Coordination Properties of Perfluoroethyl- and Perfluorophenyl-Substituted Phosphonous acids, RfP(OH)2

Article abstract of DOI:10.1002/chem.201501984

Phosphinic acids, R^fP(O)(OH)H (R^f=CF₃, C₂F₅, C₆F₅), turned out to be excellent preligands for the coordination of phosphonous acids, R^fP(OH)₂. Addition of C₂F₅P(O)(OH)H to solid PtCl₂ under different reaction conditions allows the isolation and full characterization of the mononuclear complexes [ClPt{P(C₂F₅)(OH)O}{P(C₂F₅)(OH)₂}₂] and [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}] containing hydrogen-bridged [R^fP(OH)O]^- and R^fP(OH)₂ units. Further deprotonation of [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] leads to the formation of the dianionic platinate, [Pt{P(C₂F₅)(OH)O}₄]^2-, revealing four intramolecular hydrogen bridges. With PdCl₂ the dinuclear complex [Pd₂(μ-Cl)₂{[P(C₂F₅)(OH)O]₂H}₂] was isolated and characterized. The Cl^- free complex [Pd{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] was also prepared and deprotonated to the dianionic palladate, [Pd{P(C₂F₅)(OH)O}₄]^2-. Both compounds were characterized by NMR spectroscopy, IR spectroscopy, and X-ray analyses. In addition, the C₆F₅ derivatives [ClPt{P(C₆F₅)(OH)O}{P(C₆F₅)(OH)₂}₂] and [Pd₂(μ-Cl)₂{[P(C₆F₅)(OH)O]₂H}₂] as well as the CF₃ derivative [Pd₂(μ-Cl)₂{[P(CF₃)(OH)O]₂H}₂] were synthesized and fully characterized. Phosphonous acid complexes are inert towards air and moisture and can be stored for several months without decomposition. The catalytic activity of the palladium complexes in the Suzuki cross-coupling reaction between 1-bromo-3-fluorobenzene and phenyl boronic acid was demonstrated. A tautomeric equilibrium between phosphinic, RP(O)(OH)H, and phosphonous acids, RP(OH)₂, is evidenced by this work (see figure). The coordination properties of phosphonous acids with electron-withdrawing CF₃, C₂F₅, and C₆F₅ groups is also described.

Full text of DOI:10.1002/chem.201501984

DOI: 10.1002/chem.201501984
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&
Coordination Chemistry |Hot Paper|
Coordination Properties of Perfluoroethyl- and Perfluorophenyl-
Substituted Phosphonous acids, RfP(OH)2
Nadine Allefeld,[a] Boris Kurscheid,[a] Beate Neumann,[a] Hans-Georg Stammler,[a]
Nikolai Ignat’ev,[b] and Berthold Hoge*[a]
Abstract: Phosphinic acids, RfP(O)(OH)H (Rf =CF3, C2F5, C6F5),
turned out to be excellent preligands for the coordination of
phosphonous acids, RfP(OH)2. Addition of C2F5P(O)(OH)H
to solid PtCl2 under different reaction conditions allows
the isolation and full characterization of the mono-
nuclear complexes [ClPt{P(C2F5)(OH)O}{P(C2F5)(OH)2}2] and
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] was also prepared and de-
protonated to the dianionic palladate, [Pd{P(C2F5)(OH)O}4]2À.
Both compounds were characterized by NMR spectroscopy,
IR spectroscopy, and X-ray analyses. In addition, the C6F5 de-
rivatives [ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2] and [Pd2(m-
Cl)2{[P(C6F5)(OH)O]2H}2] as well as the CF3 derivative [Pd2(m-
Cl)2{[P(CF3)(OH)O]2H}2] were synthesized and fully character-
ized. Phosphonous acid complexes are inert towards air and
moisture and can be stored for several months without de-
composition. The catalytic activity of the palladium com-
plexes in the Suzuki cross-coupling reaction between 1-
bromo-3-fluorobenzene and phenyl boronic acid was dem-
onstrated.
[Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}]
containing
hydrogen-
bridged [RfP(OH)O]À and RfP(OH)2 units. Further deproton-
ation of [Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] leads to the forma-
tion of the dianionic platinate, [Pt{P(C2F5)(OH)O}4]2À, reveal-
ing four intramolecular hydrogen bridges. With PdCl2 the
dinuclear complex [Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2] was iso-
lated and characterized. The ClÀ free complex
Introduction
1968 that by coordination to suitable metals the phosphinous
acid can be trapped and removed from the equilibrium.[3]
A
A number of chemical reactions in the laboratory as well as in
industry are based upon the use of catalysts. The search for
catalysts well suited for a planned transformation is usually not
trivial. Apart from a high catalytic activity, the catalyst has to
be selective, easy to handle, and resistant towards air and
moisture. Commonly used transition-metal complexes of high
catalytic activity often bear phosphorus-based ligands, for ex-
ample, alkyl- or aryl-substituted phosphanes. A serious draw-
back, however, is that these compounds are in general sensi-
tive towards oxygen and moisture. Another popular approach
is the employment of secondary phosphane oxides (SPOs),
R2P(O)H, as preligands for the synthesis of phosphinous acid
complexes.[1,2] Diorganylphosphane oxides, R2P(O)H, are in
a tautomeric equilibrium with the corresponding phosphinous
acid, R2POH. For electron-donating alkyl or aryl substituents,
the equilibrium is in general completely shifted to the pentava-
lent phosphane oxide. Chatt and Heaton demonstrated in
whole variety of such complexes is known in the literature and
was successfully tested as catalysts for, for example, cross-cou-
pling reactions.[1,2]
Formal substitution of one organyl group by a hydroxyl
group leads to the formation of a water-stable phosphinic
acid. Likewise, a tautomerization into the corresponding phos-
phonous acid can be formulated. The equilibrium in Equa-
tion (1) is, in general, completely shifted to the phosphinic
acid, for electron-donating as well as for electron-withdrawing
groups. Therefore there are no reports on a free phosphonous
acid in the literature.
The attempted coordination of phosphinic acids to a suitable
metal leads to the formation of phosphonous acid complexes.
The coordinating properties of phosphonous acids are not well
investigated and only a small number of complexes thereof
are described.[4] The topic of this work is the study of the ligat-
ing properties of phosphonous acids with electron-withdraw-
ing groups, especially the pentafluoroethyl group, towards the
catalytically relevant metals palladium and platinum. The em-
ployment of the new phosphonous acid complexes of palladi-
um as catalysts in Suzuki-type reactions will be discussed.
[a] Dr. N. Allefeld, Dr. B. Kurscheid, B. Neumann, Dr. H.-G. Stammler,
Prof. Dr. B. Hoge
Centrum für Molekulare Materialien
Fakultät für Chemie, Anorganische Chemie II
Universität Bielefeld, Universitätsstrasse 25
33619 Bielefeld (Germany)
E-mail: b.hoge@uni-bielefeld.de
[b] Dr. N. Ignat’ev
PM-APR-FT, Merck KGaA
Frankfurter Strasse 250, 64293 Darmstadt (Germany)
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gen bridge between a phosphonous acid and a phosphonito
unit.[5] The solvent THF molecule is coordinated by a hydrogen
bridge resulting in a short O7···O4 separation of 242.6(1) pm.
All hydrogen atoms were refined isotropically and the distance
O7ÀH7 of 104(5) pm indicates a protonation of THF by 1 at
least in solid state. The oxygen atoms O1 and O6 are coordi-
nated to an adjacent molecule through intermolecular hydro-
gen bridges featuring O1···O6(a)
Results and Discussion
Platinum complexes
A slurry of platinum(II) chloride in THF smoothly reacts with
3.5equivalents of pentafluoroethylphosphinic acid affording
[ClPt{P(C2F5)(OH)O}{P(C2F5)(OH)2}2], 1 (Scheme 1). After filtration
and O1(a)···O6 distances of
256.5(3) pm, respectively, build-
ing a dimer.
