The synthesis of tris-(trifluoromethylphenyl)phosphines and phosphine oxides

JoumalofFluorineChemistyv,15(1980)239-243 0 Elsevier Sequoia S.A., Lausanne -Printed in theNetherlands

239

Received: July 4,1979

SHORT

COMMUNICATION

THE SYNTHESIS PHOSPHINE

KALATHIL

C. EAPEN*

and CHRIST

Materials

TAMBORSKI

Laboratory,

Wright

Patterson

Air Force

Base,

(45433) U.S.A.

This

paper

describes

the synthesis

(trifluoromethylphenyl)phosphines and their were

oxides,

prepared

through

CF @-Br 3cF3@Li 3 During reaction

could

The phosphines

of the appropriate

2,3, or 4-

and PC13.

C4HgLi

+

PC13

4

LiBr

*

the course

mixture,

3LiCl

of isolating

it was

slowly

atmosphere

noted

+ +

CF @-Li

( cF3@+3P

phosphine

CF3C6H4)3P(I) air sensitivity

and

to the phosphine only

This oxygen

(4-CH3C6H4)3P(VII)

and stability

[l].

(3-CF3C6H4j3P(II)

during

the desired

sensitivity

as well

(C6F5j3P

(4-CF3C6H4)3P(III)

that the product

converting was used,

of the ease of synthesis

aromatic

tris-

(2,3,4-CF3C6H4)3P(I,II,III)

the reaction

+

be isolated.

analog

isomeric

3

tive and was nitrogen

of three

(2,3,4-CF3C6H4)3PO(IV,V,VI).

trifluoromethylphenyllithium

view

AND

OXIDES

Air Force Ohio

OF TRIS-(TRIFLUOROMETHYLPHENYL)PHOSPHINES

the period

from the

was air sensioxide

VI.

phosphine

If a III

was unexpected

in

of the hydrocarbon

as the perfluorinated The other

two isomers

(2-

did not show any significant of isolation

from their

reac-

tion mixtures. *National Research Council Senior Postdoctoral Associate 1978. Present address: University of Dayton Research Institute, 300 College Park, Dayton, Ohio U.S.A.

1976-

240 A qualitative the three

evaluation

phosphines

of the oxidative

I, II and III was determined

each of the pure phosphines gas chromatography of time.

The

temperature

was

(2-CF3C6H4)3P

IV.

converted

totally

showed

the

to the oxide

of a CF3-

group

oxidation

phosphines

analogs. readily

A convincing

effect

electronic tion

effects

The required

prepared

oxides

spectra

IV and V were

above

at 1400-1442

to the P-C6H5

absorption

at about

stretching

vibration

certain the same

tion)

cm -' which

band.

[4,5,6].

fragments

the

investiga-

of the phos-

by oxidation

The oxide

of

VI was

of the phosphine.

and phosphine has been

oxide

show

attributed oxides

[3,4]

have

an

may be due to the P-t0

This

assignment

however

is not

C-F absorptions

of all the phosphines

IV, V and VI

(by chemical

in I,11

ioniza-

ions at 466 and 482 respectively.

(M-F)+ at 477 and 463 as well

prominent

prepared

The phosphine

spectra

oxides

show the molecular

for the phosphines

is noteworthy

From our

due to the strong

The mass

and III and phosphine

quantita-

regarding

stability

by air oxidation

1200 cm -1 which

in our compounds region.

however

studies

acid.

of the phosphine

an absorption

absorption

detailed

as I>II>III.

with m-chloroperbenzoic

as described

The infrared

observation

of oxidative

is not

[2] net electron

await

with

I,

that

non-fluorinated

of a CF3 substitution.

was determined

the phosphine

and suggest

for this observation

of the reported

concerned

order

observations

the phosphines

than their

The above

investigators

the following

phines

e.g.,

of the CF3 and must

investigation.

for those

These

that the introduction

stability

explanation

III was In

the same conditions

oxide.

ring,

basic

in view

I converted

the phosphine

demonstrate

oxidative

are more

apparent

withdrawing tive

their

to air at ambient

the same conditions

V while

under

by

as a function

VI in only one month.

into the phenyl

II and III reduce these

II, under

to the phosphine

atmospheric

by exposing

of the oxide

left exposed

(4-CH3C6H4)3P(VII)

of

air and analyzing

8% of the phosphine

in 71% to the oxide

no oxidation

towards

when

showed

The phosphine

converted

contrast,

to atmospheric

for the formation

for 4 months

to the oxide

stabilities

as the

and phosphine observed.

(M-C6H4CF3)+

oxides

The

at 321 and 337

respectively

are the

241 EXPERIMENTAL

General

Comments

All new compounds and lH), IR, MS All melting

(chemical

points

was performed

prepared

ionization)

steel

Method

and elemental

Model

column

(19F

by NMR

analysis.

Gas chromatography

on a Hewlett-Packard

10% SE30 on Chromosorb

General

characterized

are uncorrected.

