Conformational behavior and coordination chemistry of 2,11-dithia[3.3]orthocyclophane with platinum group metals

Article abstract of DOI:10.1021/ic0256157

The compound 2,11-dithia[3.3]orthocyclophane (L) is a mesocyclic dithioether that can act as a bidentate ligand in different conformations. In the ionic heteroleptic complexes [PtL(η⁴-cod)][CF₃SO₃]₂ (1), [RhL(η⁴-cod)][CF₃SO₃] (2), and [IrL(η⁴-cod)][CF₃SO₃] (3) (cod = 1,5-cyclooctadiene), L is coordinated in the anti I conformation both in solution and in the solid state, as revealed by an X-ray diffraction study of complex 1. However, in complexes [PdL- (PPh₃)₂][SO₃CF₃]₂ (4) and [PtL(PPh₃)₂][SO₃CF₃]₂ (5), L exhibits two different conformations: anti I and anti II in a 40:60 ratio, as observed by ¹H and ³¹P NMR spectroscopy, with no exchange up to 90 °C. The homoleptic complexes [PdL₂][SO₃CF₃]₂ (6) and [PtL₂][SO₃CF₃]₂ (7), with two ligands bound to the metal, display two isomers in solution, one of them with L in conformations anti I-anti II and the other with conformations anti II-anti II with a 75:25 ratio. The X-ray structure of 6 showed only the presence of the anti II-anti II isomer in the solid state. All complexes were synthesized by the reaction of a suitable chloride complex with 2 equiv of silver triflate and 1 equiv of L.

Full text of DOI:10.1021/ic0256157

Inorg. Chem. 2002, 41, 3779−3785
Conformational Behavior and Coordination Chemistry of
2,11-Dithia[3.3]orthocyclophane with Platinum Group Metals
,‡
,†
Jorge Tiburcio,†,‡ William D. Jones,§ Stephen J. Loeb,* and Hugo Torrens*
DiVision de Estudios de Posgrado, Facultad de Qu´ımica, UniVersidad Nacional Autonoma de
Me´xico (UNAM), Ciudad UniVersitaria 04510, Distrito Federal, Me´xico, Department of Chemistry,
UniVersity of Rochester, Rochester, New York 14627, and Department of Chemistry &
Biochemistry, UniVersity of Windsor, Windsor, Ontario N9B 3P4, Canada
Received March 25, 2002
The compound 2,11-dithia[3.3]orthocyclophane (L) is a mesocyclic dithioether that can act as a bidentate ligand in
different conformations. In the ionic heteroleptic complexes [PtL(η4-cod)][CF SO ] (1), [RhL(η4-cod)][CF SO ] (2),
3
3 2
3
3
and [IrL(η4-cod)][CF SO ] (3) (cod ) 1,5-cyclooctadiene), L is coordinated in the anti I conformation both in solution
3
3
and in the solid state, as revealed by an X-ray diffraction study of complex 1. However, in complexes [PdL-
(PPh3)2][SO CF ] (4) and [PtL(PPh3)2][SO CF ] (5), L exhibits two different conformations: anti I and anti II in a
3
3 2
3
3 2
40:60 ratio, as observed by 1H and 31P NMR spectroscopy, with no exchange up to 90 °C. The homoleptic complexes
[PdL2][SO CF ] (6) and [PtL2][SO CF ] (7), with two ligands bound to the metal, display two isomers in solution,
3
3 2
3
3 2
one of them with L in conformations anti I−anti II and the other with conformations anti II−anti II with a 75:25 ratio.
The X-ray structure of 6 showed only the presence of the anti II−anti II isomer in the solid state. All complexes
were synthesized by the reaction of a suitable chloride complex with 2 equiv of silver triflate and 1 equiv of L.
Introduction
area, and the synthesis of novel complexes using azacyclo-
phanes,8 selenacyclophanes,9 thiacyclophanes,10 and mixed
aza-thiacyclophanes11 as ligands has grown steadily.
During the design of cyclophane ligands, it must be noted
that the conformational preferences of uncoordinated and
coordinated cyclophanes are necessarily very different.
Usually, a variety of conformational changes are required
to achieve coordination, and this is often greatly influenced
by the electronic properties of the metal ion.12-14 Our group
Particular attention has been recently devoted to the design
and syntheses of metal-cyclophane complexes because of
their unique molecular properties and potential applications
as anion1 and molecular2 sensors, molecular receptors,3
electron-transfer assemblies,4 and conductive polymers.5
Initially, the coordination chemistry of cyclophanes was
dominated by metal-arene compounds, the so-called met-
allocenophanes;6 however, incorporation of heteroatoms into
the alkane bridges7 has greatly expanded the scope of this
(7) Vo¨gtle, F. Cyclophanes; John Wiley & Sons: Chichester, U.K., 1993.
(8) (a) Bencini, A.; Bianchi, A.; Fusi, V.; Giorgi, C.; Paoletti, P.; Ramirez,
J. A.; Valtancoli, B. Inorg. Chem. 1999, 38, 2064-2070. (b) Inoue,
M. B.; Velazquez, E. F.; Medrano, F.; Ochoa, K. L.; Galvez, J. C.;
Inoue, M.; Fernando, Q. Inorg. Chem. 1998, 37, 4070-4075. (c) Inoue,
M. B.; Medrano, F.; Inoue, M.; Raitsimring, A.; Fernando, Q. Inorg.
Chem. 1997, 36, 2335-2340.
(9) Hou, X.-L.; Wu, X.-W.; Dai, L.-X.; Cao, B.-X.; Sun, J. Chem.
Commun. 2000, 1195-1196.
(10) (a) Giesbrecht, G. R.; Hanan, G. S.; Kickham, J. E.; Loeb, S. J. Inorg.
Chem. 1992, 31, 3286-3291. (b) de Groot, B.; Loeb, S. J. Inorg.
Chem. 1990, 29, 4084-4090.
(11) Blake, A. J.; Casabo`, J.; Devillanova, F. A.; Escriche, L.; Garau, A.;
Isaia, F.; Lippolis, V.; Kivekas, R.; Muns, V.; Schro¨der, M.; Sillanpa¨a¨,
R.; Verani, G. J. Chem. Soc., Dalton Trans. 1999, 1085-1092.
(12) Comba, P.; Ku¨hner, A.; Peters, A. J. Chem. Soc., Dalton Trans. 1999,
509-516.
(13) (a) Mascal, M.; Kerdelhue´, J.-L.; Blake, A. J.; Cooke, P. A. Angew.
Chem., Int. Ed. 1999, 38, 1968-1971. (b) Mascal, M.; Kerdelhue´,
J.-L.; Blake, A. J.; Cooke, P. A.; Mortimer, R. J.; Teat, S. J. Eur. J.
Inorg. Chem. 2000, 485-490.
* To whom correspondence should be addressed. E-mail: torrens@
servidor.unam.mx (H.T.); loeb@uwindsor.ca (S.J.L.).
† UNAM.
‡ University of Windsor.
§ University of Rochester.
(1) Sun, S.-S.; Anspach, J. A.; Lees, A. J.; Zavalij, P. Y. Organometallics
2002, 21, 685-693.
(2) Kharitonov, A. B.; Shipway, A. N.; Willner, I. Anal. Chem. 1999, 71,
5441-5443.
(3) Murphy, S. L.; Loeb, S. J.; Shimizu, G. K. H. Tetrahedron 1998, 54,
15137-15146.
(4) David, E.; Born, R.; Kaganer, E.; Joselevich, E.; Du¨rr, H.; Willner, I.
J. Am. Chem. Soc. 1997, 119, 7778-7790.
(5) Munakata, M.; Ping Wu, L.; Kuroda-Sowa, T.; Maekawa, M.; Suenaga,
Y.; Nakagawa, S. J. Chem. Soc., Dalton Trans. 1996, 1525-1530.
(6) (a) Benn, R.; Blank, N. E.; Haenel, M. W.; Klein, J.; Koray, A. R.;
Weidenhammer, K.; Ziegler, M. L. Angew. Chem., Int. Ed. Engl. 1980,
19, 44-45. (b) Mueller-Westerhoff U. T. Angew. Chem., Int. Ed. Engl.
1986, 25, 702-717.
10.1021/ic0256157 CCC: $22.00 © 2002 American Chemical Society
Published on Web 06/18/2002
Inorganic Chemistry, Vol. 41, No. 14, 2002 3779

Tiburcio et al.
probably can only be observed when nonbulky ligands are
bound to the metal. It is possible, however, for the ligand to
adopt the alternative conformation, anti II, thereby allowing
coordination of bulky ligands at the metal, as was previously
reported by Hanton and Kemmit for a series of Ru(II)
complexes.25
With the aim to further understand the factors controlling
the conformational preferences of the cyclophanes upon
coordination, thiacyclophanes in general and 2,11-dithia[3.3]-
orthocyclophane in particular, we are extending this work
to the platinum group metals rhodium, palladium, iridium,
and platinum which prefer a square planar geometry.
Experimental Section
All reagents were purchased from Aldrich and used as received.
The starting complexes [M(µ-Cl)(η4-cod)]2 (M ) Rh, Ir) were
acquired from Strem Chemical Co. The ligand (L) 2,11-dithia[3.3]-
orthocyclophane20 and the complexes [PtCl2(η4-cod)],26 [MCl2-
(PPh3)2]27 (M ) Pd, Pt), [Pd(MeCN)4][CF3SO3]2,28 and [Pt(EtCN)4]-
Figure 1. Different conformations of 2,11-dithia[3.3]orthocyclophane (L).
Benzylic hydrogens are omitted for clarity.
29
[CF3SO3]2 were prepared by published methods. All reactions
has been studying the coordination chemistry of thiacyclo-
phanes and their application to molecular recognition.15-19
In particular, we are interested in the factors controlling their
conformational behavior.
were carried out under an atmosphere of N2(g) using Schlenk
techniques, and the solvents were degassed prior to use. Mi-
croanalyses were performed using a Fisons EA1108 instrument.
1H, 13C{1H}, and 31P{1H} NMR spectra were recorded at 500.1
(Bruker 500 MHz), 75.4 (Varian 300 MHz), and 202.5 (Bruker
300 MHz), respectively, locked onto the deuterated solvent. FAB
mass spectra were obtained on a JEOL JMS-SX102A. Molecular
mechanics calculations were performed using the MM3 force field
under the graphic interface Spartan.30
A convenient synthesis of the thiacyclophane 2,11-dithia-
[3.3]orthocyclophane (L) has been reported,20 and molecular
mechanics calculations have shown that the minimum energy
conformer has an anti structure with exo oriented sulfur
atoms.21 This is also the conformation observed in the solid
state by X-ray crystallography.21 Thus L, like many cyclic
thioethers, with the notable exception of the preorganized
9S3,22 shows a conformational preference for an exo ar-
rangement of S atoms both in solution and in the solid state.23
Therefore, in order for chelation to occur, it is necessary for
donor atoms to reorient from an exo to an endo arrange-
ment.24 In the endo conformation, three isomers exist, which
are potentially capable of chelating a metal: anti I, anti II,
and syn (see Figure 1).
[Pt(S2C16H16)(η4-cod)][CF3SO3]2 (1). To a solution of the
complex [PtCl2(η4-cod)] (100 mg, 0.27 mmol) in chloroform (50
cm3) was added 2 equiv of AgCF3SO3 (137 mg, 0.54 mmol). The
mixture was stirred for 3 h and then filtered through Celite to
remove AgCl. To the resulting solution was added, with stirring, 1
equiv of L (72.8 mg, 0.27 mmol). The precipitated white solid was
1
filtered and washed with chloroform. Yield: 130 mg (56%). H
NMR (CD3CN, 300 K): δ (ppm) 7.59 (m, aromatic, L), 5.39 (br,
CH, cod, 195Pt satellite doublet at 5.46 and 5.32, 2JH-Pt ) 70.0 Hz),
2
5.13 (d, JH-H ) 13.2 Hz, benzylic, L, 195Pt satellite at 5.19 and
According to molecular mechanics calculations, the syn
isomer has the highest energy of the three conformations
and is therefore the least likely to be observed in metal
complexes.21,25 The conformation anti I is slightly more stable
than the anti II; however, it is sterically very demanding and
3
2
5.07, JH-Pt ) 60.0 Hz), 4.99 (d, JH-H ) 13.2 Hz, benzylic, L),
1.68 (m, CH2, cod). 13C{1H} NMR (CD3CN, 300 K): δ (ppm)
133.0 (s, aromatic, L), 131.9 (s, aromatic, L), 131.3 (s, aromatic,
L), 115.5 (s, CH, cod, 195Pt satellite doublet at 116.3 and 114.8,
1JC-Pt ) 113.3 Hz,), 42.4 (s, benzylic, L), 30.0 (s, CH2, cod). MS
FAB+ Calcd for [Pt(S2C16H16)(η4-cod)][CF3SO3]+: 724. Found:
724. Anal. Calcd for C26H28F6O6PtS4: C, 35.7; H, 3.2; S, 14.7.
Found: C, 35.5; H, 3.0; S, 14.7.
(14) Schooler, P.; Johnson, B. F. G.; Scaccianone, L.; Tregonning, R. J.
Chem. Soc., Dalton Trans. 1999, 2743-2749.
(15) (a) de Groot, B.; Jenkins, H. A.; Loeb, S. J.; Murphy, S. L. Can. J.
Chem. 1995, 73, 1102-1110. (b) Jenkins, H. A.; Loeb, S. J.
Organometallics 1994, 13, 1840-1850.
(16) Kickham, J. E.; Loeb, S. J. Inorg. Chem. 1995, 34, 5656-5665.
(17) Kickham, J. E.; Loeb, S. J. Inorg. Chem. 1994, 33, 4351-4359.
(18) Kickham, J. E.; Loeb, S. J. Chem. Commun. 1993, 1848-1850.
(19) (a) Kickham, J. E.; Loeb, S. J.; Murphy, S. L. J. Am. Chem. Soc.
1993, 115, 7031-7032. (b) Kickham, J. E.; Loeb, S. J.; Murphy, S.
L. Chem.sEur. J. 1997, 3, 1203-1213.
(20) Lai, Y. H.; Nakamura, M. J. Org. Chem. 1988, 53, 2360-2362.
(21) Okajima, T.; Wang, Z.-H.; Fukazawa, Y. Tetrahedron Lett. 1989, 30,
1551-1554.
[Rh(S2C16H16)(η4-cod)][CF3SO3] (2). To a solution of the
complex [RhCl(η4-cod)]2 (100 mg, 0.20 mmol) in acetone (20 cm3)
was added 2 equiv of AgCF3SO3 (104 mg, 0.40 mmol). The mixture
was stirred for 4 h and then filtered through Celite to remove AgCl.
To the resulting solution was added, with stirring, 2 equiv of L
(110 mg, 40 mmol). This mixture was stirred further for 4 h. The
(26) Clark, H. C.; Manzer, L. E. J. Organomet. Chem. 1973, 59, 411-
428.
(22) (a) Grant, G. J.; Poullaos, I. M.; Galas, D. F.; VanDerveer, D. G.;
Zubkowski, J. D.; Valente, E. J. Inorg. Chem. 2001, 40, 564-567.
(b) Blake, A. J.; Schro¨der, M. AdV. Inorg. Chem. 1990, 35, 1-80.
(23) (a) Cooper, S. R.; Rawle, S. C. Struct. Bonding (Berlin) 1990, 72,
1-72. (b) Cooper, S. R. Acc. Chem. Res. 1988, 21, 141-146
(24) Hanton, L. R.; Kemmitt, T. Chem. Commun. 1991, 700-702.
(25) Hanton, L. R.; Kemmitt, T. Inorg. Chem. 1993, 32, 3648-3653.
(27) Chatt, J.; Wilkins, R. J. Chem. Soc. 1951, 2532-2533.
(28) Beletskaya, I. P.; Chuchurjukin, A. V.; Dijkstra, H. P.; van Klink, G.
P. M.; van Koten G. Tetrahedron Lett. 2000, 41, 1081-1085.
(29) Kukushkin V. Y.; Oskarsson, Å.; Elding, L. I. Inorg. Synth. 1997, 31,
279-282.
(30) Hehre, W. J.; Huang, W. W. Chemistry with computation, An
introduction to Spartan; Wavefunction, Inc.: Irvine, CA, 1995.
3780 Inorganic Chemistry, Vol. 41, No. 14, 2002

Coordination of 2,11-Dithia[3.3]orthocyclophane
volume was reduced to ca. half in vacuo, and then, n-hexane was
PPh3), 7.41 (q, aromatic, L), 7.35 (m, aromatic, PPh3), 7.28 (q,
aromatic, L), 7.22 (m, aromatic, PPh3), 7.14 (q, aromatic, L), 6.89
added. The precipitated yellow solid was filtered and washed with
1
2
n-hexane. Yield: 198 mg (77%). H NMR (CD3CN, 300 K): δ
(m, aromatic, PPh3), 4.74 (d, JH-H ) 13.5 Hz, benzylic, anti I),
2
2
4.41 (d, 2JH-H ) 13.5 Hz, benzylic, anti I), 4.37 (d, JH-H ) 13.8
(ppm) 7.55 (m, aromatic, L), 4.84 (d, JH-H ) 12.9 Hz, benzylic,
L), 4.74 (dd, 2JH-H ) 12.9 Hz, 3JH-Rh ) 1.8 Hz, benzylic, L), 3.98
(m, CH, cod), 1.65 (m, CH2, cod). 13C{1H} NMR (CD3CN, 300
K): δ (ppm) 136.1 (s, aromatic, L), 131.9 (s, aromatic, L), 130.4
Hz, benzylic, anti II), 4.13 (d, 2JH-H ) 13.8 Hz, benzylic, anti II),
4.09 (d, 2JH-H ) 13.0 Hz, benzylic, anti II), 3.28 (d, 2JH-H ) 13.0
Hz, benzylic, anti II). 31P{1H} NMR (CD3CN, 300 K): δ (ppm)
1
1
15.7 (s, 195Pt satellite doublet at 23.5 and 7.9, JP-Pt ) 3159 Hz,
(s, aromatic, L), 89.6 (d, JC-Rh ) 11.3 Hz, CH, cod), 41.3 (s,
benzylic, L), 30.8 (s, CH2, cod). MS FAB+ Calcd for [Rh(S2C16H16)-
(η4-cod)]+: 483. Found: 483. Anal. Calcd for C25H28F3O3RhS3:
C, 47.5; H, 4.5; S, 15.2. Found: C, 47.1; H, 4.3; S, 15.8.
