heated at 75 ЊC for 4 h. Water (50 cm3) was added and the
filtered solution loaded onto Dowex 50W × 2 (pyridinium
form). The product was recovered on elution of the column
with pyridinium acetate (0.2 to 1.0 mol dmϪ3) and rotary evap-
oration of the 1ϩ fraction. It was isolated as the ClO4Ϫ salt by
treating an aqueous solution (3 cm3) with LiClO4 (1.0 g), then
EtOH (30 cm3) and ice cooling. Found for the p isomer: C,
18.20; H, 5.54; Cl, 8.73; N, 17.20; P, 7.77. C6H22ClCoN5O7P
requires C, 17.94; H, 5.52; Cl, 8.83; N, 17.44; P, 7.71%. 31P
NMR (D2O): δ 11.98, d, J PH 599 Hz. UV-vis: λmax/nm (1.0 mol
dmϪ3 HClO4) 498 (ε/dm3 molϪ1 cmϪ1 106) and 356 (90). Found
for the t isomer: C, 16.30; H, 5.97; Cl, 7.86; N, 15.81; P, 6.86.
C6H22ClCoN5O7Pؒ2H2O requires C, 16.46; H, 5.99; Cl, 8.10; N,
16.00; P, 7.07%. 31P NMR (D2O): δ 13.40, d, JPH 592 Hz. UV-vis:
λmax/nm (1.0 mol dmϪ3 HClO4) 517 (ε/dm3 molϪ1 cmϪ1 157) and
357 (117). Crystals suitable for structural determination were
obtained on layering an aqueous solution with EtOH.
Table 5 Crystal data and structure refinement for t-[Co(tren)(NH3)-
{OP(H)(O)2}]ClO4ؒ2H2O and syn(OP(H)(O)2),anti(OH2)-[Co(cyclen)-
(OH2){OP(H)(O)2}]ClO4ؒ3H2O
Chemical formula
Formula weight
Crystal system
Space group
µ(Mo-Kα)/mmϪ1
T/K
a/Å
b/Å
c/Å
α/Њ
C6H26ClCoN5O9P
437.67
C8H29ClCoN4O11P
482.70
Triclinic
Triclinic
¯
¯
P1
P1
1.422
168(2)
1.244
158(2)
7.715(3)
9.047(3)
13.478(3)
78.51(2)
83.63(2)
81.03(3)
907.5(5)
2
7.7245(8)
7.9011(7)
13.5297(7)
77.282(5)
84.402(7)
77.001(12)
783.84(11)
2
β/Њ
γ/Њ
V/Å3
Z
Reflections
measured
Unique
3978
3963
3738 [R(int) = 0.0180]
3180 [R(int) = 0.0283]
reflections
Final R1, wR2
[I > 2σ(I)]
(all data)
syn(OP(H)(O)2),anti(OH2)-[Co(cyclen)(OH2){OP(H)(O)2}]-
ClO4ؒ3H2O. To a warm (50 ЊC) solution of [Co(cyclen)(O2-
CO)]ClO4ؒH2O28 (0.408 g, 1.0 × 10Ϫ3 mol) in water (5 cm3) was
added HClO4 (1.0 mol dmϪ3, 2.5 cm3, 2.5 × 10Ϫ3 mol). Once
CO2 evolution was complete Na2HPO3ؒ5H2O (0.27 g, 1.25 ×
10Ϫ3 mol) was added and after 10 min the solution was filtered.
Lithium perchlorate (1.0 g) then EtOH (10 cm3) were added
and the solution was allowed to stand for 24 h at 4 ЊC. The
purple crystals which deposited were of crystallographic qual-
ity; these were filtered off, washed with EtOH and air dried.
Found: C, 20.11; H, 6.12; N, 11.46; P, 6.33. C8H23ClCoN4-
O8Pؒ3H2O requires C, 19.91; H, 6.06; N, 11.61; P, 6.42%. 31P
NMR in weakly acidified D2O: δ 14.11, d, J PH 604 Hz.
0.0275, 0.0675
0.0326, 0.0699
0.0385, 0.0888
0.0528, 0.0925
0.0100 mol dmϪ3 potassium hydrogenphthalate and 0.050 mol
dmϪ3 KHC2O4ؒH2C2O4ؒ2H2O buffers.
