Comparative Crystallography. 5. Crystal Structures, Electronic Properties, and Structural Pathways of Five [Cu(phen)2Br][Y] Complexes, Y = [Br]-·H2O, [ClO4]-, [NO3]-·H2O, [PF6]-, and [BPh4]-

Article abstract of DOI:10.1021/ic970458a

The crystal structures of [Cu(phenh)₂Br][Br]·H₂O (1, phen = 1.10-phenanthroline), [Cu(phen)₂][ClO₄] (2), [Cu(phen)₂Br][NO₃]H₂O (3), [Cu(phen)₂Br][PF₆] (4), and [Cu(phen)₂Br][BPh₄] (5) have been determined by X-ray diffraction. Four of the complexes, 1-4, have a CuN₄Br chromophore with a square based pyramidal distorted trigonal bipyramidal (SBPDTB) stereochemistry, while 5 involves an extreme trigonal bipyramidal distorted square based pyramidal (TBDSBP) stereochemistry. The geometries of the CuN₄Br chromophores in 1-5 are compared by scatter plot analysis with a single [Cu(phen)₂Br][ClO₄] complex, 6, of known crystal structure involving a crystallographic 2-fold axis of symmetry. The distortion isomers of 2 and 6 are significantly different. The scatter plots of the six cation distortion isomers of the [Cu(phenh)₂Br][Y] series of complexes suggest that all six complexes lie on a common structural pathway, involving a mixture of the symmetric, v_sym, C₂ mode and the asymmetric, V_asym, non-C₂ mode of vibration of the CuN₄Br chromophore. The resulting linear and parallel structural pathways are consistent with the direct observation of the effect of vibronic coupling on the stereochemistries of the complexes, which can range from near regular trigonal bipyramidal (RTB) to TBDSBP for the cation distortion isomers of the [Cu(phen)₂Br][Y] complexes.

Full text of DOI:10.1021/ic970458a

240
Inorg. Chem. 1998, 37, 240-248
Comparative Crystallography. 5. Crystal Structures, Electronic Properties, and Structural
Pathways of Five [Cu(phen)2Br][Y] Complexes, Y ) [Br]-‚H2O, [ClO4]-, [NO3]-‚H2O,
[PF6]-, and [BPh4]-
Gillian Murphy, Cathal O’Sullivan, Brian Murphy,† and Brian Hathaway*
The Chemistry Department, University College Cork, Ireland
ReceiVed April 24, 1997X
The crystal structures of [Cu(phen)2Br][Br]‚H2O (1, phen ) 1,10-phenanthroline), [Cu(phen)2Br][ClO4] (2),
[Cu(phen)2Br][NO3]‚H2O (3), [Cu(phen)2Br][PF6] (4), and [Cu(phen)2Br][BPh4] (5) have been determined by
X-ray diffraction. Four of the complexes, 1-4, have a CuN4Br chromophore with a square based pyramidal
distorted trigonal bipyramidal (SBPDTB) stereochemistry, while 5 involves an extreme trigonal bipyramidal
distorted square based pyramidal (TBDSBP) stereochemistry. The geometries of the CuN4Br chromophores in
1-5 are compared by scatter plot analysis with a single [Cu(phen)2Br][ClO4] complex, 6, of known crystal structure
involving a crystallographic 2-fold axis of symmetry. The distortion isomers of 2 and 6 are significantly different.
The scatter plots of the six cation distortion isomers of the [Cu(phen)2Br][Y] series of complexes suggest that all
six complexes lie on a common structural pathway, involving a mixture of the symmetric, νsym, C2 mode and the
asymmetric, νasym, non-C2 mode of vibration of the CuN4Br chromophore. The resulting linear and parallel structural
pathways are consistent with the direct observation of the effect of vibronic coupling on the stereochemistries of
the complexes, which can range from near regular trigonal bipyramidal (RTB) to TBDSBP for the cation distortion
isomers of the [Cu(phen)2Br][Y] complexes.
green crystals of 1 were formed after 3 days. Anal. Calcd for C24H18-
CuBr2N4O (%): C, 47.90; H, 3.01; N, 9.31; Br, 26.56; Cu, 10.56.
Found: C, 47.44; H, 2.95; N, 9.26; Br, 26.59; Cu, 10.12. [Cu(phen)2Br]-
[ClO4], 2, was prepared by adding a hot solution of phen (0.36 g, 2
mmol) in 150 cm3 of propanone to a hot aqueous solution (30 cm3) of
[Cu(OH2)6][ClO4]2 (0.37 g, 1 mmol). Hexagonal green crystals of 2
were formed overnight. Anal. Calcd for C24H16CuBrN4ClO4 (%): C,
47.78; H, 2.67; N, 9.29; Cu, 10.53. Found (%): C, 47.39; H, 2.53; N,
9.17; Cu, 10.36. [Cu(phen)2Br][NO3]‚H2O, 3, was prepared by adding
a hot solution of phen (0.72 g, 4 mmol) in 30 cm3 of ethanol to a hot
aqueous solution (30 cm3) of Cu(NO3)2‚3H2O (0.24 g, 1 mmol) and
CuBr2 (0.22 g, 1 mmol). Hexagonal green crystals of 3 were deposited
after 5 days. Anal. Calcd for C24H18CuBrN5O4 (%): C, 49.37; H,
3.11; N, 12.00; Br, 13.69; Cu, 10.89. Found (%): C, 48.95; H, 3.15;
N, 11.87; Br, 14.13; Cu, 11.00. [Cu(phen)2Br][PF6], 4, was prepared
by adding a hot solution of phen (0.36 g, 2 mmol) in 150 cm3 of
propanone to a hot aqueous solution (30 cm3) of Cu(NO3)2‚3H2O (0.24
g, 1 mmol) and NaBr (0.10 g, 1 mmol). A hot aqueous solution (20
cm3) of KPF6 (0.18 g, 1 mmol) was then added to the mixture. Needle-
like green crystals of 4 formed overnight. Anal. Calcd for C24H16-
CuBrN4PF6 (%): C, 44.43; H, 2.49; N, 8.64; Br, 12.32; Cu, 9.79. Found
(%): C, 44.70; H, 2.51; N, 8.68; Br, 12.53; Cu, 9.39. [Cu(phen)2Br]-
[BPh4], 5, was prepared by adding a hot solution of phen (0.36 g, 2
mmol) in 300 cm3 of acetonitrile to a hot aqueous solution (30 cm3) of
CuBr2 (0.22 g, 1 mmol). A hot aqueous solution (20 cm3) of NaBPh4
(0.34 g, 1 mmol) was then added to the mixture. Large olive green
crystals of 5 were obtained after 3 days. Anal. Calcd for C48H36-
CuBrN4B (%): C, 70.04; H, 4.41; N, 6.81; Br, 9.71; Cu, 7.72. Found
(%): C, 70.39; H, 4.42; N, 6.68; Br, 9.49; Cu, 7.72.
Introduction
The [Cu(bipy)2X][Y] (bipy ) 2,2′-bipyridine) complexes
form a well-established structural pathway,1,2 where X ) Cl-,
Br- and I-, Figure 1. This approach has been extended to the
eight [Cu(phen)2Cl][Y] (phen ) 1,10-phenanthroline) com-
plexes3 which show the largest range of stereochemistries4 (τ
) 0.81-0.19) for the [Cu(chelate)2X][Y] complexes, where
chelate ) bipy and phen, and τ ) (R8 - R1)/605 , where τ ) 1.0
for the regular trigonal bipyramidal (RTB) and τ ) 0.0 for a
regular square based pyramidal (RSBP) stereochemistry. To
date, [Cu(phen)2Br][ClO4], 6,6 is the only [Cu(phen)2Br][Y]
complex of known crystal structure. In order to examine the
range of stereochemistries observed and to establish the direc-
tions of the distortion present, this paper reports the crystal
structures and electronic properties of five new [Cu(phen)2Br]-
[Y] complexes, 1-5.
Experimental Section
Preparations. [Cu(phen)2Br][Br]‚H2O, 1, was prepared by adding
a hot solution of phen (0.36 g, 2 mmol) in 200 cm3 of propanone to a
hot aqueous solution (20 cm3) of CuBr2 (0.22 g, 1 mmol). Hexagonal
† Present address: School of Chemical Sciences, Dublin City University,
Dublin 9, Ireland.
X Abstract published in AdVance ACS Abstracts, December 15, 1997.
(1) Harrison, W. D.; Kennedy, D. M.; Ray, N. J.; Sheahan, R.; Hathaway,
B. J. J. Chem. Soc., Dalton Trans. 1981, 1556.
(2) Nagle, P.; O’Sullivan, E.; Hathaway, B. J.; Muller, E. J. Chem. Soc.,
Dalton Trans. 1990, 3399.
Crystallography. The crystallographic and refinement data for 1-5
are given in Table 1. The unit cell parameters of 1-5 were determined
(25 reflections, θ ) 3-25°) and their intensities collected on an Enraf-
Nonius CAD4 diffractometer. Reflections in the range 3.0 < θ < 24°
were collected, in one hemisphere for 1, 3, and 5 and in one quadrant
for 2 and 4. The data were collected at room temperature using an
ω-2θ scan mode and a constant scan speed of 7 deg min-1, with a
(3) Murphy, G.; Nagle, P.; Murphy, B.; Hathaway, B. J. J. Chem. Soc.,
Dalton Trans. 1997, 2645.
(4) Brophy, M.; Murphy, G.; O’Sullivan, C.; Hathaway, B. J.; Murphy,
B. Polyhedron, submitted for publication.
(5) Addison, A. W.; Nageswara Rao, T.; Reedjik, J.; van Rijn, J.;
Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349.
(6) Parker, O. J.; Greiner, G. T.; Breneman, G. L.; Willett, R. D.
Polyhedron 1994, 2, 267.
S0020-1669(97)00458-8 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/26/1998

[Cu(phen)2Br][Y] Complexes
Inorganic Chemistry, Vol. 37, No. 2, 1998 241
Figure 1. Forms of distortion of the RTB CuN4Br chromophore involving the (A, (B, and (A ( B routine distortions.2 (The bond distance
values have been rounded off to the nearest 0.05 Å.)
Table 1. Crystallographic and Structure Refinement Data for [Cu(phen)2Br][Br]‚H2O, 1, [Cu(phen)2Br][ClO4], 2, [Cu(phen)2Br][NO3]‚H2O, 3,
[Cu(phen)2Br][PF6], 4, and [Cu(phen)2Br][BPh4], 5
1
2
3
4
5
stoichiometry
MW
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C24H18CuBr2N4O
601.793
triclinic
P1h (Ci1, No. 2)
9.853(1)
11.363(2)
11.875(1)
67.56(1)
67.35(1)
72.09(1)
1113.82
2
C24H16CuBrN4ClO4
603.318
monoclinic
P21/n (C2h5, No. 14)
10.272(1)
12.724(2)
17.450(2)
90.00
102.70(1)
90.00
2225.05
4
C24H18CuBrN5O4
583.888
triclinic
P1h (Ci1, No. 2)
9.929(2)
11.312(2)
12.056(2)
67.03(1)
68.91(1)
71.60(1)
1136.75
2
C24H16CuBrN4PF6
648.831
monoclinic
P21/n (C2h5, No. 14)
10.437(2)
12.533(4)
18.047(2)
90.00
102.32(1)
90.00
2306.29
4
C48H36CuBrN4B
823.104
triclinic
P1h (Ci1, No. 2)
11.202(3)
11.313(3)
15.738(6)
86.87(2)
76.39(2)
79.84(2)
1907.90
2
Z
Dc (g cm-3
)
1.79
44.91
0.0601
0.0598
1.76
28.58
0.0485
0.0479
1.71
26.88
0.0642
0.0628
1.87
27.38
0.0535
0.0554
1.43
16.06
0.0489
0.0534
µ (cm-1
)
Ra
b
Rw
2
a R ) ∑(|Fo| - |Fc|)/∑|Fo|. b Rw ) {∑[w(|Fo| - |Fc|)2/∑w|Fo| ]}1/2
.
variable scan width of (0.8 + 0.2 tan θ). Lorentz and polarization
corrections were applied, but no correction was made for absorption.
Data reduction was carried out using the program XCAD.7
parameters of 0.07 Å2. Complex atom scattering factors were used
for the non-hydrogen atoms.10
For 3, the anisotropic thermal parameters of [NO3]- were high and
the maximum residual electron densities were associated with it. The
anion was refined as a rigid body, by fixing the N-O distances at
1.226 Å and the O-N-O angles at 120°. A final difference Fourier
map revealed no peaks greater than +0.92 and -1.21 e Å-3, which
were associated with the [NO3]-.
The structures were solved using the SHELX 768 and SHELXS 869
programs, developed by difference Fourier techniques and refined by
full-matrix least-squares analysis. In each case, the least-squares
calculations were on |F|, the function minimized being ∑w(|Fo| - |Fc|)2.
