Preparation and characterization of [Hg{P(C6F5) 2}2], [Hg{(μ-P(C6F5) 2)W(CO)5}2], and [Hg{(μ-P(CF 3)2)W(CO)5}2] and the x-ray crystal structure of [Hg{(μ-P(C6F5)2)W(CO) 5}2]·2DMF

Article abstract of DOI:10.1021/ic034448n

The thermally unstable compound [Hg{P(C₆F₅) ₂}₂] was obtained from the reaction of mercury cyanide and bis(pentafluorophenyl)phosphane in DMF solution and characterized by multinuclear NMR spectroscopy. The thermally stable trinuclear compounds [Hg{(μ-P(CF₃)₂)W(CO)₅}₂] and [Hg{(μ-P(C₆F₅)₂)W(CO)₅} ₂] are isolated and completely characterized. The higher order NMR spectra exhibiting multinuclear satellite systems have been sufficiently analyzed. [Hg{(μ-P(CF₃)₂)W(CO)₅} ₂]·2DMF crystallizes in the monoclinic space group C21c with a = 2366.2(3) pm, b = 1046.9(1) pm, c = 104.0(1) pm, and & = 104.01(1)°. Structural, NMR spectroscopic, and vibrational data prove a weak coordination of the two DMF molecules. Structural, vibrational, and NMR spectroscopic evidence is given for a successive weakening of the π back-bonding effect of the W-P bond in the order [W(CO)₅PH(R_f)₂], [Hg{(μ-P(R_f)₂)W(CO)₅}₂], and [W{P(R_f)₂}(CO)₅]^- with R _f = C₆F₅ and CF₃. The π back-bonding effect of the W-C bonds increases vice versa.

Full text of DOI:10.1021/ic034448n

Inorg. Chem. 2003, 42, 5422−5428
Preparation and Characterization of [Hg{P(C F ) } ],
6 5 2 2
[Hg{(µ-P(C F ) )W(CO)5}2], and [Hg{(µ-P(CF3)2)W(CO)5}2] and the X-ray
6 5 2
Crystal Structure of [Hg{(µ-P(C F ) )W(CO)5}2]‚2DMF
6 5 2
Berthold Hoge,* Tobias Herrmann, Christoph Tho1sen, and Ingo Pantenburg
Institut fu¨r Anorganische Chemie, UniVersita¨t zu Ko¨ln, D-50939 Ko¨ln, Germany
Received April 29, 2003
The thermally unstable compound [Hg{P(C F ) }2] was obtained from the reaction of mercury cyanide and bis-
6
5 2
(pentafluorophenyl)phosphane in DMF solution and characterized by multinuclear NMR spectroscopy. The thermally
stable trinuclear compounds [Hg{(µ-P(CF ) )W(CO)5}2] and [Hg{(µ-P(C F ) )W(CO)5}2] are isolated and completely
3 2
6 5 2
characterized. The higher order NMR spectra exhibiting multinuclear satellite systems have been sufficiently analyzed.
[Hg{(µ-P(CF ) )W(CO)5}2]‚2DMF crystallizes in the monoclinic space group C2/c with a ) 2366.2(3) pm, b )
3 2
1046.9(1) pm, c ) 104.0(1) pm, and â ) 104.01(1)°. Structural, NMR spectroscopic, and vibrational data prove
a weak coordination of the two DMF molecules. Structural, vibrational, and NMR spectroscopic evidence is given
for a successive weakening of the π back-bonding effect of the W−P bond in the order [W(CO)5PH(R) ], [Hg-
f 2
{(µ-P(R) )W(CO)5}2], and [W{P(R) }(CO)5]- with R ) C F and CF . The π back-bonding effect of the W−C
f 2
f 2
f
6
5
3
bonds increases vice versa.
Introduction
allowing the complete NMR spectroscopic characterization
of [Hg{P(CF3)2}2].5,6
Diphosphanidomercury derivatives [Hg(PR2)2] with R )
C6H5, C2H5, i-C3H7, and C6H11 are thermally sensitive
compounds and tend toward reductive elimination of el-
emental mercury and formation of the corresponding diphos-
phane derivatives. This decomposition pathway has been
used to prepare diphosphanes in high yields according to eq
1.1 Pure mercury compounds have not been obtained so far,
In a foregoing paper5 we described the stabilization of [Hg-
{P(CF3)2}2] in the presence of donor molecules such as
phosphanes. While [Hg{P(CF3)2}2] decomposes slowly to
elemental mercury and (CF3)2PP(CF3)2 at room temperature,
the related phosphane adducts [Hg{P(CF3)2}2(PR3)2] ((PR3)2
) (PMe3)2, dppe) exhibit decomposition points at 157 and
147 °C, respectively.5
8 [Hg(PR2)2]q f Hg + R2PPR2
Another type of stabilization is observed, coordinating the
phosphanido ligands to group VI metal carbonyl complex-
es.7,8 While [Hg(PPh2)2] is unknown so far, Peringer et al.
succeeded in the synthesis of the comparable trinuclear com-
pound [Hg{(µ-PPh2)M(CO)5}2] with M ) Cr, Mo, and W.8
Hg(t-Bu)2 + 2HPR2
-2 t-BuH
(1)
whereas homoleptic phosphanidomercury compounds with
sterically demanding groups bonded to the phosphorus atom,
such as R ) t-Bu,1,2 SiMe3,3 and SiPh3,4 exhibit remarkable
thermal stability.
