-bipyridine), 4a; biquinolyl, 4b;
κ2N,NЈ-OCPy2 (Py ϭ 2-pyridyl), 4c; dppm (Ph2PCH2PPh2),
4d; dppe (Ph2PCH2CH2PPh2), 4e; pte (PhSCH2CH2SPh),
4f).
Bisarylated complexes containing chemically non-equiva-
lent Fmes groups were obtained with bidentate ligands con-
taining two different donor atoms (L-LЈ). Thus the S,N-
donor ligand SPPh2Py gave [Pd(Fmes)2(κ2S,N-SPPh2Py)]
(5a). Remarkably, equimolar amounts of 1a and
OPPhPy2, which usually coordinates as κ2N,N-donor to
PdII,[5] gave [Pd(Fmes)2(κ2O,N-OPPhPy2)] (5b). The treat-
ment of (OH)(CH3)CPy2 with trans-[Pd(Fmes)2(SMe2)2]
(1a) did not afford the expected cis bisarylated complex, but
gave instead the binuclear complex [Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe)2] (6) (Scheme 3).
Results
Syntheses of Bisarylated Complexes
The complex trans-[Pd(Fmes)2(SMe2)2] (1a) was obtained
by arylation of trans-[PdCl2(SMe2)2] with Li(Fmes), as de-
scribed previously for trans-[Pd(Fmes)2(tht)2] (1b).[2a] This
complex is a better precursor for the preparation of other
bisarylated complexes (Scheme 2) as SMe2 has a higher
volatility (b.p. 38 °C) than tht (b.p. 119 °C). Although in
related Pd complexes (e.g. trans-[Pd(C6F5)2(SMe2)2], or
trans-[Pd(C6F5)2(tht)2]) SMe2 or tht are easily displaced by
other ligands at room temperature,[4a] in these bis-Fmes de-
Scheme 3. Preparation of 6
Characterization of Bisarylated Complexes
Solid-state IR spectra of all the bisarylated complexes
show characteristic absorptions for the Fmes group.[6] Ab-
sorption in the region 710Ϫ670 cmϪ1 for several polyfluor-
ophenyl has been associated with the RϪM fragment and
can be structurally informative: the cis isomers exhibit two
Scheme 2. Synthesis of the complexes
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C. Bartolome, P. Espinet, J. M. Martın-Alvarez, F. Villafan˜e
FULL PAPER
medium-to-strong bands in this range, whereas the trans only 5.8(4)° and the other 2.2(4)° to the coordination plane.
isomers show only one.[4a,7] This feature is also observed at The PdϪCipso distances [Pd(1)ϪC(1), 2.102(4) A;
˚
690Ϫ680 cmϪ1 for the Fmes complexes, which supports Pd(2)ϪC(21), 2.098(4) A] are similar to those found in
˚
their structural assignments. No additional evidence is pro- trans-[Pd(Fmes)2(tht)2],[2a] and somewhat longer than those
vided by the IR data of 1a (although the trans isomer was in other complexes where the ligand trans to the Fmes is
found in the structural determination of 1b, previously re- harder (see, for instance, other structures in this paper and
ported),[2a] and 1c. The trans geometry for 1e and 1f is in ref. 2). As usually observed in Fmes palladium com-
further supported by the presence of only one ν(CϵN) ab- plexes, the CϪCϪC angles at the ipso carbon are signifi-
sorption for the coordinated isocyanides.
cantly less than 120° and those at the ortho carbon atoms
trans-[Pd(Fmes)2(pTol-NC)2] (1f) was characterized by are rather larger than 120° due to the electronic effects of
solid-state X-ray diffractometry, as an example of a com- the electropositive metal and electronegative CF3 substitu-
plex with a ligand with minimal steric requirements in the ents at these positions.[8] The CϪNϪC angle of the two
vicinity of the coordination sites. The molecular structure isocyanide groups is Ͻ 180°, a common feature for isocyan-
of 1f (Figure 1) and selected distances and angles (Table 1) ides coordinated to transition metals.[9] The structure sug-
are given here.
gests that there are no important repulsive interactions
between neighbouring CF3 groups, otherwise the rings
would tilt to scatter these as much as possible. The elong-
ation of the PdϪCF3 distance compared with other com-
plexes (and similar to trans-[Pd(Fmes)2(tht)2]) is then attri-
buted mostly to a high trans influence of the Fmes group.
Presumably, with these PdϪFmes distances, there is little
steric repulsion between facing CF3 groups in a trans-
[Pd(Fmes)2L2] complex.
The 19F NMR spectra of all the trans complexes 1 display
two singlets with 2:1 intensities, except for 1d where a triplet
is observed for the ortho-CF3 due to coupling with two
equivalent phosphorus atoms. The trans geometry of com-
plexes 2 and 3 is confirmed by the chemical equivalence of
both Fmes groups.
The cis complexes 4 exhibit only one singlet for para CF3
groups (which is consistent with the equivalence of the two
Fmes groups), and another signal for the equivalent ortho-
CF3 groups. However, with biquinolyl 4b and pte 4f the
latter signal is very broad, which is interpreted as owing to
a slow concerted tilting of both Fmes groups, as observed
Figure 1. Molecular structure of trans-[Pd(Fmes)2(pTol-NC)2] (1f).
All hydrogen atoms omitted for clarity
1
for related systems.[2a] The H NMR spectra show that the
˚
Table 1. Selected bond lengths (A) and angles (°) for trans-
two halves of the chelate ligands are equivalent through a
C2 axis.
[Pd(Fmes)2(pTol-NC)2] (1f); #1: Ϫx ϩ 1, Ϫy ϩ 1, Ϫz ϩ 1; #2: Ϫx,
Ϫy, Ϫz
To explore the expected distortions when more sterically
demanding ligands are used, 4b (L-L ϭ 2,2Ј-biquinolyl) was
characterized by solid-state X-ray diffractometry (Figure 2);
Table 2 gives relevant distances and angles. The two Fmes
ligands are coordinated in a cis arrangement, and the two
N atoms of the biquinolyl ligand occupy the other coordi-
nation sites. The biquinolyl ligand is not planar, with the
two halves forming an angle of 25.0(5)°. Moreover, the av-
erage plane of the biquinolyl ligand forms a dihedral
angle of 35.8(5)° with the average coordination plane. This
Pd(1)ϪC(1)
Pd(1)ϪC(11)
C(11)ϪN(1)
N(1)ϪC(12)
Pd(2)ϪC(21)
Pd(2)ϪC(31)
C(31)ϪN(2)
N(2)ϪC(32)
2.102(4)
1.960(4)
1.152(5)
1.405(5)
2.098(4)
1.959(5)
1.152(5)
1.407(6)
C(11)ϪPd(1)ϪC(1)
C(11)ϪPd(1)ϪC(1)#1
C(6)ϪC(1)ϪC(2)
C(22)ϪC(21)ϪC(26)
C(11)ϪN(1)ϪC(12)
C(31)ϪN(2)ϪC(32)
C(31)ϪPd(2)ϪC(21)
C(31)#2ϪPd(2)ϪC(21)
92.80(14)
87.20(13)
114.4(3)
115.0(3)
171.5(4)
174.5(4)
91.93(15)
88.07(15)
There are two independent molecules of 1f in the unit makes the nitrogen atoms pyramidal, as found in
cell, but only one-half of each molecule is included in the [Pd(biquinolyl)(allyl)]ϩ complexes.[10] The square-planar ge-
asymmetric unit. The molecules show a square-planar coor- ometry of Pd is severely distorted towards tetrahedral with
˚
dination for Pd, with the two isocyanide ligands in trans the Cipso atoms of the two Fmes situated 0.42 and 0.98 A
disposition (related by an inversion centre) and the isocyan- above and below, respectively, the NϪPdϪN plane. For
ide and the Fmes group forming an angle comparison, the related complex [Pd(Fmes)2(bipy)], which
C(11)ϪPd(1)ϪC(1) ϭ 92.80(14)° in one molecule and is also tetrahedrally distorted,[2a] shows a smaller distortion
˚
C(31)ϪPd(2)ϪC(21) ϭ 91.93(15)° in the other. The two with the Cipso atoms 0.40 A above and below the NϪPdϪN
Fmes groups are coplanar and nearly perpendicular to the plane. Tetrahedral distortion is associated with angles that
coordination plane, one showing the two Fmes groups tilted differ greatly from those expected for a square-planar geo-
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Bis(fluoromesityl) Palladium Complexes
FULL PAPER
Unequivocal
characterization
of
[Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)] (6) required
an X-ray diffraction study. A perspective view of the molec-
ular structure is given in Figure 3, and selected distances
and angles are listed in Table 4.
