Why does nature use zinc-a personal view

Abstract

In this perspective some results from the work by the author's research group on the coordination chemistry of zinc are presented. They are selected so as to highlight the principles which, in the opinion of the author, make zinc unique in its ability to function as the catalytic center for an ever-increasing number of biological processes. In essence, the "non-properties" of zinc are the basis of its success: no redox chemistry, no ligand field effects, no typical coordination numbers or geometries, no stability or inertness of its complexes, no typical "hard" or "soft" characteristics. The chemistry presented here is centered around the "Freiburg Enzyme Model", the pyrazolylborate-ligated zinc-hydroxide complex. The topics discussed in detail include the zinc-water combination, the non-similarity between the Zn-OH and the Zn-SH, Zn-OR or Zn-SR complexes, and the functionalization of CO(2) by zinc-bound nucleophiles. The value of structure correlation analysis for the elucidation of mechanistic details is demonstrated, and the first examples of catalysis by the TpZn-OH complexes are presented.

Nucleophilicity of zinc-bound thiolates

“…[10] This reactivity is reproduced by many zinc biomimetic complexes [11,12] as well as by iron-, [13] cadmium-and mercury-thiolate complexes, [14] as well as by others metal-heteroatom intermediates. [15] The influence of the nature of the metal cation on the nucleophilicity of p-toluenethiolate has been studied both experimentally and by DFT computation, revealing that nickel-and zinc-thiolate complexes are more reactive than ironand cobalt-thiolate complexes.…”

Reversible Reactions of Ni and Pd Hydroxo Pincer Complexes [(iPrPCP)M–OH] with CO2: Solid‐State Study of the Decarboxylation of the Monomeric Bicarbonate Complexes [(iPrPCP)M–OCOOH] (M = Ni, Pd)

“…(1)] is an extremely important reaction for CO 2 fixation and pH regulation both in inorganic and biological systems. Under the usual ambient conditions, this is a thermodynamically spontaneous, but kinetically slow reaction.…”

Biomimetic Applications of Metal Systems Supported by Scorpionates

“…Mononuclear zinc enzymes were currently studied by several bioinorganic research groups with biomimetic complexes. Recent and substantial reviews by G. Parkin (Parkin, 2000;Parkin, 2004;Parkin, 2007), H. Vahrenkamp (Vahrenkamp, 2007) and N. Burzlaff (Fischer et al, 2009) cover almost all aspects of synthetic zinc enzyme analogues. Thus, here we will summarise some aspects of synthetic analogues of zinc enzymes that feature scorpionate ligands.…”

“…Basing on borderline properties of zinc, mixed hard and soft ligand environments make for perfectly stable complexes, purely hard or soft ligand environments making zinc unwilling to accept the ligand thiolate. This is one of the most important properties governing the biological chemistry of zinc (Vahrenkamp, 2007). Modifications regarding the sterical hindrance can easily be employed to many scorpionate ligands to prevent dimer formation e.g.…”