Leading Republicans are voicing their concerns over Rex Tillerson's ties with Russia and President Vladimir Putin

President-elect Donald Trump has officially tapped ExxonMobil CEO Rex Tillerson to be his secretary of state.

Even before Trump’s transition team announced his pick for the nation’s top diplomat on Tuesday morning, leading Republicans were voicing their concerns over Tillerson’s ties with Russia and its president, Vladimir Putin.

Florida Sen. Marco Rubio quipped, “Being a ‘friend of Vladimir’ is not an attribute I am hoping for from a Secretary of State.”

South Carolina Sen. Lindsey Graham warned, “I don’t know the man much at all, but let’s put it this way: If you received an award from the Kremlin, ‘the order of friendship,’ then we’re gonna have to do some talkin’. We’ll have some questions. I don’t want to prejudge the guy, but that’s a bit unnerving.”

And Arizona Sen. John McCain said, “It’s a matter of concern to me that he has such a close relationship with Vladimir Putin, that that would color his approach to Vladimir Putin and the Russian threat.”

Despite the pushback, Trump moved forward with his nominee for secretary of state. He praised theExxonMobil CEO in a statement, saying: “Rex Tillerson’s career is the embodiment of the American dream. Through hard work, dedication and smart deal making, Rex rose through the ranks to become CEO of ExxonMobil, one of the world’s largest and most respected companies. His tenacity, broad experience and deep understanding of geopolitics make him an excellent choice for Secretary of State. He will promote regional stability and focus on the core national security interests of the United States.”

Tillerson responded to the nomination with a statement saying: “I am honored by President-elect Trump’s nomination and share his vision for restoring the credibility of the United States’ foreign relations and advancing our country’s national security. We must focus on strengthening our alliances, pursuing shared national interests and enhancing the strength, security and sovereignty of the United States.”

Rex Tillerson
Credit: Evan Vucci/AP

As scrutiny over Trump’s latest cabinet pick continues to mount, here are five things to know about Tillerson, including his connection to Russia:

1. As CEO of the multinational petroleum company ExxonMobil, he’s negotiated major business deals with Russia

Tillerson, 64, first developed a working relationship with Putin in the 1990s while overseeing an Exxon project on Russia’s Sakhalin island, the Washington Post reports. In 2013, Tillerson was awarded the “Order of Friendship” by Putin, according to Politico. The CEO, who has worked at Exxon for more than 40 years, also made headlines in 2014 when he spoke at an energy summit in Moscow alongside Russian oil executive and Putin ally Igor Sechin.

2. A former Eagle Scout, Tillerson served as national president of the Boy Scouts of America from 2010 to 2011

Tillerson is known for pushing the organization to lift its ban on gay scouts and scout leaders, The New York Times reports. The organization voted to do so in 2013, while Tillerson served on the executive board. The Times points out, however, that Exxon has been criticized for its failure to readily adopt anti-discrimination policies protecting gay employees.

3. Tillerson was recommended to Trump by former CIA Director and Defense Secretary Bob Gates and former Secretary of State Condoleezza Rice

Rice and Gates, who have both done work for Exxon through their consulting firm, each issued statements announcing their support for Trump’s pick on Tuesday.

Gates, who said he met Tillerson years earlier through their work with Boy Scouts of America, said in statement: “He would bring to the position vast knowledge, experience and success in dealing with dozens of governments and leaders in every corner of the world. He is a person of great integrity whose only goal in office would be to protect and advance the interests of the United States. I know this Eagle Scout will be a global champion of the best values of our country.”

Rice’s statement read: “Rex Tillerson is an excellent choice for Secretary of State. He will bring to the post remarkable and broad international experience; a deep understanding of the global economy; and a belief in America’s special role in the world. I know Rex as a successful business man and a patriot. He will represent the interests and the values of the United States with resolve and commitment. And he will lead the exceptional men and women of the State Department with respect and dedication.”

4. Tillerson supported Trump’s rival Jeb Bush for president

He donated the maximum allowable contribution to Bush’s presidential campaign in September 2015, the Washington Post reports.

5. He has called the threat of climate change “real” and “serious”

Under Tillerson’s leadership, Exxon shifted its position away from its past climate skepticism, recently officially acknowledging the link between greenhouse gas emissions from fossil fuel use and the warming climate, according to the Washington Post. The company is now on record as being supportive of identifying solutions to climate change.

Tillerson’s own comments about the “real” and “serious” threat of climate change stand in contrast to those of Trump, who said on Fox News Sunday this past weekend that “nobody really knows” if climate change is real.