Tetrarhena-heterocycle from the Palladium-Catalyzed Dimerization of Re2(CO)8(μ-SbPh2)(μ-H) Exhibits an Unusual Host–Guest Behavior

The six-membered heavy atom heterocycles [Re2(CO)8(μ-SbPh2)(μ-H)]2, 5, and Pd[Re2(CO)8(μ-SbPh2)(μ-H)]2, 7, have been prepared by the palladium-catalyzed ring-opening cyclo-dimerization of the three-membered heterocycle Re2(CO)8(μ-SbPh2)(μ-H), 3. The palladium atom that lies in the center of the heterocycle 7 was removed to yield 5. The palladium removal was found to be partially reversible leading to an unusual example of host–guest behavior. A related dipalladium complex Pd2Re4(CO)16(μ4-SbPh)(μ3-SbPh2)(μ-Ph)(μ-H)2, 6, was also formed in these reactions of palladium with 3.