A symmetrically bridging triarylsilyl ligand in a dinuclear rhodium complex: Synthesis and structure of [LRh(h) (μ-Cl) (μ-SiAr2) (μ-SiAr3) Rh(H)L] (Ar = Ph, p-FC6H4; L = PiPr3)

Article abstract of DOI:10.1002/(SICI)1521-3773(19980216)37:3<349::AID-ANIE349>3.0.CO;2-Y

Simply warming solutions of the dinuclear complexes 1 provides novel complexes 2 [Eq. (a): Ar = Ph, p-FC₆H₄; L = PiPr₃], which contain a bridging triarylsilyl ligand and show unusual thermal stability. Compounds with this type of symmetric structure are of interest as models of the transition state for the migration of tertiary silyl groups in a bimetallic framework.

Full text of DOI:10.1002/(SICI)1521-3773(19980216)37:3<349::AID-ANIE349>3.0.CO;2-Y

COMMUNICATIONS
[4] a) V. J. Hruby, Life Science 1982, 31, 189 ± 199; b) H. Kessler, Angew.
Chem. 1982, 94, 509 ± 520 ; Angew. Chem. Int. Ed. Engl. 1982, 21, 512 ±
523; c) J. Rizo, L. M. Gierasch, Ann. Rev. Biochem. 1992, 61, 387 ± 418.
[5] a) J. A. Camarero, T. W. Muir, Chem. Commun., 1997, 1369 ± 1370;
b) L. Zhang, J. P. Tam, J. Am. Chem. Soc. 1997, 119, 2363 ± 2370.
[6] P. E. Dawson, T. W. Muir, I. Clark-Lewis, S. B. H. Kent, Science 1994,
266, 776 ± 779.
[7] WW domains are a novel class of protein modules which are found in a
variety of signal-transducing and cytoskeletal proteins. Reviews: a) M.
Sudol, Prog. Biophys. Molec. Biol. 1996, 65, 113 ± 132; b) M. Sudol,
H. I. Chen, C. Bougeret, A. Einbond, P. Bork, FEBS Letters 1995, 369,
67 ± 71.
[8] M. J. Macias, M. Hyvonen, E. Baraldi, J. Schultz, M. Sudol, M. Saraste,
H. Oschkinat, Nature 1996, 382, 646 ± 649.
[9] To facilate native ligation, Cys and Gly were added at the N and C
termini, respectively, of the core WW sequence (residues 165 ± 209 of
the human YAP protein).
suggests a potential application of this approach in the study
of protein-structure dynamics.
Experimental Section
All peptide synthesis were carried out according to the in situ neutraliza-
tion/HBTU activation protocol for Boc solid-phase peptide syn-
thesis (HBTU ˆ benzotriazol-1-yl-N-tetramethyluronium hexafluorophos-
phate).[16] Peptide thioester 1 was prepared by selective thioesterification of
the corresponding peptide thioacid (prepared on a glycine ± thioester
support)[17] with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB, Ellmanꢁs
reagent) as previously described[5a] and purified by preparative HPLC.
ES-MS: observed mass: 5546.3(1.4) Da; calcd for C244H361N65O76S4: 5545.5
(monoisotopic), 5549.0 (average isotope composition).
Cyclization: Purified
1 (0.4 mmol, 2.2 mg) was dissolved to a final
concentration of about 50mm in a freshly degassed buffer containing 0.1m
sodium phosphate and 1mm ethylenediamine tetraacetate (EDTA) at
pH 7.5 and 0.05 volume% each of PhSH and BnSH. In cyclization reactions
carried out under unfolding conditions, 6m GdmCl was included in the
above buffer. To monitor the course of the reaction, small aliquots (50 mL)
of the reaction mixture were periodically removed, quickly quenched by
addition of 5% trifluoroacetic acid in water (20 mL), and investigated by
analytical HPLC. The degree of conversion of 1 into 2 was calculated based
on the absorption at 280 nm. The overall yield for the cyclization reaction
following HPLC purification was 1.8 mg (0.32 mmol, 81%). Circular
protein 2 was characterized by ES-MS and tryptic digestion. ES-MS:
observed mass: 5348.5(1.0) Da; calcd for C237H356N64O72S3: 5346.5 (mono-
isotopic), 5350.0 (average isotope composition).
