A simple synthetic route to N,N′-dialkyl-2,11-diaza[3.3](2,6)-pyridinophanes. Crystal structures of N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane and its copper(II) complex

Reaction of 2,6-bis9bromomethyl)pyridine with primary amines gave the 12-membered N,N′-dialkyl-2,11-diaza[3.3](2,6)pyridinophanes. The structures of N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane (4) and its copper(II) derivative [Cu(4)Cl2] (7) have been characterized by X-ray crystal analysis. The average axial CuN (tertiary amine) distance of 2.490 Å in 7 is appreciably longer than the related value of 2.347 Å in Cu(6)Cl2·H2O.4In 4, the two planar pyridyl rings are not in the same plane, but roughly parallel and the 12 atoms of the macrocyclic ring constitute a syn chair-chair conformation. In complex 7, the copper(II) ion adopts a distorted octahedral geometry, in which the tertiary amine nitrogen atoms span axial positions approximately normal to the square plane formed by the two pyridine nitrogens and the chloro ligands. The average Cu-N (tertiary amine), Cu-N(pyridine) and Cu-Cl distances are 2.49(2), 2.03(2) and 2.287(7) Å, respectively.