6 ft. or 12 ft. stainless with

were

analysis

700 instrument (l/4 in. diam.)

using packed

W.

for the Synthesis

of tris-(trifluoromethylphenyl)

phosphines

In a dry four-necked addition

funnels,

the appropriate diethyl

(100 ml).

in one addition

ether

PC13

added

contents were

funnel

was

sample

cooled

become

colored

and G.C.

added

The reaction

analysis

deposited orange. stirred

solids After

(100 ml).

to yield

the phosphine graphy.

and the color

the crude

ether

I.

the

The C4HgLi

noted

and the The contents

of an aliquot to the

solution

reaction

was

was observed.

at ~5' by controlling became

to a yellow

solution,

turbid, and finally

the contents

hydrolyzed

layer was

product.

was done by recrystallization

See Table

through

conversion

and the solvent

phosphine

was placed

diethyl

brown.

ether

3 h. and finally

seive

was placed

the reaction

Hydrolysis

mixture

changed

of the PC13

The diethyl

a molecular

was

complete

was maintained The reaction

addition

over

30 min.

An exothermal

for an additional

6NHCl

keeping

exotherm

indicated

temperature

dried vacuum

A mild

The PC13-diethyl

1 h.

the rate of addition.

an ice bath.

20 min. while

two

freshly

was passed

from red to reddish

reagent. during

with

funnel

in anhydrous

Dry nitrogen

with

in anhydrous

(0.075 mole)

in the other

for an additional

organolithium slowly

0+5".

fitted

(0.08 mole)

dissolved

to ~0+5"

during

between

stirred

while

flask

and a thermometer

n-Butyllithium

placed.

dropwise

temperature

stirrer

(0.025 mole)

(25 ml) was

flask which was

a sealed

bromobenzotrifluoride

ether

distilled

500 ml reaction

phase

were

with

separated,

evaporated

under

Purification or column

of

chromato-

1111[I

[II [I

[I [I

tion from acetone-hexane.

(cm-‘)

F.

Recrystallization

”

7.8. m

7.5-8.1, m

63.9, s

63.5, s

55.8, s

63.6. s

63.4, s

58.0, d (J=55 Hz)

CF3 &(CFCI1l)

CHEM. SHIFT

from hexane.

from ethanol.

E.

Recrystalliza-

Column chromatography on alumina using petroleum ether as eluent.

1199

1194

6

7.1-7.4, m 7.5-7.8, m

7.6, m

--

1231

7.5, m

6.9, m 7.4, m 7.7, m

Ph-H 6(TMS)

NMR-lH

--

--

P+o

,NS4

on silica using petroleum ether as eluent followed by recrystallization

B.

D.

ether.

Recrystallized

Column chromatography

A.

from benzene-petroleum

Isolated during preparation of the phosphine.

1403

52.34, 2.89, 5.84 52.28. 2.48, 6.43

Spectra taken as KBr wafer except II which was measured as neat liquid

1423

52.03, 2.24, 6.19 52.28, 2.48, 6.43

4.

Some oxidation was observed during isolation.

1442

3.

2.

191-193

Liquid boiling above 340°/atm B.P. not determined.

4-CF33 [VII

103-104

247-248

52.25, 2.26, 6.05 52.28, 2.48, 6.43

1400

53.79, 2.70, 6.40 54.08, 2.58, 6.65

78-80

1410

54.85, 2.66, 6.34 54.08, 2.58, 6.65

-_

P-Ph

1440

b---l

IR ABSORPl

54.42, 2.65, 6.72 54.08, 2.58, 6.65

("C)

ELEMENTAL ANALYSIS FOUND EXPECTED H, P C,

174-175

M.P

1.

21

IV1

3-CF3

~

95

(IV1

71

67

71

88

METHOD OF PURIFICATION

3 AND OPB,,],

YIELD ($1

2-CF3

'HOSPHINE OXID 35 -

4-CF32

3-CF31r2

2-CF3

'HOSPHINES

Rf

PREPARATION OF PmR,l

TABLE I

N Ip N

243 Synthesis

of tris-(2-trifluoromethylphenyl)phosphine

In a three thermometer (1.86g.,

flask

fitted

with

and an addition

necked

funnel

was placed

0.004 mole)

contents

were

perbenzoic

dissolved

stirred

acid

in benzene

at room

(0.78g.,

0.0045

in small portions

during

noted

and a white

started

continued

for an additional

filtered

and the crude

duct was

stirred

m-chlorobenzoic

with

while

mole)

in benzene

20 min.

A mild

to deposit.

product

exotherm

was collected. Na2C03

The remaining

to remove

See Table

I.

solution with

obtained

aqueous

leaving

of reactants

of the 2-isomer.

and the solvent

product.

identical

difference

of the peracid.

at the end of 5 h. of stirring

Na2C03

the crude

oxide

used was

The only

on addition

proany

recrystallized

of tris-(3-trifluoromethylphenyl)phosphine

no solid was deposited

mixture

solid was

Synthesis

the preparation

oxide.

was

was

The crude

solution

the pure phosphine

and quantity

(20 ml) was

Stirring

to obtain

The method

The

m-chloro-

18 h. and then the reaction

aqueous

acid.

condenser, (2-CF3C6H4)3P

(10 ml).

temperature

added

solid

a water

oxide

removed

See Table

was

to

that

The clear

was

extracted

by evaporation

I.

ACKNOWLEDGEMENTS

The authors the synthesis

thank Mr. E.J.

Soloski

of compounds

III and VI.

R.E. Donadio

and W.J.

for his assistance

in

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