US hedge fund Platinum Partners is returning the majority of its assets to clients following the arrest of a longtime associate on allegations he orchestrated a $60,000 cash bribe to secure an investment from a New York city union. New York-based Platinum told investors on a conference call on Tuesday that recent negative media attention and requests for the return of capital had forced it to begin the liquidation of its more than $700 million Platinum Partners Value Arbitrage Fund, according to a person familiar with the situation who requested anonymity because the information is private.