The syntheses of pyridine-functionalyzed methylidynetricobalt nona-carbonyl clusters, their X-ray analyses, and its coordination to Pd(II)1

Article abstract of DOI:10.1016/S0022-328X(98)00823-7

Two kinds of methylidynetricobalt nonacarbonyls with a pyridine functional group as an apical substituent have been synthesized from trichloromethylpyridine derivatives. The structures of two new clusters have been determined by single crystal X-ray analysis. EH-MO calculations have shown that the atomic charge on the N atom in NC₅H₄-3-CCo₃(CO)₉ is close to that of β-picoline. This cluster can coordinate to Pd(II) and trans-PdCl₂{NC₅H₄-3-CCo₃(CO) ₉}₂ with a nanometer dimension has been synthesized as a precursor of molecular dot.

Full text of DOI:10.1016/S0022-328X(98)00823-7

Journal of Organometallic Chemistry 570 (1998) 113–119
The syntheses of pyridine-functionalyzed methylidynetricobalt
nona-carbonyl clusters, their X-ray analyses, and its coordination to
Pd(II)1
Satoru Onaka a,*, Yoshitaka Katsukawa a, Michito Shiotsuka b
a Department of En6ironmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku,
Nagoya 466-8555, Japan
b Department of Systems Management and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
Received 15 May 1998; received in revised form 19 June 1998
Abstract
Two kinds of methylidynetricobalt nonacarbonyls with a pyridine functional group as an apical substituent have been
synthesized from trichloromethylpyridine derivatives. The structures of two new clusters have been determined by single crystal
X-ray analysis. EH-MO calculations have shown that the atomic charge on the N atom in NC5H4-3-CCo3(CO)9 is close to that
of i-picoline. This cluster can coordinate to Pd(II) and trans-PdCl2{NC5H4-3-CCo3(CO)9}2 with a nanometer dimension has been
synthesized as a precursor of molecular dot. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Tricobalt cluster with a pyridine ligand; Single crystal X-ray analysis; Nanometer scale cluster; Molecular dot
form sized particles with a preparative scale quantity is
quite difficult except for some synthetic methods of
coordination cluster compounds [1]. Therefore, we have
proposed the synthesis of higher-nuclearity clusters in a
molecular design fashion by use of the small cluster
unit, –CCo3(CO)9, as a building block in the previous
papers, targeting the synthesis of such nanometer-size
clusters. We have successfully synthesized several proto-
type clusters [2]; a similar idea of linking two cluster
units of CCo3(CO)9 has already appeared in a previous
paper [3]. As an extension of this work, the next target
is the synthesis of spherical clusters with a nanometer-
size (Scheme 1). We propose calling such a cluster ‘a
molecular dot’. The key cluster unit to construct such a
molecular dot is a pyridine-functionalyzed tricobalt
cluster, py-CCo3(CO)9, the synthesis of which has not
been reported in spite of the plethora of studies on the
synthesis of many kinds of methylidynetricobalt
nonacarbonyls by Seyferth et al. [4]. The present paper
reports on the tailored synthesis of pyridine-functiona-
lyzed tricobalt clusters, their X-ray structural analyses,
1. Introduction
The preparation of nanometer-sized metal clusters
with uniform dimensions and shapes has now become a
challenging field of chemistry because of their possible
applications to nanotechnology [1]. So far, two major
methods have been employed to produce nanometer-
sized particles, that is, dry methods and wet methods. A
typical example of the former methods is the gas phase
synthesis from bulk solids by use of the laser ablation
and/or the electrical discharge [1] and that of the latter
methods is the solution phase synthesis of colloids,
alkoxides, and/or metal cluster coordination com-
pounds in solvents [1]. However, both methods meet
the size-distribution problem except the synthesis of
coordination compounds and the production of uni-
* Corresponding author. Fax: +81 52 7355160; e-mail: on-
klustr@ks.kyy.nitech.ac.jp
1 This work was presented to the 17th International Conference on
Organometallic Chemistry (July 7, 1996, Brisbane).
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00823-7

114
S. Onaka et al. / Journal of Organometallic Chemistry 570 (1998) 113–119
Table 1
Crystal data
and the demonstration of the coordination of one of
these clusters to a Pd(II) complex.
Compound
NC5H3-6-Cl-3-
CCo3(CO)9 (1)
C15H3ClCo3NO9
553.4
NC5H4-3-
CCo3(CO)9 (2)
C15H4Co3NO9
519.0
Monoclinic
P21/n
2. Experimental section
Formula
Formula weight
Crystal system
Space group
Triclinic
2.1. General comments
(
P1
Unit cell dimensions
˚
All reactions were carried out under an argon atmo-
sphere by standard Schlenk techniques. 3-
a (A)
10.537(2)
10.585(2)
8.781(2)
93.25(2)
93.13(1)
86.31(1)
974.5(3)
2
13.518(3)
29.887(5)
8.992(1)
90
94.96(2)
90
3819(1)
8
1.832
˚
b (A)
˚
c (A)
trichloromethylpyridine,
3-Cl3C–NC5H4
and
h (°)
i (°)
 (°)
trans-PdCl2(NCPh)2 were synthesized by the literature
methods [5,6]. The fraction of 3-Cl3C–NC5H4 with b.p.
53–55°C/0.05 mmHg was collected and used for the
3
˚
V (A )
1
synthesis of (3-py)CCo3(CO)9. H-NMR spectra were
Z
Dcalc (g cm−3
)
1.887
recorded on a JEOL EX-270 WB spectrometer. IR
spectra were recorded on a JASCO Valor-III FT-IR
spectrometer.
Crystal dimensions
0.50×0.35×0.30
0.60×0.55×0.35
(mm3)
v(Mo–Kh) (cm−1
Scan type
)
14.85
ꢀ-2q
15.10
ꢀ-2q
2.2. Synthesis of NC5H3-6-Cl-3-CCo3(CO)9 (1) and
NC5H4-3-CCo3(CO)9 (2)
Scan range
1.50+0.35 tan u
1.30+0.35 tan u
Scan speed (° min−1
2qmax (°)
)
5.0
5.0
55.0
298
4482
50.0
298
6364
5041
Temperature (K)
Unique reflections
A THF solution (30 ml) of Co2(CO)8 (920 mg, 2.77
mmol) was stirred at 55°C for 30 min. Then a THF
solution (10 ml) of 3-Cl3C–NC5H4 (330 mg) (8 mmol)
was added. The mixture was stirred at 55°C for 2.5 h
and left standing at room temperature overnight. The
brown solution was filtered by use of filter paper and
then poured into a 10% HCl solution. The purple-
brown product was extracted with each 50 ml of
CH2Cl2 several times and the solvent was partially
distilled under a reduced pressure from the combined
extracts. The remaining solution was subjected to a
Yamazen YFLC-700 medium pressure liquid chro-
matography (Wako-gel C-200). A mixed solvent of
hexane–benzene (1:1) eluted a small amount of red
Reflections with ꢀFoꢀ\ 4030
3|(ꢀFoꢀ)
No. of parameters
277
535
refined
R
Rw
0.103
0.116
0.0355
0.0284
˚
Mo–Kh radiation (u=0.71073 A); R=ꢁꢀꢀFoꢀ−ꢀFcꢀꢀ/ꢀFoꢀ; Rw=
[ꢁ (ꢀFoꢀ−ꢀFcꢀ)2/ꢁ w(Fo)2]1/2 where w=1/|2(F).
band and benzene eluted a huge purple band. Both
products
were
recrystallized
from
hexane–
dichloromethane to afford a purple-red product 1 (from
the red band, 20 mg) and a purple-brown product 2
(from the purple band, 220 mg, 30%). Single crystal
X-ray analysis has shown that 1 is NC5H3-6-Cl-3-
CCo3(CO)9; IR (w(CO), Nujol mull): 2105 (m), 2056
(vs), 2046 (s, sh), 2030 (s), 2015 (m), 1999 (m) cm−1
.