Electron-withdrawing CF3 groups bonded to the phospho-
rus atoms effect a stabilization of the mercury compounds,
Herein, we report the preparation of the novel bis(pen-
tafluorophenyl)phosphanido derivative [Hg{P(C6F5)2}2]. The
(5) Hoge, B.; Tho¨sen, C.; Pantenburg, I. Inorg. Chem. 2001, 40, 3084-
3088.
* Author to whom correspondence should be addressed. Fax: 049-221-
470-5196. E-mail: b.hoge@uni-koeln.de.
(6) Grobe, J.; Demuth, R. Angew. Chem. 1972, 84, 1153; Angew. Chem.,
Int. Ed. Engl. 1972, 11, 1097.
(1) Baudler, M.; Zarkadas, A. Chem. Ber. 1972, 105, 3844-3849.
(2) Benac, B. L.; Cowley, A. H.; Jones, R. A.; Nunn, C. M.; Wright, T.
C. J. Am. Chem. Soc. 1989, 111, 4986-4988.
(7) Eichbichler, J.; Malleier, R.; Wurst, K.; Peringer, P. J. Organomet.
Chem. 1997, 541, 233-236. Obendorf, D.; Peringer, P. J. Organomet.
Chem. 1987, 326, 375-380. Obendorf, D.; Peringer, P. J. Organomet.
Chem. 1987, 320, 47-51. Peringer, P.; Lusser, M. Inorg. Chim. Acta
1986, 117, L25-L26.
(3) Goel, S. C.; Chiang, M. Y.; Rauscher, C. D.; Buhro, W. E. J. Am.
Chem. Soc. 1993, 115, 160-169.
(4) Matchett, M. A.; Chiang, M. Y. Buhro, W. E. Inorg. Chem. 1994, 33,
1109-1114.
(8) Peringer, P.; Eichbichler, J. J. Chem. Soc., Dalton Trans. 1982, 667-
668.
5422 Inorganic Chemistry, Vol. 42, No. 17, 2003
10.1021/ic034448n CCC: $25.00 © 2003 American Chemical Society
Published on Web 07/29/2003

Preparation of Diphosphanidomercury DeriWatiWes
(C6F5)2]+; 73 (74) [(CH3)2NCOH]+. NMR for [Hg{(µ-P(C6F5)2)W-
(CO)5}2] (saturated THF-d8 solution; 298 K): δ(31P) -74.4 ppm;
δ(19Fo) -128.5 ppm (m, 2F); δ(19Fm) -160.0 ppm (m, 2F); δ(19Fp)
-149.6 ppm (m, 1F); 1J(199HgP) ) 1864 Hz; 1J(183WP) ) 218 Hz;
2J(PP) ) 137 Hz.
thermally sensitive compounds [Hg{P(C6F5)2}2] and [Hg-
{P(CF3)2}2] are stabilized by the coordination of both
phosphanido ligands to W(CO)5 moieties, forming the novel
trinuclear complexes [Hg{(µ-PR2)W(CO)5}2] (R ) C6F5 and
CF3).
Preparation of [Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF. A 0.93 g
(1.89 mmol) sample of [W(CO)5PH(CF3)2] and 0.20 g (0.80 mmol)
of Hg(CN)2 were dissolved in 5 mL of DMF. After being stirred
for 2 h at room temperature, the yellow solution was evaporated to
dryness. The resulting intense yellow residue was washed once with
5 mL of CH2Cl2 and dried in vacuo, yielding 0.34 g (0.26 mmol,
33%) of [Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF as a yellow powder.
Elemental analysis of [Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF (calcd for
C20H14F12HgN2O12P2W2): C 18.71 (18.03); H 1.23 (1.06); N 1.06
(2.10). IR (cm-1, KBr pellet): 2943 w, 2082 s, 1955 vs, 1928 vs
sh, 1650 s, 1386 w, 1175 s, 1124 s, 1064 vw, 994 vw, 931 vw,
742, vw, 670 w, 595 m, 571 m, 558 w sh, 550 w sh, 468 w, 457
vw sh, 434 w. Raman (cm-1): 2946 (7), 2080 (85), 2010 (60),
1996 (60), 1961 (87), 1651 (5), 1149 (5), 1109 (4), 968 (10), 742
(25), 575 (8), 550 (28), 451 (55), 433 (100), 400 (32), 233 (64),
169 (34), 106 (90).
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(C6F5)2, [W(CO)5PH-
(C6F5)2], and [W(CO)5PH(CF3)2].9 Solvents were purified by
standard methods.10 Standard high-vacuum techniques were em-
ployed throughout all preparative procedures; nonvolatile com-
pounds were handled in a dry N2 atmosphere by using Schlenk
techniques.
Infrared spectra were recorded on a Nicolet-5PC-FT-IR spec-
trometer using KBr pellets. Raman spectra were measured on a
Bruker FRA-106/s spectrometer with a Nd:YAG laser operating at
λ ) 1064 nm.
NMR spectra were recorded on Bruker Model AMX 300 (31P,
121.50 MHz; 19F, 282.35 MHz) and Bruker AC200 (31P, 81.01
MHz; 19F, 188.31 MHz; 1H, 200.13 MHz) spectrometers. Fluorine-
decoupled phosphorus spectra were recorded on a Bruker DRX 500
spectrometer (31P, 202.40 MHz) with positive shifts being downfield
from the external standards (85% orthophosphoric acid (31P), CCl3F
(19F), and TMS (1H)). Higher order NMR spectra were calculated
with the program gNMR.11
Preparation of [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF. A solution
of 0.28 g (1.11 mmol) of Hg(CN)2 in 5 mL of DMF was added
dropwise to a solution of 1.63 g (2.37 mmol) of [W(CO)5PH(C6F5)2]
in 5 mL of DMF at -50 °C. After the resulting solution was
warmed to ambient temperature, the product [Hg{µ-P(C6F5)2W-
(CO)5}2]‚2DMF began to precipitate as yellow-green crystals. After
precipitation was completed, the solvent was removed via a syringe
and the residue was washed several times with diethyl ether and
dried in vacuo. [Hg{µ-P(C6F5)2W(CO)5}2]‚2DMF (1.00 g, 0.58
mmol, 55%) is only moderately soluble in CH2Cl2, CHCl3, and
THF. The product loses the DMF solvent molecules at 105 °C
(TG: mass loss 6%, calcd 8.5%). The resulting [Hg{(µ-P(C6F5)2)W-
(CO)5}2] decomposes at 175 °C (TG). Elemental analysis of [Hg-
{(µ-P(C6F5)2)W(CO)5}2]‚2DMF (calcd for C40H14F20HgN2O12P2W2):
N 1.79 (1.62); C 27.86 (27.15); H 0.82 (0.76). IR (cm-1, KBr
pellet): 2942 w, 2073 s, 1987 m, 1952 vs br, 1927 vs br, 1659 s,
1651s, 1520 s, 1470 s, 1414 vw, 1387 m, 1285 w, 1254 vw, 1138
vw, 1088 s, 1022 vw, 974 s, 839 w, 827 w, 764 vw, 752 vw, 721
vw, 667 w, 623 w, 598 m, 575 m, 505 w, 420 m. Raman (cm-1):
2944 (13), 2073 (68), 1990 (100), 1950 (20), 1918 (72), 1642 (24),
1440 (6), 1414 (11), 1384 (19), 1286 (6), 1101 (5), 865 (7), 827
(28), 666 (4), 624 (4), 586 (27), 503 (13), 448 (64), 428 (56), 412
(34), 400 (38), 371 (15), 342 (66), 233 (6), 150 (15), 103 (100).
MS {m/z (%) [assignment]}: 1579 (<1) [HgP2(C6F5)4W2(CO)10]+;
1322 (4) [P2(C6F5)4W2(CO)8]+; 1294 (25) [P2(C6F5)4W2(CO)7]+;
1266 (2) [P2(C6F5)4W2(CO)6]+; 1255 (1) [HgP2(C6F5)4W(CO)5]+;
1210 (3) [P2(C6F5)4W2(CO)4]+; 1182 (30) [P2(C6F5)4W2(CO)3]+;
1154 (4) [P2(C6F5)4W2(CO)2]+; 1126 (21) [P2(C6F5)4W2(CO)]+;
1098 (32) [P2(C6F5)4W2]+; 730 (72) [P2(C6F5)4]+; 365 (100) [P-
The product loses the DMF ligands in vacuo at room temperature,
yielding [Hg{(µ-P(CF3)2)W(CO)5}2]. Elemental analysis of [Hg-
{(µ-P(CF3)2)W(CO)5}2] (calcd for C14F12HgO10P2W2): C 15.10
(14.17); H 0.02 (0.00); N 0.05 (0.00). A TG investigation exhibits
no mass loss until the decomposition temperature of 200 °C is
attained. MS {m/z (%) [assignment]}: 1186 (60) [HgP2(CF3)4W2-
(CO)10]+; 862 (18) [HgP2(CF3)4W(CO)5]+; 665 (15) [HgP(CF3)2W-
(CO)4]+; 493 (75) [P(CF3)2W(CO)5]+; 465 (64) [P(CF3)2W(CO)4]+;
409 (29) [P(CF3)2W(CO)2]+; 353 (8) [P(CF3)2W]+; 315 (100)
[W(CO)4F]+; 303 (16) [P(CF3)FW]+; 287 (8) [W(CO)3F]+; 284
(7) [P(CF3)W]+; 202 (10) [Hg]+; 73 (19) [(CH3)2NCOH]+. NMR
for [Hg{µ-P(CF3)2W(CO)5}2]‚2DMF (saturated CDCl3 solution; 298
1
K): δ(31P) 43.1 ppm (m); δ(19F) -48.8 ppm (m); J(199HgP) )
1
3
2
2685 Hz; J(183WP) ) 217 Hz; J(199HgF) ) 105 Hz; J(PP) 111
) Hz; 2J(PF) ) 63.8 Hz; 4J(PF) ) 2 Hz. The 1H NMR data of the
DMF ligand molecule are not essentially influenced in comparison
to those of noncoordinated DMF: δ(1H) 7.9 (1H); 3.0 (3H); 2.9
(3H) ppm.
