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 = SCH2CH2CH2, SCH(Me)CH2, and SCH2CH2CH2CH2 we re added to [(eta(5)-C5H5)(2)Rh-2(mu-CO)(mu-eta(2):eta(2)-CF3C2CF3)] (1), t he coordinative addition products [(eta(5)-C5H5)(2)Rh-2(CO)(mu-eta(1):eta(1 )-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 = SCH(M e)CH2) transforms to the bridging sulfide complex [(eta(5)-C5H5)(2)Rh-2{mu- eta(1):eta(1):eta(2)-C(O)C(CF3)}(mu-S)] (3a). A similar reaction occurred, but to a lesser extent, with the trimethylene sulfide complex 2a (L = SCH2C H2CH2). Comparable decompositions do not occur with the I I tetrahydrothiop hene complex 2a (L = SCH2CH2CH2CH2). The dimethylselenane complex [(eta(5)- C5H5)(2)Rh-2(CO)(mu-eta(1):eta(1)-CF3C2CF3)(SeMe2)] (4a) was formed reversi bly when SeMe2 was added to solutions of 1. The reactions of 1 with the org anotelluranes L' = TeMe2 and TeEt2 gave solid addition products [(eta(5)-C5 H5)(2)Rh-2(CO)(mu-eta(1):eta(1)-CF3C2CF3)L'] (4b,c), which remained intact when dissolved in polar solvents. No rearrangement products were formed whe n solutions of the tellurane addition products were kept for several days. The bridging sulfide complex 3a and the analogous complexes [(eta(5)-C5H5)( 2)Rh-2{mu-eta(1):eta(1):eta(2)-C(O)C(CF3)C(CF3)}(mu-E)] (3b, E = Se; 3c, E = Te) were obtained from the direct reaction between E and the complex 1. A ddition of the cyclic tellurane TeCH2CH2CH2CH2 to 1 gave [(eta(5)-C5H5)(2)R h-2(CO)(mu-eta(1):eta(1)-CF3C2CF3)(TeCH2CH2CH2CH2)] (6), which underwent ra pid intramolecular ligand scrambling in solution. The crystal and molecular structure of 6 was determined by X-ray crystallography.