In situ studies of reversible solid-gas reactions of ethylene responsive silver pyrazolates.

Solid-gas reactions and in situ powder X-ray diffraction investigations of trinuclear silver complexes {[3,4,5-(CF3)3Pz]Ag}3 and {[4-Br-3,5-(CF3)2Pz]Ag}3 supported by highly fluorinated pyrazolates reveal that they undergo intricate ethylene-triggered structural transformations in the solid-state producing dinuclear silver-ethylene adducts. Despite the complexity, the chemistry is reversible producing precursor trimers with the loss of ethylene. Less reactive {[3,5-(CF3)2Pz]Ag}3 under ethylene pressure and low-temperature conditions stops at an unusual silver-ethylene complex in the trinuclear state, which could serve as a model for intermediates likely present in more common trimer-dimer reorganizations described above. Complete structural data of three novel silver-ethylene complexes are presented together with a thorough computational analysis of the mechanism.

Low Heat of Adsorption of Ethylene Achieved by Major Solid-State Structural Rearrangement of a Discrete Copper(I) Complex.

The trinuclear copper(I) pyrazolate complex [Cu3 ] rearranges to the dinuclear analogue [Cu2 ⋅(C2 H4 )2 ] when exposed to ethylene gas. Remarkably, the [Cu3 ]↔[Cu2 ⋅(C2 H4 )2 ] rearrangement occurs reversibly in the solid state. Furthermore, this transformation emulates solution chemistry. The bond-making and breaking processes associated with the rearrangement in the solid-state result in an observed heat of adsorption (-13±1 kJ mol-1 per Cu-C2 H4 interaction) significantly lower than other Cu-C2 H4 interactions (≥-24 kJ mol-1 ). The low overall heat of adsorption, "step" isotherms, high ethylene capacity (2.76 mmol g-1 ; 7.6 wt % at 293 K), and high ethylene/ethane selectivity (136:1 at 293 K) make [Cu3 ] an interesting basis for the rational design of materials for low-energy ethylene/ethane separations.