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Ligand cone angle shows how much space is taken up by a ligand coordinated to a metal center. In coordination chemistry, the ligand cone angle (θ) is a measure of the steric bulk of a ligand in a transition metal coordination complex. It is defined as the solid angle formed with the metal at the vertex of a cone and the outermost edge of the ...
The Tolman cone angle and Tolman electronic parameter [3] are named after him. In 1972, he proposed the 16 and 18 electron rule , extending Irving Langmuir 's 18-Electron rule to include the many examples of stable 16 electron square planar d 8 complexes. [ 4 ]
The Tolman electronic parameter (TEP) is a measure of the electron donating or withdrawing ability of a ligand. It is determined by measuring the frequency of the A 1 C-O vibrational mode (ν (CO)) of a (pseudo)-C 3v symmetric complex, [LNi (CO) 3] by infrared spectroscopy, where L is the ligand of interest. [LNi (CO) 3] was chosen as the model ...
As a ligand, trimethylphosphine's Tolman cone angle is 118°. [7] This angle is an indication of the amount of steric protection that this ligand provides to the metal that to which it is bound. Being a relatively compact phosphine, several can bind to a single transition metal, as illustrated by the existence of Pt(PEt 3) 4. [8]
A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R 3 P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. [ 1 ][ 2 ] Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh (PPh 3) 3 ...
Sterimol parameters are built upon the Corey-Pauling-Koltun atomic models, which take into consideration the Van der Waals radii of each atom in the molecule. Unlike most other steric parameters such as A-value, Taft parameters and Tolman cone angle, which group all the spatial information into a single cumulative value, Sterimol parameters consist of three sub-parameters: one length parameter ...
In terms of steric bulk, PPh 3 has a Tolman cone angle of 145°, [19] which is intermediate between those of P(C 6 H 11) 3 (170°) and P(CH 3) 3 (115°). In an early application in homogeneous catalysis, NiBr 2 (PPh 3) 2 was used by Walter Reppe for the synthesis of acrylate esters from alkynes, carbon monoxide, and alcohols. [20]
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape (conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which dictate the shape and ...