BIS[2,3-NAPHTHALENEDIOLATO(2-)](PYRROLIDINIOMETHYL)SILICATE ACETONITRILE SOLVATE - SYNTHESIS AND CRYSTAL AND MOLECULAR-STRUCTURE OF A ZWITTERIONIC LAMBDA-5-SPIROSILICATE

The zwitterionic spirocyclic bis[2,3-naphthalenediolato(2-)]-(pyrrolidiniomethyl)silicate (3) was synthesized and the crystal and molecular structure of its acetonitrile solvate 3.CH3CN investigated. 3 was prepared by reaction of trimethoxy(pyrolidinomethyl)silane (8) or dimethoxy(methyl)(pyrrolidinomethyl)silane (9) with 2,3-dihydroxynaphthalene in acetonitrile. Reaction 9 --> 3 involves a remarkable Si-C cleavage with formation of CH4. The pentacoordinate silicon atom of 3.CH3CN is surrounded by 4 oxygen atoms and 1 carbon atom, the latter being in an equatorial position. The coordination polyhedron can be described as a distorted trigonal bipyramid (the structure is displaced by 20.5% from the trigonal bipyramid towards the square pyramid). The crystal lattice of 3.CH3CN contains centrosymmetric dimers of 3, built up by intermolecular N-H...O hydrogen bonds.