New synthetic and structural aspects in the chemistry of alkylaluminum fluorides. The mutual influence of hard and soft ligands and the hybridizationas rigorous structural criterion

A general synthetic strategy starting from metal alkyls is reported based o n the hydrogen difluoride anion as a suitable reagent for obtaining organom etallic fluorides. The newly prepared compounds are [Me4N][(i-Bu)(2)AlF2] ( 1), [Ph4P][(i-Bu)(2)AlF2] (2), and [Ph4P][AlF4] (3), containing the tetrahe dral anions [(i-Bu)(2)AlF2](-) and [AlF4](-). The actual structures are pro totypes that allowed a comparison of inorganic and organometallic fluorides in the frame of the hard and soft arid and base principle, by means of ab initio calculations. A new theoretical model is designed to put in equation form the qualitative statements of the Bent rule. The model allows the rat ionalization of the tendencies of bond angle variation in (R2MX2] systems c ontaining a main group metal (M), in terms of hybridization of the central atom and the reciprocal influence of hard and soft ligands.