Results and Discussion
The first preparation of a the bis(pentafluorophenyl)-
phosphanidomercury compound exploits the weak acidity of
HCN in the reaction of mercury cyanide with HP(C6F5)2 at
-30 °C in DMF solution:
Hg(CN)2 + 2HP(C6F5)2 DMF8 2HCN + [Hg{P(C6F5)2}2]
(2)
The product [Hg{P(C6F5)2}2] formed in a plain reaction
exhibits no mercury satellites in the fluorine and phosphorus
NMR spectra, which is caused through ligand exchange
processes. All attempts to determine fluorine- and phos-
phorus-mercury coupling constants using different solvents
and low temperatures have not been successful so far. The
broad and temperature-dependent 31P resonance of [Hg-
{P(C6F5)2}2] is shifted by about 35 ppm to lower field with
respect to the resonance of HP(C6F5)2; cf. Table 1.
(9) Hoge, B.; Herrmann, T.; Tho¨sen, C.; Pantenburg, I. Inorg. Chem. 2003,
42, 3623-3632.
(10) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon Press: Oxford, England, 1980.
(11) Budzelaar, P. H. M. gNMR Version 4.1; Cherwell Scientific: Oxford,
U.K., 1998.
Caused by the stabilizing electron-withdrawing effect of
the pentafluorophenyl groups, [Hg{P(C6F5)2}2] decomposes
slowly at room temperature, while the nonfluorinated deriva-
Inorganic Chemistry, Vol. 42, No. 17, 2003 5423

Hoge et al.
Table 1. Crystal Data and Structure Refinement Parameters for [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF
empirical formula
C40H14F20N2O12P2W2Hg
fw
1724.76
Data Collection
diffractometer
radiation
STOE IPDS II
exposure time (min)
detector distance (mm)
7
120
Mo KR (graphite monochromator,
λ ) 71.073 pm)
170(2)
temp (K)
index range
2θ range (deg)
no. of total data collected
no. of unique data
no. of obsd data
Rmerg
1.9-54.8
22263
5408
3139
0.1030
-26 e h e +30
-13 e k e +13
-26 e l e +26
0° e ω e 180°; ψ ) 0°
0° e ω e 70°; ψ ) 90°
∆ω ) 2°
rotation angle range
abs correction
transm max/min
numerical, after crystal shape optimization20,21
0.2552/0.4306
increment
no. of images
125
Crystallographic Data
cryst size (mm)
color, habit
cryst syst
space group
a (pm)
0.2 × 0.2 × 0.1
yellow, column
monoclinic
C2/c (No. 15)
2366.2(3)
â (deg)
vol (nm3)
Z
104.01(1)
4.871(1)
4
2.352
8.061
3208
F
calcd (g cm-3
)
µ (mm-1
F(000)
)
b (pm)
1046.9(1)
c (pm)
2026.4(3)
Structure Analysis and Refinement
b
structure determination
no. of variables
SHELXS-9722 and SHELXL-9323
360
R1 ) 0.0370
GOF (Sobsd
)
0.939
0.802
-2.050/1.173
b
GOF (Sall
)
R indexesa [I > 2σI]
largest difference map hole/peak (10-6 e pm-3
)
wR2 ) 0.0428
R1 ) 0.0891
wR2 ) 0.0493
R indexesa (all data)
2
2
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑w(|Fo| - |Fc| )2/∑w(|Fo| )2]1/2
.
b S2 ) [∑w(|Fo| - |Fc| )2/(n - p)]1/2, with w ) 1/[σ2(Fo)2 + (0.0027P)2], where
P ) (Fo + 2Fc )/3. Fc* ) kFc[1 + 0.001|Fc| λ3/sin(2θ)]-1/4
.
2
2
2
tive [Hg(PPh2)2] decomposes even at lower temperatures and
cannot be obtained so far.1 All attempts to isolate [Hg-
{P(C6F5)2}2] as a pure compound, removing the volatile
compounds in vacuo, remain unsuccessful and lead to the
reductive elimination of elemental mercury. The decomposi-
tion yields only minor amounts of (C6F5)PP(C6F5)2 besides
further unknown products.
Phosphanido-transition-metal complexes with less than
18 valence electrons show a phosphanido-phosphenium
bonding dualism.12,13 As discussed previously, diphosphani-
domercury compounds [Hg(PR2)2] may be described by the
following resonance structures:5
If strong electronegative groups are attached to the
phosphorus atoms, the electron-withdrawing effect destabi-
lizes the phosphenium bonding situation, i.e., destabilizes
the formal positive charge at the phosphorus atom in the
resonance structures B and C, resulting in a thermodynamical
stabilization.
Theoretical calculations, using a partial retention of
diatomic differential overlap (PRDDO) model, on different
phosphanidotitanium derivatives, give evidence for a reduced
phosphenium bonding contribution of (CF3)2P-Ti com-
pounds with respect to comparable R2P-Ti derivatives with
R ) H, CH3, and C6H5.14 The calculations lead to elongated
P-Ti distances and increased inversion barriers for the bis-
(trifluoromethyl)phosphanido derivatives Cl3TiPR2, CpCl2-
TiPR2, and Cp2ClTiPR2 with respect to nonfluorinated
derivatives.
