Single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal complexes with 2S,3S-diaminobutane (bn) as an in-plane ligand, [Ni1-xPdx(bn)(2)Br]Br-2, were obtained by using an electrochemical oxidation method involving mixed methanol/2-propanol (1:1) solutions containing different ratios of [Ni-II(bn)(2)]Br-2 and [Pd-II(bn)(2)]Br-2. To investigate the competition between the electron-correlation of the Ni-III states, or Mott-Hubbard states (MH), and the electron-phonon interaction of the Pd-II-Pd-IV mixed valence states, or charge-density-wave states (CDW), in the Ni-Pd mixed-metal compounds, X-ray structure analyses, X-ray oscillation photograph, and Raman, IR, ESR, and single-crystal reflectance spectra were analyzed. In addition, the local electronic structures of Ni-Pd mixed-metal single crystals were directly investigated by using scanning tunneling microscopy (STM) at room temperature and ambient pressure. The oxidation states of [Ni1-xPdx(bn)(2)Br]Br-2 changed from a M-II-M-IV mixed valence state to a M-III MH state at a critical mixing ratio (x(c)) of similar to 0.8, which is lower than that of [Ni1-xPdx(chxn)(2)Br]Br-2 (chxn=1R,2R-diaminocyclohexane) (x(c) approximate to 0.9) reported previously. The lower value of x(c) for [Ni1-xPdx(bn)(2)Br]Br-2 can be explained by the difference in their CDW dimensionalities because the three-dimensional CDW ordering in [Pd(bn)(2)Br]Br-2 observed by using X-ray diffuse scattering stabilizes the Pd-II-Pd-IV mixed valence state more than two-dimensional CDW ordering in [Pd(chxn)(2)Br]Br-2 does, which has been reported previously.