Cationic M(II)/Co(0) (M = Pd, Pt) metallomacrocycles containing tetrahedral Co2C2 cluster cores formed by self-assembly of cluster-bridged Bipyridine (4-C5H4NCO2CH 2)2C(2(Co)(2)(

Article abstract of DOI:10.1021/om049175y

The synthesis, characterization, and some reactions of the tetrahedral Co₂C₂ cluster-bridged bipyridine (4-C₅H ₄NCO₂CH₂)₂C₂Co ₂(CO)₆ (2) and the

Full text of DOI:10.1021/om049175y

700
Organometallics 2005, 24, 700-706
Cationic M(II)/Co(0) (M ) Pd, Pt) Metallomacrocycles
Containing Tetrahedral Co2C2 Cluster Cores Formed by
Self-Assembly of Cluster-Bridged Bipyridine
(4-C5H4NCO2CH2)2C2Co2(CO)6 and Diarsine-Chelated
Complex [Pd(dpab)(H2O)(OTf)][OTf] or
[Pt(dpab)(H2O)2][OTf]2
Li-Cheng Song,* Guo-Xia Jin, Wen-Xiong Zhang, and Qing-Mei Hu
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, People’s Republic of China
Received October 24, 2004
The synthesis, characterization, and some reactions of the tetrahedral Co2C2 cluster-bridged
bipyridine (4-C5H4NCO2CH2)2C2Co2(CO)6 (2) and the diarsine-chelated complexes Pd(dpab)Cl2
(3, dpab ) 1,4-bis(diphenylarsino)butane), [Pd(dpab)(H2O)(OTf)][OTf] (4, OTf ) SO3CF3),
Pt(dpab)Cl2 (5), and [Pt(dpab)(H2O)2][OTf]2 (6) have been investigated. While the bridged
bipyridine 2 could be prepared by reaction of 4-pyridinecarboxylic acid 2-butyne-1,4-diyl
ester 1 with Co2(CO)8 in 86% yield, the chelated dichloride complexes 3 and 5 were obtained
by reaction of K2PdCl4 or (PhCN)2PtCl2 with dpab in 90% and 77% yields. Further reactions
of 3 and 5 with silver triflate followed by treatment with water afforded the corresponding
chelated aqua/triflate complexes 4 and 6 in 92% and 88% yields. More interestingly, 4 and
6 were found to undergo self-assembly with 2 to give two cationic metallomacrocycles
{[M(dpab)]-µ-[(4-C5H4NCO2CH2)2C2Co2(CO)6]}2[OTf]4 (7, M ) Pd; 8, M ) Pt) in 92% and
85% yields. X-ray crystal structures were determined for the Co2C2 cluster-containing
metallomacroycles 7 and 8, as well as bipyridine 2 and complexes 4 and 6.
Introduction
tetrahedral M2FeS (M ) Mo, W) cluster cores.8 Since
we are interested in cluster-containing macrocycles,8,9
we recently initiated a study on self-assembly of the
tetrahedral Co2C2 cluster-bridged bipyridine ligand (4-
C5H4NCO2CH2)2C2Co2(CO)6 (2) with the dpab-chelated
Pd(II) complex [Pd(dpab)(H2O)(OTf)][OTf] (4, dpab )
1,4-bis(diphenylarsino)butane; OTf ) SO3CF3) or Pt(II)
complex [Pt(dpab)(H2O)2][OTf]2 (6), aimed to obtain the
corresponding Co2C2 cluster-containing metallomacro-
cyclic compounds that may have unique structures and
new properties. Now, we report our results.
It is well-known that metallomacrocycles are an
important class of metal-containing compounds that
have been involved in modern supramolecular chemistry
with unique structures and novel properties.1-3 On the
other hand, it is also known that self-assembly is one
of the most practical methodologies for synthesis of
metallomacrocycles such as molecular squares,4 rec-
tangles,5 parallelograms,6 and rhomboids,7 as well as
those metallomacrocycles that contain the redox-active
* To whom correspondence should be addressed. Fax: 0086-22-
23504853. E-mail: lcsong@nankai.edu.cn.
Results and Discussion
(1) Vo¨gtle, F. Supramolecular Chemistry, An Introduction; Wiley:
Chichester, 1991.
(2) Lehn, J.-M. Supramolecular Chemistry; Concepts and Perspec-
tives; VCH: New York, 1995.
Synthesis and Characterization of Tetrahedral
Co2C2 Cluster-Bridged Bipyridine (4-C5H4NCO2-
CH2)2C2Co2(CO)6 (2). It was found that treatment of
(3) Cram, D. J.; Cram, J. M. Container Molecules and Their Guests;
The Royal Society of Chemistry: Cambridge, U.K., 1994.
(4) (a) Stang, P. J.; Cao D. H.; Saito, S.; Arif, A. M. J. Am. Chem.
Soc. 1995, 117, 6273. (b) Stang, P. J.; Olenyuk, B.; Fan, J.; Arif, A. M.
Organometallics 1996, 15, 904. (c) Fujita, M.; Yu, S.-Y.; Kusukawa,
T.; Funaki, H.; Ogura, K.; Yamaguchi, K. Angew. Chem., Int. Ed. 1998,
37, 2082. (d) Stang, P. J.; Cao, D. H. J. Am. Chem. Soc. 1994, 116,
4981. (e) Fujita. M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am. Chem.
Soc. 1994, 116, 1151. (f) Rauter, H.; Hillgeris, E. C.; Erxleben, A.;
Lippert, B. J. Am. Chem. Soc. 1994, 116, 616. (g) Davies, S. C.; Duhme,
A.-K.; Hughes, D. L. Inorg. Chem. 1998, 37, 5380. (h) Fujita. M.;
Yazaki, J.; Ogura, K. J. Am. Chem. Soc. 1990, 112, 5645. (i) Stang, P.