Similarly, pentafluorophenyl-
phosphinic acid, (C6F5)P(O)(OH)H,
functions as a precursor for the
corresponding
phosphonous
acid as a ligand in transition-
metal complexes. Thus treat-
Scheme 1. Synthesis of the platinum complexes 1 and 3.
and removal of all volatile compounds in vacuo, the product is
obtained as a viscous oil. Its 31P NMR spectrum shows the exis-
tence of two chemically inequivalent phosphorus atoms. The
resonance for the phosphorus atom PA at d=61.3 ppm reveals
platinum satellites with
a
1J(Pt,PA) coupling constant of
phosphorus-based ligand in
4277 Hz, characteristic for
a
a trans position to a chloro ligand. Furthermore, a triplet of
2
triplets splitting due to the J(P,F) coupling of 99 Hz and the
2J(PA,PB) coupling of 28 Hz, respectively, is observed. The reso-
nance for the phosphorus atom PB at d=94.7 ppm exhibits
1
platinum satellites with a significantly lower J(Pt,PB) coupling
constant of 3172 Hz. In square-planar platinum complexes,
such a value is characteristic of a phosphane ligand in trans
position to a second phosphane ligand. Because of a long-
range 4J(P,F) coupling of a phosphorus atom PB to the CF2
group of the phosphonous acid in the trans position, the phos-
phorus atoms are magnetically inequivalent resulting in
a high-order multiplet. By 19F-decoupling of the 31P NMR spec-
trum, the spin system can be simplified and the resonance at
d=94.7 ppm reveals a doublet splitting with a 2J(PAPB) cou-
pling constant of 27 Hz. Consistently, the 195Pt NMR spectrum
is characterized by a doublet of triplets at d=À4694.1 ppm
with a 1J(Pt,PA) coupling constant of 4276 Hz and a 1J(Pt,PB)
coupling constant of 3177 Hz. Single crystals of 1, suitable for
an X-ray structure determination, were grown from THF solu-
tion. Complex 1 crystallizes with one solvent molecule in the
Figure 1. Molecular structure of [H-THF]+[ClPt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}]À
(1); 50% probability amplitude displacement ellipsoids are shown; selected
bond lengths [pm] and angles [8]: P1ÀPt1 229.53(6), P1ÀO1 152.1(2), P1ÀO2
158.8(2), P2ÀPt1 221.95(6), P2ÀO3 155.9(2), P2ÀO4 154.0(2), P3ÀPt1
231.13(6), P3ÀO5 157.2(2), P3ÀO6 155.6(2), Pt1ÀCl1 235.86(6), O1-P1-O2
107.5(1), O3-P2-O4 108.5(1), O5-P3-O6 107.2(1).
¯
triclinic space group P1 (no. 2). The molecular structure is
shown in Figure 1. Formally, compound 1 features two phos-
phonous acids and one phosphonito unit, which should be
distinguishable from each other based on the PÀO bond
lengths. A differentiation is difficult in solution because of fast
proton exchange. In the solid state, however, the phosphonous
acids at P2 and P3 exhibit two longer PÀO bonds of about
155.7 pm in accordance with single bonds. The ligand at P1 ex-
ment of a slurry of PtCl2 in diethyl ether with (C6F5)P(O)(OH)H
in a molar ratio of 1:3 at room temperature affords the mono-
nuclear complex [ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2] (2) as
a light-yellow solid in 76% yield. The 31P NMR spectrum of 2
hibits one short P1ÀO1 bond of 152.1(2) pm and one long P1À exhibits two resonances at d=49.3 and 97.1 ppm for two
O2 bond of 158.8(2) pm due to the double and single bond of
a phosphonito unit.
chemically inequivalent phosphorus atoms PA and PB, respec-
1
tively. The J(Pt,P) coupling constants of 4606 Hz for the phos-
The short O3···O1 distance of 254.1(1) pm as well as the
O4···O5 distance of 286.3(3) pm are characteristic for a hydro-
phorus atom PA trans to a chloro ligand and 3223 Hz for the
phosphorus atoms PB cis to the chloro ligand are in agreement
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with the values obtained for complex 1. Accordingly, the 195Pt
tafluorophenyl derivative under similar reaction conditions was
not observed. Recrystallization of the C2F5 derivative from di-
ethyl ether solution yielded colorless crystals. Complex 3 lies at
a center of inversion and crystallizes in the monoclinic space
group C2/c (No. 15) with two solvent molecules per formula
unit. The molecular structure reveals short O1···O3# and
O1#···O3 separations of 245.8(4) pm, indicating an intramolecu-
lar hydrogen bridge of a quasichelating unit. The platinum
center deviates slightly from an ideal square-planar geometry
(Figure 3).
NMR spectrum reveals
a
doublet of triplets at d=
À4692.2 ppm.
Single crystals of 2 were grown from diethyl ether. Com-
pound 2 crystallizes in the monoclinic space group P21/n (no.
14) with two (unprotonated) solvent molecules Et2O per for-
mula unit linked by hydrogen bridges. The molecular structure
in the solid state (Figure 2) reveals a square-planar platinum
Figure 2. Molecular structure of [ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2], 2·2(Et2O);
50% probability amplitude displacement ellipsoids are shown, solvent mole-
cules omitted for clarity; selected bond lengths [pm] and angles [8]: P1ÀPt1
228.74(6), P1ÀO1 156.3(2), P1ÀO2 155.8(2), P2ÀPt1 221.37(6), P2ÀO3 155.6(2),
P2ÀO4 156.3(2), P3ÀPt1 229.82(6), P3ÀO5 156.6(2), P3ÀO6 156.1(2), O1-P1-
O2 106.04(9), O3-P2-O4 108.73(9), O5-P3-O6 107.4(1); disorder of solvent
molecule on two positions.
center coordinated by two phosphonous acids, one phospho-
nito unit and a chloro ligand. The PÀO bond lengths vary be-
tween 155.6 and 156.6 pm, making a differentiation between
phosphonous acid and phosphonito unit impossible as well as
the distances inside the intramolecular hydrogen bridge of
H2ÀO2 113(4) pm and H2ÀO3 131(4) pm.
Figure 3. Molecular structure of [Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 3·2Et2O; H
atoms and solvent molecules omitted for clarity; selected bond lengths [pm]
and angles [8]: P1ÀPt1 231.0(1), P1ÀO1 154.9(3), P1ÀO2 153.5(3), P2ÀPt1
231.86(8), P2ÀO3 153.3(3), P2ÀO4 155.5(3), O1-P1-O2 107.8(2), O3-P2-O4
110.3(2); disorder of C2F5 groups on two positions.
As shown in Scheme 1, the treatment of (C2F5)P(O)(OH)H
with platinum dichloride in THF selectively yields the tris-sub-
stituted complex 1 in 58% yield, whereas in dichloromethane
the ClÀ free complex [Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 3, is ob-
tained in 70% yield. Two equivalents of hydrogen chloride are
eliminated under the formation of two phosphonous acid
phosphonito units, [P(C2F5)(OH)O···H···O(OH)(C2F5)P]À. Complex
3 is also prepared from [Pt(acac)2] (acac=acetylacetonato).
Both acetylacetonato ligands are protonated and replaced by
two [P(C2F5)(OH)O···H···O(OH)(C2F5)P]À units. The proton NMR
spectrum reveals one resonance at d=13.7 ppm because of
the rapid exchange of the hydrogen atoms. The 31P NMR spec-
trum is characterized by one resonance at d=93.0 ppm with
platinum satellites (1J(Pt,P)=3048 Hz). Because of the long
range coupling of the phosphorus atoms to the CF2 groups of
the adjacent ligands, the phosphorus atoms are magnetically
inequivalent. This is reflected in a multiplet of higher order in
the 31P NMR spectrum. The formation of a corresponding pen-
The treatment of platinum(II) acetylacetonate, [Pt(acac)2]
with bis(pentafluoroethyl)phosphinous acid, (C2F5)2POH, gives
rise to the selective substitution of only one acetylacetonato
ligand by a phosphinous acid phosphinito quasichelating
unit.[6] An explanation for this different reactivity could be the
decreased steric demand of the OH group compared with that
of the pentafluoroethyl group. The O···O distance of the quasi-
chelating unit [P(C2F5)2O···H···O(C2F5)2P]À of 242.02(3) pm is
comparable to the O1···O3 distance of complex 3.[6]
The pronounced tendency of the complexes 1, 2, and 3 to
coordinate solvent molecules through strong hydrogen
bridges reflects their high acidity. Deprotonation leads to the
formation of four intramolecular hydrogen bridges (Scheme 2).
