Ligand-controlled chemoselectivity in the classical oxidative addition reactions of MeI and aldehydes to rhodium(I) complexes

Article abstract of DOI:10.1002/1521-3773(20010316)40:6<1119::AID-ANIE11190>3.0.CO;2-N

The strikingly different reactivity of similar complexes of the type [P_nRhX] is strongly dependent on the number and nature of the trialkylphosphane (P) and of the anionic ligand (X), and can be selectively directed to the oxidative addition of

Full text of DOI:10.1002/1521-3773(20010316)40:6<1119::AID-ANIE11190>3.0.CO;2-N

COMMUNICATIONS
[12] Authentic samples of anti-diols were prepared as follows: 1) a-
Hydroxyketones (R1CHOHCOR2) were prepared following the
Kagan SmI2 coupling (J. Souppe, J.-L. Namy, H. B. Kagan, Tetrahe-
dron Lett. 1984, 25, 2869 ± 2872); 2) protection of the hydroxy group as
tetrahydropyranyl or benzyl ether; 3) stereoselective addition of a
vinyl Grignard reagent (W. C. Still, J. H. McDonald III, Tetrahedron
Lett. 1980, 21, 1031 ± 1034). The stereochemistry of the diols was also
confirmed by NOE experiments on the corresponding acetonides.
[13] For catalytic pinacol coupling reactions using manganese or zinc as
reductants, see: A. Gansäuer, D. Bauer, J. Org. Chem. 1998, 63, 2070 ±
2071; A. Gansäuer, M. Moschioni, D. Bauer, Eur. J. Org. Chem. 1998,
1923 ± 1927; M. S. Dunlap, K. M. Nicholas, Synth. Commun. 1999, 29,
1097 ± 1106; M. Bandini, P. G. Cozzi, P. Melchiorre, A. Umani-Ronchi,
Angew. Chem. 1999, 111, 3558 ± 3561; Angew. Chem. Int. Ed. 1999, 38,
3357 ± 3359; M. Bandini, P. G. Cozzi, S. Morganti, A. Umani-Ronchi,
Tetrahedron Lett. 1999, 40, 1997; U. Groth, M. Jeske, Angew. Chem.
2000, 112, 586 ± 588; Angew. Chem. Int. Ed. 2000, 39, 574 ± 576.
[14] a) It is known that there is a fast equilibrium between (E)- and (Z)-
crotylchromium: C. T. Buse, C. H. Heathcock, Tetrahedron Lett. 1978,
1685 ± 1688; T. Hiyama, K. Kimura, H. Nozaki, Tetrahedron Lett. 1981,
22, 1037 ± 1040; b) however, the equilibrium becomes very slow in the
case of g,g-dialkyl-substituted allylic chromium compounds: C.
Jubert, S. Nowotny, D. Kornemann, I. Antes, C. E. Tucker, P. Knochel,
J. Org. Chem. 1992, 57, 6384 ± 6386; S. Nowotny, C. E. Tucker, C.
Jubert, P. Knochel, J. Org. Chem. 1995, 60, 2762 ± 2772.
Ligand-Controlled Chemoselectivity in the
Classical Oxidative Addition Reactions of MeI
and Aldehydes to Rhodium(i) Complexes**
Roman Goikhman and David Milstein*
Rhodium(i) phosphane complexes are widely used in indus-
trial and laboratory processes owing to their catalytic properties
and high reactivities, particularly in oxidative addition reac-
tions.[1a] We report here a remarkable difference in the reactivity
of similar alkylphosphanerhodium(i) complexes bearing triflate
and chloride ligands in classical oxidative addition reactions of
aldehydes and MeI. High chemoselectivity in oxidative addition
can be achieved by the choice of complex.
