Monodentate and bidentate trifluoroacetato ligands in bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato)-thallium(III) - A new dynamic 4:3 piano stool seven-coordinate geometry

Article abstract of DOI:10.1016/S0277-5387(01)00944-5

The crystal structure of bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato) thallium(III), T1(N-Me-tpp)(CF₃CO₂)₂ (2), was established and the coordination sphere around the T1³⁺ ion is described as 4:3 tetragonal base-trigonal base piano stool seven-coordinate geometry in which the two cis CF₃CO₂^- groups occupy two apical sites. The plane of the three pyrrole nitrogen atoms [i.e. N(2), N(3) and N(4)] strongly bonded to T1³⁺ is adopted as the reference plane 3N. The pyrrole N(1) ring bearing the methyl group [i.e. C(45)H₃] is the most deviated one from the 3N plane making a dihedral angle of 23.3° whereas smaller angles of 9.9, 2.7 and 4.7° occur with pyrroles N(2), N(3), and N(4), respectively. Because of the larger size of the thallium(III) ion, T1 is considerably out of the 3N plane; its displacement of 1.02 A? is in the same direction as that of the two apical CF₃CO₂^- ligands. The intermolecular trifluoroacetate exchange process for 2 in CD₂Cl₂ solvent is examined through ¹⁹F and ¹³C NMR temperature-dependent measurements. In the slow-exchange region, the CF3 and carbonyl (CO) carbons of the CF₃CO₂^- groups in 2 are separately located at δ 114.3 [¹J(C-F) = 290 Hz, ³J(T1-C) = 411 Hz] and 155.1 [²J(C-F) = 37 Hz, ²J(T1-C) = 204 Hz], respectively, at - 106 °C. In the same slow-exchange region, the fluorine atoms of 2, T1(N-Me-tpp)(CF₃CO₂)⁺ and the free CF₃CO₂^- are located at δ - 73.76 [⁴J(T1-F) = 44 Hz], - 73.30 [⁴J(T1-F) = 22 Hz], and - 76.15 ppm at - 97 °C, respectively.

Full text of DOI:10.1016/S0277-5387(01)00944-5

Polyhedron 20 (2001) 3257–3264
www.elsevier.com/locate/poly
Monodentate and bidentate trifluoroacetato ligands in
bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato)-
thallium(III)
—a new dynamic 4:3 piano stool seven-coordinate geometry
Chiu-Hui Yang a, Jo-Yu Tung a, Bing-Chuang Liau a, Bao-Tsan Ko a,
Shanmugham Elango a, Jyh-Horung Chen a,*, Lian-Pin Hwang b
a Department of Chemistry, National Chung-Hsing Uni6ersity, Taichung 40227, Taiwan, ROC
b Department of Chemistry, National Taiwan Uni6ersity and Institute of Atomic and Molecular Sciences, Academia Sinica,
Taipei 10764, Taiwan, ROC
Received 19 June 2001; accepted 7 August 2001
Abstract
The crystal structure of bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato) thallium(III), Tl(NꢀMeꢀtpp)(CF3CO2)2
(2), was established and the coordination sphere around the Tl3+ ion is described as 4:3 tetragonal base–trigonal base piano stool
seven-coordinate geometry in which the two cis CF3CO2− groups occupy two apical sites. The plane of the three pyrrole nitrogen
atoms [i.e. N(2), N(3) and N(4)] strongly bonded to Tl3+ is adopted as the reference plane 3N. The pyrrole N(1) ring bearing the
methyl group [i.e. C(45)H3] is the most deviated one from the 3N plane making a dihedral angle of 23.3° whereas smaller angles
of 9.9, 2.7 and 4.7° occur with pyrroles N(2), N(3), and N(4), respectively. Because of the larger size of the thallium(III) ion, Tl
−
,
is considerably out of the 3N plane; its displacement of 1.02 A is in the same direction as that of the two apical CF3CO2 ligands.
The intermolecular trifluoroacetate exchange process for 2 in CD2Cl2 solvent is examined through 19F and 13C NMR
temperature-dependent measurements. In the slow-exchange region, the CF3 and carbonyl (CO) carbons of the CF3CO2− groups
in 2 are separately located at l 114.3 [1J(C–F)=290 Hz, J(Tl–C)=411 Hz] and 155.1 [2J(C–F)=37 Hz, J(Tl–C)=204 Hz],
respectively, at −106 °C. In the same slow-exchange region, the fluorine atoms of 2, Tl(NꢀMeꢀtpp)(CF3CO2)+ and the free
CF3CO2− are located at l −73.76 [4J(Tl–F)=44 Hz], −73.30 [4J(Tl–F)=22 Hz], and −76.15 ppm at −97 °C, respectively.
© 2001 Elsevier Science Ltd. All rights reserved.
3
2
Keywords: Piano stool; Intermolecular exchange; Seven-coordinate; Bidentate
1. Introduction
coordination geometry around the metal ion is a five-
coordinate distorted square-based pyramid. Iron(III)
complexes of N-methylporphyrins, e.g. [FeIII(NꢀMeꢀ
ttp)(CN)2], [FeIII(NꢀMeꢀttp)(5-MeIm)2]2+ and [FeIII-
(NꢀMeꢀtmp)Im2]2+ (with NꢀMeꢀttp=N-methyltetra-
p-tolylporphyrin monoanion, NꢀMeꢀtmp=N-methyl-
tetramesitylporphyrin monoanion, Im=imidazole, 5-
MeIm=5-methylimidazole), are known as well [6]. We
have recently reported the crystal structure of diaceta-
to(N - methyl - meso - tetraphenylporphyrinato)thallium-
(III), Tl(NꢀMeꢀtpp)(OAc)2 (1), and the coordination
sphere around the Tl3+ ion is described as an eight-
Several first-row transition metal complexes of N-
substituted porphyrin MII(NꢀMeꢀtpp)Cl (M=Zn, Co,
Mn, Fe and tpp=5,10,15,20-tetraphenylporphyrinate)
have been extensively studied by Anderson et al. [1–5].
