Elon Musk's purchase of $65 million of SolarCity debt is highly unusual and does not send a good signal to investors, says a corporate governance scholar. Musk is chairman and his cousins Lyndon and Peter Rive are CEO and CTO, respectively, at SolarCity, which is undergoing a merger with Tesla, where Musk is chief executive. The three are also SolarCity directors. The notion of a senior officer or director buying debt is highly unusual, and raises some unnerving questions, according to Charles Elson, an authority on corporate governance at the University of Delaware.

"It is very odd," Elson said in an interview with CNBC. Stephen Diamond, an advisor to Tesla investor group CtW agrees, calling it a "troubling move." "It's essentially material information that I think the Tesla board has to consider," the professor at California's Santa Clara University School of Law told CNBC's "Closing Bell." CtW Investment Group, which works with union-sponsored pension funds that own about 200,000 shares of Tesla, has already raised concerns about governance problems on the Tesla board with respect to the SolarCity merger.

Elon Musk Valentin Flauraud | Bloomberg | Getty Images