A series of unsymmetric tetradentate β-diketiminato rare-earth metal monoalkyl complexes were synthesized, and their catalytic behavior has been well developed. Indole-incorporated β-diketiminato proligands H₂L (L = MeC(NDipp)CHC(Me)NCH₂CH₂-3-(1-R-C₈H₄N), R = CH₂-(2-C₄H₇O), L¹; R = (CH₂)₂OMe, L²; Dipp = 2,6-ⁱPr₂C₆H₃) were prepared by the reaction of an arylamino-enone with 1-substituted-tryptamine in good yields. Treatment of the proligands with the rare-earth metal trialkyl complexes RE(CH₂SiMe₃)₃(THF)₂ generated the corresponding unsymmetric N,N,C,O-tetradentate β-diketiminato rare-earth metal monoalkyl complexes LRE(CH₂SiMe₃) (L¹, RE = Y (1a), Gd (1b), Yb (1c), Lu (1d); L², RE = Y (2a), Gd (2b), Yb (2c), and Lu(2d)). During the process, the activation of the sp² C–H bond at the 2-position of the indole ring led to the formation of an unprecedented β-diketiminato dianion L²⁻, bonding to the rare-earth metal ions in a chelating N,N,C,O-tetradentate manner. Further studies indicated that these tetradentate rare-earth metal complexes could initiate the Oppenauer oxidation of secondary alcohols into the corresponding ketones in high yields. In the case of primary alcohols, a tandem Oppenauer oxidation and cross-aldol condensation occurred unexpectedly. Various α-mono-substituted benzylidene acetones, α,α′-bis-substituted benzylidene acetones and cyclohexanones were obtained under mild conditions only by controlling the molar ratio of alcohols to ketones. Notably, all these alkenylation ketones exhibited exclusive E configuration.