You want to perform a copy, move or some other operation where the argument you pass in using xargs isn't at the last argument for the following command. Do as follows:

ls  -tr1  |  tail  -5  |  xargs  -i  cp  '{}'  dest/folder/

You might also need to add the option -n1 if the output from the ls command (or whatever else it may be) is larger than your shell's buffer. i.e.

...  xargs  -n1  -i  cp  '{}' dest/folder