Synergistic effect of a low-valent cobalt complex and a trimethylphosphine ligand on selective c-f bond activation of perfluorinated toluene

Article abstract of DOI:10.1021/om900589z

The aryne cobalt complex [Co(4-CF₃-η²-C6F ₃)(PMe₃)3] (1) was formed from the reaction of [Co(PMe₃)₄] and perfluorinated toluene through selective activation of two C-F bonds of perfluorotol

Full text of DOI:10.1021/om900589z

Organometallics 2009, 28, 5771–5776 5771
DOI: 10.1021/om900589z
Synergistic Effect of a Low-Valent Cobalt Complex and a
Trimethylphosphine Ligand on Selective C-F Bond Activation of
Perfluorinated Toluene
†
†
†
,†
‡
‡
€
Tingting Zheng, Hongjian Sun, Yue Chen, Xiaoyan Li,* Simon Durr, Udo Radius,
and Klaus Harms§
†School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan,
‡
€
€
People’s Republic of China, Institut fuer Anorganische Chemie, Universitat Wurzburg, Am Hubland,
D-97074 Wu€rzburg, Germany, and §Fachbereich Chemie, Philpps-Universitaet Marburg,
Hans-Meerwein-Strasse, 35032 Marburg, Germany
Received July 8, 2009
The aryne cobalt complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of
[Co(PMe3)4] and perfluorinated toluene through selective activation of two C-F bonds of perfluoroto-
luene. A mechanism for the formation of complex 1 is proposed and in most parts experimentally verified.
Following this mechanism, a synergistic effect of an electron-rich cobalt(0) center and one of its
trimethylphosphine ligands is responsible for the C-F activation of two carbon-fluorine bonds of
perfluorotoluene. The detection of difluorotrimethylphoshphorane as the sole byproduct provides strong
evidence for this mechanism. Complex [Co(4-CF3-C6F4)(PMe3)3] (4), an intermediate of the proposed
mechanism to the aryne complex, was also isolated and structurally characterized. Complex 4transforms to
complex 1 via activation of a second C-F bond of a perfluorotolyl ligand only in the presence of
trimethylphosphine in the reaction mixture. Complex 4 reacts with CO under atmospheric pressure and
room temperature to give [Co(4-CF3-C6F4)(CO)2(PMe3)2] (6) and with bromobenzene via one-electron
oxidative addition of the C-Br bond to give the cobalt(II) bromide [CoBr(4-CF3-C6F4)(PMe3)3] (8) and a
C-C-coupling product, 4-phenylheptafluorotoluene (7). The structures of complexes 1, 4, and 8 were
determined by X-ray crystallography.
Introduction
metal centers, such as Pt(II), W(0), and Ni(0), is an effective
route,3,7-9 whereas reports of carbon-fluorine bond activa-
tion mediated by cobalt complexes are scarce.10-15
Richmond et al. reported C-F bond formation with cobal-
tocenium fluoride as a novel fluoride source to obtain fluoroor-
ganic compounds. Fluoride ions are mobilized by C-F bond
activation in a saturated perfluorocarbon, e.g., perfluorodeca-
lin.12 C-F bond activation and cleavage was also discovered by
Hughes et al. for reactions of carbonyl cobaltates [Co(CO)3L]-
and [{Co(CO)3 L}2]- (L = CO, PPh3, PMe2Ph, PMe3) with
The activation of carbon-fluorine bonds by transition
metal complexes presents a significant chemical challenge.1
The design of well-defined soluble transition metal com-
plexes capable of selective activation and functionalization
of strong carbon-fluorine bonds under mild conditions is a
highly desirable goal and of considerable current interest.
Few methods have been reported for the activation of
carbon-fluorine bonds of fluorinated compounds by transi-
tion metal complexes.2-6 Oxidative addition at low-valent
(7) (a) Lopez, O.; Crespo, M.; Font-Bardia, M.; Solans, X. Organo-
metallics 1997, 16, 1233. (b) Bennett, M. A.; Wenger, E. Chem. Ber. 1997,
130, 1029–1042.
(8) Kiplinger, J. L.; King, M. A.; Arif, A. M.; Richmond, T. G.
Organometallics 1993, 12, 3382.
(9) (a) Ceder, R.; Granell, J.; Muller, G.; Font-Bardia, M.; Solans, X.
Organometallics 1995, 14, 5544. (b) Keen, A. L.; Doster, M.; Johnson, S. A.
J. Am. Chem. Soc. 2007, 129, 810–819. (c) Keen, A. L.; Johnson, S. A.
J. Am. Chem. Soc. 2006, 128, 1806–1807.
(10) Hughes, R. P.; Doig, S. J.; Hemond, R. C.; Smith, W. L.; Davis,
R. E.; Gadol, S. M.; Holland, K. D. Organometallics 1990, 9, 2745–2753.
(11) Doig, S. J.; Hughes, R. P.; Davis, R E.; Gadol, S. M.; Holland,
K. D. Organometallics 1984, 3, 1921–1922.
*Corresponding author. E-mail: xli63@sdu.edu.cn.
(1) For reviews on C-F activation see: (a) Doherty, N. M.;
Hoffmann, N. W. Chem. Rev. 1991, 91, 553. (b) Burdeniuc, J.; Jedlicka,
B.; Crabtree, R. H. Chem. Ber./Recl. 1997, 130, 145. (c) Kiplinger, J. L.;
Richmond, T. G.; Osterberg, C. E. Chem. Rev. 1994, 94, 373. (d) Murphy,
E. F.; Murugavel, R.; Roesky, H. W. Chem. Rev. 1997, 97, 3425. (e)
Mazurek, U.; Schwarz, H. Chem. Commun. 2003, 1321. (f) Braun, T.;
Perutz, R. N. Chem. Commun. 2002, 2749. (g) Torrens, H. Coord. Chem.
Rev. 2005, 249, 1957. (h) Jones, W. D. Dalton Trans. 2003, 3991. (i) Perutz,
R. N.; Braun, T. In Comprehensive Organometallic Chemistry III, Vol. 1;
Crabtree, R. H., Mingos, M. P., Eds.; Elsevier: Oxford, 2007; p 725.
€
€
(2) Bohm, V. P. W.; Gstottmayr, C. W. K.; Weskamp, T.; Herrmann,
W. A. Angew. Chem., Int. Ed. 2001, 40, 3387–89.
(12) Bennett, B. K; Harrison, R. G.; Richmond, T. G. J. Am. Chem.
Soc. 1994, 116, 11165–11166.
(13) Kiplinger, J. L; Richmond, T. G.; Osterberg, C. E. Chem. Rev.
1994, 94, 373–431.
(14) Li, X.; Sun, H; Yu, F.; Floerke, U.; Klein, H.-F. Organometallics
(3) (a) Schaub, T.; Radius, U. Chem.;Eur. J. 2005, 11, 5024. (b)
Schaub, T.; Backes, M.; Radius, U. J. Am. Chem. Soc. 2006, 128, 15964–
15965. (c) Schaub, T.; Fischer, P; Steffen, A.; Braun, T; Radius, U; Mix, A.
J. Am. Chem. Soc. 2008, 130, 9304–9317.
(4) Richmond, T. G. Angew. Chem., Int. Ed. 2000, 39, 3241–3244.
(5) Mazurek, U.; Schwarz, H. Chem. Commun. 2003, 1321–1326.
(6) Young, R. J.; Grushin, V. V. Organometallics 1999, 18, 294–296.
2006, 25, 4695–4697.
(15) Hughes, R. P.; Lindner, D. C.; Rheingold, A. L.; Yap, G. P. A.
Organometallics 1995, 15, 5678–5686.
r
2009 American Chemical Society
Published on Web 09/09/2009
pubs.acs.org/Organometallics

5772 Organometallics, Vol. 28, No. 19, 2009
Zheng et al.
octafluorocyclooctatetraene.10 We reported the synthesis of the
first organo cobalt(III) complex containing a [C-Co-F] frag-
ment through a cyclometalation reaction involving carbon-
fluorine bond activation at a cobalt(I) center using azine as an
anchoring group (eq 1).14
Scheme 1
cobalt(II) bromide [CoBr(4-CF3-C6F4)(PMe3)3] (8) under
C-C coupling, which gives 4-phenylheptafluorotoluene
(7). The structures of complexes 1, 4, and 8 were determined
by X-ray crystallography.
Results and Discussion
Selective C-F Bond Activation of Octafluorotoluene. The
reaction of [Co(PMe3)4] with perfluorinated toluene in di-
ethyl ether results in the formation of the benzyne cobalt
complex 1 (eq 2).
