A group of philanthropies working with Facebook Inc to study the social network’s impact on democracy threatened on Tuesday to quit, saying the company had failed to make data available to researchers as pledged. The funders said in a statement that Facebook had granted the 83 scholars selected for the project access to “only a portion of what they were told they could expect,” which made it impossible for some to carry out their research. The announcement comes only a few months after Facebook launched the research program, which opened the company’s propriety data to independent scholars for the first time.