The common feature in all these N-substituted metal-
loporphyrins is that the metal atom is no longer copla-
nar with the four nitrogen atoms of the macrocycle and
* Corresponding author. Fax: +886-4-2286-2547.
E-mail address: jyhhchen@dragon.nchu.tw (J.-H. Chen).
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00944-5

3258
C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
2. Experimental
co-ordinate square-based antiprism in which the two cis
chelating bidentate OAc− groups occupy two apical
sites [7]. The acetate and trifluoroacetate ions are
known to be highly versatile in binding to metal ions.
They can behave as mono- or bidentate donors to a
single metal ion or give rise to a variety of more
complicated patterns by acting as bridging groups [8].
When the OAc− of 1 was replaced by a relatively
bulkier trifluoroacetate group, CF3CO2− the coordina-
tion number (CN) decreases from 8 for 1 to 7 for
bis(trifluoroacetato) - (N - methyl - meso - tetraphenylpor-
phyrinato)thallium(III), Tl(NꢀMeꢀtpp)(CF3CO2)2 (2).
Seven-coordinate complexes of the metal ion (M(III))
(M=Sc [9], Ti [10], V [11], Cr [12,13], Fe [13,14] and In
[15–19]) have also been reported. However, until now
there were no X-ray structural data available for M(III)
complexes of porphyrin with seven-coordinate geome-
try and the stereochemistry for seven-coordination is
not reported in mononuclear thallium(III) complexes.
Seven-coordinated complexes of tungsten(II) and
molybdenum(II) are known to adopt several different
stereochemistries [20]: the 1:5:1 D5h pentagonal bipyra-
midal [21], the 1:4:2 C26 capped trigonal prismatic [22],
the 4:3 piano-stool [23,24] and the 1:3:3 C36 capped
octahedral geometries. Generally these complexes are
stereochemically non-rigid which is a consequence of
the small energy difference between different forms and
distortions exist from the idealized geometries which
can lead to ambiguities whilst describing the structure.
The acetato exchange process of 1 prompted us to
investigate a similar trifluoroacetato exchange for 2 in
CD2Cl2 by a 13C and 19F dynamic NMR method [7].
The structures of the two related heptacoordinated
complexes Mo(CO)2(PMe3)2(CF3CO2)2 [25] and
Mo(CO)2(PEt3)2(CF3CO2)2 [26] are similar capped trig-
onal prismatic geometries. The former contains two
monodentate trifluoroacetate ligands whereas the latter
contains one monodentate and one bidentate trifl-
uoroacetate groups. No evidence of an intramolecular
exchange between the two trifluoroacetate groups is
observed for these complexes in dichloromethane at
room temperature. Mo(CO)2(PEt3)2(O2CH)2 [23] is yet
another seven-coordinate d4 bis(formato) derivative
adopting a 4:3 ‘piano stool’ configuration with one
monodentate and one bidentate O2CH ligands that is
fluxional on the NMR time scale. We report herein the
preparation, structural characterization and dynamic
behavior of an intra- and inter-molecular trifluoroac-
etate exchange process for a novel seven-coordinate
mononuclear thallium(III) complex 2 having a 4:3 ge-
ometry with two differently coordinated CF3CO2 lig-
ands. To the best of our knowledge, this is the first
description of a seven-coordinate thallium N-methyl
porphyrin complex with one bidentate and one
monodentate coordinated CF3CO2 ligand.
