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Graphical Abstract (Angew. Chem. Int. Ed. Engl. 101995)

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A Journal of the
GeselIschaft
Deutscher Chemiker
International Edition in English
1995
34/10
Pages 1043- 1134
COVER PICTURE
The cover picture shows the arrangement of two 1 :1 complexes composed of a cyclic
zinc porphyrin tetramer (Zn,-1) and a central rneso-tetra-4-pyridyl-porphyrin unit
(H,-Py,P) in the solid state (view along the c axis; purple = N, blue = C, yellow =
Zn). The central porphyrin ligand, which is coordinated to each zinc center in Zn,-1
through an N atom of a pyridyl unit, locks the five-porphyrin assembly in a single
conformation. NMR spectra indicate that the complex H,-Py,P. Zn,-1 prefers to
adopt a tub-shaped geometry reminiscent of cyclooctatetraene. The picture was
produced with the program Insight I1 from Biosym Technologies of San Diego using
a Silicon Graphics Workstation. We would like to thank Dr. Robert Thomas and
Prof. Dr. Fransois Diederich (ETH Zurich Switzerland) for their help in producing
this picture. Further details of the structure and fluorescence properties of this
multicomponent system are reported by S. Anderson et al. on pp. 1096ff.
REVIEWS
Contents
The search for new metal-catalyzed asymmetric reactions provides some unique insights into the effects imposed on the metal catalysts by chiral ligands. In special
cases, the addition of a specific ligand to an existing catalyzed process enables a
faster, “ligand-accelerated” asymmetric reaction to occur. This phenomenon of
ligand-accelerated catalysis is crucial for the success of several transition metal
catalyzed reactions that are now in widespread use among chemists.
c3@;f&
enzyme
protein-scaffolds
Nature performs multistep inorganic
cluster syntheses. This is the interpretation of results coming from genet/[F.PI.IL/
ics research into the biological fixation of N,. The concepts of nature
applied to achieve the assembly of
/
/
“Fe, S
“Mo“, L
the complex reaction center-a
MoFeS cluster-of the nitrogenase
enzyme system are outlined. These lead to new guidelines for the so far unsuccessful
in vitro synthesis of this cluster.
n
n
A n g w C h e m Int.
G I . Engl. 1995, 34, No. 10
0 VCH
V~rlagsgesellschaftmbH, 0-69451 Wemheim, 1995
D. J. Berrisford, C. Bolm,
K. B. Sharpless* ....................
1059-1070
Ligand-Accelerated Catalysis
A. Muller,* E. Krahn ........... . 1 07 1- 1078
On the Synthesis of the FeMo Cofactor of
Nitrogenase: Gene-Controlled in Nature
versus Laboratory-Produced by Man
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HIGHLIGHTS
Contents
A simple recipe for tailored cavities for the recognition of neutral organic guests: just
mix difunctional chelate ligands with metal ions having a preferred coordination
geometry. Boxes, cylinders, or tetrahedra form in high yields by self-assembly. Of
course it’s not quite this easy, but the studies discussed here indicate that this strategy
for the construction of macrocyclic hosts has a bright future.
“The metallic bond still lives!” maintains the author of this highlight. In two recent
papers theoreticians argue against the concept of the metallic bond as a distinct type
of bond, and favor treating it as a limiting case of the covalent bond based on ab
initio descriptions of bonding in solids. Still, J. C. Schon is convinced that the
metallic bond, correctly understood as a qualitative concept, will continue to be used
by solid-state chemists.
C. A. Hunter * ...._,..._...._..
, . ....
1079- 1081
Self-Assembly of Molecular-Sized Boxes
J. C. Schon .............................
1081-1083
Does the Death Knell Toll for the Metallic
Bond?
COMMUNICATIONS
The helical 1,3-diiodotrigermane2 crystallizes as a conglomerate of enantiomerically
pure single crystals. Trigermane 2 is prepared from hexa-tert-butylcyclotrigermane
(1) and iodine through cleavage of a Ge-Ge bond. In contrast, photolysis of 1 leads
to tetra-tevt-butyldigermene which can be trapped with phenylacetylene to give the
cycloadduct 3.
I
3
Possible intermediates in the oxygenation of anilines
1 in the presence of complexes such as 2 are represented by adducts of these components. The formation constants for these complexes (single and
double exchange of axial dmf ligands by 1) were
determined quantitatively by Lyclic voltammetry
and by ‘H NMR spectroscopy.
B. Speiser,* H. Stahl .............. 1086-1089
&N?N;fd
o/.cd’l:.o
0
@
T. Degen, B. Harbrecht* ....... 1089-1090
(Nb,Ta),(S,Te),, a Metal-Rich Chalcogenide with a Microporous Metal Substructure
Protonation of the nitro group and heterolytic cleavage of the C-C bond in 1 are
concerted, based on the primary kinetic solvent isotope effect and the marked effect
of the arene substituents [Eq. (a)]. The cyclopropane ring of 1 undergoes acid-catalyzed ring opening via a carbocationic nitronic acid, which is transformed into a
hydroxamic acid.
Ar,,
NOzH
02N
H
fast
Complexation of [N,N’-Bis(salicy1idene)ethylenediiminato]cobalt(r~~)+
by Anilines
in Dimethylformamide
2
Nearly nanometer thick fragments of the body centered cubic arrangement (bcc) of the metallic components are found in the structure of the title compound. The network of compact columnar bcc
fragments has such a wide mesh that though the
internal surfaces of the microporous metal substructure (picture on the right, projection along b ) are
completely covered by chalcogen atoms, small channels are still present in the structure.
slow
Reactions of Hexa-tevt-butylcyclotrigermane: Isolation of an Enantioinerically
Pure 1,3-Diiodotrigermane
I
2
1
M. Weidenbruch,* A. Hagedorn, K. Peters,
H. G. von Schnering .............. 1085- 1086
W. Cao, I. Erden,*
J. R . Keeffe* ..........................
1091-1092
Formation of Nitronic Acids by Ring
Opening of Nitrocyclopropanes by a Concerted, Acid-Catalyzed Mechanism
hydroxarnic acids
H
1
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mbH. 0.69451 Wi,inheim, 1995
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AnRew. Cliem. 1111.Ed. Enpl. 1995, 34. N o . 10
Contents
Under what conditions is a hydrocarbon transformed
into a carbon skeleton in a molecular metal carbide?
Treatment with an electron-rich metal complex under reducing conditions is one possibility. The cornplex anion shown schematically on the right, in
which a "naked" C , unit lies within a square-planar
array of two titanium and two lithium cations,
formed from the reaction of ethylene with (meso-octaethy1porphyrinogen)titanium in the presence of
lithium metal.
7
2-
La,@CSo is a stronger electron acceptor than
La(([C g 2 and has a remarkably narrow HOMOLUMO gap in comparision to empty fullerenes.
This result was derived from the redox potentials of
La,(ccC,, determined by electrochemistry. Ab initio
calculations on La,@ C,, with an I,,-symmetric C,,
cage (see picture on the right) suggest that the partially filled HOMOS are occupied by six electrons
from La?. The La-La distance is 3.45 A.
S. De Angelis. E. Solari, C. Floriani,*
A. Chiesi-Villa, C. Rizzoli ..... 1092- 1094
A Li,Ti,-Substituted Acetylene Formed
from Ethylene by Reaction with (mesoOctaeth ylporphyrinogen )titanium
T. Suzuki,* Y. Maruyama, T. Kato,
K. Kikuchi, Y. Nakao, Y Achiba,
K . Kobayashi, S. Nagase* ..... 1094-1096
Electrochemistry and A b lnitio Study of the
Dimetallofullerene La,(u,C,,
S. Anderson,* H. L. Anderson,
A. Bashall, M. McPartlin.*
J. K. M. Sanders * .................. 1096 - 1099
Locked into a tub geometry, the pentaporphyrin array illustrated has a
well-defined conformation both in
solution and in the crystal. Self-assembly ofthis light-harvesting antenna model quenches the fluorescence
of both the central tetrapyridylporphyrin unit and the zinc porphyrin
tetramer.
Assembly and Crystal Structure of a Photoactive Array of Five Porphyrins
The rate of intramolecular triplet energy transfer upon excitation of the Ru" unit in
the binuclear complex 1 decreases by roughly a third when the alkyne spacer is
extended by a second ethynyl group (complex 2). The metal-metal distance increases by 2.4 A, and correspondingly the attenuation factor for electron exchange
through the C=C bonds is 0.17 A - ' . Counterion PF,.
V. Grosshenny, A. Harriman,*
1100-1102
R. Ziessel* .............................
Electronic Energy Transfer Across EthynylBridged Ru"/Os" Terpyridyl Complexes
14+
1:n=l
2:n=2
A slightly twisted C=C bond of 138.6 pm is the striking structural feature of 1, which was isolated from
aqueous solution after complexation of the corresponding r-aminocarboxylic acid to the tumor-inhibiting platinum(I1) unit. The IR band for the enolic double bond likewise reveals the presence of the
enol of a carboxylic acid.
M. Galanski, B. K. Keppler,*
B. Nuber ................................
1103-1104
First Isolation of an En01 of a Carboxylic
Acid by Complexation to an (Ethane-1,2diaminejplatinum(I1) Fragment
~
~
~~
Contents
Diastereoisomeric excesses greater than 99% are obtained for the majority of the
stereoselective four-component condensations (a), if the amino glucopyranose 1 is
used as the sugar component Y-NH, .
n
v
+ R’CHO + R2NC + R3C02H
Y-NH,
ZnCI,
,OAc
Y-NH2=
Y-N-’CH-C
R3
AcO
NHAc
’
,c,I
I
R1
0
//
(a)
\
NHR’
The complex-stabilized ligands in the title compounds 2 and 3 can be considered
diborylcarbenes >B-C-B<. They are formed from the boriranylideneborane 1
(nonclassical structure) and [Co(C,H,)(C,H,),)J or [Pt(C,H,,),J. In 2 the CoBCBCCo unit is almost planar (Dur = 2,3,5,6-tetramethylphenyl).
( Ci3H 12)
Me3Si
‘C
-?.,,
\
Stereoselective Syntheses of Peptide Derivatives with 2-Acetamido-3,4,6-tri-O-acetyl1-amino-2-deoxy-~-~-glucopyranose
by
Four-Component Condensation
1
Genetically engineered hybrid strains, in which the genes of the urdamycin-producer
Streptomyces fradiae are combined with some of the biosynthetic genes of the elloramycin-producer Streptomyces olivaceus or the genes of the tetracenomycin-producer Streptomyces glaucescens, assemble novel hybrid antibiotics of the tetracenomycin type. The results prove that this combinatorial biosynthesis method may be
a useful alternative for the production of new natural products which can then be
screened.
Me3Si0
S. Lehnhoff, M. Goebel, R. M. Karl,
R. Klosel, I. Ugi * .................. 1104-1107
H. Decker, S. Haag,
G. Udvarnoki, J. Rohr* ......... 1107-1110
Novel Genetically Engineered Tetracenomycins
A. Gunale, H. Pritzkow, W. Siebert,*
D. Steiner, A. Berndt* ........... 1111-11 23
Dicobalt and Diplatinum Complexes of
Diborylcarbenes
/”
C-B,
.
R
1 :R=Dur
2
3
A linear relationship exists between the twist angle of
the C(0)-N bond in 1 and the difference between
the ” 0 (or I3C) NMR chemical shift of 1 and that
of the corresponding amide 2. These experimental
results are of interest with regard to the discussion of
the classical amide resonance model.
Rz
0
S. Yamada* ...........................
0
R44*Me
he
sks
’
2
A synthetic analogue of the natural antibiotic
boromycin is described. The negatively charged
pseudocryptand 1 possessing a spiroborate moiety
binds the potassium cation with the highest stability
thus far observed with synthetic receptors. Furthermore, compound 1 displays high selectivity for
potassium over other alkali metal cations.
Two exceptionally long N a - 0 distances in Li/Na enolate 1 lead to a
unique
“open-stack”
structure
(sketch of the framework depicted
on the right). This can be used as a
model for the intermediates in aldol
reactions. The two outer sodium
atoms in the stack are bound to
amine ligands, which can thus influence the selectivity of an attack on
the enolate.
1048
1113-1115
Relationship between C(0)-N Twist
Angles and 170NMR Chemical Shifts in a
Series of Twisted Amides
E. Graf,* M. W. Hosseini,* R. Ruppert,
N. Kyritsakas, A. De Cian, J. Fischer,
C. Estournb, F. Taulelle ........ 3 115 - 1117
Binding of Boron and Alkali Metal Cations
by a Pseudocryptand
K. W. Henderson, P. G. Williard,*
P. R. Bernstein .......................
1117-1139
I
[L~,N~,(OC(=CH,)~BU),(~P~,NH)~]
1
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Synthesis and Characterization of the First
Mixed Alkali Metal Enolate Containing
Amine Ligands: A Novel “Open-Stack’’
Structure and its Implications for Aldol
Addition
0570-0833I9S~~010-~048
$10.00+ ,2510
Angrw. Chem. Int. Ed. Engl. 1995, 34, No. 10
Contents
The reversible photochemical conversion between the open form 1, a strong fluorophore, and the closed form containing a central, hexyl-substituted six-membered
ring, which fluoresces only weakly, makes modulation of emitted light possible.
This readily adjustable system is of interest for optical data storage. R = CH;,
counterion = CF,SO;.
F F
1
Molten InBr, and metallic indium react quantitatively to form In,Br,, which crystallizes in the trigonal
system with a crystal chemical formula of
(In3+)3(In+)5(Br-)14.The remarkable chemical
and physical sensitivity of the compound and its
ready decay are attributable to both the generally
weak In+ -Br- bonds and the electronic instability
of a particular In' position (shown on the right).
1119-1 122
Photonic Molecular Devices: Reversibly
Photoswitchable Fluorophores for Nondestructive Readout for Optical Memory
G. S. Hanan, C. R. Arana,
J.-M. Lehn,* D. Fenske ......... 1122-1124
Linear arrangements of metal centers fixed by
polydentate bridging ligands are found in new Ru"
complexes. In the redox-active complex 1 (X = H,
9-anthryl), which resembles a rack, the metal centers
can communicate through the bridging ligand.
A wealth of highly selective reactions may become
accessible thanks to the approach described herein:
A reactive functional group is placed on the inside of
a bowl-shaped molecular skeleton; in this way, for
example, dimerizations can be prevented, but reactions with added small molecules remain possible.
The sulfenic acid 1 obtained from the corresponding
S-butyl sulfoxide by pyrolysis is stable both in the
solid state and in solution, and reacts smoothly with
methyl propiolate and butanethiol.
G. M. Tsivgoulis,
J.-M. Lehn* ...........................
O
j
Synthesis, Structure, and Properties of
Dinuclear and Trinuclear Rack-Type Ru"
Complexes
K. Goto, N. Tokitoh,
R. Okazaki* ..........................
p
1124-1126
+g+J:Hb
Synthesis of a Stable Arenesulfenic Acid
Bearing a Bowl-Shaped Macrobicyclic
Cyclophane Skeleton
0
\
1
c*i
&6r(2)
66
In(5)&
&
R. Dronskowski* .................. 1126-1328
'&
Synthesis, Structure, and Decay of In,Br,
%
CBr(2)
* Author
to whom correspondence should be addressed
BOOKS
The Adventure Playground of Mechanisms and Novel Reactions
R. Huisgen
1129
Keyword Index 1130
Sources 1055
Author Index 1131
Angew. Chum. Jnr. Ed. Engi. 1995, 34, No. 10
R. N! Hoffmann ...............................
Preview 1132
0 VCH
Vurkugsgesel!.whafimhH, 0-69451 Weinheim, 1995
0570-0833~95jJ01O-l049
$10.#0+ .25/0
1049
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