Filling lists based on larger list values

Question

I have two pairs of linked lists, one pair larger than the other. How can I fill the smaller list based on the larger list values and position of those values?

For example:

list1 = [1,2,3,4,5,6,7,8,9,10]
list1-1=[1.1,2.1,3.1,4.1,5.1,6.1,7.1,8.1,9.1,10.1]

list2 = [5,6,7]
list2-1 = [5.2,6.2,7.2]

I want to make

list2 = [1,2,3,4,5,6,7,8,9,10]
list2-1 = [nan,nan,nan,nan,5.2,6.2,7.2,nan,nan,nan]