How do you deal with a toxic co-founder?

I'm working with a company with two co-founders and an interim CEO. One co-founder brings funding, the other has developed the IP which the company has patented.

I’ve been contracted to document the company’s SOPs, as the co-founder that developed the IP has been in a feud with the other, and as I’m now learning is a truly toxic individual. During the process, he failed to offer any help when asked by the CEO, provided half baked formulations to work from, has sent us down blind alleys, and provided contradictory information when asked for clarification. The company is doing everything it can to be successful working around the toxic founder, and the guy seems hell bent on sabotaging that success.

What advice would you offer in a situation like this?