Metal Complexes with Macrocyclic Ligands. Part XLIII. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio‐ and methoxy‐substituted pendant chains

Abstract

Introduction. -The functionalization of polyazamacrocycles with pendant chains containing donor atoms, which can coordinate, is a powerful technique to modify the chemical and physical properties of the metal ion [2]. Whereas this aspect has been studied in great detail, much less has been done to investigate how the metal ion modifies the properties and reactivity of the side-chain functional group. Such systems are good models for metalloenzymes, since through the side chain, the reactive group is brought close to the metal center, which can activate it in a similar way as in an enzyme-substrate complex. Examples of enhanced hydrolytic reactions of esters [3] and nitriles [4] have been observed.In contrast, nearly no mimicking of redox processes has been reported in the litera-

Helical coordination polymers and cyclic dimers formed from heteroleptic thioether-dipyrrinato copper(ii) complexes

“…Nevertheless, several examples of long Cu-S interactions with thioether ligands have been described when coordinated axially. [8][9][10] Like earlier described pyridyl-containing dipyrrins, [Cu(4mtdpm)(hfacac)] generates a 1-dimensional coordination polymer in the solid state. The polymer chains orient along the crystallographic c-axis and display a helical topology.…”

Biochemistry of methanogenesis: a tribute to Marjory Stephenson:1998 Marjory Stephenson Prize Lecture

“…In the released coenzyme, nickel is in the Ni(II) oxidation state. For the understanding of the function of coenzyme F 430 in methyl-coenzyme M reductase, the following properties of the non-protein- bound cofactor are considered to be of importance (Jaun, 1993;Won et al, 1993;Telser, 1998; see alsoStolzenberg & Zhang, 1997;Pandiyan et al, 1997;&hmid et al, 1996,1997;Jäger & Rudolph, 1997). They are di&ussed in comparison to those of cobalamin (B 12 ) (Kräutler et al, 1998) ().…”

Efficient preparation of 1,4,8-trimethylcyclam and its conversion into a thioalkyl-pendant pentadentate chelate

“…Relevant to the structure of 3 is that of a pentacoordinate Ni(II)-cyclam complex in which the macrocyclic ligand bears two pendant thioether donors. 12 Predictably, the axial Ni-S distance in that complex, 2.393 Å, is longer than the Ni-S distance in 3, a difference that is rooted in the divergent nature of their sulfur ligands (thioether vs. thiolate). The structure of 3 is also related to that of [(Me 4 cyclam)Ni(SPh)]PF 6 (4) in which a distorted square pyramidal Ni(II) ion is bound by a tetramethylcyclam ligand and an axial benzenethiolate donor.…”