that data won't be in your logs nor in any current G reports, so there's no easy or systemic way to get it.
their are services (though I don't recommend them) that "watch" ads and the keywords behind them. i don't use them so i'm not really sure if they track imps, but my general impression of these services is that they scrape ads shown to determine their outputs, so they likely do report imps (as the keywords people bid on). so you might consider "spying" on yourself. three warnings though. i personally think these services are often scams with very unreliable data. second, using them may violate the TOS of adwords. third, these services very likely focus on high volume keywords mostly, so i doubt you'll get the answers you seek with any speed or thoroughness.
my own idea on this subject is that given sufficient imps, you will likely get clicks on things you didn't anticipate or aim for, but they will happen. people are unpredictable and will click on stuff a certain percentage of the time that just doesn't make much sense - so mine your back-end log data and the adwords keyword reports knowing that even the worst twists of matching of what you intended to target, will eventually show in your logs anyhow - and for those that don't, the volume will be so minor as to hardly matter. and remember G optimizes their results, so eventually, their systems also learn to stop serving your ads for certain phrases or snippets that are largely irrelevant.
using exact and phrase match only, or using broad matching only with far lower bids that accompanying exact and phrase will also go a long way towards avoiding the need for massive negative keywords - this issue is only of high importance to the broad arena, elsewhere, it's a very minor problem.
good luck and have fun!