SYNTHESIS AND STRUCTURE OF POLYSILABRIDGED BISALLENES

Tetrasilacyclodeca-1,2,6,7-tetraenes (3a:dl) and (3b:meso) are synthes ized by the reaction of the Ph2C3 dianion with tetramethyldichlorodisi lane. X-Ray crystallographic analyses of 3a and 3b show allenic sp car bons to be bent by 4-degrees(average). The optimized structures of dis ilacycloocta-1,2,5,6-tetraenes estimated by semiempirical PM3 calculat ions are also reported.