Synthesis and Characterization of New Cationic Hexacoordinate Silanes

The reaction of N,N,N',N"-pentamethyldiethylenetriamine (pmdeta) with HSiCl3 and H2SiCl2 in dry CH2Cl2 affords the novel cationic intermolecular hexacoordinate silanes [pmdeta.HSiCl2]+Cl- (1) and [pmdeta.H2SiCl]+Cl(2), respectively. The addition of N,N,N',N',N"-pentaethyldiethylenetriamine (pedeta) to a solution of HSiCl3 in dry CH2Cl2 gives the redistribution product formulated as the salt [pedeta.H2SiCl]+Cl- (3) and SiC4. Treatment of H2SiCl2 with pedeta and N,N,N',N',N",N"'-hexamethyltriethylenetetramine (hmteta) produces [pedeta.H2SiCl]+Cl(3) and [hmteta.H2SiCl]+C1- (HCl) (4). In 4, the fourth amine is not bonded to silicon. Reactions of 2, 3, and 4 with NaBPh4 give the ion exchange products [pmdeta.H2SiC1]+BPh4- (5), [pedeta.H2SiCl]+BPh4- (6), and [hmteta.H2SiCl]+BPh4- (HCl) (7), respectively. The salts 1, 5, 6, and 7 were characterized by single-crystal X-ray diffraction analysis. Most notable is that the cations in 1, 5, 6, and 7 are slightly distorted octahedra in which two hydrogen atoms are at the trans positions. The reactions of 3 with tmeda and pmdeta afford the intermolecular ligand exchange products tmeda.H2SiCl2 and 2, respectively.