Macrocyclic Heterodinuclear ZnIIPbII Complexes: Synthesis, Structures, and Hydrolytic Function toward Tris(p-nitrophenyl) Phosphate

Article abstract of DOI:10.1021/ic9804869

A heterodinuclear Zn^IIPb^II complex ZnPb(L)(ClO₄)₂·2H₂O (1) has been obtained where (L)^2- is an unsymmetric macrocycle derived from the 2:1:1 condensation of 2,6-diformyl-4-methylphenol, ethylenediamine and diethylenetriamine and has the salen - and saldien -like metal-binding sites sharing the phenolic moiety. Its DMF adduct, ZnPb(L)(ClO₄)₂·MeOH·2DMF (1′), crystallizes in the triclinic space group P1 with a = 14.457(4) A?, b = 14.795(6) A?, c = 10.307(9) A?, α = 109.04(5)°, β = 96.24(5)°, γ = 102.56(3)°, V = 1995(2) A?³, and Z = 2. The refinement converges with R = 0.058 and R_w = 0.060 for 3532 reflections with |F₀| > 3σ(|F₀|). It has a discrete heterodinuclear core with the Zn^II in the salen site and the Pb^II in the saldien site of the macrocycle (L)^2-. The Zn has a square-pyramidal geometry together with a methanol oxygen, and the Pb has a seven-coordinate geometry together with one DMF oxygen and one perchlorate oxygen. The complex 1 is converted into [ZnPb(L)(OH)ClO₄]H₂O (2) under a weak alkaline condition. Its anhydrous form, [ZnPb(L)(OH)]ClO₄ (2), crystallizes in the monoclinic space group C2/c wich a = 25.835(4) A?, b = 13.190(6) A?, c = 16.553 A?, β = 106.31(2)°, V = 5413(2) A?³ and Z = 8. The refinement converges with R = 0.038 and R_w = 0.029 for 3944 reflections with |F₀| > 3σ(|F₀|). It has a dimer structure of a dinuclear {ZnPb(L)(OH)}⁺ unit having the Zn^II in the salen site and the Pb^II in the saldien site of the macrocycle. The hydroxide is bound to the Zn^II to afford a square-pyramidal geometry about the metal. The dimeric core [ZnPb(L)(OH)]₂²⁺ is formed by the bridge of the hydroxide oxygen to the Pb* of the adjacent molecule and vice versa. The geometry about the Pb in the dimer structure is a pentagonal pyramid showing a distortion to umbrella-like structure, with the bridging hydroxide oxygen at the apex, in a DMSO solution, an equilibrium exists between the dimeric and monomeric species: [{ZnPb(L)(OH)}₂]²⁺ ? 2[ZnPb(L)(OH)]⁺. On the basis of ³¹P NMR and visible spectra, 2 is shown to hydrolyze tris(p-nitorophenyl) phosphate (TNP) into bis(p-nitrophenyl) phosphate (BNP) in DMSO. 1 also exhibits a low activity to hydrolyze TNP into BNP due to the equilibrium [ZnPb(L)(H₂O)]²⁺ ? [ZnPb(L)(OH)]⁺ + H⁺. From the reaction mixture with 2, a BNP complex [ZnPb(L)(BNP)]ClO₄ (3) has been isolated. 3 crystallizes in the triclinic space group P1? with a = 13.494(9) A?, b = 13.88(1) A?, c = 12.765(8) A?, α = 94.71(6)°, β = 97.02(6)°, γ = 61.68(5)°, V = 2088(2) A?³, Z = 2. The refinement converges with R = 0.044 and R_w = 0.056 for 6070 reflections with |F₀| > 3σ(|F₀|). The BNP^- group bridges the pair of metal ions through its two oxygens, together with two phenolic oxygens of (L)^2-. On the basis of the above findings, a mechanistic scheme for the TNP hydrolysis by 2 is proposed; a TNP molecule is bound to the Pb center, and the hydroxide on the adjacent Zn ion attacks the phosphorus nucleus of TNP, leading to the formation of the BNP complex 3.

Full text of DOI:10.1021/ic9804869

6832
Inorg. Chem. 1998, 37, 6832-6838
Macrocyclic Heterodinuclear ZnIIPbII Complexes: Synthesis, Structures, and Hydrolytic
Function toward Tris(p-nitrophenyl) Phosphate
Masako Yamami, Hideki Furutachi, Takushi Yokoyama, and Hisashi Oh kawa*
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashiku,
Fukuoka 812-8581, Japan
ReceiVed April 29, 1998
A heterodinuclear ZnIIPbII complex ZnPb(L)(ClO4)2‚2H2O (1) has been obtained where (L)2- is an unsymmetric
macrocycle derived from the 2:1:1 condensation of 2,6-diformyl-4-methylphenol, ethylenediamine and diethyl-
enetriamine and has the “salen”- and “saldien”-like metal-binding sites sharing the phenolic moiety. Its DMF
adduct, ZnPb(L)(ClO4)2‚MeOH‚2DMF (1′), crystallizes in the triclinic space group P1h with a ) 14.457(4) Å, b
) 14.795(6) Å, c ) 10.307(9) Å, R ) 109.04(5)°, â ) 96.24(5)°, γ ) 102.56(3)°, V ) 1995(2) Å3, and Z ) 2.
The refinement converges with R ) 0.058 and Rw ) 0.060 for 3532 reflections with |F0| > 3σ(|F0|). It has a
discrete heterodinuclear core with the ZnII in the “salen” site and the PbII in the “saldien” site of the macrocycle
(L)2-. The Zn has a square-pyramidal geometry together with a methanol oxygen, and the Pb has a seven-
coordinate geometry together with one DMF oxygen and one perchlorate oxygen. The complex 1 is converted
into [ZnPb(L)(OH)ClO4]H2O (2) under a weak alkaline condition. Its anhydrous form, [ZnPb(L)(OH)]ClO4 (2),
crystallizes in the monoclinic space group C2/c with a ) 25.835(4) Å, b ) 13.190(6) Å, c ) 16.553 Å, â )
106.31(2)°, V ) 5413(2) Å3, and Z ) 8. The refinement converges with R ) 0.038 and Rw ) 0.029 for 3944
reflections with |F0| > 3σ(|F0|). It has a dimer structure of a dinuclear {ZnPb(L)(OH)}+ unit having the ZnII in
the “salen” site and the PbII in the “saldien” site of the macrocycle. The hydroxide is bound to the ZnII to afford
a square-pyramidal geometry about the metal. The dimeric core [ZnPb(L)(OH)]22+ is formed by the bridge of the
hydroxide oxygen to the Pb* of the adjacent molecule and vice versa. The geometry about the Pb in the dimer
structure is a pentagonal pyramid showing a distortion to “umbrella-like” structure, with the bridging hydroxide
oxygen at the apex. In a DMSO solution, an equilibrium exists between the dimeric and monomeric species:
[{ZnPb(L)(OH)}2]2+ h 2[ZnPb(L)(OH)]+. On the basis of 31P NMR and visible spectra, 2 is shown to hydrolyze
tris(p-nitorophenyl) phosphate (TNP) into bis(p-nitrophenyl) phosphate (BNP) in DMSO. 1 also exhibits a low
activity to hydrolyze TNP into BNP due to the equilibrium [ZnPb(L)(H2O)]2+ h [ZnPb(L)(OH)]+ + H+. From
the reaction mixture with 2, a BNP complex [ZnPb(L)(BNP)]ClO4 (3) has been isolated. 3 crystallizes in the
triclinic space group P1h with a ) 13.494(9) Å, b ) 13.88(1) Å, c ) 12.765(8) Å, R ) 94.71(6)°, â ) 97.02(6)°,
γ ) 61.68(5)°, V ) 2088(2) Å3, Z ) 2. The refinement converges with R ) 0.044 and Rw ) 0.056 for 6070
reflections with |F0| > 3σ(|F0|). The BNP- group bridges the pair of metal ions through its two oxygens, together
with two phenolic oxygens of (L)2-. On the basis of the above findings, a mechanistic scheme for the TNP
hydrolysis by 2 is proposed; a TNP molecule is bound to the Pb center, and the hydroxide on the adjacent Zn ion
attacks the phosphorus nucleus of TNP, leading to the formation of the BNP complex 3.
Introduction
respect to the geometric environments of the two metal ions. It
is thought that these phosphatases employ an unsymmetrical
dinuclear core to facilitate the concerted binding of the substrate
on one metal center and the nucleophilic attack of water or
hydroxide at the other metal center.10 Some model studies have
been carried out to mimic the phosphatase function using simple
dinuclear metal complexes,11 and these studies have clarified
the significance of two closely held metal centers in phosphate
ester hydrolysis.
Bimetallic cores exist at the active sites of many metalloen-
zymes and play essential roles in biological systems by the
interplay of a pair of metal ions.1 A typical example is
phosphatases that require at least two metal ions (Mg, Zn, Fe,
or Mn) in close proximity to hydrolyze phosphate esters.1-6
Recent X-ray structural studies for phospholipase C from
Bacillus cereus,7 phosphotriesterase from Pseudomonas diminu-
ta,8 and alkaline phosphatase from E. coli9 have revealed that
the dinuclear zinc core in these enzymes is unsymmetric with
Recently, heterobimetallic cores were recognized at the active
sites of purple acid phosphatase (FeZn),12 human calcineurin
(FeZn),13 and human protein phosphatase 1 (MnFe),14 and these
(1) (a) Fenton, D. E.; Ohkawa, H. PerspectiVes on Bioinorganic Chemistry;
JAI Press: London, 1993; Vol. 2, p 81. (b) Karlin, K. D. Science
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Int. Ed. Engl. 1996, 35, 2024.
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35, 2339.
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A.; Little, C.; Dodson, E. J.; Derewenda, Z. Nature (London) 1989,
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10.1021/ic9804869 CCC: $15.00 © 1998 American Chemical Society
Published on Web 12/04/1998

Macrocyclic Heterodinuclear ZnIIPbII Complexes
Inorganic Chemistry, Vol. 37, No. 26, 1998 6833
Chart 1. Chemical Structure of (L)2-
aminate; saldien ) N,N′-1,5-(3-azapentylene)disalicylidene-
II
II
aminate). It forms a series of heterodinuclear Ma Mb (Ma )
Cu, Ni, Co; Mb ) Pb, Mn, Fe, Co, Ni, Cu, Zn) complexes
II
II
having the Ma ion at the “salen”-like N2O2 site and the Mb
ion at the “saldien”-like N3O2 site.
In this study, this ligand is adopted to prepare ZnIIPbII com-
plexes for modeling heterobimetallic phosphatases. The metal
ion pair is chosen by taking into consideration the nature of
ZnII to form ZnII-OH linkages and the high affinity of PbII
toward phosphate oxygen. A ZnPb complex ZnPb(L)(ClO4)2‚
2H2O (1) is derived from the ligand, and 1 is converted into a
hydroxo complex, [ZnPb(L)(OH)]ClO4 (2), under a weak
alkaline condition. The main focus is placed on a phosphatase-
like function of 2 to hydrolyze tris(p-nitrophenyl) phosphate
(TNP) to bis(p-nitrophenyl) phosphate (BNP). A part of this
work was preliminarily reported.22
findings have stimulated interest in the cooperative function of
a pair of dissimilar metal ions in phosphate ester hydrolysis.
The heterobimetallic cores of these enzymes can be considered
as metamorphic forms of the unsymmetric homobimetallic cores
previously discussed. Heterodinuclear complexes bridged by a
phosphate monoester dianion or a phosphate diester anion were
reported.15,16 This study aims to provide a functional model of
heterobimetallic phosphatases to demonstrate the interplay of a
pair of dissimilar metal ions in phosphate ester hydrolysis.
The essential step for the model study is to prepare a discrete
and stable heterodinuclear core complex of an appropriate pair
of dissimilar metal ions in close proximity. For this purpose,
the use of a compartmental ligand whose two metal-binding
sites are not equivalent is recommended. The phenol-based
macrocycle (L)2- (Chart 1), having “salen”- and “saldien”-like
metal-binding sites sharing the phenolic moiety, was developed
in this laboratory17-21 (salen ) N,N′-ethylenedisalicylidene-
Experimental Section
Physical Measurements. Elemental analyses of C, H, and N were
obtained at the Elemental Analysis Service Center of Kyushu Univer-
sity. Analyses of Zn were obtained using a Shimadzu AA-660 atomic
absorption/flame emission spectrometer. Infrared spectra were recorded
on a JASCO IR-810 spectrometer using KBr disks or Nujol mulls.
