A neutral three-coordinate alkylrhodium(I) complex: Stabilization of a 14-electron species by γ-C-H agostic interactions with a saturated hydrocarbon group

Article abstract of DOI:10.1002/1521-3773(20010216)40:4<781::AID-ANIE7810>3.0.CO;2-T

γ-C-H agostic stabilization of the 14-electron metal center by a saturated hydrocarbon group characterizes the structure of the first neutral three-coordinate alkylrhodium(I) complex [(K²-dtbpm)RhNp] (1;dtbpm = bis(di-tert-butylphosphanyl) methane, Np=neopentyl). Some of its reactions, for example, N₂ complexation and C-H bond activation are reported.

Full text of DOI:10.1002/1521-3773(20010216)40:4<781::AID-ANIE7810>3.0.CO;2-T

COMMUNICATIONS
[1] a) G. C. Barrett, Chemistry and Biochemistry of Amino Acids, Chap-
man and Hall, London, 1985; b) I. Wagner, H. Musso, Angew. Chem.
1983, 95, 827; Angew. Chem. Int. Ed. Engl. 1983, 22, 816.
[2] a) M. Beller, M. Eckert, Angew. Chem. 2000, 39, 1026; Angew. Chem.
Int. Ed. 2000, 39, 1010; b) M. Beller, Med. Res. Rev. 1999, 19, 357; c) K.
Kühlein, H. Geissler in Transition Metals for Organic Synthesis:
Building Blocks and Fine Chemicals (Eds.: M. Beller, C. Bolm),
Willey-VCH, Weinheim, 1998, p. 79.
[3] a) L. F. Tietze, Chem. Rev. 1996, 96, 115; b) L. F. Tietze, U. Beifuss,
Angew. Chem. 1993, 105, 137; Angew. Chem. Int. Ed. 1993, 32, 131.
[4] a) H. Alper, H. des Abbayes, J. Organomet. Chem. 1977, 134, C11;
b) H. des Abbayes, A. Buloup, J. Chem. Soc. Chem. Commun. 1978,
1090.
A possible pathway for the formation of a-amino amides
(Scheme 1) may involve the following sequence: double
carbonylation of the iodoarene to give the a-keto amide,
RNH2
- H2O
Pd/C, CO
O
C
O
PhI + RNH2
Ph
C NH R
NEt3
- RNH3+I-
1
R
R
H2
Pd/C
N
C
O
HN O
Ph
C NH R
Ph CH C NH R
[5] a) F. Ozawa, H. Soyama, T. Yamamoto, A. Yamamoto, Tetrahedron
Lett. 1982, 23, 3383; b) T. Kobayashi, M. Tanaka, J. Organomet. Chem.
1982, 233, C64.
4
2
Scheme 1. Reaction pathway for the double carbohyroamination of
iodobenzene. a: R ˆ cyclohexyl, b: R ˆ n-butyl, c: R ˆ benzyl.
[6] H. Alper, H. Arzoumanian, J.-F. Petrignani, M. Saldana-Maldonado,
J. Chem. Soc. Chem. Commun. 1985, 340.
[7] K. Harada, T. Munegumi in Comprehensive Organic Synthesis, Vol. 8
(Eds.: B. M. Trost, I. Flemming), Pergamon Press, Oxford, 1991,
p. 139.
[8] a) R. Aldea, H. Alper, J. Org. Chem. 1998, 63, 9425; b) Z. Zhou, B. R.
James, H. Alper, Organometallics 1995, 14, 4209.
amine condensation with the a-keto group of the latter to
form an a-imino amide 4 as an intermediate, and hydro-
genation of the imino double bond of 4 to give the a-amino
amide 2. a-Keto amide formation in the double carbonylation
process can be considered to be related to that described by
Yamamoto and co-workers, via formation of an acylcarba-
moylpalladium intermediate followed by reductive elimina-
tion.[12] Palladium-catalyzed double carbonylation of aryl
halides in the presence of a secondary amine to give a-keto
amides has been extensively studied.[13] Using a primary
instead of a secondary amine in the double carbonylation
reaction has only been described in several papers.[5b, 12]
However, the double carbohydroamination reaction se-
quence, described herein can, for the first time, produce a-
amino amides in a one-pot manner. The formation of the
amide by-product results by monocarbonylation of iodoben-
zene. The formation of the by-product imine can be attributed
to competitive reactions of hydroformylation of iodobenzene
with subsequent amine condensation.
[9] a) A. Gringauz, Introduction to Medicinal Chemistry: How Drugs Act
and Why, Wiley-VCH, New York, 1997; b) A. N. Collins, G. N.
Sheldrake, J. Crosby, Chirality in Industry: The Commercial Manu-
facture and Applications of Optically Active Compounds, Wiley,
Chichester, 1992.
1
[10] For details on H and 13C NMR spectroscopy, mass spectrometry, IR
spectroscopy, and elemental analysis of a-amino amides 2 and 5, see
Supporting Information.
[11] It is noteworthy that using a catalyst other than Pd/C, such as the
palladium(0) complex [Pd(PPh3)4] or palladium(ii) complex
[PdCl2(MeCN)2], together with Ph2MeP, gave rise to the formation
of 4a and oxamide CyNHCOCONHCy as major products, respec-
tively.
[12] F. Ozawa, H. Soyama, H. Yanagihara, I. Aoyama, H. Takino, K. Izawa,
T. Yamamoto, A. Yamamoto, J. Am. Chem. Soc. 1985, 107, 3235.
[13] A. Yamamoto, Bull. Chem. Soc. Jpn. 1995, 68, 433, and references
therein.
In conclusion, palladium-catalyzed double carbohydroami-
nation, consisting of double carbonylation, amine condensa-
tion, and hydrogenation, is a novel domino reaction for the
one-pot production of a-amino amides. The reaction is simple
in execution and workup, and is of considerable potential for
the synthesis of a-amino amides and other a-amino acid
derivatives.
A Neutral Three-Coordinate Alkylrhodium(i)
Complex: Stabilization of a 14-Electron Species
by g-C H Agostic Interactions with a Saturated
Hydrocarbon Group**
Heiko Urtel, Claudia Meier, Frank Eisenträger,
Frank Rominger, Jens P. Joschek, and Peter Hofmann*
Experimental Section
Selective activation and functionalization of alkanes by
transition metals is a highly attractive goal[1] which has led to
considerable efforts to understand hydrocarbon interactions
General procedure for the double carbohydroamination: A mixture of
iodobenzene (0.112 mL, 1 mmol), cyclohexylamine (1.14 mL, 10 mmol),
triethylamine (3 mL), Pd/C (10%, 0.0213 g, 0.02 mmol), and 4Š molecular
sieves (1 g) was placed in a 45-mL stainless steel autoclave equipped with a
glass liner and magnetic stirrer. The autoclave was purged three times with
carbon monoxide and then pressurized with CO and H2, respectively, to the
desired level (see Tables 1 and 2). The reaction was carried out in an oil
bath for 24 h and the autoclave was cooled to room temperature and the gas
was released. The reaction mixture was filtered through Celite, washed
several times with CH2Cl2, and filtrate was evaporated to give a pale yellow
oily residue. Addition of ether gave a white precipitate, identified as
[*] Prof. Dr. P. Hofmann, Dipl.-Chem. H. Urtel, Dr. C. Meier,
Dr. F. Eisenträger, Dr. F. Rominger, Dr. J. P. Joschek
Organisch-Chemisches Institut, Universität Heidelberg
Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
E-mail: ph@phindigo.oci.uni-heidelberg.de
‡
[**] This work was supported by the Deutsche Forschungsgemeinschaft
(SFB 247, Graduate College Fellowship to H.U.), by the BASF AG, by
the Degussa-Hüls AG, by the Fonds der Chemischen Industrie, and by
the EU.
CyNH3 I . After filtration, the diethyl ether solution was evaporated and
the resulting oil was subjected to 1H NMR spectroscopy, and then to
preparative TLC, using hexane/ethyl acetate as eluant, affording the pure
a-amino amide.[10]
Supporting information for this article is available on the WWW under
http://www.angewandte.com/ or from the author.
Received: October 18, 2000 [Z15967]
Angew. Chem. Int. Ed. 2001, 40, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4004-0781 $ 17.50+.50/0
781

COMMUNICATIONS
with vacant sites of transition metal centers. Three-coordi-
nate, T-shaped, 14-electron d8-ML3 complexes play a vital role
as key intermediates in many stoichiometric and catalytic
transformations,[2] as exemplified by [RhCl(PPh3)2] from
Wilkinsonꢁs catalyst and its congeners.[2a,3] Usually they are
transient species generated in situ by ligand dissociation[4] or
by hapticity changes of, for example, h3-benzylic systems
[L2M(h3-CH2Ph)] (M ˆ Rh, Ir).[2b,5] Stabilization of 14-elec-
tron d8-ML3 species has been achieved by using bulky trans
ligands in trans-[RhX(PR3)2] complexes (X ˆ H, Hal, s-
carboranyl; R ˆ tBu, iPr, Cy, Ph), but their monomeric nature
is either only postulated or deduced from molecular weight
‡
measurements in solution.[6,7] To date, only [Rh(PPh3)3] ,
[Ni(Mes)3] (Mes ˆ 2,4,6-(CH3)3C6H2), and the olefin com-
plexes [(LN2)Rh(h2-ene)] (LN2 ˆ b-diiminate; ene ˆ cyclo-
octene, norbornene) have been structurally characterized.[8]
Here we report the synthesis, structure, and reactivity of the
first neutral, three-coordinate alkylrhodium(i) complex [(k2-
dtbpm)RhNp] (2), which contains the cis-chelating bis(di-tert-
butylphosphanyl)methane[9] ligand (tBu2PCH2PtBu2, dtbpm)
and a neopentyl (Np) group (Scheme 1). The 14-electron RhI
Figure 1. Molecular structure of
2 (ORTEP plot, 50% probability
ellipsoids, hydrogen atoms omitted for clarity). Selected bond lengths [Š]
and angles [8]: Rh1-P1 2.172(1), Rh1-P2 2.314(1), Rh1-C1 2.082(4), Rh1-C2
2.804, Rh1-C3 2.491(4), C1-C2 1.521(5), C2-C3 1.498(5), C2-C4 1.443(6),
C2-C5 1.463(6); P1-Rh1-P2 75.98(4), C1-Rh1-P1 101.01(11), C1-Rh-P2
176.60(14), Rh1-C1-C2 101.0(2), C1-C2-C3 109.0(3). Estimated Rh H3
(assuming standard C H bond lengths and angles): 1.55 (one H at C3
agostic) or 2.23 (for wedge position of two agostic hydrogen atoms).
Np
Rh N
P
P
P
N
RhP
Np
The unsymmetric chelate ring Rh1-P1-C10-P2 and atoms
C1, C2, and C3 of the neopentyl group are almost coplanar.
The long Rh1 P2 bond (2.314(1) Š) is a consequence of the
strong trans influence of the alkyl ligand, which is also
reflected in the small Rh ± P2 coupling constant[13] 1J(P,Rh) of
99 Hz for P2 (dd, d ˆ 21.6). The short Rh1 P1 bond of
1/2
6
+ N2
1
2.172(1) Š and the correspondingly large J(P,Rh) coupling
P
P
Cl
Rh Rh
Cl
P
P
P
P
Np
L
P
+ NpLi
- LiCl
+ L
constant of 280 Hz for the resonance of P1 (dd, d ˆ 54.2)
indicate a nearly negligible trans influence of the agostic
hydrocarbon moiety.
1/2
Rh
H
Rh
P
CH2
1
2
L =
The nature of this agostic interaction in 2 was studied by
low-temperature 1H NMR spectroscopy in [D8]THF and
[D8]toluene.[11] All three methyl groups of the neopentyl
ligand remain equivalent on the 1H NMR time scale down to
1058C, implying a very small rotational barrier for the
neopentyl tBu group. The methyl doublet resonance
3
PMe3
PPh3
Ph
Ph
+
4
5
P
P
P(tBu)2
P(tBu)2
=
=
dtbpm
- CMe4
CO
P
+
Rh
(2J(H,P) ˆ 2.2 Hz, assigned by H and H{31P} NMR spectra)
at d ˆ 0.83 ( 308C, [D8]THF) confirms time-averaged g-
agostic interactions of all nine C H bonds with the rhodium
center.[14] It is impossible to establish the weak g-C H to Rh
s-complexation through C H bond elongation in the solid-
state structure, because the neopentyl methyl hydrogen atoms
could not be localized. The very short[15] nonbonded Rh1 C3
distance of 2.491(4) Š and the small Rh1-C1-C2 angle
(101.0(2)8), however, clearly reveal an attractive relationship
of the metal center with one or two g-C H bonds and possibly
with the C2 C3 bond in the b-position. In fact, this bond
undergoes clean b-methyl elimination in the isoelectronic
1
1
P
Ph
7
Scheme 1. Synthesis and some reactions of 2.
center is weakly stabilized by agostic interactions with the g-
C H bonds and possibly the b-C C bond of the alkyl ligand.
Owing to the availability of an ªopenº coordination site, 2 is
an ideal model of uncharged three-coordinate d8-[L2Rh(alk-
yl)] transients and of isoelectronic, d8-[L2M(alkyl)] ions
‡
(M ˆ NiII, PdII), intermediates in late transition metal cata-
lyzed olefin polymerization.[10]
Treatment of [{(k2-dtbpm)RhCl}2] (1)[6] with an excess of
NpLi in a pentane suspension at 208C led to air- and
moisture-sensitive 2 in 61% yield.[11] The orange-red com-
pound is moderately stable at 258C as a solid, but solutions of
2 have to be handled at lower temperatures, as rapid,
unselective decomposition is observed above 08C. A single-
crystal X-ray diffraction analysis of 2 revealed the expected
planar T-shaped RhP2C skeleton (Figure 1).[12]
platinum cation [(k2-dtbpm)PtNp] , leading to isobutene and
‡
a metal-bound methyl group.[16] Thus, rhodium compound 2
might resemble a structure on the pathway of b-carbon
elimination at d8-ML2 templates.[17]
Owing to the averaging out of all nine methyl protons of the
Np group by tBu and Me rotations, lowered C ± H streching
frequencies, upfield NMR shifts, or reduced 13C ± 1H coupling
constants for the agostic hydrogen atoms are not observed for
782
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4004-0782 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 4

COMMUNICATIONS
2.[15] However, agostic interactions are unequivocally estab-
lished for the solid-state structure and by all NMR data of 2 in
solution.
structures were established by X-ray diffraction.[12b,c] Unlike 3
and 5, 4 dissociates in solution, forming 2 and PPh3.
Treatment of a solution of 2 in pentane with 1 bar of N2 led
to the precipitation of the air- and moisture-sensitive dinu-
clear, dinitrogen-bridged complex [{(k2-dtbpm)RhNp}2(m-
h1:h1-N2)] (6) (Figure 3).[12b] To our knowledge, 6 represents
the first dinuclear, doubly end-on dinitrogen-bridged, late
transition metal complex with a cis-chelating diphosphane
ligand.[20] Orange, sparingly soluble 6 is stable as a solid at
ambient temperature, but loses N2 in vacuo, undergoing
undefined decomposition. In solution, N2 loss above 108C
regenerates 2.
The inequivalence of the two P nuclei at ambient temper-
ature proves that barrier for T-Y-T inversion at the rhodium
1
center lies well above 20 kcalmol , consistent with theoret-
ical predictions.[6,18]
Agostic interactions in 2 were probed by density functional
theory (DFT) calculations[19] on the model system [(k2-
dhpm)RhNp]
(2a;
dhpm ˆ bis(diphosphanyl)methane,
H2PCH2PH2). Its optimized geometry (Figure 2) is in good
agreement with the solid-state structure of 2 and clearly
displays an agostic C H bond to the vacant coordination site.
Figure 3. Molecular structure of
6 (ORTEP plot, 50% probability
ellipsoids, hydrogen atoms omitted for clarity). Selected bond lengths [Š]
and angles [8]: Rh1-P1 2.258(1), Rh1-P2 2.322(1), Rh1-C1 2.133(4), Rh1-N1
1.973(3), N1-N1' 1.106(6); P1-Rh1-P2 75.35(4), N1-Rh1-C1 92.36(15), N1-
Rh1-P1 166.42(9), N1-Rh-P2 95.99(10), N1'-N1-Rh1 169.56(9).
The alkylrhodium complex 2 also coordinates olefins and
activates C H bonds under mild conditions. The NMR
spectrum recorded for the reaction of a solution of 2 in
[D8]THF with an excess of allylbenzene at 708C indicates
the formation of two transient species. On raising the temper-
ature, these transient species undergo benzylic C ± H activa-
tion and neopentane elimination. The stable allylic complex
[(k2-dtbpm)Rh(h3-1-Ph-C3H4)] (7) is formed as the main
product, which was identified by independent synthesis and
structure determination.[12b] The excess of allylbenzene is
isomerized to trans-b-methylstyrene by 7.
In conclusion, the first neutral, three-coordinate alkylrho-
dium(i) complex with g-C H agostic stabilization of a 14-
electron Rh center by a saturated alkyl ligand has been
isolated and fully characterized. Its pronounced reactivity,
which is based upon facile decoordination of the weakly
bound hydrocarbon chain, makes it a suitable precursor for
investigations of the d8-ML3 chemistry of rhodium and of
unsaturated alkylrhodium complexes; it models intermediates
in, for example, bond activation, hydroformylation, or poly-
merization reactions.
Figure 2. Optimized geometry of the model complex 2a (DFT; some
hydrogen atoms are omitted for clarity). Selected bond lengths [Š] and
angles [8]: Rh1-P1 2.190, Rh1-P2 2.360, Rh1-C1 2.057, Rh1-C2 2.795, Rh1-
C3 2.521, Rh1-H3 1.997, C1-C2 1.541, C2-C3 1.546, C3-H3 1.128; P1-Rh1-P2
74.2, C1-Rh1-P1 99.2, C1-Rh1-P2 173.4, Rh1-C1-C2 101.0, C1-C2-C3 105.2.
The metal-coordinated C3 H3 bond is elongated (1.128 Š
compared to an average of 1.097 Š for the noncoordinated
C H bonds), and the short Rh H3 distance (1.997 Š)
indicates a moderatly strong interaction, which is also
reflected in the computed low C3 ± H3 vibrational frequency
1
of 2723 cm and the short (2.190 Š) Rh P1 distance (as
opposed to Rh P2, 2.360 Š), which establishes the weak
donor character of the agostic C H bond. The NMR
equivalence of the nine methyl protons of 2 corresponds to
tiny calculated barriers to rotation for the methyl
1
1
(0.5 kcalmol ) and tBu groups (2 kcalmol ) for 2a. Neo-
pentyl rotation occurs through a three-coordinate T-shaped
transition state (8.6 kcalmol ) without s complexation of
Received: August 24, 2000
Revised: September 29, 2000 [Z15690]
1
C H bonds.
In NMR experiments, ligands L (L ˆ PMe3, PPh3, CO)
instantaneously react with 2, yielding square-planar com-
plexes [(k2-dtbpm)RhNpL] 3 ± 5 (Scheme 1). Compounds 3
and 5 were synthesized independently from NpLi, [(k2-
dtbpm)RhCl(PMe3)],[6] and [(k2-dtbpm)RhCl(CO)].[6] Their
[1] a) G. Dyker, Angew. Chem. 1999, 111, 1808; Angew. Chem. Int. Ed.
1999, 38, 1698; b) ªActivation of Unreactive Bonds and Organic
Synthesisº: Topics in Organometallic Chemistry, Vol. 3 (Ed.: S. Murai),
Springer, New York, 1999; c) S. S. Stahl, J. A. Labinger, J. E. Bercaw,
Angew. Chem. 1998, 110, 2298; Angew. Chem. Int. Ed. 1998, 37, 2180;
Angew. Chem. Int. Ed. 2001, 40, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4004-0783 $ 17.50+.50/0
783

COMMUNICATIONS
d) A. E. Shilov, G. P. Shulꢁpin, Chem. Rev. 1997, 97, 2879; e) B. A.
Arndtsen, R. G. Bergman, T. A. Mobley, T. H. Peterson, Acc. Chem.
Res. 1995, 504, 154; f) Selective Hydrocarbon Activation. Principles
and Progress (Eds.: J. A. Davies, P. L. Watson, J. F. Liebman, A.
Greenberg), VCH, Weinheim, 1990. g) Activation and Functionaliza-
tion of Alkanes (Ed.: C. L. Hill), Wiley, New York, 1989.
Np hydrogen atoms not localized but considered at calculated
positions. Final agreement factors R(F) ˆ 0.040, wR(F 2) ˆ 0.089 for
observed reflections. Largest peak and hole in the final difference
3
map: 0.70 and
0.70 eŠ
.
b) 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-148676 (2), CCDC-148678
(3), CCDC-148677 (6), and CCDC-148679 (7). 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). c) Structural data for 5: C. Meier, PhD thesis,
Technische Universität München (Germany), 1991.
[2] For typical examples see: 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) P.
Hofmann, C. Meier, W. Hiller, M. Heckel, J. Riede, M. U. Schmidt, J.
Organomet. Chem. 1995, 490, 51, and references therein; c) G. P.
Rosini, F. Liu, K. Krogh-Jespersen, A. S. Goldman, C. Li, S. P. Nolan,
J. Am. Chem. Soc. 1998, 120, 9256.
[3] a) J. A. Osborn, F. H. Jardine, J. F. Young, G. J. Wilkinson, Chem. Soc.
Inorg. Phys. Theor. 1966, 1711; b) J. Halpern, T. Okamoto, A.
Zakhariev, J. Mol. Catal. 1976, 2, 65.
[4] For some examples see: a) T. Sakakura, T. Sodeyama, K. Sasaki, K.
Wada, M. Tanaka, J. Am. Chem. Soc. 1990, 112, 7221; b) P. C. Ford,
T. L. Netzel, C. T. Spillett, D. B. Pourreau, Pure Appl. Chem. 1990, 62,
1091; c) J. A. Maguire, W. T. Boese, M. E. Goldman, A. S. Goldman,
Coord. Chem. Rev. 1990, 97, 179; d) A. Vigalok, Y. Ben-David, D.
Milstein, Organometallics 1996, 15, 1839.
[13] D. W. Meek, T. J. Mazanec, Acc. Chem. Res. 1981, 14, 266.
[14] In all tetracoordinate complexes 3 ± 6 the methyl proton resonance
signals of the neopentyl ligand appear as a singlet. This, in line with
1H{31P} NMR data, excludes 5J coupling of P1 with C3-H atoms
through covalent bonds and establishes direct Rh-H-C contacts trans
to P1 for 2.
[15] M. Brookhart, M. L. H. Green, J. Organomet. Chem. 1983, 250, 395.
[16] R. Voigt, M. R. Meneghetti, H. Urtel, F. Rominger, P. Hofmann,
unpublished results. In contrast to the Pt system, the decomposition of
2 in solution above 08C does not yield isobutene.
[5] a) H. Werner, M. Schäfer, O. Nürnberg, J. Wolf, Chem. Ber. 1994, 127,
27; b) M. Schäfer, N. Mahr, J. Wolf, H. Werner, Angew. Chem. 1993,
105, 1377; Angew. Chem. Int. Ed. Engl. 1993, 32, 1315; c) R. T. Price,
R. A. Anderson, E. L. Muetterties, J. Organomet. Chem. 1984, 367,
407; d) M. D. Fryzuk, D. H. McConville, S. J. Rettig, J. Organomet.
Chem. 1993, 445, 245.
[17] S. P. Ermer, G. E. Struck, S. P. Bitler, R. Richards, R. Bau, T. C. Flood,
Organometallics 1993, 12, 2634, and references therein.
[18] The computed T-Y-T in-plane inversion barrier for the model 2a is
1
31.6 kcalmol
with
a
Y-shaped transition state (NIMAG ˆ 1;
574.2 icm 1).[19]
[19] B3PW91; Stuttgart ± Dresden basis sets with effective core potentials
for Rh and P, 6-31G** basis sets for C and H; for details see
Supporting Information. We thank Dr. E. Clot for technical assistance.
[20] a) D. L. Thorn, T. H. Tulip, J. A. Ibers, J. Chem. Soc. Dalton Trans.
1979, 2022; b) P. R. Hoffmann, T. Yoshida, T. Okano, S. Otsuka, J. A.
Ibers, Inorg. Chem. 1976, 15, 2462; c) A. Vigalok, Y. Ben-David, D.
Milstein, Organometallics 1996, 15, 1839; d) D. W. Lee, W. C. Kaska,
C. M. Jensen, Organometallics 1998, 17, 1.
[6] P. Hofmann, C. Meier, U. Englert, M. U. Schmidt, Chem. Ber. 1992,
125, 353, and references therein.
[7] a) H. L. M. Van Gaal, F. L. A. Van Den Bekerom, J. Organomet.
Chem. 1977, 134, 237; b) T. Yoshida, T. Okano, S. Otsuka, J. Chem.
Soc. Chem. Commun. 1978, 855; c) T. Yoshida, T. Okano, D. L. Thorn,
T. H. Tulip, S. Otsuka, J. A. Ibers, J. Organomet. Chem. 1979, 181, 183;
d) H. Werner, A. Höhn, M. Dziallas, Angew. Chem. 1986, 98, 1112;
Angew. Chem. Int. Ed. Engl. 1986, 25, 1090; e) J. Wolf, L. Brandt, A.
Fries, H. Werner, Angew. Chem. 1990, 102, 584; Angew. Chem. Int. Ed.
Engl. 1990, 29, 510; f) D. Schneider, H. Werner, Angew. Chem. 1991,
103, 710; Angew. Chem. Int. Ed. Engl. 1991, 30, 700; g) S. Bresadola, B.
Longato, Inorg. Chem. 1974, 13, 539.
[8] a) S. Alvarez, Coord. Chem. Rev. 1999, 193 ± 195, 13; b) Y. W. Yared,
S. L. Miles, R. Bau, C. A. Reed, J. Am. Chem. Soc. 1977, 99, 7076;
c) R. S. Hay-Motherwell, G. Wilkinson, T. K. N. Sweet, M. B. Hurst-
house, Polyhedron 1996, 15, 3163; d) P. H. M. Budzelaar, N. N. P.
Moonen, R. de Gleder, J. M. M. Smith, Eur. J. Inorg. Chem. 2000, 753.
[9] a) H. H. Karsch, Z. Naturforsch. B 1983, 38, 1027; b) H. Heiss, P.
Hofmann (BASF AG), DE-A 4134772A, 1992.
YBa2Cu3O6‡d as an Oxygen Separation
Membrane**
Chu-sheng Chen,* Shen Ran, Wei Liu, Ping-hua Yang,
Ding-kun Peng, and Henny J. M. Bouwmeester
[10] S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 2000, 100, 1169,
and references therein.
