Depending upon the originality(Genuine/Fake/Clone) of the card, ideally your R4i SDHC (V1.4.2) may work with DSi XL V1.4.5E. However if you are going to try out the card, DO NOT update the DSi XL to any new firmware if any is available.
You could refer to below link which looks similar to your ask.
gbatemp.net/threads/r4i-v1-4-problems-getting-it-to-work-with-dsi-xl-1-4-5e.429327/