Heterometallic Chini-type clusters [Pt6-xNix(CO)12]2- (x = 0-6) were obtained by reactions of [Pt6(CO)12]2- with Ni-clusters such as [Ni6(CO)12]2-, [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, or from [Pt9(CO)18]2- and [Ni6(CO)12]2-. The Pt/Ni composition of [Pt6-xNix(CO)12]2- (x = 0-6) depended on the nature of the reagents employed and their stoichiometry. Reactions of [Pt9(CO)18]2- with [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, as well as reactions of [Pt12(CO)24]2- with [Ni6(CO)12]2-, [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, afforded [Pt9-xNix(CO)18]2- (x = 0-9) species. [Pt6-xNix(CO)12]2- (x = 1-5) were converted into [Pt12-xNix(CO)21]4- (x = 2-10) upon heating in CH3CN at 80 °C, with almost complete retention of the Pt/Ni composition. Reaction of [Pt12-xNix(CO)21]4- (x ≈ 8) with HBF4·Et2O afforded the [HPt14+xNi24-x(CO)44]5- (x ≈ 0.7) nanocluster. Finally, [Pt19-xNix(CO)22]4- (x = 2-6) could be obtained by heating [Pt9-xNix(CO)18]2- (x = 1-3) in CH3CN at 80 °C, or [Pt6-xNix(CO)12]2- (2-4) in DMSO at 130 °C. The molecular structures of these new alloy nanoclusters have been determined by single crystal X-ray diffraction. The site preference of Pt and Ni within their metal cages has been computationally investigated. The electrochemical and IR spectroelectrochemical behavior of [Pt19-xNix(CO)22]4- (x = 3.11) has been studied and compared to the isostructural homometallic nanocluster [Pt19(CO)22]4-.