Coordination of a Hemilabile N,N,S Donor Ligand in the Redox System [CuL₂]^+/2+, L = 2‐Pyridyl‐N‐(2′‐alkylthio­phenyl)methyleneimine

Abstract

The new copper(I) complexes [Cu(L1)2](BF4), L1 = 2‐pyridyl‐N‐(2′‐methylthiophenyl)methyleneimine, and [Cu(L2)2](ClO4), L2 = 2‐pyridyl‐N‐(2′‐benzylthiophenyl)methyleneimine, have been prepared and structurally characterized. In contrast to the known [Cu(L1)2](ClO4)2, which exhibits partial thioether S binding to effect five‐coordinate Cu2+, the copper(I) compounds reported here contain four‐coordinate metal ions with exclusively N‐donor binding. Cyclic voltammetry reveals a fully reversible oxidation of the CuI species, which suggests a small barrier for reorganization. The reduction at negative potentials is irreversible for compounds [Cu(L)2](X) and for the structurally characterized new compound [Cu(L1)(PPh3)2](ClO4). UV/Vis spectroelectrochemistry shows the typical low‐energy absorption bands of copper(I) (MLCT transition) and copper(II) (ligand‐field transition) in the visible region; the CuII form develops an intense band at 350 nm attributed to a S‐to‐Cu ligand‐to‐metal charge transfer (LMCT).

Correlated Coordination and Redox Activity of a Hemilabile Noninnocent Ligand in Nickel Complexes

“…The described example of reversible intramolecular double oxidative addition, based not on a metal redox process, but on ligand electron transfer, complements previous reactivity studies5, 23 where remote electron transfer at noninnocent ligands has activated addition reactions at the metal or at the ancillary ligand. This present example of nickel complexes thus complements previous related studies of copper,3 iridium,6, 24 ruthenium, and rhodium compounds24 and may be extended to complexes of other metals. Dinickel complexes of redox‐active quinonoid bischelate ligands, which have been well investigated by Braunstein et al.,25 might thus be modified accordingly in order to add another dimension to the systems described here.…”

“…2 One parameter to control hemilability is the redox state of the metal, which may prefer larger or smaller coordination numbers. The copper(II/I) redox pair is a prominent case in point 3. However, the hemilabile ligand itself can also be redox active, leading to potentially noninnocent behavior4 in transition metal complexes.…”

Structure and spectroscopic properties ofN,S-coordinating 2-methylsulfanyl-N-[(1H-pyrrol-2-yl)methylidene]aniline methanol monosolvate

“…This variance in thioether bonding is also found when reacting the pyridyl ligand with various copper complexes (Addison et al, 1984;Schnö dt et al, 2011;Patra et al, 2011b;Chatterjee et al, 2012;Balamurugan et al, 2006) where copper is our target metal centre for (1) and for our other NNS ligands. Addison and co-workers have reported a systematic study on the properties of various copper-thioether interactions (Addison et al, 1984).…”

Cd(II) and Zn(II) Complexes Containing N,N'-Bidentate N-(Pyridin-2-ylmethylene)cyclopentanamine: Synthesis, Characterisation and Methyl Methacrylate Polymerisation

“…Transition metal complexes containing ancillary ligands, pyridyl-imines and N-substituted 2-iminoalkylpyridines have been applied for synthetic, spectroscopic and kinetic studies, [1][2][3][4][5][6][7][8][9][10] photoluminescence and photochemistry, 11 as catalysts for organic transformation, [12][13][14][15][16][17][18] electrochemistry, [19][20][21] bioinorganic chemistry, 22,23 supramolecular chemistry, 24,25 molecular magnetism [26][27][28][29] and olefin polymerisation. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] In contrast, poly(methylmethacrylate) (PMMA) is a universal polymer with optical applications.…”