[Ir(S2C16H16)(η4-cod)][CF3SO3] (3). To a solution of the
complex [IrCl(η4-cod)]2 (100 mg, 0.15 mmol) in acetone (20 cm3)
was added 2 equiv of AgCF3SO3 (76.5 mg, 0.30 mmol). The
mixture was stirred for 6 h and then was filtered through Celite to
remove AgCl. To the resulting solution was added, with stirring, 2
equiv of L (82 mg, 30 mmol). This mixture was stirred further for
12 h. The volume was reduced to ca. half in vacuo, and then,
n-hexane was added. The precipitated red solid was filtered and
washed with n-hexane. Yield: 160 mg (74%). 1H NMR (CD3CN,
300 K): δ (ppm) 7.40 (m, aromatic, L), 4.95 (d, 2JH-H ) 13.1 Hz,
benzylic, L), 4.71 (d, 2JH-H ) 13.1 Hz, benzylic, L), 3.52 (m, CH,
cod), 1.33 (m, CH2, cod). 13C{1H} NMR (CD3CN, 300 K): δ (ppm)
134.5 (s, aromatic, L), 130.8 (s, aromatic, L), 129.5 (s, aromatic,
L), 74.9 (s, CH, cod), 42.6 (s, benzylic, L), 30.5 (s, CH2, cod). MS
FAB+ Calcd for [Ir(S2C16H16)(η4-cod)]+ 573. Found: 573. Anal.
Calcd for C25H28F3IrO3S3: C, 41.6; H, 3.9; S, 13.3. Found: C, 41.1;
H, 3.5; S, 13.4.
1
anti II), 12.5 (s, 195Pt satellite doublet at 20.3 and 4.6, JP-Pt
)
3179 Hz, anti I). 13C{1H} NMR (CD3CN, 300 K): δ (ppm) 134.7,
(s, aromatic), 134.5 (m, aromatic), 133.7 (s, aromatic) 133.1 (s,
aromatic), 133.0 (s, aromatic), 132.9 (s, aromatic), 132.8 (s,
aromatic), 131.2 (s, aromatic), 130.6 (s, aromatic), 130.5 (s,
aromatic), 130.2 (s, aromatic), 129.5 (m, aromatic), 43.5 (s, benzylic,
anti I), 40.9 (s, benzylic, anti II), 36.2 (s, benzylic, anti II). MS
FAB+ Calcd for [Pt(S2C16H16)(PPh3)2][CF3SO3]+: 1141. Found:
1141. Anal. Calcd for C54H46F6O6P2PtS4: C, 50.3; H, 3.6; S, 9.9.
Found: C, 49.4; H, 3.5; S, 10.1.
[Pd(S2C16H16)2][CF3SO3]2 (6). Method A. To a solution of the
complex [Pd(MeCN)4][CF3SO3]2 (100 mg, 0.18 mmol) in aceto-
nitrile (20 cm3) was added 2 equiv of L (96 mg, 0.36 mmol) under
stirring. The mixture was stirred for a further 4 h and then the
solvent removed in vacuo yielding a yellow solid. Yield: 157 mg
(94%).
Method B. To a suspension of the complex [PdCl2(S2C16H16)]31
(100 mg, 0.22 mmol) in acetone (20 cm3) was added 2 equiv of
AgCF3SO3 (114 mg, 0.44 mmol). The mixture was stirred for 2 h
in the dark and then filtered through Celite to remove AgCl. To
the resulting solution was added, with stirring, 1 equiv of L (61
mg, 0.22 mmol), and this mixture stirred for a further 2 h. The
precipitated yellow solid was filtered and washed with dichlo-
[Pd(S2C16H16)(PPh3)2][CF3SO3]2 (4). To a solution of the
complex [PdCl2(PPh3)2] (100 mg, 0.14 mmol) in acetonitrile (20
cm3) was added 2 equiv of AgCF3SO3 (73.2 mg, 0.28 mmol). The
mixture was stirred in the dark for 6 h and then was filtered through
Celite to remove AgCl. To the resulting mixture was added, with
stirring, 1 equiv of L (38.8 mg, 0.14 mmol) and stirred for a further
4 h. The solvent was then removed in vacuo yielding a yellow solid.
1
romethane. Yield: 164 mg (79%). H NMR (CD3CN, 300 K): δ
(ppm) 7.69 (m, aromatic), 7.57 (m, aromatic), 7.51 (m, aromatic),
7.44 (m, aromatic), 7.32 (m, aromatic), 7.17 (m, aromatic), 6.98
(m, aromatic), 4.84 (d, 2JH-H ) 13.2 Hz, benzylic, anti I-anti II),
4.70 (d, 2JH-H ) 13.2 Hz, benzylic, anti I-anti II), 4.66 (d, 2JH-H
1
Yield: 150 mg (88%). H{31P} NMR (CD3CN, 300 K): δ (ppm)
7.89 (q, aromatic, L), 7.79 (q, aromatic, L), 7.69 (m, aromatic,
PPh3), 7.55 (m, aromatic, PPh3), 7.47 (m, aromatic, PPh3), 7.43 (q,
aromatic, L), 7.35 (m, aromatic, PPh3), 7.30 (q, aromatic, L), 7.01
(m, aromatic, PPh3), 5.0 (d, 2JH-H ) 13.3 Hz, benzylic, anti I), 4.7
2
) 13.2 Hz, benzylic, anti I-anti II), 4.53 (d, JH-H ) 13.2 Hz,
2
benzylic, anti I-anti II), 4.31 (d, JH-H ) 13.5 Hz, benzylic, anti
2
II-anti II), 4.18 (d, JH-H ) 13.9 Hz, benzylic, anti I-anti II),
4.02 (d, 2JH-H ) 12.9 Hz, benzylic, anti II-anti II), 3.77 (d, 2JH-H
2
2
(d, JH-H ) 13.8 Hz, benzylic anti II), 4.5 (d, JH-H ) 13.3 Hz,
2
) 12.6 Hz, benzylic, anti I-anti II), 3.46 (d, JH-H ) 13.5 Hz,
benzylic, anti I), 4.2 (d, 2JH-H ) 13.8 Hz, benzylic, anti II), 4.1 (d,
benzylic, anti II-anti II), 3.21 (d, 2JH-H ) 13.9 Hz, benzylic, anti
2JH-H ) 12.9 Hz, benzylic, anti II), 3.4 (d, JH-H ) 12.9 Hz,
2
2
I-anti II), 3.15 (d, JH-H ) 12.9 Hz, benzylic, anti II-anti II),
benzylic, anti II). 31P{1H} NMR (CD3CN, 300 K): δ (ppm) 32.7
(s, anti II), 29.5 (s, anti I). 13C{1H} NMR (CD3CN, 300 K): δ
(ppm) 134.8, (s, aromatic), 134.3 (m, aromatic), 133.7 (s, aromatic)
133.3 (s, aromatic), 133.1 (s, aromatic), 133.0 (s, aromatic), 132.9
(s, aromatic), 132.8 (s, aromatic), 131.0 (s, aromatic), 130.6 (s,
aromatic), 130.1 (s, aromatic), 129.6 (m, aromatic), 42.2 (s, benzylic,
anti I), 39.2 (s, benzylic, anti II), 34.8 (s, benzylic, anti II). MS
FAB+ Calcd for [Pd(S2C16H16)(PPh3)2][CF3SO3]+: 1051. Found:
1051. Anal. Calcd for C54H46F6O6P2PdS4: C, 54.0; H, 3.9; S, 10.7.
Found: C, 54.1; H, 3.6; S, 10.5.
2.85 (d, 2JH-H ) 12.6 Hz, benzylic, anti I-anti II). 13C NMR (CD3-
CN, 300K): δ (ppm) 136.2 (s, aromatic), 135.7 (s, aromatic), 133.6
(s, aromatic), 133.5 (s, aromatic), 133.2 (s, aromatic), 132.4 (m,
aromatic), 132.3 (s, aromatic), 132.2 (s, aromatic), 132.0 (s,
aromatic), 130.7 (s, aromatic), 129.9 (s, aromatic), 43.0 (s, benzylic,
anti I-anti II), 42.3 (s, benzylic, anti I-anti II), 40.1 (s, benzylic,
anti I-anti II), 39.8 (s, benzylic, anti II-anti II), 35.2 (s, benzylic,
anti II-anti II), 34.6 (s, benzylic, anti I-anti II). MS FAB+ Calcd
(31) [MCl2(S2C16H16)] M ) Pd, Pt: To a solution of the corresponding
salt K2[MCl4] in an acetone-water mixture was added a solution of
L in dichloromethane. The mixture was stirred vigorously for 24 h at
room temperature. The precipitated solid was isolated by filtration,
washed with water, acetone, and dichloromethane, and dried in vacuo.
[PdCl2(S2C16H16)] yield: 94%. Anal. Calcd for C16H16Cl2PdS2: C,
42.7; H, 3.6; S, 14.3. Found: C, 42.4; H, 3.9; S, 13.8. FT-IR (KBr,
cm-1): 2937(m), 1490(m), 1454(s), 1241(m), 779(s), 664(m). Far-IR
(polyethylene, cm-1): 343, 321, 298, 282. [PtCl2(S2C16H16)], yield:
85%. Anal. Calcd for C16H16Cl2PtS2: C, 35.7; H, 3.0; S, 11.9.
Found: C, 35.8; H, 3.1; S, 12.1. FT-IR (KBr, cm-1): 2940(m), 1490-
(m), 1456(s), 1241(m), 779(s), 658(s). Far-IR (polyethylene, cm-1):
337, 323, 310, 308.
[Pt(S2C16H16)(PPh3)2][CF3SO3]2 (5). To a solution of the
complex [PtCl2(PPh3)2] (150 mg, 0.19 mmol) in acetonitrile (20
cm3) was added 2 equiv of AgCF3SO3 (97.5 mg, 0.38 mmol). The
mixture was stirred in the dark for 24 h and then was filtered
through Celite to remove AgCl. To the resulting mixture was added,
with stirring, 1 equiv of L (51.7 mg, 0.19 mmol), and this mixture
stirred for a further 24 h. The solvent was then removed in vacuo
yielding a white solid. Yield: 210 mg (86%). 1H{31P} NMR (CD3-
CN, 300 K): δ (ppm) 7.78 (q, aromatic, L), 7.69 (q, aromatic, L),
7.62 (m, aromatic, PPh3), 7.54 (q, aromatic, L), 7.45 (m, aromatic,
Inorganic Chemistry, Vol. 41, No. 14, 2002 3781

Tiburcio et al.
for [Pd(S2C16H16)2][CF3SO3]+: 799. Found: 799. Anal. Calcd for
C34H32F6O6PdS6: C, 43.0; H, 3.4; S, 20.3. Found: C, 42.2; H, 3.8;
S, 20.5.
Table 1. Summary of Crystal Data, Intensity Collection, and Structure
Refinement for [PtL(η4-cod)][SO3CF3]2 (1) and [PdL2][SO3CF3]2‚MeCN
(6)
1
6
[Pt(S2C16H16)2][CF3SO3]2 (7). Method A. To a solution of the
complex [Pt(EtCN)4][CF3SO3]2 (100 mg, 0.14 mmol) in dichlo-
romethane (50 cm3) was added 2 equiv of L (76 mg, 0.28 mmol)
with stirring. The mixture was stirred for a further 24 h and then
the solvent removed in vacuo yielding a white solid. Yield: 135
mg (93%).
formula
fw
a, Å
b, Å
c, Å
C26H28F6O6PtS4
873.83
C36H32F6NO6PdS6
987.39
9.4421(5)
21.7356(11)
19.1037(10)
11.0874(21)
11.5019(22)
13.4237(25)
82.617(3)
70.159(3)
66.268(3)
triclinic
P1
R, deg
â, deg
γ, deg
cryst syst
space group
V, Å3
Method B. To a suspension of the complex [PtCl2(S2C16H16)]31
(100 mg, 0.19 mmol) in acetone (20 cm3) was added 2 equiv of
AgCF3SO3 (95.4 mg, 0.37 mmol). The mixture was stirred for 40
h in the dark and then was filtered through Celite to remove AgCl.
To the resulting solution was added, with stirring, 1 equiv of L (51
mg, 0.19 mmol). This solution was stirred for a further 24 h, and
then, the solvent was removed in vacuo yielding a white solid.
orthorhombic
Pbcn
3920.6(4)
1.673
4
1474.0(3)
1.969
F(calcd), g cm-3
Z
2
µ (mm-1
λ, Å
)
5.122
0.868
0.71073
193
5.82
9.13
0.71073
293
1
T (K)
Yield: 158 mg (82%). H NMR (CD3CN, 300 K): δ (ppm) 7.65
R(Fo), % (all data)a
2.77
7.24
(m, aromatic), 7.62 (m, aromatic), 7.54 (m, aromatic), 7.45 (m,
aromatic), 7.27 (m, aromatic), 7.16 (m, aromatic), 7.12 (m,
aromatic), 6.95 (m, aromatic), 4.97 (d, 2JH-H ) 13.2 Hz, benzylic,
anti I-anti II), 4.79 (d, 2JH-H ) 13.2 Hz, benzylic, anti I-anti II),
4.77 (d, 2JH-H ) 13.2 Hz, benzylic, anti I-anti II), 4.62 (d, 2JH-H
Rw(Fo ), % (all data)a
2
2
2
a R(Fo) ) ∑||Fo| - |Fc|/∑|Fo||, Rw(Fo ) ) (∑w(|Fo| - |Fc|)2/∑wFo ).1/2
Table 2. NMR Spectroscopic Data for the Benzylic Groups in
Complexes
2
) 13.2 Hz, benzylic, anti I-anti II), 4.51 (d, JH-H ) 14.1 Hz,
δ 1H, ppm
δ
13C,
ppm
benzylic, anti II-anti II), 4.36 (d, 2JH-H ) 14.0 Hz, benzylic, anti
complex
conformation
(2JH -H , Hz)
2
a
e
I-anti II), 4.20 (d, JH-H ) 12.7 Hz, benzylic, anti II-anti II),
[PtL(η4-cod)][CF3SO3]2 (1) anti I
5.13, 4.99 (13.2)
4.84, 4.74 (12.9)
4.95, 4.71 (13.1)
5.00, 4.53 (13.3)
4.70, 4.16 (13.8)
4.07, 3.40 (12.9)
4.74, 4.41 (13.5)
4.37, 4.13 (13.8)
4.09, 3.28 (13.0)
4.84, 4.66 (13.2)
4.70, 4.53 (13.2)
4.18, 3.21 (13.9)
3.77, 2.85 (12.6)
42.4
41.3
42.6
42.2
39.2
34.8
43.5
40.9
36.2
43.0
42.3
40.1
34.6
39.8
35.2
43.8
42.7
41.2
35.0
40.8
35.8
3.97 (d, 2JH-H ) 12.9 Hz, benzylic, anti I-anti II), 3.51 (d, 2JH-H
[RhL(η4-cod)][CF3SO3] (2) anti I
2
) 14.1 Hz, benzylic, anti II-anti II), 3.29 (d, JH-H ) 14.0 Hz,
[IrL(η4-cod)][CF3SO3] (3)
anti I
2
benzylic, anti I-anti II), 3.24 (d, JH-H ) 12.7 Hz, benzylic, anti
[PdL(PPh3)2][CF3SO3]2 (4) anti I
2
II-anti II), 2.95 (d, JH-H ) 12.9 Hz, benzylic, anti I-anti II).
anti II
13C NMR (CD3CN, 300 K): δ (ppm) 135.2 (s, aromatic), 134.7 (s,
aromatic), 132.8 (s, aromatic), 132.4 (s, aromatic), 132.1 (s,
aromatic), 131.5 (s, aromatic), 131.3 (m, aromatic), 131.2 (s,
aromatic), 131.0 (s, aromatic), 129.8 (s, aromatic), 129.0 (s,
aromatic), 43.8 (s, benzylic, anti I-anti II), 42.7 (s, benzylic, anti
I-anti II), 41.2 (s, benzylic, anti I-anti II), 40.8 (s, benzylic, anti
II-anti II), 35.8 (s, benzylic, anti II-anti II), 35.0 (s, benzylic,
anti I-anti II). MS FAB+ Calcd for MS [Pt(S2C16H16)2][CF3SO3]+:
889. Found: 889. Anal. Calcd for C34H32F6O6PtS6: C, 39.3; H,
3.1; S, 18.5. Found: C, 39.9; H, 3.7; S, 18.6.
[PtL(PPh3)2][CF3SO3]2 (5)
[PdL2][CF3SO3]2 (6)
anti I
anti II
anti I-anti II
anti II-anti II 4.31, 3.46 (13.5)
4.02, 3.15 (12.9)
[PtL2][CF3SO3]2 (7)
anti I-anti II
4.97, 4.77 (13.2)
4.79, 4.62 (13.2)
4.36, 3.29 (14.0)
3.97, 2.95 (12.9)
General X-ray Diffraction Data Collection, Solution, and
Refinement. Diffraction experiments were performed on a Siemens
SMART/CCD diffractometer. Unit-cell parameters were calculated
from reflections obtained from 60 data frames collected at different
sections of the Ewald sphere. The systematic absences in the
diffraction data and the determined unit-cell parameters were
uniquely consistent for the reported space group. Diffracted data
were corrected for absorption using the SADABS program.
SHELXTL 5.03 Program Library32 was used for the structure
solution, and refinement was based on F2. All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were treated as
idealized contributions. Crystallographic data and refinement
parameters are summarized in Table 1.
anti II-anti II 4.51, 3.51 (14.1)
4.20, 3.24 (12.7)
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
[PtL(η4-cod)][SO3CF3]2 (1)
Pt-S1
Pt-S2
Pt-C17
2.370(6)
2.349(5)
2.219(13)
Pt-C18
Pt-C21
Pt-C22
2.233(16)
2.21(2)
2.19(2)
S1-Pt-S2
S2-Pt-C21
95.4(2)
87.2(6)
C18-Pt-C21
C18-Pt-C17
81.9(7)
34.2(7)
parameters, thermal parameters, and hydrogen atom parameters are
deposited as Supporting Information.
Structure Determination of [Pt(S2C16H16)(η4-cod)][CF3SO3]2
(1). Colorless crystals were grown by slow evaporation of an
acetonitrile solution of the complex. The structure was solved by
direct methods and refined with full-matrix least-squares methods.
Structure Determination of [Pd(S2C16H16)2][CF3SO3]2 (6).
Orange crystals were grown by slow evaporation of an acetonitrile
solution of the complex. The structure was solved by direct methods
and refined with full-matrix least-squares methods. A molecule of
acetonitrile is present in the unit cell. This resulted in R(Fo) ) 5.82%
2
This resulted in R(Fo) ) 2.77% and Rw(Fo ) ) 7.24% at final
2
convergence. A goodness-of-fit calculation resulted in a value of
1.027. Selected bond distances and angles are summarized in Table
3. Listings of atomic positional parameters, nonessential bonding
and Rw(Fo ) ) 9.13% at final convergence. A goodness-of-fit
calculation resulted in a value of 1.115. Selected bond distances
and angles are summarized in Table 4. Listings of atomic positional
parameters, nonessential bonding parameters, thermal parameters,
and hydrogen atom parameters are deposited as Supporting
(32) Siemens Analytical Instrument Division, Madison, WI, 1997.
3782 Inorganic Chemistry, Vol. 41, No. 14, 2002

Coordination of 2,11-Dithia[3.3]orthocyclophane
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
[PdL2][SO3CF3]2 (6)a
Pd-S1
S1-C1
2.338(1)
1.833(4)
Pd-S2
S2-C8
2.332(1)
1.835(4)
S1-C16
S1-Pd-S2
C1-S1-Pd
1.839(5)
95.04(4)
103.65(15)
S2-C9
S1-Pd-S1A
C16-S1-Pd
1.855(4)
85.06(4)
112.31(14)
a Symmetry transformations used to generate equivalent atoms: #A, -x,
3
y, -z + /2.
Scheme 1. Syntheses of Heteroleptic cod Complexes
Information. The molecule lies on a 2-fold crystallographic axis,
such that one cyclophane ligand generates a second.
Figure 2. Perspective ORTEP drawing of [PtL(η4-cod)]+, showing the
atom-numbering scheme. Ellipsoids are shown at 50% probability. Hydrogen
atoms are omitted for clarity.
Results and Discussion
Syntheses and Characterization of Heteroleptic Cy-
clooctadiene Complexes. Treatment of [MCl2(η4-cod)] (M
) Pd or Pt) and [M(µ-Cl)(η4-cod)]2 (M) Rh or Ir) with 2
equiv of silver triflate in chloroform, acetone, or acetonitrile
provides a convenient source of the [M(η4-cod)]n+ moiety,
which reacts readily with L to form air stable ionic
heteroleptic complexes [PtL(η4-cod)][SO3CF3]2 (1), [RhL-
(η4-cod)][SO3CF3] (2), and [IrL(η4-cod)][SO3CF3] (3), as is
shown in Scheme 1.
All attempts to obtain [PdL(η4-cod)][SO3CF3]2 resulted in
isolation of the homoleptic complex [PdL2][SO3CF3]2 (6),
probably because of the weakness of the Pd-olefin bond
compared with that of the platinum equivalent.33
Elemental analyses were in agreement with the proposed
formula, and in positive ion mode FAB mass spectrometry,
the fragments [PtL(η4-cod)][SO3CF3]+ for 1 (m/z ) 724),
[RhL(η4-cod)]+ for 2 (m/z ) 483), and [IrL(η4-cod)]+ for 3
(m/z ) 573) were detected with the expected isotopic
distribution. This unambiguously established the presence
of cod, L, and the metal in each complex. NMR spectra of
these complexes show resonances in the regions δ ) 3.52-
5.39 ppm and δ ) 1.33-1.68 ppm which were assigned to
the CH and CH2 of the cyclooctadiene ring, respectively.
The aromatic protons of L appear between 7.4 and 7.59 ppm,
and benzylic protons, in 4.71-5.13 ppm. The benzylic region
of the spectrum is the most informative, concerning the
conformation of the ligand in the complex. 1H and 13C NMR
data for the benzylic groups are presented in Table 2.
The benzylic region consists of one signal in the 13C NMR
Scheme 2. Syntheses of Heteroleptic PPh3 Complexes
conformational preference for the anti I conformation of L
in this class of complexes.
1
It is interesting that H NMR spectra of both [PtL(η4-
cod)][SO3CF3]2 (1) and [RhL(η4-cod)] [SO3CF3] (2) exhibit
couplings between the metal center (195Pt and 103Rh) and one
of the protons at the benzylic groups. Because the axial
protons of the cyclophane ring are formally trans to the
metal, we have tentatively assigned these coupling constants
3
(3JRh-H ) 1.8 Hz and JPt-H ) 60.0 Hz) to the M-S-C-
Haxial (M ) Pt or Rh) bond.
X-ray Structure of [PtL(η4-cod)][SO3CF3]2 (1). In the
asymmetric unit, there coexist two very slightly different
molecules of 1. Figure 2 clearly shows that the Pt atom has
square planar geometry and the conformation of the ligand
is anti I. The S-Pt-S angle of 95.4(2)° deviates slightly
from that expected for square planar coordination. The
average Pt-S distance of 2.36(1) Å compares with previ-
ously reported Pt-S(thioether) bond distances.34 The average
Pt-C bond distance of 2.21(2) Å is similar to the distance
reported for analogous complexes.35 Relevant bond and
angles are shown in Table 3.
Syntheses and Characterization of Heteroleptic Phos-
phine Complexes. Reaction of the neutral complexes [MCl2-
(PPh3)2] (M ) Pd or Pt) with 2 equiv of silver triflate in
MeCN followed by the addition of 1 equiv of L produced
the complexes [PdL(PPh3)2][SO3CF3]2 (4) and [PtL(PPh3)2]-
[SO3CF3]2 (5), as is shown in Scheme 2.
Both complexes are air stable, yellow (4) and white (5)
solids, with the expected elemental composition. The frag-
ments [PdL(PPh3)2][SO3CF3]+ (m/z ) 1051 for 4) and [PtL-
(PPh3)2][SO3CF3]+ (m/z ) 1141 for 5) with the appropriate
1
spectrum and two doublets in H NMR spectrum. This
information establishes that the cyclophane is rigidly bound
in the anti I conformation with C2V symmetry, and so, it has
four equivalent benzylic carbon atoms, each one containing
two nonequivalent protons which are axial and equatorial
with respect to the cyclophane ring, generating an AB system.
Molecular mechanics calculations are in agreement with the
(33) Maitlis, P. M.; Espinet, P.; Russell, M. J. H. In ComprehensiVe
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E.
W., Eds.; Pergamon Press: Oxford, U.K., 1982; Vol. 5, Chapter 38.6,
p 372.
(34) Murray, S. G.; Hartley, F. R. Chem. ReV. 1981, 81, 365-414.
(35) Ferguson, G.; Gallagher, J. F.; McAlees, A. J.; McCrindle, R.
Organometallics 1997, 16, 1053-1057.
Inorganic Chemistry, Vol. 41, No. 14, 2002 3783

Tiburcio et al.
Figure 3. 31P NMR of [PtL(PPh3)2][SO3CF3]2. Key: dots indicate anti I;
asterisks indicate anti II. Aromatic rings are omitted for clarity. Assignations
1
are based on H-31P NMR experiments.
Scheme 3. Syntheses of Homoleptic Complexes
Figure 4. 1H NMR spectrum of the benzylic region for [PdL2][SO3CF3]2
(6). Key: dots indicate anti I-anti II; asterisks indicate anti II-anti II.
Pt, 7) were synthesized in high yield as shown in Scheme 3.
The neutral complexes [MCl2L] (M ) Pd or Pt) were also
used as starting materials for these syntheses; however, low
solubility prevented its full characterization.31
Both complexes are air stable, yellow (6) and white (7)
solids, with good solubility and stability in organic polar
solvents, especially in acetonitrile and nitromethane. The
microanalyses are in agreement with the proposed formula.
The FAB+ mass spectra of these complexes display the
presence of the ions [ML2][CF3SO3]+ (m/z ) 799 for 6; m/z
) 889 for 7) with the expected isotopic distribution,
establishing the presence of two ligands by each metallic
atom.
isotopic distribution were observed by positive ion mode
FAB mass spectrometry. 1H{31P} NMR spectra display
overlapped signals corresponding to the aromatic protons of
the triphenylphosphine and L and six doublets, for each
compound, between 3.40-5.00 (4) and 3.28-4.74 ppm (5)
due to the benzylic hydrogens. 13C NMR spectra exhibit three
signals in the benzylic zone, as is summarized in Table 2.
The complex NMR spectra show the presence of a mixture
of two isomers with cyclophane ligands L bound in two
different conformations: anti I, which is symmetrical and
originates one signal in the 13C NMR spectrum and two
doublets in the 1H NMR spectrum, and anti II, which being
nonsymmetrical gives rise to a pair of signals in the 13C NMR
spectrum and the remaining four doublets observed in the
1H NMR spectrum. A 40:60 proportion, for both complexes,
was estimated on the basis of the integral values. Additional
COSY and HETCOR experiments were used to confirm the
assignations.
The solution 1H NMR spectra show signals in two regions
corresponding to the aromatic and the benzylic protons. The
benzylic region is shown in Figure 4. By their number and
1
position, H and 13C signals can be divided in two groups,
corresponding to two different isomers. One isomer, corre-
sponding to cyclophane L in the anti I-anti II conformation
with Cs symmetry, has four different benzylic groups
generating four signals in the 13C NMR spectrum and eight
doublets in the 1H NMR spectrum, whereas the other isomer
with the conformation anti II-anti II has C2h symmetry and
thus only two different benzyl groups, generating two signals
in 13C NMR spectrum and four doublets in 1H NMR
spectrum, as is observed in Figure 4. The ratio of isomers is
80:20 and appears to be independent of the metal ion. The
higher stability of the anti I-anti II conformation was also
suggested by molecular mechanics calculations.
X-ray Structure of [PdL2][SO3CF3]2 (6). The single-
crystal X-ray structure of 6 (Figure 5) shows the Pd atom in
a square planar geometry with a 2-fold rotation axis at the
metal generating two equivalent ligands. The conformation
of both ligands is anti II. This geometry might be preferred
because of a better molecular packing in the crystals. The
S-Pd-S angle of 95.04(4)° deviates slightly from that
expected for square planar coordination and contrasts with
the 90.4(1)° observed in the ruthenium complexes for this
cyclophane in the same conformation.19 The Pd-S distance
of 2.335(4) Å compares well with that previously reported
for other Pd-S(thioether) bond distances.34 No interactions
The presence of both isomers is clearly observed by 31P
NMR spectroscopy (Figure 3). The spectra exhibit two
signals for 4 at 29.5 (anti I) and 32.7 ppm (anti II) and for
5 at 12.5 (anti I) and 15.7 ppm (anti II), with Pt satellites of
3179 and 3159 Hz, respectively. The conformational assign-
ment is based on the known relative abundance of each
1
identified isomer by H NMR.
1H NMR spectra also display couplings between some
benzylic hydrogens and phosphorus, which disappear on
irradiation of the phosphorus atoms. Variable temperature
NMR experiments in nitromethane-d3 up to 95 °C showed
no exchange between isomers. The presence of two isomers,
in these kinds of complexes, can be rationalized as being
due to the relatively close values in energy for both
conformations of the cyclophane, as determined by molecular
mechanics calculations, and the higher steric requirements
of the triphenylphosphine ligand as compared to that of the
cyclooctadiene ligand, although electronic effects also can
play a role.
Syntheses and Characterization of Homoleptic Com-
plexes. The compounds [ML2][CF3SO3]2 (M ) Pd, 6; M )
3784 Inorganic Chemistry, Vol. 41, No. 14, 2002

Coordination of 2,11-Dithia[3.3]orthocyclophane
Heteroleptic cod derivatives [ML(η4-cod)][CF3SO3]n (n )
1 for M ) Rh and Ir; n ) 2 for M ) Pt) have the chelating
ligand with anti I configuration. Whereas replacement of cod
for the larger PPh3 ligand in the complexes [ML(PPh3)2]-
[CF3SO3]2 (M ) Pd and Pt) gives rise to mixtures of two
isomers, the thiacyclophane has anti I (ca. 40% abundance)
and anti II (ca. 60% abundance) conformations. Similarly
homoleptic compounds [ML2][CF3SO3]2 (M ) Pd and Pt)
also display a pair of isomers in which the thiacyclophane
ligands have anti I-anti II (ca. 80% abundance) or anti II-
anti II (ca. 20% abundance) configurations.
In all cases, the relative proportions of isomers appear to
be independent of the metallic center. Although mesocyclic
ring inversion could provide a mechanism for isomer
exchange, no evidence was found in this work for such a
process.
Figure 5. Perspective ORTEP drawing of cation [PdL2]2+, showing the
atom-numbering scheme. Ellipsoids are given at 50% probability. Hydrogen
atoms are omitted for clarity.
between the aromatic rings were observed in the solid state.
Relevant bond and angles are shown in Table 4.
Acknowledgment. We are grateful to DGAPA-IN116001
for financial support of this research. J.T. thanks CONACYT
(Mexico) and ICCS (Canada) for a scholarship.
Conclusions
The thiacyclophane 2,11-dithia[3.3]orthocyclophane is a
flexible bidentate ligand that, when coordinated, can adopt
two different conformations: anti I and anti II. No evidence
has been found for the presence of conformation syn, in
agreement with the relatively high energy suggested by
molecular mechanics calculations for this arrangement.
Supporting Information Available: X-ray crystallographic file
in CIF format for complexes 1 and 6. This material is free of charge
via the Internet at http://pubs.acs.org
IC0256157
Inorganic Chemistry, Vol. 41, No. 14, 2002 3785