2-(ALKOXYMETHYL)PHENYLSILICON COMPOUNDS - THE SEARCH FOR PENTACOORDINATION

The synthesis of 2-(methoxymethyl)phenylsilanes and 2-(isopropoxymethy l)phenylsilanes is described. The coordination behaviour of the ether side chains has been studied by NMR spectroscopy. In 2-(alkoxymethyl)p henylsilicon compounds with methoxy, hydride or phenyl groups the sili con atom is assumed to be tetracoordinated. Pentacoordination is confi rmed in trifluoro-[2-(methoxymethyl)phenyl]silane (11) and trifluoro-[ 2-(isopropoxymethyl)phenyl]silane (12). The free energy of activation for ligand permutation at silicon in trifluoro-[2-(methoxymethyl)pheny l]silane (11) is estimated to be below 9 kcal mol(-1). The synthesis o f phenyl-[2-(methoxymethyl)phenyl]silyl triflate (13) is described. In the solid state a short silicon-donor oxygen distance is observed, in dicating strong bonding interaction. The structure of 13 in solution i s discussed on the basis of NMR data and conductivity measurements.