Zinc Thiolate Complexes of (N,N,S)‐Tridentate Ligands for the Modeling of Thiolate Alkylating Enzymes

Abstract

Zinc thiolate complexes of three tridentate (N,N,S) ligands were prepared as models for the structure and function of thiolate alkylating zinc enzymes. N-(2-Mercaptoisobutyl)(2-pyridin-2-yl-methyl)amine (L 1 ) forms isobutylthiolatebridged dinuclear complexes with ZnN 2 S 3 coordination. N-(2-Mercaptoisobutyl)(2-pyridin-2-yl-ethyl)amine (L 2 ) yields isobutylthiolate-bridged dinuclear complexes in which the pyridine donor is not coordinated to zinc, resulting in a ZnNS 3 coordination. Only N-(2-mercaptoisobutyl)(2-pyridin-2-yl-ethyl)methylamine (L 3 ) forms the desired mononuclear

Biomimetic Thiolate Alkylation with Zinc Pyrazolylbis(thioimidazolyl)borate Complexes

“…We had found before that, under forcing conditions (i. e. in boiling DMSO), it does lead to methylation of neocuproinzinc bis(thiolates) [11] and of zinc thiolates bearing a tridentate N 2 S ligand. [12] Yet, even under these forcing conditions, it reacted extremely slowly with the zinc thiolates bearing tripodal N 2 S ligands. [19] This was now observed for complex 5d too.…”

“…The only anionic thiolate complex used for such reactions, Zn(SPh) 4 2-, [10] was found to dissociate prior to alkylation. Our own contributions to this field have involved zinc thiolates with bidentate N 2 [11] and tridentate N 2 S ligands, [12] [a] Institut für Anorganische und Analytische Chemie der Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany Fax: +49-761-203-6001 E-mail: vahrenka@uni-freiburg.de lations to be intramolecular S N 2 processes that take place at the zinc-bound thiolates.…”

Thiolate exchange in [TmR]ZnSR′ complexes and relevance to the mechanisms of thiolate alkylation reactions involving zinc enzymes and proteins

“…On the basis of such studies, it is now recognized that zinc-thiolate alkylation may proceed via two mechanistic extremes that are dissociative and associative in nature. For example, (a) anionic [Zn(SPh) 4 ] 2À is alkylated by (MeO) 3 PO by a mechanism that is proposed to proceed via initial heterolytic thiolate dissociation [24,25], while (b) neutral derivatives such as [Tp RR 0 ]ZnSR [26][27][28][29], ½Phðpz Bu t ÞBt Bu t ZnSAr [30,31], ½HCðpz Me 2 Þ 2 ðCMe 2 SÞZnX [32,33], [HB(mim R ) 2 (pz)]ZnSR [34,35] and a series of other zinc thiolates [36][37][38][39][40][41][42][43], are proposed to undergo alkylation without prior dissociation of RS À . In this paper, we address further aspects relevant to zinc thiolate alkylation in model compounds by the use of the tris(2-mercapto-1-R-imidazolyl) , but this observation does not provide definitive evidence that the mechanism is associative since a dissociative reaction can also exhibit second-order kinetics if re-coordination of RS À to the zinc center competes with alkylation by MeI [69].…”

The Adolf von Baeyer Medal for A. de Meijere / Bredereck Prize Goes to H.‐A. Wagenknecht / H. Vahrenkamp Receives Wilhelm Klemm Award / / The Karl Ziegler Prize for M. Reetz / August Wilhelm von Hofmann Medal Awarded to R. H. Grubbs and R. R. Schrock / Arfvedson–Schlenk Prize Goes to D. Stalke

“…Vahrenkamp recently reported on zinc thiolate complexes with tridentate ligands as models for thiolate alkylating enzymes. [3] Vahrenkamp Grubbs is famous for the development of a range of ruthenium-containing catalysts of olefin metathesis; [5] Schrocks name is associated with alkylidene complexes and ring-opening-metathesis polymerization. [6] Grubbs Stalkes research is concentrated on the determination of electron densities through multipole refinement, sulfurnitrogen chemistry, ligand design with N-heteroarenes, and low-temperature investigations of crystals.…”