Coordination and Rearrangement of Organic Chalcogenides on a Rhodium−Rhodium Bond:  Reactions with Strained-Ring Cyclic Thioethers and with Selenium and Tellurium Ligands

When the cyclic thioethers L = and were added to [(η⁵-C₅H₅)₂Rh₂(μ-CO)(μ-η²:η²-CF₃C₂CF₃)] (1), the coordinative addition products [(η⁵-C₅H₅)₂Rh₂(CO)(μ-η¹:η¹-CF₃C₂CF₃)L] (2a−c) were formed reversibly. When it is left in solution in the presence of excess ligand, the propylene sulfide complex 2b (L = transforms to the bridging sulfido complex [(η⁵-C₅H₅)₂Rh₂{μ-η¹:η¹:η²-C(O)C(CF₃)C(CF₃)}(μ-S)] (3a). A similar reaction occurred, but to a lesser extent, with the trimethylene sulfide complex 2a (L = Comparable decompositions do not occur with the tetrahydrothiophene complex 2a (L = The dimethylselenane complex [(η⁵-C₅H₅)₂Rh₂(CO)(μ-η¹:η¹-CF₃C₂CF₃)(SeMe₂)] (4a) was formed reversibly when SeMe₂ was added to solutions of 1. The reactions of 1 with the organotelluranes L‘ = TeMe₂ and TeEt₂ gave solid addition products [(η⁵-C₅H₅)₂Rh₂(CO)(μ-η¹:η¹-CF₃C₂CF₃)L‘] (4b,c), which remained intact when dissolved in polar solvents. No rearrangement products were formed when solutions of the tellurane addition products were kept for several days. The bridging sulfido complex 3a and the analogous complexes [(η⁵-C₅H₅)₂Rh₂{μ-η¹:η¹:η²-C(O)C(CF₃)C(CF₃)}(μ-E)] (3b, E = Se; 3c, E = Te) were obtained from the direct reaction between E and the complex 1. Addition of the cyclic tellurane to 1 gave (6), which underwent rapid intramolecular ligand scrambling in solution. The crystal and molecular structure of 6 was determined by X-ray crystallography.