106 J. Am. Chem. Soc., Vol. 120, No. 1, 1998
He and Lippard
material 1. X-ray quality pink crystals of [Co
OH) (H O)1.625]‚2.5MeOH‚0.5Et O were obtained by recrystallization
from diethyl ether/methanol (6:1) at room temperature. FTIR (KBr
2
(µ-XDK)(NO
3 2 3
) (CH -
3
2
2
-
1
cm ): 3480 (br), 3400 (br), 2922 (s), 2852 (s), 1716 (m), 1682 (s),
643 (s), 1615 (m), 1377 (m), 1366 (m), 1284 (m), 1199 (m), 1021
s), 959 (m), 851 (m), 765 (m). Anal. Calcd for C34 : C,
1
(
48 4 2
H N O17Co
4
5.24; H, 5.36; N, 6.21. Found: C, 44.85; H, 5.10; N, 6.34.
Co (µ-OH)(µ-XDK)(bpy) (EtOH)](NO ) (2). A portion of 2,2′-
bipyridine (33 mg, 0.210 mmol) was added to a solution of 1 (100 mg,
.110 mmol) in methylene chloride (15 mL)/ethanol (10 mL). The
[
2
2
3
0
Figure 1. Schematic representation of H
2
XDK.
solution, which changed color from pink to yellow-brown, was stirred
at room temperature for 30 min. To this solution was added 46 µL of
-
1
a methanolic solution of (Me
0
4
N)OH (25 wt %, d ) 0.866 g mL ,
In the present work, we describe the synthesis and charac-
terization of the hydroxo- and bis(carboxylato)-bridged dinuclear
model compound [Co2(µ-OH)(µ-XDK)(bpy)2(EtOH)](NO3) (2),
.110 mmol) and the color turned brown-pink. After 1 h of stirring at
room temperature, the solution was concentrated to dryness by rotary
evaporation. The residue was extracted with 10 mL of methylene
chloride, and the insoluble inorganic salts were filtered off. The filtrate
was concentrated to dryness and redissolved in 1 mL of ethanol. Vapor
diffusion of diethyl ether into this ethanol solution gave brown, block-
(µ-OH)(µ-XDK)(bpy) (EtOH)](NO )‚2EtOH
2 3
suitable for X-ray crystallography, which were collected and washed
with diethyl ether. Drying under vacuum overnight yielded 40 mg (34%
where H2XDK ) m-xylylenediamine bis(Kemp’s triacid imide)
9,20
(
see Figure 1) and bpy ) 2,2′-bipyridine.1
The XDK ligand
has been extensively employed in our laboratory to stabilize
carboxylate-bridged dimetallic centers.2
1-27
The syntheses of
shaped crystals of [Co
2
other dinuclear Co(II) complexes [Co2(µ-XDK)(NO3)2(CH3-
OH)2(H2O)] (1), [Co2(µ-Cl)(µ-XDK)(bpy)2(EtOH)2](NO3) (3),
and [Co2(µ-XDK)(py)3(NO3)2] (4) are also reported. Compound
-1
based on 1) of product. FTIR (KBr, cm ): 3520 (br), 2970 (m), 2929
(m), 1739 (m), 1685 (s), 1600 (s), 1360 (m), 1196 (s), 959 (m), 852
2
effects the hydrolysis of aminoguanidinium ion to urea and
-
1
-1
(
5
5
m), 737 (m). UV-vis (EtOH) [λmax (ꢀ, M cm )]: 470 nm (59),
hydrazine under conditions where free hydroxide ion is inactive.
The substrate is catalytically hydrolyzed by [Co(XDK)(bpy)-
02 nm (68), 800 nm (br, ∼3). Anal. Calcd for C54
7.20; H, 5.42; N, 8.65. Found: C, 56.74; H, 5.01; N, 8.86.
Co (µ-Cl)(µ-XDK)(bpy) (EtOH) ](NO ) (3). To a solution of 1
75 mg, 0.083 mmol) in methanol (5 mL)/methylene chloride (5 mL)
were added 2,2′-bipyridine (28 mg, 0.181 mmol) and (Et N)Cl (13.6
61 7 2
H N O13Co : C,
(H2O)] (5), [Co(CH3COO)2], or [Cu(CH3COO)2] with bpy but
[
2
2
2
3
not by [Zn(XDK)(bpy)(H2O)] (6), [Zn(CH3COO)2], [Ni(CH3-
COO)2], or [Mn(CH3COO)2] with bpy in basic 1:1 methanol/
water solutions. The mechanisms of the hydrolysis reactions
are discussed.
(
4
mg, 0.083 mmol). The reaction mixture was stirred for 30 min at room
temperature, then the solution was concentrated to dryness by rotary
evaporation. The residue was redissolved in 1 mL of ethanol, and vapor
diffusion of diethyl ether into this solution yielded X-ray quality pink
Experimental Section
blocks of [Co
2
(µ-Cl)(µ-XDK)(bpy)
2 2 3
(EtOH) ](NO )‚3EtOH, which were
General Procedures and Methods. All reagents were obtained
from commercial suppliers and used without further purification unless
otherwise noted. The reaction of aminoguanidinium nitrate with [Mn-
collected, washed with diethyl ether, and air-dried (50 mg, 47% based
-
1
on 1). FTIR (Nujol, cm ): 3063 (br), 2962 (m), 2930 (m), 2879 (m),
726 (m), 1692 (s), 1600 (s), 1560 (m), 1507 (m), 1358 (m), 1185
(m), 1022 (m), 982 (m), 957 (m), 887 (m), 851 (m), 762 (m), 736 (m).
