Synthesis of low oxidation state zinc(i) complexes and their catalytic studies in the dehydroborylation of terminal alkynes

Abstract

A new example of a structurally characterized conjugated bis-guanidinate (CBG) supported zinc(I) dimer, i.e., LZnZnL (3) (L = {(ArNH)(ArN)–CN–C(NAr)(NHAr)}; Ar = 2,6-Et₂-C₆H₃) with a Zn–Zn bond is reported. Moreover, homoleptic (3) and heteroleptic (Cp*ZnZnL, 2, (Cp* = 1,2,3,4,5-pentamethyl cyclopentadienide)) zinc(I) dimers are used as precatalysts in the dehydroborylation of a wide array of terminal alkynes. Furthermore, the active catalyst, CBG zinc acetylide (LZn-CC-Ph-4-Me)₂, (5), is isolated which is confirmed by X-ray crystal structure analysis. A series of stoichiometric experiments have been performed to propose a plausible reaction mechanism.