New Cu(I)-ethylene complexes based on tridentate imine ligands: synthesis and structure.

A new bulky facially coordinating N3-donor tach-based ligand (tach: cis,cis-1,3,5-triaminocyclohexane) [1: cis,cis-1,3,5-tris(2-fluoro-6-(trifluoromethyl)benzylideneamino)cyclohexane] has been obtained from the condensation of tach with 3 equiv of the appropriate benzaldehyde. Reaction of 1 with [Cu(NCMe)4][PF6] gave the complex [(1)Cu(NCMe)][PF6]. Displacement of the acetonitrile ligand is possible with CO and C2H4 (3-5 bar). Cu(I)-ethylene complexes of ligands 1 and 2 [2: cis,cis-1,3,5-(mesitylideneamino)cyclohexane] were prepared successfully by treatment of the ligands with CuBr and AgSbF6 in the presence of ethylene. These complexes display reversible complexation of the ethylene molecule under mild changes to pressure, suggesting possible application in olefin separation and extraction.