Selective Oxidation of a Single Metal Site of Divalent Calix[4]pyrrolide Compounds [Ln₂(N₄Et₈)(thf)₄] (Ln = Sm or Eu), Giving Mixed Valent Lanthanoid(II/III) Complexes

Abstract

The samarium(II) calix[4]pyrrolide complex [Sm2(N4Et8)(thf)4] (N4Et8 = meso-octaethylcalix[4]pyrrolide) undergoes selective oxidation of one SmII site on reaction with a range of metal carbonyls giving mixed valence Sm(II/III) complexes. Thus, reactions with TM(CO)6 (TM = Mo or Cr) entrap M2(CO)102– ions between two mixed valence hosts in [{(thf)2SmII(N4Et8)SmIII(thf)(μ–OC)TM(CO)4}2]·PhMe (TM = Mo, 1; Cr, 2), while W(CO)6 on a different stoichiometry traps W(CO)52– in [{(thf)2SmII(N4Et8)SmIII}2{(μ–OC)W(CO)4}]·PhMe 3 in which the isocarbonyl group is disordered over two sites. In contrast, [Sm2(N4Et8)(thf)4] reacts with dicobalt octacarbonyl, bis(cyclopentadienyl)tetracarbonyl diiron, and dimanganese decacarbonyl to give the mixed valence species [(thf)2SmII(N4Et8)SmIII(thf)(μ–OC)TM(CO)3]·2PhMe (TM = Co, 4; Fe, 5) and [(thf)2SmII(N4Et8)SmIII(thf)(μ–OC)Mn(CO)4]·1.5PhMe 6. However, both SmII sites of [Sm2(N4Et8)(thf)4] can be oxidized as its reaction with cyclooctatetraene (COT) yields the SmIII species [(thf)SmIII(N4Et8)SmIII(COT)] 7. The analogous EuII reagent, [Eu2(N4Et8)(thf)4] induces C–halogen activation of perfluorodecalin, hexachloroethane, and bromoethane to form the mixed oxidation state species [(thf)2EuII(N4Et8)EuIII(μ–X)]2 (X = F, 8; Cl, 9; Br, 10) despite the use of a sufficient reagent to oxidize both EuII sites. The synthetic potential of the halogenido complexes was illustrated by the reaction of 10 with sodium bis(trimethylsilyl)amide to give the mixed oxidation state [(thf)2EuII(N4Et8)EuIII(N(SiMe3)2)] 11