New half-sandwich heterobimetallic CpMPt (M = Rh, Ir) dithiolato bridged complexes. X-ray structure of [(PPh3)2Pt (μ-S (CH2)2S) RhCl (η5-C5H5)] BF4

Article abstract of DOI:10.1016/S0022-328X(02)01925-3

Cationic heterobimetallic complexes 5-7 [(PPh₃)₂Pt(μ-edt)MClCp′)]BF₄ (edt = ^-S(CH₂)₂S^-; 5: M = Rh and Cp′ = η⁵-C₅H₅; 6: M = Rh and Cp′ = η^5<

Full text of DOI:10.1016/S0022-328X(02)01925-3

Journal of Organometallic Chemistry 662 (2002) 188ꢁ191
/
www.elsevier.com/locate/jorganchem
New half-sandwich heterobimetallic CpMPt (Mꢀ
/
Rh, Ir) dithiolato
bridged complexes.
X-ray structure of [(PPh3)2Pt(m-S(CH2)2S)RhCl(h5-C5H5)]BF4
Jorge Fornie´s-Ca´mer a, Carmen Claver a, Anna M. Masdeu-Bulto´ a,*,
Christine J. Cardin b
a Departament de Qu´ımica F´ısica i Inorga`nica, Universitat Rovira i Virgili, Pl. Imperial Ta`rraco 1, 43005 Tarragona, Spain
b Department of Chemistry, The University of Reading, Whiteknights, P.O. Box 224, Reading RG6 6AD, UK
Received 23 July 2002; received in revised form 12 September 2002; accepted 23 September 2002
Abstract
Cationic heterobimetallic complexes 5ꢁ
/
7 [(PPh3)2Pt(m-edt)MClCp?)]BF4 (edtꢀꢂ
/
S(CH2)2Sꢂ; 5: Mꢀ
/
Rh and Cp?ꢀ
h5-C5H5; 6:
/
MꢀRh and Cp?ꢀ
/
/
h5-C5Me5 and 7: Mꢀ
/
Ir and Cp?ꢀ
/
h5-C5Me5) were prepared by reaction of [Pt(edt)(PPh3)2] with [Cp?ClM(m-
Cl)2MClCp?] in THF in the presence of two equivalents of AgBF4. The crystalline structure of 5 was determined by X-ray diffraction
methods.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Heterobimetallic complexes; Platinum; Rhodium; Iridium; Dithiolato metalloligands
1. Introduction
yields without the formation of polymeric species. We
therefore used Pt(II) and Pd(II) dithiolato complexes
stabilized with phosphine ligands to prepare a series of
Thiolates and sulfides have been extensively used to
synthesize cyclopentadienyl heterobimetallic complexes
because they are strong bridging ligands [1]. Although
heterobimetallic MM? (Mꢀ
Rh(I) and Ir(I)) complexes with alkyl dithiolate bridging
ligands of general
formula [(phosphine)M(m-
dithiolate)M?L2]ꢃ (L2ꢀ
1,5-cyclooctadiene, (CO)2,
/
Pt(II) and Pd(II); M?ꢀ
/
Groups 8ꢁ10 sulfide clusters have shown unique reac-
/
/
tivities [2], there are few examples of heterobimetallic
complexes with S-donor sulfide bridging ligands con-
(CO)(PR3)), and determined their structures by X-ray
diffraction methods [5]. Here we present the first
taining Groups 8ꢁ
bridging ligands are expected to provide more robust
structures than thiolates, so syn ꢁanti isomers in di-
/
10 noble metals [1f,3]. Dithiolate
examples of d8ꢁd6 cyclopentadienyl heterobimetallic
complexes containing a dithiolate bridging ligand.
/
/
nuclear complexes can be avoided. However, examples
of heterometallic complexes with dithiolate bridging
ligands (ꢂSRSꢂ) are scarce [4] and polymeric materials
are often formed. Most of these examples contain early
and late transition metals (ELHB).
In previous papers, we proved that if the appropriate
dithiolate-containing metalloligand is selected, the de-
sired heterobimetallic complexes can be prepared in high
2. Results and discussion
Our initial strategy was to prepare CpRh(I)Pt com-
plexes by reacting the cyclooctadiene species
[CpRh(cod)] with the metalloligand [Pt(edt)(PPh3)2]
(edtꢀꢂS(CH2)2Sꢂ) (1). Diene complexes such as
/
[RuClCp*(cod)] (CpꢄꢀC5Meꢂ5 ) containing cyclopenta-
dienyl ligands have been used in the synthesis of TiꢁRu
/
heterobimetallic complexes [6]. In our study, we could
not substitute the cod ligand in the rhodium complex
even by bubbling H2 through the solution.
* Corresponding author. Tel.:
559563
E-mail address: masdeu@quimica.urv.es (A.M. Masdeu-Bulto´).
ꢃ
/
34-977-559572; fax:
ꢃ34-977-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 9 2 5 - 3

J. Fornie´s-Ca´mer et al. / Journal of Organometallic Chemistry 662 (2002) 188ꢁ
/191
189
The second attempt at preparing heterobimetallic
cyclopentadienyl complexes involved the direct reaction
of the metalolligand
with dimer [CpClRh(m-
1
Cl)2RhClCp] (2), but no reaction was observed. Finally,
we prepared the cationic heterobimetallic complex 5
[(PPh3)2Pt(m-edt)RhClCp)]BF4 by initially treating di-
mer 2 with two equivalents of AgBF4 in THF and then
adding the platinum metalloligand 1 (Scheme 1). Com-
plexes
[(PPh3)2Pt(m-edt)RhClCp*)]BF4
(6)
and
[(PPh3)2Pt(m-edt)IrClCp*)]BF4 (7) were prepared fol-
lowing the same procedure. The reaction was very
selective since no byproducts were detected. Complexes
5ꢁ/7 were isolated as a air stable solids in good yields
(75ꢁ/86%) and in pure form (see analytical data in
Section 3).
We obtained crystals of 5, which were suitable for
single crystal X-ray diffraction analysis, by recrystalliza-
tion from hexane. Fig. 1 shows the ORTEP plot of the
cation complex of 5. The complex has a hinged structure
in which the dithiolate acts as a bridging ligand between
the two metals. The rhodium center has distorted
tetrahedral geometry with the centroid of the Cp, the
chloro and the dithiolato ligands occupying the coordi-
nation sites. The platinum center has a distorted square-
Fig. 1. ORTEP plot of 5. Thermal ellipsoids are drawn at the 50%
probability level. Hydrogen atoms, CH2Cl2 and BFꢂ4 are omitted for
˚
clarity. Selected bond distances (A) and angles (8): PtÃ
/
P(1) 2.282(2),
S(2) 2.387(3), PtÃRh 3.354(8),
S(2) 2.406(2), RhÃCl 2.382(2), P(1)ÃPtÃP(2)
S(2) 75.10(7), P(1)ÃPt(1)ÃS(1) 94.29(8), P(2)Ã
S(2) 94.18(8), S(1)ÃRhÃS(2) 74.73(8), S(1)ÃRh(1)ÃCl(1)
89.95(8), Cl(1)ÃRh(1)ÃS(2) 92.15(8), PtS2Rh u 124.68.
PtÃ
RhÃ
96.86(8), S(1)Ã
Pt(1)Ã
/
P(2) 2.302(2), PtÃ
S(1) 2.376(2), RhÃ
PtÃ
/
S(1) 2.376(3), PtÃ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
planar environment. The cis angles S(1)Ã
P(1)ÃPt(1)ÃP(2) are 75.10(7) and 96.86(8)8, respectively,
and the trans angles P(1)ÃPt(1)ÃS(2) and P(2)ÃPt(1)Ã
/
Pt(1)Ã/S(2) and
/
/
/
/
/
/
This was probably due to the steric requirements of
the geometry of the Rh center.
S(1) are deviated from 1808 (168.81(8) and 165.68(8)8,
respectively). A similar distortion, attributed to repul-
sion between the PPh3 terminal ligands, was observed in
the structure of parent complex [Pt(edt)(PPh3)2] [7]. The
Spectroscopic data showed that complexes 5ꢁ7 were
/
stable in solution. The 1H- and 13C-NMR spectra
showed one singlet for Cp and Cp* in all cases. The
methylenic groups of the dithiolate bridging edt ligand
˚
intermetallic distance (3.354(8) A) was longer than the
1
˚
one for metalÃ
The PtÃ
complex 5 were in the range reported for complex 1
/
metal single bond (2.6 A) [8].
appeared as two multiplet resonances in the H-NMR
˚
/
P distances (2.282(2) and 2.302(2) A) in
(:
/
d 2.5ꢁ2.9 ppm), which were attributed to the
/
protons oriented to the platinum and the rhodium or
iridium centers, and as one singlet (ca. d 40 ppm) in the
13C-NMR spectra.