A refined weighting scheme of the form w ) k/[σ2(Fo) + g(Fo)2] was
used. Anisotropic thermal parameters were employed for all of the
non-hydrogen atoms. The positions of the hydrogen atoms were
calculated geometrically and “floated” on the appropriate carbon atom
positions, assuming C-H distances of 1.08 Å and fixed thermal
(10) Cromer, D. T.; Waber, J. T. International Tables of Crystallography;
Kynoch Press: Birmingham, U.K., 1974; Vol. IV, pp 71, 148. (Present
distributor Kluwer Academic Publishers, Dordrecht, The Netherlands.)
(11) Roberts, P.; Sheldrick, G. M. XANADU, program for the calculation
of crystallographic data; University of Cambridge: Cambridge, U.K.,
1979.
(7) McCardle, P. XCAD, program for data reduction of CAD4 output;
University College Galway: Galway, Ireland, 1990.
(8) Sheldrick, G. M. SHELX 76, program for X-ray crystal structure
determination; University of Cambridge: Cambridge, U.K., 1976.
(9) Sheldrick, G. M. SHELXS 86, program for X-ray crystal structure
solution; University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(12) Henrick, K. PUBTAB, program to prepare and print crystallographic
tables for publication; University of North London: London, 1980.
(13) Spek, A. L. PLUTON-92, program to prepare and print molecular
structures; University of Utrecht: Utrecht, The Netherlands, 1992.

242 Inorganic Chemistry, Vol. 37, No. 2, 1998
Murphy et al.
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for the [Cu(phen)2Br][Y] and [Cu(phen)2I][Y] Complexes
Br
I
Y ) ClO4
(66)
Y ) Br‚H2O
(1)
Y ) ClO4
(2)
Y ) NO3‚H2O
(3)
Y ) PF6
(4)
Y ) BPh4
(5)
I‚3/4H2O
(715)
Y ) PF6
(816)
Y ) I‚S8
(917)
Cu-Cl(X)*
Cu-X
Cu-N(1)
Cu-N(2)
Cu-N(3)
Cu-N(4)
2.356(1)
2.496(1)
1.985(5)
2.091(3)
1.985(5)
2.091(3)
2.331(1)
2.471(1)
1.978(4)
2.072(4)
1.978(4)
2.086(4)
2.373(1)
2.513(1)
1.981(4)
2.095(4)
2.002(4)
2.101(4)
2.312(1)
2.452(1)
1.997(4)
2.085(3)
2.002(4)
2.108(3)
2.364(1)
2.504(1)
1.987(4)
2.088(4)
1.996(4)
2.126(4)
2.258(1)
2.398(1)
2.025(3)
2.055(3)
1.997(3)
2.217(3)
2.389(1)
2.719(1)
1.962(7)
2.089(7)
1.946(7)
2.240(7)
2.369(2)
2.699(2)
1.998(7)
2.086(7)
1.998(7)
2.086(7)
2.342(5)
2.672(5)
2.000(10)
2.100(10)
2.000(10)
2.100(10)
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
τ
119.8(1)
119.8(1)
120.6(2)
91.5(1)
91.5(1)
81.1(2)
81.1(2)
177.0(2)
97.5(2)
97.5(2)
0.95
126.5(1)
120.1(1)
113.5(2)
91.0(1)
90.5(1)
81.9(2)
82.0(2)
178.4(2)
97.5(2)
96.8(2)
0.87
125.7(1)
110.0(1)
124.3(1)
91.7(1)
90.9(1)
80.9(2)
81.6(2)
177.2(2)
98.3(2)
96.6(2)
0.86
129.8(1)
120.9(1)
109.3(1)
91.7(1)
91.3(1)
81.5(1)
81.5(1)
177.1(1)
96.6(1)
97.0(1)
0.79
133.4(1)
105.1(1)
121.5(2)
92.3(1)
91.4(1)
81.2(2)
81.0(2)
176.3(2)
96.6(2)
97.6(2)
0.72
157.2(1)
105.9(1)
96.8(1)
93.3(1)
91.0(1)
81.2(1)
79.8(1)
170.2(1)
91.5(1)
107.4(1)
0.22
115.4(2)
127.3(2)
117.2(2)
91.3(2)
89.8(2)
79.6(3)
81.7(3)
178.9(3)
100.3(3)
97.5(3)
1.06
122.3(2)
122.3(2)
115.4(2)
91.5(2)
91.5(2)
81.9(3)
81.9(3)
176.9(3)
96.5(2)
96.5(2)
0.91
125.3(3)
125.3(3)
109.4(3)
92.3(3)
92.3(3)
80.4(4)
80.4(4)
175.5(4)
97.0(4)
97.0(4)
0.84
a The Cu-X distances are corrected to Cu-Cl values using the following relationships: Cu-Br - 0.14 Å ) Cu-Cl(Br) and Cu-I - 0.33 Å )
Cu-Cl(I).
Figure 3. Atomic numbering scheme and Rn notation for the CuN4Br
chromophore.
[PF6]-, and [BPh4]- anions, respectively, and H2O molecules
for 1 and 3. None of the anions or water molecules are close
enough (<3.0 Å) to be considered even weakly semicoordinated
to the copper(II) cation.14 The cations all involve a five
coordinate CuN4Br chromophore in a general position, with a
near trigonal bipyramidal stereochemistry having a square based
pyramidal distortion2 (SBPDTB) in 1-4 and a trigonal bipy-
ramidal distorted square based pyramidal stereochemistry
(TBDSBP) in 5. These five complexes are further examples
of distortion isomers of the [Cu(phen)2X]+ cation,3,6 whose
stereochemistries are related by the structural pathways1,3 of
Figure 1. No attempt will be made to describe the individual
structures of complexes 1-5, Table 2, but scatter plot analysis
will be used to compare their structures with that of [Cu-
(phen)2Br][ClO4], 6, the only [Cu(phen)2Br][Y] complex to date
of known crystal structure.6 Table 2 summarises the selected
bond lengths and bond angles of the six [Cu(phen)2Br][Y]
complexes, sequenced in order of their τ values, where τ )
(R8-R1)/60.5 Compound 66 differs from complexes 1-5, as
the Cu and Br atoms lie on a 2-fold axis of symmetry. There
are three [Cu(phen)2I][Y] complexes of known crystal
structure,15-17 with two complexes having a 2-fold axis of
Figure 2. Molecular structure of [Cu(phen)2Br]+ of 1.
All calculations were carried out using the SHELX 76,8 SHELXS
86,9 XANADU,11 PUBTAB,12 and XCAD7 programs on a VAX 6310
computer. PLUTON-9213 was run on a Memorex 386 PC.
Selected bond lengths and bond angles for the six [Cu(phen)2Br]-
[Y] complexes are given in Table 2. Figure 2 shows a representative
molecular structure for the [Cu(phen)2Br]+ cation of 1, and Figure 3
shows the atomic numbering scheme and the angular notation used.
The diffuse reflectance spectra in the range 5000-30 000 cm-1, were
measured as polycrystalline samples on a Shimadzu UV-vis 3101
spectrometer.
The additional material, available from the Cambridge Crystal-
lographic Data Centre, comprises the final fractional atomic coordinates,
the anisotropic thermal parameters, the full bond length and angle data,
and selected mean plane data.
Results and Discussion
(14) Procter, I. M.; Hathaway, B. J.; Nichols, P. J. Chem. Soc., A 1968,
1678.
(15) Nagle, W. P. Ph.D. Thesis, National University of Ireland, 1990.
(16) Harrington, C.; Hathaway, B. J. Unpublished results.
Crystal Structures. The crystal structures of 1-5 consist
of discrete [Cu(phen)2Br]+ cations, [Br]-, [ClO4]-, [NO3]-,

[Cu(phen)2Br][Y] Complexes
Inorganic Chemistry, Vol. 37, No. 2, 1998 243
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for the [Cu(phen)2Cl][Y] Complexes
Y )
BF4‚1/2H2O
(1015)
Y )
ClO4
(1123)
Y )
PF6
Y )
Cl‚11/2H2O‚(CH3)2CO
(1324)
Y )
NO3‚H2O
(1425)
Y )
Cl‚11/2H2O‚(CH3)2CO
(1524)
Y )
CF3SO3‚H2O
(1626)
Y )
BPh4
(1726)
(1215)
Cu-Cl
2.304(2)
1.995(6)
2.078(5)
2.011(6)
2.121(6)
2.298(2)
1.986(6)
2.077(6)
2.004(6)
2.136(6)
2.294(2)
2.001(4)
2.076(4)
2.003(4)
2.157(4)
2.281(1)
1.999(4)
2.126(3)
1.995(3)
2.138(3)
2.292(1)
1.988(4)
2.091(2)
1.989(4)
2.132(2)
2.257(1)
1.990(4)
2.108(2)
1.993(4)
2.151(4)
2.280(1)
1.998(2)
2.127(2)
1.996(2)
2.151(2)
2.254(1)
2.024(2)
2.057(2)
2.008(2)
2.242(2)
Cu-N(1)
Cu-N(2)
Cu-N(3)
Cu-N(4)
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
τ
126.6(2)
118.9(2)
114.5(2)
92.8(2)
91.2(2)
81.3(2)
80.6(2)
175.3(2)
98.1(2)
95.4(2)
0.81
127.6(2)
119.0(2)
113.4(2)
92.3(2)
90.9(2)
81.7(2)
80.5(2)
176.2(2)
98.2(2)
96.0(2)
0.81
131.6(1)
114.4(1)
114.1(2)
93.4(1)
91.0(1)
81.0(2)
80.1(2)
175.2(2)
97.5(2)
96.3(2)
0.73
130.4(1)
129.6(1)
100.0(1)
94.1(1)
95.0(1)
80.1(2)
80.5(1)
170.8(1)
95.1(2)
92.5(1)
0.67
135.8(1)
119.2(1)
105.0(1)
92.7(1)
91.8(1)
81.4(1)
80.8(1)
175.6(1)
95.8(1)
96.5(1)
0.66
133.0(1)
120.6(1)
106.4(1)
96.8(1)
94.2(1)
81.1(1)
80.6(2)
168.6(2)
93.8(1)
91.0(2)
0.59
138.7(1)
127.9(1)
93.4(1)
93.2(1)
94.6(1)
80.7(1)
80.2(1)
172.1(1)
92.8(1)
95.7(1)
0.56
157.7(1)
105.9(1)
96.4(1)
92.7(1)
91.4(1)
81.0(1)
79.2(1)
169.2(1)
91.5(1)
109.1(1)
0.19
symmetry,16,17 Table 2. The chromophore of 6, has a near RTB
stereochemistry, with τ ) 0.95. The structures of 6 and 2 are
two independent isomers of the [Cu(phen)2Br][ClO4] complex.
The X-ray crystal structure determinations were carried out in
different space groups, monoclinic and triclinic, respectively,
which were checked to confirm that 6 and 2 were not identical.
The structural data show that 6 has a 2-fold axis of symmetry,
while 2 does not, with differences in bond lengths and angles
of ∼ 0.02 Å and ∼ 10° and τ values of 0.95 and 0.86,
respectively, Table 2.
Table 4. Suggested Limiting Values for the (A, +B, -A + B,
and +A + B Route Distortions
RTB
+A
-A
+B
-A + B +A + B
R1/deg
R2/deg
R3/deg
120
120
120
97.5
97.5
165
135
135
90
150
90
120
165
105
90
105
90
165
Cu-N(2)/Å 2.092 1.998 2.155 1.985 2.048
Cu-N(4)/Å 2.092 1.998 2.155 2.199 2.262
1.971
2.025
2.683
Cu-Br/Å
2.494 2.683 2.368 2.494 2.368
between the pyridine rings of 0-5°, in 5 both of these angles
are less than 1.02°. This suggests that the geometry of the
TBDSBP stereochemistry is inherently more stable, once
formed, than the range of SBDTB stereochemistries 0.72-0.95,
a stability that could be locked in place by the essential planarity
of the phen ligand. This is also reflected in the near trigonal
R1 angles of 119.8-133.4° of the SBPDTB stereochemistries,
relative to an R1 angle of 157.2° in 4.
For the six [Cu(phen)2Br][Y] complexes, the structure of the
five coordinate CuN4Br chromophore varies from near RTB to
near SBP, which is reflected in a range of τ values from 0.95
to 0.22, ∆ ) 0.73. This is the largest range seen to date for
any series of five coordinate cation distortion isomers18 involving
the same CuN4X chromophore, with the same set of ligand
atoms.3,18,19 Complex 5 has a τ value of 0.22 and TBDSBP
stereochemistry.20 The remaining four complexes have τ values
in the more limited range of 0.87-0.72 and have SBPDTB
stereochemistries. The extreme SBPDTB stereochemistry of 5
has been observed previously3 for a [Cu(phen)2Cl][Y] complex,
17, with a τ value of 0.19, Table 3. As the extreme structure
of 17 has been questioned, the X-ray structure determination
has been independently redetermined,4 with no significantly
different results. The repeated data collection was carried at
150 K, confirming that the SBPDTB stereochemistry of 17 is a
static stereochemistry20 of the copper(II) cation and is not a
consequence of a temperature variable behavior.
