A Copper(I) N,N,N′,N′′,N′′-Pentamethyldiethylenetriamine Complex and Its Carbon Monoxide Adduct in Aqueous Solutions

Copper(I) ion forms a stable 1:1 complex with pmdien (2,5,8-trimethyl-2,5,8-triazanonane, 7) in CO-saturated or CH₃CN-containing aqueous solutions, due to the formation of a stable 1:1 CO or CH₃CN adduct. The formation constants of [Cu-(pmdien)(CO)]⁺(8) and [Cu(pmdien)(NCCH₃)]⁺have been established by the pH-metric titration and polarographic methods. Moreover, crystalline [Cu(pmdien)(CO)]ClO₄ has been isolated from CO-saturated aqueous solution. The observed v_CO bands of the CO adduct 8 at 2082 cm^-1(KBr pellet) and 2088 cm^-1(aqueous solution) agree with the end-on CO coordination.