Electronic spectra were recorded using a Shimadzu UV-3100PC
spectrometer. 1H NMR and 13C NMR spectra (400 MHz) were recorded
on a JEOL JNM-GX 400 using tetramethylsilane as the internal
standard. 31P NMR spectra (400 MHz) were recorded on a JEOL JNM-
GX 400 spectrometer using H3PO4 (85%) as the external reference.
Positive ion fast atom bombardment (FAB) mass spectra were recorded
on a JEOL JMS-SX 102A BE/BE four-sector-type tandem mass spec-
trometer using m-nitrobenzyl alcohol as the matrix.
Preparation. 2,6-Diformyl-4-methylphenol was prepared by the
method of Denton and Suschitzky.23 N,N′-Bis(3-formyl-5-methylsali-
cylidene)ethylenediamine,24 N,N′-bis(3-formyl-5-methylsalicylidene)-
ethylenediaminatonickel(II),24 [NiPb(L)](ClO4)2‚H2O,18 and [Zn(salen)-
(H2O)]25 were prepared by the literature methods. Other chemicals were
of reagent grade and used as purchased. Caution: the perchlorate
complexes described below may be explosive and should be prepared
in small portions.
N,N′-Bis(3-formyl-5-methylsalicylidene)ethylenediaminatozinc-
(II). To a suspension of N,N′-bis(3-formyl-5-methylsalicylidene)-
ethylenediamine (2.0 g, 5.7 mmol) in methanol (20 cm3) was added a
methanol solution of Zn(CH3COO)2‚2H2O (1.25 g, 5.7 mmol), and the
mixture was refluxed for 1 h to form a yellow powder. It was used for
the preparation of the following complexes without further purification.
The yield was 1.5 g (63%). Selected IR data (ν/cm-1 using KBr): 2900,
1640.
ZnPb(L)(ClO4)2‚2H2O (1). A suspension of N,N′-bis(3-formyl-5-
methylsalicylidene)ethylenediaminatozinc(II) (1.66 g, 4 mmol) in
methanol (30 cm3) and a solution of lead(II) perchlorate trihydrate (1.8
g, 4 mmol) in methanol (30 cm3) were mixed and stirred at ambient
temperature for 30 min. A methanol solution (10 cm3) of diethylene-
triamine (0.41 g, 4 mmol) was added dropwise, and the mixture was
refluxed for 1 h to give a yellow powder. It was collected by suction
filtration, washed successively with 2-propanol and ether, and dried in
vacuo. The yield was 2.96 g (80%). Anal. Found: C, 30.97; H, 3.16;
N, 7.91; Zn, 6.7%. Calcd for C24H31N5O12Cl2PbZn: C, 31.16; H, 3.38;
N, 7.57; Zn, 7.1%. FAB mass [m/z]: 788 for {ZnPb(L)(ClO4)}+.
Selected IR data [ν/cm-1] using KBr: 3300, 2900, 2850, 1650, 1100.
1H NMR [δ/ppm] in DMSO-d6: 8.606 (s, 2H, -CHdN-(en)-Nd
HC-), 8.531 (s, 2H, -CHdN-(dien)-NdHC-), 7.417 (s, 2H, ring),
(11) (a) Seo, J. S.; Sung, N.; Hynes, R. C.; Chin, J. Inorg. Chem. 1996,
35, 7472. (b) Vance, D. H.; Czarnik, A. W. J. Am. Chem. Soc. 1993,
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1995, 117, 5462. (d) Yashiro, M.; Ishikubo, A.; Komiyama, M. J.
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116, 11614. (h) Ragunathan, K. G.; Schneider, H. J. Angew. Chem.,
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Engbersen, J. F. J.; Reinhoudt, D. N. J. Am. Chem. Soc. 1997, 119,
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(12) Strater, N.; Klabunde, T.; Tucker, P.; Witzel, H.; Krebs, B. Science
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L. A.; Tempczyk, A.; Kalish, V. J.; Tucker, K. D.; Showalter, R. E.;
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F.; Barker, J. E.; Bacquet, R.; Villafranca, E. Nature 1995, 378, 641.
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6834 Inorganic Chemistry, Vol. 37, No. 26, 1998
Yamami et al.
Table 1. Summary of Crystal Data for Complexes 1′, 2′, and 3
complex
formula
cryst color
MW
cryst. dimens (mm)
cryst. syst.
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
1′
2′
3
C31H45O13N7Cl2ZnPb
yellow
1067.22
0.25 × 0.10 × 0.10
triclinic
C24H28O7N5ClZnPb
yellow
C36H35O14N7ClZnPPb
yellow
806.55
939.06
0.50 × 0.10 × 0.20
monoclinic
C2/c
25.835(4)
13.190(6)
16.553(6)
90
0.25 × 0.15 × 0.15
triclinic
P1h
P1h
14.457(4)
14.795(6)
10.307(9)
109.04(5)
96.24(5)
102.56(3)
1995(2)
13.494(9)
13.88(1)
12.765(8)
94.71(6)
97.02(6)
61.68(5)
2088(2)
2
106.31(2)
90
5413(2)
8
1.979
0.038
0.029
Z
2
Dc (g cm-3
)
1.776
0.058
0.060
1.795
0.044
0.056
Ra
Rw
b,c
2
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) {∑[w(|Fo| - |Fc|)2]/∑[wFo ]}1/2
.
c w ) 1/σ2(Fo).
7.413 (s, 2H, ring), 2.268 (s, 6H, Me). 13C NMR [δ/ppm] in DMSO-
d6: 169.0 and 167.8 (azomethine C); 165.0, 141.9, 140.7, 124.7, 123.4,
and 121.4 (ring C); 63.7 (dNCH2CH2Nd); 54.9 (dNCH2CH2-
NHCH2CH2Nd); 51.5 (dNCH2CH2NHCH2CH2Nd); 19.3 (methyl C).
UV-vis [λmax/nm (ꢀ/M-1 cm-1)] in DMSO: 266 (30 700), 383 (15 000).
It was crystallized from a 2-propanol/dimethylformamide/meth-
anol mixture (2:1:1 in volume) as ZnPb(L)(ClO4)2‚MeOH‚2DMF
(1′) suitable for X-ray crystallography. Anal. Found: C, 34.60; H,
4.04; N, 9.34%. Calcd for C31H45N7O13Cl2ZnPb: C, 34.89; H, 4.25;
N, 9.19%.
b. Method 2. A portion of 1 (0.093 g, 0.1 mmol) was dissolved in
acetonitrile (10 cm3), and this solution was mixed with an acetonitrile
solution containing tris(p-nitrophenyl) phosphate (0.046 g, 0.1 mmol).
