SYNTHESIS AND CHARACTERIZATION OF COPPER(I) TRIFLUOROACETATE ALKYNE COMPLEXES OF THE TYPE CU4(MU-O2CCF3)4(MU-ALKYNE)2 AND CU2(MU-O2CCF3)2(ALKYNE)2

The complex Cu4(μ-O2CCF3)4(μ-EtC≡CEt)2 (1) is prepared from 3-hexyne and Cu4(μ-O2CCF3)4(C6H6)2 followed by recrystallization from hexane. Recrystallization from hexane containing added 3-hexyne yields Cu2μ-O2CCF3)2(EtC≡CEt)2 (2). Molecular weight studies show these stoichiometrics are retained in solution. Low-temperature NMR spectra show that complex 2 is in equilibrium with 1 and free 3-hexyne, whereas 2 is not observed in solutions of 1. The tetranuclear complexes Cu4(μ-O2CCF3)4(μ-RC≡CCO2Me)2 (R = CO2Me (3), Me (4)), analogous to 1, form in reactions of Cu4(μ-O2CCF3)4(C6H6)2 and MeO2CC≡CCO2Me or MeC≡CCO2Me, respectively. In contrast, only the dinuclear complex Cu2(μ-O2CCF3)2(PhC≡CPh)2 (5), analogous to 2, forms in the reaction with diphenylacetylene. Competition studies indicate that the affinity of these alkynes for copper(I) in this system is similar for 3-hexyne, MeO2CC≡CCO2Me, and MeC≡CCO2Me, but diphenylacetylene has a lower affinity. © 1990, American Chemical Society. All rights reserved.