Synthesis and structure of (MeN) Ph2S=C=SPh2(NMe)

Article abstract of DOI:10.1002/1521-3773(20020715)41:14<2576::AID-ANIE2576>3.0.CO;2-8

Double ylidic character in the S-C-S bonds is apparent from the single-crystal x-ray analysis of the title compound (see structure). This electronic configuration was supported by ab initio calculations on a model compound in which the phenyl groups were

Full text of DOI:10.1002/1521-3773(20020715)41:14<2576::AID-ANIE2576>3.0.CO;2-8

COMMUNICATIONS
Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge
CB21EZ, UK; fax: (‡44)1223-336-033; or deposit@ccdc.cam.ac.uk).
1) LDA (2.1 equiv), THF, –78 °C, 30 min
2) Ph2FSN (2, 1.1 equiv), THF, –78 °C, 12h
3) 10% HClO4 (aq), RT, 30 min
CH3
Ph
S
Ph
S
Ph
S
N
Ph
HN
CH
NH
ClO4
Received: March 5, 2002 [Z18830]
Ph
Ph
1
3
Ph
S
Ph
S
ion-exchange resin (OH– form)
10% HClO4 (aq), CH3OH, 1h
[1] Multiple Bonds and Low Coordination in Phosphorus Chemistry
(Eds.: M. Regitz, O. J. Scherer), Georg Thieme, Stuttgart, 1990.
[2] G. M‰rkl, R. Hennig, K. M. Raab, Chem. Commun. 1996, 2057 2058.
[3] S. Sasaki, F. Murakami, M. Yoshifuji, Angew. Chem. 1999, 111, 351
354; Angew. Chem. Int. Ed. 1999, 38, 340 343.
1) CH3I/CH3CN, RT, 1h
2) NaClO4/CH3CN, RT
HN
CH
N
Ph
Ph
4
[4] K. Takahashi, Pure Appl. Chem. 1993, 65, 127 134; K. Yui, H. Ishida,
Y. Aso, T. Otsubo, F. Ogura, A. Kawamoto, J. Tanaka, Bull. Chem.
Soc. Jpn. 1989, 62, 1547 1555.
Ph
S
Ph
S
Ph
S
Ph
S
ion-exchange resin (OH– form)
10% HClO4 (aq), CH3OH, 1h
MeN
C
NMe
MeN
CH
NMe
ClO4
Ph
Ph
Ph
Ph
[5] M. Yoshifuji, I. Shima, N. Inamoto, K. Hirotsu, T. Higuchi, J. Am.
Chem. Soc. 1981, 103, 4587 4589; M. Yoshifuji, I. Shima, N. Inamoto,
K. Hirotsu, T. Higuchi, J. Am. Chem. Soc. 1982, 104, 6167.
[6] I. J. Colquhoun, W. McFarlane, J. Chem. Soc. Dalton Trans. 1982,
1915 1921.
[7] R. Appel in Multiple Bonds and Low Coordination in Phosphorus
Chemistry (Eds.: M. Regitz, O. J. Scherer), Georg Thieme, Stuttgart,
1990, pp. 157 219.
[8] M. Geoffroy, A. Jouaiti, G. Terron, M. Cattani-Lorente, Y. Ellinger, J.
Phys. Chem. 1992, 96, 8241 8245.
[9] Tentative assignments: g ˆ 2.007, a(P1) ˆ 9.3, a(P2) ˆ 2.1 mT, g? ˆ
2.010, gk ˆ 2.003, a?(P1) ˆ 0.8, ak(P1) ˆ 27.7, a?(P2) ˆ 2.2, ak(P2) ˆ
1.2 mT.
