The complexes of Ni2+, Cu2+, and Zn2+ with two closely related pendant-arm penta-aza macrocycles 11-(2′-dimethylaminoethyl)-1,4,7,11-tetra-azacyclotetradecane, L1, and 7-(2′-dimethylaminoethyl)-3,7,11,17-tetra-azabicyclo[11.3.1]heptadeca-1(17),13,15-triene, L2, have been characterised spectroscopically. The square-planar complex of the protonated ligand L1, [Ni(HL1)][ClO4]3, previously reported to be a mixture of two isomers, has been found to isomerise in hot aqueous solution to give two further isomers. Six-co-ordinate thiocyanato-complexes of formula [Ni(L1)(NCS)]ClO4 and [Ni(HL1)(NCS)2]ClO4 have been isolated. For the protonated copper(II) complex of the ligand (L1)(but not L2), a temperature-dependent equilibrium of the type [Cu(L1)]2++ H+⇌[Cu(HL1)]3+ exists in aqueous solution, and a variable-temperature visible spectroscopic study shows that, at 298.2 K, K=(2.2 ± 0.3)× 103 dm3 mol–1 and ΔG⊖=–19.05 ± 0.29 kJ mol–1. Isomerisation of the protonated copper complex was not observed. The complexes of formula [Zn(L)][NO3]2(L = L1 or L2) were found to be single isomers which do not isomerise even at elevated temperatures. 13C N.m.r. studies show that in [Zn(L1)][NO3]2 the macrocycle is asymmetric whereas in [Zn(L2)][NO3]2 the macrocycle is in a symmetric configuration. The new, related macrocycle, 11-methyl-1,4,7,11-tetra-azacyclotetradecane, L3, and its complexes with Ni2+, Cu2+, and Zn2+ have been prepared. 13C N.m.r. studies show that the diamagnetic, planar complex [Ni(L3)][ClO4]2 is a single symmetric species, whereas [Zn(L3)][NO3]2 is a 1 : 2 mixture of a symmetric and an asymmetric species.
Two new pendant-arm quinquedentate aza-macrocyclic ligands have been prepared, and their nickel(II) and copper(II) complexes found to undergo reversible rearrangements between approximately trigonal-bipyramidal structures at neutral pH, and protonated square-planar structures at low pH in which the pendant arms are protonated and non-co-ordinating. The crystal structure of [NiL1][ClO4]2[L1= 11-(2-dimethylaminoethyl)-1,4,7,11-tetra-azacyclotetradecane] establishes an approximately trigonal-bipyramidal geometry for the complex. Crystals are orthorhombic, space group Pna21, with a= 14.559(3), b= 15.337(3), c= 10.322(3)Å, and Z= 4. The final R was 0.108 for 978 observed reflections with l/σ(l) > 2.5. The axial N–Ni–N bond angle is 172(1)°, and the equatorial bond angles are 107(2), 107(1), and 144(2)°. Ni–N distances range from 2.04(2) to 2.17(3)Å. The nickel(II) and copper(II) complexes of L1 are isomorphous.
Abstract Wie im Schema aufgezeigt, werden die Verbindungen (V) und (VII) dargestellt, die zu dem geschützten Makrocyclus (VIIIa) reagieren, dessen Hydrolyse zu dem neuen Titelliganden (VIIIb) führt.
Abstract Unter Verwendung von Ameisensäure/ Formaldehyd als Methylierungsreagens wird durch Erhitzen von (Ia) auf 90°C nach 12 h der neue Iögliedrige Ligand (Ib) dargestellt.
The new 16-membered tetra-aza macrocyclic ligand 1,5,9,13-tetramethyl-1,5,9,13-tetra-azacyclohexadecane (L4) has been prepared, and the metal complexes of Cd2+ and Hg2+ isolated and characterised. The Pb2+ complex was also investigated by 13C n.m.r. spectroscopy in nitromethane solution. Carbon-13 spectra of the Cd2+ and Hg2+ complexes revealed the presence of two isomers in methanol solution, including the complex with the unusual 'three up and one down' set of nitrogen configurations, together with the more usual 'four up' arrangement of the N-methyl groups. A crystal structure of the Cd2+ complex establishes the presence of these two structures in the solid phase. The crystals contain [CdL4(NO3)]2[Cd(NO3)4] and are monoclinic, space group C2/c, with a= 53.360(14), b= 10.248(6), c= 31.938(7)Å, β= 119.51 (2)°R= 0.063 for 4 920 diffractometer collected reflections with I/σ(I) 3.0. The cations have pseudo-trigonal-bipyramidal geometry, with bidentate nitrate groups occupying one equatorial position. They show disordered ligand conformations comprising a 'three up and one down' and two types of 'all four up' arrangements of the N-methyl groups. The anions are dodecahedral, with bidentate nitrate groups. Cd–N (axial) is 2.41 Å(average) and Cd–N(equatorial) is 2.37 Å(average), while Cd–O is the range 2.27–2.60 Å, with the anions showing greater asymmetry.
Abstract Die beiden neuen sechszehngliedrigen Makrocyclen (VIII) mit einem Dimethylaminoethylsubstituenten als zusätzliche Bindungsmöglichkeit werden wie aufgezeigt synthetisiert.
The rapid PdII-catalysed rearrangement of 3-acetoxy-1,4-dienes to 1-acetoxy-2,4-dienes [e.g.(2E,5Z)-4-acetoxydeca-2,5-diene →(3E,5Z)-2-acetoxydeca-3,5-diene (ca. 80%)] occurs in stereoselective and regio-selective manner.
The new 14-membered, pendant-arm macrocyclic ligand, 11-(2′-dimethylaminoethyl)-1,4,7-trimethyl-1,4,7,11-tetra-azacyclotetradecane (L2), and some of its complexes with CuII, NiII, and ZnII(M) of general formula [M(L2)]X2(X = ClO4– or NO3–) have been isolated. The five-co-ordinate complex [Cu(L2)][ClO4]2 undergoes reversible protonation of the pendant arm to give [Cu(HL2)][ClO4]3. The complex [Ni(L2)][ClO4]2 is also five-co-ordinate but attempted selective protonation leads to complete dissociation of (L2) from the Ni2+ ion. The 13C n.m.r. spectrum of [Zn(L2)][NO3]2 reveals the presence of two species in aqueous solution, one symmetric and the other asymmetric.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)
