New Stereoselective Routes to Macrocyclic Ligands

• Published in: Inorganic chemistry Vol. 37; no. 7; pp. 1629 - 1636
• Main Authors: Bernhardt, Paul V, Sharpe, Philip C
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06.04.1998
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic971020d

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.