Synthesis and characterization of new cationic hexacoordinate silanes

The reaction of N,N,N',N',N "-pentamethyldiethylenetriamine (pmdeta) with H SiCl3 and H2SiCl2 in dry CH2Cl2 affords the novel cationic intermolecular h exacoordinate silanes [pmdeta . HSiCl2]Cl-+(-) (1) and [pmdeta . H2SiCl]Cl- +(-) (2), respectively. The addition of N,N,N',N',N "-pentaethyldiethylenet riamine (pedeta) to a solution of HSiCl3 in dry CH2Cl2 gives the redistribu tion product formulated as the salt [pedeta . H2SiCl]Cl-+(-) (3) and SiCl4. Treatment of H2SiCl2 with pedeta and N,N,N',N',N ",N'''-hexamethyltriethyl enetetramine (hmteta) produces [pedeta . H2SiCl]Cl-+(-) (3) and [hmteta . H 2SiCl]Cl-+(-) (HCl) (4). In 4, the fourth amine is not bonded to silicon. R eactions of 2, 3, and 4 with NaBPh4 give the ion exchange products [pmdeta . H2SiCl]+BPh4- (5), [pedeta . H2SiCl]+BPh4- (6), and [hmteta . H2SiCl]+BPh 4- (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 a toms are at the trans positions. The reactions of 3 with tmeda and pmdeta a fford the intermolecular ligand exchange products tmeda . H2SiCl2 and 2, re spectively.