Democrats held the Senate for barely five months after being out of power for four decades.
Shortly after the coup, Republicans named Espada temporary president of the Senate and Republican Dean Skelos of Nassau County vice president and majority leader. Skelos was majority leader in 2008.
Those are the most powerful positions in the chamber. With them, the bipartisan coalition can direct legislation and reassign committee and leadership posts.
Democrats tried to leave the chamber, even turning off the lights briefly, and are expected to challenge Monday's action in court.
The coup throws into doubt the movement to legalize same-sex marriage, one of the major policy issues still pending for the last two weeks of the regular session. Although passed in the Democrat-led Assembly, it is stalled in the Senate. Several Republicans and Sen. Ruben Diaz, a Bronx Democrat oppose the measure.
Another major issue has a hard deadline. A law giving the New York City mayor greater control of New York City schools is scheduled to expire at the end of the month unless the full Legislature acts. Senate Democrats have sought to take away some of Mayor Michael Bloomberg's authority while maintaining overall mayoral control. But Bloomberg and the Senate's Republican conference have been very close on policy and the billionaire mayor has funded many of their campaigns.
Sen. Thomas Libous, a Binghamton Republican, secured a vote to put Sen. George Winner of Elmira in charge of the proceedings after Democratic Sen. Neil Breslin of Albany left the chamber with the other Democrats. Minutes later, Espada and Skelos were elected to their new leadership posts by 32-0 votes with Espada and Monserrate the only Democrats in the chamber.
"This is historic," Libous said in an interview on the floor. "There is going to be reform. You are going to see things that you've never seen in Albany."
Democratic leader Malcolm Smith of Queens, who was elected majority leader in January, referred to the drama as "scurrilous action" by Republicans.
"There was an illegal vote taken," Smith said. "Let me be very clear _ very clear _ the Senate majority is in Democratic hands." He said he won't reconvene the session until the coalition drops its challenge to the leadership.
The coalition immediately approved a thick new list of rules for governing the chamber. It adjourned until Wednesday, when it plans to return to run the Senate.
AP Writer Michael Virtanen contributed to this report from Albany.