Enhanced Reactivity of Dinuclear Copper(I) Acetylides in Dipolar Cycloadditions

Abstract

Dinuclear alkynyl copper(I) complexes exhibit superior reactivity toward organic azides compared to their monomeric analogues. DFT studies indicate that the second copper center facilitates the formation of the cupracycle in the rate-determining step and stabilizes the metallacycle intermediate itself. These findings support the experimentally determined rate law and shed light on the origin of high reactivity of the in situ generated copper acetylides.

Metal-catalyzed azide-alkyne “click” reactions: Mechanistic overview and recent trends

“…1) reduces the activation energy barrier by 4-6 kcal/mol, depending on the nature of the ligand on the Cu B atom indicated in Fig. 1 [57]. The effect of π-complexation of the σ-alkynyl-Cu(I) species enhances the reactivity of the alkynyl ligand by decreasing electron density on the sp carbon atoms, thus facilitating the azide attack.…”

“…In fact the µ 2 coordination mode of the alkyne to Cu B was quite distorted and dependent on the ligand nature. Concomitantly to the DFT investigation on binuclear processes of Fokin and coworkers [57], Straub published a computational investigation on copper acetylide complexes showing the same trend, i.e., di-and tetra-nuclear species display higher reactivity in the CuAAC reaction than do their mononuclear relatives [58a]. According to this study, the complexation of a supplementary copper atom reduces the Cu=C=C double bond character and therefore the ring strain in the metallocyclic A c c e p t e d M a n u s c r i p t 7 intermediate.…”

Binuclear Copper(I) Borohydride Complex Containing Bridging Bis(diphenylphosphino) Methane Ligands: Polymorphic Structures of [(µ2-dppm)2Cu2(η2-BH4)2] Dichloromethane Solvate

“…Many examples The Cu(I)-dppm complexes are emerging class of polynuclear complexes, that are drawing considerable attention because of their photophysical properties [19][20][21][22] and prospective use as a catalyst [23][24][25] and a sensor for various organic bases [26] and anions [27]. Binuclear Cu(I) species possess an enhanced reactivity toward organic azides in copper-catalysed azide-alkyne cycloaddition compared to monomeric copper complexes [28][29][30][31][32][33][34][35]. Copper(I) tetrahydroborates with phosphine ligands featuring relative stability to air oxygen and moisture are used as selective reducing agents [36][37][38][39][40], catalysts of photosensitized isomerization of dienes [41][42][43] and hydrolytic dehydrogenation of ammonia borane [44].…”

“…Binuclear Cu(I) species possess an enhanced reactivity toward organic azides in copper-catalysed azide-alkyne cycloaddition compared to monomeric copper complexes [28][29][30][31][32][33][34][35]. Copper(I) tetrahydroborates with phosphine ligands featuring relative stability to air oxygen and moisture are used as selective reducing agents [36][37][38][39][40], catalysts of photosensitized isomerization of dienes [41][42][43] and hydrolytic dehydrogenation of ammonia borane [44].…”

Supramolecular metallogels for application in catalysis

“…As a result of this rate-limiting step, a six-membered copper-containing intermediate is formed and stabilized, according to computational methods, by geminal bimetallic coordination (D). 56,59 However, it is still unclear whether Cu(III) is intermediately formed, or if both metal centres cooperate in the oxidation step. In the metallocycle formed by oxidative coupling, the azide is well positioned for subsequent ring contraction by a transannular association of the N(1) lone pair of electrons with the C(5)-Cu π-orbital.…”