Bidentate chelate complexes of palladium(II) with the carbanion 2-C 6F4PPh2 and their transformation into complexes containing bridging 2-C6F4PPh2

Article abstract of DOI:10.1021/om200179v

Reaction of the organotin compound 2-Me₃SnC₆F ₄PPh₂ (7) with the cycloocta-1,5-diene complexes [PdX ₂(cod)] at room temperature gives dinuclear halide-bridged palladium(II) complexes [Pd₂(μ-X)₂(κ²- 2-C₆F₄PPh₂)₂] [X = Cl (5), Br (8)] in which the carbanions are present as four-membered chelate rings. The bridging halides can be replaced by various anions, giving the corresponding dinuclear complexes having X = O₂CCH₃ (9), O₂CPh (10), I (12), and SCN (15), and by acetylacetonate anion (acac) to give mononuclear [Pd(acac)(κ²-2-C₆F₄PPh₂)] (17). In solution at room temperature the four-membered κ²-2- C₆F₄PPh₂ rings open, probably by one-ended dissociation of a Pd-P bond, to give compounds of the same composition containing bridging 2-C₆F₄PPh₂ units, e.g., [Pd₄(μ-X)₄(μ-2-C₆F₄PPh ₂)₄] [X = Cl (6), I (13)], [Pd₂(μ-O ₂CCH₃)₂(μ-2-C₆F ₄PPh₂)₂] (11), and [Pd₂(acac) ₂(μ-2-C₆F₄PPh₂)₂] (18). In some cases, only half the available chelate rings open; for example, complex 15 gives [Pd₄(μ-SCN)₄(μ-2-C ₆F₄PPh₂)₂(κ²-2- C₆F₄PPh₂)₂] (16) and complex 12 gives [(κ²-2-C₆F₄PPh₂)Pd(μ- I)(μ-2-C₆F₄PPh₂)Pd(μ-I) ₂Pd(μ-I)(μ-2-C₆F₄PPh₂) Pd(κ²-2-C₆F₄PPh₂)] (14), in addition to 13. Ring-opening also occurs on addition of acetonitrile to 5 or 8, forming [Pd₂X₂(NCMe)₂(μ-2-C ₆F₄PPh₂)₂] [X = Cl (19), Br (20)]. Treatment of 8 with two equivalents of PPh₃ forms [PdBr(κ²-2-C₆F₄PPh₂)(PPh ₃)] (21) as a cis-trans mixture, which reacts with more PPh ₃ to give trans-[PdBr(κC-2-C₆F₄PPh ₂)(PPh₃)₂] (23) by displacement of the Pd-P bond of the chelate ring. The bulkier ligand tricyclohexylphosphine reacts with 8 to give an analogue (22) of 21, but it does not open the chelate ring. The X-ray structures of compounds 7-11, 13-21, and 23 are reported.

Full text of DOI:10.1021/om200179v

ARTICLE
pubs.acs.org/Organometallics
Bidentate Chelate Complexes of Palladium(II) with the Carbanion
2-C6F4PPh2 and Their Transformation into Complexes Containing
Bridging 2-C6F4PPh2
Martin A. Bennett,† Gopa Kar,‡ Nedaossadat Mirzadeh,‡ Steven H. Privꢀer,‡ A. David Rae,† J€org Wagler,§
Anthony C. Willis,† and Suresh K. Bhargava*,‡
†Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
‡School of Applied Sciences (Applied Chemistry), RMIT University, GPO Box 2476 V, Melbourne, Victoria 3001, Australia
§Institut f€ur Anorganische Chemie, Technische Universit€at Bergakademie, Freiberg D-09596, Germany
ABSTRACT: Reaction of the organotin compound 2-Me3SnC6-
F4PPh2 (7) withthe cycloocta-1,5-dienecomplexes [PdX2(cod)]
at room temperature gives dinuclear halide-bridged palladium-
(II) complexes [Pd2(μ-X)2(k2-2-C6F4PPh2)2] [X = Cl (5), Br
(8)] in which the carbanions are present as four-membered
chelate rings. The bridging halides can be replaced by various
anions, giving the corresponding dinuclear complexes having
X = O2CCH3 (9), O2CPh (10), I (12), and SCN (15), and by
acetylacetonate anion (acac) to give mononuclear [Pd(acac)-
(k2-2-C6F4PPh2)] (17). In solution at room temperature the four-membered k2-2-C6F4PPh2 rings open, probably by one-ended
dissociation of a PdꢀP bond, togive compoundsofthe samecompositioncontainingbridging2-C6F4PPh2 units, e.g., [Pd4(μ-X)4(μ-2-
C6F4PPh2)4] [X = Cl (6), I (13)], [Pd2(μ-O2CCH3)2(μ-2-C6F4PPh2)2] (11), and [Pd2(acac)2(μ-2-C6F4PPh2)2] (18). In some
cases, only half the available chelate rings open; for example, complex 15 gives [Pd4(μ-SCN)4(μ-2-C6F4PPh2)2(k2-2-C6F4PPh2)2]
(16) and complex 12 gives [(k2-2-C6F4PPh2)Pd(μ-I)(μ-2-C6F4PPh2)Pd(μ-I)2Pd(μ-I)(μ-2-C6F4PPh2)Pd(k2-2-C6F4PPh2)] (14),
in addition to 13. Ring-opening also occurs on addition of acetonitrile to 5 or 8, forming [Pd2X2(NCMe)2(μ-2-C6F4PPh2)2] [X = Cl
(19), Br (20)]. Treatment of 8 with two equivalents of PPh3 forms [PdBr(k2-2-C6F4PPh2)(PPh3)] (21) as a cisꢀtrans mixture, which
reacts with more PPh3 to give trans-[PdBr(kC-2-C6F4PPh2)(PPh3)2] (23) by displacement of the PdꢀP bond of the chelate ring. The
bulkier ligand tricyclohexylphosphine reacts with 8 to give an analogue (22) of 21, but it does not open the chelate ring. The X-ray
structures of compounds 7ꢀ11, 13ꢀ21, and 23 are reported.
’ INTRODUCTION
2-C6H4PPh2 units arranged head-to-tail. The tetramer array
is broken down to binuclear fragments 2 and 3 on treatment
with silver acetate or trifluoroacetate and with PMe3 or
PMe2Ph, respectively, the bridging 2-C6H4PPh2 groups being
retained. Bulkier tertiary phosphines, such as PPh3 or PCy3,
give monomeric species [PdBr(k2-2-C6H4PPh2)(L)] (L = PPh3,
PCy3) containing a four-membered PꢀC chelate ring. This chem-
istry is summarized in Scheme 1. Related examples of the inter-
conversion between the bridging and chelate coordination modes of
2-C6H4PPh2 and its congeners have also been observed in platinum
and gold chemistry.21ꢀ23
The stability of complexes containing four-membered chelate
ringsisincreasediftheo-phenylene hydrogen atoms of 2-C6H4PPh2
are replaced by fluorine. The bis(chelate) palladium(II) complex
trans-[Pd(k2-P,C-2-C6F4PPh2)2], the 2-C6H4PPh2 analogue of
which is unknown, undergoes ligand scrambling with [PdCl2-
(NCMe)2] to give the binuclear species [Pd2(μ-Cl)2(k2-P,C-2-
C6F4PPh2)2] (5), shown in Scheme 2;24 5 rearranges slowly in
Since the discovery of the ortho-palladation of azobenzene
and N,N-dimethylaniline in the 1960s,1,2 cyclopalladated
complexes, especially those containing N-, O-, and S-donor
groups, have attracted continuous interest because of their
diverse applications, particularly in organic synthesis, and
because of the relevance of cyclopalladation to the transition
metal promoted CꢀH activation of hydrocarbons.3ꢀ16 Cy-
clopalladation of P-donor groups by CꢀH activation6,9,11ꢀ17
is generally observed only with very bulky or sterically con-
strained tertiary phosphines or with phosphites; ortho-palla-
dated complexes of triphenylphosphine cannot be obtained by
this route. Attempts to make them from Pd(0) or Pd(II)
precursors by transmetalation from [Hg(2-C6H4PPh2)2]
gave exclusively complexes in which 2-C6H4PPh2 bridges Pd
and Hg.17,18 However, Lahuerta et al.19,20 have shown that
2-BrC6H4PPh2 adds oxidatively to the palladium(0)-dibenzy-
lideneacetone complex, [Pd(dba)2], to give a tetranuclear
complex [Pd4(μ-Br)4(μ-2-C6H4PPh2)4] (1), in which an
approximate rectangle of palladium atoms is bridged on
alternate sides either by two bromine atoms or by two
Received: February 24, 2011
Published: June 22, 2011
r
2011 American Chemical Society
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Organometallics
ARTICLE
Scheme 1
Scheme 2
solution by opening of the chelate rings to a tetranuclear complex of
the same composition as 5, [Pd4(μ-Cl)4(μ-2-C6F4PPh2)4] (6),
which is structurally analogous to 1. We now report the behavior of
the corresponding bromide, iodide, carboxylate, pseudohalide, and
acetylacetonato derivatives, thereby establishing the existence of a
family of ortho-palladated compounds of a similar type, i.e., of
identical composition but containing either chelate k2-P,C-2-
C6F4PPh2 or bridging μ2-P,C-2-C6F4PPh2. We have also discovered
two compounds that display both coordination modes. Finally, we
report reactions of 5 and 8 with acetonitrile and of 8 with PPh3 and
PCy3, which also lead to irreversible opening of the chelate ring.
Figure 1. Molecular structure of 2-Me3SnC6F4PPh2 (7). Ellipsoids
show 50% probability levels, and hydrogen atoms have been omitted for
clarity. Only one molecule of the asymmetric unit is shown.
complexes required for this study. This precursor was obtained in
ca. 85% yield as a colorless, air-stable solid by treating an ether
solution of 2-BrC6F4PPh2, cooled to ꢀ78 °C, sequentially with
nBuLi and Me3SnCl. Its ESI-mass spectrum showed a [M þ H]þ
peak atm/z 499, andthe1HNMR spectrumcontained, in addition
to the expected aromatic multiplets, a triplet resonance at δ 0.48
’ RESULTS AND DISCUSSION
Transmetalation from the organotin compound 2-Me3SnC6-
F4PPh2 (7) provided a convenient route to the palladium(II)
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Scheme 3
temperature gave dimeric palladium complexes [Pd2(μ-X)2-
(k2-2-C6F4PPh2)2] [X = Cl (5), Br (8)] as yellow or orange, air-
stable solids in high yields (Scheme 3). Using a 2.5:1 molar ratio of
7 to [PdX2(cod)], 5 or 8, in refluxing CH2Cl2 for 24 h gave the
previously reported bis(chelate) complex trans-[Pd(k2-2-
C6F4PPh2)2].24
A single-crystal X-ray structural determination showed that
complex 8 consists of two palladium atoms bridged by a pair of
bromine atoms and coordinated to two chelate 2-C6F4PPh2
ligands, the phosphorus and carbon atoms of the latter being,
separately, mutually trans across the planar Pd2Br2 unit. The
molecular structure is shown in Figure 2 together with selected
bond lengths and angles.
