Alkyne complexes of copper(I) (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato): Syntheses and characterization of (η²-bis(trimethylsilyl)acetylene) copper(I) (hfac), (μ-η¹-bis(trimethylsilyl)acetylene) bis(copper(I) (hfac)) and a series of (η²-alkyne) Cu(hfac) complexes

Abstract

The reaction of Cu2O with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (Hhfac) in the presence of alkynes results in the formation of (η2-alkyne) Cu(hfac). When using bis(trimethylsilyl)acetylene (BTMSA), both a mononuclear compound BTMSACu(hfac) (1) and a dinuclear complex BTMSA(Cu(hfac))2 (2) can be isolated; each complex was characterized by X-ray crystallography, IR, 1H and 13C NMR spectroscopies. In 1, the BTMSA ligand is η2 bonded parallel to the Cu (β-diketonate) plane, the trimethylsilyl groups are cis bent away from copper with small angles of deformation (θCCSi = 157 and 171°) and the C≡C bond distance is 1.17 Å. In 2, two BTMSACu(hfac) planes with a dihedral angle of 105.8° are observed. The intramolecular Cu-Cu distance is only 2.800 Å and the central axis of BTMSA is situated perpendicular to the Cu-Cu vector. A series of η2-alkyne Cu(hfac) were synthesized and characterized by NMR and IR spectroscopy.