The photochemical activation of the C(sp)−C(sp 2 ) bond in Pt(0)-η 2 -aryl-phosphaalkyne complexes leads selectively to coordination compounds of the type L n Pt(aryl)(CP). The oxidative addition reaction is a novel, clean, and atom-economic route for the synthesis of reactive terminal Pt(II)-cyaphido complexes, which can undergo [3 + 2] cycloaddition reactions with organic azides, yielding the corresponding Pt(II)-triazaphospholato complexes. The C−C bond cleavage reaction is thermodynamically uphill. Upon heating, the reverse and quantitative reductive elimination toward the Pt(0)-phosphaalkyne-π-complex is observed.