Syntheses and metal-catalyzed C---H bond activation of Alkyne π complexes of copper(I) Trifluoromethanesulfonate

The copper(I) trifluoromethanesulfonate π complexes of 1,8-cyclotetradecadiyne and 1,7-octadiyne have been synthesized. For a series of terminal alkyne (CuO₃SCF₃) π complexes, vibrational spectra show weakening of both C ≡C and C_sp-H bonds upon copper(I) coordination. NMR analysis shows less Cu(I) caused deshielding of C(1) than C(2) of the alkyne and increased C_sp-H coupling. Copper(I) π coordination to terminal alkynes increases the rate of exchange of protium on C(1) for deuterium from CD₃COOD. Copper enhances the rate of exchange by a factor of 1.2 x 10⁵ with 1,7-octadiyne. The exchange is catalytic in copper(I) and is faster than the rate of copper alkynide formation in the absence of deuterium donor. Copper(I) catalyzes deuterium exchange for protium at C(1) between 1,7-octadiyne and 1-hexyne-1-d₁.