Another possibility to stabilize phosphanidomercury de-
rivatives, which means to reduce the phosphenium bonding
contribution (resonance structures B and C), is achieved by
the formation of 18 valence electron complexes such as [Hg-
{P(CF3)2}2(PR3)2] ((PR3)2 ) (PMe3)2, dppe).5
The resonance structures B and C both contain a nucleo-
philic phosphorus atom and an electrophilic phosphorus
atom.13 This approach explains why two phosphorus atoms
smoothly combine with reductive elimination of elemental
mercury.
This basic approach gives a qualitative description of the
thermal stability of diphosphanidomercury derivatives with
respect to a reductive elimination. If sterically demanding
groups, such as R ) t-Bu, SiMe3, or SiPh3, are attached to
the phosphorus atoms, the resulting steric shielding of the
phosphorus atoms prevents the combination of the PR2
units: kinetical stabilization.
Peringer et al.8 found that phosphanidomercury compounds
can be stabilized if the phosphorus atoms are coordinated to
low-valent transition-metal compounds, such as M(CO)5 (M
) Cr, Mo, W). Thus, the formally free phosphorus lone pairs
are no longer accessible for the realization of a phosphenium
bonding situation. The trinuclear compounds [Hg{(µ-PPh2)M-
(CO)5}2], which are accessible via the reaction of [Hg-
{N(SiMe3)2}2] and [M(CO)5PHPh2], show melting points
above 140 °C.
(12) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Application of Organotransition Metal Chemistry; University
Science Books: Mill Valley, CA, 1987.
(13) Baker, R. T.; Whitney, J. F.; Wreford, S. S. Organometallics 1983, 2,
1049-1051.
(14) Rogers, J. R.; Wagner, T. P. S.; Marynick, D. S. Inorg. Chem. 1994,
33, 3104-3110 and references cited therein.
5424 Inorganic Chemistry, Vol. 42, No. 17, 2003

Preparation of Diphosphanidomercury DeriWatiWes
Table 2. NMR Spectroscopic Data for Bis(pentafluorophenyl)phosphorus Derivativesa
δ(31P)
δ(19Fo)
δ(19Fm)
δ(19Fp)
1J(PH )
1J(PW )
1J(HgP)
2J(PP)
9
HP(C6F5)2
-137.7
-102.9
-103.9
-111.5
-74.4
-128.3
-127.2
-127.9
-125.1
-128.5
-131.2
-159.6
-162.9
-165.2
-163.5
-160.0
-160.3
-149.3
-154.7
-162.7
-159.1
-149.6
-148.5
236.5
[Hg{P(C6F5)2}2]b
nr
[W{ P(C6F5)2}(CO)5]- 18
[{W(CO)5}2{µ-P(C6F5)2}]- 18
[Hg{(µ-P(C6F5)2)W(CO)5}2]c
[W(CO)5PH(C6F5)2]9
99.5
172.8
218
1864
137
-100.1
380.5
249.9
a nr ) not resolved. b DMF, 298 K. c See the Experimental Section.
Table 3. Selected Bond Lengths (pm) and Angles (deg) for
[Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF
Hg1-P1
Hg1-O6
W2-C2
W2-C4
W2-C1
W2-C3
W2-C5
W2-P1
244.2(2)
255.3(6)
199.0(9)
200.1(9)
200.2(9)
203.6(9)
204.9(9)
254.4(2)
184.5(7)
184.7(7)
137(1)
138(1)
135.6(8)
138(1)
135.0(8)
138.2(9)
135.5(8)
120(1)
P1-Hg1-P1′
P1-Hg1-O6
P1-Hg1-O6′
O6-Hg1-O6′
C2-W2-P1
C4-W2-P1
C1-W2-P1
C3-W2-P1
C5-W2-P1
C11-P1-C21
C11-P1-Hg1
C21-P1-Hg1
C11-P1-W2
C21-P1-W2
Hg1-P1-W2
C7-O6-Hg1
O6-C7-N8
C7-N8-C81
C7-N8-C82
C81-N8-C82
170.25(9)
91.1(2)
96.2(2)
82.7(3)
174.5(3)
91.8(2)
92.6(2)
83.8(2)
92.8(2)
103.1(3)
107.6(2)
99.9(2)
106.0(2)
122.6(2)
116.33(7)
140.5(7)
126(1)
P1-C11
P1-C21
C11-C12
C11-C16
C12-F12
C12-C13
C15-F15
C15-C16
C16-F16
O6-C7
Figure 1. Central projection of the asymmetric unit of [Hg{(µ-P(C6F5)2)W-
(CO)5}2]‚2DMF showing the atom numbering scheme and thermal ellipsoids
(50%).
123.1(9)
120.9(8)
116.0(8)
C7-N8
N8-C81
131(1)
145.4(9)
Although we obtain a 4-fold coordination of the mercury
atom, the P-Hg-P unit exhibits a nearly linear arrangement.
One reason for the linear arrangement may be the bulkiness
of the two sterically demanding phosphanido substituents.
But if compared with complexes of urea derivatives with
mercury(II) chloride, [HgCl2D2], which also exhibit a nearly
linear Cl-Hg-Cl arrangement,15 the smaller coordination
strength of the amide ligands seems to be responsible for
the nearly linear P-Hg-P arrangement shown in Figure 2.
