Reversible Uptake of CO₂ by Pincer Ligand Supported Dimetallynes

Abstract

We report on the reversible uptake of carbon dioxide by dimetallynes featuring ancillary hemi-labile pincer ligands. Insertion into the GeÀ Ge/SnÀ Sn bonds yields species containing an E(CO 2 )E unit, with the mode of ligation of the CO 2 fragment determined crystallographically being found to be dependent on the identity of the Group 14 element. The thermodynamics of CO 2 uptake/loss can be established through VT NMR (ΔH°= + 24.6(2.3) kJ mol À 1 , ΔS°= + 64.9(3.8) J mol À 1 K À 1 , ΔG°2 98 = + 5.3(1.9) kJ mol À 1 for the loss of CO 2 in the Ge case), and the chemical consequences of reversibility demonstrated by thermodynamically-controlled exchange reactions.

Cooperative small molecule activation by apolar and weakly polar bonds through the lens of a suitable computational protocol

“…For instance, pincer-ligand supported dimetallynes [ArNEt 2 E] 2 (E = Ge, Sn, ArNEt 2 = C 6 H 3 (CH 2 NEt 2 ) 2 -2,6) have been shown to reversibly react with CO 2 under mild conditions to generate insertion compounds of the type [ArNEt 2 E(CO 2 )EArNEt 2 ]. 24 Analogous to digermynes, the products are not stable at ambient temperature and, after uptaking of a second CO 2 molecule, they convert into the corresponding carbonate compounds with accompanying generation of CO.…”

Applications of low-valent compounds with heavy group-14 elements

“…The reaction of the lithiated salt of 2,6-(Et 2 NCH 2 ) 2 C 6 H 3 Br with SnCl 2 in THF afforded the pincer-ligated chlorostannylene, which upon reduction with KC 8 led to the formation of the desired product ( Sn61 ) (Scheme 98). 123…”

“…Subsequently, heating it to 70 °C led to the formation of the final compound Ge54 (carbonate compound) with the evolution of CO (Scheme 207). 123…”

“…The pattern of reversible uptake of CO 2 was similar but the formation of a carbonate compound ( Sn79 ) in the presence of excess CO 2 was facile and formed at room temperature (Scheme 216). 123…”

Small molecule activation by well-defined compounds of heavy p-block elements

“…The product is not stable at ambient temperature and with uptake of a second molecule of CO 2 and elimination of CO the carbonate complex 48 is formed. 75 A product mixture of the formate 47 and compound 48 was observed when 16 or 17 were treated with CO 2 . This is rationalized by the formation of a tin hydride via reductive elimination from 16 and 17 which then reacts with CO 2 to give 47 .…”