Reactions of the 1,1-Diphenylacetone-Derived Dianion as a C,O-Dinucleophile with Organohalosilanes and -germanes

1,1-Diphenylacetone dianion reacts with diorganodichlorosilanes to give 1,1,5,5-tetraorgano-3,7-bis(diphenylmethylene)-1,5-disila-2,8-dioxacyclooctanes, while 1,1-diphenylacetone dianion reacts with diorganodifluorosilanes to give a positional isomer, 1,1,5,5-tetraorgano-3,7-bis(diphenylmethylene)-1,5-disila-2,6-dioxacyclooctane. The structures of 1,1,5,5-tetraphenyl-3,7-bis(diphenylmethylene)-1,5-disila-2,8-dioxyacyclooctane and 1,1,5,5-tetraphenyl-3,7-bis(diphenylmethylene)-1,5-disila-2,6-dioxacyclooctane were determined by X-ray crystallography. A 10-membered cyclic compound and a 6-membered cyclic compound also were prepared by the reaction of 1,1-diphenylacetone dianion with 1,2-dichlorotetramethyldisilane and 1,3-dichlorohexamethyltrisilane, respectively. The structure of 1,1,2,2,6,6,7,7-octamethyl-4,9-bis(diphenylmethylene)-1,2,6,7-tetrasila-3,10-dioxacyclodecane was determined by X-ray crystallography. 1,1-Diphenylacetone dianion reacts with diphenyldichlorogermane and diphenyldifluorogermane to give 1,1,5,5-tetraphenyl-3,7-bis(diphenylmethylene)-1,5-digerma-2,6-dioxacyclooctane. The structure of 1,1,5,5-tetraphenyl-3,7-bis(diphenylmethylene)-1,5-digerma-2,6-dioxacyclooctane was determined by X-ray crystallography. A possible explanation for the difference in the reactions observed with Ph₂SiCl₂ and Ph₂SiF₂ is presented. Experiments involving reactions of the 1,1-diphenylacetone dianion with monochlorosilanes indicate that a Si−CH₂, not an Si−O, bond is formed first.