Bis 2,6-difluorophenoxide Dimeric Complexes of Zinc and Cadmium and Their Phosphine Adducts:  Lessons Learned Relative to Carbon Dioxide/Cyclohexene Oxide Alternating Copolymerization Processes Catalyzed by Zinc Phenoxides

Dimeric phenoxide derivatives of zinc and cadmium have been synthesized from the reaction of the corresponding metal bistrimethylsilylamide and two equivalents of 2,6-F2C6H3OH in tetrahydrofuran. The zinc analogue, [Zn(O-2,6-F2C6H3)2·THF]2 (1), has been characterized in the solid state via X-ray crystallography, where the zinc centers are shown to possess distorted tetrahedral geometry containing two bridging phenoxides and a terminal phenoxide and THF ligand. The distance between the metal centers (Zn···Zn) was found to be 3.059 A, and the THF ligands lie on opposite sides of the plane formed by the two zinc atoms and two bridging phenoxide ligands' oxygen atoms. There are several Zn···F nonbonding distances involving the bridging phenoxide ligands that are less than the van der Waals internuclear distance. In addition, both the zinc and cadmium dimeric derivatives have been prepared such that the labile THF ligands are replaced by the sterically encumbering basic phosphine, PCy3. The solid-state structu...