The coordination and rearrangement of some organic chalcogenides on a rhodium-rhodium bond; the reactions with dialkylsulfanes and alkanethiols

When solutions of [Cp2Rh2(mu-CO)(mu-eta(2):eta(2)-CF3C2CF3)] (I) in petroleum ether or chlorinated hydrocarbons were treated with the dialkylsulfanes SRR'(R = R' = Me, Et, Pr, Bz; RR'= Meat), the addition products [Cp2Rh2(CO)(SRR')(mu-eta(1):eta(1)-CF3C2CF3)] (III, a-e) were formed reversibly. The complexes (III) have been characterized spectroscopically in solutions containing excess ligand. Removal of excess ligand and solvent regenerated (I). When left in solution, a number of the dialkylsulfane complexes underwent interesting transformations. The complex (IIIa, R = R' = Me) converted to [Cp2Rh2{mu-eta(1):eta(2)-C(CF3)C(CF3)H}(mu(2)-SEt)] (IVa, R = Et); this involves a beta-proton transfer accompanied by a Stevens rearrangement to convert (S(CH2-)CH3) to (SCH2CH3)(-). The structure of (IVa) was determined by X-ray crystallography. Two rearrangement products were formed when (IIIb, R = R' = Et) was left in solution. One was characterized from spectroscopic data as [Cp2Rh2{mu-eta(1):eta(2)-C(CF3)C(CF3)H}(mu(2)-SCHMeEt)] (IVb), which is formed by a Stevens rearrangement after transfer of a beta-proton. The other was identified as (IVa, R = Pt), which is formed after proton abstraction from a gamma-carbon followed by elimination of ethene. A number of mu-thiolato complexes (IVa-h, R = Me, Et, Pr, CHMeEt, Pr-i, Bu, Bu-t and Ph) were formed directly by treatment of (I) with the appropriate alkanethiol RSH. In some instances (R = CHMeEt, Pr-i, and Bu-t), a second product of formula [Cp2Rh2(mu-CO){mu-eta(2):eta(1)-CH(CF3)C(CF3)(SCRRR3)-R-1-R-2}] (VI, a-c) was formed. The molecular structure of (VI,, R-1 = H, R-2 = R-3 = Me) was determined by single crystal X-ray diffraction analysis. (C) 1998 Elsevier Science S.A.