Are S-5! clamps and brackets compatible with Corten?

In brief, Yes. Extremely corrosive environments such as salt spray may be an exception, but the corrosive process in such an environment will attack the aluminum clamp, and not the roof material. COR-TEN®, corten, CorTen, and so on are all names for “weathering” steel alloys that contain trace elements of copper. COR-TEN® is actually a trademark owned by U.S. Steel, who began marketing these alloys more than 50 years ago, and the name has since been genericized by tradespeople to include products produced by other mills and having slightly varied alloy ratios. The unique oxidation process of this material “seals” the surface to prevent the corrosion process. 

For more on CORTEN, please visit our blog, "What is COR-TEN®?"