The reaction of Os2(CO)6(μ-I)2 with Pt(dba)(PPh3)2 or Pt(PhCCPh)(PPh3)2 affords three novel complexes Os2(CO)6−n(μ-I)2(PPh3)n [n = 1 (2), n = 2 (4)] and OsPt2(CO)2(μ-CO)(μ-I)2(PPh3)3 (3). 2 and 3 were characterized by X-ray analysis. The isotopically pure 187Os2(CO)6(μ-I)2 was also used in the synthesis of the corresponding complexes 2′–4′ to study their structures in solution. It was determined that