2.1. Preparation of Tl(NꢀMeꢀtpp)(CF3CO2)2 (2)
The new compound 2 was synthesized by refluxing a
mixture of NꢀMeꢀHtpp [7,27] (0.15 g, 2.389×10−4
mol) in dry CHCl3 (50 cm3) and Tl(CF3CO2)3 (0.26 g,
4.79×10−4 mol) in dry CH3OH (2 cm3) under N2 for
30 min. After concentrating, the residue was dissolved
in CH2Cl2 and collected by filtration to remove any
precipitate. The crystals of 2 (0.13 g, 1.23×10−4 mol,
86.6%) were grown by removing CH2Cl2 and dissolving
the residue in dry ether. The crystals were dissolved in
1
1
CD2Cl2 for H and 13C NMR measurements. H NMR
(600.25 MHz, CD2Cl2, 20 °C): l 9.09 [dd, Hb(8,17),
4J(Tl–H)=76 Hz, J(H–H)=4.7 Hz], where Hb(a,b)
3
represents the two equivalent b-pyrrole protons at-
tached to carbons a and b, respectively; 9.09 [dd,
4
3
Hb(7,18), J(Tl–H)=68 Hz, J(H–H)=4.7 Hz]; 9.00
[d, Hb(12,13), 4J(Tl–H)=61 Hz]; 8.73 [d, Hb(2, 3),
4J(Tl–H)=7.1 Hz]; 8.53 (s) and 8.24–8.27 (m) for
phenyl ortho protons (o,o%-H); 7.79–7.94 (m) for phenyl
meta, para protons (m-, p-H); −4.31 [d, NꢀMe, 3J(Tl–
1
H)=37 Hz] for compound 2. H NMR (600.25 MHz,
CD2Cl2, −73 °C): l 9.12 [dd, Hb(8,17), J(Tl–H)=75
4
Hz, 3J(H–H)=4.4 Hz]; 9.06 [dd, Hb(7,18), 4J(Tl–
H)=69 Hz, 3J(H–H)=4.4 Hz]; 9.03 [d, Hb(12,13),
4J(Tl–H)=60 Hz]; 8.76 [d, Hb(2,3), 4J(Tl–H)=7.2
Hz]; 8.55 (s) and 8.24–8.28 (m) for phenyl ortho pro-
tons (o,o%-H); 7.78–7.95 (m) for phenyl meta, para
protons (m-, p-H); −4.43 [d, NꢀMe, 3J(Tl–H)=37
3
Hz] for compound 2; −4.61 [d, NꢀMe, J(Tl–H)=21
Hz] for compound Tl(NꢀMeꢀtpp)(CF3COO)+. 13C
NMR (150.87 MHz, CD2Cl2, 17 °C): l 157.1 [d,
2
Ca(C1, C4), J(Tl–C)=90 Hz]; 153.9 [d, Ca(C9, C16),
2J(Tl–C)=29 Hz]; 153.5 [d, Ca(C11, C14), 2J(Tl–C)=
70 Hz]; 151.9 [d, Ca(C6, C19), 2J(Tl–C)=17 Hz]; 141.5
4
4
(d, J(Tl–C)=42 Hz) and 141.3 (d, J(Tl–C)=41 Hz)
3
for phenyl-C1; 137.1 (d, J(Tl–C)=37 Hz), 136.0 (s),
135.7 (s), 133.4 (s), 133.2 (s), 129.1 (s), 128.5 (s), 128.3
(s), 127.7 (s), 127.2 (s) and 126.9 (s) for phenyl-C2,6
phenyl-C3,5 and phenyl-C4; 134.5 [d, Cb(C7, C18),
3J(Tl–C)=109 Hz]; 134.4 [d, Cb(C12, C13), 3J(Tl–
C)=111 Hz]; 132.8 [d, Cb(C8, C17), 3J(Tl–C)=114
,
3
Hz]; 129.6 [d, Cb(C2, C3), J(Tl–C)=10 Hz]; 126.8 [d,
3
Cm(C10, C15), J(Tl–C)=171 Hz]; 124.9 [d, Cm(C5,
3
2
C20), J(Tl–C)=141 Hz]; 32.1 [s, NꢀMe, J(Tl–C)=
32.1 Hz]; 13C NMR (150.87 MHz, CD2Cl2, −106 °C):
2
l 156.0 [d, Ca(C1, C4), J(Tl–C)=89 Hz]; 152.5 [d,
Ca(C9, C16), 2J(Tl–C)=23 Hz]; 152.3 [d, Ca(C11,
2
C14), J(Tl–C)=61 Hz]; 150.1 [s, Ca(C6, C19)]; 140.5
4
4
(d, J(Tl–C)=40 Hz) and 140.9 (d, J(Tl–C)=39 Hz)
3
for phenyl-C1; 137.1 (d, J(Tl–C)=31 Hz), 136.4 (d,
3J(Tl–C)=34 Hz), 135.2 (d, J(Tl–C)=37 Hz), 133.3
3
(s), 128.3 (s), 127.7 (s), 127.6 (s), 127.2 (s), 126.6 (s),
126.3 (s) for phenyl-C2,6, phenyl-C3,5 and phenyl-C4;

C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
3259
628 ([NꢀMeꢀtpp]+, 58.24), 627 ([NꢀMeꢀtppꢀH]+,
100.00), 205 (205Tl+, 23.22), 203 (203Tl+, 9.63). UV–Vis
spectrum: u (nm) (m×10−3 (M−1 cm−1)] (CHCl3): 440
(253), 452 (202), 556 (10.8), 601 (14.1), 648 (8.5).
3
134.0 [d, Cb(C7, C18), J(Tl–C)=107 Hz]; 133.8 [d,
Cb(C12, C13), 3J(Tl–C)=95 Hz]; 132.0 [d, Cb(C8,
C17), J(Tl–C)=129 Hz]; 129.2 [d, Cb(C2, C3), J(Tl–
C)=8.3 Hz]; 125.4 [d, Cm(C10, C15), J(Tl–C)=168
3
3
3
3
Hz]; 123.9 [d, Cm(C5, C20), J(Tl–C)=134 Hz]; 30.7
[s, NꢀMe, 2J(Tl–C)=20 Hz]; 155.1 (m, CF3COO,
2.2. Spectroscopy
2J(C–F)=37 Hz and J(Tl–C)=204 Hz); 114.3 (m,
2
Proton and 13C NMR spectra in CD2Cl2 (99.6% from
Aldrich) were recorded at 299.95 (or 600.25) and 75.43
(or 150.87) MHz, respectively, on Varian VXR-300 (or
Varian Unity Inova-600) spectrometers locked on deu-
teriated solvent and referenced to the solvent peak
CD2Cl2 at l=5.30 (1H NMR) and the center line of
CD2Cl2 at l=53.6 (13C NMR). The 19F spectra were
measured in CD2Cl2 at 564.49 MHz in a Varian Unity
Inova-600 spectrometer. 19F NMR data are internally
referenced to CFCl3. The temperature of the spectrome-
ter probe was calibrated by the shift difference of the
1
3
CF3COO, J(C–F)=290 Hz and J(Tl–C)=411 Hz).
