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Metal phosphates [Elektronische Ressource] : from syntheses and structures to applications in sorption, catalysis and teeth erosion protection / presented by Khalid Hamad Abu-Shandi

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198 pages
Metal phosphates: From syntheses and structures to applications in sorption, catalysis and teeth erosion protection. Thesis in partial fulfilment of the requirements of the Doctoral Degree in Chemistry Faculty of Chemistry and Pharmacy Albert-Ludwigs-University Freiburg im Breisgau Germany Presented by Khalid Hamad Abu-Shandi From Irbid-Jordan 15-May-2003 Vorsitzender des Promotionsausschusses: Prof. Dr. G. E. Schulz 1. Referent: Prof. Dr. Ch. Janiak 2. H. Vahrenkamp Tag der Verkündigung des Prüfungsergebnisses: 15-5-2003 iAcknowledgement This thesis was prepared in the time period September-2000 to May-2003 First and foremost I should offer my thanks, obedience and gratitude to our God the great from whom I receive guide and help. I wish to extend my thanks and appreciation to my supervisor: Professor Dr. Christoph Janiak For guidance, help, continuous support and valuable discussions which made it possible to successfully complete this work. I would like to thank the members of my supervisory committee Professor Dr. Heinrich Vahrenkamp and Professor Dr. Willi Bannwarth. Special thanks to my dear wife, the woman who I love, Rana Al-Zammar for her love, encouragement and support as well as her patience to be separated from me for three years.
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Metal phosphates: From syntheses and structures to applications in
sorption, catalysis and teeth erosion protection.






Thesis in partial fulfilment of the requirements of the
Doctoral Degree in
Chemistry


Faculty of Chemistry and Pharmacy
Albert-Ludwigs-University
Freiburg im Breisgau
Germany



Presented by
Khalid Hamad Abu-Shandi
From Irbid-Jordan



15-May-2003


































Vorsitzender des Promotionsausschusses: Prof. Dr. G. E. Schulz
1. Referent: Prof. Dr. Ch. Janiak
2. H. Vahrenkamp
Tag der Verkündigung des Prüfungsergebnisses: 15-5-2003









































iAcknowledgement
This thesis was prepared in the time period September-2000 to May-2003
First and foremost I should offer my thanks, obedience and gratitude to our God the great from
whom I receive guide and help. I wish to extend my thanks and appreciation to my supervisor:
Professor Dr. Christoph Janiak
For guidance, help, continuous support and valuable discussions which made it possible to
successfully complete this work.
I would like to thank the members of my supervisory committee Professor Dr. Heinrich
Vahrenkamp and Professor Dr. Willi Bannwarth.
Special thanks to my dear wife, the woman who I love, Rana Al-Zammar for her love,
encouragement and support as well as her patience to be separated from me for three years.
Special thanks to my lovely children Hana and Noor for their love and patience to be separated
from me for three years.
Special thanks to my parents who give so much and ask for so little and their continuous praying
to God to bless me and take my hand.
Special thanks to my brothers and sisters for their encouragement and love.
I extend my thanks to my colleges in the group Paul-Gerhard Lassahn, Thomas Dorn, Dr. Vasile
Lozan, Emma Craven, Dr. Cungen Zhang and Simon Blust. I can’t forget to thank Frau Dettinger
for her help in ordering chemicals as well as her kind behaviour.
Special thanks to Franziska Emmerling for her help in XRPD and valuable discussions.
Thanks to Dr. Biao Wu for his help in the crystal structure refinement.
Thanks to Emma Craven for her help in the potentiometric titrations.
Special thanks to my friend Rafat Ahmed, a PhD student in the Fritz-Haber-Institut (MPG),
Berlin-Germany, for valuable discussions about catalysis mechanisms.
Special thanks to my cousin Anwer Abu-Amer, a PhD student in Duisburg University, for valuable
discussions about fluoride NMR.
Special thanks to the people who helped in e collection of the X-ray data sets: Dr. Werner Deck,
Horst Brombacher, Paul-Gerhard Lassahn and Dr. Bert Kersting.
Thanks to the people who did the TGA/DTA measurements Mrs Schuler and Mr K. –P. Bickel.
Thanks to Mr. K. –P. Bickel for his help with the electronic repairs of the GC/MS system.
Thanks to Dr. Heiner Winkler in Lübeck University for carrying out Mössbauer studies.





iiList of contents
Page
Abstract………………………………………………………………………………………vi
Chapter 1 - Introduction…………………………………….……………….........................1
1.1 Crystal engineering and coordination polymers………………………….......................... 1
1.2 What are "coordination polymers"?..................................................................................... 1
1.3 The ligands in coordination polymers……………………………………………………...3
1.4 Porous coordination polymers, porosity, zeolitic behavior ………………………...……...4
1.5 Catalysis……………………………………………………………………………………6
1.6 Orthophosphoric acid and phosphates……………………………………......................... 6
1.7 Potentiometric titration........................................................................................................ 7
1.8 Metal-phosphate microporous coordination polymers………………………………….... 8
1.9 Hydrothermal reactions…………………………………………………............................9
1.10 Metal coordination with 4,4'-bipyridine and piperazine………………..……….............10
1.11 Hydrogen-bonded metal ligand networks……………………………………………….11
1.12 Aluminum phosphate, AlPO -n microporous frameworks……………….......................12 4
1.13 Gallium phosphate microporous frameworks...…………………………...................... 14
1.14 Iron phosphate microporous frameworks…………………………................................ 15
1.15 Metal-phosphate microporous frameworks with metals other than Al, Ga, and Fe….... 17
1.16 Crystallization problems.................................................................................................. 17
1.17 Framework stability of porous inorganic structures upon template extraction and
calcination…………………………………………………………...............................18
1.18 Methods employed to confirm the porosity of microporous materials............................ 18
1.18.1 X-ray powder diffraction……………………………......................................... 18
1.18.2 Gas chromatography……………………………................................................ 19
1.18.3 Infrared spectroscopy……………………………...............................................19
1.18.4 Nuclear magnetic resonance spectroscopy…………………….......................... 20
1.18.5 Gravimetric analyses ……………………………...............................................20
1.19 Purpose of the work..........................................................................................................20
Chapter 2 - Experimental part………………......................................................................22
2.1 Methods and instruments.................................................................................................22
2.1.1 Potentiometric titration...........................................................................................23
2.1.2 Autoclave for hydrothermal syntheses...................................................................25
2.1.3 Oven for calcination ..............................................................................................26
2.1.4 Gas chromatography...............................................................................................26
iii2.1.5 Autoclave used in catalytic reactions.....................................................................27
2.1.6 Mössbauer spectroscopy…………………………………………………………28
2.2 Synthesis of molecular (metal) phosphates…................................................................29
2.2.1 (C H N )(H PO ) ·2H O (1) .............................................................................29 10 12 2 2 4 2 2
2.2.2 (C H N )(HPO )·H O (2)…………………………………………...…………..29 4 12 2 4 2
2.2.3 [Co(H O) ](C H N )(HPO ) (3) and Co (PO ) ·8H O (4)…............................ 29 2 6 4 12 2 4 2 3 4 2 2
2.2.4 [Ni(H O) ](C H N )(HPO ) (5)..........................................................................30 2 6 4 12 2 4 2
2.2.5 (C H N )(HPO )·2H O (6)...................................................................................31 5 14 2 4 2
2.2.6 [Fe(H O) ](C H N )(HPO ) (7)......................................................................... 31 2 6 4 12 2 4 2
2.2.7 [Cu(4,4'-bipy) (H PO ) (H O) ] (8).......................................................................31 2 2 4 2 2 2
2.3 Syntheses of iron phosphate coordination polymers.....................................................32
2.3.1 {[Fe(H PO ) (4,4'-bipy)(H O) ]·(OH)(4,4'-bipy)} (9).........................................32 2 4 2 2 2 n
2.3.2 {[Fe(NO ) (4,4'-bipy)(H O) ]·(OH)(H O)} (10)..................................................32 3 2 2 2 2 n
2.4 Syntheses of metal phosphate (open) frameworks.........................................................33
2.4.1 {[(H N(CH ) NH ) ][Ga (PO ) (HPO ) (OH) F ]·6H O} (11)…….……….. 33 3 2 6 3 4 16 4 14 4 2 2 7 2 n
2.4.2 {[C H N ][Ga (PO ) (HPO )](H2O)} (12).........................................................34 4 12 2 3 4 3 4 n
2.4.3 {[NH ][Fe (PO ) (OH)H O)]·H O} (13)……......................................................34 4 2 4 2 2 2 n