Complexes 2 and 4 are the first [Cu(phen)2X][Y] complexes,
where X ) Cl-, Br-, and I-, to show R3 values slightly >120°
at 124.3(1) and 121.5(2)°, respectively, suggesting that a small
+A route distortion is occurring. This behavior has also been
seen for four [Cu(bipy)2Cl][Y] complexes.1,2
From Table 2 it is noticeable that within the range of τ values
of 0.22-0.95 there is a significant gap of 0.50 in τ value
between the extreme TBDSBP value of 0.22 for 4 and the next
highest value of 0.72 for 4. This gap corresponds with a change
in the ratio of the R9 and R10 angles, for τ values >0.72, R9 >
R10, but, for τ values <0.72, R9 < R10. Equally, while the phen
ligand is constrained to be essentially planar, with angles
General Principles for the Scatter Plot Analysis of the [Cu-
(phen)2Br][Y] Complexes. The surprising feature of the data
of Table 2 is the range in the τ values, the Cu-Br, Cu-N(2),
and Cu-N(4) distances and the R1, R2, and R3 angles. A general
discussion of the use of scatter plots has been given earlier3
and will now be applied to the [Cu(phen)2Br]+ cation. Data
point 6 not only has a 2-fold axis of symmetry, but also is the
nearest experimental data point to the assumed RTB data point,
which has R1 ) R2 ) R3 ) 120°, Cu-N(2,4) distances of 2.092
Å, and a Cu-Br distance of 2.494 Å, Table 4. The notation
Cu-N(2,4) is used to represent the equivalence of the Cu-
N(2) and Cu-N(4) distances, due to the 2-fold axis of
symmetry. The factors limiting the in-plane angular distortion
from RTB are that the R1, R2, and R3 angles generally have
values >90° and <180°, and the sum of the in-plane angles is
a constant, R1 + R2 + R3 ) 360°, Table 5. A constant value
for the sum of the in-plane bond lengths might also be expected
but is not subject to a geometrical constraint. However, Table
5 shows the values ranging from 6.629 to 6.718 Å, ∆ ) 0.089
Å, and they differ significantly from the RTB sum, 6.678 Å.
The Cu-N(2,4) distances are constrained by the bite of the
chelate ligand, whereas the Cu-Br distance has no constraint
of this type, which may explain why the in-plane distances do
not have an exactly constant value for the sum. Thus, the results
are more variable for the distance plots.21
(17) Hambley, T. W.; Raston, C. L.; White, A. H. Aust. J. Chem. 1977,
30, 1965.
(18) Ray, N. J.; Hulett, L.; Sheahan, R.; Hathaway, B. J. J. Chem. Soc.,
Dalton Trans. 1981, 1463.
(19) Hathaway, B. J. Struct. Bonding (Berlin) 1984, 57, 55.
(20) Hathaway, B. J.; Billing, D. E. Coord. Chem. ReV. 1970, 5, 143.
(21) Murphy, G.; Murphy, C.; Murphy, B.; Hathaway, B. J. J. Chem. Soc.,
Dalton Trans., submitted for publication.

244 Inorganic Chemistry, Vol. 37, No. 2, 1998
Murphy et al.
Table 5. Sums of (a) the In-Plane Bond Angles and (b) the
In-Plane Bond Distances for the [Cu(phen)2Br][Y] Complexes
increase from 2.086(4) to 2.217(3) Å. This plot provides a
qualitative indication of the range of the observed stereochem-
istries of the [Cu(phen)2Br][Y] complexes. There is one data
point, 6, at near RTB, with τ ) 0.95. Four data points have τ
values ranging from 0.87 to 0.72, with stereochemistries best
described as SBPDTB. Data point 5 has an exceptionally low
τ value of 0.22 at near RSBP. There are no data points lying
on the RTB f RSBP pathway. Three data points, 2-4, lie on
a parallel correlation, with the remaining three data points, 1,
5, and 6 lying nearby. Figure 4b: The data points show the R3
values decreasing from 124.3(1) to 96.8(1)° as the R1 values
increase from 119.8(1) to 157.2(1)°. All six data points have
R1 values > 119.8°, but with R3 values > 120°, for 6, 2, and 4,
and <120°, for 1, 3, and 5. The sum of the in-plane angles
gives a constant value, R1 + R2 + R3 ) 360°, Table 5. The
(A and (B axes are superimposed on the graph. The data
points lie in three different sections. Data point 6 is very close
to RTB, but it lies slightly along the +A pathway. Three data
points, 1, 3, and 5, are found in the -A + B section of the
graph. The remaining two data points, 2 and 4, are present in
the +A + B section. There are no data points lying on the
RTB f RSBP (-A + B) pathway. Three data points, 1, 3,
and 6, show an inVerse trend through the RTB data point. Each
of these data points have R2 values of 120 ( 1°. The remaining
three data points, 2, 4, and 5, lie on two possible parallel
correlations displaying R2 values of 110 and 105°, respectively.
This series of three possible parallel correlations have the same
slopes. The data points show a SBP distortion, but only with
an R2 value of 105° can the correlation end up at RSBP. For
each parallel correlation, the R2 values remain essentially
constant; therefore ∆R1v ≈ ∆R3V, as R1 + R2 + R3 ) 360°.
Table 6 shows the % (A and % +B distortion values of the
six [Cu(phen)2Br][Y] complexes calculated using the in-plane
R3 and R1 angle data. Figure 4c: The six data points show the
R3 angles decreasing from 124.3(1) to 96.8(1)°, ∆ ) 27.5°, as
the Cu-Br* distances decrease from 2.313(1) to 2.258(1) Å,
∆ ) 0.115 Å. All six data points lie on a normal linear
correlation, which is the best linear trend observed to date
(correlation coefficient ) 0.999), for the [Cu(chelate)2X][Y]
complexes.1-3 If the suggested extreme (A data points are
superimposed on the graph, the graph can be divided into two
sections, +A, where R3 > 120° and Cu-Br* > 2.354 Å, and
-A, where R3 < 120° and Cu-Br* < 2.354 Å. However, the
+A extension, data points, 2, 4, and 6, from RTB is only small,
∆R3 ) 4.3°, relative to the -A extension, data points, 1, 3, and
5, where ∆R3 ) 23.2°. Consequently the [Cu(phen)2Br][Y]
complexes involve a predominantly -A route distortion. Figure
4d: The data points show the Cu-Br* distances decreasing from
2.373(1) to 2.258(1) Å, while the Cu-N(2) distances decrease
from 2.095(4) to 2.055(3) Å. Three data points, 2, 4, and 6,
have Cu-Br* values slightly > 2.354 Å, with three data points,
1, 3, and 5, having Cu-Br* values significantly < 2.354 Å.
