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Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C 6 H 5) 3 and often abbreviated to P Ph 3 or Ph 3 P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry.
The metal–ligand bond can be further stabilised by a formal donation of electron density back to the ligand in a process known as back-bonding. In this case a filled, central-atom-based orbital donates density into the LUMO of the (coordinated) ligand. Carbon monoxide is the preeminent example a ligand that engages metals via back-donation.
Skeletal formula of a generic diphosphine ligand. R represents a side chain.The phosphine donors are connected by a backbone linker. Diphosphines, sometimes called bisphosphanes, are organophosphorus compounds most commonly used as bidentate phosphine ligands in inorganic and organometallic chemistry.
The four phosphorus atoms are at the corners of a tetrahedron surrounding the palladium(0) center. This structure is typical for four-coordinate 18 e − complexes. [2] The corresponding complexes Ni(PPh 3) 4 and Pt(PPh 3) 4 are also well known.
As a ligand PH 2 can either bond to one atom or be in a μ 2-bridged ligand across two metal atoms. [3] With transition metals and actinides, bridging is likely unless the metal atom is mostly enclosed in a ligand. In phosphanides, phosphorus is in the −3 oxidation state. When phosphanide is oxidised, the first step is phosphinite ([H 2 PO] −).
Wilkinson's catalyst is usually obtained by treating rhodium(III) chloride hydrate with an excess of triphenylphosphine in refluxing ethanol. [9] [10] [1] Triphenylphosphine serves as both a ligand and a two-electron reducing agent that oxidizes itself from oxidation state (III) to (V).
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 van der Waals spheres of the ligand atoms at the perimeter of the base of the cone.
[5] [6] This electron transfer strengthens the metal–ligand bond and weakens the C–C bonds within the ligand. [7] In the case of metal-alkenes and alkynes, the strengthening of the M–C 2 R 4 and M–C 2 R 2 bond is reflected in bending of the C–C–R angles which assume greater sp 3 and sp 2 character, respectively.