It exceedingly difficult to define what complex means, or to develop an absolute metric for its measure in a chemical system. But there are chemical phenomena that are driven by radicals that bear striking resemblances to living systems. The most striking example is perhaps the Belousov-Zhabotinsky (BZ) Reaction. It creates oscillatory patterns in 3D mixtures, but when reduced to a nearly flat 2D mixture, the same system generates very complex moving fronts and self-interactive wave patterns. It bears a superficial comparison to microbial growth patterns or a predator-prey relationship. Here is an example: