Which preposition should I use in this context or is more appropriate and grammatical?
Making a request of somebody...
Making a request to somebody...
Request means to ask for; in the dictionary of American Idioms and phrasal verb there is the following:
- requestsomeone to do something to ask someone to do something.
- request something from someone to call for something from someone.
- request something of someone to call for someone to give or do something.