Synthesis, Molecular Structure, and Reactivity of the Tetranuclear Complex [NBu4]2[Pd4(μ-PPh2) 2(μ-Cl)4(C6F5)4]. Molecular Structure of [Pd2(μ-PPh2)(C6F 5)2(bipy)2]ClO4-C6H 14

Article abstract of DOI:10.1021/ic9701930

Anionic tetranuclear complexes with the molecular formula [NBu₄]₂[Pd₄(μ-PPh₂) ₂(μ-X)₄(C₆F₅)₄] [X = Cl (1), Br (2)] were obtained by reaction of [NBu₄]₂[Pd₂(μ-PPh₂) ₂(C₆F₅)₄] and PdCl₂ (or K₂[PdCl₄]) in acetone, followed by reaction with KBr for 2. The reactions of 1 with neutral monodentate (L) or bidentate (L-L) ligands afford the dinuclear derivatives [Pd₂(μ-PPh₂)(μ-Cl)(C₆F₅) ₂L₂] [L = PPh₃ (3), py (4)] or [Pd₂(μ-PPh₂)(C₆F₅) ₂(L-L)₂]ⁿ [n = 1-, L-L = acac (6); n = 1+, L-L = bipy (7) or phen (8)]. The structures of complexes 1 and 7 were determined by single-crystal X-ray diffraction studies. The bis(acetone) solvate of complex 1, [NBu₄]₂[Pd₄(μ-PPh₂) ₂(μ-Cl)₄(C₆F₅) ₄]·2C₃H₆O, crystallizes in the monoclinic system, space group P2₁/c, with a = 11.679(5) A?, b = 16.552(7) A?, c = 23.868(8) A?, β= 101.10(3)°, V = 4527.6(15) A?³, and Z = 2. The central core of the anion has the shape of a rectangle with the four Pd atoms in the corners. The hexane solvate of complex 7, [Pd₂(μ-PPh₂)(C₆F₅) ₂(bipy)₂][ClO₄]·C₆H ₁₄, crystallizes in the monoclinic system, space group P2₁/n, with a = 16.214(3) A?, b = 10.311(2) A?, c = 28.380(6) A?, β= 100.82(3)°, V = 4660(2) A?³, and Z = 4. In both complexes, the long Pd?Pd distances (>3.1 A?) clearly point to the absence of any Pd-Pd interaction.

Full text of DOI:10.1021/ic9701930

4426
Inorg. Chem. 1997, 36, 4426-4431
Synthesis, Molecular Structure, and Reactivity of the Tetranuclear Complex
[NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4(C6F5)4]. Molecular Structure of
§
[Pd2(µ-PPh2)(C6F5)2(bipy)2]ClO4‚C6H14
Ester Alonso,† Juan Fornie´s,*,† Consuelo Fortun˜o,† Antonio Mart´ın,†
Georgina M. Rosair,‡ and Alan J. Welch‡
Departamento de Qu´ımica Inorga´nica and Instituto de Ciencia de Materiales de Arago´n, Universidad de
Zaragoza-CSIC, 50009 Zaragoza, Spain, and Department of Chemistry, Heriot-Watt University,
Edinburgh EH14 4AS, U.K.
ReceiVed February 20, 1997X
Anionic tetranuclear complexes with the molecular formula [NBu4]2[Pd4(µ-PPh2)2(µ-X)4(C6F5)4] [X ) Cl (1), Br
(2)] were obtained by reaction of [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] and PdCl2 (or K2[PdCl4]) in acetone, followed
by reaction with KBr for 2. The reactions of 1 with neutral monodentate (L) or bidentate (L-L) ligands afford
the dinuclear derivatives [Pd2(µ-PPh2)(µ-Cl)(C6F5)2L2] [L ) PPh3 (3), py (4)] or [Pd2(µ-PPh2)(C6F5)2(L-L)2]n [n
) 1-, L-L ) acac (6); n ) 1+, L-L ) bipy (7) or phen (8)]. The structures of complexes 1 and 7 were determined
by single-crystal X-ray diffraction studies. The bis(acetone) solvate of complex 1, [NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4-
(C6F5)4]‚2C3H6O, crystallizes in the monoclinic system, space group P21/c, with a ) 11.679(5) Å, b ) 16.552(7)
Å, c ) 23.868(8) Å, â ) 101.10(3)°, V ) 4527.6(15) Å3, and Z ) 2. The central core of the anion has the shape
of a rectangle with the four Pd atoms in the corners. The hexane solvate of complex 7, [Pd2(µ-PPh2)(C6F5)2-
(bipy)2][ClO4]‚C6H14, crystallizes in the monoclinic system, space group P21/n, with a ) 16.214(3) Å, b ) 10.311-
(2) Å, c ) 28.380(6) Å, â ) 100.82(3)°, V ) 4660(2) Å3, and Z ) 4. In both complexes, the long Pd‚‚‚Pd
distances (>3.1 Å) clearly point to the absence of any Pd-Pd interaction.
Introduction
nylphosphide ligands.1-3,6 These complexes have been used
as precursors in the synthesis of derivatives of higher
nuclearity.1-3,6 Thus, the complexes [NBu4]2[(C6F5)2M(µ-
PPh2)2M′(C6F5)2] (M, M′ ) Pd or Pt) react with an aqueous
solution of HCl (1:2 molar ratio), yielding the tetranuclear
derivatives [NBu4]2[(C6F5)2M(µ-PPh2)2M′(µ-Cl)2M′(µ-PPh2)2M-
(C6F5)2].6 These tetranuclear derivatives can also be obtained
by reacting Li2[cis-M(C6F5)2(PPh2)2] with PtCl2 in THF at 0
°C (1:1 molar ratio).
The structure of these tetranuclear species, established by
spectroscopic techniques, seems to be a succession of four
square-planar Pd or Pt centers connected through double
bridging (µ-PPh2)2 or (µ-Cl)2 groups and terminal pentafluo-
rophenyl ligands. The 31P{1H} NMR spectra indicate that the
phosphido ligands are not supporting M-M′ bonds, in agree-
ment with the electron counting of the whole anion.7
It is known that the reaction of mononuclear halo or organo
palladium or platinum(II) complexes with MCl2 (M ) Pd, Pt)
affords the corresponding dinuclear complexes with a double
halide bridging system “M(µ-Cl)2M”.8
Phosphido (PR2-) groups are excellent bridging ligands able
to strongly support metal centers in polynuclear derivatives.
Their flexibility allows them to bridge a range of metal-metal
distances within the polynuclear framework so that the metal
centers may or may not be involved in metal-metal bonds.1-4
Phosphido bridging systems are very stable, and the polynuclear
complexes that contain these ligands are able to participate in
many chemical reactions in which the bridging framework is
maintained.5
In the course of our current research, we have prepared several
polynuclear homo- or heterometallic palladium(II) or platinum-
(II) pentafluorophenyl complexes containing bridging diphe-
† Universidad de Zaragoza-CSIC.