The addition of two equivalents of 1,8-bis(dimethylamino)-
naphthalene
to
a
freshly
prepared
solution
of
[Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 3, in diethyl ether results in
1
the precipitation of a colorless solid. The H NMR spectrum ex-
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Scheme 2. Synthesis of complexes 3 and 5, as well as of the metallates 4 and 6.
Table 1. 1H, 31P, and 195Pt NMR spectroscopic data of 1, 2, 3, and 4.
d(1H) d(31P)
[ppm]
d(195Pt) 1J(Pt,P)
[Hz]
61.3 (PA)
4277
[ClPt{P(C2F5)(OH)O}{P(C2F5)(OH)2}2], 1[a]
11.9 94.7 (PB) À4694.1 3172
49.3 (PA)
4606
[ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2], 2[b]
[Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 3[c]
11.6 97.1 (PB) À4692.2 3223
13.7 93.0
–
3048
À5191.1 2751
2[C14H19N2]+[Pt{P(C2F5)(OH)O}4]2À, 4[d] 16.5 85.9
[a] [D]Chloroform. [b] Et2O. [c] [D8]THF. [d] [D3]Acetonitrile.
hibits two signals in the ratio of 2:1 for acidic protons at d=
16.5 ([Pt{P(C2F5)(OH)O}4]2À) and 18.7 ppm for protonated 1,8-
bis(dimethylamino)naphthalene. The NMR spectroscopic data
of 4 show significant deviations from the corresponding data
of the neutral complex 3 (Table 1).
The treatment of palladium(II) acetylacetonate, [Pd(acac)2],
with four equivalents of (C2F5)P(O)(OH)H smoothly affords
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] (5) as a colorless oil because
of solvent impurities. The 31P NMR spectrum of the compound
is characterized by one complex multiplet (d(31P)=80.0 ppm).
Figure 4. Molecular structure of 2[C14H19N2]+[Pd{P(C2F5)(OH)O}4]2À, 6·CH2Cl2;
cations and solvent molecule omitted for clarity; selected bond lengths [pm]
and angles [8]: Pd1ÀP1 234.16(6), Pd1ÀP3 235.47(7), P1ÀO1 152.4(2), P1ÀO2
155.6(2), P3ÀO5 155.6(2), P3ÀO6 153.2(2), O1-P1-O2 108.5(1), Pd1-P1-O1
116.64(7), Pd1-P1-O2 114.24(7), O5-P3-O6 108.1(1), Pd1-P3-O5 116.72(8), Pd1-
P3-O6 115.1(1).
1
The H NMR spectrum shows one signal at d=13.4 ppm. The
19F NMR spectrum reveals two sets of signals at d=À121.9
(CF2)
and
À79.7 ppm
(CF3)
for
the
C2F5
unit.
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] (5) is readily deprotonated by
1,8-bis(dimethylamino)naphthalene. The product, 2[C14H19N2]+
[Pd{P(C2F5)(OH)O}4]2À (6), was isolated as a colorless solid. The
twofold deprotonation is clearly reflected in the 31P NMR spec-
trum. Thus, the resonance of the phosphonous acid ligands is
shifted from d=80.0 ppm for the neutral compound 5 to d=
97.7 ppm for the dianion 6. The proton NMR spectrum reveals
two singlets at d=12.3 ppm for the protons of the palladate
unit and at d=18.7 ppm for the acidic proton of the cation.
Single crystals of 6 were grown from dichloromethane solu-
tion. The crystal structure (Figure 4) exhibits four intramolecu-
lar hydrogen bridges, as evidenced by four short O···O distan-
ces of about 243.6 pm. The hydrogen atoms could not be re-
fined isotropically and were included at calculated positions.
The oxygen atoms are bent out of the plane defined by the
metal and the four phosphorus atoms allowing hydrogen
bonding over all eight oxygen atoms. The C2F5 units are per-
pendicular to the complex plane in the opposite direction of
the oxygen atoms. The solid-state structure of the neutral com-
plexes 1, 2, 3, 8a, 8b, and 8c is dominated by intra- and inter-
molecular hydrogen bridges to neighboring complex units or
solvent molecules are prominent. In contrast to this, com-
pound 6 exhibits in the solid-state isolated palladate units
without any intermolecular hydrogen bridges. In the phospho-
nito units one shorter (152.9 pm) and one slightly elongated
PÀO bond (155.2 pm) differing by only 2 pm are obvious.
The treatment of palladium(II) chloride with (C2F5)P(O)(OH)H
resulted in a less selective reaction. The 31P NMR spectrum of
the reaction mixture is characterized by three resonances
(Figure 5). The signals at d=88.3 (PA) and 103.4 ppm (PB)
belong
to
the
mononuclear
palladium
complex
[ClPd{P(C2F5)(OH)O}{P(C2F5)(OH)2}2] (7a), evidenced by the
2J(PA,PB) coupling constant of 11 Hz. Accordingly the
31P{19F} NMR spectrum shows a triplet for PA and a doublet for
the phosphorus atoms PB. The second product detected in the
reaction mixture is the dinuclear palladium complex 8a with
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Figure 5. 31P NMR spectrum of the diethyl ether solution of PdCl2 and
(C2F5)P(O)(OH)H.
a broad multiplet at d=80.2 ppm. Removal of all volatile com-
ponents and heating the residue in vacuo shifted the product
ratio in favor of the dinuclear complex, however, neither
excess (C2F5)P(O)(OH)H nor 7a could be completely removed.
Satisfying results were achieved by a change of the solvent
from diethyl ether to dichloromethane. The treatment of a pal-
ladium(II) chloride slurry in dichloromethane with
(C2F5)P(O)(OH)H results in the precipitation of a colorless solid
identified as the dinuclear compound 8a. Excess phosphinic
acid was removed by washing the precipitate thoroughly with
dichloromethane. It should be noted that attempts to dissolve
8a in the presence of (C2F5)P(O)(OH)H always furnished 7a as
a byproduct (Scheme 3).
Figure 6. Molecular structure of [Pd2(m-Cl)2{[P(C2F5)(OH)Oj2H}2], 8a (co-crystal
with 2[H3O·(OEt2)2]+[Pd{P(C2F5)(OH)O}4]2À (comp. the dianion of 6)); H atoms
omitted for clarity; selected bond lengths [pm] and angles [8]: Pd1ÀP1
223.1(1), Pd1ÀP2 223.3(1), P1ÀO1 154.4(3), P1ÀO2 154.3(3), P2ÀO3 152.1(3),
P2ÀO4 154.9(3), O1ÀO3 248.6(4), O6ÀO7 249.5(4), Pd1-P1-O1 119.7(1), Pd1-
P2-O3 116.9(1).
[P(C2F5)(OH)O···H···O(OH)(C2F5)P]À units. The PÀO bond lengths
are relatively short and vary between 151.8(3) and 155.6(3) pm.
The treatment of solid palladium(II) chloride with
(CF3)P(O)(OH)H in diethyl ether furnished
a mixture of
[ClPd{P(CF3)(OH)O}{P(CF3)(OH)2}2] (7b), (d(31P)=80.4 (PA),
97.4 ppm (PB), 2J(P,P)=26 Hz) and the dinuclear complex
[Pd2(m-Cl)2{[P(CF3)(OH)O]2H}2] (8b) (d(31P)=74.8 ppm; Table 2)).
Table 2. 1H and 31P NMR spectroscopic data of 5, 6, 7a, b, 8a, b, and c.
d(1H)[a]
d(31P)
[ppm]
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 5[b]
2[C14H19N2]+[Pd{P(C2F5)(OH)O}4]2À, 6[c]
13.4
12.3
80.0
97.7
88.3 (PA)
103.4 (PB)
80.4 (PA)
97.4 (PB)
79.5
[ClPd{P(C2F5)(OH)O}{P(C2F5)(OH)2}2], 7a[b]
–
[ClPd{P(CF3)(OH)O}{P(CF3)(OH)2}2], 7b[b]
[Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2], 8a[d]
[Pd2(m-Cl)2{[P(CF3)(OH)O]2H}2], 8b[b]
[Pd2(m-Cl)2{[P(C6F5)(OH)O]2H}2], 8c[b]
–
13.1
13.5
11.3
74.8
73.2
[a] OH function. [b] Et2O. [c] [D3]Acetonitrile. [d] Dioxane.
