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Synthesis, structure, and reaction pathways of C-N containing lanthanide compounds [Elektronische Ressource] = Synthesen, Strukturen und Reaktionswege von C-N-haltigen Lanthanoid-Verbindungen / vorgelegt von Radhakrishnan Srinivasan

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112 pages
Synthesis, Structure, and Reaction Pathways of C–N containing Lanthanide Compounds Synthesen, Strukturen und Reaktionswege von C–N-haltigen Lanthanoid-Verbindungen DISSERTATION der Fakultät für Chemie und Pharmazie der Eberhard-Karls-Universität Tübingen zur Erlangung des Grades eines Doktors der Naturwissenschaften 2004 vorgelegt von Radhakrishnan Srinivasan Tag der mündlichen Prüfung: 17. Dezember 2004 Dekan: Prof. Dr. S. Laufer 1. Berichterstatter: Prof. Dr. H.-J. Meyer 2. Berichterstatter: Prof. Dr. E. Schweda Die vorliegende Arbeit wurde von Juni 2001 bis Dezember 2004 am Institut für Anorganische Chemie der Eberhard-Karls-Universität Tübingen unter der Leitung von Prof. Dr. H.-J. Meyer angefertigt. Acknowledgements My sincere thanks and gratitude are due to Prof Dr. Hans-Juergen Meyer for his constant guidance, motivation, suggestions, and fruitful discussions throughout this work. I would like to express my special thanks to Dr. Jochen Glaser, Dr. Markus Ströbele, and Sonja Tragl for their help and discussions in structure solution and refinements by powder and single crystal diffraction studies. I thank Heinz-Jürgen Kolb for the X-ray and DTA/TG measurements. I thank Dr. Jochen Glaser and Dr. Björn Blaschkowski for their help in Squid measurements and discussions.
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Synthesis, Structure, and Reaction Pathways of C–N
containing Lanthanide Compounds

Synthesen, Strukturen und Reaktionswege von C–N-
haltigen Lanthanoid-Verbindungen

DISSERTATION
der Fakultät für Chemie und Pharmazie
der Eberhard-Karls-Universität Tübingen
zur Erlangung des Grades eines Doktors
der Naturwissenschaften


2004




vorgelegt von
Radhakrishnan Srinivasan






















Tag der mündlichen Prüfung: 17. Dezember 2004

Dekan: Prof. Dr. S. Laufer
1. Berichterstatter: Prof. Dr. H.-J. Meyer
2. Berichterstatter: Prof. Dr. E. Schweda


Die vorliegende Arbeit wurde von Juni 2001 bis Dezember 2004 am Institut für Anorganische
Chemie der Eberhard-Karls-Universität Tübingen unter der Leitung von Prof. Dr. H.-J. Meyer
angefertigt.






















Acknowledgements
My sincere thanks and gratitude are due to Prof Dr. Hans-Juergen Meyer for his constant
guidance, motivation, suggestions, and fruitful discussions throughout this work.
I would like to express my special thanks to Dr. Jochen Glaser, Dr. Markus Ströbele, and
Sonja Tragl for their help and discussions in structure solution and refinements by powder and
single crystal diffraction studies.
I thank Heinz-Jürgen Kolb for the X-ray and DTA/TG measurements.
I thank Dr. Jochen Glaser and Dr. Björn Blaschkowski for their help in Squid measurements
and discussions.
I thank Peter Ziegler and Marco Häberlen for their help in translating reports from English to
Deutsch.
I thank all my other colleagues Katharina Gibson, Dr. Haipeng Jing, Michael Neukirch,
Martina Weisser, Simone Dill, and Ruth Schmitt for the good and motivating work
atmosphere.
I am thankful to DFG and Landesgraduiertenförderung of Baden-Württemberg for the
scholarship provided during this work.
I also thank my parents, brother and sister and relatives for their moral support during this
work.






















Dedicated to my parents









Table of Contents
1. Introduction……………………………………………………………..……….…..….5
2. Introduction to carbodiimides and cyanamides……………………………….….…..7
2. 1. Different synthetic methods of carbodiimides/cyanamides….………...….…...10
2. 2. Solid state metathesis reaction (SSM)……………………………...……...…..12
3. Experimental techniques………………………………………………………….…….14
3. 1. Physical Measurements and software packages used……….……………...14
3. 1. 1. Phase analysis………………………………………………………..14
3. 1. 2. Crystal structure determination………………….……………...……14
3. 1. 3. Structure solution and refinement from powder patterns…….……...14
3. 1. 4. Infrared spectra……………………………………….…...…….…...15
3. 1. 5. Thermal analysis…………………………………….……………….15
3. 1. 6. Magnetic susceptibility studies……………………...…..……..…….15
3. 1. 7. Graphics……………………………………………………………...15
3. 2. List of chemicals used…………………………………….…………….….….16
3. 3. Synthesis of starting materials……………………………………..…………17
3. 3. 1. Preparation of Li (CN ) and Ca(CN )……………….……….…..…..17 2 2 2
3. 3. 2. Decomposition of Li (CN )…………………………………………..17 2 2
3. 3. 3. Reactivity of Li (CN )……………………………….…..……….…..20 2 2
3. 3. 4. Preparation of LaX with X = Cl, Br, and I…………...………….…..20 3
3. 3. 5. Preparation of LaOCl………………………………...….………...….23
1
3. 4. Manipulations of C–N containing lanthanide compounds ..……..……….....23
4. Results and discussion………………………………………………...…………….……25
4. 1. Solid state metathesis reaction between LaCl and Li N…………..….…….25 3 3
4. 2. Synthesis and structural characterisation of LnCl(CN ) with Ln = La, Ce, 2
and Pr………………………………………………………………………………..26
4. 2. 1. Reaction between LaCl and Li (CN )………………..…………...…26 3 2 2
4. 2. 2. Thermal analysis (DTA/TG) of the reaction between LaCl and 3
Li (CN )………..……………………………………………………..….…...27 2 2
4. 2. 3. Infrared spectra of LaCl(CN ) and La Cl(CN )N………..……….…..30 2 2 2
4. 2. 4. Crystal Structure of LaCl(CN ) from X-ray powder diffraction…......31 2
4. 2. 5. Crystal structure of LaCl(CN ) from single crystal……………..…....32 2
4. 2. 6. Isotypic compounds in this structure type……………………………34
4. 3. Synthesis, structure and characterisation of Ln X(CN )N with La = La, Ce, 2 2
Pr, Nd, and Gd, X = Cl, Br, and I……………………………………………...…..39
4. 3. 1. Reaction between LnCl , Li (CN ) and Li N……………………..….39 3 2 2 3
4. 3. 2. Reaction between LnBr , Li (CN ) and Li N…………………….…..39 3 2 2 3
4. 3. 3. Reaction between LaI , Li (CN ) and Li N……………………...…...40 3 2 2 3
4. 3. 4. Thermal analysis (DTA/TG) of the reaction between LaX with X =Cl 3
and Br, Li (CN ) and Li N ………….………………………………………..41 2 2 3
4. 3. 5. Infrared spectra of La Cl(CN )N……………………...……………...44 2 2
4. 3. 6. Crystal structures of La X(CN )N with X = Cl, Br, and I…..………..44 2 2
4. 3. 7. Crystal structure of Ce Cl(CN )N………………………………….…53 2 2
4. 3. 8. Magnetic properties of Ce Cl(CN )N…………………………...…....54 2 2
2
4. 3. 9. Isotypic compounds in this structure type…………………….………54
4. 4. Reaction between LaCl , Li (CN ) and C N Cl ……………………………..56 3 2 2 3 3 3
4. 5. Reaction between LaCl and structure directing agents…………………….58 3
4. 5. 1. Reaction between La(NO ) •6H O and K[C(CN) ]………...………...59 3 3 2 3
4. 5. 2. Synthesis of KLa[C(CN) ] •H O……………………………………...59 3 4 2
4. 5. 3. Crystal structure of KLa[C(CN) ] •H O…………………………...…60 3 4 2
4. 6. Reaction between LaCl and MCN with M = Na, K…………………………67 3
4. 7. Reaction between LaCl and Li (CN ) in the presence of metal…………….67 3 2 2
4. 7. 1. Reaction between LaCl , Li (CN ) and Li…………………………....67 3 2 2
4. 7. 2. Reaction between LaCl , Li (CN ) and Ca………………………...…68 3 2 2
4. 8. Synthesis and structure of Pr O Br…………………………………………..68 3 4
4. 8. 1. Synthesis of Pr O Br………………………………………….………68 3 4
4. 8. 2. Crystal structure of Pr O Br……………………………..……………68 3 4
4. 8. 3. Isotypic compounds in this structure type…………………...………..71
4. 9. Synthesis and structure of La O(CN ) ……………………………………….71 2 2 2
4. 9. 1. Synthesis and structure of known Ln O (CN ) Ln = La, Ce, Pr, Nd, Sm, 2 2 2
Eu, and Gd……………………………………………………………….……71
4. 9. 2. Reaction between LaCl , LaOCl and Li (CN )….……………….…...73 3 2 2
4. 9. 3. Crystal structure of La O(CN ) ………………………………………74 2 2 2
4. 9. 4. Reaction between LaOCl and Li (CN )…………..…………………..80 2 2
4. 9. 5. Reaction between CeOCl and Li (CN )………………………………80 2 2
5. Summary and outlook…………………………………………………………………....82
3
5. 1. Summary……………...…………………………………………………….….82
5. 2. Outlook…………………………………………………………………….…...84
6. Appendix………………………………………………………………………………….85
7. List of publications……………………………………………………………………….97
8. Literature…………………………………………………………………………………98
