The DMF ligands are coordinated via the oxygen atom,
and the CO distance is therefore elongated by around 3 pm
in comparison with that of solid DMF.16 The CO valence
mode cannot be assigned with absolute certainty because the
C6F5 groups exhibit a strong CC valence mode in both the
infrared and Raman spectra. The latter exhibits a medium
intense band at 1642 cm-1 which is assigned to a CC valence
mode because this resonance shows the same intensity as
observed for previously investigated pentafluorophenylphos-
phorus derivatives.9 The CO valence mode of DMF shows
only a weak Raman intensity. In the infrared spectrum two
strong resonances are detected at 1659 and 1651 cm-1.
Following the assignment of the Raman resonance, we assign
the resonance at 1659 cm-1 to the CO valence mode of the
DMF ligand, which is shifted about 50 cm-1 to lower
frequencies in comparison to that of gaseous DMF17 but
Figure 2. Simplified view of [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF. The
CO groups have been omitted for clarity. A subscript atom identifier
indicates symmetry-dependent atoms.
Mercury cyanide smoothly reacts with a slight excess of
[W(CO)5PH(C6F5)2] at -50 °C to give the trinuclear
compound [Hg{(µ-P(C6F5)2)W(CO)5}2]:
Hg(CN)2 + 2[W(CO)5PH(C6F5)2] DMF8
2HCN + [Hg{(µ-P(C6F5)2)W(CO)5}2] (4)
The product crystallizes, with two DMF solvent molecules,
from the reaction mixture on warming to room temperature.
The crystal data and structure refinement parameters for [Hg-
{(µ-P(C6F5)2)W(CO)5}2]‚2DMF are given in Table 2. The
asymmetric unit of the C2 symmetric complex with the atom
numbering scheme is shown in Figure 1, whereas Figure 2
exhibits a simplified view of the trinuclear complex, the CO
groups having been omitted for clarity. Selected bond lengths
and angles are summarized in Table 3.
(15) Lewinski, K.; Sliwinski, J.; Lebioda, L. Inorg. Chem. 1983, 22, 2339-
2342. Birker, P. J. M. W. L.; Freeman, H. C.; Guss, J. M.; Watson,
A. D. Acta Crystallogr. 1977, B33, 182-184. Majeste, R. J.; Trefonas,
L. M. Inorg. Chem. 1972, 11, 1834-1836.
(16) Borrmann, H.; Persson, I.; Sandstro¨m, M.; Stålhandske, C. M. V. J.
Chem. Soc., Perkin Trans. 2 2000, 393-402.
(17) Jao, T. C.; Scott, I.; Steele, D. J. Mol. Spectrosc. 1982, 92, 1-17.
Inorganic Chemistry, Vol. 42, No. 17, 2003 5425

Hoge et al.
Table 4. 1J(PW) and the Highest Infrared CO Valence Mode of
Bis(pentafluorophenyl)phosphorus Derivatives Coordinated to a
Pentacarbonyltungsten Unit in Comparison to Their Structural Data
isotope gives rise to a magnetic nonequivalence of the two
phosphorus atoms. The theoretical chemical difference of
the two phosphorus atoms, caused by the isotopic shift, can
be neglected in this case. The calculation of the resulting
AA′X spin system ([A]2X) with A ) P and X ) 183W
(bottom trace of Figure 3) allows the determination of the
2J(PP) coupling of 137 Hz.
The calculated 31P NMR spectrum shown at the bottom
trace of Figure 3 takes into account the mercury satellites,
the tungsten satellites, and the [AX]2 spin system for the
isotopomer with two NMR-active 183W isotopes in the
W-P-Hg-P-W unit.
d(WP) (pm)
X-ray calcdb (cm-1
d(WCtr) (pm)
X-ray calcdb
1J(PW)
(Hz)
ν(CO)a
)
[W(CO)5PH(C6F5)2]9
[Hg{(µ-P(C6F5)2)-
W(CO )5}2]
249.9 247.7(1) 250.5 2084 201.1(6) 201.1
217.8 254.4(2)c 2073 199.0(9)c
[W{P(C6F5)2}(CO)5]- 18 99.5
266.4 2054
198.4
a Highest infrared CO valence mode. b B3PW91 with a LanL2DZ ECP
basis for tungsten and a 6-311G(d,p) basis for the nonmetal atoms. c X-ray
data of [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF.
Mercury cyanide reacts smoothly with [W(CO)5PH(CF3)2],
yielding the corresponding trinuclear bis(trifluoromethyl)-
phosphanido compound [Hg{(µ-P(CF3)2)W(CO)5}2]:
Hg(CN)2 + 2[W(CO)5PH(CF3)2] DMF8
2HCN + [Hg{(µ-P(CF3)2)W(CO)5}2] (5)
After evaporation of the intense yellow solution to dryness,
the powdery product is obtained as an adduct with two
solvent molecules of DMF, which can be removed on
extended evaporation of the crushed powder at room tem-
perature.
Figure 3. Experimental (top) and calculated (bottom) 31P NMR spectrum
of [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF.
In contrast to [Hg{P(CF3)2}2], which slowly decomposes
at room temperature, the solvent-free compound [Hg{(µ-
P(CF3)2)W(CO)5}2] decomposes above 200 °C. The decom-
position temperature lies more than 50 °C above the
decomposition point of the comparable phosphane complexes
[Hg{P(CF3)2}2(PR3)2] with (PR3)2 ) (PMe3)2 and dppe.5
The DMF solvent molecules exhibit only weak interaction
with the trinuclear complex, as is indicated by the remov-
ability of the solvent molecules in vacuo at room temperature.
