Dinuclear copper(II) complexes with {Cu2(μ-hydroxo)bis(μ-carboxylato)}+ cores and their reactions with sugar phosphate esters: A substrate binding model of fructose-1,6-bisphosphatase

Article abstract of DOI:10.1021/ic051942d

Reactions of CuX₂·nH₂O with the biscarboxylate ligand XDK (H₂XDK = m-xylenediamine bis(Kemp's triacid imide)) in the presence of N-donor auxiliary ligands yielded a series of dicopper(II) complexes, [Cu₂(μ-OH)(XDK)(L)₂]X (L = N,N,N′,N′-tetramethylethylenediamine (tetmen), X = NO₃ (1a), Cl (1b); L = N,N,N′-trimethylethylenediamine (tmen), X = NO₃ (2a), Cl (2b); L =2,2′-bipyridine (bpy), X = NO₃ (3); L = 1,10-phenanthroline (phen), X = NO₃ (4); L = 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy), X = NO₃ (5); L = 4-methyl-1,10-phenanthroline (Mephen), X = NO₃ (6)). Complexes 1-6 were characterized by X-ray crystallography (Cu...Cu = 3.1624(6)-3.2910(4) A), and the electrochemical and magnetic properties were also examined. Complexes 3 and 4 readily reacted with diphenyl phosphoric acid (HDPP) or bis(4-nitrophenyl) phosphoric acid (HBNPP) to give [Cu₂(μ-phosphate)(XDK)(L)₂]NO₃ (L = bpy, phosphate = DPP (11); L = phen, phosphate = DPP (12), BNPP (13)), where the phsophate diester bridges the two copper ions in a μ-1,3-O,O′ bidentate fashion (Cu...Cu = 4.268(3)-4.315(1) A). Complexes 4 and 6 with phen and Mephen have proven to be good precursors to accommodate a series of sugar monophosphate esters (Sugar-P) onto the biscarboxylate-bridged dicopper centers, yielding [Cu₂(μ-Sugar-P)(XDK)(L)₂] (Sugar-P = α-D-Glc-1-P (23a and b), D-Glc-6-P (24a and b), D-Man-6-P (25a), D-Fru-6-P (26a and b); L = phen (a), Mephen (b)) and [Cu₂(μ-Gly-n-P)(XDK)(Mephen)₂] (Gly-n-P = glycerol n-phosphate; n = 2 (21), 3 (22)), where Glc, Man, and Fru are glucose, mannose, and fructose, respectively. The structure of [Cu₂(μ-MNPP)(XDK)(phen)₂(CH₃OH)] (20) was characterized as a reference compound (H₂MNPP = 4-nitrophenyl phosphoric acid). Complexes 4 and 6 also reacted with D-fructose 1,6-bisphosphate (D-Fru-1,6-P₂) to afford the tetranuclear copper(II) complexes formulated as [Cu₄(μ-D-Fru-1,6-P₂)(XDK)₂(L)₄] (L = phen (27a), Mephen (27b)). The detailed structure of 27a was determined by X-ray crystallography to involve two different tetranuclear complexes with α- and β-anomers of D-Fru-1,6-P₂, [Cu₄(μ-α-D-Fru-1,6-P₂)(XDK) ₂(phen)₄] and [Cu₄(μ-β-D-Fru-1,6-P₂)(XDK)₂(phen) ₄], in which the D-Fru-1,6-P₂ tetravalent anion bridges the two [Cu₂(XDK)(phen)₂]²⁺ units through the C1 and C6 phosphate groups in a μ-1,3-O,O′ bidentate fashion (Cu...Cu = 4.042(2)-4.100(2) A). Notably, the structure with α-D-Fru-1,6-P₂ demonstrated the presence of a strong hydrogen bond between the C2 hydroxyl group and the C1 phosphate oxygen atom, which may support the previously proposed catalytic mechanism in the active site of fructose-1,6-bisphosphatase.

Full text of DOI:10.1021/ic051942d

Inorg. Chem. 2006, 45, 2925−2941
Dinuclear Copper(II) Complexes with
+
{
Cu2(µ-hydroxo)bis(µ-carboxylato)} Cores and Their Reactions with
Sugar Phosphate Esters: A Substrate Binding Model of
Fructose-1,6-bisphosphatase
Merii Kato,† Tomoaki Tanase,*,† and Masahiro Mikuriya‡
Department of Chemistry, Faculty of Science, Nara Women’s UniVersity, Kitauoya-higashi-machi,
Nara 630-8285, Japan, and Department of Chemistry, School of Science and Technology,
Kwansei Gakuin UniVersity, 2-1 Gakuen, Sanda-shi, Hyogo 669-1337, Japan
Received November 10, 2005
Reactions of CuX2‚nH2O with the biscarboxylate ligand XDK (H2XDK
)
m-xylenediamine bis(Kemp’s triacid imide))
-OH)(XDK)(L)2]X
-trimethylethylenediamine
1,10-phenanthroline (phen), X NO3
4-methyl-1,10-phenanthroline (Mephen), X
6 were characterized by X-ray crystallography (Cu‚‚‚Cu 3.1624(6) 3.2910(4) Å), and
the electrochemical and magnetic properties were also examined. Complexes 3 and 4 readily reacted with diphenyl
phosphoric acid (HDPP) or bis(4-nitrophenyl) phosphoric acid (HBNPP) to give [Cu2( -phosphate)(XDK)(L)2]NO3
(L bpy, phosphate DPP (11); L phen, phosphate DPP (12), BNPP (13)), where the phsophate diester
bridges the two copper ions in a -1,3-O,O bidentate fashion (Cu‚‚‚Cu 4.268(3) 4.315(1) Å). Complexes 4 and
6 with phen and Mephen have proven to be good precursors to accommodate a series of sugar monophosphate
esters (Sugar-P) onto the biscarboxylate-bridged dicopper centers, yielding [Cu2( -Sugar-P)(XDK)(L)2] (Sugar-P
-D-Glc-1-P (23a and b), D-Glc-6-P (24a and b), D-Man-6-P (25a), D-Fru-6-P (26a and b); L phen (a), Mephen
(b)) and [Cu2( -Gly-n-P)(XDK)(Mephen)2] (Gly-n-P glycerol n-phosphate; n 2 (21), 3 (22)), where Glc, Man,
and Fru are glucose, mannose, and fructose, respectively. The structure of [Cu2( -MNPP)(XDK)(phen)2(CH3OH)]
(20) was characterized as a reference compound (H2MNPP 4-nitrophenyl phosphoric acid). Complexes 4 and
6 also reacted with -fructose 1,6-bisphosphate (D-Fru-1,6-P2) to afford the tetranuclear copper(II) complexes
formulated as [Cu4( -D-Fru-1,6-P2)(XDK)2(L)4] (L phen (27a), Mephen (27b)). The detailed structure of 27a was
determined by X-ray crystallography to involve two different tetranuclear complexes with - and -anomers of
-D-Fru-1,6-P2)(XDK)2(phen)4], in which the D-Fru-
in the presence of N-donor auxiliary ligands yielded a series of dicopper(II) complexes, [Cu2(
µ
(L
(tmen), X
(4); L
)
N,N,N
′
,N
NO3 (2a), Cl (2b); L
-dimethyl-2,2 -bipyridine (Me2bpy), X
′
-tetramethylethylenediamine (tetmen), X
2,2 -bipyridine (bpy), X
NO3 (5); L
)
NO3 (1a), Cl (1b); L
) N,N,N′
)
)
′
)
NO3 (3); L
)
)
)
4,4
′
′
)
)
)
NO3 (6)). Complexes 1
−
)
−
µ
)
)
)
)
µ
′
)
−
µ
)
R
)
µ
)
)
µ
)
D
µ
)
R
â
D-Fru-1,6-P2, [Cu4(
µ
-
R
-D-Fru-1,6-P2)(XDK)2(phen)4] and [Cu4(
µ-â
+
1,6-P2 tetravalent anion bridges the two [Cu2(XDK)(phen)2]2 units through the C1 and C6 phosphate groups in a
µ-1,3-O,O′ bidentate fashion (Cu‚‚‚Cu ) 4.042(2)−4.100(2) Å). Notably, the structure with R-D-Fru-1,6-P2
demonstrated the presence of a strong hydrogen bond between the C2 hydroxyl group and the C1 phosphate
oxygen atom, which may support the previously proposed catalytic mechanism in the active site of fructose-1,6-
bisphosphatase.
Introduction
metalloproteins as a ubiquitous bioinorganic motif.1,2 In the
active sites of non-heme diiron proteins, hemerythrin (Hr),
ribonucleotide reductase (RR), and methane monooxygenase
(MMO), the redox-active diiron centers are bridged by
carboxylate groups of the amino acid side-chains and
function coupled with molecular-oxygen-metabolizing pro-
cesses.1 A wide variety of synthetic model complexes have
Recent biological studies have revealed that carboxylate-
bridged dinuclear metal units are involved in a number of
* To whom correspondence should be addressed. E-mail: tanase@
cc.nara-wu.ac.jp.
† Nara Women’s University.
‡ Kwansei Gakuin University.
10.1021/ic051942d CCC: $33.50
Published on Web 03/02/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 7, 2006 2925

Kato et al.
been prepared to mimic their structures and functions.1 It
has also been elucidated that carboxylate-bridged divalent
dimetal ions, such as Mg2+, Mn2+, Co2+, Ni2+, and Zn2+,
are involved in many nonredox-active enzymatic processes,
including biological transfer reactions of phosphoryl, acyl,
and other carbonyl groups promoted by phosphatases,
nucleases, amidases, peptidases, etc.2,3 For the metallo-
enzymes that promote phosphoryl group transfer reactions,
a cooperative two-metal activation mechanism has preva-
lently been accepted on the basis of the crystal structures
for the 3′,5′-exonuclease of DNA polymerase I.3 A substrate
phosphate ester is bound to the two metal ions in an
asymmetric monodentate fashion and activated toward in-
line attack by a nucleophile that is generated at an appropriate
open site of one metal center. The modified two-metal-ion
mechanism with a bidentate phosphate bridge has also been
proposed in regard to the X-ray structures of other
phosphatases.2e
sugar phosphates and metal ions, much less attention has
been devoted to the bioinorganic chemistry with sugar
phosphate esters, and characterized metal complexes contain-
ing free sugar phosphate esters have extremely been scarce.
Recently, we have reported the tetranuclear copper(II)
complexes of R-D-glucose-1-phosphate (R-D-Glc-1-P), [Cu4-
(µ-OH)(µ4-R-D-Glc-1-P)2(L)4(H2O)2](NO3)3 (L ) bpy, phen),
and [Cu4(µ4-R-D-Glc-1-P)2(µ-CH3COO)2(bpy)4](NO3)2, in
which the R-D-Glc-1-P dianion connects four copper(II) ions
in bidentate 1,3-η1,η1-O,O′ and monodentate η1,η1-O′′ bridg-
ing modes.10 Although several structures for sodium, potas-
sium, and barium salts of some sugar phosphate esters,
including D-glucose n-phosphate (n ) 1, 6), D-fructose
n-phosphate (n ) 1, 6), and â-D-fructose 1,6-bisphosphate,
have been reported,11 the tetracopper complexes with R-D-
Glc-1-P are the first examples of transition-metal complexes
containing free sugar phosphate esters. Despite the novelty
of the complexes, it is noteworthy that the tetranuclear
copper(II) cores did not act as efficient scaffolds binding a
series of sugar phosphate esters because of the absence of
auxiliary bridging ligands.
In the present study, we have tried to synthesize the
biscarboxylate-bridged dicopper(II) complexes containing a
series of sugar phosphate esters by utilizing the biscarboxy-
late ligand XDK (H2XDK ) m-xylenediamine bis(Kemp’s
triacid imide)) and imine-based chelating ligands. The XDK
has already proven to be an efficient dinucleating ligand in
stabilizing a variety of dinuclear metal centers.12-14 The
present ligand system has led to successful isolation of the
dinuclear and the tetranuclear copper(II) complexes with
sugar phosphate esters, [Cu2(µ-sugar monophosphate)(XDK)-
(L)2] and [Cu4(µ-D-fructose 1,6-bisphosphate)(XDK)2(L)4],
where L ) phen and 4-methyl phen. In particular, the latter
tetracopper(II) complex was characterized by X-ray crystal-
lography and could provide useful insights into the substrate
binding and activation of Fru-1,6-Pase.
Among phosphate-containing metabolites, sugar phosphate
esters are known to play crucial roles as intermediate
compounds in regulating and maintaining the bioenergetic
systems,4 and Lewis acidic divalent metal ions, such as Mg2+,
Ca2+, Mn2+, Fe2+, Co2+, and Zn2+,5-9 are frequently required
for the metalloenzymes that promote transformations of sugar
phosphate esters. In particular, fructose-1,6-bisphosphatase
(Fru-1,6-Pase) involves biscarboxylate-bridged dimetal ions
(Mn2+, Zn2+, Mg2+) and promotes the hydrolysis of R-D-
fructose 1,6-bisphosphate to produce D-fructose 6-phosphate.5
Despite the importance of elucidating interactions between
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Experimental Section
Materials. All reagents were of the best commercial grade and
were used as received. m-Xylenediamine bis(Kemp’s triacid imide)
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(11) For example, see: (a) Narendra, N.; Seshadri, T. P.; Viswamitra, M.
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Acta Crystallogr. C 1985, 41, 31. (d) Narendra, N.; Seshadri, T. P.;
Viswamitra, M. A. Acta Crystallogr. C 1985, 41, 1612.