Lately, several mechanistic studies on transition metal com-
plex mediated C-F bond activation have been published.
Perutz and co-workers employed both experimental and com-
putational methods to rationalize the diverse reactivity of
bis(phosphine)Pt(0) complexes toward fluoropyridines.16 In
a computational study on the reaction of C6F6 with
[IrMe(PEt3)3], phosphine-assisted C-F activation was pro-
posed as a novel mechanism just recently.17 Johnson et al.
presented important results on the selectivity of C-F versus
C-H bond activation using a bis(trimethylphosphine)nickel-
(II) system. Although C-H bond activation is thermodyna-
mically disfavored, it seems to be more easily accessible
kinetically.18 In many cases C-F/C-H bond activations are
competing reactions. The catalytic hydrodefluorination of
aromatic fluorocarbons was carried out by ruthenium
N-heterocyclic carbene complex. On the basis of the kinetic
investigation, the hydrodefluorination mechanisms of C6F6
and C6F5H were proposed and discussed.19
Herein, we report the selective activation of two C-F
bonds of perfluorinated toluene by a trimethylphosphine-
supported cobalt(0) complex to afford a perfluoro benzyne
cobalt complex, [Co(4-CF3-η2-C6F3)(PMe3)3] (1), and pro-
pose a mechanism of its formation. As an intermediate,
perfluorotolyl complex [Co(4-CF3-C6F4)(PMe3)3] (4) was
successfully isolated and structurally characterized. The
formation of difluorotrimethylphosphorane, where the acti-
vated fluoride in this process winds up, provides powerful
evidence for a synergistic effect of an electron-rich low-valent
complex center and one of its trimethylphosphine ligands in
the C-F bond activation process. Furthermore, the reac-
tions of complex 4 with trimethylphosphine, carbon mon-
oxide, and bromobenzene have been studied. Complex 4
reacts with bromobenzene via one-electron oxidative addi-
tion of the C-Br bond at the cobalt(I) center to produce the
Red crystals of complex 1, which are very sensitive to air,
have been obtained from recrystallization in pentane. The
molecular structure of complex 1 reveals a perfluoroaryne
complex of zerovalent cobalt (Figure 1). Two modes
of coordination, A and B, can represent complex 1
(Scheme 1). Form A is referred to as a π-bonded benzyne
complex, while form B describes a di-σ-bonded complex of
an ortho-phenylene. The bonding state of 1 is somewhere
between these two extremes.
Complex 1 exhibits a pseudotetrahedral coordination
geometry made up of three P-donors and the centroid of
the C1-C2 bond. The metal-carbon bond lengths of
˚
1.919(5) and 1.914(5) A are in the region expected for
(sp2)C-Co bonds. The distance of the coordinated bond
˚
C1-C2 of 1.345(7) A is significantly shorter compared to the
corresponding distance (1.374(7) A) in a tetrafluoro-ben-
˚
zyne-iridium complex, [Ir(η5-C5Me5)(PMe3)(η2-C6F4)],20
but closer to that observed for an η2-benzyne nickel complex
21
(1.332(6) A). The bite angle (C1-Co-C2 = 41.1(2)o) is
˚
typical for this type of three-membered chelate ring, which is
coplanar with the aromatic ring. The CF3 group shows
˚
rotational disorder. Co-P3 (2.2370(12) A) is remarkably
˚
longer than Co-P1 (2.1867(14) A) and Co-P2 (2.1865(13)
(16) Nova, A.; Erhardt, S.; Jasim, N. A.; Perutz, R. N.; Macgregor,
S. A.; McGrady, J. G.; Whitwood, A. C. J. Am. Chem. Soc. 2008, 130,
15499–15511.
(17) Erhardt, S.; Macgregor, S. A. J. Am. Chem. Soc. 2008, 130,
15490–15498.
(18) Johson, S. A.; Huff, C. W.; Mustafa, F.; Saliba, M. J. Am. Chem.
Soc. 2008, 130, 17278–17280.
(19) Reade, S. P.; Mahn, M. F.; Whittlesey, M. K. J. Am. Chem. Soc.
2009, 131, 1847-1861.
o
˚
A), and the angle P1-Co-P2 (103.74(5) ) is larger than
P1-Co-P3 (101.31(5)o) and P2-Co-P3 (101.78(15)o). The
(20) Hughes, R. P.; Williamson, A.; Sommer, R. D.; Rheingold,
A. L. J. Am. Chem. Soc. 2001, 123, 7443–7444.
(21) Bennett, M. A.; Hambley, T. W.; Roberts, N. K. Organometal-
lics 1985, 4, 1992–2000.

Article
Organometallics, Vol. 28, No. 19, 2009 5773
Figure 2. Molecular structure of 4 (the hydrogen atoms were
˚
omitted for clarity). Selected distances [A] and angles [deg]: Co1-
C1 2.036(3), Co1-P1 2.2244(12), Co1-P2 2.2434(10), Co1-P3
2.2465(11); C1-Co1-P1 110.28(9), C1-Co1-P2 116.46(10),
C1-Co1-P3 119.47(10), P1-Co1-P2 102.48(4), P1-Co1-P3
104.06(5), P2-Co1-P3 102.11(4).
˚
Figure 1. Molecular structure of 1. Selected distances [A] and
angles [deg]: Co-C1 1.914(5), Co-C2 1.919(5), C1-C2
1.345(7), C2-C3 1.350(7), C3-C4 1.425(7), C4-C5 1.395(7),
C5-C6 1.373(7), C1-C6 1.341(7), Co-P1 2.1867(14), Co-
P2 2.1865(13), Co-P3 2.2370(12); C1-Co-C2 41.1(2),
P1-Co-P2 103.74(5), P1-Co-P3 101.31(5), P2-Co-P3
101.78(5).
Scheme 2. Suggested Pathway for Formation Mechanism of
Complex 1
donor atom P3 appears to be subject to a stronger trans-
influence of the C1,C2-donor/acceptor.
A proposed mechanism for the formation of complex 1 is
given in Scheme 2. The first likely step is the precoordination
of the aromatic system to the Co(0) center under elimination
of a phosphine ligand and formation of a complex with a η2-
coordinated perfluorotoluene ligand.3c The bond activa-
tion of the first C-F bond of the substrate is facilitated by
the nucleophilicity of the low-valent Co(PMe3)3 group.
Selective oxidative addition of the carbon-fluorine bond
of perfluorinated toluene at the para position at the cobalt(0)
center should lead to a cobalt(II) intermediate, 3, which
comproportionates with PMe3 to give the cobalt(I) complex
4 and difluorotrimethylphosphorane, F2PMe3. The oxida-
tive addition of the second carbon-fluorine bond generates
intermediate 5, which transfers the fluoride ligand to PMe3
and results in the formation of the end product 1 and
F2PMe3.
The formation of F2PMe3 in solution was verified via 31
P
NMR.22 The intermediate 4 was successfully isolated as
green crystals suitable for single-crystal X-ray diffraction
from the reaction mixture through variation of the reaction
conditions employed. As the structure reveals (Figure 2), the
cobalt atom in 4 is located at the center of a distorted
˚
tetrahedron. The Co1-C bond distance is 2.036(3) A, which
is longer than those observed in complex 1, but in the range
48 h at room temperature. In this case the yield of complex 4 was
reduced from 57% to 6%. Therefore, complex 4 may
be regarded as the kinetically controlled product, whereas
complex 1 is the thermodynamically stable product. We have
also observed that the green solution of complex 4 is thermally
very stable, and for the transformation of complex 4 to complex
1 the presence of trimethylphosphine (under formation of
difluorotrimethylphosphorane, according to eq 3) is required.
Therefore, in the C-F bond activation and formation of
complex 1 the free trimethylphosphine ligand and the low-valent
cobalt complex [Co(PMe3)4] display a synergistic effect. The
mechanism proposed here is significantly different from
other phosphine-assisted C-F activation pathway suggested
earlier, in which a metallophosphorane is regarded to be an
intermediate and a fluorodialkylphosphine alkyl metal complex
expected for a (sp2)C-Co bond. The three Co-P bond
lengths are close to an average value of 2.2381 A and
unexceptional.
˚
The outcome of the reaction of [Co(PMe3)4] and perfluor-
otoluene to give complexes 1 and 4 strongly depends on the
reaction conditions. The yield of complex 4 was improved from
18% to 57% if the reaction was carried out in pentane instead of
in diethyl ether under the same reaction conditions. At the same
time the yield of complex 1 was reduced from 37% to 11%. On
the other hand, the yield of complex 1 was improved from 11%
to 44% in pentane if the reaction time was changed from 18 h to
(22) Doxsee, K. M.; Hanawalt, E. M.; Weakley, T. J. R. Inorg. Chem.
1992, 31, 4420–4421.

5774 Organometallics, Vol. 28, No. 19, 2009
Zheng et al.
is formed.16,17 Due to our investigations, the formation of
difluorotrimethylphosphorane plays a crucial role in the C-F
activation process.
Reaction of Complex 4 with Carbon Monoxide. Complex 4
slowly reacts in a pentane solution with CO under atmo-
spheric pressure and room temperature to give the dicarbo-
nyl complex [Co(4-CF3-C6F4)(CO)2(PMe3)2], 6, which was
isolated in the form of yellow crystals (eq 4). Complex 6 was
characterized by IR and NMR spectroscopy as well as C, H,
N analysis. In the IR spectrum of 6 there are two strong
absorptions of terminal carbonyl ligands at 1920 and
1895 cm-1. The 31P NMR data show a singlet at 30.4 ppm
for the two trans-PMe3 ligands. Similar carbonyl cobalt
complexes have been reported earlier.23
˚
Figure 3. Molecular structure of 8. Selected distances [A] and
angles [deg]: C1-Co1 1.973(6), P1-Co1 2.2228(16), P2-Co1
2.3069(17), P3-Co1 2.2240(16), Co1-Br1 2.4607(10); C1-
Co1-P1 87.96(16), C1-Co1-P2 111.82(19), C1-Co1-P3
87.87(17), P1-Co1-P2 96.01(6), P1-Co1-P3 167.84(7), P2-
Co1-P3 96.14(6). C1-Co1-Br1 141,40(19), P1-Co1-
Br1 87.62(5), P2-Co1-Br1 106.78(5), P3-Co-Br1 88.53(5).
the equatorial plane, the large angle C1-Co-Br (141.44(19)°)
is caused by in-plane orientation of the perfluorinated 4-
trifluoromethylphenyl ligand and F, Br repulsions. For the
˚
same steric reason the equatorial bond P2-Co1 (2.3069(17) A)
˚
is considerably longer than axial P1-Co1 (2.2228(17) A) and
˚
˚
P3-Co1 (2.2240(16) A). The distance Co-Br1 (2.4607(10) A)
is in the normal range.24
The demetalated coupling product 7 forms white crystals
suitable for an X-ray structure analysis.3b
For the formation of the coupling product 7 and complex 8
we propose a one-electron oxidative addition of bromoben-
zene to the cobalt atom of 4 in a first step under the formation
of complex 8 and an intermediate complex 9 (Scheme 3). As a
diorgano cobalt(II) species, complex 9 is not stable and
eliminates to form coupling product 7 (reductive elim-
ination) with regeneration of [Co(PMe3)4], which was iden-
tified in solution by IR spectroscopy.
C,C-Coupling Reaction of Complex 4 with Bromobenzene.
Complex 4 reacts with bromobenzene through a one-elec-
tron oxidative addition to afford C-C-coupling product 7
and complex 8 according to eq 5.
Conclusions
In summary, the benzyne cobalt complex [Co(4-CF3-η2-
C6F3)(PMe3)3], 1, is formed via a selective activation of two
C-F bonds of perfluorotoluene using a synergistic effect of
the electron-rich low-valent cobalt center [Co(PMe3)4] and
trimethylphosphine. The formation mechanism of complex 1
is proposed and supported by experiment. The formation of
difluorotrimethylphosphorane during this process provides
evidence for this mechanism. As an intermediate, [Co(4-CF3-
C6F4)(PMe3)3] (4) was isolated and structurally character-
ized. Furthermore, we have shown that 4 converted to
1 through the second C-F bond activation process only in
(23) Jiao, G.; Li, X.; Sun, H.; Xu, X. J. Organomet. Chem. 2007, 692,
4251–4258.
(24) Suzuki, H.; Abe, Y.; Ishiguro, S. Acta Crystallogr. 2001, C57,
721–722.
Complex 8 attains a trigonal-bipyramidal molecular geome-
try (Figure 3). Two trimethylphosphine ligands are located in
axial positions with an angle of P1-Co1-P3 = 167.84(7)°. In

Article
Organometallics, Vol. 28, No. 19, 2009 5775
Scheme 3. Formation Mechanism of Compound 7 and Complex 8
the presence of trimethylphosphine. Under 1 bar of CO at
20 °C complex 4 transforms to [Co(4-CF3-C6F4)(CO)2-
(PMe3)2] (6). Complex 4 reacts with bromobenzene via
one-electron oxidative addition of the C-Br bond at a
cobalt(I) center to produce the cobalt(II) bromide complex
[CoBr(4-CF3-C6F4)(PMe3)3] (8) and the C-C-coupling
product 4-phenylheptafluorotoluene (7). The structures of
complexes 1, 4, and 8 have been determined by X-ray
crystallography.
(Nujol, cm-1): complex 1, 1555 s, ν(CdC), 941 vs, ν (PMe3);
complex 4, 1558 s, ν(CdC); 938 vs, ν (PMe3).
Transformation of Complex 4 to 1. A solution of 4 (0.36 g, 0.71
mmol) in 30 mL of pentane at -80 °C was combined with a
solution of PMe3 (0.20 g, 2.63 mmol) in 10 mL of pentane. This
reaction mixture was allowed to warm to 20 °C and stirred for 18
h, and the green solution slowly turned red-brown. Crystal-
lization from pentane at -30 °C yielded 1 (0.23 g, 67%).
Synthesis of Complex 6. A solution of 4 (0.50 g, 0.99 mmol) in
50 mL of pentane was stirred under 1 bar of CO for 36 h, and the
green solution slowly turned yellow. Upon filtration and cooling
to 4 °C, complex 6 was obtained as yellow cubic crystals (0.33 g,
yield 70%). Analysis for 6, C15H18CoF7O2P2 [found (calcd)]: C,
37.61 (37.21); H, 3.38 (3.47). IR (Nujol): 1920 vs, ν(CO), 1895 vs,
ν(CO), 936 vs, ν(PMe3). 1H NMR (300.1 MHz, C6D6, 300 K): δ
1.30 (br, 18H, PCH3). 31P NMR (121.5 MHz, C6D6, 300 K): δ
30.4 (s).
Experimental Section
General Procedures and Materials. Standard vacuum techni-
ques were used in manipulations of volatile and air-sensitive
materials. Literature methods were used in the preparation
of tetrakis(trimethylphosphine)cobalt(0).25 Octafluorotoluene
was obtained from ABCR. All other chemicals were used as
purchased. Infrared spectra (4000-400 cm-1), as obtained from
Nujol mulls between KBr disks, were recorded on a Nicolet
5700. 1H, 13C, and 31P NMR (300, 75, and 121 MHz, re-
spectively) spectra were recorded on a Bruker Avance 300
spectrometer. 13C and 31P NMR resonances were obtained with
broadband proton decoupling. Elemental analyses were carried
out on an Elementar Vario EL III. Melting points were mea-
sured in capillaries sealed under argon and are uncorrected.
X-ray crystallography was performed with a Bruker Smart 1000
diffractometer.
Synthesis of Complex 1 and Complex 4. Method a: A solution
of octafluorotoluene (2.28 g, 8.26 mmol) in 10 mL of diethyl
ether was combined with a solution of Co(PMe3)4 (3.00 g, 8.26
mmol) in diethyl ether (30 mL) at -80 °C. This mixture was
allowed to warm to 20 °C and stirred for 24 h to form a red-
brown, turbid mixture. The volatiles were transferred under
vacuum, and the residue was extracted with pentane (20 mL)
and diethyl ether (40 mL), respectively. Crystallization from
pentane at -30 °C afforded red-brown single crystals of 1 (0.74
g, 37%) and green single crystals of 4 (0.37 g, 18%) suitable for
X-ray analysis. Method b: The reaction was carried out in
pentane instead of in diethyl ether. Yield: 1 (0.21 g, 11%); 4
(1.20 g, 57%). Method c: The reaction was carried out in
pentane as in method b, but the reaction time increased from
24 to 48 h at the same reaction conditions. Yield: 1 (0.89 g, 44%);
4 (0.12 g, 6%). Analysis for 1, C16H27CoF6P3 [found (calcd)]:
C, 39.20 (39.61); H, 5.98 (5.61). Analysis for 4, C16H27-
CoF7P3 [found (calcd)]: C, 37.87 (38.11); H, 5.48 (5.40). IR
Synthesis of Complex 8 and Compound 7. To the solution of 4
(0,50 g, 1.00 mmol) in 30 mL of pentane was added bromoben-
zene (0.46 g, 3.00 mmol) with stirring at -80 °C. This reaction
mixture was allowed to warm to 20 °C and stirred for 48 h. The
color changed from green to yellow-brown. The reaction mix-
ture was filtered. The solid residue was extracted with 20 mL of
diethyl ether. Complex 8 as yellow-brown crystals was obtained
from pentane/diethyl ether at -30 °C. Yield: 0.14 g (48%).
Analysis for 8, C16H27CoBrF7P3 [found (calcd)]: C, 32.71
(32.90); H, 4.38 (4.66). IR (Nujol): 1556 s, ν(CdC); 941 vs, ν
(PMe3). Compound 7 as white crystals was obtained from
pentane at -30 °C. Yield: 0.08 g (55%).
Crystallographic data of complex 1: C16H27CoF6P3, 485.22
˚
g/mol, 0.30 ꢀ 0.25 ꢀ 0.10 mm, monoclinic, P21/n, a = 9.4302(7) A;
˚
˚
b = 18.4173(17) A; c = 12.9476(12) A, R = 90°; β = 92.450(10)°;
γ = 90°, V = 2246.7(3) A , Z = 4, Dcalcd = 1.435 g-3, μ(Mo
3
˚
KR) = 1.024 mm-1, temperature = 203(2) K, data coll. range 3.84
< 2θ < 49.72°, -10 e h e 10; -21 e k e 21; -13 e l e 15, no.
reflns measured = 11 169, no. unique data = 3610 (Rint = 0.1087),
parameters 271, GoF on F2 = 1.042, R1 (I g 2σ(I)) = 0.0852,
wR2 = 0.1585.
Crystallographic data of complex 4: C16H27CoF7P3, 504.22
g/mol, 0.15 ꢀ 0.12 ꢀ 0.10 mm, orthorhombic, P212121, a =
˚
˚
˚
11.887(3) A; b = 13.135(4) A; c = 15.418(4) A, V = 2407.5
˚
(11) A , Z = 4, Dcalcd = 1.391 g-3, μ(Mo KR) = 0.964 mm-1
,
3
temperature = 273(2) K, data coll. range 4.08 < 2θ < 50.10°,
-14 e h e 12; -15 e k e 15; -18 e l e 18, no. reflns measured =
27 645, no. unique data = 4248 (Rint = 0.0403), parameters 272,
GoF on F2 = 1.027, R1 (I g 2σ(I)) = 0.0327, wR2 = 0.0810.
Crystallographic data of complex 8: C16H27BrCoF7P3, 584.13
g/mol, 0.33ꢀ0.31ꢀ0.05 mm, monoclinic, C2/c, a=15.0898(14)
(25) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1975, 108, 944.

5776 Organometallics, Vol. 28, No. 19, 2009
Zheng et al.
˚
˚
˚
A; b=9.2174(8) A; c=33.644(4) A, R=90°; β=91.620(12)°; γ=
Road, Cambridge CB2 1EZ, UK (fax:(þ44)1223-336-033;
90°, V=4677.6(8) A , Z=8, Dcalcd=1.659 g-3, μ(Mo KR)=
e-mail: deposit@ccdc.cam.ac.uk).
3
˚
2.703 mm-1, temperature=193(2) K, data coll. range 2.42 < 2θ
< 25.00°, -17 e h e 17; -10 e k e 10; -39 e l e 39, no. reflns
measured=14 255, no. unique data=3925 (Rint=0.0618), para-
meters 289, GoF on F2=1.095, R1 (I g 2σ(I))=0.0485, wR2=
0.1224.
Acknowledgment. We gratefully acknowledge sup-
port by NSF China No. 20772072. U.R. acknowledges
the Deutsche Forschungsgemeinschaft for generous
support.
Crystallographic data for compounds 1, 4, and 8 have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publications CCDC-718813 (1), CCDC-718814
(4), and CCDC-699824 (8). Copies of the data can be can be
obtained free of charge on application to CCDC, 12 Union
Supporting Information Available: Crystallographic data for
1, 4, and 8. This material is available free of charge via the
Internet at http://pubs.acs.org.