[(iPr3P)2RhOTf] (1) (OTf ˆ OSO2CF3, triflate) was synthe-
sized by a simple procedure involving chloride abstraction
from [{(iPr3P)2RhCl}2] (2)[2] with Me3SiOTf, according to our
reported method;[3] an alternative synthesis has also been
described.[4] Complex 1 was characterized by X-ray structure
analysis, which confirmed that the geometry around the metal
is square planar, and that an h2-bound triflate ligand is present
(Figure 1).[5] The structure is similar to that of another
rhodium h2-triflate complex.[4] Surprisingly, h2 coordination
of the triflate ligand in mononuclear late transition metal
complexes was not reported until 1998, and the reactivity of
these uncommon complexes has yet to be examined.[4, 6]
[15] There was no equilibrium between anti- and syn-diols through a retro
addition of the allylic chromium species.[16] This was confirmed by the
following experiment: a mixture of adducts produced at 08C (anti/
syn ˆ 93/7) was heated at 758C for 30 min before quenching; the anti/
syn ratio did not change.
[16] F. Barbot, P. Miginiac, Tetrahedron Lett. 1975, 3829 ± 3832; J. Nokami,
K. Yoshizane, H. Matsuura, S.-i. Sumida, J. Am. Chem. Soc. 1998, 120,
6609 ± 6610; P. Jones, N. Millot, P. Knochel, Chem. Commun. 1998,
2405 ± 2406.
[17] To examine the equilibrium between the cis and trans allylic
chromium species 9 and 10, the following experiment was conducted:
two reaction mixtures containing the enone 7, CrCl2, and Et3SiCl were
heated at 758C for 5 min. Nonanal was added at 758C to one mixture
and stirred at the same temperature. The other mixture was cooled to
08C before the addition of nonanal, followed by stirring at 08C. The
anti/syn ratio of the reaction at 758C was 10:90. The reaction cooled to
08C gave a ratio of 93:7, which is the same ratio obtained when the
reaction temperature is held constant at 08C (Table 1). The yield of 8
in the latter reaction decreased to 39% owing to the formation of 1,10-
diphenyldecane-3,8-dione in 27% yield, and nonanal was recovered in
45% yield.
[18] Coordination of
a siloxy group in 9 possibly stabilizes the cis
configuration, leading to an anti adduct. However, the siloxy group
is bulky and this could push the equilibrium to the sterically less
congested trans isomer 10. At higher temperatures, this steric effect
could be enhanced and the proportion of the syn isomer increased.
One possibility is that the anti/syn ratios could reflect the cis/trans
ratios, which depend on a balance between these factors.
[19] For the temperature dependence of reaction rates, see: J. Otera, K.
Sato, T. Tsukamoto, A. Orita, Tetrahedron Lett. 1998, 39, 3201 ± 3204;
T. Sakai, I. Kawabata, T. Kishimoto, T. Ema, M. Utaka, J. Org. Chem.
1997, 62, 4906 ± 4907.
[20] The following functional substrates were recovered under the
standard reaction conditions (Table 2, entry 1, 08C) owing to the mild
nucleophilicity of the organochromium reagent: 1-dodecene (94%),
1-dodecyne (98%), 1-chlorododecane (98%), ethyl octanoate (96%),
nonanenitrile (96%), 4-phenyl-2-butanone (91%), 3-phenylpropyl
acrylate (87%), and nonanal diethylene acetal (98%).
Figure 1. Structure of 1 (ORTEP plot; hydrogen atoms are omitted for
clarity). Selected bond lengths [Š] and angles [8]: Rh1-O3 2.283(2), Rh1-
O2 2.265(3), Rh1-P3 2.2099(11), Rh1-P2 2.2143(11); P3-Rh1-P2 105.41(4),
P3-Rh1-O2 95.78(7), P2-Rh1-O2 158.82(7), P2-Rh1-O3 95.38(7), P3-Rh1-
O3 158.96(7), O2-Rh1-O3 63.48(9).
[*] Prof. Dr. D. Milstein, R. Goikhman
Department of Organic Chemistry
The Weizmann Institute of Science
Rehovot, 76100 (Israel)
Fax : (‡972)8-9344142
E-mail: david.milstein@weizmann.ac.il
[**] This work was supported by the Israel Science Foundation, Jerusalem,
Israel, by the MINERVA foundation, Munich, Germany, and by the
Tashtiyot program of the Israeli Ministry of Science. D.M. is the holder
of the Israel Matz Professorial Chair of Organic Chemistry. We thank
Dr. L. Shimon and Dr. H. Rozenberg, Weizmann Institute of Science,
for performing the X-ray structural analysis.
Angew. Chem. Int. Ed. 2001, 40, No. 6
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4006-1119 $ 17.50+.50/0
1119

COMMUNICATIONS
We studied the oxidative addition reactions of 1 to probe
the influence of the h2-bound triflate ligand on the reactivity
of RhI compared to common chloro complexes such as 2 and
[(Et3P)3RhCl] (3).[7] The oxidative addition of aldehydes to
rhodium(i) is an important reaction which plays a key role in
catalytic processes such as the decarbonylation of aldehydes
and hydroacylation of olefins.[1a] However, examples of
acylrhodium ± hydride complexes resulting from the addition
of simple aldehydes to RhI centers are rare,[8±11] particularly
because of the tendency of these complexes to undergo
decarbonylation.[1b]
The oxidative addition of acetaldehyde to 1 results in the
quantitative formation of the new acylrhodium ± hydride
complex 4 (Scheme 1).[12] X-ray structure analysis of 4 shows
PiPr3
iPr3P
24 hours
MeCHO
30 min
no changes
Rh
RhOTf
H
OTf
Figure 2. Structure of 4 (ORTEP plot; hydrogen atoms, except H1, are
omitted for clarity). Selected bond lengths [Š] and angles [8]: Rh1-C2
1.949(2), Rh1-O1 2.2986(15), Rh1-P3 2.3428(7), Rh1-P2 2.3712(7), Rh1-H1
1.46(2); C2-Rh1-O1 103.64(8), C2-Rh1-P3 91.40(6), O1-Rh1-P3 93.31(5),
C2-Rh1-P2 94.10(6), O1-Rh1-P2 98.17(5), P3-Rh1-P2 165.73(2), C2-Rh1-
H1 87.3(9), P2-Rh1-H1 80.5(9), P3-Rh1-H1 86.6(9), O1-Rh1-H1 169.1(9).
Me
benzene, RT
iPr3P
C
O
4
1
PiPr3
PiPr3
H
Cl
Rh
iPr3P
iPr3P
PiPr3
RCHO
30 min
Rh
Rh
Cl
R
24 hours
PiPr3
Cl
benzene,
RT
(Scheme 1). Thus, unlike other coordinatively unsaturated
acylrhodium complexes,[1b, 11, 15] 4 is surprisingly stable towards
decarbonylation. Apparently, since the acyl ligand is located
in the apical position (Figure 2), the cis coordination site
required for decarbonylation is not available.[16] This result
also indicates that the triflate ligand does not readily
dissociate from the RhIII complex in benzene. Surprisingly,
unlike 1 and 2, complex 3 does not react with MeCHO or
PhCHO under the same conditions, or even after two days
with a 100-fold excess of benzaldehyde.
C
O
RH
PiPr3
2
R=Ph, 5
R=Me, 6
PiPr3
PEt3
Rh
RCHO
Et3P
Cl
no reaction
Rh
OC
Cl
12 hours
PEt3
7
PiPr3
3
Scheme 1. Reactions of RhI complexes with aldehydes.
The nucleophilicity of 1 was compared with that of the
chloro complexes 2 and 3, using MeI as an electrophile. The
addition of MeI to rhodium(i) complexes is a classical, well-
studied reaction of industrial significance, which usually
proceeds smoothly and is routinely used as a method for the
formation of Rh C bonds.[17] As expected, complexes 2 and 3
react smoothly with a stoichiometric amount of MeI in
benzene at room temperature to yield the square-pyramidal
complex trans-[(iPr3P)2Rh(Cl)(I)(Me)] (8) (Me in the apical
position) and the octahedral complex mer-[(Et3P)3Rh-
(Cl)(I)(Me)] (10).[12, 18] The analogous reactions of MeI with
[(Cy3P)2RhCl] (Cy ˆ cyclohexyl) and [(Me3P)3RhCl] com-
plexes result in [(Cy3P)2Rh(Cl)(I)(Me)][19a] and [(Me3P)3Rh-
(Cl)(I)(Me)],[19b] respectively. Interestingly, whereas 3 reacts
a square-pyramidal geometry in which the acyl ligand adopts
the apical position (Figure 2).[5] Interestingly, the close
analogue of 4, namely compound 5 (Scheme 1), was reported
to have a trigonal-bipyramidal structure.[11] The H-Rh-OTf
angle of 4 is 1698 and the MeC(O)-Rh-OTf angle is 1038,
whereas the H-Rh-Cl and PhC(O)-Rh-Cl angles of 5 are 1288
and 1478, respectively. It is worth noting that the Rh H bond
in 4 (1.46 Š), located trans to the triflate ligand, is much
shorter than that in 5 (1.77 Š).
Based on theoretical calculations, it was proposed that in
d6 ML5 complexes, a p-donating chloride ligand (e.g. the
chloride of 5) causes an orbital orientation towards a trigonal-
bipyramidal structure.[11, 13] In the case of 4, the triflate ion
apparently has a negligible p-donating effect. The different
structures of the closely related compounds 4 and 5 support
the significant influence of p donation on the configuration of
unsaturated RhIII complexes.
readily with one equivalent of MeI even at
208C, no
significant reaction of 1 with MeI (or with MeOTf) is
observed after several hours at room temperature, even when
a fivefold excess of MeI is used.
The difference in the configurations of 4 and 5 is reflected in
their reactivities. Whereas complex 5 and the analogous
acetaldehyde adduct 6[12, 14] undergo decarbonylation at room
temperature within a few hours, giving the carbonyl complex 7
as the main product,[11, 15] complex 4 remains unchanged in
benzene solution after 24 hours at room temperature
This difference in chemoselectivity is strikingly apparent in
competitive experiments in which complexes 1 ± 3 were
treated with a 10-fold excess of a 1:1 molar mixture of MeI
and RCHO (R ˆ Me or Ph) in a solution of C6D6. trans-
[(iPr3P)2Rh(N2)Cl] (11)[20] was also examined in the compet-
itive experiments, and the results are presented in Table 1.
1120
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4006-1120 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 6

COMMUNICATIONS
Table 1. Competitive reactivity of RhI complexes in oxidative addition
reactions.
aldehyde or MeI. The observed selectivity may be potentially
useful in reactions where substrates containing formyl groups
(and perhaps other groups with reactive nonpolar bonds) and
electrophilic centers in the same system are involved. An
example of high substrate selectivity in such mixtures is
described herein.
Complex Substrates[a]
Products
Molar ratio of
RCHO/MeI adducts[c]
1
2
MeCHO ‡ MeI MeCHO adduct 4
100:0
PhCHO ‡ MeI PhCHO adduct 12[b] 100:0
MeCHO ‡ MeI mixture of 6, 8, 9
PhCHO ‡ MeI mixture of 5, 8, 9
MeCHO ‡ MeI mixture of 6, 7, 8, 9
PhCHO ‡ MeI mixture of 5, 7, 8, 9
MeCHO ‡ MeI mainly 10
80:20
65:35
35:65
15:85
0:100
0:100
Received: October 9, 2000 [Z15928]
11
3
[1] a) J. P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke, Principles
and Applications of Organotransition Metal Chemistry, University
Science Books, Mill Valley, CA, 1987; b) J. P. Collman, L. S. Hegedus,
J. R. Norton, R. G. Finke, Principles and Applications of Organo-
transition Metal Chemistry, University Science Books, Mill Valley, CA,
1987, pp. 768 ± 775.
[2] H. Werner, J. Wolf, A. Höhn, J. Organomet. Chem. 1985, 287, 395.
[3] M. Aizenberg, D. Milstein, Chem. Commun. 1994, 411.
[4] H. Werner, M. Bosch, M. E. Schneider, C. Hahn, F. Kukla, M. Manger,
B. Windmüller, B. Weberndörfer, M. Laubender, J. Chem. Soc. Dalton
Trans. 1998, 3549.
[5] Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication nos.
CCDC-150421 (1) and CCDC-150420 (4). Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk).