The metal atoms display the expected planar coordination,
distorted as a consequence of the narrow bite angle (69°) of the
k2-C6F4PPh2 ligands, this value being typical of this mode of
coordination.29 The PdꢀBrꢀPd bridges are almost symmetrical,
and the PdꢀBr bond lengths [2.517 Å (av)] are close to those
found in the tetranuclear complex 1 [2.510 Å (av)];19 the PdꢀP
and PdꢀC bond lengths in the two compounds are also similar.
The ESI-mass spectra of 5 and 8 each showed peaks corre-
sponding to the [M þ Na]þ ions. The 31P NMR spectra of each
compound showed a pair of resonances at about δ ꢀ76 and ꢀ77,
indicating the presence in solution of two species containing a
phosphorus atom in a four-membered chelate ring.31 The relative
intensities of the two peaks varied in different preparations, the
less shielded resonance always being the more intense. The less
intense resonance may correspond to the cis isomer of [Pd2(μ-X)2-
(μ-2-C6F4PPh2)2]. In potentially coordinating solvents such as
acetone and THF, only one resonance was observed, probably
because of reversible cleavage of the Pd2Br2 bridges.
Figure 2. Molecular structure of [Pd2(μ-Br)2(k2-2-C6F4PPh2)2] (8),
one of the 4.5 independent molecules in the asymmetric unit (see
Experimental Section). Ellipsoids show 30% probability levels, and
hydrogen atoms and a dichloromethane molecule have been omitted
for clarity. Selected bond distances (Å) and angles (deg): Pd(2)ꢀBr(2)
2.510(2), Pd(2)ꢀBr(3) 2.524(2), Pd(3)ꢀBr(3) 2.517(2), Pd(3)ꢀBr-
(2) 2.518(2), Pd(2)ꢀP(2) 2.214(3), Pd(3)ꢀP(3) 2.216(4), Pd(2)ꢀC-
(24) 2.013(4), Pd(3)ꢀC(42) 2.011(4), P(3)ꢀPd(3)ꢀC(42) 69.03(2),
Pd(2)ꢀBr(3)ꢀPd(3) 91.2(1), Pd(2)ꢀBr(3)ꢀPd(3) 91.2(1), Pd-
(2)ꢀBr(2)ꢀPd(3) 91.8(1), Br(2)ꢀPd(3)ꢀBr(3) 88.3(1), Br(3)ꢀPd-
(2)ꢀBr(2) 88.6(1), P(2)ꢀPd(2)ꢀC(24) 69.5(2).
(J = 1.6 Hz) due to the SnMe3 group together with 117/119Sn
satellites (J = 54.9, 57.8 Hz). In the 13C NMR spectrum, the
SnMe3 resonance at δ ꢀ3.9 was split into a doublet of doublets
(J = 4.5, 13.3 Hz), presumably arising from three-bond coupling to
the ortho fluorine and phosphorus atoms on the aromatic ring.
Equally spaced about the main resonance were satellites arising
from the 117Sn and 119Sn isotopomers (J = 361 and 381 Hz). The
31P NMR spectrum showed a doublet of multiplets centered at
δ ꢀ0.2 with poorly resolved 117/119Sn coupling of ca. 29 Hz. The
X-ray structure of 7 is shown in Figure 1; the C(methyl) bond
lengths [2.138(2)ꢀ2.148(2) Å] are comparable to those found in
(CH3)4Sn [2.144(3) Å].25 In contrast, the SnꢀC(aryl) bond
length [2.1883(14) and 2.1904(15) Å for two independent
molecules] is significantly greater than the corresponding
distances in (C6H5)4Sn [2.137(5) Å]26 and (C6F5)4Sn
[2.126(8) Å],27 presumably owing to the presence of the bulky
ortho-PPh2 substituent. Because of the less Lewis acidic Sn site
Over a period of weeks at room temperature the 31P NMR
high-field resonances in CH2Cl2 solutions of 5 and 8, character-
istic of the four-membered PꢀC chelates, decreased in intensity
and a new peak at δ ca. 28 assignable to the tetranuclear
complexes [Pd4(μ-X)4(μ-2-C6F4PPh2)4] (X = Cl, Br) was
observed. As already reported,24 the tetranuclear chloro complex
could be isolated in ca. 40% yield from the resulting solution, but
the reaction in the case of X = Br was accompanied by consider-
able decomposition and the appearance of several additional,
unassigned 31P NMR signals. However, the tetranuclear bromo
complex was formed in high yields in CH2Cl2/MeOH over 5 d at
room temperature. Lahuerta et al.30 have isolated this compound
in moderate yield from the oxidative addition of 2-BrC6F4PPh2
to [Pd(dba)2], although a tedious purification procedure was
required. The tetranuclear chloro complex was formed in slightly
higher yields (ca. 50%) in CH2Cl2/MeOH.
(devoid of Sn-bound halide), the P
Sn separation in 7
3 3 3
[3.3694(4) and 3.3931(4) Å] is greater than those reported
in [o-Ph2PC6H4(SnPh2Cl)] [3.125(4) Å] and [(o-iPr2PC6H4)2-
SnPhCl] [3.120(1) Å].28
We now turn to the reactions of 8 with various ligands.
a. Carboxylate Ions (Scheme 4). Reaction of complex 8
with a small excess of silver acetate or benzoate in CH2Cl2
gave the corresponding carboxylate complexes [Pd2(μ-O2CR)2
Reaction of equimolar quantities of 2-Me3SnC6F4PPh2 (7)
and [PdX2(cod)] (X = Cl, Br) over a period of 2 h at room
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ARTICLE
Scheme 4
The molecular structures of 9 and 10 have been determined by
X-ray crystallography; that of 9 is shown in Figure 3, together
with selected bond lengths and angles. The structures resemble
that of 8 in possessing a pair of palladium atoms that are
coordinated to chelate 2-C6F4PPh2 ligands and bridged by two
carboxylate groups; however, in contrast to 8, the chelate rings do
not lie along the PdꢀPd axis but are stacked orthogonally to it.
Consequently the PdꢀPd separations in 9 and 10 [2.9897(2),
2.9627(2) Å, respectively] are considerably less than that in 8
[3.596(2), 3.603(2), 3.611(2), 3.619(2), 3.639(2) Å for 4.5
independent molecules]. Similar structures are observed for
μ-carboxylato o-palladated N-donor complexes, such as [Pd2(μ-OAc)2-
(k2-C,N-2-C6H4C5H4N)2]33 and [Pd2(μ-OAc)2(k2-C,N-C13-
H8N)2]34 derived from 2-phenylpyridine and benzoquinoline,
respectively. It has been argued, on the basis of the observed
Pd Pd separations (ca. 2.85 Å), the photophysical properties of
3 3 3
the complexes, and computational analysis, that there is an
attractive interaction between the 4d8 metal centers.33 Any such
interaction is likely to be weaker in complexes 9 and 10. The bite
angles of the chelate 2-C6F4PPh2 groups in 9 and 10 are about 69°,
as expected. The PdꢀO bond lengths trans to phosphorus are
close to those trans to σ-carbon atoms (ca. 2.10 Å), indicative of a
similar trans influence for these ligands.
When a solution of 9 in toluene/methanol was set aside at
room temperature, the intensity of the high-field signal in the 31P
NMR spectrum (δ ꢀ75.4 in this medium) diminished and a peak
at δ 15.6 began to appear. After 4 d, the latter was more intense,
but only after several weeks had the high-field signal disappeared
and the peak at δ 15.6 was now accompanied by several
additional resonances of unknown origin, including an intense
peak at δ 53.3. The peak at δ 15.6 is assigned to the isomeric
compound [Pd2(μ-O2CCH3)2(μ-2-C6F4PPh2)2] (11) [δP
(CDCl3) 15.5], which has been isolated by Lahuerta et al.30
from the reaction of [Pd4(μ-Br)4(μ-2-C6F4PPh2)4] with silver
acetate. Although we could not convert the k2- into a μ-2-
C6F4PPh2 acetato complex quantitatively, X-ray structure ana-
lyses of two single crystals grown from a partly isomerized
solution of 9 confirmed the assignment. One of the single crystals
was unsolvated but crystallized in the orthorhombic space group
Pna21, in contrast to the monoclinic space group C2/c reported
by Lahuerta and co-workers.30 The second crystal was in the
latter space group, the cell dimensions being similar (though not
identical) to those reported by Lahuerta and co-workers,30 and
contained 1 mol of C6H6 per formula unit. The relatively high R-
factor of the structure reported by Lahuerta et al. (8.56% for the
observed reflections) may arise from unrefined solvent that is
disordered
Figure 3. Molecular structure of [Pd2(μ-O2CCH3)2(k2-2-C6F4PPh2)2]
(9). Ellipsoids show 50% probability levels. Hydrogen atoms have
been omitted for clarity, and only the ipso carbons of the PPh2 groups
are shown. The structure contains 0.5 C6H6 (not shown) in the
asymmetric unit. Selected bond distances (Å) and angles (deg):
Pd(1)
Pd(2) 2.9897(2), Pd(1)ꢀP(1) 2.2318(3), Pd(2)ꢀP(2)
3 3 3
2.2294(3), Pd(1)ꢀC(6) 1.9886(13), Pd(2)ꢀC(24) 1.9951(14), Pd-
(1)ꢀO(1) 2.0988(9), Pd(1)ꢀO(3) 2.0951(10), Pd(2)ꢀO(2)
2.0930(10), Pd(2)ꢀO(4) 2.1043(9), P(1)ꢀPd(1)ꢀC(6) 69.93(4),
C(24)ꢀPd(2)ꢀP(2) 69.92(4). Corresponding data for 10: Pd(1)
3 3 3
Pd(2) 2.9627(2), Pd(1)ꢀP(1) 2.2247(4), Pd(2)ꢀP(2) 2.2115(4), Pd-
(1)ꢀC(6) 1.9901(14), Pd(2)ꢀC(24) 1.9886(14), Pd(1)ꢀO(1)
2.0886(10), Pd(1)ꢀO(3) 2.0938(11), Pd(2)ꢀO(2) 2.0836(11), Pd-
(2)ꢀO(4) 2.0981(10), P(1)ꢀPd(1)ꢀC(6) 69.76(4), C(24)ꢀPd(2)ꢀ
P(2) 69.83(4).
in a diffuse fashion within the voids provided by the crystal
lattice. However, the molecular dimensions of the dinuclear
palladium complex in the three forms do not differ significantly.