The complex is binuclear and the two Pd coordination
planes make a dihedral angle of 72.1(4)° (Figure 3). The
molecule contains three non-equivalent Fmes groups, two
Figure 2. Molecular structure of [Pd(Fmes)2(biquinolyl)] (4b)
˚
Table 2. Selected bond lengths (A) and angles (°) for [Pd(Fmes)2-
(biquinolyl)] (4b)
Pd(1)ϪC(21)
Pd(1)ϪC(31)
Pd(1)ϪN(1)
Pd(1)ϪN(2)
2.014(6)
2.056(5)
2.136(5)
2.248(4)
C(21)ϪPd(1)ϪC(31)
C(21)ϪPd(1)ϪN(2)
C(31)ϪPd(1)ϪN(1)
N(1)ϪPd(1)ϪN(2)
C(26)ϪC(21)ϪC(22)
C(36)ϪC(31)ϪC(32)
93.9(2)
100.46(19)
94.83(19)
75.88(18)
113.8(5)
113.5(5)
metry: C(21)ϪPd(1)ϪC(31) 93.9(2)°; C(21)ϪPd(1)ϪN(2)
100.46(19)°; C(31)ϪPd(1)ϪN(1) 94.83(19)°. The
N(1)ϪPd(1)ϪN(2) angle is 75.88(18)°, a normal value for
this small-bite chelating ligand. Despite these distortions
the PdϪC and PdϪN distances are not affected noticeably,
remaining very similar to those of the square-planar [Pd-
(bipy)(Fmes)2].[2a]
κ2O,N-Coordination of OPPhPy2 in 5b is supported by
the phosphorus chemical shift in the 31P{1H} NMR spec-
trum, which clearly differs from those shifts when OPPhPy2
acts as κ2N,N-donor (Table 3), and is closer to those of the
κ2O,N-chelate OPPh2Py.[2c,5,11] The difference with the lat-
ter can be accounted for by the higher shielding effect on P
of Py compared with Ph. The PϪO stretching absorptions
are usually useful in differentiating κ2O,N- and κ2N,N-coor-
[12]
Figure 3. (top) Molecular structure of [Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)] (6); (bottom) view of
the skeleton showing the mode of coordination of the
[O(CH3)CPy2]Ϫ ligand
dination modes of OPPhPy2
but this band is not de-
tected in the IR spectrum of 5b due to other intense absorp-
tions in the same range.
Table 3. 31P NMR chemical shifts of 2-pyridylphosphane oxide and bis(2-pyridyl)phosphane oxide palladium complexes, at room tempera-
ture in CDCl3
Complexes
Coordination mode
δ[ppm]
Ref.
[Pd(Fmes)2(OPPhPy2)] (5b)
[Pd(C6F5)2(OPPh2Py)]
[Pd(C6F5)Br(OPPh2Py)]
[Pd(Fmes)(NCMe)(OPPhPy2)]BF4
[PdCl(Fmes)(OPPhPy2)]
[Pd(C6F5)X(OPPhPy2)]
[Pd(C6F5)2(OPPhPy2)]
κ2O,N
κ2O,N
κ2O,N
κ2N,N
κ2N,N
κ2N,N
κ2N,N
39.01
49.8
49.9
21.1
20.4
20.7Ϫ21.0
20.7
this work
[5]
[5]
[11]
[2c]
[5]
[5]
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FULL PAPER
˚
associative mechanism via 18e pentacoordinate transition
states, rather than the alternative dissociative pathway via
14e three-coordinate intermediates.[16] We know of no ex-
ception to this rule for palladium, although several dissoci-
ative ligand substitution have been found in bis(aryl) deriva-
tives of platinum.[17] The aryl complexes reported here show
dramatic deviations from the normal behaviour of PdII
complexes due to the steric crowding produced by the four
ortho-CF3 groups competing for the same axial space over
the coordination plane. It is convenient to discuss first their
structural features to better understand their reactivity. For-
tunately, many results for these bis(Fmes) complexes can
be directly compared with those in the literature for C6F5
complexes, and with the mono(Fmes) complexes recently
reported.[2c]
Table 4. Selected bond lengths (A) and angles (°) for [Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)](C6H5CH3)0.5 (6·0.5
toluene)
Pd(1)ϪC(41)
Pd(1)ϪC(31)
Pd(1)ϪN(1)
Pd(1)ϪO(1)
Pd(2)ϪC(21)
Pd(2)ϪN(2)
Pd(2)ϪO(1)
Pd(2)ϪS(1)
2.011(13) C(31)ϪPd(1)ϪN(1) 167.3(4)
2.027(10) C(41)ϪPd(1)ϪO(1) 168.4(4)
2.101(8) C(21)ϪPd(2)ϪN(2)
2.147(6) N(2)ϪPd(2)ϪO(1)
2.005(11) C(21)ϪPd(2)ϪS(1)
2.049(10) O(1)ϪPd(2)ϪS(1)
2.122(7) N(2)ϪPd(2)ϪS(1)
92.4(4)
79.5(3)
94.2(3)
93.9(2)
173.3(3)
2.290(4) C(21)ϪPd(2)ϪO(1) 170.7(3)
C(41)ϪPd(1)ϪC(31) 95.6(4)
C(41)ϪPd(1)ϪN(1) 91.8(4)
C(31)ϪPd(1)ϪO(1) 93.6(3)
C(26)ϪC(21)ϪC(22) 115.5(12)
C(36)ϪC(31)ϪC(32) 113.7(10)
C(46)ϪC(41)ϪC(42) 111.8(11)
N(1)ϪPd(1)ϪO(1)
80.4(3)
Structures in the Solid State and in Solution
of them cis coordinated to one of the metal centres, Pd(1).
Each pyridyl group of the [O(CH3)CPy2]Ϫ ligand is coordi-
(A) Complexes trans-[Pd(Fmes)2L2] (L ؍ monodentate li-
nated to a different palladium atom, whereas the oxygen gand): X-ray structures of the complexes with L ϭ tht,[2a]
atom bridges the two metal centres. The SMe2 ligand occu- pTol-NC show an essentially square-planar geometry, with
pies the fourth coordination site in the monoarylated Pd the Fmes rings almost coplanar and perpendicular to the
atom.
coordination plane. The same arrangement has been found
The PdϪC distances are all very similar [Pd(1)ϪC(41) in the square planar trans-[Au(Fmes)2I2]Ϫ.[1f] However, in
2.011(13), Pd(1)ϪC(31) 2.027(10), Pd(2)ϪC(21) 2.005(11) the linear complex [Au(Fmes)2]Ϫ the aryl planes of the two
˚
A], lying in the range of other cis bisarylated or monoaryl- Fmes groups make an angle of 27.2°. For comparison, the
ated Fmes Pd complexes.[2aϪ2e] The distances and angles of complex [Au(C6F5)2]Ϫ shows coplanar rings.[18] Thus, two
the [O(CH3)CPy2]Ϫ ligand are similar to those found in trans Fmes groups are better stabilized as coplanar and lay
InIII [13] and CuII [14] complexes, where it is also coordinated perpendicular to the coordination plane when the other two
as a bridging ligand.
positions in the square-planar geometry are occupied.
