Table Of Content79
Topics ni Current Chemistry
diohtnalonagrO
:yrtsimehC Synthesis,
,erutcurtS sisylataC
Volume Editor: W. A. Herrmann
With contributions by
R. Anwander, .F .T Edelmann,
.W A. Herrmann
With 311 Figures and 74 Tables
regnirpS
This series presents critical reviews of the present position and future trends in
modern chemical research. It is addressed to all research and industrial chemists who
wish to keep abreast of advances in the topics covered.
As a rule, contributions are specially commissioned. The editors and publishers will,
however, always be pleased to receive suggestions and supplementary information.
Papers are accepted for "Topics in Current Chemistry" in English.
In references Topics in Current Chemistry is abbreviated Top.Curr.Chem and is
cited as a journal.
Springer WWW home page: http://www.springer.de
ISBN 3-540-61009-X Springer-Verlag Berlin Heidelberg NewYork
Library of Congress Catalog Card Number 74-644622
This work is subject to copyright. All rights are reserved, whether the whole or part of the
material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data
banks. Duplication of this publication or parts thereof is permitted only under the provisions
of the German Copyright Law of September 9, 1965, in its current version, and permission
for use mus! always be obtained from Springer-Verlag. Violations are liable for prosecution
under the German Copyright Law.
© Springer-Verlag Berlin Heidelberg 1996
Printed in Germany
The use of general descriptive names, registered names, trademarks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from
the relevant protective laws and regulations and therefore free for general use.
Typesetting: Macmillan India Ltd., Bangalore-25
SPIN: 10509064 51/3020 - 5 4 3 2 1 0 - Printed on acid-free paper
Volume Editor
Prof. Dr. Drs. h.c. WolfgangA. nnamrreH
Lehrstuhl ftir Anorganische Chemie I
Technische Universit~it Miinchen
Lichtenbergstr. 4
D-85747 Garching, FRG
Editorial Board
.forP Dr. Jack D. Dunitz Laboratorium fiir Organische Chemic
der Eidgen6ssischen Hochschule
eBartssti~tisrevinU 6/8, CH-8006 Ziirich
.forP .rD Klaus Hafizer Institut rit'f Organische Chemie der ,HT
eBartsnesreteP ,51 64287 Darmstadt, FRG
.forP .rD Kendal N. Hnuk University of California, Department
of Chemistry dna Biochemistry, 504 Hilgard Avenue,
Los Angeles, AC ,9851-42009 ASU
.forP .rD Sho lto Faculty of Pharmaceutical Sciences,
Tokushima Bunri University,
Tokushima 770, Japan
.forP .rD Jean-Marie Lehn lnstitut ed Chimie, Universit6 de Strasbourg,
1 rue Blaise Pascal, .B .P Z 296/Rg, F-67008 Strasbourg-Cedex
.forP .rD Kemteth N. l¢aymond Department of Chemistry, University of California,
Berkeley, AC 94720, ASU
.forP .rD Charles .W Rees Hofmann Professor of Organic Chemistry, Department
of Chemistry, hnperial College of Science and Technology,
South Kensington, London 7WS 2AY, England
.forP .rD Joachim Thiem Institut ftir Organische Chemic, tt~tisrevinU Hamburg,
Martin-Luther-King-Platz ,6 20146 Hamburg, FRG
.forP .rD Fritz Vagtle Institut ri~f Organische Chemie und Biochemie der ,ti~tisrevinU
Gerhard-Domagk-Strafie ,1 12135 Bonn, FRG
Rare-Earth Metals: Coordination Chemistry of the Periodic Table's
"Footnotes"
Horizons in Synthesis • Habit of Structures" Patterns of Reactivity
"Lanthanons ...
These elements perplex us in our rearches [sic!I, baffle
us in our speculations, and haunt us in our very
dreams. They stretch like an unknown sea before us --
mocking, mystifying and murmuring strange
relevations and possibilities."
Sir William Crookes (February ,61 1887)
Preface
The rare-earth elements -- first row of fourteen "footnotes" in the periodic table
-- have long been strongly neglected in organometallic chemistry. It was only in
the eighties that a number of research laboratories began to focus on the
lanthanides and their close relatives -- scandium and yttrium --, at a time when
selected members of this group of elements were well-established in a huge
number of apphcations. In particular, the field of "high-tech materials" is
dependent on rare-earth components to a significant extent: they tune mag-
netic/electrical properties of metallic and oxidic materials, optical properties for
colour television and electric lighting, mechanical properties of hard materials
(metal oxides and nitrides), and the performance of catalysts in mineral oil
cracking, olefin polymerization, methanol synthesis, Fischer-Tropsch synthesis
and exhaust gas chemistry (e.g., lambda sensors). An annual increase of more
than 15% in high-tech applications of lanthanides is expected in the near
future. As a matter of fact, these broad-scope applications initiated the recent
intense research into the coordination and organic chemistry of the rare-earth
elements.
For example, volatile molecular precursor compounds are a primary goal of
CVD (chemical vapor deposition) techniques for generating thin films of oxidic,
nitridic, and carbidic lanthanide coatings on top of other (mostly inorganic)
materials. Other activities are aimed at the improvement of catalysts on the
molecular level: certain organolanthanide compounds were found to exhibit
specific catalytic properties in reactions that are otherwise difficult to perform,
e.g. cyclohydroamination of olefins, polymerization of olefins, and polyconden-
sation of lactides to make biodegradable polymers (Lewis-acid catalysis). The
even simpler compound samarium(II) iodide, generated from a Grignard-type
Preface
reaction of 1,2-diiodoethane and metallic samarium (Sm + ICH2CH2I~
SmI2 + CH2=CH2; H.B. Kagan), effects a clean reductive coupling of keto
compounds to vicinal diols.
