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Some organic and organotin reactions of 2-(2' dimethylaminoethylimino-methyl) phenols
Author
Hu, Hong Juan
Supervisor
Khoo, Lian Ee
Abstract
This thesis describes the synthesis of several new N-(2'-dimethylaminoethyl)arylidene-imines (L) of the formula 2-HOC6H3(X)C(R)=N(CH2)nNR'2 and their reduced products (LH) with the formula of 2-HOC6H3(X)CH(R)NH(CH2)nNR'2 (where X = H, 3-OCH3, 5-Br and 5-NO2; R = H and CH3; n = 2 and 3; R' = CH3 and C2H5). The coordination behaviour towards diphenyltin dichloride and triphenyltin chloride of these newly synthesized Schiff bases, together with their saturated analogues, was also investigated. For the sale of convenience, the work embodied in this thesis is presented in the following chapters.
In the first chapter of the thesis, a critical review of the organic reactions as well as the complexation reactions of Schiff bases with organotins was presented.
The second chapter incorporates the details of suppliers, purity and other specifications of materials and instruments used in the present study.
The third chapter describes the preparation and characterization of a series of N-(2'-dimethylaminoethyl)arylideneimines (L) derived from the condensation reaction of substituted salicylaldehydes and N,N-dialkylethylenediamines. These newly synthesized Schiff bases were found to exist as zwitterions with a strong 6-membered intramolecular hydrogen bond between the phenolic proton and the azomethine N atom. The strength of this hydrogen bond is very much dependent on the nature of the substituents (X) attached to the phenyl ring.
The fourth chapter concerns the reactions of L with NaBH4. The results derived from the C, H, N elemental analyses, IR, 1H NMR, 13C NMR and X-ray crystallographic studies of the products (LH-1-LH-7) show that this series of saturated Schiff base analogues exists in zwitterionic forms via the formation of a 6-membered intramolecular hydrogen bond. The study on these hydrogen bonds indicates that there is a gradual proton transfer process of the phenolic proton to the secondary amine N atom (O-H...N<->O...H-N) as the phenolic proton acidity increases due to the substituents at the phenyl ring. It is also found that for LH-5 (5-nitro substituted), the most acidic in the LH series of compounds, the intramolecular hydrogen bonding is broken and replaced by an intermolecular hydrogen bonding.
Two compounds, S1 and S2, were isolated as the major products for the two reactions involving LH-4 and LH-6 respectively. These two compounds were also characterized using C, H, N elemental analyses, IR, 1H NMR and 13C NMR. An X-ray crystal structure determination of S1 was performed to confirm the proposed structure for S1 and S2 on the basis of their physico-chemical and spectral studies.
The synthesis and characterization of the triphenyltin chloride and diphenyltin dichloride adducts of L were described in Chapter 5. L compounds reacted with triphenyltin chloride or diphenyltin dichloride in zwitterionic forms and the coordination was through the phenolic oxygen atom resulting in a shift of the phenolic proton to the azomethine N atom (O-H...N<->O...H-N) in the 6-membered intramolecular hydrogen bond found in the free ligand. The structural implications derived from spectroscopic studies were also confirmed by the X-ray results for [Ph3SnCI:L-1]0.5C6H6The last chapter of the thesis deals with the synthesis and structural features of the triphenyltin chloride and diphenyltin dichloride adducts of LH compounds. It was found that all the LH ligands reacted with organotins via its phenolic oxygen atom as this atom was polarized because of the presence of the zwitterions in LH-1-LH-6. Thus the Ph3SnC1 tin atom in these adducts is pentacoordinated with the three phenyl rings in the equatorial positions while the chloride atom and the oxygen of the ligand occupying the axial positions. An X-ray structural crystallography for [Ph3SnC1:LH-3]CH3OH reveals the presence of methanol beside confirming the proposed structure for the adducts..
In the first chapter of the thesis, a critical review of the organic reactions as well as the complexation reactions of Schiff bases with organotins was presented.
The second chapter incorporates the details of suppliers, purity and other specifications of materials and instruments used in the present study.
The third chapter describes the preparation and characterization of a series of N-(2'-dimethylaminoethyl)arylideneimines (L) derived from the condensation reaction of substituted salicylaldehydes and N,N-dialkylethylenediamines. These newly synthesized Schiff bases were found to exist as zwitterions with a strong 6-membered intramolecular hydrogen bond between the phenolic proton and the azomethine N atom. The strength of this hydrogen bond is very much dependent on the nature of the substituents (X) attached to the phenyl ring.
The fourth chapter concerns the reactions of L with NaBH4. The results derived from the C, H, N elemental analyses, IR, 1H NMR, 13C NMR and X-ray crystallographic studies of the products (LH-1-LH-7) show that this series of saturated Schiff base analogues exists in zwitterionic forms via the formation of a 6-membered intramolecular hydrogen bond. The study on these hydrogen bonds indicates that there is a gradual proton transfer process of the phenolic proton to the secondary amine N atom (O-H...N<->O...H-N) as the phenolic proton acidity increases due to the substituents at the phenyl ring. It is also found that for LH-5 (5-nitro substituted), the most acidic in the LH series of compounds, the intramolecular hydrogen bonding is broken and replaced by an intermolecular hydrogen bonding.
Two compounds, S1 and S2, were isolated as the major products for the two reactions involving LH-4 and LH-6 respectively. These two compounds were also characterized using C, H, N elemental analyses, IR, 1H NMR and 13C NMR. An X-ray crystal structure determination of S1 was performed to confirm the proposed structure for S1 and S2 on the basis of their physico-chemical and spectral studies.
The synthesis and characterization of the triphenyltin chloride and diphenyltin dichloride adducts of L were described in Chapter 5. L compounds reacted with triphenyltin chloride or diphenyltin dichloride in zwitterionic forms and the coordination was through the phenolic oxygen atom resulting in a shift of the phenolic proton to the azomethine N atom (O-H...N<->O...H-N) in the 6-membered intramolecular hydrogen bond found in the free ligand. The structural implications derived from spectroscopic studies were also confirmed by the X-ray results for [Ph3SnCI:L-1]0.5C6H6The last chapter of the thesis deals with the synthesis and structural features of the triphenyltin chloride and diphenyltin dichloride adducts of LH compounds. It was found that all the LH ligands reacted with organotins via its phenolic oxygen atom as this atom was polarized because of the presence of the zwitterions in LH-1-LH-6. Thus the Ph3SnC1 tin atom in these adducts is pentacoordinated with the three phenyl rings in the equatorial positions while the chloride atom and the oxygen of the ligand occupying the axial positions. An X-ray structural crystallography for [Ph3SnC1:LH-3]CH3OH reveals the presence of methanol beside confirming the proposed structure for the adducts..
Date Issued
1997
Call Number
QD412.S7 Hu
Date Submitted
1997