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