Dow Chemical CEO Andrew Liveris said Friday the groundwork for a deal with DuPont had already been laid out.
"Our ascendancy, in terms of our strategy ... has been lifting us towards DuPont. As we got closer and closer, this deal became a reality," Liveris told CNBC's " Squawk on the Street." "There was always a deal out there at some premium, if you want to put it [like that]. The beauty of this deal is that it's a 50-50 deal, based in all the fairness tests, all the input for people out there."
The deal, which is likely to face intense regulatory scrutiny, allows the new company — to be called DowDuPont — to rejig assets based on the diverging fortunes of their businesses that make agriculture chemicals and plastics.
"I was doing a lot of my own homework on it and saying there's something very exciting here," DuPont Chief Executive Ed Breen said in the same interview.
Dow and DuPont have been struggling to cope with falling demand for farm chemicals due to falling crop prices and a strong dollar, even as their plastics businesses have thrived thanks to low natural gas prices.
The companies said the proposed split would create businesses focused on agriculture, materials and specialty products. Dow and DuPont shareholders will each own about 50 percent of DowDuPont, excluding preferred shares.
DuPont's Breen will be CEO of DowDuPont, and Dow Chemical's Liveris will be executive chairman.
DuPont shares were down 7 percent in premarket trading on Friday, while Dow's slipped 2 percent.
"This transaction is a game-changer for our industry and reflects the culmination of a vision we have had for more than a decade to bring together these two powerful innovation and material science leaders," Liveris said in a statement.
Dow Chemical shareholders will get one DowDuPont share for each Dow Chemical share held, while DuPont shareholders will get 1.282 shares in DowDuPont for each DuPont share they own.
The companies said the split would "occur as soon as feasible" and would likely happen 18-24 months after the deal closes, which is expected in the second half of 2016.
The combination will help the companies save about $3 billion in costs in the first two years, with the possibility of saving another $1 billion, Dow and DuPont said.
The biggest of the three new companies by revenue would be a material science company, which would cater to the packaging, transportation and infrastructure industries.
The combined revenue for the materials business was about $51 billion in 2014, on an adjusted basis.
The companies said a new specialty products company would focus on electronics. The combined adjusted revenue of that business was about $13 billion in 2014.
The third business, selling seed and crop protection chemicals, generated adjusted revenue of about $19 billion.
DowDuPont's board is expected to have 16 members, with each company contributing eight directors, the companies said.
In a separate announcement, Dow Chemical said it would buy the remaining stake in its 50-50 joint venture with Corning, the supplier of Gorilla Glass for iPhones.
The transaction is expected to yield more than $1 billion in additional annual EBITDA at full run-rate synergies, Dow Chemical said.
— CNBC contributed to this report.