˚
(2.296(3) and 2.281(4) A) and similar to those for
[(PPh3)2Pt(m-edt)Rh(cod)]ClO4 (2.285(2) and 2.267(2)
The 31P-NMR spectra showed one signal in the d 12ꢁ
/
˚
˚
S distances (2.376(3) and 2.387(3) A) in
A). The PtÃ
/
complex 5 were slightly longer that the PtÃ
1 (2.328(4) and 2.313(4) A) [7]. This was as expected for
the bridging coordination to the two metals.
/S distances in
14 ppm, with the corresponding satellites attributed to
the 31Pꢁ195
Pt coupling, which was as expected for the
equivalent phosphorus atoms. The coupling constants
were higher in 5ꢁ7 (ca. 3240ꢁ3270 Hz) than in the
˚
/
The torsion angle PtS2Rh u (124.68) was greater than
that of the related heterobimetallic complex
[(PPh3)2Pt(m-edt)Rh(cod)]ClO4 (111.278) [5a] and the
homodinuclear complex [Rh(m-edt)(cod)]2 (1048) [9].
/
/
mononuclear complex 1 (2884 Hz) [10]. This was also
observed for related heterobimetallic complexes, which
indicates that the MÃ/P bond became stronger as a result
Scheme 1.

190
J. Fornie´s-Ca´mer et al. / Journal of Organometallic Chemistry 662 (2002) 188ꢁ191
/
of the weakening of the MÃ
/
S bond due to bridge
of anhydrous and deoxigenated THF. The mixture was
stirred for 5 min at r.t. and complex [Pt(edt)(PPh3)2]
(131.4 mg, 0.1618 mmol) was then added. The color of
the solution changed to orange. The silver chloride salts
formed were removed by filtration through Celite. The
filtrate was concentrated to ca. 2 ml and the precipitate
was obtained by C6H14 addition. The red solid was
filtrated, washed with C6H14 and vacuum dried. Com-
plex 5 was obtained as a red solid. Yield: 142.2 mg, 75%.
1H-NMR (300 MHz, CDCl3, 20 8C): d 1.60 (s, 15H,
coordination [5].
In conclusion, the successful synthesis of these com-
plexes shows that the M-dithiolate species act efficiently
as metalloligands for heterobimetallics synthesis.
3. Experimental
3.1. General methods
Cp*), 2.61 (m, 2H, Ã
/
CHHÃ
/
CHHÃ
/
, edt), 2.55 (m, 2 H,
7.4 (m, 30 H, Ph, PPh3). 13C-
All complexes were synthesized using standard
Schlenk techniques under a nitrogen atmosphere. Sol-
vents were distilled and deoxygenated before use.
Complexes [RhCpCl2]2, [RhCp*Cl2]2 and [IrCp*Cl2]2
[11] and [Pt(edt)(PPh3)2] [10] were prepared using
methods described in the literature. All other reagents
were used as commercially supplied. Elemental analyses
Ã
/
CHHÃCHHÃ, edt), 7.2ꢁ
/
/
/
NMR (75.4 MHz, CDCl3, 20 8C): d 8.8 (s, CH3, Cp*)
42.4 (s, CH2, edt), 97.1 (s, C, Cp*). 31P{1H}-NMR
(121.4 MHz, CDCl3, 20 8C): d 12.5 (s with satellites,
1JPPt
ꢀ
/
3272.9 Hz). Anal. Calc. for C48H49BF4-
ClP2PtRhS2: C, 49.13; H, 4.18; S, 5.46. Found: C,
49.08; H, 4.16; S, 5.37%. FAB: m/z 1085 [MHꢂ
BF4]ꢃ,
823 [MHꢂPPh3ꢂCp*ꢂClꢂ
BF4]ꢃ.
