Treatment of AsP3 with 0.75 equivalents of [{GaC(SiMe3)3}4] resulted in selective insertion of three equivalents of {GaC(SiMe3)3} into the three AsP bonds to give [As{GaC(SiMe3)3}3P3] (1‐As) with an intact cyclo‐P3 ring. This yellow compound has been characterized by NMR spectroscopy, combustion analysis, single‐crystal X‐ray diffraction, UV/Vis spectroscopy, Raman spectroscopy, and cyclic voltammetry (THF, 0.2 M [TBA][B(C6F5)4]; TBA=tetrabutyl ammonium). Computational models of 1‐As and the isomeric [P{GaC(SiMe3)3}3AsP2] (1‐P) have been investigated as well, revealing several interesting electronic features of these cage molecules. Following from the cyclic voltammetry studies of 1‐As that highlight an irreversible two‐electron reduction at −2.2 V versus Fc/Fc+, treatment with one equivalent of [Mg(C14H10)(thf)3] resulted in two‐electron reduction to provide [As{GaC(SiMe3)3}3P3Mg(thf)3] (2), in which the Mg2+ ion has inserted into one of the PP bonds of the cyclo‐P3 ring. It was also found that treatment of AsP3 or P4 with one equivalent of [{GaC(SiMe3)3}4] resulted in formation of the quadruple insertion products [As{GaC(SiMe3)3}4P3] (3) and [P{GaC(SiMe3)3}4P3] (4), respectively.