J.; Chen, K.; Arif, A. M. J. Am. Chem. Soc. 1995, 117, 8793. (j) Stang,
P. J.; Chen, K. J. Am. Chem. Soc. 1995, 117, 1667.
(6) (a) Habicher, T.; Nierengarten, J.-F.; Gramlich, V.; Diederich,
F. Angew. Chem., Int. Ed. 1998, 37, 1916. (b) Fujita, M.; Aoyagi, M.;
Ogura, K. Inorg. Chim. Acta 1996, 246, 53. (c) Hartshorn, C. M.; Steel,
P. J. Inorg. Chem. 1996, 35, 6902.
(7) Schmitz, M.; Leininger, S.; Fan, J.; Arif, A. M.; Stang, P. J.
Organometallics 1999, 18, 4817.
(8) (a) Song, L.-C.; Guo, D.-S.; Q.-M. Hu; Huang, X. Y. Organo-
metallics 2000, 19, 960. (b) Song, L.-C.; Zhu, W.-F.; Hu, Q.-M.
Organometallics 2002, 21, 5066.
(9) (a) Song, L.-C.; Fan, H.-T.; Hu, Q.-M. J. Am. Chem. Soc. 2002,
124, 4566. (b) Song, L.-C.; Fan, H.-T.; Hu, Q.-M.; Yang, Z.-Y.; Sun, Y.;
Gong F.-H. Chem. Eur. J. 2003, 9, 170. (c) Song, L.-C.; Gong, F.-H.;
Meng, T.; Ge, J.-H.; Cui, L.-N.; Hu Q.-M. Organometallics 2004, 23,
823. (d) Song, L.-C.; Guo, D.-S.; Hu, Q.-M.; Sun, J. J. Organomet. Chem.
2000, 616, 140. (d) Song, L.-C.; Guo, D.-S.; Hu, Q.-M.; Su, F.-H.; Sun,
J.; Huang, X.-Y. J. Organomet. Chem. 2001, 622, 210.
(5) (a) Jeong, K.-S.; Cho, Y. L.; Song, J. U.; Chang, H.-Y.; Choi, M.-
G. J. Am. Chem. Soc. 1998, 120, 10982. (b) Fujita, M. Chem. Soc. Rev.
1998, 27, 417. (c) Woessner, S. M.; Helms, J. B.; Shen, Y.; Sullivan, B.
P. Inorg. Chem. 1998, 37, 5406. (d) Benkstein, K. D.; Hupp, J. T.; Stern,
C. L. Inorg. Chem. 1998, 37, 5404. (e) Benkstein, K. D.; Hupp, J. T.;
Stern, C. L. J. Am. Chem. Soc. 1998, 120, 12982.
10.1021/om049175y CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/12/2005

Cationic M(II)/Co(0) (M ) Pd, Pt) Macrocycles
Organometallics, Vol. 24, No. 4, 2005 701
Table 1. Selected Bond Lengths (Å) and Angles
(deg) for 2
Scheme 1
Co(1)-C(14)
Co(1)-C(15)
Co(1)-Co(2)
Co(2)-C(14)
Co(2)-C(15)
1.944(3)
1.952(3)
2.4817(9)
1.951(2)
1.962(3)
N(1)-C(10)
N(1)-C(8)
C(12)-O(8)
C(12)-O(7)
C(14)-C(15)
1.320(4)
1.329(5)
1.200(3)
1.340(3)
1.343(3)
C(1)-Co(1)-C(14) 103.65(13) C(10)-N(1)-C(8)
C(14)-Co(1)-C(15) 40.34(10) O(8)-C(12)-O(7)
C(14)-Co(1)-Co(2) 50.53(7) O(8)-C(12)-O(9)
115.9(3)
123.9(3)
124.5(3)
C(15)-Co(1)-Co(2) 50.83(7) Co(1)-C(14)-Co(2) 79.16(10)
C(14)-Co(2)-C(15) 40.16(10) Co(1)-C(15)-Co(2) 78.71(10)
4-pyridinecarboxylic acid 2-butyne-1,4-diyl ester 1 with
Co2(CO)8 in petroleum ether at room temperature for
2-3 h resulted in formation of the tetrahedral Co2C2
cluster-bridged bipyridine 2 in 86% yield (Scheme 1).
The bridged bipyridine 2 is the first bipyridine
derivative containing a cluster core, which was fully
C(13)-C(14)-C15) 139.6(2)
C(14)-C(15)-C16) 141.2(2)
Scheme 2
1
characterized by elemental analysis, IR, H NMR, 13C
NMR, and X-ray diffraction techniques. For example,
the IR spectrum of 2 showed one absorption band at
1728 cm-1 for its ester carbonyl groups and four absorp-
tion bands in the range 2105-1993 cm-1 for its terminal
carbonyls. In addition, the 1H NMR spectrum of 2
displayed one singlet at 5.55 ppm for its CH2 groups
and two broad singlets at 9.18 and 7.95 ppm for its
pyridine rings. The structure of 2 was unequivocally
confirmed by X-ray crystallography. The ORTEP draw-
ing of 2 is shown in Figure 1, while Table 1 lists its
selected bond lengths and angles. The X-ray crystal-
lography reveald that 2 is indeed a tetrahedral Co2C2
cluster-bridged bipyridine in which the C(14)-C(15)
bond is essentially perpendicular to the Co(1)-Co(2)
bond. In addition, the carbon chain of C(13)-through-
C(16) is attached to O(7) and O(9) of the two 4-pyridine
carboxylate units, whereas the two cobalt atoms Co(1)
and Co(2) each are bound to three terminal carbonyls.
The Co(1)-Co(2) (2.4817(9) Å) and C(14)-C(15) (1.343(3)
Å) distances as well as the C(13)-C(14)-C(15) (139.6(2)°)
and C(14)-C(15)-C(16) (141.2(2)°) angles are all com-
parable with those found for other tetrahedral Co2C2
systems.10 More interestingly, this complex has been
proved to be a very efficient ligand for self-assembly of
the desired cluster-containing macrocycles (vide infra).
