Main group chemistry (CH2201)
To describe the bonding in inorganic molecules and their illustration by spectroscopic methods. To describe and compare the chemical, structural and physical properties of the non-transition elements. To give students an appreciation of the differing reactivities of elements within the s and p blocks.
This module extends the principles of bonding, structure and reactivity in inorganic compounds with reference to the chemical, spectroscopic and structural properties of compounds formed by the main group elements. The chemistry of the groups and periodic trends are surveyed. Topics treated in more depth include electron deficient compounds and extended molecular structures (inorganic rings, chains and clusters).
Topics will include boranes and carboranes - synthesis, reactivity, 1H and 11B NMR and multi-nuclear NMR, bonding schemes and Wade’s rules (plus extensions to other main group systems); BX3 and BN systems and analogy to CC systems; phosphazenes; disilenes; NS systems; fullerenes. Experimental spectroscopic evidence for structure and bonding from IR, Raman, Mössbauer and NMR spectroscopies will be discussed.
Periodicity will be used to explain structures of oxides, halides (with examples of 19F NMR) and oxyanions of B, Si and oxyanions of B, Si and P.
Trends in electronic, atomic and elemental properties (catenation).
Trends in reactivity and structure of main group of main group halides, hydrides and oxides/oxyanions.
Elucidation of structural information by spectroscopic methods (multinuclear NMR, IR, Raman etc.). Coupling patterns, quadrupolar nuclei.
Electron deficient compounds, diborane, Wade’s Rules, isolobal principle, carboranes, metallaboranes other main group clusters. Synthesis, structure, reactivity.
Coordination chemistry of main group metals, crowns, cryptands, use of non-aqueous solvent systems, acidity function, super-acids (synthesis of Na- and polyhalogen cations).
p-bonding, borazine and benzene, phosphazene, S/N systems. Emphasis on difference between first row and heavier elements. Multiple bonding between heavier main group elements (disilenes, distannenes etc.). Low valent derivatives of groups 13-15, relationship to inert pair effect.
Chemistry of the Noble Gases, ionisation potentials, oxides and fluorides of xenon (structure and reactivity), KrF2.
Introduction to organometallic chemistry of main group elements, structure and bonding of main group organometallics.
Practical work :
Practical work will involve the synthesis and analysis/characterisation of main group compounds. The syntheses will be more demanding than those previously encountered and may require anhydrous and anaerobic conditions. Analysis will be primarily based on titrametric and gravimetirc methods, though spectrospic methods such as IR and UV/vis may also be used. Practicals will highlight principles in reactivity as well as elucidation of bonding in a compound.