Activation of sp3 carbon-hydrogen bonds by cobalt and iron complexes and subsequent C-C bond formation

Article abstract of DOI:10.1021/om9007218

The sp³ C-H bond activation induced by CoMe(PMe ₃)₄ and FeMe₂(PMe₃) was investigated. C(sp³)cyclometalated complexes, based on diphosphinito PCP ligand (Ph₂POCH₂)

Full text of DOI:10.1021/om9007218

6090 Organometallics 2009, 28, 6090–6095
DOI: 10.1021/om9007218
Activation of sp3 Carbon-Hydrogen Bonds by Cobalt and Iron
Complexes and Subsequent C-C Bond Formation
Guoqiang Xu, Hongjian Sun, and Xiaoyan Li*
School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan,
People’s Republic of China
Received August 17, 2009
The sp3 C-H bond activation induced by CoMe(PMe3)4 and FeMe2(PMe3)4 was investigated. C(sp3)-
cyclometalated complexes, based on diphosphinito PCP ligand (Ph2POCH2)2CH2, Co{(Ph2PO-
CH2)2CH}(PMe3)2 (1), and Fe{(Ph2POCH2)2MeC}(H)(PMe3)2 (2), were obtained under mild condi-
tions. Iodomethane is oxidatively added to 1, affording Co{(Ph2POCH2)2CH}(PMe3)(Me)(I) (3).
Monocarbonylation of the hydrido-iron complex 2 occurs with substitution of a trimethylphosphine
ligand trans to the hydrido ligand, affording Fe{(Ph2POCH2)2MeC}(H)(CO)(PMe3) (4). The reaction of
2 with phenylacetylene delivered the demetalated new diphosphine ligand (Ph2POCH2)2CHCH3 (6) and
bis(phenylethinyl)iron complex Fe(PhCC)2(PMe3)4 (5). The new complexes 1-4 were characterized by
spectroscopic methods and by X-ray diffraction analysis.
Introduction
cleave the sp3 C-H bonds of their own ancillary ligands,3
and some promising catalytic systems for the selective func-
tionalization of sp3 C-H bonds have been developed in the
past few years.4
The direct functionalization of hydrocarbons to various
useful chemicals via transition-metal-mediated C-H bond
activation has now become a major topic of research.1 Until
recently, the majority of the catalytic processes reported were
applicable to only sp2 C-H bonds. There is still no series of
general, selective, efficient catalytic functionalization reac-
tions of unactivated sp3 C-H bonds owing to the strength of
sp3 C-H bonds and the weakly coordinating nature of
aliphatic moieties.2 The transition-metal-mediated activa-
tion of unreactive C-H bonds proceeds by several mechan-
isms, which include σ-bond metathesis, substitution by
electrophilic metal complexes, and oxidative addition to
low-valent metal centers, while most of the understanding
of alkane activation has been obtained from studies of
oxidative addition reactions. The precoordination of a sub-
strate can facilitate the interaction between C-H bonds and
metal centers and results in an easier and highly selective
C-H bond cleavage. So, some transition metal species can
Transition metal complexes with PCP pincer ligands in-
corporating two phosphane arms and a central carbon atom
as donor have attracted a substantial amount of interest.5
The strong chelating nature of PCP pincer ligands makes
them bond to a wide variety of transition metals and prevents
the dissociation and ligand exchange process. However,
research activity in this field has also mainly focused on
sp2-carbon- rather than sp3-carbon-based compounds.
Compared to the systems with a rigid phenyl ring back-
bone, ligands with an aliphatic backbone exhibit high flex-
ibility as well as the higher electron-donating ability of the
sp3-metalated carbon atom in the corresponding metal com-
plexes, which increase their reactivity.6 A number of com-
plexes with aliphatic backbones were recently described in
nickel,7 platinum,8 iridium,9 ruthenium,10 and rhodium11
chemistry.
*Corresponding author. E-mail: xli63@sdu.edu.cn.
(5) (a) Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40,
3750. (b) van der Boom, M. E.; Milstein, D. Chem. Rev 2003, 103, 1759. (c)
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A. L. Organometallics 2006, 25, 602. (b) Pandarus, V.; Zargarian, D.
Organometallics 2007, 26, 4321. (c) Castonguay, A.; Beauchamp, A. L.;
Zargarian, D. Organometallics 2008, 27, 5723.
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Crabtree, R. H. J. Organomet. Chem. 2004, 689, 4083. (c) Goldman, A. S.;
Goldberg, K. I. Activation and Functionalization of C-H Bonds; American
Chemical Society: Washington, DC, ACS Symposium Series 885; 2004; pp
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Foley, N. A.; Lail, M.; Lee, J. P.; Gunnoe, T. B.; Cundari, T. R.; Petersen, J. L.
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Chem., Int. Ed. 2006, 45, 1683.
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2732. (b) Klein, H.-F.; Beck, R.; Florke, U.; Haupt, H.-J. Eur. J. Inorg.
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Crocker, C.; Empsall, H. D.; Errington, R. J.; Hyde, E. M.; McDonald, W. S.;
Markham, R.; Norton, M. C.; Shaw, B. L.; Weeks, B. J. Chem. Soc., Dalton
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D. G. J. Am. Chem. Soc. 2006, 128, 14388. (b) Weng, W.; Parkin, S.;
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Chem. 2003, 853. (c) Ohki, Y.; Hatanaka, T.; Tatsumi, K. J. Am. Chem. Soc.
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pubs.acs.org/Organometallics
Published on Web 09/09/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 20, 2009 6091
Scheme 1. Proposed Formation Mechanism of 1
Compared to the other platinum group metals (Ru, Os,
Rh, Ir, Pd, Pt, Ni), iron- and cobalt-based catalysts are
relatively underrepresented in the field of catalysis, although
they have potentially lower cost and environmental impact.
Our group has been investigating the use of first-row metals
in the transformation of strong bonds.12 The precoordina-
tion strategy in sp3 C-H bond activation proves productive
and results in the isolation and characterization of novel
cobalt and iron complexes. We herein report our initial
studies on the stoichiometric activation and functionaliza-
tion of sp3 C-H bonds under mild conditions by iron- and
cobalt-based systems.
Figure 1. Molecular structure of 1 and selected bond distances
˚
(A) and angles (deg): Co1-C1 2.081(4), Co1-P4 2.1693(13),
Co1-P5 2.2170(13); C1-Co1-P4 172.88(14), P2-Co1-P3
124.35(5), P2-Co1-P4 97.43(5), P2-Co1-P5 115.01(5),
P3-Co1-P5 114.59(5), C2-C1-C15 111.8(4).
from solution data. Two five-membered cobaltocycles with
considerable ring bending (sum of internal angles = 526.84°
and 523.85°) are formed through two P atoms of the PPh2
groups and a metalated sp3-C atom. The cobalt atom is
centered in a trigonal bipyramid. The Co1-C1 distance
Results and Discussion
3
˚
(2.081(4) A) is within the range of Co-C (sp ) bonds
1. Reaction of Co(Me)(PMe3)4 with (Ph2POCH2)2CH2.
When a solution of (Ph2POCH2)2CH2 was treated with
Co(Me)(PMe3)4 in diethyl ether, compound 1 was isolated
as a red solid in over 75% yield upon workup, which could be
crystallized from diethyl ether at 0 °C (eq 1).
3b
˚
˚
(2.03-2.15 A), and the Co1-P4 distance (2.1693(13) A)
˚
is substantially shorter than Co1-P5 (2.2170(13) A), which
is due to the electron-donating ability of the trans-C (sp3)
atom.
2. Reaction of Fe(Me)2(PMe3)4 with (Ph2POCH2)2CH2.
Treating a diethyl ether solution of (Ph2POCH2)2CH2 with
Fe(CH3)2(PMe3)4 gave rise to hydrido-iron(II) complex 2 (eq
2). Crystallization at 0 °C afforded a yellow crystalline solid
in over 50% isolated yield. Complex 2 both in the solid state
and in solution is stable at room temperature for 1 h at least.
The reaction likely begins with the coordination of the cobalt
to the phosphorus atom in ligand (Ph2POCH2)2CH2 by sub-
stituting two of the trimethylphosphines, which brings the
metal closer to the central sp3 C-H bond. This precoordination
facilitates the interaction between C-H bonds and the metal
center and results in an easier and highly selective C-H bond
cleavage (Scheme 1). The methylmetal function here can utilize
the new hydrido ligand, and reductive elimination of methane
renders the reaction irreversible and affords a Co(Ι) complex 1
with two five-membered cobaltocycles in high yield.
Similar to the formation of cobalt complex 1, the reaction
may also start with the precoordination of the iron adduct,
but the following double C-H activation process and C,C-
coupling between two sp3 carbons exhibit an unusual reac-
tion pathway (Scheme 2). The substitution of two trimethyl-
phosphines and elimination of methane afford A, then the C,
C-coupling between the methyl group and the central carbon
atom of (Ph2POCH2)2CH2 and the subsequent reductive
elimination of iron species produce a new ligand backbone
with a 3° sp3 C-H bond, and then a C-H activation process
once again in the new ligand backbone gives 2 as the final
product. Klein and co-workers have reported similar results
for the imine systems recently.13
The existence of the Co-C (sp3) bond in 1 is initially
indicated by NMR spectroscopic analysis. In the 1H NMR
spectrum the intensity ratio of the CH group (br, δ = 2.43
ppm) and the CH2 group (δ = 3.50 and 3.73 ppm) is 1:4,
which indicates that there is only one H left at the central
carbon atom, while one C-H bond has been cleaved. 1 is
stable in air for several hours. X-ray crystallography con-
firmed the molecular configuration of 1 (Figure 1) derived
€
(12) (a) Chen, Y.; Sun, H.; Florke, U.; Li, X. Organometallics 2008,
27, 270. (b) Cao, R.; Sun, H.; Li, X. Organometallics 2008, 27, 1944. (c) Shi,
Y.; Li, M.; Hu, Q.; Li, X.; Sun, H. Organometallics 2009, 28, 2206.
€
(13) Camadanli, S.; Beck, R.; Florke, U.; Klein, H.-F. Organometal-
lics 2009, 28, 2300.

6092 Organometallics, Vol. 28, No. 20, 2009
Xu et al.
Scheme 2. Proposed Formation Mechanism of 2
Figure 2. Molecular structure of 2 and selected bond distances
˚
(A) and angles (deg): C26-Fe1 2.189(2), Fe1-P3 2.2301(7),
For less sterically hindered C-H bonds and bonds with
more s character, the activation is both kinetically and
thermodynamically preferred. So, the 3° sp3 C-H bond is
the most difficult to cleave. In Klein’s earlier research, when
the monosubstituted triphenylphosphane substituents are
changed from 2-methyl to 2-ethyl or 2-isopropyl, for steric
strain reasons, the C-H activation can only happen to the
ortho-sp2 C-H bonds.3b Limited examples of transition-
metal-mediated 3° sp3 C-H bond activation have been
reported.14 However, in this whole process, A and B, with
a new ligand backbone, have not been isolated. There should
exist some interactions between the eliminated iron(0) frag-
ment and the newly formed 3° sp3-carbon; the second C-H
activation could not be a pure 3° sp3 C-H bond cleavage.
In contrast to the C-H activation, the alkane functiona-
lization, which involves replacement of a C-H hydrogen by
an organic functional group, has proved more difficult than
the activation step, since alkyl hydride complexes tend to
release alkane on attempted functionalization. Because for-
mation of carbon-carbon bonds is the foundation of or-
ganic chemical synthesis, the activation of C-H bonds and
the formation of C-C bonds in a single preparative step
combine economy, efficiency, and elegance.
Fe1-P5 2.2560(8); C26-Fe1-P3 170.02(7), P2-Fe1-P4
140.06(3), C26-Fe1-P5 93.34(7), C27-C26-C25 106.2(2),
C27-C26-C34 108.3(2), C25-C26-C34 106.7(2), C34-C26-
Fe1 119.71(18).
of 2 is confirmed by X-ray structure analysis (Figure 2). The
iron atom is centered in a slightly distorted octahedral
˚
geometry. The Fe1-C26 distance (2.185(2) A) is within the
range of Fe-C (sp3) bonds.3c The most striking feature in the
molecular structure of 2 is the methyl substituent attached to
the metalated sp3-carbon (C26).
3. Reaction of 1 with Iodomethane. Motivated by our
results of iron, we investigated the reaction of iodomethane
with 1. 1 reacted with excess iodomethane in diethyl ether by
dissociation and quaternization of a trimethylphosphine (eq
3), undergoing an oxidative substitution reaction. Crystals of
3 were obtained from diethyl ether. An X-ray diffraction
study of complex 3 revealed that the cobalt atom attains an
octahedral coordination, with PMe3 opposite CH3, and the I
atom opposite the metalated sp3-carbon (Figure 3). The
˚
Co-C9 distance is 2.019(5) A, which is slightly shorter than
the Co-C (sp3) bond length in complex 1, reflecting the
weaker trans-influence of the iodo ligand.
van Koten has also reported that, upon treatment of a Pt-
NCN pincer complex with methyl iodide or higher alkyl
halide reactants, a sp2-sp3 C-C coupling was induced
between the ipso-C-donor atom of the ligand and the methyl
or alkyl group, and the intermediate platinum-stabilized
arenium complex [Pt(1-Me-NCN)](X0) was isolated and
characterized,15 while Milstein and co-workers have focused
on C-C bond cleavage, which can be seen as the reverse
process of C-C bond formation, by using alkylated pincer
ligands.16
The IR spectrum gives evidence for hydrido-iron(II) 2,
with a typical ν(Fe-H) stretching band at 1919 cm-1. The
resonance of the hydrido hydrogen in the NMR spectrum is
registered as a broad signal at -16.4 ppm. 2 shows CH3 at
28.04 ppm and Fe-C (sp3) at 64.48 ppm. This configuration
4. Study on Iron Hydride Complex 2. The insertion of
small molecules such as CO, CO2, olefins, and alkynes into
the metal-hydride bond of mononuclear transition metal
complexes represents a fundamental reaction in organome-
tallic chemistry, which is also of great relevance for homo-
geneous catalysis, and the transition metal hydrides play a
central role. Indeed, virtually all the major industrial pro-
cesses in the petrochemical industry rely on the involvement
of an M-H moiety in one or more key steps.17 The chemistry
of iron(II) classical and nonclassical hydride complexes has
(14) Espino, C. G.; Bois, J. D. Angew. Chem., Int. Ed. 2001, 40, 3 598.
(15) Albrecht, M.; Spek, A. L.; van Koten, G. J. Am. Chem. Soc.
2001, 123, 7233.
(16) Cohen, R.; van der Boom, M. E.; W. Shimon, L. J.; Rozenberg,
H.; Milstein, D. J. Am. Chem. Soc. 2000, 122, 7723.
(17) McGrady, G. S.; Guilera, G. Chem. Soc. Rev. 2003, 32, 383.

Article
Organometallics, Vol. 28, No. 20, 2009 6093
Figure 3. Molecular structure of 3 and selected bond distances
˚
(A) and angles (deg): C9-Co 2.019(5), C32-Co 2.070(6),
Figure 4. Molecular structure of 4 and selected bond distances
˚
Co-P5 2.3040(16), I1-Co 2.6678(7); C9-Co-I1 178.6(2),
C32-Co-P5 175.3(2), P4-Co-P3 162.72(6), C27-C9-C8
110.9(6).
(A) and angles (deg): C29-Fe1 2.157(3), Fe1-P4 2.2231(10),
C32-Fe1 1.749(4), O3-C32 1.167(4); C29-Fe1-P4 174.2(1),
P3-Fe1-P2 144.0(1), C30-C29-C31 107.8(4), C28-C29-
C31 105.2(4), O3-C32-Fe1 178.1(4), C32-Fe1-C29 93.4(2),
C32-Fe1-P4 92.4(2).
considerably developed in the last 30 years, highlighting the
syntheses of a number of complexes with interesting proper-
ties.18 Our initial focus was on reactions involving insertion
of unsaturated organic molecules into an iron hydride or iron
alkyl.
Scheme 3. Proposed Formation Mechanism of 5
4.1. Reaction of Complex 2 with Carbon Monoxide. For
the catalytic C-H bond carbonylation by the RhCl(CO)-
(PMe3)2 system, the rhodium hydride complexes Rh(C6H5)-
(H)Cl(PMe3)2 and Rh(C6H5)(H)Cl(CO)(PMe3)2 were postu-
lated as catalytic intermediates.19
The carbonyl hydride complex 4 is readily formed by
placing a diethyl ether solution of 2 under an atmosphere
of CO at 20 °C (eq 4). Yellow-orange crystals of 4 were
obtained from pentane.
caused by strong back-bonding and the trans-influence of
CO ligand.
The Fe-H bond remains unaffected in this transforma-
tion. Carbon monoxide substitutes one of the trimethylpho-
sphines, selectively occupying the trans-position to the
hydrido ligand. In the infrared spectra a strong (CtO)
absorption is registered at 1907 cm-1 and clearly indicates
a terminal carbon monoxide ligand. The Fe-H band is
found at 1861 cm-1. In 1H NMR spectrum, the proton
resonance of the Fe-H is recorded at -10.01 ppm as a
doublet of triplets due to the coupling of the hydrido nucleus
with trans- and cis-diposed phosphorus atoms. In compar-
ison with 2, the downfield shifting of Fe-H resonance is
The expected configuration is confirmed by X-ray diffrac-
tion analysis (Figure 4). The iron atom is coordinated with
two five-membered metallacycles, one trimethylphosphine,
one carbonyl ligand, and one hydride ligand in a distorted
octahedral geometry.
4.2. Reaction of Complex 2 with Phenylacetylene. We first
investigated the reaction of 2 with phenylacetylene, but this
attempt resulted in total dissociation of the diphosphinito
PCP ligand to afford the bis(phenylethynyl) iron(II) 5 in over
39% yield (eq 5). 5 was identified by IR and NMR spectros-
copy. In the IR spectrum, the typical Fe-H absorption at
1919 cm-1 of the hydrido iron complex 2 is absent, and the
(18) (a) Albertin, G.; Antoniutti, S.; Bortoluzzi, M. Inorg. Chem.
2004, 43, 1328. (b) Sadique, A. R.; Gregory, E. A.; Brennessel, W. W.;
Holland, P. L. J. Am. Chem. Soc. 2007, 129, 8112. (c) Casey, C. P.; Guan, H.
J. Am. Chem. Soc. 2007, 129, 5816. (d) Field, L. D.; Messerle, B. A.;
Smernik, R. J. Inorg. Chem. 1997, 36, 5984.
1
CtC band is found at 2037 and 1986 cm-1. The H NMR
spectrum in C6D6 reveals only PMe3 and aromatic protons
at 1.4 and 7.0-7.5 ppm, respectively, indicating that the
(19) Choi, J.; Sakakura, T. J. Am. Chem. Soc. 2003, 125, 7762.

6094 Organometallics, Vol. 28, No. 20, 2009
Table 1. Crystallographic Data for Complexes 1, 2, 3, and 4
Xu et al.
1
2
3
4
empirical formula
fw
cryst syst
C
33H43CoO2P4
C34H46FeO2P4
666.44
C31H37CoIO2P3
720.35
trigonal
R3c
20.7214(10)
20.7214(10)
39.396(4)
90
90
120
14649.4(18)
18
1.470
30 111
9906
0.0265
30.46
0.0443
0.1464
C32H37FeO3P3
618.38
triclinic
P1
9.4228(8)
13.1829(11)
13.6974(12)
81.630(2)
78.7680(10)
75.4550(10)
1607.0(2)
2
1.278
9884
8220
0.0195
28.56
0.0580
0.1692
654.48
orthorhombic
P2(1)2(1)2(1)
9.352(3)
17.919(6)
20.276(6)
90
monoclinic
P2(1)/n
9.8543(11)
17.5207(19)
20.085(2)
90
102.574(2)
90
3384.7(6)
4
1.308
21 089
9426
0.0405
29.49
0.0495
0.1701
space group
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
90
90
3
˚
V, A
Z
3397.7(18)
4
1.279
19 845
7885
0.0459
27.60
0.0496
0.1208
Dc, g cm-3
no. of rflns collected
no. of unique data
Rint
θ
max, deg
R1 (I > 2σ(I))
wR2 (all data)
dissociation of the PCP ligand did occur. In the 31P NMR
spectrum, this conjecture is proved through only one singlet
assigned to PMe3 at 20.9 ppm. All of these spectroscopic data
are consistent with the results we obtained from the reaction
of thiophenoliron hydrides with alkynes.20 The proposed
mechanism is depicted in Scheme 3. The demetalated new
diphosphine ligand, (Ph2POCH2)2CHCH3 (6), was con-
firmed with LC/MS. Compound 6 is no longer a pincer
ligand and has weak coordination ability.
crystallography was performed with a Bruker Smart 1000
diffractometer. LC/MS were carried out using an Agilent 6510
Accurate-Mass Q-TOF LC/MS system. Melting points were
measured in capillaries sealed under argon and were uncor-
rected. Elemental analyses were carried out on an Elementar
Vario EL III.
Synthesis of Co{(Ph2POCH2)2CH}(PMe3)2, 1. (Ph2POCH2)2-
CH2 (2.0 g, 4.5 mmol) in 30 mL of diethyl ether was combined with
Co(CH3)(PMe3)4 (1.55 g, 4.1 mmol) in 40 mL of diethyl ether with
stirring at 0 °C. The reaction mixture changed immediately from
orange-red to deep red and was kept stirring at room temperature
for 24 h. During this period, some red powder precipitated slowly
from the diethyl ether solution. After filtration, the solvents were
reduced to give a red solid, which crystallized from diethyl ether at
4 °C. Yield: 2.07 g, 77%; mp (dec) > 112 °C. Anal. Calcd for
C33H43CoO2P4 1(1, 654.48 g/mol): C, 60.56; H, 6.62. Found: C,
60.82; H, 6.28. H NMR (300 MHz, C6D6, 294 K, ppm): δ 0.87
(d, 2J(PH) = 6.9 Hz, 9H, PCH3), 1.02 (d, 2J(PH) = 4.8 Hz, 9H,
PCH3), 2.42 (br, 1H, CH), 3.47 (m, 2H, CH2), 3.72 (m, 2H, CH2),
6.92-8.10 (m, 20H, aromatic-H). 13C NMR (75.5 MHz, C6D6, 294
Conclusion
In conclusion, using a precoordination strategy, we have
achieved the activation of sp3 C-H bonds induced by
electron-rich cobalt and iron species in reaction with alipha-
tic PCP ligand (Ph2POCH2)2CH2. The reaction of Fe(Me)2-
(PMe3)4 with (Ph2POCH2)2CH2 afforded a noteworthy
hydrido iron(II) complex with a double sp3 C-H activation
process and a subsequent C,C-coupling between the sp3
carbon of the aliphatic backbone and the CH3 fragment.
The reaction of 1 with CH3I gave rise to iodomethylcobalt-
(III) complex 3. Carbonylation reaction of hydrido iron 2
afforded a monocarbonyl substituent derivative, where pos-
sible insertion reactions of CO into the Fe-C or Fe-H
bonds were not observed. The reaction of 2 with phenylace-
tylene delivered the demetalated new diphosphine ligand 6
and bis(phenylethinyl)iron complex 5.
3
K, ppm): δ 12.9 (s, PCH3), 20.5 (d, J(PC) = 16.6 Hz, PCH3),
22.3 (s, Co-C), 71.5 (d, 2J(PC) = 6.0 Hz, CH2), 125.7-147.2 (m,
aromatic-C). 31P NMR (121.5 MHz, C6D6, 294 K): δ -12.5
(t, J(PP) = 98.5 Hz, 1P, PCH3), 12.3 (s, 1P, PCH3), 155.9 (d,
2
2J(PP) = 83.0 Hz, 2P, PPh2).
Synthesis of Fe{(Ph2POCH2)2(CH3)C}(H)(PMe3)2, 2. (Ph2-
POCH2)2CH2 (2.0 g, 4.5 mmol) in 30 mL of diethyl ether was
combined with Fe(CH3)2(PMe3)4 (1.61 g, 4.1 mmol) in 30 mL of
diethyl ether with stirring at 0 °C. The mixture was kept stirring
at room temperature for 24 h; at this time the color changed
from brown to red, and some yellow-orange powder precipi-
tated from the solution. After filtration, the solid residue was
extracted with diethyl ether. Complex 2 suitable for X-ray
diffraction as yellow crystals was obtained from diethyl ether.
Yield: 1.46 g, 53%; mp (dec) > 131 °C. Anal. Calcd for
C34H46FeO2P4 (2, 666.44 g/mol): C, 61.28; H, 6.96. Found: C,
1
60.87; H, 7.08. IR (Nujol, cm-1): ν(Fe-H); 1919 s. H NMR
(300 MHz, C6D6, 294 K, ppm): δ -16.4 (br, 1H, Fe-H), 0.69 (br,
9H, PCH3), 0.88 (br, 9H, PCH3), 3.26-3.95 (br, 4H, CH2),
7.15-8.15 (m, 20H, aromatic-H). 13C NMR (75.5 MHz, C6D6,
294 K, ppm): δ 12.5 (s, PCH3), 22.8 (d, 3J(PC) = 15.1 Hz,
PCH3), 28.0 (s, CH3), 64.5 (s, Fe-C), 78.9 (s, CH2), 126.3-130.6
(m, aromatic-C). 31P NMR (121.5 MHz, C6D6, 294 K): δ 5.7 (s,
1P, PCH3), 16.2 (s, 1P, PCH3), 176.3 (d, 2J(PP) = 59.2 Hz, 2P,
PPh2).
Synthesis of Co{(Ph2POCH2)2CH}(PMe3)(CH3)(I) 3. 1 (610
mg, 0.93 mmol) was combined with CH3I (754 mg, 5.31 mmol)
in diethyl ether with stirring at 0 °C. The reaction mixture was
kept stirring at room temperature for 24 h. During this period, a
Experimental Section
General Procedures and Materials. Standard vacuum techni-
ques were used in manipulations of volatile and air-sensitive
materials. Solvents were dried by known procedures and dis-
tilled under nitrogen before use. Infrared spectra (4000-
400 cm-1), as obtained from Nujil mulls between KBr disks,
were recorded on a Nicoler 5700. NMR spectra were recorded
using a Bruker Avance 300 or 400 MHz spectrometer. X-ray
(20) Zhen, T.; Li, M.; Sun, H.; Harms. K.; Li, X. Polyhedron, accepted
2009.

Article
Organometallics, Vol. 28, No. 20, 2009 6095
white powder precipitated slowly from the diethyl ether solu-
tion. After filtration, the solid residue was extracted with diethyl
ether four times, and then the diethyl ether was combined
together to afford reddish-pink crystals of 3 at 4 °C. Yield:
460 mg, 69%; mp (dec) > 134 °C. Anal. Calcd for C31H37-
CoIO2P31(3, 720.35 g/mol): C, 51.69; H, 5.18. Found: C, 52.03;
H, 5.02. H NMR (400 MHz, C6D6, 298 K, ppm): δ 0.84 (d,
2J(PH) = 5.2 Hz, 9H, PCH3), 1.23 (m, 3H, Co-CH3), 2.37 (br,
1H, CH), 3.22-3.82 (m, 4H, CH2), 6.67-8.66 (m, 20H, aro-
matic-H). 13C NMR (100.6 MHz, C6D6, 300 K, ppm): δ 15.8 (d,
3J(PC) = 27.3 Hz, PCH3), 25.6 (s, Co-CH3), 29.9 (s, CH3), 67.6
(s, Co-C), 71.7 (s, CH2), 128.4-144.1 (m, aromatic-C). 31P
NMR (162.0 MHz, C6D6, 298 K): δ -20.6 (s, 1P, PCH3),
148.7 (s, 2P, PPh2).
(570 mg, 0.86 mmol) in 30 mL of diethyl ether at 0 °C. The
mixture was kept stirring at 20 °C for 16 h, effecting a change
of color from yellow to orange-red and precipitation of a yellow
powder. The mixture was then filtered. The yellow solid residue
was dissolved in 20 mL of THF and crystallized at 20 °C to
give yellow crystals of 5, Fe(PhCC)2(PMe3)4, which were sui-
table for X-ray diffraction.20 Yield: 188 mg, 39%. IR (Nujol,
cm-1): ν(CtC), 2037 and 1986 cm-1 1H NMR (400 MHz,
.
C6D6, 298 K, ppm): δ 1.44 (br, 36H, PCH3), 7.07-7.51 (m, 20H,
aromatic-H). 31P NMR (162.0 MHz, C6D6, 298 K): δ 20.9 (s,
PCH3). The demetalated new diphosphine ligand, (Ph2PO-
CH2)2CHCH3 (6), was found in the mother solution with
LC/MS.
X-ray Structure Determinations. Intensity data were collected
on a Bruker SMART diffractometer with graphite-monochro-
Synthesis of Fe{(Ph2POCH2)2(CH3)C}(H)(CO)(PMe3), 4. A
sample of 2 (450 mg, 0.67 mmol) in diethyl ether was stirred
under 1 bar of CO at 20 °C. After 12 h, all volatiles were removed
in vacuo, and the residue was extracted with pentane, which
gave yellow-pink crystals of 4 at -18 °C. Yield: 270 mg, 65%;
mp (dec) > 140 °C. Anal. Calcd for C32H37FeO3P3 (4, 618.38
g/mol): C, 62.15; H, 6.03. Found: C, 62.40; H, 6.21. IR (Nujol,
cm-1): ν(CtO), 1907 s; ν(Fe-H), 1861 s. 1H NMR (400
˚
mated Mo KR radiation (λ, 0.71073 A). Crystallographic data
for complexes 1, 2, 3, and 4 are summarized in Table 1. The
structures were solved by direct methods and refined with full-
matrix least-squares on all F2 (SHELXL-97) with non-hydrogen
atoms anisotropic. CCDC-735322 (1), CCDC-735323 (2),
CCDC-735320 (3), and CCDC-735321 (4) contain the supple-
mentary crystallographic data for this paper. Copies of the data
can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax:(þ44)1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk).
2
MHz, C6D6, 298 K, ppm): δ -10.0 (td, J(PPPhH, 75.7° and
72.8°) = 56.9 Hz, 2J(PPMeH, 88.5°) = 33.1 Hz, 1H, Fe-H), 0.70
(d, 2J(PH) = 7.7 Hz, 9H, PCH3), 1.00 (t, 4J(PH) = 7.2 Hz, 3H,
CH3), 3.55 (m, 2H, CH2), 3.95 (m, 2H, CH2), 7.05-8.41 (m,
20H, aromatic-H). 13C NMR (100.6 MHz, C6D6, 300 K, ppm):
δ 22.0 (d, 3J(PC) = 24.2 Hz, PCH3), 30.9 (s, CH3), 58.1(d,
Acknowledgment. We gratefully acknowledge the sup-
port by NSF China No. 20872080/20772072.
2
2J(PC) = 12.5 Hz, Fe-C), 79.8 (t, J(PC) = 10.4 Hz, CH2),
127.3-146.0 (m, aromatic-C). 31P NMR (162.0 MHz, C6D6, 298
K): δ 20.3 (br, 1P, PCH3), 188.7 (d, 2J(PP) = 56.8 Hz, 2P, PPh2).
Reaction of 2 with Phenylacetylene. Phenylacetylene (552 mg,
5.42 mmol) in 10 mL of diethyl ether was added to a sample of 2
Supporting Information Available: Crystallographic data for
1, 2, 3, and 4. This material is available free of charge via the
Internet at http://pubs.acs.org.