5
6
Scheme 1. Synthesis of 6.
a-Lithiation of methyldiphenyl-l6-sulfanenitrile (1)[3a] with
lithium diisopropylamide (LDA), followed by treatment with
fluorodiphenyl-l6-sulfanenitrile (2)[3b] and acidification with
perchloric acid afforded 3 in 66% yield. This compound was
further treated with ion-exchange resin IRA-410 (OHÀ form)
to give 4[4 almost quantitatively. The reaction of 4 with
6]
methyl iodide in CH3CN at room temperature and then
treatment with NaClO4 afforded precursor 5, which was
isolated in 26% yield by recrystallization from MeOH and
diethyl ether.[7] The desired compound 6 was prepared in
essentially quantitative yield by passing a methanolic solution
of 5 through a column of the above basic resin.[6] The
compositions of 3 6 were identified by NMR (except for 4)
and IR spectroscopy, as well as elemental analysis, and the
molecular structures of 5 and 6 were determined by X-ray
crystallographic analysis (Figure 1 and 2).[8]
[10] M. Geoffroy, E. A. C. Lucken, C. Mazeline, Mol. Phys. 1974, 28, 839
845; B. fietinkaya, A. Hudson, M. F. Lappert, H. Goldwhite, J. Chem.
Soc. Chem. Commun. 1982, 609 610.
[11] J. R. Morton, K. F. Preston, J. Magn. Reson. 1978, 30, 577 582.
The X-ray structure of 6 indicates the following character-
istic properties (Figure 2). Each sulfur center is associated
with one imido and two phenyl groups, in a pseudo-
tetrahedral arrangement. The bond angles N1-S1-C1 and
Synthesis and Structure of
ˆ ˆ
(MeN)Ph2S C SPh2(NMe)
Takayoshi Fujii, Tomio Ikeda, Toshie Mikami,
Tetsuya Suzuki, and Toshiaki Yoshimura*
ˆ ˆ
(X)R2S C SR2(X) can be regarded as the isoelectronic
‡
ˆ ˆ
carbon analogue of the [(X)R2S N SR2(X)] ion (R ˆ Ar,
alkyl; X ˆ lone pair, NH, O).[1] There has, however, been little
reported on this compound to date.[2] In view of its chemical
properties and structural features, investigation of this com-
pound has posed an interesting challenge. Herein, we report
the first synthesis, isolation, and crystal structure of
ˆ ˆ
(MeN)Ph2S C SPh2(NMe) (6), prepared by the a-proton
abstraction of
a
new type of iminosulfonium ylide
‡
ˆ
À
[(MeN)Ph2S CH SPh2(NMe)] (Scheme 1).
Figure 1. ORTEP drawing of 5 (50% probability thermal ellipsoids for all
non-hydrogen atoms, perchlorate anion is omitted for clarity). Selected
bond lengths [ä] and angles [8]: S1-N1 1.526(2), S1-C1 1.695(2), S1-C2
1.780(3), S1-C3 1.802(3), S2-N2 1.531(2), S2-C1 1.691(2), S2-C4 1.788(3),
S2-C5 1.802(3), N1-C6 1.479(4), N2-C7 1.469(4); N1-S1-C1 123.1(1), N1-S1-
C2 103.4(1), N1-S1-C3 112.5(1), C1-S1-C2 107.8(1), C1-S1-C3 102.4(1), C2-
S1-C3 106.6(1), N2-S2-C1 119.6(1), N2-S2-C4 103.4(1), N2-S2-C5 115.4(1),
C1-S2-C4 110.7(1), C1-S2-C5 102.1(1), C4-S2-C5 104.9(1), S1-N1-C6
117.3(2), S2-N2-C7 118.0(2), S1-C1-S2 118.0(1).