[10] Cyclic protein 2 was digested with trypsin, and the peptide fragment
encompassing the ligation site (AMLSQGCFEIPDDVPLPAG-
WEMAK) characterized by Edman sequencing.
[11] H. I. Chen, M. Sudol, Proc. Natl. Acad. Sci. USA 1995, 92, 7819 ± 7823.
[12] The linear WW domain was also chemically synthesized by Boc solid-
phase protein synthesis and purified by standard procedures.
[13] Residues located at the immediate N and C termini could not be
unambiguously assigned in either the linear or cyclic WW domains.
[14] Large effective molarities were described for many intramolecular
organic reactions: F. M. Menger, Acc. Chem. Res. 1985, 18, 128 ± 134.
[15] B. Li, J. Y. K. Tom, D. Oare, R. Yen, W. J. Fairbrother, J. A. Wells,
B. C. Cunningham, Science 1995, 270, 1657 ± 1660.
[16] M. Schnolzer, P. Alewood, A. Jones, D. Alewood, S. B. H. Kent, Int. J.
Pept. Protein Res. 1992, 40, 180 ± 193.
[17] D. Yamashiro, C. H. Li, Int. J. Pept. Protein Res. 1988, 31, 322 ± 334.
[18] A. R. Viguera, J. L. Arrondo, A. Musacchio, M. Saraste, L. Serrano,
Biochemistry 1994, 33, 10925 ± 10933.
[19] a) A. Bax, D. G. Davis, J. Magn. Reson. 1985, 65, 355 ± 360; b) A.
Kumar, R. R. Ernst, K. Wuthrich, Biochem. Biophys. Res. Commun.
1980, 95, 1 ± 6.
Tryptic digestion of 2: Cyclic 2 (100 mg) was dissolved in 0.1m tris(hydroxy-
methyl)aminomethane (Tris)/HCl buffer (pH 8.4, 200 mL). Lyophilized
trypsin (10 mg, sequencing grade, Sigma) was then added, and the reaction
maintained at 378C for 3 h; a solution of 1,4-dithiothreitol (DTT, 50mm,
20 mL) was subsequently added. The three expected fragments T1
(H AMLSQGCFEIPDDVPLPAGWEMAK OH), T2 (H TSSGQR
OH), and T3 (H YFLNHIDQTTTWQDPR OH) were isolated by HPLC
and characterized by ES-MS and Edman sequencing.
The isotherms for ligand binding were obtained by monitoring the intrinsic
Trp fluoresence at 340 nm as a function of the concentration of the ligand at
228C. In all cases, the protein concentration was kept at 2mm in a buffer
containing 40mm sodium phosphate, 50mm NaCl, and 1mm DTTat pH 7.2.
Equilibrium dissociation constants were extracted from the curves by
assuming a 1:1 receptor± ligand complex.[18]
A Symmetrically Bridging Triarylsilyl Ligand
in a Dinuclear Rhodium Complex:
Synthesis and Structure of [LRh(H)(m-Cl)(m-
SiAr2)(m-SiAr3)Rh(H)L] (Arˆ Ph, p-FC6H4;
L ˆ PiPr3)**
1
Two-dimensional H NMR spectra were measured on a Bruker DPX-400
spectrometer (400.132 MHz). The NMR samples were dissolved in a buffer
containing 10 mm sodium phosphate, 100mm NaCl, 1mm [D10]DTT, 0.02%
NaN3, and 10% D2O at pH 6.2. A series of TOCSY and NOESY
experiments[19] were recorded at 278 K on samples containing both linear
and circular WW domains with WW ligand (protein concentrations 0.6 ±
1.2 mm ; ratio of peptide to protein 3:1). Typical mixing times were 30 ms for
TOCSY experiments and 50 ± 250 ms for NOESY experiments.