Anal. Calcd for 3‚EtOH‚2H 16ClCo : C, 54.40; H, 5.98;
N, 7.66. Found: C, 54.65; H, 5.86; N, 7.84.
[Co (µ-XDK)(py) (NO ) ] (4). A portion of Co(NO ) ‚6H O (131
1
(
3 2
CH COO) ] and bpy was carried out under an inert atmosphere by
1
using standard Schlenk techniques. H NMR spectra were taken on a
Varian XL-300 spectrometer. Fourier-transform infrared spectra were
2
O, C58
76 7
H N O
2
recorded on a Bio-Rad FTS135 instrument. The compounds H
2
XDK,
Zn(XDK)‚H O, and Na (XDK)‚4H O were prepared as previously
2
2
2
2
3
3
2
3
2
2
2
0,24,25
described.
Co (µ-XDK)(NO
O (130 mg, 0.447 mmol) was added to a solution of Na
O (150 mg, 0.215 mmol) in methanol (10 mL). The color of the
mg, 0.450 mmol) was added to a solution of Na (XDK)‚4H O (150
2
2
[
2
3 2
) (CH
3
OH)
2
(H
2
O)] (1). A portion of Co(NO
3
)
2
‚-
mg, 0.215 mmol) in methanol (15 mL). The color of the solution
changed from colorless to purple, and the reaction solution was stirred
at room temperature for 30 min. A portion of pyridine (1 mL) was
added, and the solution was stirred for another 30 min. The solvent
was removed by rotary evaporation, and the residue was extracted with
methylene chloride (5 mL). The insoluble inorganic salts were filtered
off, and the filtrate was concentrated to dryness. The residue was
crystallized from MeOH (1 mL)/Et O (5 mL)/hexane (0.5 mL) at -20
°C to afford purple needles which were collected, washed with diethyl
ether, and dried under vacuum overnight (200 mg, 88% based on XDK).
6
4
H
2
2
(XDK)‚
H
2
solution changed from colorless to pink, and the reaction solution was
stirred at room temperature for 1 h. The solvent was removed by a
rotary evaporator, and the residue was redissolved in 1 mL of methanol.
White inorganic salts were precipitated by addition of 5 mL of diethyl
ether to this solution. The precipitates were filtered off, and the filtrate
was concentrated to dryness by rotary evaporation. Recrystallization
from diethyl ether/methanol (6:1) at -20 °C overnight yielded pink
plates which were collected and washed with diethyl ether. The product
rapidly turned into a purple powder upon drying in air. Drying under
vacuum overnight yielded 130 mg (68% based on XDK) of the purple
2
Recrystallization of 5 from MeOH/Et O/hexane at room temperature
2
gave block-shaped crystals of [Co (µ-XDK)(py) (NO ) ]‚MeOH‚0.5Et O
2
3
3 2
2
suitable for X-ray crystallography. FTIR (KBr, cm-1): 3400 (br), 2971
(
(
s), 2930 (m), 1739 (m), 1680 (s), 1603 (s), 1500 (s), 1363 (m), 1294
m), 1195 (s), 1204 (m), 959 (m), 851 (m), 764 (m), 701 (m). Anal.
(
19) Kemp, D. S.; Petrakis, K. S. J. Org. Chem. 1981, 46, 5140-5143.
(20) Rebek, J., Jr.; Marshall, L.; Wolak, R.; Parris, K.; Killoran, M.;
Calcd for 4‚MeOH, C48
Found: C, 52.71; H, 5.19; N, 8.96.
Co(XDK)(bpy)(H O)] (5). To a solution of Na
mg, 0.287 mmol) in methanol (10 mL)/methylene chloride (5 mL) were
added Co(NO ‚6H O (100 mg, 0.344 mmol) and 2,2′-bipyridine (67
mg, 0.431 mmol). This reaction mixture was stirred at room temper-
ature for 30 min. The solvent was removed by rotary evaporation,
and the orange-pink residue was dissolved in methylene chloride (15
mL). The insoluble inorganic salts were filtered off, and the filtrate
was washed with 4 × 20 mL portions of water. The organic layer
was collected, dried with anhydrous sodium sulfite, and then concen-
trated to dryness and washed with diethyl ether. Drying under vacuum
57 7 2
H N O15Co : C, 52.90; H, 5.27; N, 9.00.
Askew, B.; Nemeth, D.; Islam, N. J. Am. Chem. Soc. 1985, 107, 7476-
481.
21) Goldberg, D. P.; Watton, S. P.; Masschelein, A.; Wimmer, L.;
Lippard, S. J. J. Am. Chem. Soc. 1993, 115, 5346-5347.
22) Watton, S. P.; Masschelein, A.; Rebek, J., Jr.; Lippard, S. J. J. Am.
Chem. Soc. 1994, 116, 5196-5205.
23) Yun, J. W.; Tanase, T.; Pence, L. E.; Lippard, S. J. J. Am. Chem.
Soc. 1995, 117, 4407-4408.
24) Tanase, T.; Yun, J. W.; Lippard, S. J. Inorg. Chem. 1995, 34, 4220-
229.
7
(
[
2
2
2
XDK‚4H O (200
(
)
3 2
2
(
(
4
3
(
25) Tanase, T.; Lippard, S. J. Inorg. Chem. 1995, 34, 4682-4690.
(
26) Tanase, T.; Yun, J. W.; Lippard, S. J. Inorg. Chem. 1996, 35, 3585-
594.
27) Herold, S.; Lippard, S. J. J. Am. Chem. Soc. 1997, 119, 145-156.
(