[*] Prof. Dr. T. Yoshimura, Dr. T. Fujii, T. Ikeda, T. Mikami, T. Suzuki
Department of Material Systems Engineering
and Life Science
Faculty of Engineering
Toyama University
Gofuku, Toyama 930-8555 (Japan)
Fax : (‡81)76-445-6850
E-mail: yosimura@eng.toyama-u.ac.jp
2576
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4114-2576 $ 20.00+.50/0
Angew. Chem. Int. Ed. 2002, 41, No. 14

COMMUNICATIONS
the natural bond orbital (NBO) analyses were performed at
the B3LYP/6-311 ‡ G(2d,p) level.[11] There is a reasonably
good agreement between the bond lengths and angles of the
N-S-C-S-N unit in the optimized structure (Figure 3), and
Figure 2. ORTEP drawing of 6 (50% probability thermal ellipsoids for all
non-hydrogen atoms). Selected bond lengths [ä] and angles [8]: S1-N1
1.553(10), S1-C1 1.635(4), S1-C2 1.801(2), S1-C3 1.802(4), S2-N2 1.550(8),
S2-C1 1.636(2), S2-C4 1.799(4), S2-C5 1.808(4), N1-C6 1.464(4), N2-C7
1.470(5); N1-S1-C1 124.1(2), N1-S1-C2 102.2(2), N1-S1-C3 110.6(3), C1-S1-
C2 115.4(1), C1-S1-C3 101.9(3), C2-S1-C3 100.5(1), N2-S2-C1 128.1(2), N2-
S2-C4 101.1(3), N2-S2-C5 110.1(3), C1-S2-C4 111.6(1), C1-S2-C5 102.1(1),
C4-S2-C5 101.0(3), S1-N1-C6 115.2(2), S2-N2-C7115.(73), S1-C1-S2
116.8(2).
Figure 3. View of the B3LYP/6-311 ‡ G(2d,p) optimized structure and
charge distribution (natural charge analysis) of 7 (all hydrogen atoms are
omitted for clarity). Selected bond lengths [ä] and angles [8]: S1-N1 1.565,
S1-C1 1.646, S1-C2 1.824, S1-C3 1.831, S2-N2 1.567, S2-C1 1.650, S2-C4
1.819, S2-C5 1.836, N1-C6 1.460, N2-C71.465; N1-S1-C1 124.9, N1-S1-C2
99.4, N1-S1-C3 111.5, C1-S1-C2 117.6, C1-S1-C3 100.8, C2-S1-C3 100.3, N2-
S2-C1 129.6, N2-S2-C4 99.1, N2-S2-C5 112.5, C1-S2-C4 110.8, C1-S2-C5
102.0, C4-S2-C5 99.2, S1-N1-C6 117.1, S2-N2-C7 118.1, S1-C1-S2 120.0.
N2-S2-C1 (124.1(2) and 128.1(2)8, respectively), those involv-
ing the bridging C1 atom, are considerably larger than the
other sulfur-centered bond angles (N-S-C; av. 106.08, C-S-C;
av. 105.48). The bonds between the sulfur centers and the
bridging carbon atom are of similar size, as are the two
those in the X-ray structure of 6. As indicated by NPA and
NBO analysis, the N-S-C-S-N unit in 7 has strongly polarized
À
À
À
terminal S N bonds, and the four bonds between the sulfur
S C and S N bonds. The NPA charges at the two sulfur
atoms, the two nitrogen atoms, and the central carbon atom
are calculated to be ‡1.603 (S1), ‡1.594 (S2), À1.000 (N1),
À0.997(N2), and À1.228 (C1), respectively. The NBO
procedure for identifying bonds and lone pairs of the N-S-
C-S-N unit in 7 clearly showed ten s bonds and six lone pairs.
Therefore, the canonical structure E in Scheme 2 shows the
best Lewis representation of the electronic configuration of 6.
The ps and p lone pairs of the central carbon atom (C1) are
highly depleted, with occupancies of 1.74e and 1.52e. NBO
second-order perturbation analysis[11b, 12] of 7 indicates five
strong orbital interactions of the lone pair (p-LP, ps-LP) at the
central carbon atom with the antibonding s* orbitals of the
À
centers and phenylic carbon atoms. The bridging S C1 bonds
in 6 (1.635(4) and 1.636(2) ä) are shorter than their counter-
parts in 5 (1.695(2) and 1.691(2) ä) and in iminosulfonium
phenacylide (1.672(2) ä[3a]). In contrast, the terminal S1 N1
À
À
and S2 N2 bonds (1.553(10) and 1.550(8) ä, respectively) are
slightly longer than those in 5 (1.526(2) and 1.531 ä) and in
iminosulfonium phenacylide (1.538(2) ä[3a]). Interestingly,
the S1-C1-S2 angle in 6 (116.8(2)8) is almost the same as the
corresponding angle in 5 (118.0(1)8), and is indicative of sp2
hybridization of the C1 atom. These findings suggest that the
S1-C1-S2 bonds have double ylidic character, such as is found
[9]
ˆ ˆ
in carbodiphosphoranes, R3P C PR3, and thus the canon-
À
À
ical Lewis structures of B E are anticipated (Scheme 2).