Synthesis and Characterization of dpab-
Chelated Pd(II) Complexes Pd(dpab)Cl2 (3) and
involves reaction of 1,4-dibromobutane with lithium
followed by treatment of the intermediate Li(CH2)4Li
with Ph2AsCl. This route has much higher yield (73%
vs 15%) than that previously reported involving reaction
of Ph3As with potassium and subsequent treatment of
the intermediate Ph2AsK with 1,4-dichlorobutane.11 In
addition, it is believed4a,b that reaction of complex 3 with
silver triflate might first give bis(triflate) complex
Pd(dpab)(OTf)2, and the monoaqua complex 4 was
produced by hydrolysis of Pd(dpab)(OTf)2 in the workup
process with 10 min stirring in open air.
Complexes 3 and 4 are new and have been character-
ized by elemental analysis and spectroscopy. For ex-
ample, the 1H NMR spectrum of 3 displayed two singlets
at 2.68 and 1.68 ppm for its R-CH2 and â-CH2 groups
in the dpab ligand, whereas the spectrum of 4 showed
two singlets at 2.55 and 2.16 ppm for its R-CH2 and
â-CH2 groups in the dpab ligand. The 19F NMR spec-
trum of 4 showed only one singlet at -78.80 ppm,
although it has one coordinated OTf and one uncoordi-
nated OTf group (see its crystal structure below). In
addition, the 1H NMR and IR spectra of 4 indicated the
presence of H2O by showing a broad singlet at 4.63 ppm
and a broad absorption band at 3201 cm-1, respectively.
The molecular structure of 4 was unambiguously
established by crystal X-ray diffraction techniques.
While Figure 2 shows its ORTEP drawing, Table 2 lists
selected bond lengths and angles. X-ray diffraction
confirmed that this molecule contains one [OTf]- anion
and one [Pd(dpab)(H2O)(OTf)]+ cation. So, it is the first
Pd(II) complex that contains one molecule of H2O and
one OTf as ligands, although numerous Pd(II) complexes
usually contain either two molecules of H2O or two OTf
ligands.4a,b The Pd(1)-As(1) distance (2.3540(10) Å) is
slightly longer than the Pd(1)-As(2) distance (2.3310(9)
Å), whereas the Pd(1)-O(1) distance (2.145(3) Å) is
2
[Pd(dpab)(H O)(OTf)][OTf] (4). We further found that
reaction of K2PdCl4 with dpab in EtOH at room tem-
perature for 12 h gave the Pd(II) dichloride complex 3
in 90% yield, whereas complex 3 reacted with silver
triflate in CH2Cl2 at room temperature for 24 h followed
by 10 min stirring in air to afford the Pd(II) monoaqua
complex 4 in 93% yield (Scheme 2).
It is worth pointing out that the starting material
dpab ligand was prepared by a new route. This route
(10) (a) Dickson, R. S.; Fraser, P. J. Adv. Organomet. Chem. 1974,
12, 323. (b) Song, L.-C.; Wang, Z.-X.; Wang, J.-T.; Yao, X.-K.; Wang,
H.-G. Sci. China (Ser. B) 1989, 32, 1281.
Figure 1. Molecular structure of 2 (thermal ellipsoids with
30% probability).
(11) Tzschach, A.; Lange, W. Ber. 1962, 95, 1360.

702 Organometallics, Vol. 24, No. 4, 2005
Song et al.
Scheme 3
of complexes 3 and 4, we also found that reaction of
(PhCN)2PtCl2 with dpab in toluene at room temparature
for 24 h afforded the Pt(II) dichloride complex 5 in 77%
yield, whereas the Pt(II) diaqua complex 6 could be
prepared by reaction of complex 5 with silver triflate in
CH2Cl2 at room temperature followed by 10 min stirring
in air (Scheme 3).
Although diphosphine-chelated Pt(II) complexes with
a general formula of diphosphine PtX2 (X ) Cl, H2O,
OTf)4a,b are known, 5 and 6 are the first such diarsine-
chelated Pt(II) complexes prepared so far. Complexes 5
and 6 are air-stable solids and have been characterized
Figure 2. Molecular structure of 4 (thermal ellipsoids with
30% probability).
Table 2. Selected Bond Lengths (Å) and Angles
(deg) for 4
1
by elemental analysis and spectroscopy. The H NMR
spectrum of 5 showed two singlets at 2.69 and 1.69 ppm
for its R-CH2 and â-CH2 groups in the dpab ligand, while
the spectrum of 6 displayed two singlets at 2.74 and 1.87
ppm for its R-CH2 and â-CH2 groups in the dpab ligand.