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Masschelein, A.; Rebek, J., Jr.; Lippard, S. J. J. Am. Chem. Soc. 1994,
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2926 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
and its sodium salt (H2XDK and Na2XDK‚4H2O) were prepared
by known methods.12f,15 The following abbreviations are used:
tetmen, N,N,N′,N′-tetramethylethylenediamine; tmen, N,N,N′-tri-
methylethylenediamine; bpy, 2,2′-bipyridine; phen, 1,10-phenan-
throline; Me2bpy, 4,4′-dimethyl-2,2′-bipyridine; Mephen, 4-methyl-
1,10-phenanthroline; HDPP, diphenyl phosphoric acid; HBNPP,
bis(4-nitrophenyl) phosphoric acid; Na2MNPP, 4-nitrophenyl phos-
phate disodium salt; Na2[Gly-2-P], glycerol 2-phosphate disodium
salt; Na2[Gly-3-P], glycerol 3-phosphate disodium salt; Na2[R-D-
Glc-1-P], R-D-glucose 1-phosphate disodium salt; Na2[D-Glc-6-
P], D-glucose 6-phosphate disodium salt; Na2[D-Man-6-P], D-man-
nose 6-phosphate disodium salt; Na2[D-Fru-6-P], D-fructose
6-phosphate disodium salt; Nan[D-Fru-1,6-P2], D-fructose 1,6-
diphosphate sodium salt.
Measurements. Electronic absorption spectra were recorded on
a Shimadzu UV-3100 spectrometer, and circular dichroism spectra
were measured on a Jasco J-720 spectropolarimeter. IR spectra were
measured on KBr pellets with a Jasco FT/IR 410 spectrometer.
Cyclic voltammograms were obtained using a Hokuto Denko HZ-
3000 voltammetric analyzer using a conventional three-electrode
system; glassy carbon as the working electrode, platinum wire as
the counter electrode, and a Ag/AgPF6 reference electrode. Variable-
temperature magnetic susceptibility measurements were carried out
with a Quantum Design MPMS-5S superconducting quantum
interference device (SQUID) susceptometer over a range of 4.5-
300 K, and the obtained magnetic susceptibility data were fitted
with the modified Bleany-Bowers equation.16 Electrospray ioniza-
tion mass spectra were recorded on an Applied Biosystems Mariner
spectrometer in positive mode of detection.
Preparation of [Cu2(µ-OH)(XDK)(L)2]X (L ) tetmen, X )
NO3 (1a), Cl (1b); L ) tmen, X ) NO3 (2a), Cl (2b)). Na2XDK‚
4H2O (50 mg, 0.072 mmol) was added to a solution of Cu(NO3)2‚
3H2O (33 mg, 0.14 mmol) in methanol (10 mL). The solution was
stirred at room temperature for 30 min. A portion of tetmen (0.14
mmol) was added to the solution, which was further stirred for 3
h. The solution was concentrated to dryness, and the residue was
extracted with dichloromethane. The extract was passed through a
glass filter to remove the inorganic salts and was concentrated to
almost dryness. After addition of MeOH (2 mL) and Et2O (0.5 mL),
the solution was allowed to stand at -4 °C to yield pale blue crystals
of [Cu2(µ-OH)(XDK)(tetmen)2]NO3‚0.5CH2Cl2 (1a‚0.5CH2Cl2),
which were collected, washed with Et2O, and dried under vacuum
(69 mg, 93% with respect to Cu). Anal. Calcd for C44.5H72O12N7-
ClCu2: C, 50.44; H, 6.85; N, 9.25. Found: C, 50.90; H, 6.80; N,
9.51. IR (KBr, cm-1): 1727 (s), 1688 (s), 1589 (s), 1466 (m), 1384
(m, br), 1201 (m). UV-vis (in CH2Cl2): λmax (ꢀ) 732 nm (3.18 ×
102 M-1 cm-1). Mass spectrum (ESI): m/z 953.454 (M+, calcd
953.387). Recrystallization of 1a‚0.5CH2Cl2 from a MeOH/Et2O
mixed solvent at room temperature yielded block-shaped crystals
of 1a‚2CH3OH suitable for X-ray crystallography.
Procedures similar to those described above using CuCl2‚2H2O
and tetmen and those using CuX2‚nH2O (X ) NO3, Cl) and tmen
yielded [Cu2(µ-OH)(XDK)(tetmen)2]Cl‚3H2O (1b‚3H2O), [Cu2(µ-
OH)(XDK)(tmen)2]NO3‚2H2O (2a‚2H2O), and [Cu2(µ-OH)(XDK)-
(tmen)2]Cl‚0.5CH2Cl2 (2b‚0.5CH2Cl2). For 1b‚3H2O, the yield was
37%. Anal. Calcd for C44H77O12N6ClCu2: C, 50.59; H, 7.43; N,
8.04. Found: C, 50.28; H, 7.58; N, 8.19. IR (KBr, cm-1): 1727
(s), 1687 (s), 1589 (s), 1466 (m), 1363 (m), 1201 (m). UV-vis (in
CH2Cl2): λmax (ꢀ) 733 nm (3.27 × 102 M-1 cm-1). For 2a‚2H2O,
the yield was 58%. Anal. Calcd for C42H71O14N7Cu2: C, 49.21; H,
6.98; N, 9.56. Found: C, 49.17; H, 7.04; N, 9.68. IR (KBr, cm-1):
1729 (s), 1690 (s), 1594 (s), 1465 (m), 1360 (m, br), 1200 (m).
UV-vis (in CH2Cl2): λmax (ꢀ) 725 nm (3.16 × 102 M-1 cm-1).
Mass spectrum (ESI): m/z 925.431 (M+, calcd 925.356). For 2b‚
0.5CH2Cl2, the yield was 69%. Anal. Calcd for C42.5H68O9N6Cl2-
Cu2: C, 50.79; H, 6.82; N, 8.36. Found: C, 50.48; H, 6.58; N,
8.38. IR (KBr, cm-1): 1729 (s), 1689 (s), 1595 (s), 1464 (m), 1360
(m), 1200 (m). UV-vis (in CH2Cl2): λmax (ꢀ) 721 nm (3.34 × 102
M-1 cm-1). Recrystallization of 1b‚3H2O and 2a‚2H2O from a
MeOH/Et2O mixed solvent at room temperature produced block-
shaped crystals of 1b‚CH3OH and 2a‚H2O suitable for X-ray
crystallography.
Preparation of [Cu2(µ-OH)(XDK)(L)2]NO3 (L ) bpy (3),
phen (4), Me2bpy (5), Mephen, (6)). A portion of Na2XDK‚4H2O
(100 mg, 0.14 mmol) was dissolved in CH3OH (8 mL), to which
Cu(NO3)2‚3H2O (35 mg, 0.14 mmol) was added. The solution was
stirred at room temperature for 30 min, and bpy (0.14 mmol) was
added to the solution. The reaction mixture was stirred for another
30 min. The solution was concentrated to dryness, and the residue
was extracted with dichloromethane. Addition of MeOH (1 mL)
and Et2O (1 mL) to the concentrated solution (1 mL) afforded blue
crystals of [Cu2(µ-OH)(XDK)(bpy)2]NO3‚CH2Cl2 (3‚CH2Cl2) in a
90% yield (74 mg). Anal. Calcd for C53H57O12N7Cl2Cu2: C, 53.85;
H, 4.86; N, 8.29. Found: C, 53.61; H, 4.72; N, 8.24. IR (KBr,
cm-1): 1730 (s), 1685 (s), 1595 (s), 1446 (m), 1358 (m, br), 1194
(m), 765 (m). UV-vis (in CH2Cl2): λmax (ꢀ) 724 nm (2.08 × 102
M-1 cm-1). Mass spectrum (ESI): m/z 1033.238 (M+, calcd
1033.262). Recrystallization of 3‚CH2Cl2 from a CH2Cl2/MeOH/
Et2O mixed solvent at room temperature gave block-shaped crystals
of 3‚4CH2Cl2 which were suitable for X-ray crystallography.
Procedures similar to those described above, but using phen, Me2-
bpy, and Mephen, yielded [Cu2(µ-OH)(XDK)(phen)2]NO3‚2CH2-
Cl2 (4‚2CH2Cl2), [Cu2(µ-OH)(XDK)(Me2bpy)2]NO3‚H2O (5‚H2O),
and [Cu2(µ-OH)(XDK)(Mephen)2]NO3‚1.5CH2Cl2‚CH3OH (6‚
1.5CH2Cl2‚CH3OH), respectively. For 4‚2CH2Cl2, the yield was
59%. Anal. Calcd for C58H59O12N7Cl4Cu2: C, 52.97; H, 4.52; N,
7.46. Found: C, 52.64; H, 4.41; N, 7.93. IR (KBr, cm-1): 1729
(s), 1685 (s), 1598 (s), 1518 (m), 1360 (m, br), 1194 (m). UV-vis
(in CH2Cl2): λmax (ꢀ) 731 nm (1.93 × 102 M-1 cm-1). Mass
spectrum (ESI): m/z 1081.250 (M+, calcd 1081.262). For 5‚H2O,
the yield was 41%. Anal. Calcd for C56H65O13N7Cu2: C, 57.43; H,
5.59; N, 8.37. Found: C, 57.40; H, 5.19; N, 8.33. IR (KBr, cm-1):
1728 (s), 1685 (s), 1617 (s), 1595 (m), 1462 (w), 1384 (m, br),
1195 (m). UV-vis (in CH2Cl2): λmax (ꢀ) 721 nm (2.15 × 102 M-1
cm-1). Mass spectrum (ESI): m/z 1089.314 (M+, calcd 1089.324).
For 6‚1.5CH2Cl2‚CH3OH, the yield was 61%. Anal. Calcd for
C60.5H66O13N7Cl3Cu2: C, 54.53; H, 4.99; N, 7.36. Found: C, 54.48;
H, 5.25; N, 7.53. IR (KBr, cm-1): 1727 (s), 1684 (s), 1596 (s),
1384 (s), 1360 (m, br), 1195 (m). UV-vis (in CH2Cl2): λmax (ꢀ)
725 nm (1.62 × 102 M-1 cm-1). Mass spectrum (ESI): m/z
1109.313 (M+, calcd 1109.293). Recrystallization of 4‚2CH2Cl2,
5‚H2O, and 6‚1.5CH2Cl2‚CH3OH from a CH2Cl2/MeOH/Et2O
mixed solvent at room temperature gave block-shaped crystals of
4‚1.5CH2Cl2, 5‚2CH2Cl2‚CH3OH‚H2O, and 6‚CH2Cl2‚2CH3OH‚
0.5H2O, respectively, which were suitable for X-ray crystallography.
Preparation of [Cu2(µ-η1,η1-(RO)2PO2)(XDK)(L)2]NO3 (R )
Ph, L ) bpy (11), phen (12); R ) 4-NO2Ph, L ) phen (13)).
HDPP (10 mg, 0.040 mmol) was added to a solution of 3‚CH2Cl2
(48 mg, 0.041 mmol) in CH2Cl2 (5 mL). The reaction mixture was
stirred at room temperature for 30 min. The solvent was evaporated
under reduced pressure, and the residue was crystallized from a
CH2Cl2/Et2O mixed solvent to give blue microcrystals of [Cu2(µ-
(15) Rebek. J., Jr.; Marshall, L.; Wolak, R.; Parris, K.; Killoran, M.; Askew,
B.; Nemeth, D.; Islam, N. J. Am. Chem. Soc. 1985, 107, 7476.
(16) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London., Ser. A 1952, 214,
451.
Inorganic Chemistry, Vol. 45, No. 7, 2006 2927

Kato et al.
η1,η1-DPP)(XDK)(bpy)2]NO3‚CH2Cl2 (11‚CH2Cl2) in a 57% yield
(33 mg). Anal. Calcd for C65H66O15N7Cl2Cu2P: C, 55.20; H, 4.70;
N, 6.93. Found: C, 55.48; H, 4.50; N, 6.94. IR (KBr, cm-1): 1728
(s), 1686 (s), 1600 (s), 1447 (m), 1384 (s), 1200 (m, br), 1095 (m),
918 (m, br), 768 (s). UV-vis (in CH3OH): λmax (ꢀ) 719 nm (1.47
× 102) (M-1cm-1). Recrystallization of 11‚CH2Cl2 from a CH2-
Cl2/MeOH/Et2O mixed solvent at room temperature gave block-
shaped crystals of 11‚2CH3OH‚2.5H2O which were suitable for
X-ray crystallography.
(1.05 × 102 M-1 cm-1). Recrystallization of 20‚CH3OH from a
CH2Cl2/MeOH/Et2O mixed solvent at room temperature gave block-
shaped crystals of 20‚5.5CH3OH‚2H2O which were suitable for
X-ray crystallography.
Preparation of [Cu2(µ-Gly-n-P)(XDK)(Mephen)2] (Gly-n-P
) glycerol n-phosphate, n ) 2 (21), 3 (22)). A solution of Na2-
[Gly-2-P] (17 mg, 0.051 mmol) in H2O (3 mL)/CH3OH (3 mL)
was added to a solution of 6‚1.5CH2Cl2‚CH3OH (57 mg, 0.043
mmol) in methanol (8 mL). The reaction mixture was stirred
overnight. The solvent was then removed to dryness, and the residue
was extracted with CH3OH (6 mL). The extract was passed through
a glass filter, and Et2O (1 mL) was slowly added to the extract.
The solution was allowed to stand at 2 °C to produce pale blue
crystals of [Cu2(µ-Gly-2-P)(XDK)(Mephen)2]‚2H2O (21‚2H2O) (22
mg, 40%). Anal. Calcd for C61H69O16N6Cu2P: C, 56.35; H, 5.35;
N, 6.46. Found: C, 56.46; H, 5.28; N, 6.28. IR (KBr, cm-1): 3398
(br), 1727 (s), 1684 (s), 1611 (s), 1360 (m), 1195 (m), 1086 (br),
725 (m). UV-vis (in CH3OH): λmax (ꢀ) 716 nm (1.96 × 102 M-1
cm-1). A similar procedure using Na2[Gly-3-P] gave [Cu2(µ-Gly-
3-P)(XDK)(Mephen)2]‚2H2O (22‚2H2O) in a 29% yield. Anal.
Calcd for C61H69O16N6Cu2P: C, 56.35; H, 5.35; N, 6.46. Found:
C, 56.37; H, 5.40; N, 6.32. IR (KBr, cm-1): 3393 (br), 1728 (s),
1682 (s), 1611 (s), 1360 (m), 1194 (m), 1106 (br), 725 (m). UV-
vis (in CH3OH): λmax (ꢀ) 716 nm (1.95 × 102 M-1 cm-1).
