Tellurium azamacrocycles: synthesis, characterization and coordination studies

Abstract

The metal-free condensation of bis(2-formylphenyl) telluride (1) with a series of diamines affords macrocyclic tellurium ligands 2-7. Crystals of the protonated macrocycle 8 are monoclinic, space group P2/n with a=10.890(5), b=7.414(4), c=24.334(13) Å, Z=2. The reaction of tellurium containing macrocyclic Schiff base 2 with Pd(C₆H₅CN)₂Cl₂ gives the expected 1:1 product [Pd(II) 2]Cl₂ (9). Complex 9 was treated with excess of NH₄PF₆ in methanol to give the analogous PF₆⁻ salt [Pd(II) 2] (PF₆)₂ (10). The crystals of 10 are monoclinic, space group P2₁/n, a=8.2250(10), b=21.280 (4), c=21.150 (4), Z=4. However, the reaction of 2 with Pt(COD)Cl₂ proceeds via novel transmetallation to yield an organoplatinum complex (11). The crystals of 11 are also monoclinic, space group P2₁/n, a=12.3253 (14), b=14.6557 (14), C=13.4054 (11), Z=4. The octahedral Ni(II) complex 12 was prepared by the reaction of NiCl₂·6H₂O with 2 and NH₄PF₆ under an inert atmosphere. For 12: triclinic, space group P1̅; Z=2; a=10.800(8), b=13.468(9), c=13.918(11), α=89.67(6)°, β=101.53(7)°, γ=81.49(3)° and V=1961(3). Cyclic voltammetry of 12 in MeCN solution shows a well-behaved quasi-reversible (ΔE=100 mV) Ni(III)↔Ni(II) couple. The metal-free condensation of bis(o-formylphenyl)telluride with a series of diamines affords macrocyclic tellurium ligands. The reaction of macrocyclic Schiff base 2 with Pd(II)/Ni(II) metal ions followed by NH₄PF₆ addition gives the corresponding 1:1 cationic complexes whereas, reaction with Pt(II) proceeds via novel transmetallation.