Under FAR 61.51 (g) Logging instrument time. (1) A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions.
The operative word here is "operates"
You can only claim the landing if you actually do it.
You can only log instrument if you actually flew it.
If its my SIC's leg he logs both as SIC, I just log the time as PIC, if it is my leg, I log both and he will log the time as SIC.
This is also on a part 91 operation in a two crew jet. Only one person can actually be a handling pilot at any one time, collaboration does not count.