The parent company of Berkshire Bank has received all regulatory approvals and expects to close on its acquisition of the parent company of Willimantic, Connecticut-based Savings Institute Bank & Trust at the end of the business day tomorrow.

Berkshire first announced the deal last December, saying it would purchase Savings Institute in an all-stock transaction valued at $180 million.

Upon completion of the merger, shareholders of Savings Institute’s parent company will receive 0.48 shares of Berkshire common stock for each of their shares. The exchange ratio is fixed and the transaction is expected to qualify as a tax-free exchange.

The deal will add another $1.6 billion in assets to Berkshire Bank, extending its lead as the largest state-chartered bank in Massachusetts other than State Street, bringing total assets close to $13.8 billion. It also adds another 18 branches to Berkshire’s Connecticut presence and comes with five branches in Rhode Island, giving Berkshire its first retail presence in the Ocean State, which better fills in the bank’s geographic footprint.

“We can take our product suite and leverage it through the existing customer base to improve profitability,” Berkshire CEO Richard Marotta said in December.

The purchase came at a precarious time for Berkshire, just weeks after the bank’s longtime CEO Michael Daly abruptly resigned from the company, due to what one analyst called a “toxic” workplace culture.

Daly’s departure also put the proposed acquisition in question and Marotta was forced to speak to Savings Institute executives to smooth things over.

When the deal closes, Rheo Brouillard, president and CEO of Savings Institute and its parent company, will join the board of directors at Berkshire Bank.

The acquisition could be the last one for Berkshire for the foreseeable future, as Marotta has made it clear in recent earnings calls that he wants to focus on profitability going forward.