Frus­tra­ted LEWIS Pairs

In the che­mi­s­try of Frus­tra­ted Lewis Pairs (FLP), ad­duct for­ma­ti­on bet­ween Lewis acid and base is sup­pres­sed by ste­ric shiel­ding and ring strain. The re­sul­ting unused re­ac­tion po­ten­ti­al can be uti­li­sed to ac­ti­va­te or bind small mole­cu­les. These pro­per­ties allow FLPs to be used as transition-​metal-free ca­ta­lysts. An im­portant examp­le is the re­duc­tion of CO₂, which sub­se­quent­ly can be used as a low-​cost C₁ buil­ding block.

Our group pre­sen­ted the first neu­tral ge­mi­nal FLPs with tet­rels as Lewis aci­dic com­po­n­ents. Most of these methylene-​bridged sys­tems are able to re­ver­si­bly bind CO₂ and de­mons­tra­te re­ac­ti­vi­ty to­wards a large va­rie­ty of sub­stra­tes (SO₂, CS₂, NO). Fur­ther­mo­re, we suc­cee­ded in sta­bi­li­zing high­ly re­ac­ti­ve short-​lived in­ter­me­dia­tes such as sul­fur mon­oxi­de.

Our cur­rent ef­forts are fo­cu­sing on ex­ten­ding the spec­trum of Lewis aci­dic com­po­n­ents to group 13 and 15 ele­ments. The stron­gly dif­fe­ring elec­tro­nic pro­per­ties of the Lewis acids and the use of va­rious brid­ging units allow a pre­ci­se tu­ning of the re­ac­ti­vi­ty which leads to selec­ti­vi­ty in the for­ma­ti­on of ad­ducts.