/
were performed on a Carloꢁ
/
Erba microanalyser. NMR
/
/
/
/
spectra were recorded on a Varian Gemini 300 MHz
spectrophotometer and chemical shifts were quoted in
ppm downfield from internal SiMe4 (1H) or external
85% H3PO4 (31P). FAB mass spectrometry was per-
formed on a VG Autospect in a nitrobenzyl alcohol
matrix.
3.4. Preparation of complex [(PPh3)2Pt(m-
S(CH2)2S)IrCl(h5-C5Me5)]BF4 (7)
AgBF4 (24.4 mg, 0.1256 mmol) was added to a
solution of complex 4 (50.0 mg, 0.0628 mmol) in 5 ml
of anhydrous and deoxigenated THF. The mixture was
stirred for 5 min at r.t. and complex [Pt(edt)(PPh3)2]
(102.0 mg, 0.1256 mmol) was then added. The color of
the solution changed to orange. The silver chloride salts
formed were removed by filtration through Celite. The
filtrate was concentrated to ca. 2 ml and the precipitate
was obtained by C6H14 addition. The red solid was
filtrated, washed with C6H14 and vacuum dried. Com-
plex 7 was obtained as a red solid. Yield: 136.2 mg, 86%.
1H-NMR (300 MHz, CDCl3, 20 8C): d 1.60 (s, 15H,
3.2. Preparation of complex [(PPh3)2Pt(m-
S(CH2)2S)RhCl(h5-C5H5)]BF4 (5)
AgBF4 (35.5 mg, 0.1826 mmol) was added to a
suspension of complex 2 (50.0 mg, 0.0913 mmol) in 5
ml of anhydrous and deoxigenated THF. The mixture
was stirred for 5 min at room temperature (r.t.) and
complex [Pt(edt)(PPh3)2] (148.3 mg, 0.1826 mmol) was
then added. The color of the solution changed to dark
red. The silver chloride salts formed were removed by
filtration through Celite. The filtrate was concentrated
to ca. 2 ml and the precipitate was obtained by C6H14
addition. The red solid was filtrated, washed with C6H14
and vacuum dried. Complex 5 was obtained as a red
solid. Yield: 161.0 mg, 80%. 1H-NMR (300 MHz,
Cp*), 2.70 (m, 2H, Ã
/
CHHÃ
/
CHHÃ
/
, edt), 2.61 (m, 2 H,
7.4 (m, 30 H, Ph, PPh3). 13C-
Ã
/
CHHÃCHHÃ, edt), 7.2ꢁ
/
/
/
NMR (75.4 MHz, CDCl3, 20 8C): d 8.5 (s, CH3, Cp*)
43.5 (s, CH2, edt), 90.1 (s, C, Cp*). 31P{1H}-NMR
(121.4 MHz, CDCl3, 20 8C): d 14.4 (s with satellites,
1JPPt
ꢀ
/
3240.7 Hz). Anal. Calc. for C48H49BF4-
ClIrP2PtS2: C, 45.66; H, 3.88; S, 5.07. Found: C, 45.58;
H, 3.89; S, 5.07%. FAB: m/z 1175 [MHꢂ
BF4]ꢃ, 911
[MHꢂPPh3ꢂCp*ꢂClꢂ
BF4]ꢃ.
CDCl3, 20 8C): d 2.95 (m, 2H, Ã
2.82 (m, 2H, ÃCHHÃCHHÃ, edt), 5.52 (s, 5H, Cp),
7.2ꢁ
7.5 (m, 30H, Ph, PPh3). 13C-NMR (75.4 MHz,
/
CHHÃ
/
CHHÃ
/
, edt),
/
/
/
/
/
/
/
/
/
CDCl3, 20 8C): d 40.6 (s, CH2, edt), 87.3 (s, CH, Cp).
31P{1H}-NMR (121.4 MHz, CDCl3, 20 8C): d 13.5 (s
1
with satellites, JPPt
ꢀ/3243.9 Hz). Anal. Calc. for
3.5. Crystal data for complex [(PPh3)2Pt(m-
S(CH2)2S)RhCl(h5-C5H5)]BF4×
CH2Cl2 (5)
C43H39BF4ClP2PtRhS2: C, 46.84; H, 3.54; S, 5.81.