MS; m/z (assignment, relative intensity): 1058
([Tl(NꢀMeꢀtpp)(CF3CO2)2]+, 1.94), 945 ([Tl(NꢀMeꢀ
tpp)(CF3CO2)]+, 4.96), 832 ([Tl(NꢀMeꢀtpp)]+, 10.76),
Table 1
Crystal data and structure refinement parameters for Tl(NꢀMeꢀtpp)-
(CF3CO2)2·Et2O (2·Et2O)
Empirical formula a
Formula weight
Space group
C53H41F6N4O5Tl (2·Et2O)
1132.27
(
P1
2
1
1
methanol resonance in the H NMR spectrum. H–13C
COSY technique was employed to correlate protons
and carbon through one-bond coupling and heteronu-
clear multiple bond coherence (HMBC) for two- and
three-bond proton–carbon coupling.
Z
Unit cell dimensions
,
a (A)
9.5350(11)
13.4138(15)
19.308(2)
96.865(2)
101.223(2)
94.785(2)
2390.4(4)
1.573
,
b (A)
,
c (A)
h (°)
i (°)
The positive-ion fast atom bombardment mass spec-
trum (FAB MS) was obtained in a nitrobenzyl alcohol
(NBA) matrix using a JEOL JMS-SX/SX 102A mass
spectrometer. UV–Vis spectra were recorded at 24 °C
in a Hitachi U-3210 spectrophotometer.
k (°)
3
,
V (A )
Dcalc (g cm−3
)
,
Radiation, u (A)
Temperature (K)
Mo, 0.71073
293(2)
3.454
3.61
11.27
Absorption coefficient (mm−1
)
b
R
(%)
2.3. Crystallography
c
Rw (%)
Goodness-of-fit
0.885
Table 1 contains the crystal data and other informa-
tion for Tl(NꢀMeꢀtpp)(CF3CO2)2·Et2O. Measurements
were taken in a Siemens SMART CCD diffractometer
for 2·Et2O using monochromatized Mo Ka radiation
a Including solvate molecules.
b R=[ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ].
c Rw=[ꢀw(ꢁꢁFoꢁ−ꢁFcꢁꢁ)2/ꢀw(ꢁFoꢁ)2]1/2; w=A/(|2Fo+BFo2).
,
(u=0.71073 A). SADABS absorption corrections were
Table 2
made for 2·Et2O. The structures were solved by direct
methods (SHELXTL PLUS) and refined by the full-matrix
least-squares method. All non-hydrogen atoms were
refined with anisotropic thermal parameters, whereas
all hydrogen atom positions were calculated using a
riding model and were included in the structure factor
calculation. Table 2 lists selected bond distances and
angles.
,
Selected bond distances (A) and bond angles (°) for compound
2·Et2O
Bond lengths
TlꢀN(1)
TlꢀN(2)
TlꢀN(3)
TlꢀN(4)
C(46)ꢀC(47)
C(48)ꢀC(49)
2.700(4)
2.276(4)
2.243(4)
2.278(4)
1.51(1)
TlꢀO(1)
TlꢀO(3)
TlꢀO(4)
O(1)ꢀC(46)
O(2)ꢀC(46)
O(3)ꢀC(48)
O(4)ꢀC(48)
2.235(5)
2.462(7)
2.514(7)
1.250(8)
1.220(9)
1.226(9)
1.21(1)
1.52(1)
Bond angles
3. Results and discussion
O(3)ꢀTlꢀO(4)
O(1)ꢀTlꢀN(1)
O(1)ꢀTlꢀN(2)
O(1)ꢀTlꢀN(3)
O(1)ꢀTlꢀN(4)
O(3)ꢀTlꢀN(1)
O(3)ꢀTlꢀN(2)
O(3)ꢀTlꢀN(3)
O(3)ꢀTlꢀN(4)
51.3(2)
75.3(2)
101(2)
165.2(2)
109.2(2)
153.4(2)
131.4(2)
80.8(2)
93.8(2)
O(4)ꢀTlꢀN(1)
O(4)ꢀTlꢀN(2)
O(4)ꢀTlꢀN(3)
O(4)ꢀTlꢀN(4)
O(2)ꢀC(46)ꢀO(1)
O(3)ꢀC(48)ꢀO(4)
C(46)ꢀO(1)ꢀTl
C(48)ꢀO(3)ꢀTl
C(48)ꢀO(4)ꢀTl
140.2(2)
83.0(2)
86.5(2)
144.4(2)
129.7(7)
124.5(8)
115.0(5)
93.0(6)
91.0(6)
3.1. Molecular structure of 2
Fig. 1 illustrates the skeletal framework of complex
2·Et2O. It is a seven-coordinate N-methylporphyrin
complex of the porphyrin N4 with two oxygen atoms of
the chelating bidentate CF3CO2− ligand from first trifl-
uoroacetate [O(3), O(4), C(48), C(49)], and one oxygen

3260
C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
structure with the 4:3 tetragonal base-trigonal base
geometry. Alternatively, the observed structure of 2
could be described as a highly distorted capped trigonal
prismatic arrangement with N(3) capping the quadrilat-
eral face generated by O(3), O(4), N(2), N(4) and the
remaining O(1), N(1) atoms being on the unique edge.
