Compounds of nickel(II) with 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rmL2: The structures of [Ni(rmL2)](ClO4)2 · 0.5H2O and cis-[Ni(rmL2)(acac)]ClO4

The imine functions of [Ni(mL1)](ClO4)2 (mL1 = meso-7RS,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) are reduced by using NaBH4 in acetonitrile/methanol to form the meso–meso and rac–meso isomeric cyclic tetramine complex cations [Ni(mmL2)]2+ and [Ni(rmL2)]2+ (mml2 = 5RS,7RS,12SR,14SR- and rmL2 = 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) in ca. 8:1 proportions. [Ni(rmL2)]2+ is also prepared from rmL2, formed in <1% yield by the reduction of mL1 by NaBH4 in ethanol. Square planar singlet ground state (S = 1) salts [Ni(rmL2)](ClO4)2 and [Ni(rmL2)][ZnCl4] and triplet ground state (S = 3) trans-di-ligand octahedral compounds trans-[Ni(rmL2)X2] (X-=Cl-,Br-,NCS-,N3-,NO3-,NO2-andHCO3-),μ-Y-trans-[Ni(rmL2)Y] (Y2-=C2O42-and[Ni(CN)4]2-) and folded macrocycle compounds cis-[Ni(rmL2)(acac)]CIO4 (acac− = pentane-2,4-dionato), cis-[{Ni(rmL2)}2(C2O4)](ClO4)2, cis-[Ni(rmL2)(H2O)2](ClO4)2 and cis-[Ni(rmL2)X2], X− = Cl−, Br−, are described. The S = 1 salt 1SR,4SR,5SR,7RS,8RS,11RS,12SR,14SR-[Ni(rmL2)](ClO4)2 · 0.5H2O has a disordered structure with Ni(II) in square planar coordination by the nitrogen atoms of the macrocycle, in N-configuration III, with Ni–Nmean = 1.96(2) Å. The six-membered chelate rings both have chair conformations, with the phenyl substituents equatorially oriented and with the methyl substituents disordered over axial and equatorial orientations. The S = 3 compound cis-1SR,4SR,5SR,7RS,8SR,11SR,12SR,14SR-[Ni(rmL2)(acac)]ClO4 has N-configuration V. The macrocycle is folded along N1–Ni–N8, adjacent to the phenyl substituents {N1–Ni–N8 = 176.45(6), N4–Ni–N11 = 98.16(6)°}, with mean Ni–N = 2.09(2) Å and mean Ni–O = 2.121(5) Å. Both six-membered chelate rings have chair conformations with the methyl substituents equatorially oriented, while one has the phenyl substituent equatorially and the other has it axially oriented. The structures of the isomeric [M(rmL2)(acac)]ClO4, [M(rrL2)(acac)]CIO4 and [M(mmL2)(acac)]ClO4 compounds are compared.

The cyclic tetraamine 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane (rmL2) with nickel(II) mainly forms compounds with the amine planar for [Ni(rmL2)]2+ salts and trans-diligand compounds trans-[Ni(rmL2)L2]. Compounds with the amine in folded coordination with cis ligands, cis-[Ni(rmL2)L2], usually metastable with respect to the trans form, or with a chelate, as for cis-[Ni(rmL2)(acac)]ClO4 are also formed. Structures of trans-[Ni(rmL2)](ClO4)2 · 1/2H2O with the methyl substituents disordered over axial and equatorial orientations, and cis-[Ni(rmL2)(acac)]ClO4 are reported.Figure optionsDownload as PowerPoint slide