Entegris and Versum Materials continued to hold onto plans for a $4 billion all-stock merger late last week as Germany’s Merck KGaA continued trying to wedge the two US companies apart.

Merck said on Friday it had engaged US investment bank Goldman Sachs as an additional adviser alongside Guggenheim and Sullivan Cromwell to help find acceptance for its counter offer.

On Feb. 27, the German family owned pharmaceuticals and chemicals producer floated a surprise non-binding proposal to acquire Versum, a 2016 spin-off of Air Products & Chemicals, for $48 in cash per share, (altogether $5.9 billion).

Within a day, the board of directors of the Tempe, Arizona-based electronic chemicals supplier announced it had rejected Merck's offer, which it said was not superior to that of Entegris, at the same time stressing that it remained committed to completing the original merger plan. 

In a letter to shareholders made public on Mar. 8, Versum chairman Seifi Ghasemi and Entegris CEO Bertrand Loy touted the “superior benefits” of their deal, saying they now expect it to achiev $125 million in cost savings – $50 million more in annual EBITDA than originally identified.

Merck had previously appealed to Versum’s shareholders to pressure management to consider its offer, pointing out that it had been received positively by the market.