‡ Heriot-Watt University.
§ Polynuclear Homo- or Heterometallic Palladium(II)-Platinum(II) Pen-
tafluorophenyl Complexes Containing Bridging Diphenylphosphido Ligands.
5.
X Abstract published in AdVance ACS Abstracts, August 15, 1997.
(1) Part 4 of this series: Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Mart´ın A.;
Orpen, A. G. J. Chem. Soc., Chem. Commun. 1996, 231.
(2) Falvello, L. R.; Fornie´s, J.; Fortun˜o, C.; Mart´ınez, F. Inorg. Chem.
1994, 33, 6242.
Our interest in the synthesis of polynuclear palladium and
platinum complexes1-3,6 prompted us to study the reaction of
[NBu4]2[M2(µ-PPh2)2(C6F5)4] with M′Cl2 (1:1 or 1:2 molar; M,
(3) Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Toma´s, M. J. Chem. Soc., Dalton
Trans. 1995, 3777.
(4) (a) Braunstein, P. NouV. J. Chem. 1986, 10, 365 and references given
therein. (b) Corrigan, J. F.; Dinardo, M.; Doherty, S.; Hogarth, G.;
Sun, Y.; Taylor, N. J.; Carty, A. J. Organometallics 1994, 13, 3572
and references given therein. (c) Yang, K.; Bott, S. G.; Richmond,
M. G. Organometallics 1995, 14, 919. (d) Baker, R. T.; Whitney, J.
F.; Wreford, S. S. Organometallics 1983, 2, 1049. (e) Boni, G.;
Sauvageot, P. E.; Mo¨ıse, C. Organometallics 1995, 14, 5652. (f)
Braunstein, P.; de Jesu´s, E.; Dedieu, A.; Lanfranchi, M.; Tiripicchio,
A. Inorg. Chem. 1992, 31, 399. (g) Leoni, P.; Pasquali, M.; Som-
movigo, M.; Albinati, A.; Pregosin, P. S.; Ru¨egger, H. Organometallics
1996, 15, 2047. (h) Johnson, B. F. G.; Lewis, J.; Nordlander, E.;
Raithby, P. R. J. Chem. Soc., Dalton Trans. 1996, 755. (i) Kourkine,
I. V.; Chapman, M. B.; Glueck, D. S.; Eichele, K.; Wasylishen, R.
E.; Yap, G. P. A.; Liable Sands, L. M.; Rheingold, A. L. Inorg. Chem.
1996, 35, 1478.
(5) (a) Berry, D. E.; Browning, J.; Dehghan, K.; Dixon, K. R.; Meanwell,
N. J.; Phillips, A. J. Inorg. Chem. 1991, 30, 396. (b) Browning, J.;
Dixon, K. R.; Meanwell, N. J. Inorg. Chim. Acta 1993, 213, 171. (c)
Asseid, F.; Browning, J.; Dixon, K. R.; Meanwell, N. J. Organome-
tallics 1994, 13, 760. (d) Hogarth, G.; Lavender, M. H.; Shukri, K.
Organometallics 1995, 14, 2325.
(6) Fornie´s, J.; Fortun˜o, C.; Navarro, R.; Mart´ınez, F.; Welch, A. J. J.
Organomet. Chem. 1990, 394, 643.
(7) (a) Mercer, W. C.; Geoffroy, G. L.; Rheingold, A. L. Organometallics
1985, 4, 1418. (b) Carty, A. J.; MacLaughlin, S. A.; Nucciarone, D.
In Phosphorus-31 NMR Spectroscopy in Sterochemical Analysis:
Organic Compounds and Metal Complexes; Verkade, J. B., Quinn,
L. D., Eds.; VCH: Deerfield Beach, FL, 1987; p 539. (c) Carty, A. J.
AdV. Chem. Ser. 1982, 196, 163. (d) Mercer, W. C.; Whittle, R. R.;
Burkhardt, E. W.; Geoffroy, G. L. Organometallics 1985, 4, 68.
S0020-1669(97)00193-6 CCC: $14.00 © 1997 American Chemical Society

Polynuclear µ-PPh2 Palladium Complexes
Inorganic Chemistry, Vol. 36, No. 20, 1997 4427
IR (cm-1): C6F5 X-sensitive 789; ν(Pd-Cl) 275. Anal. Found
(calcd for C60ClF10H40P3Pd2): C, 55.38 (55.78); H, 3.00 (3.12). FAB+
MS: m/z 1292 (C60ClF10H40P3Pd2). 31P{1H} NMR (deuteriochloro-
form): δ -2.0 (PPh2), 18.2 (PPh3) ppm; J(PPh2-PPh3) ) 350.2 Hz.
(b) X ) Cl, L ) py (4). A similar procedure was used for the
preparation of complex 4. The reaction of 1 (0.060 g, 0.029 mmol)
and 24 µL (0.298 mmol) of py gives a very pale yellow solid (4, 0.038
g, 71% yield).
IR (cm-1): C6F5 X-sensitive 785; ν(Pd-Cl) 279. Anal. Found
(calcd for C34ClF10H20N2PPd2): C, 43.83 (44.12); H, 2.12 (2.18); N,
3.22 (3.03). FAB+ MS: m/z 926 (C34ClF10H20N2PPd2). 31P{1H} NMR
(deuterioacetone): δ 23.8 (s) ppm.
M′ ) Pd, Pt) aiming to prepare other homo- or heteropoly-
nuclear derivatives with bridging PPh2 and Cl ligands. Such
reactions, the results of which are the subject of this paper, allow
the preparation of a new type of tetranuclear phosphido
palladium complex of stoichiometry [NBu4]2[Pd4(µ-PPh2)2(µ-
Cl)4(C6F5)4].
Experimental Section
C, H, and N analyses were performed with a Perkin-Elmer 240B
microanalyzer. IR spectra were recorded on a Perkin-Elmer 599
spectrophotometer (Nujol mulls between polyethylene plates in the
range 4000-200 cm-1). NMR spectra were recorded on a Varian Unity
300 instrument with SiMe4, CFCl3, and 85% H3PO4 as external
(c) X ) Br, L ) PPh3 (5). To a solution of 3 (0.120 g, 0.093
mmol) in 15 mL of acetone was added KBr (0.400 g, 3.361 mmol),
and the mixture was stirred for 27 h at room temperature. The mixture
was evaporated to dryness and extracted with 20 mL of CH2Cl2. The
1
references for H, 19F, and 31P, respectively. Conductivities (solvent
acetone, c ≈ 5 × 10-4 M) were measured with a Philips PW 9509
conductometer. Mass spectra were recorded on a VG-Autospec
spectrometer operating at 30 kV, using the standard Cs ion FAB gun
and 3-nitrobenzyl alcohol (3-NOBA) as matrix. Literature methods
were used to prepare the starting complex [NBu4]2[(C6F5)2Pd(µ-PPh2)2-
Pd(C6F5)2].6
i
yellow solution was evaporated to ca. 1 mL, and PrOH (10 mL) was
i
added. The solid obtained was filtered off, washed with PrOH (2 ×
1 mL), and dried at 90 °C for 90 min (5, 0.112 g, 90% yield).
