Postando objeto json que vinculará IDictionary <>

HomeController.cs:

public class Notification
{
    public string Name { get; set; }
    public IDictionary<string, string> Fields { get; set; }
}

[HttpPost]
public ActionResult Send(string id, Notification viewModel)
{
    string name = viewModel.Name;
    IDictionary<string, string> fields = viewModel.Fields;
    return Json("Success");
}

post.js:

$.ajax({
    type: 'POST',
    url: "/home/send",
    data: JSON.stringify({
        id: "id1",
        "Name": "name1",
        "Fields": [{
            "Key": "key1",
            "Value": "value1"
        }, {
            "Key": "key2",
            "Value": "value3"
        }]
    }),
    contentType: "application/json",
    dataType: "json",
    processData: false
});