Data point 2 has a Cu-N(2) value slightly > 2.092 Å, with the
remaining five data points having Cu-N(2) values < 2.092 Å,
to give an overall normal trend, but with a suggestion of some
inVerse correlations. The (A and (B axes can be superimposed
on the plot. Two data points, 6 and 4, lie on the RTB f +A
pathway. Data point 2 is present in the +A - B section of the
graph. Three data points, 1, 3, and 5, are found in the -A +
B section of the graph. Data point 5 lies on the RTB f RSBP
(-A + B) pathway.
6
1
2
3
4
5
R1/deg
119.8
119.8
120.6
360.2
126.5
120.1
113.5
360.1
125.7
110.0
124.3
360.0
129.8
120.9
109.3
360.0
133.4
105.1
121.5
360.0
157.2
105.9
96.8
R2/deg
R3/deg
(a) sum/deg
359.9
Cu-N(2)/Å
Cu-N(4)/Å
Cu-Br/Å
2.091
2.091
2.496
6.678
2.072
2.086
2.471
6.629
2.095
2.101
2.513
6.709
2.085
2.108
2.452
6.645
2.088
2.126
2.504
6.718
2.055
2.217
2.398
6.670
(b) sum/Å
Figure 1 illustrates the eight general stereochemistries arising
from the (A and (B senses of distortion of the RTB CuN4Br
chromophore.2 The values of the bond distances and angles in
Figure 1 are experimental values (rounded off to the nearest
0.05 Å) obtained from the [Cu(chelate)2X][Y] complexes.2 The
+A and +A ( B route distortions yield stereochemistries
distorted toward SBP, with the axial elongation along the Cu-
Br direction. The -A, +B, and -A ( B route distortions also
yield SBP distorted stereochemistries, with the axial elongation
along the Cu-N(4) or the Cu-N(2) directions. Complex 66 is
the only complex with a 2-fold axis of symmetry, and with R3
> 120° (120.6°) and Cu-Br > 2.494 Å (2.496 Å), it shows a
slight +A route distortion. The remaining five complexes do
not have a 2-fold axis of symmetry, suggesting that the routes
operate in combination, (A ( B. In order to compare the Cu-
Br distances with the Cu-N(1-4) distances, they are corrected
for the difference in the Br and N atom covalent radii, namely,
0.43 Å. If the Cu-Br distances are adjusted to Cu-N values,22
using the relation Cu-Br - 0.43 Å ) Cu-N(Br), Table 2, it
can be seen that the greatest elongation of the equatorial
distances is in the Cu-N(4) direction, indicating a +B route
distortion. Simultaneously, the R3 values decrease <120°, and
the Cu-Br distances also decrease, indicating a -A route
distortion. This suggests that +A, -A + B, and +A + B route
distortions operate for the [Cu(phen)2Br][Y] series of complexes;
however, the +A route distortion is only small.
The suggested limiting values3,21 for the (A, +B, and (A
+ B route distortions are illustrated in Table 4. The angle Versus
angle plots and the distance Versus distance plots can be divided
up to represent (A, (B axes and (A ( B sections, Figure
4a-d. The limiting values for the -B, -A - B, and +A - B
route distortions are equivalent to those for +B, -A + B, and
+A + B, respectively, since each pair ((B, -A ( B, and +A
( B) are related by a 2-fold axis of symmetry.
Scatter Plot Analysis of the [Cu(phen)2Br][Y] Complexes.
The data of the [Cu(phen)2Br][Y] complexes, Table 2, are
presented in this section using scatter plot analysis. Each plot
includes not only the [Cu(phen)2Br][Y] data points but also the
[Cu(phen)2Cl][Y] and [Cu(phen)2I][Y] data points, Tables 2 and
3, for later comparison, with the Cu-Br and Cu-I distances
corrected, by the difference in their covalent radii, to the
corresponding Cu-Cl distance.22 The scatter plots to be
discussed, using the in-plane bond lengths and angles, are as
follows: (a) τ Versus Cu-N(4), (b) R3 Versus R1, (c) R3 Versus
Cu-Br*, and (d) Cu-Br* Versus Cu-N(2). Figure 4a provides
an overview of the range of stereochemistries defined by the τ
value. Since this parameter involves two simultaneous angle
changes, R1 and R8, it will not be used further. The six data
points vary from near RTB to near RSBP (-A + B), with the
τ values decreasing from 0.95 to 0.22 as the Cu-N(4) distances
[Cu(phen)2X][Y] Complexes, X ) Cl- and I-. The eight
[Cu(phen)2Cl][Y] complexes 10-17,3,23-26 Table 3, have been
discussed elsewhere.3 When these data points are added to the
(22) Muller, E.; Piguet, C.; Bernardelli, G.; Williams, A. F. Inorg. Chem.
1988, 27, 849.

[Cu(phen)2Br][Y] Complexes
Inorganic Chemistry, Vol. 37, No. 2, 1998 245
Figure 4. Scatter plots for the [Cu(phen)2X][Y] Complexes.
Table 6. (A and +B Distortion (%) of the Complexes Calculated
Using the In-Plane R3 and R1 Angle Data, Figure 4b
enhancing the linear correlation in Figure 4c and the alternative
inVerse correlation of Figure 4d, through the RTB data point.
However, two of the I- complexes do involve a 2-fold axis of
symmetry, Table 2.
6
1
2
3
4
5
% -A
% +A
% +B
21
36
77
Possible Interpretation of the (A and (B Route Distor-
tions in Terms of Modes of Vibration. The extensive range
of the Cu-L distances and of the Rn angles, Table 3, 0.13 Å
and 37°, respectively, have only been interpreted in terms of
the (A and (B route distortions, Table 6, but it has been
suggested earlier3 that these routes may be understood, alter-
natively, in terms of the modes of vibration of the CuN4Br
chromophore,27-30 Figure 5. The symmetric, νsym, and asym-
metric, νasym, modes of vibration of the CuN4Br chromophore,
Figure 5, both have stretching and bending components. They
predict variations in the in-plane parameters, R1-3, Cu-Br, Cu-
N(2), and Cu-N(4), which show the largest ranges in distances
and angles, Table 2, as νsym and νasym modes are largely
restricted to the in-plane angles and distances. The symmetric
mode of vibration has a 2-fold axis of symmetry, so Cu-N(2)
) Cu-N(4) and R1 ) R2, and all six in-plane distances and
angles are involved. The asymmetric mode of vibration does
not have a 2-fold axis of symmetry. Here only the Cu-N(2)
and Cu-N(4) distances and the R1 and R2 angles are involved,
1
10
26
3
47
11
15
86
scatter plots of Figure 4a-d, they largely overlap the Br- data
points, with comparable ranges and spread of the data points.