IR (cm-1): C6F5 X-sensitive 788. Anal. Found (calcd for BrC60-
F10H40P3Pd2): C, 54.14 (53.92); H, 3.20 (3.02). FAB+ MS: m/z 1336
(BrC60F10H40P3Pd2). 31P{1H} NMR (deuteriochloroform): δ -3.4
(PPh2), 19.0 (PPh3) ppm; J(PPh2-PPh3) ) 349.9 Hz.
Safety Note: Perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only small amounts of material
should be prepared, and these should be handled with great caution.
Preparation of [NBu4]2[Pd4(µ-Cl)4(µ-PPh2)2(C6F5)4] (1). (a) To
a solution of [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] (0.100 g, 0.057 mmol) in
acetone (20 mL) was added PdCl2 (0.021 g, 0.118 mmol) and the
mixture was heated to reflux for 3 h. The suspension was filtered to
eliminate a small amount of black solid, and the filtrate was evaporated
almost to dryness. The resulting residue was treated with CHCl3 (4
mL) and partially evaporated. After the sample was cooled to -20
°C, a yellow solid precipitated, which was filtered off, washed with
cold CHCl3 (2 × 1 mL), and air-dried (1, 0.040 g, 34% yield).
(b) To a solution of [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] (0.500 g, 0.288
mmol) in acetone (50 mL) was added K2[PdCl4] (0.188 g, 0.576 mmol)
dissolved in H2O (6 mL), and the mixture was stirred at room
temperature for 3 h. The suspension was filtered to eliminate a black
solid. The filtrate was evaporated to 6 mL and a solid precipitated,
which was filtered off, washed with H2O (2 × 1 mL) and then EtOH
(1 mL), and dried. The solid obtained was recrystallized from acetone/
CHCl3 (1, 0.300 g, 50% yield).
IR (cm-1): C6F5 X-sensitive9 786; ν(Pd-Cl) 250. ΛM ) 179 Ω-1
cm2 mol-1. Anal. Found (calcd for C80Cl4F20H92N2P2Pd4): C, 46.49
(45.95); H, 4.61 (4.43); N, 1.36 (1.34). FAB- MS: m/z 803 (C24-
Cl2F10H10PPd2). 31P{1H} NMR (deuterioacetone): δ 48.9 (s) ppm.
Preparation of [NBu4]2[Pd4(µ-Br)4(µ-PPh2)2(C6F5)4] (2). To a
solution of 1 (0.118 g, 0.056 mmol) in acetone (15 mL) was added
KBr (0.500 g, 4.202 mmol). The mixture was stirred at room
temperature for 20 h and evaporated to dryness. The residue was
extracted with CH2Cl2 (20 mL) and the solution evaporated almost to
dryness. CHCl3 (10 mL) was added with stirring, and a yellow solid
crystallized, which was filtered off, washed with CHCl3 (2 × 1 mL),
and air-dried (2, 0.089 g, 70% yield).
Preparation of [NBu4][Pd2(µ-PPh2)(acac-K2-O,O′)2(C6F5)2] (6). To
a solution of 1 (0.100 g, 0.048 mmol) in acetone (10 mL) was added
Tl(acac) (0.072 g, 0.237 mmol). After 2 h of stirring in the dark, the
suspension was filtered off and the filtrate concentrated almost to
dryness. Treatment of the resulting residue with iPrOH (10 mL) caused
the precipitation of a pale yellow solid, which was filtered off, washed
i
with PrOH (2 × 1 mL), and air-dried (6, 0.060 g, 53% yield).
IR (cm-1): C6F5 X-sensitive 781; acac ν(CdO) 1587, ν(CdC) 1509,
ν(C-H) 768. ΛM ) 81 Ω-1 cm2 mol-1
. Anal. Found (calcd for
C70F10H60NO4PPd2): C, 51.14 (51.21); H, 5.13 (5.16); N, 1.27 (1.20).
FAB- MS: m/z 931 (C34H24O4PPd2). 1H NMR (deuterioacetone),
acac: δ 1.7 (s, 3H), 1.8 (s, 3H), 5.2 (s, 1H) ppm. 31P{1H} NMR
(deuterioacetone): δ 46.2 (s) ppm.
Preparation of [Pd2(µ-PPh2)(C6F5)2(bipy)2][ClO4] (7). To a solu-
tion of 1 (0.052 g, 0.025 mmol) in acetone (10 mL) was added 2,2′-
bipy (0.016 g, 0.102 mmol). After 10 min of stirring at room temper-
ature, the solution was evaporated to ca. 1 mL. Treatment of the
solution with iPrOH (5 mL) and NBu4ClO4 (0.020 g, 0.058 mmol) and
partial evaporation resulted in a yellow solid, which was filtered off,
washed with iPrOH (3 × 1 mL), and air-dried (7, 0.050 g, 87% yield).
IR (cm-1): C6F5 X-sensitive 789. ΛM ) 115 Ω-1 cm2 mol-1. Anal.
Found (calcd for C44ClF10H26N4O4PPd2): C, 45.60 (46.20); H, 2.35
(2.29); N, 4.48 (4.90). FAB+ MS: m/z 1045 (C44F10H10N4PPd2). 1H
NMR (deuterioacetone), bipy: δ 10.9 (s broad, HR′, 1H), 8.6 (d, Hδ,
1H), 8.5 (d, Hδ′, 1H), 8.3 (td, Hγ, 1H), 8.2 (td, Hγ′, 1H), 7.9 (m, HR,
1H), 7.6 (m, Hâ, 1H), 7.5 (m, Hâ′, 1H) ppm; JRγ ) 1.6, JR′γ′ ) 1.5, Jγδ
) Jâγ ) 8.1, Jγ′δ′ ) Jâ′γ′ ) 8.1 Hz. 31P{1H} NMR (deuterioacetone):
δ 52.0 (s) ppm.
Preparation of [Pd2(µ-PPh2)(C6F5)2(phen)2][ClO4] (8). Complex
8 was prepared in a similar way using 1 (0.050 g, 0.024 mmol), 1,-
10-phen‚H2O (0.019 g, 0.096 mmol), and NBu4ClO4 (0.020 g, 0.058
mmol). Yield of 8: 0.030 g, 48%.
IR (cm-1): C6F5 X-sensitive 786. ΛM ) 125 Ω-1 cm2 mol-1. Anal.
