Silver(I) Assisted Metal Exchange Reaction. A Generalized Synthesis of Tris-Chelated Copper(II) Complexes of Neutral N,N-Donors

Full text of DOI:10.1021/ic970819m

Inorg. Chem. 1998, 37, 1651-1654
1651
(phen)3]2+. Mixed-ligand tris(chelates) of Cu(II) are, however,
not known. The silver(I) assisted transmetalation synthetic route
to synthesize such complexes is described herein. Three
bidentate ligands (L1-L3) were chosen for this purpose. All
of them are known to form stable12-14 compounds of silver(I).
The syntheses of the complexes are elaborated by Schemes, 1
and 2.
Silver(I) Assisted Metal Exchange Reaction. A
Generalized Synthesis of Tris-Chelated
Copper(II) Complexes of Neutral N,N-Donors
Partha Majumdar,† Amit K. Ghosh,†
Larry R. Falvello,‡ Shie-Ming Peng,§ and
Sreebrata Goswami*,†
Scheme 1
Department of Inorganic Chemistry, Indian Association for
the Cultivation of Science, Calcutta 700 032, India,
Departamento de Quimica Inorganica, Universidad de
Zaragoza, Spain, and Department of Chemistry,
National Taiwan University, Taipei, Taiwan,
People’s Republic of China
CH3CN
CuCl2‚2H2O + L
8 CuLCl2
L ) L1-L3
Scheme 2
CuL′Cl2 + 2AgL′′2
+
8
L′ ) L1-L3
L′′ ) L1-L3
ReceiVed July 2, 1997
2+ + 2L′′ + 2AgCl
]
Introduction
[CuL′nL′′3-n
n ) 0-3
This report describes a general synthetic route for the
syntheses of monomeric hexacoordinated tris-chelated com-
plexes of Cu(II). The syntheses have been achieved following
the silver(I) assisted metal exchange reaction strategy,1-6 which
recently has been developed by us and successfully used for
the controlled syntheses of transition-metal complexes of desired
compositions. Using three neutral N,N-donors, viz., N-p-
tolylpyridine-2-aldimine (L1, ptsb), 2,2′-bipyridine (L2, bpy) and
1,10-phenanthroline (L3, phen), it has been possible to isolate
two complete series of tris(chelates) of general formulas
[CuL1 L23-n](ClO4)2 and [CuL2 L33-n](ClO4)2 (n ) 0-3) in the
Scheme 1 illustrates the syntheses of the dichloro compounds
CuLCl2 by the direct reaction of equimolar quantities of CuCl2‚
2H2O and L in good yields (80-85%). These are found to be
suitable starting compounds for syntheses of the tris-chelated
species. Scheme 2 describes a general synthetic methodology
for syntheses of the tris(chelates) of Cu(II). By the selection
of an appropriate combination of reactants, the mixed-ligand
complexes of desired compositions can be prepared very easily.
For example, the reaction of CuL1Cl2 and 2 mol of [AgL2 ]+
2
n
n
produces [CuL1L2 ]2+, whereas a similar reaction starting from
2
pure crystalline state. It may be noted here that monomeric
tris(chelates) of Cu(II) involving N,N-donors are uncommon7,8
due to pronounced Jahn-Teller distortions, and a mixed-ligand
complex of the above type does not exist at all. The three-
CuL2Cl2 and [AgL12]+ (1:2 molar proportion) yields [CuL2L12]2+.
The syntheses of pure tris(chelates) [CuL3]2+ can be achieved
by the direct reaction of CuLCl2 and the silver compound of
the same ligand. All of the tris complexes described above are
obtained in the crystalline state as their perchlorate salts in high
yields (ca. 75%).
dimensional structures of a mixed-ligand complex, [CuL1 L2]-
2
(ClO4)2, and a tris(chelate), [CuL2 ](ClO4)2, have been solved
3
by X-ray diffraction.
By contrast, the reaction of Cu(NO3)2‚3H2O and free L in
ethanol produces bis(chelates), CuL22+. The differences in the
compositions of the products from these two different routes
may be viewed as follows. In the reaction of solvated cupric
ion and free L, the stepwise substitution of solvents by L starts
with the two most labile trans sites (Jahn-Teller effect) whereas,
in the silver-assisted route, initial attack of the silver reagent
presumably occurs at the two chlorides which are in relative
cis positions in CuLCl2. The most important outcome of the
above synthetic methodology is the isolation of a series of mixed
tris(chelates) of predetermined compositions by the controlled
insertion of ligands to the metal ion, which have in the past not
been known.
These complexes are paramagnetic, and the magnetic mo-
ments (µeff values) fall in the range 1.75-1.85 µB. Their IR
spectral patterns are typical for complexes of these ligands.
In the synthesis of mixed-ligand complexes, the formation
of a mixture of species of different compositions due to
scrambling of ligands cannot be ruled out. However, analysis
of the spectral data as well as voltammetric responses of the
bulk materials (Table 1, Figure 1) indicated that the product
obtained from each of the above reactions is pure. All of the
Results and Discussion
A. Syntheses. The examples of tris-chelated cupric com-
plexes of neutral N,N-donors are limited. The examples9-11
are [Cu(en)3]2+ (en ) ethylenediamine), [Cu(bpy)3]2+, and [Cu-
* Corresponding author: 91-33-473-2805 (FAX); icsg@iacs.ernet.in (E-
mail).
† Indian Association for the Cultivation of Science.
‡ Universidad de Zaragoza.
§ National Taiwan University.
(1) Kharmawaphlang, W.; Choudhury, S.; Deb, A. K.; Goswami, S. Inorg.
Chem. 1995, 34, 3826.
(2) Choudhury, S.; Deb, A. K.; Kharmawaphlang, W.; Goswami, S. J.
Chem. Soc., Dalton Trans. 1994, 1305.
(3) Choudhury, S.; Deb, A. K.; Kharmawaphlang, W.; Goswami, S. Proc.
Indian Acad. Sci., Chem. Sci. 1994, 106, 665.
(4) Kakoti, M.; Deb, A. K.; Goswami, S. Inorg. Chem. 1992, 31, 1302.
(5) Choudhury, S.; Deb, A. K.; Goswami, S. Polyhedron 1992, 11, 3183.
(6) Deb, A. K.; Kakoti, M.; Goswami, S. J. Chem. Soc., Dalton Trans.
1991, 3249.
(7) Folgado, J. V.; Henke, W.; Allmann, R.; Stratemeier, H.; Porter, D.
B.; Rojo, T.; Reinen, D. Inorg. Chem. 1990, 29, 2035.
(8) Hathaway, B. J. ComprehensiVe Coordination Chemistry; Pergamon
Press: Oxford, U.K., 1987; Vol. 5, p 596.
(9) Cullen, D. L.; Lingafelter, E. C. Inorg. Chem. 1970, 9, 1858. Bertini,
I.; Dapporto, P.; Gatteschi, D.; Scozzafava, A. J. Chem. Soc., Dalton
Trans. 1979, 1409.
(12) Deb, A. K.; Choudhury, S.; Goswami, S. Polyhedron 1990, 9, 2251.
(13) Murtha, D. P.; Walton, R. A. Inorg. Chem. 1973, 12, 368.
(14) Hieber, W.; Muhlbauer, F. Ber. Dtsch. Chem. Ges. 1928, 61, 2149.
(10) Anderson, O. P. J. Chem. Soc., Dalton Trans. 1972, 2597.
(11) Anderson, O. P. J. Chem. Soc., Dalton Trans. 1973, 1247.