The Pd Pd separations in our two forms [2.68969(4),
3 3 3
(k2-2-C6F4PPh2)2] [R = CH3 (9), Ph (10)] in good yields as
pale yellow solids. Each showed in its 31P NMR spectrum in
C6D6 a single broad resonance at δ ca. ꢀ74, confirming that
2.68159(15) Å, respectively] are ca. 0.3 Å less than in complexes
9 and 10, indicative of a stronger metalꢀmetal interaction
induced by the two additional bridging groups; these values fall
in the range 2.55ꢀ2.74 Å observed in binuclear Pd(II) complexes
containing four bridging ligands with NꢀN, NꢀO, NꢀS, and
SꢀS donor sets.35
1
the chelate 2-C6F4PPh2 group was still present, and the H
NMR spectrum of 9 contained a singlet at δ 2.26 arising from
the acetate methyl group. The IR spectrum of 9 exhibited two
strong bands at 1421 and 1567 cmꢀ1 assignable to symmetric
and asymmetric COO vibrations, the separation being indica-
tive of bridging acetate groups.32 There was no evidence for
the formation of mononuclear species containing chelating
2-C6F4PPh2 and carboxylate groups.
b. Iodide Ions (Scheme 5). Treatment of the acetato complex
9 with an excess of sodium iodide in methanol gave [Pd2
(μ-I)2(k2-2-C6F4PPh2)2] (12) as a brown solid that proved
difficult to isolate reproducibly in a pure state. It was also formed
from 8 and NaI, but, in this case also, other unidentified products
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Scheme 5
Selected bond distances and angles of 13 and 14 are shown
in the captions to Figures 4 and 5, respectively. Complex 13 is
structurally similar to the tetranuclear complexes [Pd4(μ-X)4
(μ-2-C6H4PPh2)4] (X = Cl, Br),19,20 consisting of a pair of
planar Pd2I2 units bridged by two pairs of 2-C6F4PPh2 ligands,
each in a head-to-tail arrangement. The palladium atoms and,
separately, the iodide ligands occupy opposite vertices of a
cube. The distance between the two palladium atoms in 13
bridged by the 2-C6F4PPh2 groups [3.0841(3) Å] is similar to
those reported for [Pd4(μ-X)4(μ-2-C6H4PPh2)4] [X = Cl
(3.09 Å), Br (3.07 Å)]; the PdꢀP and PdꢀC bond lengths
in 13 are also comparable. The PdꢀIꢀPd bridges are slightly
asymmetric, the PdꢀI bonds trans to phosphorus [2.6525(2) Å]
being slightly shorter than those trans to carbon [2.6813(2) Å].
A similar trend has been observed in the dinuclear palladium
36
complexes [Pd2(μ-I)2(PPh3)2(C6H4-4-PPh3)2][OTf]2
and
anti-[Pd2(μ-I)2(Ph)2(PPh3)2].37
Complex 14 consists of four palladium atoms in a zigzag
arrangement, the two symmetry-related halves of the molecule
being connected by a Pd2(μ-I)2 unit. In each half of the structure,
the two metal atoms are bridged by another iodine atom and a
2-C6F4PPh2 group, the phosphorus atom of which is bound to
the terminal palladium atom, Pd(1). The remaining coordination
sites on Pd(1) are occupied by a chelate k2-2-C6F4PPh2 ligand,
while the coordination sphere of the inner palladium atom,
Pd(2), comprises three bridging iodine atoms and the carbon
atom of μ-2-C6F4PPh2. As expected, the coordination geometry
of the palladium atoms is distorted square planar and the bite
angle of the chelate 2-C6F4PPh2 ligands is ca. 69°. The separation
between the metal atoms Pd(1) and Pd(2) that are bridged by
2-C6F4PPh2 and iodide [3.0305(9) Å] is significantly smaller
than the corresponding separations in 13 [3.0841(3) Å]. This
closer approach is also manifested in the Pd(1)ꢀI(1)ꢀPd(2)
angle [69.76(2)°], which is significantly smaller than the Pd-
(2)ꢀI(2)ꢀPd(2*) angle [93.25(2)°]. The PdꢀP bond lengths
in the chelate 2-C6F4PPh2 groups [2.2647(19) Å] are signifi-
cantly shorter than those in the bridging 2-C6F4PPh2 groups
[2.326(2) Å], while the reverse trend is apparent for the PdꢀC
bond lengths [2.059(8) and 1.997(7) Å, respectively]. The
Pd2(μ-I)2 unit in 14 shows similar asymmetry to that in 13,
the PdꢀI bonds trans to phosphorus [2.6808(7) Å] being
slightly shorter than those trans to carbon [2.7009(7) Å], and
Figure 4. Molecular structure of [Pd4(μ-I)4(μ-2-C6F4PPh2)4] (13).
Ellipsoids show 50% probability levels. Hydrogen atoms and dichlor-
omethane of crystallization have been omitted for clarity. Asterisks
denote atoms generated by symmetry. Selected bond distances (Å) and
angles (deg): Pd(1) Pd(1*) 3.0841(3), Pd(1)ꢀI(1) 2.6525(2), Pd-
3 3 3
(1*)ꢀI(1) 2.6813(2), Pd(1)ꢀP(1) 2.2542(6), Pd(1)ꢀI(1)ꢀPd(1*)
90.907(7).
were present. The ESI-mass spectrum of 12 showed a peak at
m/z 1155, corresponding to the [M þ Na]þ ion, confirming the
dinuclear formulation. The 31P NMR spectrum showed two
multiplet resonances at δ ꢀ78.2 and ꢀ81.1, presumably arising
from cisꢀtrans isomers, as in the chloro and bromo analogues 5
and 8, whose relative intensity varied between different prep-
arations; the lower field resonance was always the more intense.
Attempts on separate occasions to obtain X-ray quality crystals
of 12 gave prisms that, in one case, proved to be the tetranuclear
species [Pd4(μ-I)4(μ-2-C6F4PPh2)4] (13) (Figure 4) and in the
other, [(k2-2-C6F4PPh2)Pd(μ-I)(μ-2-C6F4PPh2)Pd(μ-I)2Pd-
(μ-I)(μ-2-C6F4PPh2)Pd(k2-2-C6F4PPh2)] (14) (Figure 5),
both being formed by facile dimerization of 12.
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Figure 6. Molecular structure of [Pd2(μ-SCN)2(k2-2-C6F4PPh2)2] (15).
Ellipsoids show 50% probability levels. Hydrogen atoms have been omitted
for clarity. Asterisks denote atoms generated by symmetry. Selected bond
lengths (Å) and angles (deg): Pd(1)ꢀP(1) 2.2594(8), Pd(1)ꢀC(6)
2.015(3), Pd(1)ꢀS(1) 2.3980(8), Pd(1)ꢀN(1*) 2.060(2), N(1*)ꢀPd-
(1)ꢀS(1) 94.24(7), S(1)ꢀPd(1)ꢀC(6) 95.14(9), C(6)ꢀPd(1)ꢀ
P(1) 69.84(9), P(1)ꢀPd(1)ꢀN(1*) 100.86(7), Pd(1)ꢀN(1*)ꢀ
C(19*) 165.6(2), Pd(1)ꢀS(1)ꢀC(19) 100.36(10), S(1)ꢀC(19)ꢀN(1)
178.8(3).
Figure 5. Molecular structure of [(k2-2-C6F4PPh2)Pd(μ-I)(μ-2-
C6F4PPh2)Pd(μ-I)2Pd(μ-I)(μ-2-C6F4PPh2)Pd(k2-2-C6F4PPh2)]
(14). Hydrogen atoms and dichloromethane of crystallization have been
omitted for clarity. Ellipsoids show 50% probability levels. Asterisks
denote atoms generated by symmetry. Selected bond distances (Å) and
angles (deg): Pd(1) Pd(2) 3.0305(8), Pd(1)ꢀI(1) 2.6808(7), I(2)ꢀ
3 3 3
Pd(2) 2.6074(7), Pd(1)ꢀC(6) 2.059(8), Pd(1)ꢀP(1) 2.2647(19),
Pd(1)ꢀP(2) 2.326(2), Pd(2)ꢀC(24) 1.997(7), Pd(2)ꢀI(1)
2.6176(7), Pd(2)ꢀI(2*) 2.7009(7), Pd(2)ꢀI(1)ꢀPd(1) 69.76(2).
Scheme 6
both being significantly longer than those trans to iodide
[2.6176(7), 2.6074(7) Å].
When a solution of 12 was set aside over several days, the
high-field resonance in the 31P NMR spectrum diminished in
intensity and a peak at δ 21.8 assignable to bridging 2-C6F4PPh2
appeared, but this process did not go to completion. The final
spectrum may correspond to a mixture of 13 and 14, which could not
be separated.
Figure 7. Molecular structure of [Pd4(μ-SCN)4(k2-2-C6F4PPh2)2-
(μ-2-C6F4PPh2)2] (16). Ellipsoids show 50% probability levels. Hydro-
gen atoms and dichloromethane of crystallization have been omitted for
c. Thiocyanate Ions (Scheme 6). Reaction of 8 with silver
thiocyanate gave an 80% yield of the corresponding thiocyanato-
bridged complex [Pd2(μ-SCN)2(k2-2-C6F4PPh2)2] (15), which
showed a single resonance at δ ꢀ78.2 in its 31P NMR spectrum and
a peak at m/z 1019 in its ESI-mass spectrum, corresponding to the
[M þ Na]þ ion. The IR spectrum showed a strong ν(CtN) band
at 2142 cmꢀ1, typical of bridging thiocyanate,38 cf. 2120 cmꢀ1 for
the structurally characterized complex [P(CH2Ph)Ph3]2[Pd2
(μ-SCN)2(2,4,6-C6H2F3)4].39 The molecular structure of 15,
together with selected bond lengths and angles, is shown in Figure 6;
it is similar to that of the bromo analogue 8 described above. Two
planar-coordinated palladium atoms end-bridged by a pair of
thiocyanate ligands in a head-to-tail arrangement are each coordi-
nated by a chelate 2-C6F4PPh2 ligand in which the phosphorus
atoms are trans to the sulfur atoms of the SCN bridges. The PdꢀP
clarity. Selected bond distances (Å) and angles (deg): Pd(2) Pd(3)
3 3 3
2.9532(3), Pd(1)ꢀC(6) 2.015(3), Pd(4)ꢀC(64) 1.999(3), Pd(2)ꢀ
C(44) 1.999(3), Pd(3)ꢀC(26) 2.010(3), P(1)ꢀPd(1) 2.2576(9),
P(2)ꢀPd(2) 2.2736(8), P(3)ꢀPd(3) 2.2893(8), P(4)ꢀPd(4)
2.2734(8), Pd(1)ꢀS(1) 2.3852(9), Pd(2)ꢀS(2) 2.3959(9), Pd(3)ꢀ
S(3) 2.4008(8), Pd(4)ꢀS(4) 2.3908(8), Pd(1)ꢀN(2) 2.066(3), Pd-
(2)ꢀN(1) 2.051(3), Pd(4)ꢀN(4) 2.078(3), Pd(3)ꢀN(3) 2.028(3),
P(1)ꢀPd(1)ꢀC(6) 69.84(10), P(4)ꢀPd(4)ꢀC(64) 92.28(10).
and PdꢀC bond lengths in 15 are comparable with, but slightly
greater than, those in 8. The thiocyanate ligands are almost perfectly
linear, the S(1)ꢀC(19)ꢀN(1) angle being 178.8(3)°. As expected,
the PdꢀNꢀC unit is almost linear, the Pd(1)ꢀN(1*)ꢀC(19*)
angle being 165.6(2)°, whereas the PdꢀSꢀC unit is bent
[Pd(1)ꢀS(1)ꢀC(19) 100.36(10)°]. The PdꢀP, PdꢀC, and
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Scheme 7
Figure 9. Molecular structure of [Pd2(acac)2(μ-2-C6F4PPh2)2] (18).