Scheme 3. Treatment of (C2F5)P(O)(OH)H and (CF3)P(O)(OH)H with solid
[PdCl2] to form the complexes 7a, b and 8a, b, respectively.
The selective synthesis of the dinuclear complex 8b was
achieved in a two-phase system of diethyl ether and water.
After 3 h the reaction mixture was filtered and all volatile com-
pounds were removed in vacuo affording a light-yellow solid
identified as compound 8b. If diethylamine was condensed
Previously, the treatment of PdCl2 with 2,4-bis(trifluorome-
thyl)phenylphosphinic acid was reported to give a mixture of
a mononuclear (d(31P)=94.6 ppm) and a dinuclear complex
(d(31P)=77.8 ppm).[5] The latter resonance is well comparable
with that of complex 8a in diethyl ether (d(31P)=80.2 ppm)).
The attempts to separate preparative amounts of either 7a
or 8a from the reaction mixture by recrystallization were un-
succesful. Single crystals suitable for X-ray diffraction analysis,
however, were obtained. The structure reveals the dinuclear
palladium complex 8a (Figure 6), which cocrystallized with
a mononuclear dianionic complex unit (comp. 6). The O1···O3
distance (248.7(1) pm) and O6···O7 distance (249.5(1) pm) of
8a are characteristic for hydrogen-bridged quasichelating
onto
a
freshly
prepared
solution
of
[Pd2(m-
Cl)2{[P(CF3)(OH)O]2H}2] (8b), single crystals of 2[H2NEt2]+[Pd2(m-
Cl)2{[P(CF3)O2]2H}2]2À slowly separated. The molecular structure
in the solid state (Figure 7) is dominated by inter- and intramo-
lecular hydrogen bridges. The O1···O4 (246.9(4) pm) and
O5···O8 distance (243.0(4) pm) are characteristic for a hydro-
gen-bridged quasi-chelating unit. One complex unit is connect-
ed to a second unit by intermolecular hydrogen bridges
(O2···O7# 249.3(4) and O3···O6# 248.1(3) pm). The CF3 groups
Chem. Eur. J. 2015, 21, 13666 – 13675
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Figure 7. Molecular structure of 2[H2NEt2]+[Pd2(m-Cl)2{[P(CF3)O2]2H}2]2À; cat-
ions omitted for clarity; selected bond lengths [pm] and angles [8]: Pd1ÀP1
223.54(9), Pd1ÀP2 223.27(9), P1ÀO1 152.1(3), P1ÀO2 154.9(3), P2ÀO3
151.8(3), P2ÀO4 155.8(3), Pd1ÀP1-O1 119.5(1), Pd1-P2-O4 118.2(1); disorder
of the cation on two positions.
are located on one side perpendicular to the complex plane.
Comparable to those of the C2F5 derivative 8a, the PÀO bond
lengths vary between 151.6(3) and 156.2(3) pm.
As compared with the reaction of the CF3 and C2F5 deriva-
tives, the treatment of (C6F5)P(O)(OH)H with PdCl2 in diethyl
ether proceeds much slower and selectively yields one prod-
uct. Stirring of the reaction mixture at room temperature for
three days afforded the dinuclear complex [Pd2(m-
Cl)2{[P(C6F5)(OH)O]2H}2] (8c), and single crystals separated from
THF solutions. Compound 8c crystallizes in the triclinic space
Figure 8. Molecular structure of [Pd2(m-Cl)2{[P(C6F5)(OH)O]2H}2], 8c·2THF; sol-
vent molecules omitted for clarity; selected bond lengths [pm] and angles
[8]: Pd1ÀCl1 240.93( 3), Pd1ÀP1 221.86(3), Pd1ÀP2 222.55(3), P1ÀO1
152.94(9), P1ÀO2 155.84(9), P2ÀO3 155.0(1), P2ÀO4 156.57(9), Pd1-P1-O1
119.97(4), Pd1-P2-O4 118.81(4).
¯
group P1 (no. 2) with two solvent molecules per formula unit.
The X-ray analysis discloses a dinuclear palladium complex
(Figure 8) featuring two quasichelating phosphonous acid
phosphonito units with an O1···O4 distance of 250.0(1) pm. A
solvent molecule is coordinated through a hydrogen bridge to
O3. Intermolecular hydrogen bridges between O1···O2# and
O2···O1# lead to a zigzag structure of the complex units in the
crystal. In contrast to the C2F5 and the CF3 derivatives in which
the perfluoroalkyl groups are orientated perpendicular to the
complex plane, the pentafluorophenyl substituents of the qua-
sichelating units are orientated to different sides of the com-
plex plane.
Table 3. Results of the Suzuki cross-coupling reaction.[a]
Catalyst
Turnover
[%]
TON
TOF
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2], 5
[Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2], 8a
[Pd2(dba)3]
91
87
55
78
9100
8700
5500
7800
455
435
275
390
[Pd2(dba)3]/P(tBu)3
[a] After 20 h with a catalyst loading of 0.01 mol% Pd (0.005 mol% of the
dinuclear complex 8a and [Pd2(dba)3]). TON=turnover number; TOF=
turnover frequency.
Catalytic activity in the Suzuki cross coupling reaction
The Suzuki reaction is a well-known and frequently used cross-
coupling commonly catalyzed by palladium complexes. It is
therefore an excellent system to explore the catalytic activity
of new compounds. Previous work has shown that phosphi-
nous acid complexes bearing electron-withdrawing groups ex-
hibit a very high catalytic activity in the Suzuki reaction of 1-
bromo-3-fluorobenzene and phenyl boronic acid.[7] The most
efficient system proved to be 2-propanole as the solvent and
potassium phosphate as the base [Eq. (2)].
ture. Even with a catalyst loading of only 0.01 mol% Pd
(0.005 mol% of the dinuclear complex 8a) a turnover of 91%
for 8a and 87% for 5 was achieved. For comparison, the litera-
ture-known catalyst systems of [Pd2(dba)3] (dba=dibenzyl-
ideneacetone) and [Pd2(dba)3]/P(tBu)3 gave only turnovers of
78 and 55%, respectively.[7]
Based on this work, we investigated the catalytic activity of
[Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2]
(8a)
and
[Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] (5) (Table 3). The reaction pro-
ceeds even at room temperature and the conversion was de-
termined by 19F NMR spectroscopy after 20 h at room tempera-
Chem. Eur. J. 2015, 21, 13666 – 13675
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APCI source. Samples were introduced by direct infusion with a sy-
ringe pump. Nitrogen served both as the nebulizer gas and the
dry gas. Nitrogen was generated by a Bruker nitrogen generator
NGM 11. Helium served as the cooling gas for the ion trap and col-
lision gas for MS experiments. The spectra were recorded with
a Bruker Daltonik esquireNT 5.2 esquireControl software by the ac-
cumulation and averaging of several single spectra. Data analysis
software 3.4 was used for processing the spectra. C, H, and N anal-
yses were carried out with a HEKAtech Euro EA 3000. The crystal
data for compounds 1·THF, 2·2THF, 3·2THF and the cocrystal were
collected on a Bruker Nonius Kappa CCD diffractometer using
graphite-monochromated MoKa radiation (l=71.073 pm). Data col-
lection for X-ray structure determination for compound 2[H2NEt2]+
[Pd2(m-Cl)2{[P(CF3)O2]2H}2]2À was performed on a Bruker KAPPA
APEX II diffractometer using MoKa radiation (l=71.073 pm). The
crystal data for compounds 6·CH2Cl2 and 8c·2THF were collected
on a SuperNova, Single source at offset, Eos using MoKa radiation
(l=71.073 pm). Suitable crystals were selected, coated with para-
tone oil and mounted onto the diffractometer. The structures were
solved by Direct Methods and refined by full-matrix least-squares
cycles (programs SHELXS-97 and SHELXL-97 (Sheldrick, G. M.