Whereas the geometry of the monoarylated palladium When there are no ancillary ligands present, as in
centre is nearly square planar, that of the bisarylated pal- [Au(Fmes)2]Ϫ, the Fmes groups scatter by rotation, giving
˚
ladium centre is very distorted, since N(1) is 0.574(15) A rise to a pseudohelicoidal geometry and relieving the repul-
out of the plane defined by O(1)ϪC(41)ϪPd(1)ϪC(31). The sion between the facing ortho-CF3 groups. Such behaviour
N(1)ϪPd(1)ϪO(1) and N(2)ϪPd(2)ϪO(1) angles are signif- suggests that the steric repulsion between two trans Fmes
icantly lower than 90° [80.4(3)° and 79.5(3)°], which is com- groups is perceptible but very moderate.
pensated
for
by
the
C(31)ϪPd(1)ϪO(1)
and
(B) Complexes cis-[Pd(Fmes)2(L-LЈ)] [L-L ؍ bipy;[2a]
O(1)ϪPd(2)ϪS(1) angles [93.6(3)° and 93.9(2)°, respec- biquinolyl (4b), or the cis-bisarylated moiety of 6]: These
tively]. The cis angle involving the carbon atoms of the square-planar geometries are clearly more distorted
Fmes ligands is larger than 90° [95.6(4)°], presumably as a towards tetrahedral than those of trans bisarylated com-
result of steric constraints.
plexes. The distortion increases with the size of the ancillary
The Fmes groups are not perpendicular to the coordi- ligands. The PdϪC distances are shorter than for the trans
nation plane, but tilted in the same sense by 70.4° [C(41)], bisarylated complexes (the trans effect of the ancillary li-
64.6° [C(31)] and 78.6° [C(21)]. This tilting, observed for gands is lower than that of Fmes), and slightly longer than
other cis bis(Fmes) palladium complexes,[2a] seems to help those in monoarylated Fmes Pd complexes (the latter are
[2c]
˚
in minimizing the repulsions between the ortho-CF3 sub- usually below 2.0 A). The Fmes groups are not perpen-
stituents of cis Fmes groups.
dicular to the coordination plane, as is usual in common
19F NMR spectra of complexes 5a, 5b, and 6 reveal aryl derivatives, but tilted in the same sense by ca. 20° from
19FϪ19F through-space coupling (see below).
the perpendicular. Since the steric crowding in a cis bisaryl-
ated moiety is clearly higher than in trans bisarylated com-
plexes, so must be the corresponding repulsions. This con-
certed tilt appears to be the best distortion to minimize re-
pulsions between the ortho-CF3 of the two contiguous Fmes
Discussion
For square-planar aryl complexes, although the CϪM ligands, even if it increases the repulsions with the ancillary
bonding interaction is little affected by the dihedral angle ligands. This distortion should make chemically non-equiv-
between the aryl and the coordination plane, the aryl alent the exo and endo (relative to the CϪPdϪC angle) or-
groups tend to lie perpendicular to the coordination plane tho-CF3 groups. In solution all the cis bisarylated com-
to minimize steric repulsions.[15] Conversely, ligand-substi- plexes reported here are stereochemically dynamic, and a
tution reactions on 16e palladium() complexes follow an concerted tilting of the two Fmes ligands gives rise to an
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Bis(fluoromesityl) Palladium Complexes
FULL PAPER
averaged geometry in which the Fmes groups would be per- rise to two high-field singlets, whereas the ortho-CF3 groups
pendicular to the coordination plane. The barrier to this now constitute an A3K3M3X3 system, giving rise to four
endoϪexo exchange is low, but a broadening of the ortho- quadruplets. The coupling constants (7.5, 6.0 Hz) are simi-
CF3 signals is observed in the low-temperature 19F NMR lar to those of 5a, indicating that the observed through-
spectra of some of the cis bisarylated complexes. The tilting space coupling occurs between ortho-CF3 groups in differ-
has been frozen out in the recently reported related Ni com- ent Fmes rings, but at the same side of the coordination
plex [Ni(Fmes)2(1,2-dimethoxyethane)2],[19] where the plane. As before, no other couplings are detected.
smaller metal atom leads to greater crowding.
For [Pd(Fmes)2(µ-1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)-
No spectroscopic evidence was found in solution for the (SMe2)] (6) the 19F NMR spectrum shows three singlets in
tetrahedral distortion observed in the solid-state structures the para-CF3 region, confirming the presence of three non-
of some of the complexes. For instance, the 19F NMR of equivalent Fmes groups. Six signals (one singlet and five
4b should give four ortho-CF3 signals if the solid-state multiplets) are detected in the ortho-CF3 region (Figure 4),
structure were ‘‘frozen’’ in solution, but only one signal is indicating that they are all non-equivalent. Homonuclear
observed. This indicates that the barriers for the process decoupling experiments allowed us to assign which nuclei
averaging the coordination plane and that for the concerted are involved in each coupling (Figure 4), assuming that all
tilting are low, and that the processes are fast even at low the coupling constants observed are due to through-space
temperatures.
coupling between fluorine atoms on the same side of the
(C) Complexes cis-[Pd(Fmes)2(L-LЈ)] with Other Chelat- coordination planes, as observed for 5a and 5b. While
ing Ligands. 19F؊19F Through-Space Couplings: Complexes F3C(29) appears as non-coupled because it is far from the
5a, 5b, and 6 have less symmetric structures and their spec- rest of fluoromethyl groups, F3C(37) is coupled with
tra reveal 19FϪ19F through-space couplings between close F3C(49) (both on the same metal) and with F3C(27) (which
non-equivalent ortho-CF3 groups. The para-CF3 groups are is on the other Pd atom). The coupling constants are 10
too far away to show through-space coupling.
and 8.5 Hz, respectively. The other two fluoromethyl groups
In [Pd(Fmes)2(SPPh2Py)] (5a) the ligand SPPh2Py coor- showing couplings are F3C(47) and F3C(39), with J ϭ 8 Hz.
dinates to the bisarylated fragment as a κ2S,N-donor in an These through-space coupling constants give an estimation
averaged planar chelate ring (Scheme 4). The fast envelope- of the distance between the fluoromethyl groups;[21] the
shift movement of the five-membered chelate rings has a higher coupling the shorter distance, regardless of whether
very low activation energy, allowing us to consider the five- the fluoromethyl groups belong to Fmes coordinated to the
membered metallacycle as planar.[20] Accordingly, the 19F same or to different metal centres.
NMR spectrum of 5a shows two high-field singlets due to
the two non-equivalent para-CF3, whereas the ortho-CF3
groups form a X3A3AЈ3XЈ3 system, which affords two quad-
ruplets, with J ϭ 9.3 Hz. This value may be ascribed to
through-space coupling between the fluorine atoms on the
same side of the coordination plane (Scheme 4), as there are
too many bonds between the inequivalent atoms to permit
significant scalar coupling, and the coupling constant is
similar to those detected in some fluoroaryl complexes de-
scribed by our group.[3] No diagonal coupling is detected
between CF3 groups of different Fmes groups, nor between
different CF3 groups at opposite sides of the coordination
plane.
