PF6- reactivity

[Oxxo]

I have a methanol solution that contains PF6- anion and OCH3- anion
(roughly 1:1).

Should I be concerned about PF6- reacting with OCH3- to give
PF6-x(OCH3)x- type anions?

Another concern is the equilibrium between PF6- and PF5 + F-, and
subsequent reaction between PF5 and OCH3-

In my initial review of the literature, I could not find any good
resources about the reactivity of PF6- or PF5 toward methoxide and/or
methanol.

Any ideas, resources?

[Madalch]

Post by Oxxo
Should I be concerned about PF6- reacting
with OCH3- to give PF6-x(OCH3)x- type
anions?

That depends. How concentrated is the solution? Is there anything
else around for the methoxide to react with? Over what time scale?

I've always thought of hexafluorphosphate as being quite unreactive, so
I wouldn't worry about it. But if you want to be sure, make up a
concentrated solution of both anions, and follow it with 13P NMR. If
you don't see any change over a time period much longer than you'll be
using your solution over, it's fine.

Cheers,

[muha]

I would do 19F instead. PF6- has a nice doublet way downfield.
Appearance of F- and other products of solvolysis should be asy to see.
If you do not want to wait few weeks, you can heat up your solution to
perhaps 60C, this should accelerate the possible solvolysis by 1-2
ordesrs of magnitude.

[Oxxo]

Thank you for the replies.

I'm certain I'm getting a reaction... I confirmed LiF precipitation
(using Li salts). I'm just unsure of what reaction is possible with
PF6- and OCH3-. 31P NMR reveals several peaks ~0 to -20ppm, which I've
been unable to interpret precisely at this point... I'm thinking at
least 2 different P environments.

I just can't seem to find a good resource on the reactivity of
hexafluorophosphate. I'm curious to see if I'm somehow exchanging a F-
for a OCH3- on the PF6-.

[muha]

Probably Li+ plays some role in destabilising PF6-

I thought that PF6- in neutral or basic media should be stable...