[6] To the best of our knowledge, besides Rh complexes,[4] only two
complexes with h2-coordinated triflate to a single metal center have
been characterized: a) titanium: J. G. Donkervoort, J. T. B. H. Jastr-
zebski, B. J. Deelman, H. Kooijman, N. Veldman, A. L. Spek, G.
van Koten, Organometallics 1997, 16, 4174; b) silver: D. Gudat, M.
Schrott, V. Bajorat, M. Nieger, S. Kotila, R. Fleischner, D. Stalke,
Chem. Ber. 1996, 129, 337; c) the proposed h2 coordination of triflate
in the manganese complex (L. S. Stuhl, E. L. Muetterties, Inorg.
Chem. 1978, 17, 2148) may be incorrect, see ref. [6d]; d) for a review on
coordinated triflates, see: G. A. Lawrance, Chem. Rev. 1986, 86,
17.
PhCHO ‡ MeI mainly 10
[a] Reaction conditions: room temperature, benzene solution, molar ratio
of RCHO/MeI/RhI complex ˆ 10:10:1. [b] Complex 12, [(iPr3P)2Rh-
(OTf)(H)(COPh)], was synthesized analogously to 4.[12] [c] The ratio is
based on 31P and 1H NMR data. Compounds 7 and 9 are included in the
total ratio of the addition products of RCHO and MeI, respectively.
It is apparent that the four similar Rh complexes behave
very differently in the oxidative addition of aldehydes and
MeI. [(iPr3P)2RhOTf] (1) reacts selectively with aldehydes,
leaving MeI untouched, but [(Et3P)3RhCl] (3) reacts selec-
tively with MeI, leaving the aldehydes unconverted. Although
the reactions of [(iPr3P)2RhCl]2 (2) and trans-
[(iPr3P)2Rh(N2)Cl] (11) under the same conditions are not
selective, they exhibit opposite relative reactivity towards
aldehydes and MeI.
Further studies are required to determine the reasons for
the differences in reactivity and selectivity of the phosphane-
rhodium(i) complexes; however, a possible explanation is that
the oxidative addition of aldehydes requires a three-coordi-
nate, 14-electron RhI complex, whereas the oxidative addition
of MeI proceeds via the four-coordinate, 16-electron complex.
The oxidative addition of aldehydes to [(Me3P)3RhCl] was
shown to involve the 14-electron complex,[8] as were other
C H oxidative addition reactions to L3RhCl, which proceed
via a three-centered transition state.[21] On the other hand,
MeI reacts with L3RhCl by means of an SN2-type mechanism,
[7] G. M. Intille, Inorg. Chem. 1972, 11, 695.
[8] D. Milstein, Acc. Chem. Res. 1984, 17, 221, and references therein.
[9] a) D. Milstein, Organometallics 1982, 1, 1549; b) D. Milstein, J. Chem.
Soc. Chem. Commun. 1982, 1357; c) D. Milstein, J. Am. Chem. Soc.
1986, 108, 1336.
[10] C. Bianchini, A. Meli, M. Peruzzini, F. Vizza, Organometallics 1991,
10, 820, and references therein.
in which the four-coordinate complex is the active species.[17-
f, 17i, 22]
[11] K. Wang, T. J. Embe, A. S. Goldman, Organometallics 1995, 14,
4929.
The lack of reactivity of 3, and the lower reactivity of 11
with aldehydes than of 1 and 2, may be due to the ability of 1
and 2 to easily generate the three-coordinate species in
solution,[23] whereas phosphane dissociation from 3 and 11
may be more difficult.[24, 25] On the other hand, 3 reacts with
MeI even at low temperatures, since the generation of the
three-coordinate species is probably not required. Apparent-
ly, electron density at the metal center plays a key role in the
addition of MeI.[26] Compound 2 is more reactive than 1,
probably due to the chloride ligand being a better donor than
the triflate. Interestingly, the dimer 2 reacts preferentially
with aldehydes, whereas the monomer 11 reacts preferentially
with MeI. This result is in agreement with the greater ease of
formation of a three-coordinate complex with 2.[23a, 27]
This study demonstrates unprecedented ligand-controlled
selectivity of similar rhodium(i) complexes in classical oxida-
tive addition reactions. The reactivity of complexes of the type
[PnRhX] is strongly dependent on the number and nature of
the alkylphosphane (P) and the halide or triflate (X), and can
be selectively directed to the oxidative addition of an
[12] Selected spectroscopic data of compounds 4, 6, 8, 10, and 12. All NMR
spectra were measured on a Bruker DPX250 spectrometer at 258C in
C6D6. Frequencies used: 1H 250 MHz, 31P 100 MHz, 13C 62.5 MHz.
Standards: 1H NMR: C6D5H (d ˆ 7.15, internal); 31P NMR: H3PO4
(aq., 85%, d ˆ 0, external); 13C: C6D6 (d ˆ 128, internal). 4: 31P{1H}
NMR: d ˆ 47.2 (d, 1J(Rh,P) ˆ 129 Hz, 2P); 1H NMR: d ˆ 2.80 (s, 3H;
COCH3), 2.20 (m, 6H; PCH(CH3)2), 1.08 (dvt, J ˆ 7.2 Hz, 18H;
PCH(CH3)2), 1.00 (dvt, J ˆ 6.9 Hz, 18H; PCH(CH3)2), 19.23 (dt,
2J(Rh,H) ˆ 37 Hz, 3J(P,H) ˆ 10 Hz, 1H; RhH); IR (film): nÄ ˆ
1
ˆ
1695cm (C O). The structure of 4 was confirmed by X-ray structure
analysis (Figure 2). 6: 31P{1H} NMR: d ˆ 48.1 (d, 1J(Rh,P) ˆ 127 Hz,
1
2P); H NMR: d ˆ 2.99 (s, 3H; COCH3), 2.32 (m, 6H; PCH(CH3)2),
1.18 (overlapped dvt, 36H; PCH(CH3)2), 15.49 (dt, 2J(Rh,H) ˆ
27.6 Hz, 3J(P,H) ˆ 9.8 Hz, 1H; RhH); IR (film): nÄ ˆ 1687cm
1
(C O). 8: 31P{1H} NMR: d ˆ 20.8 (d, 1J(Rh,P) ˆ 99.3 Hz, 2P);
ˆ
1H NMR: d ˆ 2.95 (m, 6H; PCH(CH3)2), 1.23 (overlapped dvt, 39H;
PCH(CH3)2 and RhCH3); 13C{1H} NMR: d ˆ 3.77 (dt, 1J(Rh,C) ˆ
2
24.5 Hz, J(P,C) ˆ 5.6 Hz; RhCH3). The structure of 8 was confirmed
by X-ray structure analysis. 10: 31P{1H} NMR: d ˆ 19.3 (dt, 1J(Rh,P) ˆ
133.5 Hz, 2J(P,P) ˆ 26.8 Hz, 1P), 1.3 (dd, 1J(Rh,P) ˆ 94.7 Hz, 2J(P,P) ˆ
26.8 Hz, 2P); 1H NMR: d ˆ 2.20 (m, 12H; PRhP(CH2CH3)3), 1.62 (m,
6H; ClRhP(CH2CH3)3), 1.17 (m, 2J(Rh,H)ˆ 1.7 Hz, 3H; RhCH3), 1.00
(dt, 3J(P,H) ˆ 13.8 Hz, 3J(H,H) ˆ 6.8 Hz, 18H; PRhP(CH2CH3)3), 0.75
Angew. Chem. Int. Ed. 2001, 40, No. 6
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4006-1121 $ 17.50+.50/0
1121

COMMUNICATIONS
(dt, 3J(P,H) ˆ 13.6 Hz, 3J(H,H) ˆ 7.5 Hz, 9H; ClRhP(CH2CH3)3);
Leipoldt, A. Roodt, J. A. Venter, T. J. Van Der Walt, Inorg. Chem.
Acta 1986, 119, 35; b) G. J. Van Zyl, G. J. Lampbrecht, J. G. Leipoldt,
T. W. Swaddle, Inorg. Chem. Acta 1986, 143, 223; c) see also ref. [17c]
and [17i], and references therein.