Preparation of [Cu2(µ-Sugar-P)(XDK)(phen)2] (Sugar-P )
r-D-Glc-1-P (23a), D-Glc-6-P (24a), D-Man-6-P (25a), D-Fru-
6-P (26a)) and [Cu4(µ-D-Fru-1,6-P2)(XDK)2(phen)4] (27a). A
solution containing Na2[R-D-Glc-1-P] (5.1 mg, 0.017 mmol) in a
H2O (1 mL)/CH3OH (2 mL) mixed solvent was added to a solution
of 4‚2CH2Cl2 (18 mg, 0.014 mmol) in methanol (10 mL). The
reaction mixture was stirred for 12 h. The solvent was removed
under reduced pressure to dryness, and the residue was extracted
with CH3OH (5 mL). The extract was passed through a glass filter,
and Et2O (0.5 mL) was added to the solution to yield pale blue
microcrystals of [Cu2(µ-R-D-Glc-1-P)(XDK)(phen)2]‚12H2O (23a‚
12H2O; 9.9 mg, 46%). Anal. Calcd for C62H89O29N6Cu2P: C, 48.34;
H, 5.82; N, 5.46. Found: C, 48.54; H, 5.45; N, 5.56. IR (KBr,
cm-1): 3412 (s, br), 1727 (s), 1683 (s), 1614 (s), 1360 (m), 1196
(s, br), 724 (m). UV-vis (in CH3OH): λmax (ꢀ) 732 nm (1.74 ×
102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 677 nm (2.34 × 10-1
M-1 cm-1). Mass spectrum (ESI): m/z 1323.754 (MH+, calcd
1323.281).
Similar reactions of 4‚2CH2Cl2 with HDPP and HBNPP gave
[Cu2(µ-η1,η1-DPP)(XDK)(phen)2]NO3‚CH2Cl2 (12‚CH2Cl2) and
[Cu2(µ-η1,η1-BNPP)(XDK)(phen)2]NO3‚3H2O (13‚3H2O), respec-
tively. For 12‚CH2Cl2, the yield was 82%. Anal. Calcd for
C69H66O15N7Cl2Cu2P: C, 56.68; H, 4.55; N, 6.71. Found: C, 56.50;
H, 4.56; N, 6.72. IR (KBr, cm-1): 1729 (s), 1685 (s), 1614 (s),
1594 (w), 1385 (s), 1359 (m), 1198 (m), 1096 (m). UV-vis (in
CH3OH): λmax (ꢀ) 735 nm (1.06 × 102 M-1 cm-1). For 13‚3H2O,
the yield was 43%. Anal. Calcd for C68H68O22N9Cu2P: C, 53.68;
H, 4.51; N, 8.29. Found: C, 53.86; H, 4.36; N, 8.34. IR (KBr,
cm-1): 1729 (s), 1686 (s), 1610 (s), 1590 (s), 1520 (s), 1344 (m,
br), 1227 (m), 1108 (m, br), 851 (m), 723 (m). UV-vis (in CH2-
Cl2): λmax (ꢀ) 732 nm (7.62 × 102 M-1 cm-1). Recrystallization of
12‚CH2Cl2 and 13‚3H2O from a CH2Cl2/MeOH/Et2O mixed solvent
at room temperature yielded block-shaped crystals of 12‚2CH2-
Cl2‚0.5CH3OH‚0.5H2O and 13‚8CH2Cl2, respectively, which were
suitable for X-ray crystallography.
Preparation of [Cu2(µ-η1,η1-(RO)2PO2)(NO3)2(L)2] (R ) Ph,
L ) Me2bpy (14); R ) 4-NO2Ph, L ) tetmen (15)). HDPP (18
mg, 0.072 mmol) was added to a dichloromethane solution (5 mL)
containing 5‚H2O (66 mg, 0.056 mmol). The reaction mixture was
stirred at room temperature for 1h, and the solvent was removed
under reduced pressure. The residue was extracted with dichlo-
romethane (2 mL), and Et2O (0.8 mL) was added to the extract.
The resulting solution was allowed to stand at 2 °C to give blue
crystals of [Cu2(µ-η1,η1-DPP)2(NO3)2(Me2bpy)2]‚H2O (14‚H2O) in
a 58% yield (37 mg). Anal. Calcd for C48H46O15N6Cu2P2: C, 50.75;
H, 4.08; N, 7.40. Found: C, 50.98; H, 3.89; N, 7.30. IR (KBr,
cm-1): 1492 (s), 1456 (s), 1269 (s), 1208 (s), 1097 (s), 920 (s).
UV-vis (in CH3OH): λmax (ꢀ) 702 nm (1.63 × 102 M-1 cm-1). A
similar procedure using 1a‚0.5CH2Cl2 (54 mg, 0.051 mmol) and
HBNPP (34 mg, 0.10 mmol) gave blue crystals of [Cu2(µ-η1,η1-
BNPP)2(NO3)2(tetmen)2]‚0.5CH2Cl2 (15‚0.5CH2Cl2) in a 29% yield
(18 mg). Anal. Calcd for C36.5H49O22N10ClCu2P2: C, 36.40; H, 4.10;
N, 11.63. Found: C, 36.49; H, 4.06; N, 11.35. IR (KBr, cm-1):
1611 (m), 1592 (s), 1527 (s), 1517 (s), 1463 (s), 1342 (s), 1109
(s), 903 (s), 750 (m). UV-vis (in CH2Cl2): λmax (ꢀ) 723 nm (2.51
× 102 M-1 cm-1). Recrystallization of 14‚H2O and 15‚0.5CH2Cl2
from a CH2Cl2/Et2O mixed solvent at room temperature produced
block-shaped crystals of 14 and 15, respectively, which were
suitable for X-ray crystallography.
Pale blue microcrystals of [Cu2(µ-D-Glc-6-P)(XDK)(phen)2]‚
7H2O (24a‚7H2O), [Cu2(µ-D-Man-6-P)(XDK)(phen)2]‚10H2O (25a‚
10H2O), [Cu2(µ-D-Fru-6-P)(XDK)(phen)2]‚7H2O (26a‚7H2O), and
[Cu4(µ-D-Fru-1,6-P2)(XDK)2(phen)4]‚15H2O (27a‚15H2O) were
obtained using procedures simliar to those described above with
Na2[D-Glc-6-P], Na2[D-Man-6-P], Na2[D-Fru-6-P], and Nan[D-Fru-
1,6-P2]. For 24a‚7H2O, the yield was 26%. Anal. Calcd for
C62H79O24N6Cu2P: C, 51.34; H, 5.49; N, 5.79. Found: C, 50.93;
H, 5.33; N, 5.58. IR (KBr, cm-1): 3393 (s, br), 1728 (s), 1685 (s),
1613 (s), 1599 (s), 1359 (m), 1194 (m), 1106 (s, br), 723 (m). UV-
vis (in CH3OH): λmax (ꢀ) 739 nm (1.47 × 102 M-1 cm-1). CD (in
DMF): λmax (∆ꢀ) 677 nm (4.42 × 10-1 M-1 cm-1). Mass spectrum
(ESI): m/z 1323.737 (MH+, calcd 1323.281). For 25a‚10H2O, the
yield was 17%. Anal. Calcd for C62H85O27N6Cu2P: C, 49.50; H,
5.69; N, 5.59. Found: C, 49.60; H, 5.33; N, 5.69. IR (KBr, cm-1):
3404 (s, br), 1727 (s), 1683 (s), 1598 (s), 1360 (m), 1195 (m),
1091 (s, br), 724 (m). UV-vis (in CH3OH): λmax (ꢀ) 731 nm (1.55
× 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 550 (-0.84 × 10-2),
632 sh (9.15 × 10-2), 719 nm (2.10 × 10-1 M-1 cm-1). Mass
spectrum (ESI): m/z 1323.276 (MH+, calcd 1323.281). For 26a‚
7H2O, the yield was 36%. Anal. Calcd for C62H79O24N6Cu2P: C,
Preparation of [Cu2(µ-MNPP)(XDK)(phen)2(CH3OH)]‚CH3OH
(20‚CH3OH). Na2MNPP‚6H2O (15 mg, 0.040 mmol) dissolved in
a CH3OH/CH2Cl2 (6 mL) mixed solvent was added to a solution
of 4‚2CH2Cl2 (43 mg, 0.033 mmol) in CH3OH (5 mL). The reaction
mixture was stirred at room temperature for 12 h. The solvent was
then evaporated under reduced pressure, and the residue was
extracted with CH3OH (6 mL). Addition of Et2O (0.5 mL) to the
concentrated solution yielded block-shaped blue crystals of [Cu2-
(µ-MNPP)(XDK)(phen)2(CH3OH)]‚CH3OH (20‚CH3OH; 12 mg,
28%). Anal. Calcd for C64H66O16N7Cu2P: C, 57.05; H, 4.94; N,
7.28. Found: C, 57.19; H, 4.79; N, 7.45. IR (KBr, cm-1): 1727
(s), 1689 (s), 1619 (s), 1590 (s), 1359 (m), 1338 (s), 1189 (s), 880
(m), 848 (s), 723 (s) cm-1. UV-vis (in CH2Cl2): λmax (ꢀ) 727 nm
2928 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Table 1. Crystallographic Data for Complexes 1a, 1b, 2a, 3, and 4
1a‚2CH3OH
1b‚CH3OH
2a‚H2O
3‚4CH2Cl2
4‚1.5CH2Cl2
formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C46H79N7O14Cu2
1081.26
C45H75N6O10ClCu2
1022.67
orthorhombic
Pbcn (No. 60)
14.981(7)
C42H69N7O13Cu2
1007.14
orthorhombic
Cmcm (No. 63)
15.063(7)
C56H63N7O12Cl8Cu2
1436.87
triclinic
P1h (No. 2)
15.183(4)
18.529(7)
11.838(4)
101.53(3)
103.25(3)
94.61(3)
3148(2)
2
C
57.5H58N7O12Cl3Cu2
1272.58
triclinic
P1h (No. 2)
14.203(1)
18.0006(5)
11.475(2)
103.56(2)
92.28(2)
80.32(2)
2811.5(5)
2
monoclinic
P21/a (No. 14)
17.0927(5)
15.0100(5)
20.8189(5)
16.995(4)
20.765(6)
16.132(7)
21.297(8)
93.2538(4)
5332.7(3)
4
5287(2)
4
5175(3)
4
Z
T (°C)
-120
-118
-118
-119
-120
machine
AFC8R/Mercury
0.865
AFC7R
0.911
AFC7R
0.885
AFC7R
1.079
AFC8R/Mercury
0.969
µ(Mo KR) (mm-1
)
F
calcd (g cm-3
)
1.347
6-55
9420 (I > 2σ(I))
668
0.051
0.134
1.285
4-50
2595 (I > 2σ(I))
332
0.078
0.161
1.293
4-45
1294 (I > 2σ(I))
195
0.059
0.145
1.516
4-45
6554 (I > 2σ(I))
767
0.049
0.112
1.503
6-55
8948 (I > 2σ(I))
749
0.066
0.155
2θ range (deg)
no. of unique data
no. of params
R1a
wR2 b
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo - Fc )2/∑[w(Fo )2]}1/2
.
2
2
2
51.34; H, 5.49; N, 5.79. Found: C, 51.00; H, 5.12; N, 5.90. IR
(KBr, cm-1): 3393 (s, br), 1729 (s), 1685 (s), 1614 (s), 1359 (m),
1193 (m), 1105 (s, br), 723 (m). UV-vis (in CH3OH): λmax (ꢀ)
727 nm (1.45 × 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 443
(8.57 × 10-2), 655 (2.12 × 10-2), 721 nm (1.88 × 10-2 M-1 cm-1).
Mass spectrum (ESI): m/z 1323.279 (MH+, calcd 1323.281). For
27a‚15H2O, yield 20%. Anal. Calcd for C118H148O43N12Cu4P2: C,
51.75; H, 5.45; N, 6.14. Found: C, 51.58; H, 5.34; N, 6.12. IR
(KBr, cm-1): 3384 (s, br), 1728 (s), 1683 (s), 1613 (s), 1359 (m),
1194 (m), 1105 (s, br), 724 (m). UV-vis (in CH3OH): λmax (ꢀ)
720 nm (2.91 × 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 674
(-2.52 × 10-1), 762 sh nm (-8.67 × 10-2 M-1cm-1).
573 (-1.46 × 10-2), 657 sh (1.21 × 10-2), 714 (2.48 × 10-2),
768 sh nm (1.36 × 10-2 M-1 cm-1). Mass spectrum (ESI): m/z
1351.271 (MH+, calcd 1351.312). For 27b‚6CH3OH‚5H2O, the
yield was 20%. Anal. Calcd for C128H160O39N12Cu4P2: C, 54.77;
H, 5.75; N, 5.99. Found: C, 54.49; H, 6.03; N, 6.19. IR (KBr,
cm-1): 3420 (s, br), 1730 (w), 1684 (s), 1615 (s, br), 1360 (m),
1194 (m), 1088 (s, br), 725 (m). UV-vis (in CH3OH): λmax (ꢀ)
721 nm (2.51 × 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 434 sh
(1.59 × 10-1), 532 (-5.03 × 10-2), 631 (-3.19 × 10-1), 673
(-3.11 × 10-1), 745 sh (-6.63 × 10-2), 781 nm (1.04 × 10-1
M-1 cm-1).
