The partial dehydrogenation of aluminium dihydrides

Abstract

The reactions of a series of β-diketiminate stabilised aluminium dihydrides with ruthenium bis(phosphine), palladium bis(phosphine) and palladium cyclopentadienyl complexes is reported.

Molecular Main Group Metal Hydrides

“… Crimmin and coworkers isolated several palladium aluminum hydride structures by the addition of several Pd(0) and Pd­(II) sources to (Nacnac)­AlH 2 complexes. When ( Dipp Nacnac)­AlH 2 ( 485 ) and [(Cp)­Pd­(η 3 -C 3 H 4 Ph)] were combined in benzene at room temperature, the tetrametallic [Al 2 H 2 Pd 2 ] structure [{( Dipp Nacnac)­Al}­PdH 2 ] 2 ( 600 , Figure ) was isolated as poorly soluble red crystals . Using the less bulky alane ( Mes Nacnac)­AlH 2 ( 486 ) and [(Cp)­Pd­(IMes)­(η 1 -C 3 H 4 Ph)] as the palladium source yielded the bimetallic cluster [{( Mes Nacnac)­Al} 4 Pd 4 H 6 ] ( 601 ) as the result of partial dehydrogenation of the aluminum hydride.…”

Catalytic C–H to C–M (M = Al, Mg) bond transformations with heterometallic complexes

“…44,45 While a consistent mechanistic picture could be established for the alumination of sp 2 C-H bonds with Al-2, it remains unclear if and how palladium aluminylene intermediates are formed when using Al-1 as a stoichiometric reagent. 47 For example, one might imagine an elementary step that takes place in a similar but reverse fashion to the aforementioned double migration step from Pd/Al-5 (Scheme 8a). Experimental evidence for such a concerted double H-M-H bond activation at a transition metal centre has recently been provided by Aldridge and co-workers demonstrating that the analogous gallium dihydride is prone to react with a Rh(I) precursor to form the respective Rh(III) dihydride Rh/Ga-3 featuring a neutral Ga(I) gallylene ligand (Scheme 8b).…”

“…35 The position and number of the hydride ligands in Pd/Al-8 were conrmed by single crystal neutron diffraction studies of an analogue complex featuring 2,6-xylyl substituents on the metalloligand. 47…”

“…Nevertheless, stoichiometric experiments unveiled Al–H bond activation and partial dehydrogenation of the aluminium dihydride when reacted with diverse palladium precursor complexes. 47 For example, room temperature reaction of the aluminium dihydride Al- 1 with [Pd(PCy 3 ) 2 ] led to the isolation of the tetrametallic complex Pd/Al- 8 ( Scheme 7b ). 35 The position and number of the hydride ligands in Pd/Al- 8 were confirmed by single crystal neutron diffraction studies of an analogue complex featuring 2,6-xylyl substituents on the metalloligand.…”

“… 35 The position and number of the hydride ligands in Pd/Al- 8 were confirmed by single crystal neutron diffraction studies of an analogue complex featuring 2,6-xylyl substituents on the metalloligand. 47 Formation of this complex involves partial dehydrogenation of Al- 1 and proceeds with liberation of H 2 . Heating Pd/Al- 8 in benzene under static vacuum results in the regeneration of [Pd(PCy 3 ) 2 ] accompanied by C–H alumination of the solvent.…”