Synthesis and characterisation of ytterbium(II) alkyls

Abstract

The following complexes were obtained and characterised: [Yb(CHR₂)₂(OEt₂)₂]1 from YbI₂ and 2 NaCHR₂; [Yb(CHR₂)₃Na] from Ybl₂ and 3 Na(CHR₂); 1 and [Yb(CHR₂)(OR′)(OEt₂)₂] from [Yb(OR′)₂(OEt₂)₂] and 2 K(CHR₂); [Yb(CHR₂)(OR′)(thf)₃] from [Yb(OR′)₂(thf)₃] and 1 K(CHR₂); [Yb(CHR₂)₂(tmen)] from [Yb(η-C₅Me₅)₂(OEt₂)], 2 Li(CHR₂) and tmen; [Yb(CHR₂)₂(dmpe)] from 1 and dmpe; [{Yb(CHR₂)(OEt₂)}₂C₅H₄(NR)₂-1,4] from 2 1 and C₆H₄(NHR)₂-1,4; [{Yb(CR₃)(µ-OEt)(OEt₂)}₂] from YbI₂ and 1 or 2 K(CR₃); [Yb(NR₂)₂{NC₅H₄(CH₂R)-2}₂] from [{Yb(NR₂)(µ-NR₂)}₂]I and 4 NC₅H₄(CH₂R)-2; [Yb(NR₂)₂{NC₅H₄(CHR₂)-2}] from I and 4 NC₅H₄(CHR₂)-2; [[graphic omitted]HR)-2}₂(dme)] from Ybl₂ and 2 [K{NC₅H₄(CHR)-2}(dme)(OEt₂)] and [K{[graphic omitted]HR)-2]₃}(dme)₂] from Ybl₂ and 3 [K{NC₅H₄(CHR)-2}(dme)(OEt₂)](R = SiMe₃, R′= C₆H₂Bu^t₂-2,6-Me-4, thf = tetrahydrofuran, tmen = Me₂NCH₂CH₂NMe₂, dmpe = Me₂PCH₂CH₂PMe₂ and dme = 1,2-dimethoxyethane). A single-crystal X-ray diffraction study established [{Yb(CR₃)(µ-OEt)(OEt₂)}₂] to be a centrosymmetric dimer with each Yb atom in a distorted-tetrahedral environment and a central planar Yb₂O₂ ring. Variable-temperature ¹H NMR spectral data for [K{[graphic omitted]HR)-2]₃}(dme)₂] showed that the Me₃Si protons become inequivalent at low temperature, T_c= 238 K, due to a terminal–bridging NC₅H₄(CHR)-2 -site-exchange process.