REACTION OF (DIOXYGEN)(DITHIOCARBAMATO)RHODIUM COMPLEXES WITH CARBON-DIOXIDE - FORMATION AND CHEMICAL CLEAVAGE OF RHODIUM PEROXYCARBONATO AND CARBONATO RINGS

Dioxygen complexes of bis(triphenylphosphine)(dithiocarbamato)rhodium and its analogue have been prepared. The structure determined by NMR spectroscopy was interpreted by the strong electron-accepting nature of the dioxygen ligand. The complex reacts with carbon dioxide at room temperature to give the peroxycarbonato complex Rh(S2CNMe2)(C04)(PPh3)2. The structure of this complex, in which the oxygen atom originating from carbon dioxide occupies the position trans to one of the S atoms of the chelating S2CNMe2while the oxygen originating from the dioxygen is trans to one of the PPh3ligands, is proposed on the basis of its successive reactions. In the presence of excess triphenylphosphine, the peroxycarbonate was deoxygenated to give a yellow carbonato complex, Rh(S2CNMe2)(C03)(PPh3)2, which has two trans(S,O) pairs and trans triphenylphosphines, as characterized by crystallographic analysis. The complex crystallizes in the triclinic system, space group P1, with a = 12.634 (5) Å, b = 17.681 (4) Å, c = 10.449 (4) Å, α = 98.97 (3)°, β = 109.27 (4)°, γ = 99.27 (2)°, and Z = 2. When heated to 70 °C, this complex isomerizes to the thermodynamically stable form with an orange-red color. After being heated for a prolonged time in the presence of triphenylphosphine, the carbonate complex was further deoxygenated to give the carbon dioxide adduct of Ru(S2CNMe2)(PPh3)2, which was not isolated but characterized by NMR spectroscopy. © 1990, American Chemical Society. All rights reserved.