Crystal structures
Diffraction data for t-[Co(tren)(NH3){OP(H)(O)2}]ClO4 and
[Co(cyclen)(OH2){OP(H)(O)2}]ClO4 were collected on
a
Siemens P4 diffractometer, processed, and empirical absorption
corrections applied using programs from the SHELXTL pack-
age.32 The structures were solved by direct methods using the
TREF option in SHELXS 97,33 with the resulting Fourier map
revealing the location of all non-hydrogen atoms. Weighted full
matrix refinement on F 2 was carried out using SHELXL
9734 with all non-hydrogen atoms being refined anisotropic-
ally.
Physical measurements
The pKa values for p- and t-[Co(tren)(NH3){OP(H)(OH)O}]2ϩ
,
,
[Co(NH3)5{OP(H)(OH)O}]2ϩ [Co(NH3)5{OP(D)(OH)O}]2ϩ
,
H2PO3Ϫ and HDPO3Ϫ were determined by potentiometric titra-
tion using standard methods.29 The first acid dissociation con-
stant of H3PO3 (pKa1H) was obtained by 31P NMR titration.
Values are reported as concentration constants; Ka = [AϪ][Hϩ]/
[HA], with [Hϩ] = aHϩ/γ , and aHϩ = 10ϪpH for γ = 0.67 (I = 1.0
mol dmϪ3, NaClO4).30 Bromine oxidation kinetics were followed
using a Durrum D110 stopped-flow spectrometer coupled to a
North Star Horizon computer running Olis software.31 Rate
data (25.0 ЊC, I = 1.0 mol dmϪ3, NaClO4) were collected using
pseudo first-order conditions, with Br2 as the limiting reagent
for both variable (0.025–0.200 mol dmϪ3) and constant [BrϪ]T
(0.10 mol dmϪ3). Solutions were unbuffered. Reactions were
followed over at least four half-lives by monitoring the decay of
t-[Co(tren)(NH3){OP(H)(O)2}]ClO4ؒ2H2O. All hydrogen
atoms except H1 were included in calculated positions and
refined as riding atoms with individual (or group, if appropri-
ate) isotropic displacement parameters; H1 was located and
refined to a distance of 1.336 Å from P1. The goodness of fit
was 1.094 and maximum ∆/σ = 0.001. A final Fourier-difference
map showed the highest peak to be 0.480 e ÅϪ3
.
[Co(cyclen)(OH2){OP(H)(O)2}]ClO4ؒ3H2O. All hydrogen
atoms were included in calculated positions, except for H1
which was fixed at a distance of 1.300 Å from P1, and refined as
described above. The goodness of fit was 0.965 and maximum
∆/σ = 0.000. The highest peak in the final Fourier-difference
Ϫ
the Br3 absorption at 400 nm and first-order rate constants
obtained from least squares fits of the resulting absorbance–
time data. Errors in the first-order constants are estimated to be
3% (oxidation reactions) or 10% (H/D exchange processes).
pH Determinations were carried out on completion of the reac-
tions. There was no detectable difference in pH ( 0.02) between
the reaction mixtures and ‘blanks’ of identical composition, but
without added Br2. The 31P NMR spectra were recorded using a
Varian VXR-300 spectrometer operating at 121.4 MHz. Chem-
ical shifts are given relative to external H3PO4 in water (δ 0.00).
The 17O NMR spectra were recorded either using the VXR-300
spectrometer equipped with a 10 mm probe and operating at
40.662 MHz, or a Varian Inova-500 2-channel spectrometer
equipped with a 5 mm probe and operating at 67.751 MHz.
Chemical shifts are given relative to water (δ 0.00) and peak
areas were determined relative to external 17O-labelled
CH3CO2H (δ 256.3). The UV-vis spectra were recorded using
a Cary 219 spectrometer. pH Measurements were made using a
Radiometer 82 pH meter equipped with K4040 (calomel) and
G2040B (glass) electrodes. The system was standardised with
use of 0.025 mol dmϪ3 Na2HPO4–0.025 mol dmϪ3 KH2PO4,
map was 0.410 e ÅϪ3
.
Selected crystal and refinement data for both structures are
given in Table 5.
CCDC reference number 186/1661.
References
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2 D. E. Linn and E. S. Gould, Inorg. Chem., 1987, 26, 3442.
3 D. E. Linn and E. S. Gould, Inorg. Chem., 1988, 27, 3140.
4 C. R. Clark, D. A. Buckingham, A. G. Blackman and G. B.
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5 A. Moondra, A. Mathur and K. K. Banerji, Int. J. Chem. Kinet.,
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6 G. P. Haight, Jr., M. Rose and J. Preer, J. Am. Chem. Soc., 1968, 90,
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3815