Ambiphilicity: A characteristic reactivity principle of π-bound phosphorus heterocycles

Article abstract of DOI:10.1002/1521-3773(20021104)41:21<4047::AID-ANIE4047>3.0.CO;2-4

Bicycles made in crystals: The phosphorus atoms of the: π ligand 1,3-diphosphete turn out to be ambiphilic centers with pronounced intramolecular reactivity. This property results in a temperature-dependent bond formation in [(2,4-di-tBu-1,3-diphosphete)<

Full text of DOI:10.1002/1521-3773(20021104)41:21<4047::AID-ANIE4047>3.0.CO;2-4

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[15] K. Matyjaszewski, Macromolecules 1993, 26, 1787 1788.
[16] R. O©Dell, D. H. McConville, G. E. Hofmeister, R. R. Schrock, J. Am.
Chem. Soc. 1994, 116, 3414 3423.
Experimental Section
All experiments were performed under a nitrogen atmosphere in a glove
box (MBraun) or by using standard Schlenk techniques. [Mo(N-2,6-iPr2-
C6H3)(CHCMe2Ph)(OTf)2¥DME,
Ph)(OTf)2]¥DME, and [Mo(N-2,6-iPr2-C6H3)(CHCMe2Ph)(OC(CH3)3)2]
(1) as well as other compounds were prepared following literature
procedures.[20] Experimental details can be found in the Supporting
Information.
[17] R. R. Schrock, Polyhedron 1995, 14, 3177 3195.
[18] J. H. Oskam, R. R. Schrock, J. Am. Chem. Soc. 1992, 114, 7588 7590;
J. H. Oskam, R. R. Schrock, J. Am. Chem. Soc. 1993, 115, 11831
11845.
[19] R. Schlund, R. R. Schrock, W. E. Crowe, J. Am. Chem. Soc. 1989, 111,
8004 8006; R. R. Schrock, W. E. Crowe, G. C. Bazan, M. DiMare,
M. B. O©Regan, M. H. Schofield, Organometallics 1991, 10, 1832
1043.
[Mo(N-2,6-Me2-C6H3)(CHCMe2-
Received: May 6, 2002 [Z19234]
[20] J. H. Oskam, H. H. Fox, K. B. Yap, D. H. McConville, R. O©Dell, B. J.
Lichtenstein, R. R. Schrock, J. Organomet. Chem. 1993, 459, 185 197.
[1] T. A. Skotheim, R. L. Elsenbaumer, J. R. Reynolds, Handbook of
Conducting Polymers, 2nd ed., Dekker, New York, 1997; J. L. Brÿdas,
R. Silbey in Conjugated Polymers, Kluwer, Dordrecht, 1991; A. J.
Heeger, Angew. Chem. 2001, 113, 2660 2682; Angew. Chem. Int. Ed.
2001, 40, 2591 2611; A. G. MacDiarmid, Angew. Chem. 2001, 113,
2649 2659; Angew. Chem. Int. Ed. 2001, 40, 2581 2590; H. Shir-
akawa, Angew. Chem. 2001, 113, 2642 2648; Angew. Chem. Int. Ed.
2001, 40, 2574 2580; T. Masuda, S. M. Abdul Karim, R. Nomura, J.
Mol. Catal. A 2000, 160, 125 131.
Ambiphilicity: A Characteristic Reactivity
Principle of p-Bound Phosphorus
Heterocycles**
[2] H. H. Fox, R. R. Schrock, Organometallics 1992, 11, 2763 2765.
[3] H. H. Fox, M. O. Wolf, R. O©Dell, B. L. Lin, R. R. Schrock, M. S.
Wrighton, J. Am. Chem. Soc. 1994, 116, 2827 2843.
Christian Topf, Timothy Clark,*
Frank W. Heinemann, Matthias Hennemann,
Susanne Kummer, Hans Pritzkow, and
Ulrich Zenneck*
[4] J. K. Stille, D. A. Frey, J. Am. Chem. Soc. 1961, 83, 1697 1701; H. W.
Gibson, A. J. Epstein, H. Rommelmann, D. B. Tanner, X. Q. Yang,
J. M. Pochan, J. Phys. Colloq. 1983, C3, 651 656.
[5] K. J. S. Harrell, S. T. Nguyen, Abstr. Pap. Am. Chem. Soc. 1999, 217,
121.
[6] S.-K. Choi, Y.-S. Gal, S.-H. Jin, H.-K. Kim, Chem. Rev. 2000, 100,
1645 1616.
[7] C. Sivakumar, T. Vasudevan, A. Gopalan, T.-C. Wen, Polymer 2002,
43, 1781 1787.
[8] M. R. Buchmeiser, Chem. Rev. 2000, 100, 1565 1604.
[9] F. J. Schattenmann, R. R. Schrock, W. M. Davis, J. Am. Chem. Soc.
1996, 118, 3295 3296; F. J. Schattenmann, R. R. Schrock, Macro-
molecules 1996, 29, 8990 8991.
[10] M. Buchmeiser, Macromolecules 1997, 30, 2274 2277.
[11] S.-H. Kim, Y.-H. Kim, H.-N. Cho, S.-K. Kwon, H.-K. Kim, S.-K. Choi,
Macromolecules 1996, 29, 5422 5426.
Dedicated to Professor Gottfried Huttner
on the occasion of his 65th birthday.
ꢀ
Cyclooligomerization of phosphaalkynes, such as tBuC P
(1), in the coordination sphere of reactive metal complexes
predominantly leads to p complexes of the cyclodimer 1,3-
diphosphete[1 4] or the cyclotrimer 1,3,5-triphosphabenzene.[5]
However, pentaphosphametallocenes, such as the pentaphos-
phaferrocene derivative 2, are obtained with reactive iron
complexes[6,7] or free metal atoms.[8] Their formation requires
[12] R. R. Schrock, S. Luo, N. Zanetti, H. H. Fox, Organometallics 1994,
13, 3396 3398; R. R. Schrock, S. Luo, J. C. Lee, Jr., N. C. Zanetti,
W. M. Davis, J. Am. Chem. Soc. 1996, 118, 3883 3895.
ꢁ
that at least one P C triple bond be broken (Scheme 1).
Oligophosphametallocenes are easily accessible substances
with a series of interesting properties.[9] Thus, there is much
interest in determining the mechanism of their formation.
Because complete cleavage of 1 is very unlikely, even at a
transition-metal center, we assume that initially formed
cycloaddition products from 1 undergo intra- or intermolec-
[13] M. R. Buchmeiser, N. Schuler, N. Kaltenhauser, K.-H. Ongania, I.
Lagoja, K. Wurst, H. Schottenberger, Macromolecules 1998, 31, 3175
3183; M. R. Buchmeiser, N. Schuler, H. Schottenberger, I. Kohl, A.
Hallbrucker, K. Wurst, Des. Monomers Polym. 2000, 3, 421 446.
[14] G. M. Sheldrick, SHELXL-93: Program for the Refinement of Crystal
Structures, University of Gˆttingen, Gˆttingen (Germany), 1993;
G. M. Sheldrick, SHELXS-86: Program for Crystal Structure Solu-
tions, University of Gˆttingen, Gˆttingen (Germany), 1986; Z.
Otwinowski, W. Minor, Methods Enzymol. 1996, 276 Crystal size:
[*] Prof. Dr. U. Zenneck, Dipl.-Chem. C. Topf, Dr. F. W. Heinemann,
Dr. S. Kummer
ꢀ
0.4 î 0.25 î 0.1 mm, triclinic, P1 (No. 2), a ¼ 1025.99(4), b ¼
1031.93(6), c ¼ 1273.37(9) pm, a ¼ 86.885(3), b ¼ 89.483(3), g ¼
Institut f¸r Anorganische Chemie der Universit‰t
Egerlandstrasse 1, 91058 Erlangen (Germany)
Fax : (þ 49)9131-852-7367
81.720(4)8, V¼ 1.33216(13) nm3, m ¼ 0.512 mmꢁ1
1.60 ꢂ q ꢂ 22.978,
,
MoKa radiation (l ¼ 0.71073 ä), T¼ 233(2) K, reflections collected:
6249; independent reflections: 3670 (Rint ¼ 0.0223); Reflections with
I > 2s(I): 3294, Absorption correction: none; Refinement method:
Full-matrix least-squares on F2; Final R indices [I > 2s(I)]: R1 ¼
E-mail: zenneck@chemie.uni-erlangen.de
Priv.-Doz. Dr. T. Clark, Dipl. Chem. M. Hennemann
Computer-Chemie-Centrum der Universit‰t
N‰gelsbachstrasse 25, 91054 Erlangen (Germany)
Fax : (þ 49)9131-852-6565
0.0290, wR2 ¼ 0.0675;
R
indices (all data); R1 ¼ 0.0353, wR2 ¼
0.0706; Intensities were integrated using DENZO and scaled with
SCALEPACK. Structures were solved with direct methods and
refined against F2. Hydrogen atoms were added geometrically and
refined using a riding model except at the carbene atom C1, for which
they were refined as regular atoms with an isotropic displacement
parameter. All non-hydrogen atoms were refined with anisotropic
displacement parameters. CCDC-179436 contains 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, Cam-
bridge CB21EZ, UK; fax: (þ 44)1223-336-033; or deposit@ccdc.ca-
m.ac.uk).
E-mail: clark@chemie.uni-erlangen.de
Dr. H. Pritzkow
Anorganisches-Chemisches Institut der Universit‰t
Im Neuenheimer Feld 270, 69121 Heidelberg (Germany)
[**] This work was supported by the Deutschen Forschungsgemeinschaft
and the Fonds der Chemischen Industrie. M.H. and C.T. thank DFG-
Graduiertenkolleg 167 Phosphorchemie als Bindeglied verschiedener
chemischer Disziplinen (University of Kaiserslautern) for fellowships.
Supporting information for this article is available on the WWW under
http://www.angewandte.org or from the author.
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tBu
P
tBu
P
P
FeLn + n tBuC
P
Fe
tBu
– n L
1
P
P
tBu
tBu
2
Ln = (arene)(diene); (cot)2
Scheme 1. Formation of pentaphosphaferrocene 2.
ular interactions with each other that allow the exchange of
phosphorus atoms or tBuC-fragments under mild conditions.
One convincing indication that this is the case, the observation
of strong intramolecular interactions between Mo-coordinat-
ed 1,3-diphosphete ligands is reported herein. These inter-
actions serve as a novel model for the initial step in the
exchange of ring components of p-coordinated P hetero-
cycles.
Figure 1. Side view of the superimposed molecular structures of 4 in the
single crystal at 100 K (4a, full lines) and at 293 K (4b, dashed lines). The
tBu groups of the rings have been omitted for clarity.[13] Selected distances
4a {4b} [D ¼ 4a 4b] in pm: Mo1-C2 256.69(19) {254.2(3)} [ þ 2.48], C2-C21
157.6(3) {156.2(4)} [ þ 1.4], C1-P1 179.3(3) {181.5(3)} [ꢁ2.2], C2-P1 189.3(2)
{186.4(3)} [ þ 2.9], C3-P3 181.5(2) {180.1} [ þ 1.4], C1-P5 275.9(13)
{251.0(21)} [ þ 24.9], C2-P3 198.8(2) {215.1(4)} [ꢁ16.3].
We treated fac-[Mo(CH3CN)3(CO)3] with 1, with the aim of
synthesizing [Mo(CO)2(2,4-di-tBu-1,3-diphosphete)2] (3). In
contrast to earlier reactions of molybdenum carbonyl com-
plexes with 1,[10,11] we were able to isolate 3 as the main
product. However, to our surprise we also found the known
complex [Mo(2,4-di-tBu-1,3-diphosphete)3] (4) as a by-prod-
uct. The published molecular structure of 4 in the solid state
shows an unusual feature, the P C separation between two of
the rings is only 215 pm, a very short distance that is hard to
explain (Scheme 2).[12]
Structures 4a and 4b are very similar, in accord with the
requirements of a topotactic reaction.[14] The main fragment
{Mo(C3P3C4P4)(C5P5C6P6)} only changes minimally,
whereas in 4a C1P1C2P2 has moved towards the C3P3C4P4
ring. The unusually short inter-ring separation C2 P3 de-
creases from 215.1 (4b) to 198.8 pm (4a), a distance that is
consistent with a slightly stretched single bond.[15] The short-
ening of this separation by 16.3 pm occurs concurrently with a
lengthening of the inter-ring distance C1 P5 by 24.9 pm and a
localization of the p interaction in the C1P1C2P2 ring in 4a.
The other rings, in contrast, are delocalized, with essentially
ꢁ
ꢁ
equivalent bond lengths. The bonds C2 P1 and C2 P2 with
fac-[Mo(CH3CN)3(CO)3] + 4 tBuCP
ꢁ
an average length of 189.2 pm correspond to P C single
THF,
reflux, 8 h
ꢁ
ꢁ
bonds, whereas the C1 P1 and C1 P2 separations (179.2 and
179.3 pm, respectively, see Supporting Information for num-
ꢁ
bering scheme) suggest significant P C double bond charac-
ter.
tBu
tBu
An almost identical structural unit is found in 5, the iron
complex of a polycyclic heptamer of 1. The four-membered
P
P
P
P
tBu
tBu
tBu
tBu
tBu
CO
CO
Mo
+
Mo
R
P
P
P
P
R
P
P
P
P
P
P
R
R
tBu
tBu
tBu
Fe
R
P
R
3
4
P
Scheme 2. Formation of (1,3-diphosphete) Mo complexes.
R
P
Differences to the published data[12] obtained at low
temperatures led us to investigate the structural chemistry
of 4 more closely. We therefore performed single-crystal
analyses at temperatures of 100, 150, 200, 240, and 293 K. An
intramolecular, fully reversible topotactic reaction between
the ligands of 4 is observable in the crystal structures. Figure 1
shows the superposition of the two extremes of the molecular
structures of 4 at 100 (4a) and 293 K (4b). Structure 4b is
identical to the published data within the margins of error
(Figure 1).[12,13]
R = tBu
5
ring in 5 is clearly 1,3-diphosphetenyl, an sp3-carbon-bridged
p-coordinated diphosphaallyl system. The two P C separa-
tions of the diphosphaallyl unit in 5 are 178 pm and the
ꢁ
intraannular P C single bonds are 191 and 192 pm long
(Scheme 3).[16]
The same interpretation seems appropriate for 4a. The P C
contact between the rings, which is short even at room
temperature, is so strengthened at low temperatures that the
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substituted prototype compound 7 were performed to aid the
analysis of the bonding situation in 4. The calculations used
Gaussian 98[19] with the B3LYP hybrid functional[20] and the
LanL2DZ basis set.[21] The basis set was extended with a set of
d-functions with exponents of 0.6 and 0.34 on C and P,
respectively, and p-functions with an exponent of 0.072 on the
Mo center.[22] Reaction paths in which the P3 C2 separation
(comparable to C1 P5) was varied from 180 to 260 pm were
calculated for the model compounds. The resulting energy
profile for 6 is shown in Figure 3.
R
R
P
P
P
P
P
P
R
P
R
R
R
R
R
100 K
293 K
Mo
Mo
P
P
P
P
P
R
R
R
R
4b
4a
Scheme 3. Molecular description of the topotactic bond formation.
C2 P3 interaction can be seen as a covalent bond. Atom C2 is
converted into an sp3-hybridized center on formation of this
bond and thus C2 no longer contributes to the delocalized
ꢁ
p system of the ring and the Mo1 C2 bond is broken. Both
ꢁ
the formation of the P3 C2 bond and the lengthening of the
inter-ring distance between C1 and P5 occur continuously
within the temperature range investigated and are fully
reversible (Figure 2).
Figure 3. Calculated reaction profile for 6a!6b.
Two isoenergetic minima with Cs symmetry and P3 C2 (or
P5 C1) distances of 201.4 pm (6a) and a 3.5 kcalmolꢁ1 less
stable C2v transition structure (6b) were obtained for the
methyl-substituted compound (Figure 4). In contrast, the
prototype compound 7 gives a broad, flat energy profile
without a definitive structural preference. The Cs structure 6a
agrees surprisingly well with that found experimentally at
100 K in the crystal (4a). Even the critical C2 P3 and Mo1 C2
distances are almost identical. Larger differences are found
for the nonbonding inter-ring distances C1 P5 (306.0 com-
Figure 2. Temperature dependence of the P3 C2 and P5 C1 separations
in pm. 100 K: P3-C2 198.8(2), P5-C1 275.9(13); 150 K: 200.3(6), 273.0(14);
200 K: 204.0(1), 266.2(16); 240 K: 209.6(1), 259.0(15); 293 K: 215.1(4),
251.0(21).
To our knowledge such intramolecular bond-for-
mation reactions between p ligands at metal centers
have not been described before. The structural type of
the new bicyclic ligand is also without precedence.
Reversible chemical reactions in which single crystals
are conserved are also very rare, at least for metal
complexes.[17] To explain this phenomenon qualita-
tively we assume a nucleophilic attack of the lone pair
of P3 on C2. The total number of electrons supplied
by the ligands in 4a remains constant despite the loss
ꢁ
of the Mo1 C2 bond because the 1,3-diphosphaallyl
fragment can be regarded as a formal anion. In
contrast, the aromaticity of the C3P3C4P4-ring is
retained, as shown by quantum-mechanical calcula-
tions (see below). Thus, P3 formally forms a pyrami-
dal phosphonium center, a further interesting struc-
tural detail.[18]
Figure 4. Calculated structures and NICS-1-values for the minimum-energy structure
6a and the transition state 6b from 6. Selected distances 6a {6b} [D ¼ 6a 6b] in pm,
the numbering is analogous to 4: Mo1-C2 256.9 {245.8} [ þ 11.1], C2-C21 154.2 {152.3}
[ þ 1.9], C1-P1 180.3 {184.5} [ꢁ4.2], C2-P1 192.7 {184.5} [ þ 8.2], C3-P3 186.6 {182.3} [ þ
4.3], C3-P4 185.4 {185.1} [ þ 0.3], C1-P5 306.0 {260.7} [ þ 45.3], C2-P3 201.4 {260.7}
[ꢁ59.3]. Selected Wiberg bond orders 6a {6b}: Mo1-C2 0.1966 {0.3688}, Mo1-P3 0.2678
{0.3177}, C2-C21 1.0253 {1.0611}, C1-P1 1.0995 {0.9808}, C2-P1 0.8577 {0.9808}, C3-P3
0.9063 {1.0081}, C3-P4 0.9686 {0.9525}, C1-P5 0.1044 {0.2458}, C2-P3 0.6940 {0.2458}.
DFT calculations on the model compound [Mo{t-
ris(2,4-dimethyl-1,3-diphosphete)}] (6) and the un-
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pared to 275.9 pm) and P4 P6 (263.0 compared to 278.0 pm).
These differences are probably caused by simplifying the
substituents from tBu to methyl and do not decrease the value
of the modeling exercise significantly.
Wiberg bond orders[23] were used to analyze the bonding
situation. These support the interpretation derived from the
structural data. This is most clearly seen in the P3 C2
interaction, for which a bond order of 0.69 is found in 6a,
compared with only 0.25 in 6b. The value for the Mo1 C2
interaction decreases significantly (from 0.37 to 0.20) on going
from 6b to 6a, but the Mo1 P3 interaction is weakened far
less (from 0.32 to 0.27). Thus the Mo1-C3P3C4P4 fragment is
tBu
P
P
tBu tBu
CO
CO
Mo
P
P
tBu
3
1. nBuLi
2. H2O/Al2O3
ꢁ
almost unaffected by the inter-ring P3 C2 bond formation,
ꢁ
whereas the Mo1 C2 bond is weakened significantly, which
tBu
results in the Mo diphosphaallyl system Mo1-C1P1P2. The
tBu
ꢁ
ꢁ
P
H
C1 P1 and C1 P2 bonds become stronger (bond order:
ꢁ
ꢁ
P
0.98!1.10) and those between C1 P1 and C2 P2 weaker
(bond order: 0.98!0.86). Identical conclusions can be
reached from the calculated nucleus independent chemical
shifts (NICS)[24] (Figure 4), which describe the cyclic delocal-
ization of the p electrons (i.e. the aromaticity of the ligands),
and from the net atomic charges obtained from a natural
population analysis (NPA).[25] According to these criteria, the
aromaticity of the 1,3-diphosphetenyl ring C1P1C2P2 de-
creases significantly, whereas it actually increases slightly for
the C3P3C4P4-ring. The NPA shows P3 in 6a to be 0.1 more
positive than in 6b, whereas C2 becomes ꢁ0.15 more
negative. This suggests a partial charge-transfer from P3 to
C2. The NPA charges are thus in accord with the formal view
of a nucleophilic attack of P3 on C2. As all the calculated
parameters for 6a agree well with the experimentally
determined structure for 4a, we conclude that 4a represents
the real thermodynamic minimum for the complex 4. The
influence of the tBu substituents and the crystal lattice on the
bonding within the ligands is therefore of secondary impor-
tance. However, the lattice forces allow for the synchroniza-
tion of the intramoleular reaction in the crystal, which can
thus take place topotactically.
P
P
H
H
tBu
tBu tBu
tBu
nBu
CO
CO
+
Mo
CO
CO
Mo
P
P
H
P
P
tBu
tBu
nBu
nBu
nBu
8
9
Scheme 4. The addition of nucleophiles.
components leads us, however, to the central question of this
project. The constitution and the molecular structures of 8 and
9 show that Mo0-coordinated 1,3-diphosphete ligands are
electrophilic. However, the initial attack of the nucleophile
occurs at the phosphorus atom, analogously to the situation
found for the cation of the salt [Mo(CO)2(indenyl)(2,4-di-tBu-
1,3-diphosphete)]þBF4ꢁ.[29] The reaction sequence is complet-
ed for 8 by a stereoselective protonation of the metal side of
the phosphorous atom, which is evidence for the entry of the
carbanion from outside.[26] A heteroallyl system is formed, as
in the case of 4a, but in this case it is a 2-phosphaallyl.
Because, however, a ring carbon atom plays the role of the
electrophile in the intramolecular reaction, but a phosphorous
atom plays the role of the electrophile in the intermolecular
version, the electrophilicity of these two different types of ring
atom in (1,3-diphosphete)Mo0 units cannot be very different.
The ambiphilicity of 1,3-diphosphete ligands caused by the
phosphorus atoms is a characteristic that has not been
observed previously in this type of complex. We can only
begin to judge the effect of this ambiphilicity on the reactivity
of the complexes because 1,3-diphosphete complexes have
proven to be very robust.[30] The polydentate ligand in 9 shows
that the ambiphilic intramolecular reactivity of 1,3-diphos-
phete ligands can also operate despite strong competition
from other nucleophiles. The P2 C18 bond between the
remaining ring and its new side chain is the result of an
intramolecular step although three carbanions are added to
one ring. The ring that is attacked thus not only loses its
p system, but is also ring-opened.
Thus, 1,3-diphospete ligands display electrophilic character
additionally to their inherent nucleophilicity; they are thus
ambiphilic. There is only one report of the electrophilicity of
neutral diphosphete complexes.[26] Therefore, to test our
hypothesis, we treated 3 with nBuLi as the nucleophile and
protonated the resulting reaction products. In this
way we were able to add one or three n-butyl groups to
obtain [Mo(CO)2(1,3-diphosphete)(1,3-diphosphetenyl)] (8)
and [Mo(CO)2(1,3-diphospheten-3-diphosphaoctyl)] (9;
Scheme 4, Figure 5).[27]
Both of these complexes have structures that make a
detailed theoretical analysis necessary. These investigations
are not yet complete. The bonding situation of the P1C1P2C6
four-membered ring in 9 is particularly difficult to understand.
Although there seem to be no obstacles to the formation of a
phosphaallyl system in the protonation step, as found in 8, this
does not occur, but rather a 1,3-diphosphetene ligand that can
only contribute two p electrons to the metal center is formed.
