Group IB Organometallic Chemistry XIX.Synthesis and characterization of mixed-organocopper cluster compounds R4R'2Cu6 containing aryl and acetylide ligands.

Abstract

Mixed-organocopper cluster compounds Ar4Cu6(CCR)2 (Ar = 2-Me2NC6H4, R = phenyl, 4-tolyl, 2,4-xylyl or mesityl) have been prepared in high yield by the ligand-substitution reaction of Ar4Cu6Br2 with two equivalents of LiCCR. Ar4Cu6(CCC6H4CH3-4)2 has also been prepared via the aryl¡ªarylacetylide exchange reaction of ArnCun with HCCC6H4CH3-4 as well as via the reaction of ArnCun with polymeric CuCCC6H4CH3-4.

IR and NMR spectroscopy reveal that Ar4Cu6(CCR)2 and Ar4Cu6Br2 have the Ar4Cu6 skeleton as a common structural feature. Dynamic NMR spectroscopy provides information about the occurrence of intra-cluster Cu---N coordination. The position of the (CC) band (¡Ö 2040 cm−1) and considerations concerning the number of cluster electrons in Ar4Cu6X2 clusters (84e) suggest that the CCR ligand acts as a three electron ligand bridging two equatorial Cu atoms of the Cu6 core. In solution the Cu2CCR interaction is probably fluxional (, (2e¨C3c) ,).