Scheme 1: Left: Mechanism of the olefin metathesis reaction postulated by Chauvin .
Keywords: Olefin metathesis constitutes the rearrangement of C=C double bonds in the presence of transition metal catalysts based on V, Mo, W, Re, Ru, and Os together with alkylating co-catalysts.
This transformation is widely used in organic synthesis as well as in polymerization of various unsaturated monomers .
Nevertheless, adding Ru, Os and Ir salts to an aqueous solution or emulsion of a norbornene derivative led to ring-opening metathesis polymerization to give the corresponding polymer [5,6].
Through modification of the first coordination sphere by adding an N-heterocyclic carbene (NHC) ligand and a chelating styrene to the so-called Grubbs 1st generation catalyst, the relatively air- and moisture-stable Grubbs–Hoveyda type (GH-type) catalysts were obtained .
One of the challenges to overcome in the construction of artificial metalloproteins is to find a method to incorporate a synthetic metal complex into a protein scaffold . In Figure 1, the three commonly utilized methods to incorporate a synthetic cofactor are shown.
Strategies utilized are supramolecular, dative and covalent anchoring.
Metalloproteins that contain one or more metal ions such as Mg, Ca, Mn, Fe, Ni, Co, Cu, Zn etc. As metalloenzymes, these metalloproteins are capable of catalyzing various important reactions in biosynthesis and key steps in cellular energy metabolism.
The embedded metal ion mainly acts as a Lewis acid catalyst or redox catalyst.
Various metalloenzymes have been applied in laboratory-scale reactions and a few metalloenzymes such as nitrile hydratase (cobalt(III) in the active site) for the production of acrylamide have found application in industry .
Notably, however, the reaction scope of natural enzymes is quite limited.