The mixture was stirred at room temperature for 30 min. The addition
of triethylamine (0.010 g, 0.1 mmol) followed by further stirring at
room temperature resulted in the precipitation of yellow microcrystals.
The yield was 53%.
Crystal Structure Analyses. Each single crystal of 1′ and 3 was
mounted on a glass fiber and coated with epoxy resin. A single crystal
of 2′ was sealed in a glass tube. Intensities and lattice parameters were
obtained on a Rigaku AFC-7R automated four-circle diffractometer,
using graphite-monochromated MoKR radiation (λ ) 0.71069 Å) and
a 12 kW rotating anode generator at 231 °C. The cell parameters were
determined by 25 reflections in the 2θ range of 28.82° < 2θ < 29.98°
for 1′, 29.70° < 2θ < 29.98° for 2′, and 29.83° < 2θ < 30.04° for 3.
For the intensity data collections, the ω-2θ scan mode was used to a
maximum 2θ value of 45.1° for 1′, 55.0° for 2′, and 50.0° for 3 at the
scan rate of 16° min-1. The weak reflections (I < 10.0σ(I)) were
rescanned (maximum of 4 scans), and the counts were accumulated to
ensure good counting statistics. Stationary background counts were
recorded on each side of the reflection. The ratio of peak counting
time to background counting time was 2:1. The diameter of the incident
beam collimator was 1.0 mm, the crystal-to-detector distance was 235
mm, and the computer-controlled detector aperture was set to 9.0 mm
× 13.0 mm (horizontal × vertical). Three standard reflections were
monitored every 150 reflections. Over the course of the data collection,
the standards decreased by 13.84% for 1′, 7.0% for 2′, 1.8% for 3. A
linear correction factor was applied to the data to account for the
phenomena. The linear absorption coefficient, µ, for MoKR radiation
was 50.26 cm-1 for 1′, 72.60 cm-1 for 2′, and 47.8 cm-1 for 3. An
empirical absorption correction based on azimuthal scans of several
reflections was applied, which resulted in transmission factors ranging
from 0.79 to 1.00 for 1′, from 0.75 to 1.00 for 2′, and from 0.81 to
1.00 for 3. The intensity data were corrected for Lorentz and polarization
factors. Pertinent crystallographic parameters for 1′, 2′, and 3 are given
in Table 1.
ZnPb(L)(OH)ClO4‚H2O (2). To an acetonitrile solution (20 cm3)
of 1 (0.231 g, 0.25 mmol) was added triethylamine (0.026 g, 0.25
mmol). The mixture was stirred for 30 min to give yellow microcrystals.
They were collected by suction filtration, washed successively with
2-propanol and ether, and dried in vacuo. The yield was 0.144 g (70%).
Anal. Found: C, 34.95; H, 3.44; N, 8.44; Zn, 7.6%. Calcd for
C24H30N5O8ClZnPb: C, 34.96; H, 3.67; N, 8.49; Zn, 7.9%. FAB mass
[m/z]: 688 for {ZnPb(L)-H}+. Selected IR data [ν/cm-1] using KBr:
1
3580, 3250, 2900, 2850, 1640, 1100. H NMR [δ/ppm] in DMSO-d6
at 5 × 10-2 M: 8.339 (s, 2H, -CHdN-(en)-NdHC-), 7.929 (s,
2H, -CHdN-(dien)-NdHC-), 7.100 (s, 2H, ring), 7.075 (s, 2H,
ring), 2.267 (s, 6H, Me). 13C NMR [δ/ppm] in DMSO-d6: 168.7 and
165.7 (azomethine C); 164.6, 142.1, 140.0, 124.3, 122.1, and 121.5
(ring C); 61.5 (dNCH2CH2Nd); 57.1 (dNCH2CH2NHCH2CH2Nd);
49.1 (dNCH2CH2NHCH2CH2Nd); 19.4 (methyl C). UV-vis [λmax
/
nm (ꢀ/M-1 cm-1)] in DMSO: 266 (31 100), 378 (14 400).
Recrystallization from a 2-propanol/acetonitrile mixture (1:1 in
volume) formed [ZnPb(OH)]ClO4 (2′) suitable for X-ray crystal-
lography. Anal. Found: C, 35.82; H, 3.62; N, 8.65%. Calcd for
C24H28N5O7ClZnPb: C, 3.50; H, 35.74; N, 8.68%.
[ZnPb(L)(BNP)]ClO4 (3). a. Method 1. To a solution of 2 (0.083
g, 0.1 mmol) in acetonitrile (30 cm3) was added tris(p-nitrophenyl)
phosphate (0.046 g, 0.1 mmol), and the mixture was stirred for 1 h at
room temperature. The resulting yellow solution was once filtered to
separate any insoluble material and allowed to stand for 2 days to form
yellow microcrystals. They were collected by suction filtration and dried
in vacuo. The yield was 56%. Anal. Found: C, 38.57; H, 3.24; N,
8.71; Zn, 6.1%. Calcd for C36H35N7O14ClPZnPb: C, 38.31; H, 3.13;
N, 8.69; Zn, 5.8%. FAB mass [m/z]: 1028 for {ZnPb(L)(BNP)}+.
Selected IR data [ν/cm-1] using KBr: 3250, 3100, 3050, 2900, 2850,
1650, 1520, 1340, 1210, 1080. 1H NMR [δ/ppm] in DMSO-d6: 8.554
(s, 2H, -CHdN-(en)-NdHC-), 8.455 (s, 2H, -CHdN-(dien)-
NdHC-), 8.209 (d, J ) 9 Hz, 4H, ring), 7.347 (d, J ) 9 Hz, 4H,
ring), 7.260 (s, 2H, ring), 7.240 (s, 2H, ring), 2.249 (s, 6H, Me). 13C
NMR [δ/ppm] in DMSO-d6: 168.8 and 167.0 (azomethine C); 164.8,
142.0, 140.7, 124.5, 122.9, and 121.2 (ring C of the macrocycle); 157.9,
142.3, 125.1, and 120.1 (ring C of BNP-); 63.0 (dNCH2CH2Nd); 55.1
(dNCH2CH2NHCH2CH2Nd); 50.6 (dNCH2CH2NHCH2CH2Nd); 19.1
(methyl C). UV-vis [λmax/nm (ꢀ/M-1 cm-1)] in DMSO: 270 (30 800),
376 (12 400).
The structures were solved by direct methods and expanded using
Fourier techniques. Refinements were carried out by the full-matrix
least-squares method, where the function minimized is ∑w(|Fo| - |Fc|)2
with w ) 1/σ2(F0). Non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were fixed at the calculated positions and were not
refined.
Neutral atom scattering factors were taken from Cromer and Waber.26
Anomalous dispersion effects were included in Fcalc; the values for ∆f ′
and ∆f′′ were those of Creagh and McAuley.27 The values for the mass
attenuation coefficients were those of Creagh and Hubbel.28 All
(26) Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystal-
lography; Kynoch Press: Birmingham, 1974; Vol. IV.

Macrocyclic Heterodinuclear ZnIIPbII Complexes
Inorganic Chemistry, Vol. 37, No. 26, 1998 6835
Table 2. Relevant Bond Distances and Angles for 1′
Bond Distances (Å)
Zn-O(1)
Zn-O(2)
Zn-O(3)
Zn-N(1)
Zn-N(2)
2.01(1)
2.01(1)
2.09(1)
2.08(1)
2.05(1)
Pb-O(1)
Pb-O(2)
Pb-O(4)
Pb-O(5)
Pb-N(3)
Pb-N(4)
Pb-N(5)
2.52(1)
2.60(1)
2.77(2)
2.99(2)
2.50(1)
2.59(2)
2.48(1)
Bond Angles (deg)
84.8(4)
O(1)-Zn-O(2)
O(1)-Zn-O(3)
O(1)-Zn-N(1)
O(1)-Zn-N(2)
O(2)-Zn-O(3)
O(2)-Zn-N(1)
O(2)-Zn-N(2)
O(3)-Zn-N(1)
O(3)-Zn-N(2)
N(1)-Zn-N(2)
Pb-O(1)-Zn
O(1)-Pb-O(2)
O(1)-Pb-O(4)
O(1)-Pb-O(5)
O(1)-Pb-N(3)
O(1)-Pb-N(4)
O(1)-Pb-N(5)
O(2)-Pb-O(4)
O(2)-Pb-O(5)
O(2)-Pb-N(3)
O(2)-Pb-N(4)
O(2)-Pb-N(5)
O(4)-Pb-O(5)
O(4)-Pb-N(3)
O(4)-Pb-N(4)
O(4)-Pb-N(5)
O(5)-Pb-N(3)
O(5)-Pb-N(4)
O(5)-Pb-N(5)
N(3)-Pb-N(4)
N(3)-Pb-N(5)
N(4)-Pb-N(5)
63.9(3)
101.3(5)
85.7(5)
146.6(5)
106.9(5)
144.2(5)
89.0(5)
108.8(5)
111.9(5)
80.4(6)
106.7(5)
104.2(4)
146.3(5)
79.8(4)
118.9(4)
138.3(4)
68.8(4)
104.0(5)
135.0(4)
68.3(4)
136.2(4)
109.3(4)
91.5(6)
79.9(6)
73.0(5)
141.5(5)
156.7(5)
88.6(5)
78.5(5)
68.2(4)
94.7(5)
69.7(5)
Figure 1. ORTEP view of the cation of 1′ with the atom numbering
scheme.
Pb-O(2)-Zn
calculations were performed using the TEXSAN crystallographic
software package of Molecular Structure Corporation.29
Results and Discussions
Synthesis of ZnPb Complexes. In our previous studies, the
macrocyclic ligand (L)2- was prepared as MIIPbII complexes
(M ) Cu, Ni, or Co) by the stepwise template reaction that
uses two metal ions, MII and PbII, at different stages in the
cyclization.17-21 That is, an acyclic ligand complex, N,N′-bis-
(3-formyl-5-methylsalicylidene)ethylenediaminatometal(II), was
prepared that was then reacted with diethylenetriamine in the
presence of the PbII ion. In this study, this method was
successfully applied for preparing ZnPb(L)(ClO4)2‚2H2O (1).
It contains two water molecules, of which one water must be
coordinated to the Zn center as judged from the five-coordinate
geometry of [Zn(salen)(H2O)].25
Complex 1 was converted into [ZnPb(L)(OH)]ClO4‚H2O (2)
when triethylamine was added to an acetonitrile solution of 1.
This fact means that one of the water molecules is acidic enough
to be deprotonated under weak alkaline conditions. The pKa
value for the bound water could not be determined in this work
because 1 is insoluble in water and alcohols. The use of aqueous
sodium hydroxide instead of triethylamine gave unsatisfactory
results because of the elimination of ZnII as Zn(OH)2.
Crystal Structures. a. ZnPb(L)(ClO4)2‚MeOH‚2DMF (1′).
An ORTEP30 view of the cation of 1′ is shown in Figure 1
together with the numbering scheme. Selected bond distances
and angles are given in Table 2.
methanol oxygen O3 at the axial site. The displacement of the
Zn from the basal least-squares plane toward the methanol
oxygen O3 (0.60 Å) is fairly large relative to the displacement
of the metal in the analogous CuPb and CoPb complexes.17,19
The basal Zn-N and Zn-O bond distances fall in the range
2.01(1)-2.08(1) Å, which are longer than the corresponding
bond distances of the CuPb and CoPb complexes, in accord
with the large displacement of the Zn in 1′. The axial Zn-O3
bond distance (2.09(1) Å) is slightly longer than the basal bond
distances.
The Pb in the “saldien” site has a seven-coordinate geometry
together with one DMF oxygen O4 and one perchlorate oxygen
O5. The Pb deviates by 1.31 Å from the least-squares plane
defined by N3, N5, O1, and O2. The two exogenous donor
atoms occupying the open space of the PbII (the DMF oxygen
O4 and the perchlorate oxygen O5) are situated trans to the
methanol oxygen O3 bound to Zn(II), with respect to the mean
molecular plane. The Pb-O4 (2.77(2) Å) and Pb-O5 (2.99(2)
Å) bond distances are longer than the Pb-L bond distances
(2.48(1)-2.60(1) Å).
The essential part of 1′ consists of the macrocycle (L)2-, ZnII
and PbII ions, a methanol molecule, a DMF molecule, and a
perchlorate ion. One DMF molecule and one perchlorate ion
are free from coordination and located in the lattice. The ZnII
and PbII ions are bridged by the phenolic oxygens, O1 and O2,
with an intermetallic separation of 3.653(2) Å.
b. [ZnPb(L)(OH)]ClO4 (2′). The crystal has a dimer structure
of the dinuclear {ZnPb(L)(OH)}+ unit; the perchlorate ion is
free from coordination and captured in the lattice. An ORTEP
view of the {ZnPb(L)(OH)}+ unit with the atom numbering
scheme is shown in Figure 2 and that of the dimer structure is
given in Figure 3. Selected bond distances and angles are listed
in Table 3.
