New aluminum and gallium complexes of β-diketiminato and β-ketiminato ligands

Abstract

The β-diketimine (Ph2-nacnac)H [(Ph2-nacnac)=HC{C(Me)NPh}2] reacts with one equivalent of MH3·NMe2Et to produce the corresponding metal dihydride compound (Ph2-nacnac)MH2 [M=Al(1), Ga(2)] by release of hydrogen. Compounds 1 and 2 do not react with a second equivalent of (Ph2-nacnac)H even at elevated temperature. However, a single step 1:2 reaction of AlH3·NMe2Et and (Ph2-nacnac)H affords a complex with a four-coordinate aluminum atom (3) in which a monoanionic and a dianionic ligand bind to a single aluminum atom. The latter ligand may be formed by migration of an aluminum bound hydrogen atom to a carbon atom in α-position to nitrogen and has a localized CC bond. A similar reaction of the ligand and GaH3·NMe2Et yields only compound 2. The sterically less shielded β-ketimine (Ph-nacac)H [(Ph-nacac)=HC[{C(Me)NPh}{C(Me)O}] gives (Ph-nacac)AlH2 (4) when reacted with one equivalent of AlH3·NMe2Et. A mixture of 4 and (Ph-nacac)3Al (5) is obtained upon treatment of AlH3·NMe2Et with two equivalents of (Ph-nacac)H. Compound 5 forms quantitatively from a 1:3 reaction of the alane-amine adduct with the β-ketimine ligand. 1 reacts with one equivalent of LiN(SiMe3)2 to form the monohydride compound (Ph2-nacnac)AlH[N(SiMe3)2] (6) by elimination of LiH. Solid-state structures of 2, 3, 5 and 6 were determined by single crystal X-ray structure determination.