Synthesis and characterization of paramagnetic building blocks and polynuclear compounds containing FeIII, CrIII, RuIII and Os[superscript III]

Abstract

This thesis is divided into two parts. The first part is about the synthesis and characterization of a series of paramagnetic building blocks containing FeIII and CrIII. In the second part, the synthesis and characterization of a number of polynuclear compounds containing RuIII and OsIII are described. In part one, a series of tricyanoiron(III) complexes, (Ph4P)2[FeIII(5-X-salpa)(CN)3] (salpa = N-salicylidene-2-aminophenol dianions, X = H, Me, OMe, Cl or Br), have been synthesized by treatment of [FeIII(5-X-salpa)(THF)2Cl] with excess KCN in aqueous solution. These complexes have been characterized by IR, electrospray ionization mass spectrometry (ESI-MS), UV-Vis, elemental analysis and magnetic measurement. The structure of (Ph4P)2[FeIII(5-Me-salpa)(CN)3] has been determined by X-ray crystallography. The three cyanide groups are in merdorial arrangement. A series of dicyanochromium(III) complexes, A[CrIIITpX(CN)2] (A = Ph4As or Ph4P, Tp = hydrotris(pyrazolyl)borate anion, X = OEt, OMe or OH), have been synthesized by refluxing A[CrIIITpCl3] with excess KCN in various solvents. These complexes have been characterized by IR, ESI-MS, UV-Vis, elemental analysis and magnetic measurement. The structure of Ph4As[CrIIITp(OEt)(CN)2] has been characterized by X-ray crystallography successfully. In addition, a new triazidochromium(III) complex has been synthesized by reacting Ph4P[CrIIITpCl3] with excess NaN3 in methanol. This complex has been characterized by IR, ESI-MS, elemental analysis and magnetic measurement. The structure of Ph4P[CrIIITp(N3)3] has been confirmed by X-ray crystallography which shows that the three azide groups are arranged in a facial fashion. In part two, an unexpected RuIII dimer has been obtained by treatment of Bu4N[RuIII(5,5’-Cl2-salen)(CN)2] (5,5’-Cl-salen = 5,5’-dichloro-N,N’-bis(salicylidene)-o-ethyldiamine dianions) with Gd(ClO4)3 in methanol. This dimer has been characterized by IR, elemental analysis, X-ray crystallography and magnetic measurement. From its magnetic measurement, this dimer shows very weak to negligible ferromagnetic coupling between the two low spin RuIII centers below 10 K. Another unexpected RuIII 1D chain has been synthesized by slow inter-diffusion of Bu4N[RuIII(salen)(CN)2] (salen = N,N’-bis(salicylidene)-o-ethyldiamine dianions) with FeIII(salen)OAc in 1:1 of methanol: acetonitrile. This 1D chain has been characterized by IR, elemental analysis and X-ray crystallography. There is a weak ferromagnetic coupling between one low spin RuIII and one high spin RuIII centers below 2 K from its magnetic measurement. Besides, Ph4P[OsIII(salen)(CN)2] has been used as a building block to react with FeIII(salen)OAc and an unexpected OsIII 1D chain has been generated in 1:1 of methanol: acetonitrile. This polynuclear compound has been characterized by IR, elemental analysis, X-ray crystallography and magnetic measurement. The magnetic measurement shows that this 1D chain is a metamagnet at about 4.4 K.

Date of Award	15 Feb 2007
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	T C LAU (Supervisor)