Lutetium gets a crown: Synthesis, structure and reaction chemistry of the separated ion pair complex, [Li(12-crown-4)2][(C5Me5)2LuMe2]

Reaction of (C5Me5)2Lu(Me)(μ-Me)Li(THF)3 (2) with excess 12-crown-4 affords the new separated ion pair complex, [Li(12-crown-4)2][(C5Me5)2LuMe2] (3), in excellent yield. This complex reacts with 2,6-diisopropylaniline and phenylacetylene to give the methyl amide complex [Li(12-crown-4)2][(C5Me5)2Lu(Me)(NH-2,6-iPr2C6H3)] (4) and the bis(acetylide) complex [Li(12-crown-4)2][(C5Me5)2Lu(C≡C–Ph)2] (5), respectively. Attempts to promote methane loss from complexes 3 and 4 to generate a lutetium methylidene or imido complex, respectively, were unsuccessful. The ability of the bis(acetylide) complex 5 to act as a π-tweezer complex was also explored. Reaction between [Li(12-crown-4)2][(C5Me5)2Lu(C≡C–Ph)2] (5) and CuSPh gave only intractable lutetium products and the copper(I) species [Li(12-crown-4)2][Cu(C≡C–Ph)2] (8). The new lutetium complexes have been characterized by elemental analysis and NMR spectroscopy. Finally, the X-ray crystal structures of (C5Me5)2Lu(Me)(μ-Me)Li(THF)3 (2), [Li(12-crown-4)2][(C5Me5)2LuMe2] (3), [Li(12-crown-4)2][(C5Me5)2Lu(Me)(NH-2,6-iPr2C6H3)] (4), [Li(12-crown-4)2][(C5Me5)2Lu(C≡C–Ph)2] (5), and [Li(12-crown-4)2][Cu(C≡C–Ph)2] (8) are also reported.