In addition, the IR spectrum of 6 displayed a broad band
Pd(1)-O(4)
Pd(1)-O(1)
Pd(1)-As(2)
Pd(1)-As(1)
As(1)-C(1)
2.121(3)
2.145(3)
2.3310(9)
2.3540(10)
1.930(5)
As(1)-C(13)
As(2)-C(17)
S(1)-O(1)
1.943(5)
1.930(5)
1.465(3)
1.818(6)
1.306(8)
S(1)-C(29)
F(1)-C(29)
at 3054 cm-1, indicating the presence of water. The 19
F
O(4)-Pd(1)-O(1)
91.92(13) C(1)-As(1)-C(7) 107.6(2)
113.8(2)
88.14(8)
88.97(2)
O(1)-Pd(1)-As(2) 175.26(9)
O(2)-S(1)-O(1)
NMR spectrum of 6 exhibited one singlet at -77.96 ppm
for its two uncoordinated OTf groups. This singlet is just
slightly shifted downfield compared to that caused by
the two uncoordinated OTf groups in the diphosphine-
chelated complex [Pt(dppf)(H2O)2][OTf]2.4b
O(1)-Pd(1)-As(1)
As(1)-Pd(1)-As(2)
O(1)-S(1)-C(29) 102.4(3)
S(1)-O(1)-Pd(1) 133.42(19)
C(1)-As(1)-C(13) 105.2(2)
F(1)-C(29)-S(1)
111.3(4)
O(4)-Pd(1)-As(2)
90.90(11) C(1)-As(1)-Pd(1) 109.28(14)
The structure of complex 6 was confirmed by crystal
X-ray diffraction analysis. The ORTEP diagram of 6 is
presented in Figure 3, whereas selected bond lengths
and angles are listed in Table 3. As can be seen in
Figure 3, the transition metal Pt(1) is attached to two
slightly longer than the Pd(1)-O(4) distance (2.121(3)
Å). The sum of bond angles O(4)-Pd(1)-O(1), O(4)-
Pd(1)-As(2), O(1)-Pd(1)-As(1), and As(2)-Pd(1)-As(1)
is exactly 360°, implying that Pd(1) adopts a square-
planar coordination geometry. Figure 2 also shows that
there are two types of intramolecular hydrogen bond-
ing12 in the solid state of complex 4. The first one is the
O(4)-H(1)‚‚‚O(3) hydrogen bond, which is formed be-
tween the coordinated H2O and the coordinated OTf,
whose bond length and bond angle are 2.755 Å and
175.01°. Another one is O(4)-H(2)‚‚‚O(7), which is
formed between the coordinated H2O and the uncoor-
dinated OTf, whose bond length and bond angle are
2.702 Å and 169.36°, respectively. Obviously, the higher
air and thermal stability of complex 4 compared to the
intermediate bis(triflate) complex is due to the presence
of such hydrogen bonding in monoaqua comlex 4. In fact,
the role of hydrogen bonding in the stabilization of the
solid-state structure of aqua-transition metal complexes
has long been recognized.13
Synthesis and Characterization of dpab-
Chelated Pt(II) Complexes Pt(dpab)Cl2 (5) and
[Pt(dpab)(H2O)2][OTf]2 (6). Similar to the preparation
(12) Kollman, P. A.; Allen, L. C. Chem. Rev. 1972, 72, 283.
(13) See, for example: (a) Rochon, F. D.; Melanson, R. Inorg. Chem.
1987, 26, 989. (b) Britten, J. F.; Lippert, B.; Lock, C. J. L.; Pilon, P.
Inorg. Chem. 1982, 21, 1936. (c) Hollis, L. S.; Lippard, S. J. Inorg.
Chem. 1983, 22, 2605. (d) Braga, D.; Grepioni, F. Acc. Chem. Res. 1994,
27, 51. (e) Braga, D.; Grepioni, F.; Sabatino, P.; Desiraju, G. R.
Organometallics 1994, 13, 3532.
Figure 3. Molecular structure of 6 (thermal ellipsoids with
30% probability).

Cationic M(II)/Co(0) (M ) Pd, Pt) Macrocycles
Organometallics, Vol. 24, No. 4, 2005 703
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for 6
Pt(1)-O(1)
Pt(1)-O(2)
Pt(1)-As(2)
Pt(1)-As(1)
As(1)-C(1)
2.115(6)
2.126(6)
2.3272(10)
2.3311(9)
1.911(9)
As(1)-C(7)
As(2)-C(16)
S(1)-O(6)
S(1)-C(30)
F(1)-C(30)
1.926(10)
1.935(10)
1.428(7)
1.776(14)
1.284(19)
O(2)-Pt(1)-O(1)
O(2)-Pt(1)-As(2)
O(2)-Pt(1)-As(1)
As(1)-Pt(1)-As(2)
C(1)-As(1)-C(7)
O(1)-Pt(1)-As(1)
87.1(2)
C(1)-As(1)-C(13) 107.1(5)
174.06(17) O(8)-S(1)-O(7)
92.00(17) O(7)-S(1)-C(30)
111.5(5)
104.3(8)
112.1(13)
110.6(11)
93.40(4)
106.3(4)
F(1)-C(30)-S(1)
F(3)-C(30)-S(1)
178.99(17) C(1)-As(1)-Pt(1) 112.2(3)
Figure 4. Molecular structure of cationic macrocycle of 7
(thermal ellipsoids with 30% probability).
Scheme 4
Figure 5. Molecular structure of cationic macrocycle of 8
(thermal ellipsoids with 30% probability).
Table 4. Selected Bond Lengths (Å) and Angles
(deg) for 7 and 8
molecules of water through O(1) and O(2) and one
molecule of dpab through As(1) and As(2). The Pt-As
bond lengths are 2.3311(9) and 2.3272(10) Å, whereas
the Pt-O bond lengths are 2.115(6) and 2.126(6) Å,
respectively. The bond angle around Pt(1) is exactly
360°, which means that the geometry of Pt(1) is square-
planar. This molecule contains two uncoordinated coun-
teranions [OTf]-, which interact with the cation
[Pt(dpab)(H2O)2]+ through four identical intramolecular
hydrogen bonds12 formed between the two coordinated
H2O and the two uncoordinated OTf groups (Figure 3).
The bond lengths of these hydrogen bonds are O(1)-
H(101)‚‚‚O(3) ) 2.620 Å, O(1)-H(201)‚‚‚O(7) ) 2.656 Å,
O(2)-H(102)‚‚‚O(5) ) 2.683 Å, and O(2)-H(202)‚‚‚O(8)
) 2.676 Å, whereas the bond angles of these hydrogen
bonds are equal to 145.1°, 147.7°, 150.4°, and 151.5°,
respectively. Similar to the monoaqua complex 4, diaqua
complex 6, due to having such hydrogen bonding, is
much more stable than its bis(triflate) complex.13
Synthesis and Characterization of Metal Cluster-
Containing Macrocycles {[M(dpab)]-µ-[(4-C5H4-
NCO2CH2)2C2Co2(CO)6]}2[OTf]4 (7, M ) Pd; 8, M )
Pt). More interestingly, we found that the tetrahedral
Co2C2 cluster-bridged bipyridine ligand 2 could undergo
self-assembly reaction with monoaqua Pd(II) complex
4 or diaqua Pt(II) complex 6 in dichloromethane at room
temperature to give the corresponding tetrahedral
cluster-containing metallomacrocycles 7 and 8 in 93%
and 85% yields, respectively (Scheme 4).