The Zn resides in the “salen” site of the macrocycle (L)2-
and assumes a square-pyramidal geometry together with the
The ZnII and PbII ions are bridged by the endogenous phenolic
oxygens, O1 and O2, with an intermetallic Zn-Pb separation
of 3.522(1) Å. The Zn resides in the “salen” site of the
macrocycle and assumes a square-pyramidal geometry together
with the hydroxide oxygen O3 at the apex. The dimeric core
(27) Creagh, D. C.; McAuley, W. J. International Tables for X-ray
Crystallography; Wilson, A. J. C., et al., Eds.; Kluwer Academic
Publishers: Boston, 1992; pp 219-222.
(28) Creagh, D. C.; Hubbell, J. H. International Tables for X-ray Crystal-
lography; Wilson, A. J. C., et al., Eds.; Kluwer Academic Publishers:
Boston, 1992; pp 200-206.
2+
[ZnPb(L)(OH)]2 is formed by the bridge of the hydroxo
oxygen O3 to the Pb* of the adjacent molecule and the bridge
of O3* to Pb. The basal Zn-to-macrocycle bond distances fall
in the range 2.022(5)-2.088(7) Å. The axial Zn-O3 bond
(29) TEXSAN; Molecular Structure Corporation: Houston, TX, 1985.
(30) Johnson, C. K. Report 3794; Oak Ridge National Laboratory: Oak
Ridge, TN, 1965.

6836 Inorganic Chemistry, Vol. 37, No. 26, 1998
Yamami et al.
ion O3* at the axial position. The Pb is deviated by 0.54 Å
from the pentagonal least-squares plane toward the open face
to afford an “umbrella-like” distortion about the Pb. The sum
of the angles O1-Pb-O2, O2-Pb-N3, N3-Pb-N4, N4-Pb-
N5, and O1-Pb-N5 is 350.6°; that is smaller than 360°, in
accord with the “umbrella-like” distortion. It must be noted that
the Pb-O3* bond distance (2.276(5) Å) is significantly shorter
than the Pb-L bond distances (2.551(8)-2.636(6) Å).
The diversity in the core structure for the MIIPbII complexes
of (L)2- has been recognized in this laboratory.17,19,21 The rare
“umbrella-like” structure about the Pb of 2′ is probably
associated with an “active lone-pair”33 situated trans to the
bridging OH-.
Figure 2. ORTEP view of the {ZnPb(L)(OH)}+ unit of 2′ with the
atom numbering scheme.
General Properties. Selected IR spectral data of 1 and 2
are given in the Experimental Section. The IR spectra of the
complexes are similar to each other and show the ν(CdN)
vibration at 1640-1650 cm-1 and the ν(N-H) vibration of the
secondary amine on the lateral chain at 3250-3340 cm-1. 2
shows the ν(O-H) vibration at 3580 cm-1. The high frequency
of the band is in harmony with the bridging function of the
OH- group in the crystal.34
The positive ion FAB mass spectra of the ZnPb complexes
exhibit parent peaks corresponding to the respective heterodi-
nuclear ZnPb core; no peak corresponding to homodinuclear
ZnZn or PbPb species was observed. The molecular ion peak
m/z ) 788 for 1 corresponds to {ZnPb(L)ClO4}+, and the
molecular ion peak of m/z ) 688 for 2 corresponds to the
momomeric species {ZnPb(L)2+-H+}+.
Figure 3. Depiction of the dimer structure of 2′.
The electronic absorption spectra of 1 and 2 in DMSO have
two intense absorption bands at 270 and ∼380 nm. Both can
be assigned to intraligand transition bands. The absorption at
∼380 nm is typical of the azomethine group.35,36 No absorption
is seen in the visible region in accord with the electronic nature
of the ZnII and PbII ions.
The 1H NMR and 13C NMR spectra of 1 and 2 were measured
in DMSO-d6 at room temperature. The numerical data are given
in the Experimental Section. Both complexes show a Cs
symmetrical feature with respect to the macrocyclic ligand. The
1H NMR spectrum of 1 has four singlets in the region of 8.61-
7.41 ppm that are assigned to the nonequivalent azomethine
and ring protons. The 13C NMR spectrum has 12 carbon
Table 3. Relevant Bond Distances and Angles for 2′
Bond Distances (Å)
Zn-O(1)
Zn-O(2)
Zn-O(3)
Zn-N(1)
Zn-N(2)
2.022(5)
2.057(5)
1.918(5)
2.083(8)
2.088(7)
Pb-O(1)
Pb-O(2)
Pb-O(3)*
Pb-N(3)
Pb-N(4)
Pb-N(5)
2.636(6)
2.553(5)
2.276(5)
2.595(8)
2.551(8)
2.578(7)
Bond Angles (deg)
O(1)-Zn-O(2)
O(1)-Zn-O(3)
O(1)-Zn-N(1)
O(1)-Zn-N(2)
O(2)-Zn-O(3)
O(2)-Zn-N(1)
O(2)-Zn-N(2)
O(3)-Zn-N(1)
O(3)-Zn-N(2)
N(1)-Zn-N(2)
Pb-O(1)-Zn
93.7(2)
108.6(2)
87.3(3)
139.1(3)
94.4(2)
152.7(3)
83.7(3)
111.2(3)
112.3(3)
78.0(3)
97.4(2)
99.1(2)
165.0(3)
O(1)-Pb-O(2)
O(1)-Pb-O(3)*
O(1)-Pb-N(3)
O(1)-Pb-N(4)
O(1)-Pb-N(5)
O(2)-Pb-O3*
O(2)-Pb-N(3)
O(2)-Pb-N(4)
O(2)-Pb-N(5)
O(3)*-Pb-N(3)
O(3)*-Pb-N(4)
O(3)*-Pb-N(5)
N(3)-Pb-N(4)
N(3)-Pb-N(5)
N(4)-Pb-N(5)
69.9(2)
71.7(2)
137.2(2)
135.3(2)
70.7(2)
77.7(2)
71.6(2)
137.3(2)
137.8(2)
82.4(2)
80.7(2)
76.2(2)
69.3(2)
135.5(2)
69.1(3)
resonances. The 1H NMR spectrum of 2 at 5 × 10-2
M
concentration also shows four singlets due to the azomethine
and ring protons in the region of 8.34-7.07 ppm. The upfield
shift of these signals relative to those of 1 indicates that 2 exists
in the dimer structure (Figure 3). At a lower concentration (5
1
× 10-3 M), however, the H NMR spectrum has eight singlet
Pb-O(2)-Zn
Pb-O(3)-Zn
resonances comprised of four dominant resonances at 8.35, 7.94,
7.11, and 7.08 ppm, compared to those for 2 in the dimer
structure, and four weaker resonances at 8.31, 7.83, 7.35, and
7.27 ppm. At a lower concentration (1 × 10-3 M), the last four
resonances are dominant and the former resonances due to the
dimer structure practically disappear. Evidently, 2 exists in an
equilibrium between the dimeric and monomeric forms at a
length is short (1.918(5) Å) and compared to the Zn-O bond
distances found for µ-hydroxo zinc complexes.31,32 The dis-
placement of the Zn from the basal N2O2 least-squares plane
toward O3 is 0.58 Å. The Pb-O3* bond distance is 2.276(5)
Å, and the Zn-O3-Pb* bond angle is 165.0(3)°. The
Zn- -Pb* separation is 4.158(1) Å.
