Donor-stabilized silyl cations. 11. Bis-zwitterionic penta- and hexacoordinate silicon dichelate complexes derived from (ClCH₂) ₂SiCl₂ through double internal displacement of chloride

The reaction of (ClCH₂)₂SiCl₂ (4) with O-Me₃Si-hydrazides (3) yields three new types of products: a 1:2 reagent ratio leads to a neutral hexacoordinate dichelate with two six-membered rings each containing an N⁺-N^- ylide structure, as well as to the corresponding dissociated pentacoordinate dichelate siliconium chloride salt. These products readily undergo partial hydrolysis to form a dinuclear complex: dicationic disiloxane dichloride. All three product types have been characterized by means of single-crystal structure analysis. Nonempirical ab initio calculations were carried out to determine the atomic charges. Natural bond order (NBO) calculations show that there are no significant charge accumulations on either the ammonium or the imidate nitrogen in the ylide moieties and that the net charge on silicon (which could formally be -2) is between +1.8 and +2.1 e in all species, regardless of overall molecular charge.