Silica is very mildly acidic. The problem is that you need something that will exist in anionic form at pH7 which this species will not.
Also, I'm not sure (and I could be wrong, I can't remember this stuff too well) that Si is a good pi acceptor. Don't you need a vacant pi orbital for this? You have no pi* or pi orbitals period in the valence shell, empty or not, in hybridized silicon, do you? Anyway, even if you do allow back bonding, while often important, does not usually overide strong sigma bond effects, does it? I'm not saying that this hydrogen is not acidic at all, just not to the degree you require. Have you thought of something like florine? You won't get the naked anion, but it is electronegative.