Ellipsoids show 20% probability levels. Hydrogen atoms have been
omitted for clarity, and only the ipso carbons of the PPh2 groups are
shown. Selected bond distances (Å) and angles (deg): Pd(1) Pd(2)
3 3 3
2.9640(3), Pd(1)ꢀP(1) 2.2290(7), Pd(2)ꢀP(2) 2.2422(7), Pd(1)ꢀC-
(29) 2.001(3), Pd(2)ꢀC(6) 2.001(3), Pd(1)ꢀO(1) 2.0666(19), Pd-
(1)ꢀO(2) 2.060(2), Pd(2)ꢀO(3) 2.050(2), Pd(2)ꢀO(4) 2.047(2),
O(1)ꢀPd(1)ꢀO(2) 90.44(9), O(4)ꢀPd(2)ꢀO(3) 91.33(9).
d. Acetylacetonate Ion (Scheme 7). A monomeric acetylace-
tonato (acac) derivative of palladium, [Pd(acac)(k2-2-C6F4PPh2)]
(17), was obtained from the reaction of 8 with Na(acac) as a pale
yellow solid in 84% yield. The 31P NMR spectrum showed a single
peak at δꢀ71.9, and the parent ion peak at m/z538 was observed in
the EI-mass spectrum. The 1H NMR spectrum showed the expected
aromatic multiplets in addition to three singlet resonances at δ 2.01,
2.12, and 5.45 in a ratio of 3:3:1 due to the two methyl and methine
protons, respectively, of the acac ligand. The IR spectrum contained
strong bands at 1517 and 1579 cmꢀ1, arising from the CO/CC
stretching modes of bidentate acac, cf. 1524 and 1569 cmꢀ1 in
[Pd(acac)2].40 In the structure of 17, shown in Figure 8, the
palladium atom is coordinated by a chelate 2-C6F4PPh2 ligand
forming one four-membered ring with a bite angle of ca. 70° and the
two oxygen atoms of the acac group to complete the square-planar
geometry. The PdꢀO bond lengths of 2.0603(9) and 2.0594(9) Å
are slightly larger than those in [Pd(acac)2] [1.9815(10),
1.9837(10) Å],41 consistent with the greater trans-influence of P-
and C-donor ligands.
When a solution of 17 in dichloromethane/methanol was set
aside at room temperature for 2 d, or heated at 60 °C for 4 h, the
resonance at δ ꢀ71.9 was replaced cleanly by a singlet at δ 24.5,
indicating that the four-membered ring had been opened. No
change occurred under similar conditions in the absence of
methanol. The yellow solid isolated from dichloromethane/
methanol was shown by X-ray crystallography to be the dinuclear
complex [Pd2(acac)2(μ-2-C6F4PPh2)2] (18); the molecular
structure is shown in Figure 9 together with selected bond
lengths and angles. A second crystal modification of compound
Figure 8. Molecular structure of [Pd(acac)(k2-2-C6F4PPh2)] (17).
Ellipsoids show 50% probability levels. Hydrogen atoms have been
omitted for clarity. Selected bond lengths (Å) and angles (deg):
Pd(1)ꢀP(1) 2.2285(3), Pd(1)ꢀC(6) 2.0124(12), Pd(1)ꢀO(1)
2.0603(9), Pd(1)ꢀO(2) 2.0594(9), O(1)ꢀC(20) 1.2723(15), O-
(2)ꢀC(22) 1.2768(15), P(1)ꢀPd(1)ꢀC(6) 70.13(4), O(1)ꢀPd-
(1)ꢀO(2) 92.06(4).
PdꢀS bond lengths are unexceptional, as is the bite angle of the
chelate 2-C6F4PPh2 group.
When heated to 60 °C for 3ꢀ5 h, a toluene solution of 15
became pale yellow; from the solution a pale yellow solid was
isolated. Its 31P NMR spectrum showed a pair of equally intense
singlets at δ þ19.5 and ꢀ78.0, indicative of bridging and chelating
2-C6F4PPh2 groups, respectively. The ESI-mass spectrum showed
a peak at m/z 1991 and the IR spectrum contained strong ν(CtN)
bands at 2143 and 2157 cmꢀ1, consistentwith bridging thiocyanato
ligands. These data suggest that the isolated solid is [Pd4(μ-
SCN)4(k2-2-C6F4PPh2)2(μ-2-C6F4PPh2)2] (16), which was con-
firmed by X-ray crystallography. The molecular structure of 16 is
shown in Figure 7, together with selected bond lengths and angles.
The structure of 16 consists of two stacked molecules of 15 in
which the 2-C6F4PPh2 ligands at one end have undergone ring-
opening so as to bridge the palladium atoms of the other
molecule. The metalꢀligand bond lengths in 16 are comparable
to those in 15. Attempts to open the remaining chelate rings of
16 to give [Pd4(μ-SCN)4(μ-2-C6F4PPh2)4] by further heating
were unsuccessful.
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Scheme 8
Scheme 9
possibly reflecting a ring-current effect of the delocalized
π-electrons in the acac rings that lie over each other in the
structure. The IR spectrum of 18 contains two strong CC/CO
bands in similar positions to those of 17.
e. Acetonitrile (Scheme 8). On standing overnight, acetoni-
trile solutions of [Pd2(μ-X)2(k2-2-C6F4PPh2)2] [X = Cl (5), Br
(8)] deposited yellow solids of formula [Pd2X2(MeCN)2(μ-2-
C6F4PPh2)2] [X = Cl (19), Br (20)], which each showed a 31
P
NMR singlet at δ ca. 27, suggestive of the presence of bridging
2-C6F4PPh2. The presence of coordinated acetonitrile was
indicated by the presence in the 1H NMR spectra in C6D6 of a
singlet at δ ca. 0.6 due to CH3 and, in the IR spectra, of a strong
ν(CtN) band at 2300 cmꢀ1 42
The ESI-mass spectra showed
.
peaks due to [M]þ and [M ꢀ halide]þ.
Complex 19 crystallized from hot acetonitrile with one
molecule of water (monoclinic, space group C2/c). Two solvates
of 20 were obtained: a mono(acetonitrile) solvate (monoclinic,
space group P21/n) and a benzene solvate (monoclinic, space
group C2/c). The X-ray structure of the last is shown in Figure 10,
together with selected metrical data. It consists of a pair of
palladium atoms bridged by two, mutually cis, 2-C6F4PPh2
ligands in a head-to-tail arrangement; a halide ligand trans to
phosphorus and a nitrogen-bound acetonitrile ligand trans to
carbon complete the essentially planar coordination sphere
Figure 10. Molecular structure of [Pd2Br2(NCMe)2(μ-2-C6F4PPh2)2]
(20). Hydrogen atoms and solvent molecules have been omitted for
clarity. Only the bridging atoms of one of the C6F4PPh2 ligands are
about each palladium atom. The Pd Pd separations are similar
3 3 3
to those of the other Pd-μ-C6F4PPh2 complexes discussed
previously. The Pdꢀhalide distances [2.3649(3) Å (19);
2.4889(5), 2.4976(3) Å (20), acetonitrile and benzene solvates,
respectively] are in the expected ranges for halide trans to a
tertiary phosphine coordinated to Pd(II), cf., 2.351(1), 2.358(2)
Å in [PdCl2(dppp)]43 and 2.4744(9), 2.4767(9) Å in [PdBr2-
(dppp)] [dppp = 1,3-bis(diphenylphosphino)propane].44
f. Tertiary Phosphines (Scheme 9). The halide bridges in
[Pd2(μ-Br)2(k2-2-C6F4PPh2)2] (8) were rapidly cleaved by
PPh3 or PCy3 to give the mononuclear complexes cis- and
trans-[PdBr(k2-2-C6F4PPh2)L] [L = PPh3 (21), PCy3 (22)],
isolated as pale yellow solids. The 31P NMR spectra of 21 and 22
each showed a pair of resonances at δ ca. ꢀ80 and þ30,
assignable to a chelate 2-C6F4PPh2 group and coordinated PR3
ligand, respectively. Each resonance was split into a doublet of
doublets of ca. 490 Hz, typical of trans PꢀP coupling. The
resonance at δ ca. 30 in 21 was further split by ca. 8 Hz due to
coupling with the ortho-fluorine of the C6F4PPh2 group. Low-
intensity peaks at δ ca. ꢀ75 and þ17 (21) and ca. δ ꢀ73
and þ26 (22) corresponding to the cis isomers were also
observed. The ratio of cis/trans isomers for 21 and 22 varied
between preparations, but was typically about 1:9 in both cases;
the trans isomer always predominated.
shown. Selected bond distances (Å) and angles (deg): Pd(1) Pd(1*)
3 3 3
3.0184(3), Pd(1)ꢀP(1*) 2.2653(6), Pd(1)ꢀC(20) 2.001(2), Pd-
(1)ꢀN(1) 2.072(2), Pd(1)ꢀBr(1) 2.4976(3), N(1)ꢀC(1) 1.144(3),
Pd(1)ꢀN(1)ꢀC(1) 177.6(2), N(1)ꢀPd(1)ꢀP(1*) 93.96(6), N-
(1)ꢀPd(1)ꢀBr(1) 91.07(6), C(20)ꢀPd(1)ꢀP(1*) 88.05(7), C-
(20)ꢀPd(1)ꢀBr(1) 86.69(6), P(1*)ꢀPd(1)ꢀBr(1) 174.125(18),
C(20)ꢀPd(1)ꢀN(1) 174.92(9).
18 (a solvate comprising one hexane molecule per formula unit
of 18) was obtained by layering the solution of 18 with n-hexane.
Except for the fact that in the latter the center of the Pd
separation of 18 is located on a 2-fold axis and the asymmetric
Pd
3 3 3
unit therefore comprises 0.5 18 C6H14, the molecular archi-
3
tectures of the dinuclear palladium complex are very similar in
these two structures, so only the first is discussed as a repre-
sentative example. The structure consists of a pair of palladium
atoms, each of which is coordinated in a planar array by a chelate
O-bound acac group together with a phosphorus atom and a
carbon atom from a pair of bridging 2-C6F4PPh2 groups. The
Pd
Pd separation [2.9640(3) Å] is similar to that in 16
3 3 3
[2.9532(3) Å]. The metalꢀligand bond lengths in 17 and 18
are generally similar, the PdꢀC distances in the latter being ca.
1
The structure of trans-[PdBr(k2-2-C6F4PPh2)(PPh3)] (trans-
21) has been confirmed by X-ray diffraction and is shown in
Figure 11, together with selected bond distances and angles. It
0.01 Å shorter than in the former. The three H resonances
characteristic of the acac methine and methyl groups in 18 are
each shifted upfield by ca. 0.3 ppm relative to those of 17,
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Figure 11. Molecular structure of trans-[PdBr(k2-2-C6F4PPh2)-
(PPh3)] (trans-21). Ellipsoids show 30% probability levels. Hydrogen
atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (deg): Pd(1)ꢀP(1) 2.3178(5), Pd(1)ꢀP(2) 2.3355(5), Pd-
(1)ꢀBr(1) 2.4723(2), Pd(1)ꢀC(2) 2.0440(17), P(1)ꢀPd(1)ꢀC(2)
69.32(5).