To evaluate the electronic structure of 6, ab initio calcu-
lations were carried out on a model compound, (MeN)-
Me2S C SMe2(NMe) (7), where the phenyl groups in 6 are all
replaced by methyl groups.[10] Calculations by geometry
optimization, the natural population analysis (NPA), and
S N and S C bonds, and the interaction of a lone pair at each
terminal nitrogen atom with s*S-C1 and s*S-C orbitals. These
results indicate that ionic bonding, as well as LP(C1) !s* and
LP(N) !s* negative hyperconjugation exist in 7.
ˆ ˆ
In conclusion, the synthesis of 6 represents the first
successful preparation of an organosulfur compound contain-
ing the SVI C S unit, the molecular structure of which has
been determined. In addition, the electronic structure of 7, a
model compound based on 6, was predicted by ab initio
molecular calculations.
VI
ˆ ˆ
Ph
S
Ph
S
Ph
S
Ph
S
Ph
S
Ph
S
2
MeN
C
NMe
MeN
C
NMe
MeN
C
NMe
Ph
Ph
Ph
Ph
Ph
Ph
A
B
C
Experimental Section
Ph
S
Ph
Ph
Ph
2
2
2
2
2
3: Lithium diisopropylamide (4.2 mL of 2.0m solution in heptane/THF/
ethylbenzene, 8.4 mmol) was added dropwise at À788C to a solution of 1
(861 mg, 4.0 mmol) in THF (50 mL) and stirred for 30 min. A solution of 2
(965 mg, 4.4 mmol) in THF (10 mL) was then added. The mixture was
stirred for 12 h at À788C , warmed up to room temperature, and then
MeN
C
S
NMe
MeN
S
C
S
NMe
Ph
Ph
Ph
Ph
D
E
Scheme 2. Structural representation of 6.
Angew. Chem. Int. Ed. 2002, 41, No. 14
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2577

COMMUNICATIONS
quenched with 10% perchloric acid (10 ml) and then extracted with
CH2Cl2. The solvent was evaporated under reduced pressure, and the
residue was washed with MeOH and then recrystallized from EtOH/Et2O
to give colorless crystals of 3 (1.36 g, 66% yield), m.p. 175 1768C. 1H NMR
(400 MHz, CD3CN): d ˆ 5.08 (s, 1H), 7.59 7.64 (m, 8H), 7.69 7.74 (m,
4H), 8.02 8.06 ppm (m, 8H); 13C NMR (100 MHz, CD3CN): d ˆ 49.3,
127.9, 131.0, 135.2, 140.8 ppm; IR (KBr): nÄ ˆ 3315, 3269, 3094, 3062,
1095 cmÀ1; elemental analysis calcd for C25H23ClN2O4S2: C 58.30, H 4.50, N
5.44; found: C 58.29, H 4.46, N, 5.46.
0.071. 6: C27H26N2S2, Mr ˆ 442.64, monoclinic, space group P21/n, Z ˆ
4, a ˆ 7.40(5), b ˆ 15.63(8), c ˆ 20.36(6) ä, b ˆ 91.6(5)8, Vˆ
2352(20) ä3, 1calcd ˆ 1.250 cmÀ1. X-ray diffraction data were collected
on a Rigaku AFC7R diffractometer with graphite monochromated
MoKa radiation (l ˆ 0.71069 ä) at 296 K, and the structure was solved
by direct methods (SIR 92) and expanded using Fourier techniques
(DRIFT). The final cycle of full-matrix least-squares refinement was
based on 4039 observed reflections (I > 3s(I)) and 280 variable
parameters and converged to R ˆ 0.042 and Rw ˆ 0.058. CCDC-180279
(5) and CCDC-180280 (6) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ,
UK; fax: (‡44)1223-336-033; or deposit@ccdc.cam.ac.uk).