The metal attempts nevertheless to attain an 18 valence
electron structure by an agostic interaction (C6H1¥¥¥Mo1).[28]
The unequivocably determined connectivity of the molecular
1,3-Diphosphetes, and probably other unsaturated P he-
terocycles, can, by reason of their ambiphilicity, take part in
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the heptamer ligand in 5,[16] or the formal addition product of
coordinated 1,3-diphosphetes or 1-phosphetes with phos-
phaalkynes. In these cases, p-coordinated phosphaallyl struc-
tures are found once again.[32]
Received: April 23, 2002 [Z19142]
[1] P. Binger, R. Milczarek, R. Mynott, M. Regitz, W. Rˆsch, Angew.
Chem. 1986, 98, 645; Angew. Chem. Int. Ed. Engl. 1986, 25, 644; P.
Binger, R. Milczarek, R. Kr¸ger, Y.-H. Tsay, E. Raabe, M. Regitz,
Chem. Ber. 1988, 121, 637.
[2] P. B. Hitchcock, M. J. Maah, J. F. Nixon, J. Chem. Soc. Chem.
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[3] P. Binger, B. Biedenbach, R. Schneider, M. Regitz, Synthesis 1989, 960.
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Engl. 1987, 26, 908; P. Binger, S. Leininger, J. Stannek, B. Gabor, M.
Mynott, J. Bruckmann, C. Kr¸ger, Angew. Chem. 1995, 107, 2411;
Angew. Chem. Int. Ed. Engl. 1995, 34, 2227; F. Tabellion, A.
Nachbauer, S. Leininger, C. Peters, M. Regitz, F. Preuss, Angew.
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W. Rˆsch, J. Organomet. Chem. 1987, 334, C35.
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D. M. Vickers, Angew. Chem. 1994, 106, 2406; F. G. N. Cloke, K. R.
Flower, P. B. Hitchcock, J. F. Nixon, J. Chem. Soc. Chem. Commun.
1995, 1659.
[9] P. Lemoine, M. Gross, P. Braunstein, F. Mathey, B. Deschamps, J. H.
Nelson, Organometallics 1984, 3, 1303; R. F. Winter, W. E. Geiger,
Organometallics 1999, 18, 1827; B. Breit, J. Mol. Catal. A 1999, 134,
143; B. Breit, R. Paciello, B. Gei˚ler, M. Rˆper BASF AG, Germany,
DE 196 21 967 A1 1997 [Chem. Abstr. 1998, 128, 129496]; R. Paciello,
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Ganter, Chem. Eur. J. 1998, 4, 2148; C. Ganter, C. Kaulen, U. Englert,
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199670]; E. J. M. Boer, I. Gilmore, F. Korndorfer, A. D. Horton, J.
Figure 5. Molecular structures of 8 (298 K) and 9 (100 K). All hydrogen
atoms except H3 and the methyl groups on the quaternary carbons C2 and
C7 in 8 have been omitted for clarity. All hydrogens are ommitted in 9
except H6.[27]
œ
Mol. Catal. A 1998, 128, 155; E. Urnÿzius, W. W. Brennessel, C. J.
Cramer, J. E. Ellis, P. v. Raguÿ Schleyer, Science 2002, 295, 832.
[10] P. Binger in Multiple Bonds and Low Coordination in Phosphorus
Chemistry (Eds.: M. Regitz, O. J. Scherer), G. Thieme, Stuttgart, 1990,
p. 96.
nucleophilic or electrophilic intramolecular interactions. This
situation is a new starting point for determining the complex
reaction sequences of p ligands with lone pairs in the
coordination spheres of metal centers, which, for instance,
we must assume to take place in the formation of pentaphos-
phametallocenes from phosphaalkynes. If we assume the
process that forms 1,3-diphosphete and 1,3,5-triphosphinine
ligands[1 5] to be the first step, as discussed in the introduction,
[11] M. Scheer, J. Krug, Z. Anorg. Allg. Chem. 1998, 624, 399.
[12] F. G. Cloke, K. R. Flower, P. B. Hitchcock, J. F. Nixon, J. Chem. Soc.
Chem. Commun. 1994, 489.
ꢀ
[13] Crystal data for 4: C30H54MoP6, Mr ¼ 696.49, triclinic, space group P1.
Measurements taken with a Bruker AXS Smart1000 area detector
(MoKa radiation, l ¼ 0.71073 ä, graphite monochromator) at 100, 150,
200, 240, 293 K up to V¼ 328. The structure was solved with direct
methods, least-squares refinement against F2 (SHELXTL NT
V5.10).[33] Cell parameters at 100 K (4a): a ¼ 10.7538(14) b ¼
11.0127(14), c ¼ 14.9561(19) ä; a ¼ 79.585(3), b ¼ 74.568(3), g ¼
ꢁ
a P C bond can be formed between the ligands as in 4. We
have used preliminary DFT calculations for [Fe(1,3-diphos-
phete)(1,3,5-triphosphinine)] to investigate the viability of
this approach. Given this linkage between the ligands, there
are no more fundamental theoretical problems in the
exchange of ring components.
89.650(3)8; V¼ 1677.6(4) ä3; Z ¼ 2; 1calcd ¼ 1.379 gcmꢁ3
;
m ¼
0.696 mmꢁ1; F(000) ¼ 732. R1 ¼ 0.0354 (for 10962 Reflections with
I > 2s(I), wR2 ¼ 0.0925 (for all data).
Cell parameters at 293 K (4b): a ¼ 10.7548(12), b ¼ 11.0149(13), c ¼
15.3513(18) ä, a ¼ 78.310(2), b ¼ 74.916(2), g ¼ 87.842(2)8, V¼
1719.3(3) ä3; Z ¼ 2; 1calcd ¼ 1.345 gcmꢁ3; m ¼ 0.679 mmꢁ1; 8524 inde-
pendent reflections. R1 ¼ 0.0373 (for 8524 reflections with I > 2s(I),
wR2 ¼ 0.089 (for all data). CCDC 184248 184252 (4 at 100, 150, 200,
240, and 293 K) contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge via www.ccdc.ca-
m.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB21EZ, UK;
fax: (þ 44)1223-336-033; or deposit@ccdc.cam.ac.uk).
Other ligand-construction reactions that are at present not
understood may also be traced back to the ambiphilicity of
P atoms in coordinated heterocycles. This is, for instance, the
case for [W(2,4-di-tBu-1,3-diphosphete)3] with a P C inter-
ring distance of 207.1 pm at 200 K,[31] for the P C bond
ꢁ
between the pentamer cage and the four-membered ring of
Angew. Chem. Int. Ed. 2002, 41, No. 21
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COMMUNICATIONS
[14] Y. Ohashi in Reactivity in Molecular Crystals (Ed.: Y. Ohashi), VCH,
Weinheim, 1993.
[15] M. Hofmann, U. Zenneck in Phosphorus-Carbon Heterocyclic Chem-
istry: The Rise Of A New Domain (Ed.: F. Mathey), Elsevier Science,
Amsterdam, 2001, p. 170.
[16] U. Zenneck, Angew. Chem. 1990, 102, 171; Angew. Chem. Int. Ed.
Engl. 1990, 29, 126; D. Hu, H. Sch‰ufele, H. Pritzkow, U. Zenneck,
Angew. Chem. 1989, 101, 929; Angew. Chem. Int. Ed. Engl. 1989, 28,
900; D. Hu, PhD thesis, Universit‰t Heidelberg, 1990.
[28] L. Brammer, B. J. Dunne, M. Green, G. Moran, A. G. Orpen, C.
Reeve, C. J. Schaverien, J. Chem. Soc. Dalton 1993, 1747.
[29] P. B. Hitchcock, M. J. Maah, M. Green, J. F. Nixon, J. Organometal.
Chem. 1994, 466, 153.
[30] F. Knoch, S. Kummer, U. Zenneck, Synthesis 1996, 265.
[31] M. Scheer, personal communication, M. Schiffer, PhD thesis, Uni-
versit‰t Karlsruhe, 2000, p. 78.
[32] P. B. Hitchcock, C. Jones, J. F. Nixon, Angew. Chem. 1994, 106, 478;
Angew. Chem. Int. Ed. Engl. 1994, 33, 463.
[17] E. J. Miller, T. B. Brill, A. L. Reingold, W. C. Fulz, J. Am. Chem. Soc.
1983, 105, 7580; U. Englert, B. Ganter, T. Wagner, W. Kl‰ui, Z. Anorg.
Allg. Chem. 1998, 624, 970.
[33] SHELXTL NT 5.10, Bruker AXS, 1998, Madison, WI, USA.
[18] M. Driess, J. Aust, K. Merz, C. van W¸llen, Angew. Chem. 1999, 111,
3967; Angew. Chem. Int. Ed. 1999, 38, 3677.
[19] Gaussian98 (RevisionA.7), 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.
Enantioselective Stereoinversion in the Kinetic
Resolution of rac-sec-Alkyl Sulfate Esters by
Hydrolysis with an Alkylsulfatase from
Rhodococcus ruber DSM 44541 Furnishes
Homochiral Products**
Mateja Pogorevc, Wolfgang Kroutil,
Sabine R. Wallner, and Kurt Faber*
[20] a) P. J. Stephens, F. J. Devlin, C. F. Chabalowski, M. J. Frisch, J. Phys.
Chem. 1994, 98, 11623 11627; b) A. D. Becke, J. Chem. Phys. 1993,
98, 1372 1377; c) A. D. Becke, J. Chem. Phys. 1993, 98, 5648 5652;
d) C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785 789.
[21] a) P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270 283; b) W. R.
Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284 298; c) P. J. Hay, W. R.
Wadt, J. Chem. Phys. 1985, 82, 299 310; d) T. H. Dunning, Jr., P. J.