Comparison of the parameter l values (76.5, 44.6,
41.5°), to that of the idealized monocapped trigonal
prism (41.5, 0, 0°), the geometry is not indicative of the
monocapped trigonal prism (Table 3). The l values
listed in Table 3 are strongly suggestive of the observed
structure having a 4:3 tetragonal base–trigonal base
geometry. Earlier this kind of 4:3 piano stool geometry
was observed for Mo(CO)2(PEt3)2(O2CH)2 [23],
MoBr(O2CCF3)(CO)2(PPh3)2 [24], W(t-C4H9NC)3-
(CO)2I2 [31], W(CO)3(S2CN(CH3)2)2 [32] and
W(CO)2(PPh3)(S2CNEt2)2 [33] in the literature. Selected
bond distances and angles are summarized in Table 2.
The interaction of the first trifluoroacetate ligand with
thallium is bidentate chelation. This kind of bidentate
interaction was previously observed for Tl(NꢀMeꢀtpp)
(OAc)2 with Tl(1)ꢀO(1)=2.517(6) and Tl(1)ꢀO(2)=
Fig. 1. Molecular configuration and atom-labeling scheme for
Tl(NꢀMeꢀtpp)(CF3CO2)2·Et2O (or 2·Et2O), with ellipsoids drawn at
30% probability. Hydrogen atoms and solvent Et2O are omitted for
clarity. F(1)F(2)F(3) in 2·Et2O is disordered with an occupancy factor
0.7 for F(1)F(2)F(3) and 0.3 for F(1%)F(2%)F(3%).
atom of the monodentate CF3CO2− ligand from second
trifluoroacetate [O(1), O(2), C(46), C(47)]. Visual in-
spection as well as other stereo drawings suggested that
the geometrical configuration around Tl3+ could be
classified as either a 4:3 piano stool or a highly dis-
torted capped trigonal prism. To determine the stereo-
chemistry of 2, we have utilized the l parameters of
Porai-Koshits and Aslanov [28], as calculated by Muet-
terties and Guggenberger [29]. Upon viewing 2 as a 4:3
system, [N(1)N(2)N(3)N(4):O(1)O(3)O(4)], the observed
angle between the two planes of the ligating atom is
0.6°. Normalization of metal–ligand bond lengths by
projecting onto a sphere of unit radius results in an
angle (l1) of 1.1° between the two planes of the 4:3
geometry (Table 3), nearly identical with the ideal value
of 0° [30–33]. With 0° as the criteria both for the angle
between the two planes and for the dihedral angle
across the diagonal of the quadrilateral face, the corre-
sponding values of 1.1 and 8.4° (Table 3) which charac-
terize 2 indicate the compatibility of the observed
,
2.330(6) A. The second trifluoroacetate oxygen O(2) is
,
3.167(6) A distanced from thallium which is consider-
ably longer than that of the TlꢀO(1) distance and the
ligand’s interaction with thallium is classified as
monodentate. Hence only three oxygen atoms [i.e. O(1),
O(3), O(4)] are coordinated to the thallium atom.
The nitrogen atom bearing the methyl group is much
farther from the Tl3+ [TlꢀN(1) 2.700(4) A] compared
,
to the other three nitrogen atoms [TlꢀN(2) 2.276(4),
,
TlꢀN(3) 2.243(4), TlꢀN(4) 2.278(4) A]. Since the
TlꢀN(1) distance is quite large, the nitrogen atom N(1)
is probably not coordinated to the thallium. However,
in 1H NMR [599.95 MHz, Fig. 2(a)] at 20 °C the
Hb(2,3) and NꢀMe protons are observed at 8.73 ppm
[with 4J(Tl–H)=7.1 Hz] and at −4.31 ppm [with
3J(Tl–H)=70 Hz], respectively. Furthermore, 13C
NMR data [150.87 MHz] at 17 °C show Cb(C2,C3)
3
and Ca(C1,C4) resonances at 129.5 ppm [with J(Tl–
2
C)=10 Hz] and 157.1 ppm [with J(Tl–C)=90 Hz],
Table 3
Dihedral angle calculations a for comparison of molecule 2 with two trial geometries
Trial geometry
Defining planes
li li Dihedral angles (°)
Observed Idealized
l1 1.1
4:3 (piano stool), N(1)N(2)N(3)N(4):O(1)O(3)O(4)
N(1)N(2)N(3)N(4)/O(1)O(3)O(4)
N(1)N(3)N(4)/N(1)N(3)N(2)
O(3)O(4)N(3)/O(3)O(4)O(1)
O(3)N(1)N(4)/O(3)N(1)O(1)
N(1)O(4)N(2)/N(1)O(4)O(1)
0.0
0.0
l2 8.4
l1 76.5
l2 44.6
l3 41.5
1:4:2 (capped trigonal prism), N(3):O(3)O(4)N(2)N(4):O(1)N(1)
41.5
0.0
0.0
a The published coordinates were used to project the structure onto a sphere [30] after which the usual dihedral angles (l) between planes [29,31]
were calculated.