2.4.4 {[C H N ] [Fe (PO )(H PO ) ]·H O} (14)…...............................................35 4 11.2 2 1.5 2 4 0.6 4 2 2 n
2.4.5 {[Fe (PO ) (H PO ) ]} (15)……….…..........................................................…35 7 4 2 0.5 4 4 n
2.4.6 {[C H N ][Fe (PO ) (HPO )](H O)} (16)...........................................................36 4 12 2 3 4 3 4 2 n
2.5 Syntheses of biphosphinic acids and their iron derivatives..........................................36
2.5.1 Na[H N(CH CH C(OH)(PO H )(PO H)]·H O (17)..............................................36 2 2 2 3 2 3 2
2.5.2 {Fe(H NCH CH H) ) } (18)..............................................................37 3 2 2 3 2 2 n
2.5.3 Na[H N(CH ) C(OH)(PO H)(PO H )] (19)...........................................................37 2 2 3 3 3 2
2.5.4 Na [H N(CH ) H) ]·2H O (20)...........................................................38 2 2 2 4 3 2 2
2.5.5 {[(FeCl) {(Fe(H O) {H N(CH ) C(OH)(PO H ) } ]·2H O} (22)........................39 2 2 2 3 2 4 3 x 2 2 2 n
2.6 Sorption studies.................................................................................................................39
2.6.1 General....................................................................................................................39
2.6.2 {[(H N(CH ) NH ) ][Ga (HPO ) (PO ) ]} , 11, cGa1…………………...........41 3 2 6 3 4 16 4 2 4 14 n
2.6.3 {[C H N ][Ga (PO ) (HPO )]} , 12, cGa2...........................................................42 4 12 2 3 4 3 4 n
2.6.4 {[NH ][Fe (PO ) (OH)]} , 13, cFe1......................................................................43 4 2 4 2 n
2.6.5 {[C H N ][Fe (PO ) (HPO )]} , 16, cFe2............................................................43 4 12 2 3 4 3 4 n
2.7 Catalysis studies: The oxidation of pentane by molecular oxygen...............................44
2.7.1 GC/MS calibration…………………………………………………………………….44
2.7.2 {[(H N(CH ) NH ) ][Ga (HPO ) (PO ) ]} , 11, cGa1………………...............45 3 2 6 3 4 16 4 2 4 14 n
iv2.7.3 Addition of t-butyl hydroperoxide as a free radical initiator..................................48
2.7.4 {[C H N ][Ga (PO ) (HPO )]} , 12, cGa2...........................................................49 4 12 2 3 4 3 4 n
2.7.5 {[NH ][Fe (PO ) (OH)]} , 13, cFe1......................................................................50 4 2 4 2 n
2.7.6 {[C H N ][Fe (PO ) (HPO )]} , 16, cFe2............................................................50 4 12 2 3 4 3 4 n
2.8 X-ray structure determination ………………………………………...………..……...51
Chapter 3 - Results and discussion ……………………………..…………………..……...54
3.1 Potentiometric titrations…………………………………………………………………..54
3.2 Crystal structures…………………………………………………………………..……58
3.2.1 (C N H )(H PO ) ·2H O (1)…………………………..………………….…….58 10 2 12 2 4 2 2
3.2.2 [M(H O) ](C H N )(HPO ) (M = Ni, Co and Fe) (3), (5) and (7) 2 6 4 12 2 4 2
respectively………………………………………………………………....…....60
3.2.3 [Cu(4,4'-bipy) (H PO ) (H O) ] (8)……………..................................…....…….64 2 2 4 2 2 2
3.2.4 {[Fe(H PO ) (4,4'-bipy)(H O) ]·(OH)(4,4'-bipy)} (9)..........................................67 2 4 2 2 2 n
3.2.5 {[Fe(NO ) (4,4'-bipy)(H O) ]·OH(H O)} (10)…………………………….........72 3 2 2 2 2 n,
3.2.6 {[NH ][Fe (PO ) (OH)H O)]·H O} (13)…………………………......................77 4 2 4 2 2 2 n
3.2.7 {[C N H ] [Fe (PO )(H PO ) ]·H O} (14)……...........................................84 4 2 11.2 1.5 2 4 0.6 4 2 2 n
II III3.2.8 [Fe Fe (PO ) (H PO ) ] (15)..........................................................................91 5 2 4 2 0.5 4 4 n
3.2.9 {[C H N ][Fe (PO ) (HPO )(H O)]} (16)...........................................................97 4 12 2 3 4 3 4 2 n
3.2.10 {Fe(NH CH CH C(OH)(PO H) } (18).............................................................101 3 2 2 3 2 n
3.2.11 {[(FeCl) {(Fe(H O) {H N(CH ) C(OH)(PO H ) } ]·2H O} (22)....................105 2 2 2 3 2 4 3 x 2 2 2 n
3.3 Crystal design and crystal engineering.............................................................................111
Chapter 4: Porous frameworks as molecular sieves………………………………….…113
Chapter 5: Porous frameworks as catalysts in the oxidation of pentane by molecular
oxygen………………………………………………………………………….126
Chapter 6: Conclusion…………………………………………………………………….132
Appendixes
Appendix 1: GC/MS results for using Ga1 in sorption studies..............................................135
Appendix 2: GC/MS results for using Ga2 in sorption studies..............................................137
Appendix 3: GC/MS results for using Fe1 in sorption studies..............................................139
Appendix 4: GC/MS results for using Fe2 in sorption studies..............................................141
Appendix 5: GC/MS results for guest(s)/toluene) blanks used in sorption studies...............142
References…………………………………………………………………………………..146





