Pinacolato

Pinacolato is a chemical descriptor used to indicate that a substituent or ligand originates from pinacol, the vicinal diol 2,3-dimethyl-2,3-butanediol. In this usage, the pinacolato fragment encodes coordination through the two adjacent oxygen atoms of the pinacol unit, providing a bidentate, diolate donor that can bind to boron or to a metal center. The term is most common in boron chemistry and in coordination chemistry, where it denotes the presence of the pinacol-derived diol in a chelating environment.

In boron chemistry, pinacol boronate esters are the principal example of pinacolato ligands. These esters form when pinacol condenses with boronic acids or related boron species, yielding B(pin) compounds. The boron atom is coordinated by two oxygen atoms from the pinacol moiety, creating a cyclic, five-membered boronate ester that is typically four-coordinate. Pinacol boronate esters are widely used as protected boron reagents because they are relatively stable to air and moisture and can be activated under catalytic or basic conditions to participate in transmetalation steps, notably in Suzuki–Miyaura cross-coupling reactions.

In coordination chemistry, pinacolato ligands can function as chelating O,O′-donor ligands, stabilizing metal centers in various complexes. Such pinacolato complexes can serve as catalysts or precursors in materials science, where the chelate effect and tunable steric and electronic properties of the pinacolato unit influence reactivity and stability.

Overall, pinacolato denotes a pinacol-derived, two-oxygen chelating fragment that is widely exploited for its stability and versatility in organic synthesis, catalysis, and coordination chemistry.