SYNTHESIS AND CRYSTAL AND MOLECULAR-STRUCTURES OF CATION-ANIONIC COMPLEXES OF 5-COORDINATE SILICON-CONTAINING DISILOXANE DICATIONS WITH LACTAMOMETHYL AND N-METHYLACETAMIDOMETHYL C,O-CHELATING LIGANDS

The reactions of bis(chloromethyl)dichlorosilane with N-trimethylsilyl lactams and N-trimethylsilyl-N-methylacetamide taken in a ratio of 1 : 2 followed either by treatment with HgCl2 in the presence of atmosph eric moisture or by hydrolysis under a wet atmosphere afforded cation- anionic complexes, which contain disiloxane dications of the general f ormula [L2SiOSiL2](2+) (L is the lactamomethyl or N-methylacetamidomet hyl bidentate ligand) and hexachlorodimercurate, tetrachloromercurate, and hydroxonium trichloride counter-ions, respectively. X-ray diffrac tion analysis demonstrated that the disiloxane dications in these comp lexes contain two five-coordinate Si atoms and occur as silicenium ion s stabilized through two O --> Si coordination bonds. In the case of l actarnomethyl ligands, the disiloxane dications exist as diastereomers whose bischelate ligands adopt opposite configurations, whereas when N-methylacetamidomethyl ligands are present, the bischelate ligands ad opt identical configurations. The first example of the presence of a h ydroxonium trichloride ion as a counter-ion in the crystal has been fo und. It consists of the hydroxonium cation, which holds three Cl- anio ns through strong hydrogen bonds.