The Pt(IV) complexes trans-Pt(PEt3)(2)(Cl)(3)(R) 2 (R = Cl, Ph, 9-phenanthryl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl, 3-perylenyl) were prepared by chlorination of the Pt(II) complexes trans-Pt(PEt3)(2)(R)(Cl) 1 with Cl-2(g) or PhICl2. Mixed bromo-chloro complexes trans,trans-Pt(PEt3)(2)(Cl)(2)(Br)(R) (R = 9-phenanthryl, 4-trifluoromethylphenyl), trans,cis-Pt(PEt3)(2)(Cl)(2)(Br)(4-trifluoromethylphenyl), trans,trans-Pt(PEt3)(2)(Br)(2)(Cl)(R) (R = 9-phenanthryl), and trans,cis-Pt(PEt3)(2)(Br)(2)(Cl)(4-trifluoromethylphenyl) were obtained by halide exchange or by oxidative addition of Br-2 to 1 or Cl-2 to trans-Pt(PEt3)(2)(R)(Br). Except for 2 (R = Ph, 4-trifluoromethylphenyl), all of the Pt(IV) complexes are photosensitive to UV light and undergo net halogen reductive elimination to give Pt(II) products, trans-Pt(PEt3)(2)(R)(X) (X = Cl, Br). Chlorine trapping experiments with alkenes indicate a reductive-elimination mechanism that does not involve molecular chlorine and is sensitive to steric effects at the Pt center. DFT calculations suggest a radical pathway involving (LMCT)-L-3 excited states. Emission from a triplet is observed in glassy 2-methyltetrahydrofuran at 77 K where photoreductive elimination is markedly slowed.