SHELXL-97; Programs for Crystal Structure Analysis, University of
Gçttingen, 1997)). The CCDC depositions numbers for all com-
plexes are given in Table 4 and Table 5. CCDC 1016495 (1),
1016496 (2), 1016497 (3), 1016498 (8a), 1016499 (8b), 1016500 (6),
and 1016501 (8c) contain the supplementary crystallographic data
for this paper. These data are provided free of charge by The Cam-
bridge Crystallographic Data Centre.
Conclusion
A tautomeric equilibrium between phosphinic, RP(O)(OH)H,
and phosphonous acids, RP(OH)2, is evidenced by this work.
Calculations at the B3LYP/6-311 +G(2df,p) level of theory re-
vealed an energy difference of 7.6 kJmolÀ1 for the CF3 and
9.9 kJmolÀ1 for the C2F5 derivative in favor of the phosphinic
acid. In this work we described the diverse coordinative prop-
erties of phosphinic acids with the electron-withdrawing
groups CF3, C2F5, and C6F5. For the pentafluoroethylphosphinic
acid, a three- or fourfold coordination to PtCl2 under HCl elimi-
nation occurs, depending on the used solvent. Stabilizing intra-
molecular hydrogen bridges between phosphonous acid-phos-
phonito quasichelating units with a characteristic O···O dis-
tance of 240 to 250 pm are formed. With the pentafluorophen-
yl-substituted phosphinic acid, only a threefold coordination
could be achieved under the same reaction conditions. The ClÀ
free complexes [M{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2]2À (M=Pt (3),
Pd (5)) are highly acidic and can easily be deprotonated to the
dianionic complexes [M{P(C2F5)(OH)O}4] (M=Pt (4), Pd (6)) in
which two additional stabilizing intramolecular hydrogen
bridges are formed.
The treatment of PdCl2 with RfP(O)(OH)H (Rf =CF3, C2F5, C6F5)
further underlines the different reactivity of perfluoroalkyl- and
perfluoroaryl-substituted phosphinic acids. The dinuclear com-
plex [Pd2(m-Cl)2{[P(Rf)(OH)O]2H}2] is accessible for all derivatives.
Complex [ClPd{P(Rf)(OH)O}{P(Rf)(OH)2}2] is obtained as the only
product with the perfluoroalkyl phosphinic acids. A possible
explanation could be the decreased electron-withdrawing
effect of the pentafluorophenyl group, which results in a larger
energy difference between phosphinic and phosphonous acid
and a decreased acidity as compared with the CF3 and C2F5 de-
rivatives.
Synthesis of (C2F5)P(NEt2)2: CAUTION!!! LiC2F5 is highly reactive and
tends to violently decompose above temperatures of À508C. A 1.6m
n-butyl lithium solution in n-hexane (119.0 mL, 190.0 mmol) diluted
in diethyl ether (200 mL) was degassed at À788C and stirred for
30 min in an atmosphere of pentafluoroethane (228.0 mmol). After
the addition of bis(diethylamino)chlorophosphane (36.0 g,
171.0 mmol) at À788C, the mixture was warmed to room tempera-
ture and stirred overnight. The precipitate was filtered off. After
evaporation of the solvent, 43.2 g (147.0 mmol, 86%) (C2F5)P(NEt2)2
were obtained by vacuum distillation at 288C and 1”10À3 mbar as
a colorless liquid. 1H NMR ([D]chloroform, RT): d=1.1 (t, 3J(H,H)=
7 Hz, 3H, CH3), 3.2 ppm (m, 2H, CH2); 13C{1H} NMR ([D6]benzene,
RT): d=14.1 (d, 3J(C,P)=3 Hz, CH3), 44.2 ppm (d, 2J(C,P)=21 Hz,
In summary, perfluoroalkyl- and perfluoroaryl-substituted
phosphinic acids are useful preligands for the synthesis of tran-
sition-metal complexes of phosphonous acids. The phosphinic
acids as well as their platinum and palladium complexes are re-
markably stable towards oxygen and moisture. In addition, the
palladium complexes [Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] and
[Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2] proved to be excellent catalysts
for the Suzuki reaction of 1-bromo-2-fluorobenzene and
phenyl boronic acid. Both complexes exhibit a high catalytic
activity even under mild conditions.
1
CH2); 13C{19F} NMR ([D]chloroform, RT): d=119.5 (d, J(C,P)=52 Hz,
2
CF2), 120.1 ppm (d, J(C,P)=25 Hz, CF3); 19F NMR ([D]chloroform, rt):
d=À117.6 (d, 2J(P,F)=71 Hz, 2F, CF2), À81.7 ppm (s, 3F, CF3);
31P NMR ([D]chloroform, RT): d=72.4 ppm (m, P); IR (gas phase):
~
n=746 (w), 947 (w), 1146 (m), 1224 (s), 1308 (m), 1388 (w), 2882
(w), 2946 (w), 2979 cmÀ1 (w).
Synthesis of (C2F5)P(O)(OH)H: Water (1.47 g, 81.86 mmol) was
added to a solution of (C2F5)P(NEt2)2 (12.04 g, 40.93 mmol) in dieth-
yl ether (200 mL). The reaction mixture was cooled to À788C and
degassed before the addition of gaseous HBr (6.54 g, 81.84 mmol).
The temperature was slowly raised to room temperature and the
white precipitate was filtered off. The solvent was distilled off and
the product (6.44 g; 35.01 mmol, 86%) was obtained by vacuum
Experimental Section
All chemicals were obtained from commercial sources and used
without further purification. Standard high-vacuum techniques
were employed throughout all preparative procedures. Non-vola-
tile compounds were handled in a dry N2 atmosphere using
Schlenk techniques. The NMR spectra were recorded on a Bruker
Model Avance III 300 spectrometer (31P 111.92 MHz; 19F
282.40 MHz; 13C 75.47 MHz, 1H 300.13 MHz) with positive shifts
being downfield from the external standards (85% orthophosphor-
ic acid (31P), CCl3F (19F) and TMS (1H)). IR spectra were recorded on
an ALPHA-FTIR spectrometer (Bruker). ESI mass spectra were re-
corded using an Esquire 3000 ion-trap mass spectrometer (Bruker
Daltonik GmbH, Bremen, Germany) equipped with a standard ESI/
1
distillation at 438C and 1”10À3 mbar as a colorless liquid. H NMR
(neat, RT): d=7.3 (d, 1J(P,H)=640 Hz, 1H, PH), 14.0 ppm (s, 1H,
OH); 1H{31P} NMR (neat, RT): d=7.3 (s, 1H, PH), 14.0 ppm (s, 1H,
1
OH); 13C{1H} NMR (neat, RT): d=109.9 (t, d, quart, J(C,F)=275 Hz,
1J(C,P)=139, 2J(C,F)=40 Hz, CF2), 118.3 ppm (quart, t, d, 1J(C,F)=
285 Hz, 2J(C,F)=31, 2J(C,P)=19 Hz, CF3); 19F NMR (neat, RT): d=
2
À132.3 (d, J(P,F)=96 Hz, 2F, CF2), À82.5 ppm (s, 3F, CF3); 31P NMR
1
2
(neat, RT): d=9.4 ppm (d, t, J(P,H)=639, J(P,F)=96 Hz, P).
