Studies of low co-ordinate phosphorus, arsenic and antimony compounds

• Main Author: Francis, M. D.
• Published: Swansea University 1999
• Subjects: 546
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637005

The work described in this thesis revolves around one main theme: the chemistry of the group 15 elements phosphorus, arsenic and antimony in low co-ordinate states. The work is divided into seven chapters. Chapter one is a general introduction and briefly reviews the basic properties of the group 15 elements. It also introduces the double bond rule, the concept of low co-ordination and how low co-ordinate main group species can be stabilised using bulky substituents and/or delocalisation of electrons. Chapter two describes the synthesis and characterisation of a group 15 substituted cyclopentadienyl system, namely the 1,4,2-diphosphastibolyl anion [1,4,2-P<SUB>2</SUB>SbC<SUB>2</SUB>Bu<SUP>t</SUP><SUB>2</SUB>]<SUP>-</SUP> which contains two di-co-ordinate phosphorus centres and a two co-ordinate antimony centre. Chapter three describes the preparation and characterisation of a range of transition metal complexes derived from the diphosphastibolyl ring anion in which it exhibits η<SUP>5</SUP>:η<SUP>1</SUP> co-ordination behaviour. The theme of Chapter four is the synthesis and characterisation of main group compounds derived from the diphosphastibolyl anion including a polyhetero-plumbocene and-stannocene. Chapter 5 moves away from the area of substituted cyclopentadienyl systems and into the field of group 15 heteroalkynes. The first part describes the synthesis and characterisation of a compound formulated as a rare example of a σ-phosphaalkyne complex in which the phosphaalkyne bonds to a ruthenium (0) centre <I>via</I> its lone pair of electrons. The second part discusses the coupling reaction of phosphaalkynes with an alkyne at a dirhodium centre. The co-ordination properties of the coupled products are investigated. The latter part of Chapter 5 describes the synthesis and characterisation of compounds derived from the metal mediated coupling reactions of the arsaalkyne, As≈CMes<SUP>*</SUP>. These compounds are only the second and third reported to be derived from the direct reaction of an arsaalkyne. Chapter 6 discusses the 1,2-addition reactions of phenylselenyl halides to phosphaalkynes. The factors influencing the regio- and stereochemistry of the resulting selenophosphaalkenes are considered and a possible mechanism for the process is proposed. The final chapter contains some concluding remarks on the work.