Synthesis and structure of cyclen hydroxylamine ligands and their zinc(<scp>ii</scp>) complexes

Reichenbach-Klinke, Roland; Zabel, Manfred; König, Burkhard

doi:10.1039/b207571g

Cited by 8 publications

(2 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We reasoned that in our case a protecting group would be preferable which can be removed without protonation of the ligand. The Cbz function turned out to be a good choice 17. It is cleaved off by hydrogenation in the presence of a palladium catalyst in methanol.…”

Section: Resultsmentioning

confidence: 99%

Copper(II) Complexes of the Tetraazamacrocyclic Tertiary Amide Ligand Alanyl‐Cyclam

2006

View full text Add to dashboard Cite

Hydrogen bonding to the electrically neutral tertiary carboxamide nitrogen atom of peptidyl‐prolyl groups is known to facilitate the C–N bond rotation during peptide and protein folding. Since metal complexes with nitrogen‐coordinated tertiary amide ligands are formally analogous, they may be used to model this so‐called electrophilic activation. In this paper we report on the synthesis of a monoacylated cyclam complex, [(Boc‐Ala‐cyclam)Cu](CF3SO3)2 (8; Boc: tert‐butyloxycarbonyl, Ala: alanine, cyclam: 1,4,8,11‐tetraazacyclotetradecane). It contains a fully sp3‐hybridized metal‐bound amide nitrogen atom. The resonance is completely cancelled and the observed C–N distance of 147 pm is consistent with a single bond. These features are exceptional among Werner‐type complexes and define the maximal possible electrophilic distortion of an amide bond.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

show abstract

Section: Resultsmentioning

confidence: 99%

Copper(II) Complexes of the Tetraazamacrocyclic Tertiary Amide Ligand Alanyl‐Cyclam

2006

View full text Add to dashboard Cite

show abstract

“…Potentiometric Studies. The postulated coordination of the auxiliary amines of 2 to the Zn(II) center in 2-Zn would be expected to appreciably increase the acidity of the corresponding ammoniums. , In fact, such an effect is observed. Overlaid potentiometric titrations of 2 and 2-Zn are shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

2,6-Di(pyrimidin-4-yl)pyridine Ligands with Nitrogen-Containing Auxiliaries: The Formation of Functionalized Molecular Clefts upon Metal Coordination

et al. 2003

View full text Add to dashboard Cite

A series of ligands (1-4) based on a 2,6-di(pyrimidin-4-yl)pyridine scaffold have been synthesized, and their abilities to form complexes with Zn(II) and Cu(II) have been determined using UV/vis spectroscopy in buffered aqueous solution (0.01 M N-[2-hydroxyethyl]piperazine-N'-[3-ethanesulfonic acid] (HEPES) at pH = 6.8). The Zn(II) complex of 1 was determined to have a formation constant of 8.4 x 10(3) M(-)(1) while the formation constant of the Cu(II) complex was found to be 1 x 10(6) M(-)(1). The presence of auxiliary amines in 2 increased the stability of the Zn(II) complex relative to that of 1 by a factor of over 40, suggesting possible coordination of the auxiliaries to the Zn(II) center. The guanidinium and 2-amino-4,5-dihydro-imidazolinium groups of 3 and 4 considerably diminished the stability of the Zn(II) and Cu(II) complexes relative to those of 1. X-ray crystal structures of 1-Zn, 3-Zn, 4, and 4-Zn were obtained and are discussed. A significant increase in the stability of 3-Zn, but not in the stability 1-Zn, was observed upon the addition of 1 equiv of sodium phosphate, implicating a stabilizing interaction of the guanidinium groups of 3-Zn and the phosphate anion.

show abstract

“Isomerism” of Coordination Modes and Numbers in Pentanuclear Organozinc Hydroxylamides: An Exercise in Subtle Substituent Size Effects

et al. 2006

View full text Add to dashboard Cite

The first organometallic zinc hydroxylamides [Zn(RZn) 4 -(ONMe 2 ) 6 ] (1: R = Me; 2: R = iPr) and [Zn(EtZn) 4 (ONEt 2 ) 6 ] (3) have been prepared by alkane elimination from dialkylzinc solutions upon treatment with N,N-dialkylhydroxylamines. The molecular structures of 1 and 2 reveal that a subtle change in the constitution of the aggregates can make a striking difference. By the simple exchange of the MeZn + groups with iPrZn + groups, the coordination number of the central Zn 2+ nucleus increases from four (1) to six (2). The two cluster types are unprecedented in both hydroxylamine and organometallic chemistry. Compounds 1 and 3 adopt a doubly bridged fenestrane-like Zn 5 N 6 O 6 core with two dangling NR 2 moieties, whereas iPrZn species 2 comprises an octahedroid backbone with all donor atoms attached to the

show abstract

Synthesis and structure of cyclen hydroxylamine ligands and their zinc(ii) complexes

Cited by 8 publications

References 16 publications

Copper(II) Complexes of the Tetraazamacrocyclic Tertiary Amide Ligand Alanyl‐Cyclam

Copper(II) Complexes of the Tetraazamacrocyclic Tertiary Amide Ligand Alanyl‐Cyclam

2,6-Di(pyrimidin-4-yl)pyridine Ligands with Nitrogen-Containing Auxiliaries: The Formation of Functionalized Molecular Clefts upon Metal Coordination

“Isomerism” of Coordination Modes and Numbers in Pentanuclear Organozinc Hydroxylamides: An Exercise in Subtle Substituent Size Effects

Contact Info

Product

Resources

About