Synthesis of a thirteen-membered tetra-azamacrocycle employing formaldehyde and nitroalkanes directed by metal ions. Crystal structures of (12-methyl-12-nitro-1,4,7,10-tetra-azacyclotridecane)copper(II) perchlorate and µ-chloro-1,1,1-trichloro-2-(12-methyl-12-nitro-1,4,7,10-tetra-azacyclotridecane)dicopper(II)

Abstract

Reaction of formaldehyde and nitroethane or nitropropane with the copper(II) or nickel(II) complexes of 1,8-diamino-3,6-diazaoctane in methanol yields the complexed macrocycle 12-methyl-12-nitro-1,4,7,10-tetra-azacyclotridecane (L¹) or the 12-ethyl analogue (L²). Both copper(II) and nickel(II) complexes were isolated as perchlorate salts. The latter exists in the singlet ground state, but tetrahydroborato and dithiocyanate nickel(II) compounds with triplet ground states were also isolated. The perchlorate salt of [Cu(L¹)]²⁺, defined by a structure determination, consists of a linear polymer with bridging perchlorate groups occupying axial sites about a square plane of the macrocycle primary amines and the metal ion; Cu–N distances are 1.943(7) and 1.96(1)Å, with Cu–O at 2.62(1) and 2.65(2)Å. Slow crystallization of [Cu(L¹)]²⁺ from chloride ion solution yielded a dark green complex of L¹ which contained an equimolar amount of the [CuCl₄]^2– anion. An X-ray structure analysis defined the molecule as the binuclear neutral compound [Cu(L¹)Cl(CuCl₃)], with a single bridging chloride ion linking copper(II) ions in either a tetrahedron of chloride ions or a square-based pyramid of four nitrogen donors [Cu–N 2.006(4) and 2.022(3)Å] with an apical chloride ion [Cu–Cl 2.507(2)Å] which bridges to the second copper(II) ion. The Cu ⋯ Cu distance is 3.928(2)Å, and there are no antiferromagnetic exchange interactions.