Chem. Eur. J. 2015, 21, 13666 – 13675
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to Cl), 119.9 ppm (t, 2/4J(C,P)=7 Hz,
(CF3CF2)P cis to Cl); 19F NMR ([D]chloroform,
RT): d=À124.4 (d, 2J(P,F)=98, 3J(Pt,F)=
37 Hz, 2F, CF2), À122.2 (m, 4F, CF2), À79.8 (s
(br), 4J(Pt,F)=12 Hz, 6F, CF3), À79.7 ppm (s
(br), 4J(Pt,F)=23 Hz, 3F, CF3); 31P NMR
Table 4. Crystal data and refinement characteristics for 1·THF, 2·2THF, 3·2Et2O and the cocrystal.[a]
1·THF
2·2Et2O
3·2Et2O
2[H3O·(Et2O)2]+[Pd{P(C2F5)O2}4H4]2À
[Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2] (8a)
empirical
formula
a [pm]
b [pm]
c [pm]
a [8]
C6H4ClF15O6P3Pt, C18H5ClF15O6P3Pt, C8H6F20O8P4Pt,
C32H56Cl2F40O22P8Pd3
C4H9O
2(C4H10O)
890.14(9)
2909.7(4)
1432.9(2)
2(C4H10O)
2339.31(3)
952.98(1)
1729.66(2)
2
([D]chloroform, RT): d=61.3 (t, t, J(P,F)=99,
978.47(1)
1108.73(1)
1183.48(1)
68.75(1)
84.35(1)
71.97(1)
1033.9(1)
1267.3(1)
1312.1(1)
81.5(1)
80.2(1)
81.9(1)
1663.9(1)
1
1
2J(P,P)=28 Hz, J(Pt,P)=4277 Hz, 1 P, P trans
1
to Cl), 94.7 ppm (m, J(Pt,P)=3172 Hz, 2 P, P
cis to Cl); 31P{19F} NMR ([D]chloroform, RT):
d=61.3 (t, 2J(P,P)=27, 1J(Pt,P)=4279 Hz,
b [8]
g [8]
105.79 (1)
114.30(1)
2
1 P, P trans to Cl), 94.7 ppm (d, J(P,P)=27,
V [106 pm3] 1137.76(1)
3571.2(8)
4
3514.21(7)
4
1J(Pt,P)=3172 Hz, 2 P, P cis to Cl); 195Pt NMR
([D]chloroform, RT): d=À4694.1 ppm (d, t,
Z
2
1x [gcmÀ3
crystal
system
space
group
color
]
2.492
triclinic
1.997
monoclinic
2.036
monoclinic
1.638
triclinic
1
1J(Pt,P)=4276, J(Pt,P)=3177 Hz, Pt).
Synthesis
of
¯
¯
P1 (no. 2)
P21/n (no. 14)
C2/c (no. 15)
P1 (no. 2)
[ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2]
(2):
(C6F5)P(O)(OH)H (0.24 g, 1.03 mmol) was dis-
solved in diethyl ether (5 mL) and PtCl2
(0.09 g, 0.34 mmol) was added. The reaction
mixture was stirred at room temperature for
7 days and filtered. The residue was washed
with diethyl ether (5 mL). Evaporation of
the filtrate to dryness yielded 0.24 g
(0.26 mmol, 76%) of light-yellow solid 2.
1H NMR (Et2O, RT): d=11.6 ppm (s, H);
13C{19F} NMR (Et2O, RT): d=137.5 (m, 6 C,
meta-C), 142.8 (m, 1 C, para-C), 143.2 (s, 2 C,
para-C), 146.8 (s, 2 C, ortho-C), 147.2 ppm (s,
4 C, ortho-C); 19F NMR (Et2O, RT): d=À164.0
(m, 2F, meta-F), À163.5 (m, 4F, meta-F),
À153.6 (m, 1F, para-F), À151.8 (m, 2F, para-
F), À133.8 (m, 2F, ortho-F), À133.1 ppm (m,
4F, ortho-F); 31P NMR (Et2O, RT): d=49.3 (t,
colorless
colorless
colorless
colorless
crystal size 0.30”0.25”0.20 0.30”0.30”0.20 0.27”0.10”0.10 0.28”0.13”0.10
[mm3]
diffractometer
radiation
Bruker Nonius Kappa CCD
MoKa (graphite monochromator, l=71.073 pm)
T [K]
100(2)
100(2)
200(2)
100(2)
q range [8] 3.51/30.00
À13ꢀhꢀ13
À15ꢀkꢀ15
2.43/30.00
À12ꢀhꢀ12
À40ꢀkꢀ40
À20ꢀlꢀ20
3.38/29.99
À32ꢀhꢀ32
À13ꢀkꢀ13
À24ꢀlꢀ24
3.12/30.0
À14ꢀhꢀ14
À17ꢀkꢀ17
À18ꢀlꢀ18
index
range
À16ꢀlꢀ16
total data 46167
collected
72241
57121
48600
R(int)
unique
data
0.055
6636
0.0375
10433
0.052
5115
0.041
9642
observed
data
6457
9236
4606
9512
2
1
(I>2s)
m, J(P,P)=27, J(Pt,P)=4606 Hz, 1 P, P trans
to Cl), 97.1 ppm (d (br), 2J(P,P)=27,
m [mmÀ1
]
6.650
4.262
4.325
2.349
(numerical)
T min/max 0.2403/0.3497
1J(Pt,P)=3223 Hz,
2
P,
P
cis to Cl);
0.3612/0.4827
0.0241/0.0454
0.3881/0.6716
0.0319/0.0855
0.559/0.799
0.028/0.069
31P{19F} NMR ([D]chloroform, RT): d=49.3 (t,
R1/wR2
0.0212/0.0530
1
2J(P,P)=27, J(Pt,P)=4607 Hz, 1 P, P trans to
[I>2s(I)]
R1/wR2
(all data)
goodness 1.077
of fit (Sall)
Cl), 97.1 ppm (d, 2J(P,P)=27, 1J(Pt,P)=
0.0220/0.0533
0.0312/0.0471
1.099
0.0370/0.0889
1.041
0.029/0.069
1.027
3223 Hz,
2 P, P
cis to Cl); 195Pt NMR
([D]chloroform, RT): d=À4692.2 ppm (d, t,
1
1J(Pt,P)=4619, J(Pt,P)=3236 Hz, Pt).
D1max/min
[106 epmÀ3
F(000)
0.963/À2.381
0.713/À1.307
2.192/À1.165
0.988/À1.089
Synthesis
of
]
[Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2]
(3):
808
2080
2080
820
CCDC
number
1016495
1016496
1016497
1016498
(a) (C2F5)P(O)(OH)H (0.35 g, 1.90 mmol) was
added to a suspension of [Pt(acac)2] (0.18 g,
[a] Using SIR-97 and ShelXL-97.[8]
0.46 mmol) in diethyl ether (5 mL) and
stirred at room temperature for 5 days. The
resulting yellow solution was filtered and all
volatile compounds were removed in vacuo
yielding 0.43 g (0.46 mmol, 100%) of light-
yellow solid 3. (b) (C2F5)P(O)(OH)H (0.20 g, 1.09 mmol) was added
to a suspension of PtCl2 (0.08 g, 0.30 mmol) in dichloromethane
(5 mL) and stirred at room temperature for 12 days. After the re-
moval of the solvent, excess phosphinic acid was distilled off. The
residue was dissolved in diethyl ether and filtered. Evaporation of
the filtrate to dryness yielded 0.19 g (0.21 mmol, 70%) of colorless
solid 3. 1H NMR ([D8]THF, RT): d=13.7 ppm (s, H); 13C{19F} NMR
([D8]THF, RT): d=113.4 (m, CF2), 119.9 ppm (m, CF3); 19F NMR
([D8]THF, RT): d=À123.0 (m, 2F, CF2), À80.1 ppm (m, 3 F, CF3);
31P NMR ([D8]THF, RT): d=93.0 ppm (m, 1J(Pt,P)=3048 Hz, P);
Synthesis
of
[ClPt{P(C2F5)(OH)O}{P(C2F5)(OH)2}2]
(1):
(C2F5)P(O)(OH)H (0.24 g, 1.33 mmol) was added to a suspension of
PtCl2 (0.10 g, 0.38 mmol) in tetrahydrofuran (5 mL) and stirred at
room temperature for 1 h. The resulting solution was filtered and
all volatile compounds were removed in vacuo yielding a red oil.