Kohtaro Osakada,* Take-aki Koizumi, and Takakazu
Yamamoto*
Received: June 30, 1997 [Z10614IE]
German version: Angew. Chem. 1998, 110, 361 ± 364
Bridging coordination of a secondary silyl group (SiHR2) in
dinuclear complexes has become common for late transition
metals.[1] The complexes reported so far contain both a s bond
between Si and one metal and a three-center, two-electron
bond (3c ± 2e; p bond) between the Si H group and the
second metal center (Scheme 1a).
Keywords: cyclizations ´ peptides ´ protein structures ´
solid-phase synthesis
[1] a) T. W. Muir, Structure 1995, 3, 649 ± 652; b) C. J. A. Wallace, Curr.
Opin. Biotech. 1995, 6, 403 ± 410.
[*] Prof. Dr. K. Osakada, Prof. Dr. T. Yamamoto, T. Koizumi
Research Laboratory of Resources Utilization
Tokyo Institute of Technology
[2] a) P. E. Dawson, S. B. H. Kent, J. Am. Chem. Soc. 1993, 115, 7263 ±
7266; b) A. Nefzi, X. Sun, M. Mutter, Tetrahedron Lett. 1995, 36, 229 ±
230; c) L. E. Canne, A. R. Ferre-DꢁAmare, S. K. Burley, S. B. H. Kent,
J. Am. Chem. Soc. 1995, 117, 2998 ± 3007; d) J. Shao, J. Tam, ibid. 1995,
117, 3893 ± 3899; e) K. J. Rose, ibid. 1994, 116, 30 ± 33 ; f) T. W. Muir,
M. J. Williams, M. H. Ginsberg, S. B. H. Kent, Biochemistry 1994, 33,
7701 ± 7708.
[3] a) D. P. Goldenberg, T. E. Creighton, J. Mol. Biol. 1984, 179, 527 ± 545;
b) D. P. J. Goldenberg, J. Cell. Biochem. 1985, 29, 321 ± 335; c) D. P.
Goldenburg, T. E. Creighton, J. Mol. Biol. 1983, 165, 407 ± 413.
4259 Nagatsuta, Midori-ku, Yokohama 226 (Japan)
Fax: Int. code ‡ (81)45924-5276
E-mail: kosakada@res.titech.ac.jp
[**] This work was supported by the Japanese Ministry of Education,
Science, Culture, and Sports for Grants-in-Aid for Scientific Research
(nos. 09239212 and 09440229). T.K. is grateful to the Japan Society for
Promotion of Science for a Grant-in-Aid as a JSPS fellow.
Angew. Chem. Int. Ed. 1998, 37, No. 3
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3703-0349 $ 17.50+.50/0
349

COMMUNICATIONS
a)
b)
R
R
R
R
R
R
R
H
Si
H
Si
Si
M
M
M
M
M
M
Scheme 1. Common (a) and seldom (b) coordination modes of secondary
and tertiary silyl groups in dinuclear metal complexes.
The m-h1,h2-coordination of the ligand results in two M Si
bond lengths that are significantly different from each other.
Complexes with a tertiary silyl ligand in a bridging coordina-
tion (Scheme 1b) seem to be less stable than with a primary or
secondary silyl ligand, since it has no Si H group to stabilize
M-Si-M coordination by Si-H-M 3c ± 2e bonding. Multi-
nuclear Cu complexes whose metal centers are bridged by
extremely bulky Si(SiMe3)3 ligands were isolated.[2] Dinuclear
complexes with a bridging tertiary silyl ligand are of interest
as models for the transition state of the migration of the
tertiary silyl ligand from one metal to the other in a dinuclear
framework (Scheme 2).[3, 4] Bridging coordination of PR3
ligands that are isolobal to SiR3 ligands has already been
Figure 1. A perspective ORTEP drawing of the crystal structure of 4.
