The way my wife and I had it with my first was for me to start taking care of my boy at 6am when he wakes up and let her sleep until 9am every morning, when I'd start work (from home). If you can find a time where the boy does not need her (eg. those times when he's fussy but not hungry), that's the best you can do.
Sometimes that's not an option, but this worked great with our first (we couldn't do it with our second, so my wife is more of a zombie this time even though the daughter is a better sleeper on average).