S0020-1669(97)00819-7 CCC: $15.00 © 1998 American Chemical Society
Published on Web 03/07/1998

1652 Inorganic Chemistry, Vol. 37, No. 7, 1998
Table 1. Characterization Data for the Complexes
Notes
E1/2, V
λ
max, nm
(∆Ep, mV)b for
Cu(II) S Cu(I)
a
complex
(ꢀ, M-1 cm-1
)
[Cu(ptsb)3](ClO4)2
677 (94), 320 (24 600),
300 (24 300)
0.29 (180)
[Cu(bpy)3](ClO4)2
[Cu(phen)3](ClO4)2
[Cu(bpy)(ptsb)2](ClO4)2 655 (91), 330 sh (20 380),
310 sh (33 840),
680 (106), 295 (38 400)
675 (105), 290 (36 250)
0.04 (160)
0.03 (170)
0.19 (220)
300 (35 770)
[Cu(ptsb)(bpy)2](ClO4)2 680 (105), 305 sh (26 800),
295 (32 800)
0.06 (180)
[Cu(phen)(bpy)2](ClO4)2 680 (70), 295 (27 750)
[Cu(bpy)(phen)2](ClO4)2 685 (86), 290 (25 780)
0.03 (210)
0.15 (210)
0.28 (200)
0.11 (170)
0.12 (180)
[Cu(ptsb)Cl2]c
[Cu(bpy)Cl2]c
[Cu(phen)Cl2]c
725, 325
650, 370
680, 380
a Data obtained from absorption spectra: solvent, CH3CN. b Data
obtained from cyclic voltammetric experiments: solvent, CH3CN (0.1
Figure 2. Thermal ellipsoid plot of the cationic complex [Cu(bpy)-
(ptsb)2]2+. Atoms are represented by their 40% probability ellipsoids.
M TBAP); V ) 50 mV s-1 c The dihalo complexes are only sparingly
.
soluble in common organic solvents. Quantitative spectra could not be
recorded.
in the structures of the mixed-ligand compounds. In almost all
cases the compounds appear to be crystalline but were not
suitable for X-ray study. Fortunately, after several trials, X-ray-
quality crystals of [CuL1 L2](ClO4)2 could be isolated. Crystals
2
of this compound were found to be very weak scatterers, and
the structure determination was not routine (Experimental
Section). Details of the diffraction experiment are provided as
Supporting Information. For the purpose of this report we use
this structural analysis only to establish identity and gross
features of the system. The six-coordinate copper center in the
dicationic complex has distorted octahedral geometry (Figure
2), in which the distortions are of two distinct origins. First,
there is the Jahn-Teller elongation of the two Cu-ligand bonds
in relative trans positions. In this case, the two elongated bonds
are to the nitrogen atoms attached to the p-tolyl groups of the
ptsb ligands. The second main distortion of the coordination
shell around the copper atom is the contraction of three of the
N-M-N angles from the ideal octahedral values, imposed by
the three chelate ligands. The chelate angle for the bpy ligand,
N(1)-Cu(1)-N(2), is 80.6(3)°, while the values for the two
ptsb ligands are slightly smaller: N(3)-Cu(1)-N(4), 76.7(4)°;
N(5)-Cu(1)-N(6), 75.2(4)°. The cation approximates to
overall C2 symmetry. The 2-fold axis bisects the N(1)-Cu-
(1)-N(2) angle, as well as the angle N(3)-Cu(1)-N(5).
The structural analysis of [Cu(bpy)3](ClO4)2 revealed that the
coordination geometry of the complex about the copper(II) is
also distorted octahedral (Figure 3). The types of distortions
are similar to those observed for [Cu(bpy)(ptsb)2](ClO4)2. There
are four similar Cu-N(py) bonds in the mixed-ligand compound
on the equatorial plane, with a mean length of 2.023(9) Å, which
is statistically equivalent to the four equal Cu-N(py) bonds in
[Cu(bpy)3]2+, mean 2.031(3) Å. The remaining two Cu-
N(imine) bonds are of very similar lengths: Cu-N(4) and Cu-
N(6), 2.395(10) and 2.444(10) Å, respectively. By contrast,
the elongated bonds in [Cu(bpy)3]2+ are quite different: Cu-
N(4), 2.453(3) Å, and Cu-N(5), 2.237(3) Å. It may be
mentioned here that the structural analysis of [Cu(en)3](ClO4)2
showed that it is essentially nondistorted at room temperature
with strong dynamic Jahn-Teller effects operative; on the other
hand, the complex [Cu(phen)3](ClO4)2 exhibits11 a static Jahn-
Teller distortion with two long bonds of similar length.
Figure 1. Cyclic voltammograms of (a) [Cu(ptsb)3]2+ (- - -), (b)
[Cu(bpy)(ptsb)2]2+ (s), and (c) [Cu(bpy)3]2+ (-‚-‚) in CH3CN (0.1M
TBAP).
tris(chelates) showed almost similar spectral features (Table 1)
with varied absorption maxima and intensities. The lowest
energy transition, in the range 680-650 nm, is weak and broad
and is assigned to a d-d transition. In the case of dihalo
complexes these transitions occur in the range 725-650 nm.
Neither the spectra nor the voltammetric responses of the tris-
(chelates) showed any sign of the presence of a mixture of
compounds. In the series [Cu(ptsb)n(bpy)3-n]
2+ (n ) 0-3), the
E1/2 occurs at 0.29 V for [Cu(ptsb)3]2+ and decreases with the
substitution of each ptsb by a bpy ligand. Thus, the E1/2 values
(Table 1) of the mixed-ligand complexes [Cu(ptsb)2(bpy)]2+ and
[Cu(ptsb)(bpy)2]2+ lie between those of [Cu(ptsb)3]2+ and [Cu-
(bpy)3]2+. Each of the dihalo complexes also showed one quasi-
reversible redox process. The value of E1/2 for Cu(ptsb)Cl2
appears at 0.28 V, which is about 160 mV more anodic than
those for Cu(bpy)Cl2 and Cu(phen)Cl2. Final characterization
of the complexes was made by the analysis of single-crystal
X-ray data of two representative complexes which are elaborated
below.
B. Structure. A survey of the literature indicates that X-ray
structural investigations on tris-chelated Cu(II)-N6 complexes
involving neutral ligands are solely confined9-11 to the com-
plexes of three identical N,N-donors. Structurally characterized
mixed-ligand tris-chelated cupric complexes of neutral ligands
are, however, unknown. Consequently, there has been interest
Experimental Section
Materials. Cupric salts, CuCl2‚2H2O and Cu(NO3)2‚3H2O, were
obtained from S. D. Fine Chem. Ltd. The ligands and their silver

Notes
Inorganic Chemistry, Vol. 37, No. 7, 1998 1653
Table 2. Crystal Data for [Cu(bpy)(ptsb)2](ClO4)2 and
[Cu(bpy)3](ClO4)2
[Cu(bpy)(ptsb)2]-
(ClO4)2
[Cu(bpy)3]-
(ClO4)2
formula
fw
space group
a, Å
b, Å
c, Å
R (deg)
â (deg)
γ (deg)
V, Å3
Z
CuC36H32N6Cl2O8 CuC30H25N6Cl2O8.5
811.12
I2/a
739.00
P1h
26.127(3)
10.6965(7)
27.074(4)
90
7.927(3)
11.0236(14)
18.4768(22)
79.648(10)
89.793(17)
82.110(17)
1572.9(7)
2
103.90(1)
90
7344.7(14)
8
T, °C
λ, Å
23 ( 2
0.7107
1.467
25
0.7107
1.560
F
calcd, g cm-3
transm factors, max, min 0.918, 0.836
R
wR2
Rw
0.939, 1.000
0.088a
0.226b
0.036a
Figure 3. Thermal ellipsoid plot of the cationic complex [Cu(bpy)3]2+
.
Atoms are represented by their 40% probability ellipsoids.