Figure 12. Molecular structure of trans-[PdBr(kC-2-C6F4PPh2)-
(PPh3)2] (23). Hydrogen atoms have been omitted for clarity, and only
the ipso carbons of the PPh3 ligands are shown. Selected bond distances
(Å) and angles (deg): Pd(1)ꢀC(6) 2.0296(19), Pd(1)ꢀP(2) 2.3349(5),
Pd(1)ꢀP(3) 2.3416(5), Pd(1)ꢀBr(1) 2.5033(2), C(6)ꢀPd(1)ꢀP(2)
90.41(6), C(6)ꢀPd(1)ꢀP(3) 92.72(6), P(2)ꢀPd(1)ꢀP(3) 168.553(19),
C(6)ꢀPd(1)ꢀBr(1) 177.18(6).
consists of a palladium atom coordinated to an ortho-metalated
2-C6F4PPh2 group forming a four-membered chelate ring. One
PPh3 ligand trans to the phosphorus atom of the metalated group
and one bromide complete the coordination about the metal
center. The geometry about the palladium atom is distorted from
square planar as a result of the narrow bite angle (ca. 69°) of the
chelate 2-C6F4PPh2 ligand. The PdꢀBr distance is about 0.11
and 0.03 Å, respectively, shorter than those in the structurally
similar compounds trans-[PdBr(k2-2-C6H4PPh2)(L)] [L =
PPh2(2-BrC6H4),20 C5H5FeC5H4PPh245], consistent with the
lower trans influence of a fluoroaryl group relative to that of its
aryl counterpart.46
complex [Au2(μ-2-C6F4PPh2)2].23 Following the pioneering
work of Eaborn, Pidcock, et al.,47ꢀ50 (aryl)trimethyltin reagents
have been used extensively for the selective transfer, under mild
conditions, of one or two aryl groups to platinum(II),51ꢀ57 but in
the case of palladium(II) the reaction is usually successful only
when, as in our case, the aryl groups bear a donor center.58ꢀ60
The [Pd2(μ-X)2(k2-2-C6F4PPh2)2] complexes are not ther-
modynamically stable; they rearrange in solution, either at room
temperature or on heating, to give complexes containing μ-2-
C6F4PPh2. The rearrangement is probably initiated by one-
ended dissociation of the PdꢀP bond, driven by the relief of
strain in the four-membered ring. The facile, stepwise displace-
ment of the phosphorus atoms of [Pt(k2-2-C6H4PPh2)2] by
P-donors (L) to give [Pt(kC-2-C6H4PPh2)2L2]61 and the reac-
tion of [PdBr(k2-2-C6F4PPh2)(PPh3)] (21) with PPh3 to give
trans-[PdBr(kC-2-C6F4PPh2)(PPh3)] (23) described here pro-
vide models for the initial dissociation step. The rearrangements
are promoted by polar or coordinating solvents, such as metha-
nol and acetonitrile, which may stabilize the necessary vacant
sites on the metal atoms. However, as shown by the behavior of
the iodo and thiocyanato complexes, 12 and 15, respectively, not
all the available chelate groups necessarily undergo rearrange-
ment, for reasons that are not clear.
The chelate ring in [PdBr(k2-2-C6F4PPh2)(PPh3)] (21) was
opened by the addition of a stoichiometric amount of PPh3 to
give trans-[PdBr(kC-2-C6F4PPh2)(PPh3)2] (23), in which the
PPh2 group of the fluoroaryl ligand is not bound to the metal
atom. The 31P NMR spectrum of 23 showed two resonances in a
2:1 ratio at δ 20.7 and ꢀ3.7, the chemical shifts being typical of,
respectively, tertiary arylphosphines coordinated to Pd(II) and
free tertiary arylphosphines. The molecular structure of 23 has
been confirmed by X-ray crystallography and is shown in
Figure 12, together with selected metrical parameters.
In the structure of 23, the square-planar-coordinated palla-
dium atom is bound to two phosphorus atoms of mutually trans
PPh3 ligands, one bromide, and a C-bonded 2-C6F4PPh2 group.
The phosphorus atom of the 2-C6F4PPh2 group is oriented
above the palladium atom, and the large Pd(1)ꢀP(1) separation
(ca. 3.4 Å) indicates that there is little or no PdꢀP interaction.
The metalꢀligand bond lengths are similar to those in trans-21.
’ DISCUSSION
Although complex 21 has a 2-C6H4PPh2 analogue (Scheme 1),
there are no known k2-2-C6H4PPh2 analogues of the [Pd2X2(k2-
2-C6F4PPh2)2] complexes; palladaphosphaarene and palladapho-
sphacyclobutene complexes of this type are known only when
there are bulky substituents, such as 2-tolyl62 or tert-butyl,63 in the
cyclopalladated ring. The stabilizing effect on metalꢀaryl binding
of electronegative fluorine in place of hydrogen in the aromatic
ring is evident from published surveys of transition metalꢀC6F5
complexes;64,65 complete replacement of hydrogen by fluorine
The reaction of 2-Me3SnC6F4PPh2 in a 1:1 mol ratio at room
temperature with [PdX2(cod)] gives the halide-bridged dimers
[Pd2(μ-X)2(k2-2-C6F4PPh2)2] [X = Cl (5), Br (8)] in good
yields; this method is probably more convenient and provides a
purer product than ligand scrambling of the bis(chelate) complex
trans-[Pd(k2-2-C6F4PPh2)2] with [PdX2(NCMe)2].24 We have
shown previously that 2-Me3SnC6F4PPh2 is also a convenient
alternative to 2-LiC6F4PPh2 in the preparation of the digold(I)
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also serves to slow down, if not completely inhibit, the transforma-
tion from chelate to bridging coordination of the 2-C6H4PPh2
group. Two other observations point to the same conclusion: (1)
the chelaterings of trans-[M(k2-2-C6F4PPh2)2] (M =Ni, Pd, Pt)24
do not undergo k2 f μ rearrangement when the complexes
are heated, whereas cis-[Pt(k2-2-C6H4PPh2)2] dimerizes on heat-
ing to give [Pt2(k2-2-C6H4PPh2)2(μ-2-C6H4PPh2)2],22 and (2)
2-Me3SnC6H4PPh2 reacts with [PdX2(cod)] at room temperature
to give the tetramers [Pd4(μ-X)4(μ-2-C6H4PPh2)4] as the only
isolable product.66
Data were measured by use of COLLECT.70 The intensities of
reflections were extracted and the data were reduced by use of the
computer programs Denzo, SORTAV, and Scalepack.71,72 The crystal
structures of 7ꢀ11, 13ꢀ20, and 23 were solved by direct methods with
the use of SHELXS-9773 or by the Patterson method in SHELXS-97.
Structure refinement on F2 was carried out by a full-matrix least-squares
procedure with the use of SHELXL-97.74 The structure of 21 was solved
and refined on F2 with use of the programs SIR9275 and CRYSTALS,76
respectively. Refinement of the modulated structure of 8 CH2Cl2 was
3
performed on F using the program RAELS200677 with a weighting
scheme that included an uncorrelated 3% error in Fobs in addition to the
counting statistics error for Fobs. Because of weak intensity of the higher
order satellite reflections, it was decided to use a constrained refinement
model, and 870 independent variables were used to describe 249 non-
hydrogen atom positions and their atomic displacement parameters.
Hydrogen atoms were reinserted in geometrically sensible positions
after each refinement cycle and given atom displacement parameters
determined by the parameters describing the atoms to which they are
attached. The complex has pseudo 2/m local symmetry, so the con-
strained models used refinable local orthonormal coordinates relative to
refinable local orthonormal axial systems to force chemically equivalent
ring systems to have an equal local planar geometry that was refinable
while not constraining the connectivity of these rings. Atom displace-
ment parameters for these rings and attached F or H atoms were refined
using T, TL, or TLX parametrizations.78 Each disordered phenyl ring
was described by a six-variable T model, each ordered phenyl ring was
described by a 12-variable TL model centered on the P atom to which it
was attached, and each C6F4 fragment was described using a 15-variable
TLX model. CCDC reference numbers 799192ꢀ799209 refer to the
crystal structures reported in this paper.
’ CONCLUSIONS
We have prepared and characterized structurally a series of
ortho-palladated complexes containing the carbanion 2-C6F4PPh2
acting as a four-membered chelate ligand, e.g., [Pd2(μ-Br)2(k2-P,
C-2-C6F4PPh2)2], mostof which have not been isolated sofar with
the corresponding carbanion 2-C6H4PPh2. The k2-2-C6F4PPh2
complexes usually rearrange at room temperature to give com-
plexes of the same composition that contain the carbanion as a
bridging ligand, μ-2-C6F4PPh2, via solvent- or ligand-assisted
opening of the chelate ring. Some of the analogous μ-2-C6H4PPh2
compounds are known. We believe that a facile chelate to bridging
transformation of this type has not been demonstrated previously
in solutions of ortho-metalated triarylphosphine complexes. Two
compounds have been discovered in which only half the available
chelate 2-C6F4PPh2 groups have undergone ring-opening, to-
gether with one compound in which the carbanion is bound to
palladium through the σ-carbon atom only.
Syntheses. 2-Me3SnC6F4PPh2 (7). A solution of 2-BrC6F4PPh2
(6.6 g, 16 mmol) in ether (100 mL) was cooled to ꢀ78 °C and treated
slowly with a solution of nBuLi (1.6 M in hexanes, 10.0 mL, 16 mmol).
After stirring the mixture for 30 min, Me3SnCl (1.0 M in hexanes,
16.0 mL, 16 mmol) was added dropwise and the solution was stirred
at ꢀ78 °C for 2 h. After being allowed to warm to room temperature,
the suspension was hydrolyzed and the ether layer was separated.
The aqueous phase was extracted with ether (3 ꢁ 50 mL), and
the combined organic phases were dried (MgSO4). After filtration,
the solvent was removed and the gummy solid was recrystallized
from hot methanol to give white crystals of the title compound
(6.9 g, 87%).
’ EXPERIMENTAL SECTION
General Procedures. Reactions were performed under an atmo-
sphere of dry argon with the use of standard Schlenk techniques. All
glassware was oven-dried overnight. Acetone was dried over molecular
sieves and acetonitrile was refluxed over calcium hydride and distilled
under nitrogen; all other solvents were dried by the use of a standard
column drying system. The compounds 2-BrC6F4PPh2,67 [PdX2(cod)]
(X = Cl, Br),68 and Na(acac)69 were prepared by the appropriate
literature methods; all other reagents were commercially available and
used as received.