Figure 4. 19F NMR of [Pd(Fmes)2(µ-1κN:1,2κO:2κN-Py2-
MeCO)Pd(Fmes)(SMe2)] (6) (ortho-CF3) in CDCl3 at 298 K, show-
ing the through-space couplings observed
Complex 6 shows a slow dynamic process in solution that
1
involves the SMe2 group. Its H and 19F spectra in CDCl3
at room temperature accord with the solid-state structure,
but the two signals for the methyl groups of the SMe2 are
Scheme 4. 19FϪ19F through-space couplings in 5a
broad at room temperature, and coalesce at 333 K. This
equivalence can be achieved by a process requiring both
inversion of the sulfur atom and rotation about the PdϪS
In [Pd(Fmes)2(κ2O,N-OPPhPy2)] (5b) the ligand bond. The high steric crowding could be responsible for the
OPPhPy2 coordinates to the bisarylated moiety as κ2O,N- very slow exchange at room temperature. However, a pro-
donor (Scheme 6). As for 5a, the inequivalent para-CF3 give cess involving SMe2 dissociation and reassociation occurs
Eur. J. Inorg. Chem. 2004, 2326Ϫ2337
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FULL PAPER
for other isomerizations in complexes with this weakly
bound ligand[3b] and can not be discounted here.
Mechanisms of the Syntheses of Bisarylated Complexes
In contrast with the reaction features of ligand substi-
tution in [PdCl(Fmes)L2] complexes, which suggest an as-
sociative mechanism,[2c] the harsh conditions required for
ligand substitution in the bis-Fmes complexes suggest a dis-
sociative mechanism, implying a positive activation entropy,
which is favoured at high temperature.[22] Although associ-
ative ligand substitutions dominate palladium() chemistry
(so far they are the only type observed), dissociative mecha-
nisms could become competitive (faster) as the associative
are disfavoured. Dissociative ligand substitution could be
favoured by (i) PdR2 substrates where R is a good σ-do-
nor;[23] (ii) complexes with bulky ligands;[17e,22] and (c) sub-
strates with labile leaving ligands. These three requirements
are met by 1a. An associative mechanism through a five-
coordinate transition state should be disfavoured in our sys-
tem for electronic reasons (the palladium centre in bisaryl-
ated substrates is electron rich), and even more so for steric
reasons: as the z axis is occupied above and below the metal
coordination plane by the ortho-CF3 of the two Fmes
groups, the attack of even a small nucleophile looks to be
extremely difficult (ortho effect).
This leads us to propose the mechanism depicted in
Scheme 5 for the substitution reactions. The formation of
only trans bis-Fmes complexes from the reactions of trans-
[Pd(Fmes)2(SMe2)2] with monodentate ligands contrasts
with previous observations for reactions on trans-
[Pd(C6F5)2(tht)2], where cis complexes are formed in prefer-
ence.[22b] This means that trans-[Pd(Fmes)2L2] and cis-
[Pd(C6F5)2L2] are the thermodynamic products, respec-
tively, for these two aryls. Formation of the trans isomer
with Fmes complexes occurs against the antisymbiotic ef-
fect (or transphobia),[24] indicating that the relief of steric
crowding in the trans complex compensates for the higher
electronic destabilization associated with two trans Fmes
groups.
Boiling under reflux complexes 1 in NCMe furnishes
trans-[Pd(Fmes)2(NCMe)(SR2)] (2) complexes. The bis(ace-
tonitrile) complex [Pd(Fmes)2(NCMe)2] has not been de-
tected, suggesting that the first substitution of SMe2 by the
poorer donor NCMe makes the complex less electron rich,
and the dissociation of a second SR2 becomes disfavoured.
The formation of the monosubstituted products, (NnBu4-
)[trans-Pd(Fmes)2I(SR2)] (3), after the reactions of trans-
[Pd(Fmes)2(SR2)2] (1) with (NnBu4)I can be considered
normal. The formation of (NnBu4)2[Pd(Fmes)2X2] is, ap-
parently, counter-thermodynamic; similar results have been
found for non-crowded bisarylated complexes. For instance,
no [Pd(C6F5)2X2]2Ϫ complexes have been reported, despite
many studies on (pentafluorophenyl)palladium com-
plexes.[25]
Scheme 5. Dissociative mechanism of the substitution processes
(Scheme 5). Thermodynamically, the ‘‘chelate effect’’, and
in most cases the use of a stronger ligand, contribute to
compensate the destabilization caused by the higher repul-
sion between two cis Fmes groups. In addition, the first
dissociative substitution by a better σ-donor with a higher
trans influence (except for the ligand pte, where the change
is S-donor for S-donor), favors, kinetically, the dissociation
of the second SR2 ligand.
The κ2O,N-coordination of OPPhPy2 found in 5b was
unknown for square-planar palladium(), although it oc-
curs in pseudo-octahedral molybdenum() derivatives.[26]
κ2N,N-Coordination usually observed in PdII complexes is
probably disfavoured in our case by the high degree of steric
crowding due to the presence of two cis Fmes groups, quite
similarly to its prevention in octahedral complexes. The
κ2O,N-coordination takes the substituents of the phos-
phorus away from the axial positions, minimizing the steric
congestion.
Interestingly,
monoarylated
complexes
[PdCl(Fmes)(κ2N,N-OPPhPy2)] and [Pd(Fmes)(NCMe)-
(κ2N,N-OPPhPy2)]BF4 have been isolated and charac-
terized.[2c,11] Therefore, one Fmes group is compatible with
an axial disposition of the phenyl group in κ2N,N-coordi-
nation, but two Fmes groups (here) or an octahedral metal
centre (Mo complex cited above) force κ2O,N-coordination.
This highlights the very different ‘‘axial’’ encumbrance pro-
duced in monoarylated and bisarylated Fmes complexes. In
monoarylated derivatives the Fmes group is probably tilted
to accommodate the phenyl group (Scheme 6). The ability
The formation of complexes 4 and 5 involves a trans-
to-cis isomerization from the starting material to the final
product. Thus, a topomerization of the trans to the corre-
Scheme 6. Bisarylated (indicating detected 19FϪ19F through-space
sponding cis three-coordinate intermediate is needed coupling) and monoarylated OPPhPy2 complexes
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Bis(fluoromesityl) Palladium Complexes
FULL PAPER
chem was used as received, and Li(Fmes) was prepared in situ as
described in the literature.[34] The rest of the reactants were pur-
chased from commercial suppliers and used as received.
of Fmes to tilt and make the space in the z direction access-
ible to attack by nucleophiles explains why the reactions
involving monoarylated substrates can proceed by associat-
ive mechanisms,[2c] while those reported here seem to re-
quire ligand dissociation.
Infrared spectra were recorded with a PerkinϪElmer 883 apparatus
as Nujol mulls between polystyrene films from 4000 to 200 cmϪ1
.
We used
a
ligand with smaller substituents,
NMR spectra were recorded with Bruker AC-300 or ARX-300 in-
struments. 1H, 31P{1H} and 19F NMR spectra are referenced to
TMS, 85% aqueous H3PO4, and CFCl3, respectively. Elemental
analyses were performed with a PerkinϪElmer 2400B microana-
lyzer.
(OH)(CH3)CPy2, to check whether κ2N,N-coordination oc-
curred, but this yielded, unexpectedly, [Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)]
(6),
and
HFmes as by-product (Scheme 3). The alcoholic hydrogen
has been previously reported to be acidic when the ligand
trans-[Pd(Fmes)2(SMe2)2] (1a): trans-[PdCl2(SMe2)2] (0.604 g,
2 mmol) was added to a freshly prepared solution of Li(Fmes)
(7.95 mmol) in Et2O (40 mL). The reaction mixture was maintained
at 40 °C for 24 h, and then two drops of water were added to hydro-
lyse the excess organolithium reagent. The volatiles were pumped
off, and the residue was extracted with toluene and filtered through
silica gel. The solvent was then evaporated and the resultant pale
brown residue was recrystallized from dichloromethane/hexane at
Ϫ20 °C to give pale yellow crystals that were decanted, washed
with hexane and vacuum-dried. Yield 0.801 g (51%). IR: ν˜ ϭ 687
is coordinated to other metals, such as InIII [13]
However,
.
no deprotonation occurred during the reactions of
(OH)(CH3)CPy2 with the monoarylated complexes trans-
[PdClFmes(SMe2)2] or [Pd(Fmes)(NCMe)3]BF4, which lead
to [PdClFmes(κ2N,NЈ-(OH)(CH3)CPy2)][2c] and [Pd(Fmes)-
{κ2N,NЈ-(OH)(CH3)CPy2}(NCMe)]BF4,
respectively.[11]
This suggests that acidic activation of the OϪH bond might
require previous O-coordination to a putative three-coordi-
nate palladium intermediate. This might occur in the disso-
ciative mechanism for bisarylated complexes but not in the
associative substitution operating for monoarylated spec-
ies.[2c]
s cmϪ1
.
19F NMR: δ ϭ Ϫ63.18 (s, 6 F, para-CF3), Ϫ60.41 (s, 12 F,
1
ortho-CF3) ppm. H NMR: δ ϭ 1.66 [s, 12 H, S(CH3)2], 7.92 [s, 4
H, C6H2(CF3)3] ppm. C22H16F18PdS2 (792.86): calcd. C 33.33, H
2.03; found C 33.16, H 2.03.
trans-[Pd(Fmes)2(4-pic)2] (1c): 4-pic (21.4 µL, 0.021 g, 0.22 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
(10 mL) and boiled under reflux for 3 h. The so-obtained solution
was filtered through dry Celite, the volatiles were pumped off, and
the resultant white solid was washed with hexane and vacuum dried
[yield 0.055 g (65%)]. Recrystallization from dichloromethane/hex-
Conclusion
Substitution and isomerization processes in bisarylated
Fmes palladium complexes seem to occur by dissociative
mechanisms, forced by the extreme axial protection pro-
ane gave colourless crystals. IR: ν˜ ϭ 688 m cmϪ1 19F NMR: δ ϭ
.
duced by the ortho CF3 substituents (ortho effect). Conse- Ϫ63.12 (s, 6 F, para-CF3), Ϫ59.73 (s, 12 F, ortho-CF3) ppm. 1H
NMR: δ ϭ 2.22 [s, 6 H, NC5H4(CH3)], 6.76 [d, J ϭ 6.5 Hz, 4 H,
NC5H4(CH3)], 7.82 [s, 4 H, C6H2(CF3)3], 7.92 [d, J ϭ 6.5 Hz, 4 H,
NC5H4(CH3)] ppm. C30H18F18N2Pd (854.86): calcd. C 42.15, H
2.12, N 3.28; found C 42.27, H 2.38, N 3.50.
quently, harsh reaction conditions are required, unlike the
mild substitution by associative mechanisms found for the
related monoarylated Fmes complexes,[2c] or for the anal-
ogous bisarylated C6F5 complexes.[5]
The lesser steric repulsion of two bulky Fmes mutually
trans-stabilizes better the trans isomers, which should not be
the thermodynamic products on the basis of only electronic
effects (‘‘antisymbiotic effect’’ or transphobia); cis isomers
are obtained only for bidentate ancillary ligands, due to the
chelate effect.
trans-[Pd(Fmes)2(PMe3)2] (1d): In a Young-valve-fitted Schlenk
flask, PMe3 (200 µL of 1  in THF, 0.2 mmol) was added to a
solution of 1a (0.080 g, 0.1 mmol) in toluene (10 mL) and heated
to 110 °C for 7 h. Work up as for 1c then yielded 0.028 g (34%) of
material. Recrystallization from dichloromethane/hexane gave
colourless crystals. IR: ν˜ ϭ 688 s cmϪ1 19F NMR: δ ϭ Ϫ63.13 (s,
.
6 F, para-CF3), Ϫ59.51 (t, J ϭ 5.5 Hz, 12 F, ortho-CF3) ppm.
31P{1H} NMR: δ ϭ Ϫ20.12 (sept, J ϭ 5.5 Hz) ppm. 1H NMR:
δ ϭ 0.83 [A9XXЈA9Ј syst., J ϭ 7 Hz, 18 H, P(CH3)3], 7.89 [s, 4 H,
C6H2(CF3)3] ppm. C24H22F18P2Pd (820.76): calcd. C 35.12, H 2.7,
found C 34.86, H 2.59.
The 19FϪ19F couplings observed have no significant sca-
lar contribution, and are due to through-space coupling
that depends on the distance between the interacting nuclei.
This is clearly so as the magnitude of the coupling does not
depend on whether the fluoromethyl groups are on Fmes
coordinated to the same metal or on Fmes coordinated to
different metals in a binuclear complex.
trans-[Pd(Fmes)2(tBuNC)2] (1e): tBuNC (225 µL, 0.165 g, 2 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
(10 mL) and boiled under reflux for 5 h. Work up as for 1c sub-
sequently yielded 0.070 g (83%) of material. Recrystallization from
dichloromethane/hexane gave colourless crystals. IR: ν˜ ϭ 686 s
Experimental Section
cmϪ1 19F NMR: δ ϭ Ϫ63.00 (s, 6 F, para-CF3), Ϫ61.74 (s, 12 F,
.
ortho-CF3) ppm. 1H NMR: δ ϭ 1.16 (s, 18 H, CNC4H9), 7.92 [s, 4
H, C6H2(CF3)3] ppm. C28H22F18N2Pd (834.87): calcd. C 40.28, H
2.66, N 3.36; found C 40.27, H 2.61, N 3.21.
General Remarks: All reactions were carried out under dry N2. Sol-
vents were purified according to standard procedures.[27] The com-
plexes
trans-[PdCl2(tht)2],
trans-[PdCl2(SMe2)2],[28]
trans-
[Pd(Fmes)2(tht)2] (1b)[2a] and the ligands OPPhPy2,[29] SPPh2Py,[30] trans-[Pd(Fmes)2(pTol-NC)2] (1f): pTol-NC (0.100 g, 0.85 mmol)
and (OH)(CH3)CPy2,[31] were prepared according to literature pro-
was added to a solution of 1a (0.160 g, 0.2 mmol) in toluene
cedures. pTol-NC was synthesized as reported[32] using triphosgene (15 mL) and boiled under reflux for 8 h. Subsequent work up as
as dehydrating agent.[33] 1,3,5-C6H3(CF3)3 (FmesH) from Fluoro- for 1c yielded 0.045 g (28%) of material. Recrystallization from di-
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chloromethane/ethanol gave colourless crystals. IR: ν˜ ϭ 2197 s
(10 mL) and boiled under reflux for 15 h; work up as for 1c then
(ν CN), 688 s cmϪ1 19F NMR: δ ϭ Ϫ63.07 (s, 6 F, para-CF3), yielded 0.053 g (57%). Subsequent recrystallization from toluene/
.
Ϫ61.64 (s, 12 F, ortho-CF3) ppm. 1H NMR: δ ϭ 2.31 (s, 18 H,
CNC4H9), 7.01 (part B of AB system, J ϭ 8.4 Hz, 4 H), 7.10 (part
hexane then gave yellow crystals. IR: ν˜ ϭ 686 m, 669 m cmϪ1 19F
.