0.035c
GOF
1.05
0.67, -0.63
1.80
0.30, -0.24
complexes, [AgL2]X‚nH2O (X ) ClO4, NO3), were prepared as
previously described.12-14 All other chemicals and organic solvents
used in synthesis were of reagent grade commercial materials. For
electrochemical and spectral data, spectro grade CH3CN was used.
Commercial tetraethylammonium bromide was converted to tetrabut-
ylammonium perchlorate (TBAP) as described before.15
Measurements. IR spectra were recorded as KBr disks (4000-
300 cm-1) using a Perkin-Elmer IR-783 spectrophotometer. The
magnetic susceptibilities of the samples were measured on a PAR 155
vibrating sample magnetometer fitted with a Walker Scientific L 75
FBAL magnet. Microanalyses (C, H, N) were done by using a Perkin-
Elmer 240C elemental analyzer. Electrochemical measurements were
done using the PAR model 370-4 electrochemistry system as described
before.16 The potentials reported here are referenced to the SCE.
Preparation of Complexes. CAUTION! Perchlorate salts of metal
complexes are explosive. Although no detonation tendencies have been
observed, caution is advised and handling of only small quantities is
recommended.
largest difference peak
and trough, e/Å3
a R ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc2)2/∑w(Fo )2]1/2
.
2
2
c Rw ) [∑w(|Fo| - |Fc|)2/∑|Fo| ]1/2
.
2
The dark green crystals that were deposited were filtered off and washed
with ether (3 × 5 mL). Yield: 76%. Anal. Calcd for CuC39H36N6O8-
Cl2: C, 55.02; H, 4.23; N, 9.87. Found: C, 54.84; H, 4.35; N, 9.59.
µeff (298 K): 1.87 µB. νmax, cm-1 (KBr): νCdN,CdC 1625, 1590; νClO
4
1100, 625.
[Cu(bpy)3](ClO4)2. Color: blue. Yield: 80%. Anal. Calcd for
CuC30H24N6O8Cl2: C, 49.28; H, 3.28; N, 11.50. Found: C, 49.08; H,
3.29; N, 11.47. µeff (298 K): 1.84 µB. νmax, cm-1 (KBr): νCdN,CdC 1605,
1595; νClO 1100, 630.
4
[Cu(phen)3](ClO4)2. Color: blue. Yield: 75%. Anal. Calcd for
CuC36H24N6O8Cl2: C, 58.46; H, 3.25; N, 11.37. Found: C, 58.35; H,
3.15; N, 11.28. µeff (298 K): 1.79 µB. νmax, cm-1 (KBr): νCdN,CdC 1610,
1590; νClO 1100, 625.
Dichloro(N-p-tolylpyridine-2-aldimine)copper(II), CuCl2(ptsb).
CuCl2‚2H2O (0.100 g, 0.60 mmol) in 30 mL of acetonitrile was mixed
with L1 (0.117 g, 0.60 mmol), and the mixture was stirred vigorously
at room temperature for 1 h. The brown crystalline product was isolated
by filtration, washed with ether, and finally dried in vacuo. Yield:
84%. Anal. Calcd for CuC13H12N2Cl2: C, 47.20; H, 3.63; N, 8.47.
Found: C, 46.80; H, 3.64; N, 8.23. µeff (298 K): 1.76 µB. νmax, cm-1
(KBr): νCdN,CdC 1600, 1590; νCu-Cl 360.
4
Mixed-ligand complexes were also prepared similarly by using
appropriate reactants at a room temperature (298 K). For example,
for the synthesis of [Cu(bpy)(ptsb)2](ClO4)2, CuCl2(bpy) was reacted
with 2 mol of [Ag(ptsb)2](ClO4), and for the synthesis of [Cu(ptsb)-
(bpy)2](ClO4)2, CuCl2(ptsb) was reacted with hydrated [Ag(bpy)2](NO3)
and aqueous NaClO4 was added for crystallization. The yields and
selected characterization data are as follows.
The other two dichloro compounds were synthesized similarly by
using appropriate ligands.
