Cu(i) complexes based on cis, cis-1,3,5-tris(arylideneamino)cyclohexane ligands: synthesis, structure and CO binding

Abstract

A new series of sterically bulky, facially coordinating N(3)-donor tach-based ligands (tach; cis,cis-1,3,5-triaminocyclohexane) [2.1; cis,cis-1,3,5-tris(2,4-dimethylbenzylideneamino)cyclohexane, 4.1; cis,cis-1,3,5-tris(pentamethylbenzylideneamino)cyclohexane, 5.1; cis,cis-1,3,5-tris(2,6-dimethoxybenzylideneamino)cyclohexane, 6.1; cis,cis-1,3,5-tris(pentafluorobenzylideneamino)cyclohexane, 7.1; cis,cis-1,3,5-tris(3,5-bis(ditrifluoromethyl)benzylideneamino)cyclohexane, 8.1; cis,cis-1,3,5-tris(2-trifluoromethylbenzylideneamino)cyclohexane, 9.1; cis,cis-1,3,5-tris(2-methoxybenzylideneamino)cyclohexane] have been obtained from the condensation of tach with three equivalents of the appropriate substituted benzaldehyde. Reaction with [Cu(NCCH(3))(4)]PF(6) gives Cu(I) complexes of tach-based ligands {2.2-9.2, eg; 2.2; [Cu(2.1)(NCCH(3))]PF(6)}. Displacement of the acetonitrile ligand by CO was achieved successfully for all the Cu(I) complexes of tach-based ligands and the resulting complexes have been shown to bind carbon monoxide {2.3-9.3, eg; 2.3; [Cu(2.1)(CO)]PF(6)}. The X-ray single crystal structures of 5.1, 8.1, 9.1, 3.2, 7.2, 8.2, 9.2, 3.3, 5.3 and 6.3 have been determined.

New Cu(I)-Ethylene Complexes Based on Tridentate Imine Ligands: Synthesis and Structure

“…The IR spectrum of [( 1 )Cu(CO)][PF 6 ] exhibited ν(CO) at 2091 cm –1 indicative of only a moderate degree of π-back-bonding. As previously reported, copper can cause fast relaxation of proximal nuclei, and it was not possible to observe the 13 C{ 1 H} NMR resonance for the coordinated carbon monoxide ligand in this case. , …”

“…cis,cis -1,3,5-Tris(2-fluoro-6-(trifluoromethyl)benzylideneamino)cyclohexane ( 1 ) was prepared using the same method as used to obtain previous cis,cis -1,3,5-tri(arylamino)cyclohexane ligands. , Treatment of cis,cis -1,3,5-triaminocyclohexane (tach) with 3 equiv of 2-fluoro-6-(trifluoromethyl)benzaldehyde in toluene and removal of water by azeotropic distillation over an 18 h period gives 1 in 86% yield (Scheme ). The 1 H NMR spectrum of the ligand exhibited a characteristic quartet at 8.64 ppm and a broad triplet of triplets around 3.72 ppm, corresponding to the imine protons (-NC H -, H b in Scheme ) and cyclohexane protons (=N–C tach H -, H a in Scheme ) respectively.…”

“…We have previously communicated the synthesis and preliminary study of one derivative of these ligands, namely, cis,cis -1,3,5-tris(mesitylideneamino)cyclohexane, its copper(I) complex and substrate binding selectivity of this complex, , together with a broader study of novel nonfluorinated and fluorinated N 3 -donor ligands, their Cu(I) complexes and the propensity of such complexes to bind CO.…”

Tetrahedral Copper(II) Complexes with a Labile Coordination Site Supported by a Tris-tetramethylguanidinato Ligand

“…First of all, we attempted to get a mononuclear copper­(I) complex using TMG 3 tach, since the ligand might be suited to stabilize a metal complex with a four-coordinate tetrahedral geometry as seen in the reported tach-based ligand systems. ,,,, However, treatment of TMG 3 tach with [Cu I (MeCN) 4 ]­(OTf) in any copper­(I)/ligand ratio always gave the trinuclear copper­(I) complex [Cu I 3 (TMG 3 tach) 2 ]­(OTf) 3 ( 1 ) as confirmed by the elemental analysis and ESI-MS (see Experimental Section). A relatively simple 1 H NMR spectrum of 1 (Experimental Section) suggested that the trinuclear copper­(I) complex has a C 3 symmetry as illustrated in Scheme , where each copper­(I) ion takes a linear two-coordinate structure ligated by two TMG donor groups from different ligands.…”

“…In this study, we present a new N 3 -tridentate ligand, TMG 3 tach, consisting of a rigid cis,cis -1,3,5-triaminocyclohexane (tach) framework and three TMG ( N,N,N ′ N ′-tetramethylguanidino) donor groups (Scheme ). This tach derivative was acquired to construct transition metal complexes with a tetrahedral geometry to mimic reaction centers with a tetrahedral coordination environment for biological small molecule activation. − The TMG group has attracted much recent attention as a strongly electron-donating group in coordination chemistry. − Notable recent examples are the successful generation and characterization of Cu, Fe, and Ni complexes of active oxygen species (superoxide, peroxide, and oxide), relevant to reactive intermediates in biological oxidation/oxygenation chemistry. − Steric effects of the N -alkyl groups on the electron donor ability of the guanidino group have also been examined by changing the N -methyl groups to larger alkyl groups. ,− In addition, TMG-containing aromatic compounds have been developed as noninnocent ligands, to study the electronic communication between the supported transition metal ions and extended π-conjugation systems, consisting of an aromatic ring and the attached guanidino substituents. − …”