dimethylphenylphosphine

Dimethylphenylphosphine is prepared by the reaction of methylmagnesium halide with dichlorophenylphosphine.

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

The phosphine is purified by distillation under reduced pressure.{{cite book|author1=C. Frajerman|author2=B. Meunier|series=Inorganic Syntheses|title=Preparation of Dimethylphenylphosphine|year=1983|volume=22|pages=133–135|doi=10.1002/9780470132531|isbn=9780470132531}}

A solution of (C₆H₅)(CH₃)₂P in CDCl₃ shows proton NMR signals at δ 7.0-7.5 and a doublet at δ 1.2. The phosphorus-31 NMR spectrum shows a singlet at -45.9 ppm in CDCl₃.{{cite journal|author1=Laszlo T. Mika|author2=Laszlo Orha|author3=Norbert Farkas|author4= Istvan T. Horváth|title=Efficient Synthesis of Water-Soluble Alkyl-bis(m-sulfonated-phenyl)- and Dialkyl-(m-sulfonated-phenyl)-phosphines and Their Evaluation in Rhodium-Catalyzed Hydrogenation of Maleic Acid in Water|doi=10.1021/om800570r|journal=Organometallics|year=2009|volume=28|issue=5|page=1593}}

Dimethylphenylphosphine is a pyramidal molecule where the phenyl group and two methyl groups are connected to the phosphorus. The bond length 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°.Novikov, V. P.; Kolomeets, V. I., Syshchikov, Yu. N.; Vilkov, L. V.; Yarkov, A. V.; Tsvetkov, E. N.; Raevskii, O.A. "Investigation of structure of dimethylphenylphosphine by means of gas-phase electron diffraction and vibrational spectroscopy" Zh. Strukt. Khim. (J. Struc. Chem.) 1984, volume 25, No. 5, 688. {{doi|10.1007/BF00747909}}

When attached to chiral metal centers, the P-methyl groups are diastereotopic, appearing as separate doublets in the ¹H NMR spectrum.

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.S. A. Cotton, Chemistry of Precious Metals., 1997, 152-157, {{ISBN|0-7514-0413-6}}, {{ISBN|978-0-7514-0413-5}}A. R. Norris; J. A. V. Kessel, "Oxidative addition of 3,5-Dinitrobenzoyl Chloride to trans-Chlorocarbonylbis(dimethylphenylphosphine)iridium(I) Canadian Journal of Chemistry, 1973, volume 51, 4145-4151, {{doi|10.1139/CJC-51-24-4145}}.

In terms of basicity, dimethylphenylphosphine is intermediate between that of trialkyl- and triphenylphosphine:{{cite journal|author1=Russell C. Bush|author2-link=Robert Angelici|author2=Robert J. Angelici|journal=Inorg. Chem.|title=Phosphine Basicities As Determined by Enthalpies of Protonation|year=1988|volume=27|issue=4|pages=681–686|doi=10.1021/ic00277a022}}{{cite journal|author1=Tianshu Li|author2=Alan J. Lough|author3=Robert H. Morris|journal=Chemistry: A European Journal|title=An Acidity scale of Tetrafluoroborate Salts of Phosphonium and Iron Hydride compounds in [D2]Dichloromethane|year=2007|volume=13|issue=13|pages=3796–3803|doi=10.1002/chem.200601484|pmid=17245785}}.

• [HPEt₃]⁺ = 8.7
• [HPMe₂Ph]⁺ = 6.8
• [HPPh₃]⁺ = 2.7

The ligand cone angle (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:

:$\backslash theta\; =\; \backslash frac\{2\}\{3\}\backslash sum\_\{i=1\}^3\; \backslash frac\{\backslash theta\_i\}2$

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. {{doi|10.1021/cr60307a002}}

{{Reflist}}

Category:Tertiary phosphines

Category:Phenyl compounds

Category:Methyl compounds