4
1. Introduction
The research on lanthanum cyanamides dates back to 1948, when Hartmann et. al. [1]
explained the formation of La (CN ) from a reaction of lanthanum oxide and HCN gas. Later 2 2 3
Pavlov et. al. [2] in 1973 described the formation of La (CN ) by treating lanthanum oxide 2 2 3
with urea. However, the presence of cyanamide from these works were characterised only
from elemental analyses and the structural details are still not known for lanthanide
cyanamide/carbodiimide. Calcium cyanamide [3] is historically famous for its industrial
applications and an environment friendly multi-purpose fertilizer to supply nitrogen as well as
lime to plants and soil. Later many cyanamide containing compounds with alkali [4], alkaline
earth [5], transition metal [6], and main group metals [7] were known from the literature. Zinc
cyanamide was found to be useful in non-polluting anticorrosive white pigment [6].
In the system Ln/B/C/N (Ln = lanthanide), boride carbides and nitridoborates of lanthanides
were studied extensively of which some compounds are known to have interesting structural
features and properties. For lanthanide boride carbides, crystal structures with different anions
n- 5- 7- 3- n-such as (BC) , (BC ) , (BC ) , (B C ) , (B C) [8] and different anions composed from the 2 2 2 2 2
combination of these anions with the covalent B-C chains have been reported. LnNi (B C) 2 2
(Ln = lanthanide) is a well studied system for its coexistence of magnetic properties and
n-superconductivity [9]. LnNi (B C) (Ln = Sc, Y, Lu) compounds containing (B C) anions are 2 2 2
7-found to exhibit superconductivity with T = 15-16 K [10]. La Br (BC ) , containing (BC ) c 9 5 2 3 2
unit is superconducting with T = 6 K [11]. Lanthanide nitridoborates contain molecular c
n- 3- 6- 8- 9-anions such as (BN) , (BN ) , (BN ) , (B N ) , (B N ) [12]. In structures, these anions 2 3 2 4 3 6
may occur in combinations with each other and with nitride ions. In the crystal structures of
lanthanide nitridoborates, these anions are arranged in layers surrounded by the metal atoms
in a characteristic fashion. Terminal N atoms are capped by the metal atoms forming a square-
pyramid, and B atoms prefer a trigonal-prismatic environment of the metal atoms.
La Ni B N exhibit superconductivity at T = 14 K. It contains BN units capping the square 3 2 2 3 c
planar Ni layers with isolated N atoms reside in the La octahedra [13]. 6
In the metal–C–N system, there are different forms such as cyanide, cyanamide or
carbodiimide, dicyanamide, tricyanomethanide, tricyanoguanidinine, tricyanomelamine
- 2- - - 2-known in the literature as CN [14], (CN ) [4], [C(CN) ] [15] [N(CN) ] [16], [C(NCN) ] 2 3 2 3
3-[17], and [N(CN) ] [18] respectively for alkali metal compounds. The special feature of 2 3
these anions is that one form can be formed or transformed in to another anionic form. For
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