Heteroleptic copper(I) complexes incorporating sterically demanding diazabutadiene ligands (DABs). Synthesis, spectroscopic characterization and solid state structural analysis

The synthesis, isolation and structural characterization of the novel heteroleptic copper(I) complexes [Cu(RDABdipp)(LCOOMe)](PF6) (R = H (3), R = Me (4)) incorporating the sterically demanding 1,4-diaza-1,3-butadienes RDABdipp (R = H, Me; dipp = 2,6-diisopropylphenyl) is reported. 3 and 4 were isolated in high yields and spectroscopically characterized. The synthetic strategy includes the in situ reaction of the bis-acetonitrile intermediates [Cu(RDABdipp)(NCMe)2](PF6), (R = H (1), R = Me (2)) with the required amounts of the methyl-2-(pyridin-2-yl)-quinoline-4-carboxylate (LCOOMe) that was used as the ancillary ligand. 3 and 4 are rare examples of heteroleptic copper(I) complexes comprising RDABdipp and an ancillary α-diimine ligand, while 3 is the first crystallographically characterized example of this class of compounds. As a side product during the formation of 3 and 4, the homoleptic complex [Cu(LCOOMe)2](PF6) (5) is detected, that has been independently synthesized, for comparison. All the products were characterized by elemental analysis, FT–IR, UV–Vis and NMR spectroscopy. The molecular structures of 2·CH2Cl2, 3 and 5·CHCl3 were elucidated by single-crystal X-ray diffraction.