The geometrical and electronic structures of the electron-deficient dialurninum aurides Al2Aun0/- and hybrid boron-aluminum aurides BAlAun0/- (n = 1-3) are systematically investigated based on the density and wave function theories. Ab initio theoretical evidence strongly suggests that bridging gold atoms exist in the ground states of C-2v, Al2Au-(B-3(1)), C-2v Al2Au (B-2(1)), C-2v Al2Au2- ((2)A(1)), C-2v Al2Au2 ((1)A(1)), C-s Al2Au3- ((1)A'), and D-3h Al2Au3 ((2)A(1)), which prove to possess an Al-Au-Al tau bond. For BAlAu /- (n = 1-3) mixed clusters, bridging B-Au-Al units only exist in C, BAlAu3-((1)A') and C, BAlAu3 ((2)A'), whereas C-s BAlAu- ((3)A ''), C-s BAlAu ((2)A ''), C-s BAlAu2- ((2)A'), and C, BAlAu2 ((1)A') do not possess a bridging gold, as demonstrated by the fact that B-Al and B-Au exhibit significantly stronger electronic interaction than Al-Au in the same clusters. Orbital analyses indicate that Au 6s contributes approximately 98%-99% to the Au-based orbital in these Al-Au-Al/B-Au-Al interactions, whereas Au 5d contributes 1%-2%. The adiabatic and vertical detachment energies of Al2Aun- (n = 1-3) are calculated to facilitate future experimental characterizations. The results obtained in this work establish an interesting tau bonding model (Al-Au-Al/B-Au-Al) for electron-deficient systems in which Au 6s plays a major factor.