X-ray Crystallography. Crystals of 1a‚2CH3OH, 1b‚CH3OH,
2a‚H2O, 3‚4CH2Cl2, 4‚1.5CH2Cl2, 5‚2CH2Cl2‚CH3OH‚H2O, 6‚CH2-
Cl2‚2CH3OH‚0.5H2O, 11‚2CH3OH‚2.5H2O, 12‚2CH2Cl2‚0.5CH3-
OH‚0.5H2O, 13‚8CH2Cl2, 14, 15, 20‚5.5CH3OH‚2H2O, and 27a‚
8CH3OH‚11.75H2O were mounted on top of glass fibers with
Paraton N oil at low temperature. Crystal data and experimental
conditions are summarized in Tables 1-3. Reflection data for 1b,
2a, 3, 5, 12, and 15 were collected at -120 °C on a Rigaku AFC7R
diffractometer equipped with graphite-monochromated Mo KR (λ
) 0.71069 Å) radiation. Three standard reflections were monitored
every 150 reflections and showed no systematic decrease in
intensity. Reflection data were corrected for Lorentz-polarization
and absorption effects (ψ-scan method). Reflection data for 1a, 4,
6, 11, 13, 14, 20, and 27a were measured at -120 °C on a Rigaku
AFC8R/Mercury CCD diffractometer equipped with graphite-
monochromated Mo KR radiation using a rotating-anode X-ray
generator. A total of 1440 oscillation images, covering the whole
sphere of 2θ < 52°, were collected with exposure rates of 120 (6,
13) and 240 (11) s/deg by the ω-scan method (-70 < ω < 110°)
with a ∆ω of 0.25°. For 1a, 4, 14, 20, and 27a, a total of 2160
oscillation images, covering the whole sphere of 2θ < 55°, were
collected with exposure rates of 120-128 s/deg by the ω-scan
method (-62 < ω < 118°) with a ∆ω of 0.25°. The crystal-to-
detector (70 × 70 mm) distance was set to 60 mm. The data were
processed using Crystal Clear 1.3.5 (Rigaku/MSC)17 and corrected
for Lorentz-polarization and absorption effects.
Preparation of [Cu2(µ-Sugar-P)(XDK)(Mephen)2] (Sugar-P
) r-D-Glc-1-P (23b), D-Glc-6-P (24b), D-Fru-6-P (26b)) and
[Cu4(µ-D-Fru-1,6-P2)(XDK)2(Mephen)4] (27b). Following the
procedure as described for 23a, reactions of 6‚1.5CH2Cl2‚CH3OH
with Na2[R-D-Glc-1-P], Na2[D-Glc-6-P], Na2[D-Fru-6-P], and Nan-
[D-Fru-1,6-P2] yielded pale blue microcrystals of [Cu2(µ-R-D-Glc-
1-P)(XDK)(Mephen)2]‚6H2O (23b‚6H2O), [Cu2(µ-D-Glc-6-P)-
(XDK)(Mephen)2]‚4CH3OH‚2H2O (24b‚4CH3OH‚2H2O), [Cu2(µ-
D-Fru-6-P)(XDK)(Mephen)2]‚6H2O (26b‚6H2O), and [Cu4(µ-D-
Fru-1,6-P2)(XDK)2(Mephen)4]‚6CH3OH‚5H2O (27b‚6CH3OH‚
5H2O), respectively. For 23b‚6H2O, the yield was 38%. Anal. Calcd
for C64H81O23N6Cu2P: C, 52.64; H, 5.59; N, 5.75. Found: C, 52.51;
H, 5.58; N, 5.69. IR (KBr, cm-1): 3426 (s, br), 1728 (w), 1683
(s), 1615 (s, br), 1361 (m), 1197 (m), 1091 (s, br), 727 (m). UV-
vis (in CH3OH): λmax (ꢀ) 722 nm (1.66 × 102 M-1 cm-1). CD (in
DMF): λmax (∆ꢀ) 674 nm (1.33 × 10-1 M-1 cm-1). Mass spectrum
(ESI): m/z 1351.267 (MH+, calcd 1351.312). For 24b‚4CH3OH‚
2H2O, the yield was 41%. Anal. Calcd for C68H89O23N6Cu2P: C,
53.86; H, 5.92; N, 5.54. Found: C, 53.59; H, 6.15; N, 5.79. IR
(KBr, cm-1): 3411 (s, br), 1729 (w), 1684 (s), 1616 (s, br), 1360
(m), 1195 (m), 1090 (s, br), 800 (m). UV-vis (in CH3OH): λmax
(ꢀ) 720 nm (1.32 × 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 488
(-1.30 × 10-1), 676 nm (2.62 × 10-1 M-1 cm-1). Mass spectrum
(ESI): m/z 1351.273 (MH+, calcd 1351.312). For 26b‚6H2O, the
yield was 22%. Anal. Calcd for C64H81O23N6Cu2P: C, 52.64; H,
5.59; N, 5.75. Found: C, 52.73; H, 5.61; N, 5.73. IR (KBr, cm-1):
3413 (s, br), 1727 (w), 1685 (s), 1613 (s, br), 1360 (m), 1196 (m),
1087 (s, br), 725 (m). UV-vis (in CH3OH): λmax (ꢀ) 717 nm (1.46
× 102 M-1 cm-1). CD (in DMF): λmax (∆ꢀ) 400 (1.21 × 10-2),
(17) Crystal Clear, version 1.3.5; Rigaku and Molecular Structure Corp.:
The Woodlands, TX, 2003.
Inorganic Chemistry, Vol. 45, No. 7, 2006 2929

Kato et al.
Table 2. Crystallographic Data for Complexes 5, 6, 11, and 12
5‚2CH2Cl2‚CH3OH‚H2O
6‚CH2Cl2‚2CH3OH‚0.5H2O
11‚2CH3OH‚2.5H2O
12‚2CH2Cl2‚0.5CH3OH‚0.5H2O
formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C59H73N7O14Cu2Cl4
1373.17
triclinic
P1h (No. 2)
13.128(3)
19.642(3)
12.872(2)
95.58(1)
95.72(2)
101.43(1)
3213(1)
2
C61H70N7O14.5Cl2Cu2
1331.26
monoclinic
P21/c (No. 14)
12.972(1)
C66H77N7O19.5Cu2P
1438.44
monoclinic
C2/c (No. 15)
31.485(5)
C70.5H71N7O16Cl4Cu2P
1572.25
triclinic
P1h (No. 2)
16.564(7)
18.324(5)
13.000(4)
98.28(2)
102.98(3)
98.08(3)
3743(2)
2
19.444(2)
26.732(3)
27.913(3)
20.226(3)
95.026(6)
120.970(4)
6716(1)
4
15240(4)
8
Z
T (°C)
-116
-120
-120
-118
machine
AFC7R
0.895
AFC8R/Mercury
0.778
AFC8R/Mercury
0.648
AFC7R
0.801
µ(Mo KR) (mm-1
)
F
calcd (g cm-3
)
1.419
4-45
6173 (I > 2σ(I))
761
0.077
0.172
1.316
6-52
7350 (I > 2σ(I))
815
0.080
0.165
1.254
6-52
4732 (I > 2σ(I))
503
0.103
0.215
1.395
4-50
9512 (I > 2σ(I))
965
0.069
0.153
2θ range (deg)
no. of unique data
no. of params
R1a
wR2 b
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo - Fc )2/∑[w(Fo )2]}1/2
.
2
2
2
Table 3. Crystallographic Data for Complexes 13-15, 20, and 27a
13‚8CH2Cl2
14
15
20‚5.5CH3OH‚2H2O
68.5H88N7O22.5Cu2P
1527.55
triclinic
P1h (No. 2)
12.521(3)
16.704(4)
18.427(5)
91.105(2)
106.131(3)
94.116(4)
3689(1)
27a‚8CH3OH‚11.75H2O
formula
fw
cryst syst
space group
a (Å)
C76H78N9O19Cu2PCl16
2146.81
monoclinic
P21/n (No. 14)
14.401(1)
C48H44N6O14Cu2P2
1117.95
monoclinic
P21/c (No. 14)
11.384(2)
C36H48N10O22Cu2P2
1161.87
triclinic
C
C125.5H173.5N12O47.75Cu4P2
2930.43
monoclinic
C2 (No. 5)
30.928(1)
32.894(1)
P1h (No. 2)
9.849(2)
14.252(3)
8.944(2)
106.94(2)
100.49(1)
89.71(2)
1179.3(4)
1
b (Å)
c (Å)
23.416(2)
27.261(3)
19.612(2)
11.210(1)
37.034(2)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
98.033(5)
105.062(4)
105.942(2)
9102(1)
2416.6(5)
36227(3)
8
4
2
2
T (°C)
machine
µ(Mo KR)
-120
AFC8R/Mercury
1.025
-120
AFC8R/Mercury
1.021
-118
-120
AFC8R/Mercury
0.676
-120
AFC8R/Mercury
0.549
AFC7R
1.063
(mm-1
)
Fcalcd
1.566
1.536
1.636
1.375
1.074
(g cm-3
)
2θ range
(deg)
6-52
6-55
4-50
6-55
6-52
no. of
unique data
no. of
9472 (I > 2σ(I))
1109
3546 (I > 2σ(I))
326
3691 (I > 2σ(I))
326
11278(I > 2σ(I))
46995 (I > 2σ(I))
2019
929
params
R1a
0.091
0.194
0.052
0.117
0.024
0.065
0.067
0.153
0.093
0.213
wR2 b
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo - Fc )2/∑[w(Fo )2]}1/2
.
The structures of 1a, 1b, 2a, 3-6, 12-15, and 20 were solved
by direct methods with SIR9218 and were refined with full-matrix
least-squares techniques on F2 using teXsan.19 In the structures of
1a, 3, 5, and 6, all non-hydrogen atoms, except those of the nitrate
anion and solvated methanol (1a) and of solvated methanol and
water (5, 6), were refined with anisotropic thermal parameters. The
positions of the C-H hydrogen atoms were calculated, and those
of the hydroxo H atom were determined by difference Fourier
syntheses. In the structures of 1b and 2a, the tetmen and tmen
ligands were disordered with respect to the Cu2O plane and were
refined by using a two-site model with 0.5 occupancy. All non-
hydrogen atoms, except those of nitrate anion and the solvent water
molecule (2a), were refined with anisotropic thermal parameters.
The positions of the C-H hydrogen atoms were calculated and
the hydroxo H atoms were not found from difference Fourier maps.
In the structure of 4, the Cu, O, and N atoms included in the
complex cations were refined anisotropically and other non-
hydrogen atoms were refined with isotropic temperature factors.
The position of the hydroxo H atom in 4 was determined from
difference Fourier maps. In the structure of 11, the Cu, P, O, and
N atoms involved in the complex cation were refined anisotropi-
cally, and other non-hydrogen atoms were refined with isotropic
thermal factors. In the structures of 12-15 and 20, all non-hydrogen
atoms were refined with anisotropic thermal parameters and the
positions of C-H hydrogen atoms were calculated and fixed in
the refinement. The structure of 27a was solved by the Patterson
(18) Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.; Polidori,
G.; Spagna, R.; Viterbo, D. J. Appl. Crystallogr. 1989, 22, 389.
(19) TEXSAN: Crystal Structure Analysis Package; Molecular Structure
Corp.: The Woodlands, TX, 1999.
2930 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Scheme 1
Figure 1. ORTEP drawing for the complex cation of 1a.
ber of model complexes with redox-active dinuclear Fe and
Mn ions have been synthesized;1 however, analogous di-
nuclear copper(II) complexes consisting of the (µ-hydroxo)-
bis(µ-carboxylato)dimetal framework are extremely rare,
presumably because of the formation of polymeric com-
pounds with versatile bridging systems of carboxylate
ligands. The only available examples are [Cu2(µ-OH)(µ-
PhCOO)2(tetmen)2](PF6) (8a)23 and [Cu2(µ-OH)(µ-HCOO)2-
(bpy)2](BF4) (8b),24 on the basis of Cambridge Crystal
Structure Database. The present results demonstrated that
the dinucleating biscarboxylate ligand XDK is remarkably
effective for constructing the deoxy hemerythrin-type di-
copper(II) platform. The ESI mass spectra of 1-6 in CH3-
OH or CH2Cl2 exhibited the parent monocationic peaks
assignable to [Cu2(µ-OH)(XDK)(L)2]+ (m/z ) 953.45 (1a),
925.43 (2a), 1033.24 (3), 1081.25 (4), 1089.31 (5), 1109.31
(6)), indicating that the dinuclear structures are retained in
the solutions. The detailed structures of 1a, b, 2a, and 3-6
were determined by X-ray crystallography.
method with DIRDIF94 PATTY20 and was refined with full-matrix
least-squares techniques on F2 with SHELXL-97.21 The Cu and P
atoms were refined anisotropically, and the other non-hydrogen
atoms were refined with isotropic temperature factors. The C-H
hydrogen atoms were calculated, and the H atoms for hydroxyl
groups of the sugar moieties were not determined. The inherent
weak reflection data in the high-angle region and the existence of
two independent, large, complex molecules in the asymmetric unit
may result in the low quality of the present structure determination.
The relatively low calculated density indicated that a number of
solvent molecules were still not determined.
All calculations were carried out on Silicon Graphics Indigo and
O2 Stations with the teXsan program system and on a Pentium PC
with the Crystal Structure package.22
(ii) Structures. ORTEP plot for the complex cation of 1a
is illustrated in Figure 1 (ORTEP diagrams for the complex
cations of 1b, 2a, and 3-6 are shown in Figures S2-S7 in
the Supporting Information), and the structural parameters
for 1a, b, 2a, and 3-6 are summarized in Table 4. All the
complexes are composed of dinuclear Cu(II) centers that are
bridged by a hydroxo group and two carboxylates of XDK
ligand. The terminal sites of each Cu(II) ion are capped with
a chelating N-donor ligand to result in a [CuO3N2] five-
coordinate environment. The structure of complex 1a pos-
sesses a pseudo-Cs symmetry with the mirror plane vertical
to the Cu2O triangle, and both the N atoms (Nc) occupying
cis positions to the hydroxo oxygen atom (Ob) are tilted in
the same side with respect to the Cu2O plane (Figures 1 and
2a). The Cu‚‚‚Cu interatomic distance is 3.2910(4) Å, which
is longer by 0.062 Å than that in [Cu2(µ-OH)(PhCOO)2-
(tetmen)2]PF6 (8a) (3.229(1) Å),23 mainly because of the
slightly larger Cu-Ob-Cu angle (117.63(9)°) compared to
Results and Discussion
Hydroxo-Bridged Dinuclear Copper(II) Complexes
with Biscarboxylate Ligand XDK, [Cu2(µ-OH)(XDK)-
(L)2]X. (i) Syntheses. Reactions of Na2XDK‚4H2O with
CuX2‚nH2O (X ) NO3, Cl) in the presence of diamine
(tetmen, tmen) and diimine (bpy, phen, Me2bpy, Mephen)
auxiliary ligands yielded a series of discrete (µ-hydroxo)-
bis(µ-carboxylato)dicopper(II) complexes, [Cu2(µ-OH)-
(XDK)(L)2]X (L ) tetmen, X ) NO3 (1a), Cl (1b); L )
tmen, X ) NO3 (2a), Cl (2b); X ) NO3, L ) bpy (3), phen
(4), Me2bpy (5), Mephen (6)) (Scheme 1). All the complexes
were isolated as pure crystalline forms in good yields (37-
93%). Since deoxy hemerythrin has been shown to contain
a (µ-hydroxo)bis(µ-carboxylato)diiron(II) active site, a num-
(20) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; de
Gelder, R.; Israel, R.; Smits, J. M. M. DIRDIFF-94 Program System;
Technical Report of the Crystallography Laboratory; University of
Nijmegen: Nijmegen, The Netherlands, 1994.
