A new Hofmann-like heterometal (FeAuI)-Au-II two-dimensional (2D) spin-crossover compound, {[Fe-II(pyridine)(2)][Au-I(CN)(2)](2)}(n) (1) and its isotope-substituted analogues {[FeII-(pyridine-D-5)(2)][Au-I(CN)(2)](2)}(n) (2) and {[Fe-II(pyridine-(15) N)(2)][Au-I(CN)(2)](2)}(n) (3) have been synthesized in a simple synthetic method and characterized crystallographically and magnetically. Complex 1 consists of an octahedral Fell ion coordinated with the pyridine ligands and a mononuclear [Au-I(CN)(2)](-) unit with a linear coordination geometry, which combine to form an infinite 2D structure. The spin transitions observed for 1 and 3 are accompanied by drastic and reversible change of color from colorless to purple. In complexes 1 and 3, about 10 and 3.5% high-spin states are changed to low-spin states at 75 K. However, HS states in 2 are slightly more stable than those in 3.