General Route to Dissymmetric Heteroannular-Functionalized Ferrocenyl 1,2-Diphosphines: Selective Synthesis and Characterization of a New Class of Tri- and Tetrasubstituted Ferrocenyl Compounds

Several monosubstituted-cyclopentadienyl anions ( A- Li) and [1,2-bis(diphenylphosphino)-4- tert -butylcyclopentadienyl]lithium ( B -Li) react with FeCl 2 to afford a novel class of multidentate ferrocenylphosphines ( A -Fe- B ). The proposed synthetic method represents a unique means to produce achiral dissymmetric 1,1‘,2-substituted ferrocenes ( A -Fe- B ) bearing a heteroannular 1‘-substituent which is different from the homoannular 1- and 2-substituents. The selectivity for the two-step reaction favors formation of the desired dissymmetric product ( A -Fe- B ) rather than the concurrent formation of the symmetric di- and tetrasubstituted ferrocenes ( A -Fe- A and B -Fe- B ). Therefore, this method allows access to a great number of dissymmetric multidentate metalloligands, especially when one considers that functionalized-Cp salts continue to expand in terms of number and diversity. Herein, emphasis was placed upon the 1 H, 13 C, and 31 P NMR characterization of the metalloligands; several examples exhibit intriguing conformational properties and rare “through-space” phosphorus nuclear-spin couplings.