Synthesis and reactivity of organometallic complexes of divalent thulium with cyclopentadienyl and phospholyl ligands

Reaction of sodium 1,2,4-tris(trimethylsilyl)cyclopentadienide [Na(Cp' '')] with [TmI2(THF)(3)] afforded the divalent thulium complex [(Cp' '')(2)Tm(THF)]. Its crystal structure is similar to that of the previously described [(Cp-ttt)(2)Tm(THF)] (Cp-ttt = 1,2,4-tris(tert-butyl)cyclopentadienyl). [(Cp' '')(2)TmI] was prepared by reaction of TmI3 with [K(Cp' '')] and could be reduced by KC8 into a new unsolvated, homoleptic complex, [(Cp' '')(2)Tm], which was characterized by NMR. [(Cp' '')(2)Tm] gave [(Cp' '')(2)Tm(THF)] by interaction with THF. A convenient alternative pathway to [(Cp-ttt)(2)Tm] by reduction of [(Cp-ttt)(2)Tm(BH4)] with KC8 was found: [(Cp-ttt)(2)Tm(BH4)] derives from [Tm(BH4)(3)(THF)(3)], which can be prepared from the less expensive TmCl3. On the other hand, the dimer [{(Cp-tt)(2)TmI}(2)] (Cp-tt = 1,3-bis(tert-butyl)cyclopentadienyl), obtained by reaction of TmI3 with [Na(Cp-tt)], gave only intractable results by reaction with KC8. The previously described Tm-II complex [(Dtp)(2)Tm] (Dtp = 2,5-di-tert-butyl-3,4-dimethylphospholyl) and the new, homoleptic, structurally characterized Tm-II dimer [{(Htp)(2)Tm}(2)] (Htp = 2,5-di-tert-butylphospholyl) were prepared by KC8 reduction of [(Dtp)(2)TmI] and [{(Htp)(2)TmI}(2)], respectively. Reaction of [(Cp-ttt)(2)Tm] with pyridine resulted in an immediate reduction of pyridine into 1,1'-bis(1,4-dihydropyridylamide) and the formation of the structurally characterized [{(Cp-ttt)(2)Tm}(2){mu-(NC5H5-C5H5N)}], while the reaction of [(Dtp)(2)Tm] with pyridine gave no isolable complexes. An NMR study suggests that initially a simple Tm-II adduct such as [(Dtp)(2)Tm(pyridine)] is formed in this reaction.