Chinese investment in American businesses hit a record $6.5 billion in 2012 , with the third largest deal closing in Massachusetts when China’s biggest auto parts maker invested in a Cambridge alternative energy firm.

In May, auto parts conglomerate Wanxiang Group agreed to take a $420 million minority stake in GreatPoint Energy , which is working to make synthetic natural gas out of coal, as part of a $1.25 billion deal to build a coal-to-gas conversion plant in Western China.