Diphenyl-2-pyridylphosphine as a bidentate ligand in the coordination of dicobalt octacarbonyl; X-ray crystal structures of Co2(CO)4(μ-P,N-PPh2py){μ-HCCSiMe 3}, and Co4(CO)10(μ-P,N-PPh2py)

Article abstract of DOI:10.1016/S0022-328X(99)00368-X

Under mild conditions, the reaction of Co₂(CO)₈ with HCCSiMe₃ in the presence of PPh₂py gave a binuclear cobalt carbonyl complex, Co₂(CO)₄(η²-μ₂-HCCSiMe ₃)(μ-PPh₂py) (1a), which has both zero-valent cobalt centers coordinated by a bidentate ligand, PPh₂py. PPh₂py is also an effective ligand in promoting the yield of 2,5-bis(trimethylsilanyl)cyclopenta-2,4-dien-1-one. A cobalt cluster complex, Co₄(CO)₁₀(μ-P,N-PPh₂py) (9) was obtained when two equivalents of Co₂(CO)₈ were reacted with PPh₂py at a higher temperature. The phosphorus and nitrogen atoms of the ligand coordinate to cobalt in the basal and apical positions, respectively. These two compounds, 1a and 9 were characterized by spectroscopic means as well as X-ray crystal structure determination.

Full text of DOI:10.1016/S0022-328X(99)00368-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 588 (1999) 160–166
Diphenyl-2-pyridylphosphine as a bidentate ligand in the
coordination of dicobalt octacarbonyl; X-ray crystal structures of
Co2(CO)4(m-P,N-PPh2py){m-HCꢀCSiMe3}, and
Co4(CO)10(m-P,N-PPh2py)
Fung-E. Hong a,*, Yu-Chang Chang a, Ruei-E. Chang a, Chu-Chieh Lin a,
Sue-Lein Wang b, Fen-Ling Liao b
a Department of Chemistry, National Chung-Hsing Uni6ersity, Taichung 40227, Taiwan, ROC
b Department of Chemistry, National Tsing-Hua Uni6ersity, Hsinchu 30043, Taiwan, ROC
Received 19 December 1998; received in revised form 22 June 1999
Abstract
Under mild conditions, the reaction of Co2(CO)8 with HCꢀCSiMe3 in the presence of PPh2py gave a binuclear cobalt carbonyl
complex, Co2(CO)4(h2-m2-HCꢀCSiMe3)(m-PPh2py) (1a), which has both zero-valent cobalt centers coordinated by a bidentate
ligand, PPh2py. PPh2py is also an effective ligand in promoting the yield of 2,5-bis(trimethylsilanyl)cyclopenta-2,4-dien-1-one. A
cobalt cluster complex, Co4(CO)10(m-P,N-PPh2py) (9) was obtained when two equivalents of Co2(CO)8 were reacted with PPh2py
at a higher temperature. The phosphorus and nitrogen atoms of the ligand coordinate to cobalt in the basal and apical positions,
respectively. These two compounds, 1a and 9 were characterized by spectroscopic means as well as X-ray crystal structure
determination. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Bidentate-ligand; m-Alkyne-bridged; Bimetallic componds; Cobalt cluster
1. Introduction
ligand. A crystal structure of a diphenyl-2-pyridylphos-
phine-coordinated mixed-valence complex, Co0CoI(m-
PPh2py)2(m-CO)(CO)Cl, was reported [1f]. The
phosphorus atom and the nitrogen atom of the ligand
bridge to the Co(0) atom and the Co(I) atom, respec-
tively. This result is consistent with the prediction of
HSAB theory [4]. In this paper, we shall report the prepa-
rations and characterizations of the diphenyl-2-pyridyl-
phosphine-coordinated di- and tetra-cobalt systems.
These systems both have zero-valence cobalt atoms.
Trimethylamine N-oxide (TMNO) is a powerful decar-
bonyl reagent and has been extensively used in the syn-
thesis of various organometallic compounds [5]. Results
from similar reactions with the presence of TMNO and
different phosphines are reported here for comparison.
Pyridylphosphine has been used as a multi-dentate lig-
and to coordinate transition metals. The study of such
use has recently attracted much attention [1]. The labile
nitrogen–metal bond of the pyridyl-coordinated metal
center is a useful quality in various catalytic reactions in-
volving pyridylphosphine as a bi- or multi-dentate ligand
[2]. Many examples of pyridylphosphine-coordinated
bimetallic compounds are known [3]. Nevertheless, only
one structure among all the diphenyl-2-pyridylphos-
phine-coordinated bimetallic compounds has been re-
ported so far [1f]. One of the reasons for this is the
,
relatively rigid bond distance, approximately 2.7 A, be-
tween the nitrogen and phosphorus atoms (PSN) of
pyridylphosphine. Normally, the bond lengths between
two cobalt atoms in a dicobalt system are within the
,
range 2.4–2.5 A. This is an appropriate distance for the
coordination to take place with only a slight twist of the
2. Results and discussion
The reaction of Co2(CO)8 with trimethylsilylacetylene
in the presence of diphenyl-2-pyridylphosphine at 60°C
* Corresponding author. Fax: +886-4-2862547.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00368-X

F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
161
P
Table 1
Crystal data of 1a and 9
Formula
C26H24Co2NO4PSi
C27H14Co4NO10
Formula weight
Crystal system
Space group
591.38
Triclinic
779.1
Triclinic
(
(
P1
P1
,
a (A)
10.59960(10)
11.84370(10)
12.1732(2)
80.2510(10)
85.3840(10)
65.1030(10)
1366.09(3)
2
9.792(1)
10.513(1)
14.573(2)
83.65(1)
87.58(1)
81.45(1)
1473.9(3)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc. (Mg m−3
)
1.438
1.755
Scheme 1.
,
u (Mo–Ka) (A)
0.71073
1.347
0.71073
2.322
v (mm−1
)
Range (°)
Scan type
No. of reflections
collected
No. of independent
reflections
No. of observed
reflections
1.7–27.94
2q/q
13154
4.0–50.0
2q/q
5511
yielded two desired major compounds, Co2(CO)4(m-
P,N-PPh2py){m-HCꢀCSiMe3} (1a) and Co2(CO)5-
(PPh2py){m-HCꢀCSiMe3} (1b) (Scheme 1). The yields
of (1a) and (1b) are both about 15%. Both 1a and 1b
are characterized by spectroscopic means (Table 1); the
crystal structure of 1a was determined as well. Three
known compounds, Co2(CO)6{m-HCꢀCSiMe3} (2),
Co2(CO)2(m-CO)2(h4 -2,5-bis(trimethylsilyl)cyclopenta-
dienone)2 (3) and 2,5-bis(trimethylsilanyl)cyclopenta-
2,4-dien-1-one (4), were obtained along with 1a and 1b.
Our previous work has shown that the reaction of
Co2(CO)8 with trimethylsilylacetylene in the presence of
triphenylphosphine yielded two dinuclear cobalt car-
5834
(Rint=3.76%)
5179
(Rint=0.92%)
4451(F\4.0|(F))
No. of refined
parameters
316
388
Rf for significant
0.0625
0.1749
1.300
0.0283
0.0469
1.21
reflections a
Rw for significant
reflections b
Goodness-of-fit c
a Rf=[S(Fo−Fc)/SFo].
b Rw=S w1/2(Fo−Fc)/S w1/2Fo.
c GoF=[S w(Fo−Fc)2/(Nrflns−Nparams)]1/2
0.0010F2.
bonyls,
Co2(CO)3(PPh3){m-C(SiMe3)ꢁCHꢂCHꢁC(Si-
.
w
−1=|2(F)+
Me3)ꢂCHꢁC(SiMe3)} (5) and (3) (Scheme 2) [6]. Both
structures of 5 and 3 were determined by X-ray crystal-
lographic methods. A rather small quantity of 3 was
obtained until a 5:1 ratio of acetylene to Co2(CO)8 was
used [7]. It also showed that the oxidation of 3 in
solution produced 4 quantitatively. There are several
notable distinctions between the reactions shown in
Schemes 1 and 2. Compound 4 was obtained while 1.5
equivalent of trimethylsilylacetylene was used and in
the presence of PPh2py; on the contrary, no 4 was
found under similar reaction conditions in Scheme 2.
The distinct observations suggest that the bidentate
ligand, diphenyl-2-pyridylphosphine, indeed promotes
the formation of 3 which eventually converts to 4.
Another notable observation is the absence of 5 in
Scheme 1, which is in contrast to the reaction in
Scheme 2.
Several greenish–brown crystals of 1a were obtained
from the solvent diffusion method. Its structure was
determined by X-ray crystallographic methods. It
shows that two cobalt atoms are both coordinated by
the phosphorus atom and the nitrogen atom of the
PPh2py ligand, respectively (Fig. 1). It is rather unusual
for a nitrogen atom, which is classified as a hard base
according to the HSAB principle, to coordinate to a
low-valence and soft Lewis acid such as Co(0) atom.
The stability of this coordination might attribute to the
chelate effect of the bidentate ligand, diphenyl-2-
pyridylphosphine [8]. The bond length of Co(1)ꢂCo(2)
,
is 2.448 A. It is slightly shorter than most of the
dicobalt compounds with mono-dentate ligands [1a,g].
Trimethylamine N-oxide (TMNO) is a useful decar-
bonyl reagent. The reaction of 2 with PPh2py in the
presence of TMNO was pursued. By the assistance of
TMNO, the reaction was carried out at room tempera-
ture. Under that reaction condition, only 1a and 1b
were observed. The yield of 1a was up to 45%. It was a
more efficient way to obtain 1a.
(2)+PPh2py+2TMNO“(1a)+(1b)
(1)
Scheme 2.

162
F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
Fig. 2. Aerial view of 1a along the Co(1)ꢂCo(2) axis.
M(CO)2(L) fragment. It is also evidenced by the obser-
vation of four broad peaks in 13C-NMR for these COs.
The broad peaks are partly due to the coupling with
their attached cobalts (I=7/2). The fact that two
phenyl rings are in different chemical environments was
supported by two distinct sets of 13C-NMR signals of
1a. The bond angles of C(5)ꢀC(6)ꢂSi(1) and
C(6)ꢀC(5)ꢂH are 147.5 and 151.3°, respectively. The
fact that two substituents bend away from two metal
centers is consistent with the common observation for
this type of alkyne-bridged binuclear metal compounds
[9]. The 31P-NMR spectra of 1a and 1b are 56.1 and
53.9 ppm, respectively. There are large downfield chem-
ical shifts of phosphorus atoms from their free ligand
[10].
Fig. 1. ORTEP drawing with the numbering scheme of 1a.
The distance between the phosphorus atom and the
,
nitrogen atom is 2.675 A, which is longer than the bond
length of Co(1)ꢂCo(2) (Table 2). The four atoms, N,
Co(1), Co(2) and P, are not on the same plane. The
dihedral angle of NꢂCo(1)ꢂCo(2)ꢂP is 25.9°. The bond
,
lengths of Co(1)ꢂN and Co(2)ꢂP are 2.054 and 2.185 A,
respectively. The bond lengths of Co(2)ꢂP is slightly
shorter than most of the mono-dentate phosphine cases
[1a,g]. Four CO ligands are in different environments
because of the asymmetric nature of this binding geo-
metry and the inability of free rotation of the
Table 2
The fact that the bulky bidentate ligand and the
bulky SiMe3 group are on different sides of the dicobalt
center is clearly shown in Fig. 2. It is so arranged that
to prevent the steric hindrance. There is no structural
information for 1b. However, it is proposed that the
phosphorus atom, instead of the nitrogen atom, of the
PPh2Py ligand coordinates to the Co(0). In doing so,
the prediction of the HSAB principle might be fol-
lowed. A large downfield chemical shift of the phospho-
rus atom in 31P-NMR spectrum for 1b supports the
supposition. Another favorable evidence comes from
,
Selected bond lengths (A) and bond angles (°) for (1a)
,
Bond lengths (A)
Co(1)ꢂC(5)
Co(1)ꢂN(1)
Co(2)ꢂC(5)
Co(2)ꢂP(1)
P(1)ꢂC(7)
Si(1)ꢂC(6)
N(1)ꢂC(11)
1.945(7)
2.054(6)
1.972(7)
2.185(2)
1.838(7)
1.837(8)
1.354(9)
Co(1)ꢂC(6)
Co(1)ꢂCo(2)
Co(2)ꢂC(6)
P(1)ꢂC(18)
P(1)ꢂC(12)
N(1)ꢂC(7)
C(5)ꢂC(6)
2.005(7)
2.4489(13)
1.993(7)
1.833(7)
1.838(7)
1.337(9)
1.327(10)
Bond angles (°)
C(2)ꢂCo(1)ꢂC(1)
C(1)ꢂCo(1)ꢂC(5)
C(1)ꢂCo(1)ꢂC(6)
C(2)ꢂCo(1)ꢂN(1) 102.2(4)
C(5)ꢂCo(1)ꢂN(1) 95.4(3)
C(2)ꢂCo(1)ꢂCo(2) 152.8(3)
C(5)ꢂCo(1)ꢂCo(2) 51.8(2)
N(1)ꢂCo(1)ꢂCo(2) 97.3(2)
C(4)ꢂCo(2)ꢂP(1)
C(6)ꢂCo(2)ꢂP(1)
C(18)ꢂP(1)ꢂC(7)
C(6)ꢂSi(1)ꢂC(25) 108.5(4)
C(7)ꢂN(1)ꢂCo(1) 120.1(5)
C(6)ꢂC(5)ꢂCo(2)
C(5)ꢂC(6)ꢂSi(1)
C(8)ꢂC(7)ꢂP(1)
98.0(4)
140.8(3)
107.5(3)
C(2)ꢂCo(1)ꢂC(5)
C(2)ꢂCo(1)ꢂC(6)
C(5)ꢂCo(1)ꢂC(6)
C(1)ꢂCo(1)ꢂN(1) 108.3(3)
C(6)ꢂCo(1)ꢂN(1) 133.7(3)
C(1)ꢂCo(1)ꢂCo(2) 93.6(2)
C(6)ꢂCo(1)ꢂCo(2) 52.0(2)
C(3)ꢂCo(2)ꢂP(1)
C(5)ꢂCo(2)ꢂP(1)
P(1)ꢂCo(2)ꢂCo(1)
C(18)ꢂP(1)ꢂC(12) 104.1(3)
C(6)ꢂSi(1)ꢂC(26) 111.5(4)
107.2(3)
100.9(4)
39.2(3)
1
the comparison between the H-NMR spectra of 1a, 1b
and the free ligand. One distinct downfield chemical
shift peak, the proton next to nitrogen atom in
pyridine, was observed for both 1b and the free ligand.
On the contrary, it was absent in 1a. This is convincing
evidence which indicates the coordination of pyridyl to
metal in 1a, but not in 1b.
Structural data for several 1b-related compounds, 6a,
6b [11] and 7 [12], are available. The PPh3 ligands are
on the same side of the bridged alkyne for all three
cases. It is quite different from the binding pattern of
the bidentate ligand, PPh2Py, in 1a. The differences will
be attributed to the bidentate nature of the PPh2Py
101.7(3)
106.9(2)
84.55(6)
105.6(2)
135.4(2)
100.6(3)
C(6)ꢂC(5)ꢂCo(1)
Co(1)ꢂC(5)ꢂCo(2) 77.4(2)
N(1)ꢂC(7)ꢂP(1) 114.1(5)
72.8(4)
71.3(4)
147.6(6)
123.3(6)

F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
163
Fig. 3. Selected 1b-related compounds.
ligand. In the case of 1a, no free rotation of the
bidentate ligand is possible. However, in the cases of
The structure of 9 was determined by X-ray crystallo-
graphic methods. The P and N atoms of PPh2py are
coordinated to the basal and apical position of the
tetracobalt cluster, respectively (Fig. 4). The apical
cobalt atom is harder than that of the basal cobalt
atoms, probably due to the electron diffusing capacity
of the bridging COs [14]. The bond length of
monodentate-ligand-coordinated
bimetallic
com-
pounds, a free rotation of the pseudo-trident fragment
Co(CO)2(PPh3) is possible in solution. It is evidenced
by the observation of three equivalent phenyl rings
from the 13C-NMR spectra (Fig. 3).
1
Spectroscopic data, such as H-, 13C- and 31P-NMR
,
,
Co(1)ꢂCo(2) is 2.493 A; it is 2.686 A for the P, N
distance (Table 5). Four atoms, N, Co(1), Co(2) and P,
are not on the same plane; the dihedral angle of
NꢂCo(1)ꢂCo(2)ꢂP is 33.5°. The bond lengths of
spectra, for several selected bridged compounds are
listed in Table 3 for comparison. A distinguished
downfield shift for 1a in 1H-NMR spectrum implies
that the acetylenic proton bends away from the dicobalt
metal center with large angle. The largest downfield
shift in 31P-NMR spectrum for 1a also indicates that
the diphenyl-2-pyridylphosphine ligand donates more
electron density to the metal center than other
compounds.
Several selected reactions with different ratios of
Co2(CO)8/TMSA in the presence or absence of the
phosphine ligands were pursued. All these reactions
were carried out in the same reaction conditions. The
results are shown in Table 4 for comparison. As men-
tioned, 4 can be obtained quantitatively from the oxida-
tion of 3. Here below, the summation of the yields of 3
and 4 is used as an indicator for the efficiency of the
reaction. By that criterion, Entry 3 represents the best
reaction condition among the first three entries. To our
surprise, not only 4 but also 3 was observed in the
reaction (Entries 4 and 5) and the yields were fair. The
reason that 3 was absent arises from the steric hin-
drance of bidentate m-P,N-PPh2py and monodentate
PPh2py ligands. It seems reasonable to say that the
presence of the PPh2py ligand enhances the formation
of 3 and 4.
,
Co(1)ꢂN and Co(2)ꢂP are 2.053 and 2.183 A, respec-
tively. The corresponding bond lengths and angles of 1a
and 9 are very similar. This is attributed to the rigidity
of the bidentate ligand, m-P,N-PPh2py.
Three bridging COs in solid state are clearly seen
from another view of 9. IR spctroscopy also shows
bridging carbonyl stretching frequencies around 1800
cm−1. However, there is no bridging as well as terminal
CO signal observed in the 13C-NMR spectrum. This
suggests that all COs might be fluxional in solution at
room temperature (Fig. 5) [15].
3. Experimental
All operations were performed in a nitrogen-flushed
glove box or in a vacuum system. Freshly distilled
solvents were used. All processes of separation of the
products were performed by centrifugal thin-layer chro-
matography (TLC, Chromatotron, Harrison model
1
8924). H-, and 13C-NMR spectra were recorded by a
Varian VXR-400S spectrometer at 400.45 and 100.70
It has been known that tetracobalt compound,
Co4(CO)12, could be obtained from heating Co2(CO)8
in solution [13]. The reaction of Co2(CO)8 with
diphenyl-2-pyridylphosphine was carried out in toluene
at 80°C for 4 h. It yielded one major compound,
Co4(CO)10(m-P,N-PPh2py) (9) (Eq. (2)).
Table 3
Chemical shifts of selected alkyne-bridged compounds
Compound 1H-NMR
13C-NMR b 31P-NMR
a
Chemical shift l (ppm)
1a
1b
6a
6b
7
6.29 (d, JPH=5.2 Hz)
5.64 (d, JPH=6.2 Hz)
5.45 (d, JPH=3.8 Hz)
4.53 (t, JPH=3.0 Hz)
5.25 (d, JPH=10 Hz)
90.9, 93.1
73.9, 86.2
71.2, 86.0
70.8, 81.9
89.8, 95.0
56.1
53.9
51.6
50.4
54.7
(2)
a Acetyltic proton.
b HCꢀCSiMe3.

164
F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
Table 4
Reactions of Co2(CO)8 with TMSA in the presence/absence of phosphine ligand a
Entry
Reactant
Equation of TMSA
Ligand
Product (%)
3
4
3+4
8 b
1
2
3
4
5
Co2(CO)8
Co2(CO)8
Co2(CO)8
1a
10
10
10
9
–
15.9
45.3
64.0
–
5.0
1.9
21.7
31.6
35.7
20.9
47.2
85.7
31.6
35.7
–
51.1
–
PPh3
PPh2py
–
–
1b
9
–
a All these reactions were carried out in 20 ml THF at 60°C for 12 h.
b Co2(CO)5(PPh3)(m-HCꢀCSiMe3).
MHz, respectively, while some 13C- and 31P-NMR spec-
tra were recorded by a Varian VXR-300S spectrometer
at 75.46 and 121.42 MHz, respectively; chemical shifts
are reported in ppm relative to internal TMS. Mass
spectra were recorded on a Joel JMS-SX/SX 102A
GC/MS/MS spectrometer. Elemental analysis were
recorded on a Heraeus CHN-O-S-Rapid.
pyridine), 8.98(d, J=4, 1H, pyridine); 13C-
NMR(CDCl3): l 0.73(s, 3C, SiMe3), 90.90(s, 1C,
CꢂSiMe3), 93.12(s, 1C, CH), 124.19(s, 1C, pyridine),
128.44(d, J=8.4, 2C, arene), 128.52(s, J=6.9, 2C,
arene), 129.50(s, 1C, p-arene), 129.73(s, 1C, p-arene),
131.85(d, J=19.0, 2C, arene), 131.98(d, J=19.8, 2C,
arene), 134.70(s, 1C, pyridine), 136.51(d, J=77.0, 1C,
ipso of arene), 136.85(d, J=80.9, 1C, ipso of arene),
154.50(d, J=13.0, 1C, pyridine), 166.60(d, J=62.5,
1C, pyridine), 202.6(m, CO), 203.1(m, CO), 204.9(m,
CO), 206.6(m, CO); 31P-NMR(CDCl3): l 56.1; Elemen-
tal analysis: Anal. Calc. C, 52.80; H, 4.06; N, 2.37;
found C, 52.55; H, 4.27; N, 2.65; MS: m/z 563
[PꢂCO+]; IR (CH2Cl2): w(CO) 2054(m), 2055(sh),
1983(s), 1953(s).
3.1. Preparations of 1a and 1b
Into a 100 cm3 flask was placed dicobalt octacar-
bonyl, Co2(CO)8, (0.6 g, 1.75 mmol), trimethylsilyl-
acetylene (0.38 ml, 2.69 mmol) and diphenyl-2-
pyridylphosphine (0.462 g, 1.75 mmol) with 30 cm3 of
THF. The solution was stirred at 60°C for 7 h.
Subsequently, the resulting dark purple solution was
filtered through a small amount of silica gel. The filtrate
was evaporated under reduced pressure to yield the
crude product. Purification with centrifugal thin-layer
chromatography was carried out. The first three bands
were eluted with hexane. A trace amount of brown
band was characterized as the known compound,
Co2(CO)6{m-HCꢀCSiMe3} (2). The second band was
identified as the known compound, 2,5-bis(trimethylsi-
lanyl)cyclopenta-2,4-dien-1-one (4) with 10% yield. The
third band is greenish brown and was characterized as
Co2(CO)4(m-P,N-PPh2py){m-HCꢀCSiMe3} 1a. The yield
of 1a is 15% based on the amount of Co2(CO)8 being
used in the reaction. The fourth band was eluted with
mixture solvent (3:2 hexane–CH2Cl2). It was character-
ized as Co2(CO)5(PPh2Py)(m-HCꢀCSiMe3) (1b). The
yield of 1b is 15%. The last band was eluted with
CH2Cl2 and found Co2(CO)2(m-CO)2(h4-2,5-bistrime-
thylsilylcyclopentadienone)2 (3) with 15% yield.
3.2.2. Characterization of Co2(CO)5(PPh2Py)(v-HCꢀ
CSiMe3) (1b)
1H-NMR(CDCl3): l 0.01(s, 9H, SiMe3), 5.64(d, J=
6.4, 1H, CH), 7.26(1H, pyridine), 7.32(t, 1H, pyridine),
7.41(6H, arene), 7.54(t, 4H, arene), 7.62(t, 1H,
3.2. Characterization of 1a and 1b
3.2.1. Characterization of
Co2(CO)4(v-PPh2Py)(v-HCꢀCSiMe3) (1a)
1H-NMR(CDCl3): l 0.14(s, 9H, SiMe3), 6.29(d, J=
5.2, 1H, CH), 6.92(d, J=7.2, 1H, pyridine), 7.15(t, 1H,
pyridine), 7.26–7.41(m, 10H, arene), 7.51(t, 1H,
Fig. 4. ORTEP drawing with the numbering scheme of 9. Hydrogen
atoms were omitted for clarity.

F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
165
Table 5
Selected bond lengths (A) and bond angles (°) for 9
3.3. Preparation of 9
,
Into a 100 cm3 flask was placed dicobalt octacar-
bonyl, Co2(CO)8, (1.2 g, 3.509 mmol) and diphenyl-2-
pyridylphosphine (0.462 g, 1.755 mmol) with 30 cm3 of
toluene. The solution was stirred at 80°C during the
next 4 h.
Subsequently, the resulting dark green solution was
filtered through a small amount of silica gel. The fol-
lowing purification procedures for the products are
similar to those in Section 3.1. The band of
Co4(CO)10(m-P,N-PPh2py) (9) was eluted with CH2Cl2
together with a trace amount of unidentified byproduct.
The yield of 9 is 68%.
,
Bond lengths (A)
Co(1)ꢂCo(2)
Co(1)ꢂCo(3)
Co(2)ꢂCo(4)
Co(2)ꢂC(3)
Co(2)ꢂC(5)
Co(4)ꢂCo(3)
C(4)ꢂO(4)
PꢂC(16)
2.493(1)
2.530(1)
2.480(1)
1.782(4)
1.879(3)
2.442(1)
1.150(4)
1.841(3)
1.344(4)
Co(1)ꢂCo(4)
Co(1)ꢂN
Co(2)ꢂCo(3)
Co(2)ꢂC(4)
Co(2)ꢂP
C(1)ꢂO(1)
PꢂC(11)
PꢂC(22)
2.543(1)
2.053(3)
2.457(1)
1.940(3)
2.183(1)
1.129(5)
1.840(3)
1.819(3)
1.337(5)
NꢂC(11)
NꢂC(15)
Bond angles (°)
Co(2)ꢂCo(1)ꢂCo(4) 59.0(1)
C(1)ꢂCo(1)ꢂC(2)
Co(4)ꢂCo(1)ꢂN
C(1)ꢂCo(1)ꢂN
C(3)ꢂCo(2)ꢂC(5)
Co(4)ꢂCo(2)ꢂP
C(3)ꢂCo(2)ꢂP
94.4(2)
103.7(1)
105.1(1)
94.4(2)
125.7(1)
103.3(1)
101.0(1)
79.9(1)
108.4(1)
103.7(1)
102.0(1)
119.8(2)
118.2(3)
122.7(3)
Co(2)ꢂCo(1)ꢂN
Co(3)ꢂCo(1)ꢂN
C(2)ꢂCo(1)ꢂN
Co(1)ꢂCo(2)ꢂP
Co(3)ꢂCo(2)ꢂP
C(4)ꢂCo(2)ꢂP
Co(1)ꢂC(1)ꢂO(1)
Co(2)ꢂC(4)ꢂO(4)
Co(2)ꢂPꢂC(16)
Co(2)ꢂPꢂC(22)
C(16)ꢂPꢂC(22)
Co(1)ꢂNꢂC(15)
PꢂC(11)ꢂN
94.2(1)
151.7(1)
99.3(1)
83.4(1)
137.1(1)
88.2(1)
173.7(4)
141.9(3)
118.3(1)
120.1(1)
102.1(1)
122.0(2)
114.1(2)
3.3.1. Characterization of Co4(CO)10(v-PPh2Py) (9)
1H-NMR (CDCl3): l 0.14(s, 9H, SiMe3), 6.29(d, J=
5.2, 1H, CH), 6.92(d, J=7.2, 1H, pyridine), 7.15(t, 1H,
pyridine), 7.26–7.41(m, 10H, arene), 7.51(t, 1H,
pyridine), 8.98(d, J=4, 1H, pyridine); 13C-NMR
(CDCl3): l 125.26(s, 1C, p-pyridine), 129.00(d, J=9.9,
1C, pyridine), 131.01(d, J=8.5, 1C, ipso of pyridine),
131.27(s, 2C, p-arene), 131.91(d, J=41.1, 2C, ipso of
arene), 133.38(d, J=10.7, 4C, arene), 136.58(d, 4C,
arene), 155.42(d, J=13.0, 1C, pyridine), 168.65(d, J=
63.4, 1C, pyridine); 31P-NMR (CDCl3): l 38.1; Elemen-
tal Analysis: Anal. Calc. C, 41.62; H, 1.81; N, 1.80;
found C, 41.79; H, 2.21; N, 2.25; MS m/z 751
[P+ꢂCO]; IR(CH2Cl2): w(CO) 2066(m), 2055(sh), 2022(s),
1998(sh), 1832(m), 1804(m).
C(5)ꢂCo(2)ꢂP
Co(2)ꢂC(4)ꢂCo(4)
Co(2)ꢂPꢂC(11)
C(11)ꢂPꢂC(16)
C(11)ꢂPꢂC(22)
Co(1)ꢂNꢂC(11)
C(11)ꢂNꢂC(15)
NꢂC(15)ꢂC(14)
pyridine), 8.79(d, 1H, pyridine); 13C-NMR(CDCl3): l
1.41(s, 3C, SiMe3), 73.86(s, 1C, CꢂSiMe3), 86.19(s, 1C,
CH), 123.30(s, 1C, pyridine), 127.60(d, J=21.3, 1C,
pyridine), 128.18(d, J=9.9, 2C, arene), 128.20(d, J=
9.86, 2C, arene), 130.01(s, 2C, p-arene), 133.32(d, J=
11.4, 2C, arene), 133.38(d, J=10.7, 2C, arene),
134.48(d, J=39.7, 1C, ipso of arene), 134.66(d, J=
40.5, 1C, ipso of arene), 135.51(d, J=6.8, 1C, ipso of
pyridine), 149.87(d, J=16.0, 1C, pyridine), 160.11(d,
J=62.5, 1C, pyridine), 201.8(m, 2CO), 205.8(m, 3CO);
31P-NMR(CDCl3): l=53.9; Elemental Analysis: Anal.
Calc. C, 52.35; H, 3.87; N, 2.26; found C, 52.14; H,
3.89; N, 2.4; MS m/z 622 [P+3+]; IR(CH2Cl2): w(CO)
2058(s), 1996(s), 1959(sh).
3.4. General procedures for Entries 1, 2, and 3
Dicobalt octacarbonyl, Co2(CO)8, (0.2 g, 0.58 mmol)
and trimethylsilylacetylene (0.83 ml, 5.87 mmol) were
placed in a 100 cm3 flask with 20 cm3 of THF and the
corresponding ligand for each entry. They are
triphenylphosphine (0.15 g, 0.59 mmol) and diphenyl-2-
pyridylphosphine (0.15 g, 0.59 mmol) for Entry 2 and
Entry 3, respectively. The solution was stirred at 60°C
for 12 h.
The following purification procedures for the desired
compounds are similar to those in Section 3.1. The
products, 4 and 3, were eluted out by hexane and
CH2Cl2, respectively. The yields are listed in Table 4.
3.5. General procedures for Entries 4, and 5
For Entry 4, 1a (0.374 g, 0.632 mmol) and
trimethylsilylacetylene (0.81 ml, 5.74 mmol) with 20
cm3 of THF were placed in a 100 cm3 flask and stirred
at 60°C for 12 h. The resulting greenish–brown solu-
tion was subjected for purification.
The following purification procedures are similar to
those in Section 3.1. The only product of 4 was eluted
with hexane.
Fig. 5. Aerial view of 9 along the PꢂCo(2)ꢂCo(1)ꢂP plane.

166
F.-E. Hong et al. / Journal of Organometallic Chemistry 588 (1999) 160–166
(1986) 357. (f) Z.-Z. Zhang, H.-K. Wang, Z. Xi, X.-K. Yao,
Similar procedures were used for Entry 5, which
R.-J. Wang, J. Organomet. Chem. 376 (1989) 123. (g) Z.-Z.
Zhang, H. Cheng, Coord. Chem. Rev. 147 (1996) 1.
[2] (a) K. Kurtev, D. Ribola, R.A. Jones, D.J. Cole-Hamilton, G.
Wilkinson, J. Chem. Soc. Dalton Trans. (1980) 55. (b) E. Linder,
H. Rauleder, P. Wegner, Naturforschung B39 (1984) 1224.
[3] (a) M. Maekawa, M. Munakata, S. Kitagawa, T. Yonezawa,
Bull. Chem. Soc. Jpn. 64 (1991) 2286. (b) E. Lastra, M.P.
Gamasa, J. Gimeno, M. Lanfranchi, A. Tiripicchio, J. Chem.
Soc. Dalton Trans. (1989) 1499. (c) N.W. Alcock, P. Moore,
P.A. Lampe, K.F. Mok, J. Chem. Soc. Dalton Trans. (1982) 207.
(d) C.-H. Su, M.Y. Chiang, J. Chin. Chem. Soc. 44 (1997) 539.
[4] (a) R.G. Pearson, J. Am. Chem. Soc. 85 (1963) 3533. (b) R.G.
Pearson (Ed.), Hard and Soft Acids and Bases, Dowden,
Hutchinson and Ross, Stroudsburg, 1973. (c) R.G. Pearson,
Chemical hardness, in: K. Sen (Ed.), Structural Bonding 80
(1993) 1.
employed 1b (0.144 g, 0.232 mmol) and trimethylsilyl-
acetylene (0.3 ml, 2.12 mmol) as reactants. The result-
ing dark brown solution was subjected for further
purification. Compound 4 is the only isolated product.
The yields are listed in Table 4.
3.6. X-ray crystallographic study
Suitable crystals of 1a and 9 were sealed in thin-
walled glass capillaries under nitrogen atmosphere. The
crystal of 1a was mounted on a Siemens Smart CCD
diffractometer; the crystal of 9 was mounted on a
Siemens P4 diffractometer. The crystallographic data
were collected using a q−2q scan mode with Mo–Ka
radiation. The space group determination was based on
a check of the Laue symmetry and systematic absences,
and was confirmed by the structure solution. The struc-
ture was solved by direct methods using Siemens
SHELXTL PLUS package [16]. All non-H atoms were
located from successive Fourier maps. Anisotropic ther-
mal parameters were used for all non-H atoms and
fixed isotropic for H atoms that were refined using
riding model [17]. Crystallographic data of 1a and 9 are
summarized in Table 1.
[5] (a) T.-Y. Luh, Coord. Chem. Rev. 60 (1984) 255. (b) R.J. Baxter,
G.R. Knox, P.L. Pauson, M.D Spicer, Organometallics 18
(1999) 197. (c) R.J. Baxter, G.R. Knox, J.H. Moir, P.L. Pauson,
M.D. Spicer, Organometallics 18 (1999) 206.
[6] (a) R.D.W. Kemmitt, D.R. Russell, in: G. Wilkinson, F.G.A.
Stone, E.W. Abel (Eds.), Comprehensive Organometallic Chem-
istry, vol. 5, Pergamon, Oxford, 1982. (b) M.J. Chetcuti, in:
E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive
Organometallic Chemistry II, vol. 10, Elsevier Science, New
York, 1995, pp. 44. (c) M.J. Chetcuti, P.E. Fanwick, J.C.
Gordon, Inorg. Chem. 30 (1991) 4710. (d) G. Gervasio, E.
Sappa, L. Marko´, J. Organomet. Chem. 444 (1993) 203. (e) O.S.
Mills, G. Robinson, Proc. Chem. Soc. (1964) 187. (f) F.S.
Stephens, Acta Crystallogr. Sect. A Cryst. Phys. Diffr. Theor.
Gen. Crystallogr. 154 (1966) 21A. (g) F.-E. Hong, J.-Y. Wu,
Y.-C. Huang, C.-K. Hung, H.-M. Gau, C.-C. Lin, J. Organomet.
Chem. 580 (1999) 98.
4. Supplementary material available
[7] The yield of 3 is about 25%.
[8] A.L. Balch, in: M.H. Chisholm (Eds.), Reactivity of
MetalꢂMetal Bonds, American Chemical Society, 1981, pp. 167.
[9] (a) L.S. Hegedus, Transition Metals in the Synthesis of Complex
Organic Molecules, University Science Books, Mill Valley, CA,
1994 (Chapter 8). (b) R.S. Dickson, Adv. Organomet. Chem. 12
(1974) 323. (c) R.S. Dickson, G.R. Tailby, Aust. J. Chem. 23
(1971) 229. (d) U. Kru¨erke, W. Hu¨bel, Chem. Ber. 94 (1961)
2829.
Atomic coordinates of 1a and 9, tables of thermal
parameters, bond lengths and angles, anisotropic ther-
mal parameters, and H atom coordinates have been
deposited as supplementary material.
Acknowledgements
[10] The 31P-NMR peak for PPh2py occurs at −3.9 ppm.
[11] Unpublished results.
We thank the National Research Council of the
Republic of China (Grant NSC-88-2113-M-005-022)
for support.
[12] F.-E. Hong, C.-K. Hung, C.-C. Lin, J. Chin. Chem. Soc. 44
(1997) 43.
[13] (a) C.R. Eady, B.F.G. Johnson, J. Lewis, J. Chem. Soc. Dalton
Trans. (1975) 2606. (b) F. Ungvary, L. Marko´, J. Organomet.
Chem. 71 (1974) 283.
[14] C.M. Lukehart, Fundamental Transition Metal Organometallic
Chemistry, Brooks/Cole, Monterey, CA, 1985 (Chapter 3).
[15] B.F.G. Johnson, A. Rodgers, in: D.F. Shriver, H.D. Kaesz, R.D.
Adams (Eds.), The Chemistry of Metal Cluster Complexes,
VCH, 1990 (Chapter 6).
[16] G.M. Sheldrick, SHELXTL PLUS User’s Manual. Revision 4.1
Nicolet XRD Corporation, Madison, WI, 1991.
[17] The hydrogen atoms were riding on carbons or oxygens in their
References
[1] (a) J. Puddephatt, Chem. Soc. Rev. 12 (1983) 99.(b) J.P. Farr,
M.M. Olmstead, N.M. Rutherford, F.E. Wood, A.L. Balch,
Organometallics 2 (1983) 1758. (c) J.P. Farr, F.E. Wood, A.L.
Balch, Inorg. Chem. 22 (1983) 1229. (d) J.P. Farr, M.M. Olm-
stead, A.L. Balch, Inorg. Chem. 22 (1983) 3387. (e) Z.-Z. Zhang,
H.K. Wang, H.G. Wang, R.J. Wang, J. Organomet. Chem. 314
,
idealized positions and held fixed with CꢂH distances of 0.96 A.
.