vAbstract
Polymeric metal-phosphate compounds should be synthesized and characterized. An open-
framework structure of the material was a desirable feature. As a synthetic route a
hydrothermal procedure with organic amines as templates, i.e. structure-directing agents was
developed and applied. Other solution methods failed to give us open-framework materials.
Iron was focussed on as the metal because of its possible redox activity and electronic (high-
/low-spin, spin-crossover, magnetic interactions) properties. Redox activities were of interest
in the sought-after application of such open-framework materials in catalysis. The electronic
aspects were investigated in collaboration by using Moessbauer spectroscopy. The
synthesized new compounds were structurally analyzed by single-crystal X-ray diffraction.
The thermal properties and stability were investigated using thermogravimetry (TGA)
together with X-ray powder diffractometry (XRPD) to elucidate the loss of guest molecules
and the stability of the host framework.
Crystals grown from the reaction of piperazinedium phosphate, (C H N )(HPO ) with 4 12 2 4 2
Co(II) or Ni(II) at normal pressure and temperature gave only a hydrogen-bonded framework
of composition [M(H O) ](C H N )(HPO ) (M = Co, Ni). Also, the compound 2 6 4 12 2 4 2
[Cu(H PO ) (4,4'-bipy) (H O)], prepared by non-hydrothermal routes, is a molecular 2 4 2 2 2 2
complex. The possible metal-metal bridging mode of 4,4'-bipyridine is blocked by
intermolecular hydrogen bonding from the dihydrogenphosphate to the second N atom of 4,4'-
bipy. Even under hydrothermal conditions starting with N-methylpiperazine a hydrogen-
IIbonded product resulted, as was found with the compound [Fe (H O) ](C H N )(HPO ) 2 6 4 12 2 4 2
which was isostructural to the above Co and Ni complex. An N-carbon bond is easily cleaved
under hydrothermal conditions. Thus, the hydrothermal treatment of 1,3-diaminopropane or
1,4-diaminobutane with iron(III) chloride and phosphoric acid in yielded in both cases the 3-
III +D framework {[NH ][Fe (OH)(PO ) (H O)]·H O} (A), with the template NH derived 4 2 4 2 2 2 n 4
from the diamine cleavage. The 3-D mixed-valence iron phosphate
II III{Fe Fe (PO ) (H PO ) } was obtained hydrothermally starting with N-methylpiperazine 5 2 4 2 0.5 4 4 n
IIand Fe Cl . 2
II IIICompounds {[Fe (H PO ) (4,4'-bipy)(H O)]·H O·4,4'-bipy} and {[Fe (NO ) (4,4'-2 4 2 2 2 n 3 2
bipy)(H O) ](OH)(H O)} are 1-D coordination polymers synthesized using a similar 2 2 2 n
nhydrothermal procedure but replacing Bu NOH by nitric acid as the pH adjustment reagent in 4
the later.
IIICompounds {[C H N ][Fe (PO ) (HPO )(H O)]} ( B, 3-D) and mixed-valence 4 12 2 3 4 3 4 2 n
II III{[C N H ] [Fe Fe (PO )(H PO ) ]·H O} (1-D) have been synthesized using a similar 4 2 11.6 1.5 4 0.8 4 2 2 n
IIhydrothermal method (starting from Fe Cl ) with a difference of using water as a solvent in 2
the former and THF in the latter.
The 2-D layer compounds {Fe(NH CH CH CH(OH)(PO H) } and 3 2 2 3 2 n
{[(FeCl) {(Fe(H O) {H N(CH ) C(OH)(PO H ) } ]·2H O} were prepared using the 2 2 2 3 2 4 3 x 2 2 2 n
IIhydrothermal combination of biphosphonic acids with Fe Cl using water as the solvent. 2
The guest species from the open-framework materials A and B together with a gallium
analog of B and the literature material
{[H N(CH ) NH ] [Ga (PO ) (HPO ) (OH) F ]·6H O} (C) could be removed (followed by 3 2 6 3 4 16 4 14 4 2 2 7 2 n
TGA) with the framework proven to remain intact (by XRPD). The resulting guest-depleted
open-framework showed sorption activities for different types of organic compounds (namely
alkanes, alcohols, ethers, amines and aromatic) and a certain degree of selectivity towards the
size and the functionality of the sorbtive. Materials B and C but not A exhibited catalytic
properties in the regioselective oxidation of n-pentane to 3-pentanol.
viChapter 1
Introduction