Further evidence for a merely weak interaction is outlined
exhibits nearly the same frequency as that of solid or liquid
DMF, which is associated via C-H‚‚‚O interactions.16
The Hg-P distance of 244 pm is comparable to those
observed for [Hg{P(t-Bu)2}2], 244 and 245 pm, and [Hg-
{P(SiMe3)2}2], 240 and 241 pm. However, the phosphane
complex [Hg{P(CF3)2}2dppe] exhibits phosphanido-mercury
distances which are elongated by about 5 pm.5
The W-P distance of 254 pm is elongated in comparison
to that of the phosphane complex [W(CO)5PH(C6F5)2],9 248
pm (X-ray) and 250 pm (DFT calculation). The distance is
shortened in comparison to that of the phosphanido complex
[W{P(C6F5)2}(CO)5]-, 266 pm (HDFT calculation).18 These
findings are reasonable because a successive increase of
electron density at the phosphorus atoms in the series
[W(CO)5PH(C6F6)2], [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF, and
[W{P(C6F5)2}(CO)5]- has to be expected. As a consequence,
the π acidity should decrease. As outlined in Table 3, this
decrease of π acidity causes a shift of the highest symmetric
CO valence mode to lower frequencies, indicating an
increased π back-bonding effect of the CO groups as can be
observed by means of the successive shortening of the WC
distance of the trans-orientated CO group in the same series,
Table 4.
1
by the dynamic behavior in solution. The H NMR reso-
nances of the DMF moieties of the compound [Hg{(µ-
P(CF3)2)W(CO)5}2]‚2DMF dissolved in CDCl3 exhibit no
significant difference in comparison to those of a diluted
DMF solution in CDCl3.
The CO valence mode of the DMF molecule of solid [Hg-
{(µ-P(CF3)2)W(CO)5}2]‚2DMF, located at 1651 cm-1 in the
Raman spectrum and at 1650 cm-1 in the infrared spectrum,
is shifted by more than 60 cm-1 to lower frequencies in
comparison to that of DMF in the gas phase.17 On the other
hand, C-H‚‚‚O-associated solid and liquid DMF exhibits
no significant shift of the CO valence mode.16 The highest
symmetric CO valence mode of 2082 cm-1 (IR) and 2080
cm-1 (RA) is shifted about 10 cm-1 to higher frequencies in
comparison to the corresponding resonance of the pentafluo-
rophenyl derivative [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF. The
stronger electron-withdrawing effect of the CF3 increases the
π back-bonding effect of the P-W bond and therefore
decreases the π back-bonding effect of the W-C bonds,
which is indicated by the shift of the CO valence modes to
higher frequencies.
The experimental 31P NMR spectrum of [Hg{(µ-P(C6-
F5)2)W(CO)5}2]‚2DMF is shown in Figure 3. The fluorine-
phosphorus couplings are very small and could not be
resolved. The major signal is surrounded by mercury
satellites with a HgP coupling of 1864 Hz. The isotopomer
of the W-P-Hg-P-W unit with one NMR-active 183W
The highest CO mode of the series [W(CO)5PH(CF3)2],
[Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF, and [W{P(CF3)2}(CO)5]-
(18) Hoge, B.; Tho¨sen, C.; Herrmann, T. Inorg. Chem. 2003, 42, 3633-
3641.
5426 Inorganic Chemistry, Vol. 42, No. 17, 2003

Preparation of Diphosphanidomercury DeriWatiWes
Table 5. NMR Spectroscopic Data for Bis(trifluoromethyl)-
phosphorus Derivatives
δ(31P) δ(19F) 2J(PF) 1J(PH) 1J(HgP) 1J(PW) 2J(PP)
HP(CF3)9
P(CF3)2
-48.0 -47. 3 60.6 240.7
-1.9 -31. 4 47.2
- 24
[Hg{P(CF3)2}2(dppe)]5 -5.2 -39. 4 54
623
823
[Hg{P(CF3)2}2]5
1.8 -39. 8 54.2
12
[W{P(CF3)2}(CO)5]- 18 15.0 -42. 8 50.1
103. 1
2685 217
[Hg{(µ-P(CF3)2)-
43.1 -48. 8 63.8
111
W(CO )5}2]a
[W(CO)5PH(CF3)2]9
1.7 -54. 9 75.9 359.5
268. 8
3
4
a See the Experimental Section. J(199HgF) ) 105 Hz. J(PF) ) 2 Hz.
shows the expected successive shift to lower frequencies of
about 2093, 2081, and 2065 cm-1, respectively.9,18 These
frequencies describe an increasing π back-bonding effect of
the W-C bond in this series, while the π back-bonding effect
of the W-P bond increases vice versa.
Figure 4. Experimental (top) and calculated (bottom) 31P NMR spectrum
of [Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF.
Further support for an increasing π back-bonding effect
of the W-P bond in the order [W{P(CF3)2}(CO)5]-, [Hg-
{(µ-P(CF3)2)W(CO)5}2]‚2DMF, and [W(CO)5PH(CF3)2] is
given by the successively increased magnitude of the
1J(183WP) coupling of 103, 214, and 269 Hz, respectively
(Table 5).
