Rare-earth metal ethylene and ethyne complexes

Abstract

Guanidinate homometallic rare-earth ethyl complexes [LLn(μ₂-η¹:η²-Et)(Et)]₂ (Ln = Y(1-Y), Lu(1-Lu)) and heterobimetallic rare-earth ethyl complexes LLn(Et)(μ₂-η¹:η²-Et)(μ₂-η¹-Et)(AlEt₂) (Ln = Y(2-Y), Lu(2-Lu)) have been synthesized by the treatment of LLn(CH₂C₆H₄NMe₂-o)₂ (L = (PhCH₂)₂NC(NC₆H₃ⁱPr₂-2,6)₂) with different equivalents of AlEt₃ in toluene at ambient temperature. Interestingly, the unprecedented rare-earth ethyne complex [LY(μ₂-η¹-Et)₂(AlEt)]₂(μ₄-η¹:η¹:η²:η²-C₂H₂) (3-Y) containing a [C₂H₂]⁴⁻ unit was afforded from 2-Y. The formation mechanism study on 3-Y was carried out by DFT calculations. Furthermore, the nature of the bonding of 3-Y was also revealed by NBO analysis. The reactions of LLn(CH₂ C₆H₄NMe₂-o)₂ (Ln = Y, Lu) with AlEt₃ (4 equiv.) in toluene at 50 °C produced firstly the non-Cp rare-earth ethylene complex LY(μ₃-η¹:η¹:η²-C₂H₄)[(μ₂-η¹-Et)(AlEt₂)(μ₂-η¹-Et)₂(AlEt)] (4-Y), and the Y/Al ethyl complex LY[(μ₂-η¹-Et)₂(AlEt₂)]₂ (5-Y) as an intermediate of 4-Y was isolated from the reaction of LY(CH₂C₆H₄NMe₂-o)₂ with AlEt₃ (4 equiv.) in toluene at −10 °C.