High-Tc superconducting oxides exhibit fast oxygen trans-
fer across the interface between gas and solid phase and
diffusion in the bulk at elevated temperatures.[1, 2] This is of
crucial importance to the fine-tuning of the superconductivity
by intercalating oxygen into the oxides to oxidize the copper
ions. The fast oxygen transport kinetics may also be used to
develop oxygen-semipermeable dense membranes, which
have potential applications in oxygen production and oxy-
[11] NMR data of
2 (for the data in [D8]toluene see Supporting
Information): 31P{1H} NMR (121 MHz, [D8]THF, 308C): d ˆ 54.2
(dd, 1J(P,Rh) ˆ 280.0, 2J(P,P) ˆ 22.1 Hz;
P cis to Np); 21.6 (dd,
1J(P,Rh) ˆ 99.3, 2J(P,P) ˆ 22.1 Hz;
P
trans to Np); 1H NMR
(500 MHz, [D8]THF,
308C): d ˆ 3.00 (t, 2J(H,P) ˆ 7.3 Hz, 2H;
PCH2P), 1.42 (d, 3J(H,P) ˆ 12.7 Hz, 18H; tBu cis to Np), 1.37 (d,
3J(H,P) ˆ 11.5 Hz, 18H; tBu trans to Np), 0.83 (d, 2J(H,P) ˆ 2.2 Hz,
9H; CH2C(CH3)3,
‡
13C satellites: 1J(H,C) ˆ 121 Hz), 0.40 (dm,
3J(H,P) ˆ 5.3 Hz, 2H; RhCH2); 13C{1H} NMR (75 MHz, [D8]THF,
258C): d ˆ 43.9 (t, J ˆ 3.4 Hz; CMe3 from Np), 38.8 (d, J ˆ 10.6 Hz;
PCH2P), 36.9 (m, J ˆ 5.3 Hz; PCMe3 cis to Np), 35.0 (dd, J ˆ 5.9 Hz,
J ˆ 3.0 Hz; PCMe3 trans to Np), 31.6 (m; PC(CH3)3), 28.7 (t, J ˆ
4.9 Hz; (CH3)3, Np), 20.0 (m; RhC).
[*] Prof. C.-s. Chen, S. Ran, Dr. W. Liu, P.-h. Yang, Prof. D.-k. Peng
Laboratory of Internal Friction and Defects in Solids
Department of Materials Science and Engineering
University of Science and Technology of China
Hefei, Anhui 230026 (P.R. China)
[12] a) Single crystals were obtained by slowly concentrating a solution of 2
in Et2O at 158C by solvent evaporation. Crystal dimensions 0.37 Â
0.20  0.10 mm3, monoclinic, space group P21/n, Z ˆ 4, a ˆ 9.4062(1),
b ˆ 19.1825(1), c ˆ 14.2169(2) Š, b ˆ 92.462(1)8, Vˆ 2562.85(5) Š3,
1calcd ˆ 1.240 gcm 1, 2qmax ˆ 55.08, l(MoKa) ˆ 0.71073 Š, 0.38 w scans,
Tˆ 200 K, 26061 reflections collected, 5883 unique, 4379 observed
with I > 2s(I). Corrections for absorption were applied (program
SADABS), m ˆ 0.795 mm 1, Tmin ˆ 0.75, Tmax ˆ 0.94. The structure was
solved by Patterson methods and refined by full-matrix least-squares
methods on F 2 (program SHELXTL (5.10)), 271 parameters refined.
Fax : (‡86)551-3631760
E-mail: ccsm@ustc.edu.cn
Dr. H. J. M. Bouwmeester
Department of Chemical Technology, University of Twente
P.O. Box 217, 7500 AE Enschede (The Netherlands)
[**] This work was supported by the National Natural Science Foundation
of China and the National Advanced Materials Committee of China.
784
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4004-0784 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 4