Dimethylphenylphosphine

Dimethylphenylphosphine is an organophosphorus compound with a formula P(C₆H₅)(CH₃)₂. The phosphorus is connected to a phenyl group and two methyl 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 ligands in metal phosphine complexes.

Dimethylphenylphosphine

Names
Preferred IUPAC name Dimethyl(phenyl)phosphane
Other names Dimethylphenylphosphine
Identifiers
CAS Number	672-66-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:30671 Y
ChemSpider	62800 Y
ECHA InfoCard	100.010.543
EC Number	211-595-3
PubChem CID	69597
UNII	D3F6WQG46D Y
CompTox Dashboard (EPA)	DTXSID70217481
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
SMILES P(c1ccccc1)(C)C
Properties
Chemical formula	C8H11P
Molar mass	138.14 g/mol
Appearance	transparent light pale yellow liquid
Density	0.971 g/cm3
Melting point	N/A
Boiling point	74 to 75 °C (165 to 167 °F; 347 to 348 K) at 12 mmHg
Solubility in water	Insoluble
Structure
Molecular shape	Pyramidal
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H226, H315, H319, H335
Precautionary statements	P210, P233, P240, P241, P242, P243, P261, P264, P271, P280, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501
Flash point	49 °C (120 °F; 322 K)
Safety data sheet (SDS)	[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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. 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.

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°.

When attached to chiral metal centers, the P-methyl groups are diastereotopic, 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:

• [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:

$\theta ={\frac {2}{3}}\sum _{i=1}^{3}{\frac {\theta _{i}}{2}}$

Where θ_i represent the half angle.

The resulting angles for PMe₃, PMe₂Ph, PPh₃ are: PMe₃ = 118°, PMe₂Ph = 122°, PPh₃ = 145°. Thus, PMe₂Ph is intermediate in size relative to PMe₃ and PPh₃.