Synthesis and properties of bidentate coordination compounds of tin

This Thesis describes the synthesis, structural characterization and properties of some tin(II) and tin(IV) compounds containing bidentate ligands.
Chapter 1 describes the main spectroscopic techniques used in the identification of tin(II) compounds; infra-red, 119Sn Mössbauer and n.m.r spectroscopy are outlined, and relevant examples given. A comprehensive listing is given of the main spectroscopic and structural properties of known tin(]3) compounds.
Chapter 2 describes the general synthetic methods employed for the formation of tin(II)-oxygen heterocyclic compounds. A range of catecholate and related complexes of tin(II) were synthesized and the role of the substituent investigated with regard to their physical properties, especially their solubilities. The use of 4-nitrocatechol leads to a soluble product, {Sn[O-4-NO2-C6H3O][OC4H8]}>sub>n
, which enabled it to be studied spectroscopically and its solid state structure to be determined. The nature of the bonding in {Sn[O-4-NO2-C6H3O][OC4H8]}n was investigated using Extended Hiickel molecular orbital calculations.
Chapter 3 describes the chemical reactivity of the novel, soluble, tin(II)-oxygen heterocycle {Sn[O-4-NO2-C6H3O][OC4H8]}n. Reaction with iodine gives SnI2 [O-4-NO2-C6H3O][OC4H8]2. Reaction with the Lewis base such as 1,2-diaminopropane gives Sn[NH2CH2CH(Me)H2N][O-4-NO2-C6H3O][OC4H8], whilst benzyltriethylammonium chloride gives {[Et3BzN][SnCl(O-4-NO2-C6H3O)]}n. The solid-state structure of the compound consists of polymeric chains of [SnCl(O-4-NO2-C6H3O)]- and associated [Et3BzN]+ cations. Reaction with BF3.Et2O gives the adduct F3B.Sn[O-4-NO2- C6H3O][OC4H8]. Reaction with W(CO)5thf gives {(OC)3W.Sn[(O-4-NO2- C6H3O)(OC4H8)]}2 in which the tungsten atoms are believed to be bound η6 to the aromatic rings. Reaction with bis(triphenylphosphine)platinum-ethylene or tris(triphenylphosphine)platinum gives {PtH[PPh3]3}{[μ2-O][μ2-OH][Sn(O-4-NO2- C6H3O)]2}, the anion containing tin(II) and tin(IV) centres. Reaction with RhCl[CNC8H9]3 gives {RhCl[CNC8H9]3[μ2-Sn(O-4-NO2-C6H3O)]}2. Reaction with Ph3PAuCl gives the cluster Au4(PPh3)4(μ2-SnCl3)2, which is the first known example of a compound containing a μ2-SnX3 fragment. In comparison with SnCl2, {Sn[O-4-NO2- C6H3O][OC4H8]}n only weakly inserts into the platinum-chlorine bonds of PtCl2(dppe). Two molar equivalents of SnCl2 reacts with PtCl2(dppe) to give Pt(dppe)(SnCl3)2. Addition of a further equivalent of SnCl2 in the presence of tetraethylammonium chloride gives [Et4N][Pt(dppe)(SnCl3)3]. The platinum centre in this ion has a distorted trigonal bipyramidal geometry.
Chapter 4 describes the synthesis of a number of tin(II)-sulphur heterocycles. The reaction between Sn[SC6H4S] and TMEDA gives a soluble adduct, Sn[SC6H4S]TMEDA. A number of tin(II)-nitogen heterocycles were also synthesized. Their intense colours and their instability towards air oxidation indicated that they were monomeric in the solid-state.
Chapter 5 outlines the basis for non-linear optical properties, especially their SHG effects. A wide range of tris(catecholato)tin(IV) compounds were synthesized and tested for SHG activity. A number were found to have a significant SHG effect, especially [(O-4- NO,sub>2
-C6H3O)3Sn][NHEt3]2, which has an SHG effect 1.33 x urea.

Advisor: Mingos, D
Mingos, M