Five-co-ordinate, bis(catecholato) complexes of silicon(IV)

The synthesis of a series of five-co-ordinate bis(catecholato) complexes of silicon(IV) of the type [SiRL2]- is reported, where R = Ph, Me, Et, or Pr(n) and H2L = catechol and its derivatives. The complexes have been characterised by H-1, C-13 and Si-29 NMR spectroscopy in Me2SO, elemental analysis and fast atom bombardment mass spectroscopy. Complexes derived from asymmetric catechols which give rise to non-statistical, geometrical isomerism in the distorted trigonal-bipyramidal conformation have been investigated by multinuclear NMR spectroscopy. The crystal structure of the bis(3,5-dinitrocatecholato)methyl-silicate anion is reported. It exhibits a slightly distorted trigonal-bipyramidal geometry. Aryl-aryl and nitro-nitro interactions play a dominant role in the solid-state packing. Mixed-ligand complexes containing different catecholato derivatives have also been studied.