Found: C, 46.82; H, 3.46; S, 5.78%. FAB: m/z 1115
/
[MHꢂ
/
BF4]ꢃ, 753 [MHꢂ
/
PPh3ꢂ
/
Cpꢂ
/
Clꢂ
/
BF4]ꢃ.
Suitable crystals of complex 5 were grown by diffus-
ing n-hexane into a solution of the complex in dichlor-
omethane and mounted on a glass fiber. The data were
collected and processed at room temperature on a Mar
Research image plate scanner. Graphite-monochro-
3.3. Preparation of complex [(PPh3)2Pt(m-
S(CH2)2S)RhCl(h5-C5Me5)]BF4 (6)
AgBF4 (31.5 mg, 0.1618 mmol) was added to a
solution of complex 3 (50.0 mg, 0.0809 mmol) in 5 ml
mated Moꢁ
frames, 180 s per frame.
/
Ka radiation was used to measure 95/2

J. Fornie´s-Ca´mer et al. / Journal of Organometallic Chemistry 662 (2002) 188ꢁ
/191
191
(d) N. Wheatley, P. Kalck, Chem. Rev. 99 (1999) 3379;
Compound 5: C43H39BF4ClP2PtRhS2×
/
1CH2Cl2, Mꢀ
/
(e) S. Kuwata, M. Hidai, Coord. Chem. Rev. 213 (2001) 211;
(f) G. Sa´nchez, F. Momblona, M. Sa´nchez, J. Pe´rez, G. Lo´pez, J.
Casabo´, E Molins, C. Miravitlles, Eur. J. Inorg. Chem. 8 (1998)
1199;
˚
1184.97, triclinic, aꢀ
/
11.050(57) A, aꢀ87.29(6)8, bꢀ
/
/
˚
˚
˚
14.471(57) A, bꢀ
/
93.74(6)8, cꢀ
/
14.930 A, gꢀ
/
71.58(6)8,
2, Dcꢀ1.746 mg
1160. Dark red, crystal dimensions 0.1ꢅ
0.3 mm, m(MoꢁKa)ꢀ
38.55 cmꢂ1
The XDS [12] package was used to give the following:
5778 unique reflections [merging Rꢀ0.0276]. The heavy
3
¯
Vꢀ
/
2254.5 A , space group P1 (2), Zꢀ
/
/
mꢂ3, F(000)ꢀ
0.1ꢅ
/
/
(g) N. Nakahara, M. Hirano, A. Fukuoka, S. Komiya, J.
Organomet. Chem. 572 (1999) 81;
/
/
/
.
(h) T. Nagano, S. Kuwata, Y. Ishii, M. Hidai, Organometallics 19
(2000) 4176;
/
(i) A.R. Dias, M.H. Garc´ıa, M.J.V. de Brito, A. Galvao, J.
Organomet. Chem. 632 (2001) 75.
atoms were found from the Patterson map using the
SHELX-86 [13] program and refined subsequently from
successive difference Fourier maps using SHELXL-93 [14]
by full-matrix least-squares of 569 variables, to a final
[2] (a) M. Hidai, S. Kuwata, Y. Mizobe, Acc. Chem. Res. 33 (2000)
46;
(b) M. Hidai, Y. Mizobe, H. Matsuzaka, J. Organomet. Chem.
473 (1994) 1;
R-factor of 0.0418 for 5772 reflections with [Fo]ꢀ
/
(c) M. Rakowski DuBois, Chem. Rev. 89 (1989) 1.
[3] (a) V.K. Jain, Inorg. Chim. Acta 133 (1987) 261;
(b) M. Capdevila, P. Gonzalez-Duarte, C. Foces-Foces, F.
Herna´ndez Cano, M. Mart´ınez-Ripoll, J. Chem. Soc. Dalton
Trans. (1990) 143;
4s(Fo). All atoms were revealed by the difference
Fourier map. Non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were placed geometrically
and then refined with fixed isotropic atomic displace-
ment parameters. The weighting scheme wꢀ
(c) S. Takemoto, S. Kuwata, Y. Nishibayashi, M. Hidai, Inorg.