7
Pd(1)-As(2)
Co(1)-C(36)
As(1)-C(13)
As(2)-C(16)
O(1)-C(34)
C(36)-C(37)
2.374(2)
Pd(1)-As(1)
Pd (1)-N(1)
Co(1)-C(37)
Co(1)-Co(2)
N(1)-C(29)
O(2)-C(34)
2.387(2)
2.070(11)
1.949(14)
2.462(3)
1.325(15)
1.348(16)
1.906(13)
1.939(15)
1.939(13)
1.174(15)
1.322(16)
N(1)-Pd(1)-N(2A)
N(1)-Pd(1)-As(2)
N(1)-Pd(1)-As(1)
As(1)-Pd(1)-As(2)
C(45)-Co(1)-C(36)
87.0(4)
88.9(3)
177.5(3)
C(36)-Co(1)-Co(2)
C(36)-Co(2)-C(37)
C(37)-Co(2)-Co(1)
51.2(4)
39.4(5)
50.7(4)
93.60(7) C(33)-N(1)-C(29) 117.8(12)
98.2(8)
C(36)-Co(1)-C(37)
40.1(5)
8
Pt(1)-As(2)
Co(1)-C(14)
As(1)-C(35)
As(2)-C(38)
O(7)-C(12)
C(14)-C(15)
2.3733(18)
1.972(11)
1.916(14)
1.939(11)
1.192(15)
1.335(14)
Pt(1)-As(1)
Pt(1)-N(1)
Co(1)-C(15)
Co(1)-Co(2)
N(1)-C(7)
2.3746(17)
2.138(8)
1.961(11)
2.451(3)
1.282(13)
1.331(14)
O(8)-C(12)
N(1)-Pt(1)-N(2A)
N(1)-Pt(1)-As(2)
N(1)-Pt(1)-As(1)
As(1)-Pt(1)-As(2)
87.5(3)
88.5(2)
176.0(2)
C(14)-Co(1)-Co(2)
C(15)-Co(2)-C(14)
C(15)-Co(2)-Co(1)
50.7(3)
40.2(4)
51.4(3)
123.6(10)
39.7(4)
94.97(5) C(7)-N(1)-C(11)
C(1)-Co(1)-C(14) 139.2(6)
C(15)-Co(1)-C(14)
one strong absorption band at 1738 cm-1 for their ester
carbonyls. The presence of triflate counterions in 7 and
8 is indicated by one singlet in their 19F NMR spectra
at -78.26 and -77.11 ppm, respectively. Thus, the 19
F
NMR behavior of the triflates in 7 and 8 is very close to
that of the triflates in their precursors 4 and 6 and even
those of the diphosphine-chelated Pd(II) and Pt(II)
complexes.4a,b
Complexes 7 and 8 are air-stable solids, which have
been fully characterized by elemental analysis, spec-
troscopy, and X-ray diffraction study. The IR spectra of
7 and 8 showed three strong absorption bands in the
range 2100-2032 cm-1 for their terminal carbonyls and
Figures 4 and 5 show the ORTEP diagrams of the
cationic parts of 7 and 8, while selected bond lengths
and angles are given in Tables 4 and 5, respectively. In
fact, 7 and 8 are isostructural, and their macrocyclic

704 Organometallics, Vol. 24, No. 4, 2005
Table 5. Crystal Data and Structural Refinement Details for 2, 4, and 6
Song et al.
2
4
6
mol formula
mol wt
temp/K
C
22H12Co2N2O10
C
30H30As2F6O7PdS2
C30H32As2F6O8PtS2‚CH2Cl2
1128.53
293(2)
582.20
936.90
293(2)
293(2)
cryst syst
space group
a/Å
triclinic
P1h
monoclinic
P2(1)/n
10.113(3)
31.297(11)
11.349(4)
90
monoclinic
P2(1)/n
11.4180(13)
21.677(3)
16.1975(18)
90
92.132(2)
90
4006.2(8)
4
8.958(3)
11.630(4)
13.370(4)
64.807(5)
79.845(6)
70.453(5)
1187.0(7)
2
b/Å
c/Å
R/deg
â/deg
106.385(6)
90
γ/deg
V/Å3
3446(2)
Z
4
Dc/g‚cm-3
abs coeff/mm-1
cryst size/mm
F(000)
1.629
1.457
1.806
1.871
5.452
2.642
0.30 × 0.25 × 0.15
0.30 × 0.25 × 0.20
0.22 × 0.18 × 0.08
584
1856
2192
2θmax/deg
no. of reflns
no. of indep reflns
index ranges
50.06
50.70
50
4972
11 545
20 742
4172 (Rint ) 0.0180)
-10 e h e 9
-13 e k e 12
-11 e l e 15
ω-2θ
6263 (Rint ) 0.0400)
-10 e h e 12
-37 e k e 28
-13 e l e 7
ω-2θ
7053 (Rint ) 0.1505)
-12 e h e 13
-14 e k e 25
-17 e l e 19
ω-2θ
scan type
no. of data/restraints/params
4172/0/325
0.930
0.0322
0.0693
0.320/-0.316
6263/3/441
0.969
0.0435
0.0756
0.681/-0.584
7053/6/473
0.937
0.0584
0.1372
3.831/-2.826
goodness of fit on F2
R
Rw
largest diff peak and hole/e Å-3
cations each contain two dpab-chelated transition metal
Pd or Pt moieties that are held together by two
molecules of the tetrahedral Co2C2 cluster-bridged bi-
pyridine ligands. The coordination geometry around
Pd(1)/Pd(1A) or Pt(1)/Pt(1A) metal centers is normal
square-planar with slight deviations of the bond angles.
