The first examples of intermolecular weak (agostic) γ-methyl-metal interactions in organolanthanide complexes: The synthesis and X-ray structures of [{Yb(η-CP″) 2}∞.] and [{Eu(η-CP″) 2}∞] [CP″ C 5H 3(SiMe 3) 2-1,3

Abstract

The lanthanocene(II) complexes [{Yb(η-CP ) ́ 2}∞] ( 1) and [{Eu)η-Cp) 2}∞] ( 2) [Cp″ C 5H 3(SiMe 3) 2-1,31 were prepared by the desolvation via sublimation of [Yb(η-Cp″) 2(OEt 2)] ( 3) and [Eu(η-CP″) 2(THF)] ( 4), respectively. The single crystal X-ray structures of 1 and 2 reveal that each complex has unique intermolecular agostic-like interactions. 1 adopts a bent metallocene conformation, Cent(Cp1)YbCent(Cp2) 138.0° and the mean YbC bond length 2.662 Å, and a close contact between the metal of one YbCp″ unit and a methyl group of a neighbouring such unit, Yb ⋯ C(9)″ 2.872(7) Å. For 2, the low temperature X-ray study shows a similar short intermolecular contact Eu(2′) ⋯ C(62) 3.091(6) Å [ cf. the mean Eu(2)C bond length of 2.804 Å], with the closest intermolecular metal-hydrogen distance Eu(2′) ⋯ H(62A) being 2.70 Å. Complex 2 also exhibits an unprecedented conformation with a cyclopentadienyl ring bridging η 5, η 3 between two non-equivalent europium atoms.