NMR: δ ϭ Ϫ63.23 (s, 6 F, para-CF3), Ϫ57.99 (br., 12 F, ortho-
1
A,
J
ϭ
8.4 Hz,
4
H), 7.96 [s,
4
H, C6H2(CF3)3] ppm.
CF3) ppm. H NMR: δ ϭ 7.29 [t, J ϭ 7 Hz, 2 H, (NC9H6)2], 7.53
C34H18F18N2Pd (902.91): calcd. C 45.23, H 2.01, N 3.10; found C [t, J ϭ 7 Hz, 2 H, (NC9H6)2], 7.66 [s, 4 H, C6H2(CF3)3], 7.82 [d,
44.93, H 2.18, N 3.21.
J ϭ 8.5 Hz, 2 H, (NC9H6)2], 7.87 [d, J ϭ 8.5 Hz, 2 H, (NC9H6)2],
8.30 [d, J ϭ 8.5 Hz, 2 H, (NC9H6)2], 8.58 [d, J ϭ 8.5 Hz, 2 H,
(NC9H6)2] ppm. 19F NMR (CD2Cl2, 183 K): δ ϭ Ϫ62.43 (s,, 6 F
para-CF3), Ϫ59.10 (br., 6 F, ortho-CF3), Ϫ55.89 (br., 6 F, ortho-
CF3) ppm. 1H NMR (CD2Cl2, 183 K): δ ϭ 7.31 [t, J ϭ 7 Hz, 2 H,
(NC9H6)2], 7.49 [t, 2 H, J ϭ 7 Hz, (NC9H6)2], 7.66 [m, 8 H,
C6H2(CF3)3 and N2C18H12], 8.24 [d, 2 H, J ϭ 7 Hz, (NC9H6)2],
8.44 [d, J ϭ 8 Hz, 2 H, (NC9H6)2] ppm. C36H16F18N2Pd (924.91):
calcd. C 46.75, H 1.74, N 3.03; found C 46.45, H 1.87, N 2.96.
trans-[Pd(Fmes)2(NCMe)(SMe2)] (2a): 1a (0.080 g, 0.1 mmol) was
dissolved in acetonitrile (15 mL) and boiled under reflux for 7 h.
Work up as for 1c yielded then afforded 0.042 g (54%) of material.
Recrystallization from dichloromethane/hexane gave pale yellow
crystals. IR: ν˜ ϭ 686 m cmϪ1
.
19F NMR: δ ϭ Ϫ63.08 (s, 6 F, para-
1
CF3), Ϫ60.51 (s, 12 F, ortho-CF3) ppm. H NMR: δ ϭ 1.61 [s, 6
H, S(CH3)2], 1.99 (s, 3 H, NCCH3), 7.90 [s, 4 H, C6H2(CF3)3] ppm.
C22H13F18NPdS (771.79): calcd. C 34.24, H 1.70, N 1.81; found C
34.17, H 1.85, N 1.85.
[Pd(Fmes)2(κ2N,NЈ-OCPy2)] (4c): OCPy2 (0.018 g, 1 mmol) was ad-
ded to a solution of 1a (0.080 g, 0.1 mmol) in toluene (10 mL) and
boiled under reflux for 3 h. Subsequent work up as for 1c yielded
0.020 g (47%), and recrystallization from toluene/hexane then gave
trans-[Pd(Fmes)2(NCMe)(tht)] (2b): 1b (0.127 g, 0.15 mmol) was
dissolved in acetonitrile (15 mL) and boiled under reflux for 24 h.
Subsequent work up as for 1c yielded 0.042 g (35%) and recrystalli-
zation from dichloromethane/hexane gave yellow crystals. IR: ν˜ ϭ
yellow crystals. IR: ν˜ ϭ 693 m, 686 s cmϪ1 19F NMR: δ ϭ Ϫ63.28
.
(s, 6 F, para-CF3), Ϫ57.70 (s, 12 F, ortho-CF3) ppm. 1H NMR: δ ϭ
7.41 [m, 2 H, OC(NC5H4)2], 7.69 [s, 4 H, C6H2(CF3)3], 8.04 [m, 2
688 m cmϪ1
.
19F NMR: δ ϭ Ϫ63.06 (s, 6 F, para-CF3), Ϫ60.21 (s,
12 F, ortho-CF3) ppm. H NMR: δ ϭ 1.70 (m, 4 H, Hβ, SC4H8),
1.99 (s, 3 H, NCCH3), 2.21 (m, 4 H, Hα, SC4H8), 7.89 [s, 4 H,
C6H2(CF3)3] ppm. C24H16F18NPdS (798.83): calcd. C 36.13, H
1.90, N 1.76; found C 36.07, H 1.94, N 2.10.
1
H, OC(NC5H4)2], 8.22 [m,
4
H, OC(NC5H4)2] ppm.
C29H12F18N2OPd (852.80): calcd. C 40.84, H 1.42, N 3.28; found
C 40.95, H 1.60, N 3.48.
[Pd(Fmes)2(dppm)] (4d): The ligand dppm (0.046 g, 0.12 mmol) was
added to a solution of 1a (0.080 g, 0.1 mmol) in toluene (10 mL)
and boiled under reflux for 7 h. Work up as for 1c then yielded
0.063 g (60%), and subsequent recrystallization from toluene/hex-
NnBu4[trans-Pd(Fmes)2I(SMe2)] (3a): NnBu4I (0.037 g, 0.1 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
(10 mL) and boiled under reflux for 2 h. Work up as for 1c yielded
0.047 g (43%), and subsequent recrystallization from dichlorometh-
ane gave yellow crystals. IR: ν˜ ϭ 693 s, 664 w cmϪ1 19F NMR:
.
ane/hexane gave orange crystals. IR: ν˜ ϭ 687 s, 666 w cmϪ1 19F
.
δ ϭ Ϫ63.19 (s, 6 F, para-CF3), Ϫ57.25 (X6AAЈX6Ј syst., N ϭ JAX
ϩ JAXЈ ϭ 11.9 Hz, 12 F, ortho-CF3) ppm. 31P{1H} NMR: δ ϭ
Ϫ36.85 (m) ppm. 1H NMR: δ ϭ 4.18 [t, J ϭ 9.5 Hz, 2 H,
{(C6H5)2P}2CH2], 7.20 [m, 15 H, {(C6H5)2P}2CH2], 7.38 [m, 5 H,
{(C6H5)2P}2CH2], 7.64 [s, 4 H, C6H2(CF3)3] ppm. C43H26F18P2Pd
(1053.01): calcd. C 49.05, H 2.49; found C 49.59, H 2.69.
NMR: δ ϭ Ϫ62.74 (s, 6 F, para-CF3), Ϫ58.33 (s, 12 F, ortho-CF3)
ppm. 1H NMR: δ ϭ 0.93 [m, 12 H, Nn(C4H9)4], 1.31 [m, 8 H,
Nn(C4H9)4], 1.51 [m, 8 H, Nn(C4H9)4], 1.64 [s, 6 H, S(CH3)2], 3.03
[m,
8 H, Nn(C4H9)4], 7.77 [s, 4 H, C6H2(CF3)3] ppm.
C36H46F18INPdS (1100.110): calcd. C 39.31, H 4.21, N 1.27; found
C 39.52, H 4.18, N 1.52.