5: A mixture of 4 (414 mg, 1.0 mmol) and methyl iodide (187 mL, 3 mmol)
in acetonitrile (10 mL) was stirred at room temperature for 1 h. A solution
of sodium perchlorate (184 mg, 1.5 mmol) in acetonitrile (10 mL) was
added, and then the solvent was evaporated under reduced pressure. The
residue was dissolved in water (10 mL) and extracted with CH2Cl2. After
removal of the solvent, the residue was purified by recrystallization from
MeOH/Et2O to afford 5 as colorless crystals (152 mg),[7] m.p. 184 1858C.
1H NMR (400 MHz, CD3CN): d ˆ 2.75 (s, 6H), 5.18 (s, 1H), 7.52 7.57 (m,
8H), 7.65 7.70 (m, 4H), 7.87 7.90 ppm (m, 8H)1;3C NMR (100 MHz,
CD3CN): d ˆ 30.4, 39.3, 128.9, 131.0, 135.3, 136.8 ppm; IR (KBr): nÄ ˆ 2917,
2872, 2803, 1194, 1091 cmÀ1; elemental analysis calcd for C27H27ClN2O4S2:
C 59.71, H 5.01, N 5.16; found: C 59.72, H 4.97, N, 5.17.
ˆ ˆ
[9] For Ph3P C PPh3, see: a) A. T. Vincent, P. J. Wheatley, J. Chem. Soc.
Dalton Trans. 1972, 617 622; b) G. E. Hardy, J. I. Zink, W. C. Kaska,
J. C. Baldwin, J. Am. Chem. Soc, 1978, 100, 8001 8002.
[10] Gaussian98 (RevisionA.9), M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi,
V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo,
S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. Cioslowski, J. V. Ortiz, B. B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, C.
Gonzalez, M. Challacombe, P. M. W. Gill, B. G. Johnson, W. Chen,
M. W. Wong, J. L. Andres, M. Head-Gordon, E. S. Replogle, J. A.
Pople, Gaussian, Inc., Pittsburgh, PA, 1998.
6: A solution of 5 (100 mg) in methanol was passed through a column of
Amberlite IRA-410 ion-exchange resin (strong base, OHÀ form) followed
by evaporation of the solvent to give 6 as a pale yellow powder (74 mg,
98%), m.p. 163 1648C. 1H NMR (400 MHz, CDCl3): d ˆ 2.62 (s, 6H),
7.28 7.35 (m, 12H), 8.00 ppm (dd,J1 ˆ 8.0 Hz, J2 ˆ 1.4 Hz, 8H); 13C NMR
(100 MHz, CDCl3): d ˆ 30.1, 39.7, 127.7, 128.3, 130.5, 144.4 ppm; IR (KBr):
nÄ ˆ 2947, 2840, 2776, 1147 cmÀ1; elemental analysis calcd for C27H26N2S2: C
73.26, H 5.92, N 6.33; found: C 73.11, H 5.99, N, 6.29.
[11] a) NBO version 3.1, E. D. Glendeling, A. E. Reed, J. E. Carpenter, F.
Weinhold; b) A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988,
88, 899 926, and references therein; c) A. E. Reed, F. Weinhold, J.
Chem. Phys. 1985, 83, 1736 1740.
[12] a) A. E. Reed, P. von R. Schleyer, J. Am. Chem. Soc. 1987, 109, 7362
7371; b) A. E. Reed, A. P. von R. Schleyer, Inorg. Chem. 1988, 27,
3969 3987; c) A. E. Reed, P. von R. Schleyer, J. Am. Chem. Soc. 1990,
112, 1434 1445, and references therein.
Received: March 7, 2002 [Z18842]
[1] a) S. Oae, T. Numata, T. Yoshimura in The Chemistry of the Sulfonium
Groups, Part 2 (Eds.: S. Patai, C. J. M. Stirling), Wiley, Chichester,
1981, chap. 15, and references therein; b) T. Yoshimura, T. Fujii, S.
Murotani, S. Miyoshi, T. Fujimori, M. Ohkubo, S. Ono, H. Morita, J.
Organomet. Chem. 2000, 611, 272 279, and references therein.