Chem. 37 (1998) 6428;
1=[s2(Fo2)ꢃ(aP)2 ꢃbP];
2Fc2)=3; aꢀ
0.0359 and bꢀ
counting statistics, provided satisfactory agreement
analyses. The final parameters R1 ([Fo]ꢀ4s(Fo)) were
where
Pꢀmax((Fo2; 0)ꢃ
(d) W.-F. Liaw, C.-Y. Chiang, G.-H. Lee, S.-M. Peng, C.-H. Lai,
M.Y. Darensbourg, Inorg. Chem. 39 (2000) 480;
(e) J. Ruiz, J. Giner, V. Rodr´ıguez, G. Lo´pez, J. Casabo´, E.
Molins, C. Miravitlles, Polyhedron 19 (2000) 1627.
[4] (a) T.T. Nadasdi, D.W. Stephan, Organometallics 11 (1992) 116;
(b) T.T. Nadasdi, D.W. Stephan, Inorg. Chem. 33 (1994) 1532;
(c) R.C. Aggarwal, R. Mitra, Ind. J. Chem. A 33 (1994) 55;
(d) N. Singh, L.B. Prasad, Ind. J. Chem. A 37 (1998) 169;
(e) N. Singh, S. Gupta, Inorg. Chem. Commun. 3 (2000) 446.
[5] (a) J. Fornie´s-Ca´mer, A.M. Masdeu-Bulto´, C. Claver, C.J.
Cardin, Inorg. Chem. 37 (1998) 2626;
/
/18.11 with s(Fo) from
/
0.0418 and wR2 (all data) were 0.0579 for R1ꢀ
/
a jjFojꢂ
/
jFcjj/a jFoj and wR2 ꢀ[a w(F2 ꢂF2)=a w(F2)2)]1=2: The
o
c
o
ORTEP diagram for 5 was generated using ORTEP-3 [15].
4. Supplementary material
(b) J. Fornie´s-Ca´mer, A.M. Masdeu-Bulto´, C. Claver, Inorg.
Chem. Commun. 2/3 (1999) 89;
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 183660 for compound 5.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
(c) J. Fornie´s-Ca´mer, A.M. Masdeu-Bulto´, C. Claver, C. Tejel,
M.A. Ciriano, C.J. Cardin, Organometallics 21 (2002) 2609.
[6] K. Fujita, M. Ikeda, T. Kondo, T. Mitsudi, Chem. Lett. (1997)
57.
[7] S.A. Bryan, D.M. Roundhill, Acta Crystallogr. Sect. C 39 (1983)
184.
Cambridge CB2 1EZ, UK (Fax: ꢃ44-1223-336033;
/
[8] See for example: (a) J.P. Farr, M.M. Olmstead, A.L. Balch, J.
Am. Chem. Soc. 102 (1980) 6654;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
(b) R.R. Guimerans, F.E. Wood, A.L. Balch, Inorg. Chem. 23
(1984) 1307.
[9] A.M. Masdeu, A. Ruiz, S. Castillo´n, C. Claver, P.B. Hitchcock,
P.A. Chaloner, C. Bo, J.M. Poblet, P. Sarasa, J. Chem. Soc.
Dalton Trans. (1993) 2689.
Acknowledgements
[10] T.B. Rauchfuss, D.M. Roundhill, J. Am. Chem. Soc. 97 (1975)
3386.
We thank the Ministerio de Educacio´n y Cultura
(PB97-0407-C05-01) for financial support.
[11] J.W. Kang, K. Moseley, P.M. Maitlis, J. Am. Chem. Soc. Sect.
(A) (1969) 22.
[12] W.J. Kabsch, Appl. Crystallogr. 26 (1993) 795.
[13] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure
References
Solutions; University of Gottingen, Germany, 1986.
¨
[14] G.M. Sheldrick, SHELXS-93, Program for Crystal Structure
[1] (a) P.J. Blower, J.R. Dilworth, Coord. Chem. Rev. 76 (1987) 121;
(b) D.W. Stephan, Coord. Chem. Rev. 95 (1989) 41;
(c) D.W. Stephan, T.T. Nadasdi, Coord. Chem. Rev. 147 (1996)
147;
Solutions; University of Gottingen, Germany, 1993.
¨
[15] L.J. Farrugia, ORTEP-3 for Windows, J. Appl. Crystallogr. 30
(1997) 565.