Unusual reactivity of "Proton Sponge" as a hydride donor to transition metals: Synthesis and structural characterization of fluoroalkyl(hydrido) complexes of iridium(III) and rhodium(III)

Attempts to prepare fluoroalkyl(hydrido) complexes of iridium by reactions of [Ir(C5Me5)-(PMe3)(RF)I] {R-F = CF2CF2CF3, CF(CF3)(2)} with either NaBH4 or LiAlH4 afford (inter alia) iridium hydrides [Ir(C5Me5)(PMe3)(CH=CFCF3)H] or [Ir(C5Me5)(PMe3)(C{CF3}=CF2)H], in which the fluoroalkyl groups are con verted to unsaturated ligands via apparent alpha -CF activation and elimina tion of HF. A clean and selective route to desired saturated fluoroalkyl-(h ydrido) complexes [Ir(C5Me5)(PMe3)(R-F)H] {R-F = CF2CF2CF3, CF2CF3, CF(CF3) (2)} is afforded by treatment of the aqua cations [Ir(C5Me5)(PMe3)(RF)(H2O) ]BF4 with 1,8-bis(dimethylamino)-naphthalene ("Proton Sponge"). The reactio n also affords the corresponding rhodium analogue [Rh(C5Me5)(PMe3)(CF2CF2CF 3)H] from the corresponding aqua precursor. The source of the hydride is un ambiguously defined as an N-CH3 group by using the perdeuteromethylated ana logue of Proton Sponge, which provides clean routes to the corresponding fl uoroalkyl(deutero) complexes of iridium. Triethylamine or cobaltocene also effect this reaction, though not as cleanly as Proton Sponge. The mechanism of this novel transformation is discussed, The fluoroalkyl(hydrido) comple xes are thermally robust, but do react with chlorinated solvents to give th e corresponding chlorides. Single-crystal X-ray diffraction studies of the structures of [Ir(C5Me5)(PMe3)(CF2CF2CF3)H], [Rh(C5Me5)(PMe3)(CF2CF2CF3)H], and [Rh(C5Me5)(PMe3)(CF2CF2CF3)Cl] are reported and compared.