After recrystallization from dichloromethane solution colorless crys-
tals (0.17 g; 0.22 mmol, 58%) were obtained. 1H NMR ([D]chloro-
form, RT): d=11.9 ppm (s, H); 13C{19F} NMR ([D]chloroform, RT): d=
111.8 (d, 1J(C,P)=86 Hz, (CF3CF2)P trans to Cl), 113.9 (t, 1/3J(C,P)=
2
1
31P{19F} NMR ([D8]THF, RT): d=93.0 ppm (s, J(Pt,P)=3048 Hz, P); IR
48 Hz, (CF3CF2)P cis to Cl), 119.6 (d, J(C,P)=13 Hz, (CF3CF2)P trans
Chem. Eur. J. 2015, 21, 13666 – 13675
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Full Paper
tered. Addition of a solution of 1,8-bis(dimethylamino)naphthalene
(0.18 g, 0.84 mmol) in diethyl ether resulted in the precipitation of
a colorless solid. The suspension was stirred for 12 h before remov-
al of the solvent. The residue was repeatedly washed with diethyl
ether and dried in vacuo yielding 0.48 g (0.35 mmol, 78%) of color-
less solid 4. 1H NMR ([D3]acetonitrile, RT): d=3.2 (d, J=3 Hz,
Table 5. Crystal data and refinement characteristics for 2[H2NEt2]+[Pd2(m-
Cl)2{[P(CF3)O2]2H}2]2À [a]
,
6·CH2Cl2,[b] and 8c·2THF[b]
.
2[H2NEt2]+[Pd2(m-
Cl)2{[P(CF3)O2]2H}2]2À
8b
6·1/2CH2Cl2
8c·2THF
3
1J(C,H)=141 Hz, 12H, N(CH3)2), 7.7 (t, J(H,H)=8 Hz, 2H, meta-CH),
empirical for- C12H28Cl2F12N2O8P4Pd2 C36.5H43ClF20N4
C24H6Cl2F20O8
P4Pd2, 2(C4H8O)
1091.83(3)
1110.30(3)
1165.85(2)
93.3222(2)
115.626(2)
117.907(2)
1064.29(4)
1
3
3
8.0 (d, J(H,H)=8 Hz, 2H, ortho-CH), 8.1 (d, J(H,H)=8 Hz, 2H, para-
CH), 16.5 (s, 2H, OH), 18.7 ppm (s, 1H, N···H···N); 13C{1H} NMR
([D]acetonitrile, RT): d=45.8 (s, CH3), 119.2 (s, meta-C), 121.7 (s,
ortho-CH), 127.1 (s, meta-CH), 129.2 (s, para-CH), 135.4 (s, ortho-C),
144.5 ppm (s, CN); 13C{19F} NMR ([D3]acetonitrile, RT): d=113.3 (m,
CF2), 120.1 ppm (m, CF3); 19F NMR ([D3]acetonitrile, RT): d=À124.3
(m, 2F, CF2), À80.3 ppm (s, 4J(Pt,F)=13 Hz, 3F, CF3); 31P NMR
([D3]acetonitrile, RT): d=85.9 ppm (m, 1J(Pt,P)=2751 Hz, P); 195Pt
NMR ([D3]acetonitrile, RT): d=À5191.1 ppm (quint, m, 1J(Pt,P)=
mula
a [pm]
b [pm]
c [pm]
a [8]
O8P4Pd
1766.65(3)
1420.81(4)
2029.02(4)
–
1326.68(6)
1700.49(7)
1373.85(6)
–
b [8]
g [8]
99.058(2)
–
3060.8(2)
4
97.840(2)
–
5045.4(2)
4
V [106 pm3]
Z
1x
[gcmÀ3
2.092
1.727
2.113
~
2747 Hz, Pt); IR (ATR): n=418 (s), 439 (s), 467 (s), 488 (s), 543 (m),
]
590 (m), 634 (m), 744 (m), 772 (s), 836 (m), 975 (s), 1003 (s), 1029
(s), 1074 (m), 1105 (s), 1138 (m), 1194 (s), 1263 (w), 1302 (m), 1380
(w), 1415 (w), 1461 (w), 1476 (w), 1517 (w), 1665 (w), 2982 cmÀ1
(w).
crystal system monoclinic
space group P21/n (no. 14)
monoclinic
P21/n (no. 14)
colorless
triclinic
¯
P1 (no. 2)
color
colorless
colorless
crystal size
[mm3]
0.13”0.11”0.11
0.52”0.33”0.14 0.13”0.07”0.07
Synthesis of [Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] (5): Treatment of
a slurry of [Pd(acac)2] (0.08 g, 0.26 mmol) in diethyl ether (4 mL)
with (C2F5)P(O)(OH)H (0.22 g, 1.20 mmol) at room temperature
yielded a colorless solution. The solution was filtered and all vola-
tile compounds were removed in vacuo. Recrystallization from di-
chloromethane yielded 0.16 g (0.19 mmol, 73%) of colorless crys-
diffractometer Bruker Kappa APEX II SuperNova, Single source at
offset, Eos
radiation
T [K]
MoKa (l=71.073 pm)
100(2)
100.0(1)
100.0(2)
q range [8]
3.38/28.50
2.62/32.36
À24ꢀhꢀ22
À18ꢀkꢀ19
À28ꢀlꢀ28
51147
2.62/32.4255
À15ꢀhꢀ15
À15ꢀkꢀ15
À16ꢀlꢀ16
81610
À17ꢀhꢀ17
À22ꢀkꢀ22
À18ꢀlꢀ18
140095
1
talline 5. H NMR (Et2O, RT): d=13.4 ppm (s, H); 13C{19F} NMR (Et2O,
index range
RT): d=110.9 (d, 1J(C,P)=91 Hz, CF2), 119.3 ppm (t, J=7 Hz, CF3);
19F NMR (Et2O, RT): d=À121.9 (d, m, 2J(P,F)=106 Hz, 2F, CF2),
À79.7 ppm (s, 3 F, CF3); 31P NMR (Et2O, RT): d=80.0 ppm (m, P); IR
total data
collected
unique data
R(int)/R(s)
observed data 6216
7731
0.0772
14686
0.0324
12159
6200
0.0273
5954
~
(ATR): n=471 (s), 548 (m), 593 (m), 629 (m), 749 (m), 873 (s), 977
(s), 1083 (s), 1116 (s), 1200 (s), 1306 cmÀ1 (m).
2[C14H19N2]+[Pd{P(C2F5)(OH)O}4]2À
(6):
(I>2s)
m [mmÀ1
Synthesis
of
]
1.671
0.673
1.264
(C2F5)P(O)(OH)H (0.33 g, 1.78 mmol) was added to a suspension of
[Pd(acac)2] (0.14 g, 0.44 mmol) in 5 mL of diethyl ether and stirred
at room temperature resulting in a light-yellow solution. A solution
of 1,8-bis(dimethylamino)naphthalene (0.19 g, 0.89 mmol) in dieth-
yl ether was slowly added. The precipitate was filtered and washed
with diethyl ether. The residue was dissolved in acetonitrile and all
volatile compounds were removed in vacuo yielding a colorless
(numerical)
T min/max
R1/wR2
[I>2s(I)]
R1/wR2
(all data)
goodness of 1.194
fit
(Sall)
0.8058/0.8427
0.0343/0.0837
0.777/2.111
0.0421/0.0816
0.938/1.041
0.0160/0.0384
0.0525/0.0994
0.0555/0.0870
1.092
0.0169/0.0388
1.037
1
solid 6 (0.54 g; 0.42 mmol, 95%). H NMR ([D3]acetonitrile, RT): d=
3
3.1 (d, J=3 Hz, 12H, N(CH3)2), 7.7 (t, J(H,H)=8 Hz, 2H, meta-CH),
D1max/min
[106 epmÀ3
F(000)
1.789/À1.095
0.63/À0.90
0.45/À0.50
3
3
7.9 (d, J(H,H)=8 Hz, 2H, ortho-CH), 8.0 (d, J(H,H)=8 Hz, 2H, para-
CH), 12.3 (s, 2H, OH), 18.7 ppm (s, 1H, N···H···N); 13C{1H} NMR
([D3]acetonitrile, RT): d=45.8 (s, CH3), 119.2 (s, meta-C), 121.6 (s,
ortho-CH), 127.1 (s, meta-CH), 129.3 (s, para-CH), 135.4 (s, ortho-C),
144.3 ppm (s, CN); 13C{19F} NMR ([D3]acetonitrile, RT): d=112.9 (m,
CF2), 119.9 ppm (m, CF3); 19F NMR ([D3]acetonitrile, RT): d=À124.7
(m, 2F, CF2), À80.2 ppm (s, 3F, CF3); 31P NMR ([D3]acetonitrile, RT):
]
1888
1016499
2628
1016500
660
1016501
CCDC
number
[a] Using SIR-97 and ShelXL-97.[8] [b] Using Olex2,[9] the structure was dis-
solved with the ShelXS[8] structure solution program using Direct Meth-
ods and refined with the ShelXL[8] refinement package using Least
Squares minimization.
