University of Leicester
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The synthesis and reactivity of four-membered platinacycles containing S and/or N bonded ligands.

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posted on 2015-11-19, 08:46 authored by Mark Richard. Moore
Chapter 1 reviews the literature concerning transition metal n3-oxodimethylenemethane-(metallacyclobutan-3-one), metallathietane-3-oxide, metallathietane-3,3-dioxide and ureylene complexes. The review also briefly discusses the use of the oxodimethylenemethane metal fragment in organic synthesis. The preparation and characterisation of platinathiazetidine-3-imine complexes [Pt{lcub}NPhC(=NPh)S{rcub}L2] are described in Chapter 2. X-ray crystallographic studies on two of these derivatives (L = PPh3 or PMePh2) revealed the near-planarity of the four-membered ring. Both triphenylphosphine ligands in [Pt{lcub}NPhC(=NPh)S{rcub} (PPh3)2] are easily displaced by more basic phosphines or a chelating phosphine, and one is displaced by t-butyl isocyanide to give a monosubstituted derivative. The complex reacts with carbon monoxide to give a ring expansion product. Attempted ring expansions with small cumulenes were unsuccessful. Treatment of [Rh(C1)(CO)(dppm)]2 with the dianion of N,N'-diphenylthiourea led to formation of the "A"-frame complex [Rh2(micro-S)(CO)2(dppm)2]. Chapter 3 describes the synthesis and characterisation of platinathiadiazetidine-3,3-dioxide complexes of the type [Pt{lcub}NRS(O)2NR{rcub}L2] (R = H or Ph). X-ray crystallographic studies on two of the derivatives (R = H, L = PMePh2; R = Ph, L2 = COD) showed the four-membered rings to be entirely flat, the molecules possessing a two-fold rotation axis about the platinum-sulphur vector. Efforts to insert small cumulene molecules into the N-H bonds of [Pt{lcub}NHS(O)2NH{rcub}(PMePh2)2] are described. Treatment of this complex with phenylacetylene gave trans-[Pt(C=CPh)2(PMePh2)2], whereas with dimethyl acetylenedicarboxylate the complex [Pt{lcub}C(CO2Me)=C(CO2Me)NHS(O)2NH{rcub} (PMePh2)2] was obtained, formally derived from insertion of the acetylene into a platinum-nitrogen bond. An X-ray crystallographic study revealed that the six-membered ring in this complex adopted a "pseudo-boat" conformation. Reaction of [PtC12(COD)] with sulphamide and excess silver(I) oxide in refluxing dichloromethane, followed by treatment of the filtrate from this reaction with an excess of t-butyl isocyanide afforded a complex which was formulated as [Pt{lcub}C(=NBut)NHS(O)2NHC(=NBut){rcub}(CNBut)2]. One phosphine ligand in [Pt{lcub}NPhS(O)2NPh)(PPh3)2] can be replaced by t-butyl isocyanide to give a monosubstituted complex. The final Chapter briefly describes attempts to synthesise further Pt(II) complexes from cis-[PtC12L2] and ligands possessing "activated" protons. The interaction of cis-[PtC12(PPh3)2] with some p-tosylhydrazones in the presence of silver(I) oxide is investigated, and liquid ammonia as a synthetic reagent was also used in some of these reactions instead of silver(I) oxide. The complexes cis-[Pt{lcub}NHS(O)2C6H4-P-R{rcub}2L2] (R = H or Me) are obtained on reaction of cis-[PtC12L2] with the appropriate sulphon-amide and an excess of silver(I) oxide in dichloromethane. The reaction of cis-[PtC12(PPh3)2] with urea and silver(I) oxide in dichloromethane, or with urea in liquid ammonia, was investigated.


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University of Leicester

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  • Doctoral

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  • PhD



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