Physical Measurements. Elemental analyses were performed by
the Microanalytical Unit of the Research School of Chemistry at The
Australian National University (ANU). 1H (300 MHz), 13C (75 MHz),
and 31P (121 MHz) NMR spectra were recorded on a Bruker Avance
300 spectrometer in C6D6, unless otherwise stated. Coupling constants
(J) are given in hertz, and chemical shifts (δ) are given in ppm, internally
referenced to residual solvent signals (1H, 13C) or external 85% H3PO4
(31P). Mass spectra were recorded on a Bruker Apex 3 FTICR or a
Micromass Platform mass spectrometer (RMIT). Accurate mass deter-
minations were carried out on a Waters ESI-TOF Premier XE instru-
ment (ANU). Raman spectra were obtained on a Perkin-Elmer Raman
Station 400 as solid samples in glass capillary tubes. Infrared spectra
(4000ꢀ400 cmꢀ1) were obtained on a Perkin-Elmer Spectrum 2000
FT-IR spectrometer as KBr disks.
1
Mp: 77ꢀ79 °C. H NMR (CDCl3): δ 0.48 (t, J = 1.6 Hz with
117Sn/119Sn satellites, J = 54.9, 57.8 Hz, 9H, SnMe3), 7.2ꢀ7.4 (m, 10H,
aromatics). 13C NMR (CDCl3): δ ꢀ3.9 (dd, J = 4.5, 13.3 Hz with
117Sn/119Sn satellites, J = 361, 381 Hz) together with 128.5 (d, J = 6.4
Hz), 128.8 (s), 132.4 (dd, J = 1.8, 18.9 Hz), 134.6 (dd, J = 2.2, 9.2 Hz)
due to the PPh2 carbons and low-intensity peaks at δ 125.5 (m), 140.7
(m), 141.5 (m), 148.7 (m), 150.1 (m), 150.7 (m) due to the C6F4
carbons. 31P NMR (CDCl3): δ ꢀ0.2 (ddd, J = 1.6, 2.9, 22.8 Hz with
unresolved 117Sn/119Sn satellites, J = 29.4 Hz). ESI-MS (m/z): 499
[M þ H]þ. Anal. Calcd for C21H19F4PSn: C 50.75, H 3.85, F 15.29.
Found: C 51.04, H 3.96, F 15.32.
[Pd2(μ-Cl)2(k2-2-C6F4PPh2)2] (5). A mixture of 2-Me3SnC6F4PPh2
(500 mg, 1.0 mmol) and [PdCl2(cod)] (287 mg, 1.0 mmol) was
dissolved in CH2Cl2 (15 mL) to give a yellow solution, and after 2 h,
the solvent and volatile byproducts were removed in vacuo. The residue
was dissolved in CH2Cl2, hexane was added, and the solution was
evaporated under reduced pressure until a bright yellow solid precipi-
tated. This was isolated by filtration, washed with hexane, and dried in
vacuo to give 5 (400 mg, 84%). The ratio of trans:cis isomers estimated
from the 31P NMR spectrum was ca. 1.5:1, but varied between
preparations.
X-ray Crystallography. Crystals suitable for single-crystal X-ray
diffraction were obtained by layering a CH2Cl2 or benzene solution of
the complex with hexane or methanol, or by slow evaporation from
acetonitrile. Using a drop of Paratone (inert oil), crystals were mounted
on a glass capillary and transferred to a stream of cold nitrogen. The
reflection data were collected on a Nonius Kappa CCD diffractometer
equipped with a 95 mm camera and graphite-monochromated Mo KR
radiation (λ = 0.71073 Å), in j- and ω-scan modes.
3758
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Organometallics
ARTICLE
1H NMR: δ 6.7ꢀ7.5 (m, 20H, aromatics). 31P NMR: δ ꢀ76.8 (br s),
ꢀ77.5 (br s). ESI-MS (m/z): 970.8255; calcd 970.8257 [M þ Na]þ.
Anal. Calcd for C36H20Cl2F8P2Pd2: C 45.51, H 2.12, Cl 7.46, F 16.00.
Found: C 45.41, H 2.43, Cl 7.33, F 15.90.
1H NMR: δ 6.7ꢀ8.2 (m, 40H, aromatics). 31P NMR: δ 19.5 (br s),
ꢀ78.0 (br s). ESI-MS (m/z): 1991 [M]þ. IR (ν, cmꢀ1): 2143 and 2157
(CtN str.). Anal. Calcd for C76H40F16N4P4Pd4S4: C 45.55, H 2.03, N
2.81. Found: C 45.47, H 2.39, N 2.77.
[Pd2(μ-Br)2(k2-2-C6F4PPh2)2] (8). This compound was made similarly
to 5 from 2-Me3SnC6F4PPh2 (500 mg, 1.0 mmol) and [PdBr2(cod)]
(376 mg, 1.0 mmol) in CH2Cl2 (15 mL) and was obtained as a dark
yellow solid (460 mg, 88%). The trans:cis ratio was ca. 3:1, but varied
between preparations.
[Pd(acac)(k2-2-C6F4PPh2)] (17). To a dark yellow solution of 8
(100 mg, 0.1 mmol) in CH2Cl2 (15 mL) was added Na(acac) (50 mg,
0.3 mmol). The solution became turbid, and, after stirring for 30 min, the
suspension was filtered through Celite to give a pale yellow solution.
Hexane was added and the solution was evaporated under reduced
pressure to precipitate the product as a pale yellow solid, which
was isolated by filtration, washed with hexane, and dried in vacuo
(81 mg, 84%).
1H NMR: δ 6.7ꢀ7.5 (m, 20H, aromatics). 31P NMR: δ ꢀ76.5 (br s),
ꢀ77.9 (br s). ESI-MS (m/z): 1058.7267; calcd 1058.7246 [M þ Na]þ.
Anal. Calcd for C36H20Br2F8P2Pd2: C 41.61, H 1.94, Br 15.38, F 14.63.
Found: C 41.75, H 2.13, Br 15.30, F 15.14.
1H NMR (CDCl3): δ 2.01 (s, 3H, Me), 2.12 (s, 3H, Me), 5.45 (s, 1H,
CH of acac), 7.4ꢀ7.9 (m, 10H, aromatics). 31P NMR (C6D6): δ ꢀ71.9
(br s). EI-MS (m/z): 538 [M]þ. IR (ν, cmꢀ1): 1517 (CO str.) and 1579
(CC str.). Anal. Calcd for C23H17F4O2PPd: C 51.28, H 3.18, F 14.11.
Found: C 51.11, H 3.30, F 13.80.
[Pd2(μ-O2CCH3)2(k2-2-C6F4PPh2)2] (9). To a solution of 8 (100 mg,
0.1 mmol) in CH2Cl2 (15 mL) was added AgOAc (30 mg, 0.3 mmol),
and the mixture was stirred for 30 min in the dark, during which time the
color of the suspension faded to pale yellow. The insoluble silver salts
were removed by filtration, and the volume of the filtrate was reduced by
half under reduced pressure. Addition of hexane precipitated a pale
yellow solid, which was isolated by filtration, washed with hexane, and
dried to give 9 (75 mg, 78%).
[Pd2(μ-acac)2(μ-2-C6F4PPh2)2] (18). A solution of complex 17 (100
mg, 0.19 mmol) in a 1:1 mixture of dichloromethane and methanol
(20 mL) was stirred at room temperature for 2 d. The solvents were
evaporated under reduced pressure, and the residue was extracted with
dichloromethane. Filtration through Celite and evaporation of the
solvent gave 18 (154 mg, 75%).
1H NMR: δ 2.26 (s, 6H, Me), 6.6ꢀ7.2 and 7.9ꢀ8.2 (m, 20H,
aromatics). 31P NMR: δ ꢀ73.9 (br s). ESI-MS (m/z): 1019 [M þ
Na]þ. IR (ν, cmꢀ1): 1421 and 1567 (COO str.). Anal. Calcd for
C40H26F8O4P2Pd2: C 48.17, H 2.63, F 15.24. Found: C 48.39, H
2.96, F 14.50.
1H NMR (CDCl3): δ 1.61 (s, 6H, Me), 1.74 (s, 6H, Me), 5.07 (s, 2H,
CH of acac), 7.3ꢀ8.1 (m, 20H, aromatics). 31P NMR: δ 24.5 (br s). IR
(ν, cmꢀ1): 1517 (CO str.) and 1579 (CC str.). Anal. Calcd
for C46H34F8O4P2Pd2: C 51.28, H 3.18, F 14.11. Found: C 50.99,
H 3.06, F 14.14.
[Pd2(μ-O2CPh)2(k2-2-C6F4PPh2)2] (10). This compound was made
analogously to 9 above from 8 (100 mg, 0.1 mmol) and AgOBz (65 mg,
0.3 mmol) in CH2Cl2 (15 mL). The yield of 10 was 80 mg (74%).
1H NMR: δ 6.7ꢀ8.7 (m, 30H, aromatics). 31P NMR: δ ꢀ74.3 (br s).
ESI-MS (m/z): 1145 [M þ Na]þ. IR (ν, cmꢀ1): 1396 and 1596 (COO
str.). Anal. Calcd for C50H30F8O4P2Pd2: C 53.55, H 2.70, F 13.55.
Found: C 53.20, H 2.87, F 13.09.
[Pd2Cl2(NCMe)2(μ-2-C6F4PPh2)2] (19). A yellow solution of 5 (100
mg, 0.1 mmol) in MeCN (10 mL) was stirred overnight. The bright
yellow solid that precipitated was isolated by filtration, washed with
MeCN, and dried in vacuo (90 mg, 83%).
1H NMR: δ 0.59 (s, 6H, MeCN), 6.7ꢀ8.1 (m, 20H, aromatics). 31
P
NMR: δ 27.8 (br s). ESI-MS (m/z): 997 [M ꢀ Cl]þ. IR (ν, cmꢀ1):
2294 cmꢀ1 (CtN str.). Anal. Calcd for C40H26Cl2F8N2P2Pd2: C 46.54,
H 2.54, N 2.71, Cl 6.87, F 14.72. Found: C 45.92, H 2.58, N 2.43, Cl 6.58,
F 14.47.
[Pd2(μ-I)2(k2-2-C6F4PPh2)2] (12). A solution of 9 (100 mg, 0.1 mmol)
in dichloromethane (10 mL) was treated with a solution of NaI (45 mg,
0.3 mmol) in methanol (10 mL). After stirring the mixture for 15 min,
the solvents were evaporated under reduced pressure. The residue was
extracted with dichloromethane, the solution was filtered through Celite,
and the filtrate was evaporated to dryness to give a dark brown solid,
which consisted mainly of a mixture of trans and cis isomers (2:1) of 12
(91 mg, 80%). In some preparations, variable amounts of unidentified
impurities were also present.
[Pd2Br2(NCMe)2(μ-2-C6F4PPh2)2] (20). The title compound was
made from 8 (100 mg, 0.1 mmol) by the same procedure as described
above (95 mg, 88%).