lower concentration in DMSO i.e., [{ZnPb(L)(OH)}2]2+
h
2[ZnPb(L)(OH)]+.
The Pb at the N3O2 site assumes a six-coordinate geometry
together with O3* of the bridging OH-. The geometry about
the Pb can be depicted as a pentagonal pyramid with O1, O2,
N3, N4, and N5 of the “saldien” site on the base and the OH-
(33) (a) Luckay, R.; Cukrowski, I.; Mashishi, J.; Reibenspies, J. H.; Bond,
A. H.; Rogers, R. D.; Hancock, R. D. J. Chem. Soc., Dalton Trans.
1997, 901. (b) Rogers, R. D.; Bond, A. H.; Aguinaga, S. J. Am. Chem.
Soc. 1992, 114, 2960. (c) Rogers, R. D.; Bond, A. H.; Aguinaga, S.;
Reyes, A. J. Am. Chem. Soc. 1992, 114, 2967.
(31) Gorrell, I. B.; Looney, A.; Parkin, G. J. Am. Chem. Soc. 1990, 112,
(34) Ohkawa, H.; Tokii, T.; Nonaka, Y.; Muto, Y.; Kida, S. Bull. Chem.
4068.
Soc. Jpn. 1973, 46, 1462.
(32) Alsfasser, R.; Powell, A. K.; Vahrenkamp, H. Angew. Chem., Int. Ed.
Engl. 1990, 29, 898.
(35) Bosnich, B. J. Am. Chem. Soc. 1968, 90, 627.
(36) Downing, R. S.; Urbach, F. C. J. Am. Chem. Soc. 1969, 91, 5977.

Macrocyclic Heterodinuclear ZnIIPbII Complexes
Inorganic Chemistry, Vol. 37, No. 26, 1998 6837
Figure 5. Time courses of the absorbance intensity at 432 nm in the
TNP hydrolysis by 1 and 2. Conditions were as follows: [complex] )
1 × 10-3 M; [TNP] ) 3.3 × 10-5 M in DMSO (3 cm3) at at 25 °C.
Figure 4. 31P NMR spectrum for a DMSO solution containing 1 ×
10-3 mol of 2 and 1 × 10-2 mol of TNP ([2]/[TNP] ) 1/10). The
insert shows the 31P NMR spectrum with 1 under the same conditions.
Hydrolytic Activity toward TNP. The hydrolytic activity
of the ZnPb complexes 1 and 2 toward tris(p-nitrophenyl)
phosphate (TNP) has been examined by 31P NMR spectroscopy
in DMSO. A DMSO solution containing 1 × 10-3 mol of the
complex (1 or 2) and 1 × 10-2 mol of TNP ([complex]/[TNP]
) 1/10) was prepared, allowed to stand overnight, and subjected
to 31P NMR measurements. The results are given in Figure 4.
The signal at -16.040 ppm is attributed to TNP and the signal
at -9.179 ppm to BNP- liberated from TNP.16 The intensity
ratio of the signals is [TNP]/[BNP-] ≈ 9:1 for both 1 and 2,
indicating a practically stoichiometric hydrolysis of TNP by
these complexes. In parallel experiments, we confirmed that the
corresponding NiIIPbII complex, [NiPb(L)](ClO4)2‚2H2O, cannot
hydrolyze TNP. Furthermore, the addition of [Zn(salen)(H2O)]
and Pb2+ ion (1:1) could not hydrolyze TNP. These observations
clearly indicate that the pair of ZnII and PbII ions in close
proximity plays an essential role in the hydrolysis of TNP.
The hydrolysis of TNP by 1 and 2 in DMSO was also
followed by visible spectroscopy. An absorption band typical
of p-nitrophenolate ion37 appeared at 432 nm whose intensity
increased with time and converged. The time courses of the
absorbance at 432 nm at 25 °C are shown in Figure 5. It is
seen that the hydrolysis by 1 takes about 30 min, whereas the
hydrolysis by 2 is completed in 5 min. Evidently, 2 has a
high activity but 1 has a low activity, demonstrating that the
ZnII(OH)PbII core with a hydroxo group on the ZnII is essential
for the efficient hydrolysis of TNP to BNP-. The activity of 1
may be explained by a partial dissociation of 1 into 2 ([ZnPb-
(L)(H2O)]2+ h [ZnPb(L)(OH)]+ + H+). This can also explain
why the absorbance at 432 nm observed for the hydrolysis by
1 is weaker than that observed for the hydrolysis by 2; the
reaction solution with 1 is more acidic compared with that with
2 to supress the deprotonation of p-nitrophenolate liberated from
TNP.
Figure 6. ORTEP view of the cation of 3 with the atom numbering
scheme.
of the cation of 3 is given in Figure 6 together with the atom
numbering scheme. The relevant bond distances and angles are
given in Table 4.
The essential part of 3 consists of ZnII and PbII ions, the
macrocycle (L)2-, and one BNP- group; the perchlorate ion is
free from coordination and captured in the lattice. The Zn re-
sides at the “salen” site, and the Pb resides at the “saldien” site.
The two metal ions are bridged by two phenolic oxygens O1
and O2 of the macrocycle (L)2- and the BNP- group through
its O3 and O4 oxygens in the intermetallic separation of
3.464(2) Å.
The geometry about the Zn is square pyramidal with N1, N2,
O1, and O2 of the macrocycle on the basal plane and O3 of the
BNP- group at the apex. The Zn is displaced by 0.46 Å from
the basal least-squares plane toward O3. The basal Zn-N and
Zn-O bond distances are in the range 2.035(5)-2.054(7) Å.
The axial Zn-O3 distance is 1.993(6) Å, which is shorter than
the basal Zn-L bond distances.
From the TNP hydrolysis by 2, a BNP--containing complex,
[ZnPb(L)(BNP)]ClO4 (3), has been isolated. For practical
purposes, 3 is prepared in a good yield by the reaction between
2 and TNP in acetonitrile (method 1 in the Experimental
Section) or by the reaction between 1 and TNP in acetonitrile
in the presence of triethylamine (method 2). An ORTEP drawing
The Pb at the “saldien” site has a six-coordinate geometry
together with a bridging BNP- oxygen. The geometry about
the Pb is a pentagonal pyramid with O1, O2, N3, N4, and N5
(37) Dede, L.; Rosenberg, A. Ber. Deut. Chem. Ges. 1934, 67, 147.

6838 Inorganic Chemistry, Vol. 37, No. 26, 1998
Yamami et al.
Chart 2 Proposed Mechanism for TNP Hydrolysis by 2
Table 4. Relevant Bond Distances and Angles for 3
Bond Distances (Å)
Zn-O(1)
Zn-O(2)
Zn-O(3)
Zn-N(1)
Zn-N(2)
P-O(3)
P-O(4)
P-O(5)
P-O(6)
2.044(6)
2.035(5)
1.993(6)
2.046(7)
2.054(7)
1.492(6)
1.480(6)
1.592(6)
1.595(6)
Pb-O(1)
Pb-O(2)
Pb-O(4)
Pb-N(3)
Pb-N(4)
Pb-N(5)
2.519(5)
2.608(5)
2.360(5)
2.554(7)
2.549(7)
2.565(7)
Bond Angles (deg)
O(1)-Zn-O(2)
O(1)-Zn-O(3)
O(1)-Zn-N(1)
O(1)-Zn-N(2)
O(2)-Zn-O(3)
O(2)-Zn-N(1)
O(2)-Zn-N(2)
O(3)-Zn-N(1)
O(3)-Zn-N(2)
N(1)-Zn-N(2)
Pb-O(1)-Zn
Pb-O(2)-Zn
O(3)-P-O(4)
O(3)-P-O(5)
O(3)-P-O(6)
O(4)-P-O(5)
O(4)-P-O(6)
O(5)-P-O(6)
93.4(2)
92.3(2)
88.1(3)
161.0(3)
99.2(3)
143.9(3)
88.5(2)
116.8(3)
106.1(3)
79.4(3)
98.3(2)
97.5(2)
119.5(3)
109.9(3)
105.5(3)
109.5(3)
110.6(3)
99.9(3)
O(1)-Pb-O(2)
O(1)-Pb-O(4)
O(1)-Pb-N(3)
O(1)-Pb-N(4)
O(1)-Pb-N(5)
O(2)-Pb-O(4)
O(2)-Pb-N(3)
O(2)-Pb-N(4)
O(2)-Pb-N(5)
O(4)-Pb-N(3)
O(4)-Pb-N(4)
O(4)-Pb-N(5)
N(3)-Pb-N(4)
N(3)-Pb-N(5)
N(4)-Pb-N(5)
Zn-O(3)-P
70.8(2)
76.3(2)
138.3(2)
135.0(2)
71.7(2)
75.5(2)
70.5(2)
133.8(2)
138.6(2)
79.8(2)
76.4(2)
79.4(2)
68.9(2)
135.8(2)
68.5(2)
123.6(3)
138.8(3)
geometrical feature of the BNP- in 3 is similar to that found in
other bimetallic complexes bridged by phosphate ester ligands.15,16
On the basis of the above studies, a mechanistic scheme for
the TNP hydrolysis by 2 is proposed (Chart 2). A TNP molecule
is bound to the Pb center through its oxygen, and the hydroxide
on the adjacent Zn ion attacks the phosphorus nucleus of TNP,
leading to the formation of the BNP- complex 3. Thus, the
present study illustrates a functional model of the heterobime-
tallic phosphatases, and 3 can be regarded as the intermediate
in biological hydrolysis of phosphate triesters. We have noticed
that the [TNP]/[BNP-] ratio in the 31P NMR study using 2
(Figure 4) gradually decreases from 9/1 (stoichiometric) to ∼8/2
after 1 week. This fact means that the BNP- bridge is partially
dissociated and affords 1 together with water supplied from the
atmosphere. A catalytic cycle for the TNP hydrolysis may be
possible by the choice of an appropriate ZnIIMII pair.
Pb-O(4)-P
of the “saldien” site on the base and O4 of the BNP- group at
the axial position. The core geometry of 3 resembles that of
the half-unit of dimeric 2′. The sum of the bond angles
O1-Pb-O2, O2-Pb-N3, N3-Pb-N4, N4-Pb-N5, and
O1-Pb-N5 is 350.4°. The in-plane Pb-to-L bond distances
range from 2.519(5) to 2.608(5) Å. The Pb-O3 bond distance
is short (2.360(5) Å). The Pb is displaced by 0.52 Å from the
basal least-squares plane toward the open space. Thus, the Pb
assumes a similar “umbrella-like” shape.
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Research (09440231) from the Ministry
of Education, Science and Culture, Japan. We would like to
thank Daiwa Anglo of the Japanese Foundation and the British
Council for their support. Thanks are also due to Associate
Professor Kazuhiro Takahashi and Dr. Masaaki Ohba of Kyushu
University for valuable discussions.
In the BNP- bridge, the P-O3 and P-O4 bond distances
(1.492(6) and 1.480(6) Å, respectively) are significantly shorter
than the P-O5 and P-O6 bond distances (1.592(6) and 1.595-
(6) Å, respectively). The O3-P-O4 bond angle is large (119.5-
(3)°). Instead, the O5-P-O6 bond angle is small (99.9(3)°).
The remaining O-P-O bond angles fall in the range 105.5-
(3)-110.6(3)° that is common for tetrahedral phosphorus. The
Supporting Information Available: X-ray crystallographic files,
in CIF format, for 1-3 and 1′-3′ are available on the Internet only.
Access information is given on any current masthead page.
IC9804869