Found (calcd for C48ClF10H26N4O4PPd2): C, 48.50 (48.37); H, 2.28
(2.20); N, 4.53 (4.70). FAB+ MS: m/z 1093 (C48F10H26N4PPd2). 1H
NMR (deuterioacetone), phen: δ 11.4 (s broad, 1H, HR′), 9.0 (d, 1H,
Hγ), 8.6 (d, 1H, Hγ′), 8.3 (m, 2H, HR + Hâ), 8.1 (d, 1H, Hδ′), 8.0 (dd,
1H, Hâ), 7.6 (dd, 1H, Hâ′) ppm; JRâ ) 5.4, Jâγ ) 7.5, Jδδ′ ) 8.9, JR′â′
) 5.0, Jâ′γ′ ) 7.7 Hz. 31P{1H} NMR (deuterioacetone): δ 51.8 (s)
ppm.
IR (cm-1): C6F5 X-sensitive 782. ΛM ) 159 Ω-1 cm2 mol-1. Anal.
Found (calcd for Br4C80F20H92N2P2Pd4): C, 41.89 (42.35); H, 4.33
(4.09); N, 1.21 (1.23). FAB- MS: m/z 893 (Br2C24F10H10PPd2). 31P-
{1H} NMR (deuterioacetone): δ 49.9 (s) ppm.
Preparation of [Pd2(µ-PPh2)(µ-X)(C6F5)2L2] (a) X ) Cl, L ) PPh3
(3). To an acetone solution (10 mL) of 1 (0.036 g, 0.017 mmol) was
added PPh3 (0.018 g, 0.069 mmol), and the mixture was stirred at room
temperature for 2.5 h. The solution was concentrated almost to dryness,
and iPrOH (10 mL) was added with stirring, causing a yellow solid to
i
precipitate, which was filtered off, washed with PrOH (2 × 1 mL),
Preparation of Crystals of 1 and 7 for X-ray Structure Deter-
minations. Suitable crystals of 1 and 7 for diffraction purposes were
obtained by slow diffusion of n-hexane into a solution of 0.025 g of
[NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4(C6F5)4] in acetone (4 mL) and [Pd2(µ-
PPh2)(C6F5)2(bipy)2][ClO4] in 1,2-dichloroethane (3 mL), respectively,
at 4 °C.
Crystal Structure Determination of [NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4-
(C6F5)4]‚2C3H6O (1). Table 1 lists pertinent crystallographic details.
All measurements were made on an Enraf-Nonius CAD4 diffractometer
with Mo KR X-radiation at 291 K. Unit cell parameters were
and air-dried (3, 0.033 g, 75% yield).
(8) (a) Uso´n, R.; Fornie´s, J.; Espinet, P.; Alfranca, G. Synth. React. Inorg.
Met.-Org. Chem. 1980, 10, 579. (b) Goodfellow, R. J.; Venanzi, L.
M. J. Chem. Soc. 1965, 7533. (c) Uso´n, R.; Fornie´s, J.; Toma´s, M. J.
Chem. Soc., Dalton Trans. 1980, 888. (d) Uso´n, R.; Fornie´s, J.;
Mart´ınez, F.; Toma´s, M.; Reoyo, I. Organometallics 1983, 2, 1386.
(e) Uso´n, R.; Fornie´s, J.; Navarro, R.; Garc´ıa, M. P. Inorg. Chim.
Acta 1979, 33, 69.
(9) Uso´n, R.; Fornie´s, J. AdV. Organomet. Chem. 1988, 28, 219 and
references given therein.

4428 Inorganic Chemistry, Vol. 36, No. 20, 1997
Alonso et al.
Scheme 1. Representation of the Reactions Leading to
Table 1. Crystallographic Data and Structure Refinement Details
for 1 and 7
Complexes 1-8
1‚2C3H6O
7‚C6H14
empirical formula C86H104Cl4F20N2O2P2Pd4 C50H40ClF10N4O4PPd2
mol wt
space group
a, Å
b, Å
c, Å
â, deg
V, Å3
T, K
2207.1
P21/c
1230.1
P21/n
11.679(5)
16.552(7)
23.868(8)
101.10(3)
4528(2)
291
16.214(3)
10.311(2)
28.380(6)
100.82(3)
4660(2)
150
Z
2
4
λ, Å
0.710 73
1.62
10.23
0.710 73
1.75
9.55
R ) 0.0398,
wR2 ) 0.0829
R ) 0.0698,
wR2 ) 0.0875
F
calc, g cm-3
µ(Mo KR), cm-1
R indices
R ) 0.038,
(obs data)a
R indices
Rw ) 0.062
R ) 0.072,
Rw ) 0.106
(all data)a
2
a R ) Σ||Fo| - |Fc||/Σ|Fo|. Rw ) [Σw(|Fo| - |Fc|)2/Σw|Fo| ]1/2. wR2
2
2
) [Σw(Fo - Fc2)2/Σw(Fo )2]1/2
.
determined by the least-squares refinement of the setting angles of 25
reflections, 11 e θ e 13°. Diffracted intensities were measured in a
quadrant of reciprocal space for 4.0 < 2θ < 50.0° (-13 e h e 13, 0
e k e 19, 0 e l e 28). Of the 8142 intensity data collected, 7936
unique observations remained after averaging of duplicate and equiva-
lent measurements and deletion of systematic absences (Rint 0.0778);
of these, there were 4876 with I > 3σ(I).
The structure was solved by direct methods and developed and
refined in a series of alternating difference Fourier maps and least-
squares analysis. An empirical absorption correction (DIFABS) was
applied.10 All non-hydrogen atoms, except for those of the solvent,
were refined with anisotropic thermal factors. The hydrogen atoms,
except for those of the solvent, were placed in calculated positions
and refined as riding atoms (C-H distance 0.96 Å) with a common
thermal parameter. The atoms of the acetone molecule appeared
disordered over two sites related by an inversion center and were refined
with occupancy 0.5 except for two carbon atoms that were in common
positions for the two molecules and were refined with occupancy 1.
The computer program package SHELXTL PLUS11 was used for all
crystallographic work. In the final stages of refinement, data were
2
weighted such that w-1 ) σ2|Fo| + g|Fo |, where g ) 0.000 01. Final
difference electron density maps showed no peaks above 1 e Å-3
(largest difference peak 0.44; largest difference hole -1.13).
Crystal Structure Determination of [Pd2(µ-PPh2)(C6F5)2(2,2′-
bipy)2][ClO4]‚C6H14 (7). Table 1 gives details of the crystallographic
study, which employed an Enraf-Nonius FAST diffractometer. Unit
cell parameters were determined by least-squares refinement of the
setting angles of 247 reflections and updated every 15° of ω rotation.
Almost one complete sphere of reciprocal space in the range 4.2 < 2θ
< 50.2° was measured at 150 K (-17 e h e 18, -8 e k e 11, -27
e l e 31). Of the 18 297 intensity data collected, 7104 unique
observations remained after averaging of duplicate and equivalent
measurements and deletion of systematic absences (Rint 0.0765); of
these, there were 2951 with I > 2σ(I).
were eventually refined with anisotropic displacement parameters. In
the final stages of refinement data were weighted such that w-1 ) σ2-
2
2
(Fo ) + (0.0304P)2, where P ) [max(Fo or 0) + 2Fc2]/3. Final
difference electron density maps showed no peaks above 1 e Å-3
(largest difference peak 0.79; largest difference hole -0.53).
