Ligand displacement reactions of binuclear ruthenium complexes

Abstract

CHAPTER.1 states the main objective of this work, the catalytic conversion of ethene to vinyl chloride using triple-halide-bridged binuclear ruthenium complexes, and emphasises the industrial significance of such a process.A brief account of relevant ruthenium chemistry is also given.

CHAPTER.2 describes a new synthetic route to the complex RU2CI4 (PMe2Ph)5 involving photolysis of monomeric species. This and related complexes are used to prepare novel cationic triple-halide-bridged binuclear ruthenium complexes with the general formula [Ru2X3(L) (PR3)5 + where L = alkene, alkyne and dinitrogen and X = Cl or Br . The ease of formation of these cationic complexes is dependent upon the nature of the tertiary phosphine ligands and a general trend has been identified. Electrochemical studies on the C2H4 and N2 complexes are described. The former complex has been shown to undergo alkene displacement rather than modification in the presence of a variety of nucleophiles.

CHAPTER.3 describes the synthesis of the unusual asymmetric double-chloride-bridged binuclear complexes (Et2PhP)(L)2~ C1RuC12RuC1(PEt2Ph)3 (L = C2H4 , PhCHCH) via chemical reduction of the mixed-valence complex Ru2Clç-(PEt2Ph) 4 . Preliminary evidence is given for the slow conversion of ethene to ethanal in the bis-ethene complex in the presence of H20 or OH .

CHAPTER.4 discusses the reactions of RuCl2(PPh3)3 and RuC12(CO)(PPh^)2dmf with the alkenyl tertiary phosphine Ph2P(CH2)2CH=CH2 . In both cases the final products have been characterised by spectroscopic and X-ray structural analysis, and a stepwise ligand displacement pathway has been identified for RuC12(CO)(PPh3)2dmf. Attempted coupling reactions of the new alkenyl phosphine complexes are described. Triple-chloride-bridged binuclear complexes containing alkenyl phosphines, prepared using the chloride- abstracting technique covered in Chapter 2, are also described.

CHAPTER.5 is concerned with the unexpected reaction of RuC12(CO)(PPh3)2dmf and phenylacetylene to give RuC12(CO)2(PPh^)2 and toluene. A series of experiments is described which have allowed a tentative reaction pathway to be proposed for this reaction. Treatment of RuCl2 (CO)2(PPh3)2dnf with dimethylacetylenedicarboxylate is shown to be an effective route to the known complex (Ph3P) (CO) ClRuCl3Ru (CO) ( PPh3)2 .

CHAPTER.6 describes the synthesis of the novel heterotri- metallic complex Ru2C15(PEtPh2)4.Ag(PEtPh2) by reaction of RuC12(PEtPh2)3, Ru2C14 (PEtPh2)5 or [Ru2C13 (PEtPh2)g]Cl with AgCl. Preparation of the nitrato complex RuCl(02N0)(PEtPh2)3 via RuC12(PEtPh2)3 and Ag (PEtPh2)2N03 is also discussed. X-ray structural analyses have been carried out on both complexes. Attempts to prepare novel fluoride/tertiary phosphine ruthenium(II) complexes are described.