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)

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Attempts to prepare fluoroalkyl(hydrido) complexes of iridium by reactions of [Ir(C5Me5)-(PMe3)(RF)I] {RF = 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 converted to unsaturated ligands via apparent α-CF activation and elimination of HF. A clean and selective route to desired saturated fluoroalkyl(hydrido) complexes [Ir(C5Me5)(PMe3)(RF)H] {RF = 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 reaction also affords the corresponding rhodium analogue [Rh(C5Me5)(PMe3)(CF2CF2 CF3)H] from the corresponding aqua precursor. The source the hydride is unambiguously defined as an N-CH3 group by using the perdeuteromethylated analogue of Proton Sponge, which provides clean routes to the corresponding fluoroalkyl(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) complexes are thermally robust, but do react with chlorinated solvents to give the corresponding chlorides. Single-crystal X-ray diffraction studies of the structures of [Ir(C5Me5)(PMe3)(CF2CF2 CF3)H], [Rh(C5Me5)(PMe3)(CF2CF2 CF3)H], and [Rh(C5-Me5)(PMe3)(CF2CF2 CF3)Cl] are reported and compared.

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