[Cu(bpy)(ptsb)2](ClO4)2. Color: green. Yield: 82%. Anal. Calcd
for CuC36H32N6O8Cl2: C, 53.30; H, 3.94; N, 10.36. Found: C, 52.96;
H, 4.02; N, 10.48. µeff (298 K): 1.84 µB. νmax, cm-1 (KBr): νCdN,CdC
CuCl2(bpy). Color: light green. Yield: 80%. Anal. Calcd for
CuC10H8N2Cl2: C, 41.30; H, 2.75; N, 9.63. Found: C, 41.59; H, 2.65;
N, 9.65. µeff (298 K): 1.79 µB. νmax, cm-1 (KBr): νCdN,CdC 1610, 1590;
νCu-Cl 355.
CuCl2(phen): Color: light green. Yield: 82%. Anal. Calcd for
CuC12H8N2Cl2: C, 43.31; H, 2.41; N, 8.42. Found: C, 43.35; H, 2.50;
N, 8.48. µeff (298 K): 1.75 µB. νmax, cm-1 (KBr): νCdN,CdC 1605, 1590;
νCu-Cl 355.
The tris-chelated complexes were prepared by using a general
procedure. A representative example is described below.
Tris(N-p-tolylpyridine-2-aldimine)copper(II) Perchlorate, [Cu-
(ptsb)3](ClO4)2. A mixture of CuCl2(ptsb) (0.331 g, 1 mmol) and [Ag-
(ptsb)2](ClO4) (0.119 g, 2 mmol) in 30 mL of methanol was heated to
reflux for 1 h. The resulting brown solution was cooled and filtered
through quantitative filter paper to remove insoluble AgCl. The filtrate
was then concentrated to 10 mL and left overnight at room temperature.
1625, 1600; νClO 1100, 625.
4
[Cu(ptsb)(bpy)2](ClO4)2. Color: green. Yield: 72%. Anal. Calcd
for CuC33H28N6O8Cl2: C, 51.39; H, 3.63; N, 10.90. Found: C, 50.72;
H, 3.69; N, 11.20. µeff (298 K): 1.77 µB. νmax, cm-1 (KBr): νCdN,CdC
1630, 1600; νClO 1100, 630.
4
[Cu(phen)(bpy)2](ClO4)2. Color: blue. Yield: 84%. Anal. Calcd
for CuC32H24N6O8Cl2: C, 50.89; H, 3.18; N, 11.13. Found: C, 50.68;
H, 3.27; N, 11.01. µeff (298 K): 1.78 µB. νmax, cm-1 (KBr): νCdN,CdC
1620, 1600; νClO 1100, 625.
4
[Cu(bpy)(phen)2](ClO4)2. Color: blue. Yield: 80%. Anal. Calcd
for CuC34H24N6O8Cl2: C, 52.40; H, 3.08; N, 10.78. Found: C, 52.87;
H, 3.35; N, 10.62. µeff (298 K): 1.84 µB. νmax, cm-1 (KBr): νCdN,CdC
1620, 1600; νClO 1100, 630.
4
X-ray Structure Determination. Single crystals of [Cu(ptsb)2(bpy)]-
(ClO4)2 and [Cu(bpy)3](ClO4)2 were obtained directly from the respec-
tive reaction mixtures. The crystal data are summarized in Table 2.
Tables containing full listings of atom positions, anisotropic thermal
parameters, bond lengths, and bond angles are available as Supporting
Information.
(15) Sawyer, D. T.; Roberts, J. L., Jr. Experimental Electrochemistry for
Chemists; Wiley: New York, 1974; p 167.
(16) Goswami, S.; Mukherjee, R.; Chakravorty, A. Inorg. Chem. 1983, 22,
2825.

1654 Inorganic Chemistry, Vol. 37, No. 7, 1998
Notes
[Cu(bpy)(ptsb)2](ClO4)2. Diffraction data were collected at room
temperature on a Nonius CAD-4 diffractometer with graphite-mono-
chromated Mo KR radiation. Crystals of this compound were found
to be very weak scatterers, and the structure determination was not
routine. Details of the diffraction experiment are provided as Sup-
porting Information. In brief, intensity data were gathered slowly, in
keeping with the weakness of the diffraction pattern. The data were
gathered in two shells, and for the upper shell a scan time of up to 3
min/reflection was used. Absorption corrections were applied, based
on measurements of 13 ψ-scans, four of which were of scattering
vectors in general positions, that is, with the Eulerian angle ø not
approximately 90°, so as to achieve a more complete coverage of the
absorption surface of the crystal. The structure was solved by the
automated Patterson interpretation routine incorporated in the package
SHELXTL-PLUS17,18 followed by difference direct methods and peak-
list optimization. Hydrogen atoms were placed at calculated positions,
except for the methyl hydrogen atoms, which were located in a local
slant Fourier calculation. All of the hydrogen atoms were treated as
riders. In the final, convergent refinement, 462 variable parameters
were fitted to 4420 data and 396 restraints, giving an observation-to-
parameter ratio of 10.4. All reflections with non-negative intensities
were used in the refinement, and the structural model was refined to
above all by using a statistically sound refinement method, as
incorporated in the program SHELXL-93.18 The final least-squares
residuals R and R2 (Table 2) are rather high in comparison with those
that would be derived from a routine structure determination. No
unusual effects in the usual first indicators of problems, namely, the
anisotropic displacement parameters of the non-hydrogen atoms and
the final difference electron density, were observed. Nevertheless, for
the purposes of this report this structure determination was used mainly
to establish gross features of the system, and no attempts have been
made to draw conclusions based on fine details.
[Cu(bpy)3](ClO4)2. Intensity data were collected at room temper-
ature on an Enraf-Nonius diffractometer with graphite-monochromated
Mo KR radiation (λ ) 0.7107 Å). The dimensions of the crystal were
0.20 × 0.30 × 0.50 mm3. A total of 4117 unique reflections were
measured, of which 3267 with I > 2σ(I) were used in structure solution
refinement. The structure was solved by the heavy-atom method and
refined by least squares. The final least-squares cycle, calculated with
456 parameters, gave R ) 0.036 and Rw ) 0.035. The goodness of fit
is 1.80. The final difference Fourier map showed no unusual feature
with residuals in the range -0.240 to +0.300 e Å-3
.
Acknowledgment. Thanks are due to Dr. Alok K. Deb and
Ms. Wancydora Kharmawphlang, NEHU, Shillong, for carrying
out preliminary experiments. Funding from the Council of
Scientific and Industrial Research, New Delhi, and the Spanish
Comision Interministerial de Ciencia Y Technologia (Project
PB95-0792) is gratefully acknowledged. We are grateful to the
referees for suggestions.
2
Fo . The weighting scheme was adjusted in such a way as to attain, as
far as possible, a constant distribution of weighted deviates as a function
of the magnitude of Fo.
Although it was clear at the outset of the structure determination
that this was not going to be a routine case, it was hoped to be able to
extract as much valid structural information as possible through the
use of careful data collection and absorption correction techniques, and
Supporting Information Available: Tables of atomic coordinates,
anisotropic displacement parameters, and bond lengths and angles for
[Cu(bpy)(ptsb)2](ClO4)2 and [Cu(bpy)3](ClO4)2 and experimental details
and a table of hydrogen atom coordinates for [Cu(bpy)(ptsb)2](ClO4)2
(17 pages). Ordering information is given on any current masthead
page.
(17) Data reduction and initial structure solution were carried out on the
VAX cluster with the commercial package SHELXTL-PLUS Release
4.21/V: 1990, Siemens Analytical X-ray Instruments, Inc., Madison,
WI. Least-squares refinements were done by the program SHELXL-
93.18
(18) Sheldrick, G. M. SHELXL-93: Fortran-77 program for the refinement
of crystal structure from diffraction data. University of Go¨ttingen, 1993.
IC970819M