It's 99% certainly a scam. The exact same thing happened to me twice when I was in your position, including the passport scan. Guy said he was working in the UK and wanted to rent out his apartment, in a very good location in Amsterdam, for a low price. Don't bother verifying his passport. I'm sorry to have to break it to you; I realize you wanted the apartment, but it's just not going to happen.
If you contacted him via a rental search website, contact the administrators and say that you are worried about this case, asking them to look into his account and identity.
Still, for the 1% chance it is not a scam:
- Ask him for photos of the apartment; compare them against Google Street View if that's available.
- Tell him you will have someone come look at the apartment before you commit to it; if he says yes (he will refuse, I'm sure) get someone you know in NL to do you this favor.
- Suggest a bank cheque, dated forward appropriately, instead of a direct transfer.
- A passport proves nothing. Ask to see official proof of ownership.
- Ask for the contact info of the current tenant. If he says it's unoccupied, be suspicious... and ask for the contact info of the last tenant.
Again, I'm sure it's a scam - these are just a bunch of things he should fail to be able to do.