2‡
ˆ ˆ
À
À
[2] Attempts to prepare R2S C SR2 from [R2S CH2 SR2]
or
‡
ˆ
À
[R2S CH SR2] ions (R ˆ Me, Et) were unsuccessful; see: C. P.
Lillya, E. F. Miller, P. Miller, Int. J. Sulfur Chem. 1971, 1, 89 96.
[3] a) T. Fujii, T. Suzuki, T. Sato, E. Horn, T. Yoshimura, Tetrahedron Lett.
2001, 42, 6151 6154; b) T. Yoshimura, M. Ohkubo, T. Fujii, H. Kita,
Y. Wakai, S. Ono, H. Morita, C. Shimasaki, E. Horn, Bull. Chem. Soc.
Jpn. 1998, 71, 1629 1637, and references therein.
[4] Compound 4 could not be isolated from the reaction mixture of
lithiated 1 and 2, and was therefore isolated by converting it into the
corresponding perchloric salt 3 upon treatment with perchloric acid
(See Experimental Section).
Reaction of 2-Butyne with nido-[1,2-
(Cp*RuH)2B3H7]: Improved Kinetic Control
Leads to Metallacarboranes of Novel
Composition and Structure**
[5] Unexpectedly, 13C NMR spectra of 4 showed only one set of phenyl
groups, and methyne proton and carbon resonances were not observed
in the temperature range À80 to 1008C in CD3OD and [D6]DMSO. IR
and elemental analyses were consistent with the structure of 4,
although the structure of 4 in the solution is still not certain. 4:
Hong Yan, Alicia M. Beatty, and Thomas P. Fehlner*
m.p. 155 1568C; IR (KBr): nÄ ˆ 1259 cmÀ1 (S N); elemental analysis
The conventional route to metallacarboranes proceeds in a
sequence of steps leading from polyborane to carborane to
ꢀ
calcd for C25H22N2S2: C 72.43, H 5.35, N 6.76; found: C 72.36, H 5.38,
N, 6.77.
4]
metallacarborane.[1 Although a fruitful strategy, it is also
[6] Compounds 4 and 6 are considerably basic. Treatment of 4 and 6 with
perchloric acid afforded, almost quantitatively, 3 and 5, respectively.
one in which strong bonds are formed before weak ones.
Access to more diverse chemistry might arise by adoption of
[7] The side products in the reaction with methyl iodide were 3 and the N-
‡
monomethylated compound, [(MeN)Ph2S CH SPh2(NH)] [ClO4]À
(8). The structure of 8 is still preliminary as it has been difficult to
effect the separation of 3 and 8 successfully.
À
À
ˆ
À
the reverse strategy, that is, formation of B B/B M before
À
À
B C/M C bonds, thereby generating the most stable products
[8] Crystal data for 5: C27H27ClN2O4S2, Mr ˆ 547.09, monoclinic, space
group P21/n, Z ˆ 4, a ˆ 12.769(6), b ˆ 16.503(4), c ˆ 14.031(6) ä, b ˆ
115.99(3)8, Vˆ 2657(1) ä3, 1calcd ˆ 1.367cm À1. X-ray diffraction data
were collected on a Rigaku AFC7R diffractometer with graphite
monochromated Moka radiation (l ˆ 0.71069 ä) at 296 K, and the
structure was solved by direct methods (SIR 92) and expanded using
Fourier techniques (DRIFT). The final cycle of full-matrix least-
squares refinement was based on 5006 observed reflections (I > 3s(I))
and 338 variable parameters and converged to R ˆ 0.050 and Rw ˆ
[*] Prof. T. P. Fehlner, Dr. H. Yan, Dr. A. M. Beatty
Department of Chemistry and Biochemistry
University of Notre Dame
Notre Dame, IN 46556 (USA)
Fax : (‡1)219-631-6652
E-mail: fehlner.1@nd.edu
[**] This work was supported by the National Science Foundation CHE
9986880. Cp* ˆ C5Me5.
2578
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4114-2578 $ 20.00+.50/0
Angew. Chem. Int. Ed. 2002, 41, No. 14