Isolable 1-Butene Copper(I) Complexes and 1-Butene/Butane Separation Using Structurally Adaptable Copper Pyrazolates

Abstract

Non-porous small molecule adsorbents such as {[3,5-(CF3)2Pz]Cu}3 (where Pz=pyrazolate) are an emerging class of materials that display attractive features for ethene−ethane separation. This work examines the chemistry of fluorinated copper(I) pyrazolates {[3,5-(CF3)2Pz]Cu}3 and {[4-Br-3,5-(CF3)2Pz]Cu}3 with much larger 1-butene in both solution and solid state, and reports the isolation of rare 1-butene complexes of copper(I), {[3,5-(CF3)2Pz]Cu(H2C=CHC2H5)}2 and {[4-Br-3,5-(CF3)2Pz]Cu(H2C=CHC2H5)}2 and their structural, spectroscopic, and computational data. The copper−butene adduct formation in solution involves olefin-induced structural transformation of trinuclear copper(I) pyrazolates to dinuclear mixed-ligand systems. Remarkably, larger 1-butene is able to penetrate the dense solid material and to coordinate with copper(I) ions at high molar occupancy. A comparison to analogous ethene and propene complexes of copper(I) is also provided.