C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
3261
Fig. 2. 1H (600.25 MHz) NMR spectra for 2 in CD2Cl2 showing four different b-pyrrole protons Hb, phenyl protons (o-H, m, p-H) and the NꢀMe
protons at: (a) 20 and (b) −73 °C.
respectively. These two results confirm that the thal-
m(III) ion is pushed away from the 3N plane; its
,
,
liumꢀN(1) distance of 2.700(4) A is long enough, but it
displacement of 1.02 A is in the same direction as that
of the two apical CF3CO2− ligands [cf. 1.17 A for
,
does fall within the sum of the van der Waals radii of
,
thallium and nitrogen, ꢀ3.55 A. This longer Tl···N(1)
Tl(III) in Tl(NꢀMeꢀtpp)(OAc)2] [7]. The two approxi-
mately perpendicular trifluoroacetates with an angle of
81.0° are bound cis to Tl and lie above the macrocycle
making a dihedral angle of 56.2 and 43.0° with the 3N
plane for the two trifluoroacetates. The porphyrin
macrocycle is indeed distorted (Fig. 3) as a result of the
NꢀMe group. Thus, pyrrole N(1) [i.e. the plane of N(1),
C(1)–C(4)] bearing the methyl group [i.e. C(45)H3] is
the most deviated from the 3N plane, making a dihe-
dral angle of 23.3°, whereas smaller angles of 9.9, 2.7
and 4.7° occur with pyrroles N(2), N(3) and N(4),
respectively. Such a large deviation from planarity is
contact is described as a weak (secondary) bond [34–
,
36]. The TlꢀN(1) bond length of 2.700(4) A for 2 is
,
slightly shorter than the TlꢀN bond length of 2.71(3) A
for Tl[Tp(CF )2] [37] and 2.74(7) A for Tl[TpTrip] [38].
3
,
The other three non-alkylated pyrrole nitrogen atoms
[N(2), N(3), N(4)] bind strongly to the Tl(III) ion. We
adopt the plane of the three strongly bound pyrrole
nitrogen atoms [i.e. N(2), N(3), N(4)] as a reference
,
plane 3N. Fig. 3 illustrates the displacement (in A) of
various atoms (C20N4, Tl, NꢀMe, and 2CF3CO2−) from
the 3N plane. Because of its larger size, the thalliu-

3262
C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
134.4 ppm for Cb(C12, C13), and 132.8 ppm for Cb(C8,
C17). Similarly the non-planarity of porphyrin causing
upfield shifts of Cb resonances was also observed with a
magnitude of 5.6–7.0 ppm for Tl(NꢀMeꢀtpp)(OAc)2
[7]. The dihedral angles between the mean plane of the
skeleton 3N and the planes of the phenyl groups are
54.0° [C(24)], 69.1° [C(30)], 68.1° [C(36)] and 56.5°
[C(42)].
also reflected in the NMR data for pyrrole N(1) by
observing a 3.2–4.9 ppm upfield shift of Cb(C2,C3) at
129.6 ppm, compared to 134.5 ppm for Cb(C7, C18),
The Tl ion is displaced from the plane of the three
individual pyrrole groups which suggests that the
pyrrole nitrogen lone pairs are not optimally situated
for covalent bonding to the metal. The displacements of
the Tl ion from the plane of each pyrrole ring are 2.26
,
,
,
A for pyrrole N(1), 0.65 A for pyrrole N(2), 0.98 A for
,
pyrrole N(3) and 0.95 A for pyrrole N(4). The angles
between the TlꢀN vector and the corresponding pyrrole
ring are 58.0° for pyrrole N(1), 17.3° for pyrrole N(2),
26.5° for pyrrole N(3) and 24.8° for pyrrole N(4).
3.2. Dynamic NMR of 2 in CD2Cl2
The trifluoroacetate ligands engage in different bind-
ing modes in the solid state. These ligands exchange
monodentate and bidentate coordination modes rapidly
in CD2Cl2, even at −90 °C, with an activation barrier
too small to be readily measured by a variable-tempera-
ture NMR technique. The intramolecular exchange of
two different CF3CO2− groups attains equivalency in
CD2Cl2 solution on the 13C (or 19F) NMR time scale.
Hence, only one kind of CF3CO2− in 2 is observed. A
similar rapid exchange between the mono- and biden-
tate coordination modes of the carboxyate ligand has
been observed in solution of [Mo(CO)2(PEt3)2(O2CH)2],
even at −90 °C [23], and an analogous exchange
process has been described for carboxylate ligands in
the related compounds [Ru(O2CR%)2(CO)(PPh3)2] (R%=
Fig. 3. Diagram of the porphyrin core (C20N4, Tl, NꢀMe, and
2CF3CO2−) of compound 2 showing the displacement (in A) of the
,
atoms from the mean plane of 3N.
Me, CF3, C2F5 or C6F5) [39]. When a 1.22×10−2
M
solution of 2 in CD2Cl2 was cooled, the 19F signals of
two CF3CO2− being a single peak at 20 °C (l=
−74.57 ppm), first broadened (coalescence temperature
Tc= −59 °C) and then split into three set of peaks
(singlet at −76.15 ppm, one doublet at −73.30 ppm
and the other doublet at −73.76 ppm) at −97 °C at a
frequency of 564.49 MHz (Fig. 4). The singlet at
−76.15 ppm is assigned as CF3CO2−. The doublet at
−73.30 ppm is due to Tl(NꢀMeꢀtpp)(CF3CO2)+ with
4J(Tl–F)=22 Hz. The other doublet at −73.76 ppm is
4
due to 2 with J(Tl–F)=44 Hz. The relative concen-
tration of 2/Tl(NꢀMeꢀtpp)(CF3CO2)+/CF3CO2− is
1:0.11:0.09 at −97 °C. This assignment is also sup-
ported by the observations of 1H NMR for 2 in CD2Cl2
at −97 °C showing two doublets in 0.12:1 ratio for the
NꢀMe resonances at l −4.68 ppm [3J(Tl–H)=30 Hz]
due to Tl(NꢀMeꢀtpp)(CF3CO2)+ and −4.51 ppm
[3J(Tl–H)=72 Hz] due to 2. This ratio is quite close to
0.11 calculated from 19F NMR data. As a result of this
observation, the most likely cause for the loss of cou-
Fig. 4. The 564.49 MHz 19F NMR spectra for the axial trifluoroac-
etato fluorines of 2 in CD2Cl2 at 20, −59 (=Tc) and −97 °C.

C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
3263
pling should be due to reversible dissociation of
trifluoroacetate
The seven-coordinate thallium complex 2 is the first of
its kind with a 4:3 ‘piano stool’ geometry. Dynamic 13C
and 19F NMR spectra for the trifluoroacetato group of
2 reveal that this group undergoes an intermolecular
exchange. We have also shown that one large metal ion
(Tl3+) coordinates well away from the plane of the four
pyrrole nitrogen atoms and that in this location the
thallium can accommodate additional ligation.
Tl(NꢀMeꢀtpp)(CF3CO2)2
X Tl(NꢀMeꢀtpp)(CF3CO2)++CF3CO2−
(1)
with a moderate dissociation constant and reasonable
rate at room temperature [40]. The dissociation con-
stant of (1.8690.39)×10−4 mol dm−3 is evaluated at
−97 °C for reaction (1). Such a scenario would not
only lead to the change in the chemical shift with
temperature and detectable free CF3CO2− and
Tl(NꢀCH3ꢀtpp)(CF3CO2)+ at low temperature, but
also would lead to the loss of coupling between trifl-
uoroacetate and thallium at higher temperatures. The
chemical shift in the high-temperature limit is the aver-
age for all the three species in Eq. (1) weighted by their
concentration.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 162986 for compound 2.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://www.
ccdc.cam.ac.uk).
Compound 2 is unusually less soluble in CD2Cl2 at
17 °C than −106 °C. Due to poor solubility, no sig-
nals of carbonyl and CF3 carbons at 17 °C have been
found. At −106 °C, the rate of intermolecular ex-
change of CF3CO2− for 2 in CD2Cl2 is slow. Hence, at
this temperature the CO and CF3 carbons of CF3CO2−
Acknowledgements
2
in 2 are observed at 155.1 ppm [with J(C–F)=37 and
1
2J(Tl–C)=204 Hz ] and 114.3 ppm [with J(C–F)=
The financial support from the National Science
Council of the ROC under Grant NSC 89-2113-M-005-
014 is gratefully acknowledged. The NMR instrument
(Varian Unity Inova-600) is funded in part by the
National Science Council and by the Chung-Cheng
Agriculture Science & Social Welfare Foundation.
290 and 3J(Tl–C)=411 Hz], respectively. These 13C
resonance values are quite close to that of
Tl(tpp)(O2CCF3), in THF-d8 at −100 °C, i.e. 156.5
2
2
ppm [with J(C–F)=37 and J(Tl–C)=128 Hz] and
115.9 ppm [with 1J(C–F)=291 and 3J(Tl–C)=239
Hz] [41]. The increase in the J(Tl–C) coupling constant
from 128 to 204 Hz for CO and from 239 to 411 Hz for
CF3 might be in correlation to the increase in the
effective nuclear charge Zeff of the Tl atom from
Tl(tpp)(O2CCF3) to 2 and the estimated value of Zeff
[Tl in 2]/Zeff [Tl in (Tl(tpp)(O2CCF3)] is 1.1890.02.
In contrast, no intramolecular exchange between the
two trifluoroacetate groups is observed for the related
References
[1] D.K. Lavellee, A.B. Kopelove, O.P. Anderson, J. Am. Chem.
Soc. 100 (1978) 3025.
[2] O.P. Anderson, D.K. Lavellee, J. Am. Chem. Soc. 98 (1976)
4670.
[3] O.P. Anderson, D.K. Lavellee, J. Am. Chem. Soc. 99 (1977)
1404.
[4] O.P. Anderson, D.K. Lavellee, Inorg. Chem. 16 (1977) 1634.
[5] O.P. Anderson, A.B. Kopelove, D.K. Lavellee, Inorg. Chem. 19
(1980) 2101.
[6] A.L. Balch, C.R. Cornman, L. Latos-Grazynski, M.M. Olm-
stead, J. Am. Chem. Soc. 112 (1990) 7552.
[7] J.Y. Tung, J.H. Chen, F.L. Liao, S.L. Wang, L.P. Hwang,
Inorg. Chem. 39 (2000) 2120.
[8] C.D. Garner, B. Hughes, Adv. Inorg. Chem. Radiochem. 17
(1975) 1.
[9] D.D. McRitchie, R.C. Palenik, G.J. Palenik, Inorg. Chim. Acta
20 (1976) L27.