Selected bond lengths [Š] and angles [8]: Rh1 Rh2 2.684(2), Rh1 P1
2.320(4), Rh2 P2 2.337(3), Rh1 Cl1 2.551(3), Rh2 Cl1 2.534(3), Rh1 Si1
2.290(2), Rh2 Si1 2.250(3), Rh1 Si2 2.444(4), Rh2 Si2 2.487(3), Si1 C1
1.91(1), Si1 C7 1.90(2), Si2 C13 1.90(1), Si2 C19 1.931(8), Si2 C25
1.88(1); P1-Rh1-Rh2 160.10(10), P2-Rh2-Rh1 153.5(1), P1-Rh1-Cl1
111.2(1), P2-Rh2-Cl1 105.2(1), P1-Rh1-Si1 114.7(1), P2-Rh2-Si1 110.2(1),
P1-Rh1-Si2 142.0(1), P2-Rh2-Si2 149.6(1), Rh1-Si1-Rh2 72.48(8), Rh1-Si1-
C1 120.3(3), Rh1-Si1-C7 118.7(4), Rh2-Si1-C1 124.4(5), Rh2-Si1-C7
115.6(3), C1-Si1-C7 104.0(5), Rh1-Si2-Rh2 65.94(10), Rh1-Si2-C13
118.2(4), Rh1-Si2-C19 80.4(4), Rh1-Si2-C25 133.8(5), Rh2-Si2-C13
123.6(3), Rh2-Si2-C19 129.4(4), Rh2-Si2-C25 77.6(4), C13-Si2-C19
105.1(4), C13-Si2-C25 105.2(6), C19-Si2-C25 103.9(4).
R3
SiR3
M2
SiR3
M1
Si
M1
M2
M1
M2
Scheme 2. Migration of a tertiary silyl group to the second metal center in
dinuclear metal complexes.
centers (2.290(3), 2.250(3) Š). They are longer than the Rh Si
bond lengths already reported (2.203 ± 2.379 Š)[9] and com-
parable even to that in a Rh-H-Si 3c ± 2e bond (2.487 Š).[1d]
This is in contrast to the structure of Cu complexes containing
Si(SiMe3)3 ligands, in which the Cu Si bonds to the bridging
and nonbridging ligands do not show significant differences in
length.[3] The NMR spectra of 3 and 4 are consistent with the
above structure. The 1H NMR spectra show peaks due to two
equivalent nonbridging hydrido ligands at d ˆ 17.40 and
17.60, respectively;[10] the positions of the hydrogen atoms
were not determined in the crystal structure analysis of 4.
established.[5] Here we report the synthesis and structure of
novel dinuclear Rh complexes with a bridging triarylsilyl
ligand that coordinates symmetrically to the two Rh centers.
Complex 1[6] is readily converted into its fluorine-substi-
tuted derivative 2 [7] [Eq. (a)]. Both 1 and 2 undergo thermal
H
SiAr3
H
SiPh3
H
H
Ar3Si
H
H
Ph3Si
Rh
Rh
Rh
Rh
+ 2 HSiAr3
(a)
– 2 HSiPh3
L
Cl
L
L
Cl
L
1
The H and 31P{1H} NMR spectroscopic measurements of
2
1
(L = PiPr3; Ar = p-FC6H4)
the thermal transformation of 1 to 3 in C6D6 revealed there
are no Rh complexes other than 1 and 3 throughout the
reaction. Conversion of 1 into 3 obeys first-order kinetics (k ˆ
reaction at 708C in toluene to afford complexes 3 and 4 under
liberation of benzene and fluorobenzene, respectively, in
quantitative yields [Eq. (b)].
1
4.41 Â 10 5 s at 333 K). This indicates that the reaction
proceeds in an intramolecular fashion, most probably by
oxidative addition of a Si C bond of an arylsilyl ligand onto
the metal center followed by coupling of the phenyl group of
this ligand with a hydride ligand and release of benzene.
