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Title: Studies of the coordination chemistry of As(III), Sb(III), Bi(III), Sn(IV) and Ti(IV) species
Author: Kisenyi, Jonathan M.
ISNI:       0000 0001 3600 5004
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1983
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The coordination and structural chemistry of complexes of Groups (IVA), (IVB) and (VB) halides with neutral (S)-donor ligands has been investigated. The N,N'-disubstituted dithiooxamides RHN (C(S)C(S)NHR (R = CH3, -C2H5, i-C3H7, n-C4H9, -C6H11, -CH2-C6H5) and dithiomalonamides RHNC (S)CH2C (S)NHR (R = -CH3, -C2H5, n-C3H7, n-C4H9) act as (S,S)-donors towards MX3 (M = Sb, Bi, X = Cl, Br) and MX4 (M = Ti, Sn, X = Cl, Br) to form adducts with the following stoichiometries: with L = dithiooxamide ligand, we have SbCl3Li1.5, SbBr3L1.5, BiCl3.L2, SnCl4.L, SnBr4.L, and TiCl4.L, while with L'= dithiomalonamide ligand, we have SbCl3.L' and SnCl4.L'. Uncomplexed dithiooxamide ligands are (S,S)-trans as shown by the crystal structures of two examples: EtNHC(S)C(S)NHEt and Pri-NHC (S)C(S)NHPr1. The crystal structures of the complexes SbCl3 (EtNHC (S)C (S) - NHEt)1.5 and SbCl3(PriNHC (S)C (S)NHPri)1.5 show the ligands in an (S,S)-bridging bonding mode while the crystal structures of BiCl3 (EtNHC (S) C (S) NHEt) 2,SnBr4 (ButnNHC (S) C (S) NHButn) , and SbCl3(EtNHC(S)CH2C(S)NHEt) show the (S,S)-chelate bonding mode. No evidence was found for the stereochemical involvement of the lone pair of electrons associated with M(III) in the structures of SbCl3 (EtNHC (S)C(S) NHEt)1.5, SbCl3 (Pri-NHC (S)C (S) NHPri)1.5 and BiCl3(EtNHC(S)C (S)NHEt)2. However, evidence for stereochemical activity of the lone pair was observed in SbCl3 (EtNHC (S)CH2C(S)NHEt) as shown in its crystal structure. Recrystallisation of SnCl4(EtNHC(S)CH2C(S)NHEt) from benzene gave an unexpected ‘cyclisation’ product [EtNHC (S)CHC(S)NHEt][SnCl6] . A plausible reaction scheme is presented. The N,N'-disubstituted oxamide RHNC(O)C (O)NHR (R = -CH3, -C2H5, n-C3H7, n-C4H9, t-C4H9, -C6H11) and malonamides RHNC (O)CH2C(O)NHR (R = -CH3, -C2H5, n-C3H7, n-C4H9, t-C4H9, -C6H11) act as (0,0)-donors towards SbCl3 and SnCl4. Toluene-3,4-dithiol (td) reacts with MCI3 (M = As, Sb, Bi) with the expulsion of HC1 to give 1:1 M(td)Cl complexes. The crystal structure of As(td)Cl shows three coordinate metal centres with the ligand acting as an (S ,S)-chelate and a stereochemically active lone pair taking up one of the tetrahedral positions on the As. Toluene-3,4-dithiol also reacts with SbCI3 and BiCl3 to give Sb(td)2 and Bi(td)2 respectively. In the bismuth complex we have complete loss of all -SH protons on td to give the ionic species Bi(td)2 while in the antimony complex one of the -S-H protons is retained as evidenced by i.r. and H n.m.r. data. Attempts to abstract this proton with base resulted in the oxidation of Sb(III) to form a 1:3 Sb:td ionic complex featuring Sb(V). The crystal structure of this complex has been determined and it shows Sb(td)3 as a tris chelate with a distorted octahedral environment around the antimony. Reactions of d- and l-penicillamine and dimercaptosuccinic acid (DMSA) with SbCl3, NaAsO2 and a 'naked' Sb3+ solvate have been briefly studied in an effort to prepare (S)- and (0)-donor complexes with possible chemotherapeutic potential. Octahedral structures involving (S,N,O)-donors in the case of penicillamine, and (S,O)- donors in the case of DMSA are proposed.
Supervisor: Not available Sponsor: European Economic Community
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry