There is quite a lot of helpful information on MVC model binding. My problem stems from the fact that I am trying to avoid creating strongly typed data in my MVC application as
Not exactly what you're after but maybe the resolution of this issue would give you a partial workaround, by allowing you to bind to a simple wrapper object with an embedded Dictionary. It might even allow binding direct to a Dictionary. Not sure... You might also need to explicitly set the json ContentType header in your $.ajax call
"JSON model binding for IDictionary<> in ASP.NET MVC/WebAPI"