I'm adding someone to an existing very sensitive correspondence, and I would like to formally introduce between the two.
I have quoted the relevant part, and I am not quite sure about the grammar and phrasing.
Your kind assistance, hope It's not too long.
"As John's personal coordinator, I would like to introduce between the two of you.
By including John to this correspondence, you are both welcomed to communicate with each other.
John, Please meet Bob, Robbie's Manager
Bob, Please meet John
I greet you both and wish you all the best!
Hi and welcome to Using English.
I can't say I find this very natural. Of course, it's a hard thing to do in a letter. You really can't say "X, meet Y" in written correspondence.
Perhaps something like:
I believe direct communication between the two of you could be more efficient at times, so I'd like this letter to serve as an introduction of sorts.
Bob, as you know, I'm John's pesonal assistant. You are welcome to work directly with John, though of course I remain ready to assist in any way I can.
John, Bob is Robbie's manager.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.