Synthesis of Novel Alkaline Earth Tosylate Complexes through

60 Pages·2015·1.95 MB·English

by  Adam J. Brooks

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Synthesis of Novel Alkaline Earth Tosylate Complexes
through Donor Studies

Adam J. Brooks
Candidate for B.S. Degree
and Renée Crown University Honors

May 2012

Honors Capstone Project in Chemistry
Capstone Project Advisor: _______________________
Dr. Karin Ruhlandt-Senge
Capstone Project Reader: _______________________
Dr. Mathew Maye
Honors Director: _______________________
Stephen Kuusisto, Director
Date: April 25, 2012
Copyright © 2012 by Adam J. Brooks
All rights reserved
Abstract
Salt metathesis has become a critical reaction pathway in organometallic
chemistry; however, for alkaline earth metals this process is hindered by the need
of highly pure and expensive metal iodides as starting materials. This contribution
highlights recent attempts to identify inexpensive reagents for salt metathesis.
Alkaline earth-tosylates can be prepared cost effectively using p-toluenesulfonic
acid in one-pot reactions in water. The coordinated water molecules can be
removed by gentle heating under vacuum. The anhydrous tosylates, however,
have major solubility limitations as the result of extensive aggregation networks.
The goal of this study was to increase the solubility of the tosylates by the
addition of electron donating crown ethers, which may reduce aggregations.
Crown ethers are known for their ability to coordinate metal ions in the cavity of
the macrocycles and form sandwich or club sandwich complexes.
Four new complexes were synthesized and characterized using X-ray
crystallography, {[Ca(OH ) (18-crown-6)] [OTs] ·2H O} ,{[Ca(OH ) (18-
2 2 3 3 2 ∞ 2 2
crown-6)] [OTs] } , [Sr(OTs) (18-crown-6)(OH )] , and [Ba(OTs) (18-crown-
2 4 ∞ 2 2 ∞ 2
6)(OH ) ] . The two calcium complexes exhibit unique metal center
2 2 ∞
environments while the strontium and barium complexes show distinct
coordination numbers and arrangements of coordinating ligands. The arrangement
of tosylate anions in the structures is determined by the coordination atmosphere
of water molecules to the metal centers. All four characterized compounds were
found to be soluble in pyridine, which improves upon previous studies that only
show tosylate complexes soluble in water.
Table of Contents:
List of Illustrative Material i
Abbreviations iv
Acknowledgements v
1. Introduction
1.1 Alkaline Earth Metal Chemistry 1
1.2 Alkaline Earth Amides 3
1.3 Alkaline Earth Iodide Alternatives 5
1.4 Aggregations 7
1.5 Goals 9
2. Donor Studies 9
3. Experimental 14
3.1 General Experiment 14
3.2 Synthetic Routes 15
3.2.1 Donor Addition 15
3.2.2 Direct Metallation 15
3.3 Alkaline Earth Crown Tosylates 16
3.3.1 Specific Syntheses 16
4. Results and Discussion 19
4.1 Structural Characterization for Compounds 1-4 19
4.1.1 Structural characterization of {[Ca(OTs) 20
(18-crown-6)(OH ) ] [OTs] ·2H O} , (1)
2 2 3 3 2 ∞
4.1.2 Structural characterization of {[Ca(OH ) 23
2 2
(18-crown-6)] [OTs] } , (2)
2 4 ∞
4.1.3 Structural characterization of [Sr(OTs) 27
2
(18-crown-6)(OH )] , (3)
2 ∞
4.1.4 Structural characterization of [Ba(OTs) 30
2
(18-crown-6)(OH ) ] , (4)
2 2 ∞
4.2 Thermogravimetric Analysis 34
4.2.1 TGA of Compound 1 34
4.2.2 TGA of Compound 2 35
4.2.3 TGA of Compound 3 36
4.2.4 TGA of Compound 4 37
4.3 Infrared Spectroscopy 38
4.3.1 IR of Compound 1 38
4.3.2 IR of Compound 2 39
4.3.3 IR of Compound 3 39
4.3.4 IR of Compound 4 40
4.4 Solubility Studies 40
4.5 Other Reactions 41
5. Conclusions and Future Work 41
6. References 43
7. Summary 45
i

List of Illustrative Materials:
Figures:
Figure 1.1: Periodic trends for group I and II metals
Figure 1.2: HMDS ligand
Figure 1.3: Diagram of Trifluoromethanesulfonate
Figure 1.4: p-Toluenesulfonic Acid
Figure 1.5: Breaking up of polymers by donor addition
Figure 2.1: Sandwich and club sandwich orientations
Figure 2.2: Examples of crown ethers
Figure 2.3: Various donors explored
Figure 4.1: Structure of 1
Figure 4.2: Hydrogen bonded network for 1
Figure 4.3: Structure of 2
Figure 4.4: Hydrogen bonded network for 2
Figure 4.5: Structure of 3
Figure 4.6: Hydrogen bonded network for 3
ii

Figure 4.7: Structure of 4
Figure 4.8: Hydrogen bonded network for 4
Figure 4.9: TGA of 1
Figure 4.10: TGA of 2
Figure 4.11: TGA of 3
Figure 4.12: TGA of 4
Figure 4.13: IR of 1
Figure 4.14: IR of 2
Figure 4.15: IR of 3
Figure 4.16: IR of 4
Tables:
Table 2.1: Ionic and cavity diameters for alkali, alkaline earth, and crown ethers
Table 4.1: Crystallographic data and structural refinement for compounds 1-4
Table 4.2: Selected bond lengths and angles for 1
Table 4.3: Selected hydrogen bonding distances for 1
Table 4.4: Selected bond lengths and angles for 2
iii

Table 4.5: Selected hydrogen bonding distances for 2
Table 4.6: Selected bond lengths and angles for 3
Table 4.7: Selected hydrogen bonding distances for 3
Table 4.8: Selected bond lengths and angles for 4
Table 4.9: Selected hydrogen bonding distances for 4
Schemes:
Scheme 1.1: Salt metathesis reaction
Scheme 1.2: Synthesis of alkaline earth hydrated and dehydrated tosylates
Scheme 4.1: Donor addition reactions
iv

Abbreviations:
12-crown-4, 12-c-4: 1,4,7,10- Tetraoxacyclodecane
15-crown-5, 15-c-5: 1,4,7,10,13- Pentaoxacyclopentadecane
18-crown-6, 18-c-6: 1,4,7,10,13,16- Hexaoxacyclooctadecane
A: Alkali
Ae: Alkaline-Earth
Bp: Boiling Point
CVD: Chemical vapor deposition
diglyme: Diethylene glycol dimethyl ether
FT-IR: Fourier Transform Infrared Spectroscopy
HMDS: Hexamethyldisilazane
Ln: Lanthanide
Mp: Melting Point
MOCVD: Metal organic chemical vapor deposition
NMR: Nuclear magnetic resonance spectroscopy
OTs: p-toluenesulfonic acid
PMDTA: N,N,N’,N’,N”- pentamethyldiethylenetriamine
Pyr: Pyridine
RT: Room temperature
TGA: Thermogravimetric Analysis
THF: Tetrahydrofuran
TMEDA: N,N,N’,N’- Tetramethylethylenediamine