Hay in Modern Theoretical Chemistry, Vol. 3 (Ed.: H. F. Schaefer III),
Plenum, New York, 1976, p. 1.
Sulfatases catalyze the hydrolytic cleavage of the sulfate
ester bond by liberating inorganic sulfate and the correspond-
ing alcohol.[1] Depending on the nature of the enzyme and its
catalytic mechanism, enzymatic hydrolysis of sec-alkyl sul-
ꢁ
fates may proceed through retention–by cleavage of the S O
ꢁ
bond–or inversion–by the cleavage of the C O bond–of
configuration at the chiral carbon atom (Scheme 1).[2,3]
[22] a) S. Huzinaga, Gaussian Basis Sets for Molecular Calculations,
Elsevier, Amsterdam, 1984; b) K. Raghavachari, G. W. Trucks, J.
Chem. Phys. 1989, 91, 1062 1065.
[23] K. B. Wiberg, Tetrahedron 1968, 24, 1083 1096.
[24] P. v. R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao, N. v. E. Hommes,
J. Am. Chem. Soc. 1996, 118, 6317 6318.
[25] A. E. Reed, R. B. Weinstock, F. Weinhold, J. Chem. Phys. 1985, 83,
735 746.
[26] A. S. Weller, C. D. Andrews, A. D. Burrows, M. Green, J. M. Lynam,
M. F. Mahon, C. Jones, Chem. Commun. 1999, 2147.
Scheme 1. Stereochemical pathways of enzymatic sulfate ester hydrolysis.
[27] Crystal data for 8: (C26H46MoO2P4), Mr ¼ 610.45, triclinic, space group
ꢀ
The ability of sec-alkylsulfatases to effect stereoinversion
during catalysis makes them prime candidates for their
application in so-called enantioconvergent processes,[4] which
allow the enantioselective transformation of enantiomers by
opposite stereochemical pathways to furnish a single stereo-
isomeric product in 100% theoretical yield. Other enzymes,
which potentially show this ability are a) epoxide hydrolases,[5]
b) dehalogenases,[6] and c) glycosidases.[7] A limited number of
alkylsulfatases have been biochemically characterized[1] but to
date, these enzymes have not been applied to preparative
biotransformations.[8]
P1; cell parameters a ¼ 10.116(5), b ¼ 11.312(5), c ¼ 13.960(6) ä; a ¼
77.17(4); b ¼ 89.52(4); g ¼ 87.07(4)8; V¼ 1556(2) ä3; Z ¼ 2; 1calcd
¼
1.303 gcmꢁ3; m ¼ 0.647 mmꢁ1; F(000) ¼ 640. Measurements taken on
an automatic four circle diffractometer (Nicolet R3m/V, graphite
monochromatized MoKa-radiation, l ¼ 0.71073 ä) at 298 K in the 2q-
range from 3.70 to 54.008. 6790 symmetry-independent reflections.
The structure was solved as for 4, R1 ¼ 0.0479 (for 4782 reflections with
F0 ꢃ 4.0s(F)), wR2 ¼ 0.1179 (for all data). The position of the H atom
bonded to P3 was obtained from a difference-Fourier analysis. All
other hydrogen atoms are positioned according to geometrical
considerations. Crystal data for 9: (C34H66MoO2P4), Mr ¼ 726.69,
orthorhombic, space group Pbca; cell parameters a ¼ 14.4264(4), b ¼
20.6977(3), c ¼ 25.7650(6) ä; V¼ 7693.3(3) ä3; Z ¼ 8; 1calcd
¼
1.255 gcmꢁ3; m ¼ 0.534 mmꢁ1; F(000) ¼ 3104. Measurements taken on
a
Nonius KappaCCD (MoKa radiation, l ¼ 0.71073 ä, graphite
monochromator) at 100 K in the 2q-range from 6.78 to 64.08. 13322
symmetry-independent reflections. The structure was solved as for 4,
R1 ¼ 0.0445 (for 8044 reflections with F0 ꢃ 4.0s(F)), wR2 ¼ 0.0923 (for
all data). The position of all H atoms could be obtained from a
difference-Fourier analysis. CCDC-184253 (8) and CCDC-184254 (9)
contains 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: (þ 44)1223-336-033;
or deposit@ccdc.cam.ac.uk).
[*] Prof. Dr. K. Faber, Mag. Dr. M. Pogorevc, Dipl.-Ing. Dr W. Kroutil,
Mag. S. R. Wallner
Department of Organic and Bioorganic Chemistry
University of Graz
Heinrichstrasse 28, 8010 Graz (Austria)
Fax : (þ 43)316-380-9840
E-mail: Kurt.Faber@uni-graz.at
[**] We thank Degussa AG (Frankfurt) for financial support and T.
Riermeier and H. Trauthwein for their valuable contributions.
4052
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Angew. Chem. Int. Ed. 2002, 41, No. 21