Tetramethylphosphonium bromide

Tetramethylphosphonium bromide is an organophosphorus compound with the formula (CH3)4PBr. It is a white, water-soluble solid, the salt of the cation tetramethylphosphonium and the bromide anion. It is prepared by treating trimethylphosphine with methyl bromide.

Tetramethylphosphonium bromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.152.249
UNII
  • InChI=1S/C4H12P.BrH/c1-5(2,3)4;/h1-4H3;1H/q+1;/p-1
    Key: ZTXFOCMYRCGSMU-UHFFFAOYSA-M
  • C[P+](C)(C)C.[Br-]
Properties
C4H12BrP
Molar mass 171.018 g·mol−1
Appearance white solid
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Reactions
Structure of Cu2[(Me2P(CH2)2]2.

Deprotonation gives methylenetrimethylphosphine ylide, which can sustain a second deprotonation:[1]

(CH3)4PBr + BuLi → CH3)3P=CH2 + LiBr + BuH
CH3)3P=CH2 + BuLi → CH3)2P(CH2)2Li + BuH

The latter is a precursor to many coordination complexes, e.g., the dicuprous complex Cu2[(Me2P(CH2)2]2.[2]

References
  1. H. F. Klein (1978). "Trimethylphosphonium Methylide (Trimethyl Methylenephosphorane)". Inorganic Syntheses. XVIII: 138–140. doi:10.1002/9780470132494.ch23.
  2. Schmidbaur, H. (1983). "Phosphorus Ylides in the Coordination Sphere of Transition Metals: An Inventory". Angewandte Chemie International Edition in English. 22 (12): 907–927. doi:10.1002/anie.198309071.
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