The reasoning behind my suggestion:
1) Limited gear. You appear to have no light modifiers, so we'll work with that.
2) As others have mentioned, there could be a color cast from the walls, if you use the walls as a light modifier.
3) They're businessmen. Like most, they want to be seen as being powerful, whether they are obvious about it or not. Cater to that, and give them dramatic lighting, something they can envision themselves in and create a different kind of impression. They will want to be seen as something unique, and doing a textbook '5 guys seated around a conference table' image that might as well be in a company report, probably isn't going to achieve that.
My suggestion is not too specific because of all the unknowns... table surface, walls, clothes they'll be wearing, etc. With a little tweaking, you can get something close to what I like to call the 'Council Of Elders' look... something right out of a science fiction movie where the community elders seem to always be seated around a table in a vast, dark space, with minimal lighting on the table, casting dramatic shadows on their faces, yaddayaddayadda.
In your scenario, ignoring the background (imho) would give them more of a commanding presence; this is what we do, this is what we are, and everything else is irrelevant. No distractions, just five important faces at command central.