Dimethylphenylphosphine is an

organophosphorus compound Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective i ...

with a formula P(C₆H₅)(CH₃)₂. The

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...

is connected to a

phenyl In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6 H5, and is often represented by the symbol Ph. Phenyl group is closely related to benzene and can be viewed as a benzene ring, minus a hydrogen ...

group and two

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ...

groups, making it the simplest aromatic alkylphosphine. It is colorless air sensitive liquid. It is a member of series (CH₃)_3-n(C₆H₅)₂P that also includes n = 0, n = 2, and n = 3 that are often employed as

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...

s in

metal phosphine complex A metal-phosphine complex is a In coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. P ...

es.

Preparation

Dimethylphenylphosphine is prepared by the reaction of methylmagnesium halide with

dichlorophenylphosphine Dichlorophenylphosphine is an organophosphorus compound with the formula C6H5PCl2. This colourless viscous liquid is commonly used in the synthesis of organophosphines. Dichlorophenylphosphine is commercially available. It may be prepared by an ...

. :(C₆H₅)Cl₂P + 2CH₃MgBr → (C₆H₅)(CH₃)₂P + 2MgBrCl The

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

is purified by distillation under reduced pressure. A solution of (C₆H₅)(CH₃)₂P in CDCl₃ shows

proton NMR Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the struct ...

signals at δ 7.0-7.5 and a doublet at δ 1.2. The

phosphorus-31 NMR Phosphorus-31 NMR spectroscopy is an analytical chemistry technique that uses nuclear magnetic resonance (NMR) to study chemical compounds that contain phosphorus. Phosphorus is commonly found in organic compounds and coordination complexes (as ...

spectrum shows a singlet at -45.9 ppm in CDCl₃.

Structure and properties

Dimethylphenylphosphine is a

pyramidal molecule In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base, resembling a tetrahedron (not to be confused with the tetrahedral geometry). When all three atoms at the corner ...

where the

group and two

groups are connected to the phosphorus. The

bond length In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest of ...

and angles are the following: P-C_Me: 1.844, P-C_Ph: 1.845 Å, C-C: 1.401 Å, C-H_Me: 1.090 Å, C-H_Ph: 1.067 Å, C-P-C: 96.9°, C-P-C (ring): 103.4°, P-C-H: 115.2°. When attached to chiral metal centers, the P-methyl groups are

diastereotopic In stereochemistry, topicity is the stereochemical relationship between substituents and the structure to which they are attached. Depending on the relationship, such groups can be ''heterotopic'', ''homotopic'', ''enantiotopic'', or ''diastereoto ...

, appearing as separate doublets in the ¹H NMR spectrum.

Comparisons with related phosphine ligands

The ν_CO of IrCl(CO)(PPh₃)₂ and IrCl(CO)(PMe₂Ph)₂ are both at 1960 cm⁻¹, whereas ν_CO for IrCl(CO)(PMe₃)₂ is at 1938 cm⁻¹. In terms of basicity, dimethylphenylphosphine is intermediate between that of trialkyl- and triphenylphosphine: * PEt₃sup>+ = 8.7 * PMe₂Phsup>+ = 6.8 * PPh₃sup>+ = 2.7 The ligand

cone angle In coordination chemistry, the ligand cone angle (a common example being the Tolman cone angle or ''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 me ...

(θ) is the apex angle of a cylindrical cone, which is centered 2.28 Å from the center of the P atom. However, the cone angle of an unsymmetrical ligand cannot be determined in the same. In order to determine an effective cone angle for an unsymmetrical ligand PX₁X₂X₃, the following equation is used: :

\theta = \frac\sum_^3 \frac2

Where θ_i represent the half angle. The resulting angles for PMe₃, PMe₂Ph, PPh₃ are: PMe₃ = 118°, PMe₂Ph = 122°, PPh₃ = 145°. Thus, PMe₂Ph is intermediate in size relative to PMe₃ and PPh₃.C. A. Tolman, ''Chem. Rev.'', Steric effects of Phosphorus Ligands in Organometallic Chemistry and Homogeneous Catalysis., 1977, volume 77, pages 313-348.

References

{{Reflist Tertiary phosphines Phenyl compounds