1H-NMR (CD3OD): 8.583 (d, 3 Hz, 1H, C3–H), 7.711
(dd, 3 Hz, 8 Hz, 1H, C6–H), 7.293 (d, 0.6 Hz, 1H,
C5–H). Absorption spectrum (CH2Cl2 solution) (umax):
390 (m=6.4×103), 515 (m=1.8×103) nm. Single crys-
tal X-ray analysis has shown that 2 is NC5H4-3-
CCo3(CO)9. Anal.Calc. for C15H4Co3NO9(%): C, 34.71;
H, 0.78; N, 2.70. Found: C, 34.14; H, 0.79; N, 2.68. IR
(w(CO), Nujol mull): 2105 (m), 2071 (m, sh), 2053 (vs),
2036 (vs), 2019 (s), 2004 (m, sh), 1989 (m) cm−1
.
1H-NMR (CD3OD): 8.746 (s, 1H, C19–H, C29–H),
8.452 (d, 3 Hz, 1H, C18–H, C28–H), 7.964 (d, 8 Hz, 1H,
C16–H, C26–H), 7.430 (dd, 6 Hz, 5 Hz, 1H, C17–H,
C27–H). Absorption spectrum (CH2Cl2 solution) (umax):
380 (m=5.2×103), 510 (m=1.7×103) nm.
Scheme 1.

S. Onaka et al. / Journal of Organometallic Chemistry 570 (1998) 113–119
115
Found: C, 29.36; H, 1.11; N, 2.32. IR (w(CO), Nujol
mull): 2107 (m), 2059 (s, sh), 2047 (vs), 2037 (s), 2026
(s), 2017 (m, sh), 2005(m, sh) cm−1. Absorption spec-
trum (CH2Cl2 solution) (umax): 400 (m=9.5×104), 520
(m=3.0×104) nm. All attempts to get single crystals of
3 have so far been unsuccessful because of low solubil-
ity to common organic solvents.
2.4. Crystal structure determination
Dark purple brown single crystals of 2 were grown
from hexane–dichloromethane (1:1). A crystal with
approximate dimensions of 0.60×0.55×0.40 mm3 was
mounted on a MAC MXC3 diffractometer equipped
with graphite monochromated Mo–Kh radiation (u=
˚
0.71073 A). Diffraction data were collected at room
temperature. Dark brown single crystals of 1 were also
grown from hexane–dichloromethane (1:1). A crystal
with approximate dimensions of 0.50×0.35×0.30
mm3 was mounted on a MAC MXC3 diffractometer
and diffraction data were similarly measured as above.
The crystal data for 1 and 2 are given in Table 1. The
structures were solved by direct methods (Sir 92 for 1
and SHELXS86 for 2) in a Crystan-G and a Crystan
program package provided by MAC Science. All non-
hydrogen atoms were refined with anisotropic thermal
parameters and hydrogen atoms by isotropic thermal
parameters. The molecular structures for 1 and 2 are
depicted in Figs. 1 and 2, respectively. The atomic
coordinates are listed in Table 2 and selected bond
lengths and angles are collated in Table 3. The ꢀFoꢀ−
ꢀFcꢀ tables and anisotropic temperature factor tables are
available from the author.
Fig. 1. The molecular structure of NC5H3-6-Cl-3CCo3(CO)9 (1).
2.3. Synthesis of PdCl2{NC5H4-3-CCo3(CO)9}2 (3)
A 74 mg sample of trans-PdCl2(NCPh)2 (0.19 mmol)
was dissolved in 50 ml of toluene. To this was added a
toluene solution (90 ml) of 2 (200 mg, 0.39 mmol) and
the mixture was stirred at room temperature for 3 h
and then at 50°C for 1 h. The resulting dark brown
precipitates were collected by filtration, washed with a
small amount of hexane several times, and dried by
suction. Yield 190 mg (82%). Anal. Calc. for
C30H8Cl2Co6N2O18Pd (%): C, 29.65; H, 0.66, N, 2.31.
3. Results and discussion
The most important key building block for the syn-
thesis of ‘a molecular dot’ is, in our view, a pyridine-
functionalized
tricobalt
cluster,
py-CCo3(CO)9.
Therefore, we at first attempted the synthesis of
NC5H4-4-CCo3(CO)9 from 4-Cl3C–NC5H4. However,
only HCCo3(CO)9 has so far been isolated from the
similar synthetic procedure as those of 1 and 2 de-
scribed in Section 2. We have turned our attention to
the synthesis of the 3-substituted pyridine cluster from
3-Cl3C–NC5H4 and successfully obtained the targeted
tricobalt cluster with a pyridine functional group as an
apical substituent. The synthesis of NC5H3-6-Cl-3-
CCo3(CO)9 as a byproduct is well understood because
the fraction used to get 3-Cl3C–NC5H4 contained a
small amount of 6-Cl-3-Cl3C–NC5H3 which is due to
the boiling point of the latter liquid being close to that
of the former liquid [5]. Before we proceed to the
synthesis of a ‘nano cluster’, it seems appropriate to
check the molecular structures of 1 and 2 in some
Fig. 2. The molecular structure of molecule 1 of NC5H4-3-CCo3(CO)9
(2).

116
S. Onaka et al. / Journal of Organometallic Chemistry 570 (1998) 113–119
Table 2
Table 2 (Continued)
2
˚
Atomic coordinates and isotropic thermal parameters, Beq (A ) for 1
and 2
Compound 2
Compound 1
Atom
x
y
z
Beq
8.2(1)
6.0(1)
6.7(1)
Atom
x
y
z
Beq
2.85(6)
O23
O31
O32
O33
H16
H17
H18
H19
−0.1733(3)
−0.1819(2)
−0.3105(2)
−0.3592(2)
−0.244(3)
−0.278(4)
−0.201(3)
−0.056(3)
−0.0255(1)
0.0452(1)
−0.5980(4)
0.0218(3)
Co1
Co2
Co3
Cl1
N1
C1
C2
C3
C4
0.3202(2)
0.2525(2)
0.3200(2)
0.3738(2)
0.2676(2)
0.1395(2)
0.2738(4)
0.352(1)
0.269(1)
0.270(1)
0.349(1)
0.274(1)
0.192(2)
0.194(2)
0.397(1)
0.525(1)
0.389(1)
0.265(1)
0.399(2)
0.150(2)
0.098(1)
0.114(2)
0.000(2)
0.409(1)
0.620(1)
0.401(1)
0.260(1)
0.481(1)
0.076(1)
0.074(1)
0.096(1)
0.7576(2)
0.9800(2)
0.7508(2)
0.4893(5)
0.526(2)
0.787(1)
0.712(2)
0.590(2)
0.581(2)
0.690(2)
0.761(2)
0.825(3)
0.808(1)
0.554(2)
1.094(2)
1.066(2)
1.066(2)
0.813(3)
0.552(2)
0.799(3)
0.865(2)
0.842(1)
0.430(1)
1.162(1)
1.133(2)
1.124(2)
0.864(2)
0.423(2)
0.820(2)
0.54(2)
−0.1770(1)
−0.0671(1)
−0.202(2)
−0.245(2)
−0.232(2)
−0.130(2)
−0.1159(4)
−0.4238(4)
−0.422(5)
−0.634(5)
−0.853(5)
−0.661(5)
2.84(6)
3.17(6)
5.0(1)
4.3(4)
2.6(3)
3.0(4)
4.0(4)
3.1(4)
5.4(6)
4.8(5)
6.6(7)
3.1(4)
4.5(5)
3.7(4)
3.8(4)
3.9(4)
7.6(8)
5.8(6)
8.0(8)
7.1(5)
5.8(4)
6.1(4)
6.3(4)
7.0(5)
8.0(5)
7.8(5)
9.2(6)
10.8(7)
3.95(0)
5.31(0)
4.78(0)
7.9(1)
4.20(0)
4.84(0)
5.02(0)
4.69(0)
−0.3392(4)
−0.108(1)
0.182(1)
0.051(1)
0.010(1)
−0.187(1)
−0.157(1)
−0.036(2)
0.484(2)
0.244(1)
0.326(2)
0.404(2)
0.166(1)
0.171(2)
0.484(2)
0.327(2)
0.240(2)
0.586(1)
0.193(1)
0.329(1)
0.496(1)
0.111(1)
0.119(1)
0.583(1)
0.328(2)
0.190(2)
0.06(2)
Molecule 2
Co4
Co5
Co6
C2
−0.49497(3) −0.14643(2)
−0.59545(4) −0.07970(2)
−0.58371(4) −0.10625(2)
−0.6335(2)
−0 8535(2) −0.2080(1)
−0.7197(2)
−0.7506(3)
−0.8326(4)
−0.8810(3)
−0.7749(3)
−0.3732(3)
−0.4816(3)
−0.4817(3)
0.23739(5)
0.28433(5)
0.02663(5)
0.1933(3)
0.0815(4)
0.2059(4)
0.3414(5)
0.3432(6)
0.2126(6)
0.0811(5)
0.2264(5)
0.4254(5)
0.1507(5)
0.2937(5)
0.4800(5)
0.2480(4)
−0.0280(4)
−0.1039(5)
3.21(2)
3.18(2)
3.46(2)
2.78(8)
5.4(1)
2.88(9)
5.1(1)
6.0(2)
4.8(1)
4.6(1)
4.5(1)
4.4(1)
4.6(1)
4.6(1)
4.4(1)
4.3(1)
4.4(1)
5.1(1)
4.7(1)
7.1(1)
7.59(1)
7.2(1)
7.3(1)
7.4(1)
7.0(1)
7.3(1)
7.5(1)
7.3(1)
5.11(0)
5.92(0)
4.78(0)
4.56(0)
C5
C6
−0.1356(1)
C11
C12
C13
C21
C22
C23
C31
C32
C33
O11
O12
O13
O21
O22
O23
O31
O32
O33
H3
N2
C25
C26
C27
C28
C29
C41
C42
C43
C51
C52
C53
C61
C62
C63
O41
O42
O43
O51
O52
O53
O61
O62
O63
H26
H27
H28
H29
−0.1647(1)
−0.1782(2)
−0.2061(2)
−0.2196(2)
−0.1812(2)
−0.1205(1)
−0.1666(1)
−0.1999(2)
−0. 4998(3) −0.0363(1)
−0.6071(3)
−0.7078(3)
−0.4850(3)
−0.5779(3)
−0.6923(3)
−0.2998(2)
−0.4702(3)
−0.4745(3)
−0.4401(3)
−0.6166(3)
−0.7796(2)
−0.4243(2)
−0.5763(3)
−0.7613(2)
−0.714(3)
−0.844(4)
−0.940(3)
−0.753(3)
−0.0881(1)
−0.0480(1)
−0.0691(2)
−0.1511(2)
−0. 0797(2) −0.0620(4)
−0.1034(1)
−0.1793(1)
−0.2341(1)
−0.0097(1)
−0.0931(1)
−0.0292(1)
−0.0465(1)
−0.1800(1)
−0.0640(1)
−0.171(2)
−0.218(2)
−0.240(2)
−0.171(2)
0.2195(4)
0.5435(4)
0.0989(4)
0.2972(4)
0.6016(4)
0.2282(4)
−0.0613(4)
−0.1855(4)
−0.1194(4)
0.433(5)
−0.087(1)
0.41(2)
H5
H6
−0.23(2)
−0.01(2)
0.14(2)
0.14(2)
0.74(2)
0.81(2)
Compound 2
Molecule 1
Co1
Co2
Co3
C1
N1
C15
C16
C17
C18
C19
C11
C12
C13
C21
C22
C23
C31
C32
C33
O11
O12
O13
O21
−0.02997(4) −0.14187(2) −0.20489(5)
−0.05444(4) −0.07523(2) −0.36687(6)
−0.19398(3) −0.10613(2) −0.23920(5)
3.32(2)
3.43(2)
3.21(2)
3.08(9)
5.8(1)
3.1(1)
4.2(1)
4.8(1)
5.0(1)
4.7(1)
4.2(1)
4.2(1)
4.3(1)
4.4(1)
5.0(1)
5.0(1)
3.8(1)
4.4(1)
4.7(1)
6.0(1)
6.5(1)
6.3(1)
7.4(1)
7.9(1)
0.436(6)
0.209(5)
−0.1149(2)
−0.1216(3)
−0.1418(2)
−0.2104(3)
−0.2334(4)
−0.1871(4)
−0.1002(3)
0.0128(3)
−0.1327(1)
−0.1800(1)
−0.1616(1)
−0.1960(1)
−0.2218(1)
−0.2127(2)
−0.1557(2)
−0.1165(1)
−0.1596(1)
−0.1961(2)
−0.0300(1)
−0.0808(2)
−0.0447(2)
−0.0684(1)
−0.1504(1)
−0.0822(2)
−0.1008(1)
−0.1713(1)
−0.2306(1)
−0.0020(1)
−0.0838(1)
−0.3826(4)
−0.7708(4)
−0.5121(4)
−0.5110(5)
−0.6364(5)
−0.7612(5)
−0.6479(5)
−0.0238(5)
−0.2670(4)
−0.1455(4)
−0.2373(5)
−0.4602(5)
−0.5091(5)
−0.0765(4)
−0.1647(5)
−0.3536(5)
0.0871(3)
−0.011(5)
detail. There are two independent molecules in an
asymmetric unit for 2, whereas there is one molecule in
an asymmetric unit for 1. The geometrical parameters
for two independent molecules of 2 are quite close for
each other. However, the rotational angle of the
pyridine ring about the axis which passes through the
apical carbon and the center of the Co3 triangle is
somewhat different as is seen in Fig. 3; the pyridine ring
in the molecule 2 almost bisects the Co–Co bond
whereas the pyridine ring in the molecule 1 rotates a
little bit about the axis mentioned above. The N atom
side of the pyridine ring tends to direct one of the
cobalt atoms. The same result is observed for 1 and the
rotation of the apical pyridine ring is close to that of
0.0855(3)
−0.0679(3)
−0.0154(3)
0.0566(3)
−0.1270(3)
−0.1860(3)
−0.2633(3)
−0.2940(3)
0.0383(2)
0.1597(2)
−0.3034(3)
−0.1109(4)
−0.1595(4)
−0.5193(4)
−0.0916(2)
0.0087(3)
O22
0.1270(2)

S. Onaka et al. / Journal of Organometallic Chemistry 570 (1998) 113–119
117
Table 3
˚
Selected bond lengths (A) and angles (°)
Compound 1
Compound 2
Molecule 1
Molecule 2
Co1–Co2
Co1–Co3
Co2–Co3
C1–Co1
C1–Co2
C1–Co3
C1–C2
Co1–C11
Co1–C12
Co1–C13
Co2–C21
Co2–C22
Co2–C23
Co3–C31
Co3–C32
Co3–C33
N1–C3
2.468(3)
2.478(2)
2.473(3)
1.92(1)
1.82(1)
1.96(1)
1.49(2)
1.83(2)
1.79(1)
1.80(2)
1.83(2)
1.77(2)
1.78(2)
1.81(2)
1.75(2)
1.82(2)
1.33(2)
1.34(2)
1.43(2)
1.37(2)
1.33(2)
1.39(2)
1.75(1)
Co1–Co2
Co1–Co3
Co2–Co3
C1–Co1
C1–Co2
C1–Co3
2.4725(8)
2.4558(7)
2.4706(7)
1.905(3)
1.901(4)
1.916(4)
1.471(5)
1.843(4)
1.783(4)
1.794(4)
1.831(4)
1.790(5)
1.792(4)
1.844(4)
1.786(4)
1.777(4)
1.327(6)
1.333(6)
1.383(5)
1.400(6)
1.379(6)
1.359(7)
Co4–Co5
Co4–Co6
Co5–Co6
C2–Co4
C2–Co5
C2–Co6
2.4695(8)
2.4653(7)
2.4677(7)
1.908(3)
1.912(3)
1.909(3)
1.465(5)
1.829(4)
1.789(4)
1.793(4)
1.827(4)
1.798(4)
1.796(4)
1.835(4)
1.787(5)
1.794(4)
1.313(6)
1.330(6)
1.382(6)
1.384(5)
1.390(7)
1.355(7)
C1–C15
C2–C25
Co1–C11
Co1–C12
Co1–C13
Co2–C21
Co2–C22
Co2–C23
Co3–C31
Co3–C32
Co3–C33
N1–C18
N1–C19
C15–C16
C15–C19
C16–C17
C17–C18
Co4–C41
Co4–C42
Co4–C43
Co5–C51
Co5–C52
Co5–C53
Co6–C61
Co6–C62
Co6–C63
N2–C28
N2–C29
C25–C26
C25–C29
C26–C27
C27–C28
N1–C4
C2–C3
C2–C6
C4–C5
C5–C6
Cl1–C4
Co1–Co2–Co3
Co2–Co3–Co1
Co3–Co1–Co2
C1–Co1–Co2
C1–Co1–Co3
C1–Co2–Co1
C1–Co3–Co1
C1–Co3–Co2
C2–C1–Co1
60.19(8)
59.81(8)
59.99(8)
46.8(4)
51.1(4)
50.6(4)
49.7(4)
46.6(4)
130(1)
Co1–Co2–Co3
Co2–Co3–Co1
Co3–Co1–Co2
C1–Co1–Co2
C1–Co1–Co3
C1–Co2–Co1
C1–Co3–Co1
C1–Co3–Co2
C15–C1–Co1
C15–C1–Co2
C15–C1–Co3
C1–Co1–C11
C1–Co1–C12
C1–Co1–C13
C1–Co2–C21
C1–Co2–C22
C1–Co2–C23
C1–Co3–C31
C1–Co3–C32
C1–Co3–C33
59.58(2)
60.15(2)
60.17(2)
49.4(1)
50.2(1)
49.6(1)
Co4–Co5–Co6
Co5–Co6–Co4
Co6–Co4–Co5
C2–Co4–Co5
C2–Co4–Co6
C2–Co5–Co4
C2–Co6–Co4
C2–Co6–Co5
C25–C2–Co4
C25–C2–Co5
C25–C2–Co6
C2–Co4–C41
C2–Co4–C42
C2–Co4–C43
C2–Co5–C51
C2–Co5–C52
C2–Co5–C53
C2–Co6–C61
C2–Co6–C62
C2–Co6–C63
59.91(2)
60.08(2)
60.01(2)
49.8(1)
49.8(1)
49.6(1)
49.8(1)
49.4(1)
49.8(1)
49.8(1)
132.0(2)
131.7(2)
131.5(2)
143.3(2)
105.1(2)
102.3(2)
144.2(2)
104.7(2)
101.6(2)
142.2(1)
106.6(2)
102.6(2)
131.0(2)
132.2(2)
132.1(2)
142.0(2)
105.7(2)
101.2(2)
143.4(2)
104.7(2)
101.0(2)
143.4(2)
102.1(2)
102.8(2)
C2–C1–Co2
C2–C1–Co3
137(1)
125.6(9)
141.1(7)
98.7(6)
106.9(6)
144.1(6)
100.1(6)
103.9(6)
140.9(7)
106.8(7)
99.1(7)
C1–Co1–C11
C1–Co1–C12
C1–Co1–C13
C1–Co2–C21
C1–Co2–C22
C1–Co2–C23
C1–Co3–C31
C1–Co3–C32
C1–Co3–C33
˚
the molecule 2 in 2. The drawing of the crystal packing
(Fig. 4) and the intermolecular distance calculation show
that the C18–H18 and C28–H28 bonds direct to the
pyridine ring of the other molecule at almost right angles
suggesting the existence of a C–H· · ·y interaction.
However, such a C–H· · ·y interaction is not the case for
1. The comparison of the geometrical parameters be-
tween 1 and 2 has shown that the average Co–CO bond
C2–C25) for 2 (1.471(5) and 1.465(5) A) is shorter than
˚
that of 1 (1.49(2) A). The average Co–Co bond length
for 2 (1.805 A) is only slightly longer than that of 1
(1.798 A). The average C–O bond length for 2 (1.128 A)
is slightly shorter than that of 1 (1.132 A). The general
trend in the bond-lengths including the Co–Co bonds
suggests that the electron-withdrawing substituent, Cl at
the para-position with respect to the cluster in the
pyridine ring affects, if any, only slightly the electron
density of the –CCo3(CO)9 core [7,8]. The observation
is in accord with the knowledge that the –CCo3(CO)9
core is an excellent electron sink [2,4,9].
˚
˚
˚
˚
˚
length for 2 (2.467 A) is slightly shorter than that of 1
˚
(2.473 A). The average apical C–Co bond length for 2
˚
˚
(1.909 A) is essentially same as that of 1 (1.90 A). The
ipso-carbon-apical carbon bond length (C1–C15 and

118
S. Onaka et al. / Journal of Organometallic Chemistry 570 (1998) 113–119
Fig. 3. The rotation of the apical pyridine ring toward the basal tricobalt triangle in 2 (left, molecule 1; right, molecule 2).
geometry because trans-PdCl2(NCPh)2 was used as a
Pd source. Upon coordination, 3 shows a slight shift of
w(CO)’s to a higher energy and a slight shift of the
absorption peaks in the visible region to a longer wave
length with the increased molecular absorption coeffi-
cients (more than ten times greater than those of 2).
Attempts to grow single crystals of 3 have so far been
unsuccessful due to quite low solubility in common
organic solvents. Therefore, we have estimated the
molecular dimension of 3 from a molecular model,
which suggests that 3 has an approximately 1.5 nm
diameter. As a square-planar configuration is suggested
for the palladium (II) center in 3, the molecular shape
of 3 should not be spherical. Thus, our efforts to create
a supracluster with a spherical shape, that is a molecu-
lar dot, are continuing by introducing 2 into a metal
center which has a tetrahedral and/or octahedral
configuration.
Next we investigated the potential of the coordina-
tion of the cluster to transition metals by calculating
the net atomic charge on the N atom; EH-MO calcula-
tions have been made based on the atomic coordinates
from the present study by use of CAChe [10]. The
atomic charge on the N atom is −0.971, −0.900, and
−0.820 a.u. for 3-CH3–NC5H4 (i-picoline), 2, and 1
respectively; the reason for the choice of i-picoline as a
standard for the comparison is that it is the typical and
the most frequently employed ligand as a pyridine
ligand with a substituent at the 3-position. The calcula-
tion suggests that the coordinating ability of 2 is close
to that of i-picoline in terms of atomic net charge.
Therefore, we have examined the reaction of 2 with
trans-PdCl2(NCPh)2 in toluene. As is described in Sec-
tion 2, a dark brown product is obtained. This product
is characterized as trans-PdCl2{NC5H4-3-CCo3(CO)9}2
(3) by elemental analyses, IR, and the absorption spec-
trum; there is no reason to doubt that 3 has a trans
Acknowledgements
This work was supported by the Tokai Foundation
for Technology and Grant-in-Aids for Scientific Re-
search No. 08874080 from the Ministry of Education,
Science, Sports, and Culture, Japan.
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