Preparation, molecular structure and reactivity of mono- and di-nuclear sulfonato rhodium(I) complexes

Abstract

The reaction of [Rh(η3-C3H5)(PPri3)2] 1 or [Rh(η3-CH2Ph)(PPri3)2] 2 with an equimolar amount of RSO3H (R = Me, p-tolyl, CF3, F, Camph) led to the formation of the monomeric sulfonatorhodium(I) complexes [Rh{η2-O2S(O)R}(PPri3)2] 3–7 in excellent yield. An alternative route for the preparation of 4 (R = p-tolyl) and 5 (R = CF3) is based on the reaction of PPri3 with the dinuclear compounds [{Rh(C8H14)2[µ-O2S(O)R]}2], which were obtained either from [{Rh(C8H14)2(µ-Cl)}2] 8 or [{Rh(C8H14)2(µ-OH)}2] 9 as starting materials. Compounds 3–7 react smoothly with hydrogen by oxidative addition to give the dihydridorhodium(III) complexes [RhH2{η2-O2S(O)R}(PPri3)2]. Moreover, on treatment of 3–6 with CO and C2H4 the chelating bond of the sulfonate ligand is partially opened and the carbonyl and ethene complexes trans-[Rh{η1-OS(O)2R}(L)(PPri3)2] (L = CO or C2H4) are formed. The bis(stibine)rhodium(I) derivative trans-[Rh{η1-OS(O)2CF3}(C2H4)(SbPri3)2] was obtained from [{Rh(C2H4)2[µ-O2S(O)CF3]}2] and SbPri3. Reaction of the compounds [Rh{η2-O2S(O)CF3}(olefin)(PPri3)] (olefin = C8H14 or C2H4) with benzene led to the displacement of the sulfonate ligand and to the formation of the half-sandwich-type complexes [Rh{η6-C6H6)(olefin)(PPri3)][CF3SO3] containing a rather labile benzene–rhodium bond. The preparation of the vinylidene complex trans-[Rh{η1-OS(O)C6H4Me-p}(CCHPh)(PPri3)2] is also described and the crystal and molecular structures of three compounds have been determined. The four-co-ordinate sulfonato complexes 3–6 are active catalysts in the C–C coupling reaction of ethene and diphenyldiazomethane. Besides the three isomeric 1∶1 adducts of C2H4 and CPh2, quite unexpectedly also the 2∶1 adduct 3,3-diphenylpent-1-ene is formed.