All Pd-As or Pt-As distances are normal within the
range 2.374-2.387 or 2.373-2.375 Å, respectively.
Likewise, the Pd-N and Pt-N distances are normal
with the region 2.070-2.092 Å or 2.126-2.138 Å,
whereas the N-Pd-N and N-Pt-N angles are 87.0(4)°
or 87.5(3)°, respectively. In fact, the geometric param-
eters of 7 and 8 are comparable with those for other
Pd(II) and Pt(II) macrocycles containing bidentate N
ligands.4a,7 The additional important geometric features
for 7 and 8 are that (i) both molecules are centrosym-
metric, (ii) the two pyridinde rings in each bipyridine
ligand 2 of 7 or 8 are cis to the Co2(CO)6 moiety of the
tetrahedral Co2C2 cluster unit, (iii) the four pyridine
rings and the Co(1)-Co(2)-Co(1A)-Co(2A) plane in 7
and 8 are nearly perpendicular to the plane defined by
the six atoms Pd(1), C(36), C(37), Pd(1A), C(36A), and
C(37A) in 7 or the six atoms Pt(1), C(14), C(15), Pt(1A),
C(14A), and C(15A) in 8 respectively, and (iv) the two
Pd or two Pt atoms and the four Co atoms in 7 and 8
are located at six apical positions of an octahedron. It
follows that the structures of 7 and 8, in contrast to
those metallomacycles without cluster-bridged N donor
ligands,4-7 are unique and unprecedented.
Co2C2 cluster cores and represent a unique and inter-
esting class of metallomacrocycles. Further studies on
the possible new properties caused by the Co2C2 cluster
cores10a in 7 and 8 and the self-assembly reactions of
either bipyridine ligand 2 with other metal complexes
or complexes 4 and 6 with other cluster-bridged bi-
pyridine ligands are in progress in this laboratory.
Experimental Section
General Comments. All reactions were carried out under
highly purified nitrogen atmosphere using standard Schlenk
or vacuum-line techniques. Solvents for preparative use were
dried and distilled under nitrogen from CaH2 or sodium/
benzophenone ketyl prior to use. All solvents were bubbled
for at least 15 min before use. 1,4-Dibromobutane, K2PdCl4,
silver triflate, and Co2(CO)8 were of commercial origin and
used as received. 4-Pyridinecarboxylic acid 2-butyne-1,4-diyl
ester,14 Ph2AsCl,15 and (PhCN)2PtCl216 were prepared accord-
1
ing to literature methods. H NMR spectra were recorded on
a Bruker AC-P 200 or a Bruker 300M NMR spectrometer, and
chemical shifts are reported in ppm relative to internal Me4Si
(δ ) 0). 19F NMR spectra were measured on a Bruker 300M
spectrometer, and chemical shifts are referenced relative to
external CF3CO2D (δ ) 0). IR spectra were taken on a Bio-
Rad FTS 135 spectrophotometer. Elemental analysis was
performed on an Elementar Vario EL analyzer, and melting
points were determined on a Yanaco MP-500 melting point
apparatus.
Improved Preparation of Ph2As(CH2)4AsPh2 (dpab).11
A Schlenk flask was charged with 0.1 g (14.4 mmol) of lithium
and 20 mL of diethyl ether. Under stirring, the mixture was
cooled to -40 °C and then a solution of 0.41 mL (3.5 mmol) of
1,4-dibromobutane in 20 mL of diethyl ether was slowly added.
Conclusions
We have first synthesized and characterized the
tetrahedral Co2C2 cluster-bridged bipyridine ligand 2
and the diarsine dpab-chelated Pd(II)/Pt(II) complexes
3-6. Study on self-assembly of ligand 2 with complex 4
or 6 has allowed us to obtain two metallomacrocyclic
compounds 7 and 8, which contain the corresponding
(14) (a) Moser, U.; Gubitz, C.; Galvan, M.; Immel-Sehr, A.; Lam-
brecht, G.; Mutschler, E. Arzneim.-Forsch. 1995, 45, 449. (b) Badgett,
C. O.; Woodward, C. F. J. Am. Chem. Soc. 1947, 69, 2907.
(15) Barker, R. L.; Booth, E.; Jones, W. E.; Woodward, F. N. J. Soc.
Chem. Ind. 1949, 68, 277.
(16) Uchiyama, T.; Toshiyasu, Y.; Nakamura, Y.; Miwa, T.; Kawagu-
chi, S. Bull. Chem. Soc. Jpn. 1981, 54, 181.

Cationic M(II)/Co(0) (M ) Pd, Pt) Macrocycles
Organometallics, Vol. 24, No. 4, 2005 705
Table 6. Crystal Data and Structural Refinement Details for 7 and 8
7
8
mol formula
mol wt
C
104H80As4Co4F12N4O32Pd2S4
C
104H80As4Co4F12N4O32Pt2S4‚8.5H2O
3002.16
3338.68
temp/K
293(2)
293(2)
cryst syst
space group
a/Å
triclinic
triclinic
P1h
P1h
13.696(8)
14.648(8)
17.666(11)
77.777(11)
76.557(11)
73.831(12)
3269(3)
13.667(9)
17.272(11)
18.060(12)
92.019(12)
101.885(11)
104.029(11)
4031(5)
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
1
1
Dc/g‚cm-3
abs coeff/mm-1
cryst size/mm
F(000)
1.523
1.373
1.919
3.074
0.16 × 0.14 × 0.08
0.38 × 0.34 × 0.18
1492
1641
2θmax/deg
no. of reflns
no. of indep reflns
index ranges
50.02
52.82
16 932
23 261
11 379 (Rint ) 0.1011)
-16 e h e 15
-13 e k e 17
-21 e l e 21
ω-2θ
16 267 (Rint ) 0.0452)
-17 e h e 16
-20 e k e 21
-18 e l e 22
ω-2θ
scan type
no. of data/restraints/params
11 379/67/736
1.000
0.0949
0.1608
0.968/-0.604
16 267/147/828
1.041
0.0689
0.2004
1.349/-1.738
goodness of fit on F2
R
Rw
largest diff peak and hole/e Å-3
After the new mixture was warmed to room temperature and
stirred for 18 h, it was filtered to give a filtrate containing
1,4-dilithiumbutane.17 The filtrate was cooled to -20 °C, and
then 1 mL (5.57 mmol) of Ph2AsCl was added. The new
mixture was warmed to room temperature and stirred at this
temperature for 12 h. To this mixture was added 10 mL of
water, and the resulting mixture was stirred for an additional
0.5 h. The organic layer was separated, washed twice with
water, and dried over anhydrous MgSO4. After removal of
MgSO4 and solvent, the residue was recrystallized from diethyl
ether to give 1.32 g (73%) of dpab as a white solid.
Preparation of (4-C5H4NCO2CH2)2C2Co2(CO)6 (2). A
Schlenk flask was charged with 0.445 g (1.5 mmol) of 4-
pyridinecarboxylic acid 2-butyne-1,4-diyl ester and 30 mL of
petroleum ether. While stirring, a solution of 0.514 g (1.5
mmol) of Co2(CO)8 in 15 mL of petroleum ether was slowly
added. The mixture was stirred at room temperature for an
additional 2-3 h until no CO evolution was observed. Solvent
was removed under reduced pressure, and the residue was
subjected to column chromatography (alkali Al2O3) using
CHCl3 as eluent. The crude product obtained from the eluted
red band was recrystallized from CH2Cl2/petroleum ether to
give 0.747 g (86%) of 2 as a red solid. Mp: 130 °C dec. Anal.
Calcd for C22H12Co2N2O10: C, 45.39; H, 2.08; N, 4.81. Found:
C, 45.29; H, 1.93; N, 5.04. IR (KBr disk): νC≡O 2105 (s), 2066
(s), 2026 (vs), 1993 (s); νCdO 1728 (s) cm-1. 1H NMR (200 MHz,
CDCl3): δ 9.18 (br s, 4H, 4HR), 7.95 (br s, 4H, 4Hâ), 5.55 (s,
4H, 2CH2). 13C NMR (50.3 MHz, CDCl3): δ 197.66 (CtO),
164.43 (CO2), 142.53 (CR), 135.67 (Cγ), 132.92 (Câ), 87.67 (CCo),
65.29 (CH2).
2851 (w), 1578 (m), 1483 (s), 1436 (vs) 1308 (m), 1082 (s), 893
(s), 736 (vs) 692 (vs), 561 (m) cm-1. 1H NMR (300 MHz, DMSO-
d6): δ 7.75, 7.51 (2 br s, 20H, 4C6H5), 2.68 (s, 4H, 2CH2As),
1.68 (s, 4H, 2CH2).
Preparation of [Pd(dpab)(H2O)(OTf)][OTf] (4). To a
suspension of 0.126 g (0.18 mmol) of Pd(dpab)Cl2 in 35 mL of
CH2Cl2 was added 0.138 g (0.54 mmol) of AgOTf, and then
the mixture was stirred at room temperature for 24 h with
the exclusion of light. The resulting mixture was filtered to
give a filtrate, which was stirred in air for 10 min and then
was reduced to ca. 2 mL at reduced pressure. Diethyl ether
was added to give a precipitate, which was washed with diethyl
ether and dried in a vacuum to give 0.053 g (93%) of 4 as a
yellow solid. Mp: 196-198 °C dec. Anal. Calcd for C30H30-
As2F6O7PdS2: C, 38.46; H, 3.23. Found: C, 38.98; H, 3.10. IR
(KBr disk): νOH 3201 (m); νOTf 1288 (vs), 1237 (vs), 1162 (s),
1
1030 (vs) cm-1. H NMR (200 MHz, CDCl3): δ 7.58-7.41 (m,
20H, 4C6H5), 4.63 (br s, 2H, H2O), 2.55 (s, 4H, 2CH2As), 2.16
(s, 4H, 2CH2). 19F NMR (282 MHz, CDCl3): δ -78.80 (s,
SO3CF3).
Preparation of Pt(dpab)Cl2 (5). A mixture of 0.32 g (0.678
mmol) of (PhCN)2PtCl2, 0.348 g (0.678 mmol) of dpab, and 16
mL of toluene was stirred at room temperature for 24 h to
give a white precipitate. The precipitate was washed succes-
sively with toluene and diethyl ether and then dried in a
vacuum to afford 0.406 g (77%) of 5 as a white powder. Mp:
300 °C (dec). Anal. Calcd for C28H28As2Cl2Pt: C, 43.10; H, 3.62.
Found: C, 43.22; H, 3.61. IR (KBr disk): 3054 (m), 2919 (m),
2853 (w), 2036 (w), 1984 (m), 1578 (m), 1483 (s), 1436 (vs) 1309
(m), 1082 (s), 894 (s), 738 (vs), 692 (vs), 471 (vs) cm-1. 1H NMR
(300 MHz, DMSO-d6): δ 7.74, 7.52 (2 br s, 20H, 4C6H5), 2.69
(s, 4H, 2CH2As), 1.69 (s, 4H, 2CH2).
Preparation of Pd(dpab)Cl2 (3). A Schlenk flask was
charged with 0.204 g (0.63 mmol) of K2PdCl4, 0.308 g (0.60
mmol) of dpab, and 16 mL of anhydrous ethyl alcohol. The
mixture was stirred for 1 h at room temperature to give a
yellowish precipitate. The precipitate was sequentially washed
with water, ethyl alcohol, and diethyl ether and finally dried
in a vacuum to give 0.374 g (90%) of 3 as a light yellow solid.
Mp >300 °C. Anal. Calcd for C28H28As2Cl2Pd: C, 48.62; H, 4.08.
