Electron effects of substitution and reconstruction of the coordination polyhedron in main group IV element haloadducts

The NQR and X-ray data on the effects of acido-ligand substitution and coor dination polyhedron reconstruction in adducts (complexes) of tin(IV), germa nium(IV) and silicon(IV) tetrahalogenides due to the change in the central metal coordination number, are surveyed and described systematically. The e lectron density redistribution over atomic sigma- and pi-orbitals in centra l metal-halogen bond due to substitution or reconstruction of the coordinat ion polyhedron from pseudooctahedral to trigonal-bipyramidal configuration are discussed.