Synthesis, Cyclic Voltammetry, and x-ray Crystal Structures of Copper(I) and Copper(II) Complexes of Tris((6-phenyl-2-pyridyl)methyl)amine (TPPA)

Abstract

The synthesis and characterization of a new ligand, tris((6-phenyl-2-pyridyl)methyl)amine (TPPA) and some of its copper complexes are described. The complexes [Cu(TPPA)]BPh (7) and [Cu(TPPA)(AN)](ClO& (8) (AN = acetonitrile) were prepared and their X-ray crystal structures and redox potentials were determined. The X-ray structure of 7 (triclinic space group, P1; a = 14.603(3), b = 15.137(3), c = 12.974(3) A, a = 91.76(3), p = 105.87(3), y = 117.00(3)", V = 2417.4( 12) A3, Z = 2) displays a copper(1) atom with a distorted trigonal pyramidal coordination sphere, but the X-ray structure of 8 (triclinic space group, Poi; a = 13.458(3), b = 13.586(3) c = 11.082(2) A, a = 113.00(3), p = 94.48(3), y = 90.53(3)", V = 1857.7(9) A3, Z = 2 ) indicates that the copper(I1) atom has the expected trigonal bipyramid geometry. The reduction potential of 8 in dimethylformamide, dimethylacetamide, acetonitrile, and isobutyronitrile is quite positive compared to [Cu(TPA)](ClO& (TPA = tris(2-pyridylmethy1)amine) under identical conditions. The various factors that may contribute to the difference in oxidation potential are discussed. The positive redox potential combined with steric factors accounts for the lack of reactivity of [Cu(TPPA)]PF6 with molecular 0 2 .

Coordination and Bioinorganic Chemistry of Aryl-Appended Tris(2-Pyridylmethyl)amine Ligands

“…Aryl-appended TPA ligands have been used in the preparation of coordination complexes of Mn(II), [22,28] Fe(II) and Fe(III), [20,[23][24][25]28,34,35] Co(II), [22,28,31] Ni(II), [22,28,31,36] Cu(I) and Cu(II), [21,27,28,[37][38][39] and Zn(II). [22,28,31] Mn(II).…”

“…This is particularly true in the area of synthetic bioinorganic chemistry where biomimetic and bioinspired complexes are sought to further understand and=or mimic the reactivity features of biological product by column chromatography. [21] Several aryl-appended pyridinecarboxaldehydes (3,5-(dimethyl)phenyl, 3-(nitro)phenyl, 3-(trifluoromethyl)phenyl, 3-(chloro)phenyl, 3-(methyl)phenyl, 3-(methoxy)phenyl, and 4-methoxy-(phenyl), and 2,3-dihydroxo(phenyl) have been prepared using this procedure starting from the appropriate boronic acid. [22,23] The latter reaction has thus far only been used for the preparation of 6-(4-OMePh)TPA, 6-(3-CNPh)TPA, BCATTPA, and a-MePh 2 TPA ( Figure 1).…”

“…[24][25][26] A procedure for the preparation of o-d 1 -6-phenyl-2-pyridinecarboxaldehyde has also been reported. [23] To construct an aryl-appended tris(2-pyridylmethyl)amine (TPA) ligand starting from the aryl-appended carboxaldehyde, a common synthetic pathway involves (1) reduction of the aldehyde group using NaCNBH 3 [27] or NaBH 4 [28] to generate a primary alcohol, (2) treatment of this alcohol with SOCl 2 [21,22,27] or PBr 3 [28] to generate a 2-halomethyl intermediate, and (3) heating of this intermediate with a 2-(aminomethyl)pyridine derivative in the presence of base to produce a mono-, di-or triaryl-appended chelate ligand. An alternative synthetic route involves reductive amination via treatment of the aryl-appended pyridine carboxaldehyde with a 2-(aminomethyl)pyridine derivative in the presence of NaCNBH 3 .…”

Reactivity of Copper(I) Complexes Towards Dioxygen

“…[54] The introduction of steric hindrance in the tris(pyrazolyl)borate ligand [HB(3-R 1 -5-R 2 pz) 3 , Scheme 2] allowed the synthesis and structural characterization of a copperϪsuperoxo complex (see above). [21] Using the same approach, Jitsukawa, Masuda, and co-workers introduced three pivalolylamino groups at the 6-positions of the pyridine moieties of tmpa (Scheme 2; tppa).…”

Rigidified tripodal chiral ligands in the asymmetric recognition of amino compounds

“…Canary's laboratory resulted in the synthesis and characterization of Cu(I) and Cu(II) complexes of the ligand, tris[(6-phenyl-2-pyridyl)methyl]amine (TPPA). 36 In the Cu(II) complex 4 is a cavity in which a MeCN solvent molecule is bound. The complexes also displayed well-behaved electrochemistry, as determined by cyclic voltammetry.…”