1H NMR: δ 0.58 (s, 6H, MeCN), 6.7ꢀ8.1 (m, 20H, aromatics). 31
P
NMR: δ 27.5 (br s). ESI-MS (m/z): 1121 [M]þ. IR (ν, cmꢀ1):
2299 cmꢀ1 (CtN str.). Anal. Calcd for C40H26Br2F8N2P2Pd2: C
42.85, H 2.34, N 2.50, Br 14.25, F 13.56. Found: C 42.25, H 2.31, N
2.02, Br 14.26, F 13.52.
1H NMR: δ 6.2ꢀ8.6 (m, 20H, aromatics). 31P NMR: δ ꢀ78.2 (br s),
ꢀ81.1 (br s). ESI-MS (m/z): 1154.6993; calcd 1154.6969 [M þ Na]þ.
Anal. Calcd for C36H20F8I2P2Pd2: C 38.16, H 1.78, F 13.41, I 22.40.
Found: C 38.31, H 1.74, F 13.46, I 22.35.
[PdBr(k2-2-C6F4PPh2)(PPh3)] (21). A solution of 8 (180 mg, 0.17
mmol) in CH2Cl2 (5 mL) was treated with PPh3 (91 mg, 0.34 mmol) at
room temperature. Hexane was immediately added, and the volume of
the yellow solution was reduced in vacuo. The precipitated pale yellow
solid was isolated by filtration, washed with hexane, and dried in vacuo
(264 mg, 97%). The trans:cis ratio was generally ca. 9:1, but varied
between preparations.
[Pd2(μ-SCN)2(k2-2-C6F4PPh2)2] (15). To a dark yellow solution of 8
(100 mg, 0.1 mmol) in CH2Cl2 (15 mL) was added AgSCN (50 mg,
0.3 mmol). The solution became turbid, and after stirring for 15 min in
the dark, the suspension was filtered through Celite to give a pale yellow
solution. Hexane was added and the volume was partially evaporated
under reduced pressure to precipitate the product as a pale yellow solid,
which was isolated by filtration, washed with hexane, and dried in vacuo
(81 mg, 84%).
1H NMR (CDCl3): δ 5.3 (s, 2H, CH2Cl2), 7.1ꢀ8.2 (m, 25H,
aromatics). 31P NMR: δ ꢀ84.0 (d, J = 490 Hz), 29.3 (dd, J = 489, 8.0
Hz), ꢀ75.2 (br s), 17.1 (d, J = 14.0 Hz). ESI-MS (m/z): 783 [M þ H]þ.
31P NMR: δ ꢀ78.2 (br s). ESI-MS (m/z): 1019 [M þ Na]þ. IR
(ν, cmꢀ1): 2142 (CtN str.). Anal. Calcd for C38H20F8N2P2Pd2S2:
C 45.85, H 2.03, N 2.81, F 15.27, S 6.44. Found: C 45.73, H 2.31, N 2.85,
F 15.48, S 6.25.
Anal. Calcd for C36H25BrF4P2Pd 0.3CH2Cl2: C 54.00, H 3.20, Br 9.90,
3
Cl 2.63, F 9.41. Found: C 54.70, H 3.03, Br 9.46, Cl 2.92, F 9.58.
[PdBr(k2-2-C6F4PPh2)(PCy3)] (22). To an orange solution of 8 (100
mg, 0.1 mmol) in CH2Cl2 (10 mL) was added PCy3 (55 mg, 0.2 mmol).
After 5 min, hexane was added and the solution was evaporated under
reduced pressure. The very pale yellow solid that precipitated was
isolated similarly to 21. The yield was 75 mg (80%). The trans:cis ratio
was ca. 9:1, but varied between preparations.
[Pd4(μ-SCN)4(k2-2-C6F4PPh2)2(μ-2-C6F4PPh2)2] (16). A toluene so-
lution (15 mL) of 15 (100 mg, 0.1 mmol) was heated to 60 °C for 3ꢀ5 h,
during which time the solution became almost colorless. Addition of
hexane precipitated 16, which was separated by filtration, washed with
hexane, and dried in vacuo (80 mg, 80%).
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Organometallics
ARTICLE
1H NMR: δ 1.2ꢀ1.4, 1.5ꢀ1.9, 2.0ꢀ2.4, 2.8ꢀ3.1 (m, 33H, Cy),
7.1ꢀ7.4 and 8.2ꢀ8.5 (m, 10H, aromatics). 31P NMR: δ ꢀ86.7 (d,
J = 462 Hz), 37.9 (d, J = 462 Hz), ꢀ73.1 (br s), 26.7 (d, J = 14.8 Hz).
Anal. Calcd for C36H43BrF4P2Pd: C 54.05, H 5.42, Br 9.99. Found: C
53.85, H 5.42, Br 9.83.
[PdBr(kC-2-C6F4PPh2)(PPh3)2] (23). To a yellow solution of 21
(100 mg, 0.13 mmol) in CH2Cl2 (15 mL) was added PPh3 (33.5 mg,
0.13 mmol). The solution was stirred for 30 min at room temperature.
The solution was partially evaporated under reduced pressure, and
hexane was added to precipitate 23 (116 mg, 87%).
wR2 (all data) = 0.0825, GOF = 1.051, max./min. residual electron density
0.740/ꢀ0.991 e Åꢀ3
.
[Pd4(μ-I)4(μ-2-C6F4PPh2)4] 1.68CH2Cl2 (13). Empirical formula
3
C73.68H43.36Cl3.36F16I4P4Pd4, fw = 2408.80, temperature 100(2) K,
orthorhombic, space group Fddd, a = 18.7731(2) Å, b = 22.8802(3) Å,
c = 35.4070(4) Å, V = 15208.5(3) Å3, Z = 8, Fcalcd = 2.104 Mg/m3, crystal
dimensions 0.22 ꢁ 0.20 ꢁ 0.18 mm3, 65 859 reflections, 7176 indepen-
dent (Rint = 0.0734), μ = 2.839 mmꢀ1, 247 parameters, 1 restraint, R1 =
0.0286 (I > 2σ), wR2 (all data) = 0.0713, GOF = 1.023, max./min. residual
electron density 3.040/ꢀ1.179 e Åꢀ3
.
[(k2-2-C6F4PPh2)Pd(μ-I)(μ-2-C6F4PPh2)Pd(μ-I)2Pd(μ-I)(μ-2-C6F4-
1HNMR:δ6.8ꢀ8.0 (m, 40 H, aromatics). 31PNMR:δꢀ3.7 (br s), 20.7
(s). ESI-MS (m/z): 1043 [M ꢀ H]þ. Anal. Calcd for C54H40BrF4P3Pd: C
62.12, H 3.86, Br 7.65, F 7.28. Found: C 62.54, H 3.90, Br 7.48, F 6.88.
X-ray Crystal Structure Data. 2-Me3SnC6F4PPh2 (7). Empirical
formula C21H19F4PSn, fw = 497.02, temperature 110(2) K, monoclinic,
space group P21/c, a = 7.7721(1) Å, b = 27.0559(4) Å, c = 19.2390(3) Å,
β = 95.172(1)ο, V = 4029.13(10) Å3, Z = 8, Fcalcd = 1.639 Mg/m3, crystal
dimensions 0.40 ꢁ 0.32 ꢁ 0.27 mm3, 100 829 reflections, 21 885 indepen-
dent (Rint = 0.0651), μ = 1.386 mmꢀ1, 487 parameters, 0 restraints, R1 =
0.0352 (I > 2σ), wR2 (all data) = 0.0711, GOF = 1.037, largest diff. peak and
PPh2)Pd(k2-2-C6F4PPh2)] 2CH2Cl2 (14),. Empirical formula C74H44-
3
Cl4F16I4P4Pd4, fw = 2435.97, temperature 100(2) K, triclinic, space group
P1, a = 10.0756(3) Å, b = 13.3568(5) Å, c = 16.5002(6) Å, R =
83.309(2)o, β = 76.136(2)o, γ = 71.196(2)o, V = 2038.94(12) Å3,
Z = 1, Fcalcd = 1.984 Mg/m3, crystal dimensions 0.07 ꢁ 0.05 ꢁ
0.03 mm3, 35 118 reflections, 7979 independent (Rint = 0.0388), μ =
2.669 mmꢀ1, 493 parameters, 46 restraints, R1 = 0.0495 (I > 2σ), wR2 (all
data) = 0.1263, GOF = 1.068, max./min. residual electron density
1.844/ꢀ1.917 e Åꢀ3
.
[Pd2(μ-SCN)2(k2-2-C6F4PPh2)2] (15). Empirical formula C38H20-
F8N2P2Pd2S2, fw = 995.42, temperature 110(2) K, monoclinic, space
group P21/n, a = 8.2531(3) Å, b = 17.7696(5) Å, c = 12.3228(4) Å,
β = 93.809(2)o, V = 1803.20(10) Å3, Z = 2, Fcalcd = 1.833 Mg/m3,
crystal dimensions 0.19 ꢁ 0.05 ꢁ 0.04 mm3, 28 711 reflections, 4784
independent (Rint = 0.0775), μ = 1.276 mmꢀ1, 244 parameters, 0
restraints, R1 = 0.0374 (I > 2σ), wR2 (all data) = 0.0808, GOF = 1.053,
hole 0.629/ꢀ0.776 e Åꢀ3
.
[Pd2Br2(k2-2-C6F4PPh2)2] CH2Cl2 (8). Empirical formula C37H22Br2-
3
Cl2F8P2Pd2, fw = 1123.99, temperature 110(2) K, triclinic, space group
P1, a = 19.5851(3) Å, b = 20.3668(4) Å, c = 23.0951(4) Å,
R = 104.989(1)o, β = 102.553(1)o, γ = 102.556(1)o, V = 8312.4(3) Å3,
Z = 9, Fcalcd = 2.021 Mg/m3, crystal dimensions 0.40 ꢁ 0.25 ꢁ 0.10 mm3,
252 823 reflections, 62 527 independent (Rint = 0.1178), μ = 3.437 mmꢀ1
,
max./min. residual electron density 1.090/ꢀ0.868 e Åꢀ3
.
870 parameters, 0 restraints, R1 = 0.0490 (I > 2σ), wR2 (all data) = 0.1259,
[Pd4(μ-SCN)4(k2-2-C6F4PPh2)2(μ-2-C6F4PPh2)2] 2.5CH2Cl2 (16).
GOF = 1.33, max./min. residual electron density: 2/ꢀ2 e Åꢀ3
.
3
Empirical formula C78.50H45Cl5F16N4P4Pd4S4, fw = 2203.16, tem-
perature 100(2) K, triclinic, space group P1, a = 13.5687(3) Å,
b = 16.0586(3) Å, c = 20.6429(5) Å, R = 91.7337(10)o,
β = 97.6461(10)o, γ = 110.4889(10)o, V = 4161.64(16) Å3, Z = 2, Fcalcd
= 1.758 Mg/m3, crystal dimensions 0.35 ꢁ 0.25 ꢁ 0.20 mm3, 92 367
reflections, 26 517 independent (Rint = 0.0633), μ = 1.270 mmꢀ1, 1098
parameters, 129 restraints, R1 = 0.0454 (I > 2σ), wR2 (all data) = 0.1189,
Complex 8 crystallizes as a 9-fold superstructure that can be regarded
as a commensurate modulation of a Z = 1 parent structure with unit cell
axes a = 1/9(2a ꢀ 3b þ c), b = 1/9(4a þ 3b þ 2 c), c = 1/3(ꢀa þ c) and
one-ninth the cell volume.