Results and Discussion
Reaction of [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] and PdCl2. The
reaction between [NBu4]2[Pd2(µ-PPh2)2(C6F5)4]6 and PdCl2 in
acetone (molar ratio 1:1; reflux 3 h or room temperature 50 h)
results in the formation of a small amount of a black solid and
a yellow solution from which a deep-yellow solid is obtained.
The yellow solid is, in fact, a mixture of the starting material
[NBu4]2[Pd2(µ-PPh2)2(C6F5)4] and the product [NBu4]2[Pd4(µ-
PPh2)2(µ-Cl)4(C6F5)4] (1), thus indicating that the reaction
between the dinuclear [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] and PdCl2
requires a higher proportion of PdCl2 to reach completion. When
the reaction is carried out under similar conditions, but in a 1:2
molar ratio, only 1 is obtained as a deep-yellow solid, although
in low yield (34%) (Scheme 1, step a). A small amount of
palladium metal is also obtained, even if the reaction is carried
out at room temperature, indicating that reaction takes place
with partial decomposition.
The structure of complex 7 was solved by direct methods and refined
by full-matrix least-squares procedures (SHELXTL12 ). Following
isotropic convergence, an empirical absorption (DIFABS10) was applied
to the data set. All atoms were positionally refined, except for H atoms
(phenyl and bipy rings), set in idealized positions (C-H ) 0.93 Å)
-
with isotropic displacement parameters riding at 1.2U(C). The ClO4
anion was disordered over two sites (50:50) and was refined subject to
a Cl-O distance of 1.50(5) Å. In addition, residual electron density
believed to be n-hexane was located and modeled by (5 × 1) + (2 ×
0.5) carbon atoms (no H atoms included). All non-H atoms except
those of the n-hexane molecule and one of the half-perchlorate anions
Elemental analyses, conductivity, and mass spectral data (see
Experimental Section) allow us to formulate 1 as [NBu4]2[Pd4-
(µ-PPh2)2(µ-Cl)4(C6F5)4]. Furthermore, the formation of a
tetranuclear anion is in agreement with the fact that the reaction
requires a 1:2 molar ratio.
(10) Walker, N. G.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(11) SHELXTL-PLUS Software Package for the Determination of Crystal
Structures, Release 4.0; Siemens Analytical X-ray Instruments, Inc.;
Madison, WI, 1990.
(12) SHELXTL PC, version 5.0; Siemens Analytical Instruments Inc.:
Madison, WI, 1994.

Polynuclear µ-PPh2 Palladium Complexes
Inorganic Chemistry, Vol. 36, No. 20, 1997 4429
the metal are very close to 90°, Cl-Pd-Cl being the smallest,
ca. 85°, as previously reported for complexes with “Pd(µ-
Cl)2Pd” bridging systems.13 The Pd-C9 and Pd-Cl13 distances
are similar to those found in other complexes involving Pd-
C6F5 and Pd-Cl bonds. The Pd-P distances are 2.256(2) and
2.258(2) Å, and the Pd-P-Pd angle is 105.6(1)°, consistent
with the lack of a Pd-Pd bond.14
The “Pd(µ-Cl)2Pd” bridging system is not planar, as is usually
found, but is bent likely because of the existence of the
diphosphide bridge. The dihedral angle between the Pd(1) and
Pd(2) square-planar environments is 118.2(1)°. The four
palladium centers, the phosphorus, and the Cl(2) and Cl(2′)
atoms lie in an almost perfect plane. The Pd-Cl(1), Pd-Cl-
(1′), and Pd-C lines and the perpendicular to this plane subtend
angles of about 50°. Finally, the C6F5 rings are planar and
nearly perpendicular to the respective coordination planes of
the metal centers to which they are bonded [88.0° Pd(1) and
84.8° Pd(2)]. All the spectroscopic data agree with the solid
state structure.
Figure 1. Molecular structure of the anion of 1 showing the full atom-
labeling scheme.
Spectroscopic Data. The IR spectrum of 1 shows only one
absorption due to the X-sensitive mode [mainly ν(M-C)
character] of the C6F5 group9 [786 cm-1]. The 19F NMR
spectrum of 1 at room temperature is not informative since it
shows only two very broad signals, one in the o-F atom region
and the other in the m-F and p-F region. When the spectrum is
recorded at -80 °C, five signals of equal intensity (see Table
3) appear, indicating that 1 contains only one type of C6F5 ligand
and that the halves of the C6F5 rings are not equivalent on the
NMR time scale. The 31P{1H} NMR spectrum shows only one
signal (δ 48.9 ppm), indicating the equivalence of both PPh2
groups. However, this signal appears at much lower field than
the resonances found for systems containing the fragments “M-
(µ-PPh2)2M” {e.g., for [(C6F5)2M(µ-PPh2)2M′(C6F5)2]2-: M )
M′ ) Pd (δ -105.6 ppm); M, M′ ) Pd, Pt (δ -128.2 ppm); M
) M′ ) Pt (δ -146.9 ppm)}6 or “M(µ-PPh2)(µ-Cl)M” {e.g.,
for [(C6F5)2Pt(µ-PPh2)2M(µ-Cl)(µ-PPh2)Pt(PPh3)2]: M ) Pd (δ
2.37 ppm); M ) Pt (δ 1.39 ppm)}.3 Although in many cases
the 31P resonances in phosphido complexes permit the inference
that the metal centers supported by the bridging phosphido
ligand are involved in metal-metal bonding, the value observed
in this case is in the borderline region.7
Table 2. Selected Bond Distances (Å) and Angles (deg) and Their
Estimated Standard Deviations for
[NBu4]2[Pd4(µ-Cl)4(µ-PPh2)2(C6F5)4]‚2C3H6O (1‚2C3H6O)
Distances
Pd(1)-C(1)
Pd(1)-Cl(1)
Pd(1)-Cl(2)
Pd(1)-P
1.992(6)
2.417(1)
2.431(2)
2.256(2)
Pd(2)-C(7)
Pd(2)-Cl(1)
Pd(2)-Cl(2)
Pd(2)-P′
1.997(6)
2.424(2)
2.441(2)
2.258(2)
Angles
C(1)-Pd(1)-Cl(1)
C(1)-Pd(1)-Cl(2)
C(1)-Pd(1)-P
173.5(2) C(7)-Pd(2)-Cl(1)
89.0(2) C(7)-Pd(2)-Cl(2)
90.7(2) C(7)-Pd(2)-P′
85.3(1) Cl(1)-Pd(2)-Cl(2)
95.2(1) Cl(1)-Pd(2)-P′
175.1(1) Cl(2)-Pd(2)-P′
80.1(1) Pd(1)-Cl(2)-Pd(2)
105.6(1)
175.3(2)
90.5(2)
90.1(2)
84.9(1)
94.5(1)
176.7(1)
79.6(1)
Cl(1)-Pd(1)-Cl(2)
Cl(1)-Pd(1)-P
Cl(2)-Pd(1)-P
Pd(1)-Cl(1)-Pd(2)
Pd(1)-P-Pd(2′)
Similarly, [NBu4]2[Pd2(µ-PPh2)2(C6F5)4] reacts with K2-
[PdCl4] (1:2 molar ratio), rendering a small amount of palladium
and 1 in better yield (50%).