Activation of Si C bonds under mild conditions has been
found for reactions of various organotransition metal com-
plexes.[1g, 11]
Ar3
H
H
H
SiAr3
H
Rh
∆
Si
H
Ar3Si
(b)
L
Rh
Rh
Cl
L
Rh
– Ar-H
L
Cl
L
Si
(L = PiPr3)
Ar2
We succeeded in isolating rhodium complexes with a
symmetrically bridging triarylsilyl ligand. The complexes
show unexpectedly thermal stability, although the Rh Si
bond is significantly longer than common Rh Si single bonds.
Smooth conversion of a nonbridging triarylsilyl ligand into a
bridging one corroborates the proposed mechanism for
migration of the silyl ligand between the metal centers in
dinuclear complexes (Scheme 2).
1: Ar = C6H5, 2: Ar = p-FC6H4
3: Ar = C6H5, 4: Ar = p-FC6H4
Figure 1 shows the molecular structure of 4, which has two
Rh centers bridged by chloride, bis(4-fluorophenyl)silylene,
and tri(4-fluorophenyl)silyl ligands.[8] The distances from the
Rh centers to the Si atom of the triarylsilyl ligand are similar
(2.444(4), 2.487(3) Š) and significantly longer than the bond
lengths between the Si center of the silylene ligand and the Rh
350
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3703-0350 $ 17.50+.50/0
Angew. Chem. Int. Ed. 1998, 37, No. 3

COMMUNICATIONS
an AA'MM'XX' pattern, 2H; Rh H); 31P{1H} NMR (C6D6, 85%
H3PO4): d ˆ 57.4 (AA' part of an AA'XX' pattern); 29Si{1H} NMR
(C6D6, TMS): d ˆ 157.8 (t, 2J(P,Si) ˆ 50 Hz), 28.7 (tt, 2J(P,Si) ˆ 50,
Experimental Section
3: A solution of 1 (264 mg, 0.24 mmol) in toluene (5 mL) was stirred for 2 h
at 708C. During the reaction the color of the solution changed from yellow
to orange. Gas-chromatographic analysis of the solution showed quanti-
tative formation of benzene. The 31P{1H} NMR spectrum of the mixture
after the reaction showed only the signal for 3. Addition of pentane caused
separation of 3 as yellow-orange crystals, which were collected by filtration
and recrystallized from toluene/pentane (71 mg, 29% yield). The similar
reaction of 2 gave 4 in 51% yield.
1
1J(Rh,Si) ˆ 8 Hz). 4: H NMR (C6D6, TMS): d ˆ 6.76 ± 7.88 (m, 20H;
aromatic H), 1.12 (m, 6H; P CH), 0.86 (m, 36H; CH3), 17.60 (AA'
part of an AA'MM'XX' pattern, 2H; Rh H); 31P{1H} NMR (C6D6,
85% H3PO4): d ˆ 58.2 (AA' part of an AA'XX' pattern).
[11] a) M. Auburn, M. Ciriano, J. A. K. Howard, M. Murray, N. J. Pugh,
J. L. Spencer, F. G. A. Stone, P. Woodward, J. Chem. Soc. Dalton
Trans. 1980, 659; b) D. E. Hendriksen, A. A. Oswald, G. B. Ansell, S.
Leta, R. V. Kastrup, Organometallics 1989, 8, 1153; c) S. K. Thomson,
G. B. Young, ibid. 1989, 8, 2068; d) P. Burger, R. G. Bergman, J. Am.
Chem. Soc. 1993, 115, 10462; e) T. Rappert, O. Nürnberg, H. Werner,
Organometallics 1993, 12, 1359; f) M. Baum, B. Windmüller, H.
Werner, Z. Naturforsch. B 1994, 49, 859; g) D. Huang, R. H. Heyn,
J. C. Bollinger, K. G. Caulton, Organometallics 1997, 16, 292.
The kinetic measurements of the conversion were carried out in a
thermostatted (708C) NMR probe by following the changes in the
intensities of the 1H NMR signal for the hydrido ligands of 1. Dioxane
was used as an internal standard.
