Web API with claims-based authentication IFD

I hope I posted this in the correct area. I'm trying to make a simple web request to the Dynamics CRM Web API. A sample is below.

using (WebClient wb = new WebClient { BaseAddress = baseAddress, Credentials = credentials })
{
wb.Headers[HttpRequestHeader.Accept] = "application/json";
string response = wb.DownloadString("api/data/v8.0/systemusers");
}

This works fine with Dynamics CRM 2016 on-premise with basic password-based authentication, however I'm trying to get this same request to authenticate with an installation (same, Dynamics CRM 2016 on-premise) using claims-based authentication with an IFD without any success.

Does anyone know if there is a sample .Net class or application that could be compiled that could provide an example of a successful API request like the above? Just an FYI - I see this project being limtied to .Net 4.0.

Any help or suggestions are appreciated.