Maybe some SSR's in the far east who become Chinese puppet states. Other than that I don't see how.
This idea is difficult enough to make.
It's impossible, short of some sort of insane natural disaster like a meteor striking the RSFSR, there is no way the Russians are going to let the Siberian oil fields go to China, they'll defend it by force. The Russians might be falling apart, but compared to the PLA they have the advantage. If all else fails, Beijing knows just as well as Moscow that the nuclear option hasn't gone anywhere. Jiang Zemin was an intelligent Chinese leader who was moderate and presided over the mostly peaceful expansion of China's role on the world stage, he's not completely insane.
Making something like the CIS be more than just a loose economic coalition is possible.
Making the breakup of the Soviet Union more clean or even having some SSRs break apart while other nations remain tied to the Supreme Soviet is very possible (note: Ukraine, Armenia, Georgia, Azerbaijan, and the Baltics are for sure gone barring extraordinary changes that for some may go back all the way to their addition to the Soviet Union).