New Stereoselective Routes to Macrocyclic Ligands

Reaction of bis(ethane-1,2-diamine)copper(II) with
acetaldehyde and nitromethane in methanol leads, stereoselectively, to the new macrocyclic complex
(trans-5(R),7(R),12(S),14(S))-tetramethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane)copper(II) perchlorate
α-[CuL1](ClO4)2 in good
yield. Reduction of the nitro groups
affords the hexaamine (L2), which was crystallized as
[H4L2](ClO4)4·2H2O
and characterized by an X-ray crystal
structure study (monoclinic P21/n,
a = 9.763(2) Å, b = 12.1988(7) Å,
c = 13.036(2) Å, β = 105.668(7)°,
Z =
2) and complexed with CuII to produce the complex
β-[Cu(H2L2)](ClO4)4·2H2O,
which has also been characterized
by X-ray crystallography (monoclinic
P21/n, a = 9.717(4)
Å , b = 12.174(2) Å, c =
13.036(5) Å, β = 106.51(2)°, Z = 2). Reaction of
α-[CuL1]2+ with either basic hydrogen
peroxide or dilute nitrous acid leads to mild
reduction of the nitro groups to afford the ketoxime L3 as
its N-based isomeric CuII complexes,
trans-I [CuL3](ClO4)2 and trans-II
[Cu(L3)Cl]Cl·7H2O, the
latter of which has been characterized structurally:  triclinic,
P1̄ a
= 10.8441(5) Å, b = 11.6632(9) Å,
c = 11.8723(9) Å, α = 113.634(7)°, β
= 95.744(5), γ = 94.851(5)°, Z
=
2. Variations in the configurations of the coordinated amines in
[CuL1]2+,
[CuL2]2+, and
[CuL3]2+ have a profound
effect on the spectroscopy and electrochemistry of their
complexes.