[Pd(Fmes)2(dppe)] (4e): The ligand dppe (0.044 g, 0.11 mmol) was
added to a solution of 1a (0.080 g, 0.1 mmol) in toluene (10 mL)
and boiled under reflux for 3 h. Subsequent work up as for 1c af-
forded 0.080 g (75%), and recrystallization from toluene/hexane
NnBu4[trans-Pd(Fmes)2I(tht)] (3b): NnBu4I (0.037 g, 0.1 mmol) was
added to a solution of 1b (0.084 g, 0.1 mmol) in toluene (10 mL)
and boiled under reflux for 6 h. Work up as for 1c then yielded
0.036 g (32%), and subsequent recrystallization from dichloro-
methane/hexane gave orange crystals. IR: ν˜ ϭ 687 s, 663 vw. 19F
NMR: δ ϭ Ϫ62.73 (s, 6 F, para-CF3), Ϫ58.01 (s, 12 F, ortho-CF3)
ppm. 1H NMR: δ ϭ 0.92 [m, 12 H, Nn(C4H9)4], 1.28 [m, 8 H,
Nn(C4H9)4], 1.48 [m, 8 H, Nn(C4H9)4], 1.70 [m, 4 H, Nn(C4H9)4],
2.28 [m, 4 H, SCH2], 3.03 [m, 8 H, Nn(C4H9)4], 7.76 [s, 4 H,
C6H2(CF3)3] ppm. C38H48F18INPdS (1126.15): calcd. C 40.53, H
4.30, N 1.24; found C 40.38, H 4.11, N 1.27.
then gave colourless crystals. IR: ν˜ ϭ 689 s, 665 m cmϪ1 19F NMR:
.
δ ϭ Ϫ63.26 (s, 6 F, para-CF3), Ϫ56.90 (X6AAЈX6Ј syst., N ϭ JAX
ϩ JAXЈ ϭ 11.2 Hz, 12 F, ortho-CF3) ppm. 31P{1H} NMR: δ ϭ
1
35.62 (m) ppm. H NMR: δ ϭ 2.54 (X2AAЈX2Ј syst., N ϭ JAX
ϩ
JAXЈ ϭ 18.4 Hz, CH2, 4 H), 7.35 (m, C6H5, 5 H), 7.24 (m, C6H5,
15 H), 7.52 [s, C6H2(CF3)3, 4 H], 7.35 (m, C6H5, 5 H) ppm.
C44H28F18P2Pd (1067.03): calcd. C 49.53, H 2.64; found C 49.90,
H 2.85.
[Pd(Fmes)2(Me2bipy)] (4a): Me2bipy (0.022 g, 0.12 mmol) was ad-
ded to a solution of 1a (0.080 g, 0.1 mmol) in toluene (10 mL) and
boiled under reflux for 7 h. Work up as for 1c then yielded 0.067 g
(79%) of material. Recrystallization from acetone/hexane then af-
[Pd(Fmes)2(pte)] (4f): The ligand pte (0.016 g, 0.065 mmol) was ad-
ded to a solution of 1a (0.040 g, 0.05 mmol) in toluene (10 mL)
and boiled under reflux for 5 h. The usual work up, as for 1c, then
yielded 0.015 g (33%), and subsequent recrystallization from tolu-
forded yellow crystals. IR: ν˜ ϭ 692 s, 685 s cmϪ1 19F NMR: δ ϭ
.
ene/hexane gave yellow crystals. IR: ν˜ ϭ 685 s, 664 m cmϪ1 19F
.
Ϫ63.10 (s, 6 F, para-CF3), Ϫ57.73 (s, 12 F, ortho-CF3) ppm. 1H
NMR: δ ϭ 2.51 [s, 6 H, {NC5H3(CH3)}2], 7.11 [d, J ϭ 5.4 Hz, 2
H, {NC5H3(CH3)}2], 7.44 [d, J ϭ 5.4 Hz, 2 H, {NC5H3(CH3)}2],
7.77 [s, 4 H, C6H2(CF3)3], 7.88 [s, 2 H, H3, {NC5H3(CH3)}2] ppm.
C30H16F18N2Pd (852.85): calcd. C 42.25, H 1.89, N 3.28; found C
41.56, H 2.16, N 3.20.
NMR: δ ϭ Ϫ63.38 (s, 6 F, para-CF3), Ϫ56.23 (br., 12 F, ortho-
CF3) ppm. 1H NMR: δ ϭ 3.42 (s, 4 H, CH2), 7.35 (m, 10 H, C6H5),
7.65 (br., 4 H, C6H5) ppm. 19F NMR (213 K): δ ϭ Ϫ62.86 (s, 6 F,
para-CF3), Ϫ59.50 (br., 6 F, ortho-CF3), Ϫ52.50 (br., 6 F, ortho-
1
CF3) ppm. H NMR (213 K): δ ϭ 3.38 (s, 4 H, CH2), 7.37 (m, 10
H, C6H5), 7.56 [br., 2 H, C6H2(CF3)3], 7.78 [br., 2 H, C6H2(CF3)3]
ppm. C32H18F18PdS2 (914.99): calcd. C 42.01, H 1.98; found C
41.81, H 2.16.
[Pd(Fmes)2(biquinolyl)] (4b): 2,2Ј-Biquinoline (0.026 g, 0.1 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
2334
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 2326Ϫ2337

Bis(fluoromesityl) Palladium Complexes
FULL PAPER
[Pd(Fmes)2(κ2S,N-SPPh2Py)] (5a): SPPh2Py (0.033 g, 0.11 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
(10 mL) and boiled under reflux for 4 h. The usual work up, as for
1c, then yielded 0.069 g (72%), and recrystallization from toluene/
[Pd(Fmes)2(µ-1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)]
(6):
(OH)(CH3)Cpy2 (225 µL, 0.010 g, 0.05 mmol) was added to a solu-
tion of 1a (0.080 g, 0.1 mmol) in toluene (10 mL) and boiled under
reflux for 11 h. The usual work up, as for 1c, then yielded 0.022 g
(33%), and subsequent recrystallization from toluene gave yellow
hexane then gave yellow crystals. IR: ν˜ ϭ 688 s, 664 vw cmϪ1 19F
.
NMR: δ ϭ Ϫ63.18 (s, 3 F, para-CF3), Ϫ63.12 (s, 3 F, para-CF3),
Ϫ58.11 (q, JF,F ϭ 9.3 Hz, 6 F, ortho-CF3), Ϫ56.34 (q, JF,F
crystals. IR: ν˜ ϭ 694 s, 685 s cmϪ1
.
19F NMR: δ ϭ Ϫ63.21 (s, 3 F,
ϭ
para-CF3), Ϫ63.11 (s, 3 F, para-CF3), Ϫ63.07 (s, 3 F, para-CF3),
9.3 Hz, 6 F, ortho-CF3) ppm. 31P{1H} NMR: δ ϭ 57.05 (s) ppm. Ϫ61.70 (q, J ϭ 8.8 Hz, 3 F, ortho-CF3), Ϫ60.75 (s, 3 F, ortho-CF3),
1H NMR: δ ϭ 7.35 [m, 2 H, SP(C6H5)2(NC5H4)], 7.67 [s, 2 H, Ϫ59.52 (q, J ϭ 8.0 Hz, 3 F, ortho-CF3), Ϫ59.12 (qq, J ϭ 8.5,
C6H2(CF3)3], 7.68 [s,
2 H, C6H2(CF3)3], 7.70 [m, 10 H, 10.0 Hz, 3 F, ortho-CF3), Ϫ57.88 (q, J ϭ 10.0 Hz, 3 F, ortho-CF3),
1
SP(C6H5)2(NC5H4)], 7.87 [m, 1 H, SP(C6H5)2(NC5H4)], 7.99 [m, 1 Ϫ53.53 (q, J ϭ 8.0 Hz, 3 F, ortho-CF3) ppm. H NMR: δ ϭ 1.09
H, SP(C6H5)2(NC5H4)] ppm. C35H18F18NPPdS (963.95): calcd. C [br., 3 H, S(CH3)2], 2.36 [br., 3 H, S(CH3)2], 2.53 (s, 3 H, CH3),
43.61, H 1.88, N 1.45; found C 43.53, H 1.94, N 1.40.
