Diversity of triflate coordination modes in neodymocene complexes containing bulky bis(trimethylsilyl)cyclopentadienyl ligands

The reaction of Nd(OTf)3 (OTf = O3SCF3) with two molar equivalents of LiCp″ [Cp″ = C5H3(SiMe3)2-1,3] in thf solution generated the blue, tetrametallic dimer [{Nd(η5-Cp″)2(μ2-κ2-O3SCF3)(μ3-κ3-O3SCF3)Li(thf)}2] (1a), which has been shown by X-ray crystallography to contain a tricyclic, ladder-like scaffold with Nd and Li cations and OTf anions at its core. Compound 1a was relatively labile, being readily cleaved by a variety of donor molecules. 18-Crown-6 efficiently encapsulated the lithium cation to yield the salt [Li(18-crown-6)][Nd(η5-Cp″)2(κ1-O3SCF3)(κ2-O3SCF3)] (2). Addition of N,N,N′,N′-tetramethylethylenediamine (tmeda) afforded the monomeric bimetallic [Nd(η5-Cp″)2(μ2-κ2-O3SCF3)2Li(tmeda)] (3), while the more rigid donor 2,2′-bipyridine (bipy) produced the neutral, Li-free complex [Nd(η5-Cp″)2(κ1-O3SCF3)(bipy)] (4). The molecular and crystal structures of 2–4, as well as that of1b, the unstable La analogue of 1a, have been determined by X-ray methods.