13C{1H} NMR: d ˆ 0.11 (ddt, 1J(Rh,C) ˆ 21.2 Hz, 2J(P (unique),C) ˆ
2
8.2 Hz, J(P(mutually trans),C) ˆ 5.5 Hz, RhCH3). 12: 31P{1H} NMR:
d ˆ 45.8 (d, 1J(Rh,P) ˆ 123 Hz, 2P); 1H NMR: d ˆ 8.09 (m, 2H;
COPh), 7.05 (m, 3H; COPh), 2.23 (m, 6H; PCH(CH3)2), 1.06 (dvt, J ˆ
6.9 Hz, 18H; PCH(CH3)2), 0.99 (dvt, J ˆ 7.0 Hz, 18H; PCH(CH3)2),
[27] A similar tendency is observed with the dimer [{(Et3P)2Rh(Cl)}2],
which unlike the monomer 3, reacts slowly with aldehydes at room
temperature, giving predominantly carbonyl complexes.[15b]
20.92 (dt, 2J(Rh,H) ˆ 44.5 Hz, 3J(P,H) ˆ 10 Hz, 1H; RhH); IR
1
ˆ
(film): nÄ ˆ 1650cm (C O).
[13] I. El-Idrissi, O. Eisenstein, Y. Jean, New. J. Chem. 1990, 14, 671.
[14] Complex 6 was prepared from 2 and a small excess of MeCHO in
benzene at room temperature.
[15] a) Coordinatively saturated acylrhodium ± hydride complexes under-
go decarbonylation via unsaturated intermediates.[8, 9a] b) The coor-
dinatively unsaturated [(Et3P)2Rh(Cl)(MeCO)(H)] complex cannot
be observed at room temperature. It undergoes immediate decarbon-
ylation, evolving methane.
[16] However, 4 rapidly decomposes upon heating at 558C for 1 hour. A
similar reactivity was observed in the case of six-coordinate acylrho-
dium ± hydride complexes.[9a]
Quasi One-Dimensional Organic
Superconductor MDT-TSF ´ AuI2 with
Tc ˆ 4.5 K at Ambient Pressure**
[17] Selected references: a) R. F. Heck, J. Am. Chem. Soc. 1964, 86, 2796;
b) D. N. Lawson, J. A. Osborn, G. Wilkinson, J. Chem. Soc. A 1966,
1733; c) S. Franks, F. R. Hartley, J. R. Chipperfield, Inorg. Chem. 1981,
20, 3238; d) D. Forster, Adv. Organomet. Chem. 1979, 17, 255; e) A.
Haynes, B. E. Mann, G. E. Morris, P. M. Maitlis, J. Am. Chem. Soc.
1993, 115, 4093; f) P. M. Maitlis, A. Haynes, G. J. Sunley, M. J.
Howard, J. Chem. Soc. Dalton Trans. 1996, 2187, and references
therein; g) T. R. Griffin, D. B. Cook, A. Haynes, J. M. Pearson, D.
Monti, G. E. Morris, J. Am. Chem. Soc. 1996, 118, 3029; h) J. Rankin,
A. C. Benyei, A. D. Poole, D. J. Cole-Hamilton, J. Chem. Soc. Dalton
Trans. 1999, 3771; i) L. Gonsalvi, H. Adams, G. L. Sunley, E. Ditzel, A.
Haynes, J. Am. Chem. Soc. 1999, 121, 11233; j) for a recent review on
MeI addition to RhI complexes, see: P. R. Sharp in Comprehensive
Organometallic Chemistry II, Vol. 8 (Eds.: E. W. Abel, F. G. A. Stone,
G. Wilkinson, J. D. Atwood), Pergamon, 1995, pp. 190 ± 200, and
references therein.
