Boron–Ligand Cooperation: The Concept and Applications

Abstract

The term boron-ligand cooperation was introduced to describeaspecific mode of action by which certain metal-free systems activate chemical bonds. The main characteristic of this mode of action is that one covalently bound substituent at the boron is actively involved in the bond activation process and changes to ad atively bound ligand in the course of the bond activation. Within this review,h ow the term boron-ligand cooperation evolvedi s reflectedo na nd examples of bond activation by boronligand cooperation are discussed. It is furthermore shown that systemst hat operate via boron-ligand cooperation can complementt he reactivity of classic intramolecular frustrated Lewis pairs and applications of this new concept for metal-free catalysis are summarized. Scheme1.The concept and examples of metal-ligand cooperation. (a) The concept of metal-ligand cooperationaccording to the criteria defined by Khusnutdinova and Milstein. (b) Hydrogen activationbyN oyori's catalyst. (c) Reversible hydrogen activationbyM ilstein's pyridine-based pincer complex through an aromatization/de-aromatization sequence.

Calix[4]pyrrolato Aluminates: The Effect of Ligand Modification on the Reactivity of Square‐Planar Aluminum Anions

“…[10] Overall, ELC gains momentum in bond activation with earthabundant main group elements as an alternative for transition metals. [11] Controlling both aspects, planarization induced reactivity andE LC, by defined and well understood changes is vital for furtherd eveloping these promising fields. Herein, we provide the synthesis of two new planar aluminates and ac omparisono fs tructure and reactivity with the methyl-calix [4] The recently introduced meso-octamethylcalix [4]pyrrolato aluminate [1] À and its interaction with substrates.…”

“…However, against pMBA (an ELC-binder), the order [2] À < [3] À < [1] À occurred,indicating otherfactorsgoverning the trend. 4)ÀAl( 1)ÀN(2) 177.75 (11), N(3)ÀAl( 1)ÀN( 1) 177.07 (11).…”

“…Selected bondlengths [pm] and bond angles [8]: 2: AlÀ N(1) 188.3(2), AlÀN(2) 188.5(2), AlÀN(3) 187.9(2), AlÀN(4) 188.6(2), N(1)ÀAlÀ N(3) 179.04(10), N(2)ÀAlÀN(4) 178.05(10). 3: AlÀN(1/2/3/4)187.8(15), N(1)À AlÀN(3)/N(2)ÀAlÀN(4) 172.69(11).…”

“…Selectedbond lengths[ pm]a nd bond angles [8]: [Li(thf) 4 ][1-thf]: AlÀN avg 195.8(2), AlÀO 191.5(2),N 1 ÀAlÀN3 165.7(1), N2ÀAlÀN4 164.6(1). [Li(thf) 4 ][2-(thf) 2 ]: AlÀN avg 199.3(2),A l ÀO2 02.8(2),N (4)ÀAl(1)ÀN(2) 177.75(11), N(3)ÀAl(1)ÀN(1) 177.07(11).…”

Future prospects in boron chemistry: new boron compounds and Lewis acids for catalysis and materials science

“…Triarylboranes are widely used as activators, catalysts and co-catalysts in a plethora of reactions [16][17][18] . The recent development of polyfluorinated triphenyldiphenyl boranes tolerant to air and water [Figure 1A] [19] will undoubtedly open new opportunities for improving well-established boron-mediated catalytic processes [20] . Powerful boron Lewis acids and superacids with ever increasing Lewis acidity are also gaining increasing interest from the perspective of the recent intense development of new types of inorganic analogues, including diboraanthracene featuring carborane substituents [Figure 1B] [21] , pyramidal yet trivalent boron Lewis acids embedded in cage-shaped triptycene cores [Figure 1C] [22][23][24] and antiaromatic perfluorinated boroles [Figure 1D] [25] .…”