A more differentiated coordination chemistry of this and related lanthanide
elements seems necessary to eventually conduct these reactions catalytically
instead of stoichiometrically. This is clearly one of the major challenges in the
ongoing organolanthanide research. At present, the entire field of catalysis
involving the Periodic Table's "footnotes" is largely underdeveloped. This is not
so much due to the normally pronounced hygroscopicity of lanthanide com-
pounds (with this property in the first place resulting from the Lewis acidity of
Ln-ions and their "oxophilicity"), but more a result of insufficient synthesis
research. It is a known fact that increasing knowledge on the synthetic methodo-
logyo f a given group of elements or a particular class of compounds pushes their
applications by virtue of an improved understanding of reactivity and structure.
To keep up with the rapid development in the molecular (coordination)
chemistry of the rare-earth metals, a special volume of Topics in Current
Chemistry was recognized as the ideal forum for up-to-date essays on basic
compounds, their syntheses, structures and reactivities. As guest editor, I am
proud to present a small but outstanding collection of contributions from the
forefront of this field: Reiner Anwander, a former Ph,D. student of mine (Tech-
nische Universit~it Mfinchen, 1992) and later a post-doctoral fellow of Bill Evans
in Irvine/USA, has furnished two articles on "Lanthanide Amides" and "Routes
to Monomeric Lanthanide Alkoxides", both built up on a complete list of
literature references up to mid-1995. Frank Edelmann, now a professor of
inorganic chemistry at Magdeburg University, has written updated reviews on
"Lanthanide Metallocenes in Homogeneous Catalysis" and "Rare Earth Com-
plexes with Heteroallylic Ligands". Both these authors reveal thorough experi-
mental experience regarding the topics of their contributions. A "feature article"
by Reiner Anwander and myself attempts to focus on the lanthanoids' principles
regarding structure and reactivity. It is to be hoped for that the present volume
will further draw the attention of our scientific community to the virtuosity of
lanthanide molecular chemistry. It is the plethora of lanthanide compounds,
structures, and reactivities that will soon raise these "footnotes" into the main
text of .yortsimehc
Miinchen, April 1996 Wolfgang A. Herrmann
VIII
Table of Contents
Features of Organolanthanide Complexes
R. Anwander, W. A. Herrmann ......................... 1
Lanthanide Amides
R. Anwander ....................................... 33
Rare Earth Complexes with Heteroallylie Ligands
F. T. Edelmann ..................................... 113
Routes to Monomeric Lanthanide Aikoxides
R. Anwander ....................................... 149
Lanthanide Metallocenes in Homogeneous Catalysis
F. T. Edelmann ..................................... 247
Author Index Volumes 151 - 179 ...................... 277
Table of Contents of Volume 178
Small Ring Compounds in Organic Synthesis V
Cycloadditions Onto Methylene- and Alkylidene-
cyclopropane Derivatives
A. Goti, F. M. Cordero, A. Brandi
SelectiveT ransformations of Small Ring
Compounds in Redox Reactions
T. Hirao
Features of edinahtnalonagrO Complexes
Reiner Anwander I and Wolfgang A. Herrmann 2
Institut fiir Technische Chemie, Universit~t Stuttgart, D-70550 Stuttgart,
Germany
2 Anorganisch-Chemisches Institut, Technische Universit/it Mfinchen, D-85747
Garching, Germany
Table of Contents
List of Symbols and Abbreviations .......................... 2
1 Introduction .................................... 2
2 Element (-Cation) Guidelines .......................... 5
2.1 Electronic Considerations ......................... 5
2.2 Steric Considerations ............................ 7
3 Thermodynamic and Kinetic Guidelines .................... 10
3.1 Inorganic Reagents ............................ 12
3.20rganometallic Reagents ......................... 17
3.3 Thermal Stability ............................. 18
4 Ligand Guidelines ................................ 19
4.1 So-called "Spectator" Ligands ...................... 21
4.2 Concept of Donor-Functionalization .................. 23
5 Conclusion .................................... 26
6 References .................................... 27
Topics ni tnerruC yrtsimehC LoC' t79
© Springcr-Ver|ag nilreB Heidetgerg 6991
renieR rednawnA dna gnagfloW .A Herrmann
The cisnirtni properties of the edinahtnal stnemele guarantee gnisimorp snoitacilppa ni the sMeif of
sisylatac dna material .ecneics woH to cope and under on level a features molecular these with
conditions anaerobic si ,dessucsid gnidulcni thermodynamic dna kinetic .snoitaredisnoc euD to
the importance of a prolific dnagil/latem ,msigrenys current stnempoleved ni are design ligand
.dezisahpme
List of Symbols and Abbreviations
BINOL binaphthol
CN coordination number
Cp ~/5-cyclopentadienyl
DME enahteyxohtemid-2,1
Diglyme di-fl-methoxyethylether
E element
hfc 3-(heptafluoropropylhydroxymethylene)-d-camphorato
HSAB hard soft acid base
Im imidazole
L ligand
Ln lanthanide (Sc, Y, La, Ce-Lu)
MOCVD metal-organic chemical vapor deposition
Py pyridine
TBP tri-n-butylphosphane
Tf "triflate" ligand, CFaSO3
thd 2,2,6,6-tetramethyl-3,5-heptandionate
THF tetrahydrofurane
TMEDA tetramethylethylenediamine
tritox tri-tert-butyl methoxide
Z nuclear charge
1 Introduction
The terms 'contraction' and 'separation' have probably been most commonly
associated with the lanthanide elements and students are certainly confronted
with precisely these key words in textbooks and lectures. However, the modern
synthetic chemist has to consider numerous intrinsic factors, especially when it
comes to the synthesis of well-defined molecular species with potential relevance
to the catalysis and the material sciences. As a rule, most review articles covering
