Terraforming a chunk of land like the Russian east to turn it into productive farmland is possible (Brazil did something similar), but it's expensive, time-cons

Terraforming a chunk of land like the Russian east to turn it into productive farmland is possible (Brazil did something similar), but it's expensive, time-consuming, and temporary. China and Russia actually have a somewhat-standoffish relationship, and it's unlikely that Russia would invite Chinese investment into a region that it sees as a target for Chinese expansionists.