Two new heterobimetallic LNiO Cu(RPY2) (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the mononuclear side-on LNi superoxo precursor bearing a β-diketiminate ligand (L = HC-(CMeNC H (iPr) ) ) with the Cu(i) complexes. In contrast to the oxo groups in known high-valent M (μ-O) (M = Fe, Co, Ni, Cu) cores that display electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions. However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously reported LNiO Cu(MeAN) complex containing a more basic (nucleophilic) N,N,N',N',N'-pentamethyl-dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands affect the electron density of the oxygen atoms of the heterodinuclear {Ni(μ-O) } core and 3a/3b undergo slower nucleophilic and faster electrophilic reactions than the previously reported LNiO Cu(MeAN) intermediate. The present study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic Ni(μ-O) Cu cores by controlling the electron donation from the ancillary ligands, and underlines the significance of subtle electronic changes in the physical and chemical properties of the biologically relevant heterobimetallic metal-dioxygen intermediates.