He was dealt to the Islanders by the Canadiens in the 1972 Expansion Draft in exchange for not drafting a few players left unprotected by the Canadiens. He was then dealt away from the Islanders to the Red Wings on Oct 4 before the season started.
From the NY Times:
MONTREAL, June 7, 1972 — Sam Pollock, the National Hockey League's candyman, dispensed some goodies to the NeW York Islanders today in exchange for the Islanders compliance in not drafting a good young Montreal Canadiens prospect.
In a deal tor “cash and other considerations,” the Canadiens sent Denis DeJordy, an established but aging goalie, and four minor leaguers to the New Yorkers.
The transaction swelled the roster of the Islanders — who were born only yesteclay in the expansion draft — to 31
Pollock is the general manager of the Canadiens, the squad that holds the balance of power. At yesterday's draft, Pollock didn't protect three rising stars —Bob Murdoch, Dale Hoganson and Chuck Lefley.