The fluorine-decoupled 31P NMR spectrum of [Hg{(µ-
P(CF3)2)W(CO)5}2]‚2DMF dissolved in CDCl3 exhibits the
same habit as is observed for the C6F5 derivative; cf. Figure
1
3. The observed J(HgP) coupling of 2685 Hz varies less
than 10% when determined for the solvent adducts [Hg{(µ-
P(CF3)2)W(CO)5}2]‚2D with D ) CH3CN, diglyme, and
DMF. As a result of ligand exchange phenomena the 1J(HgP)
coupling of the pyridine and DMSO adducts could not be
determined. These results are in contrast to the drastic
Figure 5. Experimental (top) and calculated (bottom) 19F NMR spectrum
of [Hg{(µ-P(CF3)2)W(CO)5}2]‚2DMF.
together with the calculated spectrum in the bottom trace of
Figure 5 with respect to the 199Hg satellites. The tungsten
satellites could not be resolved in the fluorine NMR
spectrum.
1
changes in the J(HgP) coupling constant of the trinuclear
compounds [Hg{(µ-PPh2)M(CO)5}2] with M ) Cr, Mo, and
W on coordination of neutral N and O ligands.19
As a result of the 2J(PF) and 4J(PF) couplings of 63.8 and
2 Hz, respectively, the fluorine-coupled 31P NMR spectrum
of [Hg{(µ-P(CF3)2)W(CO)5}2] gives rise to a magnetic
nonequivalence of the two P(CF3)2 units. This allows the
In previous papers we provided vibrational and X-ray
structural evidence, supported by hybrid DFT calculations,
that the electronic properties of the phosphanide ions P-
-
-
(CF3)2 and P(C6F5)2 and of the comparable phosphanes
HP(CF3)2 and HP(C6F5)2 are not significantly influenced on
coordination to a W(CO)5 unit.9,18 For example, the bis-
(trifluoromethyl)phosphanidotungstate ion, [W{P(CF3)2}-
(CO)5]-, exhibits nearly the same nucleophilicity as the
noncoordinated P(CF3)2- ion. This finding can be described
by the strong π acidity of perfluoroorganylphosphorus
derivatives, which compensates the electron transfer via the
σ donation from the phosphorus atom to the tungsten atom.
As a consequence, complexation by pentacarbonyl group VI
metals shows no significant influence on the structural and
vibrational data of perfluoroorganylphosphorus derivatives,
as is impressively demonstrated by the P-C distances of
2
determination of the J(PP) coupling by the calculation of
the center signal as a A6A′6XX′ or [A6X]2 spin system,
respectively (bottom of Figure 4). The determined value of
111 Hz matches exactly with the value obtained via the
calculation of the tungsten satellites of the fluorine-decoupled
phosphorus spectrum. The 199Hg satellites, not shown in
Figure 4, exhibit the same habit as the center signal. If the
tungsten satellites are taken into account, the calculated 31
P
NMR spectrum (bottom of Figure 4) is the sum of 85.72%
of an [A6X]2 spin system and 14.28% of an [A6X]2M spin
system (A ) F; X ) P; M ) 183W). The experimental 19F
NMR spectrum is shown in the upper trace of Figure 5
-
the P(CF3)2 and the [W{P(CF3)2}(CO)5]- ions.
(19) Peringer, P, Polyhedron 1982, 1, 819-820.
(20) X-RED 1.22, STOE Data Reduction Program; Darmstadt, Germany,
2001.
(21) X-SHAPE 1.06, Crystal Optimisation for Numerical Absorption
Correction; Darmstadt, Germany, 1999.
(22) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Analysis;
University of Go¨ttingen: Go¨ttingen, Germany, 1998.
(23) Sheldrick, G. M. SHELXL-93, Program for the Refinement of Crystal
Structures, University of Go¨ttingen: Go¨ttingen, Germany, 1993.
(24) Hoge, B.; Tho¨sen, C. Inorg. Chem. 2001, 40, 3113-3116.
Negative hyperconjugation of the P(CF3)2- ion leads to a
significantly shortened P-C distance (C2 symmetry) in
comparison to those of neutral phosphane derivatives.
Because of the weak influence on coordination to a W(CO)5
unit, the [W{P(CF3)2}(CO)5]- ion exhibits the same P-C
distance within the measurement accuracy.
Inorganic Chemistry, Vol. 42, No. 17, 2003 5427

Hoge et al.
The increased stability of [Hg{(µ-PR2)W(CO)5}2] with R
) CF3 and C6F5 in comparison to the noncoordinated
monometallic counterpart is therefore interpretable in terms
of a reduced phosphenium bonding contribution (resonance
structures B and C). If the reductive elimination of mercury
were interpretable in terms of a “classical” redox process,
the coordination of the P(CF3)2 and P(C6F5)2 ligands to a
W(CO)5 unit would not lead to the observed strong increase
in thermal stability.
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.
W. Tyrra and Dr. K. Glinka for helpful discussions.
Supporting Information Available: A crystallographic file in
CIF format for [Hg{(µ-P(C6F5)2)W(CO)5}2]‚2DMF. This material
is available free of charge via the Internet at http://pubs.acs.org.
IC034448N
5428 Inorganic Chemistry, Vol. 42, No. 17, 2003