6.62 (d, J ϭ 8.0 Hz, 1 H, C5H4N), 7.09 (t, J ϭ 6.0 Hz, 1 ,
C5H4NH), 7.17 (t, J ϭ 6.0 Hz, 1 H, C5H4N), 7.29 (d, J ϭ 5.2 Hz,
1 H, C5H4N), 7.61 [s, 1 H, C6H2(CF3)3], 7.63 [s, 1 H, C6H2(CF3)3],
7.67 [m, 2 H, C6H2(CF3)3, C5H4N], 7.71 [s, 1 H, C6H2(CF3)3], 7.85
[s, 1 H, C6H2(CF3)3], 7.94 [m, 2 H, C6H2(CF3)3 and C5H4N] ppm.
C41H23F27N2Pd2OS (1317.47): calcd. C 37.38, H 1.76, N 2.17;
found C 37.67, H 1.89, N 2.17.
[Pd(Fmes)2(κ2O,N-OPPhPy2)] (5b): OPPhPy2 (0.031 g, 0.11 mmol)
was added to a solution of 1a (0.080 g, 0.1 mmol) in toluene
(10 mL) and boiled under reflux for 2 h. The usual work up, as for
1c, yielded 0.056 g (59%) of material. Subsequent recrystallization
from toluene/hexane then gave yellow crystals. IR: ν˜ ϭ 685 s, 665
w cmϪ1 19F NMR: δ ϭ Ϫ63.17 (s, 3 F, para-CF3), Ϫ63.16 (s, 3 F,
.
para-CF3), Ϫ58.23 (q, JF,F ϭ 7.5 Hz, 3 F, ortho-CF3), Ϫ57.55 (q,
JF,F ϭ 6 Hz, 3 F, ortho-CF3), Ϫ57.28 (q, JF,F ϭ 6 Hz, 3 F, ortho-
X-ray Crystallographic Study: Suitable crystals of 1f and 4b were
grown by slow diffusion of a concentrated dichloromethane solu-
CF3), Ϫ56.28 (q, JF,F ϭ 7.5 Hz, 3 F, ortho-CF3) ppm. 31P{1H} tion of the complex into diethyl ether (1f) or n-hexane (4b) at Ϫ20
NMR: δ ϭ 39.02 (s) ppm. 1H NMR: δ ϭ 7.34 [m, 1 H, °C. For 6·0.5 toluene, crystals were grown by slow evaporation of
OP(C6H5)(NC5H4)2], 7.58 [m, 4 H, OP(C6H5)(NC5H4)2], 7.68 [m, a concentrated toluene solution of the complex at 8 °C. X-ray
1 H, OP(C6H5)(NC5H4)2], 7.70 [s, 1 H, C6H2(CF3)3], 7.72 [s, 1 H,
C6H2(CF3)3], 7.76 [s, 1 H, C6H2(CF3)3], 7.79 [s, 1 H, C6H2(CF3)3], tector diffractometer with Mo-Kα radiation (λ ϭ 0.71073 A).
measurements were made using a Bruker SMART CCD area-de-
[35]
˚
7.91 [m,
1
H, OP(C6H5)(NC5H4)2], 8.00 [m,
1
H, Intensities were integrated from several series of exposures,[36] each
exposure covering 0.3° in ω, the total data set being a hemisphere.
Absorption corrections were applied, based on multiple and sym-
OP(C6H5)(NC5H4)2], 8.11 [m, 3 H, OP(C6H5)(NC5H4)2], 8.37 [t,
J ϭ 7 Hz, 1 H, OP(C6H5)(NC5H4)2], 8.88 [d, J ϭ 4.7 Hz, 1 H,
OP(C6H5)(NC5H4)2] ppm. C34H17F18N2OPPd (948.87): calcd. C metry-equivalent measurements.[37] The structure was solved by di-
43.03, H 1.81, N 2.95; found C 43.42, H 1.98, N 2.96.
rect methods and refined by least-squares on weighted F2 values for
Table 5. Crystal data and structure refinement for trans-[Pd(Fmes)2(pTol-NC)2] (1f), [Pd(Fmes)2(biquinolyl)] (4b), and [Pd(Fmes)2(µ-
1κN:1,2κO:2κN-Py2MeCO)Pd(Fmes)(SMe2)](C6H5CH3)0.5 (6·0.5 toluene)
1f
4b
6·0.5 toluene
Empirical formula
Molecular mass
Temperature
C34H18F18N2Pd
902.90
298(2) K
0.71073
C36H16F18N2Pd
924.91
293(2) K
0.71073
C44.5H27F27N2OPd2S
1363.54
293(2)
˚
Wavelength (A)
0.71073
Crystal system
Space group
triclinic
P1
9.262(5)
12.424(6)
16.720(8)
95.169(10)
102.807(10)
105.098(9)
1788.9(15)
2
triclinic
P1
triclinic
P1
¯
¯
¯
˚
a (A)
11.5004(13)
11.9885(14)
13.7943(15)
77.804(3)
67.306(2)
75.890(2)
1687.0(3)
2
15.400(4)
18.748(5)
20.396(5)
62.940(5)
79.447(6)
81.438(7)
5141(2)
˚
b (A)
˚
c (A)
α (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
4
Dcalcd. (g cmϪ3
)
1.676
0.640
888
1.821
0.682
908
1.762
0.875
2668
Absorption coefficient (mmϪ1
F(000)
)
Crystal size (mm)
Theta range for data collection
Reflections collected
0.29 ϫ 0.16 ϫ 0.15
1.26 to 23.28°
8283
0.12 ϫ 0.12 ϫ 0.06
1.61 to 23.29°
7906
0.39 ϫ 0.12 ϫ 0.05
1.13 to 23.32°
24237
Independent reflections
Absorption correction
Maximum and minimum transmission factor
Data/restraints/parameters
Goodness-of-fit on F2
5091 (Rint ϭ 0.0180)
SADABS
1.000000, 0.876647
5091/0/501
1.050
4838 (Rint ϭ 0.0400)
SADABS
1.000000, 0.652705
4838/0/514
1.006
14733 (Rint ϭ 0.0531)
SADABS
1.000000, 0.631134
14733/0/1353
1.015
R1 [I Ͼ 2σ(I)]
0.0363
0.0474
0.0611
wR2 (all data)
0.1074
0.1040
0.1926
Eur. J. Inorg. Chem. 2004, 2326Ϫ2337
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2335

´
´
´
C. Bartolome, P. Espinet, J. M. Martın-Alvarez, F. Villafan˜e
FULL PAPER
[8] [8a]
[8b]
all reflections (Table 5).[38] All non-hydrogen atoms were assigned
anisotropic displacement parameters and refined without posi-
tional constraints, except that the carbon atoms of the toluene mol-
ecule in 6·0.5 toluene were refined isotropically. Hydrogen atoms
were constrained to ideal geometries and refined with fixed iso-
tropic displacement parameters. Refinement proceeded smoothly to
give the residuals shown in Table 5. Complex neutral-atom scat-
tering factors were used.[39] CCDC-221232 (for 1f), -221233 (for
4b) and -221234 (for 6·0.5 toluene) contain the supplementary crys-
tallographic data for this paper. These data can be obtained free
of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; Fax: (internat.) ϩ44-1223-336-033; E-mail:
deposit@ccdc.cam.ac.uk].
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