The solid-state structures of germane-d₄, GeD₄ and stannane-d₄, SnD₄, have been investigated by high resolution powder neutron diffraction. These structures have been compared with those found in the gas-phase. It was found that there are weak intermolecular interaction in the solid-state. These results confirm the findings of an earlier vibrational study which suggested a decrease in molecular symmetry on moving from the gaseous to condensed state. Several examples of a new class of organic chalcogenide donor ligand have been prepared and characterised. These new have been used in preparation of a variety of main group organometallic compounds including examples of mono, di- and tri-substituted compounds. The di- and tri-substituted compounds are the first to be subject structural characterisation by X-ray diffraction and the structures include trigonal bipyramidal geometries around gallium and indium atoms. Use of the in situ crystal growth technique has resulted in the structural characterisation of lead(IV) chloride that confirms the tetrahedral geometry and suggests a non-bonding Pb^...Cl contact that lies within the sum of the van der Waals radii. Preliminary investigations of PbCl₄ under high pressure indicate a phase change from discrete tetrahedral molecules to a layered structure similar to that of polymeric SnF₄. The chemistry of PbCl₄ is limited by the instability of the compound, but the loss of Cl₂ and reduction to Pb(II) occurs upon reaction with SbCl₅, leaving the unusual cation fragment [Pb(MeCN)₉]²⁺. The structure of (Me)₃PbCl has been determined by neutron diffraction and showed that the earlier investigations by X-ray analysis had erroneously determined the unit cell. The new data disprove the previous assertion that the Cl-Pb^...Cl angle was non-linear and confirms that it is in fact 180°, in common with the structures of (Me)₃PbBr and (Me)₃PbI.