guy - 28-12-2006 at 23:44
Is it an electron withdrawing or electron donating ligand?
FYI, phosphines have backbonding from an empty antibonding sigma orbital and a filled d metal orbital. So the bonding is like that of CO. I know
that CO is electron withdrawing towards the metal because of the oxygen. Are aryl groups electron withdrawing or donating?
Sauron - 29-12-2006 at 00:11
It's a P (III) that very badly wants to be a P (V)
12AX7 - 29-12-2006 at 02:27
Yabbut, it's P(3-), analogous to phosphide, or phosphine (i.e. hydrogen phosphide), not P(3+). Hmm, we're talking molecules here, not ions...what's
the difference? Well hmm, it seems to me hydrogen or carbon is a whole lot less electron-hungry than oxygen (the typical P(3+) or P(5+) as phosphite
or -ate respectively). Aryl is electron withdrawing, so it would tend to be a lower number, phosphorous acting as a cation, as it were.
Personally I suspect it has something to do with the extra lone pair of a heavier atom (compare to nitrogen) coordinating diversely with more metal
ions, plus the steric hinderance (i.e. excess baggage) of the triphenyl-ness, for whatever purpose in mind.
Tim
[Edited on 12-29-2006 by 12AX7]