(21) Sheldrick, G. M. SHELXL-97: Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1996.
(22) Crystal Structure 3.6: Crystal Structure Analysis Package; Rigaku
and Molecular Structure Corp.: The Woodlands, TX, 2003.
(23) Geetha, K.; Nethaji, M.; Chakravarty, A. R.; Vasanthacharya, N. Y.
Inorg. Chem. 1996, 35, 7666.
(24) Tokii, T.; Nagamatsu, M.; Hamada, H.; Nakashima, M. Chem. Lett.
1992, 1091.
Inorganic Chemistry, Vol. 45, No. 7, 2006 2931

Kato et al.
Table 4. Structural Parameters of the Dicopper(II) Complexes with {(µ-Hydroxo)bis(µ-carboxylato)Cu2}+ Corea
1a
1b
2a
3
4
5
6
8ab
8bc
L
X
tetmen
NO3
tetmen
Cl
tmen
NO3
bpy
NO3
phen
NO3
Me2bpy
NO3
Mephen
NO3
tetmen
PF6
bpy
BF4
bond lengths (Å)
3.2100(8)
1.909
1.911(3)
1.907(3)
1.989
1.994(4)
1.983(4)
2.049
2.034(4)
2.064(4)
2.024
2.012(3)
2.035(3)
2.118
2.144(3)
2.091(4)
Cu1‚‚‚Cu2
av Cu-Ob
Cu1-Ob
Cu2-Ob
av Cu-Nt
Cu1-Nt
3.2910(4)
1.924
1.921(2)
1.926(2)
2.058
2.038(2)
2.077(2)
2.096
2.112(2)
2.079(2)
2.017
2.029(2)
2.005(2)
2.198
2.192(2)
2.204(2)
3.264(2)
1.925(3)
3.274(2)
1.913(3)
3.1624(6)
1.899
1.903(2)
1.895(3)
2.012
2.013(3)
2.011(3)
2.071
2.078(3)
2.064(3)
2.036
2.054(2)
2.017(2)
2.082
2.063(2)
2.101(2)
3.205(1)
1.906
1.907(4)
1.905(4)
1.976
1.965(5)
1.987(5)
2.028
2.042(6)
2.014(6)
2.020
2.059(5)
1.981(4)
2.130
2.087(4)
2.173(4)
3.2034(9)
1.915
1.907(3)
1.923(3)
1.989
1.990(4)
1.988(4)
2.045
2.058(4)
2.032(5)
1.981
1.984(3)
1.977(4)
2.181
2.193(4)
2.168(4)
3.229(1)
1.930
1.925(6)
1.934(5)
2.051
2.050(6)
2.051(8)
2.107
2.106(7)
2.107(7)
1.990
1.991(6)
1.988(6)
2.131
2.128(6)
2.134(6)
3.171(1)
1.928
1.927(4)
1.928(4)
2.008
2.004(5)
2.012(5)
2.020
2.027(5)
2.012(5)
1.999
2.029(5)
1.968(5)
2.165
2.140(5)
2.190(5)
2.016(6)
2.11f
2.037(7)
2.04(1)f
Cu2-Nt
av Cu-Nc
Cu1-Nc
Cu2-Nc
av Cu-Oeq
Cu1-Oeq
Cu2-Oeq
av Cu-Oax
Cu1-Oax
Cu2-Oax
2.068(5)
2.136(4)
2.086(4)g
2.086(4)g
bond angles (deg)
Cu1-Ob-Cu2
av Ob-Cu-Nt
Ob-Cu1-Nt
117.63(9)
174.04
116.0(3)
175.4(2)
117.7(3)
176.1(3)
114.5(2)
174.2
173.4(2)
175.0(2)
95.1
94.3(2)
95.9(1)
80.0
80.1(2)
79.8(2)
134.3
140.4(2)
128.1(2)
112.0
109.3(1)
114.7(2)
112.0
112.7(1)
173.7
174.1(1)
173.3(1)
93.6
93.4(1)
93.7(1)
80.6
80.7(1)
80.5(1)
132.3
131.2(1)
133.4(1)
110.0
111.4(1)
108.6(1)
116.3
114.4(2)
174.9
113.5(2)
175.1
113.6(3)
167.4
110.7(2)
167.8
172.8(2)
162.8(2)
174.18(8)
173.89(8)
93.01
93.02(8)
93.00(8)
84.59
84.64(9)
84.54(8)
149.97
148.80(9)
151.14(8)
98.44
99.90(9)
96.98(8)
110.78
110.48(7)
111.08(7)
176.0(2)
173.8(2)
96.0
97.7(2)
94.3(2)
80.3
79.6(2)
80.9(2)
135.8
119.5(2)
152.0(2)
111.2
123.0(2)
99.3(2)
110.5
115.1(2)
105.9(2)
178.8(2)
171.3(2)
95.4
97.8(1)
92.9(2)
80.9
81.1(2)
80.6(2)
151.3
154.6(2)
148.0(2)
92.9
87.0(1)
98.8(2)
113.8
116.2(1)
111.3(1)
169.5(3)
165.3(3)
91.7
91.6(2)
91.7(3)
84.4
84.5(3)
84.2(3)
161.1
160.1(3)
162.0(3)
97.5
98.7(3)
96.3(3)
99.5
99.3(2)
99.7(2)
Ob-Cu2-Nt
av Ob-Cu-Nc
Ob-Cu1-Nc
Ob-Cu2-Nc
av Nt-Cu-Nc
Nt-Cu1-Nc
91.0f
91.6(3)f
85.0f
84.7(3)f
Nt-Cu2-Nc
av Nc-Cu-Oeq
Nc-Cu1-Oeq
Nc-Cu2-Oeq
av Nc-Cu-Oax
Nc-Cu1-Oax
Nc-Cu2-Oax
av Oeq-Cu-Oax
Oeq-Cu1-Oax
Oeq-Cu2-Oax
146.3 f
100.2 f
112.4(2)
143.4(4) f
104.4(4) f
111.7(2)
157.7
147.2(2)
168.2(2)
108.4(1)
115.6(1)
116.1(1)
116.5(1)
τ (Cu1)d
τ (Cu2)d
0.42
0.38
0.48/0.50f
327.7
0.55
g
0.55
0.78
0.72
0.67
0.88
0.36
0.40
0.39
0.16
0.06
0.43
0.09
∑ Cu-Ob-Z (deg)e 344.73
336.6
314.9
341.8
349.2
332.6
g
a The atom labeling is shown in the chart. Oax and Oeq are the carboxylate oxygen atoms at the apical and basal positions of the pseudo-square pyramidal
structure around the Cu atoms. b Ref 23 for [Cu2(µ-OH)(µ-PhCOO)2(tetmen)2](PF6) (8a). c Ref 24 for [Cu2(µ-OH)(µ-HCOO)2(bpy)2](BF4) (8b). d τ ) (â -
R)/60, where R is the second largest basal angle and â is the largest basal angle (ref 25). e ∑ Cu-Ob-Z is the summation of three Cu-Ob-Z angles
(Z ) Cu, H). f The Nc atom is disordered, and the Oeq and Oaxatoms are crystallographically identical. g Not determined.
that of 8a (113.6(3)°). The sum of the three bond angles
around the Ob atom is 344.73°, suggesting that the sp3
character of the bridging O atom appreciably decreases in
1a compared to 8a (332.6°). The N2O3 arrangement around
the copper centers is essentially recognized as square-
pyramidal geometry with the O201 and O202 atoms oc-
cupying the respective apical positions, but the structures
are considerably distorted toward trigonal-bipyramidal
geometry as indicated by τ values25 of 0.42 (Cu1) and 0.38
(Cu2). Although the severely disordered structures of the
tetmen and tmen ligands prevent detailed discussion, the
{Cu2(µ-OH)(µ-RCO2)2}+ core structures of 1b and 2a are
similar to that of 1a (Table 4 and Figures S2 and S3).
In complexes 3-6 with diimine ligands, the Cu‚‚‚Cu
separation is noticeably reduced to 3.1624(6)-3.2100(8) Å,
which is in accord with the shorter average Cu-Ob distances
(1.899-1.915 Å) and the smaller Cu-Ob-Cu angles
(112.7(1)-114.5(2)°) compared with those of the diamine
complexes. Among them, complex 4 with phen exhibits the
shortest Cu‚‚‚Cu distance of 3.1624(6) Å which is slightly
shorter than that of 8b (3.171(1) Å).24 The Cu-Ob-Cu angle
(25) Addison, A. W.; Rao, T. N. J. Chem. Soc., Dalton Trans. 1984, 1349.
2932 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Table 5. Electrochemical Data for Complexes 1-6a
complex
E
pc (V)b
1a
1b
2a
2b
3
4
5
6
-1.24
-1.27
-1.34
-1.29
-1.07
-1.11
-1.09
-1.09
a Measured in acetonitrile containing 0.1 M [nBu4N][PF6] at a scan rate
of 100 mV/s. b Referenced to the redox potentioal of Ag/AgPF6 in
acetonitrile.
Figure 3. Cyclic voltammograms obtained for (a) 1a and (b) 5 in CH3-
CN (0.1 M [nBu4N][PF6]) at a scan rate of 100 mV s-1
.
atom takes a trigonal-bipyramidal geometry (τ ) 0.88), and
the Cu2 sits in a square-pyramidal environment (τ ) 0.36),
resulting in an asymmetric dinuclear structure (Figure 2c).
In complex 6 with Mephen, both Cu atoms have distorted
square-pyramidal structures (τ ) 0.39-0.40) with the apical
O101 and O202 atoms, resulting in a pseudo-C2 symmetrical
structure (Figure 2d).
(iii) Electrochemical and Magnetic Properties. The
electrochemical properties of complexes 1-6 were analyzed
by cyclic voltammetry (Table 5 and Figure 3). The cyclic
voltammograms (CV) of 1a, b, 2a, and b in acetonitrile
solution showed an irreversible reduction wave around Epc
) -1.24 to -1.34 V, assignable to a two-electron reduction
process, [CuII ] f [CuI2], on the basis of coulometric
2
analysis. For complexes 3-6, the similar irreversible reduc-
tion occurred at more positive potentials, around Epc ) -1.07
to -1.11 V, which is consistent with the lesser electron-
donating ability of the diimine ligands compared with
diamines. The reduction peak potentials of 3-6 were not
sensitive to the diimine ligands, as well as the copper(II)
coordination geometry. Some attemps to isolate dicopper(I)
complexes by chemical and electrochemical reduction of 1a
and 3 were not successful, whereas a series of dinuclear
copper(I) ions have been stabilized by the biscarboxylate
ligand XDK.12i
Figure 2. The dicopper(II) structures of (a) 1a, (b) 4, (c) 5, and (d) 6
viewed along the Cu2O plane. XDK, except for the carboxylate groups, is
omitted for clarity.
of 4 is small (112.7(1)°), and the sum of the three bond angles
around the Ob atom (314.9°) is also small in comparison with
the corresponding values of other diimine complexes (336.6°
(3), 341.8° (5), 349.2° (6)), indicating the sp3 character of
the bridging oxygen in 4. The geometry of the five-coordinate
copper(II) atoms delicately varied depending on the diimine
ligands (Figure 2). In complexes 3 and 4, both the Cu(II)
centers essentially adopt the trigonal-bipyramidal geometry
with the Ob and Nt atoms occupying the apical sites (τ )
0.55-0.78) (Figure 2b). In complex 5 with Me2bpy, the Cu1
The temperature-dependent magnetic susceptibility data
were analyzed by least-squares fitting procedures using the
Bleany-Bowers equation based on the Hamiltonian H )
Inorganic Chemistry, Vol. 45, No. 7, 2006 2933

Kato et al.
Chart 1
are assumed to be effective through the Cu-O-Cu pathway
in complexes 1a, 3, 4, and 5, considering that the magnetic
2
2
2
orbitals are dx -y and dz , respectively, for square pyramidal
and trigonal bipyramidal Cu(II) ions.27b,c In fact, although
the values are larger than 100°, the Cu-O-Cu angles were
revealed to have a delicate correlation with the J values in
the present case. The entirely different magnetic interactions
observed with the same N-donor ligand (tetmen) in 1a
(2J ) -49.2 cm-1) and 8a (2J ) 45.1 cm-1) are rationalized
with the values for the Cu-O-Cu angles of 117.63(9)° (1a)
and 113.6(3)° (8a). For complex 4 (Cu-O-Cu )
112.7(1)°), the positive 2J value (52.0 cm-1) indicated a
moderate ferromagnetic interaction between the two copper-
(II) ions, which is, interestingly, in contrast with the small
antiferromagnetic interactions, 2J ) -4.2 and -5.4 cm-1,
for 3 (Cu-O-Cu ) 114.5(2)°) and 5 (Cu-O-Cu ) 114.4-
(2)°), respectively. These results demonstrated that the spin-
spin coupling interaction is remarkably sensitive to the
Cu-OH-Cu angle in the (µ-hydroxo)bis(µ-carboxylato)-
dicopper(II) complexes.
Reactions of Hydroxo-Bridged Dicopper Complexes
with Organic Phosphate Diesters. Complex 4 readily
reacted with diphenyl phosphoric acid (HDPP) or bis(4-
nitrophenyl) phosphoric acid (HBNPP) in dichloromethane
to produce [Cu2(µ-η1,η1-(RO)2PO2)(XDK)(phen)2]NO3 (R )
Ph (12), 4-NO2Ph (13)) in good yields. During the reaction,
the phosphate diesters were not hydrolyzed and simply
introduced onto the dinuclear core as bridging ligands. The
reaction of 3 with HDPP also gave the similar complex, [Cu2-
(µ-η1,η1-(PhO)2PO2)(XDK)(bpy)2] NO3 (11); however, that
with HBNPP under the same conditions resulted in the
dissociation of XDK from the dinuclear core. When complex
5 was treated with HDPP, the XDK dissociated dicopper-
(II) complex, [Cu2(µ-η1,η1-(PhO)2PO2)(NO3)2(Me2bpy)2] (14),
was isolated. A similar complex, [Cu2(µ-η1,η1-(4-NO2-
PhO)2PO2)(NO3)2(tetmen)2] (15), was also isolated from the
reaction of 1a with HBNPP (Chart 1). These results
suggested that the XDK-bridged dicopper centers with phen
terminal ligands could be suitable for fixing the phosphate
Figure 4. Plots of molar susceptibility, øM (b), and effective magnetic
moment, µeff (O), vs T for (a) 3 and (b) 4 with the fitted data (s).
-2JS1S2 (Figure 4).16 The best-fitted parameters are obtained
as follows: 2J ) -49.2 cm-1, g ) 2.07 for 1a, 2J ) -4.2
cm-1, g ) 2.17 for 3, 2J ) 52.0 cm-1, g ) 2.21 for 4, and
2J ) -5.4 cm-1, g ) 2.09 for 5. For all complexes, except
4, the negative values of 2J are indicative of intramolecular
antiferromagnetic exchange interactions. While no definite
magnetostructural correlation has been established because
of the paucity of characterized examples with (µ-hydroxo)-
bis(µ-carboxylato)dicopper(II) complexes, it has been ob-
served that the geometry at the endogeneous bridging oxygen
atom could be an important indicator in predicting the major
pathway for the spin-spin coupling; the sp2 character of the
bridging oxygen enhances antiferromagnetic interaction, and
sp3 character may reduce it.23,26 The values for the sum of
angles at the monatomic bridging oxygen (Table 4) might
indicate such a tendency with the observed J values;
however, this interpretation potentially involves large errors
accompanied by the position of the X-ray determined
hydrogen atom. In general, for bis(µ-hydroxo)dicopper(II)
complexes, the well-known empirical magnetostructural
correlation has been developed as follows: the Cu-OH-
Cu pathway with a Cu-O-Cu angle larger than 97.5° mostly
transfers antiferromagnetic interactions, and the pathway with
a Cu-O-Cu angle less than 97.5° transfers ferromagnetic
interactions.27 While the observed J values are composed of
ferromagnetic and antiferromagnetic interactions, both of
which are influenced by a variety of structural and electronic
factors, magnetic interactions between the two copper ions
(27) (a) Crawford, V. H.; Richardson, H. W.; Wasson, J. R.; Hodgson, D.
J.; Hatfield, W. E. Inorg. Chem. 1976, 15, 2107. (b) Christou, G.;
Perlepes, S. P.; Libby, E.; Folting, K.; Huffman, J. C.; Webb, R. J.;
Hendrickson, D. N. Inorg. Chem. 1990, 29, 3657. (c) Youngme, S.;
Chailuecha, C.; van Albada, G. A.; Pakawatchai, C.; Chaichit, N.;
Reedjik, J. Inorg. Chim. Acta 2005, 358, 1068.
(26) Mazurek, W.; Kennedy, B. J.; Murray, K. S.; O’Connor, M. J.;
Rodgers, J. R.; Snow, M. R.; Wedd, A. G.; Zwack, P. R. Inorg. Chem.
1985, 24, 3258.
2934 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Table 6. Selected Bond Distances and Angles for 11, 12, and 13a
11
12
13
bond distances (Å)
Cu1‚‚‚Cu2
Cu1-O1
4.268(3)
1.980(7)
1.999(8)
1.954(7)
2.177(10)
2.211(9)
1.944(7)
2.045(9)
2.02(1)
4.2685(8)
1.966(3)
1.954(3)
1.942(3)
2.164(3)
2.182(3)
1.921(3)
2.029(4)
1.997(3)
2.037(3)
1.998(3)
4.315(1)
1.964(5)
1.989(5)
1.940(5)
2.181(5)
2.143(5)
1.933(5)
2.034(6)
1.981(6)
2.033(6)
2.005(6)
Cu2-O2
Cu1-O101
Cu1-O202
Cu2-O102
Cu2-O201
Cu1-N1
Cu1-N2
Cu2-N3
2.044(10)
2.00(1)
Cu2-N4
bond angles (deg)
O1-Cu1-O101
O1-Cu1-O202
O1-Cu1-N1
92.9(3)
96.8(3)
90.8(3)
159.9 (4)
106.2(3)
164.3(4)
91.2(4)
88.4(4)
100.9(4)
80.4(4)
97.2(3)
92.6(3)
93.6(3)
158.2(4)
106.5(3)
85.8(3)
103.0(4)
165.5(4)
89.6(4)
79.9(4)
121.7(5)
92.7(1)
94.9(1)
91.4(1)
160.9(1)
108.0(1)
163.5(1)
89.8(1)
87.6(1)
102.4(1)
81.3(1)
97.0(1)
94.2(1)
90.0(1)
163.2(1)
101.3(1)
92.8(1)
97.8(1)
164.7(1)
90.6(1)
81.5(1)
121.0(2)
93.1(2)
90.7(2)
90.7(2)
161.8(2)
108.3(2)
162.2(2)
89.4(2)
89.0(2)
105.7(2)
81.8(3)
95.4(2)
92.6(2)
91.2(2)
163.1(2)
102.3(2)
93.9(2)
100.2(2)
162.9(2)
90.5(2)
81.2(2)
122.8(3)
O1-Cu1-N2
O101-Cu1-O202
O101-Cu1-N1
O101-Cu1-N2
O202-Cu1-N1
O202-Cu1-N2
N1-Cu1-N2
O2-Cu2-O102
O2-Cu2-O201
O2-Cu2-N3
O2-Cu2-N4
O102-Cu2-O201
O102-Cu2-N3
O102-Cu2-N4
O201-Cu2-N3
O201-Cu2-N4
N3-Cu2-N4
Figure 5. ORTEP plots for the complex cation of 12 viewed (a) vertical
to and (b) along the PO2 plane. XDK, except for the carboxylate groups, is
omitted for clarity.
diesters as a bridging unit, and in addition, the XDK-bridged
dicopper(II) complexes with the stronger N-donors, tetmen
and Me2bpy, are likely to be decomposed by dissociation of
the XDK ligand in the treatment with organic phosphoric
acids.
O1-P1-O2
τ (Cu1)
τ (Cu2)
0.07
0.12
0.04
0.03
0.01
0.00
a Estimated standard deviations are given in parentheses. Atom labels
are shown in Figure 5.
The detailed structures of 11-13 were determined by
X-ray crystallography. ORTEP plots for the core structure
of complex 12 are illustrated in Figure 5, and selected bond
distances and angles of complexes 11-13 are listed in Table
6 (ORTEP plots for the complex cations of 11-13 are
supplied as Supporting Information Figures S8-S10). The
structure of 12 possesses a pseudo-C2 symmetry (Figure 5b)
and is composed of two copper atoms triply bridged by two
carboxylate groups of XDK and a phosphate unit of the DPP
ligand. The terminal sites of each copper ion are occupied
by the N atoms of phen to result in N2O3 five-coordinated
square-pyramidal environments (τ ) 0.04 for Cu1 and 0.03
for Cu2). While several discrete dicopper structures involving
bridging phosphate esters and their related compounds have
been synthesized by utilizing alkoxo-, phenoxo-, diimine-,
and polyamine-based dinucleating ligands,28-32 the present
structure is the first example for introduction of a phosphate
ester onto a carboxylate-bridged dicopper(II) center. More-
over, for other metal ions, the (µ-phosphate)bis(µ-carboxy-
lato)dimetal structures have barely been established by using
the XDK ligand in [ZnM(µ-η1,η1-(PhO)2PO2)(η1-(PhO)2-
PO2)(XDK)(CH3OH)2(H2O)] (M ) Zn (16), Co (17)),12g
[Ca2(µ-η1,η1-(PhO)2PO2)(η1-(PhO)2PO2)(XDK)(CH3OH)3-
(H2O)] (18),12h [Mg2(µ-η1,η1-(PhO)2PO2)(η1-(PhO)2PO2)-
(XDK)(CH3OH)3(H2O)] (19a),12h and [Mg2(µ-η1,η1-(PhO)2-
PO2)(NO3)(XDK)(CH3OH)3(H2O)] (19b).12h The Cu‚‚‚Cu
separation of 12 is 4.2685(8) Å, which is significantly longer
than those of 16 (3.869(2) Å) and 17 (3.846(1) Å) and
slightly longer compared to those of 19a (4.108(3) Å) and
b (4.240(5) Å). The appreciable elongation might have
resulted from the asymmetrical bridging mode of the
biscarboxylate units. One carboxylate oxygen attaches to the
Cu atom at the apical site (Cu1-O202 ) 2.164(3) Å, Cu2-
O102 ) 2.182(3) Å), and the other oxygen coordinates to
the next Cu center at the basal site (Cu1-O101 ) 1.942(3)
Å, Cu2-O201 ) 1.921(3) Å), resulting in a considerable
distortion from a symmetrical syn-syn bidentate bridging
structure (Cu1-O202-C201 ) 154.6(3)°, Cu1-O101-
(28) (a) Williams, N. H.; Takasaki, B.; Wall, M.; Chin, J. Acc. Chem. Res.
1999, 32, 485. (b) Wall, M.; Hynes, R. C.; Chin, J. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1633. (c) Young, M. J.; Chin, J. J. Am. Chem.
Soc. 1995, 117, 10577.
(29) (a) Mahroof-Tahir, M.; Karlin, K. D.; Chen, Q.; Zubieta, J. Inorg.
Chim. Acta 1993, 207, 135. (b) Yamaguchi, K.; Akagi, F.; Fujinami,
S.; Suzuki, M.; Shionoya, M.; Suzuki, S. Chem. Commun. 2001, 375.
(c) Gajda, T.; Kramer, R.; Jancso, A. Eur. J. Inorg. Chem. 2000, 1635.
(d) Gajda, T.; Jancso, A.; Mikkola, S.; Lonnberg, H.; Sirges, H. J.
Chem. Soc., Dalton Trans. 2002, 1757.
(30) He, C.; Lippard, S. J. J. Am. Chem. Soc. 2000, 122, 184.
(31) Barker, J. E.; Liu, Y.; Martin, N. D.; Ren, T. J. Am. Chem. Soc. 2003,
125, 13332.
(32) Raidt, M.; Neuburger, M.; Kaden, T. A. J. Chem. Soc., Dalton Trans.
2003, 1292.
Inorganic Chemistry, Vol. 45, No. 7, 2006 2935

Kato et al.
Chart 2
C101 ) 125.1(3)°, Cu2-O102-C101 ) 155.8(3)°, Cu2-
O201-C201 ) 130.8(3)°). The diphenyl phosphate (DPP)
is accommodated between the two copper(II) ions in a
symmetrical µ-η1,η1-O,O′ bidentate fashion. The endoge-
neous oxygen atoms of DPP are involved in the basal plane
of each metal center with Cu1-O1 ) 1.966(3) Å and Cu2-
O2 ) 1.954(3) Å. The O1-P-O2 angle of 121.0(2)° is
largely deformed from normal values for tetrahedral geom-
etry. Usually, in dinuclear complexes containing 1,3-bridged
phosphate and phosphinate units, two metal ions are likely
located out-of-plane for the PO2 phosphinyl plane, leading
to the cis conformation as depicted in Chart 2a.12g,12h,28,29 In
the present case, however, the two metal ions deviate up
and down with respect to the phosphinyl plane depicted as
the trans conformation in Chart 2b. The trans conformation
of 1,3-bridging phosphate is very rare and is mainly
ascribable to the longer dimetal separation than those with
cis oriented 1,3-bridging structures. Complexes 11 and 13
involve closely similar structures to that of 12. The Cu‚‚‚Cu
separation of 13 (4.315(1) Å) is longer by 0.047 Å than the
value of 12, which may result in the larger distortion around
the phosphorus atom with O1-P1-O1 ) 122.8(3)°. While
these structural features of 13 might indicate that the
incorporated bridging phosphate ester is somewhat activated
by double Lewis acid binding and by the structural deforma-
tion of the phosphate group, the BNPP was not hydrolyzed
even by treatment with a stoichiometric amount of hydroxide
ions. The result should be notably contrasted to the well-
known catalytic functions associated with copper(II) ions in
phosphoryl transfer reactions.28a,33 One of the major problems
might be the poor solubility of 13 in polar solvents containing
water. Nevertheless, the structures of 11-13 could provide
useful insights into substrate binding and activation on
carboxylate-bridged dimetal active centers in the metallo-
enzymes that promote phosphoryl transfer reactions.
Figure 6. ORTEP plots of (a) 14 and (c) 15 and the Cu2P2O4 core
structures of (b) 14 and (d) 15.
Table 7. Selected Bond Distances and Angles for 14 and 15a
14
15
bond distances (Å)
4.796(1)
Cu1‚‚‚Cu1*
Cu1-O1
Cu1-O2*
Cu1-O5
Cu1-N1
Cu1-N2
Cu1‚‚‚O6
5.1191(8)
1.965(1)
2.239(1)
1.997(1)
2.043(2)
2.063(2)
2.637(1)
1.931(3)
2.156(3)
2.019(3)
2.011(3)
2.000(3)
2.667(3)
bond angles (deg)
95.2(1)
O1-Cu1-O2*
O1-Cu1-O5
O1-Cu1-N1
O1-Cu1-N2
O2*-Cu1-O5
O2*-Cu1-N1
O2*-Cu1-N2
O5-Cu1-N1
O5-Cu1-N2
N1-Cu1-N2
O1-P1-O2
94.39(5)
91.65(6)
89.72(6)
172.99(6)
89.05(5)
97.43(6)
92.22(6)
173.26(6)
90.83(6)
87.08(7)
119.72(8)
93.9(1)
90.7(1)
170.6(1)
94.4(1)
105.1(1)
90.4(1)
159.5(1)
93.2(1)
80.6(1)
122.9(2)
a Estimated standard deviations are given in parentheses. Atom labels
are shown in Figure 6.
connects the two Cu ions in a syn-syn fashion, leading
to the [Cu2P2O4] eight-membered puckered ring with a
Cu‚‚‚Cu separation of 4.796(1) Å (Figure 6b). On the other
hand, in complex 15, the bidentate BNPP bridges the two
metals is in a syn-anti fashion, and the eight-membered core
ring is planar with a longer Cu‚‚‚Cu distance of 5.1191(8)
Å (Figure 6d).
Reactions of Complexes 4 and 6 with Sugar Phosphate
Esters. Since the dicarboxylate-bridged dicopper(II) centers
with phen-type ligands proved to be a useful platform for
binding organic phosphate diesters, as mentioned above, we
have tried to introduce sugar phosphates and their analogous
The structures of 14 and 15 were determined by X-ray
crystallography to have a centro symmetry and consist of
two square-pyramidal copper(II) ions bridged by two phos-
phate groups, resulting in an eight-membered [Cu2P2O4]
macrocycle (Figure 6 and Table 7). Complexes containing
similar eight-membered cores have been prepared with
phosphate esters and phosphinates,34 as well as with nucleo-
side monophosphates.35 In complex 14, the 1,3-bridging DPP
(33) (a) Molenveld, P.; Engbersen, F. J.; Reinhoudt, D. N. Chem. Soc. ReV.
2000, 29, 75. (b) Hendry, P.; Sargeson, A. M. Progress in Inorganic
Chemistry: Bioinorganic Chemistry; Lippard, S. J., Ed.; Wiley: New
York, 1990; Vol. 38, p 201. (c) Breslow, R.; Huang, D.-L.; Anslyn,
E. Proc. Natl. Acad. Sci. U.S.A. 1989, 86, 1746. (d) Sigman, D. S.
Acc. Chem. Res. 1986, 19, 180.
(34) (a) Deschamps, J. R.; Hartshorn, C. M.; Chang, E. L. Acta Crystallogr.
E 2002, 58, m606. (b) Koga, K.; Ohtsubo, M.; Yamada, Y.; Koikawa,
M.; Tokii, T. Chem. Lett. 2004, 33, 1606.
(35) For example, see: (a) Aoki, K. J. Am. Chem. Soc. 1978, 100, 7106.
(b) Fischer, B. E.; Bau, R. Inorg. Chem. 1978, 17, 27. (c) Cini, R.;
Giorgi, G. Inorg. Chim. Acta 1987, 137, 87. (d) Giorgi, G.; Cini, R.
Inorg. Chim. Acta 1988, 151, 153. (e) Kovari, E.; Kramer, R. J. Am.
Chem. Soc. 1996, 118, 12704.
2936 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Scheme 2
Figure 7. The dicopper(II) core structures of 20. Most of the XDK and
phen are omitted for clarity.
Chart 3
ane-N6)] ([18]ane-N6 ) 1,4,7,10,13,16-hexaazacyclooctade-
cane),31 which is the first characterized transition metal
complex of glycerol 2-phosphate and involves two monoa-
tom-bridging phosphate esters in a η1,η1-O fashion. In
complexes 21 and 22, however, the glycerol phosphate ester
is estimated to act as a 1,3-O,O′-bridging ligand, in the light
of the crystal structure of 20 and 27a and the spectral
similarity to 20. The binding constants (apparent association
constants)31 of 4 toward phosphate monoester dianions were
determined from the visible absorption spectral changes in
methanol or methanol/water solutions, and the values for
MNPP2- (1.1 × 104) and Gly-2-P2- (1.0 × 104) were about
10× larger than that for the DPP phosphodiester monoanion
(0.96 × 103).
monophosphates onto the dimetal centers using complexes
4 and 6 as starting materials. At first, the reaction of 4 with
4-nitrophenyl phosphate disodium salt, Na2MNPP, and those
of 6 with glycerol 2-phosphate disodium salt, Na2[Gly-2-
P], and racemic glycerol 3-phosphate disodium salt, Na2-
[Gly-3-P], produced pale blue crystaline complexes, [Cu2(µ-
MNPP)(XDK)(phen)2(CH3OH)] (20) and [Cu2(µ-Gly-n-
P)(XDK)(Mephen)2] (n ) 2 (21), 3 (22)), respectively (Chart
3). The structure of 20 was confirmed by X-ray crystal-
lography to be essentially similar to that of 12 (Figure 7).
The two copper ions are bridged by two carboxylate groups
of XDK and a phosphate of MNPP dianion, and each end
of the dinuclear unit is terminated by a phen ligand, resulting
in [N2O3] square pyramidal geometry. A solvent methanol
is weakly bound to the Cu1 atom (Cu1-O7 ) 2.659(3) Å),
which is recognized as a semi-coordination resulting from
Jahn-Teller distortion. The phosphate group of the MNPP
dianion bridges the two metal centers in a µ-1,3-O,O′ mode.
The Cu‚‚‚Cu separation of 20 (4.1825(8) Å) is appreciably
shorter than those with the organophosphate diesters 11-
13 (4.268(3)-4.315(1) Å), which is mainly attributed to the
shorter Cu-O(phosphate) bonds (av 1.930 Å) and the smaller
O-P-O bridging angle (116.5(1)°). Similar Cu‚‚‚Cu separa-
tions were observed in the tri- and hexanuclear copper(II)
Reactions of complexes 4 and 6 with Na2[R-D-Glc-1-P],
Na2[D-Glc-6-P], Na2[D-Man-6-P], Na2[D-Fru-6-P], and Nan-
[D-Fru-1,6-P2] in a methanol/water mixed solvent yielded a
series of dicopper(II) sugar-phosphate complexes, [Cu2(µ-
Sugar-P)(XDK)(L)2] (L ) phen, Sugar-P ) R-D-Glc-1-P
(23a), D-Glc-6-P (24a), D-Man-6-P (25a), D-Fru-6-P (26a);
L ) Mephen, Sugar-P ) R-D-Glc-1-P (23b), D-Glc-6-P
(24b), D-Fru-6-P (26b)), and the tetracopper(II) complexes
of [Cu4(µ-D-Fru-1,6-P2)(XDK)2(L)4] (L ) phen (27a),
Mephen (27b)) (Schemes 3 and 4). The IR spectra of 23-
27 closely resembled those of the glycerol phosphate
complexes 21 and 22 except for the somewhat broad peaks
around 1100 cm-1, characteristic of sugar residues. The ESI
mass spectra for methanolic solutions of 23-26 exhibited
the monocationic parent peaks corresponding to {[Cu2(Sugar-
P)(XDK)(L)2]+H}+; the distributions of the isotopomers
were also in agreement with the complex formula (Figure
S15). In the UV spectra of 23-27, a broad band appeared
in the range of 710-720 nm, corresponding to d-d transi-
tions of Cu(II) ions, and in the circular dichroism (CD)
spectra, appreciable Cotton effects were observed in the range
of 600-800 nm (Figure 8). These spectral data suggested
that the chiral sugar phosphate esters were incorporated into
the dinuclear copper(II) centers bridged by the XDK ligand.
The intensities of the CD spectra for 23-27 were at least
2-
complexes with PhOPO3 dianions.36 Recently, Ren et al.
have reported the dicopper complex [Cu2(µ-Gly-2-P)2([18]-
(36) (a) Fry, F. H.; Jensen, P.; Kepert, C. M.; Spiccia, L. Inorg. Chem.
2003, 42, 5637. (b) Itoh, M.; Nakazawa, J.; Maeda, K.; Kano, K.;
Mizutani, T.; Kodera, M. Inorg. Chem. 2005, 44, 691.
Inorganic Chemistry, Vol. 45, No. 7, 2006 2937

Kato et al.
Scheme 3
Figure 8. Circular dichroism spectra for 23a (red), 24a (blue), 25a (black),
26a (green), and 27a (violet) in DMF.
esters are bound to the dimetal centers only by the phosphate
group, and the chiral sugar moieties are away from the copper
ions, on the basis of the weak CD spectra as well as the
X-ray structures of 20 and 27a. For complexes 24-27, two
anomeric forms of the carbohydrate residue and two enan-
tiomeric {Cu2(XDK)(L)2} structures with respect to its
pseudo-C2 symmetry are estimated to be involved, which
may lead to a complicated distribution of diastereomers and,
thus, result in delicate dependency of the CD spectral patters
on the sugar units.
Scheme 4
Structure of Tetranuclear Cu(II) Complex Containing
D-Fructose 1,6-bisphosphate (27a). The detailed structure
of 27a was determined by X-ray crystallography (Figures 9
and 10; Table 8). The asymmetric unit contains two neutral
tetranuclear copper(II) complexes formulated as [Cu4(µ-D-
Fru-1,6-P2)(XDK)2(phen)4], which are not chemically identi-
cal to each other. One involves an R-anomer of D-fructose
1,6-bisphosphate ([Cu4(µ-R-D-Fru-1,6-P2)(XDK)2(phen)4]
indicated as Mol A in Figure 9) and the other has a â-anomer
of the bisphosphate ([Cu4(µ-â-D-Fru-1,6-P2)(XDK)2(phen)4]
indicated as Mol B in Figure 10). The two complex
molecules are weakly interacted through π-π stacking
between the phen ligands. In each molecule, the two
phosphate groups of D-Fru-1,6-P2 are bound in a bidentate
1,3-O,O′-bridging mode to the biscarboxylate-bridged di-
copper(II) units, {Cu2(XDK)(phen)2}2+. The structures are
essentially similar to those observed in complexes 12, 13,
and 20, consisting of two square-pyramidal [N2O3] copper-
(II) ions asymmetrically bridged by two carboxylate groups
of XDK in a pseudo-C2 symmetrical fashion.
10-fold weaker than that of [Cu3{µ-(D-Glc)2-tacn}2(XDK)]
((D-Glc)2-tacn ) N,N′-bis(â-D-glucopyranosyl)-1,4,7-triaza-
cyclononane),13 where the N-â-D-glucopyranoside bridges
two copper(II) ions through the C2 and C3 hydroxyl groups
as well as the glycosidic nitrogen atoms, the sugar hydroxyl
groups directly coordinating to the metal centers. It is
assumed that, in the present complexes, the sugar phosphate
The tetranuclear core structure of [Cu4(µ-R-D-Fru-1,6-P2)-
(XDK)2(phen)4] (Mol A) is illustrated in Figure 9. The two
phsophate groups at the C1 and C6 positions of the R-D-
Fru-1,6-P2 tetraanion bridge the two dicopper(II) units in a
syn-syn bidentate mode with a trans conformation. The two
2938 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
Table 8. Selected Bond Distances and Angles for 27aa
Mol A Mol B
bond distances (Å)
Cu11‚‚‚Cu12
4.100(2)
Cu21‚‚‚Cu22
Cu23‚‚‚Cu24
P21‚‚‚P22
4.042(2)
4.096(2)
8.458(6)
1.953(8)
2.218(7)
1.915(8)
1.997(9)
2.07(1)
2.187(8)
1.965(8)
1.892(9)
2.08(1)
Cu13‚‚‚Cu14
P11‚‚‚P12
4.047(2)
8.189(6)
2.140(9)
2.000(7)
1.890(7)
2.06(1)
Cu11-O11
Cu11-O15
Cu11-O101
Cu11-N11
Cu11-N12
Cu12-O12
Cu12-O16
Cu12-O102
Cu12-N21
Cu12-N22
Cu13-O21
Cu13-O25
Cu13-O105
Cu13-N31
Cu13-N32
Cu14-O22
Cu14-O26
Cu14-O106
Cu14-N41
Cu14-N42
Cu21-O31
Cu21-O35
Cu21-O201
Cu21-N51
Cu21-N52
Cu22-O32
Cu22-O36
Cu22-O202
Cu22-N61
Cu22-N62
Cu23-O41
Cu23-O45
Cu23-O205
Cu23-N71
Cu23-N72
Cu24-O42
Cu24-O46
Cu24-O206
Cu24-N81
Cu24-N82
2.089(8)
1.954(7)
2.213(9)
1.896(8)
2.07(1)
1.98(1)
2.05(1)
1.967(9)
2.176(8)
1.984(8)
1.98(1)
1.930(8)
2.203(8)
1.907(9)
1.983(9)
2.054(9)
2.209(8)
1.952(8)
1.943(7)
2.042(9)
2.055(9)
2.06(1)
2.214(7)
1.961(9)
1.920(8)
2.036(9)
2.04(1)
bond angles (deg)
O11-Cu11-O15
O11-Cu11-O101
O11-Cu11-N11
O11-Cu11-N12
O15-Cu11-O101
O15-Cu11-N11
O15-Cu11-N12
O101-Cu11-N11
O101-Cu11-N12
N11-Cu11-N12
O12-Cu12-O16
O12-Cu12-O102
O12-Cu12-N21
O12-Cu12-N22
O16-Cu12-O102
O16-Cu12-N21
O16-Cu12-N22
O102-Cu12-N21
O102-Cu12-N22
N21-Cu12-N22
O21-Cu13-O25
O21-Cu13-O105
O21-Cu13-N31
O21-Cu13-N32
O25-Cu13-O105
O25-Cu13-N31
O25-Cu13-N32
O105-Cu13-N31
O105-Cu13-N32
N31-Cu13-N32
O22-Cu14-O26
O22-Cu14-O106
O22-Cu14-N41
O22-Cu14-N42
O26-Cu14-O106
O26-Cu14-N41
O26-Cu14-N42
O106-Cu14-N41
O106-Cu14-N42
N41-Cu14-N42
O101-P11-O102
O105-P12-O106
111.6(3)
100.0(3)
91.9(4)
89.7(3)
95.2(3)
88.7(4)
156.2(4)
165.0(4)
91.0(3)
79.9(4)
102.7(3)
95.2(3)
166.6(4)
90.2(4)
102.0(4)
87.3(4)
94.0(4)
91.4(4)
161.6(4)
80.1(4)
108.3(3)
94.7(4)
92.0(4)
157.4(4)
101.4(3)
88.6(4)
91.8(4)
165.6(4)
91.0(4)
78.2(5)
102.9(3)
107.0(3)
93.2(3)
85.5(3)
93.7(4)
89.5 (4)
168.3(3)
158.2(3)
91.4(4)
82.0(4)
114.6(5)
116.2(5)
O31-Cu21-O35
O31-Cu21-O201
O31-Cu21-N51
O31-Cu21-N52
O35-Cu21-O201
O35-Cu21-N51
O35-Cu21-N52
O201-Cu21-N51
O201-Cu21-N52
N51-Cu21-N52
O32-Cu22-O36
O32-Cu22-O202
O32-Cu22-N61
O32-Cu22-N62
O36-Cu22-O202
O36-Cu22-N61
O36-Cu22-N62
O202-Cu22-N61
O202-Cu22-N62
N61-Cu22-N62
O41-Cu23-O45
O41-Cu23-O205
O41-Cu23-N71
O41-Cu23-N72
O45-Cu23-O205
O45-Cu23-N71
O45-Cu23-N72
O205-Cu23-N71
O205-Cu23-N72
N71-Cu23-N72
O42-Cu24-O46
O42-Cu24-O206
O42-Cu24-N81
O42-Cu24-N82
O46-Cu24-O206
O46-Cu24-N81
O46-Cu24-N82
O206-Cu24-N81
O206-Cu24-N82
N81-Cu24-N82
O201-P21-O202
O205-P22-O206
102.4(3)
94.1(4)
90.3(4)
167.4(3)
110.5(3)
91.6(3)
85.9(3)
155.8(3)
91.7(4)
79.9(4)
109.8(3)
99.3(3)
89.3(3)
92.6(4)
94.0(4)
87.2(4)
155.3(4)
170.2(3)
92.4(4)
82.7(4)
109.3(3)
94.9(4)
91.3(3)
158.5(4)
98.2(4)
92.2(3)
91.0(4)
165.3(4)
88.7(4)
80.8(4)
101.4(3)
105.7(3)
94.2(3)
89.1(4)
95.1(3)
88.3(3)
165.5(4)
158.7(4)
91.7(3)
80.7(4)
113.5(5)
117.3(5)
Figure 9. (a) ORTEP plot for the core structure of [Cu4(µ-R-D-Fru-1,6-
P2)(XDK)2(phen)4] (Mol A) in 27a and (b) that viewed vertical to the
franoside ring. The O, N, and C atoms are drawn with arbitrary spheres.
Figure 10. (a) ORTEP plot for the core structure of [Cu4(µ-â-D-Fru-1,6-
P2)(XDK)2(phen)4] (Mol B) in 27a and (b) that viewed vertical to the
franoside ring. The O, N, and C atoms are drawn with arbitrary spheres.
triply bridged dicopper(II) fragments, {Cu2(µ-PO4)(XDK)-
(phen)2}, are nearly enantiomeric with Cu11‚‚‚Cu12 )
4.100(2) Å and Cu13‚‚‚Cu14 ) 4.047(2) Å. The P11‚‚‚P12
separation is 8.189(6) Å, and the two dicopper units are
located in the same side with respect to the furanose ring.
The average bond distance between the phosphate oxygen
and the copper atoms is 1.923 Å which is somewhat shorter
than the values of 12 (av 1.960 Å) and 13 (av 1.977 Å),
indicating stronger affinity of the phosphate monoester
a Estimated standard deviations are given in parentheses. Atom labels
are shown in Figures and 10. Mol A is [Cu4(R-D-Fru-1,6-
P2)(XDK)2(phen)4], and Mol B is [Cu4(â-D-Fru-1,6-P2)(XDK)2(phen)4].
9
dianions to dicopper(II) unit compared to that of the
phosphate diester monoanions. The average O-P-O angle
Inorganic Chemistry, Vol. 45, No. 7, 2006 2939

Kato et al.
for the bidentate phosphate groups is 115.4°, indicating
smaller deformation of the tetrahedral phosphorus atoms
compared to those in the phosphate diester complexes 12
and 13. The five-membered furanose ring adopts an envelop
conformation with the C3 carbon at an apex position (3E),
which might be stabilized by the unique hydrogen-bonding
interaction around the C1 phosphate group. On the basis of
interatomic distances, a strong hydrogen-bonding interaction
may exist between the R-anomeric C2 hydroxyl group and
the C1 phosphate oxygen atom (O109‚‚‚O104 ) 2.68(1) Å),
and in addition, the C2 hydroxyl group forms a weak
hydrogen bond with the exogeneous phosphate oxygen atom
(O109‚‚‚O103 ) 2.93(2) Å). In contrast, no hydrogen
bonding interaction exists around the C6 phosphate group.
The structure of [Cu4(µ-â-D-Fru-1,6-P2)(XDK)2(phen)4] (Mol
B) has a tetranuclear core similar to that of Mol A, in which
a â-D-fructose 1,6-bisphosphate bridges two {Cu2(XDK)-
(phen)2}2+ units (Cu21‚‚‚Cu22 ) 4.042(2) Å, Cu23‚‚‚Cu24
) 4.096(2) Å) (Figure 10). The two phosphate groups are
located on the same side with respect to the sugar ring, and
the P21 and P22 atoms are 8.458(6) Å apart, 0.27 Å longer
than that observed in Mol A. Each phosphate takes the 1,3-
O,O′-bridging structure with a trans conformation, like in
Mol A, with the similar structural parameters of av P-O )
1.914 Å and av O-P-O ) 115.4°. The furanose ring adopts
an envelop conformation (E2) where the C2 carbon deviates
toward the exo direction with respect to the C6 branch. The
characteristic hydrogen bondings are also observed around
the C1 phosphate group, the â-anomeric C2 hydroxyl group
forming bifurcated hydrogen bonds with the C1 phosphate
oxygen (O209‚‚‚O204 ) 2.79(1) Å), the bridging phosphate
oxygen (O209‚‚‚O202 ) 2.83(1) Å), and the C3 hydroxyl
group (O209‚‚‚O210 ) 2.67(1) Å). The hydrogen-bonding
networks around the C1 phosphate group observed in both
Mol A and B may result in rigid orientation of the sugar
moiety with respect to the phosphate-bridged dicopper
fragment. The conformations around the C1-C2 and C1-
O1 single bonds in Mol A and B are essentially similar as
indicated by the torsion angles of C104-C501-C502-C109
) -40(1)° and P11-O104-C501-C502 ) 112(1)° for Mol
A and O204-C601-C602-O209 ) -62.6(9)° and P21-
O204-C601-C602 ) 114.1(8)° for Mol B. There is no
appreciable intramolecular hydrogen-bonding interaction
around the C6 phosphate group in Mol B, just like in Mol
A, which may allow free rotation of C5-C6 and C6-O6
single bonds and result in the different orientation of the C6
phosphate group in comparison with that in Mol A; the
torsion angles are P12-O108-C506-C505 ) -170(1)° and
O112-C505-C506-O108 ) -59(1)° for Mol A and P22-
O208-C606-C605 ) -160.0(9)° and O212-C605-C606-
O208 ) 178.1(9)° for Mol B.
Figure 11. Schematic depiction of the structure of the active site of Fru-
1,6-Pase complexed with Mn2+ ions and the substrate-analogous inhibitor
AhG-1,6-P2.5a The AhG-1,6-P2 unit is drawn in red, and the postulated
mechanistic requirements are blue.5a
of D-Fru-1,6-P2 to D-Fru-6-P. The C1 phsophate ester bond
of R-D-Fru-1,6-P2 is specifically cleaved in the presence of
divalent metal ions, such as Mg2+, Mn2+, and Zn2+. A
plausible mechanism has been proposed in light of the kinetic
studies as well as the X-ray crystal structure for Fru-1,6-
Pase complexed with Mn2+ (or Zn2+) ions and 2,5-anhydro-
D-glucitol-1,6-bisphosphate (AhG-1,6,-P2) which is a sub-
strate analogue to R-D-Fru-1,6-P2 but bearing no hydroxyl
group at the C2 position (Figures 11 and 12a).5a From model
building based on the structure of the Fru-1,6-Pase/Mn2+/
AhG-1,6-P2 complex, a plausible catalytic mechanism was
proposed as follows:5a (1) The phosphate group is activated
by binding to the two Lewis acidic metal ions, as well as by
the postulated hydrogen bond between the C2 hydroxyl group
and the C1 phosphate oxygen atoms. (2) A water molecule
is activated by binding to the Mn2 ions with the help of a
hydrogen-bonding interaction with the carboxylate group of
Glu-98. (3) The in-line nucleophilic attack occurs at the C1
phosphate group from the opposite direction to the phosphate
ester oxygen atom. The features postulated with the true
substrate R-D-Fru-1,6-P2 are superimposed as the blue-
colored parts on the schematic structure with AhG-1,6-P2
(drawn in red) in Figure 11. The structure for the part of
R-D-Fru-1,6-P2 in 27a (Mol A) is illustrated in Figure 12b.
The conformation of the furanose ring of R-D-Fru-1,6-P2 in
Mol A is quite similar to that of AhG-1,6-P2 in the enzyme
(Figure 12a), and the orientation of the C1 phosphate arms
also resemble each other. The strong hydrogen-bonding
interaction between the C2 hydroxyl group (O2) and the C1
phosphate oxygen (O1) is definitively observed (O1‚‚‚O2
) 2.68(1) Å) in the Cu2/R-D-Fru-1,6-P2 structure, which
strongly supports the corresponding intramolecular hydrogen
bond postulated in the catalytic mechanism mentioned above.
The short interatomic distance, O2‚‚‚Oγ ) 2.93(2) Å, also
suggested that a polar interaction between the C2 hydroxyl
group and the bridging phsophate oxygen (Oγ) might be
involved in the mechanism. In Mol B with â-D-Fru-1,6-P2,
the hydrogen bond between the C2 hydroxyl group and the
C1 phosphate oxygen (O1‚‚‚O2 ) 2.79(1) Å) is not as strong
as the one (2.68(1) Å) in the R-D-Fru-1,6-P2 unit of Mol A,
which is mainly attributable to the presence of a hydrogen
bond between the cis-oriented C2 and C3 hydroxyl groups
(O2‚‚‚O3 ) 2.67(1) Å) (Figure 12c). The positions of dimetal
ions with respect to the C1 phosphate group in Mol A and
Comparison of the Structures of 27a and Fructose-1,6-
bisphosphatase. It should be of significant importance to
compare the structure of R-D-fructose 1,6-bisphosphate in
complex 27a to the active site of fructose-1,6-bisphosphatase
complexed with the substrate analogue.5a Fructose-1,6-
bisphosphatase (Fru-1,6-Pase) plays a critical role in regulat-
ing the gluconeogenesis pathway and promotes hydrolysis
2940 Inorganic Chemistry, Vol. 45, No. 7, 2006

Dinuclear Cu(II) Complexes
may be responsible for nonfunctionality of the present model
system for hydrolysis of sugar phosphate esters.
Conclusion
The dicarboxylate ligand XDK has been proven to stabilize
a series of (µ-hydroxo)bis(µ-carboxylato)dicopper(II) com-
plexes with N-donor auxiliary chelating ligands, [Cu2(µ-OH)-
(XDK)(L)2]+ (L ) tetmen, tmen, bpy, Me2bpy, phen, and
Mephen). Among them, the complexes with phen and
Mephen ligands (4 and 6) have been elucidated as providing
effective carboxylate-bridged dicopper scaffolds suitable for
the fixing of organic phosphate esters and sugar phosphates.
In particular, the tetranuclear copper(II) complex with
D-fructose 1,6-bisphosphate, [Cu4(µ-D-Fru-1,6-P2)(XDK)2-
(phen)4] (27a), was characterized by X-ray crystallography
to consist of two biscarboxylate-bridged dicopper(II) frag-
ments connected by an R- or â-anomer of D-Fru-1,6-P2,
resulting in a 1:1 mixture of [Cu4(µ-R-D-Fru-1,6-P2)(XDK)2-
(phen)4] and [Cu4(µ-â-D-Fru-1,6-P2)(XDK)2(phen)4]. In the
structure with R-D-Fru-1,6-P2, the C2 hydroxyl group forms
a strong hydrogen bond with the C1 phosphate oxygen atom,
and the orientation of the sugar moiety with respect to the
C1 phosphate group is fixed by the characteristic hydrogen-
bonding interaction around the C2 hydroxyl group. These
structural features of 27a could provide useful information
as a substrate binding model for fructose-1,6-bisphosphatase.
Acknowledgment. The authors are grateful to Professor
Stephen. J. Lippard of Massachusetts Institute of Technology
for valuable discussion and comments. This work was partly
supported by Grant-in-Aid for Scientific Research from the
Ministry of Education, Culture, Sports, Science, and Tech-
nology of Japan.
Figure 12. (a) Perspective drawing for the AhG-1,6-P2 unit with its C1
phosphate group bound to the Mn2+ ions in the active site of Fru-1,6-Pase.5a
(b) Perspective drawing for the R-D-Fru-1,6-P2 unit with its C1 phosphate
bound to the Cu2+ ions in Mol A of 27a. (c) Perspective drawing for the
â-D-Fru-1,6-P2 unit with its C1 phosphate bound to the Cu2+ ions in Mol
B of 27a. Mn (green), Cu (yellow), P (violet), O (red), N (blue), and C
(gray). The systematic atomic numbering scheme is adopted to compare
the structures to each other.
Supporting Information Available: X-ray crystallographic files
in CIF format, ORTEP plots of complexes 1-6, 11-15, 20, and
27a, and ESI mass spectra of 23a, b, 24a, b, 25a, 26a, and b.
This material is available free of charge via the Internet at
http://pubs.acs.org.
B are largely different from those in the enzyme active site,
in which the coordination sites, favorable to in-line nucleo-
philic attack to the phosphate unit, are rigidly occupied by
phen and XDK ligands (Figures 12b and c). These features
IC051942D
Inorganic Chemistry, Vol. 45, No. 7, 2006 2941