Kazuo Takimiya,* Yoshiro Kataoka, Yoshio Aso,
Tetsuo Otsubo,* Hiroshi Fukuoka, and Shoji Yamanaka
Although the first organic superconductors were prepared
from radical-cation salts (Bechgaard salts) based on tetrame-
thyltetraselenafulvalene (TMTSF) under extremely cryogenic
conditions (Tc < 1.4 K), higher Tc superconductors were
developed from heterocycle-fused tetrathiafulvalenes (TTFs),
represented by bis(ethylenedithio)tetrathiafulvalene (BEDT-
TTF).[1] Whereas the Bechgaard salts have quasi one-dimen-
[18] The formation of 8 and 10 in the reaction of MeI with 2 and 3,
respectively, is accompanied by side products (20 ± 40% depending on
the temperature and on the amount of MeI added). Presumably,
diiodide complexes are formed as was reported.[19a] In the case of the
reaction of 2 or 11 with MeI (see also Table 1), we observed the
formation of trans-[(iPr3P)2Rh(I)2Me] (9) as a by-product.
[19] a) H. L. M. van Gaal, J. M. J. Verlaak, T. Posno, Inorg. Chem. Acta
1977, 23, 43; b) R. A. Jones, F. M. Real, G. Wilkinson, A. M. R. Galas,
M. B. Hursthouse, J. Chem. Soc. Dalton Trans. 1981, 126.
S
S
S
S
S
S
S
S
S
S
S
S
Se
Se
Se
Se
BEDT-TTF
BETS
S
S
S
S
S
S
[20] C. Busetto, A. DꢁAlfonso, F. Maspero, G. Perego, A. Zazetta, J. Chem.
Soc. Dalton Trans. 1977, 1828.
MDT-TTF
[21] a) J. A. Maguire, A. Petrillo, A. S. Goldman, J. Am. Chem. Soc. 1992,
114, 9492, and references therein; b) C. T. Spillett, P. C. Ford, J. Am.
Chem. Soc. 1989, 111, 1932; c) P. C. Ford, T. L. Netzel, C. T. Spillett,
D. B. Pourreau, Pure Appl. Chem. 1990, 62, 1091.
[22] G. Aullon, S. Alvarez, Inorg. Chem. 1996, 35, 3137, and references
therein.
S
S
S
S
Se
Se
S
S
Se
Se
S
S
MDS-TTF
MDT-STF
Se
Se
[23] a) Complex 2 was found to be monomeric in benzene: D. Schneider,
H. Werner, Angew. Chem. 1991, 103, 710; Angew. Chem. Int. Ed. Engl.
1991, 30, 700. b) We have observed that complex 1 reacts with
[{(cyclooctene)2RhCl}2] in benzene to give monophosphane com-
plexes, indicating the dissociation of iPr3P.
Se
Se
S
S
MDT-TSF
1
[24] In contrast to compound 3, [(Me3P)3RhCl] is reported to react
with an excess of MeCHO and PhCHO to give acyl hydride
complexes.[8, 9a] The reason for the higher reactivity of
[(Me3P)3RhCl] over [(Et3P)3RhCl] with aldehydes is not clear. It
may be due to an associative phosphane displacement, preceded by
coordination of the aldehyde, which is easier with a lower bulk at the
metal center.
[*] Dr. K. Takimiya, Prof. Dr. T. Otsubo, Y. Kataoka, Prof. Dr. Y. Aso,
Dr. H. Fukuoka, Prof. Dr. S. Yamanaka
Department of Applied Chemistry
Faculty of Engineering, Hiroshima University
Kagamiyama, Higashi-Hiroshima 739-8527 (Japan)
Fax : (‡81)824-22-7191
[25] Since complexes 2 and 11 show different selectivities in the reaction
with a mixture of MeI and aldehyde, different intermediates are likely
to be involved; hence we propose the dissociation of phosphane rather
than that of N2 from 11. Nitrogen does not readily dissociate from 11:
D. L. Thorn, T. H. Tulip, J. A. Ibers, J. Chem. Soc. Dalton Trans. 1979,
2022.
E-mail: ktakimi@hiroshima-u.ac.jp
[**] This work was supported by Grants-in-Aid for Scientific Research
from the Ministry of Education, Science, Sports, and Culture of Japan.
We thank the Cryogenic Center, Hiroshima University, for supplying
liquid helium.
[26] Electron-donating ligands coordinated to RhI centers facilitate the
oxidative addition of MeI, see for example: a) S. S. Basson, J. G.
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
1122
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4006-1122 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 6