Design of Ligands Which Improve Cu(I) Catalysis

Abstract

It seemed plausible that tri-and tetraamine ligands with a substituent which binds to Cu(I) but not to Cu(II), e.g., an allyl, stabilize Cu(I) in aqueous solutions and shift its redox potential cathodically relative to Cu + (aq). Therefore, the ligands N(CH 2 CH 2 NR 2 ) 2 (CH 2 CH 2 NRCH 2 CHd CH 2 ) (R ) H or CH 3 ) were synthesized. These ligands indeed stabilize Cu(I) in aqueous solutions and shift the redox potential of the Cu(II)/Cu(I) and Cu(I)/Cu(0) couples cathodically relative to Cu 2+/+ (aq) and the complexes Cu II L/Cu I L where L ) R 2 NCH 2 CH 2 NRCH 2 CH 2 NR(CH 2 CHdCH 2 ). Therefore, the copper complexes with the new ligands are expected to be better catalysts to processes in which the redox step is the rate-determining step.

Reversible Coordinative Bonds in Molecular Recognition

“…Tren complexes of various metals have been known since 1959 . Among all reported complexes, Cu(II), Cu(I), Ni(II), Zn(II), Co(III), Rh(III), Fe(III), and Cr(III) complexes have received the most attention (Table ).…”

Synthesis, Characterization, and in Vitro Antitumor Properties of Tris(hydroxymethyl)phosphine Copper(I) Complexes Containing the New Bis(1,2,4-triazol-1-yl)acetate Ligand

“…Moreover, we have designed and synthesized the new triazole-based heteroscorpionate ligand, bis(triazol-1-yl)acetate ([HC(CO 2 )(tz) 2 ] -); triazolebased ligands are electron-withdrawing relative to their pyrazolebased counterparts, and the exo-ring-nitrogen atoms may bridge between metal centers or may take part in hydrogen-bond interactions, assisting the formation of two-dimensional waterintercalate or water-layer clathrates, 35,36 thus leading to water soluble species. [37][38][39] Besides, because it is of great importance to obtain complexes that are soluble and stable under physiological conditions, an interesting solution is the use of water-soluble phosphine coligands bringing highly polar functional groups such as -SO 3 + , -COOH, -NR 3 + , or -OH. 40 This paper, as part of our investigations into the copper(I) coordination chemistry, [4][5][6] describes the synthesis and the spectroscopic and analytic characterization of new triazole-based scorpionate copper(I) complexes containing the tris(hydroxymethyl)phosphine coligand.…”

New N , N , O , O functionalized heteroscorpionate ligands and related Zn(II) and Cd(II) derivatives

“…Moreover, the carboxylic groups are susceptible of a further functionalization by reaction with ammines or alcohols to obtain amide-or ester-containing R groups at the 3-position of the pyrazole ring to provide an additional set of sites for secondary interactions [18]. On this basis, the ligands CH 2 (Pz COOH;Me ) 2 and CH 2 (Pz COOH;Me )(Pz Me;COOH ) can offer great opportunity to engineer architecture of supramolecular compounds [19], for the development of new systems which improve catalysts in aqueous or in protic media [20,21], or having relevant biological activity [15]. From the interaction of one equivalent of CH 2 (Pz COOH;Me ) 2 , 1, with one equivalent of zinc(II) acetate in ethanol or methanol at room temperature, the complex {Zn[CH 2 (Pz COO;Me ) 2 ] Á 2H 2 O}, 3, has been obtained in high yield, (Scheme 2).…”