Received: August 19, 1997 [Z10834IE]
German version: Angew. Chem. 1998, 110, 364 ± 366
Keywords: bridging ligands ´ rhodium ´ Si ligands
A Glucose-Containing Ether Lipid (Glc-PAF)
as an Antiproliferative Analogue of the
Platelet-Activating Factor**
[1] a) W. A. G. Graham, J. Organomet. Chem. 1986, 300, 81, and
references therein; b) U. Schubert, Adv. Organomet. Chem. 1990,
Ä
30, 151, and references therein; c) R. Carreno, V. Riera, M. A. Ruiz, Y.
Jeannin, M. Philoche-Levisalles, J. Chem. Soc. Chem. Commun. 1990,
15; d) M. D. Fryzuk, L. Rosenberg, S. J. Rettig, Organometallics 1991,
10, 2537; ibid. 1996, 15, 2871; e) H. Suzuki, T. Takao, M. Tanaka, Y.
Moro-oka, J. Chem. Soc. Chem. Commun. 1992, 476; f) T. Takao, S.
Yoshida, H. Suzuki, M. Tanaka, Organometallics 1995, 14, 3855; g)
B. K. Campion, R. H. Heyn, T. D. Tilley, ibid. 1992, 11, 3918; h) R. S.
Simons, C. A. Tessier, ibid. 1996, 15, 2604.
Michael Mickeleit, Thomas Wieder, Michael Arnold,
Christoph C. Geilen, Johann Mulzer, and
Werner Reutter*
It has long been known that the platelet-activating factor
(PAF) is a biologically highly active phosphoglyceride,[1] and
various PAF analogues have been reported as inhibitors of
proliferation.[2] However, since synthetic phospholipids are
strongly cytotoxic, their therapeutic use has hitherto been
restricted to topical applications.[3] We reported earlier the
synthesis of a new type of glyceroglucolecithin (Glc-PC)[4]
which displayed antiproliferative activity without cytotoxicity
[2] a) A. Heine, D. Stalke, Angew. Chem. 1993, 105, 90; Angew. Chem. Int.
Ed. Engl. 1993, 32, 121; b) A. Heine, R. Herbest-Irmer, D. Stalke, J.
Chem. Soc. Chem. Commun. 1993, 1729.
[3] a) P. Braunstein, M. Knorr, B. Hirle, G. Reinhard, U. Schubert, Angew.
Chem. 1992, 104, 1641; Angew. Chem. Int. Ed. Engl. 1992, 31, 1583; b)
M. Knorr, P. Braunstein, A. Tiripicchio, F. Ugozzoli, Organometallics
1995, 14, 4910; c) M. Knorr, E. Hallauer, V. Huch, M. Veith, P.
Braunstein, ibid. 1996, 15, 3868.
[4] W. Lin, S. R. Wilson, G. S. Girolami, Organometallics 1994, 13, 2309.
[5] R. Bender, P. Braunstein, A. Dedieu, Y. Dusausoy, Angew. Chem.
1989, 101, 931, Angew. Chem. Int. Ed. Engl. 1989, 28, 923.
1
at concentrations below 10 mmolL . We now present the
glycoside of the ether analogue [1-O-octadecyl-2-O-a-d-
glucopyranosyl-sn-glycero(3)]phosphorylcholine (Glc-PAF,
1), which is formally derived from the PAF by exchanging
the 2-acyl group for a glucose molecule.
The glycerol skeleton is provided by the starting material
(S)-isopropylidene glycerol (2),[5] whose hydroxyl group is
protected as the allyl ether functionality in 3 for introduction
of the end groups (Scheme 1). The primary hydroxyl group of
the diol 4 released upon acid hydrolysis cannot react directly
to form an ether, and it is therefore first converted into a
terminal benzoate ester group.[6] Compound 5 undergoes
[6] K. Osakada, T. Koizumi, T. Yamamoto, Organometallics 1997, 16, 2063.