Found: C, 48.66; H, 3.95. IR (KBr disk): 3055 (m), 2920 (m),
Preparation of [Pt(dpab)(H2O)2][OTf]2 (6). By a proce-
dure similar to that described in the preparation of 4, 0.191 g
(88%) of 6 as a white solid was obtained from 0.166 g (0.213
mmol) of Pt (dpab)Cl2, 0.137 g (0.532 mmol) of AgOTf, and 20
mL of CH2Cl2. Mp: 178-180 °C. Anal. Calcd for C30H32-
As2F6O8PtS2: C, 34.53; H, 3.09. Found: C, 34.56; H, 3.25. IR
(KBr disk): νOH 3054 (m); νOTf 1253 (vs), 1170 (vs), 1031 (vs)
1
(17) West, R.; Rochow, E. G. J. Org. Chem. 1953, 18, 1739.
cm-1. H NMR (300 MHz, DMSO-d6): δ 7.57-7.78 (m, 20H,

706 Organometallics, Vol. 24, No. 4, 2005
Song et al.
4C6H5), 2.74 (s, 4H, 2CH2As), 1.87 (s, 4H, 2CH2). 19F NMR (282
MHz, acetone-d6): δ -77.96 (s, SO3CF3).
at room temperature, respectively. While the single crystals
of 7 were grown by slow diffusion of diethyl ether into its
nitromethane solution containing several drops of glacial acetic
acid at room temperature, those of 8 were produced by slow
diffusion reaction of an acetone solution of ligand 2 into a
dichloromethane solution of complex 6 under nitrogen at room
temperature. However, since the single crystals of 8 are highly
effloresent even under nitrogen, they must be sealed with great
care in a capillary immediately after being taken out from the
crystal-growing solvent system. Each crystal suitable for X-ray
diffraction analysis was mounted on a Bruker SMART 1000
automated diffractometer. Data were collected at 293(2) K
using Mo KR graphite-monochromated radiation (λ ) 0.71073
Å) in the ω scanning mode. Absorption corrections were
performed using SADABS. The structures were solved by
direct methods using the SHELXTL-97 program. The final
refinements were accomplished by the full-matrix least-
squares method with anisotropic thermal parameters for non-
hydrogen atoms. All hydrogen atoms were located by using
the geometric method. Details of the crystal data, data
collections, and structure refinements are summarized in
Tables 5 and 6, respectively.
Preparation of {[Pd(dpab)]-µ-[(4-C5H4NCO2CH2)2C2Co2-
(CO)6]}2[OTf]4 (7). A Schlenk flask was charged with 0.058
g (0.062 mmol) of [Pd(dpab)(H2O)(OTf)][OTf], 0.056 g (0.062
mmol) of (4-C5H4NCO2CH2)2C2Co2(CO)6, and 20 mL of CH2Cl2.
The mixture was stirred at room temperature for 24 h to
produce a red precipitate. The precipitate was washed with
CH2Cl2 and recrystallized from a mixture of CH3CN and
diethyl ether to give 0.085 g (92%) of 7 as a red solid. Mp:
165 °C dec. Anal. Calcd for C104H80As4Co4F12N4O32Pd2S4: C,
41.60; H, 2.69; N, 1.87. Found: C, 41.25; H, 3.11, N, 2.13. IR
(KBr disk): νC≡O 2099 (s), 2063 (vs), 2036 (vs); νCdO 1738 (s);
1
νOTf 1275 (vs), 1223 (s), 1159 (s), 1029 (s) cm-1. H NMR (200
MHz, CDCl3): δ 7.64-7.38 (m, 56H, 8C6H5, 4C5H4N), 5.28 (s,
8H, 4CH2O), 2.38 (s, 8H, 4CH2As), 1.97 (s, 8H, 4CH2). 19F NMR
(282 MHz, acetone-d6): δ -78.26 (s, SO3CF3).
Preparation of {[Pt(dpab)]-µ-[(4-C5H4NCO2CH2)2C2Co2-
(CO)6]}2[OTf]4 (8). In a manner similar to that described for
the preparation of 7, 0.092 g (85%) of 8 as a red solid was
prepared from 0.07 g (0.068 mmol) of [Pt(dpab)(H2O)2][OTf]2
and 0.04 g (0.068 mmol) of (4-C5H4NCO2CH2)2C2Co2(CO)6.
Mp: 140 °C dec. Anal. Calcd for C104H80As4Co4F12N4O32Pt2S4:
C, 39.29; H, 2.54; N, 1.76. Found: C, 39.30; H, 2.47; N, 1.76.
IR (KBr, disk): νC≡O 2100 (s), 2063 (vs), 2032 (vs); νCdO 1738
Acknowledgment. We are grateful to the National
Natural Science Foundation of China and the Research
Fund for the Doctoral Program of Higher Education of
China for financial support.
(s); νOTf 1279 (s), 1225 (s), 1158 (s), 1030 (s) cm-1 1H NMR
.
(300 MHz, DMSO-d6): δ 9.02 (d, J ) 5.70 Hz, 8H, 8HR), 7.73
(d, J ) 5.70 Hz, 8H, 8Hâ), 7.74-7.43 (m, 40H, 8C6H5), 5.62 (s,
8H, 4CH2O), 3.06 (s, 8H, 4CH2As), 1.87 (s, 8H, 4CH2). 19F NMR
(282 MHz, DMSO-d6): δ -77.11 (s, SO3CF3).
X-ray Structure Determinations of 2, 4, 6, 7, and 8.
X-ray quality single crystals of 2 were grown by slow evapora-
tion of its dichloromethane/petroleum ether solution at 4 °C,
whereas those of 4 and 6 were obtained by slow diffusion of
diethyl ether or hexane into their dichloromethane solutions
Supporting Information Available: All crystal data,
atomic coordinates, thermal parameters, and bond lengths and
angles for 2, 4, 6, 7, and 8 as CIF files. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049175Y