[10] M.G.B. Drew, G.W.A. Fowles, D.F. Lewis, J. Chem. Soc.,
Chem. Commun. (1969) 876.
seven-coordinate
bis(trifluoroacetato)
complexes
Mo(CO)2(PMe3)3(CF3CO2)2 [25] and Mo(CO)2(PEt3)2-
(CF3CO2)2 [26] in dichloromethane at 27 °C. More-
over, the dynamic processes involving not only in-
tramolecular exchange between mono- and bidentate
trifluoroacetate groups but also intermolecular ex-
change among 2, Tl(NꢀMeꢀtpp)(CF3CO2)+ and
CF3CO2− for 2 in CD2Cl2 are observed. Interestingly,
the dynamic properties for the exchange of trifluoroac-
etate in 2 is found to be very similar to the exchange of
acetate group in 1 as reflected by variable temperature
1
13C, H and 19F NMR studies.
[11] R.A. Levenson, R.L.R. Town, Inorg. Chem. 13 (1974) 105.
[12] A. Bino, R. Frim, M.V. Genderen, Inorg. Chim. Acta 127 (1987)
95.
[13] G.J. Palenik, D.W. Wester, U. Rychlewska, R.C. Palneik, Inorg.
Chem. 15 (1976) 1814.
4. Conclusions
This work describes a new compound 2 being charac-
terized by spectroscopic and crystallographic method.
[14] H. Matsushima, K. Iwasawa, K. Ide, M.Y. Reza, M. Koikawa,
T. Tokii, Inorg. Chim. Acta 274 (1998) 224.

3264
C.-H. Yang et al. / Polyhedron 20 (2001) 3257–3264
[15] J. Davis, G.J. Palenik, Inorg. Chim. Acta 99 (1985) L51.
[16] A.S. Craig, I.M. Helps, D. Parker, H. Adams, N.A. Bailey,
M.G. Williams, J.M.A. Smith, G. Ferguson, Polyhedron 8
(1989) 2481.
[28] M.A. Porai-Koshits, L.A. Aslanov, Zh. Strukt. Khim. 13 (1972)
266.
[29] (a) E.L. Muetterties, L.J. Guggenberger, J. Am. Chem. Soc. 96
(1974) 1748;
[17] A. Riesen, T.A. Kaden, W. Ritter, H.R. Macke, J. Chem. Soc.,
Chem. Commun. (1989) 460.
(b) E.L. Muetterties, L.J. Guggenberger, J. Am. Chem. Soc. 99
(1977) 3893.
[18] C.J. Broan, J.P.L. Cox, A.S. Craig, R. Kataky, D. Parker, A.
Harrison, A.M. Randall, G. Ferguson, J. Chem. Soc., Perkin
Trans. (1991) 87.
[19] M.B. Inoue, M. Inoue, Q. Fernando, Inorg. Chim. Acta 271
(1998) 207.
[20] A.J. Deeming, M. Karim, N.I. Powell, J. Chem. Soc., Dalton
Trans. (1990) 2321.
[21] R.J. Barton, S.K. Manocha, B.E. Robertson, L.M. Mihichuk,
Can. J. Chem. 76 (1998) 245.
[22] A. Chundrasekaran, N.V. Timosheva, R.O. Day, R.S. Holmes,
Inorg. Chem. 39 (2000) 1338.
[23] D.C. Brower, P.B. Winston, T.L. Tonker, J.L. Templeton, Inorg.
Chem. 25 (1986) 2883.
[24] B.J. Brisdon, A.G.W. Hodson, G.W. Mahon, K.C. Molloy, J.
Chem. Soc., Dalton Trans. (1993) 245.
[30] (a) J.K. Kouba, S.S. Wreford, Inorg. Chem. 15 (1976) 1463;
(b) J.K. Kouba, S.S. Wreford, Inorg. Chem. 17 (1978) 1696.
[31] E.B. Dreyer, C.T. Lam, S.J. Lippard, Inorg. Chem. 18 (1979)
1904.
[32] J.L. Templeton, B.C. Ward, Inorg. Chem. 19 (1980) 1753.
[33] J.L. Templeton, B.C. Ward, J. Am. Chem. Soc. 103 (1981) 3743.
[34] J.S. Casas, M.S. Garcia-Tasende, J. Sordo, Coord. Chem. Rev.
193–195 (1999) 283.
[35] N.W. Alcock, Adv. Inorg. Chem. Radiochem. 15 (1972) 1.
[36] J.F. Sawyer, R.J. Gillespie, Prog. Inorg. Chem. 34 (1986) 65.
[37] O. Renn, L.M. Venanzi, A. Martelett, V. Gramlich, Helv. Chim.
Acta 78 (1995) 993.
[38] T. Fillebeen, T. Hascall, G. Parkin, Inorg. Chem. 36 (1997) 3787.
[39] C.J. Cresswell, A. Dobson, D.S. Moore, S.D. Robinson, Inorg.
Chem. 18 (1979) 2055.
[25] A.L. Beauchamp, F. Belanger-Gariepy, S. Arabi, Inorg. Chem.
24 (1985) 1860.
[26] S. Arabi, C. Berthelot, J.P. Barry, F. Belanger-Gariepy, A.L.
Beauchamp, Inorg. Chim. Acta 120 (1986) 159.
[27] D.K. Lavallee, A.E. Gebala, Inorg. Chem. 13 (1974) 2004.
[40] J.P. Jensen, E.L. Muetterties, in: L.M. Jackman, F.A. Cotton
(Eds.), Dynamic Nuclear Magnetic Resonance Spectroscopy,
Academic Press, New York, 1975, pp. 299–304.
[41] L.F. Chou, J.H. Chen, J. Chem. Soc., Dalton Trans. (1996)
3787.