[Pd2(μ-O2CCH3)2(k2-2-C6F4PPh2)2] 0.5C6H6 (9). Empirical formula
3
C43H29O4F8P2Pd2, fw = 1036.40, temperature 90(2) K, monoclinic,
space group P21/n, a = 12.3560(1) Å, b = 16.7991(2) Å, c = 19.4832(2) Å,
β = 105.467(1)o, V = 3897.66(7) Å3, Z = 4, Fcalcd = 1.766 Mg/m3, crystal
dimensions 0.24 ꢁ 0.18 ꢁ 0.18 mm3, 144 509 reflections, 21 221
independent (Rint = 0.0649), μ = 1.087 mmꢀ1, 532 parameters, 0
restraints, R1 = 0.0315 (I > 2σ), wR2 (all data) = 0.0666, GOF = 1.038,
GOF = 1.061, max./min. residual electron density 2.239/ꢀ1.486 e Åꢀ3
.
[Pd(acac)(k2-2-C6F4PPh2)] (17). Empirical formula C23H17F4O2PPd,
fw = 538.74, temperature 110(2) K, monoclinic, space group P21/n,
a = 14.5018(2) Å, b = 13.2373(2) Å, c = 22.7098(3) Å, β =
108.237(1)o, V = 4140.50(10) Å3, Z = 8, Fcalcd = 1.728 Mg/m3, crystal
dimensions 0.37 ꢁ 0.27 ꢁ 0.11 mm3, 107 158 reflections, 22 422 indepen-
dent (Rint = 0.0540), μ = 1.728 mmꢀ1, 559 parameters, 0 restraints, R1 =
0.0344 (I > 2σ), wR2 (all data) = 0.0770, GOF = 1.058, max./min. residual
max./min. residual electron density 0.675/ꢀ0.836 e Åꢀ3
.
[Pd2(μ-O2CPh)2(k2-2-C6F4PPh2)2)] (10). Empirical formula C50H30F8-
O4P2Pd2, fw = 1121.48, temperature 110(2) K, triclinic, space group P1, a =
11.5541(2) Å, b = 12.2585(2) Å, c = 16.5603(3) Å, R = 93.640(1)o, β =
93.386(1)o, γ = 110.655(1)o, V = 2181.99(7) Å3, Z = 2, Fcalcd = 1.707 Mg/
m3, crystal dimensions 0.45 ꢁ 0.22 ꢁ 0.10 mm3, 78 921 reflections, 20 656
independent (Rint = 0.0581), μ = 0.979 mmꢀ1, 595 parameters, 0 restraints,
R1 = 0.0313 (I > 2σ), wR2 (all data) = 0.0769, GOF = 1.048, max./min.
electron density 0.718/ꢀ0.829 e Åꢀ3
.
[Pd2(μ-acac)2(μ-2-C6F4PPh2)2] (18). Empirical formula C46H34F8O4-
P2Pd2, fw = 1077.47, temperature 150(2) K, monoclinic, space group
P21/n, a = 11.5391(2) Å, b = 29.6519(7) Å, c = 13.1661(3) Å, β =
109.696(1)o, V = 4241.30(16) Å3, Z = 4, Fcalcd = 1.687 Mg/m3, crystal
dimensions 0.19 ꢁ 0.07 ꢁ 0.06 mm3, 62 815 reflections, 11 260 indepen-
dent (Rint = 0.0522), μ = 1.003 mmꢀ1, 588 parameters, 74 restraints, R1 =
0.0381 (I > 2σ), wR2 (all data) = 0.0866, GOF = 1.051, max./min. residual
residual electron density 0.925/ꢀ1.345 e Åꢀ3
.
[Pd2(μ-O2CCH3)2(μ-2-C6F4PPh2)2] C6H6 (11). Empirical formula
3
C46H32F8O4P2Pd2, fw = 1075.46, temperature 90(2) K, monoclinic,
space group C2/c, a = 21.6513(3) Å, b = 9.5972(2) Å, c = 20.2274(3) Å,
β = 106.178(1)o, V = 4036.65(12) Å3, Z = 4, Fcalcd = 1.770 Mg/m3,
crystal dimensions 0.24 ꢁ 0.22 ꢁ 0.16 mm3, 72 254 reflections, 14 016
independent (Rint = 0.0508), μ = 1.053 mmꢀ1, 280 parameters, 0
restraints, R1 = 0.0305 (I > 2σ), wR2 (all data) = 0.0736, GOF = 1.053,
electron density 0.942/ꢀ0.756 e Åꢀ3
.
[Pd2(μ-acac)2(μ-2-C6F4PPh2)2].C6H14 (18). Empirical formula
C52H48F8O4P2Pd2, fw = 1163.64, temperature 110(2) K, monoclinic,
space group C2/c, a = 16.5901(3) Å, b = 25.6576(6) Å, c = 11.3881(2)
Å, β = 90.314(1)o, V = 4847.41(17) Å3, Z = 4, Fcalcd = 1.594 Mg/m3,
crystal dimensions 0.17 ꢁ 0.13 ꢁ 0.12 mm3, 47 195 reflections, 7068
independent (Rint = 0.0691), μ = 0.884 mmꢀ1, 319 parameters, 2
restraints, R1 = 0.0332 (I > 2σ), wR2 (all data) = 0.0821, GOF = 1.078,
max./min. residual electron density 1.511/ꢀ1.571 e Åꢀ3
.
[Pd2(μ-O2CCH3)2(μ-2-C6F4PPh2)2] (11). Empirical formula C40H26-
F8O4P2Pd2, fw = 997.35, temperature 110(2) K, orthorhombic, space
group Pna21, a = 19.7970(3) Å, b = 9.9514(1) Å, c = 18.0698(3) Å,
V = 3559.89(9) Å3, Z = 4, Fcalcd = 1.861 Mg/m3, crystal dimensions
max./min. residual electron density 0.893/ꢀ0.975 e Åꢀ3
.
[Pd2Cl2(NCMe)2(μ-2-C6F4PPh2)2] (19). Empirical formula C40H26-
Cl2F8N2OP2Pd2, fw = 1050.28, temperature 90(2) K, monoclinic, space
group C2/c, a = 20.0714(4) Å, b = 18.9384(5) Å, c = 10.4669(2) Å,
0.12 ꢁ 0.06 ꢁ 0.03 mm3, 52 431 reflections, 8467 independent (Rint
=
0.0906), μ = 1.186 mmꢀ1, 505 parameters, 1 restraint, R1 = 0.0383 (I > 2σ),
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Organometallics
ARTICLE
β = 103.150(1)o, V = 3874.35(15) Å3, Z = 4, Fcalcd = 1.801 Mg/m3, crystal
dimensions 0.28 ꢁ 0.15 ꢁ 0.06 mm3, 65 109 reflections, 13 502 inde-
pendent (Rint = 0.0562), μ = 1.224 mmꢀ1, 270 parameters, 12 restraints,
R1 = 0.0339 (I > 2σ), wR2 (all data) = 0.0756, GOF = 1.053, max./min.
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residual electron density 1.696/ꢀ1.100 e Åꢀ3
.
[Pd2Br2(NCMe)2(μ-2-C6F4PPh2)2] C6H6 (20),. Empirical formula
3
C46H32Br2F8N2P2Pd2, fw = 1199.30, temperature 100(2) K, mono-
clinic, space group C2/c, a = 19.2331(4) Å, b = 17.0626(4) Å,
c = 14.8104(3) Å, β = 118.144(1)o, V = 4285.62(16) Å3, Z = 4,
Fcalcd = 1.859 Mg/m3, crystal dimensions 0.12 ꢁ 0.08 ꢁ 0.06 mm3,
58 115 reflections, 7433 independent (Rint = 0.0850), μ = 2.850 mmꢀ1
,
282 parameters, 0 restraints, R1 = 0.0372 (I > 2σ), wR2 (all data) = 0.0900,
GOF = 1.031, max./min. residual electron density 1.091/ꢀ1.350 e Åꢀ3
.
[Pd2Br2(NCMe)2(μ-2-C6F4PPh2)2] CH3CN (20). Empirical formula
(18) Bennett, M. A.; Contel, M.; Hockless, D. C. R.; Welling, L. L.;
Willis, A. C. Inorg. Chem. 2002, 41, 844–855.
3
C42H29Br2F8N3P2Pd2, fw = 1162.24, temperature 110(2) K, mono-
clinic, space group P21/n, a = 13.0981(4) Å, b = 16.0475(6) Å,
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c = 20.4163(8) Å, β = 101.936(2)o, V = 4198.6(3) Å3, Z = 4, Fcalcd
=
1.839 Mg/m3, crystal dimensions 0.33 ꢁ 0.16 ꢁ 0.07 mm3, 36 031
reflections, 12 198 independent (Rint = 0.0781), μ = 2.907 mmꢀ1, 541
parameters, 14 restraints, R1 = 0.0467 (I > 2σ), wR2 (all data) = 0.0853,
GOF = 1.042, max./min. residual electron density 0.848/ꢀ1.062 e Åꢀ3
.
trans-[PdBr(k2-2-C6F4PPh2)(PPh3)] (21). Empirical formula C36H25-
BrF4P2Pd, fw = 781.84, temperature 200 K, monoclinic, space group
P21/n, a = 9.9090(1) Å, b = 14.4677(1) Å, c = 21.3719(2) Å,
β = 94.5475(6)o, V = 3054.24(5) Å3, Z = 4, Fcalcd = 1.700 Mg/m3,
crystal dimensions 0.22 ꢁ 0.19 ꢁ 0.03 mm3, 78 537 reflections, 8939
independent (Rint = 0.039), μ = 2.07 mmꢀ1, 397 parameters, 0 restraints,
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.
trans-[PdBr(kC-2-C6F4PPh2)(PPh3)2] (23). Empirical formula
C54H40BrF4P3Pd, fw = 1044.08, temperature 110(2) K, orthorhombic,
space group Pbcn, a = 34.8898(6) Å, b = 12.6979(2) Å, c = 20.4723(4) Å,
V = 9069.8(3) Å3, Z = 8, Fcalcd = 1.529 Mg/m3, crystal dimensions
0.20 ꢁ 0.14 ꢁ 0.08 mm3, 110 769 reflections, 15 726 independent
(Rint = 0.0704), μ = 1.450 mmꢀ1, 580 parameters, 37 restraints, R1 =
0.0401 (I > 2σ), wR2 (all data) = 0.0789, GOF = 1.019, max./min.
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residual electron density 0.654/ꢀ0.941 e Åꢀ3
’ AUTHOR INFORMATION
.
Corresponding Author
*E-mail: suresh.bhargava@rmit.edu.au.
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’ ACKNOWLEDGMENT
J.W. thanks the Deutscher Akademischer Austauschdienst
(DAAD) for the award of a Postdoctoral Fellowship.
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