A library of 14 heterobis(carbene) complexes of the general formula [Au(Pr-i(2)-bimy)(ADC)]BF4 (7-20) containing the N-heterocyclic carbene reporter Pr-i(2)-bimy and various protic acyclic diaminocarbenes (ADCs) have been prepared to estimate their stereoelectronic properties by C-13 NMR spectroscopy and percentage buried volume (%V-bur) determinations. Their preparation was achieved by nucleophilic attack of five secondary amines on six mixed NHC/isocyanide complexes of the type [Au(Pr-i(2)-bimy)(CN-R)]BF4 (1 - 6). Analyses of the Pr-i(2)-bimy carbene signals reveal that protic ADCs are stronger donors than classical and expanded-ring NHCs. On the other hand, they are weaker donating compared to NHCs with reduced-heteroatom stabilization. Moreover, stereoelectronic fine-tuning of these ligands is possible by a diverse range of substituents originating from the employed isocyanides and amines.