~
d=97.7 ppm (m, P); IR (ATR): n=378 (m), 399 (m), 419 (m), 436
(m), 463 (s), 481 (s), 543 (m), 590 (m), 744 (m), 769 (s), 834 (m), 972
(s), 1015 (s), 1099 (s), 1135 (m), 1198 (s), 1300 (m), 1340 (w), 1376
(w), 1417 (w), 1463 (w), 1477 cmÀ1 (w); elemental analysis calcd (%)
for C36H42F20N4O8P4Pd: C 34.07, H 3.33, N 4.42; found: C 34.35, H
3.56, N 4.76.
~
(ATR): n=430 (m), 449 (m), 483 (s), 548 (m), 580 (m), 592 (m), 625
(m), 667 (m), 748 (m), 769 (m), 826 (m), 923 (s), 976 (s), 1055 (m),
1117 (s), 1203 (s), 1307 (m), 1390 (w), 1453 (w), 2860 (w), 2930 cmÀ1
(w).
Synthesis of [Pd2(m-Cl)2{[P(C2F5)(OH)O]2H}2] (8a): The reaction mix-
ture of PdCl2 (0.11 g, 0.63 mmol) and (C2F5)P(O)(OH)H (0.23 g,
1.26 mmol) in dichloromethane (5 mL) during 11 d led to the pre-
cipitation of a colorless solid. All volatile compounds were re-
moved in vacuo and excess (C2F5)P(O)(OH)H was distilled off. The
residue was dissolved in diethyl ether and filtered. All volatile com-
pounds were removed in vacuo yielding 0.30 g (0.30 mmol, 95%)
Synthesis of 2[C14H19N2]+[Pt{P(C2F5)(OH)O}4]2À
, 4: Solid PtCl2
(0.12 g, 0.45 mmol), suspended in dichloromethane (6 mL), was
treated with (C2F5)P(O)(OH)H (0.37 g, 2.00 mmol) and stirred at
room temperature for 10 days. The reaction mixture was concen-
trated in vacuo. The residue was taken up in diethyl ether and fil-
Chem. Eur. J. 2015, 21, 13666 – 13675
www.chemeurj.org
13674
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1
of light-yellow solid 8a. H NMR (dioxane, RT): d=13.1 ppm (s, H);
Acknowledgements
13C{19F} NMR (dioxane, RT): d=110.6 (d, 1J(C,P)=88 Hz, CF2),
119.1 ppm (t, J=7 Hz, CF3); 19F NMR (dioxane, RT): d=À122.2 (d,
Merck KGaA (Darmstadt, Germany) is acknowledged for finan-
cial support. We are grateful to the Solvay GmbH (Hannover,
Germany) for providing chemicals. We thank Dr. Julia Bader
and Prof. Dr. Lothar Weber for helpful discussions.
2
m, J(P,F)=105 Hz, 2F, CF2), À79.6 ppm (s, 3 F, CF3); 31P NMR (diox-
~
ane, RT): d=79.5 ppm (m, P); IR (ATR): n=419 (m), 447 (m), 473
(m), 503 (m), 528 (m), 549 (m), 593 (w), 630 (w), 749 (m), 834 (m),
912 (m), 948 (m), 983 (m), 1028 (m), 1118 (s), 1200 (s), 1302 cmÀ1
(m).
Synthesis of [Pd2(m-Cl)2{[P(CF3)(OH)O]2H}2] (8b): (CF3)P(O)(OH)H
(0.22 g, 1.64 mmol) was dissolved in diethyl ether and two drops
of water were added. After the addition of PdCl2 (0.105 g,
0.60 mmol) in diethyl ether (5 mL) the reaction mixture was stirred
at ambient temperature for 3 h. The colorless reaction mixture was
filtered and all volatile compounds were removed in vacuo yield-
Keywords: coordination modes · cross-coupling · fluorine ·
palladium · phosphorus · platinum
[1] N. V. Dubrovina, A. Bçrner, Angew. Chem. 2004, 116, 6007–6010.
[2] L. Ackermann, Synthesis 2006, 1557–1571.
1
ing 0.24 g (0.29 mmol, 97%) of light-yellow solid 8b. H NMR (Et2O,
RT): d=13.5 ppm (s, H); 19F NMR (Et2O, RT): d=À73.2 ppm (d, m,
[3] J. Chatt, B. T. Heaton, J. Chem. Soc. A 1968, 2745–2757.
[4] a) C. King, D. M. Roundhill, F. R. Fronczek, Inorg. Chem. 1987, 26, 4288–
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Clegg, V. P. Fedin, A. Mederos, Chem. Commun. 2003, 140–141; d) M. N.
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Peresypkina, V. P. Fedin, Russ. Chem. Bull. 2005, 54, 615–622; e) D. N. Ak-
bayeva, M. Di Vaira, S. Seniori Costantini, M. Peruzzini, P. Stoppioni,
Dalton Trans. 2006, 389–395; f) R. Hernµndez Molina, I. Kalinina, M. Soko-
lov, M. Clausen, J. Gonzalez Platas, C. Vicent, R. Llusar, Dalton Trans. 2007,
550–557; g) A. G. Algarra, M. G. Basallote, M. J. Fernandez-Trujillo, R. Her-
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2015: DOI: 10.1021/acs.inorgchem.5b01038.
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[8] G. M. Sheldrick, Acta Cryst. 2008, 64, 112–122.
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J. Appl. Crystallogr. 2009, 42, 339–341.
2J(P,F)=112 Hz, CF3); 31P NMR (Et2O, RT): d=74.8 ppm (m, P); IR
~
(ATR): n=475 (s), 500 (s), 555 (s), 579 (m), 743 (m), 828 (m), 909
(m), 939 (m), 1042 (m), 1123 (s), 1193 (m), 1387 (w), 1444 (w), 1503
(w), 1685 (w), 2267 (w), 2852 (w), 2922 (w), 2995 cmÀ1 (w).
Synthesis of [Pd2(m-Cl)2{[P(C6F5)(OH)O]2H}2] (8c): (C6F5)P(O)(OH)H
(0.58 g, 2.52 mmol) was added to
a slurry of PdCl2 (0.11 g,
0.63 mmol) in dichloromethane (5 mL) and stirred at room temper-
ature for 3 days. The suspension was filtered and washed with di-
chloromethane. The colorless residue was dissolved in diethyl
ether and filtered. The solvent was removed in vacuo yielding
0.31 g (0.26 mmol, 83%) of colorless solid 8c. 1H NMR (Et2O, RT):
d=11.3 ppm (s, H); 13C{19F} NMR (Et2O, RT): d=137.8 (m, meta-C),
143.6 (s, para-C), 147.0 ppm (s, ortho-C); 19F NMR (Et2O, RT): d=
À162.7 (m, 2F, meta-F), À150.9 (t, 3J(F,F)=20 Hz, 1F, para-F),
À132.3 (m, 2F, ortho-F); 31P NMR (Et2O, RT): d=73.2 ppm (s, P); IR
~
(ATR): n=431 (m), 455 (m), 475 (s), 507 (m), 524 (s), 543 (m), 586
(w), 636 (m), 655 (w), 727 (m), 761 (w), 791 (m), 832 (m), 911 (s),
951 (s), 979 (s), 1059 (m), 1094 (s), 1155 (w), 1235 (w), 1297 (w),
1385 (w), 1475 (s), 1517 (m), 1643 (w), 2300 (w), 2737 (w), 2880 (w),
2986 cmÀ1 (w).
Received: May 20, 2015
Published online on August 6, 2015
Chem. Eur. J. 2015, 21, 13666 – 13675
www.chemeurj.org
13675
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim