Stabilization of the P(CF3)2- and P(C6F5)2- ions by coordination to pentacarbonyl tungsten: Structures of [18-crown-6-K]P(CF3)2, [18-crown-6-K][W{P(CF3)2}(CO)5], and [18-crown-6-K][{W(CO)5}2{μ-P(C6 F5)2}]·THF

Article abstract of DOI:10.1021/ic034165v

The stabilization of the P(CF₃)^2- ion by intermediary coordination to the very weak Lewis acid acetone gives access to single crystals of [18-crown-6-K]P(CF₃)₂. The X-ray single crystal analysis exhibits nearly isolated P(CF₃)₂-ions with an unusually short P-C distance of 184(1) pm, which can be explained by negative hyperconjugation and is also found by quantum chemical hybrid DFT calculation. Coordination of the P(CF₃)^2- ion to pentacarbonyl tungsten has only a minor effect on electronic and geometric properties of the P(CF₃)₂ moiety, while a strong increase in thermal stability of the dissolved species is achieved. The hitherto unknown P(C₆F₅)^2- ion is stabilized by coordination to pentacarbonyl tungsten and isolated as a stable 18-crown-6 potassium salt, [18-crown-6-K]- [W{P(C₆F₅)₂}(CO)₅], which is fully characterized. The tungstate, [W{P(C₆F₅)₂}(CO)₅]^-, decomposes slowly in solution, while coordination of the phosphorus atom to a second pentacarbonyl tungsten moiety results in an enhanced thermal stability in solution. The single-crystal X-ray analysis of [18-crown-6-K][{W(CO)₅}₂{μ-P(C₅ F₅)₂}]·THF exhibits a very tight arrangement of the two C₆F₅ and two W(CO)₅ groups around the central phosphorus atom. NMR spectroscopic investigations of the [{W(CO)₅}₂{μ-P(C₆ F₅)₂}]^- ion exhibit a hindered rotation of both the C₆F₅ and W(CO)₅ groups in solution.

Full text of DOI:10.1021/ic034165v

Inorg. Chem. 2003, 42, 3633−3641
Stabilization of the P(CF3)2- and P(C F ) - Ions by Coordination to
6 5 2
Pentacarbonyl Tungsten: Structures of [18-crown-6-K]P(CF3)2,
[18-crown-6-K][W{P(CF3)2}(CO)5], and
[18-crown-6-K][{W(CO)5}2{µ-P(C F ) }]‚THF
6 5 2
Berthold Hoge,* Christoph Tho1sen, Tobias Herrmann, and Ingo Pantenburg
Institut fu¨r Anorganische Chemie, UniVersita¨t zu Ko¨ln, D-50939 Ko¨ln, Germany
Received February 14, 2003
The stabilization of the P(CF ) - ion by intermediary coordination to the very weak Lewis acid acetone gives
3 2
access to single crystals of [18-crown-6-K]P(CF3)2. The X-ray single crystal analysis exhibits nearly isolated P(CF3)2-
ions with an unusually short P−C distance of 184(1) pm, which can be explained by negative hyperconjugation and
is also found by quantum chemical hybrid DFT calculation. Coordination of the P(CF ) - ion to pentacarbonyl
3 2
tungsten has only a minor effect on electronic and geometric properties of the P(CF ) moiety, while a strong
3 2
increase in thermal stability of the dissolved species is achieved. The hitherto unknown P(C F ) - ion is stabilized
6
5 2
by coordination to pentacarbonyl tungsten and isolated as a stable 18-crown-6 potassium salt, [18-crown-6-K]-
[W{P(C F ) }(CO)5], which is fully characterized. The tungstate, [W{P(C F ) }(CO)5]-, decomposes slowly in solution,
6
5 2
6 5 2
while coordination of the phosphorus atom to a second pentacarbonyl tungsten moiety results in an enhanced
thermal stability in solution. The single-crystal X-ray analysis of [18-crown-6-K][{W(CO)5}2{µ-P(C F ) }]‚THF exhibits
6
5 2
a very tight arrangement of the two C F and two W(CO)5 groups around the central phosphorus atom. NMR
6
5
spectroscopic investigations of the [{W(CO)5}2{µ-P(C F ) }]- ion exhibit a hindered rotation of both the C F and
6
5 2
6 5
W(CO)5 groups in solution.
Introduction
transition metal complexes.4,5 To offer this application for
use in asymmetric catalysis, we are investigating different
strategies for the synthesis of chiral, bidentate bis(perfluo-
roorganyl)phosphane derivatives. In view of this target, our
The electronic properties of perfluoroorganyl element
compounds are strongly affected by the electronic charac-
teristics of the perfluoroorganyl groups. For example, per-
fluoroorganylphosphanes exhibit higher ionization energies1
and increased Lewis acidity2 in comparison to nonfluorinated
derivatives. Depending on the strong π-acidity and weak
σ-basicity of perfluoroorganylphosphanes, the electron deficit
at the phosphorus atoms will be transferred to the metal atom
in corresponding perfluoroorganylphosphane transition metal
complexes.3,4 For this reason, perfluoroorganylphosphane
ligands are important tools to tune the Lewis acidity of
-
work is focused on the synthesis of nucleophilic P(CF3)2
-
and P(C6F5)2 synthons and the investigation of their
chemical properties.
For the use of the P(CF3)2- ion6 in nucleophilic substitution
reactions, it is necessary to reduce the negative hypercon-
jugation, which is associated with a C-F activation. For this
reason we synthesized different bis(trifluoromethyl)phos-
phanido complexes of mercury7 and silver8 and investigated
their implementation in nucleophilic substitution reactions.
* Author to whom correspondence should be addressed. Fax: 049-221-
470-5196. E-mail: b.hoge@uni-koeln.de.
(1) For example: Gleiter, R.; Goodmann, W. D.; Scha¨fer, W.; Grobe, J.;
Apel, J. Chem. Ber. 1983, 116, 3745-3750. Elbel, S.; Dieck, H. T. J.
Fluorine Chem. 1982, 19, 349-362.
(2) For example: Kolomeitsev, A.; Go¨rg, M.; Dieckbreder, U.; Lork, E.;
Ro¨schenthaler, G.-V. Phosphorus, Sulfur Silicon Relat. Elem. 1996,
109-110, 597-600. Deng, R. M. K.; Dillon, K. B.; Sheldrick, W. S.
J. Chem. Soc., Dalton Trans. 1990, 551-554.
(3) For example: Apel, J.; Grobe, J. Z. Anorg. Allg. Chem. 1979, 453,
53-67.
(4) Bennett, L. B.; Hoerter, J. M.; Houlis, J. F.; Roddick, D. M.
Organometallics 2000, 19, 615-621. White, S.; Bennett, B. L.;
Roddick, D. M. 1999, 18, 2536-2542. Peters, R. G.; Bennett, B. L.;
Schnabel, R. C.; Roddick, D. M. Inorg. Chem. 1997, 36, 5962-5965.
(5) Viton, F.; Bernardinelli, G.; Ku¨ndig, E. P. J. Am. Chem. Soc. 2002,
124, 4968-4969. Ku¨ndig, E. P.; Saudan, C. M.; Bernardinelli, G.
Angew. Chem., Int. Ed. 1999, 38, 1220-1222. Ku¨ndig, E. P.; Bourdin,
B.; Bernardinelli, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 1856-
1858. Bruin, M. E.; Ku¨ndig, E. P. Chem. Commun 1998, 2635-2636.
(6) Hoge, B.; Tho¨sen, C. Inorg. Chem. 2001, 40, 3113-3116.
10.1021/ic034165v CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/06/2003
Inorganic Chemistry, Vol. 42, No. 11, 2003 3633

Hoge et al.
In the synthesis of the first example of a chiral bidentate
bis(trifluoromethyl)phosphane derivative (I),9 it was neces-
sary to stabilize the P(CF3)2- ion by intermediary formation
of a donor acceptor adduct, using the extremely weak Lewis
acid acetone.10
tronic (and that means nucleophilic) characteristics of the
P(CF3)2 and P(C6F5)2 ions.
-
-
Experimental Section
Materials and Apparatus. Chemicals were obtained from
commercial sources and used without further purification. Literature
methods were used for the synthesis of HP(CF3)2 and HP(C6F5)2
and their pentacarbonyl tungsten complexes.12 18-Crown-6-potas-
sium bis(trifluoromethyl)phosphanide6 was synthesized according
to the literature method.
CAUTION! The toxic compound HP(CF3)2 reacts violently with
air. Solvents were purified by standard methods.13 Standard high-
vacuum techniques were employed throughout all preparative
procedures; nonvolatile compounds were handled in a dry N2
atmosphere by using Schlenk techniques.
Infrared spectra were recorded on a Nicolet-5PC-FT-IR spec-
trometer as KBr pellets. Raman spectra were measured on a Bruker
FRA-106/s spectrometer with a Nd:YAG laser operating at λ )
1064 nm.
-
Previous hybrid density calculations of the P(CF3)2 ion
at the B3PW91/6-311G(d) level of theory in combination
with vibrational spectroscopy predicted shortened P-C and
elongated C-F distances, as occurs in the case of negative
hyperconjugation which can be described by the following
resonance structures:6
The NMR spectra were recorded on Bruker model AMX 300
(13C, 75.47 MHz; 31P, 121.50 MHz; 19F, 282.35 MHz) and Bruker
AC 200 spectrometers (31P, 81.01 MHz; 19F 188.31 MHz; 13C, 50.32
MHz; 1H, 200.13 MHz) with positive shifts being downfield from
the external standards 85% orthophosphoric acid (31P), CCl3F (19F),
and TMS (13C and 1H). Higher order NMR spectra were calculated
with the program gNMR.14 Quantum chemical hybrid density
functional calculations were performed with the Gaussian 98
program package.15
Preparation of 18-Crown-6-potassium Pentacarbonylbis-
(trifluoromethyl)phosphanidotungstate. A solution of 0.56 g (1.70
mmol) of [18-crown-6-K]CN in 5 mL of CH2Cl2 was added
dropwise to a suspension of 0.84 g (1.70 mmol) of [W(CO)5PH-
(CF3)2] in 15 mL of CH2Cl2 at -78 °C. After the temperature was
allowed to rise to -30 °C over 3 h, the solution was cooled to
-78 °C. The product was precipitated by adding a 50 mL portion
of hexane. The solution was removed via a syringe, and the solid
residue was washed several times with hexane. Removal of all
volatile compounds was performed during the warming up to room
temperature and yielded 0.48 g (0.60 mmol, 35%) of [18-crown-
6-K][WP(CF3)2(CO)5] as a slightly green powder. The neat
compound decomposes at 255 °C (DTA/TG). Negative ESI mass
spectrum (acetone/methanol) {m/z (%) [assignment]}: 493 (10)
[WP(CF3)2(CO)5]-; 465 (36) [WP(CF3)2(CO)4]-; 437 (16) [WP(CF3)2-
(CO)3]-; 409 (100) [WP(CF3)2(CO)2]-; 381 (13) [WP(CF3)2(CO)]-;
353 (18) [WP(CF3)2]-; 315 (16) [WF(CO)4]-; 287 (20) [WF(CO)3]-.
Positive ESI mass spectrum (acetone) {m/z (%) [assignment]}: 303
To prove this prediction by single-crystal X-ray crystal-
lography it is necessary to increase the lifetime of the
P(CF3)2 ion in solution to obtain suitable single crystals.
-
While the neat phosphanides [NEt4]P(CF3)2 and [18-crown-
-
6-K]P(CF3)2 are stable up to 140 °C, the P(CF3)2 ion
decomposes above -30 °C in CH2Cl2 and THF solution.
In order to synthesize bis(pentafluorophenyl)phosphanides,
we treated bis(pentafluorophenyl)phosphane, HP(C6F5)2, with
cyanide salts at low temperature. Due to the strong nucleo-
-
philicity of the P(C6F5)2 ion, the anion oligomerizes even
at low temperature, while the synthesis in the presence of
excess CS2 allows the isolation of the thermally sensitive
CS2 adduct (II).11
A preliminary structural and density functional study on
HP(CF3)2 and HP(C6F5)2 and their pentacarbonyl tungsten
complexes proves that the pentacarbonyl tungsten moiety has
no major structural nor electronic influence on the HP(CF3)2
and HP(C6F5)2 ligand in comparison to the noncoordinated
phosphanes. In view of these results, we investigated the
influence of pentacarbonyl tungsten moieties on coordinated
(12) Hoge, B.; Herrmann, T.; Tho¨sen, C.; Pantenburg, I. Inorg. Chem. 2003,
42, 3623-3632.
(13) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon Press: Oxford, England, 1980.
(14) Budzelaar, P. H. M. gNMR, version 4.1; Cherwell Scientific: Oxford,
U.K., 1998.
(15) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts,
R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C.
Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.; Gonzalez, C.;
Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revision
A.9; Gaussian, Inc.: Pittsburgh, PA, 1998.
-
-
P(CF3)2 and P(C6F5)2 ions. The goal of this study is the
-
-
stabilization of the P(CF3)2 and P(C6F5)2 ions by the
formation of the corresponding pentacarbonyl-phosphanido-
tungstate complexes without major influence on the elec-
(7) Hoge, B.; Tho¨sen, C.; Pantenburg, I. Inorg. Chem. 2001, 40, 3084-
3088; Pantenburg, I.; Tho¨sen, C.; Hoge, B. Z. Anorg. Allg. Chem.
2002, 628, 1785-1788.
(8) Hoge, B.; Herrmann, T.; Tho¨sen, C.; Pantenburg, I. In preparation.
(9) Hoge, B.; Tho¨sen, C.; Panne, P.; Herrmann, T.; Pantenburg, I.
Phosphorus, Sulfur Silicon Relat. Elem. 2002, 177, 1457-1462.
(10) Hoge, B.; Tho¨sen, C. Phosphorus, Sulfur Silicon Relat. Elem. 2002,
177, 2151-2152.
(11) Hoge, B.; Herrmann, T.; Tho¨sen, C.; Pantenburg, I. Inorg. Chem. 2002,
41, 2260-2265.
3634 Inorganic Chemistry, Vol. 42, No. 11, 2003

-
-
Stabilization of the P(CF3)2 and P(C6F5)2 Ions
(100) [18-crown-6-K]. Elemental anal. (calcd for C19H24F6KO11-
PW): C 28.74 (28.66); H 3.10 (3.04). Infrared spectrum (cm-1
)
(KBr pellet): 2953 w, 2919 m, 2890 m, 2861 w, 2830 w, 2799
vw, 2749 vw, 2066 m, 1971 s, 1917 vs, 1865 vs, 1829 m, 1476 w,
1454 w, 1435 vw, 1352 m, 1287 w, 1250 w, 1238 w, 1150 s, 1136
m, 1109 vs, 1067 s, 1057 s, 962 m, 837 w, 729 vw, 669 vw, 598
m, 582 m, 556 w, 529 w, 457 w, 449 w, 438 vw, 417 w. Raman
(cm-1): 2955 (9), 2918 (18) 2897 (17), 2879 (16), 2849 (16), 2810
(8), 2754 (3), 2729 (3), 2064 (36), 1979 (100), 1946 (13), 1915
(13), 1869 (45), 1476 (9), 1454 (3), 1410 (3), 1292 (2), 1275 (7),
1248 (5), 1146 (5), 1111 (3), 1082 (4), 1072 (3), 1061 (2), 951 (2),
872 (6), 831 (5), 729 (6), 548 (4), 532 (3), 455 (6), 438 (22), 407
(2), 475 (10), 376 (4), 289 (5), 280 (5), 255 (3), 235 (3), 201 (4),
114 (23), 93 (39). NMR data (CDCl3; rt) of the [18-crown-6-K]+
counterion: δ(1H) 3.5 ppm; δ(13C) 70.8 ppm. The NMR spectro-
scopic data of the [WP(CF3)2(CO)5]- anion are summarized in Table
1. The experimental (top) and calculated (bottom) 31P NMR
spectrum is shown in Figure 5.
Preparation of Ethylbis(trifluoromethyl)phosphanepenta-
carbonyltungsten. Solutions of [18-crown-6-K][WP(CF3)2(CO)5]
in CH2Cl2 were treated at room temperature with an excess of ethyl
tosylate and iodoethane, respectively. The resulting clear solutions
were evaporated to dryness at 0 °C, and the product was sublimed
into a stopcock vessel warming the residue up to room temperature.
The product [W(CO)5P(CF3)2Et], a colorless solid, was identified
by mass and multinuclear NMR spectroscopy. Mass spectrum (EI;
20 eV) {m/z (%) [assignment]}: 522 (100) [W(CO)5P(CF3)2Et]+;
494 (23) [W(CO)4P(CF3)2Et]+; 453 (8) [W(CO)5P(CF3)Et]+; 438
(32) [W(CO)2P(CF3)2Et]+; 410 (24) [W(CO)P(CF3)2Et]+; 382 (44)
[WP(CF3)2Et]+. NMR data of [W(CO)5P(CF3)2Et] (CH2Cl2; rt):
δ(19F) -60.0 ppm; δ(31P) 55.8 ppm; 1J(WP) 267.4 Hz; 2J(PF) 69.4
Hz; 2J(PH) 8.1 Hz; 3J(PH) 20.4 Hz; 3J(WF) 21.8 Hz. The 19F NMR
and 31P NMR spectra are part of the Supporting Information.
Preparation of 18-Crown-6-potassium Pentacarbonylbis(penta-
fluorophenyl)phosphanidotungstate. A solution of 3.45 g (5.00
mmol) of [W(CO)5PH(C6F5)2] in 15 mL of CH2Cl2 was treated
dropwise with a solution of 1.65 g (5.00 mmol) of [18-crown-6-
K]CN in 10 mL of CH2Cl2 at -50 °C. The resulting red solution
was stirred for 1 h at -50 °C before the product was precipitated
by the addition of 50 mL of pentane. The solution was removed
via a syringe, and the solid residue was washed several times with
pentane. The remaining yellow powder, 3.32 g (3.35 mmol; 67%)
of [18-crown-6-K][W{P(C6F5)2}(CO)5], was dried in vacuo. El-
emental anal. (calcd for C29H24F10KO11PW): C 35.02 (35.10); H
2.66 (2.44). NMR data (acetone-d6; -40 °C) of the [18-crown-6-
K]+ counterion: δ(1H) 3.6 ppm; δ(13C) 71.2 ppm. The NMR
spectroscopic data of the [W[P(C6F5)2}(CO)5]- anion are sum-
marized in Table 2. Infrared spectrum (cm-1) (KBr pellet): 2903
w, 2863 vw, 2830 vw, 2054 w, 1958 m, 1906 vs, 1890 s, 1508 m,
1474 m, 1466 m, 1352 w, 1285 vw, 1252 w, 1109 s, 1072 m, 974
w, 963 m, 873 vw, 604 w, 579 w. Raman (cm-1): 2951 (22), 2918
(25), 2889 (25), 2847 (21), 2810 (9), 2071 (50), 2058 (20), 1979
(100), 1948 (52), 1925 (38), 1896 (61), 1980 (61), 1641 (15); 1472
(9); 1377 (8); 1275 (8); 1246 (3); 1138 (5); 914 (4); 870 (8); 817
(14); 586 (10); 548 (4); 465 (44); 434 (42); 396 (7); 370 (5); 324
(9); 280 (5); 108 (85).
Preparation of Ethylbis(pentafluorophenyl)phosphanepenta-
carbonyltungsten. A THF solution of [18-crown-6-K][W{P-
(C6F5)2}(CO)5] was treated at -40 °C with an excess of iodoethane.
The temperature was slowly raised to room temperature, and the
product [W(CO)5P(C6F5)2Et] was identified by mass and multi-
nuclear NMR spectroscopy. The EI mass spectrum of the residue
of the reaction mixture, which had been evaporated to dryness,
Inorganic Chemistry, Vol. 42, No. 11, 2003 3635

Hoge et al.
exhibits characteristic fragments (EI; 20 eV) {m/z (relative intensi-
ties of the compound [W(CO)5PEt(C6F5)2]) [assignment]}: 718 (80)
[W(CO)5PEt(C6F5)2]+; 690 (90) [W(CO)4PEt(C6F5)2]+; 662 (100)
[W(CO)3PEt(C6F5)2]+; 634 (70) [W(CO)2PEt(C6F5)2]+; 606 (65)
[W(CO)PEt(C6F5)2]+; 578 (75) [WPEt(C6F5)2]+; 549 (73) [WP-
(C6F5)2]+. NMR data of [W(CO)5P(C6F5)2Et] (THF-d8; rt): δ(19Fo)
-130.5 ppm; δ(19Fm) -159.6 ppm; δ(19Fp) -149.0 ppm; δ(31P)
-12.0 ppm; 1J(WP) 250.4 Hz; 3J(PH) 22.9 Hz. The 19F NMR and
31P NMR spectra are part of the Supporting Information.
Preparation of 18-Crown-6-potassium µ-Bis(pentafluoro-
phenyl)phosphanido-bispentacarbonyltungstgate. A freshly pre-
pared solution of 1.78 g (4.5 mmol) of [W(CO)5THF] in 200 mL
of THF was added to a solution of 2.98 g (3.00 mmol) of [18-
crown-6-K][W{P(C6F5)2}(CO)5] in 20 mL of THF at -50 °C. The
solution was stirred for 6 h and allowed to reach room temperature.
After evaporation of the solution to dryness in vacuo, the residue
was extracted with 20 mL of THF. The solution was treated with
20 mL of diethyl ether and filtered. The solvent was removed in
vacuo and the residue extracted several times with hexane to remove
[W(CO)6], yielding 1.96 g (1.50 mmol) of [18-crown-6-K][{W-
(CO)5}2{µ-P(C6F5)2}] as a crude yellow powder. Negative ESI mass
spectrum (acetone/methanol) {m/z (%) [assignment]}: 1013 (4)
[W2(CO)10{P(C6F5)2}]-; 985 (12) [W2(CO)9{P(C6F5)2}]-; 957 (12)
[W2(CO)8{P(C6F5)2}]-; 929 (100) [W2(CO)7{P(C6F5)2}]-; 901 (5)
[W2(CO)6{P(C6F5)2}]-; 873 (6) [W2(CO)5{P(C6F5)2}]-; 845 (4)
[W2(CO)4{P(C6F5)2}]-; 817 (20) [W2(CO)3{P(C6F5)2}]-; 689 (4)
[W(CO)5{P(C6F5)2}]-; 661 (6) [W(CO)4{P(C6F5)2}]-. NMR data
(acetone-d6; rt) of the [18-crown-6-K]+ counterion: δ(1H) 3.6 ppm;
δ(13C) 71.2 ppm. The NMR spectroscopic data of the [{W(CO)5}2-
{µ-P(C6F5)2}]- anion are summarized in Table 2. The temperature
dependent 19F NMR spectra are shown in Figure 6. The 31P NMR
spectrum showing tungsten satellites and tungsten satellites of the
tungsten satellites is part of the Supporting Information.
Crystal Structure Determination. Crystals of [18-crown-6-K]P-
(CF3)2 slowly grew while diethyl ether was distilled onto an acetone
solution of [18-crown-6-K]P(CF3)2 at -45 °C. Single crystals of
[18-crown-6-K][W{P(CF3)2}(CO)5] were obtained by the same
method. Intense yellow single crystals of [18-crown-6-K][{W-
(CO)5}2{µ-P(C6F5)2}]‚THF were obtained by slow evaporation of
a THF/hexane solution of this compound at room temperature. One
suitable single crystal of each compound was carefully selected
under a polarizing microscope and mounted in a glass capillary.
The scattering intensities were collected by an imaging plate
diffractometer (IPDSII, STOE & CIE) equipped with a normal
focus, 1.75 kW, sealed tube X-ray source (Mo KR, λ ) 71.073
pm) operating at 50 kV and 40 mA. Intensity data for [18-crown-
6-K]P(CF3)2 were collected at 170 K by ω-scans in 116 frames
(0° e ω e 180°, ψ ) 0°; 0° e ω e 52°, ψ ) 90°; ∆ω ) 2°,
exposure time of 10 min) in the 2θ range of 3.8-70.6°. Intensity
data for [18-crown-6-K][WP(CF3)2(CO)5] were collected at 170 K
by ω-scans in 108 frames (0° e ω e 180°, ψ ) 0°; 0° e ω e 36°,
ψ ) 90°; ∆ω ) 2°, exposure time of 7 min) in the 2θ range of
2.3-59.5°. The intensity data for [18-crown-6-K][{W(CO)5}2{µ-
P(C6F5)2}]‚THF were collected at 170 K by ω-scans in 146 frames
(0° e ω e 180°, ψ ) 0°; 0° e ω e 112°, ψ ) 90°; ∆ω ) 2°,
exposure time of 5 min) in the 2θ range of 1.9-54.8°. The structures
were solved by direct methods SHELXS-9716 and difference Fourier
syntheses. Full matrix least squares structure refinements against
|F2| were carried out using SHELXL-93.17 H atom positions for
(16) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Analysis;
University of Go¨ttingen: Go¨ttingen, Germany, 1998.
(17) Sheldrick, G. M. SHELXL-93, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
3636 Inorganic Chemistry, Vol. 42, No. 11, 2003

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-
Stabilization of the P(CF3)2 and P(C6F5)2 Ions
Table 3. Crystal Data and Structure Refinement Parameters for
[18-crown-6-K]P(CF3)2 (I), [18-crown-6-K][W{P(CF3)2}(CO)5] (II), and
[18-crown-6-K][{W(CO)5}2{µ-P(C6F5)2}]‚THF (III)a
I
II
III
empirical formula
cryst syst
space group
color, habit
unit cell dimens
a [pm]
b [pm]
c [pm]
R [deg]
â [deg]
C14H24O6F6PK C19H24O11F6PKW C38H32O17F10PKW2
monoclinic
triclinic
triclinic
C2/c (No. 15)
P1h (No. 2))
P1h (No. 2)
colorless, plate yellow, plate
yellow, polyhedron
1633.5(8)
964.1(3)
1370.2(6)
1045.0(2)
1139.8(2)
1318.1(3)
75.51(2)
70.58(1)
88.30(2)
1.431(1)
2
917.2(1)
1556.0(2)
1700.7(2)
81.96(1)
87.45(1)
75.43(1)
2.326(1)
2
97.14(4)
Figure 1. Unit cell packing of [18-crown-6-K]P(CF3)2 in the b, c plane
showing all non-hydrogen atoms.
γ [deg]
vol [nm3]
Z
2.141(2)
4
with weak interionic interactions, i.e., the [18-crown-6-K]
salt, where the potassium cation should be shielded by the
coordination of the crown ether, preventing strong inter-
formula mass
472.40
1.465
0.400
796.30
1.848
4.327
numerical
1388.41
1.982
5.175
F
calc [g cm-3
]
µ [mm-1
]
abs correction
transm max/min
θ range [deg]
total data collected 6761
index ranges
numerical
0.9538/0.9801 0.3899/0,6868
2.46-23.00
numerical
0.3604/0.6236
1.36-27.29
30062
-11 e h e 11
-20 e k e 19
-21 e l e 21
10320
-
actions with the P(CF3)2 ion. Several attempts to obtain
single crystals of [18-crown-6-K]P(CF3)2 via cooling of
saturated CH2Cl2, CHCl3, or THF solutions yielded poly-
crystalline material. If slow cooling rates are used, decom-
position of the P(CF3)2- ion occurs. The slow distillation of
hexane or diethyl ether onto CH2Cl2, CHCl3, or THF
solutions of the salt at -78 °C yielded also polycrystalline
material, or resulted, if slow distillation rates were used, in
1.69-26.00
11971
-17 e h e 17 -13 e h e 14
-10 e k e 10 -15 e k e 15
-14 e l e 15 -17 e l e 18
1493
757
STOE image plate diffraction system
Mo KR (graphite monochromator, λ ) 71.073 pm)
170(2)
unique data
obsd data
diffractometer
radiation
temp [K]
Rmerg
R indexes
[I > 2σ(I)]
R indexes
(all data)
5445
3101
5988
-
170(2)
0.0932
R1 ) 0.0396
170(2)
0.0845
a complete decomposition of the P(CF3)2 ion in solution.
0.1413
R1 ) 0.0752
During our research in the synthesis of chiral bidentate bis-
(trifluoromethyl)phosphane derivatives, we found that ac-
R1 ) 0.0395
wR2 ) 0.0781
R1 ) 0.0838
wR2 ) 0.0898
0.824
0.824
599
1336
-2.163/1.683
wR2 ) 0.1428 wR2 ) 0.0528
R1 ) 0.1535 R1 ) 0.0978
wR2 ) 0.1744 wR2 ) 0.0679
0.954
0.954
177
-
etone stabilizes the P(CF3)2 ion by formation of dynamic
Lewis acid Lewis base adducts III. The intermediary
formation of the adduct III was proven by reaction with
tetrakis(trifluoromethyl)diphosphane, (CF3)2PP(CF3)2, yield-
ing the novel phosphane phosphinite derivate IV.10
GOF (Sobs
GOF (Sall
)
)
0.678
0.641
357
no. of variables
F(000)
976
776
largest diff map
hole/peak
-0.284/0.773 -1.146/0.827
[e 10-6 pm-3
]
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑w(|Fo| )2]1/2
,
S2 ) [∑w(|Fo| - |Fc| )2/(n - p)]1/2, with w ) 1/[σ2(Fo)2 + (0.0771P)2]
2
2
for I, w ) 1/[σ2(Fo)2] for II, and w ) 1/[σ2(Fo)2 + (0.0403P)2] for III, P
) (Fo + 2Fc )/3. Fc* ) kFc[1 + 0.001|Fc| λ3/sin(2θ)]-1/4
.
2
2
2
[18-crown-6-K]P(CF3)2 were taken from the difference Fourier card
at the end of the refinement. The hydrogen atoms in [18-crown-
6-K][W{P(CF3)2}(CO)5] and [18-crown-6-K][{W(CO)5}2{µ-P-
(C6F5)2}]‚THF were placed geometrically and held in the riding
mode (except the solvent molecule in [18-crown-6-K][{W(CO)5}2-
{µ-P(C6F5)2}]‚THF). Numerical absorption corrections were applied
after optimization of the crystal shapes (X-RED18 and X-SHAPE19).
The last cycles of refinement included atomic positions for all
atoms, anisotropic thermal parameters for all non-hydrogen atoms
(except the C and O atoms of the solvent molecule in [18-crown-
6-K][{W(CO)5}2{µ-P(C6F5)2}]‚THF), and isotropic thermal param-
eters for all hydrogen atoms. Details of the refinements are given
in Table 3.
By slow distillation of diethyl ether onto a solution of [18-
crown-6-K]P(CF3)2 in acetone at -45 °C we were able to
obtain colorless single crystals, suitable for single-crystal
X-ray structure analysis. The compound [18-crown-6-K]P-
(CF3)2 crystallizes in the monoclinic space group C2/c. The
packing in the unit cell at the b, c plane is given in Figure
1. The long phosphorus potassium distance of 363.6(2) pm
confirms the packing of isolated ions, as it was previously
predicted by the very good agreement between calculated
vibrational frequencies of a noninfluenced P(CF3)2- ion and
the experimentally observed frequencies of the P(CF3)2- ion
in its [18-crown-6-K] salt. The molecular structure of the
Results and Discussion
-
P(CF3)2 ion is shown in Figure 2. Depending on the
-
F12C1C1′F12′ and F11C1C1′F13′ dihedral angles of 3.3°
and 5.8°, respectively, the P(CF3)2- is a member of the point
group C2, as predicted by density functional theory. The
calculated dihedral angle of 3.7° exhibits an unexpected good
agreement with the experimental values. The bond lengths
To describe the bonding situation of the P(CF3)2 ion by
single-crystal X-ray crystallography we chose a compound
(18) X-RED 1.22, STOE Data Reduction Program; Darmstadt, Germany,
2001.
(19) X-SHAPE 1.06, Crystal Optimisation for Numerical Absorption
Correction; Darmstadt, Germany, 1999.
-
and angles of the P(CF3)2 ion as its [18-crown-6-K] salt
Inorganic Chemistry, Vol. 42, No. 11, 2003 3637

Hoge et al.
-
Figure 2. Molecular structure and the atom-numbering scheme of P(CF3)2
anion in the compound [18-crown-6-K]P(CF3)2. Probability amplitude
displacement ellipsoids (50%) are shown.
-
Table 4. Bond Lengths (pm) and Angles (deg) of the P(CF3)2 Anion
in the Compound [18-crown-6-K]P(CF3)2
P1-C1
C1-F12
C1-F11
184(1)
134.5(9)
135(1)
C1-F13
P1-K1
136(1)
363.6(2)
Figure 3. Molecular structure and the atom-numbering scheme of
[W{P(CF3)2}(CO)5]- in the compound [18-crown-6-K][W{P(CF3)2}(CO)5].
Probability amplitude displacement ellipsoids (50%) are shown.
C1-P1-C1
96.9(5)
104.7(7)
103.9(8)
104.2(8)
F12-C1-P11
F11-C1-P11
F13-C1-P1
108.9(6)
118.6(7)
115.1(6)
F12-C1-F11
F12-C1-F13
F11-C1-F13
P(CF3)2 group transfer reagent. While [P(CF3)2CS2]- reacts
with iodoethane to give EtP(CF3)2, no reaction could be
observed by treatment of [P(CF3)2CS2]- with ethyl tosylate.
To allow selective nucleophilic substitution reactions of
are summarized in Table 4. The experimental P-C distance
of 184(1) pm is in reasonably good agreement with 186.1
pm obtained at the B3PW91/6-311G(3d) level of theory.
HDFT calculations of the SCF3 ion exhibit an enhanced
accuracy of the geometric parameters, if an increased set of
d-polarization functions is used.20 The same effect is observed
-
-
the P(CF3)2 ion, a Lewis acid that stabilizes the P(CF3)2
ion without significant influence on the nucleophilicity of
the P(CF3)2 moiety is needed. Low oxidation state transition
metal phosphane complexes exhibit a σ-donation and π-back-
bonding bonding dualism. The unexpected minor influence
on the electronic properties of HP(CF3)2 and HP(C6F5)2 on
coordination to pentacarbonyl tungsten, which is evidenced
by the small change on the ν(PH) vibrational modes, can be
described by a compensation of the σ-donation with the
π-back-bonding effect.
-
-
if the geometry of the P(CF3)2 is optimized at the same
level of theory. The resulting P-C distance of 185.4 pm is
in very good agreement with the experimental value. A
comparison between experimental and theoretical geometric
parameters is given in Table 7, where the data of the P(CF3)2-
are also compared with the calculated data of the neutral
To investigate the influence on the electronic properties
-
HP(CF3)2. The phosphorus carbon distance in P(CF3)2 is
-
of the P(CF3)2 ion by coordination to pentacarbonyl
shortened by comparison to those in HP(CF3)2 and solid or
gaseous tetrakis(trifluoromethyl)diphosphane, (CF3)2PP-
(CF3)2,21 by 4.8, 4.1, and 5.4 pm, respectively. The shortening
of the P-C distance in the P(CF3)2- ion is accompanied by
a slight elongation of the C-F distances, which can be
attributed to negative hyperconjugation or formulation of
additional resonance structures, eq 2. This kind of C-F
activation favors intermolecular decomposition reactions of
the dissolved compound. The nature of the decomposition
is not completely resolved. The novel phosphoranide,
[P(CF3)2F2]-, is the only identified decomposition product
so far.22
tungsten, [W(CO)5PH(CF3)2] was treated with [18-crown-
6-K]CN.
[W(CO)5PH(CF3)2] + [18-crown-6-K]CN CH Cl 8
2
2
HCN + [18-crown-6-K][W{P(CF3)2}(CO)5] (5)
The anion [W{P(CF3)2}(CO)5]- exhibits a remarkably
increased thermal stability. Solutions of [18-crown-6-K]-
[W{P(CF3)2}(CO)5] in CH2Cl2 or acetone exhibit no sign of
decomposition after 3 days at room temperature. The solid
decomposes at 255 °C. Colorless crystals of [18-crown-6-
K][W{P(CF3)2}(CO)5] were obtained by distilling diethyl
ether onto a solution in CH2Cl2 at -45 °C. The compound
crystallizes in the triclinic space group P1h. The molecular
structure of the tungstate, [W{P(CF3)2}(CO)5]-, with ap-
proximate Cs symmetry is shown in Figure 3. Selected bond
lengths and angles of the [W{P(CF3)2}(CO)5]- ion are
summarized in Table 5. A comparison of the geometric
parameters of [W(CO)5PH(CF3)2] with the deprotonated
counterpart, [W{P(CF3)2}(CO)5]-, reveals an elongation of
the P-W distance by more than 15 pm, which can be
-
For an electronic stabilization of the P(CF3)2 ion, it is
necessary to reduce the negative hyperconjugation. This can
be achieved by reducing the electron density at the phos-
phorus atom. The carbon phosphorus distance in the Lewis
acid Lewis base adduct [P(CF3)2CS2]- is increased by around
5 pm in comparison to that in the P(CF3)2- ion, indicating a
reduced negative hyperconjugation which is accompanied
by a reduced electron density at the phosphorus atom. As a
result of the reduced electron density, the CS2 adduct
[P(CF3)2CS2]- exhibits a reduced reactivity as a nucleophilic
-
attributed to a reduced π-back-bonding effect of the P(CF3)2
ion in comparison with HP(CF3)2. The elongation of the
(20) Tyrra, W.; Naumann, D.; Hoge, B.; Yagupolskii, Y. L. J. Fluorine
Chem. 2003, 119, 101-107.
P-W distance is accompanied by a reduction of the
1
magnitude of the J(PW) coupling constant from 268.6 to
(21) Becker, G.; Golla, W.; Grobe, J.; Klinkhammer, K. W.; Van, D. L.;
Maulitz, A. H.; Mundt, O.; Oberhammer, H.; Sachs, M. Inorg. Chem.
1999, 38, 1099-1107.
103.1 Hz.
-
As expected for the weaker π-acidic ligand, P(CF3)2 , the
(22) Ro¨schenthaler, G.-V.; Shyshkov, O.; Kolomeitsev, A.; Hoge, B. 16th
Winter Fluorine Conference, St. Pete Beach, FL, 2003;Paper 54.
highest vibrational ν(CO) valence mode of the complex
3638 Inorganic Chemistry, Vol. 42, No. 11, 2003

-
-
Stabilization of the P(CF3)2 and P(C6F5)2 Ions
Table 5. Selected Bond Lengths (pm) and Angles (deg) of the
[W{P(CF3)2}(CO)5]- Anion in the Compound
[18-crown-6-K][W{P(CF3)2}(CO)5]
Table 7. Selected Experimental and Theoretical Geometric Parameters
-
of P(RF)2 [W{P(RF)2}(CO)5]- (RF ) CF3; C6F5), Their Protonated
Derivatives, and [{W(CO)5}2{µ-P(C6F5)2}]- and
[{W(CO)5}2{µ-P(CF3)2}]-
W1-C5
194.2(9)
201(1)
C210-F212
C210-F211
C210-F212
F112-K2
F212-K2
C1-O1
135.3(8)
136(1)
W1-C4
W1-C2
203(1)
136.7(9)
308.8(6)
311.2(6)
114(1)
W1-C3
205(1)
205(1)
W1-C1
W1-P1
257.9(2)
184.4(9)
186.0(9)
134.4(9)
135(1)
P1-C210
P1-C110
C110-F112
C110-F111
C110-F113
C2-O2
115(1)
C3-O3
114(1)
C4-O4
117(1)
C5-O5
118(1)
136.2(9)
O5-K1
278.6(7)
C4-W1-C1
C2-W1-C1
C3-W1-C1
C5-W1-P1
C210-P1-C110
174.4(4)
87.9(3)
91.4(4)
179.1(3)
95.1(4)
C210-P1-W1
107.0(3)
107.5(3)
103.9(7)
105.4(6)
104.6(7)
C110-P1-W1
F112-C110-F111
F112-C110-F113
F111-C110-F113
Table 6. Selected Bond Lengths (pm) and Angles (deg) of the
[{W(CO)5}2{µ-P(C6F5)2}]- Anion in the Compound
[18-crown-6-K][{W(CO)5}2{µ-P(C6F5)2}]‚THF
W1-C141
W1-C151
W1-C111
W1-C121
W1-C131
W1-P1
C111-O111
C121-O121
C131-O131
C141-O141
C151-O151
O151-K1
W2-C231
198.7(8)
202.5(9)
203.7(9)
204(1)
207.2(8)
261.4(2)
114.3(9)
115(1)
112.3(9)
114.6(9)
115(1)
310.7(7)
200.3(8)
W2-C211
W2-C221
W2-C251
W2-C241
W2-P1
204.0(8)
204(1)
205.2(9)
205.7(8)
262.9(2)
113.7(9)
115(1)
115(1)
112.7(9)
115(1)
186.9(8)
187.5(7)
C211-O211
C221-O221
C231-O231
C241-O241
C251-O251
P1-C31
P1-C21
C151-W1-C121
C111-W1-C121
C141-W1-C131
C151-W1-C131
C111-W1-C131
C121-W1-C131
C141-W1-P1
176.5(3)
90.4(3)
91.9(3)
88.7(3)
177.0(3)
92.4(3)
176.0(2)
92.1(2)
89.1(2)
91.2(2)
91.7(2)
175.7(7)
175.7(7)
O131-C131-W1
O141-C141-W1
O151-C151-W1
C151-O151-K1
C221-W2-C251
C231-W2-P1
C31-P1-C21
C31-P1-W1
177.1(7)
178.3(7)
176.9(6)
143.6(6)
174.1(3)
175.3(3)
97.1(3)
119.2(2)
99.9(2)
101.3(2)
119.9(2)
118.46(7)
a For the trifluoromethyl derivatives, a 6-311G(3d) basis set was used
on all nonmetal atoms, and for the pentafluorophenyl derivatives, a
6-311G(d) basis set was used on all nonmetal atoms. In the presence of a
hydrogen atom, the basis set was extended by a set of p functions on the
hydrogen atom. On the tungsten atom a LanL2DZ basis and ECP were
used.
C151-W1-P1
C111-W1-P1
C21-P1-W1
C121-W1-P1
C31-P1-W2
C131-W1-P1
C21-P1-W2
O111-C111-W1
O121-C121-W1
W1-P1-W2
the calculated harmonic frequencies on the order of 80 cm-1.
This effect is generally observed for CO moieties: the
calculated C-O distances of the noncoordinated molecules,
CO, and HCO+ are also close to the experimental values (in
parentheses) 112.5 (112.8)23 and 110.1 (110.7) pm,24 respec-
tively, while the calculated CO valence modes of 2219 and
2270 cm-1 overestimate the experimental values of 214323
and 2184 cm-1,25 respectively, by around 80 wavenumbers.
The remaining bond lengths of the [W{P(CF3)2}(CO)5]- ion
are overestimated by 2-4 pm, one reason why most of the
calculated harmonic frequencies exhibit nearly the same
value as their experimental anharmonic counterpart, without
the use of a scaling factor. The approximate mode descrip-
tions of the vibrational frequencies are presented in Table 8
and based on the corresponding calculated displacement
vectors.
[W{P(CF3)2}(CO)5]- is shifted by about 28 cm-1 to lower
frequencies, in comparison with the protonated counterpart
[W(CO)5PH(CF3)2], indicating an increased π-back-bonding
contribution of the CO groups in the tungstate, [W{P(CF3)2}-
(CO)5]-. This increased π-back-bonding contribution causes
a shortening of the W-C distance of the trans bonded CO
group by more than 5 pm, Table 7.
Both the 31P and 19F NMR resonances of [W(CO)5PH-
(CF3)2] are shifted to lower field on deprotonation, which
corresponds to the noncoordinated moieties, HP(CF3)2 and
-
P(CF3)2 , Table 1. The experimental molecular dimensions
of the [W{P(CF3)2}(CO)5]- ion are in good agreement with
the optimized structure at the B3PW91/6-311G(3d) level of
theory, using a LanL2DZ basis and ECP on the tungsten
atom, Table 7. The following frequency analysis at the same
level of theory results in a good agreement between
experimental and theoretical frequencies. The calculated
averaged C-O distance of 114.9 pm matches nearly exactly
with the experimental value of 115.6 pm. Nevertheless the
experimental anharmonic frequencies are overestimated by
(23) Huber, K. P.; Herzberg, G. P. Constants of Diatomic Molecules; Van
Nostrand Reinhold: New York, 1979.
(24) Woods, R. C.; Saykally, R. J.; Anderson, T. G.; Dixon, T. A.; Szanto,
P. G. J. Chem. Phys. 1981, 75, 4256.
(25) Jacox, M. E. J. Phys. Chem. Ref. Data, Monogr. 1994, No. 3.
Inorganic Chemistry, Vol. 42, No. 11, 2003 3639

Hoge et al.
Table 8. Calculateda Vibrational Frequencies and Observed Infrared
and Raman Spectra of the [W{P(CF3)2}(CO)5]- Ion
Figure 4. A central projection and the atom-numbering scheme of the
anion [{W(CO)5}2{µ-P(C6F5)2}]- in the compound [18-crown-6-K][{W-
(CO)5}2{µ-P(C6F5)2}]‚THF. Probability amplitude displacement ellipsoids
(50%) are shown.
-
P-C bond lengths of the free P(CF3)2 ion and the
comparable pentacarbonyl tungstate complex are nearly
identical indicates that the electronic properties of the P(CF3)2
unit are practically unaffected by coordination, which is also
supported by the distinct nucleophilicity of the [W{P(CF3)2}-
(CO)5]- ion. While the [P(CF3)2CS2]- ion exhibits no
reaction toward ethyl tosylate, [W{P(CF3)2}(CO)5]- reacts
smoothly with ethyl tosylate to give [W(CO)5PEt(CF3)2],
which was identified by multinuclear NMR and mass
spectroscopy.
All attempts to synthesize a bis(pentafluorophenyl)phos-
phanide salt by reacting HP(C6F5)2 with ionic cyanides at
low temperature led to oligomerization of the initially formed
P(C6F5)2- ion. On the other hand, we succeeded in synthesiz-
ing the bis(pentafluorophenyl)phosphanide anion as the
pentacarbonyl tungsten complex, [W{P(C6F5)2}(CO)5]-.
Treatment of [W(CO)5PH(C6F5)2] at low temperature with
[18-crown-6-K]CN yielded [18-crown-6-K][W{P(C6F5)2}-
(CO)5] as a bright yellow powder.
a B3PW91: 6-311G(3d) basis on all nonmetallic atoms and a LanL2DZ
basis and ECP on tungsten. b Relative intensities.
[W(CO)5PH(C6F5)2] + [18-crown-6-K]CN CH Cl 8
2
2
HCN + [18-crown-6-K][W{P(C6F5)2}(CO)5] (7)
The elongated W-P bond length of the [W{P(CF3)2}-
(CO)5]- ion in comparison to that of the protonated derivative
of about 16 pm is accompanied by a shift of the ν(W-P)
valence mode by less than 10 cm-1 to lower frequencies.
The P-C bond length of the P(CF3)2- ion of 184(1) pm (C2
symmetry) is very close to the distances found in the
comparable pentacarbonyl tungsten complex, [W{P(CF3)2}-
(CO)5]-, of 184.4(9) and 186.0(9) pm, while the adduct
The neat compound [18-crown-6-K][W{P(C6F5)2}(CO)5]
is stable at room temperature and can be stored for several
weeks at -20 °C, while the [W{P(C6F5)2}(CO)5]- ion
decomposes in solution even at -30 °C, yielding the same
oligomeric material observed in the decomposition of the
P(C6F5)2 ion. The experimental 31P NMR spectrum of the
[W{P(C6F5)2}(CO)5]- ion is compared with a calculated
-
-
formation of the P(CF3)2 ion with CS2 is accompanied by
a P-C bond length elongation of ca. 5 pm. The fact that the
spectrum in Figure 5. It exhibits a quintet of quintets splitting,
3640 Inorganic Chemistry, Vol. 42, No. 11, 2003

-
-
Stabilization of the P(CF3)2 and P(C6F5)2 Ions
Figure 6. Temperature dependent 19F NMR spectra of the [{W(CO)5}2-
{µ-P(C6F5)2}]- ion.
is shown in Figure 4 as a central projection. Selected bond
lengths and angles of the [{W(CO)5}2{µ-P(C6F5)2}]- ion are
summarized in Table 6. The molecular structure of the [{W-
(CO)5}2{µ-P(C6F5)2}]- ion exhibits a tight arrangement of
the spatially demanding W(CO)5 and C6F5 groups around
the central phosphorus atom. As expected by this tight
arrangement, the C6F5 as well as the W(CO)5 groups show
a hindered rotation in their 19F and 13C NMR spectra,
respectively. The temperature dependent 19F NMR spectra
of the [{W(CO)5}2{µ-P(C6F5)2}]- ion are shown in Figure
6 and exhibit a splitting of the ortho fluorine nuclei of 1.1
ppm at -30 °C in THF solution, while the resonances
coalesce at around 90 °C. The low-temperature 13C NMR
spectrum of [{W(CO)5}2{µ-P(C6F5)2}]- exhibits a splitting
of the cis-oriented CO groups into two resonances, separated
by 0.2 ppm at -40 °C. A separation of the multiplet
resonances of the C6F5 groups could not be resolved in the
13C NMR experiment. The 31P NMR spectrum of the [{W-
(CO)5}2{µ-P(C6F5)2}]- ion exhibits two sets of tungsten
Figure 5. Experimental (top) and calculated (bottom) 31P NMR spectrum
of [W{P(C6F5)2}(CO)5]-.
3
4
caused by a J(PF) and J(PF) coupling, surrounded by a
set of tungsten satellites.
1
On addition of iodoethane at -40 °C, the [W{P(C6F5)2}-
(CO)5]- ion reacts in a plain reaction to give the novel
compound [W(CO)5PEt(C6F5)2], while the reaction with the
less reactive ethyl tosylate is not selective. It was necessary
to enhance the lifetime of the [W{P(C6F5)2}(CO)5]- ion in
solution in order to obtain suitable single crystals for an X-ray
structure analysis. For this purpose we reacted 18-crown-6-
K][W{P(C6F5)2}(CO)5] dissolved in THF with a freshly
prepared solution of [W(CO)5THF] at low temperature.
satellites with a J(WP) coupling constant of 172.8 Hz.
Acknowledgment. We are grateful to Prof. Dr. D.
Naumann for his generous support and the Fonds der
Chemischen Industrie for financial support. We thank Dr.
K. Glinka for helpful discussions. Thanks to Dr. M. Scha¨fer
for collecting ESI-MS spectra. Dr. L. Packschies is acknowl-
edged for providing a Perl-script program, g98 frequency
finder.26
Supporting Information Available: Crystallographic file in
CIF format for the compounds [18-crown-6-K]P(CF3)2, [18-crown-
6-K][W{P(CF3)2}(CO)5], and [18-crown-6-K][[{W(CO)5}2{µ-
P(C6F5)2}]‚THF. 19F NMR and 31P NMR spectra of [W(CO)5PEtR2]
with R ) CF3 and C6F5 and the 31P NMR spectrum of [{W(CO)5}2-
{µ-P(C6F5)2}]. This material is available free of charge via the
Internet at http://pubs.acs.org. Crystallographic data for the struc-
tures of [18-crown-6-K]P(CF3)2, [18-crown-6-K][W{P(CF3)2}-
(CO)5], and [18-crown-6-K][{W(CO)5}2{µ-P(C6F5)2}]‚THF re-
ported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publications CCDC-
203184, CCDC-203185, and CCDC-203186, respectively. Copies
of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, U.K. (fax, (+44)1223-336-
033; e-mail, deposit@ccdc.cam.ac.uk).
The bimetallic µ-phosphanido bridged complex, [{W-
(CO)5}2{µ-P(C6F5)2}]-, exhibits no sign of decomposition
even after 1 week in solution and is stable on short contacts
with air. The compound [18-crown-6-K][{W(CO)5}2{µ-
P(C6F5)2}] crystallizes in the triclinic space group P1h. The
molecular structure of the anion, [{W(CO)5}2{µ-P(C6F5)2}]-,
(26) Program available at http://www.uni-koeln.de/themen/Chemie/software/
g98ff/.
IC034165V
Inorganic Chemistry, Vol. 42, No. 11, 2003 3641