The hydridopentafluorophosphate anion [PF5H]−

INORG.

NUCL..

CHEM.

LETTERS

Val.

5,

pp.

295-299,

1969.

Pergamon

THE HYDRIDOPENTAFLUOROPHOSPHATE

Press.

ANION

Printed

In

Great

Britain

[PF~N]-

J. F. Nixon and J. R. Swain The Chemical Laboratory, Brighton,

University

BNI 9QJ, Sussex,

of Sussex,

England.

(Recelv~ 23 Dec~be, 1~8)

We wish to describe phosphate

ion

syntheses

of the novel hydridopentafluoro

[PFsH ]- (I) which has been identified by its

characteristic

proton and fluorine nuclear magnetic

resonance

spectra. H

(I)

F(1) F(2) Trifluorophosphine room temperature

and potassium in the presence

bifluoride

react on shaking at

of acetonitrile

according

to

equation i. PF 3 + HF 2

room temperature .> [PFsH ] in CH 3 C~!

The most likely mechanism would seem to involve dissociation

of HF 2

to hydrogen

(a) initial

fluoride and fluoride ion,

(b) addition of HF to PF 3 to give the pentaeoordinate followed by (c) nucleophilic acid PF~H.

Step

(i

attack by fluoride

ion on the Lewis

(a) is known to occur in aqueous

295

PFL}{

solution

(i),

296

HYDRIDOPENTAFLUOROPHOSPHATE ANION IPFsHI"

and r e c e n t l y

it has been shown that a l k y l or aryl f l u o r o p h o s p h i n e s ,

R n P E 3 _ n, do r e a d i l y add h y d r o g e n phosphoranes

Vol. 5, No.4

RnPF~-nH

reported

addition

phoranes

(4)-

(n = 1,2)

of fluoride

We have also obtained aminodifluorophosphine

fluoride (2,3).

producing

the fluoro-

Ivin and coworkers

have

ion to alkyl and aryl t r i f l u o r o p h o s -

(I) from the r e a c t i o n between d i m e t h y l -

and p o t a s s i u m b i f l u o r i d e

possibly according

to e q u a t i o n 2. 70 o M e 2 N P F 2 + 3HF 2 -

~ [Me2NH2] + + [PFsHj

+ 3F

(2)

in M e C N Hydrogen

fluoride

p r o d u c e d via

phosphorus-nitrogen which

(a) would

immediately

bond of He2NPF 2 g e n e r a t i n g

cleave

trifluorophosphine

then reacts with excess HF 2- as in e q u a t i o n i.

amounts

of b i s ( d i m e t h y l a m i n o ) f l u o r o p h o s p h i n e ,

formed in a side r e a c t i o n

the

Very small

(He2N)2PF , are also

involving aminolysis

of d i m e t h y l a m i n o

difluorophosphine. Further

support

comes from the r e a c t i o n b e t w e e n d i m e t h y l a m i n e

and t r i f l u o r o p h o s p h i n e , suggested bifluoride

originally

that the solid residues

the b i f l u o r i d e

~

the d i m e t h y l a m m o m i u m

2Me2NPF 2 + (He2~2)+[KF2] -

salt might

difluorophosphine

formed,

excess,

to equations

according

solution

excess PF 3 .

then react w i t h

the d i m e t h y l a m i n o

or w i t h any t r i f l u o r o p h o s p h i n e 2 or i, again p r o d u c i n g

ion, and this has been confirmed nitrile

contained

(5), who

salt. 3 M e 2 N H + 2PF 3

However

studied by Cavell

by n.m.r,

of the solid products

studies

present

the

in

[PF~H!-

on an aeeto-

from the r e a c t i o n u s i n g

Vol. 5, No. 4

HYDRIDOPENTAFLUOROPHOSPHATE ANION IPFsH!"

297

The proton n.m.r, of (I) consists of a widely spaced doublet of quintets from spin coupling with phosphorus and the four F(I ) fkuorine nuclei.

There was no resolvable splitting of these lines

by further interaction with the fluorine nucleus F(2 ) trans- to hydrogen.

The fluorine n.m.r,

spectrum which may be interpreted

on a first order basis consists of two doublets of doublets for the resonance of the F(I ) nuclei, because of spin coupling with phosphorus, hydrogen and the unique fluorine F(2), together with the expected weaker doublet of quintets for the F(2 ) resonance. Chemical shift and coupling constant data for [PFsH ]- (I) are summarised in Table I. Table I Chemical Shift and Coupling Constant Data for K + [PFsH ]- in MeCN TH

4.6 a

JF(1)F(2 )

41

c./sec.

mF (1

+36.4 b

aF(2)M

"-o c./seoo

mF (2

+66o2 b

JF(1) H

126~ c./sec. 128~ c./sec.

aeF(l aeF(2

817 c./sec.

JPH

955

c./sec.

729 c./sec.

In p.p.m.

[rel.external SiMe~ : i0] t

From 19F spectrum

b ~

In p.p.m, tel. CCI3F. From IH spectrum

I~ is interesting to note that the coupling constant 2J(HPF ) between hydrogen and the trans-fluorine, F(2 ), ls very small (possibly zero), and inspection of the rather limlted available data for pentavalent phosphorus compounds (summarised in Table II), suggests that the magnitude of 2J(HPF ) depends not only on the nature of

298

HYDRIDOPENTAFLUOROPHOSPHATE ANION [PF$H]"

the other groups attached angle,

and increases

to phosphorus

but also on the HPF bond

as the HPF angle decreases. Table

Variation

Voh 5, No. 4

of 2J(HPF )

II

(c./sec.) with the HPF bond angle

in pentavalent

phosphorus

derivatives

(Approx. HPF bond angle) Compound

120 o

180 °

[HPFs]-

0

[CF3PF~H][ (CF3)2PF3H]-

18.0

90 o

Reference

127

this work

120

6

69.5

MePF3H

29.9

117

EtPF3H

3O

121

PhPF3H

31.5

124

Me2PF2H

3,8

98.4

Me-C6H~PF~H

34

118

References i.

D.G. TUCK, Progress p. 161, Interscience

2.

G.I. DROZD,

In Inorganic Chemistry,

S, Z. IVIN, V.V. SHELUCHENK0,

F. SEEL, W. GOMBLER,

9, 1968,

Publishers.

and A. D. VARSHAVSKII, .

Vol.

J. Gen. Chem.,

K. H. RUDOLPH,

B. I. TETEL'BAUM,

(USSR_~, 1968,

Z. Naturforsch,

38, 551. 23(b),

587, 1968. .

G. I. DROZD,

S. Z. IVIN, V. V. SHELUCHENK0,

G. 4. LUGANSKII 1967,

37, 1269.

and A.D. VARSHAVSKII,

B. I. TETEL'BAUM,

J. Gen. Chem.

(USSR),

Vol. 5, No. 4

HYDRIDOPENTAFLUOROPHOSPHATE ANION [PFsHI-

299

5o

R. G. CAVELL, J. Chem. Soc., 1964, 1992.

6.

R. G. CAVELL and J. F. NIKON, proc. Chem. Soc., 1964, 229.

7o

J. F. NIXON and J. R. SWAIN, Chemo Comm., 1968, 997.

8.

R. A. GOODRICH and P. M. TREICNEL, Inorg. Chem., 1968, ~, 694

9.

E. L. MUETTERTIES, W. ~ H L E R ,

Inorg. Chem., 1964, ~, 1298.

K. J. PACKER and R. SCNMUTZLER,