[7] 2: 1H NMR (C6D6, TMS): d ˆ 7.59 (dd, 3J(H,H) ˆ 9, 3J(H,F) ˆ 2 Hz,
12H; aromatic H), 6.90 (t, 3J(H,H) ˆ 3J(H,F) ˆ 9 Hz, 12H; aromatic
H), 1.54 (m, 3J(P,H) ˆ 7 Hz, 6H; P CH), 0.82 (br, 36H; CH3), 12.55
(tt, 1J(Rh,H) ˆ 58, 2J(P,H) ˆ 25 Hz, 1H; Rh-H-Rh), 16.07 (AA' part
of an AA'MM'XX' pattern, 2H; Rh H); 31P{1H} NMR (C6D6, 85%
H3PO4): d ˆ 54.2 (AA' part of an AA'XX' pattern).
[8] Crystallographic data for 4: C48H64ClF5P2Rh2Si2, Mr ˆ 1095.41, mono-
clinic, space group P21/c (no. 14), a ˆ 18.146(10), b ˆ 12.806(8), c ˆ
1
21.512(9) Š, b ˆ 90.39(3)8,
V
ˆ 4998 Š3, Z ˆ 4, m ˆ 8.74 cm
,
F(000) ˆ 2248, 1calcd ˆ 1.455 g cm 3. The final R factor was 0.075
(Rw ˆ 0.059) for 7999 reflections with I > 3s(I). Data collection on a
RIGAKU-AFC5R diffractometer at 298 K with graphite-monochro-
mated MoKa radiation (l ˆ 0.71073 Š). The structure was solved with
the program teXsan. Crystallographic data (excluding structure
factors) for the structure reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-100766. Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: int. code ‡ (49)1223-336033; e-mail: depos-
it@ccdc.cam.ac.uk).
[*] Prof. Dr. W. Reutter, Dr. T. Wieder
Institut für Molekularbiologie und Biochemie der Freien Universität
Arnimallee 22, D-14195 Berlin (Germany)
Fax: Int. code ‡ (49)30838-2141
Prof. Dr. J. Mulzer
Institut für Organische Chemie der Universität Wien (Austria)
Dr. M. Mickeleit
Institut für Organische Chemie der Freien Universität Berlin
[9] a) K. W. Muir, J. A. Ibers, Inorg. Chem. 1970, 9, 440; b) M.-J.
Fernandez, P. M. Bailey, P. O. Bentz, J. S. Ricci, T. F. Koetzle, P. M.
Maitlis, J. Am. Chem. Soc. 1984, 106, 5458; c) F. L. Joslin, S. R. Stobart,
J. Chem. Soc. Chem. Commun. 1989, 504; d) D. L. Thorn, R. L.
Harlow, Inorg. Chem. 1990, 29, 2017; e) K. Osakada, K. Hataya, Y.
Nakamura, M. Tanaka, T. Yamamoto, J. Chem. Soc. Chem. Commun.
1993, 576; ibid. 1995, 2315.
Priv.-Doz. Dr. Dr. C. C. Geilen, M. Arnold
Haut- und Poliklinik des Universitätsklinikums Benjamin Franklin
Freie Universität Berlin
[**] These investigations were supported by the Bundesministerium für
Bildung, Wissenschaft, Forschung und Technologie (W.R.), zentrale
Mittel (FNK) der Freien Universität Berlin, the Fonds der Chem-
ischen Industrie, and the Deutsche Forschungsgemeinschaft (Ge 641/
3-3).
[10] 3: 1H NMR (C6D6, TMS): d ˆ 6.9 ± 8.2 (m, 25H; aromatic H), 1.18 (m,
3J(P,H) ˆ 7 Hz, 6H; P CH), 0.95 (m, 36H; CH3), 17.40 (AA' part of
Angew. Chem. Int. Ed. 1998, 37, No. 3
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3703-0351 $ 17.50+.50/0
351