Azobenzene Reduction and Derivatization and Al–H Bond Insertion with β-Diketiminate Gallium(I) Complexes

High Resolution Image Download MS PowerPoint Slide Using backbone modification of popular β-diketiminate ligands, RDip nacnac = HC(RCNDip) 2, with R = Et, i Pr (Dip = 2,6- i Pr 2 C 6 H 3 ), we have prepared the new β-diketiminate gallium(I) complexes [( EtDip nacnac)Ga] 2a and [( i PrDip nacnac)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 [( RDip nacnac)Ga{(C 6 H 5 )NNPh}] 4a (R = Et) and 4b (R = i Pr) 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 [( EtDip nacnac)Ga{(C 6 H 4 )N(H)NPh}] 5, and reaction with DMSO and benzaldehyde afforded [( EtDip nacnac)Ga(PhNNHPh)(CH 2 S(O)Me)] 6 after DMSO deprotonation and [( EtDip nacnac)Ga(PhNN(Ph)CH(Ph)O)] 7 from C–N coupling, respectively. Compound 2a also reacted with the aluminum(III) hydride complexes (NHC)AlH 3 (NHC = {MeCN( i Pr)} 2 C) and (Me 3 N)AlH 3 to the Ga–Al-bonded complex [( EtDip nacnac)Ga(H)–Al(H 2 )(NHC)] 8 and [( EtDip nacnac)GaH 2 ] 9, respectively. Gallium(I) complex 2a is a good alternative to commonly used [( MeDip nacnac)Ga] (R = Me) for the study and application of low-oxidation-state gallium complexes.