Aiming to prepare the analogous heteropolynuclear Pd/Pt
derivative, we have carried out the reaction between [NBu4]2-
[Pd2(µ-PPh2)2(C6F5)4] and PtCl2 under similar conditions.
However, in this case a higher quantity of a black solid (metals)
and a very small amount of 1, the homonuclear palladium
derivative, are obtained.
On the other hand, the reaction between [NBu4]2[(C6F5)2Pt-
(µ-PPh2)2Pt(C6F5)2]6 and K2[PtCl4] does not yield the analogous
tetranuclear platinum derivative but a mixture of compounds,
which we have not been able to identify.
Reactivity of [NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4(C6F5)4] (1). Sub-
stitution of the bridging chlorides in the tetranuclear complex
[NBu4]2[Pd4(µ-PPh2)2(µ-Cl)4(C6F5)4] (1) can easily be achieved.
Thus, complex 1 reacts with an excess of KBr in acetone at
room temperature, yielding the corresponding bromo derivative
2 (Scheme 1, step b). There is no evidence for the formation
of the anionic [Pd2(µ-PPh2)Br4(C6F5)2]3-, which would be the
result not only of substitution but also of bridge cleavage, even
Structure Characterization of [NBu4]2[Pd4(µ-PPh2)2(µ-
Cl)4(C6F5)4].2C3H6O (1‚2C3H6O). Crystal Structure. The
structure of the anion of complex 1 together with the atom
labeling scheme is shown in Figure 1. Selected bond distances
and angles are listed in Table 2. The complex anion in 1 is a
tetrametallic unit and can be regarded as formed by two (non-
coplanar) dinuclear palladium subunits “(C6F5)Pd(µ-Cl)2Pd-
(C6F5)”, these subunits being held together by two bridging PPh2
groups. The halves of the molecule are related by an inversion
center, and the palladium atoms lie at the corners of a rectangle.
The intermetallic distances are long enough [Pd(1)‚‚‚Pd(2)
3.119(1) Å; Pd(1)‚‚‚Pd(2′) 3.596(1) Å] to preclude the possibility
of metal-metal bonding.
(13) See for example: (a) Alyea, E. C.; Ferguson, G.; Malito, J.; Ruhl, B.
L. Organometallics 1989, 8, 1188. (b) Albanese, J. A.; Staley, D. L.;
Rheingold, A. L.; Burmeister, J. L. J. Organomet. Chem. 1989, 375,
265. (c) Crispini, A.; De Munno, G.; Ghedini, M.; Neve, F. J.
Organomet. Chem. 1992, 427, 409. (d) Ang, H. G.; Cai, Y. M.; Kwik,
M. L.; Rheingold, A. L. J. Chem. Soc., Chem. Commun. 1990, 1580.
(e) Newkome, G. R.; Evans, D. W.; Fronczek, F. R. Inorg. Chem.
1987, 26, 3500. (f) King, C.; Roundhill, D.; Fronczek, F. R. Inorg.
Chem. 1987, 26, 4288.
(14) (a) Berry, D. E.; Bushnell, G. W.; Dixon, K. R.; Moroney, P. M.;
Wan, C. Inorg. Chem. 1985, 24, 2625. (b) Manojlovic-Muir, L.; Lloyd,
B. R.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans. 1987, 201. (c)
Arif, A. M.; Heaton, D. E.; Jones, R. A.; Nunn, C. M. Inorg. Chem.
1987, 26, 4228. (d) Hadj-Bagheri, N.; Browning, J.; Dehghan, K.;
Dixon, K. R.; Meanwell, N. J.; Vefghi, R. J. Organomet. Chem. 1990,
396, C47. (e) Albinati, A.; Lianza. F.; Pasquali, M.; Sommovigo, M.;
Leoni, P.; Pregosin, P. S.; Ru¨egger, H. Inorg. Chem. 1991, 30, 4690.
(f) Sommovigo, M.; Pasquali, M.; Leoni, P.; Braga, D.; Sabatino, P.
Chem. Ber. 1991, 124, 97. (g) Leoni, P.; Sommovigo, M.; Pasquali,
M.; Sabatino, P.; Braga, D. J. Organomet. Chem. 1992, 423, 263.
The square-planar environment of each palladium atom
comprises a pentafluorophenyl group, two mutually cis chlorine
bridges to one adjacent metal center, and a diphenylphosphide
ligand bridging to another palladium atom. The angles around

4430 Inorganic Chemistry, Vol. 36, No. 20, 1997
Table 3. 19F NMR Data [δ (ppm)] for complexes 1-8
Alonso et al.
complex
T, °C
δ(Fortho
)
δ(Fmeta
)
δ(Fpara)
[NBu4]2[Pd4(µ-Cl)4(µ-PPh2)2(C6F5)4] (1)a
[NBu4]2[Pd4(µ-Br)4(µ-PPh2)2(C6F5)4] (2)a
[Pd2(µ-Cl)(µ-PPh2)(C6F5)2(PPh3)2] (3)a
-80
-80
20
-80
20
-80
20
-55
20
-80
55
20
55
20
-112.9 (1F), -118.8 (1F)
-111.5 (1F), -116.3 (1F)
-113.9 (2F)
-164.8 (1F), -167.8 (1F)
-163.1 (1F), -166.1 (1F)
-163.4 (2F)
-165.9 (1F)
-164.4 (1F)
-163.1 (1F)
-162.3 (1F)
-156.2 (1F)
-160.4 (1F)
-162.9 (1F)
-162.3 (1F)
-165.7 (1F)
-164.4 (1F)
-160.5 (1F)
160.4 (1F)
-114.4 (2F)
-162.6 (2F)
[Pd2(µ-Cl)(µ-PPh2)(C6F5)2(py)] (4)a
[Pd2(µ-Br)(µ-PPh2)(C6F5)2(PPh3)2] (5)b
[NBu4][Pd2(µ-PPh2)(acac)2(C6F5)2] (6)a
[Pd2(µ-PPh2)(C6F5)2(bipy)2][ClO4] (7)a
[Pd2(µ-PPh2)(C6F5)2(phen)2][ClO4] (8)a
-110.2 (2F)
-156.0 (2F)
-115.5 (2F)
-162.0 (2F)
-115.2 (2F)
-163.7 (2F)
-115.4 (2F)
-163.1 (2F)
-114.4 (2F)
-166.0 (2F)
-114.4 (2F)
-165.1 (2F)
-117.0 (1F), -119.0 (1F)
-117.2 (1F), -119.1 (1F)
-116.9 (1F), -118.3 (1F)
-117.1 (1F), -118.5 (1F)
-117.5 (1F), -117.9 (1F)
-160.4 (1F), -162.8 (1F)
-160.3 (1F), -162.7 (1F)
-160.5 (1F), -162.8 (1F)
-160.4 (1F), -162.7 (1F)
-160.3 (1F), -161.8 (1F)
-160.5 (1F)
-160.4 (1F)
-160.1 (1F)
-80
a Measured in deuterioacetone. b Measured in deuteriochloroform. c Broad signals.
Figure 2. Possible isomers of complexes of stoichiometry [Pd2Cl-
(C6F5)2L2(PPh2)].
when a great excess of NBu4Br is used. The spectroscopic data
indicate that 2 has a structure similar to that of 1.
Treatment of 1 with neutral monodentate ligands such as PPh3
or py, in a 1:4 molar ratio in acetone, results in the formation
of the dinuclear species [Pd2(µ-Cl)(µ-PPh2)(C6F5)2L2] (L ) PPh3
(3), py (4)) (Scheme 1, step c) (for elemental analysis and mass
spectra, see Experimental Section).
Figure 3. Molecular structure for the cation of 7 showing the full
atom labeling scheme.
Spectroscopic data indicate that only one of the four possible
isomers (A-D) (see Figure 2) has been obtained in both cases.
The IR spectra of 3 and 4 show only one absorption
assignable to the X-sensitive mode of the C6F5 groups,9 and
thus structure A can be ruled out.
d), for which a structure similar to that of 3 can be inferred
from spectroscopic data.
Finally, the elimination of all bridging halides can be achieved
by using bidentate chelating ligands. Thus, the reactions of 1
with Tl(acac) or N-N ligands (N-N ) bipy or phen), in a 1:4
molar ratio, result in the formation of the corresponding anionic
(6) or cationic (7 and 8) dinuclear complexes (Scheme 1, steps
e and f) with only one PPh2 ligand bridging both metal centers.
Elemental analysis, conductivity measurements in solution, and
FAB mass spectra are consistent with this formulation (see
Experimental Section).
Structure Characterization of Complexes 7-9. Crystal
Structure of [Pd2(µ-PPh2)(C6F5)2(bipy)2]ClO4‚C6H14 (7‚C6H14).
The structure of the cation of 7 is shown in Figure 3, and
selected bond distances and angles are given in Table 4. The
cation consists of two “Pd(C6F5)(bipy)” moieties which are held
together by a bridging PPh2 ligand. The long Pd‚‚‚Pd distance
[3.670(1) Å] and the consequent wide Pd-P-Pd angle [106.11-
(6)°] clearly point to the absence of any Pd-Pd interaction.
The Pd atoms are located in nearly square-planar environ-
ments with the metal centers displaced 0.114 Å [Pd(1)] and
0.112 Å [Pd(2)] from the best (least-squares) coordination plane.
The dihedral angle between these coordination planes is 131.9°.
The pentafluorophenyl rings are almost perpendicular to the
palladium coordination plane, the dihedral angles being 86.9°
[Pd(1)] and 83.6° [Pd(2)]. Finally, the chelating bipy ligands
are not perfectly planar since each pyridine ring is slightly
The 19F NMR spectra (at room and low temperature) show
three resonances due to o-F, p-F, and m-F atoms in a 2:1:2 ratio,
respectively (see Table 3). This pattern (AA′MM′X spin
system) indicates that only one type of C6F5 group is present in
both cases and allows elimination of structure C.
The 31P{1H} NMR spectrum of 3 consists of eight lines
corresponding to a typical pattern of an AB2 spin system. The
value of 2J(PPh2-PPh3) (350.2 Hz) seems to indicate that PPh2
and PPh3 are mutually trans, i.e. that complex 3 displays the
structure B. The spectrum of complex 4 shows, as expected, a
singlet, although from the spectroscopic data it is not possible
to infer whether 4 has structure B or D.
If it is assumed that the “Pd(µ-PPh2)Pd” bridging system is
preserved in the course of the reaction, initial bridge cleavage
and bridge formation with concomitant halide elimination have
to occur in the formation of the neutral complexes 3 and 4
(Scheme 1, step c).
When complex 3 is reacted with an excess of PPh3 in acetone,
with the intention of cleaving the “Pd(µ-Cl)(µ-PPh2)Pd” bridging
system, no reaction takes place, indicating the strength of that
bridging system.
On the other hand, the reaction of 3 with excess KBr in
acetone produces the substituted derivative 5 (Scheme 1, step

Polynuclear µ-PPh2 Palladium Complexes
Inorganic Chemistry, Vol. 36, No. 20, 1997 4431
Table 4. Selected Bond Distances (Å) and Angles (deg) and Their Estimated Standard Deviations for
[Pd2(µ-PPh2)(C6F5)2(2,2′-bipy)2][ClO4]‚C6H14 (7‚C6H14)
Distances
Pd(1)-C(1)
Pd(1)-P(1)
Pd(2)-N(3)
P(1)-C(13)
2.004(5)
2.304(2)
2.113(4)
1.832(5)
Pd(1)-N(2)
Pd(2)-C(29)
Pd(2)-P(1)
2.108(4)
2.019(5)
2.289(2)
Pd(1)-N(1)
Pd(2)-N(4)
P(1)-C(7)
2.115(4)
2.108(4)
1.827(5)
Angles
C(1)-Pd(1)-N(2)
C(1)-Pd(1)-P(1)
C(29)-Pd(2)-N(4)
C(29)-Pd(2)-P(1)
C(7)-P(1)-C(13)
C(7)-P(1)-Pd(1)
C(6)-C(1)-Pd(1)
C(30)-C(29)-Pd(2)
94.4(2)
88.5(2)
96.7(2)
C(1)-Pd(1)-N(1)
N(2)-Pd(1)-P(1)
C(29)-Pd(2)-N(3)
N(4)-Pd(2)-P(1)
C(7)-P(1)-Pd(2)
C(13)-P(1)-Pd(1)
C(2)-C(1)-Pd(1)
169.4(2)
170.93(12)
173.0(2)
168.32(13)
114.4(2)
114.7(2)
125.0(4)
N(2)-Pd(1)-N(1)
N(1)-Pd(1)-P(1)
N(4)-Pd(2)-N(3)
N(3)-Pd(2)-P(1)
C(13)-P(1)-Pd(2)
Pd(2)-P(1)-Pd(1)
C(34)-C(29)-Pd(2)
77.4(2)
100.72(13)
78.2(2)
97.53(13)
108.8(2)
106.11(6)
120.0(4)
88.3(2)
104.1(2)
108.9(2)
120.7(4)
124.8(4)
twisted about the C-C bond {C(23)-C(24) [10.0°], C(39)-
C(40) [7.1°]}.
in which the starting material [Pd2(µ-PPh2)2(C6F5)4]2- acts as
an arylating agent toward PdCl2.
The Pd-P distances in 7 are slightly longer than the
corresponding ones found in 1, and the Pd-N distances are in
the range of other Pd-N distances.15
It seems reasonable that complexes 6 and 8 display a structure
similar to the one found for 7.
As a consequence of this rearrangement process, the increase
in the nuclearity of the final product (complex 1) results not in
a linear chainlike structure of Pd square-planar environments
linked by PPh2 and Cl ligands but in a rectangular closed
structure. This kind of disposition is not unknown for Pd or Pt
complexes, but in most previous cases, the metal centers are
involved in metal-metal bonds.17 The Pd-Pd distances in 1
preclude any kind of intermetallic interaction. A few examples
of tetranuclear Pd(II) or Pt(II) derivatives with the metal centers
in a tetrahedral array and without metal-metal bonds were also
reported recently.18
The phosphido bridging system in 1 is very stable, since it is
not cleaved by the addition of ligands such as Br-, PPh3, py,
acac-, bipy, or phen. In all cases, the “Pd(µ-PPh2)Pd” unit
remains intact and it is the chloride ligands which undergo
substitution or cleavage reactions. For complexes 6-8, PPh2
is the only ligand responsible for the link between both Pd
centers (no Pd-Pd bond is present), an unusual situation which
proves the stability of the “Pd(µ-PPh2)Pd” system.
Spectroscopic Data. The 19F NMR spectrum of complex 6
(at room and low temperature) shows three signals in a 2:1:2
ratio pointing to only one type of C6F5 group, in which both
o-F (and both m-F) atoms are equivalent (see Table 3).
The 19F NMR spectra of complexes 7 and 8 show five signals
of equal intensity (even at 50 °C), indicating that the N-N
ligands are more sterically demanding than the acac ligand and
that neither are the coordination planes of the palladium atoms
symmetry planes (on the NMR time scale) nor are the C6F5
groups free to rotate around the Pd-Cipso bonds even at 50 °C.
1
The H NMR spectrum of 6 shows three signals, in a 1:3:3
ratio, as expected for equivalent acac ligands. Eight signals of
equal intensity, due to the bipy or phen ligands, are observed
in the 1H NMR spectra of 7 and 8. The complete assignments
of the chemical shifts and coupling constants (see Experimental
1
Section) have been carried out by H-1H COSY experiments.
Acknowledgment. We thank the Direccio´n General de
Investigacio´n Cient´ıfica y Te´cnica (DGICYT) of Spain (Project
PB95-003-C01 and a grant to A.M.) for financial support. E.A.
acknowledges the Diputacio´n General de Arago´n for a grant.
We also thank Prof. M. B. Hursthouse (University of Wales,
Cardiff, U.K.) for data collection at the EPSRC National
Crystallographic Service.
The 31P{1H} NMR spectra of complexes 6-8 show only a
singlet, in accordance with the proposed formulation. The
positions of the respective resonances (≈50 ppm; see Experi-
mental Section) are similar to that of complex 1. These types
of complexes in which the two metal centers are linked solely
Via one PPh2 bridging ligand are scarce, since in most previously
reported complexes metal-metal bonds and/or other bridging
ligands are also present.4e,4g,16
Supporting Information Available: Tables of crystallographic
data, full atomic positional and equivalent isotropic displacement
parameters, anisotropic displacement parameters, full bond distances
and bond angles, and hydrogen coordinates and isotropic displacement
parameters for 1 (10 pages). A X-ray crystallograpic file, in CIF format,
for complex 7 is available on the Internet only. Ordering and access
information is given on any current masthead page.
Concluding Remarks
In this paper, we present the synthesis, structural characteriza-
tion, and reactivity studies of polynuclear pentafluorophenyl Pd
complexes containing the ligand diphenylphosphide acting as
a bridge. It is well-known that the bridging “M(µ-PPh2)2M”
systems are very stable and the reactions of complexes contain-
ing this bridging system usually involve the other ligands present
in the molecule. Nevertheless, complex 1 is formed in a process
in which the integrity of the polynuclear “Pd(µ-PPh2)2Pd” is
not maintained. The mechanism of the formation of 1 cannot
be established but implies a severe rearrangement of the ligands
IC9701930
(17) (a) Rauter, H.; Hillgeris, E. C.; Erxleben, A.; Lippert, B. J. Am. Chem.
Soc. 1994, 116, 616. (b) Yamaguchi, T.; Ueno, T.; Ito, T. Inorg. Chem.
1993, 32, 4996. (c) Mimoun, H.; Charpentier, R.; Mitschler, A.;
Fischer, J.; Weiss, R. J. Am. Chem. Soc. 1980, 102, 1047. (d)
Stromnova, T. A.; Busygina, I. N.; Katser, S. B.; Antsyshkina, A. S.;
Porai-Koshits, M. A.; Moiseev, I. I. J. Chem. Soc., Chem. Commun.
1988, 114. (e) Stang, P. J.; Cao, D. H. J. Am. Chem. Soc. 1994, 116,
4981. (f) Yamaguchi, T.; Shibata, A.; Ito, T. J. Chem. Soc., Dalton
Trans. 1996, 4031.
(15) Orpen, A. G.; Brammer, L.; Allen, F. A.; Kennard, O.; Watson, D.
G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1.
(16) (a) Shyu, S.-G.; Hsu, J.-F.; Wen, Y.-S. J. Organomet. Chem. 1993,
453, 97. (b) Shyu, S.-G.; Lin, P.-J.; Wen, J.-S. J. Organomet. Chem.
1993, 443, 115. (c) Shyu, S.-G.; Lin, P.-J.; Lin, K.-J.; Chang, M.-C.;
Wen, Y.-S. Organometallics 1995, 14, 2253. (d) Doherty, S.; Elsegood,
M. R. J.; Clegg, W.; Waugh, M. Organometallics 1996, 15, 2688. (e)
Blenkiron, P.; Enright, G. D.; Taylor, N. J.; Carty, A. J. Organome-
tallics 1996, 15, 2855.
(18) (a) Cuevas, J. V.; Garc´ıa-Herbosa, G.; Mun˜oz, M. A.; Hickman, S.
W.; Orpen, A. G.; Connelly, N. J. J. Chem. Soc., Dalton Trans. 1995,
4127. (b) Yang, H.; Khan, M. A.; Nicholas, K. M. J. Chem. Soc.,
Chem. Commun. 1992, 212. (c) Kawamoto, T.; Nagasawa, I.; Kuma,
H.; Kushi, Y. Inorg. Chem. 1996, 35, 2427. (d) Zhang, Y.; Puddephatt,
R. J.; Manojlovic-Muir, L.; Muir, K. W. J. Chem. Soc., Chem.
Commun. 1996, 2599.