Dimethylphenylphosphine

Dimethylphenylphosphine
IUPAC name Dimethylphenylphosphane
Other names Dimethylphenylphosphine
Identifiers
CAS number	672-66-2 Y
PubChem	69597
ChemSpider	62800 Y
EC number	211-595-3
ChEBI	CHEBI:30671 Y
Jmol-3D images	Image 1
SMILES P(c1ccccc1)(C)C
InChI InChI=1S/C8H11P/c1-9(2)8-6-4-3-5-7-8/h3-7H,1-2H3 Y Key: HASCQPSFPAKVEK-UHFFFAOYSA-N Y InChI=1/C8H11P/c1-9(2)8-6-4-3-5-7-8/h3-7H,1-2H3 Key: HASCQPSFPAKVEK-UHFFFAOYAS
Properties
Molecular formula	C8H11P
Molar mass	138.14 g/mol
Appearance	Colorless light pale yellow liquid
Density	0.971 g/cm3
Melting point	N/A
Boiling point	74-75°C @ 12 mmHg
Solubility in water	Insoluble
Structure
Molecular shape	Pyramidal
Hazards
MSDS	[1]
R-phrases	R10 R36 R37 R38
S-phrases	S26 S36
Flash point	49°C
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Dimethylphenylphosphine is a organophosphorus compound with a formula P(C₆H₅)(CH₃)₂. The phosphorus is connected to a phenyl group and two methyl groups. This colorless air sensitive liquid is commonly used as a ligand in transition metal complexes. These complexes are often soluble in organic solvents.

Preparation

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.^[1] 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 -45.89 ppm in CDCl₃.^[2]

Structure and properties

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°.^[3]

Comparisons with related phosphine ligands

The υ_CO of Ir-Cl(CO)(PPh₃)₂ and Ir-Cl(CO)(PMe₂Ph)₂ are both at 1960 cm^-1, whereas the υ_CO for Ir-Cl(CO)(PMe₃)₂ is at 1938 cm^-1.^[4][5] Also when comparing the acidity of HPR₃ (PR₃ = PMe₂Ph, PPh₃, PEt₃) in CD₂Cl₂, the resulting pK_a value is the following: [HPMe₂Ph]⁺= 6.8, [HPPh₃]⁺ = 2.7, [HPEt₃]⁺ = 8.7.^[6][7] Thus PMe2Ph is intermediate in basicity relative to PPh₃ and PEt₃.

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:

$\theta = \frac{2}{3}\sum_{i=1}^3 \frac{\theta_i}2$

Where θ_i represent the half angle.

The resulting angles for -PMe₃, PMe₂Ph, PPh₃ are the following: PMe₃= 118°, PMe₂Ph= 122°, PPh₃= 145°. Thus PMe₂Ph is intermediate in size relative to PMe₃ and PPh₃.^[8]

References

1. ^ C. Frajerman; B. Meunier; M. E. Strem., Inorganic Syntheses, Preparation of Dimethylphenylphosphine, 2007, volume 22, 133-135, doi:10.1002/9780470132531. ch29
2. ^ Laszlo T. Mika, Laszlo Orha, Norbert Farkas and Istvan T. Horvath, Organometallics, 2009, 28, 1593
3. ^ Novikov, V.P., Kolomeets, V.I., Syshchikov, Yu.N., Vilkov, L.V., Yarkov, A.V., Tsvetkov, E.N., Raevskii, O.A.: Zh. Strukt. Khim., J. Struc. Chem., Investigation of structure of dimethylphenylphosphine by means of gas-phase electron diffraction and vibrational spectroscopy, 1984, volume 25, No.5, 688. doi:10.1007/BF00747909
4. ^ S.A. Cotton, Chemistry of Precious Metals., 1997, 152-157, ISBN 0751404136, 9780751404135
5. ^ A.R. Norrris ; J.A.V. Kessel, Canadian Journal of Chemistry, Oxidative addition of 3,5-Dinitrobenzoyl Chloride to trans-Chlorocarbonylbis(dimethylphenylphosphine)iridium(I), 1973, 51, 4145-4151, doi:10.1139/CJC-51-24-4145.
6. ^ Russell C; Bush and Robert J. Angelici. Inorg. Chem, Phosphine Basicities As Determined by Enthalpies of Protonation 1988, 27, 681-686. DOI: 10.1021/ic00277a022
7. ^ Tianshu Li ; Alan J.; Robert H., Chemistry- A European Journal, An Acidity scale of Tetrafluoroborate Salts of Phosphonium and Iron Hydride compounds in [D2]Dichloromethane, 2007, volume 13, 3796-3803, doi: 10.1002/chem..200601484.
8. ^ C.A.Tolman, Chem.Rev., Steric effects of phosphorus ligands in organometallic chemistry and homogeneous catalysis., 1977, 313-348, doi:10.1021/cr60307a002