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The application of phosphoramidites as effective monodentate ligands for transition metal catalysis was first reported by Dutch chemist Ben Feringa. The introduction of phosphoramidite ligands challenged the notion that high flexibility in the metal–ligand complex is detrimental for high stereocontrol. General Structure of Phosphoramidite Ligand
Polyfunctional ligands can attach to metals in many ways and thus can bridge metals in diverse ways, including sharing of one atom or using several atoms. Examples of such polyatomic ligands are the oxoanions CO 2− 3 and the related carboxylates, PO 3− 4, and the polyoxometalates.
Many ligands are capable of binding metal ions through multiple sites, usually because the ligands have lone pairs on more than one atom. Such ligands are polydentate. [12] Ligands that bind via more than one atom are often termed chelating. A ligand that binds through two sites is classified as bidentate, and three sites as tridentate.
The facial bonding mode is reminiscent of cyclopentadienyl ligands, although the ligand field stabilization energy of Tp − is weaker as indicated by the fact that Fe(Tp) 2 is a spin-crossover complex whereas ferrocene is low-spin. The Tp ligands are usually prepared from the reaction of pyrazole with potassium borohydride: [3]
Nucleophiles add to odd-hapticity acyclic polyene ligands at a terminal position if the metal is highly electrophilic, otherwise they add at an internal site. Simplified: even before odd and open before closed. The following is a diagram showing the reactivity trends of even/odd hapticity and open/closed π-ligands.
Ligands of proteins can be characterized also by the number of protein chains they bind. "Monodesmic" ligands (μόνος: single, δεσμός: binding) are ligands that bind a single protein chain, while "polydesmic" ligands (πολοί: many) [ 31 ] are frequent in protein complexes, and are ligands that bind more than one protein chain ...
A reaction that illustrates an enzyme cleaving a specific bond of the reactant in order to create two products Bond specificity, unlike group specificity, recognizes particular chemical bond types. This differs from group specificity, as it is not reliant on the presence of particular functional groups in order to catalyze a particular reaction ...
These ligands are sometimes referred to as ancillary ligands. [2] Several different classes of ligand exist that can be considered spectator ligands. A few examples include trispyrazolylborates (Tp), cyclopentadienyl ligands (Cp), and many chelating diphosphines such as 1,2-bis(diphenylphosphino)ethane ligands (dppe). Varying the substituents ...