The transition team of President-elect Donald Trump announced Tuesday that Rex Tillerson, the longtime CEO of Exxon Mobil, would be the future president’s nominee to become secretary of state come January. Tillerson would be taking over one of the highest profile jobs in American government and would be tasked with leading U.S. diplomacy worldwide.

His announced nomination has not been without controversy as some have questioned whether his close ties to the oil giant — and the close relationship he has developed with Russian President Vladimir Putin while chasing profit for that company — might pose significant conflicts of interest for him when attempting to represent American interests abroad.

Here’s what you need to know about Tillerson:

His experience has been entirely in the private sector and he is known for working with foreign leaders to advance Exxon interests abroad. That’s a trait that Trump’s team wants to emphasize and says will help Tillerson as he works for the State Department. Tillerson, Trump said in a Medium post, “knows how to manage a global enterprise, which I crucial to running a successful State Department, and his relationships with leaders all over the world are second to none.”

Tillerson has been CEO of Exxon since 2006.

He has received a high honor from Putin. Tillerson has become known recently for cleverly maneuvering within Russia for Exxon as the United States has looked to punish its former Cold War foe with economic sanctions for an aggressive annexation of the Crimean Peninsula in 2014. Tillerson, who has pushed to extract more and more oil from Russian soil, was named by Putin as a friend of the country.

The company he’s leaving has billions of dollars in interest in Russian oil. Exxon has billions of dollars’ worth of deals that are currently tied up by those sanctions. The sanctions have halted some of the company’s biggest projects and those would only get the green light to continue should the U.S. government and Russia reach some level of resolve.

Tillerson’s stake in those deals could lead to real or perceived conflicts of interest. Tillerson owned $218 million in company stock, company filings this year said, and his pension was worth $70 million, according to the New York Times.

Tillerson pushed for allowing openly gay young men in the Boy Scouts. His presidency of the organization was on the side while still at Exxon and spanned from 2010 to 2012. During that time he reportedly pushed for inclusion of gay youth in the group. It wasn’t until 2015 that Exxon changed its Equal Employment Opportunity policy to ban discrimination based on sexual orientation or gender identity, according to the Human Rights Campaign. The Boy Scouts lifted their ban on gay adults in 2015.

His Senate confirmation may be difficult. Lawmakers on both sides of the aisle have expressed concerns with Tillerson’s close ties to Russia, according to Reuters. For instance, Arizona Sen. John McCain, who is known as a major foreign policy voice in the capitol, said of Tillerson: “I have concerns. It's very well-known that he has a very close relationship with Vladimir Putin.”