1.1 Crystal engineering and coordination polymers
There is a wide interest to achieve control of the aggregation of organic ligands and metal
ions. Crystallization and crystal structure design are of great importance in inorganic
coordination chemistry but are often highly unpredictable and incompletely understood.
Recent interest in crystal engineering indicates the need for a greater understanding of
crystallization processes [1]. Major interactions relevant to inorganic crystal engineering are
covalent metal-ligand interactions, hydrogen bonding [2,3,4,5,6,7,8,9,10,11,12,13,14,15,
16,17] and even π-stacking or C-H···π interactions [18,19,20,21,22,23,24].
The formation mechanisms of coordination materials synthesized under mild hydrothermal
conditions are still not elucidated and it is necessary to utilize in situ characterizations for
gaining information and new insights concerning the chemical processes which take place
within the reaction cell. These mild, solvent-mediated reaction conditions have allowed access
to many novel materials with important applications. Good examples include zeolites and
other microporous materials used in gas separation and shape-selective catalysis or in layered
cathode materials for use in efficient rechargeable batteries [25,26].

1.2 What are "coordination polymers"?
Coordination polymers [27,28], also known as metal-organic coordination networks
(MOCNs) or metal-organic frameworks (MOFs), are metal-ligand compounds that extent
"infinitely" into one, two or three dimensions (1D, 2D or 3D, respectively) via more or less
covalent metal-ligand bonding (Figure 1.1) [29]. The ligand must a bridging organic group.
At least in one extended dimension the metal atoms must solely be bridged by this organic
ligand. Furthermore, at least one carbon atom must lie between the donor atoms. The last
– 2–requirement excludes groups such as organyloxides (RO ), organophosponates (RPO ) or 3
–organosulfonates (RSO ), which bridge with their one "inorganic" end group only, from 3
giving rise to coordination polymers. Infinite metal-ligand assemblies where the metal-
organic connectivity is interrupted by "inorganic" bridges, such as -(R,H)O-, -Cl-, -CN-, -N -, 3
-(R,O)PO - and -(R,O)SO - or where an extended inorganic metal-ligand network is lined by 3 3
only terminal organic ligands are called organic-inorganic hybrid-materials (Figure 1.2) [30].



1

1D ... MDCDM ...
... ...
... M DCDM ...
2D
D D
C C
D D
... MDCDM ...
......
... ...
... ...
... M DCDM ...
D D3D ... ...C C
D DD D
... DCDM ...M ...... C C
D D
D D Figure 1.1. Schematic representation of the C C
... ... definition of 1D, 2D or 3D coordination
... M DCDM ...
D D D polymers having organic bridging ligands
C C... ... with at least one carbon atom in-between the D D
... MDM CDM ... donor atoms. Donor atoms can be O, N, S, Se ... ...
etc. ... ...


Weaker noncovalent interactions, such as hydrogen bonding or π-π stacking are important for
the packing of the one-dimensional chains, two-dimensional nets and three-dimensional
frameworks [31,32]. However, the multi-dimensional supramolecular architectures of metal
complexes which are created by purely hydrogen bonding (Figure 1.2) [33,34,35,36] are not
viewed as coordination polymers.
2

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