The Cl- data points also have an extreme data point, 17, with
a τ value of 0.19. However, none of the Cl- complexes involve
a 2-fold axis of symmetry. The addition of the eight Cl- data
points to the scatter plots of Figure 4a-b consolidates the trends,
and only in the case of the R3 Versus Cu-Br* plot, Figure 4c,
does the Cl- data suggest two additional correlations, parallel
to the central +A f RTB f -A correlation. Addition of the
three [Cu(phen)2I][Y] data points 7-9,15-17 Table 2, to the
scatter plots has a less significant impact as all three data points
tend to cluster close to the RTB data point, although still
(23) Boys, B.; Escobar, C.; Martinez-Carrera, S. Acta Crystallogr., Sect.
B 1981, 37, 351.
(24) Chilkevich, A. K.; Ponomarev, B. P.; Lyavrentjeu P. P.; Atoumjan,
L. O. Koord. Khim. 1987, 13, 1532.
(25) Boys, D. Acta Crystallogr., Sect. C 1988, 44, 1539.
(26) Murphy, G. Ph.D. Thesis, National University of Ireland, 1997.
(27) Nakamoto, K. Infrared Spectra of Inorganic and Coordination
Compounds, 3rd ed.; John Wiley and Sons: New York, 1978.
(28) Bacci, M. J. Chem. Phys. 1986, 104, 191.
(29) Reinen, D.; Atanasov, M. J. Chem. Phys. 1989, 136, 27.
(30) Reinen, D.; Atanasov, M. Magn. Reson. ReV. 1991, 15, 167.

246 Inorganic Chemistry, Vol. 37, No. 2, 1998
Murphy et al.
Figure 5. Symmetric and asymmetric modes of vibration for the five
coordinate CuN4Br chromophore, including the relative magnitudes
(L).2,6
Figure 6. Diagram of how the linear and parallel pathways are formed
by the sequential operation of the νsymstr and νsymbend modes of vibration.
with the Cu-Br distance and the R3 angle being invariant. In
the next section, the [Cu(phen)2Br][Y] data of the scatter plot
analysis of the in-plane bond lengths and angles are considered
to determine if the distribution of data points is alternatively
determined by the νsym and νasym modes of vibration as the
dominant modes of distortion of the CuN4Br chromophore,
Figure 5.
The first problem associated with this suggestion is that the
effect of a single mode of vibration of the nuclear framework
of the CuN4X chromophore, of ca. 200 cm-1, would only result
in bond distance and bond angle changes of 0.005 Å and 1°,
respectively.31 These values are at least an order of magnitude
too small to account for the observed changes, Table 2.
Consequently, either a progression of 20-40 modes of vibration
must be involved or the “amplification factor”32 of the pseudo-
Jahn-Teller effect33 must be in operation, with the possibility
that the former accounts for the latter.
Figure 7. One-electron orbital levels of the RTB stereochemistry and
their symmetries in various point groups.
(B route distortions, which are only related by an external
2-fold axis of symmetry. In practice the bulk of CuN4Br*
chromophores lack any symmetry at all, namely, C1.
One of the most significant features of Figure 4c is that the
six Br- data points lie strictly along the +A f RTB f -A
pathway, suggesting that the changes in the R3 angle and Cu-
Br* distance are closely linked. One such linking process
suggests that the changes in these parameters is determined only
by the underlying nuclear modes of vibration,27,28 Figure 5, of
a vibronic coupling mechanism.33 A feature of the parameters
The most convincing evidence for the vibronic coupling
model has been seen in accounting for the dynamic pseudo-
Jahn-Teller distortion29,30 of the high-symmetry RTB [CuCl5]3-
anion, D3h symmetry, to the lower symmetry RSBP stereo-
chemistry, C2V or C2 symmetry, with distortion via the ꢀ′ mode
str
of vibration29,30 (equivalent to νsym + νsymbend), with C2
symmetry along the three in-plane directions at 120° to each
other. This requires that the CuN4Cl chromophore has effectiVe
symmetry D3h and ignores the presence of non-equivalent donor
atoms and the effect of two chelate ligands. If this assumption
can be accepted, then the ꢀ′ mode of vibration, in D3h symmetry,
of Figure 4c is that the R3 angle can only be changed by the
bend
νsym
mode of vibration and the Cu-Br* distance can only
str
be changed by the νsym mode of vibration. If such modes
operated separately from RTB, point I in Figure 6, the former
would only produce a vertical linear correlation of data points
and the latter a horizontal correlation. While such limited
correlations can be identified in Figure 4c, the most convincing
correlation of six data points occurs at an angle of 34° to the
Cu-Br* axis. The only way such a positive correlation can
occur is if the two modes of vibration are strongly coupled
together (they both transform as A in C1 symmetry, Figure 7),
as shown in Figure 6, to produce a stepped displacement.
However, such a single displacement due to one quantum of
each mode of vibration would still be too small to be observed
on the scale of Figure 4c, namely, 0.005 Å and 1°.31 For the
scale of the +A f RTB f -A pathway in Figure 4c to be
observed, a change of 0.13 Å in the Cu-Br* distance and a
change of 37° in the R3 angle, a progression of 20-40 coupled
vibrations must occur to account for the magnitude of the
str
bend
and the νsym and νsym
modes of vibration (C2 symmetry)
models are equivalent. However, the present authors prefer the
ν modes of vibration notation, as it is chemically more intuitive
than the ꢀ′ mode notation. While the authors admit29,30 that
this model is only justified for small distortions, the above
“amplification factor”32 or progressions could equally be operat-
ing to account for the larger distortions observed. The highest
possible symmetry for the CuN4Br* chromophore is C2, which
is restricted to the Cu-Br direction of the CuN4Br* chro-
mophore (+A route) and one that is quite distinct from the two
(31) Brint, P. Private communication.
(32) Bersuker, I. B. Coord. Chem. ReV. 1975, 14, 357.
(33) Bersuker, I. B. The Jahn-Teller Effect and Vibronic Interactions in
Modern Chemistry; Plenum Press: New York, 1983.

[Cu(phen)2Br][Y] Complexes
Inorganic Chemistry, Vol. 37, No. 2, 1998 247
observed changes. Such a progression can be considered as a
plot of the structural pathway from the +A route to the -A
route of Figure 6, involving the coupled νsymstr + νsymbend modes
of vibration, with the six data points representing six individual
structures along the structural pathway, with each data point
characterized by a full single crystal X-ray structure determi-
nation. Two further data points are involved along the central
correlation of Figure 4c if the phen/Cl data points are included.
In order to explain the occurrence of the parallel correlations
in Figure 4c, n modes of a single vibration, (ν, where n )
8-10, must be involved in order that the parallel displacement
can be observed, Figure 6, points II and III. This is then
followed by a progression of the coupled modes (in order that
a linear correlation can be observed) separate but parallel to
the central linear correlation. This observation of parallel linear
correlations in the same plot, Figure 4c, requires the addition
of both the Cl- and I- data points but is then one of the best
pieces of evidence for both structural pathways and parallel
pathways and originates from the amplification factor32 in the
pseudo-Jahn-Teller effect.33
Figure 8. Electronic reflectance spectra of some [Cu(phen)2Br][Y]
complexes.
The various plots also suggest that the directions of distortion
from RTB to RSBP could be associated with the modes of
vibration of the CuN4Br chromophore, Figure 5. The (A route
str
bend
is restricted to the νsym and νsym
modes of vibration and
the (B route distortions with the νasymstr and νasymbend modes of
vibration. However, as the actual data points rarely involve
pure % A or % B contributions, Table 6, all four modes are
generally involved in the distortion of each complex, unless a
2-fold axis of symmetry is involved. Even with the six linear
Br- data points of Figure 4c, each is accompanied by some
+B route distortion, Table 6.
Implications. The four scatter plots of the [Cu(phen)2X]-
[Y] data points, X ) Cl-, Br-, and I- clearly suggest that the
distribution with respect to the RTB and RSBP data points is
not random, but consistent with linear and parallel structural
pathways, in which the effect of vibronic coupling33 is seen
directly in the scatter plots of Figure 4. If so, the [Cu(phen)2X]-
[Y] data represent the best evidence for the involvement of
vibronic coupling to account for the structural consequences of
the plasticity effect34 in the series of cation distortion isomers18,19
of the copper(II) ion. Of equal importance is the wide range
of stereochemistry displayed by the same [Cu(phen)2Br]+ cation,
from near RTB, τ ) 0.95, to TBDSBP, τ ) 0.22. In the past,
a number of accounts have been given35-37 to describe the static
geometries of the five coordinate stereochemistries of different
ML5 chromophores and try to account for these changes in terms
of the different bonding roles of the ligands present.36 The
present paper emphasizes that, in the special case of the low-
symmetry CuN4X chromophore, vibronic coupling associated
with the pseudo-Jahn-Teller effect33 can also produce the same
range in stereochemistry of the five coordinate ML5 chro-
mophore with the same set of ligands. Small differences in
the crystal field effects of the different counteranions, balancing
the vibronic coupling effects, result in the observed small
differences in the observed structures of the cations. The present
script suggests a dynamic involvement of a number of the modes
of vibration of the central chromophore to produce the changes
Figure 9. Electronic criterion of stereochemistry illustrated by
correlating the peak energy and appearance with the change in
stereochemistry from RTB to RSBP.
associated with the movements about the potential energy
surface of the structural pathway in which individual points are
characterized by single crystal X-ray structure determinations
of the same cation distortion isomers.18,19
Electronic Properties of the [Cu(phen)2Br][Y] Complexes.
The polycrystalline electronic reflectance spectra of 1-5 are
shown in Figure 8. For 1, 2, and 4, a broad asymmetric peak
occurs at 12 600, 12 000, and 11 800 cm-1, respectively, with
some evidence for a possible low-energy shoulder at 11 000,
11 100, and 10 900 cm-1, respectively, consistent with near TB
stereochemistries (τ ) 0.87-0.72). The spectrum of 3, τ )
0.79, shows a broad peak beginning to split into two. These
two peaks involve energies of 10 800 and 12 800 cm-1 and
appear to evolve from the single peak at 12 000 cm-1 for a
RTB stereochemistry. The suggested one-electron ground state
configuration20,38 is dz > dxy ≈ dx -y > dxz ≈ dyz. The principal
2
2
2
2
absorption may be assigned as a dxz ≈ dyz f dz transition, with
2
2
2
the low-energy shoulder assigned as a dx -y f dz transition.
Complex 5, τ ) 0.22, which has a TBDSBP stereochemistry,
involves a high-energy peak at 14 400 cm-1, with a low-energy
shoulder at lower intensity at 10 700 cm-1. The suggested one-
2
2
2
electron ground state configuration is dx -y > dz > dxy > dxz
2
2
2
≈ dyz. The transitions may be assigned as the dz f dx -y
(34) Gazo, J.; Bersuker, I. B.; Garaj, J.; Kabesova, M.; Kohout, J.;
Langfelderova, H.; Melnik, M.; Serator, M.; Valach, F. Coord. Chem.
ReV. 1976, 21, 253.
(35) Muetterties, E. L.; Guggenberger, L. T. J. Am. Chem. Soc. 1974, 96,
1748.
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3960, 3970, 3982.
2
2
transition for the low-energy peak and the dxz ≈ dyz f dx -y
transition for the high-energy peak.
The change in peak energy and intensity for the series of six
[Cu(phen)2Br][Y] complexes can be used to establish an
(38) Hathaway, B. J. J. Chem. Soc., Dalton Trans. 1972, 1192.

248 Inorganic Chemistry, Vol. 37, No. 2, 1998
Murphy et al.
electronic criterion of stereochemistry,38 Figure 9. RTB ster-
eochemistry shows a single peak at ∼12 000 cm-1, SBPDTB
stereochemistry shows two clearly resolved peaks at ∼11 000
and ∼13 000 cm-1, with near SBP stereochemistry showing a
high-energy peak at ∼14 500 cm-1 and a low-energy shoulder
Professor G. M. Sheldrick and Drs. P. Roberts, S. Motherwell,
K. Henrick, A. L. Spek, and P. McCardle, for the use of their
programs, and the Microanalysis Section, UCC, for analysis.
Supporting Information Available: Tables of fractional atomic
coordinates (Table S1), fractional atomic coordinates for the hydrogen
atoms (Table S2), anisotropic thermal parameters (Table S3), complete
bond distances (Table S4), complete bond angles (Table S5), and
selected mean plane data (Table S6) for complexes 1-5 (38 pages).
Ordering information is given on any current masthead page.
at ∼11 000 cm-1
.
Acknowledgment. The authors acknowledge the award of
Forbairt and University College Cork (UCC) Studentships (to
G.M., C.O.’S. and B.M.), an EOLAS grant for the diffracto-
meter, the Computer Bureau, UCC for computing facilities,
IC970458A