Azobenzene reduction and derivatization and Al–H bond insertion with β-diketiminate gallium(I) complexes

Using backbone modification of popular β-diketiminate ligands, ^RDipnacnac = HC(RCNDip)₂, with R = Et, iPr (Dip = 2,6-iPr₂C₆H₃), we have prepared the new β-diketiminate gallium(I) complexes [(^EtDipnacnac)Ga] 2a and [(i^PrDipnacnac)Ga] 2b by salt metathesis/reduction using “GaI” in moderate to good (68%, 2a) and poor (10%, 2b) isolated yields, respectively, highlighting the influence of the ligand backbone substitution on the reaction success. The gallium(I) complexes were converted with azobenzene to the gallium(III) complexes [(^RDipnacnac)Ga{(C₆H₅)NNPh}] 4a (R = Et) and 4b (R = iPr) with reduced former azobenzene fragments showing an N,ortho-C(H)-chelating coordination to the Ga centers. Complex 4a was further converted to its C–H-activated tautomer [(^EtDipnacnac)Ga{(C₆H₄)N(H)NPh}] 5, and reaction with DMSO and benzaldehyde afforded [(^EtDipnacnac)Ga(PhNNHPh)(CH₂S(O)Me)] 6 after DMSO deprotonation and [(^EtDipnacnac)Ga(PhNN(Ph)CH(Ph)O)] 7 from C–N coupling, respectively. Compound 2a also reacted with the aluminum(III) hydride complexes (NHC)AlH₃ (NHC = {MeCN(iPr)}₂C) and (Me₃N)AlH₃ to the Ga–Al-bonded complex [(^EtDipnacnac)Ga(H)–Al(H₂)(NHC)] 8 and [(^EtDipnacnac)GaH₂] 9, respectively. Gallium(I) complex 2a is a good alternative to commonly used [(^MeDipnacnac)Ga] (R = Me) for the study and application of low-oxidation-state gallium complexes.