Organotrifluoroborate
Encyclopedia
Organotrifluoroborates are organoboron compounds that contain an anion with the general formula [RBF3]. They can be thought of as protected boronic acid
Boronic acid
A boronic acid is an alkyl or aryl substituted boric acid containing a carbon–boron bond belonging to the larger class of organoboranes. Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic...

s, or as adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...

s of carbanion
Carbanion
A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid.where B...

s and boron trifluoride
Boron trifluoride
Boron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...

. Organotrifluoroborates are tolerant of air and moisture and are easy to handle and purify. They are often used in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 as alternatives to boronic acids (RB(OH)2), boronate esters (RB(OR′)2), and organoboranes (R3B), particularly for Suzuki-Miyaura coupling.

Structure

thermal ellipsoid
Thermal ellipsoid
Thermal ellipsoids, more formally termed atomic displacement parameters, are ellipsoids used in crystallography to indicate the magnitudes and directions of the thermal vibration of atoms in crystal structures...

 model of [PhBF3], as found
in the crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...

 of K[PhBF3]
space-filling
Space-filling model
In chemistry a space-filling model, also known as calotte model, is a type of three-dimensional molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic...

 packing diagram of
the crystal structure of K[PhBF3]

Synthesis

Boronic acid
Boronic acid
A boronic acid is an alkyl or aryl substituted boric acid containing a carbon–boron bond belonging to the larger class of organoboranes. Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic...

s RB(OH)2 react with potassium bifluoride
Potassium bifluoride
Potassium bifluoride is the inorganic compound with the formula KHF2. This colourless salt consists of the potassium cation and the bifluoride anion. The salt is used in etchant for glass...

K[HF2] to form trifluoroborate salts K[RBF3].

Mechanism

The mechanism of organotrifluoroborate-based Suzuki-Miyaura coupling reactions has recently been investigated in detail. The organotrifluoroborate hydrolyses to the corresponding boronic acid in situ, so a boronic acid can be used in place of an organotrifluoroborate, as long as it is added slowly and carefully.
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